Fangli Jing

Self-Propagated Flaming Synthesis of Highly Active Layered CuO-δ-MnO2 Hybrid Composites for Catalytic Total Oxidation of Toluene Pollutant

A new self-propagated flaming (SPF) technique was applied to the synthesis of highly active layered CuO-δ-MnO2 hybrid composites, for the de-polluting catalytic total oxidation of gaseous toluene vapor. Other transition metal oxide-doped MnO2 hybrid composites were also successfully prepared and investigated, ensuring a feasible strategy for the fabrication of various layered MOx-δ-MnO2 (M═Co, Ni, or Zn) hybrids. By changing the molar ratio of the precursors (KMnO4 and acetate salt) and the type of transition metal oxide introduced, it is possible to control the crystal structure and reducibility of the sheetlike hybrid composites as well as the catalytic activity for the total oxidation of toluene. The catalyst sample (CuO-δ-MnO2) with a Mn/Cu molar ratio of 10:1 exhibited the highest catalytic performance, with a lower reaction temperature of 300 °C for complete toluene removal, which was comparable to the reaction temperature for total toluene conversion by the Pt-based catalyst. The SPF technique provides an approach for developing highly efficient catalysts for the complete removal of volatile organic compounds, by allowing the facile and energy-saving fabrication of large quantities of layered CuO-δ-MnO2 hybrids.

Ordered mesoporous Sn-SBA-15 as support for Pt catalyst with enhanced performance in propane dehydrogenation

Abstract A series of Sn-incorporated SBA-15 materials with high specific surface areas and highly ordered mesoporous structures were synthesized by a facile one-pot method and used as catalyst supports. A reference sample was also prepared using a conventional impregnation method. The catalysts were characterized using various methods, and their activities in propane dehydrogenation were investigated. The incorporation of Sn into the SBA-15 matrix led to strong interactions between Sn species and the support, and these helped to maintain the oxidation states of Sn species during the reaction. Substitution with Sn changed the interfacial properties of the Pt species and improved the function and effect of the Sn promoter. The catalytic activities and stabilities of the Pt catalysts supported on Sn-incorporated SBA-15 were better than those of the impregnated sample. However, the catalytic performance deteriorated when an excessive amount of Sn was introduced and the interactions among Pt, Sn species, and the support became weaker. The Pt/0.5Sn-SBA-15 catalyst gave the best propene selectivity, i.e., 98.5%, with a corresponding propane conversion of about 43.8%.

Facile synthesis of CuMAl (M = Cr, Mn, Zn, and Co) with highly dispersed Cu and tailorable surface acidity for efficient 2-methylpyrazine synthesis

Synthesis of 2-methylpyrazine (2-MP) from 1,2-propylene glycol (PG) and ethylenediamine (ED) was investigated in the presence of multifunctional catalytic systems (CuMAl) possessing acidic and metallic functional sites. Catalytic systems were prepared from mixed CuMAl-layered double hydroxides (CuMAl-LDHs, M = Cr, Mn, Zn, and Co) via their thermal decomposition. CuMAl-LDH were prepared from Cu(NO3)2, M(NO3)x and Al(NO3)3 and NaOH/Na2CO3 as a precipitating agent. X-ray diffraction (XRD), N2 adsorption–desorption, temperature-programmed desorption with ammonia (NH3-TPD), N2O chemisorption, transmission electron microscopy (TEM), and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) were used to characterize the physical and chemical properties of the catalysts. The results showed that the nature of the secondary metal M inserted into the LDH structure significantly affected the crystalline structure, the dispersion of copper nanoparticles, and the density of surface acidic sites of the catalysts. The as-prepared CuMAl catalysts displayed promising catalytic performances towards the synthesis of 2-MP. Among them, CuCoAl showed the highest PG conversion (97%) and 2-MP selectivity (55%). These high catalytic activities were found to be associated with the ultra-small Cu nanoparticles (∼2 nm) and high surface acidity (2433 μmol g−1).