Methanol synthesis from CO2 hydrogenation over copper based catalysts

Preparation of Copper-Based Catalysts for Obtaining Methanol by the Chemical Impregnation Method

This paper presents the preparation of heterogeneous catalysts for the direct hydrogenation process of CO2 to methanol. The development of the modern chemical industry is inextricably linked to the use of catalytic processes. As a result, currently over 80% of new technologies introduced in the chemical industry incorporate catalytic processes. Since the basic factor of catalytic processes is the catalysts, the studies for the deepening of the knowledge regarding the nature of the action of the catalysts, for the development of new catalysts and catalytic systems, as well as for their improvement, represent a research priority of a fundamental or applied nature. The Cu/ZnO/Al2O3 catalyst for the synthesis of green methanol, using precursors of an inorganic (copper nitrate, denoted by Cu/ZnO/Al2O3-1) and organic (copper acetate, denoted by Cu/ZnO/Al2O3-2) nature, are obtained by chemical impregnation that includes two stages: preparation and one of calcination. The preparation methods and conditions, as well as the physico-chemical properties of the catalyst precursor, play a major role in the behavior of the catalysts. The prepared catalysts were characterized using atomic adsorption analysis, scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis, specific surface area and pore size analyses, adsorption, and the chemisorption of vapor (BET).

Reaction Mechanism and Kinetics for the Selective Hydrogenation of Carbon Dioxide to Formic Acid and Methanol over the [Cu2]0,±1 Dimer

With the rapid growth of industrialization, deforestation, and burning of fossil fuels, undeniably there has been an incredible escalation of the CO2 concentration in the atmosphere. In order to mitigate the problem, the capture and utilization of CO2 in different value-added chemicals have thus remained topics of concerned research for more than a decade. Accordingly, we have performed molecular -level catalytic hydrogenation of CO2 to formic acid using bare [Cu2]0,±1 dimers as catalysts. The entire investigation has been performed using a density functional theory (DFT) method employing the Perdew-Burke-Ernzerhof (PBE) functional with the def2TZVPP basis set to explore the different possible routes and efficiency of the catalysts. Results reveal the feasibility of H2 dissociation on all three Cu2, Cu2+, and Cu2- dimers. The negatively charged hydride formed during H2 dissociation on Cu2 and Cu2+ dimers facilitates the formation of the HCOO* intermediate over COOH*, thereby providing product selectivity for HCOOH above CO. However, the reaction on the Cu2- dimer forms both HCOO* and COOH* intermediates, but HCOO*, being kinetically more favorable, results in HCOOH production. The free-energy change suggests that the complete reaction on Cu2 and Cu2+ dimers forms a stable product compared to the Cu2- dimer. Furthermore, H3COH production is studied using the title catalysts via the obtained HCOOH* intermediate from the reaction channel. Transition state theory (TST) has been considered to evaluate the rate constants for each step of the reaction. Overall results suggest Cu2 to be better compared to Cu2+ and Cu2- dimers for HCOOH formation and Cu2+ over Cu2 and Cu2- dimers to be more efficient for H3COH formation. This work opens the way for further investigation of the reaction mechanism and development of an efficient catalyst for CO2 hydrogenation.

Constructing carbon supported copper-based catalysts for efficient CO2 hydrogenation to methanol

An activated carbon-supported Cu/ZnO catalyst (CCZ-AE-ox) was successfully obtained by the ammonia evaporation method for the hydrogenation of carbon dioxide to methanol, and the surface properties of the catalyst post-calcination and reduction were investigated. Activated carbon facilitated the increased dispersion of the loaded metals, which promote the CO₂ space-time yield (STY) of methanol and turnover frequency (TOF) on the active sites. Furthermore, the factors affecting the catalyst in the hydrogenation of CO₂ to methanol were in-depth investigated. The larger surface area and higher CO₂ adsorption capacity are found to make possible the main attributions of the superior activity of the CCZ-AE-ox catalyst.

Electronic properties and adsorption mechanism of Ru-doped copper clusters towards CH3OH molecule: A DFT investigation

In this study, we have investigated the stability and electronic properties of the Cu_nRu (n = 2-10) nanoclusters and their interaction with the CH₃OH molecule without and with the presence of O₂ molecule by using DFT calculations with TPSS/SDD/6-311g(d,p) level of theory. Based on the second energy difference (Δ²E), the results reveal that the Cu_nRu (n = 4, 6 and 8) clusters are relatively more stable than their neighboring clusters. The values obtained for the Fukui function (f^-) proves that the Ru atom in the Cu_nRu clusters is an excellent adsorption site for the molecules. The interaction of the Cu_nRu clusters with CH₃OH molecule exhibits that the Ru atom is the preferred adsorption site for the CH₃OH molecule, where the O atom of the CH₃OH molecule is strongly chemisorbed onto the Ru site of the clusters, forming a strong bond between the Ru and O atoms. The copper sites of the clusters were found less preferred for the adsorption of CH₃OH, and the complexes formed between both species are less stable than those obtained from the CH₃OH chemisorption over the Ru site of the clusters. The interaction of CH₃OH with the clusters was also evaluated in an oxidizing environment, and the results obtained reveal that the molecule is greatly chemisorbed over the ruthenium site with adsorption energies which vary from - 1.18 to - 2.05 eV. In the presence of the oxygen, the gap energy of the clusters was sharply changed after their interactions with the CH₃OH molecule, suggesting that these clusters can easily detect the above molecule with great sensitivity. Therefore, the presence of the oxygen not only does not prevent the adsorption process, but it considerably promotes the CH₃OH chemisorption onto the ruthenium site of the clusters and therefore significantly rises their sensitivity performance. In conclusion, the Cu_nRu clusters could be employed as effective nanosensors for the CH₃OH molecule detection.

Recent Advances in Carbon Dioxide Adsorption, Activation and Hydrogenation to Methanol using Transition Metal Carbides

The inevitable emission of carbon dioxide (CO₂ ) due to the burning of a substantial amount of fossil fuels has led to serious energy and environmental challenges. Metal-based catalytic CO₂ transformations into commodity chemicals are a favorable approach in the CO₂ mitigation strategy. Among these transformations, selective hydrogenation of CO₂ to methanol is the most promising process that not only fulfils the energy demands but also re-balances the carbon cycle. The investigation of CO₂ adsorption on the surface of heterogeneous catalyst is highly important because the formation of various intermediates which determines the selectivity of product. Transition metal carbides (TMCs) have received considerable attention in recent years because of their noble metal-like reactivity, ceramic-like properties, high chemical and thermal stability. These features make them excellent catalytic materials for a variety of transformations such as CO₂ adsorption and its conversion into value-added chemicals. Herein, the catalytic properties of TMCs are summarize along with synthetic methods, CO₂ binding modes, mechanistic studies, effects of dopant on CO₂ adsorption, and carbon/metal ratio in the CO₂ hydrogenation reaction to methanol using computational as well as experimental studies. Additionally, this Review provides an outline of the challenges and opportunities for the development of potential TMCs in CO₂ hydrogenation reactions.

Towards High CO2 Conversions Using Cu/Zn Catalysts Supported on Aluminum Fumarate Metal-Organic Framework for Methanol Synthesis

Green methanol is a viable alternative for the storage of hydrogen and may be produced from captured anthropogenic sources of carbon dioxide. The latter was hydrogenated over Cu-ZnO catalysts supported on an aluminum fumarate metal-organic framework (AlFum MOF). The catalysts, prepared via slurry phase impregnation, were assessed for thermocatalytic hydrogenation of CO2 to methanol. PXRD, FTIR, and SBET exhibited a decrease in crystallinity of the AlFum MOF support after impregnation with Cu-Zn active sites. SEM, SEM-EDS, and TEM revealed that the morphology of the support is preserved after metal loading, where H2-TPR confirmed the presence of active sites for hydrogen uptake. The catalysts exhibited good activity, with a doubling in Cu and Zn loading over the AlFum MOF, resulting in a 4-fold increase in CO2 conversions from 10.8% to 45.6% and an increase in methanol productivity from 34.4 to 56.5 gMeOH/Kgcat/h. The catalysts exhibited comparatively high CO selectivity and high yields of H2O, thereby favoring the reverse water-gas shift reaction. The selectivity of the catalysts towards methanol was found to be 12.9% and 6.9%. The performance of the catalyst supported on AlFum MOF further highlights the potential use of MOFs as supports in the heterogeneous thermocatalytic conversion of CO2 to value-added products.

Aerosol processing technique for the synthesis of mixed-phase copper on carbon catalyst: insights into CO2adsorption and photocatalytic activity

In this study, spray pyrolysis; an aerosol processing technique was utilized to produce a mixed-phase copper on carbon (Cu/Cu_xO@C) catalyst. The catalyst production was performed via chemical reduction of copper nitrate by a reducing sugar, i.e. glucose, using aqueous solution. The physical and chemical properties of the produced particles was assessed using various characterization techniques. The synthesis temperature had pronounced effect on the final particles. Since CO₂adsorption onto the catalyst is an important step in catalytic CO₂reduction processes, it was studied using thermogravimetric and temperature programmed desorption techniques. Additionally, photocatalytic activity of the particles was evaluated by gas-phase oxidation of acetylene gas which revealed excellent activity under both UV and visible light irradiation indicating the possible use of wider range of the solar spectrum.

Synthesis of MeOH and DME From CO2 Hydrogenation Over Commercial and Modified Catalysts

Growing concern about climate change has been driving the search for solutions to mitigate greenhouse gas emissions. In this context, carbon capture and utilization (CCU) technologies have been proposed and developed as a way of giving CO2 a sustainable and economically viable destination. An interesting approach is the conversion of CO2 into valuable chemicals, such as methanol (MeOH) and dimethyl ether (DME), by means of catalytic hydrogenation on Cu-, Zn-, and Al-based catalysts. In this work, three catalysts were tested for the synthesis of MeOH and DME from CO2 using a single fixed-bed reactor. The first one was a commercial CuO/γ-Al2O3; the second one was CuO-ZnO/γ-Al2O3, obtained via incipient wetness impregnation of the first catalyst with an aqueous solution of zinc acetate; and the third one was a CZA catalyst obtained by the coprecipitation method. The samples were characterized by XRD, XRF, and N2 adsorption isotherms. The hydrogenation of CO2 was performed at 25 bar, 230°C, with a H2:CO2 ratio of 3 and space velocity of 1,200 ml (g cat · h)−1 in order to assess the potential of these catalysts in the conversion of CO2 to methanol and dimethyl ether. The catalyst activity was correlated to the adsorption isotherms of each reactant. The main results show that the highest CO2 conversion and the best yield of methanol are obtained with the CZACP catalyst, very likely due to its higher adsorption capacity of H2. In addition, although the presence of zinc oxide reduces the textural properties of the porous catalyst, CZAWI showed higher CO2 conversion than commercial catalyst CuO/γ-Al2O3.

Thermocatalytic Hydrogenation of CO2 to Methanol Using Cu-ZnO Bimetallic Catalysts Supported on Metal–Organic Frameworks

The thermocatalytic hydrogenation of carbon dioxide (CO2) to methanol is considered as a potential route for green hydrogen storage as well as a mean for utilizing captured CO2, owing to the many established applications of methanol. Copper–zinc bimetallic catalysts supported on a zirconium-based UiO-66 metal–organic framework (MOF) were prepared via slurry phase impregnation and benchmarked against the promoted, co-precipitated, conventional ternary CuO/ZnO/Al2O3 (CZA) catalyst for the thermocatalytic hydrogenation of CO2 to methanol. A decrease in crystallinity and specific surface area of the UiO-66 support was observed using X-ray diffraction and N2-sorption isotherms, whereas hydrogen-temperature-programmed reduction and X-ray photoelectron spectroscopy revealed the presence of copper active sites after impregnation and thermal activation. Other characterisation techniques such as scanning electron microscopy, transmission electron microscopy, and thermogravimetric analysis were employed to assess the physicochemical properties of the resulting catalysts. The UiO-66 (Zr) MOF-supported catalyst exhibited a good CO2 conversion of 27 and 16% selectivity towards methanol, whereas the magnesium-promoted CZA catalyst had a CO2 conversion of 31% and methanol selectivity of 24%. The prepared catalysts performed similarly to a CZA commercial catalyst which exhibited a CO2 conversion and methanol selectivity of 30 and 15%. The study demonstrates the prospective use of Cu-Zn bimetallic catalysts supported on MOFs for direct CO2 hydrogenation to produce green methanol.

Electrocatalysts for direct methanol fuel cells to demonstrate China's renewable energy renewable portfolio standards within the framework of the 13th five-year plan

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Methanol synthesis via carbon dioxide hydrogenation is reviewed.

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Up to date review on high yield catalysts for methanol synthesis are discussed.

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Catalytic performance parameters (temperature, Pressure, Support) are reviewed.

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Policy framework towards renewable energy for China is extensively reviewed.

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The catalytic mechanism and the role of promoters, bi-metallic catalyst is also discussed.

A unified treatment of the renewable portfolio standards is given concerning direct methanol fuel. The current mechanism of electrocatalysis of methanol oxidation on platinum and non-platinum-containing alloys is summarized for the systematic improvement of the rate of electro-oxidation of methanol are discussed. Policy realignment under the five-year plan is discussed in length to demonstrate how policy, markets, and engineering designs contribute towards the development of model direct methanol fuel cells operational enhancement, and factors that affect critical performance parameters for commercial exploitation are summarized for catalytic formulations and cell design within the context of why this investment in technology, education, and finances is required within the global context of sustainable energy and energy independence as exposed by thirteenth the five-year plan. The prolog focuses on the way, whereas the section on methanol fuel cells on the how and the post log on what is expected post-COVID-19 era in science and technology as China pivots to a post-fossil fuel economy.

China's industrial growth has been through internal market reforms and supplies side economics from the Chinese markets for fossil fuels except for petroleum. The latest renewable portfolio standards adopted have common elements as adopted from North American and the United Kingdom in terms of adaptation of obligation in terms of renewable portfolio standards as well as a realization that the necessity for renewables standards for the thirteen five year plan (from 2016 to 2020) need to less rigorously implemented due to performance targets that were met during the eleventh (06–10) and twelfth five-year plans (11–15) in terms of utilization of small coal-ire power plants, development of newer standards, led to an improvement of energy efficiency of 15 %, reduction of SO_x/NO_x by an average of 90 % and PM2.5 by 96 % over the last two five-year plans.

The current phase of the plan has a focus on energy generation from coal and a slowing down of renewables or Renewable energy curtailment of approximately 400 T Wh renewables including 300 T Wh of non-hydro power, principally from Guangdong, and Jiangsu for transfer of hydropower and Zhejiang, Tianjin, Henan for non-hydro power transfer with Beijing and Shanghai playing important roles in renewables energy curtailment and realignment using an integrated approach to optimize each provinces energy portfolio. The realignment of the renewable energy portfolio indicates that the newly installed capacity in Sichuan, Yunnan, Inner Mongolia, and Zhejiang will account for less than 20 % of the current renewable energy portfolio but with the NO_x SO_x and PM_2.5 savings already accrued.

The catalytic reduction of carbon dioxide to methanol (70 / 110 million metric tons from all sources in 2019 for China/world) is one technological approach to reduce global carbon dioxide emissions and suggests that catalytic methanol synthesis by CO₂ hydrogenation may be a plausible approach, even if it is more expensive economically than methanol synthesis by the syngas approach. This is because the CO₂ emissions of the synthesis are lower than other synthesis methodologies. The Chinese government has placed a premium on cleaner air and water and may view such an approach as solving the dual issues of fuel substitution and reduction of CO₂. Thus, the coupling of hydrogen generation from sustainable energies sources (Solar 175 / 509 GW) or wind (211/591.5 GW in 2019) may be an attractive approach, as this requires slightly less water than coal gasification. Due to the thermodynamic requirement of lower operating pressure and higher operating pressure, currently, there is no single operational approach, although some practice approaches (220 °C at 48 atm using copper) and zinc oxide/alumina are suggested for optimal performance.

UV/Vis Spectroscopy of Copper Formate Clusters: Insight into Metal-Ligand Photochemistry

The electronic structure and photochemistry of copper formate clusters, Cu^I₂(HCO₂)₃⁻ and Cu^II_n(HCO₂)_2n+1⁻, n≤8, are investigated in the gas phase by using UV/Vis spectroscopy in combination with quantum chemical calculations. A clear difference in the spectra of clusters with Cu^I and Cu^II copper ions is observed. For the Cu^I species, transitions between copper d and s/p orbitals are recorded. For stoichiometric Cu^II formate clusters, the spectra are dominated by copper d–d transitions and charge‐transfer excitations from formate to the vacant copper d orbital. Calculations reveal the existence of several energetically low‐lying isomers, and the energetic position of the electronic transitions depends strongly on the specific isomer. The oxidation state of the copper centers governs the photochemistry. In Cu^II(HCO₂)₃⁻, fast internal conversion into the electronic ground state is observed, leading to statistical dissociation; for charge‐transfer excitations, specific excited‐state reaction channels are observed in addition, such as formyloxyl radical loss. In Cu^I₂(HCO₂)₃⁻, the system relaxes to a local minimum on an excited‐state potential‐energy surface and might undergo fluorescence or reach a conical intersection to the ground state; in both cases, this provides substantial energy for statistical decomposition. Alternatively, a Cu^II(HCO₂)₃Cu⁰⁻ biradical structure is formed in the excited state, which gives rise to the photochemical loss of a neutral copper atom.

Study on the Adsorption and Activation Behaviours of Carbon Dioxide over Copper Cluster (Cu4) and Alumina-Supported Copper Catalyst (Cu4/Al2O3) by means of Density Functional Theory

The adsorption and activation of carbon dioxide over copper cluster (Cu4) and copper doped on the alumina support (Cu4/Al2O3) catalytic systems have been investigated by using density functional theory and climbing image nudged elastic band. The adsorption energies, geometrical configurations, and electronic properties are analysed. The results show the strong chemical interaction between the copper cluster and the alumina support. Both the Cu4 cluster and Cu4/Al2O3 systems have a high adsorption ability for CO2, and the adsorption process is of chemical nature. The role of the alumina support in the adsorption and activation of CO2 has been addressed. The calculated results show that the “synergistic effect” between Al2O3 and Cu4 is the key factor in the activation of CO2.

Tailoring of Hydrotalcite-Derived Cu-Based Catalysts for CO2 Hydrogenation to Methanol

Ternary CuxZnyAlz catalysts were prepared using the hydrotalcite (HT) method. The influence of the atomic x:y:z ratio on the physico-chemical and catalytic properties under CO2 hydrogenation conditions was probed. The characterization data of the investigated catalysts were obtained by XRF, XRD, BET, TPR, CO2-TPD, N2O chemisorption, SEM, and TEM techniques. In the “dried” catalyst, the typical structure of a hydrotalcite phase was observed. Although the calcination and subsequent reduction treatments determined a clear loss of the hydrotalcite structure, the pristine phase addressed the achievement of peculiar physico-chemical properties, also affecting the catalytic activity. Textural and surface effects induced by the zinc concentration conferred a very interesting catalyst performance, with a methanol space time yield (STY) higher than that of commercial systems operated under the same experimental conditions. The peculiar behavior of the hydrotalcite-like samples was related to a high dispersion of the active phase, with metallic copper sites homogeneously distributed among the oxide species, thereby ensuring a suitable activation of H2 and CO2 reactants for a superior methanol production.

Decomposition of Copper Formate Clusters: Insight into Elementary Steps of Calcination and Carbon Dioxide Activation

The decomposition of copper formate clusters is investigated in the gas phase by infrared multiple photon dissociation of Cu(II) n (HCO2)2n+1 -, n≤8. In combination with quantum chemical calculations and reactivity measurements using oxygen, elementary steps of the decomposition of copper formate are characterized, which play a key role during calcination as well as for the function of copper hydride based catalysts. The decomposition of larger clusters (n >2) takes place exclusively by the sequential loss of neutral copper formate units Cu(II)(HCO2)2 or Cu(II)2(HCO2)4, leading to clusters with n=1 or n=2. Only for these small clusters, redox reactions are observed as discussed in detail previously, including the formation of formic acid or loss of hydrogen atoms, leading to a variety of Cu(I) complexes. The stoichiometric monovalent copper formate clusters Cu(I) m (HCO2) m+1 -, (m=1,2) decompose exclusively by decarboxylation, leading towards copper hydrides in oxidation state +I. Copper oxide centers are obtained via reactions of molecular oxygen with copper hydride centers, species containing carbon dioxide radical anions as ligands or a Cu(0) center. However, stoichiometric copper(I) and copper(II) formate Cu(I)(HCO2)2 - and Cu(II)(HCO2)3 -, respectively, is unreactive towards oxygen.

Low-Temperature Electrocatalytic Conversion of CO2 to Liquid Fuels: Effect of the Cu Particle Size

A novel gas-phase electrocatalytic system based on a low-temperature proton exchange membrane (Sterion) was developed for the gas-phase electrocatalytic conversion of CO2 to liquid fuels. This system achieved gas-phase electrocatalytic reduction of CO2 at low temperatures (below 90 °C) over a Cu cathode by using water electrolysis-derived protons generated in-situ on an IrO2 anode. Three Cu-based cathodes with varying metal particle sizes were prepared by supporting this metal on an activated carbon at three loadings (50, 20, and 10 wt %; 50% Cu-AC, 20% Cu-AC, and 10% Cu-AC, respectively). The cathodes were characterized by N2 adsorption–desorption, temperature-programmed reduction (TPR), and X-ray diffraction (XRD) and their performance towards the electrocatalytic conversion of CO2 was subsequently studied. The membrane electrode assembly (MEA) containing the cathode with the largest Cu particle size (50% Cu-AC, 40 nm) showed the highest CO2 electrocatalytic activity per mole of Cu, with methyl formate being the main product. This higher electrocatalytic activity was attributed to the lower Cu–CO bonding strength over large Cu particles. Different product distributions were obtained over 20% Cu-AC and 10% Cu-AC, with acetaldehyde and methanol being the main reaction products, respectively. The CO2 consumption rate increased with the applied current and reaction temperature.

Microstructure analysis of complex CuO/ZnO@carbon adsorbers: what are the limits of powder diffraction methods?

Activate carbon impregnated with a mixture of copper oxide and zinc oxide performs well as active adsorber for NO2 removal in automotive cabin air filters. The oxide-loaded activated carbon exhibits superior long-term stability in comparison to pure activated carbon as has been shown in previous studies. The carbon material was loaded only with 2.5 wt% of each metal oxide. Characterization of the oxide nanoparticles within the pores of the activated carbon is difficult because of the rather low concentration of the oxides. Therefore, a systematic study was performed to evaluate the limits of line profile analysis of X-ray powder diffraction patterns. The method allows evaluation of crystalline domain size distributions, crystal defect concentrations and twinning probabilities of nanoscopic materials. Here, the analysis is hampered by the presence of several phases including more or less amorphous carbon. By using physical mixtures of defined copper oxide and zinc oxide particles with activated carbon, potential errors and limits could be identified. The contribution of the activated carbon to the scattering curve was modeled with a convolution of an exponential decay curve, a Chebyshev polynomial, and two Lorentzian peaks. With this approach, domain size distributions can be calculated that are shifted only by about 0.5-1.0 nm for very low loadings (≤4 wt%). Oxide loadings of 4 wt% and 5 wt% allow very reliable analyses from diffraction patterns measured in Bragg-Brentano and Debye-Scherrer geometry, respectively. For the real adsorber material, mean domain sizes have been calculated to be 2.8 nm and 2.4 nm before and after the NO2 removal tests.

Effect of the components' interface on the synthesis of methanol over Cu/ZnO from CO2/H2: a microkinetic analysis based on DFT + U calculations

During the methanol synthesis over Cu/ZnO catalysts, the phase interface was observed to supply spillover hydrogen to active copper sites.

Recycling of carbon dioxide to methanol and derived products - closing the loop

Starting with coal, followed by petroleum oil and natural gas, the utilization of fossil fuels has allowed the fast and unprecedented development of human society. However, the burning of these resources in ever increasing pace is accompanied by large amounts of anthropogenic CO2 emissions, which are outpacing the natural carbon cycle, causing adverse global environmental changes, the full extent of which is still unclear. Even through fossil fuels are still abundant, they are nevertheless limited and will, in time, be depleted. Chemical recycling of CO2 to renewable fuels and materials, primarily methanol, offers a powerful alternative to tackle both issues, that is, global climate change and fossil fuel depletion. The energy needed for the reduction of CO2 can come from any renewable energy source such as solar and wind. Methanol, the simplest C1 liquid product that can be easily obtained from any carbon source, including biomass and CO2, has been proposed as a key component of such an anthropogenic carbon cycle in the framework of a "Methanol Economy". Methanol itself is an excellent fuel for internal combustion engines, fuel cells, stoves, etc. It's dehydration product, dimethyl ether, is a diesel fuel and liquefied petroleum gas (LPG) substitute. Furthermore, methanol can be transformed to ethylene, propylene and most of the petrochemical products currently obtained from fossil fuels. The conversion of CO2 to methanol is discussed in detail in this review.