Coprocessing Biomass Fast Pyrolysis and Catalytic Fast Pyrolysis Oils with Vacuum Gas Oil in Refinery Hydroprocessing
Daniel M. Santosa, Igor V. Kutnyakov, Matthew Flake, Huamin Wang
Abstract
Fast pyrolysis and catalytic fast pyrolysis (CFP) have been considered to be promising approaches for converting lignocellulosic biomass into liquid bio-oils followed by upgrading to produce fuel-range hydrocarbon products. Coprocessing fast pyrolysis and CFP bio-oils with petroleum feedstocks leverages the existing petroleum refining infrastructure, which reduces capital expenditure for the overall conversion technologies for biomass to fuel and enables fast adoption of the technologies and biofuels. Here, we reported the coprocessing of different woody fast pyrolysis and CFP bio-oils with petroleum vacuum gas oil (VGO) at 5–25% bio-oil blending levels over a NiMo sulfide catalyst for hydrotreating/mild hydrocracking. The catalyst activities over ∼300 h time on stream, the product yield and properties, and the biogenic carbon content in products are provided. Coprocessing of the raw fast pyrolysis bio-oil in our configuration was not successful because the instability of the bio-oil resulted in reactor plugging, and bio-oil stabilization by hydrogenation enabled their stable coprocessing with VGO, whereas the CFP bio-oil can be coprocessed without pretreatment. Simultaneous hydrodesulfurization, hydrodeoxygenation, and hydrocracking reactions occurred during coprocessing, and no obvious decrease in hydrodesulfurization and hydrocracking conversion of VGO was observed, suggesting the minimal impact of coprocessed bio-oils on the reaction of VGO and also the simultaneous conversion of bio-oil and VGO to produce fuel products with much-reduced S and O content. Biogenic carbon content in coprocessed products calculated by yield mass balance, together with results from isotopic measurements, indicates biogenic carbon incorporation into liquid hydrocarbon products. Higher biogenic carbon incorporation into fuel products was observed when coprocessing CFP bio-oils as compared to the fast pyrolysis bio-oils, and over 90% of carbon in CFP bio-oil was incorporated into liquid hydrocarbon products.