Catalysis, Kinetic and Mechanistical Studies for the Transformation of Ethylene Glycol by Alumina and Silica Gel under Autogenous Pressure and Solvent-free Conditions

Taoufik Rohand,Kiyoshi Tanemura

doi:10.17344/acsi.2020.6422

Taoufik Rohand, Kiyoshi Tanemura

Open Access

https://doi.org/10.17344/acsi.2020.6422

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Abstract

A kinetic and mechanistical studies of the new pathway for competitive transformation of ethylene glycol by alumina and silica gel have been described. Commercial alumina (Al com), synthetic alumina (Al syn), commercial silica gel (Si com) and synthetic silica gel (Si syn) were used for the transformation of ethylene glycol to a mixture of diethylene glycol, 1,4-dioxane and 2-methyl-1,3-dioxolane via acetaldehyde by heating at 150 °C under autogenous pressure without solvent. The results show that the yield of these three products strongly depends on the nature of the used catalyst and the reaction time.

Highlights

In recent years, the use of silica gel as a catalyst in environmentally friendly conditions became an interesting topic for investigations in organic chemistry reactions
It is noted that the prolongation of the duration of the heating of this reaction mixture from 2 h to 2 days considerably increased the yield of dimer 2 while keeping 1,4-dioxane (3) as a minor product of this reaction, whereas acetaldehyde (4) and 2-methyl-1,3-dioxolane (5) were not obtained (Table 1, entries 2, 4 and 6)
The best results were obtained using sulfuric acid as the catalyst. These unexpected results motivated us to generalize this type of conversion by using imported and commercial solid catalysts, such as commercial silica gel (Si com) (Aldrich) and a local catalyst such as inexpensive synthetic Moroccan silica (Si syn) and easy to prepare from sand originating from the sea side of Safi in Morocco,[4] while the alumina is commercial (Al com) (Aldrich) (Table 2), alumina (Al syn) was synthesised following the standard procedure published by Ghulam.[22]

Summary

Introduction

The use of silica gel as a catalyst in environmentally friendly conditions became an interesting topic for investigations in organic chemistry reactions. The use of pollutant and harmful organic solvents has been replaced by solvent-free reactions which became very advantageous alternatives.[1,2,3] protic acids are well-known to suffer from a number of shortcomings, including their corrosive and noxious nature.[4,5] The recent move towards green chemistry has seen silica gel and alumina gradually replacing mineral acids in the synthesis of organic compounds. These acetalization and ketalization reactions are typically carried out in ecologically harmful organic solvent, in the presence of noxious protic acids at various temperatures, and typically, at atmospheric pressure.[18,19,20]

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