Adsorption mechanism of Boscan porphyrins on MoO3' Co3O4and CoMoAl2O3

Asphaltene Adsorption, a Literature Review

“…Alumina impregnated with metal oxides showed a significant increase in adsorption of vanadium-containing asphaltenes . Likewise, cobalt and molybdenum supported on alumina, CoMoAl 2 O 3 , adsorbed more porphyrins than any of its individual constituents which adsorbed porphyrins in the following order: Al 2 O 3 > MoO 3 > Co 3 O 4 . , Here it was shown that the increased acidity correlated to an increase in adsorption because Lewis acid centers were mainly responsible for the interactions between the surface and the asphaltenic porphyrins. Similarly, it was established that acidic metal oxides supported on alumina are mainly Lewis acids, but when supported on pyrogenic alumina they become Brønsted acids. , WO 3 and Ta 2 O 5 supported on alumina showed a high affinity for basic asphaltenes removing up to 20% by weight. , For the sulfide metal alumina catalysts CoMo-Al 2 O 3 , Mo-Al 2 O 3 , and Co-Al 2 O 3 , it was shown that asphaltene adsorption blocked catalytically active acidic centers when heated in a fixed bed reactor between 200 and 300 °C .…”

“…Alumina impregnated with metal oxides showed a significant increase in adsorption of vanadium-containing asphaltenes. 125 Likewise, cobalt and molybdenum supported on alumina, CoMoAl 2 O 3 , adsorbed more porphyrins than any of its individual constituents which adsorbed porphyrins in the following order: 16,185 Here it was shown that the increased acidity correlated to an increase in adsorption because Lewis acid centers were mainly responsible for the interactions between the surface and the asphaltenic porphyrins. Similarly, it was established that acidic metal oxides supported on alumina are mainly Lewis acids, but when supported on pyrogenic alumina they become Brønsted acids.…”

“…For asphaltenes containing metal porphyrins adsorption increased in the order of pyridine and acetonitrile (both showed no adsorption), followed by benzene, and then by cyclohexane which showed significant adsorption. 185 Adsorption onto glass plates showed a greater buildup of asphaltenes with decreasing solubility parameter of the solvent in the following order: chloroform < THF < toluene < heptol, and further increases were reported with increasing proportions of heptane for the heptol solutions. 173 The correlation between decreasing Hildebrand solubility parameter and increased asphaltene adsorption onto silica surfaces modified with self-assembled monolayers was also observed in the following order: 1-methylnaphthalene < tetralin < toluene < decalin < heptol (20:80 heptane/toluene).…”

“…Most studies report that increasing the solvent strength effectively decreases aggregate size and/or reduces adsorption by competing for surface active sites. For asphaltenes containing metal porphyrins adsorption increased in the order of pyridine and acetonitrile (both showed no adsorption), followed by benzene, and then by cyclohexane which showed significant adsorption . Adsorption onto glass plates showed a greater buildup of asphaltenes with decreasing solubility parameter of the solvent in the following order: chloroform < THF < toluene < heptol, and further increases were reported with increasing proportions of heptane for the heptol solutions .…”

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

“…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.…”