Low‐temperature phase behavior of vegetable oil/co‐solvent blends as alternative diesel fuel

Abstract

Vegetable oils (triacylglycerols) have many characteristics that make them attractive candidates as renewable alternative fuels for compression-ignition (diesel) engines. Unfortunately, vegetable oils are too viscous to be compatible with modern direct-injection diesel fuel systems and engines. Co-solvent blending is a simple and flexible technology that reduces viscosity by mixing the oil with low molecular weight alcohol. A co-solvent (A), consisting of surfactant plus an amphiphilic compound, is added to solubilize otherwise nearly immiscible oil-alcohol mixtures into a single-layer (isotropic) solution. This work examines low-temperature phase behavior of two soybean oil (SBO)/methanol mixtures solubilized by A = unsaturated long-chain (C 18 ) fatty alcohol/medium-chain alkanol (n-butanol and 2-octanol), one SBO/methanol mixture solubilized by A = triethylammonium linoleate/2-octanol, and one SBO/95 wt% ethanol (E95) mixture solubilized by n-butanol. The E95-blend was further blended in 1:1 (vol/vol) mixtures with No. 2 diesel fuel. Two types of anisotropic phase behavior were observed; formation of a cloudy layer of solid crystals suspended in bulk solution (Type I) and formation of two immiscible liquid layers (Type II). The type of phase separation in a given solution was influenced by phase separation temperature (T ϕ ) relative to the crystallization characteristics of compounds in the SBO and fatty alcohol or amine constituents present in solution. Solutions with relatively low T ϕ values experienced crystallization of small solid particles favoring Type I separations. Conversely, solutions with T ϕ sufficient to avert crystallization of high melting point compounds favored Type II separations where T ϕ = critical solution temperature (T critical ). Increasing the A/oil (SBO or No. 2 diesel/SBO mixture) mass ratio decreased T ϕ while increasing the mass fraction of alcohol (methanol or E95) increased T ϕ . This work shows that vegetable oil/A-based blends can be formulated with cold flow properties superior with respect to cloud point and comparable with respect to kinematic viscosity (ν) of methyl soyate (biodiesel), either neat or blended with petroleum middle distillates.Paper no. J9269 in JAOCS 77, 1315 -1323 (December 2000.KEY WORDS:-Alternative diesel fuels, anisotropic phase behavior, cloud point, co-solvency, kinematic viscosity, phase separation temperature.Over the past two decades, interest in developing vegetable oil (triacylglycerol)-based alternative fuels for combustion in compression ignition (diesel) engines has steadily increased. During the early 1980s, engine tests showed that combustion of neat vegetable oils caused durability problems relating to incomplete combustion such as nozzle coking, engine deposits, ring sticking, and contamination of crankcase lubricant (1-5). These problems were traced to poor fuel atomization aggravated by relatively high kinematic viscosities (ν) of the vegetable oils (6). Subsequent emphasis was placed on developing conversion technologies to reduce...

Fish industry waste: treatments, environmental impacts, current and potential uses

“…, 2000). However, during the early 1980s, engine tests showed that the combustion of vegetable oils caused durability problems related to incomplete combustion such as nozzle coking, engine deposits, ring sticking and crankcase lubricant contamination (Dunn & Bagby, 2000). Furthermore, the higher viscosity of vegetable oils compared with diesel fuel caused excessive carbon deposition and thickening of lubricating oil, and was largely responsible for the problems encountered in using vegetable oils as a diesel fuel especially in relative cold areas and during cold seasons (Clark et al.…”

Direct use of vegetable oil and animal fat as alternative fuel in internal combustion engine

“…80 Direct use of vegetable oil can lead to many problems (particularly in direct-ignition engine) like coking and trumpet formation on the injectors to such an extent that fuel atomization does not occur properly or is even prevented as a result of plugged orifi ces, carbon deposits, and oil ring sticking. 81,82 Th ickening or gelling of the lubricating oil may also occur due to contamination by vegetable oils. 3 Two severe problems associated with the use of vegetable oils as fuel are oil deterioration and incomplete combustion.…”

Development of low-temperature properties on biodiesel fuel: a review

“…One method of mitigating the Low-temperature properties of biodiesel fuel G. Liu effects of wax crystal formation is to blend the methyl esters with diesel fuel, kerosene, or ethanol. This dilutes the fraction of saturated long-chain methyl esters in the mixture, lowering both CP and LTFT [89][90][91][92][93]. Kim et al [94] studied the cold flow behavior of biodiesel blends in a passenger car and a light duty truck.…”