Diesel is known to contain high presence of hydrogen, which makes them a favorite source for catalytic conversion process of fuel. Hydrogen, which provides clean energy to the environment, is often produced through the catalytic conversion form of steam reforming process due to its high optimality and selectivity towards hydrogen.
The catalyst majorly used in a catalytic conversion of fuels to hydrogen in the steam reforming process, is nickel-based with other supporting materials such as alumina and yttrium-stabilized zirconia. However, deposition of carbon on catalyst during the steam reforming process limits the efficiency of the nickel supported catalyst. This as a result led to the introduction of second catalytic material such as K2Ti2O5 which has high thermal stability and ability to oxidize the carbon deposits at the same time.
Researchers led by Professor Jong Shik Chung from Pohang University of Science and Technology in Republic of Korea investigated the addition of K2Ti2O5 particles on nickel supported on alumina Ni-Al2O3 and yttrium-stabilized zirconia Ni-YSZ catalyst in the steam reforming reaction of n-dodecane. The research work is now published in peer-reviewed journal, International Journal of Hydrogen Energy.
The authors investigated the performance of the added K2Ti2O5 on nickel-based supported catalyst with the use of Brunauer-Emmett-Teller analysis, x-ray diffraction, thermogravimetric analysis, transmission electron microscopy and electron energy loss spectrometer coupled with their total selectivity towards hydrogen, carbon monoxide, carbon dioxide and methane.
At gas hourly space velocity of 15000h-1, the yttrium-stabilized zirconia supports on the nickel catalyst possessed more selectivity towards hydrogen and other gases compared to other alumina supported catalyst. However, the addition of K2Ti2O5 particles on the nickel supports on yttrium-stabilized zirconia catalyst maintained the conversion process without a decrease in its activities compared to others.
The decreased activity of K2Ti2O5 particles on the nickel supported on alumina catalyst was due to the low contact between the nickel particles and K2Ti2O5 phase as a result of the hindered presence of nickel particles in the alumina pores. This was a different case for that of yttrium-stabilized zirconia catalyst as nickel particles were found in the zirconia supports, aiding good contact.
At high gas hourly space velocity below 20000h-1, the addition of K2Ti2O5 particles on the nickel-supported yttrium-stabilized zirconia catalyst maintained good stability due to the oxidation of deposited carbon on the surface of the catalyst. The addition of K2Ti2O5 particles on the nickel-supported yttrium-stabilized zirconia catalyst also aided the non-existence of hard carbons except at gas hourly space velocity of 30000h-1.
Results from transmission electron microscopy and electron energy loss spectroscopy the authors indicated that both the present and absent K2Ti2O5 particles on the nickel-based yttrium-stabilized zirconia catalyst were effective in selectivity of hydrogen at a gas hourly space velocity of 5000h-1. The absence and presence of K2Ti2O5 particles on the nickel-based yttrium-stabilized zirconia catalyst deactivates at gas hourly space velocity of 5000h-1 and 20000h-1 respectively.
This study was able to provide an absolute range of effectiveness of the added K2Ti2O5 on yttrium-stabilized zirconia catalyst for the steam reforming process of n-dodecane.
Kim, T., Song, K.H., Yoon, H., Chung, J.S. Steam Reforming of n-dodecane over K2Ti2O5-added Ni-alumina and Ni-zirconia (YSZ) Catalysts, International Journal of Hydrogen Energy 41 (2016) 17922-17932.
Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), 77 Cheongam-Ro, Pohang, 37673, Republic of Korea.