本文選題：分子篩 + 固體核磁��； 參考：《中國科學院大學(中國科學院武漢物理與數(shù)學研究所)》2017年碩士論文

【摘要】：分子篩具有可調節(jié)的酸性活性位點和孔隙結構,這使其成為廣泛應用的工業(yè)催化劑,可以催化多種反應如催化裂化、加氫裂解、異構化等。分子篩的催化機理與其他酸性催化劑相同,都涉及碳正離子這種重要的中間體物種,所以可以通過在分子篩體系內捕捉碳正離子并觀察其轉化情況,來研究分子篩的催化機理。分子篩催化石油的裂解和汽油的重整一直備受關注,其催化反應機理主要涉及C4物種的轉化,其中研究最多的是叔丁基碳正離子。這種具有支鏈結構的中間體,一直被認為可以用來揭示短鏈的碳氫物種在分子篩體系內的異構化機理。本文主要是在ZSM-5分子篩中觀測叔丁基碳正離子并且研究其轉化過程。(1)短鏈的碳正離子由于其活性高、壽命短,在分子篩體系內的觀測一直是實驗上的難點。本文采用共吸附堿性捕捉劑(氨氣)的方法,在ZSM-5分子篩孔道內捕捉重要的C4中間體,并且通過13C-13C二維相關譜和理論計算對捕捉到的物種進行了結構分析,確定叔丁基碳正離子的存在。在此基礎上,利用13C-27Al相關實驗表征了叔丁基碳正離子與分子篩骨架的相互作用關系。(2)C4物種在分子篩孔道內的轉化一直是研究的熱點,本文利用原位固體核磁觀測了選擇性標記的2-13C-叔丁醇在ZSM-5分子篩內的轉化情況,發(fā)現(xiàn)13C標記的季碳遷移到伯碳位置,而且標記碳在最終產物中混亂分布的現(xiàn)象。為了解釋這兩種實驗現(xiàn)象,我們采取了理論計算的方法,給出了包含質子化的甲基環(huán)丙烷中間體的反應機理,并預測了可能存在的C4中間體物種。通過堿性捕捉劑法和過量吸附法觀察到了理論計算預測的C4烯烴物種(2-13C-2-丁烯、1-13C-異丁烯、2-13C-異丁烯),在實驗上印證了反應機理的正確性。通過實驗和理論手段,我們觀測到了 C4物種骨架異構化的實驗現(xiàn)象,并且給出了合理的解釋。
[Abstract]:Molecular sieve has adjustable acidic active sites and pore structure which makes it a widely used industrial catalyst which can catalyze many reactions such as catalytic cracking hydrocracking isomerization and so on. The catalytic mechanism of molecular sieve is the same as that of other acidic catalysts, which involves carbon ion as an important intermediate species. Therefore, the catalytic mechanism of molecular sieve can be studied by capturing carbon positive ion in molecular sieve system and observing its conversion. Molecular sieve catalyzes the cracking of petroleum and the reforming of gasoline. The mechanism of catalytic reaction is mainly related to the conversion of C4 species, among which the tertiary Ding Ji carbon ion is the most studied. This intermediate with branched structure has been thought to be used to reveal the isomerization mechanism of short-chain hydrocarbon species in molecular sieve system. In this paper, the observation of tert Ding Ji carbon positive ions in ZSM-5 molecular sieve and its conversion process. 1) because of its high activity and short lifetime, the observation in molecular sieve system is always difficult. In this paper, the important C4 intermediates were captured in the pore of ZSM-5 molecular sieve by the method of coadsorption alkaline catcher (ammonia), and the structure of the captured species was analyzed by 13C-13C two-dimensional correlation spectrum and theoretical calculation. The existence of tertiary Ding Ji carbon ion was determined. On this basis, the interaction between tertiary Ding Ji carbon cations and molecular sieve framework was characterized by 13C-27Al correlation experiments. The transformation of C 4 species in molecular sieve channels has been a hot topic. The transformation of selective labeled 2-13C- tert-butanol in ZSM-5 molecular sieve was observed by in situ solid state NMR. It was found that the 13C-labeled quaternary carbon migrated to the primary carbon position and the labeled carbon was misdistributed in the final product. In order to explain these two experimental phenomena, the reaction mechanism of methyl cyclopropane intermediates containing protonation is given by theoretical calculation, and the possible C4 intermediate species are predicted. The theoretical calculation of 2-13C-2-butene (2-13C-2-butene) 2-13C- (isobutene) -2-13C- (isobutene) was observed by alkaline trapping agent method and excessive adsorption method, which proved the correctness of the reaction mechanism. Through experimental and theoretical means, we observed the experimental phenomenon of the isomerization of C4 species skeleton, and gave a reasonable explanation.
【學位授予單位】：中國科學院大學(中國科學院武漢物理與數(shù)學研究所)
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：O643.36

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