Abstract
A new procedure based on closed vessel Microwave-Induced Combustion (MIC) technique is proposed for the decomposition of petroleum coke and further determination of sulfur by Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES). The procedure is based on sample ignition by microwave radiation using closed quartz vessels pressurized with oxygen and use of NH4NO3 as an ignition aid. The nature and concentration of absorbing/refluxing solution were studied, as well as the operational parameters related to MIC technique. Results were compared with those obtained by conventional wet digestion in closed vessels, certified reference materials (agreement was better than 98%), and also using ion chromatography for S determination.
The authors are grateful to CNPq, CAPES, and FAPERGS for supporting this study and also to CENPES/PETROBRAS S.A. for financial support and for supplying the petroleum coke samples.
Notes
∗initial O2 pressure = 20 bar, 6 mL H2O as absorbing solution, n ≥ 10.
a 150 mg of sample, initial O2 pressure = 20 bar, 6 mL of absorbing solution.
b certified value for sulfur in CRM NIST 2718 (green petroleum coke) = 47030±79 µg g−1.
∗150 mg of sample mass, initial O2 pressure = 20 bar, 6 mL 0.05 mol L−1 (NH4)2CO3 as absorbing solution, 50 µL of 6 mol L−1 NH4NO3.