42903-71-9

The invention provides novel, low-cost catalysts and methods for their preparation and application in CO2 adsorption and conversion to long-chain hydrocarbons via photosynthesis with ambient CO2 and solar energy.

Isotopic exchange reactions of isobutane, n-heptane, and n-hexane with deuterium gas have been investigated near atmospheric pressure in the temperature range 500-650 K over the flat (111) and kinked (10,8,7) crystal faces of platinum.The exchange kinetics at low conversion displayed zero activation energy, a first-order dependence on D2 pressure, and a strong negative-order dependence on the surface coverage by strongly bound carbonaceous species.Initial exchange rates and product distributions were not influenced appreciably by the presence of steps and kinks on the platinum surface, and the exchange product distributions varied little with temperature, D2 pressure, and surface composition.Hydrocarbon (HC) conversion and deuterium exchange rates measured simultaneously for n-hexane reactions catalyzed over Pt(111) revealed that deuterium exchange always occurs more rapidly as compared to all other competing chemical reactions.

Enthalpies and entropies of ionization (ΔH0ion and ΔS0ion) of alkylcyclohexanes, as well as cycloheptane, cyclooctane, and trans-Decalin, have been determined by charge-transfer equilibrium measurements.Values of ΔHion, in units of kcal mol-1 (or eV), range from 229.6 (9.96) for cycloheptane to 210.7 (9.14) for trans-Decalin.A major effect of alkyl substitution is observed following substitution at a site α to a tertiary hydrogen atom (as from methylcyclohexane to 1,2-dimethylcyclohexane), or following replacement of a tertiary hydrogen atom (as from methylcyclohexane to 1,1-dimethylcyclohexane).In both cases, ΔH0 ion decreases by ca. 5 kcal mol-1.Entropies of ionization are near zero for alkylcyclohexanes but range up to 5 cal deg-1 mol-1 for nonsubstituted cycloalkanes (cyclooctane).The charge-transfer reactions involving the cycloalkanes are shown to be fast processes; i.e., the sum of the reaction efficiencies (r=k/kcollision) of the forward and reverse processes is near unity.The efficiencies of these processes appear to be determined uniquely by the overall free energy change (or equilibrium constant K).Specifically, the reaction efficiencies are defined, within a factor of 2 by the relation r=K/(1+K), which can be justified by using transition-state theory applied to the decomposition of a collision complex over surfaces lacking energy barriers.These reactions are defined as intrinsically fast processes in that they are slowed only by the overall reaction thermochemistry and not by any properties or reactions of the intermediate complex.

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