The mixtures which can be used for the process of the present invention are, for example, mixtures compris- ing one or more C6+ hydrocarbons selected from alkanes, alkenes with one or more unsaturations, aromatic com- pounds. In particular, these mixtures can be fractions from mineral oil, fractions from catalytic or thermo con- version plants, and fractions deriving therefrom by hy- drogenation.

Mixtures of hydrocarbons rich in aromatic components are very common in the petrochemical industry: for exam- ple, those deriving from the steam-cracking of virgin naphtha to olefins, or those obtained from the reforming of petroleum fractions, can be mentioned.

Low molecular weight aromatic compounds (< 9 carbon atoms) which can be obtained from these mixtures, are widely used as chemical intermediates and as components of motor-vehicle fuels. The use of medium molecular

weight (up to 12 carbon atoms) components of these mix- tures as chemical intermediates and in fuels is more re- strained, but still economically important. The use of higher molecular weight components is less advantageous and their main destination is as a low-price fuel.

The percentage of aromatic compounds which are used as fuel components is inevitably decreasing. The legisla- tion in Europe, as well as in other parts of the world, is in fact tending to progressively decrease the aromatic content in fuel, for environmental reasons, and there will therefore be an excess production of aromatic prod- ucts with 7 and 8 carbon atoms, which will not easily find alternative uses in the chemical field and a sig- nificant loss in the value of these fractions is expected in a reasonably near future.

Higher molecular weight fractions already have a current low market value, in fact, with the rare excep- tions of mixtures with a moderate content of asphaltenes, they are at the same price level as fuel oil.

In particular, mixtures containing hydrocarbons with a different chemical structure for which the necessity is presently felt for finding alternative means of exploita- tion, are those deriving from so-called cracking gasoli- nes and reforming residues. These hydrocarbon fractions derive from cracking gasolines (also called pyrolysis

gasoline or pygas) or from reforming gasoline after the more valuable components, such as benzene, toluene and xylenes, have been at least partially separated from them. Cracking/reforming gasolina residue does not have a fixed composition, also because mixtures of a different origin can be joined in varying proportions. From the point of view of the components, it should be pointed out that benzene, toluene and xylenes are still present in these mixtures, as the previous separation process is never total, the main components present are aliphatic hydrocarbons with varying structures having 7-9 carbon atoms, ethyl benzene and other alkyl benzenes with 9-12 carbon atoms, styrene and methyl styrenes, methyl cyclopentadiene, dicyclopentadiene and various co-dimers of cyclopentadiene and methyl cyclopentadiene starting from 9 carbon atoms (for example in the case of the co- dimer between cyclopentadiene and butadiene) up to 15 carbon atoms (for example in the case of co-dimers be- tween methyl styrene and methyl cyclopentadiene), indene and methyl indenes, naphthalene and methyl naphthalenes.

In mixtures of this type there are therefore carbon- carbon bonds prevalently of the aromatic type, but bonds of the aliphatic, olefinic and dienic type are present, prevalently with cyclic structures.

Fractions containing alkanes and/or alkenes with one

or more unsaturations for which the necessity is felt for finding alternative means of exploitation, can directly derive from the fractionation of crude mineral oil, but for the purposes of the present invention, mixtures de- riving from other processings and which, being by- products, have a low commercial value, are considered as being preferential. Mixtures of hydrocarbons of particu- lar interest are those which do not require any further preliminary intervention of a chemical or physico- chemical nature, for example residual paraffinic waxes from the dewaxing treatment of lubricants, mixtures, how- ever, obtained with known treatments, which are rela- tively simple and with a wide application, can also be well used, such as for example naphthene fractions deriv- ing from the hydrogenation of aromatic hydrocarbon mix- tures.

With respect to the possible exploitation of various hydrocarbon cuts described above, conversion processes of mineral oil fractions comprising cyclic and aromatic al- kanes to non-cyclic branched alkanes, are known in the state of the art.

US 5,831, 139, for example, describes a process for the production of aliphatic fuels from naphtha with a high boiling point. The naphtha is subjected to hydro- genation, in a first step, to transform the aromatic com-

pounds into cyclic alkanes. After the hydrogenation, the synthesis of isoparaffins is effected in a second phase.

Aliphatic gasoline components are produced with this process by the opening of the ring and the synthesis of isoparaffins, with as many branchings as possible, with- out a decrease in the number of carbon atoms with respect to the hydrocarbons charged. The octane number of the product must in fact be high.

US 5,334, 792, as in the above patent US 5, 831, 139, describes a process for the opening of the ring for aro- matic and cyclo-aliphatic compounds. This opening step is followed by an isomerization step. Also in this case, iso-alkanes are produced without a reduction in the num- ber of carbon atoms with respect to the starting hydro- carbons.

The conversion, by means of ring opening, of frac- tions containing naphthenes in diesel fuels, is also known. A process of this type is described, for example, in WO 97/09288. Also in this case, alkanes are produced without a decrease in the number of carbon atoms with re- spect to the hydrocarbons charged. The cetane number of the product must be as high as possible.

The processes of the known art therefore aim at transforming aromatic or cyclo-aliphatic compounds into iso-alkanes or alkanes with a high number of carbon at-

oms, suitable for diesel fuels, i. e. the transformations take place without a substantial variation in the number of carbon atoms.

An object of the present invention relates to a process which allows hydrocarbons mixtures deriving from mineral oil, to be transformed by means of a catalyzed hydrocracking reaction, into linear alkanes with a lower molecular weight, in particular linear alkanes containing less than 6 carbon atoms, which are an excellent charge for steam-cracking plants.

WO 01/27223 claims, for this purpose, the use of zeolites with a Spaciousness Index (S. I. ) lower than 20, exchanged with hydrogenating metals. The preferred zeo- lite is ZSM-5 exchanged with palladium.

Using this catalyst, the complete conversion of model charges (toluene, cyclo-hexane or pseudo-cumene) is obtained with a distribution of the reaction products ranging from methane to butanes. Approximately 5% of methane is formed among the alkanes, which is a compound that in the subsequent steam-cracking treatment of the mixture obtained with the process indicated, does not give any yield to olefins. In WO 01/27223, it is demon- strated that large pore zeolites, such as Y-zeolite (S. I.

= 21) cannot be used in this reaction as their catalytic activity rapidly declines. After only 8 hours of life,

using Y-zeolite in acidic form, the conversion, in fact, passes from 100% to 74%. The life of ZSM-5 zeolite/Pd, on the contrary, is at least 10 hours.

Italian patent application MI2003A000347 describes a process for the conversion of mixtures containing aro- matic compounds in linear alkanes which uses a catalytic composition containing at least one lanthanide, at least one metal of group VIII and a Y-type zeolite.

It has now been found that by using catalytic compo- sitions containing a Y-type zeolite in a mixture with suitable elements, it is possible to produce linear al- kanes with a low molecular weight, in particular linear alkanes containing less than 6 carbon atoms, from mix- tures comprising one or more hydrocarbons whose structure contains at least 6 carbon atoms.

An object of the present invention therefore relates to a process for the production of linear alkanes con- taining less than 6 carbon atoms which comprises putting a mixture comprising one or more hydrocarbons containing at least 6 carbon atoms, in contact with a catalytic com- position comprising: a) at least an element Me selected from Zn, Mo, Cu, Ga, In, W, Ta, Zr, Ti, metals of group VIII Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, b) a zeolite selected from Y-zeolite and Y-zeolite modi-

fied by partial or total substitution of the Si with Ti or Ge and/or partial or total substitution of the alumi- num with Fe, Ga or B, with the exclusion of a catalytic composition comprising at least one lanthanide, at least one metal belonging to group VIII and a zeolite selected from Y-zeolite and Y- zeolite modified by partial or total substitution of the Si with Ti or Ge and/or partial or total substitution of the aluminum with Fe, Ga or B when the mixture treated is a mixture containing aromatic compounds.

The process, of the present invention allows n- alkanes to be obtained, with a lower number of carbon at- oms than that of the hydrocarbon fed. In particular, prevalently linear alkanes containing from 2 to 5 carbon atoms, are obtained.

Various kinds of hydrocarbon charge can be used and the resulting products form an excellent feed for steam- cracking plants, where they undergo transformation into olefins, mainly ethylene and propylene. With these cata- lytic compositions optimum results are obtained in terms of activity and catalytic life.

The mixtures which can be subjected to the process of the present invention are mixtures comprising one or more hydrocarbons, whose structure contains at least 6 carbon atoms, selected from aromatic compounds, alkanes

or alkenes with one or more unsaturations. The aromatic compounds can contain several condensed benzene rings.

Mixtures containing aromatic compounds or mixtures containing one or more alkanes with open chains or cyclic structures and/or alkenes having one or more unsatura- tions with open-chains or cyclic structures, optionally mixed with aromatic compounds, are preferably used.

For mixtures containing aromatic, catalytic compo- sitions are used, comprising: (a) at least an element Me selected from Zn, Mo, Cu, Ga, In, W, Ta, Zr, Ti, metals belonging to group VIII, (b) a zeolite selected from Y-zeolite and Y-zeolite modi- fied by partial or total substitution of the Si with Ti or Ge and/or partial or total substitution of the alumi- num with Fe, Ga or B, with the exclusion of a catalytic composition comprising at least one lanthanide, at least one metal belonging to group VIII and a zeolite selected from Y-zeolite and modified Y-zeolite.

Modified Y-zeolite always refers in this description to a Y-zeolite modified by partial or total substitution of the Si with Ti or Ge and/or partial or total substitu- tion of the aluminum with Fe, Ga or B.

In particular, the mixtures containing aromatic com- pounds can be treated with catalytic compositions which

essentially consist of: (a) at least an element Me selected from Zn, Mo, Cu, Ga, In, W, Ta, Zr, Ti, metals belonging to group VIII, (b) a zeolite selected from Y-zeolite and modified Y- zeolite.

According to an aspect of the invention, catalytic compositions additionally containing one or more lantha- nides, can be used.

A further aspect of the present invention therefore relates to a process for the production of linear alkanes containing less than 6 carbon atoms which comprises put- ting a mixture comprising one or more hydrocarbons con- taining at least 6 carbon atoms, in contact with a cata- lytic composition comprising: a) at least an element Me selected-from Zn, Mo, Cu, Ga, In, W, Ta, Zr, Ti, metals of group VIII, Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, b) a zeolite selected from Y-zeolite and Y-zeolite modi- fied by partial or total substitution of the Si with Ti or Ge and/or partial or total substitution of the alumi- num with Fe, Ga or B, c) one or more lanthanides, with the exclusion of a catalytic composition comprising at least one lanthanide, at least one metal belonging to group VIII and a zeolite selected from Y-zeolite and

modified Y-zeolite when the mixture treated is a mixture containing aromatic compounds.

In the case of mixtures containing aromatic com- pouds, compositions can be well used, containing: a) at least an element Me selected from Zn, Mo, Cu, Ga, In, W, Ta, Zr, Ti, b) a zeolite selected from Y-zeolite and Y-zeolite modi- fied by partial or total substitution of the Si with Ti or Ge and/or partial or total substitution of the alumi- num with Fe, Ga or B, c) one or more lanthanides, with the exclusion of a catalytic composition comprising at least one lanthanide, at least one metal belonging to group VIII and a zeolite selected from Y-zeolite and modified Y-zeolite.

In particular, mixtures containing aromatic com- pounds can be converted using catalytic compositions es- sentially consisting of: a) at least an element Me selected from Zn, Mo, Cu, Ga, In, W, Ta, Zr, Ti, b) a zeolite selected from Y-zeolite and Y-zeolite modi- fied by partial or total substitution of the Si with Ti or Ge and/or partial or total substitution of the alumi- num with Fe, Ga or B, c) one or more lanthanides.

Y-zeolite is described for the first time in US 3,130, 007 and has the following formula expressed in terms of moles of oxides 0. 90. 2 Na2O#Al2O3#w SiO2#x H2O wherein w has a value greater than 3 up to about 6 and x can be a value up to about 9. Its preparation is de- scribed for example in"Verified Synthesis of Zeolitic materials"H. Robson Editor, Elsevier, second revised edition 2001, whereas the post-synthesis treatment to which the Y-zeolite can be subjected, including dealumi- nation, is described in"Introduction to Zeolite Science and Practice"chapter 5, H. van Bekkum et al. Editors, Studies in Surface Science and Catalysis, vol. 58, El- sevier. In the compositions of the present invention, Y- zeolites can be used with a molar ratio Si02/Al203 ranging from 3 to 400.

Modifications of the Y-zeolite obtained by partial or total isomorphous substitution of the aluminum of the zeolite with Fe, Ga or B, and/or partial or total substi- tution of the Si with Ti or Ge, can also be used in the process of the present invention. These modifications of the Y-zeolite can be prepared, for example, by substitut- ing, in the synthesis process of the Y-zeolite described in US 3,130, 007, part of the silicon and/or aluminum sources with sources of Fe, Ga, B, Ti and/or Ge. The Y-

zeolite in which Ge has totally substituted the Si is de- scribed in R. M. Barrer et al. J. Chem. Soc. , 195-208 (1959) and in G. M. Johnson, Microporous and Mesoporous Material, 31,195-204 (1999) ; the Y-zeolite in which the Si and Al have been completely substituted by Ge and Ga are described in Barrer, J. Chem. Soc. , 195-208 (1959).

The catalytic composition of the present invention preferably contains the zeolite in partially acidic form, that is part of the cationic sites present in the zeolite is occupied by hydrogen ions.

A particularly preferred aspect is to use Y-zeolite.

In the Y-zeolite, the molar ratio between silicon oxide and aluminum oxide preferably ranges from 5 to 50., With respect to the element Me, compositions con- taining Pt, Pd, Ti, Mo, Zn, Cu or Ni, are preferably used. Among the metals of group VIII, Pd is preferably adopted. The mixtures of elements preferably used are se- lected from Pd/Ti, Zn/Mo, Cu/Zn and Ni/Mo.

The element Me can be present in the catalytic com- position in the form of an oxide, ion, metal, sulfide or a mixture of these forms can be present. In particular, the elements Zn, Mo, Cu, Ga, In, W, Ta, Zr, Ti, are prevalently present in the form of oxides, the elements of group VIII are prevalently present in the metal form.

When Me is an element selected from Zn, Mo, Cu, Ga,

In, W, Ta, Zr, Ti, the quantity of Me, expressed as an element, can vary from 0.1 to 50% by weight, preferably from 0.5 to 30% by weight, with respect to the total weight of the catalytic composition.

When Me is an element selected from metals of group VIII, the quantity of Me, expressed as an element, can vary from 0.001 to 10% by weight, preferably from 0.1 to 5% by weight with respect to the total weight of the catalytic composition.

When present, the element belonging to the group of lanthanides which is preferably used is lanthanum.

The lanthanide, or lanthanides, present in the cata- lytic composition can be in the form of an oxide or ion or a mixture of these forms can be present. The quantity of lanthanide, or lanthanides, expressed as an element^-, can vary from 0.5 to 20% by weight, preferably from 1 to 15% by weight, with respect to the total weight of the catalytic composition.

The catalytic compositions of the present invention are prepared by introducing the element Me by means of the ionic exchange or impregnation techniques.

If the element Me is introduced by ion exchange, the zeolite, preferably in acidic form, is treated with an aqueous solution of a salt of the element Me. For exam- ple, in the case of metals of group VIII, an aqueous so-

lution can be used with a concentration of 0.01-0. 5 M, preferably 0.01-0. 1 M, of a corresponding complex. For palladium, Pd (NH3) 4 (NO3) 2, can be used, for example.

The sample deriving from the ion exchange, is dried, after suitable washings, and then calcined at a tempera- ture ranging from 400 to 600°C for 1-10 hours.

If the element Me is introduced by impregnation, the known incipient wetness inbibition technique (wet imbibi- tion) is adopted, wherein the volume of solution contain- ing a salt of the element Me corresponds to the pore vol- ume of the zeolite, it is then dried and calcined as in the case of the ion exchange. Also in this case, an aque- ous solution of a salt of the element Me is used, pref- erably with an anion which does not leave residues in the end-product, for example a nitrate or an acetate decom- posable by calcination. When the quantity of the element Me to be introduced is high, the salt to be added is di- vided and various impregnations are effected, with drying phases in between. The drying is carried out by heating the sample and, in order to facilitate the evaporation of the solvent, vacuum or a stream of gas can be optionally used.

As a result of the calcination, an at least partial transformation of the ion of the element Me into the cor- responding oxide, can take place.

Impregnation is the preferred technique for intro- ducing the element Me.

In catalytic compositions in which the introduction of more than one element Me selected from Zn, Mo, Cu, Ga, In, W, Ta, Zr, Ti and metals of group VIII on the zeo- lite, preferably in acidic form, is required, the ele- ments can be introduced separately or contemporaneously.

In the former case, the calcination between the introduc- tion step of a first element and the introduction step of a second element is optional; if this calcination is not effected, the partial transformation of the ions into the corresponding oxides, takes place contemporaneously dur- ing the calcination effected at the end of the second step.

According to the preferred technique, the introduc- tion of several elements is effected contemporaneously and for this purpose, aqueous solutions containing said elements in the desired atomic ratio, are used.

When the catalytic composition envisages the intro- duction of a lanthanide, any of the known techniques can be used, such as exchange in the solid state with a lan- thanide salt, ion exchange in aqueous solution or impreg- nation.

Ion exchange or impregnation is preferably used.

In the former case, the zeolite, preferably in

acidic or ammonium form, is treated with an aqueous solu- tion of a lanthanum salt having a concentration varying from 0.01 to 1.0 M, preferably from 0.01 to 0.5 M. For example, an aqueous solution can be used, within the con- centration limits indicated above of lanthanum nitrate, citrate, acetate, chloride or sulfate, at reflux tempera- ture for 1-24 hours. After suitable washings with dis- tilled water, the sample deriving from the ion exchange is dried and then calcined at a temperature ranging from 400 to 600°C for 1-10 hours.

If the lanthanide is introduced by impregnation, the incipient wetness imbibition technique is used and it is then dried and calcined as in the case of ion exchange.

As a result of the calcination, an at least partial transformation of the lanthanide ion into the correspond- ing oxide, takes place.

Ion exchange is the preferred technique for intro- ducing the lanthanide.

The catalytic compositions of the present invention containing one or more lanthanides and one or more ele- ments Me can be prepared using a mixture of compounds of these elements and any of the techniques described above.

These catalytic compositions are preferably prepared by introducing first the lanthanide and then the element Me onto the zeolite. The zeolite used in the preparation

is preferably in acidic form. When these catalytic compo- sitions contain one or more lanthanide or more than one element Me, a mixture of compounds of these elements is used in their preparation.

According to a particularly preferred aspect, the catalytic compositions of the present invention contain- ing lanthanum are prepared by inserting the lanthanide in the zeolite in acidic form by means of ion exchange, op- tionally calcining the product thus obtained, and then depositing the element Me by ion exchange and calcining the product obtained.

Whatever technique may have been selected for intro- ducing the lanthanide and element Me, the calcination be- tween the introduction of the lanthanide and the intro- duction of the element Me is generally optional and if it is not effected, the partial transformation of the ions into the corresponding oxides takes place contemporane- ously during the calcination effected at the end of the second step.

Catalytic compositions containing or consisting of Y-zeolite and Pd, Y-zeolite and Pt, Y-zeolite and Zn, Y- zeolite and Mo, Y-zeolite and Ni; Y-zeolite and Pd to- gether with Ti, Y-zeolite and Zn together with Mo, Y- zeolite and Zn together with Cu, Y-zeolite and Mo to- gether with Ni, Y-zeolite and La together with Zn and Mo,

Y-zeolite and La together with Zn and Cu, are particu- larly preferred.

When the catalytic composition contains elements of group VIII, following the synthesis step, there may be an at least partial reduction step of the relative ions to the corresponding elements. Reduction to the element can be obtained by means of treatment of the catalytic compo- sition with hydrogen or with a reducing agent, and it can be effected on the catalytic composition before its use or in the reactor itself in which the catalytic composi- tion is used.

The catalytic composition of the present invention can be used in a mixture with suitable binders such as silica, alumina, clay. The catalytic composition and the binder are mixed in a proportion ranging from 5 : 95 to 95: 5, preferably from 30: 70 to 95: 5, even more preferably from 50: 50 to 90: 10. The mixture of the two components is processed, according to the known techniques, into the desired end-form, for example cylindrical extruded prod- ucts or other known forms.

The mixtures containing aromatic compounds which are suitable for being treated according to the process of the present invention, are for example fractions coming from thermal or catalytic conversion plants, and mineral oil fractions rich in aromatic compounds, such as for ex-

ample pyrolysis gasolines or pygas, fractions coming from pyrolysis gasolines, in particular those from which the light aromatic compounds (from 6 to 8 carbon atoms) have been separated and residual fractions with a low commer- cial value coming from production plants of aromatic com- pounds and reforming.

In particular, pyrolysis gasolines are a by-product of steam cracking processes in which ethylene and propyl- ene are obtained from light hydrocarbon cuts such as straight-run naphtha (oil fraction substantially contain- ing C5 and C6 hydrocarbons), LPG (Liquefied Petroleum Gas, an oil fraction containing C3 and C4 hydrocarbons), propane or ethane.

Mixtures containing one or more alkanes with open chains or with cyclic structures and/or alkenes having one or more unsaturations with open chains or cyclic structures, which are suitable for being treated accord- ing to the process of the present invention, are those deriving from the fractionation of crude mineral oil or from the hydrogenation of mineral oil fractions or the hydrogenation of cracking plant fractions.

The hydrogenation of these fractions can be carried out with any of the known methods and catalysts, such as, for example, those based on Ni carried on alumina. The fractions deriving from this treatment prevalently or

completely contain alkane compounds with a cyclic struc- ture.

The charges suitable for being treated with the process of the present invention can be optionally mixed with heavier fractions, coming for example from fuel oil from steam cracking (FOK) or Light Cycle Oil (LCO) from fluid bed catalytic cracking. These heavy fractions con- tain polycyclic aromatic compounds having up to 20-21 carbon atoms. As these heavy fractions also contain sul- fur, which is known to be poisonous for hydrogenation catalysts, an unexpected and extremely advantageous as- pect is that the catalytic compositions of the present invention do not, on the contrary, undergo any deactiva- tion due to the sulfur and are therefore capable of proc- essing mixtures of aromatic hydrocarbons also containing heavier fractions, such as, for example, FOK and LCO.

During the treatment of these mixtures, there may be an at least partial transformation of the elements Me con- tained in the catalytic composition used, for example Mo, Zn, Cu, into the corresponding sulfides. As already men- tioned, this transformation does not seem to invalidate the activity of the catalytic composition.

The dilution of very heavy mixtures (FOK, LCO) with lighter fractions is not indispensable. Another unex- pected aspect of the present invention relates to the

processing of heavier fractions, coming, for example, from fuel oil from steam cracking (FOK) or Light Cycle Oil (LCO) from fluid bed catalytic cracking, also without dilution with fractions coming from gasolines, provided a process is effected which avoids feeding heavier poly- cyclic components such as asphaltenes, to the conversion reactor to light paraffins. For this purpose, the fuel oil fraction can be subjected to treatment such as ex- traction with a solvent, distillation or, even better, evaporation with suitable equipment (Luwa thin film evaporator or similar equipment).

US 5,932, 090 describes, for example, a process for the conversion of heavy crude oils or distillation resi- dues which, after a hydrocracking phase in the presence of hydrogen and a suitable catalyst, comprises distilla- tion of the product to recover the most volatile hydro- carbons. By deasphalting the distillation residue, a mix- ture of hydrocarbons is obtained (called DAO, deasphalted oil), from which a feed can be obtained, which is suit- able for the process of the present invention.

Also in these cases, the catalytic compositions of the present invention unexpectedly do not undergo any de- activation due to the sulfur which can be contained in these mixtures and there can be an at least partial transformation of the elements Me contained in the cata-

lytic composition used into the corresponding sulfides without a loss in the catalytic activity.

The mixtures containing aromatic compounds which can be subjected to the process of the present invention, and in particular pyrolysis gasolines, generally prevalently contain toluene, ethyl benzene, xylenes, benzene and Cg aromatic compounds, but also naphthalene and alkyl de- rivatives of naphthalene, for example mono and poly- substituted methyl and ethyl derivatives. The intermedi- ate fractions and fuel oils such as FOK and LCO can con- tain aromatic compounds with >20 carbon atoms, such as, for example, aromatic compounds with 2-4 condensed ben- zene rings, naphthalene, phenanthrene, anthracene, ben- zanthracene, with the relative alkyl derivatives (in par- ticular methyl and/or ethyl derivatives) and phenyl de- rivatives, indene, biphenyl, fluorene, binaphthyl.

According to an aspect of the present invention, the resulting fraction of n-alkanes is prevalently made up of ethane, propane, n-butane and n-pentane.

According to a preferred aspect of the present in- vention, the fraction of linear alkanes containing from 2 to 5 carbon atoms ranges from 50 to 90% by weight of the resulting product.

The process of the present invention is carried out in the presence of hydrogen or a mixture of hydrogen and

H2S at a pressure ranging from 5 to 200 bar, preferably from 25 to 100 bar, at a temperature ranging from 200C to 700°C, preferably from 300° to 600°C. A weight ratio H2/charge ranging from 0.1 to 1.4, more preferably from 0.1 to 0.7, is preferably adopted.

According to a particular aspect of the invention, it is possible to operate with the use, in addition to hydrogen, of a diluent, and for this purpose, a paraffin, for example methane or ethane, can be used.

A particular advantageous aspect of the present in- vention relates to the possibility of using hydrogen or a diluent containing H2S impurities. As specified above, the catalysts used in the present invention are not gen- erally sensitive to the presence of sulfur.

The process is preferably carried out in continuous, in a fixed bed or fluid bed reactor, in gaseous or par- tially liquid phase, at a WHSV (Weight Hourly Space Ve- locity, expressed in kg of charge/hour/kg of catalyst) ranging from 0.1 to 20 hours~1, preferably from 0.2 to 5 hours~1, even more preferably from 0.5 to 3 hours~1.

The alkenes with one or more unsaturations present in the feed are converted according to the process de- scribed in the present invention analogously to the other hydrocarbons, both alkanes and aromatic compounds. It has been verified however that the presence of compounds of

this type can, in some cases, facilitate the formation of oligomers/polymers under the conditions in which the process, object of the invention, is carried out, and it may therefore be preferable to previously subject the mixtures containing them to hydrogenation in order to prolong the duration of the industrial run, without fre- quent stoppages and intermediate regenerations of the catalytic bed. The preliminary hydrogenating treatment can be carried out at a low temperature, in liquid phase, according to technologies already known, for example ap- plied to the fractions of hydrocarbons destined for use as fuel for motor vehicles; this is generally light hy- drogenating treatment normally but not exclusively ef- fected with Pd-based catalysts on alumina.

Before use, the catalytic composition of the present invention is preferably activated in nitrogen at a tem- perature ranging from 300 to 700°C, for a time ranging from 1 to 24 hours and at a pressure varying from 0 to 10 barg.

In addition to or in substitution of the above, in particular when elements of group VIII are present, an activation with hydrogen can be effected at a temperature of 300-700°C, a pressure of 0-10 barg, for a time ranging from 1 to 24 hours.

The catalyst allows long operating periods before

showing signs of deactivation; the catalyst however can be subjected to regeneration treatment, re-establishing its original performances. The most suitable method is by the combustion of the carbonaceous deposits accumulated in the operating period, according to what is known in the state of the art, operating, for example, at a tem- perature ranging from 450 to 550°C, at a pressure ranging from 1 to 3 bar, with mixtures of oxygen and nitrogen in a ratio ranging from 0.1 to 20% by volume and with a space velocity (GHSV = Gas Hourly Space Velocity, ex- pressed in 1 of gas mixture/hour/1 of catalyst) ranging from 3000 to 6000 hours~1. Considering the low regenera- tion frequency, it is not necessary for the regeneration to be effected in the same reactor in which the catalyst is introduced for the reaction; the catalyst can be dis- charged during the periodic plant maintenance phases and regenerated elsewhere, in this way the reactor can be constructed without control devices necessary for carry- ing out the regeneration.

The catalytic compositions used in the present in- vention are new and a further object of the present in- vention therefore relates to a catalytic composition com- prising: (a) at least one element Me selected from Zn, Mo, Cu, Ga, In, W, Ta, Zr, Ti and metals of group VIII Fe, Co, Ni,

Ru, Rh, Pd, Os, Ir, Pt, (b) a zeolite selected from Y-zeolite and Y-zeolite modi- fied by partial or total substitution of the Si with Ti or Ge and/or partial or total substitution of the alumi- num with Fe, Ga or B, with the exclusion of catalytic compositions comprising at least one lanthanide, at least one metal belonging to group VIII and a zeolite selected from Y-zeolite and modified Y-zeolite.

These compositions can additionally contain one or more lanthanides.

An object of the present invention also relates to a process for the production of linear alkanes containing less than 6 carbon atoms from mixtures containing aro- matic compounds having a structure with at least 6 carbon atoms using a catalytic composition essentially consist- ing of: (a) at least one element Me selected from Zn, Mo, Cu, Ga, In, W, Ta, Zr, Ti in a mixture with one or more metals of group VIII, (b) a zeolite selected from Y-zeolite and Y-zeolite modi- fied by partial or total substitution of the Si with Ti or Ge and/or partial or total substitution of the alumi- num with Fe, Ga or B, c) one or more lanthanides.

The catalytic compositions used in said process are also new and object of the present invention.

Some illustrative but non-limiting examples are provided for a better understanding of the present invention and for its embodiment, but should in no way be considered as limiting the scope of the invention itself.

EXAMPLES OF CATALYST PREPARATION EXAMPLE 1 20 g of Y-zeolite in commercial extruded acidic form (Zeolyst CBV500 CY (1.6)) with a molar ratio SiO2/A1203 equal to 5.2, and a solution consisting of 160 ml of wa- ter and 11.2 g of an aqueous solution of tetra-amine pal- ladium nitrate (Pd 5% max. , Alfa Aesar), are charged into a glass flask. The solution is stirred for 4 hours at room temperature; at the end of this period, it is. fil- tered on a Buckner funnel, washed and dried in an oven at 120°C for 16 hours. Calcination is effected at a tempera- ture of 400°C in air, for 12 hours. A Y-zeolite is ob- tained, containing 2. 1% by weight of Pd.

The material is crushed to granules within the 20-40 mesh range.

EXAMPLE 2 30 g of the same Y-zeolite used in Example 1 are charged into a glass flask. A solution is prepared, using 4.6 g of ammonium heptamolybdate, 5.2 g of hexahydrated

zinc nitrate and 62.4 g of demineralized water. The ex- truded zeolite is impregnated using the incipient wetness imbibition technique, with a third of the previous solu- tion, dried at 120°C, impregnated again with a third of the solution, dried again, further impregnated with the remaining volume of the solution, dried and then calcined at 500°C for 4 hours.

A catalyst is obtained with 7.0% by weight of Mo and 3.2% by weight of Zn.

The material is crushed to granules within the 20-40 mesh range.

EXAMPLE 3 30 g of the same Y-zeolite used in Example 1 are charged into a glass flask. A solution is prepared, using 6.08 g of tri-hydrated copper nitrate, 4.76 g of hexahy- drated zinc nitrate and 62.4 g of demineralized water.

The extruded zeolite is impregnated using the incipient wetness imbibition technique, with a third of the previ- ous solution, dried at 120°C, impregnated again with a third of the solution, dried again, further impregnated with the remaining volume of the solution, dried and then calcined at 500°C for 4 hours.

A catalyst is obtained with 4. 8% by weight of Cu and 3. 1% by weight of Zn.

The material is crushed to granules within the 20-40

mesh range.

EXAMPLE 4 30 g of the same Y-zeolite used in Example 1 are charged into a glass flask. A solution is prepared using 2.316 g of ammonium heptamolybdate and 62.4 g of deminer- alized water. The extruded zeolite is impregnated using the incipient wetness imbibition technique, with a third of the previous solution, dried at 120°C, impregnated again with a third of the solution, dried again, further impregnated with the remaining volume of the solution, dried and then calcined at 500°C for 4 hours.

A catalyst is obtained with 4.0% by weight of Mo.

The material is crushed to granules within the 20-40 mesh range.

EXAMPLE 5 30 g of the same Y-zeolite used in Example 1 are charged into a glass flask. A solution is prepared, using 2.72 g of hexa-hydrated zinc nitrate and 30 g of deminer- alized water. The extruded zeolite is impregnated using the incipient wetness imbibition technique, with a third of the previous solution, dried at 120°C, impregnated again with a third of the solution, dried again, further impregnated with the remaining volume of the solution, dried and then calcined at 500°C for 4 hours.

A catalyst is obtained with 1. 9% by weight of Zn.

The material is crushed to granules within the 20-40 mesh range.

EXAMPLE 6 75 g of commercial Y-zeolite (Tosoh HSZ 320 HOA) with a molar ratio Si02/Al203 equal to 5.5 and a sodium content, as Na20 oxide, of 4% by weight, and 1500 g of a 2 molar aqueous solution of ammonium nitrate, are charged into a 2 liter glass flask. The suspension is maintained under reflux conditions for 3 hours, under stirring; af- ter this period, it is filtered on a Buckner vacuum fun- nel, is dried in an oven and calcined at a temperature of 550°C in air, for 5 hours, obtaining a Y-zeolite in acidic form. 20 g of the solid product thus obtained are exchanged with a solution consisting of 160 ml of water and 11.2 g of an aqueous solution of tetra-amine palla- dium nitrate (Pd 5% max. , Alfa Aesar). The mixture is stirred for 4 hours, at room temperature. After this pe- riod, it is filtered on a Buckner funnel, washed and dried in an oven at 120°C for 16 hours. Calcination is effected at a temperature of 400°C in air for 12 hours.

16 g of the catalyst thus obtained are mixed with 10.81 g of pseudoboehmite VERSAL 250 (UOP) and 64 g of an aqueous solution of acetic acid at 1. 5%. The whole mixture is stirred for 30 minutes at room temperature, and is then dried on a heated plate. It is subsequently dried at

120°C for 16 hours and is calcined at 500°C for 4 hours.

A Y-zeolite is obtained, containing 1. 5% by weight of Pd, bound with alumina, wherein the amount of binder corresponds. to about 30% of the total weight of the cata- lytic composition.

The material is crushed to granules within the 20-40 mesh range.

EXAMPLE 7 25 g of the same Y-zeolite used in Example 1 are treated with a solution containing 43.3 g of hexahydrated lanthanum nitrate in 500 g of demineralized water. The solution is maintained under reflux conditions for 3 hours under stirring. At the end of this period, the so- lution is filtered, the filtrate is washed with distilled water and is dried in an oven. The above operation is re- peated three more times, with a total of four exchanges with the lanthanum nitrate solution.

The material obtained, after the last exchange, is dried in an oven and then calcined in a muffle at 550°C.

A solution is prepared, using 1.38 g of ammonium heptamolybdate, 1.56 g of hexahydrated zinc nitrate and 38 g of demineralized water. 18 g of the previously pre- pared zeolite containing lanthanum, are impregnated by means of the incipient wetness imbibition technique, with a third of the previous solution, dried at 120°C, impreg-

nated again with a third of the solution, dried again, further impregnated with the remaining volume of the so- lution, dried and then calcined at 500°C for 4 hours.

A catalyst is obtained with 4. 4% by weight of La, 4.2% by weight of Mo and 1.6% by weight of Zn.

The material is crushed to granules within the 20-40 mesh range.

EXAMPLE 8 75 g of the same Y-zeolite used in Example 6 and 1,500 g of a 2 molar aqueous solution of ammonium ni- trate, are charged into a 2 liter glass flask. The sus- pension is maintained under reflux for 3 hours under stirring; after this period, it is filtered on a vacuum Buckner funnel, dried in an oven and calcined in air at a temperature of 550°C for 5 hours, obtaining a Y-zeolite in acidic form.

25 g of the solid product thus obtained are treated with a solution containing 43.3 g of hexahydrated lantha- num nitrate in 500 g of demineralized water. The solution is maintained under reflux conditions for 4 hours, under stirring. At the end of this period, the solution is fil- tered, the filtrate is washed with distilled water and dried in an oven. The above operation is repeated three more times, with a total of four exchanges with the lan- thanum nitrate solution.

The material obtained after the last exchange, is dried in an oven and then calcined in a muffle at 550°C.

20 g of the calcined product are treated at room temperature with a solution consisting of 160 ml of water and 11.2 g of an aqueous solution of tetra-amine palla- dium nitrate (Pd 5% max. , Alfa Aesar). The whole mixture is stirred for 4 hours, at room temperature. After this period, it is filtered on a Buckner funnel, washed and dried in an oven at 120°C for 16 hours. Calcination is effected at a temperature of 400°C in air for 12 hours.

16 g of the catalyst thus obtained are mixed with 10.81 g of pseudoboehmite VERSAL 250 (UOP) and 64 g of an aqueous solution of acetic acid at 1.5%. The whole mix- ture is stirred for 30 minutes at room temperature, and is then dried on an heated plate. It is subsequently dried at 120°C for 16 hours and is calcined at 500°C for 4 hours.

A Y-zeolite is obtained, containing 2. 1% by weight of La and 1. 0% by weight of Pd, bound with alumina, wherein the amount of binder corresponds to about 30% of the total weight of the catalytic composition.

The material is crushed to granules within the 20-40 mesh range.

EXAMPLE 9 30 g of the same Y-zeolite used in Example 1 are

charged into a glass flask. A solution is prepared using 2.3 g of ammonium heptamolybdate, 2.6 g of hexahydrated zinc nitrate and 62.4 g of demineralized water. The ex- truded zeolite is impregnated using the incipient wetness inbibition procedure, with a third of the previous solu- tion, dried at 120°C, impregnated again with a third of the solution, dried again, further impregnated with the remaining volume of the solution, dried and then calcined at 500°C for 4 hours.

A catalyst is obtained with 3. 8% by weight of Mo and 1.7% by weight of Zn.

The material is crushed to granules within the 20-40 mesh range.

EXAMPLES OF CATALYTIC PERFORMANCES The catalytic activity tests indicated in the fol- lowing examples were carried out in the experimental equipment and with the operative conditions described hereunder.

Catalytic test: equipment and operative conditions The conversion of hydrocarbon mixtures is carried out in a fixed bed tubular reactor having the following characteristics: material = AISI 316L stainless steel, length 400 mm, internal diameter = 12 mm, external diame- ter of the internal thermocouple sheath = 3 mm. The reac- tor is placed in an oven having differential-zone heat-

ing, which allows the selected reaction temperature to be reached.

The catalyst used for the test has a particle size of > 10 mesh. The catalyst charge is of 2. 8 g and is placed in the reactor between two layers of granular co- rundum.

The flow rate of the hydrocarbon mix is regulated by means of an HPLC pump. The hydrogen flow rate is con- trolled by means of a thermal mass flow meter. The reac- tor is of the down-flow type. The two feedings are in- jected and mixed at the inlet of the reactor, in the zone filled with inert material (granular corundum) where the reaction temperature is reached before coming in contact with the catalyst. The plant pressure is controlled through a setting valve at the outlet of the reactor (back pressure valve control). After the pressure setting valve, the stream is sent to a volume flow meter. An ali- quot of the gaseous stream is periodically deviated (about every two hours) to an on-line gas chromatograph, for analysis of the products.

In the starting phase of the activity test, the catalyst is heated to the reaction temperature, under a nitrogen stream or, alternatively, a hydrogen stream, at low pressure and for one hour, in order to dry the cata- lyst and remove air from the reactor. Hydrogen is subse-

quently fed, if nitrogen was used before, and the pres- sure is increased to the value established for the reac- tion. The feeding of the hydrocarbon mixture is then started, at the flow rate established for the reaction.

The mix of hydrocarbons at the outlet of the reactor is partially cooled before reaching the pressure setting valve, it is then cooled to about 50°C, said temperature being maintained in the whole line to the gas chromato- graph. Before reaching the flow volume meter, the gas is cooled to room temperature.

The composition of the hydrocarbon mix in the feed- ing is established through an out-of-line gas chroma- tographic analysis, with sample injection in liquid phase.

The catalytic performances are evaluated by calcu- lating the conversion of the reagents and the yield of the products on the basis of the gas chromatographic analysis integrated with the process data, such as the inlet and outlet flow rates.

The regeneration of the catalyst is effected, when required, after the activity test. Regeneration is car- ried out in the same reactor used for the reaction. The regeneration operative conditions are the following: tem- perature = 450. 550°C, pressure = 1-. 3 bar, oxygen concen- tration = 0. 1-20% and GHSV space velocity-3, 000=6, 000

hours-1. In particular, the treatment starts with a ni- trogen flow, to which an equal air flow is progressively added (in about 1 hour), the nitrogen flow is then pro- gressively reduced to zero (in about 1 hour) and the treatment is prolonged from 5 to 24 hours, in relation to the duration of the previous activity test. At the end of the treatment the reactor is purged with a nitrogen flow and the catalytic activity test can be re-started.

Catalytic test : performances Examples of catalytic activity follow, using the catalysts whose preparation was described in Examples 1- 9.

The results are indicated in the tables which spec- ify the catalyst characteristics, references to the preparation example, the operative conditions and the catalytic performances obtained.

As far as the operative conditions are concerned, it should be pointed out that WHSV means the weight space velocity (Weight Hourly Space Velocity) expressed as kg of hydrocarbons fed/hour/kg of catalyst, and TOS means the working time of the catalyst (Time On Stream), calcu- lated starting from the beginning of the test with fresh catalyst or, in the case of an operating period following a regeneration, from the re-starting of the test with the regenerated catalyst.

The performances are expressed in terms of total conversions of the hydrocarbon (or mix of hydrocarbons) fed and composition of the mix of hydrocarbons at the outlet of the reactor. In particular the concentration of the following products are specified: methane (CH4), eth- ane (C2H6), propane (C3H8), n-butane (n-C4Hio), isobutane (i-C4Hlo), summation of paraffins with more than 4 carbon atoms (E. Par. >C4) and summation of all linear paraffins with the exclusion of methane (X n-Par. >C1).

In the following Table 1 (3 examples, from Ex. 10/A to Ex. 10/C) the operative conditions are indicated to- gether with the catalytic performances obtained using a catalyst based on Pd on USY-zeolite, prepared as de- scribed in Example 1. In particular, the results shown were obtained under different operative conditions, by varying the reaction temperature between 400 and 450°C and the molar ratio Ha/Hydrocarbons between 10.3 and 32.7. The results demonstrate that this catalyst can be advantageously used for the purposes of the present in- vention.

Tables 2-5 (12 examples, from Ex. 11/A to Ex. 14/C) specify the results obtained with catalysts having a com- position different from that of Example 10. They are based on Zn/Mo, Zn/Cu, Mo and Zn, all on USY-zeolites; their preparation is described in examples 2-5. Also in

this case, the results were obtained under different op- erative conditions, with reaction temperatures of 400-450°C and molar ratio H2/Hydrocarbons of 9. 8-35. 4.

The results show that the purposes of the present inven- tion can be achieved with all these catalysts, in a wide composition range.

Table 1 - EXAMPLES 10/A - 10/C Catalyst Type and Preparation Reference | Pd/USY Zeolyst CBV 500 ; See Ex. 1 Example IO/A Operative conditions Hydrocarbons fed 100% 1, 2, 4-trimethyl benzene Reaction temperature (°C) 400 WHSV (hours 0. 8 Pressure (bar) 60 H2/Hydrocarbons molar ratio 10. 3 * Catalytic performances TOS Conv. Mix composition at the reactor outlet (weight %) (hr) (%) CH4 CZH6 C3H$ n-C4Ho I-C4Hqp Par. >C4 Fn. Par >Cl 7 100 7. 0 16. 6 52. 2 12. 9 9. 5 1. 8 82. 8 Example 10/B * Operative conditions Hydrocarbons fed 100% 1, 2, 4-trimethyl benzene Reaction temperature (°C) 450 WHSV (hours') 0. 8 Pressure (bar) 60 H2/Hydrocarbons molar ratio 10. 3 * Catalytic performances TOS Conv. Mix composition at the reactor outlet (weight %) (hr) (%) CH4 C2H6 C3H8 n-C4H, o I-c4H, o E Par. >C4 En. Par >C1 17. 5 100 19. 9 38. 2 39. 7 1. 2 0. 8 0. 1 79. 2 Example 10/C * Operative conditions Hydrocarbons fed 100% 1, 2, 4-trimethyl benzene Reaction temperature (°C) 450 WHSV (hours'. 8 Pressure (bar) 60 H2/Hydrocarbons molar ratio 32. 7 * Catalytic performances TOS Conv. Mix composition at the reactor outlet (weight %) (hr) (%) CH4 C2Hg CgHg n-CqHp I-C4Ho E Par. >C4 En. Par >C1 17 100 14. 9 25. 6 52. 9 3. 8 2. 8 0. 0 82. 4

Table 2-EXAMPLES 11/A-11/C * Catalyst Type and Preparation Reference ZnMo/USY Zeolyst CBV500 ; See Ex. 2 Example 111A * Operative conditions Hydrocarbons fed 100% 1, 2, 4-trimethyl benzene Reaction temperature (°C) 400 WHSV (hours-) 0. 8 Pressure (bar) 60 H2/Hydrocarbops molar ratio 10. 5 * Catalytic performances TOS Conv. Mix composition at the reactor outlet (weight %) (hr) (%) CH4 C2H6 C3H8 n-C4H10 I-C4Ho E Par. >C4 n. Par >C1 7 100 4. 8 11. 4 48. 4 18. 5 13. 5 3. 5 80. 3 Example 11/B Operative conditions Hydrocarbons fed 100% 1, 2, 4-trimethyl benzene Reaction, temperature ('C) 450 WHSV (hours~1) 0. 8 Pressure. (bar) 60 H2/Hydrocarbons molar ratio 10. 7 * Catalytic performances TOS Conv. Mix composition at the reactor outlet (weight %) (hr) (%) CH4 CZH6 C3H8 n-C4Ho I-C4Ho E Par. >C4 En. Par>C1 17 100 16. 1 30. 9 49. 9 1. 8 1. 2 0. 1 82. 7 Example 11/C * Operative conditions Hydrocarbons fed 100% 1, 2, 4-trimethyl benzene Reaction temperature (°C) 450 WHSV (hours'') Pressure (bar) 60 H2/Hydrocarbons molar ratio 35. 4 * Catalytic performances TOS Conv. Mix composition at the reactor outlet (weight %) (hr) (%) CH4 C2H6 C3H8 n-C4Ho I-C4Hio E Par. >C4 En. Par >C1 17. 5 100 14. 6 19. 9 47. 2 10. 9 7. 0 0. 4 78. 3

Table 3 EXAMPLES 12/A-12/C Cafalyst Type and Preparation Reference ZnCu/USY Zeolyst CBV500 ; See Ex. 3 Example 12/A * Operative conditions Hydrocarbons fed 100% 1, 2, 4-trimethyl benzene Reaction temperature ('C) 450 WHSV : (hours~1) 0. 8 Pressure (bar) 60 H2/Hydrocarbons molar ratio * Catalytic, performances TOS Conv. Mix composition at the reactor outlet (weight %) (hr) (%) CH4 C2H6 C3H8 n-C4HIO I-C4H, EPar. >C4 En. Par >C1 17 99. 2 4. 6 4. 5 31. 2 14. 1 18. 7 23. 4 57. 6 Example 12/B * Operative conditions Hydrocarbons fed 100% 1, 2, 4-trimethyl benzene Reaction temperature (°C) 400 WHSV (hours~1) 0. 8 I Pressure (bar) 60 H2/Hydrocarbons molar ratio 32. 0 * Catalytic performances TOS Conv. Mix composition at the reactor outlet (weight %) (hr) (%) CH4 | 3H8 n-C4HIO C3Hs EPar. >C4 Sn. Par>C1 7 100 2. 3 3. 9 29. 7 21. 6 29. 8 12. 7 63. 3 Example 12/C * Operative conditions Hydrocarbons fed 100% 1, 2, 4-trimethyl benzene Reaction temperature (°C) 450 WHSV (hours 0. 8 Pressure (bar) 60 H2/Hydrocarbons molar ratio 32. 0 * Catalytic performances TOS Conv. Mix composition at the reactor outlet (weight %) (hr) (%) CH4 CZH6 C3H8 n-C4Ho I-C4Ho E Par. >C4 n. Par >C1 17 100 6. 7 8. 8 46. 8 19. 9 15. 1 2. 6 77. 2

Table 4-EXAMPLES 13/A-1, 3/C * Catalyst Type and Preparation Reference Mo/USY Zeolyst CBV500 ; See Ex. 4 Example 131A * Operative conditions Hydrocarbons fed 100% 1, 2, 4-trimethyl benzene Reaction temperature (°C) 400 WHSV (hours 1 0. 8 Pressure (bar) 60 H2/Hydrocarbons molar ratio 10. 0 * Catalytic performances TOS Conv. Mix composition at the reactor outlet (weight %) (uhr) (%) CH4 C'H C2H6 n-cho C3H8 EPar. >C4 En. Par>C1 17 100 1. 4 9. 4 40. 1 21. 3 18. 7 9. 0 76. 0 Example 13/B * Operative conditions Hydrocarbons fed 100% 1, 2, 4-trimethyl benzene Reaction temperature (°C) 450 WHSV (hours~1) 0. 8 Pressure (bar) 60 H2/Hydrocarbons molar ratio 10. 0 * Catalytic performances TOS Conv. Mix composition at the reactor outlet (weight %) (hr) (%) CH4 CH6 C3H8 n-C4Ho I-C4Ho E Par. >C4 En. Par >C1 17 100 6. 0 20. 7 56. 6 8. 8 5. 8 2. 1 87. 0 Example 13/C * Operative conditions Hydrocarbons fed 100% 1, 2, 4-trimethyl benzene Reaction temperature (°C) 450 WHSV (hours") 0. 8 Pressure (bar) 60 H2/Hydrocarbons molar ratio 31. 9 Catalytic performances TOS Conv. Mix composition at the reactor outlet (weight %) (hr) (%) CH4 CZH6 C3H8 n-C4Ho I-C4Hp E Par. >C4 | zn. Par >C1 17 100 12. 9 26. 3 47. 8 7. 7 5. 1 0. 2 81. 9

Table 5 EXAMPLES 141A-141C * Catalyst Type and Preparation Reference Zn/USY Zeolyst CBV500 ; See Ex. 5 Example 14/A * Operative conditions Hydrocarbons fed 100% 1, 2, 4-trimethyl benzene Reaction temperature (°C) 450. WHSV (hours~1) 0. 8 Pressure (bar) 60 H2/Hydrocarbons molar ratio 10. 1 * Catalytic performances TOS Conv. Mix composition at the reactor outlet (weight %) (hr) (%) CH4 CzHe CsHg nHip iHio EPar. >C4 En. Par >C1 17. 5 97. 4 4. 2 4. 4 29. 1 11. 6 14. 5 20. 3 48. 0 Example 14lob * Operative conditions Hydrocarbons fed 100% 1, 2, 4-trimethyl benzene Reaction temperature (°C) 400 WHSV (hours~1) 0. 8 Pressure (bar) 60 H2/Hydrocarbons molar ratio 32. 8 * Catalytic performances TOS Conv. Mix composition at the reactor outlet (weight %) (hr) (%) CH4 C2H6 C3H8 n-C4Ho I-C4Ho E Par. >C4 Fn. Par>C1 7 99. 6 1. 5 2. 2 31. 4 21. 5 29. 1 12. 0 59. 2 Example 14/C * Operative conditions Hydrocarbons fed 100% 1, 2, 4-trimethyl benzene Reaction temperature (°C) 450 WHSV (hours 0. 8 Pressure (bar) 60 H2/Hydrocarbons molar ratio 32. 3 * Catalytic performances TOS Conv. Mix composition at the reactor outlet (weight %) (hr) (%) CH4 C2H6 C3H8 n-C4Ho I-C4Ho Par. >C4 En. Par >C1 17 99. 6 6. 1 7. 0 50. 1 18. 5 14. 5 3. 0 76. 5 Table 6 (3 examples, from Ex. 15/A to Ex. 15/C) shows the operative conditions and the catalytic performances ob- tained using a catalyst based on Pd on USY-zeolite, pre- pared as described in example 6.

Table 6 EXAMPLES 15/A - 15/C * Catalyst Type and Preparation Reference Pd/USY Tosoh HSZ 320 HOA; See Ex. 6 Example 15/A * Operative conditions Hydrocarbons fed 100% 1,2, 4-trimethyl benzene Reaction temperature (OC) 400 WHSV hours-1) 0. 7 Pressure (bar) 60 H2/Hydrocarbons molar ratio 10. 1 * Catalytic performances TOS Conv. Mix composition at the reactor outlet (weight %) (hr) (%) CH4 C2H6 C3H8 n-C4H10 I-C4H10 # Par. >C4 #n.Par >C1 7 100 7.9 16. 0 48.8 14.2 11.0 2.1 79. 0 Example 15/B * Operative conditions Hydrocarbons fed 100% 1,2,4-trimethyl benzene Reaction temperature (°C) 450 WHSV hours-1) 0.7 Pressure (bar) 60 H2/Hydrocarbons molar ratio 10. 1 * Catalytic performances TOS Conv. Mix composition at the reactor outlet (weight % (hr) (%) CH4 C2H6 C3H8 n-C4H, o I-C4H, o E Par. >C4 En. Par >C1 17. 5 100 17.0 32. 4 47. 4 1. 9 1.3 0. 2 81. 7 Example 15/C * Operative conditions Hydrocarbons fed 100% 1,2, 4-trimethyl benzene Reaction temperature (°C) 450 WHSV (hours~1) 0. 7 Pressure (bar) 60 H2/Hydrocarbons molar ratio 35. 7 * Catalytic performances TOS Conv. Mix composition at the reactor outlet (weight % (hr) (%) CH4 C2H6 C3Hs n-C4H10 I-C4H10 # Par. >C4 #n.Par >C1 17.5 100 11.5 21.2 51.7 9. 1 6. 5 0. 1 82.0 Table 7 (3 examples, from Ex. 16/A to Ex. 16/C) shows the operative conditions and the catalytic performances ob- tained using a catalyst based on Zn/Mo on USY-zeolite previously exchanged with La, prepared as described in Example 7. Also in this case, the results obtained are extremely good and show that it is possible to operate in an advantageous way also using compositions having a more complex composition, as mentioned in the description of the present invention.

Table 8 (2 examples, from Ex. 17/A to Ex. 17/B) shows the results relating to the same catalyst used in Examples 16/A-16/C of Table 7, adopted in a test of a longer duration. The results of Example 17/A were ob- tained after 260 hours of operation after the last regen- eration and it was demonstrated that an excellent cata- lytic performance is maintained. The results of Example 17/B (270 hours after the last regeneration), were ob- tained after increasing the reaction temperature to 500°C ; the yield to light paraffins, particularly ethane and propane, is extremely good and the methane production is reasonably contained.

Table 7 EXAMPLES 16/A-16/C * Catalyst Type and Preparation Reference Zn-Mo/La-USY Zeolyst CBV500 ; See Ex. 7 Example 16/A Operative conditions Hydrocarbons. fed 100% 1, 2, 4-trimethyl benzene Reaction temperature (°C) 400 WHSV (hours1) 0. 8 Pressure (bar) 60 H2/Hydrocarbohs molar ratio 10. 1 Catalytic performances TOS Conv. Mix composition at the reactor outlet (weight %) ru 7 100 2. 7 8. 3 41. 8 22. 1 18. 2 6. 9 76. 4 100 1 2 7 | 83 | 418 | 22. 1 | 18. 2 \ 6. 9 | 76. 4 Example 16/B Operative, conditions- Hydrocarbons fed 100% 1, 2, 4-trimethyl benzene Reaction temperature (°C) 450 WHSV (hours") 0 Pressure (bar) 60 H2/Hydrocarbons molar ratio 10. 1 Catalytic performances TOS Conv. Mix composition at the reactor outlet (weight %) (hr) (%) CH4 CZH6 C3H8 n-C4Ho I-C4Ho Par. >C4 En. Par >C1 17. 5 100 11. 4 24. 2 56. 6 4. 3 2. 9 0. 6 85. 5 Example 161C * Operative conditions Hydrocarbons fed 100% 1, 2, 4-trimethyl benzene Reaction temperature (°C) 450 WHSV (hours~1)"0. 8 Pressure (bar) 60 H2/Hydrocarbons molar ratio 31. 9 * ytic performances TOS Conv. Mix composition at the reactor outlet (weight %) (hr) (%) CH4 C2H6 C3H8 n-C4Ho I-C4H, o F, Par. >C4 En. Par >C1 17 100 12. 6 18. 8 46. 6 13. 1 8. 2 0. 7 78. 9

: Talile 8 EXAM'P. LES 17% A-171B. *'Catalyst., Type. and Preparation Reference Zn-Mo/La-USY Zeolyst CBV500 ; See Ex. 7 Example 17/A n * Upeqråtive co. nditions'. N, ydrocarbons fed.. 100% 1, 2, 4-trimethyl benzene Reaction temperature (°C) 450 WHSV 0. 8 Pressure (bar) 60 H2/Hydrocarbons molar ratio 31. 6 * Catalytic performances Mix composition at the reactor outlet (weight %) (hr) (%) CH4 CzHe CgHs n-C4Hio tHio Epar. >C4 En. Par>Cl 260 100 6. 9 17. 7 48. 5 15. 1 10. 1 1. 3 81. 8 Example 17/B * Operative conditions Hydrocarbons fed 100% 1, 2, 4-trimethyl benzene Reaction temperature (°C) 500 WHSV (hours'*) 0. 8 Pressure (bar) 60 H2/Hydrocarbons molar ratio. 31. 7 * Catalytic performances TOS Conv. Mix composition at the reactor outlet (weight %) (hr) (%) CH4 C2H6 C3H8 n-C4Ho I-C4Ho E Par. >C4 n. Par >C1 270 100 17. 1 33. 8 46. 1 1. 8 1. 1 0. 0 81. 7 Table 9 (Example 18) shows the results obtained with a Pd on an La-USY based catalyst, prepared according to the description in Example 8. The test was carried out with a feed consisting of dicyclopentadiene. The catalyst effec- tively converted the feed into low molecular weight par- affins.

Table 9 EXAMPLE 18 * Catalyst Type and Preparation Reference Pd/La-USY Tosoh HSZ 320 HOA ; See Ex. 8 * conditions t Hydrocarbons fed 100% di-cyclopentadiene Reaction temperature (°C) 450 WHSV (hours~1) 0. 7 Pressure (bar) 60 H2/Hydrocarbons molar ratio 34. 8 1 * Catalytic performances TOS Conv. Mix composition at the reactor outlet (weight %) (hr) (%) CH4 C2H6 C3H8 n-C4H10 I-C4Ho E Par. >C4 En. Par >C1 17 100 4. 3 10. 0 39. 1 19. 7 13. 1 13. 8 74. 1 Table 10 (8 examples, from Ex. 19/A to Ex. 19/H) indi- cates the results obtained with a Pd on USY based cata- lyst, prepared according to the description in Example 6.

The test was carried out by repeatedly changing the feed, as shown in Table 10. 40-50 working hours were effected with each different feed, and the catalyst was always re- generated before passing to the subsequent feed. The test clearly shows that the catalyst is capable of effectively converting all the hydrocarbons tested and, at the same time, that the catalyst can be repeatedly regenerated.

Table 10 - Examples 19/A - 19/H Catalyst Type and Preparation Reference Pd/USY Tosoh HSZ 320 HOA; See Ex. 6 Operative conditions Reaction temperature (°C) 450 WHSV (hours-1) 0. 7 Pressure (bar) 60 TOS (hr) 17 * Catalytic performances Feed Conv. Mix composition at the reactor outlet (weight %) type (%) CH4 C2H6 C3H8 n-C4Ho I-C4H10 # Par. >C4 En. Par >C1 19/A 100 8.6 21.1 63.9 3.6 2.6 0.3 88.7 19/B 98.1 1.2 7.9 21.7 11. 2 7.7 19.9 42. 7 19/C 100 0.9 8.4 30.7 18.4 20.6 17.9 66.3 19/D 100 2. 1 11.3 42.2 20.6 15.9 8.0 77.1 19/E 100 12.2 14.5 44.3 16.6 11.7 0.8 75.6 19/F 100 10.4 22.1 48.1 11.2 7.9 0.2 81.6 19/G 100 2.9 11.2 36.0 23.2 18.1 8.6 73.7 19/H 100 5.1 14.3 44.9 19.8 13.2 2.6 80.0 19/A : hydrocarbon = 100% cumene, H2/Hydrocarbon molar ratio = 10.1 19/B: hydrocarbon = 100% indane, H2 / Hydrocarbon molar ratio = 10.3 19/C : hydrocarbon =100% indane, H2 / Hydrocarbon molar ratio = 19.5 19/D: hydrocarbon = 100% indane, H2/Hydrocarbon molar ratio = 31.7 19/E: hydrocarbon = 100% 1,2, 4-trimethyl cyclohexane H2/Hydrocarbon molar ratio = 38.3 19/F: hydrocarbon = mix ethyl benzene + xylene isomers, H2 / Hydrocarbon molar ratio = 35. 0 19/G: hydrocarbon = mix tetramethyl benzene isomers H2/Hydrocarbon molar ratio = 34.8 19/H : hydrocarbon = 85% weight 1,2, 4-trimethyl benzene + 15% weight naphthalene H2/Hydrocarbon molar ratio = 36.0 Table 11 (5 examples, from Ex. 20/A to Ex. 20/E) indi- cates the results obtained with a catalyst based on Zn and Mo on USY-zeolite, prepared according to the descrip- tion in Example 9. The test was carried out by feeding different types of hydrocarbons, as shown in the same Ta- ble 11.

20~30 working hours were effected with each hydrocarbon, and the catalyst was always regenerated before passing to the subsequent feed. The test shows that the catalyst is capable of effectively converting all the hydrocarbons fed and that it can be regenerated.

Table 11 - Examples 20/A - 20/E Catalyst type and Preparation Reference ZnMo/USYZeofystCBVSOO ; See Ex. 9 * Operative conditions Reaction temperature (°C 420 WHSV '(hours~1) 0. 8 Pressure (bar) 60 TOS (hr) 11 * Catalytic performances Feed Conv. Mix composition at the reactor outlet (weight %) type (%) CH4 C2H6 C3H8 n-C4H10 I-C4H10 # Par. >C4 En. Par >C1 20/A 100 6.4 15. 5 57.9 10.9 7.7 1.6 84.9 20/B 100 10.3 17.1 55.7 9.6 6. 5 0.7 82.9 20/C 100 6.4 12.0 42.1 19.2 13.2 7.0 77.7 20/D 100 10.4 18.7 53.0 10.1 6. 9 0. 9 82.4 20/E 100 3.4 11.5 44. 9 20.5 15.5 4. 0 79.3 20A: hydrocarbon = 100% decahydronaphthalene (decaline) H2/Hydrocarbon molar ratio = 11.6 20B: hydrocarbon = 100% n-decane H2/Hydrocarbon molar ratio = 14.3 20C: hydrocarbon = 100% di-cyclo pentadiene H2 I Hydrocarbon molar ratio = 33. 5 20D: hydrocarbon = 100% weight 1,2, 4-trimethyl cyclohexane H2/Hydrocarbon molar ratio = 11.8 20E: hydrocarbon = 13. 5% decahydronaphthalene + 13. 1% n-decane + 12.7% di- cyclo pentadiene + 13. 4% 1,2, 4-trimethyl cyclohexane + 13. 1% naphthalene + 34.2% 1,2, 4-trimethyl benzene, H2/Hydrocarbon molar ratio = 33.8

Table 12 (2 examples, from Ex. 21/A to Ex. 21/B) indi- cates the results obtained with the feed consisting of two different high molecular weight hydrocarbon mixtures (the composition of the mixtures is specified in the same Table 12). A catalyst based on Zn and Mo on La-USY- zeolite was used in this case (prepared according to the description in Example 9). The results show the conver- sion obtained with aromatic compounds having more than one benzene ring.

Table 12-Examples 21/A-21/B Catalyst Typè'and Preparation Reference |ZnMo/USY Zeolyst CBV500 ; See Ex. 9 * Operative conditions Reaction temperature (°C) 450 WHSV (hours ; 1) 0. 9 Pressure (bar) 60 TOS (hr) for ex. 21/A = 21 h ; for Ex. 21/B = 80 h * Catatytic performances Feed Conv."Mix composition at the reactor outlet (weight %) type (%) CH4 C2H6 C3H8 n-C4H, o I-C4Ho I Par. >C4 En. Par >C1 21 A 100 9.0 17.7 47. 0 5. 1 9.8 1.4 80.7 21/B 100 5.3 15. 7 46.3 18. 0 12. 3 2.3 81. 5 21/A: hydrocarbon = 50% by weight of dimethyl naphthalenes + 50% by weight of trimethyl naphthalenes, H2/Hydrocarbon molar ratio = 39.4 21/B: hydrocarbon = 84. 5% by weight of 1,2, 4-trimethyl benzene + 4. 4% by weight of dimethyl naphthalenes + 4. 4% by weight of trimethyl naphthalenes + 1.8% by weight of anthracene + 1. 7% by weight of di-hydro anthracene + 2.5% by weight of di-hydro phenanthrene + 0.7% by weight of methyl anthracene, H2/Hydrocarbon molar ratio = 30.1 Table 13 (Example 22) indicates the results obtained in a test of a longer duration with a catalyst based on Zn and Mo on USY-zeolite, prepared according to the description in Example 7. The feed composition was changed several

times during the'test, but the catalyst was never regen- erated. The. test was interrupted after 1, 200 working hours. As indicated in Table 13, the feed contained ;'sul- furated compounds with concentrations of 5, 000-6, 500 ppm, for long running periods, and the catalytic performance was always excellent for the purposes of the present in- vention.

Table 14 (Example 23) indicates the results obtained with a catalyst based on Zn and Mo on USY-zeolite, pre- pared according to the description in Example 7. The test was carried out with a mix of hydrocarbons containing ethyl benzene, xylenes, styrene, methyl styrenes, cumene, trimethyl benzene, methyl ethyl benzenes, indane, di- cyclo pentadiene, naphthalenes and methyl naphthalenes, according to the composition shown in the same Table 14.

The test clearly demonstrates that the catalyst is capa- ble of effectively converting the entire hydrocarbon mix fed to low molecular weight paraffins.

Table13 EXAMPLE22. *Catalyst Type and Preparation Reference Zn-Mo/La-USY Zeolyst CBV500 ; See Ex. 7 * Operative conditions Reaction temperature (°C) 450 WHSV (hours-1) 0.8 Pressure (bar) 60 H2/Hydrocarbons molar ratio 31.9 * Catalytic performances Hydrocarbons fed = 100% 1,2,4-trimethyl benzene TOS Conv : Mix composition at the reactor outlet (weight %) CH4 C2H6 C3H8 n-C4H10 I-C4H10 # Par. >C4 En. Par >C1 17 100 8.7 17.4 46.7 15. 7 10. 3 1. 2 80. 6 275 100 6. 5 16. 7 47. 2 16. 6 11.0 1.6 81. 0 479 100 6. 3 15.4 45.9 17.7 11.9 2.0 80.2 Hydrocarbons fed = 99.4% 1,2, 4-trimethyl benzene + 5000 ppm thio-octanol + 1500 ppm di-benzo thiophene TOS Conv. Mix composition at the reactor outlet (weight %) (hr) (%) CH4 C2H6 C3H8 n-C4H10 I-C4H10 # Par. >C4 En. Par >C1 526 100 6.9 21.1 55.9 9.2 6.2 0.5 86.5 581 100 7.2 22.9 56.4 7.8 5.3 0.4 87.2 623 100 7. 7 22.6 57.0 7.3 5.0 0.4 87. 1 Hydrocarbons fed = 69.5% 1,2, 4-trimethyl benzene + 30% naphthalene + 5000 ppm di- benzo thiophene TOS Conv. Mix composition at the reactor outlet (weight %) (hr) (%) CH4 C2H6 C3H8 n-C4H10 I-C4H10 # Par. >C4 En. Par >C1 625 100 7.8 22.7 56.8 7.3 5.0 0.3 87.0 819 100 6.3 20.7 57.2 8.8 6.1 0.6 87.1 999 100 5.7 19.2 57.3 9.8 6.7 0.8 86.6 1183 100 6.1 16.5 57.1 11.3 7.8 0.9 85.4

Table 14-Example 23 Catalyst Type and Preparation Reference ZnMo/La-USY Zeolyst CBV 500 ; See Ex. 7 Operative conditions Reaction temperature (°C) 420 WHSV (hours'0. 8 Pressure (bar) 60 H2/Hydrocarbons molar ratio 19. 9 * Catalytic performances TOS Conv. Mix composition at the reactor outlet (weight %) (h) (%) CH4 C2H6 C3H8 n-C4H10 I-C4H10 # Par.>C4 #n.Par >C1 11 100 3.7 16.6 47.5 16.8 11.7 3.2 82. 5 Hydrocarbons fed = 5% ethyl benzene + 10% mix of xylenes + 20% styrene + 10% mix of methyl styrenes + 3% cumene + 12% mix of trimethyl benzenes and methyl ethyl benzenes + 10% indane + 25% di-cyclo penta- diene + 5% mix of naphthalenes and methyl naphthalenes