Types Of VOCs Research Articles

Photothermal Catalytic Degradation of VOCs: Mode，System and Application.

Human production and living processes emit excessive VOCs into the atmosphere, posing significant threats to both human health and the environment. The photothermal catalytic oxidation process is an organic combination of photocatalysis and thermocatalysis. Utilizing photothermal catalytic degradation of VOCs can achieve better catalytic activity at lower temperatures, resulting in more rapid and thorough degradation of these compounds. Photothermal catalysis has been increasingly applied in the treatment of atmospheric VOCs due to its many advantages. A brief introduction on the three modes of photothermal catalysis is presented. Depending on the main driving force of the reactions, they can be categorized into thermal-assisted photocatalysis (TAPC),photo-assisted thermal catalysis (PATC) and photo-driven thermal catalysis (PDTC). The commonly used catalyst design methods and reactor types for photothermal catalysis are also briefly introduced. This paper then focuses on recent developments in specific applications for photothermal catalytic oxidation of different types of VOCs and their corresponding principles. Finally, the problems and challenges facing VOC degradation through this method are summarized, along with prospects for future research.

Volatilomics: An emerging discipline within Omics Sciences - A systematic review

Introduction Volatilomics is an omics science that is characterized as being a specific subbranch of metabolomics, which studies the different types of volatile organic compounds that may be present in a certain biological matrix. It has had impacts on the identification of new natural compounds and food safety processes, since it allows the evaluation of emerging contaminants that are present on food matrices, through the identification of biomarkers generated in response to this type of xenobiotic compounds through xenovolatilomic studies. Objective In this way, this review seeks to understand the scientific advances reported towards volatilomic studies, for which different types of primary research are reported depending on the main instrumental techniques used for the characterization of different types of VOCs that have been reported in our country between 2012 and 2022. Methodology Using a qualitative methodology, a search was carried out in the Scopus database, from which the bibliometric information of the primary research reported during this time was obtained, to later analyze the different research concerning the use of volatilomic studies and the fields of action that are currently used, as well as the different techniques for obtaining these compounds and the data analysis methodologies established for the processing of this type of research. Conclusions Finally, it can be concluded that, from the present review, the applicability of volatilomic studies is shown. The incursion carried out by this type of science on the verification of food safety in different types of matrices, in addition to allowing the study of the volatile profile formed by the different volatile organic compounds expressed by said matrix and the respective ecological role expressed by these compounds with the environment in which they are found.

Visible light enhanced selective benzene response of hexagonal atomic structured CuS microcloves

We have reported CuS microcloves (MCs) for highly selective detection of benzene using scanning kelvin probe (SKP) technique. The electron microscopy investigations revealed the formation of clove shaped CuS with a size of about 1–2 µm at 180 °C and 6 h. The time of reaction significantly affected the crystallinity as well as the morphology of resulting CuS materials. The investigations on adsorption behavior of different types of common volatile organic compounds (VOCs) with varying charge and nature revealed an outstanding selectivity towards benzene when compared to other VOCs. The difference in work function between gold tip and sensor surface modified with CuS MCs was decreased under the exposure of light, most likely caused by transfer of electrons to conduction band of CuS under illumination of light. As a result, the CuS MCs showed enhanced photo response in visible light exposure in the presence of benzene. A chemiresistive type sensor device was fabricated using CuS MCs and exposed to benzene vapor in a concentration ranging from 2.8 to 11.2 ppm. The sensitivity was found to be 1.63 × 10-3 ppm−1. Notably, a rapid response time of ∼6 s and recovery time of ∼ 16 s was achieved for the sensor at a benzene concentration of 5.6 ppm at room temperature. Also, considerable and repeatable sensor response was observed for 560 ppb of benzene vapor at 70 °C. Hence, these results suggested that the CuS MCs have huge potential as novel material for selective benzene detection in gas phase towards breath analysis and other environmental monitoring.

Analysis of O3 Sources in Yulin City in Summer Based on WRF-CMAQ/ISAM Model

In order to have a clearer understanding of the sources of ozone pollution in Yulin City in summer and put forward scientific governance suggestions, the WRF-CMAQ model was used to simulate the O3 concentration in Yulin City and surrounding areas (including Taiyuan City, Xi'an City, Yinchuan City, Hohhot City, and other provincial capital cities) in July 2019. Using the ISAM module, the sources of O3 and its precursors NOx and VOCs in a heavy pollution process in Yulin City were quantified. The results showed that on heavy pollution days, the O3 in Yulin City mainly came from the long-distance transmission outside the simulation area (55.5%), followed by the photochemical reaction of precursors in the simulation area (20.6%, 10.0%, 5.0%, 2.3%, and 2.1%, respectively, in Yulin City, Shanxi Province, Inner Mongolia Autonomous Region, and Shaanxi Province, 1.2% in Gansu Province, Ningxia Hui Autonomous Region, and Henan Province in total), and initial conditions (0.3%); the remaining sources (23.6%) could not be successfully labeled. Yulin City is in the VOCs control area, and its VOCs were composed of paraffin (76.5%), ketones (9.2%), and other types of VOCs (14.3%). The VOCs came from the emission of pollution sources in the simulation area (45.6%, 22.0%, 11.4%, 6.3%, and 5.1%, respectively, in Yulin City, Shanxi Province, Inner Mongolia Autonomous Region, and Shaanxi Province, 0.8% in Gansu Province, Ningxia Hui Autonomous Region, and Henan Province in total) and the long-distance transmission outside the simulation area (27.9%); the remaining 26.5% were not successfully marked. This research showed that to control the O3 pollution in Yulin, not only should the local VOCs emissions be controlled, but the overall planning of VOCs emissions in the peripheral areas should also be done well.

Metals incorporated into OMS-2 lattice create flexible catalysts with highly efficient activity in VOCs combustion

Catalytic combustion of different types of VOCs with various functional groups generally requires certain catalysts with high efficiency. Here, a novel manganese oxide catalyst was tuned via incorporation of small amounts of different metals, including Ce, Ir, Ag, Pd, Cu and Fe respectively, exhibiting flexible activity in the abatement of different VOC species. Pd and Ag doping was beneficial for toluene oxidation, while the addition of Cu significantly enhanced the acetone elimination performance, and Ir incorporation boosted the removal of dichloromethane. XRD, Raman, and TEM results revealed that the different metal ions were well-dispersed into the lattice of OMS-2. Elemental mapping images and ICP-OES combined with DFT calculations demonstrated that Ce, Ir, Pd, Cu and Fe were incorporated into OMS-2 by substituting for Mn on octahedral sites, and Ag could be stabilized in the tunnel of OMS-2 via replacing K ions. EXAFS results suggested that the local tunnel structures of OMS-2 were almost intact after incorporation of the different metals. Pd-OMS-2 and Ag-OMS-2 exhibited excellent activity in catalytic oxidation of toluene due to the improved reducibility and mobility of oxygen. Cu ions improved the scission of CC bonds in acetone and Ir ions facilitated the cleavage of the CCl bond in dichloromethane, all of which contributed to their highly specific activity in removal of the corresponding VOCs. This work provides information on the production of highly efficient metal sites for catalytic oxidation of specific VOC species, and may assist with the design of flexible catalysts for control of miscellaneous VOCs.

Research on the Progress of VOCs Adsorption by Biomass Nanocomposites

The avoidance and control of the air is forthcoming, and its deterioration sources have a wide range of origin. Among them, the emission of VOCs is worthy of our attention. Its source is very wide, which seriously define the improvement of green chemical industry in our country. There are many types of VOCs, and when the concentration is too high, it will cause serious harm to the human body. Therefore, the avoidance and control of VOCs gas has become one of the current research tosspots. In this paper, several methods for alter VOCs gas are related, and it is found that adsorption is more economical and safer, and the core is the preparation of adsorbents. At the same time, the preparation of high-performance VOCs adsorbents based on TiO2 as the matrix and manganese-based as the raw material of biomass waste is also prospected.

Adsorption of Volatile Organic Compounds Onto Biomass-Derived Activated Carbons: Experimental Measurement and Comparison

Abstract Volatile organic compounds (VOCs) are a class of hazardous gaseous materials emitted from certain solids or liquids. They are thought to possess serious short- or long-term adverse effects on human health. Nowadays, an energy-efficient and cost-effective volatile organic compound removal system is of absolute necessity due to its adverse effects. In this regard, solar or waste heat-driven adsorption-based technologies can provide an energy-efficient system; however, most of the time, their utilization is limited by the high cost of the adsorbent materials. Right now, only one commercial high-grade activated carbon named Maxsorb III is known to have high capturing capacities. The purchasing cost of this adsorbent is very high, and it is derived from a non-renewable source. Therefore, this study is intended for the quest for low-priced biomass-derived activated carbons for an energy-efficient and cost-effective VOCs removal system. Two biomass-derived activated carbons synthesized from mangrove wood and waste palm trunk precursors are chosen, and four types of VOCs (ethanol, dichloromethane, acetone, and ethyl acetate) adsorption onto them are measured experimentally using the inverse gas chromatography technique. The zero uptake adsorption enthalpy and specific entropy of the adsorption are theoretically computed for all the adsorbent/adsorbate pairs. After that, these data are compared with the obtained data for Maxsorb III to assess the performance of the biomass-derived activated carbons. Results show that, for all the VOCs, the cost-effective mangrove-based activated carbon can be an excellent alternative to the high-priced Maxsorb III when employed as an adsorbent material for VOCs removal.

Discrimination of Pineapples Varieties based on Volatile Organic Compounds using Chromatographic and Chemometrics Analysis

This study analyzed the volatile organic compounds (VOCs) of four different pineapple varieties (MD2, Sarawak, Josephine and Morris). Head Space-Solid Phase Micro Extraction (HS-SPME) was used to extract the VOCs of those pineapples using Gas Chromatography-Mass Spectrometry (GC-MS). Analysis of pineapples extracts identified many types of VOCS including esters, alcohols, terpenes, aldehydes, ketones, saturated hydrocarbons and phenols. Thirtyfive selected VOCs were used for varietal discrimination using chemometrics techniques namely principal components analysis (PCA), cluster analysis (CA) and discriminant analysis (DA). The application of PCA and CA was able to group the pineapple samples according to their varieties based on their respective VOCs. Standard mode DA had discriminated the samples with 98.75% correctness using all 35 VOCs. The identification of significant compounds found in the studied samples was successfully confirmed (p<0.05) by PCA. The total variance of PC1 and PC2 is 63.34% exhibiting that the ester compounds show strong and moderate loading values. One of the unique identifiers is the presence of β-Myrcene with a loading value 0.93 found in PC1 where it is described as pleasant terpenes odor and balsamic descriptor. GCMS and chemometric techniques provided meaningful chemically quantitative data.

In-situ regulation of acid sites on Mn-based perovskite@mullite composite for promoting catalytic oxidation of chlorobenzene

A series of Sm-Mn perovskite@mullite composites with different amounts of acid sites were successfully synthesized by regulating the level of in situ etched-surface modification. X-ray diffraction (XRD) test showed that the crystal structure of catalyst gradually changed from perovskite to perovskite@mullite composites and mullite. The characterization of temperature programmed desorption with ammonia (NH3-TPD) confirmed the acid sites on the surface of catalyst can be deployed by the in-situ modification. The temperature-programmed reduction with hydrogen (H2-TPR), and N2 adsorption–desorption showed that the surface modification also increased the reducibility, surface area, and mesoporosity of catalyst. The catalytic activities were compared by a long-term catalytic oxidation of chlorobenzene evaluation for 20 h of uninterrupted reaction at a relatively low temperature of 300 °C, and the Sm-Mn perovskite@mullite composite (SMPM-1.2) possessed the best catalytic stability. The X-ray photoelectron spectroscopy (XPS) measurement determined that the high ratios of lattice oxygen and tetravalent manganese did not improve the stability of catalyst in the catalytic oxidation of chlorobenzene, but the activities trends of samples were consistent with the change of surface (Mn4++Mn3+)/Mn2+ ratios. Meanwhile, the catalytic experiments for benzene, toluene, o-xylene and acetone showed that the as-prepared catalyst was also suitable for the efficient removal of the different types of VOCs. This work supplied a method for the further development of high activity catalysts for the removal of VOCs.

Gold and Ceria as Catalysts for VOC Abatement: A Review

Due to its excellent oxygen storage capacity, ceria is a well-known oxidation catalyst. However, its performance in the oxidation of volatile organic compounds can be improved by the introduction of gold. Depending on the type of VOC to be oxidized, the surface of gold nanoparticles and the gold/ceria interface may contribute to enhanced activity and/or selectivity. Choosing a proper preparation method is crucial to obtain optimal gold particle size. Deposition–precipitation was found to be more suitable than coprecipitation or impregnation. For industrial applications, monolithic catalysts are needed to minimize the pressure drop in the reactor and reduce mass and heat transfer limitations. In addition to the approach used with powder catalysts, the method employed to introduce gold in/on the washcoat has to be considered.

Exposure characteristics and risk assessment of VOCs from Chinese residential cooking

In comparison with various restaurant cuisines, common cooking methods are more represented in residential cooking. Rather than the exhaust pipe or the ambient environment in the cooking room, the respiration zone better reflects the health risks for operators. In this study, the concentrations of total volatile organic compound (TVOC) released from six typical cooking methods were monitored online in the respiratory zone, and the VOCs were analysed by GC-MS. The results demonstrated that the intensities of exposure to TVOC for the different cooking methods decreased as follows: stir-frying (3.809 mg/m3) > quick-frying (2.724 mg/m3) > deep-frying (2.465 mg/m3) > boiling (1.161 mg/m3)≈stewing (1.149 mg/m3) > limit in China (0.600 mg/m3) > steaming (0.440 mg/m3). The intense ventilation mode of the ventilator reduced exposure to TVOC by 45–63% relative to the medium mode. Eleven types of VOCs (approximately 200 compounds) were found in Chinese residential cooking fumes, and the predominant contaminants were aldehydes, followed by alkanes, unsaturated aldehydes, alcohols and alkenes. The mass percentage of aromatic hydrocarbons in all VOCs emitted from Chinese residential cooking was only 1%, while the value was 17–48% for commercial restaurants. The results of a health risk assessment revealed that the total potential carcinogenic risk level for VOCs released by six residential cooking methods decreased as follows: deep-frying (5.75) > stir-frying (3.95) > quick-frying (2.94) > stewing (1.99) > boiling (1.73) > steaming (1.48). Chinese residential cooking, and especially deep frying, has potential health impacts for the operator.

Characteristics of Volatile Organic Compounds Pollution and Risk Assessment of Nansi Lake in Huaihe River Basin

This study aimed to investigate the pollution characteristics of the volatile organic compounds in Nansi Lake and evaluate the ecological and health risks. In November 2017, water samples collected from 25 sampling points in Nansi Lake using the purge and trap technique and GC-MS detected 52 types of VOCs. The detection rate of ethylbenzene, m-/p-xylene, o-xylene, 1,2-dichlorobenzene, and naphthalene reached 100%, and cis-1,3-dichloropropene and toluene reached 96%. The detection rate of 1,2,4-trimethyl benzene was the lowest, at only 12%, the average concentration of 1,2-dichlorobenzene was the highest, reaching 3.49 μg·L-1, and 1,2,4-trimethyl benzene was only 0.02 μg·L-1. The concentration of 1,2-dichlorobenzene in Nansi Lake was generally higher than that of other VOCs. Meanwhile, the concentrations of m-/p-xylene and ethylbenzene at point NSH-24 far exceeded the other VOCs, but the median value of all VOCs did not exceed 4 μg·L-1. The spatial distribution of the VOCs concentrations in Nansi Lake presented high values in the northwest and southeast, and low in the middle. The leading cause of VOCs pollution in Nansi Lake may be the exhaust gas emitted by shipping vessels during navigation, and the secondary cause is the collection of VOCs in the upstream and downstream tributaries and the influence of human factors. The health risk assessment of Nansi Lake found that, overall, there was no carcinogenic or non-carcinogenic health risk, but the risk value of individual points was relatively high, even exceeding the risk threshold set by the US EPA. There were 12 points in Nansi Lake where the ecological risk quotient exceeded 1, indicating an ecological risk to aquatic organisms.

The emission characteristic of VOCs and the toxicity of BTEX from different mosquito-repellent incenses

Three types of mosquito-repellent incenses including disc, electric liquid and electric mat, were selected to investigate the emission of volatile organic compounds in the respiratory zone during the burning. VOCs were analyzed by GC–MS. Results showed that the average concentration of TVOCs released by using the disc, electric liquid and electric mat mosquito repellent incense types were 7.760 ± 4.724, 3.122 ± 0.866 and 1.192 ± 0.062 mg/m3, respectively. The TVOCs pollution level produced during the burning of different mosquito-repellent incense types was ranked in the order: disc > electric liquid > electric mat. The concentration of TVOCs produced by Q-liquid, L-liquid, Q-disc and L-disc mosquito-repellent incense types could cause discomfort to the human body. Other types of mosquito-repellent incense induced multiple synergistic effects on human response. About 230 kinds of VOCs including 14 types of VOCs, were found in the smoke of mosquito-repellent incense. The number and content of alkanes was the highest, followed by aromatic hydrocarbons and esters. The level of non-carcinogenic health risk presented by exposure to BTEX (toluene, xylene and ethylbenzene) was acceptable. The chronic daily intake of VOCs decreased with age for both males and females, with male exposure being higher than that of the female, except for children.

Risk assessment of inhalation exposure to VOCs in dwellings in Chongqing, China.

This paper investigated the concentrations of eight types of indoor VOCs - benzene, toluene, xylenes, butyl acetate, styrene, isopropylbenzene, undecane and formaldehyde. The tests were carried out in 50 dwellings in the main urban areas of Chongqing, China. According to the detected concentration, toluene was the most predominant among all the targeted compounds. Benzene and formaldehyde concentrations were lower than the reference levels regulated by the Chinese National Standard (GB/T 50325). Based on the activity patterns and exposure factors of adults in urban Chongqing, we used concentration data to estimate adults' inhalation exposures as well as health risks using Monte-Carlo simulations. The results indicated that the exposure doses of benzene and formaldehyde exceeded the benchmark. The highest hazard quotient (HQ) values were found in the case of formaldehyde (median = 0.293 for females and 0.292 for males) and the hazard index (HI) values were 0.326 and 0.325 for females and males, respectively. The highest lifetime cancer risk (LCR) values were found in formaldehyde (median = 7.16 × 10-5 for females; 6.56 × 10-5 for males). Formaldehyde was found to be the most important pollutant with relatively high toxic and carcinogenic risk levels, based on the exposure and health assessment. This was followed by benzene, toluene, xylenes and butyl acetate. This study can help us better understand the concentration levels of VOC contaminants in residential buildings, and help select appropriate decoration materials for buildings.

Desorption behavior of various volatile organic compounds from activated carbon in supercritical carbon dioxide: Measurement and kinetic modeling

The desorption behavior of various volatile organic compounds (VOCs: toluene, acetone, n-hexane, n-octane, methanol, ethanol, 2-propanol, and propylene glycol monomethyl ether) from activated carbon was measured in supercritical carbon dioxide (scCO2) using the fixed-bed method at 313–353K and 10.0–15.0MPa. The measured behavior strongly depended on the type of VOC, and the CO2 density and volatility of the VOCs were the primary factors influencing this behavior. The desorption behavior was correlated with a kinetic model that assumed material balances in the bulk and pore phases with local adsorption equilibria in the adsorbed phase. The fitting parameters determined using these correlations were reasonably explained by the CO2 density and properties of VOCs, and they provided quantitative information about the desorption phenomena in scCO2.

Oxidation of mixtures of ethyl acetate and butyl acetate over cryptomelane and the effect of water vapor

The catalytic oxidation of binary VOC mixtures, ethyl acetate, and butyl acetate, and the effect of water vapor on their oxidation, was studied over manganese oxide–cryptomelane‐type catalyst. This catalyst, prepared by a novel solid‐state reaction with ball milling, was shown to be very active for the oxidation of ethyl acetate and butyl acetate, promoting their complete oxidation at relatively low temperatures, the CO2 yield being influenced by the type of VOC. The mixture with equal amounts of each ester shows a light‐off curve similar to that observed for butyl acetate alone, but the light‐off curves are shifted to higher temperatures when different proportions of these VOCs are present in the mixture. When processing VOC mixtures, the temperature required for 100% CO2 yield depends on the VOC, which is in larger amount. Water vapor also has a significant effect on the oxidation of these VOCs, particularly in the case of ethyl acetate. © 2016 American Institute of Chemical Engineers Environ Prog, 35: 1324–1329, 2016

Effects of calcination and support on supported manganese catalysts for the catalytic oxidation of toluene as a model of VOCs

The conventional impregnation method was used to prepare 15 wt% Mn-supported catalysts, which were applied to the catalytic oxidation of volatile organic compounds (VOCs; toluene, benzene, and o-xylene). The effects of calcination temperatures in the range of 500–900 °C and supports (γ-Al2O3, SiO2, and TiO2) on the property and performance of 15 wt% Mn-supported catalysts were investigated. Their physicochemical characteristics were analyzed by the BET, XRD, NH3–TPD, H2–TPR, and XPS. The calcination temperature greatly affected the crystalline structure and O1s D (defect oxides)/O1s L (lattice oxides) area ratio of the 15 wt% Mn/γ-Al2O3 (15 Mn/Al) catalyst. The order of the O1s D/O1s L area ratios of the 15 Mn/Al catalysts with respect to calcination temperature was 900 > 500 > 700 °C, which was in good agreement with that observed for the catalytic activity. In addition, the activity order of the 15 wt% Mn-supported catalysts with respect to the type of support was γ-Al2O3 > SiO2 > TiO2. The 15 wt% Mn/Al catalyst, which had a higher O1s D/O1s L area ratio, showed better activity than the 15 wt% Mn/SiO2 (15 Mn/Si) and 15 wt% Mn/TiO2 (15 Mn/Ti) catalysts. Defect oxides played a significant role in the catalytic oxidation of VOCs. The catalytic activity with respect to the type of VOC decreased in the order of benzene > toluene > o-xylene.

Diurnal variation of volatile organic compounds emitted from Cinnamomum camphora flowers

In order to make clear the diurnal variation of plant volatiles，we collected the VOCs from Cinnamomum camphora flowers using the dynamic headspace air-circulation method at 7：30，10：00，12：30，15：00 and 17：30，identified the main compounds of VOCs with thermal desorption system/gas chromatography/mass spectrum （TDS-GC-MS）. Results showed that C. camphora flowers emitted 51 types of VOCs，mainly as terpenoids. At 15：00，species and emission of the VOCs were highest （40 species and 8 049.5 peak area units），mainly as linalool （relative content 37.0%），epoxylinalol （12.7%）， （Z-ocimene （7.2%） and perillene（6.2%）. Thus，increases in species and emissions of the VOCs from C. camphora flowers at 15：00 are both visibly increased revealed a possible affinity have strong relevance for strong light and high temperature stress. ［Ch，3 fig. 1 tab. 15 ref.］

Optical detection of volatile organic compounds using selective tensile effects of a polymer-coated fiber Bragg grating

We demonstrated a novel selective chemical sensing approach by incorporating a poly(dimethylsiloxane) (PDMS)-coated fiber Bragg grating (FBG) structure for optically detecting various volatile organic compounds (VOC's). When the proposed structure is exposed to a nonpolar solvent, a tensile stress is induced between the coated PDMS and the optical fiber by a VOC-dependent swelling effect of the PDMS, which results in a Bragg wavelength shift dependent on the concentration and the type of VOC's. Because of no need of an etching process of a fiber cladding, the proposed PDMS-coated FBG can be used as a simple, convenient, and durable chemical sensing element with a high sensitivity, compared with conventional FBG sensors requiring an evanescent wave coupling.

Development of the SAPRC-07 chemical mechanism

Abstract An updated version of the SAPRC-99 gas-phase atmospheric chemical mechanism, designated SAPRC-07, is described. The rate constants and reactions have been updated based on current data and evaluations, the aromatics mechanisms have been reformulated and are less parameterized, chlorine chemistry has been added, the method used to represent peroxy reactions has been reformulated to be more appropriate for modeling gas-phase secondary organic aerosol precursors, and representations for many types of VOCs have been added or improved. This mechanism was evaluated against the result of ∼2400 environmental chamber experiments carried out in 11 different environmental chambers, including experiments to test mechanisms for over 110 types of VOCs. The performance in simulating the chamber data was generally satisfactory for most types of VOCs but some biases were seen in simulations of some types of experiments. The mechanism was used to derive updated MIR and other ozone reactivity scales for almost 1100 types of VOCs, though in most cases the changes in MIR values relative to SAPRC-99 were not large. This mechanism update results in somewhat lower predictions of ozone in one-day ambient model scenarios under low VOC/NOx conditions. The files needed to implement the mechanism and additional documentation is available at the SAPRC mechanism web site at http://www.cert.ucr.edu/∼carter/SAPRC .