阅读说明：本技术 一种煤焦油生产btx的方法 (Method for producing BTX (benzene-toluene-xylene) from coal tar ) 是由 方梦祥 马帅 肖天存 岑建孟 王勤辉 骆仲泱 于 2020-06-04 设计创作，主要内容包括：本发明公开了一种煤焦油生产BTX的方法：将煤焦油在萃取反应器中与萃取剂甲醇混合进行萃取,过滤分离后得到萃取液和萃余物；萃取液进入甲醇转化反应器进行后续反应得到气体产物和液体产物,经过气液分离器后分别进入气体分离塔和液体分馏塔Ⅰ；气体产物在气体分离塔中分离得到包括氢气、烯烃和烷烃的气体产品,液体产物经过液体分馏塔Ⅰ分馏得到BTX产品和包含混合芳烃的塔底流出液；分馏塔Ⅰ的塔底流出液或与甲苯混合后经过高压泵加压,作为混合芳烃进料送入烷基转移反应器发生烷基转移反应,反应流出液进入分馏塔Ⅱ,分馏得到BTX产品。本发明提供的方法能够充分利用煤焦油中的芳潜和芳烃资源生产BTX。(The invention discloses a method for producing BTX by coal tar, which comprises the following steps: mixing coal tar with an extractant methanol in an extraction reactor for extraction, and filtering and separating to obtain an extract liquor and an extract residue; the extract liquid enters a methanol conversion reactor for subsequent reaction to obtain a gas product and a liquid product, and the gas product and the liquid product respectively enter a gas separation tower and a liquid fractionating tower I after passing through a gas-liquid separator; separating the gas product in a gas separation tower to obtain a gas product comprising hydrogen, olefin and alkane, and fractionating the liquid product in a liquid fractionating tower I to obtain a BTX product and a bottom effluent containing mixed aromatic hydrocarbon; and (3) pressurizing the tower bottom effluent of the fractionating tower I or the mixture of the tower bottom effluent and methylbenzene through a high-pressure pump, feeding the mixture into a transalkylation reactor as a mixed aromatic hydrocarbon feed to perform transalkylation reaction, feeding the reaction effluent into a fractionating tower II, and fractionating to obtain a BTX product. The method provided by the invention can be used for producing BTX by fully utilizing the aromatic hydrocarbon potential and aromatic hydrocarbon resources in the coal tar.)

1. A method for producing BTX from coal tar, which is characterized by comprising the following steps:

(1) mixing coal tar with an extractant methanol in an extraction reactor for extraction, and filtering and separating to obtain an extract liquor and an extract residue;

(2) the extract enters a methanol conversion reactor for subsequent reaction: in a methanol conversion reactor, the extract liquid reacts under the action of a catalyst to obtain a gas product and a liquid product, and the gas product and the liquid product respectively enter a gas separation tower and a liquid fractionating tower I after passing through a gas-liquid separator;

(3) separating the gas product in a gas separation tower to obtain a gas product comprising hydrogen, olefin and alkane, and fractionating the liquid product in a liquid fractionating tower I to obtain a BTX product and a bottom effluent containing mixed aromatic hydrocarbon;

(4) pressurizing the tower bottom effluent of the fractionating tower I or the mixture of the tower bottom effluent and methylbenzene through a high-pressure pump, feeding the mixture into a transalkylation reactor as a mixed aromatic hydrocarbon feed, adding hydrogen, and feeding the mixture into the transalkylation reactor after boosting the pressure;

(5) in the transalkylation reactor, mixed aromatic hydrocarbon is fed into a transalkylation reactor in a hydrogen atmosphere to carry out transalkylation reaction, reaction effluent liquid enters a fractionating tower II to be fractionated to obtain a BTX product, unconverted polymethylbenzene flows out from the bottom of the tower and is sent into a high-pressure pump to be circulated, and unreacted hydrogen is separated from the top of the fractionating tower II and is sent into a gas compressor to be circulated.

2. The method for producing BTX from coal tar according to claim 1, wherein in the step (1), the coal tar is pretreated, the pretreated coal tar is medium-low temperature coal tar, the ash content is lower than 0.01 wt%, the moisture content is lower than 300 μ g/g, and the metal content is lower than 50 μ g/g.

3. The method for producing BTX from coal tar according to claim 1, wherein in the step (1), the mass ratio of the coal tar to the methanol as the extracting agent is 1: 5-1: 50, the extraction temperature is 20-80 ℃, and the extraction method is mechanical stirring or ultrasonic extraction.

4. The method for producing BTX from coal tar according to claim 1, wherein in the step (2), the methanol conversion reactor is a fixed bed reactor, and the pressure is 0.1-0.5 MPa; the reaction temperature is 350-500 ℃; the liquid hourly space velocity is 0.1-2.0 h^-1。

5. A method for producing BTX from coal tar according to claim 1 or 4, characterized in that the methanol conversion reactor is packed with an acidic molecular sieve catalyst.

6. The method for producing BTX from coal tar according to claim 5, wherein the acidic molecular sieve catalyst is HZSM-5, and the atomic ratio of silicon to aluminum of the HZSM-5 is 3-200 Si/Al.

7. The method for producing BTX from coal tar according to claim 6, wherein the HZSM-5 molecular sieve is loaded with transition metal elements; the transition metal element is one or more of Ni, Mo, Fe, Co and Zn, and the metal content is 0.1-20 wt%.

8. The method for producing BTX from coal tar according to claim 1, wherein in the step (5), the transalkylation reactor is a fixed bed reactor, and the pressure is 0-6 MPa; the reaction temperature is 300-550 ℃; the liquid hourly space velocity is 0.1-2.0 h^-1(ii) a The hydrogen-oil ratio is 500:1 to 2000: 1.

9. A method for producing BTX from coal tar according to claim 1 or 8, characterized in that the transalkylation reactor is packed with an acidic molecular sieve catalyst, which is HZSM-5.

10. The method for producing BTX from coal tar according to claim 9, wherein the atomic ratio of Si to Al of HZSM-5 is 3-60 Si/Al.

Technical Field

The invention relates to the field of coal chemical industry, in particular to a method for producing BTX (benzene-toluene-xylene) by using coal tar.

Background

The energy background of China is rich coal, lean oil and less gas, the petroleum and natural gas resources are relatively deficient, and the utilization of coal resources occupies a great position in an energy consumption system. Coal tar is one of the byproducts of coal pyrolysis, and the utilization of the coal tar has important significance for the development of the coal chemical industry.

Generally, the utilization method of the coal tar comprises a fuel oil preparation route and a fine chemical route through hydrogenation, under the economic background that the international crude oil price is continuously low, the economic benefit of the hydrogenation route gradually declines, and compared with the complex process of the fine chemical route, partial hydrogenation between the two routes to prepare chemical products with high added values has a certain development prospect.

Benzene (Benzene), Toluene (Toluene) and Xylene (Xylene) are collectively called as BTX, i.e., light aromatic hydrocarbon, which is an important basic raw material in petrochemical industry, and has wide application in industries such as rubber, synthetic fiber, paint, medicine and pesticide. The traditional BTX production process is based on catalytic reformate or pyrolysis gasoline in the petroleum industry, and methanol is used as a raw material in the coal chemical industry. Aromatic hydrocarbon resources in the coal tar are reasonably utilized to produce light aromatic hydrocarbon products such as BTX and the like, so that not only can the shortage of petroleum in China be relieved, but also the problem of surplus of part of coal tar can be solved, and the gap of the light aromatic hydrocarbon industry is made up.

CN110408434A discloses a method for producing needle coke and BTX from coal tar whole fraction, which comprises the steps of firstly cutting coal tar into light and heavy components, enabling the light component to enter a hydrogenation unit for catalytic cracking reaction, separating heavy naphtha from the product, mixing the heavy naphtha with the heavy component to obtain clarified liquid and insoluble substances, separating the clarified liquid to obtain fraction I rich in BTX, and finally extracting with aromatic hydrocarbon to obtain the product. The process method has the advantages of high utilization rate of the coal tar, rich product types, complex process, cutting of the coal tar raw material, two hydrogenation units and high energy consumption.

CN106701181A discloses a method and a device for preparing monocyclic aromatic hydrocarbon by hydrogenating low-temperature coal tar in whole fraction, wherein the method comprises the steps of firstly sending the whole fraction of the coal tar into a fractionating tower to obtain a light-heavy phase material flow, carrying out cracking refining on the light phase, and carrying out refining cracking on the heavy phase after twice cracking. The method makes full use of the heavy components of the coal tar, but the heavy component cracking needs high pressure and high hydrogen consumption, and the cutting process of the coal tar also needs higher energy consumption.

CN101712889A discloses a method for preparing light aromatic hydrocarbons from coal tar, which divides the coal tar into light and heavy fractions by taking 200 ℃ as a cutting point, and only hydrofinishes the light fractions to obtain a light aromatic hydrocarbon product, wherein the process is simple, but the utilization rate of the coal tar is not high enough. In the method for preparing aromatic hydrocarbons from coal tar disclosed in CN103436288A, coal tar is distilled or cracked to obtain naphtha fraction, the naphtha fraction is pre-fractionated and pre-hydrogenated to obtain reformed raw materials, and then reforming and isomerization are performed to obtain aromatic hydrocarbon products. The method further isomerizes the components above C8 after the reforming unit, the yield of aromatic hydrocarbon is high, but the pretreatment process of the reforming raw material is complex and the energy consumption is high.

The coal tar has high aromatic hydrocarbon and aromatic hydrocarbon content, and the mainstream technical scheme at present is to firstly carry out distillation cutting and then respectively utilize light and heavy components. The invention adopts the extraction process to replace distillation cutting, thereby effectively reducing the energy consumption; the methanol is used as a hydrogen source and a part of carbon source, so that the storage and transportation are convenient; the material circulation and the transalkylation unit are increased, and the yield of BTX, especially xylene, is further improved.

Disclosure of Invention

The invention aims to provide a method for producing BTX by coal tar, which can fully utilize aromatic hydrocarbon potential and aromatic hydrocarbon resources in the coal tar to produce BTX, and can couple the hydrogenation of the aromatic hydrocarbon prepared by methanol and the coal tar, and simultaneously reduce hydrogen consumption and energy consumption, so as to realize the graded utilization of the coal tar resources and make up for the industrial gap of light aromatic hydrocarbon.

In order to achieve the purpose, the invention adopts the following technical scheme:

(1) pretreating the whole fraction of the coal tar, mixing the whole fraction with an extractant methanol in an extraction reactor for extraction, and filtering and separating to obtain an extraction liquid and an extraction residue;

(2) the extract enters a methanol conversion reactor for subsequent reaction: in a methanol conversion reactor, the extract liquid reacts under the action of a catalyst to obtain a gas product and a liquid product, and the gas product and the liquid product respectively enter a gas separation tower and a liquid fractionating tower I after passing through a gas-liquid separator;

(3) separating the gas product in a gas separation tower to obtain a gas product comprising hydrogen, olefin and alkane, and fractionating the liquid product in a liquid fractionating tower I to obtain a BTX product and a bottom effluent containing mixed aromatic hydrocarbon;

(4) pressurizing the tower bottom effluent of the fractionating tower I or the mixture of the tower bottom effluent and methylbenzene through a high-pressure pump, feeding the mixture into a transalkylation reactor as a mixed aromatic hydrocarbon feed, adding hydrogen, and feeding the mixture into the transalkylation reactor after boosting the pressure;

(5) in the transalkylation reactor, mixed aromatic hydrocarbon is fed into a transalkylation reactor in a hydrogen atmosphere to carry out transalkylation reaction, reaction effluent liquid enters a fractionating tower II to be fractionated to obtain a BTX product, unconverted polymethylbenzene flows out from the bottom of the tower and is sent into a high-pressure pump to be circulated, and unreacted hydrogen is separated from the top of the fractionating tower II and is sent into a gas compressor to be circulated.

In step (2), the raffinate may be used as a feedstock for the production of needle coke or other bitumen products.

The transalkylation reaction includes toluene disproportionation reaction, trimethylbenzene, tetramethylbenzene dealkylation reaction and other alkyl transfering reactions on the benzene ring.

In the step (1), the pretreatment process of the coal tar mainly removes moisture, metals and mechanical impurities in the coal tar to prolong the service life of the catalyst. Preferably, the pretreated coal tar is medium-low temperature coal tar, the ash content is lower than 0.01 wt%, the moisture content is lower than 300 mu g/g, and the metal content is lower than 50 mu g/g. In the step (1), the light aromatic hydrocarbon is extracted to obtain an extract liquid containing the light aromatic hydrocarbon. In the step (1), the mass ratio of the coal tar to the extractant methanol is 1: 5-1: 50, the extraction temperature is 20-80 ℃, and the extraction mode is mechanical stirring or ultrasonic extraction. And after extraction, filtering and separating to obtain an extraction liquid and a solid raffinate.

In the step (2), the methanol conversion reactor is a fixed bed reactor, and the pressure is 0.1-0.5 MPa; the reaction temperature is 350 ℃500 ℃; the liquid hourly space velocity is 0.1-2.0 h^-1. Preferably, the pressure is 0.1-0.2 MPa; the reaction temperature is 380-450 ℃; the liquid hourly space velocity is 0.5-1.5 h^-1。

In the step (3), an acidic molecular sieve catalyst is filled in the methanol conversion reactor. HZSM-5 is preferred. The atomic ratio of silicon to aluminum of HZSM-5 is 3 to 200. Preferably, the atomic ratio of silicon to aluminum of the HZSM-5 is 30 to 160 Si/Al.

Transition metal elements are loaded on the HZSM-5 molecular sieve. Preferably, the transition metal element is one or more of Ni, Mo, Fe, Co, and Zn, and the metal content is 0.1 to 20 wt%, and more preferably 1 to 10 wt%.

In the step (5), the transalkylation reactor is a fixed bed reactor, and the pressure is 0-6 MPa; the reaction temperature is 300-550 ℃; the liquid hourly space velocity is 0.1-2.0 h^-1(ii) a The hydrogen-oil ratio is 500:1 to 2000: 1. Preferably, the pressure is 2-5 MPa, the reaction temperature is 350-450 ℃, and the hourly space velocity is 0.5-1.5 h^-1The hydrogen-oil ratio is 1000: 1-1500: 1.

And filling an acidic molecular sieve catalyst into the transalkylation reactor, wherein the acidic molecular sieve catalyst is HZSM-5. The atomic ratio of silicon to aluminum of the HZSM-5 is 3-60 Si/Al. Preferably, the atomic ratio of silicon to aluminum of the HZSM-5 is 10 to 50 Si/Al.

Compared with the prior art, the invention has the following advantages:

(1) the extraction method is used for separating the coal tar by replacing a distillation cutting method, the operation is simple and convenient, and the energy consumption is reduced; (2) the methanol has good solubility to monocyclic aromatic hydrocarbon in the coal tar, and also has certain solubility to part of polycyclic aromatic hydrocarbon at the same time, thereby effectively utilizing aromatic hydrocarbon potential and light aromatic hydrocarbon resources in the coal tar; (3) the methanol is convenient to transport and store, is used as a hydrogen source and a part of carbon source in the reaction, saves the cost, and has byproducts of hydrogen and olefin, thereby enriching the product types; (4) compared with the traditional high-pressure hydrogenation process, the methanol conversion reaction pressure is lower, hydrogen is generated, and the energy consumption is reduced; (5) the transalkylation reaction further converts the polymethylbenzenes, increasing the production of BTX, particularly xylene.

Drawings

FIG. 1 is a schematic diagram of a reaction flow and a device for producing BTX from coal tar provided by the invention;

FIG. 2 is a GC-MS spectrum of the extract in the example;

wherein, 1-coal tar; 2-methanol; 3-an extraction reactor; 4-extracting liquid; 5-raffinate; a 6-methanol conversion reactor; 7-a reaction product; 8-a gas-liquid separator; 9-gas production; 10-liquid product; 11-a gas separator; 12-alkane; 13-olefins; 14-hydrogen; 15-fractionating column I; 16-benzene; 17-toluene; 18-xylene; 19-bottoms stream; 20-a high pressure pump; 21-mixed aromatics feed; a 22-transalkylation reactor; 23-neo hydrogen; 24-a gas compressor; 25-high pressure hydrogen; 26-reaction effluent; 27-fractionation column ii; 28-recycle hydrogen; 29-polymethylbenzenes.

Detailed Description

The present invention will be further described with reference to specific examples, which are provided for the purpose of illustration and description only and are not intended to be limiting. The endpoints and ranges recited in this application are not limited to the range or the precise value, and each endpoint and endpoint, range and range, and precise value, are combined with each other to provide one or more new ranges and values, and such ranges of values should be considered as disclosed herein. Any modifications to the process of the present invention that would be obvious to a practitioner of the art in light of the background of the knowledge are intended to be included within the scope of the present invention.

As shown in fig. 1, the method for producing BTX from coal tar provided in this embodiment includes the following steps:

s1, mixing coal tar 1 of Alfa Aesar company with methanol 2 in a mass ratio of 1:10, placing the mixture in an ultrasonic reactor (extraction reactor 3) for treatment at 25 ℃ for 30min, and then filtering and separating to obtain extract liquid 4 and raffinate 5, wherein the extraction ratio of the coal tar is 69.1%. The GC-MS spectrum of extract 4 is shown in FIG. 2.

S2, preheating the extract 4 at 200 ℃, and feeding the preheated extract into a methanol conversion reactor 6, wherein the reaction pressure is normal pressure, the temperature is 400 ℃, and the liquid hourly space velocity is 1.2h^-1The catalyst is supported NiO and MoO₃HZSM-5(Si/Al 160) with a Ni and Mo content of 10 wt% in a 1:1 molar ratio. In the methanol conversion reactor 6, the extract 4 reacts under the action of a catalyst to obtain a reaction product 7, which comprises a gas product 9 and a liquid product 10, and the reaction product passes through a gas-liquid separator 8 and then enters a gas separation tower (a gas separator 11) and a fractionating tower I15 respectively.

S3, separating the gas product 9 in a gas separation tower (a gas separator 11) to obtain a gas product comprising hydrogen 14, olefin 13 and alkane 12, and fractionating the liquid product 10 in a liquid fractionating tower I15 to obtain BTX products (benzene 16, toluene 17 and xylene 18) and a bottom liquid 19 containing mixed aromatic hydrocarbons.

Wherein the distribution of gaseous products 9 and liquid products 10 after the reaction is shown in table 1.

TABLE 1 distribution of gaseous products 9 and liquid products 10 after methanol conversion

S4, feeding a mixed aromatic hydrocarbon feed 21 having a composition shown in table 2, into a transalkylation reactor 22 via a high pressure pump 20, while adding hydrogen: the reaction pressure is 3MPa, the temperature is 380 ℃, the hydrogen-oil ratio is 1500:1, and the liquid hourly space velocity is 1h^-1。

S5, in the transalkylation reactor 22, the mixed aromatic hydrocarbon feed 21 is subjected to transalkylation reaction in the presence of hydrogen, the reaction effluent 26 enters a fractionating tower II 27, and the reaction product is obtained by fractionation: the BTX products (benzene 16, toluene 17 and xylene 18), unconverted polymethylbenzenes 29, are recycled from the bottom of the column to the high pressure pump 20, and unreacted hydrogen (recycle hydrogen) 28 is separated from the top of the fractionation column II 27 and recycled to the gas compressor 24.

The composition of the reaction product under HZSM-5(Si/Al ═ 75) catalysis is shown in table 2. Wherein, the toluene in the mixed aromatic hydrocarbon feed is toluene 17; the hydrogen gas is hydrogen gas 14 and fresh hydrogen 23 is fed to the transalkylation reactor 22 after passing through a gas compressor 24 to form high pressure hydrogen 25.

TABLE 2 Mixed aromatics feed 21 and product distribution for transalkylation reactors

The content wt%

Toluene

Xylene

Propyl benzene

Trimethylbenzene

Tetramethylbenzene

Naphthalene

1-methylnaphthalene

Biphenyl

Mixed aromatics feed

30％

0

0

39.7％

14.9％

10.5％

5％

0

Reaction product

31％

24％

0.5％

18.7％

12.2％

7.8％

5.5％

0.2％