December 1948
INDUSTRIAL AND ENGINEERING CHEMISTRY
2295
CONCLUSIONS
ACKNOWLEDGMENT
The contention is, then, that with reclaim dispersion, GR-S latex, casein dip solutions, the best flex life in woven rayon passenger tires is obtained with lower amounts of dip pickup. High single cord adhesion values do not guarantee good tire performance; therefore, less emphasis should be placed on such tests.
The authors wish to express their appreciation t o It. Schmahl who drew the figures used in illustrations.
SUMMARY
The tests described herein show that in woven rayon passenger tires, tire performance is improved when the quantity of dip Pickup is reduced, even though there is a sacrifice in adhesion values.
LITERATURE CITED
(1) Gillman, H. H., and Thoman, R., IND. ENG.CHEM.,40, 1237 (1948). (2) Lyons, W. J., Nelson, M. L., and Conrad, C. M., India Rubhe7 World, 114, 213-17, 219 (1946). RECEIVEDSeptember 23, 1947. Piesented before t h e Division of Rubbei Chemistry at the 112th hleeting of the A,IERICAV CHE,~IICAL SOCIETY, N~~ Yo&, N. Y .
Diolefins in Alkylation Feedstocks J
Conversion to Mono-oleJins by Selective Hydrogenation JOHN ANDEKSON, S. H. IMCALLISTER, E. L. DERR, AND W. H. PETERSON Shell Development Company, Emeryville, Calif.
During the critical wartime shortage of light olefins for alkylate gasoline manufacture, means of extending the supply of butylenes and amylenes were sought and possible processes for purification of unsuitable refinery fractions were investigated. Materials contaminated with diolefins were available to some extent, and a vapor phase process for converting the diolefins i n such materials to monoolefins by selective hydrogenation was devised. The supported nickel sulfide catalysts employed in the hydrogenation process have a remarkable degree of selectivity i n t h a t they are active for hydrogenation of diolefins to monoolefins but relatively inactive for the hydrogenation of mono-olefins to paraffins in the temperature range of 200 to 300 'C., even i n the presence of a large excess of hydrogen. Butene and pentene fractions having diolefin contents rendering them unsuitable for isoparaffin alkylation were converted b y hydrogenation over nickel sulfide catalysts
to fractions giving excellent alkylation results. The hydrogenated materials had mono-olefin contents corresponding to the combined concentrations of diolefins and mono-olefins originally present and alkylate yields were improved by amounts depending on the increase in monoolefins in the feedstocks. Investigation was directed primarily to continuous vapor phase operation under conditions readily obtainable i n existing hydrogenation units of the types used for hydrogenating catalytically cracked gasolines or for converting butene dimers to iso-octanes. The nickel sulfide catalyst employed in most of the work was prepared from a commercially available nickel carbonate-alumina by merely treating with hydrogen sulfide a t 400" C. This material proved to have a life of over 1000 hours when treating a Ci fraction containing 23 mole 7 0 butadiene, and, after losing activity, i t was again rendered active by burning and resulfiding.
I
Although examples of the partial hydrogenation of diolefins 0 1 acetylenes to mono-olefins in the presence of active mctal hydrogenation catalysts are well known in the literature (?), the conversion of the poly unsaturated materials to the corresponding mono-olefins by vapor phase hydrogenation is rendered difficult by the tendency of the mono-olefin first formed to add more hydrogen and become completely saturated. This difficulty is enhanced when the diolefin undergoing hydrogenation is present, as in alkylation feedstocks, along with a high concentration of mono-olefin which can compete for the catalyst surface and the hydrogen. Nevertheless, in the preliminary stages of the present investigation i t was found possible by limiting the proportion of hydrogen, with nickel metal catalysts, to remove substantially all diolefins from C4 and Cs fractions containing initially 4 t o 60% of diolefins without taking a n accompanying net loss in mono-olefin content. Figures 1 and 2 show typical vapor phase hydrogenation results obtained with a nickel catalyst. It will be seen that a hydrogen to diolefin mole ratio of around 2 t o 1 was required for complete diolefin removal and that the products using this ratio had mono-olefin contents similar to those of the feeds. With a nickel tungsten sulfide hydrogenation catalyst i t was possible to adjust conditions, even with a severalfold excess of
N THE alkylation of isobutane (2-methylpropane) with olefins
for the production of highly branched paraffins (1, %), the life of the sulfuric acid or hydrogen fluoride catalyst is usually limited through dilution with soluble hydrocarbon by-products. When pure feedstocks are employed, these by-products are apparently formed b y hydropolymerization of the olefin (3,6) urhich occurs to a small extent as a competing reaction with alkylation. When diolefin impurities are present in the charging stocks, diolefin polymers and diolefin-mono-olefin copolymers also dissolve in the acid catalyst, curtailing its life still further. Concentrations of diolefins above about 2 to 3% of the olefin reactants are usually sufficient to render the alkylation rconomically impractical because of high acid consumption. Removal of diolefins from olefin fractions can be accomplished by selective polymerization (6), but polymerization methods are not entirely satisfactory because of losses due to accompanying mono-olefin polymerization. I n view of the need for a widely applicable process for removing diolefins from butylene (butene) and amylene (pentene) alkylation feedstocks and the possibility that a suitable process might be based on hydrogenation, a search was undertaken for catalysts and conditions that would allow selective hydrogenation of diolefins in the presence of monoolefins.
INDUSTRIAL AND ENGINEERING CHEMISTRY
2296
Vol. 40, No. 12
h
%sa
60
r"
o*
840 W
4,0
=20
2
I
d
0 0
3
I
H,/ C,H,
n ,
0.5
F i g u r e 1. Hydrngenation of Butadiene over h-icliel Metal Catalyst, nickel m e t a l s u p p o r t e d on ~ n a j o l i c a(nppron. 10 wt. 9% Ni) Conditions, 3 LHSV a t 90' C. a n d a t n ~ o s p h e r i cpressure Feedstocks. I. 49.9 mole 70 2-butene, 4.6 m o l e 70 butadiene, 45.5 mole % butanes. 11. 16.8 mole 70 2merhyl propene. 28.0 mole 9% n-butenes, 5.6 mole 70b u tadiene, 49.6 mole 9% b u t a n e s
Figure 2.
IO
1.5
2.0
IIydrogenation of I'entadicncs Niclrel Metal
over
Catalyst, nickel m e t a l supported o n niajolica (approx. 10 w t . % Ni) Conditions. 1.5 t o 2.0 LHSV a t 110' C. a n d atmosoherio pressure Feedstocks, 26.h mole % tert-amylenes. 16.1 mole % n-amylenes, 0.6 mole 70 Csi noetylenes,56.7 mole '70pentadirnra
ao
I
60
I
\
I
0.
8
24 0
- \
I
-: a, b.:
'3 1
Figure 3. Hydrogenation of P'entadieiies o v e r Niclrel Tungsten Sulfide Catalyst Catalyst, commercial niokcl t u n g s t r n sulfide obtained f r o m Shell Oil Co. Conditions, 0.7 t o 1.0 L H S V a n d 12 to 1 mole r a t i o of hydrogen t o diolefin Feedstocks, 35 wt. 70pentenes, 0.5 wt. 70Cb; acet>lenea. 63.5 wt. 9% pentadienes, 1 wt. 9% p e n t a n e s
hydrogen, so that hydrogenation of diolefin to mono-olcfin occurred while hydrogenation of mono-olcfin to paraffin did not take place extensively. Results using this type of catalyst arc shown in Figure 3; selectivity was obtaincd through worliing in ti selective temperature range rather than by limiting tlic proportion of hydrogcn supplied. It is indicated from the data that, diolefin removal could be acconiplislicd undcr conditions which allowed a net gain of mono-olefins through taking advimtagc of t,he faster rate of diolefin hycirogcnation coinpared to mono-olcfin hydrogenation. Nickel sulfide c:ttalysts prcparcd by treating support,cd nickel oxide or carbonate with hydrogen sulfide at 400' C. provcd much more selective for diolcfin removal than either nickel tungsten sulfide or nickel metal. In fact, in Ihc ranges of 200" t o 300" C. and 0 to 100 pounds per squarc iiicli gage n-lien a twelvefold e s c c w of hydrogen was employed, supported nickel sulfide was active for diolefin hydrogenation and inert for mono-olefin hydrogcnation. The data in Figure 4 illustrate this remarkable selectivity when catalysts supported on alumina, kieselguhr, or majolica were used. Diolefin removal was substantially complete and little, if any, evidence of mono-olefin hydrogenation was noted under the conditions used. The nickel sulfide catalyst prepared from the carbonat,e form of a Harshaw nickel-alumina was chosen for the bulk of the investigation. Representative feedstocks containing diolefins were hydrogenated and the resulting products were then tested in alkylation runs using sulfuric acid as catalyst.
20
100
Figure 4.
140
180 220 TEMP, "C
260
300
Hydrogenation
of Z'entadienes over ,n-ickel s tdfide C a Lalys kS NiS s u p p o r t e d on 8-mesh a l u m i n a (10 wt. 70 Ni)
I. 11. Piiled NiS-alumina ( l / g i n c h ) f r o m IIarshaw hydrogenation catalyst (Type 99, 10 wt. % Yi) 111. Pilled NiS-kieselguhr (1,'s i n c h ) from U.O.1'. hydrogenation catalyst (53 wt. 70 Ni) IV. NiS o n majolica chips, from Shell hydrogenation catalyst (10 wt. 5% h'i) Conditions, 1.0 LHSV, 1 2 t o 1 mole ratio of hydrogen to diolefin a n d 30 lh./sq. i n c h gage E'EEDSTOCk S
Thc! C, feedstocks einploycd in the ~jcI(:ctivc hydrogeriatioii work vm-e blends of butadicnc with refincr,v butane-hutenc fractions obtained from Slicll Oil Coinpaiiy, Inc. The CSfeedstocks, also obtaincd from Shell Oil Company, Inc., con iainod sufficient diolefins, so that none had t o bo addd. Electrolytic hydrogcn vias used in the majority 01 the r u m , although hydrogin of 9976 purity from commercial isopropyl alcohol dehydrogenation was a,lso cmployed in some tests. APPARATUS AND M E l I I Q D O B OPERATION
The hydrogenation experiments wcrc made in conventioii:il vap0.r phase hydrogenation units 01" thc type shown in Figurc 5.
I n the operation, the hydrogen and liquid hydrocarbon feed streams were mixed, conducted through a vaporizer, and passed through thc 2.5 X 50 em. cat,algst bed under the desired conditions of temperature and pressure. Hydrocarbon wa.s condensed from the efnuent reaction mixture by means of a condenser cooled bv carbon dioxide and acetone, and the liquid product was passed 'to an accumulator while the effluent hydrogen mas passed through a gas meter and vented. Around 250 ml. of catalyst were employed in each run. ANALYSES.The feed and product samples were analyzed by a combination of gas analysis, bromine number, distillation, and epectroscopic methods. Butadiene in C, fractions was determined
INDUSTRIAL AND ENGINEERING CHEMISTRY
December 1948
2297
complished a t temperatures as low as 200" C., and that the catalyst could be reduced prior to the sulfiding step without ill effect. Spent nickel catalysts from other hydrogenations were satisfactory starting materials for preparation of nickel sulfide hydrogenation catalysts. Finished catalysts were substantially in equilibrium with one atmosphere of hydrogen sulfide under the sulfiding conditions used and normally contained nickel and sylfur in the atomic ratio range of 1.1:1 to 1.3:l.
1
HYDROGENATION OF BUTADIENE IN Ci FRACTIONS
PRODUCT RECEIVER
The effects of the operating temperature and pressure on the hydrogenation of a C4 feed containing 10.9 mole % butadiene are illustrated by the data in Figure 6 .
These effects were measured during a run of 400 hours' duration made mostlv at 250" C. and 50 r d s per square in& gage, using Reactor i s stainless steel tube located i n Meehanite block and heated by multiplea liquid ourly space velocity of 2 and a hyu n i t electric furnace. Block temperature controlled by Celectray, C drogen t o butadiene mole ratio of G t o 1; a summary of the run is given in Table I. Around 500 pounds of feed were treated per pound of catalyst in 400 hours either by maleic anhydride absorption incidental t o the gas of operation, and the diene content of the feed was decreased from analysis for tertiary and total olefins or by the ultraviolet spectro10.9 t o 0.05-0.15 mole %, while the butylene content was inphotometric method, which is considered more accurate. Pentacreased correspondingly from-43 t o 54 mole %. Polymer formadiene concentration in Cg fractions was estimated from bromine was limited t o a few tenths of l%,and the used catalyst at tion number and the total unsaturates content as determined by gas the end of the run showed no evidence of serious carbonization. analysis or from the maleic anhydride value. Estimation of the polymer resulting from olefin or diolefin polymerization during hydrogenation wa6 made from distillation of large samples. I n the periods of variation from standard conditions (Figure G ) , a product containing 0.5 mole butadiene was obtained a t CAT4LYST PREPARATION space rates of 1, 3.5, and G liquid hourly space velocity (LHSV) when operating a t 50 pounds per square inch gage and temperaA number of nickel sulfide catalysts were investigated and these tures of 200°, 250°, and 270" C., respectively, while a similar all showed similar properties for diolefin hydrogenation. Exdegree of diene removal was attained a t 100 pounds per square cellent activity was observed with materials made by: inch gage with space rates of 1,4.5, 5, and 6.5 liquid hourly space Soaking lump alumina in nickel nitrate solution t o give a velocity a t temperatures of 175 ', 200 O, 250 ', and 300 C. Higher material containing 10 weight % ' nickel on a dry basis, drying and processing rates were feasible a t the higher operating pressure decomposing this material by heating to 300" C. for 3 hours, and through increased residence time. No evidence of mono-olefin then treating the resulting oxide with a stream of hydrogen hydrogenation or serious polymerization was noted even under sulfide for 4 hours a t 400" C. to form the final pickel sulfide composition. the most severe conditions used in these tests. Treating 0.125-inch pellets of the black stabilized form of U.O.P. nickel-kieselguhr hydrogenation catalyst (approximately 50 weight yonickel) with a stream of hydrogen sulfide for 4 hours at 400' C. Treating 0.125-inch pellets of a nickel parbonate-alumina 50 ?$IF. '2 0 ) EFFECT OF PRESSURE catalyst received from the Harshaw Chemical Company (10 weight % nickel) with a stream of hydrogen sulfide for 4 hours at 400' C. Figure 5.
Diagrani o f Selective Hydrogenation Apparatus
O
1
I
4
The last of these materials was used in most of the experimental work. It was found that satisfactory sulfiding could be ac-
TABLEI.
HYDROGENATION O F BUTADIENE SULFIDECATALYST
USING
NICKEL
I
250°C.
[Catalyst, pilled NiS-alumina (I/s-inch) made from Harshaw nickel catalyst (Type 99, 10% Nil. Conditions 250° C.5, 50 lb./sq. inch gage, 6 to 1 H2/C;He, 2 LHSV]
Hours ,of Operation 0
87 140 311 371b 400C
Lb. Feed/Lb. Catalyst . . . (feed)
54.8 125.4 357.1 440.1 490 .O
Mole 76 CrHe
10.9 0.04 0.06 0.16 0.3 0.7
Analysis of Product Mole % ' C4Hs Wt. % polymer
43.3 54.7 ..
400° C.) and deactivated at 955th
TABLE 11.
~
~
. I .
hour] 922-988 1143 3.2 92.7 0.9 (Catalyst burned with air at, 300' C. and treated v i t h HnS a t 2500 C.)C 11 0-10 11 10-20 0.8 96.1 1.9 12 10-23 26 10 0.03 .. 0.6 'L Average catalyst bed temperature 250' C. Reaction hot s p o t 290' C. b Material boiling above 15' C. Some of this material wa$ present in feed. C Temperature during air burnin- controlled by limiting air \ u p l ~ l s . , Burning required 36 hours and 8 hourFof H t S treatment were given.
lO(a) and (b)
20 I
Figure
#
I
120
80
7.
#
l
160 200 TEMPERATURE,
240
Experimental results showing the effects of temperature and pressure on the hydrogenation of pentadienes are shown in ' pentadienes Figure 7. A feedstock containing around 58 mole % and 37 mole 70pentenes was used in this work, and the nickel sulfide catalyst employed was supported on 8-mesh alumina. A definite threshold temperature for activity was exhibited by the catalyst and this temperature was lower as the operating pressure was increased. At atmospheric pressure, using a hydrocarbon feed rate of 1liquid hourly space velocity and a hydrogen to diene mole ratio of 12 t o 1, substantially complete diene hydrogenation was evidenced when the average reaction trmperature was maintained above about 280 ' C., whereas little activity was shown at temperatures below about 200" C. At 15 pounds per square inch gage diene hydrogenation was complete a t 260" C., and a t 30 pounds per square inch gage a temperature of 220" C. gavc the same degree of reaction. The mono-olefin concentration irr the product increased as the diene concentration decreased, a n d a t the point of complete diene removal was invariably above 957"" An extended run made on the hydrogenation of pentadiene is summarized in Table 111. This run, employing the sulfided Harshan. nickel-alumina catalyst, was mado mostly a t 260 t o 270" C. average temperature using a 5 to 1 mole ratio of hydrogen to diene and a liquid hourly space velocity of 1.0. Around 220 pounds of fee;d (containing initially 70 mole % pentadienes) were successfully treated per pound of catalyst, and under normal operating conditions the diene content was reduced to 2 to 3 mole 7",while the mono-olefin content was increased from 26 t o over 90 mole 7G.h o u n d 2 to 3 weight % of polyrnrr was formed in the treatment. O
280
O C
Hydrogenation of P e n t a d i e n e s h-icliel Sulfide Catalyst
HYDROGENATIOY O F PENTADIENES IN Cs FRACTIONS
over
Catalyst, NiS on lump alumina @-mesh, 107' hi) Conditione, 1 LHSV, 12 to 1 mole ratio of hydrogen to pantadiene
Feedstock, 58 mole % pentadieno, 37 mole 70pentenes, 5 mole
% pentane
Another extended hydrogenation run using a Cq feed is summarized in Table 11. This was made with a mixture of 23 mole 70butadiene, 17 mole % 2-methylpropene, 55.5 mole % n-butenes, and 4.5 mole '%butanes, and conditions of operation were 250 C. (hot spot due t o exothermic heat of reaction was 30" to 50' C. hotter), 150 pounds per square inch gage, 1 to 1 ratio of hydrogen t o total hydrocarbon, and a space rate of 2 liquid hourly space velocity. The temperature of 250 t o 300' C. was chosen, because i t could readily be duplicated in a n isothermal commercial unit employing hot oil as a heat exchange medium, and the pressure of 150 pounds per square inch gage was chosen, because it would allow easy condensation of the hydrocarbon in the effluent stream under reactor pressure, Over 200 gallons of feed were processed per pound of catalyst in 955 hours, and with the exception of three instances where plugging of a 0.125-inch nipple in the preheater tube occurred (presumably because of high skin temperature), operation mas smooth and uneventful. O
The butadiene content of the feed was reduced from 23 to less than 0.1 mole yo,and the butene content increased correspondingly from 72 to 95 mole %; less than 17; of the feed was con-
OF PENTADIENES USING TABLE 111. HYDROGENATION NICKELSULFIDECATALYST
[Catalyst, pilled SiS-alumina ('/pinch) made from Harshaw nickel catalyst (Type 99, 10% S i ) . Conditions, 260' C.a, 1 LHSV, 5 : l to 8:l HdC4HsI Analysis of Products Operating c5 Fraction Heavy Position of Lb. Reaotion Hot Pressure Mole Mole ends Hours ,of Feed/Lb. Spat, % of Lb./Sq.' % % >45' C., Operation Catalyst Catalyst Bed Inch CsHs CaHio wt. % 0 . . feed .. .. 70 26 3 22 50 1 . 8 94.0 5.0 34 3o"o . 30 2 . 1 95.6 5.9 60 39 80 1.2 95.8 5.4 108 71 50-70 222 145 70-100 80 1.8 95.4 5.0 264 173 .. 80 2 . 7 94.3 4.8 330 216 , . 100 0 . 3 91.5 6.8 Catalyst burned with air (Operation terminated because of back pressure. a t 350-400° C. 7 hours and treated with HzS a t 400° C. 5 hours) 5.2 25 50 0 . 6 91.4 26 267 3.0 0.0 96.3 46 276 30 50 4.0 30 50 0 . 0 97.4 69 287 83 294 35 50 0 . 6 91.6 9.5 87 297 35 50 0 . 0 91.6 5.5 0
Rcaction hot spot averaged 3OUto 40° C. higher.
INDUSTRIAL AND ENGINEERING CHEMISTRY
December 1948
I
I
2
Figure 8.
IO 12 14 VOLS. ALKYLATE / VOL. ACID
6
4
8
16
Alkylation Using Hydrogenated C4 Feeds
2299
are amply demonstrated. Olefin feedstocks containing 10.9, 3.5, 2.5, and 0.6 mole % ' butadiene gave acid lives, to a reactor acidity of 90% as sulfuric acid of 1.1, 4.3,4.7, and 9.5 volumes of alkylate per volume of acid, respectively, while the product from selective hydrogenation of the first of these gave a life of 19.5 volumes per volume. The acid life improvement was obtained by hydrogenation alone and no attempt was made to redistill the feeds to eliminate traces of polymer prior t o alkylation. Engine data on the light alkylate products (15" to 150" C.) from the various runs indicate that no advantage in engine performance is gained by butadiene removal. Octane ratings of 95 to 95.5, performance index numbers of 158 to 162, and octane blending equivalent values of 107.5 to 108.5 were found for all the light alkylate products, even though some were made from feeds containing impractically high concentrations of butadiene.
Conditions, 100.0% sulfuric acid, 0' C., 20-minute contact t i m e 1 to 1 acid-hydrocarbon phase ratio, 10 t o 1 mole ratio of methylpropane to unsaturates Feedstocks. I. 10.9 mole %butadiene,41.5 mole % butene 11. 0.3 mole % butadiene, 52.5 mole 70 butene 111. 0.02 mole %butadiene, 52.5 mole % butene
A hot spot, about 35 C. above the average temperature of the catalyst bed, passed through the reactor in the above run. This hot spot has been found in all hydrogenation tests and appears to designate the portion of the catalyst in which most of the hydrogenation is taking place. While substantial conversion of dienes to mono-olefins still occurred after the hot spot had passed through the bed (180 hours), the operation was terminated by development of back pressure due to deposition of a yellowishbrown resinous material in the first 3070 of the catalyst. Perhaps traces of oxygen in the electrolytic hydrogen used in this run catalyzed the formation of this resin from pentadienes. From the results obtained with the C6 fraction i t would appear that shorter hydrogenation cycles should be expected using feedstocks containing high concentrations of diolefin. The use of higher mole ratios of hydrogen to diene and the recycling of hydrogenation product to the incoming feed stream should prove useful in allowing longer operating cycles with high diolefinic feeds. After catalyst regeneration by burning with air at 400' C. for 3 hours and treating with hydrogen sulfide a t 400" C. for 5 hours, satisfactory operation was experienced during an additional 87-hour test period. O
0
e,
,
,
I
Figure 9. Effect of Butadiene on Acid Consumption during Alkylation with Butenes See Table IV and Figure 8 for alkylation conditione
Composite product from runs on the hydrogenation of a Cb fraction, containing 67 weight % pentadiene initially, was tested for alkylation. This material contained 2.3 weight % pentadienes and a portion was repassed over the hydrogenation catalyst to give an alkylation feed of still lower diene content; a reduction in pentadiene content to 0.6 weight % mas achieved by the repassing operation. The original C6 fraction contained around 3 weight % of heavy ends and 2 to 3 weight % of additional heavy ends was formed during hydrogenation. I n order to determine the effects of these higher boiling impurities, alkyla-
ALKYLATION OF ISOBUTANE WITH HYDROGENATED FEEDSTOCKS
OF METHYLPROPAXE WITH C4 TABLE IV. ALKYLATION FRACTIONS CONTAINING BUTADIENE
Composite product from a number of butadiene hydrogenation experiments was tested for alkylation.
(100.0% HaS04, Oo C., 20-min. contact time, 1/1 acid to hydrocarbon phase ratio and 10 to 1 isobutane to unsaturates mole ratio) Experiment No. I I1 I11 IV V VI Olefin feed Treatment None I(hydrog. II(hydrog. hTone None None over Xis) over NiS) Composition Mole 9% CIHE 1 0 . 9 0.3 0.02 3.5 2.5 0.6 Mole Yo C I H ~ 4 1 . 5 52.5 52.5 46.0 46.5 47.0 Alkylation results 13.2 Vol. alkvlate 1.1 19.5 4.3 4.7 9.5
This material was obtained by hydrogenation of a blend containing 10.9 mole % butadiene (C~HE) under a wide range of hydrogenation conditions and because i t had a higher diene content (0.28 mole %) than would be expected from steady operation, a portion of i t was repassed over the nickel sulfide catalyst and the product from this repassing operation (0.03 mole % butadiene) was also tested for alkylation. I n addition, alkylation runs were made with a refinery butane-butene fraction (0.6 mole % butadiene) and with blends of this fraction and butadiene (2.5, 3.5, and 10.9 mole % butadiene) for comparison. All the alkylation runs were made in the usual manner in laboratory alkylation equipment (4) at 10' C. using 100 % sulfuric acid as catalyst 1 to 1 acid-hydrocarbon phase ratio, 10 to 1 mole ratio of methylpropane (isobutane) to olefin, and 20 minutes contact time. Results are shown in Table IV and Figures 8 and 9.
numberc
By the acid decline data in Figure 8 and the acid life data in Figure 9, the deleterious effect of butadiene and the marked improvement following diene removal by selective hydrogenation
208
210
203
205
216
268
267
..
..
..
96
96
88
90
93
95.5
95.5
95
95
95
a
To 90% reactor acidity.
0
Octane No. of 15O t o 160' C. fraction.
b Based on C4Hs in feed I prior t o hydrogenation.
23QQ
INDUSTRIAL AND ENGINEERING CHEMISTRY
TARI,E
i-, .~LKYLATION
OF ISoBCTASE
WITH
c,
due to the high terti
ylerie (from isoprcne al]cvlationfecdstoc]r, Performance index numbers, octitiie blcriding equivalent values, and octane numbers for the debutanized alkylate were in the ranges of 110-150, 104.5-107, and 91-91.5; these values \\.we in the high ranges from the standpoint of pentenc alkylate quality. Only slight improvement resulted from depentanization.
FRIICTIOSS CO
PESTADIESES
(100.0% F12SOd,O o C., 20-min. contact tinie, l t o l acid-hydrocarbon phase ratio, and 10 t o l isobutarie-unsntiira~esmole ratio) __ Experiment __~ No. -
-
I
I1
Olefin feed Xone I (hydrog. Treatment over RIS) CompoRition Wt. 70c6Hs e7 .o 2.3 X7t. % C5HlO 26.6 85.I Wt: 70heavy ends 3 . 3 a.3 Alkylation results Val. alkylate per < 1 4 .i vol. acida Debutanizcd alkyl. .. 191 ate Tield, wt. Q on d ~ l a Alkylate properties Wt. 7 b 20-5og c: ... :B 503-1400 C. .. 65 i40°-1700 C . ... 10 1170 6 C.F.R. octane A-0. b
IY
111
I1 (dist. T O 500 c., Z.F.)
5'
11- (dist. t o 500 c.,
ZI (h\;drog
13.P.)
NiS)
oyer
2.4 111.5
0.6 90.0 4 0
0 ti '13 8
5.8
5 3
10.4
...
200
20 66 9 5 90.5
210
2 10
23 66
21
5 91
Vol. 40, No. 12
COMPARISON OF SELECTIVE HYDKQGEXATION AND SELECTIVE POLYhPERHZATIONOF PENTENEPEYTANE ALKYLATION FEED . w o C K s
It nw of interest t o compare selective hydrogcnation nith selective poiymerization ( 5 )as a means for removing diolefins from a refinery pentenc-pentane alkylation feedstock. Hydrogenation at 250 C., 50 pounds per square inch gage, 1 liquid hourly space velocity and 1 to 1 mole ratio of hydrogen to
67 8 4
.o
91.5
TABLEVI.
ALKYLATIOKOF ISOBI-TANI-: WITII H Y I ~ ~ ~ O G E I A T I I : D ASI) ACID-TREATED C j FRACTIOXS Experiment No.
I Olefin feed
Treatment
, Figure 10.
Analysis Bromine No., g./100 g . 116 Maleic anhydride value, 2 2 , ,?I mg./ml. Alkylation results Yol. debutanized alkylate 4.5 per vol. acid' Alkylate yield, me. % on 83 C Sfeed Alkylate yield, wt. % on 83 original Ca feedb Alkylate properties Wt. % b. 20-40' C. 42 40-150' C . 49 > 1600 c. R C.F.R. octane No.C 91.5
I
2 4 6 VOLS ALKYLATE / VOL ACID
8
.Urylation Csing Hydrogenated C , Feeds
Conditions, 100.0% s u l f u r i c acid, O 5 C., 20-minute oontact time, 1 t o 1 acid-hydrocarbon phaae ratio, 10 to 1 mole ratio of methylpropano to unsaturates Feedstock compositions indicated in T a b l r V
tion tests were also made on redistilled fractions. In all, alkylation runs were made with (1) composite of hydrogenated material, ( 2 ) hydrogenated material distilled to a 50" C. end point, (3) repassed material, and (4) repassed material distilled t o a 50" C. end point. No alkylation test was made with the original Cj fraction, since it. v a s considered impractical because of its 67% pentadiene content. The alkylation data i n Table V and Figure 10 indicate that from 4.5 t'o 10.4 volumes of debutanized alkylate per volume of acid were obtained using the hydrogenated C6 fractions; improvement from 4.5 to 7.3 was accomplished by a second hydrogenation treatmerit arid improvements from 4.5 to 5.8 and from 7.3 t o 10.4 volumes per volume were accomplished by redistillation to remove polymeric materials. Around 20 to 25 weight % pcnt'anes (most'ly 2-methylbutane and 35 to 45yo octanes) were found in the alkylate products from the above runs (Table V) and the relatively high conccntrations of these materials apparently resulted from hydrogen exchange reactions taking: place
None
b C
TI
111
I (acid-treated and rpdistilled)
I (hydrogenated over Xis)
113
103 15.4
2.5
7.5
5.9
86
87.5
83
57.5
45
39.5
46
50
10.5
9 Yl.5
91 5
To 90% reactor acidity. Based on feed I before hydrogenation or acid treating. Octane No. of 40-150' C. fraction.
VENT !
I (
tAltK
-7
[-VENT
ACCUMULATOR
)
1 PRODUCT STREAM
VAPORlZER
HYDROCARBON MAKE-UP FEED HYDROGEN
Figure 11.
Simplified Process Flow for Selective Hydrogenation of ' Diolefins
December 1948
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
hydrocarbon allowed a reduction in the maleic anhydride value of the feed from 22.5 to 2.5 mg. per ml., while treatment with 65% sulfuric acid a t 40" C. allowed a reduction to 6.4 mg. per ml. Little or no polymer was formed during hydrogenation, while 4% of polymer was formed in the acid pretreatment and redistillation for polymer removal was required prior to alkylation. Alkylation runs comparing the hydrogenated and acid-treated Cg fractions are summarized in Table VI, which shows that similar increases in acid life were obtained by the two methods. However, a yield advantage, due to conversion of dienes to monoolefins and the absence of polymer formation during hydrogenation, is indicated for the hydrogenation case. This advantage would, of course, be amplified with Cg fractions containing higher concentrations of diolefins. PROCESS CONSIDERATIONS
The simplified flow diagram shown in Figure 11roughly outlines the essential features required in the design of a commercial selective hydrogenation unit based on the above experimental work. For this scheme it is assumed that the feedstock contains sufficiently low concentrations of diolefins so that an adiabatic reactor can be employed. The exothermic heat of hydrogenation of a diolefin to a mono-olefin is about 28 kilocalories per gram mole, and an initiating temperature of 220" C. and a maximum temperature of around 300" C. are considered as safe limits for adiabatic operation with C4 or C6 fractions. The use of an isothermal reactor or the incorporation of a product to feed recycle would probably be required for feedstocks containing high concentrations of diolefins. Sufficient data are not available to place limits on the hydrogen purity, but satisfactory results have been obtained using a 1 to 1 mole ratio of hydrogen t o hydrocarbon. I n view of the high degree of selectivity of the nickel sulfide catalyst for diolefin hydrogenation, olefins, paraffins, and light hydrocarbon impurities in the hydrogen all function as inert diluents in the system. Satisfactory results should be obtained with dilute hydrogen
230 1
streams, provided that the partial pressure of hydrogen is maintained in a suitable operating range. Depending on the operating pressure and the temperature t o which the effluent product stream from the hydrogenation unit is cooled, varying proportions of hydrocarbon would be present in the hydrogen recycle stream and in the vented hydrogen. Within limits, the operating pressure could be adjusted to keep the hydrocarbon content of these streams to a minimum and refrigeration could also be employed for control. While pressures of over 150 pounds per square inch gage have not been investigated, the use of higher pressures should offer no difficulties with feedstocks of moderate diolefin content. I n the diagram in Figure 11 provision is shown for catalyst sulfiding and regeneration in place, but in view of the long operating cycles anticipated, external facilities may prove more desirable. Temperatures of around 300' to 400" C. are believed suitable for burning and sulfiding the catalyst. ACKNOWLEDGMENT
The authors wish to express appreciation to their colleagues in the Shell Development Company who assisted in the experimental work. LITERATURE CITED
(1) Anglo-Iranian Dil Co., Ltd., Humble Oil and Refining Go., Shell Development Go., Standard Oil Development Go., and Texas CO., Oil GUSJ.,38, NO.27, 104-8 (1939). (2) Gerhold, Iverson, Nebeck, and Newman, Trans. Am. Inst. Chem. Engis., 39, 793 (1943). (3) Ipatieff and Pines, J. 07gqChem., 1, 464 (1936). (4) McAllister, Anderson, Ballard, and Ross, I b i d . , 6, 647 (1941). (5) McA!lister, Anderson, and Ross, U. 5. Patent 2,399,240 (April 30, 1946). (6) Ormsndy and Craven, J. Inst. Petroleum Tech., 13, 311 (1927).
(7) Young, Meier, Vinograd, Bollinger, Kaplan, and Linden, J. Am. Chem Soc., 69,2046 (1947).
RECZIVED February 27, 1948. Presented before the Division of Petroleum Chemistry, Symposium on Modern Motor Fuels, a t the 113th Meeting of the AMERICAN CHEMICAL SOCIETY, Chicago, Ill.
BUTADIENE FROM ETHANOL Utilization of By-Product Ethyl Acetate E. E. STAHLY, H. E. JONES, AND B. B. CORSON Mellon Institute of Industrial Research, Pittsburgh, Pa. I t was-shown that butadiene results from the reaction of ethyl acetate with acetaldehyde in the presence of a tantala-silica catalyst at 325" to 350' C. Therefore, i t is pos-
sible to increase the efficiency of the ethanol process for the manufacture of butadiene by recycling the by-product ethyl acetate. The first step in the utilization of ethyl acetate probably is the formation 'of ethanol by hydrolysis. The steady-state concentration, at which the amount of ethyl acetate formed per pass equaled the amount consumed, was determined for the commercial operating conditions.
T
HE Carbide and Carbon Chemicals Corporation's process for manufacturing butadiene from ethanol (8) comprises passing a mixture of approximately 62.7 mole yc ethanol, 22.8 mole % acetaldehyde, and 14.5 mole % water over a tantalum pentoxide (2%)-silica (98%) catalyst. A number of by-products are formed in this process. During World War 11, when the process was applied extensively, some of these by-products were recovered as marketable chemicals, others were recycled with recovered
ethanol and acetaldehyde, but most of them, including a major Dart of the ethvl acetate, were burned as fuel. Part of this byproduct ethyl acetate was formed in the acetaldehyde converters (in the dehydrogenation of ethanol) and part in the butadiene converters. This acetate-corresponding t o about 3 weight % of the ethanol lost in by-reaction-regardless of its point of formation was separated azeotropically with a by-product oil fraction boiling intermediate to the ethanol and acetaldehyde fractions and thus was not fed t o the butadiene converters. This paper presents experimental evidence that ethyl acetate can be converted to butadiene under the conditions employed in the commercial plants. The utilization of ethyl acetate n~ould increase butadiene production 2y0: this would have amounted t o an increase in butadiene production of 14,000,000 pounds in 1944, or a saving of 43,000,000 pounds of 92 weight Ycethanol. EXPERIMENTAL
APPARATUS AND PROCEDURE. The laboratory apparatus is shown diagrammatically in Figure 1. The premixed ethanol-acetaldehyde feed was pumped for &hour periods through a 12-inch
