Properties of Desilicated ZSM-5, ZSM-12, MCM-22 and ZSM-12/MCM-41 Derivatives in Isomerization of α-Pinene

Abstract

Limited information is available on the isomerization of a-pinene proceeding on zeolites and related desilicated materials. We wish therefore to report on the title reaction proceeding over ZSM-5, ZSM-12 and MCM-22 type zeolites, parent and modified by the sodium hydroxide treatment. The NaOH solutions of various concentrations (0.05-1 M) were used as a desilicating agent. Such treatments with basic solutions were applied: (i) under atmospheric pressure, and (ii) under hydrothermal conditions. It was shown that ZSM-12 was more resistant towards the basic solutions treatment, and its structure was retained over a whole range of NaOH concentrations studied. Nitrogen sorption revealed strong influence of the desilication process on the pore structure of modified materials-the mesopores system was formed in the zeolite crystals. Finally, catalytic studies were carried out using ZSM-5, ZSM-12, MCM-22, their desilicated derivatives and a ZSM-12/MCM-41 composite material. Catalytic properties of the samples studied were affected to a large extent by the NaOH treatment.

Catalytic role of different pore systems in MCM-49 zeolite for liquid alkylation of benzene with ethylene

“…It has been reported that the RC of zeolite can be effectively improved with the mild alkali-treatment conditions [38] and then decreases with harsh treatment conditions [46,47]. We also observe a similar phenomenon.…”

Hierarchy concepts: classification and preparation strategies for zeolite containing materials with hierarchical porosity

“…90,91 This method can be used to introduce intracrystalline mesopores with high degree of interconnectivity in zeolite crystals of different framework types. 36,[92][93][94][95][96] In contrast to dealumination, desilication does not significantly affect the acidity and the crystalline structure of zeolites. 97 As also depicted schematically in Fig.…”

Desilication Mechanism Revisited: Highly Mesoporous All‐Silica Zeolites Enabled Through Pore‐Directing Agents

“…[6][7][8][9][10][11][12] Nowadays, an impressive variety of approaches forms a nanoscale toolbox that can be used to design high-performance zeolite catalysts by optimizing porosity, as well as other key parameters as, for example, acidity and composition. [12][13][14][15][16][17] The selective extraction of silicon from the zeolite framework in alkaline medium (typically NaOH) has proven to be an effective, versatile, and simple post-synthesis treatment to introduce mesoporosity in a broad variety of zeolite structures such as MFI, [18] MTW, [19] MOR, [20] BEA, [21] AST, [22] FER, [23] MWW, [24] IFR, [25] and STF. [26] Nevertheless, a major drawback of desilication remained that its applicability is limited by the silicon/aluminum ratio in the framework.…”