What is the manufacturing process of ethyl acetate?
Ethyl acetate process
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Our novel technology has received a number of industry awards, including the Kirkpatrick Chemical Engineering Achievement Award, the Institution of Chemical Engineers Crystal Faraday Award and the Royal Academy of Engineering MacRobert Award.
Johnson Matthey has developed a process that enables ethyl acetate and a valuable hydrogen by-product stream to be produced directly from ethanol. The process takes advantage of the current industrial focus on renewable resources and the expansion in fermentation ethanol production and breaks the feedstock link to volatile oil prices.
Dry ethanol is dehydrogenated to produce a crude ethyl acetate stream. This is selectively hydrogenated to remove certain by-products that cannot be separated by distillation. The innovative refining section then splits the azeotrope to produce a high purity ethyl acetate product. Unreacted ethanol is recycled to a dehydration unit where it is combined with fresh ethanol and dried.
Contact us for more information on the DAVY ethyl acetate process.
USA - Process for ethyl acetate production
FIELD OF THE INVENTION
This invention relates to a process for the conversion of ethanol to ethyl acetate.
Ethyl acetate is mainly used as a solvent in the paint and coatings industry. It is a very useful chemical which has valuable solvent properties. Its physiologic harmlessness in combination with its oleophilic character has made it especially suitable for extraction processes in the food industry and for the preparation of cosmetics. Its low boiling point is the basis for its application as a high grade defatting agent. The high standard purity of the commercial product accounts for its use as an anhydrous reaction medium and also as an intermediate in chemical syntheses.
BACKGROUND OF THE INVENTION
The commercial production of ethyl acetate is mainly by two processes: the Tischenko reaction produces ethyl acetate by direct conversion of ethanol via acetaldehyde using an aluminum alkoxide catalyst; and the production of ethyl acetate by direct esterification of ethanol with acetic acid with a sulphuric acid catalyst. The Tischenko reaction is the main industrial process for the manufacture of ethyl acetate. Industrial scale production by this method took place mainly in Europe during the first half of this century. Ethyl acetate is also produced as a by-product in the liquid phase oxidation of n-butane and as a co-product in the production of polyvinyl butyryl from vinyl acetate and ethanol.
In the Hoechst process, a catalyst solution of aluminum ethoxide is first prepared by dissolving granular aluminum in an ethanol-ethyl acetate mixture in the presence of aluminum chloride and a small amount of zinc chloride. The reaction evolves hydrogen and is exothermic. Intensive cooling is required to prevent the loss of organic matter. The final solution contains about 2% aluminum. The next step in the process is to introduce the catalyst solution along with acetaldehyde simultaneously into a reactor. The reaction varies according to the temperature and the catalyst quantity. These parameters are adjusted to accomplish about 98% conversion in one pass through the reactor. A further 1.5% transformation is obtained in the stirring vessels where a residue is separated from the product. The reactor is kept cooled to about 0 C. by the use of a chilled brine. The residence time in the reactor is about one hour.
The distillable products are removed in the residue separation vessel by evaporation. The residue is treated with water to convert as much as possible to ethanol. The remainder can either be treated in a biological degradation plant or incinerated. The combined distillable products are then separated in a series of distillation steps to give ethyl acetate, the product; unconverted acetaldehyde, for recycle; light ends which can be used for fuel; a mixture of ethyl acetate and ethanol, which can be used in the catalyst preparation step; and a by-product, acetaldehyde diethyl acetal, which can be recovered for sale or hydrolyzed for recovery of acetaldehyde and ethanol.
In the esterification process, ethanol and acetic acid are combined with a recycle of crude ethyl acetate in a reactor which is also an azeotropic distillation column. The reaction produces water as a waste product. The water impedes the reaction, and the reaction column removes the water as an azeotrope as it is generated. The overhead condensate is collected in a decanter where the product separates into two phases. The organic phase is partially recycled to the reaction column and the balance is fed to a second distillation column which produces a bottoms product of ethyl acetate and an overhead product of an azeotrope of ethyl acetate, water and ethanol. The overhead condensate is collected in a second decanter, where it separates into two phases as before. The organic phase is recycled to the column while the aqueous phase is combined with the aqueous phase from the first column and fed to a third column to produce a wastewater stream from the bottom and the azeotrope from the top. The azeotrope is recycled to the reaction column.
In another process ethyl acetate is synthesized from ethylene and acetic acid. This method claims ecological benefits in that it produces less wastes than the aluminum chloride catalyzed process. In this process, disclosed in U.S. Pat. No. 4,275,228, ethyl acetate is prepared by the vapor phase reaction of ethylene and acetic acid utilizing as a solid catalyst ion exchange fluoropolymer comprising sulfonic acid moieties. The feed usually has an excess of ethylene. Conversions of acetic acid vary from 30% with a residence time of 55 hours at 126 C. to 60% with a residence time of 30 hours at 150 C. As a consequence of this slow reaction-rate, the process requires an extremely large reactor size.
U.S. Pat. No. 5,241,106 reveals a variation on the process whereby the catalyst comprises tungstophosphoric acid of which 10-90% of the total amount of proton is replaced by a cesium cation or a combination of a cesium cation plus at least one cation from alkali metal cations other than cesium or a combination of a cesium cation plus at least one cation of iron group metal cations. This process can produce ethyl acetate by either a vapor phase reaction or a liquid phase reaction and the reaction rate can be improved by the addition of water to the feed. The reaction times are significantly shortened, but they are still longer than desired.
U.S. Pat. No. 4,886,905 describes another approach based on acetic anhydride as the feed material. The acetic anhydride is hydrogenated at elevated temperatures and pressures in the presence of a homogeneous ruthenium catalyst, methyl iodide and, optionally, lithium iodide. The process produces either ethyl acetate or ethylidene diacetate or both, depending on reaction conditions. This process can provide high reaction rates, but the process is complex. Acetic acid is produced as a co-product, which must be separated and converted back to acetic anhydride, and the process requires the availability of hydrogen at high pressure. The catalyst and iodides must be removed from the reaction products and recycled.
U.S. Pat. No. 4,780,566 describes another approach based on methyl acetate. The methyl acetate, either alone or in a mixture with acetic acid in the presence of a ruthenium compound and a promotor of hard acid type in an atmosphere of hydrogen and carbon dioxide produces ethyl acetate and acetic acid. This process is also complex and provides poor selectivity. In addition to acetic acid, alcohols, ethers, propionates, methane and ethane are co-produced significant quantities.
There is a need in the industry for a more efficient process for the production of ethyl acetate.
The disclosures of the above patents are incorporated herein by reference.
SUMMARY OF THE INVENTION
The present invention provides a single step, single vessel conversion of ethanol to ethyl acetate. The first part of the process is the partial oxidation of part of the ethanol to acetic acid by oxygen (or air), and the second part is the esterification of the acetic acid with a second part of the ethanol. The first reaction is catalyzed by a palladium type catalyst, while the second reaction proceeds spontaneously or can be catalyzed by a solid ion exchange resin in the acid form. The catalysts can be mixed so that the reactions proceed in parallel, or separated so that the reactions proceed sequentially.
The products of reaction are limited to ethyl acetate, acetic acid, acetaldehyde and water. The feed ethanol can be either pure ethanol or commercial ethanol (constant boiling or lower purity).
The reaction system is well suited for a trickle bed catalytic type process. Because water is present, the oxidation reaction is enhanced if the oxidation catalyst, Pd, is supported on a hydrophobic carrier.
Thus, a single step, single vessel process for the conversion of ethanol to acetic acid is provided, comprising reacting the alcohol with oxygen or air in the presence of a noble metal oxidation catalyst preferably on a hydrophobic support with excess liquid ethanol present as a solvent to absorb the acetic acid as it forms. The acetic acid formed reacts with the liquid ethanol to form ethyl acetate. The esterification reaction proceeds spontaneously and in parallel with the oxidation reaction, but reaches equilibrium concentrations more rapidly in the presence of an acid catalyst, such as a solid ion exchange resin for example Amerlyst 15 in the acid form.
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BRIEF DESCRIPTION OF THE DRAWING
The FIGURE is a schematic diagram of a typical apparatus used to carry out the process of this invention.
DESCRIPTION OF THE INVENTION
The experimental proofs of the concept were conducted in an apparatus of the type illustrated in the FIGURE. As seen in FIG. 1, a pressurized packed trickle bed reactor 10 made from type 316 stainless steel contains the catalyst(s) 11. The reactor volume was approximately 80 cc's. The catalyst(s) were supported on glass beads 12. The reactants were distributed over the catalysts by another layer of glass beads 13 at the top of the bed.
The oxidation catalyst was an oxidation catalyst containing a noble metal (Pt, Pd, Rh, or Ir) or combinations thereof, on a hydrophobic support, e.g. styrene-divinylbenzene co-polymer, fluorinated carbon and silicalite or on activated carbon. See U.S. Pat. No. 5,009,872, the disclosure of which is incorporated herein by reference. The surface area should be high enough so that sufficient metal catalyst can be deposited with good dispersion, say in the range of 50-800 square meters per gram.
The solid acid catalyst can be a solid ion exchange resin in the acid form. Specifically, Amberlyst 15 in the acid form has been found to be effective.
The bed packing was a mixture of the catalyst and an inert support. In the case where the reaction proceeds in parallel, the oxidation catalyst and the solid acid catalyst were blended together with glass beads and placed on a bed of sized glass beads. Layers of sized glass beads were then placed on top of the catalyst bed and the reactor was closed.
In the case where the reactions proceeded sequentially, the solid acid catalyst mixed with glass beads was placed on a bed of sized glass beads, a layer of glass beads was placed on top of the catalyst and bed of oxidation catalyst mixed with glass beads was placed on top of the separating layer of glass beads. Finally, a layer of glass beads was placed on top of the hydrophobic catalyst and the reactor was closed.
The reactor was then placed inside a heating jacket 14 to control the reaction temperature. A heat transfer liquid was circulated through the jacket in series with a constant temperature bath to maintain the reactor temperature.
Temperatures in the range of from 75 to 150 C. are contemplated.
Pressures ranging from 20 bar to 40 bar are suitable.
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