發(fā)布時間：2018-04-15 11:02

  本文選題：MTO + SAPO-34��； 參考：《中國礦業(yè)大學》2017年碩士論文

【摘要】：近幾年來,隨著石油資源的持續(xù)短缺以及可持續(xù)發(fā)展戰(zhàn)略的要求,非石油資源合成低碳烯烴的技術(shù)路線迅速發(fā)展;使用以煤或天然氣合成的甲醇為原料,生產(chǎn)低碳烯烴的化工工藝技術(shù)(簡稱MTO)受到人們的廣泛關注。而SAPO-34分子篩在MTO反應中展現(xiàn)出了優(yōu)異的催化性能,這主要是由于其適宜的酸性、較小的孔道以及高溫下的水熱穩(wěn)定性。本文使用水熱晶化法以三乙胺為模板劑合成不同硅鋁比的SAPO-34分子篩,使用XRD,SEM,FT-IR,BET,TPD等進行表征,并在固定床反應器上測試所合成的SAPO-34分子篩的MTO反應性能。考察了在SAPO-34分子篩的MTO反應中,添加少量的苯、甲苯、環(huán)己烷、環(huán)己烯、環(huán)戊烷等對催化劑壽命及產(chǎn)品選擇性的影響;并使用不同濃度的硝酸鋁水溶液或硝酸鋁乙醇溶液對SAPO-34分子篩進行浸漬法改性,探索鋁改性對MTO反應性能的影響以及使用不同溶劑改性時對SAPO-34分子篩的影響。在原料甲醇中添加5%的苯、甲苯、環(huán)己烷、環(huán)己烯或環(huán)戊烷會影響SAPO-34分子篩的MTO反應性能,導致催化劑壽命縮短。其中,環(huán)己烷對催化劑壽命的影響程度最大,甲苯的影響程度最小,苯、環(huán)己烯和環(huán)戊烷則居中。烴類的添加對不同硅鋁比的SAPO-34分子篩壽命的影響也不同,硅鋁比越高,催化劑壽命變化越大;這主要是因為C5+和C6+作為碳池物種對甲醇的轉(zhuǎn)化起著重要的作用,而烴類的加入會加速碳池的形成,并容易形成積碳,導致催化劑的失活,而酸含量越高形成積碳的速率越快。使用硝酸鋁水溶液改性后,SAPO-34分子篩的酸強度沒有發(fā)生變化,酸濃度變化較大;其中弱酸的變化較小,中強酸(B酸)隨著硝酸鋁濃度的升高而明顯降低。改性后的分子篩B酸含量降低,但催化劑壽命卻隨之縮短;主要是因為改性后的分子篩雖然B酸含量減少,但是鋁的引入導致L酸含量的增加以及孔道的減小,從而導致催化劑壽命的縮短。而使用硝酸鋁乙醇溶液改性時,催化劑壽命的變化則較小,主要是因為其酸量的變化較小。
[Abstract]:In recent years, with the continuous shortage of petroleum resources and the requirement of sustainable development strategy, the technical route of synthesizing low carbon olefins from non-petroleum resources has developed rapidly; methanol synthesized from coal or natural gas is used as raw material.The chemical technology of producing low-carbon olefin (MTO) has been paid more and more attention.However, SAPO-34 molecular sieve showed excellent catalytic performance in MTO reaction, which was mainly due to its suitable acidity, small pore channels and hydrothermal stability at high temperature.In this paper, SAPO-34 molecular sieves with different Si / Al ratios were synthesized by hydrothermal crystallization with triethylamine as the template. The MTO reaction properties of the synthesized SAPO-34 zeolites were tested in a fixed bed reactor.The effects of a small amount of benzene, toluene, cyclohexane, cyclohexene and cyclopentane on the catalyst life and product selectivity in the MTO reaction of SAPO-34 molecular sieve were investigated.The SAPO-34 molecular sieve was modified with different concentration of aluminum nitrate solution or ethanol solution. The effect of aluminum modification on MTO reaction performance and the effect of different solvent modification on SAPO-34 molecular sieve were explored.The addition of 5% benzene, toluene, cyclohexane, cyclohexene or cyclopentane into methanol will affect the MTO reaction performance of SAPO-34 molecular sieve and shorten the catalyst life.Among them, the influence of cyclohexane on catalyst life is the largest, toluene is the least, benzene, cyclohexene and cyclopentane are in the middle.The effect of hydrocarbon addition on the lifetime of SAPO-34 zeolites with different ratio of Si to Al is also different. The higher the ratio of Si to Al, the greater the change of catalyst life, which is mainly due to the important role of C5 and C6 as carbon pool species in methanol conversion.The addition of hydrocarbons accelerates the formation of carbon ponds and easily leads to the deactivation of catalysts, and the higher the acid content is, the faster the rate of carbon deposition is.The acid strength of SAPO-34 molecular sieve modified with aluminum nitrate aqueous solution did not change, and the acid concentration of SAPO-34 molecular sieve changed greatly, among which the change of weak acid was small, and that of moderate and strong acid B acid decreased obviously with the increase of aluminum nitrate concentration.The modified molecular sieve has lower B acid content, but shorter catalyst life, which is mainly due to the increase of L acid content and the decrease of pore channel due to the decrease of B acid content in the modified molecular sieve, but the introduction of aluminum leads to the increase of L acid content and the decrease of pore channel.As a result, the catalyst life is shortened.However, the change of catalyst life is smaller when modified with aluminum nitrate ethanol solution, mainly because of the small change of acid content.
【學位授予單位】：中國礦業(yè)大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：O643.36;TQ221.211

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