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Selective methoxylation of α-pinene to α-terpinyl methyl ether over Al3+ ion-exchanged clays

Paper ID Volume ID Publish Year Pages File Format Full-Text
39407 45822 2015 9 PDF Available
Title
Selective methoxylation of α-pinene to α-terpinyl methyl ether over Al3+ ion-exchanged clays
Abstract

•α-Terpinyl methyl ether can be selectively produced from pinene over clay catalysts.•High layer charge clays are preferred as starting materials for catalyst preparation.•Al-ion exchange lead to the best catalytic performances.•The co-existence of Bronsted acid sites and of a 2-D gallery favours the reaction.

In this study, we report the use of clay-based catalysts in the methoxylation of α-pinene, for the selective synthesis of α-terpinyl methyl ether, TME. The main reaction products and intermediates were identified by GC–MS. The reaction conditions (stirring rate and catalyst load) that afford a kinetic regime were established. SAz-1 (Cheto, Arizona, USA) source clay and a montmorillonite (SD) from Porto Santo, Madeira Archipelago, Portugal, were modified by ion-exchange with Al3+ to produce catalysts with markedly different acidities and textural properties. The catalysts based on the high layer-charge SAz-1 montmorillonite proved to be the most active. Ion-exchange with Al3+, followed by thermal activation at 150 °C, afforded the highest number of Brønsted acid sites – a significant proportion of which were located in the clay gallery – and this coincided with the maximum catalytic activity. The influence of various reaction conditions, to maximize α-pinene conversion and selectivity, was studied over AlSAz-1. When the reaction was performed for 1 h at 60 °C, the conversion reached 65% with 65% selectivity towards the mono-ether, TME. Similar conversions and selectivities required up to 50 h over zeolites and other solid acid catalysts. The kinetic dependencies of this reaction on temperature and reagent concentration, over the selected clays were also investigated. It was established that, in the temperature and reagent concentration regime studied, the reaction was first order with respect to α-pinene. The apparent activation energies over the two catalysts, calculated from Arrhenius plots, were almost identical at 72 kJ mol−1.

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Keywords
Ion-exchanged clays; Clay acidity; Catalysis; Pinene; Methoxylation; Terpinyl methyl ether
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Selective methoxylation of α-pinene to α-terpinyl methyl ether over Al3+ ion-exchanged clays
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 489, January 2015, Pages 171–179
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us