Heat of combustion of biofuels mixed with fossil diesel oil

The Brazilian government has presented a biofuel program, which aims the addition of 2% of biofuel in fossil diesel in 2008 and 5% up to 2013. Thus, the knowledge of heat of combustion of biofuel/diesel blends is necessary. The biodiesel was produced by transesterification of soybean oil with a yield of 87%. The diesel-like was obtained by pyrolysis of soybean oil. This biofuel presented all parameters according to ANP. The obtained heats of combustion were 41.36 ± 0.17; 38.70 ± 0.16; and 36.71 ± 0.17 MJ/kg for diesel, diesel-like and biodiesel, respectively. The results show that the heats of combustion of biofuels are approximately 17% smaller than fossil diesel. The obtained data also show that the heats of combustion depend on the methodology used for the biofuel production. Addition of biofuels to traditional diesel fuel results in a linear decreasing of the heat of combustion with the amount of the alternative fuel added to the diesel.     

Analytical strategies for chemical characterization of bio‐oil

Bio‐oils, produced by biomass pyrolysis, have become promising candidates for feedstocks of high value‐added chemicals and alternative sources for transportation fuels. Bio‐oil is such a complicated mixture that contains nonpolar hydrocarbons and polar components which cover almost all kinds of organic oxygenated compounds such as carboxylic acids, alcohols, aldehydes, ketones, esters, furfurals, phenolic compounds, sugar‐like material, and lignin‐derived compounds. Comprehensive characterization of bio‐oil and its subfractions could provide insight into the conversion process of biomass processing, as well as its further utilization as transportation fuels or chemical raw materials. This review focuses on advanced analytical strategies on in‐depth characterization of bio‐oil, which is concerned with gas chromatography, high‐resolution mass spectrometry, FTIR spectroscopy and NMR spectroscopy, offering complementary information for previous reviews.     

Investigation on total and instantaneous energy balance of bio-alternative fuels on an SI internal combustion engine

This paper investigates the effect of some biofuels on thermal balance and performance characteristics of a single-cylinder, four-stroke SI internal combustion engine. In this study, total and instantaneous energy balance of an air-cooled, small-scale engine using various biofuels is investigated. An experimental study is carried out on gasoline engine to validate the numerical calculations. Bio-alternative fuels which include methanol, ethanol and 2-ethanol–gasoline-blended fuels consisting of E85, E15 are examined numerically. Results indicate that methanol is the most effective fuel in aspect of power generation. Ethanol, E85, E15 and gasoline are placed in next positions, respectively. Break specific fuel consumption shows totally reversed trend. It is evaluated that by increasing engine speed, heat transfer to brake power ratio decreases and lower percentage of energy in form of heat transfer is lost. The least heat transfer to brake power ratio among studied fuel is related to methanol which approves it as the most efficient biofuel. Based on instantaneous in-cylinder energy balance analysis, at the end of combustion and during expansion stroke, instantaneous brake work of fuels outpaces each other at around 40° crank angle aTDC.

     

Biofuels today and tomorrow: effects of fuel composition on exhaust gas emissions

Due to current and future policy targets, and rapid technical developments, biofuel options are already available and in use in commercial applications. However, there is still doubt about which of the more promising alternatives will be widely accepted in future within the transportation sector. This includes aspects of biofuel properties and their effects on exhaust gas emissions and engine technology. This article addresses the status of current technology, reviews the progress of commercialisation of biofuel production, and gives an outline of its future development. Moreover, it provides an insight into the influence of biofuel composition on the internal combustion process and exhaust gas emissions. To assess biofuel sustainability, all aspects such as fuel production, fuel chemical composition, combustion behaviour, engine technology, and exhaust gas emissions have to be taken into account. Potential application fields and emerging challenges for measurement technology are identified in all these areas.     

Advanced Biofuels and Beyond: Chemistry Solutions for Propulsion and Production

Sustainably produced biofuels, especially when they are derived from lignocellulosic biomass, are being discussed intensively for future ground transportation. Traditionally, research activities focus on the synthesis process, while leaving their combustion properties to be evaluated by a different community. This Review adopts an integrative view of engine combustion and fuel synthesis, focusing on chemical aspects as the common denominator. It will be demonstrated that a fundamental understanding of the combustion process can be instrumental to derive design criteria for the molecular structure of fuel candidates, which can then be targets for the analysis of synthetic pathways and the development of catalytic production routes. With such an integrative approach to fuel design, it will be possible to improve systematically the entire system, spanning biomass feedstock, conversion process, fuel, engine, and pollutants with a view to improve the carbon footprint, increase efficiency, and reduce emissions.     

Heats of combustion of biofuels obtained by pyrolysis and by transesterification and of biofuel/diesel blends

The obtained heats of combustion were 46.65 ± 0.20; 38.09 ± 0.31; 39.67 ± 0.22; 41.88 ± 0.31; 37.86 ± 0.46; 39.89 ± 0.09; 41.28 ± 0.31 MJ/kg for diesel, transesterified soybean oil, pyrolysed soybean oil and crude soybean oil, transesterified palm tree oil (Elaeis sp.), pyrolysed palm tree oil, crude palm tree oil, respectively. The results show the heats of combustion of biofuels are approximately 17% smaller than traditional diesel. The data also show the heats of combustion depend on the methodology used for the biofuel production. Addition of biofuels to traditional diesel fuel results in a linear decrease of the heat of combustion with the amount of the alternative fuel added to the diesel. However, for blends with 5% biofuels, which is the limit demanded by Brazilian legislation, no significant decrease of the heat of combustion of the commercial diesel was observed.     

氨能源作为清洁能源的应用前景

合成氨是一种成本低廉的化工原料,具有较高能量密度和辛烷值、易于压缩储运、燃烧不产生CO2等优点,是一种应用前景广泛的新型清洁能源。氨既可替代汽油、柴油等化石燃料,为汽车发动机直接提供清洁燃料,也可以经催化分解制取氢气,为车载燃料电池提供安全氢气。作为传统石油燃料的理想替代品,氨为解决环境污染和能源短缺问题提供了新的燃料选择。本文主要从发动机燃料和燃料电池原料两方面,介绍氨用于汽车动力源的优越性和可操作性,以及国内外相关研究进展;集中分析了氨分解制氢的催化剂体系的研究进展和局限性,以及合成氨的研究现状。     

Single‐Enzyme Biofuel Cells

Herein, we demonstrate that the intramolecular electron transfer within a single enzyme molecule is an important alternative pathway that can be harnessed to generate electricity. By decoupling the redox reactions within a single type of enzyme (for example, Trametes versicolor laccase), we harvested electricity efficiently from unconventional fuels including recalcitrant pollutants (for example, bisphenol A and hydroquinone) in a single‐laccase biofuel cell. The intramolecular electron‐harnessing concept was further demonstrated with other enzymes, including power generation during CO₂ bioconversion to formate catalyzed by formate dehydrogenase from Candida boidinii . The novel single‐enzyme biofuel cell is shown to have potential for utilizing wastewater as a fuel as well as for generating energy while driving bioconversion of chemical feedstock from CO₂.     

Challenges and perspectives of combustion chemistry research

In the past decades, combustion chemistry research grew rapidly due to the development of combustion diagnostic methods,quantum chemistry methods, kinetic theory, and computational techniques. A lot of kinetic models have been developed for fuels from hydrogen to transportation fuel surrogates. Besides, multi-scale research method has been widely adopted to develop comprehensive models, which are expected to cover combustion conditions in real combustion devices. However, critical gaps still remain between the laboratory research and real engine application due to the insufficient research work on high pressure and low temperature combustion chemistry. Besides, there is also a great need of predictive pollutant formation model. Further development of combustion chemistry research depends on a closer interaction of combustion diagnostics, theoretical calculation and kinetic model development. This paper summarizes the recent progress in combustion chemistry research briefly and outlines the challenges and perspectives.     

Automotive fuels and internal combustion engines: a chemical perspective

Commercial transportation fuels are complex mixtures containing hundreds or thousands of chemical components, whose composition has evolved considerably during the past 100 years. In conjunction with concurrent engine advancements, automotive fuel composition has been fine-tuned to balance efficiency and power demands while minimizing emissions. Pollutant emissions from internal combustion engines (ICE), which arise from non-ideal combustion, have been dramatically reduced in the past four decades. Emissions depend both on the engine operating parameters (e.g. engine temperature, speed, load, A/F ratio, and spark timing) and the fuel. These emissions result from complex processes involving interactions between the fuel and engine parameters. Vehicle emissions are comprised of volatile organic compounds (VOCs), CO, nitrogen oxides (NO(x)), and particulate matter (PM). VOCs and NO(x) form photochemical smog in urban atmospheres, and CO and PM may have adverse health impacts. Engine hardware and operating conditions, after-treatment catalysts, and fuel composition all affect the amount and composition of emissions leaving the vehicle tailpipe. While engine and after-treatment effects are generally larger than fuel effects, engine and after-treatment hardware can require specific fuel properties. Consequently, the best prospects for achieving the highest efficiency and lowest emissions lie with optimizing the entire fuel-engine-after-treatment system. This review provides a chemical perspective on the production, combustion, and environmental aspects of automotive fuels. We hope this review will be of interest to workers in the fields of chemical kinetics, fluid dynamics of reacting flows, atmospheric chemistry, automotive catalysts, fuel science, and governmental regulations.     

Natural gas and biofuel as feedstock for hydrogen production on Ni catalysts

In this article,the aptitude of natural gas as feedstock in steam reforming process for hydrogen production is compared with that of different liquid fuels (pure compounds and commercial fuels),with the aim to investigate the potentialities of biofuels to overcome the CO2 emission problems deriving from fossil fuel processing.The performances of a nickel based catalyst (commercially used in steam reforming of natural gas) were evaluated in terms of feed conversion and yield to the different products as function of temperature,space velocity and water/fuel ratio.Furthermore,a preliminary evaluation of catalyst durability was effected by monitoring yield to H2 versus time on stream and measuring coke formation at the end of experimental tests.High yields to hydrogen were obtained with ail fuels investigated,whereas the deactivation phenomena,which are correlated to carbon deposition on the catalyst,were observed with all tested fuels,except for methane and biofuel.     

High‐Temperature Study of 2‐Methyl Furan and 2‐Methyl Tetrahydrofuran Combustion

The ignition behavior of methyl furan (2‐MF) and methyl tetrahydrofuran (2‐MTHF) is investigated using the shock tube technique. Experiments are carried out using homogeneous gaseous mixtures of fuel, oxygen, and argon with equivalence ratios, ?, of 0.5, 1.0, and 2.0 at average pressures of 3 and 12 atm over a temperature range of 1060–1300 K. In addition to ignition delay time measurements, fuel concentration time histories during ignition and pyrolysis of 2‐MTHF are obtained by means of laser absorption spectroscopy using a He–Ne laser at a fixed wavelength of 3.39 µm. With respect to ignition delay times, it is observed that under similar conditions of equivalence ratio and argon/oxygen ratio (D), 2‐MTHF has longer ignition delay times than 2‐MF at 3 atm. In addition, 2‐MTHF has longer ignition delay times than 2‐MF at higher temperatures for the case of 12 atm and under the same conditions of ? and D. The higher reactivity of 2‐MF, as indicated by shorter ignition delay times, is attributed to differences in chemical structure, whereby weaker C–H bond sites are more readily susceptible to radical attack than in 2‐MTHF. It is observed that ignition delay times of 2‐MTHF decrease with increasing equivalence ratio at 12 atm for fixed argon/oxygen ratio. Ignition delay times are compared with model predictions using recent chemical kinetic models of both fuels, showing that both models generally predict shorter ignition delay times than measured. The relatively higher absorption cross section of 2‐MTHF at 3.39 µm allows for its concentration time histories to be determined and compared to model predictions. In line with the observed discrepancy in ignition predictions, predicted 2‐MTHF concentration profiles are such that the fuel is shown to be more rapidly consumed than observed in the experiments. The study advances understanding of the combustion chemistry of these cyclic ethers that are potential alternative fuels.     

氨燃烧及反应机理研究进展

现今的一系列环境和能源问题迫使人类急需寻找清洁的燃料以替代传统的化石燃料。氨作为一种富氢的无碳燃料,具有能量密度高、成本低、储运安全等优势,近年来受到了越来越多学者的关注,成为了一个研究热点。本文介绍了氨燃料的物化特性及燃烧特性,分析了氨与各种燃料混合燃烧在燃烧速度、火焰结构、污染物形成等方面的表现以及在发动机的应用情况,详述了氨燃烧机理及动力学模型的研究现状,指出有待进一步研究的问题并展望了氨燃烧研究的发展方向。     

Biofuels from microalgae biomass: A review of conversion processes and procedures

Achieving the EU 2030 vision of a 15% minimum amount of biofuels utilized in the road transportation require more research on biofuel production from biomass feedstock. To this end, this review study examines the use of green, deep eutectic solvents and direct transesterification approaches for biomass conversion to biofuels. Next, biogas production from anaerobic co-digestion of microalgae biomass is presented. Lastly, the effect of operating conditions, as well as advantages and limitations of several biomass conversion techniques are outlined. Of note, this study presents promising microalgae conversion processes which could be progressed are the use of bio-based solvents and supercritical fluids for biodiesel production, hydrothermal liquefaction for biogas production, microwave-induced pyrolysis for syngas production, and ultrasound/microwave enhanced extraction for bio-oil production. These are based on the possibility of high yield and process economics. We have also enumerated knowledge gaps needed to propel future studies.     

Making JP‐10 Superfuel Affordable with a Lignocellulosic Platform Compound

The synthesis of renewable jet fuel from lignocellulosic platform compounds has drawn a lot of attention in recent years. So far, most work has concentrated on the production of conventional jet fuels. JP‐10 is an advanced jet fuel currently obtained from fossil energy. Due to its excellent properties, JP‐10 has been widely used in military aircraft. However, the high price and low availability limit its application in civil aviation. Here, we report a new strategy for the synthesis of bio‐JP‐10 fuel from furfuryl alcohol that is produced on an industrial scale from agricultural and forestry residues. Under the optimized conditions, bio‐JP‐10 fuel was produced with high overall carbon yields (≈65 %). A preliminary economic analysis indicates that the price of bio‐JP‐10 fuel can be greatly decreased from ≈7091 US$/ton (by fossil route) to less than 5600 US$/ton using our new strategy. This work makes the practical application of bio‐JP‐10 fuel forseeable.     

The Effect of Alcohol and Carbonyl Functional Groups on the Competition between Unimolecular Decomposition and Isomerization in C4 and C5 Alkoxy Radicals

Presented here are computed rates for the thermal unimolecular decomposition of a variety of alkoxy radicals with four‐ and five‐carbon length backbones. Three classes of molecules are examined: alkoxy radicals with saturated hydrocarbon backbones, those with alcohol functional groups, and those with carbonyl functional groups. The chosen species represent many of those found during the combustion of fossil fuels as well as bio‐derived alternatives. Density functional theory calculations were benchmarked against higher level coupled cluster calculations and used to explore the potential energy surfaces of these systems. Transition state theory was used to calculate high‐pressure limit rate coefficients of all radical intermediates in the regimes relevant to atmospheric chemistry and combustion. We show that the assumption that alkoxy radicals quickly decompose via β‐scission to aldehydes and other radicals is not valid for some of the alkoxy radicals investigated in this work. We further illustrate how intra‐H migrations in larger alkoxy radicals with carbonyl and alcohol functional groups can dominate unimolecular decomposition under combustion and atmospheric relevant conditions. Finally, we discuss why carbonyl groups can increase or decrease intra‐H migration barriers depending on their location relative to the transferring H‐atom.     

Experimental and modeling study of C5H10O2 ethyl and methyl esters

Due to the world's over-reliance on fossil fuels there has been a developing interest in the production of renewable biofuels such as methyl and ethyl esters derived from vegetable oils and animal fats. To increase our understanding of the combustion chemistry of esters, the oxidation of methyl butanoate and ethyl propanoate, both with a molecular formula of C5H10O2, have been studied in a series of high-temperature shock tube experiments. Ignition delay times for a series of mixtures, of varying fuel/oxygen equivalence ratios (phi = 0.25-1.5), were measured behind reflected shock waves over the temperature range 1100-1670 K, and at pressures of 1.0, and 4.0 atm. It was found that ethyl propanoate was consistently faster to ignite than methyl butanoate, particularly at lower temperatures. Detailed chemical kinetic mechanisms have been assembled and used to simulate these experiments with good agreement observed. Rate of production analyses using the detailed mechanisms shows that the faster reactivity of ethyl propanoate can be explained by a six-centered unimolecular decomposition reaction with a relatively low activation energy barrier producing propanoic acid and ethylene. The elimination reaction itself is not responsible for the increased reactivity; it is the faster reactivity of the two products, propanoic acid and ethylene that leads to this behavior.     

Computational Kinetic Study for the Unimolecular Decomposition of Cyclopentanone

Among various categories of potential biofuel molecules, ketones are of significant interest. Cyclopentanone is a cyclic ketone that can be produced from biomass, and its combustion is still unknown. Moreover, its cyclic configuration makes it an interesting feedstock for the further production of high‐density fuels such as bi(cyclopentane). This study reports the first computational kinetic investigation of the unimolecular decomposition pathways of cyclopentanone by using the compound G3B3 method. The rate constants were calculated using Rice–Ramsperger–Kassel–Marcus theory in the temperature range of 800–2000 K. The results presented here can be used in a future kinetic combustion mechanism.     

Electrochemical Determination of Organic Compounds in Automotive Fuels

This article critically reviews the electroanalytical methods devoted for the determination of organic compounds in automotive fuels that can range from contaminants to additives typically introduced into liquid biofuels and liquid fossil fuels. Contaminants such as aldehydes and ketones in bioethanol, free fatty acids and glycerol in biodiesel, and sulfur and nitrogen organic compounds in gasoline and diesel fuel, and additives such as colour markers and antioxidants added to fuels were determined by electroanalytical methods. Special focus is given to electrodes, electrochemical techniques, and sample preparation strategies. Future directions of research on electroanalysis of liquid fuels are presented.     

Plasma Assisted Low Temperature Combustion

This paper presents recent kinetic and flame studies in plasma assisted low temperature combustion. First, the kinetic pathways of plasma chemistry to enhance low temperature fuel oxidation are discussed. The impacts of plasma chemistry on fuel oxidation pathways at low temperature conditions, substantially enhancing ignition and flame stabilization, are analyzed base on the ignition and extinction S-curve. Secondly, plasma assisted low temperature ignition, direct ignition to flame transition, diffusion cool flames, and premixed cool flames are demonstrated experimentally by using dimethyl ether and n-heptane as fuels. The results show that non-equilibrium plasma is an effective way to accelerate low temperature ignition and fuel oxidation, thus enabling the establishment of stable cool flames at atmospheric pressure. Finally, the experiments from both a non-equilibrium plasma reactor and a photolysis reactor are discussed, in which the direct measurements of intermediate species during the low temperature oxidations of methane/methanol and ethylene are performed, allowing the investigation of modified kinetic pathways by plasma-combustion chemistry interactions. Finally, the validity of kinetic mechanisms for plasma assisted low temperature combustion is investigated. Technical challenges for future research in plasma assisted low temperature combustion are then summarized.