Sulphonation loop

The undiluted mixture from the sulphonation stage typically contains 60 - 70% alkylbenzene sulphonic acid, 30-40% sulphuric acid, about 1% water and up to 1% free oil. For the purpose of determining what separation will take place, the small amount of free oil may be neglected. Without free oil, a product post-sulphonation loop could have, for example, the following composition ... 

A related, but alternative, approach uses layer-by-layer adsorption driven by hydrogen-bonding interactions [51]. This has been accomplished with polyvinylpyrrohdone, polyvinyl alcohol, polyacrylamide, and polyethylene oxide. In the case of polyaniline, comparisons with films assembled via the electrostatic mechanism, using sulphonated polystyrene, indicate that the nonionic polymers adsorb onto polyanihne with a greater density of loops and tails and form highly interpenetrated bilayers with high polyaniline content. 

Much of the colour produced during sulphonation is contained in the spent acid. The upper layer in the separator, which contains around 90% alkylbenzene sulphonic acid (the remainder being primarily dissolved sulphuric acid) is also removed from the separator and neutralised with sodium hydroxide solution or with sodium carbonate solution to yield the active paste. When sodium hydroxide is used a considerable amount of heat must be removed. This is done in the third loop reactor of this process, the neutralisation heat exchanger (also known as the neutraliser). If sodium carbonate solution is used, the neutralisation is much less exothermic and no heat exchanger is needed at this stage. 

From heat balance calculations it is possible to determine the heat load (i.e. heat transferred in the heat exchangers of the sulphonation, dilution and neutralisation loops) at each stage of the total process, and hence the amount of cooling water needed. The results of these calculations are summarised in table 42. The recirculation ratio (volume of recirculating material divided by the volume of throughput) is 15 1 to give small temperature differences in the sulphonation, dilution and neutralisation loop process-side streams. 

Chemithon are known to have "tandem" sulphonated mixtures of alkylbenzene/primary alcohols. The process is similar to the normal operation. In the first loop 20% oleum and alkylbenzene are dosed, in the second loop (the diluter) the alcohol with extra oleum is introduced, followed by immediate neutralisation (see figure 54). A product mix of ABS/alcohol sulphate/sodium sulphate is finally obtained. 

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