CN111748375B

CN111748375B - Method and system for producing superposed raw material by hydrorefining mixed carbon four raw material

Info

Publication number: CN111748375B
Application number: CN201910243401.2A
Authority: CN
Inventors: 张登前; 习远兵; 李中亚; 褚阳; 李会峰; 田鹏程; 李善清
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: 2019-03-28
Filing date: 2019-03-28
Publication date: 2021-12-17
Anticipated expiration: 2039-03-28
Also published as: CN111748375A

Abstract

A method for producing a superposed raw material by hydrorefining a mixed C-C raw material and a system thereof. The method comprises the following steps: the mixed C-IV raw material and inert gas contact with a mercaptan etherification catalyst in a first reactor to react, reaction effluent is separated to obtain thioether and low-sulfur mixed C-IV material, and the obtained low-sulfur mixed C-IV material contacts with a selective diene removal catalyst in a second reactor to carry out diene removal reaction to obtain a low-sulfur and low-diene mixed C-IV product. The invention greatly reduces the risk of sulfur poisoning of the selective diene-removing catalyst and obviously prolongs the service cycle of the selective diene-removing catalyst. The invention has the characteristics of simple flow, environmental sanitation, safe production, low cost and the like.

Description

Method and system for producing superposed raw material by hydrorefining mixed carbon four raw material

Technical Field

The invention relates to a method and a system for refining a mixed C-C four raw material, in particular to a method and a system for producing a superposed raw material by hydrofining the mixed C-C four raw material.

Background

Along with the establishment and implementation of the national fifth and sixth standards, the requirement of high-octane clean gasoline components is increasing day by day, and meanwhile, along with the large-scale popularization of domestic ethanol gasoline, the high-octane component methyl tert-butyl ether (MTBE) widely used for blending gasoline cannot be added into the ethanol gasoline, so that a large number of MTBE substitution technologies are developed at home and abroad in the face of the deficiency of the high-octane component of the clean gasoline. One of these is the polymerization of isobutene. The carbon tetraolefin polymerization technology can replace the MTBE technology, fully utilizes the refinery mixed carbon four raw material, and simultaneously, the polymerization product is a clean gasoline component with high octane value.

The superimposed raw material generally adopts mixed carbon four components produced by catalytic cracking and other processes, and the mixed carbon four raw material generally contains 0.1-1.2% of butadiene. In the case of the carbon tetraolefin polymerization technique, butadiene can deactivate the polymerization catalyst by rapid carbon deposition. The best way to solve this problem is to remove butadiene from the feedstock by selective hydrogenation. The raw material in the mixed carbon four is removed by adopting a hydrogenation method, and a noble metal catalyst and a liquid phase hydrogenation method, such as a supported Pd catalyst, are usually adopted. However, this technique has problems of high price of noble metal and high cost of catalyst.

In addition, in the selective hydrogenation and diene removal process of the mixed C-C four raw material, the raw material contains a certain amount of sulfur (10-200 mu g/g), and sulfur-containing compounds can poison the selective diene removal catalyst, so that the activity of the selective diene removal catalyst is rapidly reduced, and the operation cycle of the catalyst is seriously influenced. In addition, sulfides in the mixed C4 can enter the superimposed product, so that the sulfur content of gasoline blending components can not meet the requirements of national fifth and sixth standards.

In the prior art, the method for removing the sulfides in the mixed C4 mainly comprises the steps of carrying out crude desulfurization by using solid alkali, and then removing various sulfides contained in the crude desulfurization by using a hydrolytic agent or an adsorbent at one time, so that the problem of low desulfurization rate exists.

CN101249366A discloses a fine desulfurization method, which comprises the steps of firstly, carrying out coarse desulfurization on four carbon components in a refinery by using solid alkali, and then contacting with a carbonyl sulfide adsorbent to adsorb and remove most of carbonyl sulfide and mercaptan in the carbonyl sulfide; then contacting with a fine desulfurization adsorbent to adsorb and remove the residual sulfur. After the four components of the carbon in the refinery are subjected to fine desulfurization treatment by the method, the total sulfur content of the four components can be reduced to 1mg/m³The following.

CN103102987A discloses a fine desulfurization method for four carbon fractions, which comprises the steps of carrying out amine washing desulfurization and alkali washing mercaptan removal on liquefied petroleum gas which is a byproduct of a catalytic cracking device, a catalytic cracking device and the like, and then carrying out the amine washing desulfurization and alkali washing mercaptan removal on the liquefied petroleum gasThe gas separation device separates the carbon three components, the mixed carbon four fraction from the gas separation device is separated out to be rich in isobutane components and trace carbonyl sulfide COS through the top of the light component removal tower, and the rest fraction enters the heavy component removal tower; separating refined mixed carbon four fraction rich in butene component at the top of the de-heavy tower, wherein the sulfur content of the component is less than 3mg/m³。

TW201011100A discloses a process for removing mercaptans from a gaseous mixture by first feeding a gaseous mixture comprising hydrocarbons and mercaptans to a reactor, carrying out an etherification reaction over a catalyst comprising palladium and silver, and after the etherification, fractionating the reactor product mixture to separate lower boiling hydrocarbons from thioethers for the purpose of desulfurization.

Disclosure of Invention

The invention aims to provide a method and a system for producing a superposed raw material by hydrorefining a mixed C-C four raw material, which are used for solving the problems that a selective diene removal catalyst is easy to deactivate, a noble metal catalyst is high in cost and the like in the prior art.

The invention provides a method for producing a superposed raw material by hydrorefining a mixed carbon four raw material, which comprises the following steps:

(1) the mixed C4 raw material and inert gas enter a first reactor together, contact with a mercaptan etherification catalyst, and carry out mercaptan etherification reaction to ensure that most of mercaptan and diene react to generate thioether, wherein the mercaptan etherification catalyst is a non-noble metal catalyst;

(2) separating the reaction effluent obtained in the step (1) in a first separation zone to obtain four materials of thioether and low-sulfur mixed carbon,

(3) and (3) feeding the low-sulfur mixed carbon four material obtained in the step (2), hydrogen and selective regulating gas into a second reactor, contacting with a selective diene removal catalyst, performing diene removal reaction, and separating the reaction effluent of the second reactor in a second separation zone to obtain a low-sulfur low-diene mixed carbon four product, wherein the selective diene removal catalyst is a non-noble metal catalyst.

In the invention, the mixed C-C raw material is a C-C material or a C-C mixed material obtained by a catalytic cracking, atmospheric and vacuum distillation, coking and hydrocracking device, the volume fraction of butadiene in the mixed C-C raw material is 0.005-1%, the sulfur content is 10-500 mu g/g, and the mercaptan sulfur accounts for 50-98% based on the mass of a sulfur-containing compound.

In a preferable case, the inert gas in the step (1) is selected from one or more of nitrogen, helium and argon; the volume ratio of the inert gas to the mixed C-C raw material in a standard state is 10-500: 1, and preferably 20-400: 1.

In one preferred embodiment of the present invention, the reaction atmosphere in the first reactor in step (1) does not contain hydrogen, and the mixed C-C feedstock is contacted with a mercaptan etherification catalyst in an inert gas atmosphere to carry out mercaptan etherification reaction, so that most of mercaptan and diene react to form high-boiling thioether.

In another preferred embodiment of the present invention, the reaction atmosphere of the first reactor in step (1) further contains hydrogen; the method comprises the steps of enabling inert gas and hydrogen to exist in a reaction atmosphere at the same time, wherein the volume ratio of the hydrogen to the mixed carbon four raw material in a standard state is 1-100: 1, and preferably 2-60: 1.

In a preferred aspect, the reaction conditions of the first reactor in step (1) are: the pressure is 0.3-4.0 MPa, the reaction temperature is 30-250 ℃, and the volume space velocity is 1.0-20.0 h^-1. More preferred reaction conditions are: the pressure is 0.5-2.5 MPa, the reaction temperature is 60-200 ℃, and the volume space velocity is 2.0-10.0 h^-1。

In the invention, a mercaptan etherification catalyst is filled in a first reactor, and the preferred mercaptan etherification catalyst is a catalyst which is loaded on an alumina carrier and contains at least one VIII group non-noble metal component and at least one VIB group metal component, wherein the VIII group non-noble metal component is selected from cobalt and/or nickel, and the VIB group metal component is selected from molybdenum and/or tungsten; calculated by oxides and taking a mercaptan etherification catalyst as a reference, the mass fraction of the VIII group non-noble metal component is 1-40%, and the mass fraction of the VIB group metal component is 0.1-10%.

Preferably, the VIII group non-noble metal component in the mercaptan etherification catalyst is nickel, the VIB group metal component is molybdenum, the mass fraction of the nickel is 3-25% and the mass fraction of the molybdenum is 0.5-4.5% in terms of oxides and on the basis of the mercaptan etherification catalyst.

In the invention, the sulfur-containing compounds in the mixed C-C raw material mainly exist in the form of mercaptan, and in the first reactor, the mercaptan and the olefin are subjected to an addition reaction to generate the high-boiling-point thioether. And (3) separating the reaction effluent of the first reactor in the first separation zone of the step (2) to obtain the four materials of the thioether and the low-sulfur mixed carbon. Preferably, the separation is carried out in the first separation zone by adopting a fractional distillation method, the upper part of the fractional distillation tower obtains low-sulfur mixed carbon four materials, and the lower part of the fractional distillation tower obtains the thioether.

Preferably, the sulfur content of the low-sulfur mixed carbon four material is 0-10 mu g/g, and more preferably 0-6 mu g/g.

In the step (3), the low-sulfur mixed carbon four material, hydrogen and selective control gas enter a second reactor together, and contact with a selective diene removal catalyst to perform selective diene removal reaction. Preferably, the selective control gas is selected from CO and CO₂、NO、H₂One or more of S; based on the total volume of the second reactor feed mixture, the volume fraction of the selective tuning gas is: 0.001 to 10 percent. The feeding mixture of the second reactor is the mixture of low-sulfur mixed carbon four material, hydrogen and selective regulating gas entering the second reactor.

In a preferred case, the reaction conditions of the second reactor in the step (3) are as follows: hydrogen partial pressure of 0.3-4.0 MPa, reaction temperature of 30-150 ℃ and volume space velocity of 1.0-20.0 h^-1And the molar ratio of the hydro-diene is 0.5-20. Further preferred reaction conditions are: hydrogen partial pressure of 0.5-3.0 MPa, reaction temperature of 40-130 ℃ and volume space velocity of 2.0-10 h^-1And the molar ratio of the hydro-diene is 1.0-8.0.

In the invention, the second reactor is filled with a selective diene removal catalyst, and the preferred selective diene removal catalyst contains a carrier, an auxiliary agent component and a hydrogenation active metal component loaded on the carrier, wherein the carrier is alumina and/or silica-alumina, the hydrogenation active metal component comprises at least one VIII group non-noble metal component and an optional VIB group metal component, the VIII group non-noble metal component is nickel and/or cobalt, the VIB group metal component is molybdenum and/or tungsten, and the auxiliary agent component is at least one component selected from alkali metals and alkaline earth metals. In the present invention, the optional group VIB metal component means that the group VIB metal component is an optional component, and may or may not be present.

More preferably, the mass fraction of nickel and/or cobalt is 1-40%, the mass fraction of molybdenum and/or tungsten is 0-10%, and the mass fraction of the auxiliary component is 0.1-9%, calculated by oxide and based on the selective diene removal catalyst.

The preferred selective diene removal catalyst may be prepared as follows:

the hydrogenation active metal component is loaded on an alumina carrier containing alkali metal or alkaline earth metal. A certain amount of aluminum oxide containing alkali metal or alkaline earth metal is taken, dipped for 3-6 hours in a solution prepared from a compound of a hydrogenation active metal component, filtered after dipping, dried for 4-8 hours at 80-120 ℃, and then roasted for 4-6 hours at 400-500 ℃ to prepare the selective diene removal catalyst.

And separating the reaction effluent of the second reactor in a second separation zone to obtain a low-sulfur and low-diene mixed C4 product. Preferably, the volume fraction of the diolefins in the low-sulfur and low-diolefin mixed C4 product is 0-0.005%, and more preferably 0-0.003%.

The invention also provides a system for producing the superposed raw material by hydrofining the mixed C-C four raw material, which comprises a first reactor, a second reactor, a first separation area and a second separation area;

a mixed carbon four raw material pipeline and an inert gas pipeline are communicated with an inlet of a first reactor, a mercaptan etherification catalyst is filled in the first reactor, and the mercaptan etherification catalyst is a non-noble metal catalyst; the outlet of the first reactor is communicated with the inlet of the first separation area, and the first separation area is provided with a high-boiling-point thioether outlet and a low-sulfur mixed carbon four material outlet; the low-sulfur mixed carbon four material outlet is communicated with the inlet of the second reactor, the hydrogen pipeline and the selective control gas pipeline are communicated with the inlet of the second reactor, and the second reactor is filled with a selective diene removing catalyst which is a non-noble metal catalyst; the outlet of the second reactor is communicated with the inlet of the second separation zone, and the second separation zone is provided with a low-sulfur and low-diene mixed carbon four product outlet.

In a preferred case, the mercaptan etherification catalyst is a catalyst containing at least one group VIII non-noble metal component and at least one group VIB metal component, wherein the group VIII non-noble metal component is selected from cobalt and/or nickel, and the group VIB metal component is selected from molybdenum and/or tungsten, which are supported on an alumina carrier; calculated by oxides and taking a mercaptan etherification catalyst as a reference, the mass fraction of the VIII group non-noble metal component is 1-40%, and the mass fraction of the VIB group metal component is 0.1-10%.

In a preferred case, the selective diene removal catalyst comprises a carrier, an auxiliary component, and a hydrogenation active metal component supported on the carrier, wherein the carrier is alumina and/or silica-alumina, the hydrogenation active metal component comprises at least one group VIII non-noble metal component and optionally a group VIB metal component, the group VIII non-noble metal component is nickel and/or cobalt, the group VIB metal component is molybdenum and/or tungsten, and the auxiliary component is at least one component selected from alkali metals and alkaline earth metals.

The method and the system for producing the superposed raw material by hydrofining the mixed carbon four raw material can process the mixed carbon four raw material with high butadiene content and high sulfur content to produce the superposed raw material with the sulfur content of less than 10 mu g/g and the diene content of less than 0.005 volume percent. Compared with the prior art, the method has the advantages of good selectivity of desulfurization and diene removal, high yield of mono-olefin, long system running period, low cost, good environmental protection and the like.

Drawings

FIG. 1 is a schematic diagram of a system for producing a superimposed feedstock by hydrofining a mixed carbon four feedstock according to the present invention.

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 present invention will be further described with reference to the drawings, but the present invention is not limited thereto.

As shown in FIG. 1, the system for producing a superimposed feedstock by hydrorefining a mixed carbon four feedstock provided by the present invention comprises a first reactor 11, a second reactor 12, a first separation zone 5 and a second separation zone 13;

a mixed carbon four raw material pipeline 1 and an inert gas pipeline 2 are communicated with a general pipeline 3 connected with the inlet of a first reactor 11, a mercaptan etherification catalyst is filled in the first reactor, and the mercaptan etherification catalyst is a non-noble metal catalyst; the outlet of the first reactor is communicated with the inlet of a first separation zone 5 through a pipeline 4, the first separation zone 5 is a fractionating tower, the bottom of the fractionating tower is provided with a high-boiling-point thioether outlet and is connected with a pipeline 6, the top of the fractionating tower is provided with an inert gas outlet and is connected with a pipeline 7, the outlet of a low-sulfur mixed carbon four-material of the fractionating tower is connected with the inlet of a second reactor 12 through a pipeline 8, hydrogen and a selective control 9 are communicated with the inlet of the second reactor 12, a selective diene removal gas pipeline catalyst is filled in the second reactor, and the selective diene removal catalyst is a non-noble metal catalyst; the outlet 10 of the second reactor is communicated with the inlet of a second separation zone 13 which is provided with a low sulfur and low diene mixed carbon four product outlet and is communicated with a pipeline 14.

The process of the present invention is further illustrated by the following examples, but is not limited thereto.

The mercaptan etherification catalyst used in the examples was catalyst a, the carrier of catalyst a was alumina, the mass fraction of nickel was 15% and the mass fraction of molybdenum was 4% in terms of oxide and based on catalyst a. The selective diene removal catalyst is a catalyst B, a carrier of the catalyst B is lithium modified alumina, the mass fraction of nickel is 25 percent and the mass fraction of lithium is 1.2 percent based on the oxide and the catalyst B.

In order to fully exert the performance of the catalyst, the catalyst a needs to be presulfided before contacting with the main raw material. The catalyst B needs to be subjected to reduction treatment before contacting with the raw materials, and the reduction conditions are as follows: the hydrogen pressure is 0.5MPa, the temperature is 450 ℃, the reduction time is 20h, and the hydrogen volume space velocity is 200h^-1. In the following examples, the catalyst reduction process was the same.

Comparative example 1

The properties of a mixed carbon four as a raw material C are shown in Table 1. Directly feeding the mixed C-C raw material C into a reactor to contact with a catalyst B for selective diene removal reaction. The reaction conditions and product properties are shown in table 2, and it can be seen from table 2 that the sulfur content of the product is unchanged after the selective diene removal reaction of the mixed C-C four raw material, the sulfur content of the product is the same as that of the raw material, the diene content of the product reaches 0.001 vol%, the feeding requirement of the superposition technology is met, but the yield of mono-olefin is only 96.5%. Also, as the run time increased, the diolefin content of the product increased faster due to poisoning of catalyst B by sulfur in the mixed carbon four feedstock.

Comparative example 2

The properties of a mixed carbon four as a raw material D are shown in Table 1. Directly feeding the mixed C-C raw material D into a reactor to contact with a catalyst B for selective diene removal reaction. The reaction conditions and product properties are shown in table 2, and it can be seen from table 2 that the sulfur content of the product is unchanged after the selective diene removal reaction of the mixed C-C four raw material, the sulfur content of the product is the same as that of the raw material, the diene content of the product reaches 0.004 volume%, the feeding requirement of the superposition technology can be met, but the yield of mono-olefin is only 96.0%. Moreover, as the sulfur content in the raw material D is higher, the content of the dialkene in the product is rapidly increased along with the increase of the running time.

Example 1

The properties of a mixed carbon four as a raw material C are shown in Table 1. Mixing C and N₂The mixed materials enter a first reactor, contact with a catalyst A in the first reactor to carry out mercaptan etherification reaction, the reaction product enters a fractionating tower, thioether and low-sulfur mixed carbon four are separated, the separated low-sulfur mixed carbon four is mixed with hydrogen and selective control gas CO to enter a second reactor, and contact with a catalyst B in the second reactor to carry out selective diene removal reaction. The reaction conditions and the product properties are shown in table 3, and it can be seen from table 3 that after the etherification and selective diene removal reaction of the mixed C4 raw material, the sulfur content of the product is greatly reduced, most of the mercaptan sulfur is removed, the diene content of the product reaches 0.001 volume percent, the feeding requirement of the superposition technology is met, and the yield of the mono-olefin reaches 99.8 percent. And, with the increase of the running time, the alkadiene in the product is basically unchanged, and the activity of the catalyst B is stable.

Example 2

The properties of a mixed carbon four as a raw material D are shown in Table 1. Mixing C four raw materials D and N₂The mixed materials enter a first reactor, contact with a catalyst A in the first reactor to carry out mercaptan etherification reaction, the reaction product enters a fractionating tower, thioether and low-sulfur mixed carbon four are separated, the separated low-sulfur mixed carbon four is mixed with hydrogen and selective control gas CO to enter a second reactor, and contact with a catalyst B in the second reactor to carry out selective diene removal reaction. The reaction conditions and the product properties are shown in table 3, and it can be seen from table 3 that after the etherification and selective diene removal reaction of the mixed C4 raw material, the sulfur content of the product is greatly reduced, most of mercaptan sulfur is removed, the diene content of the product reaches 0.004 volume percent, the feeding requirement of the superposition technology is met, and the yield of mono-olefin reaches 99.6 percent. And, with the increase of the running time, the alkadiene in the product is basically unchanged, and the activity of the catalyst B is stable.

Example 3

The properties of a mixed carbon four as a raw material E are shown in Table 1. Mixing C four raw materials E and N₂And H₂Mixed intoThe first reactor is contacted with a catalyst A in the first reactor to carry out mercaptan etherification reaction, reaction products enter a fractionating tower to separate thioether and low-sulfur mixed carbon four, the separated low-sulfur mixed carbon four is mixed with hydrogen and selective control gas NO to enter a second reactor, and the second reactor is contacted with a catalyst B in the second reactor to carry out selective diene removal reaction. The reaction conditions and the product properties are shown in table 3, and it can be seen from table 3 that after the etherification and selective diene removal reaction of the mixed C4 raw material, the sulfur content of the product is greatly reduced, most of the mercaptan sulfur is removed, the diene content of the product reaches 0.003 volume percent, the feeding requirement of the superposition technology is met, and the mono-olefin yield reaches 98.5 percent.

TABLE 1

Name of raw materials	C	D	E
				Sulfur,. mu.g/g	30	400	100
Mercaptan sulfur,. mu.g/g	25	390	94
				Mixed carbon four composition, volume%
Isobutane	26.7	26.7	26.8
				N-butane	12.9	12.2	13.6
Isobutene	24.9	26.1	23.8
				1-butene	18.7	19.1	16.2
Cis-2-butene	6.2	5.8	7.1
				Trans-2-butene	10.3	9.5	11.5
1, 3-butadiene	0.3	0.6	1

TABLE 2

TABLE 3

Claims

1. A method for producing a superimposed raw material by hydrorefining a mixed C-C four raw material comprises the following steps:

(1) the mixed C4 raw material and inert gas enter a first reactor together, and contact with a mercaptan etherification catalyst to carry out mercaptan etherification reaction, wherein the mercaptan etherification catalyst is a non-noble metal catalyst; the inert gas is selected from one or more of nitrogen, helium and argon, and the volume ratio of the inert gas to the mixed carbon four raw material in a standard state is 10-500: 1;

(2) separating the reaction effluent obtained in the step (1) in a first separation zone to obtain four materials of thioether and low-sulfur mixed carbon;

(3) the low-sulfur mixed carbon four material obtained in the step (2), hydrogen and selective regulation gas enter a second reactor together, and contact with a selective diene removal catalyst to carry out diene removal reaction, and the reaction effluent of the second reactor is separated in a second separation zone to obtain a low-sulfur low-diene mixed carbon four product, wherein the selective diene removal catalyst is a non-noble metal catalyst; the above-mentionedThe selective control gas is selected from CO and CO₂、NO、H₂One or more of S; based on the total volume of the second reactor feed mixture, the volume fraction of the selective tuning gas is: 0.001 to 10 percent.

2. The method according to claim 1, wherein the mixed C-IV raw material is a C-IV material or a C-III-C-IV mixed material obtained by a catalytic cracking, atmospheric and vacuum distillation, coking and hydrocracking device, the volume fraction of butadiene in the mixed C-IV raw material is 0.005-1%, the sulfur content is 10-500 μ g/g, and the mercaptan sulfur accounts for 50-98% of the mass of the sulfur-containing compound.

3. The method according to claim 1, wherein the standard state volume ratio of the inert gas to the mixed C-C feedstock in step (1) is 20-400: 1.

4. The method according to claim 1, wherein the reaction atmosphere of the first reactor in the step (1) further contains hydrogen; the volume ratio of the hydrogen to the mixed carbon four raw material in the standard state is 1-100: 1.

5. The method according to claim 1, wherein the standard state volume ratio of the hydrogen gas and the mixed carbon four raw material in the step (1) is 2-60: 1.

6. The method according to claim 1, wherein the reaction conditions of the first reactor in step (1) are: the pressure is 0.3-4.0 MPa, the reaction temperature is 30-250 ℃, and the volume space velocity is 1.0-20.0 h^-1。

7. The method of claim 6, wherein the reaction conditions of the first reactor in step (1) are: the pressure is 0.5-2.5 MPa, the reaction temperature is 60-200 ℃, and the volume space velocity is 2.0-10.0 h^-1。

8. The method according to claim 1, wherein the sulfur content of the low-sulfur mixed carbon four material in the step (2) is 0-10 μ g/g.

9. The process according to claim 1, wherein the mercaptan etherification catalyst in step (1) is a catalyst comprising at least one group VIII non-noble metal component selected from cobalt and/or nickel and at least one group VIB metal component selected from molybdenum and/or tungsten, supported on an alumina carrier; calculated by oxides and taking a mercaptan etherification catalyst as a reference, the mass fraction of the VIII group non-noble metal component is 1-40%, and the mass fraction of the VIB group metal component is 0.1-10%.

10. The method according to claim 9, wherein the non-noble group VIII metal component in the mercaptan etherification catalyst is nickel, the group VIB metal component is molybdenum, and the mass fraction of nickel is 3-25% and the mass fraction of molybdenum is 0.5-4.5% in terms of oxides and based on the mercaptan etherification catalyst.

11. The method of claim 1, wherein the reaction conditions of the second reactor in step (3) are as follows: hydrogen partial pressure of 0.3-4.0 MPa, reaction temperature of 30-150 ℃ and volume space velocity of 1.0-20.0 h^-1And the molar ratio of the hydro-diene is 0.5-20.

12. The process of claim 1, wherein the reaction conditions of the second reactor are: hydrogen partial pressure of 0.5-3.0 MPa, reaction temperature of 40-130 ℃ and volume space velocity of 2.0-10 h^-1And the molar ratio of the hydro-diene is 1.0-8.0.

13. The method of claim 1, wherein the volume fraction of diolefins in the low sulfur, low diolefin mixed carbon four product of step (3) is 0-0.005%.

14. The process of claim 1, wherein the volume fraction of diolefins in the low sulfur, low diolefin mixed carbon four product of step (3) is 0 to 0.003%.

15. The process of claim 1, wherein the selective diene removal catalyst in step (3) comprises a carrier, an auxiliary component, and a hydrogenation-active metal component, wherein the carrier is alumina and/or silica-alumina, the hydrogenation-active metal component comprises at least one non-noble group VIII metal component and optionally a group VIB metal component, the non-noble group VIII metal component is nickel and/or cobalt, the group VIB metal component is molybdenum and/or tungsten, and the auxiliary component is at least one component selected from alkali metals and alkaline earth metals.

16. The process of claim 15 wherein the mass fraction of nickel and/or cobalt, the mass fraction of molybdenum and/or tungsten and the mass fraction of promoter component is from 1 to 40%, calculated as oxides and based on the selective diene removal catalyst, from 0 to 10% and from 0.1 to 9%.

17. A system for use in a process for hydrorefining a mixed carbon four feedstock as defined in any one of claims 1 to 16 to produce a stratified feedstock comprising a first reactor, a second reactor, a first separation zone and a second separation zone;

18. The system of claim 17, wherein the mercaptan etherification catalyst is a catalyst comprising at least one group VIII non-noble metal component selected from cobalt and/or nickel and at least one group VIB metal component selected from molybdenum and/or tungsten on an alumina support; calculated by oxides and taking a mercaptan etherification catalyst as a reference, the mass fraction of the VIII group non-noble metal component is 1-40%, and the mass fraction of the VIB group metal component is 0.1-10%.

19. The system according to claim 18, wherein the non-noble group VIII metal component of the mercaptan etherification catalyst is nickel, the group VIB metal component of the mercaptan etherification catalyst is molybdenum, and the mass fraction of nickel is 3 to 25% and the mass fraction of molybdenum is 0.5 to 8% in terms of oxides and based on the mercaptan etherification catalyst.

20. The system of claim 17, wherein the selective diene removal catalyst comprises a carrier, an auxiliary component, and a hydrogenation-active metal component, wherein the carrier is alumina and/or silica-alumina, the hydrogenation-active metal component comprises at least one group VIII non-noble metal component and optionally a group VIB metal component, the group VIII non-noble metal component is nickel and/or cobalt, the group VIB metal component is molybdenum and/or tungsten, and the auxiliary component is at least one component selected from alkali metals and alkaline earth metals.

21. The system of claim 20, wherein the mass fraction of nickel and/or cobalt, the mass fraction of molybdenum and/or tungsten, and the mass fraction of the promoter component are 1 to 40%, 0 to 10%, and 0.1 to 9%, calculated as oxides and based on the selective diene removal catalyst.