Chemoselective nitrilation of dimethyl adipate with ammonia over carbon encapsulated WOx catalysts under continuous flow conditions†
Adiponitrile (ADN) is a key intermediate for the industrial production of polyamides represented by nylon 66. In this study, the chemoselective nitrilation of dimethyl adipate (DMA) with ammonia (NH3) under continuous flow conditions was studied on carbon encapsulated oxygen-deficient WOx<3 catalysts (WOx@C/C). A combination of dispersed anchor sites at a poly(ionic liquid) (PIL) template, the porosity of active carbon support, and the calcination procedure allows the formation of effective WOx@C-600-0.25-A1, persisting high BET specific surface area and WO2.83 active phase of appropriate size. It delivers ADN and methyl 5-cyanopentanoate (MCP) with an excellent selectivity of up to 95.8% at a weight hourly space velocity of DMA (WHSVDMA) of ∼0.64 gDMA gcat−1 h−1 and an NH3/DMA molar ratio of 13 : 1. A tandem reaction route from DMA to ADN via MCP was elucidated, wherein the second nitrilation of MCP to ADN proceeds very slowly. Besides, both CDMA and TONADN/TONMCP are significantly influenced by the physical dispersion and size of the active WO2.83 phase in WOx@C/C.