CN102000578A - Catalyst for preparing methyl alcohol by carbon dioxide catalytic hydrogenation and preparing method thereof - Google Patents

Abstract

The invention discloses a catalyst for producing methanol through catalytic hydrogenation of carbon dioxide and a preparation method thereof, belonging to the technical field of catalysts. It is characterized in that the mass ratio of the carbon dioxide catalytic hydrogenation methanol catalyst components is: CuO:ZnO _{:Al 2} O ₃ :MgO=3:6:1:X (X=0.001-0.2), and it is prepared by a co-precipitation method. Preparation steps: (1) Dissolve the weighed nitrates of copper, zinc, aluminum and magnesium in absolute ethanol or water, and drop into the above mixed solution with oxalic acid ethanol solution or oxalic acid aqueous solution, heat and stir to prepare the catalyst precursor (2) drying the catalyst precursor, roasting at a certain temperature for a certain period of time, grinding, tableting, crushing, and sieving after cooling down to prepare a methanol catalyst for catalytic hydrogenation of carbon dioxide. The effect and benefit of the present invention are that compared with the CuO-ZnO-Al ₂ O ₃ catalyst with the same component mass ratio without MgO, it has better activity, stability and methanol selectivity, and the preparation method is simple, low in cost and less in pollution , is an efficient catalyst for catalytic hydrogenation of carbon dioxide to methanol.

Description

Catalyst and preparation method for catalytic hydrogenation of carbon dioxide to methanol

technical field

The invention belongs to the technical field of catalysts, and relates to a catalyst for methanol production by catalytic hydrogenation of carbon dioxide and a preparation method.

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 harmonious coexistence between human beings and nature, which has aroused worldwide concern. Wide range of concerns, the 2009 Copenhagen Conference once again focused the world's attention on 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 generate 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 , has multiple meanings in chemical industry, environmental protection and economy.

Catalytic hydrogenation of carbon dioxide to produce methanol is a current research focus. In 1923, the world's first methanol plant was established in BASF Corporation. The catalyst used was ZnO/Cr ₂ O ₃ , and the reaction conditions were 300°C and 20MPa. At present, the CuO-ZnO-Al ₂ O ₃ catalyst with high activity and high selectivity is used most, which has good activity and methanol selectivity at 200°C. However, with the further deepening of research, new high-efficiency catalysts and more moderate reaction conditions are constantly emerging. The preparation technology of CuO-ZnO-Al ₂ O ₃ catalyst is constantly being innovated. The ultra-fine 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 performance 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. The common carriers include ZrO ₂ , Al ₂ O ₃ , TiO ₂ , activated carbon (AC), etc. At present, catalysts using carbon nanotubes (CNTs) as carriers and composite carriers have appeared, showing higher activity, methanol selectivity and thermal stability. At present, the research on copper-based catalysts for the catalytic hydrogenation of carbon dioxide to methanol is mainly focused on the further optimization and improvement of the preparation method. one of the goals pursued by the authors.

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 is added, and is prepared by co-precipitation or step-by-step precipitation.

The methanol synthesis catalyst involved in the Chinese patent CN1329938 is composed of CuO/ZnO/Al ₂ O ₃ according to a certain ratio. The preparation method is different from other methods. The preparation of the catalyst masterbatch is divided into two parts. One is prepared by coprecipitation method Co-precipitation precursors containing copper, zinc, and aluminum, and the second is to prepare aluminum-free copper and zinc co-precipitation precursors by co-precipitation method.

The addition of surfactant in patent CN1660490 can not improve the adsorption of carbon dioxide, and the selectivity of methanol is not improved much. The two-part preparation of the catalyst precursor only needs to add the co-catalyst MgO, the preparation process is simple, the environmental pollution is small, and the cost is low.

Contents of the invention

The invention provides a catalyst for producing methanol by catalytic hydrogenation of carbon dioxide and a preparation method. The performance of the catalyst is improved by adding a co-catalyst MgO, and the technical problem to be solved is to improve the activity of the catalyst, the selectivity of methanol and the stability of the catalyst.

Technical scheme of the present invention is:

The methanol catalyst for catalytic hydrogenation of carbon dioxide according to the present invention includes the following components in mass fraction: CuO: ZnO: Al ₂ O ₃ : MgO=A: B: C: D, and the range of A: B is 1/5 ~5/1, C ranges from 1 to 10%, D ranges from 0.1 to 20%, CuO: 20 to 70% (W/W%), ZnO: 20 to 70% (W /W%), Al ₂ O ₃ : 5-10% (W/W%), MgO: 0.1-20% (W/W%).

The preparation of catalyst of the present invention adopts coprecipitation method, comprises the following steps:

Step (1): Dissolving the nitrates of copper, zinc, aluminum, and magnesium in absolute ethanol or water to obtain a mixed solution with a concentration of 0.1-5 mol/L, wherein the amount of magnesium oxide added is controlled between 0.1-20% ;

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

Step (3): Add the oxalic acid ethanol solution or oxalic acid aqueous solution in step (2) dropwise into the mixed solution in step (1) under the condition of heating and stirring. Ethanol is completely evaporated, if the solvent is water, react for 4 hours, age for 1 hour, then filter and wash the precipitate precursor, control the pH value of the filtrate between 7 and 8, dry the catalyst precursor at 110°C overnight, and then The temperature was programmed to 3.0°C/min to 350°C and roasted for 4 hours, cooled to room temperature, ground, pressed into tablets, crushed, and sieved to obtain a catalyst for catalytic hydrogenation of carbon dioxide to methanol.

The effects and benefits of the present invention are that the methanol catalyst for catalytic hydrogenation of carbon dioxide prepared by the method has better activity, methanol selectivity and stability than the CuO-ZnO-Al ₂ O ₃ catalyst in the same proportion without adding MgO additives, It meets the requirements of energy saving and environmental protection, and is suitable for the reaction of carbon dioxide and hydrogen at relatively low temperature and pressure.

Detailed ways

The specific implementation manner of the present invention will be described in detail below in conjunction with the technical solutions.

Example 1

Weigh 4.55g Cu(NO ₃ ) ₂ ·3H ₂ O, 10.95g Zn(NO ₃ ) ₂ ·6H ₂ O, 3.68gAl(NO ₃ ) ₃ ·9H ₂ O, 0.64gMg(NO ₃ ) ₂ ·6H ₂ O In 100ml of ethanol, the solution is called A solution, weigh 8.91g H ₂ C ₂ O ₄ ·H ₂ O and dissolve it in 50ml of ethanol, and the solution is called B solution. At 70°C and stirring, drop B solution into A Liquid co-precipitation reaction to obtain the precipitation solution (1), under 70 ° C and stirring conditions until the ethanol is completely evaporated, then the obtained catalyst precursor was dried at 110 ° C for 12 hours, and the temperature was raised to 350 °C at a rate of 3.0 ° C / min. Roasting at ℃ for 4 hours, lowering to room temperature, grinding, tableting, crushing, and sieving to obtain particles with a certain particle size, that is, a catalyst for catalytic hydrogenation of carbon dioxide to methanol is obtained.

Example 2

Weigh 4.55g Cu(NO ₃ ) ₂ ·3H ₂ O, 10.95g Zn(NO ₃ ) ₂ ·6H ₂ O, 3.68gAl(NO ₃ ) ₃ ·9H ₂ O, 0.64gMg(NO ₃ ) ₂ ·6H ₂ O In 100ml of water, the solution is called A solution, weigh 8.91g H ₂ C ₂ O ₄ ·H ₂ O and dissolve it in 50ml of water, and the solution is called B solution. At 70°C and stirring, drop B solution into A solution Precipitation reaction to obtain precipitation solution (1), react at 70°C for 4 hours under stirring conditions, age for 1 hour, then filter and wash the precipitated catalyst precursor obtained, control the pH value of the filtrate between 7 and 8, and filter Dry the cake at 110°C for 12 hours, heat up to 350°C with a program of 3.0°C/min and bake for 4 hours, then cool down to room temperature, grind, tablet, crush, and sieve to obtain particles of a certain size, that is, to obtain carbon dioxide catalytic hydrogenation Methanol catalyst.

Example 3

Weigh 4.55g Cu(NO ₃ ) ₂ ·3H ₂ O, 10.95g Zn(NO ₃ ) ₂ ·6H ₂ O, 3.68gAl(NO ₃ ) ₃ ·9H ₂ O, 0.64gMg(NO ₃ ) ₂ ·6H ₂ O In 100ml of water, the solution is called A solution, weigh 8.22g Na ₂ CO ₃ and dissolve it in 50ml of water, and the solution is called B solution. At 70°C and stirring, drop B solution into A solution for co-precipitation reaction to obtain a precipitation solution (1), react at 70°C under stirring conditions for 4 hours, age for 1 hour, then filter and wash the obtained catalyst precursor precipitation, control the pH value of the filtrate between 7 and 8, and dry the filter cake at 110°C Dry for 12 hours, heat up to 350°C at a rate of 3.0°C/min and roast for 4 hours, cool down to room temperature, grind, tablet, crush, and sieve to obtain particles with a certain particle size, and then obtain a catalyst for catalytic hydrogenation of carbon dioxide to methanol.

Example 4

Weigh 4.55g Cu(NO ₃ ) ₂ ·3H ₂ O, 10.95g Zn(NO ₃ ) ₂ ·6H ₂ O, 3.68gAl(NO ₃ ) ₃ ·9H ₂ O, 0.64gMg(NO ₃ ) ₂ ·6H ₂ O In 100ml of water, the solution is called A solution, weigh 11.12g K ₂ CO _{3 and} dissolve it in 50ml of water, and the solution is called B solution, at 70°C and under agitation, drop B solution into A solution for co-precipitation reaction to obtain a precipitation solution (1), react at 70°C under stirring conditions for 4 hours, age for 1 hour, then filter and wash the obtained catalyst precursor precipitation, control the pH value of the filtrate between 7 and 8, and dry the filter cake at 110°C Dry for 12 hours, heat up to 350°C at a rate of 3.0°C/min and roast for 4 hours, cool down to room temperature, grind, tablet, crush, and sieve to obtain particles with a certain particle size, and then obtain a catalyst for catalytic hydrogenation of carbon dioxide to methanol.

Attached table: Catalyst performance (g cat)

Catalyst: CuO-ZnO-Al ₂ O ₃ /MgO, CuO/ZnO/Al ₂ O ₃ /MgO=3/6/1/X (mass ratio, where X=0.001～0.2)

Reaction conditions: T = 195°C, P = 3.2MPa, SV = 3600h ^-1 , H ₂ /CO ₂ = 3:1 (volume ratio), use 10% H ₂ /N ₂ to program the temperature to 250°C before the reaction to reduce 2 Hour.

Claims (6)

1. the catalyst of a catalytic hydrogenation of carbon dioxide system methyl alcohol and preparation method is characterized in that: the constituent mass of described catalytic hydrogenation of carbon dioxide system catalyst for methanol is than being CuO: ZnO: Al ₂O ₃: MgO=A: B: C: D, the scope of its A: B is between 1/5～5/1, and the scope of C is between 1～10%, and the scope of D adopts coprecipitation to make between 0.1～20%.

2. the Preparation of catalysts method of a kind of catalytic hydrogenation of carbon dioxide system methyl alcohol according to claim 1 is characterized in that Preparation of Catalyst may further comprise the steps:

Step (1): the nitrate of copper, zinc, aluminium, magnesium is dissolved in absolute ethyl alcohol or the water, obtains the mixed solution that concentration is 0.1～5mol/L, wherein the addition of MgO is controlled between 0.1～20%;

Step (2): configuration oxalic acid ethanolic solution or oxalic acid aqueous solution 0.1～3mol/L, its mesoxalic acid can be used sodium carbonate, urea, potash, wherein a kind of replacement of carbonic acid ammonia;

Step (3): with the oxalic acid ethanolic solution of step (2) or oxalic acid aqueous solution under heating and stirring condition, splash in the mixed solution of step (1), temperature is controlled at 50～80 ℃, reaction is evaporated fully until ethanol, if solvent is a water, reacted 4 hours, aging 1 hour, then the sediment presoma is filtered, washing, control filtrate pH value is between 7～8, afterwards with the residual catalyst presoma or filter catalyst precursor put into oven drying and spend the night, with temperature programming to the 350 ℃ roasting of 3.0 ℃/min 4 hours, reduce to room temperature then, grind, compressing tablet, broken, screening promptly obtains catalytic hydrogenation of carbon dioxide system catalyst for methanol.

3. the catalyst of a kind of catalytic hydrogenation of carbon dioxide system methyl alcohol according to claim 1 is characterized in that described catalytic hydrogenation of carbon dioxide catalst for synthesis of methanol also comprises co-catalyst MgO, and its quality percentage composition is 0.1～20%.

4. the Preparation of catalysts method of a kind of catalytic hydrogenation of carbon dioxide system methyl alcohol according to claim 2 is characterized in that described carrier precipitation agent is aluminum nitrate/magnesium nitrate mixed solution 0.1～0.2mol/L.

5. the Preparation of catalysts method of a kind of catalytic hydrogenation of carbon dioxide system methyl alcohol according to claim 2 is characterized in that described precipitating reagent is that oxalic acid or sodium carbonate, potash, urea, carbonic acid ammonia are wherein a kind of.

6. the Preparation of catalysts method of a kind of catalytic hydrogenation of carbon dioxide system methyl alcohol according to claim 2, it is characterized in that 50～80 ℃ of co-precipitation, it is intact to continue to be stirred to ethanol evaporation after titration finishes, catalyst precursor 110 ℃ dry 12 hours down, with temperature programming to the 350 ℃ roasting of 3.0 ℃/min 4 hours.