FAME sulphonation

FAME may become in the future a possible organic feedstock to be sulphonated to Fatty Acid Methyl Ester Sulphonate (FAMES). This feedstock is naturally renewable as it is produced from oils/fats or fatty acids. There are several possible process routes for the manufacture of FAME. Transesterification of fat triglycerides is the predominant method for manufacture of mixed fatty acid methyl esters, and direct esterification of fatty acids (FA) is practised if very selective cuts of product, in general as an intermediate detergent range alcohol, are desired. Methyl cocoate is a mobile, oily liquid above 25"C with a yellow tint and a characteristic fatty acid pungent odour. FAME sulphonation to FAMES is technically possible but hardly applied up to now (1990). 

Fatty acid methyl ester (FAME) sulphonation... 

The chemistry of FAME sulphonation is complicated and not yet fully elucidated but may be summarised as depicted in the following reaction scheme. 

Me-ester sulphonation has to be carried out at relatively high temperatures as the initial reactions and the decomposition of intermediate products are relatively slow compared with sulphonation reaction rates for alkyl benzenes, primary alcohols, ethoxylated alcohols and alpha-olefins. The required ageing time for conversion of the intermediates to FAME Sulphonation Acid is long (about 45 minutes at 85 C). It is not possible to sulphonate Me-esters without an excess of SO3. 

Factors which affect the quality of the FAME sulphonates are summarised in table 35. Tablg 35 Factors, which affect EiydE su lphonatQ..quality... 

Thus, if a mole ratio of about 1.2 1 of SO3 to ester is used, the initial reaction gives about 50% conversion of starting material, the products being intermediates I and II. On ageing, these intermediates release SO3, which reacts with the remaining ester, and the final product is a mixture of FAMES acid (FAMES = Fatty Acid Methyl Ester Sulphonate) and SFAS acid (SFAS = Sulphonated Fatty Acid Sodium salt, RCH-COONa). 

Sulphonation of the common feedstocks proceeds with a highly exothermic instantaneous initial reaction, followed by a fast but not instant step, also highly exothermic. The second rieaction does not always proceed to completion (e.g. LAB, FAME) in the lower zone of a short residence time falling-film reactor (FFR). For these organic feedstocks ageing under well-defined conditions of temperature and reaction time is required. 

The process consists of an exothermic reaction between a neutralising agent and either sulphonic acid (ex LAB, alpha-olefins, FAME) or acid sulphate (ex primary alcohols, ethoxylated alcohols). Neutralisation can be carried out after prolonged storage, if the acid stability permits (LABSA, FAME-SA). 

In practice the sulphonation conditions required for FAMES are much more severe than for the other materials, with the result that FAMES poses the worst colour problems. Branched alkylbenzenes may require bleaching notably from long residence-time reactor systems (cascade of continuous stirred tank reactors). 

FAME-SA Fatty Acid Methyl Ester - Sulphonic... 

FAMES Fatty Acid Methyl Ester Sulphonate... 

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