發(fā)布時間：2018-06-10 21:30

  本文選題：復(fù)合分子篩 + 臨氫異構(gòu)化　； 參考：《西安石油大學(xué)》2017年碩士論文

【摘要】：烷烴臨氫異構(gòu)化是目前生產(chǎn)高辛烷值汽油最有效的手段之一,復(fù)合分子篩因具有合適的孔結(jié)構(gòu)、酸性分布以及良好的水熱穩(wěn)定性,成為近年來臨氫異構(gòu)化催化劑載體研究的熱點(diǎn),此外使用非貴金屬代替貴金屬對復(fù)合分子篩進(jìn)行改性,能夠在提高催化劑性能的同時大大降低成本。因此本文在制備出MCM-41/A、MCM-41/B和MCM-41/C三種復(fù)合分子篩的基礎(chǔ)上分別負(fù)載非貴金屬對其改性,研究了復(fù)合分子篩催化劑的正己烷臨氫異構(gòu)化反應(yīng)性能,并對其臨氫異構(gòu)化反應(yīng)機(jī)理進(jìn)行了初步探索。分別以堿處理A、B和C的漿液為部分硅鋁源,在水熱體系中采用外加硅鋁源法分別制備了MCM-41/A、MCM-41/B和MCM-41/C三種復(fù)合分子篩,并采用XRD、BET、FT-IR、Py-IR、TEM等手段分別對復(fù)合分子篩樣品進(jìn)行了表征。結(jié)果表明,合成的復(fù)合分子篩均具有良好的微孔和介孔雙重孔結(jié)構(gòu),其比表面積、孔容和平均孔徑均明顯高于普通沸石分子篩。由Py-IR表征可知,三種復(fù)合分子篩均具有L酸和B酸中心,且金屬離子的引入使得復(fù)合分子篩的酸性再分布,更有利于提高臨氫異構(gòu)化反應(yīng)性能。此外,合成的復(fù)合分子篩均具有良好的熱穩(wěn)定性和水熱穩(wěn)定性。對比研究了非貴金屬改性后的上述三種復(fù)合分子篩催化劑的正己烷臨氫異構(gòu)化反應(yīng)性能,M-MCM-41/A催化劑因具有較大的孔結(jié)構(gòu)尺寸及較多的中強(qiáng)酸中心而表現(xiàn)出較高的催化活性和選擇性,且反應(yīng)72 h內(nèi)正己烷轉(zhuǎn)化率和異構(gòu)化選擇性分別保持在40%和60%左右,表明其反應(yīng)穩(wěn)定性良好。同時還考察了還原溫度、反應(yīng)溫度、體積空速和金屬負(fù)載量等因素對正己烷臨氫異構(gòu)化反應(yīng)性能的影響。結(jié)果表明,當(dāng)還原溫度為450℃、反應(yīng)溫度為260℃、體積空速為3 h-1、催化劑的金屬負(fù)載量為3 wt%時,M-MCM-41/A催化劑的正己烷臨氫異構(gòu)化反應(yīng)性能較好,正己烷轉(zhuǎn)化率為48.58%,i-C6異構(gòu)烷烴選擇性高達(dá)64.45%,液體收率為91.10%。此外還比較了復(fù)合分子篩催化劑在臨氫和非臨氫條件下的正己烷異構(gòu)化反應(yīng)性能,與非臨氫條件相比,臨氫條件下氫氣的存在對正己烷轉(zhuǎn)化率無明顯影響,但異構(gòu)化選擇性提高了10%~20%,裂化選擇性降低了約15%,液體收率也大幅提高,因此臨氫異構(gòu)化較非臨氫異構(gòu)化有更好的反應(yīng)性能。對反應(yīng)機(jī)理的初步探索表明,復(fù)合分子篩催化劑上的正己烷臨氫異構(gòu)化反應(yīng)遵循正碳離子反應(yīng)機(jī)理,金屬離子及分子篩本身的酸中心一起協(xié)同構(gòu)成了異構(gòu)化反應(yīng)的活性中心。
[Abstract]:Hydroisomerization of alkanes is one of the most effective methods to produce gasoline with high octane number at present. Because of its suitable pore structure, acid distribution and good hydrothermal stability, the composite molecular sieve has good hydroisomerization. In recent years, it has become a hot topic to study the support of hydroisomerization catalyst. In addition, the use of non-precious metal instead of precious metal to modify composite molecular sieve can greatly reduce the cost while improving the performance of the catalyst. Therefore, on the basis of the preparation of MCM-41 / Agna MCM-41 / B and MCM-41 / C composite molecular sieves, respectively, the non-precious metals were supported to modify them, and the properties of n-hexane hydroisomerization over composite molecular sieve catalysts were studied. The mechanism of hydroisomerization was also studied. Three kinds of composite molecular sieves MCM-41A1- 41B and MCM-41C were prepared in hydrothermal system using the slurry of alkali treated Agna B and C as partial Si-Al source, respectively. The composite molecular sieve samples were characterized by XRDX BETFT-IRPy-IRTEM. The results show that the synthesized composite molecular sieves have good microporous and mesoporous double pore structures, and their specific surface area, pore volume and average pore size are obviously higher than those of ordinary zeolites. The results of Py-IR show that all of the three zeolites have L acid and B acid sites, and the introduction of metal ions makes the acid redistribution of the composite molecular sieves, which is more conducive to improving the performance of hydroisomerization reaction. In addition, the synthesized composite molecular sieves have good thermal stability and hydrothermal stability. The catalytic properties of M-MCM-41 / A catalyst for the isomerization of n-hexane over the above three modified molecular sieve catalysts were compared and studied. Due to their larger pore size and more moderate and strong acid centers, M-MCM-41 / A catalyst exhibited higher catalytic activity. Chemical activity and selectivity, The conversion and isomerization selectivity of n-hexane were about 40% and 60% within 72 h, respectively, which indicated that the reaction was stable. The effects of reduction temperature, reaction temperature, volume space velocity and metal loading on the isomerization of n-hexane were also investigated. The results show that when the reduction temperature is 450 鈩，

本文編號：2004755