CN109321267B

CN109321267B - Liquid oil rich in aromatic hydrocarbon compounds and preparation method thereof

Info

Publication number: CN109321267B
Application number: CN201811189433.0A
Authority: CN
Inventors: 杨海平; 李淑娟; 陈旭; 陈应泉; 王贤华; 邵敬爱; 张�雄; 杨晴; 张世红; 陈汉平
Original assignee: Huazhong University of Science and Technology
Current assignee: Huazhong University of Science and Technology
Priority date: 2018-10-12
Filing date: 2018-10-12
Publication date: 2020-02-21
Anticipated expiration: 2038-10-12
Also published as: CN109321267A

Abstract

The invention belongs to the field of biomass utilization, and particularly discloses liquid oil rich in aromatic hydrocarbon compounds and a preparation method thereof, wherein the liquid oil is prepared by the following steps: crushing the biomass to 80-120 meshes of particles, and then drying to obtain a pyrolysis raw material; uniformly mixing a pyrolysis raw material and a calcined calcium-based additive, placing the mixture into a fixed bed reactor, and carrying out pyrolysis reaction in an inert atmosphere, wherein the pyrolysis temperature is 450-750 ℃, the reaction time is 10-20min, and volatile components generated by pyrolysis are reformed through a catalyst bed layer at the same temperature; and cooling the obtained reformed volatile component by adopting an ice-water mixture, and collecting a liquid product, namely the liquid oil product rich in the aromatic hydrocarbon compound. The method has the advantages of low cost, simple process and capability of continuously and efficiently preparing a large amount of aromatic-rich liquid oil.

Description

Liquid oil rich in aromatic hydrocarbon compounds and preparation method thereof

Technical Field

The invention belongs to the field of biomass utilization, and particularly relates to liquid oil rich in aromatic hydrocarbon compounds and a preparation method thereof.

Background

Aromatic hydrocarbons (including benzene, toluene, xylene, naphthalene, etc.) are basic organic raw materials, and various important products can be derived from aromatic hydrocarbons, and are widely applied to the fields of synthetic resins, synthetic fiber monomers, coatings, medicines, fine chemicals, etc. At present, the production of aromatic hydrocarbon at home and abroad mainly depends on petroleum resources, and aromatic hydrocarbon compounds are obtained by adding catalysts and carrying out processes such as hydrogenation, reforming, aromatic hydrocarbon conversion, separation and the like under the conditions of high temperature and high pressure. However, the process and equipment of the method are very complicated, and the limited reserves of petroleum lead to the rising cost of the chemical industry which is dominated by petroleum. In addition, petroleum refining processes produce large amounts of environmentally harmful by-products. Biomass is used as a unique renewable carbon source, has abundant reserves, can produce various organic chemicals and fuels through reasonable conversion, and is widely concerned. The bio-oil obtained by biomass pyrolysis contains various aromatic hydrocarbon substances, but the relative content of the bio-oil is low, the oxygen content in the pyrolysis oil is high, and the subsequent application is not facilitated, so that a novel method for preparing the aromatic hydrocarbon compound with high selectivity is urgently needed to be developed.

In order to increase the content of aromatic hydrocarbon substances in liquid oil, the conventional catalyst mainly adopts a catalytic pyrolysis mode, and comprises the following components: soluble inorganic substances, metal oxides, zeolite molecular sieves, and the like, wherein the zeolite molecular sieves perform well in terms of pyrolysis oil deoxygenation efficiency and aromatic hydrocarbon production. HZSM-5 can remove oxygen in pyrolysis oil to a high degree because of regular pore characteristics and proper acidity, and becomes the most effective molecular sieve catalyst for producing aromatic hydrocarbon. However, the HZSM-5 has limited pore size, so that the diffusion of aromatic hydrocarbon in the pyrolysis process is blocked, carbon is easily accumulated, and the yield of the bio-oil is low. In order to improve the catalytic property of HZSM-5, methods such as an alkali treatment method, a chemical vapor deposition method, a loaded metal nanoparticle modification method and the like are developed, but the methods are complex in process, high in cost and harmful to the environment. When the calcium-based additive is used as the catalyst, hydrogen atoms in the bio-oil can be retained to a higher degree, the hydrogen-carbon ratio of the bio-oil is improved, but the deoxidation efficiency is relatively low, and the bio-oil obtained by pyrolysis cannot be directly used.

Therefore, there is a need to develop a novel method for preparing aromatic hydrocarbon-rich liquid oil by catalytic pyrolysis of biomass, which can meet the requirements of simple operation, low cost, environmental protection, harmlessness and continuous and efficient preparation of a large amount of aromatic hydrocarbon-rich liquid oil.

Disclosure of Invention

Aiming at the defects or improvement requirements of the prior art, the invention provides the liquid oil rich in the aromatic hydrocarbon compound and the preparation method thereof, aiming at preparing the liquid oil rich in the aromatic hydrocarbon compound by using biomass in-situ mild deoxidation and coupled ex-situ deep deoxidation, realizing the preparation of aromatic hydrocarbon substances with high added values by biomass catalytic pyrolysis, improving the added value of the biological oil, avoiding corrosive catalysts in the pyrolysis process, reducing the harm to equipment and environment, and having the advantages of low cost, simple process and continuous and efficient preparation of a large amount of aromatic hydrocarbon-rich liquid oil.

In order to achieve the above object, according to one aspect of the present invention, there is provided a method for preparing a liquid oil rich in aromatic hydrocarbon compounds, comprising the steps of:

s1, crushing the biomass to particles of 80-120 meshes, and then drying to obtain a pyrolysis raw material;

s2, uniformly mixing the pyrolysis raw material and the calcined calcium-based additive, placing the mixture into a fixed bed reactor, and carrying out pyrolysis reaction in an inert atmosphere, wherein the pyrolysis temperature is 450-750 ℃, the reaction time is 10-20min, and the volatile component generated by pyrolysis is reformed through a molecular sieve catalyst bed layer at the same temperature;

s3, cooling the reformed volatile component obtained in the step S2 by adopting an ice-water mixture, and collecting a liquid product, namely a liquid oil product rich in aromatic hydrocarbon compounds.

More preferably, the biomass in step S1 is one or more of corncob, straw, chestnut shell and bamboo shavings.

More preferably, the drying temperature in the step S1 is 100 to 105 ℃, and the drying time is 12 to 24 hours.

As a further preference, the calcium-based additive is calcined at 850 ℃ for 4h and the molecular sieve catalyst is calcined at 600 ℃ for 2h in step S2.

Further preferably, the temperature rising rate of the pyrolysis raw material in the biomass pyrolysis process in the step S2 is 10 ℃/S to 100 ℃/S.

More preferably, in step S2, the mass ratio of the pyrolysis raw material to the calcium-based additive is 1:2 to 1:5, and the mass ratio of the pyrolysis raw material to the molecular sieve catalyst is 1: 4.

As a further preference, in the step S2, the pyrolysis temperature is preferably 600 ℃, and the reaction time is preferably 15 min.

Preferably, in step S2, the calcium-based additive is dolomite powder, and the molecular sieve catalyst is HZSM-5 molecular sieve catalyst.

According to another aspect of the present invention, there is provided a liquid oil rich in aromatic compounds, which is prepared by the method.

As a further preferred, the aromatic compound-rich liquid oil includes benzene, toluene, p-toluene, naphthalene, and 2-methylnaphthalene.

Generally, compared with the prior art, the above technical solution conceived by the present invention mainly has the following technical advantages:

1. the method adopts the in-situ catalysis coupled non-in-situ catalytic pyrolysis technology to carry out thermochemical conversion on the biomass to prepare the liquid oil product rich in aromatic substances with high added value, and has the advantages of simple process, convenient operation, continuity, high efficiency and the like.

2. According to the invention, the aromatic compound can be efficiently prepared by adjusting the amounts of the pyrolysis raw material, the calcium-based additive, the catalyst and the reaction temperature rise rate, and the calcium-based catalyst and the molecular sieve catalyst used in the invention can be recycled, so that the problem of resource waste in the traditional catalytic pyrolysis process is avoided.

3. The method takes the biomass as the raw material, achieves the aim of continuously and efficiently preparing the aromatic hydrocarbon compound, is simple and convenient to operate, and reduces the cost for preparing the aromatic hydrocarbon compound.

4. The aromatic compounds obtained by the method comprise benzene, toluene, xylene, naphthalene, 2-methylnaphthalene and the like, and the higher selectivity creates good conditions for subsequent separation and purification, thereby realizing high-value utilization of biomass resources.

5. The invention also researches and designs the proportion of the raw materials in the pyrolysis reaction, so that the mass ratio of the pyrolysis raw materials to the calcium-based additive is 1: 2-1: 5, the mass ratio of the catalyst to the pyrolysis raw materials is 4:1, aromatic hydrocarbon substances with higher content are obtained in the product, and substances such as toluene, naphthalene and the like are kept as far as possible.

6. The invention also researches and designs the specific process of the pyrolysis reaction to obtain the optimal pyrolysis process, wherein the pyrolysis temperature is 450-750 ℃, the reaction time is 10-20min, and preferably 600 +15min, so as to improve the yield of various aromatic substances.

7. The invention also researches and designs the calcination process of the calcium-based additive and the molecular sieve catalyst, so that the calcination process of the calcium-based additive is performed for 4 hours at 850 ℃, and the calcination process of the molecular sieve catalyst is performed for 2 hours at 600 ℃, thereby fully removing the moisture in the calcium-based additive and the molecular sieve catalyst, improving the reaction efficiency, protecting reaction equipment and reducing the oxygen content in the product.

Drawings

FIG. 1 is a flow chart of a method for producing a liquid oil rich in aromatic compounds according to an embodiment of the present invention;

FIG. 2 is a graph showing the relative content of aromatic hydrocarbons produced by the catalytic pyrolysis of corncobs at different calcium-based catalyst addition levels at a temperature rise rate of 10 ℃/s in the example of the present invention.

FIG. 3 is a graph showing the comparison of the relative contents of aromatic hydrocarbons produced by the catalytic pyrolysis of corncobs at different calcium-based catalyst addition levels at a temperature rise rate of 100 ℃/s in the example of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

As shown in fig. 1, the method for preparing liquid oil rich in aromatic hydrocarbon compounds, which is provided by the embodiment of the present invention, by using biomass in-situ mild deoxygenation coupled with ex-situ deep deoxygenation of a molecular sieve catalyst, includes the following steps:

s1 preparation of pyrolysis feedstock

The biomass is crushed to 80-120 meshes of particles, and then is dried to obtain a pyrolysis raw material, wherein the biomass is crushed to 80-120 meshes, the heating area of the biomass particles is increased, the reaction rate is increased, the full reaction is ensured, the biomass can be corncobs, rice straws, chestnut shells, bamboo chips and the like, the drying temperature is 100-105 ℃, the drying time is 12-24 hours, the moisture in the calcium-based additive and the molecular sieve catalyst can be sufficiently removed under the drying process, the reaction efficiency is improved, the reaction equipment is protected, and the oxygen content in the product can be reduced.

S2 carrying out pyrolysis reaction

Uniformly mixing a pyrolysis raw material and a calcined calcium-based additive (such as dolomite powder), putting the mixture into a fixed bed reactor, and carrying out pyrolysis reaction in an inert atmosphere (such as nitrogen, argon and the like), wherein the pyrolysis temperature is 450 ℃ and 750 ℃, the reaction time is 10-20min, volatile components generated by pyrolysis are reformed through a catalyst bed layer at the same temperature (namely the same as the pyrolysis temperature), the pyrolysis temperature is preferably 600 ℃, and the reaction time is preferably 15min, and under the pyrolysis conditions, the pyrolysis method is favorable for obtaining aromatic hydrocarbon substances with higher yield; specifically, the calcium-based additive is calcined for 4 hours at 850 ℃, and the catalyst in the catalyst bed layer is calcined for 2 hours at 600 ℃ in advance, so that the moisture in the calcium-based additive and the molecular sieve catalyst is fully removed, the reaction efficiency is improved, and the oxygen content in the product is reduced; the heating rate of the pyrolysis raw material in the pyrolysis process is 10-100 ℃/s, so as to respectively verify the influence of slow pyrolysis and fast pyrolysis on the distribution of the product; the mass ratio of the pyrolysis raw material to the calcium-based additive is 1:5-1:2, the mass ratio of the catalyst to the pyrolysis raw material is 4:1, and under the mass ratio, the product has high content of aromatic substances, and toluene, naphthalene and other components are kept as far as possible; specifically, the catalyst is a molecular sieve catalyst, preferably an HZSM-5 molecular sieve catalyst, and HZSM-5 has regular pore characteristics and proper acidity and can remove oxygen in the pyrolysis oil to a higher degree;

s3 collecting liquid product

And (4) cooling the reformed volatile component obtained in the step S2 by using an ice-water mixture, wherein the liquid product obtained by cooling is the required liquid oil product rich in aromatic hydrocarbon compounds, and the liquid oil rich in aromatic hydrocarbon compounds comprises benzene, toluene, p-toluene, naphthalene, 2-methylnaphthalene and the like.

The principle of the above inventive concept of the present invention is: the volatile component obtained by mixing and pyrolyzing the calcium-based catalyst and the biomass raw material is reformed under the catalysis of the molecular sieve catalyst, so that the content of aromatic substances in the biological oil is greatly improved. The action principle is as follows: the addition of the calcium-based catalyst can promote the biological oil to deoxidize in a reasonable mode, so that hydrogen atoms in the biological oil are retained to a greater extent, the hydrogen-carbon ratio of the biological oil is improved, but the deoxidation efficiency is lower, the molecular sieve catalyst can efficiently remove oxygen in the biological oil, and the biological oil product with higher aromatic hydrocarbon content can be obtained by coupling the in-situ mild deoxidation of the calcium-based catalyst in the pyrolysis process of the biomass raw material with the ex-situ deep deoxidation of the molecular sieve catalyst.

In the method, the in-situ mild deoxidation of the calcium-based catalyst is coupled with the ex-situ deep deoxidation of the molecular sieve catalyst, so that the content of aromatic hydrocarbon substances in the liquid oil can be obviously improved, the content of aromatic hydrocarbon compounds in the liquid oil reaches 60 percent, and the obtained aromatic hydrocarbon can be used in the fields of synthetic resin, synthetic fiber monomers, coatings, medicines, fine chemicals and the like after separation and purification. The method not only expands the application of the biomass, but also opens up a wide prospect for the subsequent utilization of the bio-oil.

In order to illustrate the process of the invention in more detail, reference is made to the following specific examples.

Example 1

The embodiment of the invention discloses a method for preparing liquid oil rich in aromatic hydrocarbon compounds by using biomass in-situ mild deoxidation and ex-situ deep deoxidation of a coupled molecular catalyst, which specifically comprises the following steps:

s1, crushing and screening the corncobs to 80-120 meshes, and drying the corncobs in an oven at 100-105 ℃ for 12-24 hours;

s2, carrying out catalytic cracking by using a fixed bed reactor, heating the reactor to 600 ℃ at a heating rate of 10 ℃/S, and carrying out catalytic pyrolysis on a mixture of a pyrolysis raw material and a calcium-based catalyst, wherein the mass ratio of the calcium-based catalyst to the pyrolysis raw material is 1:10, and the reaction time is 15 min; carrying out catalytic reforming on the pyrolyzed volatile component by using an HZSM-5 molecular sieve catalyst at the same temperature (namely 600 ℃), wherein the mass ratio of the HZSM-5 molecular sieve catalyst to the pyrolysis raw material is 4: 1;

s3 pyrolysis volatile component is brought into the condenser by the mixed gas, and is cooled by the ice water mixture to become liquid oil product rich in aromatic hydrocarbon compounds, wherein the aromatic hydrocarbon compounds mainly comprise benzene, toluene, xylene, naphthalene, 2-methylnaphthalene and the like.

Example 2

This example is the same as example 1 except that the mass ratio of calcium-based catalyst to pyrolysis feedstock is 1: 5.

example 3

This example is the same as example 1 except that the mass ratio of calcium-based catalyst to pyrolysis feedstock was 3: 10.

example 4

This example is the same as example 1 except that the mass ratio of calcium-based catalyst to pyrolysis feedstock is 2: 5.

example 5

This example is the same as example 1 except that the mass ratio of calcium-based catalyst to pyrolysis feedstock is 1: 2.

example 6

This example is the same as example 1 except that no calcium-based catalyst was added, only the biomass feedstock was pyrolyzed, and the resulting volatiles were condensed after catalytic reforming over a molecular sieve catalyst to obtain a liquid oil.

Example 7

This example is the same as example 1 except that the temperature rise rate was 100 ℃/s and the mass ratio of the calcium-based catalyst to the pyrolysis feedstock was 1: 2.

example 8

This example is the same as example 7, except that the mass ratio of calcium-based catalyst to pyrolysis feedstock is 1: 1.

example 9

This example is the same as example 7 except that no calcium-based catalyst was added and only the biomass feedstock was pyrolyzed and the resulting volatiles were condensed after catalytic reforming over a molecular sieve catalyst to obtain a liquid oil.

FIG. 2 is a graph showing the relative contents of aromatic hydrocarbons produced by the catalytic pyrolysis of corncobs at various calcium-based catalyst addition levels at a temperature rise rate of 10 ℃/s in examples of the present invention, which shows the results of the experiments in examples 1 to 6. As shown in figure 2, after the corncob raw material is subjected to ex-situ deep deoxidation by the calcium-based catalyst in-situ temperature and deoxidation coupling HZSM-5 molecular sieve catalyst at 600 ℃, compared with a result without the calcium-based catalyst, the contents of toluene, xylene, naphthalene and 2-methylnaphthalene in the pyrolysis oil are all increased, the yield of aromatic substances is increased by increasing the proportion of the calcium-based catalyst, and the yield of polycyclic aromatic hydrocarbon is obviously higher than that of monocyclic aromatic hydrocarbon. The yield of aromatic hydrocarbon substances in the pyrolysis oil is highest when the mass ratio of the calcium-based catalyst to the biomass raw material is 1: 2.

FIG. 3 is a graph showing the relative contents of aromatic hydrocarbons produced by the catalytic pyrolysis of corncobs at various calcium-based catalyst addition levels at a temperature rise rate of 100 ℃/s in examples of the present invention, which shows the results of experiments in examples 7 to 9. As shown in fig. 3, when the mass ratio of the calcium-based catalyst to the corncobs is not more than 1, increasing the ratio of the calcium-based catalyst can increase the total yield of aromatic products.

The method utilizes the characteristics that the calcium-based additive is helpful for improving the hydrogen-carbon ratio in the bio-oil pyrolysis oil and the molecular sieve catalyst is helpful for reducing the oxygen content in the biomass pyrolysis oil, has the advantages of simple process, convenience in operation, continuity, high efficiency and the like, has high selectivity of aromatic hydrocarbon compounds in the liquid oil obtained by pyrolysis, can be widely used in the fields of synthetic resin, fiber monomers, paint, fuel, medicine, fine chemicals and the like, and is favorable for providing a new potential path for preparing the aromatic hydrocarbon compounds for biomass.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. The preparation method of the liquid oil rich in the aromatic hydrocarbon compounds is characterized by comprising the following steps:

s2, uniformly mixing a pyrolysis raw material and a calcined calcium-based additive, placing the mixture into a fixed bed reactor, and carrying out pyrolysis reaction in an inert atmosphere, wherein the pyrolysis temperature is 450-750 ℃, the reaction time is 10-20min, the heating rate of the pyrolysis raw material is 10-100 ℃/S, the volatile component generated by pyrolysis is reformed through an HZSM-5 molecular sieve catalyst bed layer at the same temperature, the calcium-based additive is calcined at 850 ℃ for 4h, the molecular sieve catalyst is calcined at 600 ℃ for 2h, the mass ratio of the pyrolysis raw material to the calcium-based additive is 1: 2-1: 5, and the mass ratio of the pyrolysis raw material to the molecular sieve catalyst is 1: 4;

2. The method of claim 1, wherein the biomass in step S1 is one or more of corncob, straw, chestnut shell, and bamboo shavings.

3. The method of claim 1, wherein the drying temperature in step S1 is 100-105 ℃ and the drying time is 12-24 hours.

4. The method of claim 1, wherein the pyrolysis temperature is 600 ℃ and the reaction time is 15min in step S2.

5. The method for preparing liquid oil rich in aromatic hydrocarbon compounds according to claim 1, wherein in the step S2, the calcium-based additive is dolomite powder.

6. A liquid oil rich in aromatic compounds, characterized in that it has been prepared by a process according to any one of claims 1 to 5.

7. The aromatic compound-rich liquid oil of claim 6, wherein the aromatic compound-rich liquid oil comprises benzene, toluene, p-toluene, naphthalene, and 2-methylnaphthalene.