Potassium Alum [KAl(SO4)2∙12H2O] solid catalyst for effective and selective methoxylation production of alpha-pinene ether products

Abstract

Methoxylation is a relevant technological process applied in the production of high-value a-pinene derivatives. This report investigates the use of potassium alum [KAl(SO4)2 · 12H2O] as a catalyst in the methoxylation of a-pinene. In this study, the methoxylation reaction was optimized for the highest conversion of a-pinene and selectivity, assessed for the factors, catalyst loading (0.5; 1.0; and 1.5 g), volume ratio of a-pinene: methanol (1:4, 1:7, 1:10), reaction temperature (50, 55, 60 and 65 °C), and reaction time (72, 144, 216, 288, 360 min). The highest selectivity of KAl(SO4)2·12H2O in the methoxylation of a-pinene was achieved under an optimal condition of 1 g of catalyst loading, volume ratio of 1:10, as well as the reaction temperature and incubation time of 65 °C and 6 h, respectively. GC–MS results revealed the yields of the methoxylated products from the 98.2% conversion of a-pinene, to be 59.6%, 8.9%, and 7.1% for a-terpinyl methyl ether (TME), fenchyl methyl ether (FME), bornyl methyl ether (BME), respectively. It was apparent that a lower KAl(SO4)2·12H2O loading (0.5–1.5 g) was more economical for the methoxylation reaction. The findings seen here indicated the suitability of the KAl(SO4)2 · 12H2O to catalyze the methoxylation of a-pinene to produce an commercially important ethers.