The S. W. Polarographic Determination of Disulfide, Mercaptan and Free Sulfur in Petroleum Naphtha

Abstract

The application of square-wave polarography to the determination of small amounts of disulfide, mercaptan and free sulfur in a mixed solution of methanol, glacial acetic acid, and sodium acetate was studied. Disulfide, mercaptan, and free sulfur in concentrations below 10 ppm were easily determined in these mixed solvents. The derivative wave heights were proportional to the concentrations predicted by the theory of s. w. polarography. The effects of changes in solvent and in supporting electrolyte concentration, dissolved oxygen, and temperature were discussed. It was determined that concentrations of 2 vol% glacial acetic acid and 1.4 m sodium acetate were necessary to obtain a constant peak height. The temperature coefficients of disulfide, mercaptan and free sulfur were about 4.5 (first wave), 0.7 and 4.5% per degree respectively in the neighborhood of 25°C. The effect of the dissolved oxygen was removed by passing nitrogen through for 5 min.

Electrochemical determination of elemental sulfur in Brazilian naphtha: method and validation

“…A copper column was used for each sample to eliminate the interference of disulfides in voltammetric analyses [21]. The optimized parameters were: column diameter (0.5 cm), column height (18.0 cm), mass of copper (2.0 g), naphtha sample volume (2.0 mL) and flow of naphtha sample in the column (atmospheric pressure).…”

“…According to Table 1, Kashiki et al reported a methodology for quantifying elemental sulfur in naphtha samples using the same technique and working electrode employed in the proposed method [21]. The detection limit was found to be 0.5 mg L -1 .…”

“…Voltammetry in the petroleum industry was initially used in the analysis of sulfur and its compounds, naphthalene and its derivatives, hydroperoxides, antioxidants and trace metals [17]. Table 1 shows some voltammetric applications for elemental sulfur determination in petroleum and its derivatives [18][19][20][21][22][23][24][25][26][27][28]. Elemental sulfur has been studied for many decades [17], and few changes have been observed from one methodology to another.…”

“…Aliquots of real naphtha samples (300 lL) were analyzed in triplicate in the presence of the supporting electrolyte after purging with nitrogen for an additional 300 s. Some specific parameters used in all analyses were a 50 lm capillary size, 3.8 s drop-growing time, 500 rpm stirring rate, 15 mV potential step, 50 mV pulse amplitude, 1 s pulse time, 1 s potential step time, 0.5 bar pressure, 300 mV s -1 scan rate and potential range from -0.100 to -0.800 V. All parameters were optimized in this work and differ significantly from previously reported determinations [21]. A calibration curve was constructed before each set of analyses.…”

Boron Doped Diamond Electrode as a Novel Sensor for Elemental Sulfur

“…[4][5][6] Fernandes et al 7 apresentaram a validação de uma metodologia usando a voltametria de onda quadrada (VOQ) para determinação S 0 em nafta com limites de detecção e quantificação de 0,003 mg L -1 e 0,009 mg L -1 , respectivamente, usando como eletrodo de trabalho o eletrodo de gota pendente de mercúrio (HMDE, do inglês: Hanging Mercury Drop Electrode) e como eletrólito suporte, uma solução tampão de ácido acético glacial 2 % (v/v) e acetato de sódio 1,4 mol L -1 em metanol. 8 Um trabalho anterior, utilizando o mesmo eletrólito de suporte e VOQ com eletrodo gotejante de mercúrio (DME, do inglês: Dropping Mercury Electrode) apresentou um limite de detecção de 0,5 mg L -1 . 9 Embora exista uma intolerância por parte da comunidade científica quanto ao uso do eletrodo de mercúrio, uma alternativa é o uso de eletrodos de filme de mercúrio (MFE, do inglês: Mercury Film Electrode).…”