Neutron Scattering Studies of Heterogeneous Catalysis.

Understanding the structural dynamics/evolution of catalysts and the related surface chemistry is essential for establishing structure-catalysis relationships, where spectroscopic and scattering tools play a crucial role. Among many such tools, neutron scattering, though less-known, has a unique power for investigating catalytic phenomena. Since neutrons interact with the nuclei of matter, the neutron-nucleon interaction provides unique information on light elements (mainly hydrogen), neighboring elements, and isotopes, which are complementary to X-ray and photon-based techniques. Neutron vibrational spectroscopy has been the most utilized neutron scattering approach for heterogeneous catalysis research by providing chemical information on surface/bulk species (mostly H-containing) and reaction chemistry. Neutron diffraction and quasielastic neutron scattering can also supply important information on catalyst structures and dynamics of surface species. Other neutron approaches, such as small angle neutron scattering and neutron imaging, have been much less used but still give distinctive catalytic information. This review provides a comprehensive overview of recent advances in neutron scattering investigations of heterogeneous catalysis, focusing on surface adsorbates, reaction mechanisms, and catalyst structural changes revealed by neutron spectroscopy, diffraction, quasielastic neutron scattering, and other neutron techniques. Perspectives are also provided on the challenges and future opportunities in neutron scattering studies of heterogeneous catalysis.

The adsorption of nitrobenzene over an alumina-supported palladium catalyst: an infrared spectroscopic study.

As part of an on-going programme of development of an aniline synthesis catalyst suitable for operation at elevated temperatures, the geometry of the adsorption complex for nitrobenzene on a 5 wt% Pd/Al2O3 catalyst is investigated by infrared (IR) spectroscopy. Via an appreciation of the reduced site symmetry resulting from adsorption, application of the metal surface selection rule, and observation of in-plane modes only, the adsorption complex (Pd-nitrobenzene) at 28 °C is assigned as occurring vertically or tilted with respect to the metal surface, adopting Csσv(yz) symmetry. Moreover, adsorption occurs via a single Pd-O bond. Single molecule DFT calculations and simulated IR spectra assist vibrational assignments but indicate a parallel adsorption geometry to be energetically favourable. The contradiction between calculated and observed structures is attributed to the DFT calculations corresponding to an isolated molecule adsorption complex, while IR spectra relate to multi molecule adsorption that is encountered during sustained catalytic turnover. Residual hydrogen from the catalyst reduction stage leads to aniline formation on the Pd surface at low nitrobenzene coverages but, on increasing nitrobenzene exposure, the aniline is forced on to the alumina support. A reaction scheme is proposed whereby the nitrobenzene adsorption geometry is inherently linked to the high aniline selectivity observed for Pd/Al2O3 catalysts.

Combining quasielastic neutron scattering and molecular dynamics to study methane motions in ZSM-5.

Quasi-elastic neutron scattering (QENS) and molecular dynamics (MD) simulations are applied in combination to investigate the dynamics of methane in H-ZSM-5 zeolite catalysts used for methanol-to-hydrocarbons reactions. Methane is employed as an inert model for the methanol reaction feedstock, and studies are made of the fresh catalyst and used catalysts with varying levels of coke buildup to investigate the effect of coking on reactant mobility. Measurements are made in the temperature range from 5 to 373 K. Methane mobility under these conditions is found to be extremely high in fresh ZSM-5, with the majority of movements occurring too fast to be resolved by the QENS instrument used. A small fraction of molecules undergoing jump diffusion on QENS time scales is identified and found to correspond with short-range jump diffusion within single zeolite pores as identified in MD simulations. Agreement between QENS and MD mobility measurements is found to be within 50%, validating the simulation approach employed. Methane diffusion is found to be minimally affected by moderate levels of coke buildup, while highly coked samples result in the confinement of methane to single pores within the zeolite with minimal long-range diffusion.

Athletes with primary glenohumeral instability demonstrate lower rates of bone loss than those with recurrent instability and failed prior stabilization.

BACKGROUND: The purpose of this study was to compare the preoperative magnetic resonance arthrography findings in patients who underwent glenohumeral stabilization with a history of primary instability, recurrent instability, or failed stabilization. METHODS: All patients who presented with glenohumeral instability and underwent stabilization performed by a single surgeon in our institution between 2008 and 2020 were considered for inclusion in this study. The magnetic resonance arthrography findings of all patients were recorded. Imaging findings were compared between patients with primary instability, those with recurrent instability, and those with failed prior stabilization. P < .05 was considered statistically significant. RESULTS: Overall, 871 patients were included, of whom 814 (93.5%) were male patients; the mean age was 23.1 years (range, 13-57 years). There were 200 patients with primary instability, 571 with recurrent instability, and 100 who required revision stabilization surgery, with no significant differences in demographic characteristics between the groups. A significantly higher amount of glenoid bone loss was noted in patients with recurrent instability (43.4%) and failed prior stabilization (56%) than in those with primary instability (26.5%) (P < .0001). Additionally, a significantly higher number of Hill-Sachs lesions were observed in patients with recurrent instability (70.1%) and failed prior stabilization (89%) than in those with primary instability (67.5%) (P < .0001). We found no significant differences between the groups regarding articular cartilage damage, glenolabral articular disruption, anterior labral periosteal sleeve avulsion, humeral avulsion of the glenohumeral ligaments, or superior labral anterior-posterior tears (P > .05). CONCLUSION: Patients presenting for stabilization with recurrent instability or following a failed stabilization procedure have higher rates of glenohumeral bone loss than those with primary instability. Therefore, stabilization of primary instability, particularly in high-functioning athletes with a view to preventing recurrence, may reduce the overall progression of glenohumeral bone loss and potential subsequent inferior clinical outcomes.

The interaction of CO with a copper(ii) chloride oxy-chlorination catalyst.

The interaction of CO with an attapulgite-supported, KCl modified CuCl2 catalyst has previously been examined using a combination of XANES, EXAFS and DFT calculations. Exposing the catalyst to CO at elevated temperatures leads to the formation of CO2 as the only identifiable product. However, phosgene production can be induced by a catalyst pre-treatment stage, where the supported CuCl2 sample is exposed to a diluted stream of dichlorine; subsequent CO exposure at ∼643 K then leads to phosgene production. This communication describes a series of FTIR based micro-reactor measurements, coupled with characterisation measurements utilising TEM, XRD and XPS to define the nature of the catalyst at different stages of the reaction coordinate. The CuCl2 catalyst is able to support Deacon activity , establishing this work with the possibility of utilising the oxy-chlorination of CO to produce phosgene. Continuous dosing of CO at elevated temperatures over the chlorine pre-dosed CuCl2 catalyst shows diminishing phosgene production as a function of time-on-stream, indicating surface chlorine supply to be rate-limiting under the reaction conditions studied. A pictorial reaction scheme is proposed to account for the surface chemistry observed.

Ankle conFUSION: The quality and readability of information on the internet relating to ankle arthrodesis.

BACKGROUND: The internet is an important source of information for patients undergoing surgery. Multiple studies have identified inappropriately high reading levels of patient information online. The average reading level in the United States is 7-8th grade. Multiple organisations have recommended that patient information not exceed 6th grade level. This study aims to evaluate the reading levels and quality of information regarding ankle fusion surgery online. METHODS: Google, Bing and Yahoo were searched (MeSH "ankle fusion", "ankle arthrodesis") and the top 30 URLs analysed. Readability was assessed using an online readability calculator to produce 3 scores (Gunning FOG, Flesch Kincaid Grade and Flesch Reading Ease). Quality was assessed using a HONcode detection web-extension and the JAMA benchmark criteria. RESULTS: Ninety-eight webpages were identified. The mean Flesch Kincaid Grade level was 9.24 ± 2.33 (95% CI 8.78-9.71). The mean Gunning FOG grade was 10.88 ± 3.1 (95% CI 10.26-11.5). The mean Flesch Reading Ease score was 49.88 ± 14.46 (95% CI 46.98-52.78). 7 webpages were at or below the 6th grade reading level. The mean JAMA score was 1.34 ± 1.32 out of 4 (95% CI 1.07-1.6). 14 websites were HONcode accredited. CONCLUSION: The overall readability of medical information online is too high for the average patient. Given the important role that health literacy provides in patient reported outcomes, improving the readability and quality of these materials is imperative. Awareness by the general public is essential for them to critically appraise the information they receive online.

Structural behaviour of copper chloride catalysts during the chlorination of CO to phosgene.

The interaction of CO with an attapulgite-supported Cu(ii)Cl2 catalyst has been examined in a micro-reactor arrangement. CO exposure to the dried, as-received catalyst at elevated temperatures leads to the formation of CO2 as the only identifiable product. However, phosgene production can be induced by using a catalyst pre-treatment where the supported Cu(ii)Cl2 sample is exposed to a diluted stream of chlorine. Subsequent CO exposure at ∼370 °C then leads to phosgene production. In order to investigate the origins of this atypical set of reaction characteristics, a series of X-ray absorption experiments were performed that were supplemented by DFT calculations. XANES measurements establish that at the elevated temperatures connected with phosgene formation, the catalyst is comprised of Cu+ and a small amount of Cu2+. Moreover, the data show that unique to the chlorine pre-treated sample, CO exposure at elevated temperature results in a short-lived oxidation of the copper. On the basis of calculated CO adsorption energies, DFT calculations indicate that a mixed Cu+/Cu2+ catalyst is required to support CO chemisorption.

An assessment of hydrocarbon species in the methanol-to-hydrocarbon reaction over a ZSM-5 catalyst.

A ZSM-5 catalyst is examined in relation to the methanol-to-hydrocarbon (MTH) reaction as a function of reaction temperature and time-on-stream. The reaction profile is characterised using in-line mass spectrometry. Furthermore, the material contained within a catch-pot downstream from the reactor is analysed using gas chromatography-mass spectrometry. For a fixed methanol feed, reaction conditions are selected to define various stages of the reaction coordinate: (i) initial methanol adsorption at a sub-optimum reaction temperature (1 h at 200 °C); (ii) initial stages of reaction at an optimised reaction temperature (1 h at 350 °C); (iii) steady-state operation at an optimised reaction temperature (3 days at 350 °C); and (iv) accelerated ageing (3 days at 400 °C). Post-reaction, the catalyst samples are analysed ex situ by a combination of temperature-programmed oxidation (TPO) and spectroscopically by electron paramagnetic resonance (EPR), diffuse-reflectance infrared and inelastic neutron scattering (INS) spectroscopies. The TPO measurements provide an indication of the degree of 'coking' experienced by each sample. The EPR measurements detect aromatic radical cations. The IR and INS measurements reveal the presence of retained hydrocarbonaceous species, the nature of which are discussed in terms of the well-developed 'hydrocarbon pool' mechanism. This combination of experimental evidence, uniquely applied to this reaction system, establishes the importance of retained hydrocarbonaceous species in effecting the product distribution of this economically relevant reaction system.

Metal Fluorides, Metal Chlorides and Halogenated Metal Oxides as Lewis Acidic Heterogeneous Catalysts. Providing Some Context for Nanostructured Metal Fluorides.

Aspects of the chemistry of selected metal fluorides, which are pertinent to their real or potential use as Lewis acidic, heterogeneous catalysts, are reviewed. Particular attention is paid to ß-aluminum trifluoride, aluminum chlorofluoride and aluminas γ and η, whose surfaces become partially fluorinated or chlorinated, through pre-treatment with halogenating reagents or during a catalytic reaction. In these cases, direct comparisons with nanostructured metal fluorides are possible. In the second part of the review, attention is directed to iron(III) and copper(II) metal chlorides, whose Lewis acidity and potential redox function have had important catalytic implications in large-scale chlorohydrocarbons chemistry. Recent work, which highlights the complexity of reactions that can occur in the presence of supported copper(II) chloride as an oxychlorination catalyst, is featured. Although direct comparisons with nanostructured fluorides are not currently possible, the work could be relevant to possible future catalytic developments in nanostructured materials.

The development of a new generation of methyl chloride synthesis catalyst.

In previous work by the authors, aspects of the surface chemistry connected with methyl chloride synthesis over an η-alumina catalyst have been examined. This communication considers a role for Group 1 metal salts to modify the catalytic performance of the well characterised η-alumina catalyst. Firstly, based on a previously postulated mechanism for the reaction of methanol on η-alumina, a mechanism for methyl chloride synthesis over the η-alumina catalyst is proposed. Secondly, the validity of the new mechanism is tested by observing how the (i) type and (ii) loading of the Group 1 metal salt may perturb methyl chloride selectivity. The outcomes of these measurements are rationalised with reference to the postulated mechanism. Overall, this study represents an example of how a proposed reaction mechanism has been used to inform and guide a catalyst development strategy for a large-scale industrial process.

Different routes to methanol: inelastic neutron scattering spectroscopy of adsorbates on supported copper catalysts.

We have investigated methanol synthesis with model supported copper catalysts, Cu/ZnO and Cu/MgO, using CO/H2 and CO2/H2 as feedstocks. Under CO/H2 both catalysts show chemisorbed methoxy as a stable intermediate, the Cu/MgO catalyst also shows hydroxyls on the support. Under CO2/H2 the catalysts behave differently, in that formate is also seen on the catalyst. For the Cu/ZnO catalyst hydroxyls are present on the metal whereas for the Cu/MgO hydroxyls are found on the support. These results are consistent with a recently published model for methanol synthesis and highlight the key role of ZnO in the process.

The application of inelastic neutron scattering to investigate the interaction of methyl propanoate with silica.

A modern industrial route for the manufacture of methyl methacrylate involves the reaction of methyl propanoate and formaldehyde over a silica-supported Cs catalyst. Although the process has been successfully commercialised, little is known about the surface interactions responsible for the forward chemistry. This work concentrates upon the interaction of methyl propanoate over a representative silica. A combination of infrared spectroscopy, inelastic neutron scattering, DFT calculations, X-ray diffraction and temperature-programmed desorption is used to deduce how the ester interacts with the silica surface.

Inelastic neutron scattering studies of methyl chloride synthesis over alumina.

Not only is alumina the most widely used catalyst support material in the world, it is also an important catalyst in its own right. One major chemical process that uses alumina in this respect is the industrial production of methyl chloride. This is a large scale process (650,000 metric tons in 2010 in the United States), and a key feedstock in the production of silicones that are widely used as household sealants. In this Account, we show how, in partnership with conventional spectroscopic and reaction testing methods, inelastic neutron scattering (INS) spectroscopy can provide additional insight into the active sites present on the catalyst, as well as the intermediates present on the catalyst surface. INS spectroscopy is a form of vibrational spectroscopy, where the spectral features are dominated by modes involving hydrogen. Because of this, most materials including alumina are largely transparent to neutrons. Advantageously, in this technique, the entire "mid-infrared", 0-4000 cm(-1), range is accessible; there is no cut-off at ~1400 cm(-1) as in infrared spectroscopy. It is also straightforward to distinguish fundamental modes from overtones and combinations. A key parameter in the catalyst's activity is the surface acidity. In infrared spectroscopy of adsorbed pyridine, the shifts in the ring stretching modes are dependent on the strength of the acid site. However, there is a very limited spectral range available. We discuss how we can observe the low energy ring deformation modes of adsorbed pyridine by INS spectroscopy. These modes can undergo shifts that are as large as those seen with infrared inspectroscopy, potentially enabling finer discrimination between acid sites. Surface hydroxyls play a key role in alumina catalysis, but in infrared spectroscopy, the presence of electrical anharmonicity complicates the interpretation of the O-H stretch region. In addition, the deformations lie below the infrared cut-off. Both of these limitations are irrelevant to INS spectroscopy, and all the modes are readily observable. When we add HCl to the catalyst surface, the acid causes changes in the spectra. We can then deduce both that the surface chlorination leads to enhanced Lewis acidity and that the hydroxyl group must be threefold coordinated. When we react η-alumina with methanol, the catalyst forms a chemisorbed methoxy species. Infrared spectroscopy clearly shows its presence but also indicates the possible coexistence of a second species. Because of INS spectroscopy's ability to discriminate between fundamental modes and combinations, we were able to unambiguously show that there is a single intermediate present on the surface of the active catalyst. This work represents a clear example where an understanding of the chemistry at the molecular level can help rationalize improvements in a large scale industrial process with both financial and environmental benefits.

The application of inelastic neutron scattering to explore the significance of a magnetic transition in an iron based Fischer-Tropsch catalyst that is active for the hydrogenation of CO.

An iron based Fischer-Tropsch synthesis catalyst is evaluated using CO hydrogenation at ambient pressure as a test reaction and is characterised by a combination of inelastic neutron scattering (INS), powder X-ray diffraction, temperature-programmed oxidation, Raman scattering, and transmission electron microscopy. The INS spectrum of the as-prepared bulk iron oxide pre-catalyst (hematite, α-Fe2O3) is distinguished by a relatively intense band at 810 cm(-1), which has previously been tentatively assigned as a magnon (spinon) feature. An analysis of the neutron scattering intensity of this band as a function of momentum transfer unambiguously confirms this assignment. Post-reaction, the spinon feature disappears and the INS spectrum is characterised by the presence of a hydrocarbonaceous overlayer. A role for the application of INS in magnetic characterisation of iron based FTS catalysts is briefly considered.

Risk scoring models for patients with proximal femur fractures: Qualitative systematic review assessing 30-day mortality and ease of use.

BACKGROUND: Hip fractures are a common orthopaedic injury affecting a particularly frail and vulnerable patient cohort. They are at risk of many complications, including prolonged length of stay and mortality. Efforts to identify those at high risk may be beneficial. Over 25 risk prediction models are published for patients with hip fractures. AIM: The primary aim of this study was to assess the performance of predictor scores in predicting 30-day mortality. The secondary aim was to assess the ease of use of these systems. METHODS: A qualitative systematic review was performed. A search was conducted on online databases, including PubMed, CINAHL, Clinical Trials.gov, Cochrane, DARE, EMBASE, SCOPUS, and Web of Science.. The terms fragility hip fractures and risk prediction models were utilised while performing the search. These were then expanded using Boolean operators and similar terms. Search results were imported to Covidence. Primary observational studies using one or more hip fracture mortality prediction models and 30-day mortality as an outcome were included. Systematic reviews and studies on specific patient groups defined other medical conditions (e.g. COVID positive or dialysis patients) were excluded. RESULTS: 3,101 studies were screened following duplicate removal. 34 papers were included in the review, in which 23 scoring systems were reported. Six of these were pre-operative and reported in multiple studies. Most demonstrated appropriate fit and fair discrimination. Five of the six pre-operative scoring systems examined, displayed appropriate ease of use, allowing risk calculation at the time of admission. CONCLUSION: Nottingham Hip Fracture Score remains the most extensive reported scoring system and performs fair overall with AUROCs of 0.64-0.80 and good fit in calibration across all studies. However, new systems utilise many similar predictors. There is a need for the standardisation of publications on scoring systems to allow further systematic review and meta-analyses.

Increasing hip fracture volume following repeated lockdowns: an Irish multicentre study of periods pre-Covid, during Covid lockdown and following vaccination.

BACKGROUND: Older age groups were identified as a high-risk cohort for Covid-19 and thus were a focus of lockdown measures enacted internationally. Resultant decreased social mobility and physical activity levels are associated with sarcopenia, which may lead to increased risk of hip fracture upon resuming social integration and physical activities after easing of lockdown restrictions. AIMS: Our aim was to compare the incidence of hip fractures during the period following vaccination with subsequent relaxation of restrictions, to those prior to and during the Covid pandemic. METHODS: A multicentre retrospective cohort study was performed consisting of all patients presenting with a "hip" fracture to 3 regional trauma units over the relevant time periods in 2019, 2020 and 2021. Tallaght, Galway and Waterford University Hospitals are large academic teaching hospitals with a combined mixed urban and rural catchment of over 1 million people. FINDINGS: Four-hundred-fourteen patients in total were included in the final analysis, with 133 eligible hip fractures observed proceeding to operative treatment across the study period in 2019, 132 in 2020 and 149 in 2021, representing a 12.88% increase. Demographic data revealed similar patient cohorts with respect to age and gender, fracture pattern and treatment. CONCLUSIONS: An increase in hip fracture volume was observed during the period post vaccination with subsequent relaxation of restrictions and increased social mobility, compared to those prior to and during the Covid pandemic. These findings have implications for hospital planning and orthopaedic resourcing as we navigate our way forward past the Covid-19 Pandemic.

The association between weather warnings and hip fractures in the Republic of Ireland.

This study examined the relationship between hip fractures and weather warnings with the hypothesis higher rates of fractures occur during warnings. National hip fracture database and weather warning records were utilised. Higher rates of hip fractures were found with severe warnings. This has implications for planning in future severe warnings. BACKGROUND: Hip fractures represent a significant burden on the Irish Health system with 3666 in 2020. The Irish National Meteorological Service operates a colour coded warning system. Yellow being least severe, while orange represents weather with capacity to impact individuals in affected areas and red represents advice to protect themselves and property. Previous studies investigated the seasonality of hip fractures, which remains but none have investigated the relationship between weather warnings and rates of hip fractures. The hypothesis was that increasing weather warnings would be associated with increased hip fractures. The aim was to investigate the relationship between weather warnings and hip fractures in the Republic of Ireland. METHODS: Comparison of national weather warning archives from 2013 to 2019 to Fracture Database records. Reviews assessed whether fractures occurred on days a weather warning was in place in the individual's local county. A statistical analysis of warning features and their relationship to hip fractures was then performed. Fractures and weather warnings were stratified by county with both a panel and case crossover analysis performed. RESULTS: There was a tendency towards increased incidence of hip fractures with weather warnings in adjusted analysis (IRR 1.02; 95%CI 0.99-1.06; p-value 0.123). Orange warnings were associated with a statistically higher incidence of fractures (IRR 1.06; 1.01-1.12; p-value 0.026). In both panel and case crossover analysis, both orange and yellow warnings were associated with fractures. Red warnings were associated with a lower incidence of fracture on day of warning (adjusted incidence rate ratio 0.92; 0.70-1.22; p-value 0.569) but a higher incidence on the following day (adjusted incidence rate ratio 1.14; 0.88-1.46; p-value 0.313). CONCLUSION: An increased incidence of hip fractures appears to occur during weather warnings. Consideration should be given when preparing for periods of extreme weather, ensuring sufficiently resources.

Surgical management strategies for colorectal malignancies of the splenic flexure - A systematic review and network meta-analysis.

BACKGROUND: Extended right hemicolectomy (ERHC) or left hemicolectomy (LHC) are accepted as the standard-of-care for colonic tumours of the splenic flexure. Lymphatic drainage at this site is poorly defined and subject to significant heterogeneity. Nevertheless, emerging evidence demonstrates the potential oncological safety of segmental splenic flexure colectomy (SFC). AIM: To perform a systematic review and network meta-analysis (NMA) to compare outcomes following ERHC, LHC and SFC for splenic flexure tumours (SFTs). METHODS: A systematic review was performed as per PRISMA guidelines. NMA was performed using R Shiny and Netmeta packages. RESULTS: A total of 13 studies, involving 6176 patients (ERHC n = 785; LHC n = 1527; SFC n = 3864) were included in the NMA. There was no difference in overall survival (OS) (SFC vs LHC Hazard Ratio [HR] 1.0, 95% Credible Interval [CrI] 0.76,1.34; SFC vs ERHC HR 1.18, 95% CrI 0.85,1.58) between the groups. SFC had a shorter operation time (Mean 176.37 min; Mean Difference [MD] SFC vs LHC 20.34 min 95% CrI 10.9, 29.97; SFC vs ERHC MD 22.19 95% CrI 11.09, 33.29) but also had a lower average lymph node yield (LNY) compared with ERHC (MD 7.15, 95% CrI 5.71, 8.60). ERHC had a significantly higher incidence of post-operative ileus (Odds Ratio [OR] 3.47, 95% CrI 1.11, 10.84). There was also no difference observed for minimally invasive approaches, anastomotic leak rate, perioperative mortality, reoperation rates or length of stay. CONCLUSIONS: While SFC may allow for reduced operative duration and improved bowel function postoperatively. SFC, LHC, ERHC are all acceptable approaches for curative resection of cancers of the splenic flexure, with no difference in OS observed. Thus, surgeon preference and candidate-specific factors will likely determine the management of SFTs.

In situ real-time neutron imaging of gaseous H2 adsorption and D2 exchange on carbon-supported Pd catalysts.

We use in situ neutron imaging to observe the adsorption/absorption of hydrogen within a packed catalyst bed of a Pd/C catalyst at a spatial and temporal resolution of ∼430 µm and a ∼9 s respectively. Additionally, the H2/D2 exchange process across the catalyst bed is followed in real time.