| 51. |
- Abdelgaid, Mona, et al.
(författare)
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Multiscale modeling reveals aluminum nitride as an efficient propane dehydrogenation catalyst
- 2023
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Ingår i: Catalysis Science and Technology. - 2044-4753 .- 2044-4761. ; 13:12, s. 3527-3536
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Tidskriftsartikel (refereegranskat)abstract
- Nonoxidative propane dehydrogenation (PDH) is a promising route to meet the steadily increasing demand for propylene, an important building block in the chemical industry. Wurtzite group-IIIA metal nitrides are potential catalysts for PDH with high chemical, thermal, and mechanical stability alongside inherent Lewis acid-base properties that can activate the C-H bond of alkanes. Herein, we investigate the catalytic behavior of pristine (AlN) and gallium-doped (Ga/AlN) aluminum nitride for PDH via concerted and various stepwise mechanisms using density functional theory (DFT) calculations and microkinetic modeling (MKM). The reaction profiles investigated with DFT calculations are used in MKM, which reveals that the stepwise mechanisms produce >99% of propylene on both AlN and Ga/AlN. AlN has approximately one order of magnitude higher activity than Ga/AlN due to lower barriers along the dominant PDH reaction pathway. In summary, we propose the potential application of AlN as an efficient dehydrogenation catalyst for the conversion of light alkanes into valuable olefins. In addition, we show that multiscale simulations are essential to evaluate the catalytic behavior of complex alkane conversion reaction networks and obtain activity trends for dehydrogenation catalysts.
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| 52. |
- Abdelhameed, A. H., et al.
(författare)
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Cryogenic characterization of a LiAlO2 crystal and new results on spin-dependent dark matter interactions with ordinary matter: CRESST Collaboration
- 2020
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Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 80:9
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Tidskriftsartikel (refereegranskat)abstract
- In this work, a first cryogenic characterization of a scintillating LiAlO2 single crystal is presented. The results achieved show that this material holds great potential as a target for direct dark matter search experiments. Three different detector modules obtained from one crystal grown at the Leibniz-Institut fur Kristallzuchtung (IKZ) have been tested to study different properties at cryogenic temperatures. Firstly, two 2.8 g twin crystals were used to build different detector modules which were operated in an above-ground laboratory at the Max Planck Institute for Physics (MPP) in Munich, Germany. The first detector module was used to study the scintillation properties of LiAlO2 at cryogenic temperatures. The second achieved an energy threshold of (213.02 +/- 1.48) eV which allows setting a competitive limit on the spin-dependent dark matter particle-proton scattering cross section for dark matter particle masses between 350 MeV/c2 and 1.50 GeV/c2. Secondly, a detector module with a 373 g LiAlO2 crystal as the main absorber was tested in an underground facility at the Laboratori Nazionali del Gran Sasso (LNGS): from this measurement it was possible to determine the radiopurity of the crystal and study the feasibility of using this material as a neutron flux monitor for low-background experiments.
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| 53. |
- Abdolahi-Mansoorkhani, Hamed, et al.
(författare)
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CO 2 capture by modified hollow fiber membrane contactor: Numerical study on membrane structure and membrane wettability
- 2020
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Ingår i: Fuel Processing Technology. - : Elsevier BV. - 0378-3820. ; 209
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Tidskriftsartikel (refereegranskat)abstract
- This work aims at capturing CO2 from natural gas using a verified finite element mathematical model by improving the membrane wettability, membrane structure, the type of absorbents used in the system, and the physical parameters like membrane porosity and the number of fibers used in hollow fiber membrane contactor (HFMC). The model is developed to simulate the CO2 removal using membranes by considering mass transfer equations in the presence of chemical reactions. Simulations were performed using a membrane system including 10 fibers with 175 mm length, 830 μm outer fiber radius and 450 μm inner fiber radius. The effect of adding montmorillonite nanoparticles (MMT) in weight percentages of 1%, 3%, and 5% to the PVDF membrane was perused to demonstrate the influence of membrane structure modification on system performance. The results show that the modification of membrane structure with montmorillonite nanoparticles could increase the efficiency of the system in the removal of CO2 particles by 8%. Four absorbents including MEA (monoethanol amine), PZ (piperazine), TEA (triethanolamine), and EDA (ethylenediamine) are used to identify the most effective absorbent where PZ absorbent shows the highest and EDA absorbent has the lowest carbon capture efficiency. Wettability is found to have a considerably negative impact on membrane carbon capture capacity. For instance, the modeling results show that even a 10% wetting of the membrane reduces the efficiency of the CO2 removal process by more than 47%. In addition, the results illustrate that the increase in membrane tortuosity and gas velocity have negative impacts on the separation process, while increase in the absorbent concentration, packing density and porosity enhance the separation of CO2.
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| 54. |
- Abdollahi, Mehdi, 1985, et al.
(författare)
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A novel cold biorefinery approach for isolation of high quality fish oil in parallel with gel-forming proteins
- 2020
-
Ingår i: Food Chemistry. - : Elsevier BV. - 0308-8146 .- 1873-7072. ; 332
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Tidskriftsartikel (refereegranskat)abstract
- The pH-shift process for isolation of gel-forming proteins from fish processing by-products was extended to allow parallel isolation of fish oil. Subjecting the floating emulsion layer formed during pH-shift processing of salmon by-products to pH-adjustment or freeze/thawing efficiently released the emulsified oil at 4 °C. However, for herring by-products higher temperature (10 °C) and a combination of the emulsion-breaking techniques was required for efficient oil release. Oil recovery yield using the adjusted pH-shift process was lower than with classic heat-induced oil isolation (90 °C/20 min), but pH-shift-produced oils had higher amounts of n-3 polyunsaturated fatty acids (n-3 PUFA). Also, alkaline pH-shift processing produced oils with remarkably less oxidation products and free fatty acids compared with acid pH-shift process or heat-induced isolation. Extending the pH-shift process with emulsion breaking techniques can thus be a promising biorefinery approach for parallel cold production of high-quality fish oil and gel-forming proteins from fish by-products.
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| 55. |
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| 56. |
- Abdollahi, Mehdi, 1985, et al.
(författare)
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Impact of processing technology on macro- and micronutrient profile of protein-enriched products from fish backbones
- 2021
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Ingår i: Foods. - : MDPI AG. - 2304-8158. ; 10:5
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Tidskriftsartikel (refereegranskat)abstract
- Impacts of processing technology (mechanical separation and pH-shift processing) on protein recovery from salmon, herring and cod backbones and the content of macro- and micronutrients in the recovered protein enriched products were investigated. Mechanical separation led to higher protein recovery compared with the pH-shift process and using both techniques, recovery ranked the species as herring > salmon > cod. However, the pH-shift process up-concentrated protein from herring and salmon backbones more efficiently than mechanical separation by removing more fat and ash. This consequently reduced n-3 PUFA and vitamin D content in their protein isolates compared with the backbones and mechanically separated meat (MSM). Cod protein isolate, however, contained higher levels of these nutrients compared with MSM. Mechanical separation concentrated vitamins E and C in salmon MSM but not for cod and herring. Opposite, pH-shift processing reduced levels of these two vitamins for cod and herring backbones, while vitamins D and C were reduced for salmon. For minerals, selenium, calcium, magnesium, and potassium were lower in protein isolates than MSM, while copper, zinc, iron and manganese were similar or higher. Overall, there is a major potential for upcycling of fish backbones to food ingredients, but processing technology should be carefully balanced against the desired nutrient profile and final application area.
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| 57. |
- Abdollahi, Mehdi, 1985, et al.
(författare)
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Minimizing lipid oxidation during pH-shift processing of fish by-products by cross-processing with lingonberry press cake, shrimp shells or brown seaweed
- 2020
-
Ingår i: Food Chemistry. - : Elsevier BV. - 0308-8146 .- 1873-7072. ; 327
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Tidskriftsartikel (refereegranskat)abstract
- The potential of cross-processing herring or salmon by-products with brown seaweed, shrimp peeling by-products and lingonberry press cake (called “helpers”) to minimize lipid oxidation during acid/alkaline pH-shift protein isolation was evaluated. Lingonberry press cake remarkably reduced levels of lipid hydroperoxides, malondialdehyde (MDA) and 4-hydroxy-trans2-hexenal (HHE) in both herring and salmon protein isolates (PI) while seaweed and shrimp by-product mitigated generation of MDA and HHE in herring PI. The salmon PI, however, by itself had very low oxidation levels. Cross-processing reduced protein yield compared with the classical pH-shift process by diminishing protein solubility, but still, the alkaline process version was promising. The color of the PIs varied greatly between different process combinations, reflecting partitioning of natural pigments into isolates. Altogether, cross-processing seems a promising tool for inhibition of lipid oxidation during pH-shift processing of sensitive fish by-products, with the alkaline version and lingonberry press cake being closest at hand for further studies.
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| 58. |
- Abdolshahi, Anna, et al.
(författare)
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Edible Film Based on Lallemantia peltata L. Seed Gum: Development and Characterization
- 2022
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Ingår i: Journal of Chemical Health Risks. - 2251-6719 .- 2251-6727. ; 12:1, s. 47-61
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Tidskriftsartikel (refereegranskat)abstract
- A novel edible film was developed using Lallemantia peltata (L.) seed gum (LSG), and its water sensitivity, physico-mechanical, barriers, microstructural and thermal properties as a function of glycerol concentration (20, 30, 40, 50 and 60% w/w) were studied. Different models were also used to investigate the water sorption of the LSG films. Unplasticized LSG films were brittle and difficult to handle which were effectively modified by glycerol addition. Water sensitivity, oxygen permeability, and elongation of LSG films were increased with increasing glycerol concentration. Also, increasing of glycerol concentration resulted in reduction of tensile strength, glass transition temperature (Tg) and melting temperature (Tm) of the films. Electron scanning micrographs revealed a smooth surfaceand compact cross-section microstructure in LSG films.The films showed sigmoid shape type II water sorption isotherms, representing typical features of most of biopolymers. Accordingly, the results suggest that LSG films containing desired glycerol concentration could potentially be used as edible films in food packaging.
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| 59. |
- Abdul-Jabbar, Thealfaqar A., et al.
(författare)
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Efficient Battery Cell Balancing Methods for Low-Voltage Applications: A Review
- 2022
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Ingår i: 2022 IEEE International Conference in Power Engineering Application, ICPEA 2022 - Proceedings.
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Konferensbidrag (refereegranskat)abstract
- Battery balancing technologies are a crucial mech anism for the safe operation of electrochemical energy storage systems, such as lithium-ion batteries. Moreover, balancing be tween battery cells is essential for battery systems' life. Without any balancing circuitry, individual cell voltages can reach their maximum/minimum battery voltage limit faster than others, posing safety hazards. Furthermore, battery capacity reduction can occur when overcharging/over-discharging individual cells. So far, many balancing methodologies have been proposed and discussed in available literature. This paper presents a review of different state-of-The-Art cell balancing methods suitable for low voltage applications. The required control complexity, switch stress, balancing speed, cost and circuit size are considered as key aspects. Typically, cell bypass techniques, such as passive balancing, have the lowest cost and require no complex control strategies. In contrast, cell-To-cell balancing techniques can significantly increase the energy efficiency compared to cell bypass balancers, but these come with higher system costs and control complexity.
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| 60. |
- Abdurrokhman, Iqbaal, 1991
(författare)
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Binary mixtures and cationic modification of protic ionic liquids. Local structure and transport properties
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Protic ionic liquids are a subclass of ionic liquids, which in many cases are obtained by mixing an equimolar amount of Brønsted acid and base. Protic ionic liquids possess an exchangeable proton that gives them distinct features, e.g. the potential to conduct protons and the ability to form extended hydrogen bonds, which is different from the case of their aprotic counterparts. The protic ionic liquids considered in this thesis are limited to those based on the imidazolium and triazolium cation, which (compared to aprotic ionic liquids) are less developed and have been investigated to a lesser extent. The work included in this thesis has been devoted to investigate strategies that could possibly promote a fast proton motion. These strategies have primarily consisted in mixing a protic ionic liquid with a molecular solvent or another parented ionic liquid and in modifying the cationic structure by either attaching alkyl chains of different length to the imidazolium cation or synthesizing new protic ionic liquids derived from another heterocyclic ring such as triazole. In both cases, a detailed characterization by means of vibrational spectroscopy could provide valuable information about intermolecular interactions. An important finding from the studies conducted in this thesis is that altering the cation's structure or adding a co-solvent leads to a significant change in chemical and transport properties. This thesis also includes an extensive work devoted to develop a new solvent-free method to synthesize dry and pure protic ionic liquids, in the laboratory scale. An analytical approach to accurately quantify their purity using nuclear magnetic spectroscopy has also been developed. In addition, the ionic conductivity of the investigated protic ionic liquid systems has been evaluated by use of impedance spectroscopy, from room temperature up to 140 °C. The results included in my work indicate that the two investigated strategies can potentially be used, each with its limitations, to develop thermochemically stable proton conducting materials based on protic ionic liquids.
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