دانلود رایگان مقاله (Hydrodeoxygenation (HDO گایاکول بر نیکل - پالادیم و نیکل - پلاتین

ABSTRACT

principle computational studies have predicted that formation of Pd or Pt overlayer on Ni base metal would cause a negative shift of the d-band center of surface Pd or Pt, resulting in reduced binding strength for adsorbed species. In this paper, silica alumina supported Ni@Pd and Ni@Pt overlayer catalysts were synthesized via directed deposition technique and tested for hydrodeoxygenation of guaiacol at atmospheric pressure. Several characterization techniques such as hydrogen chemisorption, ethylene hydrogenation descriptor reaction, XRD and TEM studies were employed to characterize the catalysts. H2 chemisorption results showed that Ni@Pd and Ni@Pt overlayer catalysts had reduced H2 adsorption strength compared to Pd or Pt only catalysts, which agreed with the computational prediction. As predicted, the overlayer catalysts also showed lower activity for ethylene hydrogenation than Pd or Pt only catalysts. XRD and TEM studies indicated that overlayers have been successfully deposited atop supported nickel. Guaiacol hydrodeoxygenation results showed that, especially at low reaction temperature, Pd and Pt active sites of overlayer catalysts showed significantly enhanced deoxygenation activity compared with that of Pd or Pt only catalysts. Further studies showed that guaiacol could be completely deoxygenated using silica alumina supported metal catalysts, yielding benzene, toluene, and xylenes as major products.

4. Conclusions

In this work, hydrodeoxygenation of guaiacol was studied using silica alumina supported Ni@Pd and Ni@Pt overlayer catalysts under atmospheric pressure. Hydrogen chemisorption, ethylene hydrogenation, XRD and TEM studies have demonstrated that palladium or platinum could be deposited atop supported nickel catalysts and the prepared overlayer showed behavior consistent to that of computational predictions. When normalized per active site, Pd and Pt active sites of overlayer catalysts showed signifi- cantly enhanced deoxygenation activity compared with that of Pd or Pt only catalyst. However, overlayer catalysts didn’t show better stability than Ni, Pd or Pt only catalysts. Results of guaiacol HDO with different W/F showed that selectivity of benzene,toluene, and xylenes could be up to 80% on Ni@Pd overlayer catalyst at high W/F condition. In addition, major reaction pathways of guaiacol HDO on silica alumina supported metals catalysts were proposed.