The present, invention relates to a process for prepar- ing bisphenols which comprises reacting an aromatic com- pound containing a hydroxyl group with a carbonyl compound in the presence of a zeolite characterized by a spacious- ness index equal to or higher than 8.

Bisphenols are products of great industrial interest and are mainly used for the synthesis of numerous polymeric materials and fine chemical products. They are products de- riving from the condensation of two molecules of a phenolic compound with a molecule of a carbonyl compound. Among these, bisphenol A (4,4'-isopropylidenediphenol), is par- ticularly important. This bisphenol, which is a condensa- tion product between acetone and phenol, is the main de- rivative of phenol and has a rapidly expanding market (yearly increase of 7-10%). Bisphenol A is mainly used for the production of polycarbonates and epoxy resins and also for fine chemical products as flame retardants. Another bisphenol of industrial interest is bisphenol Z, the con-

densation product between phenol and cyclohexanone, which is used for the production of polycarbonate films.

Other bisphenols used are, for example: 1. o, o, o', o'-tetramethylbisphenol A which can be proc- essed better than bisphenol A in that, as a polycar- bonate, it has a much lower viscosity in the molten state and a greater resistance to hydrolysis; 2.4,4'bis (hydroxyphenyl)-pentanoic acid, which is used for binding resins based on polyesters to phenolic resins; 3. Bisphenols A and Z containing an alkyl group in ortho which are used as drugs against coccidiosis in poul- try.

These compounds are, currently synthesized using min- eral acids, especially hydrochloric acid, or sulfonic ex- changer resins, as condensation catalysts. In the former case, mineral acids, in addition to creating possible prob- lems of corrosion due to the presence of strong and concen- trated acid, at the end of the reaction cycle must be sepa- rated from the product by neutralization with strong bases, obtaining the formation of considerable quantities of inor- ganic salts contaminated by aromatic products, which must be disposed of at the end of the process. Sulfonic resins overcome these problems relating to separation. Unfortu- nately however, their catalytic activity decreases with

time due to the effect of fouling phenomena or the partial poisoning of the acid sites. When the residual activity is no longer such as to guarantee a correct running of the re- action, they must be substituted with fresh resin and the resin discharged can no longer be re-used and must be dis- posed of. The substitution of these two types of acids with solid and easily regenerable acids, such as zeolites, is therefore greatly desired both for environmental reasons and for the safety of the plant.

The patent EP 265017 describes the condensation of aromatics with carbonyl compounds such as, for example, the condensation of phenol with formaldehyde, carried out in the presence of zeolites belonging to the MFI group. A. P.

Singh compares in"Catalysis Letters 16 (1992) 431-435, the activity of RE-Y, H-Y, H-mordenite, H-ZSM-5 zeolites with that of an ion exchange resin (Amberlyst-1. 5) in the prepa- ration of bisphenol A by the condensation of phenol with acetone.

The tests are carried out at 90°C. and at atmospheric pressure. The conversions of phenol with respect to RE-Y, H-mordenite, H-Y, H-ZSM-5, and Amberlyst-15 are respec- tively 4. 61,2.88,0.51,0.42 and 20.14%. The zeolites tested consequently have a much lower reactivity than that of sulfonic resins. The main reaction product is bisphenol A, followed by 2,4'-isopropylidenediphenol (ortho isomer).

Chromanes, which are condensation by-products of the ortho isomer with a second acetone molecule, are formed in sig- nificant quantities, ranging from 4.6 to 15% by weight.

These condensation products are harmful as they not only lower the reaction yield, but also contain only one free hydroxyl group. In the case of the synthesis of polycarbon- ates, these compounds consequently interrupt the polymeric chain growth, lowering the molecular weight of the polymer formed, thus causing a deterioration in quality.

The use of a zeolite, in particular beta zeolite, in the condensation of phenol with formaldehyde to give bisphenol F is described in JP 11269113: formaldehyde is an extremely reactive carbonyl compound and the condensation can be easily effected under rather bland reaction condi- tions.

The applicant has now found that zeolites character- ized by a spaciousness index equal to or higher than 8, used under suitable reaction conditions, give higher per- formances than those described in the prior art and are also active in the condensation of phenolic compounds with carbonyl compounds having a much lower reactivity than that of formaldehyde.

The object of the present invention therefore relates to a process for preparing bisphenol compounds which com- prises subjecting a carbonyl compound, containing at least

two carbon atoms, to condensation with an aromatic compound containing a hydroxyl group and having at least one hydro- gen atom bound to the aromatic ring, in the presence of a catalyst containing a zeolite having a spaciousness index greater than or equal to 8, at a temperature ranging from 120 to 250°C and a pressure higher than the atmospheric value.

The spaciousness index is a parameter which provides a real measurement of the pore amplitude of materials such as zeolites and is described in"Zeolites and Related Micropo- rous materials: state of art 1994", Studies in surface sci- ence and catalysis, vol. 84, (1994), page 37 onwards. The following table taken from U. S. 4,795,847, is also provided for illustrative purposes Zeolite Spaciousness index Y 21 ZSM-20 21 Beta 19 L 17 MCM-22 = ERB-1'8 Mordenite 7 NU-1 5 Offretite 5 ZSM-12 3 ZSM-5 t 1 ZSM-22 1

Zeolites which can be well used in the process of the present invention are zeolites belonging to the BEA, FAU, MWW and LTL groups.

In particular, belonging to the BEA group is beta zeo- lite, described for the first time in U. S. 3,308,069, hav- ing the formula [ (x/n) M (1 0.1-x) Z] A102 Y sio2 W H20 wherein x is less than 1, preferably less than 0.75,. Y var- ies from 5 to 100, W varies from 0 to 4, M is a metal of group IA, IIA and IIIA or a transition metal, n is the va- lence of M, Z is hydrogen, an ammonium ion or organic ca- tion.

Modifications of beta zeolite obtained by partial or total isomorphous substitution of the aluminum of the zeo- lite with boron, iron or gallium, described in BE 877205 and EP 55046, also belong to the BEA group, together with beta zeolite containing controlled quantities of sodium, potassium, calcium or nickel described in EP 629599.

Zeolites of the FAU group preferably used are Y zeo- lite, described for the first time in U. S. 3,130,007 and ZSM-20 zeolite, described in U. S. 3,972,983, and a particu- larly preferred aspect is the use of Y zeolite.

Zeolites of the MWW group preferably used are MCM-22, described for the first time in U. S. 4,954,325 and ERB-1 described for the first time in EP 293,032.

The zeolite of the LTL group preferably used is L zeo- lite, described in U. S. 3,216,789.

The zeolites used in the process of the present inven- tion are in acid form, i. e. in the form in which most of the cationic sites are occupied by hydrogen ions.

These zeolites can be used as such or bound with a li- gand selected for example from alumina, silica, zirconia and magnesia.

A particularly preferred aspect of the present inven- tion is to use beta zeolite, in acid form.

The beta zeolite can be advantageously used in the form bound with an inorganic ligand as described in EP 687500 and in EP 847802. In particular, the catalyst de- scribed in EP 687500, comprising a beta zeolite bound with an inorganic ligand, is characterized in that its extra- zeolitic porosity, i. e. the porosity obtained by summing up the mesoporosity and macroporosity of the catalytic compo- sition itself, is such as to consist of a fraction of at least 25% of pores with a radius higher than 100 A.

The catalyst described in EP 847802, comprising a beta zeolite bound with an inorganic ligand, having an extra- zeolitic porosity consisting of a fraction of at least 25% of pores with a radius higher than 100 A, is characterized by a total volume of extra-zeolitic pores greater 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 conveniently used in the present inven- tion are those represented by the following general for- mula: wherein the substituents Rl, R2, R3, R4 and R5, the same or different, are selected from H, linear alkyl containing from 1 to 6 carbon atomsand branched or cyclic alkyl con- taining from 3 to 6 carbon atoms, and wherein at least one of said substituents is hydrogen.

Phenol, cresol, xylenol are preferably used.

The carbonyl compound used is selected from aldehydes and ketones, and is preferably a compound having the gen- eral formula wherein R5 is selected from linear alkyl containing from 1 to 6 carbon atoms, branched or cyclic alkyl containing from 3 to 6 carbon atoms, an aryl group and aryl substituted

group; and wherein R7 is hydrogen and has the same meaning as R6 ; or R6 and R7 together form a bivalent radical, containing 4 or 5 carbon atoms, ring closed on the carbonyl carbon atom.

A particularly preferred aspect of the present inven- tion is to use acetaldehyde, benzaldehyde, acetone, methy- lethylketone, cyclohexanone and benzophenone, as carbonyl compounds.

According to a particularly preferred aspect of the present invention, two phenol molecules are condensed with an acetone molecule, in the presence of a zeolite having a spaciousness index greater than or equal to 8, preferably beta zeolite, to give bisphenol A. A preferred aspect of the present invention is also to prepare bisphenol Z (4,4' cyclohexylidenebisphenol) by condensing two phenol mole- cules with a molecule of cyclohexanone, in the presence of a zeolite having a spaciousness index greater than or equal to 8, preferably beta zeolite.

The process, object of the present-invention is pref- erably carried out at a temperature ranging from 130 to 230°C.

The condensation takes place in liquid phase, in a closed environment, at autogenous pressure. The pressure preferably ranges from 1. 2 to 15 atmospheres.

It is also possible to operate in the presence of a

solvent selected from toluene, xylene or trimethylbenzene.

The aromatic compound containing a hydroxyl group and the carbonyl compound are reacted in a molar ratio ranging from 2.2 to 15, preferably from 2.5 to 7.

The process can be carried out batchwise, in semi- continuous or in continuous: under semi-continuous condi- tions, in order to maintain a high aromatic com- pound/carbonyl compound ratio in the reactor containing the catalyst and the aromatic compound, the carbonyl compound is added gradually.

Under continuous conditions, the aromatic compound containing the hydroxyl group and the carbonyl compound are fed contemporaneously into the reactor containing the cata- lyst. The product and excess reagent (aromatic compound containing the hydroxyl group and at least one hydrogen atom bound to the aromatic ring) are then continuously dis- charged from the reactor.

In order to maintain a high aromatic compound/carbonyl compound ratio, the catalyst can be distributed into a re- actor on several catalytic layers and the feeding of the carbonyl compound partialized at the beginning of each layer, whereas the feeding of the aromatic compound con- taining the hydroxyl group and at least one hydrogen atom bound to the aromatic ring is effected only at the begin- ning of the first layer.

The zeolites used in the process of the present inven- tion, once exhausted or even only partially deactivated, can be regenerated by means of high temperature thermal treatment (500-600°C) in an oxidative environment (oxygen or air). This in fact allows the combustion of the pitches present in the zeolite pores and regeneration of the mate- rial under such conditions as to allow it to be used again in the reaction.' We have now unexpectedly found'a simpler and more eco- nomic method for regenerating these exhausted catalysts.

The Applicant has in fact found that the zeolite-based catalysts used in the process of the present invention for the preparation of bisphenols by the reaction of an aro- matic compound containing a hydroxyl group with a carbonyl compound, once deactivated by pitches, can be regenerated by means of hot treatment with a suitable aromatic com- pound.

This treatment not only removes the soluble component of the pitches, but is capable of also chemically degrad- ing, by means of a reactive process, the insoluble pitches: the aromatic compound, in fact, reacts with the pitches, probable through a series of alkylation and/or transalkyla- tion 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 spreading through the zeolitic pores.

An object of the present invention therefore relates to a process for the regeneration of an at least partially exhausted zeolitic catalyst, coming from a process for pre- paring bisphenols by the condensation of a carbonyl com- pound 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 pres- ence of a catalyst comprising a zeolite having a spacious- ness index greater than or equal to 8, at a temperature ranging from 120 to 250°C and a pressure higher than the atmospheric value, said regeneration process comprising subjecting the exhausted Catalyst to treatment with an aro- matic compound containing at least one substituent selected from OH, O-, NH2, NHR, NR2, OR, NHCOR, in at least partially liquid phase and at a temperature equal to or higher than that at which the preparation process of bisphenols from which the exhausted catalyst derives, has been effected.

Aromatic compounds suitable for the treatment are aro- matic compounds containing at least one activating group on the aromatic ring, preferably phenolic compounds, and even more preferably aromatic compounds having the general for- mula:

wherein the substituents Rl, R2, R3, R4, and R5, the same or different, are selected from H, linear alkyl containing from 1 to s carbon atoms and branched or cyclic alkyl con- taining from 3 to 6 carbon atoms, and wherein at least one of said substituents is hydrogen.

Phenol, cresol, xylenol are preferably used.

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

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

The regeneration process is preferably carried out at a temperature higher than that of the preparation process

of bisphenols from which the exhausted catalyst derives.

The process of the present invention can be effected by recovering the exhausted catalyst from the bisphenol preparation reactor and subjecting it to regenerating treatment with the pre-selected aromatic compound in a spe- cific reactor, but a preferred aspect of the present inven- tion is for the regeneration process of the at least par- tially exhausted-catalyst to be carried out in the bisphe- nol preparation reactor itself, by feeding the aromatic compound pre-selected for the regenerating treatment, after suspending the feeding of the reagents used for the synthe- sis of bisphenols. This embodiment is particularly conven- ient and preferred when the synthesis reactor of bisphenols is a continuous reactor, even more preferably a continuous reactor with a fixed catalytic bed.

When the regeneration process of the at least par- tially exhausted catalyst is carried out in the same bisphenol synthesis reactor, a particularly preferred as- pect of the present invention is to use, as aromatic com- pound for the regenerating treatment, the hydroxylated aro- matic substrate itself of the bisphenol synthesis process, after suspending the feeding of the carbonyl compound to the reactor. If the synthesis is carried out in the pres- ence of a solvent, the feeding of the solvent to the reac- tor is also suspended.

This embodiment, in which the same hydroxylated aro- matic substrate adopted in the synthesis process of bisphe- nols is used for the regeneration, is particularly conven- ient and preferred when the preparation reactor of bisphe- nols is a continuous reactor, even more preferably a con- tinuous fixed catalytic bed reactor. In practice, according to this particular embodiment in continuous of the regen- eration of the present invention, when the zeolitic cata- lyst used in the synthesis process of bisphenols of the present invention is exhausted, the feeding stream of the carbonyl compound to the alkylation reactor is suspended, whereas the stream of aromatic substrate containing the hy- droxyl group continues to be fed to the reactor, optionally by raising the temperature of the catalytic bed when the regeneration treatment is to be effected at a higher tem- perature than that of the synthesis process of bisphenols.

A preferred aspect is that the stream of aromatic substrate containing the hydroxyl group be fed to the reactor in countercurrent.

When the regeneration process has terminated, the feeding of the carbonyl compound is re-started to re- initiate the synthesis process of bisphenols, after possi- ble cooling of the catalytic bed.

According to a preferred aspect of the present inven- tion, an exhausted catalyst based on beta zeolite coming

from a synthesis process of bisphenol A by the reaction of phenol with acetone, is regenerated in the synthesis reac- tor of bisphenol A itself, using the stream of phenol.

In all these cases in which the regeneration is ef- fected in the synthesis reactor of bisphenols itself, and said reactor is in continuous, the operating WHSV prefera- bly ranges from 0.1 to 20 hours-', even more preferably from 1 to 10 hours-l.

In accordance with what is specified above, a further aspect of the present invention relates to a process for preparing bisphenols which comprises 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 catalyst comprising a zeolite having a spaciousness index greater than or equal to 8, at a temperature ranging from 120 to 250°C and at a pressure higher than the atmospheric value, until said catalyst shows at least partial deactivation; b) suspension of the feeding of the carbonyl compound and treatment of said deactivated catalyst with the sole feeding of the aromatic substrate containing the hydroxyl group, in at least partially liquid phase and at a tempera- ture at least equal to and preferably higher than the tem- perature of the condensation process of step a) until the

at least partial regeneration of the catalyst, c) reactivation of the feeding of the carbonyl com- pound, after re-establishing the temperature conditions used in the condensation in step a) as the regeneration is preferably carried out at a temperature higher than that of the condensation step.

The multi-step process described above is preferably used for the preparation of bisphenol A by the reaction of phenol and acetone in the presence'of a catalytic composi- tion containing beta zeolite, which is regenerated in the same synthesis reactor of bisphenol A using the stream of phenol.

EXAMPLE 1-SYNTHESIS OF BETA ZEOLITE 58.8 g of tetraethylammonium hydroxide at 40% by weight in aqueous solution and 1.9 g of sodium aluminate (56% of A1203) are added to 58.4 g of demineralized water.

The mixture is heated to about 80°C and is left under stir- ring until complete dissolution.

The limpid solution thus obtained is added to 37.5 g of LUDOX HS colloidal silica at 40% by weight of SiO2. A homogeneous suspension is obtained, having a pH equal to 14, which is charged into a steel autoclave and left to crystallize under hydro-thermal 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 hu- mid panel of zeolite is obtained, containing the organic templating agent tetraethylammonium and sodium.

The humid zeolitic panel, prepared as described above, is dried in an oven for 1 hour at 150°C, calcined in muffle for 5 hours at 550°C in a stream of air.

The calcined solid is dispersed in an aqueous solution of ammonium acetate for ion exchange. This zeolite in ammo- nium form is calcined in muffle for 5 hours at 550°C in a stream of air obtaining beta zeolite in acid form.

Upon elemental chemical analysis, the sodium residue of this zeolite is 106 ppm whereas the aluminum content is equal to 3.14% ( [All/ [Nal=252).

The product is characterized by means of X-ray dif- fraction from powders.

EXAMPLE 2-SYNTHESIS OF ERB-1 ZEOLITE An alkaline solution consisting of sodium hydroxide is charged into a 1000 cm3 three-necked flask equipped with a reflux cooler and rod stirrer. The solution is brought to the desired temperature (70-80°C) by means of a heating jacket and the aluminum source, consisting of sodium alumi- nate, is then added, under stirring, obtaining a limpid so- lution. The organic templating agent consisting of hex- amethyleneimine is added to the reaction mixture and the silica source, consisting of Areosil 200, is then slowly added.

Molar SiO2/Al2O3 N/SiO2 Na+/SiO2 OH-/SiO2 H2O/SiO2 ratios 30 0.35 0.18 0.18 45 At the end of the addition, the reaction mixture is kept under magnetic stirring for about four hours at the temperature indicated above and is then cooled to room tem- perature and left in static aging for 24 hours. A homogene- ous slurry is obtained, which is charged into a stainless steel autoclave, placed in a rocking oven and kept under stirring for 10 days at a temperature of 150°C.

At the end of the reaction, a suspension is dis- charged, from which a solid is recovered by filtration, which, after repeated washings with demineralized water, is dried in an oven at 120°C. The dried solid is characterized by means of X-ray diffraction from powders (XRD). The solid is then calcined at 550°C for 5 hours in a stream of air.

A material is obtained, which has the same diffraction spectrum indicated in figure 4 and table 3 of European pat- ent 293,032.

This material is then exchanged with ammonium acetate and obtained in acid form.

EXAMPLE 3-SYNTHESIS OF ZSM-12 ZEOLITE 2.4 g of sodium aluminate at 56% of Al203 are dis-

solved in 84 g of an aqueous solution of tetraethylammonium hydroxide at 35%. The limpid solution thus obtained is poured, under stirring, into 200 g of Ludox HS40 colloidal silica. After brief stirring, a limpid, homogeneous gel is obtained, which is poured into an AISI316 stainless steel autoclave, equipped with an anchor stirrer. The gel is crystallized under hydro-thermal conditions at 165°C for 90 hours. At this point, the autoclave is cooled and the solid separated from the mother liquor and washed with demineral- ized water until the washing water has a pH of less than 9.

The solid is calcined in an atmosphere of air for 5 hours. The material is then exchanged with ammonium acetate and obtained in acid form.

The solid is then definitely separated from the aque- ous environment, dried and calcined for 5 hours at 500°C in an atmosphere of air. The zeolitic catalyst is thus ob- tained in acid form. An XRD analysis is carried out on the final sample, which reveals the presence of the MTW crys- talline phase alone, and also a chemical analysis on the basis of which the residual sodium proves to be less than 50 ppm and the molar ratio SiO2/Al203 is 102.

EXAMPLE 4 (Synthesis of Bisphenol A with Beta Zeolite- Batch test) 9.4 g of phenol (0.1 moles) and 1.16 g (0.02 moles) of acetone, molar ratio phenol/acetone = 5/1, and 1 g of Beta

zeolite prepared according to Example 1, with a molar ratio SiO2/Al203 25, a spaciousness index of 19, previously treated at 550°C in a stream of air to obtain the acid form starting from the ammonium form, are charged into a glass autoclave. The autoclave is closed and is kept under stir- ring for 12 hours at 180°C.

At the end, the mass is cooled to room temperature.

The reaction product is analyzed by means of mass G. C. with the analytical method described in Analytical Chemistry, volume 40, number 14, December 1968, pages 2212-2215.

Acetone conversion: 99.9% Selectivity to p, p'Bisphenol A: 48.97% Selectivity to o, p' Bisphenol A: 27.3% Selectivity to trimers and heavy products: 23.73% Selectivity to mesityl oxide (undesired by-product) : lower than the analytical limit (0.01%) Selectivity to chromanes (undesired by products) : lower than the analytical limit (0. 01%) EXAMPLE 5 (Synthesis of Bisphenol A with Y Zeolite-Batch test) 9.4 g of phenol (0.1 moles) and 1.16 g (0.02 moles) of acetone, molar ratio phenol/acetone = 5/1, and 1 g of Y zeolite, Toyosoda HSH-320 HUA with a molar ratio SiO2/Al203 = 5. 5, a spaciousness index of 21, previously treated at 550°C in a stream of air, are charged into a glass auto-

clave. The autoclave is closed and is kept under stirring for 12 hours at 180°C.

At the end, the mass is cooled to room temperature.

The reaction product is analyzed by means of mass G. C. with the analytical method described in Analytical Chemistry, volume 40, number 14, December 1968, pages 2212-2215.

Acetone conversion: 90.94% Selectivity to p, p' Bisphenol A: 38.42% Selectivity to o, p' Bisphenol A: 21'. 46% Selectivity to trimers and heavy products: 40.11% Selectivity to mesityl oxide (undesired by-product) : lower than the analytical limit (0.01%) Selectivity to chromanes (undesired by products) : lower than the analytical limit (0. 01%) EXAMPLE 6 (Synthesis of Bisphenol A with ERB-1 Zeolite- Batch test) 9.4 g of phenol (0.1 moles) and 1.16 g (0.02 moles) of acetone, molar ratio phenol/acetone = 5/1, and 1 g of ERB-1 zeolite, iso-structural with MCM-22 zeolite, with a molar ratio SiO2/Al203 = 30, a spaciousness index of 8, prepared according to the procedure described in Example 2 and pre- viously treated at 550°C in a stream of air, are charged into a glass autoclave. The autoclave is closed and is kept under stirring for 12 hours at 180°C.

At the end, the mass is cooled to room temperature.

The reaction product is analyzed by means of mass G. C. with the analytical method described in Analytical Chemistry, volume 40, number 14, December 1968, pages 2212-2215.

Acetone conversion: 81.5% Selectivity to p, p' Bisphenol A: 44.2% Selectivity to o, p' Bisphenol A: 21.27% Selectivity to trimers and heavy products: 47.27% Selectivity to mesityl oxide (undesired by-product) lower than the analytical limit (0.01%) Selectivity to chromanes (undesired by products) : lower than the analytical limit (0.01%) EXAMPLE 7 COMPARATIVE (Synthesis of Bisphenol A with ZSM-12 Zeolite-Batch test) 9.4 g of phenol (0.1 moles) and 1.16 g (0.02 moles) of acetone, molar ratio phenol/acetone = 5/1, and 1 g of ZSM- 12 zeolite, with a molar ratio SiO2/Al203 = 102, a spa- ciousness index of 3, prepared according to the procedure described in Example 2 and previously treated at 550°C in a stream of air, are charged into a glass autoclave. The autoclave is closed and is kept under stirring for 12 hours at 180°C.

At the end, the mass is cooled to room temperature.

The reaction product is analyzed by means of mass G. C. with the analytical method described in Analytical Chemistry, volume 40, number 14, December 1968, pages 2212-2215.

Acetone conversion: 76.43% Selectivity to p, p'Bisphenol A: 11.43% Selectivity to o, p'Bisphenol A: 7.9% Selectivity to trimers and heavy products: 34.45% Selectivity to mesityl oxide (undesired by-product): 46. 22% EXAMPLE 8 (Synthesis of Bisphenol Z with Beta Zeolite- Batch test) 9.4 g of phenol (0.1 moles) and 3.27 g (0.033 moles) of cyclohexanone, molar ratio phehol/cyclohexanone = 3/1, and 1 g of Beta zeolite, prepared according to Example 1, with a molar ratio SiO2/Al203 = 25, a spaciousness index of 19, previously treated at 550°C in a stream of air, are charged into a glass autoclave. The autoclave is closed and is kept under stirring for 6 hours at 160°C.

At the end, the mass is cooled to room temperature.

The reaction product is analyzed by means of mass G. C. with the analytical method described in Analytical Chemistry, volume 40, number 14, December 1968, pages 2212-2215.

Cyclohexanone conversion: 100% Selectivity to p, p' Bisphenol Z: 31.53% Selectivity to o, p' Bisphenol Z: 68. 47% Selectivity to trimers and heavy products: 0% EXAMPLE 9- (Synthesis of Bisphenol A with Beta zeolite- Test in continuous) 5 cm3 of beta zeolite prepared according to Example 1,

previously treated at 550°C in a stream of air to obtain the acid form starting from the ammonium form and sieved at 70-100 mesh, are charged into a tubular reactor having a diameter of 12.5 mm and a length of 390 mm. A mixture of phenol/acetone are then fed to the reactor in a molar ratio of 10/1, at a temperature of 180°C, at a pressure of four bars and an LHSV of 2 h-1.

The reaction product is analyzed by means of mass G. C. with the analytical method described in Analytical Chemistry, volume 40, number 14, December 1968, pages 2212- 2215.

Acetone conversion: 99.87% Selectivity to p, p' Bisphenol A: 52.9% Selectivity to o, p' Bisphenol A: 32.5% the complement to 100% consisting of condensation products with a higher molecular weight.

EXAMPLE 10-REGENERATION TEST The previous example is repeated and prolonged until the acetone conversion drops to 92% with a selectivity to bisphenol A (p, p'isomer + o, p' isomer) in the reaction product of 78%, the complement to 100 consisting of conden- sation products with a higher molecular weight.

At this point the regeneration procedure of the par- tially exhausted catalyst is activated: * the feeding of the phenol-acetone mixture is interrupted,

whereas pure phenol is fed at the same space velocity; the catalytic bed is heated to a temperature of 280°C by subjecting the reactor to a counterpressure of eleven bars; the temperature reached is maintained for 8 hours, feed- ing pure phenol for this period at the same space veloc- ity; the catalytic bed is brought back to the reaction tem- perature (l80°C).

At the end of the reaction procedure described, the feeding of the phenol-acetone mixture 10/1 is re-started, obtaining an acetone conversion of 99.96% with a selectiv- ity to bisphenol A (p, p' isomer + o, p' isomer) in the reac- tion product of 85.37%, the complement to 100 consisting of condensation products with a higher molecular weight.

EXAMPLE 11-REGENERATION TEST The previous example is repeated and prolonged until the conversion of the acetone fed drops to 91.8%.

At this point the regeneration procedure of the par- tially exhausted catalyst is activated. The feeding of the phenol-acetone mixture is interrupted, whereas pure phenol is fed at the same space velocity; * the catalytic bed is heated to a temperature of 250°C by subjecting the reactor to a counterpressure of eleven bars;

the temperature reached is maintained for 8 hours, feed- ing pure phenol for this period at the same space veloc- ity; # the catalytic bed is brought back to the reaction tem- perature (180°C).

At the end of the reaction procedure described, the feeding of the phenol-acetone mixture 10/1 is re-started, obtaining an acetone conversion of 98.48% with a selectiv- ity to bisphenol A (p, p' isomer + o, p' isomer) in the reac- tion product of 85.51%, the complement to 100 consisting of condensation products with a higher molecular weight.

EXAMPLE 12 (COMPARATIVE REGENERATION TEST) 5 cm3 of beta zeolite, previously treated at 550°C in a stream of air to obtain the acid form starting from the ammonium form and sieved at 70-100 mesh, are charged into a tubular reactor having a diameter of 12.5 mm and a length of 390 mm. A mixture of phenol/acetone are then fed to the reactor in a molar ratio of 10/1, at a temperature of 180°C, at a pressure of four bars and an LHSV of 2 h-l.

An acetone conversion of 99.87% is obtained, with a selectivity to bisphenol A (p, p'isomer + o, p'isomer) in the reaction product of 85.42%, the complement to 100 consisting of condensation products with a higher molecu- lar weight.

The test is prolonged until the acetone conversion

drops to 92% with a selectivity to bisphenol A (4,4'BFA + 2, 2 BFA) in the reaction product of 78%, the complement to 100 consisting of condensation products with a higher mo- lecular weight.

At this point the regeneration procedure of the par- tially exhausted catalyst is activated: the feeding of the phenol-acetone mixture is interrupted, whereas n-decade is fed at the same space velocity; 'the catalytic bed is heated to a temperature of 280°C by subjecting the reactor to a counterpressure of 11 bars; 'the temperature reached is maintained for 8 hours, feed- ing pure phenol for this period at the same space veloc- ity ; the catalytic bed is brought back to the reaction tem- perature (180°C).

At the end of the reaction procedure described, the feeding of the phenol-acetone mixture 10/1 is re-started, obtaining an acetone conversion of 91% with a selectivity to bisphenol A (p, p' isomer + o, p' isomer) in the reaction product of 76%, the complement to 100 consisting of conden- sation products with a higher molecular weight.

It can therefore be noted how the washing with n- decane, contrary to what occurs for the phenol, is not ca- pable of re-establishing either the conversion or the ini- tial selectivity.