properties are virtiiall~;unchanged by addition of solvent. ..Ic.oinl)lairit sorrictitnes heard is that r e s i d u a l solvent caiiscs l)listering at thc t.esii.l surface i n a molding operation. ' I his problem \vas not rncl3untered i n inaking X 9 X 2.5-inch boxes i t t a n A L P ( : hlodrl 5200 niatclird-metal die inold with those resiiis containing 1 L;.; solvent.
Acknowledgment
Conclusions
literature Cited
Proccssing c>cles of unsaturated polyrstcrs c a n he effrctivcly Icduced with csrcrilicatioti catal>sis. It is ditlicult t o pwdict i n advancr. however. ~vtiirhcatalyst to use. O n e should not be discouragrd by initial failurrs. s i n c r this studv has sho\vn that difleretit foirriulatioii~~ favoi difIc-rciit ( atalyst s>.stcnls. 'l'his stud!- c n v r t s those g l ~ c o l s\vhic.h are most cornrnoiil) u s t ~ but I aril!, i n a liniitcd s r t oi'LrSiiis. Catal!st sclt,ctivity \\.it11 less cotninon gl!c~ols is (,iirrrtitly undrr irivcsrigation i n thrse I a bora t orics. I V h c i i catalysts are not sufficiciitlb- effective. solvent processitig rail he used. It inay not bc iiccessar) to remove last tiaces of solvent a t t h c end of a r u n because they apparently d o not signiiicantl>- altrr msin propcrtirs. A cornbination o f catal\.st aiid solvrnt in t \ v o - s t r p p i cparations ma!. somrtirnrs be profitable.
(I)
-
I lie authors are gi-atcf'ul to J. \'. Prcoriotn arid I'. E . I h t y lor help i n obtaining iriari! of these data. a n d to the Oronite Divisioti of (hlifor-ilia Chcniical C h . for suppot tirig this \voi.k.
:\!TI.
Soc. 'I'rsting Matrrials.
Philadrlphia, Pa.. ' V S ' I M (;,,
Hugginr, I>.(;,:
( 3 ) 1)unlap. 1.. H.. H r c k l r s . .J. S . , J . Ani. O i l Cherrii.c/.r' ,Sue. 37, 285 (1900). (4) Enctirian Kodak C h , , 'l'rcli. 1)ata Kcpt. N - 1 0 6 , Kochrster. S . I,., 1959.
( 5 ) 1.r B i n s . 1.. K.. Stalir. 1). F. ( t o Pittst)rit.gh Plat(%G l a s s Ch.), L..S. l'atcnts 3,055,867 (Scpt. 25, 1962) : 3,057,824 (Oct. 9,
1962).
(0)'\Vriher. F'. S. ( t o R . t . Goodiicli C h . ) , / b i d . , 3,056,818 (Ocr. 2 > 1962). ( 7 ) LViIson t. LV.. Hiitc~liins. .T. F,. (tci l..astrndn Kodak Co.)? / h i d . . 3,055,869 (Srpt. 2.3, 1 9 6 2 ) .
RASCHIG SYNTHESIS OF HYDRAZINE
The hydrazine-forming stage of the Raschig synthesis has been investigated in a continuous tubular reactor operating a t 480 p.s.i.g., 160" C., and residence times up to 12.5 seconds using 2.070 (ethylenedinitril0)tetraacetic (acid (EDTA) as inhibitor. Four methods of operation have been studied: direct reaction of aqueous chloramine, reaction of chloramine with anhydrous and with 3570 ammonia, and direct reaction of sodium hypochlorite with ammonia. The optimum reactor outlet temperature was found to be between 1 6 0 " and 200" C. and hydrazine yield was shown to increase linearly with reciprocal residence time in the first system. Mole ratios of NH I/NH,CI effect in all four systems.
gave increased yields and chloramine molarity exerted an important
€ I t , t i n t stag- tlie addition of solid -ields tend I O Ir\,el off at 1 6 n o to 200' C.. f u r t h r r rises in temperature giving only small increases in yield. ' r h e ciirve given by Reed is similar in shapr to rhe ciirvrs presrntcd. b i i r thrrr is disagreenirnt in the lo\v temperarui~errgion and in clie p i t i o n ing of the curve Lvitli respect to mole ratio. These points can br rsplainrd b\. thr fact that Reed gives no chloraminr molarity and his yirld is hasrd on initial sodiiim h>~mcl-iloritt~ instcad of chloramine.
I I i l I
1
9
or
8
0.
,
-
8 0.1
-
70. 70.-
60.-
s!
60.-
4
a W
0,
2
0
50..
2
W
3z >
_1
0
-9
40.-
I
40.'
z
z
$
50.-
2
I-
3 0.
-
30.20.-
20.-
10.O t
0. C.
0.05.
010.
045.
CH1.0RAHINE
Figure 6.
0.20.
0.25.
CHLORAMINE
MOLARITY
Figure 7. contours
Hydrazine concentration and yield contours Anhydrous ammonia used
'l'he conclusion that can be dra\\-n is that the most suitable reactor outlet temperature is bet\\een 160' and 200' C , . depending on the mole ratio S H s S a O C l emplo!,ed. l'igure .'Idemonstrates that both S H 3 NH?C:l mole ratio and chloramine molarit!- grt-atly aifect >.ield, The yield contours iiicieasr \\-ith increasing mole ratio but she\\- a turning point \\-ith chloramine molarit!, a t 0.1 1.11. It is difficul t to compare these yield contours \\ ith the results of previous Lvorkers f 7 . 3. 6). as they have not reporrcd the chloramine concentrations a t \vhich they studird the effects of mole ratio. or the mole ratio a t \vhich the!. studied the ef?vct of concentration. The!. d o shoiv. ho\vever. that increasing mole ratio increases > ield and increasing chloramine molarit). decreases !-ield. agreeing basically \vith the results presenied here. 'The relationship bet\vt:en residence time and )-ield
0.1 5.
0.1 0.
0.05
0.30,
0.2 5.
0-20.
MOLARlTY
Hydrazine concentration and yield 0.880 sp. gr. ammonia
8O.V
7c
I \
60.-
0 c (L 4
50.-
W
-2
U
40.-
0
demonstrates that the maximum possible yield improvementi.e.. Lvhen the residence time is infinity-is 2.'67;;. T h e equation enables a n actual residence time to be chosen that \vi11 give a )-ield improvement as close to the maximum as possible. Anhydrous Ammonia Make-up System. From Figure 3 it can be seen that "the effect of reactor outlet temperature" curve is very similar in shape to that in Figure 2. T h e yields again level off bet\ceen 160 and 200 O C . . but \vith anhydrous ammonia. hydrazine is formed from 40' C. uplvard. T h e curve agrees Lvith the work of Sisler (5). lvho gives curves for three higher mole ratios a t temperatures u p to 100' C. His Lvork, hoLvever. does not sho\v the leveling off of yield between 160" and 200' C. Figure 6 sholvs that over the range investigated hydrazine yields vary from 35 to S07c. increasing Xvith increase in mole
-5 I
z
30.-
-
20.
IO.
-
I , , , , , ,
0.
0.05.
015.
OiO.
HYPOCHLORlTE
Figure 8. contours
Hydrazine
0.20.
0.25.
030
MOLARITY
concentration
and
yield
Separate pumping
VOL. 4
NO.
1
JANUARY
1965
75
I t is difficult to compare the yields for separate pumping, as these include a loss of )-ield in the chloramine stage. Extrapolation of the data given previousl!. (2) shoivs that the chloramine Jield expectednould be of the order of907,or more a t the higher mole ratios and this s!-stem would be as efficient as the aqueous chloramine s).stem in this region. I n the low mole ratio rrgion the chloramine yields \\.auld be as lo\v as 70% in a nvo-stage process? indicating that the separate pumping system \vould be the most efficient.
loor
80
-
D I
60-
> w
t
2
40-
Conclusions
0
20
40
"~/NH,CI
Figure
9. H
X 0
A
eo
60
100
MOLE RATIO
Yield from four systems Aqueous NH2CI solution 0.880 sp. gr. NHI solution Separate pumping Anhydrous NH3 system
ratio u p to a mole ratio of 60 to 1 and then leveling off. -In increase in chloramine molarity reduces the yield over the whole range of 0 to 0 . 3 0 M . T h e h>-drazine concentration decreases with increasing mole ratios, but increases Lvith increasing chloramine molarity. These findings agree with the curves given b>- Sisler et ai. (5),which show a n increase in hydrazine yield ivith increase in mole ratio but decrease in yield u.ith increase in chloramine molarity. Thirty-Five P e r Cent Ammonia M a k e - u p System. T h e yield and concentration contours (Figure 7 ) demonstrate that the values and directions of both sets of contours resemble those obtained using an aqueous chloramine feed more Than the contours obtained using anhydrous ammonia. This section of the investigation is intermediate between these two extreme values and 35% ammonia has a molarit)- closer to that of aqueous than anhydrous ammonia. T h e yield contours with 35% ammonia vary between 50 and 9OyGin the range studied. Separate P u m p i n g of Ammonia a n d Sodium Hypochlorite. T h e )-ield and concentration contours are again similar to those obtained for aqueous chloramine: except that no turning point with sodium hypochlorite molarity has been obtained. I n addition. the yield contours appear to be less dependent on sodium hypochlorite concentration above a value of 0,O.j.V. Comparison of Yield O b t a i n e d from Four Systems. For compariion purposes a chloramine or sodium hypochlorite reactor concentration of 0.15hl has been chosen and the yields obtained \vith various mole ratios a t this concentration are plotted in Figure 9 for the four methods of operation. T h e curves show that the highest yield is obtained. a t a given mole ratio. \vhen aqueous chloramine solution alone is pumped into the reactor, Xt a mole ratio of 30 to 1 a hydrazine yield of 657, is obtained. To obtain the same yield with the anh>-drous ammonia system a mole ratio of 60 to 1 is required. a n d \vith the 0.880 specific gravity ammonia system, a mole ratio of 37.5 to 1 . 76
l&EC
PROCESS DESIGN A N D
DEVELOPMENT
Operation of the apparatus described in this investigation a t a pressure of 480 p.s.i.g.. E D T A concentration of 2.OYG> residence time up to 12.5 seconds. and reactor outlet temperature of 160" C , has enabled the follouing conclusions to be drawn on the formation of hydrazine from chloramine. Using the aqueous chloramine system h>-drazineformation commences a t 75' C.. while with anh)-drous ammonia 45' C. is sufficient. I n both systems above these temperatures the yield a t first increases rapidly I\ ith increase in temperature and then levels off a t 160' to 200" C. decrease in reactor residence time from 1 2 . 5 to 3.5 seconds with the aqueous chloramine system leads to a decrease in hydrazine yield. obeying the equation:
Extrapolation of this equation to R = m sho\vs that the greater than that obtained maximum possible yield is 2'6% a t a residence time of 12.5 seconds. At constant chloramine molarity a n increase in mole ratio S H 3 SH&1 in all four systems increases hydrazine yield. At constant mole ratio S H 3 SHzCl an increased chloramine molarity leads first to a n increased yield? ivhich then decreases bvith aqueous chloramine and 0.880 specific gravity make-up systems. Experiments employing anhydrous make-up resulted in a decreased yield. while Ivith the separate pumping this system sho\\-ed a n increased )-ield. Of the four methods of operation. the highest hydrazine yield is obtained for a given set of conditions using the aqueous chloramine feed. T h e lowest yields are obtained \Then anhydrous ammonia is employed. \vhile the use of 3jyc ammonia gives intermediate yields. Finally. pumping the reactants into the apparatus separately appeared to give yields comparable \vith those obtained using aqueous chloramine. Acknowledgment
T h e authors thank S. R . M. Ellis, Chemical Engineering Department, University of Birmingham, for his help and advice throughout the invebtigation: and the directors of Whiffen's, Ltd.. for financial support that made this study possible. literature Cited
(1) Drago. R . S . . Sisler, H. H.: J . Am. Chem. Soc. 77, 3191 (1954). (2) Ellis. S. R. IvI.. Jeffrel-s, G. V., FVharton, J. T., ISD.ENG.CHELI. PROCESS DESIGN DEVELOP. 3. 18 11964). (3) Jones, M. M., Audrieth, i.F.,'Cotton, E.. J . Am. Chem. SOL. 7 7 , 2 7 0 1 ( 1 955). (4) Reed. R. A , . "Hydrazine and Its Derivatives:" Royal Institute of Chemistry. Rept. 5 (1957) H. H., Boatman. C. E., Ne
RECEIVED for review October 25. 1 9 6 3 ACCEPTED Januarv 27, 1964
