Veronika Vachova, Petr Straka
Statement of the Problem: The hydrotreating of vegetable oils is nowadays a very promising way to produce renewable components of engine fuels. Using reduced nickel-based catalysts for this purpose seems to be very perspective. However, these catalysts are characterized by relatively low stability during the deoxygenation of triglycerides, mainly due to the deposition of coke on their surface. For this reason, bimetallic nickel-based catalysts with Ag and Cu promoters were tested and their activities and stabilities were compared.
Methodology & Theoretical Orientation: The hydrotreating was performed in a tubular fixed-bed reactor with the co-current flow of a feedstock and hydrogen. Commercially available rapeseed oil was used as a feedstock and Ni, Ni-Ag and Ni-Cu catalysts with γ-Al2O3 support were prepared and tested. Temperatures in the range of 220 – 320 °C, the pressure of 4 MPa, weight hourly space velocity of 1 h-1 and hydrogen to feedstock ratio of 1000 m3·m-3 were used.
Findings: For all tested catalysts, the conversion of triglycerides increased with the increasing reaction temperature and the full conversion was achieved for Ni and Ni-Ag catalysts at the reaction temperature of 260 °C and at 280 °C for the Ni-Cu catalyst. The key component of all gaseous products was methane, probably due to the strong hydrogenolysis activity of all compared catalysts.
Conclusion & Significance: If Ni-Cu/γ-Al2O3 catalyst was used, hydrogenolysis reactions were slightly suppressed and the higher stability at the higher reaction temperatures was observed. For this reason, Ni-Cu/γ-Al2O3 seems to be a perspective catalyst for the hydrotreating of vegetable oils with the aim of the production of renewable components of engine fuels.
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