Síntese de pontos quânticos de carbono a partir de biomassas naturais para implementação como fluidos traçadores verdes na indústria petrolífera

Abstract

The use of green precursors for the production of biomaterials is a way of using waste, adding value to materials that would otherwise be discarded. This perspective is supported by the toxic nature of the current fluids used for this purpose. Although nanotechnology is not yet widely used in this industry profile, it has been attracting wide interest for research development, especially CQDs, due to properties such as good stability, optical properties, biocompatibility, ecologically viable and low cost. This work aimed to synthesize environmentally friendly Carbon Quantum Dots (CQDs) using biowaste, for application as tracer fluids in hydrocarbon reservoirs. Plantain (Musa spp), pear orange (Citrus sinensis) and kapok pod (Ceiba pentandra) peels were the raw materials in the hydrothermal carbonization syntheses of CQDs, due to their low cost, efficiency and environmental friendliness. The optical properties, chemical structure and functional groups were determined by characterization such as Fourier Transform Infrared Spectroscopy (FTIR), Ultraviolet-Visible Spectrophotometry (UV-vis) and Photoluminescence Spectroscopy (PL) and Quantum Yield (RQ). Optical Tensiometer (Contact Angle), Compatibility Test and Porous Media Test were used to analyze the material's performance. The results showed that the common functional groups present in the samples are O-H, C-N and C-O, favoring solubility in water. Furthermore, CQDs showed excellent optical properties such as high emission intensity, good stability and long lifetime. The quantum yield was high, greater than 10%, a value above the average for green materials, mainly because they do not have additional doping, so they have immense potential for tracking. The contact angle of the fluid-rock interaction, in oil-soaked and pure carbonate rock (without oil), showed that in the rock with oil they were greater than 90º for all samples, and decreased over the analysis time (30 min.). However, for pure rock it was noted that at the beginning of the analysis, in all CQDs, they were lower than 90º. In compatibility tests using brine and petroleum solutions, the CQDs did not interact with the petroleum and there is no additional phase formation and the increase in temperature does not significantly interfere with the emission. The absorption rate of nanoparticles by the different porous media was low, since the absorbance recorded in UV-vis was high, close to 0.1 and even at low concentration it was still possible to record fluorescence. Considering the above, the studied biomasses have a high potential for application as tracer fluids in oil reservoirs.