The abrasion rate is one of the most critical mechanical quality indicators for organic sulfur hydrogenation catalysts, directly reflecting their ability to resist attrition during transport, loading, and long-term operation in hydrodesulfurization service. This article presents a comprehensive technical guide to the determination of abrasion rate for organic sulfur hydrogenation catalysts, covering the testing principle, sample preparation, apparatus, step-by-step procedures based on recognized standards such as ASTM D4058, result calculation, and typical industrial applications. It is intended for catalyst manufacturers, plant engineers, quality control personnel, and accredited third-party laboratories involved in catalyst evaluation and acceptance testing.
Technical Overview
Organic sulfur hydrogenation catalysts, typically cobalt–molybdenum (Co-Mo) or nickel–molybdenum (Ni-Mo) oxides supported on high-surface-area alumina, are widely used to convert organic sulfur compounds such as carbonyl sulfide (COS), carbon disulfide (CS2), mercaptans, sulfides, and thiophenes into hydrogen sulfide (H2S). The H2S is subsequently removed by zinc oxide absorbents, protecting downstream synthesis and hydrogenation catalysts from sulfur poisoning in ammonia plants, methanol plants, hydrogen production units, and natural gas purification systems.
Because these catalysts are subjected to repeated handling, screening, dense loading, pressure fluctuations, and thermal cycling, their mechanical integrity is as important as their catalytic activity. The abrasion rate, also called the attrition rate, quantifies the tendency of shaped catalyst particles to break down and generate fines under standardized mechanical stress. A high abrasion rate leads to increased bed pressure drop, dust carryover, flow maldistribution, and contamination of downstream equipment. Determination of the abrasion rate is therefore a mandatory quality control item in most product specifications and acceptance inspections for organic sulfur hydrogenation catalysts.
- The abrasion rate is expressed as the mass percentage of fines generated after a sample is tumbled in a standard rotating drum.
- The test evaluates the combined effects of formulation, binder content, forming quality, drying, and calcination on particle robustness.
- Results are used for factory quality control, incoming material inspection, supplier comparison, and research and development of new catalyst formulations.
Testing Samples
Commercial Shaped Catalyst Extrudates
The most common sample type is extruded catalyst in the form of cylinders, trilobes, quadralobes, or hollow extrudates, typically 3–6 mm in nominal diameter. These samples are taken directly from production lots or delivered containers and should be representative of the whole batch.
Spherical and Pelletized Catalysts
Spherical catalysts produced by oil-drop forming, pan granulation, or spray drying can also be tested. The sieve aperture used to define fines is selected according to the nominal particle size of the product.
Laboratory and Pilot-Scale Samples
Small-scale samples prepared during formulation development, binder optimization, or calcination studies are tested to compare mechanical performance before scale-up. Sufficient quantity, typically 100–200 g per test, should be prepared to allow duplicate determinations.
Retained and Used Catalyst Samples
Retained reference samples are tested periodically to verify consistent product quality, while used catalysts withdrawn from industrial reactors can be evaluated to assess mechanical degradation after service, provided that fouling by dust, carbon, or condensates is considered during interpretation.
Testing Items
The core testing item is the abrasion rate, which is usually reported together with supporting measurements that allow a complete mechanical characterization of the catalyst:
- Abrasion rate (attrition rate), expressed as the mass percentage of fines generated under the specified tumbling conditions.
- Fines content of the as-received sample, determined by sieving before the attrition test.
- Mass loss after testing, used as a cross-check of the sieving result.
- Side crush strength and bulk crush strength, determined in accordance with ASTM D4179, ASTM D6175, or ASTM D7084 as complementary mechanical indicators.
- Particle size distribution, bulk density, and loss on ignition or moisture content, which support interpretation of the attrition behavior.
Testing Methods
Reference Standards
The rotating tumbler method described in ASTM D4058 is the internationally recognized basis for determining the attrition and abrasion of formed catalyst particles and is directly applicable to extruded and pelleted organic sulfur hydrogenation catalysts. For fluidizable powders, the air-jet attrition method of ASTM D5757 may be referenced for comparison. Sampling of solid chemical products is normally performed in accordance with GB/T 6679 or an equivalent statistical sampling plan, and product-specific requirements for hydrogenation and desulfurization catalysts are specified in the relevant national or chemical industry (HG/T) product standards. Testing should be carried out by laboratories operating under an ISO/IEC 17025-compliant quality management system or by accredited third-party laboratories.
Apparatus
- An abrasion drum, usually made of stainless steel, fitted with an internal baffle or lifter bar, with dimensions and rotational speed as specified in the standard.
- A calibrated motorized sieve shaker with test sieves of the aperture specified by the method or product standard.
- An analytical balance with a readability of 0.01 g or better.
- A drying oven capable of maintaining 105–120 °C, a desiccator with silica gel, soft brushes, and a timer.
Sample Preparation
- Draw a representative sample from the lot in accordance with the applicable sampling standard and reduce it by quartering or riffling.
- Dry the sample at 105–120 °C for the specified time, commonly 1–2 hours, and cool it to room temperature in a desiccator.
- Pre-sieve the sample gently to remove pre-existing fines, which are reported separately as the initial fines content.
- Weigh a test portion of approximately 50–100 g, or the mass specified in the product standard, to the required precision.
Test Procedure
- Charge the weighed test portion into the clean, dry abrasion drum and secure the closure.
- Rotate the drum at the specified speed, commonly about 30 rpm, for the specified duration, typically 30–60 minutes.
- After tumbling, carefully transfer the entire contents of the drum onto the designated sieve using a soft brush.
- Sieve mechanically or manually for the standardized period, then weigh the material retained on the sieve.
- Run a duplicate determination on a second test portion and verify that the results agree within the repeatability limit of the method.
Calculation
The abrasion rate A is calculated as the percentage of mass converted to fines during the test:
A (%) = (m0 − m1) / m0 × 100, where m0 is the initial mass of the pre-sieved test portion and m1 is the mass retained on the sieve after tumbling and sieving.
Precision and Quality Control
The difference between duplicate determinations performed by the same operator should normally not exceed 0.5 percentage points in absolute terms, or the repeatability limit stated in the applicable product standard. Sieves must be inspected for damage and calibrated periodically, the drum interior must be kept clean and rust-free, and reference samples with known abrasion rates should be tested regularly to monitor the consistency of the apparatus and procedure.
Applications
Abrasion rate determination is applied throughout the entire life cycle of organic sulfur hydrogenation catalysts, from development to plant operation:
- Factory quality control of every production batch before release and shipment.
- Incoming inspection and acceptance testing by purchasing parties, including independent verification by accredited third-party laboratories.
- Comparison of catalysts from different suppliers or production lines during procurement and technical bidding.
- Research and development support for optimizing binders, forming parameters, drying profiles, and calcination temperature to improve mechanical strength.
- Assessment of the suitability of packaging, transport routes, and handling or dense-loading procedures before reactor charging.
- Evaluation of used or regenerated catalysts to judge mechanical degradation and residual serviceability.
- Failure analysis when excessive pressure drop, dust formation, or carryover is observed in industrial reactors.
FAQ
What is a typical acceptance criterion for the abrasion rate?
For most commercial organic sulfur hydrogenation catalysts, product specifications require an abrasion rate of no more than about 5%, although limits between 3% and 6% are common depending on the product standard, shape, and customer requirements. The value stipulated in the applicable product standard or supply contract always prevails.
How does the abrasion rate differ from crush strength?
The abrasion rate measures resistance to surface wear and gradual breakdown under tumbling, reflecting fines generation, while crush strength measures the force required to fracture an individual particle or a bulk bed. Both properties are complementary: a catalyst may have adequate crush strength yet still exhibit unacceptable attrition, so specification sheets normally include both.
Which factors most strongly influence the test result?
The main influencing factors include residual moisture, incomplete removal of pre-existing fines, drum geometry and speed, tumbling time, sieve aperture and condition, and operator handling. Strict adherence to drying, pre-sieving, and apparatus parameters is essential for reproducible results.
How much sample is needed and what is the typical turnaround time?
Approximately 100–200 g of catalyst is usually sufficient for duplicate determinations, including pre-sieving and weighing. The complete determination, including drying, tumbling, sieving, and calculation, can typically be completed within one working day.
Can used catalysts be tested by this method?
Yes, but results must be interpreted with caution. Deposited dust, carbon, sulfides, or absorbed liquids can bias the measured fines generation, so used samples are often gently pre-cleaned and dried, and the results are compared with the original fresh-catalyst certificate of analysis.
Which organization standards govern the test?
The tumbler method is covered by ASTM D4058, with related mechanical test methods in ASTM D4179, ASTM D6175, and ASTM D7084, sampling guidance in GB/T 6679, and product-specific limits in the relevant national and HG/T industry standards for hydrogenation and desulfurization catalysts.