Hydrogenation of catering waste grease catalyzed by Yolk-shell type alloy catalyst

Abstract

The invention belongs to the technical field of catalytic hydrogenation, and relates to application of a Yolk-shell type alloy catalyst. The Yolk-shell type alloy catalyst Ni-M-mSiO2 provided by the invention has relatively high catalytic activity in the reaction of catalyzing catering waste oil and fat hydrogenation to prepare low-acid-value biodiesel, so that the condensation point of the biodiesel can be reduced, the stability of the biodiesel can be improved, the low-temperature fluidity of the biodiesel can be improved, and the development of the biodiesel can be promoted.

Description

Technical Field

[0001] The invention belongs to the technical field of catalytic hydrogenation and relates to a method for preparing low-acid value biodiesel by hydrogenating waste catering oil using a Yolk-shell alloy catalyst. Background Art

[0002] Producing biodiesel from waste cooking oil is currently the primary method for biodiesel production. Conventional production methods often rely on thermal cracking or catalytic thermal cracking. Although the carbon chain length and calorific value of the biodiesel obtained by these two methods meet the standards of petrochemical diesel, the resulting biodiesel has an excessively high acid value, which not only affects the stability of the biodiesel but is also corrosive to equipment. Catalytic hydrogenation can directly react with the carboxyl groups in waste cooking oil, reducing its acid value, which is an effective way to address the high acid value of biodiesel based on waste cooking oil. Currently, the catalysts commonly used in the oil hydrogenation field are mainly metal sulfide catalysts and precious metal catalysts. Although these catalysts have high catalytic activity and selectivity, the metal sulfide contains sulfur, which leaches sulfur during the reaction, resulting in sulfur-containing products and causing environmental pollution. Precious metal catalysts, on the other hand, are inherently expensive and resource-scarce, limiting their large-scale application. Therefore, the research and development of new non-precious metal catalysts with excellent catalytic performance has become a key to promoting the development of biodiesel based on waste cooking oil. Summary of the Invention

[0003] In view of this, the present invention provides a Yolk-shell alloy catalyst for catalyzing the hydrogenation of waste catering oil to produce low-acid value biodiesel.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for preparing a Yolk-shell alloy catalyst Ni-M@mSiO2, characterized by comprising the following steps:

[0006] S1. Cetyltrimethylammonium bromide (CTAB) is mixed with water, stirred and heated, and then a salt solution of Ni(NO3)2 and metal M is added, stirring is continued, and an aqueous ascorbic acid solution is added dropwise, and stirring is performed to obtain a colloidal solution of the corresponding metal;

[0007] S2, adding NaOH solution to the colloidal solution to adjust the pH value of the solution, then adding TEOS solution dropwise to initiate silica gel polymerization reaction, and finally adding BTME solution dropwise to react, and centrifuging to obtain the product Ni-M@SiO2;

[0008] S3. calcining the product Ni-M@SiO2 and reducing it under the action of hydrogen to obtain a Yolk-shell alloy catalyst Ni-M@mSiO2.

[0009] Preferably, the M metal salt is selected from one of Ce(NO3)3·6H2O, Al(NO3)3·9H2O, Zr(NO3)4·5H2O, Co(NO3)2·6H2O, Mg(NO3)2·6H2O, Fe(NO3)3·9H2O, Cu(NO3)2·6H2O, Zn(NO3)2·6H2O, and Mn(NO3)2·4H2O.

[0010] Low-acid-value biodiesel was produced by hydrogenating waste cooking oil using a Yolk-shell alloy catalyst Ni-M@mSiO2 prepared by the method. The mass ratio of the Yolk-shell alloy catalyst Ni-M@mSiO2 to waste cooking oil was 1:3-15, the reaction temperature was 240-280°C, the hydrogen pressure was 1.0-3.0 MPa, and the reaction time was 3.0-5.0 hours. The product had an acid value of less than 0.5 mgKOH / g. DETAILED DESCRIPTION

[0011] The present invention discloses a method for preparing low-acidity biodiesel by hydrogenating waste cooking oil using a Yolk-shell alloy catalyst. Those skilled in the art can refer to the contents of this article and appropriately improve the process parameters to achieve the desired result. It should be noted in particular that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in the present invention. The methods and applications of the present invention have been described through preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0012] In order to enable those skilled in the art to better understand the present invention, the present invention is further described in detail below in conjunction with specific embodiments.

[0013] Example 1 Synthesis of Yolk-shell Alloy Catalyst Ni-Ce@mSiO2

[0014] S1. Mix 0.10 g of CTAB with 45 mL of deionized water in a flask, raise the temperature to 95°C, stir continuously and maintain for 30 minutes, then add 5 mL of 0.02 mol / L NiNO3 and Ce(NO3)3·6H2O salt solution, continue stirring for 15 minutes, and the solution changes from colorless and transparent to orange-red. Add ascorbic acid aqueous solution and continue stirring for 30 minutes to obtain a colloidal solution of metal Pd and Ce;

[0015] S2. Add 2.5 mL of 0.5 mol / L NaOH solution to the above colloidal solution to adjust the solution pH to about 10-11, then dropwise add 0.42 mL of TEOS solution to initiate silica gel polymerization reaction. After 3 h, add 0.3 mL of BTME solution and react for 50 min. Centrifuge to obtain Ni-Ce@SiO2 product, and dry at 60 °C.

[0016] S3, calcining the dried Ni-Ce@SiO2 in a muffle furnace, raising the temperature from 2°C / min to 500°C for 3 h to obtain powdered Ni2O-CeO2@mSiO2;

[0017] S4. The obtained powder Ni2O-CeO2@mSiO2 was reduced under H2 at a flow rate of 60 mL / min and a temperature of 500°C for 4 h to finally obtain a Yolk-shell type alloy catalyst Ni-Ce@mSiO2.

[0018] Example 2 Method for preparing biodiesel using Ni-Ce@mSiO2 catalyst to catalyze waste cooking oil

[0019] 1.0g of catering waste oil and 0.2g of Ni-Ce@mSiO2 prepared in Example 1 were added to a stainless steel high-pressure reactor. The air in the reactor was replaced with nitrogen 5 times and then filled with 3.0MPa of hydrogen. The reactor was heated and stirred at 260°C for 5h and allowed to stand and cool to room temperature. Under the action of high-speed centrifugation, the product phase was separated from the catalyst phase, and the separated catalyst could be directly recycled without post-treatment. The conversion rate of catering waste oil was 100%, the yield of biodiesel with a carbon chain greater than 12 was 70%, and the acid value was 0.3mgKOH / g. The calculation formulas for the conversion rate of catering waste oil and the yield of biodiesel with a carbon chain greater than 12 are as follows:

[0020]

[0021] Example 3 Method for preparing biodiesel using Ni-Al@mSiO2 catalyst to catalyze waste cooking oil

[0022] 1.0g of waste cooking oil and 0.25g of Ni-Al@mSiO2, synthesized according to the same steps and material ratios as in Example 1, were added to a stainless steel autoclave. The air in the autoclave was replaced with nitrogen five times, then filled with 2.0MPa of hydrogen. The reaction mixture was heated and stirred at 250°C for 4 hours, and then allowed to cool to room temperature. Under the action of high-speed centrifugation, the product phase was separated from the catalyst phase. The separated catalyst could be directly recycled without post-treatment. The conversion rate of waste cooking oil was 100%, the yield of biodiesel with a carbon chain greater than 12 was 75%, and the acid value was 0.4mgKOH / g.

[0023] Example 4 Method for preparing biodiesel using Ni-Co@mSiO2 catalyst to catalyze waste restaurant oil

[0024] 1.5g of waste cooking oil and 0.3g of Ni-Co@mSiO2, synthesized according to the same steps and material ratios as in Example 1, were added to a stainless steel autoclave. The air in the autoclave was replaced with nitrogen four times, followed by 3.0MPa of hydrogen. The reaction mixture was heated and stirred at 280°C for 3h, and then allowed to cool to room temperature. Under the action of high-speed centrifugation, the product phase was separated from the catalyst phase. The separated catalyst could be directly recycled without post-treatment. The conversion rate of waste cooking oil was 100%, the yield of biodiesel with a carbon chain greater than 12 was 77%, and the acid value was 0.5mgKOH / g.

[0025] Example 5 Method for preparing biodiesel using Ni-Zn@mSiO2 catalyst to catalyze waste restaurant oil

[0026] 1.2g of waste cooking oil and 0.15g of Ni-Zn@mSiO2, synthesized using the same steps and material ratios as in Example 1, were added to a stainless steel autoclave. The air in the autoclave was replaced with nitrogen six times, followed by a 3.0MPa hydrogen atmosphere. The reaction mixture was heated and stirred at 270°C for 5 hours, and then allowed to cool to room temperature. The product phase was separated from the catalyst phase by high-speed centrifugation, and the separated catalyst could be directly recycled without post-treatment. The conversion rate of the waste cooking oil was 100%, the yield of biodiesel with a carbon chain greater than 12 was 74%, and the acid value was 0.4mgKOH / g.

[0027] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a Yolk-shell alloy catalyst Ni-M@mSiO2, characterized in that: The following steps are involved: S1. Cetyltrimethylammonium bromide (CTAB) is mixed with water, stirred and heated, and then a salt solution of Ni(NO3)2 and metal M is added, stirring is continued, and an aqueous ascorbic acid solution is added dropwise, and stirring is performed to obtain a colloidal solution of the corresponding metal; S2, adding NaOH solution to the colloidal solution to adjust the pH value of the solution, then adding TEOS solution dropwise to initiate silica gel polymerization reaction, and finally adding BTME solution dropwise to react, and centrifuging to obtain the product Ni-M@SiO2; S3. calcining the product Ni-M@SiO2 and reducing it under the action of hydrogen to obtain a Yolk-shell alloy catalyst Ni-M@mSiO2.

2. The method for preparing Yolk-shell alloy catalyst Ni-M@mSiO2 according to claim 1, characterized in that: M metal salt is selected from Ce(NO3)3·6H2O, Al(NO3)3·9H2O, Zr(NO3)4·5H2O, Co(NO3)2·6H2O, Mg(NO3 )2·6H2O, Fe(NO3)3·9H2O, Cu(NO3)2·6H2O, Zn(NO3)2·6H2O, one of Mn(NO3)2·4H2O.

3. A Yolk-shell alloy catalyst Ni-M@mSiO2 prepared by the method according to any one of claims 1 and 2 Catalytic hydrogenation of waste cooking oil to produce low acid value biodiesel.

4. The use according to claim 3, characterized in that The mass ratio of the Yolk-shell alloy catalyst Ni-M@mSiO2 to catering waste oil is 1:3-15, the reaction temperature is 240-280°C, the hydrogen pressure is 1.0-3.0 MPa, the reaction time is 3.0-5.0 h, and the product acid value is lower than 0.5 mgKOH / g.

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