阅读说明：本技术 烯烃齐聚制备航油并联产汽油的催化剂及制备方法和应用 (Catalyst for preparing aviation oil and co-producing gasoline by olefin oligomerization, preparation method and application ) 是由 吴晋沪 李建青 訾仲岳 何涛 王志奇 武景丽 刘广波 于 2019-11-12 设计创作，主要内容包括：本发明公开烯烃齐聚制备航油并联产汽油的催化剂及制备方法和应用,所述催化剂包括纳米ZSM-5分子筛和拟薄水铝石,其中纳米ZSM-5分子筛与拟薄水铝石的重量百分比为70％～95％:5％～30％。本发明中,所述纳米ZSM-5分子筛合成过程简单,晶化时间短,对反应釜材质要求较低；分子筛晶粒小且大小均一可控,结晶度高；所述催化剂制备过程简单；催化剂不含贵金属及重金属元素,在成型过程中不需要添加硝酸、硫酸等无机酸,对环境友好。本发明所述催化剂对低碳烯烃齐聚反应具有较高的催化活性,烯烃转化率可达99％以上,油收率可达95％以上,航油选择性可达90％以上,并且生成航油的过程中联产汽油。(The invention discloses a catalyst for preparing aviation oil and co-producing gasoline by olefin oligomerization, a preparation method and application thereof, wherein the catalyst comprises a nano ZSM-5 molecular sieve and pseudo-boehmite, and the weight percentage of the nano ZSM-5 molecular sieve to the pseudo-boehmite is 70-95% and 5-30%. In the invention, the synthesis process of the nano ZSM-5 molecular sieve is simple, the crystallization time is short, and the requirement on the material of a reaction kettle is low; the molecular sieve has small crystal grains, uniform and controllable size and high crystallinity; the preparation process of the catalyst is simple; the catalyst does not contain noble metals and heavy metal elements, does not need to add inorganic acids such as nitric acid, sulfuric acid and the like in the forming process, and is environment-friendly. The catalyst has high catalytic activity for oligomerization of low-carbon olefin, the olefin conversion rate can reach more than 99%, the oil yield can reach more than 95%, the aviation kerosene selectivity can reach more than 90%, and gasoline is co-produced in the aviation kerosene generation process.)

1. The catalyst for preparing aviation oil and co-producing gasoline by oligomerization of low-carbon olefin is characterized by comprising a nano ZSM-5 molecular sieve and pseudo-boehmite, wherein the weight percentage of the nano ZSM-5 molecular sieve to the pseudo-boehmite is 70-95% and 5-30%.

2. The preparation method of the catalyst for preparing aviation oil and co-producing gasoline by oligomerizing low-carbon olefins according to claim 1, which is characterized by comprising the following steps:

preparing a nano ZSM-5 molecular sieve;

and uniformly mixing the nano ZSM-5 molecular sieve and the pseudo-boehmite, tabletting, forming, crushing and screening to obtain the catalyst for preparing the aviation oil and co-producing gasoline by the oligomerization of the low-carbon olefin.

3. The method for preparing the catalyst for the preparation of aviation oil and gasoline by the oligomerization of the low-carbon olefins according to claim 2, wherein the method for preparing the nano ZSM-5 molecular sieve comprises the steps of:

a) dissolving a template agent and an aluminum source in deionized water, stirring at 25-40 ℃ until the mixture is clear, adding a silicon source, adding an alkali source, hydrolyzing the obtained mixed solution at 25-40 ℃ for 3-48h under the stirring condition, placing the mixed solution in a hydrothermal reaction kettle, and sealing for static constant-temperature crystallization at 180 ℃ for 4-72 h;

b) sequentially carrying out centrifugal separation, washing, drying and roasting on the crystallized reaction mixture;

c) mixing the roasted product with NH₄NO₃Solution or NH₄And carrying out ion exchange on the Cl solution to obtain the nano ZSM-5 molecular sieve.

4. The method for preparing the catalyst for preparing aviation oil and co-producing gasoline by oligomerizing low-carbon olefins according to claim 3, wherein in the step a), the template agent is tetrapropylammonium hydroxide or tetrapropylammonium bromide; the aluminum source is sodium metaaluminate, aluminum isopropoxide or aluminum sulfate; the silicon source is tetraethyl orthosilicate; the alkali source is sodium hydroxide.

5. The method for preparing the catalyst for the preparation of aviation oil and gasoline by the oligomerization of the low-carbon olefins according to claim 3, wherein in the step a), the molar ratio of the silicon source: an aluminum source: template agent: alkali source: deionized water 30-60:1:6-9:1-2.5: 2000-.

6. The method for preparing the catalyst for the oligomerization of the low-carbon olefins to prepare the aviation oil and the co-production of the gasoline according to claim 3, wherein in the step b), the drying temperature is 90-120 ℃, and the drying time is 4-12 h; the roasting temperature is 500-600 ℃, and the roasting time is 4-8 h.

7. The method for preparing the catalyst for the oligomerization of the low-carbon olefins to prepare the aviation oil and the co-production of the gasoline according to claim 3, wherein in the step c), the temperature of the ion exchange is 70-90 ℃, the time is 2-6h, and the times are 2-5; drying at 90-120 deg.C for 4-12h after exchange treatment; after drying, roasting at the temperature of 500-600 ℃ for 4-8h to obtain the nano ZSM-5 molecular sieve.

8. The method for preparing the catalyst for preparing the aviation oil and the co-production of the gasoline by the oligomerization of the low-carbon olefin as the claim 2 is characterized in that the catalyst for preparing the aviation oil and the co-production of the gasoline by the oligomerization of the low-carbon olefin is obtained by uniformly mixing the obtained nano ZSM-5 molecular sieve and the pseudo-boehmite, tabletting and molding, crushing and screening the mixture into 40 to 60 meshes, and roasting the mixture for 4 to 6 hours at the temperature of 500 ℃ and 600 ℃, wherein the weight percentage of the nano ZSM-5 molecular sieve to the pseudo-boehmite is 70 to 95 percent and 5 to 30 percent.

9. The use of the catalyst of claim 1 in the oligomerization of lower olefins to produce aviation oil and co-produce gasoline.

10. The application of the method as claimed in claim 9, wherein the process conditions for preparing aviation oil and co-producing gasoline by oligomerizing the low-carbon olefins are as follows: the reaction temperature is 220-^-1；

The low-carbon olefin is one or more of ethylene, propylene, n-butene and isobutene.

Technical Field

The invention relates to the technical field of molecular sieve catalysis, in particular to a catalyst for preparing aviation oil and co-producing gasoline by oligomerization of low-carbon olefin, and a preparation method and application thereof.

Background

With the development of social economy, petroleum resources are increasingly exhausted, and the demand of high-quality liquid fuels in the aspects of industrial production, transportation, military, aviation and the like is continuously increased. The development of non-petroleum routes for producing clean fuel has important strategic significance for reasonably adjusting the energy structure of China and producing environment-friendly liquid fuel. The oligomerization reaction carried out by taking the low-carbon olefin as the raw material is not only an effective way for preparing chemical products such as engine fuel, lubricating oil, antifreeze and the like, but also an important way for preparing high-quality clean liquid fuel such as gasoline, aviation oil and the like.

The key of the low-carbon olefin oligomerization technology lies in the research and development of high-efficiency catalysts. In recent years, the olefin oligomerization catalysts mainly used in the method comprise a solid phosphoric acid catalyst, a molecular sieve catalyst and a heterogeneous nickel-supported catalyst, wherein the heterogeneous nickel catalyst can be divided into a homogeneous nickel-supported catalyst and a nickel-supported solid acid catalyst according to different active components and preparation methods. The HZSM-5 molecular sieve with MFI type three-dimensional pore channel structure and good acidity shows good carbon deposition resistance in olefin oligomerization due to the confinement effect of the proper pore channel, and the product is not easy to branch and is considered to be C₃ ^＝、C₄ ^＝The low-carbon olefin oligomerization is used for preparing the catalyst with the greatest prospect for preparing the high-quality liquid fuel.

Chinese patent ZL 201310713200.7 discloses a catalyst for oligomerization of low-carbon olefin of Fischer-Tropsch synthesis products, and preparation and application thereof; the catalyst mainly comprises a ZSM-5 molecular sieve and contains one or more of zirconia, zinc oxide, lanthanum oxide, nickel oxide or nonmetal auxiliary agents, the preparation of the catalyst comprises the synthesis of the ZSM-5 molecular sieve and the modification of the molecular sieve, and the prepared catalyst is used for producing liquid fuel by oligomerization of low-carbon olefin synthesized by high-temperature Fischer-Tropsch. The catalyst prepared by the invention has higher low-carbon olefin oligomerization reaction activity, and gasoline and diesel oil products are controllable, wherein the highest selectivity of gasoline reaches 95.2 percent, and the highest selectivity of diesel oil reaches 60.5 percent. The preparation method comprises the steps of firstly synthesizing the ZSM-5 molecular sieve, then modifying the synthesized ZSM-5 molecular sieve by adopting an ion exchange method or an impregnation method through one or more of nitrates or sulfates of zirconium, zinc, lanthanum or nickel, and the preparation process is complex; meanwhile, nitrate or sulfate is used in the preparation process of the catalyst, so that certain pollution is caused to the environment.

Chinese patent ZL 01119414.6 discloses an H-type ZSM-5 molecular sieve catalyst for synthesizing C from low-carbon olefin₁₂-C₁₈The catalyst comprises the following components in percentage by weight: zr: 2.0-7.0% of ZSM-5 molecular sieve, 93.0-98.0% of ZSM-5 molecular sieve, and introducing Zr ions into the ZSM-5 to adjust the physical properties of the ZSM-5 molecular sieve by adopting a method of carrying out ion exchange on the H-type ZSM-5 molecular sieve in an acid solution. The invention has the advantage that C in the propylene oligomerization product₁₂-C₁₈The fraction can reach 78%, but the preparation process of the catalyst is also that the ZSM-5 molecular sieve is synthesized firstly, and then the ion exchange method is adopted to carry out Zr modification on the synthesized ZSM-5 molecular sieve, so that the preparation process is complex; meanwhile, the ion exchange process of the catalyst is carried out in an acid solution, and the catalyst relates to strong acid substances such as nitric acid, sulfuric acid and the like, thereby causing serious pollution to the environment. In addition, the catalyst related by the invention is limited to oligomerization reaction taking propylene as a raw material, and the application range is narrow.

Chinese patent CN 109651436A discloses a nickel-loaded ionic liquid catalyst, a preparation method thereof and a method for catalyzing n-butene or mixed C₄The oligomerization method uses a novel nickel catalyst loaded by ionic liquid to catalyze the oligomerization of n-butene with high activity under certain temperature and pressure conditions. The method uses the nickel loaded by the ionic liquid as the catalyst, the catalyst and the product are layered after the reaction is finished, the catalyst can be directly separated, the recycling activity of the catalyst is not obviously reduced, and the cost of the catalyst and the generation of three wastes are greatly reduced. But the invention relates toThe preparation process of the catalyst is to prepare the ionic liquid first and then carry out Ni modification on the ionic liquid, and the preparation process has certain complexity; meanwhile, fluoride and organic matters containing benzene rings are used in the preparation process of the ionic liquid, so that the environment is seriously polluted. In addition, the catalyst related to the invention is limited to n-butene or mixed C₄The oligomerization reaction of the raw materials has narrow application range.

Chinese patent ZL 201610222515.5 discloses a method for preparing gasoline components by oligomerization of carbon tetraolefin, wherein a related catalyst is a ZSM-35 molecular sieve, the reaction temperature for preparing gasoline by oligomerization of carbon tetraolefin is 310-350 ℃, and the reaction pressure is 0.2-1 MPa. The method has the advantages of high yield of gasoline components and low content of aromatic hydrocarbon in the gasoline components. However, the catalyst related by the invention is only limited to the oligomerization of the carbon tetraolefin, the application range is narrow, and the oligomerization product is pure gasoline and does not relate to a aviation fuel component.

Therefore, the catalysts for olefin oligomerization disclosed in the invention patents are metal-modified HZSM-5 molecular sieves, ZSM-35 molecular sieves or metal-modified ionic liquids, and have the defects of complex preparation process, environmental pollution, narrow range of applicable raw materials of the catalysts, single oligomerization products and the like. Therefore, the catalyst which has simple preparation process, wide range of used raw material olefin, high activity for olefin oligomerization reaction and high oil yield is obtained, and is the target direction of the development of the olefin oligomerization catalyst preparation technology.

Disclosure of Invention

In view of the defects of the prior art, the invention aims to provide a catalyst for preparing aviation oil and co-producing gasoline by low-carbon olefin oligomerization, and a preparation method and application thereof, and aims to solve the problems of complex preparation process, environmental pollution, narrow range of applicable raw materials of the catalyst and single oligomerization product of the traditional low-carbon olefin oligomerization catalyst.

The technical scheme of the invention is as follows:

a catalyst for preparing aviation oil and co-producing gasoline by oligomerization of low-carbon olefin is disclosed, wherein the catalyst comprises a nano ZSM-5 molecular sieve and pseudo-boehmite, wherein the weight percentage of the nano ZSM-5 molecular sieve to the pseudo-boehmite is 70% -95% and 5% -30%.

The invention relates to a preparation method of a catalyst for preparing aviation oil and co-producing gasoline by oligomerization of low-carbon olefins, which comprises the following steps:

preparing a nano ZSM-5 molecular sieve;

and uniformly mixing the nano ZSM-5 molecular sieve and the pseudo-boehmite, tabletting, forming, crushing and screening to obtain the catalyst for preparing the aviation oil and co-producing gasoline by the oligomerization of the low-carbon olefin.

Further, the method for preparing the nano ZSM-5 molecular sieve comprises the following steps:

a) dissolving a template agent and an aluminum source in deionized water, stirring at 25-40 ℃ until the mixture is clear, adding a silicon source, adding an alkali source, hydrolyzing the obtained mixed solution at 25-40 ℃ for 3-48h under the stirring condition, placing the mixed solution in a hydrothermal reaction kettle, and sealing for static constant-temperature crystallization at 180 ℃ for 4-72 h;

b) sequentially carrying out centrifugal separation, washing, drying and roasting on the crystallized reaction mixture;

c) mixing the roasted product with NH₄NO₃Solution or NH₄And carrying out ion exchange on the Cl solution to obtain the nano ZSM-5 molecular sieve.

Further, in step a), the template agent is tetrapropylammonium hydroxide or tetrapropylammonium bromide; the aluminum source is sodium metaaluminate, aluminum isopropoxide or aluminum sulfate; the silicon source is tetraethyl orthosilicate; the alkali source is sodium hydroxide.

Further, in step a), the ratio of the silicon source: an aluminum source: template agent: alkali source: deionized water 30-60:1:6-9:1-2.5: 2000-.

Furthermore, in the step b), the drying temperature is 90-120 ℃, and the drying time is 4-12 h; the roasting temperature is 500-600 ℃, and the roasting time is 4-8 h.

Furthermore, in the step c), the temperature of ion exchange is 70-90 ℃, the time is 2-6h, and the times are 2-5; drying at 90-120 deg.C for 4-12h after exchange treatment; after drying, roasting at the temperature of 500-600 ℃ for 4-8h to obtain the nano ZSM-5 molecular sieve.

Further, the obtained nanometer ZSM-5 molecular sieve and the pseudo-boehmite are uniformly mixed, then the mixture is tableted and molded, the crushed mixture is sieved to 40-60 meshes, and the crushed mixture is roasted for 4-6h at the temperature of 600 ℃, so that the catalyst for preparing the aviation oil and co-producing the gasoline by the oligomerization of the low-carbon olefin is obtained, wherein the weight percentage of the ZSM-5 molecular sieve to the pseudo-boehmite is 70-95 percent and 5-30 percent.

The invention relates to an application of the catalyst in the preparation of aviation oil and gasoline co-production by low-carbon olefin oligomerization.

Further, the process conditions for preparing aviation oil and co-producing gasoline by oligomerization of the low-carbon olefins are as follows: the reaction temperature is 220-^-1；

The low-carbon olefin is one or more of ethylene, propylene, n-butene and isobutene.

Has the advantages that: in the invention, the synthesis process of the nano ZSM-5 molecular sieve is simple, the crystallization time is short, and the requirement on the material of a reaction kettle is low; the nano ZSM-5 molecular sieve has small crystal grains (about 50nm), uniform and controllable size and high crystallinity; the preparation process of the catalyst for preparing the aviation oil and co-producing the gasoline by the oligomerization of the low-carbon olefin is simple; the catalyst does not contain noble metals and heavy metal elements, does not need to add inorganic acids such as nitric acid, sulfuric acid and the like in the forming process, and is environment-friendly. The catalyst has high catalytic activity for oligomerization of low-carbon olefin, the olefin conversion rate can reach more than 99%, the oil yield can reach more than 95%, the aviation kerosene selectivity can reach more than 90%, and gasoline is co-produced in the aviation kerosene generation process.

Drawings

FIG. 1 is an XRD pattern of a small-grained nano ZSM-5 molecular sieve provided in example 1 of the present invention.

FIG. 2 is an SEM image of a small-grained nano ZSM-5 molecular sieve provided in example 1 of the present invention.

Detailed Description

The invention provides a catalyst for preparing aviation oil and co-producing gasoline by oligomerization of low-carbon olefin, a preparation method and application thereof, and the invention is further described in detail below in order to make the purpose, technical scheme and effect of the invention clearer and clearer. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The embodiment of the invention provides a catalyst for preparing aviation oil and co-producing gasoline by oligomerization of low-carbon olefin, wherein the catalyst comprises a nano ZSM-5 molecular sieve and pseudo-boehmite, wherein the weight percentage of the nano ZSM-5 molecular sieve to the pseudo-boehmite is 70-95% and 5-30%.

In the embodiment, the synthesis process of the nano ZSM-5 molecular sieve is simple, the crystallization time is short, and the requirement on the material of the reaction kettle is low; the nano ZSM-5 molecular sieve has small crystal grains (about 50nm), uniform and controllable size and high crystallinity; the preparation process of the catalyst for preparing the aviation oil and co-producing the gasoline by the oligomerization of the low-carbon olefin is simple; the catalyst does not contain noble metals and heavy metal elements, does not need to add inorganic acids such as nitric acid, sulfuric acid and the like in the forming process, and is environment-friendly. The catalyst has high catalytic activity for oligomerization of low-carbon olefin, the olefin conversion rate can reach more than 99%, the oil yield can reach more than 95%, the aviation kerosene selectivity can reach more than 90%, and gasoline is co-produced in the aviation kerosene generation process.

The embodiment of the invention provides a preparation method of the catalyst for preparing aviation oil and co-producing gasoline by oligomerization of low-carbon olefins, which comprises the following steps:

s10, preparing a nano ZSM-5 molecular sieve;

and S20, uniformly mixing the nano ZSM-5 molecular sieve and the pseudo-boehmite, and performing tabletting, forming, crushing and screening to obtain the catalyst for preparing the aviation oil and co-producing the gasoline by the oligomerization of the low-carbon olefin.

The embodiment has the following advantages:

1. the catalyst for preparing aviation oil and co-producing gasoline by oligomerization of low-carbon olefin mainly comprises a small-grain nano ZSM-5 molecular sieve, metal modification treatment on the synthesized nano ZSM-5 molecular sieve is not needed, and the nano ZSM-5 molecular sieve has the advantages of simple synthesis process, short crystallization time and lower requirement on the material of a reaction kettle; the synthesized nano ZSM-5 molecular sieve has small crystal grain (about 50nm), uniform and controllable size and high crystallinity;

2. the preparation process of the catalyst for preparing the aviation oil and co-producing the gasoline by oligomerization of the low-carbon olefin is simple; the nano ZSM-5 molecular sieve does not contain noble metals and heavy metal elements, does not need to add inorganic acids such as nitric acid, sulfuric acid and the like in the forming process, and is environment-friendly.

3. The catalyst for preparing the aviation oil and co-producing the gasoline by oligomerizing the low-carbon olefins has excellent catalytic activity on the low-carbon olefins such as ethylene, propylene, n-butene, isobutene and the like and mixtures thereof, the applicable raw material range of the catalyst is wide, the olefin conversion rate is more than 99%, the oil yield is more than 95%, the aviation oil selectivity is more than 90%, and the gasoline is co-produced in the aviation oil generating process.

In step S10, the method for preparing a nano ZSM-5 molecular sieve includes the steps of:

s11, dissolving a template agent and an aluminum source in deionized water, stirring at 25-40 ℃ until the mixture is clear, adding a silicon source, adding an alkali source, hydrolyzing the obtained mixed solution at 25-40 ℃ for 3-48h under the stirring condition, placing the mixed solution in a hydrothermal reaction kettle, sealing, and crystallizing at a static constant temperature of 180 ℃ for 4-72 h.

In one embodiment, the silicon source (in SiO) is present in molar ratio₂Calculation): aluminum source (with Al)₂O₃Calculation): template agent: alkali source: deionized water 25-80:1:5-12:0.5-3.0: 1500-.

Further in one embodiment, the silicon source (in SiO) is present in molar ratios₂Calculation): aluminum source (with Al)₂O₃Calculation): template agent: alkali source: deionized water 30-60:1:6-9:1-2.5: 2000-.

In one embodiment, the templating agent is tetrapropylammonium hydroxide (TPAOH) or tetrapropylammonium bromide; the aluminum source is sodium metaaluminate, aluminum isopropoxide or aluminum sulfate; the silicon source is tetraethyl orthosilicate; the alkali source is sodium hydroxide.

In one embodiment, the hydrolysis temperature is 30-35 ℃ and the hydrolysis time is 8-45 h.

In one embodiment, the crystallization temperature is 140-170 ℃, and the crystallization time is 6-48 h.

In the preparation process of the ZSM-5 molecular sieve, the crystal grain size of the molecular sieve is reduced by prolonging the hydrolysis time of the silicon-aluminum gel liquid and shortening the crystallization time of the gel liquid, so that the nano ZSM-5 molecular sieve with the crystal grain size of about 50nm is obtained; in addition, the strong acid nano ZSM-5 molecular sieve suitable for olefin oligomerization reaction is prepared by adjusting the proportion of the synthetic raw materials.

And S12, sequentially carrying out centrifugal separation, washing, drying and roasting on the crystallized reaction mixture.

In one embodiment, the drying temperature is 90-120 ℃ and the drying time is 4-12 h.

In one embodiment, the roasting temperature is 500-600 ℃, and the roasting time is 4-8 h.

S13, mixing the roasted product with NH₄NO₃Solution or NH₄And carrying out ion exchange on the Cl solution to obtain the nano ZSM-5 molecular sieve of the embodiment. The specific surface area of the nano ZSM-5 molecular sieve is between 350-450m²The pore volume is between 0.1 and 0.3m³(g), the particle diameter is about 50 nm.

In one embodiment, S13 specifically includes: mixing the roasted product in S12 with NH with the concentration of 0.1mol/L₄NO₃Or NH₄Carrying out ion exchange on the Cl aqueous solution, wherein the temperature of the ion exchange is 70-90 ℃, the exchange time is 2-6h, and the exchange times are 2-5; drying at 90-120 deg.C for 4-12h after exchange treatment; after drying, the mixture is roasted for 4 to 8 hours at the temperature of 500-600 ℃ to obtain the nano ZSM-5 molecular sieve of the embodiment.

In the embodiment, the synthesis process of the nano ZSM-5 molecular sieve is simple, the crystallization time is short, and the requirement on the material of the reaction kettle is low; the nano ZSM-5 molecular sieve has small crystal grain (about 50nm), uniform and controllable size and high crystallinity.

Step S20 includes: the nano ZSM-5 molecular sieve and the pseudo-boehmite (used as a binder) are uniformly mixed, pressed into tablets, crushed and screened into 40-60 meshes, and calcined at the temperature of 500-600 ℃ for 4-6h to obtain the catalyst for preparing the aviation oil and co-producing the gasoline by the oligomerization of the low-carbon olefin. Wherein, the weight percentage of the nano ZSM-5 molecular sieve to the pseudo-boehmite is 70-95 percent and 5-30 percent.

The embodiment of the invention provides application of the catalyst in preparation of aviation oil and co-production of gasoline by oligomerization of low-carbon olefin.

In one embodiment, the method for preparing aviation oil and co-producing gasoline by oligomerizing low-carbon olefins comprises the following steps: the catalyst is filled in a fixed bed reactor, and the reaction raw material, namely low-carbon olefin, is mixed with 10ml/min of nitrogen through a micro pump and then enters the reactor through a preheater. Wherein the process conditions are as follows: the reaction temperature is 220-^-1。

Further in one embodiment, the process conditions for preparing aviation oil and co-producing gasoline by oligomerization of the low-carbon olefins are as follows: the reaction temperature is 250 ℃ and 300 ℃, the reaction pressure is 2-5MPa, and the mass space velocity is 1-5h^-1。

In one embodiment, the lower olefins are one or more of ethylene, propylene, n-butene, isobutene, and the like.

The present invention will be further described with reference to specific examples.