The use of inexpensive hydrogels as supports to significantly improve H2 enclathration kinetics and capacities in THF–H2O clathrate hydrate with respect to bulk solutions is demonstrated. Polymer hydrogels give rise to significant rate and capacity enhancements for hydrogen clathrate formation with respect to unmixed bulk systems, suggesting potential for accelerated gas-storage kinetics in clathrate-based technologies

High-pressure NMR methods for the study of the kinetics of gas−solution reactions are presented, and the importance/interplay of mass transport and chemical resistances are discussed. For reactions that are slow compared with mass transport, the true reaction kinetics can be obtained and used to confirm that the observed species are relevant to the catalytic reaction. Conversely, the ability to determine the catalyst speciation during the catalytic reaction aids interpretation of the kinetic data. When chemical reaction is fast compared with diffusion across the gas−liquid interface, reaction is shown to occur in the liquid layer; for such a transport-controlled reaction, chemical reaction can increase the concentration gradient across the boundary layer, enhancing diffusion both across the phase boundary and within the liquid layer, resulting in apparent positive orders in catalyst, substrate, or both. These dependencies do not reflect the chemical dependence of the reaction rate on these concentrations.

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The fragmentation and redistribution reactions of [Rh4(CO)12-x{P(OPh)3}x] (x = 1-4) with carbon monoxide have been studied using high-resolution, high-pressure NMR spectroscopy. Under the conditions of efficient gas mixing in a high-pressure NMR bubble column, [Rh4(CO)9{P(OPh)3}3] fragments to give mainly [Rh2(CO)6{P(OPh)3}2]; [Rh4(CO)11{P(OPh)3}] is also observed,implying redistribution of the phosphite ligand and/or recombination of the dimers to tetrameric clusters. Fragmentation of[Rh4(CO)10{P(OPh)3}2] is found to be pressure-dependent giving predominantly [Rh2(CO)6{P(OPh)3}2] at low CO pressure (1-40 bar), and increasing amounts of [Rh2(CO)7{P(OPh)3}] at higher (40-80 bar) pressure. Using Syngas (CO : H2 (1 : 1)) instead of CO in the above fragmentations, homolytic addition of H2 to the dimer [Rh2(CO)6{P(OPh)3}2] to give [RhH(CO)3{P(OPh3}] and [RhH(CO)2{P(OPh)3}2] is observed. The distribution of tetrameric species obtained is similar to that obtained under the same partial pressure of CO. On depressurisation/out-gassing of the sample, the original mixture of tetrameric clusters is obtained.

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