New Sorbents for Separation and Purification Processes

分离和净化过程的新型吸附剂作为满足更严格的汽油和柴油硫标准的一种手段，环境条件下的吸附已成为一种有吸引力的替代方法（加氢脱硫是一种高压催化过程）。在以前的工作中，pi络合已被用于燃料脱硫。以苯中的噻吩为模型体系，分别表示含硫化合物和汽油。初步结果表明，Cu(I)Y和AgY分子筛在低浓度下对噻吩的吸附都比NaY强得多，是脱硫的最佳吸附剂之一。分子轨道计算表明，这些分子筛与噻吩之间的pi络合键比与苯之间的pi络合键更强。基于这些有希望的结果，对气相和液相吸附进行了全面的研究。两类pi-络合吸附剂被使用：离子交换沸石和单层盐支撑在高表面积的底物上，包括Cu+和Ag+以及其他有前途的d-嵌段阳离子。研究了噻吩、苯并噻吩和二苯并噻吩溶解苯和甲苯。此外，该研究还探讨了碳纳米管独特而有前途的吸附特性。初步结果表明，在1 atm H2条件下，掺碱纳米管中可以储存2.5% （wt.）的氢气，在1 atm H2条件下，含ni纳米管中可以储存高达1% （wt.）的氢气。本课题研究了掺杂碱金属、贵金属和过渡金属的多壁和单壁碳纳米管和石墨纳米纤维对H2的吸附。实验条件包括氢气压力高达1000 psig，温度高达500℃，以及各种内径的纳米管。通过分子轨道和蒙特卡罗计算，对纳米管储氢机理进行了理论研究。多壁纳米管似乎可以有效地去除燃烧气体中的二恶英，表现出比活性炭更好的能力，所以这种应用也在测试中。该项目旨在开发在环境条件下用于汽油和柴油脱硫的高效吸附剂。该计划的成功将使炼油厂能够轻松满足新的（2006年）硫标准。该项目的第二个目标是开发碳纳米管作为储氢吸附剂，以及探索碳纳米管的其他独特吸附剂特性。该项目的研究成果将在碳纳米管的应用方面取得重大进展，并为保护环境做出贡献。

New Sorbents for Separation and Purification ProcessesAs a means of meeting more stringent sulfur standards for gasoline and diesel fuels, adsorption under ambient conditions has become an attractive alternative (to hydrodesulfurization, which is a high-pressure catalytic process). In prior work pi-complexation has been exploited for fuel desulfurization. Thiophene in benzene was used as the model system to represent sulfur compounds and gasoline, respectively. Preliminary results showed that Cu(I)Y and AgY zeolites both adsorbed thiophene at low concentrations much more strongly than NaY, which is among the best sorbents for desulfurization. Molecular orbital calculations showed stronger pi-complexation bonds between these zeolites and thiophene than with benzene. Based on these promising results, a comprehensive study of both vapor-phase and liquid-phase adsorption has been undertaken. Two classes of pi-complexation sorbents are used: ion exchanged zeolites and monolayer salts supported on high-surface-area substrates involving Cu+ and Ag+ aswell as other promising d-block cations. The study investigates thiophene, benzothiophene, and dibenzothiophene dissolved benzene and toluene. Also, the study examines the unique and promising adsorption properties of carbon nanotubes. Preliminary results showed that 2.5% (wt.) of hydrogen could be stored inalkali-doped nanotubes at 1 atm H2, and up to 1% (wt.) H2 could be stored inNi-containing nanotubes, also at 1 atm H2. The project studies H2 adsorption by multi-wall and single-wall carbon nanotubes and graphite nanofibers doped with alkali metals, noble metals, and transition metals. Experimental conditions include hydrogen pressures up to 1000 psig, temperatures up to 500oC, and nanotubes of various inner diameters. The mechanisms of hydrogen storage in nanotubes are studied theoretically through molecular orbital and Monte Carlo calculations. Multiwall nanotubes appear to be effective for dioxin removal from combustion gases, exhibiting much better capacity that activated carbon so this application is also being tested. This project is aimed at developing efficient sorbents for desulfurization of gasoline and diesel fuels under ambient conditions. Success of this program will enable refiners to meet easily the new (2006) sulfur standards. The second aim of this program is to develop carbon nanotubes as sorbents for hydrogen storage as well as to explore other unique sorbent properties of carbon nanotubes. The results of this program will make a significant advance in the applications of carbon nanotubes and contribute to protection of the environment.