a b s t r a c tThe interactions between lignin and cellulose during the slow pyrolysis of their blends were studied by means of Thermogravimetric Analysis (TGA) and Scanning Electron Microscopy (SEM). Fast pyrolysis was studied using Pyrolysis-Gas Chromatography/Mass Spectroscopy (Py-GC/MS). Crystalline cellulose (Avicel), amorphous cellulose, organosolv lignin, and their blends containing 20, 50, and 80 wt.% of lignin were used for the experiments. Differential thermogravimetry (DTG) revealed that the interaction between crystalline cellulose and lignin resulted in a shift toward higher decomposition temperatures, but for lignin/amorphous cellulose mixtures this effect was small. No effect of adding lignin to cellulose was observed on the yields of bio-char. Cellulose-lignin interactions during fast pyrolysis in Py-GC/MS did occur. Products from cellulose fragmentation reactions (hydroxyl-acetaldehyde and acetol) were not influenced by the presence of lignin. In general, production of lignin derived phenolics remains quite similar at 500 • C, but the yield of many methoxylated monophenols increases at 350 • C in the presence of both types of cellulose. Importantly, it was found that the presence of lignin enhanced the yield of levoglucosan, but decreased the yield of some of their dehydration products (e.g., levoglucosenone, 5-Hydrosymethylfurfural, Furfural). This result could be explained by the reduction of residence time of cellulose products in liquid intermediates, a phase where most of the dehydration reactions occur. Lignin seems to enhance micro-explosions, decreasing in this way the residence time of cellulose derived products in the liquid intermediates.

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A systematic approach was applied to study the process of hydrotreating vegetable oils. During the three phases of conceptual, detailed, and final design, unit operations were designed and sized. Modeling of the process was performed with UniSim Design®. Producing green diesel and jet fuel from vegetable oils was found to be technically possible via a flexible process of hydrotreatment. The resulting mass and energy balances indicated high carbon atom and energy yield. An economic evaluation proved that the operational expenses mainly depend on the cost of raw materials. Currently, the margin between crude palm oil and the retail diesel price is too low to operate an economically viable process. However, production and utilization of biofuels is required by international regulations.