Dow Water & Process Solutions

Silane Inter-Conversion and Processing

Silanes are widely used chemicals, showing up in a variety of consumer products. DOWEX™ ion exchange resins are convenient tools for the production and inter-conversion of these valuable chemicals in a variety of reactions.

Chloro-silanes are interconverted with a weak base ion exchange functionalized resin where the tertiary amine group is believed to act as a reservoir of HCl and stabilizes the intermediate complex. DOWEX M-43 resin is a chemical process grade weak base resin with proven performance in this application. More recently, uniform particle size products such as XUS 43568.00 resins are being introduced that offer the advantage of more uniform diffusional paths for reactants and products.

Na₂SiO₃ + DOWEX G-26 (H⁺ form) DOWEX G-26 (Na⁺ form) + H₂SiO₃
Silica sol is produced by converting sodium silicate to silicic acid using a cation exchange resin in the hydrogen form. Silica acid is quite unstable and the conversion is done rapidly to avoid polymerization. This is a rigorous reaction that can result in severe resin breakage. The resin of choice is DOWEX G-26 (H) cation exchange resin because of its excellent strength and attrition resistance.

Products and Applications

Dow offers a variety of cation, anion and chelating resins for chemical processing applications. They are available in different particle sizes with macroporous or gel morphologies.

• Dow offers a wide variety of fine mesh resins (183KB PDF) with varying levels of cross-linking that allow interaction of the catalyst site with cumbersome reaction groups. Cross-linking levels range from 2 to 8% and particle sizes from 300 microns to 37 microns.
• Dow offers the pre-dried DOWEX DR-2030 and DOWEX MONOSPHERE™ DR-2030 catalysts. These catalysts are also available in the wet form as DOWEX M-31 and DOWEX MONOSPHERE M-31 catalysts.

Features and Benefits of DOWEX Resins for Silane

Improved Productivity with Uniform Particle Size Products – Continuous catalyst operations in packed beds must be optimized for maximum throughput. Kinetic limitations for diffusion of reactants into the catalyst sites and diffusion of product back out into the bulk solution should be considered. Because of their relatively long diffusion paths, the largest beads are the most kinetically limited with an effective "dead zone" present at the center of the bead. Pressure drop through the bed is another potential limitation. While the smallest beads have very fast diffusional kinetics, they contribute more to the pressure drop. XUS 43568.00 resins are made by a patented process resulting in excellent uniformity of bead size. Many customers have experienced as much as 15% increase in productivity when switching from a standard bead size to uniform particle size products.

DOWEX Resins

Product	Description	Type	Matrix	Total Exchange Capacity* eq/l (kgr/ft3)	Available Forms
DOWEX M-43	Corrosion control with DOWEX M-43 ion exchange resin.	Weak Base Anion	Styrene-DVB, Macroporous	1.55	FB (Free Base) form
DOWEX G-26 (H)	Uniform particle size strong acid cation exchange resin for specialty demineralization and catalyst applications.	Strong Acid Cation	Styrene-DVB, Gel	2.0	H+
DOWEX DR-2030	Dry acid catalysts for chemical processing.	Strong Acid Cation	Styrene-DVB, Macroporous	4.7 eq/kg	H+
DOWEX MONOSPHERE DR-2030	Dry acid catalysts for chemical processing.	Strong Acid Cation	Styrene-DVB, Macroporous	4.7 eq/kg	H+
DOWEX M-31	Standard grade product for general catalytic applications. This catalyst has unmatched durability and dependability within the MTBE/TAME industry.	Strong Acid Cation	Styrene-DVB, Macroporous	1.7	H+
DOWEX MONOSPHERE M-31	A uniform bead size strong acid catalyst. This is our highest performance catalyst for MTBE/TAME.	Strong Acid Cation	Styrene-DVB, Macroporous	1.85	H+