Nonregenerative desulfurization processes

Processes that are termed regenerative use amine solutions (MEA or DEA) and involve gas scrubbing alone (MEA for natural gases and DEA for sulfur-bearing refinery or steam cracking gases). 

Nonregenerative processes use caustic soda scrubbing sometimes in combination with air oxidation. They generate three types of spent caustic  

In the Merox process, cold mild oxidation of RSH by air in an alkaline environment is catalyzed by a chelating agent, cobalt phthalocyanine. Four main reactions are involved the first two are avoided or curtailed as the reagents are expensive  

The major aim of oxidation processes is therefore to remove mercaptans. These are present in high concentrations in light gasolines and in low concentrations in gas oils where sulfides prevail. 

Mercaptans can represent 1% of the total S in sour crudes, but up to 30% in sweet crudes. Possible concentrations may go up to 90 ppm (light gasolines) or 300 ppm (heavy gasolines), or even 1000 ppm in CC heavy gasolines. 

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