| Volatile organic compounds(VOCs) are existing as vapor at ambient temperature. They may damage the human health and causing cancer while contacting for long terms, due to their stimulation, toxicity and carcinogenicity. VOCs are one of the culprits causing haze as the precursor of PM2.5, which can threaten public health and the environment severely. The ubiquitous VOCs have been paid more and more attentions at home and abroad since they are dangerous to the air. Therefore, it is urgent to control the pollution of VOCs. For the low concentrations of VOCs waste gas which has no value of recycling, the adsorption technology is widely used in petrochemical, electronics, chemical, and other industrial exhaust treatment, owing to its convenient operation and simple process. VOCs emitted have various components in the practical application, so it’s indispensable to explore pollution control methods for two-component or multi-component VOCs. Since the studies of adsorption kinetics and competitive adsorptions on molecular sieve are scarce, it is necessary to carry out researches so as to lay a foundation in industrial scale and production applications.The fixed-bed made by dip method was filled with Cu-Mn-Ce/5A molecular sieve, and the adsorption performances of single and mixed VOCs(toluene, ethyl acetate and acetone) on fixed-bed were investigated in this research. The adsorption kinetics of Cu-Mn-Ce/5A molecular sieve with multi-component VOCs were also analyzed in this study. Based on the experimental study, the results obtained are as follows:(1) In the single factor experiment, the most suitable conditions for toluene adsorption are: C=400mg/m3, Q=0.5m3/h, A=800g.(2) The experiments show that, the major factor in the adsorption performance of Cu-Mn-Ce/5A bed is VOCs polarity. Adsorption performance of toluene, ethyl acetate and acetone on the supported molecular sieve improves with the increasing polarity of the organic molecules.(3) The adsorption of Cu-Mn-Ce/5A can be described by type I isotherm. It is a Langmuir monolayer reversible adsorption process. According to the adsorption isotherms of toluene, ethyl acetate, acetone and the fitting results of Langmuir, it comes to the following results: under the same conditions, the order of adsorption capacity of the three organic compounds is: acetone>ethyl acetate>toluene. Based on the comparison of specific surface area and other indicators, the adsorption capacity of acetone is the best of the three different adsorbates and toluene is the worst.(4) The results also show that the breakthrough process of single VOCs is similar to that of mixed VOCs, whereas the latter’s penetration time is shortened significantly, and the adsorption of per unit mass adsorbent decreases sharply. It exhibits an obvious hump sign in the breakthrough curve, indicating a co-adsorption and competitive adsorption.(5) The Thomas model and Yoon-Nelson model are utilized to fit the results, which show a linear relationship of ln(C/(Co-C)) and t. At the same time, they can reflect the relationship of the two important variables during the adsorption process directly. So it is better applied in simulating adsorption behavior of gas.(6) Yoon-Nelson model can comparatively better simulate adsorption processes of different components of VOCs on Cu-Mn-Ce/5A molecular sieve, which indicates that there is a link between the different outlet concentrations of VOCs and the adsorption time on the Cu-Mn-Ce/5A molecular sieve. In this way, it has practical significance for industrial scale and production applications. |
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