Catalytic Oxidative Cracking of Propane Over Nanosized Gold Supported Ce0.5Zr0.5O2 Catalysts

Structural and catalytic properties of copper silicate nanomaterials

Nanosized copper silicates with three different structural morphology (amorphous, nanotubes and MEL) were prepared using different synthesis methods. The physico-chemical properties of copper silicates were characterized by XRD, FT-IR, SEM, HRTEM, N₂-physisorption, XPS and H₂-TPR techniques. The results indicated that the preparation conditions affect reduction behavior and textural properties of nanosized copper silicates. Hydrothermal synthesis method yielded chrysocolla-like CuSiO₃ nanotubes, which possessed high surface area and pore volume with easy reducibility. The catalytic performances of synthesized copper silicate nanostructures were evaluated for dehydrogenation of methanol. It was found that dehydrogenation activity is depended on the structural properties of copper silicates. Highest activity was observed for copper silicates with nanotube morphology. Catalytic dehydrogenation activity of copper silicates was also related to presence of more number of Cu-O-Si species, easy reducibility and Lewis acid centers. The CuSiO₃ nanotubes sample also exhibited good stability under investigated reaction conditions that deactivation was not detected for 48 h.

Selective Oxidative Cracking of n-Butane to Light Olefins over Hexagonal Boron Nitride with Limited Formation of COx

In recent years, hexagonal boron nitride (hBN) has emerged as an unexpected catalyst for the oxidative dehydrogenation of alkanes. Here, the versatility of hBN was extended to alkane oxidative cracking chemistry by investigating the production of ethylene and propylene from n-butane. Cracking selectivity was primarily controlled by the ratio of n-butane to O₂ within the reactant feed. Under O₂ -lean conditions, increasing temperature led to increased selectivity to ethylene and propylene and decreased selectivity to CO_x . In addition to surface-mediated chemistry, homogeneous gas-phase reactions likely contributed to the observed product distribution, and a reaction mechanism was proposed based on these observations. The catalyst showed good stability under oxidative cracking conditions for 100 h time-on-stream while maintaining high selectivity to ethylene and propylene.

Lanthanum Exchanged Keggin Structured Heteropoly Compounds for Biodiesel Production

La-exchanged 12-tungstophosphoric acid (LaxTPA) and 12-molybdophosphoric acid (LaxMPA) salts (x = 0.25, 0.50, 0.75 and 1.00) were prepared via an ion exchange method. The physico-chemical characteristics of the materials were analyzed by using elemental analysis, X-ray diffraction (XRD), Fourier transformed infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), N2-physical adsorption, X-ray photoelectron spectroscopy (XPS), and acidity-basicity measurements. The results indicated that La was introduced into the secondary structure of heteropolyacid (HPA) and have not influenced the primary structure, which effectively improved the surface area and pore size. Acidity-basicity studies indicated that incorporation of La resulted in a decrease in the number of acid sites and an increase in the number of basic sites. The catalytic activity of samples was studied in transesterification of glyceryl tributyrate with methanol and LaxTPA samples which exhibited high activity compared to LaxMPA samples due to having more active basic sites and a larger surface area. Calcined LaxTPA samples showed excellent stability, outstanding recyclability, and high activity for one pot transesterification and esterification processes. This outcome was attributed to the presence of balanced acidic and basic sites.

Selective Oxidation of Veratryl Alcohol over Au-Pd/Ce0.62Zr0.38O₂ Catalysts Synthesized by Sol-Immobilization: Effect of Au:Pd Molar Ratio

The selective oxidation of veratryl alcohol (VA), a model compound of lignin, with oxygen molecules to produce veratraldehyde (VAld) was studied over monometallic Au, Pd, and bimetallic Au:Pd nanoparticles supported on a Ce_0.62Zr_0.38O₂ mixed oxide for the first time. These bimetallic Au-Pd catalysts with Au:Pd molar ratios from 0.4 to 4.3 were synthesized by the sol-immobilization method. Furthermore, all the catalysts were characterized by inductively coupled plasma-atomic emission spectroscopy (ICP-AES), N₂ physisorption, X-ray photoelectron spectroscopy (XPS), scanning transmission electron microscopy-high angle annular dark field (STEM-HAADF) imaging, energy dispersive X-ray spectroscopy (EDXS), and temperature programmed reduction (TPR) techniques. A synergistic effect between gold and palladium was observed over all the bimetallic catalysts in a wide range of studied Au:Pd ratios. Remarkably, the optimum Au:Pd ratio for this reaction was 1.4 with a turnover frequency of almost six times larger than for the monometallic gold and palladium catalysts. Selectivity to veratraldehyde was higher than 99% for the monometallic Au, Pd, and all the bimetallic Au-Pd catalysts, and stayed constant during the reaction time.