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Adsorption Of Esters On Activated Carbons

Posted on:2009-02-18Degree:MasterType:Thesis
Country:ChinaCandidate:B ZhangFull Text:PDF
GTID:2121360242984441Subject:Physical chemistry
Abstract/Summary:PDF Full Text Request
Esters as volatile organic compounds are harmful for human being, which are emitted in many industrial activities. In particular, methyl acrylate (MA) and ethyl acetate (EA) are widely used in industry. Therefore, the investigation for removal of them from the exhaust gas and further for the recovery of them from the exhaust gas is of great importance in terms of economic and social benefic meaning.In this thesis, adsorption of MA and EA on activated carbons was investigated in dynamic adsorption method in the MA/N2 and EA/N2 system, respectively. For the investigation, two kinds of activated carbons, AC and Y2, made from coconut shells, and one kind of activated carbon, C5, made from coal were used. On the activated carbons, the adsorption influenced by the concentration of esters in gas mixtures, adsorption temperature and relative humidity of the gas mixtures was discussed in detail.It indicated that the adsorption isotherm could be described well by the Langmuir-Freundlich model and that the saturated adsorption amount of MA on the AC at 40℃was always the largest among those obtained on the three activated carbons when the volume percentage of MA (ρMA) in the gas mixture was ranged from 0.015 % to 0.34 %. Nevertheless, whenρMA was lower than 0.015 %, Y2 gave the largest adsorption amount in equilibrium. The results indicated that pore structure of activated carbons had much effect on their adsorption capacities. The above adsorption performence of AC and Y2 in different conditions can be interpreted by the abundant micropores and mesopores in AC and the smaller average pores in Y2, respectively. Similar to the case of MA, larger saturated adsorption amount of EA was obsverved on activated carbons AC and Y2 compared to that on C5 at 40℃when the volume concentration of EA (ρEA) in the gas mixture falls in the range of 0.10~0.30 %. In the gas mixture of EA/N2 with a concentration of 0.15 % in volume percentage, the adsorption amount of EA on the activated carbons AC and Y2 were 0.28 g·g-1 and 0.27 g·g-1, respectively. On the other hand, no significant change in the saturated adsorption amount of EA was observered for the activated carbons with modified surface chemistry properties compared to those unmodified activated carbons. These results indicated that the adsorption capacity of activated carbons for EA was mainly determined by the micropore less than 1.70 nm (in diameter) but not surface chemistry of the adsorbents. The influence of temperature on adsorption for MA and EA on AC was studied. The saturated adsorption amount of MA on AC at 40, 30, 20 and 10℃were 0.29, 0.33, 0.35 and 0.37 g·g-1. In the case of EA, the saturation adsorption amount on the activated carbon were 0.27,0.30 and 0.31 g·g-1 at 40, 30 and 20℃in the gas mixture of EA/N2 with a concentration of 0.15 % in volume percentage. As temperature had little effect on the esters adsorption on the activated carbon, it is suggested that the adsorption technique using the activated carbon as adsorbent can be put to use for remove the esters from exhaust at room temperature.Saturated adsorption amount of MA and EA on AC that is as high as 90 % of that achieved in dry conditions was still obtained when an adsorption experiment was conducted under a relative humidity of 40 %.The regeneration of activated carbon and the recovery of EA and MA could be effectively performed by heating the absorbent after adsorption. The adsorption (40℃)-desorption (300℃) recycle was conducted for six times in experiment, and the result has revealed that the adsorption property of activated carbon was unchanged, indicating that the activated carbon AC can be well used repeatedly as an adsorbent for esters adsorption.
Keywords/Search Tags:Methyl Acrylate, Ethyl Acetate, Adsorption, Activated Carbon, Breakthrough Curve
PDF Full Text Request
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