The “degree of rate control” (DRC) is a mathematical approach for analyzing multistep reaction mechanisms that has proven very useful in catalysis research. It identifies the “rate-controlling ...transition states and intermediates” (i.e., those whose DRCs are large in magnitude). Even in mechanisms with over 30 intermediates and transition states, these are generally just a few distinct chemical species whose energies, if they could be independently changed, would achieve a faster net reaction rate to the product of interest. For example, when there is a single “rate-determining step”, the DRC for its transition state (TS) is 1, which means (by definition) that if this TS’s energy could be decreased by k B T (where k B is Boltzmann’s constant and T is temperature), the net rate would increase by a factor of e. Because the (relative) energies of these key adsorbed intermediates and transition states can be adjusted by modifying the catalyst or solvent, or even a reactant’s molecular structure, the DRC values provide important ideas for catalyst improvement. The species with large DRCs are also the ones whose energetics must be most accurately measured or calculated to achieve an accurate kinetic model for any reaction mechanism. A tutorial on DRC analysis, the calculation of DRCs, and examples of the applications of DRCs in catalysis research is presented here. Applications of DRC analysis include the following: clarifying reaction kinetics, improving the accuracy of computational models, improving reaction conditions, improving choice of oxidant in selective oxidation, incorporation in algorithms which calculate net reaction rates of multistep mechanisms without solving the differential equations involved, and high-throughput computational screening of catalyst materials. Because DRC values can be determined experimentally, a full microkinetic model is not required to take advantage of DRC analysis.
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Hydrothermal gasification in subcritical and supercritical water is gaining attention as an attractive option to produce hydrogen from lignocellulosic biomass. However, for process optimization, it ...is important to understand the fundamental phenomenon involved in hydrothermal gasification of synthetic biomass or biomass model compounds, namely cellulose, hemicellulose and lignin. In this study, the response surface methodology using the Box-Behnken design was applied for the first time to optimize the process parameters during hydrothermal (subcritical and supercritical water) gasification of cellulose. The process parameters investigated include temperature (300–500 °C), reaction time (30–60 min) and feedstock concentration (10–30 wt%). Temperature was found to be the most significant factor that influenced the yields of hydrogen and total gases. Furthermore, negligible interaction was found between lower temperatures and reaction time while the interaction became dominant at higher temperatures. Hydrogen yield remained at about 0.8 mmol/g with an increase in the reaction time from 30 min to 60 min at the temperature range of 300–400 °C. When the temperature was raised to 500 °C, hydrogen yield started to elevate at longer reaction time. Maximum hydrogen yield of 1.95 mmol/g was obtained from supercritical water gasification of cellulose alone at 500 °C with 12.5 wt% feedstock concentration in 60 min. Using these optimal reaction conditions, a comparative evaluation of the gas yields and product distribution of cellulose, hemicellulose (xylose) and lignin was performed. Among the three model compounds, hydrogen yields increased in the order of lignin (0.73 mmol/g) < cellulose (1.95 mmol/g) < xylose (2.26 mmol/g). Based on the gas yields from these model compounds, a possible reaction pathway of model lignocellulosic biomass decomposition in supercritical water was proposed.
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•Hydrothermal gasification was studied by response surface methodology using Box-Behnken design.•Cellulose, hemicellulose and lignin were gasified in subcritical and supercritical water.•Process parameters e.g. temperature, reaction time and feed concentration were studied.•Temperature was found to be the most significant factor impacting H2 yields.•Maximum H2 yields were obtained from xylose (2.26 mmol/g) followed by cellulose (1.95 mmol/g) and lignin (0.73 mmol/g).
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Flow-electrode capacitive deionization (FCDI) is a new electrochemical-based desalination technology that addresses the limitations of preceding CDI processes through the use of a stationary carbon ...electrode and ion-exchange membrane. As with conventional CDI configurations, non-Faradaic reactions (i.e., ion electrosorption) of the electric double layer model is the principal ion separation mechanism of FCDI. This technology also offers the unique ability for continuous ion/salt separation by circumventing constraints with electrode saturation. This paper reviews recent advances in FCDI, discusses the feasibility and applicability of this technique, and suggests potential niche applications for saline water/wastewater treatment and resource recovery. Additionally, it also critically discusses factors that deteriorate FCDI performance, operating conditions, process energy efficiency, and optimization of the electrode, electrolyte, and cell design. The insights from this review will shed light on directions for future FCDI research and inform the implementation of FCDI technology.
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•Comprehensive review of recent advances in flow-electrode capacitive deionization (FCDI)•FCDI process optimization to improve desalination efficiency•Critical energy analysis in comparison with existing desalination technologies•FCDI in desalination, softening, nutrient recovery, and toxic metal removal•Future research directions for expanding practical application of FCDI
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Process temperature is under-characterized for protein A chromatography.•Novel temperature-controlled chromatography heating jacket designed and evaluated.•Dynamic binding capacity increased with ...increasing temperatures.•Productivity and resin utilization improved with increasing temperatures.•The data were fit to correlation-based and mechanistic-based models.
Maximizing product quality attributes by optimizing process parameters and performance attributes is a crucial aspect of bioprocess chromatography process design. Process parameters include but are not limited to bed height, eluate cut points, and elution pH. An under-characterized chromatography process parameter for protein A chromatography is process temperature. Here, we present a mechanistic understanding of the effects of temperature on the protein A purification of a monoclonal antibody (mAb) using a commercial chromatography resin for batch and continuous counter-current systems. A self-designed 3D-printed heating jacket controlled the 1 mL chromatography process temperature during the loading, wash, elution, and cleaning-in-place (CIP) steps. Batch loading experiments at 10, 20, and 30 °C demonstrated increased dynamic binding capacity (DBC) with temperature. The experimental data were fit to mechanistic and correlation-based models that predicted the optimal operating conditions over a range of temperatures. These model-based predictions optimized the development of a 3-column temperature-controlled periodic counter-current chromatography (TCPCC) and were validated experimentally. Operating a 3-column TCPCC at 30 °C led to a 47% increase in DBC relative to 20 °C batch chromatography. The DBC increase resulted in a two-fold increase in productivity relative to 20 °C batch. Increasing the number of columns to the TCPCC to optimize for increasing feed concentration resulted in further improvements to productivity. The feed-optimized TCPCC showed a respective two, three, and four-fold increase in productivity at feed concentrations of 1, 5, and 15 mg/mL mAb, respectively. The derived and experimentally validated temperature-dependent models offer a valuable tool for optimizing both batch and continuous chromatography systems under various operating conditions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Silver performs synergistic effects with CaO for biodiesel production.•CaO/Ag exhibited strong basicity, superior pore structure and catalytic activity.•Process optimization was performed using ...response surface methodology.•Kinetic and thermodynamic studies were undertaken to deepen understanding.•Economic evaluation was performed to provide insights of industrial application.
A heterogeneous CaO/Ag nano catalyst was developed and applied for biodiesel production from transesterification of soybean oil. The silver performed synergistic effects with CaO on promoting biodiesel production. The CaO/Ag nano catalysts exhibited abundant strong basic sites with larger BET surface area (7.02 vs 2.05 m2/g), pore diameter (58.84 vs 37.08 nm) and pore volume (0.070 vs 0.016 cm3/g), which significantly reduced mass transfer resistance of triglycerides during transesterification and improved the mass transfer constants. Response surface methodology was applied to investigate the influence reaction parameters and optimize biodiesel yield. A maximized biodiesel yield of 90.95 ± 2.56 % was achieved using methanol:oil molar ratio of 13, CaO/Ag loading of 5%, reaction time of 90 min and reaction temperature of 72℃. The optimized biodiesel yield for CaO catalyzed transesterification was 88.40 ± 3.34 %, using similar reaction conditions but with 180 min of reaction time. Both nano catalysts were consecutively reused for five times. Kinetic and thermodynamic studies of CaO and CaO/Ag catalyzed transesterification were performed and compared. Economic evaluation of biodiesel production using CaO and CaO/Ag was performed and compared to provide insights for heterogeneous catalyst application for biodiesel production on industrial scale.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•A novel extractive distillation was proposed for separating xylene isomers.•Double extractants were used in the extractive distillation process.•The o-xylene, m-xylene and p-xylene ...were effectively separated with high purity.•The energy consumption was greatly reduced.
Xylene is a crucial chemical raw material, serving as a synthetic monomer and solvent extensively employed in coating, medicine, rubber and other industries. It contains of three isomers: o-xylene (OX), m-xylene (MX), and p-xylene (PX), their separation is considered a worldwide challenge due to their extremely close boiling points. A novel extractive distillation based on double extractants is first proposed to separate these isomers in this paper, while it was considered impractical to separate these isomers by distillation technology alone in the past. Through the analysis of residual curve and extractant screening, two potential solvents, i.e., N-Methylpyrrolidone (NMP) and Tetramethylene sulfone (Sul) were used as extractants, and then the separation sequences were designed and optimized. The extractive distillation processes were optimized by sequential iterative method according to the minimum total annual cost (TAC), and the best separation sequence and process parameters were determined. For comparison, it was found that the optimized double extractant-based extractive distillation (DEED) process has the best economic performance with TAC of 5.72×106$, and the energy consumption was greatly reduced by 41.2% compared to the single extractant-based extractive distillation (SEED). This article provides a new perspective on energy-efficient distillation technology for industrial xylene separation and purification production.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
28.
Review on CO2 capture by blended amine solutions Aghel, Babak; Janati, Sara; Wongwises, Somchai ...
International journal of greenhouse gas control,
September 2022, 2022-09-00, 2022-09, Volume:
119
Journal Article
Peer reviewed
•The role of blended solvents, their advantages, and disadvantages in the CO2 capture•Investigation of the chemical adsorption process of CO2 in different types of the mixture, and technical-energy ...analysis•The current limitations and challenges of amine mixtures in CO2 capture
The procedure of CO2 removal through the absorption/desorption system based on chemical amine solvents offers an interesting commercial technology to absorb CO2. However, it has a major drawback regarding the high energy required in the regeneration of the solvent, which has turned into the most important challenge of chemical absorption procedures. Through precise analysis and integration of the rise in CO2 absorption with energy consumption in the desorption process, this review article has investigated two approaches. The first approach evaluates the development of solvents and the use of amine blends in four forms, i.e., aqueous solutions, non-aqueous solutions, two-phase blends, and ionic blends, with high capacity and absorption. The second approach discusses the changes in operational conditions, process modifications, and integration of thermal power plants to improve efficiency and reduce the high energy demand for PCC technologies. Moreover, an effort has been made to help further the development of absorption technology by presenting future perspectives considering the current condition of absorption, the barriers of amine scrubbing in steam boilers, and reduced thermal efficiency.
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Martensitic steels have gained renewed interest recently for their use in automotive, aerospace, and defense applications due to their ultra-high yield strengths and reasonable ductility. A recently ...discovered low alloy martensitic steel, AF9628, has been shown to exhibit strengths greater than 1.5 GPa with more than 10% tensile ductility, due to the formation of ε-carbide phase. In an effort to produce high strength parts with a high degree of control over geometry, the work herein presents the effects of selective laser melting (SLM) parameters on the microstructure and mechanical properties of this new steel. An optimization framework to determine the process parameters for building porosity-free parts is introduced. This framework utilizes the computationally inexpensive Eagar-Tsai model, calibrated with single track experiments, to predict the melt pool geometry. A geometric criterion for determining maximum allowable hatch spacing is also developed in order to avoid lack of fusion induced porosity in the as-printed parts. Using this framework, fully dense samples were successfully fabricated over a wide range of process parameters, allowing the construction of an SLM processing map for AF9628. The as-printed samples displayed tensile strengths of up to 1.4 GPa, the highest reported to date for any 3D printed alloy, with up to 11% elongation. The demonstrated flexibility in process parameter selection, while maintaining full density, opens up the possibility of local microstructural refinement and parameter optimization for improved mechanical properties in as-printed parts. The process optimization framework introduced here is expected to allow successful printing of new materials in an accelerated fashion.
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•Facile one pot in situ synthesis of GO-cellulose nanocomposite.•Application of modified Hummers’ method directly for the synthesis of nanocomposite.•0.03 g L−1 of GOCNC yielded 98 % ...adsorptive removal of toxic dye methylene blue.•Process is guided by both Langmuir and Freundlich isotherms.•Novel adsorbent synthesis at low cost using waste jute as a source of cellulose.
This is the first report on utilization of modified Hummers’ method for in-situ synthesis of novel graphene oxide-cellulose nanocrystals nanocomposite in a single reaction vessel. Cellulose used for nanocomposite preparation was extracted from waste jute. The synthesized nanocomposite was characterized with FTIR, XRD, SEM, EDX, DLS, and Zeta potential analyzer. It was applied as an adsorbent for the removal of toxic dye methylene blue from aqueous solutions. Around 98 % MB removal was achieved in 135 min. Under optimum experimental conditions recommended by response surface methodology, adsorption capacity of the nanocomposite was found to be 334.19 mg g−1 while the maximum adsorption capacity as determined by Langmuir isotherm 751.88 mg g−1. Further analysis revealed that the process was guided by both Langmuir and Freundlich isotherm and followed pseudo-second-order kinetics. This cost-effective synthesis route and efficient adsorption capacity of the nanocomposite indicate its immense potential for large-scale application in wastewater treatment.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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