CN116445186B

CN116445186B - Deep dearomatization method for inferior diesel oil

Info

Publication number: CN116445186B
Application number: CN202210014492.4A
Authority: CN
Inventors: 代萌; 丁贺; 张瀚; 李士才; 徐大海
Original assignee: Sinopec Dalian Petrochemical Research Institute Co ltd; China Petroleum and Chemical Corp
Current assignee: Sinopec Dalian Petrochemical Research Institute Co ltd; China Petroleum and Chemical Corp
Priority date: 2022-01-06
Filing date: 2022-01-06
Publication date: 2025-03-04
Anticipated expiration: 2042-01-06
Also published as: CN116445186A

Abstract

The present invention discloses a method for deep dearomatization of low-quality diesel. The method comprises the following steps: (1) low-quality diesel feedstock and hydrogen enter a first reactor to carry out a gas phase desulfurization reaction; (2) the effluent of the first reactor enters a second reactor after being pressurized, wherein the gas phase component is discharged upward from the second reactor, and after being treated with desulfurized hydrogen, a hydrogenated light component is obtained, and the liquid phase component is subjected to a liquid phase hydrogenation dearomatization reaction downward to obtain a hydrogenated heavy component which is discharged from the bottom of the second reactor; (3) the hydrogenated heavy component is mixed with the hydrogenated light component to obtain a refined diesel product. The method of the present invention can achieve the effect of deep dearomatization, and at the same time, it also simplifies the process flow, reduces the reaction severity, and improves the chemical reaction efficiency in general.

Description

Deep dearomatization method for inferior diesel oil

Technical Field

The invention belongs to the fields of oil refining and chemical industry, and particularly relates to a method for deeply dearomatizing inferior diesel oil.

Background

Emissions from the combustion of sulfur and polycyclic aromatic hydrocarbons in diesel fuel can pollute the atmosphere in which humans live, and for this reason, the upgrading steps of diesel fuel quality standards are continually being accelerated in all countries. The national V diesel standard implemented in 2017 in china requires a sulfur content of not more than 10 mg/kg, and in the national VI diesel quality standard proposed in 2019, no more than 11% of polycyclic aromatic hydrocarbons is required, and in the national VIB standard to be implemented in 2023, no more than 5% of polycyclic aromatic hydrocarbons is required. Meanwhile, the processing demands of China on secondary processing raw materials are increasing, inferior raw materials such as catalytic diesel oil and the like have aromatic hydrocarbon content up to 60%, and the requirements on the activity of the catalyst are higher. However, there is a great difference in the requirements of the reaction environment from the reaction mechanism of deep desulfurization and deep dearomatization. For desulfurization reactions, the removal of small molecule sulfur mainly follows the direct desulfurization route, i.e., hydrogenolysis desulfurization. The macromolecular sulfides with lower reactivity follow the hydrodesulfurization reaction route, namely aromatic ring hydrogenation is carried out first, and then hydrogenolysis desulfurization is carried out. So that the hydrogenolysis (endothermic) of small molecular weight sulfides and the hydrogenation reaction (substantial exothermic) of aromatic ring-containing substances mainly occur in the environment of relatively low temperature and high hydrogen partial pressure in the upper part of the reactor. The accumulation of heat and hydrogen sulfide at the lower part of the reactor leads the reaction environment to be high temperature and low in hydrogen partial pressure, and the reaction environment is favorable for further hydrogenolysis of hydrogenated macromolecular sulfides, but is very unfavorable for further saturation of aromatic hydrocarbon because of the thermodynamic limitation of aromatic hydrocarbon hydrogenation. Especially, when the reaction is finished, the activity of the catalyst is attenuated, and no better operation means is provided except for temperature raising, so that the dearomatization effect is further influenced. Besides different requirements of the two on reaction environment, competitive adsorption of aromatic hydrocarbon on the surface of the catalyst also has an inhibition effect on deep desulfurization, so that the traditional hydrogenation technology is difficult to meet the double requirements of ultra deep desulfurization and efficient saturation of aromatic hydrocarbon, and the necessity and urgency of upgrading the diesel oil cleaning technology are further highlighted.

In the prior art, the deep dearomatization is carried out on the basis of the deep desulfurization, and the method for reducing the reaction space velocity, namely reducing the treatment capacity or increasing the reactor by adopting the existing catalyst system is not reasonable from the economical aspect. Secondly, by adopting a two-stage process technology, after conventional hydrogenation, the generated oil is stripped to remove hydrogen sulfide and then enters a noble metal hydrogenation reactor, so that the use cost and the process complexity of the catalyst are greatly increased, and the method is still not an optimal scheme.

CN108085058B discloses a process for deep dearomatization of hydrocarbon oils. The method adopts mild temperature and pressure conditions to lead the raw oil and the hydrogen to pass through a highly dispersed Pt-Pd/Al ₂O₃ catalyst, the reacted gas phase is compressed and recycled, the liquid phase is a low aromatic product, but the Pt-Pd/Al ₂O₃ hydrogenation catalyst is mainly applicable to dearomatization of low-sulfur diesel raw materials, and the desulfurization and dearomatization effect on inferior diesel is not ideal.

CN109926067a discloses a platinum-palladium-cobalt ternary metal hydrodearene catalyst and a preparation method thereof. The method adopts a method of stepwise dipping active metal precursors, so that the prepared catalyst platinum-palladium noble metal has high utilization rate and strong synergistic catalytic capability, and the hydrogenation performance of the non-noble metal cobalt is enhanced due to the introduction of platinum-palladium. However, the catalyst is still aimed at hydrocarbon oil from which sulfur compounds are basically removed, so that the influence of hydrogen sulfide on deep dearomatization of noble metal is avoided, and desulfurization and dearomatization of inferior diesel cannot be realized.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a method for deeply dearomatizing inferior diesel. The method can achieve the effect of deep dearomatization, and simultaneously simplifies the process flow, reduces the reaction severity and improves the chemical reaction efficiency.

The invention provides a method for deeply dearomatizing inferior diesel oil, which comprises the following steps:

(1) The poor diesel oil raw material and hydrogen enter a first reactor to carry out gas-phase desulfurization reaction;

(2) The effluent of the first reactor is pressurized and then enters a second reactor, wherein the gas phase component is discharged upwards from the second reactor, hydrogenation light components are obtained after the hydrogen sulfide is removed, the liquid phase component is downwards subjected to liquid phase hydrogenation dearomatization reaction, and hydrogenation heavy components are discharged from the bottom of the second reactor;

(3) And mixing the hydrogenation heavy component with the hydrogenation light component to obtain a refined diesel product.

Further, the low-grade diesel oil has the characteristics that the initial distillation point is 150-200 ℃, the final distillation point is 320-400 ℃, the S content is no more than 20000 mug/g, preferably no more than 15000 mug/g, the N content is no more than 1000 mug/g, preferably no more than 800 mug/g, and the polycyclic aromatic hydrocarbon content is no more than 50wt%. For example, the S content of the low-grade diesel oil is exemplified by, but not limited to, 8000. Mu.g/g, 9000. Mu.g/g, 10000. Mu.g/g, 11500. Mu.g/g, etc., the N content is exemplified by, but not limited to, 500. Mu.g/g, 600. Mu.g/g, 700. Mu.g/g, etc., and the polycyclic aromatic hydrocarbon content is exemplified by, but not limited to, 25wt%, 30wt%, 35wt%, 40wt%, 45 wt%.

Further, the inferior diesel oil can be one or more of straight-run diesel oil, catalytic diesel oil, coker diesel oil, ebullated bed residual oil hydrogenated diesel oil and the like.

Further, the first reactor and the second reactor are both fixed bed reactors. The second reactor is preferably a fixed bed reactor provided with a flash zone.

Further, a flash evaporation zone is arranged in the second reactor, no catalyst is filled in the flash evaporation zone and above, a reaction zone is arranged below the flash evaporation zone, the effluent of the first reactor is fed into the flash evaporation zone of the second reactor after being pressurized, the obtained gas phase component is discharged from the second reactor upwards, the obtained liquid phase component is subjected to dearomatization reaction downwards, and the obtained product, namely the hydrogenation heavy component, is discharged from the bottom of the second reactor.

Further, the operation condition of the first reactor is that the pressure is 0.1-2.8 MPa, preferably 0.5-2.0 MPa, the temperature is 260-400 ℃, preferably 320-390 ℃, the hydrogen oil volume ratio is 100-900, preferably 300-700, and the volume airspeed is 0.5-3.0 h ^-1, preferably 0.8-2.0 h ^-1.

Further, the catalyst filled in the first reactor may be a conventional catalyst having a hydrodesulfurization function, preferably a Mo-Co hydrodesulfurization catalyst, and generally an alumina-based carrier is used, wherein the content of Mo is 15wt% to 30wt% based on the mass of the catalyst, and the content of Co is 2wt% to 6wt% based on the mass of the catalyst. The catalyst may further contain an auxiliary component such as at least one of phosphorus, silicon, boron, magnesium, fluorine, etc., and the mass content in the catalyst is generally 6wt% or less. Such as Mo-Co type diesel oil deep desulfurization catalyst developed by China petrochemical smoothing petrochemical institute (FRIPP). For example FHUDS-5, FHUDS-7, etc.

Further, the first reactor effluent is pressurized by a compressor, which may be a conventional commercial compressor, such as a reciprocating, centrifugal compressor. The pressurization can ensure the normal feeding of the second reactor and meet the operating pressure requirement of the second reactor.

Further, the second reactor is operated under the conditions that the pressure is 2.0-8.0 MPa, preferably 3.0-6.0 MPa, the temperature is 200-400 ℃, preferably 260-360 ℃, and the volume space velocity is 0.1-3.0 h ^-1, preferably 0.5-1.0 h ^-1.

Further, the pressure of the second reactor is at least 1.0MPa higher than that of the first reactor, preferably 1.5-7.0 MPa higher, preferably 2.5-6.0 MPa higher.

Further, the catalyst filled in the second reactor may be a catalyst having a hydrodearomatics function, such as a non-noble metal catalyst or a noble metal catalyst, where the non-noble metal catalyst is a Mo-Ni type catalyst, typically, an alumina-based carrier is used, based on the mass of the catalyst, mo is 15wt% to 30wt% based on molybdenum oxide, and Ni is 2wt% to 5wt% based on cobalt oxide. The catalyst may further contain an auxiliary component such as at least one of phosphorus, silicon, boron, magnesium, fluorine, etc., and the mass content in the catalyst is generally 6wt% or less. The Mo-Ni catalyst is FHUDS-10, FHUDS-6, FHUDS-8 and the like developed by China petrochemical and smooth petrochemical institute (FRIPP), and the noble metal catalyst is FHDA-10 developed by China petrochemical and smooth petrochemical institute (FRIPP) and takes Pt, pd and the like as active metals.

Further, the gas phase component discharged from the second reactor exchanges heat through a heat exchanger and then enters a high-pressure separator for separation to obtain a hydrogenation light component and hydrogen containing hydrogen sulfide.

Further, the gas phase component discharged from the second reactor is cooled to 100-200 ℃, preferably 120-150 ℃ by a heat exchanger.

Further, after the hydrogenation heavy component and the hydrogenation light component are mixed, the mixture enters a stripping and fractionating system to obtain a refined diesel oil product. Wherein the purpose of the fractionation is mainly to cut out a naphtha fraction.

Further, the aromatic hydrocarbon content in the refined diesel oil product is below 5wt%, and the S content is below 10 mug/g.

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

(1) The process method provided by the invention avoids the defect that the deep desulfurization and dearomatization are placed in the same reaction system and the reaction conditions are difficult to be compatible. The inventor researches and discovers that aromatic ring-containing substances are not easy to adsorb on the surface of a catalyst by controlling the reaction conditions of the first reactor, so that competitive adsorption of aromatic hydrocarbon substances is greatly reduced, targeted desulfurization reaction is facilitated, and meanwhile, the reaction conditions of the first reactor are controlled not only for gas-phase desulfurization, but also for better cooperation with the second reactor, so that follow-up deep dearomatization is facilitated.

(2) According to the invention, the effluent of the first reactor is pressurized at a high temperature, so that synchronous liquefaction of hydrogen and oil products is promoted, and because the solubility of hydrogen and hydrogen sulfide in the oil products is different, namely, the solubility of hydrogen is high and the solubility of hydrogen sulfide is low at the high temperature, the concentration of hydrogen in the liquefied liquid phase is high and the concentration of hydrogen sulfide is low, when the liquefied liquid phase enters the subsequent second reactor, the influence of hydrogen sulfide on the activity of a catalyst is avoided, and the arrangement of stripping and removing hydrogen sulfide between the two reactors is omitted.

(3) The invention realizes deep desulfurization and dearomatization by taking the inferior diesel oil as the raw material under milder operation conditions and simpler process flow. In the effluent of the first reactor, the reacted micromolecules are not liquefied in the pressurizing process of the compressor, and are liquefied through the heat exchanger and the high-pressure separator, so that the liquefying means is beneficial to separating hydrogen from raw materials, a large amount of hydrogen can be recycled, and the hydrogen utilization rate is improved. The hydrogenation light component separated by the high-pressure separator can be mixed with the hydrogenation heavy component and then enter a subsequent stripping and fractionating system. The whole set of reaction system does not need a hydrogen compressor in a fixed bed reaction system and a circulating oil pump in a liquid phase hydrogenation reaction system, so that the investment cost is reduced, the process flow is simplified, the reaction efficiency is improved, and the reaction severity is reduced.

Drawings

FIG. 1 is a schematic diagram of a process flow of deep dearomatization of poor diesel oil in the invention;

Wherein, the diesel oil raw material and hydrogen gas-1, the first reactor-2, the first reactor effluent-3, the compressor-4, the second reactor-5, the hydrogenation heavy component-6, the gas phase component-7, the heat exchanger-8, the high pressure separator-9, the hydrogen gas-10 containing hydrogen sulfide, the hydrogenation light component-11, the stripping and fractionating system-12 and the refined diesel oil product-13.

Detailed Description

The present invention will be further described with reference to examples, but it should be understood that the scope of the present invention is not limited by the examples.

In the present invention, percentages and percentages are by mass unless explicitly stated otherwise.

The process flow of the present invention is described in detail below in conjunction with fig. 1.

The diesel oil raw material and hydrogen 1 enter a first reactor 2 to generate gas phase desulfurization reaction to obtain a first reactor effluent 3, enter a compressor 4, enter a second reactor 5 after being pressurized by the compressor 4, wherein the liquid phase component enters a reaction zone downwards to generate hydrogenation dearomatization reaction to obtain a hydrogenation heavy component 6, the gas phase component 7 is discharged upwards out of the second reactor and enters a heat exchanger 8, then enters a high-pressure separator 9 to be separated into a hydrogenation light component 11 and hydrogen 10 containing hydrogen sulfide, and the hydrogenation heavy component 6 and the hydrogenation light component 11 are mixed and enter a stripping and fractionating system 12 to finally obtain a refined diesel oil product 13.

Examples 1 to 3

A schematic flow chart as in fig. 1 is employed. Two 100mL fixed bed hydrogenation reactors are connected in series, namely a first reactor and a second reactor. A conventional power reciprocating compressor is arranged between the reactors. The first reactor is a gas-phase hydrogenation reactor filled with 50mLMo-Co type diesel hydrogenation catalyst A, and the second reactor is a liquid-phase hydrogenation reactor filled with 50mLMo-Ni type diesel hydrogenation catalyst B. And a gas phase outlet is arranged above the second reactor and is sequentially connected with a heat exchanger (cooled to 130 ℃) and a high-pressure separator, a liquid phase outlet pipeline at the bottom of the second reactor is connected with a liquid phase outlet pipeline at the bottom of the high-pressure separator, and the gas phase outlet and the liquid phase outlet pipeline enter a subsequent stripping and fractionating system together to cut out naphtha fractions, so that a refined diesel product is obtained.

Adopts the mixed oil of straight firewood, jiao Chai and catalytic firewood as raw materials. The catalyst properties are shown in Table 1, the raw oil properties are shown in Table 2, and the reaction conditions and results are shown in Table 3.

Comparative example 1

A hydrogenation reactor is arranged as a reactor 1 by adopting a conventional diesel fixed bed hydrogenation process flow. According to the traditional catalyst grading system, a mode that the Mo-Ni type catalyst B is filled up and the Mo-Co type catalyst A is filled down is adopted, and the filling volume is 50mL respectively. And normally setting high-fraction, low-fraction, steam stripping and other processes after the reactor to obtain the diesel oil product. The hydrogen is pressurized and recycled through a recycle hydrogen compressor after hydrogen sulfide is removed. The raw materials and the catalyst properties were the same as in examples 1-3, and the reaction conditions and results are shown in Table 3.

Comparative example 2

A hydrogenation reactor is arranged as a reactor 1 by adopting a conventional diesel fixed bed hydrogenation process flow. According to the same catalyst gradation sequence as in examples 1 to 3, the loading volumes of the Mo-Co type catalyst A and the Mo-Ni type catalyst B were 50mL each. And normally setting high-fraction, low-fraction, steam stripping and other processes after the reactor to obtain the diesel oil product. The hydrogen is pressurized and recycled through a recycle hydrogen compressor after hydrogen sulfide is removed. The raw materials and the catalyst properties were the same as in examples 1-3, and the reaction conditions and results are shown in Table 3.

Comparative example 3

Two hydrogenation reactors are connected in series, namely a reactor 1 and a reactor 2, and a stripping tower is arranged between the two reactors. Reactor 1 was charged with 50mLMo-Co type diesel hydrogenation catalyst A and reactor 2 was charged with 50mLMo-Ni type diesel hydrogenation catalyst B. The reactor is provided with high-fraction, low-fraction, steam stripping and other processes to obtain diesel oil product. The hydrogen is pressurized and recycled through a recycle hydrogen compressor after hydrogen sulfide is removed. The raw materials and the catalyst properties were the same as in examples 1-3, and the reaction conditions and results are shown in Table 3.

Comparative example 4

The hydrogenation process flows of examples 1-3 were used, with the only difference that the high power reciprocating compressor was provided between the first and second reactors and the control of the process conditions, the reaction process conditions and results are shown in Table 3.

TABLE 1 catalyst physicochemical Properties

Catalyst numbering	A	B
			Number plate	FHUDS-7	FHUDS-8
Reactive metal	Mo-Co	Mo-Ni
			MoO₃,wt%	20	24
NiO or CoO, wt%	3.5	5.0
			Shape and shape	Clover with three leaves	Clover with three leaves
Diameter of mm	1.2	1.2
			Specific surface area, m ²·g^-1	180	180
Pore volume, mL.g ^-1	0.35	0.35

TABLE 2 oil Properties of raw materials

Oil Properties
		Density (20 ℃), g.cm ^-3	0.89
The distillation range, C	180~370
		S,μg·g^-1	10360
N,μg·g^-1	713
		Aromatic hydrocarbon, wt%	63.5
Polycyclic aromatic hydrocarbon, wt%	32.2
		Monocyclic aromatic hydrocarbon, wt%	31.3

TABLE 3 hydrogenation process conditions and results

As can be seen from Table 3, in comparative example 1, the conventional fixed bed hydrogenation technology and the conventional catalyst loading system are adopted, the hydrogenation of the polycyclic aromatic hydrocarbon occurs at the upper part of the reactor, the deep desulfurization occurs at the lower part of the reactor, and in order to achieve the deep desulfurization effect, the reaction condition of the hydrogenation of the aromatic hydrocarbon is difficult to be considered, and the removal effect of the polycyclic aromatic hydrocarbon is poor. The pressure of the reaction system is obviously reduced, and the desulfurization and dearomatization areas are divided into two reaction systems, so that the reaction conditions can be optimized in a targeted manner, and a better dearomatization effect is obtained.

The fixed bed hydrogenation technology of comparative example 2 adopts the same catalyst filling sequence as the example, sulfide removal occurs at the upper part of the reactor, aromatic hydrocarbon hydrogenation saturation reaction occurs at the lower part, and the sulfide removal effect and the aromatic hydrocarbon hydrogenation effect are poor due to the fact that the temperature rise of the bottom of the reactor is large and the aromatic hydrocarbon hydrogenation is limited by thermodynamic.

The two reactors used in the comparative example 3 are both conventional fixed bed hydrogenation reactors, the reaction conditions are severe, the energy consumption of hydrogen is high, and the space velocity of aromatic hydrocarbon hydrogenation in the second reactor is increased and the polycyclic aromatic hydrocarbon removal effect is poor because the effluent of the first reactor completely enters the second reactor.

In comparative example 4, since the hydrogen-oil ratio of the gas phase reactor was too high, the partial pressure of the raw oil was lowered, the adsorption of sulfides on the catalyst surface was affected, and the desulfurization effect was not ideal. Meanwhile, the liquefying difficulty of gasified gas phase reactor effluent is obviously increased, and even the reaction pressure of 10MPa is difficult to fully liquefy heavy components, so that the removal effect of polycyclic aromatic hydrocarbon is affected.

Claims

1. The method for deeply dearomatizing the inferior diesel oil is characterized by comprising the following steps of:

(3) The hydrogenation heavy component is mixed with the hydrogenation light component to obtain a refined diesel product;

The operation condition of the first reactor is that the pressure is 0.1-2.0 MPa, the temperature is 260-400 ℃, the hydrogen-oil volume ratio is 100-900, and the volume airspeed is 0.5-3.0 h ^-1;

the operation condition of the second reactor is that the pressure is 3.0-8.0 MPa, the temperature is 200-400 ℃, and the volume space velocity is 0.1-3.0 h ^-1.

2. The method according to claim 1, wherein the poor diesel fuel raw material has the characteristics of initial distillation point of 150-200 ℃ and final distillation point of 320-400 ℃, S content of no more than 20000 mug/g, N content of no more than 1000 mug/g and polycyclic aromatic hydrocarbon content of no more than 50wt%.

3. The method according to claim 2, wherein the poor diesel fuel feedstock has the properties of S content no more than 15000 μg/g and N content no more than 800 μg/g.

4. The process of claim 1, wherein the first reactor and the second reactor are fixed bed reactors, and wherein the second reactor is a fixed bed reactor provided with a flash zone.

5. The method according to claim 1, wherein the first reactor is operated under the conditions of a pressure of 0.5 to 2.0MPa, a temperature of 320 to 390 ℃, a hydrogen-oil volume ratio of 300 to 700 and a volume space velocity of 0.8 to 2.0h ^-1.

6. The method according to claim 1, wherein the second reactor is operated under the conditions of a pressure of 3.0 to 6.0MPa, a temperature of 260 to 360 ℃ and a volume space velocity of 0.5 to 1.0h ^-1.

7. The process of claim 6, wherein the pressure in the second reactor is at least 1.0MPa higher than the pressure in the first reactor.

8. The method according to claim 6, wherein the pressure of the second reactor is 1.5 to 7.0MPa higher than the pressure of the first reactor.

9. The method of claim 6, wherein the pressure in the second reactor is 2.5 to 6.0mpa higher than the pressure in the first reactor.

10. The process of claim 6 wherein the gaseous component exiting the second reactor is subjected to heat exchange by a heat exchanger and then passed to a high pressure separator for separation to produce a light hydrogenated component and hydrogen comprising hydrogen sulfide.

11. The method of claim 10, wherein the gas phase component exiting the second reactor is cooled to 100-200 ℃ by a heat exchanger.

12. The method of claim 10, wherein the gas phase component exiting the second reactor is cooled to 120-150 ℃ by a heat exchanger.

13. The process of claim 1 wherein the catalyst packed in the first reactor is a catalyst having a hydrodesulfurization function and the catalyst packed in the second reactor is a catalyst having a hydrodearomatization function.

14. The method according to claim 1 or 13, wherein the refined diesel product has an aromatic hydrocarbon content of 5wt% or less and an S content of 10 μg/g or less.