CN112321379A - Energy-saving and environment-friendly method for preparing ethylbenzene from dry gas - Google Patents
Energy-saving and environment-friendly method for preparing ethylbenzene from dry gas Download PDFInfo
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- YNQLUTRBYVCPMQ-UHFFFAOYSA-N Ethylbenzene Chemical compound CCC1=CC=CC=C1 YNQLUTRBYVCPMQ-UHFFFAOYSA-N 0.000 title claims abstract description 228
- 238000000034 method Methods 0.000 title claims abstract description 54
- UHOVQNZJYSORNB-UHFFFAOYSA-N Benzene Chemical compound C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 claims abstract description 567
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- 238000000926 separation method Methods 0.000 claims abstract description 149
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C2/00—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms
- C07C2/54—Preparation of hydrocarbons from hydrocarbons containing a smaller number of carbon atoms by addition of unsaturated hydrocarbons to saturated hydrocarbons or to hydrocarbons containing a six-membered aromatic ring with no unsaturation outside the aromatic ring
- C07C2/64—Addition to a carbon atom of a six-membered aromatic ring
- C07C2/66—Catalytic processes
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C6/00—Preparation of hydrocarbons from hydrocarbons containing a different number of carbon atoms by redistribution reactions
- C07C6/08—Preparation of hydrocarbons from hydrocarbons containing a different number of carbon atoms by redistribution reactions by conversion at a saturated carbon-to-carbon bond
- C07C6/12—Preparation of hydrocarbons from hydrocarbons containing a different number of carbon atoms by redistribution reactions by conversion at a saturated carbon-to-carbon bond of exclusively hydrocarbons containing a six-membered aromatic ring
- C07C6/126—Preparation of hydrocarbons from hydrocarbons containing a different number of carbon atoms by redistribution reactions by conversion at a saturated carbon-to-carbon bond of exclusively hydrocarbons containing a six-membered aromatic ring of more than one hydrocarbon
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C7/00—Purification; Separation; Use of additives
- C07C7/11—Purification; Separation; Use of additives by absorption, i.e. purification or separation of gaseous hydrocarbons with the aid of liquids
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C2529/00—Catalysts comprising molecular sieves
- C07C2529/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites, pillared clays
- C07C2529/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
- C07C2529/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11
- C07C2529/48—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11 containing arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
Abstract
The invention provides an energy-saving and environment-friendly method for preparing ethylbenzene by using dry gas, which is mainly used for gas-liquid separation and tail gas debenzolization of a reaction product of preparing ethylbenzene by using dry gas. The method is characterized in that gas-liquid separation and tail gas absorption of a reaction product of preparing ethylbenzene from dry gas are carried out in the same tower, the absorption separation tower is divided into four sections, the upper section of the tower is a filler section, the middle section of the tower is a tube array cooling section, the lower section of the tower is a plate tower, and the bottom section of the tower is a tower kettle. The reaction product enters from the upper part of the tower kettle, and the absorbent enters from the top of the packing section; after the absorption and separation processes of the absorption and separation tower, tail gas enters a fuel gas pipe network from the top of the tower, rich absorption liquid is mixed with condensed liquid in reaction products, and the mixture flows out from the bottom of the tower and enters a benzene tower. The non-condensable gas at the top of the benzene tower returns to the absorption separation tower, the upper section of the benzene tower pumps out the circulating benzene 1 to an alkylation reactor, the circulating benzene 2 at the bottom of a benzene tower reflux tank goes to a transalkylation reactor, the benzene tower bottom material enters an ethylbenzene tower, a product ethylbenzene is obtained at the top of the ethylbenzene tower, the bottom liquid of the ethylbenzene tower is divided into three strands, one strand is used as an absorbent to return to the absorption separation tower, the other strand goes to the transalkylation reactor, and the other strand is used for obtaining aromatic oil. The invention has simple and reliable separation process, fully utilizes the reaction heat, reduces the tower equipment, saves the equipment investment and the subsequent operation cost, and reduces the energy consumption of the device. The recovery rate of the benzene carried by the tail gas of the separation method is more than 99.9 percent, and the purity of the ethylbenzene product is more than 99.8 percent.
Description
Technical Field
The invention provides an energy-saving and environment-friendly method for preparing ethylbenzene by using dry gas, which is mainly used for gas-liquid separation and tail gas debenzolization of a reaction product of preparing ethylbenzene by using dry gas. The method has simple and reliable separation process, gas-liquid separation of reaction products and tail gas absorption are carried out in the same tower, heat energy is fully utilized, tower equipment is reduced, equipment investment and subsequent operation cost are saved, and energy consumption of the device is reduced. The recovery rate of the benzene carried by the tail gas is high, the purity of the ethylbenzene product meets the requirement, and the economic benefit and the environmental benefit of a refinery are greatly improved.
Background
Ethylbenzene is an important organic chemical raw material, and is mainly used for producing styrene, and further producing polystyrene, engineering plastics, styrene butadiene rubber and the like. In recent years, with the development of economy, the demand of China for ethylbenzene is continuously increased, the ethylbenzene is in a state of short supply and short demand all the year round, and more than 40% of the demand depends on import every year.
Meanwhile, with the continuous development of the oil refining industry in China, a large amount of dry gas is produced as a byproduct in a refinery, the ethylene in the dry gas is considerable, and the dry gas is usually used as fuel or directly burned by putting a torch, so that huge waste of resources is caused. The technology for preparing the ethylbenzene by the dry gas can effectively utilize the dry gas used as fuel to produce ethylbenzene products with high added values which are not in demand in the market, and can greatly improve the economic benefit of refineries.
The technology for preparing ethylbenzene by using dry gas is extended from the technology for preparing ethylbenzene by using ethylene, which is developed in the middle of the last century, and raw materials are changed from high-concentration ethylene or pure ethylene into dilute ethylene or dry gas with lower ethylene concentration. For conventional catalytic cracking dry gas, the ethylene concentration is about 5-20%, and inert gases such as hydrogen, methane, ethane and the like account for most of the conventional catalytic cracking dry gas. The inert gases are mixed in the reaction product of the ethylbenzene preparation from ethylene and directly enter a rectification separation system such as a benzene tower and the like, so that a large load is brought to a device, the gas flux in the tower is several times or even dozens of times larger than that of the gas flux to be treated under other process conditions, the liquid phase flux in the tower kettle is correspondingly increased, so that great energy consumption is brought, meanwhile, because the gas phase and the liquid phase are balanced, a large amount of benzene and other aromatic hydrocarbons can be carried away in tail gas at the top of the tower, so that the consumption of the benzene not only can cause economic loss, but also can bring great harm to the natural environment and the human health.
Therefore, compared with the technology for preparing ethylbenzene from ethylene, the technology for preparing ethylbenzene from dry gas is more noteworthy in that: the method can effectively separate gas and liquid of a reaction product of preparing ethylbenzene from dry gas under the condition of not influencing the yield and purity of the ethylbenzene product, and recover benzene in tail gas.
The conventional separation method of the process for preparing ethylbenzene from ethylene needs to cool reaction products to normal temperature, carry out flash evaporation absorption twice or more under different pressures, then heat and raise the temperature, and enter rectification systems such as a benzene tower and the like, the process has high energy consumption, and the flash evaporated gas phase and the non-condensable gas at the top of the benzene tower can carry benzene.
CN2004100211028 discloses a process flow for preparing ethylbenzene by catalytic dry gas, wherein a reaction product separation system of the method is a conventional separation flow, namely, reaction products are subjected to heat exchange and then enter a rough separation tower, non-condensable gas at the top of the tower is condensed and cooled to 5-20 ℃, the reaction products enter an absorption tower, the bottom liquid of the rough separation tower enters a benzene tower, a toluene tower, an ethylbenzene tower, a polyethylbenzene removal tower and a diethylbenzene tower, and circulating benzene, toluene, ethylbenzene, propylbenzene, heavy components and diethylbenzene are sequentially separated. Wherein the rough separation tower is used for gas-liquid separation, and the absorption tower is used for recovering benzene and aromatic hydrocarbon carried in gas phase. The benzene recovery rate of the method can reach 99.5 percent.
CN2009100063071 discloses a method for preparing ethylbenzene by reacting dilute ethylene with benzene. After the alkylation reaction product is subjected to gas-liquid separation, tail gas passes through a low-temperature absorption discharge device, a liquid product is sequentially separated into circulating benzene, ethylbenzene, propyl benzene, diethyl benzene and heavy components through a separation system, and the diethyl benzene and the benzene return to an transalkylation reactor for further reaction to generate ethylbenzene. In example 1, the gas-liquid separation device is a rough separation tower, in example 2, the gas-liquid separation device is cooled by chilled water, the gas at the top of a benzene tower reflux tank enters a non-aromatic removal tower, non-condensable gas at the top of the non-aromatic removal tower is discharged, and tower bottom materials return to the benzene tower. The purity of the ethylbenzene product of the method is 99.7%, wherein the content of xylene is 721ppm, the total selectivity of the ethylene to the ethylbenzene is 99.3%, and the recovery rate of the benzene carried by the tail gas is 99.5%.
CN2013103576085 discloses a separation process of ethylbenzene and/or propylbenzene products from ethylene and/or propylene-containing gas by a gas phase method. In the method, reaction products directly enter a benzene tower, gas phase at the top of the benzene tower enters a low-temperature absorption tower, tail gas of the absorption tower is discharged from the top of the tower, and liquid phase at the bottom of the absorption tower returns to the benzene tower. The circulating benzene is pumped out from the upper part of the benzene tower, and the materials at the bottom of the tower are sequentially separated into a plurality of or all of toluene, ethylbenzene, propyl benzene, diethylbenzene and high-boiling residues. The method has no rough separation tower, the reaction product and the inert gas directly enter a benzene tower, and the material at the bottom of the benzene tower needs to be sequentially separated into aromatic hydrocarbon components through each rectifying tower. No embodiment data of the method supports the technical effect of the invention.
CN981138470 discloses a process for preparing ethylbenzene and propylbenzene by reacting dilute ethylene, propylene and benzene. The reaction product of the method directly enters a stable absorption tower, gas-liquid separation and tail gas recovery of aromatic hydrocarbon are simultaneously carried out in the stable absorption tower, an absorbent is a mixture of materials at the bottoms of a benzene tower and a toluene tower, or materials at the bottoms of an ethylbenzene tower and a propylbenzene tower, tail gas at the top of the tower is used as fuel, or the tail gas enters a gas pipe network, liquid at the bottom of the tower enters each rectifying tower, and benzene, toluene, ethylbenzene, propylbenzene and polyalkylbenzene are sequentially separated. The purity of the ethylbenzene of the method is 99.7 percent, wherein the content of dimethylbenzene is 945ppm, the total selectivity of the ethylene to the ethylbenzene is 99 percent, and the recovery rate of benzene carried by tail gas is not given.
The invention provides an energy-saving and environment-friendly method for preparing ethylbenzene from dry gas. According to the invention, the reaction product of the ethylbenzene preparation from dry gas enters the absorption separation tower after heat exchange, so that gas-liquid separation and tail gas absorption and debenzolization are realized. The absorption separation tower is divided into four sections, the upper section of the tower is a filler section, the middle section of the tower is a tube array cooling section, the lower section of the tower is a plate tower, and the bottom section of the tower is a tower kettle. After the alkylation reaction product enters the absorption separation tower, the absorption separation tower can complete four processes, namely flash evaporation, depressurization and temperature reduction, gas-liquid fractionation and separation of a plate tower section, cooling and condensation of a tube array cooling section and absorption and liquid removal of tail gas. The invention makes full use of the reaction heat, can effectively separate the gas and the liquid of the reaction product of preparing the ethylbenzene from the dry gas under the condition of not influencing the yield and the purity of the ethylbenzene product, and can recover the benzene in the tail gas.
The invention reduces a rough separation tower, a tail gas benzene absorption tower and subsequent aromatic hydrocarbon rectifying towers, directly circulates the aromatic hydrocarbons except the product ethylbenzene back to a reaction system, further generates alkylation reaction and transalkylation reaction, saves equipment investment and subsequent operation cost, and simultaneously improves the yield of the product ethylbenzene.
Disclosure of Invention
The invention provides an energy-saving and environment-friendly method for preparing ethylbenzene by using dry gas, which is mainly used for gas-liquid separation and tail gas debenzolization of a reaction product of preparing ethylbenzene by using dry gas. Specifically, gas-liquid separation and tail gas absorption of the reaction product of preparing ethylbenzene from dry gas are carried out in the same tower, so that reaction heat is fully utilized, crude separation tower equipment and subsequent aromatic hydrocarbon rectifying towers are reduced, and aromatic hydrocarbons except the product ethylbenzene are directly circulated back to the reaction system. The purity of the ethylbenzene product meets the requirement, the recovery rate of the benzene carried by the tail gas is high, and the economic benefit and the environmental benefit of a refinery are greatly improved.
The invention provides an energy-saving and environment-friendly method for preparing ethylbenzene from dry gas, which comprises the following steps:
(1) after the propylene of the raw material dry gas is removed by pretreatment, the raw material dry gas enters the reactor from the top of the alkylation reactor and between the catalyst bed layers in a segmented manner;
(2) the alkylation reaction product of the dry gas ethylbenzene preparation enters an absorption separation tower after heat exchange, the tower is divided into four sections, the upper section of the tower is a filler section, the middle section of the tower is a tube cooling section, the lower section of the tower is a plate tower section, and the bottom section of the tower is a tower kettle section;
(3) the alkylation reaction product enters from the upper part of a tower kettle of the absorption separation tower, the absorbent enters from the top of a packing section, after the absorption and separation processes, tail gas enters a fuel gas pipe network from the top of the tower, rich absorption liquid is mixed with condensed liquid of the reaction product, and the mixture flows out from the bottom of the tower kettle and enters a benzene tower;
(4) adding fresh benzene at normal temperature from a benzene tower reflux tank, returning noncondensable gas of a benzene tower to an absorption separation tower, pumping circulating benzene 1 from the upper section of the benzene tower to an alkylation reactor, dividing the circulating benzene 1 into circulating hot benzene and circulating cold benzene, respectively entering the reactor between the top of the reactor and a catalyst bed layer, leading circulating benzene 2 at the bottom of the benzene tower reflux tank to an alkyl transfer reactor, leading benzene tower substrate to an ethylbenzene tower, obtaining a product ethylbenzene at the top of the ethylbenzene tower, dividing ethylbenzene tower bottom liquid into three strands by using multiple ethylbenzene mainly containing diethylbenzene, obtaining aromatic oil by one strand, returning the aromatic oil serving as an absorbent to the absorption separation tower after one strand is pressurized and cooled, and leading the other strand to the alkyl transfer reactor;
(5) circulating benzene 2 at the bottom of a benzene tower reflux tank and polyethylbenzene at the bottom of an ethylbenzene tower both enter from the bottom of a transalkylation reactor, and a transalkylation reaction product flowing out of the top of the reactor directly enters a benzene tower to participate in a subsequent separation process.
In the invention, the gas-liquid separation of the reaction product of the dry gas-to-ethylbenzene and the tail gas absorption and debenzolization are carried out in the same tower. The absorption separation tower is divided into four sections, wherein the upper section of the tower is a filler section, the middle section of the tower is a tube array cooling section, the lower section of the tower is a plate tower section, and the bottom section of the tower is a tower kettle section.
The reaction product from the alkylation reactor contains dry gas, benzene, ethylbenzene, diethylbenzene and a small amount of polyethylbenzene, and enters an absorption separation tower after heat exchange. In the absorption separation tower, the absorbent gets into from packing section top, with reaction tail gas low temperature countercurrent contact, absorb the benzene of most in the reaction tail gas, accomplish the debenzolization of tail gas, later tail gas goes to the fuel gas pipe network from the top of the tower, rich absorption liquid then flows through the tubulation cooling section, plate tower section, the tower cauldron section of absorption separation tower downwards, passes through condensation cooling separation, gas-liquid fractionation separation, flash separation in proper order, the liquid phase flows out from the absorption separation tower bottom of the tower, goes to follow-up piece-rate system.
The upper section of the absorption separation tower is a filler section, the absorbent from the top of the filler is cold polyethylbenzene, the absorbent flows downwards and is in countercurrent contact with the rising tail gas to complete the absorption and debenzolization of the tail gas, and the tail gas is discharged from the top of the tower. The middle section of the tower is a tube cooler, the cooling medium is circulating water or other refrigerants, and the materials are condensed and cooled while being separated. The lower section of the tower is a plate section, and gas-liquid fractionation and separation are completed under the action of a tower plate and a tower bottom reboiler. The bottom section is a tower kettle section, and a reboiler is arranged at the bottom of the tower to finish flash evaporation and reboiling.
In a word, after the alkylation reaction product enters the absorption separation tower, the absorption separation tower can complete four processes, namely flash evaporation, depressurization and temperature reduction, gas-liquid fractionation and separation of the plate tower section, cooling and condensation of the tube array cooling section to provide reflux for the plate tower section, and absorption and liquid removal of tail gas.
In the invention, the alkylation reaction product and the circulating benzene 1 extracted from the upper section of the benzene tower exchange heat and then enter the absorption and separation tower, the temperature of the absorption and separation tower is gradually reduced from bottom to top, the reaction product is contacted with the absorbent, and the gas-liquid separation and the tail gas absorption are completed section by section. The invention combines the characteristics of each section of separation mode and fully utilizes the heat brought by the reaction product.
In the invention, the circulating benzene 1 is extracted from the upper section of the benzene tower and goes to an alkylation reactor, the circulating benzene 1 is divided into circulating hot benzene and circulating cold benzene, and the circulating hot benzene and the circulating cold benzene respectively enter the reactor in sections between the top of the reactor and a catalyst bed layer, the circulating hot benzene indirectly utilizes reaction heat, reaction feeding is preheated, and the circulating cold benzene can control the temperature rise of the catalyst bed layer, so that the ideal alkylation reaction temperature is obtained.
In the invention, the fresh benzene at normal temperature is directly injected into the reflux tank at the top of the benzene tower, so that the cold energy of the fresh benzene is fully utilized, and the energy is saved.
The raw material dry gas mainly refers to catalytic cracking dry gas, thermal cracking, MTO dry gas, MTP dry gas and alkene-containing gas generated in the secondary processing of other petroleum or coal processing, and the ethylene concentration in the composition of the dry gas is 5-95 percent (V).
In the invention, the alkylation reaction adopts gas phase reaction, and the reaction product enters an absorption separation tower after heat exchange; the transalkylation reaction adopts a liquid phase reaction, and the reaction product directly enters a benzene tower and a subsequent separation system.
In the step (2) and the step (3), the temperature of the alkylation reaction product entering the absorption separation tower after heat exchange is 150-200 ℃, and the feeding position is the upper part of a tower kettle of the absorption separation tower.
In the step (4), the non-condensable gas at the top of the benzene tower is mixed with the alkylation reaction product and then returns to the absorption separation tower from the upper part of the tower kettle, so that the non-condensable gas is debenzolized.
In the step (3) and the step (4), the temperature of the absorbent entering the absorption separation tower is 0-30 ℃, the pressure is 2.0-4.5 MPa, and the feeding position is the top of the packing section of the absorption separation tower. In the invention, the absorbent of the absorption separation tower is the bottom liquid of the ethylbenzene tower.
The operation pressure of the absorption separation tower is 0.2-1.0 MPa, the tower top temperature is 0-50 ℃, and the tower bottom temperature is 80-150 ℃.
The invention can obtain ideal separation effect and tail gas benzene recovery rate by adjusting the dosage and temperature of the absorbent of the absorption and separation tower, the dosage and temperature of the circulating water in the middle section of the absorption and separation tower, the temperature of the reboiler at the tower bottom of the corresponding absorption and separation tower, and the like.
In the invention, the aromatic hydrocarbons except the product ethylbenzene are all circularly returned to the reaction system: circulating benzene 1 extracted from the upper section of the benzene tower goes to an alkylation reactor, circulating benzene 2 at the bottom of a benzene tower reflux tank goes to a transalkylation reactor, and the circulating benzene and the transalkylation reactor are used as raw materials of the alkylation reaction and the transalkylation reaction and continuously react to generate a target product ethylbenzene; the liquid at the bottom of the ethylbenzene tower is divided into three streams, one stream is used as an absorbent to return to the absorption separation tower, and the other stream is used as a raw material of the transalkylation reaction to go to a transalkylation reactor to obtain aromatic oil.
The operating pressure of the benzene tower is 1.0-2.5 MPa, and the operating temperature is 150-250 ℃; the operating pressure of the ethylbenzene tower is 1.0-2.5 MPa, and the operating temperature is 200-350 ℃.
The invention can adjust the temperature of the reboiler at the bottom of the benzene tower to ensure that the bottom oil of the benzene tower does not contain benzene, adjust the dosage and temperature of the reflux at the top of the ethylbenzene tower to ensure that the top of the ethylbenzene tower does not contain diethylbenzene, thereby obtaining the ideal purity of the ethylbenzene product.
To achieve the desired ethylbenzene yield and purity, the raw dry gas requires pretreatment for removal of propylene and other deleterious impurities that can form propylbenzene. In the reaction part of the process for preparing ethylbenzene from dry gas, the invention is mainly characterized in that:
(1) the alkylation reaction adopts gas phase reaction, the reaction temperature is 360-400 ℃, the reaction pressure is 0.7-1.2 MPa, the weight ratio of benzene to ethylene is 10-20, and the weight hourly space velocity of ethylene is 0.2-1.0 h-1。
(2) The transalkylation reaction adopts a liquid phase reaction, the reaction temperature is 150-250 ℃, the reaction pressure is 2.5-3.5 MPa, the weight ratio of benzene to polyethylbenzene is 1-10, and the weight hourly space velocity of the polyethylbenzene is 0.1-5.0 h-1。
(3) The alkylation reaction of ethylene and benzene in the raw material dry gas is a strong exothermic reaction, and in order to control the reaction temperature rise, the raw material cold dry gas and the circulating cold benzene enter the reactor from the space between the catalyst bed layers in a sectional feeding mode so as to achieve the purposes of preheating the raw material, reducing the reaction heat effect and adjusting the temperature of the catalyst bed layers.
(4) The catalyst can be a commercial alkylation catalyst and a commercial transalkylation catalyst, and more preferably is a novel catalyst which is developed by Beijing Whitltrigi Green chemistry technologies, Inc.: WJH series alkylation catalysts and WJZY series transalkylation catalysts. The two novel catalysts are ZSM-5 molecular sieve catalysts modified by alkaline earth metal, rare earth elements and VA group element compounds together, wherein the content of the alkaline earth metal is 2-10% (wt), the content of the rare earth elements is 2-10% (wt), and the content of the VA group element is 3-15% (wt). The molecular sieve and the alumina adhesive are jointly used as a carrier of metal, and the metal is loaded on the catalyst by adopting an impregnation method.
Methods of shaping the catalyst are known to the person skilled in the art, such as extrusion, tabletting, spheronization, dropping balls. Mixing the molecular sieve, aluminum hydroxide, sesbania powder, etc., adding water and acid, extruding, kneading, extruding, drying, and breaking into strips or rolling into balls; or mixing all the raw materials to obtain colloid, and dropping the colloid in hot oil or oil ammonia bath to form spheres. Drying the formed catalyst at room temperature to 150 ℃, depositing metal on the catalyst by using a metal soluble salt (generally nitrate) impregnation method after drying, and then roasting for 1-24 hours in air and/or steam atmosphere at the temperature of 400-700 ℃ to obtain the catalyst.
In conclusion, the invention provides an energy-saving and environment-friendly method for preparing ethylbenzene by using dry gas, which mainly comprises gas-liquid separation of a reaction product of preparing ethylbenzene by using dry gas and tail gas debenzolization. The gas-liquid separation of the reaction product of the dry gas-to-ethylbenzene reaction and the tail gas absorption and debenzolization are carried out in the same tower, the absorption and separation tower is divided into four sections, the upper section of the tower is a filler section, the middle section of the tower is a tube array cooling section, the lower section of the tower is a plate tower, and the bottom section of the tower is a tower kettle. After the alkylation reaction product enters an absorption separation tower after heat exchange, the absorption separation tower can complete four processes, namely flash evaporation, depressurization and temperature reduction, gas-liquid fractionation and separation in a plate tower section, cooling and condensation in a tube array cooling section, and absorption and liquid removal of tail gas. The absorption separation tower of the invention fully utilizes the heat energy of the reaction product, can effectively carry out gas-liquid separation on the reaction product of preparing the ethylbenzene from dry gas under the condition of not influencing the yield and the purity of the ethylbenzene product, and can recover the benzene in the tail gas.
The invention reduces a rough separation tower, a tail gas benzene absorption tower, and subsequent aromatic fine towers such as a toluene tower, a diethylbenzene tower, a propylbenzene tower and the like, directly circulates aromatic hydrocarbons except the product ethylbenzene back to a reaction system, and further generates alkylation reaction and transalkylation reaction to generate the target product ethylbenzene.
The invention has the following effects:
(1) the invention converts the dry gas used as fuel into ethylbenzene with high added value, fully utilizes reaction heat, simplifies tower equipment, reduces device energy consumption, improves the recovery rate of the tail gas benzene, and has obvious economic benefit and positive environmental benefit.
(2) The alkylation reaction of ethylene and benzene in dry gas is a strong exothermic reaction, and the raw material cold dry gas and the circulating cold benzene enter the alkylation reactor from the space between catalyst bed layers in a sectional feeding mode, so that the reaction heat effect is reduced, the reaction temperature rise is controlled, the reaction heat is fully utilized, and the purposes of preheating the reaction feeding and adjusting the temperature of the catalyst bed layers are achieved.
(3) The invention fully utilizes the heat brought by the reaction product to ensure that the alkylation reaction product exchanges heat with the circulating benzene 1 pumped out from the upper section of the benzene tower, thereby achieving the purpose of preheating the feeding of the alkylation reaction.
(4) The alkylation reaction product directly enters an absorption separation tower after primary heat exchange; the temperature of the absorption separation tower is gradually reduced from bottom to top, alkylation reaction products are contacted with an absorbent, and gas-liquid separation and tail gas absorption and debenzolization are completed section by section. The invention combines the characteristics of each section of separation mode and fully utilizes the heat brought by the reaction product.
(5) In the invention, the normal-temperature fresh benzene is directly injected into the reflux tank at the top of the benzene tower, so that the cold energy of the fresh benzene is fully utilized, and the energy is saved.
(6) In the invention, the gas-liquid separation of the alkylation reaction product and the tail gas absorption debenzolization are carried out in the same tower, and the aromatic hydrocarbon except the ethylbenzene product is completely circulated and returned to the reaction system, thereby reducing the crude separation tower equipment and the subsequent aromatic hydrocarbon rectifying towers, and saving the equipment investment and the subsequent operation cost.
(7) The separation process is simple and reliable, and according to the absorption separation tower and the separation method provided by the invention, the purity of the obtained ethylbenzene product is more than 99.8%, and the recovery rate of the benzene carried in the tail gas is not less than 99.9%.
Drawings
FIG. 1 is a schematic view of the structure of an absorption separation column of the present invention, and n is the number of plates of a plate column section.
As shown in FIG. 1, the absorption and separation tower is divided into four sections, the upper section of the tower is a packing section, the middle section of the tower is a tube array cooling section, the lower section of the tower is a plate tower, and the bottom section of the tower is a tower kettle. The absorbent enters from the top of the packing section, the alkylation reaction product enters from a feed inlet at the upper part of the tower kettle of the absorption and separation tower, after four-section gas-liquid separation and tail gas absorption and benzene removal in the tower, the benzene-free tail gas goes to a fuel gas pipe network from the tower top, and the liquid flows out from the bottom of the tower kettle and enters a subsequent separation system.
FIG. 2 is a schematic process flow diagram of the method of the present invention, but the present invention is not limited thereto.
The process flow of the method shown in figure 2 is as follows:
the method comprises the steps of pretreating raw material dry gas, then feeding the pretreated raw material dry gas into an alkylation reactor in a segmented manner, pumping out circulating benzene 1 from the upper section of a benzene tower, dividing the circulating benzene into circulating hot benzene and circulating cold benzene, respectively feeding the circulating hot benzene and the circulating cold benzene into the reactor between the top of the reactor and a catalyst bed layer, enabling a reaction product to flow out of the bottom of the alkylation reactor, exchanging heat with the circulating benzene 1 pumped out from the upper section of the benzene tower, and then feeding the reaction product into the upper part of a tower.
The absorbent enters from the top of the packing section of the absorption separation tower, after absorption and separation processes, the tail gas enters a fuel gas pipe network from the top of the tower, rich absorption liquid is mixed with condensed liquid in reaction products, and the mixture flows out from the bottom of the tower and enters a benzene tower.
Adding fresh benzene at normal temperature from a benzene tower top return tank, returning noncondensable gas at the benzene tower top to an absorption separation tower for debenzolization, pumping circulating benzene 1 from the upper section of a benzene tower to an alkylation reactor, returning circulating benzene 2 from the benzene tower return tank bottom to a transalkylation reactor, feeding benzene tower bottom material into an ethylbenzene tower, obtaining a product ethylbenzene at the ethylbenzene tower top, dividing ethylbenzene tower bottom liquid into three strands, returning one strand as an absorbent to the absorption separation tower, and feeding the other strand to the transalkylation reactor to obtain aromatic oil.
Circulating benzene 2 at the bottom of a benzene tower reflux tank and polyethylbenzene at the bottom of an ethylbenzene tower both enter from the bottom of a transalkylation reactor, and a transalkylation reaction product flowing out of the top of the reactor directly enters a benzene tower to participate in a subsequent separation process.
Detailed Description
The present invention will be further described with reference to the following examples, but the present invention is not limited thereto.
Specification of raw materials
(1) The raw dry gas comes from an MTP device of a Hami factory in Xinjiang, and the composition of the raw dry gas is shown in Table 1; the raw material benzene is commercially available petroleum pure benzene, and the main properties are shown in table 2.
(2) Alkylation catalyst: model WJH-31, the appearance is 1.8mm 3.2mm butterfly section strip, 3 ~ 10mm long. Transalkylation catalyst: the model WJZY-3 is a strip with a butterfly section of 1.8mm multiplied by 3.2mm in appearance and 3-10 mm in length. Both catalysts are available from green chemical technology, Inc., Hulterji, Beijing.
Example 1
This example was carried out on an 8-million ton/year dry gas ethylbenzene plant from Hami, Sinkiang using the absorption and separation column shown in FIG. 1 and the process flow shown in FIG. 2.
After the raw material MTP dry gas is pretreated to remove propylene, the dry gas enters an alkylation reactor in a segmented mode. The circulating hot benzene extracted from the upper section of the benzene tower enters from the top of the reactor, the feeding temperature is 360 ℃, and the pressure is 1.0 MPa. The circulating cold benzene pumped from the upper section of the benzene tower enters from the space between catalyst beds, the feeding temperature is 200 ℃, and the pressure is 1.2 MPa. The alkylation reaction temperature is 360-400 ℃, the reaction pressure is 1.0MPa, the weight ratio of benzene to ethylene is 15, and the weight hourly space velocity of ethylene is 0.8h-1。
And (3) after heat exchange is carried out between the alkylation reaction product and the circulating benzene 1 pumped out from the upper section of the benzene tower, reducing the temperature to 150-180 ℃, and feeding the alkylation reaction product into an absorption separation tower from the upper part of a tower kettle. The absorbent from the bottom of the ethylbenzene tower is cooled to 15 ℃ and the pressure is 2.5MPa, and enters the absorption separation tower from the upper part of the packing section. The pressure of the dry gas tail gas at the tower top is controlled by a regulating valve and enters a fuel gas pipe network. The temperature of the bottom liquid is 90 ℃, and the bottom liquid enters a benzene tower.
Adding fresh benzene at normal temperature directly into the benzene tower top reflux tank. The vapor temperature at the top of the benzene tower is 200 ℃, the pressure is 1.5MPa, and the cooled vapor enters a reflux tank at the top of the benzene tower. The non-condensable gas at the top of the benzene tower flows out from the top of the reflux tank and returns to the absorption separation tower to be debenzolized. The material at the bottom of the benzene column top reflux tank is divided into two streams, one stream is refluxed to the benzene column, and the other stream is used as recycle benzene 2 to a transalkylation reactor. The circulating benzene 1 is extracted from the fifth tower plate below the top of the tower, divided into circulating hot benzene and circulating cold benzene, and enters the alkylation reactor in sections between the top of the reactor and the catalyst bed layer. The benzene tower bottom liquid enters an ethylbenzene tower.
The ethylbenzene tower is a plate tower with 100 layers of tower plates. The feeding temperature of the ethylbenzene tower is 300 ℃, and the pressure is 1.4 MPa. The temperature at the top of the ethyl benzene tower is 220 ℃, and the pressure is 1.0MPa, so that an ethyl benzene product is obtained. The temperature of the bottom of the ethylbenzene tower is 240 ℃, the pressure is 1.2MPa, the ethylbenzene tower is divided into three strands, one strand is pressurized and cooled and then returns to the absorption separation tower as an absorbent, the other strand goes to the transalkylation reactor, and the aromatic oil is obtained.
The transalkylation reactor is fed from the bottom and the reaction product is withdrawn from the top. The transalkylation reaction temperature is 220 ℃, the reaction pressure is 3.0MPa, the weight ratio of the circulating benzene 2 to the polyethylbenzene is 5, and the weight hourly space velocity of the polyethylbenzene is 2.0h-1. The reaction product directly enters a benzene tower.
The reaction was continued for 30 days with daily equilibration of the feed, see Table 3, in which the crude propene came from the raw dry gas pretreatment section and the aromatic oil came from the ethylbenzene column bottom. And (3) measuring the benzene content by taking the gas at the top of the absorption and separation tower, wherein the recovery rate of the tail gas benzene is 99.8%. The ethylbenzene product was collected for mass analysis, and the purity of ethylbenzene was 99.7%, which reached petrochemical standard SH/T1140-2001, as shown in Table 4.
TABLE 1 composition of raw Dry gas
| Components | By volume percent% |
| Hydrogen gas | 16.25 |
| Methane | 28.21 |
| Ethane (III) | 5.9 |
| Ethylene | 48.25 |
| Propane | 0.12 |
| Propylene (PA) | 0.77 |
| Butane | 0.2 |
| Butene (butylene) | 0.3 |
| Total of | 100 |
TABLE 2 main properties of the starting benzene
| Item | Unit of | Index (I) |
| Benzene content | wt | ≥99.9％ |
| Toluene content | wt | ≤0.05％ |
| Sulfur content | ppm | ≤0.5 |
| Nitrogen content | ppm | ≤1.0 |
| Color intensity | ≤20 | |
| Freezing point | ℃ | 5.4 |
| Boiling point | ℃ | 80 |
| Density of | kg/m3 | 879 |
| Latent heat of vaporization | kcal/kg | 94 |
| Molecular weight | g/mol | 78 |
TABLE 3 Material balance Table
| Item | Flow rate, t/h |
| Raw materials | |
| MTP dry gas | 4.00 |
| Benzene and its derivatives | 7.152 |
| Product(s) | |
| Ethylbenzene production | 9.597 |
| Crude propene | 0.12 |
| Aromatic oil | 0.156 |
| Tail gas | 1.280 |
TABLE 4 specification of ethylbenzene product
| Item | Unit of | Index (I) |
| Ethylbenzene content | wt | ≥99.5％ |
| Xylene content | wt | ≤0.15％ |
| Content of propylbenzene | wt | ≤0.03 |
| Content of diethylbenzene | ppm | 10 |
| Sulfur content | ppm | ≤3 |
| Freezing point | ℃ | |
| Boiling point | ℃ | 136 |
| Density of | kg/m3 | 867 |
| Latent heat of vaporization | kcal/kg | 460 |
| Molecular weight | g/mol | 106 |
Claims (18)
1. An energy-saving and environment-friendly method for preparing ethylbenzene by using dry gas mainly comprises the following steps of gas-liquid separation of reaction products of the dry gas preparation of ethylbenzene and tail gas debenzolization:
(1) after the propylene of the raw material dry gas is removed by pretreatment, the raw material dry gas enters the reactor from the top of the alkylation reactor and between the catalyst bed layers in a segmented manner;
(2) the alkylation reaction product of the dry gas ethylbenzene preparation enters an absorption separation tower after heat exchange, the tower is divided into four sections, the upper section of the tower is a filler section, the middle section of the tower is a tube cooling section, the lower section of the tower is a plate tower section, and the bottom section of the tower is a tower kettle section;
(3) the alkylation reaction product enters from the upper part of a tower kettle of the absorption separation tower, the absorbent enters from the top of a packing section, after the absorption and separation processes, tail gas enters a fuel gas pipe network from the top of the tower, rich absorption liquid is mixed with condensed liquid in the reaction product, and the mixture flows out from the bottom of the tower kettle and enters a benzene tower;
(4) adding fresh benzene at normal temperature from a benzene tower reflux tank, returning noncondensable gas of the benzene tower to an absorption separation tower, pumping circulating benzene 1 from the upper section of the benzene tower to an alkylation reactor, dividing the circulating benzene 1 into circulating hot benzene and circulating cold benzene, respectively entering the reactor between the top of the reactor and a catalyst bed layer, leading circulating benzene 2 at the bottom of the benzene tower reflux tank to an transalkylation reactor, leading benzene tower substrate to an ethylbenzene tower, obtaining a product ethylbenzene at the top of the ethylbenzene tower, dividing the ethylbenzene tower bottom liquid into three strands by using polyethylbenzene mainly containing diethylbenzene, obtaining aromatic oil by using one strand, returning the other strand as an absorbent to the absorption separation tower, and leading the other strand to the transalkylation reactor;
(5) circulating benzene 2 at the bottom of a benzene tower reflux tank and polyethylbenzene at the bottom of an ethylbenzene tower both enter from the bottom of a transalkylation reactor, and a transalkylation reaction product flowing out of the top of the reactor directly enters a benzene tower to participate in a subsequent separation process.
2. An absorption and separation tower for gas-liquid separation of reaction products and benzene removal from tail gas in the preparation of ethylbenzene from dry gas is characterized in that the absorption and separation tower is divided into four sections, the upper section of the tower is a filler section, the middle section of the tower is a tube array cooling section, the lower section of the tower is a plate tower section, and the bottom section of the tower is a tower kettle section.
3. The method for separating benzene from a liquid phase in an absorption separation tower comprises the steps of feeding an absorbent from the top of a packing section in the absorption separation tower, enabling the absorbent to be in low-temperature countercurrent contact with reaction tail gas, absorbing most of benzene in the reaction tail gas to complete benzene removal of the tail gas, enabling the tail gas to enter a fuel gas pipe network from the top of the tower, enabling rich absorption liquid to flow downwards through a pipe array cooling section, a plate tower section and a tower kettle section of the absorption separation tower, sequentially performing condensation cooling separation, gas-liquid fractional separation and flash separation, and enabling a liquid phase to flow out of the bottom of the absorption separation tower and to a subsequent separation system.
4. The method according to claim 1 and claim 2, characterized in that the gas-liquid separation of the reaction product and the absorption of the off-gas are carried out in the same column; after the alkylation reaction product enters the absorption separation tower, the absorption separation tower can complete four processes, namely flash evaporation, depressurization and temperature reduction, gas-liquid fractionation and separation of a plate tower section, cooling and condensation of a tube array cooling section and absorption and liquid removal of tail gas.
5. The method according to claim 4, wherein the alkylation reaction product exchanges heat with the circulating benzene 1 extracted from the upper section of the benzene tower and then enters an absorption separation tower, the temperature of the absorption separation tower decreases from bottom to top section by section, the reaction product contacts with an absorbent, gas-liquid separation and tail gas absorption and debenzolization are completed section by section, and the heat brought by the reaction product is fully utilized.
6. The method according to claim 1, wherein in the step (4), the upper section of the benzene column is used for extracting the circulating benzene 1 to the alkylation reactor, the circulating benzene 1 is divided into circulating hot benzene and circulating cold benzene, and the circulating hot benzene and the circulating cold benzene enter the reactor in sections between the top of the reactor and the catalyst bed layer respectively, and the purposes of preheating the raw materials, reducing the reaction heat effect, controlling the reaction temperature rise and adjusting the temperature of the catalyst bed layer are achieved by utilizing the characteristic that the alkylation reaction is a strong exothermic reaction.
7. The method according to claim 1, characterized in that in the step (1), the fresh benzene at normal temperature is directly injected into the reflux tank at the top of the benzene tower, so that the cold energy of the fresh benzene is fully utilized, and the energy is saved.
8. The process of claim 1, wherein aromatics other than ethylbenzene are recycled back to the reaction system: circulating benzene 1 extracted from the upper section of the benzene tower goes to an alkylation reactor, and circulating benzene 2 at the bottom of a benzene tower reflux tank goes to an transalkylation reactor; the liquid at the bottom of the ethylbenzene tower is divided into three streams, one stream is pressurized and cooled and then returns to the absorption separation tower as an absorbent, and the other stream goes to the transalkylation reactor to obtain the aromatic oil.
9. The method as claimed in claim 1 and claim 2, wherein the raw dry gas is mainly catalytic cracking dry gas, thermal cracking, MTO dry gas, MTP dry gas and other alkene-containing gas generated in secondary petroleum processing or coal processing, and the ethylene concentration in the dry gas composition is 5-95% (V).
10. The method according to claim 1, wherein in the step (2) and the step (3), the temperature of the alkylation reaction product entering the absorption separation tower after heat exchange is 150-250 ℃, and the feeding position is the upper part of the tower kettle of the absorption separation tower.
11. The method according to claim 1, wherein in the step (4), the non-condensable gas at the top of the benzene column is mixed with the alkylation reaction product and returned to the absorption separation column from the upper part of the column bottom to remove benzene from the non-condensable gas.
12. The method according to claim 1, wherein in the step (3) and the step (4), the temperature of the absorbent entering the absorption separation tower is 0-30 ℃, the pressure is 2.0-4.5 MPa, and the feeding position is the top of a packing section of the absorption separation tower.
13. The method as claimed in claim 1 and claim 2, wherein the middle section of the absorption separation tower is a tube cooling section, and the cooling medium is circulating water or other cooling medium.
14. The method according to claim 1 and claim 2, wherein a column bottom reboiler is provided at the bottom of the absorption separation column.
15. The process according to claim 1 and claim 2, wherein the operating pressure of the absorption-separation column is 0.2 to 1.0MPa, the temperature at the top of the column is 0 to 50 ℃ and the temperature at the bottom of the column is 80 to 150 ℃.
16. The method according to claim 1 and claim 2, wherein the desired separation effect and the desired benzene recovery from the off-gas can be obtained by adjusting the amount and temperature of the absorbent in the absorption separation column, the amount and temperature of the circulating water in the middle section of the absorption separation column, and the temperature of the reboiler in the column bottom of the absorption separation column.
17. The method of claim 1, wherein the benzene column is operated at a pressure of 1.0 to 2.5MPa and at a temperature of 150 to 250 ℃; the operating pressure of the ethylbenzene tower is 1.0-2.5 MPa, and the operating temperature is 200-350 ℃.
18. The method of claim 1, wherein the desired separation and ethylbenzene product purity is achieved by adjusting the temperature of the benzene column bottom reboiler and the amount and temperature of the ethylbenzene overhead reflux.
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| CN112661597A (en) * | 2021-01-13 | 2021-04-16 | 北京惠尔三吉绿色化学科技有限公司 | Industrial production and regeneration method for preparing ethylbenzene from dry gas |
| CN113480395A (en) * | 2021-07-02 | 2021-10-08 | 大连理工大学 | Flash separation process and device for preparing ethylbenzene from ethylene-rich gas |
| CN114671732A (en) * | 2022-04-07 | 2022-06-28 | 中石化广州工程有限公司 | Process for preparing ethylbenzene by ethylene-containing dry gas-liquid phase method |
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| CN112661597A (en) * | 2021-01-13 | 2021-04-16 | 北京惠尔三吉绿色化学科技有限公司 | Industrial production and regeneration method for preparing ethylbenzene from dry gas |
| CN113480395A (en) * | 2021-07-02 | 2021-10-08 | 大连理工大学 | Flash separation process and device for preparing ethylbenzene from ethylene-rich gas |
| CN113480395B (en) * | 2021-07-02 | 2022-07-08 | 大连理工大学 | Flash separation process and device for preparing ethylbenzene from ethylene-rich gas |
| CN114671732A (en) * | 2022-04-07 | 2022-06-28 | 中石化广州工程有限公司 | Process for preparing ethylbenzene by ethylene-containing dry gas-liquid phase method |
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Denomination of invention: An energy-saving and environmentally friendly method for producing ethylbenzene from dry gas Granted publication date: 20230509 Pledgee: Urumqi Bank Co.,Ltd. Hami Branch Pledgor: Beijing Huiersanji Green Chem-Tech Co.,Ltd. Registration number: Y2024980011873 |