Chemically Modified Soluble Starches as Green Scale Inhibitors in Petroleum Production.

The development of green scale inhibitors is crucial for the petroleum industry. This work investigates chemically modified starches as green alternatives for scale control. Soluble starch was modified through two routes: carboxymethylation with chloroacetic acid and esterification with maleic anhydride. The modifications were confirmed by infrared spectroscopy, and degrees of substitution were quantified by titration. Tube-blocking tests demonstrated that both modified starches markedly improved calcium carbonate inhibition, reducing the minimum inhibitory concentration from 500 mg L-1 for unmodified starch to 150 mg L-1 for carboxymethyl starch and 125 mg L-1 for starch maleate. The superior performance of starch maleate can be attributed to its higher degree of substitution and presumable steric effects. Scanning electron microscopy and X-ray diffraction analysis revealed that carboxymethyl starch promoted distortion of both the shape and size of calcium carbonate solids, while starch maleate more effectively reduced particle size. These morphological modifications were more pronounced than those induced by unmodified starch, contributing to the enhanced inhibitory performance. In addition to superior performance, the maleic anhydride esterification route offers a simpler and more sustainable modification process, as it proceeds under solvent-free conditions and eliminates neutralization and purification steps. Overall, these results demonstrate that chemically modified starches, particularly starch maleate, are promising candidates for effective and sustainable scale inhibition in petroleum facilities.