CN107987882B

CN107987882B - Hydrocracking method for blended coal tar

Info

Publication number: CN107987882B
Application number: CN201610955217.7A
Authority: CN
Inventors: 赵广乐; 孟勇新; 胡志海; 赵阳; 毛以朝
Original assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Current assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Priority date: 2016-10-27
Filing date: 2016-10-27
Publication date: 2021-01-08
Anticipated expiration: 2036-10-27
Also published as: CN107987882A

Abstract

The invention relates to the field of coal tar processing, and discloses a hydrocracking method for blended coal tar, which comprises the following steps: carrying out hydrogenation protection treatment and hydrogenation pretreatment on the heavy raw material, and carrying out temperature and pressure separation on the product; then separating the warm high-temperature oil and the low-temperature oil; carrying out gas-liquid separation on the low temperature separated oil, introducing at least part of debutanizer bottom oil into a hydrofining area, and carrying out thermal high-pressure separation on the obtained refined product, wherein the heavy raw material contains coal tar distillate; then mixing hot high-temperature-content gas, warm high-temperature-content gas and water, performing cold high-pressure separation, and performing hot low-pressure separation on the hot high-temperature-content liquid; and carrying out cold low-pressure separation on the cold high-separated liquid; then the cold low-fraction liquid and the hot low-fraction liquid are fractionated, and the heavy fraction is subjected to hydrocracking, and the obtained cracked product and the refined product are subjected to hot high-pressure separation together. The method can improve the naphtha yield to the maximum extent on the premise of ensuring low sulfur content in naphtha and high potential content of aromatic hydrocarbon.

Description

Hydrocracking method for blended coal tar

Technical Field

The invention relates to the field of coal tar processing, in particular to a hydrocracking method for blending coal tar.

Background

With the continuous development of social economy, the demand of people on petroleum products is increasing day by day, and the requirements on the quality of oil are stricter and stricter. However, under the background that crude oil resources are heavy and have serious deterioration tendency, and our country has greater and greater dependence on foreign crude oil, a new process technology is developed to effectively utilize inferior raw materials, and broaden the raw material range of refineries, so that the method is one of effective ways for solving the shortage of petroleum resources.

At present, coal resources in China are rich, coal-based industrial byproduct coal tar is a large amount, but the processing method of the coal tar is single, the processing cost is high, and a large amount of pollution is accompanied. Therefore, the coal tar is fully utilized, and the coal tar partially replaces petroleum resources to produce chemical products and motor fuels through a reasonable and environment-friendly way, so that the method has important economic value and social significance.

CN1952071A discloses a combined method for producing clean oil from coal tar, which is to mix the coal tar after removing mechanical impurities and water with hydrogen and then to enter a hydrofining reactor to remove metals, sulfur, nitrogen and the like, the obtained liquid is separated into gas, gasoline, diesel oil, tail oil and the like through a fractionating tower, the diesel oil enters a hydro-upgrading reactor, the tail oil enters a hydrocracking reactor and can be thrown outwards, and the oil generated by hydrocracking returns to the fractionating tower to obtain gasoline, aviation kerosene, diesel oil, tail oil and the like. However, the quality of the hydrofined oil diesel oil obtained by the method in the prior art is poor, the quality of the diesel oil product needs to be improved by hydro-upgrading, the nitrogen content of the tail oil of the hydrofined oil is high, the catalyst used in the hydrocracking reactor needs to be mainly an amorphous catalyst, and the flexibility of the product is limited due to the poor activity of the amorphous catalyst.

CN101307257A discloses a coal tar hydro-upgrading method by a two-stage method, wherein coal tar is cut into coal tar light fraction and coal tar heavy fraction by atmospheric distillation and/or vacuum distillation, the coal tar light fraction and optional distillate oil are mixed with hydrogen and then enter a first hydrogenation reaction zone to contact with a hydrofining catalyst, the effluent is subjected to gas phase impurity removal by an intermediate flash tower or a high-pressure stripper, then enters a second hydrogenation reaction zone to contact with a hydro-upgrading catalyst or a hydro-cracking catalyst, and the obtained effluent is cooled, separated and fractionated to obtain diesel fraction and naphtha fraction. The cutting point of the coal tar light fraction used in the method is 300-380 ℃, the boiling point range of the distillate oil is 180-400 ℃, and a diesel oil product is mainly obtained by a hydrofining-hydrogenation modification method.

CN101781577A discloses a method for producing light fuel oil by using mixed coal tar. The method utilizes high, medium and low temperature coal tar and mixed coal tar thereof to remove sulfur and nitrogen in raw materials through hydrofining reaction, and modifies oil products into clean light fuel through hydrocracking reaction. The reaction pressure required by the method disclosed by the prior art is 150-200MPa, and the requirement on equipment is high.

CN105586087A discloses a hydrocracking method. The method utilizes two stages of process flows, wherein the first stage carries out hydrogenation pretreatment on the raw material doped with the coal tar distillate to remove mechanical impurities, metals, partial heteroatoms and aromatic hydrocarbon saturation, and the second stage carries out hydrocracking to generate naphtha, diesel oil, tail oil and the like. The method has limited naphtha yield, and the quality of diesel oil and tail oil is not high when a large proportion of coal tar distillate is blended.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a hydrocracking method for blended coal tar, which has mild reaction conditions and can flexibly and simultaneously produce a plurality of high-quality light product oils at low cost.

The second purpose of the invention is to provide a hydrocracking method for blended coal tar, which can improve the naphtha yield to the maximum extent on the premise of ensuring low sulfur content in naphtha and high potential content of aromatic hydrocarbon.

In order to achieve the above object, the present invention provides a hydrocracking process for blending coal tar, which is implemented in a system including a hydrotreating pretreatment unit and a hydrocracking unit, comprising:

(1) introducing a heavy raw material into the hydrogenation pretreatment unit to sequentially carry out hydrogenation protection treatment and hydrogenation pretreatment, and carrying out temperature and high pressure separation on the obtained product to obtain temperature and high-pressure gas and temperature and high-pressure oil; then, separating the temperature and high-temperature oil at low pressure to obtain temperature and low-temperature gas and temperature and low-temperature oil; carrying out gas-liquid separation on the low temperature separated oil to obtain debutanizer bottom oil, wherein the heavy raw material contains coal tar distillate;

(2) introducing at least part of the debutanizer bottom oil into a hydrofining area of the hydrocracking unit for hydrofining, and carrying out thermal high-pressure separation on the obtained refined product to obtain thermal high-pressure separation gas and thermal high-pressure separation liquid; then mixing the hot high-temperature gas, the warm high-temperature gas and the water, and then carrying out cold high-pressure separation to obtain cold high-temperature gas and cold high-temperature liquid;

(3) carrying out thermal low-pressure separation on the thermal high-pressure separation liquid to obtain thermal low-pressure separation gas and thermal low-pressure separation liquid; performing cold low-pressure separation on the cold high-liquid to obtain cold low-liquid; then fractionating the cold low-fraction liquid and the hot low-fraction liquid to obtain naphtha fraction and heavy fraction with the initial boiling point of more than 145 ℃; and

(4) introducing the heavy fraction into a hydrocracking zone of the hydrocracking unit for hydrocracking, and carrying out thermal high-pressure separation on the obtained cracked product and the refined product.

By adopting the method, the cheap coal tar distillate which is difficult to process can be mixed into the conventional hydrocracking raw material, and the light oil product with high added value can be obtained under the mild reaction condition. Wherein, the obtained light oil comprises light naphtha fraction and heavy naphtha fraction, the light naphtha fraction can be used as gasoline blending component and can also be used as raw material for preparing ethylene by steam cracking; the heavy naphtha fraction has a high potential content of aromatics and can be used directly as a feedstock for a catalytic reformer.

Additional features and advantages of the invention will be set forth in the detailed description which follows.

Drawings

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

FIG. 1 is a schematic flow diagram of a hydrocracking process for blending coal tar according to a preferred embodiment of the present invention.

Description of the reference numerals

1. Heavy raw material 2, heating furnace 3, low temperature and low temperature gas

4. Hydrogenation protection reactor 5, protection treatment material flow 6 and hydrogenation pretreatment reactor

7. Hydrogenation pretreatment mixture 8, warm high pressure separator 9, warm low pressure separator

10. A debutanizer 11, residual debutanizer bottom oil 12 and high temperature and high pressure gas

13. A part of debutanizer bottom oil 14, a hydrofining reactor 15 and a refined product

16. Hot high pressure separator 17, hot low pressure separator 18, cold low pressure separator

19. Cold high-pressure gas 20, cold high-pressure separator 21 and fractionating tower

22. Light hydrocarbon 23 at the top of the column, light naphtha fraction 24, heavy naphtha fraction

25. Heavy fraction 26, hydrocracking reactor 27, cracked products

28. Recycle hydrogen compressor 29, fresh hydrogen 30, recycle hydrogen

Detailed Description

The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

The invention provides a hydrocracking method for blending coal tar, which is implemented in a system comprising a hydrogenation pretreatment unit and a hydrocracking unit and comprises the following steps:

Preferably, the method further comprises: in step (2), a portion of the debutanizer bottoms is introduced into a hydrofinishing zone of the hydrocracking unit for hydrofinishing, and the remaining debutanizer bottoms are recycled to the hydrotreating pretreatment unit. More preferably, in step (2), a portion of the debutanizer bottoms is introduced into a hydrofinishing zone of the hydrocracking unit for hydrofinishing, and the remaining debutanizer bottoms are recycled to the inlet of the hydrotreating unit.

Preferably, the hydrocracking zone contains a hydrocracking catalyst. In the method of the present invention, the kind of the hydrocracking catalyst is not particularly limited, and those skilled in the art can select various hydrocracking catalysts conventionally used in the art. RHC-5 may be used, for example, as a hydrocracking catalyst in the process of the present invention. In particular, the inventors of the present invention have found in their studies that when a catalyst of the following silica-alumina-containing hierarchical pore hydrocracking catalyst provided by the present invention is used as a hydrocracking catalyst in a hydrocracking zone, the naphtha yield obtained by the method of the present invention can be significantly increased, and in particular, the potential content of aromatic hydrocarbons in heavy naphtha can be increased.

The silicon-aluminum-containing hierarchical pore hydrocracking catalyst contains a carrier and a hydrogenation active metal component loaded on the carrier, wherein the carrier contains a Beta-type molecular sieve, weakly acidic silicon aluminum and aluminum oxide, the hydrogenation active metal component is selected from molybdenum and/or tungsten and nickel and/or cobalt, and the pore distribution of the hydrocracking catalyst meets the following requirements: the pore volume of pores with the pore diameter of less than 2nm accounts for 2-50% of the total pore volume of the hydrocracking catalyst, the pore volume of pores with the pore diameter of 2-100 nm accounts for 20-85% of the total pore volume of the hydrocracking catalyst, and the pore volume of pores with the pore diameter of more than 100nm accounts for 3-70% of the total pore volume of the hydrocracking catalyst; more preferably, the pore distribution of the hydrocracking catalyst is such that: the pore volume of pores with the pore diameter of less than 2nm accounts for 4-21% of the total pore volume of the hydrocracking catalyst, the pore volume of pores with the pore diameter of 2-100 nm accounts for 20-85% of the total pore volume of the hydrocracking catalyst, and the pore volume of pores with the pore diameter of more than 100nm accounts for 4-60% of the total pore volume of the hydrocracking catalyst. "the hydrogenation-active metal component is selected from molybdenum and/or tungsten and nickel and/or cobalt" means that there are at least two metal elements in the hydrogenation-active metal component, and at least one of them is molybdenum or tungsten and at least another one is nickel or cobalt.

Preferably, the silicon-aluminum ratio of the Beta type molecular sieve is (15-300): 1, the specific surface area is 150-750 m²Per gram, the pore volume is 0.20-1.05 ml/g; more preferably, the silicon-aluminum ratio of the Beta type molecular sieve is (20-120): 1, the specific surface area is 200-650 m²The pore volume is 0.20-0.75 ml/g.

Preferably, in the hydrocracking catalyst, based on the carrier, the content of the Beta-type molecular sieve is 3-70 wt%, the content of alumina is 10-85 wt%, and the content of weakly acidic silicon-aluminum is 5-60 wt%; more preferably, based on the carrier, the Beta-type molecular sieve has a content of 5-60 wt%, the alumina has a content of 15-60 wt%, and the weakly acidic silicon-aluminum has a content of 5-60 wt%.

Preferably, based on the hydrocracking catalyst, the hydrocracking catalyst contains 45-85 wt% of a carrier, 1-15 wt% of nickel and/or cobalt calculated by oxide and 5-40 wt% of molybdenum and/or tungsten calculated by oxide; more preferably, the hydrocracking catalyst contains 60 to 80 wt% of a carrier, 2 to 10 wt% of nickel and/or cobalt in terms of an oxide, and 10 to 35 wt% of molybdenum and/or tungsten in terms of an oxide, based on the hydrocracking catalyst. "the content of nickel and/or cobalt is 1 to 15% by weight" means that when only nickel or cobalt is contained, the content of nickel or cobalt is 1 to 15% by weight; when nickel and cobalt are contained, the content of nickel and cobalt is 1 to 15 wt%, and the similar explanation is also made for "the content of molybdenum and/or tungsten is 5 to 40 wt%".

Preferably, in the hydrocracking catalyst, the Beta-type molecular sieve is a hydrogen-type Beta-type molecular sieve.

Preferably, in the hydrocracking catalyst, the alumina is γ -alumina.

Preferably, the hydrocracking catalyst further contains an organic additive, the organic additive is at least one selected from oxygen-containing and/or nitrogen-containing organic matters, and the content of the organic additive in the hydrocracking catalyst is 2-20 wt% based on the hydrocracking catalyst.

Preferably, in the hydrocracking catalyst, the oxygen-containing organic matter is selected from at least one of organic alcohol and organic acid, and the nitrogen-containing organic matter is selected from one or more of organic amine and organic ammonium salt. Preferably, the oxygen-containing organic substance is at least one selected from the group consisting of ethylene glycol, glycerol, polyethylene glycol having a relative molecular mass of 200 to 1500, diethylene glycol, butanediol, acetic acid, maleic acid, oxalic acid, citric acid, tartaric acid, and malic acid, and more preferably, the oxygen-containing organic substance is selected from the group consisting of ethylene glycol, glycerol, polyethylene glycol having a relative molecular mass of 200 to 1500, and citric acid. Preferably, the nitrogen-containing organic substance is selected from at least one of ethylenediamine, diethylenetriamine, cyclohexanediaminetetraacetic acid, glycine, nitrilotriacetic acid, EDTA and ammonium salts thereof.

According to a preferred embodiment, in the hydrocracking catalyst, the preparation method of the support comprises the steps of:

(1) mixing Beta type molecular sieve with weakly acidic silicon-aluminum, pseudo-boehmite, peptizing agent, lubricant and water to obtain a mixture, wherein the dosage of each component is such that the ratio of the mass of the peptizing agent in the mixture to the total weight of the powder is 0.28 multiplied by 10^-4～4.8×10^-4mol/g, the ratio of the weight of water to the amount of mass of peptizing agent is 2.0X 10³～30×10³g/mol, wherein the total weight of the powder is the sum of the weights of the Beta type molecular sieve, the pseudo-boehmite and the weakly acidic silicon-aluminum, and the mass of the peptizing agent refers to the molar number of H protons metered in the peptizing agent; the lubricant is sesbania powder and/or graphite, and the ratio of the lubricant to the total weight of the powder is as follows by taking the total weight of the powder as a reference: (1-9): 100, respectively;

(2) and (2) kneading, molding, drying and roasting the mixture obtained in the step (1) to obtain the carrier.

The peptizing agent includes components capable of providing H protons and capable of reacting during the preparation of the carrier to help generate a substance with a binding effect.

Preferably, in the carrier for preparing the hydrocracking catalyst, the pseudoboehmite comprises PB1 and is characterized by X-ray diffraction, kappa 1 and kappa 2 of PB1 satisfy 1 & lt kappa 1 & ltoreq 3 and 1 & lt kappa 2 & ltoreq 3, wherein kappa 1 & lth 2/h1, kappa 2 & lth 3/h2, and h1, h2 and h3 are peak heights of three diffraction peaks at an angle of 24-30 degrees, 35-41 degrees and 46-52 degrees of PB1 in the X-ray diffraction spectrum. More preferably, the PB1 has a kappa 1 of 1.2-2.3 and a kappa 2 of 1.02-1.4 as characterized by X-ray diffraction. Preferably, the specific surface area of the PB1 is 100-350 m²Per gram, the pore volume is 0.7-1.2 ml/g; more preferably, the specific surface area of the PB1 is 150-280 m²The pore volume is 0.85-1.12 ml/g.

Preferably, in the preparation of the carrier of the hydrocracking catalyst, the components in the step (1) are used in such an amount that the hydrocracking catalyst is supported on the carrierThe ratio of the mass of peptizing agent in the mixture to the total weight of the powder is 0.7 x 10^-4～4.0×10^-4mol/g, the ratio of the weight of water to the amount of mass of peptizing agent is 2.0X 10³～15×10³g/mol。

Preferably, the coal tar distillate is contained in an amount of 10 to 95 parts by weight, preferably 20 to 90 parts by weight, relative to 100 parts by weight of the heavy feedstock.

Preferably, the reaction conditions of the hydro-protective treatment and the hydro-pretreatment each independently comprise: the hydrogen partial pressure is 10.0-20.0 MPa, the reaction temperature is 300-430 ℃, and the volume ratio of hydrogen to oil is 300-3000 Nm³/m³。

Preferably, in the hydrogenation protection treatment, the total volume space velocity of the hydrogenation protection reactor is 0.5-8.0 h^-1。

Preferably, in the hydrogenation pretreatment, the total volume space velocity of the hydrogenation pretreatment reactor is 0.1-5.0 h^-1。

Preferably, according to the flow direction of the reactants, the hydrogenation protection reactor is sequentially filled with a protection catalyst and a demetallization catalyst, and the filling volume ratio of the protection catalyst to the demetallization catalyst is 1: (0.1 to 9).

According to a preferred embodiment, the present invention employs a two-stage process, wherein the first stage is a hydroprocessing pretreatment unit comprising a hydroprocessing guard reactor and a hydroprocessing pretreatment reactor, the hydroprocessing guard reactor being filled with a guard catalyst and a demetallization catalyst, and the hydroprocessing pretreatment reactor being filled with a hydroprocessing pretreatment catalyst, optionally together with a guard catalyst. The hydroprocessing protection reactor and the hydroprocessing pretreatment reactor may also be combined into one reactor. The second section is a hydrocracking unit which processes the debutanizer bottoms of the first section. The hydrocracking unit comprises a hydrofining reactor and a hydrocracking reactor. The two sections share a cold high pressure separator and a fresh hydrogen compressor and a recycle hydrogen compressor.

Preferably, the filling volume of the hydrogenation pretreatment catalyst accounts for 70-100% of the total filling volume of the catalyst in the hydrogenation pretreatment reactor. Preferably, the hydrogenation pretreatment reactor is sequentially filled with a guard catalyst and a hydrogenation pretreatment catalyst in terms of the direction of flow. Preferably, the filling volume of the protective catalyst accounts for 1-30%, preferably 1-20% of the total filling volume of the catalyst in the hydrogenation pretreatment reactor.

Preferably, the reaction conditions of the hydrocracking unit include: the hydrogen partial pressure is 10.0-20.0 MPa, the reaction temperature is 300-430 ℃, and the volume ratio of hydrogen to oil is 300-3000 Nm³/m³The total volume airspeed is 0.1-8.0 h^-1。

Preferably, a hydrofining catalyst is filled in a hydrofining area of the hydrocracking unit, and the filling volume of the hydrofining catalyst accounts for 70-100% of the total volume of the catalyst in the hydrofining area. More preferably, the hydrofinishing zone of the hydrocracking unit is sequentially loaded with a protective catalyst and a hydrofinishing catalyst in terms of the direction of reactant flow. Preferably, in the hydrofining zone, the loading volume of the protective catalyst accounts for 1-30% of the total volume of the catalyst in the hydrofining zone, and more preferably 1-15%.

To prevent H₂S and olefins possibly generated in the cracking process further react to generate mercaptan sulfur, and a certain amount of post-refining catalyst is filled at the bottom of a hydrocracking zone of the hydrocracking unit. Preferably, a hydrocracking catalyst and a post-refining catalyst are sequentially filled in a hydrocracking zone of the hydrocracking unit according to the direction of reactant flow, and the filling volume ratio of the post-refining catalyst to the hydrocracking catalyst is 1: (4-20).

Preferably, the heavy feedstock further comprises at least one of Vacuum Gas Oil (VGO), Atmospheric Gas Oil (AGO), and Coker Gas Oil (CGO).

In the present invention, the kind of the protection catalyst of each catalyst bed may be the same or different, and the method of the present invention is not particularly limited to the kind of the protection catalyst, and those skilled in the art can select various protection catalysts conventionally used in the art. For example, the RG series protected catalysts are exemplarily employed in the examples of the present invention as the protected catalysts in the process of the present invention.

In the method of the present invention, the kind of the demetallization catalyst is not particularly limited, and those skilled in the art can select various demetallization catalysts conventionally used in the art. For example, the examples of the present invention illustratively employ RDM-35 as the demetallization catalyst in the process of the present invention.

In the method of the present invention, the types of the hydrotreating pretreatment catalyst, the hydrotreating catalyst, and the post-refining catalyst may be the same or different, and the method of the present invention is not particularly limited to the types of the hydrotreating pretreatment catalyst, the hydrotreating catalyst, and the post-refining catalyst, and a person skilled in the art can select various hydrotreating catalysts conventionally used in the art. For example, RN-32V is exemplarily employed in the examples of the present invention as the hydrotreating pretreatment catalyst, the hydrofinishing catalyst and the post-refining catalyst in the process of the present invention.

Preferably, the coal tar distillate is a distillate obtained by atmospheric distillation or reduced pressure distillation of coal tar and having a distillation range of 200-500 ℃; more preferably, the coal tar distillate is obtained by distilling coal tar under atmospheric pressure or reduced pressure, and the distillation range is 220-450 ℃.

According to a preferred embodiment, the hydrocracking process of the blended coal tar of the present invention is carried out according to the process flow shown in fig. 1, specifically:

the heavy raw material 1 doped with coal tar distillate is heated by a heating furnace 2 through a pipeline and then mixed with new hydrogen 29 and/or circulating hydrogen 30, and enters a hydrogenation protection reactor 4 in a hydrogenation pretreatment unit for hydrogenation protection treatment, and the heavy raw material and hydrogen mainly undergo reactions such as carbon residue removal, metal removal, dehydration and the like under the action of a protection catalyst and a demetallization catalyst. The protective treatment material flow 5 obtained after the reaction mainly generates desulfurization, denitrification and aromatic saturation reaction after entering a hydrogenation pretreatment reactor 6 through a pipeline, a hydrogenation pretreatment mixture 7 generated by the reaction enters a temperature and high pressure separator 8 through a pipeline to separate gas, water and mixed liquid hydrocarbon, the top of the temperature and high pressure separator 8 obtains temperature and high pressure gas 12, the bottom of the temperature and high pressure separator 8 obtains temperature and high pressure oil, the temperature and high-pressure oil enters a temperature and low-pressure separator 9 for temperature and low-pressure separation to obtain temperature and low-pressure gas 3 and temperature and low-pressure oil, and the low-temperature separated oil enters a debutanizer 10 to be subjected to gas-liquid separation to remove hydrogen sulfide and gaseous light hydrocarbon to obtain debutanizer bottom oil, a part of the debutanizer bottom oil 13 enters a hydrofining reactor 14 of the hydrocracking unit through a pipeline, and the rest debutanizer bottom oil 11 returns to the hydrogenation pretreatment unit through a pipeline. The part of debutanizer bottom oil 13 further undergoes desulfurization, denitrification and aromatic saturation reactions in a hydrofining reactor 14, and the obtained refined product 15 enters a thermal high-pressure separator 16 for thermal high-pressure separation to obtain thermal high-pressure separation gas and thermal high-pressure separation liquid; the hot high-pressure gas and the high-temperature gas 12 obtained from the top of the high-temperature and high-pressure separator 8 enter a cold high-pressure separator 20 together with water through a pipeline for cold high-pressure separation to obtain cold high-pressure gas 19 and cold high-pressure liquid; the hot high-pressure liquid enters a hot low-pressure separator 17 for hot low-pressure separation to obtain hot low-pressure gas and hot low-pressure liquid; the cold high-pressure liquid and the hot low-pressure gas enter a cold low-pressure separator 18 together for cold low-pressure separation to obtain cold low-pressure liquid; the cold low-fraction liquid and the hot low-fraction liquid are then introduced into a fractionating tower 21 together for fractionation to obtain an overhead light hydrocarbon 22, a light naphtha fraction 23, a heavy naphtha fraction 24 and a heavy fraction 25, respectively. The heavy fraction 25 and recycle hydrogen 30 are introduced into a hydrocracking reactor 26 of the hydrocracking unit for hydrocracking and the resulting cracked product 27 is subjected to thermal high pressure separation together with the refined product 15. The cold high-pressure separator 20 performs cold high-pressure separation to obtain cold high-pressure gas 19, the pressure of the cold high-pressure gas is increased by a recycle hydrogen compressor 28, and the cold high-pressure gas enters a recycle hydrogen system for circulation.

In conclusion, the two-stage process flow of the hydrogenation pretreatment unit and the hydrocracking unit can convert the raw material mixed with the coal tar distillate into the light oil product under the conditions of mild and relatively low reaction pressure and temperature; the yield of gas, especially dry gas, can be effectively reduced, and the hydrogen consumption of the device is reduced; the hydrogenation pretreatment unit and the hydrocracking unit share the cold high-pressure separator, the new hydrogen compressor and the recycle hydrogen compressor, and the construction cost and the operation cost of the device can be reduced.

The method of the invention also has the following specific advantages:

1. because of the characteristics of high nitrogen content, high metal content and low hydrogen content of the coal tar distillate, the hydrodenitrogenation difficulty is high, the hydrogen consumption required by a target product is high, and the exothermic heat of reaction is far higher than that of a conventional hydrocracking device, the invention adopts the protective agent, the demetallizing agent and the hydrogenation pretreatment catalyst to carry out hydrogenation pretreatment on the poor-quality raw material through the independent hydrogenation pretreatment unit, so that the feeding requirement of the hydrocracking unit is met, the severity of the hydrocracking unit is reduced, the product quality is improved, and the operation period of the device is prolonged.

2. Because the coal tar distillate has high aromatic hydrocarbon composition, the heavy naphtha distillate obtained as the hydrocracking raw material has the characteristic of high potential aromatic hydrocarbon content. In addition, the invention sets up the independent warm high, low pressure separator and debutanizer in the pretreatment unit of hydrogenation, hydrogen sulfide, ammonia and gaseous light hydrocarbon that can remove the pretreatment unit of hydrogenation produced, and then improve the hydrogen purity of the hydrocracking unit and reduce hydrogen sulfide and ammonia content in the reaction atmosphere, the improvement of hydrogen purity can improve the hydrogenation activity of the hydrocracking unit catalyst by a wide margin under the situation that the total pressure is invariable, make the aromatic hydrocarbon fully saturated.

3. The two-stage process flow of the hydrocracking unit can lead naphtha fraction obtained in the refining reaction zone to be discharged out of the product in time, avoid over cracking into gas with low added value and improve liquid yield; the cracking reaction zone is operated in an environment basically without ammonia, so that the activity of the hydrocracking catalyst is greatly improved, the operation severity is reduced, the operation flexibility of the device is improved, and the operation period is prolonged; the content of hydrogen sulfide in the circulating hydrogen of the hydrocracking unit section is reduced, so that the sulfur content in light naphtha fraction and heavy naphtha fraction can be reduced, the light naphtha fraction meets the corrosive requirement, and the heavy naphtha fraction meets the requirement of being used as a reforming raw material.

4. The hydrogenation pretreatment catalyst and the hydrogenation refining catalyst in the hydrogenation pretreatment unit and the hydrocracking unit fully denitrify the raw materials, so that a heavy naphtha fraction can be obtained in a high selectivity manner under mild conditions by adopting a molecular sieve type hydrocracking catalyst with higher activity under the condition that a cracking reaction zone is ensured to run for a long period, and the gas yield is reduced.

5. The present invention has at least part of the debutanizer bottom oil circulated back to the hydrogenation pretreatment unit, and this part of the circulating line can raise the volume space velocity inside the reactor of the hydrogenation pretreatment unit, so that carbon deposit, metal deposit and other phenomena are distributed homogeneously inside the reactor, the pressure difference inside the reactor is reduced and the operation period is prolonged.

The present invention will be described in detail below by way of examples. In the following examples, various raw materials used were commercially available unless otherwise specified.

The following protective catalysts were used as RG series protective catalysts (including RG-20, RG-30E, RG-30A and RG-30B which were sequentially loaded); the demetallization catalyst is RDM-35 catalyst; the hydrofining catalyst is an RN-32V catalyst; the hydrocracking catalyst comprises RHC-5 catalyst, which is produced by Changling catalyst factory of China petrochemical catalyst division.

The following XRD was performed on a D5005X-ray diffractometer from Siemens Germany, Cu target, Ka radiation, solid detector, 40kV, 40mA, step scan, step by step 0.02 °, scan range 5-70 °.

The pseudoboehmite used, the preparation method or the source:

PB1：

600mL of clear and transparent aluminum sulfate with the concentration of 48g/L and 8% ammonia water are simultaneously and slowly added into a 2L reaction kettle with a stirrer for reaction and filtration, and then the ammonia water is added to control the reaction temperature to be 35 ℃ and the pH value to be 6.0. After the reaction is completed, filtering, pulping the filter cake, and adding ammonium bicarbonate while stirring until the pH value of the solution is 9.5. After the reaction is carried out for 12 hours at the constant temperature of 35 ℃, the filtration is carried out, the deionized water is used for washing for three times, and the drying is carried out for 3 hours at the temperature of 120 ℃ in an oven by ventilation, thus obtaining the pseudo-boehmite PB 12. H1, h2, h3, k of PB1₁，k₂And the pore volumes are listed in table 1.

SB: pseudo-boehmite produced by Sasol corporation under the trade name SB powder. H1, h2, h3, k of SB₁，k₂And the pore volumes are listed in table 1.

Table 1: x-ray diffraction characterization of pseudoboehmite

	h1	h2	h3	k₁	k₂	Pore volume/(mL/g)
							PB1	1223	2721	3730	2.22	1.37	0.85
SB	5740	4278	6089	0.74	1.42	0.55

Preparation example 1: preparation of silicon-aluminum-containing hierarchical pore hydrocracking catalyst C-1

236.5 g of pseudo-boehmite PB1 (dry basis 0.74) and 122 g of molecular sieve Beta (produced by China petrochemical catalyst Ministry of China, China and China²The weight content of silicon dioxide is 40 percent, the acidity value of the infrared B acid is 0.04mmol/g, the dry basis is 0.76), 7.7mL of concentrated nitric acid with the purity of 65 percent and 310mL of deionized water are uniformly mixed, extruded into trilobe strips with the circumscribed circle diameter of 1.6 mm, dried for 3 hours at 120 ℃, and roasted for 3 hours at 600 ℃ to obtain the carrier, and the composition is shown in Table 2.

After the temperature is reduced to 25 ℃, 100 g of the carrier is dipped in 78mL of aqueous solution containing 50 g of ammonium metatungstate (82 wt% of tungsten oxide in Sichuan tribute cemented carbide factory), 8.7 g of basic nickel carbonate (51 wt% of nickel oxide in Jiangsu Yixing brady chemical Co., Ltd.) and 10.5g of citric acid, and is dried for 10 hours at 180 ℃ to obtain the catalyst C-1.

The mass fractions of the respective metal components (calculated values, the same applies hereinafter) based on the total amount of the catalyst are shown in table 2, and the pore distribution characterization results are shown in table 3.

Preparation example 2: preparation of silicon-aluminum-containing hierarchical pore hydrocracking catalyst C-2

233.3 g of pseudo-boehmite SB (dry basis 0.75, dry basis determination method is that a certain amount of raw powder is put into a crucible with a cover and put into a muffle furnace, after the temperature is raised to 700 ℃ and the constant temperature is kept for 1hr, the ratio of the residue to the raw powder is calculated, the same is shown below), 122 g of molecular sieve Beta (produced by China petrochemical catalyst division, the silica-alumina ratio is 27, the pore volume is 0.395mL/g, the dry basis is 0.82), 78.9 g of weakly acidic silicon-aluminum (produced by Germany Condea company, the trade name is Sira-40, the pore volume is 0.88mL/g, and the specific surface is 468m²The weight content of silicon dioxide is 40 percent, the acidity value of the infrared B acid is 0.04mmol/g, the dry basis is 0.76), 11 g of sesbania powder, 13.7mL of concentrated nitric acid with the purity of 65 percent (the molar concentration is 14.4mol/L, the same below) and 226.8mL of deionized water are uniformly mixed, extruded into trilobe strips with the circumscribed circle diameter of 1.6 mm, dried for 3 hours at 120 ℃, and roasted for 3 hours at 600 ℃ to obtain the carrier, and the composition of the carrier is shown in Table 2.

After the temperature is reduced to 25 ℃, 100 g of the carrier is dipped in 78mL of aqueous solution containing 50 g of ammonium metatungstate (82 wt% of tungsten oxide in Sichuan tribute cemented carbide factory), 8.7 g of basic nickel carbonate (51 wt% of nickel oxide in Jiangsu Yixing brady chemical Co., Ltd.) and 10.5g of citric acid, and is dried for 10 hours at 180 ℃ to obtain the catalyst C-2.

The mass fractions of the metal components in C-2 based on the total amount of the catalyst are shown in Table 2, and the pore distribution characterization results are shown in Table 3.

Table 2: support and catalyst characterization

Table 3: catalyst pore distribution characterization

Catalyst and process for preparing same	<2nm,％	2～100nm,％	>100nm,％
				C-1	10.8	75.5	13.7
C-2	20.4	77.8	1.8

The properties of the heavy feedstock used below are listed in table 4.

Table 4: properties of heavy feedstocks

Raw oil name	Raw oil A	Raw oil B	Coal tar distillate C	Coal tar fraction D
					Density, g/cm³	0.912	0.920	1.05	1.13
Sulfur, wt.%	1.70	1.45	0.50	0.81
					Nitrogen,. mu.g/g	1000	1500	8000	5500
Oxygen, wt.%	-	-	1.42	1.60
					Total metal content,. mu.g/g	-	-	10.5	12.0
Distillation range (D-1160), DEG C
					Initial boiling point	283	236	229	250
10％	401	355	241	296
					50％	446	421	251	329
90％	486	496	264	379
					End point of distillation	531	571	317	443
BMCI value	45.7	50.6	-	-

Example 1

The present example was carried out by using the process route shown in fig. 1, specifically:

the heavy raw material doped with coal tar distillate is heated by a heating furnace through a pipeline and then mixed with new hydrogen and circulating hydrogen, and enters a hydrogenation protection reactor in a hydrogenation pretreatment unit for hydrogenation protection treatment, and the heavy raw material and the hydrogen mainly undergo reactions such as carbon residue removal, demetalization, dehydration and the like under the action of a protection catalyst and a demetalization catalyst. The protective treatment material flow obtained after the reaction mainly undergoes desulfurization, denitrification and aromatic saturation reactions after entering a hydrogenation pretreatment reactor through a pipeline, a hydrogenation pretreatment mixture generated by the reaction enters a high-temperature high-pressure separator through a pipeline to separate gas, water and mixed liquid hydrocarbon, high-temperature gas is obtained at the top of the high-temperature high-pressure separator, high-temperature oil is obtained at the bottom of the high-temperature high-pressure separator, the high-temperature oil enters a low-temperature low-pressure separator to undergo high-temperature low-pressure separation to obtain low-temperature gas and low-temperature oil, the low-temperature oil enters a debutanizer to undergo gas-liquid separation to remove hydrogen sulfide and gaseous light hydrocarbon to obtain debutanizer bottom oil, and all debutanizer bottom oil enters a hydrofining reactor of the hydrocracking unit through a pipeline. The bottom oil of the debutanizer further undergoes desulfurization, denitrification and aromatic saturation reactions in a hydrofining reactor, and the obtained refined product enters a thermal high-pressure separator for thermal high-pressure separation to obtain thermal high-pressure separation gas and thermal high-pressure separation liquid; the hot high-pressure gas and the high-temperature gas obtained from the top of the high-temperature and high-pressure separator enter a cold high-pressure separator together through a pipeline for cold high-pressure separation to obtain cold high-pressure gas and cold high-pressure liquid; the hot high-pressure liquid enters a hot low-pressure separator for hot low-pressure separation to obtain hot low-pressure gas and hot low-pressure liquid; the cold high-pressure liquid and the hot low-pressure gas enter a cold low-pressure separator together for cold low-pressure separation to obtain cold low-pressure liquid; and then introducing the cold low-fraction liquid and the hot low-fraction liquid into a fractionating tower together for fractionating to obtain light hydrocarbon at the top of the tower, light naphtha fraction, heavy naphtha fraction and heavy fraction respectively. The heavy fraction and recycle hydrogen are introduced into a hydrocracking reactor of the hydrocracking unit for hydrocracking, and the obtained cracked product and the refined product are subjected to thermal high-pressure separation together. And after the cold high-pressure separator performs cold high-pressure separation, the obtained cold high-pressure gas is boosted by a recycle hydrogen compressor and then enters a recycle hydrogen system for circulation.

In this example, the feedstock oil A and the coal tar fraction C in Table 4 were used as heavy feedstock, the hydrocracking catalyst was RHC-5 catalyst, the test conditions are shown in Table 5, and the product distribution and the main properties are shown in Table 6.

Example 2

The present example was carried out by a process similar to that of example 1, except that in this example, raw oil B, coal tar fraction C, and coal tar fraction D in table 4 were used as heavy raw materials; and a portion of the debutanizer bottoms was piped to the hydrofinishing reactor of the hydrocracking unit, the remainder was piped back to the inlet of the hydrotreating unit, and the test conditions are listed in table 5, and the product distribution and key properties are listed in table 6.

Example 3

This example was carried out using a similar process flow to that of example 1, except that the hydrocracking catalyst of this example was catalyst C-1 obtained in the aforementioned preparation example 1, and the test conditions are shown in Table 5, and the product distribution and the main properties are shown in Table 6.

The rest is the same as in example 1.

Example 4

This example was carried out using a similar process flow to that of example 1, except that the hydrocracking catalyst of this example was catalyst C-2 obtained in the foregoing preparation example 2, and the test conditions are shown in table 5, and the product distribution and the main properties are shown in table 6.

The rest is the same as in example 1.

Table 5: test conditions

1) The cracking agent is the catalyst C-1 prepared in the preparation example 1

2) The cracking agent is the catalyst C-2 prepared in the preparation example 2

Table 6: product distribution and key properties

	Example 1	Example 2	Example 3	Example 4
					Hydroprocessing unit (fresh feed 100%)
Chemical hydrogen consumption, wt.%	1.88	2.72	3.46	3.46
					H₂S+NH₃To weight percent	1.73	1.54	1.61	1.61
H₂O, wt.%	0.40	0.68	0.80	0.80
					C₁+C₂To weight percent	0.24	0.24	0.25	0.25
C₃+C₄To weight percent	0.37	0.35	0.39	0.39
					C₅+, by weight%	99.14	99.91	100.41	100.41
Hydrocracking unit (hydrocracking unit feed is 100%)
					Chemical hydrogen consumption, wt.%	2.17	2.28	2.68	2.87
H₂S+NH₃To weight percent	0.09	0.10	0.11	0.11
					C₁+C₂To weight percent	0.67	0.71	0.75	0.81
C₃+C₄To weight percent	11.01	11.24	10.73	11.75
					C₅Light naphtha at-65 ℃ in% by weight	20.72	21.43	20.17	22.09
Heavy naphtha at 65-175 ℃ by weight%	68.81	68.71	71.33	68.52
					Sulfur content of 65-175 deg.C heavy naphtha, μ g/g	<0.5	<0.5	<0.5	<0.5
Aromatic hydrocarbon potential content of heavy naphtha at 65-175 deg.C, wt%	60.2	62.6	68.7	65.3

From the above results, it can be seen that the method provided by the present invention can incorporate an inexpensive coal tar fraction which is difficult to process into a conventional hydrocracking feedstock, and obtain a light oil product with a high added value under relatively mild reaction conditions, and in particular, the method of the present invention can obtain a high-quality naphtha product with a high yield.

The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.

It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.

In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.

Claims

1. A hydrocracking process for blending coal tar, the process being carried out in a system comprising a hydrotreating pretreatment unit and a hydrocracking unit, comprising:

(1) introducing a heavy raw material into the hydrogenation pretreatment unit to sequentially carry out hydrogenation protection treatment and hydrogenation pretreatment, and carrying out temperature and high pressure separation on the obtained product to obtain temperature and high-pressure gas and temperature and high-pressure oil; then, separating the temperature and high-temperature oil at low pressure to obtain temperature and low-temperature gas and temperature and low-temperature oil; performing gas-liquid separation on the low temperature separated oil to obtain debutanizer bottom oil, wherein the heavy raw material contains coal tar distillate, and the content of the coal tar distillate is 10-95 parts by weight relative to 100 parts by weight of the heavy raw material;

(4) introducing the heavy fraction into a hydrocracking zone of the hydrocracking unit for hydrocracking, and carrying out thermal high-pressure separation on the obtained cracked product and the refined product;

the hydrocracking zone contains a hydrocracking catalyst, the hydrocracking catalyst is a hierarchical pore hydrocracking catalyst containing silicon and aluminum, the hydrocracking catalyst contains a carrier and a hydrogenation active metal component loaded on the carrier, the carrier contains a Beta-type molecular sieve, weak acid silicon and aluminum and alumina, the hydrogenation active metal component is selected from molybdenum and/or tungsten and nickel and/or cobalt, and the pore distribution of the hydrocracking catalyst meets the following requirements: the pore volume of pores with the pore diameter of less than 2nm accounts for 2-50% of the total pore volume of the hydrocracking catalyst, the pore volume of pores with the pore diameter of 2-100 nm accounts for 20-85% of the total pore volume of the hydrocracking catalyst, and the pore volume of pores with the pore diameter of more than 100nm accounts for 3-70% of the total pore volume of the hydrocracking catalyst;

based on the carrier, the Beta type molecular sieve has the content of 3-70 wt%, the content of alumina is 10-85 wt%, and the content of weakly acidic silicon-aluminum is 5-60 wt%.

2. The method of claim 1, wherein the method further comprises: in step (2), a portion of the debutanizer bottoms is introduced into a hydrofinishing zone of the hydrocracking unit for hydrofinishing, and the remaining debutanizer bottoms are recycled to the hydrotreating pretreatment unit.

3. The method of claim 2, wherein the remaining debutanizer bottoms are recycled to the inlet of the hydroprocessing pretreatment unit.

4. The process of claim 1, wherein the hydrocracking catalyst has a pore distribution such that: the pore volume of pores with the pore diameter of less than 2nm accounts for 4-21% of the total pore volume of the hydrocracking catalyst, the pore volume of pores with the pore diameter of 2-100 nm accounts for 20-85% of the total pore volume of the hydrocracking catalyst, and the pore volume of pores with the pore diameter of more than 100nm accounts for 4-60% of the total pore volume of the hydrocracking catalyst.

5. The method according to claim 1, wherein the Beta-type molecular sieve has a silica to alumina ratio of (15-300): 1, the specific surface area is 150-750 m²The pore volume is 0.20-1.05 ml/g.

6. The process according to claim 1, wherein the hydrocracking catalyst contains 45 to 85 wt% of a carrier, 1 to 15 wt% of nickel and/or cobalt in terms of oxide, and 5 to 40 wt% of molybdenum and/or tungsten in terms of oxide, based on the hydrocracking catalyst.

7. The process of claim 6, wherein the Beta-type molecular sieve is a hydrogen Beta-type molecular sieve.

8. The method of claim 6, wherein the alumina is gamma alumina.

9. The process according to any one of claims 1 to 3, wherein the coal tar distillate is contained in an amount of 20 to 90 parts by weight relative to 100 parts by weight of the heavy feedstock.

10. The method of any one of claims 1-3, wherein the reaction conditions of the hydro-protective treatment and the hydro-pretreatment each independently comprise: the hydrogen partial pressure is 10.0-20.0 MPa, the reaction temperature is 300-430 ℃, and the volume ratio of hydrogen to oil is 300-3000 Nm³/m³。

11. The method of claim 10, wherein the total volume space velocity of the hydrogenation protection reactor in the hydrogenation protection treatment is 0.5-8.0 h^-1。

12. The method of claim 10, wherein the total volume space velocity of the hydrotreating pretreatment reactor in the hydrotreating pretreatment is 0.1 to 5.0h^-1。

13. The method of claim 10, wherein the hydrogenation protection reactor is sequentially filled with a protection catalyst and a demetallization catalyst according to the flow direction of the reactants, and the filling volume ratio of the protection catalyst to the demetallization catalyst is 1: (0.1 to 9).

14. The process of any one of claims 1-3, wherein the reaction conditions of the hydrocracking unit comprise: the hydrogen partial pressure is 10.0-20.0 MPa, the reaction temperature is 300-430 ℃, and the volume ratio of hydrogen to oil is 300-3000 Nm³/m³The total volume airspeed is 0.1-8.0 h^-1。

15. The process of any one of claims 1 to 3, wherein a hydrocracking catalyst and a post-refining catalyst are sequentially loaded in the hydrocracking zone of the hydrocracking unit in terms of the direction of the reactant flow, and the loading volume ratio of the post-refining catalyst to the hydrocracking catalyst is 1: (4-20).

16. The process of claim 1, wherein the heavy feedstock further comprises at least one of vacuum gas oil, atmospheric gas oil, and coker gas oil.

17. The method according to claim 1, wherein the coal tar fraction is a fraction obtained by subjecting coal tar to atmospheric distillation or vacuum distillation and having a distillation range of 200-500 ℃.

18. The method according to claim 1, wherein the coal tar fraction is a fraction obtained by subjecting coal tar to atmospheric distillation or vacuum distillation and having a distillation range of 220-450 ℃.