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Item type:Publication, Access status: without files , Evaluation of membrane-assisted hybrid processes for the separation of a tetrahydrofuran-methanol-water mixtureThe combination of pervaporation (PV) and distillation provide considerable potential for the separation of azeotropic multicomponent mixtures. However, only a proper techno-economic evaluation of these processes compared to a reference process enables a reliable evaluation of benefits. Within this work, the potential of a PV-assisted distillation process is evaluated for the mixture of tetrahydrofuran methanol and water compared to a heat-integrated pressure-swing distillation process. Since initial evaluations reveal a significant potential of the PV-assisted processes regarding the required energy demand, experimental investigations of three polymeric and two inorganic membranes were conducted. A detailed characterization of the most promising membranes PERVAP™ 4155–40 and Hybrid Silica HybSi® AR was performed, and the latter one provided the highest permeance and selectivity. Based on the derived flux models, an economical optimization was performed. Despite the energy-benefits of the PV-assisted processes, the reference process was still evaluated more favorable under the considered framework, mainly caused by high investment and cooling costs. The current study illustrates the benefits of a tight integration of model-based process design and experimental investigations. Despite possible energy savings and promising performance metrics of the membrane, an assessment of the techno-economic performance of these processes is of major importance to identify applications.Publicationtype: Journal Article77 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Model-based evaluation of a membrane-assisted hybrid extraction-distillation process for energy and cost-efficient purification of diluted aqueous streams(2021-08-31); ; The concentration of diluted aqueous streams is an important task in bio-based production processes, as well as the recovery of valuable impurities prior to wastewater purification. Affinity-based separation processes, such as liquid-liquid extraction, are generally considered favorable to distillation, which however is regularly used for solvent recovery. To reduce the effort for a solvent-based extraction and improve the economic performance, an extended hybrid process concept is considered, which exploits energy-efficient pressure-driven membrane separations, i.e. reverse osmosis or nanofiltration, for preconcentration. The current work presents a systematic evaluation of this process for purification of a diluted aqueous γ-valerolactone stream, considering two solvents. The potential economic savings are first evaluated in a model-based assessment prior to an experimental screening of suitable membranes. Finally, a detailed economic evaluation of the processes is conducted by an optimization-based process design. The proposed approach allows to quickly identify a considerable saving potential for the membrane-assisted hybrid process.Publicationtype: Journal Article78 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Continuous co-product separation by organic solvent nanofiltration for the hydroaminomethylation in a thermomorphic multiphase system(2021-04-01); ; ; ; While homogeneous catalysts can be used to efficiently produce intermediate and specialty chemicals, the separation of the precious catalyst from products, by-products or co-products can be a major challenge. Consequently, novel processes need to be developed to effectively separate and reuse the active catalyst, while avoiding accumulation of the various reaction products. Therefore, this work presents the development and demonstration of a hybrid, continuous reaction and separation process for the catalytic auto-tandem hydroaminomethylation (HAM) reaction. Herein, long-chain alkenes are converted to valuable higher aliphatic amines with high atom economy, while producing only water as co-product. Since the HAM is a rhodium-catalyzed reaction, a thermomorphic multiphase system is used as an integrated catalyst recycling strategy, which is further combined with a membrane-based separation of the co-product via organic solvent nanofiltration. Based on initial screening of various membranes and investigation on the water influence on the phase separation after the reactor, the full process for the HAM of 1-decene with diethylamine with separation of the co-product water was operated continuously for 75 h in a miniplant. The continuous operation of the process successfully demonstrated stable process operation, avoiding a steady accumulation of water while maintaining high catalyst rejection between 97% and 99.3%. The overall leaching of rhodium was kept below 3% of the total amount supplied. This corresponds to a loss of only 11 mg of catalyst per kg of product.Publicationtype: Journal Article161 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Conceptual study of co-product separation from catalyst-rich recycle streams in thermomorphic multiphase systems by OSNHomogeneous transition metal catalysts allow for high selectivity at mild reaction conditions. However, very high recoveries of the precious catalyst are decisive for the development of economic processes, especially in case of reactions with an atom economy below 100% since co-products and their potential accumulation have to be considered. To address this issue, an innovative process concept is investigated, which exploits thermomorphic multiphase systems combined with organic solvent nanofiltration for homogeneous catalyst recovery and co-product removal. In this concept, the reaction takes place at elevated temperature in a homogeneous liquid phase, while the reactor effluent is cooled down, inducing a phase split. This allows for the separation of a product-rich non-polar and a catalyst-rich polar phase that is recycled into the reactor. The current article investigates this concept considering a reductive amination reaction as case study based on an experimental membrane screening and a model-based evaluation. DuraMem 150 (T1) proved to be the best membrane for all tested solvents as catalyst ligand rejections higher than 99% and a removal of the co-product water were achieved. The model-based evaluation indicated a final OSN-process of three stages for the solvent methanol and the requirement of a subsequent solvent recovery that is realized by distillation.Publicationtype: Journal Article83 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Efficient optimization-based design of energy-integrated azeotropic distillation processes(2020-02-02); ; ; The separation of azeotropic mixtures is frequently performed by extractive or heteroazeotropic distillation processes. The design of these processes requires careful selection of a suitable solvent and is specifically challenging since feasibility and optimality of the processes require consideration of the closed loop design including solvent recovery. Consideration of energy integration further complicates the design task and is usually conducted as post-evaluation step. The current publication proposes an efficient optimization-based design approach, which allows for the direct evaluation of several energy-integrated process concepts, while significantly reducing manual effort and computational time through a polylithic modeling and solution approach. The developed approach allows for a simultaneous evaluation of solvent selection and energy integration and is illustrated for different case studies, including the evaluation extractive and heteroazeotropic distillation for the dehydration of ethanol, as well as the evaluation of multiple solvent candidates for the extractive distillation of acetone and methanol.Publicationtype: Journal Article44 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Efficient optimization-based design of energy-integrated distillation processes(2019-10-04); While providing only low thermodynamic efficiency, distillation is still the default option for the separation of liquid mixtures in the chemical industry. Fortunately, various concepts for energy integration have been proposed to improve the energy efficiency. Yet, the selection of the cost-optimal process among the potential alternatives is tedious, as the performance of the different options has to be evaluated for each specific separation. Thus, efficient means for rigorous design are required, that allow for a comparison of the competing alternatives. For this purpose, a computationally efficient method for a rigorous optimization-based design of various energy-integrated distillation sequences is proposed in the current article and demonstrated for 16 different process variants for the separation of a multicomponent mixture into three product streams. The application to three case studies, including the separation of ideal, non-ideal and azeotropic mixtures, demonstrates its computational efficiency and effectiveness in identifying economically attractive energy-integrated distillation processes.Publicationtype: Journal Article39