J.
F. S H U L T Z
F. 5 . K A R N
R. E. ANDERSON
CYLINDERS FOR STORING SULFURCONTAINING GASES If iron carbonyls are Jirst removed from the gas, containers of
stainless steel, aluminum or plastic-lined carbon
steel are excellent
L44
INDUSTRIAL AND ENOtN€Mt"&CHEMlSTRY
ing low concentrations of hySynthesis dm& sulfidi or other sulfur compounds is useful for studying catalyst poisoning and as analytical standards. However storav of these gas mixtures presents a prohlem: conventional carbon steel gas cylinders cannot be used because many sulfur compounds react not only with the steel but also with iron carbonyls. For example, synthesis gas (lHI -I- 1CO) Containing 2.9 grains of sulfur per 100 cubic feet contained only 0.25 grain after storage for seven days in a conventional cyliider. This storage problem, however, can be solved by using different materials of construction for the cylinders and by removing carbonyls from the gas. This was confirmed by tests on three types of cylinders. Two were custom built: One was fabricated (Overly Mfg. CO., Pittsburgh, Pa.) from 8-inch seamless pipe of Type 304 stainless steel, and one from an aluminum alloy 6061 spun cylinder, 9 inches in diameter (Benson Mfg. CO., Kansas City, Mo.). The third was a carbon steel standard type, ICC Specification3A2015,coated on the inside with Heresite (baked phenolic resin) by the Heresite Chemical Co., Manitowoc, Wis. This cylinder was of carbon steel, ICC Specification 3A2015, coated on the inside with baked phenolic resin. Volume of each was about 1.5 cubic feet and working pressure was 1500 p.s.i.g. or higher. The special cylinders were equipped with stainless steel valves. The method of removing carbonyls is simple. Synthesis gas containing less than 0.1 grain of sulfur per 100 cubic feet from conventional carbon steel cylinders [Cham. Eng. Progr. 45, 651 (1949)l was pagned through a bed of activated charcoal. The stored synthesis gas, analyzed at periods varying from six to 22 days, showed no significant decrease in sulfur content. The stainless steel and plastic-lied cyliidm have been in continuous use for 32 months and the aluminum cylinders for 14 months. However, the plastic-lined containers are recommended because
they cost less than one fifth as much as those of stainless steel or aluminum. For example, cost of the aluminum and stainless steel cylinders was in the neighborhood of $600. Plastic coating of a cyliider, of standard design, costs about $35. These cylinders should he suitable for storing higher concentrations of sulfur compounds in hydrogen, carbon monoxide, or inert gases. Exprhenhll Procdun
Volumes of the cylinders were determined accurately by two methods: weighing the water required to fill the cylinder and metering the gas delivered during a known pressure drop. Gas mixtures containing sulfur compounds were prepared with a special gas-blendmg apparatus. Hydrogen sulfide was measured by determining pressure and temperature in calibrated glass vessels having 2 capacity of 106.8 or 298.1 cc., and then expanded into an evacuated cylinder. The synthesis gas charged to the cylinder was passed through a charcoal trap to remove volatile iron carbonyls. Otherwise the H*S reacts with iron carbonyl to form an amorphous (to x-ray diffraction) brown solid. Dust from the ch& coal was prevented from entering the cylinder by a glass wool filter. The following blending procedure was used: Each cylinder was evacuated hefore filling. The desired amount of hydrogen sulfide was introduced into the glass measuring bulb and subsequently into the evacuated cylinder. Synthesis gas was then introduced to increase the pressure of the system to atmospheric. The glass vessel was then isolated by stainless steel valves and synthesis gas was introduced to increase pressure in the cylmder to 1500 p.s.i.g. One side of the cylinder was warmed with an dectrid heater for a few hours to increase the rate of mixing by convection. The gas was analyzed for sulfur by a modified Referee method (“Gas Analysis and Testing of Gaseous Materials,” pp. 147-51, American Gas Association, 1945). Ten cubic feet of gas at a rate of 5 cubic feet per hour was burned with sulfur-free air in a stainless steel burner. The oxides of sulfur were absorbed in a solution of am: monium carbonate, oxidized with bromine water, precipitated, and determined ‘as barium sulfate. The usual procedure included two Referee analysesone after six days on the newly filled cylinder at 1500 p.s.i.g., and one after the cylinder had been used in a poisoniing experiment for about 14 days and the pressure had decreased to about 400 p.s.i.g. However, in some cases as many as four analyses were made to study analytical reproducibility. . In a few experiments, mixtures containlng carbon disulfide or thiophene were prepared by intrcducing the sulfur compound as liquid into the evacuated
AUTHORS J . I.: Shultr, F. S. Kmn, and R. B. Anderson me Su@msing Physical Chamids with tk Bureau of Minzs,
Coal Reseqch Ccnkr, PiNSburgh, Pa.
~ounoi~ l l n rnon ~ r nyorogen
ided with the Synthesis Gar ,,umtturrr
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21
cylinder through a serum cap using a calibrated hypodermic syringe. One mixture containing sulfur dioxide prepared by the volumetric method was also tested. For hydrogen sulfide at six days, stindard deviations of the analyses from the calculated value were within experimental error of the analytical method. For mixtures containimg other sulfur compounds, deviations were greater, but the differencm are attributed to inaccuracies in introducing s m a l l liquid samples. Analytical values over the period of 6 to 22 days did not change widely or show a trend. In other tests this was also true after periods as long as 40 to 60 days. Names of manufactufvs are given for identification only Such mention does not necessarily imply recommendation by the Bureau of Mines. VOL 54
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