Publications
215 results found
Brown NJ, Harris JE, Yin X, et al., 2014, Mononuclear phenolate diamine zinc hydride complexes and their Reactions with CO2, Organometallics, Vol: 33, Pages: 1112-1119, ISSN: 1520-6041
The synthesis, characterization, and zinc coordination chemistry of the three proligands 2-tert-butyl-4-[tert-butyl (1)/methoxy (2)/nitro (3)]-6-{[(2′-dimethylaminoethyl)methylamino]methyl}phenol are described. Each of the ligands was reacted with diethylzinc to yield zinc ethyl complexes 4–6; these complexes were subsequently reacted with phenylsilanol to yield zinc siloxide complexes 7–9. Finally, the zinc siloxide complexes were reacted with phenylsilane to produce the three new zinc hydride complexes 10–12. The new complexes 4–12 have been fully characterized by NMR spectroscopy, mass spectrometry, and elemental analyses. The structures of the zinc hydride complexes have been probed using VT-NMR spectroscopy and X-ray diffraction experiments. These data indicate that the complexes exhibit mononuclear structures at 298 K, both in the solid state and in solution (d8-toluene). At 203 K, the NMR signals broaden, consistent with an equilibrium between the mononuclear and dinuclear bis(μ-hydrido) complexes. All three zinc hydride complexes react rapidly and quantitatively with carbon dioxide, at 298 K and 1 bar of pressure over 20 min, to form the new zinc formate complexes 13–15. The zinc formate complexes have been analyzed by NMR spectroscopy and VT-NMR studies, which reveal a temperature-dependent monomer–dimer equilibrium that is dominated by the mononuclear species at 298 K.
Silverwood IP, Keyworth CW, Brown NJ, et al., 2014, An Attenuated Total Reflection Fourier Transform Infrared (ATR FT-IR) Spectroscopic Study of Gas Adsorption on Colloidal Stearate-Capped ZnO Catalyst Substrate, APPLIED SPECTROSCOPY, Vol: 68, Pages: 88-94, ISSN: 0003-7028
Arcelus-Arrillaga P, Millan M, Hellgardt K, 2014, Effect of pressure, O/ostoich ratio and temperature on the partial oxidation of heavy oil model compound phenanthrene, Pages: 483-485
An increasing world energy demand and the proportions of heavy oil reserves relative to lighter and more valuable feedstocks have enabled the development of new emerging research fields. A novel method to upgrade heavy oil through partial oxidation in supercritical water (SCW) is being developed in the research group. This method takes advantage of the properties of SCW (T=374°C, P=220 bar and δ=0.32 g/ml and above), in which water changes from a good solvent for polar to non-polar species. At these conditions a change in the ion product, in the viscosity and a decrease in the dielectric constant are observed [1]. Studies with model compounds representing chemical structures found in heavy oils give relevant information about the reactivity in the medium and the reaction mechanisms occurring in the system. Reactions with polycyclic aromatic hydrocarbons have been studied in the presence and absence of an oxidizer [2, 3]. The aim of this work is to investigate and get an understanding about the effect of process conditions pressure, temperature and O/Ostoich ratio in the yield and selectivity to different reaction products of the partial oxidation of heavy oil model compound phenanthrene at near and supercritical water conditions.
Azizan MT, Hellgardt K, Chadwick D, 2014, Ethanol Steam Reforming Over Calcium Doped Ni/Al<sub>2</sub>O<sub>3</sub> Catalyst, 3rd International Conference on Process Engineering and Advanced Materials (ICPEAM), Publisher: TRANS TECH PUBLICATIONS LTD, Pages: 271-+, ISSN: 1660-9336
Azizan MT, Hellgardt K, Chadwick D, 2014, Thermodynamic Analysis of Autothermal Reforming of Oxygenated Hydrocarbons At Thermoneutral Condition for Hydrogen Production, 3rd International Conference on Process Engineering and Advanced Materials (ICPEAM), Publisher: TRANS TECH PUBLICATIONS LTD, Pages: 730-+, ISSN: 1660-9336
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- Citations: 6
Alshammari YM, Hellgardt K, 2014, A new HYSYS model for underground gasification of hydrocarbons under hydrothermal conditions, International Journal of Hydrogen Energy, ISSN: 0360-3199
A new subsurface process model was developed using the ASPEN HYSYS simulation environment to analyse the process energy and gasification efficiency at steady-state equilibrium conditions. Injection and production wells were simulated using the HYSYS pipe flow utilities which makes use of the Beggs and Brill flow correlation applicable for vertical pipes. The downhole reservoir hydrothermal reactions were assumed to be in equilibrium, and hence, the Gibbs reactor was used. It was found that high W/C ratios and low O/C ratios are required to maximise gasification efficiency at a constant hydrocarbon feed flowrate, while the opposite is true for the energy efficiency. This occurs due to the dependence of process energy efficiency on the gas pressure and temperature at surface, while the gasification efficiency depends on the gas composition which is determined by the reservoir reaction conditions which affects production distribution. Another effect of paramount importance is the increase in reservoir production rate which was found to directly enhance both energy and gasification efficiency showing conditions where the both efficiencies are theoretically maximised. Results open new routes for techno-economic assessment of commercial implementation of underground gasification of hydrocarbons. © 2014 Hydrogen Energy Publications, LLC.
Patel B, Hellgardt K, 2013, Hydrothermal upgrading of algae paste: Application of <sup>31</sup>P-NMR, Environmental Progress and Sustainable Energy, Vol: 32, Pages: 1002-1012, ISSN: 1944-7442
Although already proposed in the 1940s, hydrothermal upgrading of biomass, and specifically algae, to produce biocrude has only recently become a much researched topic. Algae are of special interest as they are capable of much higher biomass accumulation rates than terrestrial plants. To understand the transformation of algal biomass into biocrude, this process needs to be scrutinized in as much detail as possible to identify the most appropriate reaction conditions. It is usually not possible to identify individual transformation steps; however, in this article we demonstrate the use of 31P-NMR to follow the fate of derivatized (2-chloro-4,4,5,5- tetramethyl-1,3,2-dioxaphospholane) hydroxyl groups to start understand, which chemical species are involved in the initial degradation steps. Our data show the occurrence of a very fast degradation of acidic OH groups (derived from the hydrolysis of lipids) and aliphatic OH groups (derived from the fast hydrolysis of carbohydrates). The degradation of proteins leads to polyphenols, which appear to be rather stable even over prolonged treatment periods. Small quantities of aromatic compounds are also formed as secondary degradation products through sugar dehydration and cyclization as well as peptide transformation. It appears that additional deoxygenation routes exist as the deoxygenation rate using 31P-NMR and that determined by elemental analysis differ. The formed oil (biocrude) is compared with typical North Sea oils using simulated distillation and was found to contain a significant high boiling faction, which would require further treatment (e.g., hydrocracking) to shift the boiling range to a more valuable oil composition. © 2013 American Institute of Chemical Engineers Environ Prog, 32: 1002-1012, 2013 Copyright © 2013 American Institute of Chemical Engineers Environ Prog.
Richard CJ, Patel B, Chadwick D, et al., 2013, Hydrothermal deoxygenation of pyrolysis oil from Norwegian spruce: <i>Picea abies</i>, BIOMASS & BIOENERGY, Vol: 56, Pages: 446-455, ISSN: 0961-9534
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- Citations: 9
Maguire N, Sasegbon A, Abdelkader A, et al., 2013, Using temporal analysis of products and flux response technology to determine diffusion coefficients in catalytic monoliths, CHEMICAL ENGINEERING SCIENCE, Vol: 87, Pages: 224-233, ISSN: 0009-2509
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- Citations: 8
Patel B, Hellgardt K, 2013, Simultaneous supercritical transesterification and hydrothermal liquefaction of algae paste, Pages: 639-640
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- Citations: 1
Brown NJ, Weiner J, Hellgardt K, et al., 2013, Phosphinate stabilised ZnO and Cu colloidal nanocatalysts for CO<sub>2</sub> hydrogenation to methanol, CHEMICAL COMMUNICATIONS, Vol: 49, Pages: 11074-11076, ISSN: 1359-7345
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- Citations: 44
Tamburic B, Dechatiwongse P, Zemichael FW, et al., 2013, Process and reactor design for biophotolytic hydrogen production, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 15, Pages: 10783-10794, ISSN: 1463-9076
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- Citations: 28
Hellgardt K, Richard C, Patel B, 2012, Supercritical upgrading of algae paste, AIChE 2012 - 2012 AIChE Annual Meeting, Conference Proceedings
Biodiesel is commonly produced via transesterification of plant derived oils (rape, palm). However, biodiesel produced from algae paste has the potential to be more lucrative due to the intrinsically higher productivity of algae. The current method of only transesterifying extracted algae oil is not particularly economical as it requires water removal, drying and extraction processes prior to transesterification. Thus direct supercritical treatment of wet algal paste is suggested to convert the lipids but also the algal biomass itself into a useful biofuel. Algal biomass might be amenable to this processing technique because algae do not contain lignocellulose and therefore could yield a hydrocarbon fuel with much lower oxygen content. The kinetics of the transformation of algal paste is followed using GC MS, 13C NMR and 1H NMR to observe functional group distribution/concentration within the product mixture. Batch stainless steel and quartz reactors are employed to evaluate the effect of catalyst addition on the rate and selectivity of algae paste conversion. First results of the continuous processing of algae paste in a flow reactor to yield bio-crude will be shown.
Okpoko E, Fennell PS, Hellgardt K, 2012, Cu based oxygen carriers for chemical looping processes
Chemical looping combustion (CLC) is a process developed to efficiently burn gaseous fuels and at the same time capture CO2 without an additional energy intensive separation unit. CLC is a two stage processes which involves supplying oxygen to the fuel for combustion using an oxygen carrier and the subsequent regeneration of the oxygen carrier back to its original state with air. CLC might be economically viable and depending on the design, specific reaction products can be obtained. Hydrogen and syngas are two very important products useful for power generation and intermediates production in the chemical industry. This project focuses on the investigation of Cu based oxygen carriers for the CLC process with particular respect to the stability and kinetics of the synthesised materials. Particles composed of 40, 60 and 80 % CuO supported on Al2O3 have been prepared by co-precipitation methods with Na2CO3 and NH4OH. X-ray analysis (XRD) reveals the presence of a mixture of CuO and CuAl2O4, both being reducible as evidenced by CO/CH4-TPR analysis. The reduction and oxidation kinetics where investigated in a TGA system for particle sizes < 355 μm. Reaction orders for CO, CH4 and O2 were determined as 2, 1.5 and 0.7, respectively and activation energies were in the order O2 > CO > CH4 at temperatures T ≤ 700 °C. The reactivity of the Cu-based oxygen carriers during 20 cycles was investigated both by TGA and fixed-bed reactor operation at temperatures ≤ 700 °C. SEM analysis revealed no sign of sintering with the carriers prepared with Na2CO3 but little sintering effects were observed with carriers prepared with NH4OH. The experimental results suggest that Cu-based oxygen carriers prepared by co-precipitation appear to be very suitable for CLC operation.
Ong CK, Dennison S, Kelsall G, et al., 2012, Titanium supported iron oxide for photo-electrochemical hydrogen production, AIChE 2012 - 2012 AIChE Annual Meeting, Conference Proceedings
The total global energy consumption today is about 14 TW and is expected to double by the year 2050. There is a heavy dependency on fossil fuels to meet this energy demand, which contributes significantly to global CO2 emissions. Hydrogen is a clean energy carrier, which could supply future energy demand whilst minimising CO2 emissions, provided that the hydrogen is produced in a clean and sustainable process such as by photo-electrolysis. Photo-electrolysis offers a potentially elegant solution to the capture of solar energy by directly facilitating the splitting of water to produce hydrogen and oxygen. The feasibility of this process is well established and much work is devoted to finding and developing improved photo anodes for oxygen evolution. The current state of the art for photo-electrolysis systems is restricted to small, lab-scale, photo-electrochemical cells which cannot produce useful quantities of hydrogen. In order to scale up photo-electrochemical systems the photo-electrodes need to be deposited onto larger electrode areas. Conventional support electrodes are ITO (indium doped tin oxide) or FTO (fluorine doped tin oxide) substrates. Our previous work has shown that the use of fluorine-dope tin oxide (FTO) substrates would result in a large lateral potential drop, rendering most of the exposed photo electrode surface area inactive for the photo oxidation/reduction of water. This can be avoided if a more conductive substrate such as stainless steel or titanium is employed. In this paper we will present and compare our results of the photo-activity of Fe2O3 deposited by spray pyrolysis onto both, FTO and titanium substrates (Figure 1). We will show that the control of the metal oxide interface layer is crucial in achieving high photocurrents in the case of titanium substrates.
Sasegbon A, Hellgardt K, 2012, Flux response technology applied in zero length column diffusivity measurements, ADSORPTION-JOURNAL OF THE INTERNATIONAL ADSORPTION SOCIETY, Vol: 18, Pages: 403-415, ISSN: 0929-5607
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- Citations: 1
Tamburic B, Zemichael FW, Maitland GC, et al., 2012, Effect of the light regime and phototrophic conditions on growth of the H-2-producing green alga Chlamydomonas reinhardtii, 19th World Hydrogen Energy Conference (WHEC), Publisher: Elsevier, Pages: 710-719, ISSN: 1876-6102
Development of the capacity to produce hydrogen economically from renewable energy resources is of critical importance to the future viability of that fuel. The inexpensive and widely available green alga Chlamydomonas reinhardtii has the ability to photosynthetically synthesise molecular hydrogen. Green algal hydrogen production does not generate any toxic or polluting bi-products and could potentially offer value-added products derived from algal biomass. The growth of dense and healthy algal biomass is a vital requirement for efficient hydrogen production. Algal cell density is principally limited by the illumination conditions of the algal culture and by the availability of key nutrients, including the sources of carbon, nitrogen, sulphur and phosphorus. In this study, the effect of different light regimes and carbon dioxide feeds on Chlamydomonas reinhardtii growth were investigated. The objective was to increasing the algal growth rate and the cell density, leading to enhanced biohydrogen production. State-of-the art photobioreactors were used to grow algal cultures, and to measure the pH and optical density of those cultures. Under mixotrophic growth conditions, using both acetate and carbon dioxide, increasing the carbon dioxide feed rate increased the optical density of the culture but reduced the growth rate. Under autotrophic growth conditions, with carbon dioxide as the only carbon source, a carbon dioxide feed with a partial pressure of circa 11% was determined to optimise both the algal growth rate and the optical density.
Daud M, Pinilla JL, Arcelus-Arrillaga P, et al., 2012, Heavy oil upgrading in subcritical and supercritical water: Studies on model compounds, 244th National Fall Meeting of the American-Chemical-Society (ACS), Publisher: AMER CHEMICAL SOC, ISSN: 0065-7727
Tamburic B, Zemichael FW, Maitland GC, et al., 2012, A novel nutrient control method to deprive green algae of sulphur and initiate spontaneous hydrogen production, INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, Vol: 37, Pages: 8988-9001, ISSN: 0360-3199
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- Citations: 21
Alshammari YM, Hellgardt K, 2012, Thermodynamic analysis of hydrogen production via hydrothermal gasification of hexadecane, INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, Vol: 37, Pages: 5656-5664, ISSN: 0360-3199
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- Citations: 23
Carver C, Ulissi Z, Ong CK, et al., 2012, Modelling and development of photoelectrochemical reactor for H<sub>2</sub> production, 10th Annual Meeting of AIChE, Publisher: PERGAMON-ELSEVIER SCIENCE LTD, Pages: 2911-2923, ISSN: 0360-3199
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- Citations: 61
Zotova N, Roberts FJ, Kelsall GH, et al., 2012, Catalysis in flow: Au-catalysed alkylation of amines by alcohols, GREEN CHEMISTRY, Vol: 14, Pages: 226-232, ISSN: 1463-9262
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- Citations: 55
Hellgardt K, Kelsall G, Kaewpet P, et al., 2011, Indirect carbon air fuel cells, 11AIChE - 2011 AIChE Annual Meeting, Conference Proceedings
The chemical energy in fossil fuels can be converted directly and efficiently into electrical energy by a direct carbon fuel cell with a calculated equilibrium potential of ca. 1.02 V, which is almost temperature independent for carbon dioxide (CO 2) formation from a carbonaceous solid fuel. Separate evaluation and operation of a liquid metal based reformer (or partial oxidation reactor) in conjunction with a solid oxide electrolyte based electrochemical cell demonstrates our novel approach of an 'indirect' carbon-air fuel cell, incorporating a liquid metal anode as a solvent for the anodically-evolved oxygen, coupled to an external reformer supplied with oxygen from the liquid metal. The concurrent production of electricity, heat as well as fuels such as synthesis gas (CO + H 2) as functions of temperature and other experimental variables will be presented.
Hellgardt K, Ong CK, Kelsall G, et al., 2011, High photon flux photoelectrochemical reactor: modelling and operation, 11AIChE - 2011 AIChE Annual Meeting, Conference Proceedings
Production of hydrogen via sustainable technologies using renewable resources is an important goal for future global energy generation and storage. Photoelectrolysis is an attractive approach in this context, both, for its simplicity and the opportunity of employing relatively cheap materials. Considerable effort has been expended on the development of materials for photoelectrolysis - less so on the development of photoelectrochemical reactors. Here we model and demonstrate the operation of a high photon flux photoelectrochemical reactor and identify some of the key criteria for the rational design of an efficient, practical device. Mathematical models have already been developed to account for fluid flow and current distribution. An additional model rationalises the minority carrier distribution within the photoelectrochemical film itself. Process intensification through solar concentration will be demonstrated with a flat plate device, leading to a 5-fold increase in hydrogen production rate per unit active semiconductor area, or, conversely a significant reduction in device cost.
Alshammari Y, Hellgardt K, 2011, Continuous-flow reforming of hydrocarbons underground: Kinetic analysis, 11AIChE - 2011 AIChE Annual Meeting, Conference Proceedings
Water-producing oil wells are potential candidates for clean and economic production of hydrogen, syngas and low sulphur fuels. This may be achieved by transforming the passive production well into a high-pressure, high-temperature, continuous-flow reactor, eliminating the need for above surface reforming steps, and reducing the carbon footprint. As a part of this study, thermodynamic analysis of hydrothermal gasification of hexadecane, a heavy-saturate oil model was carried out and presented in the AIChE meeting 2010. The present work reports the experimental analysis of the hydrothermal gasification of hexadecane at various reaction residence times , temperatures, and H 2O 2 concentrations. The aim is to develop an uncatalysed continuous-flow hydrothermal reactor model for hydrogen generation from hydrocarbon resources. While some researchers have studies hydrothermal reactions of hydrocarbons in batch-type reactors, none has determined the kinetic data of heavy-saturate hydrocarbons in continuous flow systems (Arai et al, 2000, Watanabe et al, 2001, Watanabe et al, 2000, and Tsuzuki et al, 1999). Continuous flow systems offer high potential for commercial scale-up compared with batch systems. Online gas analysis was carried out using a quadruple mass spectrometer while produced oil-water residue was analysed using GC-MS. Moderate yields of syngas, and cracked n-alkanes/1-alkenes (C 9-C 15) were produced at 300-565°C and 250 bar. The conversion of hexadecane has been found to be inversely proportional to the residence time, and directly proportional to the water density. In addition, increasing the concentration of H 2O 2 enhanced the gasification of hexadecane as observed by the significant rise in the gas flowrate. On the other hand, coke formation due to hexadecane thermolysis was experienced at 565°C and 250 bar. It was also found that increasing the pressure at a constant temperature and H 2O 2 concentration reduces the formation of n-alkanes/1-alkene
Palmer C, Sasegbon A, Hellgardt K, 2011, In situ measurement of gas adsorption processes using Flux Response Technology, ADSORPTION-JOURNAL OF THE INTERNATIONAL ADSORPTION SOCIETY, Vol: 17, Pages: 783-794, ISSN: 0929-5607
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- Citations: 6
Tamburic B, Zemichael FW, Maitland GC, et al., 2011, Parameters affecting the growth and hydrogen production of the green alga <i>Chlamydomonas reinhardtii</i>, INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, Vol: 36, Pages: 7872-7876, ISSN: 0360-3199
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- Citations: 35
Tamburic B, Zemichael FW, Crudge P, et al., 2011, Design of a novel flat-plate photobioreactor system for green algal hydrogen production, INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, Vol: 36, Pages: 6578-6591, ISSN: 0360-3199
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- Citations: 47
Alshammari Y, Hellgardt K, 2011, Continuous-flow reforming of hydrocarbons underground: Kinetic analysis
Burgess SJ, Tamburic B, Zemichael F, et al., 2011, Solar-Driven Hydrogen Production in Green Algae, ADVANCES IN APPLIED MICROBIOLOGY, VOL 75, Vol: 75, Pages: 71-110, ISSN: 0065-2164
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- Citations: 34
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