How to Specify Zeolite Honeycomb or VOC Catalyst Honeycomb for a Replacement Project

Replacement requests often begin with a photograph and an external block size.

That is not enough.

Two blocks measuring:

100 × 100 × 100 mm

can perform completely different functions.

One may be:

• zeolite adsorbent;
• bare catalyst substrate;
• finished VOC oxidation catalyst;
• heat-storage ceramic.

The first task in a replacement project is therefore to identify what the existing honeycomb actually does.

Step 1 — Identify the Function

Ask:

Is the existing block used for:

• adsorption?
• VOC concentration?
• catalytic oxidation?
• RTO heat storage?

This determines which properties matter.

Do not identify the product only from appearance.

Step 2 — Measure External Dimensions

Record:

• width;
• height;
• length.

Measure several intact pieces.

Old ceramic may contain:

• chipped corners;
• deposits.

One damaged block should not define the replacement size.

Step 3 — Determine CPSI or Channel Pattern

Count channels across a known dimension.

This allows approximate determination of:

• CPSI;
• channel pitch.

Provide clear frontal photographs with a scale if exact counting is difficult.

Step 4 — Measure Channel Opening

Channel size helps distinguish products that have similar CPSI but different wall thickness.

For coated catalysts, measure the final coated opening where possible.

Step 5 — Estimate Wall Thickness

Wall thickness influences:

• open frontal area;
• strength;
• density.

It is particularly important when comparing bare and coated substrates.

Step 6 — Weigh an Intact Block

Block weight provides useful information about:

• material quantity;
• density.

A major weight difference between the old and proposed replacement may indicate a different structure.

Step 7 — Identify the Material

For thermal honeycomb, material may be:

• cordierite;
• cordierite-mullite.

For adsorbent products, determine whether:

• zeolite is incorporated;
• zeolite is coated onto a support.

For catalyst products, identify the substrate and active coating if possible.

Step 8 — Determine Whether It Is Coated

Inspect the channel surface.

A coated product may have:

• different texture;
• color;
• surface layer

from bare ceramic.

However, appearance alone is not reliable for identifying catalyst chemistry.

Documentation or analysis may be required.

Step 9 — Record Operating Temperature

Provide:

• normal inlet temperature;
• maximum temperature;
• regeneration temperature if applicable.

This is essential for distinguishing adsorption duty from thermal-regeneration duty.

Step 10 — Provide VOC Composition

For zeolite adsorption or catalyst service, the supplier should know:

• VOC species;
• concentration;
• gas composition.

“VOC exhaust” is not sufficiently specific.

Step 11 — Provide Humidity

For adsorbent honeycomb, water content may significantly affect working capacity.

Include:

• humidity;
• gas temperature.

Step 12 — Provide Gas Flow

Flow data are needed to evaluate:

• face velocity;
• pressure drop.

A block that physically fits may still be hydraulically unsuitable.

Step 13 — Record Existing Pressure Drop

Historical ΔP is valuable.

If the original system performed reliably, it provides a practical replacement benchmark.

If ΔP had risen significantly, determine whether the cause was:

• fouling;
• catalyst coating;
• wrong geometry.

Step 14 — Identify the Failure Reason

Why is the media being replaced?

Possible reasons include:

• adsorption capacity loss;
• catalyst deactivation;
• plugging;
• cracking;
• normal scheduled replacement.

The answer determines whether identical replacement is appropriate.

Step 15 — For Zeolite, Ask About Breakthrough

Useful operating history includes:

• original adsorption cycle time;
• current cycle time;
• outlet VOC trend.

If breakthrough has become earlier, the issue may be:

• adsorbent aging;
• humidity;
• contamination;
• incomplete regeneration.

Step 16 — For Catalyst, Ask About Conversion

A mechanically intact block may have lost catalytic activity.

Provide:

• inlet VOC;
• outlet VOC;
• temperature.

This helps distinguish catalyst deactivation from hydraulic damage.

Step 17 — Check Fouling

Photograph deposits.

If the previous high-CPSI product repeatedly plugged, replacing it with an identical fine channel may not be the correct solution.

Geometry should be reviewed.

Step 18 — Check Chamber Fit

Record:

• total chamber dimensions;
• number of blocks;
• arrangement;
• joint gaps.

Small dimensional differences accumulate across large arrays.

Step 19 — Specify Quantity by Pieces and Layer

For structured blocks, piece count is meaningful.

Provide:

• blocks per row;
• rows;
• layers.

This reduces quantity uncertainty.

Step 20 — Define What You Are Buying

The RFQ should explicitly state one of:

Zeolite Adsorption HoneycombBare VOC Catalyst SubstrateFinished VOC Catalyst Honeycomb

These are different commercial products.

Why a Physical Sample Can Help

For an old or undocumented system, one intact sample can help evaluate:

• geometry;
• material;
• coating.

However, process information is still necessary.

A sample cannot reveal:

• inlet VOC concentration;
• humidity;
• required conversion.

Do Not Copy a Failed Design Blindly

Replacement is an opportunity to ask:

• Did the old product plug too quickly?
• Was adsorption capacity insufficient?
• Did catalyst activity decline prematurely?
• Was pressure drop excessive?

If the answer is yes, exact duplication may reproduce the same problem.

Engineering Takeaway

A replacement honeycomb project must match both physical geometry and process function.