October, 1929
INDUSTRIAL AND ENGINEERING CHEMISTRY
899
Amyl Alcohols from the Pentanes' Eugene E. Ayres THESHARPLES SOLVENTS CORPORATION, PHILADELPHIA, P A .
hlYL alcohols are being manufactured a t present in a plant in which 22 tons of chlorine per day are being fed continuously into a 60-mile-per-hour stream of hot pentane vapor. One hundred thousand gallons of pentane pass through the reaction zone every 24 hours, but a t any given moment only 3 gallons of pentane are present within the reaction zone. This is possible because the reaction is completed in 2*/2 seconds. Kot more than 8 ounces of free chlorine are in contact with pentane a t any given moment. A train of fractionating columns separate tthe reacted vapors into three components: (1) hydrogen chloride, which is absorbed in water to produce 33 tons of 21' BB. hydrochloric per day; ( 2 ) a small amount of polychloride residue; and ( 3 ) pure amyl chloride. Hydrolysis is accomplished in a system of reservoirs, heaters, and pumps, through which a hot emulsion of amyl alcohol and water is being circulated a t the rate of 500 gallons per minute. Amyl chloride and an aqueous solution of caustic soda are continuously pumped into this circulating material. and two things are continuously withdrawn: (1) a saturated salt solution: which is r e t u r n e d t o e l e c t r o l y t i c cells for manufacture of chlorine and caustic soda; and ( 2 ) a vapor containing principally a m y l a l o o hols. Three h u n d r e d gallons of amyl chloride are present at all times in the hydrolysis s y s t e m , and 300 gallons of amyl chloride are hydrolyzed per hour. I I The vapors from hydrolysis are separated by a train of fractionating columns into five components: (1) amyl chloride which is returned to hydrolysis; (2) amylene, which is later hydrated to amyl alcohols; ( 3 ) diamyl ether; (4) amyl alcohol fractions that are cut out for special uses; and ( 5 ) the mixture of amyl alcohols marketed under the trade n a m e A p p a r a t u s for Conversion of "Pentasol" f o r u s e i n pyroxylin lacquers. If structurai formulas are avoided, the reactions are simply expressed: ChH12 + C1, = CsHiiCl HC1 (1) CsHllCl + NaOH = C~HIIOH NaCl (2) But as soon as molecular structure is taken into account, the reactions become somewhat involved, and it will be seen
A
I
+
+
1 Presented before the meeting of the American Institute of Chemical Engineers, Philadelphia, P a , June 19 t o 21, 1929
that Equation 2 merely expresses a result and in no sense describes what takes place. There are three possible arrangements of C5H12,and all three of the pentanes are known. Disregarding optical isomers, there are eight possible arrangements of CaHIIOH. and all eight of the amyl alcohols are known. I n the operation briefly described above, two of the pentanes are used as starting points. Six, out of a possible seven, amyl chlorides are formed, from which are obtained the six corresponding amyl alcohols. Of the six chlorides, three isomers are primary, two are secondary, and one is tertiary. Chemically, the primary isomers all act about alike, and the secondary isomers are indistinguishable, but each class differs materially from the obher classes. The amyl chlorides of all classes have in common the property of not reacting under any conditions with sodium hydroxide to form either alcohols or amylenes. But the differences are: REACTIOX Hydrolysis with HzO a t 80" C. With sodium acetate a t 180' C. Amylene formation a t 180" C.
PRIMARYSECONDARY TERTIARY CHLORIDE CHLORIDE CHLORIDE Slow Rapid S o t a t all Slow A-ot a t all Rapid Moderate Rapid Slow
Because of these diff e r e n c e s a hydrolysis procedure, to work successfully on a mixture of c h l o r i d e s , must have versatile characteristics, and because of the difference in the properties of the d e r i v e d a l c o h o l s , the best procedure for chlorination will depend upon which class of alcoI J hols is chiefly desired. Those who preceded us in research o n t h i s synthesis had in mind the production of amyl alcohols, the acetates of which would be identical or comparable with the acetates of fusel oil amyl alcohols. They desired the primary compounds. The value of secondary a m y l a c e t a t e in comm e r c i a 1 pyroxylin lacq u e r formulation h a s only recently become apP e n t a n e s to Amyl Alcohols parent and the tertiary a c e t a t e i s difficult to manufacture and is unsuitable for lacquer formulation. It may be assumed, therefore, that the methods of chlorination of pentanes that have been attempted have been methods which the investigators have believed to be suitable for the production of primary chlorides, although there is nothing in the scant literature to indicate to what extent they were successful in this regard. Nor is there anything to indicate what the predominating pentane in their raw product.
INDUSTRIAL AND ENGINEERING CHEMISTRY
900
Source of Pentanes The source of pentane is natural gas gasoline. The examination of samples from many localities in Texas, Oklahoma, Kansas, Kentucky, Ohio, and West Virginia has shown that natural gas gasolines of all grades and origins contain substantial proportions of the pentanes unless these hydrocarbons are removed by fractional distillation during or subsequent to manufacture. The three pentanes are: BOILINGPOINT
c.
Normal pentane Isopentane (2-methylbutane) Tetramethylmethane
36 28 9.5
Tetramethylmethane is the least known. It has been found to the extent of about 2 per cent in many natural gas gasolines from Texas and West Virginia. It is not difficult to obtain by careful rectification. In 1925 several hundred gallons were obtained and chlorinated to form the only possible monochloride, and the monochloride was hydrolyzed to form tertiary butylcarbinol-a primary 5-carbonatom alcohol boiling a t about 114" C. The alcohol has the stability to be expected of a primary alcohol and can be esterified by the usual procedure. Tetramethylmethane has not been regarded as a suitable starting point for commercial synthesis. Katural gas gasolines contain from 20 to 40 per cent of the other two pentanes, usually in about equal proportions. Normal butane, boiling a t 0" C., is present in substantial proportions, but there is no hydrocarbon in natural gas gasoline boiling between 0" and 28" C. except the small amount of tetramethylmethane. Katural gas gasolines contain no unsaturated chain hydrocarbons and no cyclic hydrocarbons boiling below the hexanes. When we get above normal pentane a t 36" C., the next known saturated chain hydrocarbon is one of the hexanes, trimethylethylmethane, CH3.CH2.C(CH3)3,boiling a t 49" C. Natural gas gasolines contain only a trace of this hydrocarbon. About a 10 per cent fraction is composed of the hexanes boiling a t 58" C. (diisopropyl) and 62" C. (dimethylpropylmethane). Thus, it is seen that the recovery of a relatively pure mixture of normal pentane and isopentane by fractional distillation is an easy matter. It is not so easy to obtain the normal pentane and isopentane separately, but with modern distillation equipment the pure isomers have been prepared on a large scale. Chlorination of Pentanes The procedure used in the study of chlorination of normal and isopentanes was to work backwards from the alcohols to the chlorides in order to devise a suitable method for the identification of isomeric chlorides and to study the reactions of the separate isomers under hydrolysis conditions. Most of the alcohols could be purchased on the market, and the others were synthesized from available alcohols. Inspection of the structural formula for isopentane will show four positions for hydroxyl substitution:
The primary isoamyl alcohols in which the hydroxyls are substituted a t 1 and a t 4 are well known because they occur in fusel oil. Tertiary amyl alcohol (2-hydroxy-2-methylbutane) or dimethylethylcarbinol can be easily synthesized from the fusel oil alcohols by dehydrating the primary alco; hols to obtain amylenes and absorbing the amylenes in sulfuric acid a t 25" C. The secondary isoamyl alcohol or 3hydroxy-2-methylbutane was not attempted.
VOl. 21, No. 10
The structural formula for normal pentane shows three different positions for hydroxyl substitution:
1-Hydroxypentane, or normal butyl carbinol, has been on the market in small quantities prepared from castor oil. 2-Hydroxypentane, or methyl propyl carbinol, has been available from the hydration of petroleum cracking olefins. This alcohol is easily converted to 3-hydroxypentane, or diethyl carbinol, by dehydrating to amylene and absorbing the amylene in sulfuric acid a t 25" C. From these amyl alcohols, the chlorides were prepared by reacting with concentrated hydrochloric acid in the presence of sulfuric acid. The boiling points of the chlorides were determined as follows: BOILIXGPOINT
c.
1-Chloropentane 2-Chloropentane 3-Chloropentane 1-Chloro-Z-methylbutane 2-Chloro-2-methylbutane 4-Chloro-2-methylbutane
107 97 96 99 86 101
The separate pure chlorides were mixed in various known proportions for the testing of analytical methods. Fractional distillation was unsatisfactory because of tendencies for some of the chlorides to decompose on boiling. The pure chlorides were therefore independently studied for reactivity, and the composition of the chloride mixtures was determined by utilizing a standardized hydrolysis procedure as an analytical method. This made it possible to compare the results of different methods of chlorination intelligently. One would not expect the chlorination of pentanes under widely differing conditions to produce identical results, in view of the known methods of chlorinating toluene to obtain either a high yield of chlorobenzene or a high yield of benzyl chloride, or the chlorination of acetic acid to obtain a high yield of either the chloroacetic acids or acetyl chloride. Although these examples are not perfectly comparable with the chlorination of aliphatic hydrocarbons, there are ample reasons for suspecting that the primary, secondary, and tertiary hydrogen atoms would possess differing reactivity. There appear, in fact, to be two independent factors that influence results: (1) the chlorine "prefers" to react with one hydrogen rather than with another under certain conditions; and ( 2 ) the primary chlorides tend to transpose, after formation, to secondary or tertiary chlorides when certain catalysts are present. The various methods of chlorination of pentanes which haye been studied fall into two general classes: (1) Chlorination below 100' C. in either vapor or liquid phase requires either light or catalysts. The yields of primary chlorides are low. (2) Chlorination above 200" C. in the vapor phase (the liquid phase requires inconveniently high pressures) can be accomplished without light or catalysts and gives the highest yields of primary chlorides. The presence of anhydrous polyvalent metallic chlorides reduces the yield of primary chlorides. Carbon, or pumice, seems to have little effect either on primary yield or on reaction velocity. Light was not tried at the higher temperatures.
Actinic rays do not seem to accelerate transposition, nor do such catalysts as iodine, sulfur chloride, or red phosphorus. These catalysts, because they are soluble in liquid pentane and are volatile, have the disadvantage of causing the excessive production of polychlorides, as will be discussed later. The insoluble and non-volatile metallic chlorides can be used to produce high monochloride yields in either liquid or vapor phase, but they cause transposition of primary to secondary or tertiary chlorides, Particularly a t the higher tempera-
INDUSTRIAL AND ENGINEERING CHEMISTRY
October, 1929
tures, such catalysts tend also to accelerate the formation of amylenes and the polymerization of the amylenes. Many references may be found to such effects with the propyl and butyl chlorides (1 to 11). Action of Amyl Chlorides
When 1-chloro-2-methylbutane is caused to decompose, it forms unsymmetrical methylethylethylene, an amylene boiling a t 31" C. CH3
CHI
1
1
CHzC1. CH * CHz CH3 +HC1 f CH2 C CHz CH3 The reaction is not reversible because, when this amylene reacts with hydrogen chloride, tertiary amyl chloride, or 2chloro-2-methylbutane, is chiefly formed: CHI
CHI
I
+
CHz.A.CH2.CH3 HCl ----f CH3.CCl.CHz.CH3 This reaction, again, is not reversible for, when tertiary amyl chloride is decomposed, it forms chiefly trimet hylethylene instead of unsymmetrical methylethylethylene. CHI
1
CH3. CC1. CH,. CH3
CHI
I
HC1 f CHI. C : CH CH3
Trimethylethylene boils a t 38.4" C. This reaction is truly reversible. I n general, higher temperatures favor the formation of the amylenes, while lower temperatures favor the union of amylene with hydrogen chloride to form amyl chlorides. Pressure favors the formation of amyl chlorides At room temperature trimethylethylene will readily react with hydrogen chloride under atmospheric pressure to form tertiary amyl chloride, but above 100" C., tertiary amyl chloride breaks down to trimethylethylene. The equilibria have not yet been quantitatively studied. When I-chloro-2-methylbutane is heated under pressure it thus becomes, through the above described mechanism, 2-chloro-2-methylbutane. The transposition can be accelerated by the use of catalysts. 1-Chloro-2-mrthylbutane is slowly converted, even a t room temperature, t o 2-chloro2-methylbutane by anhydrous aluminum chloride. At higher temperatures the conversion is rapid. It would be natural to expect 4-chloro-2-methylbutane to decompose to form isopropylethylene, an amylene boiling a t 20" C. CH3
CHI
I
1
CH3 CH CHz CHiCl --f HC1f CH3. CH . CH : CHj Instead of isopropylethylene, only trimethylethylene has been observed to form. There is no evidence foy the above reaction, but such a reaction is plausible because it could be followed by a union of isopropylethylene with hydrogen chloride to form secondary isoamyl chloride (3-chloro-2methylbutane), which, in turn, could break down to form trimethylethylene. The reactions would be: CH3 CHI I CHI AH CH : CHI f HCl ----f CHI; CH . CHCl . CHI CHI 1 CH3 CH ' CHCl CH3 --f HCI
+ CH3
CHI I C : CII . CH3
Thus, both of the primary isoamyl chlorides are capable of transposition to tertiary amyl chloride. When I-chloropentane is heated it would be expected to form I-pentene thus:
CHzCl.CHz.CHz.CHz~CH3+HCIfCHZ:
901
CH.CHZ.CHz.CH8
and it is natural to expect 1-pentene to react with hydrogen chloride to form 2-chloropentane. Whether the above reactions take place or not is not definitely kmown. We have never examined 1-pentene, because all three monochlorides of normal pentane yield 2-pentene. 2-Pentene or symmetrical methylethylethylene boils a t 36.3" C. and reacts with hydrogen chloride to form 3-chloropentane, thus: CH3.CH: CH.CHZ.CH3
+ HCI=*CH3.CH2.CHCl.CHP.CH,
The union of 2-pentene with hydrogen chloride is much slower a t low temperatures than the union of trimethylethylene with hydrogen chloride, but above 100" C. the reaction is rapid. The transposition of both the 1-chloro- and the 2-chloropentanes to the 3-chloropentane, which can be accomplished by heat and pressure alone, can be accelerated by the use of a great variety of substances exerting a catalytic influence, such as glass wool, silica gel, asbestos, rare metals, and polyvalent metallic chlorides. Because of the apparent nature of the transposition mechanism, no transposition of chlorides can occur when they are heated with alkali (which takes up the hydrogen chloride formed), and in the absence of a catalyst only slight transposition can occur when the chlorides are heated in an open vessel from which both amylenes and hydrogen chloride can escape as formed. One of the most important objects to be attained in chlorination of pentane is the production of a minimum proportion of polychlorides. Polychlorides can be formed either by the action of more than one molecule of chlorine on a molecule of pentane or by the union of chlorine with unsaturated hydrocarbons. The ideal condition for the avoidance of reactions of the first class is to mix chlorine with an infinite excess of pentane under conditions that will not permit any reaction during the mixing and then, when the chlorine is dispersed, to cause the reaction to take place instantaneously. If a soluble catalyst is used in the liquid phase, the reaction occurs during the introduction of the chlorine unless it can be introduced a t a sufficiently low temperature to inhibit reaction. When the reaction occurs during mixing, excessive polychlorides are sure to form, because the concentration of chlorine will vary from 100 per cent a t the point of entry of chlorine down to the percentage represented by thorough dispersion. The same is true of chlorination in the vapor phase by the use of volatile catilysts. Chlorine can be mixed with pentane in the dark in the absence of catalysts a t temperatures below 120" C. without sensible reaction. In causing the reaction to take place, we have the alternatives of passing the mixture over non-volatile catalysts or of merely heating. It is in this reaction step that polychlorides of the second class are formed, because amylenes formed in the reaction zone cannot be separated by fractional distillation from the excess of pentanes and the amylenes are therefore necessarily returned with pentane to the reaction zone, where they add chlorine and become dichloro compounds. Some amylenes are formed by the decomposition of amyl chlorides by merely heating for a short period, but a much more rapid formation of amylenes is caused by such catalysts as aluminum chloride or ferrous chloride. Under the most favorable conditions for the avoidance of amylene formation, about 4 per cent by volume of the chlorides formed are amylene dichlorides, and with ratios of 20 parts pentane to 1 part chlorine not more than 1 per cent of the chlorides consists of polychlorides formed by multiple contact. Any amyl chloride returned to the reaction zone immediately becomes an amylene dichloride. The reactions are quantitative because the amyl chlorides are in equilibrium
INDUSTRIAL AND ENGINEERING CHEMISTRY
902
with amylenes and hydrogen chloride, and the fixation of the amylenes with chlorine causes the decomposition of amyl chlorides to be rapid and complete. CaHiiCl+ CsKo
CsHio
+ HCI
+ C1z +CaHioClz
It is because of the ease with which amyl chloride can be chlorinated to amylene dichloride that a rapid reaction is preferred to a slow one. A very slow reaction, such as would be obtained by holding a mixture of pentane and chlorine vapors a t 100" C. for several hours in a glass vessel in the dark, will yield almost nothing but amylene dichloride, even when the pentane-chlorine ratio is as high as 50 to 1. The reason is obvious. There is little tendency to form the tetrachlorides of pentane, because the amylene dichlorides are much more stable than the amyl chlorides. Some diolefines and acetylenes can be produced by severe heating, but these polymerize so easily in the presence of anhydrous hydrochloric acid that they promptly become non-volatile tarry deposits and are thus removed from contact with the chlorine vapor. Catalysts, in general, above 200" C. in the presence of hydrochloric acid, accelerate the polymerization of amylenes to tarry compounds. This is true also of the amylene dichlorides. Even without catalysts, the amylene dichloride formed from trimethylethylene (2,3-dichloro-2-methylbutane)is polymerized rapidly a t 250" C. The other amylene dichlorides are polymerized more slowly. I n the commercial synthesis isopentane yields 85 per cent primary isoamyl chlorides and 15 per cent tertiary amyl chloride. No secondary isoamyl chloride is formed. Of the primary chlorides, one third is 4-chloro-2-methylbutane, and two-thirds is 1-chloro-Z-methylbutane. This is in proportion to the number of hydrogen atoms in the respective positions. The 1-chloro-2-methylbutane is capable of optical isomerism. The corresponding alcohol as it occurs in fusel oil is optically active. But the chloride obtained by the chlorination of isopentane is not optically active, nor is the alcohol derived from this chloride. The fact that partially decomposed or partially reacted chloride shows no optical activity indicates that the optical isomers are equally reactive and stable under the conditions used in the synthesis. One-half of the monochloride formed from normal pentane is primary and the other half is secondary. This is in proportion to the number of primary and secondary hydrogen atoms in the normal pentane molecule. Of the secondary fraction there is much more 3-chloropentane than 2-chloropentane, which is not consistent with probabilities but may be caused by transposition. 2-Chloropentane is capable of optical isomerism, but the 2-chloropentane formed by the chlorination of normal pentane is not optically active. There are ten possible dichlorides of isopentane and nine possible dichlorides of normal pentane. Most of these compounds have been described in the literature. Almost none of the dichlorides formed by multiple contact, such as 1,lor 1, 5-dichloropentane1 can be found in the commercial mixture because, as we have stated, the dichlorides are mostly formed from amylenes. There are five amylene dichlorides derived from the five amylenes. The dichloride of isopropylethylene (3,4-dichloro-2-methylbutane) is not formed, because no isopropylethylene is formed by the decomposition of amyl chlorides. 1, 2-Dichloropentane, derived from I-pentene, is present in minor proportion. The 2, 3-dichloropentane1derived from 2-penbene, is the major constituent. This compound boils a t 138" C. The 2, 3-dichloro-2-methylbutane is formed, but is mostly destroyed by polymerization. 1, 2-Dichloro-2-
Vol. 21, No. 10
methylbutane, derived from the unsymmetrical methylethylethylene from 1-chloro-Z-methylbutane, is present in minor proportion. Conversion of Amyl Chlorides to Amyl Alcohols
The three classes of monochlorides have already been differentiated in a general way as regards their hydrolysis with water, their reactions with salts of fatty acids, and their rates of decomposition. The rates of hydrolysis with water of the amyl chlorides are shown in Table I. Table I-Rates
of Hydrolysis of Amyl Chlorides HEATED IN COLCONTACT WITH WATERAT lSOo C.
LOIDAL
AMYLCHLORIDE
Tertiary Secondary Primary
AGITATED WITH WATERAT SOo C.
P e r cent per minute
Per cent per mtnute
1 20 0 05 0 00
2 85 0 60 0 00
The presence of alkali or dilute hydrochloric acid does not accelerate hydrolysis. An alkali, however, serves the useful function of removing the hydrochloric acid formed by the reversible reaction: CaHiiCl
+ H,O 5---c CaHiiOH + HCI
The reactions of the amyl chlorides with salts of fatty acids have received considerable attention. The salts of acetic acid, being insoluble in amyl chloride, react very slowly, even with primary compounds, unless some means are used to obtain contact. Amyl chloride is miscible with a solution of potassium acetate in ethanol, but when this mixture is heated the products of the reaction are amyl acetates, ethyl acetate, amyl alcohols, ethanol, amylenes, unreacted amyl chlorides, potassium acetate, potassium chloride, and acetic acid. The ethanol acts as a hydrolyzing agent. When glacial acetic acid is substituted for ethanol, hydrolysis is eliminated as a factor, and we have a convenient method of studying the reactivity of the chlorides with salts of fatty acids. Table I1 shows rate of reaction of 4-chloro-2-methylbutane to be somewhat less than the rates of the other two primary amyl chlorides. Table 11-Rates
of R e a c t i o n w i t h P o t a s s i u m Acetate In Molecular C o n t a c t a t 180° C. Per cent per minute 1-Chloropentane 1-Chloro-%methylbutane 4-Chloro-2-methylbutane Secondary amyl chlorides Tertiary amyl chloride
3 17 3 17 1 20 0 60
0 00
The rates of reaction about double every 10" C. They are of the same order with potassium, sodium, or calcium salts of acetic, butyric, oleic, and stearic acids provided the salts are put in "solution" with the amyl chloride. The problem of contact becomes simple when the molecular weight of the fatty acid becomes high enough to give colloidal characteristics to the salts, for sodium oleate or stearate is highly soluble in amyl alcohol or water, and even forms gels with amyl chloride. Sodium oleate has two functions: (1) It puts water into colloidal contact with amyl chloride, which permits the most effective hydrolysis of tertiary and secondary chlorides; and (2) it is, itself, in colloidal contact with the amyl chloride, so that the primary and secondary chlorides can react to form the amyl oleates, which can be easily*hydrolyzedwith caustic soda to produce amyl alcohols. Yields of amyl alcohols from amyl chlorides are dependent upon the proportions of the amyl chlorides that decompose to amylenes. The formation of amylenes from amyl chlorides
INDUSTRIAL A N D ENGINEERING CHEMISTRY
October, 1929
903
Flow S h e e t s for Conversion of P e n t a n e t o A m y l Alcohols CHI.CH~.CHZ.CNZ.CH~ liormal pentane (36' C.)
(or alcohol), while in the presence of water it varies from 65 per cent a t 180" C. to 100 per cent a t 100' c. Water probably does not affect the reactions of the primary chlorides, but for the use of salts of high-molecular-weight fatty acids watter is required t o gire colloidal contact between the salt and * CHa.CHz.CHOH.CHz.CH3 CH~.CHOH.CHZ.CH~.CHI CHzCH.CH2. CHz.CHz.CHI the chloride. 3-hydroxypentane (115.7' C . ) 2-hydroxypentane (119' '2.) 1-hydroxypentane (138' C.) Primary amyl chlorides heated to 160' C. with the corresponding amyl alcohols and with 5 per cent aqueous caustic soda react to form diamyl ethers. The rate of ether formation a t 160" C. + is about 1 per cent of the rate of esteriCHa.CHCl.CHC1.CHz.CHa + CH~.CH~.CHOH.CHZ.CH~ fication. At 200" C. the rate rises to 4 a-hydroxypentane (115.7 ' C.) 2,3-dichloropentane (138' C . ) Der cent. Amvl chloride heated with CHI alcoholic potash yieids ethyl ami1 ether because of the I presence of some alcoholate, but the following reactions do CHa.CH.CHz.CH3 2-methylbutane (28' C.) not seem perfectly plausible for diamyl ether:
!+
+ +
Clr
CSHllOH NaOH ----f CSH1lONa4- HzO C5H1tONa CjHl,Cl+ (CBH11)zO NaCl
i
CHI $HI.C&I.CH~.CH~ --chloro-2-methylbutane (86' C.)
CH3.CH.CH?.CHzCI 4-chloro-2-rnethylbutane (101' C.)
C H ~ O H . & H . C H ~ C H ~ CHz.dOH.CHz.CHa 2-hydroxy-2-methyl1-hydroxy-2-methylbutane ( l O 1 . S o C.) butane (128" C . )
CHs.CH.CH?.CHzCH 4-hydroxy-2-methylbutane (130.5' C . )
CHzCI.kH.CHzCH3 1-chloro-2-methylbutane (99' C.)
1
+Heat
t
CHI
1
c
+Heat
CHI
CH2:d.CHz.CWz Unsymmetrical methylethylethylene (31O C.)
CHs.k:CH.CH: Trimethylethylene (38;4O C . )
CHJ.&OH.CH~.CH~ 2-hydroxy-2-methylbutane (lO1.So C . )
is not accelerated by moisture, caustic soda, amyl alcohols, amyl esters of fatty acids, or fatty acids. At temperatures below 200" C. the amyl alcohols are not dehydrated in the presence of any of the above materials except the watersoluble fatty acids. The only amylene formed in an alkaline hydrolysis is that from the decomposition of amyl chloride by heat. The rates of decomposition of the amyl chlorides to amylenes are shown in Table 111. of Decomposition t o Amylene8 a t 180' C. Per cent p e r mtnute Primary amyl chlorides 0.0s
T a b l e 111-Rates
Secondary amyl chlorides Tertiary amyl chloride
0.65 3.70
+
Both the isoamyl and the normal amyl ethers have been found. No other materials are formed in hydrolysis of amyl chlorides. No system of hydrolysis or esterification can completely react the amyl chlorides. It is exceedingly difficult to get rid of the last traces of amyl chloride in amyl alcohol by chemical reaction. Sereral hours' digestion of amyl alcohol containing 1 per cent amyl chloride with 5 per cent metallic sodium will reduce the amyl chloride content only to about 0.3 per cent. Fortunately, the properties of the amyl chlorides and the amyl alcohols afford a relatively simple method of separation by distillation. The separation is accomplished in the presence of water by virtue of the constantboiling mixtures of the chlorides and alcohols with water. All the amyl chlorides form constant-boiling mixtures with water. Tertiary chloride boils with water a t i 6 " C., while 1-chlwopentane boils with water a t 82" C. The other chlorides have intermediate boiling points with water. The constant-boiling mixtures are composed of about 3 volumes of amyl chloride to 1 volume of water. The chlorides and alcohols form a three-component constant-boiling mixture with water. This distillate separates into two layers-water containing alcohol in solution, and a non-aqueous layer containing 20 per cent alcohol and 80 per cent chloride. of t h e Amyl Alcohols BOILING BOILING SPECIFIC POINT W A ~ E R POINT GRAVITY WITH IN DEDRY 2 0 ° / 2 0 0 C. WATERTILLATE C. Per cent 138 0.817 95.5 47.8 119 0.810 92.3 32.2 115.7 0.815 91.4 32.2 128 93,s 41.5 0.816 101.8 S7,2 22.0 0,812 130.5 95.0 42.4 0,812
T a b l e IV-Properties
AMYLALCOHOL
c.
1-Hydroxypentane 2-Hydroxypentane 3-Hydroxypentane 1-Hydroxy-2-methylbutane 2-Hydroxy-2-methylbutane 4-Hydroxy-2-methylbutane
Chemical yields in hydrolysis or esterification can be computed from the rates of reaction and of decomposition. As the temperature is lowered from 180" C. the ratio of rate of I n putting the above predetermined principles into pracdecomposition of secondary chlorides to rate of esterification tice, very few difficulties have been encountered. Physical remains about the same, but the rate of hydrolysis is not operation consists largely of fractional distillation, and the reduced nearly so rapidly as the rate of decomposition. At 100" C. the rate of decomposition of tertiary chloride be- distillation equipment, designed by George P. Lunt, of E. comes zero, while the rate of hydrolysis is still high. Thus, B. Badger and Sons Company, has functioned better than low temperatures are favorable to high yields from both the was predicted on the basis of small-scale experimentation. secondary and tertiary chlorides. A Novel Principle for Combating Corrosion I n a dry esterification reaction tertiary chloride can give only amylene. The yield from secondary chlorides a t any I n handling large volumes of hydrochloric acid in metal temDerature is about 48 Der cent in the absence of water . . equipment one naturally expects corrosion. None of the
I N D U S T R I A L A N D ENGINEERING CHEMISTRY
904
five iron distillation columns in the chlorination plant have shown any evidences of corrosion during more than two years of operation. At several points in the plant iron pipe has been replaced with Toncan iron2 pipe, for an interesting reason. Toncan iron is not particularly resistant to aqueous hydrochloric acid, but it has the property of preferring to be wetted with pentane or amyl chloride rather than with aqueous acid, while the reverse is true of ordinary iron or steel. Hydrogen chloride is not corrosive to metals when it is in solution in dry pentane or amyl chloride. When a trace of moisture is present, an emulsion is formed in which the moisture is dispersed and the continuous phase is anhydrous and non-corrosive. Such an emulsion will deposit aqueous acid on ordinary iron but not on Toncan iron. This is a rather unusual reason for the selection of a material of construction, but the phenomenon probably will be found to have numerous parallels in the chemical industries. The hydrolysis and final distillation operations are not subject to corrosion because the liquids handled are neutral or alkaline. An alloy with iron of ropper and molybdenum. Corporation, Massillon, Ohio.
Central Alloy Steel
Vol. 21, No. 10
The solubilities of amyl alcohols in water and of water in amyl alcohols are given in Table V. Table V-Solubilities of A m y l Alcohols a n d Water ALCOHOL DISSOLVED WATERDISSOLVED I N 100 ML. WATER IN 100 ML. ALCOHOL 10 30 50 70 10 30 50 70 AMYLALCOHOL OC. o c . = c . o c . o c . oc. o c . OC.
Ml. 1-Hydroxypentane 2.6 2-Hydroxypentane 7.5 3-Hydroxypentane 8.0 1-Hydroxy-2-methylbutane 5 . 0 2-Hydroxy-2-methylbutane 2 0 . 5 4-Hydroxy-2-methylbutane 3 . 7
MI. 2.1 5.3 5.5 3.6 14.0 2.8
M1.
M1. Ml. 1.8 6.4 4.1 8.0 4.2 8.2 3.0 7.0 10.6 8 . 7 1 7 . 6 2.5 2.4 6.5 1.9 4.4 4.5 3.1
M1. 7.2 8.8 9.1 7.8 17.7 7.4
MI.
M1.
8.5 9.9 10.2 9.2 17.8 8.7
10.7 11.4 11.8 11.3 17.9 10.8
Literature Cited (1) Bauer, Jahresb., 1861, 660.
(2) (3) (4) (5) (6)
(7) (8)
(9) (10)
(11)
Brunel, Ber.. 44, 1000 (1911). Eltekoff, I b i d . , 6, 1244 (1875). Faworsky. Ann., 364, 325 (1907). Gustavson, 3. SOL. 9hys. chim. rime, 16, 61 (1883). KekulC and Schrotter, Ber., 12, 2279 (1879). Konawalow, I b i d . , 18, 2808 (1885). Menchutkin and Konawalow, I b i d . , 17, 1361 (1884). Michael and Leupold, Ann., 379, 263 (1911). Michael, Scharf, and Vogt, J . A m . Chem. Soc., 38, 653 (1916). Mouneyrat, Bull. soc. chim., [3] 21, 616 (1899).
Carbon Deposits from Lubricating Oils’ Experiments with Heavy-Duty Engines C. J . Livingstone and W. A. Gruse MELLONINSTITUTE
OF
INDUSTRIAL RESEARCH, UNIVERSITY O F PITTSBURGH,PITTSBURGH,
PA.
Previous work published by this laboratory had incontinuously on schedule over dicated that the tendency to deposit carbon in gasoline the same territory and under m u n i c a t i o n s from this engines shown by lubricating oils bore an approximately heavy load. A t t h e s a m e laboratory (1, 2, 3) the direct relation to the carbon residue values of the oils. time it was desirable to emstudy of carbon deposits in Three very heavy oils of different characteristics were ploy conditions not so artiautomotive engines has been studied under service conditions for 180,000 car-miles ficially regular as to have no carried on with a view to esin a fleet of motor coaches powered by sleeve-valve connection with actual sertablishing any possible conengines. These same oils were also tested in the singlevice. These requirements nection between the propercylinder laboratory engine used in the previous work. seemed to be met by a fleet of ties of lubricating oils and the From the road studies it was found that in sleevemotor coaches in actual comconduct of these oils in use mercial service, where schedvalve engines paraffinic oils differing markedly in carbon (particularly with regard to ules are maintained, where the residue value differed only slightly in amount of carbon carbon deposits). The work weight of the vehicle is such deposited, while a naphthenic oil was greatly superior has so far covered laboratory that the engines are operated to both. For poppet-valve engines the laboratory exe x p e r i m e n t s with a small under full throttle most of the periments indicate that the carbon residue value resingle-cylinder engine under time, and where maintenance mains a fairly reliable index of the carbon deposit to rigid control employing oils and care are closely superbe expected. of medium and heavy to exvised. The requirements of tra-heavy grades, the conditions being altered to simulate those under which such oils such service would be such that, while conditions are in general would be used in actual service. I n general, that work has very uniform, the main consideration is that operation be conbrought out two points: first, that the carbon-depositing tend- tinuous and schedules be maintained. Because of this any encies of automobile oils can be predicted approximately from academic adherence to desirable conditions beyond what is the carbon residue test of these oils; and second, that the car- necessary for satisfactory functioning need not be feared. For bon residue test is significant probably because it is a rough instance, carbureter adjustment would in general not be closer indication of the volatility, a t flame temperatures, of the oils. than is needed for flexibility and maximum power. At the I n an effort to confirm these conclusions by actual observa- same time any mal-adjustment beyond these limits would be tions of road work, the writers were faced with the necessity of quickly observed and corrected. The facilities for carrying on this work were obtained finding an environment which would permit the operation of automotive equipment under the same uniform conditions as through codperation with the Pittsburgh Motor Coach are possible in the laboratory. The only suitable equipment Company, which placed a t the disposal of the writers eighteen appeared to be a selected fleet of heavy-duty vehicles operated sleeve-valve engine coaches. The maintenance and supervision of these coaches were turned over completely to the Presented before the Division of Petroleum 1 Received July 29, 1929. writers with only the stipulation that the operating schedules Chemistry at the 78th Meeting of the American Chemical Society, Minneof the company be maintained. In general, no deviation from apolis, Minn., September 9 t o 13, 1929.
N THREE previous com-
I
