Ba-Doped Pd/Al₂O₃ for Continuous Synthesis of Diphenylamine via Dehydrogenative Aromatization

Abstract

A series of alkaline-earth-metal-modified Pd/Al2O3 nanocatalysts were prepared by an impregnation and kneading method. It was found that all of the catalysts doped by alkaline metals exhibit better catalytic performance in the continuous dehydrogenative aromatization of the Schiff base derived from cyclohexanone and aniline to diphenylamine (DPA) than that of Pd/Al2O3, in which, Pd1/Al3BaO presents a remarkable catalytic performance. X-ray diffraction, CO chemisorption, transmission electron microscopy, X-ray photoelectron spectroscopy, temperature-programmed hydrogen reduction, NH3-temperature-programmed desorption, Fourier transform infrared spectroscopy of pyridine adsorption, and a N2 adsorption–desorption method were employed to explore their structure–activity relationship. It was found that the doped Ba in Pd1/Al3BaO could promote the dispersion of Pd nanoparticles and reduce its acidity compared with that of Pd1/Al2O3. Therefore, the better Pd dispersion facilitated the dehydrogenation of Schiff base to DPA and the lower acidity of catalysts restrained the hydrolysis of the Schiff base and other side reactions, achieving good DPA selectivity. Moreover, Pd1/Al3BaO exhibited good stability. This work provides a promising strategy for the highly selective continuous synthesis of diarylamine or its derivatives from nonaromatic compounds.

Pd Nanoparticles Supported on Triangle‐Shaped La2O2CO3 Nanosheets: A New Highly Efficient and Durable Catalyst for Selective Hydrogenation of Cinnamaldehyde to Hydrocinnamaldehyde

“…The Pd 3d regions of the XP spectra of as‐prepared Pd/La 2 O 2 CO 3 ‐TNS and Pd/La 2 O 2 CO 3 ‐NR (Figure ) were deconvoluted into two pairs of doublets. The peaks at 334.8 and 340.1 eV are assigned to the binding energies of Pd 0 3d 5/2 and 3d 3/2 , and those at 335.9 and 341.3 eV are attributed to Pd II 3d 5/2 and 3d 3/2 , respectively, possibly due to oxidation on exposure to air . The shift of the binding energy of Pd 0 3d 5/2 of Pd/La 2 O 2 CO 3 ‐TNS to lower binding energy by 0.7 eV compared with Pd/La 2 O 2 CO 3 ‐NR indicated weakened 3d electron binding for Pd in Pd/La 2 O 2 CO 3 ‐TNS, which likely results from partial electron transfer from La 2 O 2 CO 3 ‐TNS to Pd.…”

“…The peaks at 334.8 and3 40.1 eV are assigned to the binding energies of Pd 0 3d 5/2 and 3d 3/2 ,a nd those at 335.9 and 341.3 eV are attributedt oP d II 3d 5/2 and 3d 3/2 ,r espectively,p ossibly due to oxidation on exposure to air. [32] The shift of the binding energy of Pd 0 3d 5/2 of Pd/ La 2 O 2 CO 3 -TNS to lower binding energy by 0.7 eV compared with Pd/La 2 O 2 CO 3 -NR indicated weakened 3d electron binding for Pd in Pd/La 2 O 2 CO 3 -TNS, which likely results from partial electron transfer from La 2 O 2 CO 3 -TNS to Pd. This electron transfer would increase the electron density of Pd and enhance the penetration of outer-layer electrons into the inner layer,w hich changes the binding energiesa nd substantially enhances the catalytic activity.…”

Liquid organic hydrogen carriers: Process design and economic analysis for manufacturing N‐ethylcarbazole

“…More specifically, the pathway mentioned by Zeng et al [25] describes a synthesis route for DPA through the dehydrogenative aromatization of a Schiff base (N-phenylcyclohexanimine) over a homogeneous palladium catalyst, similar to catalysts described by Chiang et al, [26] in the presence of nitrobenzene as a H 2 acceptor (see SI Section D for full mechanism). This Schiff base is formed through the reaction between the reactants, aniline, and cyclohexanone, with an additional water molecule as byproduct.…”

Synthesis of Nickel Vanadate Anchored on Reduced Graphene Oxide for Electrochemical Determination of Antioxidant Radical Cations of Diphenylamine H•+

“…Due to its distinctive antioxidant properties and antiscalding activity, DPA has been used mainly as the forerunner in the pharmaceutical industry and photographic synthetic substances such as plastic and dyes . It is also used as a stabilizer in perfume products, fuels, and explosive gun powder . It also finds usage as an antioxidant for different polymers and elastomers, as insulation for rubber condensates, and as the chiggers against biocide of the housefly .…”

“…31 It is also used as a stabilizer in perfume products, fuels, and explosive gun powder. 32 It also finds usage as an antioxidant for different polymers and elastomers, as insulation for rubber condensates, and as the chiggers against biocide of the housefly. 33 DPAH •+ has been used in the food industry as an inhibitor to manipulate the generally appearing terpenes and diverse pathogens on fruits.…”