Size-Dependent Halogenated Nitrobenzene Hydrogenation Selectivity of Pd Nanoparticles

Abstract

The selective hydrogenation of halogenated nitrobenzene (HNB) has been a great important chemical reaction in the fine chemical productions. In this study, the effect of metal particle size on the selective hydrogenation of HNB over Pd/C catalysts has been extensively investigated through the combination of theoretical (density functional theory calculations, DFT) and experimental methods. DFT calculations showed that the reaction barriers for dechlorination strongly depend on the type of reaction sites (terrace or edge), while the hydrogenation reaction barriers are nearly the same on different sites, which indicates that Pd nanoparticle size significantly affects the catalyst selectivity. Moreover, Pd nanoparticles with different sizes (from 2.1 to 30 nm) supported on activated carbon were synthesized using the methods developed by our group. In a 500 mL reactor, the selectivity is over 99.90% when the Pd nanoparticles are bigger than 25 nm. Finally, the industrial applications of the proposed catalyst were evaluated in several pilot factories. This study provides useful information on controlling the selectivity of other similar reactions catalyzed by noble-metal nanocatalysts.

Mechanistic insights into the structure‐dependent selectivity of catalytic furfural conversion on platinum catalysts

“…We found the adsorption energies of all surface species on the three Pt model facets increase in the order of Pt(111) < Pt(211) < Pt 55 , which agrees with the general adsorption trend that the adsorbate exhibits stronger adsorption strength at the low coordinated site on the metal surfaces. 41 Furfural. On the flat Pt(111) surface, furfural adsorbs at the threefold hollow site with the carbonyl group tilting away from the surface.…”

“…41,43 In the present study, the flat Pt(111) surface, stepped Pt(211) surface, and Pt 55 nanocluster are used to represent the terrace, step, and corner sites. We assume the supported Pt catalysts used in the experiments are all in the same cubooctahedral shape of various sizes (Figure 8).…”

Insights into the mechanism of nitrobenzene reduction to aniline over Pt catalyst and the significance of the adsorption of phenyl group on kinetics

“…In fact, with respect to the aromatic compounds having multiple functional groups, the selectivity towards the desired functional group reaction is a big challenge in heterogeneous catalysis. For example, in the reduction of halonitrobenzene, to achieve a selective hydrogenation to haloaniline but avoiding the occurrence of dehalogenation requires a precise design of highly selective catalysts [14][15][16][17][18][19][20]. It is essential to get a deep understanding of the possible reaction mechanisms to enable us to achieve the selective catalysis.…”

“…A wide range of catalysts for reduction of nitrobenzene to aniline have been studied experimentally. Among them, noble Pt and Pd based catalysts were identified to be highly effective under modest conditions [6,10,[14][15][16][17][18][19][20]. Most of the investigations have been focused on the catalytic performance but not on the mechanisms.…”

Supported Bimetallic AuPd Nanoparticles as Catalyst for the Solvent-Free Selective Hydrogenation of Nitroarenes

“…[24,25] Fine tuning of Pd-, [26,27] Pt-, [25,28] and Ni-based [29] catalysts through nanostructure modification, selective poisoning and other strategies have been reported. However, for a given catalyst, optimization of reaction condition to increase the selectivity of CAN has not been reported yet.…”