Influence of acid structure and acidity strength on thermochemical, in-situ nitrogen generation

Sodium nitrite and ammonium chloride are commonly used thermochemicals in the oil field, mostly for in-situ nitrogen (N₂) generation-a developing technique for enhancing oil recovery and eliminating blockages. Additionally, the kinetics of this reaction, particularly when activated with acids, has been extensively studied. In this work, the effects of five acids-acetic, citric, monochloroacetic, dichloroacetic, and trichloroacetic acids-on thermochemicals were studied, and the impact of several parameters on sodium nitrite (NaNO₂) and ammonium chloride (NH₄Cl) was examined, such as concentration, temperature, and pH. Experimental results show that acetic acid produced the maximum volume of nitrogen, generating up to 20% more gas than other acids at 82 °C and 3.39 mol/L concentration. Furthermore, the concentration of reactants strongly affected the gas production rate, showing a near-linear relationship. The reaction's efficiency improved at elevated temperatures, with optimal gas generation between 70 and 90 °C. Additionally, pH control within the studied range minimized by-products NO and NO₂. Due to its optimal molecular structure and catalytic properties, Acetic acid enhances the efficiency of N₂ generation, making it promising for oilfield operations and reservoir enhancement. The study also highlights that the acid's strength and structure play important roles in the reaction, with the structure being a key factor as a catalyst.