A fundamental approach to separate azeotropic mixtures by tuning the phase behavior using pressurized CO2 as a tunable solvent was studied. Following this new process concept, two process variants were put forward to separate aqueous pressure-insensitive and pressure-sensitive azeotropic mixtures. The two process variants were studied in process simulations, and the potential was evaluated by comparison with a conventional pressure-swing distillation process for the acetonitrile–water system. The new process shows significant potential to reduce the separation costs by 30.5% up to 68.9% for a broad variety of mixtures with water fractions in the range of 0.1 ≤ xH2O ≤ 0.9. Thus, these results clearly indicate that the novel fundamental separation approach is a promising alternative to conventional processes for the separation of azeotropic mixtures.

An indirect hydration process route for the production of cyclohexanol was proposed by Steyer et al., which uses formic acid as a reactive entrainer (Steyer, F.; Freund, H.; Sundmacher, K. Ind. Eng. Chem. Res. 2008, 47, 9581−9587; Steyer, F.; Sundmacher, K. Ind. Eng. Chem. Res. 2007, 46, 1099–1104). This route overcomes several limitations of the conventional Asahi process for cyclohexene hydration to cyclohexanol (Steyer, F.; Sundmacher, K. Ind. Eng. Chem. Res. 2007, 46, 1099−1104; Mitsui, O.; Fukuoka, Y. Process for producing cyclic alcohol. U.S. Patent 4,588,846, 1986; Ishida, H. Catal. Surv. Jpn. 1997, 1, 241–246; Ishida, H.; Fukuoka, Y.; Mitsui, O.; Köono, M. Liquid-Phase Hydration of Cyclohexane with Highly Silicious Zeolities. In Zeolites and Microporous Crystals: Proceedings of the International Symposium on Zeolites and Microporous Crystals, Nagoya, August 22–25, 1993; Hattori, T., Yashima, T., Eds.; Studies in Surface Science and Catalysis, Vol. 83; Elsevier: Tokyo, NY, 1994; pp 473–480). A coupled-column reactive distillation process concept, developed earlier in our group (Kumar, R.; Katariya, A.; Freund, H.; Sundmacher, K. Org. Process Res. Dev. 2011, 15, 527−529; Katariya, A.; Freund, H.; Sundmacher, K. Ind. Eng. Chem. Res. 2009, 48, 9534–9545; Freund, H.; Katariya, A.; Kumar, R.; Steyer, F.; Sundmacher, K. DGMK Tagungsber. 2007, 2, 237–239), is feasible, but the energy consumption is very high, and the process concept is limited by multiple steady states with a narrow operating window. There is a need to develop other promising process options. In this direction the present work analyses different process concepts and discusses in detail the challenges involved. Various process options were developed and analyzed. Dedicated experiments were carried out in order to ensure the validity of the kinetic model at a wide range of process conditions. Long-time batch experiments provided an accurate estimation of the heat of formation of cyclohexylformate. The developed process concepts are compared and evaluated with respect to the benchmark Asahi process. As an important indicator of the economic viability, the energy consumption is analyzed.

Models utilizing cubic equation of state and excess Gibbs free energy-based mixing rules (CEoS/GE) were used for predicting the multicomponent VLE phase behavior involving CO2-expanded liquids. Four such models were selected out of 36 models (four CEoS in conjunction with nine mixing rules each) and evaluated with regard to their predictive capability using 14 systems, including 12 sub-systems (eight ternary systems, three quaternary systems and one quinary system) of 1-octene hydroformylation in CO2-expanded acetone (with the components H2, CO, CO2, 1-octene, n-nonanal, and acetone), a CO2-expanded toluene ternary system and a CO2-expanded acetonitrile ternary system. Model discrimination was based on their relative abilities to predict experimental VLE data generated within this work (ternary, quaternary or quinary systems with various combinations of H2, CO, CO2, 1-octene or n-nonanal) and from the literature. The results indicate that the CEoS/GE modeling approach is successful in predicting the phase behavior of the 14 investigated CO2-expanded liquid systems. The selected models are expected to be useful in the rational selection of CO2-expanded liquids and operating conditions (p & T) for optimal performance of reaction and/or separation units.Graphical abstractHighlights► Investigation of 1-octene hydroformylation in CO2-expanded liquid systems. ► Phase behavior modeling of multicomponent CO2-expanded liquid systems using CEoS/GE models. ► Successful prediction of the VLE of ten ternary systems, three quaternary systems and one quinary system, validated by experimental data. ► CEoS/GE model as efficient tool for the prediction of multicomponent phase behavior of CO2-expanded liquid systems especially when experimental data is limited.

A new, two-step process concept for the production of cyclohexanol by indirect hydration of cyclohexene using formic acid as a reactive entrainer is suggested, and its principle technical feasibility is demonstrated. The first step of this process is based on an ester formation reaction of cyclohexene with formic acid. This reaction was carried out in a mini plant stainless steel catalytic distillation column of 2.35 m height. The column was packed with noncatalytic structured packings (SULZER-DX) and catalytic structured packings (KATAPAK-S). The experiments were conducted under low-pressure conditions (<0.6 bar) to avoid formic acid decomposition. Concentration and temperature profiles were obtained under steady-state conditions. Up to 98.3% conversion of cyclohexene and 75.5 mol % ester concentration in the bottom product of the column was obtained. In a similar manner, the second step of the process, i.e. the hydrolysis of the cyclohexyl formate formed in the first step, was investigated experimentally in a continuous catalytic distillation column under low-pressure conditions (<0.4 bar). Important process design parameters such as the feed mole ratio of the reactants, the reboiler duty, the feed flow rate, and the column pressure were investigated with regard to their effect on the cyclohexene conversion and the purity of the bottom product. Furthermore, the experimental data were compared with results obtained from steady-state simulations of the catalytic distillation process.

The (vapour + liquid) equilibria (VLE) and (vapour + liquid + liquid) equilibria (VLLE) binary data from literature were correlated using the Peng–Robinson (PR) equation of state (EoS) with the Wong–Sandler mixing rule (WS). Two group contribution activity models were used in the PRWS: UNIFAC–PSRK and UNIFAC–Lby. The systems were successfully extrapolated from the binary systems to ternary and quaternary systems. Results indicate that the PRWS–UNIFAC–PSRK generally displays a better performance than the PRWS–UNIFAC–Lby.Highlights► Phase behaviour modelling of H2O–MeOH–DME under pressurized CO2 (anti-solvent) using PRWS. ► PRWS–UNIFAC–PSRK has better performance than PRWS–UNIFAC–Lby in general. ► Reliable to extend the VLE and VLLE phase behaviour from binary to multicomponent systems. ► Successful prediction of the VLE and VLLE of binary, ternary, and quaternary systems. ► Potential to apply the model for designing new DME separation process.

In this contribution, a methodology for the optimal design of chemical reactors based on the best reaction route in the thermodynamic state space is proposed. This route is obtained by tracking a fluid element on its way through the reactor and manipulating the fluxes into this element. Instead of choosing the reactor design a priori and optimizing the free parameters of the chosen reactor setup, an innovative reactor design is developed based on the optimal flux profiles. Besides classical reactor concepts, this methodology is suited to investigate the potential of different process intensification options such as integration of reaction, cooling and separation in a single apparatus, or the application of high interface areas for heat and mass transfer. The methodology is exemplarily illustrated for the development of a new SO2 oxidation reactor. The residence time as an example for a meaningful objective is minimized, and a reduction of 69% compared to the optimized technical reference case is achieved.

In this work, a recently proposed multi-level reactor design methodology (Peschel et al., 2010) is extended and applied for the optimal design of an ethylene oxide reactor. In a first step, the optimal reaction route is calculated taking various process intensification concepts into account. The potential of each reaction concept can be efficiently quantified, which is the economic basis for the design of advanced reactors. Based on these results, a promising concept is further investigated and a technical reactor is designed. As an extension to the design method, reactor design criteria for external and internal heat and mass transfer limitations are directly included in the optimization approach in order to design the catalyst packing. The derived reactor concept is investigated with a detailed 2D reactor model accounting for radial concentration and temperature gradients in addition to a radial velocity profile.The example considered in this work is the production of ethylene oxide which is one of the most important bulk chemicals. Due to the high ethylene costs, the selectivity is the main factor for the economics of the process. A membrane reactor with an advanced cooling strategy is proposed as best technical reactor. With this reactor design it is possible to increase the selectivity of the ethylene epoxidation by approximately 3% compared to an optimized reference case.Highlights► Best reactor concept for the maximization of ethylene oxide selectivity is derived. ► Design methodology is suited to derive classical and innovative reaction concepts. ► Membrane reactor with dosing ethylene and advanced cooling strategy is optimal. ► Design criteria for external and internal heat and mass transfer are considered. ► Validation of the derived reactor design by optimizing a 2D radial dispersion model.

Author-Highlights•Model-based method to determine best reaction concept within the overall process for multiphase systems.•Apparatus independent model of reaction system yields optimal reaction route as basis for reactor design.•Detailed process model for the hydroformylation of 1-dodecene in a thermomorphic solvent system.•Minimization of production costs considering costs for raw material, utilities, and depreciation.In complex chemical processes optimizing the reactor with respect to a stand-alone reactor performance criterium such as product selectivity does not necessarily yield the best process-wide reaction concept. Especially in case of multiphase reaction systems, which often involve complex reaction networks, nonideal phase behavior and multiple recycles, reactor and process have to be optimized simultaneously since the reactor affects the separation units and vice versa. In order to derive the process-wide optimal reaction concept in combination with optimal process parameters, a systematic optimization procedure based on a large scale optimization problem constrained by a system of differential algebraic equations (DAE) is presented. The optimization problem contains a detailed model of the reaction section, a process model describing the other units of the process, and models for operational and fixed costs. The solution of the optimization is a set of process parameters and optimal profiles of heat and material fluxes over the reaction coordinate which minimize the production costs. The method is exemplified on the rhodium catalyzed hydroformylation of 1-dodecene in a thermomorphic solvent system.