Potentials of boiling heat transfer in advanced thermal energy systems

Journal of Thermal Analysis and Calorimetry - Boiling process is a highly efficient mechanism of heat transfer, which has an important role in industrial and domestic sectors. In this process, a...     

CH_4 reforming with CO_2 for syngas production over La_2O_3 promoted Ni catalysts supported on mesoporous nanostructured γ-Al_2O_3

Nanostructured γ-Al2O3 with high surface area and mesoporous structure was synthesized by sol-gel method and employed as catalyst support for nickel catalysts in methane reforming with carbon dioxide. The prepared samples were characterized by XRD, N2adsorption-desorption,TPR, TPO, TPH, NH3-TPD and SEM techniques. The BET analysis showed a high surface area of 204 m2 g-1and a narrow pore-size distribution centered at a diameter of 5.5 nm for catalyst support. The BET results revealed that addition of lanthanum oxide to aluminum oxide decreased the specific surface area. In addition, TPR results showed that addition of lanthanum oxide increased the reducibility of nickel catalyst. The catalytic evaluation results showed an increase in methane conversion with increasing lanthanum oxide to 3 mol% and further increase in lanthanum content decreased the catalytic activity. TPO analysis revealed that the coke deposition decreased with increasing lanthanum oxide to 3 mol%. SEM and TPH analyses confirmed the formation of whisker type carbon over the spent catalysts. Addition of steam and O2 to dry reforming feed increased the methane conversion and led to carbon free operation in combined processes.     

The synthesis,characterization and reactions of a binuclear tetramethylplatinum(IV) complex

Reaction of excess MeLi and MeI with [PtCl₂SMe₂)₂] gives the first binuclear tetramethylplatinum(IV) complex [Pt₂Me₈(μ-SMe₂)₂]. The characterization of this complex, and its reactions with donor ligands to give cis-[PtMe₄L₂] (L₂ = Ph₂PCH₂PPh₂, Ph₂PCH₂CH₂PPh₂, 2,2′-bipyridyl, 1,10-phenanthroline or L = PMe₂Ph, PMePh₂) are described.     

Oxidative addition of methyl iodide to a new type of binuclear platinum(II) complex: a kinetic study

A new organodiplatinum(II) complex cis,cis-[Me2Pt(mu-NN)(mu-dppm)PtMe2] (1), in which NN = phthalazine and dppm = bis(diphenylphosphino)methane, is synthesized by the reaction of cis,cis-[Me2Pt(mu-SMe2)(mu-dppm)PtMe2] with 1 equiv of NN. Complex 1 has a 5d(pi)(Pt) --> pi(imine) metal-to-ligand charge-transfer band in the visible region, which was used to easily follow the kinetics of its reaction with MeI. Meanwhile, the complex contains a robust bridging dppm ligand that holds the binuclear integrity during the reaction. A double MeI oxidative addition was observed, as shown by spectrophotometry and confirmed by a low-temperature 31P NMR study. The classical S(N)2 mechanism was suggested for both steps, and the involved intermediates were suggested. Consistent with the proposed mechanism, the rates of the reactions at different temperatures were slower in benzene than in acetone and large negative deltaS values were found in each step. However, some abnormalities were observed in the related rate constants and deltaS values, which were demonstrated to be due to the associative involvement of the polar acetone molecules in the reactions. The rates are almost 6 times slower in the second step as compared to the first step because of the electronic effects transmitted through the ligands and the steric effects.