Effect of palladium on activity and selectivity of nickel catalyst in hydrogenation of castor oil

Abstract

In this study, a Raney nickel catalyst was prepared at various conditions. The effects of the following parameters were studied; digestion time, digestion temperature, concentration of aqueous NaOH solution, and ratio of Ni-Al alloy to NaOH (anhydrous). It was found that the best Raney nickel catalyst was obtained when digested at 110 C for 2 hours using a 25% NaOH solution and a ratio of alloy to NaOH of 1 tp 3. The catalyst was then used in the hydrogenation of castor oil in order to determine the optimum reaction conditions which were found to be 150 C, and 125 psig with a catalyst concentration as Ni-/oil of 0.3%. The resulting castor wax had an iodine value of 5.80, a hydroxyl value of 160.80 and an acid value of 1.00 When the catalyst was incorporated with palladium compound and the percentage of Pd/Ni was varied to 0.5, 1.0, 1.5 and 2.0%, the maximum activity was found for a percentage of Pd/Ni of 1.0%. The hydrogenated castor wax obtained, using this catalyst, had an iodine value of 3.29, a hydroxyl value of 160.83 and an acid value of 0.96. It was concluded that the activity of the Raney nickel was improved by the presence of up to 1.0% of palladium. The selectivity of the catalyst was changed to one used for dehydroxylation when palladium was incorporated in the amount of over 1.0%.