MAXWELL NAGER' Shell Oil Co., Houston, Tex.
Dealkylation of Ethylbenzene An exploratory study has developed conditions for the cracking of ethylbenzene to produce lower aromatics without degrading xylene
advent of catalytic reforming has resulted in production of considerable quantities of Cs aromatics. These generally consist of mixtures of 0 - , rn-, and p xylenes and ethylbenzene. If the feed stock contains an appreciable quantity of ethylcyclohexane, ethylbenzene may be a major component of the product. During a study of the separation of, uses for, and subsequent processing of the C S aromatics, a brief exploratory investigation of the dealkylation of ethylbenzene over microspheroidal cracking catalyst was carried out.
T H E
Experimental
Ethylbenzene obtained from the Dow Chemical Co. was used as a feed in all Present address, Shell Oil Co., New York, N. Y . 1
runs. Infrared and mass spectrometric analyses of this material are: Composition, Vol. % By Mass Spectrometer
Paraffins Naphthenes Benzene Toluene CSaromatics CSand higher aromatics
0.1 0.1 0.0 0.3 99.5 0.0
By Infrared (Basis 1 0 0 ~ oAromatics) Benzene 0.0 Toluene 0.1 o-xylene 0.1 m-xylene 1.2 p-xylene 0.0 Ethylbenzene 98.6 Cumene 0.0
American Cyanamid microspheroidal cracking catalyst was used for all runs. Equilibrium catalyst was drawn from
-
Product n--
Internal Preheater
the Shell Oil Co. Houston Refinery Catalytic Cracking Unit and regenerated at 100Oo F. T h e catalyst had a surface area of 102 square meters per gram and a pore volume of 0.260 ml. per gram after regeneration. A new sample was used for each run. This work was carried out in a laboratory scale fluidized fixed-bed unit. (This terminology conveniently describes a reactor containing a bed of fluidized catalyst. Although there is circulation of catalyst within the bed, the bed itself remains essentially stationary with respect to the reactor. No catalyst is added or withdrawn during the processing period.) A schematic flow diagram of this unit is shown in Figure 1. The ethylbenzene feed and water were pumped separately through the external preheater which was maintained at 950' F. and then mixed prior
1
I I Product Receiver qeactor
11
Water Manometer Gage Glass Diaphragm Pump
Displacement Pump Figure 1.
Water -wGas Holder
I
Flow diagram of fluidized fixed-bed unit VOL. 49, NO. 1
JANUARY 1957
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0\
Temperature
to the inlet of the internal preheater. T h e reactor generally contained 300 grams of catalyst. Stainless steel filter cloth was used to keep the catalyst from getting into the product lines. After passing through the reactor, the hydrocarbon-steam mixture was passed through a water condenser. T h e liquid product was collected in the product receiver. The total gaseous product was collected in a displacement-type gas holder. After the process period, the catalyst was stripped for 15 minutes with helium or nitrogen. Product gases were analyzed by the mass spectrometer. Spot Podbielniak distillations showed the liquid products to contain more than 99.5y0 Cs.i As a result, they were submitted directly for mass spectrometric and infrared analyses. The two analytical methods checked fairly well and were further confirmed in a few cases by analytical distillation in a 22-rnm. Heligrid column.
1085 F.
H20/Oil Mole Ratio 0.2-1.8
Discussion of Results
0 o\ 0.5 Figure 2.
1
I .o
I .5 2 .o LIQUID* HOURLY SPACE VELOCITY
2.5
3
Effect of space velocity on C6-C7 aromatics yield
* Ethylbenzene only
I
\
-
6
0
I .o
20 3 .O H20/01L MOLE RATIO
Ob; I 1000 2000 3000 TOTAL GAS HOURLY SPACE VELOCITY
1
Figure 3. Effects of water-oil mole ratio and gas hourly space velocity on Cs-Cj aromatics yield
40
INDUSTRIAL AND ENGINEERING CHEMISTRY
Typical operating data and product compositions are given in Table I. The early runs a t 1000" to 1050" F. and space velocities of 2 to 3 over equilibrium microspheroidal catalyst indicated that much more severe conditions would be required to obtain appreciable conversion of the ethylbenzene. As a result, most of the later runs were carried out a t 1085" F. and space velocities ot 2 or less. T h e data obtained were not sufficient to define clearly the effect of temperature, but, as anticipated, increased temperature increased conversion. T h e effect of space velocity is shown in Figure 2. I t is clear that the yield of benzene and toluene is essentially a linear function of space velocity. An important effect noted in earlier work on xylene isomerization (2) was that of the diluent. I t was shown that steam enhanced both the conversion to isomeric xylenes and the recovery of C S aromatics. In this investigation, the major effects resulting from the use of steam as a diluent were reduction in coke make, changes in gas composition, and a decrease in conversion. At both low severities (runs B-9 and B-10) and high severities (runs B-11 and B12), the use of water-oil mole ratios of less than one caused considerable reduction in coke make. Figure 3 shows the effect of water-oil mole ratio on the yield of Cb and C7 aromatics a t constant space velocity and temperature. However, when the abscissa (water-oil mole ratio) is replaced by total gas hourly space velocity, the two curves are almost identical in shape. This indicates that the decrease in CS and C7 aromatics yield a t higher water-oil mole ratios is due to the lower severity resulting from the lower partial pressure (and resulting lower contact time) of the C , aromatics in
Table I. Run No. Operating conditions Av. reactor temp., O F. Wt. oil/hr./wt. catalyst Liquid hourly space velocity HzO-oil mole ratio Process period, hr. Pressure, lb./sq. inch abs.
Dealkylation of Ethylbenzene-Typical Operating Conditions and Yields B2 B3 B4 B5" B6 B7 B8 B9 B10 B11 B1
Yields, basis charge (no-loss basis), wt. % Total liquid product ' Gas Coke Cs-and-lighter compn., basis charge, wt. % H.,
C3
+
Total gas composition, basis charge (mass spectrometer), vol. % Paraffins Naphthenes Benzene Toluene CSaromatics CSaromatics CIOaromatics Total CP,+
B13
B14
1085 1085 0.8 0.7 0.9 0.8 0.54 0 3.0 2.0 15 15
1085 0.8 0.9 0.02 2.0 15
1085 0.6 0.7 0.60 3.0 15
1000 3.0 3.3 1.05 3.0 15
1000 1.7 1.9 0.81 6.0 15
99.7 0.3
99.2 99.2 99.2 95.2 96.8 95.2 97.1 0.8 0.7 0.8 3.7 3.1 4.5 2.7 0.0 0.1 1.1 0.0 0.1 0.3 0.2
98.4 98.5 93.8 1.0 1.5 5.8 0.5 0.1 0.4
91.2 92.4 91.9 6.9 6.0 7.4 0.7 1.8 1.5
0.0 0.0 0.3 0.0 0.0 0.3
0.0 0.0 0.8
0.0
1050 1050 1050 1085 1085 1085 1050 3.6 1.6 1.3 1.3 1.9 3.4 3.4 4.0 3.7 3.8 1.7 1.5 1.9 2.1 0 0.85 0 0.45 0.32 1.84 0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 15 15 15 15 15 15 15
B12
0.0 0.8
0.0 0.1 0.5 0.1 0.0 0.7
0.0 0.0 0.8 0.0 0.0 0.8
0.0 0.0 2.2 0.9 96.8 0.1
0.0
0.0
0.0 0.0 0.3 0.0 8.1 8.5 0.5 2.1 88.9 79.8 1.0 0.3 0.8 3.3 98.9 94.7
2.9 0.0 0.0 0.0 0.0 95.7 0.4
4.1 0.0
0.0
0.2 0.5 1.8 0.9 0.3 3.7
0.0 0.2 2.6 0.2 0.1 3.1
0.1 0.4 3.2 0.6 0.2 4.5
0.1 0.1 2.2 0.2
0.1 0.2 0.6 0.1
0.1
0.0
2.7
0.0 0.1 10.7 1.5 83.2 0.2 1.0 96.7
0.1
0.0 14.3 1.6 77.0 0.4 1.0 94.4
11.0 13.5 1.8 1.2 2.0 0.0 1.5 1.6 0.9 0.5 74.9 76.7 1.8 0.9
1050 1.6 1.8 0.89 3.0 15
0.2 0.6 4.9 1.2 0.5 7.4
1.0
0.0 0.1 1.4 0.1 0.0 1.5
0.1 0.3 4.4 0.7 0.3 5.8
0.5 1.3 2.8 1.9 0.4 6.9
0.3 0.9 3.0 1.4 0.4 6.0
0.2 0.1 7.2 0.8 87.9 0.3 0.0 96.5
0.0 0.0 4.6 1.3 91.0 0.3 1.0 98.2
0.0 0.0 4.4 0.8 92.5 0.0 0.7 98.4
0.1
0.4 0.2 0.0 0.0 19.3 16.5 6.0 4.3 61.7 68.4 0.6 0.5 0.8 0.7 88.8 90.6
0.2 0.0 18.8 2.2 67.8 0.5 0.9 90.4
7.7 0.4 0.3 0.9 0.0 87.8 0.5
4.1 6.1 14.9 0.1 0.0 1.3 0.0 0.0 0.1 0.0 0.2 1.9 0.0 0.0 0.3 87.0 86.9 73.8 0.7 0.9 0.4
16.3 4.8 0.2 4.0 0.7 61.3 1.6
18.4 1.9 0.2 2.4 0.2 66.8 0.5
c6+
0.1 4.4 1.8 91.3 0.9 0.0 0.6 100.0 99.1
0.4 3.8 1.3 91.7 0.5 1.2 98.8
c@+ composition, basis charge (infrared), vol. % Benzene Toluene o-Xylene m-Xylene p-Xylene Ethylbenzene Cumene a Fresh catalyst used for this run.
the diluted feed. T h e presence of steam also had a considerable effect on the composition of the product gas. This is especially noticeable in runs B-11 and B-12. T h e addition of steam results in less methane and ethane with a corresponding increase in ethylene production. T h e effect of added steam on conversion, coke make, and gas composition is summarized by the comparison of runs B-11 and B-12 : Run No. B-11 HzO-oil mole ratio 0.54 Gas composition, mole % Hz 2.4 CH4 5.9 CZH4 74.6 CZ? 11.9 Ca 5.2 Coke 0.4 Conversion [ 100-vol.% ethylbenzene (basis charge) in product] 26.2
B-12 0 6.5 19.0 40.5 27.7 6.3 1.8
38.7
T o determine the effect of very small amounts of diluent, run B-13 was carried out with the ethylbenzene feed saturated with water and no other steam added, However, this yielded only 0.02 weight % water in the feed and the effects, although in the predicted direction, are probably too small to be significant. The use of fresh rather than equilib-
3.7 0.0 0.0 0.0 0.0 0.0 0.0 0.2 92.4 88.9 0.2 0.8
4.8 0.0 0.0 0.0 0.0 92.2 0.7
.. .. *.
.. .. ....
rium catalyst results in a considerable increase in activity, as evidenced by a comparison of runs B-3 and B-5. However, a t comparable CS and C , aromatics yield (runs B-4 and B-5) fresh catalyst has a lower selectivity, which results in higher coke and gas makes. T h e major reaction encountered in this work appears to be the cracking of ethylbenzene to benzene and ethylene. At the higher severities, small amounts of xylenes are formed. Infrared analyses indicate that the xylenes are primarily m-xylene; however, these results may be questionable. Small amounts of Cs and higher materials are known to introduce inaccuracies into the Cs aromatics breakdown. I t is believed that if any xylenes are produced, they will probably be in equilibrium ratio. Earlier work (7) on xylene isomerization included runs with the feed consisting primarily of ethylbenzene. I t was concluded that over fresh catalyst, the rate of isomerization of ethylbenzene to xylenes was slower than the rate of isomerization of the xylenes themselves. This work indicates that, over equilibrium catalyst, there will be little, if any, isomerization of ethylbenzene to xylenes under relatively severe conditions. I t appears that the yields of Ca and C, aromatics at reasonable severities are
0.0 14.5 1.0 74.4 1.3 1.3 92.6
15.4 3.2 0.0 3.2 0.3 67.7 0.9
of the order 20%. At 1085' F., 0.6 l.h.s.v., and 0.6 water-oil mole ratio (run B-14), 32 volume Yo of the ethylbenzene is converted to yield on a charge basis, 18.8 volume yo benzene and 2.2 volume yo toluene. This represents a combined conversion efficiency to benzene and toluene of 89 mole % : Conversion efficiency = moles of Ca and C, aromatics moles of ethylbenzene converted
x
100
T h e total liquid product represented a yield of 91.9 weight yo charge, with 7.4 weight 7 0 gas and 0.7 weight yo coke making up the remainder. Ethylene comprised 66Y0of the product gas. Acknowledgment
The author wishes to express his appreciation to the Shell Oil Co. for permission to publish the results of this investigation. literature Cited (1) Bennet, C. S., Bailey, W. A., Jr., private communication. (2) Bennet, C. S., Eailey, W. A., Jr. (to Shell Development Co.), U. S. Patent 2,564,388 (Aug. 14, 1951 ).
RECEIVED for review January 7, 1956 ACCEPTEDJuly 26, 1956 VOL. 49, NO. 1
JANUARY 1957
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