CAJ | 학술논문

通过在回流法制备流程中引入CTAB(十六烷基三甲基溴化铵)、PEG6000(聚乙二醇6000)及P123(聚环氧乙烷-聚环氧丙烷-聚环氧乙烷三嵌段共聚物)等表面活性剂对γ-MnO2催化剂进行形貌控制,同时采用X射线衍射(XRD)、扫描电镜(SEM)、N2吸附(BET)、热重分析(TGA)、O2程序升温脱附(O2-TPD)以及H2程序升温还原(H2-TPR)等技术对不同形貌γ-MnO2的结构、氧脱附及还原性能进行表征,并考察了其在常压和无溶剂条件下甲苯选择性氧化反应体系的催化特性.同时,对于陈化时间对形貌的影响作用进行了考察.结果表明:不同形貌的γ-MnO2的氧化还原特征及催化活性存在显著差异,其中在经PEG6000进行修饰的γ-MnO2中含有较多的阴离子空位及混合价态,因此有助于分子氧在表面的活化,具有较高的表面比活性;而经P123进行表面修饰的γ-MnO2成晶结构规整、比表面积大,对甲苯液相直接氧化反应则表现出最佳的质量比活性,甲苯转化率达18.1%,含氧化合物总选择性为87.4%,其中苯甲酸的选择性达到73.2%.
통과재회류법제비류정중인입CTAB(십륙완기삼갑기추화안)、PEG6000(취을이순6000)급P123(취배양을완-취배양병완-취배양을완삼감단공취물)등표면활성제대γ-MnO2최화제진행형모공제,동시채용X사선연사(XRD)、소묘전경(SEM)、N2흡부(BET)、열중분석(TGA)、O2정서승온탈부(O2-TPD)이급H2정서승온환원(H2-TPR)등기술대불동형모γ-MnO2적결구、양탈부급환원성능진행표정,병고찰료기재상압화무용제조건하갑분선택성양화반응체계적최화특성.동시,대우진화시간대형모적영향작용진행료고찰.결과표명:불동형모적γ-MnO2적양화환원특정급최화활성존재현저차이,기중재경PEG6000진행수식적γ-MnO2중함유교다적음리자공위급혼합개태,인차유조우분자양재표면적활화,구유교고적표면비활성;이경P123진행표면수식적γ-MnO2성정결구규정、비표면적대,대갑분액상직접양화반응칙표현출최가적질량비활성,갑분전화솔체18.1%,함양화합물총선택성위87.4%,기중분갑산적선택성체도73.2%.
Introducing surfactants including hexadecyltrimethylammonium bromide (CTAB), macrogol 6000 (PEG6000), and poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) triblock copolymer (P123) into the refluxing aqueous crystal nucleus slurry yielded morphology-tuned microcrystal ineγ-MnO2.γ-MnO2 and the influence of surfactant modification were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 adsorption (BET), thermogravimetry analysis (TGA), O2 temperature programmed desorption (O2-TPD), and temperature programmed H2 reduction (H2-TPR). Surfactants led to differences inγ-MnO2 morphology, surface area, oxygen desorption behavior and reducibility. The effect of reflux time on catalyst morphology is discussed. The catalytic performance of γ-MnO2 during the solvent-free atmospheric oxidation of toluene was evaluated. PEG6000 modified γ-MnO2 exhibited the highest catalytic activity judging by surface area because of a greater mixed valency and more anion vacancies. The greatest mass specific activity was obtained for P123 modified γ-MnO2 with the largest surface area. Optimized reaction conditions yielded an 18.1% toluene conversion, and 87.4 and 73.2%total selectivity and selectivity for benzoic acid, respectively.