WO2012151776A1 - Modified catalyst for producing methanol by catalytic hydrogenation of carbon dioxide and method for preparing same - Google Patents

Abstract

Provided is a modified catalyst for producing methanol by catalytic hydrogenation of carbon dioxide, which comprises components in mass ratio as CuO: ZnO: Al₂O₃: SiO₂: TiO₂=A: B: C: D: E, wherein A: B is between 1/5 and 5/1, C: (A+B) is between 1% and 10%, E: (A+B) is between 0.1% and 20%, and D: E is greater than or equal to zero. The catalyst is prepared by a coprecipitation method. The catalyst has better activity, stability and methanol selectivity as compared with the CuO-ZnO-Al₂O₃ catalyst having the same components mass ratio but free of SiO₂-TiO₂. The method can be performed conveniently with low cost and less pollution.

Description

[Inventive name formulated by ISA according to Rule 37.2] A modified catalyst for catalytic hydrogenation of carbon dioxide to methanol and preparation method thereof

Technical field

 The invention belongs to the technical field of catalysts, and relates to a novel auxiliary modified carbon dioxide catalytic hydrogenation methanol catalyst and a preparation method thereof.

 Background technique

With the accelerated development of industrialization, especially the rapid development of the petrochemical industry, the 'greenhouse effect' and 'ozone hole' caused by the excessive emission of carbon dioxide greenhouse gases have increasingly affected the harmony between mankind and nature. Wide range of concerns, 2009 The Copenhagen conference once again brought the world's attention to the greenhouse gas emissions. The random discharge of carbon dioxide gas not only causes serious environmental problems, but also causes serious waste of carbon resources. Catalytic hydrogenation of carbon dioxide can produce high value-added chemical products such as methanol, methane, formic acid, dimethyl ether, ethanol, etc. These products can be further converted to produce gasoline and other organic polymers, which can alleviate the current shortage of resources. It has multiple meanings such as chemical industry, environmental protection and economy.

Catalytic hydrogenation of carbon dioxide to methanol is currently a hot research topic. In 1923, the world's first methanol plant was established at BASF. The catalyst used was ZnO/Cr ₂ O ₃ , and the reaction conditions were 300 °C and 20 MPa. At present, the most active and highly selective CuO-ZnO-Al ₂ O ₃ catalyst has good activity and methanol selectivity at 200 °C. However, as the research progressed further, new high-efficiency catalysts and more gradual reaction conditions continued to emerge. The preparation technology of CuO-ZnO-Al ₂ O ₃ catalyst is constantly evolving. The ultrafine particle catalyst has the characteristics of high specific surface area, high dispersion, good thermal stability, high surface energy and many surface active points. The unique catalytic properties of conventional materials, while the ultra-fine catalyst has the characteristics of less by-products and high methanol selectivity. The carrier selection is more novel. Common carriers include ZrO ₂ , Al ₂ O ₃ , TiO ₂ , activated carbon (AC ), etc. Currently, catalysts using carbon nanotubes (CNTs) as carriers and composite carriers have appeared to exhibit higher Activity, methanol selectivity and thermal stability. At present, the research on the catalytic hydrogenation of carbon dioxide to copper-based catalysts mainly focuses on the further optimization and improvement of the preparation method. The purpose is to improve the activity of the catalyst, the selectivity and stability of the methanol, and improve the performance of the catalyst by adding additives. One of the goals pursued by the people.

The methanol synthesis catalyst involved in Chinese patent CN101690894A consists of LaCr _1-x Cu _x O ₃ , where x is the relative mole fraction of Cu as the main component, x = 0.1 to 0.9, and La : Cr : Cu = 1 : (1 x) : x , prepared by citric acid complexation-rapid combustion method.

The methanol synthesis catalyst involved in Chinese patent CN1660490 is composed of CuO/ZnO/Al ₂ O ₃ with a molar ratio of 6/3/1 and a certain amount of surfactant. It is prepared by coprecipitation or step precipitation.

The methanol synthesis catalyst involved in Chinese patent CN1329938, CuO/ZnO/Al ₂ O _{3 is} composed according to a certain ratio. In the preparation method, unlike the other methods, the preparation of the catalyst masterbatch is divided into two parts, one is made by coprecipitation method. The coprecipitation precursor containing copper, zinc and aluminum, and the second is a coprecipitation method for preparing copper and zinc coprecipitate precursors without aluminum.

The addition of surfactant to patent CN1660490 does not increase the adsorption of carbon dioxide, and the selectivity of methanol is not much improved. The patent CN1329938 is complicated in preparation method. Compared with the above two patents, the invention does not add surfactant or The preparation of the catalyst precursor in two parts requires only the addition of the promoter SiO ₂ -TiO ₂ , the preparation process is simple, the environmental pollution is small, and the cost is low.

 Summary of the invention

The invention provides a novel auxiliary modified carbon dioxide catalytic hydrogenation methanol catalyst and a preparation method thereof, and the catalyst is improved by adding a promoter SiO ₂ -TiO ₂ , and the technical problem is to improve catalyst activity and methanol selectivity. And the stability of the catalyst.

 The technical solution of the present invention is:

The carbon dioxide catalytic hydrogenation methanol catalyst of the present invention comprises the following mass fraction components: CuO : ZnO : Al ₂ O ₃ : SiO ₂ : TiO ₂ = A : B : C : D : E , A : B The mass ratio is between 1/5 and 5/1, the range of C is between 1 and 10% of the sum of A and B, and the range of D is between 0 and 20% of the sum of A and B. The range of E is between 0.1 and 20% of the sum of the amounts of A and B added, and D: E is mixed in any ratio.

 The preparation of the catalyst of the invention adopts a coprecipitation method and includes the following steps:

 Step 1: Dissolving copper, zinc, and aluminum nitrate in water to obtain a mixed solution having a concentration of 0.1 to 5 mol/L;

 Step 2: Configure oxalic acid ethanol solution or oxalic acid aqueous solution 0.1~3mol/L , wherein oxalic acid can be replaced by one of sodium carbonate, urea, potassium carbonate and ammonium carbonate.

 Step 3 Configure a mixed solution of tetra-n-butyl titanate and n-butanol 0.001~3mol/L : Weigh a certain amount of tetra-n-butyl titanate, or drip the weighed tetra-n-butyl titanate into 5~20ml of n-butanol to form a mixed solution, stir for 2~10 minutes, and let stand for 5~30 minute;

 Step 4 Weigh a certain amount of ethyl orthosilicate;

 Step 5: The aqueous oxalic acid solution of the step 2 is dropped into the mixed solution described in the step 1 under heating and stirring, and simultaneously dropped into the step 3 The mixed solution of tetra-n-butyl titanate and n-butanol and the ethyl orthosilicate described in step 4, the temperature of the solution in the reaction vessel is controlled at 50-80 ° C, heated, stirred, reacted for 4 hours, aged 1 After an hour, the precipitate precursor is filtered, washed, and the pH of the filtrate is controlled between 7 and 8, after which the filter cake is dried at 110 ° C for 24 hours and then at 3.0 ° C / min. The temperature is programmed to 350 ° C for 4 hours, to room temperature, grinding, tableting, crushing, and sieving to obtain a catalyst for catalytic hydrogenation of carbon dioxide to methanol.

The invention has the advantages and benefits that the catalyst for hydrogenation of carbon dioxide prepared by the method has the advantages of activity, methanol selectivity and stability, and is superior to the same proportion of CuO-ZnO-Al ₂ without adding SiO ₂ -TiO ₂ promoter. O ₃ catalyst meets energy saving and environmental protection requirements and is suitable for carbon dioxide and hydrogen to react at lower temperatures and pressures.

Patent CN101690894A The raw materials used in the preparation of the catalyst are expensive and pollute the environment. The surfactant added by the patent CN1660490 can not increase the adsorption of carbon dioxide, and the selectivity of methanol is not greatly improved. The patent CN1329938 is complicated in the preparation method, and the present invention and the above two patents In contrast, neither the surfactant is added nor the catalyst precursor is prepared for two parts, and only the promoter SiO ₂ -TiO ₂ can be added, the preparation process is simple, the environmental pollution is small, and the cost is low.

 detailed description

 Example 1

Weigh 22.76 g of Cu(NO ₃ ) ₂ ·3H ₂ O , 21.91 g of Zn(NO ₃ ) ₂ ·6H ₂ O , 11.03 g of Al(NO ₃ ) ₃ ·9H ₂ O, dissolved in 300 ml of water, and the solution is recorded as A. Liquid, weigh 32.06g H ₂ C ₂ O ₄ · 2H ₂ O dissolved in 150ml of water, the solution is recorded as B liquid, weighed 5.11g of tetra-n-butyl titanate dissolved in 10 ml of n-butanol, the solution is recorded as C In a solution, at 70 ° C and stirring, B is dropped into the solution A to coprecipitate, and the solution is added dropwise to the solution C to obtain a precipitate (1), which is reacted at 70 ° C for 4 hours under stirring, and allowed to stand for 1 hour. , filter, and then the obtained filter cake is dried at 110 ° C for 24 hours, programmed to 3.0 ° C / min to 350 ° C for 4 hours, cooled to room temperature, grinding, tableting, crushing, screening to obtain a certain particle size The particles are obtained by catalytic hydrogenation of carbon dioxide to a methanol catalyst.

 Example 2

Weigh 22.76 g of Cu(NO ₃ ) ₂ ·3H ₂ O , 21.91 g of Zn(NO ₃ ) ₂ ·6H ₂ O , 11.03 g of Al(NO ₃ ) ₃ ·9H ₂ O, dissolved in 300 ml of water, and the solution is recorded as A. Liquid, weighed 26.96g Na ₂ CO ₃ dissolved in 150ml water, the solution is recorded as B liquid, weighed 5.11g of tetra-n-butyl titanate dissolved in 10 ml of n-butanol, the solution is recorded as C liquid, at 70 ° C and Under stirring, B is dropped into the A solution and coprecipitated. At the same time, the solution C is added dropwise to obtain a precipitate (1). The reaction is carried out at 70 ° C for 4 hours under stirring, and allowed to stand for 1 hour, filtered, and then obtained. The filter cake is dried at 110 °C for 24 hours, heated to 350 °C at a temperature of 3.0 °C /min for 4 hours, and then cooled to room temperature. It is ground, compressed, crushed and sieved to obtain particles of a certain size. Hydrogenation to methanol catalyst.

 Example 3

Weigh 22.76 g of Cu(NO ₃ ) ₂ ·3H ₂ O , 21.91 g of Zn(NO ₃ ) ₂ ·6H ₂ O , 11.03 g of Al(NO ₃ ) ₃ ·9H ₂ O, dissolved in 300 ml of water, and the solution is recorded as A. Liquid, weigh 32.06g H ₂ C ₂ O ₄ · 2H ₂ O dissolved in 150ml water, the solution is recorded as B liquid, weigh 0.64g tetra-n-butyl titanate dissolved in 10 ml n-butanol, the solution is recorded as C For the solution, weigh 0.52 g of ethyl orthosilicate, and record it as D solution. At 70 °C and stirring, B is dropped into the solution A to coprecipitate, while dropping the solution C and D to obtain a precipitate (1 After reacting at 70 ° C for 4 hours with stirring, standing and aging for 1 hour, filtering, and then drying the obtained cake at 110 ° C for 24 hours, heating to 350 ° C for 3.0 hours at 3.0 ° C / min. , to room temperature, grinding, tableting, crushing, sieving to obtain particles of a certain size, that is, a catalyst for hydrogenation of carbon dioxide to methanol.

Table 1 : Catalytic properties of catalyst CuO-ZnO-Al ₂ O ₃ - SiO ₂ -TiO ₂ ( g · cat )

Catalyst : CuO-ZnO-Al ₂ O ₃ - SiO ₂ -TiO ₂ , CuO/ZnO/Al ₂ O ₃ / SiO ₂ -TiO ₂ =5/4/1/X (mass ratio, where X=0.001~0.2, m _SiO2 : m _TiO2 =0,1 ) .

Reaction conditions: T=260 °C, P=2.6Mpa, WHSV=3600 h ^-1 , H ₂ /CO ₂ =3/1 (volume ratio), and the temperature was reduced to 270 °C by 10% H ₂ /N ₂ before the reaction. 2 hours.

Promoters (wt.%)	CO 2 Conversion (%)	CH 3 OH Selectivity (%)	CO Selectivity (%)	CH 3 OH Yield (%)
Without	15.81	23.31	76.69	3.69
2 wt.% TiO 2	16.10	25.29	74.71	4.07
4 wt.% TiO 2	24.53	30.98	69.02	7.60
6 wt.% TiO 2	18.37	25.83	74.17	4.74
8 wt.% TiO 2	16.58	23.31	76.69	3.86
2 wt.% TiO 2 -SiO 2 m SiO2 : m TiO2 =1	40.70	41.17	58.83	16.76

Claims (1)

1 . A novel promoter-modified catalyst for catalytic hydrogenation of carbon dioxide to methanol, characterized in that: CuO : ZnO : Al ₂ O ₃ : SiO ₂ : TiO ₂ = A : B : C : D : E , wherein A : B mass ratio is between 1/5~5/1, C is 1~10% of the sum of A and B addition, D is 0~20% of the sum of A and B addition, E is A and The addition amount of B is 0.1~20%, and D: E is mixed in any ratio.

2. The method for preparing a catalyst according to claim 1, which is prepared by a coprecipitation method and comprises the following steps:

Step 1: dissolving copper, zinc, and aluminum nitrate in water to obtain a mixed solution having a concentration of 0.1 to 5 mol/L, and adding TiO ₂ and SiO ₂ according to the ratio of claim 1;

Step 2 : Dispose of oxalic acid aqueous solution 0.1~3mol/L;

Step 3: Configure a mixed solution of tetra-n-butyl titanate and n-butanol 0.001~3mol/L: tetra-n-butyl titanate or tetra-n-butyl titanate in 5~20ml A mixed solution is formed in n-butanol, stirred for 2 to 10 minutes, and allowed to stand for 5 to 30 minutes;

Step 4: Weighing orthosilicate;

Step 5: The aqueous oxalic acid solution of step 2 is dropped into the mixed solution of step 1 under heating and stirring, and simultaneously dropped into step 3 a mixed solution of tetra-n-butyl titanate and n-butanol and ethyl orthosilicate according to step 4, the temperature is controlled at 50-80 ° C, the reaction is 4 hours, and the aging is 1 After the hour, the precipitate precursor is filtered, washed, and the pH of the filtrate is controlled between 7 and 8. After that, the filtered catalyst precursor is dried; then the temperature is raised to 350 ° C at 3.0 ° C /min. After calcination for 4 hours, and then to room temperature, grinding, tableting, crushing, and sieving, a catalyst for catalytic hydrogenation of carbon dioxide to methanol is obtained.

3. The method of claim 2 The preparation method is characterized in that the oxalic acid is replaced with one of sodium carbonate, urea, potassium carbonate and ammonium carbonate.