China
Africa
Explore chapters and articles related to this topic
Advances in the Photo-Oxidation of Nitro-Organic Explosives Present in the Aqueous Phase
Published in Maulin P. Shah, Removal of Refractory Pollutants from Wastewater Treatment Plants, 2021
Pallvi Bhanot, Anchita Kalsi, S. Mary Celin, Sandeep Kumar Sahai, Rajesh Kumar Tanwar
Catalysts are established as vital tools/sources for the reduction of waste. A catalyst is usually explained as a material/compound which can change the rate of chemical reaction without being used or altered in the process. It enhances the rate of the reaction towards chemical equilibrium in order to reduce the activation energy and improve the treatment process. They are also called “green chemicals” that lessen the usage and production of harmful compounds. To achieve zero waste in chemical treatment processes, catalyst selection should be done with utmost care. The application of theses green chemicals has gained considerable interest among researchers as it displays the largest prospective of progression. Literature displays that numerous catalytic agents can be applied for various conventional photo-oxidation processes to minimalize the operational costs. To date, various catalytic agents have been recognized to be beneficial for oxidation processes in wastewater management.
Biodiesel Production from Municipal Wastewater Sludge
Published in Ozcan Konur, Biodiesel Fuels Based on Edible and Nonedible Feedstocks, Wastes, and Algae, 2021
Muhammad Nurunnabi Siddiquee, Sohrab Rohani
Catalyst selection is an important consideration in biodiesel production. Different catalysts are used, for example, homogeneous and heterogeneous base and acid catalysts, zeolite-based catalysts, and enzymatic catalysts. Basic catalytic transesterification is very fast compared to other catalyst types and widely used commercially. But FFAs in the raw materials produce soap in the presence of a base catalyst (Reaction IV). It is not only consumed in the reaction but also inhibits the glycerine separation from biodiesel and contributes to emulsion formation during the water wash. Homogeneous acid (H2SO4, for instance) catalyzed transesterification is much slower (by approximately 4,000 times) than base catalyzed transesterification and requires excess alcohol (Demirbas, 2005). But the main advantage of an acid catalyst is that it can catalyze both the esterification and transesterification and produce more biodiesel.
Natural Rubber and Bio-based Thermoplastic Elastomer
Published in Abdullah Al-Mamun, Jonathan Y. Chen, Industrial Applications of Biopolymers and their Environmental Impact, 2020
NR molecules contain isoprene groups, which are not chemically saturated and hence can react with hydrogen molecules (H2) or hydrogen releasing chemicals. The existence of unsaturated double bonds in isoprene group results in lower thermal and oxidation resistance performances of NR, and therefore it is beneficial to overcome those drawbacks by saturating the double bonds via hydrogenation. There are two major approaches for NR hydrogenation: catalytic and non-catalytic [15]. Catalytic hydrogenation initiates the reaction between H2 and double bonds in NR by catalyst. Typical catalysts include platinum, nickel, palladium, cobalt, molybdenum, cobalt oxide, calcium carbonate, and copper chromite, etc. [15]. NR with different hydrogenation degrees have been achieved by multiple research groups applying different catalysts/catalytic systems. Shahab and Basheer [18] reported the production of 23% hydrogenated NR using Rh(I) complex in benzene as a catalyst. Singha et al. [19] produced 100% hydrogenation of NR with RhCl(PPh3)3 catalyst, and investigated the effects of processing parameters. Hundred percent hydrogenated NR was also reported by Inoue et al. [20]. According to these researches, the increasing hydrogenation degree can result in higher thermal stability, hardness, and abrasion resistance of NR.
Utilization of zinc doped biochar catalyst for biodiesel production from waste cooking oil: process optimization and characterization
Published in Biofuels, 2023
Kasinathan Cholapandian, Rajendran Naveenkumar, Gurunathan Baskar
The production of biodiesel from any feedstock needs a suitable catalyst. There are many types of catalysts: homogeneous (acid/base), heterogeneous (acid/base), enzymatic, biomass-based, and bifunctional catalysts [14]. The disadvantages of using base homogeneous catalysts are the high cost and their tendency to produce a soap with the free fatty acids (FFAs) present during the process. Acid catalysts are corrosive and difficult to store, making them unsuitable for industrial use [15]. Heterogeneous catalysts form visible physical phases with reactants that can be easily separated, unlike homogeneous catalyst that results in a uniform undifferentiated mixture [16]. However, the reaction rate with a heterogeneous catalyst is much lower compared to using a homogeneous catalyst. Heterogeneous catalysts are reusable, non-corrosive, and less susceptible to the saponification process [6,17]. Despite being advantageous, heterogeneous catalysts can cause environmental damage. Enzyme catalysts can be used only around 35 to 40 °C and have disadvantages such as deactivation, high cost and slower reaction rates, making them unsuitable for the large-scale production of biodiesel [18].
Catalysts used in biodiesel production: a review
Published in Biofuels, 2021
Besides the molar ratio of alcohol to oil, the concentration of the catalyst and the reaction temperature play a key role in the performance of biodiesel [4]. Catalysts reduce reaction activation energy (primary energy for the reaction) and, therefore, they increase the reaction rate. Transition metals in the periodic table of the elements are the most common catalysts [5] but catalysts that are used in the transesterification process include homogeneous, heterogeneous and enzymatic catalysts [3,6]. Nano-catalysts have also been used in the production of biodiesel [7]. It appears that nanotechnology has become a globally popular field of research and development over the past decade. For example, heterogeneous catalysts have been categorized as successful initiatives that have had great benefits for society [8]. Recent advances in the field of nano-catalysts show improvement in the effective surface of reactants. Regarding the contact surface in the reaction, it seems that the lifetime of nano-catalysts and their efficiency have also been boosted [7]. In this review study, the authors review different types of catalysts as well as their advantages, disadvantages and performance under different transesterification reaction conditions in the production of biodiesel.
A hydrometallurgical process for the recovery of metal values from spent Cu–Cr catalyst
Published in Mineral Processing and Extractive Metallurgy, 2018
J. Panigrahi, P.C. Rout, B. Garnaik, K. Sarangi
The catalysts are used in many chemical processes to enhance the rate of reaction with less energy consumption. The combination of cupric chromite and cupric oxide or Cu–Cr catalyst has been used for hydrogenation, dehydrogenation, hydrogenolysis and oxidation of carbon monoxide and hydrocarbon, etc. The Cu–Cr catalyst is used for hydrogen production by partial oxidation of methanol (Wang et al. 2003). The catalyst Cu60Cr40 exhibits high CH3OH conversion and H2 selectivity when compared with other binary catalysts. The hydrogenation of the furfural and levulinic acid to furfuryl alcohol and biofuel γ-valerolactone, respectively, was achieved using Cu–Cr catalyst (Yan & Chen 2013). Propylene glycol was manufactured by hydrogeneolysis of glycerol and in this process Cu:Zn:Cr:Zr-based catalyst was used (Sharma et al. 2014). Cu–Cr catalyst was also used for the oxidation of carbon monoxide (Xanthopoulou & Vekinis 1998).