Molecular sieve supported metal catalyst and application thereof in preparation of long-chain alkane diesel oil by hydrodeoxygenation of stearic acid

Abstract

The invention discloses an application of a molecular sieve supported metal catalyst in preparation of long-chain alkane diesel oil by hydrodeoxygenation of stearic acid. The catalyst is composed of metal and an FAU molecular sieve, and the metal active component accounts for 0.1-20 wt%. According to the invention, the metal is loaded on the molecular sieve by adopting improved wet impregnation, the acid-metal catalyst with high metal dispersity is prepared, and the dual-function attribute of the catalyst can be effectively exerted. The catalysis method comprises the following steps: adding stearic acid, the catalyst, an organic solvent and an internal standard substance (n-octane) into a closed high-pressure reaction kettle, filling hydrogen, and reacting at 150-350 DEG C to obtain the long-chain alkane diesel oil (octadecane and heptadecane). Preferably, the catalyst can achieve complete conversion and the yield of 90% or above in preparation of long-chain alkane diesel oil through hydrodeoxygenation of stearic acid, has good catalytic stability, and is not inactivated after continuous circulation for five times.

Description

Technical Field

[0001] The invention relates to a hydrodeoxygenation catalyst, in particular to a molecular sieve-supported metal catalyst and application thereof in preparing long-chain alkane diesel by hydrodeoxygenation of stearic acid. Background Art

[0002] Since humans entered the industrial age, fossil energy has become one of the main forms of energy needed for human development. With the progress of society and the development of industry, the demand for energy in countries around the world has continued to rise. However, due to the limitation of energy reserves, non-renewable energy such as fossil energy will eventually face exhaustion. At the same time, the combustion of fossil energy will bring about a series of environmental problems such as greenhouse effect and environmental pollution. Therefore, it is urgent to find new environmentally friendly and renewable clean energy to replace fossil energy that is facing exhaustion. Biomass has large reserves, is carbon neutral, and is renewable. After rapid pyrolysis, pyrolysis bio-oil is produced, which can be used as a substitute for fossil fuels such as petroleum. It is not only of great significance in energy security, but also helps to reduce CO2 emissions without affecting food production. However, compared with fossil fuels, bio-oil has a high oxygen content, resulting in lower calorific value, hydrogen-carbon effective ratio and pH value, so that bio-oil cannot be used directly as a substitute for petroleum. The components of bio-oil must be hydrodeoxygenated to improve the quality. Hydrodeoxygenation is a key step in converting biomass into green hydrocarbon fuels. The rational design of efficient and stable catalysts is the core research topic of catalyst development. Zeolite-supported metal catalysts containing hydrogenation centers and acid sites have shown excellent catalytic performance in the chemoselective hydrodeoxygenation of biomass platform molecules. However, there is still a problem of poor catalyst stability during the catalytic liquid phase hydrodeoxygenation reaction.

[0003] Therefore, there is an urgent need to develop a new stable catalyst for the hydrodeoxygenation of stearic acid to produce long-chain alkane diesel. Summary of the invention

[0004] In view of the above problems, the present invention provides a molecular sieve-supported metal catalyst that can be recycled for multiple times without obvious deactivation. In the process of stearic acid hydrodeoxygenation, the catalyst utilizes the synergistic catalytic effect between the metal and the molecular sieve acid sites to achieve excellent catalytic performance.

[0005] The catalyst uses FAU molecular sieve as carrier and metal as active component. The metal is loaded onto the FAU molecular sieve by an improved impregnation method to prepare an acid-metal catalyst. Preferably, the loading amount of the active component metal in the catalyst is 0.1-20wt%.

[0006] The acid-metal catalyst preparation steps of the present invention are as follows:

[0007] Step 1: Weigh the metal into a beaker containing deionized water and stir;

[0008] Step 2: Weigh the FAU molecular sieve into the beaker in step 1 and stir;

[0009] Step 3: Heat at a constant temperature until the water evaporates;

[0010] Step 4: Grind the sample into powder and place it in a quartz boat for calcination and reduction;

[0011] Preferably, the metal described in step one is ruthenium or nickel, the stirring temperature of step one is 30-80°C, the stirring time is 10-60min, the FAU molecular sieve in step two is one or more of Y-type molecular sieve and USY molecular sieve, the stirring temperature is 50-120°C, the stirring time is 1-10h, the constant temperature heating temperature in step three is 60-150°C, and the calcination reduction temperature in step four is 300-600°C and maintained for 2-8h.

[0012] The acid-metal catalyst uses metal nanoparticles as hydrogenation active centers and the acid sites of the carrier molecular sieve as deoxygenation active centers.

[0013] The present invention further provides a method for preparing long-chain alkane diesel by hydrogenating and deoxygenating stearic acid, comprising the following steps: adding stearic acid, a catalyst, a solvent and an internal standard into a reactor, charging hydrogen, and reacting at 150-350° C. to obtain long-chain alkane diesel.

[0014] Preferably, the mass ratio of stearic acid to catalyst is 1 to 6;

[0015] Preferably, the reaction time is 1 to 6 hours;

[0016] Preferably, the hydrogen pressure is 1 to 5 MPa;

[0017] Preferably, the solvent is at least one of n-decane, n-octane and n-heptane;

[0018] More preferably, the solvent is n-octane.

[0019] Specifically, the catalyst of the present invention uses metal components as hydrogenation functional sites and molecular sieve acid sites for deoxygenation, and the catalytic performance is improved by the synergistic effect between acid and metal. The catalyst has high activity and selectivity and can achieve complete conversion of stearic acid. The yields of heptadecane and octadecane are >90%, and carbon loss is reduced. It has good stability and can be reused five times without deactivation. The preparation process is simple and the environmental pollution is small. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 STEM image of Ru / USY-21 metal-acid catalyst with metal loading of 1 wt%. DETAILED DESCRIPTION

[0021] The present invention will be further explained and illustrated below in conjunction with specific embodiments, but these examples do not limit the contents of the present invention.

[0022] Example 1 Screening of loaded metals

[0023] Experimental 1. Preparation of 1%Ru / USY-21 catalyst

[0024] 1) Weigh 0.06g of Ru(NH3)6Cl3 into a 50ml clean beaker and add 30ml

[0025] Ultrapure water, place the beaker in a 50℃ water bath and stir at constant temperature for 0.5h;

[0026] 2) Weigh 3g of USY-21 and put it into a beaker and continue heating it to 60℃ in a water bath and stirring it constantly

[0027] 5h;

[0028] 3) Then, the water bath was heated to 80°C, and after the water was evaporated, the mixture was placed in an oven and dried at 120°C for 10 h to obtain USY-21 molecular sieve loaded with ruthenium;

[0029] 4) The USY molecular sieve powder solid loaded with ruthenium was placed in a tubular reactor and reduced at 450°C in a 10 vol.% hydrogen / argon atmosphere for 5 hours to obtain a metal-acid catalyst with a metal loading of 1 wt%, which was labeled as 1% Ru / USY-21.

[0030] Experiment 2. Preparation of 1% Ni / USY-21 Catalyst

[0031] 1) Weigh 0.06g of Ni(NH3)6Cl3 into a 50ml clean beaker and add 30ml

[0032] Ultrapure water, place the beaker in a 50℃ water bath and stir at constant temperature for 0.5h;

[0033] 2) Weigh 3g of USY-21 and put it into a beaker and continue heating it to 60℃ in a water bath and stirring it constantly

[0034] 5h;

[0035] 3) Then, the water bath was heated to 80° C., and after the water was evaporated, the mixture was placed in an oven and dried at 120° C. for 10 h to obtain a USY-21 molecular sieve loaded with nickel;

[0036] 4) The nickel-loaded USY molecular sieve powder solid was placed in a tubular reactor and reduced at 450° C. in a 10 vol.% hydrogen / argon atmosphere for 5 h to obtain a metal-acid catalyst with a metal loading of 1 wt%, labeled as 1% Ni / USY-21.

[0037] Experiment 3. The specific steps of preparing long-chain alkane diesel by hydrogenation deoxygenation of stearic acid catalyzed by the above catalyst are as follows:

[0038] 0.4g of stearic acid, 0.3g of the catalyst prepared in Experiment 1 and Experiment 2, 0.065g of n-octane and 40mL of dodecane were added to a 100ml autoclave, nitrogen was introduced to replace the gas three times, hydrogen was introduced to replace the gas three times, and then hydrogen was filled to 3MPa, and the temperature was raised to 240℃ and stirred for 3h. After the reaction was completed, it was cooled to room temperature, the supernatant was filtered, and the product was detected by gas chromatography. The conversion rate of stearic acid and the selectivity of octadecane, heptadecane, etc. in the product were calculated, and the results are as follows:

[0039] Table 1 Screening results of loaded metals

[0040]

[0041] It can be seen from Table 1 that under the same reaction conditions, the catalytic performance of the catalyst Ru / USY-21 loaded with metallic ruthenium is the best.

[0042] Example 2 Screening of Catalyst Support

[0043] Experimental 1. Preparation of 1%Ru / USY-21 catalyst

[0044] 1) Weigh 0.06g of Ru(NH3)6Cl3 into a 50ml clean beaker and add 30ml

[0045] Ultrapure water, place the beaker in a 50℃ water bath and stir at constant temperature for 0.5h;

[0046] 2) Weigh 3g of USY-21 and put it into a beaker and continue heating it to 60℃ in a water bath and stirring it constantly

[0047] 5h;

[0048] 3) Then, the water bath was heated to 80°C, and after the water was evaporated, the mixture was placed in an oven and dried at 120°C for 10 h to obtain USY-21 molecular sieve loaded with ruthenium;

[0049] 4) The USY molecular sieve powder solid loaded with ruthenium was placed in a tubular reactor and reduced at 450°C in a 10 vol.% hydrogen / argon atmosphere for 5 hours to obtain a metal-acid catalyst with a metal loading of 1 wt%, which was labeled as 1% Ru / USY-21.

[0050] Experiment 2. Preparation of 1%Ru / USY-54 Catalyst

[0051] 1) Weigh 0.06g of Ru(NH3)6Cl3 into a 50ml clean beaker and add 30ml

[0052] Ultrapure water, place the beaker in a 50℃ water bath and stir at constant temperature for 0.5h;

[0053] 2) Weigh 3g of USY-54 and put it into a beaker and continue heating it to 60℃ in a water bath and stirring it constantly

[0054] 5h;

[0055] 3) Then, the water bath was heated to 80°C, and after the water was evaporated, the mixture was placed in an oven and dried at 120°C for 10 h to obtain USY-54 molecular sieve loaded with ruthenium;

[0056] 4) The USY molecular sieve powder solid loaded with ruthenium was placed in a tubular reactor and reduced at 450°C in a 10 vol.% hydrogen / argon atmosphere for 5 hours to obtain a metal-acid catalyst with a metal loading of 1 wt%, labeled as 1% Ru / USY-54.

[0057] Experiment 3. Preparation of 1%Ru / USY-80 Catalyst

[0058] 1) Weigh 0.06g of Ru(NH3)6Cl3 into a 50ml clean beaker and add 30ml

[0059] Ultrapure water, place the beaker in a 50℃ water bath and stir at constant temperature for 0.5h;

[0060] 2) Weigh 3g of USY-80 and put it into a beaker and continue heating it to 60℃ in a water bath and stirring it constantly

[0061] 5h;

[0062] 3) Then, the water bath was heated to 80°C, and after the water was evaporated, the mixture was placed in an oven and dried at 120°C for 10 h to obtain USY-80 molecular sieve loaded with ruthenium;

[0063] 4) The USY molecular sieve powder solid loaded with ruthenium was placed in a tubular reactor and reduced at 450°C in a 10 vol.% hydrogen / argon atmosphere for 5 hours to obtain a metal-acid catalyst with a metal loading of 1 wt%, which was labeled as 1% Ru / USY-80.

[0064] Experiment 4. The specific steps of preparing long-chain alkane diesel by hydrogenation deoxygenation of stearic acid catalyzed by the above catalyst are as follows:

[0065] 0.4g of stearic acid, 0.3g of the catalyst prepared in Experiment 1, Experiment 2 and Experiment 3, 0.065g of n-octane and 40mL of dodecane were added to a 100ml autoclave, nitrogen was introduced to replace the gas three times, hydrogen was introduced to replace the gas three times, and then hydrogen was filled to 3MPa, and the temperature was raised to 240℃ and stirred for 3h. After the reaction was completed, it was cooled to room temperature, the supernatant was filtered, and the product was detected by gas chromatography. The conversion rate of stearic acid and the selectivity of octadecane, heptadecane, etc. in the product were calculated, and the results are as follows:

[0066] Table 2 Screening results of catalyst carriers

[0067]

[0068] From Table 2, it can be seen that under the same reaction conditions, the smaller the molecular sieve silicon-aluminum ratio, the better the catalytic performance, the higher the stearic acid conversion rate and the selectivity of octadecane and heptadecane. From Example 2, it can be determined that the preferred catalyst is Ru / USY-21.

[0069] Embodiment 3:

[0070] Cyclic experiments using the best catalyst:

[0071] 1) Weigh 0.06g of Ru(NH3)6Cl3 into a 50ml clean beaker and add 30ml

[0072] Ultrapure water, place the beaker in a 50℃ water bath and stir at constant temperature for 0.5h;

[0073] 2) Weigh 3 g of USY-21 and put it into a beaker and continue heating it to 60°C in a water bath and stirring for 5 hours;

[0074] 3) Then, the water bath was heated to 80°C, and after the water was evaporated, the mixture was placed in an oven and dried at 120°C for 10 h to obtain USY-21 molecular sieve loaded with ruthenium;

[0075] 4) placing USY-21 molecular sieve powder solid loaded with ruthenium in a tubular reactor.

[0076] 450 ° C, 10 vol.% hydrogen / argon atmosphere reduction for 5 h, and finally obtained a Ru / USY-21 metal-acid catalyst with a metal loading of 1 wt%. Its STEM image is shown in Figure 1 5) Add 0.4g of stearic acid, 0.3g of the catalyst of Example 3, 0.065g of n-octane and 40mL of dodecane into a 100ml autoclave, introduce nitrogen to replace the gas three times, introduce hydrogen to replace the gas three times, fill the hydrogen to 3MPa, heat to 240℃ and stir for 1h. After the reaction is completed, cool to room temperature, take the supernatant and filter,

[0077] The product was detected by gas chromatography. The conversion rate of stearic acid and the selectivity of octadecane, heptadecane, etc. in the product were calculated. Catalyst recovery: The mixture in the autoclave was washed with anhydrous ethanol for 4 to 6 times and dried at room temperature for 24 hours.

[0078] 6) Catalyst Repeat Experiment: 0.4 g of stearic acid, the recovered catalyst, 0.065

[0079] 100 g of n-octane and 40 mL of dodecane were loaded into a high-pressure reactor. After nitrogen was introduced to replace the gas three times, hydrogen was introduced to replace the gas three times, and then hydrogen was filled to 3 MPa. The stirring speed was controlled to 1000 rpm, and the reaction was carried out at 240°C for 1 hour. The catalyst was recycled and used repeatedly for 5 times. The catalyst repeatability test results are shown in the following table:

[0080] Table 3 Catalyst repeatability test results

[0081]

[0082]

[0083] It can be seen from Table 3 that after the Ru / USY-21 catalyst of the present invention is recycled and reused for 5 times, it still has a good catalytic effect, the raw material conversion rate can reach 91.98%, and the selectivity of octadecane and heptadecane can reach 55.59%.

[0084] Comparative Example 1

[0085] Experimental 1. Preparation of 1% Fe / USY-21 Catalyst

[0086] 1) Weigh 0.06g of Fe(NH3)6Cl3 into a 50ml clean beaker and add 30ml

[0087] Ultrapure water, place the beaker in a 50℃ water bath and stir at constant temperature for 0.5h;

[0088] 2) Weigh 3g of USY-21 and put it into a beaker and continue heating it to 60℃ in a water bath and stirring it constantly

[0089] 5h;

[0090] 3) Then, the water bath was heated to 80°C, and after the water was evaporated, the mixture was placed in an oven and dried at 120°C for 10 h to obtain USY-21 molecular sieve loaded with iron;

[0091] 4) The iron-loaded USY molecular sieve powder solid was placed in a tubular reactor and reduced at 450° C. in a 10 vol.% hydrogen / argon atmosphere for 5 h to obtain a metal-acid catalyst with a metal loading of 1 wt%, labeled as 1% Fe / USY-21.

[0092] Experiment 2. Preparation of 1%Ru / ZSM-5 Catalyst

[0093] 1) Weigh 0.06g of Ru(NH3)6Cl3 into a 50ml clean beaker and add 30ml

[0094] Ultrapure water, place the beaker in a 50℃ water bath and stir at constant temperature for 0.5h;

[0095] 2) Weigh 3 g of ZSM-5 and put it into a beaker and continue heating it to 60°C in a water bath and stirring for 5 hours;

[0097] 3) Then, the water bath was heated to 80°C, and after the water was evaporated, the mixture was placed in an oven and dried at 120°C for 10 h to obtain a ZSM-5 molecular sieve loaded with ruthenium;

[0098] 4) placing the ruthenium-loaded ZSM-5 molecular sieve powder solid in a tubular reactor.

[0099] The catalyst was reduced at 450°C in a 10 vol.% hydrogen / argon atmosphere for 5 h, and a metal-acid catalyst with a metal loading of 1 wt% was obtained, which was labeled as 1% Ru / ZSM-5.

[0100] Experiment 3. Preparation of 1% Ni / ZSM-5 Catalyst

[0101] 1) Weigh 0.06g of Ni(NH3)6Cl3 into a 50ml clean beaker, add 30ml of ultrapure water, and place the beaker in a 50℃ water bath and stir at constant temperature for 0.5h;

[0102] 2) Weigh 3 g of ZSM-5 and put it into a beaker and continue heating it to 60°C in a water bath and stirring for 5 hours;

[0103] 3) Then heat the water bath to 80°C, and after the water is evaporated, place it in an oven at 120°C.

[0104] Dry for 10 h to obtain the nickel-loaded ZSM-5 molecular sieve;

[0105] 4) The nickel-loaded ZSM-5 molecular sieve powder solid is placed in a tubular reactor and reduced at 450° C. in a 10 vol.% hydrogen / argon atmosphere for 5 h to obtain a metal-acid catalyst with a metal loading of 1 wt%, which is labeled as 1% Ni / ZSM-5.

[0106] Experiment 4. The specific steps of preparing long-chain alkane diesel by hydrogenation deoxygenation of stearic acid catalyzed by the above catalyst are as follows:

[0107] 0.4g of stearic acid, 0.3g of the catalyst prepared in Experiment 1, Experiment 2 and Experiment 3, 0.065g of n-octane and 40mL of dodecane were added to a 100ml autoclave, nitrogen was introduced to replace the gas three times, hydrogen was introduced to replace the gas three times, and then hydrogen was filled to 3MPa, and the temperature was raised to 240℃ and stirred for 3h. After the reaction was completed, it was cooled to room temperature, the supernatant was filtered, and the product was detected by gas chromatography. The conversion rate of stearic acid and the selectivity of octadecane, heptadecane, etc. in the product were calculated, and the results are as follows:

[0108] Table 4 Comparative Example Test Results

[0109]

[0110] According to the above experimental results, it can be found that the catalyst of the present invention uses metal components as hydrogenation functional sites and molecular sieve acid sites for deoxygenation, and the catalytic performance is improved by the synergistic effect between acid and metal. The catalyst has high activity and selectivity and can achieve complete conversion of stearic acid. The yields of heptadecane and octadecane are >90%, reducing carbon loss, and has good stability and can be reused five times without deactivation.

[0111] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A molecular sieve-supported metal catalyst, characterized in that: The catalyst comprises FAU molecular sieve and metal particles loaded on the FAU molecular sieve; the loading amount of the metal particles in the catalyst is 0.1 to 20 wt%; The catalyst is prepared by the following method: 1) Weigh the metal salt into deionized water and stir; 2) Weighing FAU molecular sieves and adding them to the solution in step 1) and stirring; 3) heating the solution of step 2) at a constant temperature until the water is evaporated; 4) Grinding the sample obtained in step 3) into powder and reducing it to obtain the target catalyst; The metal in step 1) is ruthenium or nickel, the stirring temperature is 30 to 80° C., and the stirring time is 10 to 60 min; The FAU molecular sieve in step 2) is a Y-type molecular sieve and a USY molecular sieve with a silicon-aluminum ratio between 20 and 80, the stirring temperature is 50 to 120°C, the stirring time is 1 to 10 hours, and the constant temperature heating temperature in step 3 is 60 to 150°C; The calcination reduction temperature in step 4) is 300-600° C. and maintained for 2-8 hours.

2. A method for preparing long-chain alkane diesel by hydrogenating and deoxygenating stearic acid, characterized in that: The method comprises the following steps: adding stearic acid, a catalyst, a solvent and an internal standard substance n-octane into a reactor, charging with hydrogen, reacting at 150-350° C. to obtain long-chain alkane diesel; the catalyst is the catalyst according to claim 1.

3. The method for preparing long-chain alkane diesel by hydrogenating and deoxygenating stearic acid according to claim 1, characterized in that: The mass ratio of stearic acid to the metal catalyst is 1 to 6.

4. The method for preparing long-chain alkane diesel by hydrogenating and deoxygenating stearic acid according to claim 2, characterized in that: The reaction time is 1 to 6 hours.

5. The method for preparing long-chain alkane diesel by hydrogenating and deoxygenating stearic acid according to claim 2, characterized in that: The hydrogen pressure is 1~5MPa.

6. The method for preparing long-chain alkane diesel by hydrogenating and deoxygenating stearic acid according to claim 2, characterized in that: Stearic acid was completely converted, and the total yield of heptadecane and octadecane was greater than 90%.

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