EP0085718A4

EP0085718A4 - Selectively calcined dehydrogenation catalyst.

Info

Publication number: EP0085718A4
Application number: EP19820903004
Authority: EP
Inventors: David L Williams
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-08-17
Filing date: 1982-08-17
Publication date: 1984-01-10
Also published as: WO1983000687A1; EP0085718A1; JPS58501272A

Abstract

A catalyst found to be particularly effective in the dehydrogenation of ethylbenzene, diethylbenzene, and ethyltoluene, to olefinic compounds or vinyl aromatics where the catalyst includes iron oxide, at least 20% by weight alkali water gas promoter and at least 1.3% by weight chromium oxide where the catalyst is formed into pellets of selected configuration which are calcined at 900<o>F to 1110<o>F for 15 minutes to 8 hours.

Description

Description _Selectively Calcined Dehydrogenation Catalyst Technical Field

This invention relates generally to 5 catalysts particularly useful for the production of olefins by dehydrogenatin and more specifically to the composition and method of manufacture and use of improved dehydrogenation catalyst. 10 Considerable research has been directed in the past toward improving the production of olefins by dehydrogenation. Background Art

Steam active dehydrogenation catalysts 15 are widely used in the dehydrogenation to olefins and diolefins, e.g., butanes to butadienes; alkyl aromatics to alkenyl aromatics, e.g., ethylbenzene to styrene. Various catalysts and the dehydrogenation 20 conditions and other operating data are disclosed in Pitzer, U.S. Patent Nos. 2,866,790 and 2,866,781; Gutzeit, U.S. Patent No. 2,408,140, and Eggertsen, et al., U.S.

SUBSTITUTE SHEET Patent No. 2,414,585, Hills, et al,; U.S.

Patent No. 3,360,579 and Sie , U.S. Patent

No. 3,364,277.

Pitzer discloses a catalyst where the catalyst which contains about 50% K-CO-., up to 10% Cr_0, and the balance Fe*®_? is heat treated at at least 1000 degrees or

(in terms of the Pitzer specifications) 16 to 24 hours. Siem teaches calcining a similar catalyst at 600 degrees C to 650 degrees C.

U.S. Patent No. 3,360,579 teaches calcination at 800 degrees to 1 00 degrees

The steam active alkalized iron dehydrogenation catalysts disclosed in these patents contain various amounts^'of iron oxide and potassium carbonate with a minor but effective amount of chromium oxide incorporated therein as a stablizer or structural promoter. Facilities for dehydrogenation are advantageously operated at the highest practical throughput rates and small improvements in selectivity and activity of dehydrogenation catalyst can result in substantial savings. However, it is very difficult to obtain a catalyst which has both

OMP

SUBSTITUTE SHEET Λ. IP high selectivity and high activity because generally, high selectivity is accompanied by low activity and vice versa. Activity, of the catalyst is defined as the percent of the starting material, e.g., ethylbenzene, which is converted from the original state during the dehydrogenation process.

Selectivity of the catalyst is defined as the ratio of the amount of the desired product produced in the process, for example styrene, to the total feedstock converted.

A high conversion by catalytic dehydrogenation is generally favored by a high temperature and a low pressure. In the dehydrogenation of ethylbenzene to styrene there are also undesirable side reactions which simultaneously occur to produce benzene and toluene. The side reactions go to completion and are not limited by equilibrium considerations. The benzene produced can be recycled for later processing but the toluene cannot and must be disposed of. Accordingly, in the evaluation of a system where the. by products are produced, the production of benzene as opposed to toluene is preferred.

SUBSTITUTE SHEET OMPI In catalyst dehydrogenation processes, steam is mixed with the feed stock in varying ratios, commonly referred to as the steam/oil (s/o) ratio, where the rate of steam usage directly affects the process cost. In the present environment with increasing cost of energy, processing costs are increased accordingly, so that a catalyst operable at a lower steam/oil ratio is desirable. In prior catalysts the conversion rate or activity of the catalyst has diminished more rapidly with on stream time at low steam/oil ratios than at higher ratios so it has not been feasible, using prior art catalyst to utilize lower steam to oil ratios to economize on steam usage because the lower steam/oil ratios involve more frequent shutdowns for catalyst regeneration or, more importantly, permanent deactivation. Disclosure of Invention

The present invention provides a new and useful catalyst for the production of olefinic

SUBSTITUTE SHEET

/,, components by dehydrogenation of more saturated materials, where the catalyst maintains both a high activity and a high selectivity in the dehydrogenation. The present invention also provides a method for production of a catalyst for the dehydrogenation of ethylbenzene to styrene at low steam to oil ratios where the catalyst maintains stability at lower steam/oil ratios and where, unexpectedly, the relative production of toluene is substantially diminished over a wide range of steam/oil weight ratios. Moreover, catalysts in accordance with the present invention provide longer operating periods between regeneration cycles even at lower steam/ oil ratios and reaction temperatures. It has been further found that catalysts provided by the present invention unexpectedly

SUE_STϊTUTE SHEET provide good activity and selectivity in the dehydrogenation of diethylbenzene ethyltoluene, propylbenzene, butylbenzene and other alkyl substituted benzenes.

5 More particularly, the present invention provides a catalyst found to be particularly effective in the dehydrogenation of ethylbenzene, diethylbenzene, and ethyltoluene, to olefinic compounds or

10 vinyl aromatics where the catalysts includes iron oxide, at least 20% by weight alkali water gas promoter and at least 1.0% by weight chromium oxide where the catalyst is formed into pellets of selected configuration

15 which are calcined at 900 degrees to 1110 degrees for 15 minutes to 8 hours.

The present invention is described in the following specification with reference to several examples but it will be understood

20 that such examples are by way of illustration only and the scope of the invention is limited only by the scope of the claims appended hereto and the equivalent thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

25 Illustrations of the characteristics of catalysts within the scope of the present

SUBSTITUTE SHEET OMPI invention are illustrated in the Figures wherein;

Figure 1 is an illustration of a Mercury Porosimetry Evaluation of a catalyst within the scope of the present invention;

Figure 2 is an illustration of the result of a Mercury Porose itry Evaluation of a comparison catalyst calcined in accordance with the present invention; Figure 3 is an illustration of the result of Mercury Porosimetry Evaluation of a catalyst within the scope of the present invention and one having the same composition but calcined for a different length of time; Figures 4a-4b are comparative illustrations of selectivity of a catalyst within the scope of the present invention and a prior art catalyst calcined for a longer time at higher temperatures; Figure 5 is a comparison of a catalyst shown in Figure 1 illustrating benzene/ toluene ratios in the effluent; and

Figure 6 is a graphic illustration of the conversion or activity of the catalysts of Figures 4a-4b over a period of time.

SUBSTITUTE SHEET Best Mode for Carrying Out the Invention The method of the present invention provides a dehydrogenation catalyst including iron oxide, at least 25% by weight of potassium carbonate and at least 1.3% by weight chromium oxide. The composition is formed into pellets of selected size and heat treated at 950 degrees to 1100 degrees for 15 minutes to 8 hours to provide the pore volume characteristics found to be beneficial in the subject invention, in that the catalyst unexpectedly yields excellent selectivity and longer catalyst life at lower steam to oil ratios, all as discussed hereinafter. The iron oxide customarily is of pigmentary grade but may also be prepared by the thermal decomposition of ferric nitrate, ferric oxalate, ferrous sulfate and the like. The iron oxide in the finished catalyst is usually in the alpha form. The iron oxide may constitute up to 53.5% by weight of the catalyst but is preferably within the range from about 25% to about 45%.

Compounds of the alkali metals such as the oxides, hydroxides, carbonates, and

SUBSTITUTE^"SHEET

OMP to about 55% by weight of the water gas promoter.

One example of a catalyst of the present invention was prepared with the following analysis by dry mixing the necessary ingredients and calcining at 1000-1100§F for 2 hours:

Analysis: 50.0% K₂C0₃

(weight) 2.8% Cr₂0₃

46.0% Fe-O-

The percentage of the components may vary, it having been found that within the scope of the present invention, the concentration of alkali water gas promotor may vary from 20% to 55% and the proportion of chromium oxide may vary from 1.3% to 5.0% with the balance of the composition iron oxide.

The characteristics of the example Of the invention catalyst, after calcining were determined by Mercury Porosimetry evaluation- and the results presented in graphical form in Figure 1. It can be seen in the chart that mercury penetration in cc/g vs. equivalent pore diameter provides a curve of specific characteristics different from the curve illustrated in Figure 2 for a first comparison catalyst with the same components which was calcined at 1700§F for 2 hours. It will be seen that the high temperature calcining significantly increased the slope of the curve so most of the penetration occured in the

_O range of 0.1 to 0.6 micron equivalent pore diameter. On the other hand, with the catalyst of the present invention the curve sloped smoothly throughout the penetration range.

Figure 3 is an illustration of the pore volume distribution of two catalysts of similar composition in a Mercury Porosemetry evaluation, each catalyst including equivalent amounts of Fe~0,, K-CO.. and Cr-O...

The catalyst represented by curve A was calcined in air at 1100 degrees for 24 hours. The catalyst represented by curve 3 was calcined in acordance with the present invention at 15 900 degrees 1100 degrees for 2 hours.

While the differences are not as marked as in Figures 1 and 2 the effect of longer calcining time can be seen in curve A where the curve is steeper

It has been found that calcining the catalyst at 95G degrees-1100 degrees for 15 minutes to a maximum of 8 hours provides the desired pore distribution as indicated by the test results in the Mercury Porosimetry

Evaluation. As discussed hereinafter it is believed that the improved performance

^SUB^STITUTE SHEET characteristics of the catalyst of the present invention are related to the pore volume distribution of the catalyst.

A catalyst in accordance with the present invention as described above was placed in a reactor, for example a tubular reactor (in the following examples lOOcc of catalyst was used for each test in a 1" stainless steel reactor) where the feedstock, for example ethylbenzene, diethylbenzene, or ethlytoluene, was fed through the reactor with selected proportions of steam.

In the example of the present invention the steam to oil (or feedstock) ratio was varied between 6:1 to 0.6:1 by weight as described hereinafter at liquid hourly space velocity (LHSV) of 1.0 to 2.0 as indicated hereinafter.

Each of the feed stocks were tested with the catalyst above described and the results are shown in TABLES I-III.

TABLE I is a tabulation of the results of the dehydrogenation of ethyltoluene to vinyltoluene over the catalyst previously described at the conditions noted.

SUBSTITUTE SHEET __O TABLE I

-

ETHYLTOLUENE

DEHYDROGENATION PERFORMANCE DATA

Hours Temp. Steam/ % % % on °F Oil Con- Yield Selec¬

Steam (wgt. ) vers. tivity

4.0 1150 2.0 41.3 37.7 91.3

21.5 1150 2.0 51.5 48.2 93.5

45.0 1150 2.0 54.9 51.1 92.2

69.0 1150 2.0 60.9 56.2 92_^4

92.5 1150 2.0 60.3 55.4 92.0

117.5 1150 2.0 60.7 56.0 92.3

141.0 1150 2.0 60.3 55.8 92.5

166.0 1150 2.0 62.9 58.1 92.3

171.0 1150 2.0 63.2 57.8 91.4

189.0 1150 2.0 63.8 57.4 89.9

213.5 1150 2.0 63.0 58.1 92.2

238.0 1150 2.0 64.6 59.1 91.4

260.5 1150 2.0 64.6 59.1 91.y

285.5 1150 2.0 64.0 59.0 92.1

309.5 1150 2.0 64.4 59.1 91.8

334.0 1150 2.0 63.1 58.1 92.1

357.5 1150 2.0 66.1 60.3 91.3

380.0 1150 2.0 59.7 55.2 92.6

403.5 1150 2.0 59.0 54.6 92.6

432.5 1150 2.0 61.2 56.3 91.9

456.5 1150 2.0 64.5 59.0 91.6

474.5 1150 2.0 63.7 58.5 91.9

501.0 1150 2.0 60.8 56.0 92.1

521.0 1150 2.4) 61.1 56.5 92.4

SUBSTITUTE SHEET TABLE I (continued)

Hours Temp. Steam/ % % % on °F Oil Con- Yield Selec¬

Steam (wgt. ) vers. tivity

546.0 1150 2.0 63.2 58.1 92.0

570.0 1150 2.0 62.0 57.2 92.2

571.0 Decreased reactor temperature to 1100 >° F.

575.0 1100 2.0 49.6 46.8 94.3

594.0 1100 2.0 49.6 46.7 94.2

617.5 1100 2.0 49.3 46.8 95.0

641.0 1100 2.0 49.1 46.3 94.3

641.5 Decreased reactor temperature to 1050 °F.

647.0 1050 2.0 32.5 31.0 95.5

662.0 1050 2.0 32.4 31.0 95.6

690.0 1050 2.0 31.2 30.5 97.8

714.5 1050 2.0 27.4 27.1 98.7

720.0 1050 2.0 28.0 27.1 96.8

739.5 1050 2.0 26.8 25.7 96.0

763.5 1050 2.0 30.6 29.3 96.6

768.5 1050 2.0 30.6 29.6 97.7

788.0 1050 2.0 2.7.2 26.6 97.8

813.5 1050 2.0 32.0 30.5 95.4

836.5 1050 2.0 30.5 30.0 98.1

859.5 1050 2.0 30.6 30.0 98.2

884.0 1050 2.0 24.4 24.3 99.4

906.0 1050 2.0 28.8 27.2 94.5

930.0 1050 2.0 31.2 30.0 96.2

955.0 1050 2.0 31.8 30.5 95.9

956.5 Reduced 3/0 to 1.8

960.0 1050 1.8 31.2 29.8 95.7

983.0 1050 1.8 28.7 27.5 95.8

1002.5 1050 1.8 28.2 26.8 95.2

1026.0 1050 1.8 29.5 28.3 95.9

1050.0 1050 1.8 29.4 28.2 95.8

1074.0 1050 1.8. 29.3 28.1 95.8

1075.0 Reduced S/O to 1.5

1079.5 1050 . 1.5 23.9 22.9 96.0

1123.0 1050 1.5 18.6 17.9 96.4

1148.0 1050 1.5 21.1 20.1 95.3

1172.0 1050 1.5 20.0 95.8 95.8

1195.0 1050 1.5 20.8 20.0 96.2

1197.0 Increased reactor ^■temperature to 1150^c 'F. and S/O to 2.0

1201.0 1150 2.0 51.8 47.6 91.6

1222.0 1150 2.0 59.3 54.4 91.8

1226.0 1150 2.0 60.9 56.2 92.3

1247.5 1150 2.0 61.8 56.5 91.5

1267-5 1150 2.0 60.0 55.1 91.7

Constant Test Conditions:

1.0 LHSV, 0 psig, 100 cc catal}St

SUBSTITUTE SHEET The data in Table I illustrates that not only is conversion responsive to temperature but that even at the lowest test temperature (1050° F) where any tendency toward catalyst instability is most apparent, the catalyst will permit a reduction of steam to oil ratio to 1.8:1 without adverse effect on conversion or selectivity. The date in Table I further illustrates that a steam to oil ratio as low as 1.5:1 results in steady performance.

Likewise, (by comparing data at hours 21-570 and 1201-1267.5) Table I illustrates that even in an extended heat run, reaction conditions can be modified then returned to initial conditions without adverse effect on catalyst performance.

Table II provides the results of tests to demonstrate performance of the invention catalyst and the aforementioned comparison catalyst in the dehydrogenation of diethylbenzene (DEB) to divinylbenze (DVB) and ethylvinyl benzene (EVB) at the indicated conditions.

O

SUBSTITUTE SHEET Run Temp. Steam/ Press, % Conv, .% Yield %Se.lectivity

Hours (°F) Oil (psig) of DEB 1 of DVB 2 of DVB+ to DVB 4 to DVE +

( t) EVB 3 EVB 5

46.0 1150 3.0 0 82.0 43.4 74.1 52.9 90.3

70.0 1150 3.0 0 82.6 43.2 75.2 52.3 91.0

93.5 1150 3.0 0 83.3 43.2 75.0 51.9 90.1

117.5 1150 3.0 0 82.4 43.4 75.9 52.7 92.1

142.5 1100 3.0 0 63.9 24.2 62.1 37.9 97.2

165.5 1100 3.0 0 64.3 24.3 62.4 37.8 97.0

189.5 1100 3.0 0 64.2 24.1 62.1 37.5 96.7

215.5 1050 3.0 0 41.5 9.3 40.7 22.4 98.1

238.0 1050 3.0 0 40.9 9.3 39.8 22.7 97.4 tΛ 261.5 1050 3.0 0 40.4 9.4 40.0 23.3 98.9 C 286.5 1100. 3.0 0 66.1 25.9 63.5 39.2 96.0 ro 310.0 1100 ω 3.0 4 64.8 23.3 60.0 36.0 92.5

H 334.0 1100 3.0 4 65.4 24.4 62.2 37.3 95.1 1

357.5 1100 3.0 9 62.9 21.2 59.6 33.7 94.7 y

-I c 380.5 1100 3.0 9 61.0 19.7 57.8 32.3 94.7 1

405.5 1100 3.0 9 61.6 20.3 57.6 33.0 93.5 rπ 429.5 1100 3.0 9 61.9 20.4 58.5 33.0 94.6

455.0 1100 6.0 9 58.3 20.6 55.2 35.3 94.7

(0

:c 478.0 1100 6.0 9 58.0 20.4 55.4 45.2 95.5 rπ 502.5 1100 2.5 9 47.8 12.6 45.9 26.4 96.1 m 526.0 1100 2.5 9 53.6 15.3 50.8 28.5 94.7 H 550.5 1100 2.5 9 54.1 15.7 51.5 29.0 95.3

574.0 1100 2.5 9 53.3 15.5 51.3 29.1 96.2

COMPARISON CATALYST

24.0 1150 3.0 0 87.5 40.5 68.6 46.2 78.4

48.0 1150 3.0 0 87.0 40.4 69.1 46.5 79.2

71.5 1150 3.0 0 83.0 38.4 68.9 46.3 83.1

95.5 1150 3.0 0 78.7 35.6 65.5 45.2 83.2

119.0 1150 3.0 0 71.3 32.2 62.5 45.2 83.2

143.5 1150 3.0 0 68.7 31.2 60.7 45.5 88.4

167.5 1150 3.0 0 66.6 30.5 59.8 45.8 89.8 Constant Test Conditions: 1.0 LHSV, 100 cc catalyst

As shown in Table II reaction temperature was varied stepwise between 1050°F; 1100° F; and 1150°F; steam/oil ratio varied from 2.5:1 to 6.0:1 and pressure varied from OPSIG to PSIG. In the process several characteristics of the present invention catalyst are found.

First, by comparing results obtained at 1150°F (hours 46.0 - 117.5) 1100°F (hours 142.5-189.5), and 1050°F (hours

215.5-261.5), it is obvious that not only is there significant reduction in total conversion at reduced temperature but also a aked increase in the ratio of EVB to DVB in the product. Further, it has been found that at low positive pressures 0-9 (opsig) conversion is satisfactory at approximately 3:1 steam to oil ratio whereas the aforementioned comparison catalyst exhibited a significant decline in conversion with time on steam when operated at a steam to oil ratio of 3:1. Further prior art catalysts provide satisfactory performance only when operated at significant higher steam to oil ratios (usually in the range of 6:1) and even when operating at these higher steam oil ratios

_SUBSTITUTE SHEET OM j WIP require periodic steam regeneration which is unexpectedly not required by the catalyst in accordance with the present invention as shown by the extended test periods without regeneration.

Finally, it has been found that catalyst in accordance with the present invention is useful in dehydrogenation of ethylbenzene to styrene and unexpectedly provides improved characteristics as described hereinafter.

Table III is a tabulation of the results of the dehydrogenation of ethylbenzene to styrene over the invention catalyst previously described at the conditions noted.

_SUB_STITUTE^"SHEET OM Λ, WIP TABLE III

PERFORMANCE OF CATALYST IN

DEHYDROGENATION OF ETHYLBENZENE (EB)

Run Steam/ Temp. %Con- %Yld % Benzene

Hrs. Oil °F versiont Sel. Toluene ( t) of EB ( t)

25.0 2.5 1150 65.8 60.8 92.8 0.53

45.0 2.5 1150 67.8 62.8 95.6 0.50

76.0 2.5 1150 64.9 60.6 93.4 0.47

96.5 2.5 1150 64.8 60.8 93.8 0.49

102.0 1.5 1100 43.7 42.0 96.1 0.57

121.0 1.5 1100 44.5 42.6 95.8 0.56

145.0 1.5 1100 45.1 43.2 95.9 0.56

168.5 1.5 1100 43.3 41.6 96.1 0.56

193.0 1.5 1100 44.8 43.0 95.6 0.56

197.5 1.25 1100 43.4 43.0 95.8 0.56

219.0 1.25 1100 44.2 42.4 95.9 0.56

241.5 1.25 1100 43.5 41.8 96.1 0.56

266.5 1.25 1100 42.5 40.8 96.0 0.55

290.5 1.25 1100 42.6 40.9 96.0 0.54

314.5 1.0 1100 42.3 40.5 95.7 0.55

338.0 1.0 1100 41.9 40.1 95.8 0.57

361.5 1.0 1100 42.7 40.8 95.7 0.53

387.5 1.0 1100 42.6 40.8^" 95.8 0.53

409.5 1.0 1100 42.2 40.1 95.1 0.58

433.5 1.0 1100 ^" 42.3 40.6 95.8 0.56

439.5 0.8 1100 40.9 39.2 95.7 0.58

459.0 0.8 1100 40.1 38.5 95.8 0.54

482.5 0.8 1100 40.1 38.6 96.2 0.60

507.0 0.8 1100 ^' 38.6 37.2 96.3 0.61

531.0 0.8 1100 39.9 38.4 96.3 0.60

554.C \J « O llυυ U.5 38.9 96.1 0.55

578.0 0.6 1100 36.6 35.3 96.5 0.64

601.5 0.6 1100 34.3 33.3 96.9 0.68

626.0 0.6 1100 33.8 32.8 97.0 0.69

650.0 0.6 1100 33.6 32.6 97.0 0.69

675.5 0.6 1100 33.9 32.9 96.9 0.68

697.5 0.6 1100 34.2 33.1 96.8 0.65

Constant Test Conditions:

2.0 LHSV, 4 psig, 100 cc catalyst

SUBSTITUTE SHEET The same conditions were then utilized for comparison using a catalyst which included the same components but which had been heat treated at 1700°F. with the pore 5 distribution curve shown in Figure 2,

(Comparison Catalyst) for dehydrogenation of ethylbenzene and the results shown in Table IV were obtained.

TABLE IV

PERFORMANCE OF COMPARISON CATALYST

Run Steam / Temp. %Con. %Yld. %Sel Benzene

Hrs. Oil °F Toluene (wt) (wt)

69.5 2.5 1150 73.2 64.4 88.0 0.40

71.0 ...Reduced Reactor temperature to 1100°F and S/O to 1

93.5 . 1.5 1100 55.0 50.7 • 92.0 0.45

118.0 1.5 1100 53.5 49.4 92.3 0.44

142.5 1.5 1100 54.4 50.2 92.2 0.43

166.0 1.5 1100 53.9 49.7 92.4 0.43

237.0 1.5 1100 53.1 49.1 92.4 0.43

239.0 ...Reduced S/O to 1.25

262.0 1.25 1100 51.6 47.5 92.0 0.44

286.5 1.25 1100 50.2 46.3 92.3 0.43

310.0 1.25 1100 49.6 45.9 92.6 0.41

334.5 1.25 1100 49.4 45.6 92.4 0.44

378.5 1.25 1100 49.7 46.0 92.5 0.44

403.5 1.25 1100 49.1 46.5 92.7 0.44

405.5 ...Reduced S/O to 1.0

414.0 1.0 1100 46.7 43.1 92.3 0.45

432.0 1.0 1100 47.9 44.2 92.4 0.46

454.5 1.0 1100 46.2 42.9 92.9 0.46

478.5 1.0 1100 44.5 41.8 ^'94.3 0.50

502.0 1.0 1100 40.3 38.2 94.6 0.50

574.0 1.0 1100 37.6 35.8 95.2 0.52

575.5 ...Terminated Run...

Constant Test Conditions:

2.0 LHSV, 4 psig, 100 cc catalyst

SUBSTITUTE SHEET

/M. IIPPOO The results of the test shown in Table III and Table IV are shown graphically in Figures 4-6 and will be considered with respect to these Figures. Figure 4a graphically illustrates the selectivity of ethylbenzene conversion to styrene using the catalyst of the invention - at indicated steam/oil ratios by weight while Figure 4b indicates selectivity for the comparison catalyst.

Figures 4a and 4b illustrate that the selectivity of catalysts within the scope of the present invention is superior to the selectivity of the comparison catalyst. In the dehydrogenation of ethylbenzene the principal by-products are benzene and toluene. The benzene is the more desirable by-product because it can be recycled whereas toluene cannot. Accordingly, the benzene/toluene distribution in the. dehydrogenation product is important as an indication of lost raw material, namely toluene.

Figure 5 is a graphic representation of the benzene/toluene ratio for selected conditions utilizing the catalyst of the

SUBSTITUTE SHEET O invention and the comparison catalyst.

Accordingly, in use of the catalyst of the present invention, while conversion may in some instances be lower, the benefit derived from improved selectivity results in less by-product production and as illustrated in Figure 5 even the by-product produced contains a greater proportion of the more desirable benzene. Finally, Figure 6 is a comparison of the conversion achieved utilizing the catalyst of the invention and the comparison catalyst. While the conversion provided by the invention catalyst is initially lower at 1.5 and 1.25 steam/oil than the comparison catalyst, Figure 6 illustrates one of the unexpected advantages of the present invention; that is that the difference between the conversion rate of the catalyst diminishes with lower steam oil ratios and the catalyst of the present invention provides satisfactory and stable conversion at steam/oil ratios of 0.8 and 0.6 over an extended period of time where the comparison catalyst becomes unsatable at 1.0 S/O. As previously stated this advantage is important because the lower steam/oil ratios permit energy cost savings.

SUBSTITUTE SHEET Specifically, Figure 6 illustrates that the conversion of ethylbenzene provided by the comparison catalyst diminishes to the point that the conversion provided by the catalyst of the invention catalyst at 0.8 steam/oil ratio is equivalent to the conversion provided by the comparison catalyst at 1.0 steam/oil.

It will be noted in Figure 5 that the difference in conversion provided by the two catalysts unexpectedly converge because of the conversion rate for the comparison catalyst drops off sharply even though the steam/oil ratio is maintained at 1:1. Conversely, when the steam/oil ratio for the catalyst of the invention was decreased to 0.8:1 the conversion rate was nearly equivalent to the rate for the comparison catalyst at a steam/oil ratio 1:1.

Extrapolation of the results shown in Figure 5 show that with time the conversion for the catalyst of the invention would surpass the conversion characteristics of the comparison catalyst even at a steam/oil ratio of 1:1 because of the inability of the comparison catalyst to operate in a stable manner at steam/oil ratios much below 1.25.

SUBSTITUTE SHEET OMP

Claims

1. A catalyst found to be particularly effective in the dehydrogenation of ethylbenzene, diethylbenzene, and ethyltoluene, to olefinic compounds or vinyl aromatics where the catalysts includes iron oxide, at least 20% by weight alkali water gas promoter and at least 1.3% by weight chromium oxide where the catalyst is formed into pellets of selected configuration which are calcined at 900°F to 1110°F for 15 minutes to 8 hours.

2. The invention of Claim 1 wherein the proportion of potassium carbonate is between 50% and 60% by weight.

3. The Invention of Claim 1 wherein the proportion of chromium oxide is between 1% and 4% by weight.

4. A process for the dehydrogenation of alkyl aromatic to a vinyl aromatic comprising contacting steam and the alkyl aromatic at a weight ratio of about 0.6:1 to 1:2 with a catalyst containg iron oxide, at least 20% by weight potassium carbonate and at least 1% by weight

SUBSTITUTE SHEET chromium oxide where the catalyst is formed into pellets of selected configuration which are calcined at 900°F for a period of between 15 minutes and 8 hours and the dehydrogenation occurs. The invention of Claim 4 wherein the average pressure of the dehydrogenation reaction is between 0 and 10 pounds per

10 square inch gauge.

The invention of Claim 4 wherein the alky aromic is principally ethylbenzene. The invention of Claim 4 wherein the alkyl aromatic is principally

15 diethylbenzene.

The invention of Claim 4 wherein the alkyl aromatic is principally ethyltoluene.

The invention of Claim 8 wherein said

20 ethyltoluene includes selected proportions of paraethytoluene..

SUBSTITUTE SHEET O Λ- WI