Correlations for Easy Calculation of the Critical Coalescence Concentration (CCC) of Simple Frothers

Can the critical coalescence concentration (CCC) of the flotation frothers be predictable? What is the relation between their molecular structure and their CCC values? A literature survey found specific correlations between the hydrophilic-lipophilic balances (HLB) and HLB/Mw (where Mw stands for the molecular mass) of homologue series of frothers and their CCC values, but the results are invalid when the molecule’s functional groups change. For this reason, 37 frothers with known values of CCC were analyzed. The CCC values of seven frothers were determined, and the rest were taken from the literature. The frothers were subdivided in homologue series with an increasing number of the carbon atoms with an account for the type and the location of the functional group, thus deriving three types of correlations lnCCC = f(HLB) applicable for: (i) alcohols; (ii) propylene glycols alkyl ethers and propylene glycols; (iii) ethylene glycols alkyl ethers. The average accuracy of these correlations between CCC and HLB is 93%.

Thermodynamic Analysis of Autothermal Reforming of Oxygenated Hydrocarbons at Thermoneutral Condition for Hydrogen Production

The thermodynamic analysis of autothermal reforming of homologue series consisted of ethanol, ethylene glycol, propylene glycol and glycerol representing oxygenated hydrocarbons were studied. The main investigation was to compare the effect of thermoneutral condition where no external air/oxygen supplied for the reaction to sustain and controlled amount of air/oxygen supplied. It was found that the higher number of oxygen atoms in these homologues molecule, the higher tendency of the reaction to be sustained at the desired temperature, and thus it only requires lesser amount of air for heating. The hydrogen selectivity however depends on the ratio of hydrogen atoms with respect to the oxygen atoms in each molecule. The presence of air however, though providing extra heating to the reactor, is offset by a lower hydrogen production.

Conformational study of internally retrograde and quasi-retrograde molecules — An ab initio and DFT study

A conformational study of the symmetrical and nonsymmetrical homologue series was carried out. In this study, ab initio (RHF/3-21G and RHF/6-31G(d)) and density functional theory (B3LYP/6-31G(d)) calculations were performed. The presence of two symmetrical aromatic systems (identical or not) reduces notably the conformational possibilities of these compounds. Our results indicate that RHF/3-21G calculations are sufficient to use in a preliminary form. However, from our results it is prudent to use this technique only for a preliminary or exploratory conformational analysis. Thus, at least, the HF level of theory in conjunction with more extended basis sets and the inclusion of electron correlation appear to be necessary to confirm critical points at the potential energy hyper surfaces (PEHSs) and to assign the conformational preferences of these compounds. In the present paper, we report a complete and comprehensive picture of the conformational intricacies of the compounds with a small flexible connecting chain (n = 1–5). In addition, an "educated guess" for the conformational behaviour of large-size homologues (n = 6–10) is also reported.Key words: ab initio and DFT calculations, conformational study, homologue series.