Bisphenols are products of great industrial interest and are mainly used for the synthesis of numerous poly- meric materials and fine chemical products. They are products obtained from the condensation of two molecules of a phenolic compound with a molecule of a carbonyl com- pound. Among these, bisphenol A (4, 4'-isopropylidene bisphenol) is particularly important. Said bisphenol, a condensation product of acetone with phenol, is the main phenol derivative and has a rapidly expanding market (an- nual increase of 7-10%). Bisphenol A is mainly used for the preparation of polycarbonates and epoxy resins and also for fine chemical products such as fire-retardants.

Another bisphenol of industrial interest is bisphenol Z,

the condensation product of phenol with cyclohexane, which is used for the production of polycarbonate films.

Other bisphenols which are normally used are, for exam- ple: 1. o, o, o', o'-tetramethyl bisphenol A, which can be processed better than bisphenol A as it has, as polycarbonate, a lower viscosity in the molten state and a higher resistance to hydrolysis; 2.4, 4'bis (hydroxy phenyl) -pentanoic acid, used for binding resins based on polyesters to phenolic resins; 3. bisphenol A and Z containing an alkyl group in ortho position, which are used as drugs against chicken coccidiosis.

These compounds are currently synthesized using min- eral acids, mainly hydrochloric acid, or sulfonic ex- change resins as condensation catalysts. In the former case, the mineral acids, in addition to generating corro- sion problems due to the presence of a strong and concen- trated acid, are separated from the product at the end of the reaction cycle by means of neutralization with strong bases, obtaining the formation of large quantities of in- organic salts contaminated by aromatic products, which must be disposed of at the end of the process. The sulfo- nic resins allow separation problems to be overcome. Un-

fortunately however, their catalytic activity decreases with time, due to fouling phenomena or partial poisoning of the acid sites. When the residual activity cannot guarantee a correct running of the reaction, the resin must be substituted with fresh resin and the resin dis- charged can no longer be used and must be disposed of.

The substitution of these two types of acids with solid acids which can be easily regenerated, such as zeolites, is consequently greatly desirable both for environmental and plant safety reasons. Patent EP 265017 describes the condensation of aromatics with carbonyl products, such as, for example, the condensation of phenol with formal- dehyde, in the presence of zeolites belonging to the MFI family.

In Catalysis Letters 16 (1992) 431-435, A. P. Singh compares the activities of zeolites RE-Y, H-Y, H- mordenite, H-ZSM-5 with that of an ion exchange resin (Amberlyst-15) in the preparation of bisphenol A by the condensation of phenol with acetone. The tests are car- ried out at 90°C and at atmospheric pressure. The phenol conversions on RE-Y, H-mordenite, H-Y, H-ZSM-5 and Amber- lyst-15 proved to be 4.61, 2.88, 0.51, 0.42 and 20. 14% respectively. The zeolites tested therefore showed a much lower reactivity with respect to that of the sulfonic resins. Bisphenol A is the main reaction product, fol-

lowed by 2, 4'-isopropylidene biphenol (ortho isomer).

Chromans, which are condensation by-products of the ortho isomer with a second acetone molecule, are formed in quite a significant quantity, ranging from 4.6 to 15% by weight. These condensation products prove to be harmful, as in addition to decreasing the reaction yield, they contain only one free hydroxyl group. These compounds consequently interrupt the growth of the polymeric chain, in the synthesis of polycarbonates, thus lowering the mo- lecular weight of the polymer produced and therefore de- . teriorating its quality.

JP 11269113 describes the use of a zeolite, in par- ticular beta zeolite, in the condensation of phenol with formaldehyde to give bisphenol F: formaldehyde is an ex- tremely reactive carbonyl product and the condensation can be easily carried out under rather mild reaction con- ditions.

Patent application MI 2001A001143 describes a process for preparing bisphenol compounds which comprises the condensation of a carbonyl compound containing at least two carbon atoms with an aromatic compound containing a hydroxyl group and having at least one hydrogen atom bound to the aromatic ring, in the presence of a zeolite having a spaciousness index higher than or equal to 8, at a temperature ranging from 120 to 250°C and a pressure

higher than atmospheric pressure.

The Applicant has now found that beta zeolite, as such or isomorphically substituted with gallium, iron or bo- ron, gives better performances than those described in the prior art and it is also active in the condensation of phenol compounds with carbonyl compounds having a much lower reactivity than that of formaldehyde.

An object of the present invention therefore relates to a process for preparing bisphenol compounds which com- prises the condensation of a carbonyl compound containing at least two carbon atoms with an aromatic compound con- taining a hydroxyl group and having at least one hydrogen atom bound to the aromatic ring, in the presence of a catalyst containing a beta zeolite or a beta zeolite modified by partial or total isomorphic substitution of the aluminum of the zeolite with boron, iron or gallium, said process being carried out at a pressure lower than, equal to or higher than atmospheric pressure, on the con- dition that, when the pressure is higher than atmospheric pressure, the temperature is lower than 120°C.

Beta zeolite is described for the first time in US 3,308, 069 and corresponds to the formula (x/n) M (1+0. 1-x) Z | AlO2 Y SiO2 W H20 wherein x is lower than 1, preferably lower than 0.75, y ranges from 5 to 100, w ranges from 0 to 4, M is a metal

of group IA, IIA and IIIA or a transition metal, n is the valence of M, Z is hydrogen, ammonium ion or an organic cation. A beta zeolite containing controlled quantities of sodium, potassium, calcium or nickel, is described in EP 629599.

Modifications of beta zeolite obtained by partial or total isomorphic substitution of the aluminum of the zeo- lite with boron, iron or gallium described in BE 877205 and EP 55046 can also be appropriately used in the proc- ess of the present invention.

In the process of the present invention, the zeolite is used as such or bound with a binder selected from alu- mina, silica and zirconia.

The use of the zeolite in its acid form, i. e. in the form in which the majority of the cationic sites of the zeolite are occupied by hydrogen ions, is a particularly preferred aspect of the present invention. Zeolite beta in acid form is preferably used.

The zeolites adopted in the present invention, in particular beta zeolite, can be advantageously used in the form bound by an inorganic binder, as described in EP 687500 and EP 847802. In particular, the catalyst de- scribed in EP 687500, including these zeolites, in par- ticular beta zeolite, bound by an inorganic binder, is characterized in that its extra-zeolite porosity, i. e.

the porosity obtained by adding the mesoporosity to the macroporosity of the catalytic composition, is such to be made up of pores with a radius higher than 100 A for a fraction of at least 25%.

The catalyst described in EP 847802, comprising these zeolites, in particular beta zeolite, bound by an inorganic binder, having an extra-zeolite porosity con- sisting of pores with a radius higher than 100 A for a fraction of at least 25%, is characterized by a total volume of extra-zeolitic pores higher than or equal to 0.80 ml/g.

Aromatic compounds containing a hydroxyl group and having at least one hydrogen atom bound to the aromatic ring, which can be advantageously used in the process of the present invention are those represented by the fol- lowing general formula: wherein the substituents Ri, R2, R3, R4 and Rg, the same or different, are selected from H, a linear alkyl con- taining from 1 to 6 carbon atoms and a branched or cyclic

alkyl containing from 3 to 6 carbon atoms, and wherein at least one of these substituents is hydrogen.

Phenol, cresol and xylenol are preferably used.

The carbonyl compound used is selected from alde- hydes and ketones, and is preferably a compound having the general formula wherein R6 is selected from a linear alkyl containing from 1 to 6 carbon atoms, a branched or cyclic alkyl con- taining from 3 to 6 carbon atoms, an aryl and substituted aryl group; and wherein R7 is a hydrogen or has the same meaning as R6 ; or R6 and R7 together form a bivalent radical contain- ing 4 or 5 carbon atoms, closed as a ring on the carbonyl carbon atom.

The use of acetaldehyde, benzaldehyde, acetone, methyl ethyl ketone, cyclohexanone and benzophenone as carbonyl compounds, is a particularly preferred aspect of the present invention.

According to a particularly preferred aspect of the present invention, two phenol molecules are condensed with an acetone molecule in the presence of beta zeolite, as such or isomorphically substituted with gallium, iron or boron, to give bisphenol A. Zeolite beta is preferably

used.

A preferred aspect of the present invention, is also to prepare bisphenol Z (4,4'cyclohexylidene-bisphenol) by condensing two molecules of phenol with a molecule of cyclohexanone, in the presence of zeolite beta as such or isomorphically substituted with gallium, iron or boron.

Zeolite beta is preferably used.

The process, object of the present invention, is preferably carried out at a pressure which is equal to or lower than atmospheric pressure, more preferably at at- mospheric pressure. When a pressure equal to or lower than atmospheric pressure is used, the temperature pref- erably ranges from 50°C to 250°C, preferably from 90 to 180°C. When a pressure higher than atmospheric pressure is used, the temperature is preferably higher than 90°C.

The condensation takes place in liquid or mixed phase and it is also possible to operate in the presence of a solvent selected from toluene, xylene or trimethyl benzene.

The aromatic compound containing a hydroxyl group is reacted with the carbonyl compound in a molar ratio of between 2.2 and 15, preferably 2.5 and 7.

The process can be carried out batchwise, in semi- continuous or continuous: under semi-continuous condi- tions, the carbonyl compound is gradually added in order

to maintain a high aromatic compound/carbonyl compound ratio in the reactor containing the catalyst and aromatic compound.

Under continuous conditions, the aromatic compound containing the hydroxyl group and carbonyl compound are fed contemporaneously into the reactor containing the catalyst. The product and excess reagent, i. e. the aro- matic compound containing the hydroxyl group and at least one hydrogen atom bound to the aromatic ring, are then continuously discharged from the reactor.

In order to maintain a high aromatic com- pound/carbonyl compound ratio, the catalyst can be dis- tributed in a reactor on several catalytic layers, and the feeding of the carbonyl compound partialized at the beginning of each layer, whereas the feeding of the aro- matic compound containing the hydroxyl group and at least one hydrogen atom bound to the aromatic ring, is prefera- bly effected at the beginning of the first layer.

A particular object of the present invention relates to a process for the production of bisphenols which in- cludes the reaction of a phenolic and a carbonyl com- pound, in the presence of beta zeolite, as such or iso- morphically substituted with gallium, iron or boron, at a pressure equal to or lower than atmospheric pressure, continuously discharging the reaction water and the water

possibly contained in the reagents. Beta zeolite is pref- erably used.

A particularly preferred aspect of this method con- sists in contemporaneously feeding a solvent together with the carbonyl compound and aromatic compound contain- ing a hydroxyl group, giving an azeotropic minimum with water.

A process configuration is based on the use of slurry reactors, both stirred and bubbled. Both the re- agents and the catalyst can be contemporaneously fed into said slurry reactor. The feeding can also be in continu- ous or the addition of one or more components of the re- action mixture can be partialized over a period of time.

The operating pressure is equal to or lower than the atmospheric value, at a reaction temperature ranging from 50 to 250°C, preferably from 90 to 180°C, whereas the wa- ter formed during the reaction and that possibly ini- tially contained in the reagents, is continuously re- moved, for example by means of a suitable distillation system connected to the reactor.

The catalyst/charge weight ratio is between 1/20 and 1/300.

A further process configuration is based on the use of reactive column reactors, on whose trays there is the catalyst, including a beta zeolite or a beta zeolite iso-

morphically substituted with gallium, iron or boron, and the carbonyl compound is preferably fed to the bottom of the column, together with the aromatic compound contain- ing the excess of the hydroxyl group. Water, which is a reaction product, condenses at the head of the column, whereas the aromatic substrate-containing the hydroxyl group in which the bisphenol compound produced during the reaction is dissolved-is collected at the bottom of the column.

With a suitable number of theoretical trays, which can be easily calculated by an expert in the field, a complete conversion of the carbonyl compound is obtained.

A preferred aspect of the above reactor configurations consists in feeding a solvent, together with the carbonyl compound and aromatic compound containing a hydroxyl group, giving an azeotropic minimum with water.

A particular aspect of the present invention is to use the process configuration described above, based on the use of reactive column reactors on whose trays the catalyst, containing the zeolite, preferably beta zeo- lite, is present, for the condensation of phenol with acetone. Water condenses at the head of the column, whereas the phenol in which the bisphenol A produced dur- ing the reaction, is dissolved, is collected at the bot- tom of the column. With a suitable number of theoretical

trays, the complete conversion of acetone can be ob- tained. According to a preferred aspect of this reactor configuration, a solvent is also fed together with phenol and acetone, which gives an azeotropic minimum with wa- ter, preferably toluene.

Toluene gives an azeotropic minimum with water (79. 8% toluene, 20. 2% water) which boils at 85°C. The wa- ter-toluene azeotropic mixture is collected at the head of the column, as its boiling point is much lower than that of water (100°C) and also of the water-phenol azeotropic mixture (99. 52°C, with 90. 79% water and 9. 21% phenol): the water is therefore removed from the reaction equilibrium and the total conversion of acetone to bisphenol A is obtained, with a number of theoretic trays in the column lower than that necessary for the same con- version in the absence of toluene.

Furthermore, as the water-toluene azeotropic mixture demixes at room temperature, the water produced is elimi- nated and toluene is recycled to the column, according to the plant scheme shown in Fig. 1. In this figure: 1 represents the phenol flow at the inlet, 2 represents the acetone flow at the inlet, 3 the phenol flow at the out- let, containing bisphenol A, 4 represents the flow of toluene coming from the demixed azeotropic mixture, which is fed again to the column, and 5 represents the flow of

water demixed from the azeotropic mixture, which is eliminated.

The zeolite used in the process of the present in- vention, once exhausted or even only partially deacti- vated, can be regenerated by means of thermal treatment at high temperature (500-600°C) in an oxidizing environ- ment (oxygen or air). This, in fact, allows the combus- tion of the pitches present in the zeolite pores and the regeneration of the material under such conditions as to enable it to be used again in the reaction.

According to a further aspect of the present inven- tion, the catalyst based on beta zeolite as such or iso- morphically substituted with gallium, iron or boron, or beta zeolite containing sodium, potassium, calcium or nickel, used in the process of the present invention for the preparation of bisphenols through the reaction of an aromatic compound containing a hydroxyl group with a car- bonyl compound, under the above described conditions, once deactivated as a result of the pitches, can be re- generated by means of heat treatment with a suitable aro- matic compound.

This treatment not only removes the soluble compo- nent of the pitches, but also chemically degrades the in- soluble pitches by means of a reactive process: the aro- matic compound reacts with the pitches, probably through

a series of alkylation and/or trans-alkylation reactions catalyzed by the same zeolitic material, transforming the pitches into molecules characterized by a lower molecular weight, soluble in the aromatic compound and, above all, capable of being diffused through the zeolitic pores.

The zeolite catalyst coming from the process for the preparation of bisphenols according to the present inven- tion can consequently be regenerated by treating the ex- hausted catalyst with an aromatic compound containing at least one substituent selected from OH, NH2, NHR, NR2, OR, NHCOR, in at least partially liquid phase and at a temperature equal or higher than that at which the proc- ess for the preparation of bisphenols, from which the ex- hausted catalyst derives, has been carried out.

Aromatic compounds suitable for this treatment are: aromatic compounds containing at least one activating group on the aromatic ring, preferably phenolic com- pounds, and even more preferably aromatic compounds hav- ing general formula:

wherein the substituents RI, R2, R3, R4 and R5, the same or different, are selected from H, linear alkyl contain- ing from 1 to 6 carbon atoms and branched or cyclic alkyl containing from 3 to 6 carbon atoms, and wherein at least one of these substituents is hydrogen.

Phenol, cresol and xylenol are preferably used.

A preferred aspect of the present invention is that the aromatic compound used for the regenerating treatment is the same as the aromatic compound containing a hy- droxyl group of the preparation process of bisphenols from which the catalyst to be regenerated derives.

The temperature at which the regenerating treatment can be carried out ranges from 180 to 350°C, preferably from 250 to 350°C. The treatment is carried out during a time ranging from 6 to 30 hours, preferably from 8 to 24 hours, at a pressure of between 2 and 25 atm, preferably between 5 and 10 atm.

The regeneration process is preferably carried out at a higher temperature with respect to the temperature of the process for the preparation of bisphenols, from which the exhausted catalyst derives.

The regeneration process can be effected by recover- ing the exhausted catalyst from the preparation reactor of bisphenols and subjecting it to regenerating treatment with the selected aromatic compound in a specific reac-

tor, a preferred aspect of the present invention, how- ever, is that the regeneration process of the catalyst at least partially exhausted, is carried out in the same re- actor as that used for the preparation of bisphenols, by feeding the aromatic compound selected for the regenerat- ing treatment, after suspending the feeding of the re- agents used for the synthesis of bisphenols. This embodi- ment is particularly convenient and preferred when the reactor for the synthesis of bisphenols is a continuous reactor, even more preferably a continuous reactor with a fixed catalytic bed, or in the case of a reactive column.

When the regeneration process of the at least par- tially exhausted catalyst is carried out in the same re- actor as the synthesis of bisphenols, a particularly pre- ferred aspect of the present invention is to use, as aro- matic compound for the regenerating treatment, the same hydroxylated aromatic substrate as the synthesis process of bisphenols, after suspending the feeding of the car- bonyl compound to the reactor. When the synthesis is ef- fected in the presence of a solvent, the feeding of the solvent to the reactor is also suspended.

This embodiment, in which the same hydroxylated aro- matic substrate of the synthesis process of bisphenols is used, is particularly convenient and preferred when the reactor for the preparation of bisphenols is a continuous

reactor, even more preferably a fixed catalytic bed con- tinuous reactor, or a reactive column. In practice, ac- cording to this particular embodiment in continuous of the regeneration process of the present invention, when the zeolite catalyst used in the synthesis process of bisphenols of the present invention is exhausted, the feeding flow of the carbonyl compound to the alkylation reactor is suspended, whereas the flow of the aromatic substrate containing the hydroxyl group continues to be fed to the reactor, possibly by raising the temperature of the catalytic bed if the regeneration treatment is to be effected at a higher temperature with respect to that of the synthesis process of bisphenols. A preferred as- pect is to feed the flow of the aromatic substrate con- taining the hydroxyl group to the reactor in counter- current. When the regeneration process is concluded, the carbonyl compound is re-fed in order to restart the syn- thesis process of bisphenols, after possibly cooling the catalytic bed.

According to a preferred aspect of the present in- vention, an exhausted catalyst based on beta zeolite is regenerated in the same synthesis reactor as bisphenol A, using the phenol flow.

In all cases in which the regeneration is effected in the same reactor as the synthesis of bisphenols, and

said reactor is in continuous, the WHSV preferably ranges from 0.1 to 20 hours~1, even more preferably from 1 to 10 hours-'.

In accordance with the above, a further aspect of the present invention relates to a process for the prepa- ration of bisphenols comprising the following steps: a) condensation of a carbonyl compound containing at least two carbon atoms with an aromatic compound containing a hydroxyl group and having at least one hydrogen atom bound to the aromatic ring, in the presence of a beta zeolite or a beta zeolite isomorphically substituted with gallium, iron or boron, at a pressure lower than, equal to or higher than atmospheric pressure, on the condi- tion that when the pressure is higher than the atmospheric value the temperature is lower than 120°C, until said catalyst shows at least partial deactivation; b) interruption of the feeding of the carbonyl com- pound and treatment of said deactivated catalyst feeding only the aromatic substrate containing the hydroxyl group, in at least partially liquid phase, at a temperature at least equal to, and preferably higher than the temperature of the condensation process of step (a) until the cata-

lyst has been regenerated; c) restarting of the feeding of the carbonyl com- pound after re-establishing the pressure and tem- perature conditions used in the condensation of step (a).

The multi-step process described above is preferably used for the preparation of bisphenol A through the reac- tion of phenol with acetone in the presence of a cata- lytic composition containing beta zeolite which is regen- erated in the same synthesis reactor as bisphenol A, us- ing the phenol flow.

EXAMPLE 1-SYNTHESIS OF ZEOLITE BETA 58,8 g of tetraethyl ammonium hydroxide at 40% weight in a water solution and 1.9 g of sodium aluminate (56% of A1203) are added to 58.4 g of demineralized wa- ter. The mixture is heated to about 80°C and is left un- der stirring until complete dissolution.

The limpid solution thus obtained is added to 37.5 g of LUDOX HS colloidal silica at 40% weight of Si02. A ho- mogeneous suspension is obtained, having a pH equal to 14, which is charged into a steel autoclave and crystal- lized under hydrothermal conditions at 150°C for 10 days, under static conditions and autogenous pressure.

The crystallized product is separated by filtration, re-dispersed in demineralized water and re-filtered. A

humid panel of zeolite is obtained, containing the or- ganic templating agent tetraethyl ammonium and sodium.

The humid zeolitic panel, prepared as above, is dried in an oven for 1 hour at 150°C, calcined in a muf- fle for 5 hours at 550°C in an air flow.

The calcined solid is dispersed in a water solution of ammonium acetate for ion exchange. This zeolite in am- monia form is calcined in a muffle for 5 hours at 550°C in an air flow, obtaining beta zeolite in acidic form.

Upon elemental chemical analysis, the sodium residue of this zeolite proves to be 106 ppm whereas the aluminum content is equal to 3. 14% ( [Al]/ [Na] = 252). This zeolite has a SiO2/Al203 molar ratio of 25.

The product is characterized by X ray diffraction from powders.

EXAMPLE 2-SYNTHESIS OF BISPHENOL A WITH BETA ZEOLITE Bath test at atmospheric pressure 9.4 g of phenol (0.1 moles) and 1.16 g of acetone (0.02 moles) with a phenol/acetone molar ratio of 5/1, and 1 g of beta zeolite prepared according to example 1, are charged into a glass flask, equipped with a stirrer and water cooler, immersed in a thermostat-regulated oil bath. The above suspension is maintained under stirring for 12 hours, at atmospheric pressure (1 atm), with a bath temperature of 120°C.

At the end the mass is cooled down to room tempera- ture. The reaction product is analyzed by means of HPLC, with the analysis method described in Journal fur Prak- tische Chemie, Band 328, Heft 1,1986, pp. 142-148.

Acetone conversion: 99. 9% Selectivity to p, p'bisphenol A: 63. 20% Selectivity to o, p'bisphenol A: 16. 54% Selectivity to trimers and heavy products: 20.14% Selectivity to mesityl oxide (undesired by-product) lower than the analytical limit (0.01%).

EXAMPLE 3-SYNTHESIS OF BISPHENOL A WITH BETA ZEOLITE Bath test, at atmospheric pressure with extraction in continuous of the water formed 9.4 g of phenol (0. 1 moles) and 1.16 g of acetone (0.02 moles) with a phenol/acetone molar ratio of 5/1, and 1 g of beta zeolite prepared according to example 1, are charged into a glass flask, equipped with a stirrer and Dean-Stark trap with a water cooler, immersed in a thermostat-regulated oil bath. The suspension described above is maintained under stirring for 6 hours with a bath temperature of 120°C. The system is at atmospheric pressure (1 atmosphere).

The toluene-water azeotropic mixture formed during the reaction is continuously removed by means of the Dean- Stark trap. Said azeotropic mixture demixes at room tem-

perature: the aqueous phase is removed, whereas toluene is re-fed to the flask.

At the end the mass is cooled down to room tempera- ture. The reaction product is analyzed by means of HPLC, with the analysis method described in Journal fur Prak- tische Chemie, Band 328, Heft 1,1986, pp. 142-148.

Acetone conversion: 99. 9% Selectivity to p, p'bisphenol A: 72. 31% Selectivity to o, p'bisphenol A: 11. 43% Selectivity to trimers and heavy products: 16.16% Selectivity to mesityl oxide (undesired by-product) lower than the analytical limit (0. 01%).