JP2010253374A - Catalyst for dehydrating glycerin and method for producing acrolein - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst which is used for dehydrating glycerin to produce acrolein and deterioration of the acrolein yield of which with time can be suppressed and to provide a method for producing acrolein. <P>SOLUTION: The catalyst for dehydrating glycerin is obtained by essentially carrying the crystallized salt containing phosphorus and at least one element selected from aluminum, zirconium and boron and/or at least one element selected from rare earth elements on an amorphous porous carrier which contains ≥90 mass% silica and has micropores having 0.1-30 μm pore size and nanopores having 1-50 nm pore size. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a glycerol dehydration catalyst and a method for producing acrolein using the catalyst.

  Biodiesel produced from vegetable oil is attracting attention not only as a substitute for fossil fuels but also because it emits less carbon dioxide, and demand is expected to increase. When this biodiesel is produced, glycerin is produced as a by-product, so it is necessary to make effective use of it. One embodiment of the use of glycerin includes the use of glycerin as a raw material for acrolein.

  For example, Patent Document 1 discloses that acrolein is produced by performing a gas phase dehydration reaction of glycerin using a catalyst prepared by immersing a support in an aqueous copper phosphate solution, followed by drying and firing. Yes. Patent Document 2 discloses that acrolein is produced by performing a gas-phase dehydration reaction of glycerin using a catalyst prepared by immersing a carrier in an aqueous phosphoric acid solution, drying and calcining. . However, the catalysts disclosed in Patent Documents 1 and 2 have a problem that their lifetime is insufficient for industrial use.

  Patent Document 3 discloses that one or more metal phosphates selected from specific metal phosphates such as aluminum salts, zirconium salts, manganese salts, alkali metal salts, and alkaline earth metal salts. Is disclosed. In Patent Document 4, acrolein can be produced from glycerin using a metal phosphate having a crystal structure as a catalyst, and a carbonaceous substance generated by a dehydration reaction of glycerin can be prevented from adhering to the catalyst, and the yield of acrolein is increased. It is disclosed that it can be manufactured stably. However, in Patent Document 3 and Patent Document 4, it is not sufficient to suppress a decrease in activity over time while maintaining a high acrolein yield.

  Patent Document 5 discloses a method for producing acrolein in which glycerin is reacted in the presence of a heteropolyacid catalyst. Catalysts supported on dual pore silica have both macropores with excellent mass transport capability and nanopores with high specific surface area, sufficient mechanical strength, and low pressure loss. There is a description that it is suitable as a catalyst carrier and that it is possible to further improve the selectivity and yield of acrolein. However, the knowledge about a time-dependent fall of the acrolein yield was not described.

  Even if acrolein is produced using the above-mentioned catalyst, it is not sufficient for the problem of suppressing the yield loss of acrolein when the catalyst is continuously used, and a controllable catalyst and a method for producing acrolein are desired. Yes.

US Patent No. 1916743 French Patent Invention No. 695931 International Publication No. 2007/119528 JP 2008-307521 A JP 2008-88149 A

  In view of the above circumstances, an object of the present invention is to provide a catalyst for producing acrolein by dehydrating glycerin, and a method for producing an acrolein which can suppress a decrease in the acrolein yield over time.

  The catalyst for dehydrating glycerin of the present invention is an amorphous porous carrier containing 90% by mass or more of silica and having two kinds of pores in a macro region of 0.1 to 30 μm and a nano region of 1 to 50 nm. A crystalline salt containing at least one element selected from aluminum, zirconium and boron and / or at least one element selected from rare earth elements and phosphorus is essential, and the crystalline salt is supported on the porous carrier. preferable. The porous carrier is sometimes referred to as binary pore silica.

  The present invention is also a method for producing acrolein by dehydrating glycerin in the presence of the glycerin dehydrating catalyst. The method is preferably a gas phase dehydration reaction in which glycerin is dehydrated by a gas phase reaction in which a glycerin gas is brought into contact with a catalyst.

  According to the glycerol dehydration catalyst of the present invention, the yield of acrolein is high and the change with time of the yield of acrolein is small. Therefore, acrolein and acrolein derivatives can be produced at low cost.

  The present invention is a method for producing acrolein by dehydrating glycerin in the presence of a catalyst for dehydrating glycerin (hereinafter, “catalyst for dehydrating glycerin” is simply referred to as “catalyst”) and the catalyst.

  The catalyst of the present invention is a catalyst that promotes an intramolecular dehydration reaction of glycerin to produce acrolein. The catalyst is selected from aluminum, zirconium and / or boron in an amorphous porous support containing 90% by mass or more of silica and having 0.1-30 μm macropores and 1-50 nm nanopores. A crystalline salt containing at least one element selected from the group consisting of at least one element selected from the group consisting of rare earth elements and phosphorus is essential, and the crystalline salt is supported on the porous carrier.

  The porous carrier preferably contains 90% by mass or more of silica, and has 0.1 to 30 μm macropores and 1 to 50 nm nanopores. The porous carrier is suitable as a catalyst carrier for use in the above production method because it has both macropores excellent in material transportability and nanopores having a high specific surface area and is excellent in mechanical strength. It is possible to improve the selectivity and yield of acrolein.

  The porous carrier is preferably binary porous silica. Binary pore silica is composed of amorphous silica that has both macropores with micrometer range pore diameters and nanopores with nanometer range pore sizes (mesopores). It is a porous material.

  The macropores of the binary porous silica are 0.5 to 200 μm, more preferably 1 to 100 μm, and even more preferably 1 to 20 μm. The nanopores of the binary pore silica are 1 to 50 nm, more preferably 1 to 30 nm, and even more preferably 1 to 10 nm. The macropores can be measured by mercury porosimetry or direct observation with an electron microscope, and the nanopores can be confirmed by mercury porosimetry or nitrogen adsorption.

  The binary fine silica is preferably in the form of particles having an average particle size of 0.5 mm to 10 mm. By compression or the like, a binary porous silica molded body having an arbitrary shape such as a spherical shape, a plate shape, a cylinder shape, or a ring shape can be used.

The pore volume is preferably 0.3 to ⁴ cm ³ per gram of support. In consideration of ease of production, it is preferably 1 to ³ cm ³ .

  A commercial item can be used for the said binary pore silica, and what was synthesize | combined by the conventionally well-known method can also be used. The synthesis method is not particularly limited. For example, according to JP-A-3-8729, a sol solution composed of an organic polymer such as silicon alkoxide represented by tetraethoxysilane, polyethylene oxide and an acid and an acid is used as a starting material. There are known ones that form macropores by utilizing the gelation phenomenon and phase separation phenomenon of a sol liquid.

The specific surface area of the binary porous silica support is preferably 100 to 900 m ² / g. More preferably, it is 150-850 m < ² > / g. More preferably, it is 200-800 m < ² > / g. Most preferably, it is 250-800 m < ² > / g. By having such a specific surface area, the support can be supported in a highly dispersed state, and high activation can be expected. In addition, since it has excellent material transport capability, it suppresses sequential reactions due to the rapid diffusion effect of the product. It can be expected that the selectivity of the catalyst will be improved, and it can be an excellent catalyst carrier.

  The crystalline salt used in the catalyst of the present invention essentially comprises at least one element selected from aluminum, zirconium and boron, and / or a crystalline salt containing phosphorus and at least one element selected from rare earth elements, and a metal phosphate A crystalline salt of the salt is more preferred.

  The rare earth elements used as the constituent atoms of the catalyst crystal salt of the present invention are cerium group (La, Ce, Pr, Nd, Pm, Sm), yttrium group (Sc, Y, Eu, Gd, Tb, Dy, Ho, Any of Er, Tm, Yb, and Lu) may be used. A particularly preferred rare earth metal is Nd.

  The crystal system in the crystal salt may be one kind or may contain two or more kinds of crystal systems. The crystal salt may be a composite crystal salt of two or more kinds of crystal salts. The essential requirement for the crystalline salt is that it includes a part of the crystalline salt composed of the above-described elements, and may include a compound composed of another element.

  The compound which consists of said other element is not specifically limited, 1 type, or 2 or more types may be sufficient. The compound may be a composite compound of two or more elements. Examples of elements constituting the compound include typical metal elements such as alkali metals, alkaline earth metals, aluminum, and lead; metalloid elements such as tin and bismuth; titanium, hafnium, vanadium, niobium, chromium, manganese, iron, Transition metal elements such as cobalt, nickel, silver, zinc, cadmium, and mercury; Further, it may be a crystalline salt containing the above-mentioned other elements, at least one element selected from aluminum, zirconium and boron, and / or at least one element selected from rare earth elements and phosphorus.

  The crystal salt in the catalyst of the present embodiment has a crystal structure of a compound containing at least a part of at least one element selected from aluminum, zirconium and boron and / or at least one element selected from rare earth elements and phosphorus. . As long as the crystal structure is a metal phosphate, a plurality of types of crystal structures may be mixed.

  Examples of the crystal structure of the crystal salt include a quartz type, a tridymite type, and a cristobalite type in the case of aluminum phosphate (hereinafter, “aluminum phosphate” is referred to as “AlP”). The tridymite type and the cristobalite type are preferred because the change in the acrolein yield with time is particularly small. On the other hand, the quartz type is preferable because the amount of carbonaceous material attached is particularly small. The smaller the amount of carbonaceous material attached, the easier the catalyst regeneration can be expected by removing it. Moreover, the following metal phosphate crystal can be mentioned as an example. Examples of the boron phosphate crystals include tetragonal crystals and cristobalite crystals.

When the crystalline salt is zirconium phosphate (hereinafter, “zirconium phosphate” is referred to as “ZrP”), the crystal structure thereof is α-ZrP (α-Zr (HPO ₄ ) ₂ .H ₂ O). , Ε-ZrP (ε-Zr (HPO ₄ ) ₂ ), pyro-ZrP (crystalline ZrP ₂ O ₇ ), γ-ZrP (γ-Zr (HPO ₄ ) ₂ · 2H ₂ O), γ-ZrP anhydride , Β-ZrP (β-Zr (HPO ₄ ) ₂ ) and the like.

  In order to produce the catalyst of the present embodiment, a known crystal salt production method may be used. Examples are coprecipitation and precipitation. In addition, the following production methods are known as methods for producing AlP crystals and ZrP crystals.

(AlP crystal manufacturing method)
Quartz-type AlP is produced after passing through cristobalite-type AlP as a metastable phase by reacting aluminum isobroboxide and triethyl phosphate in toluene in the presence of a small amount of water at 250 ° C. Tridymite-type and cristobalite-type AlP can be produced by heating quartz-type AlP in the atmosphere to cause phase transition. It is known that the heating temperature for the phase transition from the quartz type to the tridymite type is about 707 ° C., and the heating temperature for the phase transition from the tridymite type to the cristobalite type is known to be about 1047 ° C. Yes.

In addition, the AlP crystal can be manufactured by the following method. An AlP crystal can be produced by preparing metavalvite (AlPO ₄ .2H ₂ O) from phosphoric acid and aluminum hydroxide, adding an aqueous phosphoric acid solution to the metavalvite, drying it, and treating the dried product with a solvent. By selecting a solvent to be used at this time, quartz, tridymite, and cristobalite crystals can be formed. Quartz-type AlP can be produced by using a hydrophilic solvent such as n-butanol, and cristobalite-type AlP can be produced by using a hydrophobic solvent such as isobutyl methyl ketone.

(Method for producing ZrP crystal)
α-ZrP is produced by heating Zr (HPO ₄ ) ₂ under reflux in a 10-15 mol / L phosphoric acid aqueous solution. When producing ZrP having a high degree of crystallinity, it is preferable to perform reflux heating for about 50 hours or more. Further, α-ZrP can also be obtained by heating a mixture of Zr (HPO ₄ ) ₂ and concentrated phosphoric acid under reduced pressure (pressure: about 200 mmHg, heating temperature: about 130 ° C.) and taking out distilled water out of the reaction system. Can be manufactured.

In order to produce ε-ZrP and pyro-ZrP, it is preferable to use a method in which the pressure and heating temperature in the α-ZrP production method in which the mixture of Zr (HPO ₄ ) ₂ and concentrated phosphoric acid is heated under reduced pressure are changed. . In this method, when the pressure is about 200 mmHg, ε-ZrP is obtained when the heating temperature is about 180 ° C., and pyro-ZrP is obtained when the heating temperature is about 300 ° C. To produce gamma-ZrP, and beta-ZrP _is preferably performed hydrothermal reaction and ZrOCl ₂ · 8H ₂ O and _NaH 2 PO _4.

The composition of the crystalline salt comprising phosphorus and rare earth elements contained in the catalyst of the present invention is not particularly limited. Examples of the composition include ScPO ₄ , YPO ₄ , LaPO ₄ , CePO ₄ , PrPO ₄ , NdPO ₄ , SmPO ₄ , EuPO ₄ , GdPO ₄ , TbPO ₄ , HoPO ₄ , ErPO ₄ , TmPo ₄ , and TmPo _4. Can be mentioned.

  The crystal structure of the crystal salt of phosphorus and rare earth elements is not particularly limited, and examples thereof include tetragonal crystal, monoclinic crystal, and hexagonal crystal. For example, tetragonal crystals as yttrium phosphate crystals; monoclinic columnar crystals as lanthanum phosphate crystals; monoclinic crystals and orthorhombic columnar crystals as cerium phosphate crystals; .

  The production of the crystalline salt composed of phosphorus and a rare earth element involves preparing a liquid containing water and a hydroxide of the rare earth element and / or a dehydration condensate of the hydroxide, and including phosphate ions in the liquid. The solid content produced by this is fired. Although the reason is not clear, the acrolein yield can be increased by using the crystalline salt obtained by such a production method as a catalyst.

  A method for producing a catalyst in which a crystalline salt is supported on the binary pore silica support of the present invention may be a known production method and is not particularly limited. For example, (1) a method of mixing a support and a crystal salt having a crystal structure, and (2) impregnating the support with a liquid in which a crystal salt raw material is mixed, and then drying and then crystallizing the crystal salt And a method of firing at an appropriate temperature.

  Next, a method for producing acrolein using the catalyst of the present embodiment will be described. The method for producing acrolein according to the present embodiment produces acrolein by a gas phase dehydration reaction in which a glycerin-containing gas and a catalyst are contacted in a reactor arbitrarily selected from a fixed bed reactor, a moving bed reactor, a fluidized bed reactor and the like. To do. The catalyst according to the present invention is not limited to an acrolein production method in which a glycerin-containing gas and a catalyst are contacted, but can also be used in a liquid phase dehydration reaction in which an acrolein is produced by contacting a glycerin solution and a catalyst. .

  The glycerin used in the glycerin-containing gas may be either purified glycerin or crude glycerin. The glycerin concentration in the glycerin-containing gas is not particularly limited, but is preferably 0.1 to 100 mol%, preferably 1 mol% or more, and 5 mol% or more capable of producing acrolein economically and highly efficiently. Further preferred. When adjustment of the glycerin concentration in the glycerin-containing gas is necessary, one or more gases selected from water vapor, nitrogen, air, and the like can be used as the concentration adjusting gas. Moreover, when water vapor is included in the glycerin-containing gas, it is preferable because the decrease in the activity of the dehydrating catalyst is suppressed and the acrolein yield is increased.

The amount of glycerin-containing gas in the reactor is preferably 100 to 10,000 hr ⁻¹ in terms of glycerol-containing gas flow rate (GHSV) per unit catalyst volume. Preferred is a 5000 hr ^-1 or less, the production of acrolein economically and efficiently, in order to carry out the 3000 hr ^-1 or less is more preferable. The temperature when the intramolecular dehydration reaction of glycerin proceeds is preferably 200 to 500 ° C, preferably 250 to 450 ° C, more preferably 300 to 400 ° C. And the pressure in a dehydration reaction will not be specifically limited if it is a pressure of the range which glycerin does not condense. Usually, it is good that it is 0.001 to 1 MPa, and preferably 0.01 to 0.5 MPa.

  Acrolein can be produced by the above method. The acrolein thus produced can be used as a raw material for producing acrolein derivatives such as acrylic acid, 1,3-propanediol, allyl alcohol, polyacrylic acid, polyacrylate and the like as already known.

  Hereinafter, the present invention will be specifically described with reference to examples. However, the scope of the present invention is not limited to these examples.

  The catalysts of Examples and Comparative Examples were prepared as follows, and acrolein was produced using these catalysts. Details of the catalyst preparation method and the acrolein production method are as follows.

(Example of preparation of dual pore silica supported catalyst)
The biporous silica-supported boron phosphate catalyst was produced by the method shown below using a biporous silica support obtained by the method described in Example 1 of JP-A-2008-179520. The binary porous silica support had a pore structure in a macro region of 1 to 10 μm and a meso region of 4 nm.
The two-dimensional pore silica support was previously dried in an oven at 120 ° C. for 12 hours or more in an air flow, then taken out and allowed to stand at room temperature in a dry box. Transfer a small amount of two-dimensional pore silica onto a porcelain dish, add a small amount of distilled water with a pipette, finish when the entire silica surface gets wet, and the amount of water that can be absorbed by the dried silica carrier (water absorption) Was measured. 1.6 g of distilled water was absorbed with respect to 1 g of dry binary pore silica.

  2.59 g of boric acid (manufactured by Wako Pure Chemicals, special grade) was dissolved in 30.1 g of distilled water on a hot water bath, and 4.80 g of 85 mass% phosphoric acid (manufactured by Kishida Chemical Co., Ltd.) was added thereto, and cooled to room temperature. At this time, it was confirmed that no precipitate was formed. The total amount of this mixed aqueous solution of boric acid and phosphoric acid was added to 25 g of dried dual pore silica placed on a porcelain dish, and 5.0 g of washing water was used. The total amount of water used was 43.2 g, which was slightly higher than the amount absorbed by the dual pore silica support. The binary porous silica to which a mixed aqueous solution of boric acid and phosphoric acid was added was allowed to stand at room temperature for about 30 minutes, and then dried while gently swirling in an 80 ° C. hot water bath. The obtained dried product was dried overnight in a dryer at 120 ° C. under air flow, and then calcined at 800 ° C. for 5 hours under air flow to obtain a catalyst. The composition of the obtained catalyst excluding oxygen was B1P1Si10.

(Silica supported catalyst preparation example)
The boron phosphate silica-supported catalyst was prepared by the method shown below using a spherical silica carrier (Carteact Q50) manufactured by Fuji Silysia Chemical Ltd. The silica support has a single pore structure of 50 nm.

  When the amount of water absorption was measured in the same manner as in the dual pore silica, 1.3 g of distilled water was absorbed with respect to 1 g of the dry silica carrier.

  2.59 g of boric acid (manufactured by Wako Pure Chemicals, special grade) was dissolved in 28.2 g of distilled water on a hot water bath, and 4.80 g of 85% by mass phosphoric acid (manufactured by Kishida Chemical Co., Ltd.) was added thereto, and cooled to room temperature. At this time, it was confirmed that no precipitate was formed. A total amount of this mixed aqueous solution of boric acid and phosphoric acid was added to 25 g of dried silica placed on a porcelain dish, and 5.0 g of washing water was used when added. The total amount of water used was 33.2 g, which was slightly higher than the amount absorbed by the silica support. The silica to which the mixed aqueous solution of boric acid and phosphoric acid was added was allowed to stand at room temperature for about 30 minutes, and then dried while gently swirling on an 80 ° C. hot water bath. The obtained dried product was dried overnight in a dryer at 120 ° C. under air flow, and then calcined at 800 ° C. for 5 hours under air flow to obtain a catalyst. The composition of the obtained catalyst excluding oxygen was B1P1Si10.

(Experimental example 1)
A gas obtained by vaporizing an 80% by mass glycerin aqueous solution and a reaction raw material gas composed of nitrogen (reaction gas composition: glycerin 10 mol%, water 12 mol%, nitrogen 78 mol%) were prepared.

15 ml of the above-mentioned boron phosphate-supported dual pore silica catalyst was filled in a stainless steel reaction tube (inner diameter 10 mm, length 500 mm), and this reactor was immersed in a molten salt bath at 360 ° C. to react the reaction raw material gas. It was distributed to the vessel. The GHSV at this time was 1700 hr ⁻¹ .

  30 to 0.5 to 1 hour, 2.5 to 3.0 hours, 4.5 to 5.0 hours, and 6.5 to 7.0 hours after circulating the reactor inlet gas. The effluent gas for 1 minute was collected by cooling (hereinafter, the “cooled liquefied product of the collected effluent gas” is referred to as “effluent”), and the effluent was identified and quantitatively analyzed by gas chromatography (GC). As a result of qualitative analysis by GC, by-products such as 1-hydroxyacetone were detected together with glycerin and acrolein. Moreover, the glycerol conversion rate, acrolein selectivity, and 1-hydroxyacetone selectivity were computed from the quantitative analysis result.

  Here, the glycerin conversion rate is a value calculated by (1− (mol number of glycerin in the collected effluent) / (mol number of glycerin introduced into the reactor in 30 minutes)) × 100. . The acrolein selectivity is a value calculated by ((molar number of acrolein) / (molar number of glycerin introduced into the reactor in 30 minutes)) × 100 / glycerin conversion × 100. The hydroxyacetone selectivity is a value calculated by (number of moles of 1-hydroxyacetone) / (number of moles of glycerin introduced into the reactor in 30 minutes)) × 100 / glycerin conversion × 100. The results obtained are shown in Table 1.

(Comparative Example 1)
The reaction was carried out in the same manner as in Example 1 except that 15 ml of boron phosphate silica-supported catalyst was charged in the same reaction tube as shown in Experimental Example 1. The results obtained are shown in Table 1.

In Table 1, when a catalyst using binary porous silica as a support was used, the selectivity for acrolein was higher and the decrease over time was smaller than when the silica-supported catalyst of the comparative example was used.

Claims (4)

An amorphous porous carrier containing 90% by mass or more of silica and having 0.1-30 μm macropores and 1-50 nm nanopores, at least one element selected from aluminum, zirconium and boron, And / or a catalyst for dehydration of glycerine characterized by comprising and supporting a crystalline salt containing phosphorus and at least one element selected from rare earth elements. The catalyst for glycerin dehydration according to claim 1, wherein the porous carrier is binary pore silica. A method for producing acrolein by dehydrating glycerol in the presence of a catalyst, wherein the catalyst is the glycerol dehydrating catalyst according to claim 1 or 2. The method for producing acrolein according to claim 3, wherein glycerin is dehydrated by a gas phase reaction in which vaporized glycerin is brought into contact with a catalyst.