Role of CO2 During Oxidative Dehydrogenation of Propane Over Bulk and Activated-Carbon Supported Cerium and Vanadium Based Catalysts

CeO2, V2O5 and CeVO4 were synthesised as bulk oxides, or deposited over activated carbon, characterized by XRD, HRTEM, CO2-TPO, C3H8-TPR, DRIFTS and Raman techniques and tested in propane oxidative dehydrogenation using CO2. Complete oxidation of propane to CO and CO2 is favoured by lattice oxygen of CeO2. The temperature programmed experiments show the ~ 4 nm AC supported CeO2 crystallites become more susceptible to reduction by propane, but less prone to re-oxidation with CO2 compared to bulk CeO2. Catalytic activity of CeVO4/AC catalysts requires a 1–2 nm amorphous CeVO4 layer. During reaction, the amorphous CeVO4 layer crystallises and several atomic layers of carbon cover the CeVO4 surface, resulting in deactivation. During reaction, V2O5 is irreversibly reduced to V2O3. The lattice oxygen in bulk V2O5 favours catalytic activity and propene selectivity. Bulk V2O3 promotes only propane cracking with no propene selectivity. In VOx/AC materials, vanadium carbide is the catalytically active phase. Propane dehydrogenation over VC proceeds via chemisorbed oxygen species originating from the dissociated CO2. Graphic Abstract

The Effect of the Presence of GdVO3 and GdVO4 in the Conversion of Propane

The GdVO3 and GdVO4 catalyst has been prepared via solid-phase synthesis. It has been shown by a complex of physical and chemical methods that or GdVO3, the main one is the phase with the structure of the first homologue of the Roldlesden-Popper series of a rhombical distorted perovskite. Orthovanadate of GdVO4 crystallize in the structural type of zircon. The catalytic properties of GdVO3 and GdVO4 are studied in the propane cracking process to form propylene and ethylene. It was found that GdVO3 and GdVO4 has a high selectivity and catalytic properties. It was shown that propane conversion started at 773 K, was only 2% at 873 K, and raising the temperature to 923 K increased propane conversion to 21%. In the presence of GdVO4 and GdVO3, a considerable increase in propane conversion was observed that reached 60% at 923 K. The structure of the catalyst is stable under the conditions of preferential C3H8 reduction. Deactivation was much faster with GdVO3, and it was observed after 20 h of operation at a rate that was slightly slower than the one for GdVO4.

Density functional theory calculation of propane cracking mechanism over chromium (III) oxide by cluster approach

The catalyst coking and production of undesired products during the transformation of propane into propylene has been in a critical challenge in the on-purpose approach of propylene production. The mechanism contributing to this challenge was theoretically investigated through the investigation of cracking reaction routes to understanding how to promote the coking of this catalyst. The study carried out employed the use of a DFT and cluster approach in the search for the kinetic and thermodynamic data of the reaction mechanism involved in the process over Cr2O3. The RDS and feasible route that easily promote the production of small hydrocarbons like ethylene, methane, and many others were identified. The study suggests, Cr-site substitution or co-feeding of oxygen, as a way that aids in preventing deep dehydrogenation in the conversion of propane to propylene. This information will help in improving the Cr2O3 catalyst performance and further improve the production yield.

Effects of temperature pretreatment on propane cracking over H-SSZ-13 zeolites

The effect of thermal treatment of SSZ-13 on catalytic activity has been investigated by using monomolecular propane conversion as a probe reaction.