吸附剂表面修饰和结构调变对焦化苯中噻吩深度脱除的影响及其再利用研究

Crude benzene, which is one of the main by-products from coal coking process, accounts for about 40-50% in the total amount of benzene in China. But it is only below 20% in the total amount of pure benzene because the removal of some impurities in it is very difficult. The existing methods are already not able to meet the requirements for the environment and purity with the clean and efficient development of coal chemical industry and the rising of the limitation of sulfur content in benzene as raw meterial.The thiophene containing in coking benzene, wich has very slmilar physical and chemical properities, is one of the main factors influencing the quality of benzene. The deep removal of thiophene from coking benzene by effective method without second pollution and recycling thiophene/sorbent is the purpose of this research topic. The research results will present the great theoretical significance and the remarkable social and economic benefits. The main contents in this research are shown as follow. To select the active component precursor and support materials with excellent performances and then to prepare sorbents and modify them under different conditions; modify the active group and structure of sorbent by different acid and alkali solution; improve the active center on the surface of sorbent by different metal component; evaluate the selective adsorption capacity of deep removing thiophene in benzene over improvement sorbent; characterize the physical and chemical properties (e.g. the surface acidity or basicity, the porous structure, the load and distribution of metal components and so on) of sorbents before and after modifying and desulfurization reaction; relate the experimental results of preparation, modification, evaluation and characterization to discuss the mechanism of selective adsorption thiophene from benzene. The polymerization of thiophene and synthesization of thiophene/molecular sieve composite materials are also preliminarily explored. We want to finally obtain a kind of sorbent with good performances to deeply remove thiophene, and a desulfurization method with environmental friendly advantage to recycle thophene and used sorbent based on the analysis of above mechnisms and the structure-activity relationship of sorbent.

焦化苯作为煤焦化的副产物约占我国苯总产量的40-50%，但所含杂质难以脱除使其在纯苯中的比例小于20%。随着下游产品对原料苯纯度要求的提高及人们对二次环境污染的重视，现有焦化苯精制方法越来越难以满足需求。噻吩与苯的物化性质非常相近，是影响噻吩深度脱除的主要因素。基于脱硫机理对吸附剂进行表面修饰和结构调变，深度脱除焦化苯中噻吩，达到原料用纯苯对噻吩ppb级含量的要求，并对噻吩和废吸附剂回收利用进行聚噻吩分子筛复合材料合成，研究结果具有重要的理论意义和显著的经济、社会效益。研究内容主要包括：吸附剂载体和活性组分优选及制备条件的优化；酸碱溶液对吸附剂表面酸碱基团和孔结构改性，金属组分对吸附剂表面活性中心改性；改性前后与噻吩吸附前后吸附剂表面酸碱性、孔结构参数和金属元素存在形态表征；吸附剂选择性脱硫机理及再生过程中硫、碳变迁机理探讨；吸附苯中噻吩的吸附剂合成聚噻吩复合材料条件的优化及其性能表征。

焦化粗苯组成复杂，所含杂质难以脱除，不能满足下游产品对原料苯纯度不断提高的要求，噻吩与苯的物化性质非常相近，是影响噻吩深度脱除的关键。项目在对噻吩脱除机理掌握的基础上，对吸附剂进行表面修饰和结构调变，以噻吩和废吸附剂合成聚噻吩分子筛复合材料。提出了吸附法辅助烷基化法进行焦化苯中噻吩深度脱除的新工艺；实现了温和条件下噻吩烷基化转化催化剂的高效、清洁制备，优化条件下制得的催化剂可脱除苯中约95%的噻吩并同时脱除苯中的烯烃，且整个过程对设备材质要求不高、避免了二次污染；用铈改性NaY分子筛制得CEYE2吸附剂，在室温、常压下可深度脱除苯中的微量噻吩；得到NaY分子筛上不同强度、不同类型的酸性位对噻吩吸附的影响规律，揭示了噻吩在CEYE2吸附剂上的吸附机理、苯对噻吩吸附产生竞争作用的原因；得到了再生气氛和再生温度通过改变TY样品中碳和硫的含量及其结构而影响其再生性能，CeYE2吸附剂经历3次吸附—再生循环，脱硫精度不变，穿透吸附量仍能保持新鲜吸附剂的69.44 %；吸附噻吩后的CeYE2吸附剂（TBY）作为原料制备聚噻吩/CeY分子筛复合材料，聚噻吩与CeY分子筛复合后对分子筛的晶体结构影响不大，并且聚噻吩也具有较好的热稳定性，当噻吩与TBY的配比为2.5:1 g/mL时制备的聚噻吩/CeY分子筛复合材料具有较高的导电率（1.001 S/m）。研究工作申报和授权获国家发明专利2件，得到的实验结果在Green Chemistry、Fuel Processing Technology等期刊发表论文16篇，培养研究生7名。.焦化作为煤转化利用的主要工艺，焦化苯是其主要副产物，资源量丰富。吸附剂制备条件—表面酸碱特性、孔结构特性及金属元素种类和价态—噻吩吸附性能间的关联研究，为焦化苯的高效提质提供了基础理论支撑；优选的吸附剂具有活性好、吸附容量大优势的同时，具有对苯中微量噻吩吸附的高选择性，可将苯中的噻吩深度脱除到ppm级，具有较为广泛的应用前景；吸附苯中噻吩的吸附剂和苯中分离出的烷基噻吩为原料，合成热稳定性和电化学性能优异的聚噻吩/分子筛纳米复合材料，实现了资源利用的最大化和环境污染的最小化，具有较好的环境和社会效益。