Sulphonation Process
(A) Common Features of Sulphonation:
1. Different sulphonating agents which are used for sulphonation, include SO3, chlorosulphonic acid (ClSO3H), oleum, H2SO4.
2. For sulphonation, some special type of equipments (reactors) are used which are generally falling film type reactors.
3.generally, sulphonation reactions are highly exothermic, where heat of reaction is in the range of 40 kcal/mole (-ΔHr ≈ 40 kcal/mol).
4.most of the sulphonates found their application in detergents, emulsifying agents, solublizing agents, wetting agents. Some sulphonating agents are used in elastomers, water soluble thickening agents and synthetic gums etc.
(B) Preliminary Process System (PPS) for manufacture of Linear Alkyl Benzene Sulphonate (LABS) from Linear Alkyl Benzene (LAB) and SO3 as sulphonating agent:
To develop this PPS, use following guidelines / hints/ description.
i)LAB from its day tank is passed to falling film reactor (FFR) and introduced in reactor from the top.
ii)SO3 liquid from its storage tank is passed to SO3 evaporator, which gives SO3 vapors.
iii)Hot dry air is also passed to evaporator and mixed with SO3 vapors and then it is passed to FFR.
iv)Reaction takes place in FFR and product, LABS is formed which is removed from the bottom of reactor.
(C) Reason for mixing hot dry air with SO3 vapors:
During sulphonation, where SO3 is used as sulphonating agent, hot dry air is also passed through evaporator and mixed with SO3 vapors. This is done for maintaining the concentration of SO3in between 3 to 5%. Because if the concentration of SO3 will be increased, then, over sulphonation may take place which will disturb the quality of required sulphonate product; also it may give rise to some undesired products. Generally, these sulphonates are being used in detergents; so oversulphonated product, if used in detergents, then it may disturb the colour of the detergents. Hence, SO3 vapors are dispersed with hot dry air and then passed to FFR.
(D) PID for SO3 Evaporator:
While drawing PID of SO3 evaporator, the control aspects to be shown include:
(i)One temperature controller should be provided on steam inlet line. This is because ------
Boiling point of SO3 liquid is 44.8oC. Hence, we have to maintain the temperature inside evaporator equal to this value. For this we need to control the temperature. For doing this, one temperature controller is mounted on steam line. Also one non return valve to be mounted on steam line.
SO3 polymerizes easily. It undergoes chain type polymerization due to which its structure gets converted and it converts into solid state at room temperature. But solid state SO3 can not be used as sulphonating agent. Hence we have to use only liquid SO3 here for sulphonation
(ii)Also one flow controller has to be mounted on inlet stream of SO3 liquid, so that its concentration inside the reactor can be maintained at around 3 to 5% (as we have seen above).
(E) Sketches for Falling Film reactor (FFR) used for sulphonation:
Refer the diagrams shown at the time of tutorial.
** While drawing the PPS, show all equipments / tanks by rectangular or square box as necessary.
** Below PPS, make a legend showing list of equipments in PPS, for e.g. DT1 – day tank for H2SO4, C – Reactor, etc.
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