Conversion of CO2 to fuels using supported Cu catalysts

Amid global warming concerns and skyrocketing CO2 emissions in the atmosphere, mainly associated with the combustion of fossil fuels to produce energy, the research community has gained a large interest in CO2 capture and reutilization to produce renewable fuels such as methanol (MeOH), dimethylether (DME) and additional hydrocarbons. MeOH is currently produced from syngas (H2 + CO + CO2) over a Cu/ZnO/Al2O3 (CZA) catalyst at mild temperature (200 - 270 °C) and high pressure (50 - 100 bar) and has a global demand exceeding 98 Mt/annum. Syngas is produced from the steam reforming of hydrocarbons, predominantly methane, and consequently the overall process has a great environmental cost (ca. 88 Mt GHG eq). Therefore, a more effective approach such as CO2 hydrogenation to MeOH is required to enable the synthesis of CO2-neutral fuels whilst mitigating anthropogenic emissions. The catalytic conversion of CO2 into methanol and DME bears a strong potential to transform large amounts of CO2 in a short span of time due to the commonly reported high reaction rates. In order for the process to be sustainable in the light of the carbon cycle, H2 should be produced in a greener way, e.g., photocatalytic water splitting and water electrolysis sourced by natural/renewable energy sources. The literature surrounding the synthesis of methanol from CO2 hydrogenation has predominately been based on Cu catalysts and this is due to its remarkable hydrogenation activity and abundance. Although many new active catalyst formulations have been developed, they still carry the problem of incorporating harmful/expensive elements, making them less valuable for commercial use. As such this thesis explores the use of various supported Cu catalysts; Chapter 3 investigates the effect of various supported Cu catalysts prepared via the oxalate gel synthesis method, with a particular focus on Cu/ZrO2, towards the conversion of CO2 to MeOH. The role of various promoters (Pd, Pt, Ce, Ni and Ag) and the stability of these catalysts is also investigated. Chapter 4 explores the impact of varying the calcination temperature and reduction temperature of the Cu/ZrO2 catalysts prepared via oxalate gel, towards their hydrogenation of carbon dioxide to methanol. The deposition of Cu onto the ZrO2 polymorphs by oxalate gel and wet impregnation is also investigated to understand the effects of preparation method and support phase on catalytic activity. Finally, Chapter 5 investigates the synthesis of MeOH, DME and higher chain hydrocarbon between various CuZn or CuZr Zeolite integrated catalysts prepared via chemical vapour impregnation (CVI) and oxalate gel precipitation. Physical mixtures of the catalysts, as well as changes to the catalyst bed, are also explored in order to compare the catalyst activit

Predicting responders to prone positioning in mechanically ventilated patients with COVID-19 using machine learning

Background: For mechanically ventilated critically ill COVID-19 patients, prone positioning has quickly become an important treatment strategy, however, prone positioning is labor intensive and comes with potential adverse effects. Therefore, identifying which critically ill intubated COVID-19 patients will benefit may help allocate labor resources. Methods: From the multi-center Dutch Data Warehouse of COVID-19 ICU patients from 25 hospitals, we selected all 3619 episodes of prone positioning in 1142 invasively mechanically ventilated patients. We excluded episodes longer than 24 h. Berlin ARDS criteria were not formally documented. We used supervised machine learning algorithms Logistic Regression, Random Forest, Naive Bayes, K-Nearest Neighbors, Support Vector Machine and Extreme Gradient Boosting on readily available and clinically relevant features to predict success of prone positioning after 4 h (window of 1 to 7 h) based on various possible outcomes. These outcomes were defined as improvements of at least 10% in PaO2/FiO2 ratio, ventilatory ratio, respiratory system compliance, or mechanical power. Separate models were created for each of these outcomes. Re-supination within 4 h after pronation was labeled as failure. We also developed models using a 20 mmHg improvement cut-off for PaO2/FiO2 ratio and using a combined outcome parameter. For all models, we evaluated feature importance expressed as contribution to predictive performance based on their relative ranking. Results: The median duration of prone episodes was 17 h (11-20, median and IQR, N = 2632). Despite extensive modeling using a plethora of machine learning techniques and a large number of potentially clinically relevant features, discrimination between responders and non-responders remained poor with an area under the receiver operator characteristic curve of 0.62 for PaO2/FiO2 ratio using Logistic Regression, Random Forest and XGBoost. Feature importance was inconsistent between models for different outcomes. Notably, not even being a previous responder to prone positioning, or PEEP-levels before prone positioning, provided any meaningful contribution to predicting a successful next proning episode. Conclusions: In mechanically ventilated COVID-19 patients, predicting the success of prone positioning using clinically relevant and readily available parameters from electronic health records is currently not feasible. Given the current evidence base, a liberal approach to proning in all patients with severe COVID-19 ARDS is therefore justified and in particular regardless of previous results of proning. Keywords: Acute respiratory distress syndrome; COVID-19; Mechanical ventilation

Combination of Cu/ZnO methanol synthesis catalysts and ZSM-5 zeolites to produce oxygenates from CO2 and H2

Cu/ZnO methanol catalysts were deposited over several ZSM-5 acid zeolites to directly synthesise oxygenates (methanol and dimethyl ether) from a CO2/H2 feed. Catalysts were prepared by two different preparation methodologies: chemical vapour impregnation (CZZ-CVI) and oxalate gel precipitation (CZZ-OG). Chemical vapour impregnation led to Cu/ZnO being deposited on the zeolite surface, whilst oxalate gel precipitation led to the formation of Cu/ZnO agglomerates. For both sets of catalysts a higher concentration of mild and strong acid sites were produced, compared to the parent ZSM-5 zeolites, and CZZ-CVI had a higher concentration of acid sites compared to CZZ-OG. Nevertheless, CZZ-OG shows considerably higher oxygenate productivity, 1322 mmol Kgcat−1 h−1, compared to 192 mmol Kgcat−1 h−1 over CZZ-CVI (ZSM-5(50), 250 ℃, 20 bar, CO2/H2 = 1/3, 30 ml min−1), which could be assigned to a combination of smaller particle size and enhanced methanol mass transfer within the zeolites

Triethylamine-water as a switchable solvent for the synthesis of Cu/ZnO catalysts for carbon dioxide hydrogenation to methanol

Cu/ZnO catalyst precursors for industrial methanol synthesis catalysts are traditionally synthesised by coprecipitation. In this study, a new precipitation route has been investigated based on anti-solvent precipitation using a switchable solvent system of triethylamine and water. This system forms a biphasic system under a nitrogen atmosphere and can be switched to an ionic liquid single phase under a carbon dioxide atmosphere. When metal nitrate solutions were precipitated from water using triethylamine–water as the anti-solvent a hydroxynitrate phase, gerhardite, was formed, rather than the hydroxycarbonate, malachite, formed by coprecipitation. When calcined and reduced, the gerhardite precursors formed Cu/ZnO catalysts which showed better productivity for methanol synthesis from CO2 hydrogenation than a traditional malachite precursor, despite their larger CuO crystallite size determined by X-ray diffraction. The solvents could be recovered by switching to the biphasic system after precipitation, to allow solvent recycling in the process, reducing waste associated with the catalyst synthesis

Production of He-4 and (4) in Pb-Pb collisions at root(NN)-N-S=2.76 TeV at the LHC

Results on the production of He-4 and (4) nuclei in Pb-Pb collisions at root(NN)-N-S = 2.76 TeV in the rapidity range vertical bar y vertical bar <1, using the ALICE detector, are presented in this paper. The rapidity densities corresponding to 0-10% central events are found to be dN/dy4(He) = (0.8 +/- 0.4 (stat) +/- 0.3 (syst)) x 10(-6) and dN/dy4 = (1.1 +/- 0.4 (stat) +/- 0.2 (syst)) x 10(-6), respectively. This is in agreement with the statistical thermal model expectation assuming the same chemical freeze-out temperature (T-chem = 156 MeV) as for light hadrons. The measured ratio of (4)/He-4 is 1.4 +/- 0.8 (stat) +/- 0.5 (syst). (C) 2018 Published by Elsevier B.V.Peer reviewe

Flavonoid Production: Current Trends in Plant Metabolic Engineering and De Novo Microbial Production

Flavonoids are secondary metabolites that represent a heterogeneous family of plant polyphenolic compounds. Recent research has determined that the health benefits of fruits and vegetables, as well as the therapeutic potential of medicinal plants, are based on the presence of various bioactive natural products, including a high proportion of flavonoids. With current trends in plant metabolite research, flavonoids have become the center of attention due to their significant bioactivity associated with anti-cancer, antioxidant, anti-inflammatory, and anti-microbial activities. However, the use of traditional approaches, widely associated with the production of flavonoids, including plant extraction and chemical synthesis, has not been able to establish a scalable route for large-scale production on an industrial level. The renovation of biosynthetic pathways in plants and industrially significant microbes using advanced genetic engineering tools offers substantial promise for the exploration and scalable production of flavonoids. Recently, the co-culture engineering approach has emerged to prevail over the constraints and limitations of the conventional monoculture approach by harnessing the power of two or more strains of engineered microbes to reconstruct the target biosynthetic pathway. In this review, current perspectives on the biosynthesis and metabolic engineering of flavonoids in plants have been summarized. Special emphasis is placed on the most recent developments in the microbial production of major classes of flavonoids. Finally, we describe the recent achievements in genetic engineering for the combinatorial biosynthesis of flavonoids by reconstructing synthesis pathways in microorganisms via a co-culture strategy to obtain high amounts of specific bioactive compound

Phenolic contents-based assessment of therapeutic potential of Syzygium cumini leaves extract

Syzygium cumini (S. cumini) is an evergreen tropical plant that is well recognized for its therapeutic potential of common diseases. In this study, the therapeutic potential and biomedical application of S. cumini are assessed in vitro and in vivo to find its effectiveness for different complications. The methanolic crude extract of S. cumini leaves were screened for total phenolic and flavonoid content. In vitro, the DPPH scavenging assay, XTT assay, prothrombin and activated partial thromboplastin time were used to assess antioxidant, cytoprotective and thrombolytic activity of the S. cumini extract, respectively. The anti-inflammatory potential and the analgesic activity of the S. cumini extract were analyzed in rabbits by the Carrageenan induced paw edema method and the writhing method, respectively. Phytochemical analysis showed the presence of considerable amounts of total phenolic (369.75 � 17.9 mg GAE/g) and flavonoid (75.8 � 5.3 mgRE/g) content in the S. cumini extract. The DPPH assay demonstrated a higher antioxidant potential (IC-50 value of 133 ?g/ml), which was comparable to the IC-50 of ascorbic acid (122.4 ?g/ml). Moreover, the S. cumini extract showed a dose dependent cytoprotective effect against H2O2 treated bone marrow mesenchymal stem cells (BM-MSCs). S. cumini also possesses significant anticoagulant activity with a prothrombin time of 28.3 � 1.8 seconds vs 15.8 � 0.2 seconds of control, p&lt;0.05. The leaf extract also demonstrated an analgesic effect in rabbits as indicated by the decrease in writhing (12.2 � 1.7 control vs. 3.7 � 0.6 treated) and anti-inflammatory activity in rabbits paw with a protection against inflammation of 64.1 � 2.4%. Our findings suggest that the methanolic extract of S. cumini leaves has antioxidant, cytoprotective, anticoagulant, analgesic and anti-inflammatory properties, and therefore, can be applied for treating cardiovascular diseases and cancers. - 2019 Ahmed et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Scopu

Purification and characterization of novel isoforms of the polyphenol oxidase from Malus domestica fruit pulp.

Polyphenol oxidases (PPOs), belong to the group of oxidoreductases that are copper containing enzymes and are responsible for plant browning. PPOs are extensively distributed in plant kingdom and can oxidize wide range of aromatic compounds of industrial importance. The aim of this study was purification and characterization of PPO isoforms from the fruit pulp of Golden delicious apple. High performance liquid chromatography was used to purify the two novel isoforms of PPO and further their molecular weights (45 and 28 kDa) were determined using sodium dodecyl sulfate polyacrylamide gel electrophoresis. The purified isoforms have optimum pH (6.5), optimum temperature (40°C), the Vmax (4.45 μM/min) and Km (74.21 mM) with catechol substrate. The N-terminal microsequences of both PPO isoforms were determined using a pulse liquid protein sequencer and found to be AKITFHG (28 kDa) and APGGG (45 kDa). Polyphenol oxidases are efficiently used in the pharmaceutical, paper and pulp, textiles and food industries. Recently, the PPOs have been used for bioremediation and in the development of biosensors