Double bond isomerization of ethyl linoleate and vegetable oils to conjugated derivatives over an LDH supported ruthenium catalyst

Abstract

MgAl-layered double hydroxides (LDHs) with different Mg/Al atomic ratios were prepared by co-precipitation and studied for the catalytic double bond isomerization of ethyl linoleate. Among them, MgAl₄-LDH (Mg/Al atomic ratio of 4.0) showed maximum conversion (15%) and yield of isomerized products (15%) at 90 °C in the presence of 1-butyl-3-methyl imidazolium chloride using toluene as solvent in 12 h. The catalytic performance improved significantly upon supporting 5% Ru on MgAl₄-LDH which gave 42% conversion with 29% yield of isomerized products under similar conditions. However, while reusing, the catalyst showed a reduced yield (18%). CO₂-TPD studies revealed an increase in the amount of weak basic sites along with a decrease in the amount of high strength medium basic sites is probably the reason for this drop. Under the optimized conditions, vegetable oils were also converted to their corresponding conjugated oils though with lesser conversion and yield.