Effect of Pd, Cu, and Ni additions on the kinetics of NiCl2 reduction by hydrogen

Abstract

Differential thermal analysis (DTA) and thermal gravimetric analysis (TGA), at a heating rate of 10 ЊC/min, revealed a complete reduction of NiCl 2 by hydrogen in a temperature interval of 375 ЊC to 450 ЊC. However, addition of 0.1 mass pct of Pd, Cu, or Ni to the sample caused the reduction to occur at considerably lower temperatures, in the rather narrow range of 315 ЊC to 370 ЊC. The activation energy of NiCl 2 reduction by hydrogen (between 300 ЊC and 550 ЊC) without additives is 54 kJ/mol, and with Pd and Cu or Ni added, under isothermal conditions (from 260 ЊC to 380 ЊC), is 33 and 50 kJ/mol, respectively. These values confirm a positive effect of additives on the reduction kinetics. The positive effect of Pd is a consequence of the dissociation and spillover of hydrogen, whereas in the case of Cu and Ni(HCOO) 2 , it is manifested in a decrease in bonds energy in the nickel lattice because of good Cu solubility, and in the formation of artificial nickel nuclei that intensify the reduction, respectively. Scanning electron microscopy (SEM) analysis of nickel powders obtained under isothermal conditions shows relatively rounded spherical particles (0.321 to 0.780 m in size) of powder samples with additives, and particles of irregular shape (2.085 m mean size) of the sample without additives. This illustrates the positive effect of Pd, Cu, or Ni added in the reduction process, in decreasing the size of nickel particles and in the production of a more uniform particle shape.

Physico-chemical and structural characterization of mucilage isolated from seeds of Diospyros melonoxylon Roxb.

“…The analysis of mucilage was performed on differential thermal analysis (Linseis Germany, Stapt-1600) in which accurately weighed 5 mg samples were placed into platinum cups and sealed. The temperature range was from 0 °C to 240 °C at a heating rate of 15 °C/min (Stopic, Ilic, Uskokovic, 1997;Soumen et al, 2010).…”

Influence of additives on the properties of spherical nickel particles prepared by ultrasonic spray pyrolysis

“…3(a)] revealed the presence of NiCl 2 and NiCl 2 × 2H 2 O phases, indicating an incomplete reduction of the starting material at this temperature. 9 Artificially prepared Ni nuclei present in NiCl 2 produce an autocatalytic effect on the reduction process and cause a decrease in the reduction temperature. 3(b)].…”

Kinetics of NiO and NiCl2 Hydrogen Reduction as Precursors and Properties of Produced Ni/Al2O3 and Ni‐Pd/Al2O3 Catalysts

“…They obtained the activation energy value of 104 kJ/mol. Stopić et al [ 17 ] conducted kinetic analysis of NiCl 2 reduction, with 0.1 wt% of Pd, Cu, or Ni and without additives. The activation energy of NiCl 2 reduction, at temperatures from 573 to 823 K, was 54 kJ/mol.…”