CN103922893B - A kind of composite catalyst hydrogenolysis catalysis of glycerin prepares the method for 1,2-PD - Google Patents

Abstract

The invention discloses a method for preparing 1,2-propanediol by intermittent hydrogenolysis reaction of glycerol under the action of a bifunctional composite catalyst. It is characterized in that it is based on the dehydration-hydrogenation mechanism of glycerin hydrogenolysis, using acid-functional heteromulti-type ionic liquid [HMIM] ₃ PW ₁₂ O ₄₀ as the catalytic dehydration center, and the commercial RaneyNi as the catalytic hydrogenation center, coupled into a dual-functional composite catalyst. Preparation of 1,2-propanediol by hydrogenolysis of glycerol. Heteromultiple ionic liquid [HMIM] ₃ PW ₁₂ O ₄₀ is partially soluble in the reaction system under the reaction conditions, which increases the probability of activation of the acid center and the glycerol hydroxyl group, and precipitates from the system after the reaction and returns to a solid state. Simple separation from reactants with RaneyNi. The catalytic hydrogenolysis method has the advantages of simple catalyst preparation, low cost, no need for high-temperature reduction, environmental friendliness, etc., and provides an effective new way for the catalytic hydrogenolysis of glycerol.

Description

A kind of composite catalyst catalyzes the method for glycerin hydrogenolysis to prepare 1,2-propanediol

technical field

The invention relates to a method for catalyzing the hydrogenolysis of glycerol, specifically, a dual-functional composite catalyst formed by coupling acid-functionalized heteromulti-type ionic liquid [HMIM] ₃ PW ₁₂ O ₄₀ with commercial RaneyNi in a batch reactor A method for preparing 1,2-propanediol by hydrogenolysis of glycerol.

Background technique

With the rapid development of biodiesel worldwide, the application of a large amount of glycerol by-products has become the key to determining the economics of biodiesel; meanwhile, the demand for propylene glycol, a downstream product of glycerin, is also rising. Both 1,2-propanediol and 1,3-propanediol are widely used chemical raw materials, good solvents and antifreeze agents, among which 1,2-propanediol is an important raw material for unsaturated polyester, epoxy resin and polyurethane; 1,3 -Propylene glycol is a key precursor for the preparation of high-performance polyester PTT. The industrial production methods of propylene glycol products mostly use petroleum-based propylene oxide as raw materials, which requires large equipment investment, high technical difficulty, and complex catalytic systems. In response to the requirements of new synthesis methods for the development of propylene glycol products and the development needs of the biodiesel industry, the deep processing of glycerol hydrogenolysis has become a guarantee of competitive advantages in the oil industry and biodiesel industry and a research and development hotspot.

There are many reports on the preparation of 1,2-propanediol by the chemical method of glycerol, among which the research on the use of noble metals such as Ru, Rh, Pt, and Pd as catalysts is the main one. Such as: supported Ru/TiO ₂ catalyst prepared by impregnation method ([J]. Catalysis Journal, 2011, 32(9): 1545-1549), under the mild reaction conditions of 170°C and 3MPa, with LiOH as the additive , the conversion rate of glycerol and the selectivity of 1,2-propanediol reached 89.6% and 86.8%, respectively. Although these methods using noble metals as catalysts have high low-temperature hydrogenation activity, they are expensive and have little significance in reducing the cost of the biodiesel industry chain and increasing the added value of glycerin.

Compared with expensive noble metal catalysts, non-noble metals such as Cu, Ni, and Co have attracted more attention due to their low prices. Among them, Cu-based catalysts are suitable for the hydrogenolysis of glycerol to prepare 1,2- The mainstream of propylene glycol research: Low-pressurehydrogenolysisofglyceroltopropyleneglycol[J].AppliedCatalysisA:General,2005,281(1-2):225-231reported that Cu-Cr catalyst was used, and glycerol was hydrogenolyzed in two steps. 1. Under the condition of 80% glycerin aqueous solution, glycerin first generates acetol by dehydration, and then hydrogenates to obtain propylene glycol, and the yield of 1,2-propylene glycol reaches 73%, but the metal chromium used in this catalyst will cause environmental pollution. US5616817 adopts co-precipitation method to prepare multi-component catalytic hydrogenolysis of glycerol containing cobalt, copper, manganese and molybdenum to produce propylene glycol. In the process of preparing the catalyst, inorganic acid is added to improve the mechanical properties of the catalyst. Under the conditions of reaction temperature of 240-280°C and hydrogen pressure of 25-35MPa, the conversion rate of glycerin is close to 100%, and the selectivity of 1,2-propanediol can reach 95%. Under these conditions, the requirements for reaction pressure are relatively high. CN4302464A uses a multi-component supported catalyst composed of copper, chromium, barium, silicon and manganese to catalyze the hydrogenolysis of glycerol, and almost only produces 1,2-propanediol, but the preparation of the catalyst is relatively complicated.

Generally speaking, the noble metal and non-noble metal catalysts currently used in the hydrogenolysis of glycerol are usually prepared in the form of oxides, and often need to add various additives to improve the selectivity and stability of the reaction. The preparation of the catalyst is complicated and the reproducibility is poor. ; The oxide catalyst needs to be reduced in situ in the reaction process to obtain hydrogenation activity, which requires a higher reduction temperature and high energy consumption. Therefore, the development of a high-efficiency catalyst with simple preparation and low cost for the hydrogenolysis of glycerol to produce propylene glycol is a realistic demand for the development of the biodiesel industry and the deep processing of glycerin.

Contents of the invention

The present invention adopts acid-functionalized heteromulti-type ionic liquid [HMIM] ₃ PW ₁₂ O ₄₀ as the catalytic dehydration center, commercial RaneyNi as the catalytic hydrogenation center, coupled into a dual-functional composite catalyst, and hydrogenolyzes glycerin in a batch reactor to prepare 1,2-Propanediol. The method has the advantages of simple reaction steps in the hydrogenolysis process of glycerol, convenient post-treatment and the like.

The purpose of the present invention is to provide a method for preparing 1,2-propanediol by hydrogenolysis of glycerol, which is a low-cost, simple preparation, no high-temperature reduction, mild operating conditions and easy separation of bifunctional composite catalysts.

Technical scheme of the present invention is as follows:

The method for preparing 1,2-propanediol by the composite catalyst catalytic hydrogenolysis of glycerol described in the technical solution of the present invention is carried out in a batch-type autoclave reactor, and the raw material is glycerin aqueous solution:

In a 75mL stainless steel autoclave batch reactor, add 20g of 40% glycerol aqueous solution, and bifunctional composite catalyst [HMIM] ₃ PW ₁₂ O ₄₀ (0.2mmol)/RaneyNi (0.3g), replace the air with nitrogen three times, and then replace it with hydrogen After replacing the nitrogen three times, fill it with hydrogen until the initial test pressure is 6MPa, and heat to 230°C for 11 hours under magnetic stirring. After the reaction, the bifunctional composite catalyst is separated by centrifugal decantation and directly recycled.

The bifunctional composite catalyst [HMIM] ₃ PW ₁₂ O ₄₀ /RaneyNi described in the above-mentioned technical scheme, its preparation method is:

[HMIM] ₃ PW ₁₂ O ₄₀ /RaneyNi catalyst is prepared by precipitating [HMIM] ₃ PW ₁₂ O ₄₀ in aqueous solution, and then coupled with commercial RaneyNi by simple mixing. Among them, the preparation of acid-functionalized heteromulti-type ionic liquid [HMIM] ₃ PW ₁₂ O ₄₀ is to use phosphotungstic acid and N-methylimidazole as raw materials, and add three times the amount of N-methylimidazole dropwise under stirring at room temperature Add it to the aqueous solution of phosphotungstic acid, continue to react at room temperature for 24 hours after the dropwise addition, and filter, wash and dry to obtain [HMIM] ₃ PW ₁₂ O ₄₀ white solid. Mix [HMIM] ₃ PW ₁₂ O ₄₀ with commercial RaneyNi at a ratio of 0.15g RaneyNi/mmol [HMIM] ₃ PW ₁₂ O ₄₀ to obtain a bifunctional composite catalyst.

The composite catalyst described in the above technical scheme does not need to be activated and pretreated before use.

The preparation method of the bifunctional composite catalyst prepared by the present invention is simple, and the acid-functional heteromulti-type ionic liquid [HMIM] ₃ PW ₁₂ O ₄₀ with the performance of "high temperature dissolution, low temperature precipitation" in the reaction system is used as the catalytic dehydration center, and the activity is high The commodity RaneyNi, which is low in cost and does not require high temperature reduction, is a hydrogenation catalytic center and is prepared by a simple mixing method. It overcomes the disadvantages of using noble metal and non-noble metal oxide catalysts, such as high cost, complicated preparation and harsh use conditions. The catalyst shows good catalytic activity and stability in the hydrogenolysis of glycerol, the reaction conditions are relatively mild, the process is simple, and the product is easy to separate. It provides a new and effective way for the catalytic hydrogenolysis of glycerol to prepare 1,2-propanediol.

Specific implementation method

The method of the present invention will be further described below with regard to specific implementation examples.

Example 1

Catalyst preparation:

Add 14.4g (0.005mol) of phosphotungstic acid into a three-necked flask (100mL), transfer 15mL of deionized water to dissolve it completely, add 1.23g (0.015mol) of N-methylimidazole dropwise under magnetic stirring, and add dropwise within 30min After completion of the reaction at room temperature for 24 hours, suction filtration, washing and drying, the resulting white solid is [HMIM] ₃ PW ₁₂ O ₄₀ . Before the hydrogenolysis reaction, [HMIM] ₃ PW ₁₂ O ₄₀ and commercial RaneyNi were directly mixed into the reactor at a ratio of 0.15gRaneyNi/mmol [HMIM] ₃ PW ₁₂ O ₄₀ to obtain a bifunctional composite catalyst.

Glycerol hydrogenolysis reaction:

Using a 75mL batch autoclave reactor, add 20g of 40% glycerol aqueous solution and 0.2mmol

[HMIM] ₃ PW ₁₂ O ₄₀ /0.3g RaneyNi composite catalyst, replace the air with nitrogen three times, then replace the nitrogen with hydrogen three times, fill in hydrogen to the initial test pressure of 6MPa, and heat to 230°C for 11 hours under magnetic stirring.

After the reaction, the liquid mixture and the solid catalyst are simply separated by centrifugal decantation. The product mixture was sampled and analyzed by gas chromatography. The conversion rate of glycerol was 83.3%, and the selectivity of 1,2-propanediol was 57.3%. Propylene glycol is still up to 76.9% and 50.7% respectively.

Claims (1)

1. composite catalyst hydrogenolysis catalysis of glycerin prepares a method for 1,2-PD, it is characterized in that: adopt acid functionalization to mix multiclass ionic liquid [HMIM] ₃pW ₁₂o ₄₀as catalytic dehydration center, commodity RaneyNi is shortening center, is coupled into dual-function composite catalyst and prepares 1,2-PD for glycerine intermittent type hydrogenolysis;

Wherein said dual-function composite catalyst preparation method is: be added drop-wise in phosphotungstic acid aqueous solution by three times of amount of substance N-Methylimidazoles under stirring at room temperature condition, after dropwising rear continuation room temperature reaction 24h, suction filtration, washing, drying, obtain acid functionalization and to mix multiclass ionic liquid [HMIM] ₃pW ₁₂o ₄₀white solid, according to every mmole [HMIM] ₃pW ₁₂o ₄₀both mix by the ratio composite with 0.15g commodity RaneyNi, i.e. the dual-function composite catalyst of obtained hydrogenolysis of glycerin reaction, and this composite catalyst is before use without the need to activated pre-treatment;

Wherein said hydrogenolysis method is: adopt 75mL stainless steel autoclave batch reactor, add 40% aqueous glycerin solution of 20g, and by [HMIM] of 0.2mmol ₃pW ₁₂o ₄₀with the dual-function composite catalyst that the RaneyNi of 0.3g is re-dubbed, with nitrogen replacement air three times, use hydrogen exchange nitrogen again three times, being filled with hydrogen to preliminary examination pressure is 6MPa, 11h is reacted at being heated to 230 DEG C, after reaction terminates, the dual-function composite catalyst method of centrifugal decant is separated and direct reuse.