Optimal catalyst activity profiles in pellets: 9. Study of ethylene epoxidation

Heterogeneous catalytic reactor design with optimum temperature profile II: application of non-uniform catalyst

“…11, the values of effectiveness factor increase as the layer moves towards the surface. As demonstrated in the research of Gavriilidis and Varma (1992), the difference between the effectiveness factors for the main and combustion reaction becomes smaller and it finally becomes nearly zero at the catalyst surface. For this reason, higher yield and selectivity can be obtained by using a surface-layered catalyst pellet in ethylene oxidation reaction.…”

“…Whilst it has been demonstrated extensively that Dirac-catalysts (and their step-function equivalent) can be optimised to give the best reactor performance for undegraded catalyst, when catalyst manufacture and degradation are considered, other profiles might offer advantages. It will be demonstrated later that catalyst Table 1 Studies on the application of non-uniform catalyst to various reactions Author Reactions Mars and Gorgels (1964) Selective hydrogenation of acetylene Minhas and Carberry (1969) SO 2 oxidation Smith and Carberry (1975) Phthalic anhydride production from naphthalene Verykios et al (1983) Ethylene oxidation Johnson and Verykios (1983) Morbidelli et al (1984) Pavlou and Vayenas (1990b) Gavriilidis and Varma (1992) Baratti et al (1994) Yeung et al (1998) Pavlou and Vayenas (1990b Propylene oxidation Lee and Varma (1988) CO oxidation Wu et al (1988) Methanation of CO Masi et al (1988) Hydrogenation of ethylene Wu et al (1988) profiles other than Dirac-can be optimised to provide a performance approaching that of Dirac-under undegraded conditions. In this work, issues including multiple-beds, different arrangements of non-uniform catalyst pellets, shape and size are all considered simultaneously.…”

“…Their results also showed that the surface is the optimum point for the highest selectivity of the ethylene oxide. Gavriilidis and Varma (1992) investigated the selectivity and yield of the ethylene oxidation reaction experimentally by applying five different types of layered catalysts in a laboratory-scale single pellet reactor. A cylindrical pellet with diameter of 20.4 mm and thickness of 7.1 mm was used and various active layer locations were applied with the same thickness of 0.45 mm.…”

Optimization of Fischer‐Tropsch Process in a Fixed‐Bed Reactor Using Non‐uniform Catalysts

“…Results showed that egg-shell catalysts are more active and selective than uniform catalysts for C 5 + production. Furthermore, Johnson and Verykios [21], Lee et al [22], Gavriilidis and Varma [23] and Baratti et al [24] also studied the application of non-uniform catalysts in fixed-bed reactors while Khanaev et al [25,26] studied optimum loading of active components through isothermal and adiabatic reactors. Zarrin et al [20] showed that the optimal location of active components inside the catalyst pellet is highly dependent on the catalyst performance index, such as effectiveness factor or product yield.…”

“…Zarrin et al [20] showed that the optimal location of active components inside the catalyst pellet is highly dependent on the catalyst performance index, such as effectiveness factor or product yield. Furthermore, Johnson and Verykios [21], Lee et al [22], Gavriilidis and Varma [23] and Baratti et al [24] also studied the application of non-uniform catalysts in fixed-bed reactors while Khanaev et al [25,26] studied optimum loading of active components through isothermal and adiabatic reactors.…”