Simple Method for Directly Synthesizing Ag Nanoparticles with Silver Ammonia and Polydopamine in a Microreactor toward the Conversion of 4-NP to 4-AP
Kun Wang, Rong Chen, Xun Zhu, Qiang Liao, Dingding Ye, Gang Chen, Ming Liu
Abstract
In this study, a simple method for directly synthesizing Ag nanoparticles on the inner wall of a microreactor was proposed to catalytically convert 4-NP to 4-AP. The proposed method employed silver ammonia as the precursor and polydopamine (PDA) to modify the surface of the microreactor. Because PDA contains numerous reducing agents of phenolic hydroxyl groups, the silver ions can be effectively reduced to Ag nanoparticles. Moreover, due to the zwitterionic nature of PDA, the use of silver ammonia as a precursor, which intrinsically has a high pH value, can allow for more silver ions to be adsorbed on the surface than the conventionally used AgNO3 as a precursor. Accordingly, the precursor utilization could be greatly improved, leading to the increase of the catalyst loading and thereby boosting the catalytic conversion and durability. It was also found that an increase in the reduction time required for the catalyst preparation could lead to the increase of the catalyst loading and thereby the catalytic performance but a too long reduction time did not continue to make more contribution. Experimental results demonstrate that the microreactor prepared by this simple method is able to exhibit good catalytic activity and durability, providing a new approach for developing high-performance microreactors.