JPH06501875A - Hydrogenation catalyst and method for producing tetrahydrofuran - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] name of invention Hydrogenation catalyst and method for producing tetrahydrofuran Cross-reference with previous applications This application is filed under application number 071588.991 on July 27, 1990. This is a continuation application.

Background of the invention field of invention This invention provides novel ternary- or multi-element metals in backmixing or plug flow reactors. Hydrogenation of water to tetrahydrofuran as a hydrogenatable precursor in the presence of a catalytic complex Regarding basicization. Said ternary or multi-element metal catalyst complex essentially comprises (1 ) a catalytically effective amount of palladium (Pd); (2) a catalytically effective amount of palladium (Pd); Rhenium (Re); and (3) support, i.e. rhodium deposited on the carrier (Rh), cobalt (Co), platinum (PI), ruthenium (Ru), iron ( Fe), thulium (Tm), cerium (Ce), yttrium (Y), neodymium aluminum (Nd), aluminum (AI), praseodymium (Pr), holmium (Ho), copper (Cu), samarium (Sm), europium (Eu), Funium (llf), manganese (Mal), vanadium (V), chromium (C r), gold (Au), terbium (Tb), lutetium (Lu), nickel (Ni), scandium (Sc), and niobium (Nb). It consists of a mediatingly effective amount of one or more metals.

In other aspects, the invention provides an efficient method for producing high purity tetrahydrofuran. Regarding good aqueous methods. This method involves the use of a suitable hydrogenation catalyst in a backmixing reactor. Continuous hydrogenation and reaction of hydrogenatable tetrahydrofuran precursors in the presence of including maintaining the concentration of acid in the mixture within a predetermined range.

Description of related applications Maleic acid, maleic anhydride, fumaric acid, succinic acid, malic acid, dimethyl succinic acid by hydrogenation of suitable THF precursors such as esters and γ-butyrolactone. For the preparation of trahydrofuran (THF) and 1,4-butanediol (BDO) Many catalysts have been disclosed in the art as being useful.

Many of these catalysts incorporate the metals palladium and rhenium on a suitable support. I'm letting you do it. For example, U.S. Pat. No. 4.6091636 describes various hydrogenatable For the production of THF, BDO or mixtures thereof from precursors on a carbon support The use of a catalyst complex with palladium and rhenium is described.

U.S. Pat. No. 4,973,717 discloses, for example, calphonic acid using a paranram-based catalyst. Batch or continuous production of alcohols and/or ethers from acid esters It also discloses the significant effects of metals that can form alloys with palladium. It shows. Selection of THF/BDO from precursors containing one or more carboxylic acid groups The direct use of these alloy catalysts for selective production is described in U.S. Patent No. 4.973.71. It is not disclosed in issue 7.

Methods for the selective production of THF by catalytic reduction of hydrogenatable precursors are well known in the art. It is publicly known. For example, U.S. Patent No. 4.609.636 provides a The relative ratio of THF to be used depends on the operating temperature, contact time and hydrogen space time. can be increased by increasing one or more variables selected from It teaches that Many references such as U.S. Patent No. 3.726.905 The dehydrogenation of BDO to obtain THF from carbon dioxide is catalyzed by acid and the acid concentration is It is also known that increasing leads to an increase in the relative ratio of THE to BDO. deer However, in the presence of water, the rhenium containing hydrogenation catalyst is inhibited by the acid. It is also known that Bulletin of Thejapan Pet roleum In5titute, volume 12, pages 89 to 96 (+970) ``Maleic anhydride and intermediates using nickel-rhenium on diatoms'' A kinetic study of the hydrogenation of γ-butyrolac and intermediate succinic anhydride is described. Water and cono-acid are considered to be the main inhibiting components of the process involving reduction to ton. It has been reported that this can be achieved. In order to increase the rate of rTHF production, this author concluded that it is necessary to reduce the concentration of cono-acid as much as possible. There is.

Other known catalysts and methods for the production of THF from hydrogenatable precursors include: Although all are improvements, they are cited in the above teachings and may not be as intended. It is useful for the purpose of

One of the key areas that has been improved is catalyst performance, i.e. selectivity, space time. , yield and activity. Selectivity is here defined as a plug-flow reactor or a back-mixing reactor. consisting of THF/BDO/γ-butyrolactone (GBL) in the reaction equipment. Defined as a measure of the rate of exit stream . Space time yield (STY) is here: THE (g)/catalyst (kg)/ Defined as the amount of time.

Activity is here defined as the acid converted for a given residence time in a plug flow reactor. is defined as the percentage of Other key areas of improvement are high selectivity and selective production of THF using catalysts that provide both high space-time yields and be. Such improvements could make THF more economical, a commodity with numerous uses. It is of great commercial significance to enable manufacturing. For example, Tetrahy Dorofuran is a useful solvent for polymers such as polyvinyl chloride. It is useful as a monomer for polyether polyols.

In this invention, rhodium, cobalt, white Gold, ruthenium, iron, thulium, cerium, yttrium, aluminum, aluminum um, praseodymium, holmium, copper, samarium, europium, no lambda Mu, manganese, 1 sodium, chromium, gold, terbium, lutetium, nickel , scandium and niobium. Production of tetrahydrofuran using base metal/zaladium-rhenium catalyst complex The method is to maintain high selectivity in the backmixing reactor and to maintain high space-tightness of THF. 2.2.2.2.2.2.2.2.2.2.2.2.2.2.2. has been done.

In addition, in this invention, THF in an aqueous medium under back-mixing conditions containing a highly active catalyst. Continuous production and removal by steam distillation, in which the concentration of carboxylic acid is controlled within a predetermined range. As a result, over reduction (Cover reduction) There is almost no loss of catalytic activity, and surprisingly, there is almost no loss of catalytic activity. It has also been found that high selectivity can be obtained.

Summary of the invention According to this invention, maleic acid, maleic anhydride, fumaric acid, succinic acid, Hydrogenatable precursors (such as succinic acid, malic acid, or mixtures thereof) That is, these precursors are dicarboxylic acids or anhydrides, or these acids and and/or anhydride) in a back-mixing reactor or in a plug flow reactor at a temperature of about 150°C to 300°C and a temperature of about 100°C. Novel ternary- or multi-component metal catalysts at pressures from 0 to 3000 ps i g. react with hydrogen in the presence of a media complex to achieve high selectivity in a backmixing reactor. Maintain high space-time yields of THF, or in plug flow reactors. produces high acid conversion. This novel ternary- or multi-metal catalyst complex is approximately An activated porous carbon support having a surface area of more than 650 m''/g, or e.g. alumina, zirconia, titania, hafnium oxide, phosphor or carbonate A catalytically effective amount of Palladium, rhenium and one or more metals (M), namely rhodium, cobalt Ruthenium, platinum, ruthenium, iron, thulium, cerium, yttrium, neodymium, Aluminum, praseodymium, holmium, copper, samarium, europium, fnium, manganese, vanadium, chromium, gold, terbium, lutetium, nickel Contains a metal component selected from Kel, scandium and niobium.

The multi-component metal catalyst composite of the present invention comprises (1) about 01 to 10% by weight of palladium; (2) about 1 to 20% by weight rhenium component; and (3) about 001 from 1.0% by weight of a metal component and an activated porous carbon support or refractory oxide. and the remaining weight including any of the carriers.

In another aspect of the invention, a suitable hydrogenation catalyst is added to the backmixing reactor. in the presence of a temperature of about 150°C to 300°C and a temperature of about 1000 to 3000°C. The THF is continuously removed by steam distillation at a pressure of ps i g, and then the hydrogen is a precursor that can be reacted with hydrogen on a continuous substrate in an aqueous medium, and the reaction mixture The concentration of acid in the mixture is kept within a predetermined range.

One aspect of this invention essentially comprises (1) catalytically effective mushroom palladium (P); d); (2) a catalytically effective amount of rhenium (Re); and (3) a support. Rhodium (Rh), cobalt (co), platinum (p+), and rutheni attached to the body Ru (Ru), iron (Fe), thulium (Tm), cerium (Ce), iron Thorium (Y), neodymium CNd>, aluminum (,’II), praseodymium (Pr), Holmium (Do), Copper CCu), Samarium (Sm), Yu Uropium (Eu), Hafnium (Hl), IIin, Vanadium (■), chromium (Cr), gold (Au), terbium (Tb), lutetium (Lu), nickel (Ni), scandium (Sc), and niobium (N a combination of one or more metals (~l) in a catalytically effective amount selected from b); The present invention relates to a novel ternary or multi-element metal catalyst composite consisting of This ternary system- or the multi-element metal catalyst composite essentially has a content of about 0.1 to about 0.1 to 10% by weight palladium, about 1 to 20% by weight rhenium and about 0.5% by weight. Olly It consists of 1.0% by weight of one or more metals (M). Unexpectedly improved catalyst performance What improves this is the addition of one or more metals M. Suitable supports include activated porous Carbon supports and, for example, alumina, zirconia, titania, hafnium oxide, Included are refractory oxide supports such as silica or barium carbonate. A preferred carrier is The activated porous carbon support preferably has a surface area greater than about 1500 m2/g. are doing. Catalytic carbon supports are also made of fine powder particles used in slurry reactors. or larger support particles used in fixed bed reactors.

The ternary- or multi-metal catalytic composites of the present invention can be synthesized from a number of methods known in the art. It can be adjusted by any of the different methods. However, the catalyst Preferred steps in the preparation method include U.S. Pat. The teachings of publications are incorporated herein by reference) as described in more detail. This includes continuous deposition of palladium and rhenium components. for example, The method for preparing the catalyst comprises, in order: (a) a source of metal M and palladium; impregnating a carbon support with the solution and removing the solvent; (b) metal M and paradidine; The carbon impregnated with aluminum is heated to a temperature in the range of 100°C to 500°C under reducing conditions. a step of drying at a temperature of about 0.5 to 24 hours; (c) Applying a rhenium source solution to carbon impregnated with metal M and palladium. , removing the solvent to produce the catalyst, and (d) Metal ~ 1/palladium/rhenium impregnated carbon under reducing conditions at 100°C. drying for 0.5 to 24 hours at a temperature in the range of 500°C; or included.

Before adding palladium, after adding palladium, after adding rhenium, or after adding rhenium. A variation of the second method in which a metal (M) source is simultaneously applied to the support and reduced is also It will be appreciated by those skilled in the art that it can be advantageously utilized in the preparation of the catalysts of this invention. Probably. This allows the metals to be deposited in a different order (Rh is deposited and reduced before Pd). (Example 30) gives similar performance characteristics. This is illustrated by example 65-6'7.

Solutions containing palladium compounds typically have the required amount of palladium An aqueous medium containing an amount of palladium compound to produce a catalytic product. parajiu The compound is typically PdCfJ, including but not limited to PdCfJ. dBr　5Pd(NO)　,Pd(C2H302)2(Here, C2H502 is acetate), Pd(CH,O) (here, C3H702 is acetyl 5 , 2 2 acetonate), and (NH3)4Pd It may also be a coordination compound such as C12 or (NH4)2Pdc16. Re Solutions containing rhenium compounds are typically prepared using a catalytic converter with the required amount of rhenium. The compound is an aqueous solution containing a rhenium compound.

Rhenium compounds are typically Re2O7, but perrhenic acid or ammonia um or alkali metal perrhenate, K, ReCΩ, (C2H302 )2ReCΩ, (NH4)2Re2CΩ8, or the like. metal compound The solution containing substance N1 is typically aqueous and has the required amount of deposited metal. Contains a sufficient amount of metal to produce a catalytic product. For example, the metal is rhodium. In some cases, the rhodium compound is typically RhCf3, but , Rh　B　r　E　book　x　H? O, Rh, (C2H302) 4, R h6(Co)　Rh　(Co)　(Rh　(Co)　Cf)2, I6ゝ　4　1 2ゝ　2 Rh (C5H7o2)3 or Rh (No3) 3BH20°Rh, (S0 4) 3, and their salts exemplified by N a 3 Rh CΩ6, and (C 4H9) Rhodium compounds such as 4NRh (CO)2CD2, and and Rh(NH3)6Cg3. It may also be a coordination compound to which ruboxylate, -carbon oxide, etc. are bonded. metal is iron, the iron compound is typically FeC13*6H20, but F e C12 zero X H201F e B r2, F e (NO3) 3 Book 9H20S F e (S04) Book 7H9OS F C2 (S04 ) 3, F e (C5Hl 02) 3, (C5H5)2Fe (this Here, C3H5 represents cyclobentadienyl), Fe (Co), FC Even iron compounds such as 2(Co)9 and their salts and coordination compounds good. If it is a metal or cobalt, is the cobalt compound typical 1? ]l This is Co C4) $6 HO or 2 CoB r KH20, Co (OH), C o (No) Ne 6H201Co 5O4 7HO-Co (CHO) , CO304, Co (CHO), Co (C5H702) 3. Co(C It may also be a salt such as Ω04)2. If metal or platinum, platinum compound is typically H2PtCΩ66HO or PtC(1, Na2PtC47 4, PtC, Q, PtBr2, PtBr4, H2PtBr6, HPt (OH ), platinum compounds such as Pt (C5H702)2, (NH) PtCg, (C2H8N2)3PtCg, or (NH)Pt(No3)2 coordination compound, and (n-C,+H9)4NPtBr3fco) It may also be an organometallic precursor such as If metal or ruthenium, ruthenium The compound is typically RuC, Q 3 HO, RuBr 3 x H 2O, RuNO (NO), RuO zero x H2O.

Ru(CH,O), Ru2 CC2H502) 5 of 4CΩ, 23 Ruthenium compounds such as Ru(NH3)5CΩ3 and metal compounds. It's okay. When the metal is thulium, the Haum compound is typically T CI) 3 * 7 HV O, but TmB r 3 pieces XH20, T m Fe, Tm I 3, Tm203, Tm (CHO) Ne X 8 2 0. Tm (C5H702>3.Tm, (CO3)3NEXH, Os It may also be a thulium compound such as Tm(NO3) 3 5H90. Money When the genus is cerium, the cerium compound is typically CeC (J3 xH, O or 3 CeBr 6H20, Ce F S Ce I S CC 2 (C2H302) 3 zero 3H2o1CC2 (C03) 3 books 5H20 Seri like S Ce (NO3) 3 zero 6H2olCe (C5H702)3 compounds, as well as salts such as (NH4)2Ce (NO3)6 .

When the metal is yttrium, the yttrium compound is typically YCg Although this is book 6H20, Y B r 3 * K H20-YF3, Y2O3, Y (C2H302)3*4H2o1Y(CHO), Y(CHO), 5723. 37 3 (C5I5) 3 YSY2 (C03) 3 Ne 3H201 and Y (NO3) 3 pieces It may also be an yttrium compound such as 6H20. metal or neodymium In this case, the neodymium compound is typically NdCρ306H20, but Nd B r 3 Ne X H20, Nd Fe, Nd I 3, Nd203 , Nd (C2H302) 3 Zero 3H20S Nd (C5H702) 3 , Nd (NO3) 3 pieces 6H20 and Nd2 (CO3) 3 pieces XADCΩ 5 6Ho, AΩCΩ, AgB r3 and hydrate, AgF and water Summono, AgI3, Ag(0■)3, Aff (CH, -0) Nikode, C3H7 is isopropoquine), Ag (C5H702)3, and Ag (No. 3) It may be an aluminum compound such as 3 pieces 9H20. metal or brassiere When praseodymium, the praseodymium compound is typically PrCρ 07H20 or PrBr and hydrate, PrF, PrI, Pr, O, 333 *11 PrCCHO) Book 3H○, Pr (C5H702) 3. or holmium , the holmium compound is typically HoC, &, t6HO , Ho B r 3 and hydrate, HoF, Ho I, Ho203, Ho (C5H702)3, a rum compound may be used. The M precursor is used in the preparation of catalysts. Any M compound with suitable properties (e.g. being soluble in a suitable solvent) It could be something like that. Suitable compounds include oxides, carbonates, alkoxides, -dike tonates, halides, nitrates, sulfates, hydroxides, carboxylates, cal Bonyls, coordination compounds and combinations of the above, and their solvent phases and salts or included. Preferred N1 compounds are of the general formula MCΩKomoto xH,O.

Preparation of the catalyst complex may be present in the carbon as received or may be added , in the presence of a Group IA or Group IIA metal. For example, Kariu The beneficial effect of the addition of silica is illustrated in Example 70. In a slurry reactor, this It is believed that the addition of potassium to the slurry catalyst of the invention is beneficial.

In other aspects of this invention, the fixed bed catalyst support carbon may contain, for example, about 90% potassium as obtained. For example, approximately 280 gT in a backmixing reactor while maintaining high selectivity up to To achieve high space-time yields exceeding HF/kg catalyst/hour , using the above-mentioned ternary- or multi-element metal catalyst composites in a backmixing reactor. A catalytic step for the preparation of THF is included. Or alternatively, the second step, The catalyst of the present invention can be used in a plug flow reactor.

The catalyst is heated, for example, at 250°C, 2000 ps i g total pressure, and contact time. High activity exceeding 58% acid conversion of raw material containing 5% by weight of maleic acid in 0.016 hours demonstrate. A more preferred complex used in this step is the metal component or rhodium , cobalt, platinum, ruthenium, iron, thulium, cerium, ythtrium, neo selected from aluminum, aluminum, brazed aluminum and forminium. Ru.

Hydrogenatable precursors, i.e. starting reactants useful in the practice of this invention, include, for example , Marin acid anhydride, Marin acid anhydride, Fumaric acid, Polylic acid, Succinic anhydride, Ri malic acid or mixtures thereof. These precursors are dicarboxylic acids or Can it be described as an anhydride or a mixture of these acids and/or anhydrides? can. Preferred hydrogenatable precursors include maleic acid and maleic anhydride. included. For example, when these precursors are used in aqueous solution, this process MAC acid (MAC) is first reduced to succinic acid (SAC), which is further reduced to It can be reduced directly to THF, or it can also be reduced to BDO, which eventually dehydrates and becomes THF. It is believed that this will proceed in a gradual manner. By-products include alcohol (1-propertool (PrOH) and l-phthanol CBuOH)) and Contains lucans (-butane, methane). The method of this invention It will be clear to those skilled in the art that it is equally applicable to the production of trahydrofuran. cormorant. Suitable hydrogenatable precursors to 3-methylTHF include itaconic acid, anhydrous Taconic acid, citraconic acid, citraconic anhydride, mesaconic acid, citric acid and aco These include, but are not limited to, nitrate acids.・Itaconic acid is The 1rj precursor is preferred because of its ease of storage and reduction. 3-EthylTHF and Similar precursors to other substituted THFs such as 3-propyl THF and 3-propyl THF are It is further recognized that it can be used in a number of ways.

The production of THF requires the use of the hydrogenatable precursor water in an aqueous or organic solvent. Contains some elementalization. That is, the precursor solution is mixed in a backmix reactor or a plug flow reactor. react with hydrogen at The preferred solvent for the process of this invention is water. Hydrogenation Conditions include: A temperature in the range of 150°C to 300°C, preferably about 250°C, and about 100°C. 0 to 3000 ps i g, preferably about 2000 ps i g of hydrogen pressure, hydrogen space time of about 1 to 14 minutes, and liquid contact time of about 0.5 to 7 hours. Includes contact time. The hydrogenation of this invention is carried out in a backmixing reactor or a plug flow reactor. can be carried out using conventional equipment and techniques. hydrogen is continuous Generally, a large stoichiometric excess is supplied. Unreacted hydrogen is recycled as a stream. Can be returned to the reactor. The precursor solution, e.g. maleic acid in water, is Continuously feed concentrations ranging from dilute solution to maximum solubility level. Typically, The content is about 30 to 40% by weight. The catalytic carbon support is placed in the slurry reactor. fine powder particles for use in a fixed bed reactor or for use in a fixed bed reactor. The larger support particles. The amount of catalyst required varies over a very wide range. , depends on many factors such as reactor size and design, contact time, etc.

One way to practice this invention is as described in more detail in the Examples. The reaction is carried out in a plug flow reactor. Selectivity is what percentage of the exit stream is THF , BDO and GBL. High activity of this invention The catalyst, when tested in a plug flow reactor, is typically a similarly prepared binary system. It exhibits higher activity and nearly comparable selectivity than metallic Pd5Re/C catalysts. sometimes The observed loss in selectivity may be due to overhydrogenation. specific temperature smell If the catalyst is highly active or non-selective, lowering the temperature will Decrease activity and increase selectivity.

Implementation at low temperatures is a significant advantage.

The preferred method of preparing THF is by back mixing, e.g. in a continuous slurry reactor. This is carried out in a synthesis reactor.

In this invention, the high activity of the above-mentioned ternary or multi-component metal catalyst composite is , is the best for providing higher STY and selectivity to THF in this type of reactor. It has also been discovered that it can be used effectively. The outline of this reactor or reactor Surprisingly, this High activity as described in the specification of Palladium/rhenium on carbon still remains in reaction mixtures containing high concentrations of acid. It has been found to work well. Particularly suitable for the production of THF from maleic acid One of the major advantages of the backmixed reactor is the vapor distillation of THF. Sunawa First, it is possible to burn the reactor immediately after THF is formed; Therefore, “overhydrogenation” of alcohols and alkanes is desirable. -hydrBenation) J, i.e. further addition of the desired THF product. Keep rebates to a minimum. The second advantage of backmix reactors is that the acid in the feedstock or the entire reactant distribution, and thus the final step in the sequence from maleic acid to THF, i.e. It can be used as a catalyst for ring closure from BDO to THF. This is B.D.O. also undergoes overhydrogenation, and rapid conversion of BDO to THF results in overreduction of BDO. It has been found to work to minimize yield losses due to This is important. These two features of the backmixing reactor result in a loss of selectivity. Those skilled in the art will appreciate that this contributes to the ability to use highly active catalysts without . Alternatively, a suitable recirculation approximately equivalent to a backmix reactor can be used instead. The invention can be practiced using a fixed bed reactor.

Tetrahydrofuran and 1,4-butanediol are prepared by the method of this invention. It is a product produced in a plug flow reactor or a back-mixing reactor. this invention The catalyst and process are particularly suitable for the production of THF. Other aspects of this invention are essentially offers clear advantages for THF separation and recovery in backmix reactors. This is the production of THF using a continuous process. This advantage includes, for example, (1) THF and The excess reduction by-products are volatile and should be removed from the backmixing reactor as soon as they are formed. If necessary, the THF can be further distilled off using normal procedures. (2) Maleic acid starting materials and intermediates (including BDO and prior to (3) TH is less volatile and tends to remain in the reactor; and (3) TH Small amounts of THF precursors or intermediates, such as GBL, are distilled off along with F. It can be separated and recycled into the reactor. The continuous hydrogenation method of this invention In this case, BDO and THF are formed initially and the relative amounts obtained are as described in U.S. Pat. ．． 609.636, as well as the characteristics of the catalyst used. Depends on gender. Conversion of the produced BDO to THF requires no further hydrogenation , requiring only acid-catalyzed ring closure.

This transformation is performed when the carboxylic acid concentration in the reaction mixture is within a given range, e.g. A back-mixing reactor maintained between approximately 1 to 10 liters (calculated as succinic acid) is easily achieved. The concentration of carboxylic acid in the reaction mixture is It is preferable to maintain a concentration of more than about 3% by weight. Good STY and selectivity is obtained in graves of greater than about 3% by weight, or about 10% by weight, typically less than about 8% by weight. Currently, several problems are encountered related to acid coagulation within processing equipment. This continuity method is , a binary, ternary or multi-metallic catalyst deposited on an activated porous carbon support. Particularly suitable for use with highly active hydrogenation catalysts containing composite fine metal particles. Ru. For example, the catalyst used in this continuous process exceeds about 1000 m2/g. About 0.1 to 10% by weight of the powder, based on the total amount, is deposited on a carbon support having a surface area. radium, about 1 to 20% by weight rhenium and optionally rhodium, cobal metal, platinum, ruthenium, iron, thulium, cerium, yttrium, neodymium, aluminum Luminium, praseodymium, holmium, copper, samarium, europium, haf Ni, manganese, vanadium, chromium, gold, terbium, lutetium, nickel about 0.0 It has a content of 1 to 1.0% by weight. Preferred hydrogenations used in this continuous process A possible precursor is an aqueous solution of maleic acid. In the continuous method of this invention, the necessary acid backmix reactor for maleic acid, succinic acid, and to a lesser extent the other acid distributed throughout the reaction mixture. Therefore, this invention By controlling the acid level according to the method of Regardless of the relative amount of HF, there is little over-reduction and, surprisingly, the catalyst High selectivity for THE can be obtained with almost no loss of activity. this The continuous process of the invention is equally applicable to the production of 3-methyltetrahydrofuran. Those skilled in the art will recognize this. Preferred hydrogenation possibilities for 3-methylTHF Precursors include itaconic acid, itaconic anhydride, citraconic acid, and citraconic anhydride. , including but limited to mesaconic acid, citric acid and aconitic acid It's not a thing. Itaconic acid is the preferred precursor due to cost and ease of reduction. Ru. For other substituted THFs such as 3-ethylTHF and 3-propylTHF, It is further recognized that similar precursors of be recognized.

The following examples, while helpful in illustrating the invention, are intended to limit the scope of the invention. It's not a thing.

Example 1 An example of the preparation of a catalyst suitable for use in a slurry reactor is presented. Items in parentheses are table The parameters of heading 1 are shown. Preparation of the remaining slurry catalyst, i.e. Example 2-4 was carried out in a similar manner. The parameters used in the preparation of Example 2-4 are listed in Table 1. I will post it.

This example shows the Rh of this invention suitable for use in a slurry reactor (type). The preparation of a +Pd, Re/C ternary metal catalyst composite is described. M 10P d, The notation Re/C means that M and Pd are attached together and reduced, and then R This means that e is attached and reduced.

3 RhCΩ containing RhO,lOg (Wl ~1) H,O (~1 precursor (wlc 3.30 ml of PdC1-H20 raw material solution containing l) (vol l = l ls+3.3) was added. Add commercially available Dirco KBB carbo to this solution. Added 50 g of N (C1) and added the slurry for 1 hour at room temperature for 3 hours. The mixture was stirred from time to time. This slurry was dried at 115°C overnight. Rh, Pd/ After collecting the C powder, the resulting powder was cooled to 50°C, purged with He, and placed in a He flow. After cooling to room temperature, passivate for 30 min in a N2 stream containing 1% O. I did it. Contains Re1.03g (wf Re) (vol 2 = 13. A solution was prepared by adding 1+77).

This solution was added to reduced Re, Pd/C36,4g (v+C2) and room temperature The mixture was stirred occasionally for 3 hours. The Rh, Pd, Re/C samples were dried as described above. It was dried, reduced and passivated. The nominal blending ratio is 0.2% Rh (%M), 10%Pd (%Pd), and 28%Re (%Re). The nominal mixing ratio is , IQL] *wt metal/w as support Defined as a composite (support + previously deposited metal).

A second example is the ternary metal Rh+Pd, R of this invention, suitable for use in a fixed bed. The preparation of an e/C catalyst composite is described.

Items in parentheses indicate heading parameters in Table 1. Fixed bed contact in Example 5-12 The medium was prepared in a similar manner. The parameters used in the preparation of Example 5-12 are shown in Table 1. Published on.

RhC13 x H2O containing Rh O, (127g lM) 0,064g (&I precursor), Pd　O,l]99g　(Wt　Pd)　This gold-containing solution Calgon PCB+2X30 baked at 400’C for 2 hours in the air carbon (commercial product) added to IOg (Wt C1) and the resulting lettuce lamina The mixture was stirred occasionally at room temperature for 3 hours. Dry the cono slurry at 115℃ overnight. It was dry. After collecting the Rh, Pd/C powder, it was heated for 30 min in H-He (1:1) flow. It was reduced to 0'C for 8 hours. The reduced powder was cooled to 50°C and purged with He. After cooling to room temperature in an e-stream, 1% 0. Passivate for 30 minutes in a N2 stream containing did. ReO--H20 raw material containing 29g of ReO (WIRe) Solution 3. ”, 6ml H2011)ml+I A solution was prepared by adding (vol 2 = 3.76 + IO).

This solution was added to the reduced Rh, Pd/C8, Og (W+C2) and room temperature The mixture was stirred occasionally for 3 hours. This Rh+Pd, Re/C sample was dried as described above. Dry, reduce and passivate. The nominal blending ratio is 0.3% Rh (%M ), ], 0%Pd (%Pd), and 3.6%Re (%Re) .

The catalysts of Examples 13-29 were prepared similarly, but using slightly different reduction protocols.

To illustrate some of these differences, the preparation of Example 13 is described in detail. Example 1.3- The 29 preparation parameters are listed in Table 1.

Example 13 3 pieces of TmCΩ containing Tm 0.093g (WtM) 7H200, 22g (M precursor), PdCΩ2- containing PdO, 147g (WtPd) H2029ml containing 1.00ml of HCΩ raw material solution (vol. l = 1.0 O+29) and mixed well. This solution was heated to 400 ml for 2 hours in the atmosphere. Calgon PCB 12x30 carbon fired at °C (commercial product) was added and the resulting slurry was stirred occasionally at room temperature for 3 hours. This sura The lees were dried overnight at 1+5°C. After collecting Tm, Pd/C powder, H, -H e (3:97) flow at 300°C for 5.8 hours. The reduced powder Purge with He for 05 hours at 300 °C and leave at room temperature overnight (>5 hours) in flowing He. It was cooled to Re 207-H2 containing Re 0.52 g (Wt Re) 0 raw material solution 6.5 ml H2O 19.5 ml (vol 2 = 6.5 + 1 A solution was prepared by adding 9.5). In the second solution, reduced Tm, P d/C71,0g CWIC2) was added and stirred occasionally at room temperature for 3 hours. T m +Pd,Re/C samples were dried and reduced as described above.

The above blending ratio is 06%Tm (%M), 0.98%Pd (%Pd), and 4.0%Re (%Re).

The Rh, Pd, Re/C catalyst of Example 30 used a different metal deposition procedure than the previous example. . Rh was deposited on a carbon support and reduced. Next, Pd is attached and reduced, and then After that, Re was attached and reduced.

Example 30 Rh CJI’ $ x H200,094g containing Rh 0.040g was added to 2036ml of H and mixed well. This solution was added for 40 min in air. Calgon PCB 12X30 carbon fired at 0°C for 2 hours (commercially available product) was added and the resulting slurry was stirred occasionally at room temperature for 3 hours. child The slurry was dried at 115°C overnight.

After collecting the Rh/C powder, it was heated at 300°C in a J-He (1:l) flow. I returned it for 8 hours. PdCg-HCf contained by cooling the reduced powder to 50°C Prepare the solution by adding 1.12 ml of I raw solution to 30 ml of H2O did. Add 16.8 g of reduced Rh/C to this solution and stir occasionally at room temperature for 3 hours. did.

Rh, Pd/C samples were dried, reduced, and passivated as described above.

H2015 4.80g of Re207-HO raw material solution containing 8g of ReOj A solution was prepared by adding ml. In this solution, reduced Rh, Pd /C8, Og was added and stirred occasionally at room temperature for 3 hours. Rh, Pd.

Re/C samples were dried, reduced, and passivated as described above. given name The nominal blending ratio is 02% Rh, 1.0% Pd.

and 4.8% Re.

Comparative example A Preparation of binary metal Pd, Re/C slurry catalyst PdC containing 0.96 g of Pd g - 630 g of HCN raw material solution was added to 224 cc of water. This solution was mixed with commercially available D Added to 77g of a+co KBBcarbon and mixed the slurry at room temperature. Stir occasionally for 3 hours. The slurry was dried at 1+5°C overnight. P After collecting the d/C powder, it was placed in a J-He (II) stream and heated at 300°C for 8 Time was saved. The reduced powder was cooled to 50°C, purged with He, and heated in a He flow. Re207-H,O raw material solution containing 2.78g of 1% Re after cooling to room temperature Add 36.3 ml of the solution to 1.0 g of reduced Pd/C and leave at room temperature for 3 hours. Stir thoroughly. Two Pd, Re/C samples were dried, reduced and packaged as described above. I was ssivated. The nominal blending ratio is 125', 6Pd and 3.95'5 Re It is.

Comparative example B Preparation of binary metal Pd, Re/C fixed bed catalyst PdCg containing 1.01 g of Pd , -HCΩ raw material solution 6.80ml was added to 172cc of water and mixed well. child Calgon PCB was prepared by baking the solution at 400°C in the atmosphere for 2 hours. 12X 30c3rbOn <commercial product) let) g and the resulting slurry The mixture was stirred occasionally at room temperature for 3 hours. This slurry was heated at 115°C (Ill. ) Reduction was carried out at 300° C. for 8 hours in a flowing stream. Cool the reduced powder to 50°C. After purging with He and cooling to room temperature in a stream of He, 1% 0. N containing and passivated for 30 minutes. R containing Re3.60g cwt Re) e2o7- Add 45.1ml of H,0 raw material solution to 116ml of JO A solution was prepared by This solution was added to 90 g of reduced Pd/C and Stir occasionally for an hour. This Pd, Re/C sample was dried and reduced as described above. and passivated it.

The nominal blending ratio is 10% Pd and 4.0% Re.

Comparative example C Preparation of potassium-containing binary metal Pd, Re/C slurry catalyst 191 g of KCΩ was dissolved in 230 c of DI water and mixed well.

Add this mixture to commercially available Darco de BB carbon! Add to OOg and bring to room temperature The mixture was stirred occasionally for 3 hours. The slurry was dried at 1+5°C overnight.

5.4 ml of PdCg, -Hi raw material solution containing 82 g of PdO was added to 192 cc of water. and mixed well. This solution was added to Ni/C35,Ig, and the resulting slurry The mixture was stirred occasionally at room temperature for 3 hours. Dry this slurry at 115℃ overnight. It was dry. After recovering the K, Pd/C powder, 3 Reduction was performed at 00°C for 8 hours. Cool the reduced powder to 50°C and purge with He L ,, Cool 36,;) ml to room temperature in a He flow and add 1 J to 200 ml of H2O. A solution was prepared by This solution was reduced and added to 7g of Pd/C70. and stirred occasionally at room temperature for 3 hours. 20, Pd, Re/C samples were added as described above. dried, reduced and passivated. The nominal blending ratio is 1.0% K, 0 ．． 96% Pd and 4.0% Re.

Catalyst performance in backmix reactor A slurry catalyst 70-1 contained in 150 ml of water was used as a catalyst for a back-mixing reactor. Put 5g (dry) into a 300m Eastaloy C autoclave. It was tested by This autoclave includes a stirrer, thermocouple, hydrogen and oleic acid feed line and through it with the product or excess hydrogen and water. Equipped with discharge line or removed. This catalyst was heated for 17 minutes at 1,000 m. By heating at 250°C for 1 hour at 2000 psig under a plain flow. activated. 18 to 36ml as a 40% by weight aqueous solution of maleic acid The reactor was heated to 2000 psig and 25 It was kept at 0°C. Volatile products and 7K controlled by hydrogen feed rate was discharged from the reactor at a rapid rate. The hydrogen supply speed is determined by the hydrogen gas being carried out The amount of water produced by the lid and reaction of water added with the maleic acid feedstock The amount was adjusted to balance the amount of water.

The reactor level was maintained at 100-21)Oc. In all cases, This is because a very large excess of hydrogen was supplied compared to the amount consumed by the reaction. I want you to understand. Therefore, the hydrogen supply rate does not affect catalyst performance.

Several different feed rates of maleic acid were used in the catalyst tests. typical Generally, the feed rate was increased in each run until optimal performance was achieved. after that, The production suitability of this optimal performance is tested over two or more tests under the same conditions. did.

Catalyst tests were performed several times and summarized. Typically, each run consists of a The reactor is used for 6-10 hours and lasts for 8-12 hours. obtained during steady state operation The product composition data obtained were averaged and THFSBD○, GBL, PrOH, Bu Oh.

and the average production rate (g/hour) of alkanes (-butane and methane). Ta. Product composition data was determined in the following manner. Volatile products/water in the effluent gas stream The --H of is concentrated and collected as a "liquid product". Liquid product collected hourly A calibrated gas chromatograph with a flame ionization detector ( Its composition was analyzed using GC). Unconcentrated products that remain in the effluent gas stream (THF and alkanes) with a constant gas flow rate of 7jP1, then every 2 hours. by analyzing gas streams using procedures similar to those used for liquid analysis. analyzed. The contents of the reactor were sampled every 4 hours and separated by GC and titration. analyze. GC analysis was performed using Supelcowax 10 capillary one column DOm 0.052ml). The column was heated at 75° for 5 minutes after injection. It was then heated at 10°C per minute to a final temperature of 200°C. Mixed liquid The acid level was determined by titration with sodium hydroxide and expressed in weight percent of succinic acid. reported. The combination of these three types of analysis is the catalyst performance (C3TY and selectivity) and allows calculation of the material balance for each run.

Selectivity = ((THF (gas) + THF (liquid) + GBL (liquid) +B moles of DO (liquid))/hour)/((THF (gas) + THF C liquid) + GBL C liquid) + BDO (liquid) + PrOHC liquid) + BuOH (liquid) + A 1%, 4% Pd, Re/C slurry of Comparative Example A -The maximum measured THF STY of the catalyst was 2SOgTHF/kg catalyst/hour. . The ternary metal catalyst of this invention has THF exceeding 280gTHF/kg catalyst/hour. Give STY. The selectivity is the proportion of the effluent with THF, BDO and This is a measurement of whether it consists of GLB. The addition of rhodium maintains high selectivity while Significantly improve STY.

The backmixing execution results are summarized in Table 2.

Another aspect of the second invention provides that the acid concentration in the reaction mixture is about 1 to 10 times the concentration of the reaction mixture. Control is within the range of amount% (calculated as succinic acid). Shows beneficial effects of acid control For this purpose, the binary metal catalyst composite of Comparative Example A was operated for several days in a backmixing reactor. .

The results listed in Table A show beneficial effects on STY and selectivity. . For example, increasing the acid concentration from about 3% to about 10% increases STY and selectivity. benefit.

selectivity 31 8.0 280 91 30 9.9 2132 93 40% maleic acid in water at 1250°C 1 excess H2 flow, 2000 psig total pressure Basicization 2 40% maleic acid/water feed rate in cc/hour 3 Acid-based titration Acid concentration in the reactor measured by and reported as weight percent of succinic acid The beneficial effect of increasing acid concentration in the reactor on STY and selectivity is obvious. Ru. Lower acid feed rates not listed here may result in lower acid concentrations, STY and result in selectivity.

Catalyst performance in plug flow reactors One method of preparing THF is described in great detail in U.S. Patent No. 4.609.636. Using conventional equipment and techniques in plug flow reactors, as described in This is liquid phase hydrogenation. The teachings of said patents are incorporated herein by reference.

Catalyst for plug flow reactors immersed in heated sand stone for temperature control 1/4 inch Tested by placing 3g of catalyst in a diameter Exstaloy U-tube reactor. . The catalyst was heated at 2000 psig in a hydrogen flow of 100 ml/min. Activation was performed by heating at 250°C for 1 hour. Hydrogen and maleic acid react The liquid/gas flow is fed together from one end of the reactor to control the pressure to the desired level. It exited the reactor through a pressure drop valve provided for this purpose. excess gas , 9Q psig pressure. these In an experiment, maleic acid was used as a 5% aqueous solution for 6 to 300 m for 17 hours. was supplied at a flow rate ranging from . Hydrogen flow is 100 to 200m long for 17 hours kept in excess. The temperature was maintained at 250°C and the pressure at 2000 piig.

Each catalyst was tested in four different ways to properly characterize its performance characteristics. Evaluation was made based on the maleic acid supply rate. Gases and liquids are separated by GC as described above. analyzed. Since neither maleic acid nor succinic acid can be detected by GC, The a degree (inic acid + succinic acid) is determined directly by titration of the acid haze and is expressed as the weight percent of succinic acid. reported.

Fixed bed performance data is summarized in Table 3. converted to a given hold up time The proportion of acid is an indicator of catalyst activity.

CTHF+BDO+GBL) This is the maximum value observed in the fitted plot of contact time for all cases. THF ST Y (gTHF/kg catalyst/hour) is the contact between STY and four different flow rates. Curve maxima from the fitted plot of touch time.

The catalyst of this invention has higher activity than the binary metal Pd, Re/C catalyst of Comparative Example B. , showed comparable selectivity. The loss of selectivity observed in some cases is “Overhydrogenation”, i.e. alcohols and alkyls in excess of the desired THF product. It is caused by reactions that proceed to the formation of cans. As shown in Table 4, the catalyst is Although very active at this temperature, this results in excessive hydrogenation, and lowering the temperature is not recommended. Decreasing its activity by increasing selectivity increased. Operation at low temperatures per se It can be advantageous.

■ --He - Sai ψ〉mouth (jO-～-The ψ Toro OO- is one inch outside ψωC31P d, Re/C example A 280 9032 Rh+Pd, Re/C example 1 500 8 B-9033Ru 10 Pd, Re/C example 2 350 8B-9034Co+Pd , Re/C (column 3 4 pieces 0 90-92 pieces 5 Pd in Fe, Re/C example 4 41'3 901 250'C1 Excess H2 flow at 2,000 psio total pressure Hydrogen acid conversion of 40% maleic acid Biselectivity THF -Toichi Catalyst □ 121-JM-D KO6 Pd, Re/C example B 5s(t) afu(t) 38937 Rh+P d, Re/C Example 5 77.5 74: +7438 Ru+Pd, Re/C Example 6 72(4) 70 384 Co9 Co+Pd, Re/C1 row 7 81.6 ( 4) 85’ 48440 Pd in Fe, Re/C example 8 93.5 82 65841 Pt+Pd, Re/C Example 1175.2 76 4:1242 Tm +Pd, Re/C example 1388 85 40743 Ca+Pd, Re/C example m 4 91 81 5 core 44 Y+Pd, Re/CM2S 88 85 383 45 Nd+Pd, Re/CM 16 85 86 42546 Al+Pd, Re/C example 1781 79 39347 Pr+Pd/Re/C example 1886 85 461 Determined by 7:W instead of titration 67 Rh, Pd, R e/CM 30200 76 84 14268 Pd+Re, Rh Example 5 250 97 74 17469 Pd+Rh, Re Example 5 200 79 84 124 Determined by difference rather than titration 3 (THF+BDO+G Maximum % selectivity for BL) 3 by weight % of succinic acid, determined by acid-based titration The acid concentration in the reactor, reported as The beneficial effects of potassium addition to binary metal Pd, Re/C catalysts are obvious-S TY increased from 280 to about 335.

international search report international search report Continuation of front page (81) Designated countries EP (AT, BE, CH, DE.

DK, ES, FR, GB, GR, IT, LU, NL, SE), 0A (B F, BJ, CF, CG, CI, l, GA, GN, NiL, NiR, SN, TD, TG), AU, BB, BG, BR, CA, C3, FI, HU, JP, KP.

KR, LK, ~IC,',,・IG, ~IN, MW, No, PL, R○, SD, 5U (72) Inventor: Mitchell, John Byrun, Pennsylvania, USA a state 2062 Parkersville Road, West Chester, 19383

Claims (24)

[Claims] 1. essentially a catalytically effective amount of (a) a palladium component attached to a support; ; (b) a rhenium component; and (c) Rhodium, cobalt, platinum, ruthenium, iron, thulium, cerium, Selected from thorium, neodymium, aluminum, praseodymium and holmium one or more metal components, A multi-element metal catalyst composite consisting of a combination of fine particles. 2. The palladium component is in the range of about 0.1 to 10% by weight based on the total amount, The rhenium component is in the range of about 1 to 20% by weight, and the metal component is about 0.01% by weight. The multi-component metal catalyst composite according to claim 1 in the range of 1.0 to 1.0% by weight. . 3. The support is an activated porous carbon carrier having a surface area of more than 650 m2/g. or a refractory oxide support. is the multi-component metal catalyst composite according to item 2. 4. Essentially an activated porous carbon support with a surface area greater than 650 m2/g Palladium, rhenium, rhodium, cobalt, platinum, ruthenium attached to aluminum, iron, thulium, cerium, yttrium, neodymium, aluminum, plastic Ozim, holmium, copper, samarium, eurobium, hafnium, manganese, Vanadium, chromium, gold, terbium, lutetium, nickel, scandium and A multi-component metal catalyst composite of fine particles of one or more metal components selected from niobium and niobium. and about 0.1 to 10% by weight of palladium and rhenium. about 1 to 20% by weight and about 0.01 to 1.0% by weight of metal components. This allows the product to be space-tied while maintaining high selectivity in the backmixing reactor. water to achieve increased product yield or high activity in plug flow reactors. hydrogenation catalyst. 5. Metal components include rhodium, cobalt, platinum, ruthenium, iron, thulium, and cerium. aluminum, yttrium, neodymium, aluminum, praseodymium and holmium? The catalyst according to claim 4, which is selected from the following. 6. Tetrahydrofuran or substituted tetrahydrofuran from hydrogenatable precursors A method for producing a psig to about 3000 psig in the presence of a multi-metal catalyst complex. contacting the hydrogenatable precursor with hydrogen; The media complex has a catalytically effective amount of (a) a palladium component attached to a support; (b) a rhenium component; and (c) Rhodium, cobalt, platinum, ruthenium, iron, thulium, cerium, Thorium, neodymium, aluminum, praseodymium, holmium, copper, samarium Mu, eurobium, hafnium, manganese, vanadium, chromium, gold, terbium one or more selected from aluminum, lutetium, nickel, scandium, and niobium metal components, A method involving a combination of microparticles. 7. Hydrogenatable precursors include itaconic acid, itaconic anhydride, citraconic acid, anhydrous Citraconic acid, mesaconic acid, citric acid and aconitic acid and mixtures thereof 7. The method of claim 6, wherein the method is selected from: 8. Metal components include rhodium, cobalt, platinum, ruthenium, iron, thulium, and cerium. aluminum, yttrium, neodymium, aluminum, praseodymium and holmium? 7. The method according to claim 6, wherein the method is selected from: 9. The support is an activated porous carbon carrier with a surface area of more than 650 m2/g or is selected from the group consisting of refractory oxide carriers. Method described. 10. Contains about 0.1 to 10% by weight of palladium component and ruthenium component about 1 to 20% by weight of the total amount, and about 0.01 to 1% of the total amount of metal components. ．． 10. The method of claim 9, comprising 0% by weight. 11. Hydrogenatable precursors include maleic acid, maleic anhydride, fumaric acid, and succinic acid. acid, succinic anhydride, malic acid or mixtures thereof, and if aqueous. 11. The method according to claim 10, wherein the organic solvent is present in an organic solvent. 12. A claim in which the hydrogenatable precursor is selected from maleic acid and the solvent is water. The method according to item 11. 13. Producing tetrahydrofuran from aqueous maleic acid solution and maintaining high selectivity Achieving increased space-time yield while exhibiting high activity or A method comprising: a temperature of about 150°C to about 300°C and about 1000 psig. at a pressure of about 3000 psig in the presence of a ternary metal catalyst complex. contacting the maleic acid with hydrogen, the ternary metal catalyst composite comprising 6 (a ) about 0.9 to 1.0% by weight palladium component; (b) about 2.1 to 4.5%; and (c) about 0.1 to 0.6% rhodium by weight. , cobalt, platinum, ruthenium, iron, thulium, cerium, yttrium, neo one or more selected from gym, aluminum, praseodymium and holmium metal components, A method involving a combination of microparticles. 14. Tetrahydrofuran is produced from hydrogenatable precursors in a backmixing reactor. A method of manufacturing comprising: a temperature of about 150°C to about 300°C and about 1000 p. sig to about 3000 psig in the presence of a multimetallic catalyst complex. contacting the hydrogenatable precursor with hydrogen; The complex has a catalytically effective amount of (a) a palladium component attached to a support; (b) a rhenium component; and (c) Rhodium, cobalt, platinum, ruthenium, iron, thulium, cerium, Thorium, neodymium, aluminum, praseodymium, holmium, copper, samarium Mu, eurobium, hafnium, manganese, vanadium, chromium, gold, terbium one or more selected from aluminum, lutetium, nickel, scandium, and niobium metal components, A method involving a combination of microparticles. 15. Producing tetrahydrofuran from hydrogenatable precursors in a plug flow reactor A method of manufacturing, comprising: a temperature of about 150°C to about 300°C and a pressure of about 1000 ps; ig to about 300 psig in the presence of a multimetallic catalyst complex. contacting the hydrogenatable precursor with hydrogen; a catalytically effective amount of (a) a palladium component attached to a support; (b) a rhenium component; and (c) Rhodium, cobalt, platinum, ruthenium, iron, thulium, cerium, Thorium, neodymium, aluminum, praseodymium, holmium, copper, samarium Mu, eurobium, hafnium, manganese, vanadium, chromium, gold, terbium one or more selected from aluminum, lutetium, nickel, scandium, and niobium metal components, A method involving a combination of microparticles. 16. The hydrogenatable precursors are essentially maleic acid, maleic anhydride, and fumaric acid. , succinic acid, succinic anhydride and malic acid are selected from the group consisting of mixtures thereof. 16. The method according to claim 14 or 15. 17. further comprising the hydrogenatable precursor being in an aqueous or organic solvent. The method according to claim 16. 18. The support is an activated porous carbon carrier having a surface area of more than 650 m2/g. or claim 13 or 14 or claim 1, which is a refractory oxide carrier. The method described in Section 5. 19. the hydrogenatable precursor is maleic acid and the carboxylic acid in the reaction mixture Further includes aqueous continuous methods in which the concentration is from 1 to 10% by weight of the reaction mixture; High selection over tetrahydrofuran while minimizing over-reduction of lahydrofuran 15. A method according to claim 14 for achieving the desired properties. 20. High purity tet by continuous hydrogenation of hydrogenatable tetrahydrofuran precursors An aqueous method for producing lahydrofuran or substituted tetrahydrofuran, the method comprising: The subsequent hydrogenation comprises steam distillation of the tetrahydrofuran and the presence of a suitable hydrogenation catalyst. The concentration of carboxylic acid in the reaction mixture was maintained within a specified range. The precursor is maleic acid, maleic anhydride, fumaric acid, succinic acid, succinic anhydride. Citric acid, malic acid and mixtures thereof, as well as itaconic acid, itaconic anhydride, citric acid, Traconic acid, citraconic anhydride, mesaconic acid, citric acid, aconitic acid or An aqueous production method selected from the group consisting of mixtures thereof. 21. Claim 20 wherein the precursor is selected from maleic acid or itaconic acid. The method described in. 22. A suitable hydrogenation catalyst encapsulates fine metal particles attached to an activated porous carbon support. The fine metal particles contain about 0.1 to 10% by weight of palladium based on the total amount. about 1 to 20% by weight of rhenium, and optionally about 0.01 to 1.0% by weight of rhenium. % rhodium, cobalt, platinum, ruthenium, iron, thulium, cerium, iron ttrium, neodymium, aluminum, praseodymium, holmium, copper, summary um, eurobium, hafnium, manganese, vanadium, chromium, gold, terbi one or more selected from aluminum, lutetium, nickel, scandium and niobium 22. A method according to claim 20 or claim 21, comprising the above metal component. 23. Claims 19 or 20, wherein the acid concentration is 3 to 8% by weight. or the method described in paragraph 21. 24. The catalyst is the catalyst according to claim 4, and the support is 1000 m2/g. Claim 19, wherein the activated porous carbon support has a surface area exceeding The method according to paragraph 20.