A facile approach to enhancing activity of Ni₂P/SiO₂catalyst for hydrodechlorination of chlorobenzene: promoting effect of water and oxygen

Abstract

An effective approach to enhancing the activity of the Ni 2 P/SiO 2 catalyst for the hydrodechlorination of chlorobenzene (CB) was reported. At atmospheric pressure, 513 K, a CB WHSV of 4.1 h −1 and a H 2 /CB molar ratio of 9.0, Ni 2 P/SiO 2 gave a chlorobenzene conversion of 5.6%. Surprisingly, after Ni 2 P/SiO 2 was pretreated with a 0.8-3.0% H 2 O/H 2 flow below 543 K, the conversion reached as high as 99%. As the pretreatment temperature increased, the conversion tended to decrease; however, a conversion of 42.6% was still obtained even at the pretreatment temperature of 673 K. The activity of Ni 2 P/SiO 2 was also improved when 0.8% H 2 O or 0.5% O 2 was introduced into the reaction system. In addition, the passivation of Ni 2 P/SiO 2 followed by the reduction led to a conversion of 33%. The Ni 2 P/SiO 2 catalysts before and after the pretreatment were characterized by N 2 -sorption, XRD, ICP-AES, XPS, in situ DRIFT, and H 2 -and NH 3 -TPD. The results show that the pretreatment did not obviously influence specific surface area, pore structure, Ni 2 P crystallite size, the electron density of Ni in Ni 2 P, and the Ni and P contents, while it created new P-OH groups and reduced the amount of surface Ni sites. We propose a surface model of Ni 2 P/SiO 2 containing the Ni sites and the P-OH groups and consider that the synergism between the Ni site and the P-OH group can explain the promoting effect due to H 2 O and O 2 on the activity of Ni 2 P/SiO 2 , and the synergism mainly took place on the Ni 2 P particles and at the interface between the Ni 2 P particles and SiO 2 .

HDO of Methyl Palmitate over Silica-Supported Ni Phosphides: Insight into Ni/P Effect

“…Metal phosphides contain weak Brønsted and Lewis acid sites attributed to the presence of unreduced PO x groups and the metal sites with small positive charge, respectively [7,[26][27][28]. The various aspects of preparation technique, such as precursor nature, reduction temperature, metal content and Ni/P ratio were observed to affect the physicochemical and catalytic properties of the Ni x P y /SiO 2 catalyst [24,[29][30][31][32].…”

Promoting Light Hydrocarbons Yield by Catalytic Hydrodechlorination of Residual Chloromethanes Using Palladium Supported on Zeolite Catalysts

“…HDC has been extensively studied for the removal of chloromethanes due to the mild required conditions of pressure and temperature [7]. However, only a few works have reported high selectivity to olefins in the HDC reaction, using different types of supports and metallic active phases [8][9][10][11][12]. In most of those studies, deactivation and low concentration of chloromethane reactant considerably limited the possible application of the results.…”

Thioetherification of isoprene and butanethiol on transition metal phosphides

“…The P-OH groups and the metal sites with positive charge belong to Brönsted and Lewis acidity, respectively. The P-OH groups are derived from the unreduced phosphate as well as the passivation process [23] . The electron deficiency of metal sites is attributed to the charge transfer from metal atoms to P ones [24,25] , which is also demonstrated by (7) 15%Ni.…”