Predicting the physical properties of three-component lignocellulose derived advanced biofuel blends using a design of experiments approach†

Abstract

Acid-catalysed alcoholysis of lignocellulosic biomass produces a tailorable advanced biofuel blend, with the primary products being an alkyl levulinate, a dialkyl ether, and alcohol. Varying process parameters during production has the potential to produce differing quantities of the three components, affecting both physical and combustion properties. Starting alcohols, ethanol, n-butanol, and n-pentanol were chosen to investigate the effects of carbon chain length on the physical properties of model ethyl, butyl, and pentyl-based blends, produced from alcoholysis. Blends were designed to contain ≥50 vol% alkyl levulinate, with the remainder composed of the corresponding ether and alcohol. Existing fuel standards set limits for different physical and chemical properties that should be met to enhance commercial viability. In the present work, the flash point, density at 15 °C and kinematic viscosity at 40 °C (KV40) were measured for a range of three-component blends. The study also investigated the impact of diesel (EN 590 compliant) blending on these properties, at 0–95% volume diesel. A design of experiments approach selected optimal blends for testing and was used to develop predictive physical properties models based on polynomial fits. The predictive models for the properties of the three-component blends had average absolute relative deviations <5%, indicating their utility for predicting generalised blend properties. The models facilitated the determination of blend boundaries, within which the formulations would meet existing fuel standards limits. Flash points ranged from 26–57 °C and 54–81 °C for the butyl and pentyl-based blends without diesel, respectively. Densities at 15 °C ranged between 0.879–0.989 g cm⁻³, 0.874–0.957 g cm⁻³, and 0.878–0.949 g cm⁻³ for the ethyl, butyl and pentyl-based blends without diesel, respectively. The KV40 ranged from 1.186–1.846 mm² s⁻¹ and 1.578–2.180 mm² s⁻¹ for butyl and pentyl-based blends without diesel, respectively. Butyl-based blends with diesel were found to be the most practically suitable and met the BS 2869 density limits.