CN114437782A

CN114437782A - Coking naphtha hydrofining method

Info

Publication number: CN114437782A
Application number: CN202011126215.XA
Authority: CN
Inventors: 孙进; 郭蓉; 李扬; 郑步梅; 段为宇
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: 2020-10-20
Filing date: 2020-10-20
Publication date: 2022-05-06
Anticipated expiration: 2040-10-20
Also published as: CN114437782B

Abstract

The invention discloses a coking naphtha hydrofining method, which comprises the following steps: enabling the coked naphtha and hydrogen to flow into a hydrogenation reactor in a concurrent manner, and reacting with a catalyst; a hydrodesilicification catalyst bed layer and n hydrofining catalyst bed layers are sequentially arranged in the hydrogenation reactor along the material flowing direction, wherein n is more than or equal to 2; the N hydrofining catalyst beds are a first hydrofining catalyst bed, a second hydrofining catalyst bed and an … … Nth hydrofining catalyst bed in sequence along the material flowing direction; the volume of the hydrogenation desilication catalyst bed layer accounts for 10-50% of the total catalyst bed layer volume; according to the method, aiming at the technical processes of removing impurity silicon in the coking naphtha and olefin hydrogenation saturation, a hydrodesiliconizing agent and a hydrofining catalyst are combined and graded in a sectional mode, and a hydrogen feeding mode is adjusted, so that the carbon deposition resistance and the desiliconizing resistance of the catalyst bed layer are improved.

Description

Coking naphtha hydrofining method

Technical Field

The invention belongs to the field of petrochemical industry, and particularly relates to a coking naphtha hydrofining method.

Background

Delayed coking is one of the important means for processing inferior heavy oil, the naphtha yield in the delayed coking process is usually about 15%, and the coking naphtha contains high content of impurities such as sulfur, nitrogen, olefin, colloid and the like, has poor stability and is not suitable for being used as motor gasoline, so many refineries are provided with coking naphtha hydrogenation devices. In the process of hydrofining of the coking naphtha, on one hand, because the content of olefin and colloid in the coking naphtha is high, the olefin is easy to be subjected to hydrogenation saturation, most of reactions are usually completed on the upper part of a catalyst bed layer, so that the heat release is huge, for example, if the coking gasoline containing 40 percent is used, the adiabatic reaction temperature rise can reach 130-170 ℃ if the reactions are completely performed, the colloid is coked at high temperature, so that the pressure drop of the device is rapidly increased, and the single start cycle of the device is short; on the other hand, because the upstream coking unit is added with the silicon-containing defoaming agent, silicon enters the reactor along with the raw oil and is deposited on the catalyst, so that the catalyst is poisoned and permanently deactivated, and the single start-up period of the device is short.

CN200710012085.5 discloses a hydrofining method of silicon-containing distillate oil, which is to pass a silicon-containing distillate oil raw material and hydrogen through at least two hydrofining catalyst beds under the hydrofining condition, wherein the silicon-containing distillate oil raw material firstly passes through a hydrogenation catalyst bed with a silicon capturing function and then passes through a conventional hydrofining catalyst bed; wherein, the hydrogenation catalyst with the function of silicon capture has larger pore volume and specific surface area and relatively lower metal content. The method has simple process, keeps good hydrodesulfurization and hydrodenitrogenation performances on the premise of improving the silicon capacity, and has a certain effect of prolonging the running period of the device.

CN201310397681.5 discloses a method for hydrofining silicon-containing coking distillate oil, which comprises the following steps: passing the silicon-containing coking distillate oil raw material through a hydrofining catalyst bed layer added with a desiliconization agent, removing a silicon-containing compound under the action of the desiliconization agent, and carrying out hydrofining reaction; the reaction pressure is 2-8 MPa, and the weight airspeed is 2.0-8.0 h^-1The reaction temperature is 200-280 ℃, and the volume ratio of hydrogen to oil is 50-100: 1Nm³/m³(ii) a The desiliconization agent takes alumina and MCM-41 molecular sieve as carriers, the pore volume is 0.7-1.2 mL/g, and the specific surface area is 500-800 m²The MCM-41 molecular sieve content in the carrier is 5-20 wt%; supporting metals Ni and W, WO₃The content of the NiO is 1-5 wt% of the carrier, and the NiO content is1-5 wt% of a carrier; the method is used for deep desilication of the coking distillate oil, and the coking distillate oil hydrofining catalyst is protected from silicon poisoning.

In the scheme, the conventional hydrofining catalyst beds are single beds, and the problem that the heat release of the olefin hydrogenation reaction is concentrated on the upper part of the refining catalyst, so that the pressure drop generated by the colloid coking on the upper part is rapidly increased, and the single start cycle of the device is short is considered. Therefore, if the operation period of the coker naphtha hydrogenation unit is further increased, on one hand, the silicon capacity of the desilication catalyst needs to be increased, and the situation that the hydrofining catalyst is subjected to silicon poisoning due to insufficient silicon capacity is avoided when the operation period is prolonged; on the other hand, the whole bed layer of the hydrofining catalyst needs to release heat uniformly through process flow improvement, and rapid coking and inactivation of part of the catalyst caused by over-high local temperature are avoided.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a coking naphtha hydrofining method. Aiming at the technical processes of impurity silicon removal and olefin hydrogenation saturation in the coking naphtha, the method adopts a novel hydrogenation desiliconization agent and hydrogenation refining catalyst combination sectional grading, and adjusts the scheme of sectional hydrogen feeding, thereby being beneficial to the long-period stable operation of the device.

The coking naphtha hydrofining method comprises the following steps: enabling the coked naphtha and hydrogen to flow into a hydrogenation reactor in a concurrent manner, and reacting with a catalyst; a hydrodesilicification catalyst bed layer and n hydrofining catalyst bed layers are sequentially arranged in the hydrogenation reactor along the material flowing direction, wherein n is more than or equal to 2, and preferably 3-5; the N hydrofining catalyst beds are a first hydrofining catalyst bed, a second hydrofining catalyst bed and an … … Nth hydrofining catalyst bed in sequence along the material flowing direction; the volume of the hydrogenation desilication catalyst bed layer accounts for 10-50% of the total catalyst bed layer volume; the catalyst active metals in the N hydrofining catalyst beds are increased layer by layer from the first layer to the Nth layer, preferably, the increase range between two adjacent layers is 1-30%, and more preferably 3-20%.

In the method, the filling volumes of the hydrogenation catalysts filled in each hydrogenation refining catalyst bed layer can be equal or unequal, a scheme that the filling volumes of the catalysts are increased layer by layer is preferably adopted, the volume of the catalyst in each layer is taken as a reference, and the volume of the catalyst in each layer is increased by 10-60% compared with that in the previous layer, namely the increase amplitude of the hydrogenation refining catalyst bed layers in the two adjacent layers is 10-60%.

In the method, hydrogen enters the hydrodesilicification and hydrofining catalyst bed layer in a sectional feeding mode, wherein the hydrogen feeding amount of the hydrodesilicification catalyst bed layer is 25-50% of the total hydrogen feeding amount; the hydrogen make-up feed amount of each bed layer of hydrofining is carried out as follows: the volume of the N bed hydrofining catalyst is recorded as V_nAnd the active metal content of the N bed hydrofining catalyst is recorded as M_nThe required make-up hydrogen feed is denoted as H_nThe total feed quantity of the hydrogen for the total supply of the n hydrofining catalyst beds is H, the adjustment coefficient is recorded as A, and the feed quantity of the hydrogen for each bed is

(ii) a Wherein A is 0.5-1.5, and is adjusted according to the temperature control requirement of each bed layer.

In the method of the invention, the reaction conditions in the hydrogenation reactor are as follows: the reaction pressure is 1-10 MPa, the volume ratio of hydrogen to oil is 50-1000: 1, and the volume space velocity (calculated by a hydrofining catalyst) is 0.5-8.0 h^-1And the reaction temperature is 200-400 ℃. The specific process conditions can be adjusted according to the quality difference of the raw materials.

In the method, the hydrofining catalyst can be a commercial hydrofining catalyst selected as required or prepared according to the general knowledge in the field, and the catalyst generally takes alumina as a carrier, takes one or more of W, Mo, Ni and Co as an active hydrogenation component, and can contain one or more of P, Si, F, B, Ti, Zr and the like as an auxiliary agent. Wherein the content of the total active metal components is 3-35%, and the preferable molar ratio of (W + Mo)/(Ni + Co) is 1-5%.

In the method, the hydrogenation desilication catalyst has the following properties: the total acid amount of the catalyst is 0.3-0.7 mmol/g, wherein the medium-strength acid amount at 250-450 ℃ is 0.2-0.4 mmol/g; the specific surface of the catalyst is 200-400 m²Preferably 250 to 350 m/g²Per g, pore volume is 0.4 to1.0mL/g, preferably 0.5-0.9 mL/g, and an average pore diameter of 4-15 nm, preferably 5-12 nm.

The hydrogenation desilication catalyst comprises a carrier and a hydrogenation active component, wherein the carrier is a Zr and rare earth element modified alumina carrier, the rare earth element is one or more of Ce, La or Y, the hydrogenation active component is Ni and X, wherein X is Mo and/or W, and Zr is ZrO based on the total weight of the catalyst₂2-20% of the total amount, preferably 4-18%, 0.5-3% of rare earth elements in terms of oxides, 3-10% of Ni in terms of NiO, and 1-4% of X in terms of oxides; the molar ratio of Ni to X is 3-25, preferably 5-20, and more preferably 6-15.

The preparation method of the hydrogenation desilication catalyst comprises the following steps:

(1) introducing Zr and rare earth elements in a parallel flow manner in the gelling process of the alumina to obtain slurry;

(2) adjusting the pH value of the slurry obtained in the step (1) to 8-11, aging under a certain pressure, filtering, washing, drying, performing a molding process to obtain a Zr and rare earth element modified alumina carrier, and loading a hydrogenation active component on the carrier to obtain the desilication catalyst.

In the method, the alumina gelling process in the step (1) is a method well known in the art, and generally adopts an acid-base neutralization process, specifically an operation mode of forming gel by two materials in a parallel flow mode, or an operation mode of placing one material in a gelling tank and continuously adding the other material into gelling. The gelling material typically comprises a source of aluminum (Al)₂(SO₄)₃、AlCl₃、Al(NO₃)₃And NaAlO₂One or more of the above), precipitant (NaOH, NH)₄OH or CO₂Etc.), can be selected according to different gelling processes. The conventional operation modes mainly comprise: (1) acidic aluminum salt (Al)₂(SO₄)₃、AlCl₃、Al(NO₃)₃) With alkaline aluminium salts (NaAlO)₂) Or alkaline precipitants (NaOH, NH)₄OH) neutralization to form gel, 2 alkaline aluminum salt (NaAlO)₂) With acidic precipitants (CO)₂Nitric acid) to form gel. The pH value of the neutralized slurry is 6-10, preferablySelecting 6.5-9.5. The neutralization temperature is 30-100 ℃, preferably 45-95 ℃.

In the method of the present invention, Zr in the step (1) is one or more selected from water-soluble zirconium salts such as zirconium nitrate, zirconium sulfate, zirconium oxychloride and the like.

In the method of the present invention, the rare earth element in step (1) is derived from a water-soluble salt of a rare earth element, such as nitrate, sulfate, and more preferably cerium nitrate, lanthanum sulfate, yttrium nitrate, or the like.

In the method of the present invention, Al is contained in the slurry obtained in the step (1)₂O₃：H₂The mass ratio of O is 15-65: 1000

In the method of the present invention, in step (2), organic base and/or inorganic base may be used to adjust the pH value, organic amine is preferably used, and organic amine with carbon number less than 15 is further preferably used, such as one or more of ethylamine, propylamine, dimethylamine, ethylenediamine, dipropylamine, butylamine, diethylamine, diisopropylamine, hexyldiamine, 1, 2-dimethylpropylamine, sec-butylamine, 1, 5-dimethylhexylamine, ethylenediamine, 1, 2-propylenediamine, 1, 4-butylenediamine, monoethanolamine, diethanolamine, triethanolamine, 3-propanolamine, monoisopropanolamine, diisopropanolamine, triisopropanolamine, tetramethylammonium hydroxide, tetraethylammonium hydroxide or tetrapropylammonium hydroxide; preferably, the pH is adjusted to 8.5 to 10.5.

In the method of the present invention, the aging process of step (2) is generally performed in a pressure-resistant vessel, such as a high-pressure reaction kettle; the aging conditions are as follows: the aging temperature is 100-200 ℃, preferably 150-200 ℃, and the aging time is 6-48 hours, preferably 12-36 hours; the aging pressure is the autogenous pressure of the system.

In the method of the present invention, the drying conditions in step (2) are as follows: the drying temperature is 80-150 ℃, and the drying end point is that the water content of the powder is not higher than 30%.

In the method of the present invention, the carrier in step (2) is formed by a method well known in the art, for example, adding an extrusion aid, a peptizing agent and water into the composite powder to mix into a plastic body, and then kneading, forming, drying and roasting to obtain the carrier. Wherein the extrusion aid is one or more of methylcellulose, sesbania powder, starch and polyvinyl alcohol. The peptizing agent is one or more of dilute nitric acid, dilute phosphoric acid and silicic acid. Wherein the kneading, molding, drying and baking are carried out by the conventional method in the field. The drying condition is that the temperature is not higher than 130 ℃, and preferably 90-120 ℃. The roasting condition is that the temperature is not higher than 800 ℃, and preferably 450-750 ℃.

In the method, the loading mode in the step (2) can adopt a conventional impregnation method, the carrier is impregnated by impregnation liquid containing the hydrogenation active component, and then the carrier is dried and roasted to obtain the desilication catalyst, wherein the drying temperature in the process is 80-150 ℃, and the roasting temperature is 250-750 ℃.

Compared with the prior art, the inventor improves the long-period stable operation of the whole coking naphtha hydrogenation unit by improving the desiliconization capacity of the desiliconization catalyst, combining the desiliconization catalyst and the hydrofining catalyst in a grading way and adjusting the scheme of sectional hydrogen feeding. As for the novel hydrodesiliconizing agent, Zr and rare earth elements are added in the gelling process of alumina powder, and under the conditions of certain pressure and the existence of amine, the forming and the growth of alumina particles are guided, the pore structure of the alumina powder is increased, and the silicon capacity of the catalyst is improved. In addition, through carrier modification, the medium-strength acid content of the prepared catalyst at 250-450 ℃ is superior to that of a common catalyst, so that the catalyst has excellent silicon conversion and removal performance. Compared with the hydrogenation active metal Ni and Mo and/W of the coking naphtha desilication catalyst in the prior art, the molar ratio of the hydrogenation active metal Ni to the hydrogenation active metal Mo and/W is generally 0.2-1.3, such as CN 200910188090.0. The inventor accidentally finds that when the molar ratio of Ni to Mo and/W is 3-25, the medium-strength acid content of the catalyst at 250-450 ℃ is higher than that of a common catalyst, the remarkably excellent hydrogenation performance can still obviously reduce the carbon deposition on the surface of the catalyst, reduce the carbon deposition inactivation rate of the desiliconization catalyst and improve the silicon-containing capacity of the catalyst. Active grading of a hydrofining catalyst and hydrogen supplement are adopted for segmented feeding, the reaction depth is controlled by adjusting the activity of the catalyst and the hydrogen partial pressure, and the olefin hydrogenation saturation reaction is dispersed to each catalyst bed layer from the upper section of the hydrofining catalyst, so that the reaction heat is released stably; hydrogen is supplemented between each bed layer, and the hydrogen not only serves as a reaction raw material to participate in the reaction, but also serves as a cold source, so that the bed layer temperature is controlled by adjusting the hydrogen feeding amount of each bed layer, and further the reaction rate is controlled. Through catalyst gradation and temperature control of the whole catalyst bed, the carbon deposition rate of each layer of catalyst is matched with the service life of the catalyst, and two problems in the long-period operation process are effectively solved: 1. the problem of removing more impurity silicon in the raw oil; 2. the pressure drop of the device is rapidly increased due to coking of the upper hydrofining catalyst, and the running period of the device can be effectively prolonged.

Detailed Description

The following examples further illustrate the present invention and the effects thereof, but are not intended to limit the present invention.

The infrared acid amount of the catalyst is tested according to a Q/SHFRIPP 040024-one 2001 method, specifically, pyridine reagent is adopted to carry out gas-solid adsorption under certain steam pressure, then the change of an adsorbed vibration band and a sample pressure surface acid hydroxyl band is measured by infrared spectrum, and the acid amount of different types is calculated according to the absorption coefficient. The specific surface area, pore volume and pore diameter of the catalyst are tested according to the method of GB/T19587-2017. The content of metal on the catalyst was analyzed by X-ray fluorescence spectrometry.

The following examples and comparative examples illustrate the desilication effect of the novel hydrodesiliconizing agent.

Example 1

1000g of aluminum nitrate, 100g of zirconium nitrate, 6g of cerium nitrate and 3000g of water are prepared into an aqueous solution, and then the aqueous solution and a sodium hydroxide solution with the mass concentration of 20% are added into a reaction kettle containing 1L of purified water in a concurrent flow mode, and the temperature of the reaction kettle is controlled to be 50 ℃. Controlling the flow rate of the liquid to ensure that the pH value of the solution in the reaction tank is constant at 7.4, and neutralizing the mixed solution of aluminum nitrate for 180min to obtain slurry after the reaction is finished.

To the resulting slurry was added a small amount of tetramethylammonium hydroxide to adjust the pH of the slurry to 8.8. Putting the mixture into a closed high-pressure kettle, aging the mixture for 24 hours at 185 ℃, taking the mixture out, washing and filtering the mixture, and drying the mixture at 120 ℃ to obtain the composite powder.

And (3) crushing and sieving the obtained composite powder (200 meshes), adding 2g of sesbania powder, 15g of 10% nitric acid and 110mL of deionized water, molding, drying at 110 ℃, and roasting at 550 ℃ to obtain the carrier.

And soaking the obtained carrier in an aqueous solution prepared from 60g of nickel nitrate and 4g of ammonium heptamolybdate in the same volume, drying at 110 ℃, and roasting at 550 ℃ to obtain the catalyst Cat-1.

Example 2

30g of zirconium sulfate, 16g of lanthanum sulfate and 1000g of water are prepared into a water solution, and then the water solution and 1L of sodium metaaluminate solution with the concentration of 400g/L are added into a reaction kettle containing 1L of purified water in a concurrent flow mode, and the temperature of the reaction kettle is controlled to be 65 ℃. And simultaneously adding 10% sulfuric acid in a parallel flow manner, controlling the flow rate of the liquid, keeping the pH value of the solution in the reaction tank constant at 8.0, and neutralizing for 90min to obtain slurry after the mixed solution of zirconium and lanthanum and the sodium metaaluminate solution react.

A small amount of triethanolamine was added to the resulting slurry to adjust the pH of the slurry to 9.2. Putting the mixture into a closed high-pressure kettle, aging the mixture for 30 hours at 160 ℃, taking the mixture out, washing and filtering the mixture, and drying the mixture at 110 ℃ to obtain the composite powder.

And (3) crushing and sieving the obtained composite powder (200 meshes), adding 2.1g of sesbania powder, 16g of 10% nitric acid and 115mL of deionized water, molding, drying at 110 ℃, and roasting at 650 ℃ to obtain the carrier.

And soaking the obtained carrier into an aqueous solution prepared from 70g of nickel nitrate and 9g of ammonium metatungstate in equal volume, drying at 110 ℃, and roasting at 450 ℃ to obtain the catalyst Cat-2.

Example 3

1000g of aluminum nitrate, 150g of zirconium nitrate, 12g of cerium nitrate and 3000g of water are prepared into an aqueous solution, and then the aqueous solution and a 20% sodium hydroxide solution are added into a reaction kettle containing 1L of purified water in a concurrent flow manner, and the temperature of the reaction kettle is controlled to be 75 ℃. Controlling the flow rate of the liquid to ensure that the pH value of the solution in the reaction tank is constant at 8.6, and neutralizing the mixed solution of aluminum nitrate for 180min to obtain slurry after the reaction is finished.

A small amount of ethylenediamine was added to the resulting slurry to adjust the pH of the slurry to 9.6. Putting the mixture into a closed high-pressure kettle, aging the mixture for 24 hours at 170 ℃, taking the mixture out, washing and filtering the mixture, and drying the mixture at 110 ℃ to obtain the composite powder.

And (3) crushing and sieving the obtained composite powder (200 meshes), adding 2.6g of sesbania powder, 19g of 10% nitric acid and 130mL of deionized water, molding, drying at 110 ℃, and roasting at 500 ℃ to obtain the carrier.

And soaking the obtained carrier in an aqueous solution prepared from 40g of nickel nitrate, 2g of ammonium heptamolybdate and 3g of ammonium metatungstate in the same volume, drying at 110 ℃, and roasting at 650 ℃ to obtain the catalyst Cat-3.

Example 4

1000g of aluminum nitrate, 70g of zirconium nitrate, 15g of yttrium nitrate and 3000g of water are prepared into an aqueous solution, and then the aqueous solution and a 20% sodium hydroxide solution are added into a reaction kettle containing 1L of purified water in a concurrent flow manner, and the temperature of the reaction kettle is controlled to be 85 ℃. Controlling the flow rate of the liquid to ensure that the pH value of the solution in the reaction tank is constant at 9.2, and neutralizing the mixed solution of aluminum nitrate for 180min to obtain slurry after the reaction is finished.

A small amount of tetraethylammonium hydroxide was added to the resulting slurry to adjust the pH of the slurry to 10. Putting the mixture into a closed high-pressure kettle, aging the mixture for 24 hours at 190 ℃, taking the mixture out, washing and filtering the mixture, and drying the mixture at 110 ℃ to obtain the composite powder.

And (3) crushing and sieving the obtained composite powder (200 meshes), adding 2.2g of sesbania powder, 17g of 10% nitric acid and 120mL of deionized water, forming, drying at 110 ℃, and roasting at 550 ℃ to obtain the carrier.

Soaking the obtained carrier in an aqueous solution prepared from 50g of nickel nitrate, 4g of ammonium heptamolybdate and 5g of ammonium metatungstate in equal volume, drying at 110 ℃, and roasting at 700 ℃ to obtain the catalyst Cat-4.

Comparative example 1

The synthesis scheme of example 1 was repeated, but zirconium nitrate was not added during the synthesis of the composite powder, to obtain comparative catalyst Cat-5.

Comparative example 2

The synthesis scheme of example 1 was repeated, but cerium nitrate was not added during the synthesis of the composite powder, to obtain comparative catalyst Cat-6.

Comparative example 3

The synthesis scheme of example 1 was repeated, but the aging process was reduced during the synthesis of the composite powder to obtain comparative catalyst Cat-7.

Comparative example 4

The synthesis scheme of example 4 was repeated, but in the course of impregnating the desiliconized catalyst with the active metal component, an aqueous solution prepared from 50g of nickel nitrate, 10.5g of ammonium heptamolybdate and 9.6g of ammonium metatungstate was impregnated in an equal volume, followed by drying at 110 ℃ and calcination at 550 ℃ to obtain comparative catalyst Cat-8.

Comparative example 5

The synthesis scheme of example 1 was repeated, but in the course of impregnating the desiliconized catalyst with the active metal component, an aqueous solution prepared from 50g of nickel nitrate, 0.6g of ammonium heptamolybdate and 1g of ammonium metatungstate was impregnated in an equal volume, followed by drying at 110 ℃ and calcination at 550 ℃ to obtain comparative catalyst Cat-9.

Comparative example 6

Catalyst Cat-10 was prepared as in CN200910188090.0, example 7.

The properties of all prepared catalysts are shown in table 1 below.

TABLE 1 catalyst key Properties

The desiliconization performance and the carbon deposition resistance evaluation of the catalyst are carried out on a 100mL small hydrogenation device, and the catalyst evaluation process conditions are as follows: the reaction pressure is 5.0MPa, the volume ratio of hydrogen to oil is 500, and the volume airspeed is 2.5h^-1The reaction temperature was 280 ℃. The raw material is industrial coking naphtha and 0.01 percent of hexamethylcyclotrisiloxane is added, and the bromine number is 80gBr/100 g. The catalyst was sampled for analysis after 60 days on stream and the Si and C content on the catalyst is shown in Table 2 below.

TABLE 2 Si, C content of the catalyst after operation

As can be seen from Table 2, under the same evaluation process conditions, the desilication catalyst of the invention has a better silicon removal effect than the comparative desilication catalyst, and the carbon deposition amount on the catalyst is greatly reduced, and the catalyst has good desilication and carbon deposition resistance, so that the catalyst has long-period high silicon capacity, and avoids silicon poisoning of a downstream hydrofining catalyst caused by impurity silicon penetrating through a bed layer.

The following examples and comparative examples illustrate the effect of the novel desilication catalyst and hydrofinishing catalyst combined grading/staged hydrogen addition.

According to the method, the whole naphtha hydrofining reactor unit is divided into a desiliconization agent unit and three hydrofining units, three hydrofining catalysts meeting requirements, a novel desiliconization agent and a comparative desiliconization agent are provided, and the three hydrofining catalysts, the novel desiliconization agent and the comparative desiliconization agent are subjected to catalyst grading filling and are used for the hydrofining reaction of the coking naphtha.

Example 5

The catalyst grading scheme is shown in table 3.

TABLE 3 catalyst grading scheme

Example 6

The catalyst grading scheme is shown in table 4.

TABLE 4 catalyst grading scheme

	Silicon removal region	Refining bed 1	Refining bed 2	Refining bed 3
					WO₃，wt%	0.88	7.25	8.40	13.60
MoO₃，wt%	0.54	3.25	4.60	6.40
					NiO，wt%	5.13	2.50	3.00	3.00
CoO，wt%	-	-	-
					Filling volume, v%	25	18	23	34
The hydrogen supplement proportion%	30	13	15	42

Comparative example 7

The hydrofining catalyst does not adopt a grading and zoning hydrogen supplement method, the catalyst is selected from a catalyst with moderate metal content and activity, and the filling scheme is as follows:

TABLE 5 catalyst loading scheme

	Silicon removal region	Refining bed layer
			WO₃，wt%	0.88	9.75
MoO₃，wt%	0.54	4.75
			NiO，wt%	5.13	2.83
CoO，wt%	-	-
			Filling volume, v%	30	70
The hydrogen supplement proportion%	100	0

Comparative example 8

The catalyst cat-10 prepared in the comparative example 6 is selected as the desilication catalyst, the grading and zoning hydrogen supplement method in the example 6 is adopted, and the filling scheme is as follows:

TABLE 6 catalyst grading Loading scheme

	Silicon removal region	Refining bed 1	Refining bed 2	Refining bed 3
					WO₃，wt%	5.00	7.25	8.40	13.60
MoO₃，wt%	2.00	3.25	4.60	6.40
					NiO，wt%	2.00	2.50	3.00	3.00
CoO，wt%	-	-	-
					Filling volume, v%	25	18	23	34
A hydrogen supplement proportion%	30	13	15	42

The process conditions evaluated were: the reaction pressure is 5.0MPa, the volume ratio of hydrogen to oil is 500, and the volume airspeed is 2.5h^-1And the reaction inlet temperature was 260 ℃. The raw material was a pacified coker naphtha, the properties of which are shown in table 7. After 1000 hours of operation, the hydrofining catalyst was sampled and analyzed, and in order to compare the carbon deposit and silicon deposit contents of the catalyst at different positions, the hydrofining catalyst in comparative example 7 was divided into three parts according to the bed positions of example 5, and the specific data are shown in table 8 below.

Table 7 compliant coker naphtha properties

Density (20), g/cm³	0.7315
		Distillation range, deg.C
Initial boiling point to final boiling point	53~198
		Sulfur,. mu.g/g	1135
Nitrogen,. mu.g/g	123
		Silicon,. mu.g/g	3.3
Olefin, v%	45.2

TABLE 8 amount of deposited carbon/silicon on hydrofinishing catalyst

As can be seen from the results of the deposition amounts of carbon/silicon on the hydrorefining catalyst in table 8, in comparative example 7, a method of catalyst grading and staged hydrogen supplement is not employed, and the amount of carbon deposited on the upper portion of the hydrorefining catalyst increases significantly after a long-time operation, which is likely to cause coking of the catalyst and increase in pressure drop of the apparatus, and is not favorable for long-term operation of the whole unit. Comparative example 8 no novel desilication catalyst was selected, and the amount of silicon deposition on the hydrorefining catalyst after a long operation was significantly higher than that of the corresponding example, which was also disadvantageous for a long-term operation of the whole unit.

Claims

1. A coking naphtha hydrofining method is characterized by comprising the following steps: enabling the coked naphtha and hydrogen to flow into a hydrogenation reactor in a concurrent manner, and reacting with a catalyst; a hydrodesilicification catalyst bed layer and n hydrofining catalyst bed layers are sequentially arranged in the hydrogenation reactor along the material flowing direction, wherein n is more than or equal to 2, and preferably 3-5; the N hydrofining catalyst beds are first to Nth hydrofining catalyst beds in sequence along the material flowing direction; the volume of the hydrogenation desilication catalyst bed layer accounts for 10-50% of the total catalyst bed layer volume; the active metal content of the catalyst in the N hydrofining catalyst bed layers is increased from the first layer to the Nth layer by layer.

2. The method of claim 1, wherein: in the n hydrofining catalyst beds, the increase range between two adjacent layers is 1-30%, and the more preferable range is 3-20%.

3. The method of claim 1, wherein: in the n hydrofining catalyst beds, the filling volume of the hydrofining catalyst increases layer by layer, and the increase amplitude between two adjacent layers is 10-60%.

4. The method of claim 1, wherein: hydrogen enters each catalyst bed layer in a sectional feeding mode, wherein the feeding amount of the hydrogen of the hydrogenation and desilication catalyst bed layer is 25-50% of the total feeding amount of the hydrogen.

5. A method as claimed in claim 1, characterized by: the hydrogen make-up feed amount of each bed layer of hydrofining is carried out as follows: the volume of the N bed hydrofining catalyst is recorded as V_nAnd the active metal content of the N bed hydrofining catalyst is recorded as M_nThe required make-up hydrogen feed is denoted as H_nThe total feed quantity of the hydrogen for the total supply of the n hydrofining catalyst beds is H, the adjustment coefficient is recorded as A, and the feed quantity of the hydrogen for each bed is

(ii) a Wherein A is 0.5 to 1.5.

6. The method of claim 1, wherein: the reaction conditions in the hydrogenation reactor are as follows: the reaction pressure is 1-10 MPa, the volume ratio of hydrogen to oil is 50-1000: 1, and the volume space velocity is 0.5-8.0 h calculated by a hydrofining catalyst^-1And the reaction temperature is 200-400 ℃.

7. The method of claim 1, wherein: the hydrogenation desilication catalyst comprises a carrier and a hydrogenation active component, wherein the carrier is a Zr and rare earth element modified alumina carrier, the rare earth element is one or more of Ce, La or Y, the hydrogenation active component is Ni and X, wherein X is Mo and/or W, and Zr is ZrO based on the total weight of the catalyst₂2-20% of the total amount, preferably 4-18%, 0.5-3% of rare earth elements in terms of oxides, 3-10% of Ni in terms of NiO, and 1-4% of X in terms of oxides; the molar ratio of Ni to X is 3-25, preferably 5-20, and more preferably 6-15.

8. The method of claim 7, wherein: the hydrodesilicification catalyst has the following properties: the total acid amount of the catalyst is 0.3-0.7 mmol/g, wherein the medium-strength acid amount at 250-450 ℃ is 0.2-0.4 mmol/g; the specific surface of the catalyst is 200-400 m²(iv)/g, pore volume of 0.4 to 1.0mL/g, and average pore diameter of 4 to 15 nm.

9. The method of claim 7, wherein: the preparation method of the hydrodesilicification catalyst comprises the following steps: (1) introducing Zr and rare earth elements in a parallel flow manner in the gelling process of the alumina to obtain slurry; (2) adjusting the pH value of the slurry obtained in the step (1) to 8-11, aging under a certain pressure, filtering, washing, drying, then carrying out a molding process to obtain a Zr and rare earth element modified alumina carrier, and then loading a hydrogenation active component on the carrier to obtain the desilication catalyst.

10. The method of claim 9, wherein: the Zr in the step (1) is selected from one or more of zirconium nitrate, zirconium sulfate or zirconium oxychloride water-soluble zirconium salt.

11. The method of claim 9, wherein: the rare earth element in the step (1) is from a water-soluble salt of a rare earth element.

12. The method of claim 9, wherein: al in the slurry obtained in the step (1)₂O₃：H₂The mass ratio of O is 15-65: 1000.

13. the method of claim 9, wherein: and (2) adopting organic base and/or inorganic base to adjust the pH value.

14. The method of claim 9, wherein: the aging process of the step (2) is carried out in a pressure-resistant container; the aging conditions are as follows: the aging temperature is 100-200 ℃, and the aging time is 6-48 hours; the aging pressure is the autogenous pressure of the system.

15. The method of claim 9, wherein: the drying conditions in the step (2) are as follows: the drying temperature is 80-150 ℃, and the drying end point is that the water content of the powder is not higher than 30%.