Publications
218 results found
Ebri G, Hellgardt K, 2024, Flow synthesis development and photocatalytic activity optimization of copper oxide nanoparticles using design of experiments, Chemical Engineering Journal, Vol: 486, ISSN: 1385-8947
Many studies have focused on reducing the impact of carbon dioxide (CO2) on climate change. A promising approach for CO2 utilization is to use a photocatalyst to activate CO2 and generate valuable chemical compounds. One of the most commonly synthetized photocatalysts is cuprous oxide (Cu2O); however, low efficiency and fast deactivation still limit its industrial application. Here, a batch synthesis in nonaqueous media of Cu2O containing small amounts of metallic copper (Cu0) is investigated. By adjusting the ratio between Cu2O and Cu0 an enhanced photocatalytic efficiency is obtained. To overcome the deactivation limitations of Cu2O, a flow synthesis is developed that continuously supplies fresh photocatalysts to the reaction environment. The flow synthesis has the potential to allow the separate evaluation of the intrinsic reaction kinetic from the photocatalyst deactivation. This work optimizes the flow synthesis using a design of experiments (DOE) approach coupled with response surface methodology (RSM). The obtained surface responses for the measured factors were highly significant (p-value < 0.01 and R2 > 0.95). This novel methodology makes it possible to identify the optimum process conditions to simultaneously improve photocatalytic performance of the obtained material and reaction productivity. This approach enabled us to obtain in flow a combination of Cu2O/Cu0 photocatalyst and to propose a reaction mechanism and kinetic model for the Cu2O formation. The optimization procedure for flow synthesis proposed here provides an efficient path that can be extended to flow synthesis of a wide range of nanoparticles for photocatalytic applications.
Horvath-Gerber F, Ohlig D, Hii KKM, et al., 2024, Liquizald─Thermally Stable N-Nitrosamine Precursor for Diazomethane, Organic Process Research and Development, Vol: 28, Pages: 597-608, ISSN: 1083-6160
N-Methyl-N-nitroso-p-toluenesulfonamide (Diazald) and N-nitroso-β-methylaminoisobutyl methyl ketone (Liquizald) were compared in this study as diazomethane precursors for process scale-up. Thermal assessment flagged Diazald for explosion propagation and impact sensitivity using the Yoshida methodology, while Liquizald only indicated potential for impact sensitivity under more conservative Pfizer correlations. A higher onset temperature of Liquizald at 170 °C was determined. Compared to the onset temperature for Diazald (80 °C), Liquizald made a favorable candidate for exploitation of increased reaction rates at high temperatures using microreactor technologies. New kinetic parameters of decomposition were further used to study the potential for process intensification and identify the microreactor channel sizing for thermally stable and near-isothermal reactor operation.
Schrecker L, Dickhaut J, Holtze C, et al., 2024, A comparative study of transient flow rate steps and ramps for the efficient collection of kinetic data, Reaction Chemistry and Engineering, ISSN: 2058-9883
Transient cumulative flow rate varying methods have proven very effective for the collection of residence time series data for reactions in continuous flow. In this study, comparisons will be made between data collected from step changes and linear flow rate ramps, to inform method choice and minimise the complexity of automation and control needed to implement these methods, without compromising the quality of the data. Using two different analytical tools (in-line FTIR and on-line HPLC), the methods were compared in two different flow system configurations, and across three chemical reactions of increasing complexity. This work finds that the quality of the data collected using simpler step changes are comparable to that collected using more complex ramping methods, when performed in a reverse push-out (high to low flow rate) manner.
Chadha D, Hellgardt K, 2024, A case of conceptualisation: using a grounded theory approach to further explore how professionals define engineering judgement for use in engineering education, European Journal of Engineering Education, Vol: 49, Pages: 348-369, ISSN: 0304-3797
Students are expected to have developed their engineering judgement throughout the course of their studies as part of their accreditation requirements (as stipulated by the Accreditation Board of Engineering and Technology for example), and yet conceptually it is often ill-defined and therefore difficult to teach. This work was carried out in an attempt to better conceptualise engineering judgement for use in higher education. As such, semi-structured interviews were conducted with established members of academic staff who additionally had extensive industrial experience – who were asked to define engineering judgement and which aspects students ought to develop in their studies. A pragmatic grounded theory approach was used, based on the assumption that a theoretical idea/framework could be developed, enabling us to refer to previous literature and the emerging categories from our data set to help clarify engineering judgement. Several terms help define engineering judgement, including accumulated experience, fundamental theoretical knowledge, and imagination/intuition. Essential criteria for developing judgement includes students’ ability to identify and reduce complex problems, and embrace failure. A theoretical framework has been proposed accommodating a more enhanced definition and conceptualisation of engineering judgement which can be applied and adapted for use within engineering education for students’ ultimate benefit.
Schrecker L, Dickhaut J, Holtze C, et al., 2023, An efficient multiparameter method for the collection of chemical reaction data via ′one-pot′ transient flow, Reaction Chemistry and Engineering, Vol: 8, Pages: 3196-3202, ISSN: 2058-9883
The advent of transient flow methods has increased the efficiency and diversity of reaction data collected through the collection of data series in a wider reaction space, beyond traditionally temporal series. Thus far, these methods have been limited to studying continuous reaction parameters. In this work, transient flow is combined with “one-pot” chemistry (OP-TF) to efficiently collect diverse reaction data on a continuous-discrete multiparameter space, exemplified with the aromatic Claisen rearrangement. Six independent substrates were studied simultaneously, producing data on temperature and substituent effects in a single experiment, extending into the supercritical phase. This data allowed us to extract thermodynamic information and predict kinetic parameters for other substrates accurately, thus allowing synthetic feasibility of a substrate to be assessed a priori.
Hare LV, Parveen F, Cookson J, et al., 2023, Using the colloidal method to prepare Au catalysts for the alkylation of aniline by benzyl alcohol, International Journal of Molecular Sciences, Vol: 24, ISSN: 1422-0067
Using the colloidal method, attempts were made to deposit Au NPs on seven different material supports (TiO2, α and γ-Al2O3, HFeO2, CeO2, C, and SiO2). The deposition between 0.8 and 1 wt% of Au NPs can be generally achieved, apart for SiO2 (no deposition) and α-alumina (0.3 wt%). The resultant sizes of the Au NPs were dependent on the nature as well as the surface area of the support. The catalytic activity and selectivity of the supported Au catalysts were then compared in the alkylation of aniline by benzyl alcohol. Correlations were made between the nature of the support, the size of the Au NP, and the H-binding energy. A minimum H-binding energy of 1100 μV K−1 was found to be necessary for high selectivity for the secondary amine. Comparisons of the TEM images of the pre- and post-reaction catalysts also revealed the extent of Au NP agglomeration under the reaction conditions.
Takle MJ, Deadman BJ, Hellgardt K, et al., 2023, A flash thermal racemization protocol for the chemoenzymatic dynamic kinetic resolution and stereoinversion of chiral amines, ACS Catalysis, Vol: 13, Pages: 10541-10546, ISSN: 2155-5435
A highly practical and effective ‘Flash Thermal Racemization’ (FTR) protocol was developed in continuous flow, without needing a base or a H donor. This can be integrated with an enzyme to enable the chemoenzymatic kinetic resolution of primary amines to be achieved in a more atom-efficient manner without additives. An unprecedented space-time yield of up to 1362 μmol mL–1 h–1 can be achieved for the dynamic kinetic resolution of 1-aminoindane, which is at least 10 times more productive than previously reported, and up to 1700-fold more productive when the Pd catalyst loading is taken into account. With a slight modification, the flow reactor system can also be used to convert an optically active amine to its opposite enantiomer.
Newton OJ, Hellgardt K, Richardson J, et al., 2023, 'Homeopathic' palladium catalysis? The observation of distinct kinetic regimes in a ligandless Heck reaction at (ultra-)low catalyst loadings, Journal of Catalysis, Vol: 424, Pages: 29-38, ISSN: 0021-9517
The catalytic behaviour of ‘ligandless’ palladium(II) acetate in the Heck arylation reaction of iodobenzene with methyl acrylate is examined at (ultra-)low catalyst loadings using in situ spectroscopy. The study reveals two distinctive kinetic regimes with distinct Pd orders. A simplified microkinetic model revealed the presence of at least two kinetically competent catalysts, represented by a monomeric (Pd1) and dimeric (Pd2) species. The relative catalytic activity and deactivation rates for both species can also be estimated from the experimental results. This work provides direct kinetic evidence that a higher-order Pd species can be more active than a monomeric species, and the key role played by catalyst deactivation, particularly at higher catalyst loadings. This implies that lowering the catalyst loading may be an effective strategy to combat catalyst deactivation without necessarily incurring significant deterioration in reaction rate.
Horvath-Gerber F, Hii KKM, Holtze C, et al., 2023, Mass transport of diazomethane across Teflon AF2400 membrane for scale-up development, Organic Process Research and Development, Vol: 27, Pages: 899-909, ISSN: 1520-586X
Diazomethane is an attractive C1 building block in organic chemistry, but its hazardous nature presents scale-up challenges to this date. The use of a Teflon AF2400 membrane, most commonly in a tube-in-tube reactor setup, is the current state-of-the-art methodology for inherently safer laboratory-scale generation, separation, and consumption of anhydrous diazomethane. For the successful scale-up of this membrane process, the key mass transfer coefficient of the AF2400 membrane, its permeability for diazomethane, was investigated. We report in this contribution a novel methodology to determine diazomethane permeability for the rational scale-up of membrane processes for the safe handling of diazomethane. Missing physical properties of diazomethane were established, and the full mass balance of in situ-generated diazomethane within the tube-in-tube reactor was experimentally validated. A numerical model of the membrane reactor system in combination with experimental data yielded a permeability value of 414 barrer. This result enables scale-up development of the laboratory membrane reactor toward production-scale systems.
Schrecker L, Dickhaut J, Holtze C, et al., 2023, Discovery of unexpectedly complex reaction pathways for the Knorr pyrazole synthesis via transient flow, Reaction Chemistry and Engineering, Vol: 8, Pages: 41-46, ISSN: 2058-9883
Kinetic data for reactions between phenyl hydrazine and 1,3-diketones (Knorr pyrazole synthesis) were acquired by using transient flow methods. Supported by further spectroscopic and mass spectrometry data, a microkinetic model was subsequently constructed, which provided new insights into the mechanism, including autocatalysis and the involvement of an unexpected reaction intermediate. During this work, a novel reactant stoichiometry transient flow methodology was demonstrated, allowing the robustness of these models to be asserted.
de Carvalho Servia MÁ, Sandoval IO, Zhang D, et al., 2023, Automated Kinetic Model Discovery – A Methodological Framework, Computer Aided Chemical Engineering, Pages: 33-38
The industrialization of catalytic processes benefits strongly from kinetic models for optimization and control purposes. Nevertheless, mechanistic models are difficult to construct; data-driven and hybrid models lack interpretability and the flexibility to leverage physical knowledge. Thus, a different approach called automated knowledge discovery has been recently popularized. Existing methods in literature suffer from important drawbacks: necessitating assumptions about model structures, a lack of model selection automation, and sensitivity to noise. To overcome these challenges, the present work constructs a methodological framework for the automated generation of catalytic kinetic models. We leverage symbolic regression for model generation, a hybrid optimization algorithm for parameter estimation, and a robust criterion for model selection. The framework is tested with an illustrative isomerization case study, where it showcases the ability to retrieve the underlying kinetic model with a limited amount of noisy data from the catalytic system.
Bian H, Ai L, Heng JYY, et al., 2023, Effects of chemical potential differences on methane hydrate formation kinetics, Chemical Engineering Journal, Vol: 452, Pages: 1-11, ISSN: 1385-8947
To underpin the increasing interest in practical applications of gas hydrates, for gas storage and separation for instance, the formation and growth of hydrates at liquid-gas interfaces are of fundamental importance. Although the thermodynamics of hydrate formation has been widely studied and is well understood, the kinetics of these processes is not well characterised. In this work, a high-pressure, low-temperature stirred reactor was used to conduct hydrate formation kinetic studies in a temperature range from 276.5 to 283.5 K and a pressure range from 5 to 10.5 MPa, with a special focus on 1) the impact of agitation conditions on the available water-gas interfacial surface area for mass transfer and growth rate during hydrate formation, and 2) the effect of the chemical potential driving force on the formation rate. Five hydrate growth regimes were identified, with varying degrees of gas mass transfer control across the gas-water interface depending on the extent to which hydrate layers built up at this interface, gas needed to move through solid hydrate layers, and the extent to which the gas was entrained within the water phase. The formation rate in the initial linear growth regime, before the onset of solid hydrate gas mass transfer effects, was found to depend in an essentially exponential manner on the chemical potential difference from the equilibrium state. Semi-empirical models related to Arrhenius-type kinetic models were used to correlate the data, the best of which reproduced the formation rates from the chemical potential differences to within ± 5 %. The approach has general applicability to help determine the balance between kinetic and thermodynamic factors in identifying the optimum pressure-temperature conditions for processes for gas storage, gas separation and other hydrate applications.
Yusuf M, Beg M, Ubaidullah M, et al., 2022, Kinetic studies for DRM over high-performance Ni-W/Al<sub>2</sub>O<sub>3</sub>-MgO catalyst, INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, Vol: 47, Pages: 42150-42159, ISSN: 0360-3199
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- Citations: 19
Parkinson B, Balcombe P, Speirs JF, et al., 2022, Levelized cost of CO<sub>2</sub> mitigation from hydrogen production routes (vol 12, pg 19, 2019), ENERGY & ENVIRONMENTAL SCIENCE, ISSN: 1754-5692
Chadha D, Hellgardt K, 2022, Flipping classrooms, sowing seeds, and developing confidence: teaching engineering judgement to undergraduate engineering students, American Society for Engineering Education Annual Meeting
Gan HS, Kanao S, Sato T, et al., 2022, Identifying marine debris source position using adjoint marginal sensitivity method and stranded beach litter data in Singapore, MARINE POLLUTION BULLETIN, Vol: 182, ISSN: 0025-326X
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- Citations: 1
Yusuf M, Farooqi AS, Alam MA, et al., 2022, Response surface optimization of syngas production from greenhouse gases via DRM over high performance Ni-W catalyst, INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, Vol: 47, Pages: 31058-31071, ISSN: 0360-3199
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- Citations: 12
Stark RT, Pye D, Chen W, et al., 2022, Assessing a sustainable manufacturing route to lapatinib, Reaction Chemistry and Engineering, Vol: 7, Pages: 2420-2426, ISSN: 2058-9883
A synthetic route to an anti-cancer drug, lapatinib, was devised to support the development of a sustainable manufacturing process in South Africa. Quantitative metrics were employed to evaluate the sustainability of the key steps of the reaction.
Deadman BJ, Gian S, Lee VEY, et al., 2022, On-demand, in situ, generation of ammonium caroate (peroxymonosulfate) for the dihydroxylation of alkenes to vicinal diols, Green Chemistry, Vol: 24, Pages: 5570-5578, ISSN: 1463-9262
Using the dihydroxylation of alkenes as a benchmark, the reactivities of fresh and aged solutions of (NH4)2S2O8 (electrochemically generated) were compared to commercially-procured peroxydisulfate and Oxone®. The study revealed that peroxymonosulfate (Caro’s acid, PMS) is the active oxidant in such reactions. Using complementary redox colorimetry and in situ IR spectroscopy to monitor the oxidants, the competitive decomposition of peroxydisulfate in an acidic solution into PMS and H2O2 can be quantified for the first time. The new insight enabled the design and implementation of both batch and flow processes to maximise the concentration of active PMS oxidant. The utility of these oxidants for organic synthesis is demonstrated by the dihydroxylation of eight styrenes and seven alkyl alkenes, where the ammonium PMS solutions performed better than Oxone® (counterion effect). Last but not least, a non-chromatographic method for isolating and purifying the water-soluble diol product was developed.
Ibadurrohman M, Hellgardt K, 2022, Effects of PEG templating of spray-pyrolyzed TiO<sub>2</sub> films on their nanoscale roughness and eventual photoelectrochemical properties, JOURNAL OF APPLIED ELECTROCHEMISTRY, Vol: 52, Pages: 929-940, ISSN: 0021-891X
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- Citations: 1
Chadha D, Campbell J, Maraj M, et al., 2022, Engaging students to shape their own learning: driving curriculum re-design using a Theory of Change approach, Education for Chemical Engineers, Vol: 38, Pages: 14-21, ISSN: 1749-7728
Curriculum review is challenging, although if carried out strategically can be less so. The adoption of a theory of change approach for reviewing a chemical engineering curriculum at a research-intensive university in the UK is discussed. The curriculum review was undertaken as part of an institutional drive to modularise the curricula and align the number of contact and independent study hours for all undergraduate students in the institution. At the heart of our curriculum review is the student experience, which is often ignored in favour of the views of institutional management. The curriculum has been redesigned using a theory of change approach, which has enabled us to establish short and long-term plans based on our efforts to create a less burdensome, student-centred curriculum that incorporates our institutional learning and teaching strategy. As part of the process, assumptions needed to be surfaced, meaningful evidence collated, and a central end-goal identified These plans are evidence-based and include: the provision of a departmental wellbeing advisor, the application and development of interactive pedagogies, appropriate mechanisms that support slow learning through formative assessment and less of an assessment burden, and nurturing links with industry-based partners ensuring a greater emphasis on students’ professional development and their exposure to chemical engineering industries.
Yusuf M, Farooqi AS, Ying YX, et al., 2021, Syngas production employing nickel on alumina-magnesia supported catalyst via dry methane reformingSynthesegasherstellung unter Verwendung von Nickel auf Aluminium-Magnesium unterstutztem Katalysator durch Trockenreformierung von Methan, MATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Vol: 52, Pages: 1090-1100, ISSN: 0933-5137
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- Citations: 14
Cardoso A, Pastor-Perez L, Reina TR, et al., 2021, Lignin to Monoaromatics with a Carbon-Nanofiber-Supported Ni-CeO<sub>2-<i>x</i></sub> Catalyst Synthesized in a One-Pot Hydrothermal Process, ACS SUSTAINABLE CHEMISTRY & ENGINEERING, Vol: 9, Pages: 12800-12812, ISSN: 2168-0485
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- Citations: 5
Wang S, Panayides J-L, Riley D, et al., 2021, Rapid formation of 2-lithio-1-(triphenylmethyl)imidazole and substitution reactions in flow, Reaction Chemistry and Engineering, Vol: 6, Pages: 2018-2023, ISSN: 2058-9883
The functionalisation of imidazoles is a necessary step in the formation of many active pharmaceutical intermediates. Herein, we report a flow chemistry approach for the rapid and efficient formation of 2-lithio-1-(triphenylmethyl)imidazole at ambient temperature and its reaction with a range of electrophiles, achieving modest to high yields (40–94%) in short reaction times (<1 min). The method is amenable to the scale-up of this highly reactive lithio-imidazole intermediate.
Chadha D, Kogelbauer A, Campbell J, et al., 2021, Are the kids alright? Exploring students’ experiences of support mechanisms to enhance wellbeing on an engineering programme in the UK, European Journal of Engineering Education, Vol: 46, Pages: 662-677, ISSN: 0304-3797
In this paper, we aim to explore students’ experiences of support mechanisms that support their wellbeing on an engineering degree programme at a research-intensive higher education institution and understand how theory relates to practice. This study was conducted using a mixed-methods approach involving student survey responses (N = 173), interviews with 16 students and focus groups. Kahu and Nelson’s conceptual framework was used as a lens through which to explore student support mechanisms. Preliminary data analysis indicates that the intense workload adversely affects students as do some of the interactions they have with personal tutors and their peers. Our findings suggest that workload needs to be reduced, personal tutors need to fill gaps in their skills set, especially associated with student support, and institutional and departmental protocols be continually updated to support student wellbeing. Additionally, student wellbeing officers and professional, dedicated wellbeing advisors could be part of a long-term solution.
Yusuf M, Farooqi AS, Al-Kahtani AA, et al., 2021, Syngas production from greenhouse gases using Ni-W bimetallic catalyst via dry methane reforming: Effect of W addition, INTERNATIONAL JOURNAL OF HYDROGEN ENERGY, Vol: 46, Pages: 27044-27061, ISSN: 0360-3199
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- Citations: 23
Parkinson B, Patzschke CF, Nikolis D, et al., 2021, Molten salt bubble columns for low-carbon hydrogen from CH<sub>4</sub> pyrolysis: Mass transfer and carbon formation mechanisms, CHEMICAL ENGINEERING JOURNAL, Vol: 417, ISSN: 1385-8947
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- Citations: 14
Yunus IS, Wang Z, Sattayawat P, et al., 2021, Improved Bioproduction of 1-Octanol Using Engineered <i>Synechocystis</i> sp. PCC 6803, ACS SYNTHETIC BIOLOGY, Vol: 10, Pages: 1417-1428, ISSN: 2161-5063
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- Citations: 10
Patzschke CF, Parkinson B, Willis JJ, et al., 2021, Co-Mn catalysts for H<sub>2</sub> production <i>via</i> methane pyrolysis in molten salts, CHEMICAL ENGINEERING JOURNAL, Vol: 414, ISSN: 1385-8947
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- Citations: 21
Wichmann J, Lauersen KJ, Biondi N, et al., 2021, Engineering Biocatalytic Solar Fuel Production: The PHOTOFUEL Consortium, TRENDS IN BIOTECHNOLOGY, Vol: 39, Pages: 323-327, ISSN: 0167-7799
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- Citations: 8
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