CN111068721A

CN111068721A - Biomass ash solid base catalyst and preparation method and application thereof

Info

Publication number: CN111068721A
Application number: CN201911370540.8A
Authority: CN
Inventors: 牛胜利; 龙慎伟; 张运虎; 李冠兵; 韩奎华; 路春美; 张玉娇
Original assignee: Shandong Fengyuan Biomasspower Co ltd; Shandong University
Current assignee: Shandong Fengyuan Biomasspower Co ltd; Shandong University
Priority date: 2019-12-26
Filing date: 2019-12-26
Publication date: 2020-04-28
Anticipated expiration: 2039-12-26
Also published as: CN111068721B

Abstract

The invention discloses a biomass ash solid base catalyst, a preparation method and application thereof, wherein the preparation method comprises the following steps: heating biomass ash to not less than 750 ℃ for calcination, mixing the calcined biomass ash with strontium salt, adding a precipitator to precipitate strontium ions to obtain a precursor, heating the precursor to not less than 800 ℃ for activation to obtain a biomass ash solid base catalyst; the biomass ash is middle-layer ash of a low-temperature superheater for burning biomass to generate power. The biomass ash solid base catalyst provided by the invention has high catalytic activity and good catalytic stability.

Description

Biomass ash solid base catalyst and preparation method and application thereof

Technical Field

The invention belongs to the technical field of catalyst preparation, and relates to a biomass ash solid base catalyst, and a preparation method and application thereof.

Background

The information in this background section is only for enhancement of understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art that is already known to a person of ordinary skill in the art.

Gradual depletion of petroleum resources and environmental pollution caused by petroleum combustion promote people to develop renewable green resources capable of replacing petroleum. Biodiesel has received much attention in recent years because of its excellent environmental protection, combustion and lubrication properties. At present, the industrial production of biodiesel mainly uses a homogeneous base catalyst to catalyze the ester exchange method between animal and vegetable oil and short-chain alcohol. The method has the advantages of high reaction rate and high catalytic efficiency, but has the problems of difficult product separation, equipment corrosion, generation of a large amount of wastewater and the like. Compared with homogeneous catalysts, solid catalysts have the advantages of easy recovery and reusability. Although various solid catalysts have been developed, such as molecular sieves, hydrotalcites, solid heteropolyacids, and the like, these catalysts are generally expensive. In order to solve this problem, it is necessary to develop a solid catalyst having high activity and low cost from the catalyst raw material.

The adoption of waste as a catalyst raw material is an important way to reduce the cost of the catalyst. In the prior patent CN105344344A, eggshells are used as raw materials to prepare solid base catalysts through sodium salt modification, and the eggshells contain rich calcium-based components, so that the catalysts have good activity for preparing biodiesel through catalysis. In the prior patent CN 106799220A, sunflower stem ash is used as a raw material to prepare the potassium-based solid base catalyst, the production process is simple, the catalytic activity is high, but the reusability of the catalyst needs to be improved. China generates a large amount of biomass waste every year, and biomass combustion power generation is an effective method for treating the biomass waste. However, the plant ash obtained by biomass combustion power generation has not been effectively utilized.

Disclosure of Invention

In order to solve the defects of the prior art, the invention aims to provide a biomass ash solid base catalyst and a preparation method and application thereof.

In order to achieve the purpose, the technical scheme of the invention is as follows:

on the one hand, the preparation method of the biomass ash solid alkali catalyst comprises the steps of heating biomass ash to not less than 750 ℃ for calcination, mixing the calcined biomass ash with strontium salt, adding a precipitator to precipitate strontium ions to obtain a precursor, and heating the precursor to not less than 800 ℃ for activation to obtain the biomass ash solid alkali catalyst; the biomass ash is middle-layer ash of a low-temperature superheater for burning biomass to generate power.

The calcium element content of biomass ash generated by biomass combustion power generation fluctuates between 6.0 wt.% and 20.7 wt.%, a high-temperature superheater and a low-temperature superheater exist in the process of combustion power generation, the biological ash generated after biomass combustion can be deposited on the wall of the high-temperature superheater and the low-temperature superheater, the biological ash is deposited on the wall and divided into three layers, the inner layer is a combination of the biological ash after the wall surface of the superheater is corroded, and the ash is tightly combined with the wall of the superheater due to the corrosion of the wall surface and can be called as in-wall ash; the research of the inventor of the invention finds that the middle layer ash of the low-temperature superheater has the highest calcium content, and the biomass ash solid base catalyst obtained by strontium modification by the method has the advantages of high catalytic activity, good stability and the like.

In another aspect, a biomass ash solid base catalyst is obtained by the above preparation method.

In a third aspect, the application of the biomass ash solid base catalyst in catalyzing transesterification reaction is provided.

In a fourth aspect, the biomass ash solid base catalyst is applied to catalytic synthesis of biodiesel.

In a fifth aspect, the biomass ash solid base catalyst is adopted to catalyze the palm oil and methanol to perform ester exchange reaction.

The invention has the beneficial effects that:

1. the catalyst prepared by the invention has wide raw material source and low cost. The biomass resources in China are rich, and the biomass ash is used as the raw material of the catalyst, so that the waste can be changed into valuable, and the aim of reducing the cost of the catalyst is fulfilled.

2. The catalyst provided by the invention has high catalytic activity. The biomass ash calcium content is high, and the strontium modification is adopted to promote the ester exchange reaction, so that the yield of the biodiesel is improved.

3. The catalyst provided by the invention has good stability and can be repeatedly used. The strontium modification is beneficial to reducing the leaching of active centers in the using process of the catalyst, so that the catalyst can keep high catalytic activity and can be used for multiple times.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.

Fig. 1 is an XRD pattern of the modified pomegranate branch ash catalyst prepared in example 1 of the present disclosure, a being the catalyst prepared in example 2, and b being the catalyst prepared in example 1.

Detailed Description

It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

In view of the problem that the biomass ash is difficult to prepare the catalyst with better catalytic performance in the combustion power generation process, the invention provides a biomass ash solid base catalyst and a preparation method and application thereof.

The invention provides a typical embodiment of a preparation method of a biomass ash solid alkali catalyst, which comprises the steps of heating biomass ash to not less than 750 ℃ for calcination, mixing the calcined biomass ash with strontium salt, adding a precipitator to precipitate strontium ions to obtain a precursor, heating the precursor to not less than 800 ℃ for activation to obtain the biomass ash solid alkali catalyst; the biomass ash is middle-layer ash of a low-temperature superheater for burning biomass to generate power.

The invention discovers that the calcium content in the middle layer ash of the low-temperature superheater is highest, and the biomass ash solid base catalyst obtained by strontium modification by the method has the advantages of high catalytic activity, good stability and the like.

The strontium salt of the present invention refers to a compound which is dissolved in water to generate strontium ions as cations, such as strontium nitrate, strontium chloride, strontium acetate, etc. The invention adopts strontium nitrate to carry out verification experiments, and has good effect.

The biomass refers to plant materials capable of being combusted, such as pomegranate branches, apple branches, pear branches and the like.

In one or more embodiments of this embodiment, the calcination temperature is 750 to 950 ℃. When the calcination temperature is 845-855 ℃, the catalytic effect of the catalyst is better.

In one or more embodiments of this embodiment, the calcination time is 2 to 5 hours. When the calcination time is 3h, the catalytic effect of the catalyst is better.

In one or more embodiments of the present disclosure, the mass ratio of the calcined biomass ash to the strontium salt is 1: 0-1, and the strontium salt is not 0. When the mass ratio of the calcined biomass ash to the strontium salt is 1: 0.55-0.65, the catalytic effect of the catalyst is better.

The precipitating agent in the present invention is a compound capable of precipitating strontium ions, such as carbonate, such as sodium carbonate, potassium carbonate, ammonium carbonate, etc., and in one or more examples of this embodiment, the precipitating agent is ammonium carbonate. Can prevent doping other metal elements from influencing the catalytic performance of the catalyst.

In the series of embodiments, the molar ratio of the precipitator to the strontium salt is 1-1.3: 1. The precipitation effect is best when the molar ratio of the precipitant to the strontium salt is 1: 1.

In one or more embodiments of this embodiment, the precursor is dried and then activated. Preventing excessive water from influencing the catalyst structure in the high-temperature activation process.

In the series of embodiments, the drying temperature is 90-110 ℃. The drying effect is best when the drying temperature is 100 ℃.

In one or more embodiments of this embodiment, the activation temperature is 800 to 950 ℃. When the activation temperature is 845-855 ℃, the catalytic performance of the catalyst is better.

In another embodiment of the invention, a biomass ash solid base catalyst is provided, which is obtained by the preparation method. Book (I)

In a third embodiment of the invention, an application of the biomass ash solid base catalyst in catalyzing transesterification reaction is provided.

In a fourth embodiment of the invention, the application of the biomass ash solid base catalyst in catalyzing transesterification reaction is provided.

In a fifth embodiment of the invention, a method for synthesizing biodiesel is provided, wherein the biomass ash solid base catalyst is used for catalyzing palm oil and methanol to perform transesterification reaction.

In one or more embodiments of the present disclosure, the amount of the catalyst added is 2.5 to 10% by mass of the palm oil.

In one or more examples of this embodiment, the molar ratio of methanol to palm oil is 6 to 24: 1.

In one or more embodiments of this embodiment, the transesterification temperature is 55 to 70 ℃.

In one or more embodiments of this embodiment, the transesterification reaction is heated by microwaves.

In one or more embodiments of this embodiment, the transesterification reaction time is 2 to 4 hours.

In one or more embodiments of the present invention, after the transesterification reaction is completed, the catalyst is recovered by centrifugation, the liquid phase product is separated into layers by a separating funnel, and the upper layer is the biodiesel obtained by the reaction.

In order to make the technical solution of the present invention more clearly understood by those skilled in the art, the technical solution of the present invention will be described in detail below with reference to specific examples and comparative examples.

Example 1

Calcining the middle-layer ash in the low-temperature superheater for biomass power generation for 3 hours at the high temperature of 850 ℃ in a muffle furnace. 5g of calcined ash is dissolved in deionized water, 3g of strontium nitrate tetrahydrate is added, and the solution is uniformly stirred to obtain a salt solution. 1.12g of ammonium carbonate is dissolved in deionized water, and after stirring uniformly, the solution is dripped into a salt solution to obtain a precipitate. The resulting precipitate was filtered and dried at 100 ℃. And calcining the dried sample in a muffle furnace at 850 ℃ for 3h for activation to obtain the catalyst. The theoretical mass ratio of strontium oxide to pomegranate branch ash in the catalyst is 0.2:1, and the structural representation diagram of the catalyst is shown in figure 1.

In FIG. 1, the catalyst crystal phase is changed after Sr addition compared to the middle ash in the calcined low temperature superheater, resulting in a new crystal phase SrSO₄(PDF 05-0593), and CaSO₄The crystal phase disappears (PDF 37-1496), and the crystallinity of CaO (PDF 48-1467) is enhanced. This indicates that the addition of Sr changes the crystalline phase of the catalyst, enhancing the stability of the catalyst.

10.5g of methanol, 20g of palm oil and 1.5g of catalyst (7.5 percent of the mass of the palm oil) are added into a three-neck flask, and the mixture is condensed and refluxed for reaction for 3 hours at the temperature of 64 ℃ in a microwave reactor. Separating the catalyst from the reaction product by a centrifuge at 3000r/min, and placing the product into a separating funnel for standing, wherein the upper layer is the biodiesel and the lower layer is the glycerol. The biodiesel was washed to neutrality with deionized water and the transesterification product was evaporated to separate the remaining deionized water and methanol from the biodiesel with a biodiesel yield of 93.61% by GC.

Example 2

Calcining the middle-layer ash in the low-temperature superheater for biomass power generation for 3 hours at the high temperature of 850 ℃ in a muffle furnace. The calcined ash was used directly in the transesterification reaction without being modified with strontium.

10.5g of methanol, 20g of palm oil and 1.5g of catalyst (7.5 percent of the mass of the palm oil) are added into a three-neck flask, and the mixture is condensed and refluxed for reaction for 3 hours at the temperature of 64 ℃ in a microwave reactor. Separating the catalyst from the reaction product by a centrifuge at 3000r/min, and placing the product into a separating funnel for standing, wherein the upper layer is the biodiesel and the lower layer is the glycerol. The biodiesel was washed to neutrality with deionized water and the transesterification product was evaporated to separate the remaining deionized water and methanol from the biodiesel with a biodiesel yield of 78.98% by GC.

Example 3

Calcining the middle-layer ash in the low-temperature superheater for biomass power generation for 3 hours at the high temperature of 900 ℃ in a muffle furnace. 5g of calcined ash is dissolved in deionized water, 3g of strontium nitrate tetrahydrate is added, and the solution is uniformly stirred to obtain a salt solution. 1.12g of ammonium carbonate is dissolved in deionized water, and after stirring uniformly, the solution is dripped into a salt solution to obtain a precipitate. The resulting precipitate was filtered and dried at 100 ℃. And calcining the dried sample in a muffle furnace at 850 ℃ for 3h for activation to obtain the catalyst.

10.5g of methanol, 20g of palm oil and 1.5g of catalyst (7.5 percent of the mass of the palm oil) are added into a three-neck flask, and the mixture is condensed and refluxed for reaction for 3 hours at the temperature of 64 ℃ in a microwave reactor. Separating the catalyst from the reaction product by a centrifuge at 3000r/min, and placing the product into a separating funnel for standing, wherein the upper layer is the biodiesel and the lower layer is the glycerol. The biodiesel was washed to neutrality with deionized water and the transesterification product was evaporated to separate the remaining deionized water and methanol from the biodiesel with a biodiesel yield of 92.89% by GC.

Example 4

To examine the stability of the catalyst, the catalyst of example 1 was reused several times. The catalyst is centrifugally separated after each reaction is finished, and is directly used for the next reaction without any activation treatment. The reaction process is as follows: 10.5g of methanol, 20g of palm oil and 1.5g of catalyst (7.5 percent of the mass of the palm oil) are added into a three-neck flask, and the mixture is condensed and refluxed for reaction for 3 hours at the temperature of 64 ℃ in a microwave reactor. Separating the catalyst from the reaction product by a centrifuge at 3000r/min, and placing the product into a separating funnel for standing, wherein the upper layer is the biodiesel and the lower layer is the glycerol. Washing the biodiesel to be neutral by using deionized water, separating residual deionized water and methanol in the biodiesel from ester exchange products by evaporation, measuring the yield of the biodiesel by a GC method, and directly using the separated catalyst for the next reaction. The catalyst reacts for 5 times continuously, and as shown in table 1, the yield of the biodiesel is kept between 90% and 94%.

TABLE 1 catalyst reusability test results

Comparative example 1

The inner layer ash (the content of calcium element is 7.5 wt.%) of the high-temperature superheater for biomass power generation is calcined in a muffle furnace at 850 ℃ for 3 hours. 5g of calcined ash is dissolved in deionized water, 3g of strontium nitrate tetrahydrate is added, and the solution is uniformly stirred to obtain a salt solution. 1.12g of ammonium carbonate is dissolved in deionized water, and after stirring uniformly, the solution is dripped into a salt solution to obtain a precipitate. The resulting precipitate was filtered and dried at 100 ℃. And calcining the dried sample in a muffle furnace at 850 ℃ for 3h for activation to obtain the catalyst.

10.5g of methanol, 20g of palm oil and 1.5g of catalyst (7.5 percent of the mass of the palm oil) are added into a three-neck flask, and the mixture is condensed and refluxed for reaction for 3 hours at the temperature of 64 ℃ in a microwave reactor. Separating the catalyst from the reaction product by a centrifuge at 3000r/min, and placing the product into a separating funnel for standing, wherein the upper layer is the biodiesel and the lower layer is the glycerol. The biodiesel was washed to neutrality with deionized water and the transesterification product was evaporated to separate the remaining deionized water and methanol from the biodiesel with a biodiesel yield of 42.31% by GC.

Comparative example 2

The middle-layer ash in the low-temperature superheater for biomass power generation is directly used for transesterification reaction without calcination. 10.5g of methanol, 20g of palm oil and 1.5g of catalyst (7.5 percent of the mass of the palm oil) are added into a three-neck flask, and the mixture is condensed and refluxed for reaction for 3 hours at the temperature of 64 ℃ in a microwave reactor. Separating the catalyst from the reaction product by a centrifuge at 3000r/min, and placing the product into a separating funnel for standing, wherein the upper layer is the biodiesel and the lower layer is the glycerol. The biodiesel was washed to neutrality with deionized water, and the transesterification product was evaporated to separate the remaining deionized water and methanol from the biodiesel with a biodiesel yield of 1.72% by GC.

Comparative example 3

5g of intermediate layer ash of a low-temperature superheater for biomass power generation without calcination is dissolved in deionized water, 3g of strontium nitrate tetrahydrate is added, and the solution is uniformly stirred to obtain a salt solution. 1.12g of ammonium carbonate is dissolved in deionized water, and after stirring uniformly, the solution is dripped into a salt solution to obtain a precipitate. The resulting precipitate was filtered and dried at 100 ℃. And calcining the dried sample in a muffle furnace at 850 ℃ for 3h for activation to obtain the catalyst.

10.5g of methanol, 20g of palm oil and 1.5g of catalyst (7.5 percent of the mass of the palm oil) are added into a three-neck flask, and the mixture is condensed and refluxed for reaction for 3 hours at the temperature of 64 ℃ in a microwave reactor. Separating the catalyst from the reaction product by a centrifuge at 3000r/min, and placing the product into a separating funnel for standing, wherein the upper layer is the biodiesel and the lower layer is the glycerol. The biodiesel was washed to neutrality with deionized water and the transesterification product was evaporated to separate the remaining deionized water and methanol from the biodiesel with a biodiesel yield of 81.29% by GC.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A preparation method of a biomass ash solid alkali catalyst is characterized in that biomass ash is heated to not less than 750 ℃ for calcination, the calcined biomass ash is mixed with strontium salt, a precipitator is added to precipitate strontium ions to obtain a precursor, and the precursor is heated to not less than 800 ℃ for activation to obtain the biomass ash solid alkali catalyst; the biomass ash is middle-layer ash of a low-temperature superheater for burning biomass to generate power.

2. The method for preparing the biomass ash solid base catalyst according to claim 1, wherein the calcination temperature is 750 to 950 ℃; preferably, the calcining temperature is 845-855 ℃;

or, the calcination time is 2-5 h; preferably, the calcination time is 3 hours.

3. The preparation method of the biomass ash solid base catalyst according to claim 1, wherein the mass ratio of the calcined biomass ash to the strontium salt is 1: 0-1, and the strontium salt is not 0; preferably, the mass ratio of the calcined biomass ash to the strontium salt is 1: 0.55-0.65.

4. The method for preparing the biomass ash solid base catalyst according to claim 1, wherein the precursor is dried and then activated;

preferably, the drying temperature is 90-110 ℃.

5. The method for preparing the biomass ash solid base catalyst according to claim 1, wherein the activation temperature is 800-950 ℃; preferably, the activation temperature is 845-855 ℃.

6. A biomass ash solid base catalyst, which is obtained by the preparation method of claim 1 to 5.

7. Use of the biomass ash solid base catalyst of claim 6 to catalyze a transesterification reaction.

8. Use of the biomass ash solid base catalyst of claim 6 to catalyze a transesterification reaction.

9. A method for synthesizing biodiesel, which is characterized in that the biomass ash solid base catalyst of claim 6 is used for catalyzing the ester exchange reaction of palm oil and methanol.

10. The method for synthesizing biodiesel according to claim 9, wherein the amount of the catalyst added is 2.5-10% by mass of palm oil;

or the molar ratio of the methanol to the palm oil is 6-24: 1;

or, the ester exchange reaction temperature is 55-70 ℃;

or, the ester exchange reaction adopts microwave heating;

or, the time of the ester exchange reaction is 2-4 h;

or, after the ester exchange reaction is finished, centrifugally recovering the catalyst, layering the liquid-phase product by using a separating funnel, and obtaining the biodiesel by the reaction at the upper layer.