1976-02-01

Rejuvenation of Lead-Poisoned Noble Metal Catalysts 760321

The acetic acid-ammonium acetate methods of catalyst rejuvenation by lead removal have been of considerable interest. The effectiveness of these methods was therefore investigated in the laboratory as a function of temperature, duration of treatment, type of agitation, and cation, using mainly catalyst samples poisoned by treatment with a lead acetate solution, with confirmation by vehicle-aged catalyst samples. The results have, in general, been encouraging. For instance, washing of poisoned catalyst samples with 10 wt % acetic acid solution at room temperature for half an hour was sufficient to improve the hydrocarbon conversion of a catalyst poisoned with 5 wt % Pb (typical of a catalyst aged for about 50,000 miles with fuel containing 0.03 g Pb/gl) by 15%. However, we found that such a rejuvenated catalyst, if subjected to a laboratory repoisoning test with 0.03 g Pb/gl fuel, loses hydrocarbon activity rapidly. The rate of activity loss upon repoisoning appears to be about 6 times faster than the average loss rate experienced before the rejuvenation treatment. On the other hand, a poisoned catalyst sample which was rejuvenated by a more drastic treatment (e.g. two treatments for 3 hrs each, at 195°F with ultrasonic agitation), appeared to have the same rate of activity loss upon further aging as a fresh catalyst after the initial aging. This study also showed that there is no significant difference in rejuvenation effectiveness among acetic acid or ammonium acetate at the same concentration.

SAE MOBILUS

Subscribers can view annotate, and download all of SAE's content. Learn More »

Access SAE MOBILUS »

Members save up to 43% off list price.
Login to see discount.
Special Offer: With TechSelect, you decide what SAE Technical Papers you need, when you need them, and how much you want to pay.
X