Natural Gas Storage on Nanoporous Biocarbon*Sarah Barker, *Carol Faulhaber, Jacob Burress, Peter Pfeifer

Physics Department, University of Missouri-Columbia

*Work done at University of Missouri-Columbia as part of the ALL-CRAFT Internship Program

Introduction:Natural gas adsorption on activated carbons has shown promise in addressing thelimitations of the storage of natural gas as an alternative fuel. The Alliance for Collaborative Research in Alternative Fuel Technology, ALL-CRAFT, produces nanoporous biocarbon from agricultural waste corn cob that has metthe DOE’s goals for Adsorbed Natural Gas(ANG) storage, figure 1. The methane uptakeis measured gravimetrically, figure 2, and volumetrically. The experimental procedurehas been optimized for time without loss ofaccuracy. Methane isotherms were used todetermine the pore size distribution.

Fig. 1: Missouri corn cob starting material and finished briquette.

Fig. 2: Gravimetric sample cell and methane adsorption set-up.

Conclusions:

The results of the equilibration and outgassing experiments have enabled the lab to test a sample of carbon in about one-fourth of the original time. In addition several samples of carbon were tested and a complete isotherm was performed on one sample using the results of the equilibration andoutgassing experiments. Using the data collected from the isotherm, the pore size distribution and deliverable amount of methane were found. Analysis of the properties of carbon has lead to increased storage capacity. Our current best performer, S-33/k, has a storage value of 115-119 grams methane for liter carbon, compared to the DOE target of 118 g/L. Further analysis needs to be to help optimize the carbons for both methane storage.

Acknowledgements:

This research is based on work supported by the National Science Foundation, under grant No. EEC-0438469, and the University of Missouri.

Outgassing time experiment:

The outgassing time optimization experimentdetermined that a minimum outgassing timeof two hours is required to maintain theaccuracy of the uptake results, figure 3. Alloutgassing was done at 400°C.

Fig. 3: This bar graph shows that the two hour outgassing time is the minimum time required.

Equilibration time experiment:

This experiment was done at 500 psig onsample B-21/k. The outcome of theequilibration time experiment has reducedthe equilibration time from four hours to onehour, figure 4.

Fig. 4: This plot shows that the 1 hour is the minimum time needed for equilibration

Methane Storage:

The storage of methane is determined gravimetrically. This is done at room temperature (293 K) and typically at 500 psig (3.5 MPa). Methane adsorption isotherms at pressures from 25 to 500 psig, figure 5, are also done to determine deliverable pressure as well as to determine the pore size distribution, PSD, figure 6.

0.000

0.100

0.200

0.300

0.400

0.500

0.4

- 0.6

0.6

- 1.0

1.0

- 1.5

1.5

- 2.0

2.0

- 4.0

4.0

- 6.0

6.0

- 10.

0

10 -

15

15 -

20

20 -

50 >

50

Pore Width Range [nm]

Po

re V

olu

me

[cc

/g]

Fig. 6 PSD determined from methane isotherm. This shows a predominance of nanopores with width around 1.1 nm.

Fig. 5 S-33/k isotherm compared with compressed natural gas and DOE Target