Enhanced catalyst for hydrogenation of carbon dioxide to methanol

Abstract

An enhanced catalyst for the hydrogenation of carbon dioxide to methanol comprises a copper-zinc oxide catalyst supported on an alumina support and at least one accelerator selected from the group consisting of manganese, niobium and zirconium wherein the catalyst is activated prior to use in a process for the hydrogenation of carbon dioxide to methanol.

Description

Technical Field

[0001] The present invention relates to a catalyst, particularly a catalyst for hydrogenating carbon dioxide to methanol. Background Art

[0002] Traditionally, methanol has been commercially produced by reacting carbon monoxide and hydrogen over a catalyst, which is typically a mixture of copper and zinc oxides supported on alumina.

[0003] CO + 2H2 → CH3OH

[0004] Another method is to use carbon dioxide instead, using Cu / ZnO / silica as the catalyst, which has the additional benefit of utilizing carbon emissions and increasing the carbon compensation effort.

[0005] CO2 + 3H2 → CH3OH + H2O

[0006] However, the disadvantage of the above-mentioned another method is the low yield, less than 1%. Although attempts have been made to increase the yield, such as using a promoted Cu / Zn catalyst supported on silica (SBA-15), which can increase the yield to about 19%, but SBA-15 cannot be recycled, which results in very poor catalytic performance and high implementation cost.

[0007] Therefore, an object of the present invention is to provide a catalyst suitable for hydrogenating carbon dioxide to methanol, which overcomes at least some of the above problems. Summary of the Invention

[0008] In one aspect of the present invention, there is provided an enhanced catalyst for hydrogenating carbon dioxide to methanol, comprising:

[0009] a copper-zinc oxide catalyst supported on an alumina carrier; and

[0010] at least one promoter;

[0011] characterized in that the promoter is added to the copper-zinc oxide catalyst in an amount of up to 1% by weight to form a promoted copper-zinc oxide catalyst on the alumina carrier.

[0012] In one embodiment, the promoted copper-zinc oxide catalyst is activated for 1 to 7 hours in the range of a hydrogen flow rate of 20 to 1000 ml / min, a pressure of 1 to 10 bar, a reduction temperature of 190 to 390 °C, and a heating rate of 1 to 38 °C / min.

[0013] Preferably, the alumina carrier is aluminium oxide.

[0014] Advantageously, the alumina support enables outstanding catalytic performance with high CO2 conversion, methanol selectivity, and methanol yield. Additionally, compared to the supports used in the prior art, alumina is more stable and cost-effective.

[0015] In one embodiment, at least one promoter is selected from manganese, niobium, and zirconium.

[0016] Preferably, at least one promoter is a combination of manganese, niobium, and zirconium, typically in a ratio of 4:1:1.

[0017] In one embodiment, manganese is present in an amount of 0.06 wt%, niobium is present in an amount of 0.015 wt%, and zirconium is present in an amount of 0.015 wt%.

[0018] In another embodiment, a method for producing methanol by reacting carbon dioxide with hydrogen on the enhanced catalyst as described herein is provided.

[0019] In one embodiment, the ratio of hydrogen to carbon dioxide is in the range of 3:1 to 10:1, the temperature is in the range of 200 to 300 °C, the pressure is in the range of 20 to 100 bar, and the gas hourly space velocity (GHSV) is in the range of 2160 to 31200 ml / g·h. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] It will be convenient to further describe the present invention with reference to the drawings which illustrate possible arrangements of the present invention. Other arrangements of the present invention are possible, and thus the particularity of the drawings should not be construed as superseding the generality of the foregoing description of the present invention.

[0021] Figure 1 is a schematic diagram of a system for the hydrogenation of CO2 to methanol according to an embodiment of the present invention. DETAILED DESCRIPTION

[0022] Figure 1 shows a schematic diagram of a catalyst in a system for the hydrogenation of CO2 to methanol.

[0023] The present invention describes an enhanced catalyst for the hydrogenation of carbon dioxide to methanol, comprising a copper-zinc oxide catalyst supported on Al2O3 promoted with manganese, niobium, and zirconium in an amount of up to 1 wt%.

[0024] The promoted catalyst undergoes an activation process before being used for the hydrogenation of carbon dioxide to methanol.

[0025] The present invention further describes a method for producing methanol by reacting carbon dioxide with hydrogen on the promoted catalyst.

[0026] Further details are provided below.

[0027] Catalyst preparation

[0028] Preparation of Promoted Cu / ZnOAl2O3 Catalyst

[0029] A fixed metal loading of 15 wt% Cu / ZnO (7:3 ratio) and 0.09 wt% total promoter (Mn / Nb / Zr) was prepared using incipient wetness impregnation. The amount of each precursor and promoter added was calculated based on the mass of the catalyst prepared on the Al2O3 support.

[0030] The metal precursors copper nitrate trihydrate (Cu(NO3)2.3H2O) and zinc nitrate hexahydrate (Zn(NO3)2.6H2O) were dissolved in deionized water along with the promoters manganese(II) nitrate tetrahydrate (Mn(NO3)2.4H2O), hydrated ammonium niobate(V) oxalate (C4H4NNbO9.xH2O), and hydrated zirconium(IV) nitrate (ZrO(NO3)2.H2O) to obtain a 0.5M aqueous solution. The solution was stirred for one hour on a hot plate stirrer using a magnetic stir bar. The prepared aqueous precursor solution was then added dropwise to a beaker containing the powdered Al2O3 support using a pipette.

[0031] During the addition of the precursor and promoter solutions, the pH of the mixture was maintained at 7 using either a 10% ammonia solution or a 10% nitric acid solution. The mixture was stirred for 24 hours, filtered, and washed with deionized water. The resulting paste was dried in an oven at 120°C for 12 hours. The dried catalyst was then placed in a ceramic crucible and calcined in an air muffle furnace at 350°C for 4 hours.

[0032] The alumina support used in the present invention results in outstanding catalytic performance with high CO2 conversion, methanol selectivity and methanol productivity.

[0033] In addition, alumina is more stable and cost-effective than the SBA-15 used in the prior art. In addition, SBA-15 cannot be recycled, which results in very poor catalytic performance.

[0034] Promoter Ratio Evaluation

[0035] Promoted Cu / ZnO Al2O3 catalysts were evaluated using default hydrogenation operating conditions (reduction temperature of 250°C, reaction temperature of 250°C, pressure of 22.5 bar, gas hourly space velocity (GHSV) of 10,800 ml / g·h, and H2:CO2=3:1) to determine the promoter ratio combination (Mn, Zr and Nb) that achieved the highest methanol yield.

[0036] The promoted catalyst formulation that achieved the highest methanol yield was selected to further optimize the activation and hydrogenation process reactions.

[0037] Catalyst activation

[0038] Before the hydrogenation reaction, the promoted Cu / ZnO Al2O3 catalyst is activated for 1 to 7 hours within a hydrogen flow rate range of 20–1000 ml / min, a pressure range of 1 to 10 bar, a reduction temperature range of 190 to 390 °C, and a heating rate range of 1 to 38 °C / min.

[0039] Activation is necessary to reduce the conversion of metal oxides to the metallic form so that the catalyst is active during the hydrogenation reaction. Optimized activation conditions ensure that the promoted catalyst is fully reduced, enabling outstanding catalytic performance with high CO2 conversion, methanol selectivity, and methanol yield.

[0040] Method for CO2 hydrogenation reaction

[0041] The calcined promoted catalyst sample is placed in the reactor tube of a fixed-bed reactor and sandwiched between layers of quartz wool. Then the reactor is purged with He or N2 to remove impurities and ensure inert conditions. The activation of the catalyst is carried out under the determined activation conditions. After the promoted Cu / ZnO Al2O3 catalyst is activated, the reactant gases (H2 and CO2) in a determined ratio (3∶1–10∶1) are fed into the reactor column at a total flow rate of 30–600 ml / min. The reaction temperature is set within the range of 200 to 300 °C, and the reaction pressure is within the range of 20 to 100 bar (using a pressurization system of He / CO □ and H2), and the gas hourly space velocity (GHSV) is within the range of 2160 to 31200 ml / g·h (converted from the mass of the catalyst used and the total flow rate). The increase in pressure and the H2∶CO2 ratio further improve the methanol selectivity and methanol yield. The hydrogenation reaction is carried out for 5 hours to 30 days for catalyst stability studies.

[0042] Table 1 shows the catalyst performance data, where under comparative conditions, the catalyst formulation promoted with Mn, Nb, and Zr (ratio 4∶1∶1, with a total Cu / ZnO weight of at most 1 wt%) used in the present invention has a methanol yield of 63.59%, while other catalyst formulations promoted with Mn, Nb, and Zr (ratio 1∶1∶1) supported on Al2O3 or SBA-15 have a methanol yield of <19.40%. The goal of the increased methanol yield is to reduce the recycle rate and is expected to result in a reduction in operating costs.

[0043] Table 1

[0044]

[0045] Those skilled in the art will understand that the present invention may also include further additional modifications to the system that do not affect the overall function of the system.

Claims

1. An enhanced catalyst for hydrogenating carbon dioxide to methanol, comprising: A copper-zinc oxide catalyst supported on an alumina carrier; And At least one promoter; Characterized in that the promoter is added to the copper-zinc oxide catalyst in an amount of up to 1 wt% to form a promoted copper-zinc oxide catalyst on the alumina carrier.

2. The enhanced catalyst according to claim 1, wherein the promoted copper-zinc oxide catalyst is activated for a duration of 1 to 7 hours within a hydrogen flow rate range of 20 to 1000 ml / min, a pressure range of 1 to 10 bar, a reduction temperature range of 190 to 390 °C, and a heating rate range of 1 to 38 °C / min.

3. The enhanced catalyst according to claim 1, wherein the alumina carrier is aluminium oxide.

4. The enhanced catalyst according to claim 1, wherein the at least one promoter is selected from manganese, niobium, and zirconium.

5. The enhanced catalyst according to claim 1, wherein the at least one promoter is a combination of manganese, niobium, and zirconium in a ratio of 4:1:

1.

6. The enhanced catalyst according to claim 1, wherein manganese is present in an amount of 0.06 wt%, niobium is present in an amount of 0.015 wt%, and zirconium is present in an amount of 0.015 wt%.

7. A method for producing methanol by reacting carbon dioxide with hydrogen over the enhanced catalyst according to claim 1.

8. The method according to claim 7, wherein the ratio of hydrogen to carbon dioxide is in the range of 3:1 to 10:1, the temperature is in the range of 200 to 300 °C, the pressure is in the range of 20 to 100 bar, and the gas hourly space velocity (GHSV) is in the range of 2160 to 31200 ml / g·h.

Images