利用高选择性脱硫吸附剂制备超清洁汽油

Hydrogen desulfurized gasoline is an ideal hydrogen source of the automotive PEMFC because of its high energy density, safety, and ease of transportation. However the trace amount of thiophene organic sulfur compounds in gasoline could cause the noble metal PEMFC electrodes and the Ni catalyst of catalytic steam reforming of gasoline poisoned and failure. The aim of this project is to prepare highly selective adsorbents, i.e., metal ion (Bi, Ru, Sb, Zr and Ce) modified molecular sieves, and to systemically evaluate the performance of low-sulfur gasoline desulfurization at ambient temperature and pressure. The effect of the type, load volume and chemical state of loaded metal ions in adsorbents on the thiophene selective adsorption will be investigated. Moreover, the influence of the structure (such as pore structure, ratio of surface area, pore diameter and volume) of adsorbent carrier molecular sieves on the thiophene selective absorption will be studied. The reaction conditions of solid state ion-exchange process for adsorbent preparation will be optimized. In addition, the mechanism of adsorption desulfurization of adsorbent will be clarified and new adsorbent with high selectivity, high sulfur uptake and low preparation cost will be obtained.

加氢脱硫汽油以能量密度高、安全、易运输等优点有望作为车载式PEMFC的氢源。但汽油中的少量噻吩类有机硫化合物，会使PEMFC电极上的贵金属催化剂和汽油催化蒸汽重整用镍催化剂产生硫中毒而失效。本项目拟制备高选择性吸附剂即负载金属（Bi、Ru、Sb、Zr、Ce）的分子筛，并在常温常压下对低硫汽油的吸附脱硫性能进行系统评价。考察吸附剂活性组分金属的种类、负载量和价态对噻吩选择吸附性能的影响因素；考察吸附剂载体分子筛的孔道结构特征如孔结构、比表面积、孔径和孔容等对噻吩择形吸附性能的影响因素；优化固相离子交换法制备吸附剂的反应条件，阐明吸附剂脱硫机理，获得具有高选择性、高硫容和低制备成本的新型吸附剂，克服吸附剂的选择性差、硫容低、再生困难等缺点。

质子交换膜燃料电池（PEMFC）的氢源可采用碳氢化合物燃料汽油来制备。加氢脱硫汽油以能量密度高、安全，易运输等优点有望作为车载式PEMFC的氢源。但汽油中的少量噻吩类有机硫化合物，会使PEMFC电极上的贵金属催化剂和汽油催化蒸汽重整用镍催化剂产生硫中毒而失效。针对PEMFC对超清洁汽油（硫含量小于1ppm）的需求，在本项目中我们制备了金属离子(M: Bi, Ru, Sb, Zr 和 Ce)修饰Y型沸石分子筛吸附剂MY，采用吸附脱硫技术在温和环境下对模拟汽油（正庚烷、甲苯和噻吩，S=20ppm）进行深度吸附脱硫制备超清洁汽油。考察了吸附剂活性组分金属的种类、负载量和价态等因素对噻吩选择吸附性能的影响。MY吸附剂的脱硫率顺序为RuY-1 > SbY-1 > ZrY-1 > BiY-1 > HY，表明吸附剂的活性组分金属离子Mn+相比H+对噻吩更具有亲和性。考察了吸附剂载体分子筛的孔道结构特征如孔结构、比表面积、孔径和孔容等因素对噻吩择型吸附性能的影响。液相法合成了Ce离子修饰分子筛吸附剂（A、ZSM、Mordenite、L沸石、X型沸石）。脱硫率依次降低Ce-X (83%)> Ce-L (31%)> Ce-Mor= Ce-ZSM(14%) > Ce-A(9%)。Ce-X显示最高约83%的脱硫率，表明大孔径分子筛有利于噻吩吸附质的快速扩散。优化了固相离子交换法制备吸附剂的反应条件。阐明吸附剂脱硫机理，高价金属离子Mn+易与噻吩形成S-M σ键结合的有机金属配合物。S-M σ键能的强度依赖于Mn+电荷的高低和离子半径的大小。采用改良的液相离子交换法制备的新型吸附剂RuY-L对噻吩具有高选择性，脱硫率达99%，能将模拟汽油硫含量降至1ppm，是制备超清洁汽油的理想吸附剂。