The project looked at the direct conversion of C1 through C5 alkanes to low vapor-pressure, low-sulfur, non-aromatic gasoline and diesel fuels by exploring proton- exchange reactive membranes (PERM) for the homologation reaction. Coupling the catalytic homologation reaction with proton-exchange membranes is an innovative, multi-functional technology for enhanced alkane dehydrogenation, hydrogen separation, and oligomerization.
Equilibrium shifting of catalytic membranes was tested for conversion of light alkanes to non-aromatic, liquid hydrocarbons.
The non-oxidative homologation catalytic reaction has been shown to be a unique and promising technology for upgrading light alkanes. Run isothermally, the reaction has a positive Gibbs free energy of reaction, limiting conversion and yields. Researchers have found that this reaction can be split into two steps, significantly improving the thermodynamic constraints. In the first step, a flowing hydrocarbon chemisorbs and dehydrogenates on the catalyst surface. The flow is switched to hydrogen in the second step, forming re-hydrogenated higher hydrocarbons that are released from the catalyst.
Technical issues explored in the project were:
- Obtaining high hydrogen-flux rates across the membrane, such that the alkane upgrading reaction is promoted.
- Achieving rapid catalyst kinetics that promote the chemisoption/dehydrogenation and rehydrogenation/higher-hydrocarbon formation reaction.
- Determining optimum process conditions that positively affect both the catalytic reaction and the membrane performance.
- Avoiding negative catalyst-membrane interactions.
- Exploring material stability in the reaction environment.
The developed PERM was tested in an automated flowing reactor system. The alkane/hydrogen reactor affluent stream was analyzed to determine alkane conversion, product yield, selectivity, and production rate as a function of process variables. The goal of this effort was to increase reaction kinetics to the point that a continuous steady-state process can be established.
