CN113603115A

CN113603115A - Process for producing hydrogen cyanide using catalyst bed

Info

Publication number: CN113603115A
Application number: CN202110888751.1A
Authority: CN
Inventors: 约翰·C·卡顿; 布兰特·J·斯塔尔曼
Original assignee: Invista North America LLC
Current assignee: Invista North America LLC
Priority date: 2012-12-18
Filing date: 2013-12-12
Publication date: 2021-11-05
Also published as: WO2014099592A1; TWI519470B; CN103864114A; TW201431780A; HK1205996A1

Abstract

The invention relates to a method for producing hydrogen cyanide by using a catalyst bed. The method comprises (a) contacting a three-way gas mixture with a catalyst bed comprising a braided catalyst material and a catalyst support to produce a hydrogen cyanide crude product; and (b) recovering hydrogen cyanide; wherein the catalyst support has a corrugated surface abutting the braided catalyst material, the corrugated surface having an undulating shape including one or more rounded valleys to conform the shape of the braided catalyst to the corrugated surface.

Description

Process for producing hydrogen cyanide using catalyst bed

The application is a divisional application of an application with the application date of 2013, 12 months and 12 days, the application number of 201310683502.4 and the name of 'a method for producing hydrogen cyanide by using a catalyst bed'.

Cross Reference to Related Applications

This application claims priority to U.S. application 61/738,691 filed on 12/18/2012, the entire contents and disclosure of which are incorporated herein.

Technical Field

The present invention relates to a process for producing hydrogen cyanide and to a reactor containing a catalyst bed with a knitted catalyst material and a catalyst support having a corrugated surface to reduce cracking and deformation of the knitted catalyst material.

Background

Traditionally, Hydrogen Cyanide (HCN) is produced on an industrial scale by the Andrussow process or the BMA process (see, for example, Ullman's Encyclopedia of Industrial Chemistry, Volume A8, Weinheim 1987, P.161-163). For example, in the Andrussow process, HCN can be commercially produced by reacting ammonia with a methane-containing gas and an oxygen-containing gas at elevated temperatures in a reactor in the presence of a suitable catalyst (U.S. Pat. nos. 1,934,838 and 6,596,251). Sulfur compounds and higher homologues of methane may affect the parameters of oxidative ammonolysis of methane. See, for example, Trosov, Effect of Sulfur Compounds and high Hologrouges of Methane on friend cyanamide Production by the Andrussow Method, Russian J. applied Chemistry, 74: 10(2001), pp.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, Version 3), 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, Weinheim 1987, 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, JHazMat 142 (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, Economic Impact Analysis For The deployed Cyanide Manufacturing NESHAP, EPA, May 2000).

US patent US 3,033,658 describes a catalyst disposed within a reaction chamber which is supported and disposed on a non-metallic, substantially thermally non-conductive but thermally resistant support and/or is bounded or bounded by such non-metallic material. The catalyst may be provided in the form of a gauze or mesh structure.

Us patent 3,423,185 describes a grid for supporting a wire mesh catalyst in a reactor in which ammonia and methane are reacted to produce HCN, the grid comprising a plurality of horizontally disposed ceramic blocks having holes for passage of reaction gases, the upper portion of the grid containing catalyst contacting members for supporting the wire mesh catalyst and the lower portion of the grid containing gas distribution means for distributing the reaction gases evenly throughout the cross-section of the reactor.

U.S. Pat. No. 5,356,603 describes a process for the production of hydrogen cyanide by using an element comprising a porous structure made of a material mainly containing a metal selected from platinum, rhodium, palladium and alloys or mixtures thereof, this element being characterized by (a) a novel configuration and thus obtaining a primary product having the formula: the rate of kogation (C/F) multiplied by the mesh and filament diameters is at least about greater than 0.08 for the element, and (b) the conversion is a function of the combination of the rate of kogation, mesh diameter, and filament diameter for a given methane and ammonia production, and the conversion can be increased by increasing the mesh diameter for a given filament diameter, increasing the filament diameter for a given mesh diameter, and increasing the rate of kogation (C/F) to a ratio greater than 1.0. The elements are woven webs, knits, fibers and combinations thereof. The element may be a series of elements that act as a multiple rectification network.

Us patent 5,527,756 describes a catalyst assembly comprising a plurality of layers of expanded metal wires disposed in closely nested relation to one another along the broad surfaces thereof, the wire layers defining a non-planar cross-section comprised of a plurality of undulating grooves. The edges of the catalyst assembly are flattened so that it can be securely installed in the ammonia synthesis column. The invention comprises single layers stacked adjacent to each other and a plurality of layers of padding material joined at their edges to form a united part. The catalyst assembly provides a unique composition of increased surface area and reduced pressure drop that contributes to increased service life with corresponding reduction in cost and down time. The catalyst assembly is easy to manufacture and install and can be made in a variety of sizes and shapes to suit the specifications and requirements of different reactors.

Us patent 7,101,525 describes a catalytic reaction unit for reactions carried out in gaseous media at elevated temperature conditions, such as HCN synthesis or ammonia oxidation, comprising at least one woven material effective as a catalyst for the above reactions, a support comprising at least one ceramic member having a structure allowing the passage of gases, said member of the support having a corrugated surface such that the increase in surface area produced by the curved surface relative to a flat surface is at least equal to the value calculated as a saw-tooth corrugation, which is between about 1.1 and about 3. The woven material is mounted against the corrugated surface of the component of the support and maintains the same shape. "woven material" is any assembly of strips or filaments in the form of linear and/or helical members through which gas can pass. Components of such a screen may include wovens, knits or felts, which may be obtained by various techniques, such as weaving, knitting, sewing, embroidery, and the like.

U.S. patent publication 2002/0127932 discusses three-dimensional catalyst gauzes for gas reactions that are woven from precious metal wires in two or more layers with weft threads interposed between layers of the mesh material. These layers of mesh material are preferably joined by pile filaments. The weft threads are made from the same type of wire as the mesh material and pile threads, i.e., preferably a platinum-rhodium alloy made from about 4 to about 12 wt.% rhodium, and a platinum-palladium-rhodium alloy made from about 4 to about 12 wt.% palladium and rhodium. The alloys commonly used are platinum rhodium 5, platinum rhodium 8 and platinum rhodium 10.

However, existing reactor configurations for producing HCN using such configurations suffer from a number of deficiencies, including catalyst cracking and distortion. Thus, there is a need for improved HCN reactor configurations and HCN production processes.

Disclosure of Invention

In a first embodiment, the present invention relates to a catalyst bed for the production of hydrogen cyanide comprising: knitting a catalyst material; and a catalyst support having a corrugated surface adjacent to the braided catalyst material, wherein the corrugated surface has a wavy shape including one or more rounded valleys to conform the shape of the braided catalyst to the corrugated surface. The catalyst support has a substantially uniform thickness. The catalyst bed may further comprise one or more peaks corresponding to one or more rounded troughs. Each of the one or more rounded wave troughs is substantially parallel to an adjacent wave trough. The corrugated surface may also have one or more openings. The one or more openings may be located at an inclined portion of the corrugated surface. The one or more openings may have a diameter of 0.01-3 centimeters. The corrugated surface may be free of sharp edges. The catalyst support may comprise at least 90 wt.% alumina. The corrugated surface has a surface area equivalent to 1.1 to 3 times the surface area of the planar cross section of the reaction vessel in which the catalyst bed is installed. The distance between adjacent valleys on the corrugated surface may be 2-15 cm. The braided catalyst material may include a platinum catalyst having a platinum content of at least 85 wt.%. The braided catalyst material may be flexible. The catalyst bed may further comprise an upper catalyst support having a corresponding corrugated shape conforming to the shape of the catalyst support.

In a second embodiment, the present invention is directed to a reactor for the production of hydrogen cyanide comprising: a flame arrestor; a catalyst bed comprising a knitted catalyst material; and a catalyst support having a corrugated surface adjacent to the braided catalyst material, wherein the corrugated surface has a wavy shape including one or more rounded valleys to conform the shape of the braided catalyst to the corrugated surface.

In a third embodiment, the present invention relates to a process for producing hydrogen cyanide comprising: (a) contacting the three-way gas mixture with a catalyst bed comprising a knitted catalyst material and a catalyst support to produce a crude hydrogen cyanide product; and (b) recovering the hydrogen cyanide. The catalyst support has a corrugated surface adjacent to the braided catalyst material, the corrugated surface having a corrugated shape including one or more rounded valleys to conform the shape of the braided catalyst to the corrugated surface. The catalyst support may have a substantially uniform thickness. The catalyst support may contain at least 90 wt.% alumina and 10% or less silica, preferably at least 94 wt.% alumina and 6% or less silica. The ternary gas mixture may comprise an oxygen-containing gas, a methane-containing gas and an ammonia-containing gas. The oxygen-containing gas may be pure oxygen. The ternary gas mixture may comprise at least 25 vol.% oxygen, preferably 25-32 vol.% oxygen. The braided catalyst material may comprise at least 85 wt.% platinum, preferably at least 90 wt.% platinum. The corrugated surface has a surface area equivalent to 1.1 to 3 times the surface area of the planar cross section of the reaction vessel in which the catalyst bed is installed. The corrugated surface may contain one or more radiused peaks that coincide with one or more radiused valleys to conform the shape of the braided catalyst to the corrugated surface. The corrugated surface may be free of sharp edges. The velocity through the catalyst bed may be greater than 2m/s, preferably greater than 5m/s, more preferably greater than 7 m/s. The pressure drop across the catalyst bed is in the range of 120kPa to 145 kPa. The corrugated surface may have one or more openings. The one or more openings may be located at an inclined portion of the corrugated surface. The method may further include an upper catalyst support adjacent to the upper surface of the braided catalyst material, wherein the upper catalyst support has a shape conforming to the catalyst support.

In a fourth embodiment, the present invention is directed to a catalyst bed for the production of hydrogen cyanide comprising: knitting a catalyst material; and a catalyst support having a corrugated surface adjacent to the braided catalyst material, wherein the corrugated surface has a wavy shape including one or more rounded peaks to conform the shape of the braided catalyst to the corrugated surface.

In a fifth embodiment, the present invention is directed to a catalyst bed for the production of hydrogen cyanide comprising: knitting a catalyst material; and a catalyst support having a corrugated surface proximate to the braided catalyst material, wherein the corrugated surface has a wave shape comprising one or more rounded valleys and corresponding peaks to conform the shape of the braided catalyst to the corrugated surface.

In a sixth embodiment, the present invention is directed to a catalyst bed for the production of hydrogen cyanide comprising: knitting a catalyst material; and a catalyst support having a corrugated surface adjacent to the braided catalyst material, wherein the catalyst support has a substantially uniform thickness and the corrugated surface is free of sharp edges.

In a seventh embodiment, the present invention is directed to a catalyst bed for the production of hydrogen cyanide comprising: knitting a catalyst material; and a catalyst support comprising ceramic foam, wherein the catalyst support has an upper portion and a lower portion, and the braided catalyst material is disposed between the upper portion and the lower portion and in contact with a non-planar surface of the upper portion and a non-planar surface of the lower portion.

Drawings

Fig. 1 is a simplified schematic flow diagram of an HCN synthesis system according to one embodiment of the present invention.

FIG. 2A is a cross-sectional view of a catalyst bed having a corrugated support according to the present invention.

FIG. 2B is a perspective view of the catalyst bed of FIG. 2A.

FIG. 3 is a cross-sectional view of a catalyst bed having a corrugated upper support member according to the present invention.

FIG. 4 is a cross-sectional view of a catalyst bed with a ceramic foam catalyst support according to the present invention.

Detailed Description

The terminology used herein 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, a group of components, a process or method step, or any other expression is introduced by the transitional phrase "comprising," "including," or "containing," it is understood that the same component, group of components, process or method step, 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 that component, group of components, process or method step, 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.

Hydrogen Cyanide (HCN) can be produced on an industrial scale according to the Andrussow process or according to the BMA process. In the Andrussow process, methane, ammonia and an oxygen-containing starting material (also referred to herein as "reactant") are reacted at a temperature in excess of 10000 ℃ in the presence of a catalyst to produce a crude hydrogen cyanide product containing HCN, hydrogen, carbon monoxide, carbon dioxide, nitrogen, residual aqueous ammonia, residual methane and water. Natural gas is typically used as the source of methane, while air, oxygen-enriched air, pure oxygen may be used as the source of oxygen. The catalyst is typically a mesh platinum/rhodium alloy or a mesh platinum/iridium alloy. Other catalyst components may also be used, including but not limited to platinum group metals, platinum group metal alloys, supported platinum group metals, or alloys of supported platinum group metals. Other catalyst configurations may also be used, including but not limited to porous structures, screens, sheets, spheres, monoliths, foams, dip coatings, and wash coatings. However, the catalyst is cracked or deformed both at the beginning and at the end of the reaction, and during the reaction. Catalyst breakage can bypass the reactants, reducing reactant to HCN conversion, reducing HCN yield, and allowing downstream detrimental reactions to occur. Catalyst deformation may require a reduction in the flow of reactants, thereby reducing HCN yield. These difficulties can be partially alleviated by using a catalyst bed comprising a catalyst on a support. However, the catalyst may still crack and deform. In addition, depending on the support used, a reduced reactant flow may be required over the catalyst bed.

Surprisingly and unexpectedly, catalyst cracking and distortion is reduced and/or eliminated by using a braided platinum catalyst loaded on a corrugated support. The braided platinum catalyst may contain greater than 85 wt.% platinum, for example 90 wt.% platinum. The catalyst was loaded in the reactor in the range of 0.7-1.4(g catalyst)/(kg feed gas/hr). The knitted catalyst may further comprise one or more metals selected from the group consisting of nickel, cobalt, palladium, rhodium, ruthenium, iridium, gold, silver and copper. In some embodiments, the braided catalyst contains 90 wt.% platinum and 10 wt.% rhodium (90/10). When loaded on a planar catalyst support, a braided catalyst containing 90 wt.% platinum and 10 wt.% rhodium may not be able to withstand high productivity and may deform, crack and/or shrink. Thus, a flat support may require 85/15 of a platinum/rhodium catalyst to have sufficient strength to withstand higher production rates. The higher productivity may be due to operation with oxygen-enriched air or pure oxygen, and from operation at high rates through the catalyst bed. This speed is sufficient to overcome the tempering speed. In one aspect, the velocity through the catalyst bed is at least 2m/s, for example at least 5m/s or at least 7 m/s. As the velocity increases, there can be a large pressure differential across the catalyst bed, which can cause the bed to pack. The pressure differential across the catalyst bed may be 120-145kPa, for example 125-140 kPa. If the catalyst bed does not have sufficient strength, the catalyst bed will crack at higher rates. In order to increase the strength of a braided catalyst containing 90 wt.% platinum and 10 wt.% rhodium, it is advantageous to use a catalyst bed containing a corrugated support. This allows higher productivity without damage to the braided catalyst. Typically, a catalyst containing 90 wt.% platinum has a shorter life than a catalyst containing 85 wt.% platinum. Advantageously, using the corrugated support of the present invention, the catalyst life of a catalyst containing 90 wt.% platinum can be extended to 2 times, more preferably 3 times, the catalyst life of a catalyst containing 85 wt.% platinum. In addition, the life of the catalyst containing 85 wt.% platinum is also extended using the corrugated support of the present invention.

Reactant gases for the production of HCN include ammonia-containing gas, methane-containing gas, and oxygen-containing gas. The reactant gases are mixed prior to entering the reactor to form a ternary gas mixture. In some embodiments, the ternary gas mixture contains at least 25 vol.% oxygen, for example 25-32 vol.% oxygen, or 26-30 vol.% oxygen. The oxygen-containing gas may be air, oxygen-enriched air or pure oxygen. The use of oxygen-enriched air or pure oxygen provides the opportunity to reduce the size and operating costs of downstream equipment that would otherwise be required to handle the large quantities of inert nitrogen present in the air. In one embodiment, the oxygen-containing gas contains greater than 21 vol.% oxygen, e.g., greater than 28 vol.% oxygen, greater than 80 vol.%, greater than 90 vol.%, greater than 95 vol.%, or greater than 99 vol.% oxygen. The ternary gas mixture comprises a molar ratio of ammonia to oxygen of from 1.2 to 1.6, for example from 1.3 to 1.5, a molar ratio of ammonia to methane of from 1 to 1.5, for example from 1.1 to 1.45, and a molar ratio of methane to oxygen of from 1 to 1.25, for example from 1.05 to 1.15. For example, the ternary gas mixture contains ammonia and oxygen in a molar ratio of 1.3 and methane and oxygen in a molar ratio of 1.2. In another exemplary embodiment, the ternary gas mixture comprises a molar ratio of ammonia to oxygen of 1.5 and a molar ratio of methane to oxygen of 1.15. The oxygen concentration in the ternary gas mixture may vary with these molar ratios.

The use of a braided platinum catalyst in combination with a corrugated support, as described herein, may reduce catalyst cracking and deformation. Catalyst cracking can bypass the reactants, e.g., the reactants pass through the catalyst bed without reacting. The oxygen, methane and ammonia content of the hydrogen cyanide crude is tightly controlled and the by-pass of the catalyst bed has an effect on each reactant. Further, because the oxygen, methane, and ammonia content is tightly controlled, the by-pass of the reactants makes it difficult to control the reactant content in the crude hydrogen cyanide product. By-product nitriles may accumulate in the HCN separation unit as methane bypasses the catalyst bed. When oxygen bypasses the catalyst bed, system upsets may occur, including possible explosive events. When ammonia bypasses the catalyst bed, the downstream ammonia recovery would have to be adjusted to handle different amounts of ammonia. Catalyst distortion may require a reduction in the flow rate of the three-way gas mixture, resulting in a corresponding reduction in HCN yield. This can exacerbate the inefficiency of production of the desired crude hydrogen cyanide product and lead to yield losses.

Figure 1 generally shows an HCN synthesis system 10. Typically, HCN is produced in reaction module 12 comprising elongated conduit 14 and reaction tank 16. In the Andrussow process, reactant gases (including an oxygen-containing gas 18, a methane-containing gas 20, and an ammonia-containing gas 22) are fed into an elongated conduit 14. It should be noted that the feed locations shown in fig. 1 are merely schematic and are not intended to show the order of feeding the reactants into the elongated conduit 14. In some embodiments, the methane-containing gas 20 and the ammonia-containing gas 22 may be combined prior to being fed into the elongated conduit 14. In one embodiment, the elongated conduit 14 may contain one or more static mixing zones having tab inserts for producing a well-mixed ternary gas 24. In one embodiment, the ternary gas mixture 24 contains at least 25 vol.% oxygen. The tertiary gas mixture 24 exits the elongated conduit 14 and contacts the catalyst contained in the reaction vessel 16 to produce a crude hydrogen cyanide product 26 containing HCN. The catalyst may be loaded into a catalyst bed 100 having a corrugated catalyst support, as described below in the present disclosure.

The three-way gas mixture contacts distributor plate 28 prior to contacting catalyst bed 100, which distributor plate 28 is porous to aid in distributing the three-way gas mixture in reaction vessel 16 and to disrupt all jets. In one embodiment, the distributor plate 28 has a void area that is 50-80% of its total surface. The HCN synthesis reaction occurring in the reaction vessel is an exothermic reaction carried out at a reaction temperature range of 1000-1250 ℃ and a pressure range of 100-400 kPa. The reaction vessel 16 may further include a flame arrestor 30, a radiation shield 32 adjacent the catalyst bed 100, and a lower support 34. Igniter holes 36 may extend through the radiation shield 32 to allow the igniter to contact the upper surface of the catalyst bed 100. Other ignition techniques that do not require openings in the radiation shield 32 may also be used in embodiments of the present invention. The igniter for the catalyst bed 100 may be performed in any manner known to those skilled in the art.

The reaction vessel 16 may also include a heat exchanger 38, such as a waste heat boiler, for cooling the hydrogen cyanide crude 26. Ammonia may be recovered from the crude hydrogen cyanide product 26 in the ammonia recovery section 40 and returned via line 42. HCN may also be further purified in HCN purification section 44 to achieve the desired purity for the desired application. In some embodiments, the HCN can be high purity HCN containing less than 100mpm of water.

Fig. 2A and 2B show a catalyst bed 100 of the present invention. In the cross-sectional view of fig. 2A, the catalyst bed 100 includes a catalyst support 102 that provides strength and rigidity to hold the braided catalyst material 104 in a corrugated shape. The catalyst support 102 and the braided catalyst material 104 are permeable to allow passage of gases. The braided catalyst material 104 may contain a number of superimposed layers. The braided catalyst material 104 may have a mesh size of 15-40 openings per centimeter of length, with a wire diameter of about 0.076-0.228 millimeters. To practice the present invention, woven materials cannot be used for the catalyst bed 100.

The catalyst support 102 has a corrugated surface 106, i.e., a wave, adjacent the upper portion of which the braided catalyst material 104 abuts. As shown, the corrugated surface 106 is adjacent to the lower surface of the braided catalyst 104. The catalyst support 102 may maintain a uniform flow over the corrugated surface 106. In one embodiment, the braided catalyst material 104 is flexible and can be formed into the shape of a corrugated surface 106. In other embodiments, the catalyst material 104 may have a rigid shape that is capable of forming a wave shape corresponding to the wave shape of the corrugated surface 106. The braided catalyst material 104 preferably does not adhere or fasten to the corrugated surface 106.

The catalyst support 102 includes a plurality of peaks 108 and valleys 110. The number of peaks 108 and valleys 110 varies depending on the diameter of the reaction vessel. Preferably, the number of peaks 108 is comparable to the number of valleys 110, and may vary, for example, from 2 to 500. In one embodiment, the surface area of the corrugated surface 106 may be 1.1 to 3 times, for example, 1.1 to 1.5 times the planar cross-sectional surface area of the reaction vessel. In one embodiment, the valleys 110 are curved or rounded to eliminate all sharp edges. The corresponding peaks 108 are also curved or rounded. Without being bound by theory, the braided catalyst material 104 may be susceptible to cracking within the sharp edges formed by the sawtooth, right angle, or triangular corrugated supports. The breakage in the sharp edges can be severe, leading to increased by-pass of reactants into the crude hydrogen cyanide product. Advantageously, the rounded peaks 108 and valleys 110 may eliminate sharp edges on the corrugated surface 106. The absence of sharp edges, particularly edges having a 90 ° angle, may further reduce cracking of braided catalyst material 104 and increase the strength of braided catalyst material 104 for operation at high productivity conditions. In addition, the by-pass of reactants can be significantly reduced.

In one embodiment, the height from trough to peak is 0.05-10 cm, such as 0.1-3.5 cm. Optionally, the height of the catalyst support 102 is substantially uniform. The distance from a trough to an adjacent trough depends on the size of the corrugated surface and may be 2-15 cm, for example 4-15 cm or 4-10 cm. The distance between adjacent valleys may be equal to the distance between adjacent peaks. Each peak and valley is substantially parallel to adjacent peaks and valleys across the width of the catalyst support 102.

The corrugated surface 106 may have a number of openings 112 therein. The number of openings 112 may be 0.5-5 openings/cm²For example, the number of openings per centimeter may be 1-2². The openings 112 create holes that extend through the thickness of the catalyst support and allow gas to pass therethrough. Opening 112 may be circular, oval, square, rectangular, triangular, or other polygonal shapeThe shape of the shape. The maximum diameter of the opening may be 0.01-3 cm, for example 0.05-1.5 cm. There may also be one or more recesses (not shown) which are depressions in the corrugated surface which do not extend through the thickness. The recesses do not directly contact the knitted catalyst material 102. In one embodiment, the recesses may separate the openings 112.

The openings 112 may be disposed on the corrugated surface 106 in any manner. In one embodiment, the valley regions 116 closest to the valleys 110 may be solid and not contain any openings 112. The valley regions 116 may be subject to maximum stress at high production rates, and preventing gas from passing through the valley regions 116 may reduce the stress on the valley regions 116. Likewise, the peak region 118 closest to the peak 108 may also be solid. Thereby, there are one or more openings on the inclined portion of the corrugated surface. This may prevent gas from collecting in the valleys 110 or peaks 108 and reduce the likelihood of the knitted catalyst material 104 adjacent to the valley regions 116 or peak regions 108 from rupturing. In other embodiments, the peaks and/or valleys may contain openings 112 therein. In particular, openings may be provided in either the valley regions 116 or the peak regions 108 to allow gas to pass therethrough.

In one embodiment, the thickness of the catalyst support 102 is substantially uniform and ranges from 0.2 cm to 2 cm, such as 0.25 cm to 0.75 cm. If the catalyst support is too thin, it may lack structural integrity. Conversely, if the support is too thick, it may be susceptible to cracking due to increased pressure. The thickness of the braided catalyst material 104 may also be substantially uniform. By substantially uniform thickness is meant that the thickness does not vary by more than 5%, for example by not more than 1%. This provides a lower surface having a corrugated shape similar to the corrugated surface 106. The substantially uniform thickness provides for a uniform pressure drop across the catalyst support 102. In other catalyst supports, there may be thicker regions under the peaks which result in a tendency for gas to flow towards the thinner valley regions and increase the pressure in the valleys. The increase in pressure may cause the braided catalyst material to rupture.

The pressure drop across the catalyst bed 100 can be overcome by using a corrugated shaped catalyst support having a substantially uniform thickness. A corrugated support of substantially uniform thickness has a lower pressure drop than a support having a varying support thickness. At higher productivity conditions, such as high velocity, the pressure drop across the catalyst bed 100 is 120-145kPa, such as 125-140 kPa.

One or more ribs 120 may also be provided on the lower surface to provide support to the catalyst support 102. The ribs 120 may be evenly spaced across the width of the catalyst support 102. Further, ribs may be provided at the outer edge of the catalyst support 102. The ribs may define cavities on the lower surface. The ribs may be provided on the shelves and/or on the lower support along the edge of the inner wall of the catalyst. The catalyst support 102 may be rectangular, oval, or circular to accommodate the reaction vessel 16 in shape. In some embodiments, the catalyst support 102 may be disposed in the reaction vessel 16 in sections.

The catalyst support 102 may have an integral assembly made of a ceramic matrix composite material containing at least 90 wt.% alumina, such as at least 94 wt.% alumina. The ceramic matrix composite material can bear higher reaction operation temperature. Preferably, the ceramic matrix composite material contains a small amount of silicon, such as silicon dioxide and other silicon oxides or compounds. In one embodiment, the ceramic matrix composite may contain less than 10 wt.%, such as less than 6 wt.%, and more preferably less than lwt% silica. Other oxides, including but not limited to oxides of titanium, zirconium, cerium, yttrium, calcium, and combinations thereof, may be used in the ceramic matrix composite. Additionally, the ceramic matrix composite material may be substantially free of magnesium. In one embodiment, it is preferred that the catalyst support 102 not be ceramic foam in order to control openings and reduce stress in the valley regions.

In one embodiment, when operating with an oxygen-containing gas comprising oxygen-enriched air or a stream of pure oxygen, i.e. the ternary gas mixture contains at least 25 vol.% oxygen, additional hydrogen may be formed in the crude product. In one embodiment, the crude product may contain 20 vol.% to 50 vol.% hydrogen, for example 30 vol.% to 40 vol.% hydrogen or 34 vol.% to 36 vol.% hydrogen. Hydrogen can increase the vaporization and re-precipitation of silica that can leach from silicate-containing refractory materials in lower and higher temperature environments. Thus, if silica is present in the catalyst support, the presence of hydrogen may cause deformation or cracking of the catalyst support. In one embodiment, the ceramic matrix composite is substantially free of silicon, including oxides such as silicon dioxide and compounds thereof.

In some embodiments, in addition to the catalyst support 102, a radiation shield 130 is disposed upstream of the braided catalyst material 104 as shown in fig. 3. The catalyst upper support 120 may have a structure corresponding to the catalyst support 102, but inverted to lock the catalyst material 104 between the catalyst support 102 and the catalyst upper support 120. In addition, the radiation shield 130 may also have corresponding upper ribs 132. This can control the effect of gas expansion on the braided catalyst material 104 during the reaction. Further, the catalyst upper support may be in direct contact with one or more of the insulating and refractory layers.

In fig. 4, a catalyst bed 200 having a ceramic foam catalyst support 202 and a braided catalyst material 204 according to the present invention is provided. The ceramic foam may have a non-uniform cross-section that allows gas to pass through the pores. The ceramic foam may be made from at least 90 wt.% alumina, for example at least 94 wt.% alumina. The ceramic foam contains small amounts of silicon or oxides and compounds thereof, such as 10 wt.% or less, 6 wt.% or less, or 1 wt.% or less.

An upper portion 206 (e.g., a radiation shield) and a lower portion 208 may be provided around the braided catalyst material 204. Upper portion 206 has a non-planar surface 210 in contact with braided catalyst material 204 and an opposing planar surface 212. Lower portion 208 also has a non-planar surface 214 in contact with knitted catalyst material 204 and an opposing planar surface 216. Each non-planar surface (e.g., a corrugated surface) may be a wave-like shape having peaks and valleys. Thus, the thickness of the upper portion 206 and the lower portion 208 may vary with non-planar surfaces. In one embodiment, the peaks and valleys formed by the wave-like shape may have a uniform or irregular shape. In one embodiment, the upper portion 206 may be equidistant from the lower portion 208.

Returning to elongated conduit 14, one or more mixers (not shown) for mixing the reactant gases to form ternary gas mixture 24 may be provided. The mixer is shaped and sized to mix the reactant gases sufficiently and quickly, i.e., to form a well-mixed ternary gas mixture. The mixer may be any mixer that functions in the process of the present invention. Non-limiting examples of mixers that may be used in the practice of the present invention are binary mixers, ternary mixers, hot air mixers, static mixers, and the like. The size of the mixer can vary widely and will depend to a large extent on the processing capacity of the reaction vessel.

Well-mixed ternary gases for the practice of the present invention have a CoV across the diameter of the catalyst bed of less than 0.1, or more preferably less than 0.05, and even more preferably less than 0.01. In terms of its range, the CoV may be 0.001 to 0.1, or more preferably 0.001 to 0.05. A low CoV is beneficial to increase the productivity of the reactants converted to HCN. The well mixed ternary gas is beneficial to improving the production rate of HCN and obtaining high yield of HCN. When the CoV exceeds 0.1, the reactant gas may have a concentration outside the safe operating range of the catalyst bed. For example, when operating at higher oxygen concentrations in the tertiary gas, a larger CoV may increase oxygen, which may lead to flashback. In addition, when the CoV is larger, the catalyst bed may be exposed to more methane, which may lead to the formation of coke. Carbon deposits can reduce catalyst life and performance. Thus, a larger CoV may result in a higher feedstock requirement.

In one embodiment, the mixer may also include an optional flow stabilizer (not shown). Alternative flow stabilizers may have a configuration that homogenizes the gas flow before the gas contacts the static mixing zone. The flow stabilizer may also distribute the gas throughout the entire area of the tube and may substantially prevent the reactant gas from being transported directly along the middle of the tube. A flow stabilizer may be provided downstream of each inlet and upstream of the static mixer in use.

The flame arrestor may be spatially disposed above the catalyst bed such that a space is provided therebetween. Flame arrestors can eliminate all upstream combustion resulting from flashback in the reactor. The ceramic foam may be disposed along at least a portion of an inner wall of the housing defining the reaction chamber and the catalyst. Ceramic foams can minimize feed gas bypass caused by catalyst shrinkage when the reactor is shut down. Ceramic foam is loaded above the catalyst bed and serves to minimize the volume of the three-way gas and reduce the pressure drop. A sleeve is disposed within each outlet of the housing and provides fluid communication between the catalyst bed and the upper portion of the heat recovery boiler. The lower support having a generally honeycomb configuration may reduce the pressure drop across the lower support. The lower support may be disposed generally adjacent to a lower surface of the catalyst bed, such as a lower surface of the corrugated catalyst support.

Various control systems may be used to regulate the reactant gas flow. For example, flow meters may be used to measure the flow rate, temperature, and pressure of the reactant gas feed stream, allowing the control system to provide "real-time" feedback of the pressure and temperature compensated flow rates to the operator and/or control equipment. As will be appreciated by one of ordinary skill in the art, the aforementioned functions and/or processes may be embodied as a system, method or computer program product. For example, the functions and/or processes may be embodied in the form of 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 processes described in embodiments herein. In particular embodiments, the computer system may include one or more central processing units, computer memory (e.g., read-only memory, random access memory) and a data storage device (e.g., a hard disk drive). The computer-executable instructions may be programmed using any suitable computer programming language (e.g., C + +, JAVA, etc.). Accordingly, this aspect of the present invention may take the form of an entirely software embodiment or an embodiment combining software and hardware aspects.

From the foregoing it will be seen that this invention is one well adapted to attain all the ends and advantages mentioned as well as those inherent in the disclosure. While preferred embodiments of the invention have been described for purposes of this disclosure, it will be understood that variations which are obvious to those skilled in the art and which can be made within the spirit of the invention may be made.

The invention may be further understood with reference to the following examples.

Example 1:

the ternary gas mixture is formed by combining pure oxygen, ammonia-containing gas and methane-containing gas. The reactant gases were mixed in such a way that the molar ratio of methane to oxygen was 1.2 and the molar ratio of ammonia to oxygen was 1: 1.5 to produce a ternary gas mixture containing about 28.5 vol.% oxygen. The ternary gas mixture is fed at a relatively high rate of more than 7.3 m/s. The ternary gas mixture reacts at the temperature of 1000-1200 ℃ in the presence of a platinum/rhodium catalyst to form a hydrogen cyanide crude product. The platinum/rhodium catalyst contained 90 wt.% platinum and 10 wt.% rhodium (90/10). The platinum/rhodium catalyst was braided and supported by a corrugated support having 12 radiused troughs and crests. The corrugated support does not have sharp edges. The distance between each peak is 10-10.5 cm. The height of the corrugated supporting piece from the base to the wave crest is 5 cm, the height from the base to the wave trough is 2 cm, and the thickness is uniform. The support is ceramic and contains greater than 90 wt.% alumina and less than 10 wt.% silica. The surface area of the corrugated surface is 4 times of the surface area of the plane section of the reaction kettle. The corrugated support has about 1.7 openings/cm except that the valleys are solid²(11 openings/inch)²). The corrugated surface is adjacent to the braided catalyst and has a corrugated shape such that the braided catalyst conforms to the shape of the corrugated support. The rounded valleys and the corrugated shape of the corrugated support can minimize the deformation of the catalyst and the flow rate of the three-way gas mixture does not have to be adjusted. Further, after 150-180 days of continuous operation, no observation was made in the catalystTo rupture. The catalyst life was increased compared to the comparative example.

Example 2:

the process and apparatus were the same as in example i except that the catalyst contained 85 wt.% platinum and 15 wt.% rhodium (85/15). After 150-180 days of continuous operation, no cracking was observed in the catalyst. Although the braided catalyst was not deformed and the catalyst life was extended, the HCN yield was lower than that of example l under the same flow rate conditions as in example 1. This is due to the low loading of platinum in the braided catalyst.

Comparative example a:

the process and apparatus were the same as in example i except that the corrugated support contained 15 wt.% silica. After the reaction has started, the silica inside the corrugated support decomposes due to the increase in the hydrogen concentration in the crude hydrogen cyanide product, and the corrugated support breaks down.

Comparative example B:

the process and apparatus were the same as in example i except that the catalyst was flat and non-corrugated. With the 90/10 platinum/rhodium catalyst, the catalyst deformed very quickly after the reaction started. Further cracking was observed in the catalyst.

Comparative example C:

the 90/10 platinum/rhodium catalyst gauze was supported by a corrugated support having a saw-tooth shape with sharp edges as shown in us patent 7,101,525. Reactant gas fed at high velocity compresses the catalyst gauze, which can break at sharp edges, resulting in reduced yield. This can lead to reactor shutdown.

Comparative example D:

the method and apparatus were the same as example i except that 90/10 platinum/rhodium catalyst was woven and supported by a ceramic foam support having a similar shape to example 1. After the reaction has started, the catalyst breaks, in particular in the wave troughs. This results in an increase in reactant leakage through the catalyst bed.

Claims

1. A process for producing hydrogen cyanide comprising:

(a) contacting the three-way gas mixture with a catalyst bed comprising a braided catalyst material and a catalyst support to produce a hydrogen cyanide crude product; and

(b) recovering hydrogen cyanide;

wherein the catalyst support has a corrugated surface abutting the braided catalyst material, the corrugated surface having an undulating shape including one or more rounded valleys to conform the shape of the braided catalyst to the corrugated surface, wherein the corrugated surface further includes one or more rounded peaks corresponding to the one or more rounded valleys to conform the shape of the braided catalyst to the corrugated surface,

the catalyst support contains at least 90 wt.% alumina and 10 wt.% or less silica,

the braided catalyst material contains at least 90 wt.% platinum,

the corrugated surface is free of sharp edges,

the corrugated surface has a surface area 1.1 to 3 times as large as that of a plane cross section of a reaction vessel in which a catalyst bed is installed, and

the height from the radiused valley to the radiused peak is 0.05 to 10 centimeters and the distance from the radiused valley to an adjacent radiused valley is 2 to 15 centimeters.

2. The method of claim 1, wherein the catalyst support has a substantially uniform thickness.

3. The process of claim 1, wherein the catalyst support contains at least 94 wt.% alumina and 6 wt.% or less silica.

4. The method of claim 1, wherein the ternary gas mixture comprises an oxygen-containing gas, a methane-containing gas, and an ammonia-containing gas.

5. The method of claim 4, wherein the oxygen-containing gas is pure oxygen.

6. The method of claim 1, wherein the ternary gas mixture comprises at least 25 vol.% oxygen.

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

8. The process of claim 1, wherein the corrugated surface has a surface area of 1.1 to 1.5 times the surface area of a planar cross section of a reaction vessel in which the catalyst bed is installed.

9. The process of claim 1, wherein the flow velocity through the catalyst bed is greater than 2 m/s.

10. The process of claim 1, wherein the flow velocity through the catalyst bed is greater than 5 m/s.

11. The process of claim 1, wherein the flow velocity through the catalyst bed is greater than 7 m/s.

12. The process as claimed in claim 1, wherein the pressure drop across the catalyst bed is 120-145 kPa.

13. The method of claim 1, wherein the corrugated surface has one or more openings.

14. The method of claim 13, wherein the one or more openings are located at an inclined portion of the corrugated surface.

15. The method of claim 1, further comprising an upper catalyst support adjacent to an upper surface of the braided catalyst material, the upper catalyst support having a shape corresponding to the catalyst support.