Catalytic transformation of methane over in-loaded ZSM-5 zeolite in the presence of ethene.

Methane is shown to react with ethene over In-loaded ZSM-5 to higher hydrocarbons such as propene and toluene at around 673 K. Such methane conversion is not catalyzed by proton-exchanged ZSM-5 (H-ZSM-5) under the same conditions, only C2H4 being converted to higher hydrocarbons. By using 13C-labeled methane (13CH4) as a reactant, the reaction paths for the formation of propene, benzene and toluene were examined. 13C-labeled propene (13CC2H6) is formed by the reaction of 13CH4 with C2H4. The lack of 13C-labeled benzene revealed that propene is not transformed to benzene, which instead originates entirely from C2H4. The 13C atom is inserted both into the methyl group and benzene ring in the toluene formed. This indicates that toluene is formed by two reaction paths; the reaction of 13CC2H6 with butenes formed by the dimerization of C2H4 and the reaction of benzene with 13CH4. The existence of the latter path was proved by the direct reaction of 13CH4 with benzene. The reaction of methane with benzene was also carried out in a continuous flow system over In-loaded ZSM-5. The reaction afforded 7.6% and 0.9% yields of toluene and xylenes, respectively, at 623 K.

Nucleophilic reaction by carbonic anhydrase model zinc compound: characterization of intermediates for CO2 hydration and phosphoester hydrolysis.

The partially hydrophilic and hydrophobic tripodal ligands, tris(hydroxy-2-benzimidazolylmethyl)amine L1h and tris(2-benzimidazolyl)amine L1 were used for the preparation of biomimetic complex of carbonic anhydrase. The CO(2) hydration using [L1hZn(OH)]ClO(4).1.5H(2)O provided the zinc-bound and free HCO(3)(-)s, which were formed by nucleophilic attack of Zn-OH toward CO(2) in dimethyl sulfoxide (DMSO). The phenolic OH in L1h can recognize water molecules through hydrogen bonds to facilitate the collection of the water molecules around a biomimetic zinc compound; the molecular structure of [L1hZn(OH)](+) was revealed. The packing diagram has demonstrated the all the water molecules are hydrogen bonded to each phenolic OH. The nucleophilic attack of zinc-bound OH(-) to substrate is used to catalyze the CO(2) hydration and phosphoester hydrolysis. The carbonic anhydrase model compound [L1Zn(OH(2))](2+) was applied for the hydrolysis of phosphoesters, parathion and bis(p-nitrophenyl)phosphate (BNPP(-)). The low reactivity of [L1Zn(OH)](+) for parathion hydrolysis is attributed to the stability of the intermediate [L1Zn(OP(S)(OEt)(2))](+). Since the structures of the intermediates [L1Zn(OH(2))](BNPP)(2) (1) and [L1Zn(OP(S)(OEt)(2))]ClO(4) (2) formed on the way of hydrolysis are too stable to realize the catalytic cycle and are not active for hydrolysis, carbonic anhydrase model compound [L1Zn(OH(2))](2+) was not suitable for phosphoester hydrolysis; the zinc model compound surrounded by three benzimidazolyl groups is used to have the steric hindrance for bulky substrate, such as parathion and BNPP(-).