Molybdenum area and hydrogenation and hydrogenolytic activities of hydrorefining catalysts

1983 ◽  
Vol 48 (6) ◽  
pp. 1703-1709 ◽  
Author(s):  
Rafael López ◽  
Miloš Kraus
Keyword(s):  
Hydrogenation Activity ◽  
Oxygen Chemisorption ◽  
Molybdenum Catalysts ◽  
Reduced Forms ◽  
Nickel Tungsten

A series of nickel or cobalt promoted molybdenum catalysts and one nickel-tungsten catalyst have been studied by oxygen chemisorption on reduced oxidic samples, by activities of oxidic and sulphided samples for 1-hexene hydrogenation and by activities of sulphided samples for benzothiophen and pyridine hydrogenolyses. A good correlation was obtained between oxygen chemisorption and hydrogenation activity on oxidic, partially reduced, forms of the catalysts, and a limited correlation for activities of sulphided forms. Parallel activities for hydrogenation and hydrogenolyses were observed.

Hydrogenolytic cleavage of pyridine on different cobalt-molybdenum and nickel-tungsten catalysts

1981 ◽  
Vol 46 (6) ◽  
pp. 1348-1354 ◽  
Author(s):  
Mirko Černý ◽  
Miloš Kraus
Keyword(s):  
Reaction Products ◽  
Hydrogenation Activity ◽  
Catalyst Composition ◽  
Tungsten Catalysts ◽  
Nickel Tungsten ◽  
And Tungsten

Composition of the reaction products formed by hydrogenation of pyridine at 300 °C and 15 MPa in the presence of 15 sulphided and unsulphided molybdenum and tungsten catalysts promoted by cobalt and by nickel, respectively, using alumina as the support in most cases, has been examined. It has been proved that the catalyst composition affects both its hydrogenation activity and the ratio of transalkylation to cracking (or hydrocracking) reactions. Relations between the catalyst composition and its activity and selectivity found for the reaction of pyridine differ from those reported for hydrogenolytic cleavage of thiophene, hydrogenation and isomerization of cyclohexene.

Relation between reduction and sulphidation process during the activation of a Co-Mo/Al2O3 hydrodesulphurization catalyst

1985 ◽  
Vol 50 (7) ◽  
pp. 1573-1581 ◽  
Author(s):  
Hana Zahradníková ◽  
Václav Kárník ◽  
Ludvík Beránek
Keyword(s):  
Activation Energy ◽  
Catalytic Activity ◽  
Apparent Activation Energy ◽  
Ethylene Hydrogenation ◽  
Hydrogenation Activity ◽  
Oxygen Chemisorption ◽  
Predominant Process ◽  
Chemisorption Capacity

The course of activation at 673 and 773 K of an industrial hydrodesulphurization catalyst CHEROX 36-01 was followed gravimetrically. Reduction with hydrogen, reductive sulphidation with a H2S/H2 mixture, non-reductive sulphidation with a H2S/He mixture and sulphidation of prereduced catalysts were compared. All sulphidation procedures are much faster than the reduction alone, the latter has, however, a higher apparent activation energy. In the reductive sulphidation with H2S/H2, reduction and sulphidation take place simultaneously, sulphidation being a predominant process at the beginning of the activation, especially at 673 K. It has been shown how the two processes can be decoupled or superposed. The catalytic activity in ethylene hydrogenation develops much more slowly when the catalyst is activated only by reduction than when it is activated by reductive sulphidation, in accordance with the relative velocities of these two activation procedures. The hydrogenation activity of catalysts reduced to a different extent correlates with their oxygen chemisorption capacity at 195 K.

Effect of carvedilol on the redox-status of plasma low-molecular-weight aminothyols in rats with acute cerebral ischemia

2018 ◽  
pp. 12-18
Author(s):  
К.А. Никифорова ◽  
В.В. Александрин ◽  
П.О. Булгакова ◽  
А.В. Иванов ◽  
Э.Д. Вирюс ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Cerebral Ischemia ◽  
Carotid Arteries ◽  
Redox Status ◽  
Global Cerebral Ischemia ◽  
Low Molecular Weight ◽  
Adrenergic Antagonist ◽  
Acute Cerebral Ischemia ◽  
Common Carotid Arteries ◽  
Reduced Forms

Цель. Установить влияние неспецифического адреноблокатора карведилола на редокс-статус низкомолекулярных аминотиолов (цистеин, гомоцистеин, глутатион) в плазме крови при моделировании глобальной ишемии головного мозга у крыс. Методика. Нами была использована модель глобальной ишемии (пережатие общих сонных артерий с геморрагией длительностью 15 мин). Препарат вводили за 1 ч до операции. Уровни аминотиолов измеряли через 40 мин после начала реперфузии. Анализ уровня аминотиолов проводили методом жидкостной хроматографии. Результаты. Установлено, что у крыс, не подвергавшихся ишемии, карведилол в дозе 10 мг/кг вызывает рост редокс-статуса цистеина и глутатиона (в 3 и 3,5 раза соответственно по сравнению с контролем, p = 0,04 и p = 0,008) за счет увеличения их восстановленных форм. При ишемии данного эффекта не наблюдалось. Редокс-статус у крыс с ишемией на фоне карведилола (Цис = 0,85 ± 0,14%, Глн = 1,8 ± 0,7%, Гцис = 1,1 ± 0,8%) оставался таким же низким, как и у крыс с ишемией без введения карведилола (р > 0,8). Заключение. Полученный результат демонстрирует, что в условиях ишемии головного мозга карведилол не оказывает эффекта на гомеостаз аминотиолов плазмы крови, несмотря на выраженный антиоксидантный эффект в нормальных условиях. Aim. Effect of a nonspecific adrenergic antagonist carvedilol on the redox status of plasma low-molecular-weight aminothiols (cysteine, homocysteine, glutathione) was studied in rats with global cerebral ischemia (occlusion of common carotid arteries with hemorrhage). Methods. A model of global ischemia (occlusion of common carotid arteries with 15-min hemorrhage) was used. The drugs were administered one hour before the operation. Aminothiol levels were measured by HPLC with UV detection at 40 minutes after the onset of reperfusion. Results. Carvedilol 10 mg/kg increased the redox status of cysteine and glutathione in rats not exposed to ischemia (3 and 3.5 times, respectively, compared with the control, p = 0.04 and p = 0.008, respectively) but not of homocysteine, by increasing their reduced forms. However, this effect was not observed in ischemia. In rats with ischemia treated with carvedilol, the redox status (Cys = 0.85 ± 0.14%, GSH = 1.8 ± 0.7%, Hcys = 1.1 ± 0.8%) remained low similar to that in rats with ischemia not treated with carvedilol (p >0.8, 0.8, and 0.9, respectively). Conclusion. Carvedilol did not affect the homeostasis of blood plasma thiols in cerebral ischemia despite the pronounced antioxidant effect under the normal conditions.

Type 2 diabetes mellitus in patients with acute ischemiс stroke is associated with a decrease in plasma glutathione levels

2020 ◽  
Vol 25 (5) ◽  
pp. 29-35
Author(s):  
M. Yu. Maksimova ◽  
A. V. Ivanov ◽  
K. A. Nikiforova ◽  
F. R. Ochtova ◽  
E. T. Suanova ◽  
...  
Keyword(s):  
Diabetes Mellitus ◽  
Type 2 Diabetes ◽  
Type 2 Diabetes Mellitus ◽  
Redox Status ◽  
Reduced Form ◽  
Glutathione Level ◽  
Total Glutathione ◽  
Diabetes Mellitus Group ◽  
Reduced Forms

Ischemic stroke (IS) and type 2 diabetes mellitus are factors that affect the homeostasis of low-molecularweight aminothiols (cysteine, homocysteine, glutathione etc.). It has already been shown that IS in the acute period led to a decrease a level of reduced forms of aminothiols, but it is not clear whether type 2 diabetes mellitus has a noticeable effect there. Objective: to reveal the features of homeostasis of aminothiols in patients with type 2 diabetes mellitus in acute IS. Material and methods. The study involved 76 patients with primary middle cerebral artery IS in the first 10–24 hours after development of neurological symptoms. Group 1 included 15 patients with IS and type 2 diabetes mellitus, group 2 — 61 patients with IS and stress hyperglycemia. Their total plasma levels of cysteine, homocysteine, and glutathione, their reduced forms, and redox status were determined at admission (in the first 24 hours after IS). Results. There was a decrease in the level of total glutathione level (1.27 vs. 1.65 μM, p = 0.021), as well as its reduced form (0.03 vs. 0.04 μM, p = 0.007) in patients with IS and type 2 diabetes mellitus. Patients with type 2 diabetes mellitus who had a low redox status of homocysteine (0.65–1.2%) and glutathione (0.7–2.0%) were also characterized by a decrease in total glutathione level (p = 0.02; p = 0.03). Conclusion. Thus, type 2 diabetes mellitus is associated with a decrease in the level of total glutathione in acute IS. Probably, type 2 diabetes mellitus is characterized by a particular relationship between the metabolism of homocysteine, glutathione and glucose. Therefore, the search for homocysteine-dependent approaches to correct glutathione metabolism in type 2 diabetes mellitus may be of interest as an adjuvant therapy for IS.

CARPENTER AMS 5700

Alloy Digest ◽  
1975 ◽  
Vol 24 (7) ◽  
Keyword(s):  
Fracture Toughness ◽  
Corrosion Resistance ◽  
High Temperature ◽  
Heat Treating ◽  
Temperature Performance ◽  
Technology Corporation ◽  
Valve Steel ◽  
Carpenter Technology Corporation ◽  
Exhaust Valves ◽  
Nickel Tungsten

Abstract CARPENTER AMS 5700 is an austenitic chromium-nickel-tungsten valve steel which offers good high-temperature properties and resistance to corrosion in exhaust valves. This datasheet provides information on composition, physical properties, hardness, and tensile properties as well as fracture toughness and creep. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, and machining. Filing Code: SS-313. Producer or source: Carpenter Technology Corporation.

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