To realize large-scale CO 2 separation to prevent global warming, energy and space saving separation technologies are required. Flexible metal−organic frameworks (flexible MOFs) with gate-opening properties have been found to be promising adsorbents, but the unconventional sigmoidal shapes and hysteresis of the isotherms have hindered quantitative evaluation of their applications in separation processes. This paper is the first to evaluate ELM-11, a flexible MOF that exhibits sigmoidal isotherms with hysteresis, in a process model and quantify its advantages over a conventional adsorbent. Based on the experimental uptake data, isotherm models for adsorption and desorption were developed, and their parameters were estimated. The resulting isotherm models are incorporated into a rigorous dynamic model of partial differential algebraic equations (PDAEs) to simulate a vacuum pressure swing adsorption (VPSA) process to evaluate the process performance. Numerical challenges to solve the PDAEs, including sigmoidal and hysteresis isotherm models, were resolved with the proposed numerical approaches. Sensitivity analysis for feed pressure and temperature was performed to identify the optimal operating strategy. A comparison with a conventional adsorbent, zeolite 13X, showed that high selectivity and sigmoidal isotherms of ELM-11 give higher productivity and CO 2 product purity exceeding 99% without rinse and purge operations as well as lower power consumption for the compressor and vacuum pump.

No abstract

No abstract

No abstract

A solute was transferred from an aqueous solution to deionized water in a microchannel device with a rectangular channel of 200 lm × 200 lm. The two liquid layers flowed in parallel within the rectangular channel. After making contact in the channel, the layers were split into two streams through a knife-edge. The amount of solute transferred was determined by analyzing liquid samples taken from the outlet. Thus, conventional analytical instruments were readily available for obtaining the total concentration. Mass tansfer characteristics were examined through the measurement of diffusion coefficients for several solutes. Although the two liquids were carefully supplied at the same velocity, equal flow splitting was difficult to obtain. The unequal splitting led to scattering of the observed solute concentrations at a fixed supply flow rate. This could be a serious drawback as a mass tansfer device; however, a method was proposed to choose an appropriate value for equal splitting. The ratio of effluent flow rate of one liquid to another was changed intentionally. The solute concentration in the receiving liquid for the flow rate ratio of unity corresponds to the data for equal flow splitting. On the basis of the solute concentrations defined, the diffusion of benzoic acid was successfully analyzed using a conventional penetration model with a correction parameter. Furthermore, diffusion coefficients for sucrose and glycine were determined using the basic equation obtained with benzoic acid. The observed values compared fairly well with reported ones. The correction parameter expresses characteristics of the microchannel device; however, the physical picture is still unclear.