Synthesis of ZSM‐5 by hydrothermal method with pre‐mixing in a stirred‐tank reactor

Abstract

This work proposed a synthesis route of ZSM‐5 via the hydrothermal method with premixing in a stirred tank reactor (STR). Effects of various operating conditions, including pre‐mixing time, molar ratio of SiO2/Al2O3, TPAOH (organic template agents) concentration, NaCl (alkali metal cations) concentration, crystallization temperature, and crystallization reaction time, on the average particle size (PS) and particle size distribution (PSD) were investigated. It was found that the pre‐mixing time in the STR significantly affect the formation of proto‐nuclei in premixing process and crystal growth in hydrothermal reaction process, and consequently influence the PS and PSD of the prepared ZSM‐5. ZSM‐5 with good thermal stability, a PS of 380 nm, PSD of 0.17–0.9 µm, pore diameter of 2.31 nm, pore volume of 0.19 cm3 · g−1 and specific surface area of 337.25 m2 · g−1 were obtained under the optimal conditions of a crystallization reaction time of 24 h, a crystallization temperature of 130 °C, a molar ratio of SiO2/Al2O3 of 200, a TPAOH concentration of 3.5 mol · L−1, NaCl concentration of 0.3 mol · L−1, and a pre‐mixing time of 5 h. This work indicated that the operating conditions including premixing time have a significant effect on its PS and PSD.

Synthesis of large single crystals of analcime in a template-free system

“…36,37 For example, Sun et al showed that the Na + cations interact with water molecules and break the hydrogen bonds of water. 38 This hydrated Na + group can be moderately replaced by silicon and an aluminium tetrahedron and induce the zeolite crystallization. 38,39 Thus, the crystal size of the ANA crystal increases from 50 μm to 210 μm by increasing the molar This journal is © The Royal Society of Chemistry 2022 Na 2 O/SiO 2 ratio y from 1.43 to 1.79 (Fig.…”

Effect of ZSM-5 zeolite porosity on catalytic cracking ofn-heptane

“…The Na + cation plays a very important role in the ZSM-5 zeolite synthesis such as structure-directing and charge-balancing agents. [40][41][42] Sun et al reported that the Na + cations interact with H 2 O molecules and break the hydrogen bonds between H 2 O molecules. 40 The hydrated Na + groups can be reasonably replaced by silicon and aluminum tetrahedron and started the zeolite crystallization process.…”

“…40 The hydrated Na + groups can be reasonably replaced by silicon and aluminum tetrahedron and started the zeolite crystallization process. 42,43 Fig. 1 shows that the crystallization rate of the ZSM-5 zeolite is increased by increasing the concentration of SiO 2 in the initial gel, due to the higher rate of Al incorporation into the framework of zeolite at a low concentration of Al 2 O 3 .…”

“…45 In addition, the structure-sensitive adsorption bands at 1225 and 550 cm À1 are assigned to the external asymmetric stretching of four chains and double chains of five-membered rings of T-O tetrahedron in the zeolite framework. 40 The XRD patterns of the ZSM-5 zeolites at various temperatures and initial gel composition are shown in Fig. 3.…”

Structural Effects of HZSM‐5 Zeolite on Methanol‐to‐Propylene Reaction

“…The initial gel composition such as Si/Al molar ratio, structure, and concentration of organic template agent, alkali metal concentration, pH, and water content may be changed by the nucleation and crystal growth rates which modify the final zeolite morphologies [22]. Sun et al indicated that the premixing time of the initial gel has a significant effect on the crystal size and morphology of the prepared ZSM-5 zeolite [23].…”