Analysis of Sulfur Compounds inPetroleum Gases and Natural Gas

Application Note
Energy & Chemicals

Authors

Abstract

Yamin Wang

Agilent J&W DB-Sulfur SCD columns were evaluated by analyzing different sulfur

Research Institute of Petroleum

gaseous standards. Sulfur compounds in petroleum gases and natural gas samples

Processing

were also analyzed using an Agilent Inert Flow Path GC/SCD with the DB-Sulfur

SINOPEC Corp,

SCD column according to ASTM D5504. The column, with low bleed and exceptional

Beijing, P. R. Chinainertness, provided good resolution and peak shape to these reactive sulfur compounds. Good results confirmed that the Inert Flow Path GC/SCD configured with

Yun Zou and Hua Wu

the DB-Sulfur SCD column was a useful tool for analysis of sulfur compounds.

Agilent Technologies, Inc.

Introduction
Petroleum gases and natural gas are well-established contributors to the world'senergy needs. Monitoring sulfur compounds in these products is very important, notonly to protect expensive catalysts and ensure product quality, but also to protect
the environment and human health. The analysis of gaseous sulfur compounds ischallenging because they are polar, reactive, and present in widely varying concentrations. The sulfur chemiluminescence detector (SCD) is known as an excellent
device for sulfur compound analysis because its response is inherently linear,equimolar, and far less susceptible to hydrocarbon interferences. For example,
ASTM Method D5504 [1] uses SCD for the detection of sulfur compounds ingaseous fuels and natural gas, but the SCD requires low-bleed GC columns to be
used to avoid fouling of the SCD ceramics, and decreasing sensitivity. In addition,
volatile sulfur compounds are highly reactive and have absorptive, adsorptive, andmetal-catalytic properties. Therefore, analysis of sulfur compounds requires thatsample pathways, especially the GC column, be inert to ensure reliable results.

The Agilent J&W DB-Sulfur SCD GC column with low bleed
and exceptional inertness is specifically developed for sulfur
compound analyses and optimized for GC/SCD. This application note demonstrates the performance of the DB-Sulfur SCD
column in analyzing sulfur compounds in petroleum gases
and natural gas using an Agilent Inert Flow Path GC/SCD.

GC conditions 2Columns:

Agilent J&W DB-Sulfur SCD, 70 m × 0.53 mm, 4.3 µm(p/n G3903-63003)

Carrier:

Helium, constant pressure mode, 8.6 psi

Inlet:

Volatiles interface inlet, 200 °C , split ratio 4:1

Oven, sample loop, and SCD conditions as for Conditions 1

Materials and Methods
Table 1. Sulfur standards.

The experiments were performed on two sets of Agilent
7890A GC configured with an Agilent 355 SCD with dual
plasma burner. Split/splitless inlet and volatiles interface (VI)were equipped with GC/SCD. Sample introduction consistedof a six-port gas sample valve connected directly to thesplit/splitless inlet or VI with inert Agilent UltiMetal tubing. A
point-of-use gas blending system controlled by auxiliary EPC
was used for preparation of low level samples.
Table 1 lists the sulfur compounds included in the study. All
sulfur standards were purchased from Beijing AP BAIF Gases
Industry Company. All sulfur standards were blended in nitrogen and the concentrations were modified by the point-of-use
gas blending system.
GC conditions 1Columns:
Tubing:Union:

No.

CompoundCAS No.

Formula1

Hydrogen sulfide (H2S)

7783-06-4

H2S

2

Sulfur dioxide (SO2)7446-9-5

SO2

3

Carbonyl sulfide (COS)

463-58-1

COS

4

Methanethiol (MeSH)

74-93-1

CH3SH

5

Ethanethiol (EtSH)

75-08-1

C2H5SH

6

Dimethyl sulfide (DMS)

75-18-3(CH3)2S

7

Carbon disulfide (CS2)75-15-0

CS2

8

2-Propanethiol (i-PrSH)

75-33-2

C3H8S

9

2-methyl-2-Propanethiol (t-BSH)

75-66-1

C4H10S

10

1-Propanethiol (n-PrSH)

107-03-9

C3H8S

11

Ethyl methyl sulfide (MES)624-89-5

C2H5SCH3

121-methyl-1-Propanethiol (s-BuSH)

513-53-1

C4H10S

Agilent J&W DB-Sulfur SCD,
70 m × 0.53 mm, 4.3 µm (p/n G3903-63003)

13Thiophene (TP)110-02-1

C4H4S

14

2-methyl-1-Propanethiol (i-BuSH)

513-44-0

Deactivated fused silica,
1 m × 0.18 mm (p/n 160-2615-1)

C4H10S

15

Diethyl sulfide (DES)352-93-2(C2H5)2S

16

1-Butanethiol (n-BuSH)

109-79-5

C4H10S

17

Dimethyl disulfide (DMDS)

624-92-0(CH3S)218

Tetrahydrothiophene (THT)110-01-0

C4H8S

19

Ethyl methyl disulfide (MEDS)

20333-39-5

C3H8S2

Deactivated Ultimate union (p/n G3182-60580)

Carrier:

Helium, constant pressure mode, 8.6 psi

Inlet:

Inert flow path split/splitless inlet, 240 °C,
split ratio 10 :1

Liner:

Ultra Inert liner (p/n 5190-2295)

20

Dipropyl sulfide (DPS)

111-47-7

C6H14SOven:

35 °C for 2 min, 35 °C to 80 °C at 10 °C/min,
80 °C for 6 min, 80 °C to 220 °C at 15 °C /min,
220 °C for 10 min

21

Diethyl disulfide (DEDS)

110-81-6(C2H5S)222Dimethyl trisulfide (DMTS)

3658-80-8

C2H6S3Sample loop:

1 mL

Detector:

Agilent 355 SCD

SCD conditions
Burner temperature:

800 °C

Vacuum of burner:

350 Torr

Vacuum of reaction cell: 5 Torr
H2:

40 mL/min

Air:

60 mL/min2

As shown in Figure 1, the column provided satisfactory separation for most of 1# and 2# sulfur standards. In particular,
good resolution and retention of carbonyl sulfide andhydrogen sulfide were achieved at ambient temperature.
According to chromatogram overlays of 1# and 2# standards,
carbonyl sulfide and sulfur dioxide normally coelute on a regular 60 m × 0.53 mm, 4 pm nonpolar column, but they can bepartially separated on the 70-m DB-Sulfur SCD column with
1-m deactivated fused silica tubing. This is confirmed byanalysis of a sulfur gaseous mix that was made by mixing 1#and 2# sulfur standards, and adding some common sulfur
compounds.

Results and Discussion
GC conditions 1
To achieve better resolution of COS and SO2, 1-m deactivatedfused silica tubing was used as a restrictor, connected to a70 m × 0.53 mm, 4.3 µm DB-Sulfur SCD GC column. Different
sulfur gaseous standards applicable to different applications
were tested and the analysis initiated at 35 °C. Compared to atypical initial temperature at 30 °C or below ambient temperature, the GC system was more stable, no cryogenic cooling
was required, and the system was suitable for different
laboratory conditions.
15 µV

1# Standard

3000
2500

MeSH

2000

MES

DES

1500
SO21000

n-PrSH

500

i-BuSHs-BuSHDMDS00510152025 min

15 µV
H2S

3000

2# Standard

2500
CS2MeSH

2000

EtSH
DMS15001000

THTi-PrSH t-BSH

COS50000510152025 min

Figure 1. Chromatogram overlays of sulfur standards using an Agilent GC/SCD system and Agilent J&W DB-Sulfur SCD column.

3Better resolution can be obtained with a lower initial oventemperature and longer GC columns with deactivated fusedsilica tubing. Due to complete sulfur compounds combustion,better sensitivity can be achieved if a relatively lower flowrate is selected. However, run time will be increased.

Figure 2 shows the chromatogram of the 22 sulfur
compounds. Most of the peaks were well resolved on theDB-Sulfur SCD column with excellent peak shapes.
Resolution of carbonyl sulfide and sulfur dioxide was about
0.8. 1-methyl-l-propanethiol, thiophene, and2-methyl-l-propanethiol are normally difficult to separate
because they often show coelution on commonly used
nonpolar (dimethylpolysiloxane) stationary phase GCcolumns. Figure 2 exhibits improved separation of these threecompounds using the DB-Sulfur SCD column.
15 µV

COSH2S
4000

Rs = 0.8

SO23666.5

77.58min

3000
4172000

1852221315171000

810 119141221

1619

2005
1.
2.
3.
4.
5.

H2S
SO2COS
MeSH
EtSH

6. DMS
7. CS28. i-PrSH
9. t-BSH
10. n-PrSH

10
11. MES
12. s-BuSH
13. TP
14. i-BuSH
15. DES15
16. n-BuSH
17. DMDS
18. THT
19. MEDS
20. DPS

20

253035min

21. DEDS
22. DMTS

Figure 2. Chromatogram of sulfur gaseous mix using an Agilent GC/SCD system and Agilent J&W DB-Sulfur SCD column.

4Figure 3 shows the chromatogram of the 2# sulfur standard
and 1# sample (LPG sample after desulfurization) that
included a large amount of light hydrocarbons. Good resolution and repeatability also indicated no hydrocarbon
interferences in the analysis.

and the mass concentrations of total sulfur in the sample
were calculated by summing the sulfur content of all sulfurcomponents (known and unknown) in the sample. The total
amount of sulfur for the 1# sample was 62 ppm. Individual
sulfur compounds in the 1# sample could be identified byretention time. Each major individual sulfur compound wascalculated by external standardization. Thus, hydrogen sulfide
was 20.46 ppm, COS was 17.22 ppm, and MeSH and CS2 were0.75 ppm and 10.41 ppm, respectively.

Equimolar response of a detector refers its ability to yield
equal responses to equal amounts of analytes on a molar
basis. Relying on the equimolarity of the Agilent 355 SCD, the1# sample (LPG sample after desulfurization) was detected,
H2 S

A

2# Standard

CS2

MeSH
EtSH
DMS

THTi-PrSH t-BSH

COS

H2S

B

1# Sample
Total sulfur 62 ppm
COSCS2
MeSH

Figure 3. Chromatograms of sulfur standard (A) and 1# sample (LPG sample after desulfurization) (B).

5

As shown in Figure 4, the concentration of some major sulfur
compounds varied greatly before and after desulfurization,
especially H2S. A wide linear range (that is, from 10 ppb to10 ppm) for major sulfur compounds was required. R2 correlation coefficients of the tested sulfurs in this study were better
than 0.997. Figure 5 shows the chromatogram of the 3# standard and Figure 6 demonstrates the chromatogram of eachmajor sulfur compound at 15 ppb. Signal-to-noise ratios ofH2S, COS, and DMS were 4.8, 11.2, and 9.3, respectively.

GC Conditions 2
Some previous publications have discussed how SCD offers
equimolar/sulfur-specific detection to ppb level [2,3,4]. The
DB-Sulfur SCD column is specifically developed for sulfur
compound analyses and optimized for SCD. The column wasconfigured with a volatiles interface inlet and SCD detector tomeasure the total sulfur amount of natural gas before andafter desulfurization.

H2S

15 µVA

60,000

NGA, total sulfur 20 ppm
50,00040,00030,00020,000
EtSH

10,000DMSCOS0015 µV

510152025 min

BDMS

60,000NGA after desulfurization,
total sulfur 1 ppm

50,000
COSEtSH40,000H2S

30,00020,00010,000005101520

Figure 4. Chromatograms of real samples; natural gas (A) and natural gas after desulfurization (B).

625 min15 µV80000
21560000

3# Standard4

1. H2S
7.0 ppm
2. COS
9.5 ppm
3. ETSH 6.8 ppm
4. DMS 10.2 ppm
5. THT 11.5 ppm

40000
3200000024681012141618min

Figure 5. Chromatogram of the 3# standard.
15 µVCOS220DMS200
180160H2 S

14012010080Figure 6. Chromatogram of major sulfur compounds at 15 ppb.
To check suitability, a calibration gas was analyzed severaltimes. Excellent repeatability of major sulfur compounds wasobtained, as shown in Table 2, with RSD% below 2.25%.

The total amount of sulfur was calculated by summing all
peak areas in the chromatogram of natural gas and quantitated using the response factor of COS. Table 3 shows theresults of the natural gas samples. No hydrocarbon interferences were found in the analysis.

Table 2. Repeatability of major sulfur compounds.
RunH2S (ppm)

COS (ppm)

DMS (ppm)

1

8.33

10.15

11.18

28.36

10.42

11.27

3

8.62

10.00

10.76

4

8.74

10.18

11.18

58.63

10.09

10.94

6

8.30

10.14

10.95

Average

8.50

10.16

10.95

RSD%

2.24

1.38

1.74

Table 3. Major individual sulfur compounds and total sulfur
amount in natural gas.

7SulfurcompoundAverage content (ppm)
before desulfurization

Average content (ppm)
after desulfurization

H2S

8.98

0.01

COS

0.21

0.04

EtSH

5.07

0.10

DMS

0.02

0.00

Total sulfur

20.21

1.37

Conclusions

References

The Agilent J&W DB-Sulfur SCD column was evaluated byanalyzing different sulfur gaseous standards and common
GC/SCD configurations. The results showed that the column
could provide good resolution and symmetrical peak shape forpolar and reactive sulfur compounds due to its low bleed andimproved inertness performance. In particular, using a 70-m
DB-Sulfur SCD column with 1-m deactivated fused silica
tubing, resolution of hydrogen sulfide and sulfur dioxide wasabout 0.8. Hydrogen sulfide and carbonyl sulfide could bebaseline separated at ambient temperature without cryogeniccooling. Excellent linearity, repeatability, and response wereachieved for major sulfur compounds when the DB-Sulfur
SCD column was used with the volatiles interface and SCD. Insummary, the combination of an Agilent Inert Flow Path,
DB-Sulfur SCD column, and Agilent 355 sulfur chemiluminescence detector can offer excellent performance in theanalysis of sulfur components in fuel gases and natural gas.

1. ASTM. ASTM D5504-12: Standard test method for determination of sulfur compounds in natural gas and gaseous
fuels by gas chromatography and chemiluminescence.
ASTM, Philadelphia, PA, USA (2012).
2. Wenmin Liu, Mario Morales. Detection of Sulfur
Compounds in Natural Gas According to ASTM D5504
with Agilent's Dual Plasma Sulfur Chemiluminescence
Detector (G6603A) on the 7890A Gas Chromatograph.
Application note, Agilent Technologies, Inc. Publication
number 5988-9234EN (2008).
3. Anon. Agilent 355 Sulfur Chemiluminescence Detector(355 SCD): Odorants and Other Sulfur Compounds in
Liquefied Petroleum and Natural Gases. Technicaloverview, Agilent Technologies, Inc. Publication number
5989-6788EN (2007).
4. Anon. Application D5504, Trace Sulfur Gas Analyzer, determination of Sulfur Compounds in Natural Gas andGaseous Fuels. Technical overview, Agilent Technologies,
Inc. Publication number 5988-7674EN (2002).

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© Agilent Technologies, Inc., 2014
Published in the USA
December 15, 2014
5991-4643EN