Browsing by Author "Pradhan, Sivaram"

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Method for decomposing asphaltene using a supported catalyst
    (2020-12-29) Pradhan, Sivaram; Wellington, Scott; Shammai, Houman; Wong, Michael; Rice University; Baker Hughes, a GE company, LLC; United States Patent and Trademark Office
    Asphaltene produced during the production of hydrocarbons in an underground reservoir may be reduced and decomposed by introducing into the underground reservoir a fluid having a catalyst of from about 3 to about 7% Ni with a magnesium oxide support or a catalyst of from about 15 to about 25% tungsten oxide with a zirconium oxide support or a mixture thereof. The viscosity of heavy oil within the underground reservoir is reduced in the presence of the catalyst.
  • Thumbnail Image
    Item
    Ring-locking enables selective anhydrosugar synthesis from carbohydrate pyrolysis
    (Royal Society of Chemistry, 2016) Chen, Li; Zhao, Jinmo; Pradhan, Sivaram; Brinson, Bruce E.; Scuseria, Gustavo E.; Zhang, Z. Conrad; Wong, Michael S.
    The selective production of platform chemicals from thermal conversion of biomass-derived carbohydrates is challenging. As precursors to natural products and drug molecules, anhydrosugars are difficult to synthesize from simple carbohydrates in large quantities without side products, due to various competing pathways during pyrolysis. Here we demonstrate that the nonselective chemistry of carbohydrate pyrolysis is substantially improved by alkoxy or phenoxy substitution at the anomeric carbon of glucose prior to thermal treatment. Through this ring-locking step, we found that the selectivity to 1,6-anhydro-β-D-glucopyranose (levoglucosan, LGA) increased from 2% to greater than 90% after fast pyrolysis of the resulting sugar at 600 °C. DFT analysis indicated that LGA formation becomes the dominant reaction pathway when the substituent group inhibits the pyranose ring from opening and fragmenting into non-anhydrosugar products. LGA forms selectively when the activation barrier for ring-opening is significantly increased over that for 1,6-elimination, with both barriers affected by the substituent type and anomeric position. These findings introduce the ring-locking concept to sugar pyrolysis chemistry and suggest a chemical-thermal treatment approach for upgrading simple and complex carbohydrates.
  • Thumbnail Image
    Item
    Viscosity reduction of crude oil through structure determination of asphaltene molecule
    (2019-05-14) Verma, Manjusha; Venkataraman, Pradeep; Pradhan, Sivaram; Shammai, Houman Michael; Billups, Wilbur Edward; Wellington, Scott; Rice University; NextStream Heavy Oil, LLC; United States Patent and Trademark Office
    Asphaltene may be effectively broken into smaller molecules by first elucidating the structure of the asphaltene and then developing a catalyst system based on the elucidated structure. The structure may be determined based on a series of analytical techniques including NMR, FTIR, Raman spectroscopy, XPS, and LDI. The most probable structure is determined using computational methods based on quantum mechanics and classical molecular dynamics and the catalyst system is developed for the most probable structure.
  • Thumbnail Image
    Item
    Viscosity reduction of crude oil through structure determination of asphaltene molecule
    (2021-04-20) Verma, Manjusha; Venkataraman, Pradeep; Pradhan, Sivaram; Shammai, Houman Michael; Billups, Wilbur Edward; Wellington, Scott; Rice University; NextStream Heavy Oil, LLC; United States Patent and Trademark Office
    Asphaltene may be effectively broken into smaller molecules by first elucidating the structure of the asphaltene and then developing a catalyst system based on the elucidated structure. The structure may be determined based on a series of analytical techniques including NMR, FTIR, Raman spectroscopy, XPS, and LDI. The most probable structure is determined using computational methods based on quantum mechanics and classical molecular dynamics and the catalyst system is developed for the most probable structure.