Catalytic Transformation of Positional Nitrophenol Isomers on Highly Active Ag/Linde‐Type A4 Zeolite: A Comparative Analysis

Abstract

AbstractThe catalytic transformation of ortho‐(o‐NP), meta‐(m‐NP) and para‐nitrophenols (p‐NP) by Ag nanoparticles (Ag‐NPs) stabilised on zeolite A4 (ZA4) is presented for the first time. The catalysts are prepared by microwave‐assisted synthesis (Ag/ZA4‐MW) or ion exchange (Ag/ZA4‐IE). The results indicate that the nitrophenol reduction rate depends on the molecule structure and the presence of low‐coordinated metallic Ag‐NPs (∼2 nm and sub nanometric species). Meanwhile, the reactivity tendency depends on the synthesis methodology (m‐NP>p‐NP>o‐NP and o‐NP>m‐NP>p‐NP for Ag/ZA4‐MW and Ag/ZA4‐IE, respectively). The turnover frequency (TOF) values estimated for nitrophenols reduction are superior for Ag/ZA4‐MW catalyst by several orders of magnitude compared with those obtained for Ag/ZA4‐IE catalyst. In addition, the catalyst exhibits remarkable catalytic stability for the reduction of p‐NP even after the fifth consecutive catalytic run. The presently prepared catalysts are characterised by superior catalytic activity for the reduction of nitroaromatic compounds than similar Ag‐based materials reported in the literature.