1 research outputs found
Mercury Capture from Petroleum Using Deep Eutectic Solvents
Mercury
capture is a major challenge in petroleum and natural gas
processing. Recently, ionic liquids (ILs) have been introduced as
mercury extractants from oil and gas. ILs yield very high mercury
extraction efficiencies (>95%) from hydrocarbons, but their drawbacks
include complex synthesis, toxicity, and difficult regeneration after
mercury capture. In this work, a new technology using deep eutectic
solvents (DESs) for elemental mercury (Hg<sup>0</sup>) extraction
from hydrocarbons is demonstrated. DESs are an innovative class of
designer solvents exhibiting similar properties as ILs, such as low
vapor pressure and low flammability, but DESs are formed from inexpensive
hydrogen-bond donor and acceptor compounds that are often biodegradable.
In this work, four DESs were investigated including choline chloride:urea,
choline chloride:ethylene glycol, choline chloride:levulinic acid,
and betaine:levulinic acid, where the molar ratio is 1:2 in all cases.
The DESs were tested for their thermal stability, density, and viscosity.
Their performance for mercury extraction was assessed using saturated
solutions in <i>n</i>-dodecane as the model oil. It was
found that solvent to feed ratios of 1:1 and 2:1 at temperatures of
303.15 and 333.15 K and atmospheric pressure yield extraction efficiencies
greater than 80% for all four DESs. First-principles molecular dynamics
simulations probing the solvation in choline chloride:urea indicate
a tight first coordination shell for mercury. Calculation of the Hg–Hg
potential of mean force supports formation of a mercury–mercury
polycation for a pair of Hg<sup>1+</sup> ions, but not for pairs of
Hg<sup>0</sup> and Hg<sup>2+</sup> species. Geometric analysis of
the speciation and Mulliken population analysis support a redox reaction
involving Hg<sup>2+</sup> + 2Cl<sup>–</sup>