Hydrotreatment of Nylon 66 and Amide Model Compounds Over Sulfided NiMo Catalysts

ABSTRACT Molybdenum sulfide‐based catalysts, such as nickel–molybdenum on alumina (NiMoS x /Al 2 O 3 ), are widely used in hydrotreating and have potential for catalyzing waste plastic conversion via hydrogenolysis, yet their performance, such as reaction kinetics and network, for amide‐rich polymer feeds is poorly defined. Here we combine Nylon 66 with the amide model compound, N,N‐dibutylhexanediamide (DBDAD), to quantify hydrodeoxygenation (HDO) and hydrodenitrogenation (HDN) chemistry in a stirred batch reactor (53 bar H 2 , 280–320°C). DBDAD conversion is near‐linear with time, indicating strong adsorption of the substrates on the active sites. Time‐resolved product identification indicates parallel C─O first‐cleavagedeoxygenation (DO) and C─N first‐cleavagedenitrogenation (DN) sequences proceeding through amine and diol intermediates, respectively, to C 4 ─C 6 alkanes. Increasing temperature shifts selectivity toward DN, decreasing the initial r(DO)/r(DN) from 1.38 (280°C) to 0.69 (320°C), with an apparent activation energy of 173 kJ mol − 1 for DBDAD conversion. At 300°C, nylon 66 converts faster than DBDAD, producing a complex mixture of oxygen‐ and nitrogen‐containing species and an initial rate ratio r(DO)/r(DN) of 1.6. No heteroaromatic nitrogen products are detected by the method used. These results provide reaction pathways and product signatures relevant to hydro‐processing catalysts exposed to polyamide‐derived streams.