Preparation and acidic properties of aluminated ZSM-5 zeolites

Catalytic Upgrading of Lignite Pyrolysis Volatiles over AlF3-Modified HZSM-5 to Light Aromatics: Synergistic Effects of One-Step Dealumination and Realumination

“…It is noted that the reintroduction of Al into zeolites can optimize the framework SAR to some extent and compensate for the reduction of acid sites caused by excessive dealumination. 18,23 Therefore, dealumination to enlarge pores while combining with alumination to regulate acid sites should be a more feasible modification method. There are, however, only a few studies on the dealumination/alumination synergistic modification, especially on the simultaneous modification.…”

“…However, although the single acid dealumination methods (HCl, HNO 3 , H 2 SO 4 , and HF) can generate secondary pores and regulate the acidity, they only tend to adjust the acid sites unidirectionally that is difficult to create new multifunctional acid active sites. It is noted that the reintroduction of Al into zeolites can optimize the framework SAR to some extent and compensate for the reduction of acid sites caused by excessive dealumination. , Therefore, dealumination to enlarge pores while combining with alumination to regulate acid sites should be a more feasible modification method. There are, however, only a few studies on the dealumination/alumination synergistic modification, especially on the simultaneous modification.…”

In Situ Aluminum Migration into Zeolite Framework during Methanol-To-Propylene Reaction: An Innovation To Design Superior Catalysts

“…By contrast, there has been relatively fewer studies on acidity modification by controlling Al insertion into silica-rich zeolite for the improvement of catalytic performance. Several articles reported Al insertion into high-silica ZSM-5 or B-ZSM-5 framework through gas–solid reaction with aluminum halide vapor or gas–liquid reaction with aqueous fluoaluminates, which showed similar catalytic performance, compared with as-synthesized ZSM-5 with similar acidity. − However, to the best of our knowledge, few studies have focused on in situ Al insertion into zeolite structure during high-temperature reaction. ZSM-5 with lower Si/Al showed a long period of propylene selectivity growth stage before reaching steady state, finally resulting in lower average propylene selectivity.…”

Hydroxylation of Aromatics with Hydrogen Peroxide over Titanosilicates with MOR and MFI Structures: Effect of Ti Peroxo Species on the Diffusion and Hydroxylation Activity

“…The obvious difference between Ti-M and TS-1 in the hydroxylation of various aromatics seems to be due to the shape selectivity owing to their different pore sizes. However, it is not quite reasonable that the very lower activity of TS-1 for the hydroxylation of ethylbenzene and cumene is simply attributed to its reactant shape selectivity because its aluminosilicate derivative, ZSM-5, catalyzes readily ethylbenzene alkylation and cumene cracking in solid−gas reactions though the reaction temperatures are higher. , To clarify the diffusion effects on the hydroxylation, we have carried out the adsorption experiments in the liquid phase under the conditions similar as possible to those adopted for the hydroxylation reactions.…”

“…The former catalyzes with relatively high activity the oxidation or epoxidation of linear alkanes and alkenes and the hydroxylation of phenol and benzene, but it hardly catalyzes the reactions of cyclic alkanes, cyclic alkenes, and aromatics bulkier than benzene . On the contrary, the latter catalyzes toluene or ethylbenzene alkylation, toluene disproportionation, xylene isomerization, and cumene cracking. − Though the reaction conditions are different for these cases, it must be an open question whether these differences between TS-1 and ZSM-5 are simply attributed to the reactant shape selectivity. Moreover, it could be possible that the Ti peroxo active species in the TS-1 catalyzed reactions affects the shape selectivity.…”