Effect of the pretreatment conditions on the activity of an industrial Co-Mo/Al2O3 catalyst

1983 ◽  
Vol 48 (3) ◽  
pp. 691-697 ◽  
Author(s):  
Lachezar Petrov ◽  
Chavdar Vladov ◽  
Dimitar Shopov ◽  
Věnceslava Friebová ◽  
Ludvík Beránek
Keyword(s):  
Catalytic Activity ◽  
Atmospheric Pressure ◽  
Ethylene Hydrogenation ◽  
Kinetic Methods ◽  
Pretreatment Temperature ◽  
Pretreatment Conditions ◽  
Al2o3 Catalyst ◽  
Active Centres

The processes of reduction and sulphidation of an industrial Co-Mo/Al2O3 catalyst have been studied by means of gravimetric and kinetic methods at atmospheric pressure. The effect of the pretreatment temperature on the catalytic activity for ethylene hydrogenation and thiophene hydrodesulphurization has been studied. Two types of active centres, for hydrogenation and for hydrodesulphurization, have been characterized on the basis of their different properties.

Hydrogenation of ethylene on a Co-Mo/Al2O3 catalyst under transient conditions

1986 ◽  
Vol 51 (12) ◽  
pp. 2760-2769
Author(s):  
Jana Samková ◽  
Karel Klusáček ◽  
Petr Schneider
Keyword(s):  
Atmospheric Pressure ◽  
Active Sites ◽  
Total Concentration ◽  
Ethylene Hydrogenation ◽  
Response Curves ◽  
Feed Composition ◽  
Rate Determining Step ◽  
Al2o3 Catalyst ◽  
Adsorbed Ethylene ◽  
Hydrogenation Of Ethylene

Hydrogenation of ethylene on a Co-Mo/Al2O3 catalyst at 353 K and atmospheric pressure has been studied. The unsteady-state method was used, in which reactor feed-rate and feed-composition were changed in a defined way. The analysis of transient response curves proved negligible adsorption of hydrogen and ethane and confirmed the reaction mechanism of ethylene hydrogenation which involves reaction of adsorbed ethylene with hydrogen from gas phase in the rate determining step. Combined stationary and transient experimental data were used to calculate kinetic parameters: rate constant of ethylene hydrogenation, total concentration of active sites on the catalyst surface and equilibrium adsorption coefficient of ethylene.

scholarly journals CO Oxidation Efficiency and Hysteresis Behavior over Mesoporous Pd/SiO2 Catalyst

Catalysts ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 131 ◽  
Author(s):  
Rola Mohammad Al Soubaihi ◽  
Khaled Mohammad Saoud ◽  
Myo Tay Zar Myint ◽  
Mats A. Göthelid ◽  
Joydeep Dutta
Keyword(s):  
Carbon Monoxide ◽  
Catalytic Activity ◽  
Co Oxidation ◽  
Active Sites ◽  
Bond Activation ◽  
Dissociative Adsorption ◽  
High Catalytic Activity ◽  
Good Catalytic Activity ◽  
Pretreatment Conditions ◽  
Oxidation Efficiency

Carbon monoxide (CO) oxidation is considered an important reaction in heterogeneous industrial catalysis and has been extensively studied. Pd supported on SiO2 aerogel catalysts exhibit good catalytic activity toward this reaction owing to their CO bond activation capability and thermal stability. Pd/SiO2 catalysts were investigated using carbon monoxide (CO) oxidation as a model reaction. The catalyst becomes active, and the conversion increases after the temperature reaches the ignition temperature (Tig). A normal hysteresis in carbon monoxide (CO) oxidation has been observed, where the catalysts continue to exhibit high catalytic activity (CO conversion remains at 100%) during the extinction even at temperatures lower than Tig. The catalyst was characterized using BET, TEM, XPS, TGA-DSC, and FTIR. In this work, the influence of pretreatment conditions and stability of the active sites on the catalytic activity and hysteresis is presented. The CO oxidation on the Pd/SiO2 catalyst has been attributed to the dissociative adsorption of molecular oxygen and the activation of the C-O bond, followed by diffusion of adsorbates at Tig to form CO2. Whereas, the hysteresis has been explained by the enhanced stability of the active site caused by thermal effects, pretreatment conditions, Pd-SiO2 support interaction, and PdO formation and decomposition.

Effect of Impurity and Pretreatment Conditions on the Catalytic Activity of Au Powder for CO Oxidation

2004 ◽  
Vol 97 (3/4) ◽  
pp. 203-208 ◽  
Author(s):  
Yasuo Iizuka ◽  
Aya Kawamoto ◽  
Kazuhiro Akita ◽  
Masakazu Daté ◽  
Susumu Tsubota ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Co Oxidation ◽  
Pretreatment Conditions

Vanadium-Chromium Oxide: Effective Catalysts for Ammoxidation of 3-Picoline

2013 ◽  
Vol 634-638 ◽  
pp. 624-627 ◽  
Author(s):  
Feng Jiang ◽  
Wei Xu ◽  
Lei Niu ◽  
Guo Min Xiao
Keyword(s):  
Raman Spectroscopy ◽  
Catalytic Activity ◽  
Chromium Oxide ◽  
Atmospheric Pressure ◽  
High Selectivity ◽  
Surface Acidity ◽  
N2 Adsorption ◽  
Composite Oxide ◽  
Highly Active

Bulk vanadium-chromium oxide (VCrO) catalyst was prepared and characterized by N2 adsorption, XRD, NH3-TPD, H2-TPR, and Raman spectroscopy. XRD and Raman results showed that the VCrO catalyst was a kind of VV-CrIII composite oxide mainly consisted of crystalline V2O5 and CrVO4-Ⅲ (orthorhombic). NH3-TPD and H2-TPR results revealed that this catalyst had negligible surface acidity, and was easily reduced due to the formation of CrVO4-Ⅲ. Their catalytic activity was evaluated in the ammoxidation of 3-picoline to nicotinonitrile. Catalytic results showed that the bulk VCrO catalyst was highly active and selective; the nicotinonitrile selectivity and yield was up to 96.1%, 88.2% respectively at atmospheric pressure and 360 °C. The high selectivity was related closely to the low surface acidity of the catalyst.

Effective toluene oxidation under ozone over mesoporous MnOx/γ-Al2O3 catalyst prepared by solvent deficient method: Effect of Mn precursors on catalytic activity

2021 ◽  
Vol 195 ◽  
pp. 110876
Author(s):  
Kannapu Hari Prasad Reddy ◽  
Beom-Sik Kim ◽  
Su Shiung Lam ◽  
Sang-Chul Jung ◽  
JiHyeon Song ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Toluene Oxidation ◽  
Method Effect ◽  
Al2o3 Catalyst

scholarly journals Novel Kinetic Models of Xylan Dissolution and Degradation during Ethanol Based Auto-Catalyzed Organosolv Pretreatment of Bamboo

Polymers ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 1149 ◽  
Author(s):  
Jing Liu ◽  
Zhenggang Gong ◽  
Guangxu Yang ◽  
Lihui Chen ◽  
Liulian Huang ◽  
...  
Keyword(s):  
Kinetic Models ◽  
Degradation Products ◽  
Practical Significance ◽  
Order Kinetic ◽  
Organosolv Pretreatment ◽  
Dependent Parameter ◽  
Pretreatment Temperature ◽  
Pretreatment Conditions ◽  
Main Components ◽  
The Relationship

Due to the invalidity of traditional models, pretreatment conditions dependent parameter of susceptible dissolution degree of xylan (dX) was introduced into the kinetic models. After the introduction of dX, the dissolution of xylan, and the formation of xylo-oligosaccharides and xylose during ethanol based auto-catalyzed organosolv (EACO) pretreatments of bamboo were well predicted by the pseudo first-order kinetic models (R2 > 97%). The parameter of dX was verified to be a variable dependent of EACO pretreatment conditions (such as solvent content in pretreatment liquor and pretreatment temperature). Based on the established kinetic models of xylan dissolution, the dissolution of glucan and the formation of degradation products (furfural and acetic acid) could also be empirically modeled (R2 > 97%). In addition, the relationship between xylan and lignin removal can provide guidance for alleviating the depositions of lignin or pseudo-lignin. The parameter of dX derived novel kinetic models can not only be used to reveal the multi-step reaction mechanisms of xylan, but also control the final removal of main components in bamboo during EACO pretreatments, indicating scientific and practical significance for governing the biorefinery of woody biomass.

The Effect of Ni Precursor Salts on Diatomite Supported Ni-Mg Catalysts in Methanation of CO2

2021 ◽  
Vol 1016 ◽  
pp. 1417-1422
Author(s):  
Chao Sun ◽  
Jugoslav Krstic ◽  
Vojkan Radonjic ◽  
Miroslav Stankovic ◽  
Patrick da Costa
Keyword(s):  
Catalytic Activity ◽  
Atmospheric Pressure ◽  
Textural Properties ◽  
Catalytic Performance ◽  
Nickel Salt ◽  
Nitrate Salt ◽  
Efficient Catalyst ◽  
Mild Conditions ◽  
The Difference ◽  
Supported Ni

This study is aimed to investigate the effect of Ni precursor salts on the properties (textural, phase-structural, reducibility, and basicity), and catalytic performance of diatomite supported Ni-Mg catalyst in methanation of CO2. The NiMg/D-X catalysts derived from various nickel salts (X = S-sulfamate, N-nitrate or A-acetate) were synthesized by the precipitation-deposition (PD) method. The catalysts were characterized by N2-physisorption, XRD, TPR-H2, and TPD-CO2 techniques. The different catalytic activity (conversion) and selectivity, observed in CO2 methanation carried out under relatively mild conditions (atmospheric pressure; temperatures: 250-450 °C) are related and explained by the difference in textural properties, metallic Ni-crystallite size, reducibility, and basicity of studied catalysts. The results showed that catalyst derived from Ni-nitrate salt (NiMg/D-N) is more suitable for the preparation of efficient catalyst for CO2 methanation than its counterparts derived from sulfamate (NiMg/D-S) or acetate (NiMg/D-A) nickel salt. The NiMg/D-N catalyst showed the highest specific surface area and total basicity, and the best catalytic performance with CO2 conversion of 63.3 % and CH4 selectivity of 80.9 % at 450 °C.

scholarly journals A Comprehensive Approach of Eucalyptus globulus Acid Sulfite Pretreatment for Enzymatic Hydrolysis

2020 ◽  
Vol 10 (11) ◽  
pp. 3764
Author(s):  
Vera D. Costa ◽  
Ana Costa ◽  
Maria Amaral ◽  
Rogério S. Simões
Keyword(s):  
Sulfuric Acid ◽  
Enzymatic Hydrolysis ◽  
Eucalyptus Globulus ◽  
High Performance ◽  
Sodium Bisulfite ◽  
Hydrolysis Rate ◽  
Hemicellulose Removal ◽  
Pretreatment Temperature ◽  
Pretreatment Conditions ◽  
Very High

The effect of different acid sulfite pretreatment conditions on released components in the hydrolysates and the pretreated solid residues’ response to enzymatic hydrolysis for Eucalyptus globulus chips was investigated. Sodium bisulfite (0–15%), and sulfuric acid (0–5%) were used to pretreat chips at 170 °C and 190 °C, for as long as 30 min. The hydrolysates were analyzed through high-performance liquid chromatography (HPLC) and spectrophotometry. Overall porosity and pores larger than 2.65 nm (size of a typical cellulase) on the solid residues were estimated using glucose and two dextrans with different hydrodynamic radii as probes. The external specific surface area was analyzed by dynamic light scattering. The solid residues underwent enzymatic hydrolysis with an enzymatic cocktail. Very high (84–95%) carbohydrate conversion was achieved for either an extensively delignified biomass or a biomass with very high content of sulfonated residual lignin (23.4%), since internal porosity enables enzymes accessibility. At least 5% sodium bisulfite and 1% sulfuric acid was required to attain a carbohydrate release above 90% in the enzymatic hydrolysis. Results suggest that the presence of sulfonated lignin does not impair the enzymatic hydrolysis rate and extent. The increase of pretreatment temperature had a positive effect mainly on the initial rate of carbohydrates release in the enzymatic hydrolysis. The increase of the wood material dimensions from pins to conventional chips significantly decreased the hemicellulose removal in acid sulfite pretreatment but had a small effect on the enzymatic yield.

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