Highly Active Nanosized Anatase TiO2–x Oxide Catalysts In Situ Formed through Reduction and Ostwald Ripening Processes for Propane Dehydrogenation

Promoted oxygen adsorption on porous CeO2 cubes with abundant oxygen vacancies for efficient gaseous formaldehyde removal

Photocatalytic degradation stands as a promising method for eliminating gas-phase pollutants, with the efficiency largely hinging on the capture of photogenerated electrons by oxygen. In this work, we synthesized a porous CeO2 single crystal cube with abundant oxygen vacancies as photocatalyst, employing urea as a pore-forming agent and for gas-phase formaldehyde degradation. Compared with the CeO2 cubes without pores, the porous ones were superior in specific surface area, akin to conventional CeO2 nanoparticles. The photocatalytic degradation for gas-phase formaldehyde on porous CeO2 cubes was significantly accelerated, of which degradation rate is 3.3 times and 2.1 times that of CeO2 cubes without pores and CeO2 nanoparticles, respectively. Photoelectric tests and DFT calculations revealed that this enhancement stemmed from facilitated oxygen adsorption due to pronounced oxygen vacancies. Consequently, the capture of photoelectrons by oxygen was promoted and its recombination with holes was suppressed, along with an accelerated generation of curial free radicals such as ·OH. This work reveals the pivotal role of surface oxygen vacancies in promoting adsorbed oxygen, proposing a viable strategy to enhance the photocatalytic degradation efficiency for gas-phase pollutants.

Defective TiOx overlayers catalyze propane dehydrogenation promoted by base metals

The industrial catalysts utilized for propane dehydrogenation (PDH) to propylene, an important alternative to petroleum-based cracking processes, either use expensive metals or metal oxides that are environmentally unbenign. We report that a typically less-active oxide, titanium oxide (TiO2), can be combined with earth-abundant metallic nickel (Ni) to form an unconventional Ni@TiOx catalyst for efficient PDH. The catalyst demonstrates a 94% propylene selectivity at 40% propane conversion and superior stability under industrially relevant conditions. Complete encapsulation of Ni nanoparticles was allowed at elevated temperatures (>550°C). A mechanistic study suggested that the defective TiOx overlayer consisting of tetracoordinated Ti sites with oxygen vacancies is catalytically active. Subsurface metallic Ni acts as an electronic promoter to accelerate carbon-hydrogen bond activation and hydrogen (H2) desorption on the TiOx overlayer.

High-Density Coordinatively Unsaturated Zn Catalyst for Efficient Alkane Dehydrogenation

The exploration of non-noble metal catalysts for alkane dehydrogenation and their catalytic mechanisms is the priority in catalysis research. Here, we report a high-density coordinatively unsaturated Zn cation (Zncus) catalyst for the direct dehydrogenation (DDH) of ethylbenzene (EB) to styrene (ST). The catalyst demonstrated good catalytic performance (∼40% initial EB conversion rate and >98% ST selectivity) and excellent regeneration ability in the reaction, which is attributed to the high-density (HD) distribution and high-stability structure of Zncus active sites on the surface of zinc silicate (HD-Zncus@ZS). Density functional theory (DFT) calculations further illustrated the reaction pathway and intermediates, supporting that the Zncus sites can efficiently activate the C-H bond of ethyl on ethylbenzene. Developing the high-density Zncus catalyst and exploring the catalytic mechanism laid a good foundation for designing practical non-noble metal catalysts.

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.

Recent progress in heterogeneous metal and metal oxide catalysts for direct dehydrogenation of ethane and propane

Metal and metal oxide catalysts for non-oxidative ethane/propane dehydrogenation are outlined with respect to catalyst synthesis, structure–property relationship and catalytic mechanism.

C–H and C–C bond activation of propane to propylene and ethylene selectivity assisted by CO2 over titania catalysts

C–H and C–C bond activation of propane to propylene and ethylene selectivity assisted by CO2 over titania catalysts.