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.

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

The recent advances in the development of heterogeneous catalysts and processes for the direct hydrogenation of CO2 to formate/formic acid, methanol, and dimethyl ether are thoroughly reviewed, with special emphasis on thermodynamics and catalyst design considerations. After introducing the main motivation for the development of such processes, we first summarize the most important aspects of CO2 capture and green routes to produce H2. Once the scene in terms of feedstocks is introduced, we carefully summarize the state of the art in the development of heterogeneous catalysts for these important hydrogenation reactions. Finally, in an attempt to give an order of magnitude regarding CO2 valorization, we critically assess economical aspects of the production of methanol and DME and outline future research and development directions.

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Challenges in the Greener Production of Formates/Formic Acid, Methanol, and DME by Heterogeneously Catalyzed CO2 Hydrogenation Processes.

The utilization of fossil fuels has enabled an unprecedented era of prosperity and advancement of well-being for human society. However, the associated increase in anthropogenic carbon dioxide (CO2) emissions can negatively affect global temperatures and ocean acidity. Moreover, fossil fuels are a limited resource and their depletion will ultimately force one to seek alternative carbon sources to maintain a sustainable economy. Converting CO2 into value-added chemicals and fuels, using renewable energy, is one of the promising approaches in this regard. Major advances in energy-efficient CO2 conversion can potentially alleviate CO2 emissions, reduce the dependence on nonrenewable resources, and minimize the environmental impacts from the portions of fossil fuels displaced. Methanol (CH3OH) is an important chemical feedstock and can be used as a fuel for internal combustion engines and fuel cells, as well as a platform molecule for the production of chemicals and fuels. As one of the promising approaches, thermocatalytic CO2 hydrogenation to CH3OH via heterogeneous catalysis has attracted great attention in the past decades. Major progress has been made in the development of various catalysts including metals, metal oxides, and intermetallic compounds. In addition, efforts are also put forth to define catalyst structures in nanoscale by taking advantage of nanostructured materials, which enables the tuning of the catalyst composition and modulation of surface structures and potentially endows more promising catalytic performance in comparison to the bulk materials prepared by traditional methods. Despite these achievements, significant challenges still exist in developing robust catalysts with good catalytic performance and long-term stability. In this review, we will provide a comprehensive overview of the recent advances in this area, especially focusing on structure-activity relationship, as well as the importance of combining catalytic measurements, in situ characterization, and theoretical studies in understanding reaction mechanisms and identifying key descriptors for designing improved catalysts.

Recent Advances in Carbon Dioxide Hydrogenation to Methanol via Heterogeneous Catalysis.

The ever-increasing amount of anthropogenic carbon dioxide (CO2) emissions has resulted in great environmental impacts. The selective hydrogenation of CO2 to methanol, the first target in the liquid sunshine vision, not only effectively mitigates the CO2 emissions, but also produces value-added chemicals and fuels. This critical review provides a comprehensive view of the significant advances in heterogeneous catalysis for methanol synthesis through direct hydrogenation of CO2. The challenges in thermodynamics are addressed first. Then the progress in conventional Cu-based catalysts is discussed in detail, with an emphasis on the structural, chemical, and electronic promotions of supports and promoters, the preparation methods and precursors of Cu-based catalysts, as well as the proposed models for active sites. We also provide an overview of the progress in noble metal-based catalysts, bimetallic catalysts including alloys and intermetallic compounds, as well as hybrid oxides and other novel catalytic systems. The developments in mechanistic aspects, reaction conditions and optimization, as well as reactor designs and innovations are also included. The advances in industrial applications for methanol synthesis are further highlighted. Finally, a summary and outlook are provided.

State of the art and perspectives in heterogeneous catalysis of CO2 hydrogenation to methanol.

Recently, carbon dioxide capture and conversion, along with hydrogen from renewable resources, provide an alternative approach to synthesis of useful fuels and chemicals. People are increasingly interested in developing innovative carbon dioxide hydrogenation catalysts, and the pace of progress in this area is accelerating. Accordingly, this perspective presents current state of the art and outlook in synthesis of light olefins, dimethyl ether, liquid fuels, and alcohols through two leading hydrogenation mechanisms: methanol reaction and Fischer-Tropsch based carbon dioxide hydrogenation. The future research directions for developing new heterogeneous catalysts with transformational technologies, including 3D printing and artificial intelligence, are provided. Carbon dioxide (CO2) capture and conversion provide an alternative approach to synthesis of useful fuels and chemicals. Here, Ye et al. give a comprehensive perspective on the current state of the art and outlook of CO2 catalytic hydrogenation to the synthesis of light olefins, dimethyl ether, liquid fuels, and alcohols.

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CO 2 hydrogenation to high-value products via heterogeneous catalysis.

The synergistic interaction among different components in complex catalysts is one of the crucial factors in determining catalytic performance. Here we report the interactions among the three components in controlling the catalytic performance of Cu–ZnO–ZrO2 (CZZ) catalyst for CO2 hydrogenation to methanol. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements under the activity test pressure (3 MPa) reveal that the CO2 hydrogenation to methanol on the CZZ catalysts follows the formate pathway. Density functional theory (DFT) calculations agree with the in situ DRIFTS measurements, showing that the ZnO–ZrO2 interfaces are the active sites for CO2 adsorption and conversion, while the presence of metallic Cu is also necessary to facilitate H2 dissociation and to provide hydrogen resource. The combined experiment and DFT results reveal that tuning the interaction between ZnO and ZrO2 can be considered as another important factor for designing high performance catalysts for methanol generation from CO2. Despite great efforts, the reaction mechanism of CO2 hydrogenation to methanol and the nature of the active sites on Cu–ZnO–ZrO2 (CZZ) catalysts are still under debate. Herein, the authors report the interactions among the three components in controlling the catalytic performance of CZZ catalyst for CO2 hydrogenation to methanol.

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Exploring the ternary interactions in Cu-ZnO-ZrO 2 catalysts for efficient CO 2 hydrogenation to methanol.

Strong Evidence of the Role of H2O in Affecting Methanol Selectivity from CO2 Hydrogenation over Cu-ZnO-ZrO2

Dimethyl ether synthesis from CO2 hydrogenation on La-modified CuO-ZnO-Al2O3/HZSM-5 bifunctional catalysts

Carbon-Modified CuO/ZnO Catalyst with High Oxygen Vacancy for CO2 Hydrogenation to Methanol

A series of Au–CuO/SBA-15 catalysts with 1–3 wt% Au and 30 wt% CuO were successfully prepared for CO2 hydrogenation to methanol by chemical reduction and the following impregnation. The influence of Au content on the physicochemical properties of Au–CuO/SBA-15 catalysts was investigated in terms of ICP-AES, N2 physisorption, XRD, TEM, N2O titration, XPS and H2–TPR technique. The results showed that the as-prepared Au–CuO/SBA-15 catalysts exhibited higher catalytic activity than CuO/SBA-15 catalyst. 2 % Au–CuO/SBA-15 catalyst showed the best catalytic activity with 13.5 % methanol selectivity and 24.2 % CO2 conversion for CO2 hydrogenation to methanol. The addition of Au NPs played an important role in improving the catalytic activity for CO2 hydrogenation to methanol, which may be attributed to the interaction between Au and CuO.

Gao Wengui

Papers

Exploring the ternary interactions in Cu-ZnO-ZrO 2 catalysts for efficient CO 2 hydrogenation to methanol.

Strong Evidence of the Role of H2O in Affecting Methanol Selectivity from CO2 Hydrogenation over Cu-ZnO-ZrO2

Dimethyl ether synthesis from CO2 hydrogenation on La-modified CuO-ZnO-Al2O3/HZSM-5 bifunctional catalysts

Carbon-Modified CuO/ZnO Catalyst with High Oxygen Vacancy for CO2 Hydrogenation to Methanol

Hydrogenation of CO2 to methanol over Au-CuO/SBA-15 catalysts