Method for preparing aromatic hydrocarbon by cracking and aromatizing coal liquefied oil

Abstract

The invention relates to a method for preparing aromatic hydrocarbon by cracking and aromatizing coal liquefaction oil, which comprises the following steps: carrying out hydrodesulfurization refining on a direct coal liquefaction oil raw material, rectifying the refined coal liquefaction oil to separate out fractions rich in monocyclic and bicyclic aromatic hydrocarbon, carrying out cracking and aromatization reaction on the fractions at 110-260 DEG C, loading a catalyst in a fluidized bed, and carrying out hydrogenation and aromatization on the fractions at 110-260 DEG C to obtain the aromatic hydrocarbon. The operation conditions are as follows: the reaction pressure is 0.1-1.0 MPa, the temperature is 300-450 DEG C, and the weight space velocity is 0.5-2.5 h <-1 >. Finally, a product containing monocyclic aromatic hydrocarbon BTX, bicyclic aromatic hydrocarbon and low-carbon olefin is obtained. According to the method, the aromatic hydrocarbon oil is prepared from the coal liquefaction oil, the BTX and naphthalene contents in the product are high, the low-carbon olefin is co-produced, the method is easy to operate and control, the reaction condition is mild, the process route is simple, the cost is low, and the added value of the aromatic hydrocarbon oil is high. The method for preparing aromatic hydrocarbon from coal liquefied oil can replace a new source for producing aromatic hydrocarbon in petrochemical industry, solves the urgent problem of large demand of aromatic hydrocarbon in China, and has better economic and social benefits.

Description

Technical Field

[0001] The present invention relates to a method for preparing aromatic hydrocarbons by cracking and aromatizing coal liquefaction oil, and in particular to a method for producing monocyclic aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene and trimethylbenzene and naphthalene by hydrogenating and refining coal liquefaction oil and cracking and aromatizing aromatic hydrocarbon side chains. Background Art

[0002] Coal liquefaction oil (CLE) is a complex mixture with a wide range of molecular weight fractions, from low to high boiling points. CLE is primarily composed of alkanes and cycloolefins, along with monocyclic and polycyclic aromatic hydrocarbons such as benzene, naphthalene, fluorene, anthracene, and pyrene. It also contains high levels of oxygen and nitrogen. CLE produced during the direct coal liquefaction process contains a high concentration of aromatic hydrocarbons. CLE can be used as a hydrogen-donating solvent oil or undergo self-cracking to produce light oil fractions. Furthermore, CLE can be used to produce valuable aromatic hydrocarbons.

[0003] Aromatic hydrocarbons, a common basic raw material in the petrochemical industry, play a vital role in the national economy. Monocyclic and dicyclic aromatics are widely used in polymer materials, dyes, pharmaceuticals, textiles, and other fields. Among monocyclic aromatics, triphenyl (BTX) and naphthalene are particularly important, comparable to ethylene and propylene in the national economy. Their production technology is a key indicator of a country's level of industrialization. Traditional aromatics production relies on petroleum-based routes, which are costly. Coal liquefied oil (CLE) boasts high aromatics potential and oxygen content. Producing aromatics from CLE is more economical than traditional petroleum-based routes. This not only effectively reduces the aromatics content of oil products and reduces pollutant emissions during use, but also addresses the significant domestic shortage of aromatics feedstock and enhances the market competitiveness of CTL companies. While traditional direct coal liquefaction (DCL) technologies for producing liquid fuels have been extensively researched both domestically and internationally, DCL technologies for producing aromatics are relatively limited. Research primarily focuses on the development of new, early-stage liquefaction technologies and the hydrogenation of liquefied crude oil to aromatics.

[0004] CN109926076A discloses a coal liquefaction oil hydrogenation catalyst and its preparation method. This patent uses a hydrogenation catalyst to hydrogenate coal liquefaction oil to produce a hydrogen-donating solvent oil. CN1224677C discloses a combined process method for producing high-quality diesel from coal liquefaction oil. This method uses coal liquefaction oil as a raw material and produces a diesel product through a hydrogenation refining and hydrogenation modification process. CN101085936 discloses a method for preparing aromatic-based heat transfer oil from coal liquefaction oil. CN101591564 discloses a method for hydrogenating and refining the diesel fraction of direct coal liquefaction oil. CN101085933 discloses a coal liquefaction oil ebullating bed hydrogenation process. It uses one or more hydrogenation catalysts to treat coal liquefaction oil. It can remove nitrogen, sulfur and other heteroatoms in the coal liquefaction oil to the maximum extent, reduce its olefin and aromatic content, improve the stability of the product, and provide high-performance coal liquefaction solvent oil to the upstream.

[0005] The aforementioned patents all primarily utilize processes such as hydrorefining, hydrocracking, and hydroupgrading of coal liquefied oil (CLE). The resulting products primarily include fuel oil (diesel, aviation fuel), solvent oil, and heat transfer oil. While CLE hydrogenation methods produce oil products with acceptable aromatic content, hydrogenation itself consumes hydrogen. When the aromatic content of CLE exceeds 30% by volume, a single hydrogenation step is difficult to reduce to the required level. Further hydrogenation, or even repeated hydrogenation steps, are required to reduce the aromatic content to the required level of no more than 5% by volume. This consumes significant amounts of hydrogen, and even if acceptable diesel is produced, it presents no economic advantage. Furthermore, the aromatics in CLE, a high-value-added product, are not fully utilized. In summary, the production of various oil products using CLE hydrogenation is associated with high equipment and investment costs.

[0006] Currently reported technologies for obtaining aromatics from coal liquefaction oil primarily rely on purification or extraction. CN100340641C discloses a method for purifying aromatics from coal liquefaction oil. This involves distilling coal liquefaction oil with an aromatic content of over 30% by volume to a fraction at 110-250°C. This fraction is then subjected to a complex process involving extraction, multiple adsorption separations, and other steps to obtain aromatic oil. However, this method still suffers from issues such as high investment, high energy consumption, and a complex process flow. Consequently, there are currently very few reports on technologies for producing aromatics from coal liquefaction oil through light cracking. Summary of the Invention

[0007] The present invention aims to provide a method for producing aromatic hydrocarbons by cracking and aromatizing coal liquefaction oil. The method can efficiently crack coal liquefaction oil into aromatic hydrocarbon oil. The method has the advantages of readily available raw materials, high added value, low cost, simple technical route and process, and the aromatic hydrocarbon oil produced has high contents of BTX (benzene, toluene, xylene) and naphthalene (naphthalene, methylnaphthalene, dimethylnaphthalene).

[0008] The present invention proposes a method for producing aromatic hydrocarbons by cracking and aromatizing coal liquefaction oil, which comprises the following specific steps: (1) Coal liquefaction oil raw material is hydrodesulfurized and refined in a fixed bed reactor; (2) separating the coal liquefaction oil refined in step (1) by distillation to obtain an intermediate fraction rich in monocyclic and bicyclic aromatic hydrocarbons as a raw material; (3) The fraction with a temperature of 110-260° C. obtained in step (2) is subjected to cracking and aromatization reaction in a fluidized bed to obtain a final product containing monocyclic aromatic hydrocarbons BTX (benzene, toluene, xylene), bicyclic aromatic hydrocarbons (naphthalene, methylnaphthalene, dimethylnaphthalene) and light olefins (ethylene, propylene). The fluidized bed operation conditions are reaction pressure 0.1-1.0 MPa, temperature 300-450° C., reaction weight space velocity 0.5-2.5 h -1 .

[0009] In the present invention, the operating conditions for the hydrodesulfurization of the coal liquefaction oil raw material in step (1) are a reaction pressure of 2-5.0 MPa, a reaction space velocity of 0.5-2.0 h -1 , temperature 280-360°C, hydrogen to hydrocarbon ratio 2-10.0 mol / mol.

[0010] In the present invention, the coal liquefaction oil hydrodesulfurization refining in step (1) can also be placed after the cracking and aromatization reactions.

[0011] In the present invention, the fixed bed reactor in step (1) adopts a two-layer fixed bed reactor, and catalysts are used in both the upper layer and the lower layer, wherein the upper layer catalyst adopts any one of Co, W, Ni, Cu or Mn metal oxides, and the lower layer catalyst adopts any one of Mo, Fe, Ni, Ti or Bi metal oxides.

[0012] In the present invention, a metal oxide is used to modify a solid acid in the cracking catalytic reaction in step (3), wherein the metal oxide is any one of La, Ce, Mo, W, Zn or Fe; and the solid acid is any one of silica-alumina molecular sieve, phosphoric acid / silicon oxide, heteropoly acid or silica-alumina composite oxide relative to the content of the solid acid of 0.5-10.0 wt%.

[0013] In the present invention, the coal liquefaction oil raw material in step (1) is any one of coal direct liquefaction oil, coal-oil co-refining liquefaction oil, coal indirect liquefaction oil or coal coking oil.

[0014] In the present invention, in step (3), aromatic oil products are produced by cracking coal liquefaction oil, and monocyclic aromatic hydrocarbons and dicyclic aromatic hydrocarbons are obtained by distillation separation, and light olefins are produced in parallel.

[0015] This invention proposes a method for producing aromatics through cracking and aromatization of coal liquefied oil. This method efficiently cracks coal liquefied oil into aromatic side chains and then aromatizes them with saturated side rings, opening up a new route for producing aromatics from coal. Compared with existing technologies, this method can produce aromatics at low cost and high efficiency, with a simple technical process. The resulting aromatic oil has high added value and high BTX and naphthalene content.

[0016] Compared with the prior art, the present invention has the following beneficial effects: (1) Coal liquefaction oil is cracked and aromatized to produce aromatic oil. The product has high content of BTX and naphthalene, and produces low-carbon olefins as by-products. It is easy to operate and control, and the reaction conditions are mild.

[0017] (2) The method of the present invention is different from the traditional technical route of producing aromatics from coal liquefaction. It eliminates the catalytic reforming process of naphtha and uses the coal liquefaction oil to separate the intermediate fraction rich in monocyclic and dicyclic aromatics as raw materials, and directly catalytically cracks them to produce aromatics. The process route is simple, the cost is low, and the added value of aromatic oil is high.

[0018] (3) The use of coal liquefaction oil to produce aromatics can replace the new source of aromatics produced by petrochemicals, break the limitation of relying on imported oil to produce aromatics, solve the urgent problem of my country's large demand for aromatics, and have good economic and social benefits. DETAILED DESCRIPTION

[0019] The present invention is further described below by way of examples. Example 1:

[0020] (1) The coal direct liquefaction oil raw material is subjected to hydrodesulfurization refining in a two-layer fixed bed reactor. The specifications of the two-layer fixed bed reactor are: inner diameter 20mm×length 1500mm, the catalyst is loaded in two layers, and the upper layer is filled with 10g of WO x -NiO x Catalyst, the lower layer is loaded with 10g of Mo x -NiO x The catalyst was prepared by filling the bottom of the two-layer fixed bed reactor, the middle of the upper and lower catalyst layers, and the top layer of the catalyst with glass beads of about 2 mm in diameter. The operating conditions for the hydrodesulfurization of coal liquefaction oil feedstock were a reaction pressure of 5.0 MPa and a reaction space velocity of 1.0 h -1 , temperature 360°C, hydrogen to hydrocarbon ratio 8.0 mol / mol; (2) The refined coal liquefaction oil is distilled to separate the middle fraction rich in monocyclic and bicyclic aromatic hydrocarbons as the raw material, and the fraction with a temperature of 110-260°C is selected as the raw material for step (3); (3) The fraction raw materials were cracked and aromatized in a fluidized bed. 20 g of Zn2.5% / ZSM molecular sieve catalyst was loaded in the fluidized bed. The operating conditions were reaction pressure 0.2 MPa, temperature 350 °C, and weight space velocity 0.5 h -1 The aromatic oil finally obtained was analyzed by gas chromatography using a polysiloxane non-polar column. The appearance properties of the aromatic oil, the content of monocyclic aromatic hydrocarbons BTX (benzene, toluene, xylene), the content of bicyclic aromatic hydrocarbons (naphthalene, methylnaphthalene, dimethylnaphthalene), and the content of light olefins (ethylene, propylene) are shown in Table 1.

[0021] Example 2 (Comparative Example): The coal direct liquefaction oil raw material was hydrodesulfurized and refined in a single-layer fixed bed reactor, and 10g of WO x -NiO x The catalyst and the remaining steps were the same as those in Example 1. The appearance properties, content of monocyclic aromatic hydrocarbons BTX, content of bicyclic aromatic hydrocarbons and content of light olefins of the obtained aromatic hydrocarbon product are shown in Table 1. Example 3:

[0022] Coal direct liquefaction oil feedstock was hydrodesulfurized and purified in a two-layer fixed-bed reactor. The upper layer was loaded with 10g of CuOx-MnOx catalyst, and the lower layer was loaded with 10g of Mox-NiOx catalyst. The remaining steps were the same as in Example 1. The appearance properties of the resulting aromatics product, as well as the content of monocyclic aromatic hydrocarbons (BTX) (benzene, toluene, and xylene), bicyclic aromatic hydrocarbons (naphthalene, methylnaphthalene, and dimethylnaphthalene), and light olefins (ethylene and propylene) are shown in Table 1. Example 4:

[0023] Coal direct liquefaction oil feedstock was hydrodesulfurized and refined in a two-layer fixed-bed reactor. The upper layer was loaded with 10g of CoOx-NiOx catalyst, and the lower layer was loaded with 10g of Mox-TiOx catalyst. The remaining steps were the same as in Example 1. The appearance properties, monocyclic aromatic hydrocarbon (BTX) content, bicyclic aromatic hydrocarbon content, and light olefin content of the resulting aromatic product are shown in Table 1. Example 5:

[0024] The operating conditions for the hydrodesulfurization of coal liquefaction oil raw materials are reaction pressure 6.0 MPa, reaction space velocity 2.0 h -1 The reaction mixture was stirred at 340°C and a hydrogen-to-hydrocarbon ratio of 6.0 mol / mol. The remaining steps were the same as in Example 1. The appearance and properties of the resulting aromatic product, as well as the content of monocyclic aromatic hydrocarbons (BTX) (benzene, toluene, and xylene), bicyclic aromatic hydrocarbons (naphthalene, methylnaphthalene, and dimethylnaphthalene), and light olefins (ethylene and propylene) are shown in Table 1. Example 6:

[0025] The operating conditions for the hydrodesulfurization of coal liquefaction oil raw materials are reaction pressure 2.0 MPa, reaction space velocity 2.0 h -1 , temperature 360 ​​° C, hydrogen to hydrocarbon ratio 6.0 mol / mol. The remaining steps are the same as in Example 1. The appearance properties, monocyclic aromatic hydrocarbon BTX content, bicyclic aromatic hydrocarbon content, and light olefin content of the obtained aromatic product are shown in Table 1. Example 7:

[0026] The operating conditions for the hydrodesulfurization of coal liquefaction oil raw materials are reaction pressure 6.0 MPa, reaction space velocity 2.0 h -1 , temperature 340°C, hydrogen-to-hydrocarbon ratio 6.0 mol / mol. The remaining steps were the same as in Example 1. The appearance properties, monocyclic aromatic hydrocarbon BTX content, bicyclic aromatic hydrocarbon content, and light olefin content of the obtained aromatic product are shown in Table 1. Example 8:

[0027] The operating conditions for the hydrodesulfurization of the coal liquefaction oil feedstock were a reaction pressure of 6.0 MPa, a reaction space velocity of 1.0 h⁻¹, a temperature of 340°C, and a hydrogen-to-hydrocarbon ratio of 6.0 mol / mol. The remaining steps were the same as in Example 1. The appearance properties, monocyclic aromatic hydrocarbon (BTX) content, bicyclic aromatic hydrocarbon content, and light olefin content of the resulting aromatic product are shown in Table 1. Example 9:

[0028] The operating conditions for the hydrodesulfurization of the coal liquefaction oil feedstock were a reaction pressure of 6.0 MPa, a reaction space velocity of 2.0 h⁻¹, a temperature of 340°C, and a hydrogen-to-hydrocarbon ratio of 8.0 mol / mol. The remaining steps were the same as in Example 1. The appearance properties, monocyclic aromatic hydrocarbon (BTX) content, bicyclic aromatic hydrocarbon content, and light olefin content of the resulting aromatic product are shown in Table 1.

[0029] Example 10: The hydrodesulfurization, refining, and fractionation processes for coal liquefaction oil were the same as in Example 1. Cracking and aromatization reactions were carried out in a fluidized bed using 20 g of a 0.5% Mo / ZSM molecular sieve catalyst. The operating conditions were a reaction pressure of 1.0 MPa, a temperature of 380°C, and a weight space velocity of 0.5 h⁻¹. The appearance properties of the resulting aromatics product, as well as the content of monocyclic aromatic hydrocarbons (BTX), bicyclic aromatic hydrocarbons, and light olefins, are shown in Table 1.

[0030] Example 11: The hydrodesulfurization, refining and fractionation process of coal liquefaction oil was the same as in Example 1. The cracking and aromatization reactions were carried out in a fluidized bed. 20 g of Zn1.5% / ZSM molecular sieve catalyst was loaded in the fluidized bed. The operating conditions were reaction pressure 1.5 MPa, temperature 400 ° C, weight space velocity 0.5 h -1The appearance properties, the content of monocyclic aromatic hydrocarbons BTX, the content of bicyclic aromatic hydrocarbons and the content of light olefins of the obtained aromatic hydrocarbon products are shown in Table 1.

[0031] Example 12: The hydrodesulfurization, refining, and fractionation processes for coal liquefaction oil were the same as in Example 1. Cracking and aromatization reactions were carried out in a fluidized bed using 20 g of a 0.5% Mo / ZSM molecular sieve catalyst. The operating conditions were a reaction pressure of 1.5 MPa, a temperature of 400°C, and a weight space velocity of 2.0 h⁻¹. The appearance properties of the resulting aromatics product, as well as the content of monocyclic aromatic hydrocarbons (BTX), bicyclic aromatic hydrocarbons, and light olefins, are shown in Table 1.

[0032] Example 13: The hydrodesulfurization, refining and fractionation process of coal liquefaction oil was the same as in Example 1. The cracking and aromatization reactions were carried out in a fluidized bed. 20 g of La0.5% / ZSM molecular sieve catalyst was loaded in the fluidized bed. The operating conditions were reaction pressure 0.2 MPa, temperature 350 ° C, weight space velocity 1.0 h -1 The appearance properties, the content of monocyclic aromatic hydrocarbons BTX, the content of bicyclic aromatic hydrocarbons and the content of light olefins of the obtained aromatic hydrocarbon products are shown in Table 1.

[0033] Example 14: The hydrodesulfurization, refining and fractionation process of coal liquefaction oil was the same as that in Example 1. The cracking and aromatization reactions were carried out in a fluidized bed. 20 g of W0.5% / ZSM molecular sieve catalyst was loaded in the fluidized bed. The operating conditions were reaction pressure 0.2 MPa, temperature 350°C, weight space velocity 1.0 h -1 The appearance properties, the content of monocyclic aromatic hydrocarbons BTX, the content of bicyclic aromatic hydrocarbons and the content of light olefins of the obtained aromatic hydrocarbon products are shown in Table 1.

[0034] Example 15: The hydrodesulfurization, refining and fractionation process of coal liquefaction oil was the same as in Example 1. The cracking and aromatization reactions were carried out in a fluidized bed. 20 g of Zn0.5% / heteropolyacid catalyst was loaded in the fluidized bed. The operating conditions were reaction pressure 1.0 MPa, temperature 350°C, weight space velocity 1.0 h -1 The appearance properties, the content of monocyclic aromatic hydrocarbons BTX, the content of bicyclic aromatic hydrocarbons and the content of light olefins of the obtained aromatic hydrocarbon products are shown in Table 1.

[0035] Example 16: The liquefied oil raw material was kerosene co-refined liquefied oil, and the other conditions were the same as in Example 1. The appearance properties, content of monocyclic aromatic hydrocarbons BTX, content of bicyclic aromatic hydrocarbons and content of light olefins of the obtained aromatic product are shown in Table 1.

[0036] Example 17: The liquefied oil raw material was coal indirect liquefied oil, and the other conditions were the same as in Example 1. The appearance properties, content of monocyclic aromatic hydrocarbons BTX, content of bicyclic aromatic hydrocarbons and content of light olefins of the obtained aromatic product are shown in Table 1.

[0037] Table 1 Appearance, shape, content of monocyclic aromatic hydrocarbons, bicyclic aromatic hydrocarbons and light olefins of aromatic products of each embodiment.

Claims

1. A method for producing aromatic hydrocarbons by cracking and aromatizing coal liquefaction oil, characterized in that The specific steps are as follows: (1) Coal liquefaction oil raw material is hydrodesulfurized and refined in a fixed bed reactor; (2) separating the coal liquefaction oil refined in step (1) by distillation to obtain an intermediate fraction rich in monocyclic and bicyclic aromatic hydrocarbons as a raw material; (3) The fraction with a temperature of 110-260° C. obtained in step (2) is subjected to cracking and aromatization reaction in a fluidized bed to obtain a final product containing monocyclic aromatic hydrocarbons BTX, bicyclic aromatic hydrocarbons and light olefins. The fluidized bed operation conditions are reaction pressure of 0.1-1.0 MPa, temperature of 300-450° C., reaction weight space velocity of 0.5-2.5 h -1 .

2. The method for preparing aromatic hydrocarbons by cracking and aromatizing coal liquefaction oil according to claim 1, characterized in that The operating conditions for the hydrodesulfurization of the coal liquefaction oil raw material in step (1) are a reaction pressure of 2-5.0 MPa, a reaction space velocity of 0.5-2.0 h -1 , temperature 280-360°C, hydrogen to hydrocarbon ratio 2-10.0 mol / mol.

3. The method for preparing aromatic hydrocarbons by cracking and aromatizing coal liquefaction oil according to claim 1, characterized in that The coal liquefaction oil hydrodesulfurization refining in step (1) can also be placed after the cracking and aromatization reactions.

4. The method for preparing aromatic hydrocarbons by cracking and aromatizing coal liquefaction oil according to claim 1, characterized in that The fixed bed reactor in step (1) adopts a two-layer fixed bed reactor, and catalysts are used in both the upper and lower layers, wherein the upper layer catalyst adopts any one of Co, W, Ni, Cu or Mn metal oxides, and the lower layer catalyst adopts any one of Mo, Fe, Ni, Ti or Bi metal oxides.

5. The method for preparing aromatic hydrocarbons by cracking and aromatizing coal liquefaction oil according to claim 1, characterized in that In the cracking catalytic reaction in step (3), a metal oxide is used to modify the solid acid, wherein the metal oxide is any one of La, Ce, Mo, W, Zn or Fe, with a content of 0.5-10.0 wt% relative to the solid acid content, and the solid acid is any one of silica-alumina molecular sieve, phosphoric acid / silicon oxide, heteropoly acid or silica-alumina composite oxide.

6. The method for preparing aromatic hydrocarbons by cracking and aromatizing coal liquefaction oil according to claim 1, characterized in that The coal liquefaction oil raw material in step (1) is any one of coal direct liquefaction oil, coal-oil co-refining liquefaction oil, coal indirect liquefaction oil or coal coking oil.

7. The method for preparing aromatic hydrocarbons by cracking and aromatizing coal liquefaction oil according to claim 4, characterized in that The upper catalyst layer of the two-layer fixed bed reactor, the middle of the lower catalyst layer, the top layer of the upper catalyst layer and the bottom layer of the lower catalyst layer are all filled with glass beads.

Images