Catalytic Decomposition of Long‐Chain Olefins to Propylene via Isomerization‐Metathesis Using Latent Bicyclic (Alkyl)(Amino)Carbene‐Ruthenium Olefin Metathesis Catalysts

Abstract

AbstractOne of the most exciting scientific challenges today is the catalytic degradation of non‐biodegradable polymers into value‐added chemical feedstocks. The mild pyrolysis of polyolefins, including high‐density polyethylene (HDPE), results in pyrolysis oils containing long‐chain olefins as major products. In this paper, novel bicyclic (alkyl)(amino)carbene ruthenium (BICAAC−Ru) temperature‐activated latent olefin metathesis catalysts, which can be used for catalytic decomposition of long‐chain olefins to propylene are reported. These thermally stable catalysts show significantly higher selectivity to propylene at a reaction temperature of 75 °C compared to second generation Hoveyda–Grubbs or CAAC−Ru catalysts under ethenolysis conditions. The conversion of long‐chain olefins (e.g., 1‐octadecene or methyl oleate) to propylene via isomerization‐metathesis is performed by using a (RuHCl)(CO)(PPh3)3 isomerization co‐catalyst. The reactions can be carried out at a BICAAC−Ru catalyst loading as low as 1 ppm at elevated reaction temperature (75 °C). The observed turnover number and turnover frequency are as high as 55 000 and 10 000 molpropylene molcatalyst−1 h−1, respectively.