Water as the solvent for the process of phenol hydroxylation over the Ti-MWW catalyst

Agnieszka Wróblewska

doi:10.1007/s11144-012-0517-2

Agnieszka Wróblewska

Open Access

https://doi.org/10.1007/s11144-012-0517-2

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Abstract

This work presents the studies on the process of phenol hydroxylation over the Ti-MWW catalyst. The medium of the reaction was water, whose amount was a sum of water introduced into the reactor with the 30 wt% hydrogen peroxide (oxidizing agent) and formed during the hydroxylation from the hydrogen peroxide (the first variant of the process) or water, which was the sum of water introduced additionally to the reaction mixture, water introduced with the oxidizing agent and formed during the reaction from the hydrogen peroxide (the second variant of the process). Studies have shown that in water solution, it is best to conduct phenol hydroxylation process at the temperature of 100 °C, phenol/hydrogen peroxide molar ratio 1, water content 62 wt%, catalyst content 8 wt% and during the reaction time of 180 min. Under these conditions, it is possible to achieve a selectivity of hydroquinone 43 mol%. A total conversion of phenol 28 mol%, and a selectivity of transformation to organic compounds in relation to phenol consumed 97 mol%.

Highlights

Hydroquinone and pyrocatechol are very useful semi-products for the chemical industry
Our preliminary studies indicate that the syntheses of Ti-MWW catalyst are more reproducible and the catalyst is characterized by greater stability [8]
From both technological and environmental points of view, it would be beneficial to develop variants of this process carried out in the aqueous medium, wherein the amount of water used in the process is only a sum of water which come from solution of the oxidizing agent— hydrogen peroxide (30 wt% aqueous solution of the compound is used in the process) and water which is formed in the process or the amount of water used in the process is a sum of water which is introduced to the reaction mixture, water introduced with oxidizing agent and water formed in the process

Summary

Introduction

Hydroquinone and pyrocatechol are very useful semi-products for the chemical industry. It would be interesting to verify the applicability of Ti-MWW catalyst instead of TS-1 catalyst in this process Another disadvantage associated with the industrial process of phenol hydroxylation is the use of large amounts of methanol (solvent) in the process (30 wt%). From both technological and environmental points of view, it would be beneficial to develop variants of this process carried out in the aqueous medium, wherein the amount of water used in the process is only a sum of water which come from solution of the oxidizing agent— hydrogen peroxide (30 wt% aqueous solution of the compound is used in the process) and water which is formed in the process (the first variant of this process—hydroxylation of phenol without added external water) or the amount of water used in the process is a sum of water which is introduced to the reaction mixture, water introduced with oxidizing agent and water formed in the process (the second variant of this process—hydroxylation of phenol with added external water). The results will be compared with our previous results obtained during phenol hydroxylation process over Ti-MWW catalyst, but in an acetonitrile medium

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