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Bioenergy From Activated Sludge and Wastewater
Published in Veera Gnaneswar Gude, Green chemistry for Sustainable Biofuel Production, 2018
Andro Mondala, Rafael Hernandez, Todd French, Emmanuel Revellame, Dhan Lord Fortela, Marta Amirsadeghi
Among the fuel compatible compounds produced from raw sludge, 9 wt.% accounts for olefins, 20 wt.% for paraffins, and 69 wt.% for aromatics on a dry sludge basis. On the other, cracking of enhanced sludge is more selective towards aromatic hydrocarbons with distributions of (base on dry sludge) 7 wt.% olefins, 15 wt.% paraffins and 78 wt.% aromatics. The enhanced sludge is cleaner than the raw sludge, which could contain unwanted species that could deactivate the catalyst (i.e., heavy metals in raw sludge). With shape-selective H+ZSM5 as catalyst, low molecular weight hydrocarbons act as precursors to formation of aromatics. The eventual catalyst deactivation results to higher proportion of olefins and paraffins and lower aromatics fraction. Catalyst deactivation is probably present in the enhanced sludge as well, but is not as severe as in the raw sludge. Decarboxylation and decarbonylation are the two deoxygenation reactions observed for the process as indicated by high amount of CO2 and CO formation for both sludges. Cracking of both sludges also resulted to formation of acetonitrile. Acetonitrile is an important solvent in chemical syntheses that could contribute to the economics of this process [172,176].
List of Chemical Substances
Published in T.S.S. Dikshith, and Safety, 2016
Acetonitrile liquid or vapor is irritating to the skin, eyes, and respiratory tract. Acetonitrile has only a modest toxicity, but it can be metabolized in the body to hydrogen cyanide and thiocyanate. Acetonitrile causes delayed symptoms of poisoning (several hours after the exposure) that include, but are not limited to, salivation, nausea, vomiting, anxiety, confusion, hyperpnea, dyspnea, respiratory distress, disturbed pulse rate, unconsciousness, convulsions, and coma. Cases of acetonitrile poisoning in humans (or, more strictly, of cyanide poisoning after exposure to acetonitrile) are rare but not unknown, by inhalation, ingestion, and (possibly) by skin absorption. Repeated exposure to acetonitrile may cause headache, anorexia, dizziness, weakness, and macular, papular, or vesicular dermatitis.
Technical Implementation of Melt Crystallization
Published in Gerard F. Arkenbout, Melt Crystallization Technology, 2021
As was shown in Section 12.3, an interesting example in the field of fine chemicals is the upgrading of acetonitrile (Nienoord and Arkenbout, 1993). Acetonitrile is used as a solvent in the analytical technique called High Pressure Liquid Chromatography (HPLC). In the case of acetonitrile, the starting material already contained more than 99.5% of the main compound. High purity feed materials usually show a strong tendency to incrustate on the surface of the heat exchanger due to the limited contribution of the mass transfer resistance by which very low undercoolings already result in large growth rates on the surface. These incrustation problems can usually be reduced to a satisfactory level by adding an amount of an artificial impurity (2 to 5 %) to the material in the crystallizer during the startup time. In this way it was possible to grow acetonitrile crystals with favorable filtration properties from the beginning (Nienoord and Arkenbout, 1993). This problem is never met in the situation of steady-state operation because then the impurities are sufficiently concentrated in the crystallizer due to the high yield of over 90%, which is usually aimed at. When using a centrifuge to separate the crystals from the melt, the attainment of a high purity product usually requires a substantial amount of reflux melt to be used as wash-liquid. The consumed wash-liquid has to be recycled, e.g., to the crystallizer, after which it has to be crystallized again, reducing in this way the capacity of the installation. The product quality may easily be improved and the wash-liquid consumption decreased by adding a forced transport wash-column to the melt crystallization installation as indicated in Figure 14.1.
Green synthesis of benzimidazole derivatives under ultrasound irradiation using Cu-Schiff base complexes embedded over MCM-41 as efficient and reusable catalysts
Published in Journal of Coordination Chemistry, 2020
M. Bharathi, S. Indira, G. Vinoth, T. Mahalakshmi, E. Induja, K. Shanmuga Bharathi
We have also compared the activity of our catalysts with some previously reported homogeneous/heterogeneous catalysts (Table 6). The activity of our catalyst is much better than entries 2, 3, 5, 6 and 8. Although the catalysts in entries 1, 4, 7 and 9 gave similar or slightly higher yields when compared to our catalysts, they possess some crucial disadvantages. Our catalyst overcomes those disadvantages and has given better yields. In entry 1, TBAF (tetrabutylammonium fluoride) has been used as a homogeneous catalyst. Hence, it is very difficult to recover and reuse. Although NiEuFe2O4 has been used as a heterogeneous catalyst in entry 4, the cost of one of the reactants (rare earth europium salt) is much higher than that of the simple copper acetate, that we have used. Moreover, the calcination of their catalyst required much-elevated temperature (800 °C) over our MCM-41 (550 °C). In entries 7 and 9, heterogeneous catalysts AlKIT in acetonitrile under reflux for 4 h and Co/SBA-15 in ethanol at 60 °C for 4 h were used, respectively. From an environmental perspective, acetonitrile is not a green solvent [49]. Our catalysts give the same/competitive yield by using alcohols (ethanol/methanol) as solvents, in a shorter reaction time of 90 min under ultrasonic irradiation.