LPG contains 5-10 volppm of sulfur compounds such as thiols, sulfi des, and disulfi des. Use of LPG as the hydrogen source for fuel cells will require the removal of sulfur content to the ppb level. Active carbon, CuO/ ZnO/Al2O3, Ag-exchanged β zeolite and Ag/CeO2 were examined as sulfur adsorbents at room temperature using propane containing 2-methyl-2-propane thiol (TBM: t-butyl mercaptane), dimethylsulfide (DMS), dimethyldisulfide (DMDS), and carbonyl sulfide (COS). Sulfur compounds were not removed effectively by active carbon. CuO/ZnO/Al2O3 showed excellent removal of TBM, but removal of DMS ceased after a short time. Ag-exchanged β zeolite achieved excellent removal of TBM, DMS and DMDS, but COS was not removed. Ag/ CeO2 removed all types of sulfur compounds and provided superior removal of COS compared to the other sulfur adsorbents. Ag/CeO2 and CuO/ZnO/Al2O3 tended to adsorb reactive sulfur compounds more strongly. Agexchanged β zeolite adsorbed sulfur compounds associatively, and the larger the negative charge of the sulfur atom of the compound, the stronger the coordination bonding between the Ag cation and the sulfur atom of the compounds. In contrast, Ag/CeO2 adsorbed sulfur compounds dissociatively, and produced sulfur atoms at room temperature.
Two-phase coexistence curves were measured for ternary solutions of bimodal polystyrene in methylcyclohexane with the molecular weight ratio near the tricritical value 23. Coexistence curves were determined by the refractive index method on a diagram of temperature versus volume fraction of total polystyrene. The diameter was strongly curved near the top. The double logarithmic plots of volume fraction difference between two coexisting phases versus reduced temperature yielded the critical exponent beta=0.250+/-0.005 for the tricritical solution and, 0.412+/-0.005 and 0.383+/-0.016 for solutions not far from the tricritical one. The former value could be compared with the classical tricritical exponent beta=1 / 4 and the latter values near 0.40 could be explained by a crossover between the ordinary critical exponent 0.32 or the tricritical exponents 1 / 4 and the classical exponent 1 / 2.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.