Furfural degradation through heat-activated persulfate: Impacts of simulated brine and elevated pressures

Abstract

Persulfate is used as an oxidizing breaker in hydraulic fracturing fluids to breakdown gelling agents and clean out wellbores. Persulfate may be activated using conditions like those encountered in the wellbore, producing strong oxidizing radicals that degrade organic compounds. Thus, this study examined persulfate activated transformation of organic additives in a simulated hydraulic fracturing brine by investigating the transformation of furfural. Pseudo-first-order reactions kinetics of furfural degradation in conditions that mimic a fracture, including high temperature, acidified pH, ferric sulfate, and a laboratory simulated hydraulic fracturing brine, were established. The activation energies for furfural removal in acidic (pH 2.54) hydraulic fracturing brine was 105.6 kJ mol−1 without ferric sulfate and 105.1 kJ mol−1 with 23.3 mg L−1 ferric sulfate. A high-pressure reactor was used to simulate the effects of pressure on persulfate activation. Increasing pressure was shown to increase activation of persulfate at 55 °C. Applying 3000 psi to the reactor nearly halved the apparent furfural activation energy compared to experiments at atmospheric pressure. Finally, reaction byproducts were presented with the findings showing that halogenated organic byproducts form in hydraulic fracturing brine during persulfate use.