US3048611A - Making tetraethyl lead - Google Patents

Description

United States Patent 3,048,611 MAKENG TETRAETHYL LEAD Laszlo F. lliritz, Chicago, Ill., assignor, by mesne assignments, to Houston Chemical Corporation, New York, N.Y., a corporation of Texas N0 Drawing. Filed Nov. 24, 1961, Ser. No. 154,817 6 Claims. (Cl. 260--437) It has been proposed in Pagliarini U.S. Patent 2,848,- 471, August 19, 1958, to catalyze this reaction with various aryl or mixed aryl alkyl phosphates. The minimum reaction time in Pagliarini is 60 minutes.

It is an object of the present invention to provide a process of preparing tetraethyl lead in a shorter time than that disclosed by Pagliarini.

Another object is to utilize a lesser weight of catalyst than that employed by Paglian'ni, while at the same time obtaining at least an equal catalytic efiect.

Still further objects and the entire scope of applicability of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications Within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

It has now been found that these objects can be attained by reacting a lead-sodium alloy with ethyl chloride in the presence of a small amount, e.g., 0.002%, based on the moles of sodium in the lead-sodium alloy of a trialkyl phosphate having 1 to 4 carbon atoms in the alkyl groups. The preferred alkyl phosphates do not have over 3 carbon atoms in the alkyl groups.

While preferably lead-monosodium alloy is employed, there can be used other lead-sodium alloys such as Na Pb and Na Pb The sodium can be 5-20% of the alloy by weight. The ethyl chloride and lead-sodium alloy can. be reacted on an equimolar basis. an excess of the ethyl chloride is used, e.g., 1.3- moles per mol of lead-monosodium alloy, to obtain better yields.

Examples of suitable trialkyl phosphates which can be used as accelerators are trimethyl phosphate, triethyl phosphate, dimethyl ethyl phosphate, tripropyl phosphate, triisopropyl phosphate, tribu-tyl phosphate, tri secondary butyl phosphate and tri tertiary 'butyl phosphate.

The savings in catalyst over those disclosed in Pagliarini will be apparent when it is realized that there need be used in place of triphenyl phosphate (the simplest triaryl phosphate) only as much trimethyl phosphate, 59% as much triethyl phosphate, 72% as much tripropyl phosphate and 86% as much tributyl phosphate. The preferred material in Pagli-arini is tricresyl phosphate, since he employs it in all of his examples. Based on tricresyl phosphate there need be used only 76% as much tributyl phosphate, 64% as much tripropyl phosphate, 52% as much triethyl phosphate and 40% as much trimethyl phosphate.

The lowest molecular weight compound mentioned by However, preferably took 35-38 minutes to obtain a total yield of about 95% about 7073 C. in these runs.

"Ice

2 Pagliarini is dibutyl phenyl phosphate. There can be used 93% as much tributyl phosphate and 78% as much tripropyl phosphate to obtain an equivalent catalytic effect. While Pagliarini always considered it necessary to have an aryl group present the present invention is predicated on the fact that the aryl grouping can be omitted and an equivalent or better catalytic effect obtained utilizing less weight of catalyst and an attendant savings in cost.

The examples were carried out using the following conditions. A 150 ml. stainless steel bomb was purged with nitrogen (an inert atmosphere). Then 46 grams of leadmonosodium alloy (0.2 mol) of 12-24 mesh size were placed therein. The particle size of the alloy is conventional and is not critical. (Thus it can be widely varied, e.g., from 4 to 300 mesh.) The bomb was evacuated to about 1 mm. or less and put in a Dry Ice-acetone bath and then there were condensed in the bomb 80 grams of ethyl chloride. (This is a substantial excess of the ethyl chloride over theoretical and can be varied, for example between 70 and grams, without significant change in yields.) The bomb was then pressured with nitrogen to 10 p.s.i above atmospheric pressure. The alkyl phosphate catalyst (accelerator) was then put in the cold mixture and the bomb placed in a shaker bath maintained at about 70 C. It took about 3 minutes for the bomb to get to bath temperature. In the examples, in recording the time, the time to reach bath temperature is included. Hence the reaction time at the bath temperature was actually somewhat less than the times stated.

It may be noted that the temperature of reaction is not critical but can be varied, e.g., from 50-120" C.

In the examples total yield was obtained by determining the amount of sodium chloride formed and yield of tetraethyl lead (T.E.L.) was determined by iodine titration.

As previously indicated in the examples, the alloy employed was lead-monosodium alloy.

A series of controls were run, omitting the catalyst. 1t

and a T.E.L. yield of about 76% at a temperature of Approximately 18-20% of the total yield was by-product, rather than the desired tetraethyl lead.

Example I The catalyst employed was 0.728 grams of triethyl phosphate and the temperature was 70.2-70.6 C. There was a total yield of 95.5% and a T.E.L. yield of 84.8% in 21 minutes. This was a material reduction in time for completion of reaction and also was a reduction in side reaction from the 18-20% down to 11.16%. In contrast, certain other catalysts e.g., tetraethyl ortho silicate and acetone while reducing the time of reaction do not reduce the amount of side reaction.

When 1.408 grams of tn'cresyl phosphate were em-' ployed in place of the triethyl phosphate there was a total yield of 89.1% and a T.E.-L. yield of 71.54% in 27 minutes. The main reaction was about 80.3%. Thus with almost twice as much tricresyl phosphate it took a longer time to obtain a yield comparable to that obtained with the triethyl phosphate.

Example 11 presence of a trialkyl phosphate having 1 to 4 carbon atoms in the alkyl groups as a catalyst.

2. A process according to claim 1 wherein the catalyst is present in an amount of 0.002-5 mol percent based on the sodium in the alloy.

3. A process according to claim 2 wherein the leadsodium alloy is lead-monosodium alloy and the ethyl chloride is used in an amount in excess of that required to react with the alloy.

4. A process of preparing tetraethyl lead comprising 10 reacting a lead-sodium alloy and ethyl chloride in the presence of trimethyl phosphate as a catalyst.

5. A process of preparing tetraethyl lead comprising reacting a lead-sodium alloy and ethyl chloride in the presence of triethyl phosphate as a catalyst.

6. A; process of preparing tetraethyl lead comprising reacting a lead-sodium alloy and ethyl chloride in the presence of a tripropyl phosphate as a catalyst.

No references cited.

Claims (1)

1. A PROCESS OF PREPARING TETRAETHYL LEAD COMPRISING REACTING A LEAD-SODIUM ALLOY AND ETHYL CHLORIDE IN THE PRESENCE OF A TRIALKYL PHOSPHATE HAVING 1 TO 4 CARBON ATOMS IN THE ALKYL GROUPS, AS A CATALYST.