Hierarchical Low Si/Al Ratio Ferrierite Zeolite by Sequential Postsynthesis Treatment: Catalytic Assessment in Dehydration Reaction of Methanol

Abstract

In contrast to high silica zeolites, it is difficult to obtain mesoporosity in zeolites with low Si/Al ratio (e.g., <20) via conventional NaOH-based treatment, making the obtainment of hierarchical zeolites with high acidity a challenging target. In this paper, we report the preparation of hierarchical FER-type zeolite at low Si/Al molar ratio (about 10) by postsynthesis etching involving a sequence of three treatments with NaAlO 2 , HCl, and NaOH solutions and investigate the effect of both NaAlO 2 solution concentration and time of treatment on the textural properties. e obtained materials exhibit a mesoporous volume higher than the parent ferrierite with no significant effect on the sample acidity. e catalytic activity of some samples was investigated in vapour-phase methanol dehydration to dimethyl ether, revealing the superiority of hierarchical zeolites in terms of methanol conversion, although the presence of mesopores causes formation of light hydrocarbons at high temperatures.

The Effect of Zeolite Features on Catalytic Performances of Cuznzr/Zeolite Hybrid Catalysts in One-pot CO2-to-DME Hydrogenation

“…Crystallization was carried in a Teflon-lined stainless steel autoclave rotated with a speed of 20 rpm and kept at 175 °C for 3 days for FER (10) and at 165 °C for 5 days for FER (30) and FER (60).…”

“…Furthermore, catalyst resistance to deactivation as well as catalyst effectiveness can be improved by changing size and morphology of zeolite crystals. In particular, application of nano-sized or hierarchical zeolite crystals permits to reduce coke formation and enhance diffusion of reactant species improving catalyst performances [30][31].…”

Incorporating Hierarchy into Conventional Zeolites for Catalytic Biomass Conversions: A Review

“…During the last decade, many review articles have been published covering various aspects of the topic i.e., hierarchical zeolite synthesis methods and their applications [17,19,20,[31][32][33][34][35][36][37][38][39]. Moreover, various articles have highlighted the effective approaches for producing secondary mesoporosity without selective extraction of Al or Si [40][41][42][43][44][45][46][47][48][49][50][51]. In this section, we aim to evaluate the emerging strategies for the modification of conventional zeolites into hierarchical zeolites and compare the post-synthesis and pre-synthesis or in situ modification strategies.…”

Direct CO2-to-dimethyl Ether Hydrogenation over CuZnZr/zeolite Hybrid Catalyst: New Evidences on the Interaction Between Acid and Metal Sites

“…Activity, selectivity and stability of zeolites applied in acid-catalysed reactions are recognised to depend upon several factors as zeolite structure, acidity and crystal size. Zeolite channel system (channel orientation and opening size) is a well-known factor affecting strongly products distribution and catalyst deactivation [29][30][31][32][33][34][35][36][37][38].…”

“…Structures with both small/medium channels and cages, as MFI type, don't permit trapping of heavy compounds inside the crystal and coke is preferably formed on external surface of crystals and catalyst deactivation occurs by coke deposition on the mouth of the channels [29,37]. Catalyst deactivation rate is also affected from crystal morphology: small or hierarchical crystals exhibits higher resistance to deactivation by coke deposition than large crystal with microporous textural [34][35]. On small 1-D structures, as MTF, no hydrocarbon pool mechanisms are observed even at high temperature (400 °C) and DME is the only product detected in reactor outstream; nevertheless, this structure exhibits fast deactivation over time [45].…”