CN101185903A - A kind of solid base catalyst for biodiesel synthesis, preparation method and application thereof - Google Patents

Abstract

The invention discloses a solid base catalyst for synthesizing biodiesel, a preparation method and use thereof. The method of the invention has the advantages of simple technique, rich raw materials, low catalyst production cost and the prepared catalyst has high catalytic efficiency, good reproducibility and environmental protection.

Description

A kind of solid base catalyst for biodiesel synthesis, preparation method and application thereof

technical field

The invention relates to the technical field of green and renewable energy, and specifically refers to a high-efficiency and cheap solid base catalyst for catalyzing the transesterification reaction of fatty acid glycerides and methanol to synthesize biodiesel, a preparation method and an application thereof.

Background technique

At present, biodiesel preparation methods mainly include direct mixing method, microemulsion method, pyrolysis method and transesterification method. The microemulsion method is a method of mixing animal and vegetable oils, solvents and microemulsifiers to make a microemulsion liquid with a lower viscosity than the original animal and vegetable oils. Although the biodiesel prepared by this method can reduce the viscosity of animal and vegetable oils, the cetane number is not high, and problems such as carbon deposition in combustion and lubricating oil pollution are difficult to solve. The direct mixing method is to directly mix plants and mineral diesel for combustion, and the viscosity of this type of fuel is too high to be eliminated. The pyrolysis method is simple in process and produces no pollutants. The disadvantage is that it is carried out at high temperature, requires catalysts, expensive cracking equipment, difficult to control the degree of reaction, and low yield.

The industrial production of biodiesel mainly adopts transesterification method. The transesterification method is to transesterify animal and vegetable oils with various short-chain alcohols under the action of a catalyst to obtain fatty acid esters and glycerol with smaller molecular weights. These fatty acid esters with smaller molecular weight can be directly used as diesel fuel due to their lower viscosity. The transesterification methods currently used to prepare biodiesel can be roughly divided into homogeneous catalyzed transesterification, enzyme-catalyzed transesterification, supercritical transesterification and heterogeneous catalyzed transesterification.

The homogeneous catalysis method is the most commonly used method at present. The catalyst used is generally sodium hydroxide or potassium hydroxide. The advantage is that the requirements for the reaction conditions are not high and the reaction efficiency is good. But the disadvantage is that saponification side reactions are prone to occur, the reaction products are difficult to separate, and the catalyst cannot be reused. Especially in the refining process, water washing is required, resulting in more sewage and great environmental pollution. Enzyme catalysis and supercritical synthesis have high requirements on reaction conditions and high cost, and there is still a long way to go in actual production and application. The heterogeneous catalyzed transesterification method is actually a method catalyzed by a solid catalyst. The main advantages of using solid catalysts are that the catalysts are easy to separate, the post-treatment is simple, and the pollution to the environment is small.

Solid catalysts for biodiesel synthesis are mainly divided into solid acids and solid bases. Solid acid catalysts generally have a better catalytic effect on the synthesis of biodiesel using low-carbon alcohols and fatty acids, but for the use of low-carbon alcohols and fatty acid glycerides The catalytic effect of synthetic biodiesel is relatively poor. Since the main component of animal and vegetable oils is fatty acid glycerides, only waste animal and vegetable oils contain some free fatty acids, so solid acid catalysts are generally only used in the pretreatment of waste animal and vegetable oils as raw materials for biodiesel production. The solid base catalyst has a better effect on catalyzing the synthesis of biodiesel from low-carbon alcohols and fatty acid glycerides, so the solid base catalyst is the focus of current development.

At present, there are many types of solid base catalysts, such as supported catalysts, strongly basic anion exchange resins, various metal oxides or hydroxides insoluble in low-carbon alcohols, and the like. However, these catalysts have problems such as high price, complicated preparation process, or poor catalytic effect.

There have been many reports of directly using calcium carbonate, calcium oxide, and calcium hydroxide as basic solid catalysts for biodiesel synthesis. The effect is too poor. In order to improve the conversion rate of biodiesel, it is necessary to prolong the reaction time or adopt reaction conditions such as high temperature and high pressure (Patent Publication 2001-271090, Patent Publication 2004-35873), so the practicability is relatively poor.

Contents of the invention

The purpose of the present invention is to provide a solid base catalyst for synthesizing biodiesel with methanol and animal and vegetable oil.

The object of the present invention is also to provide a method for preparing a solid base catalyst for synthesizing biodiesel from methanol and animal and vegetable oils. The catalyst has simple manufacturing process, low raw material price, convenient recycling and utilization, and good catalytic effect.

Another object of the present invention is to provide the use of the above-mentioned solid base catalyst, which is used for synthesizing biodiesel from methanol and animal and vegetable oils.

The solid base catalyst of the present invention is a solid base catalyst of calcium oxide whose surface contains methanol, which is prepared by calcining calcium carbonate, calcium oxide hydrogen or calcium oxide at high temperature, and then directly cooling with methanol or methanol steam.

The preparation method of solid base catalyst of the present invention comprises the following steps:

1. Calcining calcium carbonate, calcium oxide or calcium hydroxide in a high-temperature furnace at 600-1000°C for 0.5-4 hours.

2. Take out the calcined calcium carbonate, calcium oxide, and calcium hydroxide directly or naturally cool down to 400-950°C in a high-temperature furnace.

3. Pouring the calcined product taken out in step 2 with methanol liquid or putting the calcined product into methanol liquid to cool to room temperature to obtain the catalyst prepared in the present invention. The calcined product in step 2 and the container containing the calcined product can also be directly placed in a closed container filled with methanol vapor and naturally cooled to room temperature to obtain the catalyst prepared in the present invention. To make the airtight container full of methanol vapor, various methods such as putting methanol liquid in the airtight container in advance and then vacuuming it can be adopted.

4. Store the catalyst obtained in step 3 in a sealed package, or directly use it in the reaction of methanol or methanol and animal and vegetable oil to synthesize biodiesel.

Experiments have shown that the solid base catalyst prepared according to the above steps has a high catalytic efficiency for transesterifying methanol and fatty acid glycerides into fatty acid methyl esters (biodiesel). In order to find out the reason why the solid base catalyst prepared by the present invention has high catalytic efficiency, its composition was detected by infrared spectroscopy, as shown in Figure 1. And the diffraction characteristics of ordinary calcium oxide and the catalyst of the present invention were compared by an X-ray scattering detector, as shown in FIG. 2 . The solid base catalyst prepared by the invention has the characteristics of calcium methoxide. This may be an important reason why the catalytic efficiency of the solid base catalyst prepared by the present invention is much higher than that of ordinary calcium carbonate, calcium oxide and calcium hydroxide.

The advantages of the present invention are:

1. The catalyst prepared by this method has high catalytic efficiency, which is equivalent to the calcium methoxide prepared by metal calcium in the literature report.

2. The process route and equipment used for preparing the catalyst are simple, the raw materials are abundant and cheap, and the production cost of the catalyst is low.

3. The prepared catalyst can be regenerated, and the regeneration method is simple.

4. The prepared catalyst has no pollution to the environment and is a green and environment-friendly catalyst.

Description of drawings

Fig. 1 is the infrared spectrogram of solid catalyst of the present invention.

Fig. 2 is an X-ray scattering comparison diagram of the solid catalyst of the present invention and ordinary calcium oxide.

In Fig. 2, A is the solid catalyst of the present invention, and B is the calcium oxide reagent.

Detailed ways

The present invention is described in further detail below in conjunction with embodiment, but content of the present invention can not be limited.

Example 1

Weigh 10g of CaO and 25g of (NH ₄ ) ₂ CO ₃ into an 800ml beaker, add 200ml of water, add 2g of emulsifier (Tween), cool in a cold water bath, and stir at high speed for 1 hour to generate CaCO ₃ . Suction filter the prepared calcium carbonate, then put it into an oven to dry, keep it at 105°C for 2 hours, grind it until it is completely dry, put it into a desiccator and save it for later use. Weigh 1.786g CaCO ₃ in a crucible, raise the temperature to 900°C in a high-temperature resistance furnace, calcinate for 2 hours, cool down to 650°C, take it out and cool it with anhydrous methanol to prepare the catalyst.

50g soybean oil (density is 0.92g/cm ³ ), 1g of the above-mentioned catalyst and 21.5ml methanol (density is 0.792g/cm ³ ) mixed solution is put into a 250ml conical triangular grinding neck flask, placed on a constant temperature magnetic stirrer for stirring and heating To 67-68 ° C, after 2 hours of reaction, stop stirring and heating. Move the reaction solution to a centrifuge to separate the catalyst, then pour it into a separatory funnel, let it stand, and separate it into upper and lower layers. After methanol was distilled off in the upper layer water bath, the conversion rate was measured to be 97.3%.

Example 2

Weigh 3 g of calcium carbonate reagent (analytically pure) in a crucible, heat up to 900°C in a high-temperature resistance furnace, calcinate for 2 hours, cool down to 650°C, take it out and cool it with anhydrous methanol to prepare the catalyst.

50g soybean oil (density is 0.92g/cm ³ ), 1g of the above-mentioned catalyst and 21.5ml methanol (density is 0.792g/cm ³ ) mixed solution is put into 250ml triangular grinding neck flask, placed on a constant temperature magnetic stirrer and stirred and heated To 67-68 ° C, after 2 hours of reaction, stop stirring and heating. Move the reaction solution to a centrifuge to separate the catalyst, then pour it into a separatory funnel, let it stand, and separate it into upper and lower layers. After methanol was distilled off in the upper layer water bath, the conversion rate was measured to be 95.6%.

Example 3

Weigh 40g of Ca(Ac) ₂ and 30g of (NH4) ₂ CO ₃ into an 800ml beaker, add 300ml of water, add 3g of emulsifier (Tween), cool in a cold water bath, and stir at high speed for 1 hour to generate CaCO ₃ . The prepared calcium carbonate was suction filtered, then dried in an oven, kept at 105°C for 2 hours, ground into fine pieces after drying, and stored in a desiccator for later use. Weigh 1.786g CaCO ₃ in a crucible, raise the temperature to 900°C in a high-temperature resistance furnace, calcinate for 2 hours, cool down to 500°C, take it out and cool it with anhydrous methanol to prepare the catalyst.

50g soybean oil (density is 0.92g/cm3), 1g above-mentioned catalyst and 21.5ml methanol (density is 0.792g/cm3) mixed solution is put into 250ml triangular grinding mouth flask, is placed on the constant temperature magnetic stirrer and is heated to 67 -68°C, after 2 hours of reaction, stop stirring and heating. Move the reaction solution to a centrifuge, separate the self-made catalyst, then pour it into a separatory funnel, let it stand, and divide it into upper and lower layers. After methanol was distilled off in the upper layer water bath, the conversion rate was measured to be 93.5%.

Example 4

Weigh 40g of Ca(Ac) ₂ and 30g of (NH ₄ ) ₂ CO ₃ into an 800ml beaker, add 300ml of water, cool in a cold water bath, and stir at high speed for 1 hour to generate CaCO ₃ . The prepared calcium carbonate was suction filtered, then dried in an oven, kept at 105°C for 2 hours, ground into fine pieces after drying, and stored in a desiccator for later use. Weigh 1.786g CaCO ₃ in a crucible, raise the temperature to 950°C in a high-temperature resistance furnace, calcinate for 3 hours, cool down to 700°C, take it out and cool it with anhydrous methanol to prepare the catalyst.

Put 50g soybean oil (density is 0.92g/cm ³ ), 1g above-mentioned solid catalyst and 20.5ml methanol (density is 0.792g/cm ³ ) mixed solution is put into 250ml triangular grinding mouth flask, be placed on constant temperature magnetic stirrer and stir Heating to 67-68°C, after 2 hours of reaction, stop stirring and heating. Move the reaction solution to a centrifuge to separate the self-made catalyst, then pour it into a separatory funnel, let it stand, and divide it into upper and lower layers. After methanol was distilled off in the upper layer water bath, the conversion rate was measured to be 98.4%.

Example 5

Weigh 40g of Ca(Ac) ₂ and 30g of (NH ₄ ) ₂ CO ₃ into an 800ml beaker, add 300ml of water, add 3g of emulsifier (Tween), cool in a cold water bath, and stir at high speed for 1 hour to generate CaCO ₃ . The prepared calcium carbonate was suction filtered, then dried in an oven, kept at 105°C for 2 hours, ground into fine pieces after drying, and stored in a desiccator for later use. Weigh 1.786g of CaCO ₃ into a crucible, raise the temperature to 900°C in a high-temperature resistance furnace, and calcinate for 2 hours. After taking it out, put it into a desiccator with methanol remaining in the lower layer, and vacuum it for 0.5 hours.

50g soybean oil (density is 0.92g/cm ³ ), 1g of the above-mentioned catalyst and 20.5ml methanol (density is 0.792g/cm ³ ) mixed solution is put into 250ml triangular grinding neck flask, placed on a constant temperature magnetic stirrer and stirred and heated To 67-68 ° C, after 2 hours of reaction, stop stirring and heating. Move the reaction solution to a centrifuge, separate the self-made catalyst, then pour it into a separatory funnel, let it stand, and divide it into upper and lower layers. After methanol was distilled off in the upper layer water bath, the conversion rate was measured to be 96.7%.

Example 6

Weigh 40g of Ca(Ac) ₂ and 30g of (NH ₄ ) ₂ CO ₃ into an 800ml beaker, add 300ml of water and 3g of emulsifier (Tween), and stir at high speed for 1 hour to generate CaCO ₃ . The prepared calcium carbonate was suction filtered, then dried in an oven, kept at 105°C for 2 hours, ground into fine pieces after drying, and stored in a desiccator for later use. Weigh 1.786g CaCO ₃ in a crucible, raise the temperature to 900°C in a high-temperature resistance furnace, burn for 2 hours, cool down to 650°C, take it out and cool it with anhydrous methanol to prepare the catalyst.

Put 50g of rapeseed oil, 1g of the above-mentioned catalyst and 21.5ml of methanol (density of 0.792g/cm ³ ) into a 250ml triangular ground-mouth flask, stir and heat to 67-68°C on a constant temperature magnetic stirrer, and react After 2 hours, stirring and heating were stopped. Move the reaction solution to a centrifuge, separate the self-made catalyst, then pour it into a separatory funnel, let it stand, and divide it into upper and lower layers. After methanol was distilled off in the upper layer water bath, the conversion rate was measured to be 97.4%.

Example 7

Weigh 40g of Ca(Ac) ₂ and 30g of (NH ₄ ) ₂ CO ₃ into an 800ml beaker, add 300ml of water, add 3g of emulsifier (Tween), cool in a cold water bath, and stir at high speed for 1 hour to generate CaCO ₃ . The prepared calcium carbonate was suction filtered, then dried in an oven, kept at 105°C for 2 hours, ground into fine pieces after drying, and stored in a desiccator for later use. Weigh 1.786g CaCO ₃ in a crucible, raise the temperature to 900°C in a high-temperature resistance furnace, calcinate for 2 hours, cool down to 650°C, take it out and cool it with anhydrous methanol to prepare the catalyst.

Put 50g of the filtered waste oil for frying, 1g of the above catalyst and 21.5ml of methanol (density 0.792g/cm3) into a 250ml triangular grinding-mouth flask, stir and heat on a constant temperature magnetic stirrer to 67-68 °C, after reacting for 2 hours, stop stirring and heating. Move the reaction solution to a centrifuge, separate the self-made catalyst, then pour it into a separatory funnel, let it stand, and divide it into upper and lower layers. After methanol was distilled off in the upper layer water bath, the conversion rate was measured to be 97.3%.

Example 8

With the catalyst separated in Example 4, add fresh soybean oil 50g (density is 0.92g/cm ³ ) and 21.5ml methyl alcohol (density is 0.792g/cm ³ ) mixed solution and put into 250ml conical grinding mouth flask each time , placed on a constant temperature magnetic stirrer, stirred and heated to 67-68° C., and reacted for 2 hours, then stopped stirring and heating. The reaction solution was transferred to a centrifuge to separate the catalyst. After using the catalyst 10 times repeatedly according to the above operation steps, pour the reaction solution into a separatory funnel, let it stand still, and divide it into upper and lower layers. After methanol was distilled off in the upper layer water bath, the conversion rate was measured to be 90.3%.

Example 9

The catalyst separated in Embodiment 4 was dried, placed in a crucible, heated to 900°C in a high-temperature resistance furnace, calcined for 2 hours, cooled to 650°C, taken out and cooled with anhydrous methanol to prepare the catalyst.

50g soybean oil (density is 0.92g/cm ³ ), 1g of above-mentioned regenerated catalyst and 20.5ml methanol (density is 0.792g/cm ³ ) mixed solution is put into 250ml conical grinding mouth flask, is placed on constant temperature magnetic stirrer and stirs Heating to 67-68°C, after 2 hours of reaction, stop stirring and heating. Move the reaction solution to a centrifuge, separate the self-made catalyst, then pour it into a separatory funnel, let it stand, and divide it into upper and lower layers. After methanol was distilled off in the upper layer water bath, the conversion rate was measured to be 97.3%.

Comparative example:

Put 50g of soybean oil (density of 0.92g/cm ³ ), 1g of drug calcium oxide (analytically pure) and 20.5ml of methanol (density of 0.792g/cm ³ ) into a 250ml conical triangular grinding neck flask, and place it in a constant temperature magnetic Stir and heat on the stirrer to 67-68°C, and stop stirring and heating after 2 hours of reaction. Move the reaction solution to a centrifuge, separate the self-made catalyst, then pour it into a separatory funnel, let it stand, and divide it into upper and lower layers. After methanol was distilled off in the upper layer water bath, the conversion rate was measured to be 14.3%.

The above content is only a basic description of the concept of the present invention, and any equivalent transformation made according to the technical solution of the present invention shall fall within the scope of protection of the present invention.

Claims (8)

1. one kind is used for the synthetic solid base catalyst of biodiesel, it is characterized in that described solid base catalyst is by high-temperature calcination calcium carbonate, calcium oxide or calcium hydroxide, directly cool off the solid base catalyst that calcium methoxide is contained on the surface that makes with methyl alcohol or methanol steam then.

2. a preparation method who is used for the synthetic solid base catalyst of biodiesel as claimed in claim 1 is characterized in that: high-temperature calcination calcium carbonate, calcium oxide or calcium hydroxide; Above-mentioned calcined material is cooled to 400-950 ℃, then with methyl alcohol or cool to room temperature obtains in methanol steam solid base catalyst; Described calcining heat is 600-1000 ℃, and calcination time is 0.5-4 hour.

3. a kind of preparation method who is used for the synthetic solid base catalyst of biodiesel as claimed in claim 2, it is characterized in that: described calcium carbonate is natural whiting or synthetic calcium carbonate.

4. a kind of preparation method who is used for the synthetic solid base catalyst of biodiesel as claimed in claim 2, it is characterized in that: described calcining heat is 700-950 ℃.

5. a kind of preparation method who is used for the synthetic solid base catalyst of biodiesel as claimed in claim 2, it is characterized in that: described calcination time is 1-2 hour.

6. a kind of preparation method who is used for the synthetic solid base catalyst of biodiesel as claimed in claim 2 is characterized in that: the temperature of described calcined material before directly cooling off with methyl alcohol or methanol steam is 600-800 ℃.

7. the synthetic solid base catalyst of biodiesel that is used for as claimed in claim 1 is used for catalytically synthesizing biological diesel oil.

8. the application that is used for the synthetic solid base catalyst of biodiesel as claimed in claim 7 is characterized in that: being used for catalysis is that the biodiesel of raw material is synthetic with methyl alcohol and vegetable and animals oils.

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