Plants for continuous sulfation and sulfonation

Overview of the manufacturing process

Organic sulfates and sulfonates are industrially manufactured by reacting organic compounds (alkybenzenes, fatty alcohols, ethoxilated fatty alcohols, methyl esters, alfa-olefines, etc.) with diluted gaseous SO₃. The reaction is called sulfation or sulfonation depending on the functional group created in the reaction product: sulfates R–O–SO₃H or sulfonates R–SO₃H.
The sulfonic acids obtained by processing some alkylates (most notably: LABSA) can be marketed as such, as they can find direct industrial application. Otherwise, the organic acids coming either from sulfation or sulfonation reaction are neutralized to form the relevant organic salts (most notably: SLES, SLS, LABS and AOS). A finishing phase is required in order to remove possible impurities produced by secondary reactions (e.g.: dioxane and sultones), as well as to stabilize, homogenize and dilute the products.
The products of IIT sulphonation plants find prominent application as cleaning and foaming agents in detergents, as well as wetting and emulsifying agents in dyes, pigments, medicines, pesticides, etc.

Gaseous SO₃ production

Gaseous SO₃ can be produced either by sulfur burning or by liquid SO₃ evaporation, respectively best suited for industrial and small-sized plants.

IIT highly reliable sulfur furnaces guarantee continuous SO₃ production for long periods of time. They can be coupled either with a direct or indirect heat recovery system.

The gaseous SO₃ needed for the sulfonation reaction must be produced with very dry air. The special design of IIT desiccant driers guarantees that the dew point of dried air permanently remains lower than −70°C. This makes the installation of an oleum demister unnecessary, eliminating all the problems introduced by this device, such as pressure drop, SO₃ surge, maintenance difficulties and delayed startup.
IIT air dryers are desiccant-type: they rely on two towers filled with desiccant material, alternating between air drying phase and desiccant regenerating phase. IIT air dryers are equipped with an autonomous regeneration system that allows to regenerate the desiccant material also before the plant startup, when external hot air isn't available.

Sulfation and sulfonation

Perfected in years of research, IIT proprietary sulfonation reactor is a multi-tube falling film reactor with unique features.

• The gas feeding device efficiently removes condensed oleum and uniformly distributes the gas to all the reaction tubes.
• The reagents distribution is assembled as a cartridge that can be taken apart from the reactor body, allowing fast and easy cartridge cleaning and/or replacement. The cartridge features permanently calibrated distribution plates, that never require calibration, not even for the first startup.
• The protection device, included in the reagents distribution cartridge:
  • feeds barrier air in order to protect the top of the reactor from charring during the steady state operation.
  • lets recirculate the organic matters to the reactor during the plant preheating, allowing to substantially reduce the production of off-spec acid, without the need to absorb SO₃ with a sulfuric acid tower.
• The reactor body is a shell-and-tube heat exchanger. Since the reaction tubes never need to be removed, they are welded to the tube sheets, eliminating any risk of cooling water leakage into the product.
• The gas/liquid separator features self-cleaning internal surfaces and guarantees high separation efficiency as well as minimum liquid residence time.

IIT sulfonation reactor allows to treat the vast majority of sulfatable or sulfonatable raw materials obtaining the best product quality. Alkylates, fatty alcohols, ethoxilated fatty alcohols, alfa-olefines and methyl esters are just some of the possible compounds that can be sulfated or sulfonated by IIT reactor.

Neutralization

The key equipment of IIT neutralization technology is the proprietary continuous in-line high shear mixer homogenizer. This equipment is suitable for different operations, including blending, mixing, emulsifying, solid suspending or dispersing, dissolving, diluting, homogenizing, miling and accelerating reactions.

The mixing action is performed through a 'rotor/stator high-shear group'. The rotor turns at high speed forcing the liquid through small interstices. Product (liquid and some solids) is subjected to intense mechanical and hydraulic shear action by the high speed of the rotor, ensuring a very homogenous mixing.

Exhaust gas cleaning

Gases leaving the reactor contain mists of organic sulfonic and sulfuric acid as well as sulfur dioxide (byproduct of sulfur combustion) and therefore they cannot be directly discharged into the atmosphere.

IIT electrostatic precipitators have been specifically designed to remove acid mists from the exhaust gases of sulfonation plants. They feature an original, simple system for easy and fast electrode installation and centering and they can be equipped with an optional washing system of the collecting tubes.

IIT SO₂ scrubbers are packing towers for the removal of SO₂ and SO₃ from exhaust gases. They're built in plastic materials, in order to avoid corrosion, and they're equipped with a recycle pump, a liquid phase distribution system and all necessary monitoring equipment (pressure, pH, etc.).

Product finishing

IIT manufactures equipment for Dioxane reduction, AOS hydrolysis, as well for degassing, diluting and adjusting the qualities of active surfactants.

Our DeDiox system is designed for the reduction of 1.4-dioxane from 70% SLES paste. The DeDiox system can be added to the plant as a standalone unit or integrated into the neutralization unit, even in already existing plants.

During the sulphonation of Alpha Olefins, secondary reactions produce Sultones. These cyclic compounds can be converted to AOS by ageing the product at high temperature for about an hour. IIT supplies complete hydrolysis units, that consist of a feeding pump, a heater, a pressure tank (for holding the product at the required temperature) and a cooler.

IIT dilution equipment has been specifically designed to treat Active Matter surfactants. The surfactants have, in an intermediate concentration range, a very high viscosity that makes their manipulation difficult. The concentrated surfactant and the water are fed to an intensive high-shear mixer of small volume that makes the dilution instantaneous and complete.

Equipment for final adjustment of product quality, i.e. color, pH, stability, etc. may optionally complete the plant.