A moving bed reactor concept for alkane isomerization

Abstract

We consider the isomerization of 2-methylpentane (2MP) to the di-branched isomer 2,2 dimethylbutane (22DMB) and examine various strategies for improving the conversion of 2MP, exceeding the limitation imposed by reaction equilibrium. Firstly, we examine the conventional reactor-followed-by-separation strategy. We show that a properly optimized true moving bed (TMB) adsorber with MFI zeolite is able to achieve near perfect separation of 2MP and 22DMB. Next, we examine the strategy of in situ separation in a true moving bed reactor (TMBR). The success of the TMBR unit in achieving supra-equilibrium conversion depends crucially on proper choice of feed and product withdrawal strategies, as also on the number of column sections and flow rates to be employed. We demonstrate that a properly optimized TMBR unit can yield conversions in excess of 99%. We also examine the performance of a simulated moving bed reactor (SMBR) and find its performance inferior to that of the corresponding TMBR with conversion levels only of the order of 90%. Higher conversions are possible by increasing the number of columns in each section. Our studies underline the significant advantages of in situ separations to improve the performance of an isomerization reactor.