| Ultra-deep desulfurization of liquid hydrocarbon fuels has become anincreasingly important subject worldwide due to the environmental and healthconcerns, and its limitation for fuel cell applications. Among the available techniques,adsorptive desulfurization has drawn attentions because sulfur can be significantlyremoved at moderate conditions. Since adsorbent is the core of the adsorptivedesulfurization, it is critical to develop desulfurization adsorbents with high capacity.This work investigated the effects of surface modifications of zeolite/activatedcarbon on the textural properties and surface chemical properties of the adsorbents,and its adsorption of benzothiophene (BT) and dibenzothiophene (DBT). The work isthe research field of chemical engineering and surface science. This work mainlycontributes to science and practical applications.In this work, activated carbon and Y-zeolite were chosen as the support toprepare supported activated carbon/zeolite adsorbents. Effect of textual property ofmodified zeolite/activated carbon adsorbents on their adsorption of BT and DBT wasinvestigated. Results show that (1) there was no adsorption of DBT on Na(I)/Ybecause the aperture size of NaI/Y was smaller than the molecular size of BT, (2) atlow BT concentrations (Cs < 3mmol/L), the ion-exchanged Y zeolites had a higheradsorption capacity of BT compared to the modified ACs because of their largersurface area of micropores, while at higher BT concentrations (7 < Cs < 10 mmol/L),the modified ACs had a higher adsorption capacity of BT because of their much largersurface area. This is one of the new findings in this work, not being reported inprevious literature.In this work, different transition metal ions (Ag+, Ni2+, Zn2+, Cu2+, and Fe3+) werechosen to modify surface chemistry of activated carbon and zeolite. Effect of differenttransition metal ions on their adsorption of benzothiophene (BT) anddibenzothiophene (DBT) was investigated. Results indicated that the equilibriumamounts adsorbed of BT and DBT on the modified zeolites followed the order: Ag(I)/Y > Ni(II)/Y, Cu(II)/Y, Zn(II)/Y > Fe(III)/Y > Na(I)/Y, while the equilibriumamounts on the modified ACs followed the order: Ag(I)/AC > Cu(II)/AC, Ni(II)/AC,Zn(II)/AC > AC > Fe(III)/AC. Hard and Soft Acid and Base (HSAB) theory wasapplied here to understand effect of different metal ions. DBT belong to soft basebased on molecular calculation. Impregnating soft acid Ag+, or borderline acid Ni2:Cu2: and Zn2: onto activated carbon increases its surface acidity. Therefore,adsorption of DBT was increased. In contrast, Impregnating hard acid Fe3: ontoactivated carbon decreases its surface acidity. This finding is an extension of theapplication of the HSAB theory.In this work, ultrasound was applied on the preparation of Ag/Cu/Fe-supportedactivated carbons (ACs). Effects of ultrasound on textural properties and surfacechemistry of modified sorbents was studied. Results indicated that the modificationmethods have significant influence on the adsorption abilities of the modified ACstoward DBT. The application of UIr to prepare metal ion-impregnated ACs can makethe metallic particles on the carbon surfaces become finer and disperse better incomparison with the use of impregnation only. As a consequence, the Ag/AC-UI andCu/AC-UI prepared by using the UIr have higher adsorption capacities of DBT thanthe Ag/AC and Cu/AC prepared using impregnation, while the Fe/AC-UI prepared byusing the UIr has lower adsorption capacities of DBT than the Fe/AC prepared usingimpregnation. This is the third new finding in this work. |
