The chemistry of copper-containing sulfur adsorbents in the presence of mercaptans

A brief review of the chemistry of copper and thiols is given and a contrast is made to the behavior of copper-containing adsorbents used for the desulfurization of liquid hydrocarbon streams that are routinely treated in refinery processes. A study was made of the chemistry between copper adsorbents and model liquid feed streams containing mercaptans. It was found that sulfur capacity can be quite high, greater than 8% by weight, and is dependent on the dispersion of the copper oxide on the adsorbent. In addition, it is shown that bulk copper is involved in the adsorption of mercaptans, as there is significantly more sulfur than there is copper on the surface. At a temperature of approximately 150 °C, very well formed lamellar crystals of copper(I) thiolate are formed, which indicates that the copper migrates from the surface of the catalyst to expose bulk copper for further reaction. When the temperature is raised to 190 °C, there is evidence that the copper(I) butanethiolate decomposes to copper(I) sulfide. Reaction mechanisms are proposed for the process of desulfurization of liquid hydrocarbon streams containing mercaptans when using a copper-containing adsorbent.