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• What are the symptoms of Silicone (Si) poisoning of a hydrotreating catalyst? How is it best avoided?

  Mar-2021

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Answers

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• Guillaume Vincent, Porocel, gvincent@porocel.com

  Silicon is the most common contaminant for hydrotreating units. Silicon contamination is a major concern for coker naphtha, but small quantities can be found in the diesel and kerosene fractions. The use of anti-foaming agents (mainly polydimethylsiloxane, PDMS) in delayed coker operations can lead to about 80% of silicon ending up in the coker naphtha fractions. Typically, PDMS is thermally decomposed as cyclic siloxanes, which induce pore mouth plugging and deactivation of the main catalyst bed. Up to 6°C of activity loss for each 1.0 wt% of Si on the hydrotreating catalyst is possible due to decreased accessibility of active sites leading to higher weighted average bed temperature (WABT) to achieve the desired specifications in the product. This deactivation phenomenon will result in shorter cycle length, underperformance of the unit, and shutdown of the unit for catalyst change-out.
  In order to maximise the HDS/HDN reactor performance, Legacy Porocel, now part of Evonik, has specially designed CatGuard Si21 as a silicon trap to:
  -    Gently saturate the olefins and mitigate the delta pressure build-up
  -    Trap silicon due to its high surface area (silicon capacity ≥ 20 wt%)
  -    Maximise volumetric retention
  -    Minimise diffusional limitations due to its optimised pore size structure

  CatGuard Si21 silicon trap is a key part of Legacy Porocel’s hydroprocessing product line. Legacy Porocel’s technology portfolio enables refiners to meet their product quality and cycle length targets in hydroprocessing applications for a fraction of the cost of conventional catalysts. CatGuard Si21, as a part of the top bed grading supply, will allow refiners to:
  -    Maximise unit performance
  -    Protect against poisoning
  -    Increase life cycle

  Mar-2021