scholarly journals Effects of NO<sub>2</sub> and C<sub>3</sub>H<sub>6</sub> on the heterogeneous oxidation of SO<sub>2</sub> on TiO<sub>2</sub> in the presence or absence of UV–Vis irradiation

2019 ◽  
Vol 19 (23) ◽  
pp. 14777-14790 ◽  
Author(s):  
Biwu Chu ◽  
Yali Wang ◽  
Weiwei Yang ◽  
Jinzhu Ma ◽  
Qingxin Ma ◽  
...  
Keyword(s):  
Active Sites ◽  
Heterogeneous Reaction ◽  
Reaction System ◽  
Heterogeneous Reactions ◽  
Heterogeneous Oxidation ◽  
Inorganic Species ◽  
Sulfate Formation ◽  
Dark Conditions ◽  
Diffuse Reflectance Infrared ◽  
Reaction Processes

Abstract. The heterogeneous reactions of SO2 in the presence of NO2 and C3H6 on TiO2 were investigated with the aid of in situ diffuse reflectance infrared fourier transform spectroscopy (DRIFTS) under dark conditions or with UV–Vis irradiation. Sulfate formation with or without the coexistence of NO2 and/or C3H6 was analyzed with ion chromatography (IC). Under dark conditions, SO2 reacting alone resulted in sulfite formation on TiO2, while the presence of parts per billion (ppb) levels of NO2 promoted the oxidation of SO2 to sulfate. The presence of C3H6 had little effect on sulfate formation in the heterogeneous reaction of SO2 but suppressed sulfate formation in the heterogeneous reaction of SO2 and NO2. UV–Vis irradiation could significantly enhance the heterogeneous oxidation of SO2 on TiO2, leading to copious generation of sulfate, while the coexistence of NO2 and/or C3H6 significantly suppressed sulfate formation in experiments with UV–Vis lights. Step-by-step exposure experiments indicated that C3H6 mainly competes for reactive oxygen species (ROS), while NO2 competes with SO2 for both surface active sites and ROS. Meanwhile, the coexistence of NO2 with C3H6 further resulted in less sulfate formation compared to introducing either one of them separately to the SO2–TiO2 reaction system. The results of this study highlighted the complex heterogeneous reaction processes that take place due to the ubiquitous interactions between organic and inorganic species and the need to consider the influence of coexisting volatile organic compounds (VOCs) and other inorganic gases in the heterogeneous oxidation kinetics of SO2.

scholarly journals Effects of NO<sub>2</sub> and C<sub>3</sub>H<sub>6</sub> on the heterogeneous oxidation of SO<sub>2</sub> on TiO<sub>2</sub> in the presence or absence of UV irradiation

2019 ◽  
Author(s):  
Biwu Chu ◽  
Yali Wang ◽  
Weiwei Yang ◽  
Jinzhu Ma ◽  
Qingxin Ma ◽  
...  
Keyword(s):  
Uv Irradiation ◽  
Active Sites ◽  
Heterogeneous Reaction ◽  
Reaction System ◽  
Heterogeneous Reactions ◽  
Heterogeneous Oxidation ◽  
Inorganic Species ◽  
Sulfate Formation ◽  
Dark Conditions ◽  
Reaction Processes

Abstract. The heterogeneous reactions of SO2 in the presence of NO2 and C3H6 on TiO2 were investigated with the aid of in situ DRIFTS under dark conditions or with UV irradiation. Sulfate formation with or without the coexistence of NO2 and/or C3H6 was analyzed with IC. Under dark conditions, SO2 reacting alone resulted in sulfite formation on TiO2, while the presence of ppb levels of NO2 promoted the oxidation of SO2 to sulfate. The presence of C3H6 had little effect on sulfate formation in the heterogeneous reaction of SO2 but suppressed sulfate formation in the heterogeneous reaction of SO2 and NO2. UV irradiation could significantly enhance the heterogeneous oxidation of SO2 on TiO2, leading to a copious generation of sulfate, while the coexistence of NO2 and/or C3H6 significantly suppressed sulfate formation in experiments with UV lights. Step-by-step exposure experiments indicated that C3H6 mainly competes for reactive oxygen species (ROS), while NO2 competes with SO2 for both surface active sites and ROS. Meanwhile, the coexistence of NO2 with C3H6 further resulted in less sulfate formation compared to introducing either one of them separately to the SO2-TiO2 reaction system. The results of this study highlighted the complex heterogeneous reaction processes that take place due to the ubiquitous interactions between organic and inorganic species, and the requirement to consider the influence of coexisting VOCs and other inorganic gases in the heterogeneous oxidation kinetics of SO2.

scholarly journals Kinetics and mechanism of heterogeneous oxidation of sulfur dioxide by ozone on surface of calcium carbonate

2006 ◽  
Vol 6 (9) ◽  
pp. 2453-2464 ◽  
Author(s):  
L. Li ◽  
Z. M. Chen ◽  
Y. H. Zhang ◽  
T. Zhu ◽  
J. L. Li ◽  
...  
Keyword(s):  
Heterogeneous Reaction ◽  
Global Climate ◽  
Chemical Properties ◽  
Heterogeneous Oxidation ◽  
Reactive Component ◽  
Rate Determining Step ◽  
Important Pathway ◽  
Sulfate Formation ◽  
Heterogeneous Formation ◽  
Diffuse Reflectance Infrared

Abstract. Sulfate particles play a key role in the air quality and the global climate, but the heterogeneous formation mechanism of sulfates on surfaces of atmospheric particles is not well established. Carbonates, which act as a reactive component in mineral dust due to their special chemical properties, may contribute significantly to the sulfate formation by heterogeneous processes. This paper presents a study on the oxidation of SO2 by O3 on CaCO3 particles. Using Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), the formation of sulfite and sulfate on the surface was identified, and the roles of O3 and water in oxidation processes were determined. The results showed that in the presence of O3, SO2can be oxidized to sulfate on the surface of CaCO3 particles. The reaction is first order in SO2 and zero order in O3. The reactive uptake coefficient for SO2 [(0.6–9.8)×1014 molecule cm-3] oxidation by O3 [(1.2–12)×1014 molecule cm-3] was determined to be (1.4±0.3)×10-7 using the BET area as the reactive area and (7.7±1.6)×10-4 using the geometric area. A two-stage mechanism that involves adsorption of SO2 followed by O3 oxidation is proposed and the adsorption of SO2 on the CaCO3 surface is the rate-determining step. The proposed mechanism can well explain the experiment results. The atmospheric implications were explored based on a box model calculation. It was found that the heterogeneous reaction might be an important pathway for sulfate formation in the atmosphere.

scholarly journals Kinetics and mechanism of heterogeneous oxidation of sulfur dioxide by ozone on surface of calcium carbonate

2006 ◽  
Vol 6 (1) ◽  
pp. 579-613 ◽  
Author(s):  
L. Li ◽  
Z. M. Chen ◽  
Y. H. Zhang ◽  
T. Zhu ◽  
J. L. Li ◽  
...  
Keyword(s):  
Heterogeneous Reaction ◽  
Global Climate ◽  
Chemical Properties ◽  
So2 Oxidation ◽  
Heterogeneous Oxidation ◽  
Reactive Component ◽  
Rate Determining Step ◽  
Sulfate Formation ◽  
Heterogeneous Formation ◽  
Diffuse Reflectance Infrared

Abstract. Sulfate particles play a key role in the air quality and the global climate, but the heterogeneous formation mechanism of sulfates on surfaces of atmospheric particles is not well established. Carbonates, which act as a reactive component in mineral dust due to their special chemical properties, may contribute significantly to the sulfate formation by heterogeneous processes. This paper presents a study on the oxidation of SO2 by O3 on CaCO3 particles. Using Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), the formation of sulfite and sulfate on the surface was identified, and the roles of O3 and water in oxidation processes were determined. The results showed that in the presence of O3, SO2 can be oxidized to sulfate on the surface of CaCO3 particles. The reaction is first order in SO2 and zero order in O3. The reactive uptake coefficient for SO2 oxidation by O3 was determined to be (1.4±0.3)×10−7 using the BET area as the reactive area and (7.7±1.6)×10−4 using the geometric area. A two-stage mechanism that involves adsorption of SO2 followed by O3 oxidation is proposed and the adsorption of SO2 on the CaCO3 surface is the rate-determining step. The proposed mechanism can well explain the experiment results. The atmospheric implications were explored based on a box model calculation. It was found that the heterogeneous reaction might be an important pathway for sulfate formation in the atmosphere.

scholarly journals Effects of temperature on the heterogeneous oxidation of sulfur dioxide by ozone on calcium carbonate

2011 ◽  
Vol 11 (13) ◽  
pp. 6593-6605 ◽  
Author(s):  
L. Y. Wu ◽  
S. R. Tong ◽  
W. G. Wang ◽  
M. F. Ge
Keyword(s):  
Sulfur Dioxide ◽  
Atmospheric Chemistry ◽  
Ambient Pressure ◽  
Oxidation Reactions ◽  
Heterogeneous Oxidation ◽  
Fourier Transform Spectrometry ◽  
Different Temperatures ◽  
Chemistry Modeling ◽  
Sulfate Formation ◽  
Diffuse Reflectance Infrared

Abstract. The heterogeneous oxidation of sulfur dioxide by ozone on CaCO3 was studied as a function of temperature (230 to 298 K) at ambient pressure. Oxidation reactions were followed in real time using diffuse reflectance infrared Fourier transform spectrometry (DRIFTS) to obtain kinetic and mechanistic data. From the analysis of the spectral features, the formation of sulfate was identified on the surface in the presence of O3 and SO2 at different temperatures from 230 to 298 K. The results showed that the heterogeneous oxidation and the rate of sulfate formation were sensitive to temperature. An interesting stage-transition region was observed at temperatures ranging from 230 to 257 K, but it became ambiguous gradually above 257 K. The reactive uptake coefficients at different temperatures from 230 to 298 K were acquired for the first time, which can be used directly in atmospheric chemistry modeling studies to predict the formation of secondary sulfate aerosol in the troposphere. Furthermore, the rate of sulfate formation had a turning point at about 250 K. The sulfate concentration at 250 K was about twice as large as that at 298 K. The rate of sulfate formation increased with decreasing temperature at temperatures above 250 K, while there is a contrary temperature effect at temperatures below 250 K. The activation energy for heterogeneous oxidation at temperatures from 245 K to 230 K was determined to be 14.63 ± 0.20 kJ mol−1. A mechanism for the temperature dependence was proposed and the atmospheric implications were discussed.

scholarly journals Enhanced heterogeneous uptake of sulfur dioxide on mineral particles through modification of iron speciation during simulated cloud processing

2019 ◽  
Vol 19 (19) ◽  
pp. 12569-12585 ◽  
Author(s):  
Zhenzhen Wang ◽  
Tao Wang ◽  
Hongbo Fu ◽  
Liwu Zhang ◽  
Mingjin Tang ◽  
...  
Keyword(s):  
Sulfur Dioxide ◽  
Active Sites ◽  
Bet Surface Area ◽  
Heterogeneous Oxidation ◽  
Oh Groups ◽  
Cloud Processing ◽  
Mineral Particles ◽  
Mineral Aerosols ◽  
Fe Speciation ◽  
Diffuse Reflectance Infrared

Abstract. Iron-containing mineral aerosols play a key role in the oxidation of sulfur species in the atmosphere. Simulated cloud processing (CP) of typical mineral particles, such as illite (IMt-2), nontronite (NAu-2), smectite (SWy-2) and Arizona Test Dust (ATD) is shown here to modify sulfur dioxide (SO2) uptake onto mineral surfaces. Heterogeneous oxidation of SO2 on particle surfaces was firstly investigated using an in situ DRIFTS apparatus (diffuse reflectance infrared Fourier transform spectroscopy). Our results showed that the Brunauer–Emmett–Teller (BET) surface area normalized uptake coefficients (γBET) of SO2 on the IMt-2, NAu-2, SWy-2 and ATD samples after CP were 2.2, 4.1, 1.5 and 1.4 times higher than the corresponding ones before CP, respectively. The DRIFTS results suggested that CP increased the amounts of reactive sites (e.g., surface OH groups) on the particle surfaces and thus enhanced the uptake of SO2. Transmission electron microscopy (TEM) showed that the particles broke up into smaller pieces after CP, and thus produced more active sites. The “free-Fe” measurements confirmed that more reactive Fe species were present after CP, which could enhance the SO2 uptake more effectively. Mössbauer spectroscopy further revealed that the formed Fe phases were amorphous Fe(III) and nanosized ferrihydrite hybridized with Al ∕ Si, which were possibly transformed from the Fe in the aluminosilicate lattice. The modification of Fe speciation was driven by the pH-dependent fluctuation coupling with Fe dissolution–precipitation cycles repeatedly during the experiment. Considering both the enhanced SO2 uptake and subsequent promotion of iron dissolution along with more active Fe formation, which in turn led to more SO2 uptake, it was proposed that there may be a positive feedback between SO2 uptake and iron mobilized on particle surfaces during CP, thereby affecting climate and biogeochemical cycles. This self-amplifying mechanism generated on the particle surfaces may also serve as the basis of high sulfate loading in severe fog–haze events observed recently in China.

scholarly journals The effects of nitrate on the heterogeneous uptake of sulfur dioxide on hematite

2014 ◽  
Vol 14 (8) ◽  
pp. 11577-11623
Author(s):  
L. D. Kong ◽  
X. Zhao ◽  
Z. Y. Sun ◽  
Y. W. Yang ◽  
H. B. Fu ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Diffuse Reflectance ◽  
Significant Contribution ◽  
Chemical Reactivity ◽  
Formation Rate ◽  
White Cell ◽  
Heterogeneous Reactions ◽  
Sulfate Formation ◽  
Diffuse Reflectance Infrared

Abstract. Nitrate is often found to be associated with atmospheric particles. Surface nitrate can change the hygroscopicity of these particles, and thus impact their chemical reactivity. However, the influence of nitrate on the heterogeneous reactions of atmospheric trace gases is poorly understood. In this work, the effects of nitrate on heterogeneous conversion of SO2 with hematite at 298 K were investigated using an in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and a White cell coupled with Fourier transform infrared spectroscopy (White cell-FTIR). It is found that nitrate participates in the heterogeneous reactions of SO2, accelerates the formation rate of sulfate, and leads to the formation of surface-adsorbed HNO3 and gas-phase N2O and HONO, revealing that nitrate has a significant impact on the heterogeneous conversion of SO2 to sulfate. The results indicate that small amounts of nitrate significantly enhance the reactivity of hematite-nitrate mixtures and favor the enhancement in SO2 uptake and an increase in the amount of sulfate on hematite. For mixtures, the sample containing 24% nitrate exhibits the highest sulfate formation rate, and its corresponding average sulfate formation rate is about 5 times higher than that of hematite alone. No uptake of SO2 and formation of sulfate are observed on the pure nitrate. Evidence presented herein implies a significant contribution of the unreleased HNO3 and HONO in the particles for the conversion of SO2 and the enhanced formation of sulfate in the atmosphere. A possible mechanism for the influence of nitrate on the heterogeneous conversion of SO2 on hematite is proposed, and atmospheric implications based on these results are discussed.

scholarly journals Effects of temperature on the heterogeneous oxidation of sulfur dioxide by ozone on calcium carbonate

2011 ◽  
Vol 11 (1) ◽  
pp. 3493-3527 ◽  
Author(s):  
L. Y. Wu ◽  
S. R. Tong ◽  
W. G. Wang ◽  
M. F. Ge
Keyword(s):  
Sulfur Dioxide ◽  
Ambient Pressure ◽  
Oxidation Reactions ◽  
Heterogeneous Oxidation ◽  
Pressure Oxidation ◽  
Model Studies ◽  
Fourier Transform Spectrometry ◽  
Different Temperatures ◽  
Sulfate Formation ◽  
Diffuse Reflectance Infrared

Abstract. The heterogeneous oxidations of sulfur dioxide by ozone on CaCO3 were studied as a function of temperature (230 to 298 K) at ambient pressure. Oxidation reactions were followed in real time using diffuse reflectance infrared Fourier transform spectrometry (DRIFTS) to obtain kinetics and mechanistic data. From the analysis of the spectral features, the formation of sulfate was identified on the surface in the presence of O3 and SO2 at different temperatures from 230 to 298 K. The results showed that the heterogeneous oxidations and the rate of sulfate formation were sensitive to temperature. An interesting stage-transition state was observed at temperatures range from 230 to 257 K, but it became ambiguous gradually above 257 K. The reactive uptake coefficients at different temperatures from 230 to 298 K were acquired for the first time, which can be used directly in the model studies to predict the formation of secondary sulfate aerosol in the troposphere. Furthermore, the rate of sulfate formation had a turning point at about 250 K. The sulfate concentration at 250 K was about twice as large as that at 298 K. The rate of sulfate formation increased with decreasing temperature at temperatures above 250 K, while there is a contrary temperature effect at temperatures below 250 K. The activation energy for heterogeneous oxidations at temperatures from 245 K to 230 K was determined to be 14.63 ± 0.20 kJ mol−1. Mechanism of temperature dependence was proposed and the atmospheric implications were discussed.

scholarly journals The effects of nitrate on the heterogeneous uptake of sulfur dioxide on hematite

2014 ◽  
Vol 14 (17) ◽  
pp. 9451-9467 ◽  
Author(s):  
L. D. Kong ◽  
X. Zhao ◽  
Z. Y. Sun ◽  
Y. W. Yang ◽  
H. B. Fu ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Chemical Reactivity ◽  
Formation Rate ◽  
White Cell ◽  
Heterogeneous Reactions ◽  
Uptake Coefficient ◽  
Sulfate Formation ◽  
Diffuse Reflectance Infrared ◽  
Geometric Surface

Abstract. Nitrate is often found to be associated with atmospheric particles. Surface nitrate can change the hygroscopicity of these particles, and thus impact their chemical reactivity. However, the influence of nitrate on heterogeneous reactions of atmospheric trace gases is poorly understood. In this work, the effects of nitrate on heterogeneous conversion of SO2 with hematite at 298 K are investigated using an in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and a White cell coupled with Fourier transform infrared spectroscopy (White cell-FTIR). It is found that nitrate participates in heterogeneous reactions of SO2, accelerates the formation rate of sulfate, and leads to the formation of surface-adsorbed HNO3 and gas-phase N2O and HONO. The results indicate that low to moderate amounts of nitrate significantly enhance the reactivity of hematite–nitrate mixtures, the uptake of SO2, and the formation of sulfate on hematite. For mixtures, the sample containing 24% nitrate exhibits the highest sulfate formation rate, and its corresponding uptake coefficient calculated by geometric surface area is about 5.5 times higher than that of hematite alone. The sample containing 48% nitrate presents the highest Brunauer–Emmett–Teller (BET) uptake coefficient, and the value is about 8 times higher than that of pure hematite. No uptake of SO2 and formation of sulfate are observed on pure nitrate. Evidence presented herein implies a significant contribution of the unreleased HNO3 and HONO in the particles for the conversion of SO2 and the enhanced formation of sulfate in the atmosphere. A possible mechanism for the influence of nitrate on the heterogeneous conversion of SO2 on hematite is proposed, and atmospheric implications based on these results are discussed.

scholarly journals Heterogeneous reactions of NO<sub>2</sub> with CaCO<sub>3</sub>-(NH<sub>4</sub>)<sub>2</sub>SO<sub>4</sub> mixtures at different relative humidities

2016 ◽  
Author(s):  
Fang Tan ◽  
Shengrui Tong ◽  
Bo Jing ◽  
Siqi Hou ◽  
Qifan Liu ◽  
...  
Keyword(s):  
Diffuse Reflectance ◽  
Heterogeneous Reaction ◽  
Calcium Nitrate ◽  
Heterogeneous Reactions ◽  
Weight Percentage ◽  
Inhibiting Effect ◽  
Promotive Effect ◽  
Dry And Wet Conditions ◽  
Significant Uptake ◽  
Diffuse Reflectance Infrared

Abstract. In this work, the heterogeneous reactions of NO2 with CaCO3-(NH4)2SO4 mixtures with a series of weight percentage (wt%) of (NH4)2SO4 were investigated using a diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) at different relative humidity (RH) values. For comparison, the heterogeneous reactions of NO2 with pure CaCO3 particles and pure (NH4)2SO4 particles, as well as the reaction of CaCO3 with (NH4)2SO4 particles were also studied. The results indicated that NO2 did not show any significant uptake on pure (NH4)2SO4 particles, and it reacted with pure CaCO3 particles to form calcium nitrate at all the RHs investigated. The heterogeneous reactions of NO2 with CaCO3-(NH4)2SO4 mixtures were markedly dependent on RH. Calcium nitrate was formed from the heterogeneous reactions of NO2 with the mixtures under both dry and wet conditions, whereas CaSO4·0.5H2O (bassanite), CaSO4·2H2O (gypsum) and (NH4)2Ca(SO4)2·H2O (koktaite) were produced depending on RH. The NO3− mass concentrations of the CaCO3-(NH4)2SO4 mixtures had a negative linear relation with (NH4)2SO4 mass fraction under dry condition. In this condition, the heterogeneous uptake of NO2 on the mixtures was similar to that on pure CaCO3 particles. The CaCO3-(NH4)2SO4 mixtures exhibited a promotive effect on the heterogeneous uptake of NO2 and the formation of nitrate under wet conditions. Additionally, the reaction between CaCO3 and (NH4)2SO4 was enhanced with increasing RH, and it exhibited an inhibiting effect on the formation of nitrate. On the contrary, the interaction between Ca(NO3)2 and (NH4)2SO4 promoted the nitrate formation during the heterogeneous reaction process. Furthermore, the heterogeneous uptake of NO2 on CaCO3-(NH4)2SO4 mixtures was found to favor the formation of bassanite and gypsum due to the decomposition of CaCO3 and the coagulation of Ca2+ and SO42−. A possible reaction mechanism was proposed and atmospheric implications were discussed.

scholarly journals On the mechanism of catalysis induced by mechano-activation of solid body

2014 ◽  
Vol 32 (4) ◽  
pp. 583-591 ◽  
Author(s):  
Andrzej Kulczycki ◽  
Czesław Kajdas ◽  
Hong Liang
Keyword(s):  
Activation Energy ◽  
Reaction Rate ◽  
Catalytic Effect ◽  
Arrhenius Equation ◽  
Mechanical Energy ◽  
Reaction System ◽  
Heterogeneous Reactions ◽  
A Value ◽  
Mechanism Of Catalysis ◽  
Reaction Processes

AbstractThe paper presents a new model of the mechanism of mechanocatalysis and tribocatalysis. The reason for the increase in heterogeneous catalysis effect after mechanical activation of a catalyst has not been fully understood yet. There is no known theory, which would explain the mechanism of the influence of mechanical energy introduced to catalyst particles on the rate of chemical reaction. All existing theories are based on Arrhenius equation and assume that catalysts increase reaction rate due to decreasing of activation energy E a. We hypothesize that both for standard and catalyzed heterogeneous reactions the same E a (real activation energy) is needed to trigger the reaction processes and the catalytic effect is the result of energy introduced to the reaction system, its accumulation by a catalyst and then emission of high flux of energy to the space near the catalyst particles. This energy emitted by molecules of reagents can reach a value equal to the value of E a at lower ambient temperature than it would result from Arrhenius equation. This hypothesis is based on α i model described in previous papers by Kajdas and Kulczycki as well as the results of tribochemical research described by Hong Liang et al., which demonstrate that the reaction rate is higher than that resulting from temperature.

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