Unwanted alkylation during direct methylation of fatty (di)acids using tetramethyl ammonium hydroxide reagent in a Curie-point pyrolysis unit

The formation of alpha -methylated and alpha,alpha -dimethylated (di)acids during on-line (trans)methylation with tetramethylammonium. hydroxide (TMAH ) in a Curie-point pyrolysis unit is studied. The reaction of TMAH with non anedioic, hexadecanedioic and octadecanoic acids is investigated to determi ne the contribution of the solvent system and the amount of TMA-H added to this phenomenon. The results obtained clearly show a different behaviour of diacids in methanolic solutions compared to aqueous systems. At least thre e different reaction products were identified for the acids when using a me thanolic. solution of TMAH, Different relative amounts of by-products were formed when varying the amount of TMAH reagent relative to the normal methy lated reaction product. A mechanism is postulated for their formation and a hypothesis is drawn up to explain the observed differences in reactivity f or both solvents. (C) 2001 Elsevier Science B.V. All rights reserved.