HK1079279B - Reduced moisture compositions comprising an acid gas and a matrix gas, articles of manufacture comprising said compositions, and processes for manufacturing same - Google Patents

Description

Reduced moisture compositions containing an acidic gas and a matrix gas, articles containing the compositions, and methods of making the same

Background

1. Field of the invention

The present invention relates generally to the field of preparing compositions containing acid gases and matrix gases that have been dehumidified and that can be stable at acid concentrations for a significantly long period of time. The invention also relates to articles comprising these compositions, such as metal cylinders comprising the compositions, volume unit elements (ton units) comprising the compositions, and the like.

2. Correlation technique

It is known that moisture reacts with reactive gases such as so-called "acid gases", for example hydrogen sulphide, carbonyl sulphide, carbon disulphide and mercaptans (mercaptans), also known as mercaptans (thiols), to form complex compounds. (the term "acid gas" is used herein to mean a gas phase, a liquid phase, or a mixture of gas and liquid phases unless the phase is specifically indicated).

This presents a difficult problem: if one wants to generate a standard reactant gas composition, in other words a reactant gas with a known concentration of one of the reactant gases in the matrix or carrier fluid, one must consider how to reduce or remove the moisture. The gas standard may have to have, and preferably does have, a long shelf life, as the standard reactant gas may not be required immediately after production. The reactive gas source may contain a considerable amount of moisture. Therefore, if the stability of the reaction gas in the standard gas is to be maintained, it is of primary importance to reduce or remove moisture from the reaction gas. It has also been observed recently that moisture in the matrix gas (before mixing with the acid gas) is also one of the causes of this problem, because if moisture is removed from the reaction gas and then the dry reaction gas is mixed with the wet matrix gas, the problem is not completely solved even if the moisture content in the matrix gas is rather low.

A second related problem relates to the containers that store the reactive gas standards. If the vessel is metallic or metal-lined, the reactive gas will react with and/or adsorb onto the metal and will eventually change the concentration of the reactive gas.

Grossman et al (U.S. patent No. 4,082,834) describe alloys such as nickel, titanium and zirconium alloys that react with water and reactive gases such as hydrogen, hydrogen-containing compounds such as hydrocarbons, carbon monoxide, carbon dioxide, oxygen and nitrogen at temperatures ranging from about 200 ℃ to about 650 ℃. Although this patent does not discuss acid gases, it is clear that hydrogen sulfide, carbonyl sulfide and mercaptans are all hydrogen-containing compounds, and thus the removal of moisture from these acid gases with these alloys would not yield any desired benefit. Although carbon disulfide does not contain hydrogen and thus the use of these alloys enables the moisture content of compositions containing carbon disulfide and moisture to be reduced, the high temperatures prevent its commercial use.

Tamhankar et al (U.S. patent No. 4,713,224) describe a one-step process for removing very small amounts of impurities from inert gases, wherein the impurities are selected from the group consisting of carbon monoxide, carbon dioxide, oxygen, hydrogen, water and mixtures thereof. The method includes contacting the gas with a particulate material containing at least about 5% by weight nickel, based on elemental nickel, and having a thickness of about 100to about 200m²Large surface area in g. It does not disclose the removal of moisture from the reactant gases and therefore does not relate to the removal of moisture from the reactant gasesTo remove moisture, to remove moisture from the matrix gas, and to mix the two to form a standard gas composition.

Tom et al (U.S. Pat. nos. 4,853,148 and 4,925,646) disclose methods and compositions for drying gaseous hydrogen halides of the formula HX, where X is selected from the group consisting of bromine, chlorine, fluorine and iodine. The use of supported organometallic compounds such as alkyl magnesium compounds, for example, is described in this patent. The halide replaces the alkyl functionality. Suitable supports are alumina, silica and aluminosilicates (natural or synthetic). However, there is no description or suggestion about reducing or removing moisture from a sulfur-containing reaction gas, or removing moisture from a matrix gas and mixing the dehumidified gas to form a standard gas. Alvarez, jr. et al (U.S. patent No. 5,910,292) describe a method and apparatus for removing water from corrosive halogen gases using high silica zeolites, preferably high silica mordenite. Moisture removal from halogen gases, particularly chlorine-or bromine-containing gases, to water concentrations of less than or equal to 100ppb is described in this patent, but again, any teaching as to suggesting standard gas compositions is lacking. U.S. patent No. 6,183,539 discloses the use of high sodium low silicon faujasite particles to adsorb carbon dioxide and water vapor from a gas stream. The disclosed gas stream classes for which such high sodium low silicon faujasite crystals can be used in the gas stream include air, nitrogen, hydrogen, natural gas, single hydrocarbons and monomers such as ethylene, propylene, 1, 3-butadiene, isoprene, and other such gas systems. There is no mention of the purification of sulfur-containing acid gases or the production of standard gas compositions with faujasite.

U.S. Pat. No. 4,358,627 discloses the use of "acid resistant" molecular sieves, such as those known under the trade designation "AW 300", to reduce the concentration of chlorides in chlorinated liquid hydrocarbons containing olefinically unsaturated chlorinated hydrocarbons, water and hydrogen chloride. The method includes providing a specific nitrogen-containing compound to a system and contacting the system with a molecular sieve. However, there is no disclosure or suggestion of removing or reducing moisture from a gas phase composition or producing a standard gas composition.

Given the problem of moisture reacting with sulfur-containing acid gases and other reactant gases, and the fact that some or all of the reactant gases will react with metals, there is a clear and unmet need for standard gas compositions, articles containing those standards that are stable for relatively long periods of time, and methods for their production.

Summary of The Invention

The present invention overcomes many, if not all, of the above-mentioned problems. In accordance with the present invention, a particular "acid gas-resistant" molecular sieve composition is employed to reduce or remove moisture from a fluid composition containing a reactant gas (preferably an acid gas, more preferably a sulfur-containing acid gas), and the moisture in the matrix gas is removed in the same or a different manner. The dehumidified reactant gas and the dehumidified matrix gas are then combined, either prior to entering the vacuum-baked and passivated vessel, or while continuously adding the vacuum-baked and passivated vessel, or while simultaneously adding the vessels while mixing (e.g., through respective valves). The term "removed" as used herein means that the water content in the final composition containing the reaction gas will be equal to or less than 100ppb, more preferably less than 10ppb, more preferably less than 1 ppb. The term "reduced" as used herein means that the water content in the final composition containing the reactive gas will be no more than 0.1 times the water concentration of the initial fluid composition, preferably no more than 0.01 times, more preferably no more than 0.001 times the initial water concentration. Currently, the moisture detection limit of reaction gases including sulfur-containing compounds is about 4 ppm. The composition was made to a concentration of 4ppm and then diluted to the desired reduced moisture concentration. The term "sulphur-containing compound" as used herein includes carbon disulphide, carbonyl sulphide and compounds within the scope of formula (I):

Y-S-X (I)

wherein S is a sulfur atom, and S is a sulfur atom,

x and Y are the same or different and are independently selected from the group consisting of hydrogen, alkyl, aryl, oxygen, and alcohol.

Examples of preferred sulfur-containing compounds within the scope of formula (I) include hydrogen sulfide, sulfur dioxide, methyl mercaptan, ethyl mercaptan, n-propyl mercaptan, isopropyl mercaptan, benzyl mercaptan and the like.

In accordance with the present invention, a method of passivating the interior surfaces of cleaned and vacuum baked containers is employed to enhance the shelf life of gaseous compositions, particularly low concentration reactive gas products. The term "shelf life" as used herein refers to the time during which the initial concentration of the stored reactant gas in the vessel is maintained sufficiently at a desired or ideal concentration. Herein, the term "substantially maintained" means that the concentration of the reaction gas does not vary by more than ± 10% for a concentration of about 1000 ppb; for a concentration of about 500ppb, the concentration does not vary by more than. + -. 15%; for a concentration of about 100ppb, the concentration does not vary by more than. + -. 20%. "Low concentration" of a reactant gas refers to a gas having a concentration of 1000ppb or less in another gas, such as an inert gas or a matrix gas.

The passivated inner metal surface of the container comprises (1) the reaction product of a silicon-containing material and an oxygen-containing material, preferably selected from the group consisting of moisture, molecular oxygen, metal oxides, and mixtures thereof, and (2) an effective amount of a reactant gas, the effective amount being many times the desired reactant gas concentration to be substantially maintained. Preferred articles of the invention include products wherein the passivated inner surface is a passivated metal. Preferably, the metal is selected from the group consisting of aluminum, aluminum alloys, steel, iron, and combinations thereof. Other preferred articles of the invention are those in which the silicon-containing material is selected from compounds within the scope of formula (II):

SiR¹R²R³R⁴ (II)

wherein R is¹、R²、R³And R⁴The same or different and are independently selected from the group consisting of hydrogen, halogen, amine, alkyl, aryl, haloalkyl and haloaryl; and those wherein the compound is a silane or a methylsilane-containing product, more preferably wherein the methylsilane-containing product is selected from the group consisting of methylsilane, dimethylsilaneTrimethylsilane and tetramethylsilane.

Reactive gases that benefit from the passivation techniques of the present invention include nitrous oxide, nitric oxide, hydrogen chloride, chlorine, boron trichloride, and any acid gas other than those that will react with silicon-containing compounds.

The first aspect of the present invention is a composition comprising a reaction gas (preferably an acid gas, preferably a sulfur compound) and a substrate gas, wherein the sulfur compound in the composition is not more than 1ppm relative to the substrate gas concentration, and the composition has a moisture concentration of not more than 100ppm, preferably not more than 10ppm, more preferably not more than 1 ppm. Preferred compositions are those wherein the reactant gas is selected from the group consisting of nitrous oxide, nitric oxide, hydrogen chloride, chlorine, boron trichloride, and any acid gas other than those which will react with the silicon-containing compound, including sulfur-containing compounds selected from the group consisting of carbon disulfide, carbonyl sulfide, and compounds within the scope of formula (I).

A second aspect of the present invention is an article comprising:

a) a container having an interior space and a passivated inner metal surface;

b) a composition of the first aspect of the present invention included in said interior space and in contact with said passivated inner metal surface, wherein the acid gas has a desired concentration substantially maintained; and

c) a passivated inner metal surface comprising:

1) a reaction product of a silicon-containing material and an oxygen-containing material (preferably selected from the group consisting of moisture, molecular oxygen, metal oxides, and mixtures thereof), and

2) an effective amount of the reactant gas that is many times the desired reactant gas concentration to be adequately maintained.

Preferred articles of the invention are those in which the reactive gas is selected from those described in the first aspect of the invention. Other preferred articles include products wherein the passivated internal surface is a passivated metal. The metal is preferably selected from the group consisting of aluminum, aluminum alloys, steel, iron, and combinations thereof. Also preferred articles of the invention are those wherein the silicon containing material is selected from compounds within the scope of formula (II).

Preferred articles of the invention are those wherein the composition comprises a reactive gas having a concentration of about 1000ppb, and the concentration does not vary by more than ± 10%; and wherein the composition includes those products having a concentration of about 500ppb of reactive gas with a variation in concentration of no more than ± 15%; and compositions therein including those having a concentration of about 100ppb of reactant gas with a variation in concentration of no more than + -20%. Articles wherein the composition includes a higher or lower concentration of the reactive gas and correspondingly greater or lesser concentration variations are also contemplated within the scope of the present invention.

Preferred articles of the invention comprise only a single reactant gas and an inert gas such as nitrogen, argon, helium, and the like. The composition may comprise a mixture of two or more reactive gases. Also, in some preferred embodiments, the equilibrium component of the fluid is a hydrocarbon, such as ethylene, propylene, and the like.

A third aspect of the present invention is a method of making an article of the present invention, the method comprising the steps of:

i) reducing the moisture content of the reaction gas (preferably an acid gas, preferably a sulfur-containing gas) with an acid gas-resistant molecular sieve to form a dehumidified reaction gas;

ii) reducing the moisture content of the matrix gas by dehumidifying means to form a dehumidified matrix gas;

iii) vacuum baking the inner metal surface of the container (preferably any metal surface including the metal valve associated with the container) at a temperature of from about 30 ℃ to about 75 ℃ for no less than 1 hour (preferably no less than 6 hours, more preferably no less than 12 hours) under a vacuum of no more than 100torr, preferably no more than 1torr, more preferably no more than 0.01torr, to form a vacuum baked inner metal surface of the container;

iv) exposing the vacuum baked inner metal surface of the container to a first fluid composition comprising a silicon-containing compound, preferably selected from compounds within the range of formula (II), for a time sufficient to react at least some of the silicon-containing compound with an oxygen-containing compound present, preferably selected from moisture, molecular oxygen, metal oxides and mixtures thereof, to form a silicon-treated surface on at least a portion of the vacuum baked inner metal surface of the container;

v) evacuating the vessel for a time sufficient to remove substantially all of the silicon-containing compound that has not reacted with the oxygen-containing compound to form the silicon-treated surface;

vi) exposing the silicon treated surface to a second fluid composition comprising a reactive gas at a concentration higher than the desired reactive gas concentration of the article;

vii) evacuating the vessel for a sufficient time to remove just enough of the second fluid composition to enable the low concentration of reactant gas for extended shelf life to be maintained at the desired concentration in the vessel; and

viii) combining at least a portion of the dehumidified reactant gas and at least a portion of the dehumidified substrate gas to form a desired gas composition in the vessel

Preferred processes in this aspect of the invention are those wherein the silicon-containing compound is selected from the group consisting of silane, methylsilane, dimethylsilane, trimethylsilane and tetramethylsilane. Also preferred are processes wherein the reactive gas concentration of the second fluid composition is at least 10 times the concentration of the desired reactive gas species; and wherein the method of steps iv) and v) is repeated before step vi); and wherein the metal surface is cleaned prior to step iii); and wherein the concentration of the silicon-containing compound used in step vi) is in the range of about 100ppm to 100%; and wherein the second composition is heated to a temperature of not more than 75 ℃ during step vii). Other preferred methods are those wherein the container is a gas cylinder with an attached cylinder valve and the cylinder valve is removed prior to step iv). After completion of steps i) to vi), the process steps iv) to vi) are repeated, preferably at the very high temperatures used for steps iv) and vi), followed by attachment of the cylinder valve, but steps iv) and vi) are carried out at not more than 75 ℃.

Preferred acid gas-resistant molecular sieves are selected from molecular sieves having an effective pore size in the range of from about 1 angstrom to about 10 angstroms, more preferably from about 3 angstroms to about 8 angstroms. Preference is given to molecular sieves known under the trade names AW300 and AW500, in particular molecular sieve AW300 here.

Preferably, in the present invention, the moisture removal step is carried out at a combination of temperature and flow rate that ensures that water in the fluid does not freeze and that the reaction gas does not decompose. The preferred temperature range is from just above 0 ℃ to just below the temperature at which the reaction gases decompose. Temperatures below 0 c are disfavored due to the possibility of water freezing in the vessel or in the pores of the molecular sieve or both. It is not favoured to use temperatures above the decomposition temperature of the reaction gas during moisture removal due to possible decomposition of the reaction gas. By increasing the flow rate (or decreasing the residence time) conditions in the vessel, it may be possible to temporarily operate below 0 ℃ or above the decomposition temperature. Generally, it is preferred to operate at reduced temperatures because acid gas resistant molecular sieve materials appear to function more efficiently at these temperatures.

Further aspects and advantages of the invention will become apparent from a reading of the following description of the preferred embodiments.

Brief Description of Drawings

FIG. 1 is a logic diagram illustrating the method of the present invention;

FIG. 2 is a graph showing data for removing moisture from hydrogen sulfide (reactant gas) in one embodiment of the present invention; and

FIG. 3 shows 1ppm H₂Stability data for a standard mixture of S, which is first as shown2, and mixed with a purchased vinyl-based gas initially containing 1ppm moisture, and vacuum-baked at 65 c under 1torr vacuum for 6 hours.

Description of the preferred embodiments

Adsorption of moisture from fluid compositions comprising moisture and sulfur-containing compounds can be estimated by a variety of theories, except for those theories that do not recognize the benefit of using acid gas-resistant molecular sieves. The extent to which moisture adsorbs onto the acid gas-resistant adsorbent depends in a complex manner on the physical and chemical characteristics of the adsorbent, the temperature and pressure employed during this step, and the chemical and physical characteristics of the particular sulfur-containing fluid from which the moisture is removed. These parameters in turn depend on the final moisture concentration of the sulfurous fluid to be generated.

A useful discussion in this regard regarding the adsorption of gaseous samples onto surfaces is contained in Daniels, F.et al, "Experimental Physical Chemistry", 7 th edition, McGraw-Hill, 369-374 (1970). Although the inventors are less certain, it is believed that the attractive forces attracting the reactant gases to the surface layer are physical in nature, including dipoles or induced interactions between dipoles, but may also be chemical in nature, including chemical bonds, when oxygen is adsorbed onto the carbon. A combination of physical and chemical forces may also act simultaneously.

As described by Daniels et al, the infrared experimental data of adsorption can be plotted as adsorption isotherms, where the amount of gas adsorbed per gram of adsorbent material is plotted against the equilibrium pressure (expressed as milliliters of 0 ℃ and 760 mm). In many adsorption cases, the amount of substance adsorbed can be correlated to the equilibrium pressure using the Freundlich empirical formula:

V＝kPⁿ

wherein

V is ml of gas adsorbed per gram of adsorbent, corrected to 0 ℃ and 760 mm;

p is pressure; and

k and n are constants that can be calculated from the slope and intercept of the line obtained by plotting logV against logP.

Alternatively, Langmuir considers that adsorption distributes molecules as a monolayer onto the surface of the adsorbent. Taking into account the dynamic equilibrium between adsorbed and free molecules, the following relationship is obtained:

P/V＝P/V_u+1/kV_u

wherein P and V are as previously defined and V_uIs the volume at 0 ℃ and 760mm of gas adsorbed per gram of adsorbent after monolayer formation, and k is the characteristic constant of the adsorbent-adsorbate. Thus, if P/V is plotted against P, a straight line is obtained if the Langmuir equation is used. The slope of the line is 1/V_u(ii) a When the wire is extended to a low voltage region, e.g., P to 0, P/V reaches a finite limit of 1/kV_u. The value of the constant can also be obtained by plotting 1/V against 1/P. By assuming that a monolayer of adsorption is established on the surface, Brunauer, Emmett and Teller extend the Langmuir derivation for monolayer adsorption, resulting in isothermal equations for more complex cases. Thus, the surface area of the coating obtained by the practice of the present invention can be determined by the b.e.t method, and is preferably at least about 1m²A/g, more preferably at least 10m²(ii) in terms of/g. If the coating is slightly porous, the pore volume can be determined by nitrogen isothermal adsorption, preferably at least 0.1 ml/g. The b.e.t method is described in detail in Brunauer, s.emmet, p.h. and Teller, e.et al, j.am.chem.soc., 60, 309-16 (1938). Nitrogen isothermal adsorption methods are described in detail in Barrett, e.p., Joyner, l.g., Helenda, p.p., et al, j.am.chem.soc., 73, 373-80(1951), which is incorporated herein by reference.

As previously mentioned, the term "removal" means that the water content of the final composition comprising the sulfur-containing compounds will be equal to or less than 100ppb, more preferably less than 10ppb, still more preferably less than 1 ppb. (as previously indicated, these moisture concentrations are not presently directly measurable, but rather are obtained by dilution.) the term "reduced" as used herein means that the moisture concentration of the final composition comprising the sulfur-containing compound will be no more than 0.1 times, preferably no more than 0.01 times, and more preferably no more than 0.001 times the initial moisture concentration of the initial fluid composition.

Acid gas resistant molecular sieves useful in the present invention are typically, and preferably, those described by Ameen et al (U.S. Pat. No. 4,358,627), incorporated herein by reference. Preferred are acid gas resistant molecular sieves known under the trade names AW300 and AW500, available from Universal Oil Products (UOP). The molecular sieve known under the trade designation AW300 has an effective pore size of about 4 angstroms and the molecular sieve known under the trade designation AW500 has an effective pore size of about 5 angstroms. A discussion of Acid Gas Resistant Molecular sieves can be found in "A Report on Acid-Resistant Molecular Sieve type sAW-300 and AW-500" of Collins, J.J., Oil and Gas Journal, 1963, 12, 2, which is incorporated herein by reference. Such molecular sieves can be used as particles having diameters of about one-eighth of an inch and one-sixteenth of an inch.

As described in U.S. patent No. 4,358,627, molecular sieves are crystalline metal aluminosilicates. The molecular sieve being substantially SiO₄And AlO₄A three-dimensional framework of tetrahedra, the tetrahedra being cross-linked by sharing oxygen atoms, such that the ratio of oxygen atoms to the total number of aluminum and silicon atoms is equal to 2. The electrovalence of the aluminum-containing tetrahedra is balanced by the inclusion in the crystal of a cation, such as an alkali or alkaline earth metal ion. One cation may be exchanged for another by known ion exchange techniques. The spaces between the tetrahedra are occupied by water molecules prior to dehydration. Dehydration produces crystals that are interwoven with channels on a molecular scale, providing a very high surface area for the adsorption of foreign molecules. Furthermore, the term "molecular sieve" as used herein is not meant to be only aluminosilicate but also includes materials in which aluminum has been partially or fully substituted with, for example, gallium and/or other metal atoms, and further includes materials in which some or all of the silicon has been substituted with, for example, germanium.Substitution of titanium and zirconium is also possible. Most molecular sieves, also known as zeolites, are prepared in the sodium form or are naturally occurring such that sodium cations are associated with negative potentials in the crystal structure. However, the molecular sieve may be ion exchanged. Suitable cations for replacing sodium in the molecular sieve crystal structure include ammonium (which can be decomposed to hydrogen), hydrogen, rare earth metals, alkaline earth metals, and the like. Various suitable ion exchange steps and cations that can be exchanged into the crystal structure are known to those skilled in the art. Examples of naturally occurring crystalline aluminosilicate zeolites which may be employed or included in the present invention are faujasite, mordenite, clinoptilolite, chabazite, analcime, erionite, and levyne, dachiardite, boehmite, tetrahedron, tetrahedrite, ferriorite, heulandite, stibnite, harmotome, calamine, brewsterite, flarite, wailbosite, gmelinite, caumnite, leucite, celestite, andalusite, tholite, nepheline, matrolite, offretite and sodalite. Examples of synthetic aluminosilicate zeolites useful in the practice of the present invention are zeolite X, see U.S. patent nos. 2,882,244; zeolite Y, see U.S. Pat. nos. 3,130,007; zeolite a, see U.S. patent nos. 2,882,243; and zeolite B, see U.S. patent nos. 3,008,803; zeolite D, see canadian patent 661,981; zeolite E, see canadian patent 614,495; zeolite F, see U.S. patent No. 2,996,358; zeolite H, see U.S. patent No. 3,010,789; zeolite J, see U.S. patent No. 3,001,869; zeolite L, see belgian patent No. 575,177; zeolite M, see U.S. patent No. 2,995,423; zeolite O, see U.S. patent No. 3,140,252; zeolite Q, see U.S. patent No. 2,991,151; zeolite S, see U.S. patent No. 3,054,657; zeolite T, see U.S. patent No. 2,950,962; zeolite W, see U.S. patent No. 3,012,853; zeolite Z, see canadian patent No. 614,495, and zeolite omega, see canadian patent No. 817,915. ZK-4HJ, alpha, beta and ZSM-type zeolites are also effective. In addition, the molecular sieves described in U.S. Pat. Nos. 3,140,249, 3,140,253, 3,044,482 and 4,137,151, the disclosures of which are incorporated herein by reference, are also effective.

Referring now to FIG. 1, there is schematically illustrated a logical block diagram for implementing the method of the present invention. At step 12, a container having a metallic inner surface is selected. In step 13, the metal surface is vacuum baked at a temperature in the range of about 30 ℃ to about 75 ℃ for no less than 1 hour, preferably no less than 6 hours and more preferably no less than 12 hours under reduced pressure of preferably no more than 100torr, more preferably no more than 1torr, even more preferably no more than 0.01 torr. This forms a vacuum baked inner metal surface which is subsequently exposed to a silicon containing passivating species in step 14 for a sufficient length of time and at a temperature and pressure sufficient to react a substantial portion of the silicon containing species with oxygen containing compounds present on the metal surface. The single step 14 is a known passivation technique, typically combined with a nitrogen bake, and does not require much explanation to the skilled person. See, for example, "Wechter on Stable polarization Gas Standards", p.44, ASTM (1976). The vessel is then evacuated at step 16 for a time sufficient to remove most of the unreacted silicon-containing material. Next, at step 18, the metal surface is contacted with a high concentration of the reactant gas or fluid of the desired end product to be loaded into the container. Step 18 is also known as an alternative passivation technique to step 14 and does not require much explanation to the skilled person. See "Wechter on Stable polutionGas Standards", p.43-44, ASTM (1976). At step 20, the vessel is again evacuated for a time sufficient to remove substantially all of the non-adsorbed reactant gases. The container is then ready for filling at step 22, or filled with a composition of the desired materials having the desired moisture and reactive gases, or with the dehumidified substrate gas and the dehumidified reactive gases, or with the dehumidified substrate gas and then the dehumidified reactive gases, or with the dehumidified reactive gases and then the dehumidified substrate gas. Here, the vessel is equilibrated and the concentration of the gas in the vessel is detected at different times to determine the concentration of the reactive gas in the vessel. At step 24, if shelf life is acceptable, the product is prepared according to the subsequent steps at step 26. If the gas concentration increases or decreases beyond a specified tolerance, the process of steps 20, 22, 24 is repeated. Optionally, steps 14 and 16 may be repeated, as shown at step 26.

Moisture may be removed from the reaction gas as taught in co-pending U.S. serial No. 10/157467 filed concurrently with this application. The co-pending application describes an apparatus comprising a fluid inlet end, a fluid outlet end, a vessel, and an acid gas-resistant molecular sieve contained within the interior space of the vessel. The container may take any shape desired by the user, including cylindrical, kidney-shaped, spiral, and the like. The container is preferably cylindrical. The fluid outlet port may be connected to a conduit that preferably conveys some or all of the effluent fluid having a reduced moisture content to a means for moisture detection, preferably a diode laser detector as described in U.S. patent nos. 5,880,850, 5,963,336 and 6,154,284, all incorporated herein by reference. Such detectors typically include one or more diode laser sources, temperature control circuits and the like, as well as a spectroscopic chamber through which the diode laser passes and encounters all or part of the gas sample to be analyzed. By analyzing the sample of interest for absorbed radiation, here moisture, the concentration of the sample of interest can be determined. Similar equipment and moisture detectors are preferably used to remove moisture from the matrix gas. In practice, a source of reactive gas, such as a storage tank or truck trailer, or other fluid source, such as a gas cylinder or volume unit cell, is provided. The volume unit element may be a liquid or gas source. In any event, the fluid comprising the reaction gas and moisture enters the means for removing moisture, as described in accordance with co-pending serial application No. The means for removing moisture may have a spare unit or a unit installed in parallel. The bypass enables one container to be taken out of service or replaced if required. The reduced moisture fluid exits the vessel and is then either mixed with the dehumidified matrix gas or sent directly to a vacuum baked and passivated vessel. Alternatively, the reduced moisture reaction fluid may be passed through a downstream processing unit, preferably one that removes particulate matter that may have escaped from the molecular sieve. An optional temperature control unit is preferred. As a general rule, acid gas-resistant molecular sieves appear to be more effective at lower temperatures (25 ℃ and below), although we must take care not to freeze the water to be removed. In addition, the temperature can also be above 25 ℃, at which chemisorption plays a significant role throughout the adsorption due to the higher kinetic rate constants at higher temperatures. However, as the temperature is raised higher, this effect will tend to be inhibited by physical desorption of moisture from the molecular sieve.

The means for retaining the molecular sieve in the vessel is a material that is substantially inert to acid gases. Preferably, the means for retaining the molecular sieve in the vessel is the molecular sieve material itself contacting the inner surface of the vessel. For economic reasons it is preferred to keep the acid gas resistant molecular sieve in an auxiliary or material inside the container, for example end sieves made of porous metal such as stainless steel, aluminum, VCR connections, packings, glass frits and the like at the fluid inlet and outlet ends. In addition, the acid gas resistant molecular sieve is preferably mixed with one or more acid resistant materials, preferably another molecular sieve material. The use of more than one vessel in parallel or in series with the flow of feed fluid is within the scope of the invention. For example, it may be desirable to have a series arrangement in which the second or subsequent vessels have the same or different molecular sieve materials. In a parallel arrangement, two vessels containing the same molecular sieve in each vessel are preferred, and flow in one vessel is preferably achieved while the other vessel is being regenerated, such as by heating, contacting a dry fluid, or combinations thereof. These parallel or series arrangements are known in the art of adsorption, for example in the field of air separation.

The dehumidified composition of the present invention preferably includes a dehumidified reactive gas and a dehumidified substrate gas, the composition including at least one reactive gas having a reactive gas concentration and a moisture concentration that is no more than 0.1 times the concentration of the reactive gas in the substrate gas. The fluid composition may contain one or more reactive gases. If there is more than one, two reactant gases, the molar ratio of the two gases is in the range of about 1: 99 to about 99: 1, more preferably in the range of about 20: 80 to about 80: 20, and more preferably in the range of about 40: 60 to about 60: 40. Examples of fluid compositions contemplated in the present invention include mixtures of carbonyl sulfide and hydrogen sulfide in a nitrogen matrix gas, wherein the molar ratio of carbonyl sulfide to hydrogen sulfide is in the range of from about 20: 80 to about 80: 20; mixtures of hydrogen sulfide and methyl mercaptan (also known as methyl mercaptan) in a nitrogen base gas, wherein the molar ratio of hydrogen sulfide to methyl mercaptan is in the range of about 20: 80 to about 80: 20, and the like.

In the moisture removal step, the flow rate of the aqueous partial fluid (reactant gas or matrix gas) will be sufficient to establish a space velocity of preferably at least 1 container volume per minute, more preferably at least 5 container volumes per minute. Although not preferred, it is also possible to mix the wet reaction gas and the wet matrix gas and then remove moisture from both the reaction gas and the matrix gas. It is believed, however, that the removal of moisture from the reactant gas and the substrate gas, respectively, is more controllable and thus more preferred. The space velocity of the process depends on the temperature of the feed stream, the moisture content of the feed stream, and the flow pattern through the apparatus of the present invention. If the fluid is gaseous, higher temperatures and higher flow rates will tend to create more difficulty in removing moisture from the fluid, as the fluid volume will tend to be larger and the contact time less. Conversely, a generally lower temperature and lower feed flow rate will favor greater moisture removal. The feed pressure is not critical, but should not be so high as to drop the pressure across the vessel too high to damage the molecular sieve. Preferably, a method for filtering the product stream is provided (downstream of the molecular sieve) to filter out particles that may be dislodged from the bulk portion of the molecular sieve.

FIG. 2 is a graph illustrating data for removing moisture from hydrogen sulfide in one embodiment of the present invention. The unit includes 14 grams of a molecular sieve known under the trade name AW300 through which flows a gas stream containing hydrogen sulfide and from about 60 to about 80ppm moisture. The experiment was carried out at room temperature (about 20 ℃). The flow rate of the gas stream through the molecular sieve was 1 liter/min. The moisture in the air stream exiting the apparatus is measured with a diode laser measurement system, as described in U.S. patent nos. 5,880,850, 5,963,336, and 6,154,284, which have been previously incorporated herein by reference, although other methods of moisture analysis may also be used. As can be seen from the data of fig. 2, molecular sieves work very well in reducing the moisture content of hydrogen sulfide gas streams.

Sulfur dioxide gas streams were also tested and similar moisture removal capabilities were observed.

FIG. 3 is a graph showing that H contained in 1ppm₂S38-day stability data for standard mixtures, which were first dehumidified as shown in FIG. 2, mixed with a commercially available ethylene-based Gas (ethylene purity 99.99995, commercially available from Special Gas Service, initially containing 1ppm of moisture), and vacuum baked at 65 ℃ under 1torr vacuum for 6 hours. It can be seen that the stability of the mixture is quite good after this period of time. Although these data are obtained with commercially available ethylene base gases having reduced moisture, it is anticipated that the same or very similar results will be obtained when a "wet" mixture of reactant gas and base gas is used, the mixture is then dehumidified and the dehumidified mixture is placed in a passivated vessel in accordance with the present invention, or when the "wet" reactant gas and "wet" base gas are taken separately, dehumidified separately, and then mixed in a passivated vessel.

While the description herein is intended to be representative of the invention, it is not intended to limit the scope of the appended claims.

Claims (9)

1. An article of manufacture, comprising:

a) a container having an interior space and a passivated inner metal surface;

b) a composition contained within said interior space and in contact with said passivated inner metal surface,

wherein the composition comprises a reactive gas and a matrix gas, wherein the concentration of the reactive gas in the composition relative to the matrix gas is not more than 1ppm,

wherein the reactive gas has a desired concentration sufficiently maintained, and the composition has a moisture concentration of not more than 100ppm,

wherein the passivated inner metal surface comprises:

a reaction product of a silicon-containing material and an oxygen-containing material, and a portion of the reaction gas absorbed on the reaction product,

wherein the portion of the reaction gas absorbed on the reaction product is formed by prior exposure of the reaction product to a high concentration of the reaction gas prior to evacuation of the high concentration of the reaction gas therefrom for charging the composition into the interior space,

wherein the high concentration is many times the desired concentration of reactant gas to be adequately maintained.

2. The article of claim 1, wherein the reactive gas has a concentration of about 100ppb, and the concentration does not vary by more than ± 20%.

3. The article of claim 1 wherein the oxygen-containing material is selected from the group consisting of moisture, molecular oxygen, metal oxides, and mixtures thereof.

4. The article of claim 1, wherein the passivating metal is selected from the group consisting of aluminum, aluminum alloys, steel, iron, and combinations thereof.

5. The article of claim 1, wherein the silicon-containing material is selected from compounds within the range of general formula (II):

SiR¹R²R³R⁴ (II)

wherein R is¹、R²、R³And R⁴The same or different and are independently selected from the group consisting of hydrogen, halogen, amine, alkyl, aryl, haloalkyl, and haloaryl.

6. The article of claim 5 wherein the silicon-containing compound is selected from the group consisting of silane, dimethylsilane, trimethylsilane, tetramethylsilane, and mixtures thereof.

7. The article of claim 1 wherein the matrix gas is selected from the group consisting of nitrogen, argon, helium, and mixtures thereof.

8. The article of claim 1, comprising a mixture of two or more reactive gases in a matrix gas.

9. The article of claim 1, wherein the gas composition comprises a hydrocarbon.