Impacts of Sonochemical Process Variables on Number Average Molecular Weight Reduction of Asphaltene

Athabasca asphaltene was ultrasonically processed under a variety of conditions. Five discrete ultrasonic frequencies and four saturating gases were explored. The kinetics of the reduction in the number average molecular weight (NAMW) were determined by vapor pressure osmometry measurements and UV/visible spectrophotometric measurements. The NAMWs decreased significantly after short treatment times (from ~1200 to ~470 g/mol in 15 min). The observed reduction in the NAMWs of asphaltene was greatest at 358 kHz. At a frequency of 205 kHz, the observed reduction in NAMW was fastest with a mixture of Ar/H2 (50%/50% v/v), whereas saturating with hydrogen, air, and oxygen gases exhibited minimal effect on the kinetics. Visible light absorption spectra of asphaltene samples demonstrate that heptane soluble fractions increase by >50% after sonochemical treatment as an upgrading process.