Polymerization Reactions in the Presence of a Catalyst Containing Aluminum Oxide, Boron Oxide and Halogen

This invention concerns a process for polymerizing hydrocarbons, particularly for polymerizing olefinic hydrocarbons in order to produce synthetic oils, gasolines of high octane number, jet fuels, base products for platicizers such as hexenes, heptenes or nonenes, base products for detergents such as dodecenes, hydraulic fluids and oils of high viscosity index and low pour point.

Polymerization processes used on industrial scale make use, as catalyst, of aluminum trichloride or complexes or solutions thereof. These processes have however a disadvantage: in view of the formation of complexes between the olefinic hydrocarbons and the aluminum chloride, it is necessary to proceed with two additional steps, one for decomposition of the complex, the other for a thorough washing of the reaction products. If these treatments were not performed, the resulting hydrocarbons would have unacceptable chlorine contents.

According to this invention, the polymerization reactions are performed in the presence of a solid catalyst, of excellent stability and which does not lead to the formation of undesirable complexes with olefinic hydrocarbons; this catalyst (already used for alkylation of aromatic hydrocarbons: U.S. Pat. Nos. 4,062,805 and 4,092,371) contains aluminum and boron. It further contains, by weight, 0.5 to 20%, preferably 4 to 12%, of halogen. In the catalyst, boron oxide amounts to 0.01 to 1 part by weight per part by weight of aluminum oxide. Preferably, for the considered polymerizations, the molar ratio of boron oxide to alumina is from 0.07 to 0.15.

This catalyst is obtained by contacting an aluminum halide or aluminum hydrocarbyl halide with a carrier containing aluminum oxide and boron oxide. This treatment is advantageously followed with heating at a temperature from 300.degree. to 800.degree. C. Although the foundamental mechanism of this operation is still not well known, it seems that a true reaction takes place between aluminum halide or aluminum hydrocarbyl halide and the boron and aluminum oxides mixture. The presence of boron oxide appears, moreover, to be essential; as a matter of fact, when a catalyst is prepared by the same method, in the absence of boron oxide, and is used in polymerization, it is observed that this catalyst quickly losses its initial activity and that the polymerizate contains a substantial amount of aluminum compound or complex. The effect of boron is thus to provide for a better fixation of the aluminum compound on the catalyst so that the aluminum compound cannot be carried away by the reaction products of the polymerization reaction.

As above mentioned, for one part by weight of aluminum oxide, the usual amount of boron oxide is from 0.01 to 1 part by weight. Additional refractory oxides may be present, for example acid oxides such as silica, although this is not preferred.

Aluminum oxide is preferably used in a form having, either during the admixture of the components or after calcination at 300.degree.-800.degree. C., a substantial specific surface, preferably at least 5 m.sup.2 per gram, so that the final catalyst itself has a substantial specific surface, advantageously at least 5 m.sup.2 /g and preferably from 50 to 100 m.sup.2 /g.

Boron oxide may be introduced as such or preferably in the form of a compound decomposable to boron oxide by heating. It is preferred to make use of anyone of the boric acids.

The mixture of aluminum oxide with boron oxide may be performed in any known manner, for example by mechanical admixture of powders, in dry state or in the presence of water, or, preferably, by impregnating alumina by means of an aqueous solution of boric acid. In lieu of oxides or acids, the starting compounds may be compounds decomposable to oxides by heating, particularly nitrates. After this admixture, a drying step is performed, if necessary, for example by heating at 100.degree.-500.degree. C.

During the step of contacting the mixture of aluminum and boron oxides with an aluminum halide or an aluminum hydrocarbyl halide, the operation is conducted preferably in the absence of water and oxygen, by making use of dry oxides, in order to avoid an useless and sometimes noxious secondary reaction of hydrolysis of the aluminum halide or aluminum hydrocarbyl halide.

The reaction of the aluminum halide or aluminum hydrocarbyl halide with the mixture of aluminum and boron oxides may be effected at ordinary temperature or at any temperature compatible with the stability of the reactants, usually between -20.degree. and 250.degree. C. or more.

As above mentioned, the amount of aluminum halide or aluminum hydrocarbyl halide, calculated as halogen, to be introduced in the catalyst, usual amounts to 0.5 to 20%, preferably 4 to 12% of the alumina weight.

The fixation of the aluminum halide or aluminum hydrocarbyl halide on the carrier being generally relatively rapid and complete, it is not usually necessary to use an excess of said halide.

The aluminum hydrocarbyl halide is used preferably as a solution in a non-reacting solvent, for example a hydrocarbon containing preferably from 5 to 20 carbon atoms per molecule or a halogenated hydrocarbon.

The aluminum or aluminum hydrocarbyl halides comply with the general formula AlX.sub.y R.sub.(3-y) wherein y is 1, 3/2, 2 or 3, X is halogen, preferably chlorine, the case being however excepted where simultaneously X is fluor and y is equal to 3, and R is a monovalent hydrocarbon radical containing, for example, from 1 to 20 carbon atoms. There can be used, for example, diethylaluminum chloride, dodecylaluminum dichloride, di-isobutyl aluminum chloride, diethylaluminum fluoride, benzylaluminum dichloride, phenylaluminum dichloride, cyclohexylaluminum dichloride or ethylaluminum sesquichloride.

The aluminum trihalide may be for example a trichloride or a tribromide, e.g. aluminum trichloride or aluminum tribromide. This compound may be introduced in the catalyst by impregnation or by sublimation; in the case of AlCl.sub.3 and of sublimation, the temperatures are about 185.degree. to 400.degree. C. On the contrary, when proceeding by impregnation, any temperature compatible with the existence of an imprenation liquid phase may be convenient. Aluminum trifluoride does not provide for an active catalyst.

The fixation of the halide on the carrier is performed under neutral or reducing atmosphere, for example in the presence of nitrogen, hydrogen, methane, under normal pressure or a different pressure.

After the fixation of the aluminum halide or aluminum hydrocarbyl halide, the material may be brought to 300.degree.-800.degree. C., preferably 400.degree.-600.degree. C. The duration of this treatment is usually from 10 minutes to 24 hours, these values being however not limitative. As a matter of fact, at very high temperatures, the treatment may be considerably shortened.

The polymerizable olefins are preferably those having from 2 to 16 carbon atoms, for example: ethylene, propylene, 1- and 2-butenes, isobutylene, pentenes and isopentenes, hexenes, propylene trimer or tetramer, diisobutylene.

The polymerization temperature is selected from 0.degree. to 90.degree. C., preferably from 20.degree. to 80.degree. C. and more particularly from 30.degree. to 75.degree. C. The pressure is usually from 10 to 100 atmospheres and preferably from 20 to 60 atmospheres.

Although it is possible to proceed with a dispersed catalyst, it is however preferred to circulate the reactants through the catalyst in fixed bed. The flow rate (V.V.H.) is, for example, from 0.25 to 20 and preferably from 0.5 to 2 (volume of olefinic hydrocarbon per volume of catalyst and per hour).

The reaction being strongly exothermic, the temperature will be maintained to an acceptable value by removing heat excess in a known manner, for example by cooling the reactor walls, vaporizing a portion of the liquid stream, recycling a portion of the reactor effluent, previously cooled, diluting the olefin with a saturated hydrocarbon such as propane, butane, pentanes, hexanes or heptanes.

The operation is preferably performed by adding a halogen promoter to the reactants, either continuously or periodically, particularly a halohydric acid, for example hydrochloric acid or hydrofluoric acid, or a hydrocarbyl mono- or poly-halide, for example methyl choloride, ethyl chloride, tert. butyl chloride, chloroform, carbon tetrachloride of dichlorodifluoromethane. This promoter is usually present in an amount from 10 to 20,000 ppm by weight with respect to the hydrocarbons to polymerize. It is advantageous to recycle the unconverted reactants as well as the gas effluent from the reactor, containing halogen compounds, so that the halogen consumption may be very low.

The desired reaction product (which is then separated by distillation from the effluent obtained by the present process), is substantially free of halogen. It is thus unnecessary to subject it either to the usual treatments of decomposition of the chloroaluminic complexes, or to a thorough washing.

A particular example of application of the olefin polymerization is a process for manufacturing hydraulic fluids, process which consists of treating an olefinic charge issued from a steam cracking unit and selected either from a cut containing a major portion of olefins with four carbon atoms per molecule or from a cut containing a major portion of propylene or from a cut containing a major portion of propylene and olefins with four carbon atoms per molecule, said process being characterized in that:

(a) said charge is subjected to polymerization at a temperature from 0.degree. to 200.degree. C., in the presence of the above-described catalyst,

(b) the polymerization effluent is fractionated so as to obtain at least, on the one hand, a cut having a final distillation point of about 180.degree. to 200.degree. C. (preferably about 180.degree. C.), said cut being partially hydrogenated before being used as gasoline of high octane number, and on the other hand, a cut whose initial distillation point is about 180.degree.-200.degree. C.,

(c) the cut of distillation point higher than about 180.degree. C. is subjected to complete hydrogenation, and

(d) the effluent from the total hydrogenation step is fractionated so as to obtain at least:

(.alpha.) a cut distilling between about 180.degree. and 250.degree. C., complying with the specifications JET A-1 given in Table I,

(.beta.) a cut distilling between about 250.degree. and 330.degree. C., complying with specifications LHM and AIR 3520 A given in Table II.

Optionally a cut 330.degree. C..sup.30 is recovered.

The above process for manufacturing hydraulic fluids with the catalyst of the present invention, provides improved hydraulic fluids as compared to those obtained by the processes wherein the polymerization is conducted in the presence of silica-alumina, the processes making use of silica-alumina being themselves substantially superior to those wherein the polymerization catalyst is of the phosphoric acid type.

In a tubular reactor of stainless steel, there is arranged a fixed bed of 50 g of alumina having a specific surface of 200 m.sup.2 /g and a pore volume of 0.5 cc/g, previously roasted for one hour in air at 500.degree. C.

The reactor is then scavenged with a dry hydrogen stream at a rate of 20 liters of hydrogen per hour, a temperature of 450.degree. C., under a pressure of 40 atmospheres. After that, the temperature is decreased to 150.degree. C. and the pressure maintained at 40 atmospheres; there is then introduced, by means of a pump, 300 cc of a solution containing 0.25 mole per liter of Al.sub.2 Cl.sub.3 (C.sub.2 H.sub.5).sub.3 in hexane, at a rate of 60 cc/h.

After 5 hours of circulation, the pump is stopped and the temperature decreases to 60.degree. C. An analysis, performed on the solid, shows that the latter contains 10.2% by weight of chlorine. There is then injected over the so-formed catalyst a charge whose composition by weight is as follows:

The operating conditions were as follows:

The chlorinated promoter is tert.butyl chloride in a proportion of 0.5% by weight with respect to the charge.

The reaction product, analyzed by mass spectrometry, had the following composition by weight:

The carbon distribution was as follows:

Moreover the analysis of the products obtained after 75 hours and 200 hours of operation shows that the latter respectively contain, after washing with a 1/10 N sodium hydroxide solution and neutralization (for removing HCl):

It has been observed, during this heat, that the reaction products were strongly coloured to a brown-red colour which indicates the presence of complexes of the olefinic AlCl.sub.3 type.

In the same tubular reactor as in example 1, there is arranged a fixed bed of 50 g of a boron oxide-aluminum oxide carrier containing 90% by mole of alumina and 10% by mole of boron oxide obtained by co-mixing, extrusion and calcination of a mixture of alumina hydrate and boric acid.

After the product has been roasted at 500.degree. C. and the reactor scavenged with a dry hydrogen stream as described in example 1, 300 cc of a solution containing 0.25 mole per liter of Al.sub.2 Cl.sub.3 (C.sub.2 H.sub.5).sub.3 in hexane are introduced at a rate of 60 cc/h.

After 5 hours of circulation, the temperature is decreased to 60.degree. C. An analysis performed on the so-obtained catalyst shows that the latter contains b 10.2% by weight of chlorine. The charge of example 1 is passed through the catalyst under the same operating conditions as in example 1, with the same chlorinated promoter.

The reaction product, analyzed by mass spectrometry, had the following composition by weight:

The carbon distribution was as follows:

The product had the following characteristics:

bromine number: 59

specific gravity at 20.degree. C.: 0.802

The analysis of the obtained products, as well after 75 hours as after 200 hours of operation, has shown that the latter respectively contained, after washing with a 0.1 N sodium hydroxide solution and neutralization:

chlorine ppm<10

aluminum ppm<1

The products were perfectly clear and colourless.

This liquid phase has then been fractionated in a column with 35 theoretical plates, with a reflux rate of 8/1, so as to obtain 2 cuts, i.e.:

a first cut, having a final distillation point of 180.degree. C., amounting to 16% by weight of the total liquid phase, and

a second cut 180.degree. C..sup.+, amounting to 84% by weight of the total liquid phase.

The first cut, whose final distillation point is 180.degree. C., has the following characteristics:

This first cut has been partially hydrogenated in the presence of a catalyst based on palladium, deposited on alumina (0.4% by weight of palladium), in the following operating conditions:

For a hydrogenation rate of 50%, the characteristics of the gasoline were the following:

For a hydrogenation rate of 80%, the gasoline characteristics were the following:

The second cut 180.degree. C..sup.+ has been completely hydrogenated in the presence of a catalyst on platinum deposited on alumina (0.4% of platinum by weight), in the following operating conditions:

After complete hydrogenation, the product was fractionated under vacuum and three cuts were recovered:

a 180.degree.-250.degree. C. cut amounting to 25% by weight of the total product,

a 250.degree.-330.degree. C. cut amounting to 51% by weight of the total product,

a 330.degree. C..sup.+ cut amounting to 8% by weight of the total product.

The 180.degree.-250.degree. C. cut had the characteristics shown in Table I, with reference to the corresponding values of the specifications JET A-1.

It can be observed that this cut complies with all the specifications concerning the jet fuels. Such a cut, in view of its low aromatic content is also an excellent solvent.

The 250.degree.-330.degree. C. cut had the characteristics shown in Table II, in relation with the specifications LHM for motor-cars and aircraft AIR 3520 A.

It can be observed that the considered cut complies with all the specifications.

The product had the further advantage of being substantially inert with respect to different types of synthetic rubbers and plastic materials.

By adding to said hydrogenated 250.degree.-330.degree. C. cut a convenient viscosity index improver, there was obtained a hydraulic liquid complying with specification SAE 71R1, as shown in Table III below.

The starting feed charge is an olefinic C.sub.4 cut of lower isobutene content than the charge of the preceding examples and having the following composition by weight:

This charge is passed over the catalyst of example 2 under the following operating conditions:

The reaction product, analyzed by mass spectrometry, had the following composition by weight:

The carbon distribution was as follows:

The product further exhibited the following characteristics:

The analysis of the products obtained after 100 and 300 hours of operation has shown that the latter respectively contained, after whashing with a 0.1 N sodium hydroxide solution and neutralization for removing the hydrochloric acid:

chlorine ppm:<10

aluminum ppm:<1

After fractionation in a column of 35 theoretical plates there was obtained a first fraction having a final point of 180.degree. C., amounting to 8% by weight of the total liquid phase and a second fraction of 180.degree. C..sup.+ amounting to 92% by weight of the total liquid phase.

The first cut of final point 180.degree. C. had the following characteristics:

This cut has been partially hydrogenated in the presence of the palladium catalyst of example 2, under the same operating conditions as in said example 2.

For a hydrogenation rate of 50%, the gasoline characteristics were the following:

For a hydrogenation rate of 80%, the gasoline characteristics were the following:

The second cut 180.degree. C..sup.+ has been completely hydrogenated in the presence of the platinum catalyst of example 2 and under the same operating conditions as in said example 2.

After complete hydrogenation, the product fractionated under vacuum and 3 cuts were recovered:

a 180.degree.-250.degree. C. cut amounting to 13% by weight of the total product,

a 250.degree.-330.degree. C. cut amounting to 42% by weight of the total product,

a 330.degree. C..sup.+ cut amounting to 37% by weight of the total product.

The 200.degree.-250.degree. C. cut had the characteristics shown in Table IV below:

This cut complies with all the specifications concerning the jet fuels and is also an excellent solvent of the "white spirit" type, in view of its low aromatics content.

The 250.degree.-330.degree. C. cut had the characteristics shown in Table V.

This cut complies with the specifications concerning the hydraulic fluids.

By adding a convenient viscosity index improver to said hydrogenated 250.degree.-330.degree. C. cut, there was obtained a hydraulic liquid conforming to specification SAE 71R1 as shown in Table VI below.

The product was, in addition, substantially inert with respect to different types of synthetic rubbers and plastic materials.

The 330.degree. C..sup.+ cut was then fractionated under vacuum in two cuts:

a 330.degree.-380.degree. C. cut amounting to 17% by weight of the total product,

a 380.degree. C..sup.+ amounting to 20% of the same total product.

This latter cut has the following characteristics:

and it is accordingly convenient as oil base for combustion engines.

The feed charge was an olefinic C.sub.3 cut having the following composition by weight:

This charge is passed over the catalyst of example 2 under the following operating conditions:

The reaction product, analyzed by mass spectrometry, had the following composition by weight:

The carbon distribution was as follows:

The type of catalyst used was consequently perfectly adapted to the production of dodecenes, base products for detergents.

The starting charge was the olefinic C.sub.3 cut of example 4 and the catalyst that of example 2. The operating conditions were as follows:

The reaction product, analyzed by mass spectrometry, had the following composition by weight:

The carbon distribution was as follows:

The type of catalyst used was according very well adapted to the production of nonenes and hexenes, which are base products for plasticizers.

The starting charge was a C.sub.3 -C.sub.4 olefinic cut having the following composition by weight:

This charge was passed over the catalyst of example 2, in the following operating conditions:

The reaction product, analyzed by mass spectrometry, had the following composition:

The carbon distribution was as follows: (in %)

The catalyst is thus well adapted to the production of heptenes which are base products for plasticizers.

The starting charge was the same as in example 1. This charge was passed over the catalyst of example 2, under the following operating conditions:

The resulting product was then fractionated in a column with 35 theoretical plates, with a reflux rate of 8/1, so as to obtain two cuts, i.e:

a first cut, having an initial distillation point of 65.degree. C. and

a final distillation point of 200.degree. C., amounting to 88% by weight of the total liquid phase, and a second 200.degree. C..sup.+ cut amounting to 12% by weight of the total liquid phase.

The first 65.degree.-200.degree. C. cut had the following characteristics:

This cut has been partially hydrogenated, in the presence of a catalyst containing palladium deposited on alumina (0.4% by weight of palladium), in the following operating conditions:

For a hydrogenation rate of 50%, the characteristics of the gasoline were as follows:

For a hydrogenation rate of 80%, the gasoline characteristics were the following:

The type of catalyst used is thus very well adapted to the production of gasolines of high octane number.