MX2015000246A - Method for obtaining vanillin from aqueous basic compositions containing vanillin. - Google Patents

Abstract

The invention relates to a method for obtaining vanillin from an aqueous, basic composition containing vanillin, in particular from a composition produced in the oxidation, especially in the oxidation by means of electrolysis, of aqueous alkaline compositions containing lignin, comprising at least one treatment of an aqueous, basic composition containing vanillin, in particular the treatment of a composition produced in the oxidation, especially in the oxidation by means of electrolysis, of aqueous alkaline compositions containing lignin, with a basic adsorbent, in particular an anion exchanger.

Description

METHOD FOR OBTAINING VAINILLINA FROM BASIC AQUEOUS COMPOSITIONS CONTAINING VAINILLINA Description The present invention relates to a process for the production of vanillin from aqueous basic compositions comprising vanillin as they arise, for example, in the oxidation of aqueous alkaline solutions or suspensions comprising lignin.

The transformation of renewable raw materials to valuable chemicals, which are suitable, in particular, as fragrances and aromatic substances, is of great interest. Lignin and also substances comprising lignin such as alkaline lignin, lignin sulfate or lignin sulfonate arise as waste materials or by-products of wood processing to provide pulp. The total production of substances comprising lignin is estimated at approximately 20 billion tons per year. Lignin is therefore a valuable raw material. Parts of this lignin are in the meantime also used. For example, alkaline lignin, which can be produced through the alkaline treatment of black liquor that arises in papermaking, is used in North America as a binder for particle boards based on wood and cellulose, as dispersants, to clarify sugar solutions, stabilize asphalt emulsions and also for stabilization foam. However, by far the largest amount of waste lignin is used through combustion as an energy source, eg. , for the pulp process.

Biopolymer lignin is a group of three-dimensional macromolecules that are produced in the cell wall of plants that is composed of various building blocks of phenolic monomer such as p-coumaryl alcohol, coniferyl alcohol and sinapyl alcohol. Because of its composition, it is the only significant source of aromatic compounds in nature. The use of this renewable natural material, moreover, does not compete with a use as food.

Vanillin, 4-hydroxy-3-methoxybenzaldehyde, is a synthetic aromatic substance that is widely used in place of expensive natural vanilla as an aromatic substance for food, as a fragrance in deodorants and perfumes, and also for improving the flavor of pharmaceutical products and vitamin preparations. Vanillin is also an intermediate in the synthesis of various drugs such as, for example, L-dopa, methyldopa and papaverine.

To date, aromatic aldehydes have generally been produced from petrochemical precursors. Because of the structural similarity of vanillin to the building blocks of lignin, lignin should be suitable as a starting material for the production of vanillin. The oxidative cleavage of lignin to vanillin and other aromatic aldehydes has therefore been the subject of numerous studies since 1940. The conversions of lignin most commonly used are chemical oxidation with copper oxide (see JM Pepper, BW Casselman, JC Karapally, Can. J. Chem. 1967, 45, 3009-3012) or nitrobenzene (see B. Leopold, Acta. Chem. Scand., 1950, 4, 1523 to 1537; B. Leopold, Acta. Chem. Scand. 1952, 6, 38 to 39), acidolysis (see JM Pepper, PET Baylis, E. Adler, Can. J. Chem. 1959, 37, 1241-1248), hydrogenolysis (see FE Brauns, Academic Press 1952, New York, 51 1 to 535) or ozonolysis (C Doree, M. Cunningham, J. Chem. Soc. 1913, 103, 677 to 686). One of the main methods is the treatment of lignin with oxygen at temperatures above 100 ° C in an alkaline medium in the presence of copper or cobalt catalysts (see HR Bjorsvik, Org. Proc. Res. Dev. 1999, 3, 330 to 340).

Occasionally, the preparation of vanillin from lignin has been reported by electrolysis of suspensions or aqueous alkaline solutions comprising - see WO 87/03014, WO 2009/138368 and C.Z. Smith et al. J. Appl. Electrochem. 2011, DOI 10, 1007 / s10800-010-0245-0.

Various processes are known for the production of vanillin from the basic reaction solutions of such oxidation, in addition to conventional extraction, optionally after acidification.

The extraction of vanillin or vanillin from basic lignin solutions is successful, for example, through the exchange of cations, with the neutralization of the basic solution. In this case, the vanilla is passed through a cation exchanger resin in the H + form, whereby it is protonated to form vanillin. This exchange of cations is coupled to the neutralization in the presence of a buffer solution (vanillin / vanillin) - see M. Zabková et al., Sep. Purif. Technol. 2007, 55, 56 to 68. He proved that it is disadvantageous that vanillin is not extracted from the solution. Therefore, this method offers no protection against over-oxidation. In addition, large amounts of acid are required for the neutralization of the basic reaction medium. By acidification, the lignin is precipitated out of the solution, needs to be filtered and therefore can cause a loss of vanillin due to filtration.

CH 245671 describes the production of vanillin from aqueous solutions comprising impurities, the aqueous solution first adsorbs vanillin in a basic ion exchanger comprising amino groups, and is then eluted with an acid. In this regard, in the examples, the humic acid present is precipitated out of the aqueous solutions by acidification, and the pH of the aqueous vanillin solution is then set to 7.

The precipitation outside the lignin can be omitted by, for example. , the extraction of sodium vanillin directly from the alkaline solution by the use of n-butyl alcohol or isopropanol. However, this extraction is limited by the poor solubility by the vanilla salts in the organic solvents. In addition, this method has the disadvantage that the fraction extracted from the unreacted lignin is very large and therefore oxidation is not available.

In addition, the elimination of vanillin from the alkaline aqueous reaction streams that arise in the oxidation of Kraft lignin by the use of ultrafiltration through tubular ceramic membranes is known - see M. Zabková et al. , J. Membr. Sci. 2007, 301 (1-2), 221 to 237. The disadvantages are the comparatively high expense in a ultrafiltration and the costs associated with it and its low capacity. Therefore, effective separation of vanillin is only possible at low permeation rates. Membranes that allow higher permeation rates lead to an increase in lignin discharge, the separation of which requires additional separation steps and also eliminates oxidation. In addition, oxidic membrane structures are not suitable for long exposure in the alkaline medium, as they are subject to corrosion.

The aim of the invention is to provide a robust process for the production of vanillin from aqueous alkaline compositions comprising vanillin, the process of which does not require the neutralization of the composition. The process should be suitable, in particular, for the production of vanillin from aqueous alkaline compositions, as it arises in the oxidation of aqueous alkaline compositions comprising lignin which, in addition to vanillin, also comprise lignin and polymeric oxidation products. These solutions typically have a pH of at least 10, often at least 12 and in particular pH above 13. In particular, the process must allow the production of vanillin from these compositions without the removal of relatively large amounts. large lignin together with vanillin. The process must also be suitable for the elimination of vanillin from the aqueous alkaline reaction mixtures that arise in the oxidation during the oxidation process, in order to thereby reduce the risk of over-oxidation of vanillin.

This and other objects are achieved by means of the process described hereinafter, in which a basic and aqueous composition comprising vanillin, in particular a composition as it arises in oxidation, especially in the oxidation by electrolysis, of Aqueous alkaline compositions comprising lignin are treated with a basic solid adsorbent, in particular an anion exchanger.

Therefore, the present invention relates to a process for the production of vanillin from a basic and aqueous composition comprising vanillin, in particular from a composition as it arises in oxidation, especially in oxidation by electrolysis, of aqueous alkaline compositions comprising lignin, comprising at least one treatment of a basic and aqueous composition comprising vanillin, in particular the treatment of a composition as it arises in oxidation, especially in oxidation by electrolysis, of aqueous alkaline compositions comprising lignin, with a basic solid adsorbent, in particular an anion exchanger.

The process according to the invention is linked to a series of advantages: because vanillin is present as a weak acid in the aqueous alkaline composition, predominantly or completely in anionic form, i.e., as vanillate, it is adsorbed by the adsorbent and then it can be released or eluted in a simple manner by means of treatment with a suitable eluent, typically with an acid, in particular with a dilute solution of a mineral acid in an organic solvent or in a mixture of organic solvent aqueous. The introduction of acid in the basic or alkaline composition can thus be avoided. This allows, in the case of aqueous compositions that arise in the oxidation of alkaline aqueous compositions of compositions comprising lignin, a release of the vanillin formed in the oxidation during oxidation, such that in the first place the risk of over-oxidation of the the vanillin is reduced and secondly the composition comprising exhausted aqueous vanillin lignin can be returned directly to oxidation. In this way, the conversion of lignin can be maximized and the total yield of aromatic compounds can be increased. This allows a virtually complete utilization of the renewable raw material lignin. The vanillin released from the adsorbent was also pre-purified very well and comprises much smaller amounts of lignin than in the processes of the previous technique. In addition, the salt load can be significantly reduced, since all the basic reaction mixture does not need to be neutralized but only the vanillate bound to the adsorbent.

The process has mainly the advantage that it can be carried out directly with basic or alkaline vanillin solution, which can still comprise large amounts of impurities, even at pH's of at least 10, in particular at least pH 12 or even at pHs above 13. It is surprising that vanillin is adsorbed from the basic solution by the basic adsorbent even at these pHs, since, due to the relatively low density of the vanilla anion charge and the relatively high concentration of ions of OH at these pH, one I would have expected the OH ions to displace the vanilla anion and no significant adsorption of the vanillate to the basic adsorbent would take place.

The process according to the invention thus allows an oxidation of repeated or continuous lignin in the alkaline medium a simultaneous, repeated or continuous vanillin production. The production of vanillin by the use of the solid basic adsorbent is particularly economical, since the basic adsorbent can be easily regenerated and used repeatedly to produce vanillin.

Here and from now on, the expressions "basic vanillin solution", "alkaline vanillin solution", "basic composition", "alkaline composition", "composition comprising basic aqueous vanillin", "composition comprising aqueous alkaline vanillin", "basic vanillin solution", "alkaline vanillin solution" and "Alkaline composition" are used as synonyms. These are taken to mean aqueous compositions comprising vanillin in dissolved form, optionally in addition to impurities, and having a basic or alkaline pH of generally above 9, often at a pH of at least 10, in particular at least pH 12, and especially a pH above 13.

For the treatment of the basic or alkaline composition with the basic adsorbent, in particular the anion exchanger resin, for example the adsorbent can be added to the composition comprising alkaline aqueous vanillin. After a certain residence time, the basic adsorbent is separated from the composition that g it comprises alkaline aqueous vanillin and then the vanillin is released from the absorbent by means of treatment with the eluent. The separation can be proceeded by means of usual solid-liquid separation processes, by e j. , by filtration, sedimentation or centrifugation.

Preferably, the composition is first passed through a bed, or fixed bed, of the basic adsorbent, for example a column filled with the adsorbent, and then the basic adsorbent is eluted with the eluent.

Suitable adsorbents are in principle all substances which comprise basic groups or which are treated with hydroxide ions. These include alkalized activated carbons, basic aluminum oxides, clays, basic adsorbent resins, in particular anion exchangers or anion exchanger resins. Anion exchanger or anion exchanger resin exchangers usually comprise functional groups which are selected from tertiary amino groups, quaternary ammonium groups and quaternary phosphonium groups.

The anion exchangers used are preferably crosslinked organic polymer resins comprising cationic groups, for example quaternary ammonium groups, quaternary phosphonium groups, imidazolium groups or guanidinium groups, in particular quaternary ammonium groups or imidazolium groups.

In a preferred embodiment, the basic adsorbents used are anion exchanger resins selected from the group of crosslinked polystyrene resins (hereinafter the ion exchanger of group i), wherein some of the phenyl rings of the cross-linked polystyrene support quaternary ammonium groups, in particular those of the formula I: R1 # - A-N-R2 (I) l 3 R3 wherein R1, R2 and R3, independently of each other, are C ^ -Cg alkyl, wherein one of the radicals R1, R2 or R3 can also be hydroxyalkyl Ci-Cg, A is C1-C4 alkanediyl, and # denotes the site of binding to a phenyl group of the polystyrene resin.

Here and hereinafter, Ci-C8 alkyl is a linear or branched aliphatic hydrocarbon radical having 1 to 8 carbon atoms, in particular having 1 to 4 carbon atoms (alkyl 0? -04), such as, for example, , methyl, ethyl, n-propyl, isopropyl, n-butyl, 2-butyl, n-pentyl, n-hexyl, n-heptyl or n-octyl.

Here and hereinafter, C 4 -C 8 hydroxyalkyl is a linear or branched aliphatic hydrocarbon radical having 1 to 8 carbon atoms, in particular having 2 to 4 carbon atoms (C 2 -C 6 hydroxyalkyl), which supports an OH group . Examples of such radicals are 2-hydroxyethyl, 3-hydroxypropyl, 2-hydroxypropyl, 4-hydroxybutyl and 6-hydroxyhexyl.

Here and hereafter, alkanediyl 0 · i-04 is a bivalent aliphatic hydrocarbon radical having 1 to 4 carbon atoms, such as methylene (CH2), ethane-1, 1-diyl, ethane-1, 2- diyl, propane-2,2-diyl, propane-1,2-diyl, propane-1,3-diyl, butane-1,1-diyl, butane-2,2-diyl, butane-1, 2-diyl, butane-1,3-diyl, butane-2,3-diyl or butane-1,4-diyl.

Among the adsorbents of group i), above all, those which are preferred when A, R1, R2 and R3, independently of one another, and in particular preferably in combination, have the following meanings: R1, R2, R3, independently of one another, are methyl or ethyl and especially methyl; A is methylene.

The adsorbents of group i) are known and commercially available, for example the types Amberlite® IRA400, IRA401, IRA402, IRA410, IRA458, IRA478, IRA900, IRA904, IRA910, FPA40, FPA 90, FPA 91 (Dow), Amberlyst® A26 (Dow), Amberjet® types 4200, 4400 and 4600 (Dow), Ambersep® 900 and 920U types (Dow), Dowex® Dowex Monosphere 550A OH, Dowex 1X100, 1X850 and 1X850 (Dow) types and Applexion types ® XA4001, XA 4013, XA4023, XA4041, XA4042 and XA4043.

In a further preferred embodiment, the basic adsorbents used are anion exchanger resins which are cross-linked polyvinylpyridines (hereinafter the ion exchanger of group ii), wherein some of the pyridine groups are present in quaternized form, for example as group of the formulas lia or 11 b, in particular lia: (Ha) (llb) wherein R 4 is Ci-Ce alkyl, in particular C 1 -C 4 alkyl and especially methyl, and # denotes the binding site to a carbon atom of the polymer backbone of the polyvinylpyridine resin.

The adsorbents of group ii) are known and are commercially available, for example the quaternized Reillex®HP types such as Reillex® HPQ.

In a further preferred embodiment, the basic adsorbents used are anion exchanger resins which are crosslinked acrylate resins (hereinafter the ion exchanger of group iii), wherein some of the copolymerized monomers comprise quaternary ammonium groups, for example as a group of the formula III: wherein R5, R6 and R7, independently of one another, are Ci-C8 alkyl, A 'is C2-C4 alkanediyl, and # denotes the binding site to an oxygen atom or a nitrogen atom of a carboxyl group or a group carboxamide attached to the polymer backbone of the acrylate resin.

The adsorbents of group iii) are known and commercially available, for example the types Applexion® XA 4122 and XA 4141 (Novasep).

Suitable adsorbents are also polymers comprising alkylimidazolium N-Ci-Ce groups (hereinafter the ion exchanger of group iv). In these polymers, the groups Alkylimidazolium N-C ^ -Cs are attached to the polymer backbone directly or through a spacer. Such polymers can be obtained by analogous polymer reaction with alkylimidazole N-Ci-Ce compounds, for example by reaction of polymers comprising haloalkyl groups, in particular chlorobenzyl groups, e.g. , copolymers of styrene and chloromethylstyrene, with alkylimidazoles N-Ci-Cs. Also, it is possible to produce such polymers by homo- or copolymerization of monomers comprising imidazolium groups, for example methylimidezol (N-Ci-Cs alkylimidazolium), alkylimidazolium N-vinyl-N-Ci-Cs, co- (alkylimidazolium N-acrylate) Ci-Cej-C2-C8 alkyl or co- (alkylimidazolium methacrylate N-CVCej-C2-C8 alkyl, optionally with comonomers such as C ^ Ce alkyl acrylates, Ci-C8 alkyl methacrylates, C2- hydroxyalkyl acrylates C8, hydroxyalkyl acrylates or C2-C8 styrene, for example by means of free radical polymerization or by controlled radical polymerization such as RAFT or ATRP Such polymers are known and described, for example, by J. Yuan, M. Antonietti , Polymer 2011, 52, 1469 to 1482; J. Huang, C. Tao, Q. An, W. Zhang, Y. Wu, X. Li, D. Shen, G. Li, Chemical Communications 2010, 46, 967; R. Marcilla, J. Alberto Blazquez, J. Rodriguez, JA Pomposo, D. Mecerrcyes, Journal of Polymer Science Part A: Polymer Chemistry 2 004, 42, 208 to 212; J. Tang, H. Tang, W. Sun, M. Radosz, Y. Shen, Journal of Polymer Science Part A: Polymer Chemistry 2005, 43, 5477-5489; J. Tang, Y. Shen, M. Radosz, W. Sun, Industrial & Engineering Chemistry Research 2009, 48, 9113 to 91 18.

The anion exchanger resins of groups i), ii), iii) and iv) can be macroporous or gel-like, wherein the gel-type anion exchanger resins, in particular the gel-type anion exchanger resins of the group i), are preferably suitable.

Typically, the charge density, i.e. the number of ionic groups in anion exchanger resins which are suitable according to the invention, is in the range of 0.5 to 5 mmol / g, in particular 1 to 4.5 mmol / g ion exchange resin (dry). Typically, adsorbents or anion exchanger resins have a capacity for hydroxide (OH) ions in the range of 0.1 to 3 eq / l (moles equivalent per liter, wet), particularly in the range of 0 , 3 to 2.5 eq / l (wet) and especially in the range of 0.5 to 2 eq / l.

The basic adsorbents are particulate. The average particle size of the particulate adsorbents (average diameter in weight, determined, eg, through sieve lines), is typically in the range of 10 mm to 2500 mm, and particularly in the range from 100 p.m. to 1000 p.m., and especially in the range of 400 to 1000 p.m. The adsorbents typically have particle sizes in the range of 10 to 650 mesh, in particular 15 to 350 mesh, and especially in the range of 15 to 60 mesh.

The polymer resins that are preferred according to the invention (anion exchangers or anion exchanger resins) can be gel or macroporous type. The resins of Particles are typically in the form of macroscopic polymer particles, for example in the form of a finely divided powder or granules. The average particle size of the anion exchangers is typically in the range of 10 mm to 2000 mm, and in particular in the range of 100 μm to 1000 μm and especially in the range of 400 to 1000 μm ( average weight, determined by sifting). They typically have particle sizes in the range of 10 to 650 mesh, in particular 15 to 350 mesh and especially in the range of 15 to 60 mesh.

In the process according to the invention, the adsorbent, in particular the anion exchanger resin, can be used in its OH form, that is, the groups present in the adsorbent, in particular in the anion exchanger resin for the neutralization of the charge are OH ions. The adsorbent, in particular the anion exchanger resin, can also be used in the salt form, ie, the cationic groups present in the anion exchanger resin for charge neutralization are non-basic counterions such as chloride or sulfate. The OH form is then generated by means of the basic aqueous vanillin composition and represents the actual adsorbent.

The vanillin adsorbed by the adsorbent during the treatment of the basic and aqueous composition comprising vanillin is adsorbed from the adsorbent by means of treatment of the adsorbent with at least one eluent and can be produced in purified form from the eluent in this manner. The suitable eluents are, in particular, the acid solutions, in particular mineral acids in organic solvents, and also acid solutions, in particular mineral acids in aqueous mixtures of organic solvents. Through the treatment of the adsorbent with the eluent, the vaillinate ions adsorbed by the adsorbent are neutralized to provide vanillin, which is then adsorbed from the adsorbent.

Suitable organic solvents are, in particular, those that are unlimitedly miscible with water at 22 ° C, or that at least dissolve in an amount of at least 200 g / l in water at 22 ° C. These include, in a special form, dimethyl sulfoxide, acetone, C1-C4 alkanols such as methanol, ethanol, isopropanol, n-propanol, 1-butanol, 2-butanol and tert-butanol, alkanediols such as glycol, 1, 4- butanediol, and also cyclic ethers such as dioxane, methyltetrahydrofuran or tetrahydrofuran, nitrogen heterocycles, such as pyridine or N-methylpyrrolidine and mixtures. Preference is given to the C1-C4 alkanols, and especially methanol. Organic solvents can also be used in a mixture with water. The water fraction preferably does not exceed 70% by volume, in particular 50% by volume, and especially 30% by volume, based on the total volume of organic solvent and water. When, as eluents, acid solutions are used, in particular mineral acids in aqueous mixtures of organic solvents, solutions of mineral acids such as hydrochloric acid, phosphoric acid, and in particular sulfuric acid are in particular suitable form. The solutions of organic carboxylic acid and sulfonic acids, in particular those that they have 1 to 3 carbon atoms such as methanesulfonic acid, formic acid, acetic acid and propionic acid, are also particularly suitable. Preferably, the acid solution has an acid concentration in the range of 0.01 to 10 mol kg 1, in particular 0.1 to 5 mol kg 1.

The basic and aqueous composition comprising vanillin is generally treated with the adsorbent, in particular the anion exchanger resin at temperatures below 150 ° C, often at a temperature below 100 ° C, preferably at a temperature in the range of 10 to 150 ° C, and in particular 10 to 100 ° C, and especially in the range of 10 to 70 ° C or 15 to 50 ° C.

For the treatment of the basic and aqueous composition comprising vanillin with the adsorbent, that is, for loading the adsorbent, in particular the anion exchanger resin with the vanillin, preferably, the basic composition comprising vanillin is passed from a in a conventional manner through an adsorbent arrangement, i.e., through one or more fixed beds of the adsorbent, eg, through one or more columns that are filled with the adsorbent (eg, the anion exchanger). ). The pass through can proceed either in a descending or ascending manner. The passage through proceeds preferably at a specific flow rate (specific load) in the range of 0.2 to 35, in particular 0.5 to 10, in particular 1 to 10 bed volumes per hour or a flow rate volumetric in the range of 0.1 to 50 m / h.

The relative amount of the aqueous alkaline composition and The adsorbent is generally selected in such a way that at least 35%, and in particular at least 50%, of the vanillin present in the aqueous alkaline composition are adsorbed by the adsorbent. The amount of aqueous alkaline composition is usually 1 to 1500 times, in particular 2 to 1000 times the amount of the bed volume. Depending on the degree of adsorption, the effluent that emerges at the outlet of the adsorbent arrangement, e.g. , the column filled with adsorbent, can still comprise vanillin, so that the effluent can optionally be passed to an additional adsorbent arrangement, eg, a column filled with adsorbent.

The loading process can be followed by a washing step. For this purpose, water is passed through the adsorbent arrangement. The amount of wash water is in this stage usually 0.1 to 10 times the bed volume, in particular 0.5 to 5 times the bed volume. The wash water is usually passed through at a specific flow rate (specific load) in the range of 0.2 to 35, in particular 0.5 to 10, in particular 1 to 10 bed volumes per hour. or at a volumetric flow rate in the range of 0.1 to 50 m / h. The resulting wash water may comprise small amounts of vanillin and may then be combined with the effluent that arises during loading. In contrast to the processes of the prior art, such washing step is not required, and thus a preferred embodiment of the process according to the invention does not comprise the washing step, and the elution proceeds directly after loading.

The loading step or the washing step carried out in the optional are followed by the elution of vanillin. For this purpose, the eluent is passed through the adsorbent arrangement. The vanillin is adsorbed thereto and eluted and the adsorbent, for example the anion exchanger resin is regenerated. The amount of eluent is usually 0.1 to 20 times, in particular 0.5 to 10 times, eg, 1 to 8 times the amount of the bed volume. The eluent is usually passed through at a specific flow rate (specific load) in the range of 0.5 to 20, in particular 1 to 10, in particular 2 to 8 bed volumes per hour. After elution, any of cationic groups in the adsorbent are present in the salt form. Optionally, therefore, before the next loading, a regeneration to the OH form can be carried out, eg, by treatment with an aqueous solution of an alkali metal hydroxide is, for example, with aqueous NaOH.

With respect to the temperatures and the flow rate, that established for the load is applied. The elution can be carried out either ascending or descending. The elution can be carried out in the same direction as the load or in the opposite direction to it.

The elution can be followed by an additional washing step, in order to remove impurities in optional form present. For this purpose, water is passed through the anion exchanger arrangement. The amount of wash water is usually 0.1 to 10 times, in particular 0.5 to 5 times, eg, 2 to 4 times the bed volume. The wash water is usually passed to through a specific flow rate (specific load) in the range of 0.5 to 20, in particular 1 to 10, in particular 2 to 8 bed volumes per hour. The effluent that emerges during the washing step is usually fed as wastewater to a usual wastewater treatment or other processing.

The adsorbent arrangement can be operated discontinuously and then comprises one or more, eg, 2, 3 or 4, stationary stationary beds connected in series filled with adsorbent. It can also be operated continuously and then generally comprises 5 to 50, and in particular 15 to 40, adsorbent beds which can be, eg, a component of a "True Mobile Bed" arrangement (see K. Tekeuchi J Chem. Eng. Jpn., 1978, 1 1 pp. 216-220), an "Annular Continuous Circulation" provision (see JP Martin, Discuss Farraday Soc. 1949, p.7) or a "Simulated Mobile Bed" provision. , as described, for example, in US 2,985,589 and WO 01/72689 and also by GJ Rossiter et al. Proceedings of AlChE Conference, Los Angeles, CA, Nov. 1991 or H. J. Van Walsem et al., J. Biochtechnol. 1997 59, p. 127 The eluate that arises during elution is processed in a usual manner to produce vanillin. Generally, the acid is first removed, for example by aqueous extractive processing, or neutralized by the addition of a base and the salts formed are separated. Optionally, the eluate can be concentrated in advance, eg, by removing the solvent in a usual evaporator arrangement. The resulting condensate can be reused, example in a subsequent elution.

In this manner, a crude product comprising vanillin is obtained which optionally comprises other low molecular weight components such as acetovanillone or vanillic acid and also optionally other components of the aqueous composition used, for example lignin.

In principle, in the process according to the invention, any of the aqueous compositions comprising vanillin having a basic pH can be used, wherein the pH is generally above 9, often at least 10, in particular at least 12, and especially at least or above 3.

The concentration of vanillin in the aqueous composition comprising vanillin is typically in the range of 1 to 5000 mg / kg, in particular 5 to 2000 mg / kg. In a special embodiment, the concentration of vanillin is in the range of 5 to 500 mg / kg, and especially in the range of 10 to 250 mg / kg. In another embodiment, the vanillin concentration is in the range of 10 to 5000 mg / kg, and in particular in the range of 20 to 2000 mg / kg.

Aqueous compositions comprising vanillin are typically liquids having a water content of generally at least 30% by weight, often at least 50% by weight, in particular at least 60% by weight, on the basis of the total weight of the composition. When the aqueous compositions comprising vanillin comprise solids, before treatment with the adsorbent, a filtration can be carried out, but this is not absolutely necessary.

The procaccording to the invention has, in particular, advantages when the basic and aqueous composition comprising vanillin is an aqueous alkaline composition comprising lignin which, in addition to vanillin, comprises lignin or lignin derivatives, for example lignin sulfate, lignin sulphonate, Kraft lignin, alkaline lignin, soda lignin, or Organosolv lignin or a mixture thereof, as a component of lignin and having an alkaline pH, usually at a pH of at least 9, often at lthan 10, in particular at least 12, and especially at least or above 13. The aqueous alkaline composition comprising lignin generally comprises 0.5 to 30% by weight, preferably 1 to 15% by weight. weight, in particular 1 to 10% by weight, of lignin, on the basis of the total weight of the aqueous composition comprising lignin.

The procaccording to the invention is suitable, in particular, for the production of vanillin from aqueous basic compositions comprising vanillin which were obtained by partial oxidation, especially by electrolysis, of a suspension or aqueous alkaline solution containing lignin .

The suspension or aqueous alkaline solution containing lignin used for the partial oxidation typically has a pH of at least 10, in particular of at least 12, and especially of at least or above 13. The suspension or aqueous alkaline solution containing lignin used for oxidation usually it comprises 0.5 to 30% by weight, preferably 1 to 15% by weight, in particular 1 to 10% by weight, of lignin, on the basis of the total weight of the aqueous composition comprising lignin.

The aqueous alkaline solution or suspension used for partial oxidation may be an aqueous solution or suspension arising as a by-product in an industrial procsuch as the production of pulp, pulp or cellulose, e.g. , black liquor, and also the wastewater streams that comprise lignin from the sulphite proc the sulphate proc the Organocell or Organosolv proc the ASAM proc the Kraft procor the natural pulp manufacturing proc The aqueous alkaline solution or suspension for oxidation may be an aqueous solution or suspension which is prepared by dissolving a lignin or lignin derivative in aqueous alkali, eg, lignin sulfate, lignin sulfonate, Kraft lignin. , alkaline lignin, soda lignin or Organosolv lignin, or a lignin that arises in an industrial procsuch as the production of pulp, pulp or cellulose, eg, black liquor lignin, the sulfite proc the procof sulphate, the Organocell or Organosolv proc the ASAM proc the Kraft proc or the natural pulp manufacturing proc As bases for adjusting the pH of the suspension or aqueous alkaline solution containing lignin, inorganic bases, eg, alkali metal hydroxides such as NaOH or KOH, ammonium salts such as ammonium hydroxide and carbonates, can be used in particular. of alkali metals such as sodium carbonate, eg, in the form of soda. Preference is given to hydroxides of alkali metals, in particular NaOH and KOH. The concentration of inorganic bases in the suspension or aqueous solution containing lignin should not exceed 5 mol / l, in particular 4 mol / l, and is typically in the range of 0.01 to 5 mol / l, in particular in the range of 0.1 to 4 mol / l.

The partial oxidation of the suspension or aqueous alkaline solution containing lignin can be carried out in a manner known per se, e.g. , in accordance with the methods described in the above-mentioned prior art, in particular by controlled oxidation with atmospheric oxygen at elevated temperature in the presence of suitable transition metal catalysts, eg, copper or cobalt catalysts (see HR Bjorsvik , Org. Proc. Res. Dev. 1999, 3, 330 to 340) or in a special form by electrolysis of suspensions or aqueous alkaline solutions comprising, as described, for example, in WO 87/03014, WO 2009 / 138368 or CZ Smith et al., J. Appl. Electrochem. 2011, DOI 10, 1007 / s10800-010-0245-0 or hereafter.

In the preparation of the aqueous alkaline composition comprising vanillin, an aqueous electrolyte comprising lignin or a substance comprising lignin and which is present in the form of an aqueous suspension or solution is subjected to electrolysis under alkaline conditions. In this case, the oxidation of the lignin or lignin derivative present takes place at the anode. In the cathode, typically, the reduction of aqueous electrolytes proceeds, eg, with hydrogen formation.

The electrode materials used for electrolysis can be selected from known electrode materials for these purposes such as nickel, silver, mixed oxides of RuOxTiOx, platinized metals such as platinum titanium or platinum niobium, platinum, graphite or carbon, or between what are called base alloys, such as Ni-based alloys, Co-based alloys, Fe-based alloys, Cu-based alloys or Ag-based alloys. The use of base alloys has not been described for this purpose to date in the previous technique and is the subject of discussion of a parallel patent application. It has been found to be advantageous if the electrodes used in the electrolysis, at least the anodes, comprise an electrode material that is selected from Co-based alloys, Fe-based alloys, Cu-based alloys, base alloys. of Ag and alloys based on Ni, and in special form of alloys based on Co and Ni.

A base alloy is taken to mean an alloy comprising at least 50% by weight, in particular at least 55% by weight, especially at least 58% by weight, eg, 50 to 99% by weight , preferably 50 to 95% by weight, in particular 55 to 95% by weight, in particular preferably 55 to 90% by weight, and in particular 58 to 90% by weight of the respective base metal (in the case from a Co-based Co alloy, in the case of a Cu-based Cu alloy, in the case of a Ni-based Ni alloy, in the case of an Ag-based Ag alloy, and in the case of a Fe-based Fe alloy) and at least one additional alloy component, wherein the The total amount of all additional alloying components that are different from the base metal is typically at least 1% by weight, in particular at least 5% by weight, and especially at least 10% by weight, and it is found, for example, , in the range of 1 to 50% by weight, preferably in the range of 5 to 50% by weight, in particular in the range of 5 to 45% by weight, particularly preferably in the range of 10 to 45% by weight, and especially in the range of 10 to 42% by weight, in which all figures in% by weight refer in each case to the total weight of the alloy. The typical additional alloy components are, in special form, Cu, Fe, Co, Ni, Mn, Cr, Mo, V, Nb, Ti, Ag, Pb and Zn, but also Si, C, P and S. It is given Preference is consequently given to the base alloys comprising at least one additional alloy component mentioned above other than the base metal. Preference is given, in particular with respect to its stability with simultaneously a good selectivity, to alloys based on Ni, Fe-based alloys and Co-based alloys, in particular Ni-based alloys and Co.-based alloys. Preference is given, in particular with respect to its selectivity with simultaneously satisfactory stability, to Cu-based alloys and Ag-based alloys.

Typical nickel-based alloys comprise substantially, ie, at least 95% by weight, and in particular at least 98% by weight, and especially at least 99% by weight a1) 50 to 95 % by weight, in particular 55 to 95% by weight, in particular preferably 55 to 90% by weight, and especially from 58 to 90% by weight Ni weight and b1) 5 to 50% by weight, in particular 5 to 45% by weight, in particular preferably 10 to 45% by weight, and especially 10 to 42% by weight, of at least one additional alloying component, selected from Cu, Fe, Co, Mn, Cr, Mo, W, V, Nb, Ti, Si, Al, C and S.

Among the Ni-based alloys, preference is given in particular to those comprising 5 to 35% by weight, in particular 10 to 30% by weight, Cu as additional alloying component. These alloys are hereinafter referred to as group 1.1. In addition to Cu, the base alloys of group 1.1 may comprise one or more of the following alloy components in an amount of up to 45% by weight, in particular up to 40% by weight: Fe, Co, Mn, Cr, Mo, W , V, Nb, Ti, Si, Al, C and S. The examples of Ni base alloys of group 1.1 are alloys of the abbreviations EN NiCu30Fe (Monel 400) and NiCu30AI and also the Ni-Cu alloy of the following composition : 63% by weight of Ni, 30% by weight of Cu, 2% by weight of Fe, 1.5% by weight Mn, 0.5% by weight of Ti (Monel 500K).

Among the Ni-based alloys, preference is also given, in particular, to those comprising 5 to 40% by weight, in particular 15 to 30% by weight, Cr as an additional alloying component. These alloys are hereinafter referred to as group 1.2. In addition to Cr, the base alloys of group 1.2 can comprise one or more of the following alloy components in an amount of up to 40% by weight, in particular up to 35% by weight: Fe, Co, Mn, Cu, Mo, W , V, Nb, Ti, Si, Al, C and S. Among the Ni base alloys of group 1.2, there is preference in particular to those comprising Mo, Nb and / or Fe as additional alloying component, in particular of a total amount of 1 to 30% by weight. Examples of Ni base alloys of group 1.2 are alloys of the abbreviations EN NiCr19NbMo (Inconel® alloy 718) and NiCr15Fe (Inconel® alloy 600), NiCr22Mo19Fe5 (Inconel® 625), N¡Mo17Cr16FeWMn (Hastelloy® C276), a Ni-Cr-Fe alloy having a nickel content of 72-76% by weight, a Cr content of 18 to 21% by weight, a C content of 0.08-0.13% by weight and a Fe content of 5% by weight, and a Ni-Cr-Co-Mo alloy having a nickel content of 48 to 60% by weight, a Cr content of 19% by weight, a Co content of 13 , 5% by weight and a Mo content of 4.3% by weight (Waspaloy®). Among the Ni-based alloys, preference is also given in particular to those which comprise 5 to 35% by weight, in particular 10 to 30% by weight, Mo as an additional alloying component. These alloys are hereinafter referred to as group 1.3. In addition to Mo, the base alloys of group 1.3 may comprise one or more of the following alloy components in an amount of up to 40% by weight, in particular up to 35% by weight: Fe, Co, Mn, Cu, Cr, W , V, Nb, Ti, Si, Al, C and S. Among the Ni-based alloys of group 1.3, preference is given in particular to those comprising Cr, Nb and / or Fe as an additional alloying component, in particular of a total amount of 1 to 30% by weight. Examples of Ni-base alloys of group 1.3 are alloys of the abbreviations EN NiMo28 (Hastelloy® B and Hastelloy® B-2) and NiMo29Cr (Hastelloy® B-3).

Typical cobalt-based alloys comprise substantially, ie, at least 95% by weight, and in particular at least 98% by weight, and especially at least 99% by weight: a1) 50 a 95% by weight, in particular 55 to 95% by weight, in particular preferably 55 to 90% by weight, and especially from 58 to 90% by weight of Co and b1) 5 to 50% by weight, in particular 5 to 45% by weight, in particular preferably 10 to 45% by weight, and especially 10 to 42% by weight, of at least one additional alloying component, selected from Cu, Fe, Ni, Mn, Cr, Mo, W, V, Nb, Ti, Si, P and C. Among Co-based alloys, preference is given in particular to those comprising 5 to 40% in weight, in particular 7 to 30% by weight, Cr as an additional alloying component. These alloys are hereinafter referred to as group 2.1. In addition to Cr, the base alloys of group 2.1 may comprise one or more of the following alloy components in an amount of up to 40% by weight, in particular up to 35% by weight: Fe, Ni, Mn, Cu, Mo, W , V, Nb, Ti, Si, C and P. Among the Co-based alloys of group 2.1, preference is given in particular to those comprising Mo, W and / or Fe as an additional alloying component, in particular of a total amount 1 to 30% by weight. Examples of Co-based alloys of group 2.1 are alloys of the compositions: i. 53% by weight of Co, 31% by weight of Cr, 14% by weight of Fe, 1, 2% by weight of C (Stellite® 4), ii. 65% by weight of Co, 28% by weight of Cr, 4.5% by weight W, 1, 2% by weight weight of C, 1, 1% by weight of Si (Stellite® 6), iii. 66.5% by weight of Co, 28% by weight of Cr, 5% by weight of Mo, 0.5% by weight of C (Stellite® 21), iv. 58-62% by weight of Co, 25-30% by weight of Cr, 5-10% by weight of Mo (Vitallium types, eg, Haynes 21 alloy); v. 59% by weight of Co, 8.5% by weight of Cr, 29.5% by weight of Mo, 2, 1% by weight of Si (T 400).

Typical iron-based alloys are high alloy stainless steels. They generally comprise substantially, that is to say, at least 95% by weight, and in particular at least 98% by weight, and especially at least 99% by weight: a1) 50 to 95% by weight, in particular 55 to 95% by weight, particularly preferably 55 to 90% by weight, and especially 58 to 90% by weight of Fe and b1) 5 to 50% by weight, in particular 5 to 45% by weight, in particular preferably 10 to 45% by weight, and especially 10 to 42% by weight, of at least one additional alloying component, selected from Cu, Co, Ni, Mn, Cr, Mo, W, V, Nb, Ti, Si, P, S and C. Among the Fe-based alloys, in particular preference is given to stainless steels comprising chromium which , in addition to the base metal, they comprise Cr as an alloying component, wherein the chromium content is generally in the range of 5 to 30% by weight, in particular 10 to 25% by weight. These alloys are hereinafter referred to as group 3.1. In addition to Cr, the base alloys of group 3.1 may comprise one or more of the following alloy components in an amount of up to 40% by weight, in particular up to 35% by weight: Co, Ni, Mn, Cu, Mo, V, Nb, Ti, Si, C, S and P. Among the base alloys of Fe of group 3.1, preference is given in particular to those comprising Ni, Mo, V, Ti, Si and / or Nb as additional alloying component, in particular of a total amount of 1 to 30% by weight. Examples of Fe-based alloys of group 3.1 are chromium steels, eg, X12CM3, X6Cr17 and X20Cr13, chromium-nickel steels, eg, X2CrNi12, X5CrNi18-10, X8CrNiS18-9, X2CrNi19-1 1 , X2CrNi18-9, X10CrNi18-8, X1 CrNi19-9, X2CrNiMo17-12-2, X2CrNiMo19-12, X2CrNiMo18-14-3, X2CrNiMoN 18-14-3, X13CrN¡MoN22-5-3, X6CrNiTi18-10, X6CrNiMoT 17-12-2, GX5CrNiMoNb19-1 1 -2 and X15CrNiSi25-21, chromium-molybdenum steels, eg, X12CrMoS17 and 25CrMo4, and also chrome-vanadium steels.

Typical copper-based alloys generally comprise substantially, i.e., at least 95% by weight, and in particular at least 98% by weight, and especially at least 99% by weight a1) 50 to 95% by weight, in particular 55 to 95% by weight, in particular preferably 55 to 90% by weight, and especially 58 to 90% by weight of Cu and b 1) 5 to 50% by weight, in particular 5 to 45% by weight, in particular preferably 10 to 45% by weight, and especially 10 to 42% by weight, of at least one additional alloy component , selected from Ag, Pb, Ni and Zn.

The examples of Cu-based alloys of group 3.1 are alpaca (alloy of 62% by weight of Cu, 18% by weight of Ni and 20% by weight Zn) and cupro-nickel (alloy of 75% by weight of Cu and 25% by weight of Ni).

In principle, as an anode, any type of electrode known to those with experience in the technique can be used. This may completely comprise the respective electrode material or be a support electrode having an electrically conductive support that is coated with the electrode material. The electrodes used as an anode can be, for example, electrodes in the form of expanded metals, grids or metal plates.

As a cathode, in principle, any electrode known to those skilled in the art and suitable for the electrolysis of aqueous systems can be used. Since the reduction processes take place at the cathode and the lignin is oxidized at the anodeWhen a heavy metal electrode is used such as, for example, a nickel cathode, the charge of the vanillin with this heavy metal is so low that the resulting vanillin can be used without problems in the food industry. Preferably, the electrode materials have a low hydrogen overvoltage. Preference is given here to electrodes having an electrode material selected from nickel, Ni-based alloys, Co-based alloys, Fe-based alloys, Cu-based alloys, silver, Ag-based alloys, ie , silver-rich alloys having a silver content of at least 50% by weight, mixed oxides of RuOxTiOx, platinum titanium, platinum, graphite or carbon. In particular, the cathode electrode material is selected from alloys based on Ni, base alloys of Co, Fe-based alloys, Cu-based alloys, in particular with preference between Ni-based alloys, Co-based alloys and Fe-based alloys, and especially between the base alloys of groups 1.1 , 1.2, 1.3, 2.1 and 3.1.

In principle, as a cathode, any type of electrode known to those skilled in the art can be used. These may completely comprise the respective electrode material or be a support electrode having a support that is coated with the electrode material. Preference is given to electrodes comprising the respective electrode material, in particular one of the base alloys mentioned above, in particular one of the base alloys of groups 1.1, 1.2, 1.3, 2.1 and 3.1. The electrodes used as the cathode can be, for example, electrodes in the form of expanded metals, grids or metal plates.

The arrangement of the anode and the cathode is not restricted and comprises, for example, arrangements of flat bars and / or plates that can also be organized in the form of a plurality of alternate polarity batteries and cylindrical arrangements of grids, grilles or tubes formed that can also be organized in the form of a plurality of cylinders alternating in polarity.

To achieve optimum space-time performance, various electrode geometries are known to those skilled in the art. Advantageous electrode geometries are a bipolar arrangement of a plurality of electrodes, an arrangement in which a bar-type anode is surrounded by a cylindrical cathode, or a arrangement in which both the cathode and the anode comprise a wire grid and these wire grids are placed one above the other and rolled cylindrically.

The anode and the cathode can be separated from one another by a separator. In principle, as separators, all separators usually used in electrolysis cells are suitable. The separator is typically a flat porous structure disposed between the electrodes, e.g. , a grid, grid, woven or non-woven fabric, made of an electrically non-conductive material that is inert under the conditions of electrolysis, eg, a plastic material, in particular a Teflon material, or a plastic material coated with Teflon.

For electrolysis, any electrolysis cell known to those skilled in the art can be used, such as a divided or undivided continuous flow cell, capillary space cell or plate stack cell. Particular preference is given to the undivided continuous flow cell, eg, a continuous flow cell with circulation, in which the electrolyte is conducted continuously beyond the circulating electrodes. The process can be carried out successfully, both discontinuously and continuously. The electrolysis can also be carried out on an industrial scale. The corresponding electrolysis cells are known to those skilled in the art. All embodiments of this invention relate not only to the laboratory scale, but also to the industrial scale.

In a preferred embodiment, the contents of the cell are mixed of electrolysis. For this mixture of the contents of the cells, any mechanical agitator known by those with experience in the technique may be used. The use of other mixing methods such as the use of Ultraturrax, ultrasound or jet nozzles is also preferred.

By applying the electrolysis voltage to the anodes and cathodes, electric current is conducted through the electrolytes. In order to avoid secondary reactions such as over-oxidation and formation of detonating gas, a current density of 1000 mA / cm2, in particular 100 mA / cm2, will generally not be exceeded. The current densities at which the process is carried out are generally 1 to 1000 mA / cm2, preferably 1 to 100 mA / cm2. Particularly preferably, the process according to the invention is carried out at current densities between 1 and 50 mA / cm2.

The total electrolysis time depends clearly on the electrolysis cell, the electrodes used and the current density. An optimal time can be determined by those skilled in the art by means of routine experiments, e.g. , by means of sampling during electrolysis.

In order to avoid a deposit in the electrodes, the polarity can be changed in short time intervals. The polarity change can proceed in a range of 30 seconds to 10 minutes. Preference is given to an interval of 30 seconds to 2 minutes. For this purpose, it is convenient that the anode and the cathode comprise the same material.

The electrolysis is generally carried out at a temperature in the range of 0 to 160 ° C, preferably 50 to 150 ° C, where the anodes made of the base alloys mentioned above allow the electrolysis to be carried out at relatively low temperatures, without loss of selectivity occurring. The electrolysis then proceeds preferably at temperatures in the range of 10 to 100 ° C, in particular in the range of 50 to 95 ° C, and especially in the range of 70 to 90 ° C. The electrolysis is generally carried out at a pressure below 2000 kPa, preferably below 1000 kPa, in particular below 150 kPa, eg. , in the range of 50 to 1000 kPa, in particular 80 to 150 kPa. It is particularly preferable that the process according to the invention is carried out at a pressure in the atmospheric pressure range (101 ± 20 kPa).

The particular advantages of the invention are useful, in particular, when the basic composition comprising vanillin is prepared by oxidation, in particular by electrolysis, of an aqueous alkaline suspension or solution containing lignin, and the vanillin formed in the oxidation is removed or it is exhausted during the oxidation of the resulting vanillin-based basic composition by treating the basic composition comprising vanillin with the adsorbent. In this way, the over-oxidation of vanillin is reduced and the yield of vanillin, based on the lignin used, can be significantly increased.

The elimination or depletion of vanillin from the mixture of alkaline aqueous reaction that arises in the oxidation can proceed in intervals or continuously. In the elimination or depletion of vanillin at intervals, the oxidation of the suspension or aqueous alkaline solution containing lignin is interrupted and the resulting alkaline aqueous reaction mixture is treated in the manner described above with the adsorbent, in particular the exchanger of anions. In the continual elimination or depletion of vanillin, usually a stream of the alkaline aqueous reaction mixture arising in the oxidation is discharged from the oxidation reactor, eg, an electrolysis cell, the current is treated with the adsorbent, in particular with the anion exchanger, and the current that is exhausted in the vanillin in this way is returned to the oxidation reactor.

For the elimination or depletion of vanillin in intervals or continuously from the alkaline aqueous reaction mixture arising in the oxidation, preferably the reaction mixture or the discharged stream of the reaction mixture is passed from the previously described way through a bed of the adsorbent and then the adsorbent is treated with a dilute solution of a mineral acid in at least one organic solvent or a mixture of aqueous organic solvent, where vanillin is eluted which is adsorbed by the adsorbent.

The examples hereinafter serve for a more detailed illustration of the invention.

Analysis: The reaction products were analyzed by means of gas chromatography. In this process, the stationary phase used was an Agilent HP-5 column, 30 m long, 0.25 mm in diameter and 1 mm thick layer. This column was heated by a temperature program in the course of 10 min at a heating rate of 10 ° C / min from 50 ° C to 290 ° C. This temperature was maintained for 15 min. As the carrier gas, hydrogen was used having a flow rate of 46.5 mL / min.

The anion exchangers used: Amberlite® IRA402 (OH) from Dow: an OH form of a cross-linked styrene / divinylbenzene copolymer having trimethylammonium groups bonded through CH2 in the form of gel-like particles (20 to 25 mesh) having a moisture content from 50 to 60%. The anion exchanger has a capacity of 1.2 meq / ml, based on an anion exchanger bed swollen with water, or 4.1 meq / g, based on solids (approximately 1.3 meq / ml) in the form of chloride).

Reillex® HPQ from Vertellius Specialties (Sigma Aldrich): Cl form of a cross-linked poly-4-vinylpyridine which was quaternized with methyl chloride and in the form of gel-like particles (particle size 300-1000 μm) having a content humidity 55%. The anion exchanger has a capacity of 4.1 meq / g, based on solids.

Dowex Monosphere 550A OH from Dow: an OH form of a cross-linked styrene / divinylbenzene copolymer having groups trimethylammonium bound through CH2 in the form of gel-like particles (average particle size 590 pm) having a moisture content of 55 to 65%. The anion exchanger has a capacity of 1.0 meq / ml, based on a bed of the anion exchanger swollen with water.

Ambersep 900 OH from Rohm & Haas (now Dow): an OH form of a cross-linked styrene / divinylbenzene copolymer having trimethylammonium groups bonded through CH2 in the form of gel-like particles (20 to 25 mesh) having a moisture content of 65% . The anion exchanger has a capacity of 0.8 meq / ml, based on an anion exchanger bed swollen with water.

Amberlite® IRA910 (CI) from Dow: a Cl form of a crosslinked styrene / divinylbenzene copolymer having dimethyl-2-hydroxyethylammonium groups bonded through CH2 in the form of macroporous particles (16 to 50 mesh) having a content of humidity of 52%. The anion exchanger has a capacity of 1.0 meq / ml, based on an anion exchanger bed swollen with water, or 3.8 meq / g, based on solids.

Resin modified with 1-methylimidazolium I 99.7 g of poly (styrene-co-chloromethylstyrene) (75 to 150 mm, loading (chloromethylstyrene): 0.94 mmol / g) were suspended in 1000 ml of toluene and mixed with 46.97 g of 1-methylimidazole. . The reaction mixture was stirred for 17.5 h at 110 ° C. The resin was filtered and washed successively with 300 ml of toluene, 250 ml of 0.1 M HCl, 600 ml of demineralized H2O and 300 ml of methanol. Subsequently, the resin by means of freeze drying. Weight: 110.30 g.

Elemental analysis: C 85.74 H 8.33 N 2.44 The dried resin was allowed to swell in 900 ml of methanol / H2O 2: 1 for 1 day and then filtered. 5 ml of the 1-methylimidazolium resin thus produced was filled into a separation column (diameter: 0.5 to 1.0 cm) and first washed with demineralized H20, then with 1 M aqueous NaOH solution, then with 0 , 1 M aqueous AgN03 solution until the chlorine ions were no longer detectable. Then, the column was washed with demineralized H20 until the wash water had a pH = 7. Activity was examined by acid-base titration. The column was then washed with 100 ml of 2.5% by weight aqueous NaCl solution and then washed with demineralized water. The wash solution was collected in a 250 ml volumetric flask. The washing solution was evaluated in 50 ml aliquots. The result of the volumetric analysis after a plurality of successive activation cycles is summarized in the following table.

Total exclusion capacity (TEC) after successive activation cycles (Production of) Resin modified with 1-propylimidazolium II 49.35 g of poM (styrene-co-chloromethylstyrene) (75 to 150 mm, loading (chloromethylstyrene): 0.94 mmol / g) were suspended in 500 ml of toluene and mixed with 30.87 g of 1-propylimidazole. . The reaction mixture was stirred for 23 hrs at 10 ° C. The resin was filtered and washed in succession with 300 ml of toluene, 300 ml of 0.1 M HCl, 600 ml of demineralized H2O and 300 ml of methanol. Subsequently, the resin was dried by means of freeze drying. Weight: 57.49 g.

Elemental analysis: C 84.98 H 9.02 N 2.38 The dried resin was allowed to swell in 450 ml of methanol / H20 2: 1 for 1 day and then filtered.

(Production of) Resin modified with 1-Pentylimidazolium III 49.70 g of poly (styrene-co-chloromethylstyrene) (75 to 150 μm, loading (chloromethylstyrene): 0.94 mmol / g) in 500 ml of toluene were suspended and mixed with 38.78 g of 1-pentylimidazole. . The reaction mixture was stirred for 23 hrs at 10 ° C. The resin was filtered and washed in succession with 300 ml of toluene, 300 ml of 0.1 M HCl, 600 ml of demineralized H20 and 900 ml of methanol. Subsequently, the resin was dried by means of freeze drying. Weight: 55.82 g.

Elemental analysis: C 85, 12 H 9.69 N 2, 19 The dried resin was allowed to swell in 450 ml of methanol / H20 2: 1 for 1 day and then filtered. 1. Example 1 2,513 g of kraft lignin were placed in a single cell vessel (V = 600 mL) without a cooling jacket and dissolved with stirring in 300 g of 1 M NaOH. 1 1 nickel plates (each 5.0 cm * 2.1 cm) were connected in a bipolar fashion at a spacing of 0.3 cm such that the cell comprised ten half chambers. The solution was electrolyzed for about 9.7 hours (Q = 700 C, on the basis of electrolyte: Q = 7000 C). The established cell voltage was in the range of 3.0 to 3.2 V. After the amount of charge that had flowed through, the contents of the cells were brought to room temperature and placed on a column bed. of Amberlite® IRA402 (OH) (mAmberiit = 10,072 g, dCOiUmna = 2 cm, a = 5 cm). The ion exchanger used in water had swollen for several hours beforehand. After the reaction solution had completely passed through the column material (i) (droplet rate: 1 drop / sec), the filtrate (i) was electrolyzed again under the conditions mentioned above. In total, the solution was electrolyzed and filtered five times.

For the production of the vanillin adsorbed by the anion exchanger, the anion exchanger was washed in portions by the use of a 2% by weight HCl solution in methanol (Vt0, = 250 mL, droplet rate: 1 drop / sec). The resulting filtrate was mixed with 150 ml of H2O and extracted three times, each time with 100 ml of dichloromethane. The combined organic phases were washed with 80 mL of saturated common salt solution, dried over Na2SO4 and freed from the solvent under reduced pressure. A bronze foam remained, which was purified by column chromatography (d = 2 cm, a = 20 cm gel). silica 60) (eluent: cyclohexane / ethyl acetate in the volumetric ratio 3: 2). On the basis of the Kraft lignin used, 2.59 wt.% Of vanillin containing 8% by weight of acetovanillone (GC fraction) were obtained.

For processing the filtrate, it was acidified with concentrated hydrochloric acid with cooling and the acidified filtrate was filtered through a bed of diatomaceous earth, in order to remove the lignin that had precipitated out. The diatomaceous earth bed was thoroughly rinsed with dichloromethane. The aqueous phase was extracted three times, each time with 100 mL of dichloromethane. The combined organic phases were washed with 100 mL of saturated common salt solution, dried over Na2SO4 and freed from the solvent under reduced pressure. A viscous solid remained (mRp = 17.2 mg, 0.68% by weight, based on Kraft lignin used). Analysis by gas chromatography gave the following typical composition (GC fractions): 68.9% vanillin, 9.5% acetovanillone, 21.6% vanillic acid. 2. Example 2 The electrolysis was carried out in a manner similar to that of Example 1 with the following change: the reaction solution, after the amount of charge that had flowed through and had been cooled to room temperature was placed on a column bed of Amberlite® IRA402 (OH) (mAmberiit = 50 g, dCOiUmna = 2 cm, a = 24.5 cm). After carrying out the electrolysis and filtration five Sometimes, the processing proceeds in a manner similar to Example 1.

Column chromatographic purification of the organic crude product gave the following typical composition, based on Kraft lignin used (% by weight): 2.54% by weight vanillin, 2.45% by weight guaiacol.

Example 3: 2.011 g of kraft lignin were placed in a single container cell (V = 600 mL) without a cooling jacket and dissolved with agitation in 300 g of 3 M NaOH. 11 Monel 400K plates (4.9 cm c 2.1 cm) were connected in a bipolar manner at a spacing of 0.3 cm, such that the cell comprised ten half chambers. The solution was electrolyzed for approximately 7.8 hours (Q = 560 C, on the basis of electrolyte: Q = 5600 C). The set cell voltage was in the range of 3.0 to 3.1 V. After the amount of charge that had flowed through, the contents of the cells were brought to room temperature and placed on a column bed. of Amberlite IRA402 (OH) (rnAmberiite = 40 g, dC0 Umna = 2 cm, a = 20 cm). The ion exchanger used for several hours in water had been inflated in advance. After the reaction solution had completely passed through the column material (droplet rate: 1 drop / sec), the filtrate was electrolyzed again under the conditions mentioned above. In total, the solution was electrolyzed and filtered five times.

For the production of vanillin adsorbed by the exchanger of anions, the anion exchanger was washed in portions by the use of a 2% by weight HCl solution in methanol (V, 0t = 350 ml_, droplet rate: 1 drop / sec). The resulting filtrate was mixed with 100 ml of H2O and extracted three times, each time with 150 ml of dichloromethane. The combined organic phases were washed with about 100 mL of saturated common salt solution, dried over Na2SO4 and freed from the solvent under reduced pressure. A bronze colored foam remained and was purified by column chromatography (d = 2 cm, a = 20 cm of silica gel 60) (eluent: cyclohexane / ethyl acetate in the volumetric ratio 3: 2). On the basis of the Kraft lignin used, 2.47 wt.% Of vanillin was obtained and contaminated with 8 wt% of acetovanillone (GC fraction).

For processing the filtrate, it was acidified with concentrated hydrochloric acid with cooling and the acidified filtrate was filtered through a bed of diatomaceous earth, in order to remove the lignin that had precipitated out. The diatomaceous earth bed was thoroughly rinsed with dichloromethane. The aqueous phase was extracted three times, each time with 150 mL of dichloromethane. The combined organic phases were washed with 100 mL of saturated common salt solution, dried over Na 2 SO 4 and freed from the solvent under reduced pressure. A viscous solid remained (mRP = 1 1, 9 mg, 0.59% by weight, based on Kraft lignin used). Analysis by gas chromatography gave the following typical composition (GC fractions): 75.2% vanillin, 11.0% acetovanillone. 3. Example 4 Each 50 mg of vanillin was dissolved in each case in 50 ml of 1 M aqueous sodium hydroxide solution in a screw-capped flask and mixed with 1 g of ion exchange resin that had been swollen in distilled water overnight in advance for approximately 8 hours. The suspension was shaken for 45 minutes at approximately 300 rpm, then filtered through a frit and rinsed twice with 10 ml of water.

For the recovery of the vanillin adsorbed by the anion exchanger, the anion exchanger was filtered from the basal vanillin solution through a frit and transferred from the frit to a screw cap bottle with 20 ml of a Methanolic acid solution (90% methanol, 10% concentrated hydrochloric acid). The frit was then thoroughly rinsed with dichloromethane. The suspension was again shaken for 45 minutes at approximately 300 rpm, it was filtered again through a frit, and this was thoroughly rinsed with approximately 15 ml of dichloromethane. The filtrate was mixed with 2 ml of n-hexadecane and 30 ml of water, extracted 3 times, each time with 30 ml of dichloromethane, washed with 30 ml of saturated common salt solution and then dried over Na 2 SO 4. The solvent was removed under reduced pressure and the remaining light yellow solid was analyzed by means of gas chromatography.

For filtering processing, 2 ml of n- hexadecane to the filtrate and the solution was acidified by the addition of concentrated hydrochloric acid with ice cooling. The aqueous phase was extracted 3 times, each time with 30 ml of dichloromethane. The combined organic phases were washed with saturated common salt solution and then dried over Na2SO4. The solvent was removed under reduced pressure and the remaining light yellow solid was analyzed by means of gas chromatography.

The amount of vanillin recovered each time from the two fractions (at least 95% of the amount originally used, i.e.,> 47.3 mg) was determined from the gas chromatogram by the use of the n-hexadecane internal standard .

The results of the ion exchange experiments in basic vain solutions with the use of various ion exchange resins are summarized in Table 1. recovered b) Ion exchangers were converted to their OH form before use by treatment with 1 M NaOH Example 5 5 ml of 1-methylimidazolium resin was filled, according to what was described above, in a separation column (diameter: 0.5 to 1.0 cm) and first washed with demineralized H2O, then with 1 M solution of Aqueous NaOH by means of 0.1 M aqueous AgN03 solution, no more chloride ions were detected. The ion exchange resin was washed with demineralized H20 until the wash water had a pH = 7. Subsequently, a solution of 49.4 mg of vanillin in 25 ml of 1 M aqueous NaOH was passed through the exchange resin of ions by overpressure or gravitation of N2. Then, the resin was washed with 25 ml of demineralized H20 until the wash water had a pH = 7. Subsequently, ion exchange resin was washed in succession with 4% by weight methanolic HCl solution and methanol. The two methanolic fractions were combined, the solvent was removed and the residue was mixed with demineralized H20. The resulting mixture was extracted with ethyl acetate, the combined organic phase was dried and the solvent was removed. The residue was taken up in ethyl acetate and the vanillin content was quantified by means of gas chromatography analysis. In this way, 42.2 mg of the vanillin used was recovered (= 86% of the vanillin used). After the reactivation of the resin used, TEC was established reproducibies by valuation. 4. Example 6 49.2 mg of vanillin dissolved in 1 M NaOH (50 ml) was mixed with 1.03 g ion exchange resin (Dowex Monosphere 550a OH) and shaken for 1 h (frequency: 300 rpm). The ion exchange resin was filtered and the residue was washed with 10 ml of demineralized H2O. The washed ion exchange resin was then mixed with 20 ml of 5% by weight H2SO4methane and an additional 10 ml of methanol and shaken for 1 h (frequency: 300 rpm). The ion exchange resin was filtered and the solvent was removed from the filtrate under reduced pressure. The resulting residue was mixed with H20, the aqueous phase was extracted with toluene and the combined organic phases were dried over MgSO4.

After removal of toluene, the residue was taken up in ethyl acetate and the vanillin content was quantified by means of gas chromatography analysis. In this way, 40, 1 mg of vanillin (= 82% of the vanillin used) was recovered.

Example 7 The procedure was carried out in a manner similar to Example 6, where a solution of 48.0 mg of vanillin in 1 M NaOH (50 ml) was used and this was mixed with 1.01 g of ion exchange resin ( Dowex Monosphere 550a OH) and the suspension was shaken for 1 h (frequency: 300 rpm). The ion exchange resin that was filtered, after washing with 10 ml of demineralized H20, was mixed with 20 ml of a 10% by weight methanolic acetic acid solution and an additional 10 ml of methanol and shaken for 1 h (frequency: 300 rpm). After processing, 39.3 mg of vanillin (= 82% of the vanillin used) was recovered. 5. Example 8 The procedure was carried out in a manner similar to the example 6, where a solution of 49.2 mg of vanillin in 1 M NaOH (50 ml) was used and this was mixed with 1.02 g of ion exchange resin (Dowex Monosphere 550a OH) and the suspension was shaken for 1 hour. h (frequency: 300 rpm). The ion exchange resin which was filtered, after washing with 10 ml of demineralized H2O, was mixed with 20 ml of a solution of 10% by weight acetic acid in ethyl acetate and an additional 10 ml of ethyl acetate and shaken for 1 h (frequency: 300 rpm). After filtration of the ion exchange resin and removal of the solvent under reduced pressure, the resulting residue was taken up in ethyl acetate and the vanillin content was quantified by means of gas chromatography analysis. In this way, 42.2 mg of vanillin (= 86% of the vanillin used) was recovered.

Claims (16)

1. A process for the production of vanillin from a basic and aqueous composition comprising vanillin, comprising at least one treatment of a basic and aqueous composition comprising vanillin with a basic solid adsorbent, wherein the basic and aqueous composition comprising Vanillin has a pH of at least 10.

2. The process according to claim 1, wherein the basic and aqueous composition comprising vanillin is first passed through a bed of the basic adsorbent and then the basic adsorbent is eluted by the use of a dilute solution of an acid at less an organic solvent or in a mixture of aqueous organic solvent.

3. The process according to claim 2, wherein the diluted acid solution is selected from alcoholic solutions and aqueous / alcoholic solutions of a mineral acid.

4. The process according to any one of the preceding claims, wherein the basic adsorbent is a cross-linked organic polymer resin comprising functional groups selected from tertiary amino groups, quaternary ammonium groups and quaternary phosphonium groups.

5. The process according to any one of the preceding claims, wherein the basic adsorbent is a resin of cross-linked organic polymers comprising quaternary ammonium groups or quaternary phosphonium groups.

6. The process according to claim 4 or 5, wherein the polymer resin comprises 0.1 to 3 molar equivalents per liter (wet) of functional groups.

7. The process according to any one of claims 4 to 6, wherein the basic adsorbent is selected from (i) cross-linked polystyrene resins comprising functional groups of the formula I: R1 # - A-N-R2 (I) < 3 R3 wherein R1, R2 and R3, independently of one another, are C1-C8 alkyl, wherein one of the radicals R1, R2 or R3 may also be C1-C8 hydroxyalkyl, A is C1-C4 alkanediyl, and # denotes the site of binding to a phenyl group of the polystyrene resin; (ii) crosslinked polyvinylpyridine resins comprising functional groups of the formulas lia and / or 11 b: wherein R 4 is C 1 -C 8 alkyl, and # denotes the carbon atom binding site of the polymer backbone of the polyvinylpyridine resin; (iii) crosslinked acrylate resins comprising functional groups of formula III: wherein R5, R6 and R7, independently of one another, are C1-C8 alkyl, A 'is C2-C4 alkanediyl, and # denotes the attachment to an oxygen atom or a nitrogen atom of a carboxyl group or a group carboxamide attached to the polymer backbone of the acrylate resin.

8. The process according to any one of claims 1 to 3, wherein the basic adsorbent is selected from polymers comprising alkylimidazolium N-C1-C8 groups.

9. The process according to any one of the preceding claims, wherein the basic and aqueous composition comprising vanillin has a pH of at least 12.

10. The process according to any one of the preceding claims, wherein the basic and aqueous composition comprising vanillin was obtained by oxidation of an aqueous alkaline suspension or solution containing lignin.

The process according to claim 10, wherein the basic and aqueous composition comprising vanillin was obtained by electrolysis of a suspension or aqueous alkaline solution containing lignin.

12. The process according to any one of the claims 10 or 11, wherein the suspension or aqueous alkaline solution containing lignin has a pH of at least 12.

13. The process according to any one of claims 10, 11 or 12, wherein, as suspension or aqueous solution containing lignin, an aqueous stream comprising lignin is used from the production of pulp, pulp or cellulose.

14. The process according to any one of claims 10 to 13, wherein the suspension or aqueous alkaline solution containing lignin is prepared by dissolving or suspending at least one material comprising lignin in aqueous alkali, wherein the material comprising lignin is selected from black liquor lignin, Kraft lignin, lignin sulfonate, alkaline lignin, Organosolv lignin and corresponding waste from the pulp or pulp industry production.

15. The process according to any one of claims 10 to 14, wherein the basic composition comprising vanillin is prepared by oxidation of a suspension or aqueous alkaline solution containing lignin, and the vanillin formed in the oxidation is removed during the oxidation of the basic composition comprising vanillin resulting by treatment of the basic composition comprising vanillin with the basic adsorbent.

16. The process according to claim 15, wherein the basic composition comprising vanillin arising during oxidation is passed through a bed of the basic adsorbent and then the basic adsorbent is eluted with a dilute solution of a acid in at least one organic solvent or in a mixture of aqueous organic solvent.