沸石分子筛和活性炭吸附/脱附甲苯性能对比

Relative performance of zeolites and activated carbon in gaseous phase adsorption and desorption of toluene

考察了甲苯在NaY型沸石分子筛(简写为NaY)、13X型沸石分子筛(简写为13X)、Hβ型沸石分子筛(简写为Hβ)、MCM-22型沸石分子筛(简写为MCM-22)和ZSM-5型沸石分子筛(简写为ZSM-5)上的吸附/脱附性能,同时与椰壳活性炭(AC)的吸附/脱附性能进行对比。结果表明,各吸附剂对甲苯的平衡吸附量大小依次为:AC>NaY>Hβ>13X>MCM-22>ZSM-5,甲苯从吸附剂表面脱附难易程度依次为:AC>NaY、13X>Hβ>MCM-22>ZSM-5;ZSM-5对甲苯的平衡吸附量和吸附强度都最小,这是由于甲苯无法进入ZSM-5的内部孔道造成的;在低甲苯质量浓度(<1000mg/m3)时,NaY平衡吸附量超过AC,因此NaY更适合应用在低浓度有机废气吸附治理中;Langmuir吸附方程比Freundlich吸附方程更符合沸石分子筛吸附甲苯的行为。

The relative performance of five commercial zeolites （NaY,ZSM-5,MCM-22, Hβ and 13X） and a co-conut activated carbon in gaseous phase adsorption/desorption of toluene was studied in the lab. The observed adsorptive loadings of toluene on the small adsorbers were in the declining order of AC〉NaY〉 Hβ〉 13X〉 MCM-22〉 ZSM-5. Under the TPD conditions, the order of the desorption time was the same as the loadings （AC〉NaY,13X〉 Hβ〉MCM-22〉ZSM-5）. Among the zeolites, NaY performed just a little differently from AC in the adsorption and desorption runs. Based on the effects of influent flow rate and toluene concentration on the breakthrough profiles,the adsorption of toluene process was primarily controlled by either internal diffusion （NAY） or external diffusion （ZSM- 5）. The loading data were well represented by the Langmuir adsorption isotherm model; the adsorption capacities were influenced less by toluene concentration at an low concentration. The experimental results suggest NaY molecular sieves is more fit to remove low concentration VOCs from waste gaseous streams.