【作者】 张彦禹；

【导师】 范彬彬；

【作者基本信息】 太原理工大学 ， 化学工艺， 2011， 硕士

【摘要】 目前国家石油供应严重短缺已经影响到我国的战略安全和国民经济快速发展,充分利用我国煤炭资源丰富的优势,大力发展煤制燃料油作为石油资源的补充是解决石油短缺问题的最好办法之一。针对我国煤化工中甲醇产业经历了多年的高增长、高需求的发展,目前出现产能过剩状况非常严重的情况,利用甲醇脱水制备燃料油来弥补全国能源缺乏这一问题,将是我国未来可持续发展的一条有利途径。本文采用三种不同方法制备了多级孔HZSM-5催化剂,利用现代分析技术对各种催化剂进行了表征分析,并将其用于甲醇合成燃料油的催化反应,考察了各种催化剂对甲醇催化性能的影响。具体内容如下：(1)在60℃,利用浓度为0.1-1mol/L的NaOH溶液对HZSM-5(SiO2/Al2O3=36)分子筛进行6h的碱处理,制备了HZSM-5-AT分子筛催化剂。通过XRD表征表明ZSM-5-AT分子筛仍然保持了典型的MFI晶体结构,并且随着碱溶液浓度的增大,ZSM-5-AT分子筛的特征衍射峰较未处理样品逐渐减弱,这主要是由于碱处理过程导致了ZSM-5沸石的部分骨架破坏；SEM和N2吸附等温曲线证实了ZSM-5-AT分子筛上出现了明显的介孔结构,并且随着碱溶液浓度的增大,N2吸附等温曲线中滞后环逐渐增大,这也是由于碱处理过程中碱蚀脱硅形成了更多介孔所致；吡啶红外表征表明多级孔HZSM-5-AT催化剂较未处理样品B酸的含量降低,L酸的含量明显增加,NH3-TPD表征表明多级孔HZSM-5-AT分子筛催化剂较未处理样品的强酸位明显降低,弱酸位增加,进一步表明催化剂的强酸位为B酸中心,弱酸中心为L酸,这都表明沸石在碱处理过程中铝物种部分从沸石骨架中抽出形成非骨架铝物种。(2)在合成过程中加入有机硅烷合成了HZSM-5-Z分子筛。XRD表征揭示了ZSM-5-Z分子筛较未加有机硅烷合成的样品具有明显宽化的MFI的特征衍射峰,表明有机硅烷的加入抑制了ZSM-5沸石晶体的生长而形成了小晶粒沸石晶体,并得到了SEM观察结果的证实；HRTEM和N2吸附表征充分证实了这种ZSM-5-Z分子筛具有多级孔结构；2,6-二甲基吡啶红外结果表明,多级孔的引入明显提高了HZSM-5-Z分子筛中的酸中心对碱性大分子的利用几率,提高了大分子反应物对酸位活性中心的可接近性。(3)采用两步合成法合成了HZSM-5-F复合分子筛。XRD,SEM表征手段证实了复合结构的ZSM-5-F分子筛具有MFI的特征衍射峰和晶体形貌；N2吸附表明ZSM-5-F复合分子筛具有多级孔结构,这是由于第二步合成过程中合成溶液对第一步合成的ZSM-5沸石的碱蚀或晶粒堆积形成了介孔(4)催化反应评价结果表明,与纯粹微孔HZSM-5催化剂相比,多级孔HZSM-5-AT、HZSM-5-Z和HZSM-5-F催化剂均表现出了较高的甲醇转化率、燃料油收率和较长的催化寿命。由于多级孔的引入,一方面提高了反应物和产物分子在催化剂孔道中的扩散速率；另一方面,提高了催化剂的酸位可接近性,因而提高了甲醇转化率；再一方面,多级孔的引入减少了二次裂解反应发生的几率,抑制反应中积炭的产生,提高了催化剂的的稳定性和燃料油的收率。更多还原

【Abstract】 At present, the shortage of petroleum supplies has seriously affected national strategic security and the rapid development of national economy. Making full use of rich coal resources and developing project of CTL as a substituendum for petroleum resource will be one of the most effective solutions for petroleum shortage. The capacity of methanol production has been surplus with the development of high growth and high demand of several years, so methanol to fuel oil to make up the shortage of energy resource will be a favorable way according to our country sustainable development in the future.In this paper, we prepared hierarchically porous HZSM-5 catalysts by three different synthesis methods, characterized them by the modern analysis technologies and investigated their catalytic performance in catalytic conversion of methanol to fuel oil. Main content can be listed as following points:(1) A HZSM-5-AT zeolite was prepared by treating HZSM-5 (SiO2/Al2O3=36) at 60℃for 6 h in 0.1-1mol/L NaOH solution. XRD patterns showed that ZSM-5-AT still maintained its original MFI crystal structure upon post-treating in NaOH solution, but the crystallinity of ZSM-5-AT zeolites decreased compared with its original precursor and the decreasing degree increased with the increase of the employed NaOH solution concenration, indicating that the structure of ZSM-5-AT zeolites were partly damaged. SEM and N2 adsorption-desorption results showed that mesopores were created in the ZSM-5-AT zeolites upon alkali-treating and the amount of the mesopore increased with the increase of the alkalinity. Infrared spectroscopy of adsorbed pyridine and NH3-TPD showed that the HZSM-5-AT catalysts possessed fewer Bronsted strong acid sites and more Lewis weak acidic sites compared with its original precursor, indicating that a part of aluminum species were extracted from the framework of HZSM-5 and no-framework aluminum species were formed during the alkali treatment process.(2) A HZSM-5-Z zeolite was synthesized by adding organic silane during the ZSM-5 synthesis process. XRD patterns showed that the MFI characteristic diffraction peaks of the as-synthesized were widened compared with those of ZSM-5 synthesized in the absent of organic silane. The result suggested that the organic silane inhibited the growth of ZSM-5 crystals, which resulted in the formation of small crystal particles, this suggestion could be further confirmed by the results of SEM. HRTEM and N2 adsorption-desorption showed that ZSM-5-Z zeolites had a hierarchically porous structure. Infrared spectroscopy of adsorbed large size 2,6-dimethyl pyridine indicated that the acidity accessibilities of HZSM-5-Z was significantly improved due to the hierarchical pores.(3) A HZSM-5-F composite zeolite was prepared by a two-step synthesis. XRD and SEM showed the as-synthesized samples have the same characteristic diffraction peaks and the crystalline morphology as that synthesized by a one-step synthesis. N2 adsorption-desorption result showed that HZSM-5-F had the hierarchically porous structure. The mesoporous pores could be attributed to the dissolution of the framework of MFI by the synthesis solution in the second step or cumulate crystal particles.(4) Catalytic reaction of methanol to fuel oil indicated the hierarchically porous HZSM-5-AT, HZSM-5-Z and HZSM-5-F catalysts showed higher the conversion of methanol and the yield of fuel oil and enhanced resistance towards deactivation as compared to the HZSM-5 catalysts without hierarchically porous structure. The better catalytic performance for the prepared hierarchically porous HZSM-5 catalyts can be attributed to the following reasons:1) hierarchical pores in the catalysts improved diffusion of reactant and product; 2) hierarchical pores in the catalysts improved acid accessibility, which is favourable for the conversion of methanol; 3) hierarchical pores in the catalysts could inbibited secondary cracking process and the deposition of coke, which is favourable for improving the stability of the catalysts and increasing the yield of fuel oil.更多还原