Exploring the confined space and active sites of Ni@OCNTs catalyst for chemoselective hydrogenation of cinnamaldehyde to hydrocinnamaldehyde

Abstract

Herein, Ni nanoparticles (NPs) were anchored and confined in open end CNTs (OCNT) to obtain Ni@OCNT catalyst using “wet chemistry”. The catalyst was prepared with an intention to explore confined space and high surface area of OCNT to utilize maximum available active sites for the reaction. The physicochemical properties of the Ni@OCNT catalyst were studied by different characterization techniques and then investigated for the selective hydrogenation of CAL to yield hydrocinnamaldehyde (HCAL). Remarkably, the 30 wt% Ni@OCNT catalyst presented 96 % conversion and 93 % selectivity with 89 % yield towards HCAL. TOF calculated for 30 wt% Ni@OCNTs catalyzed hydrogenation reaction of cinnamaldehyde is 28.12 h−1. The obtained characterization results and activity studies confirmed that synergistic effect of presence of electron deficient Ni NPs confined inside and highly dispersed Ni NPs on the outer surface of OCNT assisted in achieving superior catalytic performance in terms of activity and selectivity. This catalyst also exhibited an excellent stability up to seven recycles without appreciable loss in its activity. High selectivity towards the desire product resulted in the less formation of by-products therefore minimizing the generation of waste. Additionally the reaction in the presence of Ni@OCNTs catalyst was performed at moderate reaction conditions thereby reducing the usage of energy. Moreover, interaction of metal NPs with CNTs lessens the possibility of leaching of metal which could reduce the discharge of hazardous waste in the environment. All these factors might have a positive environmental impact.