CN101353291B - Method for preparing 1,2-propanediol by catalytic hydrogenation of biodisel-based crude glycerine - Google Patents

Abstract

A method for preparing 1, 2-propylene glycol by directly adding hydrogen into glycerol comprises the steps as follows: biodiesel-based crude glycerol is taken as raw material, and intermittent one-step reaction is carried out on the biodiesel-based crude glycerol to prepare the 1, 2-propylene glycol at the temperature of 220 DEG C for 6-20 hours under the action of a solid alkali-metal catalyst. The conversion rate of the glycerol is up to 92%, and the yield of the 1, 2-propylene glycol is up to 87%. Compared with the existing preparation method for 1, 2-propylene glycol, the solid alkali-metal catalyst of the method can effectively avoid the influences of alkali impurities in the biodiesel-based crude glycerol solution; and the method has the advantages of simple process, high yield, low cost, little environmental pollution and simple separation.

Description

Method for preparing 1,2-propanediol by catalytic hydrogenation of biodiesel-based crude glycerol

Technical field:

The invention relates to a reaction process and a catalyst for preparing 1,2-propanediol by direct catalytic hydrogenation using biodiesel-based crude glycerin as a raw material under the action of a metal catalyst supported by a solid base.

Background technique:

1,2-Propylene glycol (1,2-PDO for short) is a colorless, viscous, stable water-absorbing liquid, basically tasteless and odorless, flammable, with a melting point of -60°C. Boiling point 187.3°C, relative density 1.036 (25/4°C), miscible with water, ethanol and various organic solvents. It is easily oxidized above 150°C. 1,2-propanediol is an important raw material for unsaturated polyester, epoxy resin, polyurethane resin, and this unsaturated polyester is widely used in surface coatings and reinforced plastics. 1,2-propanediol has good viscosity and hygroscopicity, and is non-toxic, so it is widely used as a hygroscopic agent, antifreeze, lubricant and solvent in the food, pharmaceutical and cosmetic industries. In the food industry, propylene glycol reacts with fatty acids to form propylene glycol fatty acid esters, which are mainly used as food emulsifiers; propylene glycol is an excellent solvent for seasonings and pigments. 1,2-Propanediol is commonly used as a solvent, softener and excipient in the manufacture of various ointments and ointments in the pharmaceutical industry. Because propylene glycol has good miscibility with various spices, it is also used as a solvent and softener for cosmetics. agent and so on. Propylene glycol is also used as a tobacco moisturizer, anti-mold agent, lubricant for food processing equipment, and a solvent for food marking inks. Aqueous solutions of propylene glycol are effective antifreeze agents.

At present, there are three main production methods of 1,2-propylene glycol: (1) direct hydration of propylene oxide, which is a pressurized non-catalytic hydrolysis method; It can be obtained by direct hydration, and the reaction product can be obtained by evaporation and rectification. (2) Propylene oxide indirect hydration method is obtained by indirect hydration of propylene oxide and water with sulfuric acid as a catalyst. (3) Direct catalytic oxidation of propylene. These methods have problems such as serious environmental pollution and high cost, and are difficult to produce on a large scale. At the same time, due to the rapid rise in the price of petrochemical raw materials such as propylene, the cost of the above-mentioned production process is also getting higher and higher. Therefore, research and development of low-cost, high-efficiency, and environmentally friendly heterogeneous catalytic glycerol direct catalytic hydrogenation to prepare 1,2-propanediol method is of great significance.

There have been some patent reports on the preparation of 1,2-propanediol from glycerol, such as: German patent DE-PS-541362 first reported the method of hydrogenating glycerol under the action of a nickel-based catalyst to prepare 1,2-propanediol, but the reaction needs to be carried out at a high temperature. (more than 270 degrees) can be carried out at a certain temperature, and a large amount of gas products are generated (mainly methane) in the reaction simultaneously, so the waste of raw materials is serious and the yield of the target product is not high. European Patent EP-A-72629 describes a hydrogenation process of polyols under the action of nickel, platinum, and palladium catalysts (glycerol is also included in the middle). In order to obtain the corresponding diols, an inorganic base must be added to the reaction solution. This process was also adopted by many later research papers (Journal of Catalysis 249 (2007) 328-337 and Catalysis Letters 117 (2007) 62-67), but the pollution is large and the product separation is difficult. U.S. Patent No. 4,642,394 describes a method for preparing propylene glycol by reacting glycerin with synthesis gas under the action of a homogeneous catalyst containing tungsten and Group VIII elements. When using rhodium carbonyl acetylacetonate and H ₂ WO ₄ acid as catalyst, 1-methyl- 2-Pyrrolidone is used as a solvent, the reaction temperature is 200 degrees, the synthesis gas (CO:H ₂ =1:2) pressure is 4600 psig, and the reaction time is 24 hours, the yield of propylene glycol is 44%, and the yield of n-propanol is 4%. The efficiency is low, the reaction pressure is high, and the homogeneous catalyst is difficult to separate and recover, and the metal rhodium catalyst is expensive, etc., so that the economy is poor and there is no competitiveness. US Patent No. 5,214,219 reports a method for producing 1,2-propanediol from glycerol, which uses a bimetallic supported catalyst of Cu and Zn. However, the reaction temperature is higher than 250° C., the hydrogen pressure is above 150 atmospheric pressure, and the consumption of the catalyst is higher (5-15% of the glycerol concentration), and the glycerol concentration is low (20-40%), so it is difficult to realize industrialization. U.S. Patent No. 5,276,181 provides a method for preparing 1,2-propanediol by hydrogenation of glycerol with sulfide and alkali-modified Ru/activated carbon as a catalyst. %, the selectivity of propylene glycol is still very low. U.S. Patent US5616817 and Chinese Patent CN1061968C have reported the method for preparing 1,2-propylene glycol by hydrogenation of glycerol on Co-Cu-Mn-Mo catalyst, but the reaction pressure is particularly high (250 atmospheric pressure), and the preparation method of catalyst is complicated and the equipment investment is high , The selectivity of 1,2-propanediol is very low. Chinese invention patent application CN200610105255.X discloses a method for preparing 1,2-propanediol by hydrogenation of glycerol. The method uses a CuO- _SiO2 catalyst prepared by an alcohol thermal method, but the reaction is carried out in a highly toxic methanol solvent. Chinese invention patent application CN101085719 discloses a process for preparing 1,2-propanediol by direct hydrogenation of glycerol under the action of a multi-component composite Co-Cu-Al catalyst, but the temperature required for the reaction is above 220 degrees and the reaction pressure Above 100 atmospheric pressure, the amount of catalyst is large (the amount of catalyst accounts for more than 2% of the reaction liquid). In recent years, with the rapid development of the biodiesel industry, the output of glycerol as the main by-product in the biodiesel production process will increase year by year; it is estimated that by 2010, the output of biodiesel-based crude glycerol will exceed 1.2 million tons, surplus 500,000 tons. Therefore, the production of high value-added propylene glycol from biodiesel-based crude glycerol is an important way to solve the problem of excess glycerin, and it is of great significance to promote the healthy development of biodiesel and biomass energy industries.

Although the above-mentioned series of invention patents have all reported the process of synthesizing 1,2-propanediol from glycerol, the ubiquitous problems are: high reaction temperature (generally above 220 degrees), high reaction pressure (generally above 100 atmospheric pressure); The specific characteristics of biodiesel-based crude glycerin are not fully considered, that is: the general content of biodiesel-based crude glycerin is 80-85% of glycerol, and the raw material often also contains a small amount of catalyst for biodiesel production (such as alkali (NaOH , Ca(OH) ₂ and NaH ₂ PO ₄ , etc.), residual biodiesel production raw materials and components (such as: methanol, methyl glycerol alkylate), these impurities are also involved in the previously published patents; Among them, inorganic bases have a poisonous effect on most solid acid catalysts with dehydration activity.

Contents of the invention

The purpose of the present invention is to provide a biodiesel-based crude glycerol that can directly use biological A method for preparing 1,2-propanediol in a batch-type one-step reaction under the action of a metal catalyst loaded on an alkaline carrier as a raw material with diesel-based crude glycerol has the advantages of simple process, low reaction temperature, high yield, low cost, and less environmental pollution , The advantages of simple separation.

The solution of the present invention is to use a solid alkali-metal catalyst to eliminate and get rid of the influence of a small amount of alkaline impurities in biodiesel-based crude glycerol, and to realize the hydrogenation of glycerol with different concentrations in an autoclave to prepare 1,2-propanediol in one step.

The method for directly preparing 1,2-propanediol by catalytic hydrogenation of biodiesel-based crude glycerol according to the present invention is to use unpurified biodiesel-based crude glycerol as raw material, and the reducing agent is high-purity hydrogen in a solid alkali-metal catalyst Under the action, catalytic hydrogenolysis of biodiesel-based crude glycerol is obtained to obtain high-yield 1,2-propanediol. The preparation steps are as follows:

1. Add a biodiesel-based crude glycerin solution with a glycerin mass concentration of 15%-90% into a stainless steel high-pressure reactor with a lining, and then add a certain amount of catalyst to the biodiesel-based crude glycerin solution to control the catalyst The ratio of the mass of the metal to the glycerin mass is 1/100-1/10000.

2. After sealing the above reaction kettle, replace the air in the reaction kettle with hydrogen, and then fill it with hydrogen to 30 atmospheres.

3. Heat up the temperature to make the temperature in the reactor reach 180-260°C, start the agitator at the same time, and react for 6-20 hours.

4. After the reaction is finished, cool the reactor to room temperature, centrifuge first, and then filter under reduced pressure to separate the reaction product solution from the catalyst and recover the catalyst.

5. After the catalyst is separated by filtration, the reaction solution is constant volume and analyzed by gas chromatography.

The solid alkali-metal catalyst of the present invention, carrier comprises: hydrotalcite, magnesia, aluminum oxide, Beta molecular sieve, HZSM5 molecular sieve, zirconia or cerium oxide; Metal active component comprises: platinum, palladium, ruthenium, gold Or nickel, the loading amount of the metal is: 1-10wt%. Preferred catalyst supports are hydrotalcite and magnesia. Preferred active metals are platinum and ruthenium.

The preparation steps of solid alkali-metal catalyst of the present invention are as follows:

(1) Pretreat hydrotalcite, magnesium oxide, aluminum oxide, Beta molecular sieve, HZSM5 molecular sieve, zirconia or ceria carrier at 400-550°C for 4 hours;

(2) Loading the metal on the carrier by an equal volume impregnation method, impregnating the pretreated carrier to support the metal active component, controlling the loading of the metal to 1-10 wt%, and impregnating at room temperature for 12 hours;

(3) The above metal-loaded carrier was dried in an oven at 110° C. for 12 hours, and then calcined at 400-550° C. for 4 hours to obtain a solid alkali-metal catalyst.

In the preparation of the solid alkali-metal catalyst of the present invention, the carrier hydrotalcite is pretreated at 400° C. for 4 hours, and other carriers are pretreated at 550° C. for 4 hours.

In the preparation of the solid alkali-metal catalyst of the present invention, the loading of ruthenium, gold and palladium is 2wt%, the loading of nickel is 10wt%, and the loading of platinum is 1wt%, 2wt% and 5wt%.

In the preparation of the solid alkali-metal catalyst of the present invention, the metal catalyst supported by hydrotalcite is calcined at 400°C for 4 hours; the metal catalysts supported by other carriers are calcined at 550°C for 4 hours.

The solid alkali-metal catalyst of the present invention is reduced in a hydrogen flow at a certain temperature for 2 hours before the reaction.

Advantages of the present invention:

Biodiesel-based crude glycerol catalytic hydrogenation of the present invention directly prepares the method for 1,2-propanediol, is to be raw material with unpurified biodiesel-based crude glycerol, contains a small amount of catalyst produced by biodiesel in this raw material ( Such as alkali: NaOH, Ca(OH) ₂ , NaH ₂ PO ₄ ), residual biodiesel components (such as: methanol, methyl glycerol alkylate, sodium C14-C18 alkylate, etc.), the embodiment of the present invention The composition of the representative crude glycerol is: glycerol 85.1% (percentage by weight, the same below), C14-C17 methyl alkanoate 8.3%, methanol 3.3%, water 2.8%, C14-C17 sodium alkanoate 0.4%, NaOH+ Ca(OH) ₂ 0.1%.

Compared with the existing method for preparing 1,2-propanediol, the solid alkali-metal catalyst of the present invention can effectively overcome the influence of alkaline impurities in the biodiesel-based crude glycerol solution, and this catalyst not only has high activity, but also The purity requirements for raw materials are low. The method has the advantages of simple process, high yield, low cost, less environmental pollution and simple separation.

The catalyst used in the invention has a low dosage, and the mass ratio of glycerin/metal in the reaction system is greater than 100.

The reaction conditions of the present invention are mild, the reaction pressure is low (the initial hydrogen pressure is lower than 30 atmospheric pressure), and the reaction temperature is lower than 230 degrees. The highest conversion rate of glycerol can reach 92%, and the yield of 1,2-propanediol can reach 87%. Under the action of Pt/hydrotalcite catalyst, the conversion rate of glycerol reaches the highest 92%, and the yield of 1,2-propanediol reaches 87%; under the action of Pt/MgO catalyst, the conversion rate of glycerin reaches 50%, 1, The yield of 2-propanediol reached 40%.

The process of the present invention provides a novel approach for the industrial production of 1,2-propanediol, using a solid base as a carrier and supporting Pt, Ru, Ni, Au, Pd and other metals to catalyze the hydrogenolysis of glycerol to produce 1,2- Propylene glycol, abandoning the problems of low yield, high cost and environmental pollution in the past industrial production of 1,2-propanediol.

Detailed ways:

Example 1

Accurately measure 20 grams of biodiesel-based crude glycerol with a glycerol content of 85.1% and put it into an autoclave, add 2.0 grams of reduced Pt/MgO catalyst (Pt loading is 2wt%), and replace the reactor with hydrogen after sealing The air inside is filled with 3.0MPa hydrogen. Heating and starting stirring at the same time, controlling the temperature in the reaction kettle to 220° C., and reacting for 20 hours. After the reaction was finished, the reactor was cooled to room temperature, centrifuged first, then vacuum filtered the reaction solution to separate the reaction product solution from the catalyst, and the reaction solution was analyzed by gas chromatography, and the conversion rate of glycerol was calculated to be 50% and 1, The molar yield of 2-propanediol was 40%.

Example 2

Accurately measure 20 grams of biodiesel-based crude glycerol with a glycerol content of 85.1% and put it into an autoclave, add 2.0 grams of reduced Pt/MgO catalyst (Pt loading is 2wt%), and replace the reactor with hydrogen after sealing The air inside is filled with 3.0MPa hydrogen. Heating while starting stirring, controlling the reaction temperature to 250° C., and reacting for 20 hours. The final analysis showed that the conversion rate of glycerin was 92%, and the molar yield of 1,2-propanediol was 67%.

Example 3

Accurately measure 20 grams of biodiesel-based crude glycerol with a glycerin content of 85.1% and put it into an autoclave, add 2.0 grams of reduced Pt/hydrotalcite catalyst (Pt loading is 2wt%), and replace the reaction with hydrogen after sealing The air in the kettle is then filled with 3.0MPa hydrogen. Heating and starting stirring at the same time, controlling the reaction temperature to 220° C., and reacting for 20 hours. The final analysis shows that the conversion rate of glycerin is 92%, and the molar yield of 1,2-propanediol is 87%.

Example 4

Accurately measure 20 grams of biodiesel-based crude glycerol with a glycerol content of 85.1% and put it into an autoclave, and add 2.0 grams of reduced Pt/Al ₂ O ₃ catalyst (Pt loading is 2 wt%). After sealing, replace the air in the reactor with hydrogen, and then fill it with 3.0MPa hydrogen. Heating and starting stirring at the same time, controlling the reaction temperature to 220° C., and reacting for 20 hours. Finally, the conversion rate of glycerin was 50%, and the molar yield of 1,2-propanediol was 41%.

Example 5

Accurately measure 20 grams of biodiesel-based crude glycerol with a glycerol content of 85.1% and put it into an autoclave, and add 2.0 grams of reduced Pt/Beta molecular sieve catalyst (Pt loading is 2 wt%). After sealing, replace the air in the reactor with hydrogen, and then fill it with 3.0MPa hydrogen. Heating and starting stirring at the same time, controlling the reaction temperature to 220° C., and reacting for 20 hours. Finally, the conversion rate of glycerol was 6.9%, and the yield of 1,2-propanediol was 0.61%.

Example 6

Accurately measure 20 grams of biodiesel-based crude glycerol with a glycerol content of 85.1% and put it into an autoclave, and add 2.0 grams of reduced Pt/HZSM5 molecular sieve catalyst (Pt loading is 2 wt%). After sealing, replace the air in the reactor with hydrogen, and then fill it with 3.0MPa hydrogen. Heating and starting stirring at the same time, controlling the reaction temperature to 220° C., and reacting for 20 hours. Finally, the conversion rate of glycerol was 4.0%, and the yield of 1,2-propanediol was 0.76%.

Example 7

Accurately measure 20 grams of biodiesel-based crude glycerol with a glycerol content of 85.1% and put it into an autoclave, and add 2.0 grams of reduced Ni/MgO catalyst (Ni loading is 10 wt%). After sealing, replace the air in the reactor with hydrogen, and then fill it with 3.0MPa hydrogen. Heating and starting stirring at the same time, controlling the reaction temperature to 220° C., and reacting for 20 hours. The final analysis showed that the conversion rate of glycerin was 32%, and the yield of 1,2-propanediol was 25.3%.

Example 8

Accurately measure 20 grams of biodiesel-based crude glycerol with a glycerol content of 85.1% and put it into an autoclave, and add 2.0 grams of reduced Au/MgO as a catalyst (Au loading is 2 wt%). After sealing, replace the air in the reactor with hydrogen, and then fill it with 3.0MPa hydrogen. Heating and starting stirring at the same time, controlling the reaction temperature to 220° C., and reacting for 20 hours. The final analysis shows that the conversion rate of glycerol is 3.7%, and the yield of 1,2-propanediol is 2.8%.

Example 9

Accurately measure 20 grams of biodiesel-based crude glycerol with a glycerol content of 85.1% and put it into an autoclave, and add 2.0 grams of reduced Ru/MgO catalyst (Ru loading is 2 wt%). After sealing, replace the air in the reactor with hydrogen, and then fill it with 3.0MPa hydrogen. Heating and starting stirring at the same time, controlling the reaction temperature to 220° C., and reacting for 20 hours. The final analysis shows that the conversion rate of glycerin is 61%, and the yield of 1,2-propanediol is 50%.

Example 10

Accurately measure 20 grams of biodiesel-based crude glycerin with a glycerin content of 85.1% and put it into an autoclave, add 2.0 grams of reduced Pt/hydrotalcite catalyst (Pt loading is 1wt%), and replace the reaction with hydrogen after sealing The air in the kettle is then filled with 3.0MPa hydrogen. Heating and starting stirring at the same time, controlling the reaction temperature to 220° C., and reacting for 20 hours. The final analysis shows that the conversion rate of glycerol is 33%, and the molar yield of 1,2-propanediol reaches 30%.

Example 11

Accurately measure 20 grams of biodiesel-based crude glycerin with a glycerol content of 85.1% and put it into an autoclave, add 2.0 grams of reduced Pt/hydrotalcite catalyst (Pt loading is 5wt%), and replace the reaction with hydrogen after sealing The air in the kettle is then filled with 3.0MPa hydrogen. Heating while starting stirring, controlling the reaction temperature to 220° C., and reacting for 6 hours. The final analysis shows that the conversion rate of glycerin is 81.7%, and the molar yield of 1,2-propanediol reaches 73.5%.

Example 12

Accurately measure 20 grams of biodiesel-based crude glycerol with a glycerin content of 85.1% and put it into an autoclave, add 2.0 grams of reduced Pd/MgO catalyst (Pd loading is 2wt%), and replace the reactor with hydrogen after sealing The air inside is filled with 3.0MPa hydrogen. Heating and starting stirring at the same time, controlling the reaction temperature to 220° C., and reacting for 20 hours. The final analysis shows that the conversion rate of glycerin is 4%, and the molar yield of 1,2-propanediol reaches 3.6%.

Example 13

The implementation steps and catalyst are the same as in Example 3, the reaction time is changed to 12h, the final conversion rate of glycerin is 87.6%, and the yield of 1,2-propanediol is 82.6%.

Claims (4)

1. a biodiesel base crude glycerine shortening directly prepares 1; The method of 2-Ucar 35; It is characterized in that: with the biodiesel base crude glycerine raw material, under the effect of Natural manganese dioxide, hydrotalcite, aluminium sesquioxide, Beta molecular sieve, HZSM5 molecular sieve or silicon dioxide carried metal catalyst, intermittent type single step reaction preparation 1; The 2-Ucar 35, preparation process is following:

1). with qualities of glycerin concentration is the biodiesel base crude glycerine solution of 15%-90%; Join in the stainless steel autoclave that has liner; In biodiesel base crude glycerine solution, add catalyzer then, the quality of the metal in the control catalyst is that the ratio of qualities of glycerin is 1/100-1/10000;

2). after the aforesaid reaction vessel sealing, fall the air in the reaction kettle, charge into hydrogen to 30 normal atmosphere then with hydrogen exchange;

3). heat temperature raising, make the temperature in the reaction kettle reach 180-260 ℃, agitator was reacted 6-20 hour simultaneously;

4). after reaction finished, with the reaction kettle cool to room temperature, first spinning, decompress filter again made reaction product solution and catalyst separating, catalyst recovery.

Described catalyzer is: Pt/MgO catalyzer, Pt/ hydrotalcite catalyst, Pt/Al ₂O ₃Catalyzer, Pt/Beta sieve catalyst, Pt/HZSM5 sieve catalyst, Ni/MgO catalyzer, Au/MgO are catalyzer, Ru/MgO catalyzer, Pd/MgO catalyzer.

2. according to the said preparation 1 of claim 1, the method for 2-Ucar 35 is characterized in that: the catalyzer that is adopted, and carrier comprises: hydrotalcite, Natural manganese dioxide, aluminium sesquioxide, Beta molecular sieve, HZSM5 molecular sieve; Metal active constituent comprises: platinum, palladium, ruthenium, gold or nickel; The charge capacity of metal is: 1～10wt%.

3. according to the direct hydrogenation preparing 1 of the said glycerine warp of claim 2, the method for 2-Ucar 35 is characterized in that: support of the catalyst is hydrotalcite or Natural manganese dioxide.

4. glycerine according to claim 2 is through direct hydrogenation preparing 1, and the method for 2-Ucar 35 is characterized in that: metal active constituent is platinum or ruthenium.