本文選題：納米ZSM-5 + 甲醇制烴��； 參考：《太原理工大學(xué)》2017年碩士論文

【摘要】：逐年遞增的能源需求和日趨緊張的石油供給使中國(guó)能源安全面臨嚴(yán)峻挑戰(zhàn)。結(jié)合我國(guó)能源結(jié)構(gòu)特點(diǎn),充分發(fā)揮我國(guó)煤炭資源相對(duì)豐富的優(yōu)勢(shì),發(fā)展新型煤化工技術(shù)變得愈加重要。其中以煤基甲醇為基礎(chǔ)的甲醇制烴反應(yīng)(MTH),是在酸性分子篩催化下可將甲醇轉(zhuǎn)化為烷烴、低碳烯烴和芳烴等多種烴類的過(guò)程。通過(guò)該技術(shù)可實(shí)現(xiàn)煤炭的清潔高效利用,是未來(lái)替代石油路線的重要途徑。作為MTH反應(yīng)關(guān)鍵技術(shù)的催化劑,ZSM-5分子篩由于其良好的熱穩(wěn)定性、合適的酸性和有序微孔結(jié)構(gòu),可以高活性、高選擇性地催化甲醇轉(zhuǎn)化生成烴類。然而,也正是其規(guī)整有序微孔結(jié)構(gòu)限制了反應(yīng)物和產(chǎn)物的擴(kuò)散,使積炭前驅(qū)體容易在微孔內(nèi)積累,促進(jìn)積炭的生成,同時(shí)覆蓋活性位并最終引起孔道堵塞,致使催化劑失活。諸多研究表明,減小晶粒尺寸和引入介孔是解決分子篩微孔擴(kuò)散限制的重要方法。它們均可縮短催化劑擴(kuò)散路徑,增加其外比表面積,促進(jìn)反應(yīng)大分子擴(kuò)散。本論文主要圍繞納米ZSM-5分子篩不同孔結(jié)構(gòu)構(gòu)建進(jìn)行研究。首先選取具有較好催化性能的納米ZSM-5為對(duì)象,通過(guò)調(diào)控其NaOH堿處理時(shí)間,實(shí)現(xiàn)了納米ZSM-5介孔結(jié)構(gòu)的構(gòu)建。結(jié)合MTH反應(yīng)評(píng)價(jià)結(jié)果和XRD、NH3-TPD、BET、TEM、ICP-AES等系列表征,考察了納米ZSM-5孔構(gòu)建過(guò)程對(duì)其催化性能的影響;然后,在上述納米ZSM-5介孔構(gòu)建研究基礎(chǔ)上,我們基于ZSM-5分子篩上存在的鋁分布梯度和骨架鋁對(duì)脫硅的抑制作用,通過(guò)調(diào)控NaOH堿處理時(shí)間并結(jié)合季銨堿四丙基氫氧化銨(TPAOH)的引入,實(shí)現(xiàn)了不同孔結(jié)構(gòu)納米ZSM-5的定向制備。結(jié)合MTH反應(yīng)評(píng)價(jià)結(jié)果和系列表征,系統(tǒng)研究了這些特殊孔結(jié)構(gòu)和酸性微觀因素與其催化性能之間的構(gòu)效關(guān)系�；谏鲜鲅芯�,以期實(shí)現(xiàn)納米ZSM-5擴(kuò)散性能的可控調(diào)變,找到影響其催化性能的關(guān)鍵孔結(jié)構(gòu)和酸性特征,為高性能催化劑的設(shè)計(jì)提供理論依據(jù)。本論文的主要結(jié)論如下:(1)研究納米ZSM-5堿脫硅介孔構(gòu)建過(guò)程及其對(duì)MTH反應(yīng)性能的影響發(fā)現(xiàn),延長(zhǎng)堿脫硅時(shí)間,分子篩晶粒依次經(jīng)歷小介孔形成、小介孔連通形成大介孔和大介孔融合為空心結(jié)構(gòu)的成孔過(guò)程。分子篩外比表面積、總酸量和酸強(qiáng)度隨脫硅時(shí)間的增加先增加后降低。當(dāng)堿處理5 h,外比表面積和總酸量分別達(dá)到最大的115 m~2 g~(-1)和0.71 mmol g~(-1),酸性也最強(qiáng)�；钚栽u(píng)價(jià)結(jié)果顯示,催化劑壽命也隨堿脫硅時(shí)間先增加后降低,且均明顯長(zhǎng)于母粉。其中15 h堿處理制備的空心ZSM-5,由于其良好的擴(kuò)散性能和適宜的酸性,在4.7 h~(-1)下壽命可達(dá)150 h。另外,研究發(fā)現(xiàn)催化劑擴(kuò)散性能和酸性顯著影響產(chǎn)物選擇性:催化劑良好的擴(kuò)散性能可提供充足的空間結(jié)構(gòu),有利于異構(gòu)烷烴的生成;而強(qiáng)的酸性則可加速芳構(gòu)化反應(yīng),促進(jìn)芳烴的生成。(2)定向制備不同孔結(jié)構(gòu)納米ZSM-5催化劑的研究發(fā)現(xiàn),通過(guò)延長(zhǎng)堿處理時(shí)間發(fā)現(xiàn)其外比表面積增加至一定程度后很難再繼續(xù)提升,只能形成空心結(jié)構(gòu)。然而當(dāng)以NaOH和TPAOH混合堿二次處理初步具備空心結(jié)構(gòu)的納米ZSM-5時(shí),其殼層進(jìn)行保護(hù)性深度脫硅形成豐富介孔,酸量也顯著提升。對(duì)比不同孔結(jié)構(gòu)催化劑反應(yīng)性能發(fā)現(xiàn),介孔分布均勻ZSM-5孔擴(kuò)散性能良好,內(nèi)部弱酸位的利用,體現(xiàn)出長(zhǎng)的催化壽命;規(guī)整空心ZSM-5盡管孔擴(kuò)散性能優(yōu)異,但強(qiáng)酸性導(dǎo)致其壽命略短于介孔分布均勻的納米ZSM-5;殼層富孔空心ZSM-5,由于殼層豐富介孔的引入,外比表面積可達(dá)母粉的2倍,催化壽命最長(zhǎng),在9.4 h~(-1)空速下可達(dá)149 h。此外,發(fā)現(xiàn)催化劑孔結(jié)構(gòu)也顯著影響產(chǎn)物選擇性。規(guī)整的納米空心結(jié)構(gòu)更易于芳烴和異構(gòu)烷的生成;體相介孔均勻分布的結(jié)構(gòu)和殼層富孔的納米空心結(jié)構(gòu)利于異構(gòu)烷烴和C6以下低碳烴的生成。
[Abstract]:With the increasing demand of energy and the increasing supply of petroleum, China's energy security is facing a severe challenge. Combining the characteristics of China's energy structure and giving full play to the abundant coal resources in China, the development of new coal chemical technology becomes more and more important. The methanol based hydrocarbon generation reaction (MTH) based on coal based methanol is an acid fraction. Under the catalysis of sieves, methanol can be converted into hydrocarbons, such as alkanes, low carbon olefin and aromatics. Through this technology, the clean and efficient use of coal can be realized. It is an important way to replace the petroleum route in the future. As a catalyst for the key technology of MTH reaction, ZSM-5 molecular sieve has good thermal stability, suitable acidic and ordered micropores. The structure, which can catalyze the conversion of methanol to a high selectivity, catalyzes the conversion of methanol to hydrocarbons. However, its orderly and orderly microporous structure restricts the diffusion of the reactants and products, which makes the carbon precursors accumulate easily in the micropores and promotes the formation of the carbon deposits. At the same time, it covers the active sites and causes the clogging of the pores at the end of the pore. Many studies have been made. It is shown that reducing the size of grain and introducing mesoporous pores is an important method to solve the limiting diffusion of microporous molecular sieves. They can shorten the diffusion path of the catalyst, increase the surface area and promote the diffusion of macromolecules. This paper mainly focuses on the construction of different pore structure of nano ZSM-5 molecular sieve. First, the better catalytic performance is selected. Nanoscale ZSM-5 is the object. By regulating the time of NaOH alkali treatment, the mesoporous structure of nano ZSM-5 is constructed. Combined with the evaluation results of MTH reaction and the series characterization of XRD, NH3-TPD, BET, TEM and ICP-AES, the effect of nano ZSM-5 pore construction process on its catalytic performance is investigated. The distribution gradient of aluminum and the inhibition of skeleton aluminum on desilication on ZSM-5 molecular sieve. By regulating the treatment time of NaOH base and combining quaternary ammonium four propyl ammonium hydroxide (TPAOH), the directional preparation of nano ZSM-5 with different pore structure was realized. The special pore structure was systematically studied in combination with the evaluation results and series characterization of MTH reaction. The structure-activity relationship between the acid micro factors and their catalytic properties. Based on the above study, the controllable modulation of the nano ZSM-5 diffusion properties is realized, and the key pore structure and acid characteristics that affect its catalytic performance can be found, which provide the theoretical basis for the design of high performance catalysts. The main conclusions of this paper are as follows: (1) study on the nanoscale ZSM-5 alkali removal. The construction process of mesoporous silicon and its effect on the reaction performance of MTH found that the time of alkali desilication was extended, and the small mesoporous grains were formed in turn. Small mesoporous pores were connected to form large mesoporous and large mesoporous pores, and the specific surface area, total acid content and acid strength increased first and then decreased with the increase of the time of desilication. The alkali treatment was 5 h, and the outer surface area and total acid content reached the maximum 115 m~2 g~ (-1) and 0.71 mmol g~ (-1), and the acidity was the strongest. The activity evaluation showed that the catalyst life also increased first and then decreased with the alkali desilication time, and all were obviously longer than the mother powder. The hollow ZSM-5 prepared by 15 h alkali treatment was due to its good diffusion properties and suitable The acid, under 4.7 h~ (-1), can reach 150 h.. The study found that the catalyst diffusivity and acidity significantly affect the selectivity of the product: the good diffusion properties of the catalyst can provide sufficient space structure and be beneficial to the formation of isomeric alkanes, while strong acidity can accelerate aromatization and promote the formation of aromatics. (2) directional preparation of different pores. The study of nanostructured ZSM-5 catalyst shows that it is difficult to continue to enhance the outer surface area to a certain extent by prolonging the alkali treatment time to a certain extent and only form a hollow structure. However, the protective depth of deilication is rich in the shell layer when the nano ZSM-5 is initially treated with NaOH and TPAOH mixed alkali two times. Compared to the pore structure, the reaction performance of different pore structure catalysts shows that the diffusion property of the mesoporous ZSM-5 hole is good and the internal weak acid position is used, which shows the long catalytic life. Although the porous ZSM-5 has excellent pore diffusion properties, the strong acidity leads to the short life of the nano ZSM-5 with uniform mesoporous distribution; the shell is rich. Core ZSM-5, with the introduction of rich mesoporous shell, the outer surface area can reach 2 times that of the mother powder, the longest catalytic life and up to 149 h. at the speed of 9.4 h~ (-1). It is found that the pore structure of the catalyst also affects the selectivity of the product significantly. The shell hollow nano hollow structure is favorable for the generation of low carbon hydrocarbons under ISO alkanes and below C6.
【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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本文編號(hào)：1975532