Title Chemical kinetics in the reaction between NH3 and ... · 15 F,~ry3 : Pt03 m 2 1 190°C 6xp.35 t3 1~ t l00°C Exy.3 m B t 1 190°C Sry. PS ° 9 4 1 150°C 6xP-1B 11 4 1 100°C

Title Chemical kinetics in the reaction between NH3 and CO2 underpressure

Author(s) Kiyama, Ryo; Suzuki, Keizo

Citation The Review of Physical Chemistry of Japan (1951), 21: 23-30

Issue Date 1951

URL http://hdl.handle.net/2433/46664

Right

Type Departmental Bulletin Paper

Textversion publisher

Kyoto University

The Review of Physical Chemistry of Japan Vol. 21 No. 1 (1950)

CHEMICAL KINETICS IN THE REACTION BETWEEN

NHa AND COz UNDER PRESSURE.

liy Ryo Ktva~ta and Kcizo Suzu~:~.

The study of the field of kinetics of the reaction behcecn \ I I, and CO_ under

pressure has scarcely been done. Therefore there are many obscure points. In the view of chemical kinetics, this investigation is carried out in order to clear

the mecl'anism of the reaction.

Apparatus and Procedure.

The schematic layout of the equipment is shown in Fig. I. ~\, is the reaction

vessel made of mild steel, the volume of which is 43 cc ; A_ and .4;,, the bombs,

each being filled with liquid Nff, or liquid CO,; r\„ the spiral tube in m~der to

preheat CO, gas ; G, and G.,, the burdon type pressure gauges ; "1'„ the copper-

constantan thermocouple, which is

put into the reaction vessel ; T.;and T„ the mercury thermometers;

the train of points denotes the

electric heater; V„ ......, V,,, the

valves. The samples, N11, and

CO_, arc stored in :\, or A; 6om

each convnerdll bomb and high

pressure is obtained by heating.

The procedure to carry out

the experiment at a given ratio of

pariial pressure of NI [; and CO_

is as (ollotrs; gaseous CO, is charged in

of G, becomes equal as' the partial pre:

and then until the reading of G, comes to

then the reading of G. falls down from

is charged into the vessel in use of the

reaction.

The esperintental procedure is as fo

>I5 As

Va

T~

vq

va

ez

vi

~ ,~ Pig. 1 Schematic layuW of equipment.

1 into the reaction vessel until the reading

pressure of \ H.; in the case of espcriment

to a definite total pressure of esperimen4

m P, to Yo. Tlius a given quantity of CO,

the reading of P, and P_. in performing the

follws; gaseous NH, is charged into the

TM

I

n

II 1 ,A..

i--®

nI

k n:*an

`t91:.,

i

t

I

i i

i

I

I

~,

.i

I

N 6

Y

O

O

m

9


,°,} it. K71':filL1 and I:. SU'LDK7

reaction t•essel under a constant pressure and a definite quantity of gaseous CO,

is led into fhc acsscl in use of G,, as above mentioned. ~~ftenvards the readings

of G, against time arc recorded. `1'hc ratio of packing calculated as NII,C0~1'I-I _, from the pressure is 0.0~~-

0.`21 s/cc in tltc range of the reaction.

Moreover, after the reaction finished, the resultanU are cooled rapidly and

the sravimetric analysis of urea is carried out. The reproducibilih• of the csperimcot is within >°,n of the initial pressure

in the readings of Gr.

Experimental Results.

The experiments are perform=d in the range of pressure, 15210 1:5/cm-,

temperature, GO-•200°C, under various rations of partial pressure. Fig. ?-Fig. fi arc the pressure change curves plotted Crow the data of t;•le readings of pressure

sauce against time. Fig. 7 is the results of the urea Conversion percent curves.

s y PNNS~ PCOt

15 F,~ry3 : Pt03 m 2 1 190°C 6xp.35 t3 1~ t l00°C Exy.3 m B t 1 190°C Sry. PS

° 9 4 1 150°C 6xP-1B 11 4 1 100°C ffi9.5 m 6

9 m E t 100°0 6x9.2 n~ 2 : 1 150°0 6t9. 17 7

n 10 5 ~ t 3 13tl°C 6x9.8

J ~ 30 2 I 60°C 6x91 ~ EO i

10 EO 30 q0 50 ed 30 EO 30 40 50 80 00 lE0 'limo ;r.in.~ T1ae l~n.,

Fig. 9 Pressure change tunes. Fig. 7 Pressure change curres. Initial Preswre lb kgJeni=. Suitial press'are 36 pgja~,=.

Discussions.

Prom the pressure chance curves, there are bl•o cases; ate, a rapid pressure

decrease occurs, and the other does not, at the initial step. of the reaction. .\lso,

it is shown in the Urea co~mersion percent c_uves. Pig. 7, that there is some

difference in the forms of the reaction.

(I) The formation of NH,GQ_N~_

From the reason discussed below it can be considered that the rapid pres-

t6

t3

it

5

FHry3

i

P~Oy

I00°C 6xy.s

i

4 toa°C IDro. S

9

9

6

l

~~ O8 ~0

E

2

l taa°c

60°G

6LP.2

Bxy.l

~ J

B

PNNb

2

FCOp

1 1 90°C 8xp.35

L 1 170°C!i

7q

,aI6

~O

40

30

YO

Sry. ?5

150°CO

1 1 ~p.1B

_~6Yy,17

ID[P•B

2

t

i

3

150°C

13tl~C0 0

30 EO 3G 40 50 80 00 1b0


CIIE~1rC AI. 1iINF.T1(.S IN TIIE RF.ACTInN RETNF.EN Nlr} AN17 CO. Sl

d[NH4CONHe] =k,[Lrtennediate product]. (4) dt

As K, is the equilibrium constant, from the step (1)

[Intermediate product]=K,[NH,]'[CO,J. (5)

In such a case as N}hCO.NH_ is not formed, accordingly, from Equations (4) and

(u"") the velocity of urea formation gives

d[NII,CONHo] =K,k,[N[I,]°[COs]=k[N}1~=[CUo], (8) dt

where

k=Krks• (~

Aifferentiating with respect to temperature from the Equation (~,

d LIk d I nK tl hlk ( ) dT dT r+ dT ~• 8

If A is the activation energy corresponping to d•, A„ the activation energ}• of

step (3), and Q„ the heat of reaction in (1), the next relations are given,

d lnk _ A d lnk,= A, d InK,= Q, (9) d T RT' ~ d T RT= ~ d T RT' '

where it is presumed that the endothermic heat of reaction has a positive sign.

From Equations (3) and (9),

The heat of reaction in the case of the formation of NI I,CO,NH~ from NH, and

COYìs about -40 kcal'r. Then, it is permitted that the heat of reaction in the

step (I) tikes the value nearly -40 kcal. The value of A is about -20 kcal as

above described and so A, can take a positive value. From these considerations it can be recognized that the velocity constant, k, of this reaction in which

NH,COpNIie is not produced has the negative temperature coefficient.

The authors express hearty thanks to the Ministry n( Edccation for the Scientific Research Grant.

Tke z~r,~•~~ry of Physitn! Ckeouistry, ICyato University.

4) k. C. Clark and II. Q Iietheringlnn, f. Anr. Chrm. 3oa, 99, 1909 (19:;)


CI [F.V ICe11.

sure ch:mec aC the

K iNE'CI(S IN 'CI{Is Rt:AC'1'1f)N IiE'CWhaiN Ntia ANn Cf)_ 9."t

initial time of the reaction is due to the formation of

grw LJO

le0

~ll0 2100

à YO

e ~

70 9 2w

enns.

a`---a_ 0^0+

A

L: ~?-

a;

~O=

E:

xos

• aoo°e re.~e

i

i

i

i

i i

lOTt: O[p, 56 O

190°C tip.51

r r may, ya

19WC Zrp. aO 160°C pp,El

~~

180°C isp.>Q

1' __ --

0140 a .

150

i la

110

100

° 00

o ~

m 90

[e1t181 pneaurs

150 t~a~ tiy.50

lE0 tg/~ tip.>e -O

40 tg/mtOtap.B

60 aH/cnE Rp.E9

10 a0 tO 60 1M 10 W 80 10 0 aD Oti- 140 Tla~ (Vy.t 91ma Imf °-1 Pig. ~1 l'n5surc change curvt5. Fig.:i Prtssure change tunes.

hlilial pressure 1501;gfcm=. 1',t•Ha: YCYS_C: 1, 1;0°C.

I) From the dissociation pressure cf NII,CO.NH.,.

In the case of F:xp. 1 at (i0°C in Fig. 2, the rapid pressure decrease and the

heat cvolntion follow at the initial tiute, then pressure decrease, to L kg/cni'.

The pressure, 1 kgjnv°, is the dissociation pressure of NH.,COe\H.1 at 60°C't and

under such condition file formation oC urea does not occur. Accordingly the

curve can be considered as the one of the formation of \II,CO_\I-1._

The comparison between the pressure at the inlle~ion point*, where the curve

showing the rapid pressure decrease at the initial step crosses the following slow

change curve,:md the dissociation pressure of .\'ILiC(J_\FI_ estralx~lated frrnn the

data of Egan ct al"., at the same temperature, is shua'n in Table I. Moth pres-

Tahle ]

Eep ~~ ~ Temperature t°I } Initi9l press. f~Sfrnl=)

v

~I

30

:LI

101 (lOD)

l3G (130)

15S (150)

16i (100) li5 (li0)

134 (lS0)

!a

UO

1•iU

15U

I:~

X10

Press. al the in0esion Disncial ion press. at pt. (kg/cm-) NII,CD_\IL (kg/cm=)

B

Sri

qti

100

la::

li'

i

'J

,li

4~

1(la

ldl

13~

1) ] I'. 1?gun, f. li. 1'ous and r.. D. I'ous, Jd. h.'qs. C/r~iu., 3d, -4:i4 (19-IG) ~ Lr the graphical e.pr4sinn n( the equntiun cunxrning In the Ihinl order reLrcity constant

, desvibed Inter (Chemical lr inerics in the cenClion ..t um &rtinnliwu), !wn strnigh! lines crcns a! the initial

rirate. 'l'ire trussing point is rtganle<l as the in8esiou Iwiur.


°6

surer in

rz

_ laa

~'ltaa +~lm

~Iro L lao

2 ~

L o ~

° ~o

a

~ ~ eo

the

R. KTl'A~IA

comoarison nearly coincid

to ro x ~o so rm. tm.i

Fig. 6 Pressure cLange carves. lu0°C. Initial pressure

Q l50 kg/cm= Insp. CO ~ 1E01:G(cme Esp. 19

~ 53 k~(cm= Exp. 1'i Yvxy: Yaw_=a.1:1

3) Prom the relation of the dins The relation of 81e dissociation e

N' H,CO,NH: (solid)-- 2NH,+CO:. In next relations are derived from the DI

r 3 ~~ a ~~ ra, where c„ e, are respectively excess in

normal dissociation pressure of NH,C

of NH, and CO, is stoichiomctric,

NH,CO,NHq in the vapor in the case

dingly, the total pressures are c,+^ 1

T

and K. SUZUKI

e. The value shown in the parenthesis in

the temperature cohtmn is the tem-

perature before the reaction begins,

but owing to the heat evolved

at the initial time of the reaction,

the temperature rises, and then at

the inflexion point it becomes the

value shown on the left hand of

the temperature column. Fig. 6 e

shows the rapid pressure decrease

e~ at the initial time in every case of the initial pressure except

v3 kg/an",less than the dissociation

pressure of NH,CO,NII,, has the inflexion point at nearly the same

point. ociation equilibrium of NH.,CO_NH,.

quilibrium of NH,CO VrH., is as follows ; the case of excess of NH;, or of CO_, the

ass Law"'.

T~ 3 ~~ Za/ R~, presure of NH, and of CO._ T~ is the

O;NH_ when the ratio of partial pressure

a is the partial pressure of dissociated

of having exccs§ iu NH, or CO_. Accor-

vhcu NH, is in excess, e,+- in excess of

able 3

Esp. No.Temperature

(eC)Initial prc5s.

(via=m')

3

18

31

los (loo)

loa (look

153 (150J 774 (170J

15

15

150

4:1

1°

~:1

4:1

Press. (kg(cm=)

obs.

11.0

13.8

73.5

140

cilc.

11.0

13.4

73.9

]43

9) T. R. Briggs and V. \ligrdichian, J. P/ry.r. Chnu., 28, 11_1 (194)

The Review of Physical Chemistry of Japan Vol. 21 No.

CIB's?IICAL KINETICS IN THE 1:E:1CT10N BETWEEN NI[a AND CO= 117

CO_. It has been experimentaly proved that this relation holds in the ]ow pres-sure rcgion't. In Table 2 the conaparisoas bchvicen the obaelved pressure at the

inflcsion point and the pressure calculated from the above relation are shown and the consistency in both values is good. The parenthesis in the temperature column denotes the same as in Table 1.

Nfi.~CO,NII, is not formed under the lolver pressure than the pressure of

dissociated NI-I,CO.,NII_. ~Yhen the dissociation pressure is 750 kg/cm', the tem-

perature is 176'C*. Prom the pressure dlange curves in Fig. 4, the rapid pressure decrease at the initial time occurs at the Ycmerature below 770°C, while this rapid drange does not above 180'C. From Che correlation between the condition of

the NI-I,CO,NH_ formation and these pressure change cnrves, NH,CO.~I-L, is

formed not above 1.80°C, bat below I70°C. .11so, in Pig. >, NIIaCO_NlI_ having the dissociation pressure of L6l:y/uii= at 170°C, in the case of the initial pres-

sure 1c70 kg/au=, the pressure decreases rapidly at the initial time, while in the case of the initial pressure below L'261cg/cm=, the rapid change does not occur.

In other cases, the elperimental results are satisfactory in consideration. According to the above consideration, the rapid pressure decrease at the

initial time of the reaction is due to the formation of NH,CO,NH. and the for-mation of NH,CO~NH, is dependent upo~1 t11c initial pressure which is higher

than the dissociation pressure of NH,CO.NH...

(II) The formation of urea. 1) General consideration.

From the results of the quantitative analysis of urea it may be found that

it is always possible to produce urea whether NH,CO,NH_ is Im'c

formed or not. The urea conver-

sion percent curves, Fig. 7, are

the results in the same condition

as the pressure change carves in

Fig° 4. At 150°C and 1.60°C NH,-

CO.,NH° is fornted and at 180°C

and 190°C is not, as described

before. However, the formation

of urea occurs in both cases.

accordingly the view that NH,-

w a 0

:~

G,a

O

1 (1950)

O lso°c

IYO°c

30 JO 00 pp T1ma (m1n.l

Pig. 7 Urea convereien °6 Nn•es. Initial pressure 150 kg~cm~. Ps~~; : Pcvi.=::1

* ct. 1J

L10

i


i:8 P.. K11'A\tA and li. 5UZUK1

CO,NH., is the direct iutermediatc substance in the reaction mechanism is not

generally admitted. In the pressure change cun•es at the condition that iVII,CO_NH, is not

formed (i. c. above ISO°C in Fig. 4), the pressure, in any case, decreases below

the equilibrium pressure" in the formation of urea. From this result it may be

considered that the reaction oP urea at this conditiat goes on in the gaseous

state.

In the urea conversion percent curves, Fig. !, the temperature effect on the

urea conversion is reverse between 160730°C, namely the limiting temperature

of the existence of VH,CO.NH_,.

The effects of pressure and the ratio of partial pressure on the urea con-

version percent from the results of analysis are shown in 'T'able 3. Excess of

'1'xble 3

F..p..iu.

t', n~

3i,

3f,,

3V

31

°:~

^G

i

i

'temperature (`r)

15U

lu0

7.90

]9l1

liU

liU

770

7iU

Tiive of rcactiov (mint

Initial press. (~Sicm=)

I',w?a : I'cn,

:.o

:.a

ca

ca

is

i~

i:;o

1 ~~

~o

tso

so

~so

iso

i~o

su

90

~:,

~:,

,~:1

3:1

~:1

d:l

~:I

11

is rea cnm'ersion lip)

1.. 0

O.:i

0.0

10.8

Sri. 0

$li.

i. i

11. fi

• The case , $I[,CO:NIi_ is formed.

NH, and the pressure effect upon

CO~,ATI-h_ is formed or rot.

?) Chemical kinetics in the

The order of the reaction is

lion velocities in the rivo cases 7

the yield of

reaction

obtiined

and 3.

urea are recognized o~hether Nl-I,-

of urea formation.

from the folllvina relations of the reac-

lvhen [Peon]

dt

i-[hCOz]er

[Pco,]

~u=

~r

rtx log

dt~

~~

_)o~~r~, qtr

IOSLhYH.;~~-IOgLY\H~~e~

3) ~f. 1'nkunka, f. Agr. C~kvu. Snt. Jrspmq IQ 1333 (19.`34) C. )falignon and )L Frejacques, Cumis[. rwd., 174, lib (10"_2)

R. KiYanu and II. Kinoshita, ThIS,JJId'n,1(, 21, 0 (1051)

• The Review of Physical Chemistry of Japan Vol. 21 No.

CHE31h1AI. R]N]iTICS 1N 'CI[li P.fiAC1'fON ]1GT1\'EEN NI1~ AND Cp._ _9

logdr,-lood..t"e

11= ~~ (fR

\vhere Psea and Yco_ are the initial partial pressure of ATH, and CO_ respectively.

Table 4 Substituting the experimental results in

the above relations, the values of In and

FÌ'• Ine~l P. n, P~.,. ,,, a arc obtained, which are shown in Nn. III '6lcm=)

_ Table 4. Prom the sum of fra and ra the

s, so co ~ ,au ~, 0 1• o ' order of the reaction is regarded as the .„ too cn :1o third order. Assuming that r: and h

s~ oo 40 ô t.s 1•o are respectively the initial partial pres-

:ta oo ;ro i °o sure of NH, and CO_ and OP is the

('Cempemtnre, 1:(VC) quantity of pressure change, the third I'.vui, 4=. 40 of Fsp. No. 1LR, ̀̂ ~ are

rcgardea as o,e same presure, order velocity earstant is given as

.follows ;

1 ~ 3 P(2G-a) h~n-~~ ;1 ~•- }?. 3q3 IoQ c~) {rr~n-~.; ~ n~L 3

but when a=?b,

Accordingly. the valves n( the bracket in the former equation or (3b-OP)-= in

the latter against time arc plotted as linear relations and also the tangents arc

proportional to the velocity constants. The time range satisfied with linearit}' in the case of Psn,:Pco.=2:1, is sho+ter than in the case of Yxu,:Pco_=4: 1.

Table 5

i i ~.~~; so i co ~ ao s. o

~Y! ~~ ~ ~~~ i~~

An f0 ;Q n~ ~ ~.5 ~.

.W ~U id ~~

1 (1950)

Esy. \aTemperaturc

(`~ )Initial press.

(kgl«n%) Puts:It~q Vclncih' mnsl.'mt 10~ (cndfkgs . min)

'-

~~

_~

ss

s^

sc

1S

170

170

170

1~0

190

°00

so

90

loo

l00

160

160

~:,

~:~

~:,

~:,

,, :,

~:,

~.~~ ,.~

,. o

~.:;

~,.

- The Review of Physical Chemistry of Japan Vol. 21 No. 1 (1950)

3o K. Kll'ADfA and R. S[17.UK1

It may 6e considered that the continuation of linearity is due to the opposite

reaction that is prevented by c~cess of \I-i,. The veloeity constants obtained

from the above relation, are shown in Table 5. That is, the velocity constants

have the negative temperature coefficient and the activation energy calculated from

the relation of logk- ,1-r is about -30 kcal.

The velocity constants shown in Table G are the values obtained when

NH,CO,NH_ is not formed. The yields of urea calctdated from the velocity

constants and the observed yields in the case of the formation of NHaC0~1\TH.

are shown in Table C. The calculation is as follows;

Table ~

E <p, Nn.

_-4R~ ...

80.

=1i

"A.

Tempentum (°<7

_ 1HO 170

1f0

];.n

Velocity constant 10+

1.0

l.G

3.1

a.

Weight of urea (g)

talc. ~ nhs.

O.S

0.7

o. a

0. A3.4

0.7"_0

0. &03

0. fi.^.4

(Grilinl pressuc, 1fi0 kg~cm=; Pn up: PcM=~:1; lime n( reaction, 130 min.) • extrapolated vaL~e.

field of urea m wci ht =nk ~ Iu I'co_ =uk ~ 2P :( P

where P is the reading n( pre>sure gauge, a is the pn,pottional constant deter-

mined by substituting the 1;•thles at 130'C (NH,C(~ \H, is not formed) in Table G. The calculated weight of urea and the observed arc the values at 30 minutes.

Accordingly, it can be crnysidered that the reaction of urea formation almost

proceeds in the gaseoas state, even in such a case as NIf,CO\II4is formed; at least in the initial state of the reaction.

3) The reaction mechanism. From the reason above described the following mechanism is proposed.

2NH,+CO, ~ Intermediate product. (1) Intel mediate product F NH,CO,NH4, (?)

Intermediate product -~ ATH.CONFI_+fLO. (3)

The step (°_) is )tossible only when the initial pressure is higher than the

dissociation pressure of NH,CO,NhI,. Assuming the equilibrium relation is always CgtalJll$hMI in the steps of (I) :cod (3) and ka is the velocity constant of (3), the Velo:ity of urea formation redeces to

Documents

Title Chemical kinetics in the reaction between NH3 and ... · 15 F,~ry3 : Pt03 m 2 1 190°C 6xp.35 t3 1~ t l00°C Exy.3 m B t 1 190°C Sry. PS ° 9 4 1 150°C 6xP-1B 11 4 1 100°C