Rapid Polyolefin Hydrogenolysis by a Single‐Site Organo‐Tantalum Catalyst on a Super‐Acidic Support: Structure and Mechanism

Abstract

The novel electrophilic organo-tantalum catalyst AlS/TaNp_x (1) (Np=neopentyl) is prepared by chemisorption of the alkylidene Np₃ Ta=CH^t Bu onto highly Brønsted acidic sulfated alumina (AlS). The proposed catalyst structure is supported by EXAFS, XANES, ICP, DRIFTS, elemental analysis, and SSNMR measurements and is in good agreement with DFT analysis. Catalyst 1 is highly effective for the hydrogenolysis of diverse linear and branched hydrocarbons, ranging from C2 to polyolefins. To the best of our knowledge, 1 exhibits one of the highest polyolefin hydrogenolysis activities (9,800 (CH₂ units) ⋅ mol(Ta)^-1 ⋅ h^-1 at 200 °C/17 atm H₂ ) reported to date in the peer-reviewed literature. Unlike the AlS/ZrNp₂ analog, the Ta catalyst is more thermally stable and offers multiple potential C-C bond activation pathways. For hydrogenolysis, AlS/TaNp_x is effective for a wide variety of pre- and post-consumer polyolefin plastics and is not significantly deactivated by standard polyolefin additives at typical industrial concentrations.