Viscosity–Temperature Relationship and Binary Viscosity Mixing Rules for Fast Pyrolysis and Hydrothermal Liquefaction Oil Blends

Abstract

Blending of oils from fast pyrolysis and hydrothermal liquefaction processes is relevant, and might be even necessary, in the context of biofuel production. From a practical point of view, blending of oils can be desirable to adjust the composition and properties of the oil feed (e.g., oil viscosity) to facilitate handling, transport, and conversion in further upgrading operations. Yet, published experimental data that involves mixing different pyrolysis oils, hydrothermal liquefaction (HTL) oils, or a combination of both is limited. The present investigation focused on evaluating (i) the viscosity−temperature relationship of fast pyrolysis and HTL oils over the temperature range of 30−100 °C and (ii) the predictive performance of selected binary mixing rules to estimate the viscosity of fast pyrolysis and HTL oil blends, with a concentration of HTL oil varying from 5 to 40 wt %. The binary viscosity mixing rules evaluated in this study were restricted to those that required only the viscosity and density of the individual oils and their concentration in the blend. It was found that the viscosity−temperature relationship of fast pyrolysis and hydrothermal liquefaction oils could be described in the same way as that of petroleum using the MacCoull relationship in ASTM D341. Measured densities of binary mixtures were consistently higher than the calculated densities for ideal liquids, but despite the bias, the differences were within the experimental uncertainty. Of the nine viscosity mixing rules evaluated, the mixing rule by Miadonye et al. (Petrol. Sci. Technol. 2000, 18, 1−14) gave the best viscosity estimation with an absolute average relative deviation of 7% and a bias of 2%.