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한영택,하백현 ( Young Taek Han,Baik Hyon Ha ) 한국공업화학회 1991 공업화학 Vol.2 No.1
염산 및 불산으로 모더나이트를 처리하여 실리카/알루미나 비가 다른 일련의 시료를 만들었다. 이러한 시료에 대하여 암모니아 TPD와 피리딘 흡착으로 IR을 이용하여 산성도를 측정하고 o-xylene 반응의 활성과 이성화반응에 대한 선택성을 측정하였다. 그 결과 염산처리 시료는 실리카/알루미나 비가 증가할수록 구조알루미늄이 추출되어 산량이 감소하였으며 실리카/알루미나 비가 22인 시료가 다른 시료들보다 활성이 좋았다. 불산처리 시료는 불산처리 시 불소가 구조 중 규소원자와 결합하였으며 처리시간이 증가함에 따라 결합된 불소는 증가하였다. 이 경우의 활성은 염산처리와는 달리 알루미늄의 추출과 함께 모더나이트의 수산기가 불소로 치환되어 이로 인하여 산점이 줄어 활성이 감소하나 불산은 규소도 추출하므로 표면을 파고들어 새로운 면이 노출되어 산점이 형성되고 이 산점은 증가된 결합불소의 영향을 받아 강해지면서 활성이 다소 증가하였다. A series of samples having different SiO_2/Al_2O_3 ratios were prepared by treating hydrogen mordenites with boiling hydrochloric acid and with hydrofluoric acid. The acidities of these samples were measured by TPD of NH_3 and by pyridine adsorption using IR, and the catalytic activities and selectivities of isomerization were measured for the reaction of ortho-xylene. For the samples treated by boiling hydrochloric acid, the acidities decreased with the increasing SiO_2/Al_2O_3 ratio caused by the extraction of framework aluminum. The sample having the SiO_2/Al_2O_3 ratio of 22 showed better activity than the others. For the samples treated by hydrofluoric acid, the content of chemically binding fluorine increased with the increasing contact time of hydrofluoric acid solution. The catalytic activities decreased with the hydrofluoric acid treatment due to the decreased acid sites resulted from the extraction of aluminum and silicon as well as the hydroxyl group replacement by the fluoride ion. The slightly increasing catalytic activities, however, came from the newly created acid sites, due to the removal of surface silicon, having enhanced by the inductive effect of binding fluorin with further acid treatment.
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한영택,하백현 ( Young Taek Han,Baik Hyon Ha ) 한국화학공학회 1991 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.29 No.5
A series of aluminum-deficient mordenites were prepared by treating hydrogen mordenites with hydrochloric acid and hydrofluoric acid, respectively. Isotherms of nitrogen adsorption, XRD analysis, silicon NMR, and characteristics of cyclohexane adsorption were studied. Mordenites treated by hydrochloric acid formed secondary pores at more than SiO₂/A1₂O₃ of 30 and the crystal lattice contracted by removing framework aluminum. Modernites treated by hydrofluoric acid made also secondary pores by extracting framework silicon simultaneously. For the treatment with hydrochloric acid, initial equilibrium constant, k₁ decreased continuouly by removing aluminum but initial heat of adsorption, q₁ showed a maximum point and a minimum point. The maximum point would be explained by the improvement of site efficiency due to the enlarged pores. The minimum point could be said by the change of surface property due to the erosed surface of the crystals which revealed new strong adsorption sites.
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