Alpha-olefin sulphonic acid

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. 

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). 

Neutralisation of the sulphonation product from alpha-olefins is more complex than neutralisation of the corresponding products of alkylbenzenes. This is because the SOj-alpha-olefin acid product contains about 50% free sulphonic acid, the rest being C(l,3)- and D(l,4) sultones, assuming that with acid ageing the B(l,2) sultones have disappeared. In the case of alpha-olefins an excess of caustic (1.5-2.0% excess) must be added to neutralise both the sulphonic acid initially present and that formed on subsequent hydrolysis of the C(l,3)- and D(l,4) sultones. The sultones (ring structured esters) cannot be converted into their proper salts by a simple neutralisation but need a hydrolysis step. 

Alpha-Olefins and Fatty Acid Methyl Esters , paper presented at Practical Sulphonation Seminar, April 1989 - The Hague, The Netherlands. Center for Professional Advancement, P.O. Box H, East Brunswick, New Jersey 08816, USA. 

The exhausted gas and organic acid mixture which leave the bottom of the reactor flow into two high-efficiency liquid-gas separators in series. The exhaust gas then flows to the exhaust gas treatment plant. The organic acid is transferred to the next stage, ageing and stabilisation of alkylbenzene sulphonic acid, or straight to the neutralisation unit for alcohols, alcohol ethoxylates and alpha-olefin feedstocks. 

In the case of alpha-olefins, alcohols and alcohol ethoxylates high levels of decomposition products can also be present, notably high levels of 1,4-dioxane (0.5 - 1.0%) when alcohol ethers are sulphated and the residue remains in its acid form for long periods (hours). Residues from a plant running exclusively on alkylbenzene can be blended with the main production stream at a low level to meet sulphonic acid colour standards. 

The book covers sulphonation of alkylbenzenes, primary alcohols, alcohol ethers, alpha-olefins and fatty acid methyl esters, with a strong emphasis on the sulphur-based SOs/air sulphonation technology. 

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