2358 Ind. Eng. Chem. Res.

1995,34, 2358-2363

Hydrogenolysis of Methyl Formate by HdCO Mixtures with

CuO/ZnO/Al203 Based Methanol Synthesis Catalysts
G. BracaJ A. M. Raspolli Galletti, N. J. Laniyonu, and G. Sbrana*
Dipartimento di Chimica e Chimica Industriale, Universita di Pisa, Via Risorgimento 35, 1-56126 Pisa, Italy

E. Micheli, M. Di Girolamo, and M. Marchionna

SNAMPROGETTI S.p.A., Research Division, Via Maritano 26, 1-20097 San Donato Milanese, Italy

Ternary copper-based catalysts of type CuO/ZnO/Al203, CuO/ZnO/Crz03, and CuO/ZnO/La203

have been advantageously used in the hydrogenolysis of methyl and ethyl formate to methanol.
The catalysts are active under mild conditions (150-185 "C; 5-10 MPa) both in gas-solid and
in gas-liquid-solid phases with high selectivities to methanol (80-90%). The decarbonylation
of the formic ester is the only side reaction, but the catalysts, different from other copper-based
systems, do not suffer from the presence of CO in the reaction gases. Accordingly the
hydrogenolysis may be carried out with a hydrogen feed containing CO without any poisoning
of the catalyst or decrease of the selectivity to methanol. A preliminary screening of different
copper catalysts points out that the insensitivity to CO might be related t o the presence of basic
sites on the catalysts.

Introduction In the gas-phase hydrogenolysis described in the

literature over copper chromite (Evans et al., 1983;
Several process alternatives have been proposed for Gormley et al., 1992)or silica-supported copper catalysts
converting CON2 to methanol at milder conditions with (Monti et al., 1985,1986a) at temperatures from 120 t o
respect to the current copper-catalyzed process (Wain- 190 "C and atmospheric pressure two main effects of
wright, 1988) in order to improve the thermodynamic carbon monoxide have been observed: (i) a reversible
efficiency of the process. Among these alternatives, one kinetic inhibition attributed to Hz displacement from
of the most notable is the synthesis of methanol via an the surface and (ii) a long-term irreversible and pro-
alkyl formate, generally methyl formate (Wainwright, gressive poisoning attributed to the deposition on the
1988). surface of the catalyst of a HCHO polymer as a
consequence of the reduced hydrogenation rate (Evans
CH,OH + CO r+ HCOOCH, (1) et al., 1983; Monti et al., 1985, 1986a).

+ 2H, - 2CH30H
Also in the liquid phase, in spite of some preliminary
HCOOCH, (2) optimistic conclusions (Sorum and Onsager, 1984) it is
reported that carbon monoxide inhibits the hydro-
CO + 2H, - CH,OH
genolysis rate of methyl formate in the presence of
net: (3) either copper chromite catalysts (Monti et al., 198613;
Gormley et al., 1992)or the more active copper catalysts
In the first step, methanol is carbonylated to methyl (Cu Raney) (Gormley et al., 1992). With the latter
formate, and then its subsequent hydrogenolysis results catalysts the inhibition by CO was found to be lower at
in the gain of a methanol molecule over the total higher temperatures. In any way decarbonylation of
reaction. methyl formate takes place at 130-170 "C accounting
While the carbonylation step is commercially avail- for 10-20% of the converted product (conversion 70-
able (Reutemann and Kiezcka, 1989), the hydrogenoly- 80%)in the gas-solid (Evans et al., 1983) and 1-2% at
sis, in order to be economically advantageous, must be 160 "C in the liquid phase (Gormley et al., 1992).
carried out using a hydrogen feed containing the CO Economic reasons related to the use as hydrogenating
not converted in previous carbonylation stages; as a stream of a syngas with some residual CO not converted
consequence, the hydrogenolysis catalyst must be in- in the carbonylation stage prompted us to search for a
sensitive to CO poisoning. Furthermore the same catalyst not irreversibly poisoned by CO and sufficiently
catalyst should be able to supress the undesired side active in the hydrogenolysis of the ester. The choice was
reactions of decarbonylation and decarboxylation (eqs oriented toward ternary (CuO/ZnO/Alz03, CuO/ZnO/
4 and 5); the latter reaction may follow an intermediate Cr2O3, etc.) copper-based catalysts active in methanol
hydrolysis step occurring when water is present (eq 6): synthesis (low-pressureprocess) which should not likely
suffer in the presence of CO.
Actually, catalysts of this type have been previously
+ CO
HCOOCH3
HCOOCH3 - CHjOH
CH4 + CO2
(4)

(5)
proposed for the hydrogenolysis of higher esters (ac-
etates and esters of fatty or dicarboxylic acids) at
temperatures in the range 200-300 "C, with good
HCOOCH3 + H20 * CH30H + HCOOH selectivities toward the alcohols produced (Turek et al.,
COP + H2 (6) 1994).
The present paper deals with the applications of the
CuO/ZnO/Ah03 and other copper-zinc-based catalysts
* To whom correspondence should be addressed. to the gas-liquid or gas-phase hydrogenolysis of methyl
+Deceased. and ethyl formate to methanol.
0888-5885/95/2634-2358$09.00/00 1995 American Chemical Society
 Ind. Eng. Chem. Res., Vol. 34, No. 7, 1995 2359
Table 1. Chemical Composition and Physical ProDerties of the Catalysts
~~

elemental a i l y s i s physical properties

cu Zn Al Cr La alkali surface area pore volumeb pore bulk density
catalystQ (wt%) (wt%) (wt%) (wt%) (wt%) (ppm) (m2/g) (cm3/g) radius (A) (g/cm3)
A 55.0 18.2 4.4 890 101 0.32 61 1.41
B 34.2 38.2 5.1 290 53 0.19 88 1.12
C 27.5 27.9 4.6 8.6 300 96 0.19 39 1.40
D 55.0 18.2 4.4 2720 101 0.32 61 1.12
E' 58.3 18.5 3.4 92 nd nd nd
A CuO/ZnO/AlzOS; B, CuO/ZnO/Al203; C, CuO/znO/Al203/Cr203;D, CuO/ZnO/Al203/alkaliadded as KzC03; E, CuOJZnOJLa203. Hg
porosimetry. ' The sample was amorphous by XRD analysis; no other characterization except for surface area was performed on this
catalyst due to the highly hygroscopic character of the lanthanum catalyst (nd = not determined).

Experimental Section The autoclave was subsequently heated to the desired

reaction temperature without stirring; when the reac-
Catalyst Preparation. Catalyst compositions have tion temperature was reached a sample of liquid was
been chosen on the basis of catalysts described in the taken to determine the actual composition, confirming
literature to be active in CO hydrogenation (Bartand that no reaction occurs while the temperature is raised.
Sneeden, 1987). Then, the reaction was started by stirring.
The composition and the main physico-chemical prop- A constant pressure was maintained ( f 0 . 3 MPa) by
erties of the catalysts are summarized in Table 1. supplying pure hydrogen from a reservoir.
The catalysts were prepared according to procedures The experiments were generally carried out at alkyl
described in the literature (Gherardi et al., 1983); formate conversions of nearly 20-40% (time = 6 h).
nitrates of the elements were dissolved in demineralized The overall material balance was performed by draw-
water (approximate concentration of overall metals ca. ing off the liquid through a siphon and discharging gas
1 M) in the desired ratios, and coprecipitation was and the residual liquids through cooled traps at -70
carried out at constant temperature (60 "C) by means "C condensing there all evaporated material. Account-
of a slight excess of a NaHC03 solution (ca. 1 M). abilities, based on methyl formate, higher than 95%
The precipitate was digested for 1h and then washed were obtained.
with hot water up to the disapperance of NO3- ions; the The liquid reaction mixture was analyzed by GC
cake was dried a t 100 "C overnight and then calcined (Sigma 3B/HWD Perkin Elmer instrument equipped
in air at 350 "C for 4 h. with Porapack PS packed column; peak integration was
Catalyst D was obtained from the corresponding performed using a Perkin Elmer Sigma 15 integrator)
unpromoted catalyst (catalyst A) by incipient wetness by withdrawing the samples (1.5 mL) through the outlet
impregnation with an aqueous solution of K2C03 and valve in a cooled trap.
subsequent drying at 120 "C for 16 h. It was, finally, GC analyses were performed using a silica gel column
calcined in air a t 350 "C for 4 h. for the determination of COZand a molecular sieve 5 A
Catalyst E was obtained under the same conditions column for the determination of CO, CH4, and C2H6.
as the other catalysts but with the following major dif- Further details on the sampling procedure and analysis
ferences: the precipitation was carried out by maintain- may be obtained elsewhere (Raspolli Galletti et al.,
ing a constant molar ratio of 2 between co32-anions 1985).
(precipitatingagent, a 2 M K2CO3 solution) and the sum 2. Gas-Phase Experiments. Experiments were
of the metals (Cu + Zn + La). In this case, the carried out in a tubular fixed-bed laboratory unit
precipitate was then washed until the disappearance equipped with a 10 mm i.d. stainless steel reactor; about
of Nos- occurred. 5 g of catalyst (14-20 mesh) was loaded in the reactor
A Fisons Instruments Sorptomatic model 1900 with in each test, and the space above and below the catalyst
N2 adsorption was used to measure the surface area, bed was packed with inert a-alumina.
the total volume, and the distribution of pores; elemen- Reactor heating was provided by an electric oven, and
tal composition of the final catalysts was determined the temperature of the catalytic bed was measured with
by atomic adsorption analysis. an internal thermocouple.
Apparatus and Procedure. 1. Liquid-Phase Hydrogen was supplied by cylinders and measured
Experiments. Experiments were carried out in a 1 L by a mass flow meter, while methyl formate was fed by
stainless-steel autoclave fitted with gas inlet and outlet means of a Waters HPLC pump; the gas and liquid feeds
lines and a liquid sampling line. were mixed at the entrance of the reactor, and the upper
The catalyst pellets (4 = 2 mm) were loaded in a part of the inert filling also ensured preheating and
perforated basket fitted on the arm of the stirrer thus vaporization of the reactants.
allowing a good gas-liquid-solid contact. The catalysts The effluent from the reactor was cooled down and
(10-20 g) were introduced in the container, and after condensed a t -10 "C; the liquid product was then
the evacuation of air and moisture, the reduction stage collected in a gas-liquid separator.
was carried out in the same reactor by treatment with Samples of the effluent gas stream were periodically
hydrogen (10 MPa) and methanol (10-100 mL) at 200 analyzed on line by a 5730 Hewlett-Packard gas chro-
"C for 4-5 h. After the reduction, methanol was matograph equipped with both a thermal conductiv-
evaporated in vacuo and the reduced catalyst kept in ity detector (TCD) and a flame ionization detector
HZatmosphere before use. (FID) Porapak QS and Carbosieve columns were
The liquid reactants (pure methyl or ethyl formate) used in order to separate CO and C02 and light
were loaded by suction into the autoclave which was hydrocarbons.
pressurized, a t room temperature, with hydrogen or H2/ Analyses of the liquid products were performed on a
CO mixtures up to the required pressure. 5890 Hewlett-Packard gas chromatograph, equipped
2360 Ind. Eng. Chem. Res., Vol. 34,No. 7, 1995

100 R tures of the DRIFT cell are reported elsewhere (Basini

et al., 1991).

8ol\ Results and Discussion

Liquid-PhaseHydrogenolysis. Preliminary infor-
mation on the performance of a ternary methanol
synthesis catalyst CuO/ZnO/Al203 (catalyst A, Table 1)
has been obtained by studying the hydrogenolysis of
ethyl formate in the liquid phase, which allowed a more
immediate indication of the methanol formation by
reduction of the formyl moiety.
Actually, the hydrogenolysis took place rapidly at a
not too high temperature (185 "C) (Figure l), with
formation of methanol (eq 7) and methyl formate
produced by a transesterification reaction (eq 8) with a
0 5 10 15 20 25 selectivity to C1 products of about 70-75%.
t-lme. h Decarbonylation of the ester (eq 9) is the only side
Figure 1. Ethyl formate hydrogenolysis with CuO/ZnO/Al203 reaction, whereas no decarboxylationtook place (eq 10):
(catalyst A). Reaction conditions: ethyl formate, 320 g; catalyst,
10.1 g; temperature, 185 "C; PH*, 10 MPa; rpm, 200. 0, Ethyl
formate; A, ethanol; 0, methanol; 0 , methyl formate.
HCOOC,H, + 2H2 -+ C2H,0H
CH,OH (7)
CH,OH + HCOOC,H, zz C2H,0H + HCOOCH, (8)
with a flame ionization detector; products separation
CO + C2H,0H
was effected by a 50 m capillary column (Hewlett-
Packard, HP5 5% cross-linked phenylsilicone). HCOOC,H, (9)
Before feeding the methyl formate the catalyst was
pre-reduced raising the temperature to 300 "Cby 100 HCOOC,H, - CO, + C2H, (10)
"CAI in a Hfl2 stream, the Hz content being progres-
sively increased from 5 to 100%. A rapid decarbonylation initially occurred in the first
Before collecting the liquid sample, the reaction was hour accounting for more than 40% of the converted
performed for 1 h in order t o stabilize the reaction ester; successivelythis reaction proceeded more slowly
conditions;afker that the catalytic tests were performed so that after 24 h it was reduced to less than 30% at a
for 1 or 2 h, and the catalyst was left under hydrogen conversion of the ester of 70%; this seemed to indicate
flow overnight. that evolved CO probably poisons the basic sites of the
Reaction conditions were selected in order to ensure catalyst where the ester is activated for the decarbony-
a complete vaporization of reactants depending on the lation.
total pressure; total contact time (GHSV, H2 MF; MF + It was then surprisingly found that the catalyst was
not poisoned by the initial presence in the gases of CO
= methyl formate)) has been kept constant.
Material Balance. The material balance was al- (10%) but, on the contrary, a slight advantage was
ways higher than 95%. gained by its presence both in activity and in selectivity
Data Presentation. Conversion and selectivity are of the process (Table 2).
defined by the following equations: The promising results obtained with ethyl formate
prompted us to extend the experimentation to methyl
conversion % = [(mol of ester initial - formate.
Initially the following points were ascertained: (1)
mol of ester final)/mol of ester initial] x 100 methyl formate could be hydrogenolyzed,beginning to
display some reactivity a t 125 "C; an increase of the
Selectivities to methanol in the case of methyl formate temperature in the range 125-200 "C resulted in a
(MF) hydrogenolysis are evaluated as decrease of the selectivity to methanol and an increase
of the decarbonylation reaction (Table 3);(2) a chemical
selectivity % = [0.5(mol of MeOH produced)/ kinetic regime was assured by a stirring velocity of 200
(mol of converted MF)] x 100 rpm (velocities checked, 100, 150, 200, and 300 rpm);
(3)the recycled catalyst maintained nearly unchanged
and in the case of ethyl formate (EF) hydrogenolysis the reaction activity and selectivity; the catalyst was
from the relation actually recycled 7 times without significant loss of
activity (Figure 2); and (4)no production of methanol
selectivity % = was observed by direct CO-Hz reaction under the
[(mol of MeOH + 2(mol of MF produced))/ hydrogenolysis conditions (when the reaction was car-
(mol of converted EF)] x 100 ried out using ethyl acetate as the medium a t 185 "C,
under 11 MPa of H$CO (lO/l), with 10.1 g of catalyst
Separated repeated experiments showed that the no methanol was formed after 24 h; under these
experimental errors were generally within 24.5% in the conditions ethyl acetate did not react).
gas phase (for both conversion and selectivity) and To give a quantitative account of the performances
f2.5% for conversion and f 2% for selectivity in the of the ternary Cu0/ZnO/Al~03(catalyst A), some experi-
liquid phase. ments were carried out varying P H ~and pco.
Spectroscopic Analysis. IR spectroscopic experi- As in the case of the copper-basedcatalysts (Monti et
ments were performed with a Nicolet 20 SXC spectrom- al., 1986b; Liu et al., 1988; Gormley et al., 19921, the
eter equipped with a mercury, cadmium telluride (MCT) methyl formate disappearance rate may be considered
detector (resolution of 4 cm-l). The experimental fea- nearly of first order in (Table 41, even though the
 Ind. Eng. Chem. Res., Vol. 34,No. 7, 1995 2361
Table 2. Hydrogenolysis of Ethyl Formate in the Liquid Phase with CuO/ZnO/AlzOS (Catalyst A)"
hydrogenolysis with pure Hz hydrogenolysis with a HdCO mixture
P H ~ , 10 MPa pnz, 9.3 MPa; pco, 0.7 MPa
C1 products (mol %) sel to C1 products (mol %) sel to
time(h) MeOH HCOOMe conv (%) MeOH (%) MeOH HCOOMe conv (%) MeOH (%)
1 2.4 8.4 57 3.3 9.3 71
4 1.4 7.9 24.8 70 2.1 8.5 26.2 73
8 4.3 12.4 40.0 73 8.1 12.4 43.5 76
12 6.9 14.7 50.0 73 13.0 14.3 56.2 74
24 20.0 14.5 69.0 71 25.6 14.9 73.0 76
a Reaction conditions: ethyl formate, 320 g; catalyst, 10.1 g; temperature, 185 "C; rpm, 200.
Table 3. Hydrogenolysis of Methyl Formate: Effect of Table 6. Hydrogenolysis of Methyl Formate: Effect of
the Temperaturea Dmna

temp "C conv (%I sel to MeOH (%I sel to CO (%) PCO (MPa) P H ~(MPa)
125b 5.8 99.0 trace initial final initial final conv (%) sel to MeOH (%)
150 13.0 85.0 12.0
175 23.0 80.0 18.2 2.5 7.7 5.2 23.0 79
200 50.0 78.0 22.0 1.3 2.8 7.9 6.4 26.0 82
5.0 5.9 7.5 6.5 28.0 86
a Reaction conditions: methyl formate, 389 g; catalyst (A), 19.8 7.4 7.7 7.5 7.2 27.0 85
g; time, 6 h; pressure, 11 MPa; rpm, 200. Conditions as in a
a Reaction conditions: methyl formate, 389 g; catalyst (A), 20
except times, 5 h.
g; temperature, 175 "C; time, 6 h; rpm, 200.
Table 6. Gas-PhaseHydrogenolysis of Methyl Formate:
Effect of Temperaturea ~ ~~

run temp "C conv (%) MeOH sel (%)

1 150 35.8 97.8
2 170 65.7 96.5
3 190 80.3 92.3
Catalyst, CuO/ZnO/Al203 (catalyst A); LHSV, 1.0 h-l; H m F ,
5.5 M; pressure, 2.5 MPa.

Table 7. Gas-Phase Hydrogenolysis of Methyl Formate:

Effect of Hz Pressurea
~~

run temp ("C) press. (MPa) conv (%) MeOH sel (%)
4 125 2.5 56.1 98.9
5 125 7.5 68.6 99.0
6 125 10.0 82.3 98.7
0 2 3 4 5 6 a Catalyst, CuO/ZnO/Al203; LHSV, 0.5 h-l; H m F , 10.0 M.
*<me, h
Figure 2. Methyl formate hydrogenolysis with CuO/ZnO/Alz03 raising the concentration of CO in the reactant gases
(catalyst A). Reaction conditions: methyl formate, 386 g; catalyst, up to 50% (Table 5 ) .
19.9 g; temperature, 175 "C; p ~ 11 ~ MPa;
, rpm, 200. 0 , methyl However, because it was impossible to maintain
formate and A, methanol (fresh catalyst). A, methyl formate and simultaneously constant values of bothpco and pa,, due
0,methanol (catalyst recycled after one cycle). 0 ,methyl formate to the occurrence of the decarbonylation reaction, the
and . ,
methanol (catalyst recycled after five cycles). positive or negative (inhibition) order with respect t o
Table 4. Hydrogenolysis of Methyl Formate: Effect of pco cannot be accurately evaluated.
PASa Gas-PhaseHydrogenolysis. The catalytic behavior
PH2 conv
of the ternary CuO/ZnO/A.l203 (A) catalyst was also
run (MPa) (lh)(%) Pb C' contemporarly tested in the gas-phase hydrogenolysis
of methyl formate a t temperatures in the range 125-
rl 3.2 5.3 p(r2)/p(rl) = 2.0 C(r2)/C(rl)= 1.9 190 "C (HflF, 5.5; LHSV, 1.0 h-l), and the results are
r2 6.45 10.1 p(r3)/p(r2) =1.8 C(r3)/C(r2) = 1.7
r3 12.0 17.0 p(r3)/p(rl) = 3.7 C(r3)/C(rl) = 3.2 summarized in Table 6.
When the reaction was conducted at 150 "C only 36%
a Reaction conditions: methyl formate, 389 g; catalyst (A), 19.9
conversion was obtained, but it increased up to 80%
g; temperature, 175 "C; rpm, 200. b P = ratio between P H ~in when the reaction was carried out at 190 "C. The
Werent runs. C = ratio between the conversion in different runs.
selectivity to MeOH was higher than 95% at 170 "C a t
a conversion of 60-70% of the ester. As observed for
partial decarbonylation of the ester to CO did not allow the liquid phase, the decarbonylation side reaction is
PH, and pco to be maintained strictly constant with favored by an increase of the temperature.
respect to the reaction time. The influence of total pressure was evaluated at a
fured temperature (125 "C): under these conditions an
The experiments carried out with the initial presence increase of the total pressure resulted in an increase of
of CO in the range CO/H2 of 1/6-l/l (Table 5) working the conversion of the ester whereas the selectivity was
a t an initial PH,of 7.5 MPa confirmed the insensitivity not affected within the experimental error (Table 7).
of these catalysts to CO, as in the case of ethyl Likewise, in the gas-liquid-solid phase experiments
formate: in isochronous runs the conversions of the the catalytic activity and the selectivity were practically
ester and the selectivity t o MeOH slightly increased by not affected by the addition of CO t o the gas feed up to
2362 Ind. Eng. Chem. Res., Vol. 34,No. 7, 1995
Table 8. Gas-Phase Hydrogenolysis of Methyl Formate: observed between the activity and the physical proper-
Effect of CO Additiona ties of the catalysts.
temp press. LHSV % CO conv MeOH All ternary catalytic systems CuO/ZnO/Alz03 com-
run i"C) iMPa) (h-li (inlet) (%) sel (%I prising part A1203 substituted by Cr203 did not suffer
7 190 2.5 1.0 0.0 80.3 92.6 in the activity from the initial presence of carbon
8 190 2.5 1.0 9.4 80.4 91.7 monoxide; this performance was attained by the pres-
9 190 2.5 1.0 7.3 77.6 90.1 ence, in the formulation of the catalyst, of the basic
10 150 2.5 0.5 0.0 70.8 93.9 component ZnO as also results for binary CuOhasic
11 150 5.0 0.5 50.0 59.0 90.0 oxide systems (Di Girolamo et al., manuscript in prepa-
a Catalyst, CuOlZnOlAl~03(catalyst A); H m F , 5.5 M. ration). On the other hand the doping of the ternary
catalyst A with a significant amount of alkaline oxide
Table 9. Hydrogenolysis of Methyl Formate with (KzO, 2500 ppm) (catalyst D) did not cause important
Catalysts of Different Formulationa
variations in the activity and selectivity in the initial
PH~PCO conv sel to absence of CO, whereas when CO was initally present
catalyst initial (%) MeOH(%) an increase of the activity was observed.
(A)
CuOlZnOlAl~0~ 7.710 23.0 79 The reformulation of the catalyst with an improved
66/21/13 7.711.3 26.0 82 CuO content (73%)and with substitution of A1203 with
CuOlZnOlAl203 (B) 7.710 12.7 84 the more basic La203 (catalyst E) resulted in an
41/45/14 7.212 14.0 92 improvement worth noting of the catalytic activity of
CuOlZnOlAl~03/Cr~0~
(C) 7.710 10.6 74 the system without a significant decrease of the selec-
36/36/14/14 7.712 11.7 68 tivity.
CuOlZnOlAl~03/K~0 (D) 7.710 36.0 83 In order to gain more information on the reasons for
66/21/13/2720 ppm 7.212 42.0 81 the insensitivity of these catalytic systems to the CO
C~OlZnO/Laz03~ (E) 7.710 41.0 82 poisoning a preliminary IR spectroscopic investigation
7312314 7.711.3 52.0 73 was performed comparing the spectra of the ternary
a Reaction conditions: methyl formate, 320 g; catalyst, 20 g;
system (catalyst A) with those recorded under the same
temperature, 175 "C; rpm, 200; time, 6 h. * Conditions as in a conditions on a CdSiOz catalyst which typically suffered
except catalyst, 10 g. from CO poisoning (Monti et al., 1985).
Exposure of the CuO/ZnO/Al203 catalyst to mixtures
a level of 10% (Table 8, runs 7-9); only when CO be- of carbon monoxide and hydrogen at atmospheric pres-
came higher than 50%of the gases was a small negative sure and 100-200 "C did not result in the appearance
effect, particularly on the conversion, observed (compare of any CO absorption band whereas CO was rapidly
runs 10 and 11). adsorbed on the C d S i 0 2 catalyst as indicated by a
However, preliminary results indicated that a pro- strong large peak a t 2120-2110 cm-', also observed for
gressive deactivation takes place on aging the catalyst analogous catalysts (Monti et al., 1985, 1986a).
for long reaction times with a continuous flow of MF The absence of the CO bands on the ternary catalyst
and H2, probably due to the formation of residual might be due to the low surface concentration of the
materials originating from polymerization of a formal- adsorbed CO species beyond the detection sensitivity of
dehyde intermediate as also previously reported for the DRIFT spectrum or to the opacity, under strongly
CuO-based catalysts (Monti et al., 1986a): after 30 h a reducing conditions, of the catalyst sample with the high
loss of 10% of the activity was observed. The different Cu content. Nevertheless this observation, also con-
behavior observed when the reaction is carried out in firmed by other studies (Slaa et al., 1992; Neophytides
the liquid phase could likely be related to a continuous at al., 1992) is a strong indication that the CuO/ZnO/
renewal of the catalyst surface by the liquid thus catalysts do not undergo a significant coverage by
preventing any catalyst fouling. co.
Methyl formate, which was mainly physisorbed (YCO
Screening of Catalysts for the Liquid-Phase band a t 1726 cm-l) on the binary CuO/SiOn catalysts,
Hydrogenolysis. As the experiments in the liquid appeared to be chemisorbed on the ternary CuO/ZnO/
phase seemed to be more promising for a further A1203 catalysts both on zinc oxide and alumina sites
development of the process, no further experimentation (complex double signal centered at 1600 and 1360 cm-')
in the gas phase was performed and a number of and also on the copper sites (YCO band a t ca. 1660 cm-l,
different copper-based systems (Table 9) were tested in absent in the systems without Cu) (Millar et al., 1991).
the liquid phase with the aim of improving the perfor- The chemisorption of the ester seems to be favored
mances of the catalytic system and gaining preliminary by the presence of basic sites (ZnO and, although to a
information on the importance and role played by the minor extent, A12031 as indicated by the growing
oxide components of the catalyst: (1)the CuO/ZnO ratio intensity of the bands of inorganic formates. It is worth
in the ternary catalysts was varied (catalysts A and B); noting that the activation of alkyl formates by basic sites
(2) a fourth component (Crz03) was introduced (catalyst was recently proposed (Onsager and Andersen, 1990)
C); (3) the ternary catalyst CuO/ZnO/Al203 was doped in a related work on the direct synthesis of methanol
with increasing amounts of an alkaline oxide (K20) by HdCO with Cu chromite/MeONa catalysts.
(catalyst D); and (4) alumina was replaced with lantha-
num oxide (catalyst E).
It is worth noting that also for these catalysts the Conclusion
reactivity was under chemical control for stirring veloci- The most striking result of the present investigation
ties higher than 150 rpm. is represented by the observed insensitivity to CO
The results obtained (Table 9) showed that the poisoning of the ternary CuO/ZnO/Al203 catalyst both
catalytic activity for hydrogenolysis increased with in the gas- and in the liquid-phase hydrogenolysis of
increasing the CuO content (compare catalysts A, B, and the formic esters, different from the behavior of other
also C); on the other hand, no marked correlation was copper catalysts (Evans et al., 1983; Monti et al., 1985,
 Ind. Eng. Chem. Res., Vol. 34,No. 7, 1995 2363
1986a, 1986b; Gormley et al., 1992). Accordingly the Millar, G. J.; Rochester, C. H.; Waugh, K. C. Infrared Study of
hydrogenolysismay be carried out with a hydrogen feed Methyl Formate and Formaldehyde Adsorption on Reduced and
containing CO without any poisoning of the catalyst and Oxidised Silica-supported Copper Catalysts. J . Chem. SOC.,
Faraday Trans. 1991,87,2785-2793.
decreasing of the selectivity to methanol.
Monti, D. M.; Wainwright, M. S.; Trimm, D. L.; Cant, N. W.
The catalysts are active under mild conditions (150- Kinetics of the Vapor- Phase Hydrogenolysis of Methyl Formate
185 "C; 5-10 MPa) both in gas-solid and in gas- over Copper on Silica Catalysb. Z n d . Eng. Chem. Prod. Res. Dev.
liquid-solid phases with high selectivities t o methanol 1986,24,397-401.
(80-90%). Monti, D. M.; Cant, N. W.; Trimm, D. L.; Wainwright, M. S.
Deactivation phenomena were observed in the gas Hydrogenolysis of Methyl Formate over Copper on Silica. I
phase whereas the catalyst could be recycled several Study of Surface Species by in Situ Infrared Spectroscopy. J .
times in the liquid phase without losing its activity. Catal. 1986a,100,17-27.
A preliminary screening of different copper catalysts Monti, D. M.; Kohler, M. A.; Wainwright, M. S.; Trimm, D. L.;
in the liquid phase points out that the insensitivity to Cant, N. W. Liquid Phase Hydrogenolysis of Methyl Formate
CO seems to be related to the presence of basic oxide in a Semi Batch Reactor. Appl. Catal. 1986b,22,123-136.
components (ZnO and La2031 and to their higher affinity Neophytides, S. G.; Marchi, A. J.; Froment, G. F. Methanol
Synthesis by Means of Diffise Reflectance Infrared Fourier
toward the ester than toward CO, avoiding the coverage Transform and Temperature-Programmed Reaction Spectros-
and the deactivation of the hydrogenating copper cen- copy. Appl.Cata1. A: General 1992,86,45-64.
ters. Onsager, 0. T.; Andersen, M. S. The Coproduction of Methanol
Work is in progress on the effect of basic oxides and and Acetic Acid. EUROGAS '90,Proceedings of the European
alkaline promoters on copper catalysts, and more de- Applied Research Conference on Natural Gas, 1990,157-164.
tailed data will be reported and discussed in a subse- Raspolli Galletti, A. M.; Braca, G.; Sbrana, G.; Marchetti, F.
quent paper (Di Girolamo et al., manuscript in prepa- Homologation of Methyl Acetate to Ethyl Acetate with Ruthe-
ration). nium Catalysts. Part I. Effect and Role of Ion-pairing. J . Mol.
Catal. 1986,32,291-308.
Reutemann, W.; Kiezcka, H. Formic Acid Production. Ullmann's
Acknowledgment Encyclopedia of Industrial Chemistry, 5th ed.; VCH: Weinheim,
L. Basini and A. Aragno (SNAMPROGE'M'I S.p.A.) 1989;Vol. A12,pp 16-22.
are kindly acknowledged for the IR work. Slaa, J. C.; Weierink, G. J. M.; van Ommen, J. G.; Ross, J. R. H.
TPR and Infrared Measurements with CdZnOIAl203 Based
Catalysts for the Synthesis of Methanol and Higher Alcohols
Literature Cited +
from CO H2. Catal. Today 1992,12,481-490.
Bart, J. C. J.; Sneeden, R. P. A. Copper-Zinc Oxide-Alumina Sorum, P. A.; Onsager, 0. T. Hydrogenolysis of Methyl Formate
Methanol Catalysts Revisited. Catal. Today 1987,2,1-124. to Methanol. Proceedings of the VZZZ International Congress on
Basini, L.; Aragno, A.; Raffaelli, A. Vibrational Infrared Spectros- Catalysis, Berlin 1984;Verlag Chemie: Weinheim, 1984;Vol.
copy Studies of 1-Butene Skeleton Isomerization at the Surface 11, pp 233-244.
of a Silicated Alumina in a Micro Plug Flow Reactor. J. Phys. Turek, T.; Trimm, D. L.; Cant, N. W. The Catalytic Hydrogenolysis
Chem. 1991,95,211-218. of Esters to Alcohols. Catal. Rev.-Sci. Eng. 1994,36,645-683.
Di Girolamo, M.; et al. Manuscript in preparation. Wainwright, M. S. Catalytic Processes for Methanol Synthesis-
Evans, J. W.; Casey, P. S.;Wainwright, M. S.; Trimm, D. L.; Cant, Established and Future. Methane Conversion; Bibby, D. M.,
N. W. Hydrogenolysis of Alkyl Formates over a Copper Chromite. Chang, C. D., Howe, R. F., Yurchak, S., Eds.; Elsevier: Am-
Catalyst. Appl. Catal. 1983,7,31-41. sterdam, 1988;pp 95-108.
Gherardi, P.; Ruggeri, 0.;Trifirb, F.; Vaccari, A.; Del Piero, G.;
Manara, G.; Notari, B. Preparation of Cu-Zn-Al Mixed Hydroxy-
carbonates Precursors of Catalysts for the Synthesis of Metha- Received for review May 20, 1994
nol at Low Pressure. Preparation of Catalysts ZZ& Poncelet, G., Revised manuscript received November 18,1994
Grange, P., Jacobs, P. A., Eds.; Elsevier: Amsterdam, 1983;pp Accepted April 7, 1995@
723-733.
Gormley, R. J.; Rao, V. U. S.; Soong, Y.; Micheli, E. Methyl IE940324U
Formate Hydrogenolysis for Low-Temperature Methanol Syn-
thesis. Appl. Catal. A: General 1992,87,81-101.
Liu, Z.;Tierney, J. W.; Shaw, Y. T.; Wender, I. Kinetics of Two-
step Methanol Synthesis in the Slurry Phase. Fuel Process. @Abstract published in Advance ACS Abstracts, June 1,
Technol. 1988,18,185-199. 1995.