Synchronous catalytic elimination of malodorous mercaptans based VOCs: Controlling byproducts and revealing sites-pathway relationship

Controlling byproducts and unveiling "sites-pathway" relationship during synchronous catalytic degradation of sulfur-containing VOCs mixtures remains a huge challenge due to their variability, multi-components and multiple-sites characteristics. This work proposes the competitive adsorption combined with bifunctional catalysts as a strategy to avoid malodorous sulfur-containing byproducts. Experimental and theoretical researches demonstrated that ceria incorporated ZSM-5 was a bifunctional material with the coupled, but geometrically separated oxygen site and acid site, while praseodymium-incorporated one was a dual acid site catalyst. A "sites-pathway" relationship for decomposing a mixture of methyl mercaptan (CH3SH) and ethyl mercaptan (C2H5SH) was revealed, i.e., C2H5SH occupies preferentially on acid site, whereas CH3SH is converted into intermediate of CH3SCH3 over acid site, and then CH3SCH3 is forced to occupy on oxygen site, which accelerates the oxidation of CH3SCH3 to CO2. This work provides mechanistic understanding of "sites-pathway" relationship to control toxic byproducts for simultaneous catalytic degradation of sulfur-containing VOCs mixtures.