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The use of pyrolysis-derived bio-oil as a diesel-fuel extender or substitute has long been a goal of the bio-oil research community. In this paper, a simple system to accomplish that goal is described. The production of pine-chip-derived bio-oils, the preparation, and fuel properties of bio-oil/biodiesel blends are presented. Pyrolysis-condensed liquids were obtained from the pyrolysis of pine chips and pine pellets in batch and auger slow-pyrolysis reactors. These liquids were composed of two phases:  an oily bottom phase and an aqueous phase. The removal of most of the water present in the aqueous phase results in the formation of a second oily phase called, in this paper, polar oil. The oily bottom phases were more soluble in biodiesel than the polar oils. Monolignols, furans, sugars, extractive-derived compounds, and a relatively small fraction of oligomers were the main bio-oil compounds soluble in biodiesel. Water and low-molecular-weight compounds responsible for many of the undesirable fuel properties of bio-oils were poorly dissolved in biodiesel. Select fuel properties of bio-oil/biodiesel blends, such as viscosity, density, calorific value, water content, and pH, are reported.

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The rheological properties of two complex mixtures of short-chain triglycerides were experimentally determined. Dynamic or absolute viscosities of the mixtures were measured for shear rates of 0.32 to 64.69 s −1 at temperatures between 25 and 80°C. The compositions of the mixtures were based on the oil of the plant species Cuphea viscosissima VS-320, a natural source of short-chain triglycerides. The dynamic viscosities of these mixtures were compared to those of a traditional vegetable oil (peanut oil) and diesel fuel. The results of this comparison were used to make estimates of the performance of such triglyceride mixtures as diesel fuel substitutes, since viscosity can be a key indicator of fuel performance for possible substitute diesel fuels. The crystallization temperatures of these two mixtures were also determined experimentally, and the effects of crystallization on fuel performance were projected. Additionally, the dynamic viscosities of pure triglycerides from C6:0 to C18:0 at 75°C were plotted vs. chain length. These viscosities were measured at high shear rates (>6 s −1 ) where dynamic viscosity is shear-independent. An obvious trend in the relationship between triglyceride chain length and viscosity was observed. A second-order regression was used to obtain an equation for this relationship. This equation was used as a model for composition dependence of viscosity. This model was applied to the viscosities of the triglyceride mixtures examined here. There was good agreement between the model and the actual, measured viscosity values determined in this study.The physical properties, including viscosity, of pure, shortchain triglycerides such as tricaproin (C6:0), tricaprylin (C8:0), and tricaprin (C10:0) have been evaluated in previous studies (1-3). These studies sought to develop models for the use of oils containing such compounds as diesel fuel substitutes, i.e., biodiesel. The results obtained suggest that vegetable oils containing high concentrations of short-chain saturated triglycerides may provide effective diesel fuel substitutes without the additional processing costs incurred when converting commercial vegetable oils into effective alternative fuels. Studies on the properties of binary mixtures of triglycerides have also been published (1,4,5). These investigations have been useful in understanding how such compounds interact with each other and how triglyceride chain length affects the physical properties of vegetable oils. This information has been useful in the design and evaluation of equipment used for the chemical processing of oils containing low-molecular-weight saturated triglycerides for cosmetic and pharmaceutical applications. Such information is also important for the development of triglyceride-based diesel fuel substitutes derived from vegetable oils.Studies concerning the behavior and properties of shortchain triglycerides in the pure state and in simple mixtures can be very useful in the development of biologically derived fuels and other valuable products. However, natu...