and sulfur contents were significantly reduced the dry catalyst was then returned to the regenerator and contacted with hot regeneration gas the inlet temperature of the gas being adjusted to hold the temperature of the gas effluent from the regeneration zone within a few degrees on either side of 400 u00b0 f total residence time of the catalyst in the regeneration during this step was approximately one hour regeneration gas was passed through the catalyst during this step at a rate of 45 pounds of gas per pound of catalyst per hour oxygen content of the regeneration gas was approximately 17 by volume during this step substantially all of the sulfur and some of the carbon was burned from the catalyst the catalyst effluent from the regeneration zone was again returned to the regeneration zone and contacted with regeneration gas the temperature of the inlet gas was adjusted so as to hold the temperature of the gas effluent from the regeneration zone within a few degrees on either side of 800 u00b0 f total residence time during this step was approximately two hours since the physical arrangement of the rotary kiln type regeneration zone was such that catalyst passed through it in about one hour two passes of the catalyst through the zone were required to achieve the two hour total residence time the regeneration gas in this step had an oxygen content approximately 15 5 by volume and the gas was introduced into the regeneration zone at a rate about 45 pounds of gas per pound of catalyst in the zone per hour the following table summarizes the procedure ______________________________________ gas gaspass in u00b0 f out u00b0 f carbon w______________________________________1 drying 500.