CATALYTIC OXIDATION OF HYDROCARBONS Oxidation of Isobuplene over Copper Catalyst R. S . M A N N A N D D E N I S ROULEAU Chemical E n p w r r i n g Department, T h p l'nzverszty of Ottawa. Ottau'n, Canada
The vapor phase catalytic oxidation of isobutylene to methacrolein over a pumice-supported copper oxide catalyst was investigated in a flow system between 350" and 450" C. and at atmospheric pressure. By using modern analytical techniques with suitable modifications for identification and isolation, quantitative analysis of the products was obtained. The data for the product distribution as a function of the operating conditions are presented.
particularly of ethylene to ethylene oxide, has received much attention in recent years. However, the catalytic oxidation of propylene and butylenes to unsaturated carbonyl compounds has received very little attention ( 8 ) . Several patents (7-7, 9. 70, 72) have appeared during the past 10 years which describe the use of various metal oxides of the first and the fourth to the eighth group of periodic table. Most of the patents (3-6. 9, 70. 72) recommend the use of copper oxide, either alone or. mixed with other oxides, supported on silica or silicon carbide as catalyst. T h o u g h the patents refer to the catalysts as being excellent for the oxidation of propylene and isobutylene to methacrolein, no data are given sholving the effect of various operating variables on the composition of products for isobutylene oxidation specifically. T h e scarcity of published scientific data and the vague nature of patent claims indicated a definite need for more Lvork on the partial oxidation of isobutylene to methacrolein. T h e oxidation of isobutylene to methacrolein, taking place according to the equation: XIDATION O F OLEFINS:
0
HZC=C-CHS
+
0 2
+
HZC=C-CHO 1
i
+ HZO
1
CH,
CH3
was studied over copper oxide supported on pumice in a flow system. T h e present paper reports the effect of a number of reaction variables on the conversion of isobutylene to methacrolein. Experimental
Apparatus and Procedure. T h e experimental apparatus used in the study of the reaction is sho\vn schematically in Figure 1. T h e reactants. dry air and chemically pure isobutylene (minimum 99yc purity). obtained from high pressure cylinders through a series of pressure regulating devices and metered over Brook's glass rotameters. Ivere mixed and preheated before entering the reactor. T h e reactor \vas heated in a liquid metal (50% bismuth, 50% lead) bath Tvhich in turn was located in a n electrically heated furnace. T h e temperature of the furnace was controlled to within -3' C . by a Honeywell Pyrovane temperature controller. T h e design of the reactor was such that the reaction took place more or less under isothermal conditions. T h e temperature of the catalyst bed during the reaction was measured by a thermocouple embedded in the center of the catalyst bed. T h e temperarures of the catalyst bed and of the liquid metal bath were the same. T h e catalyst, copper oxide supported on 20- to 40-mesh pumice stone, was placed in a 0.5-inch inside diameter Type 304 stainless steel reactor, held in place by two stainless steel porous plates. T h e catalyst bed volume was 5 cc.
T. C.
3
&
I I 1
Rotameter
Liquid
I
;
r
61-1 I I
J
.-
TemDemture Contiol ler and Indicator
Cylinder
Vapor Fractometer
isobutylene Cylinder Figure 1.
94
Flow diagram for the oxidation of isobutylene
I & E C PRO D U C T R E S E A R C H A N D D E V E L O P M E N T
Table 1. Kurt
.Vn
70 75 80 85 95 100 105 110 115 120 125 1 30 135 140 14i 150 175 178
1"emp
e.
400 400 400 400
400 400 400 400 400 400 400 400 400 400 400 40C 400 350
18i
3'5 400 425 450 400
190
400
1'7
180 181
182
,
Effect of Variables on Conversion and Yields of Products in Isobutylene Oxidationa
0 , Iso-
Ct'/P~ 0 1-5 0 175 0 175
0 071 0 071 0 175 0 834 0 834 0 834 0 834 0 453 0 453 0 453 0 453 0 071 0 0'1 0 112 0 112 0 112 0 112 0 112 0 112 0 112 0 112
__
~~
but$ene
Iso-
Ratio 2 037 4 028 3 00 3 00 2 037 1 038 1 038 2 037 3 00 4 028 1 038 2 017 3 00 4 028 4 028 1 038 3 00 2 037 2 03' 2 037 2 037 2 037 1 038 4 028
butylene
0 0 0 0 0 0 0
0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0
0
2679 1420 18'5 1875 2679 4821 4821 2(i79 18'5 1420 4821 2h79 18'5 1420 1420 4821 18'5 2679 2679 2677 2679 2679 4821 1420
~
__
Analysis of Products, ;MoieiHr. ~~~~
0>
0 0 0 0 0 0 0
0 0 0 0 0
0 0
0 0 0 0
0 0 0 0 0
0
5456 5721 5625 5625 5456 5006 5006 5456 5625 5721 5006 5456 5625 i-21 5721 5006 5625 5456 5456 5456 5456 5456 5006 5721
-C*H60 0 0300 0 0227 0 0276 0 0137 0 01'0 0 0484 0 0510 0 0320 0 0736 0 0226 0 0511 0 0310 0 0250 0 0240 0 0108 0 0300 0 0222 0 0216 0 0233 0 0240 0 0225 0 0205 0 0400 0 01'5
'I'hr cxit gases from the reactor were led to a n ice-cooled rrap. Lvherr the acids a n d a small fraction of the aldehydes c\ere coriderised. 'l'he noncondensed gases lvere passed through a sanipling valve leading to a Fisher gas partitioner which coiild anal!ze C O ? . CO. isobutylene. Om.and Sr. T h e off5 from the sampling valve were passed through a liquid air trap where tht: remainder of the aldehydes, \vhich did nor contirn\r a t ice t ~ m p r r a t n r e condensed. , l o r [tie > [ a r t of the run. air \cas slo\vly passed through the reactor tvhile the ratalybt \cas brought to the required temperature. kl'heli the r q u i r e d temperature \cas attained, isobutylene a n d air rarios were adjusted to the desired values a n d mainrained a t their specified rates. over a period of 15 minutes, and rhe i ~ ~ c t temperature or was brought to a steady state. 'The srratiy+tarc run \cas continued for 30 to 60 minutes by collwting the samples. T'he gases \$.ere analyzed periodically by iniwting a 0.5-ml. sample into the Fisher gas partitioner. At the c:nd of the run, the liqiiid samples collected from traps 1 and 1 I \rere measured and analyzed. P r e p a r a t i o n of Catalyst. A 0.025-gram a t o m of C u per gram ( J f piiniic.r was prepared by impregnation and evaporation of the required amount of a 1 .V solution of copper nitrate: C I ~ ( N O GH?O, ~ ) ~ on 20- to 40-mesh crushed pumice stone, supplied by Fisher Scientific Co. T h e impregnated material was dried overnight a t 105' C. and calcined a t 550' C. for 6 hours in a furnace. Analytical Procedures. ACIDS. T h e total acid content was obtained by titration of the condensate from the traps with 0.1 .\' K O H (:ASI.S. T h e inlet feed gas and the product gases were anal>,zed for isobutylene, 602:0 4 : and s:! by periodic injection of 0.5 ml. of sample into the Fisher gas partitioner containing a 6-foot hexamethylphosphoramide column and a 13-foot 13X hlolecular Sieve column connected in series. ALDEHYDES.T h e sample from both traps was diluted with 10 ml. of diethyl ether and placed in a cold temperature bath. Once temperature equilibrium \cas reached, 5 p l . of the mixture was injected into a 154D Perkin-Elmer gas chromatograph containing 4.2-meter columns of Carbowax 1500 on Teflon. T h e aldehydes were separated a t 110' C. using 1 6 X as the sensitivi t y .
co,
Results and Discussion
Feed rates were calcidated on the basis of the rotameter readings and the analysis of the feed. T h e effluent rates were computed on the basis of the product streams and the iso-
CO 2 0 2606 0 2913 0 2822 0 1429 0 1550 0 2288 0 2702 0 3080 0 3526 0 3363 0 2558 0 3024 0 3226 0 3228 0 1380 0 1228 0 2063 0 1702 0 18'8 0 1959 0 2120 0 2200 0 1587 0 2245
CO 0 0132 0 0105 0 0053 0026 0129 0155 0130 0129 0078 0 0129 0 0077 0 0026
0 0 0 0 0 0
0 0 0 0 0 0
0027 0054 0054 0054 0054 0054
0 002-
0 2
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
1105 1050 1012 3353 2937 1066 0308 0188 0104 0388 0600 0439 0413 0589 3532 2865 2277 264' 2361 2281 2093 1759 2260 2192
HlO 0 306 0 327 0 320 0 158 0 175 0 282 0 334 0 356 0 380 0 370 0 317 0 346 0 358 0 351 0 151 0 153 0 231 0 192 0 212 0 220 0 237 0 243 0 200 0 242
Butylrne Reacted ,tlolp/Hr
0 0994 0 0974
0 0996 0501 0531 1077 1219 1126 0 1149 0 1110 0 1180 0 10-6 0 1075 0 1061 0 0454 0 0618 0 0-50 0 0653 0 0720 0 074' 0 0"4 0 0'74 0 0813 0 0752
0 0 0 0 0
37.1 68 6 53 1 26 20 5 22 3 25 3 42 0 61 3 78 2 24 5 40 2 5- 3 74 32 0 12 8 40 0 24 4 26 9 2- 9 28 7 28 9 16 9 53.0
30.2 23 3 2' 7 27 3 31 0 44 9 41 8 28 4 20 5 20 4 43 3 28 8 23 3 22 6 23 8 48 5 28 4 33 1 32 4 32 1 29 1 26 5 49 2 23 3
butylene consumed. T h e a m o u n t of isobutylene reacted was calculated on the basis of the analysis of the effluent streams. All the experiments Lvere carried out a t atmospheric pressure. Though air \cas used for oxidation, the calculations are based on the ox!'gen so that the effect of oxygen on the course of thr reaction can be easily visualized. 'Table I sho\\,s some typical results obtained from the various runs \vhere variations \cere employed in feed compositions, temperature, and catalyst to feed and air to butylene ratios. 'T'he mass of the catalyst in grams employed for each experiment is denoted by 11.. and the rate of flo\v of the total feed in gram moles per houi is represented by F . T h e conversions reported are based upon the amount of isobutylene consumed during the r u n ? \chile the yields are based upon the moles of methacrolein produced in proportion to the isobutylene consumed. T h e copper oxide catalyst supported on pumice !cas highly selective in its activity, the products being methacrolein, COS.HZO. and very small amounts of CO. Other aldehydes a n d acids \cere not detected in the products in measurable amounts. T h e effect of the oxygen (in the air) to isobut~,leneratio is shown in Figure 2 for a Ll- F ratio of 0.453 a t 400' C . \Vith increasing oxygen to isobutylene ratio. the conversion increases but a t a sacrifice in methacrolein yield, indicating further oxidation of niethacrolein to COS and \carer. I n Figure 3. the effect of temperature on the oxidation reaction a t a 11;'F ratio of 0.112 and oxygen to isobutylene ratio of 2.03' is shotvn. \l-ith increasing temperature from 350' to 4.50' C., the conversion increases, but the yield decreases. At temperatures of 400' C . and above, much overoxidation occurs. as is evidenced bJ- a higher percentage of COS formation in the product. T h e highest yield of 33Yc \vas obtained a t a 23,4Yc conversion. Figure 4 shows the effect of various oxygen to isobutylene ratios on the conversion a t several TI-;F ratios a t 400' C. There is not much change in the conversion for all oxygen to isobutylene ratios in feed for I17;F ratios exceeding 0.2. though 787' of butllene \vas converted for oxygen to isobutylene ratios of 4.028 and a 11',F of 0.8. T h e conversion is dependent on VOL. 3
NO. 2
JUNE
1964
95
80.
I 60.
20 2’ Moles
1
O2 /Moles
Iso-C4Hg~n Feed
2-6 A
lo
3
O+T
4
375
400 Temperature, “C.
350
Moles Oxygen/Moles Isobutylene in Feed
Figure 2. Effect of oxygen to isobutylene ratios on conversions and yields of rnethacrolein
30 4.0 4.0
L
425
450
Figure 3. Effect of temperature on conversions and yields of rnethacrolein
02
04
W/F-Gm
Cololyst/Grn
0.6
08
Mole Feed/Hr
Figure 4. Effect of W / F ratios for different oxygen to isobutylene ratios on percentage conversions
Conclusions COL D
co
A
Methocrolein
- 60 a U
a
-4Ol
‘l’he catalytic air oxidation of isobutylene over a pumicesupported copper oxide catalyst was investigated between 350‘ and 450’ C.. a It7,’Fratioof 0,071to 0.833: and a n oxygen to isobutylene ratio of 1 to 4, to establish the conditions for a maximum conversion and yield. T h e highest yield of 51.67’ \vas obtairied at 21.9y0 conversion a t 350’ C. \vith a n oxygen to isobutylene ratio of 1.038 and a lt’/F of 0.176. However, a t a sacrifice in yield (22.6%), higher conversions (74.7y0) were obtained a t 400’ C., for a 11’;F of 0.453 and a n oxygen to isobutylene ratio of 4.028. literature Cited
P
0
0.4 0.6 W / F - Om. Cotolyst/Gm. Moler/Hr.
0.2
0.8
Figure 5. Effect of W / F ratios on the percentage compositions of the products
the oxygen to isobutylene ratio a n d temperature only for a ratio of 0.2 or more. T h e percentages of COZ, CO: and methacrolein produced per mole of isobutylene consumed for various T I - F ratios a t 350’ C. and a n oxygen to isobutylene ratio of I are shown in Figure 5. T h e best yield, 51.6%. was obtained a t a II’/F ratio of 0.176 a t a n oxygen-isobutylrne ratio of 1.038. \Vith higher temperatures, higher oxygen to isobutylene ratios. and higher TI’IF, the yield drops considerably though conversion increases. Figure 5 and the d a t a of Table 1 suggest that methacrolein and CO2 \vere formed as primary products. T h e negative slope of the curve for the production of methacrolein shows that a t larger L1SF ratios, or lower space velocity, methacrolein underLvent further oxidation to form COi, water, and small amounts of CO. l ‘ h e positive slope of the curve for the production of C 0 2 and C O supports this contention, which is in agrerment \vith the findings of Isaev and Margolis ( 7 7).
96
l&EC PRODUCT RESEARCH A N D DEVELOPMENT
(1) Barclay, J. I>., Bethell, J . R., Bream, J. B.: Hadley. D. J., Jenkins. R. H.. Stewart, D. G., LVood, B. (to Distillers Co.. I.td.), Brit. Patent 864,666 (hpril 6, 1961). ( 2 ) Barclay, J. L.. Hadley, D. J.. Stewart, D. G. (to Distillers Co.. Ltd.), I b i d . , 873,712 (July 26, 1961). (3) Chem. Enq. . V w s 39, 56 (Oct. 9, 1961).
Breier, I. I,. (to Shell Development Co.), (4) Cheney, H. ‘4.. LT. S. Patent 2.879.300 (March 24. 19591. (5) Clark, .A,, Skutt,’ R. S . (to Battelle Mdmorial Institute), Ibid., 2,383,711 (Aug. 28. 1945). (6) Connolly, G. C., Cottle, D. L. (to Standard Oil Development Co.), Zbid.,2,627,527 (Feb. 3, 1953). (7) Dowden. D. A , Caldwell, A. M. U. (to Imperial Chemical Industries). Brit. Patent 828.812 (Feb. 24. 1960). (8) Emmett; P. H., ‘.Catalysis,” \‘ol. 7. p. 250,’ Reinhold. New York. 1960. (9) Farbenfabriken Bayer A-G.. Brit. Patent 839,808 (June 29, 1960). (10) HBdley, D. J . , Heap, R. (to Distillers Co.. Ltd.). Ibid., 704,388 (Feb. 24, 1954). (11) Isaev, 0.V., Margolis. I,. Ya.. Rinetika i Katnlir 1, 237 (1960). (12) Mbntecatini, Brit. Patent 847,564 (Sept. 7 . 1960) KXEIVLDfor review Decernbrr 2, 1963 ACCEPTED March 9, 1964 kl’ork supported by the National Research Council of Canada, Ottawa. Experimental data from this study have been deposited as Document No. 7889 with the .AD1 Auxiliary Publications Prqject, Photoduplication S e n ice; Library of Congress. \\’ashington 25, D. C. A copy may be secured by citing the docurncnt number and by remitting $1.25 for photoprints or 51.25 for 35-mm. microfilm. Advance payment is required. Make checks or money orders payable to Chief, Photoduplication Service, Library of Congress.
