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

The novel electrophilic organo-tantalum catalyst AlS/TaNpx (1) (Np=neopentyl) is prepared by chemisorption of the alkylidene Np3Ta=CHtBu onto highly Bronsted 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) & sdot; mol(Ta)-1 & sdot; h-1 at 200 degrees 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/TaNpx 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. The cationic organo-tantalum catalyst AlS/TaNp3 (94 %) and AlS/TaNp2_AlNp (6 %) was synthesized via Np3Ta=CHtBu chemisorption on Bronsted acidic sulfated alumina (AlS). The proposed structures are in good agreement with SSNMR, DRIFTS, XANES, EXAFS, and DFT computation. Highly efficient AlS/Ta-mediated hydrogenolysis of diverse pre- and post-consumer polyolefin plastics to lighter alkanes is achieved.image

Automated summary

This article reports a novel electrophilic organo-tantalum catalyst AlS/TaNpx, which exhibits high activity for the hydrogenolysis of diverse hydrocarbons ranging from C2 to polyolefins. It shows good stability and efficiency in converting various pre- and post-consumer polyolefin plastics.