Microwave-assisted synthesized porous clay heterostructure-Zn/Si from montmorillonite for citronellal conversion into isopulegol

Abstract

Microwave-assisted synthesis method was applied for producing porous clay heterostructure-Zn/Si heterostructure from Indonesian natural montmorillonite. The porous montmorillonite heterostructure was prepared by previously intercalating cetyl trimethyl ammonium as templating agent and surfactant, and trimethyl ammonium hydroxide as co-surfactant, followed by the introducing Zn–Si precursor solution for the sol-gel reaction of porous formation. The comparison of the use of microwave-assisted synthesis and hydrothermal method for the porous formation was studied. Physicochemical characterization by using XRD, SEM-EDX, TEM, gas sorption analysis, and FTIR method. Effect of the evolution of the surface characters on its catalytic activity in citronellal conversion into isopulegol was studied. The characterization by XRD informed the increasing basal spacing d _001 from 1.57 nm into 3.71 nm by the microwave-assisted method, meanwhile the hydrothermal method produced 3.56 nm spacing. The increasing specific surface area from 98.82 m ^2 g ^−1 into 752.95 m ^2 g ^−1 and 409.95 m ^2 g ^−1 for microwave-assisted synthesized and hydrothermal synthesized composites, were obtained. These profiles are attributed to the increasing surface acidity determined by pyridine-adsorption method and n-butylamine titration method, and contributed to the significant increasing catalytic activity. The time-efficient synthesis method obtained by the microwave-assisted method is good alternative for the preparation of highly active montmorillonite heterostructure composite for acid-catalyzed organic reaction.

Keywords

• clay
• heterogeneous catalysis
• isomerization