Feasibility of the tandem reaction of isomerization-telomerization

The aim of this project consists of detennining the feasibility of a new tandem reaction comprising isomerization and telomerization steps starting from internal diolefins. This type of reactions achieves not only a minimization 9fthe number of steps but also potentially reduces waste fonnation and process capital costs, thus fulfilling the main objectives of Green Chemistry towards the design of sustainable processes. Telomerization is a 100% atom efficient route to the fonnation of functionalized long chain molecules. However, only telomerization of tenninal . conjugated dienes has been reported which limits its applications due to the thennodynamically unfavourable presence of tenninal dienes in natural feedstocks. If proved feasible, the proposed tandem reaction would open opportunities for the utilization ofnew feedstocks and a potentially significant industrial impact. Titanate nanotubes was found to be a good support for metal catalysts (Pd, Rh, Ru), showing high activity in the isomerization of diolefins and very high selectivity for the reaction with allylbenzene. A novel Ru-PPh3-resin catalyst was also highly active in diolefins isomerization (including linoleic acid) with similar catalytic activity than homogeneous catalysts and the possibility of being reused without loss of activity. Screening of homogeneous catalysts based on phosphorus and carbene ligands was carried out for the telomerization reaction and the influence of different operation conditions such as temperature, initial concentration and the nature of nucleophiles was investigated. Heterogeneous catalysts based on DVBresins were also studied, revealing an unusual selectivity to tail-to-head products by Pd-(dvds)-PPh3-resin in the reaction of isoprene with methanol. The telomerization reaction was extended to 1,3-hexadiene when long-chain alcohols are used as nucleophiles and Pd(Imes)(dvds) as catalyst, opening opportunities for long-chain reactants. Finally, the feasibility of tandem reactions was successfully demonstrated with the best results obtained with homogeneous isomerization and telomerization catalysts in the presence of free carbene ligands in the reaction medium.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Continuous synthesis of hollow silver-palladium nanoparticles for catalytic applications.

Hollow bimetallic nanoparticles exhibit unique surface plasmonic properties, enhanced catalytic activities and high photo-thermal conversion efficiencies amongst other properties, however, their research and further deployment are currently limited by their complicated multi-step syntheses. This paper presents a novel approach for their continuous synthesis with controllable and tuneable sizes and compositions. This robust manufacturing tool, consisting of coiled flow inverter (CFI) reactors connected in series, allows for the first time the temporal and spatial separation of the initial formation of silver seeds and their subsequent galvanic displacement reaction in the presence of a palladium precursor, leading to the full control of both steps separately. We have also demonstrated that coupling the galvanic replacement and co-reduction leads to a great kinetic enhancement of the system leading to a high yield process of hollow bimetallic nanoparticles, directly applicable to other metal combinations

Sour compression process for the removal of SOx and NOx from oxyfuel-derived CO2

AbstractCoal-fired power stations under oxyfuel combustion produce a raw CO2 product which contains impurities such as water, oxygen, nitrogen and argon from excess oxygen and air leakages. There are also acid gases present, such as SO3, SO2, HCl and NOX produced as by-products of combustion. These acidic impurities will need to be removed from the CO2 stream before it is introduced into the pipeline to prevent corrosion and comply with possible regulations. There may also be stringent requirements on purity, particularly for applications such as enhanced oil recovery. A novel compression method of producing NOx-free, SO2free CO2 was proposed in GHGT-8 [1–6] where SO2 and NOx are removed as H2SO4 and HNO3respectively by compression and water contact of the flue gas. At GHGT-9, initial experimental results were presented using actual fluegas via a sidestream from Doosan Babcock’s 160 kW coal-fired oxyfuel rig, showing the feasibility of the process eliminating 99% SOx and 90% NOx compounds. In this paper, we report on the effects of pressure, temperature, residence time and presence of water in a laboratory scale apparatus using synthetic flue gas

Tandem isomerization/telomerization of long chain dienes.

The first example of a tandem reaction involving double-bond migration in combination with telomerization is reported. Homogeneous and heterogeneous Ru catalysts were employed as isomerization catalysts, and telomerization was realized using a homogeneous Pd(0) precursor complex with a N-heterocyclic carbene (IMes) ligand. Overall conversions approaching 60% were achieved with the best selectivity to telomerization products of 91% attained at 11% conversion. Conversion was markedly higher in the presence of longer-chain alcohol (1-butanol) as the nucleophile (telogen).Financial support from Engineering and Physical Sciences Research Council (EPSRC, UK) via grant GR/S86112/01 is gratefully acknowledged.This is the final published version, which can also be found on the publisher's website at: http://journal.frontiersin.org/Journal/10.3389/fchem.2014.00037/ful

Highlights from faraday discussion on designing nanoparticle systems for catalysis, London, UK, May 2018

The 2018 Faraday Discussion on “Designing Nanoparticle Systems for Catalysis” brought together leading scientists to discuss the current state-of-the-art in the fields of computational chemistry, characterization techniques, and nanomaterial synthesis, and to debate the challenges and opportunities going forward for rational catalyst design. The meeting was a vivid discussion of how the communities accummulate knowledge and on how innovativeness can be combined to have a stronger scientific impact. In the following, we provide an overview of the meeting structure, including plenaries, papers, discussion points and breakout sessions, and we hope to show, to the wider scientific community, that there is great value in continued international discussion and scientific collaboration in these fields

N-Doped Fe@CNT for Combined RWGS/FT CO ₂ Hydrogenation

The conversion of CO₂ into chemical fuels represents an attractive route for greenhouse gas emission reductions and renewable energy storage. Iron nanoparticles supported on graphitic carbon materials (e.g., carbon nanotubes (CNTs)) have proven themselves to be effective catalysts for this process. This is due to their stability and ability to support simultaneous reverse water-gas shift (RWGS) and Fischer–Tropsch (FT) catalysis. Typically, these catalytic iron particles are postdoped onto an existing carbon support via wet impregnation. Nitrogen doping of the catalyst support enhances particle–support interactions by providing electron-rich anchoring sites for nanoparticles during wet impregnation. This is typically credited for improving CO₂ conversion and product selectivity in subsequent catalysis. However, the mechanism for RWGS/FT catalysis remains underexplored. Current research places significant emphasis on the importance of enhanced particle–support interactions due to N doping, which may mask further mechanistic effects arising from the presence or absence of nitrogen during CO₂ hydrogenation. Here we report a clear relationship between the presence of nitrogen in the CNT support of an RWGS/FT iron catalyst and significant shifts in the activity and product distribution of the reaction. Particle–support interactions are maximized (and discrepancies between N-doped and pristine support materials are minimized) by incorporating iron and nitrogen directly into the support during synthesis. Reactivity is thus rationalized in terms of the influence of C–N dipoles in the support upon the adsorption properties of CO₂ and CO on the surface rather than improved particle–support interactions. These results show that the direct hydrogenation of CO₂ to hydrocarbons is a potentially viable route to reduce carbon emissions from human activities

Effect of nanostructured ceria as support for the iron catalysed hydrogenation of CO2 into hydrocarbons.

This paper demonstrates the key role of the property-structure relationship of the support on iron/ceria catalysts on the hydrocarbon selectivity and olefin-to-paraffin ratio for the direct hydrogenation of carbon dioxide into hydrocarbons. The effect is directly related to the reducibility of the different nanostructured ceria supports and their interaction with the iron particles. Herein, we demonstrate that the iron-based catalysts can be modified not only by the addition of promoters, commonly reported in the literature, but also by careful control of the morphology of the ceria support.The authors thanks the UK Engineering and Physical Science Research Council (EPSRC, grant numbers: EP/L020432/2 and EP/G03768X/1).This is the final version of the article. It first appeared from the Royal Society of Chemistry via http://dx.doi.org/10.1039/C5CP07788

Single-step synthesis of nanostructured g-alumina with solvent reusability to maximise yield and morphological purity

The mechanism of the hydrothermal synthesis of nanostructured alumina shows that the NaOH : Al molar ratio affects not only the resulting morphology but also the yield. Successful reusability of the reaction medium opens the door to large scale manufacturing.</p

Size Control in the Colloidal Synthesis of Plasmonic Magnesium Nanoparticles.

Nanoparticles of plasmonic materials can sustain oscillations of their free electron density, called localized surface plasmon resonances (LSPRs), giving them a broad range of potential applications. Mg is an earth-abundant plasmonic material attracting growing attention owing to its ability to sustain LSPRs across the ultraviolet, visible, and near-infrared wavelength range. Tuning the LSPR frequency of plasmonic nanoparticles requires precise control over their size and shape; for Mg, this control has previously been achieved using top-down fabrication or gas-phase methods, but these are slow and expensive. Here, we systematically probe the effects of reaction parameters on the nucleation and growth of Mg nanoparticles using a facile and inexpensive colloidal synthesis. Small NPs of 80 nm were synthesized using a low reaction time of 1 min and ∼100 nm NPs were synthesized by decreasing the overall reaction concentration, replacing the naphthalene electron carrier with biphenyl or using metal salt additives of FeCl3 or NiCl2 at longer reaction times of 17 h. Intermediate sizes up to 400 nm were further selected via the overall reaction concentration or using other metal salt additives with different reduction potentials. Significantly larger particles of over a micrometer were produced by reducing the reaction temperature and, thus, the nucleation rate. We showed that increasing the solvent coordination reduced Mg NP sizes, while scaling up the reaction reduced the mixing efficiency and produced larger NPs. Surprisingly, varying the relative amounts of Mg precursor and electron carrier had little impact on the final NP sizes. These results pave the way for the large-scale use of Mg as a low-cost and sustainable plasmonic material.Support for this project was provided by the EU Framework Programme for Research and Innovation Horizon 2020 (ERC Starting Grant SPECs 804523). E.R.H. is thankful for funding from the EPSRC NanoDTC Cambridge (EP/L015978/1). J.A. acknowledges financial support from Natural Sciences and Engineering Research Council of Canada and Fonds de Recherche du Québec–Nature et Technologies postdoctoral fellowships (BP and B3X programs). C.B. is thankful for funding from the Engineering and Physical Sciences Research Council (Standard Research Studentship (DTP) EP/R513180/1). B.P. and L.T.M. acknowledge support from UK Engineering and Physical Science and Research Council (grant number EP/L020443/2). Thanks to Giulio I. Lampronti for helpful discussions and support