High Energy Density Fuels Research Articles

(Invited) Photo-Electro-Chemical Water Splitting and the Making of Renewable Chemicals

Hydrogen is the simplest solar fuel to produce and in this presentation we shall give a short overview of the pros and cons of various tandem devices [1,2]. The large band gap semiconductor needs to be in front, but apart from that we can chose to have either the anode in front or back using either acid or alkaline conditions. Since most relevant semiconductors are very prone to corrosion the advantage of using buried junctions and using protection layers offering shall be discussed [3-5]. In particular we shall show how doped TiO2 is a very generic protection layer for both the anode and the cathode [6]. Next we shall discuss the availability of various catalysts for being coupled to these protections layers and how their stability and amount needed may be evaluated [7, 8, 9]. Examples of half-cell reaction using protection layers for both cathode and anode will be discussed though some of recent examples both under both alkaline and acidic conditions. Notably NiOx promoted by iron is a material that is transparent, providing protection, and is a good catalyst for O2 evolution [10]. Si is a very good low band gap semiconductor and the optimal thickness of this in a tandem device will be discussed [11]. Finally if time allows we shall also discuss the possibility of making high energy density fuels by hydrogenation of CO2 instead of hydrogen evolution [12]. We shall here show how we can investigate the recent ethanol synthesis on oxygen derived Cu found by Kanan et al. and show how acetaldehyde seems to be an important intermediate [13].

Boron Nanoparticles for Room‐Temperature Hydrogen Generation from Water

Boron nanoparticles (BNPs) are of great interest for applications such as neutron capture therapy of cancer cells, hydrogen generation from water, and high energy density fuels. Boron is particularly interesting for chemical water splitting, because of its high gravimetric hydrogen generation potential of 277 g H2 per kg B. However, only a few studies of water splitting by reaction with boron are available, and those have used high temperature steam with external heating. Room‐temperature boron hydrolysis is of great interest from both scientific and practical perspectives. The studies presented here demonstrate that high purity amorphous BNPs can be oxidized by water to produce H2 at room temperature, without external energy input, in the presence of catalytic quantities of an alkali metal or alkali metal hydride. The BNPs are produced in a single step gas phase process via CO2 laser‐induced pyrolysis of mixtures of B2H6 and SF6. The BNPs are spherical with a primary particle diameter of 10–15 nm, narrow size distribution, and specific surface area exceeding 250 m2 g−1. This first demonstration of room‐temperature chemical splitting of liquid water using boron opens up exciting new possibilities for on‐demand hydrogen generation at high gravimetric capacity.

Using GC-MS to Analyze Bio-Oil Produced from Pyrolysis of Agricultural Wastes - Discarded Soybean Frying Oil, Coffee and Eucalyptus Sawdust in the Presence of 5% Hydrogen and Argon

Pyrolysis is a thermal process for converting various biomasses, wastes and residues to produce high-energydensity fuels (bio-oil). In this paper, we have done some important analysis of bio-oil which is obtained from the pyrolysis of agricultural wastes - discarded soybean frying oil, coffee and eucalyptus sawdust in the presence of 5% Hydrogen and Argon. The bio oil was obtained in one step pyrolysis in which temperature of the system kept 15°C and then increased up to 800°C but in two step condensation processes. 1st condensation step is done on temperature 100°C and 2nd is done on 5°C. So we got two types of fractions, HTPO (Oil condensed at high temperature 100°C after pyrolysis) and LTPO (Oil condensed at low temperature 5°C after pyrolysis). After pyrolysis the thermal cracking is done for both types of oil on the same two temperatures, then we again got two type of fractions HTCO (high temperature 100°C condensed oil after cracking) and LTCO (Low temperature 5°C condensed oil after cracking), these fractions are distillated and analyzed in GC-MS. The resulted compounds are given in the paper and are explained with the help of graphs and tables. The ultimate aim of hydrogenation and Argon is to improve stability and fuel quality by decreasing the contents of organic acids and aldehydes as well as other reactive compounds, as oxygenated and nitrogenated species because they not only lead to high corrosiveness and acidity, but also set up many obstacles to applications.

Closing the carbon cycle through rational use of carbon-based fuels.

In this paper, a brief overview is presented of natural gas as a fuel resource with subsequent carbon capture and re-use as a means to facilitate reduction and eventual elimination of man-made carbon emissions. A particular focus is shale gas and, to a lesser extent, methane hydrates, with the former believed to provide the most reasonable alternative as a transitional fuel toward a low-carbon future. An emphasis is placed on the gradual elimination of fossil resource usage as a fuel over the coming 35 to 85 years and its eventual replacement with renewable resources and nuclear power. Furthermore, it is proposed that synthesis of chemical feedstocks from recycled carbon dioxide and hydrogen-rich materials should be undertaken for specific applications in the transport sector which require access to high energy density fuels. To achieve the latter, carbon dioxide capture is imperative and possible synthetic routes for chemical feedstock production are briefly reviewed.

A comparison of product yields and inorganic content in process streams following thermal hydrolysis and hydrothermal processing of microalgae, manure and digestate

Thermal hydrolysis and hydrothermal processing show promise for converting biomass into higher energy density fuels. Both approaches facilitate the extraction of inorganics into the aqueous product. This study compares the behaviour of microalgae, digestate, swine and chicken manure by thermal hydrolysis and hydrothermal processing at increasing process severity. Thermal hydrolysis was performed at 170°C, hydrothermal carbonisation (HTC) was performed at 250°C, hydrothermal liquefaction (HTL) was performed at 350°C and supercritical water gasification (SCWG) was performed at 500°C. The level of nitrogen, phosphorus and potassium in the product streams was measured for each feedstock. Nitrogen is present in the aqueous phase as organic-N and NH3–N. The proportion of organic-N is higher at lower temperatures. Extraction of phosphorus is linked to the presence of inorganics such as Ca, Mg and Fe in the feedstock. Microalgae and chicken manure release phosphorus more easily than other feedstocks.

Catalysts, Protection Layers, and Semiconductors: The Challenge of Interfacing

Hydrogen is the simplest solar fuel to produce and in this presentation we shall give a short overview of the pros and cons of various tandem devices [1,2]. The large band gap semiconductor needs to be in front, but apart from that we can chose to have either the anode in front or back using either acid or alkaline conditions. Since most relevant semiconductors are very prone to corrosion the advantage of using buried junctions and using protection layers offering shall be discussed [3-5]. In particular we shall show how doped TiO2 is a very generic protection layer for both the anode and the cathode [6]. Next we shall discuss the availability of various catalysts for being coupled to these protections layers and how their stability and amount needed may be evaluated [7, 8, 9]. Examples of half-cell reaction using protection layers for both cathode and anode will be discussed though some of recent examples both under both alkaline and acidic conditions. Notably NiOx promoted by iron is a material that is transparent, providing protection, and is a good catalyst for O2 evolution [10]. Si is a very good low band gap semiconductor and the optimal thickness of this in a tandem device will be discussed [11]. We have also recently started searching for large band gap semiconductors like III-V based or pervoskite materials and follow the same strategy by using protection layers and catalysts [12]. Finally if time allows we shall also discuss the possibility of making high energy density fuels by hydrogenation of CO2 instead of hydrogen evolution [13].

Size Resolved High Temperature Oxidation Kinetics of Nano-Sized Titanium and Zirconium Particles.

While ultrafine metal particles offer the possibility of very high energy density fuels, there is considerable uncertainty in the mechanism by which metal nanoparticles burn, and few studies that have examined the size dependence to their kinetics at the nanoscale. In this work we quantify the size dependence to the burning rate of titanium and zirconium nanoparticles. Nanoparticles in the range of 20-150 nm were produced via pulsed laser ablation, and then in-flight size-selected using differential electrical mobility. The size-selected oxide free metal particles were directly injected into the post flame region of a laminar flame to create a high temperature (1700-2500 K) oxidizing environment. The reaction was monitored using high-speed videography by tracking the emission from individual nanoparticles. We find that sintering occurs prior to significant reaction, and that once sintering is accounted for, the rate of combustion follows a near nearly (diameter)(1) power-law dependence. Additionally, Arrhenius parameters for the combustion of these nanoparticles were evaluated by measuring the burn times at different ambient temperatures. The optical emission from combustion was also used to model the oxidation process, which we find can be reasonably described with a kinetically controlled shrinking core model.

Experimental Study on the Combustion and Microexplosion of Freely Falling Gelled Unsymmetrical Dimethylhydrazine (UDMH) Fuel Droplets

The increasing demand for high energy density fuels and the concern for their safety have propelled research in the field of gelled propellants, where understanding the combustion of single gelled fuel droplets is the first stage to predict the spray combustion characteristics. The experiments utilized single-isolated freely falling gelled unsymmetrical dimethylhydrazine (UDMH) droplets instead of the conventional suspended droplet approach, in order to eliminate the perturbation associated with the suspension mechanism. Morphological transformations of the gelled droplet involved in the combustion processes were monitored by employing a high-speed digital camera, while the effects of ambient pressure and oxygen concentration on burning rate constants were also studied. The experimental results show that four main phenomena (droplet deformation, bubble formation and growth, vapor jetting and luminous jetting flame with “horn” shape) and three distinct phases were identified in the droplet combustion process; the high yield stress and polymer chain structure of polymer gellant are responsible for the appearance of bubbles with almost the same order of magnitude as the droplets. Increasing the ambient pressure can increase the burning rate, postpone the appearance of microexplosions, and weaken microexplosion intensity; while increasing the ambient oxygen concentration can promote the appearance of microexplosions, strengthen microexplosion intensity and increase the burning rate.

(Invited) Efficient Generation of High Energy Density Fuel from Water

Carbon-free energy generation is a necessity to meet rising global energy needs while minimizing environmental impact. Hydrogen has the potential to be a cost competitive and scalable solution to replace fossil fuels, and water electrolysis is an attractive concept for producing hydrogen with zero carbon footprint when integrated with a renewable energy source. Proton Energy Systems is a world leader in hydrogen generation from PEM electrolysis and has demonstrated the commercial viability of this technology in the industrial gas market, with pathways defined to reach targets in the energy markets. Recent catalyst research at Proton has demonstrated efficiency improvements while maintaining stability. Ongoing collaboration with 3M has also shown feasibility to reduce the catalyst loading by over an order of magnitude vs. current commercial loadings. This paper will discuss Proton's fueling efforts, particularly at high pressure, and advancements in efficiency which enable localized generation of hydrogen where it is needed.

(Invited) Efficient Generation of High Energy Density Fuel from Water

not Available.

A mediator-adapted diaphorase variant for a glucose dehydrogenase–diaphorase biocatalytic system

Biofuel cell is an energy conversion device of the next generation which enables use of safer and higher energy-density fuels such as glucose. We have been developing a biofuel cell that comprises the three enzymes: glucose dehydrogenase (GDH) and diaphorase (DI) on anode, and bilirubin oxidase (BOD) on cathode. In this work, we have developed a DI variant suitable for our biofuel cell by using directed molecular evolution method. A gene library of DI variants was constructed by using error-prone PCR and the variant proteins were expressed in an Escherichia coli system. 8000 isolated variants have been screened with activity against 2-amino-1,4-naphthoquinone (ANQ), and 10 of them have been qualified which were then purified and examined their activities against ANQ. A highest activity was observed in G122D variant of which glycine residue at position 122 is substituted to aspartate. Enzymatic kinetic analyses show that K M for ANQ in G122D is 1/3 of that in wild type (G122D: 356 μM, wild type: 1.08 mM), whereas k cat and K M for NADH is almost the same, clearly showing that G122D mutation has given DI an improvement in enzymatic activity at lower ANQ concentration. The effect of this mutation was considered electrochemically in solution and in immobilized layer. The results show that G122D variant DI gave a higher current at lower ANQ concentration in solution, as well as in immobilized condition where GDH is co-immobilized within.

Solid Oxide Fuel Based Auxiliary Power Unit for Regional Jets: Design and Mission Simulation With Different Cell Geometries

Although it accounts for only 4.2% of the total global warming potential, the concern today is that aviation generated CO2 is projected to grow to approximately 5.7% by 2050. Aviation emissions are growing faster than any other sector and they risk undermining the progress achieved through emission cuts in other areas of the economy. Rapidly emerging hydrogen and fuel-cell-based technologies could be developed for future replacement of on-board electrical systems in “more-electric” or “all-electric” aircrafts. Primary advantages of deploying these technologies are low emissions and low noise (important features for commuter airplanes, which takeoff and land in urban areas). Solid oxide fuel-cell (SOFC) systems could result advantageous for some aeronautical applications due to their capability of accepting hydrocarbons and high energy-density fuels. Moreover they are suitable for operating in combined-heat-and-power configurations, recovering heat from the high-temperature exhaust gases, which could be used to supply thermal loads therefore reducing the electric power requested by the aircraft. ENFICA-FC is a project selected by the European Commission in the Aeronautics and Space priority of the Sixth Framework Programme (FP6) and led by Politecnico di Torino, in Turin, Italy. One of the objectives of the project is to carry out a feasibility study on a more-electric intercity aircraft (regional jet: 32 seats). After the characterization of the power consumption of electrical and nonelectrical loads, and the definition of a mission profile, the design of the SOFC-based energy system as well as the simulation of a complete mission is performed hypothesizing different system configurations. The simulation concerns both the stack (current and current density, cell and stack voltage, etc.) and the balance-of-plant (air compressor power, gross stack power, system efficiency, etc.). The obtained results are analyzed and discussed.

Oxide-Free, Catalyst-Coated, Fuel-Soluble, Air-Stable Boron Nanopowder as Combined Combustion Catalyst and High Energy Density Fuel

Elemental boron has one of the highest volumetric heats of combustion known and is therefore of interest as a high energy density fuel. The fact that boron combustion is inherently a heterogeneous process makes rapid efficient combustion difficult. An obvious strategy is to increase the surface area/volume ratio by decreasing the particle size. This approach is limited by the fact that boron forms a ∼0.5 nm thick native oxide layer, which not only inhibits combustion, but also consumes an increasing fraction of the particle mass as the size is decreased. Another strategy might be to coat the boron particles with a material (e.g., catalyst) to enhance combustion of either the boron itself or of a hydrocarbon carrier fuel. We present a simple, scalable, one-step process for generating air-stable boron nanoparticles that are unoxidized, soluble in hydrocarbons, and coated with a combustion catalyst. Ball milling is used to produce ∼50 nm particles, protected against room temperature oxidation by oleic acid f...

Air-stable, unoxidized, hydrocarbon-dispersible boron nanoparticles

Here we describe a simple method to produce boron nanoparticles with control over surface chemistry and dispersiblity in different solvents, with potential applications ranging from high energy density fuels to neutron capture therapy. The methodology should be adaptable to many hard materials; indeed, we have produced hydrocarbon-dispersible silicon nanoparticles using a procedure similar to that described below. The method, based on high-energy milling, with subsequent sedimentation to separate aggregates, produces gram quantities of nanoparticles in a narrow distribution of particle sizes centered around 50 nm, and should be readily scalable to industrial scale production.

Analysis of Solid Oxide Fuel Cell Systems for More-Electric Aircraft

Aviation emissions are growing faster than any other sector and they risk undermining the progress achieved through emission cuts in other areas of the economy. Rapidly emerging hydrogen- and fuel-cell-based technologies could be developed for future replacement of onboard electrical systems in more-electric or all-electric aircraft. The primary advantages of deploying these technologies are low emissions and low noise (important features for commuter airplanes that take off and land in urban areas). Solid oxide fuel-cell systems could be advantageous for some aeronautical applications due to their capability of accepting hydrocarbons and high energy-density fuels. Moreover, they are suitable for operating in combined heat and power configurations; they recover heat from hightemperature exhaust gases, which could be used to supply thermal loads and thereby reduce the electric power requested by the aircraft. Environmentally Friendly Inter City Aircraft Powered by Fuel Cells is a Sixth Framework Programme project selected by the Aeronautics and Space division of the European Commission and led by the Politecnico di Torino in Turin, Italy.One of the objectives of the project is to carry out a feasibility study on different typologies of more-electric intercity aircraft. After the characterization of the power consumption of electrical and nonelectrical loads, and the definition of mission profiles for three different typologies of passenger aircraft, the design of the solid oxide fuel-cell-based energy system as well as the simulation of complete missions is performed by hypothesizing different system configurations. The simulations concern both the stack (current and current density, cell and stack voltage, etc.) and the balance of plant (air compressor power, gross stack power, system efficiency, etc.). Obtained results are analyzed and discussed

Silanes as Fuel for Aerospace Propulsion

In the light of recently revived interest in high energy density fuels for aerospace applications1,2), a new look is being given at unconventional fuels. Among the latter are hydrides, because their hydrogen content and density. Among hydrides silanes are of interest because of their combustion and energetic properties.Silanes are silicon hydrides organized in molecular chains similar to those of hydrocarbons; at STP, lower silanes (SiH4, Si2H6) are gaseous and extremely pyrophoric; with increasing chain length, silanes become liquid from trisilane (Si3H8) on, and therefore easily pumped. Another important feature of silanes is the large amount of hydrogen theoretically available by thermal decomposition: in fact at moderate temperatures (about 500 K) the chains begin to break and at 700 K their decomposition is complete, yielding silicon and gaseous hydrogen, useful for propulsion in combination with air nitrogen and oxygen. This last feature, if confirmed, could identify silanes not only as energy carriers but also components in bi-fuel systems. To assess their theoretical performance, simulations were conducted assuming silanes and/or their thermal decomposition products in combination with various oxidizers and air. Preliminary results are suggestive of their potential for some specialized applications, especially where compactness is at premium.

Recent Developments in High-Energy Density Liquid Hydrocarbon Fuels

The evolution of high-energy density fuels over the past three decades is briefly described. This period can be characterized by exceedingly slow progress and notable lack of success toward the development of practical, economically viable fuel systems. Recently, two novel ultrahigh-energy density fuels, one naturally occurring and one synthetic, have emerged; these fuels, which are both composed of compact hydrocarbon molecules, have energy contents or heating values significantly greater than that of currently used standard missile fuel JP-10 (up to 160K Btu/gal (44.7K MJ/m3) vs 141.7K Btu/gal (39.6K MJ/m3)). In addition, these fuels also exhibit superior low-temperature, viscometric, flash-point, and other properties that are desired and, indeed, required for practical fuels. Initial research and development of these fuels are described, and their chemistries, properties, and, in the case of the naturally occurring fuel, engine test results are provided.

Ignition Characteristics of a New High-Energy Density Fuel in High-Speed Flows

were measured. The results indicate that compared with hydroxy-terminated-polybutadiene fuel at the same thermodynamic conditions and geometrical cone guration the dimer ignition times are one order of magnitude faster. The heat released by combustion by the dimers is more than twice as large. Phase change, ignition, and combustion processes of these fuels are investigated with the aid of scanning electron microscope, high-speed photography, and pressure and temperature measurements.