Progress in Catalytic Hydrodechlorination

Catalytic hydrodechlorination (HDC) is a technology with great potential for the treatment and valorization of organic chlorinated wastes [...]

Preparation, characterization, and catalytic performance of Pd–Ni/AC bimetallic nano-catalysts

Palladium–nickel (Pd–Ni) bimetallic nano-catalysts supported on activated carbon (Pd–Ni/AC) have been successfully prepared by impregnation method enhanced with ultrasonic. The prepared Pd–Ni/AC catalysts were used for the catalytic hydrodechlorination reaction of bleached shellac and characterized by Fourier-transform infrared spectroscopy, nitrogen adsorption, X-ray diffraction, X-ray photoelectron spectroscopy, field-emission scanning electron microscope, and high-resolution transmission electron microscopy. The results show that Pd–Ni bimetallic structures in catalytic particles with the diameter of 4 and 14 nm were distributed uniformly on AC support, and the lattice fringe spacing in catalytic particles was measured as 0.213 nm which is lying in the region between monometallic Pd (111; 0.225 nm) and Ni (111; 0.203 nm), and that Pd1–Ni1/AC catalyst exhibits the best catalytic hydrodechlorination performance with the dechlorination efficiency of 92.58 wt% while it is used for the hydrodechlorination of bleached shellac, and the optimum catalytic performance is related to the synergistic electronic effect and bimetallic structure of the Pd1–Ni1/AC sample.

Two Scenarios of Dechlorination of the Chlorinated Hydrocarbons over Nickel-Alumina Catalyst

Dechlorination processes attract great interest since they are involved in environmental protection and waste disposal technologies. In this paper, the process of gas-phase dechlorination of 1,2-dichloroethane, chloroform, and chlorobenzene over Ni/Al2O3 catalyst (90 wt% Ni) prepared by a coprecipitation technique was investigated. The reduction behavior of the oxide precursor NiO/Al2O3 was studied by thermogravimetric analysis in a hydrogen medium. A thermodynamic assessment of the conditions under which metallic nickel undergoes deactivation due to the formation of nickel chloride was performed. The dechlorination of chlorinated substrates was studied using a gravimetric flow-through system equipped with McBain balances in a wide range of temperatures (350–650 °C) and hydrogen concentrations (0–98 vol%). The impact of these parameters on selectivity towards the products of hydrodechlorination (C2H4, C2H6, and C6H6) and catalytic pyrolysis (carbon nanomaterial and CH4) was explored. The relationship between the mechanisms of the catalytic hydrodechlorination and the carbide cycle was discussed, and the specific reaction conditions for the implementation of both scenarios were revealed. According to the electron microscopy data, the carbonaceous products deposited on nickel particles during catalytic pyrolysis are represented by nanofibers with a disordered structure formed due to the peculiarity of the process including the side carbon methanation reaction.

The Effect of Shape-Controlled Pt and Pd Nanoparticles on Selective Catalytic Hydrodechlorination of Trichloroethylene

Tailoring the shape of nanoscale materials enables obtaining morphology-controlled surfaces exhibiting specific interactions with reactants during catalytic reactions. The specifics of nanoparticle surfaces control the catalytic performance, i.e., activity and selectivity. In this study, shape-controlled Platinum (Pt) and Palladium (Pd) nanoparticles with distinct morphology were produced, i.e., cubes and cuboctahedra for Pt and spheres and polyhedra/multiple-twins for Pd, with (100), (111 + 100), curved/stepped and (111) facets, respectively. These particles with well-tuned surfaces were subsequently deposited on a Zirconium oxide (ZrO2) support. The morphological characteristics of the particles were determined by high resolution transmission electron microscopy (HR-TEM) and X-ray diffraction (XRD), while their adsorption properties were investigated by Fourier transform infrared spectroscopy (FTIR) of CO adsorbed at room temperature. The effect of the nanoparticle shape and surface structure on the catalytic performance in hydrodechlorination (HDCl) of trichloroethylene (TCE) was examined. The results show that nanoparticles with different surface orientations can be employed to affect selectivity, with polyhedral and multiply-twinned Pd exhibiting the best ethylene selectivity.