Mesoporus MCM-22 Zeolites Prepared through Organic Amine-Assisted Reversible Structural Change and Protective Desilication for Catalysis of Bulky Molecules

Abstract

Mesoporous MCM-22 zeolite (meso-MCM-22) has been prepared by treating MCM-22 with sodium hydroxide solution through an organic amine-assisted reversible structural change. The alkaline treatment conditions, such as temperature, time, organic amine type, and its amount, were examined in detail. The desilication with sole NaOH caused an easy collapse of the crystalline structure of MWW topology. In contrast, the NaOH treatment with the coexistence of piperidine introduced mesopores of ∼20 nm into the MCM-22 crystals. Meanwhile, the calcined MCM-22 with three-dimensional (3D) MWW crystalline structure was converted to a 2D layered precursor with a well retained framework. The acid sites related to framework aluminum cations were almost intact after mesopore creation, as evidenced by pyridine or ammonia adsorption–desorption and 27Al NMR investigation. In comparison with MCM-22, meso-MCM-22 possessed a larger external surface, which mitigated effectively the steric restrictions to bulky molecules imposed by the intracrystal micropores. Meso-MCM-22 was superior to MCM-22 in the cracking of 1,3,5-triisopropyl benzene as well as the alkylation of benzene with isopropyl alcohol.

Sinter-resistant gold nanoparticles encapsulated by zeolite nanoshell for oxidation of cyclohexane

“…The X-ray diffraction (XRD) data (Fig. 2) of Au@ZSM-5 and Au@MCM-22 possess diffraction peaks 32,33 of corresponding zeolites matching with previous reports and also with the JCPDS data (JCPDS les 42-0023 and 47-0242). To check the effect of heat treatment on crystallinity of ZSM-5, XRD analysis was also carried out for ZSM-5 dried at 200 C (Fig.…”

“…In another beaker 0.031 g of sodium hydroxide was mixed together with 0.34 ml hexamethyleneimine (HMI) and 0.041 g of sodium aluminate in 8 ml H 2 O. 31,32 The mixture thus obtained was added in silica coated gold nanoparticles. The nal mixture was transferred to autoclave and the reaction was carried out at 158 C for 3 days.…”

Control of amine functionality distribution in polyvinylamine/SBA-15 hybrid catalysts for Knoevenagel condensation

“…It is interesting to see that higher pH during neutralization led to the increase of atomic ratios N/Si (from 0.17 for PVAm ( ). This effect may be attributed to partial desilication of support with the NaOH solution [22]. After acid hydrolysis of PNVF, only 14% of nitrogen atoms detected by XPS are assigned to the unhydrolyzed formamide groups.…”

Development of hierarchical MCM-49 zeolite with intracrystalline mesopores and improved catalytic performance in liquid alkylation of benzene with ethylene

“…Chal et al [17] and García-Martínez et al [18] drew similar conclusion in the case of alkali-treatment upon Y zeolite in the presence of CTAB. Also, Ji et al [19] prepared hierarchical MCM-22 zeolite with the mesopore diameter of c.a. 20 nm through organic amine-protective desilication.…”