Equilibrium, rate studies, and economic evaluation on adsorption and variable-temperature stepwise desorption

An ideal adsorption would only remove the desired component. Many times one or more other components are also adsorbed. If two or more components are adsorbed, an adsorption separation may not be satisfactory or may require additional separation procedures, even though one is highly preferentially adsorbed. In such cases it may be possible to get additional separation during the desorption stage by using variable-temperature stepwise desorption. It has been found previously that a variable-temperature stepwise desorption (VTSD) procedure following the adsorption stage can significantly increase the degree of separation achieved compared to a complete desorption of all adsorbed components, with the more weakly adsorbed components being desorbed first at lower temperatures followed by desorption of the more strongly adsorbed components at higher temperatures. This study also considers the economics of several possible uses of VTSD methods. An estimation of economic factors in partially separating low concentration propylene in propane indicates VTSD is favorable compared to distillation for the same separation, primarily because of lower energy costs. A hybrid separation system including distillation, adsorption, and VTSD was calculated to be marginal in economic value compared to distillation only. A method of separating methanol from propylene for polymerization was studied experimentally and calculations indicated reasonably low costs. However, these results cannot be compared with industrial methods, because of lack of information on industrial separations of this type. The requirements for separating hydrogen sulfide from fuels was also determined, and this indicated promising separation possibilities. In order to obtain equilibrium and rate data rapidly for rnulticomponent adsorption, a differential sorption bed apparatus was developed and used to obtain data on adsorption and desorption of propane-propylene mixtures. Certain rate and equilibrium data are presented --Abstract, page iii