Two-Stripper/Flash/Distillation Column System Design, Operation, and Control for Separating 2‑Pentanone/4-Heptanone/Water Azeotropic Mixture via Navigating Residue Curve Maps and Balancing Total Annual Cost and Product Loss

A novel method for the synergetic production of 2-pentanone and 4-heptanone has been explored recently at the Institute of Coal Chemistry, Chinese Academy of Sciences (ICC, CAS). The collected mixture, containing mainly 2-pentanone/4-heptanone/water/carbon dioxide, presents heterogeneous azeotropes. The separation of this quaternary mixture is the main problem urgently to be effectively solved. In this work, a two-stripper/flash/column flow sheet is proposed to achieve the separation, in which the heterogeneity of the system is fully utilized by using an overhead vapor–liquid–liquid (VLL) flash. A general total annual cost (GTAC) for balancing total annual cost (TAC) and product loss (PL) is proposed as an optimization function, and several optimization sequences are presented to facilitate the optimization. Four candidate sequences (S1, S2, S3, and S4) are derived from <i>navigating</i> the ternary and residue curve maps, of which the S4 cuts the GTAC with a marked margin (83.9%) compared with the S1. The rigorous economic design and optimum operation of the flow sheet are further investigated in detail. Moreover, several control structures (TCS1, TCS2, and DTCS, CTCS, C&TCS) are successively explored with consideration of ordinary-purity and high-purity separations. Dynamic control shows that whereas the flow sheet can be controlled by controlling one tray temperature in each stripper/column for ordinary-purity separation, an expensive and high-maintenance online composition control should be considered for high-purity separation

Deep Eutectic Solvents: Green Solvents and Catalysts for the Preparation of Pyrazine Derivatives by Self-Condensation of d‑Glucosamine

Deep eutectic solvents (DESs) exhibit similar physicochemical properties to the ionic liquids. They are inexpensive, renewable, nontoxic, and environmentally benign solvents and have gradually attracted attention in several fields, for example, biorefinery. Here choline chloride-based DESs have been used as solvents and catalysts for the preparation of deoxyfructosazine (DOF) through a self-condensation reaction of d-glucosamine (GlcNH₂). The catalytic performances of a “green cocatalyst”, amino acids, and the reaction mechanism were also studied. The results displayed that choline chloride/urea was capable to convert GlcNH₂ efficiently, with a 13.5% yield of DOF at low temperature and with a short reaction time (100 °C, 150 min). Among the screened amino acids, arginine showed the highest activity and gave the highest yield of DOF (30.1%) under the optimized reaction conditions. Nuclear magnetic resonance (NMR) studies revealed a strong hydrogen bond interaction between GlcNH₂ and arginine. Moreover, a detectable intermediate, namely dihydrofructosazine, in the condensation of GlcNH₂ to DOF/fructosazine (FZ) was captured by in situ NMR technique