CN101284234A - Preparation of Hydroxyacetone by Selective Dehydration of Natural Glycerol and Its Catalyst - Google Patents

Abstract

The invention relates to a reaction process for producing hydroxyacetone through selective dehydration of natural glycerin and a corresponding catalyst. The catalyst is composed of a low activity carrier such as SiO ₂ and 20-90 wt% of active metal components, and is prepared by an impregnation loading method. The active metal components used are group IB elements, or a combination of IB and VIB group elements, or a combination of IB, VIB and light rare earth elements. The selective dehydration of natural glycerol to produce hydroxyacetone is carried out in a fixed-bed flow reactor at a raw material concentration of 10-100%, normal pressure, temperature 200-400°C, and liquid-hourly space velocity (LHSV) of 0.01-0.60h ^-1 Under the conditions, the conversion rate of glycerin can be as high as 99.89%, and the molar selectivity of hydroxyacetone can be as high as 89.74%. The preparation process of the catalyst of the invention is simple, the price is low, and the concentration and liquid-hour space velocity range of the reaction raw material glycerin aqueous solution are wide.

Description

Preparation of Hydroxyacetone by Selective Dehydration of Natural Glycerol and Its Catalyst

technical field

The invention relates to the selective dehydration reaction of natural glycerin to prepare hydroxyacetone and a catalyst.

Background technique

Hydroxyacetone is mainly used to synthesize the intermediate 4-methylimidazole of the _H2 blocker cimetidine in the digestive system, and the intermediate (s)-(+)-2-amino of the quinolone antibacterial drug levofloxacin Propanol, intermediate 4-hydroxymethylimidazole of racemic histidine, vitamin H, antipyretic and analgesic drug aspirin acetonate without ulcer side effects, chiral intermediate (1)-(-)-1, 2-propanediol and other fine chemicals can also be used as biochemical reagents and food additives.

Hydroxyacetone is currently mainly produced by the esterification/alcoholysis of bromoacetone and the oxidation of 1,2-propanediol. Relatively speaking, the former reaction conditions are milder, the production equipment is simpler, and the product yield and purity are higher. However, there are problems such as high price of raw material bromoacetone, bromine pollution in the production process, complicated separation of reaction by-products, high cost of waste liquid treatment and discharge; the latter has low raw material cost and can be produced continuously or semi-continuously, but there are also problems Problems such as harsh reaction conditions, high equipment requirements and low product yield. In addition, U.S. Patents USP6191308B1 and USP6107525 also reported a synthetic method, involving the reaction of aldehydes or ketones with alcohols or orthoesters to generate acetals or ketals, and the formation of acetals or ketals from acetals or ketals Formation of alkenyl ethers, alkenyl ethers are oxidized to α-hydroxy ketones or aldehydes with carbonyl protecting groups under the action of organic or inorganic peracids, and α-hydroxy ketones or aldehydes with carbonyl protecting groups are finally hydrolyzed to α-hydroxy ketones or aldehyde steps. However, this method has problems such as many reaction steps, long process, relatively harsh conditions, low yield of target product, and the separation and discharge of by-products lead to increased operating costs.

The above-mentioned three methods for preparing hydroxyacetone all use petroleum-based products as raw materials, and as we all know, petroleum resources are in a state of continuous shortage in the world. Due to severe challenges, it is inevitable to develop a process for preparing hydroxyacetone from non-petroleum route products.

At present, there are few patents in the world reporting the preparation of hydroxyacetone by using biomass resources. World Patent WO9928481 reports that sugar and starch are used as starting materials, and enzymes are used as catalysts to produce hydroxyacetone and 1,2-propanediol, wherein the yield of 1,2-propanediol is lower than 0.2g/L, and the yield of hydroxyacetone is higher Much lower than 1,2-propanediol. Due to its low yield, the above enzyme-catalyzed conversion process is difficult to realize industrialization. U.S. Patent USP2036940 reports that 125 grams of pure glycerin is added dropwise at a rate of 1 drop/minute to 20 milliliters of copper chromate catalyst preheated to 240-260 ° C. After the gas phase product is condensed and rectified, about 41 grams of hydroxyl acetone. The catalyst consumption of this process is large, and the yield of hydroxyacetone is low (about 33%). The world patent WO93/05006 reports that the mixed metal oxides of the IB and VIB groups are used as catalysts after _H2 reduction, and under the conditions of ~280°C temperature and 0.25h ^-1 liquid hourly space velocity, 80-100% glycerol Dehydration reaction is carried out as the raw material, the conversion rate is greater than 99%, and the best selectivity of the product hydroxyacetone is about 54%. USP20050244312 reports that using Cu-Cr alloy powder catalyst or CuO-Cr ₂ O ₃ mixed oxide powder catalyst formed after hydrogen reduction, in a tank reactor, at 240 ° C temperature, 98KPa vacuum pressure and 2 hours Under the condition of reaction time, pure glycerol is used as raw material for dehydration reaction, and both the conversion rate of glycerol and the selectivity of hydroxyacetone can reach about 90%. However, the catalyst is easily solidified and deactivated during the reaction.

Natural glycerin is a general term for saponified glycerin, fermented glycerin and biological glycerin, which is a biomass resource. In nature, glycerol exists in animal and vegetable oils in the form of glycerides. Saponified glycerin can be directly recovered as a by-product during soap making; fermented glycerin is starchy (such as corn) with abundant sources and cheap price, dried potato and sugar. (for example, sugar beet, sugarcane) etc. are used as raw materials for production, and are produced through microbial fermentation. At present, the technology is mature. In the future, with the development of technologies such as microbial strains and fermentation process extraction and separation, the production of fermented glycerin will develop faster at home and abroad; bioglycerol is one of the main by-products in the production of biodiesel and bioalcohol, and its About 10% of biodiesel and bioethanol. As more and more biodiesel and bioethanol plants come on stream, there will be a significant surplus of bioglycerol in the market. Therefore, the selective dehydration of natural glycerol to prepare hydroxyacetone has broad prospects for development.

Contents of the invention

The purpose of the present invention is to provide a reaction process for the selective dehydration of natural glycerol to produce hydroxyacetone and a corresponding catalyst preparation method. The catalyst consists of a low activity oxide support and active metal components supported thereon by a simple impregnation process. Said reaction of selective dehydration of natural glycerol to produce hydroxyacetone is carried out in a fixed-bed flow type reactor. Using the catalyst and the reaction process of the present invention to carry out the selective dehydration reaction of natural glycerol to produce hydroxyacetone has the outstanding advantages of: 1) the catalyst is simple to prepare and the price is low; 2) the concentration range of the reaction raw material solution is wide (10-100%) , various concentrations of natural glycerin can be used. Directly using low-concentration glycerin as raw material can save energy consumption due to glycerin distillation and concentration; 3) adopting a fixed bed flow reactor can carry out continuous production; 4) the conversion rate of glycerin and the selectivity of hydroxyacetone are high, which can be as high as 99.89% and 89.74mol%.

The purpose of the present invention is achieved in the following manner:

The catalyst used for the selective dehydration of glycerol to produce hydroxyacetone consists of a low-activity carrier and active metal components loaded thereon. Its technical feature is that said catalyst carrier is one of silicon dioxide, aluminum oxide, amorphous silicon aluminum, magnesium oxide, zirconium oxide, titanium oxide and molecular sieve, among which silicon dioxide is preferred. The active metal component is one of IA, IIA, IB-VIIIB groups and light rare earth elements, or two of these elements, or any combination of two or more in any proportion. Among them, preferably one of IIA, IB, VIB, VIIIB and light rare earth elements, preferably one of IB group elements, the content of its oxide form in the catalyst accounts for 20-90wt%; or IIA , IB, VIB, VIIIB and light rare earth elements in any combination in any proportion, it is best to select a combination of IB and VIB group elements respectively, and the content of the oxide form in the catalyst is respectively Accounting for 20-50wt% and 0-50wt%; or a combination of two or more of IIA, IB, VIB, VIIIB and light rare earth elements in any proportion, preferably one of IB, VIB and light rare earth elements respectively For the combination carried out, the content of the oxide form in the catalyst accounts for 20-50wt%, 0-50wt% and 0-30wt% respectively. Among the various catalysts mentioned above, the total content of the active metal in the form of its oxide in the catalyst is preferably 40-80 wt%.

The catalyst is prepared by impregnation loading method, and its specific steps are as follows: first, weigh the calculated amount of one or more soluble salts of active metals, such as nitrate, chloride, carbonate or phosphate, etc., dissolve Prepare a solution in water. Then add the calculated amount of catalyst carrier into the above solution, and stand or stir at room temperature for 1-12 hours, preferably 2-6 hours. Then the liquid is removed and dried at 80-120°C, and the obtained solid matter is calcined at 400-650°C for 2-12 hours, preferably at 500-600°C for 4-8 hours. Using the prepared catalyst as a carrier, repeat the above impregnation loading and roasting process for 1 to 3 times until the catalyst with the required amount of active metal component loading is obtained.

Described catalyzer is used for glycerol selective dehydration and produces hydroxyacetone reaction, proceeds as follows: adopt fixed bed flow type tubular reactor (as shown in Figure 1), catalyzer is placed in reaction tube middle part, and reaction temperature is controlled by thermocouple and Temperature control unit detection and control. Before the reaction, the catalyst is activated in situ at a temperature of 100-500° C. for 1-10 hours in a hydrogen atmosphere, preferably at a temperature of 200-400° C. for 2-5 hours. The raw material glycerol solution is contained in the raw material storage tank, and the glycerol concentration is 10-100 wt%, preferably 30-60 wt%. During the reaction, the glycerol solution is sent from the raw material storage tank to the top of the catalytic dehydration reactor through a constant flow pump, and flows through the catalyst bed, the reaction pressure is normal pressure, and the reaction temperature is 200-400°C, preferably 240-340°C. The liquid-hourly space velocity (LHSV) of the reaction system is 0.01-0.60h ^-1 , preferably 0.10-0.30h ^-1 . The reaction product mixture flows out from the bottom of the reactor and is analyzed qualitatively and quantitatively by gas chromatography and mass spectrometer.

Description of drawings

Figure 1 Schematic diagram of the reaction device for the selective dehydration of natural glycerol to prepare hydroxyacetone

Detailed ways

Example 1:

20g of silicon dioxide was calcined at 600°C for 6 hours, cooled to room temperature, pressed into tablets and granulated, and the catalyst of 20-30 meshes was screened for use.

A proper amount of catalyst is filled in the quartz reaction tube of the fixed bed reactor, and 20-30 mesh quartz sand is filled in the upper part of the catalyst bed and the lower part of the reactor space. Hydrogen gas was introduced into the reactor, and the catalyst was reduced for 6 hours under the conditions of a pressure of 0.01 MPa and a temperature of 300°C. After the reaction tube was cooled to room temperature, 40% glycerol aqueous solution was fed into the reactor with a constant flow pump to carry out selective dehydration of glycerin. The LHSV was 0.1h ^-1 and the dehydration reaction temperature was 310°C. The reaction results are as follows:

Glycerin conversion rate is 10.50%; Product molar selectivity is: hydroxyacetone 3.33%, 1,2-propanediol 2.35%, acetaldehyde 0.90%, and other components (mainly acetic acid, dihydrofuran, dihydroxyfuran, glycerol acetate esters, etc.) 93.42%.

Example 2:

Weigh 5g of copper nitrate trihydrate, 15g of silicon dioxide and 50g of deionized water in a beaker and mix evenly, stir at room temperature for 6 hours, remove the liquid and dry at 120°C, bake at 600°C for 6 hours, cool to room temperature, repeat the above The process of impregnation, loading and calcination was performed three times to obtain a Cu/SiO ₂ catalyst with a CuO content of 20%. The catalyst is tableted and granulated, and the granules with 20-30 meshes are screened for the reaction of glycerin dehydration to produce hydroxyacetone.

Reaction process condition is with embodiment 1. The result of the reaction is as follows:

Glycerin conversion rate is 51.64%; Product molar selectivity is: hydroxyacetone 38.18%, 1,2-propanediol 1.69%, acetaldehyde 6.78%, and other components (mainly acetic acid, dihydrofuran, dihydroxyfuran, glycerol acetate esters, etc.) 53.35%.

Example 3:

Weigh 9g of ferric chloride hexahydrate, 15g of silicon dioxide and 50g of deionized water in a beaker and mix evenly, stir at room temperature for 6 hours, remove the liquid and dry at 120°C overnight, roast at 600°C for 6 hours, and cool to room temperature , repeating the above impregnation loading and roasting process twice to obtain a Fe/SiO ₂ catalyst with a Fe ₂ O ₃ content of 28%. Tablet granulation, screening of 20-30 mesh catalysts for use.

Reaction process condition is with embodiment 1. The result of the reaction is as follows:

Glycerin conversion rate is 16.90%; Product molar selectivity is: hydroxyacetone 1.92%, 1,2-propanediol 1.71%, acetaldehyde 7.10%, and other components (mainly acetic acid, dihydrofuran, dihydroxyfuran, glycerol acetate esters, etc.) 89.27%.

Example 4:

Weigh 15g of chromium nitrate nonahydrate, 15g of silicon dioxide and 50g of deionized water in a beaker and mix evenly, stir at room temperature for 6 hours, remove the liquid and dry at 120°C overnight, bake at 600°C for 6 hours, cool to room temperature, repeat The above impregnation, loading and calcination process was carried out twice to prepare a Cr/SiO ₂ catalyst with a Cr ₂ O ₃ content of 36%. Tablet granulation, screening of 20-30 mesh catalysts for use.

Reaction process condition is with embodiment 1. The result of the reaction is as follows:

Glycerol conversion rate is 12.95%; product molar selectivity is: hydroxyacetone 7.33%, 1,2-propanediol 5.25%, acetaldehyde 14.59%, and other components (mainly acetic acid, dihydrofuran, dihydroxyfuran, glycerol acetate esters, etc.) 72.83%.

Embodiment 5～9:

Weigh 12.2g of copper nitrate trihydrate, 16g of the corresponding carrier of each embodiment in Table 1 and 50g of deionized water and mix them uniformly in a beaker, stir at room temperature for 6 hours, dry overnight at 120°C, and roast at 600°C for 6 hours. After cooling to room temperature, a Cu/supported catalyst with a CuO content of 20% was prepared. Tablet granulation, screening of 20-30 mesh catalysts for use.

Reaction process condition is with embodiment 1. The reaction results are shown in Table 1:

The reaction result of table 1 embodiment 5～9

^a : Refers to all other components including acetic acid, dihydrofuran, dihydroxyfuran, glycerol acetate, etc.

Example 10:

Weigh 8g of copper nitrate trihydrate, 8g of zinc nitrate hexahydrate, 12g of silicon dioxide and 50g of deionized water, mix them evenly in a beaker, stir at room temperature for 6 hours, remove the liquid and dry overnight at 120°C, and roast at 600°C for 6 hours , cooled to room temperature, and repeated the impregnation loading and roasting process twice to obtain a Cu-Zn/SiO ₂ catalyst with a CuO content of 25% and a ZnO content of 33%. Tablet granulation, screening of 20-30 mesh catalysts for use.

Reaction process condition is with embodiment 1. The result of the reaction is as follows:

The conversion rate of glycerol is 98.77%; the product molar selectivity is: hydroxyacetone 40.93%, 1,2-propanediol 1.61%, acetaldehyde 12.32%, and other components (mainly acetic acid, dihydrofuran, dihydroxyfuran, glycerol acetate Esters, etc.) 45.14%

Example 11:

Weigh 24g copper nitrate trihydrate, 21g chromium nitrate nonahydrate, 4g silicon dioxide and 50g deionized water and mix them evenly in a beaker, stir at room temperature for 6 hours, dry overnight at 120°C, bake at 600°C for 6 hours, and cool to At room temperature, a Cu-Cr/SiO ₂ catalyst with a CuO content of 40% and a Cr ₂ O ₃ content of 40% was prepared. Tablet granulation, screening of 20-30 mesh catalysts for use.

Reaction process condition is with embodiment 1. The result of the reaction is as follows:

The conversion rate of glycerol is 99.35%; the product molar selectivity is: hydroxyacetone 81.60%, 1,2-propanediol 3.17%, acetaldehyde 0.50%, and other components (mainly acetic acid, dihydrofuran, dihydroxyfuran, glycerol acetate esters, etc.) 14.73%.

Example 12:

Weigh 14g copper nitrate trihydrate, 13g chromium nitrate nonahydrate, 4g α-alumina and 50g deionized water and mix them evenly in a beaker, stir at room temperature for 6 hours, remove the liquid and dry overnight at 120°C, and bake at 600°C for 6 hours , cooled to room temperature, and repeated the impregnation loading and roasting process twice to obtain a Cu-Cr/α-alumina catalyst with a CuO content of 42% and a Cr ₂ O ₃ content of 45%. Tablet granulation, screening of 20-30 mesh catalysts for use.

Reaction process condition is with embodiment 1. The result of the reaction is as follows:

The conversion rate of glycerol is 91.10%; the product molar selectivity is: hydroxyacetone 81.66%, 1,2-propanediol 1.93%, acetaldehyde 1.35%, and other components (mainly acetic acid, dihydrofuran, dihydroxyfuran, glycerol acetate esters, etc.) 15.06%.

Example 13:

Weigh 15g copper nitrate trihydrate, 14g chromium nitrate nonahydrate, 1.6g lanthanum nitrate hexahydrate; mix 4g silicon dioxide and 50g deionized water in a beaker, stir for 6 hours, remove the liquid and dry overnight at 120°C , roasted at 600°C for 6 hours, cooled to room _temperature , _{and repeated} the above impregnation loading and roasting process _twice to obtain a Cu-Cr- La/ _SiO2 catalyst. Tablet granulation, screening of 20-30 mesh catalysts for use.

Reaction technology is with embodiment 1. The result of the reaction is as follows:

Glycerol conversion rate is 99.84%; product selectivity is: hydroxyacetone 82.50%, 1,2-propanediol 1.02%, acetaldehyde 0.5% and other components (mainly acetic acid, dihydrofuran, dihydroxyfuran, glycerol acetate, etc. ) 15.98%.

Embodiment 14～16:

The preparation of the catalyst was as in Example 13, the reaction process was the same as in Example 1, the catalyst reduction time was 4 hours, and different reaction temperatures were used. The reaction results are shown in Table 2.

The reaction result of table 2 embodiment 14～16

^a : Refers to all other components including acetic acid, dihydrofuran, dihydroxyfuran, glycerol acetate, etc.

Embodiment 17～19:

The catalyst was prepared as in Example 13, and the reaction process was the same as in Example 16, using different LHSVs. The reaction results are shown in Table 4.

The reaction result of table 3 embodiment 17～19

^a : Refers to all other components including acetic acid, dihydrofuran, dihydroxyfuran, glycerol acetate, etc.

Embodiment 20～22:

The catalyst was prepared as in Example 13, and the reaction process was the same as in Example 18, using different concentrations of aqueous glycerol solutions. The reaction results are shown in Table 4.

The reaction result of table 4 embodiment 20～22

^a : Refers to all other components including acetic acid, dihydrofuran, dihydroxyfuran, glycerol acetate, etc.

Embodiment 23～25:

The catalyst was prepared as in Example 13, and the reaction process was the same as in Example 20, using different catalyst reduction temperatures. The reaction results are shown in Table 5.

The reaction result of table 5 embodiment 23～25

^a : Refers to all other components including acetic acid, dihydrofuran, dihydroxyfuran, glycerol acetate, etc.

Claims (10)

1. A catalyst for the selective dehydration of natural glycerol to prepare hydroxyacetone, which is composed of a low activity carrier and one or more active metal components, wherein the total content of the active metal in the form of its oxide is 20 -90 wt%, preferably 40-80 wt%. 2. A reaction process for preparing hydroxyacetone through selective dehydration of natural glycerin. 3. According to claim 1, the low activity carrier is selected from silica, alumina, amorphous silica alumina, magnesia, zirconia, titania or molecular sieve, among which silica is preferred. 4. According to claim 1, the active metal component in the catalyst is one of IA, IIA, IB-VIIIB groups and light rare earth elements, or two or more of these elements in any proportion random combination. 5. According to claims 1 and 4, the active metal component in the catalyst is one of IIA, IB, VIB, VIIIB and light rare earth elements, or one of IIA, IB, VIB, VIIIB and light rare earth elements Any combination of two in any proportion, or a combination of two or more of IIA, IB, VIB, VIIIB and light rare earth elements in any proportion. 6. According to claims 1, 4 and 5, the active metal component in the catalyst is a kind of IB group element, and the content of its oxide form in the catalyst accounts for 20-90wt%, or respectively from IB and A combination of one kind of VIB group elements, the content of its oxide form in the catalyst accounts for 20-50wt% and 0-50wt% respectively, or a combination of one kind of IB, VIB and light rare earth elements The content of the oxide form in the catalyst is respectively 20-50wt%, 0-50wt% and 0-30wt%. 7. According to claim 1, the catalyst adopts the impregnation loading method to mix the active metal salt solution and the carrier evenly, and stand or stir at room temperature for 1 to 12 hours, preferably 2 to 6 hours, then remove the liquid and dry at 80 to 120 Drying at a temperature of 50°C, and calcining the obtained solid material at a temperature of 400-650°C for 2-12 hours, preferably at a temperature of 500-600°C for 4-8 hours. 8. According to claims 1 and 2, the catalyst is used in the selective dehydration of natural glycerin to prepare hydroxyacetone in a fixed-bed flow reactor. The reaction conditions are: the concentration of glycerin is 10-100wt%, preferably 30-60wt%; the reaction pressure is normal pressure; the reaction temperature is 200-400°C, preferably 240-340°C; the liquid-hourly space velocity (LHSV) of the reaction system is 0.01- 0.60h ^-1 , preferably 0.10 to 0.30h ^-1 . 9. According to claims 1, 2 and 8, before the catalyst is used in the reaction of selective dehydration of natural glycerol to prepare hydroxyacetone, it is activated in situ with hydrogen in the reactor at a temperature of 100-500°C for 1-10 hours, It is preferably activated at a temperature of 200-400° C. for 2-5 hours. 10. According to claims 1-9, the catalyst is preferably supported by silica, with Cu, or Cu-Cr, or Cu-Cr-La as the active metal component. In the selective dehydration of natural glycerol to prepare hydroxyacetone, the conversion rate of glycerin can reach 99.89%, and the molar selectivity of hydroxyacetone can reach 89.74%.

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