NISCAIR Online Periodicals Repository Collection: IJC-A Vol.51A(09-10) [September-October 2012]

Chitosan biohydrogel beads: A recyclable, biodegradable, heterogeneous catalyst for the regioselective synthesis of 5-aryl-2-oxazolidinones from carbon dioxide and aziridines at mild conditions

Wed, 29 Aug 2012 22:58:59 GMT

Title: Chitosan biohydrogel beads: A recyclable, biodegradable, heterogeneous catalyst for the regioselective synthesis of 5-aryl-2-oxazolidinones from carbon dioxide and aziridines at mild conditions

Authors: Watile, Rahul A; Bhanage, Bhalchandra M

Abstract: In the search for efficient catalysts for a reaction under mild conditions, cycloaddition reactions of carbon dioxide with various aziridines catalyzed by chitosan biohydrogel beads without additional solvent and metal co-catalyst to form five-membered 5-aryl-2-oxazolidinones in high yields and selectivity has been studied. Reaction rate, conversion and selectivity are studied as a function of a series of input variables including catalyst loading, temperature, pressure and solvent system. The catalyst is easily recovered and has been reused in five consecutive cycles without any significant loss of its catalytic activity and selectivity. The catalyst, chitosan biohydrogel beads, has been characterized by a variety of techniques, namely, scanning electron microscopy and Fourier transform infrared spectroscopy. A plausible reaction mechanism for the hydrogen-bond assisted ring-opening of aziridine to five-membered 5-aryl-2-oxazolidinones is also proposed.

Page(s): 1354-1360

Pt nanoparticles supported on mesoporous ZSM-5: A potential catalyst for reforming of methane with carbon dioxide

Wed, 29 Aug 2012 22:58:59 GMT

Title: Pt nanoparticles supported on mesoporous ZSM-5: A potential catalyst for reforming of methane with carbon dioxide

Authors: Sarkar, Bipul; Suman, Shashank; Tiwari, Ritesh; Singha, Rajib Kumar; Ghosh, Shilpi; Shankha; Acharyya, Shubhra; Konathala, L N Sivakumar; Pendem, Chandrashekar; Mantri, Kshudiram; Bal, Rajaram

Abstract: Pt-nanoparticles supported on ZSM-5 have been prepared and characterized by X-ray diffraction, field emission-scanning electron microscopy, X-ray photoelectron spectroscopy and N₂ adsorption/desorption study. The catalyst shows very high methane conversion in the reforming of methane with CO₂. The effect of Pt loading and various reaction parameters like temperature, gas hourly space velocity and time-on-stream have been examined during the course of study. It is found that the catalyst is stable and the deactivation negligible even after 24 h of time-on-stream study.

Page(s): 1348-1353

Carbon dioxide reforming of methane over ruthenium substituted strontium titanate perovskite catalysts

Wed, 29 Aug 2012 22:58:59 GMT

Title: Carbon dioxide reforming of methane over ruthenium substituted strontium titanate perovskite catalysts

Authors: Gurav, Hanmant R; Bobade, Richa; Das, Vineetha Lakshmi; Chilukuri, Satyanarayana

Abstract: Strontium titanate (SrTiO₃)doped with varying amounts of ruthenium (7.9, 15.6 and 31 wt%) have been prepared by the citrate gel synthesis method. Structural and textural characterizations reveal that at lower concentrations, a major part of Ru is incorporated in the lattice of SiTiO₃. The content of surface Ru (outside lattice) increases with increasing amounts of the doped Ru. The surface Ru reduced at lower temperatures compared to Ru incorporated into the lattice. The reduction of the lattice substituted Ru occurs only at temperatures above the collapse of the perovskite structure. The catalyst sample with 7.9 wt% of Ru shows good conversions in the dry reforming of methane with CO₂. The conversion of CO₂is in excess compared to methane under the studied reaction conditions. As a result, H₂/CO ratio of the product gases which should have been equivalent to unity is lower than the stoichiometric value. This ratio is particularly low when lower reaction temperatures (873–973 K) were used. Similar was the case when high space velocities were used. Low methane conversion and reverse water gas shift reaction are the causes for the low H₂/CO ratios.

Page(s): 1339-1347

Synthesis of 1,2-glycerol carbonate from carbon dioxide: The role of methanol in fluid phase equilibrium

Wed, 29 Aug 2012 22:58:59 GMT

Title: Synthesis of 1,2-glycerol carbonate from carbon dioxide: The role of methanol in fluid phase equilibrium

Authors: Podila, S; Plasseraud, L; Cattey, H; Ballivet-Tkatchenko, D; Carrera, G V S M; Nunes da Ponte, M; Neuberg, S; Behr, A

Abstract: The effect of methanol on the synthesis of 1,2-glycerol carbonate from CO₂ and glycerol is studied in the presence of Bu₂Sn(OCH₃)₂, n-Bu₂SnO, and tert-Bu₂SnO. At 423 K, up to 2.7 mol% yield in glycerol carbonate, based on glycerol, could be obtained in the pressure range 14-20 MPa. Addition of acetonitrile promotes notably the yield to 7 mol%. Fluid phase equilibrium experiments with the ternary mixture CO₂/glycerol/methanol show that the reaction takes place in a liquid phase where methanol dissolves glycerol, CO₂, and the tin complexes. Above ~0.6 mole fraction, CO₂ behaves as an anti-solvent, separating methanol from glycerol, thus inhibiting the formation of 1,2-glycerol carbonate. Dimethyl carbonate is a side-product of glycerol carbonation resulting mainly from transesterification between glycerol carbonate and methanol. Glycerol coordination to tin center is evidenced by the isolation of di-tert-Bu₂Sn(1,2-glycerolate) complex. Its structure determination by single-crystal X-ray diffraction shows that the remaining OH group of glycerol promotes the formation of one-dimensional polymeric chain.

Page(s): 1330-1338