[Hydrolysis of COS over MgAl Mixed Oxides Derived from Hydrotalcites].

A series of MgAl hydrotalcite-derived composite oxides were prepared by co-precipitation methods. The effects of calcination temperature, reaction temperature, water vapor volume fraction, and alkali metal addition on the hydrolysis activity of the samples were investigated. The crystal structure, specific surface area, pore structure, and basic position distribution of the composite oxides were characterized using XRD, BET, TPD, and XPS. The results shown that the catalytic activity firstly increased and then decreased with the rise of calcination temperature. Furthermore, the sample that calcined at 650℃ can achieve the best catalytic activity (complete removal of COS lasted for 180 min). Increasing the reaction temperature improved the catalytic activity, which can present excellent catalytic activity and stability at temperatures above 70℃. In addition, the doping of the alkali metal Cs improved the catalytic activity, the complete removal time for COS can be maintained for 480 min.

[Source Apportionment and Health Risk Assessment of VOCs During the Haze Period in the Winter in Beijing].

A method for determining volatile organic compounds (VOCs) by cryogenic dynamic adsorption in solid adsorbent tubes, subsequent thermal desorption with cryofocusing in a cold trap and analysis by gas chromatography and mass spectrometry was adapted for continuous ambient air monitoring. VOCs pollution characteristics and health risk assessment (HRA)were researched in detail. Moreover, the sources apportionment was reliably analyzed by positive matrix factorization (PMF) model. The results showed that the average concentration of VOCs was 332.34 µg·m-3 per day, the concentrations of aromatic hydrocarbon and halo hydrocarbon were remarkably high compared to the other VOCs. Particularly, the PMF analysis results revealed that solvent/paint use emission, biomass or coal combustion and motor vehicle exhaust emissions were the main pollutants emission sources. Additionally, the cancer risk index of all carcinogenic substances was higher than the suggested value of USEPA(1×10-6), which could cause potential harm to human health.

[Comparison Analysis of Economic and Engineering Control of Industrial VOCs].

Volatile organic compounds (VOCs) pollutant has become China's major air pollutant in key urban areas like sulfur dioxide, nitrogen oxides and particulate matter. It is mainly produced from industry sectors, and engineering control is one of the most important reduction measures. During the 12th Five-Year Plan, China decides to invest 40 billion RMB to build pollution control projects in key industry sectors with annual emission reduction of 605 000 t x a(-1). It shows that China attaches a great importance to emission reduction by engineering projects and highlights the awareness of engineering reduction technologies. In this paper, a macroeconomic model, namely computable general equilibrium model, (CGE model) was employed to simulate engineering control and economic control (imposing environmental tax). We aim to compare the pros and cons of the two reduction policies. Considering the economic loss of the whole country, the environmental tax has more impacts on the economy system than engineering reduction measures. We suggest that the central government provides 7 500 RMB x t(-1) as subsidy for enterprises in industry sectors to encourage engineering reduction.

[Evaluation and selection of VOCs treatment technologies in packaging and printing industry].

Volatile organic compounds (VOCs) play an important role in urban air pollution. Activities of industries including the packaging and printing industries are regarded as the major sources. How to select the suitable treating techniques is the major problem for emission control. In this article, based on the VOCs emission characteristics of the packaging and printing industry and the existing treatment technologies, using the analytic hierarchy process (AHP) model, an evaluation system for VOCs selection was established and all the technologies used for treatment were assessed. It showed that the priority selection was in the following order: Carbon Fiber Adsorption-Desorption > Granular Carbon Adsorption-Desorption > Thermal Combustion > Regenerative Combustion > Catalytic combustion > Rotary adsorption-concentration and combustion > Granular Carbon adsorption-concentration and combustion. Carbon Fiber Adsorption-Desorption was selected as the best available technology due to its highest weight among those technologies.

[Selective catalytic oxidation of H2S over supported Fe catalysts on CeO2-intercalated laponite clay].

A series of Fe/CeO2-intercalated clay catalysts were synthesized successfully, the physicochemical properties of the catalysts were characterized by XRD, BET, XRF, TG, FT-IR, O2-TPD, H2-TPR and XPS methods. The catalytic performances for selective catalytic oxidation of H2S were further investigated, all catalysts exhibited high catalytic activities. Among them 5% Fe/Ce-Lap presented the best activity at 180 degreeC and the maximum sulfur yield was up to 96% due to the interaction between iron and cerium, which improved the redox ability of Fe3+ . Moreover, the strong oxygen adsorption capacity and the well dispersion of iron species improved the catalytic performance efficiently.

[Fe-ZSM-5 catalysts with different silica-alumina ratios for N2O, catalytic decomposition].

The Fe-ZSM-5 catalysts were prepared with H-ZSM-5 of different Si/Al ratios by wet ion exchange and chemical vapor deposition. Then the catalysts were investigated by XRD, BET, TEM, UV-vis and NH3-TPD technologies to analyze the iron states in Fe-ZSM-5 zeolites. The results showed that after H-ZSM-5 zeolites were prepared by chemical vapor deposition and heating wet ion exchange, the nano Fe2 O3 particles were uniformly dispersed with the sizes of 8 nm in the Fe-ZSM-5-25 (Si/A1-25). Moreover, there were more oligonuclear Fe3+ Oy clusters in the Fe-ZSM-5-25 catalysts than in Fe-ZSM-5-300 (Si/Al-300). The results of catalytic performance on N2O decomposition showed that Fe-ZSM-5-25 catalysts had higher catalytic activities than Fe-ZSM-5-300 catalysts. The Fe-ZSM-5 catalysts prepared by chemical vapor deposition achieved the best catalytic activity in N2O decomposition among the catalysts prepared by the three methods. Moreover, the presence of O2 only slightly reduced N2O conversion, while NO promoted the N2O decomposition. Finally, after reaction for more than 100 h, Fe-ZSM-5 catalyst showed no obvious deactivation under simulated emission conditions.

[Study of VOCs emission prediction and control based on dynamic CGE].

Researches on controlling volatile organic compounds (VOCs) through macroeconomic policy from the view of cost-benefit analysis are very important for our country to improve the air environment. Based on our previous study, this paper predicted future VOCs emissions until 2020 under current policies with 2007 as reference year by using dynamic CGE model. Meanwhile, environmental tax was imposed in ten industries with high emission and the impacts of emissions and economic system were discussed. Finally, policy implementations for VOCs emission control were suggested for policy-makers. The results showed that environment tax could mitigate VOCs emission, but it also resulted in high cost. Owing to the highly related relationship between different sectors, although transport sector was not taxed, it also suffered a great economic influence. Thus, when using the tax policy for reducing VOCs, subsidy for special sector is necessary.

[Current research situation of H2S selective catalytic oxidation technologies and catalysts].

This review summarizes and discusses different selective catalytic oxidation technologies and various catalysts for removing H2S, the undesirable byproduct of the fluid catalytic cracking (FCC) processing. Currently the selective oxidation technologies used include Superclaus, Euroclaus, Clinsulf-Do, BSR/Hi-Activity, Selectox and Modop techniques, which have various characteristics and application areas. Catalysts for H2S selective oxidation mainly contain the following systems: carbon, supported SiC, zeolite, oxide, and pillared clay. Former studies focused on carbon and oxide systems. The research interest on zeolite system decreased in recent years, while SiC is regarded as a typical support with great potential for this reaction and continues to be attractive. Pillared clay system is at the preliminary research stage, and is still far from practical application.

[Study on control and management for industrial volatile organic compounds (VOCs) in China].

Volatile organic compounds (VOCs) emitted from industrial sources account for a large percent of total anthropogenic VOCs. In this paper, VOCs emission characterization, control technologies and management were discussed. VOCs from industrial emissions were characterized by high intensity, wide range and uneven distribution, which focused on Bejing-Tianjin Joint Belt, Shangdong Peninsula, Yangtze River Delta and the Pearl River Delta. The current technologies for VOCs treatment include adsorption, catalytic combustion, bio-degradation and others, which were applied in petrochemical, oil vapor recovery, shipbuilding, printing, pharmaceutical, feather manufacturing and so on. The scarcity of related regulations/standards plus ineffective supervision make the VOCs management difficult. Therefore, it is suggested that VOCs treatment be firstly performed from key areas and industries, and then carried out step by step. By establishing of actual reducing amount control system and more detailed VOCs emission standards and regulations, applying practical technologies together with demonstration projects, and setting up VOCs emission registration and classification-related-charge system, VOCs could be reduced effectively.

[Countermeasures for priority control of toxic VOC pollution].

VOC pollution is worsening, not only affects the environment, air quality, but also directly harm human health, and Chinese relevant departments need to improve control measures. U. S. toxic air pollutants (HAPs) control system was studied, and Chinese environment countermeasures were proposed based on pollution features. U. S. recognized sources of hazardous air pollutants in the Clean Air Act (CAA), and reduced their emissions by industrial regulations and regional policies. In urban areas, VOC occupied a great part of toxic air and were controlled as a major project in U. S. Due to relatively weak management and technical base, China should screen some VOC components for priority pollutant control. The feature of Chinese VOC pollution was described as complex components, industry sources widely distributed, strong regional characteristics and processes, and gradual development of regional pollution. It was suggested to carry out investigation assessment activities, enhance cumulative risk assessment and environmental impact assessment management, and strengthen emergency risk prevention.

[Evaluation of treatment technology of volatile organic compounds for fixed industrial resources].

The reduction of the emission of volatile organic compounds (VOCs) from fixed industrial resources is considered more necessary than before. The traditional treatment techniques, newly developed ones and some combinations of these treatment techniques are reviewed in this paper. The applying conditions, developing trend and existing problems of these techniques are also evaluated.

[Study on foreign regulations and standards of stationary sources VOCs emission control].

By investigating volatile organic compounds (VOCs) emission control regulations and standards of the United States, the European Union and Japan, the suggestions on VOCs emission control and standards formulating in China were presented. Referencing foreign successful environmental management approach and experience, as well as the corresponding regulations and standards, the author believed that China can find a simple and highly effective way for controlling VOCs, through establishing the emission standards system, innovating VOCs emission control approach, improving VOCs emission control efficiency and unifying VOCs monitoring methods.

[VOCs tax policy on China's economy development].

In this paper, environmental tax was designed to control volatile organic compounds (VOCs) emissions. Computable general equilibrium (CGE) model was used to explore the impacts of environmental tax (in forms of indirect tax) on the macro-economy development at both national and sector levels. Different levels of tax were simulated to find out the proper tax rate. It is found out that imposing environmental tax on high emission sectors can cause the emission decreased immediately and can lead to negative impacts on macro-economy indicators, such as GDP (gross domestic products), total investment, total product and the whole consumption etc. However, only the government income increased. In addition, the higher the tax rate is, the more pollutants can be reduced and the worse economic effects can be caused. Consequently, it is suggested that, the main controlling policies of VOCs abatement should be mandatory orders, and low environmental tax can be implemented as a supplementary.

[Health risk assessment of atmospheric volatile organic compounds in urban-rural juncture belt area].

A method for determining volatile organic compounds (VOCs) by cryogenic dynamic adsorption in solid adsorbent tubes, subsequent thermal desorption with cryofocusing in a cold trap and analysis by gas chromatography and mass spectrometry was adapted. An internationally recognized four-step evaluation model of health risk assessment (HRA) was adapted to preliminarily assess the health risks caused by volatile organic compounds (VOCs) in urban-rural juncture belt area in Beijing. Results of HRA indicated that non-carcinogenic risk indexes of VOCs are below 1 and non-carcinogenic risk indexes of aromatic substances range from 10(-4)-10(-5), halohydrocarbons in the 10(-4)-10(-1). Volatile pollutants would not cause non-carcinogenic health hazard to exposed population. However, the cancer risk index exposed to carcinogenic benzene was 2.21 x 10(-5), which is higher than that suggested value of USEPA (1x10(-6)) and may cause potential harm to human health. The greatest health risk is in winter, followed by autumn, summer minimum.

[Pollution and source of atmospheric volatile organic compounds in urban-rural juncture belt area in Beijing].

A method for determining volatile organic compounds (VOCs) by cryogenic dynamic adsorption in solid adsorbent tubes, subsequent thermal desorption with cryofocusing in a cold trap and analysis by gas chromatography and mass spectrometry was adapted. Volatile organic content levels, spatial and temporal distribution and sources were studied. Results indicated that 265 species were detected in atmospheric environment of this area, including alkanes, alkenes, aromatics, halohydrocarbons and oxygenated compounds. The average concentration of VOCs is 431.7 microg x m(-3), followed by aromatics 248.1 microg x m(-3), alkanes 130.5 microg x m(-3) alkenes 11.7 microg x m(-3), halohydrocarbons 22.4 microg x m(-3), oxygenated compounds 18.6 microg x m(-3), respectively. Benzene, toluene, ethylbenzene, xylene and so on have a comparatively high content. Aromatics and alkanes are the most abundant VOCs; Organic pollutants generally occurred at a relatively high level in the morning and evening traffic rush hours. VOCs varied with seasons: winter maximum, followed by autumn, summer minimum. Source analysis showed that atmospheric VOCs mainly come from vehicular exhaust, gasoline evaporation, use of adhesive and solvent and vegetation emission. They accounted for 53.4%, 20.1%, 11.0% and 5.93%, respectively.

Mesoporous Co3O4 and Au/Co3O4 catalysts for low-temperature oxidation of trace ethylene.

Low-temperature catalysts of mesoporous Co(3)O(4) and Au/Co(3)O(4) with high catalytic activities for the trace ethylene oxidation at 0 degrees C are reported in this paper. The catalysts were prepared by using the nanocasting method, and the mesostructure was replicated from three-dimensional (3D) cubic KIT-6 silicas. High resolution transmission electron microscopy (HRTEM) studies revealed that {110} facets were the exposed active surfaces in the mesoporous Co(3)O(4), whereas the Co(3)O(4) nanosheets prepared by the precipitation method exhibited the most exposed {112} facets. We found that the mesoporous Co(3)O(4) was significantly more active for ethylene oxidation than the Co(3)O(4) nanosheets. The results indicated that the crystal facet {110} of Co(3)O(4) played an essential role in determining its catalytic oxidation performance. The synthesized Au/Co(3)O(4) materials, in which the gold nanoparticles were assembled into the pore walls of the Co(3)O(4) mesoporous support, exhibited stable, highly dispersed, and exposed gold sites. Gold nanoparticles present on Co(3)O(4) readily produced surface-active oxygen species and promoted ethylene oxidation to achieve a 76% conversion at 0 degrees C, which is the highest conversion reported yet.

NO(x) decomposition, storage and reduction over novel mixed oxide catalysts derived from hydrotalcite-like compounds.

Effective control and removal of nitrogen oxides (NO(x)) emission from vehicles exhausts under lean-burn condition is one of the most important targets in scientific research of environmental protection. A comprehensive introduction of NO(x) storage and reduction (NSR), the most promising lean-NO(x) control technology, is given including the sum-up of NSR materials, catalytic activity and related reaction mechanisms. Emphasis is put on the novel multifunctional NSR catalysts, derived from hydrotalcite-like compounds, with characteristic of simultaneous NO(x) strorage-decomposition-reduction. Finally, future research directions in the area of lean-NO(x) control based on mixed oxide catalysts derived from hydrotalcite-like materials is also proposed.

Surface charging of layered double hydroxides during dynamic interactions of anions at the interfaces.

In this research, we investigated the effect of dynamic anion adsorption/exchange on the surface charging property of Mg(2)AlClLDH and Mg(2)AlCO(3)LDH particles that show the average zeta potential of 41 and 34 mV in the as-prepared suspension, respectively. The addition of NaCl up to 3x10(-3) M in the suspension does not obviously affect the zeta potential of both LDHs, which can be attributed to the less affinity of Cl(-) to LDH. The introduction of Na(2)CO(3) severely reduces the zeta potential at the CO(3)(2-) concentration higher than 1x10(-4) M, and to the negative value in both LDH systems at ca. 2x10(-3) M, which is presumably resulted from the exchange and the re-orientation of CO(3)(2-) in a tilt/vertical style on the surface. All four organic anions (dodecyl sulfate, folate, citrate and polyacrylate) also significantly affect the zeta potential of the LDH particles. At the lower concentrations of organic anionic groups (<1x10(-4) M), the zeta potential was slightly affected, i.e. limited exchange/adsorption. However, the concentration increasing to some point suddenly decreases and reverses the zeta potential of the LDH particles, which is presumably caused by the hydrophobic interactions that bind the hydrophobic hydrocarbon chains (especially in dodecyl sulfate) into the micelle-like bilayer bunches on the LDH surface. In addition, the effect of pH in 5.5-11.0 on the LDH particle surface charging is mainly reflected through the conversion of CO(3)(2-) to HCO(3)(-)/H(2)CO(3) when pH decreases from ca. 11 to 6, with limited contribution from protonation/deprotonation and exchange/adsorption.

High-temperature adsorption of carbon dioxide on mixed oxides derived from hydrotalcite-like compounds.

Various XnY(3-n)Al-hydrotalcite-like compounds (HTlcs) were synthesized by the constant pH coprecipitation method with the (X2+ + Y2+)/Al3+ molar ratio fixed at 3.0. Well-mixed oxides Xn,Y(3-n)AlO were derived from corresponding HTlcs precursors upon calcination. Physicochemical characterization with X-ray diffraction analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis (TGA), and the Brunauer-Emmett-Teller equation indicates that the derived oxides are of either periclase or spinel phase, with an interparticle pore diameter of 9.6-15.4 nm. These oxides generally show a high CO2 adsorption capability at 350 degrees C. For example, CaCoAlO captures 1.39 mmol/g of CO2 (i.e., 6.12 wt %) from a gas mixture (8% CO2 in N2) at 350 degrees C and 1 atm in a fixed-bed reactor within 20 min. All other mixed oxides adsorb 0.87-1.28 mmol/g (3.83-5.63 wt %) of CO2. Therefore, these mixed oxides are potential cost-effective CO2 sorbents for environmental remediation. In addition, the CO2 adsorption behavior is well-described with the deactivation model. The species of CO2 formed on the sorbents are various carbonates, as revealed by in situ IR spectra as well as TGA.

Fe-USY zeolite catalyst for effective decomposition of nitrous oxide.

Zeolite matrix FAU is applied as an effective support that can be readily exchanged with ferric ions simply by wet ion exchange. The high exchange degree in this zeolite (USY) probably benefits from its larger channel dimension, which makes the diffusion of hydrated ferric ions into the channels easier. The as-prepared and subsequently calcined Fe-USY samples contain various kinds of iron species, which enable Fe-USY to efficiently decompose N2O to N2 and O2. The presence of O2 (20%), H2O (2%), or both reduces the N2O conversion only to a small extent at the same temperature. To test the feasibility and the catalytic activity in a practical situation, we prepared a monolithic Fe-USY/cordierite sample and investigated the N2O conversion under similar conditions. Such a cordierite-supported Fe-USY catalyst (approximately 9 wt % USY and 0.5 wt % Fe) shows the catalytic performance in N20 decomposition similar to the pure Fe-USY catalyst. Remarkably, both the pure Fe-USY and Fe-USY/cordierite catalysts demonstrate a very good durability because there is no activity lost after 100 and 144 h tests. Thus, the Fe-USY zeolite shows its potential as a cost-effective catalyst for N2O elimination in future applications.