BMC Chemical Engineering最新文献

Ionic liquids (ILs) have been recently considered as potential entrainers for extractive distillation. The use of ILs may affect the vapor-liquid properties to aid the separation of azeotropic mixtures. In particular, their effectiveness has been observed for ethanol dehydration, showing promising perspectives for their industrial implementation. However, there is still a lack of information about the effect of ILs on the system controllability. The objective of this work is to explore the dynamic implications of the use of two types of ionic liquids on the ethanol dehydration process. An equimolar feed mixture of ethanol and water was considered, and different IL concentrations were tested. The results show that changing the IL concentration affect the degree of stabilization of the product stream, even when smooth dynamic responses were in many cases observed.

Living organisms in analogy with chemical factories use simple molecules such as sugars to produce a variety of compounds which are necessary for sustaining life and some of which are also commercially valuable. The metabolisms of simple (such as bacteria) and higher organisms (such as plants) alike can be exploited to convert low value inputs into high value outputs. Unlike conventional chemical factories, microbial production chassis are not necessarily tuned for a single product overproduction. Despite the same end goal, metabolic and industrial engineers rely on different techniques for achieving productivity goals. Metabolic engineers cannot affect reaction rates by manipulating pressure and temperature, instead they have at their disposal a range of enzymes and transcriptional and translational processes to optimize accordingly. In this review, we first highlight how various analytical approaches used in metabolic engineering and synthetic biology are related to concepts developed in systems and control engineering. Specifically, how algorithmic concepts derived in operations research can help explain the structure and organization of metabolic networks. Finally, we consider the future directions and challenges faced by the field of metabolic network modeling and the possible contributions of concepts drawn from the classical fields of chemical and control engineering. The aim of the review is to offer a current perspective of metabolic engineering and all that it entails without requiring specialized knowledge of bioinformatics or systems biology.

Recent advances in metabolic engineering have enabled the production of chemicals via bio-conversion using microbes. However, downstream separation accounts for 60–80% of the total production cost in many cases. Previous work on microbial production of extracellular chemicals has been mainly restricted to microbiology, biochemistry, metabolomics, or techno-economic analysis for specific product examples such as succinic acid, xanthan gum, lycopene, etc. In these studies, microbial production and separation technologies were selected apriori without considering any competing alternatives. However, technology selection in downstream separation and purification processes can have a major impact on the overall costs, product recovery, and purity. To this end, we apply a superstructure optimization based framework that enables the identification of critical technologies and their associated parameters in the synthesis and analysis of separation processes for extracellular chemicals generated from microbial conversions. We divide extracellular chemicals into three categories based on their physical properties, such as water solubility, physical state, relative density, volatility, etc. We analyze three major extracellular product categories (insoluble light, insoluble heavy and soluble) in detail and provide suggestions for additional product categories through extension of our analysis framework. The proposed analysis and results provide significant insights for technology selection and enable streamlined decision making when faced with any microbial product that is released extracellularly. The parameter variability analysis for the product as well as the associated technologies and comparison with novel alternatives is a key feature which forms the basis for designing better bioseparation strategies that have potential for commercial scalability and can compete with traditional chemical production methods.

The recent roadmap of SPIRE initiative includes the development of “new separation, extraction and pre-treatment technologies” as one of the “key actions” for boosting sustainability, enhancing the availability and quality of existing resources. Membrane condenser is an innovative technology that was recently investigated for the recovery of water vapor for waste gaseous streams, such as flue gas, biogas, cooling tower plumes, etc. Recently, it has been also proposed as pre-treatment unit for the reduction and control of contaminants in waste gaseous streams (SO_x and NO_x, VOCs, H₂S, NH₃, siloxanes, halides, particulates, organic pollutants).

This perspective article reports recent progresses in the applications of the membrane condenser in the treatment of various gaseous streams for water recovery and contaminant control. After an overview of the operating principle, the membranes used, and the main results achieved, the work also proposes the role of this technology as pre-treatment stage to other separation technologies. The potentialities of the technology are also discussed aspiring to pave the way towards the development of an innovative technology where membrane condenser can cover a key role in redesigning the whole upgrading process.

The non-inertive-feedback thermofluidic engine (NIFTE) is a two-phase thermofluidic oscillator capable of utilizing heat supplied at a steady temperature to induce persistent thermal-fluid oscillations. The NIFTE is appealing in its simplicity and ability to operate across small temperature differences, reported as low as 30 ^°C in early prototypes. But it is also expected that the NIFTE will exhibit low efficiencies relative to conventional heat recovery technologies that target higher-grade heat conversion. Mathematical modeling can help assess the full potential of the NIFTE technology.

Our analysis is based on a nonlinear model of the NIFTE, which we extend to encompass irreversible thermal losses. Both models predict that a NIFTE may exhibit multiple cyclic steady states (CSS) for certain design configurations, either stable or unstable, a behavior that had never been hypothesized. A parametric analysis of the main design parameters of the NIFTE is then performed for both models. The results confirm that failure to include the irreversible thermal losses in the NIFTE model can grossly overpredict its performance, especially over extended parameter domains. Lastly, we use the NIFTE model with irreversible thermal losses to assess the optimization potential of this technology by conducting a multi-objective optimization. Our results reveal that most of the optimization potential is achievable via targeted modifications of three design parameters only. The Pareto frontier between exergetic efficiency and power output is also found to be highly sensitive to these optimized parameters.

The NIFTE is of practical relevance to a range of applications, including the development of solar-driven pumps to support small-holder irrigation in the developing world. Given its low capital cost, potential improvements greater than 50% in efficiency or power output are significant for the uptake of this technology. Conventional heat recovery technologies are known to have higher efficiencies than those reported in this work, but they also have more complex designs and operations, higher capital costs, and may not even be feasible for the temperature differences considered herein. Future work should focus on confirming this model-based assessment via dedicated experimental campaigns and on investigating design modifications to mitigate irreversible thermal losses.

Pervaporation (PV), a membrane process in which the feed is a liquid mixture and the permeate is removed as a vapour, offers an energy-efficient alternative to conventional separation processes such as distillation, and can be applied to mixtures that are difficult to separate, such as azeotropes. Here the principles of pervaporation and its industrial applications are outlined. Two classes of material that show promise for use in PV membranes are described: Polymers of intrinsic microporosity (PIMs) and 2D materials such as graphene. The literature regarding PV utilizing the prototypical PIM (PIM-1) and it hydrophilic hydrolysed form (cPIM-1) is reviewed. Self-standing PIM-1 membranes give competitive results compared to other membranes reported in the literature for the separation of alcohols and other volatile organic compounds from aqueous solution, and for organic/organic separations such as methanol/ethylene glycol and dimethyl carbonate/methanol mixtures. Blends of cPIM-1 with conventional polymers improve the flux for dehydration of alcohols. The incorporation of fillers, such as functionalised graphene-like fillers, into PIM-1 to form mixed matrix membranes can enhance the separation performance. Thin film composite (TFC) membranes enable very high fluxes to be achieved when a suitable support with high surface porosity is utilised. When functionalised graphene-like fillers are introduced into the selective layer of a TFC membrane, the lateral size of the flakes needs to be carefully controlled. There is a wide range of PIMs and 2D materials yet to be explored for PV applications, which offer potential to create bespoke membranes for a wide variety of organic/aqueous and organic/organic separations.

Chromatography with step changes in modulator properties such as pH, solvent strength, or ionic strength to facilitate desorption is widely used in the purification of proteins and other chemicals. Step changes can be incorporated into non-isocratic simulated moving beds; however, applications of such systems have been limited because one must select numerous operating parameters (zone velocities and port velocities). The operating parameters must be selected correctly to achieve high purity, yield, and productivity and depend on a large number of system parameters (feed, material, and equipment parameters). To address this challenge, the Standing-Wave Design method has been developed for three-zone, open-loop, non-isocratic, and non-ideal systems with both linear and non-linear isotherms. This method directly links the operating parameters to the system parameters. The operating parameters can be solved from a set of algebraic equations. In contrast, for non-ideal systems, previous literature design methods require extensive search using rate model simulations, which involve solving partial differential equations at each grid point. Two examples were tested for the effectiveness of the SWD method using rate model simulations. In both examples, sorbent productivity was pressure limited. Higher pressure sorbents or equipment would lead to higher sorbent productivity. In the first example, a 3-zone open-loop simulated moving bed was designed and compared with an optimal batch step-wise elution system. Compared to batch step-wise elution systems, the simulations showed that the 3-zone open-loop SMB could give an order of magnitude higher productivity in systems with weakly competing impurities and two orders of magnitude higher in systems with strongly adsorbing impurities. In the second example, the simulations showed that an SMB designed using the Standing-Wave method could achieve an order of magnitude higher productivity than a system designed using the Triangle Theory.

Compared to standard time and solvent consuming procedures, mechanically-assisted processes offer numerous environmentally-friendly advantages for nano-catalytically active materials design. Mechanochemistry displays high reproducibility, simplicity, cleanliness and versatility, avoiding, in most cases, the use of any solvent. Moreover, mechanically-assisted procedures are normally faster and cheaper as compared to conventional processes. Due to these outstanding characteristics, mechanochemistry has evolved as an exceptional technique for the synthesis of novel and advanced catalysts designed for a large range of applications. The literature reports numerous works showing that mechanosynthetic procedures offer more promising paths than traditional solvent-based techniques. This review aims to disclose the latest advances in the mechanochemical assisted synthesis of catalytically active materials, focusing on nanocatalysts designed for biomass conversion and on bio-based catalysts.

The catalytic performance of NiMoAl catalysts derived from layered double hydroxide (LDH) precursors with molybdenum species incorporated into the interlayers was investigated for the hydrodeoxygenation (HDO) of anisole as a model compound of the lignin. The results showed that high dispersion of small Ni nanoparticles with 2–5?nm due to the pinning effect of Mo from Mo₇O₂₄^6? intercalated the LDHs. Due to presence of the oxygen vacancy sites on the molybdenum oxide, the NiMoAl catalysts exhibit higher conversion of anisole than the corresponding NiAl catalyst. The activity for hydrodeoxygenation was enhanced with the increased content of molybdenum species, which can be attributed to the larger amount of acid sites-promoted removal of oxygen from anisole. In addition, the NiMoAl catalysts show higher resistance to deactivation than the NiAl catalyst, and can be broadly applied to other hydrodeoxygenation reactions.

In Forward Osmosis the diffusion of the solute is counter to that of the solvent i.e. there is so-called “reverse salt diffusion”. Furthermore, the ratio of the two fluxes is generally taken to be a constant because of the assumption of ideal semi-permeability. However with the Spiegler-Kedem (S-K) model there is an allowance for a minor deviation from ideal semi-permeability and the ratio of the solute flux and solvent flux is no longer constant. The theoretical variation of the solute flux with increasing draw solution concentration is illustrated for various degrees of deviation from ideal semi-permeability. A novel variant of the S-K model is also introduced and predictions compared with those obtained using the standard form. With the acceptance that the form of “breakthrough” involving co-current flow is impossible, a limitation is imposed upon the S-K model but even with this limitation the theoretically predicted variation of solvent flux with increasing draw concentration is for certain sets of parameters of an unexpected form for minor deviation from ideal semi-permeability. That intriguing counter-intuitive outcomes can result from application of the S-K model indicates a need to rethink its formulation of the equations and the expressions for the coefficients. This will have implications for forward osmosis and possibly reverse osmosis modelling.