Synthesis, characterization and catalytic activity of sulphonated multi-walled carbon nanotubes as heterogeneous, robust and reusable catalysts for the synthesis of bisphenolic antioxidants under solvent-free conditions

Abstract

In this study, a simple and green method has been developed for the synthesis of bisphenolic antioxidants by the reaction of 2-tert-butyl-4-methylphenol and aldehydes in the presence of sulphonated multiwalled carbon nanotubes (MWCNTs-SO 3 H) as heterogeneous, robust and reusable catalysts under solventfree conditions. MWCNTs-SO 3 H was prepared and characterized by some microscopic and spectroscopic techniques including scanning electron microscopy, transmission electron microscopy, FT-IR spectroscopy and Raman spectroscopy. Acidity of the catalyst was measured by acid-base titration. The catalyst was reused several times without efficient loss of its activity for the preparation of bisphenolic antioxidants. In addition, high yields of the products, relatively short reaction times, being solvent-free and non-toxicity of the catalyst are other worthwhile advantages of the present method.

Solvent-free synthesis of trisphenols as starting precursors for the synthesis of calix[4]arenes using sulfonated multi-walled carbon nanotubes

“…54,55 Due to the importance of trisphenols and their utilization as precursors for calix [4]arenes, we were interested in developing an efficient method for the preparation of trisphenols and polyphenolic compounds. 14,16,[56][57][58] Herein, we aim to synthesise trisphenols in the presence of SO 3 H@MWCNTs as a heterogeneous catalyst from 2,6-bis(hydroxymethyl)phenols (BMP) and various substituted phenols under solvent-free conditions.…”

Highly sulfonated graphene and graphene oxide nanosheets as heterogeneous nanocatalysts in green synthesis of bisphenolic antioxidants under solvent free conditions

“…The synthesis of bisphenolic antioxidants has been performed in the presence of different homogeneous and heterogeneous catalysts such as H 2 SO 4 , [14][15][16] HCl, 17 CF 3 COOH, 18 heteropolyacid, 19,20 zeolites, 21 silica sulfuric acid, 22 [Ir(COD)Cl] 2 -SnCl 4 , 23 AuCl 3 or AuCl 3 /AgOTf, 24 Cu(OTf) 2 , 25 FeCl 3 , 26 Yb(OTf) 3 , 27 AcBr/ZnBr 2 /SiO 2 , 28 and multi-walled carbon nanotubes-SO 3 H. 29 However, the usages of these homogeneous catalytic systems are not suitable for practical application because they are toxic, corrosive, non-reusable, and non-recoverable. Other disadvantages of homogeneous catalyst include environmental pollution, difficulty in work-up, and generally they need additional neutralization stages.…”

Application of highly sulfonated single-walled carbon nanotubes: An efficient heterogeneous catalyst for the one-pot synthesis of 14-aryl-14H-dibenzo[a,j]xanthenes under solvent-free conditions

“…In continuation of our interest towards green methodologies [49][50][51][52][53], we wish to report an efficient and green method for the synthesis of 14-aryl-14Hdibenzo[a,j]xanthenes in the presence of reusable and robust SWCNTs-SO 3 H under solvent-free conditions (Scheme 1).…”