Noble metal promoted supported indium oxide catalyst for the hydrogenation of CO.SUB.2 .to methanol and process using said catalyst

Abstract

Supported catalyst for use in a process for the synthesis of methanol, characterized in that the supported catalyst comprises indium oxide in the form of In.sub.2O.sub.3 and at least one noble metal being palladium, Pd, wherein both indium oxide and at least one noble metal are deposited on a support remarkable in that the supported catalyst is a calcined supported catalyst comprising from 0.01 to 10.0 wt. % of palladium and zirconium dioxide (ZrO.sub.2) in an amount of at least 50 wt. % on the total weight of said supported catalyst.

Claims

1. Supported catalyst for use in a process for the synthesis of methanol, characterized in that the supported catalyst comprises indium oxide in the form of In.sub.2O.sub.3 and at least one noble metal being palladium, Pd, wherein both indium oxide and at least one noble metal are deposited on a support characterized in that the supported catalyst is a calcined supported catalyst comprising: from 0.01 to 10.0 wt. % of palladium and zirconium dioxide (ZrO.sub.2) in an amount of at least 50 wt. % on the total weight of said supported catalyst; wherein the average particle size of the noble metal phase is less than 5 nm as determined by STEM-EDX or the average crystal size of In.sub.2O.sub.3 is less than 20 nm, as determined by XRD.

2. The supported catalyst according to claim 1, characterized in that the supported catalyst comprises from 0.5 wt. % to 2.0 wt. %. of palladium based on the total weight of said supported catalyst.

3. The supported catalyst according to claim 1, characterized in that the support comprises zirconium dioxide (ZrO.sub.2) in an amount of at least 80 wt. %, based on the total weight of said supported catalyst.

4. The supported catalyst according to claim 1, characterized in that the support comprises zirconium dioxide (ZrO.sub.2) in an amount of at least 90 wt. % based on the total weight of said supported catalyst.

5. The supported catalyst according to claim 1, characterized in that the supported catalyst is a calcined supported catalyst and in that the indium oxide content in the form of In.sub.2O.sub.3 ranges from 1 to 20% by weight based on the total weight of said supported catalyst.

6. The supported catalyst according to claim 1, characterized in that the supported catalyst is a calcined supported catalyst and in that the indium oxide content in the form of In.sub.2O.sub.3 ranges from 5 to 15% by weight based on the total weight of said supported catalyst.

7. The supported catalyst according to claim 1, characterized in that the supported catalyst is a calcined supported catalyst.

8. The supported catalyst according to claim 1, characterized in that the supported catalyst is a calcined supported catalyst and has a surface area in the range of about 30 m.sup.2 g.sup.−1 to about 200 m.sup.2 g.sup.−1, as determined according to N.sub.2 sorption analysis according to ASTM D3663-03.

9. A method to prepare a supported catalyst according claim 1 characterized in that the supported catalyst is prepared by impregnation or by deposition precipitation.

10. A method according to claim 9, characterized in that the supported catalyst is a calcined supported catalyst, and in that the method comprises a step of calcination of the supported catalyst performed at a temperature of at least 473 K (199.85° C.).

11. The method according to claim 9, characterized in that the supported catalyst is a calcined supported catalyst, and in that the method comprises a step of calcination of the supported catalyst performed at a temperature of at least 573 K (299.85° C.).

12. Process for methanol synthesis comprising: providing a feed stream comprising hydrogen and carbon oxides selected from carbon dioxide or a mixture of carbon dioxide and carbon monoxide, wherein carbon dioxide represents from 1 to 50 mol % of the total molar content of the feed stream, carbon monoxide is contained from 0 to 85 mol % of the total molar content, and H.sub.2 is comprised from 5 to 99 mol % of the total molar content of the feed stream; providing a catalyst according to claim 1; putting in contact said feed stream with said catalyst at a reaction temperature of at least 373 K (99.85° C.) and under a pressure of at least 0.5 MPa; and recovering the methanol from the effluents by a separation process; wherein the feed stream is put in contact with the supported catalyst at a weight hourly space velocity ranging from 1,000 to 60,000 cm3.sub.STP g.sub.cal h.sup.−1.

13. Process according to claim 12, characterized in that: the reaction temperature is at least 463 K (189.85° C.).

14. Process according to claim 12, characterized in that the feed stream is put in contact with the supported catalyst at a weight hourly space velocity ranging from 10,000 to 60,00cm.sup.3.sub.STP g.sub.cal h.sup.−1.

15. Process according to claim 12, characterized in that the feed stream is put in contact with the supported catalyst at a weight hourly space velocity ranging from 24,000 to 48,000 cm.sup.3.sub.STP g.sub.cal h.sup.−1.

16. Process according to claim 12, characterized in that the molar ratio of hydrogen to carbon dioxide in the feed stream is at least 1:1.

17. Process according to claim 12, characterized in that the molar ratio of hydrogen to carbon dioxide in the feed stream is at least 3:1.

18. Process according to claim 12, characterized in that prior to reaction the supported catalyst is activated in situ by raising the temperature to at least 553 K (279.85° C.) in a flow of a gas feed stream for activation selected from inert gases, hydrogen, carbon monoxide, carbon dioxide or mixture thereof.

Description

DESCRIPTION OF THE FIGURES

(1) FIG. 1 depicts the STY of methanol over indium oxide, 10 wt. % indium oxide on zirconia, and 0.05 wt. % palladium and 9.95 wt. % indium oxide on zirconia over a 24-h period. Conditions: WHSV=24,000, molar H.sub.2:CO.sub.2=4, 5.0 MPa, 553 K, catalyst prepared via wet impregnation.

(2) FIG. 2 demonstrates the evolution of conversion, selectivity, and STY over 0.05 wt. % palladium and 9.95 wt. % indium oxide on zirconia. Conditions: WHSV=48,000, molar H.sub.2:CO.sub.2=4, 5.0 MPa, 553 K, catalyst prepared via deposition precipitation.

(3) FIG. 3 shows scanning transmission electron microscopy coupled to energy dispersive X-ray mapping (STEM-EDX) images of the same sample as in FIG. 2 at low (top row) and high (bottom row) magnification.

(4) FIG. 4 shows the power X-ray diffraction pattern of the same sample as in FIG. 2, in which the reflections specific to In.sub.2O.sub.3 and ZrO.sub.2 phases are marked.

DETAILED DESCRIPTION OF THE INVENTION

(5) As used herein the generic term “catalyst” refers to both a “bulk” and a “supported catalyst”. A bulk catalyst is a catalyst containing only the main active phase (i.e., indium oxide). A supported catalyst comprises the bulk catalyst and a support (e.g., ZrO.sub.2). A noble metal promoted catalyst is a catalyst in which a noble metal has been added.

(6) A co-precipitated catalyst is a catalyst wherein the active phase is intimately mixed with the support, in contrast with deposition precipitation techniques and impregnation techniques wherein the active phase is deposited on the support.

(7) According to the invention, a supported catalyst comprises a catalyst and a support to provide mechanical support to the supported catalyst as well as to further enhance exposure of a feed stream to active sites of the supported catalyst.

(8) In methanol synthesis according to the invention, a feed gas composed of hydrogen gas and carbon oxides (CO.sub.2 alone or a mixture of CO.sub.2 and CO gases) are caused to interact on a ternary catalyst comprising indium oxide, a noble metal and a support.

(9) Catalyst and Preparation of the Supported Catalyst

(10) The present invention contemplates the use of a supported catalyst in a process for the synthesis of methanol wherein, the supported catalyst comprises indium oxide in the form of In.sub.2O.sub.3 and at least one noble metal, wherein both indium oxide and the at least one noble metal are deposited on a support.

(11) The catalyst comprises both indium oxide in the form of In.sub.2O.sub.3 and an additional metal selected from noble metals, being palladium. The amount of the catalyst (represented as weight loading of the catalyst based on the total weight of the calcined supported catalyst) can be in the range of about 0.1-95 wt. %.

(12) The supported catalyst is a calcined catalyst. This feature can be evidenced by the crystalline structure of indium oxide observed in the X-ray diffraction and/or the absence of organic and/or nitrogen compounds in HCN analysis, that would be derived from the metal precursors, e.g., In(NO.sub.3).sub.3.xH.sub.2O. Indeed, the non-calcined catalyst would exhibit organic and/or nitrous and/or hydrogen content in its HCN analysis.

(13) In a preferred embodiment, the average size of the noble metal phase is less than 5 nm as determined by STEM-EDX, preferably less than 4 nm, more preferably less than 2 nm.

(14) In an embodiment, the supported catalyst is a calcined supported catalyst and comprises from 0.01 to 10 wt. % of the at least one noble metal based on the total weight of the calcined supported catalyst.

(15) The supported catalyst is a calcined supported catalyst and comprises at least 0.05 wt. % of the at least one noble metal based on the total weight of the calcined supported catalyst, preferably at least 0.1 wt. %, more preferably at least 0.3 wt. %, even more preferably at least 0.5 wt. %, and most preferably at least 0.7 wt. %.

(16) The supported catalyst is a calcined supported catalyst and comprises at most 10.0 wt. % of the at least one noble metal based on the total weight of the calcined supported catalyst, preferably at most 7.0 wt. %, more preferably at most 5.0 wt. %, even more preferably at most 2.0 wt. %, and most preferably at most 1.0 wt. %.

(17) In an embodiment, the supported catalyst is a calcined supported catalyst and the indium oxide content in the form of In.sub.2O.sub.3 of the supported catalyst, is at most 70 wt. %, preferably at most 60 wt. %, preferably of at most 50 wt. %, more preferably of at most 40 wt. %, even more preferably of at most 30 wt. %, most preferably of at most 20 wt. %, and even most preferably of at most 14 wt. % based to the total weight of the calcined supported catalyst.

(18) In an embodiment, the supported catalyst is a calcined supported catalyst and the indium oxide content in the form of In.sub.2O.sub.3 of the supported catalyst, is at least 1 wt. %, preferably at least 5 wt. %, more preferably at least 8 wt. % based to the total weight of the calcined supported catalyst.

(19) With the support being zirconium dioxide (ZrO.sub.2), the zirconium dioxide can be monoclinic, tetragonal, or cubic.

(20) The supported catalyst is a calcined supported catalyst and the support comprises zirconium dioxide (ZrO.sub.2) in an amount of at least 50 wt. %, even more preferably at least 80 wt. %, and most preferably at least 90 wt. % based on the total weight of the calcined supported catalyst.

(21) In an embodiment, the support is zirconium dioxide or a combination of zirconium dioxide with another support in which zirconium dioxide is contained in an amount of at least 50 wt. %, more preferably at least 80 wt. %, and even more preferably at least 90 wt. % based on the total weight of the support, the other support being selected from silica (SiO.sub.2), alumina (Al.sub.2O.sub.3), gallium oxide (Ga.sub.2O.sub.3), cerium oxide (CeO2), vanadium oxide (V.sub.2O.sub.5), chromium oxide (Cr.sub.2O.sub.3), titanium dioxide (TiO.sub.2), magnesium oxide (MgO), zinc oxide (ZnO), tin oxide (SnO.sub.2), carbon (C), and combinations thereof; preferably the other support is selected from zinc oxide (ZnO), titanium dioxide (TiO.sub.2), and combinations thereof.

(22) A catalyst support can be porous or non-porous. In some embodiments, a catalyst support can be provided in a particulate form of particles having a surface area (i.e., BET surface area) as determined by N.sub.2 sorption analysis according to ASTM D3663-03, in the range of about 5 m.sup.2 g.sup.−1 to about 400 m.sup.2 g.sup.−1, such as from 30 m.sup.2 g.sup.−1 to about 200 m.sup.2 g.sup.−1 as determined according to N.sub.2 sorption analysis, a pore volume in the range of about 0.1 cm.sup.3/g to about 10 cm.sup.3 g.sup.−1, such as from about 0.2 cm.sup.3 g.sup.−1 to about 5 cm.sup.3 g.sup.−1.

(23) The calcined supported catalyst has preferably a surface area (i.e., BET surface area) as determined by N.sub.2 sorption analysis according to ASTM D3663-03, in the range of about 5 m.sup.2 g.sup.−1 to about 400 m.sup.2 g.sup.−1, such as from 30 m.sup.2 g.sup.−1 to about 200 m.sup.2 g.sup.−1.

(24) The catalyst can be combined with a catalyst support or other support medium through, for example impregnation, such that the catalyst can be coated on, deposited on, impregnated on or otherwise disposed adjacent to the catalyst support. For example, a supported catalyst can be synthesized by an impregnation step followed by a calcination step. The catalyst can be provided in technical shapes such as extrudates, granules, spheres, monoliths, or pellets and might contain additives such as lubricants, peptizers, plasticizers, porogens, binders, and/or fillers.

(25) In a preferred embodiment the calcination step is performed at a temperature above 500 K (226.85° C.), preferably above 530 K (256.85° C.), more preferably above 550 K (276.85° C.), even more preferably above 570 K (296.85° C.).

(26) The above catalyst is useful for the synthesis of methanol from hydrogen and carbon oxides or the reverse reaction thereof.

(27) Hydrogenation of Carbon Dioxide to Methanol

(28) In methanol synthesis according to the invention, a feed gas composed of hydrogen gas and carbon oxides (CO.sub.2 alone or a mixture of CO.sub.2 and CO gases) are caused to interact on an indium oxide-based catalyst.

(29) The invention provides a process for methanol synthesis comprising the following steps: providing a feed stream comprising hydrogen and carbon oxides selected from carbon dioxide or a mixture of carbon dioxide and carbon monoxide, wherein carbon dioxide represents from 1 to 50 mol % of the total molar content of the feed stream, carbon monoxide is contained from 0 to 85 mol % of the total molar content, and H.sub.2 is comprised from 5 to 99 mol % of the total molar content of the feed stream; providing a supported catalyst comprises indium oxide in the form of In.sub.2O.sub.3 and at least one noble metal, wherein both indium oxide and the at least one noble metal are deposited on a support; putting in contact said feed stream with said catalyst at a reaction temperature of at least 373 K (99.85° C.) and under a pressure of at least 0.5 MPa; and recovering the methanol from the effluents by a separation process.

(30) The process can be carried out in a gaseous phase or in a liquid phase. The solvent that can be used for the reaction in liquid phase includes hydrocarbons and other solvents which are preferably insoluble or only sparingly soluble in water. Preferably, the process is carried out in a gaseous phase.

(31) Prior to reaction the supported catalyst is activated in situ by raising the temperature to at least 553 K in a flow of a gas feed stream for activation selected from inert gases, hydrogen, carbon monoxide, carbon dioxide, or a mixture thereof, preferably the gas feed stream for activation is or comprises an inert gas, more preferably the gas feed stream for activation is or comprises nitrogen.

(32) The process is carried out in a reactor comprising: lines to introduce a feed stream to the reactor and remove products from the reactor; a device for heating the reactor; a temperature sensor and controller for detecting and controlling the temperature of the reactor at a reaction temperature chosen between 373 K (99.85° C.) and 673 K (399.85° C.); flow controllers to control the rate of the feed stream to the reactor; and a pressure controller to control the reactor pressure in order to set it at a pressure of at least 0.5 MPa.

(33) In accordance to the invention, the feed stream comprises hydrogen and carbon oxides selected from carbon dioxide (CO.sub.2) or a mixture of carbon dioxide and carbon monoxide.

(34) However, in a preferred embodiment, the feed stream comprises hydrogen and carbon dioxide.

(35) When the feed stream comprises hydrogen and a mixture of carbon dioxide and carbon monoxide, the feed stream can be CO-rich or CO.sub.2-rich. In accordance to the invention, CO.sub.2-rich feed stream contains more than 30 mol % of CO.sub.2 based on the total molar content of the carbon oxide. In a preferred embodiment of the invention, the feed stream is CO.sub.2-rich.

(36) The feed stream comprises CO.sub.2 and H.sub.2, or H.sub.2 and a mixture of CO.sub.2 and CO, preferably the feed stream may also comprise a further gaseous component such as an inert gas. The inert gas is for example nitrogen.

(37) In a preferred embodiment, the molar ratio of hydrogen to carbon dioxide in the feed stream is at least 1:1, preferably at least 3:1, more preferably at least 4:1, even more preferably at least 6:1; and/or the molar ratio of hydrogen to carbon dioxide in the feed stream is at most 50:1, preferably at most 25:1.

(38) In a preferred embodiment, the feed stream contains hydrogen and carbon oxides selected from carbon dioxide or a mixture of carbon dioxide and carbon monoxide and the feed stream comprises at least 10 mol % of H.sub.2 based on the total molar content of the feed stream, preferably at least 20 mol %, more preferably at least 30 mol %.

(39) In a preferred embodiment the feed stream contains hydrogen and carbon oxides selected from carbon dioxide or a mixture of carbon dioxide and carbon monoxide and the feed stream comprises at most 99 mol % of H.sub.2 based on the total molar content of the feed stream, preferably at most 90 mol %, more preferably at most 80 mol %, even more preferably at most 70 mol %, and most preferably at most 60 mol %.

(40) In a preferred embodiment, the process is carried out at a reaction temperature of at least 473 K (199.85° C.), preferably of at least 523 K (249.85° C.), more preferably of at least 553 K (279.85° C.).

(41) In another preferred embodiment, the pressure is at least 1 MPa, preferably at least 2 MPa, more preferably at least 3 MPa, even more preferably at least 4 MPa and most preferably at least 5 MPa.

(42) In a preferred embodiment, the weight hourly space velocity (WHSV) is in the range of 1,000 to 100,000 cubic centimeters at standard temperature and pressure (STP) of reactant gases per gram of catalyst charged to the reactor per hour, preferably 2,000 to 70,000 cm.sup.3.sub.STP g.sub.cat.sup.−1 h.sup.−1, more preferably 5,000 to 60,000 cm.sup.3.sub.STP g.sub.cat.sup.−1 h.sup.−1, and more preferably 15,000 to 50,000 cm.sup.3.sub.STP g.sub.cat.sup.−1 h.sup.−1.

(43) In a preferred embodiment the process can be carried out with a stable performance with respect to activity and selectivity during more than 100 h, preferably more than 300 h, more preferably more than 1000 h, without the need of reactivation or replacement of the supported catalyst.

(44) In an embodiment, the process is carried out in a fixed-bed or in a fluidized-bed reactor comprising at least one catalytic bed. Such reactors are well-known from the person skilled in the art and for instance described in EP2257366 or in U.S. Pat. No. 7,279,138.

Test Methods and Definitions

(45) Activity for methanol synthesis reaction is determined using a home-made fixed-bed reactor set-up, which has been described in detail previously (M. S. Frei et al. J. Catal., 2018, 361, 313-321). Briefly, it comprises a high-pressure continuous-flow fixed-bed reactor with an inner diameter of 2.1 mm surrounded by an electric furnace. The reactor was loaded with 100 mg of catalyst with a particle size of 100-125 μm, which was held in place by a bed of quartz wool and was heated from ambient temperature to 553 K (5 K min.sup.−1) at 5 MPa under a He flow of 20 cm.sup.3.sub.STP g.sub.cat min.sup.−1. After 3 h, the gas flow was switched to the reactant mixture (40 cm.sup.3.sub.STP min.sup.−1) comprising H.sub.2 and CO.sub.2 (Messer, 99.997% and 99.999%, respectively) in a molar ratio of 4:1. A constant flow (2.5 cm.sup.3.sub.STP min.sup.−1) of 20 mol % CH.sub.4 in He (Messer, both 99.999%) was added to the effluent stream to serve as an internal standard. The effluent stream was sampled every 12 min and analyzed by an online gas chromatograph (GC, Agilent 7890A), equipped with two parallel columns (Agilent GS Gaspro and Agilent DB-1) connected to a flame ionization detector (FID) and a thermal conductivity detector (TCD), to determine the mol % content of the reactants H.sub.2, CO.sub.2, and CO in the feed stream and the mol % content of the reactants and the methanol product in the outlet stream.

(46) For each compound i, the response factor F.sub.i respective to the internal standard (CH.sub.4) was calculated by the following equation:

(47) $F_i=\frac{A_i/{\stackrel{.}{n}}_i^{\mathrm{in}}}{A_{{\mathrm{CH}}_4}/{\stackrel{.}{n}}_{{\mathrm{CH}}_4}^{\mathrm{in}}}$
where A.sub.i is the integrated area determined for compound i by the GC and {dot over (n)}.sub.i.sup.in corresponds to its known adjusted molar flowrate. Each response factor was calculated as the average of 5 calibration points around the expected concentration of the respective analyte i.

(48) Upon reaction the unknown effluent molar flowrate {dot over (n)}.sub.i.sup.out was determined by the following equation:

(49) ${\stackrel{.}{n}}_i^{\mathrm{out}}=\frac{A_i\times F_i}{A_{{\mathrm{CH}}_4}}\times {\stackrel{.}{n}}_{{\mathrm{CH}}_4}^{\mathrm{in}}$

(50) CO.sub.2 conversion (X.sub.CO2), methanol selectivity (S.sub.MeOH) and yield (Y.sub.MeOH) in percent and methanol space-time yield (STY.sub.MeOH) were calculated applying the following equations:

(51) $X_{{\mathrm{CO}}_2}=\frac{{\stackrel{.}{n}}_{{\mathrm{CO}}_2}^{\mathrm{in}}-{\stackrel{.}{n}}_{{\mathrm{CO}}_2}^{\mathrm{out}}}{{\stackrel{.}{n}}_{{\mathrm{CO}}_2}^{\mathrm{in}}}\times 100S_{\mathrm{MeOH}}=\frac{{\stackrel{.}{n}}_{\mathrm{MeOH}}^{\mathrm{in}}-{\stackrel{.}{n}}_{\mathrm{MeOH}}^{\mathrm{out}}}{{\stackrel{.}{n}}_{{\mathrm{CO}}_2-}^{\mathrm{in}}{\stackrel{.}{n}}_{{\mathrm{CO}}_2}^{\mathrm{out}}}\times 100Y_{\mathrm{MeOH}}=X_{{\mathrm{CO}}_2}\times S_{\mathrm{MeOH}}{\mathrm{STY}}_{\mathrm{MeOH}}=\frac{{\stackrel{.}{n}}_{\mathrm{MeOH}}^{\mathrm{in}}-{\stackrel{.}{n}}_{\mathrm{MeOH}}^{\mathrm{out}}}{W_{\mathrm{cat}}}\times M_{\mathrm{MeOH}}$
where W.sub.cat is the weight of the loaded catalyst and M.sub.MeOH is the molar weight of methanol (32.04 g mol.sup.−1).

(52) Data reported correspond to the average of the 4 measurements preceding a specific time-on-stream, or to the average of 7 measurements collected during each individual condition when temperature or gas flows were altered. The carbon loss in percent was determined for each experiment according to equation 4 and was found to be always less than 3%.

(53) ${\epsilon }_C=\frac{{\stackrel{.}{n}}_{{\mathrm{CO}}_2}^{\mathrm{out}}-{\stackrel{.}{n}}_{\mathrm{MeOH}}^{\mathrm{out}}-{\stackrel{.}{n}}_{\mathrm{CO}}^{\mathrm{out}}}{{\stackrel{.}{n}}_{{\mathrm{CO}}_2}^{\mathrm{in}}+{\stackrel{.}{n}}_{\mathrm{MeOH}}^{\mathrm{in}}}\times 100$

(54) Specific surface area and pore volume were determined from the sorption isotherm of N.sub.2 at 77 K (−196.15° C.). The Brunauer-Emmett-Teller (BET) method was applied for calculating the specific surface area and the volume of gas adsorbed at saturation pressure was used to determine the pore volume.

(55) Scanning transmission electron microscopy (STEM) imaging and energy dispersive X-ray spectroscopy (EDX) measurements were performed using a Talos F200X instrument operated at 200 kV and equipped with an FEI SuperX detector.

(56) The metal composition of the calcined samples was determined by inductively coupled plasma-optical emission spectrometry (ICP-OES) using a Horiba Ultra 2 instrument equipped with photomultiplier tube detector. Prior to analysis, the catalysts were dissolved in aqua regia and the resulting solutions were diluted with twice-distilled water.

(57) Carbon, hydrogen, nitrogen (CHN) were determined by using the standard method in which a solid sample is combusted in a pure oxygen environment above 1173 K. The gases produced are carried by helium and quantified as CO.sub.2, H.sub.2O, and N.sub.2 by a thermal conductivity detector (TCD). The method is based on ASTM D5921.

EXAMPLES

(58) The advantages of the present invention are illustrated in the following examples. However, it is understood that the invention is by no means limited to these specific examples.

Example 1—Catalyst Synthesis

(59) Wet Impregnation (WI)

(60) To obtain 9.5 wt. % In.sub.2O.sub.3 and 0.5 wt. % Pd on ZrO.sub.2, In(NO.sub.3).sub.3.xH.sub.2O (0.821 g, Sigma-Aldrich, 99.99%) and Pd(NO.sub.3).sub.2.xH.sub.2O (0.014 g, Sigma-Aldrich, >99.99% metals basis) were placed in a 250-cm.sup.3 round-bottom flask and dissolved in deionized water (100 cm.sup.3). Then ZrO.sub.2 (3.00 g, Alfa Aesar, 99.9% metals basis excluding Hf) was added and the slurry was stirred at room temperature for 30 min. The water was then removed using a rotary evaporator (100 rpm, 313 K, 8 kPa, ca. 90 min) and the sample was further dried in a vacuum oven (1.5 kPa, 323 K, ca. 90 min). Thereafter the sample was calcined at 573 K (2 K min.sup.−1) for 3 h static air.

(61) Coprecipitation (CP)

(62) To obtain 9.9 wt. % In.sub.2O.sub.3 and 0.1 wt. % Pd on ZrO.sub.2, In(NO.sub.3).sub.3.xH.sub.2O (0.57 g), Pd(NO.sub.3).sub.2.xH.sub.2O (0.01 g), and zirconyl nitrate solution (9.67 g, Sigma-Aldrich, 35 wt. % in dilute nitric acid) were placed with 70 cm.sup.3 of deionized water in a 250-cm.sup.3 round-bottom flask. A 10 wt. % Na.sub.2CO.sub.3 solution was prepared by dissolving Na.sub.2CO.sub.3 (5.0 g, Merck, >99%) in deionized water in a 50-cm.sup.3 volumetric flask. 33.9 cm.sup.3 of the Na.sub.2CO.sub.3 solution were then added drop-wise to the mixture until a pH of 9.2 was reached. The slurry was aged at room temperature for 60 min, then quenched with deionized water (70 cm.sup.3), thereafter the solid was separated by high-pressure filtration and washed with deionized water (3 times, 500 cm.sup.3 each time). The solid was then dried in a vacuum oven (1.5 kPa, 323 K, 90 min) and calcined at 573 or 773 K for 3 h (2 K min.sup.−1) in static air.

(63) Sol-Gel Synthesis (SG)

(64) To obtain 9.5 wt. % In.sub.2O.sub.3 and 0.5 wt. % Pd on ZrO.sub.2, In(NO.sub.3).sub.3.xH.sub.2O (0.55 g), Pd(NO.sub.3).sub.2.xH.sub.2O (0.02 g), and zirconyl nitrate solution (9.65 g, 35 wt. % in dilute nitric acid) were placed with nitric acid (0.38 g, Fisher Scientific UK, 65%) and deionized water (3.65 cm.sup.3) in a 250-cm.sup.3 round-bottom flask and stirred at ambient temperature until dissolution of all solids was observed by eye. A 66.7 wt. % citric acid solution, prepared by dissolving citric acid (1.00 g, Sigma-Aldrich, >98%) in 0.5 cm.sup.3 deionized water, was added dropwise to the zirconia mixture. Excess water was removed by evaporation at ambient pressure and 333 K over 3 h, yielding a highly viscous gel. The gel was dried to a powder in a vacuum oven (1.5 kPa, 323 K) and calcined in a tubular oven under a stream (ca. 1 dm.sup.3.sub.STP min.sup.−1) of air at 773 K for 3 h (2 K min.sup.−1).

(65) Deposition Precipitation (DP)

(66) To obtain 9.0 wt. % In.sub.2O.sub.3 and 1 wt. % Pd, In(NO.sub.3).sub.3.xH.sub.2O (0.63 g) and Pd(NO.sub.3).sub.2.xH.sub.2O (0.05 g) were dissolved in 70 cm.sup.3 deionized water in a round bottom flask. ZrO.sub.2 (1.80 g) was sieved to have a particle size of ≤125 μm and was added to the metal salts solution. To this mixture, an aqueous Na.sub.2CO.sub.3 solution (ca. 10 cm.sup.3, 10 wt. %) was added dropwise until a pH of 9.2 was reached at which the slurry was aged for 60 min. The solid was then separated by high-pressure filtration and washed with deionized water (3 times, 500 cm.sup.3 each time). Thereafter, it was then dried in a vacuum oven (1.5 kPa, 323 K, 90 min) and calcined either at 773 K for 3 h (2 K min.sup.−1) in static air.

Co-Precipitation (CP)—Comparative Example

(67) An example of a catalyst containing 0.75 wt. % Pd is as follows: In(NO.sub.3).sub.3.xH.sub.2O (3.48 g) and Pd(NO.sub.3).sub.2.xH.sub.2O (34.8 mg) were dissolved in deionized water (50 cm.sup.3) in a round-bottomed flask. In a second vessel, a Na.sub.2CO.sub.3 solution was prepared by hydrolyzing Na.sub.2CO.sub.3 (10.0 g) in deionized water (100 cm.sup.3). 38.8 cm.sup.3 of the Na.sub.2CO.sub.3 solution were added dropwise (3 cm.sup.3 min.sup.−1) to the solution of metal nitrates under magnetic stirring at ambient temperature to reach a pH value of 9.2. The resulting slurry was aged for 60 min. After adding deionized water (50 cm.sup.3), the precipitate was separated by high-pressure filtration, washed with deionized water (3 times, 500 cm.sup.3 each time), dried in a vacuum oven (1.5 kPa, 323 K, 1.5 h), and calcined in static air (573 K, 3 h, 2 K min.sup.−1).

Wet Impregnation (WI)—Comparative Example

(68) To obtain 10 wt. % In.sub.2O.sub.3 on ZrO.sub.2, In(NO.sub.3).sub.3.xH.sub.2O (0.821 g) were placed in a 250 cm.sup.3 round-bottom flask and dissolved in deionized water (100 cm.sup.3). Then ZrO.sub.2 (3.00 g, Alfa Aesar, 99.9% metals basis excluding Hf) was added and the slurry was stirred at room temperature for 30 min. The water was then removed using a rotary evaporator (100 rpm, 313 K, 8 kPa, ca. 90 min) and the sample was further dried in a vacuum oven (1.5 kPa, 323 K, ca. 90 min). Thereafter the sample was calcined at 573 K (2 K min.sup.−1) for 3 h static air.

Example 2—Catalyst Testing

(69) Different catalytic system including Pd/In.sub.2O.sub.3/ZrO.sub.2 of various Pd loadings were evaluated in a methanol synthesis reaction, the results are given in Table 1.

(70) From this table it can be seen that the presence of palladium improves the STY by comparison to system without palladium, when applied using the correct synthesis method.

(71) TABLE-US-00001 TABLE 1 Catalyst testing, all samples were measured at 280° C., 5.0 MPa, molar H.sub.2:CO.sub.2 = 4, WHSV 24,000 cm.sup.3.sub.STP g.sub.cat.sup.−1 h.sup.−1. Synthesis T.sub.calcination Temperature Pd.sub.nominal In.sub.2O.sub.3,nominal X.sub.CO2 S.sub.MeOH STY.sub.MeOH Catalyst method [K] [K] [wt. %] [wt. %] [%] [%] [g.sub.MeOHg.sub.cat.sup.−1h.sup.−1] Ga.sub.2O.sub.3—Pd/SiO.sub.2.sup.a IW 673 523 2.0 2.6.sup.b 13.0 70.0  0.253 10 In.sub.2O.sub.3/ZrO.sub.2 WI 573 553 0.0 10.00 4.8 79.0 0.26 Pd—In.sub.2O.sub.3 CP 573  553.sup.a  0.75 99.25 11.5 78.0 0.66 9.5/0.5 In.sub.2O.sub.3—Pd/ZrO.sub.2 WI 573 553 0.5 9.50 6.9 78.8 0.37 9.9/0.1 In.sub.2O.sub.3—Pd/ZrO.sub.2 CP 573 553 0.1 9.90 0.0 — 0.00 9.5/0.5 In.sub.2O.sub.3—Pd/ZrO.sub.2 SG 573 553 0.5 9.50 1.3 98.6 0.09 9.9/0.1 In.sub.2O.sub.3—Pd/ZrO.sub.2 DP 573 553 0.1 9.90 5.2 75.6 0.27 9.9/0.1 In.sub.2O.sub.3—Pd/ZrO.sub.2 DP 773 553 0.1 9.90 6.1 77.8 0.33 9.0/1.0 In.sub.2O.sub.3—Pd/ZrO.sub.2 DP 553 553 1.0 9.00 12.1 75.9 0.63 9.0/1.0 In.sub.2O.sub.3—Pd/ZrO.sub.2 DP 773 553 1.0 9.00 14.0 73.2 0.70 9.0/1.0 In.sub.2O.sub.3—Pd/ZrO.sub.2 WI 773 553 1.0 9.00 11.2 81.3 0.63 .sup.aConditions: molar H.sub.2:CO.sub.2 = 3, 3.0 MPa, space velocity = 7800 h.sup.−1. IW = incipient wetness, Reference: S. E. Collins, et al. Catal. Lett. 2005, 103, 83-88. .sup.bGa.sub.2O.sub.3.

Example 4 Conversion of Carbon Dioxide, Selectivity Towards Methanol, and the Resulting STY.SUB.MeOH .Over Time

(72) FIG. 2 reports the catalytic data collected during a 300-h test to evaluate the selectivity in methanol (S.sub.MeOH) and the conversion of CO.sub.2 achieved by the Pd/In.sub.2O.sub.3/ZrO.sub.2 catalytic system (1.0 wt. % Pd loading and 9.0 wt. % In.sub.2O.sub.3 loading) of the present invention. The tests was performed at 553.15 K (280° C.), 5.0 MPa, molar H.sub.2:CO.sub.2=4, WHSV=48,000 cm.sup.3.sub.STP g.sub.cat.sup.−1 h.sup.−1, 0.1 g of catalyst.

(73) It is thus demonstrated that the selectivity in methanol is slightly below 80% (79.9%) and stays unaltered over 300 hours on stream.

(74) Similarly, the conversion in CO.sub.2 is slightly above 10% (10.1%) and does not change over 300 hours on stream.

(75) The space-time yield of methanol (STY.sub.MeOH) for the same test is shown to be stable at 1.10 g.sub.MeOH g.sub.cat.sup.−1 h.sup.−1. By comparison with the supported catalyst devoid of palladium, the productivity (STY) was around 2.5-times higher when palladium is present. The STY of the bulk oxide (In.sub.2O.sub.3) is on the other hand around 4.0-times lower when compared to the STY of the ternary catalytic system of the present invention.

Example 5 Stability of the Catalyst of the Present Invention

(76) FIG. 1 reports the catalytic data collected during a 24-h test to evaluate the stability of the Pd/In.sub.2O.sub.3/ZrO.sub.2 catalytic system (0.05 wt. % Pd loading) of the present invention and to compare it with the stability of the corresponding catalytic system devoid of palladium (In.sub.2O.sub.3/ZrO.sub.2) and unsupported (In.sub.2O.sub.3).

(77) Reaction conditions: 553 K (279.85° C.), 5.0 MPa, 24,000 cm.sup.3.sub.STP g.sub.cat.sup.−1 h.sup.−1, 0.1 g of catalyst, molar H.sub.2:CO.sub.2=4:1.

(78) After an initial STY above 0.30 g.sub.MeOH g.sub.cat.sup.−1 h.sup.−1, a quick rise in the productivity (STY) to reach a STY of 0.36 g.sub.MeOH g.sub.cat.sup.−1 h.sup.−1 has been observed in the first hour of the reaction. Thereafter, the productivity of the catalyst stays unaltered. By comparison with the supported catalyst devoid of palladium, the productivity (STY) was around 1.5-times higher when palladium is present. The STY of the bulk oxide (In.sub.2O.sub.3) is on the other hand around 2.5-times lower when compared to the STY of the ternary catalytic system of the present invention.