Sieving di-branched from mono-branched and linear alkanes using ZIF-8: experimental proof and theoretical explanation.

We study the adsorption equilibrium isotherms and differential heats of adsorption of hexane isomers on the zeolitic imidazolate framework ZIF-8. The studies are carried out at 373 K using a manometric set-up combined with a micro-calorimeter. We see that the Langmuir model describes well the isotherms for all four isomers (n-hexane, 2-methylpentane, 2,2-dimethylbutane and 2,3-dimethylbutane). The linear and mono-branched isomers adsorb well, but 2,2-dimethylbutane is totally excluded. Plotting the differential heat of adsorption against the loading shows an initial plateau for n-hexane and 2-methylpentane. This is followed by a slow rise, indicating adsorbate-adsorbate interactions. For the di-branched isomers the differential heat of adsorption decreases with loading. To gain further insight, we ran molecular simulations using the grand-canonical Monte Carlo approach. Comparing the simulation and the experimental results shows that the ZIF framework model requires blocking of the cages, since 2,2-dimethylbutane cannot fit through the sodalite-type windows. Practically speaking, this means that ZIF-8 is a highly promising candidate for enhancing gasoline octane numbers at 373 K, as it can separate 2,2-dimethylbutane and 2,3-dimethylbutane from 2-methylpentane. Our results prove the potential of ZIF-8 as a new adsorbent that can be employed in the upgrade of the Total Isomerization Process for the production of high octane number gasoline, by blending di-branched alkanes in the gasoline.

Reuse of wastewaters on dyeing of polyester fabric with encapsulated disperse dye.

The textile industry can benefit from the use of microcapsules, both adding value to products through the production of technical or functional textiles and improving the processes in the production chain. Some applications have been widely explored in academic research, but many are not feasible for use in industrial scale. Thus, the aim of this study was to develop consistent and efficient methodologies for the encapsulation of active compounds commonly used in the textile industry, employing materials which are viable for large-scale application. In this study, polyurethane-urea microcapsules were formulated by interfacial polymerization and encapsulated with C.I Disperse Blue 60 for the dyeing of polyester fabric without the use of dispersing agents and other auxiliaries. The dyeing was carried out in a high temperature dyeing machine with a very simple dyebath, in which there are only dissolved dye molecules, microencapsulated dyes and the fabric. Additionally, the dyebath wastewaters were reused on a further dyeing as 100% bathwater and mixed with 50% distilled water. Colorimetric measurements show excellent colour removal in both samples.