The project goal is to investigate the moderate-temperature conversion of light alkanes to non-aromatic liquid hydrocarbons by employing the equilibrium-shifting potential of catalytic membranes.

Idaho National Laboratory
Idaho Falls, ID

Ceramatec Inc.
Salt Lake City, UT

BP Products North America
Houston, TX

Modern refinery processes produce significant quantities of light alkane byproducts that have limited potential for blending in liquid transportation fuels. These byproducts, which contain low levels of sulfur, are typically burned as low-value fuel gas or flared, representation a significant economic loss.

This experimental research project will explore the catalytic homologation of light alkanes to liquid fuels via a PERM. Catalytic homologation reaction has a high potential for success, since the reaction can be manipulated to produce primarily low vapor-pressure, non-aromatic hydrocarbons. The PERM reactor can be a net hydrogen producer or could be coupled with a fuel cell to produce power from the hydrogen byproduct.

Since processed light alkanes contain low levels of sulfur, and the reaction products are low vapor-pressure alkanes and cyclo-alkanes, this process has a high potential for producing clean liquid transportation fuels.

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.

Additional funding for this project was received in August 2004. The Cooperative Research and Development Agreement with Ceramatec Inc. was modified to cover a new scope of work under this project. This included a scale-up of the process to a pilot by Ceramatec. Positive results from the pilot study will lead to full-scale development and demonstration of the PERM alkane upgrading process.

 $ 440,000

$55,000 (11% of total)

NETL - Kathy Stirling (Kathy.Stirling@netl.doe.gov or 918-699-2008)
INL - Daniel M. Ginosar (Daniel.Ginosar@inl.gov or 208-526-9049)