Recover and re-use of catalysts
Homogeneous catalysts are very efficient but expensive materials that are difficult to separate in an active form with conventional separation technology. They are generally large molecules that are well retained by OSN membranes, which allows them to be recovered and re-used in a production process.
Homogeneous catalysts have the potential to be used in many chemical processes. However, they are complex chemical structures, containing metals such as the platinum group species, which makes them very expensive to produce. In most cases, unless the catalyst can be recovered and re-used, the process economics do not favour the use of homogeneous catalysts and consequently homogeneous catalysts are not as widely used in industry as they potentially could be. Homogeneous catalysts are usually significantly larger than the reactants/products from the chemistry they catalyse and thus they are quite amenable to separation with OSN membranes. In fact, near quantitative recovery of homogeneous catalysts can be achieved with OSN membranes. Recovery of the intact catalyst has a very positive impact on the process economics. Evonik's range of DuraMem® and PuraMem® membranes can be used for homogeneous catalyst recovery.
Decolorization and polishing of products
In many cases, the output of a chemical reaction is not the product in pure form. There is a variety of unwanted compounds present that originate from side reactions or postreaction processing steps. These unwanted compounds lower the quality of the final product (undesired color, composition, density, melting and boiling point etc.) and have to be removed. When the MW of product and impurities differs OSN membrane can be successfully applied for the product purification.
Separation of paraffin waxes from lube oil
Lube oil dewaxing is an energy-intensive operation of an oil refinery involving the evaporation and condensation of large volumes of solvent. OSN membranes can be applied to reduce the energy consumption in this process.
Solvent dewaxing of raffinates from refinery distillation units to produce lube oil basestock is a well-known unit operation. It is an energy-intensive unit operation involving the evaporation and condensation of large volumes of solvent, typically a mixture of MEK and toluene. The MEK/toluene solvent mixture is selected to promote the crystallisation of paraffinic waxes for physical separation from the lube oil, which remains dissolved in the MEK/toluene mixture. Once the wax is removed, OSN membranes can be used to retain and concentrate the valuable lube oil dissolved in the MEK/toluene mixture and the essentially pure MEK/toluene mixture permeating the membrane can be returned to the front-end of the dewaxing operation for re-use. The filtration occurs at the chilled temperature (-10 to -20 degC) required for the crystallisation process. By applying OSN membranes, the energy requirement of the dewaxing process can be reduced significantly, as no phase change (evaporation and condensation) occurs. Furthermore, this OSN membrane-based approach can be used to optimise solvent flows in the dewaxing unit to maximise wax crystallisation and hence lube oil quality. Evonik's PuraMem® membranes are recommended for us in apolar solvents such MET/toluene.
Additive removal from light hydrocarbon
Large molecules (e.g. additives) are commonly used in processing light hydrocarbons. The large difference in molecular weight between the additive and the hydrocarbon makes the removal of the additive possible with PuraMem® series membranes. This is a low-energy approach to additive removal.