Publications
218 results found
Harun I, Del Rio-Chanona EA, Wagner JL, et al., 2018, Photocatalytic Production of Bisabolene from Green Microalgae Mutant: Process Analysis and Kinetic Modeling, INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, Vol: 57, Pages: 10336-10344, ISSN: 0888-5885
Sawa M, Fantuzzi A, Nixon P, et al., 2018, Development of printed solar biobattery for use in bioelectronics, Arm Summit 2018, Publisher: Arm
There is an urgent need to develop a sustainable battery technology that is cheap, environmentally friendly, easy to fabricate and to dispose of, especially to tackle the world-wide increase in illegally dumped electronic wastes. Microbial biophotovoltaic (BPV) technology is a renewable bioenergy system currently being developed at the laboratory scale. It generates electricity from the photosynthetic metabolism of cyanobacteria and microalgae and exploits their ability to convert light energy into electrical current using water as the source of electrons. Innovative approaches are needed to solve scale-up issues such as cost, ease of fabrication (particularly the fabrication of the inorganic and biological (microbes) parts).In this talk, I will report the feasibility of using a simple commercial thermal-inkjet printer to fabricate a thin-film paper-based BPV cell consisting of a layer of cyanobacterial cells on top of a carbon nanotube conducting surface on plain copy paper. The digitally printed thin-film BPV system produced electricity both in the light and dark, with a maximum electrical power output of 0.38 mW m-2 in one system and the sustained electrical current production over 100 hours in another more fully printed system. I will address limitations and challenges as well possible applications in the area of printed bioelectronics.
Hii KM, hellgardt, barreiro, et al., 2018, Spatial, temporal and quantitative assessment of catalyst leaching in continuous flow, Catalysis Today, Vol: 308, Pages: 64-70, ISSN: 0920-5861
Catalyst leaching is a major impediment to the development of commercially-viable processes conducted in a liquid-phase. To date, there is no reliable technique that can accurately identify the extent and dynamics of the leaching process in a quantitative manner. In this work, a tandem flow-reactor system has been developed, which allowed us to distinguish between surface-catalyzed reactions from those occurring in solution by comparing%conversion at the exit of each reactor (S1, S2) corresponding to predominance of heterogeneous/homogeneous reactions (spatial) and two different residence times (temporal). A multiscale model is subsequently established to quantify the two types of reaction rate and simulate the catalyst leaching from a cross-coupling catalyst, PdEncat™ 30; including: (1) a multi-particle sizes model for catalyst scale; and (2) a dispersion model for reactor scale. The results show that catalyst leaching occurs via more than one process, and that the homogeneous Pd-catalyst (leached from the immobilized catalyst and dissolved in the flow) dominates the reaction and possesses a much higher activity than the heterogeneous (immobilized) Pd-catalyst. Additionally, the change of leached Pd stream inside reactors can be predicted along with the axial direction and the reaction time through the reactor-scale dispersion model.
Daggash HA, Patzschke CF, Heuberger CF, et al., 2018, Closing the carbon cycle to maximise climate change mitigation: Power-to-Methanol vs Power-to-Direct Air Capture, Sustainable Energy and Fuels, Vol: 2, Pages: 1153-1169, ISSN: 2398-4902
It is broadly recognised that CO2 capture and storage (CCS) and associated negative emissions technologies (NETs) are vital to meeting the Paris agreement target. The hitherto failure to deploy CCS on the required scale has led to the search for options to improve its economic return. CO2 capture and utilisation (CCU) has been proposed as an opportunity to generate value from waste CO2 emissions and improve the economic viability of CCS, with the suggestion of using curtailed renewable energy as a core component of this strategy. This study sets out to quantify (a) the amount of curtailed renewable energy that is likely to be available in the coming decades, (b) the amount of fossil CO2 emissions which can be avoided by using this curtailed energy to convert CO2 to methanol for use as a transport fuel – power-to-fuel, with the counterfactual of using that curtailed energy to directly remove CO2 from the atmosphere via direct air capture (DAC) and subsequent underground storage, power-to-DAC. In 2015, the UK curtailed 1277 GWh of renewable power, or 1.5% of total renewable power generated. Our analysis shows that the level of curtailed energy is unlikely to increase beyond 2.5% until renewable power accounts for more than 50% of total installed capacity. This is unlikely to be the case in the UK before 2035. It was found that: (1) power-to-DAC could achieve 0.23–0.67 tCO2 avoided MWh−1 of curtailed power, and (2) power-to-Fuel could achieve 0.13 tCO2 avoided MWh−1. The power-to-fuel concept was estimated to cost $209 tCO2 avoided−1 in addition to requiring an additional $430–660 tCO2 avoided−1 to finally close the carbon cycle by air capture. The power-to-DAC concept was found to cost only the $430–660 tCO2 avoided−1 for air capture. For power-to-fuel to become profitable, hydrogen prices would need to be less than or equal to $1635 tH2−1 or methanol prices must increase to $960 tMeOH−1. Absent this ch
Holmes-Gentle I, Agarwal H, Alhersh F, et al., 2018, Assessing the scalability of low conductivity substrates for photo-electrodes via modelling of resistive losses., PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 20, Pages: 12422-12429, ISSN: 1463-9076
When scaling up photo-electrochemical processes to larger areas than conventionally studied in the laboratory, substrate performance must be taken into consideration and in this work, a methodology to assess this via an uncomplicated 2 dimensional model is outlined. It highlights that for F-doped SnO2 (FTO), which is ubiquitously used for metal oxide photoanodes, substrate performance becomes significant for moderately sized electrodes (5 cm) under no solar concentration for state of the art Fe2O3 thin films. It is demonstrated that when the process is intensified via solar concentration, current losses become quickly limiting. Methodologies to reduce the impact of substrate ohmic losses are discussed and a new strategy is proposed. Due to the nature of the photo-electrode current–potential relationship, operation at a higher potential where the photo-current saturates (before the dark current is observed) will lead to a minimum in current loss due to substrate performance. Crucially, this work outlines an additional challenge in scaling up photo-electrodes based on low conductivity substrates, and establishes that such challenges are not insurmountable.
Bystron T, Horbenko A, Syslova K, et al., 2018, 2-Iodoxybenzoic acid synthesis by oxidation of 2-Iodobenzoic acid at a Boron-doped diamond anode, ChemElectroChem, Vol: 5, Pages: 1002-1005, ISSN: 2196-0216
For the first time, the electrochemical synthesis of 2-iodoxybenzoic acid (IBX), a benign, well-established, popular and highly selective oxidising agent, is described. The objective of the work was to investigate the possibility of generating IBX electrochemically in aqueous solutions by using boron-doped diamond anodes. In 0.2 M H2SO4 aqueous solution, 2-iodobenzoic acid (IBA) was found to be oxidised at potentials >1.6 V vs. SCE, initially to 2-iodosobenzoic acid (IsBA), which was oxidised to IBX at potentials >1.8 V vs. SCE. Reductions of IBX to IsBA and IsBA to IBA occurred at similar potentials of ca. −0.7 V vs. SCE. The voltammetry results were confirmed by performing a series of batch electrolyses at different electrode potentials. Thus, depending on the electrode potential chosen, IBA can be oxidised anodically either to IsBA or IBX with 100 % overall selectivity. The only side-reaction was O2 generation, but charge yields did not decrease below 55 % even at conversions >95 %.
Keung Leung AY, Hellgardt K, Leung A, et al., 2018, Catalysis in flow: nickel-catalyzed synthesis of primary amines from alcohols and NH3, ACS Sustainable Chemistry and Engineering, Vol: 6, Pages: 5479-5484, ISSN: 2168-0485
A highly selective synthesis of primary amines from alcohols and NH3 was achieved on using a commercially available Ni catalyst, without adding H2. Using a continuous flow reaction platform, the amination of aliphatic alcohols can be achieved in good yields and selectivities, as the accumulation of water byproduct can be removed. Competitive formation of the nitrile side-product was suppressed when the catalyst was prereduced. Modes of catalyst deactivation were also briefly examined.
Iruretagoyena Ferrer D, Hellgardt K, Chadwick D, 2018, Towards autothermal hydrogen production by sorption-enhanced water gas shift and methanol reforming: a thermodynamic analysis, International Journal of Hydrogen Energy, Vol: 43, Pages: 4211-4222, ISSN: 0360-3199
Hydrogen production by the water gas shift reaction (WGS) is equilibrium limited. In the current study, we demonstrate that the overall efficiency of the WGS can be improved by co-feeding methanol and removing CO2 in situ. The thermodynamics of the water gas shift and methanol reforming/WGS (methanol-to-shift, MtoS) reactions for H2 production alone and with simultaneous CO2 adsorption (sorption-enhanced, SEWGS and SEMtoS) were studied using a non-stoichiometric approach based on the minimisation of the Gibbs free energy. A typical composition of the effluent from a steam methane reformer was used for the shift section. The effects of temperature (450–750 K), pressure (5–30 barg), steam and methanol addition, fraction of CO2 adsorption (0–95%) and energy efficiency of the shift systems have been investigated. Adding methanol to the feed facilitates autothermal operation of the shift unit, with and without CO2 removal, and enhances significantly the amount of H2 produced. For a set methanol and CO input, the MtoS and SEMtoS systems show a maximum productivity of H2 between 523 and 593 K due to the increasing limitation of the exothermic shift reaction while the endothermic methanol steam reforming is no longer limited above 593 K. The heat of adsorption of CO2 was found to make only a small difference to the H2 production or the autothermal conditions.
Arcelus-Arrillaga P, Hellgardt K, Millan M, 2017, Effect of process conditions on the hydrothermal partial oxidation of phenanthrene as a heavy oil model structure, FUEL, Vol: 209, Pages: 434-441, ISSN: 0016-2361
Sawa M, Fantuzzi A, Bombelli P, et al., 2017, Electricity generation from digitally printed cyanobacteria, Nature Communications, Vol: 8, Pages: 1-10, ISSN: 2041-1723
Microbial biophotovoltaic cells exploit the ability of cyanobacteria and microalgae to convert light energy into electrical current using water as the source of electrons. Such bioelectrochemical systems have a clear advantage over more conventional microbial fuel cells which require the input of organic carbon for microbial growth. However, innovative approaches are needed to address scale-up issues associated with the fabrication of the inorganic (electrodes) and biological (microbe) parts of the biophotovoltaic device. Here we demonstrate the feasibility of using a simple commercial inkjet printer to fabricate a thin-film paper-based biophotovoltaic cell consisting of a layer of cyanobacterial cells on top of a carbon nanotube conducting surface. We show that these printed cyanobacteria are capable of generating a sustained electrical current both in the dark (as a ‘solar bio-battery’) and in response to light (as a ‘bio-solar-panel’) with potential applications in low-power devices.
Hii KM, Newton MA, Nicholls R, et al., 2017, Effect of retained chlorine in ENCAT™ 30 catalysts on the development of encapsulated Pd: insights from in situ Pd K, L3 and Cl K-edge XAS, Catalysis, Structure & Reactivity, Vol: 3, Pages: 149-156, ISSN: 2055-074X
In situ X-ray absorption spectroscopy (XAS) and Pd K, LIII, and Cl K-edges shows that Cl can be present in significant amounts in ENCAT™ 30 catalysts and that it can severely retard Pd nanoparticle (NP) development in flowing solvents. We also show that whilst polymeric encapsulation protects the Pd against solvent induced agglomeration of Pd nanoparticles the evidence suggests it does not prevent the formation PdHx through reaction with the aqeous ethanol solvent, and that, as received, ENCAT™ 30 NP catalysts are not, for the most part, comprised of nanoparticulate Pd0 irrespective of the presence of Cl.
Antunes MM, Lima S, Fernandes A, et al., 2017, MFI Acid Catalysts with Different Crystal Sizes and Porosity for the Conversion of Furanic Compounds in Alcohol Media, CHEMCATCHEM, Vol: 9, Pages: 2747-2759, ISSN: 1867-3880
Martins Lima S, Klaus Hellgardt KH, David Chadwick DC, 2017, Towards sustainable hydrogenation of 5-(hydroxymethyl)furfural: a two-stage continuous process in aqueous media over Raney catalysts, RSC Advances, Vol: 7, Pages: 31401-31407, ISSN: 2046-2069
The hydrogenation of 5-(hydroxymethyl)furfural (HMF) to 2,5-bis(hydroxymethyl)tetrahydrofuran (DHMTHF) in aqueous media under relatively mild reaction conditions has been investigated over heterogeneous RANEY® Cu and Ni catalysts using a continuous-flow hydrogenation reactor. These RANEY® catalysts were selected following a screening of several catalysts including precious metals supported on carbon for the hydrogenation of HMF. A single-stage versus a two-stage process for the hydrogenation of HMF into DHMTHF, i.e. via 2,5-dihydroxymethylfuran (DHMF) has been evaluated. The best result with an average selectivity of 98% for DHMTHF was obtained using a two-stage process; RANEY® Cu was used as a catalyst for the highly selective hydrogenation of HMF to DHMF (92 mol%) in the first stage and this product was used without further purification for in a second-stage selective hydrogenation of DHMF into DHMTHF using RANEY® Ni as a catalyst. The influence of the HMF concentration in the feeding solution (1–3 wt%), flow rate (0.05–0.25 mL min−1) and total pressure (20–90 bar) were investigated for the first-stage hydrogenation of HMF into DHMF over RANEY® Cu. HMF was found to exert an inhibiting effect on the conversion due to strong adsorption. The RANEY® Ni catalyst used in the second stage gradually deactivated. A procedure for in situ regeneration of the partially deactivated RANEY® Ni catalyst using acetic acid washing was investigated with limited success.
Deadman BJ, Hellgardt K, Hii KM, 2017, A colorimetric method for rapid and selective quantification ofperoxodisulfate, peroxomonosulfate and hydrogen peroxide, Reaction Chemistry and Engineering, Vol: 2, Pages: 462-466, ISSN: 2058-9883
Redox colorimetric tests have been devised for the rapid analysis of the individual components of aqueous mixtures of peroxodisulfate, peroxomonosulfate and hydrogen peroxide; providing a convenient and selective method for the determination of these industrially relevant oxidants, which are known to inter-convert in solution.
Hii KM, Loponova KN, Deadman BJ, et al., 2017, Controlled multiphase oxidations for continuous manufacturing of fine chemicals, Chemical Engineering Journal, Vol: 329, Pages: 220-230, ISSN: 0300-9467
The feasibility of an integrated continuous biphasic oxidation process was studied, incorporating (i) electrochemical generation of an oxidant, (ii) membrane emulsification and an Oscillatory Flow Reactor (OFR) to facilitate mass-transfer in a biphasic reaction system and (iii) product extraction to enable regeneration of the oxidant. The biphasic, organic solvent-free dihydroxylation of styrene by ammonium peroxodisulfate solutions (including electrochemically generated peroxodisulfate) was investigated as a model reaction, both in batch and in an OFR. Heating of peroxodisulfate in a strongly acidic solution was demonstrated to be essential to generate the active oxidant (Caro’s acid). Membrane emulsification allowed mass-transfer limitations to be overcome, reducing the time scale of styrene oxidation from several hours in a conventional stirred tank reactor to less than 50 min in a dispersion cell. The influence of droplet size on overall reaction rate in emulsions was studied in detail using fast image capturing technology. Generation of unstable emulsions was also demonstrated during the oxidation in OFR and product yields >70% were obtained. However, the high-frequency/high-displacement oscillations necessary for generation of fine droplets violated the plug flow regime. Membrane emulsification was successfully integrated with the OFR to perform biphasic oxidations. It was possible to operate the OFR/cross-flow membrane assembly in plug flow regime at some oscillatory conditions with comparable overall oxidation rates. No mass-transfer limitations were observed for droplets <60 μm. Finally, the continuous post-reaction separation was demonstrated in a single OFR extraction unit to enable continuous regeneration of the oxidant.
Deadman BJ, 2017, On-demand electrochemical generation of oxidants and their applications in organic synthesis, 254th ACS National Meeting
Holmes-Gentle I, Hoffmann F, Mesa CA, et al., 2017, Membrane-less photoelectrochemical cells: product separation by hydrodynamic control, Sustainable Energy and Fuels, Vol: 1, Pages: 1184-1198, ISSN: 2398-4902
A key step in order to realise photo-electrochemical (PEC) water splitting to produce hydrogen sustainably, is reactor design. Good engineering will minimise energy losses (both optical and ohmic) due to reactor construction, whilst ensuring the H2 and O2 produced are separated, and this can subsequently relax the requirements on the photo-absorber material and/or electro-catalysts. In this paper we show that separation of the products through hydrodynamic flow alone would negate the need for the conventionally used membrane, which has an associated ohmic drop and cost. This is demonstrated to be possible using a ‘laminar flow between two parallel plates’ reactor design and AR/Pe and AR are found to be the two key dimensionless numbers that predict product cross-over (where AR, Pe are aspect ratio and Péclet number respectively). Supersaturation was used as an indicator of bubble formation, which disrupts the laminar flow required for separation and it is shown that by increasing the reactor pressure, higher current densities can be tolerated before supersaturation occurs. Removal of the dissolved hydrogen and oxygen from electrolyte is discussed. A multi-physics model, which employs an optical transfer matrix method, is used to validate the previous conclusions. Experimental data for hematite and Pt deposited on FTO was used as the anode and cathode respectively. Parasitic optical losses and efficiency improvement with stacking are shown for the example reactor configuration. Additionally, the concept of stacking this reactor design in order to absorb light in multiple passes is introduced. This approach relaxes a classical constraint on photo-absorber materials: large absorption length compared to small diffusion length of charge carriers in the semiconductor.
Arcelus-Arrillaga P, Pinilla JL, Hellgardt K, et al., 2017, Application of Water in Hydrothermal Conditions for Upgrading Heavy Oils: A Review, ENERGY & FUELS, Vol: 31, Pages: 4571-4587, ISSN: 0887-0624
Hii KM, Brazier JB, 2017, Effects of Cl on the reduction of supported PdO in ethanol/water mixtures, Catalysis, Structure & Reactivity, Vol: 3, Pages: 54-62, ISSN: 2055-074X
The reduction of γ-Al2O3-supported PdO in flowing aqueous ethanol was investigated. Quick EXAFS (QEXAFS) performed at the Pd K-edge reveals that the presence of Cl can have a profound effect on the reduction process. At low loadings of Pd (1 wt-%), the size dependency of the process is inverted, compared to Cl-free samples. The extent of reduction was found to be dependent on loading/particles size. It is shown, using in situ QEXAFS at the Cl K- and Pd L3-edges, that residual Cl is not removed by the flowing solvent mixture, even at an elevated temperature of 350 K. The origins of these behaviours are discussed in terms of the differing effects that Cl may have when bonded to oxidic or reduced metal centres and the results were compared to earlier observations made on the effects of Cl on commercial polyurea encapsulated Pd ENCAT™ NP 30 catalysts.
Phanopoulos A, Leung AHM, Yow S, et al., 2017, Binuclear β-diketiminate complexes of copper(I), Dalton Transactions, Vol: 46, Pages: 2081-2090, ISSN: 1477-9226
The reaction of a series of dinucleating bis(β-diketiminate) pro-ligands with mesitylcopper in the presence and absence of mono and diphosphines has allowed the isolation of a new series of dicopper(I) complexes. Inclusion of trans-1,2-cyclohexyl (1), 2,6-pyridyl (2), and 2,2′-oxydiaryl (3) spacers between the β-diketiminate units has been studied. The isolation of three new copper(I) phosphine complexes [1·Cu2(PPh3)2], [2·Cu2(PPh3)2] and [3·Cu2(PPh3)2] is reported. While these compounds display large Cu⋯Cu separations of 5.4–7.9 Å in the solid state, solution data are consistent with a large degree of conformational freedom. Modification of the monophosphine to a diphosphine, DPPE, allowed the isolation of the novel 11-membered bimetallic macrocycle [2·Cu2(DPPE)] containing both a binucleating nitrogen based ligand and a chelating diphosphine. While acetonitrile adducts of this series could also be generated in situ, under forcing conditions reaction of the 2,6-pyridyl bridged ligand with mesityl copper led to the formation [2·Cu2]2. This latter complex is a dimer of dicopper(I) units in which the bis(β-diketiminate) ligand now binds four copper(I) centers through not only the expected κ2-N,N′-chelation but also κ1- and η2-binding of the central pyridine through orthogonal Cu–N and Cu–arene interactions. Reversible coordination of alkenes, pyridine and quinoline to the copper cluster was identified allowing the isolation and structural characterisation of a further series of dinuclear complexes [2·Cu2(pyridine)2], [2·Cu2(cyclopentene)2] and [2·Cu2(norbornene)2]. Solution studies allow quantification of the reversible binding event through a van't Hoff analysis. Both solution and the solid state data suggest a weak anagostic interaction exists in the latter two alkene complexes of copper(I). The new complexes have been characterized by X-ray dif
Hii KM, Brazier JB, Hellgardt K, 2017, Catalysis in flow: O2 effect on the catalytic activity of Ru(OH)x/Al2O3 during the aerobic oxidation of an alcohol, Reaction Chemistry and Engineering, Vol: 2, Pages: 60-67, ISSN: 2058-9883
Changes in the turnover frequency (TOF) of Ru(OH)x/γ-Al2O3 during aerobic oxidation of benzyl alcohol in a plug flow differential reactor were monitored online using an inline FTIR instrument over extended periods of time (up to 72 h). A new equation for catalyst deactivation is derived, to account for the different lengths of time the catalyst is exposed to the reactants (benzyl alcohol and O2). Catalyst activity and stability are dependent on the amount of O2 in the system; catalyst deactivation can be attributed to two simultaneous processes: a fast and reversible inhibition by the benzoic acid side product and a slower and irreversible loss of catalytic sites due to reduction of Ru. At steady state, the reaction rate is zero-order in benzyl alcohol and partial positive order in O2. Finally, the suitability of a packed-bed (integral) reactor for the reaction is discussed.
Hellgardt K, Mimi Hii KK, 2017, Continuous flow technologies in the development of “green” organic reactions and processes, Advanced Green Chemistry: Part 1: Greener Organic Reactions and Processes, Pages: 257-284, ISBN: 9789813228108
Newton MA, Brazier JB, Barreiro EM, et al., 2016, Restructuring of supported Pd by green solvents: an operando Quick EXAFS (QEXAFS) study and implications for the derivation of structure-function relationships in Pd catalysis, Catalysis Science & Technology, Vol: 6, Pages: 8525-8531, ISSN: 2044-4753
Transmission electron microscopy (TEM) is commonly used as an ex-situ technique to determine structural changes by comparing images of catalyst particles before and after a reaction. This requires the use of an alcoholic solvent to disperse the particles on a grid. In this work, we will show that Pd catalysts can be transformed during the procedure, by using EXAFS to determine the structure of Pd catalysts in different environments (as dry or wet samples). Supported palladium nanoparticles exposed to aqueous ethanolic solution (50% w/v) are transformed to a common, reduced, and hydrogen-contaminated state, irrespective of their initial habit or support. Catalysts comprised of nanosize PdO are reduced at ca. 350 K, whereas samples comprised of very small (ca. ≤ 10 atoms) Pd particles react with the solvent at just above room temperature and agglomerating with considerable loss of dispersion. As such any potential benefits to catalysis sought through the synthesis of very highly dispersed metallic Pd supported upon a range of inorganic dispersants will be rapidly erased through the action of such solvents.
Patel B, Arcelus-Arrillaga P, Izadpanah A, et al., 2016, Catalytic Hydrotreatment of algal biocrude from fast Hydrothermal Liquefaction, RENEWABLE ENERGY, Vol: 101, Pages: 1094-1101, ISSN: 0960-1481
Alshammari YM, Hellgardt K, 2016, CFD analysis of hydrothermal conversion of heavy oil in continuous flow reactor, CHEMICAL ENGINEERING RESEARCH & DESIGN, Vol: 117, Pages: 250-264, ISSN: 0263-8762
Barretto S, Michoux F, Hellgardt K, et al., 2016, Pneumatic hydrodynamics influence transplastomic protein yields and biological responses during in vitro shoot regeneration of Nicotiana tabacum callus: Implications for bioprocess routes to plant-made biopharmaceuticals, Biochemical Engineering Journal, Vol: 11, Pages: 73-81, ISSN: 1369-703X
Transplastomic plants are capable of high-yield production of recombinant biopharmaceutical proteins. Planttissue culture combines advantages of agricultural cultivation with the bioprocess consistency associated withsuspension culture. Overexpression of recombinant proteins through regeneration of transplastomic Nicotianatabacum shoots from callus tissue in RITA® temporary immersion bioreactors has been previously demonstrated.In this study we investigated the hydrodynamics of periodic pneumatic suspension of liquid medium duringtemporary immersion culture (4 minutes aeration every 8 hours), and the impact on biological responses andtransplastomic expression of fragment C of tetanus toxin (TetC). Biomass was grown under a range of aerationrates for 3, 20 and 40-day durations. Growth, mitochondrial activity (a viability indicator) and TetC protein yieldswere correlated against the hydrodynamic parameters, shear rate and energy dissipation rate (per kg of medium).A critical aeration rate of 440 ml min-1 was identified, corresponding to a shear rate of 96.7 s-1, pneumatic powerinput of 8.8 mW kg-1and initial 20-day pneumatic energy dissipation of 127 J kg-1, at which significant reductionsin biomass accumulation and mitochondrial activity were observed. There was an exponential decline in TetCyields with increasing aeration rates at 40 days, across the entire range of conditions tested. These observationshave important implications for the optimisation and scale-up of transplastomic plant tissue culture bioprocessesfor biopharmaceutical production.
Hii KM, Hellgardt K, Gavriilidis A, et al., 2016, Aerobic oxidations in flow: opportunities for the fine chemicals and pharmaceuticals industries, Reaction Chemistry & Engineering, Vol: 1, Pages: 595-612, ISSN: 2058-9883
Molecular oxygen is without doubt the greenest oxidant for redox reactions, yet aerobic oxidation is one of the most challenging to perform with good chemoselectivity, particularly on an industrial scale. This collaborative review (between teams of chemists and chemical engineers) describes the current scientific and operational hurdles that prevent the utilisation of these reactions for the production of speciality chemicals and active pharmaceutical ingredients (APIs). The safety aspects of these reactions are discussed, followed by an overview of (continuous flow) reactors suitable for aerobic oxidation reactions that can be applied on scale. Some examples of how these reactions are currently performed in the industrial laboratory (in batch and in flow) are presented, with particular focus on the scale-up strategy. Last but not least, further challenges and future perspectives are presented in the concluding remarks.
Patel B, Hellgardt K, 2016, Hydrothermal liquefaction and: In situ supercritical transesterification of algae paste, RSC Advances, Vol: 6, Pages: 86560-86568, ISSN: 2046-2069
In this manuscript we demonstrate and present the outcome of performing in situ supercritical transesterification (SCT) during hydrothermal liquefaction (HTL) of algal biomass at reaction conditions between 300-380 °C and reaction time (RT) of 5-30 min in the presence of water and solvent methanol. The biocrude obtained was fractioned into hexane soluble and methyl ester (ME) containing light crude (LC) and hexane insoluble heavy crude (HC). The gravimetric yield showed an increase in the LC content at increasing RT with ~50% of the biocrude composed of LC at severe condition. Elemental analysis confirmed deoxygenation and denitrogenation levels similar to HTL produced biocrude for the LC, whereas the HC contained elevated levels of both elements and formed an asphaltene/tar like product to give an energy density for the crudes in the range of 36-39.2 MJ kg-1 and 29.5-34.5 MJ kg-1, respectively. LC formed at 380 °C and 30 min RT had a boiling point distribution (BPD) similar to crude oil and was better than hydrotreated biocrude as deciphered by simulated distillation (SIMDIST) owing to the difference in bonds detected via Fourier transform infrared spectroscopy (FT-IR). ME formation was achieved within the first 10 min of the reaction after which its decomposition observed and subsequent kinetic parameters calculated assuming a first-order reaction. The fractionation of solvent (methanol) processed biocrude infers an alternative method of obtaining algal fuel, however the high nitrogen content of both crudes still persists, necessitating an additional denitrogenation step, albeit at a different extent.
Evans A, Luebke R, Hellgardt K, et al., 2016, Investigation of the Dynamic Adsorption of CO Using Metal-Organic Frameworks, AIChE Fall meeting 2016
Roberts F, 2016, Kinetic Studies of Alcohol Oxidation to Methyl Esters and Amides Catalysed by Gold Nanoparticles on Titania (Au/TiO2) in Continuous Flow Systems
Methyl esters and amides are valuable compounds in fine chemicals synthesis, with methyl esters used in flavourings and perfumes, while amides are used in many industries from polymers to pharmaceuticals. Alcohols are desirable starting materials as they can be sustainably sourced, however both methyl ester synthesis from alcohols and methanol, and amide synthesis from alcohols and amines conventionally involve wasteful processes using stoichiometric quantities of metal oxidants and other toxic reagents. In this project a greener synthesis route was developed and studied for each reaction, employing plug flow reactors with a heterogeneous catalyst in the form of Au/TiO2 and green oxidants and solvents. A continuous flow methyl ester synthesis route from benzyl alcohol and methanol with hydrogen peroxide over Au/TiO2 was studied, Scheme 1. Using experimental observations, a reaction model was constructed in Berkeley Madonna (a differential equation solver), to draw conclusions about the reaction pathway, including the role of H2O2 and factors determining product selectivity. This model was then fitted to experimental data to determine reaction parameters such as rate constants and activation energies. Initial attempts at amide synthesis over Au/TiO2 in a single plug flow reactor were unsuccessful, therefore a system with two reactors in series was built and characterised. In the first reactor of the tandem system, the alcohol to aldehyde transformation took place over Au/TiO2 with oxygen gas, while the second reactor was for amide synthesis from the aldehyde and amine using H2O2, Scheme 2. After initial screenings of process conditions, solvents and catalysts to maximise product yields for each step, both stages of the reaction were studied separately for the reaction of benzyl alcohol and morpholine. As with the methyl ester synthesis above, a reaction model was developed in Berkeley Madonna and fitted to experimental data. Finally amide synthesis from decanol an
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.