Highly selective skeletal isomerization of cyclohexene over zeolite-based catalysts for high-purity methylcyclopentene production.

Cyclohexene skeletal isomerization towards methylcyclopentene is an economically favorable process due to the higher added value of the product. Traditional oxide-based catalysts face the challenge of achieving both high activity and stability. In this work, cyclohexene skeletal isomerization is achieved under mild conditions over designed zeolite-based catalysts with 96.8 wt.% liquid yield, 95.8 wt.% selectivity towards methylcyclopentene and satisfactory stability for multiple runs. The favorable performance is attributed to the unique acidic, structural and morphological features of the optimized cobalt/NaUZSM-5 catalyst. Further experimental data and DFT studies suggest that a carboncationic mechanism might be followed and that the reaction mainly occurs within the internal pores of the zeolite structures.

Highly Selective Aromatization of Octane over Pt-Zn/UZSM-5: The Effect of Pt-Zn Interaction and Pt Position.

The effects of Zn-Pt interaction and Pt dispersion over a uniform compact cylindrical shape ZSM-5 (UZSM-5) on the catalytic octane aromatization performance are investigated. The comparison between different Pt- and Zn-modified ZSM-5 catalysts demonstrates the significance of ZSM-5 morphology and, more importantly, the metal distributions on it. For the UZSM-5 support, Pt atoms prefer to occupy the sites within its inner pores, resulting in high selectivity to xylenes during the octane aromatization. The Zn deposit in inner pores and higher dispersion of Pt lead to the spillover of Pt sites to the external surface, which is critical for the activation of octane to produce reaction intermediates that are further converted to aromatics over the inner pore catalytic sites. These effects are evidenced by a diffuse reflection infrared Fourier transform spectroscopy study of CO adsorbed on the catalyst surface. In situ X-ray absorption fine structure spectra are collected to probe the coordination number and the chemical environment of Pt and Zn atoms in the catalysts during the octane aromatization reaction. Pt and Zn are well dispersed and stable during the reaction, and a partial reduction of Pt during the reaction is observed. A theoretical study using the density functional theory method predicts that the reaction and transition-state intermediates upon octane activation are better stabilized by Pt(111) of Pt external surface sites with a smaller activation barrier, indicating their significance in C-H activation. This hypothesis is further evidenced by comparing the octane aromatization performance of various modified catalysts through varying Zn loading, blocking inner pores, and covering the external catalytic sites with SiO2.

Participation of methane in an economically and environmentally favorable catalytic asphaltene upgrading process.

A catalytic asphaltene upgrading process was performed in the presence of methane. Through 13C isotope labelling, methane was proven to be successfully incorporated into the liquid product, preferably in aliphatic structures. Control experiments suggested that the presence of both catalyst and methane is indispensable for improving product quality.

Nonthermal Plasma-Assisted Photocatalytic Conversion of Simulated Natural Gas for High-Quality Gasoline Production near Ambient Conditions.

We report a novel nonthermal plasma-assisted photocatalytic approach that could efficiently convert the main components of natural gas, methane and propane, into high-quality gasoline chemicals abundant with C6-C9 branched-chain paraffins at low temperature and atmospheric pressure. The conversions of methane and propane can reach up to 15.0% and 48.6%, respectively. A 58.4 C% yield of gasoline products with limited coke deposition (6.3 C%) can be achieved via the combination of plasma with photocatalysis. Isotope labeling experiments show that methane prefers to be incorporated into 1-C or 2-C of the formed alkanes as a terminal group. Our work demonstrates an industrially promising strategy for the cost-efficient utilization of natural gas.

Non-thermal plasma induced photocatalytic conversion of light alkanes into high value-added liquid chemicals under near ambient conditions.

We reported a novel non-thermal plasma induced photocatalytic transformation of light hydrocarbons over Ti-Ga/UZSM-5, which gives 47.8 C% of liquid products, with C6-C9 iso-alkanes being the major components, and limited coke (5.5 C%). Combining the plasma with a photocatalyst displays great potential to produce gasoline range chemicals from low-cost gaseous hydrocarbons under near ambient conditions.