Characteristics of La-modified Ni-Al2O3 and Ni-SiO2 catalysts for COx-free hydrogen production by catalytic decomposition of methane

Hydrotalcite precursors of La modified Ni-Al₂O₃ and Ni-SiO₂ catalysts prepared by co-precipitation method and the catalytic activities were examined for the production of CO_x-free H₂ by CH₄ decomposition. Physico-chemical characteristics of fresh, reduced and used catalysts were evaluated by XRD, TPR and O₂ pulse chemisorptions, TEM and BET-SA techniques. XRD studies showed phases due to hydrotalcite-like precursors in oven dried form produced dispersed NiO species upon calcination in static air above 450 °C. Raman spectra of deactivated samples revealed the presence of both ordered and disordered forms of carbon. Ni-La-Al₂O₃ catalyst with a mole ratio of Ni : La : Al = 2 : 0.1 : 0.9 exhibited tremendously high longevity with a hydrogen production rate of 1300 mol_H2 ·mol^?1_Ni. A direct relationship between Ni metal surface area and hydrogen yields was established.     

A composite grid solver for conjugate heat transfer in fluid–structure systems

We describe a numerical method for modeling temperature-dependent fluid flow coupled to heat transfer in solids. This approach to conjugate heat transfer can be used to compute transient and steady state solutions to a wide range of fluid–solid systems in complex two- and three-dimensional geometry. Fluids are modeled with the temperature-dependent incompressible Navier–Stokes equations using the Boussinesq approximation. Solids with heat transfer are modeled with the heat equation. Appropriate interface equations are applied to couple the solutions across different domains. The computational region is divided into a number of sub-domains corresponding to fluid domains and solid domains. There may be multiple fluid domains and multiple solid domains. Each fluid or solid sub-domain is discretized with an overlapping grid. The entire region is associated with a composite grid which is the union of the overlapping grids for the sub-domains. A different physics solver (fluid solver or solid solver) is associated with each sub-domain. A higher-level multi-domain solver manages the entire solution process.     

A new synthesis of the phytotoxic 10-membered lactone herbarumin I

Herbarumin I a phytotoxic 10-membered lactone has been synthesized from d-(?)-isoascorbic acid in 12 steps with an overall yield of 16.8%. The methodology involved in generating the stereogenic center at C-8 is a Sharpless asymmetric epoxidation, as well 1,2-asymmetric induction followed by macrolactonization via RCM.     

Characteristics of La-modified Ni-Al2O3 and Ni-SiO2 catalysts for COx-free hydrogen production by catalytic decomposition of methane

Hydrotalcite precursors of La modified Ni-Al2O3 and Ni-SiO2 catalysts prepared by co-precipitation method and the catalytic activities were examined for the production of COx-free H2 by CH4 decomposition. Physico-chemical characteristics of fresh, reduced and used catalysts were evaluated by XRD, TPR and O2 pulse chemisorptions, TEM and BET-SA techniques. XRD studies showed phases due to hydrotalcite-like precursors in oven dried form produced dispersed NiO species upon calcination in static air above 450 C. Raman spectra of deactivated samples revealed the presence of both ordered and disordered forms of carbon. Ni-La-Al2O3catalyst with a mole ratio of Ni : La : Al = 2 : 0.1 : 0.9 exhibited tremendously high longevity with a hydrogen production rate of 1300 molH2 mol 1 Ni. A direct relationship between Ni metal surface area and hydrogen yields was established.     

Stereoselective synthesis of umuravumbolide

An efficient stereoselective total synthesis of umuravumbolide has been developed. The key features of the synthesis include Jacobsen resolution, Wadsworth Emmons olefination and silyl-tethered ring closing metathesis.     

Asymmetric organocatalytic Michael-type reaction of phosphorus ylides to nitroolefins: synthesis of γ-nitro-β-aryl-α-methylene carboxylic esters

We report, for the first time, asymmetric organocatalytic Michael-type addition of stabilized phosphorus ylides to nitroolefins mediated by bisthiourea catalyst. Its subsequent reaction with formaldehyde provides γ-nitro-α-methylene carboxylic esters in moderate to good yields and enantioselectivities (up to 63% ee).