100$^{\circ}$C, and the sorbed NH$_3$ could be recovered for other usage. Additionally, a primary study was conducted on siloxane removal over commercially available adsorbents such as silica gel and lab-prepared mesoporous molecular sieves including MCM-41 and SBA-15 using hexamethyldisiloxane (L2, or MM) as the model siloxane compound. The silica gel material had a good performance for siloxane capture. MCM-41 and SBA-15 showed a much better capacity (about twice that of silica gel) due likely to their higher surface area and uniform pore structure.

\section{Deep Desulfurization of ULSD}

The effect of fuel composition on the performance of Ti-Ce-O adsorbent for adsorptive desulfurization has been studied using a model diesel, which suggested that critical inhibiting or competitive components for ADS are present in real diesel fuel. The selectivity decreased as the order: Indole $>$ DBTO$_2$ $>$ DBT $>$ MDBT $>$ BT $>$ DMDBT $>$ Phe $>$ Flu $\sim$ MNap $>$ Nap. The competitive adsorption of nitrogen compounds may inhibit ADS over the Ti-Ce-O adsorbent. The adsorption temperature influenced the ADS performance. Higher temperature resulted in a lower capacity. Adding in situ air flow greatly improved the ADS performance of Ti-Ce-O adsorbent. The ADS breakthrough capacity increased significantly from 2.5 to 22.5 g-F/g-sorb. The promotion effect can be attributed to the oxidation of sulfur compounds which are more prone to be adsorbed, as proven by gas chromatography flame ionization detector (GC-FID) and S-X-ray absorption near edge structure (XANES). The role of Ce in Ti-Ce-O adsorbent has been studied by X-ray absorption technique and HRTEM. The addition of CeO$_2$ significantly promoted the adsorption capacity of TiO$_2$, especially with in situ air flow. Besides, the MCM-48 supported Ti-Ce-O adsorbent has also been studied. By adding small amount of silver oxide, the ADS capacity of Ti-Ce-Ag-O/MCM-48 adsorbent reached as high as 95 g-F/g-sorb, suggesting a promotion role of silver oxide.

\section{Delphi SOFC Stack Running on Alternative Fuels}

A combined steam reforming-SOFC test system was developed and used to generate electric power from commercial diesel fuel. The SOFCs used in these experiments were NextCell-B button cells with 1.256 cm$^2$ active area (Fuel Cell Materials). The SOFC membranes in these cells were 150 $\mu$m dense yttria stabilized zirconia (YSZ), 8 mol\% yttria. The anode layer was a porous 50 $\mu$m Ni-YSZ cermet, and the cathode layer was a porous 50 $\mu$m lanthanum strontium manganite (LSM).

Cell performance was tested with hydrogen, ADG, and reformed diesel, and a comparative study on the data was carried out. Extended power generation and degradation characterization tests were carried out using ADG as fuel. EIS and equivalent circuit modeling were used to track the degradation of SOFC performance over a period of 200+ hours. During the extended power generation testing, periodic polarization and EIS tests were carried out in an effort to characterize the nature of SOFC performance degradation. The polarization testing carried out was done by applying a series of decreasing external electronic loads between the SOFC electrodes while monitoring current and voltage responses. Figure~\ref{fig:figure_2} shows the change in polarization behavior between 175 and 225 hours of power generation; this time period corresponds to a 20\% overall power reduction shown. The EIS Nyquist plots shown in Figure~\ref{fig:figure_3} demonstrate separate contributions to overall inefficiencies in the electrochemical system. An equivalent circuit has been developed to fit the measured impedance behavior to individual kinetic, ohmic, and mass transport resistance contributions.

\begin{figure}
\centering
\includegraphics{figure_2.pdf}
\caption{Polarization analysis of Ni-YS anode fueled with anaerobic digester gas for 175 and 225 hours.}
\label{fig:figure_2}
\end{figure}

\begin{figure}
\centering
\includegraphics{figure_3.pdf}
\caption{Nyquist plot of SOFC system after 175 and 225 hours of power generation from anaerobic digester gas.}
\label{fig:figure_3}
\end{figure}