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  本文關(guān)鍵詞： 多級孔道復(fù)合分子篩 合成 包埋結(jié)構(gòu) 核殼結(jié)構(gòu) 甲醇轉(zhuǎn)化　出處：《太原理工大學(xué)》2016年碩士論文　論文類型：學(xué)位論文

【摘要】：多級孔道復(fù)合分子篩可利用微孔和介孔結(jié)構(gòu)分子篩各自的優(yōu)勢,改善單一分子篩形貌結(jié)構(gòu)、酸性分布,并協(xié)同二者孔道結(jié)構(gòu),在催化反應(yīng)中表現(xiàn)不同的催化性能。本論文對EU-1晶種進行酸改性處理,采用兩步水熱晶化合成具有包埋結(jié)構(gòu)特征ZSM-5/EU-1復(fù)合分子篩,根據(jù)分析可知,酸處理影響了晶種骨架結(jié)構(gòu)及表面酸性,促進ZSM-5分子篩在EU-1團聚體內(nèi)成核生長。該復(fù)合分子篩為同時具有微孔和介孔結(jié)構(gòu)多級孔道復(fù)合分子篩,其微孔孔徑為0.82nm,介孔孔徑分布在1.42nm、2.20nm處,且復(fù)合以后強酸量有所增強。在甲醇轉(zhuǎn)化反應(yīng)中,包埋結(jié)構(gòu)復(fù)合分子篩的甲醇轉(zhuǎn)化率提高到98.16%,二甲苯在芳香烴產(chǎn)物分布中的比例達到64.65%,也進一步提升了對二甲苯在二甲苯產(chǎn)物中的分布。核殼結(jié)構(gòu)復(fù)合分子篩因其特殊核層、殼層構(gòu)造,具有較合理的酸分布和孔道結(jié)構(gòu)性質(zhì),在催化反應(yīng)中表現(xiàn)良好的催化性能。本文在添加適量檸檬酸的條件下采用雙模板劑一步法,一次晶化合成高結(jié)晶度ZSM-5/EU-1核殼共生復(fù)合分子篩,通過表征可知,EU-1分子篩沿ZSM-5分子篩表面缺陷處外延生長,核殼分子篩的強酸量比單一分子篩相對提高,且核殼分子篩為融合度較高的微孔-介孔多級孔道結(jié)構(gòu),其微孔孔徑達到0.94nm,明顯高于包埋結(jié)構(gòu)復(fù)合分子篩,在1.24nm及1.84nm處出現(xiàn)介孔結(jié)構(gòu)。通過對合成工藝分析,獲得合成核殼共生結(jié)構(gòu)的最佳條件:n(citrate)/n(Al2O3)=0.8~1.2,pH為10.5~11.5,晶化時間為72~96h。推測核殼分子篩可能的生長過程為:先合成ZSM-5晶體,隨著時間的延長及HMBr2的導(dǎo)向作用,EU-1分子篩的結(jié)構(gòu)單元形成并在ZSM-5表面缺陷外延生長,從而形成ZSM-5/EU-1核殼共生復(fù)合分子篩。在甲醇轉(zhuǎn)化制對二甲苯催化反應(yīng)中,核殼分子篩催化產(chǎn)物的選擇性明顯高于機械復(fù)合物,而且隨著檸檬酸濃度的增大,催化產(chǎn)物中對二甲苯的選擇性也在增強。Beta分子篩由于其十二元環(huán)的特殊孔道結(jié)構(gòu)及較強的酸性,具有較高的甲醇轉(zhuǎn)化率,結(jié)合EU-1與Beta沸石結(jié)構(gòu)相似性,合成EU-1/β多級孔道復(fù)合分子篩,可進一步提升甲醇轉(zhuǎn)化率并應(yīng)用于一些大分子反應(yīng)。本論文采用預(yù)置晶種法,在堿性體系中,以EU-1為晶種,四乙基氫氧化銨為模板劑,水熱合成EU-1/β復(fù)合分子篩。通過分析可知,Beta分子篩粘附于EU-1分子篩表面生長,復(fù)合分子篩同時具有微孔-介孔多級孔道,其微孔孔徑約為0.82nm,介孔孔徑分布在2.19nm左右,其酸性、酸量明顯高于機械混合物,最佳合成條件為:EU-1晶種添加量10%~20%,堿硅比n(OH-)/n(SiO2)=0.24~0.48,模板劑量n(TEAOH)/n(SiO2)=0.55~0.68,晶化時間72h~96h。
[Abstract]:The advantages of micropore and mesoporous molecular sieve can be utilized to improve the morphology and acid distribution of single molecular sieve. In this paper, EU-1 seeds were modified with acid, and ZSM-5/EU-1 composite molecular sieves with entrapped structure were synthesized by two steps hydrothermal crystallization. Acid treatment affected the crystal skeleton structure and surface acidity, and promoted the nucleation and growth of ZSM-5 molecular sieve in EU-1 agglomeration. The micropore size is 0.82 nm and the mesoporous pore size is 1.42 nm and 2.20 nm. The methanol conversion of the entrapped molecular sieve increased to 98.16 and the proportion of xylene in the distribution of aromatic hydrocarbon products reached 64.65, which further enhanced the distribution of p-xylene in xylene products. The structure of the shell layer has reasonable acid distribution and pore structure, and it has good catalytic performance in the catalytic reaction. In this paper, the double template method is used under the condition of adding proper amount of citric acid. High crystallinity ZSM-5/EU-1 core-shell symbiotic composite molecular sieve was synthesized by single crystallization. The epitaxial growth of ZSM-5/EU-1 core-shell complex molecular sieve along the defects of ZSM-5 molecular sieve was obtained by characterization. The strong acid content of core-shell molecular sieve was higher than that of single molecular sieve. The core-shell molecular sieve is a microporous and mesoporous multilevel pore structure with a high degree of fusion. The micropore pore size of the core-shell molecular sieve is 0.94nm, which is obviously higher than that of the embedded composite molecular sieve. The mesoporous structure appears at 1.24nm and 1.84nm. The optimum conditions for the synthesis of core-shell symbiotic structure were obtained. The pH value and crystallization time of the core-shell core-shell molecular sieve were as follows: ZSM-5 crystal was synthesized firstly, and the pH value was 10.5 ~ 11.5H and the crystallization time was 72U / 96h. the possible growth process of the core-shell molecular sieve was as follows: first, the ZSM-5 crystal was synthesized. With the prolongation of time and the orientation of HMBr2, the structure unit of ZSM-5/EU-1 EU-1 molecular sieve was formed and epitaxially grown on the surface of ZSM-5, resulting in the formation of ZSM-5/EU-1 core-shell symbiotic composite molecular sieve. The selectivity of the catalytic products of core-shell molecular sieves was obviously higher than that of mechanical complexes, and with the increase of citric acid concentration, The selectivity of p-xylene in the catalytic product is also enhanced. Beta zeolite has higher methanol conversion due to its special pore structure and strong acidity of 12 member ring. The structure of EU-1 and Beta zeolite is similar to that of Beta zeolite. The synthesis of EU-1 / 尾 multilevel pore composite molecular sieve can further enhance methanol conversion and be used in some macromolecular reactions. In this paper, in alkaline system, EU-1 was used as seed and tetraethyl ammonium hydroxide as template. EU-1 / 尾 composite molecular sieve was synthesized by hydrothermal synthesis. It was found that the composite molecular sieve was grown on the surface of EU-1 molecular sieve. The composite molecular sieve also had micropore and mesoporous multilevel channels, its micropore pore size was about 0.82 nm, the mesoporous pore size distribution was about 2.19 nm, and its acidity. The optimum synthesis conditions are as follows: 10% EU-1 seed addition 10 ~ 20%, the ratio of alkali to silicon 0.24 ~ 0.48, the template dosage n ~ (2 +) ~ (-) ~ (-) ~ ((1)) ~ 0.55 ~ 0.68, and the crystallization time 72 h ~ 96 h ~ (-1). The optimum synthesis conditions are as follows: (1) the content of acid is significantly higher than that of the mechanical mixture, and the optimum conditions are as follows: (1) 10% EU-1 seed addition.
【學(xué)位授予單位】：太原理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2016
【分類號】：O643.36

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本文編號：1515867