Investigation of sol–gel supported palladium catalysts for Heck coupling reactions in o/w-microemulsions

• Aqueous surfactant solutions are used as reaction medium for Heck reactions.
• Supported palladium catalysts are prepared by sol–gel process and investigated.
• Supported catalysts are selective and stable with negligible leaching.
• Reaction rates for supported and unsupported Pd catalysts are compared.
• Overall efficiency is increased by successful catalyst recycling.

Sol–gel supported palladium catalysts are investigated for the Heck coupling reaction between styrene and iodo-/bromobenzene to trans-stilbenes in o/w-microemulsions as alternative reaction medium. High conversions and selectivities are obtained with these catalysts and they show better catalytic performance than their commercial analogs Pd@SiO2 or Pd/C. The influence of the catalyst structure on the activity is investigated in detail showing mass transport limitations that can be optimized by the palladium loading. The catalyst is recyclable >6 times with negligible palladium leaching into the solution. Because of the good recyclability under retention of activity and selectivity, the influence of transport limitations is suppressed and the total catalyst efficiency is increased to more than 2.

Figure optionsDownload high-quality image (75 K)Download as PowerPoint slide