Two-step coating method for improved high temperature filtration

A method to create nano-scale membrane coated porous ceramic filtration material to dramatically improve both initial filtration efficiency and soot loading behavior of conventional DPFs/GPFs and filters used in other high temperature applications.
Technology No. 2020-334
IP Status: Provisional Patent Application Filed; Application #: 63/049,778


  • Gasoline Particulate Filter (GPF) and Diesel Particulate Filter (DPF), especially for catalyst-coated filters
  • High performance filters for high temperature applications, e.g., petrochemical, incineration, industrial flue gas, etc.

Key Benefits & Differentiators

  • Increase of 5 times or more in filtration efficiency with <30% increase in backpressure penalty
  • Highly porous (porosity >95%) layer on top of conventional ceramic layer (porosity 45-65%)
  • Extended filter lifetime by promoting surface cake formation of contaminates
  • Universally applicable method based on target application
  • Improved efficiency and longevity of filters

Technology Overview

Ceramic wall-flow substrates (such as cordierite or silicon carbide filters) are widely used in vehicle engine after-treatment applications to remove particulate matter as regulated by emission standards. The more stringent emission regulations world-wide requires DPFs/GPFs to be more efficient, which is often associated with undesired back pressure increase, and in turn affects vehicle fuel economy and power output adversely. Moreover, when the bare ceramic material is coated with catalysts (to simultaneously remove gaseous pollutants from engine), its filtration behavior is largely deteriorated due to the unfavorable change of micro-pore structure.

Prof. David Pui’s research group at the University of Minnesota have developed a two-step coating method to form a nanoscale porous membrane layer on top of conventional porous ceramic filtration material for improved filtration. In this method, 1st coating of removable porous material to occupy micro-pore ceramic structure is applied, followed by a 2nd coating of nanomaterial on top of 1st coating. Subsequent regeneration removes 1st coating, leaving the 2nd step nanomaterial coating on top of the substrate. The nanomaterial coated ceramic wafers by this two-step coating method show better efficiency-back pressure tradeoff and soot loading capability than the single-step methods. This two-step coating method can be potentially used on other filtration substrates, for improved filtration performance in air and/or liquid filtration applications.

This method can form a highly porous (porosity>95%) membrane layer on top of the conventional ceramic (porosity ~45-65%), with a much smaller pore size (nanoscale), which significantly improves the filtration performance. The initial filtration efficiency can be enhanced by more than one order of magnitude, with only a small amount of backpressure penalty. The membrane layer on the top surface also largely extends the lifetime of ceramic filters between each regeneration cycle in engine emission applications.

Phase of Development

TRL: 3-4
Experimental characterization in a lab/emulated environment. Long-term stability testing underway.

Desired Partnerships

This technology is now available for:
  • License
  • Sponsored research
  • Co-development

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  • swap_vertical_circlelibrary_booksReferences (1)
    1. Qisheng Ou and David Y.H. Pui (Oct. 11, 2019), Improving Filtration Performance of Ceramic Wall-Flow Filters with Heat Resistant Membrane by a Two-Step Coating Method, Presented at 56th CFR Review Meeting, Xinxiang, Henan China
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