The fractionation of crude-oil mixtures through distillation is a large-scale, energy-intensive process. Membrane materials can avoid phase changes in such mixtures and thereby reduce the energy intensity of these thermal separations. With this application in mind, we created spirocyclic polymers with N-aryl bonds that demonstrated noninterconnected microporosity in the absence of ladder linkages. The resulting glassy polymer membranes demonstrated nonthermal membrane fractionation of light crude oil through a combination of class- and size-based “sorting” of molecules. We observed an enrichment of molecules lighter than 170 daltons corresponding to a carbon number of 12 or a boiling point less than 200°C in the permeate. Such scalable, selective membranes offer potential for the hybridization of energy-efficient technology with conventional processes such as distillation.

Membranes with high selectivity offer an attractive route to molecular separations, where technologies such as distillation and chromatography are energy intensive. However, it remains challenging to fine tune the structure and porosity in membranes, particularly to separate molecules of similar size. Here, we report a process for producing composite membranes that comprise crystalline porous organic cage films fabricated by interfacial synthesis on a polyacrylonitrile support. These membranes exhibit ultrafast solvent permeance and high rejection of organic dyes with molecular weights over 600 g mol−1. The crystalline cage film is dynamic, and its pore aperture can be switched in methanol to generate larger pores that provide increased methanol permeance and higher molecular weight cut-offs (1,400 g mol−1). By varying the water/methanol ratio, the film can be switched between two phases that have different selectivities, such that a single, ‘smart’ crystalline membrane can perform graded molecular sieving. We exemplify this by separating three organic dyes in a single-stage, single-membrane process.

Three imine-linked covalent organic framework (COF) films are incorporated as active layers into separate thin-film composite (TFC) membranes and tested for their ability to reject an organic pollutant surrogate and salt from water. The synthesized membranes consist of a polyacrylonitrile (PAN) support and a TAPB-PDA-H, TAPB-PDA-Me, or TAPB-PDA-Et COF thin film. The latter two COFs direct six methyl and ethyl substituents per tiled hexagon into the pores, respectively, while maintaining the same topology across the series. These substituents decrease the effective pore size of the COF compared to the parent TAPB-PDA-H COF. The TFC TAPB-PDA-Me membrane rejects Rhodamine-WT (R-WT) dye and NaCl better than the TFC TAPB-PDA-H membrane, and the TFC TAPB-PDA-Et membrane exhibits the best rejection overall. The solution-diffusion model used to analyze this permeation behavior indicates that there is a systematic difference in rejection as subsequent pendant groups are added to the interior of the COF pores. These findings demonstrate the concept of tuning the selectivity of COF membranes by systematically reducing the effective pore size within a given topology.

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A liquid–solid fluidized bed reactor was used to carry out sulfate reduction with a mixed culture of sulfate reducing bacteria. The bacteria were immobilized on porous glass beads. Stable fluidized bed operation with these biofilm‐coated beads was possible. The low specific gravity of the hydrated beads allowed operation at low liquid recirculation rates. H2S level in the reactor was controlled by N2 sparging, which also served as the location for liquid feed and removal. Ethanol was used as the electron donor/carbon source for the bacteria. Sulfate reduction rates up to 6.33 g sulfate L−1 day−1 were attained in the reactor at a hydraulic retention time of 5.1 h. The effect of hydraulic retention time and biomass loading on the beads, on reactor performance, and efficiency were examined. The efficiency of sulfate reduction increases considerably as the hydraulic retention increases, until the bacteria became very strongly substrate‐limited at 55h HRT. The effect of bead biomass loading on bed expansion at various liquid superficial velocities was studied. A model for the reactor was developed. Simulations of the continuous flow experiments indicate that the model can describe the system well, and thus could be used in the design/scale‐up of such reactors. The model suggests that a significant increase in the sulfate reduction capacity of the system is possible by increasing the volume of the bed relative to the total liquid volume of the system. © 2000 John Wiley & Sons, Inc. Biotechnol Bioeng 70: 370–380, 2000.

Herein, ao ne-pot liquid phase peptide synthesis featuring iterative addition of amino acids to a" nanostar" support, with organic solvent nanofiltration (OSN) for isolation of the growing peptide after each synthesis cycle is reported. Ac ycle consists of coupling,F moc removal, then sieving out of the reaction by-products via nanofiltration in areactor-separator,orsynthesizer apparatus where no phase or material transfers are required between cycles.T he threearmed and monodisperse nanostar facilitates both efficient nanofiltration and real-time reaction monitoring of each process cycle.T his enabled the synthesis of peptides more efficiently while retaining the full benefits of liquid phase synthesis.P EPSTAR was validated initially with the synthesis of enkephalin-like model penta-and decapeptides,t hen octreotate amide and finally octreotate.T he crude purities compared favorably to vendor produced samples from solid phase synthesis.

This paper describes ideas together with preliminary experimental results for applying solvent nanofiltration to liquid phase organic synthesis reactions. Membranes for organic solvent nanofiltration have only recently (during the 1990s) become available and, to date, have been applied primarily to food processing (vegetable oil processing, in particular) and refinery processes. Applications to organic synthesis, even at a laboratory feasibility level, are few. However, these membranes have great potential to improve the environmental performance of many liquid phase synthesis reactions by reducing the need for complex solvent handling operations. Examples that are shown to be feasible are solvent exchanges, where it is desired to swap a high molecular weight molecule from one solvent to another between separate stages in a complex synthesis, and recycle and reuse of homogeneous catalysts. In solvent exchanges, nanofiltration is shown to provide a fast and effective means of swapping from a high boiling point solvent to a solvent with a lower boiling point—this is a difficult operation by means of distillation. Solvent nanofiltration is shown to be able to separate two distinct types of homogeneous catalysts, phase transfer catalysts and organometallic catalysts, from their respective reaction products. In both cases the application of organic solvent nanofiltration allows several reuses of the same catalyst. Catalyst stability is shown to be an essential requirement for this technique to be effective. Finally, we present a discussion of scale‐up aspects including membrane flux and process economics.