Method and system for preparing styrene through ethylbenzene dehydrogenation

Abstract

The invention provides a method and a system for preparing styrene through ethylbenzene dehydrogenation. The method comprises a first dehydrogenation reaction and a second dehydrogenation reaction which are sequentially carried out, a) first reheating the first dehydrogenation reactant after first heating of the water vapor stream; then carrying out second heating and then carrying out second reheating on the first dehydrogenation reactant; then carrying out third heating; b) carrying out heat exchange on a mixed material flow of ethylbenzene and water, a second dehydrogenation reactant and the third heated water vapor material flow obtained in the step a) to obtain a preheated mixed material flow of ethylbenzene and water; and c) performing fourth heating on the third heating water vapor material flow subjected to heat exchange in the step b), mixing the third heating water vapor material flow with the preheated ethylbenzene and water mixture flow in the step b) to obtain a mixture flow raw material, and performing the first dehydrogenation reaction. The method provided by the invention solves the problem that the outlet temperature of the heating furnace of the existing styrene production device is too high and exceeds the upper limit of the use temperature of equipment under the reaction condition of ultralow water ratio (less than 1.0), reduces the equipment investment, and reduces the energy consumption.

Description

Technical Field

[0001] The present invention belongs to the field of chemical raw material production, and relates to a system and method for preparing styrene by dehydrogenation of ethylbenzene. Background Art

[0002] Styrene is one of the most important basic organic chemical raw materials, and is used to manufacture copolymers such as polystyrene (PS) and expanded polystyrene (EPS), acrylonitrile-butadiene-styrene (ABS) and styrene-acrylonitrile (SAN), styrene / butadiene copolymer latex (SB), styrene-butadiene rubber and latex (SBR), unsaturated polyester, and others such as styrene / methyl methacrylate latex, methyl methacrylate / butadiene / styrene copolymer (MBS), ion exchange resin, and drugs.

[0003] In industry, the production technologies for preparing styrene by dehydrogenation of ethylbenzene include adiabatic dehydrogenation process, isothermal dehydrogenation process, and dehydrogenation selective oxidation process. Among them, the most widely used and technically mature one is the ethylbenzene negative pressure adiabatic dehydrogenation process. It is reported that more than 80% of the world's styrene production uses the ethylbenzene negative pressure adiabatic dehydrogenation production process.

[0004] The process principle of dehydrogenation of ethylbenzene to styrene is as follows: in the presence of a catalyst and water vapor and at a high temperature of 530 - 650°C, ethylbenzene undergoes a selective dehydrogenation reaction to generate styrene. This reaction is a strongly endothermic reaction. A large amount of superheated steam is also required for the dehydrogenation reaction of ethylbenzene. On the one hand, the superheated steam is the heat carrier for the dehydrogenation reaction of ethylbenzene, providing the heat required for the reaction. On the other hand, the presence of water vapor reduces the reaction partial pressure, which is beneficial for the reaction to proceed in the positive direction of generating styrene. Water vapor can also undergo a water-gas shift reaction with the carbon deposition on the catalyst surface, preventing the reduction of the active components of the catalyst to metals and being beneficial for extending the catalyst life. The water ratio is the mass ratio of water to ethylbenzene in the feed of the first reactor, and the water ratio usually used in industry is 1 - 1.6.

[0005] Currently, most of the technologies for producing styrene by dehydrogenation of ethylbenzene are the azeotropic energy-saving rectification technologies proposed in CN103030522A. In this technology, the ethylbenzene dehydrogenation reaction unit adopts a negative pressure adiabatic dehydrogenation process with a two-stage series reactor with inter-stage secondary heating. Specifically, the raw material from the ethylbenzene superheater is mixed with the superheated steam from the B chamber of the steam superheater furnace and enters the first dehydrogenation reactor. The obtained first-stage reaction product exchanges heat with the superheated steam from the A chamber of the steam superheater furnace through an intermediate heat exchanger and then enters the second dehydrogenation reactor to obtain the second-stage reaction product. The steam after heat exchange enters the B chamber of the steam superheater furnace for heating, and the second-stage reaction product is the heat source for the ethylbenzene superheater.

[0006] The production process of styrene is at high temperature and requires a large amount of fuel and steam, making the energy consumption of this process relatively high. The reduction of the water ratio can save a large amount of energy consumption for styrene production. It is calculated that when the water ratio is reduced from 1.4 to 1.1, the comprehensive energy consumption of styrene can be saved by more than 10%. In the current process, the temperature of the first-stage reaction depends on the temperature of the superheated steam from the B chamber of the steam superheater and the temperature of the raw material from the ethylbenzene superheater. The temperature of the second-stage reaction depends on the flow rate and temperature of the superheated steam from the A chamber of the steam superheater. To ensure the conversion rate of ethylbenzene and overall economy, the temperatures of the first-stage and second-stage reactions cannot be changed. Since the heat source of the ethylbenzene superheater is the product of the second-stage reaction (~560°C), it is difficult to further increase the temperature of the raw material. When the water ratio is reduced, the outlet temperatures of the A chamber and B chamber of the steam superheater must be increased to provide the heat required for ethylbenzene dehydrogenation. It is calculated that when the water ratio is reduced from 1.25 to 1.0, the outlet temperatures of the A chamber and B chamber of the steam heating furnace are increased from 830°C and 828°C to 878°C and 867°C respectively. When the water ratio is reduced to 0.9, the outlet temperatures of the A chamber and B chamber of the steam heating furnace need to be increased to 919°C and 917°C. Heat exchangers and pipelines must use high-temperature resistant materials. When the temperature is below 880°C, 800HT material with a relatively high price can be used. When the temperature exceeds 880°C, higher-specification high-temperature resistant materials must be used, and the price doubles. When the temperature exceeds 920°C, there is even no suitable material to meet the process requirements, resulting in a significant increase in equipment investment and a significant reduction in energy-saving effect, seriously affecting the economic benefits of styrene enterprises.

[0007] CN111848323A discloses a process method for producing styrene by dehydrogenation of ethylbenzene with a low water ratio. This method adds a heating furnace hearth and an intermediate reheater to the existing process, enabling the outlet of the first-stage reaction product to conduct secondary heat exchange with steam, so that the device can operate at an ultra-low water ratio (0.85), and the hearth temperature is lower than 880°C. However, this method has certain defects. The main problem is that the raw material containing ethylbenzene and water is preheated by the product of the second-stage reaction. The temperature of the product of the second-stage reaction is generally 560°C (water ratio 0.85) at the initial stage of the device operation. Due to the need for a certain temperature difference for heat exchange (generally greater than 50°C), this limits the preheating temperature of the raw material containing ethylbenzene and water (~510°C). Therefore, only by increasing the steam temperature can the heat required for the first-stage reaction be met. The lower the water ratio, the lower the outlet temperature of the second-stage reaction, the lower the preheating temperature of the raw material containing ethylbenzene and water, the higher the steam temperature, and the greater the investment in high-temperature materials. Summary of the Invention

[0008] The object of the present invention is to solve the problem that the outlet temperature of the heating furnace is too high and exceeds the upper limit of the equipment operating temperature under the reaction conditions of an ultra-low water ratio (<1.0) in the current styrene production device; to provide a system and method for preparing styrene by dehydrogenation of ethylbenzene.

[0009] According to the first aspect of the present invention, the present invention provides a method for preparing styrene by dehydrogenation of ethylbenzene, the method comprising: a first dehydrogenation reaction and a second dehydrogenation reaction carried out in sequence;

[0010] a) After the first heating of the water vapor stream, the first dehydrogenation reactant is reheated for the first time; then after the second heating, the first dehydrogenation reactant is reheated for the second time; then the third heating is carried out;

[0011] b) The mixed stream of ethylbenzene and water exchanges heat with the second dehydrogenation reactant and the third heated water vapor stream in step a) respectively or simultaneously to obtain a preheated mixed stream of ethylbenzene and water;

[0012] c) The third heated water vapor stream after heat exchange in step b) is subjected to a fourth heating and mixed with the preheated mixed stream of ethylbenzene and water in step b) to obtain a mixed stream raw material for carrying out the first dehydrogenation reaction.

[0013] According to the second aspect of the present invention, the present invention provides a system for preparing styrene by dehydrogenation of ethylbenzene for use in the method of the present invention, the system comprising:

[0014] A first dehydrogenation reactor and a second dehydrogenation reactor connected in series in sequence along the material flow direction for carrying out the first dehydrogenation reaction and the second dehydrogenation reaction,

[0015] A heating unit for carrying out the first heating, the second heating, the third heating, and the fourth heating;

[0016] A first raw material preheater and a second raw material preheater provided on the feed pipeline of the first dehydrogenation reactor, the first raw material preheater being used for the mixed stream of ethylbenzene and water to exchange heat with the second dehydrogenation reaction product for the first heat exchange; the second raw material preheater being used for the mixed stream of ethylbenzene and water to exchange heat with the third heated water vapor stream for the second heat exchange;

[0017] A first intermediate reheater and a second intermediate reheater provided on the discharge pipeline of the first dehydrogenation reactor, the first intermediate being used for carrying out the first reheating; the second intermediate reheater being used for carrying out the second reheating;

[0018] Preferably, the heating unit is a heating furnace containing four chambers; each chamber is respectively used for carrying out the first heating, the second heating, the third heating, and the fourth heating.

[0019] According to the third aspect of the present invention, the present invention provides a method for preparing styrene by dehydrogenation of ethylbenzene, the method being carried out in the system of the present invention, the heating unit being a heating furnace containing four chambers, from left to right being chamber A, chamber B, chamber C, chamber D; code chamber n 1 , chamber n 2 , chamber n 3 , chamber n 4They are arranged as Chamber A, Chamber C, Chamber D, Chamber B, or Chamber A, Chamber B, Chamber C, Chamber D;

[0020] i) The water-containing logistics sequentially enter the heating furnace Chamber n 1 , the first intermediate reheater, Chamber n 2 , the second intermediate reheater, Chamber n 3 , the second raw material preheater, and Chamber n 4 , and are mixed with the logistics 2 containing ethylbenzene and water from the second raw material preheater to form logistics 3;

[0021] 2) The logistics 2 containing ethylbenzene and water sequentially enter the first raw material preheater E-101 and the second raw material preheater E-102 for the first heat exchange and the second heat exchange, and are mixed with the water-containing logistics from Chamber n 4 to form logistics 3;

[0022] 3) Logistics 3 enters the first dehydrogenation reactor R-101 to undergo the first dehydrogenation reaction to generate the logistics 4 containing styrene;

[0023] 4) Logistics 4 sequentially enters the first intermediate reheater E-103 and the second intermediate reheater E-104, and then enters the second dehydrogenation reactor R-102 to further undergo the second dehydrogenation reaction to generate the logistics 5 containing styrene. Logistics 5 passes through the first raw material preheater E-101 to go to the subsequent unit.

[0024] In the present invention, by adding an ethylbenzene and water raw material preheater and a first reaction product reheater, the preheating medium is from the heating steam. By adding the ethylbenzene and water raw material preheater, the limitation that the raw material preheating temperature of ethylbenzene and water in the existing process must be lower than the temperature of the second-stage reaction product is eliminated. After secondary preheating, the raw material temperature of ethylbenzene and water entering the first-stage reactor can be increased from the original 480 - 520 °C to 480 - 600 °C; by adding the intermediate reheater preheater, the reaction material entering the second-stage reactor can be directly increased from the original 525 °C to 623 °C to first be increased from 525 °C to 585 °C and then to 623 °C, thereby reducing the outlet temperature of the steam heating furnace, reducing the use of high-temperature materials, reducing the equipment investment, and reducing the energy consumption.

[0025] The method of the present invention solves the problem that the outlet temperature of the heating furnace is too high under the reaction conditions of an ultra-low water ratio (<1.0) in the current styrene production device, exceeding the upper limit of the equipment use temperature, reduces the use of high-temperature materials, reduces the equipment investment, and reduces the energy consumption. In particular, the technical solution of sequentially heating the first-stage reaction raw materials and the second-stage reaction raw materials by the heating steam from the four-in-one heating furnace is preferably adopted, which preferably solves this problem and can be directly used in the industrial production of styrene, having good industrial application value.

[0026] In a preferred embodiment of the present invention, the feedstock for the first reaction and the feedstock for the second reaction are heated step by step by heating steam from a four-in-one heating furnace, so as to solve the problem that the outlet temperature of the heating furnace is too high under the reaction conditions of an ultra-low water ratio (<1.0) in the current styrene production unit, exceeding the upper limit of the equipment operating temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 FIG. is a process flow diagram according to some embodiments of the present invention.

[0028] Figure 2 FIG. is a process flow diagram of the existing technology for dehydrogenating ethylbenzene to produce styrene.

[0029] The present invention will be further described below through examples.

[0030] DESCRIPTION OF THE REFERENCE NUMERALS

[0031] Figure 1 In FIG., F-101 is a heating furnace, which from left to right is chamber A, chamber B, chamber C and chamber D, R-101 is the first dehydrogenation reactor, R-102 is the second dehydrogenation reactor, E-101 is the first feedstock preheater, E-102 is the second feedstock preheater, E-103 is the first intermediate reheater, E-104 is the second intermediate reheater, 1 is the main steam (a logistics containing water), 2 is the feedstock logistics containing ethylbenzene and water, 3 is the reactant logistics entering the first reactor, 4 is the reaction product logistics containing styrene exiting the first reactor, and 5 is the reaction product logistics containing styrene exiting the second reactor.

[0032] Figure 2 In FIG., F-101 is a steam heating furnace, which from left to right is chamber A and chamber B, R-101 is the first dehydrogenation reactor, R-102 is the second dehydrogenation reactor, E-101 is the feedstock preheater, E-102 is the intermediate reheater, 1 is the main steam, 2 is the feedstock ethylbenzene and water, 3 is the reactant entering the first reactor, 4 is the reaction product exiting the first reactor, and 5 is the reaction product exiting the second reactor. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] In the ranges disclosed herein, the endpoints and any value are not limited to the exact range or value, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and a single point value, and between single point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0034] The present invention provides a method for dehydrogenating ethylbenzene to produce styrene, the method comprising: a first dehydrogenation reaction and a second dehydrogenation reaction carried out in sequence;

[0035] a) The first dehydrogenation reactant is reheated for the first time after the first heating of the water vapor stream; then it is reheated for the second time after the second heating; then the third heating is carried out.

[0036] b) The mixed stream of ethylbenzene and water exchanges heat with the second dehydrogenation reactant and the third heated water vapor stream in step a) separately or simultaneously to obtain a preheated mixed stream of ethylbenzene and water.

[0037] c) The third heated water vapor stream after heat exchange in step b) is subjected to the fourth heating and mixed with the preheated mixed stream of ethylbenzene and water in step b) to obtain a mixed stream raw material for the first dehydrogenation reaction. The method of the present invention solves the problem that the outlet temperature of the heating furnace is too high under the reaction conditions of an ultra-low water ratio (<1.0) in the current styrene production device, exceeding the upper limit of the equipment operating temperature, reduces the use of high-temperature materials, reduces equipment investment, and reduces energy consumption.

[0038] According to a preferred embodiment of the present invention, the steps of step b) include: the mixed stream of ethylbenzene and water exchanges heat with the second dehydrogenation reaction product for the first heat exchange, and then exchanges heat with the third heated water vapor stream in step a) for the second heat exchange.

[0039] In the present invention, the optional range of the conditions for the first heat exchange and the second heat exchange is relatively wide. For the present invention, it can be selected according to the actual situation. For the present invention, preferably, the conditions for the first heat exchange include: the outlet temperature of the tube side is 450 °C to 550 °C, preferably 480 °C to 530 °C.

[0040] According to a preferred embodiment of the present invention, the conditions for the second heat exchange include: the outlet temperature of the tube side is 480 °C to 600 °C, preferably 550 to 590 °C.

[0041] In the present invention, there are no special requirements for the dehydrogenation conditions. The present invention is particularly suitable for dehydrogenation reactions with a low water ratio. According to an embodiment of the present invention, in step c), the conditions for the first dehydrogenation reaction include: the weight ratio of water to ethylbenzene in the mixed stream raw material is 0.8 to 1.2, preferably 0.85 to 1; however, the present invention is not limited thereto.

[0042] According to an embodiment of the present invention, in step c), the weight ratio of water to ethylbenzene in step b) is 0.3 - 0.5. However, the present invention is not limited thereto.

[0043] In the present invention, there are no special requirements for the conditions of the first reheating and the second reheating, and they can be selected according to the actual situation. For the present invention, according to a preferred embodiment of the present invention, among them, the conditions for the first reheating include: the outlet temperature of the tube side is 550 to 610 °C, preferably 580 to 590 °C; however, the present invention is not limited thereto.

[0044] According to a preferred embodiment of the present invention, the conditions for the second reheat include: the tube-side outlet temperature is 600-650°C, preferably 610-630°C; however, the present invention is not limited thereto.

[0045] In the present invention, the conditions for the first heating, second heating, third heating, and fourth heating can be selected and determined according to specific needs. According to an embodiment of the present invention, the conditions for the first heating, second heating, third heating, and fourth heating each include: the outlet temperature is 700-850°C, preferably 730-830°C, more preferably 730-800°C; however, the present invention is not limited thereto.

[0046] The present invention has no special requirements for the conditions of dehydrogenation reactions, etc. The object of the present invention can be achieved as long as the process flow of the present invention is followed. According to an embodiment of the present invention, the first dehydrogenation reaction and the second dehydrogenation reaction are each carried out in a dehydrogenation reactor, and preferably the dehydrogenation reactor is an adiabatic fixed-bed reactor; however, the present invention is not limited thereto.

[0047] According to an embodiment of the present invention, the conditions for the first dehydrogenation reaction and the second dehydrogenation reaction each include: the reaction temperature is 510°C - 650°C, and the reaction pressure is 30 kPaA - 60 kPaA; however, the present invention is not limited thereto.

[0048] The present invention provides a system for preparing styrene by dehydrogenation of ethylbenzene for use in the method of the present invention. The system includes:

[0049] A first dehydrogenation reactor R-101 and a second dehydrogenation reactor R-102 connected in series in the material flow direction for carrying out the first dehydrogenation reaction and the second dehydrogenation reaction,

[0050] A heating unit for carrying out the first heating, second heating, third heating, and fourth heating;

[0051] A first raw material preheater E-101 and a second raw material preheater E-102 provided on the feed pipeline of the first dehydrogenation reactor R-101. The first raw material preheater E-101 is used for the first heat exchange of the mixed stream of ethylbenzene and water with the product of the second dehydrogenation reaction; the second raw material preheater E-102 is used for the second heat exchange of the mixed stream of ethylbenzene and water with the third heating steam stream after that;

[0052] A first intermediate reheater E-103 and a second intermediate reheater E-104 provided on the outlet pipeline of the first dehydrogenation reactor. The first intermediate reheater E-103 is used for carrying out the first reheat; the second intermediate reheater E-104 is used for carrying out the second reheat;

[0053] Preferably, the heating unit is a heating furnace F-101 with four chambers; each chamber is respectively used for performing the first heating, the second heating, the third heating, and the fourth heating.

[0054] According to a preferred embodiment of the present invention, a method for preparing styrene by dehydrogenation of ethylbenzene is provided. This method is carried out in the system described in the present invention. The heating unit is a heating furnace (F-101) with four chambers, which are chamber A, chamber B, chamber C, and chamber D from left to right; the code chamber n 1 , chamber n 2 , chamber n 3 , chamber n 4 are arranged as chamber A, chamber C, chamber D, chamber B, or chamber A, chamber B, chamber C, chamber D;

[0055] 1) The stream 1 containing water sequentially enters chamber n of the heating furnace F-101 1 , the first intermediate reheater E-103, chamber n 2 , the second intermediate reheater E-104, chamber n 3 , the second feed preheater E-102, and chamber n 4 , and is mixed with the stream 2 containing ethylbenzene and water from the second feed preheater E-102 to form stream 3;

[0056] 2) The stream 2 containing ethylbenzene and water sequentially enters the first feed preheater E-101 and the second feed preheater E-102 for the first heat exchange and the second heat exchange, and is mixed with the stream containing water from chamber n 4 to form stream 3;

[0057] 3) Stream 3 enters the first dehydrogenation reactor R-101 to carry out the first dehydrogenation reaction, generating stream 4 containing styrene;

[0058] 4) Stream 4 sequentially enters the tube side of the first intermediate reheater E-103 and the tube side of the second intermediate reheater E-104, and then enters the second dehydrogenation reactor R-102 to further carry out the second dehydrogenation reaction, generating stream 5 containing styrene. Stream 5 passes through the first feed preheater E-101 to subsequent units.

[0059] According to a preferred embodiment of the present invention, the stream 2 containing ethylbenzene and water sequentially enters the tube side of the first feed preheater E-101 and the second feed preheater E-102 for the first heat exchange and the second heat exchange.

[0060] According to a preferred embodiment of the present invention, stream 4 sequentially enters the tube side of the first intermediate reheater E-103 and the tube side of the second intermediate reheater E-104.

[0061] According to a preferred embodiment of the present invention, the outlet temperature of the tube side of the first raw material preheater E-101 is 450°C to 550°C, preferably 480°C to 530°C; however, the present invention is not limited thereto.

[0062] According to a preferred embodiment of the present invention, the outlet temperature of the tube side of the second raw material preheater E-102 is 480°C to 600°C, preferably 550 to 590°C; however, the present invention is not limited thereto.

[0063] According to a preferred embodiment of the present invention, the outlet temperature of the tube side of the first intermediate reheater E-103 is 550 to 610°C, preferably 580 to 590°C; however, the present invention is not limited thereto.

[0064] According to a preferred embodiment of the present invention, the outlet temperature of the tube side of the second intermediate reheater E-104 is 600 to 650°C, preferably 610 to 630°C; however, the present invention is not limited thereto.

[0065] According to a preferred embodiment of the present invention, the weight ratio of water to ethylbenzene in stream 3 is 0.8 to 1.2, preferably 0.85 to 1; however, the present invention is not limited thereto.

[0066] According to a preferred embodiment of the present invention, the weight ratio of water to ethylbenzene in stream 2 containing ethylbenzene and water is 0.3 - 0.5; however, the present invention is not limited thereto.

[0067] According to a preferred embodiment of the present invention, the outlet temperature of the heating furnace is 700 to 850°C, preferably 730 to 830°C, more preferably 730 to 800°C; however, the present invention is not limited thereto.

[0068] According to a preferred embodiment of the present invention, the first dehydrogenation reactor and the second dehydrogenation reactor are adiabatic fixed bed reactors, and their respective conditions include: the reaction temperature is 510°C to 650°C, and the reaction pressure is 30 kPaA to 60 kPaA; however, the present invention is not limited thereto.

[0069] Figure 1 The device for dehydrogenating ethylbenzene to styrene according to an embodiment of the present invention is shown, including F-101, a steam heating furnace with four chambers combined into one, from left to right are chamber A, chamber B, chamber C, and chamber D, R-101 is the first dehydrogenation reactor, R-102 is the second dehydrogenation reactor, E-101 is the first raw material preheater, E-102 is the second raw material preheater, E-103 is the first intermediate reheater, E-104 is the second intermediate reheater, and the dehydrogenation reactor is an adiabatic reactor.

[0070] In this device, the raw material 2 containing ethylbenzene and water sequentially enters the tube sides of E-101 and E-102, and is preheated by the logistics 5 from R-102 and the steam from chamber D of F-101. Subsequently, after being mixed with the main steam from chamber B of F-101, it serves as the reactant 3. The reactant 3 enters R-101 to undergo a dehydrogenation reaction, generating the logistics 4 containing styrene. The logistics 4 sequentially enters the tube sides of E-103 and E-104, and is reheated by the steam from chamber A of F-101 and chamber C of F-101. After reheating, the logistics enters R-102 to further undergo a dehydrogenation reaction, generating the logistics 5 containing styrene. The logistics 5 serves as the heat source for E-101 and is discharged after preheating the logistics 2.

[0071] In this device, the heat exchange temperature difference between the cold end and the hot end of E-101, E-102, E-103, and E-104 is greater than 50 °C.

[0072] In the present invention,

[0073] The calculation method for the total conversion rate of ethylbenzene, % is:

[0074]

[0075] The calculation method for the total selectivity of styrene, % is:

[0076]

[0077] The calculation method for the total investment of high-temperature pipelines and equipment, in ten thousand yuan is: = total mass of high-temperature pipelines × unit price + total price of equipment;

[0078] The calculation method for the energy consumption, kg of standard oil / ton of styrene is:

[0079]

[0080] Figure 2 The device for dehydrogenating ethylbenzene to produce styrene in the comparative example is shown, including F-101 which is a steam heating furnace integrating two chambers, from left to right are chamber A and chamber B, R-101 is the first dehydrogenation reactor, R-102 is the second dehydrogenation reactor, E-101 is the raw material preheater, E-102 is the intermediate reheater, and the dehydrogenation reactor is an adiabatic reactor.

[0081] In this device, the raw material 2 containing ethylbenzene and water enters the tube side of E-101 and is preheated by the logistics 5 from R-102. Subsequently, it is mixed with the main steam from chamber B of F-101 and serves as the reactant 3. The reactant 3 enters R-101 to undergo a dehydrogenation reaction, generating the logistics 4 containing styrene. The logistics 4 enters the tube side of E-102 and is reheated by the steam from chamber A of F-101. The reheated logistics enters R-102 to further undergo a dehydrogenation reaction, generating the logistics 5 containing styrene. The logistics 5 serves as the heat source for E-101 and is discharged after preheating the logistics 2.

[0082] The catalyst is the catalyst prepared in Example 1 of Invention Patent CN103769151B.

[0083]

Example 1

[0084] A 100,000-ton ethylbenzene dehydrogenation to styrene device adopts Figure 1 the shown process flow. The total water ratio is 0.9. At the initial stage of the device operation, the inlet temperatures of the first dehydrogenation reactor and the second dehydrogenation reactor are 623 °C (the inlet temperature of R101). The main process operation parameters are listed in Table 1.

[0085] Table 1

[0086] Project Parameter Mass ratio of water and ethylbenzene in Stream 3 0.9 Inlet / Outlet temperature of Chamber F-101A, °C 149 / 776 Inlet / Outlet temperature of Chamber F-101B, °C 550 / 763 Inlet / Outlet temperature of Chamber F-101C, °C 574 / 770 Inlet / Outlet temperature of Chamber F-101D, °C 633 / 764 Mass ratio of water and ethylbenzene in Stream 2 0.358 Inlet / Outlet temperature of the tube side of E-101, °C 98 / 500 Outlet temperature of the tube side of E-102, °C 575 Inlet / Outlet temperature of the tube side of E-103, °C 525 / 583 Outlet temperature of the tube side of E-104, °C 623 Inlet / Outlet temperature of R-101, °C 623 / 525 Inlet pressure of R-101, kPaA 55 Inlet / Outlet temperature of R-102, °C 623 / 563 Inlet pressure of R-102, kPaA 45 Total conversion rate of ethylbenzene, % 65.0 Total selectivity of styrene, % 96.0 Total investment in high-temperature pipelines and equipment, 10,000 yuan 1800 Energy consumption, kg of standard oil per ton of styrene 290

[0087]

Example 2

[0088] A 100,000-ton ethylbenzene dehydrogenation to styrene device adopts Figure 1 the shown process flow. The total water ratio is 0.85. At the initial stage of the device operation, the inlet temperatures of the first reactor and the second reactor are 623 °C. The main process operation parameters are listed in Table 2.

[0089] Table 2

[0090] Project Index Mass ratio of water and ethylbenzene in Stream 3 0.85 Inlet / Outlet temperature of Chamber F-101A, °C 149 / 798 Inlet / Outlet temperature of Chamber F-101B, °C 550 / 777 Inlet / Outlet temperature of Chamber F-101C, °C 572 / 798 Inlet / Outlet temperature of Chamber F-101D, °C 632 / 785 Mass ratio of water and ethylbenzene in Stream 2 0.358 Inlet / Outlet temperature of the tube side of E-101, °C 98 / 500 Outlet temperature of the tube side of E-102, °C 575 Inlet / Outlet temperature of the tube side of E-103, °C 522 / 583 Outlet temperature of the tube side of E-104, °C 623 Inlet / Outlet temperature of R-101, °C 623 / 522 Inlet pressure of R-101, kPaA 55 Inlet / Outlet temperature of R-102, °C 623 / 561 Inlet pressure of R-102, kPaA 45 Total conversion rate of ethylbenzene, % 64.9 Total selectivity of styrene, % 95.9 Total investment in high-temperature pipelines and equipment, 10,000 yuan 2400 Energy consumption, kg of standard oil per ton of styrene 285

[0091]

Example 3

[0092] A 100,000-ton ethylbenzene dehydrogenation to styrene device adopts Figure 1 the shown process flow. The total water ratio is 0.85. Different from Example 2, the device is at the end stage of operation. Due to the decline in the performance of the catalyst, it is necessary to increase the reaction temperature to maintain the reaction performance. The inlet temperatures of the first reactor and the second reactor are 645 °C. The main process operation parameters are listed in Table 3.

[0093] Table 3

[0094] Project Index Mass ratio of water and ethylbenzene in Stream 3 0.85 Inlet / Outlet temperature of Chamber F-101A, °C 149 / 818 Inlet / Outlet temperature of Chamber F-101B, °C 585 / 821 Inlet / Outlet temperature of Chamber F-101C, °C 595 / 823 Inlet / Outlet temperature of Chamber F-101D, °C 655 / 775 Mass ratio of water and ethylbenzene in Stream 2 0.358 Inlet / Outlet temperature of the tube side of E-101, °C 98 / 530 Outlet temperature of the tube side of E-102, °C 590 Inlet / Outlet temperature of the tube side of E-103, °C 545 / 605 Outlet temperature of the tube side of E-104, °C 645 Inlet / Outlet temperature of R-101, °C 645 / 545 Inlet pressure of R-101, kPaA 55 Inlet / Outlet temperature of R-102, °C 645 / 583 Inlet pressure of R-102, kPaA 45 Total conversion rate of ethylbenzene, % 64.9 Total selectivity of styrene, % 95.8 Total investment in high-temperature pipelines and equipment, 10,000 yuan 2800 Energy consumption, kg of standard oil per ton of styrene 288

[0095]

Example 4

[0096] A styrene production plant by dehydrogenation of ethylbenzene adopts Figure 1 the process flow shown in the figure. The total water ratio is 0.85. The plant is in the initial stage of operation. The inlet temperature of the first reactor is 615 °C, and the outlet temperature is 522 °C. The inlet temperature of the second reactor is 623 °C, and the outlet temperature is 565 °C. The main process operation parameters are listed in Table 4.

[0097] Table 4

[0098] Project Index Mass ratio of water and ethylbenzene in Stream 3 0.85 Inlet / Outlet temperature of Chamber F-101A, °C 149 / 785 Inlet / Outlet temperature of Chamber F-101B, °C 580 / 726 Inlet / Outlet temperature of Chamber F-101C, °C 572 / 788 Inlet / Outlet temperature of Chamber F-101D, °C 630 / 722 Mass ratio of water and ethylbenzene in Stream 2 0.351 Inlet / Outlet temperature of the tube side of E-101, °C 95 / 530 Outlet temperature of the tube side of E-102, °C 578 Inlet / Outlet temperature of the tube side of E-103, °C 522 / 583 Outlet temperature of the tube side of E-104, °C 623 Inlet / Outlet temperature of R-101, °C 615 / 522 Inlet pressure of R-101, kPaA 55 Inlet / Outlet temperature of R-102, °C 623 / 565 Inlet pressure of R-102, kPaA 45 Total conversion rate of ethylbenzene, % 59.4 Total selectivity of styrene, % 95.9 Total investment in high-temperature pipelines and equipment, 10,000 yuan 2100 Energy consumption, kg of standard oil per ton of styrene 285

[0099]

Example 5

[0100] A styrene production plant by dehydrogenation of ethylbenzene adopts Figure 1 the process flow shown in the figure. The total water ratio is 0.8. The plant is in the initial stage of operation. The inlet temperatures of the first reactor and the second reactor are 623 °C. The main process operation parameters are listed in Table 5.

[0101] Table 5

[0102] Project Index Mass ratio of water and ethylbenzene in Stream 3 0.8 Inlet / Outlet Temperature of Room F-101A, °C 149 / 806 Inlet / Outlet Temperature of Room F-101B, °C 550 / 772 Inlet / Outlet Temperature of Room F-101C, °C 570 / 807 Inlet / Outlet Temperature of Room F-101D, °C 633 / 770 Mass Ratio of Water to Ethylbenzene in Logistics 2 0.351 Inlet / Outlet Temperature of the Tube Side of E-101, °C 95 / 510 Outlet Temperature of the Tube Side of E-102, °C 578 Inlet / Outlet Temperature of the Tube Side of E-103, °C 520 / 582 Outlet Temperature of the Tube Side of E-104, °C 623 Inlet / Outlet Temperature of R-101, °C 623 / 520 Inlet Pressure of R-101, kPaA 55 Inlet / Outlet Temperature of R-102, °C 623 / 560 Inlet Pressure of R-102, kPaA 45 Total Conversion Rate of Ethylbenzene, % 64.8 Total Selectivity of Styrene, % 95.8 Total Investment in High-Temperature Pipes and Equipment, 10,000 yuan 2400 Energy Consumption, kg of Standard Oil per Ton of Styrene 280

[0103]

Example 6

[0104] A 100,000-ton styrene production plant by dehydrogenation of ethylbenzene adopts Figure 1 the process flow shown in the figure. The total water ratio is 1.0. The plant is in the initial stage of operation. The inlet temperatures of the first reactor and the second reactor are 623 °C. The main process operation parameters are listed in Table 6.

[0105] Table 6

[0106] Project Index Mass Ratio of Water to Ethylbenzene in Logistics 3 1.0 Inlet / Outlet Temperature of Room F-101A, °C 149 / 766 Inlet / Outlet Temperature of Room F-101B, °C 550 / 741 Inlet / Outlet Temperature of Room F-101C, °C 578 / 753 Inlet / Outlet Temperature of Room F-101D, °C 639 / 731 Mass Ratio of Water to Ethylbenzene in Logistics 2 0.358 Inlet / Outlet Temperature of the Tube Side of E-101, °C 98 / 500 Outlet Temperature of the Tube Side of E-102, °C 575 Inlet / Outlet Temperature of the Tube Side of E-103, °C 529 / 590 Outlet Temperature of the Tube Side of E-104, °C 623 Inlet / Outlet Temperature of R-101, °C 623 / 529 Inlet Pressure of R-101, kPaA 55 Inlet / Outlet Temperature of R-102, °C 623 / 564 Inlet Pressure of R-102, kPaA 45 Total Conversion Rate of Ethylbenzene, % 65.1 Total Selectivity of Styrene, % 96.1 Total Investment in High-Temperature Pipes and Equipment, 10 million yuan 1500 Energy Consumption, kg of Standard Oil per Ton of Styrene 310

[0107]

Comparative Example 1

[0108] A 100,000-ton styrene production plant by dehydrogenation of ethylbenzene adopts Figure 2 the process flow shown in the figure. The total water ratio is 0.9. The main process operation parameters are listed in Table 7.

[0109] Table 7

[0110] Project Index Mass Ratio of Water to Ethylbenzene in Logistics 3 0.9 Inlet / Outlet Temperature of Room F-101A, °C 149 / 919 Inlet / Outlet Temperature of Room F-101B, °C 563 / 910 Mass Ratio of Water to Ethylbenzene in Logistics 2 0.358 Inlet / Outlet Temperature of the Tube Side of E-101, °C 98 / 520 Inlet / Outlet Temperature of the Tube Side of E-102, °C 528 / 623 Inlet / Outlet Temperature of R-101, °C 623 / 528 Inlet Pressure of R-101, kPaA 55 Inlet / Outlet Temperature of R-102, °C 623 / 566 Inlet Pressure of R-102, kPaA 45 Total Conversion Rate of Ethylbenzene, % 65.0 Total Selectivity of Styrene, % 96.0 Total Investment in High-Temperature Pipes and Equipment, 10 million yuan 5500 Energy Consumption, kg of Standard Oil per Ton of Styrene 290

[0111]

Comparative Example 2

[0112] A 100,000-ton styrene production plant by dehydrogenation of ethylbenzene adopts Figure 2 the process flow shown in the figure. The total water ratio is 1.0. The main process operation parameters are listed in Table 8.

[0113] Table 8

[0114]

[0115]

[0116] It can be seen from the operating parameters of Example 1 and Comparative Example 1 that when the technical solution of the present invention is adopted, under the condition of an ultra-low water ratio of 0.9, the outlet temperature of the steam heating furnace F-101 is reduced from ~920°C to ~770°C, a decrease of ~150°C, and the total investment in high-temperature pipelines and equipment is reduced from 55 million yuan to 18 million yuan, greatly saving the investment and achieving good technical effects.

[0117] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for preparing styrene by dehydrogenation of ethylbenzene, the method comprises: a first dehydrogenation reaction and a second dehydrogenation reaction carried out in sequence; characterized in that, a) After the first heating of the steam stream, the first dehydrogenation reactant is reheated for the first time; then after the second heating, the first dehydrogenation reactant is reheated for the second time; then the third heating is carried out; b) The mixed stream of ethylbenzene and water exchanges heat with the second dehydrogenation reactant and the third heating steam stream in step a) respectively or simultaneously to obtain a preheated mixed stream of ethylbenzene and water; c) The third heating steam stream after heat exchange in step b) is subjected to the fourth heating and mixed with the preheated mixed stream of ethylbenzene and water in step b) to obtain a mixed stream raw material for carrying out the first dehydrogenation reaction.

2. The method according to claim 1, wherein, The steps of step b) include: The mixed stream of ethylbenzene and water exchanges heat with the second dehydrogenation reaction product for the first heat exchange, and then exchanges heat with the third heating steam stream in step a) for the second heat exchange; Preferably, The conditions for the first heat exchange include: the outlet temperature of the tube side is 450 °C to 550 °C, preferably 480 °C to 530 °C; and / or The conditions for the second heat exchange include: the outlet temperature of the tube side is 480 °C to 600 °C, preferably 550 to 590 °C.

3. The method according to claim 1 or 2, wherein, In step c), the conditions for the first dehydrogenation reaction include: the weight ratio of water to ethylbenzene in the mixed stream raw material is 0.8 to 1.2, preferably 0.85 to 1; The weight ratio of water to ethylbenzene in step b) is 0.3 - 0.

5.

4. The method according to any one of claims 1 - 3, wherein, The conditions for the first reheating include: the outlet temperature of the tube side is 550 - 610 °C, preferably 580 - 590 °C, and the conditions for the second reheating include: the outlet temperature of the tube side is 600 - 650 °C, preferably 610 - 630 °C.

5. The method according to any one of claims 1 - 4, wherein, The conditions for the first heating, the second heating, the third heating, and the fourth heating each include: the outlet temperature is 700 - 850 °C, preferably 730 - 830 °C, more preferably 730 - 800 °C.

6. The method according to any one of claims 1 - 5, wherein, The first dehydrogenation reaction and the second dehydrogenation reaction are each carried out in a dehydrogenation reactor, preferably the dehydrogenation reactor is an adiabatic fixed bed reactor; The conditions for the first dehydrogenation reaction and the second dehydrogenation reaction each include: the reaction temperature is 510 °C to 650 °C, and the reaction pressure is 30 kPaA to 60 kPaA.

7. A system for preparing styrene by dehydrogenation of ethylbenzene for the method according to any one of claims 1 - 6, characterized in that, The system includes: A first dehydrogenation reactor (R - 101) and a second dehydrogenation reactor (R - 102) connected in series in sequence along the material flow direction for carrying out the first dehydrogenation reaction and the second dehydrogenation reaction, A heating unit for carrying out the first heating, the second heating, the third heating, and the fourth heating; The first raw material preheater (E-101) and the second raw material preheater (E-102) are arranged on the feed pipeline of the first dehydrogenation reactor (R-101). The first raw material preheater (E-101) is used for the first heat exchange of the mixed stream of ethylbenzene and water with the second dehydrogenation reaction product for heat exchange; the second raw material preheater (E-102) is used for the second heat exchange of the mixed stream of ethylbenzene and water with the third heated steam stream for heat exchange; The first intermediate reheater (E-103) and the second intermediate reheater (E-104) are arranged on the outlet pipeline of the first dehydrogenation reactor. The first intermediate reheater (E-103) is used for the first reheating; the second intermediate reheater (E-104) is used for the second reheating; Preferably, the heating unit is a heating furnace (F-101) with four chambers; each chamber is respectively used for the first heating, the second heating, the third heating, and the fourth heating.

8. A method for preparing styrene by dehydrogenation of ethylbenzene, characterized in that, This method is carried out in the system described in claim 7. The heating unit is a heating furnace (F-101) with four chambers, which are chamber A, chamber B, chamber C, and chamber D from left to right; the code chamber n 1 , chamber n 2 , chamber n 3 , chamber n 4 are arranged as chamber A, chamber C, chamber D, chamber B, or chamber A, chamber B, chamber C, chamber D; 1) The logistics (1) containing water sequentially enters chamber n of the heating furnace (F-101) 1 , the first intermediate reheater (E-103), chamber n 2 , the second intermediate reheater (E-104), chamber n 3 , the second raw material preheater (E-102) and chamber n 4 , and is mixed with the logistics (2) containing ethylbenzene and water from the second raw material preheater (E-102) to form logistics (3); 2) The stream (2) containing ethylbenzene and water successively enters the first feed preheater (E-101) and the second feed preheater (E-102) to perform the first heat exchange and the second heat exchange, and is mixed with the stream containing water from chamber n 4 to form stream (3); 3) The stream (3) enters the first dehydrogenation reactor (R-101) to carry out the first dehydrogenation reaction to generate a stream (4) containing styrene; 4) The stream (4) successively enters the first intermediate reheater (E-103) and the second intermediate reheater (E-104), and then enters the second dehydrogenation reactor (R-102) to further carry out the second dehydrogenation reaction to generate a stream (5) containing styrene. The stream 5 passes through the first raw material preheater (E-101) to go to the subsequent unit.

9. The method according to claim 8, wherein, The stream (2) containing ethylbenzene and water successively enters the tube side of the first raw material preheater (E-101) and the second raw material preheater (E-102) for the first heat exchange and the second heat exchange; The stream (4) successively enters the tube side of the first intermediate reheater (E-103) and the tube side of the second intermediate reheater (E-104); Preferably, The outlet temperature of the tube side of the first raw material preheater (E-101) is 450 °C to 550 °C, preferably 480 °C to 530 °C; and / or The outlet temperature of the tube side of the second raw material preheater (E-102) is 480 °C to 600 °C, preferably 550 to 590 °C; and / or The outlet temperature of the tube side of the first intermediate reheater (E-103) is 550 to 610 °C, preferably 580 to 590 °C; and / or The outlet temperature of the tube side of the second intermediate reheater (E-104) is 600 to 650 °C, preferably 610 to 630 °C.

10. The method according to claim 8 or 9, wherein, The weight ratio of water to ethylbenzene in the stream (3) is 0.8 to 1.2, preferably 0.85 to 1; and / or The weight ratio of water to ethylbenzene in the stream (2) containing ethylbenzene and water is 0.3 - 0.5; and / or The outlet temperature of the heating furnace is 700 to 850 °C, preferably 730 to 830 °C, more preferably 730 to 800 °C; The first dehydrogenation reactor and the second dehydrogenation reactor are adiabatic fixed bed reactors, and their respective conditions include: the reaction temperature is 510 °C to 650 °C, and the reaction pressure is 30 kPaA to 60 kPaA.

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