Test and Characterization of Some Zeolite Supported Gas 

Phase Desulfurization Sorbents 

by Charles Rong, Deryn Chu, and John Hopkins 

ARL-TR-4859 June 2009 

Approved for public release; distribution unlimited. 
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Army Research Laboratory 

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ARL-TR-4859 June 2009 

Test and Characterization of Some Zeolite Supported Gas 

Phase Desulfurization Sorbents 

Charles Rong, Deryn Chu, and John Hopkins 

Sensors and Electron Devices Directorate, ARL 

Approved for public release; distribution unlimited. 
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Test and Characterization of Some Zeolite Supported Gas Phase Desulfurization 

Sorbents 

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6. AUTHOR(S) 

Charles Rong, Deryn Chu, and John Hopkins 

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14. ABSTRACT 

This report presents the results of sulfidation and regeneration of mixed metal oxide supported on zeolite-Y for hydrogen 

sulfide (H2S) at 650 and 800 °C, along with results for unsupported mixed metal oxide. The capacity for the unsupported 

oxide was higher than that for the supported oxide, but the unsupported mixed metal oxide showed evidence of sintering at 

higher temperatures, which resulted in a decreased desulfurization capacity. The sulfidation capacity of the zeolite supported

mixed metal oxide, although it started with a lower capacity, was found to be independent of temperature at both 650 and 800 

°C, suggesting the mixed metal ions supported on zeolite are resistant to sintering at higher temperature, and they appear to 

have only surface interaction with H2S. 

15. SUBJECT TERMS

Desulfurization, sorbent, zeolite, hydrogen sulfide 

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19a. NAME OF RESPONSIBLE PERSON

Charles Rong 

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iii 

Contents 

List of Figures iv

List of Tables iv

Acknowledgments v

1. Introduction 1

2. Experimental 1

2.1 Materials..........................................................................................................................1 

2.1.1 Mixed Metal Oxide .............................................................................................1 

2.1.2 Zeolite Supported Mixed Metal Oxide................................................................2 

2.2 Characterization...............................................................................................................2 

2.3 Sulfidation and Regeneration Test ..................................................................................2 

3. Results and Discussion 3

3.1 Mixed Metal Oxide .........................................................................................................3

3.2 Mixed Metal Oxide Supported on Zeolite.......................................................................6 

3.3 Effect of Metal Ion on Zeolite Structure .........................................................................8 

4. Conclusions 10

5. References 11

List of Symbols, Abbreviations, and Acronyms 12

Distribution List 13 
iv 

List of Figures 

Figure 1. The schematic of the desulfurization reactor system. .....................................................3 

Figure 2. Sulfidation capacity of 5% CuO/CeO2 tested at 650 and 800 °C....................................4 

Figure 3. XRD of 5% CuO/CeO2 after being tested at 650 and 800 °C. ........................................4 

Figure 4. BET surface area of 50% CuO/CeO2 and 50% CuO/Al2O3 calcined at different 

temperatures...............................................................................................................................6 

Figure 5. Sulfidation capacity of Cu-Ce-zeolite tested at 650 and 800 °C.....................................7 

Figure 6. XRD of Cu-Ce-zeolite––upper: after being tested at both 650 and 800 °C; middle: 

after being calcined at 650 °C; and lower: as prepared. ...........................................................7 

Figure 7. XRD of Cu-zeolite—upper: after being tested at 800 °C and lower: after being 

calcined at 650 °C. .....................................................................................................................9 

Figure 8. XRD of Ce-zeolite—upper: after being tested at 800 °C and lower: after being 

calcined at 650 °C. .....................................................................................................................9 

List of Tables 

Table 1. Sulfidation/regeneration cycling results of 5% CuO/CeO2 at 650 and 800 °C. ...............4 

Table 2. BET results of 5% CuO/CeO2 before and after testing at 650 and 800 °C. .....................5 

Table 3. BET surface area (m2/g) of CuO/CeO2 oxides calcined at 650 °C...................................5 

Table 4. BET surface area (m2/g) of oxides calcined at different temperatures.............................5 

Table 5. Sulfidation/regeneration cycling results of Cu-Ce-zeolite at 650 and 800 °C..................7 

Table 6. BET surface area (m2/g) of Cu-Ce-zeolite........................................................................8 

Table 7. Sulfidation/regeneration cycling results of pure zeolite and metal ion exchanged 

zeolites tested at 800 °C............................................................................................................8 

Table 8. BET surface area (m2

/g) of pure zeolite and metal ion exchanged zeolites calcined 

at 800 °C and tested at 800 °C. ..................................................................................................9 
v 

Acknowledgments 

Part of the work was the result of a Collaborative Technology Alliance (CTA) staff rotation with 

the assistance provided by Tufts University. Zheng Wang, Mann Sakbodin, and Dr. Maria 

Flytzani-Stephanopoulos are gratefully acknowledged for their help with the sulfidation and 

regeneration measurements. We would also like to thank the U.S. Army Materiel Command for 

the support. 
vi 

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1 

1. Introduction 

The development of fuel cell technology and logistics fuel reformation technology for power 

generation in the battlefield has received much attention in the Science & Technology (S&T) 

community in recent years (1–5). One of the key issues to be understood and addressed is the 

desulfurization of logistics fuels such as JP-8, in which the sulfur content may be up to a few 

thousands ppm while commercial fuels contain less sulfur due to strict Environmental Protection 

Agency (EPA) requirements for low sulfur fuels. The sulfur contents in the logistics fuel must 

be reduced to a near zero level since fuel cells require a clean and essentially sulfur-free fuel 

stream for proper operation. The Army relies on JP-8 as a major logistics fuel; thus, the 

desulfurization of JP-8 becomes a unique problem to be solved for advanced energy conversion 

technology development. Technically, sulfur removal from the fuel can be achieved by either 

liquid phase desulfurization or gas phase desulfurization, and in most cases with high sulfur 

contents in the fuel, both of the liquid and gas phase processes may be required. 

Advanced energy conversion technology includes components such as fuel reformation and solid 

oxide fuel cell (SOFC) development. SOFCs have the advantages of using a non-noble-metal 

catalyst and working at high temperatures, and they are more versatile, being able to run on 

different fuels, than polymer electrolyte membrane fuel cells. JP-8 reformation converts liquid 

hydrocarbon fuel to a gaseous reformate consisting of hydrogen, carbon monoxide, carbon 

dioxide, water, and some lower molecular weight hydrocarbon molecules such as methane. 

SOFCs can be fed with this gas mixture as a suitable fuel stream as long as it is sulfur free. From 

a system integration and heat management point of view, SOFCs should be coupled closely with 

the fuel reformer. Therefore, gas phase desulfurization should be accomplished at a temperature 

range of 600 to 800 oC, the temperature at which both of the reformer and SOFC operate. 

Although the sulfur tolerance of the-state-of-the-art SOFC electrode material is improving, the 

gas phase desulfurization step at high temperature is still essential to SOFCs. Our report focuses 

on gas phase desulfurization at these high temperature conditions. 

2. Experimental 

2.1 Materials 

2.1.1 Mixed Metal Oxide 

The copper (Cu) and cerium (Ce) mixed metal oxide was prepared by hydrothermal synthesis 

and is described as follows. A 5% (in molar ratio) of copper to cerium (CuO/CeO2) was formed 

by reaction of copper nitrate (Cu(NO3)2), cerium nitrate (Ce(NO3)3), and potassium hydroxide 
2 

(KOH) in aqueous solution at 180 oC for 48 h. The product was then filtered out and washed 

with water thoroughly. It was further calcined at 650 or 800 °C for 4 h before the corresponding 

sulfidation test. 

2.1.2 Zeolite Supported Mixed Metal Oxide 

The copper and cerium oxide incorporated in zeolite-Y was prepared by ion-exchange method as 

described: 

• Cu-zeolite: 2 g of zeolite-Y was placed in 20 ml 0.5 M Cu(NO3)2 solution and stirred for 

48 h at room temperature. It was then filtered out, washed with water, and dried at 110 oC 

for 2 h. 

• Ce-zeolite: 2 g of zeolite-Y was placed in 20 ml 0.5 M Ce(NO3)2 solution (with a few 

drops of HNO3 added) and stirred for 48 h at room temperature. It was then filtered out, 

washed with water, and dried at 110 oC for 2 h. 

• Cu-Ce-zeolite: 1 g of Cu-zeolite was placed in 20 ml 0.014 M of Ce(NO3)3 solution with 

10–3 M HNO3, which is close to 1⁄4 of the exchangeable site of the zeolite, and stirred 

overnight. It was filtered out, washed with water, and dried at 110 oC for 2 h. The copper 

to cerium ratio on the zeolite support is expected to be larger than 0.05. 

2.2 Characterization 

The x-ray diffraction (XRD) results were obtained using a Rigaku Ultima III instrument with Cu 

Kα radiation with a Bragg-Brentano Configuration, and a Philips PW1840 X-ray Diffractometer 

with iron (Fe) Kα radiation. A Micromeritics ASAP 2010 instrument was used to measure the 

surface area of the samples. 

2.3 Sulfidation and Regeneration Test 

The sulfidation and regeneration test was carried out at Tufts University, a Collaborative 

Technology Alliance (CTA) Power and Energy consortium member of the Army, as part of a 

CTA staff rotation effort. The schematic of the reactor system is shown in figure 1. About 0.2 g 

of sorbent materials was used for the test. After the test, the material was recovered for further 

characterization. The sorbent was first subjected to pre-reduction under the conditions of 

50%H2-10%H2O-balanced helium (He) for 1 h. Then it was subjected to sulfidation under the 

conditions of 0.1%H2S-50%H2-10%H2O-balanced He with a space velocity of 80,000/h. When 

the concentration of H2S in the stream after the reactor reached 30 ppm, which is the pre-defined 

breakthrough point, the reactor conditions were changed to regeneration mode of 50%H2-

10%H2O-balanced He, space velocity 80,000/h. The sulfidation and regeneration test was 

conducted at two temperatures, 650 and 800 °C. The hydrogen sulfide (H2S) level in the exit gas 

was measured in real time using an AMETEK 922 UV Photometric Analyzer. 
3 

Figure 1. The schematic of the desulfurization reactor system. 

3. Results and Discussion 

3.1 Mixed Metal Oxide 

A 5% in molar ration of CuO in CeO2 (5%CuO/CeO2) was tested at 650 and 800 °C for 

sulfidation and regeneration. The results are shown in table 1 and figure 2 for a total of eight 

cycles. The initial capacity was higher than the subsequent runs at both 650 and 800 °C, but they 

were all stabilized to about the same values after several cycles. The percentage of the desorbed 

H2S from the sorbent was found to be over 80% for most cycles, as shown in table 1, indicating 

the reversibility of the sorbent. Although the capacity was basically the same for both 

temperatures, the temperature effect on the sorbent was obvious when the XRD measurements 

were taken to examine the tested samples. As shown in figure 3, narrower peaks were observed 

for the 800 °C tested sorbent, which means the 5%CuO/CeO2 mixed metal oxide crystalline size 

increased due to a high temperature sintering effect. 
4 

Table 1. Sulfidation/regeneration cycling results of 5% CuO/CeO2 at 650 and 800 °C. 

Cycled at 650 °C 1 2 3 4 5 6 7 8 

Capacity (mg S /g sorbent) 4.18 3.34 2.85 3.18 2.85 2.51 2.34 2.34 

Desorbed /adsorbed H2S (%) 81 88 89 95 91 95 98 95 

 

Cycled at 800 °C 1 2 3 4 5 6 7 8 

Capacity (mg S /g sorbent) 2.45 2.45 2.18 2.45 2.18 2.18 2.18 2.45 

Desorbed /adsorbed H2S (%) 81 83 81 79 83 84 82 73 

Note: Experimental conditions: pre-reduction at 650 and 800 °C, respectively, 50%H2-10%H2O-balanced He, 

1 h; Sulfidation at 650 and 800 °C, respectively, 0.1%H2S-50%H2-10%H2O-balanced He, space velocity 

80,000/h; regeneration: 650 and 800 °C, respectively, 50%H2-10%H2O-balanced He, space velocity 

80,000/h. 

0

1

2

3

4

5

6

0 1 2 3 4 5 6 7 8 9 10

Cycle

Capacity (mg S/g sorbent)

650 °C 

800 °C 

Figure 2. Sulfidation capacity of 5% CuO/CeO2 tested at 650 and 800 °C. 

10000

20000

30000

40000

50000

60000

70000

25 35 45 55 65 75 85

2 Theta / degree

Intensity / a.u.

800°C Tested

650°C Tested

Figure 3. XRD of 5% CuO/CeO2 after being tested at 650 and 800 °C. 
5 

In addition to the XRD measurements, Brunauer-Emmett-Teller (BET) surface area 

measurements were also conducted for the samples before testing and after being tested. The 

results are listed in table 2. The surface area of the samples was reduced from 54 m2

/g before the 

sulfidation test to 30 m2

/g after being tested at 650 °C, and severely reduced to 1.6 m2/g after 

being tested at 800 °C. The BET surface area results are in agreement with the XRD results in 

figure 3. To further investigate if composition change will affect the sintering, 3%, 10%, and 

50% CuO/CeO2 were made and their surface area was measured after being calcined at 650 °C. 

The results are listed in table 3, and the surface areas were found to be basically independent on 

the ratio of copper to cerium. However, when the sample of 50% CuO/CeO2 was calcined at the 

higher temperatures of 800 and 950 °C, the surface area was decreased from 52 m2/g (calcined at 

650 °C) to 13.5 m2

/g and 0.49 m2/g, respectively, as shown in table 4. This shows that neither 

copper nor cerium oxide were able to resist sintering at the temperature above 650 °C. 

Furthermore, a sample of 50% CuO/Al2O3 calcined at the same temperatures had a similar 

degree of reduction of the surface area, as shown in figure 4. 

Table 2. BET results of 5% CuO/CeO2 before and after testing at 650 and 800 °C. 

 BET Surface Area 

(m2

/g) 

Micropore V 

(cm3/g) 

Micropore Area 

(m2/g) 

Before testing 54 0.00133 1.55 

650 °C tested 30 0.00088 2.05 

800 °C tested 1.6 0.00036 0.67 

Table 3. BET surface area (m2/g) of CuO/CeO2 oxides calcined at 650 °C. 

 3% CuO/CeO2 10% CuO/CeO2 50% CuO/CeO2

650 °C calcined 45.7 45.6 52.0 

Table 4. BET surface area (m2/g) of oxides calcined at different temperatures. 

 650 °C Calcined 800 °C Calcined 950 °C Calcined 

50% CuO/CeO2 52.0 13.5 0.49 

50% CuO/Al2O3 42.1 24.9 3.13 
6 

0

10

20

30

40

50

60

500 600 700 800 900 1000

Temperature (°C)

Surface Area (m2/g) 

50% CuO/CeO2

50% CuO/Al2O3

Figure 4. BET surface area of 50% CuO/CeO2 and 50% CuO/Al2O3 calcined at 

different temperatures. 

3.2 Mixed Metal Oxide Supported on Zeolite 

In order to better understand the sulfidation behavior of the active copper and cerium ions that 

were supported on high surface area porous materials in comparison to the corresponding oxide 

itself, zeolite-Y was chosen as the support. Through ionic exchange reactions, the mono 

positively charged sodium ion in the zeolite structure was easily replaced by a double positively 

charged copper ion in solution. The copper exchanged zeolite can be further exchanged by a 

triple positively charged cerium ion so that a mixed metal supported sorbent can be prepared. 

The sulfidation experiment was conducted as discussed previously for the mixed metal oxide 

under the same conditions. The results are shown in figure 5 and table 5. This zeolite supported 

sorbent has a lower sulfidation capacity than the oxide, and the capacity seemed to be 

independent of the number of the sulfidation and regeneration cycles, especially for the initial 

run that was the same as the last run, indicating a near perfect reversible process. Unlike the 

unsupported oxide, the capacity of this supported sorbent is also temperature independent at both 

650 and 800 °C. The XRD in figure 6 demonstrates that the zeolite support structure remained 

intact after being tested; although, we suspect that some extent of dealumination (6) of zeolite-Y 

may have happened during the sulfidation test in which water vapor was present at 650 and 

800 °C. The BET results in table 6 show a slight decrease in surface area from 575 to 521 m2

/g. 

Table 5 also shows the adsorbed H2S can be desorbed completely during the regeneration 

process. Based on these experimental observations, we may characterize it as surface only 

activity with the supported copper and cerium oxide. For using unsupported 5% CuO/CeO2

oxide as sorbent, the activity may involve both surface and some bulk domains of the oxide. 
7 

0

1

2

3

4

012345678

Cycle

Capacity (mg S/g sorbent)

650 °C 

800 °C 

Figure 5. Sulfidation capacity of Cu-Ce-zeolite tested at 650 and 800 °C. 

Table 5. Sulfidation/regeneration cycling results of Cu-Ce-zeolite at 650 and 800 °C. 

Cycled at 650 °C 1 2 3 4 5 6 

Capacity (mg S /g sorbent) 1.58 1.38 1.58 1.77 1.58 1.38 

Desorbed /adsorbed H2S ( %) 90 101 102 97 98 99 

 

Cycled at 800 °C 1 2 3 4 5 6 

Capacity (mg S /g sorbent) 1.58 1.58 1.78 1.58 1.58 1.38 

Desorbed /adsorbed H2S ( %) 100 99 92 99 102 97 

Note: Experimental conditions: pre-reduction: 650 and 800 °C, 50%H2-10%H2O-balanced He, 1 h; 

sulfidation: 650 and 800 °C, 0.1%H2S-50%H2-10%H2O-balanced He, space velocity 80,000/h; 

regeneration: 650 and 800 °C, 50%H2-10%H2O-balanced He, space velocity 80,000/h. 

0

10000

20000

30000

40000

50000

60000

70000

80000

15 20 25 30 35 40 45

2 Theta / degree

Intensity / a.u.

Figure 6. XRD of Cu-Ce-zeolite––upper: after being tested at both 650 and 800 °C; 

middle: after being calcined at 650 °C; and lower: as prepared. 
8 

Table 6. BET surface area (m2/g) of Cu-Ce-zeolite. 

Cu-Ce-Zeolite BET Surface Area 

(m2

/g) 

650 °C calcined 575 

800 °C calcined 540 

800 °C tested 521 

3.3 Effect of Metal Ion on Zeolite Structure 

Table 7 summarizes the sulfidation capacity of zeolite-Y, the supported copper, cerium, and 

copper/cerium sorbents, and table 8 summarizes their BET surface area changes after the test at 

800 °C. From table 7, we see that zeolite-Y has a minimal capacity, but the incorporation of 

copper provided an additional more than 1 mg S/g in capacity, and the incorporation of cerium 

provided less than 1 mg S/g in capacity than zeolite-Y by itself as a sorbent. The supported 

copper and cerium mixed metal sorbent Cu-Ce-zeolite has a capacity between those of the Cuzeolite and Ce-zeolite, as shown in table 7. Noticeably in table 8, the BET results show that 

(1) the surface area of zeolite-Y by itself was significantly reduced to 20 under the sulfidation 

conditions, (2) the surface area of copper supported on zeolite (Cu-zeolite) was reduced to an 

even lower value of 9.4 under the same conditions, and (3) only Ce-zeolite and Cu-Ce-zeolite 

can keep the surface area above 500 m2

/g after being tested, indicating the structure of the 

cerium ion exchanged zeolite was stable during the test, even if some extent of dealumination of 

zeolite-Y (7) may have occurred, as mentioned previously. XRD measurements of these zeolite 

samples (figures 7 and 8) after the test at 800 °C revealed that significant structural change only 

occurred for Cu-zeolite, as shown in figure 7. It shows the formation of copper metal (three 

narrow peaks between 40 and 80 degrees, and a broad peak centered around 22 degrees as 

possible aluminate and silicate amorphous phases. This is most likely due to the combined result 

of high temperature, highly reducing atmosphere, and the presence of water. The reduction of 

copper ions to copper metal within the structure of the zeolite and the high temperature steam 

may lead to the collapse of the zeolite structure. This suggests that both the cerium exchanged 

zeolite and the copper/cerium mixed metal exchanged zeolite should be better candidates than 

the copper only exchanged zeolite for H2S desulfurization at 800 °C. 

Table 7. Sulfidation/regeneration cycling results of pure zeolite and metal ion exchanged zeolites 

tested at 800 °C. 

Tested at 800 °C Capacity 

(mg S/g Sorbent) 

Desorbed/Adsorbed H2S 

(%) 

Zeolite-Y 0.26 99 

Cu-zeolite 1.80 87 

Ce-zeolite 1.04 98 

Cu-Ce-zeolite 1.58 98 

Note: Experimental conditions: pre-reduction: 800 °C, 50%H2-10%H2O-balanced He, 1 h; sulfidation: 

800 °C, 0.1%H2S-50%H2-10%H2O-balanced He, space velocity 80,000/h; regeneration: 800 °C, 

50%H2-10%H2O-balanced He, space velocity 80,000/h. 
9 

Table 8. BET surface area (m2/g) of pure zeolite and metal ion exchanged zeolites 

calcined at 800 °C and tested at 800 °C. 

BET Surface Area (m2

/g) 800 °C Calcined 800 °C Tested 

Zeolite-Y 581 20.3 

Ce-zeolite 576 542 

Cu-Ce-zeolite 575 521 

10 20 30 40 50 60 70 80

2 Theta (degree)

Intensity (a.u.)

Figure 7. XRD of Cu-zeolite—upper: after being tested at 800 °C and 

lower: after being calcined at 650 °C. 

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

10 20 30 40 50 60 70

2 Theta / degree

Intensity / a.u.

Figure 8. XRD of Ce-zeolite—upper: after being tested at 800 °C and lower: 

after being calcined at 650 °C. 
10 

4. Conclusions 

The overall sulfidation capacity of the mixed metal oxides was found to be higher than 

corresponding zeolite supported counterparts, but the mixed metal oxide also showed evidence 

of sintering at higher temperatures, which resulted in a decreased capacity. The sulfidation 

capacity of the zeolite supported mixed metal oxide, although started with a lower capacity, was 

found to be independent of the temperature at both 650 and 800 °C, suggesting the mixed metal 

ions supported on zeolite are resistant to the sintering at higher temperature. The experimental 

evidence confirmed that the mixed metal ions supported on zeolite have only surface 

interaction with H2S. 
11 

5. References 

1. Flytzani-Stephanopoulos, M.; Sakbodin, M.; Wang, Z. Science 2006, 312, 1508–1510. 

2. Yang, H. Y.; Cahela, D. R.; Tatarchuk, B. J. Chem. Eng. Sci. 2008, 63, 2707–2716. 

3. Wang, X. X.; Ma, X. L.; Xu, X. C.; Sun, L.; Song, C. S. Top. Catal. 2008, 49, 108–117. 

4. Wang, Y.; Yang, R. T.; Heinzel, J. M. Chem. Eng. Sci. 2008, 63, 356–365. 

5. Huang, X. W.; King, D. A.; Zheng, F.; Stenkamp, V. S.; TeGrotenhuis, W. E.; 

Roberts, B. Q.; King, D. L. Catal. Today 2008, 136, 291–300. 

6. Garcia, P.; Lima, E.; Aguilar, J.; Lara, V. Catal. Lett. 2009, 128, 385–391. 
12 

List of Symbols, Abbreviations, and Acronyms 

BET Brunauer-Emmett-Teller 

Ce cerium 

Ce(NO3)3 cerium nitrate 

CTA Collaborative Technology Alliance 

Cu copper 

Cu(NO3)2 copper nitrate 

CuS copper sulfide 

EPA Environmental Protection Agency 

Fe iron 

H2S hydrogen sulfide 

He helium 

KOH potassium hydroxide 

S&T Science & Technology 

Si elementary silicon 

SOFCs solid oxide fuel cells 

XRD x-ray diffraction 
13 

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