Influence of Acidity Properties on the Hβ Catalytic Performance of the Olefin Alkylation Thiophenic Sulfur in Gasoline
Zhang ZK(张泽凯); Niu XL(牛雄雷); Zhu XC(朱向嚐); Liu SL(刘盛林); Xu LY(徐龙伢)
会议名称4th asia pacific congress on catalysis
英文摘要Influence of Acidity Properties on the Hβ Catalytic Performance of the Olefin Alkylation Thiophenic Sulfur in Gasoline Zekai Zhang1,2, Xionglei Niu1,2, Xiangxue Zhu1, Shenglin Liu1, Longya Xu1 1. Laboratory of Natural Gas Utilization and Applied Catalysis. Dalian Institute of Chemical Physics. The Chinese Academy of Sciences, Dalian 116023, P. R. China 2. The graduate School of Chinese Academy of Science, Beijing 100084, P. R. China E-mail: zzk@dicp.ac.cn; lyxu@dicp.ac.cn Introduction To remove the sulfur from gasoline efficiently, many desulfurization technologies were studied in the past decades, and one of them was the olefin alkylation thiophenic sulfur (OATS) [1]. The OATS process first added one or two brunch carbochain to the sulfur compounds (mainly thiophene and its derivates) through alkylation reactions by some catalyst, and then separated the alkalized heavy sulfur compounds from gasoline by distillation. As thiophenes alkylation reaction was easy to achieve, OATS process could be handled under rather mild conditions. Besides, the alkenes oligomerization and the aromatics alkyaltion could not be omitted, as they have the same carbocation mechanism with thiophenes alkylation and are easy to happen during OATS. Considering of that, we have discussed the behavior of thiophenes alkylation, aromatics alkylation,and hexene oligomerization in a model gasoline system that was made up of thiophenes-aromatics-1-hexene -methylcyclohexane, and found that the reaction rates of thiophenes are much higher than the other two [2]. As the alkyaltion was an acid catalyzed reaction, the paper reported the influence of acidity properties on the catalytic performance of H zeolites. Experiment The Hβ zeolites were obtained by an ion exchange method. The OATS process was carried out in a stainless steel reactor with ID 9mm × L 300mm. The thiophene: 1-hexene: xylene: methycyclohexane ratio is 1.6: 4.9: 12.8: 500(v/v) in the model system. The products were detected by FID and FPD. Results and discussion Many reactions may happen during OATS process, such as mentioned above, thiophenes alkylation, aromatics alkylation and alkenes oligomerization [2]. In our model system, they are embodied as the change of thiophene conversion, the xylene conversion and the hexene oligomerization. Besides, the C12-T, one of thiophene products, whose relative content change was introduced as another criterion. Table 1 displays the results that were catalyzed by the Hβs with different Si/Al2 mole ratios. It showed that, though thiophene alkylation, xylene alkylation and hexene oligomerization were acid catalyzed reactions, and the total acidity of Hβs was decreased with the increase of Si/Al2, but the catalytic performance of the Hβs on the three reactions was not corresponding to its acidity order. At the reaction time of 1h, when the Si/Al2 ratio of Hβ increased from 40, 60 to 120, the conversions of thiophene were all over 98%, while the C12-T relative contents changed from 51.75%, 95.20% to 81.01%; at the same time, the conversion of xylene got 13.64%, 13.71% and 6.27%; the hexene oligomerization got 9.59%, 3.84% and 10.31%, respectively. Thus, the Hβ60 got the best catalytic performance on the thiophene alkylation. The conversion of xylene got max at Si/Al2 60 too; different from the alkylation of thiophene and xylene, hexene oligomerization got its min value. The lower Si/Al2 ratio was good for xylene alkylation while the higher Si/Al2 was good for thiophene alkylation, and the hexene oligomerization was influenced by the thiophene alkylation and xylene alkylation clearly. If the conversions of thiophene and xylene both were high, hexene oligomerization would be low, and if one of the former two reactions decreased, hexene oligomerization would change to be higher. According the above results, it seems to have an appropriate Si/Al2 ratio of Hβs for the three reactions where their initial conversions got extreme. The Si/Al2 ratio of Hβ also influenced the thiophene conversion via reaction time. The higher thiophene conversion got, the slower it decreased. For example, catalyzed by Hβ60, at 8h the thiophene conversion was still kept above 80%, while it has decreased to be lower than 50% by the other two Hβs. Meanwhile, the Si/Al2 ratio did not influence the xylene conversion and hexene oligomerization via time clearly. Their conversion curves all appeared an inflexion at about 4h. Before 4h the conversions decreased very fast, after that they would decrease slower and keep stable at a rather low level. The appearance of the optimism Si/Al2 for thiophene alkylation shall come from two factors, the carbocation activation capability and hydrogen transformation capability, which are mainly caused by Brőnsted acid sites of catalyst [3]. The strong Brőnsted acid sites of the catalyst are preferable to activate the alkenes into carbocation form, transport it to the accepters, and finish the alkylation reaction mechanism. However, these strong Brőnsted acid sites also can cause the hydrogen transformation reactions, form the coke, make the zeolites pore be blocked and decrease catalytic ability of the zeolites at last. The inflexion of the side reactions may come from that reason too. FT-IR and TPO showed that the Hβ40 had the most Brőnsted acid sites and caused the most coke, while Hβ60 had less Brőnsted acid sites and caused less coke, which seemed to be a support for the deduction. Table 1: The catalytic performance of H zeolites Conversion /% Hexene oligo. /% Distribution of alkalized thiophenes /% Hβs Time /h thiophene xylene dodecene C6-T C12-T C18-T Hβ40 1.0 98.32 13.64 9.59 47.32 51.75 0.92 2.0 99.15 8.84 3.86 74.11 25.62 0.27 4.0 83.45 2.49 1.85 94.22 5.67 0.12 8.0 47.18 1.32 0.56 98.51 1.34 0.16 Hβ60 1.0 99.74 13.71 3.84 4.16 95.20 0.64 2.0 99.99 8.29 3.30 13.44 85.72 0.84 4.0 97.11 3.41 2.04 96.03 3.96 0.01 8.0 80. 65 2.11 0.93 97.09 2.90 0.00 Hβ120 1.0 99.36 6.27 10.31 18.83 81.01 0.16 2.0 99.50 2.04 8.00 59.04 40.62 0.34 4.0 87.86 1.99 3.17 93.80 6.15 0.05 8.0 48.12 0.39 1.00 98.36 1.51 0.13 Reaction conditions: T = 90oC, P = 1.5 MPa, WHSV = 9.0 h-1. Cx-T: the alkalized thiophenes, x is the carbon number of the brunch chain on the thiophene. References [1] I.V. Babich, J.A. Moulijn, Fuel, 2004, 82, 607-631. [2] Z. K. Zhang, S. L. Liu, et al, Chin. Petro. Chem. , 2006, 35, 113-117. [3] K. S. Yoo, P. G. Smirniotis. Catal. Lett., 2005,103, 249-255
通讯作者Xu LY(徐龙伢)
GB/T 7714
Zhang ZK,Niu XL,Zhu XC,et al. Influence of Acidity Properties on the Hβ Catalytic Performance of the Olefin Alkylation Thiophenic Sulfur in Gasoline[C],2006:270/2.
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