【作者】 孟璇；

【导师】 翁惠新；

【作者基本信息】 华东理工大学 ， 化学工艺， 2012， 博士

【摘要】 我国汽油的80%来自于催化裂化(FCC)汽油,FCC汽油硫含量高,汽油中90%以上的硫化物都来源于FCC汽油。传统的加氢脱硫技术会引起烯烃加氢饱和,造成汽油辛烷值损失过大,因此在生产超低硫汽油中的应用受到限制。反应吸附脱硫(RADS)技术兼具催化加氢脱硫以及吸附的优点,能够有效地使汽油达到深度脱硫的效果。S-Zorb工艺遵循反应吸附脱硫的机理,是目前最具广阔发展空间及应用前景的脱硫工艺之一。吸附剂是S-Zorb工艺的核心技术。本论文以Ni-ZnO基吸附剂为研究基础,以模型溶液为对象,采用实验室固定床装置,系统研究了载体种类、活性组分种类及类型对吸附剂反应吸附脱硫性能的影响,采用BET、XRD、H2-TPR、TG-DTA及FT-IR等分析手段对吸附剂进行表征；对吸附剂的再生性能及稳定性进行考察；并对反应吸附脱硫机理进行探讨。主要研究内容如下：本文首先以噻吩-正辛烷为模型溶液,Ni-ZnO作为活性组分,硅藻土-Al203为载体,采用混捏法制备NiZnO/硅藻土-Al203吸附剂。通过吸附剂评价实验得出NiZnO/硅藻土-Al203吸附剂的最佳组成为：载体中硅藻土与A1203含量比为1：1；硅藻土-Al203含量占吸附剂总质量为50%；Zn/Ni摩尔比为0.4。吸附剂的最佳制备条件为：焙烧温度为600℃；焙烧时间为1h。吸附剂最适宜的还原工艺条件为：H2还原流量为30ml/min;还原温度为370℃；还原压力为0.5MPa。吸附剂最适宜的反应工艺条件为：反应温度为400℃；反应压力为1MPa；H2/oil体积比为400。在最佳条件下,NiZnO/硅藻土-Al203吸附剂的硫容为1.073%。接着对Ni-ZnO基吸附剂载体进行筛选,同样以噻吩-正辛烷为模型溶液,考察不同活性白土、各类分子筛以及各种金属氧化物作载体的吸附剂的脱硫性能,结果表明三种载体吸附剂的脱硫性能都较NiZnO/硅藻土-Al203吸附剂有不同程度的提高,不同载体吸附剂的脱硫性能由大到小排序依次为NiZnO/HY分子筛>NiZnO/ZrO2-TiO2> NiZnO/TiO2>NiZnO/白土-Al2O3>NiZnO/硅藻土-Al203。由于FCC汽油中含有大量烯烃,采用噻吩-烯烃-正辛烷模型溶液,考察烯烃对不同载体吸附剂脱硫性能的影响,结果表明不同载体吸附剂的脱硫性能均有不同程度的下降,其中NiZnO/硅藻土-Al203和NiZnO/HY分子筛的脱硫性能下降最小,NiZnO/ZrO2-TiO2和NiZnO/白土-Al203次之,而NiZnO/TiO2的脱硫性能下降最明显,达到30.39%。从烯烃饱和率数据可见,以HY分子筛为载体的吸附剂的烯烃饱和率最高,达到70.19%,而吸附剂NiZnO/硅藻土-Al203、NiZnO/ZrO2-TiO2和NiZnO/TiO2的烯烃饱和率相对较小,因此对油品造成的辛烷值损失较小。综合考虑,ZrO2-TiO2作为吸附剂载体既具有相对较佳的噻吩脱除性能又具有相对较低的烯烃饱和率。在上述研究基础上,以噻吩-烯烃-正辛烷模型溶液为原料,研究了不同ZnO前躯体对镍基氧化锌吸附剂脱除噻吩性能的影响。XRD表征结果表明,NiZnO(硝酸锌)/TiO2-ZrO2.NiZnO(氯化锌)/TiO2-ZrO2和NiZnO(：碱式碳酸锌)/TiO2-ZrO2的ZnO晶粒尺寸较NiZnO/TiO2-ZrO2明显减小,同时这三种吸附剂中归属于惰性的金红石结构的Ti02消失,表明碱式碳酸锌、氯化锌及硝酸锌作为氧化锌前躯体可以有效抑制载体中Ti02锐钛矿向惰性金红石晶相的转化,从而增强了载体的机械性能。经筛选确定硝酸锌前躯体吸附剂具有最高的脱硫活性。接着研究了不同加氢活性组分对镍基氧化锌吸附剂脱除噻吩性能的影响,结果表明Mo系吸附剂较Ni系和Co系吸附剂具有较高的脱硫活性,但是其烯烃饱和率较高,相比之下,Ni系和Co系吸附剂的烯烃饱和率则相对较低,Ni-Co双组份吸附剂的烯烃饱和率最低,经考察筛选得出最佳CoZnO/ZrO2-TiO2吸附剂组成为：Co含量为35%,ZnO含量为15%,吸附剂硫容达到1.245%,烯烃饱和率为27.20%。采用空气氧化-氢气还原两步法使Ni-ZnO基吸附剂得以再生,结果表明本论文制备的Ni-ZnO基吸附剂具有优良的再生性能及稳定性。提出噻吩在Ni-ZnO基吸附剂上的反应吸附脱硫机理,并用具体实验验证了这一机理的正确性。首先噻吩以S-M的模式吸附在吸附剂表面的Ni0活性位上,通过氢气进一步弱化噻吩的C-S键,导致C-S键断裂使Ni被硫化成Ni3S2,从而释放出C4物种；第二步,Ni3S2在氢气的作用下再次被还原成具有活性的单质Ni,生成H2S；最后,H2S迅速与吸附剂中ZnO组分反应生成ZnS,将系统中的S储存至ZnO中,自此实现吸附剂的“自再生”循环。以上研究结果可为S-Zorb吸附剂的国产化开发提供依据。更多还原

【Abstract】 FCC gasoline, accounting for more than 80% of commercial gasoline in China, contains very high levels of sulfur compounds. More than 90% of sulfur compounds in commercial gasoline come from FCC gasoline. The removal of sulfur compounds traditional by hydrodesulfurization (HDS) techniques will inevitably result in the saturation of many olefins and cause serious octane number lost. Therefore, the application of the traditional HDS techniques in producing ultra-low sulfur containing gasoline is limited. Reactive adsoption desulfurization (RADS) is effective for deep desulfurization because it combines the advantages of the catalytic HDS and adsorption. S-Zorb process for desulfurization follows the mechanism of reactive adsorption and it is a novel green process with extensive development space and application prospects. Adsorbents play a vital role in S-Zorb process. In this paper, Ni-ZnO based adsorbent were chosen as main research basement and model fuel was chosen as treatment object to explore the performance of adsorbents with different types of supports and active components on RADS using a lab fixed bed continuous flow reactor. The adsorbents were characterized by BET, XRD, H2-TPR, TG-DTA and FT-IR in order to find out the influence of specific types of surface chemistry and structural characteristics on the sulfur adsorptive capacity. The regeneration property and stability and the adsorption Mechanism have been studied. The main and important results are described as follows:The model fuel(thiophene-n-octane) was chosen as treatment object and ZnNi/diatomite-Al2O3 adsorbents were prepared by kneading method. According to the activity measurement results, the optimal composition for ZnNi/diatomite -Al2O3 was diatomite:Al2O3=25%:25%, Zn/Ni molar ratio=0.4.The optimal preparation condition for the adsorbent was Tcalcination =600℃, tcalcination=1h. The optimal reduction condition for the adsorbent was LH2=30ml/min, Treduction=370℃, Preduction=0.5MPa. The optimal reaction condition for the adsorbent was Treaction=400℃, Preaction=1 MPa,H2/oil=400. Under these conditions, the adsorptive capacity of ZnNi/diatomite-Al2O3 adsorbent was about 1.073%.Next, the model fuel(thiophene-n-octane) was chosen as treatment object and Ni-ZnO chosen as active components to explore the performance of adsorbents with different types of supports (caly-Al2O3, zeolites, metal oxides) on RADS. The adsorption results shown that the adsorptive capacity of different support adsorbents is in the following order:NiZn/Ti-Zr> NiZn/Ti> NiZn/Al-clay> NiZn/Al-diatomite. The commercial FCC gasoline contains amounts of olefins. To examine the effect of olefin on the adsorption of thiophene, the adsorptive desulfurization of the model fuel (thiophene -1-octene -n-octane) over the five different support adsorbents at the same reaction conditions was examined. The results showed that the desulfurization rate of the five different support adsorbents samples decreased in various degrees. The adsorptive capacity of NiZn/HY and NiZn/Al-diatomite samples decreased only slightly, while the adsorptive capacity of NiZn/Ti sample decreased extensively(Reduction rate was 30.39%). The olefin saturation rate of NiZn/ HY sample (70.19%)was higher than that of the other four samples, implying that the HY-supported adsorbent will lead to a great loss of octane number for gasoline, while, the olefin saturation rates of NiZnO/diatomite-Al2O3、NiZnO/ZrO2-TiO2和NiZnO/TiO2 were relatively low. On the basis of comprehensive compare, ZrO2-TiO2 was the most suitable support of the adsorbent.The model fuel(thiophene-l-octene-n-octane) was chosen as treatment object. The four Ni/ZnO-based adsorbents with different ZnO precursors of ZnO,2ZnCO3·3Zn(OH)2 (ZN), ZnCl2(ZC) and Zn(NO3)2·6H2O(BZC) were prepared in this study. The RADS performance of the four different ZnO textures was evaluated in the same conditions. According to XRD patterns, the characteristic XRD peaks of ZnO crystalline phase for the modified ZnO precursor adsorbents (NiZnO(BZC)/ZrO2-TiO2, NiZnO(ZC)/ZrO2-TiO2and NiZnO(ZN)/ ZrO2-TiO2) become much boarder than that for the NiZnO/ZrO2-TiO2, implying that Zn(NO3)2·6H2O, ZnCl2 and 2ZnCO3·3Zn(OH)2 as ZnO precursors can significantly improve the dispersion of ZnO on the support surface. In addition, for NiZn/Ti-Zr sample the crystallite phases of TiO2 are attributed to the anatase phase and the rutile phase;however, there are, X-ray diffraction data indicated only the anatase phase of TiO2 at the NiZnO(BZC)/ ZrO2-TiO2, NiZnO(ZC)/ ZrO2-TiO2 and NiZnO(ZN)/ZrO2-TiO2 samples, without detection of rutile phase. This indicates that the addition of 2ZnCO3·3Zn(OH)2, ZnCl2 or Zn(NO3)2·6H2O can inhibit the transformation of anatase to rutile, thus improve the desulfurization activity of the adsorbents. The effect of types of hydrogenated active components(Mo,Co,Ni) was investigated, the results shown that the desulfurization performances of Mo series adsorbents were higher than Co series and Ni series adsorbents, while the olefin saturation rates of Mo series adsorbents were higher than that of Co series and Ni series adsorbents, implying that the Mo series adsorbents will lead to a great loss of octane number for gasoline. The olefin saturation rate of Ni-Co series adsorbents was the lowest. The optimal composition for CoNZnO/ZrO2-TiO2was Co(wt%)=35%, ZnO(wt%)=15%, the adsorptive capacity and the olefin saturation rate of CoNZnO/ZrO2-TiO2 adsorbent were 1.245% and 27.20% separately. The muticycle fixed-bed tests show promise for adsorption desulfurization over the Ni/ZnO-based adsorbents.A two-step regeneration schemes are deemed to be appropriate to return the adsorbent to its original state.The thiophene RADS reaction mechanism was proposed and it was proved to be convenient and accurate. Firstly, S-M adsorbed thiophene in the model fuel is first decomposed on surface Ni of the adsorbent to form Ni3S2 while the C4 hydrocarbon portion of the molecule is released back into the process stream, followed by the reduction of Ni3S2 to form H2S in the presence of H2, and then H2S is rapidly stored in the adsorbent accompanied by the conversion of ZnO into ZnS. The above conclusion can provide practice experiences for the Localization of S-Zorb process adsorptive desulfurization adsorbent.更多还原