Crush Strength Testing of Catalyst Pellets

Solution

• Software-controlled compression test system.
• Self-leveling steel compression plates.
• Sample container and plunger fixtures for bulk testing.

Benefits

• Capability to test all pellet geometries on a single platform.
• Software-controlled routines for repeatable testing across multiple material standards.
• High-capacity connector grips are crimped.

Requirement

The industrial chemical reactions would not be possible without catalysts, which lower the activation energy levels and make the reaction faster at lower temperatures. Their productivity is not only a factor of their chemical activity but also of their mechanical integrity. Pellets may fracture due to weak or brittle material and may result in blockages, a drop in pressure, and uneven heat transfer that may influence the overall process reliability. Mechanical strength of catalysts is thus a critical assessment that can be used to guarantee homogeneous efficiency.

The catalyst particles are available in different shapes or forms, such as pellets, granules, tablets, spheres, rings, and extrudates, and they are usually delicate and easily deform without any breakage. Testing these requires carefully designed methods, leading to several standardized approaches for different geometries and particle types.

Solution

For single-pellet testing, ASTM D4179 measures compressive ‘side crush strength’ (SCS) of regular-shaped pellets like spheres, short cylinders, or tablets. Tests may be radial or axial, with radial crush providing a more representative measure of in-reactor behavior. Force is applied uniformly until the pellet fractures, recording the maximum crush strength.

ASTM D6175 focuses on radial crush strength for extruded catalyst particles of 1.6–3.2 mm diameter and length-to-diameter ratios ≥ 1:1. The compressive force is applied until failure, with the force per millimeter deformation documented, typically covering 0–65 N/mm.

For irregular or bulk catalyst materials, ASTM D7084 defines the bulk crush strength (BCS) test. Particles are placed in a cylindrical container and compressed with a piston at a controlled rate. Pressure is maintained briefly, and the amount of fines (particles passing through a half-size sieve) is measured. Typical BCS values range from 0.1 to 0.35 MPa for small granules to 1 to 3.5 MPa for larger formed pellets.

Presto Stantest’s universal testing systems are ideal for both single-pellet and bulk crush testing. Robust frames, precision load cells, and user-friendly software enable high-frequency data capture, clear graphical representation of fracture events, pass/fail determination, and exportable results. A full suite of self-aligning compression plates and custom or standard fixtures ensures compatibility with a variety of catalyst shapes and sizes.

Test Equipment

• OmniTest (replaces MultiTest-i)
• Self-leveling compression plates
• Custom or standard succulometer/dual-extrusion fixtures
• Force testing software

Test Standards

• ASTM D7084 – Bulk Crush Strength of Catalysts and Catalyst Carriers
• ASTM D6175 – Radial Crush Strength of Extruded Catalyst Particles
• ASTM D4179 – Single Pellet Crush Strength of Formed Catalyst Shapes