Apparatus and method for producing styrene by gas phase dehydration of phenethyl alcohol

Abstract

The application discloses a device and method for preparing styrene by gas-phase dehydration of phenethyl alcohol, and belongs to the field of chemical industry. The system comprises a tubular fixed-bed reactor, phenethyl alcohol material is delivered to a dehydration vaporizer, a gas-liquid separator is arranged above the dehydration vaporizer, the output end at the top of the gas-liquid separator is connected with the tubular fixed-bed reactor, and the tubular fixed-bed reactor is provided with a heat carrier heating furnace. The phenethyl alcohol material is heated and dehydrated after being mixed with water vapor, and the mixing ratio with the water vapor is adjusted, so that the generation of heavy components in the dehydration reaction is reduced, the polymerization of styrene is reduced, and the operation period of the catalyst is prolonged.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of fixed bed dehydration reaction, and particularly relates to a device and method for preparing styrene by gas phase dehydration of phenethyl alcohol in a combined production process of propylene oxide and styrene. BACKGROUND

[0002] The combined production process of propylene oxide and styylene is known, and currently there are industrialized devices at home and abroad. A typical combined production process of propylene oxide and styrene includes the following steps:

[0003] (a) ethylbenzene reacts with oxygen in the oxygen-containing gas to generate ethylbenzene hydroperoxide;

[0004] (b) ethylbenzene hydroperoxide reacts with propylene to generate propylene oxide, phenethyl alcohol and acetophenone;

[0005] (c) phenethyl alcohol is dehydrated to obtain styrene. Acetophenone can be hydrogenated to generate phenethyl alcohol after or before the dehydration of phenethyl alcohol.

[0006] Among them, step c is an endothermic reaction and can be carried out in gas phase and liquid phase.

[0007] Taking the combined production technology of propylene oxide and styrene as an example, the patent US3526674 of Halcon Company of the United States reports a liquid phase dehydration method of aromatic alcohol, which adopts alumina microparticle catalyst and carries out high-temperature liquid phase dehydration in a reactor with a stirrer. Then, the patent CN201080013775 of Lyondell Company of the United States discloses a method for producing styrene by dehydration of a-phenethyl alcohol, which adopts a mixture of p-toluenesulfonic acid and o-toluenesulfonic acid as catalyst and carries out dehydration in liquid phase.

[0008] The patent (US6504038, CN200880120037) of International Shell Research Limited discloses a combined production method of propylene oxide and styrene, which adopts a gas phase dehydration method to prepare styrene, adopts alumina particles with a multimodal pore size distribution as catalyst and carries out dehydration reaction in a fixed bed reactor.

[0009] Currently, there are actual operation industrial device cases of liquid phase dehydration and gas phase dehydration methods of organic alcohol (for example, a-phenethyl alcohol liquid phase dehydration of Zhenhai Refining and Chemical Company and a-phenethyl alcohol gas phase dehydration of China Offshore Shell).

[0010] Another advantage of liquid phase dehydration is that reaction rectification separation coupling can be achieved, the target product, heavy components, etc. are continuously discharged from the reaction system in the reactor, which is beneficial to improve the conversion rate, increase the selectivity of the target product styrene and eliminate the adverse effects of heavy components on the catalyst.

[0011] However, using an organic strong acid catalyst exposes the liquid phase reaction raw material and the olefin product to an acidic environment for a long time, causing more olefin polymerization to generate heavy tar, increasing the material loss of the olefin product, and at the same time, the amount of generated tar also increases significantly, which increases the economic cost of tar treatment.

[0012] Gas phase dehydration does not have the problem of olefin acid polymerization, but generally uses titanium dioxide or aluminum oxide as the catalyst. As the reaction proceeds, the active centers of the catalyst will be gradually covered with coke, requiring regular regeneration and catalyst switching operations.

[0013] In order to prolong the operation period of phenethyl alcohol gas phase dehydration, researchers have made corresponding efforts in catalysts, reactors, etc. For example, the patent of International Shell Research Limited (CN200880120037) uses an alumina catalyst with a multi-peak pore size distribution. The dehydration of phenethyl alcohol to produce styrene is carried out at a pressure of 1.0 bara and a temperature of 300°C. The conversion rate of phenethyl alcohol is 99.8%, and the selectivity of styrene is 94.9-95.4%, and the activity decline rate is 0.48% / 100h. The patent of Changzhou Ruifeng Chemical Engineering Technology Co., Ltd. (CN201711349721) discloses a catalyst preparation method suitable for a-phenethyl alcohol dehydration. When the catalyst is used for the dehydration of a-phenethyl alcohol to prepare styrene, the content of heavy component products in the dehydration product is lower, and the content is approximately between 0.1% and 0.2%, which is much lower than the value of 2%-4% of the heavy component in the dehydration product using the existing γ-alumina catalyst.

[0014] Existing reports mainly focus on improving catalysts and reactors, but there is still a need to propose a better method to reduce the generation of styrene polymers, prolong the operation period of phenethyl alcohol gas phase dehydration reaction, and recover the dehydration product. SUMMARY

[0015] The present application provides a device and method for preparing styrene by gas phase dehydration of phenethyl alcohol.

[0016] The object of the present application can be achieved by the following technical solutions:

[0017] A method for preparing styrene by gas phase dehydration of phenethyl alcohol, the method comprising the following steps:

[0018] Raw material processing: After the phenethyl raw material and the output of the tubular fixed bed reactor are heated by heat exchange and the temperature is increased, they enter the dehydration vaporizer for further heating and partial vaporization. The output of the vaporizer enters the gas-liquid separator. The liquid at the bottom of the gas-liquid separator is a material containing phenethyl and heavy components, which is sent to the phenethyl / heavy component separation tower in the front-end process.

[0019] Raw material steam and water: The gas and water vapor coming out of the top of the gas-liquid separator enter the dehydration heat exchanger. In the dehydration heat exchanger, the gas at the outlet of the tubular fixed bed reactor is heated and then enters the top of the fixed bed reactor.

[0020] Phenylacetyl alcohol dehydration reaction: The fixed-bed reactor is a fixed tube sheet reactor, with the catalyst packed in the tubes. The heat required for the dehydration reaction is provided by the heat transfer medium in the outer shell of the reactor tubes.

[0021] Preparation of crude styrene: The gas formed after the dehydration reaction is cooled and condensed to remove the aqueous phase, and then crude styrene is obtained.

[0022] In the technical solution of this invention: the liquid discharged from the bottom of the gas-liquid separator in the step is 3% to 10% of the total amount of raw materials.

[0023] In the technical solution of the present invention: the mass ratio of water vapor to phenylethanol in the step is 0.01 to 1:1; preferably: the mass ratio of water vapor to phenylethanol in the step is 0.012 to 0.55:1.

[0024] In the technical solution of this invention: the heating temperature of the tubular fixed-bed reactor is 200-380℃, preferably 230-350℃. The temperature mentioned here refers to the temperature of the carrier.

[0025] In this invention, the outlet temperature of the tubular fixed-bed reactor is higher than the inlet temperature, and the internal temperature difference of the tubular fixed-bed reactor bed is less than 20°C. The length of the tubular fixed-bed reactor bed is less than 5 meters, preferably less than 4 meters.

[0026] An apparatus for preparing styrene by gas-phase dehydration of phenylethanol as described above, the apparatus comprising a tubular fixed-bed reactor, wherein phenylethanol is conveyed to a dehydration vaporizer, a gas-liquid separator is provided above the dehydration vaporizer, the output end of the top of the gas-liquid separator is connected to the tubular fixed-bed reactor, and the tubular fixed-bed reactor is equipped with a heat transfer furnace.

[0027] The above-mentioned device also includes a dehydration heat exchanger and a dehydration preheater. The output end of the phenylethanol material is connected to the dehydration vaporizer through the dehydration preheater, and the gas output end of the gas-liquid separator is connected to the top of the tubular fixed bed reactor through the dehydration heat exchanger.

[0028] In the device, the output end of the bottom of the tubular fixed bed reactor is connected with the oil-water separator through the dewatering heat exchanger and the dewatering preheater in sequence.

[0029] In the device, the dewatering vaporizer, the dewatering preheater and the dewatering heat exchanger are all vertical heat exchangers.

[0030] In some specific technical solutions, the method comprises the following steps:

[0031] In the method, the reactant material enters the tubular fixed bed reactor in an up-down mode, and the heat required by the dewatering reaction is provided by the heat carrier in the shell outside the reactor tube.

[0032] In the method, the high-temperature material out of the tubular fixed bed reactor is used to heat the reactor feed, and the temperature of the material into the tubular fixed bed reactor is lower than that of the material out of the tubular fixed bed reactor. The catalyst bed layer that has completed the main reaction is defined as a reaction zone. Since the reaction is an endothermic reaction, the temperature difference between the reaction material and the heating medium is large in the reaction zone. After passing through the reaction zone, the temperature of the material is significantly increased. The length of the catalyst bed layer behind the reaction zone cannot be too long, that is, the length of the catalyst bed layer behind the reaction zone is reduced, the residence time of the high-temperature section in the reactor is shortened, and the continuous heating is prevented, while the axial temperature of the reactor bed layer is controlled to be greatly increased, the axial temperature difference is reduced, the temperature difference of the catalyst bed layer in the tube is controlled in a small range, and the temperature of the material out of the reactor is the highest. Further, the length of the catalyst bed layer in the reactor is less than 5 meters, and preferably less than 4 meters. The heating medium outside the reactor tube also flows from top to bottom, that is, the same direction as the feed in the reactor tube. This method makes the heating medium behind the reaction zone low in temperature, and the temperature of the catalyst bed layer in the tube is controlled in a small range.

[0033] At the same time, since the catalyst in the tube is heated by the high-temperature heat carrier, the vaporized raw material phenethyl alcohol is uniformly distributed by the feed distributor, and the steam added to the raw material further enhances the uniform distribution of the raw material. Since the feed is not uniformly distributed to the catalyst bed layer, the radial temperature difference is basically eliminated, and the radial temperature difference of the catalyst bed layer in the tube is controlled in a small range. Usually, the radial temperature difference is less than 5℃.

[0034] The dewatering reaction of phenethyl alcohol is an endothermic reaction. If heat is not supplemented during the reaction process, the temperature from the inlet to the outlet of the reactor will be significantly reduced, that is, the outlet temperature of the reactor is lower than the inlet temperature. In order to reach the required temperature of the reaction, the phenethyl alcohol raw material must be heated to a very high temperature before entering the reactor. In this case, the outlet temperature of the reactor is lower than the inlet temperature,

[0035] In the technical scheme of the present application: the epoxidation reaction product formed in the combined production process of propylene oxide / styrene still contains ethylbenzene and other impurities after removing excess propylene and propylene oxide product. The raw material treatment does not include the steps of removing ethylbenzene and removing heavy and light components, which are in the process unit before the benzene ethanol dehydration device.

[0036] The removal of light components such as benzaldehyde and phenol from the crude benzene ethanol can reduce the polymerization of benzaldehyde with benzene ethanol in the dehydration reaction, thereby reducing the consumption of materials, reducing the generation of polymers, reducing the coverage of the active centers of the catalyst, and prolonging the operation period. The removal of heavy components from the crude benzene ethanol can reduce the deposition of heavy components on the dehydration catalyst, which is more conducive to the extension of the operation period of the dehydration reaction.

[0037] The above separation and purification steps of the crude benzene ethanol cannot completely eliminate the entrainment of heavy components in the raw material benzene ethanol, but only reduce the entrainment of heavy components in the raw material benzene ethanol. Due to the high boiling point of benzene ethanol, the heating and vaporization process of the raw material benzene ethanol into the dehydration reactor will inevitably produce heavy components due to condensation and other side reactions at high temperature. The deposition of heavy components on the dehydration catalyst reduces the service life of the catalyst.

[0038] Therefore, before the raw material benzene ethanol enters the dehydration reactor, the raw material is not completely vaporized, that is, 3% to 10% of the raw material is not vaporized and returned to the crude benzene ethanol heavy component removal tower, thereby further reducing the heavy components entering the reactor and prolonging the service life of the catalyst.

[0039] In the technical scheme of the present application: the dehydration reaction is carried out in a separate dehydration reactor, and the dehydration reactor feed is heated by a reactor outlet high-temperature gas material heater.

[0040] The dehydration reaction is an endothermic reaction, and the reactor is filled with catalyst pipe outside the heat carrier to heat and maintain the reaction temperature, so as to ensure that the internal temperature of the reactor is uniform, the axial temperature difference is less than 20 degrees Celsius, and the radial temperature difference is less than 5 degrees Celsius. Such design can avoid the coking cleaning problem in the pipe caused by increasing the inlet temperature of the reactor to maintain the reaction temperature.

[0041] In the technical scheme of the present application: in order to ensure that the conversion rate of benzene ethanol is ≥90%, the heating is carried out by heating the heat carrier with a heating furnace, and the heat carrier is heated outside the catalyst pipe to maintain the temperature of the reaction bed. The heating temperature is 200-380℃, more preferably 230-350℃; and the heat carrier heating method adopts direct heating by a heating furnace. The heat carrier generally includes high-temperature heat-conducting oil, synthetic heat-conducting silicon oil, and molten salt.

[0042] In the technical scheme of the present application: since the dehydration reaction of phenethyl alcohol is an endothermic reaction, suitable reaction temperature is conducive to controlling the conversion rate and selectivity of the dehydration reaction within a reasonable range. The axial temperature difference of the catalyst bed is less than 20 DEG C, the radial temperature difference is less than 5 DEG C, and the catalyst activity is different in different stages.

[0043] In the technical scheme of the present application: in order to prolong the reaction period, the heating temperature gradually increases with the gradual decrease of the activity of the catalyst used in the dehydration reaction. Due to the gas phase reaction characteristics of phenethyl alcohol, the catalyst will gradually deactivate during the reaction process. In order to maintain the continuous production of the industrial device, a standby dehydration reactor or a standby dehydration reaction line is generally required, and the reaction period is prolonged, which can greatly reduce the production cost. Due to the characteristics that the outlet temperature of the catalyst bed of the dehydration reactor is higher than the inlet temperature, the activity of the catalyst gradually decreases from the direction of the raw material inlet to the product outlet.

[0044] When this happens, the heat supply adjustment range of the heat carrier is small, and the system is relatively stable.

[0045] In the technical scheme of the present application: in order to reduce the polymerization of styrene, the gas after cooling is quenched, and the quenching method is to add low-temperature water to the tail gas, and condense the condensate, and the condensate temperature is 30-55 DEG C.

[0046] The beneficial effects of the present application are:

[0047] 1. The raw material entering the gas phase dehydration reactor is partially vaporized to remove heavy components, which can further remove heavy component impurities in the raw material, reduce the coverage of the active center of the catalyst, and effectively prolong the operation period.

[0048] 2. The raw material gas enters the fixed bed reactor in an upward and downward manner, which can remove the tar heavy component impurities in the reactor with the gas flow, reduce the coverage of the active center of the catalyst, and effectively prolong the operation period.

[0049] 3. The method of heating outside the reactor tube to maintain the reaction temperature can reduce the inlet raw material temperature of the reactor and reduce the tar generation during the vaporization temperature rising process of the raw material. The axial and radial temperature difference of the fixed bed reactor of the tube is small, and the bed temperature control range is narrow, which is conducive to obtaining the optimal conversion rate and selectivity.

[0050] At the same time, the reduction of tar generation can also reduce the material consumption of the device and improve the economic benefit.

[0051] 4. The outlet temperature of the reactor is higher than the inlet temperature of the raw material, which can better adapt to the trend of the decrease of the catalyst activity from top to bottom.

[0052] 5. The phenethyl alcohol material is mixed with water vapor and then heated for dehydration reaction, and the mixing ratio of water vapor is adjusted, so that the generation of heavy components in dehydration reaction is reduced, the polymerization of styrene is reduced, and the operation period of the catalyst is prolonged.

[0053] 6. The reactor outlet gas is directly mixed with low-temperature water for cooling and condensation, so that the cooling time is shortened, and the ratio of styrene polymerization into tar is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0054] Figure 1 The figure is a process flow diagram of the present application.

[0055] 1 is a heat carrier circulating pump; 2 is a heat carrier heating furnace; 3 is a tubular fixed bed reactor; 4 is a dehydration heat exchanger; 5 is a dehydration preheater; 6 is a dehydration vaporizer; 7 is a gas-liquid separator; and 8 is an oil-water separator. DETAILED DESCRIPTION

[0056] The present application will be further described below in conjunction with examples, but the scope of protection of the present application is not limited thereto:

[0057] As Figure 1 A system for preparing styrene by gas phase dehydration of phenethyl alcohol, which comprises a tubular fixed bed reactor 3, a dehydration vaporizer 6 to which the phenethyl alcohol material is fed, a gas-liquid separator 7 arranged above the dehydration vaporizer 6, an output end at the top of the gas-liquid separator 7 connected to the tubular fixed bed reactor 3, and a heat carrier heating furnace 2 arranged in conjunction with the tubular fixed bed reactor 3. The system further comprises a dehydration heat exchanger 4 and a water preheater 5, the output end of the phenethyl alcohol material is connected to the dehydration vaporizer 6 through the dehydration preheater 5, the gas output end of the gas-liquid separator is connected to the top of the tubular fixed bed reactor 3 through the dehydration heat exchanger 4, and the output end at the bottom of the tubular fixed bed reactor 3 is connected to an oil-water separator 8 through the dehydration heat exchanger 4 and the dehydration preheater 5 in sequence.

[0058] Example 1

[0059] As Figure 1The raw material 4019 (61985 kg / h) with a mass content of 91% phenylethanol is shown. The raw material 4017 is preheated in the dehydration preheater 5 and heat exchanged with the outlet material of the tubular fixed bed reactor (3) to recover the heat of the outlet material of the tubular fixed bed reactor (3). After preheating, the raw material 4017 is heated and evaporated in the dehydration vaporizer 6. The heating amount is controlled, and 90% of the material is vaporized and evaporated. The material 4012 is separated from the gas-liquid separator 7 in a mass ratio of 0.1:1 with the raw material phenylethanol feed amount 4019. The separated liquid stream 4012, with a flow rate of 6198.5 kg / h, contains phenylethanol and heavy components, etc. and is returned to the phenylethanol heavy component removal tower in the upstream raw material treatment process to remove the heavy components. The separated gas stream 4001 is heat exchanged with the high-temperature gas 4003 from the outlet of the tubular fixed bed reactor 3 in the dehydration heat exchanger 4. Water vapor 4008 is added to the dehydration heat exchanger 4, and the material 4001 is heat exchanged with the water vapor 4008 in a mass ratio of 1:0.25. The stream 4002 is heated to 244°C and enters the dehydration reactor 3 from the upper part. The catalyst is packed in the tube of the dehydration reactor 3.

[0060] The heat carrier heating furnace 2 provides heat for the tubular fixed bed reactor 3. The heat carrier circulating pump pumps the heat carrier into the heating furnace 2. The temperature of the heat carrier 4013 from the outlet of the heating furnace 2 is 275°C, and the temperature of the heat carrier 4013 from the outlet of the tubular fixed bed reactor 3 is 260°C. In this embodiment, the outlet temperature of the dehydration reactor is increased to 260°C, and the catalyst bed temperature is between 250-260°C. After the dehydration reaction in the reactor, about 91% of the phenylethanol is dehydrated to generate styrene, and the dehydration reaction material 4003 (69733.125 kg / h) with a mass content of about 61.7% styrene is obtained. The dehydration reaction stream 4003 is cooled in the dehydration heat exchanger 4 and then cooled in the dehydration preheater 5. The stream 4018 from the outlet of the dehydration preheater 5 is cooled by passing through the cold water 4015. The temperature of the material 4010 after the reaction outlet is rapidly cooled and condensed is 43°C. After entering the oil-water separator 8, the waste water 4011 is separated, and the crude styrene 4005 is obtained.

[0061] The operation period of the catalyst can reach more than 2300 hours, the selectivity of styrene is ≥99.2%, and the generation amount of tar is ≤0.18% by using the method of this embodiment.

[0062] Example 2

[0063] On the basis of Example 1, the mass ratio of the material 4012 to the raw material phenylethanol feed amount 4019 is adjusted to 0.05:1.

[0064] The operation period of the catalyst can reach more than 2230 hours, the selectivity of styrene is ≥99.05%, and the generation amount of tar is ≤0.18% by using the method of this embodiment.

[0065] Example 3

[0066] On the basis of the embodiment 1, the mass ratio of the material 4012 to the raw material phenylethanol feed amount 4019 is adjusted to 0.03.1. By using the method of the present embodiment, the operation period of the catalyst can reach more than 2120 hours, the styrene selectivity is ≥99%, and the tar generation amount is ≤0.18%.

[0067] Comparative example 1

[0068] On the basis of the embodiment 1, the material amount of the material 4012 is adjusted to 0, and the material amount of the material 4013 is adjusted to 0, that is, no raw material evaporation is carried out, and no heating by the heat carrier is used. The material 4002 is heated by a heater to 290 degrees, so as to achieve the same condition that the catalyst bed temperature in the embodiment 1 is between 250-260 degrees. The operation period of the catalyst is about 2000h, the styrene selectivity is ≥99%, and the tar generation amount is ≤0.2%.

[0069] The production method disclosed in the present application can effectively reduce the styrene polymerization and reduce the tar generation amount, so as to prolong the operation period of the reaction.

[0070] The embodiments of the present application are only the preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Any person skilled in the art, according to the technical solution and the inventive concept of the present application, can make equivalent replacement or change within the technical range disclosed in the present application, which should be covered in the protection scope of the present application.

Claims

1. A process for the vapor phase dehydration of phenethyl alcohol to produce styrene, characterized by: The method comprises the following steps: (1) raw material treatment: after the phenylethanol raw material and the outlet heat exchange of the tubular fixed bed reactor (3) are raised in temperature, they are fed into a dehydration vaporizer (6) to be heated and raised in temperature and partially vaporized, and the outlet of the dehydration vaporizer (6) is fed into a gas-liquid separator, the liquid at the bottom of the gas-liquid separator is a material containing phenylethanol and heavy components, and it is fed into a phenylethanol / heavy component separation tower at the front end; (2) raw material water vapor: the gas and water vapor at the top of the gas-liquid separator are fed into a dehydration heat exchanger (4), and after the gas at the outlet of the tubular fixed bed reactor (3) is heated and raised in temperature in the dehydration heat exchanger (4), it is fed into the top of the tubular fixed bed reactor (3); (3) phenylethanol dehydration reaction: the tubular fixed bed reactor (3) adopts a fixed tube sheet reactor, the catalyst is filled in the tubes, and the heat required by the dehydration reaction is provided by the heat carrier in the shell outside the tubes; (4) preparation of crude styrene: after the gas formed after the dehydration reaction is cooled and condensed, the water phase is removed, and crude styrene is obtained.

2. The process for the vapor phase dehydration of phenyl ethanol to produce styrene according to claim 1, characterized in that: The liquid discharged at the bottom of the gas-liquid separator in step (1) is 3% to 10% of the total amount of the raw material.

3. The process for the vapor phase dehydration of phenyl ethanol to produce styrene according to claim 1, characterized in that: The mass ratio of the water vapor to the raw material phenylethanol in step (2) is 0.01 to 1:

1.

4. The process for the gas phase dehydration of phenyl ethanol to produce styrene according to claim 3, characterized in that: The mass ratio of the water vapor to the raw material phenylethanol in step (2) is 0.012 to 0.55:

1.

5. The process for the vapor phase dehydration of phenyl ethanol to produce styrene according to claim 1, characterized by: The heating temperature of the tubular fixed bed reactor in step (3) is 200-380 ℃.

6. The process for the vapor phase dehydration of phenyl ethanol to produce styrene according to claim 5, characterized in that: The heating temperature of the tubular fixed bed reactor is 230-350 ℃.

7. The process for the vapor phase dehydration of phenyl ethanol to produce styrene according to claim 1, characterized by: The outlet temperature of the tubular fixed bed reactor is higher than the inlet temperature, and the temperature difference inside the bed layer of the tubular fixed bed reactor is less than 20 ℃.

8. An apparatus for carrying out the process of claim 1 for the vapor phase dehydration of phenyl ethanol to produce styrene, characterized by: The device comprises a tubular fixed bed reactor (3), phenylethanol material is fed into a dehydration vaporizer (6), a gas-liquid separator (7) is arranged above the dehydration vaporizer (6), the output end at the top of the gas-liquid separator (7) is connected with the tubular fixed bed reactor (3), and the tubular fixed bed reactor (3) is equipped with a heat carrier heating furnace (2).

9. The apparatus of claim 8, wherein: The device further comprises a dehydration heat exchanger (4) and a dehydration preheater (5), the output end of the phenylethanol material is connected with the dehydration vaporizer (6) through the dehydration preheater (5), and the gas output end of the gas-liquid separator is connected with the top of the tubular fixed bed reactor (3) through the dehydration heat exchanger (4).

10. The apparatus of claim 8, wherein: The output end at the bottom of the tubular fixed bed reactor (3) is connected with an oil-water separator (8) through the dehydration heat exchanger (4) and the dehydration preheater (5) in sequence.

11. The apparatus of claim 8, wherein: The dehydration vaporizer (6), the dehydration preheater (5) and the dehydration heat exchanger (4) are all vertical heat exchangers.

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