CN101579638A - Catalyst for preparing ethylene by ethanol dehydration and preparation method thereof - Google Patents

Abstract

The invention discloses a catalyst for ethanol dehydration to ethylene and a preparation method thereof, which belong to the technical field of biomass energy and catalyst preparation. The catalyst is SAPO-34 molecular sieve modified by metal Mn ions, that is, Mn/SAPO-34, which is prepared by introducing modified metal ions before molecular sieve crystallization by using morpholine as a template agent through a direct synthesis method. The invention overcomes and solves the high cost and shortage of petroleum raw materials, reduces process energy consumption, and solves the problems of low concentration of ethanol in biomass fermentation and difficulty in subsequent application; the conversion rate of ethanol is high, the selectivity and purity of ethylene are high, and the catalyst It has good activity, is not easy to deposit carbon, and has a long operating cycle; the obtained molecular sieve is a large-grained single crystal, which can be directly used in a fluidized bed, has good wear resistance, and reduces the granulation steps; That is, the introduction of modified metal ions has good activity and stability, and the modified ions are not easy to lose during the reaction process.

Description

Catalyst for ethanol dehydration to ethylene and preparation method thereof

technical field

The invention belongs to the technical field of biomass energy and catalyst preparation, and in particular relates to a catalyst for ethanol dehydration to ethylene and a preparation method thereof.

Background technique

Ethylene is an important basic organic chemical raw material and the cornerstone of the chemical industry. About 75% of chemical products use ethylene as raw material, which is widely used in many important organic chemicals such as polyethylene, ethylene oxide/ethylene glycol, dichloroethane, styrene, ethanol, vinyl acetate, propionaldehyde, etc. Production of products and polymers. The scale and level of the ethylene industry has become an important symbol reflecting the development level of a country's chemical industry. my country's ethylene production has increased rapidly, but it is still far from meeting consumption needs. For example, in 2005, my country's ethylene production was 7.55 million tons, while consumption reached 18.76 million tons that year, and domestic ethylene production can only meet 40.2% of demand. It is estimated that the demand for ethylene equivalent in my country will be 25-26 million tons in 2010 and 37-41 million tons in 2020.

At present, most countries use naphtha, ethane, propane and gas oil as raw materials to produce ethylene through cracking. This process has a large number of associated products, and the ethylene separation and purification process is very complicated, requiring large and expensive equipment. In addition, oil is a non-renewable resource, its reserves are decreasing day by day, and its regional distribution is very uneven. In addition, its use has caused serious environmental pollution, and oil prices have risen rapidly in recent years. This requires the development of substitutes for oil resources to reduce the impact on oil degree of dependence.

Biomass is renewable organic matter, including crops, trees and other plants and their residues, organic waste, etc. The production of ethylene from biomass is a process of "hydrolysis of biomass to produce sugar, fermentation of sugar to produce ethanol, dehydration of ethanol to produce ethylene", which is not only a supplement to petroleum ethylene, but also in line with the sustainable development strategy. The bioethanol obtained from biomass fermentation generally has a low concentration (mass concentration is about 10%), while the separation and purification of ethanol aqueous solution consumes a lot of energy, so the direct use of low-concentration ethanol to prepare bioethylene by dehydration has great economic value and strategic significance .

In fact, the catalytic dehydration of ethanol to ethylene is the earliest ethylene production method. Before the 1940s, most ethylene was obtained through this process. Only after the large-scale and rapid development of petrochemical industry, the production of ethylene by fossil raw material cracking gradually became the mainstream. At present, there are still small and medium-scale industrial production in some countries, and some small and medium-sized chemical enterprises in my country also use this process. Catalytic dehydration to ethylene with bioethanol as raw material has high product yield and purity, and the investment is only 1/10 of that of petroleum ethylene.

catalyst considerations

High-efficiency catalyst is one of the key technologies in the process of ethanol catalytic dehydration to ethylene. The traditional process catalyst of this method is mainly activated alumina and some other metal oxides. These catalysts generally require the volume fraction of raw material ethanol to be above 95%, which is not suitable for low-concentration ethanol. In addition, they also have disadvantages such as small reaction space velocity, small processing capacity, small equipment production capacity and high energy consumption. Catalysts suitable for the catalytic dehydration of low-concentration ethanol to ethylene mainly include heteropolyacids and molecular sieves. Heteropolyacid catalysts have low reaction temperature, high selectivity and yield, but require high catalyst preparation technology and are expensive. The zeolites involved in this reaction include ZSM-5 and SAPO-34. Compared with ZSM-5, SAPO-34 has three-dimensional channels, small pore size, high porosity, large available surface, and uniform acid distribution; in addition, SAPO molecular sieves have medium-strength acid centers, which limit the further reaction of ethylene and propylene . These characteristics make SAPO molecular sieves show outstanding advantages in the reaction of ethanol dehydration to ethylene.

However, the direct use of SAPO-34 as a catalyst also has disadvantages: firstly, SAPO-34 has poor stability and is easy to deactivate, so metal ions need to be introduced to modify its acidity and pore structure to increase its stability. The metal ion modification of molecular sieves usually adopts post-synthesis modification, that is, the synthesized SAPO-34 molecular sieve is introduced into metal ions by impregnation method. The disadvantage of this modification method is that the metal ions are easy to be lost during the reaction process, which reduces the activity.

Reactor considerations

The endothermic catalytic dehydration reaction of raw ethanol in the gas phase after preheating and vaporization is a typical gas-solid catalytic reaction, and the fluidized bed has unique advantages in this reaction because of its excellent heat and mass transfer characteristics. Under the same device scale, the use of fluidized bed reactors has higher conversion rate per pass and lower unit energy consumption of raw materials than fixed bed reactors, and the production cost is low and the economic benefits are good. In addition, in terms of equipment construction investment, the use of fluidized bed reactors also has great advantages. Therefore, in the process of ethanol catalytic dehydration to ethylene, it is of great significance to prepare highly active catalysts suitable for use in fluidized beds.

Fluidized bed reactors have special requirements on the strength and particle size of solid catalysts. If the synthesized molecular sieve is modified by impregnation method by introducing metal ions, the activity may decrease due to the loss of metal ions due to the violent collision of fluidized reaction particles in the fluidized bed. Secondly, the synthesis of SAPO-34 usually uses tetraethylammonium hydroxide (TEAOH) or triethylamine (TEA) as a template, and the particle size is small (1-5μm), which cannot be directly used in an industrial fluidized bed, but only Granules suitable for fluidization can be obtained by adding binders or granulating by spraying and other methods, but the abrasion resistance of the particles obtained by these methods is not good, and in addition, the complexity of the whole process is increased.

In view of the current deficiencies, the present invention intends to select a suitable template and introduce modified metal ions before the crystallization of the molecular sieve through a direct synthesis method to obtain a large-grain single-crystal SAPO-34 modified molecular sieve that can be used for fluidization, thereby developing A new process for preparing ethylene by catalytic dehydration of bioethanol was obtained.

Contents of the invention

The object of the present invention is to provide a catalyst for ethanol dehydration to ethylene and a preparation method thereof.

A catalyst for producing ethylene by ethanol dehydration is characterized in that the catalyst is SAPO-34 molecular sieve modified by metal Mn ions, ie Mn/SAPO-34.

The anhydrous chemical formula of the SAPO-34 molecular sieve is 1Al ₂ O ₃ ·(0.1-5)P ₂ O ₅ ·(0.1-5)SiO ₂ .

A preparation method of a catalyst for ethanol dehydration to prepare ethylene, characterized in that, using morpholine as a template agent and introducing modified metal ions before molecular sieve crystallization by a direct synthesis method, the method steps are as follows:

(1) Synthesize SAPO-34 molecular sieve with silica sol as silicon source, pseudoboehmite as aluminum source, orthophosphoric acid as phosphorus source, morpholine as template, and water as solvent, and the molar ratio of each component is 1Al ₂ O ₃ : (0.1~5)P ₂ O ₅ :(0.1~5)SiO ₂ :(1~10)R:(1~100)H ₂ O, wherein R is the template agent morpholine, according to the ratio relationship Weigh silicon source, aluminum source, phosphorus source, templating agent and solvent, use Mn(NO ₃ ) ₂ as modifier, weigh Mn(NO ₃ ) ₂ according to the loading amount of metal ions (2-10)%, And add deionized water to prepare a solution;

(2) Preparation of gel: under the condition of stirring, add phosphorus source, aluminum source, silicon source and template agent in sequence in the aqueous solution, adjust the pH value to 7-10, add Mn(NO ₃ ) ₂ solution, Then add the finished SAPO-34 molecular sieve as a crystallization guide agent, and stir the mixed solution evenly to form a gel-like crystallization solution;

(3) Crystallization: transfer the crystallization liquid to a stainless steel reaction kettle lined with polytetrafluoroethylene, and crystallize at 80-200°C for 10-100 hours;

(4) Post-treatment: the crystallized product is cooled in a natural state, filtered, washed until neutral, and then dried at 50-150°C for 0.5-10 hours;

(5) Template release agent: put the dried molecular sieve raw powder at 400-800° C. for 0.5-10 h to remove the template agent, and obtain a SAPO-34 molecular sieve modified with metal Mn ions.

The _mass fraction of SiO in the silica sol is 40%.

The mass fraction of Al ₂ O ₃ in the pseudo-boehmite is 70%.

The mass fraction of orthophosphoric acid is 85%.

The added amount of the finished SAPO-34 molecular sieve accounts for 1-5% of the theoretically calculated weight of the SAPO-34 molecular sieve in the metal Mn ion modified SAPO-34 molecular sieve.

The SAPO-34 molecular sieve modified by metal Mn ions is used as a catalyst for ethanol dehydration in a fluidized bed to produce ethylene, and the mass concentration of the ethanol solution in the fluidized bed is 5-100%.

The beneficial effects of the present invention are:

(1) Using low-concentration bioethanol as a raw material can overcome and solve the high cost and shortage of petroleum raw materials; at the same time, it does not need to purify the raw materials, which reduces the energy consumption of the process and solves the problem of low concentration of ethanol in biomass fermentation and subsequent applications difficult questions;

(2) The modified Mn/SAPO-34 catalyzes high conversion rate of bioethanol, high selectivity and purity of ethylene, good catalyst activity, not easy to deposit carbon, and long operation period;

(3) The obtained molecular sieve is a large-grain single crystal, which can be directly used in a fluidized bed, has good wear resistance, and also reduces the granulation step;

(4) The modified metal ions are introduced before the crystallization of the molecular sieve by the direct synthesis method, the activity and stability are good, and the modified ions are not easy to be lost during the reaction process.

Detailed ways

The present invention will be further described below in conjunction with embodiment:

Example 1

A catalyst for ethanol dehydration to ethylene, the catalyst is a metal Mn ion modified SAPO-34 molecular sieve, namely Mn/SAPO-34, and the anhydrous chemical formula of the SAPO-34 molecular sieve is 1Al ₂ O ₃ ·1.06P ₂ O ₅ · 1.08 SiO ₂ .

A preparation method of a catalyst for ethanol dehydration to prepare ethylene, using morpholine as a template agent to introduce modified metal ions before molecular sieve crystallization by a direct synthesis method, the method steps are as follows:

(1) With silica sol (SiO ₂ mass fraction is 40%) as silicon source, pseudo-boehmite as aluminum source (Al ₂ O ₃ mass fraction is 70%), and orthophosphoric acid with a mass fraction of 85% as phosphorus source (The used raw material silica sol, pseudo-boehmite, orthophosphoric acid are all industrial products, and the following examples are the same), morpholine is a template agent, and water is a solvent to synthesize SAPO-34 molecular sieve, each component and its molar ratio 1Al ₂ O ₃ : 1.06P ₂ O ₅ : 1.08SiO ₂ : 3R: 60H ₂ O, wherein R is the template agent morpholine, and the silicon source, aluminum source, phosphorus source, template agent and solvent are weighed according to the proportioning relationship, With Mn(NO ₃ ) ₂ as modifier, weigh Mn(NO ₃ ) ₂ according to the loading of metal ions as 5% (loading is the mass ratio of modified metal ions to the mass of SAPO-34 molecular sieve × 100% ), and adding deionized water to prepare a solution;

(2) Preparation of gel: under the condition of stirring, add phosphorus source, aluminum source, silicon source and template in sequence in the aqueous solution, adjust the pH value to 8-9 with ammonia water, add Mn(NO ₃ ) ₂ solution, then add the finished SAPO-34 molecular sieve (commercially available, chemical formula 1Al ₂ O ₃ :0.4P ₂ O ₅ :0.8SiO ₂ ) as a crystallization directing agent, and the addition of the finished product SAPO-34 molecular sieve accounts for 10% of the metal prepared by theoretical calculation. 1.5% of the SAPO-34 molecular sieve weight in the SAPO-34 molecular sieve modified by Mn ions, the mixed solution is stirred evenly to form a gel crystallization solution;

(3) Crystallization: Transfer the crystallization solution to a stainless steel reaction kettle lined with polytetrafluoroethylene, and crystallize at 200°C for 60 hours;

(4) Post-treatment: the crystallized product is cooled in a natural state, filtered, washed to neutrality, and then dried at 120°C for 4 hours;

(5) Template release agent: the dried molecular sieve powder was calcined at 600° C. for 4 hours to remove the template agent to obtain the SAPO-34 molecular sieve Mn/SAPO-34 modified with metal Mn ions.

The obtained Mn/SAPO-34 is a large grain single crystal with a single crystal size of about 50 μm.

The metal Mn ion-modified SAPO-34 molecular sieve Mn/SAPO-34 prepared by the present embodiment and the unmodified SAPO-34 molecular sieve (the unmodified SAPO-34 molecular sieve and the metal Mn ion-modified SAPO-34 molecular sieve The preparation method is the same, except that Mn ions are not doped) In comparison, in a fluidized bed reactor, at 340 ° C and a mass space velocity of 2.4 h ^-1 , the unmodified SAPO-34 molecular sieve catalytic ethanol dehydration conversion rate is 98.2 %, the ethylene selectivity is 70.1%; the SAPO-34 molecular sieve Mn/SAPO-34 modified by the metal Mn ion is used as the catalyst, the ethanol dehydration conversion rate is 99.7%, and the ethylene selectivity is 98.5%. It can be seen that the effect of the SAPO-34 molecular sieve Mn/SAPO-34 modified by metal Mn ions is significantly better than that of the unmodified SAPO-34 molecular sieve.

Get the metal Mn ion-modified SAPO-34 molecular sieve Mn/SAPO-34 catalyst 250g that this embodiment prepares in the fluidized bed reactor, ethanol mass concentration is 30%, reaction condition: temperature is 340 ℃, mass space velocity is 2.5h ^-1 , the fluidization gas velocity is 0.6m/s, the reaction result: the ethanol conversion rate is 99.3%, the ethylene selectivity is 98.2%, other conditions remain unchanged, only the ethanol mass concentration is changed to 12%, and the ethanol conversion rate is obtained It is 99.2%, and the ethylene selectivity is 98.62%. It can be seen that when the SAPO-34 molecular sieve Mn/SAPO-34 modified by metal Mn ions is used as the catalyst, the ethanol mass concentration, that is, the water content of the raw material, has little influence on the reaction result.

Get the metal Mn ion-modified SAPO-34 molecular sieve Mn/SAPO-34 catalyst 250g that this embodiment prepares in the fluidized bed reactor, ethanol mass concentration is 12%, reaction condition: temperature is 320 ℃, mass space velocity is 2.5h ^-1 , the fluidization gas velocity is 0.6m/s, the reaction result: the ethanol conversion rate is 99%, and the ethylene selectivity is 98.62%. The composite modified catalyst has been continuously operated for 142 hours, and its catalytic activity has not changed significantly, which shows that this catalyst has good stability and a long operating period.

Example 2

A catalyst for ethanol dehydration to ethylene, the catalyst is a metal Mn ion modified SAPO-34 molecular sieve, namely Mn/SAPO-34, and the anhydrous chemical formula of the SAPO-34 molecular sieve is 1Al ₂ O ₃ ·1.06P ₂ O ₅ · 1SiO ₂ .

A preparation method of a catalyst for ethanol dehydration to prepare ethylene, using morpholine as a template agent to introduce modified metal ions before molecular sieve crystallization by a direct synthesis method, the method steps are as follows:

(1) With silica sol (SiO ₂ mass fraction is 40%) as silicon source, pseudo-boehmite as aluminum source (Al ₂ O ₃ mass fraction is 70%), and orthophosphoric acid with a mass fraction of 85% as phosphorus source , morpholine as a template, water as a solvent to synthesize SAPO-34 molecular sieve, each component and its molar ratio are 1Al ₂ O ₃ : 1.06P ₂ O ₅ : 1SiO ₂ : 3R: 60H ₂ O, wherein R is a template For morpholine, silicon source, aluminum source, phosphorus source, templating agent and solvent are weighed according to the proportioning relationship, Mn(NO ₃ ) ₂ is used as modifier, and Mn(NO ₃ ) ₂ , and add deionized water to prepare a solution;

(2) Preparation of gel: under the condition of stirring, add phosphorus source, aluminum source, silicon source and template in sequence in the aqueous solution, adjust the pH value to 8-9 with ammonia water, add Mn(NO ₃ ) ₂ solution, then add the finished SAPO-34 molecular sieve (commercially available, chemical formula 1Al ₂ O ₃ :0.4P ₂ O ₅ :0.8SiO ₂ ) as a crystallization directing agent, and the addition of the finished product SAPO-34 molecular sieve accounts for 10% of the metal prepared by theoretical calculation. 2.5% of the SAPO-34 molecular sieve weight in the SAPO-34 molecular sieve modified by Mn ions, the mixed solution is stirred evenly to form a gel crystallization solution;

(3) Crystallization: transfer the crystallization solution to a stainless steel reaction kettle lined with polytetrafluoroethylene, and crystallize at 150°C for 80 hours;

(4) Post-treatment: the crystallized product is cooled in a natural state, filtered, washed to neutrality, and then dried at 100°C for 5 hours;

(5) Template release agent: the dried molecular sieve powder was calcined at 550° C. for 6 hours to remove the template agent to obtain the SAPO-34 molecular sieve Mn/SAPO-34 modified with metal Mn ions.

The obtained Mn/SAPO-34 is a large-grain single crystal with a single crystal size of about 55 μm.

The metal Mn ion-modified SAPO-34 molecular sieve Mn/SAPO-34 prepared by the present embodiment and the unmodified SAPO-34 molecular sieve (the unmodified SAPO-34 molecular sieve and the metal Mn ion-modified SAPO-34 molecular sieve The preparation method is the same, except that it is not doped with Mn ions) In comparison, at 340 ° C and a mass space velocity of 2.2 h ⁻¹ , the unmodified SAPO-34 molecular sieve catalyzes ethanol dehydration conversion rate of 92.6%, and ethylene selectivity of 68.3 %; The SAPO-34 molecular sieve Mn/SAPO-34 modified by metal Mn ions is used as a catalyst, the ethanol dehydration conversion rate is 98.4%, and the ethylene selectivity is 97.2%. It can be seen that the effect of SAPO-34 modified by metal Mn ions is obviously better than that of unmodified SAPO-34 molecular sieve.

Get the metal Mn ion-modified SAPO-34 molecular sieve Mn/SAPO-34 catalyst 250g that this embodiment prepares in the fluidized bed reactor, ethanol mass concentration is 30%, reaction condition: temperature is 340 ℃, mass space velocity is 2.0h ^-1 , the fluidization gas velocity is 0.6m/s, the reaction result: the ethanol conversion rate is 98.5%, the ethylene selectivity is 97.8%, other conditions remain unchanged, only the ethanol mass concentration is changed to 12%, and the ethanol conversion rate is obtained It is 98.9%, and the ethylene selectivity is 98.1%. It can be seen that when the SAPO-34 molecular sieve Mn/SAPO-34 modified by metal Mn ions is used as the catalyst, the ethanol mass concentration, that is, the water content of the raw material, has little influence on the reaction result.

Get the metal Mn ion-modified SAPO-34 molecular sieve Mn/SAPO-34 catalyst 250g that this embodiment prepares in the fluidized bed reactor, ethanol mass concentration is 12%, reaction condition: temperature is 320 ℃, mass space velocity is 2.0h ^-1 , the fluidization gas velocity is 0.6m/s, the reaction result: the ethanol conversion rate is 99%, and the ethylene selectivity is 98.1%. The composite modified catalyst has been continuously operated for 120 hours, and its catalytic activity has not changed significantly, which shows that this catalyst has good stability and a long operating period.

Example 3

A catalyst for ethanol dehydration to ethylene, the catalyst is a metal Mn ion modified SAPO-34 molecular sieve, namely Mn/SAPO-34, and the anhydrous chemical formula of the SAPO-34 molecular sieve is 1Al ₂ O ₃ ·1.06P ₂ O ₅ · 1.08 SiO ₂ .

A preparation method of a catalyst for ethanol dehydration to prepare ethylene, using morpholine as a template agent to introduce modified metal ions before molecular sieve crystallization by a direct synthesis method, the method steps are as follows:

(1) With silica sol (SiO ₂ mass fraction is 40%) as silicon source, pseudo-boehmite as aluminum source (Al ₂ O ₃ mass fraction is 70%), and orthophosphoric acid with a mass fraction of 85% as phosphorus source , morpholine as template, and water as solvent to synthesize SAPO-34 molecular sieve, each component and its molar ratio are 1Al ₂ O ₃ : 1.06P ₂ O ₅ : 1.08SiO ₂ : 3R: 66H ₂ O, wherein R is a template Morpholine agent, according to the ratio of silicon source, aluminum source, phosphorus source, template agent and solvent, with Mn(NO ₃ ) ₂ as a modifier, according to the metal ion load of 5%, weigh Mn(NO ₃ ) ₂ , and add deionized water to prepare a solution;

(2) Preparation of gel: under the condition of stirring, add phosphorus source, aluminum source, silicon source and template in sequence in the aqueous solution, adjust its pH value to 8 with ammonia water, add Mn(NO ₃ ) ₂ solution, Then add the finished SAPO-34 molecular sieve (commercially available, chemical formula 1Al ₂ O ₃ :0.4P ₂ O ₅ :0.8SiO ₂ ) as a crystallization directing agent, and the addition of the finished product SAPO-34 molecular sieve accounts for the amount of metal Mn ions prepared by theoretical calculation. 3% of the SAPO-34 molecular sieve weight in the modified SAPO-34 molecular sieve, the mixed solution is stirred evenly to form a gel crystallization liquid;

(3) Crystallization: transfer the crystallization solution to a stainless steel reaction kettle lined with polytetrafluoroethylene, and crystallize at 100°C for 90 hours;

(4) Post-treatment: the crystallized product is cooled in a natural state, filtered, washed to neutrality, and then dried at 140°C for 3 hours;

(5) Template release agent: the dried molecular sieve powder was calcined at 700° C. for 5 hours to remove the template agent to obtain the SAPO-34 molecular sieve Mn/SAPO-34 modified with metal Mn ions.

The obtained Mn/SAPO-34 is a large grain single crystal with a single crystal size of about 60 μm.

The metal Mn ion-modified SAPO-34 molecular sieve Mn/SAPO-34 prepared by the present embodiment and the unmodified SAPO-34 molecular sieve (the unmodified SAPO-34 molecular sieve and the metal Mn ion-modified SAPO-34 molecular sieve The preparation method is the same, except that it is not doped with Mn ions) In comparison, at 340 ° C and a mass space velocity of 2.2 h ^-1 , the unmodified SAPO-34 molecular sieve catalyzed ethanol dehydration conversion rate was 91.4%, and the ethylene selectivity was 62.8 %; The SAPO-34 molecular sieve Mn/SAPO-34 modified by metal Mn ions is used as a catalyst, the ethanol dehydration conversion rate is 97.6%, and the ethylene selectivity is 91.8%. It can be seen that the effect of SAPO-34 modified by metal Mn ions is obviously better than that of unmodified SAPO-34 molecular sieve.

Get the metal Mn ion-modified SAPO-34 molecular sieve Mn/SAPO-34 catalyst 250g that this embodiment prepares in the fluidized bed reactor, ethanol mass concentration is 30%, reaction condition: temperature is 340 ℃, mass space velocity is 2.1h ^-1 , the fluidization gas velocity is 0.6m/s, the reaction result: the ethanol conversion rate is 98.7%, the ethylene selectivity is 93.6%, other conditions remain unchanged, only the ethanol mass concentration is changed to 12%, and the ethanol conversion rate is obtained It is 98.3%, and the ethylene selectivity is 94.5%. It can be seen that when the SAPO-34 molecular sieve Mn/SAPO-34 modified by metal Mn ions is used as the catalyst, the ethanol mass concentration, that is, the water content of the raw material, has little influence on the reaction result.

Get the metal Mn ion-modified SAPO-34 molecular sieve Mn/SAPO-34 catalyst 250g that this embodiment prepares in the fluidized bed reactor, ethanol mass concentration is 12%, reaction condition: temperature is 320 ℃, mass space velocity is 2.1h ^-1 , the fluidization gas velocity is 0.6m/s, the reaction result: the ethanol conversion rate is 98.3%, and the ethylene selectivity is 94.5%. The composite modified catalyst has been operated continuously for 136 hours, and its catalytic activity has not changed significantly, which shows that this catalyst has good stability and a long operating period.

Claims (8)

1, a kind of producing ethylene from dehydration of ethanol catalyst is characterized in that, this catalyst is the SAPO-34 molecular sieve of metal M n ion modification, i.e. Mn/SAPO-34.

2, a kind of producing ethylene from dehydration of ethanol catalyst according to claim 1 is characterized in that, the anhydrous chemical formula of described SAPO-34 molecular sieve is 1Al ₂O ₃(0.1～5) P ₂O ₅(0.1～5) SiO ₂

3, a kind of producing ethylene from dehydration of ethanol Preparation of catalysts method is characterized in that, is that the template agent is introduced the modified metal ion by direct synthesis technique before the molecular sieve crystallization with the morphine quinoline, and this method step is as follows:

(1) be that silicon source, boehmite are that aluminium source, orthophosphoric acid are that phosphorus source, morphine quinoline are that template agent, water are the synthetic SAPO-34 molecular sieve of solvent with the Ludox, each component and mole proportioning thereof are 1Al ₂O ₃: (0.1～5) P ₂O ₅: (0.1～5) SiO ₂: (1～10) R: (1～100) H ₂O, wherein R is a template agent morphine quinoline, takes by weighing silicon source, aluminium source, phosphorus source, template agent and solvent according to proportion relation, with Mn (NO ₃) ₂Be modifier, take by weighing Mn (NO for (2～10) % according to the load capacity of metal ion ₃) ₂, and the adding deionized water is mixed with solution;

(2) preparation gel: under stirring condition, add phosphorus source, aluminium source, silicon source and template agent in order successively in the aqueous solution, regulating its pH value is 7～10, adds Mn (NO ₃) ₂Solution adds finished product SAPO-34 molecular sieve again as crystallization director, and mixed liquor is stirred forms the gel crystallization liquid;

(3) crystallization: crystallization liquid is transferred in the band teflon-lined stainless steel cauldron, at 80～200 ℃ of following crystallization 10～100h;

(4) post processing: crystallization product cools off under nature, filters, washs to neutrality, at 50～150 ℃ of down dry 0.5～10h;

(5) stripper plate agent: dried molecular screen primary powder is placed 400～800 ℃ of following roasting 0.5～10h, and removed template method obtains the SAPO-34 molecular sieve of metal M n ion modification.

4, a kind of producing ethylene from dehydration of ethanol Preparation of catalysts method according to claim 3 is characterized in that SiO in the described Ludox ₂Mass fraction is 40%.

5, a kind of producing ethylene from dehydration of ethanol Preparation of catalysts method according to claim 3 is characterized in that Al in the described boehmite ₂O ₃Mass fraction is 70%.

6, a kind of producing ethylene from dehydration of ethanol Preparation of catalysts method according to claim 3 is characterized in that, described orthophosphoric acid mass fraction is 85%.

7, a kind of producing ethylene from dehydration of ethanol Preparation of catalysts method according to claim 3, it is characterized in that 1～5% of the SAPO-34 molecular sieve weight in the SAPO-34 molecular sieve of the metal M n ion modification that the reasonable opinion of the addition of described finished product SAPO-34 molecular sieve is calculated.

8, a kind of producing ethylene from dehydration of ethanol catalyst according to claim 1, it is characterized in that, the SAPO-34 molecular sieve of described metal M n ion modification is used for the fluid bed producing ethylene from dehydration of ethanol as catalyst, and the ethanolic solution mass concentration is 5～100% in the fluid bed.