Asterios Gavriilidis

Optimal Distribution of Catalyst in Pellets

Abstract A large fraction of the chemical and refinery processes are catalytic in nature. While the worldwide sales of catalysts are only about

Optimization of a nonisothermal nonadiabatic fixed-bed reactor using dirac-type silver catalysts for ethylene epoxidation

4 billion annually, the economic impact of catalysis comes from the fact that approximately

Catalyst Design: Optimal Distribution of Catalyst, in Pellets, Reactors and Membranes

200 worth of products are manufactured for every

Preparation of Pt/γ-Al2O3Pellets with Internal Step-Distribution of Catalyst: Experiments and Theory

1 worth of catalyst consumed [1]. The active materials used as catalysts are often expensive metals, and in order to be utilized effectively, they are deposited on high surface area supports. This approach in many cases introduces intrapellet activity gradients during the preparation process, which were traditionally thought to be detrimental to catalyst performance. However, the effects of deliberate nonuniform distribution of the catalytic material within the support on the performance of a catalyst pellet started receiving attention in the late 1960s (see Refs. 2–6). These, as well as later studies, both experimental and theoretical, demonstrated that nonuniformly distributed catalysts can offer superior conversion, se...

Effects of 1,2 Dichloroethane Addition on the Optimal Silver Catalyst Distribution in Pellets for Epoxidation of Ethylene

Abstract A heterogeneous, nonadiabatic, nonisothermal plug-flow reactor where ethylene epoxidation over silver catalyst occurs is studied theoretically. The catalyst distribution in the pellets is of a Dirac-delta type. The location of the Dirac distribution is optimized both the ethylene oxide yield and selectivity maximazation. Single-pellet results indicate that yield can be maximized either by surface or subsurface catalyst locations, depending on the operating conditions. However, for all practical purposes, selectivity is maximized only by surface catalysts. Significant improvements in reactor performance are found by using the appropriate Dirac catalyst, as compared to a uniform catalyst distribution. Further improvements can be achieved by using a two-zone reactor, with different catalyst location in each zone. Reactor runaway behavior can also be avoided by the use of Dirac catalysts.