Zinc oxide catalyst testing

We pack catalyst (10–50 mL) into a fixed‑bed quartz tube and pass a gas mixture of 1000–5000 ppm H₂S in nitrogen (or natural gas) at a space velocity of 1000–5000 h⁻¹ and temperature of 25–300°C (depending on application). A continuous H₂S analyser (GC‑SCD or electrochemical sensor) monitors outlet concentration. Breakthrough capacity (mg H₂S/g catalyst) is calculated as the amount of H₂S adsorbed until outlet reaches 1 ppm (or 5 ppm). For high‑performance catalysts, capacity at 50°C is typically 200–350 mg H₂S/g ZnO.

5. Sulfidation Rate (Kinetics) – Thermogravimetric Analysis (TGA)

We place a small sample (10–20 mg) in a TGA pan and expose it to 1% H₂S in N₂ at 50–300°C. The weight gain due to ZnS formation is recorded as a function of time. The reaction rate constant (k) is derived. Slow sulfidation leads to poor utilisation of bed depth, causing premature breakthrough.

6. Bulk Density and Porosity – ASTM D4180

We measure loose bulk density by pouring catalyst into a 250 mL graduated cylinder, tapping gently, and weighing. Apparent density is measured by mercury intrusion or helium pycnometer. From these, we calculate void fraction and porosity. For fixed‑bed reactors, bulk density of 0.8–1.2 g/cm³ is typical for ZnO extrudates.

7. Trace Metal Analysis – ICP‑OES / ICP‑MS – ASTM E3060

We digest a 0.5 g sample in aqua regia or microwave acid, then analyse for impurities: iron (Fe), sodium (Na), calcium (Ca), silicon (Si), chloride (Cl), and transition metals. Acceptable limits: Fe < 0.1%, Na < 0.05%, Cl < 0.1%. High sodium or chloride accelerates sintering and reduces catalyst life.

8. Crystalline Phase Identification – X‑ray Diffraction (XRD)

We scan the powdered sample (2θ = 20–80°) to identify ZnO (zincite), ZnS (sphalerite) in spent catalysts, and any residual carbonates or promoters. For fresh catalysts, only ZnO phase should be present. Detection of ZnS before use indicates exposure to H₂S during storage or poor sealing.

9. Morphology and Particle Size – Scanning Electron Microscopy (SEM)

We image the catalyst surface and cross‑section at magnifications of 500–5000× to assess particle agglomeration, grain boundaries, and pore structure. For extrudates, we also measure the external diameter uniformity and presence of surface cracks.

10. Thermal Stability – X‑Ray Diffraction and BET After Aging

We heat catalyst samples to 400°C, 600°C, and 800°C under air for 4 hours. After aging, we re‑measure BET surface area and crystallite size (by XRD peak broadening). A loss of > 50% surface area after 600°C indicates poor thermal stability, unsuitable for high‑temperature desulfurisation.

11. Residual Chloride and Sulfur (Fresh Catalyst) – Ion Chromatography

We extract a sample with deionised water under reflux and analyse the extract for Cl⁻, SO₄²⁻, and S²⁻. High residual chloride (> 0.2%) can promote downstream corrosion when the catalyst is regenerated. High residual sulfate (> 1%) indicates incomplete washing.

12. Pressure Drop Testing (for fixed‑bed loading)

We load catalyst into a transparent column and measure pressure drop (kPa/m) at various superficial gas velocities (0.1–1 m/s). This helps process engineers verify that the packed bed does not exceed the blower capacity.

Quality Grading and Acceptance Criteria

Based on our zinc oxide catalyst testing, we classify materials into three grades (clients provide specific acceptance criteria based on their feed gas composition and operating conditions):

• Grade A (Premium – High‑Efficiency Desulfurisation) – BET surface area ≥ 100 m²/g, crush strength ≥ 80 N, attrition loss < 2%, H₂S breakthrough capacity ≥ 300 mg/g at 50°C, Fe < 0.05%, thermal stability (surface area loss < 30% at 600°C).
• Grade B (Standard – General Refining) – BET area 50–100 m²/g, crush strength 50–80 N, attrition loss 2–5%, breakthrough capacity 200–300 mg/g, Fe < 0.1%, area loss 30–50% at 600°C.
• Grade C (Reject – Not Recommended) – BET area < 30 m²/g, crush strength < 30 N, attrition loss > 10%, breakthrough capacity < 150 mg/g, high impurities – immediate quality improvement required.

Reporting and Deliverables

Our zinc oxide catalyst testing report includes: sample identification (form, supplier, batch number, nominal composition), BET surface area and pore volume, crush strength distribution histogram, attrition loss percentage, H₂S breakthrough curve (concentration vs. time) with calculated capacity, TGA sulfidation curve, bulk density, trace metal concentrations, XRD diffractogram, SEM images, thermal stability data, and a clear pass/fail conclusion based on client‑supplied criteria. Raw data (adsorption isotherms, kinetic curves, spectra) are archived for 10 years.

In summary, thorough zinc oxide catalyst testing ensures that desulfurisation systems in Australian LNG plants, biogas facilities, and hydrogen production units achieve reliable H₂S removal, extended bed life, and compliance with downstream catalyst protection limits. Contact our laboratory to schedule batch qualification or post‑service analysis.

Applications in the Australian Industry

• LNG and natural gas processing (Karratha, Darwin, Gladstone, Moomba): H₂S removal from feed gas before liquefaction.
• Biogas purification (landfills, wastewater treatment plants, agricultural digesters): Zinc oxide polishing for fuel cell feed and grid injection.
• Hydrogen and syngas production (green hydrogen projects, ammonia plants): Trace sulfur removal to protect downstream catalysts (e.g., steam reforming, fuel cells).
• Refineries (Geelong, Brisbane, Lytton): Naphtha and gas desulfurisation before catalytic reforming.
• Tail gas treatment (Claus plants): Final polishing of off‑gas before incineration.