本文關(guān)鍵詞： ZSM-5 甲醇制烴 堿處理 介孔　出處：《太原理工大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：石油在能源和化工產(chǎn)業(yè)中扮演重要角色,是汽油、烯烴和芳烴生產(chǎn)的重要原料來源。隨著全球石油儲(chǔ)量的不斷降低和世界原油價(jià)格的頻繁波動(dòng),尋找高效、綠色的上述液烴燃料和基礎(chǔ)化工產(chǎn)品的技術(shù)路線十分迫切,也是優(yōu)化我國能源結(jié)構(gòu),降低對(duì)石油資源依賴的重要選擇。甲醇制烴反應(yīng)(MTH)是甲醇經(jīng)過酸性分子篩催化劑作用定向轉(zhuǎn)化成烷烴、烯烴和芳烴等烴類化合物的反應(yīng)。ZSM-5分子篩催化劑,硅鋁比范圍大,酸性可控性高,其擇型效應(yīng)和水熱穩(wěn)定性使其成為目前MTH反應(yīng)廣泛使用的催化劑。但是ZSM-5分子篩的擴(kuò)散限制是催化劑失活的重要原因:甲醇在ZSM-5微孔的酸性位點(diǎn)轉(zhuǎn)化成芳烴等積炭前驅(qū)物,難以從微孔孔道擴(kuò)散,堵塞擴(kuò)散孔道出口,并繼續(xù)反應(yīng)形成積炭,覆蓋微孔上的酸活性位點(diǎn),導(dǎo)致催化劑積炭失活。因此,提高ZSM-5分子篩的孔道擴(kuò)散性能是解決催化劑積炭失活的關(guān)鍵所在。介孔構(gòu)建能夠有效改善ZSM-5分子篩的擴(kuò)散性能,堿處理是目前介孔構(gòu)建的簡(jiǎn)單高效方法,但傳統(tǒng)堿處理過程中硅的脫除受鋁分布顯著影響,構(gòu)建的介孔分布不均勻,且容易形成大孔,分子篩介孔度低。為了提高堿處理后ZSM-5分子篩建的介孔度,本論文對(duì)微米和納米ZSM-5進(jìn)行保護(hù)性堿處理脫硅,控制脫硅過程,以提高介孔度,延長(zhǎng)其催化MTH反應(yīng)壽命,并明確介孔度與催化壽命的構(gòu)效關(guān)系。本文的主要結(jié)論如下:(1)對(duì)比研究堿溶液中TPA~+(四丙基氫氧根離子)/Na~+(鈉離子)比對(duì)微米ZSM-5分子篩介孔度的影響發(fā)現(xiàn),TPA~+離子的引入促進(jìn)了體相均勻分布介孔的形成,增加了介孔數(shù)量,介孔孔徑更為集中。隨著溶液中TPA~+/Na~+比增加,ZSM-5分子篩的外比表面積先增加后降低,高濃度TPA~+不利于高介孔ZSM-5催化劑的制備。當(dāng)TPA~+/Na~+比為0.5時(shí),ZSM-5分子篩的外比表面積最大,達(dá)210 m2·g-1。通過ICP-AES、XPS和29Si NMR表征手段,發(fā)現(xiàn)了TPA~+的吸附位點(diǎn)在ZSM-5分子篩的Si(4Si,0Al)位,并明確了混合堿處理高介孔度ZSM-5分子篩構(gòu)建機(jī)理,TPA~+離子的保護(hù)性脫硅和Na~+離子的選擇性脫硅的協(xié)同作用共同促進(jìn)了高介孔微米ZSM-5分子篩的形成。結(jié)合MTH反應(yīng)評(píng)價(jià),ZSM-5催化劑的催化壽命與其外比表面積成正相關(guān)關(guān)系:ZSM-5分子篩的外表面積越大,MTH反應(yīng)催化壽命越長(zhǎng)。在400 oC,1 MPa,9.4h-1反應(yīng)條件下,具有最大外比表面積的ZSM-5的MTH反應(yīng)壽命達(dá)到102 h,約為傳統(tǒng)NaOH堿處理樣品催化壽命的2倍。(2)在堿處理具有高擴(kuò)散性能納米ZSM-5分子篩催化劑時(shí),發(fā)現(xiàn)引入硝酸鋁能夠抑制空心納米ZSM-5分子篩的形成,促進(jìn)ZSM-5分子篩體相介孔的形成,有利于提高介孔度。相較于傳統(tǒng)NaOH堿處理,低濃度Al~(3+)混合堿堿處理的納米ZSM-5分子篩的外比表面積進(jìn)一步提升至144 m2·g-1。而隨著堿溶液中Al~(3+)濃度的增加,ZSM-5分子篩的外比表面積開始降低。同時(shí)結(jié)合ICP-AES和NH3-TPD表征,發(fā)現(xiàn)加入硝酸鋁的堿處理的ZSM-5分子篩的酸量隨著溶液中Al~(3+)濃度的增加而增加,但是其酸量仍然低于傳統(tǒng)NaOH堿處理的ZSM-5分子篩,而且其酸強(qiáng)度也隨堿溶液中Al~(3+)濃度的增加而增強(qiáng)。通過對(duì)比堿處理前后ZSM-5的織構(gòu)性質(zhì)和TEM圖,ZSM-5分子篩的外比表面積的利用程度直接影響了MTH反應(yīng)的催化壽命。ZSM-5催化劑的酸性和擴(kuò)散性能影響MTH反應(yīng)產(chǎn)物分布,高酸量和強(qiáng)酸性促進(jìn)氫轉(zhuǎn)移反應(yīng),有利于芳烴和烷烴的選擇性;而外表面高酸量分布的ZSM-5催化劑不利于低碳產(chǎn)物進(jìn)行二級(jí)反應(yīng)生成高碳芳烴等產(chǎn)物,具有高的烷烴選擇性和低的芳烴選擇性。
[Abstract]:The oil in the energy and chemical industry plays an important role, is an important raw material of gasoline, olefin and aromatics production. With the global oil reserves continue to reduce the frequent fluctuations, and the world crude oil price for an efficient and technical route of the liquid hydrocarbon fuel and basic chemical products green is very urgent, but also optimize the energy structure of our country. A major choice of reducing dependence on oil resources. The reaction of methanol to hydrocarbons (MTH) methanol after acidic zeolite catalyst directed into alkanes, olefins and aromatics reaction of.ZSM-5 molecular sieve catalyst such as hydrocarbons, silicon aluminum ratio, acid high controllability, the selection effect and thermal stability of the water the catalyst is widely used in MTH reaction. But the diffusion limitation of ZSM-5 molecular sieve is an important reason for the deactivation of the catalyst in methanol: ZSM-5 microporous acidic sites into aromatic hydrocarbon product Carbon precursor, difficult to diffuse from the pore pore diffusion, pore blockage and exports continue to react to form coke acid active sites on the pore cover, resulting in catalyst deactivation. Therefore, to improve the performance of ZSM-5 molecular sieve pore diffusion is the key to solve the coking of the catalyst deactivation. The mesoporous construction can effectively improve the performance of ZSM-5 diffusion molecular sieve, alkali treatment is simple and effective method at present mesoporous construct, but the traditional alkali treatment process of silicon removal by aluminum distribution significantly affects the construction of the mesoporous distribution is not uniform, and easy to form a large hole, the mesoporous molecular sieve is low. In order to improve the alkali treated ZSM-5 zeolite mesoporous degree construction in this paper, the protection of the alkali treatment desilication of micron and nanometer ZSM-5, control of the desilication process, in order to improve the mesoporous degree, prolong the life of catalyst for the MTH reaction, and clear the mesoporous degree and catalytic life of structure-activity relationship. In this paper, the main Conclusions are as follows: (1) a comparative study on TPA~+ in alkaline solution (four propyl hydroxyl ions) /Na~+ (sodium) than the micron of ZSM-5 molecular sieve mesoporous degree that TPA~+ ions promote the body to form uniform mesoporous distribution, increase the number of mesoporous, mesoporous pore size is more concentrated with the increase of TPA~+/Na~+ ratio. In the solution, ZSM-5 molecular sieve to increase the specific surface area decreased, the high concentration of TPA~+ is not conducive to high mesoporous ZSM-5 catalyst preparation. When the TPA~+/Na~+ is 0.5, ZSM-5 molecular sieve the largest specific surface area of 210 M2 - g-1. by ICP-AES, XPS and 29Si methods the characterization of NMR, found the TPA~+ adsorption sites in ZSM-5 zeolite Si (4Si, 0Al), and the mixture of alkali and high processing degree of mesoporous ZSM-5 molecular sieve structure mechanism, synergistic effect of selective protection of TPA~+ ion and Na~+ ion of the desilication of desilication promoted high mesoporous micron The formation of ZSM-5 molecular sieve. Combined with MTH reaction, catalytic lifetime of ZSM-5 catalyst and its specific surface area is a positive correlation between the ZSM-5 molecular sieve surface area is larger, longer catalyst life MTH reaction. In 400 oC, 1 MPa, 9.4h-1 reaction conditions, with the maximum reaction surface area than MTH life ZSM-5 up to 102 h, about 2 times as much as the traditional NaOH alkali treatment samples by catalytic life. (2) in alkali treatment with high diffusion properties of nano ZSM-5 molecular sieve catalyst, found that the introduction of aluminum nitrate inhibits the formation of nanometer ZSM-5 molecular sieve hollow, promote the formation of ZSM-5 molecular sieve mesoporous phase, is conducive to improve the degree. Compared with the traditional mesoporous NaOH alkali treatment, low concentration of Al~ (3+) ZSM-5 nano molecular sieve mixed alkali treatment to further enhance the external surface area of 144 m2 / g-1. with alkali solution Al~ (3+) concentration increased, ZSM-5 molecular sieve external surface area At the same time began to decrease. The combination of ICP-AES and NH3-TPD were found with aluminum nitrate alkali treatment of ZSM-5 molecular sieve with acid solution Al~ (3+) concentration increased, but the amount is still lower than the traditional NaOH ZSM-5 molecular sieve and alkali treatment, the acid strength with alkali solution concentration of Al~ (3+) the increase. The texture and TEM map contrast before and after alkali treatment of ZSM-5, ZSM-5 molecular sieve ratio surface area utilization degree directly affect the acidity and diffusion properties of MTH reaction product distribution of catalytic life of.ZSM-5 catalyst for MTH reaction, high acid and strong acid to promote the hydrogen transfer reaction, selective for aromatic hydrocarbons the surface of the ZSM-5 catalyst and alkanes; high acidity distribution outside is not conducive to low carbon products were two grade reaction of high carbon hydrocarbon products with high selectivity and low alkane compounds.

【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)】：O643.36;TQ211

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