NB/SH/T 0863-2013 Guide for determination of chemical elements in fluid catalytic cracking catalysts by X-ray fluorescence spectrometry

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NB/SH/T 0863-2013 describes several alternative X-ray fluorescence (XRF) approaches for the quantitative analysis of 29 chemical elements in fluid catalytic cracking (FCC) catalysts, and can be extended to other elements.

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Scope: Specifies several alternative methods for the quantitative analysis of 29 chemical elements in fluid catalytic cracking (FCC) catalysts by XRF, which can also be extended to other elements. The 29 elements are: aluminium (Al), silicon (Si), iron (Fe), nickel (Ni), vanadium (V), sodium (Na), sulfur (S), phosphorus (P), lanthanum (La), cerium (Ce), magnesium (Mg), potassium (K), calcium (Ca), barium (Ba), titanium (Ti), cobalt (Co), copper (Cu), lead (Pb), zinc (Zn), antimony (Sb), tin (Sn), manganese (Mn), molybdenum (Mo), strontium (Sr), zirconium (Zr), bismuth (Bi), praseodymium (Pr), neodymium (Nd) and samarium (Sm). 1.2 It applies to FCC fresh catalyst, FCC equilibrium catalyst, FCC spent catalyst and FCC catalyst fines. 1.3 This standard involves certain hazardous materials, operations and equipment, but does not purport to address all of the safety issues associated with their use; users should establish appropriate safety and protective measures before use and determine the applicability of relevant regulatory limits. 8.4.1 For FCC catalyst samples, it is relatively difficult to analyse elements with a content below 0.1% (mass fraction) using energy-dispersive X-ray spectrometry; it is even more difficult when rare earth elements are present (rare earth elements are difficult to resolve and readily produce severe matrix effects). Not applicable: no clause explicitly listing not-applicable provisions is provided in the available material.

Principle: The sample surface must be clean, homogeneous and flat; the two common sample preparation methods are the pressed powder pellet method (Method A, clause 8) and the fused bead method (Method B, clause 9). 3.2 Primary X-rays irradiate the surface of the sample that has been pressed into a pellet or fused into a bead; the secondary X-ray spectral lines (fluorescence) produced are the characteristic spectra of the chemical elements in the sample. 3.3 Two types of instrument, WDXRF and EDXRF, are used to collect and process the X-ray spectra. WDXRF: the secondary X-rays are dispersed by wavelength through a crystal or synthetic crystal, and the intensity at each wavelength is measured by the corresponding detector and recorded as counts; EDXRF: the secondary X-rays are sent to a detector, sorted by energy, and counted and processed by a multichannel analyser. From the measured X-ray intensity, the element concentration in the sample is determined by means of a calibration curve established with suitable reference materials. 3.4 Main advantages of WDXRF: high resolution and low detection limits; main advantages of EDXRF: fast measurement and lower instrument cost.

Apparatus: X-ray fluorescence spectrometer: wavelength- or energy-dispersive XRF with a vacuum sample chamber; for XRF system specifications see ASTM C 982, ASTM C1118, ASTM E1172 and Annex A (examples of instrument conditions — wavelength-dispersive X-ray fluorescence spectrometer). 5.2 Muffle furnace: capable of operating at 600 °C. 5.3 Oven: capable of maintaining a constant temperature of 200 °C. 5.4 Fusion furnace: capable of calcining a 50 g sample quantity ([to be verified] [source unclear]). 5.5 Desiccator: capable of maintaining a constant temperature of 60±20 ([to be verified] [source unclear], unit not provided in the available material). 5.6 Sample cell: used only when analysing catalyst fines; used to hold the fused bead or pressed pellet of catalyst. 5.7 Fusion furnace or fusion device: operating temperature 1100 °C. 5.8 Crucibles and moulds: material graphite or an alloy of platinum with 5% (mass fraction) gold, and shall match the sample cell of the X-ray fluorescence spectrometer. 5.9 Grinder or mill: manual (e.g. grinding vessels made of agate, mullite, alumina, tungsten carbide or boron carbide) or automatic (typically with a grinding vessel made of tungsten carbide); steel grinding vessels shall be avoided. 5.10 Mixer mill: used to mix the ground sample with the binder added before pressing; the size shall match the mixer mill ([to be verified] [source unclear]). 5.11 Pellet press: manual or automatic, used for pressed powder pellet preparation, capable of reproducibly maintaining a pressure of at least 172 MPa; the pellet size shall match the sample cell of the X-ray fluorescence spectrometer, generally 25 mm–40 mm.

Reagents and reference materials: Reagents for the fused bead method 6.1.1 Flux: lithium borate, lithium carbonate, analytical grade; or a lithium borate–lithium carbonate mixture. 6.1.2 Release agent: lithium iodide, ammonium iodide, sodium iodide, lithium bromide, ammonium bromide, analytical grade; the release agent added shall not interfere with the spectra of the elements to be analysed. 6.1.3 Oxidizing agent: potassium nitrate, ammonium nitrate, sodium nitrate, analytical grade; the oxidizing agent added shall not interfere with the spectra of the elements to be analysed. 6.2 Reagents for the pressed pellet method 6.2.1 Heavy absorber: lanthanum oxide, lead oxide, barium sulfate, analytical grade; added when necessary, and shall not interfere with the spectra of the elements to be analysed. 6.2.2 Binder: boric acid, methyl cellulose, naphthalene ([to be verified] [source unclear]), paraffin, starch; added when necessary, and shall not cause any interference with the spectra. 6.3 Detector gas: the gas used in the flow proportional counter (FPC) of wavelength-dispersive systems is P-10, consisting of 10% (by volume) methane and 90% (by volume) argon. 6.4 Isopropanol: analytical grade, used for cleaning the pellet press. 6.5 Reference materials for calibration: currently commercially available standard materials or certified reference materials, or mixed reagents prepared from ultra-high-purity reagents; the element contents of these reagents shall cover the concentration range of the elements in the sample. 6.6 Nickel oxide: spectroscopically pure, used to prepare nickel standard solutions and fusion samples. 6.7 Vanadium pentoxide: used to prepare vanadium standard solutions and fusion samples. 6.8 Standard solutions: prepare or select nickel and vanadium standard solutions of suitable concentration; commercially available nickel/vanadium standard solutions or nickel/vanadium standard solutions prepared from spectroscopically pure reagents are both acceptable, and standard solutions of other elements may be selected or prepared in a similar way; for the preparation of nickel and vanadium standard solutions, reference may be made to the preparation method in SH/T 0696-2000. 9.5.2.3 Example of flux composition: 49.75% (mass fraction) lithium carbonate, 49.78% (mass fraction) lithium tetraborate, 0.5% lithium iodide ([to be verified] [source unclear], the total does not equal 100%); the flux may be prepared from pure substances or purchased commercially. 9.5.3.2 High-purity nickel oxide: contains 78.584% (mass fraction) nickel.

Key conditions: Annex A (informative) Examples of instrument conditions (wavelength-dispersive X-ray fluorescence spectrometer): A.1 Elements analysed: no specific list is provided in the available material. A.1.1 X-ray tube: 4 kW rhodium target. A.1.2 Optical path: vacuum. A.1.3 Sample rotation motor: on. A.1.4–A.1.9 [source unclear] missing/illegible in the original ([to be verified] [source unclear]). A.2 Nickel (Ni): tube voltage 60 kV, tube current 66 mA; LiF200; 48.6450 ([to be verified] [source unclear], suspected to be the 2θ angle); 300 μm; time (measurement time) 20 s. A.2 Vanadium (V): tube voltage 60 kV, tube current 66 mA; the remaining parameters are [source unclear] missing in the original ([to be verified] [source unclear]). Annex B (informative) Examples of instrument parameters for the pressed pellet method: Table B.1 examples of operating conditions for a wavelength-dispersive X-ray fluorescence spectrometer; Table B.2 examples of reference spectral line libraries for the elements analysed; Table B.3 examples of analysis programmes; Table B.4 examples of concentration ranges of analysed samples; Table B.5 examples of precision from 20 repeated analyses of a sample (many values in the tables are severely [source unclear]; specific values [to be verified] [source unclear]). 8.6.7 Pellet pressing pressure: 172 MPa–414 MPa; example: 40 mm mould, pressure 207 MPa, time 10 s±25 ([to be verified] [source unclear], the unit is suspected to be s). 9.6.5 Fusion temperature: 1100 °C±100 °C (do not exceed 1250 °C). 9.5.2.12 Fusion: hold at 1100 °C±100 °C for 8 min–10 min. 9.5.2.8 Drying: dry at 250 °C for 30 min.

Calculation and results: Basis of quantification: from the measured X-ray intensity, the element concentration in the sample is determined by means of a calibration curve established with suitable reference materials (3.3). Definition of relative standard deviation (note 1 to 8.8, note 1 to 9.8): %RSD = (standard deviation σ/mean concentration) × 100. 9.5.3.7 Example of nickel content calculation: nickel content = 100×(mass of nickel oxide×0.78584)/(mass of crucible + bead − mass of crucible). 9.5.2.9 Calculation: adding 500 μg of nickel to a crucible containing 1.00 g of sample corresponds to 0.05% (mass fraction) nickel in the sample. 9.5.2.10 Calculation: adding 0.500 mL of 10000 μg/mL vanadium solution corresponds to 0.5% (mass fraction) vanadium per 1.00 g of sample ([to be verified] [source unclear]). Qualitative analysis: not provided in the available material.

Quality control: Table 1 Precision values (Method A, FCC equilibrium catalyst sample, obtained from 16 repeated preparations and analyses): Note 1: %RSD = (standard deviation σ/mean concentration) × 100. Note 2: because FCC catalysts differ in element content, the values in Table 1 are for reference only. Table 1 data (element analysed | mean concentration/% (mass fraction) | 2σ/(95% confidence) | %RSD): | Al₂O₃ | 29.92 | 0.16 | 0.27 | | SiO₂ | 65.48 | 0.49 | 0.37 | | Ni | 0.2332 | 0.0051 | 1.1 | | V | 0.2417 | 0.54 ([to be verified] [source unclear]) | 0.58 | | Fe | 0.54 ([to be verified] [source unclear]) | 0.0045 | 0.78 | | Cu | 1.03 ([to be verified] [source unclear]) | 0.0040 | 1.7 | | TiO₂ | 0.0142 | 0.01 | 0.49 | | Mn | 0.60 ([to be verified] [source unclear]) | 0.0002 | 4.1 | | Co | 0.085 | 0.01 | 2.0 | | Na | 0.340 | 0.0003 | 0.73 | | MgO | 0.16 | 0.0006 | 2.5 | | P₂O₅ | 0.17 | 0.01 | 1.2 | | CaO | 0.0862 | 0.004 | 1.7 | | SO₄ | 0.0255 | 0.009 | 2.3 | | Sb | 0.0077 | 0.005 | 0.77 | | ZnO | 0.030 | 0.01 | 1.4 | | Pb | 0.84 ([to be verified] [source unclear]) | 0.0013 | 1.4 | | Ba | 0.37 ([to be verified] [source unclear]) | 0.0007 | 3.3 | | La₂O₃ | 0.42 ([to be verified] [source unclear]) | 0.0002 | 0.47 | | CeO₂ | 0.13 ([to be verified] [source unclear]) | 0.002 | 1.3 | | Nd₂O₃ | 0.01 | 0.01 | 0.93 | | Pr₆O₁₁ | 1.77 ([to be verified] [source unclear]) | 0.01 | 2.3 | | Sm₂O₃ | 0.10 ([to be verified] [source unclear]) | 0.01 | 6.0 | | TotalREO | 0.011 | 0.001 | 0.60 | | K₂O | 0.009 | 0.002 | 0.92 | | Sr | 0.0028 | 0.001 | 2.9 | | Zr | 0.01 | 0.01 | 6.0 | Note: the correspondence between some values and elements in Table 1 is severely [source unclear]; the above correspondence is [to be verified] ([source unclear]). 9.8 Table 2 Precision values (Method B, FCC equilibrium catalyst sample, obtained from 11 repeated preparations and analyses, not the same sample as analysed by the pressed pellet method in 8.8): Note 1: %RSD = (standard deviation σ/mean concentration) × 100. Note 2: because FCC catalysts differ in element content, the values in Table 2 are for reference only. Table 2 data (element analysed | mean concentration/% (mass fraction) | 2σ/(95% confidence) | %RSD): | Al₂O₃ | 51.86 | 0.34 | 0.33 | | SiO₂ | 40.89 | 0.42 | 0.51 | | NiO | 0.175 | 0.01 | 3.1 | | V₂O₅ | 0.30 | 0.008 | 1.3 | | Fe₂O₃ | 2.5 | 0.17 | 3.5 | | CuO | 0.017 | 0.0008 | 2.6 | | TiO₂ | 1.19 | 0.016 | 0.67 | | CaO | 0.19 | 0.014 | 3.6 | | Na₂O | 0.5 | 0.12 | 11.5 | | MgO | 0.136 | 0.024 | 8.7 | | P₂O₅ | 0.325 | 0.01 | 1.5 | | BaO | <0.003 | — | — | | SnO | 0 | 0.008 | 6.6 | | Sb₂O₃ | 0.055 | 0 | 0 | | Bi₂O₃ | 0 | 0 | 8 | | PbO | 0.028 | 0.002 | 4.2 | | La₂O₃ | 0.835 | 0.01 | 0.63 | | CeO₂ | 0.17 | 0.004 | 1.3 | | Nd₂O₃ | 0.117 | 0.006 | 2.8 | | Pr₆O₁₁ | 0.119 | 0.004 | 1.8 | | Gd₂O₃ | <0.003 | 0.004 | 12.6 | | Sm₂O₃ | 0.013 | 0.004 | 0.86 | | TotalREO | 1.25 | 0.022 | 3.4 | | K₂O | 0.071 | 0.008 | 3.4 | Note: the correspondence between some values and elements in Table 2 is severely [source unclear]; the above correspondence is [to be verified] ([source unclear]). Annex C Informative notes: C.1 The detection limit of the pressed pellet method is 0.004% (mass fraction) (40 ppm) for nickel and 0.004% (mass fraction) (40 ppm) for vanadium; the detection limit is defined as the concentration at which the X-ray peak intensity is 3 times the background intensity (the concentration at which the peak-to-background intensity ratio is 3); the detection limit of the fused bead method is somewhat higher because the sample is diluted, but if the counting time of the fused bead method is extended to 3 times the original, the detection limits obtained by the two analytical methods are broadly the same. C.2 Technical precision of the pressed pellet method: in a sample containing 0.25% (mass fraction) (2500 ppm) nickel, the standard deviation σ is 0.0025% (mass fraction) (25 ppm), and the %RSD is about 1%; for vanadium at a content level of 0.25% (mass fraction) (2500 ppm) the standard deviation σ is 0.0014% (mass fraction) (14 ppm), and the %RSD is about 0.6%; these precision data were obtained from 20 tests on the same sample; if a sufficient number of X-ray counts can be collected, the fused bead method will be a technique comparable to or better than the pressed pellet method. Annex B Table B.5 Examples of precision from 20 repeated analyses of a sample by wavelength-dispersive X-ray fluorescence spectrometer (values in the table are severely [source unclear]; specific values [to be verified] [source unclear]).

Normative references: SH/T 0696-2000 Determination of nickel and vanadium in FCC equilibrium catalysts (hydrofluoric acid/sulfuric acid decomposition — atomic spectrometry) ASTM C 982 Standard guide for selecting components for energy-dispersive X-ray fluorescence (XRF) systems ASTM C1118 Standard guide for selecting components for wavelength-dispersive X-ray fluorescence (XRF) systems ASTM E 1172 Standard practice for describing and specifying wavelength-dispersive X-ray fluorescence spectrometers ASTM E 1361 Standard guide for correction of matrix effects in X-ray spectrometric analysis ASTM E 1621 Standard guide for X-ray emission spectrometric analysis ASTM E 1622 Standard practice for correction of spectral line overlap in wavelength-dispersive X-ray fluorescence spectrometry

Evidence note: [to be verified] and [source unclear] mark specific points that still require checking against the original text of the standard and do not indicate that they have been verified. Do not use these values or steps directly as a basis for work.

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