C. E. STARR, JR., AND W. F. R4TCLIFF Esso Laboratories, Standard Oil Company of New Jersey, Louisiana Division, Baton Rouge, La. Butadiene from petroleum sources is a low cost, highly reactive hydrocarbon which has been used mainly for polymerization to rubber, but which offers numerous possibilities for organic syntheses. It is produced to contain concentrations of 1,3-butadiene in excess of 98%; the impurities comprise chiefly hydrocarbons, individually occurring in concentrations from several tenths per cent to trace amounts. The nature and extent of these impuritieb in butadiene from several petroleum sources, all refined by copper salt extraction, have been ascertained by application of mass and infrared spectrometric measurements. The main impurities in petroleum-source butadiene are the butenes; smaller amounts of C3 hydrocarbons are included.N-Photo shows a butene dehydrogenation unit.
B
UTADIESE was produced in large quantities during the
war period and is still being made in large amounts, chiefly for synthetic rubber. A large portion of the wartime butadiene was derived from petroleum sources, and in the postwar period substantially all of it is expected to be produced from petroleum because of the inherent low cost (6). Butadiene from petroleum sources is not only utilized in synthetic rubber but offers numerous possibilities as a low cost, highly reactive hydrocarbon for organic syntheses.
Butadiene from petroleum has generally been produced to provide a grade suitable for polymerization reactions. This refined butadiene is recognized as a highly purified industrial chemical, since its 1,3-butodiene content is above 98%. The impurities comprise a number of compounds, each present in amounts of several tenths per cent t o traces. Impurities in petroleum-source butadiene may be ( a ) hydrocarbons of a similar or different boiling range, the latter being present because of inadequate fractionation or polymerization in storage, (0) oxygenated compounds, (c) sulfur compounds, ( d ) water, and ( e ) nonvolatile residues. These impurities exert varying effects upon the rubber polymerization reaction, ranging from that of the diluents which influence only the yield of desired product to that of the poisons which retard the reaction' and influence the quality of the polymer. The estent and nature of these impurities were determined in butadiene products from various petroleum sources (all refined by the copper salt extraction process) by chemical, cryoscopic, and spectroscopic methods of analysis. ANALYSES OF BUTADIEXE SAMPLES
Figure 1 is a schematic diagram shoiving the impurities that must be considered and methods for their assay. \Vith the exception of the mass spectrometer method, all the procedures employed in the study of butadiene impurities were derived from the 1020
INDUSTRIAL AND ENGINEERING CHEMISTRY
October, 1946
HYDROCARBON IMPURITIES
test methods prepared by the Butadiene Analytical Committee,
The hydrocarbons which have been, or might be, identified in crude and refined butadiene are divided into several groups (Table I). Many of the compounds boil close t o 1,3-butadiene (boiling point -4.S0C.)'and are separable only with difficulty by fractional distillation. Others have sufficiently different volatilities so that they can be removed or appreciably reduced by efficient distillation. PAR AFFIX^. The paraffin hydrocarbons that may be found in refined butadiene product are propane, butanes, and pentanes. Xone of these take part in the rubber polymerization reaction and hence do not influence the reaction other than as diluents t h a t build up in recycle operations. Since there are no chemical tests for the direct determination of paraffins, physical properties or physical methods must be used. The magnitude of the concentrations of these impurities in the various types of refined, petroleum-source butadiene was determined by mass spectrometer analyses. Samples analyzed by this hboratory were also analyzed by the National Bureau of Standards. In both laboratories the Consolidated mass spectrometer vxis employed. Table I1 gives detailed assays of paraffin impurities. The assays obtained by this laboratory were made by mass spectrometer measurements on concentrated impurities obtained by selectivc removal of 1,3-butadiene by reaction with maleic anhydride. Impurities that did not pass through the maleic anhydride but were physically retained were flushed free of the anhydride by inert gas which was subsequently removed; this permitted the accumulation of the impurities in concentrated form. To test the efficacy of the method for concentrating impurities, a synthetic sample was prepared and the impurities were analyzed by mass spectrometer after removal of 1,3-butadiene (Table 111). Within the tolerance of the analytical procedure the olefin and
a government-industry group. These methods are being assembled for publication. The mass spectrometer procedure, applying to the assay of butadiene, was described by Brewer and Dibeler of the Sational Bureau of Standards ( 2 ) . Analytical distillations, carried out to concentrate (for subsequent identification) the impurities occurring in relatively high purity butadiene, require long periods of time and large samples; therefore, use ims made in these studies of new physical methods for analysis involving infrared and mass spectrometry. Both the mass spectrometer and the infrared absorption spectrometer have particular application to the analysis of specific impurities in butadiene. In spectroscopic procedures impurities in butadiene are not individually segregated but are identified by comparing the spectra (mass and infrared) measured in sample analysis 11-ith the spectra of known pure hydrocarbons. The s h d y of impurities in petroleum-source butadiene was conducted on snrnples refined by three different types of processes, represented by the follon-ing plants at the Baton Rouge Refinery of the Standard Oil Company of S e l v Jersey: sample A, private plant employing processing of petroleum fractions; sample B, refinery conversion plant employing severe thermal cracking of naphtha feed stock; and sample C, butene dehydrogenation plant. Figure 2 shows simplified flow diagrams of the plants. A photograph of the dehydrogenation plant appears on page 1020. The copper salt extraction process employed in these plants is described by Morrell and co-authors (6). I n addition to samples of refined butadiene from each of these three plants, EL fourth sample, D, of semirefined butadiene was studied to ascertain the nature and extent of impurities that would be present in a lower grade of product requiring less processing in its manufacture.
1
+ GENER.4L ANALYSES
h I L Y S E S FOR P U R I T Y
FOR
1,a-Butadiene Chemical Maleic anhydride absorption with gas flushing of impurities Physical Freezing Doint Mass spectrometer
BUTADIENE SAMPLE (LIQUID PHASE)
4
+
+
ANALYSES FOR SPECIFIC HYDROCARBON IMPURITIES'
IMPURITIES
Water
Chemical
Peroxides
Chemical
Acetylenes
Chemical
Carbonyl
Chemical
Sulfur
Chemical
_~Total
Boiling test
Cb
1021
Inhibitor
Chemical
Dimer
Evaporation
Nonvolatile
Evaporation
-
c 3
Propylene Propane Methylacetylene Propadiene
C4 Isobutane n-Butane Isobutylene I-Butene cis-2-Butene
trans-2-Butene
Mass spectrometer Mass spectrometer
Mass spectrometer Mass spectrometer
}
1.2-Butadiene Ethylacetylene Vinylacetylene Dimethylacetylene Ca -
1,4-Pentadiene
Ca Diolefins
Cs Olefins Isopentane +Pentane Cr +
Mass spectrometer, chemical spectrometer
Mass
Mass spectrometer Mass mectrometer. infrared Chemiial Chemical iMasa spectrometer (approx.)
Infrared, mass spectrometer Mass spectrometer Mass spectrometer h4ass spectrometer Mass spectrometer Mass spectrometer
Mass spectrometer analyses for impurities preferably made on residue gas from gas flushing butadiene analysis. Figure 1.
Schematic Diagram for Analysis of Butadiene
1022
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 38, No. 10
material in such processes as the GI(-S rubber synthesis, which generally employs a recycle PRIVATE P L A N T operation. Of the olefins that might be present, butenes were shown by hlorrell arid co-authors PROCESSING AND F RACT I O N S (5)to be slightly soluble i n thc estr;rction soluF R A C T I O N A T l ON tions; butenes would be espectcd to be present BUTENES 2 in noticeable m o u n t s arid t o w r y in conrcntration with the efficiency of the estrnction procPLANT B ess employed o r the degree of extraction REFINERY CONVERSION P L A N T effect cd. Chemical methods of test for the C3-Cbolefins are available but are gener:ally :tpplicablc only to concentrated fractions obtninnble in appreciable amounts from prcilorigod distillation. Infrared nbsorption spectra me:tsuremonts provide a suitable method for determining the CRACKING PLANT C olcfin impurities i n butadiene brit iiecessitate BUTENE DEbY3ROGENATION P L A N T the use of a relatively large s:tmplc from which the 1.3-butadiene has been removed, :ind this cnlls for a rather tedious prepnr:ttion procedure. On the other hand, the mass Spectrometer offers sufficient resolution for determining olefins Figure 2. Simplified Flow D i a g r a m s of Butadiene Production Plants of different molecular n-eights. Although it Drovides less accurate distribution between the isomeric butencs, the requirement of only a small s:imple is TABLE I. HYDROCARBONS ASSOCIATEDTVITH REFISED such that the mass spectrometer can be applied to concentrated BUTADIENE FROM PETROLEUM impurities obtained by a quick 1:3-butadiene remov:rl, with conBoiling P o i n t a t 760 11m. (3) sequent improvement in the analysis for the individud C, O F components. These advantages hold particularly for high purity Paraffins Propane -42.: -43.8 butadiene in nhich the total amount of impurities is less than 2%. Isohutane -11., 10.7 n-Butane - 0.6 22.1 Because of thcse considerations the olefin impiiriticxs in the Isopentane 27.9 82,O samples of butadiene studied werc identified by ni n-Pentane 36.0 96.8 eter measurements on residual fractions aftcr maleic :tilhydride Olefins -53 7 Propene -47 6 Table IT summarizes the :iss:iys for olefin impurities. contact. - 6 9 19 6 Isobutylene l-Butlne 20 7 - 6 3 Olefins as a group, and pnrticu1:irly butenes, comprise the bulk cis-%Butene 3 6 38 5 of the impurities in refined butadiene. The olefin orrurring in trans-%Butene 0 9 33 6 Pentenes 20 1 t o 38 5 68 2 t o 101 3 greatest conecntration is 1-butene, n-hieh has the nearest boiling Diolefins point to 1,3-butadiene of all the olefins, and \vIiicli is somewhat -34 3 -29 7 Propadiene (nllene) 10 3 50.5 l,2-Butadiene (methylallene) more soluble in the copper salt extraction nlediiim than :ire 226 1 79 0 I ,4-Pentadiene butenes or isohutyli~ne(5). The highest coricentr:itio~iof olt:fins 34 1 93.4 2-\Ieth!-l-1,3-butadiene (isoprene) 41 5 , 43 6 106.7, 1 1 0 . 5 1,3-Pentadiene (piperylene) occurred in sample D 2nd an npprcri:ihk :Imount of 2-butcnrs was PLANT A
r--
hcetvlenes AI&h?-I acet3lene Vinyl acetylene E t h y l acetylene Diniethyl acetylene Polymers Butadiene dimer (4-vinyl-1-cyclohexene) Acetylene polymers
-23 2 5 0 8 6 27.1 130 100 t o zoo+
-9 8 41 0 47 5 80.8
TABLE 11. 1Iass SPECTROMETER A';.ALYSI~ OF PARAFFIN IMPURITIES IS MOLEPERCEx
266 212 t o 3 9 2 +
diolefin impurities Kere n-holly recovered. Paraffin impurities were known not to react with the maleic anhydride, and it as assumed that their recovery from any absorbed condition n-ould be as complete as that of olefins and diolefins. Figure 3 shows typical mass spectrograms of the concentrated impurities occurring in 3 normal purity product (sample B) and in a semirefined product (snmple D). The analyses for impilrities reported by the Sational Bureau of Standards (1) were made on the simple containing l,3-butndiene. I n a11 c:ises the paraffin impurity content was small, as would tie expectrd of refined butadiene which has been processed by wlective extraction methods (6). Since paraffin impurities are not considered deleterious even in significant quantities except from the standpoint of dilution, the presence of such small quantities as were found in petroleum-source butadiene is not deleterious for general polymerization utilization. OLEFIXS. Mono-olefins in refined butadiene are only mild poisons in emulsion polymerization. They do not react extensively; their presence increase8 the quantity of recycle
.4
I3
C
D
< 0 01 0 00
0 00 0 00
0 no 0 00
0 00 0 00
Isohutnne 3.0. co. S.B.S.
0 01
..
0 01
..
0 03
..
0 04 0 00
n-liutane S . O . co. N.B.S.
0.01
..
0 01
0 06 , .
0.16 0.18
s.0. c o . S.B.S.
0.02 0.02
0.02 0.01
0.11 0.03
0.20 0.18
Pentnnes 5 0 . Co. s.E. S .
0 01 0 00
0 01 0 00
ox
0 00
0 00
0 00
Sample Propane S 0.co.0 I\J.B.S.b
Tot31 hutanes
a b
0
Standnrd Oil Company of S e n . .Jer.seg-,Louisiana Diri,ion. Xationnl Bureau of Stnndardi.
TABLE111. TESTOF
l\IETHOD FOR Synthesis, Mole FG
1,3-Butadiene 1.2-Butadiene I-Butene a
..
REIIOVAL OF
1.3-BUTADIENE Reiidue xfter 1,3-C11Iq Heinoval", l l o l e 5% 0 0 2.42 2.06
By mass spectrometer anal>-sis (caiculnted on baeis of original sample).
October, 1946
INDUSTRIAL AND ENGINEERING CHEMISTRY
INDUSTRIAL AND ENGINEERING CHEMISTRY
1024
TABLE I\'.
MASSSPECTROMETER ANALYSISOF OLEFIS IMPURITIES IN MOLEPERCENT
Sample Propene S.O. c0.a
S.B.S.a Isobutylene S.O. eo. N.B.S. 1-Butene 3.0. co. N.B.S.
a
C
A
B
0.31 0.30
0.04 0.07
0.29 0.29
D 0.02 0.04
0.27
..
0.11
..
0.14
1.05
0.62 0.79
1.07 1.30
0.92 0.69
2 70 4.15
..
..
2-Butenes 6.0. eo. N.B.S. Total butenes S.O. c o . N.B.S.
0 05 0.10
0.13 0.00
0.30 0.45
1 29 0.76
0 94 0 89
1.31 1.30
1.36 1.14
5.04 4.91
Pentenes S.O. e o . N.B.S.
0.01 0.00
0.00 0.00
-lenes, Acetplenea, bielniak t,ype); the sample is separated into two roughly equal Sample Wt. % K t . 55 Sample fractions, to permit individual determination of propadiene and C 0.048 A 0.038 D 0.043 B 0.055 1,2-butadiene in the first and last fractions, respectively.
!;;:;$;;
ijb,
5
1025
INDUSTRIAL AND ENGINEERING CHEMISTRY
October, 1946
Butadiene dimer (4-vinyl-1-cyclohexene) is in a somewhat different class from other hydrocarbon impurities in that it is formed during storage. Robey, Wiese, and Morrell ( 7 ) showed -hat about lY0 of the monomer changes to dimer during two months of storage in midsummer. lnalyses of samples taken &directlyfrom the extraction plants show only traces of dimer 10.01 to 0.03 weight %). NONHYDROCARBOK ISIPURITIES
Small amounts of nonhydrocarbon impurities are occasionall\:iwxiated with refined butadiene. as indicated in Figure 1. T:ihle VI11 s h o m the concentrations of nonvolatile residue, peroxides, carbonyl compounds, and sulfur for the refined and semi:i,fined butadiene samples studied. Within the tolerances of the, a:ialytical procedures, the amounts of these impurities in pt3:I oleum-source butadiene are practically nil. I n hibitor (terthutylcatechol) is added to refined butadiene to suppress perosi.!:ition and polymerization during storage. I t is effectively re:m m d . however, by distillation or caustic washing. DETERMINATIOX OF ABSOLUTE PURITY
The direct determination of 1,3-butadiene content is of paramount importance for properly controlling plant operation and for i,nsuring that a satisfactory product will be marketed. Various chemical methods, in ahich the butadiene is reacted with maleic anhydride, have been used. They include the vapor-phase volumetric method, of Tropsch and hlattox ( I I ) , the modified gas drishing methods in which an inert gas is used to strip the reagent 1.1’ nonreacted gas, and a gravimetric method using liquid-phase reaction under pressure. Methods of analysis utilizing physical properties are mass, infrared, and ultraviolet spectrometry, and cryoscopic measurement. The latter method depends on t,he effect of impurities in lowering the freezing point of the butadiene sample; it is congidered the most accurate of all of the physical measurements. Analyses by several of these methods have been made on the refined samples representative of the various petroleum processes, as well as on the semirefined butadiene (Table IX). The gas flushing volumetric method is the most reliable of the chemical reaction methods of analysis for refined butadiene and is very adaptable to plant control, The ultraviolet and infrared spectrophotometric methods are of value for plant control when they 3re properly calibrated but usually require recalibration whenever the relative distribution of contaminants varies appreciably. .Spectrophotometric devices are usually calibrated with samples xhose purity has been established by the freezing point method. The mass spectrometer method is particularly advantageous when it is desired to follow the cpncentratior, changes of the individual impurities.
TABLE S. SUMMARY OF BVTADIENE COMPOSITION A
Sample Cs,impurities, mole % Propane Propene Propadiene Total Cd impurities. mole % Butanes Butenes 1,2-Butadiene Acetylenes Total CS impurities, mole Pentanes Pentenes Pentadienes Total
Refined Product B C
0.01
0.31
0.08 0.40
0.00 0.04 0.18 0.22
0.00 0.29
0.11 __
0.11 1.36
0.20 5.04
0.06 1 46
0.OG 0 05 1.58
E
0.01 0.01 0.01 0.03
0.01 0.00 0.00 0.01
0.03 0.01 0 2 0.05
0.01
0.029 0.001 0.000 0.001 0.000 0.03 98.12
0 013 0 00s 0 000 0 000 0.000 0.02
0.006 0.003 0.000 0.000
0.01
0.011 0.004 0.000 0.000 0.000 0.02
98.03
98.17
94.32
0.15 0.04 1.15
0.02 1.31 0.07
- - - -
i ’ t h e r impurities, weight % Butadiene dimer Sonvolatile Sulfur Carbonyl Peroxides Total 1,3-Butadiene, mole yo
0.00 0.02
0.02 0.31
0.02 0.94
5
Semirefined, D
-
O.Oo0
-
0.13
~
0.05
5.33 0.00 0.01
0.02
-
CONCLUSIONS
Butadiene from petroleum is a high purity industrial chemical which has been produced mainly for use in synthesis of Bunatype rubber. I t contains 1,3-butadiene in concentrations above 98%. The nature and extent of impurities present have been ascertained. Table X summarizes the impurities present in refined butadiene and in a semirefined product; it shows that the application of new physical methods of analysis provides an accurate assay of 1,3-butadiene content and associated impurities. I t has been possible to operate plants producing butadiene from petroleum, of a quality suitable for rubber polymerization, while maintaining the quantity of production required by the wartime and immediate postwar emergencies. The nature of the impurities found in such butadiene indicates that a, product having an even higher content of the useful 1,3-isomer can be made by existing processes through increased finishing operations permissible under less pressing peacetime conditions. ACKNOWLEDGSIEKT
The authors wish to thank the Chemical Division of Esso Laboratories, Standard Oil Development Company, for contributing experimental data, and the National Bureau of Standards for help i n conducting confirmatory analyses. LITERATURE CITED
, 1, Brewer, A. K., Natl. Bur. Standards, private communication,
Feb. TABLE
VIII.
ASALYSISO F BUTADIENE FOR NONHYDROCARBON IXPVRITIES 1s nTEIGHT PER CENT .4 B C D
Sample Sulfur Peroxides Carbonyl Sonvolatile residue TABLE
Ix.
0.0001. 0.0002 0.001
0.001
ANALYSES FOR
Sample Freezing point“ Mass spectrometer0 Gas Bushing Yolumetricb Gravimetric
0.0001 0.0001 nil 0.008
1,3-BLTADIEKE
0.0002 0,0004 nil
0.003
0.0002 0.0003 nil 0.004
PURITY I N hfOLE
PERC E ~ T A 98.12 98.45 98.21 98.9 99.3
hons”, 4th ed., New York, Texas Co., 1943. :4) Frolich. P. K., Esso Lab., private communication, Jan. 27, 1946.
W.,Asbury, W. C., and C.L., Am. Inst. Chem. Engrs., Deo. 17-19, 1945.
, 5 ) Morrell, C. E., Paltz, W. J., Packie, J. Brown,
(6) Ralph. H. D., Oil Gas J . , 44 (32), 70-2 (1945). :?) Itobey, R . F., Wiese, H. K., and Morrell, C. E.,
IND. ENQ, 36, 3-7 (1944). ’S, Rossini, F. D., Natl. Bur. Standards, private communication, CHEM.,
Jan. 27. 1948. B 98.03 98.24 98.10 98.9 99.0
C
D
98.17 98.24 98 04 99.1 98.6
94.32 94.51 94.09 96.3 95.6
Average of analyses b y t h e Esso Laboratories and t h e National Bureau ef Standards ( 8 ); all others are b y t h e Esso Laboratories only. t
5, 1945.
( 2 ) B r e w e r , A. K., and Dibeler, V. H., J . Reseaich Natl. Bur. Standards, 35, 125-39 (1945). i~3: Doss, 51. P., “Physical Constants of the Principal Hydrooar-
.\lodification of method of Tropsch a n d h f a t t o r (11).
(9) Schiller, J. C.. and Seyfried, W.D., Humble Oil and Refining Co., private communication, Sept. 15, 1944. ‘10) Swaney, 51. IT., and Vanderbilt, B. >I Esso ., Lab., private (11)
communication, March 30, 1944. Tropsch, H., and Mattox, W. J.,ISD. EKG.CHEM.,ANAL.ED., 6 , 104-6 (1934).
P R E s E s r E D before t h e Division of Petroleum Chemistry AhxERxcAN C x E s r x c A L SOCIETY, Atlantic City,
ing of t h e
a t t h e 109th Meet-
N. J.
