Liquid purification or separation – Processes – Chemical treatment
Reexamination Certificate
1998-10-30
2001-05-29
Hruskoci, Peter A. (Department: 1724)
Liquid purification or separation
Processes
Chemical treatment
C210S909000, C423S376000, C558S320000, C558S324000
Reexamination Certificate
active
06238574
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is directed to a process for catalytic upgrading of the organic compounds present in the waste streams generated during the manufacture of acrylonitrile. This upgrading is carried out by catalytic oxidation or ammoxidation of the aqueous liquid waste stream containing the organic compounds.
Typical technologies for treatment and/or disposal of waste organics from the propylene ammoxidation process for manufacture of acrylonitrile include deep welling, biotreatment, and/or incineration. In addition, there are also numerous patents describing catalytic technologies for destruction of organics in waste water streams. There are many references to vapor phase processes. Non-catalytic “wet oxidation” technologies have also been reported, including U.S. Pat. No. 5,192,453 assigned to the assignee of the instant application. These methods are characterized by destruction of organics to CO
2
, water and inorganic nitrogen compounds; in these technologies no attempt is made to recover organics.
Hydrogen cyanide is currently manufactured by direct ammoxidation of methane (the Andrussow process) and as a byproduct of ammoxidation of propylene in the acrylonitrile process. Hydrogen cyanide can also be produced by oxidation or ammoxidation of acetonitrile, as described in Japanese Patent 59/227718 (CA 102: 168669y); Japanese Patent 59/203726 (CA 102: 133968t); Japanese Patent 49/33039 (CA 82: 61264d); West German Patent 1,146,861 (CA 59: 241b); Japanese Patent 54/71100 (CA 91: 177416v); Japanese Patent 54/71800 (CA 91: 142725t); H. Seeboth and R. Mitschke,
Chem. Tech
. (Leipzig), 1971, 23, 746-748; Japanese Patent 61/111913 (CA 106: 35511b); A. Ozaki, Y. Shiratsuchi, K. Mori, Kogyo Kagaku Zasshi, 1965, 68, 283-286 (CA 63: 14105e). References to HCN manufacture by cofeeding HCN with propylene in a conventional ammoxidation process include Belgian Patent 623,100 and U.S. Pat. No. 3,516,789. In U.S. Pat. No. 5,204,079 a method is described for manufacture of HCN by ammoxidation of crude acetonitrile, a co-product stream produced in the acrylonitrile manufacturing process. This crude acetonitrile stream contains some but not all of the components of acrylonitrile process waste water. In particular, crude acetonitrile as defined in the above patent does not contain the high molecular weight compounds found in relatively large amounts in acrylonitrile process waste water, and acrylonitrile and acetonitrile were not produced. HCN can also be prepared by ammoxidation or ammoniation of coal in aqueous slurry form; see G. E. Johnson, W. A. Decker, A. J. Forney, and J. H. Field, Hydrogen Cyanide from the Reaction of Coal with Ammonia, United States Department of the Interior, Bureau of Mines, Report of Investigations 6994. The composition of the organics in coal slurry is substantially different from that of the heavy organics in acrylonitrile process waste water.
While numerous methods for preparation of acetonitrile, acrylonitrile, and HCN have been reported, applicants do not know of any specific procedure for dealing with manufacture of either acrylonitrile, HCN, or acetonitrile by ammoxidation of waste water streams or mixtures of organics and water as set forth in the instant application.
Atomization of a liquid stream has been used for reducing a liquid into small droplets for ease of vaporization and reaction. An example is a fuel oil heating system. With atomization of fuel oil in a fuel oil burner, the actual combustion reaction takes place in the vapor phase at a more rapid rate than if the fuel oil were not atomized. Atomizing burners typically use a mechanical force to atomize, such as a rotary cup (Centrifugal force), auxiliary fluid (steam pressure force), and mechanical (fluid pressure). The latter two types use a nozzle design to force the fluids through small holes or slots for high velocity and turbulence which breaks the liquid into droplets. A tube carrying a high velocity gas is also well known to function as an atomizer when a liquid is injected into the flowing gas. The high velocity gas shears the liquid into droplets.
SUMMARY OF THE INVENTION
It is the primary object of the present invention to provide a process for the upgrading of acrylonitrile process waste water into useful products such as acrylonitrile, hydrogen cyanide and acetonitrile.
It is a further object of the present invention to provide a process for upgrading acrylonitrile process waste water into useful products resulting in the substantially complete conversion of any heavy organics in the waste water into harmless byproducts (e.g. CO
2
).
The advantages of the process of the present invention include the following:
1. The use of acrylonitrile process waste water as a feedstock results not only in the production of HCN but unexpectedly in the production of acrylonitrile and acetonitrile as well, with the concomitant conversion of the organics present in the starting waste water and, in particular, the essentially complete conversion of the heavy organics.
2. When the process of this invention is carried out, as expected, as part of an acrylonitrile production process, the product mixture can be readily combined with propylene ammoxidation reactor effluent for recovery and purification of the products, saving substantially on manufacturing costs.
3. When the process of this invention is carried out in conjunction with an ammonia reduction process as described in U.S. Pat. No. 5,288,473, assigned to the assignee of the present application, the waste water is particularly suited to the catalytic reaction converting the organics to HCN, acetonitrile, and acrylonitrile, especially as a vapor-phase catalytic process.
4. It is well known that acrylonitrile process waste water can polymerize to a coke-like solid substance when heated above its boiling point. It has been unexpectedly found that this material can be fed in the vapor phase to a fluid bed catalytic reactor, in a particularly preferred mode of the invention, without polymerization or carbonization of the feed lines or vaporizer. This is accomplished with a tubular atomization feed system one type of which is described below.
5. When the process of this invention is carried out, as expected, as part of an acrylonitrile production process, the process waste water feed does not need to be stripped of volatile organics. The residual products including acrylonitrile, HCN and acetonitrile are fully recovered. This saves the cost of the waste water stripper in the plant.
Additional objects and advantages of the invention will be set forth in part in the description which follows and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the foregoing objects and in accordance with the purpose of the invention, as embodied and broadly described herein, the process of the present invention comprises atomizing an acrylonitrile waste water stream containing organic material, introducing the atomized acrylonitrile waste water stream at a temperature below the decomposition temperature of the organics present in the waste water stream, into a reaction zone containing a catalyst and at least one reactant gas, reacting the atomized waste water stream and reactant gas in the presence of the catalyst to convert at least some of the organics in the waste water stream into at least one compound selected from the group consisting of acetonitrile, hydrogen cyanide and acrylonitrile.
In a preferred embodiment of the present invention, the atomization is performed by injecting the waste water stream into a high velocity gas stream (i.e. tubular atomization). In the present invention, a tubular atomization system not only provides small droplets for more rapid reaction but also minimizes the residence time of waste water in the feed line. The droplets are rapidly conveyed into the hot reaction zone by the at
Cesa Mark Clark
Graham Anne Marie
Shuki Albert Richard
Hruskoci Peter A.
The Standard Oil Company
Yusko David P.
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