Patented Sept. 10, 1946 2,407,307 UNITED STATES‘ rATENr OFFICE _ 2,407,307 PROCESS FOR STABILIZIN G OR DEACTIVAT ENG SLUDGES, PRECIFITATES, AND RESI DUES OCCURRING OR 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. 458,580 4 Claims.’ (01. 260-437) 1 2 This invention relates to a process for stabiliz pounds which, although present in very small ing or deactivating sludges, precipitates and amounts, ?nally are deposited as sludges in the residues occurring or used in the manufacture of pipes and tanks and other processing equipment and these sludges which contain tetraethyl lead tretraalkyl leads, and which normally tend to promote decomposition and ignition of the tetra alkyl leads that may be contained therein. It is known that alkyl metal compounds in general are quite unstable and decompose readily, adsorbed therein when exposed to oxygen or air often ignite, thus presenting serious ignition and explosion hazards in the process. Methods have been advanced for the removal of particularly in the presence of air or oxygen. It practically all the sludge forming materials from has also been found that these alkyl metal com 10 the tetraethyl lead after its distillation, such as pounds are particularly unstable when adsorbed by controlled blowing with air or oxygen with on materials which present a large surface area agitation, preferably under a layer of water, fol per unit volume such as silica gel, clays, alumina, lowed by separation of the precipitated sludge. as earths, asbestos, charcoal, and materials of more particularly described in copending applica similar structure which materials appear to exert tion Ser. No. 393,680. However, even in these a catalytic e?ect in the decomposition of these cases the sludges which are deposited by the alkyl metal compounds. Even tetraalkyl leads action of the oxidizing agent and which in such as tetraethyl lead which is known to be variably contain tetra-ethyl lead, tend to ignite somewhat more stable than some of the other when exposed to air thus presenting serious igni alkyl metal compounds decomposes and often tion hazards, making it desirable that even these ignites in the presence of oxygen when small sludges should be deactivated during their forma amounts are adsorbed on materials that o?er ex tion or afterwards to permit of their removal and tended surface areas, particularly when the disposal in a safe manner. masses containing the tetraethyl lead are exposed It is therefore an object of this invention to to temperatures somewhat higher than normal provide a process for stabilizing sludges, pre atmospheric temperatures. The tendency to cipitates and residues occurring in the manufac— ture of tetraalkyl lead compounds whereby the ignition hazard presented by the lead alkyl com oxidize and ignite of course varies with the sub stance With which the alkyl metal compound is incorporated, some materials apparently exerting a greater catalytic e?ect than others in promot pounds in contact with such catalytic surfaces is 30' reduced or completely overcome. ing ignition of the alkyl lead compounds. In the manufacture of tetraalkyl leads, such as tetraethyl lead, tetramethyl lead and the mixed ethyl-methyl lead compounds, sludges are formed It is a still further object of the invention to render inactive materials which tend to exert a catalytic effect in the decomposition of tetraalkyl leads in the presence of air thus permitting the from which it is difficult and, from a practical - safe use of such materials as ?lter aids in the standpoint, impossible to entirely free from the alkyl lead compounds during the normal steam manufacture of tetraalkyl lead. I have found that sludges, precipitates and distillations or decantation operations. There is, residues occurring or involved in the production of tetraalkyl leads which offer large surface areas divided lead and impurities such as bismuth con - 40 per unit volume and which normally tend to exert therefore, carried through the process very ?nely 2,407,307 4 3 catalytic effect and cause decomposition and ignition of the tetraallryl lead which may be con tained therein can be rendered inactive con (2) An alkyl group substituted by one or more of the groups, -—OH, —COOH, —COO metal; veniently and economically by washing or other (3) A long chain alkyl (more than 8 carbon wise treating them with solutions or dispersions atoms) ; (4) of trivalent organic nitrogen compounds. These stabilizing or deactivating agents appear to be preferentially absorbed by the active materials, which materials retain their capacity to absorb the tetralkyl lead although they no longer have the property of inducing ignition of the tetra alkyl lead absorbed therein. —-(||J—NH—C——NH2 EN EN (or nitrogen substituted derivatives), (5) By the terms “sludges,” “precipitates” and “residues” We include those ?lter aids which may be employed in the production of the tetraalkyl leads and which offer a large surface area per in which R3 is an aryl group substituted by unit volume and are known to accelerate decom position of the tetraalkyl leads on exposure to air -—OI—I; (6) —-SO2-—R4 in which R4 is an aryl group or oxygen such as clays, silica, earths, charcoal, substituted by —NH2 or by an alkyl group etc. These ?lter aids are rendered. inactive by 20 or Where R4 is a long chain alkyl (more trating them with trivalent organic nitrogen com pounds either before or after they are employed in than 8 carbon atoms) ; the process. The effectiveness of the trivalent R1=I—I, alkyl, aryl, substituted alkyl or substituted aryl; (R and R1 together may be =C—aryl organic nitrogen compounds in the deactivation of these active materials is not materially reduced * substituted by -—OH) ; by washing the deactivated materials with water R2:=H,' alkyl, aryl, substituted alkyl, substituted aryl or heterocyclic. The trivalent organic nitrogen deactivators are The trivalent organic nitrogen compounds that preferably used as aqueous solutions which con may be employed for this purpose 'may be 30 tain the deactivating agent in an amount equiva primary, secondary, or tertiary, aliphatic or lent to approximately one-third of the dry weight aromatic amines, or they may be trivalent nitro of the material to be stabilized. The amount of gen compounds in which the nitrogen forms part deactivator employed may, of course, be varied of a heterocyclic ring. . Those which have been over a Wide range with equally good results. By found to be useful vary widely in chemical comemploying the stabilizer in an amount ranging position and in molecular weight. The only from 0.05% to more than 100% of the dry weight limitations upon this class of compounds, insofar of the active material, satisfactory results have as I have been able to determine, is that if they been obtained. The stabilizing e?ect may be ob are straight alkyl amines or unsubstituted ary1~ tained in some cases by using even smaller amounts of the deactivating agent, although a amines they should contain at least seven carbon atoms in at least one alkyl or aryl group and in sur?cient amount should always be used to insure both the aliphatic and aromatic series they should complete deactivation of the active material. not contain a free sulfonic acid group. The sul The use of excessively large quantities over that fonic acid group as such appears to render these actually required to deactivate the active mate or other solvents or by drying them down prior to use. amines incapable of deactivating the active . sludges and residues although substituted sulfonic acid groups may be present in the molecule with out rendering them inoperative as deactivating agents. Aniline itself, which is the simplest mem ber of the aromatic series, is very weak in its de activating power and can be used only with the less active type of residues or other materials which tend to exert the catalytic effect in a more mild degree. The simple substituted anilines such as para amino phenol, para nitro aniline, etc, s have been found to deactivate the most active types of residues. The property of deactivating active materials of the type mentioned does not appear to depend upon whether the materials are soluble or insoluble in water or other solvents from which they may be applied to these residues. As illustrative of the types of trivalent nitrogen compounds that may be employed are those hav ing the general formula rials merely contributes unnecessarily 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 su?lcient amount of solution to insure complete contact of all the material to be deactivated. To prevent the use of unnecessary large amounts of the deactivating agent, it will usually be found desirable to use a relatively large volume of so lution of a concentration of less than 5%. Where there is an advantage of employing a lesser vol ume of solution, the concentration 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 precipitated and removed from the crude tetraethyl lead in the puri?cation step. A method of precipitatting and removing these sludges by treating the crude tetraethyl lead with oxidizing agents such as with air or oxygen is more particularly disclosed in copending application Ser. No. 393,680. The pre wherein R—_—(1) An aryl group substituted by one or more of the following: -—OH, —-COOH, —COO metal, —NO2, —CHO, ——0 alkyl, --—0 alkyl OH, —NH2, aryl—NHz, --S—aryl, alkyl (more than 4 carbon atoms), phthaloyl; cipitated sludges from this process collect in the aqueous layer from which the puri?ed tetraethyl lead is separated by decantation. Although dis persed in the water layer the sludge retains su?i cient tetraalkyl lead absorbed therein to ignite on contact With oxygen or air, particularly at slight“ ly elevated temperatures. In order to permit the 2,407,307 5 In regular plant application of this method of sludge deactivation, it may not always be ‘con venient to run a laboratory analysis in order to determine the amount of sludge to be expected, safe handling and disposition of these sludges, it has been found desirable to deactivate them be fore they are removed from the system. This can be done conveniently by adding a quantity of one of the deactivating agents to the aqueous sludge dispersion and then agitating the mass to assure complete contact of all the sludge with the de activating material, or an aqueous solution of the deactivating agent may be used to cover the tetraalkyl lead during the accelerated sludge pre and such a procedure is not necessary. We have found that under usual conditions the quantity of sludge formed per 1,000 parts of tetraethyl lead seldom exceeds 2 parts, and this ?gure may be used as a basis for the calculation of the quan 10 tity of deactivator needed. Thus, if we add 0.6 part (30% of the dry sludge weight) of deacti vating agent to the water layer per 1,000 parts of tetraethyl lead, sufficient deactivator is pres cipitation treatment so that the sludge is deac tivated as fast as it is formed. The deactivating material may be employed in an aqueous solution or suspension or in other sol ent to meet any conditions which we have met. 15 Of course, tetra-ethyl lead manufactured in var vents. ious plants may vary in sludging capacity de Where the sludges or precipitates settle out in pending on quality of raw materials, but in any the pipe lines or other processing equipment dur one plant the quantity is relatively constant, and ing the manufacture or puri?cation of the tetra— a de?nite amount of deactivator per unit Weight alkyl leads, they may be deactivated, to insure safety in their removal or during repair of the 20 of tetraethyl lead may be easily set up as ade quate in all cases. equipment, by pumping a solution of one of the deactivating materials through the apparatus for Example 2 a su?icient period of time to insure complete con Approximately 2,000 parts of crude tetraethyl tact with all the sludge to be deactivated, which is usually accomplished in from 15 to 30 minutes. 25 lead were placed in a suitable container provided The?lter 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. 30 or by being washed by the solutions that are ?l 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 application No. 393,680. ' > After the precipitation treatment was com plete, ?ve parts of para-phenylene diamine were added, and the contents of the container 'were agitated for about 15 minutes. The tetraethyl storage of crude tetraalkyl lead before it is de sludged by accelerated sludge precipitation. An 35 lead and the aqueous layer were then ?ltered together, and the clear tetraethyl lead was de aqueous solution of one of the deactivators dis canted from the water layer after ?ltration was closed may be used to cover the crude tetraalkyl tered therethrough. ' A further use of the invention is found in the complete. A sample of the sludge retained on lead. Any sludge which precipitates at the sur the ?lter was tested for ignition activity as pre face of the lead alkyl on standing is stabilized by contact with the aqueous layer. If desired, all of 40 viously described, and was found to be inactive. Sludge obtained using the same crude tetraethyl the precipitated sludge may be brought into the lead and the same process, except that no para aqueous layer by suitable agitation since the phenylene diamine was added. ignited the tetra ethyl lead which it retained when placed on the 45 steam bath. activated as soon as it is formed. It is, of course, understood that other trivalent The following examples are given to illustrate stabilized sludge particles readily disperse in the water layer. In this way the sludge may be de organic nitrogen compounds may be employed in this example in place of the para-phenylene the invention. The parts used are by weight. Example 1 diamine. The quantities and concentrations em 50 ployed in this example are not to be construed as limits to the invention, for they may be varied widely without altering the results obtained. While in the preceding examples We have used Approximately 10,000 parts of crude tetraethyl lead were processed’ in a washer to precipitate the sludge-forming impurities by the method ‘ stabilizing agents which are soluble in neutral described in the co-pending application, Ser. No. . 393.680. The precipitated sludge, which by lab aqueous solutions, deactivating agents that are oratory analysis of a small sample had been cal culated to weigh 12 parts, was collected in 1,000 parts of water. The puri?ed tetraethyl lead was then decanted from the water layer. Approxi mately 10 parts of p-amino phenol were added to the aqueous phase producing a solution of about 1% p-amino phenol. The mixture was agitated for 15 minutes and ?ltered. A small portion of the ?lter cake was then tested for ignition activity by placing it on a' ?lter paper, wetting the cake with a small quan tity of tetraethyl lead and heating on a steam bath. No signs of ignition or of charring of the insoluble in neutral aqueous solutions may be effectively applied from suitable solutions, such as dilute sodium hydroxide, or from organic sol We have found that dispersions, suspen sions or solutions of the deactivating agent in solvents other than water may be effectively used. Where water is used as the solvent or dispersing medium, the method of applying the deactivator - vents. to precipitated tetraalkyl lead sludges is effective when applied as set forth in Examples 1 or 2. However, when solvents other than water are used, the aqueous layer containing the sludge may be ?ltered off, and the ?lter cake then agi tated with the solution containing the deactivat ing agent for a period of from 15 to 30 minutes ?lter paper were noted even after 24 hours on the steam bath. A sample of the same sludge which was taken in a suitable receptacle, or the solvent solution before the p-amino phenol was added to the water layer was tested for activity as outlined above. Ignition occurred shortly after the initial . ' sample was placed on the steam bath. " may be added directly to the aqueous sludge sus pension. Results obtained on agitating 10 parts of an active sludge with 50 parts of a solution of representative trivalent organic nitrogen com 2,4;07,3.07 8 7 salicylal sorbityl amine were then added to the water layer, and the sludge was precipitated ‘and pounds in various solvents are listed in the table below. 0 Steam bath stability oncen-g Compound tration - Solvent Initial After 21 hrs. No decomposi- No_ decomposi- Per cent Para phenylene diamine ___________________ _‘. _____________ .. 5 After 72 hrs. _ Water _____ .. tion. tron. _ No decomposi tion. Ortho phenylene diamine _________________________________ . _ Do. Guanyl guanidine sulfate ___________ __ Do. 1, 4 di (para tuloido) anthraquinona- Do. Anthranilic acid ___________________ _. Para amino phenol ___________________ __ _ Salicylal sorbityl amine ______________ __ Di (betaehydroxyethyl) aniline ______ ,. 50% ethanol_ Do. Water._...'. Do. Do. Do. (1 Meta-amino benzaldehyde _____ ..' ____ ._ Do. Dimethyl cetylamine _____________ __,__ Do. Para dodecylaniline. _ Do. Stearylamine. _ i _ _ _ Meta nitro aniline. ._ ____________ _ _ _ _ _ _ _ _ _ _ . _ Do. _______________________ ._ Do. Salioylal propylene d1am1nc condensation product Do; 2-hydroxy-3-naphthanilide ______________________ __ , Do. Suliapyridinc ___________________________ ____ Do. N-di-n-butyl para amyl benzene sulfonan11de_ D0. N-isobutyl para amyl benzene sulfonamidm ._ Do. 1, 4~di(p-tolylamino)_anthraquinone ____ _ _ Methyl glucamine _________________ _ . Do. Do. 3 (4 hydroxyphenyl) amino carbazo1e_ Do. Para amino phenyl acetic acid _____ ._ Do. Para phenetidine ________________ __ D0. Para (hydroxy ethoxy aniline ______ __ Do. Dodecyl sulfonyl mono ethanol amide Do. lndole _____________________ _ _ D0. N o deactivator (control) ___________ -_ removed from the tetraethyl lead by the method disclosed in the co-pendingv application Ser. No. 393,680. After this operation was complete, the tetraethyl lead was removed by decantation, and the aqueous layer containing the sludge was ?ltered. A portion‘ of the ?lter cake was then As previously stated the invention may be em ployed to stabilize active ?lter aids which are to be used in tetraalkyllead ?ltration. These ma terials may be washed in a solution of one of the deactivators and rendered suitable for tetra alky] lead. well as a structure placed on ?ltration. The following ?lter aids as number of other materials of similar were wet with tetraethyl lead and tested on the steam bath as described in Ex ample 1. a steam bath as described in Example No decomposition or ignition of the tetraethyl lead was noted. ' > ' 1 above. All were found to initiate the ignition Example 4 of tetraethyl lead. Ten parts of each of these 40 As previously stated, sludges found in tetra materials were then agitated for several hours ethyl lead are also found in other lead alkyls with 50 parts of the solution of various trivalent which are manufactured from commercial lead. organic nitrogen compounds of the concentra An example of these alkyls are the mixed tetra tions given in Table 2. Where no solvent is speci methyl-ethyl compounds of lead, formed when a ?ed, water is used. After the agitation period, I mixture of methyl chloride and ethyl chloride the solutions were ?ltered and portions of the are reacted with lead sodium alloy. All examples ?lter cakes were wet with tetraethyl lead and in which tetraethyl lead is speci?ed are equally placed on a steam bath. Results of the tests are workable with these mixed lead alkyls. given below: ~50 Material ‘Nash solution Steam bath testv Approximately 8,000 parts of crude mixed tetramethyl-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 20 parts of sodium hy 1% p-phenetidinc in No decomposition. droxide and 20 parts of 3 (4-hydroxy phenyl) ethanol. Ignited. Yellow lead oxide (N. F. amino carbazole were added. The contents of VI). the tank were aerated and agitated for two hours 2% M-nitro aniline No decomposition. in ethanol. as disclosed in the copending application Ser. No. Ignited. Bismuth subnitrate. _ _-_ 393,680. Aftera settling period of a few min 5% anthranilic acid No decomposition. in 50% ethanol. 60 utes, the clear mixed lead alkyls were decanted Ignited. Bismuth oxide (from from the aqueous layer and the aqueous mixture hydrolysis ofBi(NO3)2). 5% _rnethyl gluca» No decomposition. was ?ltered. A portion of the ?lter cake was mine. tested on the steam bath as described in Example nited. _ Ferric oxide (anh) __ _ __. 1% salicylal scrhityl No decomposition. 1, except that the ?lter cake (sludge) was wet amine. 65 with mixed lead a kyl compounds rather than 2% dimcthyl cctyla No decomposition. with tetraethyl lead. No decomposition or igni mine in ethanol. Ignited. tion of the lead alkyls was noted. ‘A similar ex Decolorizing charcoaL _ _ 5% guanyl guani No decomposition. periment Was carried out in which no stabilizing dine sulfate. Filter aid (clay) _______ __ D None _____________ _ _ Ignited. _ 5% p-amino phenoL No decomposition. Ignited. Tone _____________ __ None _____________ _. Do ________________ _ _ None _____________ __ Do ________________ - . None _____________ __ Do ________________ __ None _____________ _ . Do ________________ . _ Activated Al1unina_ _ _ __ None _____________ .i Ignited. ‘ _ Do-. _________________ ._ None _____________ _. Do ________________ ._ agent was placed in the water layer. This sludge ignited the mixed alkyls when the steam bath Example’ 3 stability test was made. Approximately 1,000 parts of crude tetraethyl I lead were placed in a suitable tank or washer, In testing the activity of the sludges before or after treatment with the deactivating agents, it and an approximately equal weight of waterwas will be noted that tetraethyl or other alkyl lead added to the tetraethyl lead. Some 8 parts of 75 was added to the residues. This was to make sure 2,407,307 9 there was su?icient tetraalkyl lead present to 10 ing such sludges with p-amino phenol in an aqueous carrying medium in an amount suf?cient ignite under the conditions employed, if the to provide at least 0.05% of the p-amino phenol sludge was not fully inactivated, for in some in based on the dry weight of the sludges. stances, it is possible that the amount of alkyl 2. The process for inhibiting the spontaneous lead may be reduced to such a small amount that ignition of tetraethyl lead adsorbed on sludges ignition might not be noted. While the elimina which are precipitated from crude tetraethyl lead tion of the alkyl lead from the residues to such and which sludges normally tend to cause spon an extent does not ordinarily take place,~ the taneous ignition of the tetraethyl lead adsorbed tests were made under conditions favoring igni thereon when exposed to oxygen, which com tion provided the sludge or ?lter aid was active. prises washing such sludges with p-amino phenol This invention makes possible the deactivation in an aqueous carrying medium in an amount of the ignitable sludges and residues occurring su?icient to provide at least 0.05 % of the p-amino in the manufacture of tetraalkyl lead compounds phenol based on the dry weight of the sludges. and is of particular value in eliminating fire and 3. The process for inhibiting the spontaneous explosion hazards involved in the removal and 15 ignition of tetraethyl‘lead adsorbed on sludges disposal of such sludges from the process and in which are precipitated from crude tetraethyl lead overcoming the potential ?re hazard arising from and which sludges normally tend to cause spon the collection of such sludges and precipitates taneous ignition of the tetraethyl lead adsorbed which accumulate in various places in the proc essing equipment and which when exposed to air 20 thereon when exposed to oxygen, which comprises washing such sludges with m-nitro aniline in an often ignite with considerable damage. The in aqueous carrying medium in an amount su?icient vention also permits the use of ?lter aids which, to provide at least 0.05% of the m-nitro aniline unless rendered inactive, tend to cause ignition based on the dry weight of the sludges. of any absorbed tetraethyl lead when they are 4. The process for inhibiting the spontaneous exposed to the air. Any other absorbent mate 25 ignition of tetraalkyl lead compounds adsorbed rials which for any reason may become saturated on sludges which are precipitated from crude with tetraethyl lead in or about the plant in tetraalkyl lead compounds and which sludges which it is being manufactured may be rendered normally tend to cause spontaneous ignition of inactive by washing or otherwise treating with the tetraalkyl lead compounds adsorbed thereon stabilizers of the type described so that poten when exposed to oxygen, which comprises wash tial ?re hazards may be removed as far as pos ing such sludges with an aromatic amine in an sible. Lagging on pipe which due to leaks may aqueous medium such aromatic amine being a become saturated with tetraethyl lead and which member of the group consisting of p-aminophe have been known to cause its ignition can be nol, m-nitro aniline, para nitro aniline, para inactivated by treating such lagging with the de activating agents. I claim: 1. The process for inhibiting the spontaneous ignition of tetraalkyl lead compounds adsorbed phenylene diamine, ortho phenylene diamine, 1,4 di(para toluido) anthraquinone, anthranilic acid, di(beta - hydroxyethyl) aniline, meta - amino benzaldehyde, para dodecylaniline, 1,4-di(p—tol on sludges which are precipitated from crude 40 ylamino) -anthraquinone, para amino phenyl ace tetraalkyl lead compounds and which sludges normally tend to cause spontaneous ignition of the tetraalkyl lead compounds adsorbed thereon when exposed to oxygen, which comprises wash tic acid, para phenetidine and para(hydroxy eth oxy) aniline. ADRIAN L. LINCH.