Derivation of activation energies from experiments on chemical activation of alkyl fluorides

1976 ◽  
Vol 72 (0) ◽  
pp. 996 ◽  
Author(s):  
P. Cadman ◽  
A. W. Kirk ◽  
A. F. Trotman-Dickenson
Keyword(s):  
Chemical Activation ◽  
Activation Energies ◽  
Alkyl Fluorides

Hydrogen–Water Deuterium Exchange over Unsupported Group VIII Noble Metals

1974 ◽  
Vol 52 (16) ◽  
pp. 2960-2967 ◽  
Author(s):  
Norman H. Sagert ◽  
Rita M. L. Pouteau
Keyword(s):  
Noble Metals ◽  
Chemical Activation ◽  
Activation Energies ◽  
Graphitized Carbon Black ◽  
Hydrogen Chemisorption ◽  
Group Viii ◽  
Hydrogen Atoms ◽  
Hydrogen Water ◽  
Surface Areas ◽  
Specific Activities

Specific activities of unsupported powders of all six Group VIII noble metals have been determined for hydrogen – water deuterium isotope exchange. The metal surface areas, which are required to calculate the specific activities were measured by hydrogen chemisorption and were checked by electron microscopy. Specific activities were measured as a function of temperature in the range 353 to 573 K and also as a function of the partial pressure of hydrogen and water at suitable temperatures and over a tenfold range of partial pressures.The variation in the specific activities was Pd < Ir ≤ Ru < Rh < Os < Pt, and these specific activities varied over a range of about 1000. The observed orders with respect to hydrogen and water are shown to be consistent with a mechanism in which chemisorbed hydrogen atoms exchange with physically adsorbed water.From the orders and the apparent activation energies, the chemical activation energies (E0) were calculated. These varied randomly within the range 61 ± 6 kJ mol−1 for all the metals studied. Previously we showed that there was a correlation of E0 with the work function of the metal when metals were supported on a highly graphitized carbon black, and suggested that electron donation from the carbon to the metal was responsible for the correlation. This suggestion is supported by the present results which show that E0 is relatively constant for all six metals in the absence of a support.

scholarly journals Effect of carbonization temperature on characterization and water vapor adsorption of coffee-shell activated carbon

2020 ◽  
Vol 38 (9-10) ◽  
pp. 377-392
Author(s):  
Shengnan Sun ◽  
Qiongfen Yu ◽  
Ming Li ◽  
Hong Zhao ◽  
Yunfeng Wang ◽  
...  
Keyword(s):  
Activated Carbon ◽  
Water Vapor ◽  
Raw Materials ◽  
Chemical Activation ◽  
Activation Energies ◽  
Water Vapor Adsorption ◽  
Carbonization Temperature ◽  
Potential Candidate ◽  
Heating Rates ◽  
Vapor Adsorption

Coffee shells, which are abundant in cellulose and lignin, are good raw materials to prepare activated carbon. In this paper, coffee shells were selected as raw materials for activated carbon preparation by KOH chemical activation. Influence of carbonization temperature on adsorption capacity of water vapor over activated carbon was researched. Thermogravimetric analysis was employed to select the scope of carbonization temperature. Activation energies of coffee shells pyrolyzed at different heating rates were calculated. Nitrogen adsorption/desorption isotherm and scanning electron microscopy (SEM) were adopted to characterize the activated carbon. And water vapor adsorption isotherms were simulated by the finite simplification model of Do-Do adsorption model. The results show that activation energies of coffee shells pyrolysis process with heating rates of 5, 10 and 20 K/min are 17.21, 18.01 and 57.52 kJ/mol, respectively. The optimal carbonization temperature of coffee shells is 923 K. The adsorption amount of water vapor can reach about 702.3 mg/g under experiment temperature of 298 K and relative humidity of 70%. The highest total pore volume and Brunauer–Emmett–Teller (BET) specific surface area are 1.41 cm3/g and 2817 m2/g, respectively. The simulation results of the finite simplification model are consistent well with water vapor adsorption experiment results. The results show that activated carbon prepared at the optimal condition would be the potential candidate for solar drying system.

Deep level study in epitaxial 4H-SiC grown on substrates inclined toward

2002 ◽  
Vol 719 ◽  
Author(s):  
Masashi Kato ◽  
Masaya Ichimura ◽  
Eisuke Arai ◽  
Shigehiro Nishino
Keyword(s):  
Deep Level Transient Spectroscopy ◽  
Deep Level ◽  
Activation Energies ◽  
Thickness Dependence ◽  
Epitaxial Layers ◽  
Transient Spectroscopy

AbstractEpitaxial layers of 4H-SiC are grown on (0001) substrates inclined toward <1120> and <1100> directions. Defects in these films are characterized by deep level transient spectroscopy (DLTS) in order to clarify the dependence of concentrations and activation energies on substrate inclination. DLTS results show no such dependence on substrate inclination but show thickness dependence of the concentration.

Activation energies of technological termodonors in neutron doped silicon

2015 ◽  
Vol 19 (1/2) ◽  
Author(s):  
L. I. Panasjuk ◽  
V. V. Kolomoets ◽  
V. N. Ermakov ◽  
S. A. Fedosov ◽  
L. V. Yashchynskiy
Keyword(s):  
Activation Energies ◽  
Doped Silicon

Activated carbon from molasses efficiency for Cr(VI), Pb(II) and Cu(II) adsorption: A mechanistic study

2019 ◽  
Author(s):  
Chem Int
Keyword(s):  
Activated Carbon ◽  
Phosphoric Acid ◽  
Sugar Industry ◽  
Chemical Activation ◽  
High Surface ◽  
High Surface Area ◽  
Mechanistic Study ◽  
Acid Mixture ◽  
Maximum Adsorption Capacity ◽  
Good Potential

Activated carbon was prepared from molasses, which are natural precursors of vegetable origin resulting from the sugar industry. A simple elaboration process, based on chemical activation with phosphoric acid, was proposed. The final product, prepared by activation of molasses/phosphoric acid mixture in air at 500°C, presented high surface area (more than 1400 m2/g) and important maximum adsorption capacity for methylene blue (625 mg/g) and iodine (1660 mg/g). The activated carbon (MP2(500)) showed a good potential for the adsorption of Cr(VI), Cu(II) and Pb(II) from aqueous solutions. The affinity for the three ions was observed in the following order Cu2+ Cr6+ Pb2+. The process is governed by monolayer adsorption following the Langmuir model, with a correlation coefficient close to unity.

Analisis Variasi Temperatur Aktivasi Terhadap Daya Serap Arang Aktif Tandan Aren (Arenga Pinnata Merr) Dengan Agen Aktivasi Potassium Silicate(K2SiO3)

2020 ◽  
Vol 5 (3) ◽  
pp. 221
Author(s):  
Muhammad Azam ◽  
Muhammad Anas ◽  
Erniwati Erniwati
Keyword(s):  
Methylene Blue ◽  
Activated Carbon ◽  
Adsorption Capacity ◽  
Temperature Variation ◽  
Chemical Activation ◽  
Weight Ratio ◽  
Potassium Silicate ◽  
Physical Activation ◽  
Activation Temperature ◽  
Pyrolysis Reactor

This study aims to determine the effect of variation of activation temperature of activated carbon from sugar palm bunches of chemically activatied with the activation agent of potassium silicate (K2SiO3) on the adsorption capacity of iodine and methylene blue. Activated carbon from bunches of sugar palmacquired in four steps: preparationsteps, carbonizationstepsusing the pyrolysis reactor with temperature of 300 oC - 400 oC for 8 hours and chemical activation using of potassium silicate (K2SiO3) activator in weight ratio of 2: 1 and physical activation using the electric furnace for 30 minutes with temperature variation of600 oC, 650 oC, 700 oC, 750 oC and 800 oC. The iodine and methyleneblue adsorption testedby Titrimetric method and Spectrophotometry methodrespectively. The results of the adsorption of iodine and methylene blue activated carbon from sugar palm bunches increased from 240.55 mg/g and 63.14 mg/g at a temperature of 600 oC to achieve the highest adsorption capacity of 325.80 mg/g and 73.59 mg/g at temperature of 700 oC and decreased by 257.54 mg/g and 52.03 mg/g at a temperature of 800 oCrespectively.However, it does not meet to Indonesia standard (Standard Nasional Indonesia/SNI), which is 750 mg/g and 120 mg/g respectively.

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