A catalyst for hydrogenation of red mud-based oil and fat and its preparation method and application

Abstract

The application provides a preparation method of a red mud-based catalyst for oil and fat hydrodeoxygenation. Compared with the prior art, the catalyst prepared by taking the acid-treated red mud as a carrier has a proper pore structure, the gradient pore channel can meet the mass transfer requirement of oil and fat probe molecules, and the surface of the carrier is rich in acid and alkali sites, so that the reaction tends to different reaction paths by adjusting the proper medium-strong acid site or medium-strong alkali site by using different nickel salts, and the hydrodeoxygenation activity of the catalyst is effectively improved. Furthermore, the preparation method has low cost, simple synthesis method and low preparation difficulty, and the obtained catalyst has high catalytic efficiency.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalysts, and particularly relates to a red mud-based catalyst for oil and fat hydrodeoxygenation as well as a preparation method and application thereof. BACKGROUND

[0002] The rapid economic development has made energy increasingly exhausted, and the traditional petrochemical diesel and other energy has caused environmental pollution, so it is urgent to find a green alternative energy. Biomass energy as a renewable resource has attracted much attention in recent years, and its raw materials are abundant and widely sourced and cause little environmental pollution. Biodiesel generally refers to fatty acid methyl ester formed by reaction of plant oil, animal oil or waste oil with methanol or ethanol, also known as BD100 biodiesel, which has the characteristics of high cetane number, low sulfur, no aromatic hydrocarbon, etc., and can be used as a blending component of diesel, and is an internationally recognized renewable clean fuel. The second generation biodiesel is prepared by hydrodeoxygenation of the first generation biodiesel, i.e. fatty acid methyl ester, and compared with the first generation biodiesel, the second generation biodiesel has the same chemical structure as diesel, has viscosity and calorific value similar to diesel, has low density and high cetane number, low sulfur content, low pour point and oxidation stability comparable to diesel, etc. Therefore, it is of great significance to further convert fatty acid methyl ester into high-quality biomass fuel by catalytic means.

[0003] Hydrodeoxygenation (HDO) is a key reaction path for preparation, and the performance of the catalyst plays a key role therein. The HDO reaction has two parts: hydrogenation reaction and deoxygenation reaction. The hydrogenation reaction is affected by Pt, Pd, Ru, Ni and other metal catalysts. The acid sites affect the deoxygenation reaction, and the C-O bond needs to be broken in the reaction, which requires high energy, so the deoxygenation reaction is difficult to occur. In addition, the synergistic effect between the metal sites and the acid sites promotes the overall HDO efficiency. The existence of Lewis acid sites and the high porosity of the carrier play a key role in the hydrodeoxygenation of oil and fat. The commonly used catalyst carriers are activated carbon, oxides and molecular sieves. Although the traditional noble metal catalyst has excellent isomerization activity and selectivity, its high price becomes an obstacle to its industrialization, so it is urgent to prepare a catalyst with high reaction activity, selectivity and stability, and low price. It is the current hotspot and trend to develop a new type of carrier by combining multi-metal components and exploring the coupling technology between the carrier and the active component for the hydrodeoxygenation of biodiesel.

[0004] Red mud, a solid waste generated during the Bayer process for extracting alumina from bauxite, is a substance containing radioactive materials, trace heavy metals, and high alkalinity (pH = 10-13). Compared to ordinary clay minerals, red mud (RM) has a higher specific surface area, higher porosity, and larger particle size. Furthermore, RM has a complex composition, containing oxides of Fe, Ti, Al, and Mn, as well as rare earth elements. These components resemble a heterogeneous polymetallic compound, and after further modification, it possesses catalytic ability for the hydrogenation of oils and fats. Therefore, this invention aims to provide a red mud-based catalyst for the hydrogenation and deoxygenation of oils and fats. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a catalyst for the hydrodeoxygenation of red mud-based oils and fats, its preparation method and application, wherein the catalyst for the hydrodeoxygenation of red mud-based oils and fats can be used to regulate the hydrodeoxygenation reaction pathway of oils and fats by regulating the active nickel precursor.

[0006] This invention provides a method for preparing a catalyst for the hydrodeoxygenation of red mud-based oils, comprising the following steps:

[0007] S1) The red mud is pretreated with an acid solution to obtain pretreated red mud;

[0008] S2) The pretreated red mud is calcined to obtain calcined red mud;

[0009] S3) After loading the nickel precursor onto calcined red mud by impregnation, the mud is calcined to obtain an intermediate product; the nickel precursor includes nickel carbonate and / or nickel chloride.

[0010] S4) After reducing the intermediate product, a catalyst for the hydrodeoxygenation of red mud-based oil is obtained.

[0011] Preferably, the acid solution is selected from one or more of hydrochloric acid solution, nitric acid solution, oxalic acid solution and acetic acid solution, and is preferably an acetic acid solution; the concentration of the acid solution is 0.1 to 1 mol / L.

[0012] Preferably, the pretreatment time is 1 to 5 hours.

[0013] Preferably, the calcination temperature in step S2) is 400℃~600℃; the calcination time is 2~6h.

[0014] Preferably, the mass of nickel in the nickel precursor is 1% to 20% of the mass of the calcined red mud.

[0015] Preferably, the calcination temperature in step S3) is 400℃~600℃; the calcination time is 2~6h.

[0016] Preferably, the temperature of the reduction treatment is 400-600 DEG C; the time of the reduction treatment is 4-6h; the reduction treatment is carried out in a hydrogen atmosphere; and the flow rate of the hydrogen is 10-100 mL / min.

[0017] The application further provides the red mud-based oil and fat hydrodeoxygenation catalyst prepared by the preparation method.

[0018] The application further provides application of the red mud-based oil and fat hydrodeoxygenation catalyst prepared by the preparation method in catalyzing fatty acid and / or fatty acid ester hydrodeoxygenation to prepare alkanes.

[0019] Preferably, the fatty acid is palmitic acid; the temperature of the hydrodeoxygenation is 260-400 DEG C; and the hydrogen pressure of the hydrodeoxygenation is 2-6 MPa.

[0020] The application provides a preparation method of a red mud-based oil and fat hydrodeoxygenation catalyst, which comprises the following steps: S1) pretreating red mud with an acid solution to obtain pretreated red mud; S2) calcining the pretreated red mud to obtain calcined red mud; S3) loading a nickel precursor on the calcined red mud by an impregnation method, and then calcining to obtain an intermediate product; the nickel precursor comprises nickel carbonate and / or nickel chloride; and S4) reducing the intermediate product to obtain the red mud-based oil and fat hydrodeoxygenation catalyst. Compared with the prior art, the catalyst prepared by the application has appropriate pore structure, gradient pore channels can meet the mass transfer requirements of oil and fat probe molecules, and the surface of the carrier is rich in acid-base sites. By using different nickel salts to adjust appropriate medium-strong acid sites or medium-strong base sites, the reaction tends to different reaction paths, and the hydrodeoxygenation activity of the catalyst is effectively improved. Furthermore, the preparation method has low cost, simple synthesis method and low preparation difficulty, and the obtained catalyst has high catalytic efficiency.

[0021] The experimental results show that the catalyst prepared by the application has 100% conversion rate and more than 80% C 15 alkane selectivity or C 16 alkane selectivity. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 FIG. 1 is a graph of the oil and fat hydrodeoxygenation reaction performance results of the red mud-based oil and fat hydrodeoxygenation catalysts obtained by different acid treatments in Example 1 of the application.

[0023] Figure 2 FIG. 2 is a graph of the oil and fat hydrodeoxygenation reaction performance results of the red mud-based oil and fat hydrodeoxygenation catalysts obtained by different nickel precursors in Example 2 of the application. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0025] The present application provides a preparation method of a red mud-based oil and fat hydrodeoxygenation catalyst, comprising the following steps: S1) pretreating red mud with an acid solution to obtain pretreated red mud; S2) calcining the pretreated red mud to obtain calcined red mud; S3) loading a nickel precursor on the calcined red mud by an impregnation method, and then calcining to obtain an intermediate product; the nickel precursor comprises nickel carbonate and / or nickel chloride; and S4) reducing the intermediate product to obtain the red mud-based oil and fat hydrodeoxygenation catalyst.

[0026] Among them, the present application does not have special restrictions on the source of all raw materials, which can be purchased on the market.

[0027] The red mud is pretreated by an acid solution to obtain pretreated red mud; the source of the red mud is not particularly limited in the application, and the red mud obtained by various methods can be used, which can be Bayer process red mud, sintering process red mud or combined process red mud, etc., and in the examples provided in the application, the Bayer process red mud is taken as an example for illustration; the red mud is preferably obtained by drying, grinding and sieving of the original red mud sample; the drying is preferably carried out at room temperature; the concentration of the acid solution is preferably 0.1-1 mol / L, more preferably 0.1-0.5 mol / L, and more preferably 0.1-0.2 mol / L; the acid solution is preferably one or more of hydrochloric acid solution, nitric acid solution, oxalic acid solution and acetic acid solution, and more preferably acetic acid solution; the ratio of the red mud to the acid solution is preferably (1-10) g:100 mL, more preferably (3-8) g:100 mL, and more preferably (4-6) g:100 mL; the pretreatment time is preferably 1-5 h, and more preferably 2-3 h; the pretreatment is preferably carried out under stirring; after the pretreatment, washing to neutral, drying are preferably carried out to obtain the pretreated red mud; the washing can be separated by filtration or centrifugation; the centrifugal speed is preferably 8000-10000 r / min; the centrifugal time is preferably 1-5 min, and more preferably 2-3 min; the drying temperature is preferably 80℃-120℃, and more preferably 100℃; and the drying time is preferably 8-12 h; by pretreating the red mud with an acid solution, the content of Fe2O3 in the catalyst is increased, and the alkaline earth components such as Na2O and CaO which may block the pore channel are removed. In addition, the treatment also significantly improves the specific surface area and pore size of the catalyst, increases the medium acid sites and oxygen vacancies, can make the reaction path tend to the HDO path, maintains the carbon chain length, and reduces the CO / CO2 generated by decarbonylation (DCO) and decarboxylation (DCO2) reactions.

[0028] The pretreated red mud is calcined to obtain calcined red mud; the pretreated red mud is preferably ground into powder before calcination; the calcination temperature is preferably 400℃-600℃, more preferably 450℃-550℃, and more preferably 500℃; the calcination time is preferably 2-6 h, more preferably 3-5 h, and more preferably 4 h.

[0029] The intermediate product is obtained by loading nickel precursor on the calcined red mud through impregnation method, and then calcining; the nickel precursor includes nickel carbonate and / or nickel chloride; the catalysts prepared by different nickel precursors have large difference in catalytic hydrodeoxygenation path; when nickel chloride is used as the nickel precursor, the reaction path tends to HDO path, and the carbon chain length of the product can be maintained; when nickel carbonate is used as the nickel precursor, the reaction tends to decarbonylation (DCO) and decarboxylation (DCO2) path, the hydrogen consumption is reduced, and the product is more CO / CO2. Therefore, the regulation of the oil catalytic hydrodeoxygenation reaction path can be realized by selecting the nickel precursor. The mass of nickel element in the nickel precursor is preferably 1% to 20% of the mass of the calcined red mud, more preferably 5% to 15%, more preferably 5% to 12%, more preferably 5% to 10%, and most preferably 7%. In the present application, the loading of the nickel precursor on the calcined red mud through the impregnation method is preferably carried out according to the following steps: the calcined red mud is stirred and impregnated in a solution containing the nickel precursor, and then dried, or the calcined red mud is mixed with the nickel precursor, and then stirred and impregnated in deionized water, and then dried; the ratio of the solution containing the nickel precursor or deionized water to the calcined red mud is preferably (50-200) mL:1 g, more preferably (80-150) mL:1 g, more preferably (80-120) mL:1 g, and most preferably 100 mL:1 g; the stirring and impregnation time is preferably 10-30 h, more preferably 15-30 h, more preferably 18-26 h, and most preferably 20-24 h; the drying temperature is preferably 80-120 DEG C, more preferably 100 DEG C; the drying time is preferably 8-12 h; after drying, the product is preferably ground into powder, and then calcined; the calcination temperature is preferably 400-600 DEG C, more preferably 450-550 DEG C, and more preferably 500 DEG C; the calcination time is preferably 2-6 h, more preferably 3-5 h, and more preferably 4 h.

[0030] The intermediate product is subjected to reduction treatment to obtain a red mud-based oil hydrodeoxygenation catalyst; the reduction treatment is preferably carried out in a hydrogen atmosphere; the flow rate of the hydrogen is preferably 10-100 mL / min, more preferably 30-80 mL / min, more preferably 40-60 mL / min, and most preferably 50 mL / min; the reduction treatment temperature is preferably 400-600 DEG C, more preferably 400-500 DEG C, and more preferably 450 DEG C; the reduction treatment time is preferably 4-6 h, more preferably 5 h; the temperature rising rate of the reduction treatment is preferably 5-20 DEG C / min, more preferably 5-15 DEG C / min, and more preferably 10 DEG C / min.

[0031] The catalyst prepared by the application has proper pore structure, gradient pore channel can meet the mass transfer requirement of oil and fat probe molecules, and the surface of the carrier is rich in acid and alkali sites, so that the reaction tends to different reaction paths by adjusting suitable medium-strong acid sites or medium-strong alkali sites by using different nickel salts, thereby effectively improving the hydrodeoxygenation activity of the catalyst.

[0032] The application further provides the red mud-based oil and fat hydrodeoxygenation catalyst prepared by the preparation method.

[0033] The application further provides application of the red mud-based oil and fat hydrodeoxygenation catalyst prepared by the preparation method in catalyzing the hydrodeoxygenation of fatty acids and / or fatty acid esters to prepare alkanes; the number of carbon atoms of the fatty acid is preferably 14-18, more preferably 15-17, and more preferably 16; the fatty acid ester is preferably a fatty acid methyl ester; the number of carbon atoms of the fatty acid in the fatty acid methyl ester is preferably 14-18, more preferably 15-17, and more preferably 16. In the application, the fatty acid is specifically palmitic acid; the fatty acid ester is specifically a fatty acid methyl ester; the temperature of the hydrodeoxygenation is preferably 260-400 DEG C; the hydrogen pressure of the hydrodeoxygenation is preferably 2-6 MPa, more preferably 3-5 MPa, and more preferably 4 MPa.

[0034] In order to further illustrate the application, the application of a red mud-based oil and fat hydrodeoxygenation catalyst, a preparation method thereof and application thereof are described in detail below with reference to the examples.

[0035] The reagents used in the following examples are commercially available; the original red mud sample used in the examples is a Bayer red mud.

[0036] Example 1

[0037] 1.1 The original red mud sample is dried, ground and sieved at room temperature, 100 mL of 0.5 mol / L acid solution (hydrochloric acid, nitric acid, oxalic acid or acetic acid is selected as the acid treatment agent) is mixed with 6 g of red mud, and stirred at room temperature for 2 h; then the mixed solution is filtered and washed to neutral, and is placed in an oven to be dried at 80 DEG C for 24 h to obtain the pretreated red mud.

[0038] 1.2 The pretreated red mud is ground into powder and is placed in a muffle furnace to be calcined for 4 h at a calcination temperature of 500 DEG C.

[0039] 1.3 The nickel precursor is loaded on the calcined red mud by an impregnation method: 7% of nickel is loaded on 1 g of the red mud sample, and the nickel precursor is nickel carbonate. After deionized water is added to the solution to about 100 mL, a magnet is added, and stirring is performed for about 24 h, and then the magnet is taken out and is washed clean with deionized water. Then the sample is dried in an oven at 100 DEG C for 24 h, and after being taken out, the sample is ground into powder and is placed in a muffle furnace to be calcined at a high temperature of 500 DEG C for 4 h to obtain an intermediate product.

[0040] 1.4 The intermediate product was reduced under a hydrogen atmosphere at a flow rate of 50 mL / min, with a temperature rise rate of 10 °C / min from 20 °C to 450 °C, and maintained for 5 h to obtain a red mud-based oil hydrogenation deoxidization catalyst, which was named as Ni / RM-HCl, Ni / RM-HNO3, Ni / RM-CA and Ni / RM-HAC, respectively, according to the type of acid treatment agent used.

[0041] In a reaction kettle, palm acid was used as an oil raw material (0.2 g), dodecane was used as a reaction solvent (20 mL), and the hydrogenation deoxidization reaction of palm acid was carried out under the catalysis of a Ni / RM-HCl, Ni / RM-HNO3, Ni / RM-CA or Ni / RM-HAC catalyst (catalyst amount 0.04 g), the reaction temperature was 280 °C or 320 °C, the reaction hydrogen pressure was 4 MPa, the stirring speed of the stirring paddle in the reaction kettle was 400 rpm, and the reaction time was 10 h, to obtain a hydrocarbon-based biodiesel, and the obtained hydrocarbon-based biodiesel was detected, to obtain a red mud-based oil hydrogenation deoxidization catalyst catalytic oil hydrogenation deoxidization reaction performance result graph obtained by different acid treatments, as shown in FIG. 1, wherein the left graph is a reaction at 280 °C, and the right graph is a reaction at 320 °C. Figure 1 It can be seen from FIG. 1 that the red mud-based catalyst obtained after acetic acid treatment (Ni / RM-HAC) can achieve 100% conversion of palm acid, and when the reaction temperature is 280 °C and 320 °C, respectively, the selectivity of hexadecanol and hexadecane is as high as 95% and 81%, respectively, which is higher than that of other several acid-treated modified red mud-based catalysts. It is indicated that the modified red mud-based catalyst treated by acetic acid has better catalytic activity. Figure 1

[0042] Example 2

[0043] 2.1 The original red mud sample was dried, ground and sieved at room temperature, and acetic acid with a concentration of 0.1 mol / L was prepared as a leaching acid to pretreat the red mud: 100 ml of acid was mixed with 6 g of red mud, stirred at room temperature for 2 h; then the mixed solution was centrifuged at a speed of 10000 r / min for 3 min until the liquid became transparent and colorless, and was placed in an oven at 100 °C overnight to dry, to obtain pretreated red mud.

[0044] 2.2 The pretreated red mud was ground into powder and placed in a muffle furnace for calcination for 4 h at a calcination temperature of 600 °C.

[0045] ​2.3 Load nickel precursor on calcined red mud by impregnation method: load 7% nickel on 1 g of red mud sample, load six kinds of nickel precursors respectively, namely nickel acetylacetone, nickel acetate, nickel carbonate, nickel oxide, nickel nitrate, nickel oxide. After adding deionized water to about 100 mL of solution, add a magnet, stir for about 24 h, then take out the magnet and rinse it clean with deionized water. Then dry in an oven at 100℃ for 24 h, after taking out, grind the sample into powder, put it into a muffle furnace and calcine at 500℃ for 4 h (hereinafter, Ni-A is nickel acetylacetone, Ni-AC is nickel acetate, Ni-C is nickel carbonate, Ni-O is nickel oxide, Ni-N is nickel nitrate, Ni-Cl is nickel chloride), to obtain an intermediate product.

[0046] 2.4 Reduce the intermediate product under a hydrogen atmosphere, with a flow rate of 50 mL / min, at a temperature rising rate of 10℃ / min from 20℃ to 450℃, and keep for 5 h, to obtain a red mud-based oil and fat hydrodeoxygenation catalyst, which is respectively recorded as Ni-A / RM, Ni-AC / RM, Ni-C / RM, Ni-O / RM, Ni-N / RM and Ni-Cl / RM.

[0047] In a reaction kettle, use palmitic acid as the oil and fat raw material (0.2 g), dodecane as the reaction solvent (20 mL), and carry out the hydrodeoxygenation reaction of palmitic acid under the catalysis of Ni-A / RM, Ni-AC / RM, Ni-C / RM, Ni-O / RM, Ni-N / RM or Ni-Cl / RM catalyst (catalyst dosage 0.04 g), the reaction temperature is 280℃ or 320℃, the reaction hydrogen pressure is 4 MPa, the stirring speed of the stirring paddle in the reaction kettle is 400 rpm, and the reaction time is 10 h, to obtain a hydrocarbon-based biodiesel, and the obtained hydrocarbon-based biodiesel is detected, to obtain the oil and fat hydrodeoxygenation reaction performance results of the red mud-based oil and fat hydrodeoxygenation catalysts obtained by different nickel precursors, as shown in Figure 2 , wherein the left graph is the reaction at 280℃, and the right graph is the reaction at 320℃. It can be seen from Figure 2 that when the reaction temperature is 280℃, under the condition of 100% conversion rate of palmitic acid, Ni-C / RM and Ni-Cl / RM can obtain higher selectivity of pentadecane and hexadecane than Ni-N / RM; when the reaction temperature is 320℃, the selectivity of Ni-C / RM for pentadecane is obviously higher than that of Ni-N / RM, and the selectivity of Ni-Cl / RM for hexadecane is higher than that of Ni-N / RM. The above results show that selecting nickel carbonate or nickel chloride as the nickel source can realize the directional preparation of alkane products, and the activity is greater than that of the red mud-based catalyst prepared by using nickel nitrate as the metal salt precursor.

[0048] The above-described specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application, and it should be understood that the above-described specific embodiments are merely examples of the present application and are not intended to limit the present application, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A process for the preparation of a catalyst for the hydrodeoxygenation of tallow-based oils and fats, characterized in that, The method comprises the following steps: S1) pretreating the red mud with an acid solution to obtain pretreated red mud; S2) calcining the pretreated red mud to obtain calcined red mud; S3) loading a nickel precursor on the calcined red mud by an impregnation method, and then calcining to obtain an intermediate product; the nickel precursor comprises nickel carbonate and / or nickel chloride; S4) reducing the intermediate product to obtain a red mud-based catalyst for oil and fat hydrodeoxygenation; The acid solution is selected from an acetic acid solution; the concentration of the acid solution is 0.1-1 mol / L; The ratio of the red mud to the acid solution is (1-10) g:100 mL.

2. The production method according to claim 1, characterized by, The pretreatment time is 1-5 h.

3. The preparation method according to claim 1, characterized in that, The calcination temperature in the step S2) is 400-600 DEG C; the calcination time is 2-6 h.

4. The production method according to claim 1, characterized by, The mass of the nickel element in the nickel precursor is 1%-20% of the mass of the calcined red mud.

5. The method of claim 1, wherein, The calcination temperature in the step S3) is 400-600 DEG C; the calcination time is 2-6 h.

6. The method of claim 1, wherein, The reduction temperature is 400-600 DEG C; the reduction time is 4-6 h; the reduction is carried out in a hydrogen atmosphere; the flow rate of the hydrogen is 10-100 mL / min.

7. A red mud-based catalyst for oil and fat hydrodeoxygenation prepared by the method of any one of claims 1-6.

8. The use of the red mud-based catalyst for oil and fat hydrodeoxygenation prepared by the method of any one of claims 1-6 in catalyzing the preparation of alkanes from fatty acids and / or fatty acid esters through hydrodeoxygenation.

9. Use according to claim 8, characterized in that, The fatty acid is palmitic acid; the hydrodeoxygenation temperature is 260-400 DEG C; the hydrogen pressure for the hydrodeoxygenation is 2-6 MPa.

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