A study of hydrodenitrogenation of pyridine over molybdenum nitride catalysts and their characterization

Abstract

A series of molybdenum nitride (Mo2N) catalysts were prepared by a topotactic synthesis method using a TPR (Temperature Programmed Reaction) at various conditions (temperature ramping rate, NH3 gas flow rate, final preparation temperature). The surface property and acidity of Mo2N catalysts prepared at various prepared conditions were studied by SEM, XRD, BET, FTTR and TGA. The hydrodenitrogenation (HDN) of pyridine in n-heptane over Mo2N catalyst (Al) was studied in a fixed bed continuous flow reactor (CATATEST) at the temperatures between 250–450°C , the pressure at 20–40 X 105 Pa and the contact time between 0.01-0.05 g cat.hr./ml feed. The microstructure of M02N catalyst was not changed at various preparation conditions by topotactic reaction. The XRD and BET studies showed that the extent of the crystallinity and the surface area of the prepared Mo2N catalysts increased when the final preparation temperature increased and the temperature ramping rate was lowered. In addition, from the TGA curve, the acid strength increased with the increase of the NH3 gas flow rate. The results of pyridine hydrodenitrogenation (HDN) over Mo2N catalyst showed that the catalytic activity (conversion % ) increased as reaction temperature, reaction pressure, and contact time increases. The selectivity for piperidine possessed a maximum at 350°C regardless of the reaction pressure. Also, the selectivity for cracked products increased as reaction temperature and pressure increased. The activation energy was determined 7.16 kcal/mol by Arrehenius plot.