Poisoning of a Pt catalyst by thiophene under reforming conditions

Summary

• 1. An investigation was made of the poisoniag of a 1% Pt-Al₂O₃ catalyst by thiophene in the dehydrogenation of cyclohexane in a flow system at 450° in presence of hydrogen at 20 atm.

• 2. When mixtures of cyclohexane and thiophene of constant composition were passed over the catalyst the dehydrogenation activity fell only during She first 1–2 hours, after which, it remained constant and no longer depended on the amount of thiophene passed over the catalyst. The reduction in the activity of the catalyst in the first hours of work is determined by the thiophene content of the original mixture.

• 3. Poisoned catalysts recover their original activity when pure cyclohexane is passed over them; however, the time required for regeneration is determined by the thiophene concentration of the original mixture used in the poisoning of the catalyst.

• 4. On the basis of the results obtained in this and our earlier investigations, it is suggested that the deactivation of platinum catalysts is determined by the rate of the desorption of thiophene and hydrogen sulfide which is formed in the decomposition of various sulfur compounds.