HK1199016A1

HK1199016A1 - Integrated process for diamine production

Info

Publication number: HK1199016A1
Application number: HK14112626.1A
Authority: HK
Inventors: 約翰．; 约翰．C．卡顿; ．卡頓; 大卫．W．瑞贝诺德; 大衛．; ．瑞貝諾德
Original assignee: 英威达科技公司
Priority date: 2012-12-18
Filing date: 2014-12-17
Publication date: 2015-06-19
Also published as: CN103864623A; TW201425277A; WO2014099610A1; CN103864623B

Abstract

Described is a process for the integrated production of hexamethylenediamine. The process includes integrating an HCN production process, a dinitrile compound production process, and a diamine production process. The HCN production process provides HCN for hydrocyanating butadiene to form a dinitrile compound and a hydrogen stream for hydrogenating the dinitrile compound to form a diamine. The HCN production process includes forming a crude hydrogen cyanide product and separating the crude hydrogen cyanide product to form an off-gas stream and a hydrogen cyanide product stream. The off-gas stream is further separated to recover hydrogen. The hydrogen cyanide product stream is further processed to recover hydrogen cyanide.

Description

Integrated process for diamine production

Cross Reference to Related Applications

Priority of the present application to U.S. provisional patent application 61/738,761 filed on 12, 18, 2012, the entire contents of which are hereby incorporated by reference.

Technical Field

The present invention relates to an integrated process for forming diamines by reducing one or more dinitrile compounds. In particular, the present invention relates to increasing process efficiency by recovering a hydrogen stream from a crude hydrogen cyanide product and a hydrogen cyanide product stream, hydrocyanating butadiene using the hydrogen cyanide product stream to form one or more dinitrile compounds, and then hydrogenating the dinitrile compounds using the hydrogen stream to form diamines. The pressure at which the dinitrile compound is hydrogenated may be less than 5000 KPa.

Background

Butadiene, also known as 1, 3-butadiene, is commonly used for further processing into industrial chemicals, including Adiponitrile (ADN), Methylglutaronitrile (MGN), Ethylsuccinonitrile (ESN), and synthetic rubbers. Butadiene can be prepared by a variety of processes, including C₄Extraction of hydrocarbons, dehydrogenation of n-butane, and from butenes, butanediols, and alcohols. For the preparation of ADN and/or MGN from butadiene, butadiene is hydrocyanated with a nickel catalyst and a boron promoter (see e.g. US5312959, US7528275, US 7709673). While ADN is typically prepared by the methods described above, it may alternatively be prepared by methods disclosed by Intergrated organic chemistry (Weissemei et al)1997, P245-250), i.e. the chlorination of butadiene to 1, 4-dichlorobutadiene, which is reacted with sodium cyanide to 1, 4-dicyanobutene, which is then hydrogenated to adiponitrile, or the preparation of adiponitrile by the hydrodimerization of acrylonitrile.

ADN is useful as an intermediate in the preparation of 6-Aminocapronitrile (ACN), Hexamethylenediamine (HMD) and combinations thereof. ACN can cyclize to form caprolactam, which is used as an intermediate for nylon-6. HMD can be produced on an industrial scale and used as an intermediate for products in the industrial, textile, resin, carpet and coating industries. In addition, HMD can also be used in coatings, curing agents, petroleum additives, adhesives, inks, scale and corrosion inhibitors, and water treatment chemicals. Large scale commercial use of HMD is as an intermediate in the phosgenation process for the preparation of hexamethylene diisocyanate, which is commonly used in the production of polyurethanes, and also as an intermediate in nylon materials of the general formula nylon-6, X, where X is the number of carbon atoms in the diacid, including nylon-6, 6, nylon-6, 10 and nylon-6, 12. For example, HMD is commercially produced by hydrogenating ADN at elevated temperatures and pressures by mixing ADN with excess ammonia and hydrogen and then passing the mixture through a supported or unsupported catalyst bed comprising copper, nickel or cobalt. The elevated temperature can range from 85 to 150 deg.C and the pressure can range from 200 to 500 atmospheres (see, e.g., US 3398195).

MGN is useful as an intermediate in the production of methylpentamethylene diamine (MPMD), also known as 2-methylpentamethylene diamine. MPMD can be produced in large scale, can be used for plastic, film, fiber, adhesive, epoxy resin curing agent and water treatment process, and can also be used as an intermediate for preparing polyamide or beta-picoline. Beta-picoline is useful as an intermediate for the production of nicotinamide. Under the action of Raney cobalt or Raney nickel catalyst, MGN is hydrogenated under a certain pressure to generate MPMD. Hydrogenation of MGN over a nickel catalyst or Raney nickel catalyst under high hydrogen pressure forms a mixture of MPMD and 3-Methylpiperidine (MPP). The pressure is less than 50 bar, such as 10 to 35 bar. (see e.g. US 8247561).

As described herein, the process for making HMD and/or MPMD requires multiple reactions and feed streams, including hydrogen, butadiene, ADN, MGN, and hydrogen cyanide. In general, hydrogen cyanide is produced on an Industrial scale by the Andrussow process or the BMA process (cf. Ullman's Encyclopedia of Industrial Chemistry, Vol. A8, Weinheim et al, 1987, P161-163). For example, in the Andrussow process, the commercial production of HCN is achieved by reacting ammonia gas with a methane-containing gas and an oxygen-containing gas in a reactor at elevated temperature in the presence of a suitable catalyst. (see US1934838 and US 6596251). Higher homologues of sulphide and methane will have an effect on the oxidative ammonolysis of methane. (see Trusov, Effect of sulfurr Compounds and high homogeneity of Methane on hydrogen Cyanide Production by the Andrussow Method, Russian J. applied chemistry, 74:10(2001), 1693-1697). Unreacted ammonia is separated from HCN by contacting the reactor effluent stream with an aqueous ammonium phosphate solution in an ammonia absorber. The separated ammonia is purified and concentrated for recycle to the conversion of HCN. HCN is typically recovered from the treated reactor effluent stream by absorption into water. The recovered HCN can be treated by a further refining step to produce purified HCN. The document Clean Development process Design document form (CDM PDD, Version3),2006 graphically explains the Andrussow HCN manufacturing process. The purified HCN can be used in hydrocyanation reactions, such as hydrocyanation of alkene-containing groups or hydrocyanation of 1, 3-butadiene and pentenenitriles, which can be used to produce adiponitrile ("ADN"). In the BMA process, HCN is synthesized from methane and ammonia in the substantial absence of oxygen and in the presence of a platinum catalyst, with the result that HCN, hydrogen, nitrogen, residual ammonia, and residual methane are produced (see, e.g., Ullman's Encyclopedia of Industrial Chemistry, Volume A8, Weinheim1987, P161-163). Commercial operators require process safety management to control the nature of the hydrogen cyanide hazard (see Maxwell et al, assay process safety in the transfer of hydrogen cyanide manufacturing technology, JHazMat142 (2007), 677-. In addition, emissions from production facilities in HCN manufacturing processes may comply with regulations, which may affect the economics of HCN production. (see Crump, eco Impact Analysis For The deployed cyanic engineering NESHAP, EPA, May 2000). US2797148 discloses a process for the recovery of ammonia from a gas mixture containing ammonia and hydrogen cyanide. The reaction off-gas in a process for the preparation of hydrogen cyanide by reacting ammonia with a hydrocarbon-containing gas and an oxygen-containing gas comprises ammonia, hydrogen cyanide, hydrogen, nitrogen, water vapor and carbon dioxide. And cooling the tail gas to 55-90 ℃, and introducing the tail gas into an absorption tower for separating ammonia gas from the tail gas.

US3647388 discloses a process for the production of hydrogen cyanide from gaseous hydrocarbons of up to six carbon atoms, such as methane, and ammonia gas. The preferred process is carried out in a combustor having a central conduit for the flow of an oxygen-containing fluid and an annular conduit adjacent the central conduit for the parallel flow of hydrogen, ammonia and gaseous hydrocarbons. The conduit terminates in a reaction chamber in which gaseous hydrocarbons and ammonia react in the flame front of the flame when hydrogen and oxygen are combusted. This process eliminates the use of catalysts.

Although the Andrussow process and the recovery of HCN are well known, little has been disclosed about the separation of tail gases from the recovery of a hydrogen stream from a process for the catalytic production of HCN. In addition, no production process has been reported which integrates the production process of the HCN and/or ACN product with the production process of the diamine product.

Therefore, there is a need for a process that can not only produce HCN in the presence of a catalyst, but also recover hydrogen from reactor off-gas, thereby integrating HCN and hydrogen with a diamine production system.

The above-mentioned publications are incorporated herein by reference.

Disclosure of Invention

In one embodiment, the present invention relates to a process for producing a diamine comprising the steps of: (a) measuring the methane content in the methane-containing gas and purifying the methane-containing gas when the measured methane content is below 90 v%; (b) reacting a tertiary gas mixture comprising at least 25% by volume oxygen in the presence of a catalyst in a first reaction zone to form a crude hydrogen cyanide product comprising HCN and a tail gas, wherein the tertiary gas mixture comprises a methane-containing gas, an ammonia-containing gas, and an oxygen-containing gas; (c) separating the crude hydrogen cyanide product to produce a hydrogen cyanide product stream and a tail gas stream comprising hydrogen, water, carbon monoxide, carbon dioxide or combinations thereof; (d) separating the tail gas stream to produce a hydrogen stream and a purge stream, the purge stream comprising carbon monoxide, carbon dioxide and water; (e) contacting at least a portion of the hydrogen cyanide product stream of step (c) with butadiene in a second reaction zone to cyanohydrogenate butadiene to form one or more dinitrile compounds, such as at least one of adiponitrile, 2-methylglutaronitrile and combinations thereof; (f) contacting at least a portion of the hydrogen stream of step (d) with one or more dinitrile compounds in a third reaction zone to reduce the one or more dinitrile compounds to a diamine, wherein the diamine is selected from the group consisting of hexamethylenediamine, 2-methylpentamethylenediamine and combinations thereof. The reduction of the one or more dinitrile compounds in step f, also referred to as hydrogenation, may be carried out at a pressure of less than 5000kPa to produce at least one of 6-aminocapronitrile, 3-methylpiperidine and combinations thereof. In some embodiments, the ternary gas mixture comprises 25-32v% oxygen. The oxygen-containing gas may contain more than 21% by volume of oxygen, for example at least 80% by volume of oxygen, at least 95% by volume of oxygen or pure oxygen. The tail gas stream may contain from 40 to 90% by volume of hydrogen, from 0.1 to 20% by volume of water, from 0.1 to 20% by volume of carbon monoxide and from 0.1 to 20% by volume of carbon dioxide. The tail gas stream may be separated using a pressure swing absorber. The pressure swing absorber may be operated at a pressure of 1400-2400kPa and a temperature of 16-55 ℃. The pressure swing absorber may comprise at least two adsorbent beds. The first and second adsorbent beds each comprise at least one adsorbent. The hydrogen stream may contain at least 95% hydrogen by volume, or at least 99% hydrogen by volume. The hydrogen cyanide product stream may contain less than 5v% hydrogen or be substantially free of hydrogen. At least 70% of the hydrogen in the crude hydrogen cyanide product may be recovered in a hydrogen stream. Step (c) may further comprise separating the crude hydrogen cyanide product to form an ammonia gas stream. The ammonia stream may be returned to the reactor.

In a second embodiment, the present invention is directed to a process for producing hexamethylenediamine comprising the steps of: (a) measuring the methane content in the methane-containing gas and purifying the methane-containing gas when the measured methane content is below 90 v%; (b) reacting the three-way gas mixture in a first reaction zone in the presence of a catalyst to form a crude hydrogen cyanide product comprising HCN and a tail gas; (c) separating the hydrogen cyanide crude product to produce a hydrogen cyanide product stream and a hydrogen stream comprising hydrogen gas; (d) contacting at least a portion of the hydrogen cyanide product stream of step (c) with butadiene in a second reaction zone to hydrocyanate butadiene to form one or more dinitrile compounds; (e) contacting at least a portion of the hydrogen stream of step (c) with one or more dinitrile compounds in a third reaction zone to hydrogenate the one or more dinitrile compounds to form a diamine, wherein said diamine is selected from the group consisting of hexamethylene diamine, methyl pentamethylene diamine, and combinations thereof; wherein the ternary gas mixture comprises a methane-containing gas, an ammonia-containing gas and an oxygen-containing gas. The ternary gas mixture may comprise methane, ammonia and at least 25% by volume oxygen. The reduction pressure is below 5000kPa, such as below 4000 kPa. The one or more dinitrile compounds may be selected from the group consisting of adiponitrile, 2-methylglutaronitrile and combinations thereof.

In a third embodiment, the present invention is directed to a method of producing hexamethylenediamine comprising the steps of: (a) measuring the methane content in the methane-containing gas and purifying the methane-containing gas when the measured methane content is below 90 v%; (b) reacting the three-way gas mixture in a first reaction zone in the presence of a catalyst to form a crude hydrogen cyanide product comprising HCN and a tail gas; (c) separating the hydrogen cyanide crude product to produce a hydrogen cyanide product stream and a hydrogen stream comprising hydrogen gas; (d) contacting at least a portion of the hydrogen cyanide product stream of step (c) with butadiene in a second reaction zone to cyanohydrogenate butadiene to produce adiponitrile; and (e) contacting at least a portion of the hydrogen stream of step (c) with adiponitrile in at least a third reaction zone to reduce adiponitrile to form hexamethylenediamine, wherein the reduction pressure in step (e) is less than 5000 kPa; and the ternary gas mixture comprises a methane-containing gas, an ammonia-containing gas and an oxygen-containing gas. The reduction of adiponitrile in step (e), also known as hydrogenation, can also produce 6-aminocapronitrile. In some embodiments, the ternary gas mixture comprises 25-32v% oxygen. The oxygen-containing gas may contain more than 21% by volume of oxygen, for example at least 80% by volume of oxygen, at least 95% by volume of oxygen or pure oxygen. The tail gas stream may contain from 40 to 90% by volume of hydrogen, from 0.1 to 20% by volume of water, from 0.1 to 20% by volume of carbon monoxide and from 0.1 to 20% by volume of carbon dioxide. The tail gas stream may be separated using a pressure swing absorber. The pressure swing absorber may be operated at a pressure of 1400-2400kPa and a temperature of 16-55 ℃. The pressure swing absorber may contain at least two adsorbent beds. The first and second adsorbent beds each comprise at least one adsorbent. The hydrogen stream contains at least 95% hydrogen by volume or at least 99% hydrogen by volume. The hydrogen cyanide product stream may contain less than 5v% hydrogen, or be substantially free of hydrogen. At least 70% of the hydrogen in the crude hydrogen cyanide product may be recovered in a hydrogen stream. Step (c) may further comprise separating the crude hydrogen cyanide product to form an ammonia gas stream. The ammonia stream may be returned to the reactor.

In a fourth embodiment, the present invention is directed to a process for producing methylpentamethylene diamine comprising the steps of: (a) measuring the methane content in the methane-containing gas and purifying the methane-containing gas when the measured methane content is below 90 v%; (b) reacting the three-way gas mixture in a first reaction zone in the presence of a catalyst to form a crude hydrogen cyanide product comprising HCN and a tail gas, (c) separating the crude hydrogen cyanide product to produce a hydrogen cyanide product stream and a hydrogen stream comprising hydrogen gas; (d) contacting at least a portion of the hydrogen cyanide product stream of step (c) with butadiene in a second reaction zone to cyanohydrogenate butadiene to produce methylglutaronitrile; and (e) contacting at least a portion of the hydrogen stream of step (c) with methylglutaronitrile in at least a third reaction zone to reduce the methylglutaronitrile to produce methylglutaronitrile, wherein the reduction pressure in step (e) is lower than 5000kPa or lower than 4000 kPa; the ternary gas mixture comprises a methane-containing gas, an ammonia-containing gas and an oxygen-containing gas. The reduction of methylglutaronitrile in step (e), also known as hydrogenation, may also lead to 3-methylpiperidine. In some embodiments, the ternary gas mixture comprises 25-32v% oxygen. The oxygen-containing gas may contain more than 21% by volume of oxygen, for example at least 80% by volume of oxygen, at least 95% by volume of oxygen or pure oxygen. The tail gas stream may contain from 40 to 90% by volume of hydrogen, from 0.1 to 20% by volume of water, from 0.1 to 20% by volume of carbon monoxide and from 0.1 to 20% by volume of carbon dioxide. The tail gas stream may be separated using a pressure swing absorber. The pressure swing absorber may be operated at a pressure of 1400-2400kPa and a temperature of 16-55 ℃. The pressure swing absorber may contain at least two adsorbent beds. The first and second adsorbent beds each comprise at least one adsorbent. The hydrogen stream contains at least 95% hydrogen by volume or at least 99% hydrogen by volume. The hydrogen cyanide product stream may contain less than 5v% hydrogen, or be substantially free of hydrogen. At least 70% of the hydrogen in the crude hydrogen cyanide product may be recovered in a hydrogen stream. Step (c) may further comprise separating the crude hydrogen cyanide product to form an ammonia gas stream. The ammonia stream may be returned to the reactor.

Drawings

Fig. 1 is a schematic diagram of a system for integrated HMD and/or MPMD production.

Detailed Description

The terminology used in the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

Words such as "comprising," "including," "having," "containing," or "involving," and variations thereof, are to be understood broadly and encompass the listed subject matter as well as equivalents, as well as additional subject matter not listed. Additionally, when a component, group of elements, process or method steps, or any other expression is introduced by the transitional phrase "comprising," "including," or "containing," it is understood that the same component, group of elements, process or method steps, or any other expression having the transitional phrase "consisting essentially of …," "consisting of …," or "selected from the group consisting of …" prior to the recitation of the component, group of elements, process or method steps, or any other expression is also contemplated herein.

The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below, if applicable, include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated. Accordingly, while the invention has been described in terms of embodiments, those skilled in the art will recognize that the invention can be practiced with modification and within the spirit and scope of the appended claims.

Reference will now be made in detail to the specific disclosed subject matter. Although the disclosed subject matter will be described in conjunction with the recited claims, it will be understood that they are not intended to limit the disclosed subject matter to those claims. On the contrary, the disclosed subject matter covers all alternatives, modifications, and equivalents as may be included within the scope of the disclosed subject matter as defined by the appended claims.

The invention provides a method for integrating diamine production and HCN production processes. The HCN process includes recovering a hydrogen stream and recovering HCN. Both hydrogen and HCN can be combined with a diamine production system, such as a system for producing at least one of HMD, MPMD, and combinations thereof. The system can include a first reaction zone for producing HCN, a second reaction zone for hydrocyanating butadiene to form one or more dinitrile compounds, such as ADN, MGN, and combinations thereof, and a third reaction zone for reducing, such as hydrogenating, the one or more dinitrile compounds to form diamines, such as HMD, MPMD, and combinations thereof. Traditionally, hydrogen has been recovered from steam reforming of methane in the prior art. The hydrogen obtained in this way contains a number of contaminants which are introduced into the respective process in which the hydrogen is used. Using the inventive process described herein, hydrogen recovered from an HCN process is of high purity and does not introduce impurities to subsequent processes. In addition, current processes require multiple feed streams and/or reaction systems to produce diamines. Therefore, by integrating these processes, process efficiency can be improved and cost can be saved.

The generation of HMD can be represented by the following equation:

NC(CH₂)₄CN+4H₂→H₂N(CH₂)₆NH₂

HMD is produced as described herein at elevated temperatures, pressures and in the presence of a catalyst, and optionally in the presence of ammonia. In some embodiments, ADN hydrogenation to form HMD may be performed at low pressures, such as at pressures below 5000KPa or below 4000 KPa. All pressures are absolute values unless otherwise indicated. In some embodiments, the low pressure range may be 1000 to 3500KPa, as described in US 8247561. The catalyst may include cobalt, nickel, iron, and noble metals including ruthenium, rhenium, platinum, and palladium. In some embodiments, the catalyst comprises nickel or cobalt. The catalyst may be on a support, comprising an alumina support.

The conversion of ADN can be 80-100%, and the selectivity of HMD and/or 6-Aminocapronitrile (ACN) is 95-99%. In some embodiments, the conversion of ADN may exceed 98%. It will be appreciated that by adjusting the residence time and/or other process conditions, the ratio of HMD and ACN formed can be controlled. The conversion of ADN was calculated as follows:

the selectivity of the HMD is calculated as follows:

the selectivity of ACN was calculated as follows:

in some embodiments, ADN may be partially hydrogenated to ACN, which may then be converted to caprolactam for the synthesis of nylon-6, as described in US5900511, the entire contents and published information of which are incorporated herein by reference.

ADN can be synthesized by the following 2-step method:

as indicated above, butadiene can be hydrocyanated to a mixture of 3-pentenenitrile ("3 PN") and 2-methyl-3-butenenitrile ("2M 3 BN"). There may be isomerization of 2M3BN to 3 PN. The 3PN is then hydrocyanated to ADN and/or MGN. Each hydrocyanation step may be catalyzed by a nickel catalyst, preferably a zero-valent nickel catalyst. Examples of such catalysts are described in US8088943, which is incorporated herein by reference in its entirety. The hydrocyanation of 3PN may be carried out in the presence of a Lewis acid promoter, as also described in US 8088943. The reaction may be carried out in the liquid phase at a pressure of 500 to 51000kPa, such as 1000 to 50000kPa, and a temperature of 0 to 200 ℃, such as 50 to 100 ℃.

The formation of MPMD is shown as follows,

NCCH(CH₃)(CH₂)₂CN+4H₂→H₂NCH₂(CH₃)(CH₂)₃NH₂

as described herein, MPMD is formed at elevated temperature, pressure and in the presence of a catalyst and optionally in the presence of ammonia. The high temperature can be in the range of 60-160 ℃, such as 80-140 ℃. In some embodiments, the hydrogenation of MGN to form MPMD may be performed at low pressure, such as at pressures below 5000KPa or below 4000 KPa. In some embodiments, the low pressure may be in the range of 1000 to 3500KPa, as described in US 8247561. The catalyst may comprise cobalt and chromium and nickel as doping elements.

The conversion rate of MGN can be 95-100%, and the selectivity of MPMD and/or MPP is 94-99%. In some embodiments, the conversion of MGN may exceed 98%.

The conversion of MGN was calculated as follows:

the selectivity of MPMD was calculated as follows:

the selectivity of MPP is calculated as follows:

the hydrogen cyanide used for the cyanohydrogenation of butadiene and 3PN can be obtained by the Andrussow or BMA process. In the Andrussow process, to obtain HCN, methane, ammonia and oxygen feedstocks are reacted at temperatures above 1000 ℃ in the presence of a catalyst to produce a hydrogen cyanide crude product comprising HCN, hydrogen, carbon monoxide, carbon dioxide, nitrogen, residual ammonia, residual methane and water. These components, i.e. the raw material, are fed to the reactor as a ternary gas mixture comprising an oxygen-containing gas, an ammonia-containing gas and a methane-containing gas. It will be appreciated by those of ordinary skill in the art that the Source of Methane may vary and may be obtained from renewable sources such as biogas from landfills, farms, fermentation, or fossil fuels such as natural Gas, petroleum associated Gas, coal Gas and Gas hydrates such as VN Parmon, "Source of Methane for Sustainable development", P.273-284, and as further described in the Desrouane Master Sustainable Strategies for the upgrading of Natural Gas: Fundamentals, changements, and Opportunities (2003). For the purposes of the present invention, the purity and consistent composition of the methane in the methane-containing gas source is important. In some embodiments, the method can include determining a methane concentration in a methane-containing gas source, and purifying the methane-containing gas source when the determined methane concentration is less than 90 v%. The methane content can be measured by gas chromatography, such as raman spectroscopy. The methane content can be measured continuously in real time or as needed when a new methane-containing gas source is introduced into the process. Alternatively, where the methane content is above 90% v, such as 90-95% v, the methane gas source may also be purified to achieve higher purity. The methane-containing gas source can be purified using known purification methods to remove oil, condensate, C2+ hydrocarbons (e.g., hexane, propane, butane, pentane, hexane, and isomers thereof), sulfur, and carbon dioxide.

Natural gas is typically used as the methane source, while air, oxygen-enriched gas, or pure oxygen is used as the oxygen source. Oxygen-enriched gas or pure oxygen is preferably used. The three-way gas mixture is passed over a catalyst to form a crude hydrogen cyanide product. The crude hydrogen cyanide product is then separated to recover HCN. In the present invention, the crude hydrogen cyanide product is also separated to recover hydrogen.

The term "air" as used herein relates to a gas mixture having a composition that is nearly identical to the original composition of the gas taken from the atmosphere (typically ground level). In some embodiments, the air is taken from the ambient environment. The composition of air is as follows, including about 78v% nitrogen, about 21v% oxygen, about 1v% argon, and about 0.04v% carbon dioxide, as well as minor amounts of other gases.

The term "oxygen-enriched air" as used herein relates to a gas mixture which contains more oxygen than air. The oxygen-enriched air is composed of greater than 21% oxygen by volume, less than 78% nitrogen by volume, less than 1% argon by volume, and less than 0.04% carbon dioxide by volume. In some embodiments, the oxygen-enriched air comprises at least 28% oxygen by volume, such as at least 80% oxygen by volume, at least 95% oxygen by volume, or at least 99% oxygen by volume.

The term "natural gas" as used herein relates to a gas mixture comprising methane and optionally ethane, propane, butane, carbon dioxide, oxygen, nitrogen and/or hydrogen sulphide. Natural gas may also contain trace amounts of noble gases including helium, neon, argon and/or xenon. In some embodiments, the natural gas may contain less than 90% methane by volume.

The formation of HCN in the Andrussow process is generally shown by the following general reaction:

2CH₄+2NH₃+3O₂→2HCN+6H₂O

however, the above reaction should be understood to represent a simplification of the more complex dynamic sequence of the reaction in which a portion of the hydrocarbons are first oxidized to produce thermal energy necessary to sustain the endothermic synthesis of HCN from the remaining hydrocarbons and ammonia.

Three basic side reactions also occur during the synthesis of HCN:

CH₄+H₂O→CO+3H₂

2CH₄+3O₂→2CO+4H₂O

4NH₃+3O₂→2N₂+6H₂O

in addition to the amount of nitrogen generated in the side reactions, additional nitrogen may be present in the crude product depending on the source of oxygen. Although oxygen-enriched air or pure oxygen has been suggested in the prior art as a source of oxygen, the advantages of using oxygen-enriched air or pure oxygen are not fully exploited. When air is used as the source of oxygen, the crude hydrogen cyanide product contains components in air, such as approximately 78v% nitrogen, and nitrogen generated in the ammonia and oxygen side reactions.

The use of oxygen-enriched air in the process for the synthesis of HCN is advantageous due to the large amount of nitrogen in the air, since the presence of large amounts of inert gas (nitrogen) when using air as the source of oxygen for the production of HCN results in larger plants for the synthesis reaction and also in lower HCN concentrations in the product gas. In addition, due to the presence of inert nitrogen, more methane needs to be burned to raise the temperature of the ternary gas mixture components to maintain them at the temperature required for the synthesis of HCN. The crude hydrocyanic acid product contains HCN, and also contains by-product hydrogen, methane combustion by-products (carbon monoxide, carbon dioxide, water), residual methane, and residual ammonia. However, when air (i.e. 21vol% oxygen) is used, the presence of inert nitrogen gas after separation of HCN and recoverable ammonia gas from other gas components can cause the residual gas stream to have a lower heating value than is required for energy recovery.

Thus, the use of oxygen-enriched air or pure oxygen instead of air to produce HCN has many advantages, including the ability to recover hydrogen. Other advantages include increased conversion of natural gas to HCN and corresponding size reduction of the production plant. Thus, using oxygen-enriched air or pure oxygen, the size of the reactor and the reduction of at least one component of the downstream gas treatment unit can be reduced by reducing the inert compounds entering the synthesis process. The use of oxygen-enriched air or pure oxygen also reduces the energy consumed to heat the oxygen-containing feed gas to reaction temperature.

When an oxygen-containing gas containing 21v% or less of oxygen is used, the amount of nitrogen makes it impractical to recover hydrogen due to energy and economic considerations. Surprisingly, it has been found that when oxygen-enriched air or pure oxygen is used, hydrogen can be recovered from the crude hydrogen cyanide product in an efficient and economical manner, such as by using a pressure swing absorber. The recovered hydrogen has a very high purity and can therefore be used in an integrated HMD production process.

When the crude hydrogen cyanide product is synthesized using oxygen-enriched air or pure oxygen, it is desirable to process the tail gas of the crude hydrogen cyanide product to recover the hydrogen component, rather than burning the tail gas off in a burner. An absorber can be utilized to separate a tail gas from the crude hydrogen cyanide product. Hydrogen may be recovered from at least a portion of the tail gas by Pressure Swing Absorbers (PSA), membrane separation, or other known purification/recovery processes. In some embodiments, the PSA unit is used to recover hydrogen. In such an example, the gas is first compressed from 130kPa to 2275kPa, such as from 130kPa to 1700kPa or from 136kPa to 1687kPa, and then fed to the PSA unit. The recovered high purity hydrogen is more valuable as a component than as a fuel, e.g., it can be used as a feed stream for other processes, such as in a process for hydrogenating ADN to 6-aminocapronitrile and/or HMD, or in a process for hydrogenating MGN to MPMD and/or MPP. It should be noted that the amount of nitrogen in the tail gas will affect the economic viability of recovering hydrogen from the tail gas rather than combusting the tail gas in a combustor. Other components or constituents may also affect the desirability of recovering hydrogen. For example, if the concentration of HCN in the tail gas exceeds a predetermined maximum, the tail gas stream may be redirected to a steam generating furnace or flame instead of hydrogen recovery.

Fig. 1 shows an integrated HMD production process in one embodiment. As shown in fig. 1, the ternary gas mixture 105 comprises a methane-containing gas 102, an ammonia-containing gas 103, and an oxygen-containing gas 104. As described herein, the oxygen content in the oxygen-containing gas 104 is higher than 21v%, i.e. oxygen-enriched gas or pure oxygen, in order to make the recovery of hydrogen economically and energy-efficient. In some embodiments, the oxygen content in the oxygen-containing gas 104 is at least 28% oxygen by volume, at least 80% oxygen by volume, at least 95% oxygen by volume, or at least 99% oxygen by volume.

The oxygen content in the ternary gas mixture 105 is controlled by the combustion limit. Certain mixtures of air, methane and ammonia are flammable and therefore flame spread once ignited. When the gas composition is between the upper and lower flammability limits, the mixture of air, methane and ammonia will burn. Mixtures of air, methane and ammonia outside the upper and lower flammability limits are generally non-flammable. The use of oxygen-enriched air changes the concentration of combustibles in the ternary gas mixture. Increasing the oxygen content of the oxygen-containing gas feed stream significantly widens the flammability range. For example, a mixture containing 45% v air and 55% v methane is generally considered fuel-rich and non-flammable, while a mixture containing 45% v oxygen and 55% v methane is flammable.

Another concern is the explosive limit. For example, a gas mixture containing 60% oxygen, 20% methane, and 20% ammonia by volume can explode at atmospheric pressure and room temperature.

It was therefore found to be advantageous in the production of HCN to use oxygen-enriched air, which necessarily leads to a change in the combustible concentration in the ternary gas mixture, which increases the upper limit value of the flammability limit of the ternary gas mixture fed to the reactor. Thus, deflagrations and explosions of the ternary gas mixture are very sensitive to the oxygen content. As used herein, the term "deflagration" refers to a combustion wave that propagates at a subsonic velocity relative to unburned gases immediately before the flame. "explosion" refers to a combustion wave that propagates at supersonic velocity immediately before the flame relative to unburned gas. Flash fires typically result in a modest pressure increase, while explosions may result in an excessive pressure increase.

While others have suggested using oxygen-enriched air to increase the production capacity of HCN, operation in a flammable zone is generally avoided. See US5882618, US6491876 and US6656442, which are incorporated herein by reference in their entirety. In the present invention, the oxygen-enriched air or pure oxygen feed is controlled so that the resulting ternary gas mixture is located in the flammable zone but not in the explosive zone. Thus, in some embodiments, the ternary gas mixture 105 comprises at least 25% oxygen by volume, such as at least 28% oxygen by volume. In some embodiments, the ternary gas mixture comprises 25-32% oxygen, such as 26-30% oxygen by volume. The molar ratio of ammonia to oxygen in the ternary gas mixture is 1.2-1.6, such as 1.3-1.5; the molar ratio of ammonia to methane is from 1 to 1.5, for example from 1.10 to 1.45; the molar ratio of methane to oxygen is 1 to 1.25, such as 1.05 to 1.15. For example, the molar ratio of ammonia to oxygen in the ternary gas mixture is 1.3 and the molar ratio of methane to oxygen is 1.2. In another specific example, the molar ratio of ammonia to oxygen in the ternary gas mixture is 1.5 and the molar ratio of methane to oxygen is 1.15. The oxygen content of the ternary gas mixture depends on the molar ratio mentioned above.

HCN is produced in the first reaction zone. The three-way gas mixture 105 is fed to a reactor 106 where a crude hydrogen cyanide product 107 is formed after the catalyst has flowed through. The catalyst is typically a platinum/rhodium or platinum/iridium gauze alloy. Other catalysts may also be used, including but not limited to platinum-based metals, platinum-based metal alloys, supported platinum-based metals, or supported platinum-based metal alloys. Other configurations of catalysts may be used including, but not limited to, porous structures including woven, non-woven and braided, metal meshes, tablets, monoliths, foams, dip coatings, washcoats.

Traditionally, the crude hydrogen cyanide product 107 is cooled in a heat exchanger and then exits the reactor. The crude hydrogen cyanide product 107 is cooled from above 1200 c to below 400 c, below 300 c or below 250 c. An exemplary hydrogen cyanide crude product composition is shown in table 1.

TABLE 1 composition of the crude Hydrogen cyanide product

As shown in table 1, the production of HCN using the air process produced only 13.3v% hydrogen, while the oxygen process may result in an increase in hydrogen to 34.5 v%. The amount of hydrogen depends on the concentration of oxygen in the feed gas and the molar ratio of the reactants and varies from 34 to 36v% hydrogen. In addition to the data listed in Table 1, the oxygen content in the crude hydrogen cyanide product is low, preferably below 0.5v%, and high oxygen contents in the crude hydrogen cyanide product can cause shutdowns or necessitate cleaning. The composition of the crude hydrogen cyanide obtained using the oxygen Andrussow process can vary as shown in table 2, depending on the molar ratio of ammonia, oxygen and methane used.

TABLE 2 composition of the crude hydrogen cyanide product formed using the oxygen Andrussow process

After the ammonia gas is removed in the ammonia gas removal unit 108, the hydrogen cyanide crude product is separated using an absorber 110 to form a tail gas stream 111 comprising hydrogen, water, carbon dioxide and carbon monoxide, and a hydrogen cyanide product stream 112 comprising hydrogen cyanide. The hydrogen cyanide product stream contains less than 10% hydrogen by volume, such as less than 5% hydrogen by volume, less than 1% hydrogen by volume, less than 100mpm hydrogen, or is substantially free of hydrogen. A comparison of the tail gas stream 111 separated from the hydrogen cyanide crude product 107 in the oxygen Andrussow process and the air Andrussow process, as well as the amount of nitrogen in the above processes, is listed in table 3.

TABLE 3 comparison of tail gas stream composition of HCN

As shown in table 3, when the oxygen Andrussow process is used, the tail gas stream 111 contains more than 80% by volume of hydrogen. In some embodiments, the tail gas stream 111 comprises 40-90% hydrogen, such as 45-85% hydrogen or 50-80% hydrogen. The tail gas stream 111 may further comprise 0.1-20v% water, such as 0.1-15 v% water or 0.1-1 v% water. The tail gas stream 111 may further comprise 1-20v% carbon monoxide, such as 1-15 v% carbon monoxide or 1-10 v% carbon monoxide. The tail gas stream 111 may further comprise 0.1-20% by volume of carbon dioxide, such as 0.5-15% by volume of carbon dioxide or 0.75-2% by volume of carbon dioxide. In one embodiment, the tail gas stream 111 comprises 78v% hydrogen, 12v% carbon monoxide, 1v% carbon dioxide, and the balance water and hydrogen cyanide. The tail gas stream 111 may also contain traces of dinitriles and small amounts of other components including methane, ammonia, nitrogen, argon and oxygen. Preferably, the total amount of these other components present is less than 10 v%. The amount of nitrogen is less than 20v%, such as less than 15v% or less than 10 v%.

The tail gas stream 111 may be separated with a PSA unit 130, as described herein. One exemplary PSA process and apparatus is described in US3430418 and US3986849, which are incorporated herein by reference in their entirety. The PSA130 may comprise at least two beds, such as at least 3 beds or at least 4 beds, and is operated at a pressure of 1400kPa to 2400kPa, such as 1600kPa to 2300kPa or 1800kPa to 2200 kPa. The PSA130 is operated at a temperature of 16-55 deg.C, such as 20-50 deg.C or 30-40 deg.C. The PSA may be a multi-bed PSA. Each bed contains an absorbent. In some embodiments, each bed contains the same absorbent. In other embodiments, each bed may contain a different absorbent. The adsorbent may be a conventional adsorbent used in PSA units, including zeolites, activated carbon, silica gel, alumina, and combinations thereof. The cycle time of each bed is 150-210 seconds, such as 180-200 seconds, and the total cycle time is 300-1000 seconds, such as 400-900 seconds.

The tail gas stream 111 is separated in the PSA130 to form a hydrogen stream 132 and a purge stream 131. The hydrogen stream 132 may be considered a high purity hydrogen stream comprising at least 95% hydrogen by volume, such as at least 99% hydrogen by volume or at least 99.5% hydrogen by volume. The purge gas stream 131 comprises carbon dioxide, carbon monoxide gas and hydrogen. The purge gas 131 may be combusted as fuel. The hydrogen stream 132 is discussed further herein.

The use of the PSA130 to recover hydrogen allows at least 70% of the hydrogen in the crude hydrogen cyanide product 107 in the oxygen Andrussow process to be recovered, such as at least 72.5%, at least 75%, or at least 76%.

Returning to fig. 1, the crude hydrogen cyanide product 107 may optionally be further processed before the tail gas is separated from the crude hydrogen cyanide product 107. When the Andrussow process is carried out under preferred conditions, it has the potential to recover residual ammonia from the hydrogen cyanide product stream. Since the rate of HCN polymerization increases with increasing pH, the remaining ammonia must be removed to avoid HCN polymerization. The polymerization of HCN not only represents a process yield problem, but also represents an operational challenge as the polymerized HCN can cause plugging of process lines which can lead to increased pressure and related process control problems. Once the crude hydrogen cyanide product has been cooled, the remaining ammonia can be separated from the crude hydrogen cyanide product before the tail gas is separated from the crude hydrogen cyanide product. The ammonia gas may be removed using an ammonia separation unit 108, which may include a scrubber, a stripper, or a combination thereof. At least a portion of the crude hydrogen cyanide product 107 can be directed to an ammonia purifier, absorber, and combination thereof 108 to remove residual ammonia gas.

The crude hydrogen cyanide product 109 after ammonia removal contains less than 1000mpm of ammonia, such as less than 500mpm or less than 300 mpm. The ammonia gas stream 113 may be returned to the reactor 106 to the ternary gas mixture 105 for reuse as a reactant feed or to a process for the production of HMD, as further described herein. The polymerization of HCN can be carried out by immediately reacting the hydrogen cyanide stream with an excess of acid (e.g., H)₂SO₄Or H₃PO₄) The reaction is inhibited so that the remaining free ammonia is absorbed by the acid as ammonium salt, while the pH of the solution remains acidic. The formic acid or oxalic acid in the ammonia recovery feed stream is absorbed in the aqueous solution of the ammonia recovery system as formate or oxalate.

The hydrogen cyanide crude product 109 can be separated to remove tail gases, as described herein, to yield a hydrogen cyanide product stream 112. Stream 112 may be further processed in HCN refining zone 120 to recover a refined hydrogen cyanide stream 121 for hydrocyanation.

The term "hydrocyanation" as used herein includes hydrocyanation of an aliphatically unsaturated compound comprising at least one carbon-carbon double bond or at least one carbon-carbon triple bond or combinations thereof, which unsaturated compound may further comprise other functional groups including, but not limited to, dinitriles, esters and aromatic hydrocarbons. Examples of such aliphatic unsaturated compounds include, but are not limited to, olefinic hydrocarbons (e.g., alkenes), alkynes, dienes, and functional group-substituted compounds thereof. Suitable dienes include 1, 3-butadiene. The functional group-substituted compound may include pentenenitrile. Hydrocyanation may include hydrocyanation of 1, 3-butadiene and pentenenitrile to ADN.

HCN recovered from the purified hydrogen cyanide stream 121 is uninhibited HCN. As used herein, the term "uninhibited HCN" means that there is substantially no stabilizing polymerization inhibitor present in the HCN. As will be appreciated by those of ordinary skill in the art, such stabilizers are typically added to minimize the polymerization of HCN and require that at least a portion of the stabilizer be removed prior to using the HCN for hydrocyanation, such as hydrocyanation of 1, 3-butadiene and pentenenitriles to ADN. HCN polymerization inhibitors include, but are not limited to: inorganic acids such as sulfuric acid and phosphoric acid; organic acids such as acetic acid; sulfur dioxide and combinations thereof.

Returning to fig. 1, at least a portion of the purified hydrogen cyanide stream 121 is passed to a second reaction zone, such as a dinitrile compound production reactor 140, to produce ADN, MGN or a combination thereof. Although only one reactor is shown, it is to be understood that this is a simplified depiction and that the production of dinitrile compounds is a 2-step process. The process for producing the dinitrile compound may comprise a separation apparatus (not shown). If desired, dinitrile compounds can be separated to form an ADN stream and an MGN stream (not shown). See US 5312959.

One or more dinitrile compounds exit dinitrile compound production reactor 140 through line 141 and enter a third reaction zone, such as diamine unit 150, to form HMD, MPMD and mixtures thereof. Additionally, reduction of one or more dinitrile compounds may form 6-aminocapronitrile, MPP or a combination thereof. An optional ammonia stream may likewise be supplied to the reactor (not shown). The optional ammonia stream can be a fresh ammonia stream or can comprise at least a portion of the recovered ammonia gas from line 113. At least a portion of hydrogen stream 132 is also passed to diamine reactor 150, thereby hydrogenating one or more dinitrile compounds to form a crude diamine product stream 151. Additional hydrogen from sources other than the process may be combined with the hydrogen stream 132, if desired. The hydrogen may be compressed prior to entering the reactor.

A crude diamine product stream 151 exits diamine reactor 150 and enters a finishing system 160, where the crude diamine product stream is separated in finishing system 160 to form a diamine product stream 161 and residue 162, which residue 162 comprises 6-aminocapronitrile, MPP, unreacted dinitrile compound, and/or Tetrahydroazepine (THA) -containing reaction by-products. HMD separation is described in US6887352, which is incorporated by reference herein in its entirety. HMD product 161 contains less than 1000mpm THA, such as less than 500mpm, less than 150mpm, less than 20mpm, or substantially no THA. If desired, 6-aminocapronitrile can also be recovered. MPMD may be further purified as described in US 8247561.

As will be appreciated by one skilled in the art, the foregoing functions and/or methods may be embodied as a system, method or computer program product. For example, the functions and/or methods may be implemented as computer-executable program instructions recorded in a computer-readable storage device that, when retrieved and executed by a computer processor, control the computer system to perform the functions and/or methods of the embodiments described above. In one embodiment, the computer system may include one or more central processing units, computer memory (e.g., read-only memory, random access memory), and data storage devices (e.g., hard disk drives). The computer-executable instructions may be encoded using any suitable computer programming language (e.g., C + +, JAVA, etc.). Accordingly, aspects of the present invention may take the form of an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects.

The invention is further illustrated by the following examples.

Example 1

Combining pure oxygen, ammonia-containing gas and methane-containing gas to form a ternary gas mixture. In the ternary gas mixture, the molar ratio of ammonia to oxygen is 1.3: 1, the molar ratio of methane to oxygen is 1.2: 1. A ternary gas mixture comprising from 27 to 29.5% by volume of oxygen is reacted in the presence of a platinum/rhodium catalyst to form a crude hydrogen cyanide product comprising from 34 to 36% by volume of hydrogen. Hydrogen is formed during the reaction. The crude hydrogen cyanide product is separated from the reactor and then fed to an ammonia removal unit to separate the remaining ammonia from the crude hydrogen cyanide product. The crude hydrogen cyanide product is then fed to an absorber to form a tail gas and a hydrogen cyanide product. The composition of the tail gas is shown in the oxygen Andrussow process in table 3, and the tail gas is fed to the PSA unit after being compressed to 2275 kPa. The PSA unit comprises four beds, each bed comprising zeolite and activated carbon. Each bed absorbs non-hydrogen components of the tail gas, such as nitrogen, carbon monoxide, carbon dioxide and water. The PSA unit was operated at 40 ℃ for a total cycle time of 800 seconds (about 190 seconds per bed). 75-80% of the hydrogen in the crude hydrogen cyanide product is recovered in a hydrogen stream. The hydrogen stream has a purity of 99.5% or greater.

Example 2

The hydrogen of example 1 was introduced into an HMD production system that included an HMD reactor in which the HDN was hydrogenated. HMD production processes are described in US 3398195. The hydrogen stream may provide at least 20% of the hydrogen required to hydrogenate ADN to HMD on a molar basis.

Example 3

The hydrogen of example 1 was introduced into a methylglutaronitrile production system shown in US 8247561. The hydrogen stream may provide at least 20% of the hydrogen required to hydrogenate methylglutaronitrile to methylglutaromethylene diamine on a molar basis.

Comparative example A

The tail gas was separated as shown in example 1, except that air was used instead of pure oxygen to form the ternary gas mixture. Thus, the ternary gas mixture contains less than 25% by volume of oxygen. Since the amount of nitrogen was increased as compared with example 1, the size of the ammonia gas separation unit was larger than that of example 1, and the size of the absorber was also larger than that of example 1. The composition of the tail gas is shown in the air Andrussow process in table 3. The tail gas was compressed and sent to the PSA unit used in example 1. The number of compressors required was eight times the number of compressors required to compress the tail gas in example 1. After the non-hydrogen components are absorbed in the first bed, the PSA unit can no longer continue to operate due to the lack of a sufficient volume of hydrogen. The recovery of hydrogen is uneconomical and not energetically feasible. Thus, hydrogen cannot be integrated with HMD and/or methylpentamethylene diamine production.

Claims

1. A process for producing a diamine comprising the steps of:

a measuring the methane content in the methane containing gas and purifying the methane containing gas when the measured methane content is below 90 v%;

b reacting a tertiary gas mixture comprising at least 25% by v oxygen in the presence of a catalyst in a first reaction zone to form a crude hydrogen cyanide product comprising HCN and a tail gas, wherein the tertiary gas mixture comprises a methane-containing gas, an ammonia-containing gas, and an oxygen-containing gas;

c separating the crude hydrogen cyanide product to produce a hydrogen cyanide product stream and a tail gas stream comprising hydrogen, water, carbon monoxide, carbon dioxide or combinations thereof;

d separating the tail gas stream to produce a hydrogen stream and a purge stream, the purge stream comprising carbon monoxide, carbon dioxide and water;

e contacting at least a portion of the hydrogen cyanide product stream of step c with butadiene in a second reaction zone to cyanohydrogenate butadiene to form one or more dinitrile compounds; and

f contacting at least a portion of the hydrogen stream in step d with one or more dinitrile compounds in a third reaction zone to reduce the one or more dinitrile compounds to form a diamine, wherein the diamine is selected from the group consisting of hexamethylenediamine, 2-methylpentamethylenediamine and combinations thereof.

2. The process of claim 1, wherein step c can further comprise separating the crude hydrogen cyanide product to form an ammonia gas stream, wherein at least a portion of the ammonia gas stream is returned to the reactor.

3. A process according to claim 1, wherein the one or more dinitrile compounds are reduced at a pressure of less than 5000 kPa.

4. The method of claim 1, wherein the ternary gas mixture comprises 25-32v% oxygen.

5. The method of claim 1, wherein the one or more dinitrile compounds are selected from the group consisting of adiponitrile, methylglutaronitrile and combinations thereof.

6. The process of claim 1, wherein the one or more dinitrile compounds in step e form at least one of 3-methylpiperidine, 6-aminocapronitrile, and combinations thereof upon reduction.

7. The method of claim 1, wherein the tail gas comprises: 40-90% by volume of hydrogen, 0.1-20% by volume of water, 0.1-20% by volume of carbon monoxide, 0.1-20% by volume of carbon dioxide and less than 20% by volume of nitrogen.

8. The process of claim 1 wherein the tail gas stream is separated using a pressure swing absorber, molecular sieve, or membrane.

9. The process as set forth in claim 8 wherein the pressure swing absorber is operated at a pressure of 1400-2600 kPa.

10. The process of claim 8 wherein the pressure swing absorber operates at a temperature of from 16 ℃ to 55 ℃.

11. The process of claim 8 wherein the pressure swing absorber comprises at least two adsorbent beds.

12. The method of claim 11, wherein each of the at least two adsorbent beds comprises at least one adsorbent selected from the group consisting of zeolites, activated carbon, silica gel, alumina, and combinations thereof.

13. The method according to claim 1, wherein the hydrogen stream contains at least 95% by volume of hydrogen, preferably at least 99% by volume of hydrogen.

14. The process of claim 1, wherein the hydrogen cyanide product stream comprises less than 10v% hydrogen, preferably less than 5v% hydrogen, more preferably is substantially free of hydrogen.

15. The process according to claim 1, characterized in that at least 70% of the hydrogen in the crude hydrogen cyanide product, preferably at least 72.5v% of the hydrogen, is recovered in the hydrogen stream.