reliably store ppb levels of the
active sulfur-containing com-
pound during transport from
the sampling site to the analyti-
cal laboratory. In contrast,
hydrogen sulfide degraded
rapidly in the untreated cylinder, andwas lost
totallywithin 24 hours.
In a similar study inwhich gas containing
18.8ppbvmethyl mercaptanwas stored for 60
hours in Sulfinert
®
treated sample cylinders,
recovery of the active sulfur compoundwas
equally high relative to the stable reference
material, dimethyl mercaptan, as shown in
Figure 1b.
SampleTransfer:Adsorptionof
SulfurCompounds toTubing
Surfaces
Comparison of the transport properties of
Sulfinert
®
treated electropolished stainless steel
tubing (TrueTube
™
EPS tubing, surface rough-
ness average (RA): 5-10, O'Brien Corporation,
St. Louis, MO), untreated electropolished stain-
less steel tubing (TrueTube
™
EP tubing, RA 5-10,
O'Brien Corporation), and raw commercial grade
stainless steel tubing (RA 23-27) show only
Sulfinert
®
treated electropolished stainless steel
has the inertness necessary for quantitatively
transferring sulfur compounds at low ppmv to
low ppbv concentrations in sample streams. An
experiment was designed to confirmwhether a
sulfur-containing stream passing through stain-
less steel tubingwould passivate active sites on
the steel surface, through adsorption of the
active sulfur species.The amount of time
elapsed before a representative sample, con-
taining a stable and accurate sulfur content,
exited the tubingwas themeasured indicator of
surface activity in the tubing.
Moreaccurate results and faster
cycle times, usingSulfinert®
treated components
SulfurCompoundSampling,
Storage, andTransferConsiderations
Introduction
Accurate analyses for parts-per-million to
parts-per-billion levels of sulfur-containing
compounds in petrochemical streams are critical
tomeeting new regulations for lower levels of
sulfur in diesel fuel and gasoline. Many organo-
sulfur compounds—hydrogen sulfide, methyl
mercaptan, and ethyl mercaptan among them—
adsorb strongly tometal surfaces. Adsorption of
sulfur compounds in sampling, storage, and/or
transfer apparatus can cause prolonged analy-
sis cycle times aswell as inaccurate, falsely low
values.
In the studies described here, active sulfur
gaseswere sampled, stored, and transferred in
control (untreated) and Sulfinert
®
treated static
(storage) and flow-through system components,
to determine quantitative losses of the sulfur
gas species. Concentrations of the sulfur gases
spanned the low parts-per-million to low parts-
per-billion range.
SulfurCompoundStorage:
Sulfinert®Treatedvs.Untreated
SampleCylinders
Figure 1a depicts results from a comparison in
which a gas containing 17ppbv of hydrogen sul-
fidewas stored for 7 days in untreated or in
Sulfinert
®
treated stainless steel sample cylin-
ders.The response ratio for hydrogen sulfide,
relative to a stable referencematerial, dimethyl
sulfide, is steady at approximately 1:1 for at
least seven days in Sulfinert
®
treated cylinders.
The data show a Sulfinert
®
treated systemwill
Avoiddowntime,
savemoney
Sulfinert® treatment adds value to
your processbyensuring:
•Accurate results
•Improved yields
•Faster cycle times
Avoid these losses!
A1-hour delay can cost:
1
•800,000 tpy ethylene plant: $50,000
•250,000 tpy LDPE unit: $36,000
•250,000 tpy EBSM styrene plant: $33,000
•200,000 tpy anti-freeze process: $3,600
ApplicationsNote
110Benner Circle • Bellefonte, PA 16823
800-356-1688•814-353-1300• fax: 814-353-1309
Restek
Performance
Coatings
Figure1
Sulfur compounds are stable inSulfinert® treated stainless steel systems
a) 17ppbvhydrogen sulfide in500mL cylinders
b) 18.8ppbvmethylmercaptan in300mL cylinders
a)
b)
