Synthesis and characterization of spent alumina catalyst and grinding sludge reinforced aluminium-based composite material

In this investigation, an attempt has been made to use the waste material in the fabrication of aluminium-based composite material. Waste spent alumina catalyst (SAC) generated from oil refinery industries has been considered as primary reinforcement particle. Waste grinding sludge (GS) produced from iron forging industry was used as secondary reinforcement material in the preparation of composite. Further, chromium (Cr) has been added to SAC and grinding sludge (GS) reinforced aluminium-based composite material to prevent grain growth as well as to control the grain structure of composite material. Experimental results concluded that by adding 4.5% of GS and SAC with 1.5% Cr in aluminium alloy, mechanical properties such as hardness, compressive strength and tensile strength were significantly improved. Hardness compressive strength and tensile strength was increased by 40.06%, 7.24% and 18.86%, respectively, with respect to the aluminium alloy. However, the reduction in toughness was observed. SEM results depicted uniform distribution of SAC and GS particles in Al/4.5% SAC/4.5% GS/1.5% Cr composite. Thermal expansion behaviour and corrosion weight loss of composite have been also investigated to observe the influence of reinforcement in the aluminium alloy.

CO2 Methanation: Nickel–Alumina Catalyst Prepared by Solid-State Combustion

The development of solvent-free methods for the synthesis of catalysts is one of the main tasks of green chemistry. A nickel–alumina catalyst for CO2 methanation was synthesized by solid-state combustion method using hexakis-(imidazole) nickel (II) nitrate complex. Using X-ray Powder Diffraction (XRD), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Hydrogen temperature-programmed reduction (H2-TPR), it was shown that the synthesized catalyst is characterized by the localization of easily reduced nickel oxide on alumina surface. This provided low-temperature activation of the catalyst in the reaction mixture containing 4 vol% CO2. In addition, the synthesized catalyst had higher activity in low-temperature CO2 methanation compared to industrial NIAP-07-01 catalyst, which contained almost three times more hard-to-reduce nickel–aluminum spinel. Thus, the proposed approaches to the synthesis and activation of the catalyst make it possible to simplify the catalyst preparation procedure and to abandon the use of solvents, which must be disposed of later on.

Recovery of Cr from chrome-containing leather waste and its utilization as reinforcement along with waste spent alumina catalyst and grinding sludge in AA 5052-based metal matrix composites

The present investigation deals with the development of AA 5052-based metal matrix composites (MMCs) by utilizing industrial wastes, spent alumina catalyst, chrome-containing leather waste, and grinding sludge as a reinforcement material. The chrome-containing leather waste has been utilized to extract the collagen powder, which is a form of chromium oxide. The presence of Al2O3, Fe2O3, and SiO2 phases in the spent alumina catalyst and grinding sludge ball-milled powder encourages its utilization as reinforcement material (in the form of Cr) for the development of MMCs. The stir-casting technique has been used to develop the aluminum-based MMC with waste spent alumina catalyst, chrome-containing leather waste, and grinding sludge. Further, results revealed that the matrix material mechanical properties compressive strength, tensile strength, and hardness were significantly increased by 12.93%, 5.34%, and 31.81% after adding spent alumina catalyst, Cr, and grinding sludge with the weight percentage (wt.%) of 4.5%, 1.5%, and 4.5%, respectively, but the toughness was reduced. The microstructural investigation indicated the uniform distribution of reinforcing elements spent alumina catalyst (4.5 wt.%), GS (4.5%), and Cr (1.5%) in the aluminum matrix material. Further, the influence of given reinforcement elements on the thermal expansion and corrosion weight loss properties of aluminum alloy matrix material has also been investigated.