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Chemical/Petrochemical
Figure 1
Stability of sulfur compounds is
remarkable in Sulfinert®-treated cylinders.
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®
cylinder 3
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®
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®
cylinder 1
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Hydrogen Sulfide
Carbonyl Sulfide
Methyl Mercaptan
Ethyl Mercaptan
Dimethyl Disulfide
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Figure 2
Siltek® treated gas sampling cylin-
ders show very good inertness toward
mercury.
Refinery and natural gas samples often contain trace amounts of sulfur- and
mercury-containing compounds, which can interfere with reactions, poison
catalysts in petrochemical processes, and damage equipment. Because these
compounds quickly react with stainless steel surfaces, accurate determination
of these compounds is impossible when samples are collected and stored in
untreated sample cylinders. Restek’s Siltek® and Sulfinert® passivation tech-
niques bond an inert layer into the surface of stainless steel, preventing active
compounds from reacting with or adsorbing to the steel.
Accurate sulfur sampling
To characterize Sulfinert® surfaces, we tested the stability of 17ppbv standards
of sulfur compounds in three Sulfinert® sample cylinders over a 54-hour period.
Dimethyl sulfide, which is not adsorbed by stainless steel, was used as an internal
standard. The Sulfinert®-treated cylinders were inert to the reactive sulfur
compounds over the 54-hour test period (Figure 1). Hydrogen sulfide exhibited
greater than 85% recovery; methyl mercaptan, ethyl mercaptan, carbonyl sulfide,
and dimethyl disulfide exhibited greater than 90% recovery.
Sulfinert®-treated gas sampling equipment is ideal for collecting and storing
samples containing ppb levels of sulfur compounds, such as natural gas or
beverage-grade carbon dioxide. Sulfinert® treatment ensures that sulfur com-
pounds or other highly active compounds remain stable during transport
from the field to the laboratory.
Stable Mercury Results
Siltek® surface treatment has been used in a wide variety of applications in
which an inert surface is of paramount importance. To measure the impact of
Siltek® treatment on adsorption of mercury during storage, we compared the
performances of 304 grade stainless steel gas sampling cylinders (Swagelok®,
Solon OH) with and without Siltek® treatment.
We filled each cylinder with 8µg/m
3
of elemental mercury (approximately 1
part per billion) (Spectra Gases, Alpha NJ) and assessed the mercury concen-
tration in each cylinder over time to determine changes in mercury concen-
tration. Detection was achieved by direct interface gas sampling to an atomic
absorption detector. The sample pathway regulator and tubing were Siltek®
treated to ensure accurate transfer.
The data in Figure 2 demonstrate that Siltek® treatment provides a stable surface
for elemental mercury, and untreated stainless steel does not. Based on these
results, we conclude that Siltek® surface treatment for steel or stainless steel
components and tubing in CMMS and sorbent tube mercury sampling systems
will improve analytical reliability.
Siltek® and Sulfinert® surface treated cylinders and sampling components
provide an inert sample path, which prevents adsorption of active compounds
and ensures accurate sampling. For more information about these treatments,
visit us at
www.restekcoatings.com.
Stable Sulfur &Mercury Sampling in Refineries
Using Siltek® and Sulfinert® Surface Treated Components
By Gary Barone, Restek Performance Coatings, and Irene DeGraff, Product Marketing Manager
• Reliably sample sulfur and mercury compounds at ppb levels.
• Reduce lab costs—obtain accurate results the first time.
• Detect costly process upsets, improving product yield.
Siltek
®
cylinders (n=2)
Untreated cylinders (n=2)
Acknowledgement
The authors wish to acknowledge Ted Neeme and Steve Mandel from Spectra Gases for their
contributions to this work.