Simulation of a simulated moving bed reactor for hydrocarbon isomerization

A process for isomerizing n-pentane in a Simulated Moving Bed Reactor (SMBR) is proposed. It consists of a catalyst bed (Pd/Y-zeolite) and several adsorbent beds (5A zeolite) for separating and recycling the unconverted reactant, as the reaction is equilibrium limited. The objective is to obtain >99% purity of the product isopentane.; A mathematical model is developed that relaxes most simplified assumptions such as equilibrium theory, plug flow and constant velocity. Twenty-two cases are studied involving variation of operating conditions. Isothermal and adiabatic simulations do not give the desired results. Constant wall temperatures are thus applied over the adsorbers to produce a thermal swing and achieve the desired purity. The equilibrium limited conversion is about 60% which increases to >99% because of the recycle stream.; The performance does not improve significantly by increasing hydrogen purge rate in modest amounts or using more beds in regeneration section. The model is robust to small variations in fresh feed temperature and flow rate. Maximum purity exists for every run at an optimum switch time. Reverse flow regeneration yields 100% purity.; Both pseudo-homogeneous and heterogeneous reactor models are developed. They differ significantly in their dynamic performance but give similar results once attaining steady state and when incorporated in the SMBR.; A sandwich reactor is also simulated that consists of a catalyst bed sandwiched between the adsorbent beds. It also yields the ideal performance of 100% purity.