Single‐Mode Microwave Heating‐Induced Concurrent Out‐of‐Plane Twin Growth Suppression and In‐Plane Epitaxial Growth Promotion of b‐Oriented MFI Film under Mild Reaction Conditions

Abstract

In this study, single-mode microwave heating was applied in epitaxial growth of b-oriented MFI seed monolayer prepared by facile manual assembly, resulting in the formation of well-intergrown and highly b-oriented MFI film with few twins. It exhibited a precise molecular sieving property at a reaction temperature no higher than 100°C within 2 hours, therefore making it possible for easy operation in an open environment. The capability for concurrent suppression of undesired out-of-plane twin growth and promotion of in-plane epitaxial growth rate under mild reaction conditions was attributed to the obvious superiority of single-mode microwave heating in comparison with conventional multi-mode microwave heating in aspects of microwave field uniformity and intensity. Our research indicated that the single-mode microwave heating technique could potentially be a useful tool for improving the microstructure and therefore the performance of diverse zeolite films.

Hierarchy Control of MFI Zeolite Membrane towards Superior Butane Isomer Separation Performance

“…Previous research indicated that relying on the unique thermal and non‐thermal effects of microwave irradiation, microwave‐assisted synthesis of zeolite membranes enabled not only a significant reduction in reaction time but also a decrease of intercrystalline defect density in comparison with conventional heating, which was quite advantageous for the production of large membrane areas [14] . Moreover, our recent study implied that single‐mode microwave heating exhibited obvious superiority over common multi‐mode microwave heating in terms of microwave field uniformity and intensity, resulting in concurrent reduction in the reaction temperature and time required for the formation of well‐intergrown MFI zeolite membranes [7, 15] . Indeed, our experimental results indicated that well‐intergrown MFI zeolite (denoted as H‐MFI) membrane could be obtained at 105 °C within 2 h (Figure 2 g).…”

“…[14] Moreover, our recent study implied that single-mode microwave heating exhibited obvious superiority over common multi-mode microwave heating in terms of microwave field uniformity and intensity, resulting in concurrent reduction in the reaction temperature and time required for the formation of wellintergrown MFI zeolite membranes. [7,15] Indeed, our experimental results indicated that well-intergrown MFI zeolite (denoted as H-MFI) membrane could be obtained at 105 8C within 2 h (Figure 2 g). The cross-sectional SEM image (Figure 2 h) clearly showed that prepared membrane was composed of an ultra-thin (ca.…”

Room-Temperature Synthesis of Zeolite Membranes toward Optimized Microstructure and Enhanced Butane Isomer Separation Performance

“…Zeolite membranes have received extensive attention for energy efficient separation, owing to their well-defined pore structure, robust framework, and excellent stability. − Previous studies confirmed that the microstructure of zeolite membranes, including preferred orientation, membrane thickness, and grain boundary structure, exerted significant influence on their separation performance. , For instance, the superior performance of b -oriented MFI zeolite membranes has been demonstrated for isomer separation (e.g., n -/ i -butane and p -/ o -xylene), − while defect-free ultrathin zeolite membranes commonly exhibited superior gas separation performance. , It should be noted that, in spite of significant progress on microstructure optimization and performance enhancement of zeolite membranes, under most circumstances, zeolite membrane growth has to be performed at relatively high temperature (commonly >100 °C), which inevitably leads to increased capital investment, operating cost, and energy consumption; simultaneously, safety concerns have to be taken into consideration under autogenous pressure. − …”

“…Recently, significant efforts have been devoted to reducing the reaction temperature of zeolite membranes. Diverse approaches, e.g., reactive growth, flux synthesis, and microwave heating ,, have been developed for mild synthesis of zeolite membranes. However, room temperature (RT) synthesis of continuous zeolite membranes, which is advantageous in terms of economic and environmental benefits, remains a great challenge.…”

“…To verify this deduction, we further conducted RT epitaxial growth from the b -oriented Si-MFI seed layer. Initially, a highly b -oriented 380 nm-thick seed layer was prepared by manual rubbing (Figure a–c) . Subsequently, RT epitaxial growth was carried out to seal the open space remaining in the seed layer.…”