CN108070400B

CN108070400B - Alkylation method

Info

Publication number: CN108070400B
Application number: CN201611002425.1A
Authority: CN
Inventors: 方向晨; 杨秀娜; 齐慧敏; 王海波
Original assignee: China Petroleum and Chemical Corp; Sinopec Fushun Research Institute of Petroleum and Petrochemicals
Current assignee: China Petroleum and Chemical Corp; Sinopec Fushun Research Institute of Petroleum and Petrochemicals
Priority date: 2016-11-15
Filing date: 2016-11-15
Publication date: 2020-03-17
Anticipated expiration: 2036-11-15
Also published as: CN108070400A

Abstract

The invention discloses an alkylation method, which comprises the following steps: (1) dehydrating the hydrocarbon feedstock; (2) carrying out alkylation reaction of hydrocarbon raw materials by taking sulfuric acid as a catalyst; (3) separating alkylation reaction products; wherein the dehydration method of the hydrocarbon raw material in the step (1) comprises the following steps: adopts the processes of impact cyclone, primary separation and deep separation. Compared with the prior art, the alkylation method disclosed by the invention has the advantages that the alkylation raw material and the alkylation product are more efficiently, energy-saving and environment-friendly treated, and the method has an important significance for improving the advancement of the whole process of the alkylation reaction.

Description

Alkylation method

Technical Field

The invention belongs to the field of petrochemical industry, and particularly relates to an alkylation method taking sulfuric acid as a catalyst, in particular to an alkylation method integrating deep purification of raw materials and deep separation of products.

Background

In recent years, with the general attention of all countries in the world on environmental protection, higher and stricter requirements are put on the octane number and cleanliness of motor gasoline, so that the overall standard of the world clean gasoline is developed towards the direction of low sulfur, low aromatic, low olefin and high octane number, and therefore, the alkylate and alkylation process becomes the focus of current attention. The alkylation process is used for producing high-quality gasoline blending components, namely, isobutane and C3-C5 olefin react to generate gasoline components with high octane number under the action of an acid catalyst, and the gasoline components are blended into gasoline to reduce the content of harmful components such as olefin, aromatic hydrocarbon, sulfur and the like and improve the octane number and the anti-explosion performance of the gasoline, so that the gasoline components are very ideal clean vehicle gasoline components.

In the existing sulfuric acid alkylation process, firstly, isobutane, olefin raw materials and a sulfuric acid catalyst are conveyed to an alkylation reactor, acid-hydrocarbon emulsion is formed in the reactor so as to complete alkylation reaction, then the acid-hydrocarbon mixed emulsion enters a settling separator, a sulfuric acid phase and a hydrocarbon phase are separated under the action of density difference, the hydrocarbon phase and a sulfuric acid phase are obtained, and the separated sulfuric acid is recycled after fresh sulfuric acid is supplemented. By adopting one-time sedimentation separation, a certain amount of sulfuric acid is still contained in the hydrocarbon phase, and further subsequent separation treatment is required.

In addition, the water content of the water in the reaction raw material (C4 hydrocarbon) is about 300mg/kg generally in the operation state, when the operation of an upstream device is unstable, the water carried by the raw material can reach about 1000mg/kg, even higher, the dilution rate of the sulfuric acid is increased if the water carried by the raw material is so serious, and because a certain requirement is provided for the concentration of a sulfuric acid catalyst in the alkylation reaction, when the concentration of the circulating sulfuric acid is lower than the requirement, the novel sulfuric acid needs to be supplemented and replaced, the water carried by the raw material greatly increases the replacement frequency of the sulfuric acid, so that the problems of high acid consumption of a system, large waste acid discharge amount, large corrosion of the quickly generated dilute sulfuric acid to equipment and.

CN104109067A proposes a separation and purification method of an alkylation product, which is to cool the alkylation product and then mix the alkylation product with alkali liquor to neutralize organic acids, and then introduce alkalescent reactants into a first-stage oil-water separator, a water washing tank and a second-stage oil-water separator in sequence; CN103772097A proposes a method for treating an alkylation product, which comprises feeding a gas-phase alkylation product into an adsorption bed filled with an oil adsorbent, wherein the adsorbent is a solid alkali adsorbent, cooling the gas-phase reaction product, feeding the cooled gas-phase reaction product into an oil-water separator, separating to obtain an oil-phase product and a water-phase product, feeding the oil-phase product into a subsequent fractionation system, and feeding the water-phase product into a start-up treatment system. The two methods both aim to solve the problem of corrosion of subsequent equipment caused by carrying organic acid due to thorough separation of alkylation products in the prior art, but still have the problems of complex separation process, high material consumption and energy consumption, large sewage discharge amount and the like.

CN201010524543.5 discloses a method for deacidifying an alkylation reaction product, which comprises the following specific steps: after the mixed emulsion of the alkylation reaction product (hydrocarbon oil) and sulfuric acid is subjected to gravity settling, the mixed emulsion is separated through a component provided with a hydrophobic modified ceramic membrane at a membrane surface flow velocity of 0.01-5 m/s, and the deacidification process of the oil product is realized in a cross-flow filtration mode within the operating pressure of 0.01-0.3 MPa and the operating temperature of 0-40 ℃. The oil is forced under pressure through a ceramic membrane, the acid is trapped and the resulting oil has an acid content of less than 100 mg/kg. The surface of the ceramic membrane (the aperture is 0.01-1.4 mu m) is subjected to hydrophobic modification, and the contact angle of water drops on the surface of the membrane is 70-160 degrees. The method utilizes the characteristic of a hydrophobic ceramic membrane to ensure that sulfuric acid micro-droplets do not pass through the ceramic membrane, but has limited effect of removing the emulsified particles of the hydrocarbon-contained acid, and particularly has unsatisfactory deacidification effect when the diameter of the emulsified particles of the hydrocarbon-contained acid is smaller than the aperture of the ceramic membrane. Meanwhile, in order to obtain a lower acid content in the hydrocarbon phase on the permeate side, the acid phase on the retentate side may contain higher hydrocarbon content.

In the aspect of raw material pretreatment, the free water content in the principle is controlled to be less than or equal to 10mg/kg generally, and the method is difficult to realize by adopting the prior art, so that the sulfuric acid is diluted more quickly, the acid consumption is increased, the generated waste acid quantity is large, the waste acid treatment pressure is increased, the corrosion of the quickly generated dilute sulfuric acid to equipment is increased, the water content in the C4 raw material is effectively controlled to be less than or equal to 10mg/kg, and the method plays an important role in the efficient and stable operation of an alkylation device.

In conclusion, a more efficient, energy-saving and environment-friendly separation and purification process for alkylation raw materials and alkylation products is developed to overcome the defects of the prior art, and the process has important significance for improving the advancement of the whole process of the alkylation reaction.

Disclosure of Invention

In view of the deficiencies of the prior art, the present invention provides a novel alkylation process that employs an economical and efficient method for the effective and stable treatment of alkylation feedstocks and alkylation products.

The alkylation process of the present invention comprises the steps of:

(1) dehydrating the hydrocarbon feedstock;

(2) carrying out alkylation reaction of hydrocarbon raw materials by taking sulfuric acid as a catalyst;

(3) separating alkylation reaction products;

wherein the dehydration method of the hydrocarbon raw material in the step (1) comprises the following steps: the process of impact cyclone-primary separation-deep separation is adopted to remove the water in the alkylation reaction hydrocarbon raw material to be less than or equal to 10mg/kg, thereby providing stable feeding for the alkylation reaction process. The hydrocarbon feed was isobutane and C3-C5 olefins.

In the dehydration method of the hydrocarbon raw material in the step (1), the impact cyclone operation is used for colliding, coalescing and cyclone separation of small water drops in the hydrocarbon raw material. An impact area is arranged at the material inlet in the cyclone separator, namely, the material is divided into two parts, the two parts of the material are oppositely introduced into the cyclone separator, and the impact action of the material is formed in the impact area. The impacted material enters a cyclone zone for cyclone operation to separate water from the hydrocarbon raw material. The general structure of the main body structure of the impact rotational flow equipment comprises a cylindrical cavity body which is positioned at the front part (the upper part when horizontally arranged or vertically arranged, the lower part is the same) and is closed at the top end and an inverted cone-shaped separation cavity body positioned at the rear part, wherein a discharge hole is formed at the bottom of the conical cavity body, feed holes are formed in the side wall of the cylindrical cavity body, and the feed holes are symmetrically arranged in two groups; the opposite feed inlet of the impact cyclone assembly forms impact flow after feeding, and the impact flow is used for accelerating the rotation rate of fluid in the conical cavity, so that the separation effect of water in the hydrocarbon raw material is accelerated.

In the dehydration method of the hydrocarbon raw material in the step (1), the primary separation adopts a corrugated plate coalescer. The corrugated plate coalescer can adopt a conventional corrugated plate coalescer in the field, and a specific corrugated plate coalescer comprises a plurality of layers of corrugated plates which are sequentially stacked up and down, and hydrophilic and oleophobic properties on the surface of the corrugated plates and a tortuous channel which flows back and forth are utilized, so that the expansion probability among small water drops is increased, the coalescence of the small water drops is promoted, the small water drops of 5-20 mu m carried in hydrocarbon raw materials are aggregated into large water drops, and the large water drops slide down along the surface of the corrugated plates under the action of gravity to reach a water outlet at the bottom to complete primary separation; the distance between the upper layer and the lower layer of the corrugated plate is generally 3-6 mm, a plurality of dewatering holes are formed in the wave trough of each layer plate, and large water drops collected and separated fall from the dewatering holes; due to the good initial distribution of the evenly distributed components, the flow capacity of the corrugated plates of each layer is nearly equal, and the separation efficiency of the primary separation component is ensured. The retention time (based on the volume of the empty coalescer) of the material in the corrugated plate coalescer is 1-10 minutes, preferably 1.5-3 minutes. In the dehydration method of the hydrocarbon raw material in the step (1), the material passes through a distributor before primary separation, and the material is uniformly distributed on a separation component of the primary separator. The distributor may be any suitable material distributor. For example, 5-10 layers of identical pore plate liquid distribution plates with staggered surface pores are adopted to uniformly distribute hydrocarbon raw material feeding, so that the subsequent primary separation and the subsequent deep separation are stabilized, the pore diameter of the pore plate is 4-8 mm, the central distance of the pores is 20-30 mm, a certain space is reserved between the upper and lower parts of the pore plate liquid distribution plate for no pore opening, the reserved height is 30-80 mm, and the flowing of side walls and gaps is prevented.

In the dehydration method of the hydrocarbon raw material in the step (1), the deep separation adopts a fiber coalescer. The fiber coalescer may be a deep dewatering fiber coalescer as is conventional in the art. After primary separation, water drops with larger size, namely more than or equal to 5 mu m, are removed, and the remaining water drops with smaller size less than or equal to 5 mu m, which are not removed, need to enter a fiber coalescence component for water inlet deep separation and are separated out under the action of the material and the structure of the coalescence material; the whole structure is a hollow cylinder structure, the cylindrical surface is made of hydrophilic materials, and the surface is in a compact honeycomb hexagonal hole shape. The residence time of the material in the fiber coalescer (based on the empty coalescer volume) is 0.5 to 5 minutes, preferably 1.0 to 2.5 minutes.

In the dehydration process of the hydrocarbon feedstock of step (1), the impinging cyclone-primary separation-deep separation may use an integrated apparatus combining the above functions.

The alkylation reaction in step (2) may adopt the existing alkylation reaction processes, such as stirred alkylation reaction, packed tower alkylation reaction, microchannel alkylation reaction, etc.

The alkylation reaction separation method in the step (3) comprises the following steps: primarily separating an alkylation reaction product with sulfuric acid as a catalyst, then feeding the product into membrane separation equipment, mixing penetrating fluid obtained by membrane separation with fresh sulfuric acid, then carrying out cyclone separation, and further deacidifying hydrocarbon oil obtained by cyclone separation by using a coalescer; wherein the aperture of the membrane separation equipment is 50-500 nm, preferably 100-300 nm, and the absolute pressure of the permeation side of the membrane separation equipment is 10-90 kPa, preferably 30-80 kPa.

In the alkylation reaction separation method in the step (3), the preliminary separation of the alkylation reaction product can be one or more of sedimentation separation, coalescence separation and centrifugal separation, and the sulfuric acid content in the material after the preliminary separation is generally 1000-8000 mg/kg, and generally 2000-7000 mg/kg. The specific equipment and conditions for the preliminary separation are well known to those skilled in the art. The acid phase obtained after the initial separation can be recycled to the alkylation reactor or can be further treated by other treatment methods.

In the alkylation reaction separation method of the step (3), the membrane separation equipment can be a tubular membrane, a plate-type membrane and the like. The invention utilizes the aperture limiting function of the membrane separation equipment, obtains a certain deacidification effect, and more importantly utilizes the comprehensive function of the membrane aperture and the negative pressure at the permeation side to demulsify the tiny emulsified liquid drops containing acid in the hydrocarbon, thereby being beneficial to the subsequent deacidification treatment, so the property of the membrane can have hydrophobicity, can not need to have hydrophobicity, but needs to have acid resistance, preferably an acid-resistant inorganic membrane, such as a ceramic membrane, and the like, but does not need complex modification treatment. The content of sulfuric acid in the penetrating fluid of the membrane separation equipment is generally 500-2000 mg/kg, preferably 800-1500 mg/kg. The concentration of the membrane separation equipment is mainly sulfuric acid, and can be partially circulated and mixed with the feed of the membrane separation equipment, and partially discharged, and the discharged part can be circularly used for alkylation reaction, and can also be further treated. The pressure difference between the inside and the outside of a penetrating fluid of the membrane separation equipment is generally 0.1-5.0 MPaG, preferably 0.5-2.0 MPaG; the flow velocity of the material at the membrane tube side of the membrane separation equipment is generally 0.5-3.5 m/s, preferably 1.0-2.0 m/s.

In the alkylation reaction separation method of step (3), various mixing devices, such as various dynamic mixing or static mixing devices, can be used for mixing the permeate and the fresh sulfuric acid, and the venturi mixer is preferably used in the present invention from the viewpoint of the simplification of the device structure. The mixing volume ratio of the supplementary fresh sulfuric acid to the penetrating fluid is 1: 20-1: 500, preferably 1: 50-1: 200.

In the alkylation reaction separation method of step (3), the cyclone separation operation may be a cyclone separator which is conventional in the art. Preferably, a material impact area is arranged in a feeding area of the cyclone separator, namely, the mixed material is divided into two materials, the two materials are impacted positively at an inlet in the cyclone separator, and the mixed material enters the cyclone separator after leaving the impact mixing area, so that the separation of sulfuric acid/hydrocarbon under a supergravity field is realized. The content of sulfuric acid in the hydrocarbon discharged from the cyclone separator is generally controlled to be 50 to 500 mg/kg, preferably 100 to 400 mg/kg. The sulfuric acid separated after the cyclone separation is circulated back to the alkylation reactor.

In the alkylation reaction separation method in the step (3), the further coalescence deacidification of the hydrocarbon oil obtained after the cyclone separation can adopt a coalescence separator mature in the field, the coalescence separator adopts a fiber filter element type structure, wherein the fiber is formed by weaving one or more of metal fiber, polytetrafluoroethylene fiber, polypropylene fiber and polyester fiber after surface hydrophilic modification treatment, tiny sulfuric acid droplets in the alkylate oil are captured through the hydrophilic and oleophobic properties of the fiber surface, and are enriched and gradually aggregated and grown on the fiber surface, and finally, large sulfuric acid droplets are separated out through sedimentation. The residence time of the material in the coalescer (based on the empty coalescer volume) is 1.5 to 5 minutes, preferably 2.5 to 3.5 minutes. The content of sulfuric acid in the alkylation product discharged from the coalescer is generally 1-10 mg/kg, preferably 5-9 mg/kg, so that the effect of deep deacidification is achieved, and subsequent steps such as alkali washing, water washing and the like can be omitted. Such coalescers are commercially available products and can be made according to the state of the art.

The alkylation process of the present invention, since the water content of the hydrocarbon feedstock in the operating state is generally 300mg/kg, when the upstream device is unstable in operation, the water carried by the hydrocarbon raw material can reach more than or equal to 1000mg/kg and even higher, the dilution rate of the sulfuric acid is increased when the raw material carries water seriously, because the concentration of the sulfuric acid catalyst has certain requirements in the alkylation reaction, when the concentration of the circulating sulfuric acid is lower than the requirements, the novel sulfuric acid needs to be supplemented and replaced, therefore, the water content in the C4 raw material is large, which increases the replacement frequency of the sulfuric acid, and also causes the problems of high acid consumption of the system, large discharge amount of waste acid, large corrosion of the quickly generated dilute sulfuric acid to equipment and the like, the invention firstly carries out deep dehydration on the raw material C4, in the deep dehydration facility, the method of impact cyclone, uniform distribution, primary separation and deep separation is adopted to remove the water in the raw materials to less than or equal to 10 mg/kg.

The method adopts the processes of primary separation, membrane separation, mixed neo-acid, cyclone separation and coalescent acid to the alkylation reaction product of the sulfuric acid process, effectively realizes the deep deacidification of the alkylation product, and can save the steps of alkali washing, water washing and the like in the conventional method. The membrane separation process of the method does not need to use a complex modified membrane, but utilizes the negative pressure operation of a tiny pore canal and a permeation side to ensure that tiny acid-in-hydrocarbon micro-droplets in an emulsified state demulsify when passing through the pore canal of the membrane, and although the deacidification rate is not high, the method lays a good physical property foundation for the subsequent deacidification operation and improves the efficiency of the subsequent deacidification device. The simple cyclone separation operation is adopted, the operation of the preorder membrane unit is matched, and a proper amount of neo-acid is supplemented, so that the alkylation product which is difficult to effectively deacidify in the cyclone separation unit can be deacidified with higher efficiency in the cyclone separation equipment, and a physical property foundation is laid for realizing deep deacidification in the subsequent coalescence deacidification process. In a word, the invention changes the action process of each unit used independently through the organic combination of the units, and realizes ideal comprehensive technical effect. The alkylation product deep acid hydrocarbon separation process can efficiently complete the deep purification and separation of the alkylation product, omits complex treatment processes of alkali washing, water washing and the like in the traditional process, simplifies the process flow, greatly reduces the material consumption and the energy consumption, ensures that the production process of the alkylate oil is more efficient and environment-friendly, and is suitable for the deep purification and separation of various alkylation products.

In conclusion, the invention provides a novel process technology for raw material pretreatment and product aftertreatment, which ensures the high efficiency and stability of the reaction process, is used for overcoming the defects of the prior art, solving a plurality of problems in the prior art and improving the overall process advancement of the alkylation reaction technology.

Drawings

FIG. 1 is a schematic process flow diagram of the present invention.

Wherein 1 is C4 raw material, 2 is C4 raw material deep dehydrator, 3 is dehydration water, 4 is C4 raw material buffer tank, 5 is C4 raw material feed pump, 6 is C4 raw material feed microchannel reactor material, 7 is refrigerant, 8 is refrigerant buffer tank, 9 is refrigerant feed pump, 10 is refrigerant feed microchannel reactor material, 11 is mixed cycle sulfuric acid, 12 is microchannel reactor, 13 is reaction product three-phase separator, 14 is separated residual gas, 15 is separated sulfuric acid phase, 16 is crude alkylate extraction pump, 17 is membrane separator feed, 18 is membrane separator, 19 is membrane tube bundle, 20 is concentrated solution, 21 is discharge concentrated solution, 22 is cycle concentrated solution, 23 is penetrating fluid, 24 is fresh sulfuric acid supplement, 25 is acid hydrocarbon mixer, 26 is acid hydrocarbon deep separator feed, 27 is acid hydrocarbon deep separator, 28 is separated sulfuric acid, 29 is deeply separated alkylate oil, and 30 is a mixed circulating sulfuric acid pump.

Detailed Description

The process and effect of the process of the present invention are further illustrated by the following examples.

Example 1 (dehydration of Hydrocarbon feedstock)

The hydrocarbon feed for a given alkylation had a water content of 326 mg/kg.

The specific structure and operation conditions of the equipment of 'impact cyclone-uniform distribution-primary separation-depth separation' are as follows: (1) the impact cyclone equipment structure consists of a cylinder cavity with a closed top end and an inverted cone-shaped cyclone separation cavity positioned at the rear part, wherein the cylinder cavity is symmetrically fed at two sides, an impact area is formed inside the cylinder cavity, and the impact flow rate is 1.5 m/s; the cone angle of the inverted cone-shaped cyclone separation cavity is 45 degrees; (2) the uniformly distributed components are 5 layers of pore plates with the pore diameter of 8mm and the pore center spacing of 30 mm; (3) the primary separation equipment adopts a stainless steel corrugated plate structure, wherein the distance between two adjacent layers of the corrugated plates is 6mm, the aperture of the open hole on the plate is 2.5mm, and the aperture ratio is 14.5%; (4) the depth separation component is a hollow cylindrical filter element structure, the cylindrical surface is made of hydrophilic viscose fiber materials, the surface is in a compact honeycomb hexagonal hole shape, and the retention time (measured by the volume of the hollow coalescer) of the materials in the fiber coalescer is 1.2 minutes.

After separation by the above procedure, the water content of the dehydrated hydrocarbon feedstock was 6.7 mg/kg.

Example 2 (dehydration of Hydrocarbon feedstock)

The water content of the alkylation hydrocarbon feed in example 1 was adjusted to provide an analytical result of 713 mg/kg. The dehydration method was the same as in example 1.

(1) The impact cyclone equipment structure is composed of a cylinder cavity with a closed top end and an inverted cone-shaped cyclone separation cavity positioned at the rear part, wherein the cylinder cavity is symmetrically fed at two sides, an impact area is formed inside the cylinder cavity, and the impact flow rate is 2.1 m/s; the cone angle of the inverted cone-shaped cyclone separation cavity is 30 degrees; (2) the uniformly distributed components are 8 layers of pore plates with the aperture of 6mm and the hole center spacing of 25 mm; (3) the primary separation equipment adopts a stainless steel corrugated plate structure, wherein the distance between two adjacent layers of the corrugated plates is 4mm, the aperture of the open hole on the plate is 2.0mm, and the aperture ratio is 13.8%; (4) the depth separation component is a hollow cylindrical filter element structure, the cylindrical surface is made of hydrophilic acetate fiber materials, the surface is in a compact honeycomb hexagonal hole shape, and the retention time (measured by the volume of the hollow coalescer) of the materials in the fiber coalescer is 1.8 minutes.

After separation by the above procedure, the water content of the dehydrated hydrocarbon feedstock was 5.4 mg/kg.

Example 3 (dehydration of Hydrocarbon feedstock)

The water content of the alkylation feed in example 1 was adjusted to 1245 mg/kg as a result of analysis. The dehydration method was the same as in example 1.

(1) The impact cyclone equipment structure is composed of a cylinder cavity with a closed top end and an inverted cone-shaped cyclone separation cavity positioned at the rear part, wherein the cylinder cavity is symmetrically fed at two sides, an impact area is formed inside the cylinder cavity, and the impact flow velocity is 2.5 m/s; the cone angle of the inverted cone-shaped cyclone separation cavity is 15 degrees; (2) the uniformly distributed components are 10 layers of pore plates with the pore diameter of 4mm and the pore center spacing of 20 mm; (3) the primary separation equipment adopts a stainless steel corrugated plate structure, wherein the distance between two adjacent layers of the corrugated plates is 4mm, the aperture of the open hole on the plate is 1.5mm, and the aperture ratio is 14.0%; (4) the depth separation component is a hollow cylindrical filter element structure, the cylindrical surface is made of a hydrophilic natural fiber blended material, the surface is in a compact honeycomb hexagonal hole shape, and the retention time (measured by the volume of the hollow coalescer) of the material in the fiber coalescer is 2.5 minutes.

After separation by the above procedure, the water content of the dehydrated hydrocarbon feedstock was 4.2 mg/kg.

Example 4 (alkylation reaction product isolation)

The content of sulfuric acid in the alkylation reaction product of a certain stirring type sulfuric acid method after primary sedimentation separation in the alkylate oil is 6367 mg/kg.

The alkylate oil adopts the membrane separation-neo-acid mixing-cyclone separation-coalescence deacidification process, and the operation conditions and results of each unit are as follows:

1. a membrane separation unit. The ceramic tubular membrane with the aperture of 300nm is adopted, and the surface of the ceramic tubular membrane does not need to be modified. The shell side of the tubular membrane is a permeate and the tube side is a concentrate. The material flow rate at the membrane tube side of the membrane separation equipment is 0.95m/s, the internal and external pressure difference of the penetrating fluid of the membrane separation equipment is 0.7MPaG, the shell side is connected with a vacuum system, and the absolute pressure at the shell side is 75 kPa. The sulfuric acid content in the penetrating fluid is 1065 mg/kg. The concentrated solution is partially circulated, and partially discharged, and the discharged concentrated solution is treated as waste acid and can also be circulated to an alkylation reaction system.

2. A neo-acid mixing unit. Fresh sulfuric acid is used as supplementary fresh sulfuric acid for the alkylation reaction system by adopting a Venturi mixer, and the mixing volume ratio of the fresh sulfuric acid to penetrating fluid is 1: 185.

3. A cyclonic separation unit. The inlet part of the cyclone separation unit adopts a two-material convection impact mode, the effluent of the neo-acid mixing unit is divided into two materials, impact is formed at the inlet of the cyclone separation unit, and then the materials enter a cyclone separation section to carry out acid-hydrocarbon separation under the action of a super-gravity field. The sulphuric acid content of the hydrocarbonaceous phase at the outlet of the cyclonic separating unit was 179 mg/kg. And the sulfuric acid at the outlet of the cyclone separation unit is circulated to the alkylation reaction unit.

4. A coalescing depth deacidification unit. The conventional fiber filter element type coalescence deacidification equipment is adopted, and the fiber surface of the fiber filter element is made of a material with hydrophilic and oleophobic properties. The residence time of the material in the coalescer (based on empty coalescer volume) was 2.75 minutes. The sulfuric acid content of the outlet material of the coalescence unit is 5.0 mg/kg.

Comparative example 1

For the alkylation reaction product described in example 1, the coalescing unit of step 4 was used to perform two treatments under the same conditions, the sulfuric acid content of the first treated product was 1375 mg/kg and the sulfuric acid content of the second treated product was 1068 mg/kg.

Comparative example 2

The membrane treatment unit of step 1 was replaced with the coalescing unit of step 4 for the alkylation reaction product described in example 1, and the procedure and conditions were otherwise the same as in example 1. The sulfuric acid content of the first coalescence deacidification product is 1375 mg/kg, the sulfuric acid content of the product at the outlet of the cyclone separation unit is 952 mg/kg, and the sulfuric acid content of the second coalescence deacidification product is 367 mg/kg.

Example 5 (alkylation reaction product isolation)

The content of sulfuric acid in the alkylate oil obtained by primary settling separation of a certain filler type sulfuric acid alkylation reaction product is 3543 mg/kg.

1. a membrane separation unit. The ceramic tubular membrane with the aperture of 200nm is adopted, and the surface of the ceramic tubular membrane does not need to be modified. The shell side of the tubular membrane is a permeate and the tube side is a concentrate. The material flow rate at the membrane tube side of the membrane separation equipment is 1.16m/s, the internal and external pressure difference of the penetrating fluid of the membrane separation equipment is 1.2MPaG, the shell side is connected with a vacuum system, and the absolute pressure of the shell side is 60 kPa. The sulfuric acid content in the permeate was 821 mg/kg. The concentrated solution is partially circulated, and partially discharged, and the discharged concentrated solution is treated as waste acid and can also be circulated to an alkylation reaction system.

2. A neo-acid mixing unit. A Venturi mixer is adopted, fresh sulfuric acid is used as supplementary fresh sulfuric acid of an alkylation reaction system, and the mixing volume ratio of the fresh sulfuric acid to penetrating fluid is 1: 110.

3. A cyclonic separation unit. The inlet part of the cyclone separation unit adopts a two-material convection impact mode, the effluent of the neo-acid mixing unit is divided into two materials, impact is formed at the inlet of the cyclone separation unit, and then the materials enter a cyclone separation section to carry out acid-hydrocarbon separation under the action of a super-gravity field. The sulphuric acid content in the hydrocarbon phase at the outlet of the cyclonic separating unit was 143 mg/kg. And the sulfuric acid at the outlet of the cyclone separation unit is circulated to the alkylation reaction unit.

4. A coalescing depth deacidification unit. The conventional fiber filter element type coalescence deacidification equipment is adopted, and the fiber surface of the fiber filter element is made of a material with hydrophilic and oleophobic properties. The residence time of the material in the coalescer (based on empty coalescer volume) was 3.0 minutes. The sulfuric acid content of the outlet material of the coalescing unit was 5.7 mg/kg.

Example 6 (alkylation reaction product isolation)

The content of sulfuric acid in the alkylation reaction product of a microchannel sulfuric acid process after primary settling separation in the alkylate oil is 2938 mg/kg.

1. a membrane separation unit. The ceramic tubular membrane with the aperture of 100nm is adopted, and the surface of the ceramic tubular membrane does not need to be modified. The shell side of the tubular membrane is a permeate and the tube side is a concentrate. The material flow rate at the membrane tube side of the membrane separation equipment is 1.72m/s, the internal and external pressure difference of the penetrating fluid of the membrane separation equipment is 1.8MPaG, the shell side is connected with a vacuum system, and the absolute pressure of the shell side is 40 kPa. The sulfuric acid content in the permeate was 675 mg/kg. The concentrated solution is partially circulated, and partially discharged, and the discharged concentrated solution is treated as waste acid and can also be circulated to an alkylation reaction system.

2. A neo-acid mixing unit. A Venturi mixer is adopted, fresh sulfuric acid is used as supplementary fresh sulfuric acid of an alkylation reaction system, and the mixing volume ratio of the fresh sulfuric acid to penetrating fluid is 1: 75.

3. A cyclonic separation unit. The inlet part of the cyclone separation unit adopts a two-material convection impact mode, the effluent of the neo-acid mixing unit is divided into two materials, impact is formed at the inlet of the cyclone separation unit, and then the materials enter a cyclone separation section to carry out acid-hydrocarbon separation under the action of a super-gravity field. The sulphuric acid content in the hydrocarbon phase at the outlet of the cyclonic separating unit was 129 mg/kg. And the sulfuric acid at the outlet of the cyclone separation unit is circulated to the alkylation reaction unit.

4. A coalescing depth deacidification unit. The conventional fiber filter element type coalescence deacidification equipment is adopted, and the fiber surface of the fiber filter element is made of a material with hydrophilic and oleophobic properties. The residence time of the material in the coalescer (based on empty coalescer volume) was 3.5 minutes. The sulfuric acid content of the outlet material of the coalescing unit is 5.2 mg/kg.

The results of the embodiment show that the method for deeply separating the alkylate can effectively carry out forced demulsification and deep separation on the crude alkylate, reduce the sulfuric acid carried by the alkylate, save the alkali washing and water washing units, and have remarkable economical efficiency, and the sulfuric acid content in the alkylate after the treatment is less than or equal to 6 mg/kg.

Claims

1. An alkylation process comprising the steps of:

(1) dehydrating the hydrocarbon feedstock;

(3) separating alkylation reaction products;

wherein the dehydration method of the hydrocarbon raw material in the step (1) comprises the following steps: adopting the processes of impact cyclone, primary separation and deep separation to remove water in the alkylation reaction hydrocarbon raw material to be less than or equal to 10mg/kg so as to provide stable feeding for the alkylation reaction process, wherein the hydrocarbon raw material is isobutane and C3-C5 olefin;

wherein the separation method of the alkylation reaction product in the step (3) comprises the following steps: after preliminary separation, the alkylation reaction product enters membrane separation equipment, penetrating fluid obtained by membrane separation is mixed with fresh sulfuric acid, then cyclone separation is carried out, and hydrocarbon oil obtained by cyclone separation is further deacidified by a coalescer; wherein the aperture of the membrane separation equipment is 50-500 nm, and the absolute pressure of the permeation side of the membrane separation equipment is 10-90 kPa.

2. The method of claim 1, wherein: in the dehydration method of the hydrocarbon raw material in the step (1), the impact cyclone operation makes small water drops in the hydrocarbon raw material generate collision, coalescence and cyclone separation, an impact area is arranged at a material inlet in the cyclone separator, namely, the material is divided into two parts, the two parts of the material are oppositely introduced into the cyclone separator, and the impact action of the material is formed in the impact area; the impacted material enters a cyclone zone for cyclone operation to separate water from the hydrocarbon raw material.

3. The method of claim 1, wherein: in the dehydration method of the hydrocarbon raw material in the step (1), the primary separation adopts a corrugated plate coalescer.

4. The method of claim 1, wherein: in the dehydration method of the hydrocarbon raw material in the step (1), the deep separation adopts a fiber coalescer.

5. The method of claim 1, 2, 3 or 4, wherein: in the dehydration method of the hydrocarbon raw material in the step (1), the integrated equipment combining the functions is used in the process of the impact cyclone-primary separation-deep separation.

6. The method of claim 1, wherein: wherein the alkylation reaction in the step (2) adopts stirring type alkylation reaction, packed tower type alkylation reaction or micro-channel type alkylation reaction.

7. The method of claim 1, wherein: the aperture of the membrane separation equipment is 100-300 nm, and the absolute pressure of the permeation side of the membrane separation equipment is 30-80 kPa.

8. The method of claim 1, wherein: the preliminary separation of the alkylation reaction product is one or more of settling separation, coalescence separation and centrifugal separation, and the sulfuric acid content in the material after the preliminary separation is 1000-8000 mg/kg.

9. The method of claim 8, wherein: the sulfuric acid content in the materials after the primary separation is 2000-7000 mg/kg.

10. The method of claim 1 or 7, wherein: the membrane separation equipment is a tubular membrane or a plate-type membrane; the nature of the membrane is hydrophobic, or not; the sulfuric acid content in the penetrating fluid of the membrane separation equipment is 500-2000 mg/kg.

11. The method of claim 10, wherein: the content of sulfuric acid in the penetrating fluid of the membrane separation equipment is 800-1500 mg/kg.

12. The method of claim 1, wherein: the feeding area of the cyclone separator is provided with a material impact area, namely, the mixed material is divided into two materials, the two materials are impacted positively at the inlet of the cyclone separator, and the mixed material enters the cyclone separator after leaving the impact mixing area, so that the separation of sulfuric acid/hydrocarbon under a supergravity field is realized; the content of sulfuric acid in the hydrocarbons discharged from the cyclone separator is controlled to be 50-500 mg/kg.

13. The method of claim 12, wherein: the content of sulfuric acid in the hydrocarbons discharged from the cyclone separator is controlled to be 100-400 mg/kg.

14. The method of claim 1, wherein: the coalescence deacidification adopts a fiber filter element type structure, wherein the fiber is woven after one or more of metal fiber, polytetrafluoroethylene fiber, polypropylene fiber and polyester fiber is subjected to surface hydrophilic modification treatment, tiny sulfuric acid drops in the alkylate oil are captured through the hydrophilic and oleophobic properties of the fiber surface, and are enriched and gradually aggregated on the fiber surface to grow up, and finally, large sulfuric acid drops are separated out through sedimentation; the content of sulfuric acid in the alkylation product discharged from the coalescer is 1-10 mg/kg.

15. The method of claim 1, wherein: the alkylation product discharged from the coalescer has a sulfuric acid content of 5 to 9 mg/kg.