Facile in situ synthesis of highly dispersed chromium oxide incorporated into mesoporous ZrO2 for the dehydrogenation of propane with CO2

Metallic Catalysts for Oxidative Dehydrogenation of Propane Using CO2

The oxidative dehydrogenation of propane using CO₂ (CO₂ -ODP) is a promising technique for realizing high-yield propylene production and CO₂ usage. Developing a highly efficient catalyst for CO₂ -ODP is essential and beneficial to the chemical industry and for realizing net-zero emissions. Many studies have investigated metal oxide-based catalysts, revealing that rapid deactivation and low selectivity remain limiting factors for their industrial applications. In recent years, metallic nanoparticle catalysts have become increasingly attractive due to their unique properties. Therefore, we summarize the performance of metal-based catalysts in CO₂ -ODP reactions by considering catalyst design concepts, different mechanisms in the reaction process, and the role of CO₂ .

Light olefin synthesis from a diversity of renewable and fossil feedstocks: state-of the-art and outlook

Light olefins are important feedstocks and platform molecules for the chemical industry. Their synthesis has been a research priority in both academia and industry. There are many different approaches to the synthesis of these compounds, which differ by the choice of raw materials, catalysts and reaction conditions. The goals of this review are to highlight the most recent trends in light olefin synthesis and to perform a comparative analysis of different synthetic routes using several quantitative characteristics: selectivity, productivity, severity of operating conditions, stability, technological maturity and sustainability. Traditionally, on an industrial scale, the cracking of oil fractions has been used to produce light olefins. Methanol-to-olefins, alkane direct or oxidative dehydrogenation technologies have great potential in the short term and have already reached scientific and technological maturities. Major progress should be made in the field of methanol-mediated CO and CO₂ direct hydrogenation to light olefins. The electrocatalytic reduction of CO₂ to light olefins is a very attractive process in the long run due to the low reaction temperature and possible use of sustainable electricity. The application of modern concepts such as electricity-driven process intensification, looping, CO₂ management and nanoscale catalyst design should lead in the near future to more environmentally friendly, energy efficient and selective large-scale technologies for light olefin synthesis.

Flowing-Air-Induced Transformation to Promote the Dispersion of the CrOx Catalyst for Propane Dehydrogenation

Highly dispersed chromium (Cr)-based catalysts are promising candidates for the catalytic dehydrogenation of propane (DHP). However, the easier aggregation of Cr species into crystalline Cr₂O₃ at the high-temperature calcination and reaction process is a big challenge, which severely restricts the improvement of activity and stability of the DHP reaction. Herein, a flowing-air-induced transformation method was first proposed, and the catalytic performance of the prepared Cr/MCM-41 catalysts was found to be significantly improved compared to that of the Cr-based catalyst prepared by the traditional calcination method, even better than that of most of the reported Cr-based catalysts and some noble metal-based catalysts. X-ray absorption spectroscopy and in situ Raman spectroscopy as well as other characterization techniques demonstrated that the in situ calcination in flowing air could not only effectively restrain the conversion of Cr(VI) into Cr(III) but also largely improve the dispersion of Cr species. Furthermore, DHP activity is found to have a positive correlation with the amount of monomeric Cr(VI) species, which is proved to be the precursor of active coordinatively unsaturated Cr sites. Our proposed flowing-air-induced transformation method provides a general strategy for preparing the highly dispersed Cr-based catalysts and other metal oxide materials with varied valence and exhibits potential application prospects in industry.

Co–Cr bimetallic oxides derived from layered double hydroxides with high catalytic performance for chlorinated aromatics oxidation

Co–Cr bimetallic oxides with different Co/Cr molar ratios were prepared through a layered double hydroxide (LDH)-derived method.

Metal-doped mesoporous ZrO2 catalyzed chemoselective synthesis of allylic alcohols from Meerwein–Ponndorf–Verley reduction of α,β-unsaturated aldehydes

The activity of the Cr_ZrO₂ catalyst is attributed to the Cr–Zr electronic interaction, which resulted in the enhanced surface acidity on ZrO₂.

Synthesizing High-Volume Chemicals from CO2 without Direct H2 Input

Decarbonizing the chemical industry will eventually entail using CO₂ as a feedstock for chemical synthesis. However, many chemical syntheses involve CO₂ reduction using inputs such as renewable hydrogen. In this review, chemical processes are discussed that use CO₂ as an oxidant for upgrading hydrocarbon feedstocks. The captured CO₂ is inherently reduced by the hydrocarbon co-reactants without consuming molecular hydrogen or renewable electricity. This CO₂ utilization approach can be potentially applied to synthesize eight emission-intensive molecules, including olefins and epoxides. Catalytic systems and reactor concepts are discussed that can overcome practical challenges, such as thermodynamic limitations, over-oxidation, coking, and heat management. Under the best-case scenario, these hydrogen-free CO₂ reduction processes have a combined CO₂ abatement potential of approximately 1 gigatons per year and avoid the consumption of 1.24 PWh renewable electricity, based on current market demand and supply.

Facilitating the reduction of V-O bonds on VO x /ZrO2 catalysts for non-oxidative propane dehydrogenation

Supported vanadium oxide is a promising catalyst in propane dehydrogenation due to its competitive performance and low cost. Nevertheless, it remains a grand challenge to understand the structure-performance correlation due to the structural complexity of VO _x -based catalysts in a reduced state. This paper describes the structure and catalytic properties of the VO _x /ZrO₂ catalyst. When using ZrO₂ as the support, the catalyst shows six times higher turnover frequency (TOF) than using commercial γ-Al₂O₃. Combining H₂-temperature programmed reduction, in situ Raman spectroscopy, X-ray photoelectron spectroscopy and theoretical studies, we find that the interaction between VO _x and ZrO₂ can facilitate the reduction of V-O bonds, including V[double bond, length as m-dash]O, V-O-V and V-O-Zr. The promoting effect could be attributed to the formation of low coordinated V species in VO _x /ZrO₂ which is more active in C-H activation. Our work provides a new insight into understanding the structure-performance correlation in VO _x -based catalysts for non-oxidative propane dehydrogenation.

Catalytic performance and stability of Fe-doped CeO2 in propane oxidative dehydrogenation using carbon dioxide as an oxidant

Propane oxidative dehydrogenation (ODH) in the presence of CO₂ was investigated over a series of Fe-doped CeO₂ catalysts.