CN1718277A - Catalyst and preparation method for carbon dioxide oxidation of ethane to ethylene - Google Patents

Abstract

The invention relates to a catalyst for oxidizing ethane to ethylene with carbon dioxide and a preparation method. The invention aims at the problem of low catalyst selectivity existing in the existing CO ₂ oxidizing ethane to ethylene technology, and prepares a supported catalyst with Cr as the main active component, containing Ce and Zr, and using γ-Al ₂ O ₃ as the carrier The catalyst is used for the catalytic reaction of _CO2 oxidizing ethane to produce ethylene, the ethane conversion rate is 41.34%-76.71%, and the ethylene selectivity can be increased to 96.02%-98.84%.

Description

Catalyst and preparation method for carbon dioxide oxidation of ethane to ethylene

Technical field:

The invention relates to a catalyst for oxidizing ethane to ethylene with carbon dioxide and a preparation method. The catalyst is a supported catalyst with Cr as the main active component, Ce and Zr, and gamma-Al ₂ O ₃ as the carrier.

Background technique:

Ethylene is a basic raw material for the chemical industry. At present, most of ethylene is produced by steam cracking. Since steam cracking consumes a lot of energy, it is of great significance to research and develop new ethylene production technology. Although the energy consumption of ethane dehydrogenation to ethylene using O ₂ as oxidant is less than that of steam cracking, but O ₂ has a strong oxidizing property and it is difficult to improve the selectivity of ethylene.

In recent years, the use of _CO2 to oxidize ethane to ethylene has attracted great attention both at home and abroad. Its reaction formula is as follows:

M.Bhasin et al. commented in the article "Dehydrogenation and oxydehydrogenation of paraffins toolfins" (Applied Catalysis A: General, 2001, Vol.221, pp.397-419), using CO _Oxidation of ethane to ethylene has low reaction temperature, It has many advantages such as not easy to coke, high ethylene selectivity, and not easy to generate C ₃ hydrocarbons and acetylene. In addition, the greenhouse gas _CO2 can be converted into useful CO during the reaction process, which is also very meaningful for reducing _CO2 emissions and protecting the environment.

At present, among the catalysts used for _CO2 oxidation of ethane to ethylene, Cr-based catalyst is a better system. Such as S.Wang et al. in "Dehydrogenation of ethane with carbon dioxide oversupported chromium oxide catalysts" (Applied Catalysis A: General, 2000, Vol.196, pp.1-8) and "Effect of promoters on catalytic performance of Cr/SiO ₂ catalysts in oxidative dehydrogenation of ethane with carbon dioxide” (Catalysis Letters, 2001, Vol.73, pp.107-111), using 8(wt)% Cr ₂ O ₃ /SiO ₂ as catalyst, at 650°C, CO ₂ Under the condition of: C ₂ H ₆ =5:1, the conversion rate of ethane was 56.1%, and the selectivity of ethylene was 92.9%. N.Mimura et al reported on "High-performance Cr/H-ZSM-5 catalysts for oxidative dehydrogenation of ethane to ethylene with CO ₂ as an oxidant" (Catalysis Communications, 2002, Vol.3, pp.257-262), Cr/ H-ZSM-5 (SiO ₂ /Al ₂ O ₃ =1900) catalyst under the conditions of 923K, CO ₂ : C ₂ H ₆ = 9: 1, the conversion rate of ethane was 68.2%, the selectivity of ethylene A result of 69.5%.

It can be seen from the existing reports that for the catalytic reaction of CO ₂ oxidizing ethane to ethylene, although Cr-based catalysts have good ethane conversion, they have low directional selectivity to ethylene. At the same time, due to the strong interaction between Cr and SiO ₂ , molecular sieve and other carriers, the active component Cr is easy to agglomerate during the reaction process, so that the activity of the catalyst decreases with the increase of reaction time. In the reaction of catalytic conversion of ethane to ethylene, the higher the selectivity of ethylene, the higher the utilization rate of carbon resources. Therefore, improving the activity of the catalyst, especially the directional selectivity of ethylene, is beneficial to CO ₂ oxidation of ethane to ethylene. process is of great significance.

Ce _(1-x) Zr _x O ₂ solid solution has good oxygen storage/release ability and oxidation-reduction performance, and it shows a good dispersion of noble metal active groups in the three-way catalyst for automobile exhaust purification loaded with noble metals. The role of points. But there is no report on dispersing Cr and preparing Cr/Ce _(1-x) Zr _x O ₂ /Al ₂ O ₃ catalyst.

Invention content:

The purpose of the present invention is to provide a catalyst and preparation method for oxidizing ethane to ethylene by _CO2 as an oxidant, and improve the directional selectivity to ethylene on the basis of improving the catalytic performance. Using this catalyst, ethane reacts with _CO2 to produce ethylene with high selectivity.

The present invention is a catalyst for carbon dioxide oxidation of ethane to ethylene, with Cr as the main active component and gamma- _Al2O3 as the supported catalyst, and its structural formula is as follows _:

Cr/Ce _(1-x) Zr _x O ₂ /Al ₂ O ₃ where x=0.1～0.9

The mass percent content of each component of the catalyst is: 1-15% of Cr, 2.5-50% of Ce _(1-x) Zr _x O ₂ (x=0.1-0.9), and the rest of γ-Al ₂ O ₃ .

The present invention also provides a method for preparing the above-mentioned catalyst, which is prepared by a step-by-step impregnation method, which is completed in two steps: composite carrier preparation and catalyst preparation, and the mass ratio of the raw materials used is: Cr(NO ₃ ) ₃ ·9H ₂ O:Ce (NO ₃ ) ₃ ·6H ₂ O:Zr(NO ₃ ) ₄ ·5H ₂ O:γ-Al ₂ O ₃ =(0.1～12):(0.1～8.9):(0.1～8.9):(3～22 ), the specific preparation process is as follows:

A: Preparation of composite carrier:

Mix the aqueous solutions of Ce(NO ₃ ) ₃ ·6H ₂ O and Zr(NO ₃ ) ₄ ·5H ₂ O evenly, impregnate them on the powdery γ-Al ₂ O ₃ support, dry and roast to make Ce _{( 1-x)} Zr _x O ₂ /Al ₂ O ₃ (x=0.1～0.9) composite carrier;

B: Preparation of catalyst:

The aqueous solution of Cr(NO ₃ ) ₃ 9H ₂ O is impregnated on the Ce _(1-x) Zr _x O ₂ /Al ₂ O ₃ composite support in step A, then dried and calcined to obtain Cr/Ce _{(1- x)} Zr _x O ₂ /Al ₂ O ₃ (x=0.1-0.9) catalyst.

In the above preparation process, in step A, the aqueous solutions of Ce(NO ₃ ) ₃ 6H ₂ O and Zr(NO ₃ ) ₄ 5H ₂ O are mixed evenly, and then impregnated in the powdery γ-Al ₂ O ₃ support 8-12 hours, dry at 90°C-110°C for 6-8 hours, and bake at 500°C for 4-6 hours to produce Ce _(1-x) Zr _x O ₂ /Al ₂ O ₃ (x =0.1～0.9) composite carrier;

In step B, dissolve Cr(NO ₃ ) ₃ .9H ₂ O in distilled water, and impregnate the Ce _(1-x) Zr _x O ₂ /Al ₂ O ₃ composite carrier obtained in step A for 8-12 hours, Dry at 90°C-110°C for 8-10 hours, bake at 400°C for 3-4 hours, and bake at 700°C for 5-6 hours to obtain Cr/Ce _(1-x) Zr _x O ₂ /Al ₂ O ₃ (x=0.1-0.9) catalyst.

In the above preparation method, the concentrations of the mixed aqueous solution of Ce(NO ₃ ) ₃ .6H ₂ O and Zr(NO ₃ ) ₄ .5H ₂ O and the aqueous solution of Cr(NO ₃ ) ₃ .9H ₂ O are different. Special requirements, subject to being able to immerse the γ-Al ₂ O ₃ support.

The invention adopts a step-by-step impregnation method to prepare the catalyst, and the last step of impregnation is the active component containing Cr. Because Cr is impregnated on the Ce _(1-x) Zr _x O ₂ /Al ₂ O ₃ composite carrier, which can weaken the strong interaction between Cr and Al ₂ O ₃ , improve the dispersion of active component Cr, and give full play to The catalytic activity of Cr. At the same time, it also has a good promotion effect on the oxidation performance of _CO2 .

The present invention can obtain a series of catalysts with different contents of active components, that is, the mass percentage range of the catalyst components is 1-15% Cr, Ce _(1-x) Zr _x O ₂ (x=0.1-0.9) is 2.5 ~50%, the rest is a Cr/Ce _(1-x) Zr _x O ₂ /Al ₂ O ₃ catalyst of γ-Al ₂ O ₃ . These catalysts can be used in the catalytic reaction of carbon dioxide oxidation of ethane to ethylene.

The catalyst of the present invention is used in the catalytic reaction of carbon dioxide to oxidize ethane to produce ethylene, and is evaluated on a normal-pressure micro-fixed-bed reaction device. Its reaction condition is: reaction temperature 500～750 ℃, reaction pressure 0.1Mpa (megapascal), reaction space velocity 2400～6000ml/g-cat h (milliliter/hour·gram catalyst), the raw material gas of reaction is molar ratio 0.125～0.25 C ₂ H ₆ /CO ₂ mixed gas and diluent gas (N ₂ ). The catalyst of the invention is used to carry out the catalytic reaction of _CO2 oxidizing ethane to produce ethylene, and the obtained ethane conversion rate is 41.34%-76.71%, and the ethylene selectivity is 96.02%-98.84%.

Through the evaluation of the catalytic reaction of carbon dioxide oxidation of ethane to ethylene, the Cr/Ce _(1-x) Zr _x O ₂ /Al ₂ O ₃ series catalysts prepared by the present invention have the following advantages:

① At a lower reaction temperature, the Cr/Ce _(1-x) Zr _x O ₂ /Al ₂ O ₃ catalyst prepared by the present invention has high directional selectivity to ethylene.

②Cr is impregnated on the Ce _(1-x) Zr _x O ₂ /Al ₂ O ₃ composite support, because the Ce _(1-x) Zr _x O ₂ solid solution has good oxygen storage/release capacity and oxidation-reduction performance , thereby weakening the strong interaction between Cr and _Al2O3 , improving the dispersion of active component Cr, giving full play to the _catalytic activity of Cr, and promoting the oxidation performance of _CO2 .

The effects of the present invention will be further described below in conjunction with examples.

Detailed ways:

Example 1

A 1 wt% Cr/10 wt% Ce _0.5 Zr _0.5 O ₂ /Al ₂ O ₃ catalyst was prepared. According to the preparation method of the present invention, the amount of raw materials used to prepare 5 grams of catalyst is as shown in Table 1. Weigh 0.73 grams of analytically pure Ce(NO ₃ ) ₃ ·6H ₂ O and 0.73 grams of analytically pure Zr(NO ₃ ) ₄ ·5H ₂ O, dissolve them in 5ml of distilled water, mix them evenly and impregnate them in 4.45 grams of γ- Al ₂ O ₃ powder, placed at room temperature for 8 hours, dried at 90°C for 6 hours, and calcined at 500°C for 4 hours to make a Ce _0.5 Zr _0.5 O ₂ /Al ₂ O ₃ composite carrier; then weighed 0.38 grams of analytically pure Cr (NO ₃ ) ₃ ·9H ₂ O was dissolved in 5ml of distilled water, impregnated in Ce _0.5 Zr _0.5 O ₂ /Al ₂ O ₃ composite carrier, left at room temperature for 12 hours, dried at 110°C for 10 hours, and calcined at 400°C for 4 hours, and then _calcined at 700°C for 6 _hours to prepare a 1wt%Cr/ _10wt % _Ce0.5Zr0.5O2 / _Al2O3 catalyst.

The evaluation results of the catalysts for _CO2 oxidation of ethane to ethylene are listed in Table 2.

Example 2

A 2 wt% Cr/10 wt% Ce _0.5 Zr _0.5 O ₂ /Al ₂ O ₃ catalyst was prepared. According to the preparation method of the present invention, the amount of raw materials used to prepare 5 grams of catalyst is as shown in Table 1. Weigh 0.73 grams of analytically pure Ce(NO ₃ ) ₃ ·6H ₂ O and 0.73 grams of analytically pure Zr(NO ₃ ) ₄ ·5H ₂ O, dissolve them in 5ml of distilled water, mix them evenly and impregnate them in 4.40 grams of γ- Al ₂ O ₃ powder, placed at room temperature for 12 hours, dried at 110°C for 8 hours, and calcined at 500°C for 6 hours to make a Ce _0.5 Zr _0.5 O ₂ /Al ₂ O ₃ composite carrier; then weighed 0.77 grams of analytically pure Cr (NO ₃ ) ₃ ·9H ₂ O was dissolved in 5ml of distilled water, impregnated in Ce _0.5 Zr _0.5 O ₂ /Al ₂ O ₃ composite carrier, left at room temperature for 8 hours, dried at 90°C for 8 hours, and calcined at 400°C for 3 2wt%Cr/10wt%Ce _0.5 Zr _0.5 O ₂ /Al ₂ O ₃ catalyst was prepared by calcining at 700°C for 5 hours. The evaluation results of the catalysts for _CO2 oxidation of ethane to ethylene are listed in Table 2.

Example 3

A 4 wt% Cr/10 wt% Ce _0.5 Zr _0.5 O ₂ /Al ₂ O ₃ catalyst was prepared. According to the preparation method of the present invention, the amount of raw materials used to prepare 5 grams of catalyst is as shown in Table 1. Weigh 0.73 grams of analytically pure Ce(NO ₃ ) ₃ ·6H ₂ O and 0.73 grams of analytically pure Zr(NO ₃ ) ₄ ·5H ₂ O, dissolve them in 5ml of distilled water, mix them uniformly and impregnate them in 4.30 grams of γ- Al ₂ O ₃ powder, placed at room temperature for 10 hours, dried at 100°C for 7 hours, and calcined at 500°C for 5 hours to make a Ce _0.5 Zr _0.5 O ₂ /Al ₂ O ₃ composite carrier; then weighed 1.54 grams of analytically pure Cr (NO ₃ ) ₃ ·9H ₂ O was dissolved in 5ml of distilled water, impregnated in Ce _0.5 Zr _0.5 O ₂ /Al ₂ O ₃ composite carrier, left at room temperature for 11 hours, dried at 100°C for 10 hours, and calcined at 400°C for 4 4wt%Cr/10wt%Ce _0.5 Zr _0.5 O ₂ /Al ₂ O ₃ catalyst was prepared by calcining at 700°C for 5 hours. The evaluation results of the catalysts for _CO2 oxidation of ethane to ethylene are listed in Table 2.

Example 4

A 6 wt% Cr/10 wt% Ce _0.5 Zr _0.5 O ₂ /Al ₂ O ₃ catalyst was prepared. According to the preparation method of the present invention, the amount of raw materials used to prepare 5 grams of catalyst is as shown in Table 1. Weigh 0.73 grams of analytically pure Ce(NO ₃ ) ₃ 6H ₂ O and 0.73 grams of analytically pure Zr(NO ₃ ) ₄ 5H ₂ O, dissolve them in 5ml of distilled water, mix them evenly and impregnate them in 4.20 grams of γ-Al ₂ O ₃ powder, placed at room temperature for 12 hours, dried at 90°C for 6 hours, and calcined at 500°C for 5 hours to make a Ce _0.5 Zr _0.5 O ₂ /Al ₂ O ₃ composite support; then weighed 2.31 grams of analytically pure Cr ( NO ₃ ) ₃ ·9H ₂ O was dissolved in 5ml of distilled water, impregnated in Ce _0.5 Zr _0.5 O ₂ /Al ₂ O ₃ composite carrier, left at room temperature for 12 hours, dried at 110°C for 5 hours, and calcined at 400°C for 3 hours , and calcined at 700°C for 5 hours to prepare a 6wt%Cr/10wt%Ce _0.5 Zr _0.5 O ₂ /Al ₂ O ₃ catalyst. The evaluation results of the catalysts for _CO2 oxidation of ethane to ethylene are listed in Table 2.

Example 5

A 10 wt% Cr/10 wt% Ce _0.5 Zr _0.5 O ₂ /Al ₂ O ₃ catalyst was prepared. According to the preparation method of the present invention, the amount of raw materials used to prepare 5 grams of catalyst is as shown in Table 1. Weigh 0.73 grams of analytically pure Ce(NO ₃ ) ₃ 6H ₂ O and 0.73 grams of analytically pure Zr(NO ₃ ) ₄ 5H ₂ O, dissolve them in 5ml of distilled water, mix them evenly and impregnate them in 4.00 grams of γ-Al ₂ O ₃ powder, placed at room temperature for 12 hours, dried at 90°C for 5 hours, and calcined at 500°C for 4 hours to make a Ce _0.5 Zr _0.5 O ₂ /Al ₂ O ₃ composite support; then weighed 3.85 grams of analytically pure Cr ( NO ₃ ) ₃ ·9H ₂ O was dissolved in 6ml of distilled water, impregnated in Ce _0.5 Zr _0.5 O ₂ /Al ₂ O ₃ composite carrier, left at room temperature for 11 hours, dried at 110°C for 10 hours, and calcined at 400°C for 4 hours , and calcined at 700°C for 5 hours to prepare a 10wt%Cr/10wt%Ce _0.5 Zr _0.5 O ₂ /Al ₂ O ₃ catalyst. The evaluation results of the catalysts for _CO2 oxidation of ethane to ethylene are listed in Table 2.

Example 6

A 15 wt% Cr/10 wt% Ce _0.5 Zr _0.5 O ₂ /Al ₂ O ₃ catalyst was prepared. According to the preparation method of the present invention, the amount of raw materials used to prepare 5 grams of catalyst is as shown in Table 1. Weigh 0.73 grams of analytically pure Ce(NO ₃ ) ₃ 6H ₂ O and 0.73 grams of analytically pure Zr(NO ₃ ) ₄ 5H ₂ O, dissolve them in 4ml of distilled water, mix well and impregnate in 3.75 grams of γ-Al ₂ O ₃ powder, placed at room temperature for 10 hours, dried at 110°C for 5 hours, and calcined at 500°C for 4 hours to make a Ce _0.5 Zr _0.5 O ₂ /Al ₂ O ₃ composite support; then weighed 5.77 grams of analytically pure Cr( NO ₃ ) ₃ ·9H ₂ O was dissolved in 6ml of distilled water, impregnated in Ce _0.5 Zr _0.5 O ₂ /Al ₂ O ₃ composite carrier, left at room temperature for 10 hours, dried at 110°C for 8 hours, and calcined at 400°C for 3 hours , and calcined at 700°C for 6 hours to prepare a 15wt%Cr/10wt%Ce _0.5 Zr _0.5 O ₂ /Al ₂ O ₃ catalyst. The evaluation results of the catalysts for _CO2 oxidation of ethane to ethylene are listed in Table 2.

Example 7

A 6 wt% Cr/2.5 wt% Ce _0.9 Zr _0.1 O ₂ /Al ₂ O ₃ catalyst was prepared. According to the preparation method of the present invention, the amount of raw materials used to prepare 5 grams of catalyst is as shown in Table 1. Weigh 0.29 grams of analytically pure Ce(NO ₃ ) ₃ ·6H ₂ O and 0.03 grams of analytically pure Zr(NO ₃ ) ₄ ·5H ₂ O, dissolve them in 5ml of distilled water, mix well and impregnate in 4.58 grams of γ-Al ₂ O ₃ powder, placed at room temperature for 12 hours, dried at 110°C for 5 hours, and calcined at 500°C for 4 hours to make a Ce _0.9 Zr _0.1 O ₂ /Al ₂ O ₃ composite support; then weighed 2.31 grams of analytically pure Cr( NO ₃ ) ₃ ·9H ₂ O was dissolved in 5ml of distilled water, impregnated in Ce _0.9 Zr _0.1 O ₂ /Al ₂ O ₃ composite carrier, left at room temperature for 11 hours, dried at 110°C for 8 hours, and calcined at 400°C for 4 hours , and calcined at 700°C for 5 hours to prepare a 6wt%Cr/2.5wt%Ce _0.9 Zr _0.1 O ₂ /Al ₂ O ₃ catalyst. The evaluation results of the catalysts for _CO2 oxidation of ethane to ethylene are listed in Table 2.

Example 8

A 6 wt% Cr/5 wt% Ce _0.7 Zr _0.3 O ₂ /Al ₂ O ₃ catalyst was prepared. According to the preparation method of the present invention, the amount of raw materials used to prepare 5 grams of catalyst is as shown in Table 1. Weigh 0.48 grams of analytically pure Ce(NO ₃ ) ₃ ·6H ₂ O and 0.20 grams of analytically pure Zr(NO ₃ ) ₄ ·5H ₂ O, dissolve them in 5ml of distilled water, mix well and impregnate in 4.45 grams of γ-Al ₂ O ₃ powder, placed at room temperature for 11 hours, dried at 90°C for 8 hours, and calcined at 500°C for 5 hours to prepare a Ce _0.7 Zr _0.3 O ₂ /Al ₂ O ₃ composite support; then weighed 2.31 grams of analytically pure Cr( NO ₃ ) ₃ ·9H ₂ O was dissolved in 5ml of distilled water, impregnated in Ce _0.7 Zr _0.3 O ₂ /Al ₂ O ₃ composite carrier, left at room temperature for 12 hours, dried at 110°C for 8 hours, and calcined at 400°C for 3 hours , and calcined at 700°C for 5 hours to prepare a 6wt%Cr/5wt%Ce _0.7 Zr _0.3 O ₂ /Al ₂ O ₃ catalyst. The evaluation results of the catalysts for _CO2 oxidation of ethane to ethylene are listed in Table 2.

Example 9

A 6 wt% Cr/25 wt% Ce _0.3 Zr _0.7 O ₂ /Al ₂ O ₃ catalyst was prepared. According to the preparation method of the present invention, the amount of raw materials used to prepare 5 grams of catalyst is as shown in Table 1. Weigh 1.18 grams of analytically pure Ce(NO ₃ ) ₃ 6H ₂ O and 2.72 grams of analytically pure Zr(NO ₃ ) ₄ 5H ₂ O, dissolve them in 6ml of distilled water, mix well and impregnate in 3.45 grams of γ-Al ₂ O ₃ powder, placed at room temperature for 10 hours, dried at 110°C for 6 hours, and calcined at 500°C for 4 hours to make a Ce _0.3 Zr _0.7 O ₂ /Al ₂ O ₃ composite support; then weighed 2.31 grams of analytically pure Cr( NO ₃ ) ₃ ·9H ₂ O was dissolved in 5ml of distilled water, impregnated in Ce _0.3 Zr _0.7 O ₂ /Al ₂ O ₃ composite carrier, left at room temperature for 12 hours, dried at 90°C for 12 hours, and calcined at 400°C for 4 hours , and calcined at 700°C for 5 hours to prepare a 6wt%Cr/25wt%Ce _0.3 Zr _0.7 O ₂ /Al ₂ O ₃ catalyst. The evaluation results of the catalysts for _CO2 oxidation of ethane to ethylene are listed in Table 2.

Example 10

A 6 wt% Cr/50 wt% Ce _0.1 Zr _0.9 O ₂ /Al ₂ O ₃ catalyst was prepared. According to the preparation method of the present invention, the amount of raw materials used to prepare 5 grams of catalyst is as shown in Table 1. Weigh 0.85 grams of analytically pure Ce(NO ₃ ) ₃ ·6H ₂ O and 7.54 grams of analytically pure Zr(NO ₃ ) ₄ ·5H ₂ O, dissolve them in 8ml of distilled water, mix them evenly and impregnate them in 2.20 grams of γ-Al ₂ O ₃ powder, placed at room temperature for 12 hours, dried at 90°C for 6 hours, and calcined at 500°C for 4 hours to prepare a Ce _0.1 Zr _0.9 O ₂ /Al ₂ O ₃ composite support; then weighed 2.31 grams of analytically pure Cr( NO ₃ ) ₃ ·9H ₂ O was dissolved in 4ml of distilled water, impregnated in Ce _0.1 Zr _0.9 O ₂ /Al ₂ O ₃ composite carrier, left at room temperature for 12 hours, dried at 110°C for 10 hours, and calcined at 400°C for 4 hours , and calcined at 700°C for 5 hours to prepare a 6wt%Cr/50wt%Ce _0.1 Zr _0.9 O ₂ /Al ₂ O ₃ catalyst. The evaluation results of the catalysts for _CO2 oxidation of ethane to ethylene are listed in Table 2.

Table 1 shows the amount of raw materials used in the Cr/Ce _(1-x) Zr _x O ₂ /Al ₂ O ₃ (x=0.1-0.9) series catalysts of the present invention.

Table 2 is the evaluation results of the catalysts of Examples 1-10 used in the catalytic reaction of CO ₂ oxidation of ethane to ethylene. It can be seen from Table 2 that the Cr/Ce _(1-x) Zr _x O ₂ /Al ₂ O ₃ (x=0.1-0.9) series catalysts of the present invention have excellent ethylene orientation selectivity.

Table 1 Example metal nitrate Mass of nitrate (g) Mass of Al ₂ O ₃ (g) Catalyst composition 1 Cr(NO ₃ ) ₃ 9H ₂ O 0.38 4.45 1wt% _Cr / _10wt % _{Ce0.5Zr0.5O2 / Al2O3} Ce(NO ₃ ) ₃ 6H ₂ O 0.73 Zr(NO ₃ ) ₄ 5H ₂ O 0.73 2 Cr(NO ₃ ) ₃ 9H ₂ O 0.77 4.40 2wt% Cr/10wt% Ce _0.5 Zr _0.5 O ₂ /Al ₂ O ₃ Ce(NO ₃ ) ₃ 6H ₂ O 0.73 Zr(NO ₃ ) ₄ 5H ₂ O 0.73 3 Cr(NO ₃ ) ₃ 9H ₂ O 1.54 4.30 4wt% Cr/10wt% Ce _0.5 Zr _0.5 O ₂ /Al ₂ O ₃ Ce(NO ₃ ) ₃ 6H ₂ O 0.73 Zr(NO ₃ ) ₄ 5H ₂ O 0.73 4 Cr(NO ₃ ) ₃ 9H ₂ O 2.31 4.20 6wt% Cr/10wt% Ce _0.5 Zr _0.5 O ₂ /Al ₂ O ₃ Ce(NO ₃ ) ₃ 6H ₂ O 0.73 Zr(NO ₃ ) ₄ 5H ₂ O 0.73 5 Cr(NO ₃ ) ₃ 9H ₂ O 3.85 4.00 10wt% Cr/10wt% Ce _0.5 Zr _0.5 O ₂ /Al ₂ O ₃ Ce(NO ₃ ) ₃ 6H ₂ O 0.73 Zr(NO ₃ ) ₄ 5H ₂ O 0.73 6 Cr(NO ₃ ) ₃ 9H ₂ O 5.77 3.75 15wt% Cr/10wt% Ce _0.5 Zr _0.5 O ₂ /Al ₂ O ₃ Ce(NO ₃ ) ₃ 6H ₂ O 0.73 Zr(NO ₃ ) ₄ 5H ₂ O 0.73 7 Cr(NO ₃ ) ₃ 9H ₂ O 2.31 4.58 _6wt %Cr/ _2.5wt % _{Ce0.9Zr0.1O2 / Al2O3} Ce(NO ₃ ) ₃ 6H ₂ O 0.29 Zr(NO ₃ ) ₄ 5H ₂ O 0.03 8 Cr(NO ₃ ) ₃ 9H ₂ O 2.31 4.45 _6wt %Cr/ _5wt % _{Ce0.7Zr0.3O2 / Al2O3} Ce(NO ₃ ) ₃ 6H ₂ O 0.48 Zr(NO ₃ ) ₄ 5H ₂ O 0.20 9 Cr(NO ₃ ) ₃ 9H ₂ O 2.31 3.45 6wt%Cr/ _{25wt % Ce0.3Zr0.7O3 / Al2O3} Ce(NO ₃ ) ₃ 6H ₂ O 1.18 Zr(NO ₃ ) ₄ 5H ₂ O 2.72 10 Cr(NO ₃ ) ₃ 9H ₂ O 2.31 2.20 6wt% Cr/50wt% Ce _0.1 Zr _0.9 O ₂ /Al ₂ O ₃ Ce(NO ₃ ) ₃ 6H ₂ O 0.85 Zr(NO ₃ ) ₄ 5H ₂ O 7.54

Table 2 Example Catalyst composition Reaction temperature (°C) Ethane/CO ₂ (molar ratio) Reaction space velocity (ml/g-cath) Conversion rate of ethane (mol%) Ethylene selectivity (mol%) Yield of ethylene (mol%) 1 1wt% _Cr / _10wt % _{Ce0.5Zr0.5O2 / Al2O3} 700 0.25 6000 41.34 96.94 40.05 2 2wt% Cr/10wt% Ce _0.5 Zr _0.5 O ₂ /Al ₂ O ₃ 700 0.25 6000 43.09 96.98 41.79 3 4wt% Cr/10wt% Ce _0.5 Zr _0.5 O ₂ /Al ₂ O ₃ 700 0.25 6000 49.48 96.62 47.81 4 6wt% Cr/10wt% Ce _0.5 Zr _0.5 O ₂ /Al ₂ O ₃ 700 0.25 6000 56.72 98.84 56.06 5 10wt% Cr/10wt% Ce _0.5 Zr _0.5 O ₂ /Al ₂ O ₃ 700 0.25 6000 51.35 96.42 49.51 6 15wt% Cr/10wt% Ce _0.5 Zr _0.5 O ₂ /Al ₂ O ₃ 700 0.25 6000 50.21 96.35 48.38 7 _6wt %Cr/ _2.5wt % _{Ce0.9Zr0.1O2 / Al2O3} 650 0.125 4000 48.16 96.21 46.33 8 _6wt %Cr/ _5wt % _{Ce0.7Zr0.3O2 / Al2O3} 680 0.125 4000 51.63 96.34 49.74 9 6wt%Cr/ _{25wt % Ce0.3Zr0.7O2 / Al2O3} 720 0.167 2500 69.68 96.64 67.34 10 6wt% Cr/50wt% Ce _0.1 Zr _0.9 O ₂ /Al ₂ O ₃ 750 0.167 2500 76.71 96.02 73.66

Claims (3)

1. a kind of catalyst that is used for carbon dioxide oxidizing ethane to make ethylene is a kind of with Cr as main active component, with gamma-Al ₂ O ₃ is the supported catalyst of support, and its structural formula is as follows: Cr/Ce _(1-x) Zr _x O ₂ /Al ₂ O ₃ where x=0.1～0.9 The mass percent content of each component of the catalyst is: 1-15% of Cr, 2.5-50% of Ce _(1-x) Zr _x O ₂ (x=0.1-0.9), and the rest of γ-Al ₂ O ₃ . 2. A preparation method of the catalyst according to claim 1, which is completed in two steps of composite carrier preparation and catalyst preparation, and the mass ratio of the raw materials used is: Cr(NO ₃ ) ₃ 9H ₂ O: Ce(NO ₃ ) ₃ 6H ₂ O: Zr(NO ₃ ) ₄ ·5H ₂ O: γ-Al ₂ O ₃ =(0.1～12):(0.1～8.9):(0.1～8.9):(3～22), the specific steps are as follows: A: Preparation of composite carrier: Mix the aqueous solutions of Ce(NO ₃ ) ₃ ·6H ₂ O and Zr(NO ₃ ) ₄ ·5H ₂ O evenly, impregnate them on the powdery γ-Al ₂ O ₃ support, dry and roast to make Ce _{( 1-x)} Zr _x O ₂ /Al ₂ O ₃ composite support; B: Preparation of catalyst: The aqueous solution of Cr(NO ₃ ) ₃ 9H ₂ O is impregnated on the Ce _(1-x) Zr _x O ₂ /Al ₂ O ₃ composite support in step A, then dried and calcined to obtain Cr/Ce _{(1 -x)} Zr _x O ₂ /Al ₂ O ₃ (x=0.1-0.9) catalyst. 3. The preparation method according to claim 2, characterized in that: in step A, the aqueous solution of Ce(NO ₃ ) ₃ ·6H ₂ O and Zr(NO ₃ ) ₄ ·5H ₂ O is mixed evenly, and then impregnated in the powder γ-Al ₂ O ₃ support for 8 to 12 hours, dried at 90°C to 110°C for 6 to 8 hours, and calcined at 500°C for 4 to 6 hours to produce Ce _(1-x) Zr _x O ₂ /Al ₂ O ₃ (x=0.1～0.9) composite support; in step B, dissolve Cr(NO ₃ ) ₃ 9H ₂ O in distilled water, and impregnate Ce _(1-x) Zr _x O ₂ obtained in step A /Al ₂ O ₃ composite carrier for 8 to 12 hours, dried at 90°C to 110°C for 8 to 10 hours, calcined at 400°C for 3 to 4 hours, and calcined at 700°C for 5 to 6 hours to obtain Cr/Ce _{(1 -x)} A catalyst of Zr _x O ₂ /Al ₂ O ₃ (x=0.1 to 0.9).