锰改性对ZIF-67衍生Co3O4低温催化氧化甲醛性能的影响

Effect of manganese modification on the low-temperature formaldehyde oxidation performance of ZIF-67 derived Co3O4

  • 摘要: 针对ZIF-67衍生Co3O4催化剂低温甲醛氧化性能不佳的问题,采用锰(Mn)对Co3O4催化剂进行改性以提升其低温甲醛氧化性能。活性评价结果表明,相比于未改性的Co3O4催化剂,Mn改性后的Mn-Co3O4催化剂甲醛氧化活性显著提升,在118 ℃下即可实现90%的甲醛转化率(进口甲醛浓度为98.16 mg/m3,空速为60000 mL /(gcat·h))。XRD、Raman和BET结果显示,Mn改性后催化剂的结晶度降低,缺陷增加,比表面积增大,这有利于反应物分子的吸附和活性位点的暴露。XPS、H2-TPR和O2-TPD表征结果表明,Mn-Co间存在的强相互作用显著改善了Mn-Co3O4催化剂的低温氧化还原性能和氧活化能力,使其具有更加丰富的Co3+和表面吸附氧物种。最终,这些因素共同促进了Mn-Co3O4催化剂对甲醛的降解。此外,in-situ DRIFTS结果表明,亚甲二氧基和甲酸盐物种是甲醛在Mn-Co3O4催化剂上催化氧化的主要中间物种。

     

    Abstract: In consideration of the inferior performance of ZIF-67 derived Co3O4 catalyst in the low-temperature formaldehyde oxidation, manganese was utilized to modify Co3O4 catalyst. The results showed that the Mn-Co3O4 catalyst exhibited the superior HCHO oxidation activity and achieved 90% HCHO conversion at a WHSV of 60000 mL/(gcat·h) and inlet HCHO concentration of 98.16 mg/m3 at 118 ℃. XRD, Raman and BET results demonstrated that the Mn-Co3O4 catalyst possessed lower crystallinity, more defects and specific surface area, which was conducive to the adsorption of reactants and exposure of more active sites. XPS, H2-TPR and O2-TPD results indicated that the strong interaction between Mn and Co species prominently improved the low temperature reducibility and O2 activation performance of Mn-Co3O4 catalyst, which endowed it with more abundant Co3+ and surface-adsorbed oxygen species. Therefore, the Mn-Co3O4 catalyst exhibited superior HCHO oxidation performance. Based on in-situ DRIFTS results, dioxymethylene and formate species were recognized as the main reaction intermediates of HCHO oxidation over the Mn-Co3O4 catalyst.

     

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