【作者】 Muhammad Yaseen（亚森）；

【导师】 李春喜；

【作者基本信息】 北京化工大学 ， 化学工程与技术， 2011， 博士

【摘要】 燃油中的硫及其衍生物是空气污染的主要来源之一。随着燃油的燃烧,其中的硫会以其氧化物的形式排放到大气中,它们对大气会有严重的危害,因此需要对这类氧化物进行控制。近二十年来,环保法规定的燃料中硫含量的允许限度一直在降低。为此,人们研究和开发了许多燃料油的脱硫技术和方法,例如氧化脱硫、生物脱硫和催化加氢脱硫(HDS)等。在这些技术中,催化加氢脱硫因为具有高效、工艺成熟的特点而占据主导地位。本工作中,我们开发了一种催化加氢脱硫的新方法,即采用Ru和Pd作为助催化剂(Co/Ni) MO-Al2O3催化剂,通过乙醇或甲醇重整产生的原位氢来实现二苯并噻吩(DBT)的催化加氢脱硫。本工作主要包括催化剂的制备及其对模型油中DBT的催化加氢性能评价。催化剂的载体选用高比表面积的三氧化二铝。在制备催化剂时,将A1203浸泡在含有Mo、Co(或Ni)、Ru(或Pd)的水溶性盐溶液中。为了减小因活性相含量变化对催化活性的影响,在整个过程中要保持金属负载量不变。由于Ru和Pd非常昂贵,其含量控制在较低水平,实验过程中其质量分数分别为1%和0.5%。本实验在体积为250m1的高压反应釜中进行,反应所需要的氢气通过甲醇重整(以Pd为助催化)或乙醇重整(以Ru和Pd为助催化剂)反应提供,而无需外界提供氢气源。实验采用含有900 ppm DBT的正辛烷溶液作为模型燃料油,反应时间为1-13h,反应温度范围为320-400℃。此外,还考察了八种有机添加物(即十氢萘、四氢萘、萘、蒽、二甘醇、苯酚、邻二甲苯和吡啶)对反应体系中DBT加氢脱硫性能的影响。结果表明,这些添加剂由于其物理和化学性质的差异,有的会抑制DBT的加氢脱硫效率,而有些则会促进DBT的催化加氢效率(如十氢萘、四氢萘、二甘醇和苯酚)。通过考察乙醇(或甲醇)重整反应和DBT的加氢脱硫反应,测试了催化剂的活性。反应产物分别采用高性能液体色谱(HPLC)和气质联用仪(GS-MS)进行了定量和定性分析,催化剂样品(新制备和用过的)通过SBET表面积性质测试进行表征。结果表明,基于原位产氢对DBT进行加氢脱硫的方法是非常有效的。无论是对于乙醇(或甲醇)的重整产氢反应还是对于DBT的催化加氢反应,镍基催化剂的活性总是高于钴基催化剂。而且,当在上述催化剂中掺入贵金属(如Ru或Pd)时,催化活性明显增加。对于钌系催化剂,其加氢脱硫活性遵循如下顺序：Ru-Ni-Mo/Al2O3> Ni-Mo/Al2O3> Ru-Co-Mo/Al203> CO-MO/Al2O3;对于钯系催化剂,其活性次序类似,即Pd-Ni-Mo/ Al2O3> Ni-Mo/Al2O3> Pd-Co-Mo/Al2O3> Co-Mo/Al2O3。重整反应产物的GC分析表明(以Pd系催化剂为例),无论在乙醇还是甲醇的重整反应过程中,都会伴随乙醇(或甲醇)脱水副反应,生成相应的醚(乙醚或二甲醚)。对于Pd助催化的甲醇或乙醇的重整反应,催化剂的活性顺序与前面的HDS反应中相同。此外,值得注意的是,Pd的加入会显著提高催化剂的活性,使用Pd负载量为0.5%的催化剂,在380℃反应13hDBT的转化率可达到97%。这些在以前的文献中没有报道。由GC-MS分析可知,DBT催化加氢的主要产物为联苯,而未发现二环己烷和苯基环己烷峰,表明本文提出的原位加氢脱硫反应遵循直接脱硫途径,这也是加氢脱硫在380℃的高温时的特征。而且,原位加氢的机理与在高温条件下采用外部氢气的催化加氢机理相同,均为直接脱硫途径。与传统的催化加氢脱硫过程相比,本文提出的基于原位产氢的催化加氢技术无需提供外部氢气,具有反应条件温和,成本低,效率高,贵金属负载量低,催化活性高等优点。因此,基于甲醇(或乙醇)重整反应的原位催化加氢技术可望作为一种替代方法,用于工业上DBT的加氢脱硫工艺过程。更多还原

【Abstract】 Sulfur (S) and its derivatives present in fuel oils are considered as the major air pollutants producers. With the combustion of fuel oils, it comes out in exhaust gases in the form of sulfur oxides and goes to the atmosphere. Being seriously dangerous to the atmosphere, special attention is needed for the control of these oxides. As a result, environmental regulating authorities are consistently making the permissible limits of S in fuel oils narrower since last two decades. In order to cope with these stringent regulations, several techniques and methods have been attempted for the desulfurization of fuel oils, for example oxidative desulfurization, biodesulfurization and catalytic hydrodesulfurization (HDS). Among these techniques, HDS has earned its position over the years based on its efficiency, diverse nature and flexibility in the process mechanization. In the present work, a novel catalytic HDS process was developed for dibenzothiophene (DBT) through in situ hydrogen production via ethanol and methanol reforming reaction over Ru and Pd promoted (Co/Ni) Mo supported Al2O3 based catalysts.There were two major steps involved in this project. The first step was the preparation of the HDS catalysts while the second was the practical experimental procedure for analyzing their HDS activity toward DBT (as model fuel). High surface area containing Al2O3 was selected as catalytic support, which was successively impregnated with water soluble salts of Mo, Co, Ni, Ru or Pd in the mentioned order. The metal loadings were kept constant throughout the process in order to minimize the effect of change in catalytic activity due to the extent of active phase formation. Ru and Pd being very expensive, were used in very low quantity i.e. 1 wt.% and 0.5 wt.% respectively as compared to those reported earlier. Catalytic activity was evaluated in a 250 ml batch autoclave reactor in the complete absence of external hydrogen supply. The hydrogen needed for the HDS reaction was supplied through the reforming reaction of ethanol (in case of Ru and Pd based catalysts) and methanol (in case of Pd promoted catalyst) separately. The in situ generated hydrogen utilization mechanism contributed the most toward the novelty in the current project. A 900 ppm DBT solution in n-octane was used as model fuel. Experiments were carried out in a temperature range of 320-400℃while reaction time was varied from 1-13 h. Apart from this, the effect of eight selected organic additives namely, decalin, tetralin, naphthalene, anthracene, diethylene glycol (DEG), phenol, o-xylene and pyridine was also studied. Each additive based on its chemical nature and structure, presented different effect on activity of the catalysts toward HDS of DBT i.e. some inhibited while some enhanced it. Decalin, tetralin, DEG and phenol type additives were found to be quite effective toward HDS reaction over all types of catalysts. Catalytic activity was measured in terms of reforming reaction of ethanol/methanol and HDS reaction of DBT separately. Reaction products were analyzed using HPLC and GC-MS techniques while catalytic samples (fresh and used) were characterized in terms of SBET surface area properties. The results showed that our process based on in situ generated hydrogen for the HDS of DBT is quite promising. It was found that in case of both ethanol and methanol reforming reactions, Ni based catalysts were more active than Co ones. Similar was the case with HDS reaction, whereas the incorporation of a noble metal i.e. Ru or Pd notably increased the catalytic activity. In all sets of experiments performed, for Ru based catalysts, HDS activity followed the order:Ru-Ni-MO/Al2O3> Ni-Mo/Al2O3> Ru-Co-Mo/Al2O3> Co-Mo/Al2O3 and for Pd promoted catalysts the order was: Pd-Ni-Mo/Al2O3> Ni-Mo/Al2O3> Pd-Co-Mo/Al2O3> Co-Mo/Al2O3. In case of Pd promoted catalyst, ethanol reforming activity was calculated; while a side reaction i.e. dehydration of ethanol, leading to the production of diethyl ether (DEE), was also confirmed by GC analyses. Similar was the case of methanol reforming, where dimethyl ether (DME) was confirmed as the dehydration product. In case of both the ethanol and methanol reforming reactions, Pd promoted catalysts followed the same order mentioned above. In this series, the increased HDS activity due to the incorporation of Pd was noteworthy, as 0.5 wt.% Pd loading showing 97% DBT conversion at 13 h reaction time and 380℃temperature has not been yet reported elsewhere. The GC-MS analyses indicated that biphenyl (BP) was the major product while bicyclohexane (BCH) or cyclohexylbenzene (CHB) were completely absent, revealing that direct desulfurization (DDS) pathway was followed, which is a trademark of HDS reaction at as high temperature as 380℃. Moreover, it was confirmed that the in situ HDS process is similar in its approach with the ex situ hydrogen utilization based process.Mild operating conditions, cost effectiveness, low metal loadings, reasonably high catalytic activity and utilization of in situ generated hydrogen proved the present process quite fruitful and superior to the currently in service conventional catalytic HDS process. Based on these results, the current process might be applied as an alternative approach toward HDS of DBT on industrial scale.更多还原