Mn掺杂对Al-ZnO吸附剂H2S常温脱除性能的促进作用

Promotional Effects of Mn Incorporation in Al-ZnO Adsorbents for H2S Removal at Ambient Temperature

摘要:

采用共沉淀法制备了一系列ZnO、Al-ZnO和x-Mn-Al-ZnO吸附剂，在常温条件下测试样品的H2S脱除性能。通过N2物理吸附、X射线衍射（XRD）、扫描电子显微镜（SEM）、X射线光电子能谱（XPS）对吸附剂进行表征，考察其形貌结构及表面物理化学性质。脱硫性能测试结果显示，随着Mn含量的增加，脱硫性能呈现先增大后减小，再增大再减小的趋势，两个极值点分别出现在0.02Mn-Al-ZnO和0.08Mn-Al-ZnO。结合表征结果发现，不同Mn掺杂量对Al-ZnO吸附剂的脱硫性能表现出不同的促进作用机制。0.02molMn掺杂主要是提高Al-ZnO吸附剂的比表面积至171.4 m2/g，进而促进其H2S脱除性能；随着Mn掺杂量增加，其比表面积下降，但更多的Mn进入ZnO晶格导致Mn和Zn之间相互作用增强，进而促进脱硫性能；然而随着Mn掺杂量进一步增加，吸附剂比表面积继续下降，并且生成ZnMn2O4晶相，导致脱硫性能的下降。0.08Mn-Al-ZnO脱硫性能最佳，在25 oC，空速3000 h-1，H2S浓度1000 ppmv条件下，穿透硫容为7.21g S/100 g sorbent。本研究表明，不同Mn掺杂量会导致吸附剂的形貌结构、晶相和表面物化性质不同程度的变化，而由不同影响因素主导的x-Mn-Al-ZnO吸附剂表现出脱硫性能的差异。

Abstract:

A series of ZnO, Al-ZnO and x-Mn-Al-ZnO adsorbents were synthesized by co-precipitation methods and investigated for the H2S desulfurization at ambient temperature.Thedifferencecaused by Mndopants in terms of structural properties, crystal structure, morphology and chemical state of reactive sites, were systematically investigated by N2adsorption, X-ray diffraction (XRD),scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. The results show that with the increasing of Mn dopants, the desulfurization performance has two extreme points, when doping 0.02 mol and 0.08 molMn to Al-ZnO matrix. According to the characterization and desulfurization performance, different amount of Mn dopants leads to different promotion mechanism. The great performance of 0.02Mn-Al-ZnO is attributed to large surface area of 171.4 m2/g. Despite the surface area drops along with the increasing doping of Mn, more Mn enter into ZnO crystal lattice,which enhances the interaction between Zn and Mn, resulting in a promotion ofdesulfurization performance.However, the further doping ofMn results in smaller surface area and formation of ZnMn2O4, which causes poor desulfurization performance.And the highestsulfur capacity can be obtained over 0.08 Mn-Al-ZnO with 7.21g S/100 g sorbent, under 25oC, GHSV of 3000 h-1and 1000 ppmv H2S. It reveals clearly that doping difference amount of Mn can change morphology, crystal structure and physicochemical properties in varyingdegree, and each of them can act as a major factor leading to various desulfurization performance.