【Chemical Engineering Theory】Desulfurization of gasoline and liquefied gas
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This post was last edited by Xiao Gong 1985 on 2016-3-7 10:54. What is the catalyst consumption rate during the desulfurization of gasoline and liquefied gas? Why is a catalyst added – due to activity degradation or loss? Is the final catalyst in the alkaline slag? Thank you!
The catalyst used for desulfurization of alcohols is cobalt titanium cyanosulfonate; this catalyst is regenerated through oxidation by an alkaline solution, and its loss is mainly due to the waste alkali being discharged during the production process!
As for the consumption rate, it depends on the operation! The main reactions are NaSR + O2 + H2O ---- NaOH + RSSR, and Na2S + O2 + H2O ------ Na2S2O3 + NaOH. The equations are not balanced; balance them by yourself! As can be seen from the equation, the regeneration of sodium thiol does not consume alkali, whereas the regeneration of sodium sulfide produces sodium thiosulfate, which consumes the alkali in the system and thus reduces the alkali concentration! This is why it is necessary to remove the old alkali and replace it with new alkali. Therefore, when the desulfurization unit upstream of the desulfurized alcohol unit does not operate properly, a large amount of hydrogen sulfide is carried in, and it reacts with the alkali solution to form sodium sulfide; as a result, the alkali consumption increases. An increase in alkali consumption inevitably leads to an increase in the amount of waste alkali that needs to be disposed of, and more waste alkali means more catalyst is consumed as well! I wonder if you understand this explanation?
That makes sense, but what about the catalyst activity in the spent alkali solution? If liquid alkali replacement is excluded, can the catalyst be used continuously?
Theoretically, if the alkali solution is not consumed, the catalyst will basically not be consumed in the system. However, in practical operation, the consumption of alkali solution (including that due to entrainment and reaction) is bound to decrease; therefore, your assumption is only valid theoretically!
As for the catalyst activity in the spent alkali, there are no special substances in the alkaline solution that could deactivate the catalyst, so it should have no impact! The main reason for adding the catalyst, or rather, the reason for the decrease in catalyst concentration, is not deactivation, but rather the addition of alkaline solution, the removal of waste alkali, and the inevitable entrainment that occurs during operation! There is little literature on the deactivation of cobalt titanium cyanosulfonate, as it is a liquid catalyst with relatively stable properties; thus, there are few studies discussing the causes of its deactivation! And it’s not very meaningful to discuss inactivation!