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Biodiesel from Second-Generation Feedstock:
Published in Bhaskar Singh, Ramesh Oraon, Advanced Nanocatalysts for Biodiesel Production, 2023
Amjad Ali, Km Abida, Himmat Singh
To address the issues associated with homogeneous catalysts, a varied range of solid acid catalysts has been utilized for VO transesterification. Solid acid catalysts are usually less reactive than their alkali equivalents and hence, usually demand high temperature, high pressure, and a higher alcohol-to-oil molar ratio to achieve adequate conversion levels. Despite their poor reactivity, the use of solid acids has several advantages over homogeneous counterparts, such as they (i) are less sensitive to FFA present in the feedstock, (ii) are capable of catalysing simultaneous esterification and transesterification, (iii) can eliminate the need for catalyst neutralization and BD washing, (iv) can be separated easily from the reaction medium, (v) are reusable, and (vi) can reduce reactor corrosion, which simplifies the reactor design and reduces its construction cost.45
Shape Selective Catalysis
Published in Subhash Bhatia, Zeolite Catalysis: Principles and Applications, 2020
Until recently, all commercial plants that make ethylbenzene via alkylation of benzene with ethylene employed Friedel craft-type catalysts, mostly aluminum chloride. A solid acid catalyst avoids pollution problems, reduces catalyst consumption, and eliminates the need for corrosion-resistant materials of construction.
Microwave Mediated Biodiesel Production
Published in Veera Gnaneswar Gude, Microwave-Mediated Biofuel Production, 2017
Glycerol-derived solvents can be classified into two very different groups. The first group called “classical” glycerol derivatives has been traditionally used as solvents, such as esters (like acetins), carbonates (glycerol carbonate), acetals (glycerol formal) and ketals (solketal). The second group, organic solvents that are usually prepared from other sources such as propylene glycol, 1,3-propanediol, ethyl lactate or butanol are synthesized from glycerol. These have the potential to become competitive as the price of glycerol decreases. Glycerol derivatives such as acetal, ketal (acetalization of glycerol with aldehydes and ketones gives respective 1,3-dioxalane and 1,3-dioxane, commercial important compounds) ether, and ester find applications in the cosmetics, plastic, pharmaceuticals, detergents, fuel additives and fine chemical industries (Pawar et al. 2014). Several catalytic systems feasible with or without solvents have been developed to perform the acetalization of glycerol ranging from harsh mineral acids like H2SO4 and mild organic acids like p-toluenesulfonic acid (PTSA) to solid acid catalysts such as alluminosilicates, resins, zeolites and others. In addition to prolonged reaction time and complicated synthesis protocols, these systems suffer either stringent environmental regulations or operational disadvantages like moisture- sensitivity of solid acid catalysts. This type of difficult reactions can be accelerated in simplified microwave enhanced reaction environment. Microwaves can provide a quick and easy alternative to carry out these reactions as shown Figure 21. Other beneficial products that can be derived from glycerol and corresponding processes or reaction pathways are shown in Table 7.
Synergistic effect of Fenton oxidation and adsorption process in treatment of azo printing dye: DSD optimization and reaction mechanism interpretation
Published in Environmental Technology, 2022
Vesna Gvoic, Miljana Prica, Maja Turk Sekulic, Sabolc Pap, Olivera Paunovic, Aleksandra Kulic Mandic, Milena Becelic-Tomin, Djordje Vukelic, Djurdja Kerkez
Solid acid catalysts have attracted the attention of researchers in the last few decades because they enable the formation of an acidic microenvironment, which facilitates catalytic reactions even at high pH values [29]. In particular, iron(III)-molybdate (Fe2(MoO4)3), as an excellent Fenton-like catalyst with high activity and selectivity, has been applied in several catalytic processes [29,30]. Tian et al. [31] found that Fe2(MoO4)3 exhibited high catalytic activities in heterogeneous Fenton reactions over a wide range of pH (3–8). Catalytic reactions at high pH values of the solution are facilitated precisely due to the existence of an acidic microenvironment near the surface of Fe2(MoO4)3.
Effect of pseudo-boehmite on the aromatization performance of Zn-P-Al/ZSM-5 catalysts
Published in Petroleum Science and Technology, 2022
Jing Zhu, Yuying Yang, Wentao Wu, Shuyao Li
Solid acid catalysts are used in aromatization of hydrocarbons, so its acid center density and acid strength affect the aromatization reaction directly. They are determined by a thermogravimetric analyzer in the experiment. Pretreatment of the catalyst is required before analysis: weigh about 20 mg of catalyst sample into the weighing bottle, adsorb it with pyridine under vacuum for 24 h, desorb it under vacuum for 10 min after the adsorption reaches equilibrium, and remove the pyridine physically adsorbed on the catalyst surface. Weigh 10–15 mg of pretreated catalyst sample and put it into the differential thermogravimetric analyzer. Set the temperature rise rate of 10 °C/min from 25 to 800 °C and start to collect data. The acid center strength and acid center density distribution of the catalyst were analyzed by a differential thermogravimetric curve. The results are shown in Figure 7.
H3PW12O40 catalyzed new and multicomponent one-pot synthesis of 6-benzo[a]phenazin-5-ol derivatives of highly functionalized oxazoles via Robinson-Gabriel-type reaction
Published in Inorganic and Nano-Metal Chemistry, 2021
Mahdieh Hoseinpour, Razieh Mohebat, Mohammad Reza Nateghi, Forough Kalantari Fotooh
The results which specified by the reaction illustrate that the nature of acid has a significant effect on the yield of the reaction. Various Brønsted acids were examined and TFA gave the best result of 62% yield in this range and after examining different amount of TFA, we found that 0.3 equiv. of TFA was the most suitable acid (Table 1, entry 8). Lewis acids has not good effect, and only trace amount of the yield was formed when AlCl3 and SnCl3 were applied (Table 1, entries 6–7). Despite the succeed of TFA in accomplishment of this synthesis, but the deficit of product and destructive of this catalyst, we decided to change it. In continuation of our work to develop reactions in ecofriendly conditions, we use solid acid catalysts because of their considerable attention in different organic reactions, for instance their environmental adjustment, high selectivity, low cost, reusability, experimental simplicity, and easy products isolation. Heteropoly acids (HPAs) have economically and environmentally advantages, they are academic and industrial attractive and useful acid catalysts because of their catalytic features that can be varied at a molecular level in different synthesis. HPAs have considerable stability and super acidity both in solid state and in solution. Many typical acid-catalyzed reactions are effective in the presence of a suitable Keggin-type heteropoly acid, H3PW12O40.