本文選題：MOFs + 改性��； 參考：《太原理工大學(xué)》2017年碩士論文

【摘要】：天然氣中含有一定量硫化物,不僅對(duì)其工藝使用中的催化劑造成毒害,一旦燃燒排放入大氣,還會(huì)對(duì)環(huán)境造成嚴(yán)重污染。因此,必須將硫化物脫除。其中,吸附脫硫因其具有操作簡便、工藝條件溫和等優(yōu)點(diǎn)成為一項(xiàng)非常有競(jìng)爭力的脫硫技術(shù)。金屬有機(jī)框架化合物(MOFs)是由含氧、氮的有機(jī)配體和過渡金屬離子通過配位鍵自組裝形成的微孔網(wǎng)絡(luò)結(jié)構(gòu)晶體。與傳統(tǒng)的多孔材料相比,MOFs具有大的比表面積和孔隙,結(jié)構(gòu)多樣性和孔尺寸可調(diào)的特點(diǎn),在氣體存儲(chǔ)、分離、催化等方面都顯示了巨大的應(yīng)用前景。同時(shí),MOFs作為吸附脫硫劑在脫硫領(lǐng)域也表現(xiàn)出了優(yōu)于活性炭和分子篩的良好性能,引起了研究者的極大關(guān)注。然而,MOFs也存在一些問題,其大的比表面積和發(fā)達(dá)的孔隙結(jié)構(gòu)說明材料的色散力較弱,當(dāng)吸附小分子時(shí),吸附質(zhì)容易從骨架逸出。因此,為了提高M(jìn)OFs吸附性能,將MOFs進(jìn)行適當(dāng)改性。本文采用活性炭(AC)和氧化石墨(GO)對(duì)MOF-199進(jìn)行改性,通過水熱法將獲得改性后產(chǎn)物,即復(fù)合材料MAC和MGO。采用固定床評(píng)價(jià)其對(duì)硫化氫、甲硫醚以及乙硫醇?xì)怏w的動(dòng)態(tài)吸附行為。運(yùn)用XRD、FTIR、氮?dú)馕?脫附、Py-IR、SEM、TG-MS和XPS表征硫化前后樣品,并將樣品結(jié)構(gòu)和脫硫性能進(jìn)行關(guān)聯(lián)。與MOF-199相比,復(fù)合材料MAC形貌沒有明顯改變,但晶體結(jié)構(gòu)更為有序、比表面積提高、孔徑減小以及金屬不飽和位增多。而MOF-199經(jīng)與石墨烯復(fù)合后形貌發(fā)生了明顯的變化,形成的是方形薄片以一種有組織的方式疊在一起類似于層狀結(jié)構(gòu)的一種新材料,并且比表面積提高。固定床實(shí)驗(yàn)顯示,與MOF-199相比,MAC和MGO對(duì)三種硫化物吸附效果有顯著提高。這是因?yàn)锳C可能會(huì)包裹進(jìn)MGO-199空腔,引起孔徑減少和比表面積提高,GO表面的含氧官能團(tuán)和MOF-199的金屬中心結(jié)合導(dǎo)致形成額外的孔,這些性質(zhì)的提高都有利于提高材料的物理吸附性能。此外,MAC不飽和金屬中心的增加也對(duì)吸附硫化物做出貢獻(xiàn)。實(shí)驗(yàn)考察吸附溫度對(duì)MAC脫除三種硫化物的影響,發(fā)現(xiàn)吸附溫度會(huì)影響硫化物的吸附,研究還發(fā)現(xiàn),水汽對(duì)于MAC脫除硫化氫有促進(jìn)作用。制備的復(fù)合材料MAC的吸附性能優(yōu)于MGO,主要是因?yàn)榍罢叩谋缺砻娣e和孔容比后者高,MAC孔徑的減小和不飽和金屬位點(diǎn)的增加也有利于脫硫效果的提高。復(fù)合材料對(duì)三種硫化物的吸附機(jī)理不同,這是由于三種硫化物在MOFs結(jié)構(gòu)中產(chǎn)生的空間位阻效應(yīng)不同。硫化氫分子直徑最小,可與金屬中心直接接觸并發(fā)生化學(xué)反應(yīng),生成CuS。乙硫醇雖然分子直徑較大,但是分子一端為-SH,也能與金屬中心產(chǎn)生不可逆吸附反應(yīng)。甲硫醚分子直徑最大且兩端連有甲基,在MOFs骨架中產(chǎn)生的空間位阻最大,因此與金屬中心不發(fā)生反應(yīng),而以弱配位形式吸附。而正是由于甲硫醚以弱作用力與復(fù)合材料結(jié)合,產(chǎn)生的吸附是可逆的。研究表明,MAC和MGO經(jīng)3次循環(huán)后,其穿透硫容仍可達(dá)到初始硫容94%,是理想的硫醚吸附劑。
[Abstract]:Natural gas contains a certain amount of sulfides, which not only poisons the catalysts used in the process, but also causes serious pollution to the environment once the combustion is discharged into the atmosphere. Sulphides must therefore be removed. Among them, adsorption desulfurization has become a very competitive desulfurization technology because of its advantages of simple operation and mild process conditions. Organometallic frame compound (MOF) is a microporous network crystal composed of organic ligands containing oxygen, nitrogen and transition metal ions, which are self-assembled by coordination bonds. Compared with the traditional porous materials, MOFs have the characteristics of large specific surface area and pore size, structural diversity and adjustable pore size. They have shown great application prospects in gas storage, separation, catalysis and so on. At the same time, as adsorptive desulfurizers, MOFs also show better performance than activated carbon and molecular sieve in the field of desulfurization, which has attracted great attention of researchers. However, there are some problems in MOFs. Their large specific surface area and developed pore structure indicate that the dispersive force of the material is weak, and when adsorbing small molecules, the adsorbate is easy to escape from the skeleton. Therefore, in order to improve the adsorption properties of MOFs, MOFs was modified appropriately. In this paper, MOF-199 was modified by activated carbon (AC) and graphite oxide (GOO). The modified products, that is, MAC and MGO, were obtained by hydrothermal method. The dynamic adsorption behavior of hydrogen sulfide, methyl sulfide and ethanethiol was evaluated in a fixed bed. The samples before and after vulcanization were characterized by XRDX FTIR, nitrogen adsorption-desorption (Py-IRM) TG-MS and XPS, and the structure and desulfurization properties of the samples were correlated. Compared with MOF-199, the morphology of MAC has no obvious change, but the crystal structure is more orderly, the specific surface area is increased, the pore size is decreased and the unsaturated potential of metal is increased. However, the morphology of MOF-199 was obviously changed after composite with graphene, and the square sheet was stacked together in an organized manner similar to the lamellar structure, and the specific surface area was increased. Fixed-bed experiments showed that the adsorption of sulfides by MOF-199 and MGO was significantly improved. This is because AC may wrap into the MGO-199 cavity, resulting in reduced pore size and increased specific surface area, resulting in the combination of oxygenated functional groups on the go surface and the metal center of MOF-199 to form additional pores. The improvement of these properties is beneficial to the improvement of the physical adsorption properties of the materials. In addition, the increase of unsaturated metal centers also contributes to the adsorption of sulfides. The effect of adsorption temperature on the removal of three sulfides by MAC was investigated. It was found that the adsorption temperature would affect the adsorption of sulfides. It was also found that water vapor could promote the removal of hydrogen sulfide by MAC. The adsorption performance of the composite MAC is better than that of MGO.The main reason is that the reduction of pore size and the increase of unsaturated metal sites in the former are also beneficial to the improvement of desulphurization efficiency. The adsorption mechanism of the three sulfides in the composite is different, which is due to the different steric resistance effect of the three sulfides in the MOFs structure. The molecular diameter of hydrogen sulfide is the smallest, which can be directly contacted with the metal center and react with the metal center to form CuSs. Although the molecular diameter of ethanethiol is large, one end of the molecule is -SH, which can also produce irreversible adsorption reaction with the metal center. The methyl sulfide molecule has the largest diameter and methyl at both ends, which results in the largest steric resistance in the MOFs skeleton, so it does not react with the metal center and is adsorbed in the form of weak coordination. It is precisely because methyl sulfide binds to the composite by weak force that the adsorption is reversible. The results show that after three cycles, the penetrating sulfur capacity of MGO can still reach the initial sulfur capacity of 94. It is an ideal sorbent for sulfides.
【學(xué)位授予單位】：太原理工大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：O647.33

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