Preparation of a Solid Phosphoric Acid Catalyst from Low-Quality KieselguhrParameters Controlling Catalyst Quality and Performance

Abstract

High-quality Kieselguhr is normally employed as the support for solid phosphoric acid (SPA), the catalyst used for the oligomerization of C3−C5 alkenes in a Fischer−Tropsch refinery. In this paper, we demonstrate that an SPA catalyst of suitable activity can be prepared from a low-quality Kieselguhr provided that the Kieselguhr bulk density is ≤0.3 g/mL. Several catalyst samples were evaluated on microreactor and pilot-plant scale using propene mixtures as feed. An increase in acid-to-Kieselguhr ratio used during catalyst preparation was shown to improve catalyst activity, although this is detrimental to catalyst particle strength under similar calcination conditions. By studying the effect of impurities on catalyst performance, it was confirmed that high impurity levels lower oligomerization activity. It was also established that a high Kieselguhr quartz content (>10% by mass) reduces the catalyst particle crushing strength.