scholarly journals Revealing the effect of water vapor pressure on the kinetics of thermal decomposition of magnesium hydroxide

2020 ◽  
Vol 22 (24) ◽  
pp. 13637-13649 ◽  
Author(s):  
Satoki Kodani ◽  
Shun Iwasaki ◽  
Loïc Favergeon ◽  
Nobuyoshi Koga
Keyword(s):  
Thermal Decomposition ◽  
Water Vapor ◽  
Vapor Pressure ◽  
Magnesium Hydroxide ◽  
Water Vapor Pressure ◽  
Kinetics Of Thermal Decomposition ◽  
Effect Of Water ◽  
Kinetics Of ◽  
Kinetic Features

Kinetic features of the thermal decomposition of Mg(OH)2 are revealed under different heating and water vapor pressure conditions.

scholarly journals Comparative study of the effect of water on the heterogeneous reactions of carbonyl sulfide on the surface of α-Al<sub>2</sub>O<sub>3</sub> and MgO

2009 ◽  
Vol 9 (3) ◽  
pp. 12483-12517
Author(s):  
Y. Liu ◽  
Q. Ma ◽  
H. He
Keyword(s):  
Water Vapor ◽  
Vapor Pressure ◽  
Heterogeneous Reaction ◽  
Water Vapor Pressure ◽  
Carbonyl Sulfide ◽  
Heterogeneous Reactions ◽  
Uptake Coefficient ◽  
Effect Of Water ◽  
Mineral Dusts ◽  
Α Al2o3

Abstract. The heterogeneous reaction on mineral dust was considered as a new sink of OCS in the troposphere. Here we compared the heterogeneous reactions of carbonyl sulfide (OCS) on the surface of α-Al2O3 and MgO and the effect of water on the reactions at 300 K using Knudsen cell – mass spectrometry, diffuse reflectance infrared Fourier transform spectroscopy, and temperature programmed reactions. H2S and CO2 were found to be hydrolysis products of OCS on both α-Al2O3 and MgO at ambient temperature. At low water vapor pressure, when water vapor pressure in the Knudsen cell reactor increased from 2.3×10−6 to 6.8×10−6 Torr, the initial true uptake coefficient of OCS on α-Al2O3 decreased from 4.70×10−7 to 3.59×10−7; while it increased from 5.19×10−7 to 6.48×10−7 on MgO under the same conditions. At high relative humidity, the observed uptake coefficients of OCS on α-Al2O3 and MgO decreased from 4.63×10−6 to 1.00×10−6 and from 9.72×10−5 to 7.68×10−5, respectively, when RH increased from 0.07 to 0.67 which corresponding to 1.7–15.9 Torr of water vapor pressure. In the RH region of 0.17–0.67, the average observed uptake coefficient of OCS on α-Al2O3 and MgO was equal to 8.34±2.19×10−7 and 8.19±0.48×10−5, respectively. The restrictive effect of water on the heterogeneous reaction of OCS on the surface of α-Al2O3 and MgO was found to be related to competitive adsorption between water and OCS molecules; while the promotive effect of water on the heterogeneous reaction of OCS on the surface of MgO at low coverage was ascribed to the formation of surface hydroxyl groups. When the environmental RH was greater than the RH of the monolayer, which occurred readily at the typical relative humidity of the troposphere, liquid membrane formed on the mineral dusts, especially, the basic liquid membrane formed on the basic component of mineral dusts may be the primary contributor to the heterogeneous hydrolysis of OCS in the troposphere.

scholarly journals Comparative study of the effect of water on the heterogeneous reactions of carbonyl sulfide on the surface of α-Al<sub>2</sub>O<sub>3</sub> and MgO

2009 ◽  
Vol 9 (16) ◽  
pp. 6273-6286 ◽  
Author(s):  
Y. Liu ◽  
Q. Ma ◽  
H. He
Keyword(s):  
Water Vapor ◽  
Vapor Pressure ◽  
Heterogeneous Reaction ◽  
Water Vapor Pressure ◽  
Carbonyl Sulfide ◽  
Water Layer ◽  
Heterogeneous Reactions ◽  
Effect Of Water ◽  
Mineral Dusts ◽  
Α Al2o3

Abstract. Here we compared the heterogeneous reactions of carbonyl sulfide (OCS) on the surface of α-Al2O3 and MgO and the effect of water on the reactions at 300 K using Knudsen cell–mass spectrometry, diffuse reflectance infrared Fourier transform spectroscopy, and temperature programmed reactions. H2S and CO2 were found to be hydrolysis products of OCS on both α–Al2O3 and MgO at ambient temperature. At low water vapor pressure (<6.8×10−6 Torr), when water vapor pressure in the Knudsen cell reactor increased from 2.3×10−6 to 6.8×10−6 Torr, the initial true uptake coefficient of OCS on α-Al2O3 decreased from 4.70±0.45×10−7 to 3.59±0.34×10−7; while it increased from 5.19±0.49×10−7 to 6.48±0.62×10−7 on MgO under the same conditions. At high relative humidity (0.07–0.67), the observed uptake coefficients of OCS on α-Al2O3 and MgO, which were measured using an in situ DRIFTS, decreased from 4.63±0.22×10−6 to 1.00±0.47×10−6 and from 9.72±0.46×10−5 to 7.68±0.36×10−5, respectively, when RH increased from 0.07 to 0.67 corresponding to 1.7–15.9 Torr of water vapor pressure. In the RH region of 0.17–0.67, the average observed uptake coefficient of OCS on α-Al2O3 and MgO was equal to 8.34±2.19×10−7 and 8.19±0.48×10−5, respectively. The restrictive effect of water on the heterogeneous reaction of OCS on the surface of α-Al2O3 and MgO was found to be related to competitive adsorption between water and OCS molecules; while the promotive effect of water on the heterogeneous reaction of OCS on the surface of MgO at low coverage was ascribed to the formation of surface hydroxyl groups. When the environmental RH was greater than the RH of the monolayer, which occurred readily at the atmospherically relevant humidity in the troposphere, thick water layer formed on the mineral dusts, especially, the basic thick water layer formed on the basic component of mineral dusts may be the primary contributor to the heterogeneous hydrolysis of OCS in the troposphere.

Quantitation of crystallinity in substantially amorphous pharmaceuticals and study of crystallization kinetics by X-ray powder diffractometry

2000 ◽  
Vol 15 (1) ◽  
pp. 2-6 ◽  
Author(s):  
Rahul Surana ◽  
Raj Suryanarayanan
Keyword(s):  
Water Vapor ◽  
Vapor Pressure ◽  
Crystallization Kinetics ◽  
Water Vapor Pressure ◽  
Three Dimensional ◽  
Weight Percent ◽  
X Ray ◽  
Amorphous Pharmaceuticals ◽  
Integrated Intensities ◽  
Kinetics Of

The first object was to develop an X-ray diffractometric method for the detection and quantification of crystalline sucrose when it occurs as a mixture with amorphous sucrose. Standards consisting of amorphous sucrose physically mixed with 1 to 5 weight percent crystalline sucrose were prepared. The sum of the background subtracted integrated intensities of the 12.7°2θ (6.94 Å) and 13.1°2θ (6.73 Å) sucrose diffraction peaks were linearly related to the weight percent crystalline sucrose. The limits of detection and quantitation of crystalline sucrose were 0.9% and 1.8% w/w, respectively. The second object was to study the kinetics of crystallization of sucrose as a function of temperature (at 102, 105 and 110 °C under a water vapor pressure of 0 Torr) and water vapor pressure (17.4, 19.8 and 21.4 Torr at 27 °C). In all cases, the crystallization kinetics was best described by the Avrami-Erofe’ev model (three-dimensional nucleation).

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