Acid-modified clinoptilolite as a support for palladium–copper complexes catalyzing carbon monoxide oxidation with air oxygen

Samples of natural clinoptilolite were modified by an acid–thermal method at nitric acid concentrations of 0.25, 0.5, 1.0, and 3.0 M and a contact time of 30 min. A series of catalysts, K2PdCl4–Cu(NO3)2–KBr/S (S = 0.25H-CLI, 0.5H-CLI, 1H-CLI, and 3H-CLI) was obtained. All samples were investigated by X-ray phase and thermogravimetric analysis, FT-IR spectroscopy, water vapor ad/desorption and pH metric method. Besides, K2PdCl4–Cu(NO3)2–KBr/S samples were tested in the reaction of low-temperature carbon monoxide oxidation. It have been found that, owing to special physicochemical and structural-adsorption properties of 3H-CLI, it promotes formation of the palladium–copper catalyst providing carbon monoxide oxidation at the steady-state mode down to CO concentrations lower than its maximum permissible concentration at air relative humidity varied within a wide range

Efficacy and Safety of Ascites Treatment in Liver Cirrhosis

Cirrhosis is one of the major health problems worldwide; and ascites is often its first and foremost manifestation. Despite the advances in modern hepatology, the presence of ascites is associated with a poor prognosis and high mortality. The aim of the study was to analyse data on the efficacy and safety of ascites treatment options, taking into account the pathophysiology of the condition. The analysis of literature and international guidelines on ascites management showed that cirrhotic ascites is treated with medication or surgery that interfere with pathogenetic mechanisms underlying the condition. Treatment of uncomplicated ascites depends on the severity of clinical manifestations. Patients with grade 1 ascites do not require treatment. Therapy for grade 2–3 ascites is aimed at reducing sodium intake and promoting its excretion with diuretics. The effect of diuretics should be assessed by daily monitoring of body weight. Close monitoring of serum creatinine and electrolyte levels is necessary to avoid severe electrolyte imbalance and mitigate the risk of diuretic-associated acute kidney injury. Another medical option to increase diuresis is the use of vasoconstrictors. Large volume paracentesis is the treatment of choice for patients with grade 3 ascites and refractory ascites. The most dangerous complication of paracentesis is circulatory dysfunction, which is prevented by limiting the volume of fluid removed to 5–6 liters per procedure and using plasma substitutes. If paracentesis is ineffective, new minimally invasive methods of treatment should be considered: transjugular intrahepatic portosystemic shunting and automated low-flow ascitic fluid removal system. However, given the poor prognosis, all patients with refractory ascites should be considered candidates for liver transplantation, which is currently the only effective treatment. The efficacy and safety of therapy may be enhanced by a personalised approach to choosing the treatment for ascites in cirrhosis, as well as further investigation of means to mitigate adverse reactions to medication and minimally invasive surgery

Aortic regurgitation: epidemiologic, etiologic, and pathophysiologic characteristics

The presented review concerns aortic regurgitation which occupies a significant place in the structure of valvular heart disease. The detailed anatomic and physiologic description of the aortic valve is provided. The characteristics of sinotubular, ventricular-aortic junctions, and virtual aortic annulus are presented. There are data about prevalence of aortic regurgitation on the basis of results of population studies, indicating the increase in incidence of aortic regurgitation among individuals older 70–74 years. The detailed etiologic structure of this valvular pathology is described with specifying of the most common causes of both aortic disease and aortic cusps alterations. In particular, there are some aortic diseases, resulting in acute aortic regurgitation, including acute aortic dissection and paravalvular regurgitation in incompetence of the prosthetic aortic valve; in chronic one – idiopathic dilation of the aortic root, inherited connective tissue dysplasias (Ehlers–Danlos, Marfan, and Loeys–Dietz syndromes), bicuspid aortic valve, aortitis of various origin, seronegative arthropathies (reactive, psoriatic arthritis, ankylosing spondylitis) etc. Infective endocarditis and traumatic exposure are commonly responsible for development of acute regurgitation due to aortic cusps abnormalities. Chronic aortic regurgitation as a consequence valve defects occurs in rheumatic heart disease, degenerative changes, congenital anomalies, systemic connective tissue diseases (systemic lupus erythematosus, rheumatoid arthritis), non-specific aortoarteritis, etc. The special attention is paid to pathophysiologic features of acute and chronic aortic regurgitation in the review. Acute aortic regurgitation is characterized by sudden increase in end-diastolic volume and due to the noncompliant left ventricle of normal size, it undergoes abrupt exposure a significant pre-load and after-load which results in decrease of left ventricle systolic function and stroke volume despite on relative preservation of contractile function of myocardium. In contrast to acute aortic regurgitation it is remarkable in its chronic form slow, progressive influence by increased overload of the left ventricle with possibility to adapt driven by its gradual dilation and hypertrophy

THE DEPENDENCE OF PROTECTIVE PROPERTIES OF A NEW LOW‑TEMPERATURE CATALYST ON CARBON MONOXIDE CONCENTRATION AND THE EFFECTIVE RESIDENCE TIME

The dependence of protective properties of a new catalyst for low-temperature carbon monoxide oxidation with air oxygen on CO concentration and the effective residence time has been found

КРИПТОМЕЛАН, МОДИФІКОВАНИЙ ІОНАМИ ПЕРЕХІДНИХ МЕТАЛІВ: СТРУКТУРА ТА КАТАЛІТИЧНА АКТИВНІСТЬ В РЕАКЦІЇ РОЗКЛАДАННЯ ОЗОНУ

Cryptomelane, OMS-2, and cryptomelane modified with transition metal ions, M/OMS-2 (M = Cu2+, Co2+, Fe3+), were synthesized by the reaction of KMnO4 reduction with manganous salts (MnCl2 and MnSO4) by the reflux method. The samples thus synthesized were characterized by X-ray diffraction and IR spectroscopic methods and their catalytic activity was tested in the reaction of ozone decomposition. Cryptomelane, OMS-2, is the main phase of the synthesized samples, bixbyite, Mn2O3, and pyrolusite, β-MnO2, are impurity phases presented in OMS-2 and M/OMS-2 at a quantity lower than 10 %. The doped metal ions did not create a new phase however they influenced the size of cryptomelane crystallites and it became almost two times lower. Our IR spectral investigations show that, in the region of stretching vibrations of OH groups in the associated water molecules, the IR absorption is very weak for all M/OMS-2 samples as opposed to OMS-2. IR spectroscopic analysis also showed that incorporation of the transition metal ions into the cryptomelane structure differently affected the vibrations of Mn-O and Mn-OH bonds. The doped Cu2+ ion practically caused no change in the OMS-2 spectrum whereas new absorption bands characteristic of Co-O and Fe-O bonds appeared in the spectra of Co/OMS-2 and Fe/OMS-2. The absorption band in 650-400 cm-1 region of the Fe/OMS-2 spectrum is complex. The catalytic activity of M/OMS-2 samples depended on the nature of the current transition metal ion doped into tunnel channels of cryptomelane. The Cu/OMS-2 sample exhibits a tendency to the steady-state mode of ozone decomposition whereas, in the case of the Cu/OMS-2 and Fe/OMS-2, the ozone concentration at the reactor outlet rapidly increases. Comparison of the activity of these three M/OMS-2 samples and OMS-2 resulted in the following order: Co/OMS-2 > OMS-2 > Cu/OMS-2 > Fe/OMS-2. Thus, the accelerating effect was observed only in the case of cobalt (II) ions.За реакцією відновлення KMnO4 хлоридом Mn(ІІ) або сульфатом Mn(II) методом зворотного холодильника (reflux method) синтезовані зразки криптомелану (ОМS-2) та криптомелану модифікованого іонами перехідних металів (M/OMS-2; M = Cu2+, Co2+, Fe3+). Зразки охарактеризовані методами РФА, ІЧ-спектроскопії та протестовані в реакції розкладання озону. Каталітична активність зразків M/OMS-2 залежить від природи іону металу та змінюється наступним чином Со/OMS-2>OMS-2>Cu/OMS-2>Fe/OMS-2

SYNTHESIS AND CATALYTIC ACTIVITY OF DISPERSED MANGANESE(IV) OXIDES IN THE REACTION OF OZONE DECOMPOSITION

MnO2 samples were prepared via different procedures: (i) permanganate ion reducing with formic acid followed by the precipitate washing with cold (IS-Mn(1)) or hot (IS-Mn(2)) water, (ii) permanganate ion reducing with Mn2+ ion (IIS-Mn), and (iii) KNO3 and MnSO4 melting together (IІІS-Mn). It has been found by X-ray diffraction (XRD) method that, among Mn(IV) samples synthesized via above procedures, IS-Mn(1), IS-Mn(2), and ІІSMn are semiamorphous and only IIS-Mn contains ε-MnO2 and g-MnO2 phases. IІІS-Mn is crystalline and positions and intensities of its reflections in XRD patterns can be attributed to the cryptomelane, KMn8O16, phase having a tunnel (2´2) structure with potassium ions in its channels. Using a Rietveld refinement, it has been determined that a size of cryptomelane crystallites is several times as much as sizes of the semiamorphous ε-MnO2 and g-MnO2 crystallites. As a result of testing the IS-Mn(1), IIS-Mn, and IІІS-Mn samples in the reaction of ozone decomposition at C in O3 = 100 mg/m3, it has been found that the reaction kinetics depends on the nature of the samples and their weights. Varying catalyst weight we draw a conclusion that an effective residence time, t¢, and a specific volume flow (wsp) of ozone-air mixture (OAM) also change. At the invariant linear velocity of OAM, the residence time increases because a height of the catalyst bed increases. Moreover, increasing the catalyst weight, we obtain a decrease in wsp. The increase in τ¢ leads to the increase in kinetic and stoichiometric parameters of the reaction for all samples under study. In the case of IIS-Mn and IІІS-Mn at the sample weight of 0.5 g, we failed to achieve the half-conversion of ozone, i.e. ozone concentration at the reactor outlet, C fO3 , didn’t become equal to 0.5 C in O3 , therefore, we stopped the experiments when C in O3 attained 5 mg/m3 for IIS-Mn and 0.28 mg/ m3 for IIISMn. Moreover, these samples have protective abilities: a time of protective action was 180 min for IIS-Mn and 1020 min for IIIS-Mn. Thus, the catalytic activity of manganese oxide forms in the reaction of ozone decomposition depends on their phase composition and crystallinity. Cryptomelane having a tunnel structure (2 × 2) shows the highest activity

MECHANISMS OF THE COMPLEX FORMATION BY d-METALS ON POROUS SUPPORTS AND THE CATALYTIC ACTIVITY OF THE FORMED COMPLEXES IN REDOX REACTIONS

The catalytic activity of supported complexes of d metals in redox reactions with participation of gaseous toxicants, PH3, CO, O3, and SO2, depends on their composition. Owing to the variety of physicochemical and structural-adsorption properties of available supports, their influence on complex formation processes, the composition and catalytic activity of metal complexes anchored on them varies over a wide range. The metal complex formation on sup-ports with weak ion-exchanging properties is similar to that in aqueous solutions. In this case, the support role mainly adds up to the ability to reduce the activity of water adsorbed on them. The interaction between a metal complex and a support surface occurs through adsorbed water molecules. Such supports can also affect complex formation processes owing to protolytic reactions on account of acidic properties of sorbents used as supports. The catalytic activity of metal complexes supported on polyphase natural sorbents considerably depends on their phase relationship. In the case of supports with the nonsimple structure and pronounced ion-exchanging properties, for instance, zeolites and laminar silicates, it is necessary to take into account the variety of places where metal ions can be located. Such location places determine distinctions in the coordination environment of the metal ions and the strength of their bonding with surface adsorption sites and, therefore, the catalytic activity of surface complexes formed by theses metal ions. Because of the energy surface inhomogeneity, it is important to determine a relationship between the strength of a metal complex bonding with a support surface and its catalytic activity. For example, bimetallic complexes are catalytically active in the reactions of oxidation of the above gaseous toxicants. In particular, in the case of carbon monoxide oxidation, the most catalytic activity is shown by palladium-copper complexes in which copper(II) is strongly fixed on a support surface as a result of the ion exchanging and palladium(II) is bound with copper(II) through a water molecule or some other ligands. The formation of surface complexes can occur as a result of the covalent binding of 3d metals with ligands preliminarily immobilized on supports. However, the examined complexes with aerosol immobilized Schiff bases are catalytically active only in the reaction of ozone decomposition

СИНТЕЗ ТА КАТАЛІТИЧНА АКТИВНІСТЬ ДИСПЕРСНИХ ОКСИДІВ МАНГАНУ(ІV) В РЕАКЦІЇ РОЗКЛАДАННЯ ОЗОНУ

MnO2 samples were prepared via different procedures: (i) permanganate ion reducing with formic acid followed by the precipitate washing with cold (IS-Mn(1)) or hot (IS-Mn(2)) water, (ii) permanganate ion reducing with Mn2+ ion (IIS-Mn), and (iii) KNO3 and MnSO4 melting together (IІІS-Mn). It has been found by X-ray diffraction (XRD) method that, among Mn(IV) samples synthesized via above procedures, IS-Mn(1), IS-Mn(2), and ІІSMn are semiamorphous and only IIS-Mn contains ε-MnO2 and g-MnO2 phases. IІІS-Mn is crystalline and positions and intensities of its reflections in XRD patterns can be attributed to the cryptomelane, KMn8O16, phase having a tunnel (2´2) structure with potassium ions in its channels. Using a Rietveld refinement, it has been determined that a size of cryptomelane crystallites is several times as much as sizes of the semiamorphous ε-MnO2 and g-MnO2 crystallites. As a result of testing the IS-Mn(1), IIS-Mn, and IІІS-Mn samples in the reaction of ozone decomposition at C in O3 = 100 mg/m3, it has been found that the reaction kinetics depends on the nature of the samples and their weights. Varying catalyst weight we draw a conclusion that an effective residence time, t¢, and a specific volume flow (wsp) of ozone-air mixture (OAM) also change. At the invariant linear velocity of OAM, the residence time increases because a height of the catalyst bed increases. Moreover, increasing the catalyst weight, we obtain a decrease in wsp. The increase in τ¢ leads to the increase in kinetic and stoichiometric parameters of the reaction for all samples under study. In the case of IIS-Mn and IІІS-Mn at the sample weight of 0.5 g, we failed to achieve the half-conversion of ozone, i.e. ozone concentration at the reactor outlet, C fO3 , didn’t become equal to 0.5 C in O3 , therefore, we stopped the experiments when C in O3 attained 5 mg/m3 for IIS-Mn and 0.28 mg/ m3 for IIISMn. Moreover, these samples have protective abilities: a time of protective action was 180 min for IIS-Mn and 1020 min for IIIS-Mn. Thus, the catalytic activity of manganese oxide forms in the reaction of ozone decomposition depends on their phase composition and crystallinity. Cryptomelane having a tunnel structure (2 × 2) shows the highest activity.У роботі досліджено вплив способу отримання діоксиду мангану на його склад та каталітичну активність в реакції розкладання озону. Методом рентгенофазового аналізу встановлено, що зразки IS-Mn(1), IS-Mn(2) і ІІS-Mn напіваморфні, а зразок IІІS-Mn – кристалічний та відповідає фазі криптомелану KMn8O16. Каталітична активність оксидних форм мангану в реакції розкладання озону визначається фазовим складом і збільшується в ряду: IS-Mn(1) < IIS-Mn < IIIS-Mn

Synthesis and Catalytic Properties of Iron Oxides in the Reaction of Low-Temperature Ozone Decomposition

Two sets of iron oxide samples were synthesized applying different iron(III) precursors (FeCl₃ and Fe₂(SO₄)₃) and calcination temperature (200, 300, and 500°C). The samples were characterized by powder X-ray analysis and the Fourier transform infrared spectroscopy. Depending on the synthesis conditions, samples of iron oxides with different phase composition were obtained: polyphase (α -Fe₂O₃, γ -Fe₂O₃, Fe₃O₄, and α -FeO(OH)) and monophase (γ -Fe₂O₃ or α -Fe₂O₃) ones. For the samples of homogeneous composition, it has been found that the activity of γ -Fe₂O₃ in the reaction of ozone decomposition at ozone concentration in gaseous phase of 1 mg/m³ is much higher than the activity of α -Fe₂O₃

Synthesis and Catalytic Properties of Iron Oxides in the Reaction of Low-Temperature Ozone Decomposition

Two sets of iron oxide samples were synthesized applying different iron(III) precursors (FeCl₃ and Fe₂(SO₄)₃) and calcination temperature (200, 300, and 500°C). The samples were characterized by powder X-ray analysis and the Fourier transform infrared spectroscopy. Depending on the synthesis conditions, samples of iron oxides with different phase composition were obtained: polyphase (α -Fe₂O₃, γ -Fe₂O₃, Fe₃O₄, and α -FeO(OH)) and monophase (γ -Fe₂O₃ or α -Fe₂O₃) ones. For the samples of homogeneous composition, it has been found that the activity of γ -Fe₂O₃ in the reaction of ozone decomposition at ozone concentration in gaseous phase of 1 mg/m³ is much higher than the activity of α -Fe₂O₃