【作者】 王文寿；

【导师】 王祥生； 郭洪臣；

【作者基本信息】 大连理工大学 ， 工业催化， 2009， 博士

【摘要】 催化裂化（FCC）汽油约占我国成品油总量的80%。FCC汽油中的烯烃和硫含量很高,常用的加氢脱硫催化剂如Ni-Mo/Al₂O₃等虽然可以降低汽油中的硫含量,但在加氢脱硫过程中会造成烯烃大幅减少,使辛烷值损失。纳米ZSM-5分子筛催化剂由于晶粒小、微孔短、孔口多和外表面酸量大等特点,在催化脱除噻吩硫及烃类芳构化方面表现出比微米ZSM-5分子筛更好的活性和稳定性。负载稀土金属氧化物和过渡金属氧化物如Ni、Mo都可以进一步提高催化剂的活性及稳定性。本论文首先采用乙酸镍、硝酸镍和硫酸镍作为镍源,比较了用不同镍盐改性的纳米HZSM-5催化剂在FCC汽油脱硫降烯烃过程中的催化活性:在此基础上研究了稀土氧化物对HZSM-5及NiSO₄改性HZSM-5催化剂催化活性的影响:研究了HZSM-5负载NiSO₄制备的芳构化降烯烃脱硫工业催化剂（FDO）再生后SO₄^2-的流失对催化剂脱硫活性的影响;最后还研究了MoO₃改性对HZSM-5负载La₂O₃和NiSO₄制备的Ni-La/HZSM-5催化脱硫活性的影响。得到如下主要结果:1.Ni（Ac）₂和Ni（NO₃）₂改性的纳米HZSM-5催化剂的脱硫稳定性有明显改善,当用NiSO₄改性后,脱硫率达80%,并且稳定性有了很大提高。以γ-Al₂O₃和SiO₂小球为载体,分别负载NiSO₄、Ni（Ac）₂和Ni（NO₃）₂所做的对比研究表明,NiSO₄中的S=O与HZSM-5催化剂和γ-Al₂O₃载体中的铝氧化物之间存在着强的相互作用。这种强相互作用可以产生以下影响:（1）产生大量的L酸中心,提高L/B比值,增强L酸与B酸的协同作用;（2）使Ni盐在催化剂表面形成单层分布;（3）减少NiO与Al₂O₃作用生成尖晶石结构NiAl₂O₄的机会:（4）增强催化剂对噻吩的选择性吸附能力,促进脱硫反应的进行。而SO₄^2-与SiO₂之间则不存在类似的相互作用。单纯γ-Al₂O₃负载SO₄^2-制备的SO₄^2-/Al₂O₃催化剂上虽然会有大量L酸产生,且酸性较强,催化剂却依然没有脱硫活性。这表明在酸性催化剂上,B酸中心是脱硫反应所必不可少的活性中心。2.用硫含量为1000μg/g的模拟油品（噻吩+环己烷）研究发现,原料中加入烯烃有利于HZSM-5以及Ni/HZSM-5催化剂的脱硫活性和稳定性。这是由于以环己烷和1-辛烯为反应原料时,烯烃和环烷烃的芳构化反应会产生大量的活性氢,这些活性氢可以极大地提高催化剂的脱硫活性和稳定性。3.适量的La₂O₃和CeO₂改性可以降低HZSM-5上强B酸中心的数量,减少噻吩在催化剂上生成噻吩衍生物的副反应,提高脱硫选择性。La₂O₃或CeO₂改性后再负载NiSO₄制备的双金属化合物改性HZSM-5催化剂上,NiSO₄与催化剂间的强相互作用被削弱,NiSO₄的分解温度从928℃降低到了827℃,NiSO₄的分布状态被改变。La₂O₃与NiSO₄双金属化合物改性HZSM-5催化剂较好的保持了NiSO₄改性催化剂的脱硫稳定性,而CeO₂与NiSO₄之间可能还存在着其它的相互作用,导致CeO₂与NiSO₄双金属化合物改性HZSM-5催化剂的脱硫稳定性急剧下降。4.以NiSO₄改性HZSM-5制备的芳构化降烯烃脱硫工业催化剂FDO的再生研究表明,经过烧炭再生后,催化剂的芳构化降烯烃活性基本恢复,但催化剂的脱硫活性降低了约20个百分点。脱硫活性的降低主要归因于长运转反应（5400 h）后,再生FDO催化剂上的SO₄^2-部分流失,部分NiSO₄转化成为NiO。SO₄^2-的流失造成S=O与Al₂O₃之间的相互作用减弱,催化剂的总酸量降低,L/B值变小。在再生FDO催化剂上补载适量NiSO₄可以恢复催化剂的脱硫活性。5.在负载La₂O₃和NiSO₄制备的Ni-La/HZSM-5催化剂上引入MoO₃,预硫化后,NiSO₄中的Ni同样可以与Mo形成Ni-Mo-S相,增强催化剂的加氢脱硫活性,尤其是提高通过裂解方式难以脱除的噻吩、苯并噻吩等硫化物的脱除能力。但是,3%Mo-Ni-La/HZSM-5的反应结果也表明,MoO₃的引入在使催化剂的总硫脱除率达到了90%以上的同时,烯烃降低幅度多达20个百分点,而芳烃只增加了约7个百分点,造成产物的辛烷值损失了约1.8个单位。更多还原

【Abstract】 Fluid catalytic cracking（FCC） gasoline contributes about 80%of the total gasoline pool in China.For high content of olefins and sulfur,the FCC gasoline provides over 95%sulfur and almost all of the olefins for the gasoline pool.The gasoline sulfur could be reduced effectively by using traditional hydrotreating catalysts,such as Ni-Mo/Al₂O₃.But there would be a great loss of RON for the decrease of olefins in the hydrotreating process.ZSM-5 zeolites are widely used in transforming olefins and light alkanes to aromatics and iso-paraffins for excellent aromatization,isomerization and alkylation activities.Nanosize ZSM-5 zeolites show more stable and higher catalytic activity because of smaller crystals, shorter micropore,more micropores and more acid sites at external surface.The catalytic activity of HZSM-5 could be promoted by supporting rare earth metal oxides and transition metal oxides,such as Ni and Mo.In this article,catalysts were prepared by supporting NiSO₄, Ni（Ac）₂ and Ni（NO₃）₂ over nano-HZSM-5.Investigations were performed to evaluate the catalytic performance for the upgrading of FCC gasoline.Effect of rare earth metal oxides modification on desulfurization activity of HZSM-5 and NiSO₄/HZSM-5 catalyst was studied. And the effect of SO₄^2- loss upon desulfruization activity of regenerated industrial catalyst FDO,which was prepared by supporting NiSO₄ on HZSM-5,was also studied.Meanwhile, effect of MoO₃ modification on desulfurization activity of Ni-La/HZSM-5,which was prepared by supporting La₂O₃ and NiSO₄ over HZSM-5,was also studied.Based on all above investigations,the following conclusions were reached:1.The incorporation of Ni（Ac）₂ and Ni（NO₃）₂ into the HZSM-5 catalysts improved the stability of desulfurization.And the incorporation of NiSO₄ increased not only the desulfurization activity,but also the desulfurization stability largely.γ-Al₂O₃ and SiO₂ were chosed as the supports to prepare catalysts by impregnating with NiSO₄,Ni（Ac）₂ and Ni（NO₃）₂.And the results showed that there was a strong interaction between S=O in SO₄^2- and alumina oxides in both HZSM-5 zeolites andγ-Al₂O₃ supports. The strong interaction could bring following effects:（1） creates a large amount of Lewis acid sites and enhances the ratio of Lewis acid sites to Brφnsted acid sites（L/B）;（2） help Ni species disperse in monolayer on catalyst;（3） prevents the forming of NiAl₂O₄ between NiO and Al₂O₃;（4） increases the adsorbing capability for thiophene impurities.Although a large of amount of lewis（L） acid sites,which was strong enough,was created on SO₄^2-/Al₂O₃,there was little desulfurization activity on the catalyst.This was because Brφnsted（B） acid sites were indispensable for the cracking of thiophenic species over acidic catalyst.2.Thiophene+cyclohexane,in which the sulfur content was 1000μg/g,was used as a model of gasoline.The study showed that the blending of 20 v%1- octene into thiophene +cyclohexane model was beneficial to desulfurization activity and stability.This was becaused that a large amount of active hydrogen was generated in the aromatization process of 1-octene and cyclohexane on HZSM-5 catalyst.And the active hydrogen could accelerate the desulfurization activity and stability.3.The modifications of La₂O₃ and CeO₂ to HZSM-5 catalysts decreased the amount of strong B acid sites of HZSM-5.The decrease of strong B acid sites inhibited thiophene from transforming into thiophene derives and increased the selectivity of H₂S.HZSM-5 modified by bimetals of La₂O₃ and NiSO₄ or CeO₂ and NiSO₄ showed that the strong interaction between NiSO₄ and HZSM-5 catalysts was weakened.The decomposition tempreture of NiSO₄ on HZSM-5 catalyst decreased from 928℃to 827℃.4.Industrial catalyst FDO was prepared by impregnating NiSO₄ into HZSM-5 and was used to transform olefin into aromatics.The deactivated FDO was sampled from the industrial unit（200 kt/a） after 5400 h.The regeneration of deactivated FDO showed that the aromatization and de-olefin activities recovered basically after carefully coke calcinations. But the desulfuriaztion activity decreased about 20%.This was because that there was a loss of SO₄^2- in RFDO catalyst after 5400 h run.And part of NiSO₄ was transformed into NiO after calcinations.The loss of SO₄^2- weakened the interaction between S=O and HZSM-5 catalyst.This led to a dcrease of total amount of acid and smaller L/B.The reloading of proper amount of NiSO₄ could recover the desulfurization activity.5.La₂O₃ and NiSO₄ were supported on nano-HZSM-5 to prepare Ni-La/HZSM-5 catalyst.The incorporation of MoO₃ into Ni-La/HZSM-5 catalyst increased the desulfurization activity largely,especially the desulfurization activity for thiophene and benzothiophene,which were difficult to be removed by cracking method on HZSM-5.The formation of Ni-Mo-S,which exhibited higher hydrogenating activity,was supposed to be the main cause.The results of 3%Mo-Ni-La/HZSM-5 also indicated that although the desufurization ratio was over 90%,the olefin content in product decreased from 34.0 v%to 14.2 v%.Meanwhile,the aromatic content increased from 31.4 v%to 38.0 v%.This led to a loss of RON,which was about 1.8.更多还原