Síntese e avaliação de derivados de Ácido Gálico como candidatos a inibidores de incrustação inorgânica

Abstract

Inorganic scale in the oil industry is a chemical problem that has gained importance, especially in Brazil due to adverse pre-salt conditions. Scale affects pipes, ducts, valves and other components present in the oil extraction process, resulting in flow reduction and limited heat exchanges. This process implies high costs to produce oil, which can lead to the inoperability of the production line. The most efficient solution is the use of chemical inhibitors - organic molecules that prevent the precipitation of inorganic salts or just prevent their adhesion on the pipe walls. Water-soluble organic substances with heteroatoms (O, N, P) in their structure are usually reported in the literature as scale inhibitors. This dissertation presents the synthesis, characterization and evaluation of gallic acid derivatives as scale inhibitors candidates. The derivatives were synthesized from transformations in the carboxylic acid group. Due to the acidic and electron donor character of the three phenolic hydroxyls present in the structure of gallic acid, protection groups were used as a synthetic strategy, resulting in seven intermediates products and five target products. All products were characterized by Hydrogen, Carbon and Phosphorus Nuclear Magnetic Resonance and High Resolution Mass Spectrometry. Yields range from 45 to 95%. The efficiency of the candidates was evaluated in the inhibition of calcium carbonate scale using hydrodynamic method and synthetic water, whose composition corresponds to a produced water of an oil field in operation. Two products, propane-1,3-diyl bis(3,4,5-trihydroxybenzoate) (P3) and N,N'- (propane-1,3-diyl)bis(3,4,5-trihydroxybenzamide) (P4), were not soluble in the tested water. The three products, 3-hydroxypropyl 3,4,5-trihydroxybenzoate (P1), 3,4,5-trihydroxy-N-(3- hydroxypropyl)benzamide (P2) and (((3,4,5-trihydroxybenzoyl)oxy)methyl)phosphonic acid (P5), did not inhibit scale in the applied condition.