Presentation is loading. Please wait.

Presentation is loading. Please wait.

1 April 26, 2004 by Ricky Magee Columbian Chemicals Company STSA – Life without CTAB.

Similar presentations


Presentation on theme: "1 April 26, 2004 by Ricky Magee Columbian Chemicals Company STSA – Life without CTAB."— Presentation transcript:

1 1 April 26, 2004 by Ricky Magee Columbian Chemicals Company STSA – Life without CTAB

2 2 Outline Introduction Theory Results Comparison with CTAB surface area Surface Chemistry Effects New Developments Conclusions

3 3 Introduction Importance of Surface Area Traditional Surface Area Techniques Timeline of STSA at ASTM

4 4 Importance of Surface Area Surface area is one of the most important characteristics of the carbon black. Surface area of carbon black is a function of particle size, degree of aggregation and porosity. Therefore, surface area alone is not a reliable measure of particle size. In the absence of porosity, surface area values are an indication of a carbon blacks particle size (fundamental property). According to IUPAC convention, micropores are characterized by diameters less than 20 Å or 2 nm.

5 5 80 m 2 /g 100 m 2 /g 400 m 2 /g Effect of Aggregation and Porosity on Surface Area

6 6 Traditional Surface Area Tests AttributeCTABIodineNSA Surface Type MeasuredExternalTotal Affect of OxidationUnknownSevereMinimal PrecisionPoorGood DifficultyHighLow Set-up CostsMediumLowHigh

7 7 Timeline of STSA at ASTM D5816 – STSA approved as ASTM standard in 1995. D1765 (CB Classification System)– In 1997, STSA was added as a typical value in Table 1, with corresponding CTAB values deleted. D6556 – Combined NSA (D4820) and STSA (D5816) into a single standard in 2000. The NSA section was modernized and data interpretation simplified. D3765 – In 2003, estimated CTAB values of SRB-6 carbon blacks was added to CTAB method.

8 8 Theory Nitrogen Adsorption Saturated Vapor Pressure de Boer t-values and V a -t plots Pore filling model Application of CB t Equation

9 9 Nitrogen Adsorption The concentration of nitrogen is expressed as relative pressure (P/P o ). A relative pressure of 0.0 is measured at absolute vacuum, while a value of 1.0 is measured at nitrogens saturated vapor pressure (P o ). The typical range for measuring NSA (BET) is P/P o = 0.05 to 0.30.

10 10 Saturated Vapor Pressure Saturated vapor pressure is the pressure at which nitrogen gas condenses. It is based on atmospheric pressure and the temperature of the liquid nitrogen in the dewar. It is usually 10 - 20 mm Hg above ambient pressure due to impurities. Critical for measuring accurate STSA values.

11 11 Saturated Vapor Pressure Elevation Sea Level 900 m Atm. Pressure 760 685 Sat. Vapor Press. 775 700 P/P o Value = 0.1 78 70 P/P o Value = 0.2 155 140 P/P o Value = 0.3 233 210 All values in mm Hg

12 12 Thickness Model

13 13 Thickness Equations 13.99 de Boer t = 0.034 - log P/P o CB t = 0.88 (P/P o ) 2 + 6.45 (P/P o ) + 2.98 Carbon Black t curve based on N762

14 14 V a –t Plot 0123456789 0 10 20 30 40 50 60 30 m /g 2 60 m /g 2 90 m /g 2 Thickness ( Å ) Vol. Ads. (cc/g)

15 15 Pore Filling Model P/P o = 0.0P/P o = 0.05 P/P o = 0.2 P/P o > 0.2

16 16 Adsorption Isotherms 0.00.10.20.30.40.50.60.70.80.9 0 20 40 60 80 100 120 140 N110 N326 N660 N472 Vol. Adsorbed (cc/g) Relative Pressure

17 17 V a –t Plot for Standard Carbon Blacks based on CB t equation 0123456789101112 0 20 40 60 80 100 120 P/P o = 0.2 N472 N110 N326 N660 P/P o = 0.5 Thickness ( Å ) Vol. Adsorbed (cc/g)

18 18 Results STSA versus CTAB Surface Chemistry Precision Statements

19 19 Tread Carbon Blacks NSA STSA CTAB N110 135.3 119.7 123.6 N121 122.8 116.5 120.4 N220 116.0 107.7 109.5 N234 117.2 111.2 115.6 N330 76.6 74.7 80.0 N339 91.0 88.5 94.8 All values in m 2 /g

20 20 Carcass Carbon Blacks NSA STSA CTAB N539 38.4 37.7 41.0 N550 38.1 38.2 38.6 N650 36.4 35.3 38.9 N660 33.0 33.1 34.9 N762 25.7 25.7 26.9 N787 29.7 29.6 31.0 All values in m 2 /g

21 21 CTAB versus STSA 020406080100120140 0 20 40 60 80 100 120 140 STSA (m 2 /g) CTAB (m 2 /g) R 2 = 0.9985

22 22 Effect of Surface Oxidation on CTAB Measurements Sample # 1 # 2 # 3 Oxygen (%) 2.0 1.9 1.5 STSA (m 2 /g) 86.4 85.7 90.8 CTAB (m 2 /g) 100.1 97.5 97.7 Difference -13.7 -11.8 -6.9

23 23 Sample Sample # 1 # 2 # 3 # 1 # 2 # 3 STSA (m 2 /g) 86.3 86.3 90.0 Initial Value 86.4 85.7 90.8 Initial Value 86.4 85.7 90.8 CTAB (m 2 /g) 87.3 85.9 89.2 Initial Value 100.1 97.5 97.7 Initial Value 100.1 97.5 97.7 Difference -1.0 0.4 0.8 Effect of Surface Oxidation on CTAB Measurements

24 24 Effect of Heat Treatment on ASTM SRB-50 5 10 15 2025NSA Iodine N683 N660N762N220N135 N330 %Change

25 25 Effect of Heat Treatment on ASTM SRB-5 -10.0 -7.5 -5.0 -2.5 0.0 2.55.0N683 N660N762N220 N135N330 %Change STSA CTAB

26 26 Precision N121 Control Chart Run # 159121620 -2.5 -1.5 -0.5 0.5 1.5 2.5 CTAB STSA Diff. From Mean (m 2 /g)

27 27 Effect of Solution Aging on CTAB Solutions 0102030405060 Run # 115 116 117 118 119 120 121 122 CTAB (m 2 /g)

28 28 Surface Area Precision Study from Original STSA Paper

29 29 Potential Errors in NSA/STSA Measurements Improper degassing time/temperature. Improper sample weight. Inaccurate or changing P o value.

30 30 NSA/STSA Control Chart using ASTM B-6 (N220) Mean = 109.6 ± 1.1 (ASTM = 110.0 ± 1.6) Mean = 105.4 ± 2.1 (ASTM = 105.4 ± 2.9) Data collected over a 4 month period

31 31 NSA/STSA Control Chart with P o Outliers Removed ( P >20mm Hg) Mean = 109.5 ± 1.1 (Previous = 109.6 ± 1.1) Mean = 105.4 ± 1.5 (Previous = 105.4 ± 2.1)

32 32 Effect of Dewar Stability A single sample of ASTM B-6 (N220) degassed at 300°C then run multiple times, measuring the P o after each run using the standard Gemini (600 ml) and a large volume (2 L) dewars.

33 33 Modified Gemini

34 34 Effect of Dewar Stability – 1 Hr. Equilibration Time NSA (m 2 /g)STSA (m 2 /g) 1 Hour Equil.Mean 3 3 Dewar #1 - Std (600 ml)110.01.83104.74.86 Dewar #2 - Std (600 ml)110.01.23104.32.16 Dewar #3 - Large (2 L)*109.90.18105.40.57 Dewar #3 - Large (+15 mm)*109.90.15105.30.33 * = Filled and covered overnight before analysis

35 35 Effect of Dewar Stability – 2 Hr. Equilibration Time NSA (m 2 /g)STSA (m 2 /g) 1 Hour Equil.Mean 3 3 Dewar #1 - Std (600 ml)110.20.60105.20.87 Dewar #2 - Std (600 ml)109.90.99104.21.95 Dewar #3 - Large (2 L)*109.90.15105.30.33 Dewar #3 - Large (+15 mm)*109.90.15105.30.33 * = Filled and covered overnight before analysis

36 36 P o Summary A minimum 2 hour dewar equilibration is required (longer is better). Large volume dewars allow improved precision. Other P o options exist for newer, higher-end instruments. Changes to D6556 are required based on this study.

37 37 Analysis Time Standard Value Standard Method (D6556) Modified Method (3 pt.) Sample IDNSASTSANSASTSANSASTSA (m 2 /g) A-6 (N134)143.9135.7142.1133.7142.7133.7 B-6 (N220)110.0105.4109.4104.6108.8105.3 C-6 (N326)78.379.278.379.177.679.8 D-6 (N762)30.629.630.429.030.729.2 E-6 (N660)36.035.135.534.735.133.8 F-6 (N683)35.334.134.733.234.632.8 Mean Values72.469.971.769.171.669.1

38 38 Analysis Time Standard Method (D6556)Modified Method (3 pt.) Sample IDAnalysis Degassing TotalAnalysis Degassing Total Time (min.) A-6 (N134)333063201030 B-6 (N220)30 60171027 C-6 (N326)233053171027 D-6 (N762)20305015520 E-6 (N660)19304915520 F-6 (N683)20305014519 Mean Values24.230.054.216.37.523.8

39 39 Conclusions STSA provides the following advantages over CTAB: over CTAB: l Improved precision and accuracy, provided proper attention to P o l Less affected by surface oxidation l Less operator time l Measured simultaneously with NSA l No reagent preparation


Download ppt "1 April 26, 2004 by Ricky Magee Columbian Chemicals Company STSA – Life without CTAB."

Similar presentations


Ads by Google