【作者】 李福祥；

【导师】 谢克昌； 李瑞丰；

【作者基本信息】 太原理工大学 ， 化学工程与技术， 2007， 博士

【摘要】 中孔分子筛具有较高的比表面积，较大的孔容以及孔分布单一等特性，因而可以允许较大的分子或基团进入其孔道内，这对于很多在微孔沸石分子筛中难以完成的大分子催化、吸附与分离等过程无疑开拓了广阔的应用前景，为重油、渣油的催化裂化等加工奠定了基础，但纯硅中孔分子筛存在严重缺陷，它的酸性较弱、催化活性低，因此合成高酸性和高催化活性的中孔分子筛是人们追求的研究目标，而合成具有超强酸性的中孔分子筛对于石油化工更具重大意义。二氧化锆是唯一同时拥有表面酸性位和碱性位以及氧化还原性能的过渡金属氧化物，并且拥有优良的离子交换能力，而P-型半导体贡献于其表面丰富的氧缺位，近年来研究发现二氧化锆经SO₄^2-促进可以制成固体超强酸，具有卓越的酸催化特性，从而使得二氧化锆在催化领域倍受瞩目。因此将二氧化锆制成或引入中孔分子筛子，并制成固体超强酸具有重大的理论和实际意义。本研究在溶胶-凝胶法和自组装理论的基础上，以Zr（NO₃）₄·3H₂O为锆源，采用浸渍晶化法、一步晶化法和二步晶化法合成了一系列中孔ZrO₂和中孔Zr-SBA-15分子筛，采用XRD、TEM、N₂吸附-脱附、TG-DTA、UV-VIS、NMR和元素分析等手段进行了表征；并将所合成的含锆材料采用硫酸浸渍法和直接加硫酸合成法制成中孔超强酸分子筛，采用正戊烷低温（35℃）异构化、吡啶红外和NH₃-TPD等表征技术研究了其酸催化性能及酸性。通过实验和研究得到以下几方面的结果：（1）以廉价的硝酸锆为前驱体，十六烷基三甲基溴化铵为结构模板剂，在醇相中采用两步晶化法可以合成出中孔氧化锆分子筛，实验中模板剂量、预晶化温度和时间、pH值、三乙醇胺量及晶化温度和时间等是影响合成的重要因素，一般模板剂量在n（CTAB）：n（Zr）（摩尔比）为0.18-0.48、pH值为8-11、预晶化温度为90℃、预晶化时间为4h、晶化温度为120℃、晶化时间为48h时可以合成出具有较大比表面和规整度较好的中孔氧化锆分子筛，最佳条件下合成的样品经450℃焙烧后比表面积为197m²／g；纯组分中孔氧化锆分子筛在550℃下其中孔结构能够稳定存在，说明其热稳定性较高，同时，样品也具有较好的水热稳定性；在合成过程中加入铝、锌、钇、镧、铈和钍等金属元素在不同程度上改善了中孔材料的热稳定性，650℃下中孔结构仍能够稳定存在，其中加入铝、镧和钍所合成的掺杂中孔氧化锆的热稳定性较好，尤其是铝的掺入使所合成的掺铝中孔氧化锆分子筛样品纳米化程度提高，经450℃焙烧后BET比表面积达到250m²／g，同时也提高了热稳定性和水热稳定性；研究表明所合成的中孔氧化锆材料都存在着不同程度的高温晶化现象，即样品在高温焙烧时，随着焙烧温度和焙烧时间的变化样品的晶体结构及孔结构在不断地变化，且这种现象越严重，样品的热稳定性就越差，这主要与氧化锆晶体的稳定性相关，加入铝、镧和钍等元素提高了氧化锆四方相的热稳定性，从而也就提高了所合成中孔氧化锆材料的稳定性。但总体来说氧化锆作为自组装体骨架组分的热稳定性较差，这是其晶体的性能所决定的。（2）采用浸渍晶化法，将焙烧后的SBA-15分子筛用硝酸锆的醇溶液浸渍后，在乙醇蒸汽下进行晶化，合成出了一系列中孔Zr-SBA-15的材料，实验结果表明：当Zr／Si小于2.1时都可以合成出具有中孔特征的Zr-SBA-15分子筛，元素分析结果显示当Zr／Si=1.34时，所合成的Zr-SBA-15中ZrO₂的含量可达50.54％，600℃焙烧后比表面积仍高达356m²／g，优于传统浸渍法制备的样品；合成中加入适量的CTAB或三乙醇胺可以提高Zr-SBA-15的有序度；TEM及UV-VIS分析结果表明采用本浸渍晶化法所合成的Zr-SBA-15中Zr组分主要存在于SBA-15的孔道内，呈高度分散状态，且有相当部分进入了骨架。（3）在水热体系中，以Zr（NO₃）₄·3H₂O为锆源，通过一步晶化法可以直接合成出了Zr-MCM-41和Zr-SBA-15中孔分子筛：①合成Zr-MCM-41的Zr／Si的摩尔比最大为0.25。随着Zr／Si摩尔比的增加，2θ=2°附近的100晶面的衍射峰强度逐渐降低。500℃焙烧6h后的样品在100晶面和110晶面的衍射峰强度普遍比焙烧前的增强，焙烧后的样品在2θ=20-70°范围内的XRD图上无ZrO₂的特征峰出现，说明样品中Zr化合物为高分散状态；②合成Zr-SBA-15的Zr／Si摩尔比最大为2.3。随硝酸锆加入量的增加，中孔特征峰强度逐渐下降，BET表面积也随之下降。在Zr／Si=1.5之前，样品都具有高的比表面积（600℃焙烧后BET比表面积大于398m²／g），孔径均保持在7.40nm左右，属于中孔材料的范围，高分辨电镜图显示这种新材料具有较厚的孔壁。从元素分析的测试结果得出，锆的实际载量不是很高，虽然增加了锆的加入量，但实际上ZrO₂的含量都小于30％，没有达到理论上ZrO₂形成超强酸要求的含量（大于50％）。（4）在醇水两种体系下，以Zr（NO₃）₄·3H₂O为锆源，采用两步晶化法通过中性模板组装路线成功地合成出了孔道规整、锆含量高的中孔Zr-SBA-15：①在盐酸体系下，可合成Zr-SBA-15的最大Zr／Si摩尔比为2.3。虽然随硝酸锆加入量的增加，SBA-15的特征峰强度、BET比表面积均呈下降趋势，但是，Zr-SBA-15样品的孔径均保持在5-6.4nm，仍属于中孔材料的范围。同时，从高分辨电镜图可看出这种新材料具有较厚的孔壁，预示其具有高的热稳定性和水热稳定性。元素分析的测试结果显示，锆的实际载入量很高，当Zr／Si摩尔比为0.7时，样品中ZrO₂含量已高达54.18％，锆有效上载率达91.9％，600℃焙烧后BET表面积可达431m²／g；当Zr／Si摩尔比为1.3时，ZrO₂含量为63.28％，锆有效上载率为88.9％，600℃焙烧后BET表面积仍可达226.8m²／g；这一结果优于一步晶化法和浸渍晶化法所合成样品的性能。TEM、NMR及UV-VIS结果表明锆组分在样品中高度分散，且大部分进入了骨架，Zr／Si摩尔比超过0.7后有聚集态ZrO₂四方相存在。XRD及孔分布结果表明所合成的Zr-SBA-15样品具有双中孔特征，孔径分别为3.5nm和5-6.4nm。②在加硫酸体系下，可合成Zr-SBA-15最大Zr／Si摩尔比为3.0。虽然随硝酸锆加入量的增加，所合成样品的各种特性的变化规律与在盐酸体系下的大致相同，但同一锆硅比的样品的比表面积一般比在盐酸体系下所合成样品的都大，尤其是Zr／Si摩尔比大于0.7以后更为明显，直到Zr／Si摩尔比高达3.0时，600℃焙烧后BET比表面积仍可达184 m²／g，但孔径降为3.74nm，不过仍属于中孔材料的范围；在同一锆硅比时不同硫酸盐酸比下所合成的Zr-SBA-15样品的比表面积不尽相同，以单一硫酸体系下所合成样品的表面积最大，但孔径变化不大，说明加入硫酸后所合成的Zr-SBA-15材料的热稳定性更好。TEM、NMR及UV-VIS结果表明锆组分在样品中高度分散，且大部分进入了骨架，即使Zr／Si摩尔比超过0.7也没有明显的聚集态ZrO₂四方相存在，证明了硫酸对锆组分有很好的稳定作用。与盐酸体系相似，XRD及孔分布结果表明所合成的Zr-SBA-15样品具有双中孔特征，孔径分别为3.5nm和5-6nm。更重要得是在加硫酸体系下所合成的Zr-SBA-15中孔分子筛可直接经焙烧后制成SO₄^2-／Zr-SBA-15固体超强酸，省去了二次浸渍硫酸和干燥过程，为工业应用奠定了基础。在两步晶化合成Zr-SBA-15过程中，不论在盐酸体系还是加硫酸体系，预晶化过程对后续形成中孔材料的自组装过程影响很大。（5）实验中所制备的中孔SO₄^2-／ZrO₂和SO₄^2-／Zr-SBA-15超强酸分子筛在正戊烷低温（35℃）异构化反应中都表现出了高的催化活性，但不同方法和条件下制备的中孔超强酸分子筛催化剂的性能有所不同：①中孔SO₄^2-／ZrO₂超强酸分子筛催化剂催化正戊烷异构化反应3 h正戊烷的摩尔转化率为47.3％，稍低于沉淀法制备的催化剂（52.2％），铝或锌掺杂后催化活性略有提高（55.3％）；NH₃-TPD分析结果表明所制备的催化剂存在强酸位。②由两步晶化法在盐酸体系下合成的Zr-SBA-15制备的SO₄^2-／Zr-SBA-15超强酸催化剂的正戊异构化催化活性受脱模板方法、浸渍硫酸的浓度、焙烧温度、活化温度及样品Zr／Si摩尔比的影响，Zr／Si摩尔比为1.1-1.3的Zr-SBA-15样品不经预脱除模板剂处理直接浸渍硫酸，当硫酸浸渍液浓度为1.0M，焙烧温度为600℃，活化预处理温度在300℃时，SO₄^2-／Zr-SBA-15催化剂的正戊烷异构化催化活性最高，3h正戊烷的摩尔转化率为52.9％～57.6％，此时催化剂样品的S／Zr摩尔比达0.28-0.35，远大于沉淀法制备的超强酸催化剂样品中的硫含量（S／Zr摩尔比约0.061）。③由两步晶化法在加硫酸体系下合成的Zr-SBA-15制备的SO₄^2-／Zr-SBA-15超强酸催化剂在正戊异构化反应中也表现出了好的催化活性，其催化活性受合成时硫酸的加入量、焙烧温度、活化温度及样品Zr／Si摩尔比的影响，Zr／Si摩尔比为1.5-2.5的Zr-SBA-15样品经600℃焙烧，活化预处理温度在300℃时，SO₄^2-／Zr-SBA-15催化剂的正戊烷异构化催化活性最好，3h正戊烷的摩尔转化率为30.8％～50.6％，同一Zr／Si摩尔比时催化剂的催化活性受合成时硫酸与盐酸的摩尔比影响较大，一般在Zr／Si摩尔比大于1.5后硫酸的量较大时合成样品的催化活性较高，此时催化剂样品的S／Zr摩尔比大于0.06。④由浸渍晶化法合成的Zr-SBA-15制备的SO₄^2-／Zr-SBA-15超强酸催化剂在正戊异构化反应中的催化活性也很好，其催化活性受浸酸浓度、焙烧温度、活化温度及样品Zr／Si摩尔比的影响，Zr／Si摩尔比为1.96-2.15的Zr-SBA-15样品当硫酸浸渍液浓度为1.0M，焙烧温度为600℃，活化预处理温度在300℃时，SO₄^2-／Zr-SBA-15催化剂的正戊烷异构化催化活性最好，3h正戊烷的摩尔转化率为40.0％～46.6％。⑤吡啶-红外光谱分析结果表明SO₄^2-／Zr-SBA-15样品同时具有L酸和B酸中心，而且L酸的量大于B酸的量。⑥SO₄^2-／Zr-SBA-15超强酸分子筛的XPS分析结果表明，能与SO₄^2-牢固结合形成超强酸位的主要是样品表面的锆组分，与本体中的锆和硅关系不大；异构化反应过程中存在积碳现象；样品的Zr3d、S2p、O1s和Si2pXPS图显示浸渍硫酸后焙烧前后的样品中Zr、S、O和Si的结合能都增大了，这说明样品焙烧过程中由于各组分间的强相互作用影响了其结合能。更多还原

【Abstract】 Mesoporous molecular sieves can be able to make huge moleculers or groups enter into their pores because of their high specific surface area, large pore volume and pore diameter as well as narrow pore size distribution. So they can be widely used in the area which microporous molecular sieves are impracticable to perform such as the process of catalysis, adsorption or separation which require macromolecules, especially for heavy oil or residual oil catalytic cracking process. But pure silicon mesoporous molecular sieves lack in acidity and stability. So synthesis of mesoporous molecular sieves with strong acidity and high stability is the key aim which researchers go in for. And synthesis of mesopocous molecular sieves with super acidity has more important value for petrochemical processing. Zirconia is the only transition metal oxide with acid sites and alkali sites as well as oxidoreduction ability and good ion-exchange capacity. And as a p-type semiconductor, it rich in surface oxygen no-bit. In recent years, zirconia can form a solid super acid after sulfated, which have excellent acid catalysis characterization. Thereby zircenia is ocused attention upon in catalysis field. So synthesis of mesoporous zirconia or zirconium-doping meroporous molecular sieves with super-acidity has great meaning on theory and practical.In this study basing on sol-gel method and self-assembly theory, using Zr（NO₃）₄·3H₂O as zirconium source, a series of mesostructure zirconia and Zr-SBA-15 mesoporous molecular sieves with high zirconium loading were synthesized with impregnating crystallization method, one-step crystallization method or two-step crystallization method, and characterized with XRD, TEM, N₂ adsorption-desorption, TG-DTA, UV-vis, NMR and element analysis et al. The as-synthesized samples were prepared as super acid molecular sieves after sulfated with impregnating in sulfuric acid solution or adding sulfuric acid during the synthesis of samples. And the acid catalysis capacity and acidity of as-synthesized super acid molecular sieves were characterized with isomerization of n-pentane at low temperature （35℃）, pyridine-IR and NH₃-TPD et al. The results obtained from experiments and studies were given in following. （1） Using cheaper Zr（NO₃）₄·3H₂O as precursor, cetyl trimethyl ammonium bromide （CTAB） as structure template agent, mesoporous zirconia molecular sieves were synthesized with two-step crystallization method in alcohol phase. The main factors were the dosage of template agent, pre-crystallization temperature and time, pH value, dosage of complexing agent triethanolamine, and crystallization temperature and time. Well ordered misoporous zirconia with high surface area had been synthesized at n_CTAB/n_Zr molar ratio 0.18-0.48, pH value 8-11, pre-crystallization temperature 90℃and time 4h, crystallization temperature 120℃and time 48h. BET specific surface area of the sample synthesized at optimum condition was 197m²/g after calcinated at 450℃, and mesostructure of pure mesoporous zirconia was still existed after calcinated at 550℃that shows the as-synthesized samples had good thermal stabilities as well as good hydrothermal stabilities. The thermal stabilities of samples were improved at various degrees after doped with aluminum, zinc, yttrium, lanthanum, cerium or thorium. Mesostructure of samples doped with Al, La, TR could exist after calcinated at 650℃. BET surface area of sample doped with Al was 251m²/g after calcinated at 450℃because of samples nanolization. At the same time, thermal stability and hydrothermal stability of samples doped with Al were improved. The results show that samples were crystallized continuously during calcinations process. This might be the key factor affecting the stabilities of samples. The stability of tetragonal phase of zirconia doped with Al was improved, and so the stability of mesostructrure zirconia was advanced too. But taking one with another, the stability of zirconia as a structural component of self-assembly material was rather poor, which was determinate by its crystal performance.（2） A series of Zr-SBA-15 mesoporous molecular were synthesized with impregnation-crystallization method by impregnating calcinated SBA-15 in zirconium nitrate alcoholic solution and then crystallizing at ethanol vapour. The results show: mesostructure Zr-SBA-15 can be synthesized when the Zr/Si molar ratio was less than 2.1. The element analysis results show: the zirconia content in Zr-SBA-15 could be 50.54% as Zr/Si molar ratio was 1.34, and the BET specific surface area was still as high as 356m²/g after calcinated at 600℃, which was advantage over traditional impregnating method. The degree of order could be improved by adding an amount of CTAB or triethanolamine in during synthesis process. TEM and UV-vis analysis results show: zirconium component in Zr-SBA-15 was mainly in the channel of SBA-15 and at high dispersed condition, and was mostly incorporated into the framework.（3） At hydrothermal system using Zr（NO₃）₄·3H₂O as zirconium source, Zr-MCM-41 and Zr-SBA-15 mesoporous molecular sieves had been synthesized with one-step crystallization method. The results show:①Zr/Si molar ratio should been less than 0.25 for synthesis of Zr-MCM-41. The peak indexed to 100 in XRD pattern was decreased with Zr/Si molar ratio increasing, and got higher after calcinated at 600℃for 6h comparing with uncalcinated one. No characteristic peaks belonging to Zr compounds at 20=20-70 could be observed. This proved that Zr is fully dispersed in MCM-41 structure.②The maximum Zr/Si molar ratio was 2.3 for synthesis of Zr-SBA-15. The characteristic peaks belonging to mesostructure were gradually fall-off in intensity with increasing of Zr/Si molars ratio, and BET surface area decreased too. When Zr/Si molar ratio was less than 1.5, samples were with high surface area （BET specific surface area was over 398m²/g after calcinated at 600℃） and pore diameter about 7.4nm, which were belong to mesoporous material. TEM images showed that the new materials possessed thick hole wall. But element analysis results showed that zirconia loading was not so high with Zr/Si molar ratio increasing, and less than 30% which came short of zirconia content in theory for forming super acid.（4） Using Zr（NO₃）₄·3H₂O as zirconium source, well-ordered Zr-SBA-15 mesoporous molecular sieves with high zirconium loading were synthesized successfully with two-step crystallization method and neutral template self-assembly route. The results show:①The maximum Zr/Si molar ratio was 2.3 for synthesis Zr-SBA-15 at only hydrochloric acid system. The intensity of characteristic peak belonging to SBA-15 was decreasing with Zr/Si molar ratio increasing, and BET specific surface area decreasing too. But pore size of samples were 5-6.4nm belonging mesopore. TEM image showed that the new materials possessed thick hole wall which indicated they had good thermal stabilities and hydrothermal stabilities. Element analysis results showed the samples with high zirconium loading. Zircomia content in sample was as high as 54.18% at Zr/Si molar ratio 0.7, and virtual rating of zirconium loading was 91.9%, and BET area was 431m²/g after calcinated at 600℃. Zirconia content in sample was 63.28% when Zr/Si molar ratio was 1.3, and virtual rating of zirconium loading was still 88.9%, and BET surface area was 226.8m²/g after calcinated at 600℃. These results were better than that of as-synthesized samples prepared with on-step crystallization method or impregnation-crystallization method. TEM, NMR and UV-vis results showed that zirconium was fully dispersed in SBA-15 structure when Zr/Si molar ratio less than 0.7. After that, the single particles of tetragonal ZrO₂ phase appeared in the samples. XRD and pore size distribution indicated that as-synthesized Zr-SBA-15 possessed two types mesopore, one 3.5nm and another 5-6.4nm.②The maximum Zr/Si molar ratio for synthesis of Zr-SBA-15 was 3.0 at adding sulfuric acid system. The variation regulars of characteristics of samples were similar to that of only hydrochloric acid system when added sulfuric acid in during synthesis process. At the same Zr/Si molar ratio, the BET surface area of the sample was bigger than that of only hydrochloric acid system, especially Zr/Si molar ratio at 3.0, and pore size down to 3.74nm which still belong to mesostructure. At the same Zr/Si molar ratio, the BET surface areas of samples were different with sulfuric acid to hydrochloric acid molar ratio changing. The samples synthesized at only sulfuric acid system had the biggest surface area. But pore sizes of samples changed little with sulfuric acid to hydrochloric acid molar ratio changing. This proved the thermal stability of sample was improved after adding sulfuric acid in during synthesis process. TEM, NMR and UV-vis results indicated that zirconium was fully dispersed in sample, and mostly incorporated into the framework. Even Zr/Si molar ratio over 0.7 no bulk particles of ZrO₂ appeared that proved sulfuric acid had good stabilization to zirconium compounds. Being similar to only hydrochloric acid system, XRD and pore size distribution indicate that the as-synthesized Zr-SBA-15 had two types mesopore, one 3.5nm and the other one 5-6nm. More important, Zr-SBA-15 synthesized at adding sulfuric acid system could form SO₄^2-/Zr-SBA-15 super acid after cacinated directly without impregating with sulfuric acid solution and drying procedure, which established bases for industrial application. During synthesis of Zr-SBA-15 process with two-step crystallization method, pre-crystallization process had great influence up on the self-assembly progress of formation of mesoporous material.（5） As-synthesized mesostructure SO₄^2-/ZrO₂ and SO₄^2-/Zr-SBA-15 super acid molecular sieves had high catalytic activities on isomerization of n-peutare at low temperature （35℃）. The catalytic activities were changed with preparing methods or conditions.①Using mesostructure SO₄^2-/ZrO₂ as a catalyst, conversion of n-pentane was 47.3% after reacting for 3h which was less than that （50.2%） of bulk SO₄^2-/ZrO₂, and increased a little after doped with Al or Zn. NH₃-TPD results showed mesoporous SO₄^2-/ZrO₂ had strong acid site.②The catalytic activities of SO₄^2-/Zr-SBA-15 prepared in only hydrochloric acid system on isomerization of n-pentane were influenced by removing method of template agent, concentration of impregnating sulfuric acid solution, calcination temperature, activation temperature and Zr/Si molar ratio. When Zr/Si molar ratio was 1.1-1.3, Zr-SBA-15 impregnated with 1M sulfuric acid solution without pre-removing of template agent, calcination temperature was 600℃, and activation temperature was 300℃, the catalytic activity of SO₄^2-/Zr-SBA-15 on n-pentane reaction was the highest, conversion of n-pentane were 52.9%-57.6%, and S/Si molar ratio of catalysis were 0.28-0.35 which was much higher than that （about 0.061） of bulk SO₄^2-/ZrO₂ prepared with precipitation method.③The catalytic activities of SO₄^2-/Zr-SBA-15 prepared in adding sulfuric acid system on isomerization of n-pentane were higher too, and influenced by dosage of sulfuric acid during synthesis process, calcinations temperature, activation temperature and Zr/Si molar ratio of samples. When Zr/Si molar ratio was 1.5-2.5, calcinations temperature was 600℃, and activation temperature was 300℃, the conversions of n-pentane were 30.8%-50.6%. At the same Zr/Si molar ratio, the catalytic activities were influenced greatly by sulfuric acid to hydrochloric acid molar ratio, and raised with increasing of dosage of sulfuric acid after Zr/Si molar ratio over 1.5. And S/Zr molar ratio were more than 0.06.④The catalytic activities of SO₄^2-/Zr-SBA-15 prepared with impregnating crystallization method on isomerization of n-pentane were good too, and influenced by concentration of impregnating sulfuric acid, calcinations temperature, activation temperature, and Zr/Si molar ratio. When Zr/Si molar ratio was 1.96-2.15, Zr-SBA-15 impregnated with 1M sulfuric acid solution, calcination temperature was 600℃and activation temperature was 300℃, the conversion of n-pentane were 40.0%-46.6% after reacting 3h.⑤Pyridine-IR analysis results showed that SO₄^2-/Zr-SBA-15 possessed L-acid and B-acid at the same time, and the quantity of L-acid was more than that of B-acid.⑥XPS analysis results show that SO₄^2- was mostly compaginate with zirconium components on the surface of Zr-SBA-15 to form strong acid sites, and was less concern with zirconium and silicon in body. Carbon deposition formed during isomerization reaction. XPS curves of Zr3d, S2p, O1s and Si2p of samples show that the binding energies of Zr, S, O and Si were increased after calcinated, which indicated the strong interaction of components in samples influenced the binding energies.更多还原