Sulphomethylation of humic acids, lignites and coals

LETTERS

TO THE EDITOR

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Sulphomethylation of humic acids, lignites and coals* s. E.

MOSCHOPEDlS

The water-solubilization of humic acids, lignites, and coals by interaction with diazotized sulphanilic acid was reported in previous communications to this journal13 2. Previously, lignites and coals have been directly sulphonateds, 8, i.e., treated with concentrated sulphuric acid or sulphur trioxide to introduce sulphonic acid groups, but these sulphonated products were not water-soluble. Attempts in this laboratory to sulphonate humic acids with concentrated sulphuric acid also resulted in water-insoluble products. Investigations concerning the water-solubilization of humic acids have continued, and the solubilization of humic acids in lignites and oxidized coals has been accomplished by the indirect introduction of the sulphonic group via the sulphomethylation reaction93 12. Of late, the water-soluble derivatives of these carbonaceous materials have been employed as drilling mud thinners, fertilizers, and soil conditioners (ammonium salts). As examples, treatment of humic acids obtained from weathered subbituminous coal from the upper seam at Sheerness, Alberta, and lignite from the Bienfait region of Saskatchewan, with an excess of sodium hydroxymethanesulphonate afforded water-soluble products. The occurrence of sulphomethylation was confirmed by the following: (a) an increase in sulphur contents (b) the appearance of a new absorption band at about 1035cm-1 in the infra-red spectra of these products, attributable to the presence of sulphonic groups in the molecule13 (Figure 2) (c) the water-solubility materialslo 121l4

of the products, a characteristic of these types of

(d) by experiments using 1% formaldehyde? These sulphomethylated humic acid and lignite products remain in solution on acidification with 5% aqueous hydrochloric acid to a pH of 2.5 to 3.0, after allowing to stand for long periods of time or centrifuging, while the original humic acids are precipitated from an alkaline solution when acidified to a pH of 6.5. The results also show that in order to produce water-soluble sulphomethylated products which will not precipitate upon acidification with 5% aqueous hydrochloric acid at refluxing temperature, approximately 1h reaction time is required, and at 150-200°C at the pressure of the reactants, water-soluble products are obtained after IO-15min. Prolonged treatment (refluxing for 24h or heating in an autoclave at 150°C for 3 h) resulted in *Contribution Number 491 from the Research Council of Alberta, Edmonton, Canada tResults of these studies will be published elsewhere

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Figure I Infra-red spectra of hutnic acids (c) sodium humate (a) parent compound (b) sulphomethylated compound (d) sulphomethylated sodium salt (e) sodium lignosulphonate

humic acid products with similar sulphur contents to the values obtained by simply refluxing for 1h. The reaction also proceeds at room temperature but requires longer periods, of the order of 12h. The yields of water-soluble products from the sulphomethylation reaction are strongly affected by coal rank and degree of coal oxidation. For example, after three successive treatments, a lignite (C = 71.5x, d.a.f.) afforded 50% w/w of water-soluble materials while sub-bituminous coal (C = 74x, d.a.f., from Drumheller, Alberta) remained unreacted after several such treatments. However, the yields of water-soluble products obtainable by this reaction can be significantly increased by preliminary oxidation of the lignite and coal. The sulphomethylation reaction can also be applied to other carbonaceous materials, e.g., asphaltenesl5, which already have phenolic hydroxyl groups in their molecule or can have them introduced by oxidation. Other preliminary investigations by the author show that carbon blacks can be rendered water-dispersible by the same treatment. (Received 23 February 1970) (Revised 6 April 1970)

Research Council of Alberta, Edmonton 7, Alberta, Canada

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REFERENCES I Moschopedis, S. E. Fuel, Lond. 1962, 41, 425 2 Moschopedis, S. E., Wood, J. C., Fryer, J. F. and Elofson, R. M. Fuel, Lond. 1964, 43, 289 3 Bafna, S. L., Pai, M. V. and Shah, H. A. J. Sci. Ind. Research (India) 1952, IlB, 134 4 Kreulen, D. J. W. BrenstoflChem. 1927, 8, 149 5 Broderick, S. J. and Bogard, D. Ind. Eng. Chem. 1941, 33, 1291 6 Mazumdar, B. K., Granguly, S., De, N. G. and Lahiri, A. Fuel, Lond. 1962, 41, 305 7 Thomas, M. and Kinney, C. R. K. Ind. Eng. Chew. 1963,55, 30 8 Partington, M. A. and Sidebotton, R. Fuel, Lond. 1959, 39, 597 9 Suter, C. M., Bair, R. K. and Bordwell, F. G. J. Org. Chem. 1945, 10, 470 10 Kin, Z. Prezzlad Parierniezy 1960, 5, 131 : Fuel Abstr. Current Tit/es 1961, 2, 16 11 Tischenko, D. and Kislitsyn, A. J. Appl. Chem. USSR (Eng. Trans.) 1961, 34, 1535 12 Moschopedis, S. E. Canadian patent 7’2 720, 1965, and United States patent 3 352 902, 1967

Bellamy, L. J., ‘The Infra-red Spectra of Complex Molecules, p 300, John Wiley, New York, 1958 I4 Moschopedis, S. E., Czakert, E. and Creighton, S. M., Canadian and United States patent applications 15 Moschopedis, S. E. and Speight, J. G. Fue/, Lond., in press 13

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