CN116333823A - Method for preparing liquid fuel by grease selective catalytic deoxidation - Google Patents

Abstract

The invention provides a method for preparing liquid fuel by grease selective catalytic deoxidation, which comprises the following steps: s1: firstly, converting the grease into fatty acid methyl ester through methyl esterification; s2: then, the fatty acid methyl ester is catalytically hydrogenated and converted into fatty alcohol; s3: then the fatty alcohol is dehydrated in the molecule and converted into long-chain hydrocarbon; s4: finally isomerizing long-chain hydrocarbon to obtain the liquid fuel. The method for preparing the liquid fuel by the grease selective catalytic deoxidation has the advantages of strong raw material adaptability, simple process flow, low-cost and easily-obtained catalyst, capability of obviously reducing hydrogen consumption, good selectivity of the obtained fuel product, capability of increasing the yield of glycerol and the like.

Description

A method for preparing liquid fuel by selective catalytic deoxygenation of grease

technical field

The invention relates to a method for preparing liquid fuel through selective catalytic deoxygenation of grease, belonging to the technical field of biomass energy.

Background technique

Liquid fuels, such as gasoline, diesel, aviation fuel, etc., are very important power fuels and an important material basis for economic and social development. The long-term extensive use of fossil resources to prepare liquid fuels has had negative impacts on the environment such as the greenhouse effect. Moreover, the reserves of these non-renewable resources will decrease year by year with continuous consumption. Deoxygenated liquid fuels prepared from renewable animal and vegetable oils have high calorific value, good combustion performance, similar composition to fossil fuels, and good compatibility, and have been widely valued. Therefore, countries all over the world pay more and more attention to the research on the technology of preparing deoxygenated liquid fuel from oil.

To prepare deoxygenated liquid fuel from oil, the oil can be hydrodeoxygenated into long-chain alkanes under the action of sulfurized NiMo/γ-Al ₂ O ₃ or CoMo/γ-Al ₂ O ₃ catalysts, and the long-chain alkanes can be loaded with Pt, Acidic molecular sieve catalysts such as Pd and other noble metals (such as Pt/ZSM-22) catalyze isomerization to prepare liquid fuels. Changing the catalyst and isomerization conditions can selectively produce gasoline, diesel or aviation kerosene fuel. For example, Canada’s Canmet Energy Technology Center has developed a technology to produce high-cetane diesel by hydrogenation of oil, a technology of oil catalytic hydrodeoxygenation to produce diesel established in Porvoo by Finland’s Neste Oil Company, and a technology to prepare aviation kerosene from biomass developed by UOP.

Sulfurized hydrogenation catalysts reduce catalytic activity due to sulfur loss and thus generate sulfur pollution. The use of hydrogenation metal catalysts such as nickel, palladium, platinum, and ruthenium can avoid sulfur-related problems. Recently, Chinese patent CN 102876350A discloses a technology for preparing alkane fuels by catalyzing the hydrodeoxygenation of fats or fatty acids with Ru-based catalysts. Alternatively, dual-functional catalysts can be used directly to couple hydrodeoxygenation and cracking/isomerization in a single stage. For example, Herskowitz et al. (Earth and Environmental Science 93(2017) 012003) used Pt/SAPO-11 to catalyze oil at 300-450°C , 1-6MPa, 0.5-5.0h ^-1 in the next step reaction to obtain a diesel component with a lower freezing point and cold filter point.

Direct hydrodeoxygenation of fats and oils, the oxygen element is completely removed in the form of water, which not only consumes a large amount of hydrogen, but also loses glycerol (hydrogenation produces propane), for example, the theoretical hydrogen consumption of complete deoxygenation per mole of fatty acid glyceride hydrogenation Not less than 12 moles.

The oil is first hydrolyzed (or methylated) to release glycerol, and then the selective decarboxylation/carbonylation of fatty acid (or fatty acid methyl ester) is catalyzed to remove oxygen in the form of CO ₂ /CO, which can significantly reduce hydrogen consumption. Murzin et al. (Top Catal (2011) 54:460–466) reported that Al ₂ O ₃ or SiO ₂ catalysts loaded with Pt and Pd noble metals can catalyze the decarboxylation of fatty acids with high selectivity. Under the conditions of 250-350°C and 0.1-2MPa, the conversion rate of stearic acid is greater than 80%, and the selectivity of n-heptadecane is about 93%. Compared with the hydrodeoxygenation reaction, the hydrogen consumption is reduced by 70%-90%. Catalysts for selective decarboxylation/carbonylation of fatty acid esters have also been reported, for example, Pt/Al ₂ O ₃ catalyzed non-hydrodeoxygenation of methyl stearate (Catal Lett (2009) 130:9-18). These non-hydrodeoxygenation reactions via decarboxylation/carbonylation are usually performed at pressures below 2 MPa and consume little or no hydrogen. These advantages have aroused great interest of researchers.

Hydrodeoxygenation of oils to obtain alkanes, or selective decarboxylation/decarbonylation of fatty acids or their methyl esters to obtain alkanes, and then hydrocracking/isomerization of alkanes requires the use of noble metals such as Pt and Pd, which will significantly increase the cost of catalysts.

In order to reduce or even avoid the use of noble metal isomerization catalysts, reduce catalyst costs, and simplify the isomerization process, Chinese patent CN107987868A discloses a method for preparing liquid fuels through step-by-step deoxygenation of oils and fats. Construct fuel. However, the water produced by catalytic deoxygenation of fatty alcohols usually leads to increased oxygen content of isomerized products and shortens catalyst life. In order to reduce the adverse effects of by-product water, Chinese patent CN110066679A discloses a method for preparing liquid fuel from fatty alcohol, which is to continuously separate the water and cracked gas produced by the deoxygenation of fatty alcohol, and hydrogenate the reaction product to obtain fuel .

In order to further reduce the hydrogen consumption of oil deoxygenation, avoid the use of vulcanized catalysts and precious metal catalysts, increase the production of glycerin, and hope to reduce consumption and increase efficiency for the preparation of deoxygenated liquid fuels for oils, a new method for the preparation of liquid fuels by selective catalytic deoxygenation of oils has been provided. Become the technical problem that needs to be solved urgently in this field.

Contents of the invention

In order to solve the above-mentioned shortcomings and deficiencies, the object of the present invention is to provide a method for preparing liquid fuel by selective catalytic deoxygenation of grease.

In order to achieve the above object, the present invention provides a method for preparing liquid fuel through selective catalytic deoxygenation of grease, wherein the method comprises:

S1: first convert the oil methyl ester into fatty acid methyl ester;

S2: then catalytic hydrogenation of fatty acid methyl esters into fatty alcohols;

S3: Then intramolecular dehydration of fatty alcohols is converted into long-chain hydrocarbons;

S4: Finally, liquid fuel is prepared by isomerizing long-chain hydrocarbons.

As a specific embodiment of the method described above in the present invention, wherein the oil is animal oil and/or vegetable oil, the fatty acid content of carbon chain length of C ₁₂ -C ₂₄ in the oil is greater than 80 wt%, fatty acid glyceride And the total content of free fatty acid is greater than 90wt%.

As a specific embodiment of the method described above in the present invention, wherein the fats include tallow, lard, chicken oil, rapeseed oil, soybean oil, cottonseed oil, palm oil, corn oil, rubber seed oil, catering industry Waste oil, gutter oil, acidified oil, rancid oil and other animal and vegetable oils, or low-quality oils such as frying oil and lubricating oil that have been used for other purposes but the main structure of fatty acids has not changed.

In order to improve the quality of liquid fuel, simplify the subsequent refining process, and prolong the life of the catalyst, the content of impurities such as sulfur, phosphorus, nitrogen, chlorine and metals in the oil raw material should be appropriately reduced. In some embodiments of the present invention, after the used oil raw materials are refined, the content of impurities such as sulfur, phosphorus, nitrogen, chlorine and metals should be less than 100ppm, 200ppm, 300ppm, 400ppm and 1000ppm respectively.

As a specific embodiment of the method described above in the present invention, wherein, in S1, the methyl esterification of the oil is to convert the oil into fatty acid methyl ester by reacting with methanol.

As a specific embodiment of the method described above in the present invention, wherein, in S1, the grease and methanol are reacted under critical methanol conditions, under enzyme-catalyzed conditions, under homogeneous or heterogeneous acid-catalyzed conditions or homogeneous or Reaction conversion to fatty acid methyl esters under heterogeneous base-catalyzed conditions.

Among them, the present invention does not make specific requirements on the reactor, process conditions and catalysts used for methyl esterification of oils and fats in S1, and those skilled in the art can make reasonable choices according to actual operation needs, as long as it is guaranteed that the purpose of the present invention can be achieved. Can.

In some embodiments of the present invention, for oil raw materials of different qualities, it is necessary to select different catalysts to catalyze the methyl esterification of oil. For oil raw materials of different qualities and different catalysts, the process conditions for the methyl esterification of oil include: temperature 60-300°C , pressure 0.1-20MPa, mass space velocity 0.3-5h ^-1 , alcohol-oil molar ratio 3:1-16:1;

The reactor used may be a continuous reactor such as a tower reactor or a tubular reactor to improve reaction efficiency.

In the above method, the mixture after methyl esterification of fats and oils can be further refined and separated or distilled under reduced pressure.

As a specific embodiment of the above-mentioned method of the present invention, wherein, in S1, after methyl esterification and refining of fats and oils, the content of fatty acid methyl ester in the obtained product is not less than 80 wt%.

As a specific embodiment of the above-mentioned method of the present invention, wherein, in S1, after oil methyl esterification and refining, the content of fatty acid methyl ester in the obtained product is not less than 85wt%.

As a specific embodiment of the method described above in the present invention, wherein, in S1, after methyl esterification and refining of oil and fat, the content of fatty acid methyl ester in the obtained product is 95-100 wt%.

As a specific embodiment of the method described above in the present invention, wherein, in S2, the catalyst used for catalytic hydrogenation of fatty acid methyl esters into fatty alcohols is a supported catalyst, and the hydrogenation active metal used by the supported catalyst includes platinum, One or more of palladium, gold, silver, cobalt, molybdenum, copper, nickel, zinc, iron, chromium, barium, and manganese, and the carrier is a high specific surface area carrier such as activated carbon, Al ₂ O ₃ or SiO ₂ .

In comprehensive consideration of catalyst cost, activity and selectivity, a supported catalyst with one or more non-precious metals such as copper, cobalt, molybdenum, nickel, iron, zinc and manganese as active centers is preferred.

As a specific embodiment of the method described above in the present invention, wherein, in S2, the process conditions for catalytic hydrogenation of fatty acid methyl esters into fatty alcohols include: temperature 160-300°C, pressure 2-20MPa, mass space velocity 0.3-3h ^-1 . The volume ratio of hydrogen to oil is 500:1-15000:1. By-product methanol can be recycled.

As a specific embodiment of the method described above in the present invention, wherein, in S2, the reactor used for catalytic hydrogenation of fatty acid methyl ester into fatty alcohol can be a reactor, a tower reactor and a fixed bed reactor, etc., preferably a tower reactors or fixed-bed tubular reactors.

As a specific embodiment of the method described above in the present invention, wherein, in S2, after fatty acid methyl ester is catalytically hydrogenated and refined, the fatty alcohol content in the product obtained is greater than 86 wt%.

As a specific embodiment of the method described above in the present invention, wherein, in S2, after fatty acid methyl ester is catalytically hydrogenated and refined, the content of fatty alcohol in the product obtained is 92-100 wt%. In order to improve the subsequent reaction effect, high boiling point components can be separated by means of adsorption and distillation.

As a specific embodiment of the method described above in the present invention, wherein, in S3, the catalyst used for intramolecular dehydration of fatty alcohols into long-chain hydrocarbons is an acid catalyst with a desorption temperature of 150-600°C after _NH3 adsorption. Wherein, the acid catalyst can selectively catalyze the intramolecular dehydration of long-chain aliphatic alcohols into long-chain hydrocarbons under non-hydrogen atmosphere conditions. As a specific embodiment of the method described above in the present invention, wherein, in S3, the acid catalyst includes γ-Al ₂ O ₃ , ZrO ₂ , ZSM-22, ZSM-23, ZSM-48, ZSM-35, SAPO One or more of -31, SAPO-11, ZSM-5, Y molecular sieve and β molecular sieve, etc.

In some preferred embodiments of the present invention, in S3, the acid catalyst includes γ-Al ₂ O ₃ and/or ZrO ₂ , and γ-Al ₂ O ₃ and/or ZrO ₂ combined with ZSM-22, ZSM- 23. One or a combination of ZSM-48, ZSM-35, SAPO-31, SAPO-11, ZSM-5, Y molecular sieve, and β molecular sieve.

As a specific embodiment of the method described above in the present invention, wherein, in S3, when γ-Al ₂ O ₃ and/or ZrO ₂ are combined with ZSM-22, ZSM-23, ZSM-48, ZSM-35, SAPO- 31. When one or more combinations of SAPO-11, ZSM-5, Y molecular sieve and β molecular sieve are used as an acid catalyst, the content of weakly acidic γ-Al ₂ O ₃ is greater than 20wt%, and the weakly acidic ZrO The content of ₂ is more than 20wt%.

As a specific embodiment of the method described above in the present invention, wherein, in S3, the reactions involved in the intramolecular dehydration conversion process of fatty alcohols include one or more of dehydration, cracking, isomerization, cyclization and other reactions.

As a specific embodiment of the method described above in the present invention, wherein, in S3, the process conditions for intramolecular dehydration of fatty alcohols into long-chain hydrocarbons include: temperature 250-400°C, pressure -0.1MPa to 0.5MPa, mass space velocity is 0.2-4h ^-1 .

As a specific embodiment of the above-mentioned method of the present invention, wherein, in S3, after intramolecular dehydration conversion and refining of the fatty alcohol, the oxygen content in the obtained long-chain hydrocarbon is less than 0.1 wt%.

As a specific embodiment of the above-mentioned method of the present invention, wherein, in S3, after intramolecular dehydration conversion and refining of the fatty alcohol, the oxygen content in the obtained long-chain hydrocarbon is less than 0.05 wt%. In order to improve the subsequent reaction effect, high boiling point components can be separated by means of adsorption and distillation.

As a specific embodiment of the method described above in the present invention, wherein, in S3, the reactor used for the intramolecular dehydration conversion of fatty alcohol can be a reactor, a tower reactor and a fixed bed reactor, etc., preferably a tower reactor or fixed bed reactor.

As a specific embodiment of the method described above in the present invention, wherein, in S4, the catalyst used for the isomerization of long-chain hydrocarbons to prepare liquid fuel is an acid catalyst with a desorption temperature of 150-600° C. after NH ₃ adsorption. Wherein, the acid catalyst can selectively catalyze the isomerization of long-chain hydrocarbons under non-hydrogen atmosphere conditions to obtain liquid fuels.

As a specific embodiment of the method described above in the present invention, wherein, in S4, the acid catalyst includes ZSM-22, ZSM-23, ZSM-48, ZSM-35, SAPO-31, SAPO-11, ZSM-5 , EU-1, Y molecular sieve and β molecular sieve etc. one or more.

As a specific embodiment of the method described above in the present invention, wherein, in S4, the reactions involved in the long-chain hydrocarbon isomerization process include one or more of cracking, isomerization, cyclization, superposition, and the like.

As a specific embodiment of the method described above in the present invention, wherein, in S4, the process conditions for preparing liquid fuel by isomerization of long-chain hydrocarbons include: temperature 200-420°C, pressure -0.1MPa to 4MPa, mass space velocity 0.2- 3h ^-1 .

As a specific embodiment of the method described above in the present invention, wherein, in S4, the reactor used for the preparation of liquid fuel by isomerization of long-chain hydrocarbons can be a reactor, a tower reactor and a fixed bed reactor, etc., preferably a tower reactor. reactor or fixed bed reactor.

According to the composition of the oil raw material, the catalyst and the difference in process conditions, the main component of the engine liquid fuel obtained by the method for preparing liquid fuel by the selective catalytic deoxygenation of oil provided by the invention is C ₆ -C ₂₀ hydrocarbons, and can be obtained by changing the oil raw material The composition of fatty acids, catalysts and process conditions, etc., to adjust the composition of liquid fuels.

In order to obtain high-quality products suitable for gasoline, diesel or aviation kerosene, the liquid fuel can be further hydrorefined or rectified and separated to obtain target products of suitable fractions.

The method for preparing liquid fuel through selective catalytic deoxygenation of grease provided by the present invention has significant beneficial effects, including:

1. The method has strong adaptability to raw materials, and can directly process low-quality oil raw materials, which can significantly reduce raw material costs;

2. This method can also avoid problems related to sulfurized catalysts, and can significantly simplify the process flow;

3. This method can also avoid the use of precious metal catalysts, and the catalysts used are cheap and easy to obtain, which reduces the cost of catalysts;

4. This method can also significantly reduce hydrogen consumption and material consumption;

5. This method can also increase the production of glycerin with higher added value, and increase the production value;

6. The reaction process of the method is highly controllable, and the selectivity of the target product is good;

7. In addition, by changing the raw materials, catalysts and process conditions in the method, the product composition can be flexibly adjusted to improve market adaptability.

Detailed ways

It should be noted that the term "comprising" and any variations thereof in the specification and claims of the present invention are intended to cover non-exclusive inclusion, for example, a process, method, system, product or process that includes a series of steps or units. The apparatus is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to the process, method, product or apparatus.

The "ranges" disclosed herein are given in terms of lower limits and upper limits. There can be one or more lower bounds, and one or more upper bounds, respectively. A given range is defined by selecting a lower limit and an upper limit. Selected lower and upper limits define the boundaries of a particular range. All ranges defined in this manner are combinable, ie, any lower limit can be combined with any upper limit to form a range. For example, ranges of 60-120 and 80-110 are listed for a particular parameter, with the understanding that ranges of 60-110 and 80-120 are also contemplated. Additionally, if the minimum range values listed are 1 and 2, and the maximum range values listed are 3, 4, and 5, the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5.

In the present invention, unless otherwise stated, the numerical range "a-b" represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in the present invention, and "0-5" is only an abbreviated representation of these numerical combinations.

In the present invention, if there is no special description, all the embodiments and preferred embodiments mentioned in the present invention can be combined with each other to form a new technical solution.

In the present invention, if there is no special description, all the technical features and preferred features mentioned in the present invention can be combined with each other to form a new technical solution.

In order to make the object, technical solution and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with the examples. The following described embodiments are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention. Those who do not indicate the specific conditions in the examples are carried out according to the conventional conditions or the conditions suggested by the manufacturer. The reagents or instruments used were not indicated by the manufacturer, and they were all conventional products that could be purchased from the market. The experimental methods used are existing conventional methods unless otherwise specified.

Example 1

This embodiment provides a method for preparing liquid fuel through selective catalytic deoxygenation of grease, wherein the method includes the following specific steps:

Esterification of oil methyl esters into fatty acid methyl esters:

Use sodium methoxide (the amount is 0.5% of the mass of refined soybean oil) to catalyze the reaction of refined soybean oil with methanol at 80°C under normal pressure, and control the molar ratio of alcohol to oil to 7:1, and the mass space velocity to 0.7h ^-1 , to Methylation of refined soybean oil. After separating methanol and glycerin (yield nearly 10wt%), the content of fatty acid methyl ester in the obtained product is 97wt%.

Catalytic hydrogenation of fatty acid methyl esters to fatty alcohols:

Fatty acid methyl esters are subjected to catalytic hydrogenation in a tubular reactor filled with a 10-mesh copper-zinc-aluminum catalyst (the molar ratio of Cu:Zn:Al is 1:0.8:4, prepared by coprecipitation method). The process conditions are: temperature 240°C, pressure 20MPa, volume ratio of hydrogen to fatty acid methyl ester 15000:1, mass space velocity 0.5h ^-1 . After the catalytic hydrogenation reaction of the fatty acid methyl ester, the content of the fatty alcohol obtained after flash evaporation reaches 98wt%.

Intramolecular dehydration of fatty alcohols into long chain hydrocarbons:

In the tubular reactor filled with ZSM-22 and γ-Al ₂ O ₃ (mass ratio: 1:1) catalyst, the intramolecular dehydration of fatty alcohol is converted into long-chain hydrocarbons. The reaction process conditions are: temperature 380°C, The pressure is 0.1MPa, the mass space velocity of the fatty alcohol is 3h ^-1 , the obtained reaction product is separated by distillation, the content of long-chain hydrocarbon is more than 98wt%, and the oxygen content in long-chain hydrocarbon is less than 0.04wt%.

Preparation of liquid fuels by isomerization of long-chain hydrocarbons:

In a tubular reactor filled with catalysts ZSM-48 and ZSM-22 (mass ratio 1:1), long-chain hydrocarbons are isomerized to obtain isomerized liquid fuel, and the reaction process conditions are: temperature 300 °C, pressure 0.1MPa, mass space velocity of long-chain hydrocarbons is 1h ^-1 .

In this example, the liquid fuel prepared by deoxygenation of refined soybean oil through a series of selective reactions is mainly hydrocarbon fuel with a main component of C ₆ -C ₂₀ , and the yield reaches 83.4 wt%. In addition, the liquid fuel obtained in this embodiment can also be divided according to the boiling range to obtain gasoline, diesel and aviation fuel components, and further hydrorefining can be used to improve the quality of the product.

Example 2

This embodiment provides a method for preparing liquid fuel through selective catalytic deoxygenation of grease, wherein the method includes the following specific steps:

Esterification of oil methyl esters into fatty acid methyl esters:

The rubber seed oil with an acid value of 30mgKOH/g was reacted with methanol at 300°C and 20MPa, the molar ratio of alcohol to oil was 16:1, and the mass space velocity was 5h ^-1 to esterify the rubber seed oil. After the reacted mixture was separated and recovered for methanol and glycerin (yield nearly 8 wt%), the content of fatty acid methyl ester was 95 wt%.

Catalytic hydrogenation of fatty acid methyl esters to fatty alcohols:

Fatty acid methyl esters are subjected to catalytic hydrogenation reaction through a tubular reactor filled with 20-mesh copper-nickel-aluminum catalyst (Cu:Ni:Al molar ratio is 1:0.3:4, prepared by co-precipitation method). The process conditions are: temperature 200°C , pressure 6MPa, volume ratio of hydrogen to fatty acid methyl ester 8000:1, mass space velocity 2h ^-1 . After the selective catalytic hydrogenation reaction of the fatty acid methyl ester is completed, the content of the fatty alcohol obtained by flashing the obtained product reaches 94wt%.

Intramolecular dehydration of fatty alcohols into long chain hydrocarbons:

In the tower reactor filled with γ-Al ₂ O ₃ catalyst, intramolecular dehydration of fatty alcohol is converted into long-chain hydrocarbons. The reaction process conditions are: temperature 380°C, pressure -0.08MPa, mass space velocity of fatty alcohol 1h ^{- 1} . After the reaction is finished, the reaction product is separated to obtain long-chain hydrocarbons with a content greater than 97 wt%, and the oxygen content in the long-chain hydrocarbons is less than 0.03 wt%.

Preparation of liquid fuels by isomerization of long-chain hydrocarbons:

In a tubular reactor filled with SAPO-31 and SAPO-11 (mass ratio 1:1) catalysts, long-chain hydrocarbons are isomerized under a nitrogen atmosphere to prepare isomerized liquid fuels. The reaction process conditions are: The temperature is 320°C, the pressure is 2MPa, and the mass space velocity of long-chain hydrocarbons is 3h ^-1 .

In this example, the liquid fuel prepared by deoxygenating rubber seed oil through a series of selective reactions is mainly a hydrocarbon fuel with a main component of C ₆ -C ₂₀ , and the yield reaches 81.3 wt%. In addition, the liquid fuel obtained in this embodiment can also be divided according to the boiling range to obtain gasoline, diesel and aviation fuel components, or further hydrorefining can improve the fuel quality.

Example 3

This embodiment provides a method for preparing liquid fuel through selective catalytic deoxygenation of grease, wherein the method includes the following specific steps:

Esterification of oil methyl esters into fatty acid methyl esters:

React the catering industry waste oil catalyzed rancid by ZSM-5 acidic molecular sieve with methanol at 160°C and 1MPa, and control the molar ratio of alcohol to oil to 7:1, and the mass space velocity to 0.5h ^-1 , so as to convert the catering industry waste oil to form Esterification. After the reaction, after separating methanol and glycerin (yield is about 5wt%), rectifying under reduced pressure to obtain refined fatty acid methyl ester, its content is 99wt%.

Catalytic hydrogenation of fatty acid methyl esters to fatty alcohols:

Fatty acid methyl esters are catalytically hydrogenated in a tubular reactor filled with a 20-mesh copper-nickel-iron-aluminum catalyst (the molar ratio of Cu:Ni:Fe:Al is 1:0.3:0.3:4, prepared by coprecipitation method). The process conditions It is: temperature 180°C, pressure 10MPa, volume ratio of hydrogen to fatty acid methyl ester 600:1, mass space velocity 0.3h ^-1 . After the fatty acid methyl ester catalytic hydrogenation reaction is completed, the content of the fatty alcohol obtained by flashing the reaction product reaches 97wt%.

Intramolecular dehydration of fatty alcohols into long chain hydrocarbons:

In the tubular reactor filled with ZSM-35 and γ-Al ₂ O ₃ (mass ratio: 1:1) molecular sieve catalyst, the intramolecular dehydration of fatty alcohol is converted into long-chain hydrocarbons. The reaction process conditions are: temperature 300°C , pressure 0.2MPa, mass space velocity of fatty alcohol 1h ^-1 . The reaction product is separated by distillation to obtain long-chain hydrocarbons with a content greater than 98 wt%, and the oxygen content in the long-chain hydrocarbons is less than 0.035 wt%.

Preparation of liquid fuels by isomerization of long-chain hydrocarbons:

In a tubular reactor filled with ZSM-5 and Y molecular sieve (mass ratio 1:1) catalysts, long-chain hydrocarbons are isomerized to prepare isomerized liquid fuels. The reaction process conditions are: temperature 240 ° C, Pressure -0.05MPa, mass space velocity of long chain hydrocarbons 0.3h ^-1 .

In this example, the liquid fuel prepared by deoxidizing the waste oil of the catering industry through a series of selective reactions is mainly a hydrocarbon fuel with a main component of C ₆ -C ₂₀ , and the yield reaches 81.3 wt%. In addition, the liquid fuel prepared in this embodiment can also be divided according to the boiling range to obtain gasoline, diesel and jet fuel components, or further hydrorefining can improve the fuel quality.

Example 4

This embodiment provides a method for preparing liquid fuel through selective catalytic deoxygenation of grease, wherein the method includes the following specific steps:

Esterification of oil methyl esters into fatty acid methyl esters:

Make tallow react with methanol at 260°C and 6MPa, control the molar ratio of alcohol to oil to 10:1, and the mass space velocity to 0.5h ^-1 to esterify tallow methyl. After the reaction, after separation and recovery of methanol and glycerin (glycerin yield is about 8wt%), the content of fatty acid methyl ester is 97wt%.

Catalytic hydrogenation of fatty acid methyl esters to fatty alcohols:

Fatty acid methyl esters are catalytically hydrogenated through a tubular reactor filled with commercial copper-zinc-aluminum catalysts. The process conditions are: temperature 230°C, pressure 16MPa, volume ratio of hydrogen to fatty acid methyl esters 6000:1, mass space velocity 1.2 h ^-1 . In the product obtained by the catalytic hydrogenation reaction of the fatty acid methyl ester, the fatty alcohol content reaches 96 wt%.

Intramolecular dehydration of fatty alcohols into long chain hydrocarbons:

In the tower reactor filled with ZSM-23 and γ-Al ₂ O ₃ (mass ratio: 1:1) catalyst, the intramolecular dehydration of fatty alcohol is converted into long-chain hydrocarbons. The reaction process conditions are: temperature 280 ° C, pressure -0.09MPa, mass space velocity of fatty alcohol 0.5h ^-1 . The reaction product is separated to obtain long-chain hydrocarbons with a content greater than 97 wt%, and the oxygen content in the long-chain hydrocarbons is less than 0.04 wt%.

Preparation of liquid fuels by isomerization of long-chain hydrocarbons:

In a tubular reactor filled with ZSM-48 and SAPO-11 (mass ratio: 1:1) catalysts, long-chain hydrocarbons are isomerized to prepare isomerized liquid fuels. The reaction process conditions are: temperature 300°C , pressure 0.1MPa, mass space velocity of long-chain hydrocarbons 1h ^-1 .

In the embodiment of the present invention, the liquid fuel prepared by deoxygenating tallow through a series of selective reactions is mainly a hydrocarbon fuel with a main component of C ₆ -C ₂₀ , and the yield reaches 82.5 wt%. In addition, the liquid fuel prepared in this embodiment can also be divided according to the boiling range to obtain gasoline, diesel and jet fuel components, or further hydrorefining can improve the fuel quality.

Example 5

This embodiment provides a method for preparing liquid fuel through selective catalytic deoxygenation of grease, wherein the method includes the following specific steps:

Esterification of oil methyl esters into fatty acid methyl esters:

Cottonseed oil is reacted with methanol at 210°C and 6MPa, and the molar ratio of alcohol to oil is controlled to be 9:1, and the mass space velocity is 0.5h ^-1 to esterify the cottonseed oil. After the reaction, the content of fatty acid methyl ester was 96wt% after separation and recovery of methanol and glycerin (yield was about 9wt%).

Catalytic hydrogenation of fatty acid methyl esters to fatty alcohols:

Fatty acid methyl esters are catalytically hydrogenated through a tubular reactor filled with commercial copper-zinc-aluminum catalysts. The process conditions are: temperature 250°C, pressure 10MPa, volume ratio of hydrogen to fatty acid methyl esters 2000:1, mass space velocity 0.5h ^-1 . In the product obtained by the catalytic hydrogenation reaction of the fatty acid methyl ester, the fatty alcohol content reaches 97wt%.

Intramolecular dehydration of fatty alcohols into long chain hydrocarbons:

In the tubular reactor filled with ZrO ₂ and ZSM-22 (the two are mixed according to the mass ratio of 1:1) molecular sieve catalyst, the intramolecular dehydration of fatty alcohol is converted into long-chain hydrocarbons, and the reaction process conditions are: temperature 250 ° C , pressure 0.1MPa, mass space velocity of fatty alcohol 0.2h ^-1 . After the reaction product is separated, the long-chain hydrocarbon content obtained is greater than 96 wt%, and the oxygen content in the long-chain hydrocarbon is less than 0.04 wt%.

Preparation of liquid fuels by isomerization of long-chain hydrocarbons:

In the tubular reactor filled with ZSM-48 and ZSM-23 (mass ratio: 1:1) catalysts, long-chain hydrocarbons are isomerized to prepare isomerized liquid fuels. The reaction process conditions are: temperature 280°C , pressure -0.06MPa, mass space velocity of long chain hydrocarbons 0.5h ^-1 .

In this example, the liquid fuel prepared by deoxygenating cottonseed oil through a series of selective reactions is mainly a hydrocarbon fuel with a main component of C ₆ -C ₂₀ , and the yield reaches 82.3 wt%. In addition, the liquid fuel prepared in this embodiment can also be divided according to the boiling range to obtain gasoline, diesel and aviation fuel components, or further hydrorefining can improve the fuel quality.

Comparative example 1

This comparative example provides a method for preparing liquid fuel by selective catalytic deoxygenation of grease, wherein the method comprises the following specific steps:

Esterification of oil methyl esters into fatty acid methyl esters:

Make the rubber seed oil with an acid value of 30mgKOH/g react with methanol at 300°C and 20MPa, and control the molar ratio of alcohol to oil to 16:1 and the mass space velocity to 5h ^-1 to methylate the rubber seed oil . After the reacted mixture was separated and recovered for methanol and glycerin (yield nearly 8 wt%), the content of fatty acid methyl ester was 95 wt%.

Catalytic hydrogenation of fatty acid methyl esters to fatty alcohols:

Fatty acid methyl esters are subjected to catalytic hydrogenation reaction through a tubular reactor filled with 20-mesh copper-nickel-aluminum catalyst (Cu:Ni:Al molar ratio is 1:0.3:4, prepared by co-precipitation method). The process conditions are: temperature 200°C , pressure 6MPa, volume ratio of hydrogen to fatty acid methyl ester 8000:1, mass space velocity 2h ^-1 . After the selective catalytic hydrogenation reaction of the fatty acid methyl ester is completed, the content of the fatty alcohol obtained by flashing the obtained product reaches 94wt%.

Preparation of liquid fuel:

Fatty alcohols are directly passed through a tubular reactor packed with SAPO-31 and SAPO-11 (mass ratio: 1:1) catalysts, and the fatty alcohols are dehydrated and isomerized under the action of the catalyst in a nitrogen atmosphere to obtain isomerization The process conditions for dehydration isomerization of liquid fuels are as follows: temperature 320°C, pressure 2MPa, mass space velocity of fatty alcohol 3h ^-1 .

Comparing Example 2 and Comparative Example 1, it can be seen that in Example 2, the intramolecular dehydration of fatty alcohols is converted into long-chain hydrocarbons, specifically: in the tower reactor filled with γ-Al ₂ O ₃ catalysts, the intramolecular dehydration of fatty alcohols Dehydration is converted into long-chain hydrocarbons. The reaction process conditions are: temperature 380°C, pressure -0.08MPa, mass space velocity of fatty alcohol 1h ^-1 . After the reaction is finished, the reaction product is separated to obtain long-chain hydrocarbons with a content greater than 97 wt%, and the oxygen content in the long-chain hydrocarbons is less than 0.03 wt%. The obtained long-chain hydrocarbons are mainly terminal olefins, the content of which is greater than 95 wt%. Then make this kind of high-purity long-chain terminal olefins in a tubular reactor filled with SAPO-31 and SAPO-11 (mass ratio is 1:1) catalysts, and carry out long-chain terminal olefin isolation under nitrogen atmosphere. The isomerized liquid fuel is obtained through the formation reaction, and the specific reaction process conditions are: temperature 320°C, pressure 2MPa, mass space velocity of long-chain terminal olefins 3h ^-1 . In Example 2, the intramolecular dehydration of fatty alcohols into long-chain hydrocarbons and then the isomerization of long-chain hydrocarbons to prepare liquid fuels can suppress the generation of cracking reaction products, wherein the selectivity of C ₁₂ -C ₁₈ components is greater than 80%, and the oxygen content in the liquid fuel is almost zero; in comparison, in Comparative Example 1, the fatty alcohol obtained by catalytic hydrogenation conversion of fatty acid methyl ester is directly dehydrated and isomerized to prepare isomerized liquid fuel. The way of preparing liquid fuel cannot suppress the formation of cracking reaction products. Correspondingly, in Comparative Example 1, the selectivity of C ₁₂ -C ₁₈ components drops to 62%, and the oxygen content in liquid fuel is about 2.8wt%.

To sum up, the method for preparing liquid fuel by selective catalytic deoxygenation of grease provided by the embodiment of the present invention first dehydrates fatty alcohols into long-chain hydrocarbons, and then prepares liquid fuels by isomerizing long-chain hydrocarbons, which can avoid The water produced by alcohol catalytic deoxygenation leads to an increase in the oxygen content of the isomer product, which can reduce the adverse effects of by-product water and prolong the service life of the catalyst. Isomerizing long-chain hydrocarbons to produce liquid fuels can also significantly reduce hydrogen consumption.

The above is only a specific embodiment of the present invention, and cannot limit the scope of the invention, so the replacement of its equivalent components, or the equivalent changes and modifications made according to the patent protection scope of the present invention, should still fall within the scope of this patent. category. In addition, the technical features and technical features, technical features and technical inventions, and technical inventions and technical inventions in the present invention can be used in free combination.

Claims (21)

1. A method of preparing a liquid fuel by selective catalytic deoxygenation of a lipid, wherein the method comprises:

s1: firstly, converting the grease into fatty acid methyl ester through methyl esterification;

s2: then, the fatty acid methyl ester is catalytically hydrogenated and converted into fatty alcohol;

s3: then the fatty alcohol is dehydrated in the molecule and converted into long-chain hydrocarbon;

s4: finally isomerizing long-chain hydrocarbon to obtain the liquid fuel.

2. The method according to claim 1, wherein the fat is animal fat and/or vegetable fat, the fat having a carbon chain length of C ₁₂ -C ₂₄ The fatty acid content of (2) is greater than 80wt%, and the total content of fatty acid glycerides and free fatty acids is greater than 90wt%.

3. The method of claim 1 or 2, wherein in S1, the fat is methyl esterified to convert the fat to fatty acid methyl ester by reacting the fat with methanol.

4. A process according to claim 3, wherein in S1 the fat is converted to fatty acid methyl esters by reacting with methanol under critical methanol conditions, by reacting under enzyme-catalyzed conditions, by reacting under homogeneous or heterogeneous acid-catalyzed conditions or by reacting under homogeneous or heterogeneous base-catalyzed conditions.

5. The process according to claim 1 or 4, wherein in S1, after methyl esterification of the fat and refining, the fatty acid methyl ester content in the obtained product is not less than 80wt%.

6. The process according to claim 5, wherein in S1, after methyl esterification and refining of the fat, the fatty acid methyl ester content of the resultant product is 95 to 100wt%.

7. The method according to claim 1, wherein in S2, the catalyst used for the catalytic hydrogenation of fatty acid methyl ester to fatty alcohol is a supported catalyst, the hydrogenation active metal used by the supported catalyst comprises one or more of platinum, palladium, gold, silver, cobalt, molybdenum, copper, nickel, zinc, iron, chromium, barium and manganese, and the carrier is activated carbon or Al ₂ O ₃ Or SiO ₂ ；

Preferably, the hydrogenation-active metal comprises one or more of copper, cobalt, molybdenum, nickel, iron, zinc and manganese.

8. The process of claim 1 or 7, wherein in S2, the process conditions for catalytic hydrogenation of fatty acid methyl esters to fatty alcohols comprise: the temperature is 160-300 ℃, the pressure is 2-20MPa, and the mass airspeed is 0.3-3h ^-1 The hydrogen oil volume ratio is 500:1-15000:1.

9. The process according to claim 1 or 7, wherein in S2, after catalytic hydroconversion and refining of the fatty acid methyl esters, the fatty alcohol content of the product obtained is greater than 86% by weight.

10. The process according to claim 9, wherein in S2, after catalytic hydroconversion and refining of the fatty acid methyl esters, the fatty alcohol content of the product obtained is 92-100% by weight.

11. The process according to claim 1, wherein in S3, the catalyst for intramolecular dehydration of fatty alcohols to longer-chain hydrocarbons is NH ₃ And the desorption temperature after adsorption is 150-600 ℃.

12. The method of claim 11, wherein in S3 the acid catalyst comprises γ -Al ₂ O ₃ 、ZrO ₂ One or more of ZSM-22, ZSM-23, ZSM-48, ZSM-35, SAPO-31, SAPO-11, ZSM-5, Y molecular sieve, and beta molecular sieve.

13. The method of claim 12, wherein in S3, when γ -Al is to be added ₂ O ₃ And/or ZrO ₂ When the catalyst is used as an acid catalyst in combination with one or more of ZSM-22, ZSM-23, ZSM-48, ZSM-35, SAPO-31, SAPO-11, ZSM-5, Y molecular sieve and beta molecular sieve ₂ O ₃ The content of (C) is more than 20wt%, zrO ₂ The content of (2) is more than 20wt%.

14. The method of claim 1, wherein in S3, the reaction involved in the intramolecular dehydration conversion of the fatty alcohol comprises one or more of dehydration, cleavage, isomerization, and cyclization reactions.

15. The method of any one of claims 1, 11-14, wherein the process conditions for intramolecular dehydration of fatty alcohols to longer chain hydrocarbons in S3 comprise: the temperature is 250-400 ℃, the pressure is-0.1 MPa to 0.5MPa, and the mass airspeed is 0.2-4h ^-1 。

16. The process according to any one of claims 1, 11 to 14, wherein in S3, the oxygen content of the resulting long-chain hydrocarbon is less than 0.1 wt.% after intramolecular dehydration conversion of the fatty alcohol and refining.

17. The method according to claim 16, wherein in S3, after intramolecular dehydration conversion of the fatty alcohol and refining, the oxygen content of the obtained long-chain hydrocarbon is less than 0.05wt%.

18. The process of claim 1, wherein in S4, the catalyst used for preparing the liquid fuel by isomerizing the long-chain hydrocarbon is NH ₃ And the desorption temperature after adsorption is 150-600 ℃.

19. The method of claim 18, wherein in S4 the acid catalyst comprises one or more of ZSM-22, ZSM-23, ZSM-48, ZSM-35, SAPO-31, SAPO-11, ZSM-5, EU-1, Y molecular sieves, and beta molecular sieves.

20. The process of claim 1, wherein in S4 the reaction involved in the isomerization of long chain hydrocarbons comprises one or more of cracking, isomerisation, cyclisation, folding.

21. The method of any one of claims 1, 18-20, wherein in S4, the process conditions for producing a liquid fuel by isomerization of long chain hydrocarbons include: temperature 200-420 ℃, pressure-0.1 MPa and 4MPa, and mass space velocity 0.2-3h ^-1 。