The SD Process is based on the semi-batch reaction of alkylene oxides (EO and PO) with a chain starter (fatty alcohols, nonylphenol, etc.) and is typically catalyzed by KOH. The reaction mix is recirculated through a heat exchanger and sprayed into the vapor space of the reactor containing the vaporized alkylene oxide. The liquid droplets in the spray are saturated with oxide before they reach the bulk liquid which moves in near plug flow down the reactor. Essentially all of the dissolved oxide is reacted in the bulk liquid with very little oxide remaining in the recirculating liquid. In the spray reactor the reaction rate is limited only by the intrinsic chemical kinetics and not by mass transfer. The reaction rate is typically more than three times faster than in a conventional stirred reactor where mass transfer controls.

Ths SD reaction unit is fully automated and the plant is controlled by a DCS. Two levels of interlocks are provided: safety interlocks normally implemented on a PLC, and operational interlocks implemented on the DCS. The DCS typically Provides the following functions:

Batch control and sequencing can be customized for any product, to include the following options:

Through the SD process, it is possible to produce standard EO/PO adducts, EO/PO block copolymers and EO/PO random copolymers.

Main Process Features :

• Very high reaction rate (> 1000 kg EO/h-m3) and lowest level of dissolved oxide in the liquid phase
• Consistent plant operations and product quality
• High rates of heat and mass transfer leading to the lowest level of by-products
• Greatest flexibility of products and batch size
• Nearly quantitative yield of the main reaction:
  • 99.9% on chain starter
  • 99.9% on EO
  • 99.9% on PO
• Very safe operating conditions compared to the use of conventional stirred reactors, specifically:
  • Extremely low unreacted quantity of oxide in the liquid phase
  • No rotating parts in contact with the oxide gas phase
  • High electrical conductivity of the atmosphere in the reaction system, preventing the build-up of an electrostatic charge
  • Non-agitated design thus eliminating the hazard of oxide leakage through the agitator's mechanical seal
  • Extremely low probability of back-flow of catalyzed chain starter to the oxide storage tanks

Product Quality : The SD process results in higher quality products than those obtained from conventional stirred reactors. In particular the final products will have:

• The lowest content of free EO, dioxane and polyglycols (around 1 to 2 ppm of dioxane and free EO, depending on the product)
• Very good color without need for bleaching

The following table gives specifications for typical surfactants produced from commercially available chain starters:

SD Scope and Capabilities:

In addition to process design we offer:

SD can also design and supply the following associated facilities: