Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
2002-03-11
2002-09-10
Siegel, Alan (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
Reexamination Certificate
active
06448456
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a catalytic process for preparing alkylene glycols from alkylene oxide and water. The preferred alkylene oxides include ethylene oxide, propylene oxide, and butylene oxide, and the preferred alkylene glycols include their respective monoalkylene glycols: ethylene glycol (EG), propylene glycol (PG), and butylene glycol (BG). Most preferably, the invention relates to the preparation of ethylene glycol from ethylene oxide and water. Particularly, the invention is directed to a method of preservation of catalysts in alkylene oxide containing systems.
BACKGROUND OF THE INVENTION
Alkylene glycols, such as ethylene glycol, propylene glycol and butylene glycol, are widely used as raw materials in the production of polyesters, polyethers, antifreeze, solution surfactants, and as solvents and base materials in the production of polyethylene terephthalates and polybutylene terephthalates (e.g. for fibers or bottles). Commercial processes for the preparation of alkylene glycols typically involve the liquid phase hydration of the corresponding epoxide in the presence of a large molar excess of water (see, e.g., Kirk-Othmer, Encyclopedia of Chemical Technology, Vol. 11, Third Edition, page 929 (1980)).
Ethylene glycol is commonly produced by the noncatalytic reaction of ethylene oxide and water. The reactions are run adiabatically, and the heat of reaction is absorbed by the reacting fluids which respond with an increase in temperature. The reaction temperature is typically 120° C. at the inlet to the reactor and often exceeds 180° C. at the exit point.
High temperatures are desirable in the preparation of ethylene glycol because the rate of reaction is maximized and selectivity is unaffected by high temperature. An added advantage of high temperature operation is that it reduces the need to supply external sources of heat to downstream purification equipment for the separation and recovery of unreacted water from the ethylene glycol product.
High ratios of water to ethylene oxide are typically fed to the commercial reactors to favor the production of mono-ethylene glycol, which is capable of also reacting with ethylene oxide to form diethylene glycol. Additionally, the diethylene glycol can react with ethylene oxide to form triethylene glycol, and so forth.
Formation of higher glycols is viewed as commercially unattractive, since the production of these higher glycols consumes valuable ethylene oxide, and markets for use of higher glycols are limited. The use of excessive quantities of water to favor mono-ethylene glycol, however, adds to the cost of manufacture because the excess water must be removed with energy through capital intensive evaporation and distillation process steps.
Catalytic systems have recently been studied for the purpose of selectively hydrolyzing epoxides, although commercialization has been an elusive goal.
For example, JP-A-57-139026 teaches a catalyzed process utilizing anion exchange resins in the chloride form in the presence of carbon dioxide resulting in superior selectivity over comparable non-catalyzed or thermal processes. One drawback to the process taught in said Japanese application is the formation of ethylene carbonate, separation of which is difficult and expensive.
Further developments at catalyzing the reaction of alkylene oxide and water, and particularly of ethylene and/or propylene oxide and water, have employed anion exchange resins in the bicarbonate form. For example, it has been shown previously that anion exchange resins in the bicarbonate form are particularly effective at catalyzing the hydrolysis of ethylene oxide. The selectivity of said reactions is high, often approaching 98% at water to ethylene oxide molar ratios less than 20:1.
More in detail, examples of such catalytic processes are taught in RU 2001901 and RU 2002726. The processes described therein require converting a catalyst to the bicarbonate form before the catalytic reaction, and reducing the concentration of carbon dioxide to as low as 0.01 wt. % in order to allow the catalyst to be more selective toward monoethylene glycol.
In addition, U.S. Pat. No. 5,488,184 also teaches a catalytic process wherein carbon dioxide is reduced or eliminated from the reaction mixture in order to enable higher reaction rates. This patent teaches that, for the bisulfite form of the catalyst, addition of carbon dioxide is beneficial to the reaction selectivity, but that for other anion forms of the catalyst, including the bicarbonate and formate forms, addition of carbon dioxide is detrimental to selectivity as well as the reaction kinetics for the bicarbonate form. The said patent thus teaches that the concentration of carbon dioxide be kept below 0.1 wt %. It also teaches using relatively low reaction temperatures of around 80° C. Such low reaction temperatures require external cooling.
International patent applications WO 99/31034 and WO 99/31033, corresponding to U.S. Pat. Nos. 6,160,187 and 6,137,015, respectively, also teach catalytic processes at relatively low reaction temperatures. Such references teach advantageously using a specific reactor design and adjusting the pH, respectively, to prolong the catalyst lifetime and minimize catalyst swelling. The aforementioned references are limited by low reaction temperature, due primarily to the fact that anion exchange resins in the bicarbonate form, if exposed to high temperatures, typically deactivate quickly, as quickly as a few days when temperatures exceed 120° C. Because the hydrolysis reaction is exothermic, even higher reaction temperatures would be desired to permit maximum temperature rise without cooling.
The catalysts used in the prior art documents discussed herein-above, and which are also useful in the process of the present invention, are based on a styrene-divinyl benzene polymer and are functionalized with a trimethyl amine attached to either a benzylic carbon which is attached to the polymer or through an alkyl or ether spacer which is attached to aromatic ring of the polymer resin. A selective form of the catalyst can be prepared by exchanging the anion with bicarbonate or metalate anions. These catalysts promote the reaction of EO with water, but to a much lesser extent promote the reaction of glycols with EO.
Unfortunately, these catalysts have been shown to swell unabatedly in the presence of the reactants while under reaction conditions by reacting with ethylene oxide. At reaction temperatures higher than 100° C., the catalysts swell at a rate of greater than 1% per day. In addition, these catalysts lose activity, and their half-life has been shown to be less than 1 year. Specifically, materials such as DOWEX MSA-1 (ex The Dow Chemical Company), Marathon A (ex The Dow Chemical Company), and XSA-1000 (ex Mitsubishi) swell due to their reaction with ethylene oxide and have half-lives of less than 100 days when a reaction temperature of higher than 100° C. is used.
In WO 99/12876 and WO 00/35 842, a process is described for the preparation of alkylene glycols by reacting an alkylene oxide with water in the presence of a catalytic composition based on a polybasic or a polycarboxylic acid derivative, which preferably is immobilized on a solid support. In WO 99/12876, the catalytic composition is based on ion-exchanging polymer materials containing as electropositive centers nitrogen atoms coordinated with anions of di- and/or tri- and/or polybasic acids in which one or more hydrogen atoms are substituted by an ion of an alkali metal and/or an ammonium ion.
WO 00/35842 appears to describe the same invention but describes the polycarboxylic acid derivatives as derivatives having in their chain molecule one or more carboxyl groups and one or more carboxylate groups, the individual carboxyl and/or carboxylate groups being separated from each other in the chain molecule by a separating group consisting of at least one atom. Suitable examples of such polycarboxylic acid derivatives are monosodium salts of citric acid and trimellitic acid. The solid support can be a solid
LaPrairie Daniel J.
Lee Guo-Shuh J.
Rievert William J.
Strickler Gary R.
Timm Edward E.
Siegel Alan
The Dow Chemical Company
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