Pt/PTA-MIL-101(Cr)的合成及其正庚烷异构催化性能

使用磷钨酸(PTA)对金属有机骨架材料MIL-101(Cr)进行改性,制备了0.4%Pt/PTA-MIL-101(Cr)催化剂,并首次应用于正庚烷异构化反应。通过对样品进行一系列表征,得出以下结论:所合成的样品为介孔-微孔复合材料,具有正八面体结构,孔道结构规整有序,比表面积高;掺杂PTA后,未破坏MIL-101(Cr)的骨架结构和热稳定性;PTA在催化剂中仍可保持其Keggin结构,可为催化反应提供良好的酸性环境;Pt在MIL-101(Cr)中的分散度较高。通过正庚烷异构化反应对催化剂性能进行评价,得出在PTA掺杂量(w)为30%、反应温度为260℃时,催化剂的酸性位点与金属位点的匹配度最适宜催化庚烷异构化反应,此时催化剂上正庚烷转化率与异庚烷选择性分别可达69.1%和93.7%。

SYNTHESIS OF Pt PTA-MIL-101(Cr)AND ITS CATALYTIC PERFORMANCE FOR n-HEPTANE ISOMERIZATION

The 0.4%Pt/PTA-MIL-101(Cr) metal-acid bifunctional catalysts with different doping amounts of PTA were prepared by modifying organometallic skeleton material MIL-101(CR) with phosphotungstic acid (PTA) and were first applied to n-heptane isomerization. The synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), N2 adsorption-desorption, thermal gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), X-ray fluorescence (XRF) and acid-base titration. The results show that the synthesized samples are mesoporous-microporous composite materials with typical octahedral structure, regular pore structure and high specific surface area; the framework and thermal stability of MIL-101(Cr) are not damaged; the Keggin structure of PTA can be maintained in the catalyst, which can provide a good acidic environment for the catalytic reaction and the higher dispersity of Pt in MIL-101(Cr). Through the evaluation of n-heptane isomerization performance of the catalyst, it was found that the best match between the acid sites and metal sites of the catalyst was the most suitable for catalyzing n-heptane isomerization, when the reaction temperature was 260 ℃ and the doping content of PTA was 30%, and the conversion of n-heptane and the selectivity of iso-heptane could reach 69.1% and 93.7%,respectively.