Stability Improvement of FAU Zeolites Ion-Exchanged with Copper–Ammonia Solution for the Removal of Thiophene and Benzothiophene from Model Fuel

Abstract

Faujasite (FAU) zeolites with low Si/Al ratios (e.g., X-type zeolites) have much more exchangeable cation sites than those with high Si/Al ratios (Y-type zeolites) for Cu­(I), which could improve the adsorption performance via π-complexation. However, the structure of Cu-exchanged X-type zeolites was unstable during autoreduction at high temperatures as reported [ Takahashi Takahashi Ind. Eng. Chem. Res.et. al.20024124872496]. Here, we proposed a scheme of Cu-exchanged X-type zeolites in copper–ammonia solution to improve the stability of the zeolite structure during autoreduction. Therefore, it makes us be able to study the adsorption properties of thiophenic compounds in Cu­(I)-exchanged FAU zeolites from low to high Si/Al ratios. The modified zeolites were characterized by X-ray diffraction, high-resolution transmission electron microscopy, inductively coupled plasma spectroscopy, X-ray fluorescence, and Brunauer–Emmett–Teller analysis and tested by adsorption desulfurization experiments in model fuels. The results indicate that the modified zeolites with various Si/Al ratios show different adsorption properties for thiophene and benzothiophene. The adsorption capacity for thiophene decreased in the order Cu­(I)­Y-5.30 > Cu­(I)­X-1.23 > Cu­(I)­Y-2.30. For benzothiophene, the adsorption capacity decreased in the order Cu­(I)­Y-2.30 > Cu­(I)­Y-5.30 > Cu­(I)­X-1.23.

Enhanced Adsorption Desulfurization Performance over CuCeY Zeolites Prepared by Low‐Temperature Calcination under H2 Atmosphere

“…In addition, as shown in Table 6, the fraction of Cu + ion in Cu 0.06 Ce 0.01 Y zeolite is the largest among CuCeY zeolites and thus its desulfurization effect is the best for TMO. However, its fraction is still lower than that of CuY or CuCe zeolites prepared by calcination at high temperature [19,21,42] . Meanwhile, a large area of peak at 935.1 eV means the water content in Cu 0.075 Y zeolite is high.…”

“…In order to enhance the reliability of comparison, several model oils containing the same compositions as the references will be prepared and tested soon. Besides, the maximum Q value of CuCeY zeolites for TMO is lower than that of CuY zeolites obtained through autoreduction at high temperatures under a N 2 atmosphere [38,42] . It means that adsorptive capacity of CuCeY zeolite for sulfur compounds has the room for improvement.…”

“…It leads to the low desulfurization capability of Cu 0.075 Y zeolite relative to that of CuY zeolite obtained by calcination at 550°C (Cu(I)-Y-0.28-550) [38] or at 400°C (Cu(I) Y zeolite). 42] The BEs at 886.8 and 883.7 in Figure 12 correspond to the photoemission peak of 3d 5/2 4f 1 and 3d 5/2 4f 2 regions of Ce 3 + ions, respectively. The BEs of their spin-orbit splitting are 906.4 and 903.4 eV, respectively.…”

“…Besides, the maximum Q value of CuCeY zeolites for TMO is lower than that of CuY zeolites obtained through autoreduction at high temperatures under a N 2 atmosphere. [38,42] It means that adsorptive capacity of CuCeY zeolite for sulfur compounds has the room for improvement. It may be enhanced by further optimizing preparation conditions CuCeY zeolites, such as using the NH 4 Y zeolite as the raw material and thus increasing the ion exchange degree, [43] altering the Si/Al ratio of Y zeolite, [42] adjusting the pH value [42,44] and concentration [3,38,45] of nitrate solution, changing the temperature and atmosphere of calcination, [3,21,39,46] and enlarging the pore diameter of Y zeolite.…”

“…However, its fraction is still lower than that of CuY or CuCe zeolites prepared by calcination at high temperature. [19,21,42] Meanwhile, a large area of peak at 935.1 eV means the water content in Cu 0.075 Y zeolite is high. It leads to the low desulfurization capability of Cu 0.075 Y zeolite relative to that of CuY zeolite obtained by calcination at 550°C (Cu(I)-Y-0.28-550) [38] or at 400°C (Cu(I) Y zeolite).…”