Depositing Different Carbon Species on MoP to Enhance Its Activity for Isoprene Production in Different Ways

To study the effects of aromatic and olefinic carbon on isoprene synthesis, different carbon sources were used to prepare a variety of carbon deposited MoP catalysts for the condensation of isobutene with formaldehyde, and fresh MoP was employed as comparison. The deposited carbon with different carbonaceous species significantly enhanced the activity of MoP for isoprene synthesis. TGA, XPS, XRD, ¹³C and ³¹P MAS NMR, TPD of ammonia, isobutene and isoprene, and GCMS coupled with solid-phase microextraction were conducted to study the carbon deposited catalysts. The nature of carbon and its effect on the reaction were described. It was suggested that the deposited carbon can change the microenvironment of MoP. More importantly, olefinic and aromatic carbon may play different roles in improving the activity. Especially, aromatic carbon could be in favor of the desorption of isoprene from the catalyst surface and give an excellent selectivity.