Catalytic Hydrogenation Of P-nitrophenol Research Articles

A CaH2-Assisted Reduction Method to Prepare Nanoscale Zero-Valent Iron (nZVI) from Fe2O3 for Water Remediation Application

In recent decades, nanoscale zero-valent iron (nZVI) has been extensively studied for application in environmental remediation because it is an eco-friendly, inexpensive nanomaterial with high reactivity. The chemical reduction of iron ions using NaBH4 in a liquid solution is the most frequently used method to obtain nZVI, but its drawbacks are the use of expensive and toxic NaBH4 and the secondary pollution caused by the B(OH)3 by-product. In this study, in order to obtain nZVI in a cleaner manner, we used a reduction method for Fe2O3 using CaH2, which is non-toxic and generates no pollutants. The results of X-ray diffraction, nitrogen adsorption, and scanning electron microscopy for the obtained samples indicated the formation of zero-valent iron nanopowder (22.5 m2/g) that was obtained via reduction at 220 °C for 5 h. The obtained nZVI was finally tested in the catalytic hydrogenation of p-nitrophenol as a model reaction of water remediation, verifying its good catalytic performance.

Demonstration of Synergistic Catalysis in Au@Ni Bimetallic Core–Shell Nanostructures

Core–shell bimetallic nanoparticles comprised of gold core and varying nickel shell have been synthesized, and their synergistic effect in catalysis is explored through catalytic hydrogenation of p-nitrophenol and p-nitrothiophenol. A clear evidence for synergism in Au@Ni core–shell nanoparticles having an ultrathin Ni shell (1–2 nm) around a Au core (6–10 nm) resulting in enhanced catalytic activity is observed. The rates observed from a thin nickel shell are higher than monometallic Au or Ni nanoparticles of similar size or with a thicker Ni shell of 6–8 nm.

Preparation of well-dispersed and anti-oxidized Ni nanoparticles using polyamioloamine dendrimers as templates and their catalytic activity in the hydrogenation of p-nitrophenol to p-aminophenol

p-Aminophenol was synthesized by catalytic hydrogenation of p-nitrophenol on Ni nanoparticles prepared by a chemical reduction method using polyamidoamine (PAMAM) dendrimers as templates. The as-prepared Ni nanoparticles were characterized by XRD, LRS, EDS, FTIR, FESEM, HRTEM and N2 sorption analysis. Smaller-sized, better-dispersed and more active Ni nanoparticles can be successfully achieved using PAMAM dendrimers as templates. Analysis results show the as-prepared Ni nanoparticles are pure f.c.c. nickel. In hydrogenation reactions of p-nitrophenol, Ni nanoparticles show higher catalytic activity than that of Ni nanoparticles prepared in the absence of PAMAM dendrimers. The weight ratio of PAMAM/Ni2+ is proved to be an important parameter on the catalytic activity of Ni nanoparticles and the optimal ratio is 15%. The reason proposed for higher catalytic activity of Ni nanoparticles is a combination effect of smaller particle size, better dispersion and more active Ni nanoparticles.

Synthesis and characterization of nano-sized nickel catalyst supported on SiO2–Al2O3

support on thecatalytic activity of nickel catalyst. The reaction used in this studywas the hydrogenation of p-nitrophenol into p-aminophenol.p-Aminophenolisconsideredtobeveryimportantintermediateinthemanufactureofmanyanalgesicandantipyreticdrugs,suchasparacetamol,acetanilide,phentacin,...etc.[9–15].Itisalsousedasadeveloper in photography (under trade names of activol or azol), inaddition of its use in chemical dye industries [16].There are several methods used in the preparation of p-aminophenolfromp-nitrophenolsuchas:(1)metal/acidreduction[17], (2) catalytic hydrogenation [18], (3) electrolytic reduction[19], (4) homogeneous catalytic transfer hydrogenation [20], and(5) heterogeneous catalytic transfer hydrogenation, etc.Among all previously mentioned methods, direct catalytichydrogenation of p-nitrophenol to p-aminophenol becomes themost important one. This is because it could be an efficient routefor synthesis [15]. Raney nickel [21], nano-sized nickel [22] andseveral noble metal catalysts, such as Pd/C [15], have been used ascatalysts for this reaction. Due to their lowest cost and highercatalytic activity, supported nickel catalysts, are widely used insuch reactions [15–21].Although nickel catalyst is used in hydrogenation reactions[23–29], only few recent researches have been carried out onhydrogenation of p-nitrophenol over nano-sized supported nickelmetal catalyst [10,30,31].The present investigation reports the results of an intensivestudy on preparation and characterization of nano-sized metallicnickel supported on SiO

Synthesis of p-aminophenol from p-nitrophenol over nano-sized nickel catalysts

p-Aminophenol was synthesized by catalytic hydrogenation of p-nitrophenol on nano-sized nickel catalysts prepared by a chemical reduction method from aqueous solutions. The catalysts were characterized by XRD, EDS, SEM, HRTEM and Mastersizer 2000. Analysis results show that as-prepared catalysts are pure f.c.c. nickel and are prone to aggregation; the average particle size of nickel catalysts is 57 nm and there are high-density defects on particle surfaces. In hydrogenation reactions of p-nitrophenol, the hydrogenation rate is zero-order dependent on nitro aromatics and increases with increasing of hydrogen pressure. Compared with commercial Raney Ni, catalytic properties (activity, selectivity, and stability) of the as-prepared nickel are superior. The reason proposed for higher catalytic activity of nano-sized nickel is a combination effect of the small particle size and high-density surface defects. The partial sintering of nano-sized nickel might lead to the deactivation of the catalytic activity of nano-sized nickel.