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Note in connexion with the paper “Kinetics of watergas conversion reaction”
Letters to the Editors ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• Note in connexlon with the paper" Kinetics of watcrgas conversion reaction' '* no eonversion of Fc 3() 4 in Fc or \'i('(~ versa. should occur for a l120/CO ratio of O·H14, usin~ data hy 1~1\IMJ":TT and SCJJUI:J'~ [1]. The eorresponding saturator tClllpcraturc is 75°C. The nuthor's cxpcrirllcntal valu(~ for the I'utio at "'hieh no reaction occurs is 0,70, ('orrcsponding to 78°C saturntor tcnlpcrature. Although the author interprctecl this cxpcrinlcnt ns It dctcflllinntion of the 1~~e3()4 - Fc() C(IUiJiw briulll, it tllust have heen the Fc 3 0 4 - Fe cquilihriuln. 'fhe discrepall('y in the I-I 20/C() ratio Illight be eaused by cxperiluental errors (ndjusttllent of saturator tClnperature, J11CaSUrelllcnt of (~atnlyst tClll»eraturc) or hy a dit'fusioJlul resistance. Ilo\vevcr if thesc nrgull1Cnts do not offer a satisfactory expJanaticn, the hypothesis that cquiJihriull1 is estahlished, on \"hit'h HlC Hutllor's further {·onsideral.iol1s ure hased, luight he at fault. G. VAN DEN IJElu; ~v. v. 1'1ckog, ~juudrJt~lI, ~\'t'lhcrl(JlI,h~
IN his discussion on the possibility of reduction of the catulyst (p. 137) the author calculated the oxidizing potentinl for the reuetioll BFeO + 1 02 = Fc 3 0 4 nt 5()()OC. l"rolll the thcnllodynuluic point of view, ho"'cvcr, J?cO is not stable lJelo\v 565 0 [1]. The reduction of 1("("3°4 should therefore proceed to Fe. If the author hus extrnpolated the iron-oxygen dntu. to belo\v the quadruple point of 5650C, the oxygen pressure for the }?cO -li'c cquilibriulll should hnve been lligher than thnt for the Fc a0 4 - I~"eO equilibrium. I-Iowevcr ill :Fig. 1 the t\,"o cquilihriuln pressures are in the natural order as would be the cnse only above the quadruple point. It is coneluded therefore that the values for the t\VO oxygen pressures as itulicated in Fig. I cannot he both correct. Sincc thc Huthor's references to the sources of his therilloclynuinic data. arc inconlplete, it is inlpossiblc to verify his (~alculations. If u mixture of FeS0 4 and Fe is contacted \vith to and 1-1 0 under conditions ,,"here cquilihriulll is obtained, at 2 • ]l. BOUTOLINI C/tCU/. E'Ilgng.
,;()()OC
Soc. 1058 9 la.;.
It 1': F J'~ [1]
P.lf.
EMl\IEl''1'
und J. F.
llcply to lite LeUer /rolli.
)u.
Kinetics of
It ENe I'~
SCHULTZ .I111U',..
G.
VAS DE!\'
*}). 11olt'1'OLINI
ehe.,,,,.
Engng. Sci. IU"S 9 la,").
llEHG, cOllccfning Ih,' arlicle
conversion reaction.
water-~as
scope of our \vork ,,"as thnt of exaunining if the Incchunislll deternlining the kinetics of \\ruter-gus conversion \vns that of the diffusion of the rcngents nod products between the gas phnsc und the surface of the eatalyst. After huving proved that this hypothesis ,,'as very reasonable, the chclnicnl nature of the catylast was of sc(>ondury ilnportl1nce. 'fhe initial brier discussion on the possihle reduced ComlS of the catalyst had the only object of' cstublishing nn H 20/CO ratio range "rherein \"C \\rould be faced with an unchanged catalyst. The thermodynanlic calcula.tion has been ,vorked out, as stated in the (~ontcnts of the article, in n.ccordan(~e "'ith the data given in P"~RnY'S (}lwNlical Euginec'l"s Ilandbook (1 U50 Edition) using the spe(~ific hents on p. 221, a.nd the enthnlpics and the free energies of forlnntion on p. 2:10. lYe confirnl that the
'filE
551:J7U.
Clll'U'. ~"'1()('.lOaa
nUlneri('al {luh'ulation is right und, if the results differ frOIH those given by 1~l\1MET and SCIIUVI'Z. the fault is due to the iJulcCUrU{~Y of' the thcrlllodynuntie dutu used. The ('usunl {!oinciden(lc of the ('()I}(Jiti()n~, thcrlnodylutlHi('ully foreseen by us, for the transfornlation }t"(la04-FcO, with the conditions experilllcntally detected fOf ,vhat I)r. v AN UES ]ll'~uo thinks rightly to be tlH.~ Fc a0 4 -Fe trallsf'orllulw tion, has led us astray. \Vc 1l1cntion on('c Illore that \"C are only interested to settle Ul(~ lilnit helo\" which t.he value of the ratio lI 2()jC() should nol go. 'Vhat happens helo\v that Jiluit is of no interest to us at nil and thus \V(~ have not bothered to (!hc(tk the (~Onslitlltion of the (~utalyst undcr (~()nditions different fronl the cxperinlcntn.1 (l1~cs. ',""c "'ish, ho\,'cVCf, to kindly thank I)r. VAN DEN BJ':uo for having ('larifiecl our l11isundcrstnnding. I). BOJlTOI.. JNl
'-"ia. 'POklltillo IU.
298
~lil(UI,
IllIly.
IN his discussion on the possibility of reduction of the catulyst (p. 137) the author calculated the oxidizing potentinl for the reuetioll BFeO + 1 02 = Fc 3 0 4 nt 5()()OC. l"rolll the thcnllodynuluic point of view, ho"'cvcr, J?cO is not stable lJelo\v 565 0 [1]. The reduction of 1("("3°4 should therefore proceed to Fe. If the author hus extrnpolated the iron-oxygen dntu. to belo\v the quadruple point of 5650C, the oxygen pressure for the }?cO -li'c cquilibriulll should hnve been lligher than thnt for the Fc a0 4 - I~"eO equilibrium. I-Iowevcr ill :Fig. 1 the t\,"o cquilihriuln pressures are in the natural order as would be the cnse only above the quadruple point. It is coneluded therefore that the values for the t\VO oxygen pressures as itulicated in Fig. I cannot he both correct. Sincc thc Huthor's references to the sources of his therilloclynuinic data. arc inconlplete, it is inlpossiblc to verify his (~alculations. If u mixture of FeS0 4 and Fe is contacted \vith to and 1-1 0 under conditions ,,"here cquilihriulll is obtained, at 2 • ]l. BOUTOLINI C/tCU/. E'Ilgng.
,;()()OC
Soc. 1058 9 la.;.
It 1': F J'~ [1]
P.lf.
EMl\IEl''1'
und J. F.
llcply to lite LeUer /rolli.
)u.
Kinetics of
It ENe I'~
SCHULTZ .I111U',..
G.
VAS DE!\'
*}). 11olt'1'OLINI
ehe.,,,,.
Engng. Sci. IU"S 9 la,").
llEHG, cOllccfning Ih,' arlicle
conversion reaction.
water-~as
scope of our \vork ,,"as thnt of exaunining if the Incchunislll deternlining the kinetics of \\ruter-gus conversion \vns that of the diffusion of the rcngents nod products between the gas phnsc und the surface of the eatalyst. After huving proved that this hypothesis ,,'as very reasonable, the chclnicnl nature of the catylast was of sc(>ondury ilnportl1nce. 'fhe initial brier discussion on the possihle reduced ComlS of the catalyst had the only object of' cstublishing nn H 20/CO ratio range "rherein \"C \\rould be faced with an unchanged catalyst. The thermodynanlic calcula.tion has been ,vorked out, as stated in the (~ontcnts of the article, in n.ccordan(~e "'ith the data given in P"~RnY'S (}lwNlical Euginec'l"s Ilandbook (1 U50 Edition) using the spe(~ific hents on p. 221, a.nd the enthnlpics and the free energies of forlnntion on p. 2:10. lYe confirnl that the
'filE
551:J7U.
Clll'U'. ~"'1()('.lOaa
nUlneri('al {luh'ulation is right und, if the results differ frOIH those given by 1~l\1MET and SCIIUVI'Z. the fault is due to the iJulcCUrU{~Y of' the thcrlllodynuntie dutu used. The ('usunl {!oinciden(lc of the ('()I}(Jiti()n~, thcrlnodylutlHi('ully foreseen by us, for the transfornlation }t"(la04-FcO, with the conditions experilllcntally detected fOf ,vhat I)r. v AN UES ]ll'~uo thinks rightly to be tlH.~ Fc a0 4 -Fe trallsf'orllulw tion, has led us astray. \Vc 1l1cntion on('c Illore that \"C are only interested to settle Ul(~ lilnit helo\" which t.he value of the ratio lI 2()jC() should nol go. 'Vhat happens helo\v that Jiluit is of no interest to us at nil and thus \V(~ have not bothered to (!hc(tk the (~Onslitlltion of the (~utalyst undcr (~()nditions different fronl the cxperinlcntn.1 (l1~cs. ',""c "'ish, ho\,'cVCf, to kindly thank I)r. VAN DEN BJ':uo for having ('larifiecl our l11isundcrstnnding. I). BOJlTOI.. JNl
'-"ia. 'POklltillo IU.
298
~lil(UI,
IllIly.