---
title: "Honeycomb catalyst"
description: "A honeycomb catalyst is a monolithic extruded ceramic block containing a dense grid of parallel square channels through which flue gas flows. The active catalytic material — typically vanadium pentoxide and tungsten trioxide on a titanium-dioxide carrier — is incorporated into the bulk ceramic. Honeycomb is the most common form of SCR catalyst."
canonical_url: "https://sylio.co/glossary/honeycomb-catalyst"
last_updated: "2026-06-28T02:29:37.148Z"
---

A **honeycomb catalyst** is a monolithic extruded ceramic block containing a dense grid of parallel square channels through which flue gas flows. The active catalytic material — typically vanadium pentoxide and tungsten trioxide on a titanium-dioxide carrier — is incorporated into the bulk ceramic. Honeycomb is the most common form of [SCR catalyst](/glossary/selective-catalytic-reduction).

## Strengths and weaknesses

<table>
<thead>
  <tr>
    <th>
      Strength
    </th>
    
    <th>
      Weakness
    </th>
  </tr>
</thead>

<tbody>
  <tr>
    <td>
      Very high geometric surface area per unit volume
    </td>
    
    <td>
      Channels susceptible to <a href="/glossary/catalyst-pluggage">
        pluggage
      </a>
      
       by ash
    </td>
  </tr>
  
  <tr>
    <td>
      Low pressure drop in clean condition
    </td>
    
    <td>
      Brittle — handle with care during install / replacement
    </td>
  </tr>
  
  <tr>
    <td>
      Mature, large supplier base
    </td>
    
    <td>
      Channels are harder to clean than open structures
    </td>
  </tr>
  
  <tr>
    <td>
      Wide range of pitch options (3.5–7.4 mm typical)
    </td>
    
    <td>
      Smaller pitch = more risk of pluggage
    </td>
  </tr>
</tbody>
</table>

## Pitch selection

Pitch (centre-to-centre channel spacing) trades surface area against pluggage risk:

- **Smaller pitch (3.5–4.5 mm)** — high surface area, used on clean gas streams (NGCC HRSGs, gas-fired duty)
- **Larger pitch (6–7.4 mm)** — used on dusty coal, biomass and WtE duty where pluggage risk dominates

## Layer assembly

Individual honeycomb blocks are loaded into a [catalyst layer / module](/glossary/catalyst-layer-module) and stacked 2–4 layers deep inside the SCR reactor. [Sonic horns](/glossary/sonic-horn) and steam [sootblowers](/glossary/sonic-sootblower) are positioned between layers to keep channels clear.

## Related terms

- [Selective Catalytic Reduction (SCR)](/glossary/selective-catalytic-reduction)
- [Plate catalyst](/glossary/plate-catalyst)
- [Corrugated catalyst](/glossary/corrugated-catalyst)
- [Catalyst layer / module](/glossary/catalyst-layer-module)
- [Catalyst pluggage](/glossary/catalyst-pluggage)