CN112675874A - For CO2Pd-Cu for preparing methanol by catalytic hydrogenation2Preparation method of O catalyst - Google Patents

Abstract

The invention discloses a method for preparing CO₂Pd-Cu for preparing methanol by catalytic hydrogenation₂The invention discloses a preparation method of an O catalyst, relates to the technical field of catalysts, and firstly utilizes CTAB and H₂PdCl₄Reacting with KI in water solution, adding ascorbic acid to prepare mixed solution containing Pd metal particles, and adding CuCl into the mixed solution containing Pd metal particles₂With alkali liquor to finally prepare Cu₂Pd-Cu of Yolk structure (Yolk-Shell) of O-coated Pd metal particles₂An O catalyst; the prepared Yolk structure (Yolk-Shell) Pd-Cu₂O catalyst, abbreviated as YS-Pd/Cu₂O, the appearance of the yolk is shown in figure 1 in an electron microscope picture, and the yolk has a yolk structure YS-Pd/Cu₂O in Cu⁺Under the action of (2), the surface adsorption of CO is favorably weakened₂C-O bond in (1) to form CO, which is then further reacted with H₂Hydrogenation reaction is carried out under the catalytic action of Pd to form methanol. In addition, the invention provides YS-Pd/Cu₂O catalyst, using Cu₂Yolk structure YS-Pd/Cu of O-coated Pd nanoparticles₂The O catalyst has more stable catalytic performance and longer service life.

Description

For CO2Pd-Cu for preparing methanol by catalytic hydrogenation2Preparation method of O catalyst

Technical Field

The invention relates to the technical field of catalysts for catalytic hydrogenation and quality improvement of biomass, in particular to a catalyst for CO₂Pd-Cu for preparing methanol by catalytic hydrogenation₂O catalyst preparation method.

Background

The excessive consumption of fossil fuels raises concerns about environmental issues and national energy safety, and thus, the demand for environmentally friendly and renewable alternative fuels is increasing. At present, CO₂As a widely-occurring carbon source, it plays an increasingly important role in the chemical industry and is one of promising renewable energy sources. To CO₂The catalytic hydrogenation is carried out to prepare high value-added chemical products such as methanol and the like, and the economic value is extremely high.

At present, CO₂The catalytic hydrogenation is carried out to prepare the methanol, and the catalytic reaction is carried out by a Pd/Cu/Zr ternary active catalyst, such as patent publications with publication numbers of CN109999833A and CN102091618A, but CO₂The conversion rate of the catalyst is very low and is not higher than 20 percent; Pd-Cu₂O catalysts are currently used mostly for acetylene hydrogenation, as disclosed in patent publication No. CN103977814B, which is used directly for CO₂The catalytic hydrogenation for preparing methanol can further improve CO₂The conversion rate of the catalyst is about 60 percent, but the yield of the methanol is less than 25 percent, the catalytic selectivity is low, in addition, the activity of the catalyst is unstable in the using process, the deactivation phenomenon appears shortly after the catalyst is used, and the catalyst needs to be replenished again.

Disclosure of Invention

The invention aims to provide a method for preparing CO₂Pd-Cu for preparing methanol by catalytic hydrogenation₂The preparation method of the O catalyst aims to solve the technical problem that the existing catalyst is low in conversion rate and selectivity.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

for CO₂Pd-Cu for preparing methanol by catalytic hydrogenation₂The preparation method of the O catalyst comprises the following steps:

(1) completely dissolving CTAB powder in deionized water to obtain a CTAB aqueous solution;

(2) adding H to the above CTAB aqueous solution₂PdCl₄Solution and KI solution, the H₂PdCl₄The molar ratio of the solution to KI is 1: 5-1: 8, the solution is stirred uniformly and then transferred into an oil bath at the temperature of 80-100 ℃, and stirring and heating are carried out for 5-10 min;

(3) adding ascorbic acid into the heated solution until the solution is brown;

(4) preserving the heat of the brown solution in an oil bath for 10-30 min, and taking out and naturally cooling;

(5) adding CuCl₂Adding the solution to the above cooled solution, CuCl₂And H₂PdCl₄At a molar ratio of 10: 1, and sequentially adding NaOH solution and NH₂Shaking the OH & HCl solution evenly, and standing at room temperature until the color of the solution becomes brownish green;

(6) centrifuging the brown green solution, collecting precipitate, centrifuging the precipitate with formaldehyde, washing for several times, and drying to obtain the Pd-Cu with yolk structure₂And (3) an O catalyst.

The invention firstly utilizes CTAB and H₂PdCl₄Reacting with KI in water solution, adding ascorbic acid to prepare mixed solution containing Pd metal particles, and adding CuCl into the mixed solution containing Pd metal particles₂With alkali liquor to finally prepare Cu₂Pd-Cu of Yolk structure (Yolk-Shell) of O-coated Pd metal particles₂An O catalyst; the prepared Yolk structure (Yolk-Shell) Pd-Cu₂O catalyst, abbreviated as YS-Pd/Cu₂O, the appearance of the yolk is shown in figure 1 in an electron microscope picture, and the yolk has a yolk structure YS-Pd/Cu₂O in Cu⁺Under the action of (2), the surface adsorption of CO is favorably weakened₂C-O bond in (1) to form CO, which is then further reacted with H₂Hydrogenation reaction is carried out under the catalytic action of Pd to form methanol.

Preferably, in the step (1), the ratio of the deionized water to the CTAB powder is 1 mL: 4-5 mg.

Further, in the step (2), H₂PdCl₄The concentration of the solution is 0.01mmol/L, the concentration of the KI solution is 0.1mmol/L, and CTAB aqueous solution and H₂PdCl₄The volume ratio of the solution is 20-30: 1.

Further, in the step (3), the concentration of the ascorbic acid solution is 0.1 mmol/L.

More preferably, in the step (5), CuCl₂The concentration of the solution is 0.1mmol/L, and the solution is diluted by 150-200 times before being added; the concentration of NaOH solution is 1mmol/L, NH₂The concentration of the OH & HCl solution was 1 mmol/L.

In particular, the yolk structure Pd-Cu prepared in the step (6)₂O catalyst, the loading of Pd is 1 wt%.

Compared with the prior art, the invention has the following beneficial effects:

1. the YS-Pd/Cu provided by the invention₂The synergistic effect of Pd and 1-valent Cu in the O catalyst is favorable for improving the catalytic activity, and the Pd-valent Cu catalyst is used in Cu⁺By the action of (2), CO is adsorbed on the surface of the catalyst₂C-O bond in the alloy is easily weakened by Cu + until the alloy is broken to form CO, and then the CO is further reacted with H₂Hydrogenation reaction is carried out under the catalytic action of Pd to form methanol.

2. The YS-Pd/Cu provided by the invention₂O catalyst, using Cu₂Yolk structure YS-Pd/Cu of O-coated Pd nanoparticles₂The O catalyst has more stable catalytic performance and longer service life;

3. the YS-Pd/Cu provided by the invention₂O catalyst, the raw material medicament is safe and easy to obtain, and is used for CO₂The catalytic hydrogenation for preparing the methanol has the advantages of relatively low cost, convenient process flow, simple operation, energy conservation and contribution to engineering popularization.

Drawings

FIG. 1 shows the yolk structure Pd-Cu prepared by the invention₂O catalyst transmission electron micrograph;

FIG. 2 shows the yolk structure Pd-Cu prepared by the present invention₂O catalyst and Pd-Cu of common structure₂O catalyst to CO₂A histogram of activity comparison results of catalytic hydrogenation to methanol;

FIG. 3 shows the yolk structure Pd-Cu prepared by the present invention₂O catalyst and Pd-Cu of common structure₂O catalyst to CO₂And comparing the stability of the activity of the methanol prepared by catalytic hydrogenation with the test result by a line chart.

Detailed Description

In order to make those skilled in the art better understand the technical solution of the present invention, the present invention is further described below with reference to various embodiments and the accompanying drawings, and the implementation manner of the present invention includes, but is not limited to, the following embodiments.

Example 1

The YS-Pd/Cu provided by the invention₂The preparation method of the O catalyst comprises the following steps:

(1) the glass containing 10mL of deionized water and 45mg of CTAB was sonicated until the CTAB powder was completely dissolved.

(2) To the above solution was added 0.5mL of H₂PdCl₄(concentration 0.01mmol/L) and 0.3mL of KI (concentration 0.1 mmol/L).

(3) The solution is stirred evenly. The vial was then placed in an oil bath at 95 ℃ and heated with gentle stirring for 5 min.

(4) After stirring under heating for 5min, 0.08mL of ascorbic acid at a concentration of 0.1mmol/L was added, and the solution turned brown, indicating the reduction of Pd ions to Pd metal particles.

(5) After 20min, the solution was removed from the oil bath and cooled for about 1h, which was designated as the Pd seed solution.

(6) 0.5mL of CuCl with a concentration of 0.1mmol/L₂Mixed with 94mL of deionized water for dilution and then added to 1.2mL of the Pd seed solution. 2.5mL of 1mmol/LNaOH and 2mL of 1mmol/LNH were added in succession₂OH & HCl, shake well. After standing at room temperature for 2h, the solution changed from brown to brownish green in color.

(7) The solution was centrifuged at 5000rpm for 10min and the product collected. The precipitate was redispersed in methanol and the centrifugal washing was repeated twice. Finally, drying the mixture to obtain the yolk structure YS-Pd/Cu with 1 wt% of Pd loading₂The transmission electron microscope picture of the O catalyst is shown in figure 1.

The obtained YS-Pd/Cu₂O catalysisAgent and conventional Pd/Cu with 1 wt% Pd loading on the market₂O catalyst for CO₂The catalytic hydrogenation is used for preparing methanol, and the operation steps are as follows:

20mg of the catalyst was charged in a straight tube quartz reactor having a diameter of 1cm, and heated to 280 ℃ for reaction. The gas flow at the inlet of the reactor was 100mL/min and the gas composition was 20% H₂，20％CO₂And 60% Ar. The gas components after the reaction were analyzed at the outlet of the reactor using a mass spectrometer.

As shown in FIG. 2, the yolk structure YS-Pd/Cu was compared₂O and ordinary 1 wt% Pd/CuO vs. CO₂The effect of catalytic hydrogenation can be seen from FIG. 2, in the yolk structure YS-Pd/Cu₂By catalysis of O, CO₂The conversion rate of (2) is up to 85%, wherein, CH₃The yield of OH reached 73%. Under the catalysis of common Pd/CuO, CO₂The conversion of (A) is only 58%, where CH₃The OH yield was only 23%. Demonstration of yolk structure YS-Pd/Cu₂O catalyst to CO₂The catalytic hydrogenation for preparing methanol has higher catalytic activity and selectivity.

As shown in FIG. 3, the yolk structure YS-Pd/Cu was compared₂O catalyst and ordinary Pd/Cu₂The O catalyst was compared for activity stability. Stability test was performed on each catalyst, yolk structure YS-Pd/Cu₂O catalyst and ordinary Pd/Cu₂The O catalysts were each tested for 20h activity. As can be seen from FIG. 3, the yolk structure YS-Pd/Cu was determined after 20h activity test₂The activity of the O catalyst is not reduced basically, and CO₂The conversion rate of the catalyst is kept above 80 percent, and the normal Pd/Cu₂After 20 hours, the deactivation phenomenon of the catalytic activity of the O catalyst is serious, and the catalytic activity is rapidly reduced after 6 hours of reaction. Cu₂The yolk structure of the O-coated Pd nano-particles is beneficial to the stability of the Pd particles, so that the catalyst has more stable activity and longer service life.

The above-mentioned embodiment is only one of the preferred embodiments of the present invention, and should not be used to limit the scope of the present invention, but all the insubstantial modifications or changes made within the spirit and scope of the main design of the present invention, which still solve the technical problems consistent with the present invention, should be included in the scope of the present invention.

Claims (6)

1. For CO₂Pd-Cu for preparing methanol by catalytic hydrogenation₂The preparation method of the O catalyst is characterized by comprising the following steps:

(1) completely dissolving CTAB powder in deionized water to obtain a CTAB aqueous solution;

(2) adding H to the above CTAB aqueous solution₂PdCl₄Solution and KI solution, the H₂PdCl₄The molar ratio of the solution to KI is 1: 5-1: 8, the solution is stirred uniformly and then transferred into an oil bath at the temperature of 80-100 ℃, and stirring and heating are carried out for 5-10 min;

(3) adding ascorbic acid into the heated solution until the solution is brown;

(4) preserving the heat of the brown solution in an oil bath for 10-30 min, and taking out and naturally cooling;

(5) adding CuCl₂Adding the solution to the above cooled solution, CuCl₂And H₂PdCl₄At a molar ratio of 10: 1, and sequentially adding NaOH solution and NH₂Shaking the OH & HCl solution evenly, and standing at room temperature until the color of the solution becomes brownish green;

(6) centrifuging the brown green solution, collecting precipitate, centrifuging the precipitate with formaldehyde, washing for several times, and drying to obtain the Pd-Cu with yolk structure₂And (3) an O catalyst.

2. The method according to claim 1, wherein the ratio of the deionized water to the CTAB powder added in step (1) is 1 mL/4-5 mg.

3. The method according to claim 2, wherein in the step (2), H is₂PdCl₄The concentration of the solution is 0.01mmol/L, the concentration of the KI solution is 0.1mmol/L, and the volume ratio of the CTAB aqueous solution to the H2PdCl4 solution is 20-30: 1.

4. The method according to claim 3, wherein the concentration of the ascorbic acid solution in the step (3) is 0.1 mmol/L.

5. The method according to claim 4, wherein in the step (5), CuCl is added₂The concentration of the solution is 0.1mmol/L, and the solution is diluted by 150-200 times before being added; the concentration of NaOH solution is 1mmol/L, NH₂The concentration of the OH & HCl solution was 1 mmol/L.

6. The method according to claim 5, wherein the yolk-structured Pd-Cu is prepared in step (6)₂O catalyst, the loading of Pd is 1 wt%.

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