KR20100060301A - Methods for high yield synthesis of furfural using tungstate catalyst on titania - Google Patents

Abstract

PURPOSE: A method for manufacturing furfural with high yield using a tungsten system catalyst dipped in a titania is provided to prepare furfural with lower cost. CONSTITUTION: A method for manufacturing furfural using xylose or hemicellulose as an raw material comprises: a step of converting the raw material to furfural using solid acid catalyst in which isopolytungstate is dipped in a titania support in a reaction medium containing supercritical fluid; and a step of extracting and isolating furfural by spraying the supercritical fluid to the reaction medium. The supercritical fluid is supercritical carbon hydroxide or supercritical propane.

Description

Method for high yield synthesis of furfural using tungstate catalyst on titania}

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

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.

Therefore, in order to achieve the purpose of high conversion of xylose and high selectivity or high yield of perfural, it is desirable to suppress the progress of side reactions by keeping the residual concentration of perfural as a product in the medium in which the reaction proceeds. Do.

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, reactants and intermediate products are used when the reaction is performed using a solid acid that is a heterogeneous catalyst. The final product and side reactants 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 In case of progressing the desired perfural production reaction while actually contacting with a high temperature aqueous solution, there is a problem of a loss of long time use and a deterioration of the catalytic activity.

Titania, on the other hand, has excellent chemical, biological, and thermal stability, and has advantages such as durability, economy, and excellent mechanical strength, and thus is used in various applications such as polymer fillers, cosmetic additives, photocatalysts, and catalyst carriers. 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 titania support having excellent thermal stability and economy, and thus are required for the characteristic loss of catalyst activity caused by long-term use and maintenance of a recycling / recycling cycle. We have developed a method for producing perfural that improves the problem of poor stability in high temperature heat treatment.

It is an object of the present invention to provide a method for producing perfural in high yield using a tungsten-based catalyst supported on a titania 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 a high yield using a tungsten-based catalyst supported on a titania support.

In the method for producing perfural according to the present invention, perfural is prepared by using a catalyst body in which a tungsten-based solid acid catalyst having excellent thermal stability and chemical stability is supported on a titania support. The manufacturing cost can be reduced and usefully used for preparing perfural.

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 titania 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 titania support and calcining at 550 to 750 ° C. It is preferred that it is a solid acid catalyst.

The titania precursor for preparing the titania support is prepared using a conventional method obtained from a precursor of titanium tetraisopropoxide, titanium ethoxide, titanium butoxide, titanium isopropoxide, titanium tetrachloride or titanium sulfate. Can be.

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.

At this time, as a raw material of isopolytungstate (WO _x , x = 1 to 3), phosphotungstic acid hydrates, which is a kind of heteropoly acid, or tungsten chloride, ammonium metatungstate or a mixture thereof are used. It is desirable to.

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 550 ~ 750 ℃.

The titania 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, etc. The catalyst is more stable under severe reaction or regeneration conditions. Due to these advantages, the titania catalyst including 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.

Synthesis of perfural under supercritical fluid extraction conditions using Titania-supported isopolytungstates as the main component of the synthetic catalyst without any particular limitation on the specific process of preparing the catalysts listed above. Can be used for the reaction, 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 Titania Support

The support was instilled while stirring 200 ml of titanium isopropoxide at room temperature for 6 hours at room temperature. A white precipitate was prepared by hydration, washed several times with 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 titania 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 titania 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 600 ° 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 l of the raw material aqueous solution was added to a 1.5 l high-pressure reactor, and the carbon dioxide was used as a supercritical fluid to maintain 200 atm and 180 ° C., 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 perfural yield according to the present invention, it was calculated from the results of liquid chromatography (HPLC) analysis. 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 was heated in an air atmosphere of 600 ~ 650 ℃ and Comparative Example 1 was heated for 6 hours in an air atmosphere of 500 ℃ to measure the yield of the furfural prepared by the process using the regenerated catalyst as described above, catalyst regeneration It is shown in Table 1 to measure the yield after repeated several times.

Example 2 Example 3 Example 4 Comparative Example 1 Initial Perfural Yield 52% 56% 54% 51% When caulking occurs 6th 6th 8th 5 times 1st catalyst regeneration time 10th 10th 10th 7th Yield after 1st catalyst regeneration 52% 56% 54%  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, the yield of the furfural synthesis of Example 2 was confirmed as 52%. 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 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%.

As a result of confirming the perfural synthesis yield of Example 3, it was calculated as 56%. It was able to use 5 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. The weight loss of the catalyst body after one regeneration treatment was found to be less than 0.3%.

The furfural synthesis yield of Example 4 was confirmed and calculated as 54%. It was able to use 7 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 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)

     A method for producing perfural using xylose or hemicellulose as a raw material, using a solid acid catalyst body in which isopolytungstate is supported on a titania support in a reaction medium containing a supercritical fluid. Converting the raw material to perfural (step 1) and extracting and separating the perfural by injecting a supercritical fluid into 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 2, wherein the solid acid catalyst body is a solid acid catalyst body prepared by supporting the isopolytungstate precursor on the titania support, and then calcined at 550 ~ 750 ℃ How to make fural. 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.