Rational screening of metal single-atom-doped ZSM-5 to promote ring-opening cracking of cycloalkanes to light olefins

Abstract

The ring-opening cracking of cycloalkanes to light olefins poses a formidable challenge due to the sluggish activation of the C–C bond. In this study, we realize the rational screening of various single metal doped M−ZSM−5 catalysts (M = Mn, Co, Ni, Cu, Zn, Zr, Ru, Rh, Pd, Ag, Pt) to promote the ring-opening cracking of cycloalkanes to light olefins. Our calculation results show that methyl cyclopentane, a model compound of cycloalkanes, tends to adsorb in the form of a “half-chair” configuration in the intersecting channels of the M−ZSM−5, which is caused by the drastic distortion of the five-membered ring, accompanied by large changes in the bond angles. Based on the host–guest interaction between the active site and hydrocarbon in ring-opening cleavage, we reveal that the binding energies of metals to H and C can respectively quantify the metal’s ability to activate C–H and C–C bonds in cycloalkanes. By solving the microkinetic model, we plot activity-selectivity TOF volcano diagrams, where Mn, Ru, Rh-ZSM-5 within the EH range of −2.5 to −3.5 eV and the EC range of −6 to −8 eV can efficiently induce the ring-opening reaction of cycloalkanes without excessive dehydrogenation leading to aromatic hydrocarbon formation. The calculation shows good agreement with catalytic experimental tests and in situ DRIFT spectra results, providing a series of potential candidate catalysts for the ring-opening cracking of cycloalkane-rich diesel fuel.