Mesoporous Silica vs. Organosilica Composites to Desulfurize Diesel

Abstract

The monolacunary Keggin-type [PW11O39]7− (PW11) heteropolyanion was immobilized on porous framework of mesoporous silicas, namely SBA-15 and an ethylene-bridged periodic mesoporous organosilica (PMOE). The supports were functionalized with a cationic group (N-trimethoxysilypropyl-N, N, N-trimethylammonium, TMA) for the successful anchoring of the anionic polyoxometalate. The PW11@TMA-SBA-15 and PW11@TMA-PMOE composites were evaluated as heterogeneous catalysts in the oxidative desulfurization of a model diesel. The PW11@TMA-SBA-15 catalyst showed a remarkable desulfurization performance by reaching ultra-low sulfur levels (<10 ppm) after only 60 min using either a biphasic extractive and catalytic oxidative desulfurization (ECODS) system (1:1 MeCN/diesel) or a solvent-free catalytic oxidative desulfurization (CODS) system. Furthermore, the mesoporous silica composite was able to be recycled for six consecutive cycles without any apparent loss of activity. The promising results have led to the application of the catalyst in the desulfurization of an untreated real diesel supplied by CEPSA (1,335 ppm S) using the biphasic system. The system has proved to be a highly efficient process by reaching desulfurization values higher than 90% for real diesel during three consecutive cycles.

Recent Advances in Functionalized Mesoporous Silica Frameworks for Efficient Desulfurization of Fuels

“…Oxidative desulfurization studies on amine functionalized SBA-15 supports revealed high performance in case of PW 11 @aptesSBA-15, which could completely desulfurize simulated diesel in solvent-free conditions with half the oxidant amount (H 2 O 2 /S = 4), whereas it showed 83.4% efficiency in case of real unthread diesel (in a biphasic system, 1:1 diesel/acetonitrile) with a recycle capacity for eight consecutive cycles. Their recent work involved impregnation of PW 11 on cationic group ( N -trimethoxysilypropyl- N, N, N -trimethylammonium, TMA) functionalized MS supports [ 101 ]. Here, two kinds of MS supports were selected (ordered MS, SBA-15, and an ethylene-bridged periodic mesoporous organosilica, PMOE) and two catalysts were prepared, PW 11 @TMA-SBA-15 and PW 11 @TMA-PMOE.…”

“…A remarkable desulfurization performance was exhibited by the PW 11 @TMA-SBA-15 catalyst, which could achieve ultra-low sulfur levels (<10 ppm) in both biphasic, as well as solvent-free conditions, and could be recycled six consecutive times without appreciable loss of catalytic activity. This promising catalyst was also tested on untreated real diesel provided by Spanish petroleum company, CEPSA (1335 ppm S) under biphasic system and demonstrated 90% desulfurization efficiency for 3 consecutive cycles [ 101 ].…”

“… Synthetic strategy to prepare Keggin’s polyoxometalate anion incorporated PW 11 @TMA- (SBA)-15 and PW 11 @TMA-PMOE [ 101 ]. …”

“…capacity for eight consecutive cycles. Their recent work involved impregnation of PW11 on cationic group (N-trimethoxysilypropyl-N, N, N-trimethylammonium, TMA) functionalized MS supports [101]. Here, two kinds of MS supports were selected (ordered MS, SBA-15, and an ethylene-bridged periodic mesoporous organosilica, PMOE) and two catalysts were prepared, PW11@TMA-SBA-15 and PW11@TMA-PMOE.…”

“…A remarkable desulfurization performance was exhibited by the PW11@TMA-SBA-15 catalyst, which could achieve ultra-low sulfur levels (<10 ppm) in both biphasic, as well as solvent-free conditions, and could be recycled six consecutive times without appreciable loss of catalytic activity. This promising catalyst was also tested on untreated real diesel provided by Spanish petroleum company, CEPSA (1335 ppm S) under biphasic system and demonstrated 90% desulfurization efficiency for 3 consecutive cycles [101]. Recently, Ribeiro et al reported on zinc-incorporated polyoxotungstates [PW11Zn(H2O)39] 5− , PW11Zn for ODS of real, as well as model, diesels, where active species were embedded in periodic mesoporous organosilicas (PMOs) composed of walls with ethane-bridges and benzene bridges [102].…”