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Patented Sept. 10, 1946 2,407,262 UNITED STATES PATENT OFFICE’ 2,407,262 PROCESS FOR STABILIZING OR DEACTIVAT ING SLUDGES, PRECIPITATES, AND RESI DUES OCCURRING 0R USED IN THE MAN- " UFACTURE OF TETRAALKYL LEADS Adrian L. Linch, Wilmington, DeL, assignor to . E. I. du Pont de Nemours & Company, Wil- _ . mington, DeL, a corporation of Delaware N0 Drawing. Application September 16, 1942, Serial No. 458,579 8 Claims. 1 This invention relates to a process for stabiliz ing or deactivating sludges, precipitates and resi dues occurring or used in the manufacture of tetraalkyl leads, and which normally tend to pr - mote decomposition and ignition of the tetraalkyl leads that may be contained therein. It is known that alkyl metal compounds in general are quite unstable and decompose readily, (Cl. 260—43’7) 2 ' such as by controlled blowing with air or oxygen with agitation, preferably under a layer of water; followed by separation of the precipitated sludge, as more particularly described in copending ap plication Ser. No. 393,680. However, even in these cases the sludges which are deposited by the action of the oxidizing agent and which» in variably contain tetraethyl lead, tend to ignite particularly in the presence of air or oxygen. It when exposed to air thus presenting serious igni has also been found that these alkyl metal com 10 tion hazards, making it desirable that even these pounds are particularly unstable when adsorbed sludges should be deactivated during their forma on materials which present a large surface area tion or afterwards to permit of their removal per unit Volume such as silica gel, clays, alumina, earths, asbestos, charcoal, and materials of simi and disposal in a safe manner. It is therefore an object of this invention to lar structure which materials appear to exert a 15 provide a process for stabilizing sludges, precipi catalytic effect in the decomposition of these tates and residues occurring in the manufacture alkyl metal compounds. Even tetraalkyl leads of tetraalkyl lead compounds whereby the igni tion hazard presented by the lead alkyl com; somewhat more stable than some of the other pounds in contact with such catalytic surfaces alkyl metal compounds decomposes and often 20 is reduced‘or completely overcome. such as tetraethyl lead which is known to be ignites in the presence of oxygen when small amounts are adsorbed on materials that o?er It is a still further object of the invention to render inactive materials which tend to exert a extended surface areas,- particularly when the catalytic-effect in the decomposition of tetra masses containing the tetraethyl lead are exposed alkyl leads in the presence of air thus permitting to temperatures somewhat higher than normal 25 the safe use of such materials as ?lter aids in atmospheric temperatures. The tendency to oxi the manufacture of tetraalkyl lead.' dize and ignite of course varies with the sub I have found that the sludges, precipitates and stance with'which the alkyl metal compound is residues occurring or involved in the production incorporated,'s‘ome materials apparently exerting of tetraalkyl leads, which offer large surface a greater catalytic e?ect than others in promot; 30 areas per unit volume and which normally tend ing ignition of the alkyl lead compounds. to/exert'a catalytic e?ect and cause decomposi In the manufacture of tetraalkyl leads, such tion and ignition of the tetraalkyl lead which as tetraethyl lead, tetramethyl lead and the mixed may be contained therein, can be rendered inac ethyl-methyl lead compounds, sludges are formed tive conveniently and economically by washing from which it is diflicult and, from a practical 35 or otherwise treating them with solutions or dis standpoint, impossible to entirely free from the persions of polyfunctional phenols. These stabi alkyl lead compounds during the normal steam lizing agents appear to be preferentially absorbed distillations or decantation operations. There is, by the active materials which appearpto retain therefore, carried through the process very ?nely their capacity to absorb the alkyl lead although divided lead and impurities such as bismuth com 40 they are no longer effective to induce ignition of pounds which, although present in very small the tetraalkyl lead absorbed therein. amounts, ?nally are deposited as sludges in the By the terms sludges, precipitates and residues pipes and tanks and other processing equipment I include those ?lter aids which may be employed and these sludges which contain tetraethyl lead in the production of the tetraalkyl leads and adsorbed therein when exposed to oxygen or air 45 which o?er a large surface area per unit volume often ignite, thus presenting serious ignition and and are known to accelerate decomposition of explosion hazards in the process. the tetraalkyl leads on exposure to air or oxygen Methods have been advanced for the removal such as clays, silica, earths, charcoal, etc. These of practically all the sludge forming materials ?lter aids are rendered inactive by treating them from ‘the tetraethyl lead after its distillation, with polyfunctional phenols either before or 2,407,262 3 hydroxy (-—OI-I), alkoxy (—OR), as with air or oxygen is more particularly dis closed in copending application Ser. No. 393,680. The precipitated sludges from this process collect in the aqueous layer from which the puri?ed tet raethyl lead is separated by decantation. Al though dispersed in the Water layer the sludge retains su?icient tetraalkyl lead absorbed therein to ignite on contact with oxygen or air, particu larly at slightly elevated temperatures. In order to permit the safe handling and disposition of carboxy these sludges it has been found desirable to de activate them before they are removed from the (-—-COOH) _ aldehyde system. This can be done conveniently by adding H (-<‘>=o) .15 a quantity of one of the deactivating agents to ketone R 4 crude tetraethyl lead with oxidizing agents such after they are employed in the process. The effectiveness of the polyfunctional phenols in the deactivation of these active materials is not ma terially reduced by washing the deactivated ma terials with water or other solvents or by drying them down prior to use. The term “polyfunctional phenols” is used in this speci?cation to cover that group of aromatic compounds which contain a hydroxy group and in addition at least one of the following groups: \. Lao) nitro (—~NO2), nitroso (-NO), hydroxy benzyl the aqueous sludge dispersion and then agitat ing the mass to assure complete contact of all the sludge with the deactivating material, or an aqueous solution of the deactivating agent may 20 be used to cover the tetraalkyl lead during the accelerated sludge precipitation treatment so that the sludge is deactivated as fast as it is formed. (—-CH2.CsI-I4.OH) , phenolic ester The deactivating material may be employed in an aqueous solution or suspension or in other 25 solvents. Where the sludges or precipitates settle out in and long chain aliphatic radicals of at least 4 the pipe lines or other processing equipment dur carbon atoms. The derivatives of the above com pounds which produce such polyfunctional com pounds by hydrolysis, for example, picryl chlo ride, hydroquinone diacetates, etc., are also effec ing the manufacture or puri?cation of the tetra alkyl leads they may be deactivated, to insure safety in their removal or during repair of the equipment, by pumping a solution of‘ one of the tive. deactivating materials through the apparatus for Further, the diketones, formed from the polyfunctional phenols by simple oxidation or tautomerization such as chloranil, benzoquinone; quinhydrone; alpha - nitroso - beta - naphthol; para-nitroso phenol, etc., are effective deactivat ing agents. The polyfunctional phenol deactivators are preferably used as aqueous solutions which con tain the deactivating agent in an amount equiv alent to approximately one-third of the dry weight of the material to be stabilized. The amount of deactivator employed may of course - be varied over a wide range with equally good results. By employing the stabilizer in an amount ranging from 0.05% to more than 100% of the dry weight of the active material satisfactory results have been obtained. The stabilizing effect may be obtained in some cases by using even smaller amounts of the deactivating agent, al though a suf?cient amount should always be used to insure complete deactivation of the ac tive material. The use of excessively large quan tities over that actually required to deactivate the active materials merely contributes unneces sarily to the cost of the process and serves no useful purpose. The deactivating agent is preferably employed in a solution of a concentration of from 1 to 5% although lower or higher concentrations may be used. It is of course advantageous to employ a sufficient amount of solution to insure com plete contact of all the material to be deactivated. To prevent the use of unnecessary large amounts of the deactivating polyfunctional phenol, it will usually be found desirable to use a relatively large Volume of solution of a concentration of less than 5%. Where there is an advantage of em ploying a lesser volume of solution the concen tration may of course be increased. An important use of the present invention in the commercial manufacture of tetraethyl lead is to deactivate the sludges which are precipi tated and removed from the crude tetraethyl lead in the puri?cation step. A method of precipitat a suf?cient period of time to insure complete contact with all the sludge to be deactivated, which is usually accomplished in from 15 to 30 minutes. The filter aids may be washed with a solution of the deactivating agent prior to their use in the process. They may be employed either before or after drying, for it has been found that they do not again become active even after being dried, or by being washed vby the solutions that are ?ltered therethrough. In view of the fact that these polyfunctional phenols are in the main volatile with steam they can be added to the crude tetraalkyl lead mass at the time of steam distillation so that they are carried over with the tetraalkyl lead and con tinually effect the stabilization of any residues ' that may occur in the process. A further use of the invention is found in the storage of crude tetraalkyl lead before it is de sludged by accelerated sludge precipitation. An _ aqueous solution of one of the deactivators dis closed may be used to cover the crude tetra alkyl lead. Any sludge which precipitates at the surface of the lead alkyl on standing is sta bilized by contact with the aqueous layer. If de sired, all of the precipitated sludge may be 60 brought into the aqueous layer by suitable agita tion since the stabilized sludge particles readily disperse in the water layer. In this way the sludge may be deactivated as soon as it is formed. Stabilization of sludge formed in crude tetra~ ethyl lead on standing is also accomplished with~ out the use of an aqueous layer over the ma terial. Some of the deactivating agents men tioned are soluble in tetraethyl lead and may be dissolved directly in the crude tetraethyl lead. Any sludge which precipitates while the tetra ethyl lead is in storage is immediately rendered safe by the reagent. The following examples are given to illustrate ing and removing these sludges by treating the 75 the invention. The parts used are by weight. 2,407,262 5 EXAMPLE 1 Approximately 25,000 parts of tetraethyllea'd the clear tetraethyl lead was decanted from the water layer after the ?ltration was complete. A were processed» in a washer to precipitate the sample of the sludge retained on the ?lter was sludge forming impurities by the method de tested for ignition activity as previously described, and was found to be inactive. Sludge obtained scribed in the co-pending application, Serial using the same crude tetraethyl lead and the Number 393,680. The-precipitated sludge which, same process, exceptthat potassium alizarinate by laboratory analysis of a small sample of the was omitted, ignited the tetraethyl lead which it tetraethyl lead, had been calculated to weigh 30 retained when placed on the steam bath. parts, was collected in 2,500 parts of water.’ The Although I use potassium alizarinate in this puri?ed tetraethyl lead was then decanted from H) example, the same procedure may be employed the water layer. Approximately 25 parts of hy with the other deactivating agents mentioned. droquinone were added to the aqueous phase pro It is also to be understood that'the quantities and ducing a solution of about 1.0% hydroquinone. concentrations given are not to be construed as The mixture was agitated for 15 minutes and ?l-l terecL l5 limits to. the invention for they may be varied A small portion of the?lter cake was then wldelr wtthout modlfytng the results tested for ignition activity by placing it on a WP“? m the preceilmg examples]: ,ha've used ?lter paper, wetting the cake with a smauquan; stabilizing agents WhlCh. are soluble in neutral tity of tetraethyl lead and heating on a, steam .aquemls 591111310115’ deactwa‘tmg age?“ that are bath <95°-100° 0.). No signs of ignition or char- 2“ 11150121318 m miutral aqua)?“ 50mm? may be ring of. the ?lter paper were noted even after 24 e?eqtlvely apphed from. Suitable Solutlons! Such hours on the Steam bath. as dilute sodium hydroxide, or from organic sol A sample of the same sludge which was taken ‘tents’ I ha“? found that dlsPerslf’nsi suspetl‘ before the hydroqumone was added to the water sions or solutions of the deactivating agent in layer was tested for activity as outlined above. 25 Solvents °ther.tha'n Water may be e?ectlvply us.ed' Ignition occurred shortly after the initial sample when Water 15 used as the sqlvent or dlspfersmg was placed on the Steam bath medium, the method of applying the deactivator In regular plant application of this method of . . . tohpgeipg?tgd teiraflfyllufild sgldges 11s eflregtlge _ we pie asse o in xampes r. sludge deactlvatlon’ lt-ma‘y analysis not always be conto 30 However, when solvents other than water are venient to run a laboratory in order used, the aqueous layer containing the sludge may determine the amount of sludge to be expected. be ?ltered off, and the ?lter cake then agitated I have found that under usual conditions the with the solution containing the deactivating quantity of sludge formed per 1,000 parts of tetra agent for a period of from 15 to 30 minutes in a ethyl lead seldom exceeds 2 parts and this ?gure suitable receptacle, or the solvent solution may be added directly to the aqueous sludge suspen sion. Results obtained on agitating 10 parts of an active sludge with 50 parts of a solution of may be used as a basis for calculating the quan tity of deactivator needed. Since tetraethyl lead manufactured in various plants may vary in sludge formation, depending on the quality of raw materials employed for any particular plant the quantity will be relatively constant the amount of 40 Table I Compound representative polyfunctional phenols in various solvents are listed in the table below. I concem tration, Steam bath stability Solvent Initial . percent Hydroquinone ___________ __- _____________ _- 5 After 24 hours 5% N21200:“.-- No decomposition--. N0 decomposition-.. 8-hydroxy quinoline _ _ . _ _ ._ _ 1 1% NaOzCzHg..- _-___do __________________ ._d0 _____________ __ Alpha-nitroso beta-naph ol _ 1 Ethyl alcohol. _ _ _ 2 Water _______ . . 2 ____.do _______ __ Pyrogallol ____________ _ _ Sodium picrate __________ __ _ __do _ After 72 hours No decomposition. Do. Do. Do. D0. Chloranil _________________________________ __ 2 Ethyl alcohol. . Do. 4,4’-dihydroxy diphenyl methane. 2 Cello Do. Catechol-mono-ethyl ether ______ . _ __ _ 2 5-methyl-2-liydroxy acetophenona _ 2 Do. 4-Iaur0yl resorcinol ____________ __ _ 2 Do. l-hydtoxy-é-napthoxy acetic acid._ __ Do. 2 D0. Para-stearylphenol ________________________ __ 2 Do. Leuco-2,2'-dimethoxy dibenzan 1 Do. Picryl chloride ______ __ 1 Salicylal aldoxime- _ __ 1 No deactivator (control)_____ Do. Ethyl alcohoL _ _ .___.do ____ __ Do. Water _________ __ Do. Ignited... _ deactivator required for that plant per unit weight to As previously stated the invention may be em of tetraethyl lead may be readily determined. ployed to stabilize active ?lter aids which are to be used in tetraalkyl lead ?ltration. These EXAMPLE 2 materials may be washed in a solution of one of Approximately 1,000 parts of crude tetraethyl lead were placed in a suitable container provided with means for agitating its contents. About 200 parts of water were added, and the sludge was precipitated and collected in the water layer as disclosed in the previously mentioned appli all cation, Serial Number 393,680. After the precipitation treatment was complete, one part of potassium alizarinate was added and the contents of the container were agitated for about 15 minutes. The tetraethyl lead and the aqueous layer were then ?ltered together, and 75 the deactivators and rendered suitable for tetra alkyl lead ?ltration. The following ?lter aids as well as a number of other materials of similar structure were wet with tetraethyl lead and placed on a steam bath as described in Example 1 above. All were found to initiate the ignition of tetra ethyl lead. Ten parts of each of these‘ materials were then agitated for several hours with 50 parts of the solution of various polyfunctional phenols of the concentrations given in Table 2. After the agitation period, the solutions were ?ltered and portions of the ?lter cakes were wet with tetra~> 2,407,262 ‘7 In testing the activity of the sludges before or after treatment with the deactivating agents it will be noted that tetraethyl or other alkyl lead ethyl lead and placed on a steam bath. Results of the tests are given below: ' ' was added to the residues. This was to make sure there was suf?cient tetraalkyl lead present Table II Cl Material Wash solution Filter aid (clay) _________ __ None _________________ __ Do __________________ __ 1% sodium alizarinate_ No decompo Filter aid (silica) ________ __ None _________________ -_ Ignited. Do __________________ __ 2% alpha-nitroso beta- naphthol. Yelyl?w lead oxide (N. F. 5% N21200:; Bismuth subnitrate _____ __ ' None _________________ __ Do _________________ __,. 3% chloranil in ethyl alcohol. Bismuth oxide (prepared by hydrolysis ited. sition. No decompo sition. None ............... _,_._ Ignited. Do__________________ __ 5% hydroquinone in . steagssath to ignite under the conditions employed, if the sludge was not fully inactivated, for in some in stances, it is possible that the amount of alkyl lead may be reduced to such a small amount that 10 ignition might not be noted. While the elimina tion of the alkyl lead from the residues to such an extent does not ordinarily take place, the tests were made under conditions favoring ignition pro vided the sludge or ?lter aid was active. No decompo sltion. 15 Ignited. No decompo sion. None _________________ __ Ignited. of Bi(NOs):l._ decompo Bismuth oxide (prepared 2% d-lauroyl resorcinol NoS1011. in ethyl alcohol. ' by hydrolysis of BKNOg); Activated Alumina _____ __ None _________________ __ Do __________________ __ 2% guaiacol in ethyl alcohol. Decolorizing charcoal ____ __ None _________________ __ Do__________________ _. 2% picric acid in 2% NaOH. Ignited. No decompo' sition. Ignited. No decompo sition. EXAMPLE 3 This invention makes possible the deactivation of theignitable sludges and residues occurring in the manufacture or tetraalkyl lead compounds '- " and is of particular value, in eliminating ?re and explosion hazards involved in the removal and disposal of such sludges from the process and in overcoming the potential ?re hazard arising from the collection of such sludges and precipitates which accumulate in various places in the processing equipment and which when exposed to air often ignite with considerable damage. The invention also permits the use of ?lter aids which unless rendered inactive tend to cause ignition of any absorbed tetraethyl lead when they are ex Approximately 2,000 parts of crude tetraethyl posed to the air. Any other absorbent materials lead were placed in a suitable tank or washer, and an approximately equal weight of water was which for any reason may become saturated with tetraethyl lead in or about the plant in which it is being manufactured may be rendered in added to the tetraethyl lead. Some 40 parts of NaOI-I and 40 parts of guaiacol were then added to the water layer, and the sludge was precipitated and removed from the tetraethyl lead by blow ing with air as more particularly disclosed in the active by washing or otherwise treating with stabilizers of the type described so that potential ?re hazards may be removed as far as possible. Lagging on pipe which due to leaks may become copending application, Serial Number 393,680. saturated with tetraethyl lead and which have After this operation was complete, the tetraethyl been known to cause its ignition can be in activated by treating such lagging with the de lead was removed by decantation, and the aqueous layer containing the sludge was ?ltered. A por tion of the ?lter cake was tested on the steam bath as described in Example 1. No decomposi tion or ignition of the tetraethyl lead was noted. 1. The process for inhibiting the spontaneous ignition of tetraalkyl lead compounds adsorbed on EXAMPLE 4 sludges which are precipitated from crude tetra As previously stated, sludges found in tetra ethyl lead are also found in other lead alkyls which are manufactured from commercial lead. An example of these alkyls is the mixed tetra methyl-ethyl compounds of lead, formed when a mixture of methyl chloride and ethyl chloride are ' reacted with lead sodium alloy. All examples in which tetraethyl lead is speci?ed are equally workable with these mixed lead alkyls. Approximately 8,000 parts of crude mixed tetra methyl-ethyl lead compounds (tetramethyl lead, trimethyl ethyl lead, dimethyl diethyl lead, methyl triethyl lead and tetraethyl lead) were placed in a suitable tank or washer, and 2,000 parts of water containing 10 parts of sodium alizarinate were added. The contents of the tank were aerated and agitated for two hours as dis closed in the copending application, Serial Num ber 393,680. After a settling period of a few minutes, the clear mixed lead alkyls were de canted from the aqueous layer and the aqueous mixture was ?ltered. A portion of the ?lter cake activating agents. 1 claim: alkyl lead compounds and which sludges normally tend to cause spontaneous ignition of the tetra alkyl lead compounds adsorbed thereon'when ex‘ posed to oxygen, which comprises incorporating with such sludges a phenol containing at least one substituent of the group consisting of hydroxy, alkoxy, carboxy, aldehyde, ketone, nitro, nitroso and ester groups attached to ring carbon atoms and which otherwise consists of carbon, hydrogen and oxygen. 2. The process for inhibiting the spontaneous ignition of tetraethyl lead adsorbed on sludges which are precipitated from crude tetraethyl lead and which sludges normally tend to cause spon taneous ignition of the tetraethyl lead adsorbed 60 thereon when exposed to oxygen, which comprises incorporating with such sludges a phenol contain ing at least one substituent of the group consist ing of hydroxy, alkoxy, carboxy, aldehyde, ketone, nitro, nitroso and ester groups attached to ring carbon atoms and which otherwise consists of car bon, hydrogen. and oxygen. 3. The process for inhibiting the spontaneous was tested on the steam bath as described in‘ ignition of tetraethyl lead adsorbed on sludges Example 1 except that the ?lter cake (sludge) which are precipitated from crude tetraethyl lead was wet with mixed lead alkyl compounds rather than with tetraethyl lead. No decomposition or 70 and which sludges normally tend to cause spon taneous ignition of the tetraethyl lead adsorbed ignition of the lead alkyls was noted. A similar thereon when exposed to oxygen, which comprises experiment was carried out in which no sodium washing such sludges with a solution of a phenol alizarinate was placed in the water layer. This containing at least one substituent of the group sludge ignited the mixed alkyls when the steam 75 consisting of hydroxy, alkoxy, carboxy, aldehyde, bath stability test was made. 2,407,262 10 ketone, nitro, nitroso and ester groups attached ignition of tetraethyl lead adsorbed on sludges which are precipitated from crude tetraethyl lead and which sludges normally tend to cause spon taneous ignition of the tetraethyl lead adsorbed thereon when exposed to oxygen, which comprises to ring carbon atoms and which otherwise con sists of carbon, hydrogen and oxygen, 4. The process for inhibiting the spontaneous ignition of tetraethyl lead adsorbed on sludges in which are precipitated from crude tetraethyl lead incorporating with such sludges guaiacol in an and which sludges normally tend to cause spon amount equivalent to at least 0.05 per cent of the taneous ignition of the tetraethyl lead adsorbed dry weight of the sludge. thereon when exposed to oxygen, which comprises 7. The process for inhibiting the spontaneous washing such sludges with an aqueous solution H) ignition of tetraethyl lead adsorbed on sludges of a phenol containing at least one substituent which are precipitated from crude tetraethyl lead‘ of the group consisting of hydroxy, alkoxy, car and which sludges normally tend to cause spon boxy, aldehyde, ketone, nitro, nitroso and ester taneous ignition of the tetraethyl lead adsorbed groups attached to ring carbon atoms and which thereon when exposed to oxygen, which comprises otherwise consists of carbon, hydrogen and oxy incorporating with such sludges picric acid in an gen. amount equivalent to at least 0.05 per cent of the 5. The process for inhibiting the spontaneous dry Weight of the sludge. ignition of tetraethyl lead adsorbed on sludges 8. The process for inhibiting the spontaneous which are precipitated from crude tetraethyl lead ignition of tetraethyl lead adsorbed on sludges and which sludges normally tend to cause spon_ " which are precipitated from crude tetraethyl lead taneous ignition of the tetraethyl lead adsorbed and which sludges normally tend to cause spon thereon when exposed to oxygen, which comprises taneous ignition of the tetraethyl lead adsorbed incorporating with such sludges hydroquinone in thereon when exposed to oxygen, which comprises an amount equivalent to at least 0.05 per cent of washing such sludges with an aqueous solution of the dry weight of the sludge. hydroquinone. 6. The process for inhibiting the spontaneous ADRIAN L. LINCH.