本文選題：催化裂化　切入點：ZSM-5　出處：《煙臺大學》2016年碩士論文

【摘要】：ZSM-5分子篩作為流化催化裂化生產(chǎn)丙烯裝置中最常用的催化劑組分,其較小的孔尺寸限制了較大的烴分子進入其孔道內(nèi)部,致使其孔道內(nèi)的活性位點難以參與反應(yīng)。為消除其擴散限制并闡明限域在分子篩孔道內(nèi)的納米金粒子在輕柴油催化裂化增產(chǎn)丙烯反應(yīng)中的催化作用,本文在不同條件下使用NaOH溶液對微米ZSM-5分子篩進行處理,并采用Au(en)_2Cl_3金前驅(qū)體對分子篩進行金元素改性,通過控制金載量,還原溫度,焙燒溫度等條件制備了一系列Au/ZSM-5催化劑。本文以直餾輕柴油餾程(235~337℃)為原料,考察了各分子篩樣和Au/ZSM-5催化劑在催化裂化柴油增產(chǎn)丙烯反應(yīng)中的丙烯等低碳烯烴的選擇性及其微反活性指數(shù)。并結(jié)合XRD,NH3-TPD,BET,ICP-AES,UV-Vis,TEM,FE-SEM等表征所得的催化劑的物化性質(zhì)進行綜合分析,得到以下結(jié)果:(1)采用不同濃度的NaOH溶液對ZSM-5進行處理,結(jié)果表明:在NaOH溶液濃度不太高的情況下,可以獲得晶相結(jié)構(gòu)保持不變的微介孔復(fù)合ZSM-5,其介孔體積和平均孔徑相對于ZSM-5原樣有明顯增加,但強酸量明顯減少,進一步的酸處理則會使弱酸量減少。經(jīng)過堿處理和堿酸連續(xù)處理的分子篩,其微反活性和丙烯等低碳烯烴的選擇性相較于分子篩原樣有明顯的提高。而對于堿處理的分子篩樣品,經(jīng)過進一步的800℃高溫水汽處理后,雖然分子篩晶相結(jié)構(gòu)得到保留,且介孔度進一步增加,但是其酸量急劇減少。與分子篩原樣相比,該系列處理的分子篩樣品的輕柴油催化裂化增產(chǎn)丙烯反應(yīng)中的微反活性及丙烯等產(chǎn)物的選擇性并沒有明顯變化,但ZSM-5中介孔的引入無疑為后續(xù)孔道限域Au/ZSM-5樣品的制備打下了基礎(chǔ)。(2)以Au(en)_2Cl_3為前驅(qū)體制備得到的一系列不同金載量的Au/ZSM-5催化劑,ICP-AES的結(jié)果表明:Au的實際負載量能達到理論值的80%以上,可見Au(en)_2Cl_3中的金物種與分子篩的結(jié)合力較強,它是適宜分子篩載金的前驅(qū)體。但是載金過程中由于需要使用高濃度的NaOH溶液對pH進行調(diào)節(jié),所以Au/ZSM-5樣品的酸性受到一定程度的影響,原有的兩個NH3脫附峰只剩一個,并且峰位置發(fā)生變化,同時隨著載金量的提高分子篩的酸性逐漸降低。但是進一步的微反活性評價結(jié)果表明,雖然金載量不同,但是各Au/ZSM-5樣品的丙烯等低碳烯烴的選擇性和微反活性等指數(shù)均相差不大。這可能是由于金對烴類的催化裂化反應(yīng)有一定的促進作用從而彌補了分子篩酸性下降帶來的催化活性降低。(3)在不同溫度下,采用H_2對載金量相同的Au/ZSM-5樣品進行還原處理,BET結(jié)果表明:隨著還原溫度的升高,Au/ZSM-5樣品的比表面積和孔體積等均減小,載金分子篩的催化活性卻隨之變大,這可能是由于高度分散在分子篩表面的金顆粒在高溫下聚集長大并對分子篩的酸性產(chǎn)生了貢獻,而且大的金顆�？赡芨采w了分子篩的外表面并阻塞孔道從而最終影響催化活性。(4)在不同溫度下,采用空氣對載金量相同的Au/ZSM-5樣品進行焙燒處理,XRD結(jié)果表明:隨著焙燒溫度的升高,Au/ZSM-5樣品的MFI特征衍射峰強度逐漸下降,但即使是1000℃的高溫也未能使分子篩的骨架結(jié)構(gòu)完全破壞。隨著焙燒溫度的升高,分子篩酸性明顯下降,在1000℃高溫焙燒后,分子篩酸性消失殆盡。然而,各不同溫度焙燒后的分子篩樣的催化活性依然沒有太大差別,我們?nèi)詫⑵錃w因于分子篩表面高度分散的金顆粒在高溫下聚集長大并對分子篩酸性產(chǎn)生了貢獻,并且大的金顆粒覆蓋了分子篩表面并阻塞孔道進而影響催化活性。
[Abstract]:ZSM-5 molecular sieve as catalyst was the most commonly used FCC propylene production device, the smaller pore size limits larger hydrocarbon molecules into the pores, causing the pores of the active site to take part in the reaction. In order to eliminate the catalytic effect of its diffusion limit and clarify the limit of gold nanoparticles in the domain of molecular sieve in the production of propylene catalytic cracking reaction of light diesel oil, this paper use NaOH solution processing of micron ZSM-5 molecular sieve under different conditions, and the use of Au (EN) on the molecular sieve Au modified _2Cl_3 gold precursor, through the control of gold loading, reduction temperature, a series of Au/ZSM-5 catalysts preparation the calcination temperature conditions. In this paper, straight-run diesel distillation (235~337 C) as raw material, the effects of the molecular sieve and Au/ZSM-5 catalyst in propylene catalytic cracking diesel reaction of propylene and other low carbon olefins Selectivity and micro activity index. Combined with XRD, NH3-TPD, BET, ICP-AES, UV-Vis, TEM, a comprehensive analysis of the physicochemical properties of the catalyst FE-SEM were obtained. The results are as follows: (1) treatment of ZSM-5 by using different concentrations of NaOH solution. The results showed that: in the solution of NaOH concentration is not too high under the condition, can obtain the crystal structure of micro mesoporous composite ZSM-5 remain unchanged, the pore volume and average pore diameter compared to the original ZSM-5 has increased significantly, but the strong acid significantly reduced, acid treatment will make the weak acid further reduced. Molecular after alkali treatment and alkali acid continuous processing sieve, the micro reaction selectivity the activity and propylene compared to the molecular sieve is significantly improved. The molecular sieve samples after alkali treatment, the high temperature of 800 DEG C after further processing of water vapor, although the molecular sieve crystal structure has been retained, and the mesoporous degree To further increase, but the amount decreased sharply. Compared with the original molecular sieve, micro reaction activity and selectivity of propylene and other products of FCC light diesel molecular sieve of the series of processing samples in the propylene reaction did not change significantly, but the introduction of ZSM-5 mesoporous undoubtedly for subsequent pore confinement of Au/ZSM-5 sample preparation the foundation. (2) to Au (EN) _2Cl_3 was prepared by a series of different gold loading Au/ZSM-5 ICP-AES catalyst, the results show that Au can reach the actual load above the theoretical value of 80% Au (EN), visible gold species and molecular sieves of the _2Cl_3 strong bonding force, it is suitable for molecular sieve precursor gold. But the gold loaded process due to NaOH solution with high concentration of pH was adjusted, so the sample Au/ZSM-5 acid affected to a certain extent, the original two NH3 desorption peak only one , and the peak position changes at the same time, with the increase of molecular sieve amount of gold loaded acid decreased gradually. But the further micro activity evaluation results show that although the gold load is different, but the selectivity of the Au/ZSM-5 samples propylene and micro activity index were not significant. This may be due to the catalytic the reaction of hydrocarbon cracking gold has certain stimulative effect to compensate for the molecular sieve catalytic activity of acid to bring down lower. (3) at different temperatures, using H_2 for the same amount of gold loaded Au/ZSM-5 samples BET reduction treatment, the results show that with the increase of reduction temperature, Au/ZSM-5 sample surface area and pore the volume decreases, the catalytic activity of Au molecular sieve has become larger, which may be due to high dispersion of gold particles on the surface of molecular sieve under high temperature and acid production of the aggregation and growth of molecular sieve had Gong Xian, and large gold particles may cover the outer surface of the molecular sieve and pore blocking and eventually affect the catalytic activity. (4) at different temperatures, the Au/ZSM-5 samples of the same amount of gold loaded air roasting treatment, XRD results showed that: with the increase of calcination temperature, MFI characteristic diffraction peak intensity of Au /ZSM-5 samples decreased, but even the skeleton structure of the high temperature of 1000 DEG C also failed to make the molecular sieve completely destroyed. With the increase of calcination temperature, zeolite acidity decreased significantly at 1000 degrees Celsius after calcination, acid molecular sieve disappeared. However, the catalytic activity of the molecular sieve samples after different calcination temperature is still not too the big difference, we will still be attributed to the molecular sieve surface of highly dispersed gold particles under high temperature and acidic agglomeration has a contribution to the molecular sieve, and gold particles covering the surface of molecular sieve and hole blocking The channel further affects the catalytic activity.

【學位授予單位】：煙臺大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：TQ221.212;O643.36
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本文編號：1684482