Micromeritics's ASAP2405 report explained (AWM)

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Device: ASAP2405 - 6-channel automatic sorption analyzer, (Micromeritics Corp., USA)

Sample: experimental active carbon RIB (Norit BV, Netherlands)

Adsorbate: N₂ at 78K

In this measurement/report:

Relative pressure range: 0.05 - 0.99

Analyses: adsorption/desorption isotherms,

BET and Langmuir specific surface area

t-plot (Harkins-Jura equation)

BJH (Barret-Joyner-Halenda) surface/volume mesopore analysis (adsorption/desorption)

All Figures are drawn according to the reported isotherm data by me (AWM).

Micromeritics Instrument Corporation      

   ASAP 2405N V1.01                  ADSORBATE: NITROGEN              PAGE  1

 

   SAMPLE DIRECTORY/NUMBER: DATA1   /142               START 08:37:51 06/26/98

   SAMPLE ID: R/B                                      COMPL 19:41:49 06/26/98

   SUBMITTER:                                          REPRT 09:35:18 06/29/98

   OPERATOR:                                           SAMPLE WT:    1.1288 g

   STATION NUMBER: 3       EQUIL INTERVAL:     5 sec   FREE SPACE:  97.4868 cc

 

                                  ANALYSIS LOG

 

      RELATIVE    PRESSURE    VOL ADSORBED    ELAPSED TIME     SATURATION

      PRESSURE     (mmHg)      (cc/g STP)       (HR:MN)       PRESS.(mmHg)

       x=p/p_s          p            V_a             time            p_s

                                                  3:02          751.057

       0.0587       44.071       314.2087         3:27

       0.0792       59.454       323.3588         3:47

       0.1324       99.427       337.2521         4:07

       0.1441      108.249       339.3304         4:16

       0.1673      125.636       342.7346         4:26

       0.2003      150.418       346.7142         4:37

       0.2483      186.494       351.5293         4:48

       0.3459      259.759       359.5118         5:01     ◄◄◄ p/p_s≈0.4 - hysteresis loop

                                                  5:03          750.953

       0.4457      334.689       366.2021         5:13

       0.5572      418.388       373.2755         5:27

       0.6436      483.263       379.0942         5:37

       0.7470      560.855       387.4077         5:54

       0.7969      598.292       391.7355         6:02

       0.8348      626.691       395.1406         6:09

       0.8701      653.209       398.2824         6:17

       0.9019      677.018       400.7671         6:23

       0.9198      690.459       402.3520         6:28

       0.9364      702.939       404.1616         6:33

       0.9500      713.115       406.0604         6:39

       0.9619      722.018       408.0504         6:44

       0.9689      727.219       409.6730         6:48

       0.9757      732.356       411.6911         6:53

       0.9812      736.465       413.5470         6:5716            ◄◄◄ V_t=V(p/p_s≈0.98)

       0.9835      738.199       414.6281         7:01

                                                  7:05          750.540

       0.9878      741.345       416.8401         7:06

       0.9892      742.436       418.0067         7:10

====== 0.9947 ==== 746.546 ===== 420.8760 ======= 7:16 <=============== ◄◄◄ p close to p_s

       0.9810      736.272       419.6332         7:19

       0.9719      729.402       418.1166         7:23

       0.9643      723.688       416.7538         7:27

       0.9643      723.688       416.5946         7:28

       0.9534      715.483       414.5608         7:34

       0.9380      703.899       412.4948         7:40

       0.9296      697.563       411.3706         7:44

       0.9031      677.722       409.2945         7:50

       0.8642      648.473       407.3190         7:57

       0.8286      621.755       405.7912         8:04

       0.8027      602.331       404.9170         8:08

       0.7285      546.619       402.5403         8:16

       0.6567      492.754       400.3286         8:23

       0.5546      416.080       396.8762         8:33

                                                  9:07          750.178

       0.4544      340.847       370.4437         9:29     ◄◄◄ p/p_s≈0.4 - hysteresis loop

       0.3507      263.102       360.4513         9:44

       0.2492      186.944       352.1268         9:58

       0.2003      150.288       347.0935        10:10

       0.1536      115.191       341.1276        10:23

       0.1018       76.394       330.9598        10:41

       0.0517       38.814       310.9733        11:05

Adsorption/desorption isotherm of N₂ on active carbon RIB (Norit), T=78K

 

 

 

                      Micromeritics Instrument Corporation      

   ASAP 2405N V1.01                  ADSORBATE: NITROGEN              PAGE  4

 

   SAMPLE DIRECTORY/NUMBER: DATA1   /142               START 08:37:51 06/26/98

   SAMPLE ID: R/B                                      COMPL 19:41:49 06/26/98

   SUBMITTER:                                          REPRT 09:35:18 06/29/98

   OPERATOR:                                           SAMPLE WT:    1.1288 g

   STATION NUMBER: 3       EQUIL INTERVAL:     5 sec   FREE SPACE:  97.4868 cc

 

                             BET SURFACE AREA REPORT

 

          BET SURFACE AREA:        1190.1411   +/-   26.5809   sq. m/g

          SLOPE:                      0.003682 +/-    0.000081

          Y-INTERCEPT:               -0.000025 +/-    0.000011

          C:                       -148.159561

          VM:                       273.394623 cc/g STP

          CORRELATION COEFFICIENT: 9.99276E-01

 

             RELATIVE          VOL ADSORBED                1/

             PRESSURE           (cc/g STP)           [VA(Po/P - 1)]

               x=p/p_s              V_a                y_BET=1/[V_a(1/x – 1)   

              0.0587             314.2087                0.000198

              0.0792             323.3588                0.000266

              0.1324             337.2521                0.000452

              0.1673             342.7346                0.000586

              0.2003             346.7142                0.000722

 

 

Adsorption isotherm of N₂ on active carbon RIB (Norit), T=78K – linear form of BET equation

This method gives reliable results for solids that do not contain large amount of micropores or supermicropores and mesopores are rather large, i.e. surface of the solid may be well approximated by the flat surface. S_BET[m²/g] = 4.35·V_a,BET[cc/g STP] – determined from the linear plot.

 

                      Micromeritics Instrument Corporation      

   ASAP 2405N V1.01                  ADSORBATE: NITROGEN              PAGE  6

 

   SAMPLE DIRECTORY/NUMBER: DATA1   /142               START 08:37:51 06/26/98

   SAMPLE ID: R/B                                      COMPL 19:41:49 06/26/98

   SUBMITTER:                                          REPRT 09:35:18 06/29/98

   OPERATOR:                                           SAMPLE WT:    1.1288 g

   STATION NUMBER: 3       EQUIL INTERVAL:     5 sec   FREE SPACE:  97.4868 cc

 

                          LANGMUIR SURFACE AREA REPORT

 

          LANGMUIR SURFACE AREA:   1576.9810   +/-    5.7505   sq. m/g

          SLOPE:                      0.002760 +/-    0.000010

          Y-INTERCEPT:                0.000026 +/-    0.000001

          b:                          0.009364

          VM:                       362.257965 cc/g STP

          CORRELATION COEFFICIENT: 9.99980E-01

 

             RELATIVE          VOL ADSORBED                1/

             PRESSURE           (cc/g STP)             [VA*Po/P]

               x=p/p_s               V_a                   y_L=1/[V_a/x]   

              0.0587             314.2087                0.000187

              0.0792             323.3588                0.000245

              0.1324             337.2521                0.000393

              0.1673             342.7346                0.000488

              0.2003             346.7142                0.000578

 

 

 

Adsorption isotherm of N₂ on active carbon RIB (Norit), T=78K – linear form of Langmuir equation

(This method gives results that are applicable for strongly microporous solids, having only small share of mesopores. Though Langmuir model has nothing to do with micropores, it approximates well enough the course of adsorption in micropores close to micropore saturation.
For microporous solid – having practically no “external area”, the “specific surface area” obtained formally from this analysis should be replaced by the “micropore volume” or adsorption capacity. However, specific surface area may be still used for comparisons) S_L[m²/g] = 4.35·V_a,L[cc/g STP] – determined from the linear plot.

                      Micromeritics Instrument Corporation      

   ASAP 2405N V1.01                  ADSORBATE: NITROGEN              PAGE  8

 

   SAMPLE DIRECTORY/NUMBER: DATA1   /142               START 08:37:51 06/26/98

   SAMPLE ID: R/B                                      COMPL 19:41:49 06/26/98

   SUBMITTER:                                          REPRT 09:35:18 06/29/98

   OPERATOR:                                           SAMPLE WT:    1.1288 g

   STATION NUMBER: 3       EQUIL INTERVAL:     5 sec   FREE SPACE:  97.4868 cc

 

                            MICROPORE ANALYSIS REPORT

 

             MICROPORE VOLUME:             0.353311 cc/g

             MICROPORE AREA:             765.7809   sq. m/g

             EXTERNAL SURFACE AREA:      424.3603   sq. m/g

             SLOPE:                       27.434721 +/-    2.557187

             Y-INTERCEPT:                228.414215 +/-   10.229213

             CORRELATION COEFFICIENT:   9.87217E-01

 

             RELATIVE           STATISTICAL           VOL ADSORBED

             PRESSURE          THICKNESS,(A )          (cc/g STP)

               x=p/p_s                 t_HJ                   V_a           

              0.0587                3.325               314.2087

              0.0792                3.510               323.3588

              0.1324                3.916               337.2521

              0.1441                3.998               339.3304

              0.1673                4.155               342.7346

              0.2003                4.371               346.7142

              0.3459                5.316               359.5118

              0.4457                6.028               366.2021

              0.5572                6.970               373.2755

 

             THICKNESS VALUES USED IN THE LEAST-SQUARES ANALYSIS

             WERE BETWEEN   3.500 AND   5.000 A .  ◄◄◄◄ thickness range (3.54Å =t_mono)

 

                                                       0.500

             t = [   13.9900/(    0.0340 - log(P/Po))]             ◄◄◄◄ HJ equation

 

             SURFACE AREA CORRECTION FACTOR IS  1.000.

 

 

In this t-plot report:

EXTERNAL SURFACE AREA, S_ext = SLOPE*4.3532*t_mono  (surface for pores larger than micropores)

MICROPORE VOLUME, V_micro = Y-INTERCEPT*0.0015468  (recalculates[cc/g STP]into[cc/g])

MICROPORE AREA, S_micro = S_BET - S_ext

 

Adsorption isotherm of N₂ on active carbon RIB (Norit), T=78K – t-plot (de Boer)

 

 

For microporous solids the Halsey (aka Frenkel-Halsey-Hill, FHH) isotherm equation is also often used in t-plot. However, this equation produces negative micropore volume estimates for solids with small amounts of micropores. Generally, the HJ isotherm is more reliable in this respect. If the low pressure data (micropore range) is available, the t/F-plot (by Kadlec) may be used. The most general is the a_s-method (alpha-s) which relies on comparison of sample isotherm with isotherm measured on some standard adsorbent.

                      Micromeritics Instrument Corporation      

   ASAP 2405N V1.01                  ADSORBATE: NITROGEN              PAGE 10

 

   SAMPLE DIRECTORY/NUMBER: DATA1   /142               START 08:37:51 06/26/98

   SAMPLE ID: R/B                                      COMPL 19:41:49 06/26/98

   SUBMITTER:                                          REPRT 09:35:18 06/29/98

   OPERATOR:                                           SAMPLE WT:    1.1288 g

   STATION NUMBER: 3       EQUIL INTERVAL:     5 sec   FREE SPACE:  97.4868 cc

BJH (Barret-Joyner-Halenda) pore distribution

                     BJH ADSORPTION PORE DISTRIBUTION REPORT     ◄◄◄◄ ADSORPTION

 

    PORE DIAMETER    AVERAGE   INCREMENTAL CUMULATIVE  INCREMENTAL CUMULATIVE 

        RANGE        DIAMETER  PORE VOLUME PORE VOLUME  PORE AREA   PORE AREA 

         (A )          (A )      (cc/g)      (cc/g)     (sq. m/g)   (sq. m/g) 

     d_max -  d_min      d_a          ΔV      ΣΔV(d < d_min)     ΔS       ΣΔS(d < d_min) 

    1813.6- 1599.0    1692.6     0.001922    0.001922      0.045       0.045  

    1599.0- 1195.7    1339.1     0.003665    0.005587      0.109       0.155  

    1195.7- 1050.2    1113.3     0.001800    0.007387      0.065       0.220  

    1050.2-  817.0     904.1     0.003110    0.010498      0.138       0.357  

     817.0-  640.6     707.0     0.003424    0.013922      0.194       0.551  

     640.6-  526.5     572.0     0.002779    0.016701      0.194       0.745  

     526.5-  404.3     448.9     0.003447    0.020148      0.307       1.052  

     404.3-  320.2     352.1     0.003355    0.023503      0.381       1.433  

     320.2-  255.6     280.3     0.003252    0.026755      0.464       1.898  

     255.6-  210.3     228.3     0.002903    0.029657      0.509       2.406  

     210.3-  160.3     178.2     0.004728    0.034385      1.061       3.468  

     160.3-  126.9     139.4     0.006349    0.040735      1.822       5.289  

     126.9-  103.8     112.8     0.007203    0.047938      2.555       7.844  

     103.8-   83.6      91.2     0.009598    0.057536      4.208      12.052  

      83.6-   59.2      66.7     0.020065    0.077601     12.038      24.090  

      59.2-   47.1      51.5     0.014658    0.092259     11.392      35.482  

      47.1-   36.6      40.2     0.019253    0.111512     19.150      54.632  

      36.6-   29.8      32.3     0.019838    0.131349     24.551      79.183  

      29.8-   24.5      26.5     0.026617    0.157967     40.196     119.379  

      24.5-   22.2      23.2     0.017230    0.175197     29.719     149.098  

      22.2-   20.6      21.3     0.015188    0.190385     28.484     177.582  

      20.6-   19.5      20.0     0.013890    0.204275     27.712     205.294  

      19.5-   19.0      19.3     0.009011    0.213286     18.713     224.007  

 

 

BJH estimates of pore volume and surface area distributions correspond here to the cylindrical pore model (compare any pair of(4ΔV/ΔS) and (d_d) )

                      Micromeritics Instrument Corporation      

   ASAP 2405N V1.01                  ADSORBATE: NITROGEN              PAGE 17

 

   SAMPLE DIRECTORY/NUMBER: DATA1   /142               START 08:37:51 06/26/98

   SAMPLE ID: R/B                                      COMPL 19:41:49 06/26/98

   SUBMITTER:                                          REPRT 09:35:18 06/29/98

   OPERATOR:                                           SAMPLE WT:    1.1288 g

   STATION NUMBER: 3       EQUIL INTERVAL:     5 sec   FREE SPACE:  97.4868 cc

BJH (Barret-Joyner-Halenda) pore distribution

                     BJH DESORPTION PORE DISTRIBUTION REPORT     ◄◄◄◄ DESORPTION

 

    PORE DIAMETER    AVERAGE   INCREMENTAL CUMULATIVE  INCREMENTAL CUMULATIVE 

        RANGE        DIAMETER  PORE VOLUME PORE VOLUME  PORE AREA   PORE AREA 

         (A )          (A )      (cc/g)      (cc/g)     (sq. m/g)   (sq. m/g) 

     d_max  -  d_min      d_d          ΔV     ΣΔV(d < d_min)     ΔS       ΣΔS(d < d_min) 

    3670.6- 1041.1    1228.9     0.002072    0.002072      0.067       0.067  

    1041.1-  708.4     812.0     0.002572    0.004644      0.127       0.194  

     708.4-  560.9     617.1     0.002349    0.006993      0.152       0.346  

     560.9-  432.7     479.9     0.003857    0.010850      0.322       0.668  

     432.7-  327.9     365.4     0.003681    0.014531      0.403       1.071  

     327.9-  289.9     306.4     0.002041    0.016572      0.266       1.337  

     289.9-  213.0     239.2     0.003800    0.020371      0.636       1.973  

     213.0-  153.5     173.1     0.003706    0.024078      0.856       2.829  

     153.5-  122.5     134.2     0.002989    0.027067      0.891       3.720  

     122.5-  106.8     113.4     0.001730    0.028796      0.610       4.330  

     106.8-   77.9      87.4     0.005084    0.033880      2.328       6.658  

      77.9-   61.5      67.5     0.005109    0.038989      3.029       9.687  

      61.5-   46.8      51.8     0.008903    0.047892      6.880      16.567  

      46.8-   37.3      40.7     0.086943    0.134835     85.467     102.034  

      37.3-   30.1      32.7     0.027577    0.162412     33.715     135.749  

      30.1-   24.6      26.6     0.021850    0.184263     32.864     168.613  

      24.6-   22.2      23.2     0.015267    0.199530     26.314     194.927  

      22.2-   20.0      20.9     0.020243    0.219773     38.692     233.619  

      20.0-   17.5      18.5     0.041958    0.261730     90.566     324.185  

 

BJH estimates of pore volume and surface area distributions correspond here to the cylindrical pore model (compare any pair of(4ΔV/ΔS) and (d_d) )

                      Micromeritics Instrument Corporation      

   ASAP 2405N V1.01                  ADSORBATE: NITROGEN              PAGE 24

 

   SAMPLE DIRECTORY/NUMBER: DATA1   /142               START 08:37:51 06/26/98

   SAMPLE ID: R/B                                      COMPL 19:41:49 06/26/98

   SUBMITTER:                                          REPRT 09:35:18 06/29/98

   OPERATOR:                                           SAMPLE WT:    1.1288 g

   STATION NUMBER: 3       EQUIL INTERVAL:     5 sec   FREE SPACE:  97.4868 cc

 

                                SUMMARY REPORT

 

 

                                     AREA

 

   BET SURFACE AREA:                                       1190.1411   sq. m/g

 

   LANGMUIR SURFACE AREA:                                  1576.9810   sq. m/g

 

   SINGLE POINT SURFACE AREA AT P/Po 0.2003:               1207.0052   sq. m/g

 

   BJH CUMULATIVE ADSORPTION SURFACE AREA OF PORES

    BETWEEN     17.0000 AND   3000.0000 A  DIAMETER:        224.0069   sq. m/g

 

   BJH CUMULATIVE DESORPTION SURFACE AREA OF PORES

    BETWEEN     17.0000 AND   3000.0000 A  DIAMETER:        324.1851   sq. m/g

 

   MICROPORE AREA:                                          765.7809   sq. m/g

 

 

 

                                    VOLUME

 

   SINGLE POINT TOTAL PORE VOLUME OF PORES LESS THAN

      1195.7146 A  DIAMETER AT P/Po 0.9835:                   0.641347 cc/g

 

   BJH CUMULATIVE ADSORPTION PORE VOLUME OF PORES

    BETWEEN     17.0000 AND   3000.0000 A  DIAMETER:          0.213286 cc/g

 

   BJH CUMULATIVE DESORPTION PORE VOLUME OF PORES

    BETWEEN     17.0000 AND   3000.0000 A  DIAMETER:          0.261730 cc/g

 

   MICROPORE VOLUME:                                          0.353311 cc/g

 

 

                                  PORE SIZE

 

   AVERAGE PORE DIAMETER (4V/A BY LANGMUIR):                 16.2677   A

 

   BJH ADSORPTION AVERAGE PORE DIAMETER (4V/A):              38.0855   A

 

   BJH DESORPTION AVERAGE PORE DIAMETER (4V/A):              32.2939   A

 

Area occupied by the adsorbate S_a [m²/g]= 4.35·V_a [cc/g STP]

Single point BET area: S_1p(x≈0.2)=4.35·(1-x)·V_a(x)

Volume occupied by the adsorbate V_liq [cc/g] = 0.0015468·V_a [cc/g STP]

 

(2V/A) => 2 · “pore volume” / “pore area” – average “hydraulic” pore diameter (slit-shaped pores)

(4V/A) => 4 · “pore volume” / “pore area” – average “hydraulic” pore diameter (cyllindrical pores)

(6V/A) => 6 · “pore volume” / “pore area” – average “hydraulic” pore diameter (spherical pores)

where: “pore volume” is the amount adsorbed [cc/g STP] recalculated into “adsobate volume” [cc/g]

Average pore diameter is calculated from Single point Total pore volume, V, and Langmuir (here for microporous solids) or BET (other solids) surface area, A.

BJH ads/des average pore diameter is the average mesopore diameter calculated as above from S_meso and V_meso

The use of Langmuir area estimate for microporous solids has very limited sense (and should be used only for comparisons between adsorbents). It comes from practical reasons – the shape of adsorption isotherm on microporous solids close to completion of micropores is generally more similar to Langmuir isotherm close to monolayer filling than to BET multilayer. Thus, in 0.05 – 0.2 region such experimental isotherm is more likely to follow the Langmuir than BET isotherm course. If the solid contains comparable amounts of micropores and meso- + macropores, then neither model may simulate such behavior properly.

The (4V/A) term used in estimation of pore average sizes corresponds to the assumed cylindrical model of pores. However, this assumption “sits” also in BJH estimates of pore volume and surface area distributions!

Adsorption/desorption isotherm of N₂ on active carbon RIB (Norit), T=78K.

Differential mesopore size distribution DV/Dd (BJH method).

Differences betwee ads/des result from discrepancies between adsorbate structure and the model of open-ended cylindrical capillaries

 

Adsorption/desorption isotherm of N₂ on active carbon RIB (Norit), T=78K.

Differential logarytmic mesopore size distribution DV/Dlog₁₀d (BJH method) (large pores are emphasized) Differences betwee ads/des result from discrepancies between adsorbate structure and the model of open-ended cylindrical capillaries

Adsorption/desorption isotherm of N₂ on active carbon RIB (Norit), T=78K.

Cumulative distribution of of mesopore volume V(2r<d) (BJH method).

Differences betwee ads/des result from discrepancies between adsorbate structure and the model of open-ended cylindrical capillaries

 

Adsorption/desorption isotherm of N₂ on active carbon RIB (Norit), T=78K.

Cumulative distribution of of mesopore surface area S_meso(2r<d) (BJH method).

Differences betwee ads/des result from discrepancies between adsorbate structure and the model of open-ended cylindrical capillaries

Adsorption/desorption isotherm of N₂ on active carbon RIB (Norit), T=78K.

Differential distribution of mesopore surface area DS/Dd (BJH method).

Differences betwee ads/des result from discrepancies between adsorbate structure and the model of open-ended cylindrical capillaries

Adsorption/desorption isotherm of N₂ on active carbon RIB (Norit), T=78K.

Differential logarithmic distribution of mesopore surface area DS/Dlog₁₀d (BJH method) (large pores are emphasized). Differences betwee ads/des result from discrepancies between adsorbate structure and the model of open-ended cylindrical capillaries