Experimental Measurement of Phase Equilibrium of Hydrate in Water + Ionic Liquid + CH₄ System

With the goal of discovering a more effective type of thermodynamic hydrate inhibitors (THIs), the phase equilibrium conditions of CH₄ hydrates were examined in the presence of morpholinium and piperidinium ionic liquids (ILs) at a mass fraction of 0.1. It was observed that the addition of ILs shifted the hydrate equilibrium conditions toward higher pressure and lower temperature compared with those of hydrates formed from pure water. Both cationic and anionic species influenced the equilibrium conditions of the CH₄ hydrate. The piperidinium ILs showed better inhibition effect than did the morpholinium ILs at the same species of counteranions. The result may be due to the more hydrophobic nature of piperidinium ILs, which have a higher affinity for CH₄ molecules. It was also seen that the inhibition effect of BF₄^– ions was stronger than that of Br^– ions for both piperidinium and morpholinium ILs. Thus, the inhibition effect became stronger in the order: <i>N</i>-ethyl-<i>N</i>-methylpiperidinium tetrafluoroborate ([EMPip]­[BF₄]) > <i>N</i>-ethyl-<i>N</i>-methylpiperidinium bromide ([EMPip]­[Br]) > <i>N</i>-ethyl-<i>N</i>-methylmorpholinium tetrafluoroborate ([EMMor]­[BF₄]) > <i>N</i>-ethyl-<i>N</i>-methylmorpholinium bromide ([EMMor]­[Br]). The best among these ILs had inhibition effectiveness comparable with ethylene glycol and triethylene glycol, which are used commercially as THIs

Adsorption of Pyruvic and Succinic Acid by Amine-Functionalized SBA-15 for the Purification of Succinic Acid from Fermentation Broth

In this study, mesoporous silica SBA-15 was functionalized with primary, secondary, and tertiary amino-functional silanes onto the channel walls using a postsynthesis method as a first attempt to purify succinic acid from a fermentation broth. Ordered mesostructures of pristine and functionalized SBA-15 were evaluated using small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM), and N2 adsorption/desorption isotherms. 13C and 29Si magic-angle spinning (MAS) nuclear magnetic resonance (NMR) with 1H cross-polarization (CP-MAS) and thermogravimetric analysis (TGA) revealed that amino-functional silanes were covalently bound to the active layer of pore walls. The distribution and accessibility of amine groups were characterized by scanning transmission electron microscopy (STEM), elemental analysis, and conductivity measurements. Adsorption isotherms were analyzed using the Sips model, simultaneously obtaining the temperature dependence of isotherms derived from the isosteric heats of adsorption. Pyruvic acid had higher adsorption capacities than succinic acid on amine-functionalized SBA-15, resulting in the selective adsorption of pyruvic acid from binary acid solution. In particular, SBA-15 functionalized with primary amino silane obtained higher selectivity on pyruvic acid compared to that of other amine-functionalized SBA-15. The adsorption capacities of pyruvic acid at equilibrium are dependent on the basicity and distribution of amino silanes. The isosteric heats between 10 and 100 kJ/mol and desorption energy between 1 and 10 kJ/mol revealed that the adsorption of pyruvic and succinic acid originated from the formation of an acid−amine complex via hydrogen bonding. It is proposed that the amine functionalization of ordered mesoporous solids provides a simple and effective method of separating or purifying useful carboxylic acids