S. Chandra Shekar

Selective hydrogenolysis of dichlorodifluoromethane (CCl2F2) over CCA supported palladium bimetallic catalysts

Abstract La, Bi, Sb, Sn, Ba, and Zn are chosen for addition on carbon covered alumina (CCA) supported Pd catalyst. The effect of these second metals on supported Pd catalysts has been studied for the hydrogenolysis activity of CCl 2 F 2 . Bi and Sb promoters have been found to improve not only the thermal stability but also selectivity towards CH 2 F 2 . Sn bimetallic catalyst exhibited high selectivity towards CHClF 2 . This may be explained on the basis of the metal–metal interactions that influence the reducibility of the palladium. These improved properties arise due to inter-metallic compound formation as evidenced from the XRD and TPR data on CCA supported bimetallic palladium catalysts. The effect of addition of second metal on Pd/CCA catalyst is screened in terms of partial dehalogenation ability and thermal stability for hydrodechlorination activity of CCl 2 F 2 to maximize the CH 2 F 2 yield.

Highly selective zirconium oxychloride modified Pd/C catalyst in the hydrodechlorination of dichlorodifluoromethane to difluoromethane

Zirconium oxychloride modified active carbon supported palladium catalyst appears to be a promising system in the hydrodechlorination of CCl2F2 to yield CH2F2 in greater yields; showing an altogether different product distribution compared to Pd/C and Pd/ZrO2 catalysts. The catalysts have been characterized by BET-surface area, CO-chemisorption, X-ray diffraction (XRD), temperature programmed reduction (TPR) analysis and fluorine contents in used catalysts. The interaction of Zr species with Pd and the formation of fluorinated zirconium species during the course of reaction led to the higher selectivity towards CH2F2.

13X分子筛负载Fe催化剂上1,4-二氧六环在空气中完全氧化

Abstract Zeolite-13X-supported Fe (Fe/zeolite-13X) catalysts with various Fe contents were prepared by the wet impregnation method. The catalysts were characterized by N2 adsorption-desorption isotherms to estimate the Brunauer–Emmett–Teller surface areas and Barrett–Joyner–Hanlenda pore size distributions. X-ray diffraction, scanning electron microscopy, temperature-programmed reduction, and temperature-programmed desorption of NH3 were used to investigate the textural properties of the Fe/zeolite-13X catalysts. Their catalytic activities were determined for the complete oxidation of 1,4-dioxane using air as the oxidant in a fixed‐bed flow reactor in the temperature range 100–400 °C. The influences of various process parameters, such as reaction temperature, metal loading, and gas hourly space velocity (GHSV), on the dioxane removal efficiency by catalytic oxidation were investigated. The stability of the catalyst was tested at 400 °C by performing time-on-stream analysis for 50 h. The Fe/zeolite-13X catalyst with 6 wt% Fe exhibited the best catalytic activity among the Fe/zeolite-13X catalysts at 400 °C and a GHSV of 24000 h−1, with 97% dioxane conversion and 95% selectivity for the formation of carbon oxides (CO and CO2). Trace amounts (

Hydrodechlorination of 1,1,2-Trichloro-1,2,2 trifluoroethane (CFC-113) over Pd supported on modified AL2O3

Hydrdechlorination (HDC) is to be not only a process for a safe disposal of chlorofluorocarbons (CFCs) but also effective in preparation of useful chemical intermediates. Palladium based catalysts have been found to be very promising in the HDC reactions. It is observed that the nature of support used for the palladium catalysts has a role to play in modifying the selectivity towards useful products. In the present investigation, the influence of modification of the alumina support on the activity and selectivity of Pd catalysts during the HDC of CFC-113 is reported.

A simple and controlled oxidative decontamination of sulfur mustard and its simulants using ozone gas

GRAPHICAL ABSTRACT ABSTRACT A simple and efficient oxidative decontamination method was developed for sulfur mustard (HD), a potential chemical warfare agent. The method involves treatment of chemical warfare agent HD and its simulants, i.e., dimethyl sulfide, diethyl sulfide, and 2-chloroethyl ethyl sulfide with ozone gas at ambient conditions in acetonitrile solvent. Ozone gas readily oxidizes sulfur mustard in a controlled manner to give its corresponding nontoxic sulfoxide. This transformation is selective and takes place even at subzero temperatures. The oxidation products of HD and its simulants were monitored and quantified by gas chromatography and gas chromatography–mass spectrometry.

Vapor Phase Selective Catalytic Oxidation of Cyclohexane over 13X Supported Metal Oxides in the Presence of Ozone

ABSTRACT This article reports the application of ozone for the selective oxidation of cyclohexane over 13X molecular sieve supported various metal oxides at ambient temperatures. From the SEM, XRD and HR-TEM results, the impregnated metal oxides are highly dispersed on the support. The activity results reveal that Co/MS, Mo/MS, Cu/MS, and Ag/MS catalysts produce cyclohexanone/cyclohexanol as selective oxidation products, whereas Ce/MS, Mn/MS, and V/MS catalysts yield, predominantly, CO and CO2. Among them, Co/MS catalyst exhibits better conversion of 12.2% with selectively of 58% to cyclohexanone/cyclohexanol, which is attributed to the simultaneous activation of ozone and cyclohexane (-C-H bond) at ambient conditions.