US3422126A - Preparation of titanium alkylorthophosphates - Google Patents

Description

United States Patent 3,422,126 PREPARATION OF TITANIUM ALKYLORTHOPHOSPHATES Carl Robert Bauer, Elkton, Md., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Filed Mar. 19, 1965, Ser. No. 441,320 U.S. Cl. '260429.5 5 Claims Int. Cl. C07f 7/00; C07f 9/06 ABSTRACT OF THE DISCLOSURE Titanium tetra (monoand dialkylorthophosphate) are prepared by reacting one mole of tetra-C 0 alkyl titanate with four moles of mixed monoand di-C -C alkyl acid phosphates at about atmospheric pressure and 150 C.

This invention is directed to the preparation of chloridefree titanium alkylorthophosphates by the reaction of one mol of a tetra-C to C alkyl titanate with four mols of a mixed C to C monoand dialkyl acid phosphate at about 15 to 150 C.

Metal-containing phosphate esters have heretofore been obtained by first forming the alkali metal salt and replacing the alkali metal with the desired metal cation, or as in the case of aluminum salts, aluminum trichloride is reacted directly with the phosphate. This procedure is described in U.S. 2,416,985. Basic metal salts have also been reacted with phosphates, e.g., basic titanium chloride with a monoalkyl phosphoric acid ester, as in U.S. 2,885,417.

These methods have the disadvantages of HCl byproduct formation. In some applications of the titanium phosphate salt, e.g., as a lubricant additive, the presence of HCl is harmful and removal of even trace amounts is necessary; this requires special equipment and copious washing of the product.

Other reactions of titanium compounds with phosphates have been described. In U.S. 2,512,063, for example, an alcoholate, phenolate or chloride of a trivalent, amphoteric cation, e.g., titanium, is condensed with a neutral or nonacidic ester of phosphorus; polymeric products are obtained.

It is, therefore, an object of the present invention to provide a novel process for the preparation of chloridefree titanium phosphate salts, said process representing a technical advance in the art.

These and other objects will become apparent from the following description and claims.

It has been discovered that a chloride-free titanium salt of an alkyl phosphate can be obtained by the reaction of a mixed monoand dialkyl acid phosphate with a tetraalkyl titanate.

Tetraalkyl titanates have been reacted with phosphates as described in the report ASTIA, 402, 755, NY. Univ. College of Engineering, wherein a tetraalkyl titanate is reacted with a dialkyl acid phosphate, in the mol ratio of 1:2, titanate to phosphate. The product produced according to the present invention is the result of the reaction of one mole of titanate with four mols of mixed phosphates, said product differing in structure from that obtained in the above reaction.

More specifically, the present invention is directed to a process for the preparation of a titanium phosphate salt which comprises reacting about one mol of tetra-C to C alkyl titanate with about four mols of a phosphate consisting of mixed C to C mono and dialkyl acid phosphates at about 15 to 150 C. A preferred embodiment is that wherein the by-product alcohol is distilled 01f 0 3,422,126 C6 Patented Jan. 14, 1969 as formed. A slight excess of either reactant may be utilized.

The tetraalkyl titanates useful in the reaction with the alkyl acid phosphate according to this invention are alkyl esters of orthotitanic acid. Many of these are readily available and well known in the art. They are prepared by reacting TiCl with the desired anhydrous alcohol in the presence of a mild HCl acceptor like ammonia. A wide variety of these tetraalkyl esters may be employed to prepare the titanium phosphate salts, e.g., the tetra-methyl, -ethyl, -propyl, -isopropyl, -n-butyl, -isobutyl, -pentyl, -hexyl, -heptyl, -octyl and -2-ethylhexyl esters.

The alkyl acid esters of orthophosphoric acid (acid phosphates) which may be utilized are those esters in which only one or two of the three acidic hydrogen atoms of orthophosphoric acid have been replaced by the alkyl groups, i.e., the monoalkyl dihydrogen phosphates and the dialkyl hydrogen phosphates. Such esters may be obtained according to the general methods of the art which involve reacting an alcohol with phosphorus pentoxide (P 0 From about two to about four mols of the alcohol may be used per mol of P 0 Preferably, about three mols of the alcohol per mol of P 0 will be used to yield about 60 to about 40 mol percent of the dialkyl esters.

The alcohol may be straight or branched chain primary alcohol having 8-18 carbon atoms or a mixture of two or more of such alcohols. Suitable readily available straight chain alcohols are octanol, decanol, dodecanol, tetradecanol, hexadecanol and octadecanol.

The branched chain primary alcohols are preferably those made by the well known oxo process from C0, H and a branched chain olefin such as the C -C monoolefinic polymers and interpolymers of propylene and butylene, as described for example by Smith et al. in U.S. Patent 2,824,836 and by Rudel et al. in U.S. Patent 2,884,379. Examples of preferred oxo-alcohols that may be used are isooctyl alcohol from the propylene-butylene dimer, branched tridecyl primary alcohols from triisobutylene and from tetrapropylene, and the branched hexadecyl primary alcohols from pentapropylene. Other branched chain primary alkanols that can be used are those that may be prepared by alkaline condensation of two primary alkanols, having the structure RCH CH OH wherein R is alkyl and totalling two to six carbon atoms, to produce branched primary alkanols that are branched in the 2-position, i.e., RCH CH CHRCH OH. For example, 2-hexyldecanol-1 is produced by heating n-octanol with caustic and zinc dust, and similarly, 2-ethylhexanol-l from butanol-I, as described by Carter in U.S. Patent 2,457,866. Other alcohols, that may be prepared by the latter and other methods known in the art and used to prepare phosphates according to the present invention, are of the formula RCH CH CHR-CH OH where R is the same or different alkyl group, each having from two to six carbon atoms. The branched alcohols may also be prepared by the conventional alcoholization of suitable aldehydes followed by hydrogenation. In this way, the well known oxo-octaldehyde, which is obtained from heptene-l, CO and H and which is a mixture consisting very largely of dimethylhexaldehydes, ethylhexaldehydes, and methylheptaldehydes containing the grouping is converted into Z-hexyldecanol, RCHRCH OI-I, where R stands for C alkyl groups such as dimethylbutyl, methylpentyl, and ethylbutyl, and R stands for C alkyl groups such as dimethylhexyl, ethylhexyl and trimethylpentyl groups.

The novel process of the present invention is conveniently carried out by forming the mixed monoalkyl dihydrogen phosphate and dialkyl monohydrogen phosphate by reaction of about three mols of alcohol with one mol of P according to the method well known in the art. It is not necessary to purify the product. To the resulting crude mixed acid phosphtae reaction product, there is added in situ about /2 mol of the tetraalkyl titanate with agitation. Heating is gradually increased until reaction temperature is reached and by-product alcohol distills off. The reaction is continued until the theoretical quantity of alcohol is collected. The residue in the reaction vessel comprises the titanium phosphate salt.

For some purposes, the by-product alcohol need not be removed during the reaction, but may be allowed to remain in the reaction vessel, thus serving as a solvent medium for the reaction product.

The operable temperature range in the invention process is about to 150 C. Below 15 C., the reactant mass becomes a viscous oil ditficult to stir. Above 150 C., the alkyl phosphate start to decompose.

The products obtained by the process of this invention impart improved load carrying ability to ester lubricants.

Representative examples further illustrating the invention follow.

EXAMPLE I Preparation of the titanate of mixed monoand di-2- ethylhexyl acid phosphate A round-bottom five-liter reaction flask was fitted with a stirrer, thermometer and cooled with an ice water bath. The flask was charged with 1282 g. (9.86 mols) of 2-ethylhexanol. Agitation was started and 455 g. (3.20 mols) of phosphoric anhydride was added over minutes. During the addition, the temperature in the reaction mixture increased from below room temperature to 74 C. Next a heating mantle was put on the flask and the charge was stirred at 62 to 72 C. for 17 hours. There resulted a clear, homogenous, yellow oil. A dropping funnel was installed on the reaction flask and charged with 455 g. (1.60 mols) of tetraisopropyl titanate. With the agitation running and with the charge at 63 C., the 455 g. of tetraisopropyl titanate was added over a 40-minute period. The temperature increased to 78 C. during this addition. Next the flask was fitted with a sidearm take-01f running to a water-cooled condenser for isopropanol by-product distillation. Heating was gradually increased and at a 99 C. reaction mass temperature distillation began. After about 45 minutes, the reaction mass temperature reached 140 C. and 246 g. of isopropanol had been distilled over. Agitation was stopped and a nitrogen bubbler was installed in the flask. Vacuum was applied and distillation resumed at 92 mm. Hg absolute pressure and 133 C. reaction mass temperature. Nitrogen was slowly bubbled into the reaction mass to help sweep out the isopropanol. When the reaction mass temperature reached 139 C., after about ten minutes, the system was held at 139 to 141 C. under 100:3 mm. Hg absolute pressure and with nitrogen bubbling for one hour. Another 98 g. of isopropanol was collected for a total of 344 g., or 94% of the theoretical quantity of isopropanol. The product, that is the reaction flask residue, was a yellow oil weighing 1808 g.

Analysis.-Percent P: Found, 11.1; calcd 10.9 Percent Ti: Found 4.2; calcd 4.2.

EXAMPLE II Titanate of mixed monoand diisodecyl orthophosphates A 500 ml. round bottom flask, fitted with a stirrer, a heating mantle, a sidearm still head and pot and head temperature thermometers, was charged with 185 g. (0.6 mol) of mixed monoand diisodecyl orthophosphates and 51 g. (0.15 mol) of tetra-n-butyl titanate. The charge was heated under agitation to C. over about an hours time. Next vacuum was applied and held at 25 to 33 mm. Hg absolute pressure until distillation stopped and the pot temperature reached 153 C.

The viscous, opaque product weighed 204 g.; it was mostly soluble at 2 wt. percent in a SAE-30, paraffinic lube oil base stock. A slight haziness was, however, imparted to the oil.

EXAMPLE III Titanate of mixed monoand ditridecyl orthophosphates In the equipment described in the preceding Example II, a mixture of 223 g. (0.6 mol) of mixed monoand ditridecyl orthophosphates and 43 g. (0.15 mol) of tetraisopropyl titanate was heated under agitation to 150 C. Next vacuum was applied, temperature dropped a few degrees, and held at 21 mm. Hg absolute pressure until distillation stopped and the temperature in the charge returned to 150 C. The clear viscous product weighed 230 g.; it was completely soluble at two weight percent on a SAE-30, paraflinic lube oil base stock.

The preceding representative examples may be varied within the scope of the present total specification disclosure, as understood and practiced by one skilled in the art, to achieve essentially the same results.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that this invention is not limited to the specific embodiments thereof except as defined in the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are as follows:

1. A process for preparing a chloride-free titanium tetra (monoand dialkylorthophosphate) which comprises reacting one mole of tetra-C 43 alkyl titanate with about four moles of mixed monoand dis-C -C alkyl acid phosphate at about atmospheric pressure and a temperature of about 15 to 150 C.

2. A process according to claim 1 wherein the byproduct alcohol is distilled off as it is formed.

3. The process of claim 1 wherein tetraisopropyl titanate is reacted with mixed monoand di-Z-ethylhexyl acid phosphate.

4. The process of claim 1 wherein tetra-n-butyl titanate is reacted with mixed monoand diisodecylortho phosphates.

5. The process of claim 1 wherein tetraisopropyl titanate is reacted with mixed monoand ditridecylortho phosphates.

References Cited ASTIA report, 402, 755, NY. Univ. College of Engineering.

TOBIAS E. LEVOW, Primary Examiner.

H. M. S. SNEED, Assistant Examiner.