Co-hydrotreatment of the Bio-oil Lignin-Rich Fraction and Vegetable Oil

Blends of lignin-rich oil (LRO) and vegetable oil (1:8, 1:4, 1:2, and 1:1) were prepared and hydrotreated over CoMo/Al2O3 (catalyst liquid ratio of 1:50) at 623 K and 500 rpm, with 9.3 MPa of cold initial H-2 pressure for 4 h. The yield of liquid, gas, and solid products was reported. The yield of coke obtained was in all of the cases very high (between 25 and 50 wt % of the LRO processed, depending upon the LRO/vegetable oil ratio used). Most of the product from the lignin-rich fraction remained in the heavy fractions. To mitigate coke formation, blends containing 0.5 g of butanol/g of LRO studied were co-hydrotreated with vegetable oils maintaining the LRO/vegetable oil ratios. The presence of 1-butanol mitigated coke formation, but it did not translate in the production of distillable fractions; the LRO contributed to the formation of a heavy oil. The LRO needs to be stabilized and cracked before co-deoxygenation. Cracking/stabilization studies in the presence of butanol and methanol were conducted over Ni/SiO2-Al2O3 at 473 K with 9.3 MPa of cold H-2 pressure for 24 h. The best results were obtained with the oils stabilized in the presence of butanol. The yield of coke formed decreased from 34.7 wt % on LRO basis to 6.65 wt %. The behavior of the stabilized/cracked LRO/vegetable oil blends (1:4) in terms of the product yield was comparable to the yields obtained when vegetable oil was deoxygenated alone. The solid residue (coke) increased from 0.04 wt % when vegetable oil was processed alone to 1.13 wt % when a 1:4 blend of stabilized/cracked lignin/vegetable oil was co-processed. Lower coke yields may be obtained in continuous co-hydrotreatment reactors.