WO2005115964A2

WO2005115964A2 - A method for catalytic oxyethylation

Info

Publication number: WO2005115964A2
Application number: PCT/PL2005/000033
Authority: WO
Inventors: Wieslaw Hreczuch; Wladyslaw Domarecki
Original assignee: Mexeo
Priority date: 2004-05-26
Filing date: 2005-05-25
Publication date: 2005-12-08
Also published as: PL368216A1; PL206132B1; WO2005115964A3; EP1789378A2

Abstract

The oxyethylation synthesis is carried out in such a manner that a total quantity of the catalyst is fed to a relatively small (preferably as small as possible) portion of the predesigned quantity of the reactant, whereafter oxyethylation is commenced by introducing a portion of the predesigned quantity of ethylene oxide to achieve the phase of fast acceleration of the conversion of ethylene oxide, i.e., activation of the catalyst that is present in a relatively high concentration in contact with the reactant and with ethylene oxide in the reaction environment. The synthesis process is then continued by introducing the remaining portion of the reactant and the remaining portion of ethylene oxide either in one step or gradually. In the method of the invention, owing to the fact that the oxyethylation reaction is commenced in the presence of the entire predesigned quantity of the catalyst and a portion of the predesigned quantity of the reactant, the catalyst’s concentration is many times as high in the reaction induction phase, thus enabling the reaction induction time to be minimized or eliminated and the rate of conversion of ethylene oxide in the first phase of synthesis to be increased. On the other hand, introduction of a substantial portion of the supplementary stream of the reactant and ethylene oxide as late as in the following phase of fast reaction will not affect the conversion of ethylene oxide or the efficiency of synthesis in time, even though the activated catalyst gets relatively diluted.

Description

[DESCRIPTION]

A method for catalytic oxyethylation

This invention relates to a method for catalytic oxyethylation of organic compounds having an ester bond, enabling the efficiency of the catalysts used to be multiplied and the synthesis process to be accelerated.

The oxyalkylation process has long been known and used commercially. The catalysts commonly used in the oxyalkylation processes are alkaline metal compounds, specifically sodium or potassium compounds. The reaction will always produce a polydisperse mixture of homologs and usually a portion of an unreacted reactant. Catalysts based on alkaline metals are effective as catalysts in oxyalkylation of reactants comprising a group with a so-called labile hydrogen atom although alkaline compounds are not effective as catalysts in oxyalkylation of an ester group. Moreover, alkaline catalysts are responsible for a relatively broad homolog distribution and they usually leave a considerable amount of the unreacted reactant in the product. Therefore, attempts have been made to find new solutions and new, so-called unconventional catalysts of oxyethylation, have been developed as a result. This category comprises a number of homogeneous and heterogeneous catalysts some of which have been used commercially. However, some problems are also frequently caused by a weak catalytic activity of the new type of the catalysts, which is manifested in longer times required to induce a reaction and/or in low reaction rates, specifically in the initial phases of the reaction. Especially, this refers to oxyethylation of esters. On the other hand, the possibility of increasing the concentrations of the said catalysts in excess is also limited because of the costs of their use on the one hand and cither the presence of an undesirable residue in the product or the expensive necessity to remove the residue on the other.

An increase in the efficiency of the used catalysts has been achieved, inter alia, by redesigning the chemical reactors used with in order to obtain a more developed contact surface of heterogeneous reactants in the form of a liquid reactant and product and a gaseous ethylene oxide. At the same time, the technology was evolving towards a maximum development of the interfacial area of contact between the gaseous ethylene oxide and the liquid mixture of the reactant/product and the catalyst, which provides improved conversion conditions and higher reaction selectivities. Cascade systems of flow of the liquid reaction medium under gaseous oxirane have been introduced along with injection dispersion systems for the liquid medium that circulates in the reactor. Consequently, ethylene oxide is fed depending on the reaction progress and the reaction mixture continues to be circulated until the desired conversion degree is achieved and is then discharged from the reactor. According to another solution, a preliminary reaction proceeds in a tank reactor where a desired quantity of oxirane is fed to a mixture of alcohol and catalyst and the reaction is continued in a tubular reactor, thus enabling the tubular reactor capacity to be sooner made available for handling more portions of the feed. However, the last case relates to superficial oxyethylation of low molecular alcohols.

The idea to achieve a continuous synthesis process is further developed by using a tubular reactor only, where a stream of alcohol with the catalyst is combined in the reactor with a stream of liquid ethylene oxide and effective synthesis takes place as the reactants are made to flow at an elevated temperature and at a sufficient positive pressure. Compared to tank systems, tubular reactors provide an opportunity to develop the heat-exchange surface in the reaction medium and to control reaction conditions by properly selecting the length of the reactor and adjusting flow rates.

One technological solution in which the most preferable conditions for reacting gaseous and liquid reactants are favored to an extreme degree is a thin-film technology. A synthesis process carried out in a film reactor with a turbulent flow of the reactants provides the best possible conditions for phase-boundary mixing and diffusion of heterogeneous components. Thin-film reactors are mainly employed in highly exothermal processes due to their high ability to carry away the heat (DE Pat. 4128827, PL Pat. 182369).

In the nineties, a possibility to directly oxyethylate fatty acid alkyl esters with the use of a new type of catalysts was reported. The reaction runs effectively when a molecule of ethylene oxide is selectively introduced between the carbonyl C atom and the alkoxy group of the ester bond.

In many instances, the reported so-called unconventional catalysts, used for obtaining oxyethylated alcohols with narrow-range homolog distributions, demonstrated catalytic activities also in reactions of ethylene oxide with fatty acid methyl esters. However, such catalysts were frequently further modified to improve reactions rates. An instance of such procedure is an improvement in the catalyst described in DE Pat. 3914131 (hydrotalcite) by adding co-catalysts, as described in DE Pat. 19611999. Similarly, the usefulness of an unconventional catalyst, referred to in PL Pat. 171663, for obtaining oxyethylated fatty alcohols with narrow-range homolog distribution in catalyzing the reaction of direct oxyethylation of fatty acid methyl esters was studied. Unfortunately, the catalyst in question displayed a rather weak activity in the investigated process of direct oxyethylation of esters. The synthesis proceeded rather slowly even at relatively high concentrations of the catalyst. Temperatures of 180°C or higher were required to induce the reaction. The catalytic systems referred to above were often used at high concentrations to ensure catalytic activities in the required ranges.

Oxyethylation as a process, specifically oxyethylation of esters, is characterized by a prolonged time required to induce a reaction and a relatively low rate of conversion of ethylene oxide in the initial phase of the reaction, i.e., until an average polyaddition degree of approx. 3 moles of ethylene oxide per mole of the ester is obtained. Another typical phenomenon is a considerable acceleration of the rate of conversion of ethylene oxide as the oxyethylation reaction proceeds; this, for instance, is observed where the catalyst referred to in the patent P 343853 is employed. The situation is typical of a majority of catalysts for oxyethylation of esters and it results from the complex mechanism of the reaction that proceeds in stages.

One could expect that the oxyethylation process could effectively be accelerated, the reaction induction time entirely eliminated and the rate of average conversion of ethylene oxide increased in general by significantly increasing the concentration of the catalyst relative to the reactant. However, as was said earlier herein, the general trend is to minimize the catalyst's concentration both because of production costs and because of its troublesome residue in the product.

Unexpectedly, it was found that the catalyst's concentration relative to the oxyethylation reactant might be multiplied in a controlled manner in the initial phase of the reaction followed by reducing the catalyst's concentration relative to the reactant in the phase of fast synthesis which takes place later, thus obtaining a relatively low concentration of the catalyst in the final product.

In previously known methods of oxyethylation, it has been a general trend that the catalyst's concentration should be constant relative to the initial reactant throughout the reaction. According to state-of-the-art methods, a predesigned quantity of the catalyst was fed to a predesigned quantity of the reactant to be oxyethylated and then a predesigned quantity of ethylene oxide was gradually fed to the resulting prepared reaction environment.

In the method of the invention, a predesigned total quantity of the catalyst is fed to a relatively small (preferably as small as possible) portion of the predesigned quantity of the reactant, whereafter oxyethylation is commenced by introducing a portion of the predesigned quantity of ethylene oxide to achieve the phase of fast acceleration of the conversion of ethylene oxide, i.e., activation of the catalyst that is present in a relatively high concentration in contact with the reactant and with ethylene oxide in the reaction environment. The synthesis process is then continued by introducing the remaining portion of the reactant and the remaining portion of ethylene oxide either in one step or gradually. Otherwise, a stream of (the remaining portion of) the reactant and a stream of ethylene oxide may be fed in parallel from the very beginning of the synthesis process.

The gist of the invention is that, owing to the fact that the oxyethylation reaction is commenced in the presence of the entire predesigned quantity of the catalyst and a portion of the predesigned quantity of the reactant, the catalyst's concentration is many times as high in the reaction induction phase, thus enabling the reaction induction time to be minimized or eliminated and the rate of conversion of ethylene oxide in the first phase of synthesis to be increased. On the other hand, introduction of a substantial portion of the supplementary stream of the reactant and ethylene oxide as late as in the phase of the following fast reaction will not affect the conversion of ethylene oxide or the efficiency of synthesis in time, even though the activated catalyst gets relatively diluted.

Oxyethylation by the method of the invention and the efficiency of using the said manner of oxyethylation in the light of state-of-the-art techniques will now be illustrated by way of examples. Example I shows an effective manner of oxyethylation according to the method of the invention. For comparison, Examples II and HI show results obtained in the oxyethylation process based on a different manner of oxyethylation, known in the art.

Example I

A 3-L stainless steel reactor is filled with 300 g of methyl esters of [fatty] acids obtained from rape seed oil (containing more than 90% of Cι₈) and 5 g of a calcium catalyst obtained according to a method referred to in the Pat. Appl. PL 343853. The reactor was closed and heated to 130°C, drying the feed by purging with nitrogen for 30 minutes. When the drying operation was completed, the contents of the reactor was heated to 185°C and feeding ethylene oxide was commenced. The reaction commenced at once without any induction time and proceeded with good efficiency and without any disturbances. After 130 g (approx. 3 moles) of ethylene oxide was fed another portion, i.e., 700 g of rape seed oil [fatty] acid methyl ester was introduced during 50 minutes. Ethylene oxide was continued to be fed: 870 g of ethylene oxide was fed in during another 60 minutes and the reactor was kept at the reaction temperature for 60 more minutes. On completion of the reaction, the material in the reactor was cooled down to 50°C, purged with nitrogen and discharged.

A diagram showing the relationship of the introduced quantity of ethylene oxide in time is shown in Fig. 1. Example II.

The synthesis was carried out as in Example I except that the reactor was filled with the total quantity of rape seed [oil fatty acid] methyl ester (1000 g) together with the catalyst (5 g) in a single step and then, as soon as the reaction temperature was achieved, feeding ethylene oxide was commenced. During 250 minutes of the synthesis merely about 280 g of ethylene oxide was introduced.

A diagram showing the relationship of the introduced quantity of ethylene oxide in time is shown in Fig. 1.

Example III.

The synthesis was carried out as in Example II except that 10 g of the catalyst was introduced to the reaction which means that the concentration used was twice as high as that in Examples I and II. During 200 minutes of the synthesis merely about 1000 g of ethylene oxide was fed in.

Claims

[CLAIMS]

1. A method for catalytic oxyethylation of esters (reactants) in a periodic reactor by introduction of ethylene oxide into the reactor filled with the reactant and in the presence of a catalyst, characterized in that the reactor is filled with a portion (x') of a predesigned total quantity (X) of the reactant to be subjected to oxyethylation and with a total predesigned quantity (Y) of the catalyst, whereupon another portion (z') of the predesigned total quantity (Z) of ethylene oxide is fed to the reactor to activate the catalyst and induce a reaction and after the introduced quantity (z') of ethylene oxide has been converted entirely or partly, the reactant feed is supplemented to the predesigned quantity (X) and ethylene oxide is continued to be fed until the predesigned quantity (Z) has been introduced, preferably, the portion (x') of the reactant introduced in the initial phase of the synthesis is as small as possible relative to the total predesigned reactant feed (X), that is, its quantity is around the minimum feed specified for a given reactor, that is, when the value of the quotient x'/X is as small as possible.

2. A method for catalytic oxyethylation as climed in Claim 1 characterised in that, that as soon as the reactor is filled with the portion (x') of the reactant and the total quantity of the catalyst (Y), the supplementary portion (X-x') of the reactant is fed in parallel with ethylene oxide until the total predesigned quantity (X) of the reactant has been introduced, or the supplementary portion (X-x') of the reactant is fed periodically, that is, alternately with ethylene oxide.

3. A method for catalytic oxyethylation as claimed in Claims 1 or 2 characterized in that, that in the first phase of the synthesis a portion of the predesigned total quantity (y') of the catalyst is added to the portion (x') of the reactant, although in a higher proportion than the ratio of part of the reactant feed to its predesigned total quantity, that is: y'/Y > x'/X, whereas the remaining portion of the predesigned total quantity (Y-y') of the catalyst is introduced together with the supplementary portion (X-x') of the reactant during the synthesis process.