CS212247B2 - Method of making the terephtale acid - Google Patents

Abstract

Terephthalic acid is prepared by oxidizing a substantially homogeneous liquid reaction mixture, comprising p-toluic acid, optionally in admixture with p-xylene and partially oxidized p-xylene derivatives, 5% to 80% by weight of water, and a catalytically-active metal compound selected from manganese compounds, cobalt compounds and mixtures thereof, with a molecular oxygen-containing gas. At least a minimum amount of M millimoles of the catalytically-active metal compound per kg of the liquid reaction mixture is used, wherein M is defined by the following equation: <IMAGE> wherein Y represents the molar ratio of water/p-toluic acid in the reaction mixture, x represents the molar ratio of manganese/total manganese + cobalt in the catalyst composition <IMAGE> A equals about 0.200, B equals about 10.9, C equals about 4.35; and D equals about 0.0724.t

Description

(54) Method for producing terephthalic acid

The present invention relates to an oxidation process, and in particular to a process for preparing terephthalic acid by oxidizing p-toluic acid or mixtures thereof with p-xylene and / or its partially oxidized derivatives such as p-tolueldehyde.

Terephthalic acid is very important from an industrial point of view for increasing use as both the starting material for the production of high molecular weight. resins, as well as for polyester-forming fibers and films.

Previous publications provide guidance on a number of processes for liquid-phase oxidation of aromatic alkyl-substituted aromatic compounds to aromatic carboxylic acids. One of the first patents in this field is U.S. Pat. No. 2,245,528, which discloses a one-step process for oxidizing alkylaromatic compounds with molar alkali in the presence of a metal catalyst, a solvent such as acetic acid, and optionally an oxidation initiator. Although strictly adhering to the conditions, the yield of dicarboxylic acids is low.

Soos Naaříklad in the oxidation of xylenes with air in acetic acid, a content of the ICI cobalt acetate and manganese-like catalysis or at temperatures of ¹⁸ 5 2 ⁰ ° C and 5,0-battery Ш * а pHtorniooti in diethyl initiator makes výtěiek phthalic acid only 2% and the main reaction products are toluic acid along with other intermediate products of the oxidation process.

A number of other patents disclose a process for oxidizing p-xylene in one step with improved terephthalic acid effluents. These patents relate mainly to the use of special activators, such as bromine-containing compounds (U.S. Patent No. 2,833,816), ketones (U.S. Patent No. 2,853,514), or aldehydes (U.S. Patent No. 3,036,122). Although some of these processes are industrially уу ^^ а ^, they still have a number of serious disadvantages. For example, when using bromine-containing activators, a number of corrosion problems arise. When a ketone or aldehyde is used, some of them are inevitably lost and the remainder is mainly converted to acetic acid, which must be collected, purified and treated for production to be economically feasible. However, in spite of these advantages of activator, it is considered necessary - a requirement for efficient production of tartaric acid from xylenes.

In many cases, this also protects the sewing of the solvent, which is necessary. Low molecular weight aliphatic acids, and in particular acetic acid, are generally used for this purpose. The quantity of solvent supplied must be sufficient to be free from bending! kept the reaction. the components and the reaction products in solution or at least in solution. As a result, the reaction mixture is easily stirred, oxygen is improved, the formation of by-products is minimized and the heat of reaction is easily removed by evaporation of the solvent.

However, under commonly used reaction conditions, a significant portion of the solvent is lost due to its co-oxidation. In addition, the solvent must be separated from the other components of the reaction mixture and then the purity and recovered. Excluding the consumption of a portion of the solvent and the operations to obtain the remaining portion thereof will incur additional manufacturing costs.

In order to avoid the above mentioned significant problems, it would be suggested to carry out the oxidation of p-xylene in the absence of a solvent. In this case, it is necessary to operate at a temperature which lies within the melting range of the acid, i.e. at about 160 ° C, in order to obtain a liquid reaction mixture. The temperature selection is therefore limited. Moreover, in the absence of solvent, it is difficult to treat the reaction mixture, as well as odd and LT ^ ^ 2 ^ CE ^ a ^ ^t acid tert- dad. Generally, the reaction is terminated when the terephthonic acid content of the mixture exceeds 60 and preferably 45% by weight. Outside this range, there are difficulties in oxidizing the reaction mixture as well as the suspension, and therefore the reaction has an adverse effect (via U.S. Patent No. 3,883,584).

In the absence of solvent, the removal of the heat of reaction in an industrial town causes further difficulties because of uncontrolled production in the reactor, although the acid is not present in large quantities. Thus, in U.S. Pat. No. 2,696,499, which relates to the oxidation of xylene to this acid in the absence of ruzpoujtёdlj, it is explained that the basic problem is that of the vascular system. with cooling of the oxidation mixture xylene, solids are prevented from settling.

U.S. Pat. No. 3,406,196 discloses a two-step process in which water is used as the suspending agent for acid. In the first step, the alkylaromatic compound, and in particular p-xylene, is oxidized by air in the absence of any additional solvent to partially oxidized compounds which in the second Suphi oxide at higher temperature in the presence of a considerable amount of water, such as the environment. As the mission oxidation promoter, bromine or a compound that contains bromine can be present. Nevertheless, very high temperatures in the range of 200-275 ° C, and in particular 225-250 ° C, are required to convert these partially oxidized compounds to terephthatic acid.

Therefore, you necessarily have the same or even greater. corrosion problems than those encountered in processes using acetic acid as the solvent. In addition, the patent teaches that there is a significant loss of polyalkylaromatic compound and other side reactions when exposed to the higher temperatures required for the effective conversion of partially oxidized products produced in the first stage of oxidation to aromatic polycarboxylic acids. . It is clear that it is emphasized in this patent that, even if bromine as a promoter is present, it will fail to produce large amounts of water, and does not give satisfactory results for the oxidation of p-xylene to tartaric acid in one step.

'NR i ⁿ it has long been known that water is a poison for catalysts used for the oxidation reaction (U.S. Pat. No. 2,696,499). According to a widespread view, water has an adverse effect on the reaction rate which it affects from the outset. Therefore, as a general rule, avoid as much as possible its presence, whether or not the solvent and / or activator is present. Thus, U.S. Pat. No. 3,064,044 discloses an improved process for maintaining the end of oxidation (the bromine promoter) under substantially anhydrous conditions. U.S. Pat. No. 3,519,684, which relates to an oxidation process using perfacic acid as a prooor, states that almost anhydrous conditions are preferred, although a water content of up to about 10% may be preferred, the water content should not exceed 5%

In a continuous process of oxidizing xylenes in the absence of any promoter and where the partially oxidized omelproducts are continuously returned, water is removed from the effluent prior to recycle to maintain a water content of the reaction mixture of less than 15% and preferably less than 5% of the total. reaction mixture (U.S. Patent No. 3,700,731).

Recently, it has been unexpectedly discovered that the oxidation of p-xylene to terephthenic acid can be carried out in the presence of a substantial amount of water as solvent, also in the absence of water. some of the bromine compounds as activator, which was previously considered to be an essential necessary component. This procedure is described in MS. No. 194,694. Such processes include oxidizing the p-xylene in the liquid phase with an oxygen-containing gas in the presence of p -butic acid, water and a heavy metal salt catalyst at a temperature of about 140 to 220 ° C, at a pressure sufficient to maintain at least a portion of water in the liquid phase.

Because the mutual solubility of p-xylene and water at the working temperature is low, mixtures of water, p-xylene and polyolic acid can be reduced to two phases, an aqueous phase and an organic phase rich in hydrocarbons and containing a significant proportion of the acid. The Lu are present in the reaction mixture. In this case, the oxidation reaction takes place mainly in the organic phase, where the water concentration is relatively nice. Therefore, the desired effect of water as solvent is partially reduced. In addition, said phase separation is the cause of significant technical difficulties due to homogeneity, oxygen dispersion and mass transfer efficiency.

It is an object of the present invention to provide a process for the production of terephthalic acid by oxidation of p-xylene, wherein terephthalic acid is obtained in high yield and good purity and in which the disadvantages of the above-described processes are avoided.

Another feature of the present invention is that a process is provided in which a high corrosion resistant device is not required and can be operated in a conventional stainless steel device.

A further feature of the invention is that a process is provided which can be carried out in the presence of a substantial amount of water without the need for any additional solvent.

A further feature of the invention is that it allows a process in which terephthalic acid is produced by oxidizing a reaction mixture consisting essentially of a homogeneous aqueous solution, mainly containing terephthalic acid precursors which will be oxidized, water and an oxidation catalyst. is dissolved in it.

A further feature of the invention is that it allows a process in which it is not necessary to use prtooOor, as a bromine compound, in addition to the oxidation catalyst.

A further feature of the invention is that it allows a process in which terephthalic acid can be readily obtained from the oxidized reaction mixture at a relatively low temperature.

A further feature of the invention is that it allows a process in which the catalyst and oxidation intermediates can be recovered and reused for oxidation.

A further feature of the invention is that it ameliorates a process in which terephthalic acid can be produced on an industrial scale at a relatively low cost.

A further feature of the invention is that it allows the batch process to be carried out as well as continuously.

A further feature of the invention makes it possible to carry out a process in which it is easy to calculate the amounts of catalyst, water and p-toluic acid required to ensure efficient oxidation of the starting material.

To achieve the above features of the present invention, a process for the production of terephthalic acid by oxidation of p-toluic acid or mixtures of p-toluic acid and p-xylene and / or partially oxidized p-xylene derivatives in the presence of water in an amount of at least 5 wt. it is sufficient to obtain a workable suspension, in the presence of an oxidation catalyst comprising at least one catalytically active manganese compound and / or a cobalt compound and optionally a nickel, lead and / or cerium compound with a molecular oxygen-containing gas at a reaction temperature of 140-220 ° C and a pressure sufficient to maintaining at least a portion of the water in the liquid phase at the reaction temperature of using a catalyst in an amount ranging from a minimum of M millimoles of catalytically active metal compound per kg of liquid reaction mixture, M being given by Equation 1, у (x + A) + Bx '= - ---- 5x> D where у stands for the molar ratio of water to p-toluic acid in the reaction mixture, x stands for the molar ratio of manganese to total manganese and cobalt in the catalyst,

A is equal to 0.200 - 0.031,

В is equal to 40.9 ^± ЦЗ,

C equals 4.35 * 0 17 and a

D is 0.0724 0.0117, up to 40 millimoles, 8 preferably up to 30 millimoles, per 1 kg of liquid reaction mixture.

By keeping the catalyst concentration at least at the minimum value mentioned above, effective oxidation of some of the starting materials of the above mixture to terephthalic acid in the homogeneous liquid phase of the reaction mixture is achieved.

Other features, features and advantages of the invention will be apparent from the detailed description of the invention and from the preferred embodiments thereof, given below with reference to the accompanying drawing.

The drawing is a phase diagram of a mixture of p-xylene, p-toluic acid and water at 185 ° C.

An important feature of the present invention is that the observed effect of water, which has been generally investigated before, can be overcome when the oxidation is carried out under the conditions specified above. A further feature of the present invention is that oxidation of various substrates, which may contain p-toluic acid alone or in admixture with p-xylene and / or partially oxidized derivatives, such as p-tolualdehyde, may be carried out. Yet another feature of the present invention is that substrates can be oxidized in a homogeneous aqueous solution if the amount of catalyst is selected in relation to the ratio of the amount of water and p-toluic acid present in the system.

The process according to the invention can be carried out either by batch or continuous processes. The reactants were dissolved in water and a catalyst was added to the resulting solution.

Oxygen is introduced into the mixture at a temperature of about 140 to 220 ° C and oxidation is carried out under pressure.

The pressure is selected in such a way that the reaction mixture is maintained substantially in the liquid phase at the operating temperature. Terephthalic acid is separated from the reaction mixture as a white crystalline precipitate.

In a continuous process, the precipitate is removed continuously by any conventional method for separating solids and liquids, such as by filtration, blasting or settling and decanting, and the remaining liquid containing unconverted reactants and oxidation products is recirculated to the oxidation zone. Fresh reagents are continuously added to compensate for the loss of terephthalic acid formed and by-products. Thus, there is no need to add extra cUemikklie.

However, in carrying out the process of the invention, at least one organic solvent which does not affect the reaction and which is relatively inert under the operating conditions may be added to the reaction mixture. Examples of such compounds that can be used as a solvent in admixture with water are benzoic acid and acetic acid. These compounds, which simultaneously penetrate in small quantities during the reaction, may be allowed to accumulate to some extent in the reaction mixture. However, advantageous results in the present invention are obtained regardless of the presence of such compounds which, when used, should not be present in an amount that exceeds the amount of water in the system.

The amount of water conveniently used in the process of the invention may be varied over a wide range, for example in the range of about 5 to 80% of the afternoon-reaction mixture, in various circumstances. As already pointed out, the basic aspect of the invention is that the oxidation is carried out in a homogeneous aqueous system. Therefore, the plurality of water will primarily be sufficient to obtain a substantially homogeneous aqueous solution of the reactants, even taking into account other production variables, such as temperature and relative amounts of the various compounds to be oxidized.

For example, if a process is used to oxidize p-toluic acid alone or a mixture thereof with other oxidizable compounds that are relatively water-soluble, such as p-tolualdehyde, a plurality of water is chosen to completely dissolve. p-toluic compounds at operating temperature. Since the solubility of p-toluic acid in water increases sharply with increasing temperature, it may be very low. reduce the water used when the temperature rises. As a general rule, however, the amount of water should not be less than 5 and preferably not more than 10% of the mono-monoxide reaction salts.

If the p-xylene is also a component of the reaction mixture, it should not be very low. water to cross the boundary above which the mixture is divided into two liquid phases. This amount is of course dependent on the mannitol of p-xylene in the mixture. The drawing shows a triangular phase diagram of a mixture of p-xylene (p-xyy), p-toluic acid (p-Ta) and water at a temperature of 185 ° C (in% UM). In this diagram, zone A is a homogeneous solution and zone B is a two-phase solution. As the man skilled in the art readily ^ ζη ^ ί, the boundary curve between the two bands does not change much with temperature. Obviously, the amount of p-xylene must be limited to prevent the presence of the substantially organic phase.

Therefore, when carrying out the oxidation of p-xylene by the process of the invention, a batch process is preferred and p-xylene should be added to the reaction mixture gradually, either occasionally or continuously, at such a rate that the system is maintained in zone A. The reaction is carried out by a continuous flow process, whereby unreacted p-xylene, together with the oxidation intermediates, i.e. mainly p-toluic acid, is not directly circulated into the reaction zone.

In this case, the molar ratio of the p-toluic acid to the p-xylene in the steady state reaction will be in the range of about 3 to 15, depending mainly on the temperature. In other words, the reaction mixture will be in the diagram in the drawing in the area delimited by dashed lines. Obviously, this area is almost entirely in the · A band, ie it corresponds to the major part of the homogeneous solution.

It follows from the above that it is always possible to adjust the temperature and / or the temperature of the water as the solvent according to the invention in such a way that a Uomo system is obtained.

If the method according to. Continuously, it is preferable to use a process which is described by the inventor in U.S. Pat. No. 194,694.

Other circumstances should also be taken into account; since the desired product, terephthalic acid, is substantially insoluble in the reaction mixture, an amount of water must be added so as to be sufficient to obtain a workable suspension. However, it is not preferred that you use more water than for example 10% based on the amount of terephthalic acid dissolved at the working temperature. Another factor to consider is the reaction rate. Although it is possible in the process of the invention to carry out the oxidation reaction in an environment containing up to 80% of mono- or even more water, the presence of an excessive amount is present. of water may have the opposite effect on the reaction rate.

In addition, in some cases, part of the catalyst may lose your catalytic functions to form a black compound that precipitates from the oxidizing environment. Furthermore, a loss of part of the reactor capacity due to economics is disadvantageous. excessive and unnecessary water. Generally from these different. The causes of the water potential present in the system should not exceed 75% and preferably 60% of the mono-mineral reaction mixture.

The ocular reaction is preferably carried out at a temperature of at least 140 ° C. Below this temperature, it is difficult to have the reaction mixture in the form of a homogeneous solution. On the other hand, working above 220 ° C can result in excessive oxidation, unwanted side reactions and corrosion problems. In most cases, the reaction temperature is about 150-190 ° C.

The pressure is adjusted as a function of temperature. To maintain the reaction mixture in a liquid state at the operating temperature, a pressure sufficiently above atmospheric pressure must be used. Pressure above this value is usually preferred because it provides active oxidation. The normal pressure is about 0.5 to 4.0 MPa.

The ooidation catalyst used in the process of the invention may be a mixture of heavy metal compounds which comprises at least one metal compound from the group consisting of manganese and cobalt compounds, or mixtures thereof, provided that it is at least partially soluble in the aqueous reaction mixture or capable of forming a soluble or at least partially soluble compound with one of the reactants in this mixture.

The metal compounds which can be used in the catalytic mixture are expediently salts. Particular preference is given to salts of carboxylic acids, for example salts of acetic, naphthenic, toluic and the like. In addition to the cobalt and / or manganese compounds, the catalyst mixtures may contain compounds, and in particular, carboxylic acid salts formed with the γ-metal, which are commonly used in oxidation catalysts.

It is an essential feature of the present invention that the minimization of the catalyst concentration necessary to ensure oxidation in a homogeneous aqueous system depends on the relative potential of water and p-tartaric acid in the system. Indeed, in a homogeneous aqueous solution of p-toluic acid and optionally p-xylene and / or its partially oxidized derivative or partially oxidized derivatives thereof, oxidation cannot be carried out when the amount of active catalyst is less than the critical concentration M expressed in millimoles of metal · Compounds per 1 kg reaction mass ₍ given by the equation:

M = in tx + A) + Bx Cx + D (1).

where y represents the molar ratio of water to p-toluic acid, x represents the molar ratio. of manganese in the metal catalyst expressed in parts by weight relative to the total amount of msoigan and cobalt in the metal catalyst, ie ΙΕΓ + CÓ '

And it's about 0.200,

B ee юупо about 10.9,

Ί

C is about 4.35 and D is about 0.0724.

The amounts of A, B, C and D as indicated above are the result of the experimental determination and are therefore subject to measurement errors. Their size was calculated to be A = 0.200 ± 0.031, B = 10.9 ± 1.3, C = 4.35 * 0.17 and D = 0.0724 * 0.0117.

Consequently, the value of M calculated with the aid of. Equation (1) For a given value of y and should be considered an estimate of the critical concentration of that statistCckého terms contained in spolehlivossi range, whose center is M. As a ^ l ^ C ^ X ^ ^e r say in the art are aware, this confidence range depends on the values y and x used in the calculation of M, but for each individual case they can be calculated from the above data using the Ta ^ Lor formula. For example, decisive. the catalyst concentration will be in the confidence range

21.46 * 0.81 if y = 70 and x = 1.0 and 2.74-0.45 if y = 1 and x = 0.5.

The increasing catalyst concentration as defined above is at least the concentration that can be used under the given conditions. When using even smaller quantities! the process will take place. Of course, it is preferable to use in practice a pickling catalyst which scents them more than minimal. In fact, the rate of oxidation increases with increasing catalyst concentration. However, a catalyst concentration of greater than about 40 millimoles of metal compound per kg of reaction mixture is not economically advantageous. The catalyst is expediently used in a feed which is somewhat higher than the minimum amount M calculated from equation (1) and is at most about 30 ml per 1 kg of reaction mixture.

As can be seen from equation (1), the decisive concentration of the catalyst increases with the increase in the water concentration and with the decrease in the concentration of β-tic acid. In other words, for the oxidation of NO, it can be sieved in an aqueous solution, except that the concentration of p-toluic acid is above a critical value which increases as the concentration of the catalyst decreases. Thus, not only the catalyst but also the oleic acid are necessary for the oxidation to take place in the presence of a substantial amount of water.

*

In fact, thanks to the combination of the catalyst effect and the olefinic acid used in the right amounts. According to the present invention, it is abundant to oxidize p-xylene to terephthatic acid without the need to resort to the use of expensive and / or corrosive activators, such as bromine compounds. This effect of p-toluic acid is a completely unexpected feature of the present invention and other carboxylic acids, including acids of similar structure to benzoic acid, have the same properties.

It is further evident from equation (1) that the critical minimum catalyst concentration required to ensure oxidation progress in a homogeneous aqueous system also depends on the relative ratio of the maroga and cobalt compounds used in the catalyst. Manganese may appear to be clearly more effective than cobalt. For example, if the oxidation is carried out in a 50% aqueous solution of p-toluic acid (the molar ratio of water to p-toluic acid is 7.56), the minimum catalyst concentration required is 4.5 or 20.9 millimoles by 1 kg, whether manganese or cobalt is used as the catalyst itself.

For practical reasons, however, it is preferred to use a network of both metals since cobalt generally has a favorable effect on the reaction rate. In addition, it has been found that the use of a mixture of the compounds of mismanate and cobalt as a catalyst results in excessive oxidation and generally results in higher yields of terephthalic acid than when used. every metal alone.

For example, the combustion ratio (molar ratio of carbon dioxide produced by oxygen absorbed) is usually 0.06 to 0.09 in the first case, while in the second case the value of 0.15 is determined.

This beneficial effect of the simultaneous use of manganese and cobalt as a catalyst is a typical feature and further advantage of the present invention. If the reaction is carried out in a two-phase system in a homogeneous solution as in this procedure, a combustion ratio of 0.12 or higher is determined regularly, irrespective of whether manganese or cobalat or mixtures thereof are used. In most cases, the x-value in Equation (1) is about 0.1 and 0.9 to ensure active oxidation in a homogeneous aqueous medium and high yields of terephthalic acid.

For some practical reasons mentioned above, it may be advantageous to have a catalyst other than cobalt and / or manganese other metal components such as nickel, lead or cerium. Although such additional metals are necessary for oxidation to occur in a homogeneous aqueous medium, they may contribute to some practical improvement with respect, for example, to the purity of the product and the reaction rate.

A surprising feature of the present invention is that the minimum catalyst concentration to be used to provide oxidation in an aqueous environment can be calculated from equation (1) for the proper composition of the reaction mixture and this equation is not critical to the production parameter. such as temperature. This is illustrated by the results shown in Table 1, where M values obtained experimentally over a wide range of conditions are compared with those calculated from equation (11). Most of these results were determined by the following test method:

A corrosion-resistant iodo-cast autoclave equipped with a mechanical stirrer, heating mantle, gas inlet tube, bore and a liquid-intake pump is charged with various components that leave a reaction mixture during oxidation, i.e. p-toluic acid, water and water. catalyst. The mixture is then heated with stirring and air purging. Once the oxidation has started, an aqueous catalyst solution of the same amount is gradually injected into the reaction mixture. a catalyst such as that in the original reaction salt. As a result, the reaction mixture is gradually diluted with water without changing the catalyst concentration. P-xylene may also be present in the original sidis, provided that its concentration does not cause phase separation upon dilution of the reaction sidis with an aqueous catalyst solution.

The degree of oxidation is determined continuously by measuring the oxygen content of the off-gas using an oxygen analyzer. When the o-tuluoate acid concentration in the system is high enough to ensure effective oxidation of the selected catalyst catalyst, the reaction proceeds at a uniform rate which gradually decreases due to dilution. However, as soon as the decomposing concentration of p-olefinic acid is reached, the reaction rate drops rapidly to near zero. The injection was then discontinued and the reaction mixture analyzed.

The molar ratio of water to oleic acid to be determined is obviously the decisive value of γ1, as given by the catalyst, or vice versa, M is the minimization of the catalyst concentration which has been used for the next time. The oxidation reaction is mixed with a mixture in which the ratio between water and p-toluic acid is given as y. In fact, M still depends on the catalyst concentration, which can be expressed as the ratio of manganese to total manganese to coba- meate content in the rich catalyst bed (x equals 1).

Such assays are apparently exposed to experimental errors, so for a given ζζ ^ πΙ mixture (for a given yax) it is assumed that different M values will be obtained that will be statistically distributed around the actual value with the standard from the delta epic. The values thus determined for the different y and x _are given in the table below. From these data, it can be found. The standard deviation from M calculated from Equation (1) is 0.70. Similarly, a free experimental value M ^ which is not different from the calculated value by more than two standard deviations, i.e. more than 1.4, can be considered to be consistent with equation (1).

OF . The results shown in Table 1 below clearly show that:

1. equation (1) is valid for y and x (see, for example, experiments 1 and 7 for y and experiments 7 and 19 for x),

2. equation (1) is not dependent on oOoutouti or szpřítooisoti plχy] e e s (cf. experiments 8 and 13),

3. equation (!) Is independent of temperature (cf., for example, experiments 3 and 9),

4. equation (1) is independent of the presence of metals other than marngan and cobalt (cf.

for example, experiments no. 2 and 5).

Table 1

Experiment no. Temperature ReekSní mix y X M (% fa ^ onc) water p-xylene p-toluic acid found calculated 1 185 0.3 9.7 90.0 70.22 1.00 20.1 21.5 2 185 0.5 20.0 79.5 30.08 1.00 10.1 10.6 3 185 ', 5 45.7 52.8 8.76 1.00 5.1 4.8 4 170 0.4 10.6 89.0 63.54 1.00 20.0 19.7 5 170 0.6 23.5 75.9 24.38 1.00 (1) 9.0 9.1 (1) 6 170 '.4 43.5 · 55.1 9.60 1.00 5.1 5.1 7 170 0.1 61.3 33.6 4.76 1.00 3.7 3.8 8 170 11.6 76.6 11.8 1.17 1.00 3.1 (2) 2.8 9 160 1.3 42.6 56.1 9.95 1.00 5.1 5.2 10 170 1.3 44.4 54.3 9.25 0.79 5.2 5.1 11 170 0.3 23.0 76.7 25.21 0.50 10.1 10.3 12 170 0.2 10.8 89.0 62.34 0.46 21.7 22.2 13 170 0.0 41.8 58.2 10.53 0.46 5.5 5.8 14 160 0.5 43.9 55.5 9.57 0.46 5.5 5.5 15 Dec 170 0.5 24.3 75.2 23.46 0.33 10.1 10.6 16 170 0.3 27.0 72.7 20.39 0.25 . 10.1 10.2 17 170 0.4 30.4 69.2 17.23 0.17 10.1 10.1 18 170 0.5 35.3 64.2 13.77 0.09 10.1 10.7 19 Dec 170 5.4 60.5 34.1 4.27 0.00 '1,7 11, 8 20 May 170 0.8 74.9 24.3 2.45 0.00 6.1 6.8 21 170 0.0 81.4 18, .6 '73 0.00 3.9 4.8

1) An equimolar mixture of manganese acetate and nickel acetate was used as the catalyst. The calculation of x and M was made without regard to nickel.

2) The value found without dilution of the reaction mixture. The beneficial ratio of water to p-toluic acid was achieved by spontaneous consumption of p-toluic acid to produce water due to oxidation.

Earlier guidance on the selection of metal compounds that can be used to oxidize p-xylene and its partially oxidized derivatives to terephthalic acid is somewhat unsatisfactory. However, as a general rule, cobalt is the best catalyst, especially in the absence of a bromine compound as activator, and that manganese is less active, if not inactive. It has been found that ш п ^ О is for the oxidation of p-toluic acid. inactive (N. Ohta et al., Chem. Abssr. $ 6, 8 · 620 g, 1962) or even acts as an inhibitor (V. N. Aleksandrov et al., Kinet. Kaaal., 505, 1974).

In the eyes of the eye, it has a catalytic activity, but it stains the acid; if the water content is higher than 10% by weight of solvent, or the manganese content of the reaction mixture is high. It is therefore completely unexpected, ie in the way. According to the invention, it has a superior activity in carrying out an oxidation reaction which takes place in the presence of a large amount of water and gives terephthalic acid in high yield as a white crystalline precipitate which is particularly suitable for further purification up to the degree of purity required for polyester production. fibergrade.

The invention will be further described in the examples, which are given for illustrative purposes and are not intended to limit the scope of the invention.

Example 1

A one-liter, corrosion-resistant autoclave equipped with a mechanical stirrer with heating jacket, gas supply tube and orifice is introduced

p-xylene 45.0 £ p-toluic acid 137.5 G various oxidized p-xylene derivatives 4,5 ε water 63.0 ε manganese acetate 1.50 mrml cobalt acetate 1.74 mml

The reactor was pressurized with air to a pressure of 2.0 M 2 and the mixture mentioned above was heated with stirring and air supply at a flow rate of 92 liters per hour.

The batch above is mooární ratio of water to acid ^E Line ptoluic y = (63.0 x 136 151 // (18.02 x 187.5) = 2.54 and the ratio mooární №i / Mn + Co in the catalyst X = 1.50 / (1.50 * 1.74) = = 0.46 According to Equation (1), the minimum catalyst concentration required in this case to ensure oxidation is calculated from

2.54 (0.46 + 0.200) + 10.9 (0.46) M = ----------------------------- ---! ------- = 3.2 mmoo / kg.

4.35 (0.46) + 0.00724

In this example, the actual catalyst concentration is 10.8 millimoles per kg, i.e., about three times the minimum amount of skin. Indeed, the reaction starts spontaneously after heating and proceeds efficiently. As a result, a rapid rise in temperature is observed, which is maintained at 170 ° C by cooling.

After a reaction time of 180 minutes, oxygen is absorbed at 40.9 L (measured at room temperature and 0.1 ° C pressure). Inlet. The air is then discontinued and the pressure is gradually reduced in the reactor to remove unreacted .beta.-xylene by stripping with water vapor. The reactor is finally cooled and opened. The precipitate therein is filtered off, washed with water and dried under vacuum at about 80 ° C. The precipitate is then analyzed by combined methods including acidimetry, polarography, and steam bath clotting. In this way, it was found that 89.4% of feed p-xylene and 23.1% of feed p-toluic acid were converted to the following products:

terephthalic acid 90.2 g 4-carboxybenzaldehyde 8.8 g other intermediates 3.8 ^g heavy by-products 2,2 g.

Considering that 4-carboxybenzaldehyde and other intermediates would in fact be recirculated in a continuous process and their major part would eventually convert to terephthalic acid, the yield of terephthalic acid in such a continuous process would exceed forage more than 90 % molar, based on m-1 of the p-xylene consumed.

In another operation carried out under the same conditions, the hot reaction mixture is filtered, the resulting cake is further washed on the filter with hot water and dried under vacuum. Aialysis of the dry product shows that 3e consists (expressed in% by weight) of:

The color of this sample is determined by measuring the optical density of its solution in dilute ammonia, according to the method described in U.S. Patent 5,354,802, except that the vials are 5 centimeters instead of 4 centimeters. The optical density values thus determined are shown in Table 2 below and are compared to the optical density values determined for a commercial terephthalic acid sample having a purity of 99% by weight of terephthalic acid of p-toluic 4-carboxybenzaldehyde.

85.6%

9.6%

3.6%.

Table 2

Raw sample Optical density at (nm) Origin Purity (% by weight) 340 380 400

Made by according to the invention 85.6 0.428 0,102 0,076 Business product 99 ⁺ 0,726 0.183 0,111

Obviously, the crude sample obtained by this process by simple filtration and finally washing has better color characteristics than a commercial sample of terephthalic acid of much better purity. This raw sample is therefore particularly suitable for further purification up to the degree of purity required for the production of polyester fibers.

Example 2

The experiment was repeated as in the previous example, except that instead of 63.0 g of water, a mixture of 33.0 g of water and 30.0 g of acetic acid was used as solvent.

After 180 minutes of reaction, oxygen was absorbed in an amount of 39.7 L, i.e. about the same amount as in the previous example. The reaction mixture was then worked up and analyzed as described in the previous example. It was found that 88.0% of the metered p-xylene and 23.5% of the metered p-toluic acid were converted to the following products:

terephthalic acid 89.4 g 4-carboxybenzaldehyde 6.5 g other intermediates 4.8 g heavy by-products 3.2 g.

By the same method as in the previous example, it can be estimated that in a continuous operation under the conditions used in this example, the yield of terephthalic acid would be about 90% based on the p-xylene consumed.

As can be seen, these results are virtually identical to those of the previous example, where water was used as the sole solvent component.

Example 3

The experiment of Example 2 was repeated except that the acetic acid was replaced by the formic acid. The solvent used in this case therefore constitutes a mixture of:

water 33.0 g and formic acid 30.0 g.

After 180 minutes of reaction, oxygen is absorbed in a quantity of 35.7 L. By the same analytical procedure as in the previous examples, it was determined that 88.0% of feed p-xylene and 15.6% of feed p-toluic acid were converted to these products. :

terephthalic acid 66.7 g 4-carboxybenzaldehyde 6.8 g other intermediates 7.0 g heavy by-products 3.7 g.

By the same method as in the previous example, it can be estimated that, under continuous operation, under the conditions used in this example, the yield of terephthalic acid would be about 85% molar based on the p-xylene consumed.

Although these results are not as good as in the previous examples, it is shown that a large amount of formic acid can be allowed to react in the reaction mixture without serious effects on yield and reaction rate being found. This is particularly unexpected since in previous publications formic acid has always been described as an effective inhibitor of oxidation reactions. Since formic acid is always produced in these reactions, it should generally be avoided that some of its accumulation in the reaction mixture is laborious and costly.

In this procedure, formic acid is burned as determined by the fact that in this test 6.0 L of carbon dioxide was generated instead of 3.8 L as measured in the experiment of Example 1. Therefore, in the process of the invention no a special operation to remove formic acid from the reaction mixture.

Example 4

The experiment of Example 1 was repeated except that cobalt was used as the catalyst itself.

The actual dose is as follows: p-xylene 45,0 g p-toluic acid 190.1 g various oxidized derivatives 1.9 g water 63.0 g cobalt acetate 3,48 oioml. At this dose, y is 2.50 i x probably 0.00. Therefore, the refinement of cobalt provides · in this case the oxidation is

2.50 (0.200)

M = ------------- = 6.9 mmoo / kg.

0.0724

The co-ocetration of cobalt acetate in the initial salt is 11.6 oiliools per kg, about twice the amount of oil. After 180 minutes of reaction, oxygen is absorbed in the medium

The reaction mixture was then worked up and analyzed as described above. It provides that:

90.8% of the metered p-xylene and 19.5% of the metered p-toluic acid were converted to the following products:

terephthalic acid 74.2 g 4-carboxybenzaldehyde 6.8 $ other intermediate 1.5 g heavy by-products 3.7 g.

Comparing these results with those of Example 1, it is clear that less terephthalic acid was produced, although oxygen absorption was somewhat higher. It is estimated, as in the previous example, that the yield of terephthalic acid, which would be achieved in a continuous process, would be 81% instead of 90%. It clearly shows that the resulting yield is the result of ingestion of a mixture of manganese and cobalt, as catalyst, instead of cobalt samoon.

EXAMPLE 5.

The experiment of Example 1 was repeated except that manganese was used as the catalyst itself. The actual composition of the lot is as follows:

p-xylene 44.0 g p-toluic acid 182.8 g various oxidized derivatives 9.2 g water 66.0 g manganese acetate 3.00 mmol.

At this dose, y is 2.60 and apparently x is 1.00. Therefore, the minimum amount of meaogan to ensure oxidation is

2.60 (1.00 + 0.200) + 10.9 M = -------------------------- = 3.2 mmo / kg.

4.35 + 0.0724

In this case, the manganese concentration is 10.0 µg / kg, i.e., about three times the minimum grain size as in Example 1.

After 180 minutes of reaction, 25.3 liters of oxygen are absorbed, ie significantly less than in the previous examples. The reaction mixture is then worked up and analyzed as previously described. It was determined that 70.2% of the metered p-xylene and 5.8% of the metered ponic acid were converted into the following products:

terephthalic acid - 31.2 g 4-carboxybenzaldehyde 5.9 g other шо ^ ргкЪНу 6.3 g heavy by-products 5.1 g.

A comparison of these results with those of Examples 1 and 2 clearly demonstrates that less reactants are consumed and less terephthalic acid is produced. In addition, the yield of terephthanoic acid in the continuous process, determined from these data as in the previous examples, is only 69%. Although manganese is clearly more effective than cobalt to achieve oxidation in water (as verified by a lower value calculated for M as compared to the value calculated for ОоЬь11 alone), the use of manganese together with cobalt, as in Example 1, is a certain advantage, both the rate and yield of the reaction.

Example 6

The experiment of Example 1 was repeated except that in this case manganese was used together with nickel. The actual composition of the handle is as follows:

p-xylene 45,0 g p-toluic acid 182.8 g various oxidized derivatives 9,2 g water 63.0 g manganese acetate 1.50 mmol nickel acetate 1.50 mmol

At this dose, у is 2.60 and x is 1.00 as in the previous example, so L 1 is 3.2 millimoles per kg (nickel and e is not included in the M calculation). In this example, the manganese concentration is 5.0 millimoles per kg, i.e. a 1.8 fold excess over the minimum amount. The actual oxidation is active.

After 180 minutes, oxygen was absorbed at 29.2 L and the reaction mixture analyzed as described above. It was determined that 79.1% of feed p-xylene and 3.3% of feed p-toluic acid were converted to the following products:

terephthalic acid 35.6 g 4-carboxybenzaldehyde 6.6 g other intermediates 2.6 g heavy by-products 3.2 g.

A comparison of these results with those of the previous example shows that somewhat greater oxygen is absorbed and produces more terephthalic acid than when using manganese alone at a concentration twice as high as in this example. This shows that metals other than cobalt can be used together with manganese to increase the rate of reaction.

Example 7

The autoclave is dosed as in the previous example:

p-xylene 45,0 g p-toluic acid 218.5 g various oxidized derivatives 6,5 g water 30,0 g manganese acetate 0.52 mmol cobalt acetate 0.45 mmol. The molar ratio is at this dose water to p-toluic acid (s) 1.04 and the molar fraction of man-

gane in catalyst (x) is 0.46. According to equation (1), the minimum catalyst concentration that must be used to ensure oxidation of M = 2.7 millimoles per kg. The actual catalyst concentration in this example is 0.97 millimoles per 300 g of initial mixture or 3.2 mmol / kg, i.e. only 0.5 millimoles of excess above the minimum concentration. However, the onset of oxidation is spontaneous and is carried out actively. As a result, the temperature rises rapidly and is maintained at 170 ° C by controlled cooling.

After 395 minutes of reaction, 62.9 L of oxygen was absorbed. The air addition is then discontinuous. The composition of the reaction mixture was determined in the same manner as in Example 1.

It was determined that 98.8% of feed p-xylene and 29.2% of feed p-toluic acid were converted to the following products:

terephtaic acid 102.5 g 4-carboxybenzaldehyde 6.6 g others oc ^ p ^^^ y ^4.6 g heavy by-products 3.6 g.

As in Example 1, these data estimate the terephthalic acid yield that would be achieved in a continuous process where 80%, i.e., 10%, of the yield obtained was recirculated, ie 10% than the calculated yield. in Example 1. The main difference between the experiments is that in Example 1, the water content of the batch is 21% by hour, compared to only 10% by weight in this case. The resulting yield roildl can thus be considered as further illustrating the advantage of carrying out the oxidation of p-xylene in the presence of a substantial water, according to the invention.

Comparative example

The same amount of compounds as in the previous example were metered into the autoclave except that only 0.30 moles of acetate and 0.35 moles of cobalt acetate were used. The total metal catalyst concentration is therefore 2.2 millimoles per kg, i.e. 0.5 millimoles lower than the minimum quantity calculated in this previous example.

After heating the mixture in a stream of air under the same conditions as in the previous example, oxygen begins to absorb similarly, but after about 70 minutes absorption suddenly drops to a negligible level. Qty! absorbed oxygen is just 6.7 liters.

Example 8

The same autoclave as in Example 1 is dosed:

ad-d 45,0 g p-toluic acid 1187.5 g various oxidized derivatives 4.5 g water 63.0 g marnganous acetate 1.5 mmol Acetate ksbaltnltV 1.74 mnol.

As can be seen, this mixture is very close to the mixture dosed in cases 1 to 5, except that p-xylene is replaced by p-toluene-ddeo. the water to p-toluic acid ratio is again 2.54. According to equation (1), the minimum concentration of catalyst to be used to purify the oxidation is M = 3.2 oiliosl per kg. The actual catalyst concentration in this example is 10.8 pounds / kg, i.e. about three times as high.

This mixture is heated in the presence of air as before. The oxygen uptake begins to spontaneously at about ³⁰ ° C. The temperature of the NEC ^hook-walls and the gone to ^170C iFizeiým cooling. After 180 minutes of reaction, the amount is absorbed! 25.6 L of oxygen. The air is then added discontinuously. 180 µl of n-heptane was injected into the reactor to extract unreacted p-toluaddehyde while stirring and heating were continued. The resulting mixture is then cooled and the reactor is opened.

The precipitate contained is filtered, washed with n-heptane, dried under vacuum at 0 ° C, washed again with water and finally dried under vacuum at about 70 ° C.

The product is then analyzed by a sterile procedure as in the previous examples.

The filtrate and the wash liquid were dispensed and the heptane extract was decanted. An aliquot of this extract is analyzed by vapor-phase chromosolysis to determine unreacted p-toluaddehyde. The remaining portion was evaporated to dryness under vacuum and the residue analyzed by the same method as for the first precipitate.

From these different analyzes, it was determined that 99.9% of the dosed p-tolualdehyde α

10.7% of metering p-toluic acid was transferred to the following products:

terephthalic acid 58.4 £ 4-carboxybenzaldehyde 7. ’ £ other intermediates 6, ’ £ heavy by-products 5.4 £ ·

Comparative Example 1

The autoclave was dosed with the same amount of compounds as in the previous example except that only 0.3 mmol of both manganese acetate and cobalt acetate were used. The total catalyst concentration is therefore 2.0 millimoles per kg, ie 1.2 mmol lower than the minimum amount calculated from equation (1) ·

This mixture was heated in the presence of air under the same conditions as in the previous example. After 160 minutes of reaction, oxygen was only absorbed in an amount of 9.0 L. The reaction mixture was then worked up and analyzed as in the previous example. It was determined that the metered p-tolualdehyde was completely converted into the following products:

terephthalic acid 2.3 g p-toluic acid 3b7 g 4-carboxybenzaldehyde 3.8 g other intermediates 0,9 g heavy by-products 2,0 g.

Thus, it is clear that in this case p-tolualdehyde was mainly converted to p-toluic acid, without producing a significant amount of terephthalic acid.

Comparative Example 2

In this example, p-tolualdehyde is used as the oxidant itself. The actual dose is as follows:

p-tolualdehyde water manganese acetate cobalt acetate 225.0 g 75.0 g 1.50 mmol 1.50 mmol.

Upon heating of the mixture in the presence of air under the same conditions as in Example 8, oxygen is similarly started to absorb, but then its absorption is clearly slowed down. After about 240 minutes of reaction at 170 ° C, oxygen was absorbed in an amount of 29.6 L. Processing and analysis of the resulting reaction mixture as described above determined that 99.7% of the metered p-tolualdehyde was converted to the following products:

terephthalic acid 4.6 g p-toluic acid 171.4 g 4-carboxybenzaldehyde 4.6 g other intermediates ’> 3g heavy by-products 1.3 g

Here, it is clear that the main product of p-tolualdehyde oxidation is p-toluic acid and that only a small amount of terephthalic acid has formed. This result clearly illustrates

That p-toluic acid must be present in sufficient quantity at the beginning of the reaction to oxidize p-tolualdehyde to terephthalic acid according to the invention.

Example 9

The experiment of Example 8 was repeated except that cobalt acetate was used as the catalyst itself. According to equation (1), it can be calculated that the minimum cobalt concentration to be used in this case is M = 7.0 millimoles per kg. The actual cobalt catalyst concentration in this example is 11.6 millimoles per kg.

Oxygen absorption again begins at low temperature. Nevertheless, the mixture must be heated to maintain a temperature of 170 ° C. After about 210 minutes of reaction, oxygen is absorbed in an amount of 20.8 L. The reaction mixture is then worked up and analyzed as in the previous example. Thus, 99.9% of the metered p-tolualdehyde and 6.0% of the metered p-toluic acid were converted to the following products:

terephthalic acid 49,1 g 4-Kerboxybenzaldehyde 6.9 g other intermediates 6,5 g heavy by-products 6,3 g.

The comparative example of the previous example is swelled:

Into the same autoclave as in

p-tolualdehyde 69,6 g p-toluic acid 123.0 g various oxidized derivatives 3.0 g water 105.0 g cobalt acetate 3.48 mml

Thus the same amount of cobalt catalyst as above (11.6 mmol / kg) is used, but here the molar ratio of water to p-toluic acid is 6.45 instead of 2.54. The minimum cobalt catalyst concentration to be used in this case is therefore M - 17.8, ie 6.2 mmol more than the actual concentration present in the batch.

The mixture is heated in the presence of air. Here again, oxygen absorption immediately begins. However, after 45 minutes it drops to zero even though heating is continued at 170 ° C. After 300 minutes of reaction, only 10.0 L of oxygen was absorbed. The reaction mixture was then processed and analyzed as described in Example 8. It was determined that 90.1% of the metered p-tolualdehyde was converted to the following products:

terephthalic acid 3.7 g p-toluic acid 53,5 g 4-carboxybenzaldehyde 3.3 g other intermediates 0.7 g heavy by-products 6,6 g

Thus, it is apparent that p-tolualdehyde was mainly converted to p-toluic acid without significant formation of terephthalic acid.

Example 10

The same autoclave as in the previous example is dosed:

p-toluic acid various oxidized derivatives water cobalt acetate manganese acetate

214.3 g

1θ, 7 &

£ 75.0

1.74 mmol

1.50 mmol.

No p-xylene or p-tolualdehyde is used in this example. The molar ratio of water to p-toluic acid (y) is 2.64 and the molar fraction of manganese in the catalyst (x) is Sine 0.46, as in Example 1. The minimum catalyst concentration to be used as calculated from equation (1). M = 3.3 millimoles per kg. In this example, the actual catalyst concentration is 3.24 mmol per 300 g of reaction mixture or 10.8 millimoles per kg, i.e. about three times the minimum amount.

The mixture was heated in the presence of air under the same conditions as in Example 1.

In this case, the reaction starts again spontaneously. After 180 minutes of reaction, 19.4 L of oxygen was absorbed and the reaction was stopped by cooling. The autoclave was then opened and the precipitate contained therein was processed and analyzed as described in Example 1. It was determined that 33.2% was converted. p-toluic acid feed into the following products:

terephthalic acid 75,5 g 4-carboxybenzaldehyde 6,1 g other intermediates 8 g heavy by-products 3.7 g

The net yield of terephthalic acid, based on the converted p-toluovoy acid, is 87 mole%. However, taking into account oxidation intermediates such as 4-carboxybenzaldehyde, the actual yield of terephthalic acid that could be achieved in a continuous process where the intermediates are recirculated can be determined to be 97 mole%.

This example clearly demonstrates that in the process of the invention p-toluic acid can be effectively oxidized in high yield to terephthalic acid, even if p-xylene or some other readily oxidizable compound is present as a promoter.

Example 11

The same autoclave as in the previous example is dosed:

p-xylene 3,0 g p-toluic acid 142.6 g various oxidized derivatives 4.4 g water 150.0 g manganese acetate 1.05 mmol cobalt acetate 1.05 mmol

In this example, water constitutes 50% by weight of the starting mixture. The symbol у is 7.95 and x is probably 0.50. According to equation (1), the minimum catalyst concentration that must be used is M = 4.9. In this example, the actual catalyst concentration is 7.0 millimoles per kg, i.e., 2.1 mmol more than the minimum concentration.

Air is introduced into the reactor at a flow rate of 110 liters per hour, at a pressure of 20 bar, and the mixture is heated with stirring. When the temperature reaches about 170 ° C, a small amount of tert-butyl hydroperoxide is introduced to aid the start of the reaction. This causes the ae to absorb oxygen immediately. The temperature then rises rapidly and is maintained at 185 ° C by controlled cooling. After 30 minutes of reaction, oxygen is absorbed at 23.5 L. The reaction is then discontinued and the resulting mixture is processed and analyzed as in Example 1. It is determined that 95.0% of feed p-xylene and 40.3% of feed p- toluene was converted into the following products:

terephthalic acid 53,5 g 4-carboxybenzaldehyde 5.0 g other intermediates 1.6 g heavy by-products 1.6 g

Comparative example

The same experiment was carried out as in the previous example except that half the amount of each metal catalyst was used. The total catalyst concentration is therefore 3.5 millimoles by 1 kg, i.e. by 1.4 mmol, below the minimum amount.

The mixture was heated in příoomnoosi air under exactly the same conditions as in Example Uve ^d enérn above. Neabssrbuje ^IAD Nu is oxygen ^{even when} the mixture is at U is ^ ud ^p te 5 ture ^{of 18} ° C for 160 minutes, and despite two successive allowances butyl hydroperoxide to usnaadál start the reaction.

Taking into account the results obtained in the example above, where active and substantial oxidation occurred in the presence of a large carbohydrate. of water, it is clear that oxidation is only feasible if the right quinoa is killed. a catalyst as specified in the present invention.

Comparative Example 2 was the same experiment as in Example 11 except that part of the p-toluic acid was replaced with benzoic acid. The actual composition of the lot is as follows:

p-xylene p-toluic acid benzoic acid various oxidized compounds water manganese acetate cobalt acetate

3,0 g

44,5 g

93.9 g

2,0 g

156.6 g

1.05 mmol

1.05 mmol.

In this example, x is 26.59, so according to equation (1), the minimum catalyst concentration that must be used to catalyze the oxidation of the above mixture is 10.7 millimoles per kg, i.e., 3.7 moo more than it is actually present. Conversely, if benzoic acid has the same effect as p-toluic acid to provide oxidation in an aqueous environment, it can be taken into account in the calculation of y and Μ. In this case, y = (156.6 / 18.02) / (44.5 / 136.15 + 93.9 / 122.12) = 7.93 ie would have the same value as calculated for yv of Example 11 where active oxidation occurred.

Svrcto uvdddn ^and the mixture looks at the fence ¹⁸ ^ 5 ° ^C under the same conditions ^to .ja přtaladu 11 s and te are added again at a certain mrino ^! tert-butyl hydroperoxide to facilitate initiation. However, no significant oxidation will occur even though heating is continued for 180 minutes. This demonstrates that at least the benzoic acid does not have the same activity as the p-toluic acid as the oxidation promoter in the water as in the process of the invention.

Comparative Example 3 '

The same experiment as in Example 11 was repeated except that the p-toluic acid was not partially treated with acetic acid. The actual composition of the handle is as follows:

p-xylene3.0 g p-toluic acid 52.7 g acetic acid 55.2 g various oxidized compounds1 »3 g water 187.8 g

In this example, y is 26.92, so M is 10.8, i.e. roughly the same as in the previous Comparative Example. Here again, if acetic acid has the same promoting effect as p-toluic acid for oxidation in an aqueous medium, it can be taken into account for the calculation of y and M.

In this case, y = (187.2 / 18.02) / (52.7 / 136.15 + 55.2 / 60.05) = 7.95, ie it would be exactly the same as in the example 11.

manganese acetate cobalt acetate

1.05 mmol

1,05 mmml.

The mixture described above is heated to ¹⁸ ° C under the same heat as in Example 11, and a certain amount of water is added again here to facilitate initiation of the reaction. After 300 minutes of reaction, oxygen is absorbed in a quantity of only &gt; 3.8 l. This result again demonstrates that the promoting effect of p-toluic acid, as it appears in the process of the invention, cannot be achieved with certain carboxylic acids and -toluovou.

Example 12

The same autoclave as in the preceding examples is dosed:

p-xylene 6,0 g acid 188.23 g various oxidized whites 5 _t 7 g water 10550 g manganese acetate 1,80 oiooo

Here, y is equal to 4.33 and is co-manganese is used as a single catalyst, x = 1.00. Therefore, according to equation (1), the minimum manganese concentration to be used in this case is M = 3.6 millimoles per kg. In this example, the actual concentration of manganese is 6.0 mrml / kg, which well exceeds the minimum amount. .

The mixture is heated in the presence of air under exactly the same conditions as in Example ^11, with the extended rim ^{says that} U is ^a temperature maintained at ⁰ ° C V7 · place at ¹⁸⁵ ° C. ^P 3 ⁰ 5 minutes of reaction, the oxygen absorption mnnoství 21.2 1. After processing and analysis of the resulting reaction mixture has as in the previous examples, it is found that about 96% of the p-xylene and 29.9% dosed kyseeiny paratoluic transferred to the following products:

terephthalic acid 44,8 g 4-carbonylbenzaldehyde 14.2 g other meeiproducts 0,9 g heavy by-products 1.2 g

Comparative example

The same number of compounds as in the previous example was metered into the reactor except that only 0.60 mmml of acetate was used as the catalyst. of manganese. Its concentration in the mixture is therefore 2.0 millimoles per kg, ie 1.6 mnol lower than the minimum end-point. As a result, during heating for 60 minutes, oxygen uptake in the presence of air does not start under the same conditions as in the previous example, even after the addition of tert-butyl peroxide to facilitate the start of the reaction.

Example · 13

The same autoclave as in the previous example is dosed:

p-xylene

6.0 g p-toluic acid various oxidized derivatives water cobalt acetate

2'8,3 g

2,2 g

73,5 g

3.48 mmol.

In this example, cobalt is used as the only catalyst, hence x = 0. On the other hand, y is 2.54. According to equation (1), the minimum cobalt concentration to be used in this case is M = 7.0 oiliools per kg. In this example, the actual cobabate concentration is 11.6 mmoo / kg.

It is introduced into the reactor. air at a flow rate of 90 liters per hour at a pressure of 2.0 MPa. and the mixture is heated up to ¹⁷⁰ ° C. When the mixture is ^heated, the reaction starts with ^p variables on ^th e 240 continues at end of reaction is absorbed by oxygen in m ^ ^ oossi: d 29.8 1. After processing and assay of the reaction mixture of S as described in Example 1, provides that 89.3% of the metered p-xylene and 37.0% of the metered p-touuic acid were transferred to the following products:

teracetic acid 81.5 g

4-Caaoxybeozaldehyde 6.8 g other intermediates 1.2 g heavy by-products 3.0 g.

Comparative example

The same amount of compound as in the previous example was metered into the reactor, except that 0.90 mol of cobalt acetate was used as the catalyst. Its concentration in the mixture is therefore 3.0 oilimoles per kg, ie 40 mmol lower than the minimum concentration. As a result, oxygen uptake does not occur after the mixture has been heated for 240 minutes in the presence of air under the same conditions as in the previous example, nor after repeated addition of tert-butyl ethyl prtxil.

It is to be understood that the foregoing description of the basic novel features of the present invention is merely illustrative of the preferred embodiments. Those skilled in the art will recognize that a number of changes can be made. For example, in carrying out the process of the invention, at least one different compound used as an activator in other processes, for example an aldehyde or ketone, or even a bromine containing compound, may be added to the reaction mixture. Such additives may also be advantageous, for example with respect to the reaction rate. Such measurements, modifications, or modifications can be made within the scope of the invention without departing from the spirit thereof.

Claims (1)

SUBJECT OF THE INVENTION A process for preparing tzozftatové oxidation of p-toluic acid or a mixture of p-touuové and p-xylene and / or partially oxidized derivatives of p-xylene in the presence of water in ornitotorí at least 5% by weight ^to a scaled simply ^P ro ZTO ^ the processor ^sjspzoiz, řítomnotti oxtoačn in ^P ^ o ^ kataty warm tor ^ ^^ Whose but Jeto tatatyticty lktivo ^í ^ Nth compounds of manganese and / or cobalt compound and optionally a compound of nickel, lead and / or cerium gas ICIM oooeku OSCE ^ ary ^{with the PPR} YSL ^{Cart CZK} and rea the temperature of ¹ 40 and ^{Z 2} 2 ⁰ ° C and under "tl ^ u ^ í Just b ^^ ^the udraní alzt CAAT ^p with ⁿ in the ^soil in ^the ALN and ^{p s p} s ftoi reaction temperatures bore, ^L is Ujica in, ^that the catalyst is used in mrižto! polh bbjícío ^r in the range from the minimum M> M 0sSví oilioolů catalytically active metal compound per 1 kg of dripping Not Responding tmmst, přččemž M is given by equation 1,