Hydroconversion of Methyl Laurate as a Model Compound to Hydrocarbons on Bifunctional Ni2P/SAPO-11: Simultaneous Comparison with the Performance of NUSAPO-11

The bifunctional Ni2P/SAPO-11 was tested for the hydroconversion (involving deoxygenation and hydroisomerization) of methyl laurate as a model compound to hydrocarbons. The influences of reaction conditions, catalyst stability, and catalyst deactivation were investigated. For comparison, the performance of Ni/SAPO-11 was also examined. The result shows that the increase of temperature and the deceases of weight hourly space velocity (WHSV) and H2 pressure favored the conversion of methyl laurate meanwhile promoted the decarbonylation and hydroisomerization as well as cracking reactions. Apart from the Ni sites that were dominating for deoxygenation, the acid sites also affected the deoxygenation pathway. Due to more medium strength acid sites, Ni/SAPO-11 gave higher selectivity to isoalkanes and more preferentially catalyzed the hydrodeoxygenation pathway to produce the C12 hydrocarbons than Ni2P/SAPO-11. During the test for 101 h, Ni2P/SAPO-11 exhibited greatly superior stability to Ni/SAPO-11 for the deoxygenation of methyl laurate, while both Ni2P/SAPO-11 and Ni/SAPO-11 were deactivated for the hydroisomerization. Under the condition of 360 degrees C, 3.0 MPa, WHSV of 2 h(1), and H-2/methyl laurate molar ratio of 25, the conversion of methyl laurate was close to 100% and the total selectivity to isoundecane and isododecane decreased from 36.9% to 28.6% on Ni2P/SAPO-11. To explore the catalyst deactivation, the fresh and the used catalysts were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, thermogravimetric analysis, Raman spectroscopy, and N-2 adsorptiondesorption. The sintering of Ni particles and carbonaceous deposit contribute to inferior stability of Ni/SAPO-11 for both deoxygenation and hydroisomerization, while no obvious sintering of Ni2P particles took place and the carbonaceous deposit mainly led to the loss of the activity for hydroisomerization on Ni2P/SAPO-11. We propose that carbonaceous deposit mostly formed on the acid sites that are indispensible for hydroisomerization.