CN112110785A - Process for preparing butadiene through oxidative dehydrogenation of butylene - Google Patents

Process for preparing butadiene through oxidative dehydrogenation of butylene Download PDF

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CN112110785A
CN112110785A CN202011048482.XA CN202011048482A CN112110785A CN 112110785 A CN112110785 A CN 112110785A CN 202011048482 A CN202011048482 A CN 202011048482A CN 112110785 A CN112110785 A CN 112110785A
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bed layer
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oxidative dehydrogenation
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孙洪涛
杨春胜
李延生
谭敏
陆敏磊
牟卫兵
戴俊
夏违
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Nanjing Chengzhi Yongqing Energy Technology Co ltd
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Abstract

The invention discloses a process for preparing butadiene by oxidative dehydrogenation of butylene, which is generated by catalytic oxidative dehydrogenation of butylene, oxygen-containing gas and steam, two axial fixed bed reactors and four sections of catalyst beds are connected in series, so that the butylene amount fed by each section of bed is reduced, the outlet and inlet temperatures of each section of catalyst bed are controlled, and the molar ratio of total water vapor to butylene is greatly reduced under the condition of keeping a certain water-olefin ratio, thereby reducing the water vapor consumption. The inert gas in the generated gas is treated and mixed with the oxygen-enriched gas to be used as the ingredient gas, and basically no tail gas is discharged. The process can improve the conversion rate, selectivity and yield of the reaction, reduce steam consumption and tail gas emission, is controllable and easy to realize, is environment-friendly and energy-saving, and is expected to produce better economic benefit.

Description

Process for preparing butadiene through oxidative dehydrogenation of butylene
Technical Field
The invention relates to a preparation method of butadiene, in particular to a process for preparing butadiene by oxidative dehydrogenation of butylene.
Background
Butadiene is an important monomer for petrochemical basic raw materials and producing high-molecular synthetic materials, and is used for producing synthetic rubber, synthetic resin, adiponitrile, hexamethylene diamine, nylon 66, sulfolane, 1, 4-butanediol and the like.
The butadiene production method comprises two methods of carbon four fraction separation and synthesis (including butane dehydrogenation, butene oxidative dehydrogenation and the like). The butadiene is obtained from the byproduct mixed carbon four fraction of the ethylene cracking device, has low price and is economically dominant, and is the main source of butadiene in the world at present. The butadiene is separated from the mixed C4 by an extraction rectification method, and commonly used extracting agents are acetonitrile, N-methylpyrrolidone, N-dimethylformamide and the like. The other is obtained by dehydrogenation of the four-carbon fraction, and the method is only adopted in places with abundant butane and butene resources. If natural gas or methanol is used as a raw material, the by-product carbon tetraolefin is obtained by a methanol-to-olefin process, the purity of the butene is up to more than 90 percent, and the butene is a very good raw material for producing butadiene by oxidative dehydrogenation of the butene.
The method for preparing butadiene by dehydrogenation of butylene uses chromium oxide and calcium-nickel phosphate as catalysts, the butadiene selectivity is high, but because of the influence of reaction balance, a large amount of steam is added into the butylene raw material to reduce the hydrocarbon partial pressure, so that the dehydrogenation reaction is favorably carried out rightwards, and the steam consumption is large. This process is gradually replaced by oxidative dehydrogenation.
The Phillips company in the United states developed a process for producing butadiene by oxidative dehydrogenation of butene in the end of the 60 s and realized industrialization in 1970. The research work of preparing butadiene by oxidative dehydrogenation of butylene in China started from the early 1960 s, a P-Mo-Bi ternary molybdenum catalyst was developed by Lanzhou chemical of the Chinese academy of sciences in 1966, and then intermediate tests of process development were respectively carried out in the chemical research institute of the Lanzhou chemical industry company and the Jinzhou oil refinery. An adiabatic fixed bed reactor is established in Lanzhou, and the problems of low butadiene yield, harsh operating conditions, difficult control of reaction and the like are found in experiments, so that the experiments are stopped. Established in Jinzhou is a tubular fixed bed reactor, and tests show that: although the single-pass conversion rate and selectivity are high, the loss of the catalyst is low, the carbon deposition of the catalyst is serious, the catalyst needs to be regenerated periodically, and the bed type test cannot be carried out due to the complex heat exchange equipment, high material requirement and high cost.
H-198 spinel type iron-based catalyst was developed by Lanzhou chemical of Chinese academy of sciences in 1981. The technological conditions and technical indexes are not only greatly superior to the original molybdenum-based catalyst in China, but also have advantages in comprehensive economic indexes compared with the Petro-Tex technology in the United states. While developing and developing the H-198 catalyst, China successfully carries out the development work of another novel catalyst (B-02). The Yanshan company rubber works developed a new generation of B-02 catalyst. The catalyst was used by the institute of chemical engineering of east China to develop a two-stage axial adiabatic fixed bed reaction process quickly, and the catalyst was applied to two axial fixed bed reactors with the diameter of DN3000 mm. The main process parameters and results of the reaction on the industrial plant are shown in tables 1 and 2.
TABLE 1 reaction conditions of the Industrial plant
Figure BDA0002708778050000021
TABLE 2 partial reaction results for the commercial plant
Figure BDA0002708778050000022
The industrial device is operated for 5137h cumulatively, the apparent yield of the butadiene is 61.0-64.0%, the apparent conversion rate of the butene is 68-70.0%, and the apparent selectivity of the butadiene is 89.0-91.6%.
The oxidative dehydrogenation of butene to butadiene is a strong exothermic reaction. In the early stage, a tubular fixed bed reactor is adopted, catalysts are filled in the tubes, and a heat carrier is introduced between the tubes to remove heat, wherein the heat carrier can be fused salt. The greatest defects of the reactor are that the temperature distribution is not uniform, the local temperature of the reactor is overhigh, hydrocarbon cracking, catalyst carbon deposition and pipe blockage are caused.
A fluidized bed reactor is adopted, and a multi-turn guide baffle and an inner cooling pipe are arranged in the fluidized bed reactor. The reaction heat is introduced into boiler feed water through an inner cooling pipe to generate low-pressure steam to remove heat so as to maintain the normal temperature of the reaction. However, several sets of devices adopting the fluidized bed process technology, which are built in China, are unsmooth in driving and incapable of normal production, and have the main defects that: 1) the performance of the catalyst is reduced quickly, so that the conversion rate, the selectivity and the yield of butadiene of the reaction are low; 2) the problem of catalyst abrasion is not solved all the time, so that the catalyst loss is overlarge; 3) the catalyst is lost in the tower kettle wastewater of the quench tower, so that the wastewater treatment cost is higher, the sewage reuse rate is reduced, and the water consumption is higher.
An axial fixed bed method for preparing butadiene by oxidative dehydrogenation of butene is proposed in patent CN 101367702A. The method adopts two sections of fixed bed reactors, wherein the two reactors are respectively provided with a section of catalyst bed layer, the burdening water vapor exchanges heat with the discharged material of the first section of reactor to heat up, and the outlet of the second section of reactor is provided with a waste heat boiler. The reactor is filled with an iron catalyst, the main active phase is zinc ferrite, magnesium ferrite or cobalt ferrite, and the secondary active phase is alpha-Fe2O3. The technical conditions of the butylene oxidative dehydrogenation reaction are as follows: the airspeed is 190-500 h-1The inlet temperature of the reactor is 315-400 ℃, the outlet temperature of the reactor is 500-600 ℃, and the molar ratio of butylene to oxygen to water in the first-stage reaction is as follows: 1: 0.5-0.7: 14-16, and no water is added in the second-stage reaction.
Patent CN 201711349707 proposes a process for producing butadiene by oxidative dehydrogenation of butene and a three-stage adiabatic fixed bed reaction system, wherein three axial fixed beds are connected in series, a waste heat boiler is arranged for recovering heat at the discharge of each reactor, and an oxygen-containing gas is only arranged at the inlet of each reactor. An iron-based catalyst is filled, and the molar ratio of Fe to Zn to Mg to Co is 10:2 to 4:3 to 5:1 to 3. The molar ratio of the total butene raw material to the water vapor is 1: 10-15, and the molar ratio of the butene feed to the oxygen-containing gas in each section is 1: 0.2-0.5. The inlet temperature of each reactor is controlled to be 315-400 ℃, and the outlet temperature is controlled to be 420-500 ℃.
The method improves the reaction process to a certain extent, and improves the conversion rate and yield of the reaction. However, the problems that the steam consumption is high and a large amount of inert gas generated after reaction needs to be treated are not solved by the improvements, and a tail gas treatment device is still required to be built to treat the tail gas and discharge the treated tail gas after reaching the standard.
Therefore, there is a need to develop a process for preparing butadiene from butene, which combines tail gas treatment with a reaction system, improves the reaction system, increases the conversion rate, selectivity and yield of the reaction, reduces energy consumption, and is more environment-friendly.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a process for preparing butadiene from butylene through oxidative dehydrogenation, which can improve the conversion rate, selectivity and yield of the reaction, reduce the steam consumption and reduce the tail gas emission, and is a green and environment-friendly process technology for preparing butadiene from butylene, and has the advantages of low energy consumption, high yield and low tail gas emission.
In order to achieve the purpose, the invention adopts the technical scheme that:
a process for preparing butadiene through oxidative dehydrogenation of butylene is characterized in that butylene, oxygen-containing gas and steam are generated through catalytic oxidative dehydrogenation reaction in an axial fixed bed reactor, the axial fixed bed reactor comprises a first oxidative dehydrogenation reactor and a second oxidative dehydrogenation reactor which are connected in series, and two sections of catalyst bed layers are filled in the first reactor and the second reactor; the system comprises a front heat exchanger, a first reactor first-stage, a second-stage feed mixer, a first reactor, a first-stage waste heat boiler, a second reactor first-stage, a second-stage feed mixer, a second reactor, a second-stage waste heat boiler, a rear heat exchanger, a quenching and acid washing unit, a generated gas compression and adsorption unit in sequence in the material flowing direction;
the process comprises the following steps:
(1) the raw material gas phase butylene is divided into four strands and respectively sent to the inlets of a first-stage bed layer and a second-stage bed layer of the first oxidative dehydrogenation reactor and the second oxidative dehydrogenation reactor; the material mixing steam and the gas generated by the discharge reaction of the second reactor exchange heat in a front heat exchanger to heat up, and the steam after heating up is mixed with the gas phase butylene fed into the first reactor section bed layer; the molar ratio of the total effective butylene to the water vapor is configured according to 1: 4-10;
(2) oxygen-containing gas formed by mixing the oxygen-rich gas and the nitrogen-rich gas from the adsorption unit is divided into four streams which are respectively sent to the inlets of the first-stage bed layer and the second-stage bed layer of the first reactor and the second reactor; wherein the molar ratio of the total effective butylene to the oxygen is configured according to 1: 0.4-0.80, and the molar ratio of the butylene to the oxygen of each section of bed layer is configured according to 1: 0.2-0.70;
(3) in a first reactor, after mixing butylene and steam entering a first-stage bed layer of the first reactor in a first-stage feed mixer of the first reactor, further uniformly mixing mixed gas and oxygen-containing gas in a second-stage feed mixer of the first reactor, controlling the feeding temperature of the first-stage bed layer of the first reactor at 260-370 ℃, after fully reacting in the first-stage bed layer, entering a second-stage bed layer, and controlling the temperature of an outlet of the first-stage bed layer of the first reactor at 430-510 ℃; introducing gas-phase butylene into the second-stage bed layer, proportionally adding oxygen-containing gas and intersegmental chilling water, controlling the inlet temperature of the second-stage bed layer to be 260-370 ℃, and controlling the outlet temperature of the second-stage bed layer to be 430-510 ℃ after the second-stage bed layer fully reacts; the generated gas at the outlet of the second-stage bed layer enters a second reactor after heat energy is recovered by a first-stage waste heat boiler;
(4) in a second reactor, fully mixing generated gas from a first reactor and gas-phase butylene in a first-stage feed mixer of the second reactor, and further uniformly mixing the gas and oxygen-containing gas in a second-stage feed mixer of the second reactor, controlling the inlet temperature of a first-stage bed layer of the second reactor to be 260-370 ℃, fully reacting in the first-stage bed layer of the second reactor, and then entering a second-stage bed layer, and controlling the outlet temperature of the first-stage bed layer to be 430-510 ℃; introducing gas-phase butylene into an inlet of the second-stage bed layer, proportionally adding oxygen-containing gas and intersegmental chilling water, controlling the inlet temperature of the second-stage bed layer to be 260-370 ℃, and controlling the outlet temperature of the second-stage bed layer to be 430-510 ℃ after the second-stage bed layer fully reacts; the generated gas at the outlet of the second-stage bed layer exchanges heat through a front heat exchanger, a second-stage waste heat boiler and a rear heat exchanger;
(5) further cooling the reaction generated gas after heat exchange in a quenching and acid washing unit and removing acid gas of the reaction generated gas; and further compressing the reaction generated gas, separating by an adsorption unit to obtain crude butadiene, mixing the nitrogen-rich gas and the oxygen-rich gas, and circulating to the oxidative dehydrogenation reactor.
In the step (1), preferably, the steam is heated by a front heat exchanger to a temperature of 380-450 ℃.
In the step (1), the pressure of the blending steam is 0.20-0.25 MPaG, and the blending steam comes from a water steam pipe network of 0.20-0.25 MPaG for stabilizing a reactor system.
The butene raw material in the step (1) is divided into four strands, wherein the mole ratio of the butene raw material fed into the first-stage bed layer and the second-stage bed layer of the first reactor to the first-stage bed layer and the second-stage bed layer of the second reactor is preferably 1.9-2.1: 0.9-1.1.
The oxygen-enriched gas in the step (2) can be a mixed gas of pure oxygen, water vapor and oxygen; the oxygen-containing gas is a mixed gas of oxygen-rich gas and recycled nitrogen-rich gas, wherein O in the oxygen-containing gas2The concentration of (A) is 18-36% vol.
The mass content of the butylene in the raw material is not less than 80 percent, and the effective butylene refers to one or more of 1-butylene, cis-2-butylene and trans-2-butylene.
In the step (3), the primary exhaust-heat boiler generates low-pressure steam which is used as the blending steam of the oxidative dehydrogenation reactor.
In the step (4), the low-grade heat recovered by the rear heat exchanger is further used for generating low-pressure steam through absorption refrigeration, and the low-pressure steam is used as the blending steam of the oxidative dehydrogenation reactor. Specifically, an absorption heat pump is adopted, circulating soft water and a rear heat exchanger exchange heat, and low-grade heat is utilized to generate 0.20-0.25 MPaG steam for supplying oxygen to a dehydrogenation reactor.
In the step (5), the adsorption unit separates carbon four components and non-condensable gas contained in the generated gas, wherein the carbon four components are mainly 1, 3-butadiene to obtain crude butadiene; the main components of the non-condensable gas are nitrogen, unreacted oxygen, a small amount of carbon dioxide and a minute amount of carbon four components, and nitrogen-rich gas is obtained.
More specifically, the nitrogen-rich gas discharged from the adsorption unit is mixed with the oxygen-rich gas after being expanded and refrigerated to do work externally and recovering cold energy. The method of the invention recycles the nitrogen-rich gas, greatly reduces the emission of the tail gas, and is environment-friendly and energy-saving.
In the method of the invention, the first reactor and the second reactor are operated under slight positive pressure, the low pressure is favorable for the reaction to be carried out towards the right, and the operating pressure is lower than 0.1 MPaG.
In order to improve the conversion rate of raw material butylene and the selectivity of butadiene, the catalysts filled in the first reactor and the second reactor are selected from spinel catalysts, and comprise iron, magnesium, zinc and manganese, wherein the iron content is 50-65 wt%, the magnesium content is 3-15 wt%, the zinc content is 3-15% and the manganese content is 0-5%.
Preferably, the first and second reactors are axial reactors, the diameters of the two reactors are the same, and the linear velocity of the gas passing through the bed layer is increased along with the increase of the volume of the gas passing through the catalyst bed layer, so that the carbon deposition rate of the catalyst bed layer is favorably reduced. Two axial fixed bed reactors with the same diameter gradually increase the linear velocity of reaction materials along with the entering of materials of each section, the residence time of the reaction is reduced, the feeding temperature of the bed layer of each section gradually increases in a small range, and the conversion rate and the yield of the reaction are improved.
Has the advantages that: the technical scheme of the invention has the following advantages:
(1) the invention adopts two reactors and four sections of catalyst beds connected in series, and because the amount of butylene fed into each section of bed is reduced, the molar ratio of total steam to butylene is greatly reduced under the condition of keeping a certain water-olefin ratio, thereby reducing the steam consumption.
(2) The butylene oxidative dehydrogenation reaction is an exothermic reaction, and the process adopts an adiabatic fixed bed reactor in order to control the outlet temperature of each section of catalyst bed layer; the inlet temperature of the first section bed layer of the first reactor is controlled by controlling the temperature rise of the heat exchange between the batching steam and the discharged material of the second reactor, the inlet temperature of the first section bed layer of the second reactor is controlled by controlling the temperature of the outlet of the first-stage waste heat boiler, and the inlet temperatures of the two sections bed layers of the first reactor and the second reactor are controlled by controlling the injected intersegmental chilling water.
(3) The process only arranges a waste heat boiler at the outlet of the first reactor, namely the second section of catalyst bed layer, to recover medium-pressure steam, but does not arrange a waste heat boiler at the outlet of each section of catalyst bed layer, thereby simplifying the process and ensuring that the pressure of the reactor is still very low.
(4) The process adopts two reactors, four bed layers are connected in series, and waste heat boilers are arranged at the outlets of the first reactor and the second reactor, so that the steam consumption in the reaction is controlled below 0.5 ton/ton (butadiene), the steam consumption of a reaction system is greatly reduced, the discharge of waste water is greatly reduced, and the treatment load of sewage treatment is reduced.
(5) The process treats most of inert gases in the reaction generated gas, such as nitrogen and the balance of carbon dioxide, and mixes the treated inert gases with the oxygen-enriched gas to be used as the ingredient gas, and the process has no tail gas emission.
(6) Because the reaction system adopts four-section feeding, the diameter of the required reactor is smaller and the occupied area is smaller under the condition of maintaining the same reaction weight hourly space velocity.
Compared with the prior art, the method has the advantages of higher three-rate reaction, controllable and easily realized process, environmental protection, energy conservation and expected generation of better economic benefit.
Drawings
FIG. 1 is a process flow diagram of the present invention;
in the figure, R-1 is a first reactor, R-2 is a second reactor, B-1 is a first-stage waste heat boiler, B-2 is a second-stage waste heat boiler, C-1 is a compression unit, Q-1 is a quenching and acid washing unit, AD-1 is an adsorption unit, HP-1 is a heat pump, FE-1 is a front heat exchanger, RE-1 is a rear heat exchanger, M-11 is a first-stage mixer of the first reactor, M-12 is a second-stage mixer of the first reactor, M-21 is a first-stage mixer of the second reactor, and M-22 is a second-stage mixer of the second reactor;
s1 is butylene, S2 is ingredient steam, W1 is chilling water, O1 is oxygen-rich gas, N1 is nitrogen-rich gas, ST1 is low-pressure steam, CN1 is condensed water, and CB1 is crude butadiene.
Detailed Description
The technical solution of the present invention is further explained in detail with reference to the following specific examples, but the following examples do not limit the scope of the present invention.
Example 1
The process flow for preparing butadiene from butylene is shown in figure 1, and the reaction process comprises a front heat exchanger FE-1, a first reactor first-stage, a second-stage feed mixer M-11, M-12, an oxidative dehydrogenation first reactor R-1, a first-stage waste heat boiler B-1, a second reactor first-stage, a second-stage feed mixer M-21, M-22, an oxidative dehydrogenation second reactor R-2, a second-stage waste heat boiler B-2, a rear heat exchanger RE-1, an absorption heat pump HP-1, a quenching and acid washing unit Q-1, a generated gas compression C-1 unit and an adsorption unit AD-1 which are sequentially connected through a pipeline; the first oxidative dehydrogenation reactor R-1 and the second oxidative dehydrogenation reactor R-2 are axial fixed bed reactors with the same diameter, and two sections of catalyst bed layers are filled in the axial fixed bed reactors; the discharged nitrogen-rich gas of the adsorption unit AD-1 is mixed with the oxygen-rich gas and then circulated to the oxidative dehydrogenation reactor.
The process method is characterized in that butylene, oxygen-containing gas and steam are subjected to catalytic oxidative dehydrogenation reaction in an axial fixed bed reactor to generate butadiene, and the process method comprises the following steps:
(1) the raw material butene is a mixed raw material containing 1-butene, cis-2-butene and trans-2-butene, wherein the content of the three butenes is 95 percent. Dividing a raw material butene gas phase into four strands, respectively sending the four strands to the inlets of a first-stage bed layer and a second-stage bed layer of an oxidative dehydrogenation first reactor R-1 and a second reactor R-2, and sending the four strands to the first-stage bed layer and the second-stage bed layer of the first reactor, the second reactor and the first-stage bed layer and the second-stage bed layer of the second reactor in a molar ratio of 2:1:1: 1; the water vapor (0.20-0.25 MPaG) from the steam pipe network is heated by the front heat exchanger and then mixed with the gas phase butylene fed into the first section of bed layer of the first reactor.
(2) The oxygen-containing gas is mixed gas formed by oxygen-rich gas and nitrogen-rich gas of the adsorption unit AD-1, the mixed oxygen-containing gas is divided into four parts respectively and is sent to the inlets of the first section bed layer and the second section bed layer of the first reactor R-1 and the second reactor R-2 respectively; iron catalysts are filled in the two axial reactors; selecting a hercynite catalyst containing 50-65 wt% of iron, 3-15 wt% of magnesium, 3-15 wt% of zinc and 0-5 wt% of manganese.
(3) In a first reactor R-1, water vapor exchanges heat with generated gas discharged from a second reactor R-2 in a front heat exchanger FE-1 to raise the temperature to 400-430 ℃, then the water vapor is mixed with a first-stage butylene in a first-stage feed mixer M-11 of the first reactor, and then the mixture is mixed with a first-stage oxygen-containing gas in a second-stage feed mixer M-12 of the first reactor, and the temperature of the water vapor after being raised in the front heat exchanger FE-1 is ensured to be 280 ℃ after being mixed and entering a first-stage material of the first reactor R-1; the mixed materials react in the first-stage bed layer, the temperature gradually rises along the axial direction of the bed layer downwards until the temperature of the outlet of the first-stage bed layer is about 460 ℃, and the materials are discharged to the inlet of the second-stage bed layer of the first reactor R-1. In the embodiment, the total amount of the butylene is 1:0.67:11 in terms of molar ratio, oxygen and water; the gas phase space velocity of the butylene raw material is 250h-1(ii) a The molar ratio of the butylene raw material to the oxygen to the water vapor at the inlet of the first-stage adiabatic fixed bed reactor is 1:0.48: 16.
The material at the outlet of the first-stage bed layer is sent to the inlet of the second-stage bed layer, the interstage chilling water, the butylene and the oxygen-containing gas are sequentially added, the temperature of the inlet of the second-stage bed layer of the reactor is controlled to be 295 ℃, the material after the reaction of the second-stage bed layer is 465.0 ℃, the material is sent to a first-stage waste heat boiler B-1, and low-pressure steam is generated and sent to a low-pressure steam pipe network; can be used as the blending steam of the oxidative dehydrogenation reactor. The molar ratio of the butylene to the oxygen to the water in the second-stage bed of the reactor is 1:0.47:16.8, and the butylene contains unreacted butylene in the first-stage bed.
(4) In a second reactor R-2, gas phase butylene and oxygen-containing gas are sequentially added into the generated gas discharged by a first-stage waste heat boiler B-1 in the step (3) in a first-stage and a second-stage material mixer M-21 and M-22 of the second reactor, the inlet temperature of a first-stage bed layer of the second reactor R-2 is controlled to be 315 ℃ by controlling the outlet gas of the waste heat boiler, and the outlet temperature of the first-stage bed layer after reaction is 474 ℃; the molar ratio of butene to oxygen to water in the first bed of the second reactor R-2 is 1:0.48: 18.
The material at the outlet of the first-stage bed layer is sent to the inlet of the second-stage bed layer, the interstage chilling water, the butylene and the oxygen-containing gas are sequentially added, the temperature of the inlet of the reactor bed layer is controlled to be 330 ℃, the material reacted by the second-stage bed layer is 482.0 ℃, the gas generated at the outlet is sent to a second-stage waste heat boiler B-2 after heat exchange by a front heat exchanger FE-1, and the second-stage waste heat boiler B-2 generates low-pressure steam; the mol ratio of butene to oxygen to water in the second-stage bed layer is 1:0.48:19, and the butene comprises unreacted butene in the first-stage bed layer.
The first and second reactors R-1, R-2 are operated under slightly positive pressure, the low pressure being favorable for the reaction to proceed towards the right, and the operating pressure being lower than 0.1 MPaG.
(5) The generated gas discharged from the secondary waste heat boiler B-2 continuously recovers heat in a rear heat exchanger RE-1, low-pressure steam generated by an absorption heat pump HP-1 is used as the ingredient steam of the reaction, and the generated gas after heat recovery is further cooled by a quenching and acid washing unit Q-1 and the acid gas of the generated gas is removed; the generated gas is compressed and enters an adsorption unit AD-1 for separation. The adsorption unit AD-1 mainly comprises four carbon components and non-condensable gas, wherein the four carbon components are mainly 1, 3-butadiene to obtain crude butadiene; the main components of the non-condensable gas are nitrogen, unreacted oxygen, a small amount of carbon dioxide and a minute amount of carbon four components, and nitrogen-rich gas is obtained. And (3) sending the crude butadiene to a subsequent butadiene extraction unit, returning uncondensed inert gas to the step (2), mixing with the oxygen-rich gas, and taking the mixture as the ingredient gas of the reactor. The mixed oxygen-containing gas is mainly a mixed gas of nitrogen and oxygen, wherein the oxygen content is controlled to be 23.0%.
The reaction results of the above process are shown in Table 3.
TABLE 3 reaction results of butene oxidative dehydrogenation process
Figure BDA0002708778050000081
Comparative example 1
Compared with the traditional two-stage axial fixed bed reaction process, the traditional oxidative dehydrogenation reactor adopts two-stage fixed bed reactors connected in series, the catalyst and the loading amount are the same, the conversion rate of the butylene is only 72.0%, the selectivity is 91.3% and the yield is 65.74% under the conditions that the inlet temperature of the first-stage reactor is 280 ℃, the total oxygen-olefin ratio is the same and the total water-olefin ratio is 12.
The results show that the steam consumption of the reaction system of the process of the invention is about 0.4 ton/ton (butadiene), while the steam consumption of the conventional process is 2.2 ton/ton (butadiene), and the process greatly reduces the steam consumption.

Claims (10)

1. A process for preparing butadiene through oxidative dehydrogenation of butylene is characterized in that butylene, oxygen-containing gas and steam are generated through catalytic oxidative dehydrogenation reaction in an axial fixed bed reactor, the axial fixed bed reactor comprises a first oxidative dehydrogenation reactor and a second oxidative dehydrogenation reactor which are connected in series, and two sections of catalyst bed layers are filled in the first reactor and the second reactor; the system comprises a front heat exchanger, a first reactor first-stage, a second-stage feed mixer, a first reactor, a first-stage waste heat boiler, a second reactor first-stage, a second-stage feed mixer, a second reactor, a second-stage waste heat boiler, a rear heat exchanger, a quenching and acid washing unit, a generated gas compression and adsorption unit in sequence in the material flowing direction;
the process comprises the following steps:
(1) the raw material gas phase butylene is divided into four strands and respectively sent to the inlets of a first-stage bed layer and a second-stage bed layer of the first oxidative dehydrogenation reactor and the second oxidative dehydrogenation reactor; the material mixing steam and the gas generated by the discharge reaction of the second reactor exchange heat in a front heat exchanger to heat up, and the steam after heating up is mixed with the gas phase butylene fed into the first reactor section bed layer; the total effective butylene and the water vapor are prepared according to the molar ratio of 1: 4-10;
(2) oxygen-containing gas formed by mixing the oxygen-rich gas and the nitrogen-rich gas from the adsorption unit is divided into four streams which are respectively sent to the inlets of the first-stage bed layer and the second-stage bed layer of the first reactor and the second reactor; wherein the molar ratio of the total effective butylene to the oxygen is configured according to 1: 0.4-0.80, and the molar ratio of the butylene to the oxygen of each section of bed layer is 1: 0.2-0.70;
(3) in a first reactor, after mixing butylene and steam entering a first-stage bed layer of the first reactor in a first-stage feed mixer of the first reactor, further uniformly mixing mixed gas and oxygen-containing gas in a second-stage feed mixer of the first reactor, controlling the feeding temperature of the first-stage bed layer of the first reactor to be 260-370 ℃, entering the first-stage bed layer for full reaction, entering a second-stage bed layer, and controlling the temperature of an outlet of the first-stage bed layer of the first reactor to be 430-510 ℃; introducing gas-phase butylene into the second-stage bed layer, proportionally adding oxygen-containing gas and intersegmental chilling water, controlling the inlet temperature of the second-stage bed layer to be 260-370 ℃, and controlling the outlet temperature of the second-stage bed layer to be 430-510 ℃ after the second-stage bed layer fully reacts; the generated gas at the outlet of the second-stage bed layer enters a second reactor after heat energy is recovered by a first-stage waste heat boiler;
(4) in a second reactor, the generated gas from the first reactor and gas-phase butylene are fully mixed in a first-stage feed mixer of the second reactor, and then are further uniformly mixed with oxygen-containing gas in a second-stage feed mixer of the second reactor, the inlet temperature of a first-stage bed layer of the second reactor is controlled to be 260-370 ℃, the generated gas enters a first-stage bed layer of the second reactor and enters a second-stage bed layer after fully reacting, and the outlet temperature of the first-stage bed layer is controlled to be 430-510 ℃; introducing gas-phase butylene into an inlet of the second-stage bed layer, proportionally adding oxygen-containing gas and intersegmental chilling water, controlling the inlet temperature of the second-stage bed layer to be 260-370 ℃, and controlling the outlet temperature of the second-stage bed layer to be 430-510 ℃ after the second-stage bed layer fully reacts; the generated gas at the outlet of the second-stage bed layer exchanges heat through a front heat exchanger, a second-stage waste heat boiler and a rear heat exchanger;
(5) cooling the reaction generated gas after heat exchange in a quenching and acid washing unit and removing acid gas of the reaction generated gas; the reaction generated gas further passes through a compression unit and then enters an adsorption unit for separation to obtain crude butadiene, and the nitrogen-rich gas and the oxygen-rich gas are mixed and then circulated to the oxidative dehydrogenation reactor.
2. The process for preparing butadiene through oxidative dehydrogenation of butene according to claim 1, wherein in the step (1), the steam is heated to 380-450 ℃ through a front heat exchanger.
3. The process for preparing butadiene through oxidative dehydrogenation of butene according to claim 1, wherein the pressure of the feed steam in step (1) is 0.20-0.25 MPaG, and the pressure of the feed steam is from 0.20-0.25 MPaG of a steam pipe network.
4. The process for preparing butadiene through oxidative dehydrogenation of butene according to claim 1, wherein the molar ratio of the butene raw material in the step (1) to the first-stage bed layer, the second-stage bed layer and the first-stage bed layer of the first reactor to the second reactor is 1.9-2.1: 0.9-1.1.
5. The process for preparing butadiene by oxidative dehydrogenation of butene according to claim 1, wherein the oxygen-rich gas in step (2) is pure oxygen or a mixture of water vapor and oxygen; o in the oxygen-containing gas2The concentration of (A) is 18-36% vol.
6. The process for preparing butadiene through oxidative dehydrogenation of butene according to claim 1, wherein the mass content of butene in the raw material butene is not less than 80%, and the effective butene is one or more of 1-butene, cis-2-butene and trans-2-butene.
7. The process for preparing butadiene through oxidative dehydrogenation of butene according to claim 1, wherein in the step (3), a primary waste heat boiler generates low-pressure steam as the blending steam of the oxidative dehydrogenation reactor.
8. The process for the oxidative dehydrogenation of butene to butadiene according to claim 1, wherein said first reactor and said second reactor are operated under slightly positive pressure, and the operating pressure is lower than 0.1 MPaG.
9. The process for preparing butadiene through oxidative dehydrogenation of butene according to claim 1, wherein the catalysts filled in the first reactor and the second reactor are spinel catalysts comprising iron, magnesium, zinc and manganese, wherein the iron content is 50-65 wt%, the magnesium content is 3-15 wt%, the zinc content is 3-15% and the manganese content is 0-5%.
10. The process for preparing butadiene by oxidative dehydrogenation of butene according to claim 1, wherein the first reactor and the second reactor have the same diameter.
CN202011048482.XA 2020-09-29 2020-09-29 Process for preparing butadiene through oxidative dehydrogenation of butylene Pending CN112110785A (en)

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