(191e) Production of Ethylene by Oxidative Dehydrogenation in Microchannel Reactors

A potentially valuable application of microchannel process technology is for the selective catalytic oxidation of paraffins to olefins. The conventional route to produce these important chemicals is steam cracking, which requires a large capital investment and is highly energy intensive. As an alternative, catalytic routes (from ethane to ethylene, or propane to propylene) have been investigated due to the great potential to reduce the size of processing equipment and the energy input to the process. However, the promise of a catalytic selective oxidative process has long been hindered by the limitations of conventional processing equipment, including the challenge of precisely controlling the temperature along the length of the reactor. Microchannel reactor architecture offers a solution to the heat management challenge and other technical hurdles; and therefore holds the potential to substantially reduce the cost to produce olefins and other selective oxidation products.

In addition to improved heat management, microchannel process technology offers other benefits for selective oxidation processes to produce olefins. These include: 1) Tailored mixing of reactants to prevent inappropriate oxygen concentrations that limit both conversion and selectivity to the desired product, and can lead to explosions or fires, 2) Rapid quenching after the reaction takes place to limit side reactions and improve overall selectivity, 3) High surface area to volume ratio that intensifies the reaction, decreasing the size and cost of the reactor, and 4) Potential for higher pressure partial oxidation, which would further intensify the process.

This presentation will describe the development efforts by Velocys , Pacific Northwest National Laboratories and Dow Chemical, on a DOE funded project, regarding the catalytic production of olefins in microreactors. Early laboratory experiments with microchannel reactors have shown very encouraging results. Per pass conversion of ethane in microchannel reactors was above 80% with 84% selectivity to ethylene. In contrast, conventional steam crackers commonly provide a selectivity of only 75% at comparable per pass conversion levels. Since the chemistry and fluid dynamics inside microchannel devices do not change during scale-up, these results should be scaleable to an industrial scale microchannel process.