CN111088066B

CN111088066B - Hydrofining process

Info

Publication number: CN111088066B
Application number: CN201811232808.7A
Authority: CN
Inventors: 曹正凯; 吴子明; 崔哲; 彭冲; 孙士可; 王仲义
Original assignee: China Petroleum and Chemical Corp; Sinopec Dalian Research Institute of Petroleum and Petrochemicals
Current assignee: Sinopec Dalian Petrochemical Research Institute Co ltd; China Petroleum and Chemical Corp
Priority date: 2018-10-23
Filing date: 2018-10-23
Publication date: 2021-10-08
Anticipated expiration: 2038-10-23
Also published as: CN111088066A

Abstract

The invention discloses a hydrofining process. Mixing raw oil with hydrogen, and passing through a hydrofining reaction zone to obtain a hydrofining reaction effluent; the hydrofining reaction zone comprises a plurality of hydrofining catalyst beds, the metal content of the catalyst in the hydrofining catalyst beds is sequentially increased according to the contact sequence of the hydrofining catalyst beds and the raw oil, the total acid amount of the catalyst is sequentially increased, the acid amount of the acid B is sequentially reduced, and the acid amount of the acid L is sequentially increased. The method is particularly suitable for the hydrocracking pretreatment or hydrofining process, can effectively relieve the polymerization and temperature runaway problems of polycyclic aromatic hydrocarbon caused by higher activity and temperature rise of the first bed catalyst while ensuring the effects of hydrodesulfurization and hydrodenitrogenation, and prolongs the service life of the catalyst and the operation period of the device.

Description

Hydrofining process

Technical Field

The invention relates to a preparation and grading method of a hydrofining catalyst. The method is particularly suitable for the hydrocracking pre-refining (pretreatment) process, and can reduce the carbon deposition amount of the catalyst and the pressure drop of the reactor while ensuring hydrodesulfurization and hydrodenitrogenation, thereby prolonging the operation period of a hydrogenation device.

Background

With increasingly strict requirements on oil quality by environmental regulations, the hydrogenation technology has been widely applied and developed under the trend of crude oil heaviness and deterioration. The hydrotreating process in refinery includes mainly aviation kerosene liquid phase hydrogenating technology, diesel oil hydrogenating and refining technology, wax oil hydrogenating and pre-treating technology, hydrocracking technology, residual oil hydrogenating technology, etc. In the technologies, the hydrofining catalyst plays an important role in oil product cleaning. The hydrofining agent is mainly used for removing sulfur, nitrogen, oxygen, metal, colloid, asphaltene and the like in the raw oil. The removal of sulfur, nitrogen and oxygen atoms in a proper range has little influence on the activity and stability of the catalyst. And the removal of metals, colloids and asphaltenes has a great influence on the activity and the service cycle of the hydrofining catalyst. The metals in the feedstock are removed which can cause a pressure drop across the bed or chemically poison the catalyst. Heavy aromatics, colloids and asphaltenes in the feedstock tend to deposit on the outer surface of the catalyst, causing a reduction in bed pressure drop and catalyst activity. The wax oil hydrogenation device often faces the problem of frequent skimming, and the main reason is that the first bed layer of the hydrofining reactor is preferentially contacted with the inferior raw material, metal and polycyclic aromatic hydrocarbon in the raw material are easily accumulated on the surface of the catalyst of the bed layer, so that inner and outer pore channels of the catalyst are blocked, the diffusion and the flow of the raw material are not facilitated, the pressure drop problem is further caused, the abnormal shutdown of the hydrogenation device is forced, and the enterprise benefit is seriously influenced.

Therefore, in order to solve the above problems, a hydrofining catalyst with high activity and stability needs to be developed, and a reasonable grading system needs to be made for the properties of material flows in different reaction areas in a hydrofining reactor, so that the requirement of refined nitrogen can be met, and carbon deposition and poisoning of the catalyst can be reduced, thereby prolonging the service life of the device and increasing the economic benefits of enterprises.

For the hydrocracking process, inferior raw materials are directly contacted with a hydrofining catalyst on an upper bed layer after simple traditional carbon residue removal and metal removal, and at the moment, the material flow has higher aromatic hydrocarbon content, particularly higher basic nitrogen content, and is easy to coke on the surface of the catalyst after being combined with an L acid center in the hydrofining catalyst. Along with the increase of the saturation depth of aromatic hydrocarbon and the increase of the removal rate of basic nitrogen, the carbon content of the lower bed lamination is reduced in sequence. This causes the most serious coking of carbon deposit on the upper bed layer of the hydrofining reactor, which causes the pressure drop of the reactor to increase. The traditional industrial hydrofining catalyst adopts a single carrier, active metal components, pore diameters, morphology and bulk density, obviously, the long-period operation of a hydrocracking device can not be ensured, so the hydrofining reactor needs to be reasonably graded according to the selection of the carrier and the physicochemical properties of the catalyst, and the purposes of slowing down the coking of the catalyst and reducing the pressure drop of the reactor are achieved.

In the hydrocracking technology, the hydrocracking catalyst grading is reported more, but the hydrofinishing catalyst grading is reported less. CN 1293228A discloses a grading filling method of hydrocracking catalyst, which selects catalysts with different activities and/or different nitrogen resistance properties for reasonable grading, can reduce the quenching hydrogen consumption of a hydrocracking reactor by 30-70 percent and the emergency hydrogen reserve of a hydrocracking device or improve the handling capacity of the hydrocracking device by 20-50 percent, and can bring huge economic benefits. But the hydrofining agent is not graded, so that the problem of bed pressure drop caused by easy coking of the first bed of the hydrofining reactor is solved.

CN 105985805 a describes a grading loading method for residual oil hydrotreating catalyst, in which the catalyst activity and the optional pore diameter are in decreasing trend in the contact sequence with the reactant flow in the same reactor. In two adjacent reactors, the catalyst activity at the bottom of the latter reactor is higher than that of the former reactor.

CN103773437A discloses a grading method of hydrodesulfurization catalysts, which comprises the steps that at least two catalyst beds are included in a hydrogenation reactor, and the bed-to-bed ratio of the catalyst beds is increased in sequence according to the contact sequence of the catalyst beds and reaction materials; more than two catalysts with different diameters are loaded in each catalyst bed layer in a grading mode. The two methods are graded in the aspect of basic physical properties of the catalyst to reduce the carbon deposition of the catalyst, but the heavy oil has higher content of the polycyclic aromatic hydrocarbon, and the method does not reduce the carbon deposition reaction by adjusting the properties of the catalyst, so the pressure drop of the reactor cannot be greatly reduced. The method does not combine the polycyclic aromatic hydrocarbon reaction conditions in different reaction areas with the physicochemical properties of the catalyst, thereby further reducing the carbon deposition of a catalyst bed and increasing the activity of the hydrofining agent.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a novel hydrofining process. By adopting a novel catalyst grading method, the defect that the top of a catalyst system is easy to coke in the existing hydrofining process, so that the device is frequently skimmed is overcome.

A hydrofinishing process comprising the following:

mixing raw oil with hydrogen, and passing through a hydrofining reaction zone to obtain a hydrofining reaction effluent; the hydrofining reaction zone comprises a plurality of hydrofining catalyst beds, the metal content of the catalyst in the hydrofining catalyst beds is sequentially increased according to the contact sequence of the hydrofining catalyst beds and the raw oil, the total acid content of the catalyst is sequentially increased, the acid content of the acid B is sequentially reduced, and the acid content of the acid L is sequentially increased.

Wherein, the raw oil is conventional diesel oil or wax oil raw material. The distillation range of the raw oil is generally 200-550 ℃, and a high-nitrogen raw material with the nitrogen content of more than 1000 mu g/g is preferred. When processing inferior raw materials, such as coking diesel oil, coking wax oil and the like, protective agents, including demetallizing agents, carbon residue removing agents, silicon capturing agents and the like, are filled before a hydrofining agent.

The hydrofining reaction zone usually comprises 2-6 hydrofining catalyst beds, and preferably comprises 3-5 hydrofining catalyst beds.

According to the contact sequence with the raw oil, in two adjacent hydrofining catalyst beds, compared with an upstream bed catalyst, the total acid amount of the catalyst in a downstream bed is 0.02-0.2 mmol/g, the acid amount of B acid is 0.01-0.1 mmol/g, and the acid amount of L acid is 0.03-0.3 mmol/g.

In the hydrorefining catalyst, the content of active metal components in terms of oxides is 10-60%, preferably 15-40%, based on the weight of the catalyst. The total infrared acid amount of the hydrofining catalyst is 0.1-1.2 mmol/g, preferably 0.2-0.80 mmol/g; the ratio of L acid/B acid is 1 to 15, preferably 2 to 10. The average pore diameter of the catalyst is generally 1-30 nm, preferably 2-20 nm; the pore volume is 0.10-1.20 cm³Preferably 0.20 to 0.80 cm/g³(ii)/g; the particle size is 1 to 30 mm, preferably 2 to 20 mm. The carrier of the hydrofining catalyst comprises alumina.

Hydrofining catalysts are typically supported on refractory inorganic porous materials using metal oxides containing elements from group viii and group vib of the periodic table. The catalyst is prepared by using gamma-alumina as a carrier, preparing a catalyst precursor through an impregnation process, and drying and roasting the catalyst precursor in a plurality of steps to prepare the finished catalyst. However, the hydrofining catalyst using gamma-alumina as a carrier has the characteristic of more surface hydroxyl groups, so that the acting force of catalyst metal and the gamma-alumina carrier is larger, and the dispersion degree of active metal is not high. In addition, because all alumina carriers only have L acid centers, even if metal is loaded or an auxiliary agent is added, B acid centers are still few, and the requirements of ultra-deep desulfurization and denitrification cannot be met.

Amorphous silica-alumina supports as well as general zeolite molecular sieves have B acid centers. The carriers have better aromatic hydrocarbon conversion capability, can improve the desulfurization and denitrification effects of the refining agent, and can reduce coking after aromatic hydrocarbon aggregation. For high-nitrogen raw materials, the acid center of the zeolite molecular sieve carrier is not resistant to nitrogen and is easy to be poisoned by alkaline nitrogen, and the molecular sieve has strong acidity, so that a large amount of secondary cracking can be caused, and the operation stability of a product liquid collection device is influenced. The amorphous silicon-aluminum carrier has good nitrogen resistance, good activity stability, high liquid yield, long service life and easy modification, and can realize flexible regulation and control of acidity, acid content, pore property and the like. Therefore, the hydrofining agent can be doped with an amorphous silicon-aluminum carrier, so that the acid property of the hydrofining agent can be adjusted, and the aim of ultra-deep desulfurization and denitrification is fulfilled. In order to adjust the total acid, L acid and B acid of the catalyst, amorphous silica-alumina is preferably further included in the catalyst. Wherein, the content of amorphous silicon-aluminum is 5-40%, preferably 10-30% based on the weight of the catalyst; the content of alumina is 50 to 95w%, preferably 60 to 85%.

The hydrofining agent takes alumina and amorphous silicon-aluminum as carriers, and can be purchased or prepared in laboratories. The preparation method of alumina can refer to patents CN103769125A, CN103787394A and CN 103787393A. The properties of the alumina were controlled as follows: the average pore diameter is 2-20 nm, preferably 5-15 nm; the pore volume is 0.2-1.5 cm³Preferably 0.6 to 1.2 cm/g³(ii)/g; the specific surface area is 100-800 m²•g^-1Preferably 200 to 600 m²•g^-1. The preparation method of amorphous silicon aluminum can refer to patents CN1210755A, CN 102039197A, CN1597093A, and its properties are generally controlled as follows: 5-60 w% of silicon oxide, preferably 10-50 w%; the specific surface area is 200-800 m²Preferably 300 to 700 m/g²A pore volume of 0.6-2 cm/g³Preferably 1.0 to 1.6 cm/g³(ii)/g; the total infrared acid amount is 0.1-0.8 mmol/g, preferably 0.2-0.7 mmol/g, and the molar ratio of L/B acid amount is = 1-6, preferably 2-5. By controlled oxidation of amorphous silica-alumina supportThe content of silicon, the roasting time and the roasting temperature so as to adjust the acid properties of the amorphous silicon-aluminum, particularly the total acid content and the B acid content.

The hydrofining catalyst uses metals in the VIII family and the VIB family as active metal components, the metals in the VIII family are Co and/or Ni, and the metals in the VIB family are W and/or Mo. The preparation method of the hydrofining catalyst comprises the following steps: respectively preparing alumina and amorphous silica-alumina, uniformly mixing two carriers (the alumina and the amorphous silica-alumina), adding an adhesive, fully rolling and forming, and then drying and roasting to obtain a catalyst carrier; and (3) dipping the catalyst intermediate obtained in the step by using a dipping solution containing an active metal component, and then drying and roasting the catalyst intermediate to obtain the hydrofining catalyst.

According to a preferred embodiment of the present invention, in the hydrofinishing catalyst grading process, the metal content is gradually reduced, the average pore diameter is gradually reduced, the pore volume is gradually reduced, and the particle size is gradually reduced.

Taking a three-bed hydrofining reactor as an example, the specific optimization implementation mode is as follows. The content of metal components of the hydrofining agent in the first bed layer is 5-22 w% (calculated by metal oxides), the average pore diameter is 10-20nm, and the pore volume is 0.60-0.80 cm³(g) the particle diameter is 3-20 mm. The metal component content of the hydrofining agent in the second bed layer is 10-25 w% (calculated by metal oxide), the average pore diameter is 8-15nm, and the pore volume is 0.40-0.60 cm³Per gram, the particle size is 2-10 mm. The content of metal components of the hydrofining agent in the third bed layer is 15-40 w% (calculated by metal oxide), the average pore diameter is 2-10nm, and the pore volume is 0.20-0.40 cm³(g) the particle size is 1-6 mm.

The process conditions of the hydrofining reaction zone comprise: the average reaction temperature is 280-450 ℃, preferably 300-420 ℃, and most preferably 330-400 ℃; the partial pressure of the reaction hydrogen is 6-20 MPa, preferably 8-18 MPa, and most preferably 10-16 MPa; the volume ratio of the hydrogen to the oil is 300-2000, preferably 400-1800, and most preferably 600-1200; the liquid hourly space velocity is 0.1-2 h^-1Preferably 0.2 to 1.8 hours^-1Preferably 0.5 to 1.5 hours^-1。

The hydrofining process has the beneficial effects that:

1. the invention deeply explores the relationship between coking and polycyclic aromatic hydrocarbon hydrogenation through the research on the coking problem at the top of the reactor of the hydrorefining device. And grading the total acid amount of the hydrofining catalyst according to the reaction depth of the polycyclic aromatic hydrocarbons in different reaction areas of the hydrofining device. Along the material flow direction, the total acid amount of the catalyst is gradually reduced, and the hydrofining activity is also gradually reduced. The total acid content of the catalyst is gradually reduced, and the problems of polycyclic aromatic hydrocarbon polymerization and temperature runaway caused by high activity and temperature rise of the catalyst of the first bed layer can be effectively avoided.

2. Due to the gradual decrease of polycyclic aromatic hydrocarbon along the material flow direction, the coking precursor is gradually reduced. And the B acid center can effectively inhibit the coking of the polycyclic aromatic hydrocarbon. The method of the invention carries out grading on the acid B and the acid L, along the material flow direction, the acid B quantity is gradually reduced, and the acid L quantity is gradually increased, thereby realizing the stepwise stable saturation of the polycyclic aromatic hydrocarbon, reducing the coking and carbon deposition of a catalyst bed layer, and prolonging the service life of the catalyst and the operation period of the device.

3. According to the invention, the metal loading, the pore diameter, the pore volume and the particle size of each bed of hydrofining agent are regulated for grading, so that the stable transition of reactions such as hydrodesulfurization, denitrification, demetalization and the like can be realized, the pressure drop of the reactor and the cold hydrogen amount between beds are further reduced, and the economic benefit of enterprises is improved.

Detailed Description

The technical characteristics of the hydrofinishing agent grading of the present invention are further illustrated by the following examples. Wherein the catalyst B acid amount, the catalyst L acid amount and the (B + L) total acid amount are obtained by pyridine infrared spectrometry, the desorption temperature corresponding to the B acid and the L acid amount is 350 ℃, the adsorption temperature corresponding to the total acid amount is 150 ℃, the pore diameters and the pore volumes of different catalysts are measured by a Tristar pore volume and specific surface measuring instrument, and N is adopted₂Adsorption and desorption. The carbon content in the catalyst was measured by a high temperature combustion method using a Multi EA 2000 carbon sulfur instrument.

TABLE 1 Properties of the stock oils

TABLE 2 reaction conditions

TABLE 3 Main physicochemical Properties of amorphous silicon-aluminum

TABLE 4 composition and physicochemical Properties of catalysts in comparative and example

The raw oil used in the following examples and comparative examples was Iranian VGO, and the properties thereof are shown in Table 1. The process conditions are the same for all comparative examples and examples as shown in table 2. The alumina carrier was purchased from Nicotiana constant Corp, model YH-28, and the main properties of amorphous silica-alumina are shown in Table 3. All catalysts are laboratory agents, the physicochemical parameters of which are shown in table 4, and the metal and carrier contents in the table are theoretical addition amounts in the synthesis of the catalysts. The hydrofinishing reactors of the comparative example and example were provided with three equal reaction zones (A, B, C) with the same catalyst loading volume per reaction zone (bed).

Example 1

The reactor is filled with catalysts A1, B2 and C1 in equal proportion from the front region to the rear region, and the raw oil passes through a reactor bed layer after contacting with hydrogen.

Comparative example 1

The reactor is filled with A1 catalyst, and the raw oil is contacted with hydrogen and then passes through the bed layer of the reactor.

Example 2

The reactor is filled with catalysts A1, B1 and C1 in equal proportion from the front region to the rear region, and the raw oil passes through a reactor bed layer after contacting with hydrogen.

Comparative example 2

The reactor is filled with catalyst B1, and the raw oil is contacted with hydrogen and then passes through the bed layer of the reactor.

Example 3

The reactor is filled with catalysts A2, B2 and C1 in equal proportion from the front region to the rear region, and the raw oil passes through a reactor bed layer after contacting with hydrogen.

Comparative example 3

The reactor is filled with C2 catalyst, and the raw oil is contacted with hydrogen and then passes through the bed layer of the reactor.

The sulfur nitrogen content, removal rate and average carbon deposition per bed of catalyst of all the above comparative examples and examples are shown in Table 5.

TABLE 5 Activity evaluation results and bed carbon deposition amount (1000 h for stationary operation)

The experimental results of the comparative example and the example show that the method can reduce the carbon deposition amount of each catalyst bed layer in the hydrofining process, particularly can greatly reduce the carbon deposition amount of the first catalyst bed layer, and therefore abnormal shutdown operation caused by 'head skimming' on a reactor can be reduced or even cancelled. Moreover, the method can improve the desulfurization rate and the denitrification rate in the hydrogenation process. As can be seen from example 1 and comparative example 1, compared with the single hydrofining agent, the carbon deposition amount of all the beds after the grading is less and more uniform, the hydrodesulfurization and denitrification activities are better, and the pressure drop is lower. As can be seen from example 2 and comparative example 2, when all the materials are loaded according to the grading method of the present invention, the hydrodesulfurization rate can reach 98%, the denitrification activity is high, and the refined nitrogen content is less than 10 ppm. In addition, the total carbon amount of the catalyst bed lamination is minimum, the carbon deposition amount of each bed layer is also minimum, and the pressure drop is minimum. As can be seen from example 3 and comparative example 3, only the alumina-supported refining agent with L acid is used, the overall desulfurization and denitrification effect is poor, the carbon deposition amount of the first bed layer is too high, and the pressure drop is highest.

Claims

1. A hydrofinishing process comprising the following:

mixing raw oil with hydrogen, and passing through a hydrofining reaction zone to obtain a hydrofining reaction effluent; the hydrofining reaction zone comprises a plurality of hydrofining catalyst beds, and according to the contact sequence of the hydrofining catalyst beds and raw oil, the metal content of the catalyst in the hydrofining catalyst beds is sequentially increased, the total acid content of the catalyst is sequentially increased, the acid content of B acid is sequentially reduced, and the acid content of L acid is sequentially increased;

in two adjacent hydrofining catalyst beds, compared with an upstream bed catalyst, the total acid amount of the catalyst in a downstream bed is 0.02-0.2 mmol/g, the acid amount of B acid is 0.01-0.1 mmol/g, and the acid amount of L acid is 0.03-0.3 mmol/g;

in the hydrofining catalyst, the weight of the catalyst is taken as a reference, the content of active metal components in terms of oxides is 10-60%, the total infrared acid content is 0.1-1.2 mmol/g, and the ratio of L acid to B acid is 1-15.

2. The hydrorefining process according to claim 1, wherein the nitrogen content of the feedstock is 1000 μ g/g or more.

3. The hydrofining process according to claim 1, wherein the number of hydrofining catalyst beds is 2 to 6.

4. The hydrorefining process according to claim 1, wherein the content of the active metal component in terms of oxide is 15 to 40%, the total infrared acid amount is 0.2 to 0.80 mmol/g, and the ratio of L acid to B acid is 2 to 10, based on the weight of the hydrorefining catalyst.

5. The hydrorefining process according to claim 1, wherein the hydrorefining catalyst has an average pore diameter of 1 to 30 nm and a pore volume of 0.10 to 1.20 cm³/g。

6. The hydrorefining process according to claim 5, wherein the hydrorefining catalyst has an average pore diameter of 2 to 20nm and a pore volume of 0.20 to 0.80 cm³/g。

7. The hydrofinishing process according to claim 1, wherein said carrier of the hydrofinishing catalyst comprises alumina and amorphous silica-alumina; based on the weight of the catalyst, the content of amorphous silicon-aluminum is 5-40%, and the content of aluminum oxide is 50-95 w%.

8. The hydrofining process according to claim 7, wherein the content of amorphous silica-alumina is 10-30% and the content of alumina is 60-85% based on the weight of the hydrofining catalyst.

9. The hydrorefining process according to claim 1, wherein the hydrorefining catalyst has a gradually decreasing average pore diameter, a gradually decreasing pore volume and a gradually decreasing particle diameter in the order of contact with the feedstock.

10. The hydrofinishing process according to claim 1, wherein the process conditions of said hydrofinishing reaction zone are: the average reaction temperature is 280-450 ℃, the reaction hydrogen partial pressure is 6-20 MPa, the hydrogen-oil volume ratio is 300-2000, and the liquid hourly volume space velocity is 0.1-2 h^-1。

11. The hydrorefining process according to any one of claims 3 to 10, wherein the number of the hydrorefining catalyst beds is 3, the content of the metal component in the hydrorefining catalyst in the first bed is 5 to 22 w%, the average pore diameter is 10 to 20nm, and the pore volume is 0.60 to 0.80 cm³(ii)/g, the particle size is 3-20 mm; the metal component content of the second bed hydrofining catalyst is 10-25 w%, the average pore diameter is 8-15nm, and the pore volume is 0.40-0.60 cm³(ii)/g, the particle size is 2-10 mm; the metal component content of the third bed hydrofining catalyst15-40 w%, average pore diameter of 2-10nm, and pore volume of 0.20-0.40 cm³(iii) a particle size of 1 to 6 mm/g.