Roles of interaction between components in CZZA / HZSM ‐5 catalyst for dimethyl ether synthesis via CO 2 hydrogenation

Hydrogenation of CO2 into Value-added Chemicals Using Solid-Supported Catalysts

Reducing CO2 emissions is an urgent global priority. In this context, several mitigation strategies, including CO2 tax and stringent legislation, have been adopted to halt the deterioration of the natural environment. Also, carbon recycling procedures undoubtedly help reduce net emissions into the atmosphere, enhancing sustainability. Utilizing Earth's abundant CO2 to produce high-potential green chemicals and light fuels opens new avenues for the chemical industry. In this context, many attempts have been devoted to converting CO2 as a feedstock into various value-added chemicals, such as CH4 , lower methanol, light olefins, gasoline, and higher hydrocarbons, for numerous applications involving various catalytic reactions. Although several CO2 -conversion methods have been used, including electrochemical, photochemical, and biological approaches, the hydrogenation method allows the reaction to be tuned to produce the targeted compound without significantly altering infrastructure. This review discusses the numerous hydrogenation routes and their challenges, such as catalyst design, operation, and the combined art of structure-activity relationships for the various product formations.

A review on high-pressure heterogeneous catalytic processes for gas-phase CO2 valorization

This review discusses the importance of mitigating CO2 emissions by valorizing CO2 through high-pressure catalytic processes. It focuses on various key processes, including CO2 methanation, reverse water-gas shift, methane dry reforming, methanol, and dimethyl ether synthesis, emphasizing pros and cons of high-pressure operation. CO2 methanation, methanol synthesis, and dimethyl ether synthesis reactions are thermodynamically favored under high-pressure conditions. However, in the case of methane dry reforming and reverse water-gas shift, applying high pressure, results in decreased selectivity toward desired products and an increase in coke production, which can be detrimental to both the catalyst and the reaction system. Nevertheless, high-pressure utilization proves industrially advantageous for cost reduction when these processes are integrated with Fischer-Tropsch or methanol synthesis units. This review also compiles recent advances in heterogeneous catalysts design for high-pressure applications. By examining the impact of pressure on CO2 valorization and the state of the art, this work contributes to improving scientific understanding and optimizing these processes for sustainable CO2 management, as well as addressing challenges in high-pressure CO2 valorization that are crucial for industrial scaling-up. This includes the development of cost-effective and robust reactor materials and the development of low-cost catalysts that yield improved selectivity and long-term stability under realistic working environments.

Ultra-thin ZrO2overcoating on CuO-ZnO-Al2O3catalyst by atomic layer deposition for improved catalytic performance of CO2hydrogenation to dimethyl ether

An ultra-thin overcoating of zirconium oxide (ZrO₂) film on CuO-ZnO-Al₂O₃(CZA) catalysts by atomic layer deposition (ALD) was proved to enhance the catalytic performance of CZA/HZSM-5 (H form of Zeolite Socony Mobil-5) bifunctional catalysts for hydrogenation of CO₂to dimethyl ether (DME). Under optimal reaction conditions (i.e. 240 °C and 2.8 MPa), the yield of product DME increased from 17.22% for the bare CZA/HZSM-5 catalysts, to 18.40% for the CZA catalyst after 5 cycles of ZrO₂ALD with HZSM-5 catalyst. All the catalysts modified by ZrO₂ALD displayed significantly improved catalytic stability of hydrogenation of CO₂to DME reaction, compared to that of CZA/HZSM-5 bifunctional catalysts. The loss of DME yield in 100 h of reaction was greatly mitigated from 6.20% (loss of absolute value) to 3.01% for the CZA catalyst with 20 cycles of ZrO₂ALD overcoating. Characterizations including hydrogen temperature programmed reduction, x-ray powder diffraction, and x-ray photoelectron spectroscopy revealed that there was strong interaction between Cu active centers and ZrO₂.

Physico-Chemical Modifications Affecting the Activity and Stability of Cu-Based Hybrid Catalysts during the Direct Hydrogenation of Carbon Dioxide into Dimethyl-Ether

The direct hydrogenation of CO₂ into dimethyl-ether (DME) has been studied in the presence of ferrierite-based CuZnZr hybrid catalysts. The samples were synthetized with three different techniques and two oxides/zeolite mass ratios. All the samples (calcined and spent) were properly characterized with different physico-chemical techniques for determining the textural and morphological nature of the catalytic surface. The experimental campaign was carried out in a fixed bed reactor at 2.5 MPa and stoichiometric H₂/CO₂ molar ratio, by varying both the reaction temperature (200-300 °C) and the spatial velocity (6.7-20.0 NL∙g_cat^-1∙h^-1). Activity tests evidenced a superior activity of catalysts at a higher oxides/zeolite weight ratio, with a maximum DME yield as high as 4.5% (58.9 mg_DME∙g_cat^-1∙h^-1) exhibited by the sample prepared by gel-oxalate coprecipitation. At lower oxide/zeolite mass ratios, the catalysts prepared by impregnation and coprecipitation exhibited comparable DME productivity, whereas the physically mixed sample showed a high activity in CO₂ hydrogenation but a low selectivity toward methanol and DME, ascribed to a minor synergy between the metal-oxide sites and the acid sites of the zeolite. Durability tests highlighted a progressive loss in activity with time on stream, mainly associated to the detrimental modifications under the adopted experimental conditions.

A Review on Deactivation and Regeneration of Catalysts for Dimethyl Ether Synthesis

The deactivation of catalysts and their regeneration are two very important challenges that need to be addressed for many industrial processes. The most quoted reasons for the deterioration of dimethyl ether synthesis (DME) concern the sintering and the hydrothermal leaching of copper particles, their migration to acid sites, the partial formation of copper and zinc hydroxycarbonates, the formation of carbon deposits, and surface contamination with undesirable compounds present in syngas. This review summarises recent findings in the field of DME catalyst deactivation and regeneration. The most-used catalysts, their modifications, along with a comparison of the basic parameters, deactivation approaches, and regeneration methods are presented.

Hybrid monometallic and bimetallic copper-palladium zeolite catalysts for direct synthesis of dimethyl ether from CO2

Nowadays, carbon dioxide is the major reason of the global climate changes. The direct CO2 hydrogenation to dimethyl ether produces an important platform molecule for synthesis of fuels and chemicals...