BMC Chemical Engineering最新文献

Oleaginous microorganisms are among the most promising feedstocks for the production of lipids for biofuels and oleochemicals. Lipids are synthesized in intracellular compartments in the form of lipid droplets. Therefore, their qualitative and quantitative analysis requires an initial pretreatment step that allows their extraction. Lipid extraction techniques vary with the type of microorganism but, in general, the presence of an outer membrane or cell wall limits their recovery. This review discusses the various types of oleaginous microorganisms, their lipid accumulating capabilities, lipid extraction techniques, and the pretreatment of cellular biomass for enhanced lipid recovery. Conventional methods for lipid quantification include gravimetric and chromatographic approaches; whereas non-conventional methods are based on infrared, Raman, nuclear magnetic resonance, and fluorescence spectroscopic analysis. Recent advances in these methods, their limitations, and fields of application are discussed, with the aim of providing a guide for selecting the best method or combination of methods for lipid quantification.

Membranes could reform the field of molecular separations by enabling new low energy manufacturing technologies. This review article discusses the current state of the art and the potential in the 2D-enabled membrane separation processes by highlighting emerging and existing areas in which robust 2D materials significantly impact the energy-efficient separation process. Analysis of 2D-enabled membrane classes and prospective materials for 2D-enabled membranes are also discussed with emphasis on the surface chemistry of basal plane engineered 2D materials.

Biorefining of microalgae biomass requires processing of high-solids (>?10%) slurries. To date there is little knowledge of how processes for weakening and rupturing microalgae cells affect the rheological properties of these materials. To fill this gap in the literature, the rheological properties of concentrated slurries of marine microalgae Nannochloropsis sp. were investigated as a function of processing and solids concentration (12, 20 and 24% w/w). Freshly harvested, incubated (autolysed), and high-pressure homogenised (HPH) slurries were found to be shear thinning up to a shear rate of approximately 200?s^??1. Viscosity increases were far more prominent for partially processed versus unprocessed algal pastes at the higher concentrations. Slurry viscosity as a function of cell volume fraction could not be fitted to the Krieger-Dougherty model due to a network structure resulting from extracellular polymeric substances (EPS) and the intracellular cell components released during incubation and cell rupture. The 24% slurry, which was near the close packing limit, was much more viscous than the less concentrated slurries when comprising whole cells (i.e. harvested and incubated slurries). Cell rupture by HPH completely altered the characteristics of the slurry, increasing the viscosity of even the less concentrated slurries, and producing irreversible shear thinning behaviour. The magnitude of the increases in viscosities and the irreversible shear thinning behaviour observed in this study, have significant implications for processing and optimising the solids concentration of algal slurries.

Development of a Crotalaria juncea based biorefinery produce large quantity of waste glycerol after trans-esterification of the juncea seeds. This glycerol, after purification, is used as a substrate for producing succinic acid on a microbial route. Hydrogenation of this bio-refined succinic acid is carried out under high pressure in order to produce 1,4-butanediol (BDO) using a batch slurry reactor with cobalt supported ruthenium bimetallic catalysts, synthesized in-house. It is demonstrated that, using small amounts of ruthenium to cobalt increases the overall hydrogenation activity for the production of 1,4-butanediol. Hydrogenation reactions are carried out at various operating temperatures and pressures along with changes in the mixing ratios of ruthenium chloride and cobalt chloride hexahydrate, which are used to synthesize the catalyst. The Ru-Co bimetallic catalysts are characterized by XRD, FE-SEM and TGA. Concentrations of the hydrogenation product are analyzed using Gas chromatography-Mass spectrometry (GC-MS). Statistical analysis of the overall hydrogenation process is performed using a Box-Behnken Design (BBD).

As future energy systems aim to be more efficient, cost-effective, environmentally benign, and interconnected with each other, their design and operation become ever challenging tasks for decision-makers, engineers, and scientists. Sustainability of life on earth will be heavily affected by the improvements of these complex energy systems. Therefore, experts from various fields need to come together to find common solution strategies. However, since different technologies are usually developed separately by their own technical community, a generally accepted unified systematic approach to tackle integrated systems is lacking. With this article, we want to introduce and highlight the power of energy systems engineering as a generic framework to arrive at synergistic solutions to complex energy and environmental problems. Tools of energy systems engineering are numerous, and its application areas cover a wide range of energy systems. In this commentary, we present an overview of state-of-the-art methodologies of energy systems engineering, list its applications and describe few examples in detail, and finally introduce some possible new directions.

As climate change becomes increasingly evident, reducing greenhouse gases including CO₂ has received growing attention. Because CO₂ is thermodynamically very stable, its conversion into value-added chemicals such as CO, CH₄, or C₂H₄ is difficult, and developing efficient catalysts for CO₂ conversion is important work. CO₂ can be converted using the gas-phase reaction, liquid-phase reaction, photocatalytic reaction, or electrochemical reaction. The gas-phase reaction includes the dry reforming of methane using CO₂ and CH₄, or CO₂ hydrogenation using CO₂ and H₂. The liquid-phase reaction includes formic acid formation from pressurized CO₂ and H₂ in aqueous solution. The photocatalytic reaction is commonly known as artificial photo-synthesis, and produces chemicals from CO₂ and H₂O under light irradiation. The electrochemical reaction can produce chemicals from CO₂ and H₂O using electricity. In this review, the heterogeneous catalysts used for the gas-phase reaction or electrochemical reactions are discussed, because the liquid-phase reaction and photocatalytic reaction typically suffer from low productivity and poor durability. Because the gas-phase reaction requires a high reaction temperature of >?600?°C, obtaining good durability is important. The strategies for designing catalysts with good activity and durability will be introduced. Various materials have been tested for electrochemical conversion, and it has been shown that specific metals can produce specific products, such as Au or Ag for CO, Sn or Bi for formate, Cu for C₂H₄. Other unconventional catalysts for electrochemical CO₂ reduction are also introduced.

This paper gives a brief review of energy and CO₂ emissions related topics resulting from the chemical and related industries. The main issues, challenges and opportunities are highlighted together with perspectives of process alternatives for more efficient energy consumption and CO₂ emission management. Analysis of the data indicate that not all available energy resources are being utilized efficiently, while the energy resources causing the largest emissions of CO₂ are being used in the largest amounts. Also, the chemical and related industries are among the largest consumers of energy, indicating that solutions for reduction of energy consumption and CO₂ emissions in these industries need to be investigated. Information on promising alternatives for reduction of energy consumption and CO₂ emissions are collected and a selection of them are evaluated. Also, two specific case studies involving energy intensive separation operations replaced by recently developed technologies that may achieve significant reductions in energy consumption, CO₂ emissions and total annualized costs are presented. Through these examples issues of energy need versus CO₂ neutral design, sustainable conversion, retrofit design, and process intensification for chemical and related industries are highlighted.

Abelmoschus esculentus okra as whole stalks was examined for its suitability for pulp and paper production. It’s, fiber dimensions, morphological and chemical characteristics were reported. The pulping trials with soda- Anthraquinone (AQ,) at different chemical charges. Application of 21% as NaOH with 0.1% AQ gave good results in degree of delignification, mechanical properties. Utilization of okra pulps and blender is recommended due to good pulp properties. Evaluation of general characteristics of okra stalks in terms of fiber dimensions morphological indices, chemical components, Soda-AQ cooking and to study their suitability for paper production. Okra Fiber dimension evaluation done after maceration with a mixture of 30% hydrogen peroxide and acetic acid (1:1) for core and bark parts separately and was carried out under microscope staining with aqueous safranin. The Soda-AQ cooks at different active alkali levels were calculated as NaOH on oven dry raw material. The fibers from okra stalks studied (core and bark) were in the range of hardwood fibers, with short fiber length, especially the core with more or less moderate walls, narrow lumen and fiber width. The fiber width of bark was medium –narrow with medium wall thickness. The ash content was rather high whereas the silica content was comparatively high The hot water extractives from okra stalks was (4.1%), cold water (0.4) ethanol/ cyclohexane (1.1), ethanol extractives (1.2%) and 1% NaOH (27.6%) were rather high. The cellulose (Kurschner-Hoffer) was (48.5%) The lignin content was (15.3%) which was relatively moderate. The use of 0.1% AQ enhanced the delignification in the three trials applied. The screened yield increase with increase of chemical dose applied while the rejects decrease. When 21% NaOH was applied, the screened yield was 32.2% with negligible amount of rejects, however with lower alkali charge 18% the screened yield was decreased to 28% with very low rejects 1.5%. on the other hand rejects were increased to 7% when 15% NaOH was applied with very low screened yield 19%.The pulps produced from okra soda-AQ are suitable for production of printing and writing papers and it is advisable to use them in blending due to good papermaking properties.

There is a demand for new chemical reaction technologies and associated engineering aspects due to on-going transition in energy and chemistry associated to moving out progressively from the use of fossil fuels. Focus is given in this review on two main aspects: i) the development of alternative carbon sources and ii) the integration of renewable energy in the chemical production. It is shown how addressing properly these aspects requires to develop also a) new tools for chemical engineering assessment and b) innovative methodologies for the development of the materials, reactors and processes. This review evidences the need to accelerate studies on these directions, being a crucial element to catalyze the transition to a more sustainable use of energy and chemistry. It is remarked, however, the need to go beyond the traditional approaches, with some examples given. In fact, the presence of radical changes in the way of production is underlined, requiring thus novel fundamentals and applied engineering approaches.

A two-step approach combining an aqueous two-phase system (ATPS) and an aqueous micellar two-phase system (AMTPS), both based on the thermo-responsive copolymer Pluronic L-35, is here proposed for the purification of proteins and tested on the sequential separation of three model proteins, cytochrome c, ovalbumin and azocasein. Phase diagrams were established for the ATPS, as well as co-existence curves for the AMTPS. Then, by scanning and choosing the most promising systems, the separation of the three model proteins was performed. The aqueous systems based on Pluronic L-35 and potassium phosphate buffer (pH?=?6.6) proved to be the most selective platform to separate the proteins (S_Azo/Cyt?=?1667; S_Ova/Cyt?=?5.33 e S_Azo/Ova?=?1676). The consecutive fractionation of these proteins as well as their isolation from the aqueous phases was proposed, envisaging the industrial application of this downstream strategy. The environmental impact of this downstream process was studied, considering the carbon footprint as the final output. The main contribution to the total carbon footprint comes from the ultrafiltration (~?49%) and the acid precipitation (~?33%) due to the energy consumption in the centrifugation. The ATPS step contributes to ~?17% while the AMTPS only accounts for 0.30% of the total carbon footprint.