Mesoporous solid acid catalysts their efficiency towards organic transformations

Abstract

Catalysis has a crucial role for efficient utilisation of our limited resources in an environmentally responsible manner. Acid-catalysed condensation and addition reactions are some of the important reaction steps employed for building large and complex molecules that characterizes many of the fine chemicals and pharmaceutical products. The development of heterogeneous catalytic systems for organic synthesis and biomass conversion is a highly attractive topic in current research. The present investigation involves the synthesis of Si-MCM-41 and Si-KIT-6 mesoporous materials by hydrothermal method. The reaction of dimedone and aromatic aldehyde was performed over various catalysts to test catalytic activity of HPWA/MCM-41 individually. All the catalysts were compared to support the activity based on the product yield, recovery and reusability. Three component reactions of 5-amino-3-methyl-1-phenylpyrazole, malononitrile and aromatic aldehyde were performed by using 10 wt. % HPWA/MCM-41 catalyst under ultrasonic irradiation. The catalytic activity of Sn-MCM-41 (Si/Sn = 152, 174 and 197) was tested over the three component reaction of 5,5-dimethyl-1,3- cyclohexanedione (Dimedone) and malononitrile/ethylcyano acetate. Conversion of glucose increases with temperature and the catalyst with Si/Al ratio = 33, was superior for the dehydration reaction and the effect is less for Al-KIT-6 (110). Also, the conversion increases in the order of increasing acidity of the aluminosilicates. The present catalyst catalyse the dehydration at higher temperatures (140°C) affording maximum HMF selectivity. The present study was undertaken to exploit the usefulness of mesoporous solid acid catalysts that are specifically active in particular reactions. Most importantly, the mesoporous catalysts facilitate the above mentioned reactions and exhibits good catalytic efficiency. This study establishes about another possible application for solid acid catalysts in organic synthesis and single step transformation reactions. newline newline newline