Patent Publication Number: US-2022219147-A1

Title: Active and stable copper-based catalyst for co2 hydrogenation to methanol

Description:
This application claims priority to, and the benefit of, U.S. Provisional Patent Application No. 63/136,542 filed Jan. 12, 2021. The entirety of this application is incorporated herein by reference for all purposes. 
    
    
     FIELD 
     This invention relates to novel lanthanum oxide-promoted Cu-based nanocomposite catalysts, their synthesis via a simple one-pot solution combustion synthesis, and their use for CO 2  hydrogenation to methanol. 
     BACKGROUND 
     The world&#39;s energy demand, fueled by population growth and improved standards of living is expected to double by 2100 and the Intergovernmental Panel on Climate Change (IPCC) study showcases that as anthropogenic CO 2  emissions continues to rise, this results in CO 2  pollution into the atmosphere. For this reason, population growth should be met responsibly and sustainably by managing CO 2  emissions. With the aim to contain these emissions, Global CO 2  Initiative (GCI) proposed reduction in CO 2  emissions by its capture and/or its re-use. This initiative was structured to accelerate innovation and development in carbon capture and its utilization (CCUS), with the goal of commercializing CO 2 -based products to result in the reduction of carbon dioxide emissions and create value out of waste. Currently, efforts are being made to develop promising catalysts for the thermochemical and/or electrochemical reduction of CO 2  into useful products, such as methanol. However, an efficient and cost-effective catalyst for CO 2  hydrogenation to methanol is yet to be developed. This is mainly due to the following:
         (i) Activity and methanol selectivity of the catalysts under moderate pressure and temperature is low and/or limited. This is because of the existence of the endothermic reverse water gas shift (RWGS) reaction that can produce carbon monoxide;   (ii) Catalysts experience deactivation with time on stream if the gaseous feed is based on pure CO 2 ; and   (iii) High reaction temperatures (&gt;280° C.) are often required to achieve better CO 2  conversion, which in turn leads to a significant decrease in methanol selectivity and deactivation of the catalyst, as well as the formation of undesirable CH 4  production.       

     The object of this invention is to provide an improved, active, and stable catalyst for CO 2  hydrogenation to methanol that yields high amounts of methanol, no significant amount of CH 4 , and exhibits high selectivity for methanol under both moderate and high temperature and pressure conditions. 
     SUMMARY 
     Described herein are novel lanthanum oxide-promoted Cu-based nanocomposite catalysts that demonstrate excellent catalytic performance for the CO 2  hydrogenation to methanol. The catalysts are stable and highly active for CO 2  conversion in both moderate to high temperature and pressure ranges (about 250° C. to 350° C. and about 60 to 85 bars), yielding significantly high amounts of methanol. In certain embodiments, the catalysts as described herein exhibit a high methanol yield of about 2.45 g MeOH  g cat   −1  h −1  when exposed to a temperature of about 325° C., a pressure of about 85 bars, and a gas hourly space velocity of about 55,000 h −1 . 
     The catalysts are also highly selective for methanol, and during the catalytic conversion, produce no significant amounts of undesirable CH 4 . Importantly, in certain embodiments, even at high operating temperatures of 350° C., no CH 4  is produced. A catalyst that exhibits stability and catalytic activity under both moderate and high temperatures is advantageous. Activity under moderate or mild conditions involves less energy consumption and stability under high conditions allows for increased MeOH production without the expected loss in selectivity and increase in undesired byproducts. 
     In one embodiment, the nanocomposite catalyst for CO 2  hydrogenation to methanol is an efficient and stable alumina supported copper and zinc nanocatalyst with a copper loading in the range of about 10 wt % to 60 wt % promoted with lanthanum oxide in the range of about 0.5 wt % to 10 wt %. 
     The active and stable catalyst and the efficient catalytic performance is attributed to various unique physicochemical properties, such as the presence of oxygen vacancies and/or surface defects, smaller metal particles size, and good dispersion. The formate pathway and the reverse water gas shift reaction (RWGS) pathway are two established pathways for CO 2  hydrogenation to methanol. The catalysts described herein exhibit improved conversion of CO 2  because once the overall reactions start by chemisorption of H 2  on the surface of copper, the CO 2  is chemisorbed onto the surface of ZnO and/or oxygen vacancy/defects. Further, the catalysts as described herein exhibit improved MeOH selectivity over carbon monoxide and high yield by improving adsorption of the formate intermediate during the formate pathway. In the absence of these surface defects, MeOH selectivity is expected to be lower as adsorption of the formate intermediate will be poor and the catalyst will tend to produce more CO. These properties make the catalysts important materials for various industrial and technological applications. 
     Also described herein is a method for the synthesis of lanthanum oxide promoted Cu-based nanocomposite catalysts supported on alumina via a single-step solution combustion synthesis. This simple one-step reaction results in the creation of more oxygen vacancies and/or surface defects due to the incorporation of lanthanum oxide-induced electronic modifications. In one embodiment, the single-step solution combustion synthesis is conducted in a batch size of about 10 g. In one embodiment, the synthesis affords an efficient and stable alumina supported copper and zinc nanocatalyst with a copper loading in the range of about 10 wt % to 60 wt % promoted with lanthanum oxide in the range of about 0.5 wt % to 10 wt %. 
     Also described herein is a method of hydrogenating CO 2  to methanol using the catalyst as described herein. In certain embodiments, the catalyst exhibits a high CO 2  conversion of about 30%, a selectivity for MeOH of about 42 wt %, and a methanol yield of about 2.45 g MEOH  g cat   −1  h −1  when the catalyst is exposed to a temperature of about 325° C., a pressure of about 85 bars, and a gas hourly space velocity of about 55,000 h −1 . 
     In certain embodiments, the material disclosed herein can be employed as a heterogeneous catalyst for various industrial processes, including, but not limited to, hydrogenation reactions, for example, hydrogenation of CO 2  to methanol and hydrogenation of CO 2  and/or CO to light olefins and paraffins. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  provides X-ray diffraction patterns of unpromoted 30 wt % CuO/50 wt % ZnO/Al 2 O 3  catalysts synthesized at various glycine/oxidant (G/O) molar ratios as described in Example 1. 
         FIG. 2  provides X-ray diffraction patterns of unpromoted 30 wt % CuO/50 wt % ZnO/Al 2 O 3  catalysts calcined at various temperatures as described in Example 1. 
         FIG. 3A  is TEM image of the 30 wt % CuO/50 wt % ZnO/1 wt % La 2 O 3 /Al 2 O 3  catalyst produced with a glycine/oxidant molar ratio (G/O) of 1.2 as described in Example 2. The sample was calcined at 600° C. TEM analysis affirmed XRD findings of  FIGS. 5A and 5B . 
         FIG. 3B  is TEM image and analysis of the 30 wt % CuO/50 wt % ZnO/1 wt % La 2 O 3 /Al 2 O 3  catalyst produced with a glycine/oxidant molar ratio (G/O) of 0.6 as described in Example 2. The sample was calcined at 600° C. TEM analysis affirmed XRD findings of  FIGS. 5A and 5B . 
         FIG. 3C  is TEM image and analysis of the 30 wt % CuO/50 wt % ZnO/1 wt % La 2 O 3 /Al 2 O 3  catalyst produced with a glycine/oxidant molar ratio (G/O) of 0.206 as described in Example 2. The sample was calcined at 600° C. As shown in  FIGS. 3A-3C , a fuel deficient mixture (lower G/O molar ratio) resulted in smaller average particle size. For example, the sample prepared with G/O molar ratio of 0.206 ( FIG. 3C ) resulted in an average particle size of 6.4 nm. TEM analysis affirmed XRD findings of  FIGS. 5A and 5B . 
         FIG. 4A  is a TEM image and analysis of the 30 wt % CuO/50 wt % ZnO/1 wt % La 2 O 3 /Al 2 O 3  catalyst produced with a glycine/oxidant molar ratio (G/O) of 0.206 calcined at 400° C. as described in Example 2. As shown in  FIG. 4A  and  FIG. 4B , particle size increases with the calcination temperature, which may be due to agglomeration. Calcination at 400° C. was effective for combustion and resulted in a minimal increase in particle size. TEM analysis affirmed XRD findings of  FIGS. 5A and 5B . 
         FIG. 4B  is a TEM image and analysis of the 30 wt % CuO/50 wt % ZnO/1 wt % La 2 O 3 /Al 2 O 3  catalyst produced with a glycine/oxidant molar ratio (G/O) of 0.206 calcined at 600° C. as described in Example 2. TEM analysis affirmed XRD findings of  FIGS. 5A and 5B . 
         FIG. 5A  is an X-ray photoelectron spectroscopy (XPS) analysis of unpromoted 30 wt % CuO/50 wt % ZnO/Al 2 O 3  catalyst as described in Example 2. 
         FIG. 5B  is an X-ray photoelectron spectroscopy (XPS) analysis of lanthanum oxide promoted 30 wt % CuO/50 wt % ZnO/1 wt % La 2 O 3 /Al 2 O 3  catalyst as described in Example 2.  FIG. 5A  and  FIG. 5B  demonstrate the effects of lanthanum oxide incorporation into the catalyst. As shown in  FIG. 5B  compared to  FIG. 5A , with incorporation of lanthanum oxide, an increase in the percentage of induced phases was recorded. The percentage of these phases in  FIG. 5A  and  FIG. 5B  is calculated based on total area of the integrated peaks. 
         FIG. 6  is a temperature programmed reduction (TPR) profile of the unpromoted 30 wt % CuO/50 wt % ZnO/Al 2 O 3  catalyst synthesized via the SCS method as described in Example 2. 
         FIG. 7  is a temperature programmed reduction (TPR) profile of the lanthanum oxide promoted 30 wt % CuO/50 wt % ZnO/1 wt % La 2 O 3 /Al 2 O 3  catalyst synthesized via the SCS method as described in Example 2. As shown in  FIG. 7  compared to  FIG. 6 , a shift in reduction temperature to higher degrees was recorded for the lanthanum oxide promoted catalyst, indicating an increase in stronger metal support interaction and the presence of surface defects and/or oxygen vacancies. 
         FIG. 8A  illustrates the CO 2  conversion, measured in percent, of the 30 wt % CuO/50 wt % ZnO/1 wt % La 2 O 3 /Al 2 O 3  catalyst at the various reaction conditions presented in Table 2 of Example 3. 
         FIG. 8B  illustrates the CO 2  selectivity, measured in weight percent, of the 30 wt % CuO/50 wt % ZnO/1 wt % La 2 O 3 /Al 2 O 3  catalyst at the various reaction conditions presented in Table 2 of Example 3. 
         FIG. 8C  illustrates the MeOH selectivity, measured in weight percent, of the 30 wt % CuO/50 wt % ZnO/1 wt % La 2 O 3 /Al 2 O 3  catalyst at the various reaction conditions presented in Table 2 of Example 3. 
         FIG. 8D  illustrates the CO yield, measured in g CO  g cat   −1  h −1 , of the 30 wt % CuO/50 wt % ZnO/1 wt % La 2 O 3 /Al 2 O 3  catalyst at the various reaction conditions presented in Table 2 of Example 3. 
         FIG. 8E  illustrates the MeOH yield, measured in g MEOH  g cat   −1  h −1 , of the 30 wt % CuO/50 wt % ZnO/1 wt % La 2 O 3 /Al 2 O 3  catalyst at the various reaction conditions presented in Table 2 of Example 3. 
         FIG. 9A  illustrates the CO 2  selectivity, the MeOH selectivity, and the CO 2  conversion percentage of the 30 wt % CuO/50 wt % ZnO/1 wt % La 2 O 3 /Al 2 O 3  catalyst for reaction conditions 7-16 for the T.O.S. (time on stream) stability test as described in Example 4. 
         FIG. 9B  illustrates the CO and MeOH yield of the 30 wt % CuO/50 wt % ZnO/1 wt % La 2 O 3 /Al 2 O 3  catalyst at reaction conditions 7-16 for the T.O.S. (time on stream) stability test as described in Example 4. 
     
    
    
     DETAILED DESCRIPTION 
     Described herein is a novel lanthanum oxide-promoted Cu-based nanocomposite catalyst that demonstrates excellent catalytic performance for CO 2  hydrogenation to methanol. The catalyst is highly active for CO 2  conversion and yields high amounts of methanol in the temperature range of 250° C. to 350° C. and a pressure range of 60 to 85 bars. Furthermore, the catalyst is highly selective for methanol, and during the catalytic conversion, produces no significant amount of the undesirable byproduct CH 4 . 
     Definitions 
     The terms “a” and “an” do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item. The term “or” means “and/or”. Recitation of ranges of values merely intend to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. The endpoints of all ranges are included within the range and independently combinable. All processes described herein can be performed in a suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of example, or exemplary language (e.g., “such as”), is intended merely to better illustrate the invention and does not pose a limitation on the scope of the invention on unless otherwise claimed. 
     “Stability” is the ability of a catalyst to resist or be resilient to deactivation due to surface changes. Stability is quantified by measuring CO 2  conversion and MeOH selectivity as reaction time proceeds. Under given conditions of pressure, temperature and gaseous feed, a stable catalyst will exhibit no change in CO 2  conversion and MeOH selectivity. Changes in conversion and/or selectivity indicate surface changes of the catalyst. 
     “Gas hourly space velocity” (GHSV) or “space velocity” is the relation between volumetric flow rate and reactor volume of the catalyst. It signifies how many volumes of feed can be fed in a unit time through the volume of the catalyst and is calculated by the following equation: volumetric flow rate of gas/external volume of the catalyst monolith. 
     “Nanoparticle” as used herein, generally refers to a particle having a diameter, such as an average diameter in the range of about 1 nm to 100 nm, for example, from about 3 nm to about 20 nm. The particles can have any shape. Nanoparticle size is calculated using Debye Scherrer&#39;s equation from the XRD spectrum using the most intense peak measured full width at half maxima). 
     “Nanocatalyst” or “nanocomposite catalyst” is a catalyst where the active components/metals are in the range of about 1 nm to 100 nm, preferably dispersed over a porous support. 
     “Sintering” refers to agglomeration due to surface migration of the active metal particles. This results in the loss of the active metal surface in the catalyst and a decrease in activity. 
     Lanthanum Oxide-Promoted Cu-Based Catalysts 
     In one embodiment, the lanthanum oxide-promoted Cu-based nanocomposite catalyst comprises: 
     (a) Nanoparticulates in the size range of about 3 nm to 20 nm comprising:
         (1) a copper oxide loading of about 20% wt % to 60 wt %;   (2) a zinc oxide of about loading of about 40 wt % to 65 wt %; and   (3) a lanthanum oxide with a loading of about 0.5 wt % to 10%; and,       

     (b) Alumina as support. 
     In another embodiment, the lanthanum oxide-promoted Cu-based catalyst comprises: 
     (a) Nanoparticulates in the size range of about 3 nm to 20 nm comprising:
         (1) a copper oxide loading of about 30% wt % to 60 wt %;   (2) a zinc oxide loading of about 50 wt % to 62 wt %; and   (3) a lanthanum oxide loading between about 0.5 wt % to 10%; and,       

     (b) Alumina as support. 
     In another embodiment, the lanthanum oxide-promoted Cu-based catalyst comprises: 
     (a) Copper oxide nanoparticles in the size range of about 3 nm to 20 nm with a copper loading of 30 wt % to 60 wt %; 
     (b) Zinc oxide with a loading of 50 wt % to 62 wt %; 
     (c) Lanthanum oxide with a loading in the range between 0.5 wt % and 10 wt %; and 
     (d) Alumina as support. 
     In certain embodiments, the catalyst is characterized by a copper oxide loading in the range of about 20 wt % to 60 wt %. In certain embodiments, the catalyst is characterized by a copper oxide loading in the range of about 30 wt % to 60 wt %. In certain embodiments, the catalyst is characterized by copper oxide loading in the range of about 20 to 50 wt %, about 20 to 40 wt %, about 25 wt % to 40 wt %, about 30 wt % to 50 wt %, or about 20 wt % to 35 wt %. In a preferred embodiment, the catalyst is characterized by a copper oxide loading of about 30 wt %. 
     In certain embodiments, including any of the foregoing, the catalyst is characterized by a zinc oxide loading in the range of about 40 wt % to 65 wt %. In certain embodiments, including any of the foregoing, the catalyst is characterized by a zinc oxide loading in the range of about 50 wt % to 62 wt %. In certain embodiments, including any of the foregoing, the catalyst is characterized by a zinc oxide loading in the range of about 40 wt % to 60 wt %, about 40 wt % to 50 wt %, or about 50 wt % to 60 wt %. In a preferred embodiment, the catalyst is characterized by a zinc oxide loading of about 50 wt %. 
     In certain embodiments, including any of the foregoing, the catalyst is characterized by a lanthanum oxide loading in the range of about 0.5 wt % to 10.0 wt %. In certain embodiments, including any of the foregoing, the catalyst is characterized by a lanthanum oxide loading in the range of about 0.5 wt % to 8.0 wt %, about 0.5 wt % to 6.0 wt %, about 0.5 wt % to 4.0, about 0.5 wt % to 2.0 wt %, or about 0.5 wt % to 1.5 wt %. In certain embodiments, including any of the foregoing, the catalyst is characterized by a lanthanum oxide loading in the range of about 0.5 wt % to 3.0 wt %. In one embodiment, including any of the foregoing, the catalyst is characterized by a lanthanum oxide loading of at least about 0.5 wt %. In one embodiment, including any of the foregoing, the catalyst is characterized by a lanthanum oxide loading of less than about 10 wt %. In a preferred embodiment, including any of the foregoing, the catalyst is characterized by a lanthanum oxide loading of about 1 wt %. 
     In certain embodiments, including any of the foregoing, the catalyst comprises between about 20 wt % to 60 wt % of copper oxide, between about 40 wt % to 65 wt % of zinc oxide, and between about 0.5 wt % to 10 wt % of lanthanum oxide. In certain embodiments, including any of the foregoing, the catalyst comprises between about 30 wt % to 60 wt % of copper oxide, between about 50 wt % to 62 wt % of zinc oxide, and between about 0.5 wt % to 10 wt % of lanthanum oxide. In certain embodiments, the catalyst comprises about 30 wt % of copper oxide, about 50 wt % of zinc oxide, and about 1 wt % of lanthanum oxide. 
     In one embodiment, including any of the foregoing, the catalyst comprises between about 20 wt % to 60 wt % of copper oxide, between about 40 wt % to 65 wt % of zinc oxide, and between about 0.5 wt % to 10 wt % of lanthanum oxide on Al 2 O 3  support. In one embodiment, including any of the foregoing, the catalyst comprises between about 30 wt % to 60 wt % of copper oxide, between about 50 wt % to 62 wt % of zinc oxide, and between about 0.5 wt % to 10 wt % of lanthanum oxide on Al 2 O 3  support. In one embodiment, including any of the foregoing, the catalyst comprises about 30 wt % of copper oxide, about 50 wt % of zinc oxide, and about 1 wt % of lanthanum oxide on Al 2 O 3  support. 
     In certain embodiments, including any of the foregoing, the nanoparticles of the nanocomposite catalyst described herein range from about 3 nm to 20 nm in diameter. In certain embodiments, including any of the foregoing, the nanoparticles of the nanocomposite catalyst described herein range from about 3 nm to 18 nm, from about 3 nm to 15 nm, from about 3 nm to 10 nm, from about 3 nm to 8 nm, or from about 3 nm to 6 nm in diameter. In certain embodiments, including any of the foregoing, the nanoparticles of the nanocomposite catalyst described herein range from about 3.87 nm to 18.1 nm in diameter. In certain embodiments, including any of the foregoing, the nanoparticles of the nanocomposite catalyst described herein is about 4 nm, about 4.5 nm, about 5 nm, about 7 nm, or about 18 nm in diameter. In one embodiment, including any of the foregoing, the nanoparticles of the nanocomposite catalyst described herein is about 3.9 nm, about 4.5 nm, about 5.0 nm, about 7.4 nm, or about 18.1 nm in diameter. 
     In certain embodiments, including any of the foregoing, the nanocomposite catalyst described herein is characterized by a BET surface area of between about 60 and 80 m 2 /g. In certain embodiments, including any of the foregoing, the catalyst is characterized by a BET surface area of between about 70 and 80 m 2 /g. In certain embodiments, including any of the foregoing, the catalyst is characterized by a BET surface area of between about 75 and 80 m 2 /g. In one embodiment, including any of the foregoing, the catalyst is characterized by a BET surface area of about 77 m 2 /g. 
     The Cu-based nanocomposite catalysts as described herein exhibit superior activity and stability during CO 2  hydrogenation. In certain embodiments, including any of the foregoing, the catalyst is stable during CO 2  hydrogenation to methanol in a temperature range between about 200° C. to 400° C. In certain embodiments, including any of the foregoing, the catalyst is stable during CO 2  hydrogenation to methanol in a temperature range between about 250° C. to 350° C. In certain embodiments, including any of the foregoing, the catalyst is stable during CO 2  hydrogenation to methanol up to a temperature of about 350° C. or about 400° C. In certain embodiments, including any of the foregoing, the catalyst is stable during CO 2  hydrogenation to methanol at a temperature greater than about 200° C. or about 250° C. 
     In certain embodiments, including any of the foregoing, the catalyst is stable during CO 2  hydrogenation to methanol at a pressure range between about 50 bars to 90 bars. In certain embodiments, including any of the foregoing, the catalyst is stable during CO 2  hydrogenation to methanol at a pressure range between about 60 bars to 85 bars. In certain embodiments, including any of the foregoing, the catalyst is stable during CO 2  hydrogenation to methanol at a pressure range between about 60 bars to 70 bars or between about 70 bars to 85 bars. In certain embodiments, including any of the foregoing, the catalyst is stable during CO 2  hydrogenation to methanol at a pressure range up to about 90 bars. In certain embodiments, including any of the foregoing, the catalyst is stable during CO 2  hydrogenation to methanol at a pressure range greater than about 50 bars. 
     In certain embodiments, including any of the foregoing, the catalyst is stable during CO 2  hydrogenation to methanol at a gas hourly space velocity (GHSV) range of about 7,000 h −1  to 55,000 h −1 . In certain embodiments, including any of the foregoing, the catalyst is stable during CO 2  hydrogenation to methanol at a GHSV range of between about 7,000 h −1  to 10,000 h −1 , between about 10,000 h −1  to 15,000 h −1 , between about 15,000 h −1  to 20,000 h −1 , between about 20,000 h −1  to 25,000 h −1 , between about 25,000 h −1  to 30,000 h −1 , between about 30,000 h −1  to 35,000 h −1 , between about 35,000 h −1  to 45,000 h −1 , between about 45,000 h −1  to 50,000 h −1 , or between about 50,000 h −1  to 55,000 h −1 . In certain embodiments, including any of the foregoing, the catalyst is stable during CO 2  hydrogenation to methanol at a GHSV range of between about 27,000 h −1  to 55,000 h −1 . In certain embodiments, including any of the foregoing, the catalyst is stable during CO 2  hydrogenation to methanol at a GHSV range of greater than about 7,000 h −1 . In certain embodiments, including any of the foregoing, the catalyst is stable during CO 2  hydrogenation to methanol at a GHSV range of less than about 55,000 h −1 . 
     In certain embodiments, including any of the foregoing, the catalyst is stable during CO 2  hydrogenation to methanol at molar ratio of H 2 :CO 2  in the range of about 2:1 to 5:1. In certain embodiments, including any of the foregoing, the catalyst is stable during CO 2  hydrogenation to methanol at molar ratio of H 2 :CO 2  in the range of about 3:1 to 4:1. In certain embodiments, including any of the foregoing, the catalyst is stable during CO 2  hydrogenation to methanol at molar ratio of H 2 :CO 2  in the range of about 3:1. In certain embodiments, including any of the foregoing, the catalyst is stable during CO 2  hydrogenation to methanol at molar ratio of H 2 :CO 2  in the range of about 3.4:1. In certain embodiments, including any of the foregoing, the catalyst is stable during CO 2  hydrogenation to methanol at molar ratio of H 2 :CO 2  in the range of about 4:1. 
     Further, in certain embodiments, including any of the foregoing, the catalyst as described herein is stable under the conditions described herein for a period of at least about 4,000 hours, about 6,000 hours, about 8,000 hours, about 9,000 hours, about 10,000 hours, about 12,000 hours, about 14,000 hours, or more. In certain embodiments, including any of the foregoing, the catalyst is stable under the conditions as described herein for a period of at least about 1,200 hours or more. In one embodiment, including any of the foregoing, the catalyst is stable under the conditions as described herein for a period of at least about 1,400 hours or more. 
     In one embodiment, including any of the foregoing, the catalyst is stable during CO 2  hydrogenation to methanol in a temperature range between about 250° C. to 350° C., a pressure range between about 60 bars to 85 bars, a gas hourly space velocity (GHSV) range of about 7,000 h −1  to 55,000 h −1  and a molar ratio of H 2 :CO 2  in the range of about 3:1 to 4:1. In one embodiment, including any of the foregoing, the catalyst is characterized by a BET surface area of about 77 m 2 /g and is stable during CO 2  hydrogenation to methanol in a temperature range between about 250° C. to 350° C., a pressure range between about 60 bars to 85 bars, a space velocity range of about 7,000 h −1  to 55,000 h −1  and molar ratio of H 2 :CO 2  in the range of about 3:1 to 4:1. 
     In certain embodiments, including any of the foregoing, the catalyst is stable during CO 2  hydrogenation to methanol for at least about 14,000 hours in a temperature range between about 250° C. to 350° C., a pressure range between about 60 bars to 85 bars, a space velocity range of about 7,000 h −1  to 55,000 h −1  and a molar ratio of H 2 :CO 2  in the range of about 3:1 to 4:1. In certain embodiments, including any of the foregoing, the catalyst is characterized by a BET surface area of about 77 m 2 /g and is stable during CO 2  hydrogenation to methanol for at least about 14,000 hours in a temperature range between about 250° C. to 350° C., a pressure range between about 60 bars to 85 bars, a space velocity range of about 7,000 h −1  to 55,000 h −1  and a molar ratio of H 2 :CO 2  in the range of about 3:1 to 4:1. 
     In one embodiment, including any of the foregoing, the catalyst is stable during CO 2  hydrogenation to methanol for at least about 14,000 hours in a temperature range between about 250° C. to 350° C., a pressure range between about 60 bars to 85 bars, a space velocity range of about 5,000 h −1  to 5,500 h −1  and a molar ratio of H 2 :CO 2  in the range of about 3.4:1 to 4:1. 
     In certain embodiments, the catalyst as described herein exhibits excellence resilience to deactivation due to sintering. In certain embodiments, including any of the foregoing, the catalyst exhibits reliance to deactivation for a period of at least about 4.00 hours, about 6,000 hours, about 8,000 hours, about 9,000 hours, about 10,000 hours, about 12,000 hours, about 14,000 hours, or more. In certain embodiments, including any of the foregoing, the catalyst exhibits resilience to deactivation for a period of at least about 1,200 hours or more. In one embodiment, including any of the foregoing, the catalyst exhibits resilience to deactivation for a period of at least about 1,400 hours or more. 
     A Method of CO 2  Hydrogenation to Methanol Using Lanthanum Oxide-Promoted Cu-Based Catalysts 
     Further, in certain embodiments, including any of the foregoing, the catalyst as described herein does not produce methane (CH 4 ) as an undesired byproduct. In one embodiment, including any of the foregoing, the catalyst does not produce methane as an undesired byproduct at a temperature of at least about 350° C. In one embodiment, including any of the foregoing, the catalyst does not produce methane as an undesired byproduct at a temperature of about 350° C. 
     In one embodiment, including any of the foregoing, the catalyst as described herein exhibits a methanol yield of about 1.0 g MeOH  g cat   −1  h −1 . In one embodiment, including any of the foregoing, the catalyst as described herein exhibits a methanol yield of about 1.5 g MeOH  g cat   −1  about 2.0 g MeOH  g cat   −1  h −1 , about 2.5 g MeOH  g cat   −1  h −1 , about 3.0 g MeOH  g cat   −1  h −1 , about 5.0 g MeOH  g cat   −1  h −1 , or about 6.0 g MeOH  g cat   −1  h −1 . In one embodiment, including any of the foregoing, the catalyst as described herein exhibits a methanol yield of about 2.45 g MeOH  g cat   −1  h −1 . 
     In one embodiment, including any of the foregoing, the catalyst as described herein exhibits a conversion of CO 2  of greater than about 10%, greater than about 20%, greater than about 30%, greater than about 40%, greater than about 50%, greater than about 60%, or higher. In one embodiment, including any of the foregoing, the catalyst as described herein exhibits a conversion of CO 2  of about 30%. 
     In one embodiment, including any of the foregoing, the catalyst as described herein exhibits a selectivity for MeOH over carbon monoxide of greater than about 10 wt %, greater than about 20 wt %, greater than about 30 wt %, greater than about 40 wt %, greater than about 50 wt %, greater than about 60 wt %, or higher. In one embodiment, including any of the foregoing, the catalyst as described herein exhibits a selectivity for MeOH over carbon monoxide between about 40 wt % and 45 wt %. In one embodiment, including any of the foregoing, the catalyst as described herein exhibits a selectivity for MeOH over carbon monoxide of about 42 wt %. 
     In one embodiment, including any of the foregoing, the catalyst as described herein comprises between about 30 wt % to 60 wt % of copper oxide, between about 50 wt % to 62 wt % of zinc oxide, and between about 0.5 wt % to 10 wt % of lanthanum oxide on Al 2 O 3  support and exhibits a CO 2  conversion of about 30% with a MeOH selectivity over carbon monoxide of about 42 wt % and a methanol yield of about 2.45 g MeOH  g cat   −1  h −1 . 
     In one embodiment, including any of the foregoing, the catalyst as described herein comprises between about 30 wt % to 60 wt % of copper oxide, between about 50 wt % to 62 wt % of zinc oxide, and about 1.0 wt % of lanthanum oxide on Al 2 O 3  support and exhibits a CO 2  conversion of about 30% with a MeOH selectivity over carbon monoxide of about 42 wt % and a methanol yield of about 2.45 g MeOH  g cat   −1  h −1 . 
     In one embodiment, including any of the foregoing, the catalyst as described herein comprises about 30 wt % CuO/50 wt % ZnO/1 wt % La 2 O 3  by weight on Al 2 O 3  support and exhibits a CO 2  conversion of about 30% with a MeOH selectivity over carbon monoxide of about 42 wt % and a methanol yield of about 2.45 g MeOH  g cat   −1  h −1 . 
     In one embodiment, including any of the foregoing, the catalyst as described herein comprises between about 30 wt % to 60 wt % of copper oxide, between about 50 wt % to 62 wt % of zinc oxide, and between about 0.5 wt % to 10 wt % of lanthanum oxide on Al 2 O 3  support and exhibits a CO 2  conversion of about 30% with a MeOH selectivity over carbon monoxide of about 42 wt % and a methanol yield of about 2.45 g MeOH  g cat   −1  h −1  under the following specific conditions for about 5 hours: 1) a temperature of about 325°; 2) a molar ratio of H 2 :CO 2  of about 4:1; a pressure range of about 85 bars; and, 4) a space velocity of about 55,000 h −1 . 
     In one embodiment, including any of the foregoing, the catalyst as described herein comprises between about 30 wt % to 60 wt % of copper oxide, between about 50 wt % to 62 wt % of zinc oxide, and about 1.0 wt % of lanthanum oxide on Al 2 O 3  support and exhibits a CO 2  conversion of about 30% with a MeOH selectivity over carbon monoxide of about 42 wt % and methanol yield of about 2.45 g MeOH  g cat   −1  h −1  under the following specific conditions for about 5 hours: 1) a temperature of about 325°; 2) a molar ratio of H 2 :CO 2  of about 4:1; 3) a pressure range of about 85 bars; and, 4) a space velocity of about 55,000 h −1 . 
     In one embodiment, including any of the foregoing, the catalyst as described herein comprises about 30 wt % CuO/50 wt % ZnO/1 wt % La 2 O 3  by weight on Al 2 O 3  support and exhibits a CO 2  conversion of about 30% with a MeOH selectivity over carbon monoxide of about 42 wt % and methanol yield of about 2.45 g MeOH  g cat   −1  h −1  under the following specific conditions for about 5 hours: 1) a temperature of about 325°; 2) a molar ratio of H 2 :CO 2  of about 4:1; 3) a pressure range of about 85 bars; and, 4) a space velocity of about 55,000 h −1 . 
     Method for the Synthesis of Lanthanum Oxide-Promoted Cu-Based Catalysts Using a Combustion Synthesis Method 
     The present invention also provides a simple method for the synthesis of lanthanum oxide promoted Cu-based catalysts/nanocomposites supported on alumina via a single step solution combustion synthesis. 
     The method for synthesizing lanthanum oxide promoted Cu-based catalysts/nanocomposites supported on alumina via a single step solution combustion synthesis comprises the steps of:
         1) dissolving metal precursor nitrates in water and adding glycine;   2) stirring the mixture to afford a homogeneous mixture and heating the resulting solution over a hot plate for combustion that upon initiation, proceeds in an auto-thermal mode without any external heating source;   3) calcining the resultant powder to remove uncombusted precursor salts in air in a muffle furnace to afford the catalyst; and,   4) activating/reducing the catalyst prior to the hydrogenation of CO 2  by passing pure hydrogen stream over the catalyst.       

     In one embodiment, the metal precursor nitrates are copper nitrate trihydrate (Cu(NO 3 ) 2 .3H 2 O), zinc nitrate hexahydrate (Zn(NO 3 ) 2 .6H 2 O), aluminum nitrate nonahydrate (Al(NO 3 ) 3 .9H 2 O), and lanthanum nitrate hexahydrate (La(NO 3 ) 3 .6H 2 O). 
     In certain embodiments, including any of the foregoing, in step 4, the hydrogen stream is passed over the catalyst at a temperature in the range of about 300° C. to 550° C. or in the range of about 350° C. to 500° C. In one embodiment, in step 4, the hydrogen stream is passed over the catalyst at a temperature of about 350° C. In one embodiment, in step 4, the hydrogen stream is passed over the catalyst at a temperature of about 350° C. at a heating rate of 1° C. 
     In one embodiment, including any of the foregoing, the glycine/nitrate precursor molar ratio (glycine/oxidant ratio) is between about 0.1 and 1.5. In one embodiment, including any of the foregoing, the glycine/nitrate precursor ratio is between about 0.2 and 1.2. In one embodiment, including any of the foregoing, the glycine/nitrate precursor ratio is at least about 0.2. In one embodiment, including any of the foregoing, the glycine/nitrate precursor ratio is less than about 1.2. In one embodiment, including any of the foregoing, the glycine/nitrate precursor ratio is about 0.21. 
     In one embodiment, including any of the foregoing, the resultant powder is calcined at a temperature between about 300° C. to 850° C. In one embodiment, including any of the foregoing, the resultant powder is calcined at a temperature between about 400° C. to 800° C. In one embodiment, including any of the foregoing, the resultant powder is calcined at a temperature between about 400° C. to 600° C. In one embodiment, including any of the foregoing, the resultant powder is calcined at a temperature of about 400° C. In one embodiment, including any of the foregoing, the resultant powder is calcined in air for about 3 hours at 400° C. with a heating and cooling rate of 1° C. 
     In certain embodiments, including any of the foregoing, the catalyst described herein is tested for CO 2  hydrogenation in a temperature range between about 200° C. to 400° C. In certain embodiments, including any of the foregoing, the catalyst described herein is tested for CO 2  hydrogenation in a temperature range between about 250° C. to 350° C. 
     In certain embodiments, including any of the foregoing, the method described here affords a nanocomposite catalyst with a copper oxide loading in the range of about 20 wt % to 60 wt %. In certain embodiments, including any of the foregoing, the method described here affords a nanocomposite catalyst with a copper oxide loading in the range of about 30 wt % to 60 wt %. In certain embodiments, including any of the foregoing, the method described here affords a nanocomposite catalyst with a copper oxide loading in the range of about 20 to 50 wt %, about 20 to 40 wt %, about 30 wt % to 50 wt %, about 30 wt % to 50 wt %, or about 20 wt % to 30 wt %. In a preferred embodiment, the method described here affords a nanocomposite catalyst with a copper oxide loading of about 30 wt % copper oxide. 
     In certain embodiments, including any of the foregoing, the method described here affords a nanocomposite catalyst with a zinc oxide loading in the range of about 40 wt % to 65 wt %. In certain embodiments, including any of the foregoing, the method described here affords a nanocomposite catalyst with a zinc oxide loading in the range of about 50 wt % to 62 wt %. In certain embodiments, including any of the foregoing, the method described here affords a nanocomposite catalyst with a zinc oxide loading in the range of about 40 wt % to 60 wt %, about 40 wt % to 50 wt %, or about 50 wt % to 60 wt %. In a preferred embodiment, the method described here affords a nanocomposite catalyst with a zinc oxide loading of about 50 wt %. 
     In certain embodiments, including any of the foregoing, the method described here affords a nanocomposite catalyst with a lanthanum oxide loading in the range of about 0.5 wt % to 10.0 wt %. In certain embodiments, including any of the foregoing, the method described here affords a nanocomposite catalyst with a lanthanum oxide loading in the range of about 0.5 wt % to 8.0 wt %, about 0.5 wt % to 6.0 wt %, about 0.5 wt % to 4.0, about 0.5 wt % to 2.0 wt %, or about 0.5 wt % to 1.5 wt %. In certain embodiments, including any of the foregoing, the method described here affords a nanocomposite catalyst with a lanthanum oxide loading in the range of about 0.5 wt % to 3.0 wt %. In one embodiment, including any of the foregoing, the method described here affords a nanocomposite catalyst with a lanthanum oxide loading of at least about 0.5 wt %. In one embodiment, including any of the foregoing, the method described here affords a nanocomposite catalyst with a lanthanum oxide loading of less than about 10 wt % lanthanum oxide. In a preferred embodiment, including any of the foregoing, the method described here affords a nanocomposite catalyst with a lanthanum oxide loading of about 1 wt % lanthanum oxide. 
     In certain embodiments, including any of the foregoing, the method described here affords a nanocomposite catalyst with a copper oxide loading in the range of about 20 wt % to 60 wt %, a zinc oxide loading in the range of about 40 wt % to 65 wt %, and a lanthanum oxide is loading in the range of about 0.5 wt % to 10 wt %. In certain embodiments, including any of the foregoing, the method described here affords a nanocomposite catalyst with a copper oxide loading in the range of about 30 wt % to 60 wt %, a zinc oxide loading in the range of about 50 wt % to 62 wt %, and a lanthanum oxide loading in the range of about 0.5 wt % to 10 wt %. In certain embodiments, the method described here affords a nanocomposite catalyst with a copper oxide loading of about 30 wt % copper oxide, a zinc oxide loading of about 50 wt %, and a lanthanum oxide loading of about 1 wt %. 
     In certain embodiments, including any of the foregoing, the method described here affords a nanocomposite catalyst with a copper oxide loading in the range of about 20 wt % to 60 wt %, a zinc oxide loading in the range of about 40 wt % to 65 wt % of zinc oxide, and a lanthanum oxide loading in the range of about 0.5 wt % to 10 wt %. In certain embodiments, including any of the foregoing, the method described here affords a nanocomposite catalyst with a copper oxide loading in the range of about 30 wt % to 60 wt %, a zinc oxide loading in the range of about 50 wt % to 62 wt %, and a lanthanum oxide loading in the range of about 0.5 wt % to 10 wt %. In one embodiment, including any of the foregoing, the method described here affords a nanocomposite catalyst with a copper oxide loading of about 30 wt % copper oxide, a zinc oxide loading of about 50 wt %, and a lanthanum oxide loading of about 1 wt %. 
     In one embodiment, including any of the foregoing, the method described here affords a nanocomposite catalyst with a copper oxide loading between about 20 wt % to 60 wt %, a zinc oxide loading between about 40 wt % to 65 wt %, and a lanthanum oxide loading between about 0.5 wt % to 10 wt % on Al 2 O 3  support. In one embodiment, including any of the foregoing, the method described here affords a nanocomposite catalyst with a copper oxide loading between about 30 wt % to 60 wt % copper oxide, a zinc oxide loading between about 50 wt % to 62 wt %, and a lanthanum oxide loading between about 0.5 wt % to 10 wt % on the Al 2 O 3  support. In one embodiment, including any of the foregoing, the method described here affords a nanocomposite catalyst with a copper oxide loading of about 30 wt %, a zinc oxide loading of about 50 wt % zinc oxide, and a lanthanum oxide loading of about 1 wt % on Al 2 O 3  support. 
     In a preferred embodiment, including any of the foregoing, the method described herein affords highly active and stable copper oxide-based nanocatalysts with a metal loading in the range between about 30 wt % to 60 wt % promoted with lanthanum oxide with a loading range between about 0.5 wt % to 10 wt % supported on alumina. 
     In certain embodiments, the addition of lanthanum oxide assists in controlling the catalytic performance, for example, the conversion percent and the selectivity for MeOH. This may be because incorporation of lanthanum oxide into the copper catalyst results in creating surface defects and oxygen vacancies without altering the metal particle size. For example,  FIG. 6  is the temperature programmed reduction (TPR) profile of the unpromoted catalyst without lanthanum oxide and  FIG. 7  is the TPR profile of the catalyst with 1 wt % of lanthanum oxide. The shift in reduction temperatures to higher degrees in the TPR of  FIG. 7  indicates the presence of surface defects and oxygen vacancies compared to the TPR of  FIG. 6 . Additionally  FIG. 5A  is the XPS of the unpromoted catalyst without lanthanum oxide and  FIG. 5B  is the XPS of the catalyst with 1 wt % of lanthanum oxide. As shown in  FIG. 5B  compared to  FIG. 5A , the addition of 1 wt % of lanthanum oxide resulted in an increase in the percentage of Cu 2+ -induced phases. Therefore, in one embodiment, including any of the foregoing, the method described herein results in the creation of more oxygen vacancies and/or surface defects due to the incorporation of lanthanum oxide-induced electronic modifications. In one embodiment, the catalyst as described herein is characterized as exhibiting Cu 2+ -induced phases of greater than about 7% as measured by XPS wherein the percentage of the induced phases is calculated based on total area of the integrated peaks. In certain embodiments, the catalyst as described herein is characterized as exhibiting Cu 2+ -induced phases of greater than about 10%, greater than about 15%, greater than about 20%, or greater than about 25% as measured by XPS wherein the percentage of the induced phases is calculated based on total area of the integrated peaks. In one embodiment, the catalyst as described herein is characterized as exhibiting Cu 2+ -induced phases of about 18% as measured by XPS wherein the percentage of the induced phases is calculated based on total area of the integrated peaks. 
     EXAMPLES 
     Abbreviations 
     Al 2 O 3  aluminum oxide
 
CH 4  methane
 
CO carbon monoxide
 
CO 2  carbon dioxide
 
CuO copper oxide
 
G/O Glycine/oxidant ratio or glycine/metal nitrate precursors ratio
 
H 2  dihydrogen
 
La 2 O 3  lanthanum oxide
 
GHSV gas hourly space velocity
 
MeOH methanol
 
     T.O.S. Time on Stream 
     ZnO zinc oxide 
     Example 1. General Synthesis of Lanthanum Oxide-Promoted Cu-Based Catalysts 
     In a typical preparation procedure, required amounts of metal precursor nitrates are dissolved in an appropriate amount of water in a 1000 mL beaker. The required amount of glycine is also added. This mixture is then stirred well to afford a homogeneous mixture and the resulting solution is heated over a hot plate for combustion. The reaction is exothermic in nature and once the combustion initiates, it proceeds in an auto-thermal mode without any external heating source. 
     After complete combustion of all precursors, the resultant powder is calcined in air at the appropriate temperature (400° C.) in a muffle furnace. 
     Example 2. The Effect of Glycine/Oxidant Ratio and Calcination Temperature on Unpromoted Cu-Based Catalysts 
     Eight unpromoted 30 wt % CuO/50 wt % ZnO/Al 2 O 3  catalysts were synthesized with various glycine/nitrate precursor (glycine/oxidants, G/O) ratios. The catalysts were synthesized according to the general procedure in Example 1. Each sample was prepared with 9.1 g of Cu(NO 3 ) 2 .3H 2 O, 18.15 g of Zn(NO 3 ) 2 .6H 2 O, and 14.12 g of Al(NO 3 ) 3 .9H 2 O dissolved in 100 mL of H 2 O. The amount of glycine for each catalyst is provided in Table 1. The samples were calcined at 600° C. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Glycine amount to prepare unpromoted  
               
               
                 30 wt % CuO/50 wt % ZnO/Al 2 O 3   
               
               
                 catalysts of FIG. 1 with various G/O ratios 
               
            
           
           
               
               
               
            
               
                   
                 Molar ratio 
                   
               
               
                   
                 of G/O 
                 Glycine (g) 
               
               
                   
                   
               
            
           
           
               
               
               
            
               
                   
                 1.236 
                 28.80 
               
               
                   
                 0.927 
                 21.60 
               
               
                   
                 0.804 
                 18.72 
               
               
                   
                 0.747 
                 17.20 
               
               
                   
                 0.618 
                 14.40 
               
               
                   
                 0.309 
                 7.20 
               
               
                   
                 0.258 
                 6 
               
               
                   
                 0.206 
                 4.80 
               
               
                   
                   
               
            
           
         
       
     
     The characterization and catalytic test results for nanocatalysts are provided below. The X-ray diffraction patterns for each catalyst demonstrate the effects of G/O (glycine/oxidants) molar ratio on the particle size ( FIG. 1 ). By varying the G/O ratio, the size of the nanoparticles was modified. The lower the glycine/oxidant ratio, the smaller the nanoparticle. For example, a G/O molar ratio of 0.206 resulted in comparatively smaller and well dispersed nanoparticles (4.46 nm). For this reason, the G/O molar ratio of 0.206 was held constant in the next study where the effect of calcination temperature on particle size was study. As shown in  FIG. 2 , as calcination temperature was lowered from 800° C. to 400° C., the particle size decreased. 
     Example 3. Characterization of Promoted Cu-Based Catalysts 
     Three promoted 30 wt % CuO/50 wt % ZnO/1 wt % La 2 O 3 /Al 2 O 3  catalysts were synthesized with various G/O (glycine/oxidants) molar ratios. The samples were calcined at 600° C. The catalysts were synthesized according to the general procedure in Example 1. Each sample was prepared with 9.1 g of Cu(NO 3 ) 2 .3H 2 O, 18.15 g of Zn(NO 3 ) 2 .6H 2 O, 0.2656 g of La(NO 3 ) 3 .6H 2 O, and 13.42 g of Al(NO 3 ) 3 .9H 2 O dissolved in 100 mL of H 2 O. The amount of glycine for the catalysts prepared with a G/O molar ratio of 1.2, 0.6, and 0.2 was the same as the amount shown in Table 1. 
     TEM images for the promoted 30 wt % CuO/50 wt % ZnO/1 wt % La 2 O 3 /Al 2 O 3  catalysts prepared with varying amounts of glycine are shown in  FIGS. 3A-3C . As shown in  FIGS. 3A-3C , a fuel deficient mixture (lower G/O molar ratio) resulted in smaller average particle size. For example, the sample prepared with G/O molar ratio of 0.206 ( FIG. 3C ) resulted in an average particle size of 6.4 nm. TEM images for the promoted 30 wt % CuO/50 wt % ZnO/1 wt % La 2 O 3 /Al 2 O 3  catalysts calcined at 400° C. and 600° C. are shown in  FIG. 4A  and  FIG. 4B , respectively. Calcination at 400° C. was effective for combustion and resulted in a minimal increase in particle size. 
       FIG. 5A  and  FIG. 5B  demonstrate the effects of lanthanum oxide incorporation into the catalyst.  FIG. 5A  is the X-ray photoelectron spectroscopy (XPS) analysis of unpromoted 30 wt % CuO/50 wt % ZnO/Al 2 O 3  catalyst and  FIG. 5B  is the X-ray photoelectron spectroscopy (XPS) analysis of lanthanum oxide promoted 30 wt % CuO/50 wt % ZnO/1% La 2 O 3 /Al 2 O 3 . As shown in  FIG. 5B  compared to  FIG. 5A , with incorporation of lanthanum oxide, an increase in the percentage of induced phases was recorded. The percentage of induced peaks in the unpromoted catalyst ( FIG. 5A ) was only 7%, while the percentage in the promoted catalyst ( FIG. 5B ) was 18%. The percentage of these phases is calculated based on total area of the integrated peaks. 
     The effect of lanthanum oxide addition is also shown in  FIG. 6  and  FIG. 7 .  FIG. 6  is the temperature programmed reduction (TPR) profile of the unpromoted catalyst (30 wt % CuO/50 wt % ZnO/Al 2 O 3 ) and  FIG. 7  is the temperature programmed reduction (TPR) profile of the lanthanum oxide promoted catalyst (30 wt % CuO/50 wt % ZnO/1 wt % La 2 O 3 /Al 2 O 3 ). As shown in  FIG. 7  compared to  FIG. 6 , a shift in reduction temperature to higher degrees was recorded for the lanthanum oxide promoted catalyst, indicating an increase in stronger metal support interaction and the presence of surface defects and/or oxygen vacancies. 
     Example 4. Catalytic Performance of 30 wt % CuO/50 wt % ZnO/1 wt % La 2 O 3 /Al 2 O 3 Catalyst 
     The catalytic performance of the lanthanum oxide promoted 30 wt % CuO/50 wt % ZnO/1 wt % La 2 O 3 /Al 2 O 3  catalyst prepared with a G/O molar ratio of 0.206 and calcined at 400° C. was evaluated in a high-pressure lab-scale test unit (PID, Micromeritics) under various conditions. 
     The unit was equipped with three gas lines controlled by high accuracy mass flow controllers and it operated with a stainless steel and hastelloy fixed bed reactor (ID: 9.3 mm), externally heated with a three-zone furnace. The exit stream of the reactor was cooled via a paltrier cold trap and was directed to a system of vessel for the separation and collection of the liquid and gaseous products. The reaction temperature was monitored with a thermocouple inserted in the catalytic bed. The gaseous products were analyzed using an on-line GC-TCD. The liquids were collected in a trap (5° C.) and were analyzed offline. The analysis was performed with a GC Agilent 7890A equipped with FID detectors. 
     Catalytic test results under the parameters in Table 2 are shown in  FIGS. 8A-8E . The highest yield of MeOH recorded was under Condition 7 where the temperature was 325° C., the pressure was 85 bar; the gas hourly space velocity was 55,000 h −1 , and the H 2 /CO 2  molar ratio was 4:1. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Conditions for Catalytic Performance Evaluations 
               
            
           
           
               
               
               
            
               
                   
                   
                 Parameters/Conditions 
               
            
           
           
               
               
               
               
               
               
            
               
                   
                   
                   
                   
                 Gas  
                 H 2 /CO 2    
               
               
                   
                   
                 Temperature  
                 Pressure  
                 Hourly Space 
                 Molar 
               
               
                   
                 Condition 
                 (° C.) 
                 (bar) 
                 Velocity (h −1 ) 
                 Ratio 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
               
            
               
                   
                 1 
                 250 
                 60 
                 27,000 
                 3.43 
               
               
                   
                 2 
                 250 
                 85 
                 27,000 
                 3.43 
               
               
                   
                 3 
                 250 
                 85 
                 27,000 
                 3.43 
               
               
                   
                 4 
                 275 
                 65 
                 27,000 
                 4 
               
               
                   
                 5 
                 300 
                 85 
                 27,000 
                 4 
               
               
                   
                 6 
                 300 
                 85 
                 55,000 
                 4 
               
               
                   
                 7 
                 325 
                 85 
                 55,000 
                 4 
               
               
                   
                 8 
                 350 
                 85 
                 55,000 
                 4 
               
               
                   
                 9 
                 350 
                 85 
                 55,000 
                 4 
               
               
                   
                   
               
            
           
         
       
     
     Example 4. Stability Test of 30 wt % CuO/50 wt % ZnO/1 wt % La 2 O 3 /Al 2 O 3 Catalyst 
     For the stability test, the 30 wt % CuO/50 wt % ZnO/1 wt % La 2 O 3 /Al 2 O 3  catalyst was first activated following the same procedure described on pages 15-16. This activation was performed by heating the catalyst to 350° C. in a gaseous stream of pure hydrogen at a ramp of 1° C. with a dwell time of three hours. The catalyst was then cooled down to the initial conditions described in Condition 1 in Table 3 (250° C.). This was followed by switching the flow to the required composition of reactants mixture gas and increasing the pressure to 60 bars (Condition 1 of Table 3). The conditions were changed over time according to Table 3. The CO selectivity, the MeOH selectivity, and the CO 2  conversion for conditions 7-16 are shown in  FIG. 9A . The CO and MeOH yield for conditions 7-16 are shown in  FIG. 9B . 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Parameters and Conditions of Stability Test 
               
            
           
           
               
               
            
               
                   
                 Parameters/Conditions 
               
            
           
           
               
               
               
               
               
            
               
                   
                   
                   
                 Gas  
                 H 2 /CO 2    
               
               
                   
                 Temperature  
                 Pressure  
                 Hourly Space 
                 Molar 
               
               
                 Condition 
                 (° C.) 
                 (bar) 
                 Velocity (h −1 ) 
                 Ratio 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                  1 
                 250 
                 60 
                 27,000 
                 3.43 
               
               
                  2 
                 250 
                 85 
                 27,000 
                 3.43 
               
               
                  3 
                 275 
                 85 
                 27,000 
                 3.43 
               
               
                  4 
                 275 
                 85 
                 27,000 
                 4 
               
               
                  5 
                 300 
                 85 
                 27,000 
                 4 
               
               
                  6 
                 300 
                 85 
                 54,000 
                 4 
               
               
                  7 
                 325 
                 85 
                 54,000 
                 4 
               
               
                   7′ 
                 325 
                 85 
                 54,000 
                 4 
               
               
                  8 
                 350 
                 85 
                 54,000 
                 4 
               
               
                  9 
                 275 
                 85 
                 7,000 
                 4 
               
               
                 10 
                 250 
                 85 
                 7,000 
                 4 
               
               
                 11 
                 275 
                 85 
                 7,000 
                 4 
               
               
                 12 
                 275 
                 85 
                 27,000 
                 4 
               
               
                 13 
                 275 
                 85 
                 54,000 
                 4 
               
               
                 14 
                 300 
                 85 
                 54,000 
                 4 
               
               
                 15 
                 325 
                 85 
                 5,400 
                 4 
               
               
                 16 
                 300 
                 85 
                 54,000 
                 4 
               
               
                   
               
            
           
         
       
     
     The previous detailed description is of a small number of embodiments for implementing the invention and is not intended to be limiting in scope. One of skill in the art will immediately envisage the methods and variations used to implement this invention in other areas than those described in detail. The following claims set forth a number of embodiments of the invention disclosed with greater particularity.