Electrolytic Preparation And Properties Of Long-chain Quaternary Ammonium Hydroxides

The quaternary ammonium hydroxides (QAHs) are organic hydroxides which have alkalinity as strong as sodium hydroxide and potassium hydroxide, and widely used in various fields, such as, organic silicon synthesis catalyst, template agent of synthesis for zeolite, phase transfer catalysts for diverse chemical transformations, organic acid titrant, circuit board etchant and cleaning agent in the manufacture of microelectronic chips, etc. However, the quaternary ammonium salts (QAS) are commonly prepared by an alkyl agent such as alkyl halide or dimethyl sulfate, which inevitably contaminate the environment and bring toxicity to the target products. Moreover, because of the limitation of alkyl agent, the counterions of QAS are confined to Cl-, Br-and CH3SO4-, if those QAHs are used as the electrolysis raw materials, halogen gas and strongly acidic substances will be produced in the electrolysis process which has environmental pollution and corrosion electrolysis equipment problems. In order to break this bottleneck, we selected dimethyl carbonate as the alkyl agent and prepared the compounds, quaternary ammonium salts methyl carbonates (QASMC) in this dissertation. In addition, the synthesis of long-chain QAHs from QASMC as the raw materials had been studied and the physical-chemical properties of the prepared QAHs were also investigated.Five compounds (QASMC) were synthesized from the dimethyl carbonate (DMC) as a quaternization agent and different long-chain alkyl tertiary amines as raw materials. The chemical structures of the purified products were characterized by IR and^-NMR spectra. The QASMC were quantitatively determined by two-phase chemical titration and the results showed that the conversions of tertiary amines were higher than99%.The long-chain QAHs were prepared from QASMC by hydrolysis and electrolysis. The effects of reaction temperature, current density, concentration of raw materials and reaction time on current efficiency, energy consumption and reaction rate, and the optimized reaction condition was determined. IR and1H-NMR spectra results showed that the QAHs with carboxylate counterions were successfully synthesized.The critical solution temperatures (Krafft points), pH value, critical micelle concentrations (CMC), thermal stability, biodegradability and complexed system with sodium dodecyl benzene sulfonate (SDBS) of the prepared long-chain QAHs were determined. The results revealed that the long-chain QAHs had lower Krafft points. In addition, the surface activities of these surfactants were also better than that of conventional QAS with chloride anions. The pH value of series long-chain QAHs are greater than12. So, long-chain QAHs have strong alkalinity. Prepared dodecyltrimethylammonium hydroxide (DTAH) and tetradecyltrimethylammonium hydroxide (TTAH) have lower decomposition temperature which is conducive to the application to the electronic etching IDM, and both good biodegradable quaternary ammonium bases, and their biodegradability are good.The surface properties, alkaline and stability of the complexed system of DTAH and SDBS were studied. Result showed that the alkalinity of DTAH and SDBS complexed system which is small affected by SDBS is mainly affected by the content of active substance in DTAH. Complexed system is better than a single component in the capacity and efficiency of reducing the surface tension. Complexed system can still exhibit a strong interaction, and has good stability, the pH value did not change significantly when the molar ratio of DTAH and SDBS was9:1.