Merging hydrogen (H
) evolution with oxidative organic synthesis in a semiconductor-mediated photoredox reaction is extremely attractive because the clean H
fuel and high-value chemicals can be ...coproduced under mild conditions using light as the sole energy input. Following this dual-functional photocatalytic strategy, a dreamlike reaction pathway for constructing C-C/C-X (X = C, N, O, S) bonds from abundant and readily available X-H bond-containing compounds with concomitant release of H
can be readily fulfilled without the need of external chemical reagents, thus offering a green and fascinating organic synthetic strategy. In this review, we begin by presenting a concise overview on the general background of traditional photocatalytic H
production and then focus on the fundamental principles of cooperative photoredox coupling of selective organic synthesis and H
production by simultaneous utilization of photoexcited electrons and holes over semiconductor-based catalysts to meet the economic and sustainability goal. Thereafter, we put dedicated emphasis on recent key progress of cooperative photoredox coupling of H
production and various selective organic transformations, including selective alcohol oxidation, selective methane conversion, amines oxidative coupling, oxidative cross-coupling, cyclic alkanes dehydrogenation, reforming of lignocellulosic biomass, and so on. Finally, the remaining challenges and future perspectives in this flourishing area have been critically discussed. It is anticipated that this review will provide enlightening guidance on the rational design of such dual-functional photoredox reaction system, thereby stimulating the development of economical and environmentally benign solar fuel generation and organic synthesis of value-added fine chemicals.
Abstract
The performance of transition metal hydroxides, as cocatalysts for CO
2
photoreduction, is significantly limited by their inherent weaknesses of poor conductivity and stacked structure. ...Herein, we report the rational assembly of a series of transition metal hydroxides on graphene to act as a cocatalyst ensemble for efficient CO
2
photoreduction. In particular, with the Ru-dye as visible light photosensitizer, hierarchical Ni(OH)
2
nanosheet arrays-graphene (Ni(OH)
2
-GR) composites exhibit superior photoactivity and selectivity, which remarkably surpass other counterparts and most of analogous hybrid photocatalyst system. The origin of such superior performance of Ni(OH)
2
-GR is attributed to its appropriate synergy on the enhanced adsorption of CO
2
, increased active sites for CO
2
reduction and improved charge carriers separation/transfer. This work is anticipated to spur rationally designing efficient earth-abundant transition metal hydroxides-based cocatalysts on graphene and other two-dimension platforms for artificial reduction of CO
2
to solar chemicals and fuels.
Electron paramagnetic resonance (EPR) spectroscopy and spin trapping were used to explore the mechanism of alcohol oxidation over gold catalysts. Reaction of secondary alcohols with supported and ...unsupported gold catalysts (e.g., Au/CeO2, polymer-incarcerated Au nanoparticles, PPh3-protected Au nanoparticles) in the presence of spin traps led to the formation of a hydrogen spin adduct. Using isotope labeling, we confirmed that the hydrogen in the spin adduct originates from the cleavage of the C−H bond in the alcohol molecule. The formation of the hydrogen spin adduct most likely results from the abstraction of hydrogen from the Au surface by a spin trap. These results thus strongly suggest intermediate formation of Au−H species during alcohol oxidation. The role of oxygen in this mechanism is to restore the catalytic activity rather than oxidize alcohol. This was further confirmed by carrying out gold-catalyzed alcohol oxidation in the absence of oxygen, with nitroxides as hydrogen abstractors. The support (e.g., metal oxides) can activate oxygen and act as an H abstractor from the gold surface and hence lead to a faster recovery of the activity. Peroxyl radicals were also observed during alcohol oxidation, consistent with a free-radical autoxidation mechanism. However, this mechanism is likely to be a minor side reaction, which does not lead to the formation of an appreciable amount of oxidation products.
The activation and use of oxygen for the oxidation and functionalization of organic substrates are among the most important reactions in a chemist's toolbox. Nevertheless, despite the vast literature ...on catalytic oxidation, the phenomenon of autoxidation, an ever-present background reaction that occurs in virtually every oxidation process, is often neglected. In contrast, autoxidation can affect the selectivity to a desired product, to those dictated by pure free-radical chain pathways, thus affecting the activity of any catalyst used to carry out a reaction. This critical review compares catalytic oxidation routes by transition metals
versus
autoxidation, particularly focusing on the industrial context, where highly selective and "green" processes are needed. Furthermore, the application of useful tests to discriminate between different oxygen activation routes, especially in the area of hydrocarbon oxidation, with the aim of an enhanced catalyst design, is described and discussed. In fact, one of the major targets of selective oxidation is the use of molecular oxygen as the ultimate oxidant, combined with the development of catalysts capable of performing the catalytic cycle in a real energy and cost effective manner on a large scale. To achieve this goal, insights from metallo-proteins that could find application in some areas of industrial catalysis are presented, as well as considering the physicochemical principles that are fundamental to oxidation and autoxidation processes.
The activation of oxygen for the functionalization of organic substrates may occur by means of transition metals or
via
autoxidation pathways affecting product selectivity and catalyst design.
Au/C catalysts prepared using aqua regia as a solvent display superior activity in the hydrochlorination reaction of acetylene to vinyl chloride monomer. A synergistic effect between HCl and HNO3 is ...observed, which is linked to the nucleation of Au nanoparticles. Display omitted
► Impregnated Au/C catalyst with aqua regia as a solvent displayed superior activity in the hydrochlorination reaction of acetylene to vinyl chloride monomer. ► A synergistic effect between HCl and HNO3 is present, driving the Au nanoparticles nucleation process over the carbon support. ► The impregnating acid mixture can affect the carbon support enriching the presence of oxygen functional groups. ► The reaction occurs over Au3+ centres at the Au/C interface.
Au/C catalysts are effective materials for the gas phase hydrochlorination of acetylene to vinyl chloride monomer, and to date, the most effective catalyst preparation protocol makes use of impregnation using aqua regia. In the present study, the effect of this solvent is evaluated and discussed in detail by modifying the ratio of HCl and HNO3 and the temperature of the impregnation step. These factors are observed to affect the Au3+/Au0 ratio of the final catalyst, in addition to the modification of the functional groups of the carbon used as support. The results can be rationalised by the oxidation effect of HNO3 on both the gold nanoparticles and the functional groups on the carbon surface, as well as a nucleation effect of HCl towards gold over the carbon support.
Au–Pt alloy nanoparticles deposited on Mg(OH)2 (see STEM‐HAADF image) show high activity in the selective oxidation of polyols using molecular oxygen as oxidant at mild and base‐free conditions.
SARS-Cov2 infection may trigger lung inflammation and acute-respiratory-distress-syndrome (ARDS) that requires active ventilation and may have fatal outcome. Considering the severity of the disease ...and the lack of active treatments, 14 patients with Covid-19 and severe lung inflammation received inhaled adenosine in the attempt to therapeutically compensate for the oxygen-related loss of the endogenous adenosine→A2A adenosine receptor (A2AR)-mediated mitigation of the lung-destructing inflammatory damage. This off label-treatment was based on preclinical studies in mice with LPS-induced ARDS, where inhaled adenosine/A2AR agonists protected oxygenated lungs from the deadly inflammatory damage. The treatment was allowed, considering that adenosine has several clinical applications.
Fourteen consecutively enrolled patients with Covid19-related interstitial pneumonitis and PaO2/FiO2 ratio<300 received off-label-treatment with 9 mg inhaled adenosine every 12 hours in the first 24 hours and subsequently, every 24 days for the next 4 days. Fifty-two patients with analogue features and hospitalized between February and April 2020, who did not receive adenosine, were considered as a historical control group. Patients monitoring also included hemodynamic/hematochemical studies, CTscans, and SARS-CoV2-tests.
The treatment was well tolerated with no hemodynamic change and one case of moderate bronchospasm. A significant increase (> 30%) in the PaO2/FiO2-ratio was reported in 13 out of 14 patients treated with adenosine compared with that observed in 7 out of52 patients in the control within 15 days. Additionally, we recorded a mean PaO2/FiO2-ratio increase (215 ± 45 vs. 464 ± 136, P = 0.0002) in patients receiving adenosine and no change in the control group (210±75 vs. 250±85 at 120 hours, P>0.05). A radiological response was demonstrated in 7 patients who received adenosine, while SARS-CoV-2 RNA load rapidly decreased in 13 cases within 7 days while no changes were recorded in the control group within 15 days. There was one Covid-19 related death in the experimental group and 11in the control group.
Our short-term analysis suggests the overall safety and beneficial therapeutic effect of inhaled adenosine in patients with Covid-19-inflammatory lung disease suggesting further investigation in controlled clinical trials.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
•New set of equations for energy balance using slug tracking approach•New term in momentum balance corrects previous -20% of dP/dz•Suppresses non-physical oscillations in dT/dz found with previous ...model•Captures intermittent nature of slug flow•Heating cases are related to higher coalescence rates
This study proposes a new set of equations for the energy balance for predicting the temperature distribution of gas-liquid slug flows using a slug tracking approach. The model proves able to work around non-physical oscillations of the temperature distribution found with a previously published set of equations for the energy balance. The main difference here is that rather than being applied to each structure (namely the liquid slug, the liquid film and the elongated bubble) individually, the temperature is assigned to the whole unit cell. Central Differencing Schemes were avoided since the problem is convection-dominant, thus preference to Upwind Differencing Schemes was given. Comparison of the new model with an experimental dataset for air-water flow in a 52-mm ID pipeline showed deviations of ±25% for the temperature and pressure gradients. An extra head loss term caused by the recirculation of liquid in the elongated bubble wake was introduced into the momentum balance, correcting an existing –20% systematic deviation found in the pressure gradient as computed by the former model. Simulations for an extended, 200-m long pipeline comparing isothermal, cooling and heating flows are also presented. These simulations demonstrate the competition of gas expansion caused by pressure drop and of gas expansion/contraction caused by mixture heating/cooling, and their consequences on the elongated bubble length increase/decrease, on the mixture acceleration/deceleration, on the coalescence rate of elongated bubbles, and on their statistic distributions.
This study analyzed the differences between firefighters and other working categories (urban policemen, employees in the service industry) in psychological well-being, anxiety, depression, ...personality and stress. Much research has evidenced that people who have to deal with emergencies are more subjected to psychological diseases. Our results showed that firefighters have lower levels of anxiety, depression, emotional instability and negative emotions in relation to urban policemen and employees. In addition, there are no significant differences in psychological well-being. Further research is necessary to define the specific psychological attitudes or traits which allow firefighters to deal with psychological disease and stress.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Lack of specific antiviral treatment for COVID-19 has resulted in long hospitalizations and high mortality rate. By harnessing the regulatory effects of adenosine on inflammatory mediators, we have ...instituted a new therapeutic treatment with inhaled adenosine in COVID-19 patients, with the aim of reducing inflammation, the onset of cytokine storm, and therefore to improve prognosis. The use of inhaled adenosine in COVID19 patients has allowed reduction of length of stay, on average 6 days. This result is strengthened by the decrease in SARS-CoV-2 positive days. In treated patients compared to control, a clear improvement in PaO
/FiO
was observed together with a reduction in inflammation parameters, such as the decrease of CRP level. Furthermore, the efficacy of inhaled exogenous adenosine led to an improvement of the prognosis indices, NLR and PLR. The treatment seems to be safe and modulates the immune system, allowing an effective response against the viral infection progression, reducing length of stay and inflammation parameters.
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