Catalysis research of relevance to carbon management: progress, challenges, and opportunities.

The goal of the "Opportunities for Catalysis Research in Carbon Management" workshop was to review within the context of greenhouse gas/carbon issues the current state of knowledge, barriers to further scientific and technological progress, and basic scientific research needs in the areas of H2 generation and utilization, light hydrocarbon activation and utilization, carbon dioxide activation, utilization, and sequestration, emerging techniques and research directions in relevant catalysis research, and in catalysis for more efficient transportation engines. Several overarching themes emerge from this review. First and foremost, there is a pressing need to better understand in detail the catalytic mechanisms involved in almost every process area mentioned above. This includes the structures, energetics, lifetimes, and reactivities of the species thought to be important in the key catalytic cycles. As much of this type of information as is possible to acquire would also greatly aid in better understanding perplexing, incomplete/inefficient catalytic cycles and in inventing new, efficient ones. The most productive way to attack such problems must include long-term, in-depth fundamental studies of both commercial and model processes, by conventional research techniques and, importantly, by applying various promising new physicochemical and computational approaches which would allow incisive, in situ elucidation of reaction pathways. There is also a consensus that more exploratory experiments, especially high-risk, unconventional catalytic and model studies, should be undertaken. Such an effort will likely require specialized equipment, instrumentation, and computational facilities. The most expeditious and cost-effective means to carry out this research would be by close coupling of academic, industrial, and national laboratory catalysis efforts worldwide. Completely new research approaches should be vigorously explored, ranging from novel compositions, fabrication techniques, reactors, and reaction conditions for heterogeneous catalysts, to novel ligands and ligation geometries (e.g., biomimetic), reaction media, and activation methods for homogeneous ones. The interplay between these two areas involving various hybrid and single-site supported catalyst systems should also be productive. Finally, new combinatorial and semicombinatorial means to rapidly create and screen catalyst systems are now available. As a complement to the approaches noted above, these techniques promise to greatly accelerate catalyst discovery, evaluation, and understanding. They should be incorporated in the vigorous international research effort needed in this field.

The effect of electric field gradient asymmetry on motionally averaged spin-1 powder patterns.

The effect of an asymmetric electric field gradient tensor on anisotropic NMR spectra of spin-1 nuclei is investigated for fast molecular rotations and 2-site jump processes. When molecular rotations are fast, continuous, and complete, the peak-to-peak splitting of motionally averaged spin-1 NMR spectra can depend significantly on the inherent electric field gradient asymmetry, eta, for eta > or = 0.05. Parameters describing low-symmetry molecular motion which are extracted from fitting experimental data depend strongly upon eta. One implication of these phenomena is that even the modest electric field gradient asymmetry around deuterons in covalent bonds can contribute considerably to motionally averaged lineshapes, especially when molecular motions are not highly symmetric.

Control of the pilocarpine release rate through hydrogels by plasma treatment.

The rate of release of an aqueous solution of pilocarpine hydrochloride sequestered in hydrogel-type materials can be reduced by plasma treatment of the polymer surface. Two plasma techniques were used. The first involves exposure of the hydrogel to the effects of a glow discharge sustained in argon, a process known as CASING. (Crosslinking by Active Species of Inert Gases). The second technique involves the deposition of a thin film by plasma polymerization of organic gases. The gases used in this study were ethane, ethylene and tetrafluoroethylene. Hydrogels were prepared by photopolymerization of 2-hydroxymethyl methacrylate (HEMA), and copolymerization of HEMA with methyl acrylate. The CASING treatment was found to be least effective. The most successful method was the plasma polymerization of tetrafluoroethylene, which yielded an order of magnitude reduction in the flux rate of pilocarpine with a film thickness of 0.25micronm. Polymerization conditions bringing about a crack-resistant film were critical in obtaining the best results.

Reduction of progesterone release rate through silicone membranes by plasma polymerization.

An investigation was performed to determine the effectiveness of thin plasma-polymerized films and CASING for controlling the flux of progesterone through poly-(dimethyl siloxane) membranes. It was concluded that up to 40-fold reductions in flux could be achieved with plasma-polymerized films. The principal factors affecting the extent of flux reduction were the nature of the monomer used (ethylene, ethane and tetrafluoroethylene), the film thickness, and the deposition conditions. CASING (Crosslinking by Activated Species of Inert Gases) of the poly-(dimethyl siloxane) membrane surface also proved effective in reducing the flux of progesterone through it.