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Akter Hossain Reaz Chanchal Kumar Roy
The catalysis process reduces the activation energy and accelerates reaction by minimizing reagent-based waste and byproducts, implying selective response. Supported-metal nanoparticles (SMN) are a kind of catalyst that is frequently utilized in processes such as reduction, oxidation, and isomerization . Nano-sized and supported catalysts are good options for fast, selective chemical transformations with high product yields, easy catalyst separation and recovery .
Considering the demand, metal nanoparticles have gained considerable interest due to their fascinating properties and potential applications complementary or superior to their bulk materials . Noble metals, transition metals and their alloys are reported for improving the conversion efficiency of this reduction reaction. Various noble metals, including Au, Ag, Pt, Au–Ag, and Au–Pt nano-catalysts, have been widely employed due to their efficient catalytic activities, but their industrial application is limited due the high cost and scarce resources . The transition metal catalysts, which are significantly less expensive than noble metal catalysts, are becoming increasingly popular for lowering the cost of noble metal catalysts [5-6]. Among them, nickel nanoparticles(Ni NPs) have received much attention because of their high catalytic activity, cheap, short reaction times and high selectivity as a catalyst in hydrogenation reactions. As compared to the traditional Raney® nickel catalyst, Ni nanoparticles are greener, too . The high performance of Ni-based catalysts could be tied to their capability to absorb hydrogen on Ni metal's surface and quickly activate hydrogen in the atomic state. However, the catalytic activity of Ni NPs could decrease as the particles tend to agglomerate due to the enormous surface energy and smaller size, thus decreasing the catalytic activity, which renders their potential applications, mainly as the catalyst. Controlling the aggregation of metal NPs in heterogeneous catalysts is an important parameter[1?]. To prevent agglomeration, Ni NPs have been dispersed onto different support matrices such as active carbon, graphene, silica (SiO2), magnetic materials, polymer, and other metal oxides. SiO2 NPs have been proven as helpful support materials for heterogeneous catalysis [8-9]. Surface properties, such as dispersion, electronic structure, surface area, pore structure and wettability, have vital roles in improving the performance of the SMN catalyst . Compared to bulk SiO2, its nanoparticles have a large surface area and inherent surface reactivity, allowing for chemical modifications. Porous SiO2 NPs could enhance the surface area significantly and thus appears to be an excellent support material in catalysis. Mesoporous SiO2 NPs have a honeycomb-like porous structure with hundreds of unfilled channels (mesopores) capable of encapsulating relatively significant quantities of analytes . Unique properties, such as high surface area, large pore volume, tunable pore size with a narrow distribution and good chemical and thermal stabilities, make them attractive for various sample preparation applications. Another potential solution is to prevent aggregation of NPs and, to get the particles stabilized in nano-state .
Nitroaromatic compounds (NAs), which are toxic and responsible for severe environmental pollution, need to be reduced to benign compouds before being discharged into the environment. For instance, 4-nitrophenol (4-NP) is one of the most refractory pollutants in industrial effluents such as phenol wastewater and agricultural wastewater . However, it has various adverse effects on human health since it damages the central nervous system, liver, kidney etc. . However, the 4-NP can easily be reduced to harmless aminophenols (APs), potential intermediates in preparing antipyretic drugs such as paracetamol, dyestuff, corrosion inhibitors, anti-corrosion lubricant etc.
In this work, Ni-SiO2 nanocatalyst has been fabricated from a biobased precursor. The catalysts will be used to reduce 4-NP and other nitroaromatics to 4-AP by NaBH4 and investigate the systematic mechanism of the catalytic processes. This study will explore the facile stretegy to develop noble materials, from cheap and locally available resources, with high catalytic efficacy to convert the hazardous materials into value-added products.
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