Preparation method and application of oil-soluble heteropolyacid ionic liquid catalyst

Abstract

The invention discloses a preparation method and application of an oil-soluble heteropolyacid ionic liquid catalyst. The catalyst is composed of organic cations and inorganic anions, the cations are one of quaternary ammonium, imidazole and pyridine cations containing long-chain alkyl, the anions are heteropolyacid anions, the long-chain alkyl enables the catalyst to have good oil solubility, the catalyst can be efficiently dispersed in the waste grease, heteropolyacid provides active sites, and the catalyst can be used for treating the waste grease. Nano-scale active particles are formed after in-situ vulcanization, and the catalytic hydrogenation effect is achieved. The invention also provides a preparation method of the oil-soluble heteropolyacid ionic liquid catalyst, the catalyst can be prepared from tertiary amine and halogenated hydrocarbon through three-step reaction of alkylation, anion exchange and acid-base neutralization, the preparation process is simple, a highly toxic reagent is avoided, and the cost is low. The catalyst provided by the invention can be used for catalytic hydroisomerization of various waste oils and fats, has the characteristics of high conversion rate, low coking rate and high product calorific value, and has relatively high industrial application potential.

Description

Technical Field

[0001] The invention relates to a preparation method and application of an oil-soluble heteropolyacid ion liquid catalyst, belonging to the technical field of petrochemical industry. Background Art

[0002] Energy is fundamental to human survival. However, due to overexploitation and utilization, fossil fuels are being depleted, necessitating the development of renewable, clean energy sources. Solar energy, biomass energy, and wind energy are all common renewable energy sources. Biomass energy is derived from plant photosynthesis and stored in biomass. Biofuels such as biodiesel and biojet fuel are renewable and sustainable energy sources that can effectively reduce carbon dioxide emissions, mitigate the greenhouse effect, and meet green and low-carbon development goals. Therefore, the conversion of bio-oils into biofuels is a current research hotspot in the petrochemical industry.

[0003] The development of biodiesel to biofuel has gone through two major phases: first generation and second generation. First-generation biodiesel is produced by esterifying vegetable oils or animal fats with methanol to produce fatty acid methyl esters. This technology is quite mature and has been mass-produced worldwide. Compared with traditional petroleum diesel, first-generation biodiesel offers advantages such as environmental friendliness, high cetane number, and renewable nature. However, it still has shortcomings in low-temperature fluidity, oxygen content, stability, and calorific value. Therefore, it is generally used only as an additive to petroleum diesel, generally not exceeding 5%.

[0004] The second generation is produced by hydrodeoxygenating oils and fats into a hydrocarbon mixture similar to petroleum diesel, namely biodiesel and biojet fuel. Compared to first-generation biodiesel, second-generation biofuel not only maintains the advantages of environmental protection, high cetane number, and renewable nature, but also has better fluidity, lower oxygen content, higher stability, and higher calorific value, and can be mixed with petroleum diesel in any proportion.

[0005] The core of the second-generation biofuel production process lies in catalysts. Oil-soluble heteropolyacid ionic liquids are highly effective hydrogenation catalysts. They can be effectively dispersed in bio-oils, improving the dispersion of active components in the feedstock and increasing contact efficiency with the reactants. The composition of ionic liquids allows for a rich selection of cation and anion combinations, as well as the grafting and modification of various functional groups. Therefore, ionic liquids have shown broad application prospects in many fields, particularly catalysis. Furthermore, heteropolyacids are widely used in catalysis due to their unique acidity, redox properties, and stability, and have demonstrated high activity in isomerization reactions. Summary of the Invention

[0006] The present invention aims to solve the problem that existing catalysts are easily deactivated by coking in waste oils and fats, and provides a preparation method and application of an oil-soluble heteropolyacid ionic liquid catalyst, so as to realize a one-step hydrogenation and deoxygenation reaction of bio-oils and fats, while avoiding the problem of incomplete contact between the catalyst and the waste oil and fat raw material in conventional reactions, and improving the dispersibility of the catalyst in the raw oil and fat. The catalyst preparation method is simple and has high potential for industrial application.

[0007] To achieve the above object, the present invention adopts the following technical solutions: An oil-soluble heteropolyacid ionic liquid catalyst, characterized in that the catalyst comprises one of a quaternary ammonium heteropolyacid salt and an imidazole heteropolyacid salt containing a long-chain alkyl group composed of an organic cation and an inorganic anion, and the chemical structure is as follows: The chemical formula of quaternary ammonium heteropolyacid salt containing long-chain alkyl is: The chemical structure of imidazole heteropolyacid salts containing long-chain alkyl groups is: Where R is C6~C 18 A straight chain or branched chain alkyl group.

[0008] The preparation method of the above-mentioned oil-soluble heteropolyacid ionic liquid catalyst comprises the following steps: (1) Dissolve equimolar amounts of a tertiary amine and a halogenated alkane in a reflux solvent, heat and reflux for 20 to 28 hours, and then remove the reflux solvent by rotary evaporation. The resulting crude product is extracted 3 to 5 times with an extraction solvent to remove unconverted raw materials, and then vacuum dried for 24 to 48 hours to obtain intermediate A; (2) Dissolve intermediate A in an organic solvent and then add it to a - The product is added to an ion exchange column of a strong basic anion exchange resin, eluted with an organic solvent, and the strong basic eluate with a pH greater than 9 is collected to obtain intermediate B; (4) adding the heteropoly acid to the intermediate B, stirring at room temperature for 6 to 8 hours, then heating to 40 to 60° C. and stirring for 10 to 16 hours, then removing the organic solvent by rotary evaporation, and finally vacuum drying for 24 to 48 hours to obtain the target catalyst; In step (1), the tertiary amine is one of a tertiary amine, methylimidazole or pyridine; In step (1), the reflux solvent is one of ethanol, acetonitrile or acetone; In step (1), the extraction solvent is a mixture of diethyl ether and ethanol, and the volume ratio of diethyl ether to ethanol is 10 to 50:1; in step (2), the organic solvent is one of ethanol, acetonitrile or acetone; In step (3), the heteropoly acid is one of phosphotungstic acid and phosphomolybdic acid; In step (3), the heteropoly acid reacts with OH in the intermediate B - The molar ratio of the content is 1:1-2; In step (1) and step (3), the vacuum drying temperature is 60-80°C.

[0009] The application of the above-mentioned oil-soluble heteropolyacid ionic liquid catalyst comprises the following steps: (1) adding bio-oil into a suspended bed reactor, and then sequentially adding an oil-soluble heteropolyacid ionic liquid catalyst and sulfur powder, sealing the reactor, and starting stirring to fully mix the raw materials to obtain a mixture; (2) The air in the reactor containing the mixture is replaced with hydrogen, and hydrogen is filled to a certain pressure. The temperature is programmed to rise at a rate of 4 to 6°C / min. The mixture is first vulcanized at the vulcanization temperature for a certain time, and then the temperature is continued to rise to carry out the hydrodeoxygenation isomerization reaction at the reaction temperature; In step (1), the bio-oil is one of waste oil, palm oil, and methyl palmitate; In step (1), the amount of the oil-soluble heteropolyacid ionic liquid catalyst is 500-1200 ppm Mo or W; In step (1), the sulfur powder is sublimed sulfur powder, and the added amount is such that the atomic ratio of S / (W or Mo) is 6 to 15; In step (1), the stirring rate is 400-600 rpm; In step (2), the vulcanization temperature is 150-300° C., and the vulcanization time is 40-60 min; In step (2), the reaction temperature is 320-400° C., the pressure of the hydrogen gas is 5-20 MPa, and the time of the hydrodeoxygenation isomerization reaction is 3-6 hours.

[0010] The technical solution of the present invention has the following advantages: (1) The present invention provides an oil-soluble heteropolyacid ionic liquid catalyst, wherein the heteropolyacid is sulfided under the action of a sulfiding agent to generate a sulfided phase for use in a hydrodeoxygenation reaction, and the catalyst can be recovered. The generated phosphoric acid continues to undergo an isomerization reaction in a suspended bed reactor, thereby achieving a one-step hydrodeoxygenation isomerization reaction and avoiding cracking of the intermediate product; (2) The oil-soluble heteropolyacid ionic liquid catalyst provided by the present invention has a simple preparation method. The long-chain alkyl group used makes the catalyst highly oil-soluble, thereby enabling the catalyst to be efficiently dispersed in waste oils and fats. By promoting the contact between the active sites and the waste oils and fats, the conversion rate of the waste oils and fats is improved. (3) The oil-soluble heteropolyacid ion liquid catalyst provided by the present invention can be used for the one-step hydrodeoxygenation isomerization reaction of various waste oils and fats in a suspended bed, and has the characteristics of high conversion rate, low coking rate and good impurity removal effect. DETAILED DESCRIPTION

[0011] The present invention is further described in detail below with reference to the embodiments. Obviously, the embodiments described are only a part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0012] 1. Example of Preparation of Oil-Soluble Heteropolyacid Ionic Liquid Catalyst Example 1: This embodiment provides a trihexylmethylammonium phosphomolybdate ([N 6661 ]5[Mo 12 O 41 P]) catalyst and preparation method thereof: (1) 25.1326 g of trihexylamine and 13.2005 g of methyl iodide were dissolved in 400 mL of ethanol, heated under reflux at 70° C. for 24 hours, and then the ethanol was removed by rotary evaporation at 45° C. and 2 MPa. The crude product was extracted five times with 50 mL of a mixture of ether and ethanol in a volume ratio of 10:1 to remove unconverted raw materials, and then vacuum dried at 80° C. for 24 hours to obtain the intermediate trihexylmethylammonium iodide ([N 6661 ][I]); (2) 4.0003 g of the intermediate trihexylmethylammonium iodide ([N 6661 ][I]) was dissolved in 100 mL of ethanol and added to an OH solution filled with 25 g of commercial model Amberlite IRA-900. - The mixture was added to an ion exchange column (inner diameter 5 cm, column height 35 cm) of a strong basic anion exchange resin, eluted with ethanol 3 times the volume of the resin bed, and the strong basic eluate with pH>9 was collected to obtain the intermediate trihexylmethylammonium hydroxide ([N 6661 ][OH]); (3) 10.0003 g of phosphomolybdic acid was added to 3.6132 g of the intermediate trihexylmethylammonium hydroxide ([N 6661 ][OH]), stirred at room temperature for 6 hours, then heated to 50 ° C and stirred for 12 hours, then ethanol and water were removed by rotary evaporation at 50 ° C and 2 MPa, and finally vacuum dried at 80 ° C for 24 hours to obtain the target catalyst trihexylmethylammonium phosphomolybdate ([N 6661 ]5[Mo 12 O 41 P]).

[0013] Example 2: This embodiment provides a 1-octyl-3-methylimidazolium phosphomolybdate ([C8mim]5[Mo 12 O 41 P]) catalyst and preparation method thereof: (1) 15.1004 g of N-methylimidazole and 19.3412 g of 1-bromooctane were dissolved in 300 mL of ethanol, and the mixture was heated under reflux at 70° C. for 24 hours, and then the ethanol was removed by rotary evaporation at 50° C. and 2 MPa. The crude product was extracted five times with 50 mL of a mixture of ether and ethanol in a volume ratio of 10:1 to remove unconverted raw materials, and then vacuum dried at 80° C. for 24 hours to obtain the intermediate 1-octyl-3-methylimidazole bromide ([C8mim][Br]); (2) 4.1829 g of the intermediate 1-octyl-3-methylimidazolium bromide ([C8mim][Br]) was dissolved in 100 mL of acetone and added to a 25 g OH-1000 flask filled with commercial Amberlite IRA-900. - The product was added to an ion exchange column (inner diameter 5 cm, column height 35 cm) of a strong basic anion exchange resin, eluted with acetone 3 times the resin bed volume, and the strong basic eluate with pH>9 was collected to obtain the intermediate 1-octyl-3-methylimidazolium hydroxide ([C8mim][OH]); (3) 17.3232 g of phosphomolybdic acid was added to 3.1536 g of the intermediate 1-octyl-3-methylimidazolium hydroxide ([C8mim][OH]), and the mixture was stirred at room temperature for 6 hours, then heated to 60°C and stirred for 10 hours, and then acetone and water were removed by rotary evaporation at 50°C and 2 MPa, and finally vacuum dried at 80°C for 24 hours to obtain the target catalyst 1-octyl-3-methylimidazolium phosphomolybdate ([C8mim]5[Mo 12 O 41 P]).

[0014] Example 3: This embodiment provides a 1-octyl-3-methylimidazolium phosphotungstate ([C8mim]3[O 40 PW 12 ]) Catalyst and preparation method thereof: (1) 15.2568 g of N-methylimidazole and 19.4689 g of 1-bromooctane were dissolved in 300 mL of ethanol, heated under reflux at 70° C. for 24 hours, and then the ethanol was removed by rotary evaporation at 45° C. and 2 MPa. The crude product was extracted five times with a mixture of ether and ethanol in a volume ratio of 10:1 to remove unconverted raw materials, and then vacuum dried at 60° C. for 24 hours to obtain the intermediate 1-octyl-3-methylimidazole bromide ([C8mim][Br]); (2) 4.2912 g of the intermediate 1-octyl-3-methylimidazolium bromide ([C8mim][Br]) was dissolved in 100 mL of acetone and added to an OH-1000 flask filled with 3 g of commercial Amberlite IRA-900. - The product was added to an ion exchange column (inner diameter 5 cm, column height 35 cm) of a strong basic anion exchange resin, eluted with acetone 3 times the resin bed volume, and the strong basic eluate with pH>9 was collected to obtain the intermediate 1-octyl-3-methylimidazolium hydroxide ([C8mim][OH]); (3) 13.5333 g of phosphotungstic acid was added to 3.1536 g of the intermediate 1-octyl-3-methylimidazolium hydroxide ([C8mim][OH]), and the mixture was stirred at room temperature for 6 hours, then heated to 60°C and stirred for 10 hours, and then acetone and water were removed by rotary evaporation at 45°C and 2 MPa, and finally vacuum dried at 60°C for 24 hours to obtain the target catalyst 1-octyl-3-methylimidazolium phosphotungstate ([C8mim]3[O 40 PW 12 ]).

[0015] Example 4: This embodiment provides a 1-decyl-3-methylimidazolium phosphomolybdate ([C 10 mim]5[Mo 12 O 41 P]) catalyst and preparation method thereof: (1) 15.2725 g of N-methylimidazole and 22.4033 g of 1-bromodecane were dissolved in 400 mL of acetonitrile, and the mixture was heated under reflux at 70° C. for 24 hours. The acetonitrile was removed by rotary evaporation at 45° C. and 2 MPa. The crude product was extracted five times with a mixture of ether and ethanol at a volume ratio of 20:1 to remove unconverted raw materials. The product was then vacuum dried at 80° C. for 24 hours to obtain the intermediate 1-decyl-3-methylimidazole bromide ([C 10 mim][Br]); (2) 4.1211 g of the intermediate 1-decyl-3-methylimidazolium bromide ([C 10 mim][Br]) was dissolved in 100 mL of acetonitrile and added to an OH-10000 flask filled with 3 g of commercial Amberlite IRA-900. - The mixture was added to an ion exchange column (inner diameter 5 cm, column height 35 cm) of a strong basic anion exchange resin, eluted with acetonitrile 3 times the volume of the resin bed, and the strong basic eluate with pH>9 was collected to obtain the intermediate 1-decyl-3-methylimidazolium hydroxide ([C 10 mim][OH]); (3) 27.3212 g of phosphomolybdic acid was added to 3.5623 g of the intermediate 1-decyl-3-methylimidazole hydroxide ([C 10 mim][OH]), stirred at room temperature for 6 hours, then heated to 60 ° C and stirred for 12 hours, then evaporating acetonitrile and water at 45 ° C and 2 MPa, and finally vacuum dried at 80 ° C for 24 hours to obtain the target catalyst 1-decyl-3-methylimidazolium phosphomolybdate ([C 10 mim]5[Mo 12 O 41 P]).

[0016] Example 5: This embodiment provides a 1-decyl-3-methylimidazolium phosphotungstate ([C 10 mim]3[O 40 PW 12 ]) Catalyst and preparation method thereof: (1) 15.2021 g of N-methylimidazole and 22.2311 g of 1-bromodecane were dissolved in 400 mL of ethanol, heated under reflux at 70° C. for 20 hours, and then the ethanol was removed by rotary evaporation at 45° C. and 2 MPa. The crude product was extracted three times with a mixture of ether and ethanol at a volume ratio of 30:1 to remove unconverted raw materials, and then vacuum dried at 80° C. for 24 hours to obtain the intermediate 1-decyl-3-methylimidazole bromide ([C 10 mim][Br]); (2) 4.1223 g of the intermediate 1-decyl-3-methylimidazolium bromide ([C 10 mim][Br]) was dissolved in 100 mL of acetone and added to an OH-1000 flask filled with 3 g of commercial Amberlite IRA-900. - The mixture was added to an ion exchange column (inner diameter 5 cm, column height 35 cm) of a strong basic anion exchange resin, eluted with acetone 3 times the volume of the resin bed, and the strong basic eluate with pH>9 was collected to obtain the intermediate 1-decyl-3-methylimidazolium hydroxide ([C 10 mim][OH]); (3) Add 27.3411 g of phosphotungstic acid to 2.2783 g of the intermediate 1-decyl-3-methylimidazolium hydroxide ([C 10 mim][OH]), stirred at room temperature for 8 hours, then heated to 60 ° C and stirred for 15 hours, then acetone and water were removed by rotary evaporation at 45 ° C and 2 MPa, and finally vacuum dried at 80 ° C for 24 hours to obtain the target catalyst 1-decyl-3-methylimidazolium phosphotungstate ([C 10 mim]3[O 40 PW 12 ]).

[0017] 2. Application Examples of Oil-Soluble Heteropolyacid Ionic Liquid Catalysts The oil-soluble heteropolyacid ionic liquid catalysts prepared in Examples 2, 3, 4, and 5 were respectively used for evaluation of suspended bed catalytic hydrodeoxygenation isomerization of methyl palmitate. The experimental steps were as follows: Weigh 30g of methyl palmitate and add it to a 300mL autoclave. Then, add 2g of an oil-soluble heteropolyacid ionic liquid catalyst and 5g of sublimed sulfur powder. Tighten the autoclave diagonally to seal it and stir to thoroughly mix the ingredients at a stirring rate of 600r / min. Replace the air in the autoclave with hydrogen and fill it with hydrogen to a pressure of 20MPa. Check for leaks using a hydrogen detector. Start a heating program at a rate of 5°C / min, first sulfurizing at 250°C for 40min, then reacting at 400°C for 5h. After the reaction is complete, cool the autoclave to room temperature, collect the product, perform vacuum distillation, and calculate the conversion. Wash the distillation residue with toluene, centrifuge it, dry it, and weigh it to calculate the coking rate.

[0018] For comparison, the results of the hydrodeoxygenation isomerization of methyl palmitate without a catalyst and with molybdenum isooctanoate developed by Eni, Italy, as a catalyst were also measured. The results are shown in the following table: As can be seen from the table, the oil-soluble heteropoly acid ionic liquid catalyst provided by the present invention has excellent catalytic activity. When applied to the suspended bed hydrodeoxygenation isomerization of methyl palmitate, the conversion rate of methyl palmitate is significantly higher than that without a catalyst, and the coking rate is significantly lower than that without a catalyst. Compared with the molybdenum isooctanoate developed by Eni, Italy, the oil-soluble heteropoly acid ionic liquid catalyst provided by the present invention is substantially equivalent in activity, but the preparation process is simple and the reagents used are nontoxic, not prone to coking, and the cost has a great advantage.

[0019] The above embodiments are merely examples for clarity of explanation and are not intended to limit the embodiments. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all embodiments here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. An oil-soluble heteropolyacid ionic liquid catalyst, characterized in that: The catalyst is one of a quaternary ammonium heteropolyacid salt or an imidazole heteropolyacid salt containing a long-chain alkyl group composed of an organic cation and an inorganic anion, and the chemical structure is as follows: The chemical formula of quaternary ammonium heteropolyacid salt containing long-chain alkyl is: The chemical formula of imidazole heteropolyacid salt containing long-chain alkyl is: Where R is C6~C 18 A straight chain or branched chain alkyl group.

2. The method for preparing an oil-soluble heteropolyacid ionic liquid catalyst according to claim 1, wherein: The following steps are involved: (1) Dissolve equimolar amounts of a tertiary amine and a halogenated alkane in a reflux solvent, heat and reflux for 20 to 28 hours, and then remove the reflux solvent by rotary evaporation. The resulting crude product is extracted 3 to 5 times with an extraction solvent to remove unconverted raw materials, and then vacuum dried for 24 to 48 hours to obtain intermediate A; (2) Dissolve intermediate A in an organic solvent and then add it to a - The product is added to an ion exchange column of a strong basic anion exchange resin, eluted with an organic solvent, and the strong basic eluate with a pH greater than 9 is collected to obtain intermediate B; (3) The heteropoly acid is added to the intermediate B, and the mixture is stirred at room temperature for 6 to 8 hours, then heated to 40 to 60° C. and stirred for 10 to 16 hours, and then the organic solvent is removed by rotary evaporation, and finally vacuum dried for 24 to 48 hours to obtain the target catalyst.

3. The preparation method according to claim 2, wherein: In step (1), the tertiary amine is one of a tertiary amine, methylimidazole or pyridine; the reflux solvent is one of ethanol, acetonitrile or acetone; and the extraction solvent is a mixture of diethyl ether and ethanol, and the volume ratio of diethyl ether to ethanol is 10 to 50:

1.

4. The preparation method according to claim 2, wherein: In step (2), the organic solvent is one of ethanol, acetonitrile or acetone; and the heteropolyacid is one of phosphotungstic acid and phosphomolybdic acid.

5. The preparation method according to claim 2, wherein: In step (3), the heteropoly acid reacts with OH in the intermediate B - The molar ratio of the content is 1:1~2.

6. The preparation method according to claim 2, wherein: In step (1) and step (3), the vacuum drying temperature is 60-80°C.

7. Use of the oil-soluble heteropolyacid ionic liquid catalyst according to claim 1 in a hydrodeoxygenation isomerization reaction.

8. The use according to claim 7, characterized in that: The following steps are involved: (1) adding bio-oil into a suspended bed reactor, and then sequentially adding an oil-soluble heteropolyacid ionic liquid catalyst and sulfur powder, sealing the reactor, and starting stirring to fully mix the raw materials to obtain a mixture; (2) The air in the reactor containing the mixture is replaced with hydrogen, and hydrogen is filled to a certain pressure. The temperature is programmed to rise at a rate of 4 to 6 °C / min. The mixture is first vulcanized at the vulcanization temperature for a certain time, and then the temperature is continued to rise to carry out the hydrodeoxygenation isomerization reaction at the reaction temperature.

9. The use according to claim 8, characterized in that: In step (1), the bio-oil is one of waste oil, palm oil, and methyl palmitate; the amount of the soluble heteropolyacid ionic liquid catalyst is 500-1200 ppm Mo or W; the sulfur powder is sublimated sulfur powder, and the addition amount is a S / W or S / Mo atomic ratio of 6-15; and the stirring rate is 400-600 rpm.

10. The use according to claim 8, characterized in that: In step (2), the hydrogen injection pressure is 5 to 20 MPa; the sulfurization temperature is 150 to 300° C., and the sulfurization time is 40 to 60 minutes; the reaction temperature is 320 to 400° C., and the hydrodeoxygenation isomerization reaction time is 3 to 6 hours.

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