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Benzene and cyclohexane (CYH) can be separated via extractive distillation using sulfolane (SULF) as entrainer. In this Article, the steady state of an extractive distillation system has been simulated using the RadFrac model in Aspen plus, and the controllability of this system with feed flow rate and feed composition disturbances has been studied in Aspen Dynamics. Sensitivity analysis is used to obtain optimal operation conditions. The common control scheme for extractive distillation is infeasible. Two control structures are demonstrated in this Article. Each control structure has three main temperature controllers, two in the extractive distillation column and one in entrainer recovery column. Although both control structures can solve all disturbance issues and maintain the product purities very close to the set points, the dynamic responses of initial control structure have large transient deviation when +20% feed flow rate disturbance is introduced, while the improved control structure can overcome this obstacle.

In this work, arbitrarily shaped multi-membrane hydrogels were successfully fabricated from gel-core templates using the layer-by-layer (LbL) method. Namely, the first gel membrane layer was formed around a gel-core template when the crosslinker loaded gel-core was soaked in a polysaccharide solution, and it was then ripened in a crosslinker solution, in which the crosslinker was loaded for the fabrication of the following layer. The formation and control of the gel membrane layer were studied in detail. The results indicated that a reasonably rapid crosslinking of the polysaccharide was essential for the successful preparation of a multi-membrane hydrogel, irrespective of chemical or physical crosslinking. The formation of a gel membrane layer was found to be controlled by the diffusion of the crosslinker. The chemically and the physically crosslinked multi-membrane hydrogels were characterized, and the chemically crosslinked chitosan multi-membrane hydrogel exhibited a unique sub-layered microstructure. The chitosan multi-membrane hydrogel which was sensitive to pH was fabricated using terephthalaldehyde as the crosslinker, and the hydrogel displayed LbL disintegration in acidic medium.Chondrocytes were cultivated in the presence of the multi-membrane hydrogel, and they could be easily attached to proliferate quickly. Because of the arbitrary shape, solid or hollow structure, pH sensitivity and biocompatibility, the polysaccharide multi-membrane hydrogels are promising materials for biomedical applications.

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