Selectivity changes of acetone transformation over ZSM-5 zeolites with different acido-basic properties

1989 ◽  
Vol 54 (8) ◽  
pp. 2054-2063 ◽  
Author(s):  
Jiří Čejka ◽  
Ludmila Kubelková ◽  
Pavel Jírů
Keyword(s):  
Main Product ◽  
High Conversion ◽  
Total Conversion ◽  
Basic Properties ◽  
Product Composition ◽  
Conversion Level ◽  
Integral Reactor ◽  
Low Activity ◽  
High Conversion Level

Acetone transformation catalyzed by HZSM-5 and NaZSM-5 zeolites and by zeolites modified with basic oxides was studied in an integral reactor at a temperature of 350 °C. Modification of acido-basic properties of ZSM-5 zeolites resulted both in the total conversion changes and in the essential changes in the product composition. Isobutene was found to be the main product over HZSM-5 zeolites exhibiting low activity, while aromatics prevailed when high conversion level was attained. Classical condensation of acetone yielding mesityloxide and phorones was observed over NaZSM-5 zeolites impregnated with CaO and ZnO.

scholarly journals Identification of a Key Enzyme for the Hydrolysis of β-(1→3)-Xylosyl Linkage in Red Alga Dulse Xylooligosaccharide from Bifidobacterium Adolescentis

Marine Drugs ◽  
2020 ◽  
Vol 18 (3) ◽  
pp. 174 ◽  
Author(s):  
Manami Kobayashi ◽  
Yuya Kumagai ◽  
Yohei Yamamoto ◽  
Hajime Yasui ◽  
Hideki Kishimura
Keyword(s):  
Main Product ◽  
Specific Activity ◽  
Red Alga ◽  
Glycoside Hydrolase Family ◽  
Bifidobacterium Adolescentis ◽  
Glycoside Hydrolase Family 43 ◽  
Key Enzyme ◽  
Hydrolysis Of ◽  
Low Activity ◽  
Hydrolase Family

Red alga dulse possesses a unique xylan, which is composed of a linear β-(1→3)/β-(1→4)-xylosyl linkage. We previously prepared characteristic xylooligosaccharide (DX3, (β-(1→3)-xylosyl-xylobiose)) from dulse. In this study, we evaluated the prebiotic effect of DX3 on enteric bacterium. Although DX3 was utilized by Bacteroides sp. and Bifidobacterium adolescentis, Bacteroides Ksp. grew slowly as compared with β-(1→4)-xylotriose (X3) but B. adolescentis grew similar to X3. Therefore, we aimed to find the key DX3 hydrolysis enzymes in B. adolescentis. From bioinformatics analysis, two enzymes from the glycoside hydrolase family 43 (BAD0423: subfamily 12 and BAD0428: subfamily 11) were selected and expressed in Escherichia coli. BAD0423 hydrolyzed β-(1→3)-xylosyl linkage in DX3 with the specific activity of 2988 mU/mg producing xylose (X1) and xylobiose (X2), and showed low activity on X2 and X3. BAD0428 showed high activity on X2 and X3 producing X1, and the activity of BAD0428 on DX3 was 1298 mU/mg producing X1. Cooperative hydrolysis of DX3 was found in the combination of BAD0423 and BAD0428 producing X1 as the main product. From enzymatic character, hydrolysis of X3 was completed by one enzyme BAD0428, whereas hydrolysis of DX3 needed more than two enzymes.

scholarly journals BUTENEDIOLS PRODUCTION FROM ERYTHRITOL ON Rh PROMOTED CATALYST

2020 ◽  
Vol 50 (2) ◽  
pp. 89-94
Author(s):  
Emanuel Martín Virgilio ◽  
Cristina Liliana Padró ◽  
Maria Eugenia Sad
Keyword(s):  
Bimetallic Catalyst ◽  
Good Activity ◽  
Reaction Conditions ◽  
Total Conversion ◽  
Reaction Orders ◽  
Temperature Programmed ◽  
Lower Temperature ◽  
Low Activity ◽  
Monometallic Catalyst ◽  
Lower Carbon

The C-O hydrogenolysis of Erythritol to Butanodiols was studied in aqueous solution at 473 K and 25 bar of H2 using Rh/ReOx/TiO2 and the monometallic Rh/TiO2 and ReOx/TiO2 catalysts. The solids were characterized by temperature programmed reduction (TPR), TEM and XPS. TPR and XPS showed that ReOx species are close to Rh particles leading to reduction at lower temperature than Re on monometallic catalyst. However, some segregated Rhenium species were suspected by TPR profile for the bimetallic catalyst and detected by TEM.  Re/TiO2 exhibited low activity forming only products from dehydration and epimerization. Although Rh/TiO2 showed high activity (total conversion at 14 h), was more selective to C-C cleavage leading to lower carbon products. Rh/ReOx/TiO2, showed instead, a good activity and selectivity towards C-O hydrogenolysis route yielding 37.5% of Butanodiols. Activation energy and reaction orders on ERY (0.58) and H2 (0.53) were estimated from experiences made at different reaction conditions

Single and competitive hydrodesulphurization of thiophene and benzo[b]thiophene on molybdenum catalysts

1981 ◽  
Vol 46 (9) ◽  
pp. 2185-2196 ◽  
Author(s):  
Pavel Pokorný ◽  
Miroslav Zdražil
Keyword(s):  
Competitive Reaction ◽  
Total Conversion ◽  
Title Reaction ◽  
Temperature Range ◽  
Molybdenum Catalysts ◽  
The Difference ◽  
Tubular Flow ◽  
Reported Data ◽  
Integral Reactor ◽  
Single Reaction

The reactivity of benzo[b]thiophene and thiophene and the amount of 2,3-dihydrobenzo[b]thiophene and tetrahydrothiophene in the title reaction on sulphided Co-Mo-Al2O3 and MoS2 catalysts has been determined at the temperature range 543-623 K and hydrogen pressures 0.5-2.0 MPa in a tubular flow integral reactor. Under above conditions, benzo[b]thiophene was more reactive than thiophene and the difference in their reactivities in the competitive reaction was substantially greater than in the single reaction. The selectivity to the intermediate 2,3-dihydrobenzo[b]thiophene and tetrahydrothiophene in the reaction of benzo[b]thiophene and thiophene respectively, was measured in the whole region of total conversion. Based on these and reported data, the mechanism of hydrodesulphurization is discussed.

Tin as a Possible Candidate for Solar Thermochemical Redox Process for Hydrogen Production

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Irina Vishnevetsky ◽  
Michael Epstein
Keyword(s):  
Hydrogen Production ◽  
Water Splitting ◽  
Redox Process ◽  
Experimental Conditions ◽  
Solar Hydrogen ◽  
Conversion Level ◽  
Reactor Temperature ◽  
Solar Hydrogen Production ◽  
Hydrolysis Of ◽  
High Conversion Level

The feasibility to produce hydrogen in the Sn–H2O/SnO2–C thermochemical water splitting redox process depends mainly on the efficiency of the tin hydrolysis step, which has not been studied adequately so far, while the cassererite carboreduction is implemented by industry for tin production. The present work deals with the hydrolysis of different kinds of tin powders at different experimental conditions at moderate temperature range 180–620°C. In spite of the fact that the rate of hydrogen production is lower compared with other metals, e.g., zinc, at the same reactor temperature, high conversion level was obtained in a controllable reaction. Consequently, tin can be a relevant candidate for solar hydrogen production considering the advantage of significant lower temperatures required for the solar carboreduction of its oxide.

scholarly journals The first general Zagreb coindex of graph operations

2020 ◽  
Vol 5 (2) ◽  
pp. 109-120
Author(s):  
Melaku Berhe Belay ◽  
Chunxiang Wang
Keyword(s):  
Tensor Product ◽  
Cartesian Product ◽  
Molecular Graphs ◽  
Basic Properties ◽  
Graph Operations ◽  
Nano Structures ◽  
Product Composition ◽  
Product Of Graphs

AbstractMany chemically important graphs can be obtained from simpler graphs by applying different graph operations. Graph operations such as union, sum, Cartesian product, composition and tensor product of graphs are among the important ones. In this paper, we introduce a new invariant which is named as the first general Zagreb coindex and defined as \overline{M}^\alpha_1(G)=\Sigma_{uv\in E(\overline{G})}[d_G(u)^\alpha+d_G(v)^\alpha] , where α ∈ ℝ, α ≠ 0. Here, we study the basic properties of the newly introduced invariant and its behavior under some graph operations such as union, sum, Cartesian product, composition and tensor product of graphs and hence apply the results to find the first general Zagreb coindex of different important nano-structures and molecular graphs.

Feasible Ways to Achieve High Conversion in Thorium-Fueled CANDU and PWR Reactors

2009 ◽  
pp. 62-72 ◽  
Author(s):  
P. Guillemin ◽  
A. Nuttin ◽  
A. Bidaud ◽  
J. Brizi ◽  
N. Capellan ◽  
...  
Keyword(s):  
High Conversion

A Comparison of the in Vitro and in Vivo Thrombogenic Activity of Factor IX Concentrates Using Stasis (Wessler) and Non-Stasis Rabbit Models

1980 ◽  
Vol 44 (02) ◽  
pp. 081-086 ◽  
Author(s):  
C V Prowse ◽  
A E Williams
Keyword(s):  
Platelet Rich Plasma ◽  
Thrombus Formation ◽  
Factor Ix ◽  
Coagulation System ◽  
In Vitro Tests ◽  
Clinical Use ◽  
Low Activity

SummaryThe thrombogenic effects of selected factor IX concentrates were evaluated in two rabbit models; the Wessler stasis model and a novel non-stasis model. Concentrates active in either the NAPTT or TGt50 in vitro tests of potential thrombogenicity, or both, caused thrombus formation in the Wessler technique and activation of the coagulation system in the non-stasis model. A concentrate with low activity in both in vitro tests did not have thrombogenic effects in vivo, at the chosen dose. Results in the non-stasis model suggested that the thrombogenic effects of factor IX concentrates may occur by at least two mechanisms. A concentrate prepared from platelet-rich plasma and a pyrogenic concentrate were also tested and found to have no thrombogenic effect in vivo.These studies justify the use of the NAPTT and TGt50 in vitro tests for the screening of factor IX concentrates prior to clinical use.

Separation of Heparin into Subtractions by DEAE-Cellulose Chromatography

1979 ◽  
Vol 42 (05) ◽  
pp. 1452-1459 ◽  
Author(s):  
Robert H Yue ◽  
Toby Starr ◽  
Menard M Gertler
Keyword(s):  
High Activity ◽  
Uronic Acid ◽  
Deae Cellulose ◽  
Exchange Chromatography ◽  
Net Charge ◽  
Uronic Acid Content ◽  
Successful Separation ◽  
Salt Gradient ◽  
Structure And Activity ◽  
Low Activity

SummaryCommercial porcine heparin can be separated into three distinct subtractions by using DEAE-cellulose chromatography and a stepped salt gradient. Gram quantities of heparin can be fractionated by this technique. All three heparin subtractions can accelerate the inhibition of thrombin by antithrombin III with different efficiency. The specific activities of the high activity heparin, intermediate activity heparin and low activity heparin are 228 units/mg, 142 units/mg and 95 units/mg, respectively. Both the uronic acid content and the quantity of N-SO4 for all three heparin subfractions have been evaluated. The high activity heparin has the lowest uronic acid and N-SO4 content. The successful separation of commercial heparin into three distinct subfractions by means of ion-exchange chromatography suggests that the net charge on these three heparin components will serve as a model system in the elucidation of the structure and activity relationship to the biological function of heparin.

On the Essence and Tipology of International Public Goods

2005 ◽  
pp. 131-141
Author(s):  
V. Mortikov
Keyword(s):  
Economic Policy ◽  
Social Construction ◽  
Public Goods ◽  
Public Good ◽  
Global Public Goods ◽  
Club Goods ◽  
Basic Properties ◽  
International Public Goods ◽  
Regional Public Goods ◽  
Joint Products

The basic properties of international public goods are analyzed in the paper. Special attention is paid to the typology of international public goods: pure and impure, excludable and nonexcludable, club goods, regional public goods, joint products. The author argues that social construction of international public good depends on many factors, for example, government economic policy. Aggregation technologies in the supply of global public goods are examined.

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