KR20100054571A - METHODS FOR HIGH YIELD SYNTHESIS OF FURFURAL USING TUNGSTATE/γ-ALUMINA CATALYST - Google Patents

Abstract

PURPOSE: A producing method of furfural is provided to improve the yield of the furfural, to reduce the fabrication cost of the furfural, and to reduce the catalyst loss rate. CONSTITUTION: A producing method of furfural using xylose or hemicellulose as a raw material comprises the following steps: converting the raw material into the furfural using a solid acid catalyst body deposited with isopolytungstate to a gamma-alumina supporting body inside a reaction medium including supercritical fluid; and extracting or separating the furfural by spraying the supercritical fluid to the reaction medium. The supercritical fluid is either supercritical carbon dioxide, or supercritical propane.

Description

Method for high yield synthesis of furfural using tungsten catalyst supported on gamma alumina {Methods for high yield synthesis of furfural using tungstate / γ-alumina catalyst}

The present invention relates to a method for producing perfural in high yield using a tungsten-based catalyst supported on gamma alumina.

Perfural, one of aliphatic aldehydes, has been used in nylon synthesis, but is a very useful general purpose chemical which is widely used in fine chemical intermediate materials, solvents, and resin raw materials for special purposes. It is not industrially produced by pure chemical synthesis but is produced by chemical conversion of biomass resources, and is made by dehydrating xylose, which is derived from xylan constituting hemicellulose, in an acid atmosphere.

In the conventional perfural manufacturing process, the excessive generation of waste due to acid catalyst waste used, waste due to low conversion rate, and side reactions proceeding in the high conversion region has been pointed out as a problem, and excessively in perpural separation and purification process. The consumption of separate process energy has also been pointed out as a technical problem to be solved. As such, perfural is very difficult to synthesize in high yield in the high conversion region, and reducing the generated waste is considered as the main problem.

Republic of Korea Patent No. 10-0295738 proposes a process technology principle using a supercritical fluid and a solid acid to solve the problem of the perfural manufacturing process, specifically using a supercritical carbon dioxide and a sulfated solid acid catalyst in combination Thus, a method of synthesizing perfural in high yield in the high conversion region is proposed.

When a solid acid is used to synthesize perfural from xylose, the desired synthesis reaction is completed through a series of unit reactions from xylose, which also includes relatively slow equilibrium reactions, which slows down the reaction rate. there is a problem. In addition, the produced perfural has a problem of generating large molecular weight side reactions by pyrolysis and polycondensation.

In order to solve the above problem, in order to achieve the purpose of high conversion of xylose and high selectivity or high yield of perfural, the residual concentration of perfural as a product in the medium in which the reaction proceeds is kept low so as to proceed with side reactions. It is desirable to suppress.

On the other hand, unlike the case of using a homogeneous acid catalyst in which the reactants and the catalyst are in a uniform phase, such as an acid catalyst in an aqueous solution, the reaction product and the intermediate product may be used when the reaction is performed using a solid acid that is a heterogeneous catalyst. Field, end product and side reactions remain in the pore structure inside the catalyst used. Therefore, the low-molecular weight side reactions accumulate in the diffusion transfer region including the catalytically active region inside the pores, thereby preventing the catalyst pore structure and shielding the active site, thereby degrading the performance of the catalyst. This phenomenon occurs more severely when the catalyst is used for a long time in high temperature reaction conditions, and may be more severe in the case of a catalyst having a well-developed pore structure. Therefore, in using the solid acid catalyst in the synthesis reaction, it is essential to apply a method of periodic regeneration and reuse to thermally reactivate the catalyst after use for a certain reaction time.

   The sulfated solid acid catalysts used in the method for preparing perfural disclosed in the Republic of Korea Patent No. 10-0295738 show characteristics of a catalyst that is very disadvantageous for heat treatment for periodic regeneration as described above. Specifically, the coked material must be heat-treated at high temperature to remove the caulk material from the inside and the surface of the catalyst pore for regeneration, wherein the sulfated solid acid catalysts are characterized by volatile volatilization of the sulfated structure, The sulfated structure is continuously damaged since it is changed and lost in the form of this large sulfur compound. Therefore, it is difficult to regenerate the catalyst at high temperatures, and must be regenerated at a low temperature of less than 350 ° C., and preferably 300 ° C. or less is preferred as the regeneration condition. However, the regeneration is very slow and incomplete at such low temperatures. There is this.

In addition, in the regeneration process, the combustion removal reaction of the deposited hydrocarbon compound is an exothermic reaction having a very high calorific value, so that a local high temperature environment, that is, a hot spot can be formed, especially in the vicinity of an acid point close to the surface showing high catalytic activity. Hot spots may be formed. As a result, the loss of the sulfated structure of the sulfated catalyst proceeds, making the catalyst very difficult to regenerate while maintaining the chemical structure of the catalytically active point near the surface.

For this reason, when the heterogeneous catalyst is brought into contact with a high temperature aqueous solution medium, it is very important to maintain the morphological stability of the catalyst in terms of the practical operation of the catalyst process, and also to act as a catalyst active site. It is necessary for the stability of the structure to be maintained for a long time.

In the case of the sulfated solid acid catalyst used in the prior art Korea Patent No. 10-0295738, the loss of the sulfated portion from the catalyst body when the catalytic role in contact with the aqueous solution phase and the reduction of the catalytic activity resulting therefrom This may be a problem, and when we actually proceed with the desired perfural manufacturing reaction in contact with a high temperature aqueous solution, there is a problem that the loss phenomenon caused by long time use and the resulting catalytic activity is lowered.

On the other hand, gamma alumina having a spinel crystal lattice structure has little structural change due to heat, very fine pores, high porosity, and a large specific surface area, so that it is highly usable for separation membranes, catalysts, catalyst carriers and adsorbents, and for a long time at high temperatures. Excellent thermal stability even after treatment. In addition, there is an advantage that the catalyst support can be economically inexpensively prepared using inexpensive precursors.

Therefore, the present inventors overcome the long-term deterioration of the catalyst in an aqueous solution using a tungsten-based catalyst supported on a gamma alumina support having excellent thermal stability, and are required to maintain a characteristic catalyst activity loss and maintenance of a recycling / recycling cycle by long-term use. A method for producing perfural has been developed to improve the high temperature stability.

An object of the present invention is to provide a method for producing perfural with high yield using a tungsten-based catalyst supported on a gamma alumina support that is economically inexpensive, has excellent thermal stability and catalytic activity, and has excellent reactivation and recyclability. .

In order to achieve the above object, the present invention provides a method for producing perfural in high yield using a tungsten-based catalyst supported on a gamma alumina support.

The method for producing perfural according to the present invention is to produce perfural using a tungsten-based solid acid catalyst having excellent thermal and chemical stability, while having excellent yield and low catalyst loss rate, thereby reducing the production cost of perfural. It can be usefully used for production.

Hereinafter, the present invention will be described in detail.

The present invention relates to a method for producing perfural using xylose or hemicellulose as a raw material, the solid acid catalyst having an isopolytungstate supported on a zirconia support in a reaction medium containing a supercritical fluid. Converting the raw material to perfural using step (step 1) and extracting and separating the perfural by injecting a supercritical fluid into the reaction medium (step 2). To provide.

Step 1 is a step of converting the biomass hemicellulose or xylose derived therefrom to the low molecular state of perfural, and step 2 is to maintain the residual concentration of the product furfural in the reaction medium to proceed with the side reactions. Extracting and separating the perfural to inhibit the.

At this time, the step 1 and the step 2 is preferably performed at the same time.

The solid acid catalyst carrying the isopolytungstate is a strong acid solid acid catalyst, stable at a high temperature of 900 ° C. or higher, easy to regenerate the catalyst, and does not change the activity of the catalyst well.

On the other hand, the isopolytungstate-carrying solid acid catalyst body may be usefully used in the reaction process such as the oxidation reaction and polymerization reaction of olefin and aromatic hydrocarbon, but the reaction promoting properties such as generating unwanted side reaction products even at low temperature There is a redundant problem.

In order to solve the above problems, the production method according to the present invention by using a supercritical fluid to provide a reaction environment in which the extraction separation occurs at the same time by extracting separation as soon as perfural is produced. In this way, the side reactions forming the high molecular weight side reactions are suppressed to a minimum, and the radical reactivity of the catalyst body and the side reactions thereof are overcome.

In the method for producing perfural in high yield according to the present invention, the solid acid catalyst includes an isopolytungstate prepared by supporting an isopolytungstate catalyst on a zirconia support and calcining at 500 to 700 ° C. It is preferred that it is a solid acid catalyst.

In order to prepare the gamma alumina support, alumina precursors include various alumina hydrates, and alumina hydrates include trihydrate (trihydrate: Al (OH) ₃ or Al ₂ O ₃ 3H ₂ O). (Gibbsite) and Bayerrite (monohydrate: AlOOH or Al ₂ O ₃ H ₂ O) to be prepared using conventional methods obtained from precursors of Boehmite and Diaspore Can be.

US patents describing the preparation of alumina supports include US Pat. Nos. 3,222,129, 3,223,483, 3,226,191, and the like. Methods of making highly porous alumina are disclosed in registered US Pat. Nos. 3,804,781, 3,856,708, 3,907,512 and 3,907,982. Other methods of making catalyst carriers are discussed in US Pat. Nos. 3,987,155 3,997,476, 4,001,144, 4,022,715, 4,039,481 4,098,874, and 4,242,234.

The solid acid catalyst used in the present invention is isopolytungstate by composition method, coprecipitation method, sol-gel synthesis method, impregnation method or suspension dispersion method. The catalyst can be supported.

In this case, as a raw material of isopolytungstate (WO _x , x = 1 to 3), phosphotungstic acid hydrates, which are a kind of heteropolyacid, or tungsten chlorides, ammonium metatungstate or theirs are used. Preference is given to using mixtures.

On the other hand, the calcination serves to separate and remove the phosphorus (P) component contained in the heteropolyacid from the catalyst body to increase the catalytic efficiency, which is preferably performed at 500 ~ 700 ℃.

The gamma alumina catalyst body including the tungsten oxide prepared as described above is cheaper than the sulfated zirconia catalyst body, the method of preparing the catalyst body is easier, the catalyst deactivation rate is slower, oxidation and reduction The catalyst is more stable under severe reaction conditions or regeneration conditions. Due to these advantages, gamma alumina catalyst containing tungsten oxide can be utilized for alkylation reaction, bromination reaction with high structure selectivity, oxidative bromination reaction, benzoylation reaction and the like. .

In this case, the supercritical fluid is preferably supercritical carbon dioxide or supercritical propane.

The supercritical fluid serves to separate and transport the converted perfural by being injected into the reaction medium in the perfural conversion reaction.

In addition, steps 1 and 2 are preferably carried out under a temperature of 100 ~ 200 ℃ and a pressure of 100 ~ 300 atm.

Carbon dioxide has a critical point at 31.1 ° C. and 72.8 atm, and propane has a critical point at 96.7 ° C. and 41.9 atm. In order to use carbon dioxide or propane as a supercritical fluid, a temperature of 100 to 200 ° C. and a pressure of 100 to 300 atm are required. It is preferably carried out under.

Without particular limitation on the specific process for the preparation of the catalysts listed above, perfural was extracted under supercritical fluid extraction conditions using gamma-alumina-supported isopolytungstates as the main component of the synthetic catalyst. It can be used in the synthesis reaction to prepare, can exhibit an excellent effect of producing perfural in high yield at high conversion conditions.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are merely to illustrate the invention, but the content of the present invention is not limited by the following examples.

Example 1 Synthesis of High Yield Perfural 1

Step 1. Preparation of Gamma Alumina Support

The support was added 100 g of boehmite powder to 400 g of distilled water under stirring. 3 g of formic acid (98% from VWR) were slowly added to the complementite slurry under vigorous stirring. The acidified slurry was heated to 95 ° C. and maintained at that temperature for 2 hours with stirring. The slurry was filtered, washed three times with hot distilled water, dried at 120 ° C. for 12 hours, finely ground and further dried at 120 ° C. for 12 hours.

Step 2. Support Isopolytungstate Catalyst

The isopolytungstate catalyst was prepared by applying injection method. Specifically, 4.96 g of phosphotugstic acid (H ₃ PW ₁₂ O ₄₀ 21H ₂ O) was added to 100 g of the zirconia support powder prepared in Step 1 above. It was prepared by suspending in a 50 ml aqueous methanol solution to prepare a suspension having a tungstate content of 5% by weight relative to the zirconia powder, which was then stirred for 10 hours.

Step 3. Drying and Firing

The isopolytungstate solid acid catalyst body prepared in step 2 was dried at 120 ° C. for 12 hours, and calcined at 500 ° C. for 6 hours to prepare a solid acid catalyst supporting the final isopolytungstate.

Step 4. Perfural Synthesis and Extraction

10 g of the solid acid catalyst prepared in Step 3 per 1.5 L of a high pressure reactor in a 1.5 L capacity was maintained at 200 atm and 180 ° C. using carbon dioxide as a supercritical fluid, followed by 20 g of xyl per liter. Rhodes was added to synthesize and extract perfural in high yield. At this time, 5 L of carbon dioxide per minute was introduced into the lower portion of the reactor at a flow rate under standard conditions, and the reaction medium was injected for 2 hours.

Example 2 Synthesis of High Yield Perfural 2

Example 1 except that the content of the tungstate in the suspension of step 2 of Example 1 was 10%.

Example 3 Synthesis of High Yield Perfural 3

Example 1 was carried out in the same manner as in Example 1 except that the content of the tungstate in the suspension of Step 2 of Example 1 was 20%.

Example 4 Synthesis of High Yield Perfural 4

Except for using propane as a supercritical fluid in step 4 of Example 1 was carried out in the same manner as in Example 1.

Comparative Example 1 Synthesis of Perfural Using Sulfated Zirconia Catalysts

In step 3 of Example 1, 10 g of a sulfated zirconia catalyst prepared from zirconyl chloride octahydrate per 1 liter of an aqueous solution of 1.5 L of a high pressure reactor was added thereto, and then maintained at 200 atm and 180 ° C. using carbon dioxide. 20 g of xylose per 1 L was added to perfural synthesis and extraction.

Experimental Example 1 Comparison of Catalyst Performance through Perfural Yield

In order to measure the Perfuran yield according to the present invention, it was calculated from the liquid chromatograph (HPLC) analysis results. Example 2, Example 3 and used to measure the initial yield of the perfural prepared through Example 2, Example 3, Example 4 and Comparative Example 1, the method was repeated several times, repeated several times Example 4 is heated in an air atmosphere of 500 ~ 550 ℃, Comparative Example 1 is heated for 6 hours in an air atmosphere of 500 ℃ to measure the yield of perfural prepared by the process using the regenerated catalyst as described above, the catalyst The yield after repeated regeneration was measured and shown in Table 1.

Example 2 Example 3 Example 4 Comparative Example 1 Initial Perfural Yield 53% 58% 56% 51% When caulking occurs 6th 6th 8th 5 times 1st catalyst regeneration time 10th 10th 10th 7th Yield after 1st catalyst regeneration 53% 58% 56%  24% After one catalyst regeneration,
Catalyst loss rate Almost none Less than 0.3% After 3 catalyst regenerations,
Catalyst loss rate Less than 1%

 As shown in Table 1 above, the yield of perfural synthesis in Example 2 was determined to be 53%. It was able to use 5 times without changing the catalytic activity. After 10 times, the caking-contaminated catalyst body was regenerated and the perfural synthesis reaction was carried out using the regenerated catalyst to confirm the yield. It was confirmed that there was little loss in catalyst activity at. Further, it was confirmed that there was no loss of catalyst activity as a result of repeated regeneration of the second and third times, and the loss of the weight of the catalyst body after the third regeneration treatment was also measured to be less than 1%.

The furfural synthesis yield of Example 3 was confirmed and calculated as 58%. It was able to use 5 times repeatedly without significant change in catalyst activity. After 10 times, the caking contaminated catalyst body was regenerated and the perfural synthesis reaction was carried out using the regenerated catalyst to confirm the yield. It was confirmed that there was almost no loss in catalyst activity within. The weight loss of the catalyst body after one regeneration treatment was found to be less than 0.3%.

As a result of confirming the perfural synthesis yield of Example 4, it was calculated as 56%. It was able to use 7 times without changing the catalyst activity. After 10 times, the caking-contaminated catalyst body was regenerated and the perfural synthesis reaction was carried out using the regenerated catalyst to confirm the yield. It was confirmed that there was almost no loss in catalyst activity within.

On the other hand, in the perfural synthesis of Comparative Example 1, the residual concentration of perfural was analyzed to be 0.28% by weight, and the yield of perfural was calculated to be 51%. The catalyst used after the end of the reaction was reused four times without significant change in catalyst activity. However, as a result of seven reuses, severe carbon deposition and caulking occurred on the surface, which lowered the catalytic activity. As a result of the perfural reaction using the first regenerated catalyst, the yield of the perfural was reduced to 24%. A marked drop in activity was observed.

Claims (6)

In the method for producing perfural using xylose or hemicellulose as a raw material, a solid acid catalyst body in which isopolytungstate is supported on a gamma alumina support in a reaction medium containing a supercritical fluid Converting the raw material into perfural (step 1) and extracting and separating the perfural by spraying a supercritical fluid on the reaction medium (step 2). The method of claim 1, wherein the step 1 and the step 2 is carried out at the same time, the method of producing perfural in high yield. According to claim 1 or claim 2, wherein the solid acid catalyst body is a solid acid catalyst body prepared by supporting the isopolytungstate precursor on the gamma alumina support, and then calcined at 500 ~ 700 ℃ in a high yield, characterized in that Method of making perfural. The raw material of the isopolytungstate catalyst is any one or two or more compounds selected from the group consisting of hydrates of tungsten-containing heteropolytungstic acid or salts thereof and ammonium metatungstate. Method for producing perfural in high yield.  The method of claim 1 or 2, wherein the supercritical fluid is supercritical carbon dioxide or supercritical propane. The method of claim 1 or 2, wherein the step 1 and step 2 is a method for producing perfural in a high yield, characterized in that carried out under a temperature of 100 ~ 200 ℃ and pressure of 100 ~ 300 atm.