Adsorption mechanism of boscan porphyrins on hdm catalysts

Mechanistic studies of initial decay of hydrodemetallization catalysts using model compounds—effects of adsorption of metal species on alumina support

“…So in each case four parameters needed estimating empirically, which were obtained by fitting the adsorption model into all the experimental sets of VO-EP or Ni-EP in the applicable range. As given in Table 3, the calculated D e was in the order of 10 −6 cm 2 /s for both of the metalloporphyrins under all the experimental temperatures, which agreed well with the published results [54,58,60]. The activation energies of D e , which were 21.07 ± 1.50 kJ/mol for VO-EP and 15.01 ± 14.38 kJ/mol for Ni-EP, were weakly dependent upon temperature as expected.…”

“…On the contrary, alumina that is a well-known adsorbent for separating porphyrinic species by "dry column" chromatography [46] was reported to have some transient capacity of demetallization [31]. A number of studies directly suggested that metalloporphyrins were adsorbed on the surface of alumina at room temperature or under hydroprocessing conditions [31,49,[51][52][53][54]. Thus, the initially very high but gradually decreasing activity was attributed to the declining adsorption of the metalloporphyrins on alumina when the available sites were continuously occupied.…”

The diffusion of liquids in pores

“…There have been a number of studies (Beck and Schultz, 1970;Prasher and Ma, 1977;Prasher et al, 1978;Thrash and Pildes, 1981;Deen et al, 1981;Galiasso and Morales, 1983) which have reported effective diffusivities of liquids within the pore structure of catalysts and other solids. The data in some studies (Sanerfield et al, 1973;Chantong and Massoth, 1983;Baltus and Anderson, 1983;Seo and Massoth, 1985) have generally been correlated by empirical equations of the type * *…”

Hydrodemetallation Catalyst Pellets With Nonuniform Radial Pore Size Distribution

“…First-order deposition kinetics were considered according to Galiasso and Morales, 1983). The reaction is assumed to be isothermal and only the period following the initial fast coking is considered.…”