Improved hydrocyanic acid production

Abstract

Improved processes for the production of hydrogen cyanide (HCN) are provided. The processes involve nitric oxide (NO) doping. The processes also involve reducing the loss of HCN due to hydrolysis. A two stage process for the production of HCN is also provided. The two stage process occurs in two separate reactors or in a singular reactor with two reactor zones. A process for the production of HCN from a gaseous hydrocarbon and NO is also provided. Reactor designs and vessels for conducting processes of the invention are also provided.

Description

[0001] IMPROVED HYDROCYANIC ACID PRODUCTION

[0002] Cross-Reference to Related Applications

[0003]

[0001] This application claims priority to U.S. Provisional Application No. 63 / 718,816, filed on November 11, 2024; the disclosure of which is incorporated herein by reference.

[0004] Field of the Invention

[0005]

[0002] This invention relates to improved processes, including a two-stage process, for the production of hydrogen cyanide (HCN) that result in a higher yield of HCN, as well as reactor designs and vessels for those processes.

[0006] Background of the Invention

[0007]

[0003] Hydrogen cyanide (HCN) is a highly volatile, colorless, and extremely poisonous gas. It can be used for many chemical processes, such as fumigation and producing the monomer methyl methacrylate and adiponitrile. HCN is also a precursor to making sodium cyanide and potassium cyanide, which are essential in hardening of iron and steel, electroplating, and in the lixiviation of ores in gold and silver mining.

[0008]

[0004] HCN is produced by heating a mixture of gaseous or vaporous carbon compounds, e.g. methane (CH4), with ammonia (NH3) in the presence of oxygen (O2), or air, and a catalyst consisting of platinum (Pt) and rhodium (Rh), where Rh contributes to catalyst activity and its strength. The ammoxidation reaction of CH4with NH3to produce HCN is considered the dominant reaction in HCN formation and is known to be fast, but also is endothermic requiring the addition of substantial amounts of heat.

[0009] Andrussow found that this endothermic reaction could be converted to an exothermic ammoxidation reaction by heating a mixture of NH3, a hydrocarbon (e.g. CH4), and an appropriate amount of O2over an oxidation catalyst. See U.S. Patent No. 1,934,838. The NH3and the hydrocarbon are catalytically converted by the O2and catalyst to produce HCN in a single stage reactor. A typical catalyst is a noble metal catalyst in the form of a gauze or similar structure. Layered gauzes woven from Pt and Rh allow a shorter contact time and less resistance to the high velocity gas flow.

[0010]

[0005] Known as the Andrussow process, the dominant commercial reaction process for making HCN is performed by mixing NH3, a hydrocarbon containing CH4, and O2 (often introduced using air) in the presence of a Pt-gauze catalyst produces HCN along with water (H2O), nitrogen (N2) gas, steam, hydrogen (H2), and carbon monoxide (CO) as by-products. The Andrussow process also produces trace amounts of nitric oxide (NO) and carbon dioxide (CO2). Ideal HCN yields are achieved when there are about 1.5 molecular proportions of O2for a mixture of 1 molecular proportion of NH3and CH4. A major undesired reaction is NH3loss to N2. The optimal yield is reached with a very short contact time, such as 0.0003 seconds. See, Pirie, J. M., Platinum Metals. Rev., 1958, 2, (1), 7-11.

[0011]

[0006] The Andrussow process is, in fact, a complex process which can be modelled as thirteen simultaneous reactions. See, Waletzko and Schmidt, AIChE Journal, Vol. 34, No. 7, p. 1146 (1988). As described by Waletzko and Schmidt, in typical industrial Andrussow reactors CH4, NH3, and O2are preheated to ~100 °C or greater in a ratio of 1:1:1.3 of CH4: NH3: O2and passed over the catalyst at between 1 and 2 atm. The exothermic reaction then produces a catalyst gauze temperature of around 1,100 °C. Yields of HCN are less than 65% without NH3recycle, and typically between 50-65% on a commercial basis. H2O, H2, and CO are major by-products with traces of NO and CO2and other carbon and nitrogen compounds. In Table 1, Waletzko and Schmidt identify thirteen major reactions, shown below, in the Andrussow process:

[0012]

[0013]

[0014] corrected from the literature reference). From their study, Waletzko and Schmidt found evidence that the production of oxidation products (CO, CO2, N2, H2O, and NO) essentially ceases as soon as O2disappears. HCN production then continues steadily until all the CH4 or NH3is consumed. N2production rises slowly after all O2is consumed and H2becomes the major product. See, Waletzko and Schmidt, p. 1150 and Figure 2. If the hydrolysis of HCN to form NH3and CO is included, the number of reactions increases to fourteen. See, McKenna et aL, l& EC Res, 1993, Vol. 32, No.9, 1906, Table 1. Other reactions may be possible in the system.

[0015]

[0007] Given the complexity of the Andrussow process and the competing non-selective reactions that lead to a reduction in yield of HCN, there is a need for a simpler and more direct process to produce higher yielding HCN systems, with reduced concentrations of by-products.

[0016] Summary of the Invention

[0017]

[0008] The invention relates to improved processes for the production of hydrogen cyanide (HCN). These processes provide an improved process of producing HCN over the known Andrussow process. The invention further relates to reactor designs and vessels for conducting the processes of the invention.

[0018]

[0009] The invention further relates to an improved process for the production of HCN comprising the steps of introducing ammonia (NH3) gas, an oxygen (O2)-containing gas, a gaseous hydrocarbon, and nitric oxide (NO) gas to a reactor as at least one gaseous feed stream; and reacting the gases in the gaseous feed stream in the presence of a suitable catalyst, preferably a platinum (Pt)-gauze catalyst, at a reaction temperature ranging from about 800 °C to about 1200 °C to produce HCN.

[0019]

[0010] The invention further relates to an improved process for the production of HCN comprising the steps of introducing NH3gas, an O2-containing gas, and a gaseous hydrocarbon to a reactor in at least one gaseous feed stream; reacting the gases in the gaseous feed stream in the presence of a suitable catalyst, preferably a Pt-gauze catalyst, at a reaction temperature ranging from about 800 °C to about 1100 °C to produce HCN while limiting the competing HCN hydrolysis reaction; separating the HCN produced; and recycling unreacted gaseous hydrocarbon, unreacted NH3gas, or unreacted gaseous feed stream to the reactor. This improved process of the invention may further comprise a step of introducing to the reactor a gaseous feed stream comprising NO gas. In some embodiments of the invention, the HCN is separated by scrubbing the HCN with a solvent other than water.

[0020] [Oil] The invention further relates to a two-stage process for the production of HCN comprising the steps of, in a first reactor, reacting NH3gas with an oxygen-containing gas in the presence of a suitable catalyst, preferably a Pt-gauze catalyst, at a reaction temperature ranging from about 600 °C to about 950 °C to produce an NO-containing gas; and, in a second reactor, reacting the NO in the NO-containing gas with a gaseous hydrocarbon (e.g., containing methane (CH4)), optionally in the presence of a suitable catalyst, preferably a Pt-gauze catalyst, under suitable reaction conditions to produce HCN. In some embodiments of the invention, the second stage can stand alone as its own process. In some embodiments of the invention, the reaction in the second reactor takes place at a reaction temperature ranging from about 600°Cto about 1,000 °C to produce HCN.

[0021]

[0012] The invention further relates to a two-stage process in a single reactor with two reactor zones for the production of HCN comprising the steps of, in a first reactor zone of the single reactor system, producing an NO-containg gas from the reaction of NH3with an O2-containing gas in the presence of a suitable catalyst, preferably a Pt -gauze catalyst, and, in the second reactor zone of the single reactor system, reacting the NO-containing gas with a gaseous hydrocarbon, optionally in the presence of a suitable catalyst, preferably a Pt -gauze catalyst, at a reaction temperature ranging from about 600 °C to about 1,000 °C to produce HCN in a single reactor system.

[0022]

[0013] The invention further relates to a process for the production of HCN from a gaseous hydrocarbon and NO comprising the step of reacting a gaseous hydrocarbon and NO gas, optionally in the presence of a suitable catalyst, preferable a Pt-gauze catalyst. Brief Description of the Figures

[0023]

[0014] FIG. 1 shows the effect of the partial pressure addition of the NO doping of the at least one gaseous feed stream on the conversions of the other gases (NH3gas, the O2-containing gas, and the gaseous hydrocarbon) and on the HCN yield.

[0024]

[0015] FIG. 2 shows a comparison of HCN yields in the presence and absence of hydrolysis for an Andrussow process at 900 °C and 1100 °C, wherein the dotted lines represent with hydrolysis.

[0025]

[0016] FIG. 3 shows exemplary comparisons of HCN yield versus catalyst gauze length for different feed compositions with various NO doping ratios.

[0026]

[0017] FIG. 4 shows a graphical illustration of partial pressure in torr versus thickness (z) of catalyst in cm when an equimolar amount of CH4as the gaseous hydrocarbon and NO are used in the feed.

[0027]

[0018] FIG. 5 shows a graphical illustration of yield of HCN versus thickness of catalyst in cm when a commercial Andrussow process is used in comparison with a process of the invention where an equimolar amount of CH4as the gaseous hydrocarbon and NO are used in the second stage feed.

[0028]

[0019] FIG. 6 shows the rate of reaction for the NO process, Rxn 11, as twelve orders of magnitude faster than the dominant Andrussow process using NH3, CH4and air, shown in Rxn 2, which has been defined as the dominant reaction for synthesizing HCN.

[0029]

[0020] FIG. 7 shows a single reactor system for producing HCN according to the invention with a gaseous feed stream of air, natural gas, and NH3.

[0030]

[0021] FIG. 8 shows a single reactor system for producing HCN according to the invention with a gaseous feed stream of air and NH3.

[0031]

[0022] FIG. 9A shows a single reactor system to produce HCN according to the invention.

[0032]

[0023] FIG. 9B shows a cross-sectional area of element A-A of FIG. 9A.

[0033]

[0024] FIG. 10 shows a two-reactor system that may be used to produce HCN according to the invention.

[0034]

[0025] FIG. 11 shows a two-reactor system with a primary reformer to produce HCN according to the invention

[0026] FIG. 12 shows a single reactor system with two reaction zones to produce HCN according to the invention.

[0035] Detailed Description

[0036]

[0027] The invention relates to improved processes for the production of hydrogen cyanide (HCN), such as improved Andrussow processes. The processes of the invention may involve reacting ammonia (NH3) gas, an oxygen (O2)-containing gas, a gaseous hydrocarbon, and / or NO gas. Some of the processes of the invention involve reacting gases in the presence of a suitable catalyst.

[0037]

[0028] The O2-containing gas used in any of the processes of the invention may be O2itself or any O2-containing gas mixture known in the art which does not contain other gases that seriously impede the reaction or which compromise the production of HCN. In a preferred embodiment of the invention, the O2-containing gas is air, which contains about 21% O2by volume. The air may be scrubbed and / or dried using means known in the art to reduce or remove the amount of impurities or water vapor that can degrade the HCN conversion and yield.

[0038]

[0029] The gaseous hydrocarbon used in any of the processes of the invention may be selected from methane (CH4) (e.g., natural gas), ethane (C2H6), propane (C3H8), butane (C4H10), or mixtures thereof. In some embodiments of the invention, the gaseous hydrocarbon is selected from CH4, C2H6, or mixtures thereof. In some embodiments of the invention, the gaseous hydrocarbon is CH4. In a preferred embodiment of the invention, the gaseous hydrocarbon is CH4which is supplied as natural gas. A cryogenic fractionator, conventionally called a de-methanizer, can be utilized as known in the art to distill the CH4to increase the CH4concentration in the natural gas. Alternatively, other means known in the art can be used to increase the CH4concentration in the natural gas. These other means include, but are not limited to, condensing higher hydrocarbons by reducing the gas temperature below the dew point or raising the pressure so that the ambient temperature is below the dew point; or scrubbing or adsorbing the higher hydrocarbons and using selective membranes. Any of these methods, or any combination thereof, may be employed to increase the CH4concentration in the natural gas.

[0030] The suitable catalyst used in any of the processes of the invention may be any catalyst used in a typical Andrussow process. In some embodiments of the invention, the suitable catalyst is a gauze catalyst that is composed of wires. In some embodiments of the invention, the wires are about 0.0075 cm in diameter. In some embodiments of the invention, a platinum (Pt)-gauze catalyst is used. In some embodiments of the invention, the Pt-gauze catalyst comprises Pt and rhodium (Rh) wires. In some embodiments of the invention, the Pt-gauze catalyst comprises up to about 30 wt% Rh, about 1 to about 25 wt% Rh, about 5 to about 25 wt% Rh, about 15 to 22 wt% Rh, or about 10 or 20 wt% Rh. In some embodiments of the invention, the Pt-gauze catalyst comprises Pt, Rh, and palladium (Pd) wires. In some embodiments of the invention, the Pt-gauze catalyst comprises up to about 15 wt% Rh and 5 wt% Pd (e.g., about 1 to about 10 wt% Rh and about 1 to about 5 wt% Pd, about 5 to about 10 wt% Rh and about 3 to about 5 wt% Pd, and about 10 to about 15 wt% Rh and about 1 to about 5 wt% Pd). The gauze catalyst may vary in thickness from 4 to 50 sheets depending on operating pressure. Less sheets are required for lower pressure systems. The thickness of a sheet is minimally equivalent to the wire diameter; however, the effective thinkness is larger due to non-uniformaties that may be introduced during the sheet stacking process.

[0039]

[0031] An improved process of the invention for the production of HCN involves NO doping. The process comprises introducing NH3gas, an O2-containing gas, a gaseous hydrocarbon, and NO gas to a reactor as at least one gaseous feed stream. The process further comprises reacting the NH3gas with the O2-containing gas, the gaseous hydrocarbon, and the NO gas in the at least one gaseous feed stream in the reactor in the presence of a suitable catalyst, preferably a Pt -gauze catalyst, at a reaction temperature ranging from about 800 °C to about 1200 °C (e.g. from about 900 °C to about 1150 °C, from about 950 °C to about 1100 °C, and from about 1000 °C to about 1050 °C) to produce HCN. In some embodiments of the invention, the reaction temperature is 1100 °C. The component gases of the at least one gaseous feed stream may be introduced as a gaseous mixture of two or more gases to the reactor or may be individually introduced to the reactor as separate gaseous feed streams. In some embodiments of the invention, the introduction step involves introducing to the reactor a first gaseous feed stream comprising the NH3 gas, the O2-containing gas, and the gaseous hydrocarbon and a second gaseous feedstream comprising the NO gas. In some embodiments of the invention, the introduction step involves introducing to the reactor a first gaseous feed stream comprising the NH3gas and the O2-containing gas and a second gaseous feedstream comprising the NO gas and the gaseous hydrocarbon. In some embodiments of the invention, the introduction step involves introducing to the reactor a first gaseous feed stream comprising the NH3gas and the O2-containing gas, a second gaseous feedstream comprising the NO gas, and a third gaseous feedstream comprising the gaseous hydrocarbon. In some embodiments of the invention, the introduction step involves introducing a first gaseous feed stream comprising the NH3gas, a second gaseous feed stream comprising the O2-containing gas, a third gaseous feed stream comprising the gaseous hydrocarbon, and a fourth gaseous feed stream comprising the NO gas. In some embodiments of the invention, the introduction step involves introducing a gaseous feed stream comprising the NH3gas, the O2-containing gas, the gaseous hydrocarbon, and the NO gas.

[0040]

[0032] Adding NO gas to the typical starting Andrussow reactant mixture reduces the possibility and probability of undesired side reactions that occur during the Andrussow process. These undesired side reactions consume reactants such as NH3, O2, CH4, and NO, which are needed for the production of HCN. Adding NO gas also lessens the formation of by-products from the undesired side reactions. NO doping of the gaseous feed stream of the Andrussow process can significantly increase the yield of HCN in the same reactor system. FIG. 1 shows the effect of the partial pressure addition of the NO doping of the at least one gaseous feed stream on the conversions of the other gases (NH3gas, the O2-containing gas, and the gaseous hydrocarbon) and on the HCN yield. In FIG. 1, the O2-containing gas is O2and the gaseous hydrocarbon is CH4. As shown in FIG. 1, the HCN yield % increases, the conversion % of NH3and CH increase, and the conversion % of O2decreases as the partial pressure addition of the NO gas increases.

[0041]

[0033] Exemplary comparisons of gaseous feed streams of different compositions and various NO doping ratios that can be used to enhance the Andrussow process reaction are described below in Example 1. The effect that doping the gaseous feed stream with NO has on the HCN yield for a modified Andrussow process at a fixed total pressure of 1600 torr and isothermal conditions ( / .e., a reaction temperature of 1127 °C) using the gaseous feed stream ratios of Table 1 below and the process parameters of Table 2 below, including a gauze catalyst length of 6.5 cm, are shown in the reactor inlet conditions of Table 3 below. In this exemplary comparison, the O2-containing gas is O2and the gaseous hydrocarbon is CH4. As shown in Table 3, the molar ratio of NH3gas to NO gas (rN) in the at least one gaseous feed stream may range from 2.5 to 20 and / or the molar ratio of carbon in the gaseous hydrocabon (CH4) to NO gas (rcx rN) in the at least one gaseous feed stream may range from 2.5 to 20. In some embodiments of the invention, rNis selected from 1, 2.5, or 20. In some embodiments of the invention, rcx rNis selected from 1, 2.5, or 20.

[0042]

[0034] Another improved process of the invention involves reducing the loss of HCN due to hydrolysis. The process comprises introducing NH3gas, an O2-containing gas, and a gaseous hydrocarbon to a reactor in at least one gaseous feed stream. The process further comprises reacting the NH3gas with the O2-containing gas and the gaseous hydrocarbon in the at least one gaseous feed stream in the reactor in the presence of a suitable catalyst at a reaction temperature ranging from about 800 °C to about 1100 °C (e.g., from about 800 °C to about 1000 °C, from about 850 °C to about 950 °C, and from about 850 °C to about 900 °C) to produce HCN while limiting the competing HCN hydrolysis reaction. In a preferred embodiment of the invention, the suitable catalyst is a Pt-gauze catalyst. In some ebmodiments of the invention, the reaction temperature is 900 °C. The process further comprises separating the HCN produced from the reaction of the gases and recycling any unreacted gaseous hydrocarbon, unreacted NH3gas, or unreacted gaseous feed stream back to the reactor. In this improved process of the invention, the molar ratios of the gases may be the same as used in current Andrussow processes. In some embodiments of the invention, NO may also be added as a dopant in a separate gaseous feed stream such as described above. In some embodiments of the invention, the separation step includes scrubbing the HCN with solvents other than water (H2O), like acetic acid. In some embodiments of the invention, the separation step includes reacting the produced HCN to form sodium cyanide (NaCN) as is known in the art. In some embodiments of the invention, the recycled gases may be dried to remove all or a portion of any H2O present prior to re-introduction into the reactor.

[0043]

[0035] FIG. 2 shows a comparison of HCN yields in the presence and absence of hydrolysis for an Andrussow process at 900 °C and 1100 °C, wherein the dotted lines represent with hydrolysis. The objective of the comparison in FIG. 2 is to compare HCN yields for the Andrussow process at 900 °C and 1100 °C both with and without hydrolysis. In FIG. 2, the O2-containing gas is O2and the gaseous hydrocarbon is CH4. The comparison was performed at a total pressure of 1600 torr with the process conditions described below in Table 4 of Example 2, including a gauze catalyst length of 6.5 cm, and reactor inlet conditions of Table 5. As shown in FIG. 2, at 900 °C, the HCN yield decreases from 38.9% without hydrolysis to 36.7% with hydrolysis, and at 1100 °C, the HCN yield decreases from 44.2% without hydrolysis to 28.4% with hydrolysis.

[0044]

[0036] In some embodiments of the invention, the NH3gas, the NO gas, and the gaseous hydrocarbon are present in substantially equimolar proportions. In some embodiments of the invention, the NH3gas and 02-containing gas are present in a molar ratio of 0.5 to 1.2.

[0045]

[0037] In some embodiments of the invention, the gases (NH3gas, O2-containing gas, gaseous hydrocarbon, and / or NO gas) may be preheated from about 100 °C to about 500 °C, without significant decomposition of the NH3gas, prior to introduction into the reactor using means known in the art. The reactant gases may be preheated using indirect heat exchange, such as a gas-gas heat exchanger, to cool the reactor outlet product gases.

[0046]

[0038] FIG. 3 shows exemplary comparisons of HCN yield versus catalyst gauze length for different feed compositions with various NO doping ratios. In FIG. 3, the catalyst gauze is a Pt-catalyst gauze, the O2-containing gas is O2, and the gaseous hydrocarbon is CH4. The reactor inlet feed conditions and reactor exit conditions are described below in Table 7 and Table 8 in Example 3, respectively. The abrupt changes in the slopes of the graphical data that generally occur at a short distance into the Pt-gauze catalyst are the result of NO being depleted from reaction CH4+ NO = HCN + ½ H2+ H2O. This is an extremely fast reaction when compared to the others. After this break in the slope occurs, the reaction relies upon NO from the oxidation of NH3versus a combination of the doped NO plus NO from the NH3oxidation. After the NO is depleted, another break in the slope can occur (see case 2 and case 4) when the CH4 / O2ratio is 0.5, since the CH4is then depleted. This causes the formation of HCN to cease. This is why the HCN yield remains constant after that gauze length is reached. In case 3, the feed is doped with 101 torr of NO (6.3 mol %) while the CH4 / O2ratio is 1.2, the CH4 / NH3ratio is 1, and the CH4 / NO ratio is 2.5. The mol% of CH4 in the feed is 15.7%. The HCN yield rapidly increases a short distance into the gauze length due to the fast reaction between CH4and NO. The slope of the HCN i / s gauze length curve is then reduced since the doped NO is consumed and it must be supplied solely from the oxidation of NH3. The HCN yield vs gauze length response then increases and produces 11 mol% of HCN in the product gas. This comparison shows that an equimolar feed composition (case 1) produces the highest HCN yield and a low composition of NO in the feed with NH3 / O2 and CH4 / O2 ratios > 1 (case 5) produces the lowest HCN yield. The fast reaction of CH4+ NO results in rapid depletion of NO and the ratios of NH3 / O2and CH4 / O2(cases 2-4) controls the HCN yield. In case 4, the lowest NO (7 torr), along with 2:1 ratios of O2 / NH3 and O2 / CH4, resulted in a HCN yield of nearly 70%.

[0047]

[0039] The invention further relates to a two-stage process for the production of HCN. In some embodiments of the invention, this two-stage process results in a yield of HCN in the range of 80% to 100%. The two-stage process reduces the contact time in the second stage and uses a lower temperature in the second stage than used to make HCN by the typical Andrussow process. In some embodiments of the invention, the first stage converts NH3to NO according to the following reaction: NH3+ 5 / 4 O2- ► NO + 3 / 2 H2O (Rxn 3).

[0048] In some embodiments of the invention, NO is generated from a source of nitric acid (HNO3) as is known in the art. In some embodiments of the invention, the second stage then produces HCN by at least the following reaction:

[0049] CH4+ NO ——► HCN + ½ H2+ H2O (Rxn 11).

[0050]

[0040] In one embodiment of the invention, the first stage of the process provides an efficient process for generating NO as a feedstock for the production of HCN in the second stage. NH3is almost fully consumed in the first stage. A gaseous hydrocarbon is introduced only in the second stage to produce HCN. In some embodiments of the invention, the gaseous hydrocarbon is CH4. The two-stage process of the invention reduces the possibility and probability of undesired side reactions, such as those in the Andrussow process, that consume reactants such as NH3, O2, CH4and NO needed for the production of HCN and lessens the formation of by-products from these undesired side reactions.

[0041] In some embodiments of the invention, the two-stage process involves, in a first reactor, a first stage of reacting NH3gas with an O2-containing gas in the presence of a suitable catalyst at a reaction temperature ranging from about 600 °C to about 950 °C (e.g., from about 650 °C to about 900 °C, from about 700 °C to about 850 °C, and from about 750 °C to about 800 °C) to produce a NO-containing gas. In some embodiments of the invention, the suitable catalyst is a Pt-gauze catalyst. In some embodiments of the invention, the two-stage process involves, in a first reactor, a first stage of producing NO from HNO3as is known in the art. In some embodiments of the invention, the two-stage process involves, in a second reactor, a second stage of reacting the NO in the NO-containing gas under suitable reaction conditions with a gaseous hydrocarbon, optionally in the presence of a suitable catalyst, preferably a Pt-gauze catalyst, to produce HCN. The reaction in the second reactor may, for example, take place at a reaction temperature ranging from about 600 °C to about 1,000 °C (e.g., from about 650 °C to about 900 °C, from about 700 °C to about 850 °C, and from about 750 °C to about 800 °C) to produce HCN.

[0051]

[0042] In some embodiments of the invention, the first and second reactors may be separate reaction vessels in which the NO-containing gas from the first reactor vessel is transferred to the second reactor vessel. In some embodiments of the invention, the first and second reactors may be a single reactor vessel having separate reactor zones. The processes of the invention may be accomplished using continuous flow or plug flow reactors under turbulent conditions. The reactors may be operated adiabatically. The gases may be preheated from about 100 °C to about 750 °C, without significant decomposition of the NH3feed, prior to its introduction into the reactors using heat generated from the process or provided by an external source. In some embodiments of the invention, the two-stage process utilizes equipment known in the art. In some embodiments of the invention, the first reactor and the second reactor are present in the same geographic location. In some embodiments of the invention, the first reactor and the second reactor are present in different geographic locations. In some embodiments of the invention, the NO-containing gas is transported from the geographic location of the first reactor to the geographic location of the second reactor. In some embodiments of the invention, the NO-containing gas is transported by pipeline from the geographic location of the first reactor to the geographic location of the second reactor.

[0052]

[0043] The first stage of a two-stage process for the production of HCN according to the invention is the step of, in a first reactor, reacting NH3 gas with an O2-containing gas in the presence of a Pt -gauze catalyst, or any other precious- or base-metal oxidation catalyst capable of efficiently performing this transformation, at a reaction temperature ranging from about 600 °C to about 950 °C (e.g., from about 650 °C to about 900 °C, from about 700 °C to about 850 °C, and from about 750 °C to about 800 °C) to produce a NO-containing gas. The reaction occurring in this first stage is:

[0053] 4 NH3(g) + 5 O2(g) — ► 4 NO(g) + 6 H2O(g) (Rxn 14)

[0054] This strongly exothermic reaction (AH = -905.2 KJ / mol) is the first step in the well-known Ostwald process for making HNO3. See, e.g., Ostwald, GB 190200698.

[0055]

[0044] In some embodiments of the invention, the NH3gas and the O2-containing gas reacted in the first reactor are present in a molar range of 0.9 to 1.1 moles NH3gas and 1.15 to 1.35 moles O2-containing gas. In a preferred embodiment, the NH3gas - O2-containing gas reaction mixture should have an NH3gas - O2-containing gas ratio such that the mixture contains about 14%, (e.g. 14.38%) NH3. A lower NH3gas - O2-containing gas ratio may be employed for a variety of reasons, the most important being that conversion decreases with too high a ratio and the combination of NH3gas and the O2-containing gas form an explosive mixture. Because the mixing of NH3gas and an O2-containing gas in industrial practice is incomplete, locally higher ratios may occur. A ratio that includes a safety margin below the explosion limit is therefore necessary. Optimum selectivity to NO may be realized at pressures between 3 to 6 bar and around 850 °C or between 7 to 12 bar at higher temperatures between 900 °C and 950 °C.

[0056]

[0045] In some embodiments of the invention, the NH3may be introduced in the first stage directly from its production in a Haber process known in the art for the production of NH3or purchased and fed from a rail car or some other storage system. The H2O produced from the reaction of the NH3and Ch-containing gas may be removed from the NO-containing gas produced using methods known in the art. This minimizes the possible reaction of NH3and NO to produce nitrogen (N2) and H2O.

[0046] Any catalyst used in the first step of the Ostwald process may be used in the first stage of a process for the production of HCN according to the invention. The first stage may be conducted at reaction temperatures ranging from about 600 °C to about 950 °C, about 700 °C to about 900 °C, about 750 °C to about 850 °C, about 750 °C to about 900 °C, or about 825 °C to about 950 °C. The reaction pressure may range from about 3 to about 12 standard atmospheres (atm) at 50 °C. See, Handbook of Commercial Catalysts: Heterogeneous Catalysts, CRC Press 2000.

[0057]

[0047] The second stage of a two-stage process for the production of HCN according to the invention is the step of, in a second reactor, reacting the NO in the NO-containing gas with a gaseous hydrocarbon under suitable reaction conditions to produce HCN, optionally in the presence of a suitable catalyst, preferably a Pt gauze. The reaction in the second reactor may, for example, take place at a reaction temperature ranging from about 600 °C to about 1000 °C (e.g., from about 650 °C to about 900 °C, from about 700 °C to about 850 °C, and from about 750 °C to about 800 °C) to produce HCN. The second stage of the two-stage process may be a separate embodiment of the invention. This second stage then produces HCN by at least the following reaction:

[0058] CH4+ NO ——► HCN + ½ H2+ H2O (Rxn ll)

[0059] Given the reactive gases present, some HCN may also be produced by the direct reaction of residual NH3and the gaseous hydrocarbon as in Rxn 2 above, but this reaction is highly dependent on a significant amount of the suitable catalyst (e.g, Pt-gauze catalyst) being present. In some embodiments of the invention, the NO and the gaseous hydrocarbon in the second reactor are present in substantially equimolar proportions. If the gaseous hydrocarbon is present in excess, then undesired combustion reactions can occur when any O2is present from the earlier stage. This produces more H2O which can promote the undesired hydrolysis of HCN. The production of HCN in the second stage may be accomplished with, or without, a suitable catalyst, preferably a Pt gauze. If present, the catalyst may be a Pt -gauze catalyst. In some embodiments of the invention, the Pt-gauze catalyst is a Pt or Pt / Rh catalyst as described above. In some embodiments of the invention, the gauze catalyst present on the second reactor has a thickness of about 0.0002 to about 0.010 cm, about 0.0005 to about 0.005 cm, about 0.001 to about 0.005 cm, about 0.0015 to about 0.0025 cm, or 0.002 cm. This is substantially less catalyst than utilized in the typical Andrussow catalyst, which typically has a thickness of between 0.076 and 0.38 cm. For 0.0002 cm, 83% conversion of CH4and NO are obtained with an HCN yield of 83%. For 0.0005 cm, 92.5% conversion of CH4and NO are obtained with an HCN yield of 92.5%. For 0.002 cm, 98% conversion of CH4and NO are obtained with an HCN yield of 98%.

[0060]

[0048] The second stage of a process of the invention is conducted at a reaction temperature ranging from about 600 °C to about 1000 °C, about 700 °C to about 1000 °C, about 850 °C to about 1000 °C, about 900 °C to about 1000 °C, about 950 °C to about 1000 °C, about 600 °C to about 900 °C, about 650 °C to about 850 °C, or about 850 °C to about 950 °C. The reaction temperature in the second stage may be the same or different from the reaction temperature of the first stage. The reaction pressure may range from about 0.2 to about 5 standard atmospheres (atm). The gas-solid contact time can be on the order of 0.1 millisecond with values ranging from 0.01 to 10 milliseconds.

[0061]

[0049] FIG. 4 shows a graphical illustration of partial pressure in torr versus thickness (z) of catalyst in cm when an equimolar amount of CH4as the gaseous hydrocarbon and NO are used in the feed. The partial pressures of CH4and NO decrease as the thickness of the catalyst increases. The partial pressures of H2O / 2 and H2 / 2 slightly increase as the thickness of the catalysts increases. The partial pressure of O2remains at or close to 0. The partial pressure of HCN increases more significantly as the thickness of the catalyst increases.

[0062]

[0050] FIG. 5 shows a graphical illustration of yield of HCN versus thickness of catalyst in cm when a commercial Andrussow process is used in comparison with a process of the invention where an equimolar amount of CH4as the gaseous hydrocarbon and NO are used in the second stage feed. In both cases, the yield of HCN increases with catalyst thickness but the yield of HCN is higher in a process of the invention. Also, as shown in FIG. 6, the rate of reaction for the NO process, Rxn 11, is twelve orders of magnitude faster than the dominant Andrussow process using NH3, CH4and air, shown in Rxn 2, which has been defined as the dominant reaction for synthesizing HCN.

[0063]

[0051] The invention further relates to a process for the production of HCN from a gaseous hydrocarbon and NO comprising the step of reacting a gaseous hydrocarbon and NO gas, optionally in the presence of a suitable catalyst, preferable a Pt-gauze catalyst. In some embodiments of the invention, the partial pressure of the gaseous hydrocarbon is substantially equal to the partial pressure of the NO gas. In some embodiments of the invention, the NO gas and the gaseous hydrocarbon are present in substantially equimolar proportions. In some embodiments of the invention, the NO gas is generated from HNO3.

[0064]

[0052] The invention further relates to reactor designs and vessels for conducting improved processes for the production of HCN according to the invention. Exemplary reactor vessels are described below in FIGS. 7-12, however, any appropriate reactor design and / or vessel known in the art may be used to practice the processes for production of HCN according to the invention.

[0065]

[0053] FIG. 7 shows a single reactor system for producing HCN according to the invention with a gaseous feed stream of air, natural gas, and NH3. A mixture of air, natural gas, and NH3enters the top of reactor 100 as the at least one gaseous feed stream. A stream of NO is introduced into the feed stream prior to entering the reactor 100. A nozzle arrangement 101 is used to introduce the NO into the feed stream to ensure adequate mixing of the mixture of air, natural gas, and NH3and the stream of NO. This mixture then passes over a disbursement element 102 that spreads the mixture across a catalyst, such as a Pt-gauze catalyst. The products of this reaction go through a heat exchanger (boiler / cooling system), which cools the HCN to avoid polymerization and decomposition. The HCN products exit through the bottom of the reactor 100.

[0066]

[0054] FIG. 8 shows a single reactor system for producing HCN according to the invention with a gaseous feed stream of air and NH3. A mixture of air and NH3enters the top of reactor 200 as the at least one gaseous feed stream. A stream of NO is introduced into a stream of natural gas. The mixture of NO and natural gas is then mixed with the feed stream of air and NH3. Nozzle arrangement 201 is used to introduce the NO into the stream of natural gas and nozzle arrangement 202 is used to introduce the natural gas into the NO and the mixture of air and NH3to ensure adequate mixing of the mixture of air and NH3, the stream of NO, and the stream of natural gas. This mixture passes over a disbursement element 203 that spreads the mixture across a catalyst, such as a Pt-gauze catalyst. The products of this reaction go through a heat exchanger (boiler / cooling system), which cools the HCN to avoid polymerization and decomposition. The HCN products exit through the bottom of the reactor 200.

[0055] FIG. 9A shows a single reactor system to produce HCN according to the invention. A mixture of air, natural gas, and NH3enters the top of the reactor 300 as the at least one gaseous feed stream. The feed stream mixture passes over a disbursement element 301 that spreads the mixture over an element A-A, with a cross-section 302, as shown in FIG. 9B. A stream of NO is introduced via element A-A into the reactor 300 above a catalyst, such as a Pt -gauze catalyst. Nozzle arrangement 303 is used to introduce the stream of NO into the reactor. Element A-A spreads the stream of NO over the Pt-gauze catalyst. The feed stream mixture of air, natural gas, and NH3is disbursed over the entering stream of NO, which reacts as it spreads across the Pt -gauze catalyst. The products of the reaction go through a heat exchanger (boiler / cooling system), which cools the HCN to avoid polymerization and decomposition. The HCN products exit through the bottom of the reactor 300.

[0067]

[0056] FIG. 10 shows a two-reactor system that may be used to produce HCN according to the invention. A mixture of air and NH3enters the top of the first reactor 401. The mixture passes over a disbursement element 402 that spreads the mixture across a catalyst, such as a Pt -gauze catalyst. The reaction products obtained from passing the air and NH3over the stationary catalyst exit the first reactor 401 and enter the top of the second reactor 403. The main products of this first reaction are NO, H2O, and any unreacted feed materials. Air may be removed along with H2O from the NO-containing gas produced from the first reactor 401. Natural gas is then mixed with the NO-containing gas entering the second reactor 403. A nozzle arrangement 404 is used to introduce the natural gas into the stream of air and a nozzle arrangement 405 is used to introduce air into the natural gas and mixture of products from the first reactor 401 to ensure adequate mixing. The natural gas is mixed with the products from the first reactor 401 prior to entering the second reactor 403. The feed of the second reactor 403 passes over a second disbursement element 406 to spread the feed across the Pt -gauze catalyst, when used. The products of the reaction pass through a heat exchanger (boiler / cooling system), which cools the HCN to avoid polymerization and decomposition. The HCN products exit through the bottom of the second reactor 403.

[0068]

[0057] FIG. 11 shows a two-reactor system with a primary reformer to produce HCN according to the invention. A mixture of air and NH3enters the top of the first reactor 501 and passes over a

[0069] Y1 disbursement element 502. The mixture is then spread over a catalyst, such as a Pt-gauze catalyst. The products of this reaction enter a heat exchanger (boiler / cooling system), if required. The product NO can also be cooled by co-mixing the hot, produced NO with the room temperature natural gas. The cooled NO exits the first reactor 501 and enters the bottom of the second reactor 503, which contains a primary reformer 504. Natural gas enters the primary reformer 504 in order to liberate the hydrogen in the production of the HCN. The HCN product exits out the top of the second reactor 503.

[0070]

[0058] FIG. 12 shows a single reactor system with two reaction zones to produce HCN according to the invention. A mixture of air and NH3enters through the top of the reactor 600 and passes over a disbursement element 601. The mixture is then spread over a catalyst, such as a Pt-gauze catalyst. A feed of natural gas is inserted below the Pt-gauze catalyst in the reactor 600 and is mixed with the NO produced by the reaction. A nozzle arrangement 602 is used to introduce the natural gas into the reactor. A distribution plate spreads the mixture over another catalyst, such as a Pt -gauze catalyst. The HCN products enter a heat exchanger (boiler / cooling system) in order to cool the HCN and avoid polymerization or decomposition. The final products exit at the bottom of the reactor 600.

[0071]

[0059] Exemplary Embodiments of the Invention

[0072]

[0060] El. A process for the production of HCN comprising the steps of:

[0073] introducing NH3gas, an oxygen-containing gas, a gaseous hydrocarbon, and NO gas to a reactor as at least one gaseous feed stream, and

[0074] reacting the gases in the gaseous feed stream in the presence of a suitable catalyst at a reaction temperature ranging from about 800 °C to about 1200 °C to produce HCN.

[0075]

[0061] E2. A process for the production of HCN comprising the steps of:

[0076] introducing NH3gas, an oxygen-containing gas, and a gaseous hydrocarbon to a reactor in at least one gaseous feed stream;

[0077] reacting the gases in the gaseous feed stream in the presence of a suitable catalyst at a reaction temperature ranging from about 800 °C to about 1100 °C to produce HCN;

[0078] separating the HCN produced; and recycling unreacted gaseous hydrocarbon, unreacted NH3gas, or unreacted at least one gaseous feed stream to the reactor.

[0079]

[0062] E3. The process of El, wherein the introduction step comprises introducing to the reactor a first gaseous feed stream comprising the NH3 gas, the oxygen-containing gas, and the gaseous hydrocarbon; and a second gaseous feed stream comprising the NO gas.

[0080]

[0063] E4. The process of E2 further comprising a step of introducing to the reactor a gaseous feed stream comprising NO gas.

[0081]

[0064] E5. The process of E2 or E4, wherein the HCN is separated by scrubbing the HCN with a solvent other than water.

[0082]

[0065] E6. The process of E5, wherein the solvent is acetic acid.

[0083]

[0066] E7. The process of any one of El, E3-E6, wherein the NH3, the NO, and the gaseous hydrocarbon are present in substantially equimolar proportions.

[0084]

[0067] E8. The process of any one of E1-E7, wherein the NH3gas and the oxygen-containing gas are present in a molar ratio of 0.5 to 1.2.

[0085]

[0068] E9. A two-stage process forthe production of HCN comprising the steps of:

[0086] in a first reactor, reacting NH3gas with an oxygen-containing gas in the presence of a suitable catalyst at a reaction temperature ranging from about 600 °C to about 950 °C to produce an NO-containing gas; and

[0087] in a second reactor, reacting the NO in the NO-containing gas with a gaseous hydrocarbon under suitable reaction conditions, optionally in the presence of a suitable catalyst, to produce HCN.

[0088]

[0069] E10. The process of E9, wherein the first reactor and the second reactor are continuous adiabatic reactors wherein the gas-phase flow pattern approaches plug-flow.

[0089]

[0070] Ell. The process of E9 or E10, wherein the NO and the gaseous hydrocarbon in the second reactor are present in substantially equimolar proportions.

[0090]

[0071] E12. The process of any one of E9-E11, wherein the suitable catalyst in the second reactor is present and has a thickness of about 0.0002 to 0.002 cm, 0.001 to about 0.010 cm, about 0.001 to about 0.005 cm, about 0.0015 to about 0.0025 cm, or 0.002 cm.

[0072] E13. The process of any one of E9-E12, wherein the suitable catalyst is present in the second reactor, and wherein the suitable catalyst is a Pt / Rh catalyst having up to about 30 wt% Rh, about 1 to about 25 wt% Rh, about 5 to about 25 wt% Rh, about 15 to 22 wt% Rh or about 20 wt% Rh.

[0091]

[0073] E14. The process of any one of E9-E13, wherein the NH3 gas and the oxygen-containing gas reacted in the first reactor are present in a molar range of 0.9 to 1.1 moles NH3gas and 1.15 to 1.35 moles oxygen-containing gas.

[0092]

[0074] E15. The process of any one of E9-E14, wherein the reaction temperature of the reaction in the second reactor is from about 600 °C to about 1000 °C.

[0093]

[0075] E16. The process of any one of E9-E15, wherein the first reactor and the second reactor are separate reaction vessels.

[0094]

[0076] E17. The process of any one of E9-E15, wherein the first reactor and the second reactor are a single reactor vessel having separate reactor zones.

[0095]

[0077] E18. The process of any one E9-E17, wherein the first reactor and the second reactor are present in the same geographic location.

[0096]

[0078] E19. The process of any one of E9-E16, wherein the first reactor and the second reactor are present in different geographic locations.

[0097]

[0079] E20. The process of E19, wherein the NO-containing gas is transported from the geographic location of the first reactor to the geographic location of the second reactor.

[0098]

[0080] E21. The process of E20, wherein the NO-containing gas is transported by pipeline from the geographic location of the first reactor to the geographic location of the second reactor.

[0099]

[0081] E22. A process for the production of HCN from a gaseous hydrocarbon and NO comprising the step of:

[0100] reacting a gaseous hydrocarbon and NO gas, optionally in the presence of a suitable catalyst.

[0101]

[0082] E23. The process of E22, wherein the partial pressure of the gaseous hydrocarbon is substantially equal to the partial pressure of the NO gas.

[0102]

[0083] E24. The process of any one of E22-E23, wherein the NO gas and the gaseous hydrocarbon are present in substantially equimolar proportions.

[0084] E25. The process of any one of E22-E24, wherein the NO gas is generated from nitric acid.

[0103]

[0085] E26. The process of any one of E1-E25, wherein the gaseous hydrocarbon is selected from methane, ethane, butane, propane, or mixtures thereof.

[0104]

[0086] E27. The process of E26, wherein the gaseous hydrocarbon is methane.

[0105]

[0087] E28. The process of any one of E1-E27, wherein the gaseous hydrocarbon is natural gas.

[0106]

[0088] E29. The process of any one of E1-E28, wherein the suitable catalyst is a Pt-gauze catalyst.

[0107]

[0089] E30. The process of E29, wherein the Pt-gauze has a thickness of about 0.001 to about 0.010 cm, about 0.001 to about 0.005 cm, about 0.0015 to about 0.0025 cm, or 0.002 cm.

[0108]

[0090] E31. The process of E29 or E30, wherein the Pt-gauze catalyst is a Pt / Rh catalyst having up to about 30 wt% Rh, about 1 to about 25 wt% Rh, about 5 to about 25 wt% Rh, about 15 to 22 wt% Rh or about 20 wt% Rh.

[0109]

[0091] E32. The process of any one of E1-E31, wherein the oxygen-containing gas is air.

[0110]

[0092] Examples

[0111]

[0093] Example 1

[0112]

[0094] The effect that doping a gaseous feed stream with NO, as in the process of the invention, has on the HCN yield for a modified Andrussow process at a fixed total pressure of 1600 torr and isothermal conditions (i.e., a reaction temperature of 1127 °C) using the gaseous feed stream ratios of Table 1 and the process parameters of Table 2, including a gauze catalyst length of 6.5 cm, are shown in the reactor inlet conditions of Table 3.

[0113] Table 1 Feed Ratios

[0114]

[0115] Table 2 Process Parameters

[0116]

[0117] Table 3 Reactor Inlet Conditions

[0118]

[0119]

[0095] In this exemplary comparison, the O2-containing gas is O2and the gaseous hydrocarbon is CH4. As shown in Table 3, the molar ratio of NH3 gas to NO gas (rN) in the at least one gaseous feed stream may range from 2.5 to 20 and / or the molar ratio of carbon in the gaseous hydrocabon (CH4) to NO gas (rcx rN) in the at least one gaseous feed stream may range from 2.5 to 20.

[0096] Example 2

[0120]

[0097] FIG. 2 shows a comparison of HCN yields in the presence and absence of hydrolysis for an Andrussow process at 900 °C and 1100 °C, wherein the dotted lines represent with hydrolysis. The objective of the comparison in FIG. 2 is to compare HCN yields for the Andrussow process at 900 °C and 1100 °C both with and without hydrolysis. In FIG. 2, the O2-containing gas is O2 and the gaseous hydrocarbon is CH4. The comparison was performed at a total pressure of 1600 torr with the process conditions of Table 4, including a gauze catalyst length of 6.5 cm, and reactor inlet conditions of Table 5. The reactor outlet conditions are shown in Table 6.

[0121] Table 4 Process Conditions

[0122] pT= 1600 torr

[0123] • Gas velocity = 500 cm / s

[0124] • Gauze length = 6.5 cm

[0125] ’ Contact time - 13 ms

[0126] Table 5 Reactor Inlet Conditions

[0127]

[0128]

[0129] 200 torr

[0130] pO2= 250 torr

[0131] pN2= 950 torr

[0132] Table 6 Reactor Outlet Conditions

[0133]

[0134]

[0098] As shown in FIG. 2, at 900 °C, the HCN yield decreases from 38.9% without hydrolysis to 36.7% with hydrolysis, and at 1100 °C, the HCN yield decreases from 44.2% without hydrolysis to 28.4% with hydrolysis.

[0135]

[0099] Example 3

[0136]

[0100] FIG. 3 shows exemplary comparisons of HCN yield versus catalyst gauze length for different feed compositions with various NO doping ratios. In FIG. 3, the catalyst gauze is a Pt-catalyst gauze, the O2-containing gas is O2, and the gaseous hydrocarbon is CH4. The reactor inlet feed conditions are shown in Table 7 and the reactor exit conditions are shown in Table 8.

[0137] Table 7 Reactor Inlet Feed Conditions

[0138]

[0139] Table 8 Reactor Exit Conditions

[0140]

[0141] Case 1 YHCN~10%

[0142] Case 4 YHCN~69%

[0143] Case 5 YHCN~20%

[0144]

[0101] The abrupt changes in the slopes of the graphical data that generally occur at a short distance into the Pt-gauze catalyst are the result of NO being depleted from reaction CH4+ NO = HCN + ½ H2+ H2O. This is an extremely fast reaction when compared to the others. After this break in the slope occurs, the reaction relies upon NO from the oxidation of NH3versus a combination of the doped NO plus NO from the NH3oxidation. After the NO is depleted, another break in the slope can occur (see case 2 and case 4) when the CH4 / O2ratio is 0.5, since the CH4is then depleted. This causes the formation of HCN to cease. This is why the HCN yield remains constant after that gauze length is reached. In case 3, the feed is doped with 101 torr of NO (6.3 mol %) while the CH4 / O2ratio is 1.2, the CH4 / NH3ratio is 1, and the CH4 / NO ratio is 2.5. The mol% of CH4in the feed is 15.7%. The HCN yield rapidly increases a short distance into the gauze length due to the fast reaction between CH4and NO. The slope of the HCN vs gauze length curve is then reduced since the doped NO is consumed and it must be supplied solely from the oxidation of NH3. The HCN yield vs gauze length response then increases and produces 11 mol% of HCN in the product gas. This comparison shows that an equimolar feed composition (case 1) produces the highest HCN yield and a low composition of NO in the feed with NH3 / O2and CH4 / O2ratios > 1 (case 5) produces the lowest HCN yield. The fast reaction of CH4+ NO results in rapid depletion of NO and the ratios of NH3 / O2and CH4 / O2(cases 2-4) controls the HCN yield. In case 4, the lowest NO (7 torr), along with 2:1 ratios of O2 / NH3and O2 / CH4, resulted in a HCN yield of nearly 70%.

[0145]

[0102] Examples of Apparatus

[0146]

[0103] Description of Apparatus

[0147]

[0104] The second reaction in a process of the invention is suitably carried out by contacting the reactants over a Pt-gauze catalyst at elevated temperature with a residence time that is sufficient to realize the reaction. The reaction can be carried out for demonstration purposes by using a quartz reactor tube with a means of maintaining a gauze catalyst in position so it is located in close proximity to the energy source used to heat the reaction zone. One method for maintaining the gauze catalyst in position during flow and heating processes is to place it between two sections of ceramic monolith where the latter does not induce any reaction to occur with gaseous species that contact its surfaces. This same technique for holding a catalyst gauze in place was used to study the partial oxidation of CH4to synthesis gas from 200°C to 900°C using a 90%Pt / 10%Rh gauze catalyst by K. H. Hofstad, O. A.

[0148] Rokstad, and A. Holmen, "Partial oxidation of CH4over a platinum metal gauze," Catalysis Letters 36 (1996) 25-30. The catalyst is typically a wire gauze that is woven from a Pt / Rh wire of about 76 μm in thickness. The wire composition is about 90 wt% Pt and 10 wt% Rh.

[0149]

[0105] The dimensions of the reactor tube are generally selected for laboratory-scale demonstration purposes so that the consumption rate of reactants can be readily met by supplying them from standard laboratory-type research grade gas cylinders. In addition, the resulting flow rate of reaction product gases should have a magnitude that allows potentially toxic species to be removed by known approaches before directing them to the system vent, such as by using a gas-liquid contactor where one or more of the gaseous species reacts with the scrubbing liquid. The reactor tube inner diameter is selected to achieve a cross-sectional area so that the volumetric flow rate of the reaction gas mixture is capable of producing a gas-to-catalyst contact time where high yields of hydrocyanic acid can be obtained. Typical tube dimensions for demonstration purposes are 6.35 mm outer diameter (OD) and 2 mm inner diameter (ID) with an overall length of 500 mm where the latter is selected so the inlet and exit of the tube extend at least 50 mm external to both ends of a standard tubular ceramic furnace. A tubular ceramic furnace equipped with suitable heating elements and a temperature controller are used to achieve the required reaction temperatures. The thermocouple used for monitoring the temperature of the reaction zone is placed in the reactor, preferably touching the catalyst gauze. Another thermocouple is placed on the upstream side of the gauze to monitor the inlet temperature of the feed gas.

[0106] Quartz is often chosen as a material of construction for the reactor since the reaction may require high temperatures. This temperature range is sufficiently below the softening point of quartz, which is 1500 to 1670°C. Quartz is also inert to the species present in the reaction mixture so that product gas composition measurements and any parameters derived from them will be representative of reactions that occur in the presence of the catalyst, or representative of reactions that occur in the gas phase in the absence of the catalyst. By operating the reactor using a fixed volumetric flow rate of the gaseous feed mixture, then a single or multiple layers of gauze can be employed as a means of varying the contact time between the reaction mixture and the external surface of the wire gauze. Alternately, the contact time between the reaction mixture and the external surface of the wire gauze can be varied by changing the volumetric flow rate of the gaseous feed mixture using single and multiple layers of the catalyst wire gauze.

[0150]

[0107] The reaction feed mixture was prepared by first creating controlled flow rates of CH4, NO, and N2using individual mass flow controllers and then blending them using an in-line gas-mixing device to create the desired feed gas composition. The CH4, NO, and N2were supplied to the mass flow controllers from standard gas cylinders with a purity of at least 98.5%. The compositions of the feed and reactor product gas stream were determined by directing a constant flow rate of the selected gas stream to an on-line gas chromatography system where the individual constituents were separated and quantified. Calibration factors were used to convert the peak areas for each component to mole% gas compositions. The factors were derived from gas chromatography experiments using gas standards having known compositions.

[0151]

[0108] Example 4

[0152]

[0109] Employing a reactor tube as described above, a section of cordierite monolith from a commercial supplier (Corning) having an overall length of 20 mm and 400 cells / sq.in. was first prepared by machining a circular section from a larger core sample. The diameter of the machined section of monolith was determined so that a frictional fit occurred when it was inserted into one end of the reactor tube. The monolith section was subsequently installed into the center of the quartz tube using a special-purpose tool fabricated for this purpose. To verify that the monolith section remained stationary

[0153] 1 within the tube, a N2 gas source was connected to the tube inlet from a gas cylinder source, and a flow rate of 600 seem was metered into the tube inlet at room temperature and exhausted from the tube at atmospheric pressure. The reactor tube was then installed in the furnace and the inlet and outlet tubes were connected to the supply and exhaust lines, respectively. A feed gas containing 20% CH4, 20% NO, and balance (60%) N2was then introduced to the reactor tube so that volumetric flow rate was 500 seem. The reactor temperature was then set to an initial set point of 300°C. While the reactor was heating up, three feed gas samples were sequentially taken and then analyzed using the on-line gas chromatography system. The reactor temperature was increased to 500°C and allowed to stabilize. Three additional product gas samples were sequentially taken again and then analyzed by the on-line gas chromatography system. This process of increasing the temperature by 50°C, allowing it to stabilize, and then taking product samples was then repeated from 550°C up to 950°C. At all temperatures, the product samples were identical to the feed samples within two standard deviations of the average feed composition, which indicated that no reaction has occurred. In addition, the monolith temperature was stable at each condition and did not undergo any sudden temperature increase that would be indicative of surface-catalyzed reactions. It was concluded that this particular ceramic monolith would be suitable for holding the gauze catalyst in position for subsequent assessment of reactivity.

[0154]

[0110] Example 5

[0155]

[0111] The same procedure was followed as described in Example 4 except a section of cordierite monolith was used that contained 5 wt% Pt deposited using a wash coating technique. When the exit reactor temperature reached 447°C, the exit temperature underwent a sudden increase and reached a constant temperature of 688°C within a period of four minutes, which indicated that light-off had occurred. Once the temperature had stabilized, three product gas samples were sequentially taken and analyzed by the on-line gas chromatography system, which also showed the presence of HCN. This process of increasing the temperature by 25°C, allowing it to stabilize, and then taking product samples was repeated from 688°C up to 775°C. A maximum in the HCN yield of 11% was observed based upon CH4at a temperature of 690°C where the CH4conversion was 85% and the NO conversion was 100%. The other products that were detected included CO, CO2, and H2O. Although this particular ceramic monolith containing a wash coated layer with Pt could be used to hold the catalyst gauze in position, it would not be suitable for such since it lacked the required chemical inertness.

[0156]

[0112] Example 6

[0157]

[0113] Two sections of cordierite monolith, each having an overall length of 10 mm, were prepared for subsequent insertion into a quartz reactor tube as described in Example 4. The first monolith section was inserted into the inlet side of reactor tube to a depth of ca. 10 mm. A section of gauze catalyst containing 90% Pt / 10% Rh was then manually compressed into the form of a wad and inserted into the reactor tube to a depth of ca. 10 mm. The second section of cordierite monolith was then inserted into the tube until it made contact with the gauze catalyst, thereby forming a layer of the wadded catalyst that was held in place on either side by the two sections of monolith. A special tool was then used to push the ensemble into the reactor tube, so the catalyst wad was located in the middle of the tube, which allowed it to be surrounded by the ceramic tube furnace heated zone. The total length of the wadded section of catalyst was ca. 10 mm. To verify that the monolith sections containing the wadded catalyst gauze remained stationary within the tube, a N2 gas source was connected to the tube inlet from a gas cylinder source and a flow rate of 600 seem was introduced at room temperature. The reactor tube containing the catalyst was then installed in the reactor furnace and the inlet and outlet tubes were connected. A feed gas containing 20% CH4, 20% NO, and balance (60%) N2, which corresponds to a CH4: NO molar ratio of 1.0:1.0, was then introduced to the reactor tube so that volumetric flow rate was 500 seem. The reactor temperature was then set to an initial set point of 700°C. While the reactor was heating up, three feed gas samples were taken sequentially and then analyzed using the on-line gas chromatography system. Three additional product gas samples were taken again and then analyzed by the on-line gas chromatography system. After less than five minutes, the temperature stabilized to ca. 725°C. The temperature was then increased in increments of 50°C up to a maximum of 950°C. The maximum HCN yield of 76% based on CH4was obtained at a temperature of 669°C, which corresponded to a HCN yield based on NO of 68%.

Claims

The claimed invention is:

1. A process for the production of HCN comprising the steps of:introducing NH3gas, an oxygen-containing gas, a gaseous hydrocarbon, and NO gas to a reactor as at least one gaseous feed stream, andreacting the gases in the at least one gaseous feed stream in the presence of a suitable catalyst at a reaction temperature ranging from about 800 °C to about 1200 °C to produce HCN.

2. A process for the production of HCN comprising the steps of:introducing NH3gas, an oxygen-containing gas, and a gaseous hydrocarbon to a reactor in at least one gaseous feed stream;reacting the gases in the at least one gaseous feed stream in the presence of a suitable catalyst at a reaction temperature ranging from about 800 °C to about 1100 °C to produce HCN;separating the HCN produced; andrecycling unreacted gaseous hydrocarbon, unreacted NH3gas, or unreacted at least one gaseous feed stream to the reactor.

3. The process of claim 1, wherein the introduction step comprises introducing to the reactor a first gaseous feed stream comprising the NH3gas, the oxygen-containing gas, and the gaseous hydrocarbon; and a second gaseous feed stream comprising the NO gas.

4. The process of claim 2 further comprising a step of introducing to the reactor another gaseous feed stream comprising NO gas.

5. A two-stage process for the production of HCN comprising the steps of:in a first reactor, reacting NH3gas with an oxygen-containing gas in the presence of a suitable catalyst at a reaction temperature ranging from about 600 °C to about 950 °C to produce an NO-containing gas; andin a second reactor, reacting the NO in the NO-containing gas with a gaseous hydrocarbon under suitable reaction conditions, optionally in the presence of a suitable catalyst, to produce HCN.

6. The process of claim 5, wherein the first reactor and the second reactor are continuous adiabatic reactors wherein the gas-phase flow pattern approaches plug-flow.

7. A process for the production of HCN from a gaseous hydrocarbon and NO comprising the step of: reacting a gaseous hydrocarbon and NO gas, optionally in the presence of a suitable catalyst.

8. The process of any one of claims 1-7, wherein the gaseous hydrocarbon is selected from methane, ethane, butane, propane, or mixtures thereof.

9. The process of any one of claims 1-7, wherein the suitable catalyst is a Pt-gauze catalyst.

10. The process of any one of claims 1-6, wherein the oxygen-containing gas is air.

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