Ethylation of Benzene in Presence of Solid Phosphoric Acid Pat,eiit Office forbade publication of 11ie results. These ortltsi have now been rescinded, anti :I brief summary of r c d t . i. prcwnted here.
phosphoric acid on kieselguhr (the bo-called solid phosphoric acid) is an excellent catalyst for the alkylation of benzene H ith ethylene in continuous-flow operation. The j ield of ethjlbenzene increases with increase in temperature and pressure; 80% conTersion of eth>lenein a single pass (at benzene space Telocity of 2 c*r./hr./cr.of catalyst) io obtained at about 325' C. and 600 pounds per squarc inch or at about 280' C. and 900 pounds pressure. The ratio of monoethylbenzene to polyethylbenzenes increases niarhedlj with inrreaqe in benaene-ethylene ratio: it ic thus readily possible to obtain an alkylation product, oler 90% of which is the desired stjrene intermediate. The life of the catalysl is \cry satisfactory.
11.4 T E K I A 1,s AND .Al'PARA'I'U S
l l e r c ~ k ' st11ic;phenc-fi~:cC.P. bmzene and ethylene (98s;1,;: O I J from T h t b Ohio Chemical a n d ;\Ianufacturiug Company, \\-ere used. The catalyst, was st:md:ii,d U.O.P. rolid phi)-phoric acid (1). It consisted of a phor-phoric acid-kieselguhr composite containing 6 2 4 3 % of thc? acid calculatcd ab>P20j. 1 :riiied
l'hc commercial extruded pellots w r e bro!yn up into 10-12 n i c 4 ~ i i o c e sfor the experiments dcscribod Iwre. Alkylations were carried out i l l i ~ i i18-8 staiiiless steel tul)c* I , & , / ~ ~ inch i.d., 3 i 4 inch 0.d.j whirl1 \\-;isheated in a vertic;ii lurnace. The latter consisted of a n iiirulated, electrically hc;rtcd, 24-inch aluminum-bronze block the temperature was controlled within 1 3 " C. The reaction tube was fitted with a 1)8-inclk stainless stwl thermocouple re11 which extended to the bottom of the cat:ily:t bcd and thus permitted the determination of temperature a t various points i 1 1 the bed; the ternpc~raturc~s in the tables are average:: of the ciyiitw of t,hc bed. The cxtaly-t (40 cc.) was held in place by a staiiile tee1 rod uf such lorigth that t h e catalyst bed (about 11 inrhi:s g) was in t,he middle of the heated zone. The space ahovc: tho catalyst was occupied ti!, a siniilar rod (having a 1ongitutlin:~lhole to fit over the thermocouple well) in which a '/*-inch iipirnl groove had been cut. Thipreheatpr for t,hr hydi,ot.:irl)oiich:jrgc>.
PAPER (4) on the cstalylic alkylation of beriaenc with ethylene showed that with phosphoric acid on kieselguhr ( 1 ) as catalyst, only 13-1570 of t,he ethylene was converted to rthylbenzene a t 239" C. and 100 pounds per square inch pressure. It was stated that i'since pressure has been found to have such a pronounced effect on the reaction when the sodium chloridcaluminum chloride-pumice catalyjt was used, this phosphoric acid-kieselguhr catalyst mould probably give eatisfactoly conversions at pressures of 300-400 pounds per square inch". Our earlier investigation had already shown that solid phosphoric, acid is an excellent catalyst for the preparation of ethylbenzenc and has many advantages over aluminum chloride and othci, catalysts. However, secrrcy orders from the ITnitrd Statw
6-6 6-9 6-13
6-17 6-20
7 8-2 8-7 8-15 8-19 8-23
9-7
9-11 9-14 9-18
202 264 327 373 410 350 201 266 326
364 424 202 278 344 399
204 253 302 351 398 350 201 264 299 347 403 202 250 300 332 261
ROO 600 600 600 600 50
40 35
600
75 75 73
600
600 600
600 900 900 900
900
33 34
38
64
2.0 1.9 1.7
1.6 10 16
1.9 1.8
15
1.7
2.1 2.1
74 74
2 0 2 .0 2 , (I
71 71
1.7 1.7
71
1.i
71
1.7
3:6
!::
15
4.9
..
0.91' 1.1 1.5
1.4
1.5.
27 31 33
2 .3
2,dd
6.1 6.5 5.7
1 .R
2.5 2.i
3 :i 2.8 3.3
716
2.9 2.6 3.3 3.2
i:6 1.9 2.2
1.ld I .4
28
2.2
..
1 4 2; 23
2.1 2 .0
13 12
:3 7
"1
1iO
36 33
57 57
51 51
s7 48 55
58
29
20 20 18 21 36
33
8
iil,
10 11
107 lo(, !47
11
8
i!i
10
82 86
11
9 11 11
7s
IO:! IO2
4 9 3.5 20 4 0 2.2 32 0 17 55 10 14 1 3 2.4 53 27 34 12 1.0 38 21 6.0 1.4 38 41 2? 362 76 1.0 40 18 4 8 1.8 I! 11.i > 301 75 4.1 14 0.7 0 5 57 13-7 The periods nere osle h o u r , except t o r ru11 ii i s i a T h e first number is the experiment; t h e aecond is the number of periods since t h e beginning of the ru11. which they were 2 hours. b Since 40 cc. of catalyst w-ere used, a charge of 35 grams/hr. of benzene represeiits a n hourly liquid space velociLy (H.L.S.V.) of 1.0. I n runs for which n o diethylbenaene yield ia given, t h e values in this column include diptbylhenzene as well :is h i g h e r - I d i n g C Residue f r o m distillation. material. d Includes mono- a n d polyethylbenzenes.
10-5 10-10 10 11-6 12-6
255 365 416 346 376 310
302 850 306
900 900 900 600 600 600
106 106 102 75
1.7
1.7 1.7
17
46 44
400
I N D U S T R I A L A N D E N G I N E E R I N.G C H E M I S T R Y
April, 1846
401
IO0 The benzene was pumped from a 90 graduated glass cylinder by a differ80 e ntial-piston-type pump. The ethyl70 ene was charged di60 rectly from the commercial steel cylin50 der through a needle valve, its rate being 40 measured by a rotameter. The de30 sired pressure was obtained a t the 20 beginning of each IO experiment with nitrogen. n The products from XK) 250 300 350 400 450 2OO 250 300 350 400 450 the reaction tube T E M P E R A T U R E OC. T E M P E R A T U R E OC. were released to atFigure 1. Effect of Temperature and Pressure on Conversion to Ethylbenzenes a t a mospheric pressure Benzene-Ethylene Mole Ratio of 2 by aTaylor pressure regulator: theliauid yield of ethylbenzene, The use of the higher pressures is esproduct was collected in a glass rcceiver, and the gaseous product sential for satisfactory operation because lower temperatures passed through a trap immersed in ice water and then through a may then be employed; loss of catalyst activity owing to dehywet test meter. The composition of the product was determined dration and to carbon formation is thus avoided. by direct distillation (without washing) through a 14-inch totalThe lower temperature limit was between 200' and 250" C., reflux column (6). The effect of temperature was studied in many of the runs by depending on contact time. For a contact time of I50 seconds (namely, a t 600 pounds pressure and a benzene space velocity keeping the pressure and charging rates constant and raising the furnace temperature in 50' C. increments. The product obof 1 cc./hr./cc. of catalyst), about 5% of the theoretical yield of monoethylbenzene based on the ethylene was obtained a t 202" C. tained while the temperature was changing was discarded. The results during the latter part of some of these runs may not have (run 6-5). At the same pressure but with twice the space velocbeen identical with those which would have been obtained with ity, a temperature of 266" was required to give a 7% yield of monoethylated product (run 8-7). On the other hand, converfresh catalyst. However, since the catalyst life is good, it was felt that the results would be sufficiently accurate for the purpose sion of more than 75% of the ethylene'could be obtained a t 278' of a rapid survey. and a t the higher space velocity by raising the pressure to 900 pounds per square inch (run 9-1 1). The alkylation was highly exothermic, the maximum rise in catalyst tempepature occurring a t about 300-350" C. The difI n all but three cases the feed to the catalyst bed was in the vapor phase under the reaction conditions. Some liquid phase ference in temperature between catalyst bed and furnace, together with gas exit rate, furnished an exrcllmt means of followwas present in the three runs, which were carried out a t about ing the progress of the experiment. 200" and a pressure of 600 pounds or higher (runs 6-5, 8-2, and I
9-71. EFFECT O F YARIABLES
Table I summarizes the results obtained a t catalyst temperatures of 201' to 424' C., at pressures from 50 to 900 pounds per square inch, and a t benzene space velocities of approximately 1, 2, and 3 cc./hr./cc. of catalyst. Figure 1 gives typical curves relating temperature and pressure to conversion. Increasing the pressure resulted in an increase in the conversion and a decrease in the temperature required to obtain a given
*
The effect of changes in ratio of benzene to ethylene is shown in runs8, 11, and 13, and Figure 2. The ratio of monoethylated
TABLE 11. DATAFROM 48-Hou~RUN
'
(40 c r 01 33.1 glams solid phosphoric acid, pressure 600 pounds per square inrh gage: benzene H.L.S.V., 2.1: mole ratio behzene/ethylene, 2.0) Composition of Product", Wt. % Temp., " C . Mono/ Time. Hr. Catalyst Furnace Mono Di Residue higher 1 335 304 24 3.4 3.5 3.5 2 341 306 35 9.7 4.2 2.4 4 343 307 36 8.3 3.0 3.2 11 333 307 37 8.0 3.0 3.4 23 318 306 34 7.7 2.8 3.2 305 31 8.4 2.5 29 315 2.8 2.7 2 6 34 314 305 31 9.3 40 312 304 29 5.4 2.9 3:s 310 304 28' 7.8 3.6 2.5 48 a The total roduct (3960 grams) contained 1312 grams of monoethyldiethylbenzene, and 119 of distillation residue (about half benzene, 328 of which was diethylbenzene). The yields per pound of catalyst are: monoethylbenzene 39.5 pounds, diethylbenaene 10,residue 3.5.
I
I
I
OB
I
2
I
3
1
4
I
5
BENZENE/ ETHYLENE,MOL RATIO
Figure 2.
Effect of Benzene-Ethylene Ratio on Composition of Alkylate
.
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
402
t o more highly ethylated benzene increased rapidly m ith increased ratio of benzene to ethylene. If monoethylbenzene ib the only desired product (as in the manufacture of styrene), the ratio of ethylene to benzene in the charge should be as low as the cost of recycling permits. Practically all of the ethylene and benzene which do not go to form ethylbenzenes are recovered as such and are available for recycle. CAT4LYST LIFE
A 48-hour run was made to obtain some information as to catalyst life and yield of ethylbenzenes. The conversion dropped no more than 207, during the run (Table 11). The yield of monoethylbenzene n a s 39.5 pounds per pound of catalyst. During the first 5 hours df the run the catalyPt temperature rose to a maximum of 343" C. or 36" above the furnace tempeiatuie During the next 12 hours the catalyst temperature dropped 19", while the yield of ethylbenzene actually remained constant or increased slightly. Longer catalyst life may be obtained by mor? careful control of catalyst temperature. A life test was carried out a t 900 pounds pressure and 273" C. (benzene space vclority,
Vol. 38, No. 4
1.5 cc./hr./cc. of catalyst) on a semipilot plant scale by klattox ( 3 ) of these laboratories; in 48 days of continuou- operation, 250 pounds of ethylbenzene and 41 pounds of polyethylh~nze~ie were obtained per pound of catalyst, with a life expectancy of 300-350 pounds of ethylbenzene per pound of catalyst. Catalyst life may be further increased by charging ethyl alcohol as well as ethylene t o the alkylation zone (2). The alcohol is dehydrated, and the liberated mater serves to keep the catalyst in the state of hydration necessary for highest artivity. -4part of the ethylene formed from the alcohol rearts to yield ethylb i ~ n z e n t ~thc : rc,mainder i i recycled. LITERATURE CITED
Ipat.ieff, V. N., and Schaad, R. E. (to Universal Oil Products Co.), U. S.Patent 2,120,702 (June 14, 1938). ( 2 ) Ipatieff, Tr. N., and Srhmerling, L.. I M . , 2,374,600 (April 24, (1)
1945). (3) Mattox, TI-. J., TTUILS. S m . Inst. Chrm. EILQTY., 41, 463 (1945). (4) Pardee, W. d.,and Dodge, B. F., ISD. Eluct. CHEM., 35, 273 (1943).
( 5 ) Thomas, C. L., Bloch, H. S., and Hoekstra, J., IND.P~NG.CHWM.. AKAL. E D . , 10, 15.3 (1938).
Correlating Vapor Pressure and Latent Heat Data LEONARD SEGLINI Ethyl Corporation, Baton Rouge,
A
new method for calculating saturation temperatures, vapor pressures, and latent heats of vaporization is based 6n comparing these properties for any given material with the same properties of another material whose properties are known. This method permits the calculation of saturation temperatures within = t O . S % , of \apor pressure withi n *4%, and of latent heats of vaporization wTithin * 5 % along the entire saturation line.
M
NY engineering problems require the knowledge of vapor pressures and latent heats of vaporization over rather wide ranges of temperature. For most materials, how.?ver, only limited data for these properties are available. Methods such as those proposed by Dnhring, Ramsay and Young, Cox, Othmer, and Gordon have spanned this gap between engineering requirements and limited data. Of these methods, the ones proposed by Gordon ( 1 ) and by Othmer ( 6 ) are of the greatest use. These two methods are similar, and are capable of giving highly accurate vapor pressuies and latent heats over the entire saturation line; the other methods are not capable of doing this. I n the Gordon and Othmer methodp, the vapor pressure a t only one temperature-for example, the normal boiling point- and the critical temperature and pressure are required. The critical constants can be obtained either from existing data or fiom the knon-n methods for estimating them; these methods are rcviewed by Herzog (2) and by RIeissner and Itedding ( 4 ) . The method proposed in this paper is a modification of the Goidon and Othmei methods but is simpler to handle because it involves the use of simple arithmetic calculations only, whereas they are based on logarithmic calculations. The accuracy of the three methods is the same. 1 Present address, Westvaco Chlorine Products Corpoiation, X e w Y ork, N. Y .
Lit.
The method presented in this paper is derived by starting with the Clapeyron-Clausius equation for two substances. Ono of these is the unknown Ti-hose vapor-liquid cquilibrium propcrties are to be determined. The other substance is the refcronce whose vapor-liquid equilibrium properties are completely arid accurately known. By equating the reduced pressures of the unknown and the reference, substituting T,T, for T , and rparranging, the following is obtained:
This equation holds for equal reduced pressures of thc unknown and the reference. T o integrate Equation 1, it was aseumcd that LIL', xhere both latent heats are taken at the same rcdiiccd presPure, is constant over the entire saturation line. This assumption introduces only small error,?as shown by the appliration of the integrated equation to actual data. Then, integration of Equation 1, lvit,h the condition a t the critical point, T , = Tv' = 1 and P, = P?'= 1, gives the following equation, holding for oqual reduced pressures of the unknown and the reference:
Thib equation is the basis of the propohcd method tor correlating the vapor data of two different matcrialh. ANALYTICAL METHOD SATURATION TEMPERATURE AT 4 G I V E X PRESbURC. Saturation temperatures for different vapor pressures can be calculated from Equation 2. These calculations can be used either to extend experimental data beyond the range of temperature covered or to smooth out dubious experimental data. The calculations involved can brqt be illustrated by an example. Consider the
.
