The direct synthesis of hydrogen peroxide using bimetallic gold and palladium supported catalysts

In this thesis the direct synthesis of hydrogen peroxide (H2O2) from hydrogen and oxygen using gold-palladium supported catalysts was investigated. The direct route represents a greener and sustainable alternative to the current industrial manufacturing process. The main objective of this study was to achieve the industrial requirements of H2O2 yields and selectivity, which would make the direct process industrially viable. In order to reach the required target, two innovative approaches for the direct synthesis of H2O2 were examined. The first part of this thesis was dedicated to the development of a biphasic solvent system comprising an organic alcohol and water. The advantages of this system was highlighted and the effect of reaction variables (such as solvent composition, pressure, reagent ratio, temperature and reaction time) were evaluated using two different catalysts. The identification of two optimum conditions resulted in an important enhancement in the H2O2 yield for the two catalysts examined. By finely tuning the reaction conditions and using two different solvent systems ((i) decan-1-o1-water (ii) diisobutyl carbinol-water) H2O2 concentrations between ~ 0.30 and 28 wt. % were achieved. The second part of this thesis was dedicated to studying the direct gas phase synthesis of H2O2 in a continuous gas flow reactor. Two lab scale flow reactors were designed and built in situ: The first was for studying the direct gas phase synthesis of H2O2 at atmospheric pressure and the second for studying the reaction at pressures above atmospheric. The results demonstrate the direct gas phase synthesis of H2O2 was challenging and the absence of solvent seriously compromises the stability of the H2O2. Despite this, the results demonstrate by using gold-palladium nanoparticles and a mixture of hydrogen and oxygen it is possible to not only oxidise organic molecules in the gas phase but the synthesis rates were high enough to detect H2O2 as a product in a fixed bed gas phase reactor and a temporal analysis of products (TAP) reactor. This observation opens up the possibility of synthesising H2O2 directly in a gas phase reaction

The direct synthesis of hydrogen peroxide using a combination of a hydrophobic solvent and water

The direct synthesis of hydrogen peroxide (H2O2) has been studied using a solvent system comprising a hydrophobic alcohol (decan-1-ol) and water. It is demonstrated that, with the optimum combination of solvent and catalyst the contribution of H2O2 degradation pathways can be minimised to achieve industrially acceptable H2O2 concentrations under moderate conditions. This is achieved through the use of a catalyst that is retained by the organic component and the extraction of synthesised H2O2 into the aqueous phase, consequently limiting contact between the synthesised H2O2, catalyst and reactant gases, resulting in an improved selectivity towards H2O2. Investigation of the reaction parameters provides an insight into the proposed solvent system, and optimised conditions to produce H2O2 from molecular H2 and O2 have been identified. Through this optimisation H2O2 concentrations up to 1.9 wt% have been achieved via sequential gas replacement experiments

Gas phase stabiliser-free production of hydrogen peroxide using supported gold-palladium catalysts

Hydrogen peroxide synthesis from hydrogen and oxygen in the gas phase is postulated to be a key reaction step in the gas phase epoxidation of propene using gold–titanium silicate catalysts. During this process H2O2 is consumed in a secondary step to oxidise an organic molecule so is typically not observed as a reaction product. We demonstrate that using AuPd nanoparticles, which are known to have high H2O2 synthesis rates in the liquid phase, it is possible to not only oxidise organic molecules in the gas phase but to detect H2O2 for the first time as a reaction product in both a fixed bed reactor and a pulsed Temporal Analysis of Products (TAP) reactor without stabilisers present in the gas feed. This observation opens up possibility of synthesising H2O2 directly using a gas phase reaction

Convalescent plasma in patients admitted to hospital with COVID-19 (RECOVERY): a randomised controlled, open-label, platform trial

SummaryBackground Azithromycin has been proposed as a treatment for COVID-19 on the basis of its immunomodulatoryactions. We aimed to evaluate the safety and efficacy of azithromycin in patients admitted to hospital with COVID-19.Methods In this randomised, controlled, open-label, adaptive platform trial (Randomised Evaluation of COVID-19Therapy [RECOVERY]), several possible treatments were compared with usual care in patients admitted to hospitalwith COVID-19 in the UK. The trial is underway at 176 hospitals in the UK. Eligible and consenting patients wererandomly allocated to either usual standard of care alone or usual standard of care plus azithromycin 500 mg once perday by mouth or intravenously for 10 days or until discharge (or allocation to one of the other RECOVERY treatmentgroups). Patients were assigned via web-based simple (unstratified) randomisation with allocation concealment andwere twice as likely to be randomly assigned to usual care than to any of the active treatment groups. Participants andlocal study staff were not masked to the allocated treatment, but all others involved in the trial were masked to theoutcome data during the trial. The primary outcome was 28-day all-cause mortality, assessed in the intention-to-treatpopulation. The trial is registered with ISRCTN, 50189673, and ClinicalTrials.gov, NCT04381936.Findings Between April 7 and Nov 27, 2020, of 16 442 patients enrolled in the RECOVERY trial, 9433 (57%) wereeligible and 7763 were included in the assessment of azithromycin. The mean age of these study participants was65·3 years (SD 15·7) and approximately a third were women (2944 [38%] of 7763). 2582 patients were randomlyallocated to receive azithromycin and 5181 patients were randomly allocated to usual care alone. Overall,561 (22%) patients allocated to azithromycin and 1162 (22%) patients allocated to usual care died within 28 days(rate ratio 0·97, 95% CI 0·87–1·07; p=0·50). No significant difference was seen in duration of hospital stay (median10 days [IQR 5 to >28] vs 11 days [5 to >28]) or the proportion of patients discharged from hospital alive within 28 days(rate ratio 1·04, 95% CI 0·98–1·10; p=0·19). Among those not on invasive mechanical ventilation at baseline, nosignificant difference was seen in the proportion meeting the composite endpoint of invasive mechanical ventilationor death (risk ratio 0·95, 95% CI 0·87–1·03; p=0·24).Interpretation In patients admitted to hospital with COVID-19, azithromycin did not improve survival or otherprespecified clinical outcomes. Azithromycin use in patients admitted to hospital with COVID-19 should be restrictedto patients in whom there is a clear antimicrobial indication