CN111073693A

CN111073693A - Naphtha modification method

Info

Publication number: CN111073693A
Application number: CN201811224121.9A
Authority: CN
Inventors: 董晨; 刘彤; 马冲; 任坚强; 王杰广; 张新宽; 马云超
Original assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Current assignee: Sinopec Research Institute of Petroleum Processing; China Petroleum and Chemical Corp
Priority date: 2018-10-19
Filing date: 2018-10-19
Publication date: 2020-04-28
Anticipated expiration: 2038-10-19
Also published as: CN111073693B

Abstract

The invention relates to a naphtha upgrading method, which comprises the following steps: introducing naphtha into a fixed bed reaction zone to contact with a dehydrogenation catalyst and carrying out dehydrogenation reaction under dehydrogenation reaction conditions so as to convert part of naphthenes in the naphtha into aromatic hydrocarbons; wherein the dehydrogenation catalyst comprises a carrier and chlorine and a group VIII metal loaded on the carrier; introducing a reaction product obtained in the fixed bed reaction zone into the moving bed reaction zone to contact with a modified catalyst and carry out modification reaction to obtain a reaction product and a spent catalyst, cooling and separating the reaction product to obtain a gas-phase product and a liquid-phase product, and returning at least part of the gas-phase product to the fixed bed reaction zone; introducing the catalyst to be regenerated into a regenerator for coke burning regeneration, and returning the obtained regenerated catalyst to the moving bed reaction zone. The liquid product yield and octane number of the modification method are high.

Description

Naphtha modification method

Technical Field

The invention relates to a naphtha upgrading method, in particular to a method for upgrading naphtha through two-stage reaction.

Background

In recent years, with the upgrading of environmental requirements, the aromatic content in gasoline is further limited. The content of aromatic hydrocarbon in the reformed gasoline is too high, which is not beneficial to gasoline blending. In addition, the catalytic reforming process has strict requirements on raw material impurities, and the device investment and production energy consumption are huge. Therefore, for naphtha feedstocks such as reformate, condensate, partially hydrogenated coker gasoline, and straight run gasoline, more suitable processing techniques need to be developed to produce high quality gasoline blending components.

The aromatization technology can convert naphtha, light hydrocarbon and other raw materials into low-sulfur and low-olefin gasoline components containing aromatic hydrocarbon under the action of a non-noble metal catalyst, and simultaneously produces hydrogen and high-quality liquefied gas as by-products. The technology has strong adaptability of raw materials, low requirements on the impurity content, the potential content of aromatic hydrocarbon and the distillation range of the raw materials, simultaneously, a reaction system is not subjected to hydrogenation and can be operated under low pressure, the device investment is low, the energy consumption is low, and an effective way is opened up for the utilization of naphtha and light hydrocarbon in a refinery.

CN1063121A and CN1080313A both disclose a catalyst for aromatization modification of low-octane inferior gasoline such as oil field condensate, straight-run gasoline and coker gasoline and a process method thereof, the low-octane inferior gasoline can be converted into high-octane gasoline with the octane number of about 90 by using the modified ZSM-5 molecular sieve catalyst, the gasoline yield is 55-65%, and meanwhile, 35-45% of liquefied petroleum gas and fuel gas are by-produced.

CN101747933A discloses a naphtha and light hydrocarbon aromatization modification method, which comprises the step of contacting naphtha and light hydrocarbon of C3-C5 with an aromatization catalyst in a moving bed reaction zone of a moving bed reaction-regeneration device in the presence of hydrogen-containing gas to carry out aromatization modification reaction, wherein the modification reaction temperature is 250-600 ℃, and the volume ratio of hydrogen to naphtha is 20-400. The method can convert naphtha with low octane number and low carbon hydrocarbon into gasoline component with high octane number and high-quality liquefied gas, the final boiling point of the liquid product and the carbon deposition rate of the catalyst are obviously reduced, and the service life of the catalyst is prolonged.

CN103361116A discloses a method for producing high-octane gasoline components, wherein a raw material rich in carbon four-carbon five-carbon six-paraffin is mixed with hydrogen and then enters a reactor filled with a dehydrogenation catalyst for high-temperature alkane dehydrogenation reaction, a dehydrogenation product passes through a non-condensable gas separation device and then is mixed with the hydrogen and enters a reactor filled with an aromatization catalyst for aromatization, and the product after reaction is separated into dry gas, liquefied gas, gasoline components and diesel components. The invention greatly reduces the generation amount of low-carbon hydrocarbons such as C1-C4 and the like, and improves the yield of gasoline. The produced gasoline component has low olefin content, high non-benzene aromatic hydrocarbon content and high octane number, and can meet the current environmental protection requirement, and the diesel component can be directly used.

US6190534 discloses a combined process for selective upgrading of naphtha to obtain aromatics-rich high-octane products. The naphtha raw material is firstly contacted with a non-acidic non-molecular sieve catalyst containing platinum group metal in a dehydrogenation section under dehydrogenation conditions to react to obtain an intermediate product containing olefin; the intermediate product containing olefin is contacted with a solid acid aromatization catalyst containing platinum group metal in an aromatization section to react under aromatization conditions to obtain a product rich in aromatic hydrocarbon.

A combined bed reactor with a fixed bed and a moving bed in series has been used in catalytic reforming processes. The fixed bed is filled with a platinum-rhenium reforming catalyst, and the moving bed is filled with a platinum-tin reforming catalyst, so that the respective advantages of the two catalysts can be fully exerted, and the reforming reaction effect is improved.

CN1111584C discloses a low-pressure combined-bed two-stage catalytic reforming process. Raw oil firstly enters a fixed bed reactor and is in contact reaction with a platinum-rhenium catalyst, and the obtained effluent directly enters a moving bed reactor without a separator or a pressure reducing valve and is in contact reaction with a platinum-tin catalyst to obtain a reformed product. The catalyst in the moving bed is continuously regenerated in the regenerator and then recycled. The method can reduce the coke formation amount of the catalyst and improve the operation period of the catalyst in the fixed bed.

Disclosure of Invention

The invention aims to provide a naphtha upgrading method, and the liquid product yield and octane number of the upgrading method are high.

In order to achieve the above object, the present invention provides a naphtha upgrading method comprising: introducing naphtha into a fixed bed reaction zone to contact with a dehydrogenation catalyst and carrying out dehydrogenation reaction under dehydrogenation reaction conditions so as to convert part of naphthenes in the naphtha into aromatic hydrocarbons; wherein the dehydrogenation catalyst comprises a carrier and chlorine and a group VIII metal loaded on the carrier; introducing a reaction product obtained in the fixed bed reaction zone into the moving bed reaction zone to contact with a modified catalyst for modification reaction, cooling and separating the reaction product to obtain a gas-phase product and a liquid-phase product, and returning part of the gas-phase product to the fixed bed reaction zone; introducing the spent catalyst flowing out of the moving bed reaction zone into a regenerator for coke burning regeneration, and returning the obtained regenerated catalyst to the moving bed reaction zone.

The invention firstly carries out dehydrogenation reaction on naphtha in a fixed bed reaction zone to ensure that part of cycloalkane is dehydrogenated and converted into aromatic hydrocarbon, and then introduces the dehydrogenation reaction product into a moving bed reaction zone to carry out modification reaction, thereby improving the yield and octane number of liquid products and producing high-quality gasoline blending components. In addition, continuous regeneration of the reforming catalyst can be realized by using the moving bed reactor for the reforming reaction, and the operation period of the device can be prolonged.

Drawings

FIG. 1 is a schematic flow diagram of one embodiment of the process of the present invention.

Description of the reference numerals

11 naphtha 12 gas phase product 13 liquid phase product

21 fixed bed reaction zone 22 moving bed reaction zone 23 regenerator

24 gas-liquid separator 25 gas compressor

Detailed Description

The naphtha is dehydrogenated in a fixed bed reaction zone to convert part of the naphthenes into aromatics, and then the dehydrogenated product is introduced into a moving bed reaction zone to carry out upgrading reaction. The method can reduce the cracking of naphthene in naphtha during the modification reaction, and increase the liquid yield and the octane number of liquid products of the modification reaction. The moving bed is used for the modification reaction, so that the modification reaction can be continuously carried out, and the performance of the catalyst can be maintained. In addition, returning a portion of the vapor phase product to the fixed bed reactor reduces the rate of carbon deposition on the dehydrogenation catalyst.

In the present invention, the fixed bed reaction zone may include one or more fixed bed reactors, and a plurality of fixed bed reactors may be connected in series; the moving bed reaction zone may comprise one or more moving bed reactors, and a plurality of moving bed reactors may be connected in series. The loading of the dehydrogenation catalyst in both reaction zones may be from 10 to 60 mass%, preferably from 20 to 40 mass%, based on the total loading of the catalyst.

The method of the invention properly converts the naphthenes in the naphtha into the aromatics, which improves the aromatics content and octane number of the product, reduces the cracking of the naphthenes in the raw material in the upgrading reaction process and effectively improves the selectivity of the naphtha upgrading process. In the fixed bed reaction zone, 10 to 80 mass%, preferably 30 to 70 mass% of naphthenes in naphtha can be converted into aromatics. The method for controlling the ratio of the naphthenic hydrocarbon to the aromatic hydrocarbon comprises the steps of detecting the composition of a reaction product in a fixed bed reaction zone, determining the condition of converting the naphthenic hydrocarbon into the aromatic hydrocarbon by comparing the content of the naphthenic hydrocarbon and the aromatic hydrocarbon in a liquid product with the composition of a naphtha raw material, and controlling the ratio of converting the naphthenic hydrocarbon into the aromatic hydrocarbon by dehydrogenation by adjusting the reaction temperature in the fixed bed reaction zone.

After the reaction product in the moving bed reaction zone exchanges heat with naphtha and is cooled,and separating into a gas-phase product and a liquid-phase product, returning part of the gas-phase product to the fixed bed reaction zone, and allowing the liquid-phase product and the rest of the gas-phase product to enter a product post-treatment unit for absorption, analysis, stabilization and other process steps to obtain a high-quality gasoline blending component and a high-quality liquefied gas component. The gas phase product in the invention is a mixed gas of hydrogen and low-carbon hydrocarbon, and comprises dry gas and liquefied gas, wherein the main components of the dry gas are hydrogen and C₁、C₂The hydrocarbon, the component of the liquefied gas being C₃、C₄A hydrocarbon. Part of the gas phase product returns to the fixed bed reaction zone and mainly acts as a diluting and transferring medium, and the contained hydrogen can reduce the carbon deposition rate of the dehydrogenation catalyst. The present invention makes it possible to return from 20 to 90% by volume, preferably from 40 to 70% by volume, of the gas-phase product to the fixed-bed reaction zone.

The fixed bed reaction zone of the present invention employs reaction conditions that favor the dehydrogenation of cycloalkanes, which may include: the reaction temperature is 360-500 ℃, preferably 380-480 ℃, the reaction pressure is 0.1-1.0MPa, preferably 0.3-0.6MPa, and the feeding mass space velocity of naphtha is 1-10h^-1Preferably 3-8h^-1。

In the invention, all reaction products in the fixed bed reaction zone directly enter the moving bed reaction zone, contact with the modified catalyst to react under the modification reaction condition, and further improve the octane number of the modified liquid product through aromatization, isomerization, alkylation and other reactions. The conditions of the upgrading reaction may include: the reaction temperature is 280-480 ℃, preferably 300-460 ℃, the reaction pressure is 0.1-1.0MPa, preferably 0.3-0.6MPa, and the feeding mass space velocity of naphtha is 0.5-5.0h^-1Preferably 1-3h^-1。

In the present invention, the naphthenes content in the naphtha containing C may be 10 to 60% by mass, preferably 20 to 50% by mass₅-C₁₂The hydrocarbon of (a) may be at least one selected from the group consisting of straight run gasoline, hydrocracked gasoline, catalytically cracked gasoline, hydrocracked gasoline, reformed topped oil, reformed raffinate oil, condensate oil, pyrolysis gasoline and pyrolysis gasoline raffinate oil. The naphtha may be subjected to conventional pre-hydrofining to remove sulfur, nitrogen and other impurities, or subjected to conventional pre-hydrofiningWith or without any pre-refining treatment, the sulfur content is no greater than 300. mu.g/g, preferably no greater than 200. mu.g/g, and the nitrogen content is no greater than 5. mu.g/g, preferably no greater than 2. mu.g/g.

The dehydrogenation catalyst has a dehydrogenation function, and comprises a carrier and chlorine element and VIII group metal loaded on the carrier, wherein the carrier can be an alumina carrier, the dehydrogenation catalyst can comprise the VIII group metal with the content of 0.05-1 mass%, preferably 0.3-0.8 mass% and chlorine with the content of 0.1-5.0 mass%, preferably 0.6-1.2 mass% based on the alumina carrier, and the VIII group metal is preferably platinum.

The reforming catalyst for the moving bed reaction zone of the present invention may include a carrier, zinc or gallium, a rare earth element, and a group VA element, and the carrier may include pentasil zeolite. The carrier may include 30-60 mass% of pentasil zeolite, which may be selected from one or more of ZSM-5, ZSM-11 and ZSM-12 zeolites, and 40-70 mass% of a binder, which may be alumina or silica; the reforming catalyst may include 0.5 to 3.0 mass% of ZnO, 0.1 to 3.0 mass% of a mixed rare earth oxide, and 1.0 to 5.0 mass% of a VA group element, based on the carrier; the mixed rare earth oxide may include 20-40 mass% of lanthanum oxide, 40-60 mass% of cerium oxide, 10-18 mass% of praseodymium oxide, and 2-10 mass% of neodymium oxide, and the group VA element may be selected from one or more of phosphorus, antimony, and bismuth. The catalyst can be formed by a conventional extruding, dropping or rolling method, and then the metal active component is introduced by an impregnation method.

Preferably, the modifying catalyst is subjected to steam treatment, the temperature of the steam treatment can be 500-600 ℃, and the treatment time is preferably 2-6 hours. The mass ratio of the water consumption for the steam treatment to the modifying catalyst can be 2-6.

In the present invention, in order to preheat naphtha to a certain temperature and then feed the naphtha to the fixed bed reaction zone, a heating furnace may be provided in front of the reactor of the fixed bed reaction zone.

Before the dehydrogenation catalyst and the upgrading catalyst are contacted with naphtha in the method, the two catalysts can be dried and activated in situ in a reactor by adopting a gas medium, the activation temperature can be 300-500 ℃, preferably 400-450 ℃, the pressure can be 0.1-1.0MPa, preferably 0.3-0.5MPa, the volume ratio of the gas medium to the catalyst can be 100-1000:1, and the activation time can be 1-5 h. The gas medium for activating the catalyst is nitrogen or hydrogen, and the purity of the gas medium is more than 99.8 percent.

The dehydrogenation catalyst and the upgrading catalyst in the method can be reused by regeneration after being deactivated. The dehydrogenation catalyst regeneration can be carried out in situ in the reactor, the regeneration medium adopts oxygen-containing inert gas, the activity of the regeneration medium is recovered by burning off carbon deposit on the catalyst, the oxygen content of the regeneration medium is 0.5-5 volume percent, and the inert gas is preferably nitrogen. The regeneration temperature is 350-500 ℃, the pressure is 0.1-1.0MPa, and the volume ratio of the regeneration medium to the catalyst is 200-1000: 1. The regeneration mode can adopt several conventional modes of the fixed bed reactor according to actual requirements, such as intermittent reaction and regeneration of a single reaction system, or switching reaction and regeneration of a double reaction system, or adopting a cyclic regeneration mode of alternately switching regeneration of multiple reactors.

The reforming catalyst is burnt and regenerated by a regenerator, the catalyst regeneration medium can be oxygen-containing inert gas, the oxygen content can be 0.5-5 vol%, the suitable regenerator inlet temperature can be 350-600 ℃, the pressure can be 0.1-2.0MPa, and the retention time of the spent catalyst in a burning zone can be 10-600 minutes. The regenerated modified catalyst returns to the moving bed reaction zone to realize the reaction-regeneration cycle of the catalyst.

The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

In the flow chart shown in FIG. 1, the solid line represents the flow of the material, and the broken line represents the flow of the catalyst. As shown in FIG. 1, naphtha 11 is heated in a heating furnace and then introduced into a fixed bed reaction zone 21 to contact with a dehydrogenation catalyst to perform dehydrogenation reaction, so that part of naphthenes in the naphtha are dehydrogenated and converted into aromatic hydrocarbons. The reaction product discharged from the outlet of the fixed bed reaction zone 21 directly enters the moving bed reaction zone 22 to contact with the reforming catalyst for reforming reaction. The reaction product discharged from the outlet of the moving bed reaction zone enters a gas-liquid separator 24, gas-liquid separation is carried out to obtain a gas-phase product 12 and a liquid-phase product 13, and a part of the gas-phase product 12 returns to the fixed bed reaction zone through a gas compressor 25. And (4) feeding the liquid phase product 13 and the residual gas phase product 12 into a product post-treatment unit to obtain a high-quality gasoline blending component and a high-quality liquefied gas component.

The spent catalyst flowing out of the moving bed reaction zone is conveyed to a catalyst regenerator 23 for coke burning regeneration, and the obtained regenerated catalyst returns to the moving bed reaction zone, thereby realizing the continuous regeneration of the reforming catalyst.

The invention is further illustrated below by way of examples, without being limited thereto.

The properties of the naphthas used in the examples of the invention and comparative examples are shown in table 1.

In the examples of the invention and the comparative examples, the liquid product yield is liquid product quality/naphtha feed quality.

Example 1

Preparing a dehydrogenation catalyst.

Taking 100 g of gamma-Al₂O₃The carrier was measured to have a saturated water absorption of 82mL, and 140mL of an impregnation solution was prepared using predetermined amounts of chloroplatinic acid and hydrochloric acid so that the impregnation solution contained 0.5 mass% of Pt and 1.9 mass% of Cl (both relative to the amount of the alumina dry substrate), and the volume ratio of the impregnation solution to the carrier was 1.05: 1. The carrier is placed in a flask separately, vacuumized, the vacuum degree is controlled at 0.085MPa, impregnation liquid is introduced, the carrier is subjected to rotary impregnation for 3 hours at 30 ℃, the rotary linear velocity is 0.10 m/s, then the carrier is dried under reduced pressure, and the carrier is roasted for 4 hours in dry air at 500 ℃ in a gas/solid volume ratio of 700:1 to prepare the dehydrogenation catalyst, wherein the dehydrogenation catalyst contains 0.5 mass percent of Pt and 1.0 mass percent of Cl based on the dry matrix amount of the alumina carrier.

Example 2

Preparing the modifying catalyst.

(1) Preparation of the support

67.6 kg of pseudo-boehmite powder (produced by Sasol Corp., alumina content: 74% by mass) was added to 300 kg of a 1.1% by mass aqueous nitric acid solution under stirring, and after peptizing by stirring for 2 hours, 55.0 kg of HZSM-5 zeolite powder (zeolite content: 91% by mass) having a silica/alumina molar ratio of 60 was added and stirred at high speed for 3 hours. The prepared slurry was dropped into an oil ammonia column containing 8 mass% of ammonia water, and the wet spheres formed in the oil ammonia column were taken out, dried at 60 ℃ for 10 hours, and calcined at 550 ℃ for 3 hours to obtain a carrier, which was alumina pellets containing 50 mass% of HZSM-5 zeolite.

(2) Preparation of upgrading catalyst

50 kg of carrier is taken, is soaked for 30 minutes by 50 kg of mixed solution containing 4.7 mass percent of zinc nitrate and 3.0 mass percent of mixed rare earth oxide (wherein lanthanum oxide accounts for 31 mass percent, cerium oxide accounts for 51 mass percent, praseodymium oxide accounts for 14 mass percent and neodymium oxide accounts for 4 mass percent), and 6.6 mass percent of phosphoric acid, is dried for 24 hours at 110 ℃, is roasted for 5 hours at 550 ℃, and is treated for 4 hours at 550 ℃ by steam to obtain the modified catalyst, wherein the total water consumption of the steam treatment is 200 kg.

The catalyst contains 2.1 mass% of zinc oxide, 2.1 mass% of phosphorus and 1.0 mass% of mixed rare earth oxide, based on the mass of the carrier, and the specific surface area of the catalyst is 303m²/g。

Example 3

Naphtha is upgraded according to the process of the present invention.

The fixed bed reaction zone consisted of a separate fixed bed reactor packed with the dehydrogenation catalyst prepared in example 1 in an amount of 30 mass% based on the total catalyst. The moving bed reaction zone consisted of a separate moving bed reactor and was charged with the reforming catalyst prepared in example 2 in an amount of 70 mass% based on the total catalyst. Before reaction, the dehydrogenation catalyst and the modification catalyst are activated in a device, wherein the activation medium is nitrogen, the pressure is 0.4MPa, the volume ratio of the nitrogen to the catalyst is 500:1, the activation temperature is 400 ℃, and the activation time is 2 hours.

According to the flow shown in figure 1, naphtha raw material is introduced into a fixed bed reaction zone for dehydrogenation reaction, and the obtained reaction product is introduced into a moving bed reaction zone for modification reaction. The reaction temperature of the fixed bed reactor is 400 ℃, the reaction pressure is 0.4MPa, and the mass space velocity of the naphtha feeding is 5h^-1. Controlling the conversion of 40-50 mass% naphthenes to aromatics in the naphtha. The reaction temperature of the moving bed reactor is 350 ℃, the reaction pressure is 0.4MPa, and the feeding mass space velocity of naphtha is 2.1h^-1. The modified reaction product is subjected to gas-liquid separation, and 60 volume percent of the obtained gas-phase product is returned to the fixed bed reactor.

The inlet temperature of the regenerator 23 was 480 ℃ and the pressure 0.4MPa, the residence time of the spent catalyst in the scorching zone was 200 minutes, and the regeneration medium was nitrogen with an oxygen content of 1 vol%.

The conditions and results of the dehydrogenation and upgrading reactions are shown in Table 2.

Comparative example 1

The naphtha is upgraded according to a conventional aromatization upgrading method.

Naphtha is directly introduced into a moving bed reactor filled with the modified catalyst prepared in the example 2 to carry out aromatization modification reaction, gas-liquid separation is carried out on reaction products to obtain gas-phase products and liquid-phase products, and 60 volume percent of the obtained gas-phase products returns to the moving bed reactor. The reaction temperature is 400 ℃, the reaction pressure is 0.4MPa, and the feeding mass space velocity of naphtha is 1.3h^-1The catalyst regeneration conditions were the same as in example 3.

The conditions and results of the upgrading reaction are shown in Table 2.

Comparative example 2

Naphtha was upgraded as in example 3, except that the gas phase product was not returned to the fixed bed reactor.

As can be seen from the results in table 2, the liquid product yield of the present invention is greatly improved compared to the conventional naphtha aromatization upgrading process under the condition that the liquid product octane number is equivalent. Part of gas phase product is circulated back to the fixed bed reactor, which can further increase the yield of liquid product.

TABLE 1

TABLE 2

Item	Example 3	Comparative example 1	Comparative example 2
				Reaction pressure, MPa	0.4	0.4	0.4
Dehydrogenation reaction temperature,. degree.C	400	-	400
				Mass space velocity of feed for dehydrogenation reaction h^-1	5	-	5
Modification reaction temperature, deg.C	350	400	350
				Mass space velocity of feed for upgrading reaction h^-1	2.1	1.3	2.1
Gas circulation ratio, volume%	60	60	0
				Liquid product RON	90.2	89.6	89.8
Yield of liquid product, mass%	84.37	62.68	80.15
				Aromatic content in liquid product, mass%	29.75	26.87	28.92

Claims

1. A naphtha upgrading process comprising:

introducing naphtha into a fixed bed reaction zone to contact with a dehydrogenation catalyst and carrying out dehydrogenation reaction under dehydrogenation reaction conditions so as to convert part of naphthenes in the naphtha into aromatic hydrocarbons; wherein the dehydrogenation catalyst comprises a carrier and chlorine and a group VIII metal loaded on the carrier;

introducing a reaction product obtained in the fixed bed reaction zone into the moving bed reaction zone to contact with a modified catalyst for modification reaction, cooling and separating the reaction product to obtain a gas-phase product and a liquid-phase product, and returning part of the gas-phase product to the fixed bed reaction zone;

introducing the spent catalyst flowing out of the moving bed reaction zone into a regenerator for coke burning regeneration, and returning the obtained regenerated catalyst to the moving bed reaction zone.

2. The process of claim 1, wherein the fixed bed reaction zone comprises one or more fixed bed reactors, a plurality of fixed bed reactors connected in series;

the moving bed reaction zone comprises one or more moving bed reactors, and a plurality of moving bed reactors are connected in series.

3. The process of claim 1, wherein the dehydrogenation catalyst loading in both reaction zones is from 10 to 60 mass% of the total catalyst loading.

4. The process according to claim 1, wherein 10 to 80 mass% of naphthenes in naphtha are converted into aromatics in a fixed bed reaction zone.

5. The process of claim 1, wherein from 20 to 90 volume percent of the vapor phase product is returned to the fixed bed reaction zone.

6. The method of claim 1, wherein the dehydrogenation reaction conditions comprise: the reaction temperature is 360-500 ℃, the reaction pressure is 0.1-1.0MPa, and the feeding mass space velocity of naphtha is 1-10h^-1。

7. The process of claim 1, wherein the upgrading reaction conditions comprise: the reaction temperature is 280 plus 480 ℃, the reaction pressure is 0.1-1.0MPa, and the feeding mass space velocity of the naphtha is 0.5-5.0h^-1。

8. The method of claim 1 wherein the naphtha contains C₅-C₁₂Wherein the content of cycloalkane is 10 to 60% by mass, the content of sulfur is not more than 300. mu.g/g, and the content of nitrogen is not more than 5. mu.g/g.

9. The process of claim 1 or 8, wherein the naphtha is at least one selected from the group consisting of straight run gasoline, hydrocracked gasoline, catalytically cracked gasoline, hydrocracked gasoline, reformed topped oil, reformed raffinate, condensate, pyrolysis gasoline, and pyrolysis gasoline raffinate.

10. The process as claimed in claim 1, wherein the support of the dehydrogenation catalyst is alumina and the dehydrogenation catalyst comprises a group VIII metal in an amount of 0.05 to 1.0 mass% and chlorine in an amount of 0.1 to 5.0 mass%, based on the alumina support.

11. The process of claim 1 or 10, wherein the group VIII metal is platinum.

12. The process of claim 1, wherein the upgrading catalyst comprises a support comprising a pentasil zeolite, zinc or gallium, a rare earth element, and a group VA element.

13. The process according to claim 1 or 12, wherein the upgraded catalyst support comprises 30-60 mass% of a pentasil zeolite selected from one or more of ZSM-5, ZSM-11 and ZSM-12 zeolites and 40-70 mass% of a binder which is alumina or silica;

on the basis of the carrier, the modifying catalyst comprises 0.5-3.0 mass percent of ZnO, 0.1-3.0 mass percent of mixed rare earth oxide and 1.0-5.0 mass percent of VA group element; the VA group element is selected from one or more of phosphorus, antimony and bismuth.

14. The method of claim 13 wherein the mixed rare earth oxide comprises 20-40 mass% lanthana, 40-60 mass% ceria, 10-18 mass% praseodymia, and 2-10 mass% neodymia.