WO2018049735A1

WO2018049735A1 - A metal oxide catalyst for methanol synthesis from co2 hydrogenation and preparation method of the catalyst

Info

Publication number: WO2018049735A1
Application number: PCT/CN2016/109130
Authority: WO
Inventors: Can LI; Jijie WANG; Zelong LI; Chizhou TANG; Shengmei LU; Jun Li
Original assignee: Dalian Institute of Chemical Physics of CAS
Current assignee: Dalian Institute of Chemical Physics of CAS
Priority date: 2016-09-14
Filing date: 2016-12-09
Publication date: 2018-03-22
Anticipated expiration: 2019-03-14
Also published as: CN106390978A; CN106390978B

Abstract

Provided are a metal oxide catalyst for methanol synthesis from CO ₂ hydrogenation and a preparation method of the catalyst. The catalyst for methanol synthesis from CO ₂ hydrogenation is composed of two kinds of metal oxides, denoted as M _AO _x-M _BO _y, which is prepared by the method of coprecipitation, wherein M _A represents Zn, Cd, In, M _B represents Zr, Cr. The catalyst can obviously increase the selectivity of methanol from CO ₂ hydrogenation than CuZnO-based catalyst. The selectivity of methanol on the ZnO-ZrO ₂ catalyst can reach 80％on the conditions of 5MPa, 330℃, 24000 mL/(g h).

Description

A metal oxide catalyst for methanol synthesis from CO2 hydrogenation and preparation method of the catalyst

Field of the invention

The invention pertains the field of catalyst, the process for preparing the catalyst, and the application for CO₂ hydrogenation to methanol.

Background of the invention

With the rapid development of the economy and the increasing population, the energy issue has become one of the most serious problems. Currently, more than 80％of the world’s energy consumption and production of chemicals comes from the use of the fossil resources. However, overuse of the fossil resource produces large amounts of CO₂ emission. The concentration of CO₂ in the atmosphere reached 400 ppm in 2016, which lead to irregular climate change. Adverse global environmental changes caused by large amounts of anthropogenic CO₂ emissions became more and more serious. One such view is that solving the problem of CO₂ is an energy revolution that renewable energy replacing fossil energy and CO₂ is just an intermediate that transmitting the renewable energy to carbon resource that mankind used now. CO₂ hydrogenation to methanol offers a possible method to practice the view. Methanol itself is an excellent fuel, fuel cells, furthermore, can be transformed to olefins and most of the chemical products currently obtained from fossil fuels. The energy and hydrogen needed for the reduction of CO₂ can come from any renewable energy source such as solar, wind and nuclear energy, then, a sustainable route of fuel and chemical production would be established.

Currently, methanol is produced industrially from CO and H₂ (containing a small amount of CO₂) over CuZnOAl₂O₃ catalysts. These CuZnO based systems have been also regarded as the most efficient catalysts for the direct CO₂ hydrogenation. Besides, PdGa₂O₃ (ZnO) were reported to be active for the CO₂ hydrogenation to methanol. However, the CO₂ hydrogenation reaction also promotes the reverse water gas shift (RWGS: CO₂+H₂→CO+H₂O) reaction to give CO, leading to a low methanol selectivity. The key issue and challenge of CO₂ hydrogenation to methanol is how to limit the RWGS side reaction. Nowadays, most of the researches focused on the promoter for CuZnO system. Ce, Cs, Ca, Zr, La, Mn, Ti, Th, Mg, Ba, et al. were reported as helpful promoters for CuZnO catalyst. Recently, Cu/CeO_x/TiO₂ and Au/CeO_x/TiO₂ catalysts were reported to be more active catalysts than Cu/ZnO catalyst for CO₂ hydrogenation, but only with about 50％methanol selectivity under the reported conditions. It seems that methanol synthesis and RWGS reaction happens at the same active site on Cu (Au) -based catalyst, which is based on the popular formate mechanism. It is evidenced by the new precursor phase “georgeite” of CuZnOAl₂O₃ catalyst not only improves methanol synthesis but also improves the WGS reaction. Further more, all the Cu-based catalysts are easy to be deactivated for long time on stream or at high temperature due to Cu particle size increasing or sintering.

Content of the invention

The invention provides a metal oxide catalyst for the production of methanol by CO₂ hydrogenation, which occurs via the following reaction: CO₂ + 3H₂→CH₃OH + H₂O, and the method of preparing the catalyst. Some CO and inert gas can be added into the feed gas, for example N₂, Ar and He. The catalyst for methanol synthesis from CO₂ hydrogenation is composed of two kinds of metal oxides, denotes as M_AO_x-M_BO_y, which is prepared by the method of coprecipitation, in M_AO_x-M_BO_y, M_A represents Zn, Cd, In, M_B represents Zr, Cr, M_A/(M_A+M_B) ＝ 5％～95％. The precursors of Zn, Cd, In, Cr, Zr are one or two of nitrate, acetate, chloride and sulfate. The precipitators are one or two of ammonium hydroxide, ammonium carbonate, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, sodium hydroxide, potassium hydroxide.

The method of preparing the metal oxide catalyst includes following steps: A series of m％M_AO_x-M_BO_y catalysts (where m％represented molar percentage) were prepared by coprecipitation method. A given concentration of M_A and M_B metal salt are dissolved in a flask with deionized water together. The same concentration of precipitator was prepared and added into the aforementioned solution under vigorous stirring at 30～90 ℃ so as to form precipitate. The amounts of precipitator is 1～3 times of the metal salt, the pH of the mother liquid when coprecipitating keeps 6～9. The suspension was continuously stirred for 1～24 h at 30～90 ℃, followed by cooling down to room temperature and filtering, washing with deionized water 3～7 times till no sodium or potassium was detected. The filter cake was dried at 60～110 ℃ for 1～24 h and then calcined at 450～700 ℃ in static air for 1～24 h.

The order of the precipitation between metal salt and precipitator include positive order (precipitator aqueous adding to metal salt aqueous) , reverse order (metal salt aqueous adding to precipitator aqueous) and together adding to water.

In another aspect, the invention provide the metal oxide catalyst for the production of methanol by CO₂ hydrogenation, wherein the structure of the catalyst is a solid solution in a certain range (see FIG. 1) .

The activity tests of the catalysts for CO₂ hydrogenation to methanol were carried out in a fixed-bed continuous-flow reactor-gas chromatography (GC) combination system. Before the reaction, the catalyst (0.1 g, diluted with 0.4 g quartz sand) was pretreated in situ in a H₂ or N₂ stream (0.1 MPa and 20 mL/min) at desired temperature. The reaction was conducted at a stationary state under reaction conditions of 1.0～5.0 MPa, 180～400 ℃, V (H₂) /V (CO₂) /V (Ar) ＝ 72/24/4, and GHSV ＝ 3000～33000 mL/ (g h) . The exit gas from the reactor was maintained at 150 ℃ and immediately transported to the sampling valve of the GC (Agilent GC-7890B) , which was equipped with dual thermal conductivity and flame ionization detectors. Propark N and 5A molecular sieves packed columns (2 m×1/8 inch, Agilent) were connected to TCD while TG-BOND-Q capillary columns were connected to FID. The packed column were used for the analysis of CO₂, Ar, CO, and the capillary column (30 m×0.32 mm×10 μm, ThermoFisher) for hydrocarbons, alcohols, and other C-containing hydrogenation products. CO₂ conversion (denoted as X(CO₂) ) and the carbon-based selectivity for the carbon-containing products, including methane, methanol, and dimethyl ether, were calculated with an internal normalization method. All data were collected 12 h after the reaction started (unless otherwise specified) .

The catalyst can obviously increase the selectivity of methanol from CO₂ hydrogenation than CuZnO-based catalyst, which is currently regarded as the most efficient catalyst for CO₂ hydrogenation to methanol. The selectivity of methanol on the ZnOZrO₂ catalyst can reach 80％on the conditions of 5 MPa， 330 ℃， 24000 mL/ (g h) and 75％on the conditions of 2 MPa， 330 ℃， 24000 mL/ (g h) . In addition, the catalyst has outstanding stability and good ability of resistant to sintering. The space time yield (STY) of methanol on the catalyst has no obvious variation during 200 h (see FIG. 2) . Increasing the reaction temperature to 400 ℃ and keep on 24 h, and then decreasing to 330 ℃, no loss of STY of methanol was observed.

Brief description of the drawings

FIG. 1 shows the XRD of ZnO-ZrO₂ catalysts.

FIG. 2 shows the stability of catalysts for CO₂ hydrogenation to methanol.

Examples

Example 1

33％ZnO-ZrO₂ catalyst was prepared by coprecipitation method. 5 mmol Zn(NO₃) ₂·6H₂O and 10 mmol Zr (NO₃) ₄·5H₂O were dissolved in a flask with 100 mL deionized water. 100 mL aqueous solution of 27.5 mmol (NH₄) ₂CO₃ as a precipitator was added into the aforementioned solution (at flow rate of 3 mL/min) under vigorous stirring at 70 ℃ so as to form precipitate. The suspension was continuously stirred for 2 h at 70 ℃, followed by cooling down to room temperature and filtering, washing with deionized water 3 times. The filter cake was dried at 110 ℃ for 4 h and calcined at 500 ℃ in static air for 3 h. The activity tests of the catalysts for CO₂ hydrogenation to methanol were carried out in a fixed-bed continuous-flow reactor-gas chromatography (GC) combination system. Before the reaction, the catalyst (0.1 g, diluted with 0.4 g quartz sand) was pretreated in situ in a H₂ stream (0.1 MPa and 20 mL/min) at 300 ℃. Then, the reaction was conducted at a stationary state under reaction conditions of 2.0 MPa, 300 ℃, V (H₂) /V (CO₂) /V (Ar) ＝72/24/4, and GHSV ＝ 24000 mL/ (g h) . The exit gas from the reactor was maintained at 150 ℃ and immediately transported to the sampling valve of the GC (Agilent GC-7890B) , which was equipped with dual thermal conductivity and flame ionization detectors. Propark N and 5A molecular sieves packed columns (2 m×1/8 inch, Agilent) were connected to TCD while TG-BOND-Q capillary columns were connected to FID. The packed column were used for the analysis of CO₂, Ar, CO, and the capillary column (30 m×0.32 mm×10 μm, ThermoFisher) for hydrocarbons, alcohols, and other C-containing hydrogenation products. CO₂ conversion (denoted as X (CO₂) ) and the carbon-based selectivity for the carbon-containing products (denoted as S (Product) ) , including methane, methanol, and dimethyl ether, were calculated with an internal normalization method. The detailed catalytic performance of the catalyst is listed in table 1. The space time yield (STY) of methanol means the amounts of methanol that can be obtained per g-catalyst per hour.

Example 2

33％In₂O₃-ZrO₂ catalyst was prepared by 5 mmol In (NO₃) ₃·5H₂O, 10 mmol Zr(NO₃) ₄·5H₂O and 30.3 mmol (NH₄) ₂CO₃. Other procedures of preparation and evaluation are same with example 1. The catalytic performance of the catalyst is listed in table 1.

Example 3

33％CdO-ZrO₂ catalyst was prepared by 5 mmol Cd (NO₃) ₂·4H₂O, 10 mmol Zr(NO₃) ₄·5H₂O and 27.5 mmol (NH₄) ₂CO₃. Other procedures of preparation and evaluation are same with example 1. The catalytic performance of the catalyst is listed in table 1.

Example 4

50％ZnO-ZrO₂ catalyst was prepared by 10 mmol Zn (NO₃) ₂·6H₂O, 10 mmol Cr(NO₃) ₃·9H₂O and 27.5 mmol (NH₄) ₂CO₃. Other procedures of preparation and evaluation are same with example 1. The catalytic performance of the catalyst is listed in table 1.

Example 5

90％In₂O₃-ZrO₂ catalyst was prepared by 4.5 mmol In (NO₃) ₃·5H₂O, 0.5 mmol Zr(NO₃) ₄·5H₂O and 8.3 mmol (NH₄) ₂CO₃. Other procedures of preparation and evaluation are same with example 1. The catalytic performance of the catalyst is listed in table 1.

Example 6

33％CdO-ZrO₂ catalyst was prepared by 5 mmol Cd (NO₃) ₂·4H₂O, 10 mmol Zr(NO₃) ₄·5H₂O and 22 mmol (NH₄) ₂CO₃. Other procedures of preparation and evaluation are same with example 1. The catalytic performance of the catalyst is listed in table 1.

Example 7

80％In₂O₃-ZrO₂ catalyst was prepared by 4 mmol In (NO₃) ₃·5H₂O, 1 mmol Zr(NO₃) ₄·5H₂O and 8.8 mmol (NH₄) ₂CO₃. The catalyst evaluation was carried out at 310 ℃. Other procedures of preparation and evaluation are same with example 1. The catalytic performance of the catalyst is listed in table 1.

Example 8

25％ZnO-ZrO₂ catalyst was prepared by 2.5 mmol Zn (NO₃) ₂·6H₂O, 7.5 mmol Zr(NO₃) ₄·5H₂O and 19.3 mmol (NH₄) ₂CO₃. The catalyst evaluation was carried out on the conditions of p ＝ 2 MPa, 5MPa， T ＝ 300 ℃, 330 ℃， GHSV ＝ 20000, 24000 mL/ (h g) . Other procedures of preparation and evaluation are same with example 1. The catalytic performance of the catalyst is listed in table 1.

Example 9

13％ZnO-ZrO₂ catalyst was prepared by 1.5 mmol Zn (NO₃) ₂·6H₂O, 10 mmol Zr(NO₃) ₄·5H₂O and 23.7 mmol (NH₄) ₂CO₃. Other procedures of preparation and evaluation are same with example 1. The catalytic performance of the catalyst is listed in table 1.

Example 10

17％ZnO-ZrO₂ catalyst was prepared by 2.05 mmol Zn (NO₃) ₂·6H₂O, 10 mmol Zr(NO₃) ₄·5H₂O and 24.3 mmol (NH₄) ₂CO₃. The catalyst evaluation was carried out at 310 ℃.Other procedures of preparation and evaluation are same with example 1. The catalytic performance of the catalyst is listed in table 1.

Example 11

15％CdO-ZrO₂ catalyst was prepared by 1.76 mmol Cd (NO₃) ₂·4H₂O, 10 mmol Zr(NO₃) ₄·5H₂O and 23.9 mmol (NH₄) ₂CO₃. The catalyst evaluation was carried out at 310 ℃.Other procedures of preparation and evaluation are same with example 1. The catalytic performance of the catalyst is listed in table 1.

Example 12 (Comparative example 1)

25％ZnO/ZrO₂ catalyst was prepared by wet impregnation, ZrO₂ support was synthesized according to the coprecipitation method described in example 1.9 mmol ZrO₂ was immersed in 25 mL of aqueous solution of 3 mmol Zn (NO₃) ₂. The mixture was stirred at 110 ℃ until the water had completely volatilized and then calcined at 500 ℃ in static air for 3 h. The procedure of catalyst evaluation is same with example 1. The catalytic performance of the catalyst is listed in table 1.

Example 13 (Comparative example 2)

ZnO+ZrO₂ catalyst was prepared by the method of mechanical grind. ZnO, ZrO₂ were synthesized according to the coprecipitation method described in example 1.3 mmol ZnO and 9 mmol ZrO₂ were mixed together in a mortar, and grinded for 10 mins, and then calcined at 500 ℃ in static air for 3 h. The procedure of catalyst evaluation is same with example 1. The catalytic performance of the catalyst is listed in table 1.

Example 14 (Comparative example 3)

CuO/ZnO/Al₂O₃ catalyst was prepared by coprecipitation analogous to the procedure described by Behrens et al. 100 mL aqueous solution of metal nitrates (18 mmol Cu(NO₃) ₂·3H₂O, 9 mmol Zn (NO₃) ₂·6H₂O, 3 mmol Al (NO₃) ₃·9H₂O) and 120 mL aqueous solution of 36 mmol Na₂CO₃ as a precipitant were added dropwise (at flow rate of 3 mL/min) into a glass reactor with a starting volume of 200 mL of deionized water under vigorous stirring at 70 ℃. During the precipitation process, controlling pH ＝ 7, followed by cooling down to room temperature and filtering, washing with deionized water 7 times. The filter cake was dried at 110 ℃ for 4 h and calcined at 350 ℃ in static air for 3 h. The procedure of catalyst evaluation is same with example 1. The catalytic performance of the catalyst is listed in table 1.

Table 1 the performance of catalysts for CO₂ hydrogenation to methanol.

0.15g catalyst, H₂/CO₂＝3/1, 24000 mL/ (g h) . *indicates the temperature is decreased from 400 ℃； **indicates the feed gas is H₂/CO₂＝4/1, 20000 mL/ (g h) .

Claims

A metal oxide catalyst for methanol synthesis from CO₂ hydrogenation and preparation method of the catalyst, wherein the catalyst is composed of two kinds of metal oxides.
A metal oxide catalyst according claim 1, wherein the catalyst is composed of two kinds of metal oxides, denotes as M_AO_x-M_BO_y, wherein M_A represents Zn, Cd, In, M_B represents Zr, Cr.
A metal oxide catalyst according claim 1 to 2, wherein M_A/ (M_A+M_B) ＝ 5％～95％, preferable 10％～50％. Wherein x ＝2～3, y ＝2～3.
A metal oxide catalyst for methanol synthesis from CO₂ hydrogenation and preparation method of the catalyst, wherein the catalyst is prepared by the method of coprecipitation.
A preparation method of the metal oxide catalyst according claim 4, wherein the precursor metal salt of Zn, Cd, In, Cr, Zr are one or two of nitrate, acetate, chloride and sulfate.
A preparation method of the metal oxide catalyst according claim 4, wherein the precipitator are one or two of ammonium hydroxide, ammonium carbonate, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, sodium hydroxide, potassium hydroxide.
A preparation method of the metal oxide catalyst according claim 4, wherein the total concentration of precursor metal salt of Zn, Cd, In, Cr, Zr are 0.01～2 mol/L.
A preparation method of the metal oxide catalyst according claim 4, wherein the concentration of precipitator is 0.01～10 mol/L.
A preparation method of the metal oxide catalyst according claim 4, wherein the amounts of precipitator is 1～3 times of the metal salt.
A preparation method of the metal oxide catalyst according claim 4, wherein the temperature of precipitation is 30～90 ℃.
A preparation method of the metal oxide catalyst according claim 4, wherein the pH of the mother liquor is 6～10.
A preparation method of the metal oxide catalyst according claim 4, wherein the temperature of aging is 30～90 ℃.
A preparation method of the metal oxide catalyst according claim 4, wherein the time of aging is 1～24 h.
A preparation method of the metal oxide catalyst according claim 4, wherein the order of the precipitation between metal salt and precipitator include positive order (precipitator aqueous adding to metal salt aqueous) , reverse order (metal salt aqueous adding to precipitator aqueous) and together adding to water.
A preparation method of the metal oxide catalyst according claim 4, wherein the precursor obtained by coprecipitating is filtered and washed till no sodium or potassium is detected.
A preparation method of the metal oxide catalyst according claim 4, wherein the precursor obtained by coprecipitating, filtering, washing, and drying is calcined at 450～700 ℃ for 1～24 h.
A metal oxide catalyst and preparation method of the catalyst, wherein the catalyst is used for methanol synthesis from CO₂ hydrogenation.
A metal oxide catalyst for methanol synthesis from CO₂ hydrogenation according claim 17, wherein the feed gas is composed of CO₂ and H₂.
A metal oxide catalyst for methanol synthesis from CO₂ hydrogenation according claim 17, wherein the ration of H₂/CO₂ in the feed gas is 8: 1～1: 1.
A metal oxide catalyst for methanol synthesis from CO₂ hydrogenation according claim 17, wherein a certain amount of the inert gas and CO can be add into feed gas, wherein the inert gas include one or two of N₂, Ar.
A metal oxide catalyst for methanol synthesis from CO₂ hydrogenation according claim 17 and 20, wherein the amount of the inert gas and CO is 5％～80％.
A metal oxide catalyst for methanol synthesis from CO₂ hydrogenation according claim 17, wherein the catalyst is pretreated with H₂, CO, N₂, or Ar.
A metal oxide catalyst for methanol synthesis from CO₂ hydrogenation according claim 17 and 22, wherein the pretreated temperature is 200～400 ℃.
A metal oxide catalyst for methanol synthesis from CO₂ hydrogenation according claim 17 and 22, wherein the pretreated time is 0.5～24 h.
A metal oxide catalyst for methanol synthesis from CO₂ hydrogenation according claim 17, wherein the pressure of the reaction is 1～20 MPa.
A metal oxide catalyst for methanol synthesis from CO₂ hydrogenation according claim 17, wherein the temperature of the reaction is 200～400 ℃.
A metal oxide catalyst for methanol synthesis from CO₂ hydrogenation according claim 17, wherein gas hourly space velocity (GHSV) is 3000～50000 mL/ (g h) .