PRODUCTION OPERATIONS & MANUFACTURING PROCESSES OF LABSA
Sulphonation – The Process
Most electrophilic substitution reactions are irreversible but sulfonation is an exception. Treatment of benzene with "oleum" (a solution of SO3 in concentrated sulfuric acid) will give the sulfonic acid, the electrophilic species being sulfur trioxide which is Lewis acidic. Fig – 1 Sulphonation : Benzene equation
The sulfonic acid can be converted back by treatment with hot aqueous acid. The reason for this reversibility is the fact that the Wheland intermediate is overall neutral and therefore more stable than other, positively charged intermediates. Hence, under forcing reaction conditions, the energy difference in progressing in either the forward or backward sense from the Wheland intermediate is proportionately smaller compared to the barrier to activation and hence discrimination is lost. Fig – 2 Progress of Reaction against Energy
This makes the SO3H a useful directing group if it is desired to carry our selective ortho– substitution of a monosubstituted benzene possessing an ortho/para– activating group. Under normal circumstances, para– substitution would dominate, despite the statistical favouring of the ortho– positions due to steric hindrance of the original substituent. Initial sulfonation para– gives a Disubstituted benzene in which both substituents direct to the same position. Subsequent directed electrophilic substitution and removal of the sulfonic acid group gives theortho– disubstituted product. [4]
Process Involved In the Manufacture of LABSA
Fig 3 – Flowchart of the process behind the production of LABSA.
The manufacturing of LABSA at Sasol gulf is a continuous process. An interval of 1 day after a period of 20-21 days for the purpose of shut-down and start-up is essential for maintenance purposes. The key reactions involved in the formation of LABSA are as follows:
• Air Drying
• Sulphur Melting - Ignition of sulphur (S) to sulphur dioxide (SO2)
• SO3 Production - Oxidation of sulphur dioxide to
Most electrophilic substitution reactions are irreversible but sulfonation is an exception. Treatment of benzene with "oleum" (a solution of SO3 in concentrated sulfuric acid) will give the sulfonic acid, the electrophilic species being sulfur trioxide which is Lewis acidic. Fig – 1 Sulphonation : Benzene equation
The sulfonic acid can be converted back by treatment with hot aqueous acid. The reason for this reversibility is the fact that the Wheland intermediate is overall neutral and therefore more stable than other, positively charged intermediates. Hence, under forcing reaction conditions, the energy difference in progressing in either the forward or backward sense from the Wheland intermediate is proportionately smaller compared to the barrier to activation and hence discrimination is lost. Fig – 2 Progress of Reaction against Energy
This makes the SO3H a useful directing group if it is desired to carry our selective ortho– substitution of a monosubstituted benzene possessing an ortho/para– activating group. Under normal circumstances, para– substitution would dominate, despite the statistical favouring of the ortho– positions due to steric hindrance of the original substituent. Initial sulfonation para– gives a Disubstituted benzene in which both substituents direct to the same position. Subsequent directed electrophilic substitution and removal of the sulfonic acid group gives theortho– disubstituted product. [4]
Process Involved In the Manufacture of LABSA
Fig 3 – Flowchart of the process behind the production of LABSA.
The manufacturing of LABSA at Sasol gulf is a continuous process. An interval of 1 day after a period of 20-21 days for the purpose of shut-down and start-up is essential for maintenance purposes. The key reactions involved in the formation of LABSA are as follows:
• Air Drying
• Sulphur Melting - Ignition of sulphur (S) to sulphur dioxide (SO2)
• SO3 Production - Oxidation of sulphur dioxide to
References: [1] www.wikipedia.com [2] www.sasol.com [3] www.uaeincorp.com [4] www.users.ox.ac.uk [5] Sasol Gulf – Operation Manual [6] Sulphonation Technology in the Detergent Industry by W. Herman de Groot [7] www.lasinfo.org [8] www.mixmedicine.com [9] www.chemicalland21.com [10] Test Method Control Room File