New Insights into the Spatial Distribution of Aluminium in Various Mesoporous Aluminosilicates

Microporosity in Mesoporous SBA-15 Supports: A Factor Influencing the Catalytic Performance of Immobilized Metalloporphyrin

“…Another factor potentially influencing the product distribution is the manner of Al incorporation. In the case of mesoporous silicas with narrower pore sizes it has been found that the post synthesis alumination promoted epoxidation pathway, as it produced more exchange sites on the external support surface, rather than on the internal pore walls, thus increasing the abundance of metalloporphyrin species free of steric hindrance and capable of catalyzing epoxidation [4,8]. However, the present study provides that the pattern of product distribution might be related to the differences in supports morphologies has to be discarded as well.…”

“…Our recent works demonstrated that Al, Si-mesoporous molecular sieves represent an extremely interesting class of supports for cationic metalloporphyrins, allowing for a strong, electrostatic binding of metalloporphyrin species and, in many cases, for tailoring of the catalyst selectivity [3][4][5][6][7][8]. In particular, the oxidation of cyclohexene with iodosylbenzene as an oxygen donor over cationic metalloporphyrin supported on mesoporous aluminosilicates of HMS (MMS), MCM-41 and FSM-16 types was shown to proceed along two different pathways: epoxidation or allylic oxidation, depending on the metalloporphyrin location within the mesoporous framework [3][4][5]8]. It has been demonstrated that the porphyrin species anchored on the internal pore wall surface favour allylic oxidation, insignificant in homogeneous systems, while those attached to the external surface of the mesoporous supports behave as unsupported metalloporphyrin catalyst and yield predominantly epoxide.…”

Microporosity in Mesoporous SBA-15 Supports: A Factor Influencing the Catalytic Performance of Immobilized Metalloporphyrin

“…Another factor potentially influencing the product distribution is the manner of Al incorporation. In the case of mesoporous silicas with narrower pore sizes it has been found that the post synthesis alumination promoted epoxidation pathway, as it produced more exchange sites on the external support surface, rather than on the internal pore walls, thus increasing the abundance of metalloporphyrin species free of steric hindrance and capable of catalyzing epoxidation [4,8]. However, the present study provides that the pattern of product distribution might be related to the differences in supports morphologies has to be discarded as well.…”

“…Our recent works demonstrated that Al, Si-mesoporous molecular sieves represent an extremely interesting class of supports for cationic metalloporphyrins, allowing for a strong, electrostatic binding of metalloporphyrin species and, in many cases, for tailoring of the catalyst selectivity [3][4][5][6][7][8]. In particular, the oxidation of cyclohexene with iodosylbenzene as an oxygen donor over cationic metalloporphyrin supported on mesoporous aluminosilicates of HMS (MMS), MCM-41 and FSM-16 types was shown to proceed along two different pathways: epoxidation or allylic oxidation, depending on the metalloporphyrin location within the mesoporous framework [3][4][5]8]. It has been demonstrated that the porphyrin species anchored on the internal pore wall surface favour allylic oxidation, insignificant in homogeneous systems, while those attached to the external surface of the mesoporous supports behave as unsupported metalloporphyrin catalyst and yield predominantly epoxide.…”

Catalytic oxidation of cyclohexene over metalloporphyrin supported on mesoporous molecular sieves of FSM-16 type—Steric effects induced by nanospace constraints

“…It has been demonstrated that the porphyrin species anchored exclusively on the internal pore wall surface, as opposed to the external surface, of the aluminosilicate supports impose selectivity which favours allylic oxidation over epoxidation. The effect is related to steric restrictions within the pore channels, which prohibit the favourable mutual orientation of the cyclohexene molecule and the metalloporphyrin required for the formation of an intermediate leading to epoxide [3,4,8]. On the other hand, porphyrins anchored on external surfaces, free from any steric hindrances, behave similarly to free metalloporphyrin catalyst, yielding predominantly epoxidation products.…”

“…Deposition of metalloporphyrin onto directly aluminated supports results in catalysts, which behave in a completely different way than free MnTMPyP and yield over 90% allylic oxidation products. As demonstrated previously [4], the selectivity pattern in the oxidation of cyclohexene with iodosylbenzene is a sensitive probe of the distribution of metalloporphyrin cations and the Al sites at which they are anchored between the internal pore spaces and the external support surface. Thus, the observed dramatic suppression of epoxidation pathway implies that the catalytically active porphyrins are confined predominantly to the internal pore system of the mesoporous supports [3,4].…”

“…As demonstrated previously [4], the selectivity pattern in the oxidation of cyclohexene with iodosylbenzene is a sensitive probe of the distribution of metalloporphyrin cations and the Al sites at which they are anchored between the internal pore spaces and the external support surface. Thus, the observed dramatic suppression of epoxidation pathway implies that the catalytically active porphyrins are confined predominantly to the internal pore system of the mesoporous supports [3,4]. When post-synthesis aluminated FSM-16 solids are used as supports, the product distribution changes-the catalysts yield epoxide as the major product, albeit in a lesser quantity than the unbound metalloporphyrin.…”

Microporosity in Mesoporous SBA-15 Supports: A Factor Influencing the Catalytic Performance of Immobilized Metalloporphyrin

“…Another factor potentially influencing the product distribution is the manner of Al incorporation. In the case of mesoporous silicas with narrower pore sizes it has been found that the post synthesis alumination promoted epoxidation pathway, as it produced more exchange sites on the external support surface, rather than on the internal pore walls, thus increasing the abundance of metalloporphyrin species free of steric hindrance and capable of catalyzing epoxidation [4,8]. However, the present study provides that the pattern of product distribution might be related to the differences in supports morphologies has to be discarded as well.…”

“…Our recent works demonstrated that Al, Si-mesoporous molecular sieves represent an extremely interesting class of supports for cationic metalloporphyrins, allowing for a strong, electrostatic binding of metalloporphyrin species and, in many cases, for tailoring of the catalyst selectivity [3][4][5][6][7][8]. In particular, the oxidation of cyclohexene with iodosylbenzene as an oxygen donor over cationic metalloporphyrin supported on mesoporous aluminosilicates of HMS (MMS), MCM-41 and FSM-16 types was shown to proceed along two different pathways: epoxidation or allylic oxidation, depending on the metalloporphyrin location within the mesoporous framework [3][4][5]8]. It has been demonstrated that the porphyrin species anchored on the internal pore wall surface favour allylic oxidation, insignificant in homogeneous systems, while those attached to the external surface of the mesoporous supports behave as unsupported metalloporphyrin catalyst and yield predominantly epoxide.…”

Catalytic oxidation of cyclohexene over metalloporphyrin supported on mesoporous molecular sieves of FSM-16 type—Steric effects induced by nanospace constraints

“…It has been demonstrated that the porphyrin species anchored exclusively on the internal pore wall surface, as opposed to the external surface, of the aluminosilicate supports impose selectivity which favours allylic oxidation over epoxidation. The effect is related to steric restrictions within the pore channels, which prohibit the favourable mutual orientation of the cyclohexene molecule and the metalloporphyrin required for the formation of an intermediate leading to epoxide [3,4,8]. On the other hand, porphyrins anchored on external surfaces, free from any steric hindrances, behave similarly to free metalloporphyrin catalyst, yielding predominantly epoxidation products.…”

“…Deposition of metalloporphyrin onto directly aluminated supports results in catalysts, which behave in a completely different way than free MnTMPyP and yield over 90% allylic oxidation products. As demonstrated previously [4], the selectivity pattern in the oxidation of cyclohexene with iodosylbenzene is a sensitive probe of the distribution of metalloporphyrin cations and the Al sites at which they are anchored between the internal pore spaces and the external support surface. Thus, the observed dramatic suppression of epoxidation pathway implies that the catalytically active porphyrins are confined predominantly to the internal pore system of the mesoporous supports [3,4].…”

“…As demonstrated previously [4], the selectivity pattern in the oxidation of cyclohexene with iodosylbenzene is a sensitive probe of the distribution of metalloporphyrin cations and the Al sites at which they are anchored between the internal pore spaces and the external support surface. Thus, the observed dramatic suppression of epoxidation pathway implies that the catalytically active porphyrins are confined predominantly to the internal pore system of the mesoporous supports [3,4]. When post-synthesis aluminated FSM-16 solids are used as supports, the product distribution changes-the catalysts yield epoxide as the major product, albeit in a lesser quantity than the unbound metalloporphyrin.…”

Microporosity in Mesoporous SBA-15 Supports: A Factor Influencing the Catalytic Performance of Immobilized Metalloporphyrin

“…Another factor potentially influencing the product distribution is the manner of Al incorporation. In the case of mesoporous silicas with narrower pore sizes it has been found that the post synthesis alumination promoted epoxidation pathway, as it produced more exchange sites on the external support surface, rather than on the internal pore walls, thus increasing the abundance of metalloporphyrin species free of steric hindrance and capable of catalyzing epoxidation [4,8]. However, the present study provides that the pattern of product distribution might be related to the differences in supports morphologies has to be discarded as well.…”

“…Our recent works demonstrated that Al, Si-mesoporous molecular sieves represent an extremely interesting class of supports for cationic metalloporphyrins, allowing for a strong, electrostatic binding of metalloporphyrin species and, in many cases, for tailoring of the catalyst selectivity [3][4][5][6][7][8]. In particular, the oxidation of cyclohexene with iodosylbenzene as an oxygen donor over cationic metalloporphyrin supported on mesoporous aluminosilicates of HMS (MMS), MCM-41 and FSM-16 types was shown to proceed along two different pathways: epoxidation or allylic oxidation, depending on the metalloporphyrin location within the mesoporous framework [3][4][5]8]. It has been demonstrated that the porphyrin species anchored on the internal pore wall surface favour allylic oxidation, insignificant in homogeneous systems, while those attached to the external surface of the mesoporous supports behave as unsupported metalloporphyrin catalyst and yield predominantly epoxide.…”

Catalytic oxidation of cyclohexene over metalloporphyrin supported on mesoporous molecular sieves of FSM-16 type—Steric effects induced by nanospace constraints

“…It has been demonstrated that the porphyrin species anchored exclusively on the internal pore wall surface, as opposed to the external surface, of the aluminosilicate supports impose selectivity which favours allylic oxidation over epoxidation. The effect is related to steric restrictions within the pore channels, which prohibit the favourable mutual orientation of the cyclohexene molecule and the metalloporphyrin required for the formation of an intermediate leading to epoxide [3,4,8]. On the other hand, porphyrins anchored on external surfaces, free from any steric hindrances, behave similarly to free metalloporphyrin catalyst, yielding predominantly epoxidation products.…”

“…Deposition of metalloporphyrin onto directly aluminated supports results in catalysts, which behave in a completely different way than free MnTMPyP and yield over 90% allylic oxidation products. As demonstrated previously [4], the selectivity pattern in the oxidation of cyclohexene with iodosylbenzene is a sensitive probe of the distribution of metalloporphyrin cations and the Al sites at which they are anchored between the internal pore spaces and the external support surface. Thus, the observed dramatic suppression of epoxidation pathway implies that the catalytically active porphyrins are confined predominantly to the internal pore system of the mesoporous supports [3,4].…”

“…As demonstrated previously [4], the selectivity pattern in the oxidation of cyclohexene with iodosylbenzene is a sensitive probe of the distribution of metalloporphyrin cations and the Al sites at which they are anchored between the internal pore spaces and the external support surface. Thus, the observed dramatic suppression of epoxidation pathway implies that the catalytically active porphyrins are confined predominantly to the internal pore system of the mesoporous supports [3,4]. When post-synthesis aluminated FSM-16 solids are used as supports, the product distribution changes-the catalysts yield epoxide as the major product, albeit in a lesser quantity than the unbound metalloporphyrin.…”