Selective vapour-phase α-pinene isomerization to camphene over gold-on-alumina catalyst

The vapour-phase isomerization of alpha-pinene for the first time was studied over a supported Au catalyst. alpha-pinene was isomerized to camphene over the 2.2% Au/gamma-Al2O3 catalyst at 463-483 K using a solution of the reagent in n-octane as the initial reaction mixture and H-2 or N-2 as a carrier gas. Under these conditions, the selectivity to camphene reaches 60-80% at 99.9% conversion of a-pinene. The reaction is found to be first-order with respect to alpha-pinene, the apparent activation energy being similar to that observed with the conventional TiO2 catalyst. The prominent catalyst deactivation has been observed at increased alpha-pinene concentrations in the inlet reaction mixture (>= 4 vol% in n-octane solution). According to HRTEM and TPO results, the deactivated catalyst contains the carbonaceous deposits that may block the catalyst surface. Almost complete regeneration was done in flowing O-2 at temperature up to 923 K required to totally eliminate the coke deposits. (c) 2010 Elsevier B.V. All rights reserved.