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

The vapour-phase isomerization of α-pinene for the first time was studied over a supported Au catalyst. α-pinene was isomerized to camphene over the 2.2% Au/γ-Al2O3 catalyst at 463–483 K using a solution of the reagent in n-octane as the initial reaction mixture and H2 or N2 as a carrier gas. Under these conditions, the selectivity to camphene reaches 60–80% at 99.9% conversion of α-pinene. The reaction is found to be first-order with respect to α-pinene, the apparent activation energy being similar to that observed with the conventional TiO2 catalyst. The prominent catalyst deactivation has been observed at increased α-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 O2 at temperature up to 923 K required to totally eliminate the coke deposits.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (128 K)Download as PowerPoint slideResearch highlights▶ Vapour-phase isomerization of α-pinene on Au. ▶ Selectivity to camphene 60–80%. ▶ First-order in α-pinene. ▶ Deactivation at increased α-pinene concentration. ▶ Complete regeneration in O2 eliminates coke deposits.