Catalytic activity of maghemite supported palladium catalyst in nitrobenzene hydrogenation

Abstract

A maghemite supported palladium catalyst was prepared and tested in nitrobenzene hydrogenation. The catalyst support was made by a newly developed combined technique, where sonochemical treatment and combustion have been used. As a first step, maghemite nanoparticles were synthesized. Iron(II) citrate was treated in polyethylene glycol by high-intensity ultrasound cavitation to get a homogeneous dispersion, then the product was combusted. The produced powder contained maghemite nanoparticles with 21.8 nm average particle size. In the second step of catalyst preparation, the magnetic nanoparticles were dispersed in the ethanolic solution of palladium(II) nitrate. The necessary energy for the reduction of Pd 2+ ions was achieved in the "hot spots" by acoustic cavitation, thus catalytically active palladium was formed. The prepared maghemite supported Pd catalyst have been tested in nitrobenzene hydrogenation at three different temperatures (283 K, 293 K and 303 K) and constant pressure (20 bar). At 293 K and 303 K, the conversion and selectivity of nitrobenzene was above 99% and 96%, respectively. However, the selectivity was only 73% at 273 K because the intermediate species (azoxybenzene and nitrosobenzene) have not been transformed to aniline. All in all, the prepared catalyst is successfully applied in nitrobenzene hydrogenation and easily separable from the reaction media.

Development of High-Efficiency, Magnetically Separable Palladium-Decorated Manganese-Ferrite Catalyst for Nitrobenzene Hydrogenation

“…Palladium catalysts on activated carbon are the main types, although their separation from the reaction medium is difficult and time-consuming due to their very small (several 10–100 nm) particle size. The use of magnetic materials as catalyst supports is a novel approach in the hydrogenation of NB [ 21 , 22 , 23 , 24 ]. Magnetic materials allow easy and efficient separation of the catalyst using an external magnet or magnetic field, avoiding complicated and time-consuming additional separation operations such as filtration and centrifugation [ 25 ].…”

Magnetite immobilized metal nanoparticles in the treatment and removal of pollutants from wastewater: a review

“…The author ascribed this drastic drop to the lack of a catalyst regeneration step between consecutive runs. [68] Other magnetic Pd catalysts include Fe 3 O 4 @SiO 2 @polysalophen-Pd(II) which incorporated the Pd(II) complex onto the magnetite surface to achieve 76% conversion of 4-nitrophenol (4-NP) with 96% selectivity for 4-aminophenol (4-AP). The magnetic Pd-complex was also investigated for the reduction of other nitro benzenes such as nitrobenzene, 1,3-dinitrobenzene and 4-methyl-1-nitrobenzene that achieved yields of 96%, 98% and 90%, respectively.…”

Recent developments of supported and magnetic nanocatalysts for organic transformations: an up-to-date review

“…CNTs are well-known supporter catalysts in metal NPs such as Ru, Pt, Rh, Ni, Fe, and Pd to improve the catalytic activity and selectivity of the NPs in a variety of chemical reactions to attributed metal-support interaction and mass transfer (Hashemi et al 2016). Maghemite-supported palladium NPs was prepared by Hajdu et al (2020) for catalytic hydrogenation of nitrobenzene derivatives. The Pd NPs exhibited 99% conversion of aniline in all cases without forming byproducts and the nanocatalyst was recovered using a magnet for subsequent use without any post-treatment.…”