CN112143523B

CN112143523B - Pretreatment method of alkylation gasoline raw material

Info

Publication number: CN112143523B
Application number: CN201910567538.3A
Authority: CN
Inventors: 李永祥; 胡合新; 张成喜; 马东强; 付强; 任奎; 慕旭宏; 罗一斌
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: 2019-06-27
Filing date: 2019-06-27
Publication date: 2024-06-11
Anticipated expiration: 2039-06-27
Also published as: CN112143523A

Abstract

The invention discloses a pretreatment method of an alkylated gasoline raw material, which is characterized by comprising the steps of pre-hydrogenation, rectification, dehydration, sulfide removal, nitrogen compound removal and oxygen compound removal. The method can delay the deactivation rate of the solid acid catalyst in the alkylation process and improve the service life of the catalyst.

Description

Pretreatment method of alkylation gasoline raw material

Technical Field

The invention relates to a pretreatment method of an alkylation gasoline raw material, in particular to a pretreatment method of an alkylation gasoline raw material which meets the requirements of a zeolite solid acid alkylation catalyst.

Background

In the petroleum refining industry, the process of alkylation of isoparaffins with olefins is an important process for producing clean, high octane gasoline components. The alkylated gasoline has low vapor pressure, low sensitivity, good antiknock performance, no aromatic hydrocarbon and olefin, and very low sulfur content, and is an ideal blending component of high-octane gasoline.

The raw materials used for the production of the alkylated gasoline are isoparaffin and olefin, and are mainly from catalytic cracking, ethylene cracking, arene reforming, coal-to-chemical industry coal-to-olefin devices and the like in petrochemical enterprises. Isoparaffins are mainly isobutane and olefins are generally C ₃ to C ₅ olefins, mainly C ₄ olefins, in addition to n-butane and some impurities.

Alkylation is an acid catalyzed reaction. The alkylation production process which is industrially applied at present comprises a sulfuric acid method and a hydrofluoric acid method, wherein sulfuric acid or hydrofluoric acid is used as a catalyst to synthesize alkylate oil from isoparaffin and olefin. The environmental hazard caused by the corrosion and toxicity of sulfuric acid and hydrofluoric acid and the waste acid emission in the process makes the alkylated gasoline production enterprises have increasingly high safety and environmental protection pressure.

To solve these problems, many large oil companies and scientific institutions in the world have been devoted to research and development of solid acid alkylation technology in the past eighties of the last century in an effort to replace the liquid acid process with an environmentally friendly solid acid process.

In the solid acid process, impurities in the raw materials can cause poisoning of the solid acid alkylation catalyst, and the catalyst deactivation is accelerated. For example, US5,986,158 recognizes that impurities in the feedstock may adsorb on the active sites of the catalyst or that diene polymers in the feedstock polymerize to form macromolecules that plug the channels, causing deactivation of the catalyst. Therefore, the impurity content needs to be controlled.

CN102171313a discloses a process for treating an alkylation feedstock, contacting the alkylation feedstock containing at least one of an oxygenate and a nitrogen-containing compound with water to produce a hydrocarbon fraction and a water fraction, the hydrocarbon fraction having a reduced concentration of at least one of an oxygenate and a nitrogen-containing compound.

CN105601460a provides a method for refining an alkylation raw material, which removes various impurities such as sulfide, nitride, chloride, oxygen-containing compound and the like in the alkylation raw material, so that the impurity content in the alkylation raw material is obviously reduced, the poisoning of a solid acid catalyst in the subsequent alkylation reaction is avoided, and the catalytic activity and the service cycle of the alkylation solid acid are improved.

Disclosure of Invention

The inventor finds that the solid acid is used as an alkylation catalyst and the carbon four is used as a main alkylation raw material (comprising C ₄ olefin and C ₄ alkane) through a proper combination flow and an optimized flow sequence, key impurities causing the poisoning of the solid acid catalyst can be effectively removed, so that the activity of the catalyst can be ensured, and the catalyst has the technical effects of delaying the deactivation rate of the solid acid catalyst in the alkylation process and prolonging the service life of the catalyst more unexpectedly. Based on this, the present invention is formed.

It is therefore an object of the present invention to address the problems of the prior art by providing a more optimal pretreatment process for an alkylated gasoline feedstock. It is a further object of the present invention to provide an alkylated gasoline feedstock that increases the stability of the solid acid alkylation catalyst and the efficiency of the alkylated gasoline production process.

The pretreatment method of the alkylated gasoline raw material is characterized by comprising the steps of pre-hydrogenation, rectification, dehydration, sulfide removal, nitrogen compound removal and oxygen compound removal.

The preferred pretreatment sequence of the process of the present invention is the sequence of steps of pre-hydrogenation, rectification, dehydration followed by the subsequent removal of sulfides, nitrogen compounds and oxygenates in any sequence of steps. For example, the process is carried out in the steps of pre-hydrogenation, rectification, dehydration, desulphurisation, nitrogen compound removal and oxygen compound removal. Wherein, the pre-hydrogenation, rectification and dehydration are carried out as the first three steps and are completed in sequence, and the sequence of the three steps of the subsequent desulphurisation, the removal of nitrogen compounds and the removal of oxygen compounds is arbitrary and is not limited.

In the method of the invention, the alkylation gasoline raw material mainly comprises four carbon components of a refinery or a chemical plant, and most mainly comprises components containing C ₄ olefin and C ₄ alkane; the preferred alkylate gasoline feed is an ether post-alkylation feed to an MTBE production process.

The refinery or chemical plant is used to alkylate components of gasoline feedstocks, mainly C ₄ olefins and C ₄ paraffins, with minor amounts of impurities. The typical weight content composition of the alkylated gasoline feedstock is isobutane: 35-49 (wt%) n-butane: 10-20% (wt%) butene: 35-45 wt% and the balance impurities, such as 1,3 butadiene (diolefins): 0.1-0.5 (wt%) of an oxygenate: 50-2000 μg/g, total sulfur: 2-150 μg/g, total nitrogen: 0-5 mug/g, water: not more than 500. Mu.g/g. If the raw material undergoes etherification reaction with methanol in the MTBE production process, the biggest difference in composition of the alkylated raw material after the ether is that isobutene in C ₄ olefin reacts with methanol to generate MTBE, and the weight content of isobutene in C ₄ olefin is generally not more than 2wt%, and the impurity content is correspondingly changed.

In the process of the present invention, the pre-hydrogenation step selectively hydrogenates diolefins in the alkylated gasoline feedstock to monoolefins, while in the pre-hydrogenation reactor of this step, the 1-butene in the alkylated gasoline feedstock may be largely isomerized to 2-butene. After the alkylation gasoline raw material is selectively hydrogenated in a pre-hydrogenation step, the utilization efficiency of butene is improved, and the diene polymerization can be reduced to generate larger molecules, so that the situations of blocking the pore channels of the solid acid catalyst and accelerating the deactivation of the catalyst are inhibited or avoided; most of 1-butene is isomerized, more 2-butene can be alkylated with isobutane to obtain octa-alkane with higher octane number, which is beneficial to improving the quality of the alkylated gasoline.

The pre-hydrogenation reactor is preferably a fixed bed reactor. A specific embodiment of the pre-hydrogenation may be carried out in the presence of a noble metal catalyst. The pre-hydrogenation conditions may be selected from the reaction temperature of 50-100 ℃, preferably 60-80 ℃, the volume space velocity of 3-8 h ^-1, preferably 4-7 h ^-1, the molar ratio of hydrogen to diolefin of 1-6: 1. preferably 2 to 4:1, a step of; the reaction pressure has little influence on the selective hydrogenation process, and the pressure is the pressure for maintaining the carbon four components to be in a liquid phase. The noble metal catalyst is preferably a group VIII noble metal-containing, preferably palladium, noble metal catalyst. After the pre-hydrogenation step, the residual amount of butadiene in the raw material is reduced to below 100 mug/g, and the 1-butene isomerization rate is more than 60 percent.

In the method, the rectification step is carried out, the pre-hydrogenated alkylated gasoline raw material is subjected to rectification by a rectification tower to remove most of oxygen-containing compounds and water in the raw material, water and impurities can form an azeotrope to be removed from the top of the tower, the pressure of the subsequent adsorbent is reduced, and the index of the catalyst is controlled to meet the requirement of a solid acid catalyst. The rectification step is carried out at the temperature of 40-110 ℃ and the pressure of 1.5-2.5 MPa. After the rectification step, the total oxygen-containing compound weight content in the raw materials is not more than 120 mug/g, preferably below 30 mug/g; the total sulfur content is not more than 50. Mu.g/g, preferably 20. Mu.g/g or less.

In the method, the dehydration step is to make the alkylation raw material contact with a drying dehydrating agent through a drying dehydrating tank to carry out adsorption dehydration, so that the moisture in the raw material is removed to meet certain requirements, and the influence on the subsequent adsorbent and the solid acid alkylation catalyst is reduced. Preferably after the rectification step. The dehydration step is to make the raw material contact with the dry dehydrating agent at the temperature of 10-60 ℃, the pressure of 0.2-2.5MPa and the volume space velocity of 0.1-5.0h ^-1. After the dehydration step, the water content in the raw material is not more than 50. Mu.g/g, preferably 20. Mu.g/g or less. The drying dehydrating agent can be a common drying dehydrating agent such as a 4A molecular sieve, a 5A molecular sieve, al ₂O₃ and the like. The regeneration of the bed layer of the dry dehydrating agent in the dry dehydrating tank can be performed by adopting a conventional method, for example, the dry gas regeneration is performed under the conditions of the operating temperature of 150-350 ℃ and the normal pressure of 0.2 MPa.

In the method, the step of removing sulfide is to make raw materials contact with a desulfurizing agent through a sulfide removing tank for adsorption desulfurization, control the content of the raw materials to meet the requirements of a catalyst, reduce or avoid the electronic effect and shielding effect of a regeneration auxiliary agent on the catalyst and the adsorption on an acidic active site, and influence the reaction and regeneration activity of the catalyst and the cycle life. Preferably after the dehydration step. The step of removing sulfide is to contact the raw material with a desulfurizing agent at the temperature of 10-60 ℃, the pressure of 0.2-2.5MPa and the volume space velocity of 0.1-5.0h ^-1, and remove sulfide in the raw material by adsorption, so that the total sulfur content (calculated by elemental sulfur) in the raw material is 3 mug/g, preferably 1 mug/g, more preferably 0.5 mug/g. The desulfurizing agent is preferably a molecular sieve loaded zinc oxide and copper oxide desulfurizing agent. The sulfide removal step adopts at least two adsorption beds, and the adsorption beds are connected in series or each adsorption bed is independently used. The desulfurization is realized by connecting two adsorption beds in series, and when the sulfur content at the outlet of the first desulfurization adsorption bed is more than 1 mug/g, the desulfurization adsorbent penetrates, and the first desulfurization adsorption bed is cut out at the moment to be used as a second desulfurization adsorption bed after the desulfurization adsorbent is regenerated. The desulfurization adsorbent regeneration adopts a sulfur burning regeneration scheme of supplementing oxygen with nitrogen, the regeneration temperature is 450-550 ℃, and the pressure is 0.4-0.6MPa.

In the method, the step of removing the nitrogen compounds is to contact the raw materials with a denitrifying compound adsorbent for adsorption denitrification, control the content of the denitrifying compound adsorbent to meet the requirements of the catalyst, and reduce or avoid the influence on the performance of the catalyst. The step of removing nitrogen compounds is preferably carried out in a nitrogen compound removing tank after the step of removing sulfide, and the conditions are that the temperature is 10-60 ℃, the pressure is 0.2-2.5MPa, and the volume space velocity is 0.1-5.0h ^-1, and the nitrogen compound removing tank is contacted with a denitrifying agent so as to remove nitride in the raw material, and the nitrogen compound content in the raw material is not more than 2 mug/g, preferably less than 1 mug/g. The denitrifying compound adsorbent is an X molecular sieve which is preferably impregnated with metal cations.

In the method, the step of removing the oxygen-containing compound is to make the raw material contact with the deoxidizing agent through a deoxidizing agent tank to adsorb the oxygen-containing compound, and the content of the oxygen-containing compound is controlled to meet the requirement of the catalyst, so that the influence on the performance of the catalyst is reduced or avoided. Preferably after the step of removing nitrogen compounds. The step condition of removing the oxygen-containing compound is that the oxygen-containing compound is contacted with a deoxidizer at the temperature of 10-60 ℃, the pressure of 0.2-2.5MPa and the volume space velocity of 0.1-5.0h ^-1, so that the oxygen-containing compound content in the raw materials is not more than 50 mug/g, preferably less than 20 mug/g, more preferably less than 2 mug/g. The deoxidizing agent is preferably an alkali metal-loaded Y-type molecular sieve. The step of removing the oxygen-containing compound adopts at least two adsorption beds, and the adsorption beds are connected in series or each adsorption bed is used independently. Preferably, the deoxidizer adopts two adsorption beds, when the oxide content at the outlet of the first deoxidizing adsorption bed is more than 20 mug/g, the deoxidizer penetrates, the first deoxidizing adsorption bed is cut out at the moment, the catalyst is regenerated, and the regenerated deoxidizer is used as a second deoxidizing adsorption bed. The deoxidizing adsorbent is regenerated with nitrogen at 300-350 deg.c and 0.3-0.7MPa.

In the process of the present invention, the operations of the respective steps may be carried out in a continuous manner or in a partial batch manner. It is preferred that all be conducted in continuous form, solely in view of the feedstock pretreatment requirements and the need for subsequent alkylation production for feedstock purity.

The invention is used for pretreating the four-component carbon, most importantly the C ₄ olefin and the C ₄ alkane component and the preferable ether-post-alkylation raw material of the MTBE production procedure of the alkylation raw material from a refinery or a chemical plant to obtain the alkylation raw material with impurities meeting the requirements of a solid acid catalyst, and the raw material can be introduced into a solid acid alkylation reactor for alkylation reaction to prepare the alkylation gasoline. The pretreatment method of the invention can simplify the pretreatment flow of the alkylation gasoline raw material and prolong the regeneration frequency of the adsorbent for removing the oxygen-containing compound and the sulfide.

The invention further provides an alkylated gasoline raw material, which is characterized in that butadiene in the alkylated gasoline raw material is below 100 mug/g, the water content is not more than 50 mug/g, the total sulfur content is less than 3 mug/g calculated by elemental sulfur, the nitrogen-containing compound content is not more than 2 mug/g, and the oxygen-containing compound content is not more than 50 mug/g. Preferably, the water content is not more than 20. Mu.g/g, the total sulfur content is less than 1. Mu.g/g, the nitrogen-containing compound content is not more than 1. Mu.g/g, and the oxygen-containing compound content is not more than 20. Mu.g/g. More preferably, the total sulfur content is less than 0.5 μg/g, the nitride content is no more than 1 μg/g, and the oxide content is no more than 2 μg/g.

The alkylation gasoline raw material provided by the invention is beneficial to prolonging the service life of a solid acid alkylation catalyst, improving the efficiency of the alkylation gasoline production process and improving the quality of the alkylation gasoline.

Drawings

FIG. 1 is a schematic flow diagram of a process for pretreatment of an alkylated gasoline feedstock of the present invention.

FIG. 2 is a schematic flow diagram of the two adsorption beds used in the sulfide removal step of the present invention.

FIG. 3 is a schematic diagram of a process for the removal of oxygenates in the present invention using two adsorbent beds.

FIG. 4 is a schematic flow diagram of a process for pretreating an alkylated gasoline feedstock in the absence of a rectifying column of comparative example 1.

Detailed Description

The present invention will be described in detail below with reference to the drawings and examples, but the present invention is not limited thereto.

FIG. 1 is a flow chart of one embodiment of the feedstock pretreatment process of the present invention. In FIG. 1, the apparatus comprises a pre-hydrogenation reactor 1, a dealkylation rectifying tower 2, a drying dehydration tank 3, a desulfurization adsorption bed 4, a denitrification tank 5 and a deoxidization adsorption bed 6.

In fig. 1, an alkylated gasoline raw material and hydrogen are subjected to a pre-hydrogenation reaction (comprising isomerization reaction of carbon four) in a pre-hydrogenation reactor 1, and the obtained material is rectified by a de-oxygenated compound rectifying tower 2; removing moisture in the drying dehydration tank 3 by using a drying agent; the dried raw material is subjected to sulfide removal in a desulfurization adsorption bed 4, nitride removal in a denitrification tank and oxygen-containing compound removal in a deoxidization adsorption bed. Also shown in fig. 1 are alkylated gasoline feedstock 7, hydrogen 8, hydrogenated carbon four feedstock 9, rectified carbon four feedstock 10, dehydrated carbon four feedstock 11, desulphurised carbon four feedstock 12, desulphurised carbon four feedstock 13, and desulphurised carbon four stream 14.

The pre-hydrogenation reactor 1 is filled with a supported noble metal catalyst, preferably a supported palladium-containing catalyst, and the like, and is used as an alkylated gasoline raw material 7 and hydrogen 8 to be subjected to a selective hydrogenation step in the pre-hydrogenation reactor 1,3 butadiene in a hydrogenated carbon four raw material 9 flowing out of the pre-hydrogenation reactor 1 is selectively hydrogenated into mono-olefin, and meanwhile, 1-butene can be mostly isomerized into 2-butene. Introducing the hydrogenated carbon four raw material 9 flowing out of the pre-hydrogenation reactor 1 into a de-oxygenated compound rectifying tower 2 for rectification, and rectifying the tower 2 to remove most oxygenated compounds and a small amount of water carried in the raw material, thereby obtaining the rectified carbon four raw material 10. The rectified carbon four raw material 10 flowing out from the bottom of the de-oxygenated compound rectifying tower 2 is subjected to the drying and dehydrating tank 3 to remove the water in the raw material. The dehydrated carbon four raw material 11 enters a desulfurization adsorption bed 4, and sulfide mainly comprising mercaptan and thioether in the raw material is removed by using a desulfurizing agent filled in the desulfurization adsorption bed 4. After the sulfide is removed, the carbon four raw material 12 enters a denitrification tank 5, and the denitrification agent filled in the denitrification tank 5 is utilized to remove the nitride in the carbon four raw material. The carbon four raw material 13 after the denitrification enters a deoxidizing adsorption bed 6, and oxide impurities mainly including ethers, ketones, alcohols and the like in the carbon four raw material are removed by using an oxidation removing agent to obtain a carbon four material flow 14 after the oxidation removal.

Fig. 2 is a schematic flow chart of a desulfurization step according to the present invention, wherein two adsorption beds are used, and the two adsorption beds include adsorption beds 4a and 4b, and the adsorption beds 4a and 4b respectively correspond to the post-sulfide-removal carbon four raw materials 12a and 12b, and the post-sulfide carbon four raw materials 12. The two adsorption beds 4a, 4b can be connected in series or in parallel, and are connected in series under normal working conditions. In the tandem operation, when the first adsorption bed 4a at the upstream is saturated, the second adsorption bed 4b at the downstream can ensure that the sulfide content in the carbon four meets the index requirement. When the sulfur content at the outlet of the first desulfurization adsorbent bed 4a is greater than 1 mug/g, the penetration of the desulfurization adsorbent is indicated, and at this time, the first desulfurization adsorbent bed 4a is cut out, and the regenerated desulfurization adsorbent is used as the second desulfurization adsorbent bed 4 b. The regeneration of the deactivated desulfurizing adsorbent adopts a regeneration scheme of burning sulfur by supplementing oxygen with nitrogen, and the regeneration temperature is 500 ℃ and the pressure is 0.4-0.6MPa.

FIG. 3 is a schematic flow diagram of two adsorbent beds for the oxygenate removal step of the present invention, comprising adsorbent beds 6a, 6b, and the adsorbent beds 6a, 6b correspond to the deoxygenated four-carbon feedstock 14a, 14b and the deoxygenated four-carbon feedstock 14, respectively. The two adsorption beds can be connected in series or in parallel. Under normal working conditions, the adsorption device is operated in series, and when the first adsorption bed 6a at the upstream is saturated, the second adsorption bed 6b at the downstream can ensure that the content of oxide in the carbon four meets the index requirement. The oxide content in the outlet stream of the first deoxidizing adsorption bed 6a is controlled to be not more than 50. Mu.g/g, preferably 20. Mu.g/g or less, and more preferably less than 2. Mu.g/g. When the outlet oxide content of the first deoxidizing adsorption bed is greater than 20. Mu.g/g, the penetration of deoxidizing adsorbent is indicated, and the first deoxidizing adsorption bed 6a is cut out at this time, regenerated, and then used as the second deoxidizing adsorption bed 6 b. The deoxidizing adsorbent is regenerated by nitrogen regeneration scheme at 300-350 deg.c and 0.4-0.6MPa.

By the method, impurities affecting the solid acid alkylation catalyst in the alkylation gasoline raw material can be effectively controlled, and the service life of the solid acid alkylation catalyst, the efficiency of the alkylation gasoline production process and the product quality can be improved.

In the examples, the content of carbon four components of the raw material is expressed as mass percent, and the impurity content is expressed in μg/g.

Example 1

This example illustrates the pretreatment method of the present invention.

This example was performed as a continuous raw material pretreatment process as shown in fig. 1.

The components of the four carbon raw materials used for alkylation reaction are isobutane: 47.49%, n-butane: 14.62%, butene: 37.56% (9.99% of isobutene content) and the balance of impurities. 1,3 butadiene: 0.26%, ethers: 126 μg/g, alcohols: 133 μg/g, acetone: 88 μg/g, total sulfur (mainly mercaptans and thioethers): 213 μg/g, total nitrogen: 35 μg/g, water: 169. Mu.g/g.

The carbon tetraalkylation raw material 7 enters a pre-hydrogenation reactor 1 and is subjected to selective hydrogenation of 1,3 butadiene with hydrogen 8 in the pre-hydrogenation reactor 1, the catalyst is an alumina-supported noble metal Pd catalyst, the Pd loading amount is 0.2-0.4 w%, the reaction temperature is 75 ℃, the pressure is 2.0MPa, the volume space velocity is 5.5h ^-1, and the molar ratio of hydrogen to diolefin is 3.2:1. after passing through the reactor, the 1,3 butadiene content in the feed was reduced to 16. Mu.g/g.

The hydrogenated carbon four raw material 9 enters a de-oxygenated compound rectifying tower 2 to remove most of oxygenated compound impurities, ethers, alcohols and acetone in the carbon four raw material 10 are respectively reduced to 38 mug/g, 8 mug/g and 7 mug/g after the rectifying step of the tower, the total oxygenated compound is about 53 mug/g, the operating temperature of a tower kettle is 70 ℃, the pressure is 1.8MPa, and the feeding amount is 2.3m ³/h; part of the water is also removed due to the azeotropic effect of the water and hydrocarbon oxygenates in the column, at a level of 29 μg/g; sulfur content 17. Mu.g/g.

The rectified C4 raw material 10 is dried and dehydrated in a water tank 3, 4A molecular sieve dehydrating agent is filled, the operation temperature is 40 ℃, the pressure is 0.7MPa, the volume space velocity is 1.2h ^-1, and the water content in the C4 raw material is reduced to 10 mug/g after the step.

The dehydrated carbon four raw material 11 passes through a desulfurization adsorption bed 4, the desulfurizing agent is molecular sieve loaded metal oxide (the metal content of a Y molecular sieve loaded with zinc oxide and copper oxide is about 3.5 percent of China petrochemical catalyst Co., ltd.), the operating temperature is 40 ℃, the pressure is 0.7MPa, the volume space velocity is 1.2h ^-1, and the total sulfur content in the raw material is reduced to 0.7 mug/g after the step.

The desulphurized carbon four raw material 12 is passed through a denitriding tank, the nitrogen-removing compound adsorbent is a modified molecular sieve (China petrochemical catalyst Co., ltd., the adsorbent is X molecular sieve impregnated with metal cations, the operating temperature is 40 ℃, the pressure is 0.7MPa, the volume airspeed is 1.2h ^-1, and the total nitrogen content in the raw material after the step is 0.6 mug/g.

The deoxidized carbon four raw material 13 passes through a deoxidized adsorption bed layer, the adsorbent is a molecular sieve loaded alkali metal type (China petrochemical catalyst Co., ltd., is a Y-type molecular sieve adsorbent loaded with calcium and potassium alkali metals, the content is about 0.5w%, the operating temperature is 40 ℃, the pressure is 0.7MPa, the volume airspeed is 1.2h ^-1, and the total amount of oxygen-containing compounds is reduced to 2 mug/g after the step.

It can be seen that key impurities such as diolefins, water, oxygenates, sulfur and nitrogen in the carbon-four feedstock are effectively controlled and removed.

Alkylation reaction is carried out on the alkylation gasoline raw material pretreated by the method.

Alkylation reaction evaluation conditions: the reaction temperature is 70 ℃, the pressure is 3.0MPa, the molar ratio of isobutane to butene is 18, the olefin feeding mass space velocity is 0.15h ^-1, and the catalyst is AIB-2 alkylation catalyst provided by China petrochemical catalyst Co. Wherein cycle life is defined as the single pass run time of the catalyst at a butene conversion of less than 99%; and detecting the olefin content at the outlet of the reactor by adopting gas chromatography analysis, and measuring the octane number of the collected alkylated gasoline serving as an alkylation product.

The alkylation reaction results were as follows: butene conversion: 100%, the cycle life of the solid acid catalyst is 55h, the octane number (RON) is 96.5, and the desulfurizing agent, the deoxidizing agent and the dehydrating agent are regenerated once in about half a year.

Example 2

The same raw material composition and raw material pretreatment steps as in example 1 were different in that the reaction temperature of the pre-hydrogenation reactor 1 was changed to 100℃and the other operating conditions of each impurity removal step were unchanged. After passing through the pre-hydrogenation reactor 1, the content of 1,3 butadiene in the raw material is 20 mu g/g, and the impurity removal condition is almost the same as that of the example 1 through other steps, so that key impurities such as diolefins, water, oxygen-containing compounds, sulfur and nitrogen in the carbon four raw material are effectively controlled and removed.

The alkylation reaction results were as follows: butene conversion: 100%, the cycle life of the solid acid catalyst is 54h, the octane number (RON) is 96.1, and the desulfurizing agent, the deoxidizing agent and the dehydrating agent are regenerated once in about half a year.

Example 3

The feed composition and impurity removal steps of example 1 were identical, except that the space velocity of the carbon four feed to the pre-hydrogenation reactor 1 was changed to 7h ^-1, and the other operating conditions of the impurity removal steps were unchanged. After passing through the pre-hydrogenation reactor 1, the content of 1,3 butadiene in the raw material is 45 mu g/g, and the impurity removal condition is almost the same as that of the example 1 through other steps, so that key impurities such as diolefins, water, oxygen-containing compounds, sulfur and nitrogen in the carbon four raw material are effectively controlled and removed.

Alkylation reaction is carried out on the alkylation gasoline raw material pretreated by the method. The alkylation reaction evaluation conditions were the same as in example 1.

The alkylation reaction results were as follows: butene conversion: 100%, solid acid catalyst cycle life 43h, octane number (RON) 95.2, desulfurizing agent, deoxidizing agent and dehydrating agent regenerated about half a year.

Example 4

The same feed composition and impurity removal step as in example 1 was followed, except that the molar ratio of hydrogen to diolefin in pre-hydrogenation reactor 1 was changed to 5:1, other operation conditions of each impurity removing step are unchanged. After passing through the pre-hydrogenation reactor 1, the content of 1,3 butadiene in the raw material is 16 mug/g, and the impurity removal condition is almost the same as that of the example 1 through other impurity removal steps, so that key impurities such as diolefin, water, oxygen-containing compounds, sulfur and nitrogen in the carbon four raw material are effectively controlled and removed.

The alkylation reaction results were as follows: butene conversion: 100%, the cycle life of the solid acid catalyst is 56 hours, the octane number (RON) is 96.6, and the desulfurizing agent, the deoxidizing agent and the dehydrating agent are regenerated once in about half a year.

Example 5

The raw material composition and impurity removal step of example 1 were the same, except that the operating temperature of the oxygenate removal rectifying tower 2 was changed to 105℃and the other operating conditions of each impurity removal step were unchanged. After passing through the oxygenate removal rectifying tower 2, the total amount of total oxygenate in the raw materials is about 65 mug/g, the water content is 31 mug/g, the total sulfur content is 19 mug/g, and the impurity removal conditions are almost the same as those of the example 1 through other impurity removal steps, so that key impurities such as diene, water, oxygenate, sulfur and nitrogen in the four-carbon raw materials are effectively controlled and removed.

The alkylation reaction results were as follows: butene conversion: 100%, the cycle life of the solid acid catalyst is 49 hours, the octane number (RON) is 95.5, and the regeneration time of the desulfurizing agent, deoxidizing agent and dehydrating agent is shortened by about 15%.

Example 6

The same raw material composition and impurity removal step as in example 1 were different in that the space velocity of the carbon four raw materials passing through the drying dehydration tank 3, the desulfurization adsorption bed 4, the denitrification tank 5, the deoxidization adsorption bed 6 was 4.1h ^-1, and the operating pressure was 1.5MPa; other operating conditions of each impurity removing step are unchanged. After drying the dehydration tank 3, the water content in the raw material C is reduced to 19 mug/g; after passing through the desulfurization adsorption bed 4, the total sulfur content in the raw material is reduced to 1.0 mug/g; after passing through the denitrification tank 5, the total nitrogen content in the raw materials is 0.9 mug/g; after passing through the deoxidizing adsorption bed 6, the total amount of oxygen-containing compounds in the raw material is reduced to 5 mug/g. Through other impurity removal steps, the impurity removal conditions are almost the same as in example 1, and key impurities such as diolefins, water, oxygenates, sulfur and nitrogen in the carbon-four feedstock are effectively controlled and removed.

The alkylation reaction results were as follows: butene conversion: 100%, the cycle life of the solid acid catalyst is 46h, the octane number (RON) is 95.3, and the desulfurizing agent, the deoxidizing agent and the dehydrating agent are regenerated for about two months.

Example 7

The same feed composition and impurity removal step as in example 1 was followed, except that the pre-hydrogenation reactor 1 was operated at a reaction temperature of 50 ℃, a pressure of 2.0MPa, a volume space velocity of 7.5h ^-1, a molar ratio of hydrogen to diolefin of 2:1, a step of; the operating temperature of the oxygenate removal rectifying tower 2 is 50 ℃ and the pressure is 2.2MPa; the airspeed, the operating pressure and the temperature of the carbon four raw materials of the drying dehydration tank 3, the desulfurization adsorption bed 4, the denitrification tank 5 and the deoxidization adsorption bed 6 are respectively 4.8h ^-1, 2.5MPa and 25 ℃; after pretreatment, the amounts of 1.3-butadiene, total oxygenate, water, total sulfur, total nitrogen and oxides in the raw materials were 31. Mu.g/g, 69. Mu.g/g, 32. Mu.g/g, 2.3. Mu.g/g, 1.4. Mu.g/g, 29. Mu.g/g, respectively. Key impurities such as diolefins, water, oxygenates, sulfur and nitrogen in the carbon-four feedstock are effectively controlled and removed.

The alkylation reaction results were as follows: butene conversion: 100%, solid acid catalyst cycle life 48h, octane number (RON) 95.5, desulfurizing agent, deoxidizing agent and dehydrating agent regenerated once a month.

Example 8

The difference from example 1 is that the impurity removal step was changed: the dry dehydration tank 3 is exchanged with the position of the pre-hydrogenation reactor 1.

After pretreatment, the amounts of 1.3-butadiene, total oxygenate, water, total sulfur, total nitrogen and oxides in the raw materials were 19. Mu.g/g, 55. Mu.g/g, 22. Mu.g/g, 1.1. Mu.g/g, 1.0. Mu.g/g, 15. Mu.g/g, respectively. Compared with the step of the embodiment 1, the drying dehydration tank 3 is more saturated by water, the regeneration frequency of the drying agent is more than 1 time more than that of the embodiment 1, and the impurity removal efficiency is reduced.

The alkylation reaction results were as follows: butene conversion: 100%, the cycle life of the solid acid catalyst is 52h, the octane number (RON) is 95.2, the desulfurizing agent, the deoxidizing agent and the dehydrating agent are regenerated once in about half a year, and the dehydrating agent is regenerated once in about two months.

Example 9

The difference from example 1 is that the impurity removal step was changed: the positions of the desulfurization adsorption bed 4 and the deoxidation adsorption bed 6 are exchanged.

After pretreatment, the amounts of 1.3-butadiene, total oxygen-containing compound, water, total sulfur, total nitrogen and oxide in the raw materials were 17. Mu.g/g, 51. Mu.g/g, 12. Mu.g/g, 0.9. Mu.g/g, 1.0. Mu.g/g and 3. Mu.g/g, respectively, which were equivalent to the impurity removing effect of example 1.

The alkylation reaction results were as follows: butene conversion: 100%, the cycle life of the solid acid catalyst is 55h, the octane number (RON) is 96.6, and the desulfurizing agent, the deoxidizing agent and the dehydrating agent are regenerated once in about half a year.

Example 10

The components of the carbon four raw material used as the post-MTBE alkylation reaction are composed of isobutane: 48.36%, n-butane: 15.19%, butene: 36.12% (wherein the isobutene content was 1.65%), the remainder being impurities, the impurity content being comparable to the starting material of example 1. It can be seen that the isobutylene content in the carbon tetraolefins is significantly reduced from the feedstock of example 1, which reduces the isobutylene superposition to reduce the impact on solid acid catalyst life and alkylated product quality.

The pretreatment procedure was as in example 1, except that the amounts of 1.3-butadiene, total oxygenates, water, total sulfur, total nitrogen and oxides in the pretreated feedstock were 15. Mu.g/g, 49. Mu.g/g, 11. Mu.g/g, 0.9. Mu.g/g, 1.0. Mu.g/g, 2. Mu.g/g, respectively.

The alkylation reaction results were as follows: butene conversion: 100%, the cycle life of the solid acid catalyst is 60 hours, the octane number (RON) is 96.7, and the desulfurizing agent, the deoxidizing agent and the dehydrating agent are regenerated once in about half a year.

Comparative example 1

This comparative example illustrates a pretreatment process for an alkylated gasoline feedstock lacking an oxygenate removal rectifying tower.

Fig. 4 shows a pretreatment flow for the rectification column 2 lacking the oxygenate removal.

The carbon four raw material 7 enters a pre-hydrogenation reactor, and is subjected to selective hydrogenation of 1,3 butadiene in the pre-hydrogenation reactor 1 together with hydrogen 8, and the operation conditions are the same as those in the example 1. After passing through the reactor, 1,3 butadiene in the raw material 9 is reduced to below 18 mug/g; the hydrogenated carbon four raw material 9 from the pre-hydrogenation reactor directly enters the drying dehydration tank 3.

The total oxygen-containing compound in the hydrogenated carbon four raw material 9 is 315 mug/g, and the water content is 65 mug/g; the water content in the raw material C4 of the hydrogenated C4 raw material 9 is reduced to 28 mug/g after the raw material C4 is dried in a dehydration tank 3; after the dehydrated carbon four raw material 11 passes through the desulfurization adsorption bed 4, the total sulfur content is reduced to 2 mug/g; after the carbon four raw material 12 is subjected to the sulfide removal, the total nitrogen content is not more than 1 mug/g; after the denitrified carbon four raw material 13 passes through the oxide adsorption bed, the total amount of oxygen-containing compounds in the carbon four material flow 14 after the oxide removal is reduced to 32 mug/g.

In contrast to the inventive scheme of fig. 1, the removal of key impurities such as diolefins, water, oxygenates, sulfur and nitrogen in the carbon four stream 14 after the present comparative example has been deoxygenated is less effective than that of fig. 1 due to the lack of the oxygenate removal rectifying column 2.

Alkylation was performed using the pretreated feedstock of this comparative example, in the same manner as in evaluation example 1.

The alkylation reaction results were as follows: butene conversion: 100%, octane number (RON): 94.2, the catalyst has stable performance, the catalyst cycle life is 39 hours, and the desulfurizing agent, deoxidizing agent and dehydrating agent are regenerated once in two months.

Comparative examples 2 and 3

Comparative examples 2 and 3 illustrate the influence of the lack of the pre-hydrogenation step or the insufficient degree of pre-hydrogenation in the pre-hydrogenation step.

Alkylated gasoline feedstock 7 was the same as in example 1 and evaluated under the same conditions as in example 1.

The alkylated gasoline raw material 7 enters a pre-hydrogenation reactor 1 and is subjected to selective hydrogenation of 1,3 butadiene in the pre-hydrogenation reactor 1 together with hydrogen 8. Butadiene is often contained in the carbon four raw materials with the mass fraction of 0.1-0.5%, and the butadiene is easy to polymerize on the surface of a solid acid alkylation catalyst to form macromolecules or colloid, so that a catalyst pore canal is blocked, and the service life of the catalyst and the quality of the alkylate oil are influenced.

Table 1 shows the 1, 3-butadiene content of the pre-hydrogenated carbon four feedstock as a function of catalyst cycle life. It can be seen that the 1, 3-butadiene removal effect in the feedstock is closely related to the catalyst cycle life.

Table 1 also shows the 1, 3-butadiene content of the pre-hydrogenated C.sub.four feedstock at 16. Mu.g/g (see example 1).

Comparative examples 2 and 3 gave the results of evaluation of the raw materials according to evaluation example 1, with the mass fractions of the carbon four raw materials after removal of butadiene being 500. Mu.g/g and 1000. Mu.g/g, respectively. Table 1 shows that the butadiene content of the pretreated feedstock has an effect on catalyst cycle life and octane number, which are significantly reduced. Therefore, it is very important to ensure the removal effect of 1, 3-butadiene in the carbon four raw material.

TABLE 1

Comparative examples 4 and 5

Comparative examples 4 and 5 illustrate the influence of insufficient desulfurization degree in the desulfurization adsorption step.

Comparative examples 4 and 5 show that the alkylated gasoline feedstock 7 enters the pre-hydrogenation reactor 1 with a total amount of sulphides of about 22 μg/g, and after passing through the sulphide removal tank 4 the sulphide content of the feedstock is maintained in the range of 3 to 10 μg/g, the catalyst cycle life and the alkylated gasoline quality are shown in table 2. In addition, the desulfurizing agent regeneration is increased from 1 time in half a year to 3 times in half a year.

The evaluation results of the sulfide content in the pretreated feedstock for the alkylation reaction are given in table 2, together with the evaluation results of example 1. It is known that ensuring the desulfurization degree of sulfur in the alkylated gasoline feedstock is a precondition for maintaining stable performance and excellent product quality of the alkylation catalyst. Therefore, the desulfurizing agent needs to maintain good adsorption activity on sulfur in the raw materials, and timely regenerate the desulfurizing adsorption tank, so that the cycle life of the catalyst and the quality of the alkylated gasoline product are improved.

TABLE 2

Comparative examples 6 and 7

Comparative examples 6 and 7 illustrate the influence of insufficient degree of deoxidation in the deoxidation adsorption step.

Alkylation gasoline feedstock 7 was the same as in example 1 and alkylation evaluation conditions were the same as in example 1.

The alkylated gasoline raw material 7 enters a pre-hydrogenation reactor, wherein the oxygenated compound impurities including methanol, acetone, butanol, dimethyl ether and the like are contained, the total amount of the oxygenated compound is about 347 mug/g, and after the alkylated gasoline raw material passes through a deoxidizing adsorption bed 6, the total amount of the oxygenated compound fluctuates between 2 mug/g and 50 mug/g under different removal conditions.

Comparative examples 6 and 7 show the effect of varying oxygenate content in the feed on catalyst cycle life. When the oxide content in the pretreated alkylation gasoline raw material has an influence relationship with the cycle life of the catalyst and the quality of the product, the regeneration frequency of the deoxidizer is obviously increased.

Table 3 illustrates the effect of oxygenate content in the feedstock on the catalyst cycle life. The evaluation results of the alkylation reaction of example 1 are also shown in the table.

TABLE 3 Table 3

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Claims

1. A pretreatment method of an alkylated gasoline raw material, which is characterized in that the alkylated gasoline raw material is pretreated in any step sequence by the step sequence of pre-hydrogenation, rectification and dehydration and then by the step sequence of desulphurizing, removing nitrogen compounds and removing oxygen compounds; the pretreated alkylation gasoline raw material is used for alkylation reaction with solid acid as a catalyst;

the pre-hydrogenation step is carried out in a fixed bed reactor in the presence of a noble metal catalyst, the reaction temperature is 50-100 ℃, the volume space velocity is 3-8 h ^-1, and the molar ratio of hydrogen to diolefin is 1-6: 1, maintaining the pressure of the liquid phase of the four carbon components in the raw materials; after the pre-hydrogenation step, the residual quantity of butadiene in the raw material is reduced to below 100 mug/g, and the 1-butene isomerization rate is more than 60%;

The rectification step is carried out at the temperature of 40-110 ℃ and the pressure of 1.5-2.5 MPa; and in the rectifying step, the total oxygen-containing compound is not more than 120 mug/g, and the total sulfur content is not more than 30 mug/g.

2. The process according to claim 1, wherein the steps of pre-hydrogenation, rectification, dehydration, desulphurisation, nitrogen-containing compound removal and oxygen-containing compound removal are carried out.

3. The process of claim 1 wherein said alkylated gasoline feedstock is a refinery component comprising C4 olefins and C4 paraffins.

4. The process of claim 1 wherein said alkylated gasoline feedstock is a component of a chemical plant comprising C4 olefins and C4 paraffins.

5. The process of claim 1 wherein said alkylated gasoline feedstock is an etherified alkylation feedstock of an MTBE production process.

6. The method according to claim 1, wherein the pre-hydrogenation step is carried out at a reaction temperature of 60-80 ℃, a volume space velocity of 4-7 h ^-1, and a molar ratio of hydrogen to diolefin of 2-4: 1.

7. The method according to claim 1, wherein the rectifying step is such that the total oxygenate is 50 μg/g or less and the total sulfur content is 20 μg/g or less.

8. The method according to claim 1 or 2, wherein the dehydration step is to contact the raw material with a dry dehydrating agent at a temperature of 10 to 60 ℃, a pressure of 0.2 to 2.5mpa, and a volume space velocity of 0.1 to 5.0h ^-1.

9. The method according to claim 1, wherein after said dewatering step the water content of the feedstock is not more than 50 μg/g.

10. The method of claim 9, wherein after said dehydrating step, the water content of the feedstock is not greater than 20 μg/g.

11. The method according to claim 1 or 2, wherein the step of removing sulfide is to contact the raw material with a desulfurization adsorbent at a temperature of 10-60 ℃ and a pressure of 0.2-2.5 mpa and a volume space velocity of 0.1-5.0 h ^-1, and remove sulfide in the raw material by adsorption, so that the total sulfur content in the raw material is less than 3 μg/g.

12. The method according to claim 11, wherein the step of removing sulfide from the feedstock by adsorption results in a total sulfur content in the feedstock of less than 1 μg/g.

13. The method of claim 12, wherein the step of removing sulfide comprises removing sulfide from the feedstock by adsorption such that the total sulfur content in the feedstock is less than 0.5 μg/g.

14. A process according to claim 1 or claim 2, wherein the step of desulphurisation employs at least two adsorption beds, either in series or separately for each bed.

15. The method according to claim 14, wherein the step of removing sulfide is carried out by connecting two adsorption beds in series, and when the sulfur content at the outlet of the first desulfurization adsorption bed is greater than 1 μg/g, cutting out the first desulfurization adsorption bed, regenerating the desulfurization adsorbent, and using the regenerated desulfurization adsorbent as the second desulfurization adsorption bed.

16. The method according to claim 15, wherein the desulfurization adsorbent regeneration is performed by adopting a nitrogen-supplemented oxygen-fired sulfur regeneration scheme, wherein the regeneration temperature is 450-550 ℃ and the pressure is 0.4-0.6 MPa.

17. The method according to claim 1 or 2, wherein the step of removing nitrogen compounds is to contact the raw material with a denitrifying agent at a temperature of 10-60 ℃ and a pressure of 0.2-2.5 mpa and a volume space velocity of 0.1-5.0 h ^-1 so as to remove nitrides in the carbon four raw material, so that the content of the nitrides in the raw material is not more than 2 μg/g.

18. The method of claim 17, wherein the step of removing nitrogen compounds results in a nitride content in the feedstock of less than 1 μg/g.

19. The method according to claim 1 or 2, wherein the step of removing the oxygen-containing compound is to contact the raw material with a deoxidizing adsorbent at a temperature of 10-60 ℃, a pressure of 0.2-2.5 mpa and a volume space velocity of 0.1-5.0 h ^-1 so as to remove the oxygen-containing compound in the carbon four raw material, so that the content of the oxygen-containing compound in the raw material is not more than 50 μg/g.

20. The method of claim 19, wherein the step of de-oxygenating results in an oxide content of less than 20 μg/g of feedstock.

21. The method of claim 20, wherein the step of de-oxygenating results in an oxide content of less than 2 μg/g of feedstock.

22. A process according to claim 1 or claim 2 wherein the oxygenate removal step employs at least two adsorbent beds, either in series or separately for each adsorbent bed.

23. The method of claim 22, wherein the step of removing oxygen-containing compounds comprises two adsorption beds, and when the content of oxide at the outlet of the first deoxidation adsorption bed is more than 20 mu g/g, the first deoxidation adsorption bed is cut out, the deoxidization adsorbent is regenerated, and the regenerated deoxidization adsorption bed is used as the second deoxidation adsorption bed.

24. The method of claim 23, wherein the deoxidizing adsorbent is regenerated with nitrogen at a temperature of 300-350 ℃ and a pressure of 0.3-0.7 mpa.

25. The method according to claim 1, wherein in the pretreated alkylated gasoline feedstock, the butadiene is below 100 μg/g, the water content is not more than 50 μg/g, the total sulfur content is less than 3 μg/g as elemental sulfur, the nitrogen-containing compound content is not more than 2 μg/g, and the oxygen-containing compound content is not more than 50 μg/g.

26. The method of claim 25, wherein the water content in the pretreated alkylated gasoline feedstock is no greater than 20 μg/g, the total sulfur content is less than 1 μg/g, the nitrogen-containing compound content is no greater than 1 μg/g, and the oxygen-containing compound content is no greater than 20 μg/g.

27. The method of claim 26, wherein the total sulfur content in the pretreated alkylated gasoline feedstock is less than 0.5 μg/g and the oxygenate content is no greater than 2 μg/g.