Avaliação de carboidratos presentes em resíduos agroindustriais como potenciais inibidores verdes de carbonato de cálcio para indústria de petróleo e gás

Abstract

Inorganic scaling is a common issue in the oil and gas industry, with calcium carbonate being one of the primary culprits. These deposits can lead to various challenges for the industry. Several methods are employed to address this problem, with the most low-cost alternative being prevention using of scale inhibitors. Commercially, these inhibitors can be categorized into three major groups: polymers, phosphate esters, and phosphonates. However, derivatives of the latter two can be considered pollutants. Therefore, it is essential to explore compounds that can replace them, considering the principles of green chemistry and environmental impact. Thus, this study assessed the potential of model carbohydrate molecules (glucose, maltose, maltodextrin, and soluble starch) and aqueous extracts of starch-rich food residues (potatoes, sweet potatoes, cassava, and potato peels) as biodegradable products with the potential to inhibit calcium carbonate scaling. Dynamic testing with the model carbohydrate molecules revealed that the polymer chain size influenced the scaling time in two different brines with varying compositions, demonstrating the inhibitory potential of these molecules. However, only soluble starch was effective in the brine with lower ion concentrations. Based on these results, starchrich foods were selected to evaluate their potential in calcium carbonate inhibition through static, dynamic, and compatibility tests. Extracts of sweet potato and potato peel residues performed better compared to others in the dynamic test. According to the adopted approval protocol, extract of sweet potato residue was the only one that efficiently inhibited deposit formation under milder conditions and was compatible at a concentration of 500 mg L-1, showing promising potential as a green inhibitor. Meanwhile, extracts of potato, potato peel, and cassava residues were found to be incompatible at the same concentration. It is believed that the superior performance of sweet potato is due to the presence of phenolic compounds, especially subclasses of chlorogenic acid, in its composition. Batch precipitation testing showed that sweet potato delayed the CaCO3 induction time by 51 minutes in the milder brine and reduced the amount of precipitated solids. SEM, XRD, and FTIR revealed the stabilization of the vaterite and calcite polymorphs, with structural deformation, suggesting adsorption of the residue components on the crystalline surface and promoting inhibition.