Quantum Efficiencies of the Photocatalytic Decomposition of Trichloroethylene in Water. A Comparative Study for Different Varieties of Titanium Dioxide Catalysts

1998 ◽  
Vol 3 (3) ◽  
Author(s):  
María I. Cabrera ◽  
Orlando M. Alfano ◽  
Alberto E. Cassano
Keyword(s):  
Titanium Dioxide ◽  
Reaction Rates ◽  
Operating Conditions ◽  
Photocatalytic Decomposition ◽  
Catalyst Loading ◽  
Initial Reaction ◽  
Irradiation Intensity ◽  
Reaction Conversion ◽  
Degussa P25 ◽  
Titanium Dioxides

AbstractQuantum efficiencies of the photocatalytic decomposition of trichloroethylene employing a suspension of titanium dioxide in water and polychromatic radiation have been investigated. Aldrich, Degussa P25 and Hombikat 100 titanium dioxides were studied using an approach that permits the correct evaluation of the true absorbed UV radiation. Computed results using initial reaction rates show that differences in efficiencies among the different varieties of titanium dioxides are not very dramatic. However, reaction conversion after several hours of identical operating conditions favors the use of the Aldrich catalyst. Quantum efficiencies show an important dependence with the initial reactant concentration, the irradiation intensity and the catalyst loading. Under some operating conditions, quantum efficiencies as high as 50 % were measured.

scholarly journals Thermally modified titania photocatalysts for phenol removal from water

2006 ◽  
Vol 2006 ◽  
pp. 1-7 ◽  
Author(s):  
Joanna Grzechulska-Damszel ◽  
Antoni W. Morawski ◽  
Barbara Grzmil
Keyword(s):  
Titanium Dioxide ◽  
Photocatalytic Activity ◽  
Thermal Treatment ◽  
Photocatalytic Oxidation ◽  
Thermal Modification ◽  
Photocatalytic Decomposition ◽  
Phenol Removal ◽  
Chemical Factory ◽  
Degussa P25 ◽  
Oxidation Of Phenol

Two kinds of titanium dioxide were used as starting materials for thermal modification: Tytanpol A11 supplied by Chemical Factory “Police” S.A. (Poland) and Degussa P25 supplied by Degussa AG (Germany). The photocatalytic activity of titania materials modified by thermal treatment was tested in the reaction of photocatalytic oxidation of phenol. It was found that the highest activity in the reaction of photocatalytic decomposition of phenol, in case of Tytanpol A11, shows the samples of material modified at temperatures of 700 and 750°C. These catalysts were more active than untreated A11, whereas materials modified at higher temperatures show lower activity. In the case of P25, all thermally treated materials were less active than the unmodified material. The photocatalyst samples were characterized by UV-Vis/DR, FTIR/DRS, and XRD methods.

Assessing the effect of light intensity and light wavelength spectra on the photoreduction of formic acid using a graphene oxide material

2020 ◽  
Vol 18 (8) ◽  
Author(s):  
Luis A. Ramos-Huerta ◽  
Lotte Laureys ◽  
Alexis G. Llanos ◽  
Patricio J. Valadés ◽  
Richard S. Ruiz ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Graphene Oxide ◽  
Light Intensity ◽  
Formic Acid ◽  
Reaction Rates ◽  
Operating Conditions ◽  
Initial Reaction ◽  
Oxide Material ◽  
Methanol Production ◽  
Effect Of Light

AbstractPhotocatalysis has been a topic of interest in recent years for both, oxidation and reduction reactions, and although there is a broad variety of research regarding photocatalytic materials and the reaction itself, studies on reactor design and related phenomena, radiation transfer and its direct impact on reaction extent specifically, are usually neglected. From this end, the present work focuses on the elucidation of the effect of light intensity and wavelength spectra in the visible light region during the photoreduction reaction of formic acid using graphene oxide as a promising catalyst. By using formic acid, one of the main intermediaries in the photoreduction of carbon dioxide, the possibility of methanol production is evaluated without the thermodynamic constraints presented by carbon dioxide. A graphene oxide material, synthetized through a modified Hummer’s method, is assessed for the reduction of formic acid evaluating four different light sources (red, green, blue and white). An analysis of energy balances in the reaction set-up allows the determination of both the energy absorbed by the GO photocatalyst and isoactinity conditions at studied radiative operating conditions. At an isoactinity environment, the adsorption rate of formic acid and production rate of methanol are then evaluated, relating them to the absorbed energy achieved at the wavelength spectra and light intensities evaluated; IR spectroscopy is utilized to follow formic acid concentration as well as methanol production. The largest initial reaction rate (ca. 57%) relates to the use of the red wavelength at its largest intensity. Reaction rates at larger times start to be apparent being affected by adsorption, reaction and radiation conditions. The maximum conversion, 14%, is attained by using the white wavelength spectra at its lowest intensity. Thus, higher intensities will not necessarily yield higher conversions, nor the highest reaction rates. This, in turn, poses the necessity of quick, reliable assessments for whichever catalyst used in this type of reactions that leads to the correct election of operating conditions that maximize the product yield. Independent evaluation for every wavelength within the visible spectra and assessing carbon dioxide photoreduction are future steps into the elucidation of solar fuel production feasibility.

Analysis of NiMoP/γ-Al2O3 Catalyst Preparation with Impregnation and Microwave Polyol Methods for Bio-Jet Production

2020 ◽  
Vol 1000 ◽  
pp. 257-264
Author(s):  
Bambang Heru Susanto ◽  
Joshua Raymond Valentino Siallagan
Keyword(s):  
Coconut Oil ◽  
Catalyst Preparation ◽  
Operating Conditions ◽  
Catalyst Loading ◽  
Impregnation Method ◽  
Conversion Yield ◽  
Jet Production ◽  
Cracking Process ◽  
Catalyst Impregnation ◽  
Rate Conversion

Bio-Jet could be produced by the synthesis of vegetable oil through the hydrodeoxygenation, decarboxylation, decarbonization, and catalytic cracking process. Physical characteristics, activities, and selectivity of the catalyst used will determine the rate, conversion, and yield of the reaction that being carried out. This study aims to compare and obtain the best characteristics of NiMoP/γ-Al2O3 catalysts synthesized using two types of preparation, impregnation and microwave polyol methods, which will be used for bio-jet production. The impregnation method takes more than 24 hours for catalyst preparation, while microwave polyols that use microwaves can synthesize catalysts faster. Both catalysts have almost the same loading on the weight of the catalyst, which in the microwave polyol method has a more dispersed promotor and active site, although the crystallinity level is deficient and tends to be amorphous compared to the impregnation method with high crystallinity. In bio-jet synthesis reaction with operating conditions of 5% catalyst loading by comparison to Coconut Oil, 400°C, and 15 bar, the conversion, yield, and selectivity of catalyst impregnation were 91.705%, 47.639%, and 84.511%, while microwave polyol catalysts were 90.296%, 42.752%, and 82.517%, respectively. In conclusion, microwave polyol provides a more effective and efficient preparation method.

Ensemble Learning Approach with LASSO for Predicting Catalytic Reaction Rates

Synlett ◽  
2020 ◽  
Author(s):  
Akira Yada ◽  
Kazuhiko Sato ◽  
Tarojiro Matsumura ◽  
Yasunobu Ando ◽  
Kenji Nagata ◽  
...  
Keyword(s):  
Ensemble Learning ◽  
Reaction Rates ◽  
Initial Reaction Rate ◽  
Training Dataset ◽  
Initial Reaction ◽  
Learning Approach ◽  
Learning Framework ◽  
Machine Learning Approach ◽  
Reasonable Prediction ◽  
Epoxidation Of Alkenes

AbstractThe prediction of the initial reaction rate in the tungsten-catalyzed epoxidation of alkenes by using a machine learning approach is demonstrated. The ensemble learning framework used in this study consists of random sampling with replacement from the training dataset, the construction of several predictive models (weak learners), and the combination of their outputs. This approach enables us to obtain a reasonable prediction model that avoids the problem of overfitting, even when analyzing a small dataset.

scholarly journals Uptake of Zn, Pb, Cu and Fe Ions from Spent and Unspent Engine Oil Using Termite Soil

2017 ◽  
Vol 9 (3) ◽  
pp. 85
Author(s):  
Iwekumo Agbozu ◽  
Bassey Uwem ◽  
Boisa Ndokiari
Keyword(s):  
Contact Time ◽  
Diffusion Constant ◽  
Reaction Rates ◽  
Second Order ◽  
Engine Oil ◽  
Initial Reaction ◽  
Kinetics Equation ◽  
Spent Engine Oil ◽  
Pseudo Second Order ◽  
Fe Ions

Removal of Zn, Pb, Cu and Fe ions from unspent and spent engine oil was studied using Termite soil. Process parameters such as contact time and adsorbent dosage were varied. Values from contact time were used for predicting kinetics equation of their uptake. At optimum time of 40 minutes, percentage adsorption was of the order Fe>Zn>Cu>Pb for both spent and unspent engine oil. Kinetics equation such as Elovich, Intra-particle, Pseudo-first order and Pseudo-second order were tested. Results obtained shows that their sequestering pattern fit into the pseudo-second order kinetics. Initial reaction rates, h (mg/g.min) and α (mg. g-1min-1) for all metal ions obtained from Pseudo-second order and Elovich kinetic models followed the trends Zn>Fe>Cu>Pb and Zn>Fe>Pb>Cu respectively in spent engine oil while for unspent engine oil, the trend was Fe>Zn>Cu>Pb for h (mg/g.min) and Zn>Fe>Pb>Cu for α (mg. g-1min-1). Electrostatic attraction existing on the surface of the adsorbent assisted in the high initial reaction of Zn and Fe ions, implying good affinity of the ions for the adsorbent. Desorption constant ᵦ (g/mg) was of the trend Cu>Pb>Fe>Zn and Cu>Pb>Zn>Fe for spent and unspent engine oils respectively. Intra-particle diffusion constant kid (mgg-1min-1/2) followed a similar pattern, revealing strong binding between Zn and termite soil than any of the metal ion. This pilot research has been able to suggest a kinetic process for uptake of the studied ions from spent and unspent engine oil.

Hard-templating synthesis and enhanced photocatalysis of mesoporous titanium dioxides nanoparticles

2018 ◽  
Vol 11 (04) ◽  
pp. 1850077 ◽  
Author(s):  
K. L. Jin ◽  
X. J. Chen ◽  
J. C. Xu ◽  
Y. S. Huang ◽  
Y. B. Han ◽  
...  
Keyword(s):  
Surface Area ◽  
Anatase Phase ◽  
High Surface ◽  
High Surface Area ◽  
Mesoporous Structure ◽  
Photocatalytic Decomposition ◽  
Titanium Dioxides ◽  
Decomposition Efficiency ◽  
Templating Synthesis ◽  
Mb Adsorption

Mesoporous titanium dioxides nanoparticles (TiO2 NPs) were synthesized using activated carbon (AC) as templates after the decomposition of AC. All results indicated that TiO2 NPs with the small grain size presented the anatase phase structure. Mesoporous TiO2 NPs showed the high surface area and the surface area decreased with the TiO2 content. The removal of methylene blue (MB) indicated that the photocatalytic decomposition efficiency of mesoporous TiO2 NPs increased up to 92% for three-times doping with the TiO2 content, and then decreased. This should be attributed to the synergistic effect from the MB adsorption of mesoporous-structure and the photocatalysis of TiO2 NPs. Therefore, the higher MB concentration near TiO2 NPs from the mesoporous-structure increased the touch chance and the MB photocatalytic decomposition was promoted greatly.

scholarly journals Studies on Epoxidation of Tung oil with Hydrogen Peroxide Catalyzed by Sulfuric Acid

2020 ◽  
Vol 15 (3) ◽  
pp. 674-686
Author(s):  
Eni Budiyati ◽  
Rochmadi Rochmadi ◽  
Arief Budiman ◽  
Budhijanto Budhijanto
Keyword(s):  
Hydrogen Peroxide ◽  
Sulfuric Acid ◽  
Unsaturated Fatty Acids ◽  
Catalyst Concentration ◽  
Reaction Rates ◽  
Catalytic Reactions ◽  
Side Reactions ◽  
Initial Reaction ◽  
Tung Oil ◽  
Epoxidation Reaction

Tung oil with an iodine value (IV) of 99.63 g I2/100 g was epoxidized in-situ with glacial acetic acid and hydrogen peroxide (H2O2), in the presence sulfuric acid as catalyst. The objective of this research was to evaluate the effect of mole ratio of H2O2 to unsaturated fatty acids (UFA), reaction time and catalyst concentration in Tung oil epoxidation. The reaction kinetics were also studied. Epoxidation was carried out for 4 h. The reaction rates and side reactions were evaluated based on the IV and the conversion of the epoxidized Tung oil to oxirane. Catalytic reactions resulted in higher reaction rate than did non-catalytic reactions. Increasing the catalyst concentration resulted in a large decrease in the IV and an increase in the conversion to oxirane at the initial reaction stage. However, higher catalyst concentration in the epoxidation reaction caused to a decrease in reaction selectivity. The mole ratio of H2O2 to UFA had an influence identical to the catalyst concentration. The recommended optimum mole ratio and catalyst concentration in this study were 1.6 and 1.5%, respectively. The highest conversion was 48.94% for a mole ratio of 1.6. The proposed kinetic model provided good results and was suitable for all variations in reaction temperature. The activation energy (Ea) values were around 5.7663 to 76.2442 kcal/mol. Copyright © 2020 BCREC Group. All rights reserved 

Can Water Dilution Avoid Flashback on a Hydrogen Enriched Micro Gas Turbine Combustion? A Large Eddy Simulations Study

2020 ◽  
Author(s):  
Alessio Pappa ◽  
Laurent Bricteux ◽  
Pierre Bénard ◽  
Ward De Paepe
Keyword(s):  
Gas Turbines ◽  
Reaction Rates ◽  
Operating Conditions ◽  
Large Eddy Simulations ◽  
Small Scale ◽  
Reference Case ◽  
Large Eddy ◽  
Pure Methane ◽  
Water Dilution ◽  
Air Humidification

Abstract Considering the growing interest in Power-to-Fuel, i.e. production of H2 using electrolysis to store excess renewable electricity, combustion-based technologies still have a role to play in the future of power generation. Especially in a decentralized production with small-scale cogeneration, micro Gas Turbines (mGTs) offer great advantages related to their high adaptability and flexibility, in terms of operation and fuel. Hydrogen (or hydrogen enriched methane) combustion is well-known to lead to flame and combustion instabilities. The high temperatures and reaction rates reached in the combustor can potentially lead to flashback. In the past, combustion air humidification (i.e. water addition) has proven effective to reduce temperatures and reaction rates, leading to significant NOx emission reductions. Therefore, combustion air humidification can open a path to stabilize hydrogen combustion in a classical mGT combustor. However accurate data assessing the impact of humidification on the combustion is still missing for real mGT combustor geometries and operating conditions. In this framework, this paper presents a comparison between pure methane and hydrogen enriched methane/air combustions, with and without combustion air humidification, in a typical mGT combustion chamber (Turbec T100) using Large Eddy Simulations (LES) analysis. In a first step, the necessary minimal water dilution, to reach stable and low emissions combustion with hydrogen, was assessed using a 1D approach. The one-dimensional unstretched laminar flame is computed for both pure methane (reference case) and hydrogen enriched methane/air combustion cases. The results of this comparison show that, for the hydrogen enriched combustion, the same level of flame speed as in the reference case can be reached by adding 10% (in mass fraction) of water. In a second step, the feasibility and flexibility of humidified hydrogen enriched methane/air combustion in an industrial mGT combustor have been demonstrated by performing high fidelity LES on a 3D geometry. Results show that steam dilution helped to lower the reactivity of hydrogen, and thus prevents flashback, enabling the use of hydrogen blends in the mGT at similar CO levels, compared to the reference case. These results will help to design future combustor towards more stability.

Influence of Operational Parameters on Photocatalytic Degradation of Linuron in Aqueous TiO2 Pillared Montmorillonite Suspension

2021 ◽  
Vol 16 (3) ◽  
pp. 673-685
Author(s):  
D. Hadj Bachir ◽  
Hocine Boutoumi ◽  
H. Khalaf ◽  
Pierre Eloy ◽  
J. Schnee ◽  
...  
Keyword(s):  
Photocatalytic Degradation ◽  
Physicochemical Characterization ◽  
Operating Conditions ◽  
Cod Removal ◽  
Pollutant Concentration ◽  
Catalyst Loading ◽  
Operational Parameters ◽  
X Ray ◽  
Pillared Montmorillonite ◽  
Initial Ph

TiO2 pillared clay was prepared by intercalation of titan polyoxocation into interlamelar space of an Algerian montmorillonite and used for the photocatalytic degradation of the linuron herbicide as a target pollutant in aqueous solution. The TiO2 pillared montmorillonite (Mont-TiO2) was characterized by X-ray photoelectron spectroscopy (XPS), X-Ray diffraction (XRD), X-Ray fluorescence (XRF), scanning electronic microscopy (SEM), thermogravimetry and differential thermal analysis (TG-DTA), Fourier transformed infra-red (FT-IR), specific area and porosity determinations. This physicochemical characterization pointed to successful TiO2 pillaring of the clay. The prepared material has porous structure and exhibit a good thermal stability as indicated by its surface area after calcination by microwave. The effects of operating parameters such as catalyst loading, initial pH of the solution and the pollutant concentration on the photocatalytic efficiency and COD removal  were evaluated. Under initial pH of the solution around seven, pollutant concentration of 10 mg/L and 2.5 g/L of catalyst at room temperature, the degradation efficiency and COD removal of linuron was best then the other operating conditions. It was observed that operational parameters play a major role in the photocatalytic degradation process. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0). 

Can Water Dilution Avoid Flashback On a Hydrogen Enriched Micro Gas Turbine Combustion? – A Large Eddy Simulations Study

2021 ◽  
Author(s):  
Alessio Pappa ◽  
Laurent Bricteux ◽  
Pierre Bénard ◽  
Ward De Paepe
Keyword(s):  
Reaction Rates ◽  
Hydrogen Combustion ◽  
Operating Conditions ◽  
Large Eddy Simulations ◽  
Reference Case ◽  
Large Eddy ◽  
Pure Methane ◽  
The Impact ◽  
Water Dilution ◽  
Air Humidification

Abstract Considering the growing interest in Power-to-Fuel, i.e. production of H2 using electrolysis to store excess renewable electricity, combustion-based technologies still have a role to play in the future of power generation. Hydrogen combustion is well-known to lead to combustion instabilities. The high temperatures and reaction rates can potentially lead to flashback. In the past, combustion air humidification has proven effective to reduce temperatures and reaction rates. Therefore, humidification can open a path to stabilize hydrogen combustion. However, accurate data assessing the impact of humidification on the combustion is still missing for real mGT combustor geometries and operating conditions. This paper presents a comparison between pure methane and hydrogen enriched methane/air combustions, with and without air humidification, in a typical mGT combustion chamber (Turbec T100) using Large Eddy Simulations analysis. In a first step, the necessary minimal water dilution, to reach stable combustion with hydrogen, was assessed using a 1D approach. The one-dimensional unstretched laminar flame is computed for both pure methane (reference case) and hydrogen enriched cases. The results of this comparison show that the same level of flame speed as in the reference case can be reached by adding 10% (in mass fraction) of water. In a second step, high fidelity LES on the 3D geometry are performed to show that water dilution helped to lower the temperature and reaction rate of hydrogen at same levels as reference case, and thus prevents flashback, enabling the use of hydrogen blends in the mGT.

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