Pavel Šimáček

Density, Viscosity and Water Phase Stability of 1-Butanol-Gasoline Blends

The aim of this work was to describe the density and viscosity and water tolerance of 1-butanol-gasoline blends. Density and viscosity of 1-butanol are higher than that for gasoline and they can affect these parameters in the final gasoline blend. Density increases linearly and viscosity exponentially with the content of 1-butanol. Water solubility in 1-butanol-gasoline blend was determined as the temperature of a phase separation. The water was separated in the solid form at negative temperature and the phase separation point was determined as the temperature of crystallization. Influence of ethanol and ethers used for gasoline blending on water phase stability of 1-butanol-gasoline blend was studied. Ethers are slightly miscible with water and they improve the phase stability. While ethanol is completely miscible water and increases the water solubility in the blends. Finally, water extractions of both alcohols from gasoline were done. In contrast to the ethanol-gasoline blends, 1-butanol remained in the hydrocarbon phase.

Middle distillates hydrogen content via GC×GC-FID

Liquid transportation fuels in the middle distillate range contain thousands of hydrocarbons making the predictions and calculations of properties from composition a challenging process. We present a new approach of hydrogen content determination by comprehensive two-dimensional gas chromatography with flame ionization detector (GC×GC-FID) using a weighted average method. GC×GC-FID hydrogen determination precision was excellent (0.005 wt% repeatability). The method accuracy was evaluated by high-resolution nuclear magnetic resonance (NMR) technique, which is non-biased, measures the H signal directly and was independently validated by controls in the current study. The hydrogen content (in the range of 12.72-15.54 wt%) in 28 fuel samples were determined using GC×GC-FID. Results were within ± 2% of those obtained via NMR. Owing to the fact that NMR is accepted as an accurate technique for hydrogen content determination, the GC×GC method proposed in this study can be considered precise and accurate.

Prediction of 2-EHN content in diesel/biodiesel blends using FTIR and chemometrics

Quantification models based on the processing of FTIR spectra by partial least squares regression (PLS) were created in order to develop a method for the determination of 2-ethylhexyl nitrate (2-EHN) in diesel fuels. The set of standards was prepared using 2-EHN, biodiesel (FAME) and various mineral diesel fuels (2-EHN free). The standards were prepared in the concentration range of 2-EHN of 0-2436mgkg-1. The set of the standards was divided into the calibration, validation and test sets. While the calibration set was used to build the model, validation set was used in order to optimize the model parameters. The test set of the standards was used to assess the predictive ability and repeatability of the model. Several hundreds of various models were developed and compared in order to find a suitable combination of the preprocessing methods and number of latent variables. The most promising model was developed using mean centered spectra in the form of their first derivative and smoothed using Gap-Segment derivative. The model showed quite good predictive ability and repeatability.