Search results for " carbon dioxide"
showing 10 items of 200 documents
Utilization of dense carbon dioxide as an inert solvent for chemical syntheses
2010
Supercritical CO2 extraction of essential oil from orange peel. Effect of operation conditions on the extract composition
1999
Abstract The supercritical fluid extraction (SFE) of orange essential oil was studied using dehydrated orange peel (0.0538 kg H2O/kg dm) from naveline cultivars as raw material and CO2 as solvent. The effect of operation conditions was analyzed in a series of experiments at temperatures between 293 and 323 K and pressures between 8 and 28 MPa. The collected extracts were analyzed and the relative composition of the essential oil was determined. Limonene was the principal component extracted, the optimum conditions for limonene extraction were 12.5 MPa and 308 K, in these conditions limonene represents more than 99.5% of the essential oil. Within the operating range conditions, the optimum f…
Solubilities of Essential Oil Components of Orange in Supercritical Carbon Dioxide
2000
The solubilities of pure limonene and linalool in compressed carbon dioxide have been measured using a flow apparatus at 318.2 K and 328.2 K and pressures ranging from 69 bar to 111 bar. The solubilities were successfully modeled using equations of state (Peng−Robinson, Soave−Redlich−Kwong, 3P1T, Dohrn and Prausnitz nopolar) and a semiempirical equation (Chrastill model). The generalized parameters for the Peng−Robinson EOS were obtained for each system. These parameters were independent of temperature, and they reproduce successfully all data available in the literature. The results show that the solubility of limonene in supercritical carbon dioxide was bigger than the solubility of linal…
Extracellular oxidoreduction potential modifies carbon and electron flow in Escherichia coli.
2000
ABSTRACT Wild-type Escherichia coli K-12 ferments glucose to a mixture of ethanol and acetic, lactic, formic, and succinic acids. In anoxic chemostat culture at four dilution rates and two different oxidoreduction potentials (ORP), this strain generated a spectrum of products which depended on ORP. Whatever the dilution rate tested, in low reducing conditions (−100 mV), the production of formate, acetate, ethanol, and lactate was in molar proportions of approximately 2.5:1:1:0.3, and in high reducing conditions (−320 mV), the production was in molar proportions of 2:0.6:1:2. The modification of metabolic fluxes was due to an ORP effect on the synthesis or stability of some fermentation enzy…
High flow nasal therapy versus noninvasive ventilation as initial ventilatory strategy in COPD exacerbation: a multicenter non-inferiority randomized…
2020
Abstract Background The efficacy and safety of high flow nasal therapy (HFNT) in patients with acute hypercapnic exacerbation of chronic obstructive pulmonary disease (AECOPD) are unclear. Our aim was to evaluate the short-term effect of HFNT versus NIV in patients with mild-to-moderate AECOPD, with the hypothesis that HFNT is non-inferior to NIV on CO2 clearance after 2 h of treatment. Methods We performed a multicenter, non-inferiority randomized trial comparing HFNT and noninvasive ventilation (NIV) in nine centers in Italy. Patients were eligible if presented with mild-to-moderate AECOPD (arterial pH 7.25–7.35, PaCO2 ≥ 55 mmHg before ventilator support). Primary endpoint was the mean di…
Regional anticoagulation with heparin of an extracorporeal CO2 removal circuit: a case report
2019
Abstract Background Extracorporeal carbon dioxide removal is an increasingly used respiratory support technique. As is true of all extracorporeal techniques, extracorporeal carbon dioxide removal needs proper anticoagulation. We report a case of a patient at risk of bleeding complications who was treated with extracorporeal carbon dioxide removal and anticoagulated with a regional technique. Case presentation A 56-year-old Caucasian man with a history of chronic obstructive pulmonary disease exacerbation required extracorporeal carbon dioxide removal for severe hypercapnia and acidosis despite mechanical ventilation. The extracorporeal circuit was anticoagulated using a regional heparin tec…
Cerebral haemodynamic changes during propofol-remifentanil or sevoflurane anaesthesia: transcranial Doppler study under bispectral index monitoring
2006
Background. Sevoflurane or propofol–remifentanil-based anaesthetic regimens represent modern techniques for neurosurgical anaesthesia. Nevertheless, there are potential differences related to their activity on the cerebrovascular system. The magnitude of such difference is not completely known. Methods. In total 40 patients, treated for spinal or maxillo-facial disorders, were randomly allocated to either i.v. propofol–remifentanil or inhalational sevoflurane anaesthesia. Transcranial Doppler was used to assess changes in cerebral blood flow velocity, carbon dioxide reactivity, cerebral autoregulation and the bispectral index to assess the depth of anaesthesia. Results. Time-averaged mean f…
Leaded Bronze Alloy as a Catalyst for the Electroreduction of CO 2
2019
Electrochemical conversion of CO2 to HCOOH at tin cathode in a pressurized undivided filter-press cell
2018
Abstract The electrochemical reduction of carbon dioxide to formic acid was performed for the first time in a pressurized filter-press cell with a continuous recirculation of the electrolytic solution (0.9 L) at a tin cathode. It was shown that the performances of the system are comparable or slightly better than that of a batch system with a smaller volume (0.05 L). The selection of proper values of both current density and CO2 pressure allowed to achieve quite high values of faradaic efficiencies. Long-time electrolyses have shown that the system is stable and that it can allow to generate quite high concentrations of HCOOH (about 0.4 M).
Development of an Electrochemical Process for the Simultaneous Treatment of Wastewater and the Conversion of Carbon Dioxide to Higher Value Products
2016
Many researchers have shown that selected anodic processes allow effective treatment of a very large amount of wastewater contaminated by pollutants resistant to biological processes. In the meantime, various authors have also shown that carbon dioxide can be converted into higher value products, such as formic acid or synthesis gas, by cathodic reduction at suitable cathodes. These two processes present interesting economic potential that, however, still needs to be improved for further development at an industrial level. Herein, these two kinds of process are combined in the same cell to improve their economic feasibility. In particular, the anodic treatment of wastewater at a boron-doped…