Enzymes are able to perform reactions under mild conditions, e.g., pH and temperature, with remarkable chemo-, regio-, and stereoselectivity. Because of this feature, the number of biocatalysts used ...in organic synthesis has rapidly increased during the last decades, especially for the production of chiral compounds. The present review highlights biotechnological processes for the production of chiral alcohols by reducing prochiral ketones. These reactions can be catalyzed by either isolated enzymes or whole cells that exhibit ketone-reducing activity. The use of isolated enzymes is often preferred because of a higher volumetric productivity and the absence of side reactions. Both types of catalysts have also deficiencies limiting their use in synthesis of chiral alcohols. Because reductase-catalyzed reactions are dependent on cofactors, one major task in process development is to provide an effective method for regeneration of the consumed cofactors. In this paper, strategies for cofactor regeneration in biocatalytic ketone reduction are reviewed. Furthermore, different processes carried out on laboratory and industrial scales using isolated enzymes are presented. Attention is turned to process parameters, e.g., conversion, yield, enantiomeric excess, and process strategies, e.g., the application of biphasic systems or methods of in situ (co)product recovery. The biocatalytic production of chiral alcohols utilizing whole cells is presented in part II of this review (Goldberg et al., Appl Microbiol Biotechnol, 2007).
Direct liquid fuel cells: A review Ong, B.C.; Kamarudin, S.K.; Basri, S.
International journal of hydrogen energy,
04/2017, Letnik:
42, Številka:
15
Journal Article
Recenzirano
Direct liquid fuel cells (DLFCs) are one of the most promising types of fuel cells due to their high energy density, simple structure, small fuel cartridge, instant recharging, and ease of storage ...and transport. Alcohols such as methanol and ethanol were the most common types of fuel used, although glycols and acids are also used. The main problem that arose in direct liquid fuel cells (DLFCs) was the high cost of the catalyst and the high catalyst loading. Other issues, such as fuel crossover, cathode flooding, the generation of various side products, fuel safety and unproven long-term durability, must also be solved to improve the performance of DLFCs. More research studies were required to increase its performance and foster commercialization. Currently, there were some commercial products using direct methanol fuel cells (DMFCs) and direct ethanol fuel cells (DEFCs), but the other types of DLFCs were generally still in the research stage. This paper aims to review the different types of liquid fuels directly used in fuel cells and identify their properties, challenges and applications.
•DLFCs are one of the most promising types of fuel cells.•DLFCs still have problems to be solved before commercialization.•Thus this paper presents different types of DLFC and applications.•It also highlights the properties, challenges and prospects of DLFC.
This study, as an observation, put its utmost effort to emphasize on the development of various physicochemical properties using multiple alcohols (C2 to C6) at different ratios compared to that of ...the conventional ethanol–gasoline blend. To optimize the properties of multiple alcohol–gasoline blends, properties of each fuel were measured first. An optimization tool of Microsoft Excel “Solver” was used for obtaining the optimum blend. Using optimizing tool, three optimum blend ratios were selected which possessed maximum heating value (MaxH), maximum research octane number (MaxR) and maximum petroleum displacement (MaxD). These blends were used for testing in a four cylinder gasoline engine at the wide open throttle condition with varying speeds and compared obtained outcomes with that of E15 (15% ethanol and 85% gasoline) as well as gasoline. Optimized blends have shown higher brake torque and brake thermal efficiency (BTE) but lower brake specific fuel consumption (BSFC) than E15. MaxR, MaxD and MaxH blends produced mean 4.4%, 1.8% and 0.4% increased BTE and mean 4.39%, 1.8% and 2.27% lower BSFC than that of E15. On the other hand, MaxR, MaxD, MaxH and E15 reduced 4.46%, 8.37%, 12.4% and 17.2%, mean CO emission and 4.5%, 11.81%, 8.19% and 16% mean HC emission respectively than that of gasoline. NOx emission of optimized blends was higher than gasoline. However, MaxR, MaxD, MaxH reduced 4%, 14.57% and 20.76% NOx than that of E15.
•Optimized C2–C6 alcohols–gasoline blends achieved better properties than E15.•Optimum blends improved BTE and torque and reduced BSFC than that of E15 fuel.•Compared to gasoline, optimum blends reduced CO and HC emission.•Optimum fuels reduced NOx emission than E15 fuel.
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•Carbon/hydrocarbon assisted water electrolysis reviewed for clean hydrogen production.•Reviewed different electrochemical technologies using carbon fuels under development.•This ...technology has been progressed to different levels of maturity for different carbon sources.•This route of hydrogen production can lower the electric input and CO2 emissions from the carbon sources.
Hydrogen is mainly produced by natural gas reforming, which is a highly efficient process with low feedstock costs. However, the rising interest in clean technologies will increase the demand for hydrogen, meaning that other sources will need to be explored. Although coal is currently the major source of power generation, its demand appears to be declining due to the rise in electricity generated from renewable energy sources and the worldwide quest for low-emission power generation. Coal reserves worldwide are abundant, but new technologies would be needed to produce hydrogen from this feedstock. Coal gasification is one well-established technology for this purpose, but it is inefficient and produces high CO2 emissions. An alternative technology that has been investigated over the past few decades is carbon assisted water electrolysis. The basic process is water/steam electrolysis, with part of the energy required for the electrolysis provided by the chemical energy of coal, which reduces the overall electrical energy input. In addition to coal, the process can also use other carbon sources, such as biomass, alcohols or gaseous hydrocarbons. Several studies have investigated this electrochemical route of hydrogen production, employing different electrolytes in a wide temperature range (room temperature to 850 °C) under different process conditions. This paper presents a comprehensive review of carbon assisted water electrolysis, associated materials used and the challenges for the development of the technology at the commercial scale.
Enzymes are able to perform reactions under mild conditions, e.g., pH and temperature, with remarkable chemo-, regio-, and stereoselectivity. Due to this feature the number of biocatalysts used in ...organic synthesis has rapidly increased during the last decades, especially for the production of chiral compounds. The present review highlights biotechnological processes for the production of chiral alcohols by reducing prochiral ketones with whole cells. Microbial transformations feature different characteristics in comparison to isolated enzymes. Enzymes that are used in whole-cell biotransformations are often more stable due to the presence of their natural environment inside the cell. Because reductase-catalyzed reactions are dependent on cofactors, one major task in process development is to provide an effective method for regeneration of the consumed cofactors. Many whole-cell biocatalysts offer their internal cofactor regeneration that can be used by adding cosubstrates, glucose or, in the case of cyanobacteria, simply light. In this paper, various processes carried out on laboratory and industrial scales are presented. Thereby, attention is turned to process parameters, e.g., conversion, yield, enantiomeric excess, and process strategies, e.g., the application of biphasic systems. The biocatalytic production of chiral alcohols utilizing isolated enzymes is presented in part I of this review (Goldberg et al., Appl Microbiol Biotechnol, 2007).
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•ZSM-5 was synthesized from the synthetic gels containing various alcohols.•The impact of the alcohols on the Al distribution was investigated.•Al distribution was considered by ...constrain index and Co2+ exchange properties.•The impact of the Al distribution on the catalytic properties was clarified.
The distribution of Al atoms in ZSM-5 has been recognized as an important factor in catalytic activity. Here, ZSM-5 zeolites were synthesized from synthetic gels containing various alcohols, including straight- and branched-chains alcohols. The effect of the alcohols in the synthetic gel on the Al distribution in the MFI framework was investigated based on 27Al MAS NMR, Co(II) ion UV−vis DRS, and constraint index value. Thus synthesized ZSM-5 zeolites were applied to catalysts for the cracking of n-hexane and the methanol-to-olefins (MTO) reactions in order to investigate the impact of the Al distribution on the catalytic properties. A unique Al distribution in the MFI framework was achieved by the use of trimethylolethane (TME) in combination with Na cations, and thus-prepared ZSM-5 catalyst showed a long catalytic life for both the cracking of n-hexane and the MTO reaction.
We report on a wearable tear bioelectronic platform, integrating a microfluidic electrochemical detector into an eyeglasses nose-bridge pad, for non-invasive monitoring of key tear biomarkers. The ...alcohol-oxidase (AOx) biosensing fluidic system allowed real-time tear collection and direct alcohol measurements in stimulated tears, leading to the first wearable platform for tear alcohol monitoring. Placed outside the eye region this fully wearable tear-sensing platform addresses drawbacks of sensor systems involving direct contact with the eye as the contact lenses platform. Integrating the wireless electronic circuitry into the eyeglasses frame thus yielded a fully portable, convenient-to-use fashionable sensing device. The tear alcohol sensing concept was demonstrated for monitoring of alcohol intake in human subjects over multiple drinking courses, displaying good correlation to parallel BAC measurements. We also demonstrate for the first time the ability to monitor tear glucose outside the eye and the utility of wearable devices for monitoring vitamin nutrients in connection to enzymatic flow detector and rapid voltammetric scanning, respectively. These developments pave the way to build an effective eyeglasses system capable of chemical tear analysis.
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•Wearable fluidic tears biosensor and wireless circuitry integrated into eyeglasses for non-invasive biomarker monitoring.•Wearable tear sensing platform placed outside the eye region mitigates drawbacks of systems requiring direct eye contact.•Real-time collection and direct measurements of stimulated tears allow the first wearable tear alcohol monitoring platform.
Diesel engines are the main source of rapidly-growing energy consumption worldwide. Diesel consumption is responsible for serious air pollution, which includes nitrogen oxides (NOx), hydrocarbon ...(HC), carbon monoxide (CO) emissions and some particulate matter (PM) discharged from the combustion chamber. In the past few decades, alternative fuels, such as alcohol, biodiesel, natural gas, and Di Methyl Ether (DME), have been used in diesel engines to reduce energy costs and environmental pollution. As a result of alternative fuels directives, an increasing number of diesel engines have adapted dual fuel blends, and an enormous amount of research is focused on new and inadequately studied combustion and emission profiles. Compared to conventional diesel fuel, the application of dual fuels would add new parameters to combustion and emission profiles for diesel vehicles worldwide. This review aims to reveal (1) Known and anticipated combustion characteristics and emissions products from dual fuels. (2) Toxic properties and the expected influence on engine performance. (3) Identifying promising alternative fuels for emissions control in compression combustion engines. The results presented herein will show a significant reduction of regular gas and PM emissions by the use of alcohol/diesel dual fuel, while unregulated emissions such as methanol, ethanol, acetaldehyde, formaldehyde, ketone, have increased compared to those from diesel fuel. PM emissions decreased significantly with the increase of alternative fuels, such as alcohols, natural gas, biodiesel and DME, while regular gaseous emissions varied depending on the type alternative fuel and the engine conditions. As one new and cleaner substitute for diesel engines, DME operation has a longer injection delay, lower maximum cylinder pressure, a lower ratio of pressure rise, and shorter ignition delay in comparison with diesel operation--the opposite of alcohol/diesel and dual fuels. This review evaluates the effects of some alternative fuels (alcohol, biodiesel, natural gas and Di Methyl Ether (DME)) on combustion characteristics and emission products from diesel engines to meet future emission regulations using alternative fuel.
I denne artikkelen undersøker vi hvilken betydning alkohol og alkoholhåndtering har for unge kvinner og menn med krysskulturell oppvekst. Vi anvender interseksjonalitet som perspektiv for å belyse ...hvordan ulike sosiale kategorier kan påvirke unges livsbetingelser og opplevelser av tilhørighet. Artikkelen bygger på kvalitative intervjuer med 13 unge voksne, som forteller om sine erfaringer med krysskulturell oppvekst. Våre analyser viser at alkohol og alkoholhåndtering har en sentral betydning i deres opplevelser og navigering av tilhørighet til majoritets- og minoritetsmiljøer. Som unge, religiøse kvinner og menn opplever de at alkoholkonsum og festing fungerer som markører for det å være ung og norsk, og at alkoholbruk er en betingelse for å bli en del av det norske majoritetsfellesskapet. Fra egne familier og minoritetsmiljøer opplever deltakerne derimot en forventning om avholdenhet og at de avstår fra fellesskap der det brukes alkohol. De motstridende forventningene vanskeliggjør navigering av tilhørighet til både majoritets- og minoritetsmiljøer. Artikkelen bidrar til å gi en økt forståelse av hvordan alkoholbruk er forbundet med hierarkiserende konstruksjoner av norskhet og fremmedhet, og inndelinger i «oss» og «dem».
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