Selective Oxidation Reactions for C3 and i-C4 Hydrocarbons in a Membrane Reactor

Partially oxygenated hydrocarbons provide the building blocks for plastics and synthetic fibers as well as precursors for specialty chemicals. The majority of these oxygenated hydrocarbons are produced through catalytic selective oxidation reactions between hydrocarbons and oxygen. Selective oxidation reactions pose a great challenge, as the combustion reactions to produce CO and CO2 are favored both thermodynamically and kinetically. Acrolein and methacrolein, the C3 and i-C4 aldehydes, are two selective oxidation products that are currently utilized extensively in the polymer industry as derivatives for various monomers due to the ease in which the aldehydes can be functionalized. Aldehydes are typically produced directly from alkenes and it is of economic interest to utilize the less expensive alkanes as a feedstock for these processes.Improved selectivity in selective oxidation reactions can be realized through catalyst and reactor design. The current studies compare inert membrane reactor (IMR) and fixed bed reactor (FBR) studies to demonstrate that the IMRs improve the selectivity for C3 and i-C4 aldehydes. Additionally, dual bed reactor studies are performed to convert alkanes to alkenes in an oxidative dehydrogenation reaction followed by a partial oxidation reaction for the conversion of alkenes to aldehydes. Catalysts prepared for these reactions are characterized with surface area, x-ray diffraction, and x-ray photoelectron spectroscopy. Theoretical reaction simulations for the FBR and IMR are performed using a MatLab program.Experimental studies of the FBR and IMR have demonstrated that the IMR improves the selectivity to selective oxidation products in comparison to the FBR. Dual bed reactors were successful in converting the alkanes to aldehydes in both C3 and i-C4 reaction studies demonstrating that the IMR concept is versatile for multiple reaction networks. Dual bed reactors demonstrated great flexibility as conditions such as temperature, residence time, oxygen to hydrocarbon ratio, and membrane or fixed bed could be altered independently in each catalyst bed to coincide with the optimum conditions for each reaction. Overall, distributive membrane reactors are beneficial in promoting the selective oxidation reactions of alkanes and alkenes to their respective aldehydes while limiting the production of CO and CO2.