Method for removing nitriles from hydrogen cyanide

Abstract

Process for making purified hydrogen cyanide. The process includes feeding a reaction product including HCN, water, and organonitriles to a separation vessel; taking a liquid slip stream of HCN, water and organonitriles from the separation vessel; and feeding the liquid slipstream into a sidestream stripper to purge nitriles from the HCN reaction product.

Claims

1. A method for making purified HCN comprising the steps of: feeding a reaction product comprising water, HCN, and organonitriles to a separation vessel; taking a liquid slipstream of the reaction product from the separation vessel and feeding the liquid slipstream into a sidestream stripper; providing sufficient heat to the sidestream stripper to effect the separation of the HCN from the organonitriles and water; purging the organonitriles from the sidestream stripper; returning the HCN to at least one of the separation vessel and purification equipment; and recovering the purified HCN.

2. The method of claim 1, wherein the sidestream stripper comprises a packed bed.

3. The method of claim 1, wherein the sidestream stripper comprises trays.

4. The method of claim 1, wherein the heat is supplied via direct injection of steam into the sidestream stripper.

5. The method of claim 1, wherein the heat is supplied via indirect heating with steam.

6. The method of claim 1, wherein the reaction product is produced by reacting methane, a source of oxygen, and ammonia.

7. The method of claim 1, wherein the reaction product is produced by reacting propylene, a source of oxygen, and ammonia.

8. The method of claim 1, wherein the reaction product is produced by reacting propane, a source of oxygen, and ammonia.

9. The method of claim 1, wherein sulfur dioxide is added to the separation vessel to minimize the formation of undesirable polymer products.

10. The method of claim 1, wherein at least one of sulfuric acid, phosphoric acid, acetic acid, and glycolic acid is added to the separation vessel to minimize the formation of undesirable polymer products.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 is a schematic diagram of the hydrogen cyanide refining process according to the invention.

(2) FIG. 2 is a graph showing the relationship between feed rate to a sidestream stripper and the nitriles concentration in the feed stream to the sidestream stripper according to Example 4.

DETAILED DESCRIPTION OF THE INVENTION

(3) The following definitions and abbreviations are to be used for the interpretation of the claims and the specification.

(4) As used herein, the terms comprises, comprising, includes, including, has, having, contains or containing, or any other variation thereof, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. For example, a composition, a mixture, a process, a method, an article, or an apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, mixture, process, method, article, or apparatus. Further, unless expressly stated to the contrary, or refers to an inclusive or and not to an exclusive. For example, a condition A or B is satisfied by any one of the following: A is true (or present) and B is false (or not present), A is false (or not present) and B is true (or present), and both A and B are true (or present).

(5) As used herein, the term consists of, or variations such as consist of or consisting of, as used throughout the specification and claims, indicate the inclusion of any recited integer or group of integers, but that no additional integer or group of integers may be added to the specified method, structure, or composition.

(6) As used herein, the term consists essentially of, or variations such as consist essentially of or consisting essentially of, as used throughout the specification and claims, indicate the inclusion of any recited integer or group of integers, and the optional inclusion of any recited integer or group of integers that do not materially change the basic or novel properties of the specified method, structure or composition.

(7) Also, the indefinite articles a and an preceding an element or component of the invention are intended to be nonrestrictive regarding the number of instances, i.e., occurrences of the element or component. Therefore a or an should be read to include one or at least one, and the singular word form of the element or component also includes the plural unless the number is obviously meant to be singular.

(8) The term invention or present invention as used herein is a non-limiting term and is not intended to refer to any single embodiment of the particular invention but encompasses all possible embodiments as described in the application.

(9) As used herein, the term about modifying the quantity of an ingredient or reactant of the invention employed refers to variation in the numerical quantity that can occur, for example, through typical measuring and liquid handling procedures used for making concentrates or solutions in the real world; through inadvertent error in these procedures; through differences in the manufacture, source, or purity of the ingredients employed to make the compositions or to carry out the methods; and the like. The term about also encompasses amounts that differ due to different equilibrium conditions for a composition resulting from a particular initial mixture. Whether or not modified by the term about, the claims include equivalents to the quantities. In one embodiment, the term about means within 10% of the reported numerical value, preferably within 5% of the reported numerical value.

(10) The invention comprises a method for making purified HCN comprising the steps of: feeding a reaction product comprising water, HCN, and organonitriles to a separation vessel; taking a liquid slipstream of the reaction product from the separation vessel and feeding the liquid slipstream into a sidestream stripper; providing sufficient heat to the sidestream stripper to effect the separation of the HCN from the organonitriles and water; purging the organonitriles from the sidestream stripper; returning the HCN to at least one of the separation vessel and purification equipment; and recovering the purified HCN.

(11) An aspect of the invention comprises the steps of reacting methane, a source of oxygen, ammonia, and a catalyst in a reactor under conditions to produce a reaction product comprising HCN, water and organonitriles; feeding the reaction product into a separation vessel; taking a liquid slip stream comprising HCN, water and organonitriles from the separation vessel; feeding the liquid slip stream into a sidestream stripper; providing heat to the sidestream stripper; purging the organonitriles from the sidestream stripper; returning the HCN to the separation vessel or purification equipment; and recovering the HCN.

(12) An aspect of the invention comprises the steps of reacting propylene, a source of oxygen, ammonia, and a catalyst in a reactor under conditions to produce a reaction product comprising HCN, water and organonitriles; feeding the reaction product into a separation vessel; taking a liquid slip stream comprising HCN, water and organonitriles from the separation vessel; feeding the liquid slip stream into a sidestream stripper; providing heat to the sidestream stripper; purging the organonitriles from the sidestream stripper; returning the HCN to the separation vessel or purification equipment; and recovering the HCN.

(13) An aspect of the invention comprises the steps of reacting propane, a source of oxygen, ammonia, and a catalyst in a reactor under conditions to produce a reaction product comprising HCN, water and organonitriles; feeding the reaction product into a separation vessel; taking a liquid slip stream comprising HCN, water and organonitriles from the separation vessel; feeding the liquid slip stream into a sidestream stripper; providing heat to the sidestream stripper; purging the organonitriles from the sidestream stripper; returning the HCN to the separation vessel or purification equipment; and recovering the HCN.

(14) In an aspect of the invention sulfur dioxide can be added to the separation vessel or any associated streams to minimize the formation of undesirable polymer products.

(15) In an aspect of the invention at least one of sulfuric acid, phosphoric acid, acetic acid, and glycolic acid can be added to the separation vessel or any associated streams to minimize the formation of undesirable polymer products.

(16) In an aspect of the invention practicing the method of the present invention can increase production of HCN by 2%.

(17) With reference to FIG. 1 a specific, exemplary embodiment of the invention will be described. In FIG. 1, a reaction product 2 comprising HCN, water, and organonitriles is fed into separation vessel 1. A liquid slip stream 3 is taken from the separation vessel 1 and fed 4 into sidestream stripper 5, which can comprise a packed bed or trayed column (not shown), with steam 7 introduced at the bottom of sidestream stripper 5 to heat the sidestream stripper 5. Upon heating the sidestream stripper 5, organonitriles are purged 8 from the sidestream stripper 5, while HCN is returned 6 to the separation vessel 1. Substantially pure HCN is produced 10. Water 9 can either be recycled or disposed.

(18) Although the invention has been described with specific reference to HCN produced by the Andrussow process, the invention can also be used in the acrylonitrile process or any process where it is desired to remove contaminants such as organonitriles from reaction products.

EXAMPLES

(19) The present invention is further defined in the following Examples. It should be understood that these Examples, while indicating preferred embodiments of the invention, are given by way of illustration only. From the above discussion and these Examples, one skilled in the art can ascertain the essential characteristics of this invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various uses and conditions.

ASPEN Model: Flowsheet

(20) Processes described herein were demonstrated using a computational model of a process based on the diagram of FIG. 1. Process modeling is an established methodology used by engineers to simulate complex chemical processes. The commercial modeling software Aspen Plus (Aspen Technology, Inc., Burlington, Mass.) was used in conjunction with physical property databases, such as DIPPR, available from the American Institute of Chemical Engineers, Inc. (New York, N.Y.) and OLI to develop an ASPEN model of the above described process.

Example 1Sidestream Stripper Feed Rate=500 Pounds Per Hour

(21) With a feed rate of 500 pounds per hour, the composition of the feed stream (3) to the Sidestream Stripper Column would have the following concentrations on a mass % basis:

(22) TABLE-US-00001 Component Mass % HCN 51.792% Acrylonitrile 1.156% Acetonitrile 9.826% Propionitrile 0.269% H.sub.2O 36.957%

(23) The total nitriles in the side stream purge would be 11.25%.

(24) The composition of the HCN stream (6) that leaves the Sidestream Stripper and is returned to the HCN purification equipment would be:

(25) TABLE-US-00002 Component Mass % HCN 91.081% ACRN 0.831% ACEN 2.610% PROPN 0.071% H2O 5.406%

(26) The composition of the Nitriles Purge stream (8) would be:

(27) TABLE-US-00003 Component Mass % HCN 0.001% ACRN 1.584% ACEN 19.338% PROPN 0.531% H2O 78.546%

Example 2Aspen ModelSidestream Stripper Feed Rate=1,000 Pounds Per Hour

(28) With a feed rate of 1,000 pounds per hour, the composition of the feed stream (3) to the Sidestream Stripper Column would have the following concentrations on a mass % basis:

(29) TABLE-US-00004 Component Mass % HCN 46.340% Acrylonitrile 0.997% Acetonitrile 5.032% Propionitrile 0.140% H.sub.2O 47.490%

(30) The total nitriles in the side stream purge would be 6.17%.

(31) The composition of the HCN stream (6) that leaves the Sidestream Stripper and is returned to the HCN purification equipment would be:

(32) TABLE-US-00005 Component Mass % HCN 91.361% ACRN 1.293% ACEN 1.662% PROPN 0.049% H2O 5.635%

(33) The composition of the Nitriles Purge stream (8) is:

(34) TABLE-US-00006 Component Mass % HCN 0.001% ACRN 0.693% ACEN 8.501% PROPN 0.233% H2O 90.571%

Example 3Aspen ModelSidestream Stripper Feed Rate=1,500 Pounds Per Hour

(35) With a feed rate of 1,500 pounds per hour, the composition of the feed stream (3) to the Sidestream Stripper Column would have the following concentrations on a mass % basis:

(36) TABLE-US-00007 Component Mass % HCN 44.071% Acrylonitrile 1.042% Acetonitrile 3.401% Propionitrile 0.095% H.sub.2O 51.391%

(37) The total nitriles in the side stream purge would be 4.54%.

(38) The composition of the HCN stream (6) that leaves the Sidestream Stripper and is returned to the HCN purification equipment would be:

(39) TABLE-US-00008 Component Mass % HCN 91.327% ACRN 1.687% ACEN 1.237% PROPN 0.038% H2O 5.712%

(40) The composition of the Nitriles Purge stream (8) would be:

(41) TABLE-US-00009 Component Mass % HCN 0.001% ACRN 0.440% ACEN 5.420% PROPN 0.149% H2O 93.991%

Example 4Aspen Model Summary

(42) FIG. 2 shows the relationship between feed rate to Sidestream Stripper and the nitriles concentration in the Feed stream to the Sidestream Stripper. This shows that higher feed rates lead to lower nitriles in the processwhich leads to a higher quality HCN product.