•Acid treatment of CNF reduces porosity, specific surface area and impurity content.•Acid modification of CNF increases a concentration of surface functional groups.•This has an influence on ...adsorptive properties and palladium dispersion in catalysts.•HCl treatment leads to higher Pd dispersion and faster 1,2-DCB adsorption on surface.•This makes Pd/CNF-HCl the most active catalyst of 1,2-DCB hydrodechlorination.
Palladium catalysts on the basis of acid treated carbon nanofibers (CNF) were studied. Using physico-chemical methods of investigation (low-temperature nitrogen adsorption–desorption, FTIR spectroscopy and Boehm titration) it has been shown that under the action of HCl and HNO3 there take place a reduction in the specific surface area and the volume of pores and an increase of the concentration of surface functional groups. This has a substantial influence on the adsorptive properties of CNF, the dispersion of palladium and the catalytic activity in the liquid-phase hydrodechlorination of 1,2-dichlorobenzene. The reaction rate was observed to be the highest in the presence of Pd/CNF-HCl. Treatment of CNF by HCl gives the highest dispersion of palladium on the external surface of CNF. There is also an increase in the adsorption capacity for 1,2-dichlorobenzene and a decreased adsorption of the solvents on the surface of the acid-modified CNF.
Removal of 1,2-DCB from water emulsion using adsorbent catalysts was studied.Purification cycle comprises adsorption and regeneration by hydrodechlorination.The adsorption involves condensation and ...coalescence of 1,2-DCB drops on carbon.1,2-DCB adsorption was found to proceed by mechanism of volume filling of pores.Regeneration rate was shown to correlate with particle size of the active component.
Purification of emulsions of 1,2-dichlorobenzene (1,2-DCB) by carbon-based adsorbent catalysts has been studied. The cycle of purification includes: (1) adsorption of 1,2-DCB from the aqueous phase and (II) reductive regeneration by hydrodechlorination of the adsorbed 1,2-DCB by molecular hydrogen in the liquid phase. 1,2-DCB adsorption from aqueous solutions has been found to proceed by the mechanism of volume filling of pores. The rate of hydrodechlorination was shown to correlate with the particle size of the active component: the finer the particles, the higher the activity of the adsorbent catalyst. Pd/FAS with an average Pd particle size of 2.8nm was found to be the most efficient catalyst.
The activity of palladium catalysts on the basis of carbon materials in the liquid-phase hydrodechlorination of chlorobenzene has been studied. It was shown that the high activity of Pd/AG-2000 can ...be explained by the presence of oxygen-containing impurities in the initial activated carbon used as the support. These oxygen-containing impurities act as centers to anchor palladium and interact with HCl decreasing its deactivating action.
The activity of palladium catalysts prepared using active carbons (AG-2000, MeKS) and Sibunit type carbon in the liquid-phase hydrodechlorination of chlorobenzene has been studied. The use of AG-2000 activated carbon prepared from coal raw material provided the highest initial activity of the catalyst (
9.4
mo
l
C
6
H
5
Cl
/mo
l
Pd
min
for the catalyst with particle size of 0.08–0.1
mm) which not reduced within next 4 cycles. However, this activity cannot be explained only on the basis of support texture characteristics. From results of chemical analysis as well as X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HR TEM) data the high activity of the Pd/AG-2000 catalyst is explainable by the presence on the surface of the initial activated carbon of oxygen-containing compounds of iron, aluminum, silicon, calcium and magnesium. The overall ash content of the activated carbon was 11.9
wt.%. It can be assumed that the oxide compounds of iron act as anchoring centers for palladium, and that oxide containing impurities may interact with HCl decreasing deactivation. The experimental data of this work has shown that the main contribution to the Pd/AG-2000 catalyst activity is made by the palladium particles with a size of 3
nm and higher which remain stable under the aggressive conditions of the chlorobenzene hydrodechlorination process.
Tablets on the basis of sodium borohydride and cobalt compounds (CoCl2·6H2O, Co(CH3COO)2·4H2O, Co3O4 and anhydrous CoSO4) have been studied as hydrogen generation materials. The kinetics of sodium ...borohydride hydrolysis upon contact of the tablets with water has been investigated. Adsorption and reaction constants have been determined for each of the catalysts using the Langmuir-Hinshelwood model which allowed us to estimate the contribution of BH4‾ adsorption to the overall rate of hydrogen generation. It was noted that the nature of the catalyst precursor has an influence not only on the specific surface area of the in situ forming catalytically active phase, the particle size of the catalyst, the degree of reduction of cobalt compounds by sodium borohydride but also on the adsorption of BH4‾ anions from the reaction medium on the catalyst surface.
•The tablets based on NaBH4 have been employed as hydrogen generation materials.•The kinetics of NaBH4 hydrolysis over different Co compounds has been studied.•According to the Langmuir-Hinshelwood mechanism the kinetic data were analyzed.•The observed reaction and adsorption constants for catalysts have been determined.•The BH4‾ anion adsorption on catalyst is a key factor in NaBH4 hydrolysis.
Hydrogen generation from tablets of sodium borohydride with chlorides of nickel and cobalt was studied. The nickel catalysts were shown to be less active in the borohydride hydrolysis than the cobalt ...catalysts. One of the reasons for the lower activity of the nickel catalyst was the presence of hydrogen on its surface, which hampered the adsorption of reactants. The addition of cobalt to the nickel catalyst increases the hydrogen generation rate. This is due to the introduction of active metal with low adsorption capacity for hydrogen and the higher dispersion of the active component.
•Tablets based on NaBH4 have been employed as hydrogen generation materials.•Kinetics of NaBH4 hydrolysis over Co and Ni catalyst has been studied.•Presence of hydrogen on surface is the reason of lower activity nickel catalyst.•Addition of cobalt to nickel catalyst increases the hydrogen generation rate.•Reasons are low adsorption capacity of H2 and high dispersion of active component.
The literature shows that practically no attention has been paid to the size and shape of the particles of bulk ammonia borane (NH3BH3). The published results about the influence of the dispersity of ...this hydride on its dehydrogenation are not numerous and contradictory. This work presents new results on the low-temperature solid-state dehydrogenation of bulk NH3BH3. The samples under study were recrystallized using different procedures and had, therefore, different particle characteristics. The reactivity of these samples of NH3BH3 was compared on the basis of thermal analysis data obtained under non-isothermal conditions, including the Kissinger kinetics, and H2 evolution under isothermal conditions (84–96°С) using Avrami-Erofeev kinetics. The finely dispersed sample with a particle size of <40 μm was found to be the most active one. A correlation between the NH3BH3 melting temperature and the temperature of its dehydrogenation has been established. A filamentous NH3BH3 with a length-to-thickness ratio of the filaments of >100 was synthesized and described for the first time. It was suggested that its relatively high reactivity was determined by its ordered structure. These results show the importance of further investigations of bulk ammonia borane with different types of particles.
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•Effect of dispersity of bulk NH3BH3 (AB) on its dehydrogenation is still contradictory.•AB of different characteristics were prepared by different recrystallization methods.•Мelting temperature of AB correlates with the temperature of its dehydrogenation.•Finely dispersed AB with a particle size of <40 μm is the most active one.•Relatively high activity of non-dispersed but ordered filamentous AB is discussed.
To estimate the incidence of new prescription of enteral opioids on hospital discharge in opioid naïve, non-surgical, critically ill patients and evaluate the risk factors associated with such ...occurrence.
Using hospital-wide and ICU databases, we retrospectively identified all patients (≥ 18 years old) who were admitted to the 20-bed adult ICU of Memorial Sloan Kettering Cancer Center (MSKCC) between July 1, 2015 and April 20, 2020. Patients' electronic medical records (EMR) were retrieved and patient demographics, peri-ICU admission data were captured and analyzed.
During the study period, a total of 3755 opioid naïve patients were admitted to the ICU and 848 patients met the inclusion criteria. Among these, 346 (40.8%) patients were discharged with a new opioid prescription. Age at ICU admission, preadmission use of benzodiazepine, and antidepressants, a diagnosis of sepsis, and use of mechanical ventilation, antidepressants or, opioid infusion for greater than 4 h during the ICU stay, hospital length of stay (LOS), and days between ICU discharge and hospital discharge were independently associated with increased odds of a new opioid prescription.
A significant proportion of opioid naïve non-surgical ICU survivors receive a new opioid prescription on hospital discharge.
•A significant proportion of opioid naïve non-surgical ICU survivors receive a new opioid prescription on hospital discharge.•An estimate of the incidence of new prescription of enteral opioids in non-surgical, opioid naïve, ICU patients•Patient and ICU specific risk factors associated with such occurrence•Limiting the duration of opioids and reducing the use of antidepressants during the ICU stay may reduce this incidence.
