CN104525241B - Solid alkali catalyst as well as preparation method and application thereof in glycerinum alcoholysis reaction - Google Patents

Abstract

The invention belongs to the technical fields of chemical engineering and energy, and specifically relates to a solid base catalyst, a preparation method thereof and an application in glycerol alcoholysis. The catalyst is an alkaline earth metal oxide catalyst supported by mesoporous materials, and the active ingredient alkaline earth metal is one of the oxides MgO, CaO, SrO, or a mixture of several of them; the loading amount of alkaline earth metal is 4% of the mass of the mesoporous material to 20%. The catalyst is environmentally friendly, has a simple and efficient preparation method, has large specific surface area, pore size and strong alkalinity; is used in glycerol alcoholysis reaction, has little loss, high catalytic activity and can be reused.

Description

A kind of solid base catalyst and its preparation method and the application in the alcoholysis reaction of glycerol

technical field

The invention belongs to the technical fields of chemistry, chemical engineering and energy, and in particular relates to a solid base catalyst, a synthesis method thereof, and an application in glycerol alcoholysis.

Background technique

Energy crisis and environmental pollution are the common concerns of human society at present, and the development of a green and pollution-free alternative energy has been a research hotspot in the past ten years. Biodiesel is a typical "green energy", which has been widely researched and applied all over the world. At present, one of the bottlenecks restricting the development of biodiesel is production cost. Exploring the application value of the by-product glycerol is beneficial to solve the production and application problems of biodiesel.

Glycerol alcoholysis of vegetable oil is one of the important methods for the application of glycerin. Its products monoglyceride and diglyceride and their mixture monoglyceride and diglyceride are an important emulsifier. They are used in food, medicine, cosmetics, health care, chemical synthesis, etc. The field has a wide range of applications. The alcoholysis reaction of glycerol is generally carried out under the high temperature condition of 200-260℃, using homogeneous base to catalyze the alcoholysis of triglyceride (the main component of vegetable oil and animal fat), and the commonly used catalysts are NaOH, KOH, Ca(OH) ₂ , etc. The product after alcoholysis is a mixture of monoglycerides, diglycerides, unreacted glycerin and oil, and high-purity monoglycerides and diglycerides are obtained through fractional distillation and purification. Among them, the color of the Ca(OH) ₂ catalyzed product is more in line with the requirements of the food industry. However, the use of homogeneous catalysts is easy to corrode equipment, the catalyst is difficult to separate and reuse, and by-products will be generated during post-processing. Therefore, solid base catalysts have become one of the most potential environment-friendly catalysts in research due to their easy separation and reusability.

Chinese patent CN 1585814A discloses a chemical method for preparing 1,3-diglyceride oil. The method uses alkali metal salts or alkaline earth metal salts of monocarboxylic or dicarboxylic acids to drive alcoholysis of glycerol under certain conditions, thereby preparing commercial, food-grade 1,3-diglyceride oil. Chinese patent CN 102191134A discloses a preparation method of partial glycerides (mono-diglycerides), which uses potassium hydroxide, sodium hydroxide or calcium hydroxide to catalyze the alcoholysis reaction of glycerol to obtain partial Glycerin mixture. A. Corma et al. investigated the application of Cs-MCM-41, Cs-Sepiolite, MgO and MgAl hydrotalcite in glycerolysis soybean oil, and found that MgO and low aluminum hydrotalcite showed better monoglyceride yield (Corma, A. et al., Catalysts for the production of fine chemicals-Production of food emulsifiers, monoglycerides, by glycerolysis of fats with solid base catalysts, Journal of Catalysis, 1998. 173(2):315-321). Volodymyr Brei et al. used a fixed-bed reactor to study MgO-TiO ₂ , MgO-La ₂ O ₃ , MgO-ZrO, hydrotalcite, ZnO-Al ₂ O ₃ , ZnO-MgO, CaO-ZnO and other catalysts in the alcoholysis of glycerol Application in soybean oil, wherein, CaO-ZnO and hydrotalcite all show higher activity (Brei, V., et al., Study of a continuous process of glycerolysis of rapeseedoil with the solid base catalysts, Chemistry & Chemical Technology, 2012, 6(1): 89-94).

Among the catalysts disclosed above, the activity and stability of the catalyst are the main reasons restricting the large-scale application of solid base catalysts in industry.

Contents of the invention

The object of the present invention is to provide a solid base catalyst with high catalytic activity and stability and its preparation method, which is applied to glycerol alcoholysis of vegetable oil. The preparation process is simple and the loss of the catalyst in the solution is small.

The solid base catalyst proposed by the present invention is an alkaline earth metal catalyst supported by mesoporous materials, and the active ingredient alkaline earth metal is one of oxides MgO, CaO, SrO, or a mixture of several of them; Between 4% and 20% of the mass.

The present invention also provides a synthetic method for the above-mentioned loaded alkaline earth metal catalyst, specifically adopting a step-by-step impregnation method, the steps of which are as follows:

(1) According to the amount of alkaline earth metal loaded on the mesoporous material, weigh the alkaline earth metal salt, mesoporous material and solvent, mix and grind until a slurry mixture is formed;

(2) Then add the slurry mixture into the solvent, stir evenly, and reflux overnight at the boiling point temperature;

(3) After filtering, a white solid is obtained, dried, and then calcined at 450-600° C. under air atmosphere for 5-8 hours.

In the present invention, the alkaline earth metal salts are Mg(NO ₃ ) ₂ , Ca(NO ₃ ) ₂ , Sr(NO ₃ ) ₂ , Ca(CH ₃ COO) ₂ , Ca(OH) ₂ , Mg(CH ₃ COO) ₂ or Sr(CH ₃ COO) ₂ , or a mixture of several of them.

In the present invention, the mesoporous material may be one of SBA-15, SBA-16, KIT-6, or a mixture of several of them.

In the present invention, the solvent is water or n-hexane.

The method of applying the loaded solid base catalyst of the present invention in glycerol alcoholysis vegetable oil reaction is as follows:

Before the reaction, the catalyst is treated with glycerin at the reaction temperature for 25-40 min; vegetable oil is added to the glycerin catalyst mixture; at a reaction temperature of 180-240 °C and a stirring speed of 300-1000 rpm, the reaction is carried out for 1-24 hours, That is, the product is obtained.

The vegetable oil described in the present invention can be one of vegetable oils such as soybean oil, corn oil, palm oil, cottonseed oil, olive oil, or a mixture of more than one.

In the present invention, the usage amount of the catalyst is 3%-10% of the vegetable oil quality.

In the present invention, the molar ratio of glycerol to vegetable oil is 2:1-10:1.

The preparation method of the supported solid base catalyst of the invention is simple, and the carrier has a large specific surface and ordered pores, and the prepared catalyst has very low solubility in glycerin, greatly reducing the loss of active components. Applied to glycerol alcoholysis of vegetable oil, the conversion rate of vegetable oil can reach 100%. The solid base catalyst can be separated by filtration or centrifugation, and can be reused; the products are monoglycerides and diglycerides, that is, monoglycerides and diglycerides. Mono- and diglycerides themselves act as an emulsifier. Also, the separation of monoglycerides and diglycerides is easier than the separation of diglycerides and triglycerides.

detailed description

The present invention is further described below by way of examples.

Example 1

Mix 2 g of SBA-16, 2.3 g of Ca(NO ₃ ) ₂ ^. 4H ₂ O and 10 ml of water, grind them evenly; add 30 ml of water, and reflux overnight at 100 °C; filter the resulting mixture to obtain a powder The precursor was dried overnight at 70 °C, and then calcined at 550 °C for 6 h in an air atmosphere to obtain the catalyst of the present invention.

Add 0.3 g of the prepared catalyst to 3.2 g of glycerin to form a mixed solution; heat the mixed solution to 220 °C for 30 min; add 10 g of corn oil to the mixed solution of glycerin and the catalyst; at a reaction temperature of 220 °C, Stirring speed of 500 rpm, reaction for 24 hours. The conversion rate of corn oil was 100%, the yield of monoglyceride was 42.9%, and the yield of diglyceride was 57.1%. Atomic absorption spectroscopic analysis of the glycerin and catalyst mixture showed no loss of Ca was detected.

Example 2

Mix 2 grams of SBA-16, 2.1 grams of Sr(NO ₃ ) ₂ and 10 milliliters of water, grind them evenly; then add 30 milliliters of water, and reflux overnight at 100°C; filter the resulting mixture to obtain a powdery precursor, and Drying at 70°C overnight, and then calcining at 550°C in an air atmosphere for 6 h, the catalyst of the present invention was obtained.

Add 0.3 g of the prepared catalyst to 3.2 g of glycerol to form a mixed solution; heat the mixed solution to 200 °C for 30 min; add 10 g of corn oil to the mixed solution of glycerin and catalyst; at a reaction temperature of 200 °C, Stirring speed of 500 rpm, reaction for 5 hours. The conversion rate of corn oil was 98.7%, the yield of monoglyceride was 23.7%, and the yield of diglyceride was 75.0%. The atomic absorption spectrometry analysis of the mixture of glycerol and catalyst did not detect the loss of Ca.

Example 3

Mix and grind 2 grams of KIT-6, 2.3 grams of Ca(NO ₃ ) ₂ ^. 4H ₂ O and 10 ml of n-hexane; then add 30 ml of n-hexane and reflux at 70°C overnight; filter the resulting mixture to obtain The powdery precursor was dried overnight at 70 °C, and then calcined at 550 °C for 6 h in an air atmosphere to obtain the catalyst of the present invention.

Add 0.3 g of the prepared catalyst to 3.2 g of glycerin to form a mixed solution; heat the mixed solution to 220 °C for 30 min; add 10 g of corn oil to the mixed solution of glycerin and the catalyst; at a reaction temperature of 220 °C, Stirring speed of 500 rpm, reaction for 5 hours. The conversion rate of corn oil was 100%, the yield of monoglyceride was 21.3%, and the yield of diglyceride was 78.7%. The atomic absorption spectrometry analysis of the mixture of glycerol and catalyst did not detect the loss of Ca.

Example 4

Mix and grind 2 grams of SBA-15, 2.3 grams of Ca(NO ₃ ) ₂ ^. 4H ₂ O and 10 milliliters of n-hexane; then add 30 milliliters of n-hexane and reflux overnight at 70°C; filter the resulting mixture to obtain a powder The catalyst was dried overnight at 70 °C, and then calcined at 550 °C for 6 h in an air atmosphere to obtain the catalyst of the present invention.

Add 0.3 g of the prepared catalyst to 3.2 g of glycerin to form a mixed solution; heat the mixed solution to 220 °C for 30 min; add 10 g of corn oil to the mixed solution of glycerin and the catalyst; at a reaction temperature of 220 °C, Stirring speed of 500 rpm, reaction for 5 hours. The conversion rate of corn oil was 98.1%, the yield of monoglyceride was 23.3%, and the yield of diglyceride was 74.8%. The atomic absorption spectrometry analysis of the mixture of glycerol and catalyst did not detect the loss of Ca.

Claims (6)

1. a kind of preparation method of solid base catalyst, it is characterised in that concretely comprise the following steps：

（1）According to the amount of mesoporous material supported alkaline earth metal, alkali salt, mesoporous material and solvent are weighed, mixed grinding is extremely Form paste mixture；Wherein, the mesoporous material is the one kind in SBA-15, SBA-16, KIT-6, or wherein several mixed Compound；The load capacity of alkaline-earth metal is between 4% to the 20% of mesoporous material quality；It is oxidation as the alkaline-earth metal of active component One kind of thing MgO, CaO, SrO；

（2）Then paste mixture is added in solvent, is stirred, flowed back at boiling temperature overnight；

（3）Jing is filtered, and obtains white solid, is dried, and then roasting 5-8 is little under the conditions of 450-600 DEG C, air atmosphere When.

2. the preparation method of solid base catalyst according to claim 1, it is characterised in that described alkali salt is Mg(NO₃)₂、Ca(NO₃)₂、Sr(NO₃)₂、Ca(CH₃COO)₂、Mg(CH₃COO)₂Or Sr (CH₃COO)₂In one kind, or wherein Several mixtures.

3. the preparation method of solid base catalyst according to claim 1 and 2, it is characterised in that：It is step 1, molten described in 2 Agent is water or n-hexane.

4. the solid base catalyst for being prepared by one of claim 1-3 preparation method.

5. application of the solid base catalyst as claimed in claim 4 in glycerolysis reaction, it is characterised in that including following Process：

Solid base catalyst is mixed in addition reactor with glycerine, 25-40 min are processed at the reaction temperatures, be subsequently adding Vegetable oil, is 180-240 DEG C in temperature, and mixing speed is under 300-1000 rpm, to react 1-24 h；

Wherein, the mol ratio of glycerine and vegetable oil is 2:1-10:1；The consumption of solid base catalyst is the 3%- of plant oil quality 10%。

6. application according to claim 5, it is characterised in that the vegetable oil is soya-bean oil, corn oil, palm oil, cottonseed One or more mixture in oil, olive oil.