CN103361101A - Catalytic conversion method for obtaining long-chain alkane from glycerin - Google Patents

Abstract

The invention relates to a method for catalytic conversion of medium and long chain alkanes through hydrogenolysis of glycerol molecules under acidic conditions and condensation between molecules. Mixing glycerin and inorganic acid aqueous solution to obtain a mixed solution, the molar ratio of glycerin and inorganic acid is 1 to 2; adding a catalytic amount of catalyst to the mixed solution, and reacting at a temperature of 120 to 350°C and a pressure of hydrogen to obtain A liquid fuel mainly composed of medium and long-chain alkanes with 6 to 24 carbon atoms. The composition of this liquid fuel is similar to that of fuel oil synthesized by Fischer-Tropsch, but the composition range is much narrower. The invention not only helps to solve the conversion problem of glycerol produced in the biodiesel production process, but also provides an effective way to synthesize fuel oil from renewable raw materials. The catalyst is composed of a main catalyst metal (Ir or Rh) and a promoter metal (one or any two selected from Re, W, Mo) supported on a carrier.

Description

A method for the catalytic conversion of medium and long chain alkanes obtained from glycerol

technical field

The invention relates to a method for catalytic conversion of medium and long chain alkanes through hydrogenolysis of glycerol molecules under acidic conditions and condensation between molecules.

Background technique

Energy is divided into non-renewable energy and renewable energy. Non-renewable energy sources include coal, oil and natural gas. Renewable energy includes water energy, wind energy, solar energy, tidal energy, wave energy, geothermal energy, ocean thermal energy, hydrogen energy, nuclear energy, and bioenergy. In 2007, the world's coal production was 6.5×10 ⁹ t, while the world's coal production was 9.09×10 ¹¹ t, that is to say, if this rate is followed, the coal will only last for 140 years. Coal power plants emit a large amount of pollution every year: 1.1×10 ⁷ t carbon dioxide, 3×10 ⁴ t nitrogen oxides, 1.6×10 ⁴ t sulfur dioxide, 1×10 ³ t dust and other small amounts of calcium, potassium, titanium and arsenic and other chemicals. With the current oil production rate, the world's oil can only be used for 50 years at most. In 1996, the reserves of natural gas in the world were 1.412×10 ¹⁵ m ³ , which could only be used for more than 60 years. Therefore, it is necessary and urgent to vigorously develop renewable energy.

Renewable energy such as hydropower, wind energy, solar energy, tidal energy, ocean wave energy, geothermal energy, and ocean thermal energy are greatly affected by the geographical environment, and their efficiency is not high. In principle, hydrogen energy cannot be used as an energy source, because hydrogen is electrolyzed from water, and a lot of energy is needed in this process, and the energy released by hydrogen combustion cannot make up for the energy in the electrolysis process. Therefore, it is very unrealistic to rely solely on these energies to replace the above fossil energy sources. The most promising ones should be nuclear energy and bioenergy. Bioenergy is generally divided into two categories - first-generation bioenergy and second-generation bioenergy. The first generation of bioenergy (such as bioethanol and biodiesel) evolved from carbohydrates and vegetable oils; the second generation of bioenergy evolved from biomass (including wood, straw, grass, etc.). The development of the first generation of bio-energy has been relatively mature, and now, the production of biodiesel by transesterification of vegetable oil has been greatly developed. However, a large amount of glycerol by-products will be produced in the process of biodiesel production, so there are a lot of research work around glycerin conversion, and the typical one is to obtain propylene glycol from glycerin, such as L.Ma[L.Ma et al.Catalysis Communications, 2008, 9: 2489-2495] and the scheme proposed by Yoshinao Nakagawa [Yoshinao Nakagawa et al, Journal of Catalysis, 2010, 272: 191-194], and obtain acrolein by glycerol, such as Okuno Zhengzhao et al. (CN101426754A) and The scheme proposed by Kondo Kenyuki et al. (CN 101619019A).

The present invention is a new reaction system, in which glycerin can be converted into oily substances mainly composed of medium and long chain alkanes (6-24 carbon atoms). Since the present invention directly converts glycerol into the final product in one step, the conversion method of the present invention has great advantages, and it is expected to alleviate the energy crisis in the future to a certain extent.

Contents of the invention

The object of the present invention is to provide a method for catalytic conversion of medium and long chain alkanes through hydrogenolysis of glycerol molecules under acidic conditions and condensation between molecules.

The method for catalytic conversion of medium and long chain alkanes obtained from glycerol of the present invention can prepare oily matter mainly composed of medium and long chain alkanes (6-24 carbon atoms). There is no special requirement on the carrier used in the present invention, but the carrier with larger specific surface area tends to have better effect. The invention adopts an equal-volume impregnation method to load metals, and the metals used include Ir, Rh, Re, W and Mo. The inorganic acid used in the present invention may be sulfuric acid or phosphoric acid. The inorganic acid must have a certain concentration, preferably 5-50 wt% (preferably 25-40 wt%). The hydrogen pressure used in the present invention has no upper limit, but is preferably 4 to 15 MPa, more preferably 6 to 10 MPa. The temperature used in the present invention is 120-350°C, preferably 150-250°C. The reaction time required in the present invention is preferably 48 to 72 hours. The present invention has also found such a rule that the higher the concentration of the acid, the higher the conversion rate of glycerol (in the same time), and the obtained medium and long-chain alkanes are as long-chain (16 to 24 carbon atoms) alkanes mostly.

The method for the catalytic conversion of medium and long-chain alkanes obtained from glycerol in the present invention is as follows: mixing glycerin with an aqueous solution of an inorganic acid with a concentration of 5 to 50 wt% (preferably 25 to 40 wt%) to obtain a mixed solution, wherein: glycerin and the inorganic acid The molar ratio is 1～2; Then add the catalyzer of catalytic amount in the mixed solution, stir (the described stirring is to utilize magnetic stirrer, and the rotating speed of described magnetic stirrer is generally about 1000rpm/min), at a temperature of Under 120～350 ℃ (preferably 150～250 ℃) and the pressure of hydrogen (preferably 4～15MPa, more preferably 6～10MPa), carry out reaction (the time of reaction is preferably 48～72 hours), obtain carbon atom number 6 to 24 medium and long chain alkanes.

The catalyst is composed of a main catalyst metal and a catalytic promoter metal loaded on a carrier, wherein the loading amount of the main catalyst metal is 1 to 3 wt% of the weight of the carrier; the ratio of the main catalyst metal and the promoter metal is The mass ratio of the substances is 0.5-5.

The main catalyst metal may be Ir or Rh, and the promoter metal may be selected from one or any two of Re, W and Mo.

Described inorganic acid is sulfuric acid or phosphoric acid.

Described catalyst is prepared by following method:

Mix 0.012～0.024g of the precursor of the main catalyst metal (H ₂ IrCl ₆ or RhCl ₃ ) and 0.01～0.036g of the precursor of the promoter metal (selected from KReO ₄ , ammonium molybdate trihydrate, phosphotungstic acid One or any two) are dissolved in 5ml of deionized water and 0.4g of carrier (such as smoke SiO ₂ or molecular sieve ZSM-5, etc.) is added, heated and stirred until the carrier becomes dry (generally, the heating temperature is 60°C) to obtain a catalyst Precursor, and then put the obtained catalyst precursor into an oven for further drying (generally baked at 60°C for 24 hours); put the dried catalyst precursor into a tube furnace at a heating rate of 2°C/ Min, raise the temperature of the tube furnace from room temperature to 300-500°C for calcination (the general calcination time is about 3 hours); add the catalyst precursor obtained after calcination and 5ml deionized water together to a magnetic In the autoclave with stirring bar, stir (the speed of the magnetic stirring bar is generally about 1000rpm/min); replace the air in the autoclave with hydrogen, and then carry out the reaction at a hydrogen pressure of 6-10MPa and a temperature of 180-300°C (the general reaction time is about 6 hours), cooling to obtain the catalyst.

When loading metals, the carrier is generally heated (preferably at about 100°C) to remove water and air adsorbed by the carrier. The main catalyst metal can be Ir or Rh, and the loading amount of the metal is (1-3)wt%; the promoter metal can be one or any two of Re, W and Mo. The precursor of the main catalyst metal and the precursor of the co-catalyst metal are dissolved with an appropriate amount of deionized water. The amount of water added should not be too much and the volume of the carrier is almost the same, and then the carrier is poured into the solution of metal ions, and stirred quickly. Until the carrier becomes dry, the obtained slurry is further dried in an oven (generally at 60° C. for 24 hours). The dried catalyst precursor was placed in a tube furnace, and the temperature of the tube furnace was raised from room temperature to 300-500° C. for calcination for 3 hours at a rate of 2° C./min. Then the calcined catalyst is reduced in an autoclave, the magnetic stirrer rotates at about 1000rpm, the hydrogen pressure is 6-10MPa, the reduction temperature is 180-300°C, and the reduction time is generally about 6 hours. In order to prevent the reduced metal from being oxidized again, an appropriate amount of water can be added to the autoclave. The reduced metals are directly subjected to the next step of glycerol conversion reaction, and an appropriate amount of glycerin mixture is added to the autoclave, wherein the glycerol mixture is an aqueous solution of glycerin and inorganic acid.

The invention not only helps to solve the conversion problem of glycerol produced in the biodiesel production process, but also provides an effective way to synthesize fuel oil from renewable raw materials. Has the following advantages:

1. The method of the present invention is simple, does not have complicated process, no matter it is the preparation of catalyst, or follow-up reaction is all relatively simple, is suitable for the needs of industrial production;

2. the liquid fuel based on medium and long-chain alkanes with carbon number of 6 to 24 obtained by the present invention is similar to the composition of the fuel oil synthesized by Fischer-Tropsch, but the component range is much narrower, and this fuel oil product can Help to alleviate the current energy crisis, long-chain alkanes oil can be used as fuel for diesel engines;

3. The reaction conditions of the present invention are relatively moderate, and the medium for glycerin conversion is water, so the requirements for equipment are not too high, which is conducive to cost reduction.

Detailed ways

In order to better understand the present invention, the content of the present invention will be further clarified below in conjunction with specific examples, but the present invention should not be regarded as only limited to the following examples.

Example 1

(1). Preparation of the mixture of glycerin and sulfuric acid

Take a 500ml Erlenmeyer flask with a stopper, add 176ml of deionized water, 100ml of 98wt% H ₂ SO ₄ and 134ml of glycerol in sequence.

(2). Preparation of catalyst

Dissolve 0.012g of H ₂ IrCl ₆ and 0.018g of KReO ₄ in 5ml of deionized water (need to be heated), then add 0.4g of fume SiO ₂ carrier, and stir at a temperature of 60°C until the carrier becomes dry to obtain the pre-catalyst body, and then put the obtained catalyst precursor into an oven at 60°C for further drying for 24 hours; put the dried catalyst precursor into a tube furnace, and make the tube furnace The temperature was raised from room temperature to 400°C for calcination for 3 hours; the catalyst precursor obtained after the calcination and 5ml of deionized water were added together in a 100ml autoclave equipped with a magnetic stirrer (equipped with a magnetic stirrer), and stirred (the rotating speed of magnetic stirrer is about 1000rpm/min); H with 1MPa Replace the air in the autoclave three times, then react at 7MPa hydrogen pressure and temperature at 200°C for 6 hours, _then cool rapidly to obtain the catalyst.

(3). Autoclave reaction

Add 10ml of the mixture of glycerin and sulfuric acid obtained in step (1) into the autoclave of step (2), stir with a magnetic stirrer with a rotation speed of about 1000rpm/min, and replace the air in the autoclave with _H2 for three times , and then filled with 6MPa H ₂ , and reacted for 72 hours at a temperature of 200°C to obtain a liquid fuel mainly composed of medium and long-chain alkanes with 6 to 24 carbon atoms.

Product analysis

The medium and long chain alkane products with 6-24 carbon atoms in the oil layer were analyzed by GC-MS, and the product-to-alkane distribution was 54.2% for C ₆ , 31.7% for C ₇ -C ₉ , and 14.1% for C ₁₀ -C ₂₀ . The conversion of glycerol in the aqueous phase was 99.5%.

Basically the same method as above was used, except that the contents of H ₂ IrCl ₆ and KReO ₄ in the catalyst were different, and the product obtained was analyzed by the above product analysis method.

Table 1

Example 2

(1) Preparation of a mixture of glycerol and sulfuric acid

Take a 500ml Erlenmeyer flask with a stopper, add 176ml of deionized water, 100ml of 98wt% H ₂ SO ₄ and 134ml of glycerol in sequence.

(2). Preparation of catalyst

Dissolve 0.012g of _RhCl3 and 0.018g of _KReO4 in 5ml of deionized water (requires heating), then add 0.4g of smoke _SiO2 carrier, stir quickly until the carrier becomes dry to obtain a catalyst precursor, and then add the obtained catalyst The precursor was further dried in an oven at 60°C for 24 hours; the dried catalyst precursor was placed in a tube furnace, and the temperature of the tube furnace was raised from room temperature to Carry out calcining at 400 ℃ for 3 hours; The catalyst precursor obtained after calcining and 5ml deionized water are joined together in the autoclave (equipped with magnetic stirring bar) of 100ml that is loaded with magnetic stirring bar, stir (the rotating speed of magnetic stirring bar is 1000rpm/min or so); use 1MPa of _H2 to replace the air in the autoclave for three times, then react at 7MPa of hydrogen pressure and temperature at 200°C for 6 hours, then rapidly cool to obtain the catalyst.

(3). Autoclave reaction

Add 10ml of the mixture of glycerin and sulfuric acid obtained in step (1) into the autoclave of step (2), stir with a magnetic stirrer with a rotation speed of about 1000rpm/min, and replace the air in the autoclave with _H2 for three times , and then filled with 6MPa H ₂ , and reacted for 72 hours at a temperature of 200° C. to obtain a liquid fuel mainly composed of medium and long-chain alkanes with 6 to 24 carbon atoms.

Product analysis

The medium and long chain alkane products with 6-24 carbon atoms in the oil layer were analyzed by GC-MS, and the product-to-alkane distribution was 50.1% for C ₆ , 21.6% for C ₇ -C ₉ , and 24.3% for C ₁₀ -C ₂₀ . The conversion of glycerol in the aqueous phase was 99.7%.

Basically adopt the above-mentioned same method, just prepare the content of _RhCl3 and _KReO4 in the catalyst to be different, the obtained product adopts the method of above-mentioned product analysis, and the result is shown in Table 2.

Table 2

Example 3

(1). Preparation of the mixture of glycerin and sulfuric acid

Take a 500ml Erlenmeyer flask with a stopper, add 176ml of deionized water, 100ml of 98wt% H ₂ SO ₄ and 134ml of glycerol in sequence.

(2). Preparation of catalyst

0.012g of H ₂ IrCl ₆ and 0.01g of ammonium molybdate trihydrate are dissolved in 5ml of deionized water (need heating), then add 0.4g of smoke SiO ₂ carrier, stir until the carrier becomes dry, obtain the catalyst precursor, then Put the obtained catalyst precursor into an oven at 60° C. for further drying for 24 hours; put the dried catalyst precursor into a tube furnace, and make the temperature of the tube furnace by 2° C./min at a heating rate of Room temperature rises to 400 DEG C and carries out calcining 3 hours; The catalyst precursor that will obtain after calcining and 5ml deionized water join in the autoclave (equipped with magnetic stirring bar) of 100ml that is loaded with magnetic stirring bar together, stir (magnetic stirring bar) The rotating speed of the sub is about 1000rpm/min); the air in the autoclave is replaced three times with 1MPa H ₂ , then the reaction is carried out at 7MPa hydrogen pressure and temperature at 200°C for 6 hours, and then cooled rapidly to obtain the catalyst.

(3). Autoclave reaction

Add 10ml of the mixture of glycerin and sulfuric acid obtained in step (1) into the autoclave of step (2), stir with a magnetic stirrer with a rotation speed of about 1000rpm/min, and replace the air in the autoclave with _H2 for three times , and then filled with 6MPa H ₂ , and reacted for 72 hours at a temperature of 200° C. to obtain a liquid fuel mainly composed of medium and long-chain alkanes with 6 to 24 carbon atoms.

Product analysis

The medium and long-chain alkane products with 6-24 carbon atoms in the oil layer were analyzed by GC-MS, and the product-to-alkane distribution was 24.2% for C ₆ , 11.7% for C ₇ -C ₉ , and 9.0% for C ₁₀ -C ₂₀ . The conversion of glycerol in the aqueous phase was 40.5%.

Basically the same method as above was used, except that the contents of H ₂ IrCl ₆ and ammonium molybdate trihydrate in the catalyst were different.

table 3

Example 4

(1). Preparation of the mixture of glycerin and sulfuric acid

Take a 500ml Erlenmeyer flask with a stopper, add 176ml of deionized water, 100ml of 98wt% H ₂ SO ₄ and 134ml of glycerol in sequence.

(2). Preparation of catalyst

Dissolve 0.012g of H ₂ IrCl ₆ and 0.01g of phosphotungstic acid in 5ml of deionized water (requires heating), then add 0.4g of smoke SiO ₂ carrier, stir until the carrier becomes dry to obtain a catalyst precursor, and then add The obtained catalyst precursor was further dried in an oven at 60°C for 24 hours; the dried catalyst precursor was put into a tube furnace, and the temperature of the tube furnace was increased from room temperature to 1°C at a heating rate of 2°C/min. Be raised to 400 DEG C and carry out calcining 3 hours; The catalyst precursor that will obtain after calcining and 5ml deionized water join in the autoclave (equipped with magnetic stirring bar) of 100ml that is loaded with magnetic stirring bar together, stir (magnetic stirring bar The rotation speed is about 1000rpm/min); the air in the autoclave is replaced three times with 1MPa _H2 , and then the reaction is carried out at 7MPa hydrogen pressure and temperature at 200°C for 6 hours, and then cooled rapidly to obtain the catalyst.

(3). Autoclave reaction

Add 10ml of the mixture of glycerin and sulfuric acid obtained in step (1) into the autoclave of step (2), stir with a magnetic stirrer with a rotation speed of about 1000rpm/min, and replace the air in the autoclave with _H2 for three times , and then filled with 6MPa H ₂ , and reacted for 72 hours at a temperature of 200° C. to obtain a liquid fuel mainly composed of medium and long-chain alkanes with 6 to 24 carbon atoms.

Product analysis

The medium and long-chain alkane products with 6-24 carbon atoms in the oil layer were analyzed by GC-MS, and the product-to-alkane distribution was 34.2% for C ₆ , 18.9% for C ₇ -C ₉ , and 12.0% for C ₁₀ -C ₂₀ . The conversion of glycerol in the aqueous phase was 60.5%.

Basically the same method as above was used, except that the contents of H ₂ IrCl ₆ and phosphotungstic acid in the catalyst were different, and the product obtained was analyzed by the above product analysis method.

Table 4

Example 5

(1). Preparation of the mixture of glycerin and sulfuric acid

Take a 500ml Erlenmeyer flask with a stopper, add 84ml of deionized water, 20ml of 98wt% H ₂ SO ₄ and 45ml of glycerol in sequence.

(2). Preparation of catalyst

0.012g of H ₂ IrCl ₆ and 0.018g of KReO ₄ were dissolved in 5ml of deionized water (need to be heated), then added 0.4g of molecular sieve ZSM-5 carrier, stirred until the carrier became dry to obtain a catalyst precursor, and then The obtained catalyst precursor was further dried in an oven at 60°C for 24 hours; the dried catalyst precursor was put into a tube furnace, and the temperature of the tube furnace was increased from room temperature to 1°C at a heating rate of 2°C/min. Be raised to 400 DEG C and carry out calcining 3 hours; The catalyst precursor that will obtain after calcining and 5ml deionized water join in the autoclave (equipped with magnetic stirring bar) of 100ml that is loaded with magnetic stirring bar together, stir (magnetic stirring bar The rotation speed is about 1000rpm/min); the air in the autoclave is replaced three times with 1MPa _H2 , and then the reaction is carried out at 7MPa hydrogen pressure and temperature at 200°C for 6 hours, and then cooled rapidly to obtain the catalyst.

(3). Autoclave reaction

Add 10ml of the mixture of glycerin and sulfuric acid obtained in step (1) into the autoclave of step (2), stir with a magnetic stirrer with a rotation speed of about 1000rpm/min, and replace the air in the autoclave with _H2 for three times , and then filled with 6MPa H ₂ , and reacted for 72 hours at a temperature of 200° C. to obtain a liquid fuel mainly composed of medium and long-chain alkanes with 6 to 24 carbon atoms.

Product analysis

The medium and long chain alkane products with 6-24 carbon atoms in the oil layer were analyzed by GC-MS, and the product-to-alkane distribution was 34.5% for C ₆ , 33.7% for C ₇ -C ₉ , and 18.3% for C ₁₀ -C ₂₀

Basically the same method as above was used, except that the contents of H ₂ IrCl ₆ and KReO ₄ in the catalyst were different, and the product obtained was analyzed by the above product analysis method, and the results are shown in Table 5.

table 5

Claims (10)

1. A method for the catalytic conversion of medium and long-chain alkanes obtained from glycerol, characterized in that: glycerin and concentration are mixed with an aqueous solution of 5 to 50 wt% mineral acid to obtain a mixed solution, wherein the molar ratio of glycerol to mineral acid is 1 to 2; then adding a catalytic amount of catalyst to the mixture, stirring, and reacting at a temperature of 120 to 350°C and hydrogen pressure to obtain medium and long chain alkanes with 6 to 24 carbon atoms; The catalyst is composed of a main catalyst metal and a catalytic promoter metal loaded on a carrier, wherein the loading amount of the main catalyst metal is 1 to 3 wt% of the weight of the carrier; the ratio of the main catalyst metal and the promoter metal is The mass ratio of the substance is 0.5-5; The main catalyst metal is Ir or Rh, and the promoter metal is selected from one or any two of Re, W and Mo. 2. method according to claim 1 is characterized in that: described catalyst is prepared by following method: Dissolve 0.012-0.024 g of the precursor of the main catalyst metal and 0.01-0.036 g of the precursor of the promoter metal in 5 ml of deionized water and add 0.4 g of carrier, heat and stir until the carrier becomes dry to obtain the catalyst precursor, and then The gained catalyst precursor is then put into an oven for drying; the dried catalyst precursor is put into a tube furnace, and the temperature of the tube furnace is raised from room temperature to 300~ Calcination at 500°C; add the catalyst precursor obtained after calcination and 5ml of deionized water into an autoclave equipped with a magnetic stirrer, and stir; replace the air in the autoclave with hydrogen, and then put it under 6-10MPa hydrogen The reaction is carried out at a pressure and temperature of 180-300° C., and cooled to obtain the catalyst; The precursor of the main catalyst metal is H ₂ IrCl ₆ or RhCl ₃ ; the precursor of the promoter metal is selected from one or any two of KReO ₄ , ammonium molybdate trihydrate, and phosphotungstic acid. 3. The method according to claim 1 or 2, characterized in that: the carrier is fume SiO ₂ or molecular sieve ZSM-5. 4. The method according to claim 2, characterized in that: the time of the calcination is 3 hours. 5. The method according to claim 1, characterized in that: the concentration of the aqueous solution of the inorganic acid is 25-40 wt%. 6. The method according to claim 1 or 5, characterized in that: the inorganic acid is sulfuric acid or phosphoric acid. 7. The method according to claim 1 or 2, characterized in that: said stirring utilizes a magnetic stirrer, and the rotational speed of said magnetic stirrer is 1000rpm/min. 8. The method according to claim 1, characterized in that: said temperature is 150-250°C. 9. The method according to claim 1, characterized in that: the pressure of the hydrogen is 4-15 MPa. 10. The method according to claim 1, characterized in that: the reaction time is 48-72 hours.