CN105536766B - Nanometer calcium lanthanium complex oxide catalyst and its preparation method and application - Google Patents

Abstract

The invention belongs to the technical field of chemical catalysis, and specifically relates to a nano-calcium-lanthanum composite oxide catalyst and its preparation method and application. In the present invention, calcium and lanthanum nitrates are mixed and dissolved in water, citric acid is added as a complexing agent, stirred at a certain temperature to form a gel, and aged; then roasted in an air atmosphere, and finally carried out in the presence of ethanol aqueous solution heat treatment to prepare nano calcium lanthanum composite oxide catalyst. The catalyst has strong basic properties, suitable surface hydrophilicity and hydrophobicity, and exhibits excellent catalytic activity in the synthesis of monoglycerides from glycerol alcoholysis. At the same time, there is a strong interaction between calcium and lanthanum. This synergistic effect makes the active components The loss of calcium in the reaction system is greatly reduced, thereby enhancing the stability of the catalyst, which can be used to synthesize monoglycerides by glycerolysis of vegetable oils. The raw materials used in the invention have low cost, the catalyst is environment-friendly, and the preparation method is simple.

Description

Nano calcium lanthanum composite oxide catalyst and its preparation method and application

technical field

The invention belongs to the technical field of chemical catalysts, and in particular relates to a nano calcium lanthanum compound oxide, a preparation method thereof and an application in synthesizing monoglyceride by glycerol alcoholysis.

Background technique

Monoglyceride (monoglyceride, MG) is a polyol-type nonionic surfactant, widely used in the food processing industry, can effectively improve food processing technology, improve product quality, extend product shelf life, etc., it can be completely degraded into glycerin And fatty acids, safe for human body, mainly used in cakes, bread, dried noodles, candy, ice cream and meat products, with very broad application prospects and huge market value. Monoglycerides are also widely used as emulsifiers in daily chemicals. For example, as emulsifier and dispersant in cosmetics, toothpaste and hair conditioner, as emulsifier in fiber finishing process, as antistatic agent in polyethylene, polypropylene, etc., it is the most consumed fatty acid ester class of surfactants. In addition, monoglycerides have good biocompatibility and have important applications in the pharmaceutical industry. For example, monoglycerides containing polyunsaturated fatty acids (CLA, EPA, DHA) have a preventive effect on cardiovascular diseases.

There are mainly chemical methods and biological enzymatic methods for the production of monoglycerides from glycerol alcoholysis. At present, chemical methods are mainly used in industry. Glycerin is hydrophilic, and animal and vegetable oils are hydrophobic. At room temperature, the solubility of glycerol in ordinary oils is very low, only 4%, and the solubility in cocoa butter is slightly larger, only 6%. Therefore, at room temperature Under these conditions, glycerin and oil are difficult to react, and the temperature needs to be increased to increase the solubility of glycerol in oil. The catalyst used in industry is mainly NaOH or KOH, and the reaction temperature is usually higher than 200°C. In the food industry, Ca(OH) ₂ is a commonly used catalyst, because under the catalysis of Ca(OH) ₂ , the color of the product is lighter, which meets the requirements of the food industry. Using a homogeneous base to catalyze the alcoholysis of glycerin, the catalyst is difficult to recover, and the base catalyst must be neutralized immediately after the reaction to prevent the reverse reaction from occurring. Solid base catalyst can effectively solve the difficult problem of product separation and reduce environmental pollution. The hydrophilicity and hydrophobicity of the solid base catalyst surface will seriously affect the alcohol-oil ratio of the microenvironment near the active site, thereby significantly affecting the performance of the catalyst. In addition, the loss of calcium is a major problem affecting its use in glycerol alcoholysis, and how to improve the stability of the catalyst is a difficult research point.

Calcium-lanthanum composite oxides have strong basic properties and exhibit good catalytic activity in methanolysis of vegetable oils. For example, Taufiq-Yap et al. prepared CaO-La ₂ O ₃ catalysts by co-precipitation method, and studied the effect of CaLa molar ratio on the performance of methanolysis of Jatropha curcas oil (Energy Conversion and Management 2014, 88, 1290-1296.). The catalyst particles prepared by this method are relatively large, and under the reaction condition of 65°C, the active component Ca has a large loss, which reduces the activity. Catalyst for vegetable oil reactions.

Contents of the invention

The purpose of the present invention is to provide a high activity and high stability nano-calcium lanthanum composite oxide catalyst and its preparation method, which is applied to the synthesis of monoglyceride from vegetable oil by glycerol alcoholysis.

When calcium oxide and lanthanum oxide form a uniformly mixed composite oxide, there will be a strong interaction between the two oxides, which further increases the alkalinity of calcium oxide, thereby improving the catalytic activity. At the same time, this strong interaction The effect can also significantly inhibit the loss of calcium oxide. The calcium-lanthanum composite oxides reported in the literature are prepared by the co-precipitation method. Due to the large gap between the ion product of calcium hydroxide and the ion product of lanthanum hydroxide, it is impossible to achieve uniform precipitation at the same time during precipitation. Therefore, it is difficult to produce a uniform composite oxide. In addition, the prepared composite oxide is calcined at high temperature, and its surface has poor affinity with glycerol, resulting in an unsuitable alcohol-oil ratio in the reaction microenvironment. The invention provides a citric acid-assisted sol-gel combustion method to prepare uniformly mixed nano-calcium-lanthanum composite oxides. At the same time, ethanol heat treatment is used to improve the hydrophilicity and hydrophobicity of the oxide surface, and the prepared catalyst has high glycerol alcoholysis of vegetable oils to synthesize glycerol Monoester catalytic activity and low calcium loss.

The preparation method of nano calcium lanthanum catalyst provided by the invention, concrete steps are as follows:

(1) Configure a certain concentration of calcium nitrate and lanthanum nitrate solution, mix, the molar ratio of metal ions and water is 1: (30-50);

(2) Heat and stir at 70-90°C, add citric acid while stirring, and the molar ratio of citric acid to metal ions is 0.5:1-2:1;

(3) Stir the solution obtained in step (2) at 70-90°C until a sol is formed, and then age at room temperature for 18-24 hours;

(4) drying the aged wet gel at a temperature of 100-140°C in an air atmosphere for 12-24 hours to obtain a catalyst precursor 1;

(5) After grinding the catalyst precursor 1, raise the temperature to 500-600°C at 1-3°C/min in the air atmosphere, keep it for 1-5 hours, and then raise the temperature to 700-800°C at 1-3°C/min, Roasting in an inert gas atmosphere for 2-8 hours to obtain a catalyst precursor 2;

(6) Mix the catalyst precursor 2 with 2-5 times the weight of absolute ethanol, place it in a pressure-resistant container, treat it at 120-150°C for 2-3 hours, and dry it at 80-120°C under an inert atmosphere after cooling After 6-12 hours, the desired catalyst is obtained.

In the above method, the molar ratio of calcium to lanthanum is 1:5-5:1.

In the above method, the stirring speed is 200-500rpm.

In the above method, the inert gas is nitrogen, argon or helium, or a mixture thereof.

The catalyst prepared by the method of the invention has a strong interaction between calcium and lanthanum, the alkali strength of the catalyst is greatly improved, and has good stability at the same time, and the solubility in glycerin is greatly lower than that of calcium oxide.

The above-mentioned calcium lanthanum composite oxide catalyst provided by the present invention can be used to catalyze glycerol alcoholysis of vegetable oil to synthesize monoglyceride, and the specific steps are:

(1) Add the catalyst to the vegetable oil to form a mixed solution, and heat the mixed solution to 180-240°C;

(2) Add glycerin to the mixture of preheated vegetable oil and catalyst; at 180-240°C, with a stirring speed of 300-1000 rpm, react for 10 min-300 min to obtain a monoglyceride-containing product thing.

In the present invention, the vegetable oil may be one or a mixture of vegetable oils such as soybean oil, corn oil, palm oil, cottonseed oil, rapeseed oil, olive oil, and jatropha oil.

In the present invention, the usage amount of the catalyst is 0.1%-5% of the oil weight.

In the present invention, the weight ratio of glycerin to vegetable oil is 1:5-1:1.

The advantages of the present invention are that the catalyst used in the preparation method is environmentally friendly, the preparation method is simple and efficient, the catalyst is easy to separate, and the catalytic activity higher than that of ordinary calcium oxide can be obtained in the reaction of synthesizing monoglyceride from glycerol alcoholysis. The churn problem has been greatly suppressed.

Detailed ways

The present invention is described in further detail below in conjunction with embodiment.

Embodiment 1, catalyst preparation

(1) Calcium nitrate, lanthanum nitrate solution are configured, the mol ratio of metal ion and water is 1:40, two kinds of solutions are mixed according to the ratio of calcium, lanthanum mol ratio 3:1;

(2) Heating the mixed solution obtained in step (1) at 80° C., adding citric acid while stirring, and the molar ratio of citric acid and metal ions is 1:1;

(3) Stir the solution obtained in step (2) at 80°C until a sol is formed, and then age it at room temperature for 18 hours;

(4) drying the aged wet gel at 110° C. for 12 hours in an air atmosphere to obtain a catalyst precursor;

(5) After grinding the catalyst precursor, raise the temperature to 600°C at 1°C/min in the air atmosphere, keep it for 2 hours, then raise the temperature to 700°C at 1°C/min, and bake it under an inert gas atmosphere for 5 hours to obtain the catalyst precursor2;

(6) Mix the catalyst precursor 2 with 2 times the weight of absolute ethanol, place it in a pressure-resistant container, treat it at 120°C for 2 hours, and then dry it at 100°C for 8 hours under an inert atmosphere after cooling to obtain the catalyst of the present invention. catalyst.

Embodiment 2, catalyst preparation

(1) calcium nitrate, lanthanum nitrate solution are configured, the mol ratio of metal ion and water is 1:50, two kinds of solutions are mixed according to the ratio of calcium, lanthanum mol ratio 2:1;

(2) Heating the mixed solution obtained in step (1) at 90° C., adding citric acid while stirring, and the molar ratio of citric acid and metal ions is 1:1;

(3) Stir the solution obtained in step (2) at 90°C until a sol is formed, and then age it at room temperature for 18 hours;

(4) drying the aged wet gel at 110° C. for 12 hours in an air atmosphere to obtain catalyst precursor 1;

(5) After grinding the catalyst precursor, raise the temperature to 600°C at 1°C/min in the air atmosphere, keep it for 2 hours, then raise the temperature to 700°C at 1°C/min, and bake it under an inert gas atmosphere for 5 hours to obtain the catalyst precursor2;

(6) Mix the catalyst precursor 2 with 3 times the weight of absolute ethanol, place it in a pressure-resistant container, treat it at 120°C for 2 hours, and then dry it at 100°C for 8 hours under an inert atmosphere to obtain the present invention. catalyst.

Embodiment 3, catalyst preparation

(1) Calcium nitrate and lanthanum nitrate solution are configured, the mol ratio of metal ion and water is 1:40, and the two solutions are mixed according to the ratio of calcium and lanthanum mol ratio 1:1;

(2) Heating the mixed solution obtained in step (1) at 80° C., adding citric acid while stirring, and the molar ratio of citric acid to metal ions is 1.5:1;

(3) Stir the solution obtained in step (2) at 80°C until a sol is formed, and then age it at room temperature for 18 hours;

(4) drying the aged wet gel at 110° C. for 12 hours in an air atmosphere to obtain a catalyst precursor;

(5) After grinding the catalyst precursor, raise the temperature to 600°C at 1°C/min in the air atmosphere, keep it for 2 hours, then raise the temperature to 700°C at 1°C/min, and bake it under an inert gas atmosphere for 5 hours to obtain the catalyst precursor2;

(6) Mix the catalyst precursor 2 with 3 times the weight of absolute ethanol, place it in a pressure-resistant container, treat it at 140°C for 2 hours, and then dry it at 100°C for 8 hours under an inert atmosphere to obtain the present invention catalyst.

The application of the catalyst prepared by embodiment 4, embodiment 1

Using the catalyst prepared in Example 1, add 0.3 gram of catalyst to 10 grams of corn oil to form a mixed solution; heat the mixed solution to 220° C.; add 3.1 grams of glycerin to the mixed solution of preheated vegetable oil and catalyst; At a reaction temperature of 220° C. and a stirring speed of 500 rpm, the reaction was carried out for 1 hour; a product containing monoglyceride was obtained. The conversion rate of corn oil was 94.9%, the yield of monoglyceride was 45.5%, and the loss of Ca in the product was 320.5 ppm.

The application of the catalyst prepared by embodiment 5, embodiment 2

Using the catalyst prepared in Example 2, 0.3 gram of catalyst was added into 10 grams of corn oil to form a mixed solution; the mixed solution was heated to 220° C.; 3.1 gram of glycerin was added to the preheated vegetable oil and the mixed solution of the catalyst; At a reaction temperature of 220° C. and a stirring speed of 500 rpm, the reaction was carried out for 2 hours; a product containing monoglyceride was obtained. The conversion rate of corn oil was 94.9%, the yield of monoglyceride was 36.8%, and the loss of Ca in the product was 234.9 ppm.

The application of the catalyst prepared by embodiment 6, embodiment 3

Using the catalyst prepared in Example 3, 0.3 gram of catalyst was added into 10 grams of corn oil to form a mixed solution; the mixed solution was heated to 220° C.; 3.1 gram of glycerin was added to the preheated vegetable oil and the mixed solution of the catalyst; At a reaction temperature of 220° C. and a stirring speed of 500 rpm, the reaction was carried out for 2 hours; a product containing monoglyceride was obtained. The conversion rate of corn oil was 95.4%, the yield of monoglyceride was 38.5%, and the loss of Ca in the product was 159.2 ppm.

Claims (7)

1. a preparation method of nanometer calcium lanthanum composite oxide catalyst, is characterized in that, adopts the sol-gel combustion method that citric acid is assisted, adopts ethanol heat treatment to improve the hydrophilicity and hydrophobicity of oxide surface simultaneously, the concrete steps of preparation are: (1) Calcium nitrate and lanthanum nitrate solutions of a certain concentration are configured, mixed, and the molar ratio of metal ions and water is 1: (30-50); (2) Heating and stirring at 70-90°C, adding citric acid while stirring, the molar ratio of citric acid and metal ions is 0.5:1-2:1; (3) Stir the solution obtained in step (2) at 70-90°C until a sol is formed, and then age at room temperature for 18-24 hours; (4) drying the aged wet gel at a temperature of 100-140° C. in an air atmosphere for 12-24 hours to obtain a catalyst precursor 1; (5) After grinding the catalyst precursor 1, raise the temperature to 500-600°C at 1-3°C/min in the air atmosphere, keep it for 1-5 hours, and then raise the temperature to 700-800°C at 1-3°C/min, Roasting in an inert gas atmosphere for 2-8 hours to obtain a catalyst precursor 2; (6) Mix the catalyst precursor 2 with 2-5 times the weight of absolute ethanol, place it in a pressure-resistant container, treat it at 120-150°C for 2-3 hours, and dry it at 80-120°C under an inert atmosphere after cooling In 6-12 hours, the required catalyst is obtained; The molar ratio of calcium and lanthanum in the catalyst is 1:5-5:1. 2. The preparation method according to claim 1, characterized in that said inert gas is argon or helium, or a mixture thereof. 3. A nano-calcium-lanthanum composite oxide catalyst prepared by the preparation method according to claim 1. 4. the application of nano-calcium lanthanum composite oxide catalyst as claimed in claim 3 in glycerolysis vegetable oil synthetic monoglyceride, it is characterized in that take vegetable oil and glycerol as raw material, concrete steps are: (1) adding the catalyst to vegetable oil to form a mixed solution, and heating the mixed solution to 180-240°C; (2) Add glycerin to the mixture of preheated vegetable oil and catalyst; stir at a speed of 300-1000 rpm at a temperature of 180-240 ° C, and react for 10 min-300 min to obtain a product containing monoglyceride things. 5. application according to claim 4, is characterized in that described vegetable oil is soybean oil, corn oil, palm oil, cottonseed oil, rapeseed oil, olive oil, jatropha oil, or the mixture of several wherein. 6. application according to claim 4, it is characterized in that the weight ratio of described glycerin and vegetable oil is 1:5-1:1. 7. application according to claim 4, is characterized in that the usage amount of described catalyst is 0.1%-5% of vegetable oil weight.