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4、2.9585 PHONE. Loss on Ignition (LOI) for Fresh, Regenerated, Used, and Spent Catalysts, Catalyst Supports, and Adsorbents UOP Method 954-11 Scope This method is for determining the loss on ignition (LOI) in air, using a specified ignition temperature and time, for fresh, regenerated, used, and spent
5、 catalysts, catalyst supports, and molecular sieves of various shapes and sizes. This method is quantitative down to 0.1 mass-%. The method is not water specific; any components that volatilize at the selected ignition temperature, for example, carbon, chlorine, and fluorine, are also included in th
6、e LOI value. Some components, for example sulfates, may volatilize fully or partially depending on ignition time and temperature. Mass gains are possible with catalysts that contain reduced metals. The criteria for selecting the temperature and time for the LOI are based on the composition of the sa
7、mple and the expected volatility of the impurities. Examples are listed in Procedure, Table 1. Length of time at temperature is dependent on the application of the LOI value. For example, it is important to drive off defined volatiles, such as halogens, for the determination of platinum concentratio
8、n. References UOP Method 918, “Collection use a porcelain cover, Cat. No. Z247235 (optional, see Note 1) Crucibles, porcelain, low, wide-form, 30-, 50-, and 100-mL capacities, Fisher Scientific, Cat. Nos. 07-955E, -955F, and 955G, respectively, with covers (optional) 07-970G, -970H, and 970J, respec
9、tively. For powder samples, a 35-mL round bottom crucible may be used to reduce the depth of the material, Fisher Scientific, Cat. No, 08-103D; the -970G cover will fit this crucible. Desiccator, 250-mm ID, and porcelain plate, Fisher Scientific, Cat. Nos. 08-631B and 08-636F, respectively Furnace,
10、muffle, capable of operation at 1000 15C, Fisher Scientific, Cat. No. 10-550-126 Hot plate, variable temperature to 250C, Fisher Scientific, Cat. No. 11-497-2A Thermometer, surface, with temperature probe, Omega Engineering, Cat. Nos. HH81 and 88108K, respectively Tongs, crucible, 530- and 230-mm le
11、ngth, Fisher Scientific, Cat. Nos. 15-207 and 15-186, respectively Reagents and Materials Reference to catalog numbers and suppliers are included as a convenience to the method user. Other suppliers may be used. Desiccant, molecular sieve, activated, moisture indicating, type 4A, 8-12 mesh, Cole-Par
12、mer, Cat. No. M1373, or, Drierite, indicating, 8-mesh, Fisher Scientific, Cat. No. 07-578-3A Grease, high-vacuum, Fisher Scientific, Cat. No. 14-635-5D Introduction There are a number of reasons for determination of the LOI. In some cases, the volatile component, typically water, is of interest. In
13、other cases, the intent is to place samples at a baseline state so that some other analysis may be made, and comparisons to another material are thus made on the same basis. The importance of the LOI value will impact the number of replicate samples analyzed. For general purposes, such as base metal
14、 determination, a single LOI determination is sufficient. For determination of noble metal on catalyst to meet specifications, duplicate LOI analyses are generally requested. Check the specific information for the material being analyzed to determine the LOI requirements before proceeding. In all ca
15、ses, the LOI must be performed with the sample in the appropriate physical state. For analysis of material to be shipped, the sample used to obtain the LOI must be in the same state as the sample when shipped: whole pill (sphere), whole extrudate, or powder; not ground. For noble metal analysis, sin
16、ce the noble metals are determined on a ground sample, the LOI must also be determined on a ground sample. Check the requirements or specifications of the material being analyzed, or any established method, standard operating procedure, or work instruction. For analyses where the LOI is used to calc
17、ulate the analysis results to a volatile free (VF) basis, always weigh the samples for LOI and elemental analysis at the same time. Where duplicate LOIs are stipulated, report the average of the two LOI values. If the two values differ by more than that expected from Precision, rerun both the LOIs a
18、nd the associated elemental analysis, since the sample may have gained or lost moisture during the interim. 954-11 3 of 8 For certain samples, or for experimental purposes, it may be desirable to measure an LOI to a constant weight. This procedure is described in Appendix B. Procedure The analyst is
19、 expected to be familiar with general laboratory practices and the equipment being used. CAUTION: Spent or used catalysts may ignite violently if introduced directly from the hot plate into the muffle furnace at 900C, due to carbon or hydrocarbon combustion. For this application, the sample is warme
20、d on a hot plate for an hour, or longer if necessary until the material is no longer visually wet or fuming. It is then introduced into the muffle furnace set at 500C or less for a specified time. The sample is then placed into a second muffle furnace set at the desired final temperature, often 900C
21、. Alternatively, the temperature of the first muffle furnace can be ramped to 900C, or other final temperature, over a period of time. The additional hardware required and the procedure are described in Appendix A. Materials that contain a high moisture level may be analyzed in the same manner. Samp
22、les should be introduced into the furnace in small batches to avoid overloading the furnace particularly for samples with specific characteristics, e.g, spent or used catalysts, etc. Typical LOI temperatures and times for various sample types are listed in Table 1. These are only examples. Specific
23、conditions are to be established for individual applications. If desired, more than one sample can be placed, each in its own crucible, into the muffle furnace at one time. Each crucible must then be marked for identification. Table 1 Time at Specified Temperature Sample Type Typical LOI Temperature
24、, C Typical Time in Muffle Furnace, hours Catalysts with Tungsten or Molybdenum 500 1 Catalysts with Potassium 700 11 Catalysts 900 11 Molecular sieves 1,000 1 Spent or used catalyst 500 to 900 See caution statement above or Appendix A.2 Calcined supports 700 or 900 1 1For platinum analysis, use 6 h
25、ours 2For convenience, this could be timed to be run overnight. 1. Obtain a representative portion of the catalyst, catalyst support, or adsorbent to be analyzed. Refer to UOP Method 918, “Collection & Grinding of Adsorbents and Catalysts for Analysis,” for sampling procedures 2. Ignite a porcelain
26、crucible and a crucible cover by heating for 20 minutes in a muffle furnace at the specified LOI temperature for the catalyst or adsorbent. The crucible cover is optional, and maybe used to contain samples that are disturbed by vigorous outgassing, or to minimize the loss of powder samples particula
27、rly due to air currents caused when opening a sealed desiccator. The crucible cover needs to be heated only once per day. 4 of 8 954-11 An Inconel crucible is also satisfactory as an alternative (see Note 1). The muffle furnace should be calibrated according to the labs quality program. 3. Remove th
28、e crucible, and cover if used, from the furnace with tongs and place them in a desiccator containing a desiccant. Discretion must be used regarding the number of crucibles placed in the desiccator at one time since an overheated desiccator may shatter. When the top of the desiccant bed, or the indic
29、ator, turns from blue to pink, stir to redistribute. The desiccant should be replaced when it is one-third spent, as indicated by the color change. To minimize exposure to moist ambient air, the desiccator should be placed close to the balance. 4. Allow the crucible and cover to cool to ambient temp
30、erature. The cooling time will vary depending on the number of crucibles being cooled. 5. Remove the crucible only from the desiccator and immediately weigh the crucible to the nearest 0.0001 g. The crucible cover remains in the desiccator. The crucible must be handled with small tongs, not with bar
31、e hands. 6. Weigh 1 to 2 grams of the sample, to the nearest 0.0001 g, into the previously ignited crucible immediately after completing Step 5. Most catalysts and adsorbents are hygroscopic and should not be unnecessarily exposed to air. Take samples for other analyses, if required, at the same tim
32、e. 7. Preheat the crucible containing the sample on a hot plate, having a surface temperature of 105-110C, for approximately one hour. 8. Using crucible tongs, transfer the crucible containing the sample to the hot muffle furnace, which has been calibrated to the specified temperature. Spent or used
33、 catalysts may require two-stage heating in the muffle furnace, see CAUTION, above, and Appendix A. 9. Allow the sample to remain in the muffle furnace at the specified temperature for the specified length of time. When multiple crucibles are placed in the furnace, additional time may be required fo
34、r the furnace to return to the specified temperature. 10. Remove the crucible from the muffle furnace with the crucible tongs, place it in the desiccator, and cover it with a crucible cover. 11. Allow the crucible and cover to cool to ambient temperature. The cooling time will vary depending on the
35、number of crucibles being cooled in the desiccator, but may be up to one hour. Never allow the crucible to remain in the desiccator for more than one hour. Most catalyst and adsorbent samples are hygroscopic and may begin to pull moisture from the desiccant. 12. Weigh the uncovered crucible and cont
36、ents to the nearest 0.0001 g. The crucible must be handled with small tongs, not with bare hands. Calculations Calculate the LOI at the specified temperature using Equation 1: LOI, mass-% = B-A C-A100 (1) 954-11 5 of 8 where: A = mass of ignited crucible and sample, before heating, g B = mass of ign
37、ited crucible, g C = mass of ignited crucible and sample, after heating, g 100 = factor to convert g/g to mass-% Report Report the LOI value to two decimal places when the value is below 5 mass-%, or to one decimal place when the value is above 5 mass-%, at the specified temperature in degrees Celsi
38、us. State the mass-% gain in cases where oxidation has occurred. Unless otherwise directed, report the average of any replicates. Notes 1. A porcelain crucible is commonly used for this analysis, however, there are special circumstances wherein an Inconel crucible may be preferred. There may be less
39、 of a tendency for some samples to stick to an Inconel crucible, so if the same sample is to be reused for further testing, Inconel may have an advantage. Also, samples containing high levels of fluoride may degrade a porcelain crucible during heating, where this may not occur with an Inconel crucib
40、le. Perform comparison tests before switching to an Inconel crucible. 2. Classical methods or Thermogravimetric Analysis/Mass Spectroscopy (TGA/MS) can be used to establish the fate of individual components upon heating. Precision The precision statements were determined using UOP Method 999. Repeat
41、ability, Site Precision, and Reproducibility A nested design was carried out for determining LOI of six different catalysts with two analysts in each of four or five laboratories. Each analyst carried out two tests on each of two separate days. The total number of tests performed was 224. Using a st
42、epwise analysis of variance procedure, the within-day estimated standard deviation (esd) was calculated and is listed in Table 2. Two tests performed by the same analyst on the same day should not differ by more than the repeatability allowable difference shown in Table 2 with 95% confidence. Two te
43、sts performed in one laboratory by different analysts on different days should not differ by more than the site precision allowable difference shown in Table 2 with 95% confidence. Two tests performed by different analysts in different laboratories on different days should not differ by more than th
44、e allowable difference shown in Table 2 with 95% confidence. The data in Table 2 are a short-term estimate of repeatability. When the test is run routinely, a control standard and chart should be used to develop a better estimate of the long-term repeatability. Time for Analysis The elapsed time for
45、 one analysis is 0.5 hour in addition to the time in the muffle furnace and cool-down time. The labor requirement is 0.5 hour. 6 of 8 954-11 Table 2 Repeatability, Site Precision, and Reproducibility, mass-% Repeatability Site Precision Reproducibility Sample Temp, C Time, hours LOI, Mean Within- Da
46、y esd Allowable Difference Within- Lab esd Allowable Difference Between- Lab esd Allowable Difference Whole pill 700 1 0.82 0.040 0.12 0.068 0.21 0.094 0.30 Ground 700 5 4.44 0.040 0.12 0.076 0.24 0.113 0.38 Whole pill 900 1 1.63 0.043 0.13 0.065 0.19 0.129 0.45 Whole pill 900 1 4.77 0.049 0.15 0.11
47、9 0.35 0.122 0.36 Ground 900 5 1.99 0.028 0.08 0.103 0.31 0.241 0.84 Whole pill 900 1 3.95 0.041 0.12 0.075 0.22 0.099 0.30 Suggested Suppliers Cole-Parmer Instrument Company, 625 East Bunker Ct., Vernon Hills, IL 60061, USA (847-549-7600) Fisher Scientific Co., 711 Forbes Ave., Pittsburgh, PA 1521
48、9-4785, USA (412-490-8300) Omega Engineering, Inc., One Omega Dr., Stamford, CT 06907, USA (203-359-1660) Sigma-Aldrich, Milwaukee, WI 53201, USA (414-438-3850) www.sigma- 954-11 7 of 8 Appendix A Analysis of Spent and Used Catalysts Apparatus The following item is required in addition to, or as a
49、n alternative to, that listed in the body of the method. References to catalog numbers and suppliers are included as a convenience to the method user. Other suppliers may be used. Furnace, muffle, programmable, capable of operation at 1000 15C, Fisher Scientific, Cat. No. 10-650-126 (replaces furnace 10-550-126) Procedure CAUTION: Spent or used catalysts may ignite violently if introduced directly from the hot plate into the muffle furnace at 900C, due to carbon or hydrocarbon
