Metal monatomic catalyst for catalyzing cracking of catering waste grease

Abstract

The invention belongs to the technical field of metal monatomic catalysis, and discloses application of a metal monatomic catalyst in catalysis of a cracking reaction of catering waste grease. The metal monatomic catalyst is prepared by taking a metal organic framework material as a precursor and taking magnesium, calcium and iron as metal sources. The metal monatomic catalyst disclosed by the invention is relatively high in catalytic activity, and the selectivity of long-chain alkane or olefin in the generated biodiesel is relatively high, so that the condensation point of the biodiesel can be reduced, and the low-temperature fluidity of the biodiesel can be improved.

Description

Technical Field

[0001] The invention relates to the application of a metal single-atom catalyst in catalyzing cracking reaction of waste restaurant oil, wherein 70% of the obtained products are long-chain alkanes or alkenes with carbon numbers greater than 12. Background Art

[0002] As an alternative to petrochemical diesel, biodiesel is gaining more and more attention in the context of global green and low-carbon development. Based on the principle of not competing with people for food and not competing with food for land, using waste catering oil as raw material and preparing hydrocarbon-rich biodiesel through catalytic cracking is an effective way to solve the current shortcomings of biodiesel, such as low calorific value, poor low-temperature fluidity and oxidation stability, and poor compatibility with engines. However, the existing catalysts for catalytic cracking of waste catering oil are mostly concentrated in acid-base type catalysts. Such catalysts generally have problems such as easy carbon deposition and deactivation, low catalytic activity, and poor selectivity for long-chain alkanes or olefins, which hinder the development of biodiesel based on waste catering oil. The development of catalysts for efficient cracking of waste catering oil is the core of promoting the development of biodiesel. Summary of the Invention

[0003] In order to solve the technical problems in the prior art such as low catalyst activity and low selectivity of long carbon chain products in the catalytic cracking of waste catering oil, the present invention provides an application of a metal single atom catalyst in the cracking reaction of waste catering oil.

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

[0005] A metal single-atom catalyst is used in the catalytic cracking reaction of restaurant waste oil, with 70% of the resulting product being long-chain alkanes or alkenes with a carbon number greater than 12. The single-atom catalyst is prepared using a metal-organic framework material as a precursor and magnesium, calcium, and iron as metal sources.

[0006] The preparation method of the metal single-atom catalyst provided by the present invention comprises the following steps:

[0007] 1) Using 2,5-dihydroxyterephthalic acid as a template and metal nitrates (magnesium, calcium, iron) as metal sources in methanol to form a gel mixture;

[0008] 2) placing the gel mixture in a synthesis reactor and crystallizing at 80° C. for 12-16 hours;

[0009] 3) The resulting crystallized product is washed with deionized water, dried at 80-110° C. for 8-12 h, and calcined at 550-650° C. for 4-6 h to obtain the corresponding metal single atom catalyst.

[0010] The cracking process is as follows: the mass percentage of the catalyst used in the amount of oil used is 2-5%, the cracking temperature is 340-400°C, and the cracking time is 3-6h. DETAILED DESCRIPTION

[0011] The present invention discloses the application of a metal single-atom catalyst in catalyzing the cracking reaction of waste catering oil. Those skilled in the art can refer to the content of this article and appropriately improve the process parameters to achieve it. It is particularly important to point out that all similar replacements and modifications are obvious to those skilled in the art, and they are all considered to be included in the present invention. The method and application 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] The raw material conversion rate and product selectivity described in the present invention are calculated using formulas (1) and (2):

[0014] Raw material conversion rate C = (initial reactant molar amount - unreacted material molar amount) / initial reactant molar number × 100% (1)

[0015] Product selectivity S = molar amount of Cn hydrocarbons in the product / molar amount of all products × 100% (2)

[0016] Example 1 Preparation of M / DOBDC (M: one of Mg, Ca, Fe) single-atom catalyst

[0017] 1) Dissolve a metal nitrate (one of Mg, Ca, and Fe) and 2,5-dihydroxyterephthalic acid in a molar ratio of 1.0:1.0-3.6 in 25 mL of methanol at room temperature and stir thoroughly to form a gel mixture;

[0018] 2) The mixed gel solution was transferred to a microwave hydrothermal crystallization reactor lined with polytetrafluoroethylene, placed in a microwave parallel synthesis instrument at 80°C for reaction for 12-16 hours, then removed, naturally cooled, and the precipitate was filtered with deionized water until neutral, placed in an oven at 80-110°C for drying for 8-12 hours, and the solid matter was ground to obtain a catalyst precursor;

[0019] 3) The precursor was transferred to a muffle furnace and heated from room temperature to 550-650°C at a heating rate of 2°C / min. After holding for 4-6 hours, it was naturally cooled to room temperature to obtain a single-atom catalyst M / DOBDC (M: one of Mg, Ca, and Fe).

[0020] Example 2 Preparation of long-chain alkanes by pyrolysis of waste restaurant oils catalyzed by Mg / DOBDC

[0021] The resulting catalyst was used to catalyze the cracking of waste restaurant oil to produce long-chain alkanes: 0.1g of waste restaurant oil was weighed and mixed evenly in 10mL of n-heptane. The mixture was then placed in a batch autoclave, and 0.04g of Mg / DOBDC catalyst was added. After the reactor was installed, the atmosphere in the autoclave was replaced with nitrogen three times. The temperature was then raised to 340°C, and the reaction was continued for 6 hours with magnetic stirring at 800 rpm. After the reaction, the reaction was allowed to cool naturally to room temperature, and the product was analyzed. The conversion rate of the waste restaurant oil was greater than 99%, and the selectivity for products above C12 was 76%.

[0022] Example 3: Preparation of long-chain alkanes by cracking of waste restaurant oils catalyzed by Ca / DOBDC

[0023] The resulting catalyst was used to catalyze the cracking of waste restaurant oil to produce long-chain alkanes: 0.1g of waste restaurant oil was weighed and mixed evenly in 10mL of n-heptane. The mixture was then placed in a batch autoclave, followed by the addition of 0.04g of Ca / DOBDC catalyst. After the reactor was installed, the atmosphere in the autoclave was replaced with nitrogen three times. The temperature was then raised to 380°C, and the reaction was continued for 6 hours with magnetic stirring at 800 rpm. After the reaction, the mixture was cooled to room temperature and the product was analyzed. The conversion rate of the waste restaurant oil was greater than 99%, with a selectivity of 75% for products above C12.

[0024] Example 4: Preparation of long-chain alkanes by pyrolysis of waste restaurant oils catalyzed by Fe / DOBDC

[0025] The resulting catalyst was used to catalyze the cracking of waste restaurant oil to produce long-chain alkanes: 0.1g of waste restaurant oil was weighed and mixed evenly in 10mL of n-heptane. The mixture was then placed in a batch autoclave, and 0.04g of Fe / DOBDC catalyst was added. After the reactor was installed, the atmosphere in the autoclave was replaced with nitrogen three times. The temperature was then raised to 400°C, and the reaction was continued for 6 hours with magnetic stirring at 800 rpm. After the reaction, the mixture was cooled to room temperature and the product was analyzed. The conversion rate of the waste restaurant oil was greater than 99%, and the selectivity for products above C12 was 80%.

[0026] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. Application of a metal single-atom catalyst in the catalytic cracking reaction of waste restaurant oil, with 70% of the resulting products being long-chain alkanes or alkenes with a carbon number greater than 12.

2. The use according to claim 1, characterized in that The single-atom catalyst is prepared using a metal organic framework material as a precursor and magnesium, calcium and iron as metal sources.

3. The method for preparing a single-atom catalyst according to claim 1, wherein: The following steps are involved: 1) Using 2,5-dihydroxyterephthalic acid as a template and metal nitrates (magnesium, calcium, iron) as metal sources in methanol to form a gel mixture; 2) placing the gel mixture in a synthesis reactor and crystallizing at 80° C. for 12-16 hours; 3) The resulting crystallized product is washed with deionized water, dried at 80-110° C. for 8-12 h, and calcined at 550-650° C. for 4-6 h to obtain the corresponding metal single atom catalyst.

4. The use according to claim 1, wherein The metal single-atom catalyst has high activity in catalytic cracking of waste catering oil and fat, and has high selectivity for the product long-chain alkanes or alkenes.

5. The use according to claim 1 or 4, characterized in that: The cracking temperature is 340-400°C and the cracking time is 3-6h.