Production of cyano-containing compounds

Abstract

In a method for producing a cyano-containing compound, ammonia, an oxygen source, and an organic compound are reacted in an ammoxidation reactor to produce a reaction product containing hydrogen cyanide and a target cyano-containing compound selected from organic nitrile compounds. The reaction product is fed to a separation section to recover at least a portion of the target compound. A waste stream containing at least one further organic nitrile compound different from the target compound is combined with at least one organic oxygenate diluent compatible with the ammoxidation reaction to produce a diluted waste stream, which is then fed to the ammoxidation reactor.

Description

Technical Field

[0001] (Cross - reference to Related Applications) This application claims the benefit of priority of U.S. Patent Application No. 63 / 419352, entitled "PRODUCTION OF CYANO - CONTAINING COMPOUNDS," filed on October 26, 2022, the disclosure of which is hereby incorporated by reference in its entirety.

[0002] (Field of the Invention) This disclosure relates to the production of cyano - containing compounds, specifically hydrogen cyanide and organic nitriles, and more particularly to methods for producing such compounds with improved yields and / or reduced nitrogen oxide [nitrogen oxide, NO x emissions.

Background Art

[0003] One widely practiced method for producing cyano - containing compounds is "ammoxidation," in which C1 hydrocarbons, C3 hydrocarbons, alcohols, carboxylic acids, ketones, low - molecular - weight polyols, tetrahydrofuran, and other organic compounds undergo chemical conversion in the presence of ammonia and an oxygen source to form hydrogen cyanide [hydrogen cyanide, HCN] and / or other organic nitrile compounds. Well - known examples include the SOHIO ammoxidation process that converts propylene or propane to acrylonitrile, and the Andrussow process in which HCN is formed from methane (natural gas), ammonia, and an oxygen source.

[0004] During the production of any given cyano-containing compound by ammoxidation, several by-product organic nitriles, known as "ON by-products," are inevitably generated. For example, the SOHIO ammoxidation process produces acetonitrile and propionitrile in addition to acrylonitrile and HCN. It is industrially known and observed that such ON by-products, as a result of decomposition / polymerization, can lead to equipment fouling, clogging, corrosion, and foaming, particularly in the product separation and recovery sections. All of these complicate the product recovery / separation process. Furthermore, unless removed, these ON by-products can be carried over to the final product as undesirable impurities.

[0005] The problem of nitrogen oxide (ON) byproduct accumulation in nitrile fractionation equipment has traditionally been addressed by accumulating ON in a designated tray (stage) or section of the fractionation column. The ON is then periodically purged from this tray (stage) or section and burned as fuel or processed in a thermal oxidizer. The problem is that this reduces the value of this ON stream to fuel value. Thermal oxidation of such nitrogen-containing purge streams also results in increased nitrogen oxide [NOx] emissions into the environment. While it is desirable to recirculate these purged ON into the process feed, nitrile production equipment is not designed to handle the wide variation in process feed composition.

[0006] Therefore, there remains an industrial need to develop improved large-scale nitrile manufacturing processes that handle organic nitrile by-product streams in a way that enhances their value while reducing or even eliminating nitrogen oxide [NOx] emissions resulting from these by-product streams. [Overview of the Initiative]

[0007] According to this disclosure, by combining the ON by-products removed from the separation system of the ammoxidation process with an oxygenate diluent, the by-products can be recycled back into the process while maintaining stable operational control, thereby NO xThis study found that it is possible to increase the value of by-product flow while reducing emissions.

[0008] Therefore, in one embodiment, the present application relates to a method for producing a cyano-containing compound, (a) A step of reacting ammonia, an oxygen source and an organic compound in an ammoxidation reactor to produce a reaction product containing a target cyano-containing compound selected from hydrogen cyanide and an organic nitrile compound, (b) A step of supplying the reaction product to a separation section to recover at least a portion of the target compound, (c) A step of providing a waste stream containing at least one further organic nitrile compound different from the target compound, (d) A step of generating a diluted waste stream by combining at least a portion of the waste stream with at least one organic oxygenate diluent that is compatible with the ammoxidation reaction, (e) A method is provided which includes the step of supplying a diluted waste stream to an ammoxidation reactor. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram of a conventional simultaneous manufacturing facility 100 for producing acrylonitrile [ACRN] and HCN.

[0010] [Figure 2] This is a schematic diagram of a simultaneous manufacturing facility 200 for producing acrylonitrile [ACRN] and HCN according to the first embodiment of the present disclosure.

[0011] [Figure 3] This is a schematic diagram of a simultaneous manufacturing facility 300 for producing acrylonitrile [ACRN] and HCN according to a second embodiment of the present disclosure.

[0012] [Figure 4] This is a schematic diagram of a manufacturing facility 400 for producing acrylonitrile [ACRN] according to a third embodiment of the present disclosure.

[0013] It should be noted that all figures in this specification contain many details relating to various flow lines [process, utility, bypass, vent, purge, sampling], instrumentation, control, pumps, valves, etc., which are known to those skilled in the art and are therefore not illustrated. [Modes for carrying out the invention]

[0014] As used herein, the terms "acrylo" or "ACRN" refer to acrylonitrile and may be used interchangeably.

[0015] As used herein, the terms "aceto" or "ACN" refer to acetonitrile and may be used interchangeably.

[0016] As used herein, the term "HCN" refers to hydrogen cyanide.

[0017] As used herein, the term “Target Compound” refers to a specific cyano compound selected from hydrogen cyanide and organonitrile compounds that is desired to be produced by the methods described herein. Examples of industrially useful Target Compounds include, but are not limited to, hydrogen cyanide, as well as C1-C6 nitriles and dinitriles such as acetonitrile, acrylonitrile, succinonitrile, adiponitrile, methylglutalonitrile, pentenenitrile, and glutalonitrile.

[0018] As referred to herein, the term "nitrile production process" or "nitrile production facility" refers to a chemical production process or facility in which useful nitriles are produced. Non-limiting examples of nitrile production processes are the Andrussow HCN process, the BMA (Degussa) HCN process, the Shawinigan HCN process, the methanol ammoxidation process to HCN; the ethanol ammoxidation process to acetonitrile, succinonitrile from heterocyclic materials [e.g., tetrahydrofuran], glycerol ammoxidation to nitrile, the ammoxidation processes of propylene and / or propane to acrylonitrile, and the acrylonitrile ammoxidation process using a methanol co-feed to produce additional HCN.

[0019] As used herein, the term "ammoxidation" refers to a well-known chemical synthesis step in which C1 hydrocarbons, C3 hydrocarbons, alcohols, carboxylic acids, ketones, low molecular weight polyols [glycerol], tetrahydrofuran [tetrahydrofuran, THF], acetonitrile, etc. undergo chemical conversion in the presence of an ammonia and an oxygen source to form a nitrile (represented by the functional group "

Number

[0020] As used herein, the term "Andrussow" refers to a well-known chemical synthesis step in which HCN is formed from methane (natural gas), ammonia, and an oxygen source. Depending on the oxygen content, the Andrussow process can be classified as an air-Andrussow process, an air-rich or enriched air Andrussow process, or a 100% oxygen supply Andrussow process.

[0021] As used herein, the interchangeable terms "organic nitrile-containing waste stream" or "organic nitrile by-product stream" or "by-product ON" refer to a stream containing organic components containing nitrile that are different from the target compound and are considered undesirable impurities to be removed from the nitrile process. In some embodiments, the organic nitrile impurities have a higher molecular weight than the target cyano compound, for example at least 10% higher. Of course, it will be understood that an organic nitrile that may be the desired target compound in one process may be considered an undesirable by-product in another process.

[0022] In one embodiment, the organic nitrile-containing waste stream may be obtainable from an adiponitrile production facility. Additional ON components present in such waste streams may include, but are not limited to, unsaturated or saturated C3-C4 nitriles and dinitriles, linear or branched pentenenitriles, 2-methylglutaronitrile (MGN), methyleneglutaronitrile, ethyl succinonitrile (ESN), and adiponitrile (ADN), by way of merely a few examples. Such organic nitrile-containing waste streams are concentrated from the adiponitrile recovery / purification process and can be used in accordance with the present disclosure.

[0023] In acrylonitrile production, undesirable by-product ONs include hydrogen cyanide, acetonitrile, propionitrile, methacrylonitrile, nitrile dimers, trimers, and oligomers, butanenitrile, 6-aminocapronitrile, 4-amino-2-methyl-5,6-trimethylene pyrimidine, cyclic nitriles, and polymers of acrylonitrile.

[0024] In HCN production, undesirable by-product ONs include acetonitrile, propionitrile, acrylonitrile, semi-cyanohydric acid, nitrile dimers, trimers, and oligomers, and butanenitrile.

[0025] Table 1 provides a list of undesirable by-products ON that may occur depending on the desired target product produced from a conventional manufacturing process. [Table 1-1] [Table 1-2]

[0026] As shown in the last row of Table 1, the undesirable by-product ON, which is generated during the process of producing polymers from bio-derived C5 diamines [pentamethylenediamine], may be useful in the disclosed process.

[0027] In conventional ammoxidation processes, these by-products ON are transported through product recovery / separation / purification steps and accumulated / concentrated in downstream rectification equipment (recovery-separation columns, HCN product rectification trains, decanters, etc.). Furthermore, by-products ON are often unsaturated or otherwise autopolymerize (forming monomers, dimers, trimers, etc.), and their molecular weight is easily constructed under separation conditions.

[0028] Conventional methods for managing / controlling these by-product ONs involve drawing a purge flow from the appropriate location where these ONs are most concentrated and removing them from the process. Often, this purging is discontinuous to minimize the loss of useful products. This implementation can lead to the accumulation of intermediate boiling point ONs, affecting unit performance.

[0029] The aforementioned organic nitrile purge streams obtained from nitrile processes are removed via off-gas and / or disposed of as concentrated liquid streams. The most common method for disposing of such organic purge streams is by thermal destruction in a thermal oxidizer (TO). Thermal destruction of such nitrogen-containing purge streams is undesirable because it not only reduces the value of the purge stream but can also lead to increased nitrogen oxide (NOx) emissions into the environment.

[0030] To address this problem, the present disclosure provides a method for producing a cyano-containing compound selected from hydrogen cyanide and organic nitrile compounds, wherein ammonia, an oxygen source, and an organic compound are reacted in an ammoxidation reactor to produce a reaction product containing the target cyano-containing compound. The reaction product is then fed to a separation section where at least a portion of the target compound is recovered. A waste stream containing at least one further organic nitrile compound different from the target compound is combined with at least one organic oxygenate diluent compatible with the ammoxidation reaction to produce a diluted waste stream, which is then fed to the ammoxidation reactor. Generally, the waste stream will include an organic nitrile byproduct-containing stream removed from the separation system used to recover the target cyano-containing compound. However, in some embodiments, at least a portion of the waste stream may be supplied from a different source than the separation system used to recover the target cyano-containing compound.

[0031] The organic compound supplied to the ammoxidation reactor will depend on the target cyano-containing compound to be produced. For example, if the target compound is HCN, the organic compound supplied to the ammoxidation reactor may be methane; on the other hand, if the target compound is acrylonitrile of acetonitrile, the organic compound may be propylene and / or propane. Other suitable organic compounds are well known to those skilled in the art. However, in conventional nitrile production processes, it is often important that the organic feed compound is of high purity, for example, at least chemical-grade propylene (92-95% purity) compared to rectification-grade propylene (65-75% purity) in the production of acrylonitrile. This is necessary because high levels of impurities in the organic feed interfere with the acrylonitrile product separation operation, degrade product quality, and increase the generation of undesirable organic nitrile by-products that generate high NOx levels. In contrast, by recirculating the organic nitrile by-products to the ammoxidation reactor, the disclosed process can accept lower purity organic feed or blends of different grades [if available] while achieving the environmental benefits derived from NOx reduction. As a result, it may not be necessary to use expensive and cumbersome feed purification methods to reduce the level of impurities in the organic feed. Similarly, lower purity oxygen and ammonia feeds may also be acceptable.

[0032] Some non-limiting examples of suitable diluents for use in this process include C1-C4 alcohols (methanol, ethanol, propanol, butanol); C1-C4 carboxylic acids (formic acid, acetic acid, propionic acid) and their salts (ammonium, amines); C2-C4 ketones (acetone, methyl isobutyl ketone); low molecular weight polyols (glycerol); certain cyclic ethers (tetrahydrofuran) and mixtures thereof. It is desirable to use diluents that are chemically compatible with the nitrile purge fluid components, have good solubility for these purge fluid components, and are acceptable in ammoxidation reaction chemistry.

[0033] For dilution, pure alcohol, crude alcohol, or a mixture of alcohols can be used. Bio-alcohols such as biomethanol, bioethanol, biopropanol, and biobutanol, as well as alcohols and glycerols from renewable feedstocks and sustainable processes, are suitable feedstocks for diluting nitrile waste flow. Suitable renewable feedstocks for biochemical production include biomass, lignocellulosic materials, corn, sugarcane, and organic municipal waste flow. Sustainable production processes may include aerobic / anaerobic digestion, fermentation, and enzymatic conversion.

[0034] The ratio of diluent to waste flow is not critical, but typically, all on a mass basis, it can be 0.01:1.0 to ≤80:1.0, e.g., 0.05:1.0 to 70:1.0, e.g., 0.1:1.0 to 50:1.0. In one embodiment, the diluent is alcohol, and the alcohol flow is 1 kg / hour per unit kg / hour of waste flow, or 5 kg / hour per unit kg / hour of waste flow, or 10 kg / hour per unit kg / hour of waste flow, or 20 kg / hour per unit kg / hour of waste flow.

[0035] Typically, the amount of waste stream recycled back to the ammoxidation reactor is 10% by weight or less, e.g., 5% by weight or less, e.g., 2% by weight or less, of the total fresh feed to the nitrile synthesis reaction zone.

[0036] In general, some purging of by-products of the ammoxidation process can be beneficial in avoiding the excessive accumulation of non-reactive species, potentially containing nitrogen-containing species. However, by diluting and recirculating some of the organic nitrile by-products, NO can be removed from the purging process. x The production can be reduced by at least 50%, and for example, at least 75%, compared to an equivalent ammoxidation process that produces the same target compound but without dilution and recycling.

[0037] Referring to the drawings, Figure 1 is a schematic diagram of a conventional co-production facility 100 for producing acrylonitrile [ACRN] and HCN. Further details of such a facility can be found in U.S. Patent No. 10,647,663, the full contents of which are incorporated herein by reference. In facility 100, an ammoxidation reactor system 101 catalytically converts a C3 hydrocarbon such as propylene or propane (flow 1) to ACRN in the presence of ammonia (flow 2) and an oxygen-containing feed source (flow 3). The ammoxidation reactor system 101 may include feed delivery / premixing / preheating / distribution, catalytic reaction zones, cyclone separators, and other auxiliary subsystems that are well described in the available ammoxidation literature.

[0038] The catalytic reaction zone within the ammoxidation system 101 generates a high-temperature gaseous effluent (flow 4) rich in ACRN, containing by-products such as acetonitrile, HCN, and propionitrile. Alongside the ammoxidation reactor system 101, a separate HCN synthesis reactor system 201 can generate crude HCN product flow 8 from a catalytic reaction between methane (flow 5), ammonia (flow 6), and an oxygen-containing feedstock (flow 7). Other examples of HCN synthesis include methanol ammoxidation and acetonitrile conversion to HCN (not shown in Figure 1). Such HCN synthesis can be carried out continuously or intermittently, depending on the demand for HCN products.

[0039] The ammonia feed (flow 2) to the ammonia oxidation reactor system 101 and the ammonia feed (flow 6) to the HCN synthesis reactor system 201 may be supplied from the same ammonia source, or each may have its own dedicated feed source and impurity control device. Similarly, the oxygen-containing feed (flow 3) to the ammonia oxidation reactor system 101 and the oxygen-containing feed (flow 7) to the HCN synthesis reactor system 201 may be supplied from the same oxygen source, or each may have its own dedicated feed source. For example, the oxygen-containing feed source may differ in the case of air, enriched air, or a 100% oxygen process used in the HCN synthesis reactor system 201.

[0040] The crude HCN product stream 8 is sent to the quenching tower 301 via stream 10 together with the ammoxidation reactor gas stream 4. The two streams 4 and 10 may be combined or supplied separately to the quenching tower 301. As shown in Figure 1, the crude HCN product stream 8 may be partially sent to the ammoxidation reactor system 101 as stream 11 by adjusting the flow control valve device 501. The use of the supplied stream 11, which has components specific to the ACRN production process, captures and conserves the inert gas required for catalyst fluidization in 101. Depending on the degree of fluidization versus the processing load in 101, the flow control valve device 501 can be adjusted to split the crude HCN product stream 8 into its partial stream 11 sent to system 101, while returning the remaining partial stream 10 to the quenching system 301.

[0041] Both the ammoxidation reactor effluent (flow 4) and the crude HCN product (flow 10) contain unconverted excess ammonia that is removed before the product is recovered and purified. The ammoxidation reactor effluent (flow 4), along with the crude HCN product (flow 10), is treated in the counterflow quenching column system 301 using a quenching liquid (flow 12) to remove excess ammonia. Since the quenching liquid is acidic (low pH), excess ammonia is efficiently washed away from the reactor effluent. Organic or inorganic acids (e.g., sulfuric acid or phosphoric acid) are used to remove ammonia as soluble ammonium salts at the bottom of the quenching column (flow 15). The flow rate and acidity of the quenching liquid (flow 12) are adjusted relative to the combined ammonia entering the quenching column via flows 4 and 10. Excess ammonia is removed from column 301 as ammonium salts via flow 15.

[0042] The quenched product gas (flow 14), from which ammonia has been removed, is then passed through a countercurrent absorption tower system 401, where an absorbent liquid (flow 16) extracts the reactor products at the bottom (flow 17), while any non-condensable and non-absorbable components are discharged as off-gas (flow 18). No ammonium salt formation is observed, and therefore there is no solid blockage at the bottom of the absorption tower system 401.

[0043] The crude product stream (17) is further processed in the downstream nitrile recovery and purification section 701 to produce high-purity ACRN along with the by-products acetonitrile and HCN. The nitrile recovery and purification section 701 includes continuous distillation and phase separation unit operations with all necessary auxiliary condensers, reboilers, recirculation, pump-around, flow lines, etc. The nitrile recovery and purification section 701 is well described in the available literature on acrylonitrile, acetonitrile and HCN and is therefore not described in detail herein. The stream 51, which is the output from section 701, is shown collectively to represent the individual product streams for purified HCN, acetonitrile and acrylonitrile. It should be understood that the products HCN, acetonitrile and acrylonitrile are separated in different subsections (not shown) of the nitrile recovery and purification system 701 and purified to the desired purity. For example, dried pure HCN (suppressed) is recovered from the HCN head / drying subsection, the acetonitrile product is recovered from the acetonitrile rectification subsection, and so on.

[0044] During the operation of the nitrile recovery and purification section 701 in this example, a substantially undesirable organic nitrile (ON) impurity stream is generated. These medium- and intermediate-boiling point organic nitrile impurities must be purged from the process, otherwise they may accumulate in the final product. The impurity purge stream, or a collection of such streams (represented by stream 21), is continuously or intermittently removed from several locations within system 701 where they are most concentrated. The removal of this purge stream 21 is necessary to maintain a stable ON impurity balance and prevent such undesirable impurities from accumulating during the process and ultimately in the final product.

[0045] The undesirable organic nitrile impurity purge stream 21 collected in the process described above is removed via an off-gas and / or liquid concentration stream. The nitrile purge stream 21 is fed to the recovery / disposal section 801, where any recoverable products of interest are stripped and returned to the process as stream 43. The residual stream 53 from section 801 is then subjected to thermal decomposition in the thermal oxidizer [TO] of section 901. The thermal decomposition of these highly concentrated nitrogen-containing impurity purge streams results in increased nitrogen oxide [NOx] emissions into the environment, represented by the off-gas stream 57 in Figure 1.

[0046] Figure 2 is a schematic diagram of a co-production facility 200 for producing acrylonitrile [ACRN] and HCN according to a first embodiment of the present disclosure. The HCN-ACRN co-production facility 200 is constructed and operated similarly to that described in Figure 1, except that disposal sections 801 and 901 are omitted and a waste stream 23 containing undesirable organic nitrile impurities is removed from the nitrile recovery and purification section 701 and recycled to the ammoxidation reactor system 101 as a recirculation stream 25. A separate stream 55 containing undesirable organic nitrile species [ON] from another production facility may be introduced and combined with this recirculation. For example, an undesirable ON purge stream containing butenenitrile, linear or branched pentenenitrile, glutalonitrile, valeronitrile, succinonitrile, or other undesirable ON purge stream from an olefin hydrocyanation process for producing adiponitrile may be eligible to be combined with the recirculation returning to reactor 101.

[0047] The organic nitrile components present in stream 23, mainly trace amounts of HCN, acetonitrile, acrylonitrile, and propionitrile, are inherent to the ammoxidation process. Unexpectedly, these components are observed to undergo further chemical transformation under the ammoxidation process conditions in 101, thereby reusing nitrogen contained in stream 25. Therefore, the yield of useful products is improved by this pathway change of nitrogen-containing stream 25.

[0048] The organic nitrile waste stream 23 can be supplied continuously or stored in an intermediate holding container (not shown in Figure 2). The supply stream 25 can be mixed with an oxygenate diluent and supplied to the ammoxidation reactor system 101 (campaigned). Small portions of the stream 23, e.g., less than 5%, less than 10%, or less than 15%, can be diverted to the thermal oxidation system if necessary or desired, for example, during throughput transitions, load fluctuations, maintenance, etc., but for the majority, undesirable ON species are not supplied to the thermal oxidation system [as shown in Figure 1].

[0049] Figure 3 is a schematic diagram of a co-production facility 300 for producing acrylonitrile [ACRN] and HCN according to a second embodiment of the present disclosure. The HCN-ACRN co-production facility 300 is constructed and operated similarly to that described in Figure 2, except that an organic nitrile waste stream 23 from system 701 is partially or entirely diverted to a holding / blending system 601 as stream 27. An oxygenate diluent stream 31 containing an alcohol such as methanol, ethanol, propanol, butanol, or a mixture thereof is introduced into the holding / blending system 601 and blended and diluted with an undesirable organic nitrile purge stream 27. The resulting diluted alcohol-organic nitrile stream 29 is supplied to an ammoxidation reactor system 101 as stream 25.

[0050] A separate stream 61 containing undesirable organic nitrile species [ON] from another manufacturing facility may be introduced and combined with this recirculation. For example, an undesirable ON purge stream containing butenenitrile, linear or branched pentenenitrile, valeronitrile, glutalonitrile, succinonitrile, or other undesirable ON purge stream from an olefin hydrocyanation process for producing adiponitrile may be suitable for combination with the recirculation returning to the reactor. Similarly, a separate stream 71 containing undesirable organic nitrile species [ON] from another manufacturing facility may be introduced before dilution if it is necessary to dilute such waste stream for fluidity and ease of handling.

[0051] The addition of alcohol is beneficial in homogenizing undesirable organic nitrile purge flows and allowing free flow between equipment without clogging or blocking the lines. Alcohols also generally participate in ammoxidation chemistry; for example, methanol contributes to HCN and ethanol contributes to acetonitrile. There are no restrictions on the amount of alcohol added / diluted, but the ratio of diluted alcohol to waste flow is determined by the operating conditions of the ammoxidation reactor system 101, throughput rate, and cost considerations.

[0052] Figure 4 is a schematic diagram of a standalone manufacturing facility 400 for producing acrylonitrile [ACRN] according to a third embodiment of the present disclosure. The facility 400 is constructed and operated similarly to that described in Figure 3, except that the HCN synthesis reactor system 201 and its auxiliary equipment and process chains are omitted. Again, the nitrile waste stream 23 is returned to the ammoxidation process unit 101 either undiluted or diluted via the holding / blending system 601 with appropriate diluents. NOx emissions are significantly reduced and even eliminated due to the fact that the nitrile purge stream is not thermally destroyed. Instead, they are returned to the ammoxidation reactor 101 to increase the yield of useful products.

[0053] A separate stream 65 containing undesirable organic nitrile species [ON] from another manufacturing facility may be introduced and combined with this recirculation. For example, an undesirable ON purge stream containing butenenitrile, linear or branched pentenenitrile, valeronitrile, glutalonitrile, succinonitrile, or other undesirable ON purge stream from an olefin hydrocyanation process for producing adiponitrile may be suitable for combination with the recirculation returning to the reactor. Similarly, a separate stream 75 containing undesirable organic nitrile species [ON] from another manufacturing facility may be introduced before dilution if it is necessary to dilute such a purge stream for fluidity and ease of handling.

[0054] The process of the present invention will be described in more detail below with reference to the following non-limiting embodiments.

[0055] Comparative Example 1- The organic nitrile impurity purging subsystem is shown in Figure 1 of U.S. Patent No. 10,562,782 [hereinafter referred to as '782']. In the embodiment of '782', the nitrile purge stream labeled (8) is removed from the side stream stripper labeled (5). From the composition data of the nitrile purge stream labeled (8) in '782', it is clear that this stream is a concentrated organic nitrile impurity purging stream that is to be disposed of after being recovered as a stream labeled (6) that is recycled back into the separation container labeled (1) in '782 with useful contents.

[0056] When thermal oxidizers with a destructive efficiency of 99.999% are used to thermally decompose each 1.0 kg / hour flow of '782 (8), approximately 0.0024 g / hour of NOx is obtained in Example 1, 0.001 g / hour of NOx in Example 2, and 0.0007 g / hour of NOx in Example 3.

[0057] Therefore, a nitrile purge flow of approximately 100 kg / hour labeled (8) releases approximately 0.07–0.24 g / hour of NOx in the '782 example.

[0058] Example 1 The process of Comparative Example 1 is repeated, but part or all of the purge flow is diluted with an organic oxygenate diluent and recycled back into the ammoxidation reactor. As a result, NOx emissions into the environment are reduced to 0.0024 g / hour per 1 kg / hour of nitrile purge flow.

Claims

1. A method for producing a cyano-containing compound, (a) A step of reacting ammonia, an oxygen source and an organic compound in an ammoxidation reactor to produce a reaction product containing a target cyano-containing compound selected from hydrogen cyanide and an organic nitrile compound, (b) A step of supplying the reaction product to a separation section to recover at least a portion of the target compound, (c) A step of providing a waste stream containing at least one further organic nitrile compound different from the target compound, (d) A step of generating a diluted waste stream by combining at least a portion of the waste stream with at least one organic oxygenate diluent that is compatible with the ammoxidation reaction, (e) A method comprising the step of supplying the diluted waste stream to the ammoxidation reactor.

2. The method according to claim 1, wherein at least a portion of the waste stream is removed from a separation system used to recover the target cyano-containing compound.

3. The process further includes purging a portion of the product flow through a thermal oxidation apparatus, and removing NO from the purging process. ｘ The method according to claim 2, wherein the amount produced is at least 50% less than that of an equivalent ammoxidation method that produces the target compound but omits steps (c), (d), and (e).

4. The method according to any one of claims 1 to 3, wherein the separation section is supplied with reaction products from two or more ammoxidation reactors that produce different target cyano-containing compounds selected from hydrogen cyanide and organic nitrile compounds, respectively.

5. The method according to any one of claims 1 to 4, wherein the target cyano-containing compound is selected from hydrogen cyanide, acetonitrile, acrylonitrile, succinonitrile, linear pentenenitrile, branched pentenenitrile, and adiponitrile.

6. The method according to any one of claims 1 to 5, wherein at least a portion of the waste stream is supplied from a source different from the separation system used to recover the target cyano-containing compound.

7. where the diluent is C １ - C ４ alcohol and polyol, C １ - C ４ carboxylic acid and their salts, C ２ - C ４ ketone, C ２ - C ６ ether, and a mixture thereof, and the method according to any one of claims 1 to 6

8. The diluent is selected from the group consisting of methanol, ethanol, propanol, butanol, and mixtures thereof. １ ~C ４ The method according to any one of claims 1 to 7, comprising alcohol.

9. The diluent is selected from the group consisting of formic acid, acetic acid, propionic acid, ammonium salts, amine salts, and mixtures thereof. １ ~C ４ The method according to any one of claims 1 to 8, comprising a carboxylic acid or a salt.

10. The diluent is selected from the group consisting of acetone, methyl isobutyl ketone, and mixtures thereof. ２ ~C ４ The method according to any one of claims 1 to 9, comprising a ketone.

11. The method according to any one of claims 1 to 10, wherein the diluent comprises tetrahydrofuran.

12. The method according to any one of claims 1 to 11, wherein the diluent comprises glycerol.

13. The method according to any one of claims 1 to 12, wherein the diluent comprises a bio-based organic oxygenate obtained from a renewable supply material.

14. The method according to claim 13, wherein the diluent comprises biomethanol, bioethanol, biopropanol, biobutanol, bioglycerol, or a mixture thereof.

15. The method according to any one of claims 1 to 14, wherein the weight ratio of diluent to waste flow is 0.01:1.0 to 80:1.

0.

16. The method according to any one of claims 1 to 15, wherein the weight ratio of diluent to waste flow is 0.05:1.0 to 70:1.

0.

17. The method according to any one of claims 1 to 16, wherein the weight ratio of diluent to waste flow is 0.1:1.0 to 50:1.

0.

18. The method according to any one of claims 1 to 17, wherein the method is operated without pretreatment of the feed to reduce the level of impurities.

19. The method according to any one of claims 1 to 18, wherein the feed is selected from oxygen and ammonia.

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