Production of 1,4-butanediol

This invention provides an improved process for converting acrolein into 1,4-butanediol via allyl alcohol and 4-hydroxy-butanal intermediates.

BACKGROUND OF THE INVENTION 
Ethylene glycol is an important constituent of commercial polyester resins. 
Also of increasing importance as resin constituents are higher polyols 
such as 1,4-butanediol. The development of new and improved commercial 
processes for production of higher polyols is under active investigation. 
1,4-Butanediol can be derived from succinic acid, maleic anhydride and 
other four-carbon organic species, but such methods are not economically 
attractive. Another method of producing 1,4-butanediol is by the reaction 
of formaldehyde and acetylene to form 1,4-butynediol as an intermediate, 
which is subsequently hydrogenated to the desired 1,4-butanediol product. 
Other investigators have endeavored to convert acrolein into 1,4-butanediol 
by subjecting acrolein to hydroformylation conditions, the objective being 
the formation of succinaldehyde as an intermediate product. The results 
have been unsatisfactory since the main conversion product recovered from 
acrolein under hydroformylation conditions is propionaldehyde. 
Other efforts to produce 1,4-butanediol have involved hydroformylation of 
allyl alcohol to yield 4-hydroxybutanal as an intermediate which is 
subsequently hydrogenated to 1,4-butanediol. The liquid phase 
hydroformylation of allyl alcohol in the presence of hydroformylation 
catalysts such as cobalt carbonyl produces significant quantities of 
propanal, propanol and 2-methyl-3-hydroxypropanal as by-products, in 
addition to the desired 4-hydroxybutanal. 
In U.S. Patent Office Defensive Publication No. 904,021 (Nov. 21, 1972) 
there is disclosed an improved hydroformylation process for converting 
unsaturated alcohols into diols. In one embodiment the Publication process 
involves the hydroformylation of allyl alcohol with rhodium-phosphine 
complex catalyst to produce a reaction mixture which is subsequently 
hydrogenated to yield 63 percent 1,4-butanediol and 25 percent 
2-methylpropanediol. based on the weight of allyl alcohol charged. For the 
purposes of economic feasibility, higher conversion yields of 
1,4-butanediol from allyl alcohol are desirable for commercial scale 
operations. 
Accordingly, it is a main object of the present invention to provide an 
improved process for converting acrolein into 1,4-butanediol. 
It is another object of the present invention to provide a catalyst for 
converting acrolein into allyl alcohol in a yield of at least 70 percent. 
It is another object of the present invention to provide 4-hydroxybutanal 
in high yield as an intermediate product in a commercially feasible 
process for converting acrolein into 1,4-butanediol. 
Other objects and advantages shall become apparent from the accompanying 
description and examples.

DESCRIPTION OF THE INVENTION 
One or more objects of the present invention are accomplished by the 
provision of a process for producing 1,4-butanediol which comprises (1) 
reacting acrolein with hydrogen in the vapor phase in the presence of a 
catalyst comprising a silver-cadmium alloy, wherein the atomic ratio of 
silver to cadmium in the alloy is in the range between about 0.1 and 3 to 
1, to yield a hydrogenation product mixture containing allyl alcohol; (2) 
contacting the allyl alcohol product mixture with hydrogen and carbon 
monoxide under hydroformylation conditions to yield a product mixture 
containing 4-hydroxybutanal; (3) separating the 4-hydroxybutanal from the 
product mixture; and (4) hydrogenating the 4-hydroxybutanal to produce 
1,4-butanediol. 
Acrolein To Allyl Alcohol 
Several methods ae known in the prior art for converting 
.alpha.,.beta.-olefinically unsaturated carbonylic compounds into the 
corresponding .alpha.,.beta.-olefinically unsaturated alcohols. 
British Pat. No. 734,247 and U.S. Pat. No. 2,763,696 disclose a process 
whereby acrolein may be converted to allyl alcohol by means of a vapor 
phase hydrogenation process. According to this process, moderate yields of 
allyl alcohol are obtained when acrolein is treated with free hydrogen in 
the vapor phase at a temperature between 210.degree. C and 240.degree. C 
in the presence of a catalyst comprising cadmium and one or more heavy 
metals of groups I, II, VI and VIII of the periodic table. Relatively high 
pressures are employed in the process on the order of 20 to 50 kilograms 
per square centimeter. 
German Pat. No. 858,247 discloses a somewhat different process which is 
also useful for the conversion of acrolein to allyl alcohol. According to 
the German patent, good yields of allyl alcohol are obtained by reacting 
acrolein with free hydrogen in the presence of a catalyst containing 
cadmium oxide and a metal hydrogenating component which is preferably 
copper. The patent teaches that the best results are obtained when the 
process is operated at high temperatures and at high pressures on the 
order of 100-300 atmospheres. 
U.S. Pat. No. 3,686,333 describes a liquid phase hydrogenation process for 
converting alkenals into alkenols in the presence of a catalyst mixture of 
a cadmium salt of a fatty acid and a transition metal salt of a fatty 
acid. 
Japanese Pat. No. 73-01,361 discloses a process for hydrogenating 
.alpha.,.beta.-olefinically unsaturated aldehydes into the corresponding 
allylic alcohol derivatives. The efficiency of the process is improved by 
the recycle of by-products to the hydrogenation zone, or by passage of the 
by-products stream into a second hydrogenation zone. The preferred 
catalysts are mixtures of cadmium and copper, cadmium and silver, cadmium 
and zinc, cadmium and chromium, copper and chromium, and the like. The 
Japanese patent states that under steady state conditions 1.5 moles/hour 
of acrolein are converted to 1.05 moles/hours of allyl alcohol annd 0.4 
mole/hour of n-propanol. 
For the purposes of the present invention process, it has been found that 
acrolein can be converted into allyl alcohol with a conversion of at least 
95 weight precent and a yield of at least 70 weight percent by the use of 
a novel catalyst comprising a silver-cadmium alloy on a carrier substrate. 
In the practice of step (1) of the invention process, the acrolein and 
hydrogen at elevated temperature and pressure are passed in vapor phase 
through a reaction zone containing a silver-cadmium alloy catalyst which 
has exceptional selective hydrogenation activity. 
The reaction temperature of the hydrogenation process can vary in the range 
between about 0.degree. C and 300.degree. C, and preferably between about 
75.degree. C and 250.degree. C, and most preferably between about 
100.degree. C and 215.degree. C. 
The pressure of the hydrogenation process can vary in the range between 
about 15 and 15,000 psi, and preferably between about 75 and 5000 psi, and 
most preferably between about 250 and 2500 psi. 
The mole ratio of hydrogen to acrolein in the vapor phase feed stream can 
vary in the range between about 1:1 and 1000:1. The preferred mole ratio 
of hydrogen to acrolein in the feed stream is in the range between about 
5:1 and 200:1, and the most preferred mole ratio is in the range between 
about 10:1 and 150:1. 
The rate at which the vapor phase gas stream is contacted with the 
silver-cadmium alloy catalyst is not critical, and can be varied consonant 
with the other processing conditions to achieve an optimal balance of 
conversion and yield parameters. The flow rate of feed gas reactants can 
vary over a broad range between about a total of 10 moles and 1000 moles 
of feed gas reactants per liter of catalyst per hour. In the case of 
acrolein, a preferred flow rate of feed gas reactants is one which 
provides a catalyst contact time between about 0.1 and 50 seconds. By the 
invention process, acrolein can be converted to allyl alcohol in step (1) 
with a space-time yield of greater than 900 grams per liter of catalyst 
per hour. 
The process step (1) can be conducted either by passing the feed mixture 
through a fixed catalyst bed, or through a reactor wherein the catalyst is 
present in finely divided form and is maintained in a fluidized state by 
the upward passage there through of the gaseous reactants. The process 
step (1) is most conveniently carried out in a continuous manner, although 
intermittent types of operation can be employed. In a preferred method of 
continuous operation, the components of the feed stream are brought 
together and under the desired pressure are passed in vapor phase through 
the catalyst heated to the desired temperature. The reaction zone 
advantageously is an elongated tube or tubes containing the catalyst. The 
feed can be brought into contact with the catalyst in either the unheated 
or preheated condition. The effluent from the reactor can then be 
separated into its various constituents by conventional means, the most 
convenient of which is fractional distillation. If desired, any 
unconverted portion of the acrolein present in the effluent from step (1) 
can be recirculated through the catalyst in the reactor, preferably 
admixed with fresh feed gases. 
The preferred selective hydrogenation catalyst for process step (1) is a 
silver-cadmium alloy on a carrier substrate, wherein the atomic ratio of 
silver to cadmium in the alloy is in the range of between about 0.1 and 3 
to 1. 
The carrier substrate can be selected from silica, Celite, diatomaceous 
earth, Kieselguhr, alumina, silica-alumina, titanium oxide, pumice, 
carborundum, boria, and the like. It is highly preferred that the 
silver-cadmium alloy be supported on a silica and/or alumina carrier 
substrate. The quantity of carrier substrate in the catalyst composition 
can vary in the range of between about 5 and 99.5 weight percent, based on 
the total catalyst weight. 
The highly preferred catalysts are prepared by coprecipitating hydroxides 
of silver and cadmium from an aqueous solution of calculated quantities of 
water-soluble salts of silver and cadmium. The precipitation is effected 
by the addition of caustic to the aqueous solution. 
The carrier substrate component of the catalyst composition can be 
incorporated during the catalyst preparation by preferably slurrying the 
finely divided carrier substrate mass in the said aqueous medium 
immediately after the silver-cadmium hydroxides are precipitated. Finely 
divided porous materials such as fumed silica or diatomaceous earth are 
highly preferred carrier substrate materials for the preparation of the 
present invention catalysts. 
After the coprecipitation of silver-cadmium hydroxides has been 
accomplished, the solids phase is recovered by filtration or other 
conventional means. The filtered solids are washed with chlorine-free 
water until essentially neutral. For the purposes of a fixed bed 
operation, the dried filter cake preparation is calcined at a temperature 
between about 175.degree. C and 300.degree. C for a period of about two to 
twenty or more hours, and then the calcined material can be ground and 
pelleted. Prior to use the catalyst pellets can be reduced in a stream of 
hydrogen at a temperature between about 50.degree. C and 250.degree. C for 
a period of about 5 hours. For a fluidized bed operation, the calcined 
catalyst preparation can be ground and sized in a conventional manner to 
satisfy process design requirements. The reduction of the catalyst can 
also be accomplished in situ during the vapor phase hydrogenation process. 
There are several critical aspects of catalyst preparation which must be 
respected in order to achieve a hydrogenation catalyst having unique and 
advantageous properties in comparison to prior art catalysts for selective 
hydrogenation of acrolein to allyl alcohol. 
Firstly, the silver-cadmium alloy in the catalyst must contain an atomic 
ratio of silver to cadmium in the range between about 0.1 to 3 to 1, and 
preferably between about 0.4 and 2.2 to 1. 
Secondly, the silver and cadmium in the catalyst must be in the free metal 
state, and must be substantially in the form of an alloy, i.e., X-ray 
diffraction spectra should confirm the absence of unalloyed silver or 
cadmium crystals. Preferred silver-cadmium alloy catalysts are solid 
solutions which nominally exhibit an X-ray diffraction pattern which is 
substantially free of detectable unalloyed metal crystallite lines. 
In terms of X-ray diffraction data as more fully described hereinbelow, a 
preferred silver-cadmium alloy catalyst can consist substantially of 
.alpha.-phase silver-cadmium, with detectable splitting of X-ray 
diffraction lines which is indicative of silver-rich and/or cadmium-rich 
.alpha.-phase crystallites. Silver-cadmium catalysts which also have 
outstanding selectivity for high yield conversion of acrolein-type 
compounds into allyl alcohol-type compounds are those in which the alloy 
composition consists of more than about 50 percent of .gamma.-phase 
silver-cadmium crystallites as characterized by X-ray diffraction pattern. 
Thirdly, it has been found that the production of silver-cadmium alloy 
catalysts which exhibit the greatest selectivity for converting acrolein 
to allyl alcohol, can be achieved if the coprecipitation step of the 
catalyst preparation is conducted within restricted limitations and under 
controlled conditions. Thus, the total concentration of the water-soluble 
salts (e.g., nitrate salts) in the aqueous solution should be maintained 
in the range between about 5 weight percent, and the solubility limit of 
the salts, and the quantity of caustic added as a precipitating agent 
should approximate the stoichiometric amount within narrow limits. It is 
particularly advantageous to employ a water-soluble hydroxide (e.g., an 
alkali metal hydroxide) as the caustic precipitating agent, and to add the 
caustic rapidly with stirring to facilitate formation of a precipitate of 
fine crystals or gel. Excellent results are obtained, for example, if 17 
grams of silver nitrate and 34 grams of cadmium nitrate are dissolved in 
200 milliliters of water, and 18 grams of potassium hydroxide are 
dissolved in 200 milliliters of water and both solutions are added rapidly 
and simultaneously to 100 milliliters of water with rapid stirring. 
Other precautions must be observed during catalyst preparation if highly 
selective silver-cadmium alloy compositions are to be achieved. It has 
beem found that the calcination step of the catalyst preparation is best 
conducted within narrowly controlled limitations. The calcination step 
should be accomplished at a temperature between about 175.degree. C and 
300.degree. C, and most preferably at a temperature between about 
200.degree. C and 250.degree. C. If calcination of a silver-cadmium alloy 
catalyst is conducted at a temperature above about 300.degree. C, the 
resultant catalyst exhibits less selectivity for high yield conversion of 
acrolein to allyl alcohol in the present invention process step (1). 
It has also been found that silver-cadmium alloy catalysts are most 
effective when supported on a carrier substrate, i.e., in combination with 
an internal diluent. Catalysts prepared without a carrier substrate have 
been found to have a lower activity and shorter catalyst life than the 
corresponding supported catalysts in vapor phase hydrogenation of 
acrolein. A typical carrier substrate will have an initial surface area of 
more than about 1-10 m.sup.2 /gm, and an average pore diameter greater 
than about 20 A. A high proportion of small pores is detrimental to 
catalyst activity, if the size of the pores are such that capillary 
condensation of acrolein occurs and causes pore blockage. This results in 
loss of catalytic activity. 
Silver-cadmium alloy catalysts and X-ray diffraction characterization are 
more fully described in copending patent application Ser. No. 714,201, 
incorporated herein by reference. 
Allyl Alcohol To 4-Hydroxybutanal 
The effluent stream from step (1) of the invention process contains a major 
proportion of allyl alcohol, and minor quantities of propanol and 
propanal. It is economically advantageous to pass the total product 
mixture of allyl alcohol, propanol and propanal from step (1) directly 
into the step (2) reaction zone as a feed stream without separating and 
removing the propanol and propanal by-product components. 
In the practice of step (2) of the invention process, hydrogen and carbon 
monoxide are contacted under hydroformylation conditions with allyl 
alcohol at a temperature between about 20.degree. C and 120.degree. C and 
a pressure between about 15 and 150 psi, preferably in the presence of a 
hydroformylation catalyst. 
In a preferred embodiment of step (2) of the invention process, 
4-hydroxybutanal is produced in high yield selectivity by reacting allyl 
alcohol with hydrogen and carbon monoxide in the presence of a 
metal-ligand complex hydroformylation catalyst at a temperature between 
about 20.degree. C and 120.degree. C and a pressure between about 15 and 
150 psi. Maintaining the pressure of the hydroformylation system below 
about 150 psi is an important aspect of step (2) of the present invention 
process for achieving conversion of allyl alcohol to 4-hydroxybutanal in 
high yield selectivity. 
For the purposes of the present invention it has been found that superior 
results are achieved if the step (2) hydroformylation reaction is 
conducted in the presence of a catalyst which is a complex of rhodium 
metal and a phosphine ligand. 
Any of the rhodium-phosphine complexes disclosed in "Carbon Monoxide in 
Organic Synthesis", Falbe, (Springer-Verlag 1970), pages 22-23, may be 
used. Preferred catalysts have the formula RhCOH(Q.sub.3 P).sub.3, 
RhCOH[(QO).sub.3 P].sub.3, RhCOCl[(QO).sub.3 P].sub.2 and RhCOCl(Q.sub.3 
P).sub.2 wherein Q is phenyl; alkyl phenyl such as tolyl, xylyl, and the 
like; cyclohexyl; alkyl substituted cyclohexyl such as methyl, propyl, 
octyl, and the like; substituted cyclohexyl; and aliphatic radical such as 
methyl, butyl, octyl, and the like; and mixtures of the foregoing, 
preferably phenyl. 
A particularly important aspect of step (2) of the present invention 
process is based on the discovery that exceptionally high yield of 
straight chain 4-hydroxybutanal is obtained when the hydroformylation 
catalyst employed is a complex of rhodium metal, carbon monoxide and 
triaryl phosphine. Illustrative of this class of catalysts is: 
EQU RH.sub.6 (CO).sub. 16 + Q.sub.3 P(excess) 
It is to be especially noted that "straight chain selectivity" of product 
yield is promoted when the molar ratio of triaryl phosphine ligand to 
rhodium metal in the hydroformylation reaction medium is at least 200 to 
1, and preferably at least 400 to 1. Hence, a higher yield of straight 
chain 4-hydroxybutanal is obtained at the expense of branched chain 
2-methyl-3-hydroxypropanal. 
Illustrative of a highly preferred embodiment of the present invention, 
4-hydroxybutanal is produced in a yield of at least 75 weight percent by 
reacting allyl alcohol with hydrogen and carbon monoxide in the presence 
of rhodium carbonyl-triaryl phosphine complex hydroformylation catalyst at 
a temperature between 70.degree. C and 110.degree. C and a pressure 
between about 60 and 100 psi. The relative amounts of hydrogen and carbon 
monoxide employed can vary in accordance with conventional 
hydroformylation processes, i.e., a molar ratio between 10:1 and 1:10. It 
has been observed that a higher yield of 4-hydroxybutanal is favored if 
the ratio of hydrogen to carbon monoxide in the hydroformylation reaction 
is maintained in the range between about 2:1 and 1:2. 
The hydroformylation catalyst is generally employed in a quantity between 
about 0.01 and 5 weight percent, based on the weight of allyl alcohol 
starting material, and preferably a weight percent quantity between about 
0.1 and 1.0, exclusive of the weight of ligand. 
The hydroformylation reaction of the invention preferably is conducted in a 
solvent, one which is inert with respect to the products or starting 
materials. The solvent generally dissolves the catalyst, starting material 
and products. It is convenient and economical to use the feed stream 
mixture of allyl alcohol, propanol and propanal as the solvent medium. If 
it is desirable to include an additional solvent component in the system, 
a wide variety of organic solvents such as, for example, aromatics, 
aliphatics, esters, ethers, nitriles, alcohols, halogenated hydrocarbons, 
and the like, including benzene, cyclohexane, ethyl acetate, methyl 
alcohol, ethyl orthoformate, tetrahydrofuran, dioxane, isopropyl alcohol, 
aliphatic hydrocarbon cuts (saturated), chlorobenzene, methylene chloride, 
propionitrile, acetonitrile, trimethyl acetonitrile, and the like, and 
mixtures thereof may be employed. 
For the operation of the present invention step (2) hydroformylation 
process on a large scale, it is advantageous to employ a rhodium carbonyl 
catalyst component which is incorporated in a large excess of triaryl 
phosphine. The said triaryl phosphine can be included in the reaction 
medium in a quantity which is between 20 and 90 percent of the total 
weight of catalyst and allyl alcohol reactant. Triphenyl phosphine at a 
temperatue above about 80.degree. C is highly fluid and performs as an 
excellent medium for the step (2) hydroformylation process. The highest 
yields are obtained when triphenyl phosphine is employed as the reaction 
medium. 
Another important advantage of including a solvent as a reaction medium is 
to insure proper temperature control. Allyl alcohol is highly reactive 
under hydroformylation conditions, and the solvent performing as a diluent 
aids in maintaining the reaction rate within controlled limits. It is 
advantageous to employ a solvent (e.g., triphenyl phosphine or benzene) in 
a quantity which is at least 50 weight percent of the total reaction 
mixture, and preferably between about 60-75 weight percent. 
The 4-hydroxybutanal which is produced as the high yield product of the 
step (2) hydroformylation reaction can be separated and recovered in step 
(3) by conventional distillation procedures. It is highly preferred, 
however, to subject the hydroformylation product mixture to aqueous phase 
extraction. Suprisingly it was found that water is capable of extracting 
4-hydroxybutanal from the product mixture substantially to the exclusion 
of the other product mixture components. In a commercial scale operation, 
an aqueous phase stream can be contacted countercurrently and continuously 
with reaction product effluent from the step (2) hydroformylation reaction 
zone. The resultant step (3) aqueous phase containing 4-hydroxybutanal is 
an excellent vehicle for subsequent processing procedures. 
4-Hydroxybutanal To 1,4-Butanediol 
The hydrogenation step (4) of the invention process can be conveniently 
accomplished by hydrogenating an aqueous solution of 4-hydroxybutanal 
employing conventional catalytic procedures. Suitable hydrogenation 
catalysts include Raney nickel, copper, cobalt, palladium, platinum, and 
other catalytically active compositions disclosed in literature such as 
U.S. Pat. No. 3,284,517. The hydrogenation of 4-hydroxybutanal normally 
can be conducted at a hydrogen pressure of about 1000-4000 psi and a 
temperature in the range between about 75.degree. C and 200.degree. C. 
Allyl Alcohol Directly To 1,4-Butanediol 
In another embodiment, this invention contemplates a process for producing 
1,4-butanediol which comprises (1) reacting acrolein with hydrogen in the 
vapor phase in the presence of a catalyst comprising a silver-cadmium 
alloy or a carrier substrate, wherein the atomic ratio of silver to 
cadmium in the alloy is in the range of between about 0.1 and 3 to 1, to 
yield a hydrogenation product mixture containing allyl alcohol; and (2) 
contacting the allyl alcohol product mixture with hydrogen and carbon 
monoxide under hydroformylation conditions in the presence of cobalt 
metal-ligand complex catalyst to yield a product mixture containing 
1,4-butanediol. 
For the operation of the step (2) hydroformylation procedure on a large 
scale, it is advantageous to react the allyl alcohol with hydrogen and 
carbon monoxide in the presence of a cobalt metal-ligand complex 
hydroformylation catalyst at a temperature between about 80.degree. C and 
120.degree. C and a pressure between about 300 and 3000 psi in a first 
zone to form 4-hydroxybutanal, and then to pass the reaction stream 
containing 4-hydroxybutanal into a second zone where it is in contact with 
the cobalt metal-ligand complex catalyst at a temperature between about 
150.degree. C and 225.degree. C and a pressure between about 300 to 3000 
psi thereby converting the 4-hydroxybutanal to 1,4-butanediol. 
The pressure in the hydroformylation system is preferably between about 
1000 and 2000 psi in the first zone, and between about 1000 and 2000 psi 
in the second zone. 
If desired, the hydroformylation can be conducted in a single reactor under 
constant pressure, wherein the hydroformylation reaction stream passes 
through the reactor which is maintained with a lower-to-higher temperature 
gradient. Allyl alcohol converts to 4-hydroxybutanal at the lower 
temperature end of the reactor, and the 4-hydroxbutanal converts to 
1,4-butanediol at the higher temperature end of the reactor. 
A preferred type of catalysts for the temperature gradient hydroformylation 
system for converting allyl alcohol to 1,4-butanediol are cobalt metal 
hydroformylation catalysts which are phosphine-modified. A suitable 
catalyst for such a process is a complex of cobalt metal, carbon monoxide 
and trialkyl phosphine (e.g., tributyl phosphine). 
The 1,4-butanediol product of the invention process can be recovered by 
conventional distillation procedures. The respective reactants and 
catalysts are recovered and recycled wherever practical, in order to 
enhance the overall economics of the acrolein to 1,4-butanediol process. 
In another embodiment, this invention provides an improved process for 
producing 1,4-butanediol which comprises (1) reacting acrolein with 
hydrogen in the vapor phase in the presence of a catalyst comprising a 
silver-cadmium-zinc alloy, wherein the atomic ratio of silver to cadmium 
in the alloy is in the range of between about 0.1 and 3 to 1, and the zinc 
is contained in the alloy in a quantity between about 0.001 and 30 weight 
percent, based on the total weight of alloy; (2) contacting the allyl 
alcohol product mixture with hydrogen and carbon monoxide under 
hydroformylation to yield a product mixture containing 4-hydroxybutanal; 
(3) separating the 4-hydroxbutanal from the product mixture; and (4) 
hydrogenating the 4-hydroxybutanal to produce 1,4-buytanediol. 
The superior properties of silver-cadmium-zinc alloy, as a catalyst for 
highly selective hydrogenation of .alpha.,.beta.-unsaturated carbonyl 
compounds to the corresponding .alpha.,.beta.-unsaturated alcohol 
derivatives, are more fully described in copending patent application Ser. 
No. 714,057, incorporated herein by reference. 
The following examples are further illustrative of the present invention. 
The reactants and other specific ingredients are presented as being 
typical, and various modifications can be derived in view of the foregoing 
disclosure within the scope of the invention. 
Examples I-VI illustrate the high conversion yield of allyl alcohol 
obtained by hydrogenation of acrolein in the vapor phase over a novel 
catalyst comprising silver-cadmium alloy on a carrier substrate, in 
accordance with step (1) of the invention. 
Example VII illustrates the invention process step (2) hydroformylation of 
allyl alcohol to yield 4-hydroxybutanal. 
Example VIII illustrates the invention process step (3) hydrogenation of 
4-hydroxybutanal to yield 1,4-butanediol. 
Example IX illustrates the invention process step (2) modification for 
direct conversion of allyl alcohol to 1,4-butanediol employing a cobalt 
catalyst. 
EXAMPLE I 
A catalyst was prepared by the rapid dropwise co-addition of 100 
milliliters of a 1.0 molar AgNO.sub.3, 0.49 molar Cd(NO.sub.3).sub.2 
solution and 100 milliliters of a 1.72 molar KOH solution to 400 
milliliters of vigorously stirred doubly distilled water. About 19 grams 
of Cab-O-Sil H-5 silica (325 m.sup.2 /g, Cabot Corp. Boston, Mass.) were 
then thoroughly mixed with the resultant slurry of silver-cadmium 
coprecipitate. The slurry was filtered, and the filter cake was wasked 
with about 600 milliliters of doubly distilled water. The filter cake was 
calcined in air at 250.degree. C for 16 hours. The resultant material was 
crushed and screened to yield a 50-80 mesh fraction. Bulk chemical 
analysis of this meterial indicated that it contained 54% SiO.sub.2, 17.3% 
Cd, 27.5% Ag with 0.3% K also present. Powder X-ray diffraction studies 
revealed that the composition contained metallic silver crystallites and 
cadmium oxyhydroxide Cd.sub.3 [O(OH)].sub.2 of two types, and cadmium 
hydroxide Cd(OH).sub. 2. The silica, being amorphous, contributed no 
significant X-ray diffraction pattern. 
Approximately 2.62 grams of the prepared silver-cadmium catalyst was 
charged to a 0.925 cm i.d. by 28 cm reactor tube. Hydrogen gas at 200 psig 
was passed over the catalyst in the reactor tube at 500 SCCM and the 
temperature was increased from 21.degree. C to 175.degree. C over the 
course of 1 hour, at which time the gas was changed to one containing 1 
part acrolein and 40 parts hydrogen. The reactor effluent was sampled 
using a gas sampling valve and gas chromatography. Table I summarizes the 
process conditions employed and the product yields obtained. 
Powder X-ray diffraction examination of the used catalyst disclosed lines 
at 2.38, 2.06, 1.46 and 1.25 A, which indicated that a silver-cadmium 
alloy of the .alpha.-type was present on the silica. Chemical analysis of 
the alloy determined the content as 61.4% Ag and 38.5% Cd by weight. No 
discrete Ag or Cd crystallites were detectable. 
TABLE I 
__________________________________________________________________________ 
Mole Weight 
Weight Percent 
Percent Reactor 
Contact 
Percent 
Product Selectivity 
Acrolein 
Catalyst 
Pressure 
Time Acrolein 
Allyl 
In Feed 
Temp. .degree. C 
psig sec. Conversion 
Alcohol 
Propanal 
Propanol 
__________________________________________________________________________ 
2.2 125 206 7.25 2.90 73.80 
26.2 0.0 
2.3 175 198 6.97 41.42 76.20 
22.0 1.8 
0.9 175 500 17.60 
97.40 76.80 
11.2 12.0 
__________________________________________________________________________ 
EXAMPLE II 
A silver-cadmium solution was prepared by dissolving 34 grams AgNO.sub.3 
(0.020 mole) and 30 grams Cd(NO.sub.3).sub.2.sup.. 4H.sub.2 O (0.097 mole) 
in doubly distilled water to a total solution volume of 200 milliliters. A 
sodium hydroxide solution was prepared by dissolving 11.9 grams of NaOH 
(0.298 mole) in sufficient doubly distilled water to adjust the volume to 
200 milliliters. Both solutions were then added dropwise with rapid 
stirring to 400 milliliters of distilled water. The resultant brown 
precipitate was recovered and added to a suspension of 100 milliliters of 
Cab-O-Sil M-5 in 200 milliliters of distilled water with rapid stirring. 
The suspension was filtered, and the filter cake was washed with 2 liters 
of distilled water. The moist filter cake was then calcined in air at 
250.degree. C for 20 hours. The material was cooled in vacuum desiccator, 
and then crushed and screened to yield a 50-80 mesh fraction which by bulk 
chemical analysis was found to contain 61% Ag, 26% Cd and 12% SiO.sub.2. 
Powder X-ray diffraction examination indicated that the silver was present 
as metallic crystallites and the cadmium was present as CdO. 
A quantity of about 7.63 grams of this catalyst precursor was placed in a 
0.925 cm i.d. by 28 cm reactor tube and 200 psig hydrogen flowing at 750 
SCCM was passed over the catalyst precursor as the temperature was raised 
from 23.degree. C to 130.degree. C over a period of 36 minutes, at the end 
of which time the gas was changed to one containing approximately 1 part 
acrolein to 40 parts hydrogen. Table II summarizes the results obtained 
under a variety of process conditions with this catalyst. 
X-ray diffraction analysis of the used catalyst exhibited strong sharp 
lines at 2.39, 2.07, 1.46, and 1.25 A with a strong, relatively sharp, 
back reflection. This indicated an .alpha. -phase silver-cadmium alloy on 
the silica with a composition of 70% Ag and 30% Cd by weight. No discrete 
silver or cadmium crystallites could be detected by bulk chemical 
analysis. 
TABLE II 
__________________________________________________________________________ 
Mole Weight 
Weight Percent 
Percent Reactor 
Contact 
Percent 
Product Selectivity 
Acrolein 
Catalyst 
Pressure 
Time Acrolein 
Allyl 
In Feed 
Temp. .degree. C 
psig sec. Conversion 
Alcohol 
Propanal 
Propanol 
__________________________________________________________________________ 
2.1 125 210 9.4 12.7 46.5 49.5 4.0 
2.1 150 214 9.6 21.2 66.2 31.5 2.3 
2.2 175 204 9.1 38.5 66.1 30.8 3.1 
2.2 210 207 5.1 .apprxeq.100 
70.3 0.37 29.3 
__________________________________________________________________________ 
EXAMPLE III 
For the preparation of a silver-cadmium solution, 34.7 grams AgNO.sub.3 
(0.204 mole) and 80.0 grams Cd(NO.sub.3).sub.2.sup.. 4H.sub.2 O (0.259 
mole) were dissolved in 100 milliliters of distilled water. To this 
solution was added 17.0 grams of 86.7% KOH (0.263 mole) dissolved in 50 
milliliters of distilled water, followed by addition of 400 milliliters of 
distilled water. The slurry mixture which formed was added to 400 
milliliters of Cab-O-Sil M-5 suspended in one liter of distilled water 
with rapid stirring. The resultant solids were filtered off, partially air 
dried overnight, and calcined in air at 250.degree. C for 16 hours. After 
cooling in a vacuum desiccator, the material was partially crushed and 
extracted with distilled water for about 24 hours, then recalcined at 
250.degree. C to 300.degree. C for 21 hours in air. The resultant material 
contained 34% by weight silver, present as metallic crystalllites, 17.9% 
by weight cadmium hydroxide crystallites of two steps, and 33% by weight 
of silica, with less than 0.05% K or Cl. 
This material was crushed and screened to yield a 50-80 mesh fraction, 3.16 
grams of which were loaded into 0.925 cm i.d. by 28 cm reactor tube. 
Hydrogen gas at 200 psig was passed over the catalyst at 750 SCCM and the 
temperature brought rapidly from 22.degree. C to 127.degree. C; then the 
gas was changed to 1 part acrolein in approximately 40 parts hydrogen. 
Table III summarizes the results obtained under various conditions 
employing this catalyst. The reactor effluent stream was analyzed by gas 
chromatographic techniques. Table III summarizes the reactor conditions, 
and the analysis of liquid products trapped at -78.degree. C in a 
collection vessel down stream from the reactor. Bulk chemical analysis of 
the used catalyst in conjunction with X-ray diffraction scanning indicated 
that a 62.9% silver and 37.1% cadmium alloy phase was present. Broad X-ray 
diffraction lines at 2.36, 2.05, 1.45, and 1.23 A along with broad back 
reflection lines were observed. No discrete silver or cadmium metallic 
crystallites were detected. 
TABLE III 
__________________________________________________________________________ 
Mole Weight 
Weight Percent 
Percent Reactor 
Contact 
Percent 
Product Selectivity 
Acrolein 
Catalyst 
Pressure 
Time Acrolein 
Allyl 
In Feed 
Temp. .degree. C 
psig sec. Conversion 
Alcohol 
Propanal 
Propanol 
__________________________________________________________________________ 
2.1 125 209 7.8 38.5 68.0 31.0 0.0 
2.0 150 223 8.3 84.7 69.5 28.0 2.0 
__________________________________________________________________________ 
TABLE IIIA 
__________________________________________________________________________ 
2.2 150 206 7.7 78.0 69.0 28.0 3.0 
1.6 170 290 5.2 99.9 66.0 24.0 10.0 
0.9 156 485 9.7 97.0 71.0 19.0 9.0 
0.9 160 515 10.3 99.9 70.0 13.0 17.0 
__________________________________________________________________________ 
EXAMPLE IV 
A solution was prepared by dissolving 13.07 grams AgNO.sub.3 (0.077 mole) 
and 37.97 grams Cd(NO.sub. 3).sub.2.sup.. 4H.sub.2 O (0.123 mole) in 100 
milliliters of distilled water. A second solution was prepared by 
dissolving 20.75 grams of KOH in distilled water. Both solutions were then 
rapidly and simultaneously added to a vigorously stirred 100 milliliters 
of distilled water, and the resulting precipitate was further suspended by 
the addition of 500 milliliters of distilled water. After 1 hour of 
stirring, 1000 milliliters of Cab-O-Sil M-5 were added, in addition to 
sufficient water at intervals to maintain mixture fluidity. The final 
volume was increased to 1800 milliliters. The pH of the supernatant phase 
was 6.5. Vacuum filtration was employed to produce a filter cake, which 
was washed with 2000 milliliters of distilled water. The filter cake was 
calcined in air at 250.degree. C for 25 hours. After cooling in a vacuum 
desiccator, the catalyst precursor was crushed and screened to yield a 
50-80 mesh fraction. Bulk chemical analysis indicated that the catalyst 
contained 63.7% SiO.sub.2, 7.9% Ag, 18.6% Cd and 0.4% K by weight. Powder 
X-ray diffraction study revealed strong lines due to CdO, and weak lines 
due to Ag. 
About 2.5 grams of this material were charged to a 0.55 cm i.d. by 28 cm 
reactor tube. Under 197 psig hydrogen flowing at 750 SCCM the temperature 
was raised from 24.degree. C to 125.degree. C over the course of 1.1 
hours, at which time 1 part acrolein in 40 parts hydrogen replaced the 
pure hydrogen. Table IV lists the reactor conditions and the analysis of 
the liquid produces collected in a trap held at -78.degree. C under 
reactor pressure. 
X-ray diffraction analysis of the used catalyst indicated the presence of 
.alpha.-phase AgCd and .gamma.-phase AgCd alloys. No discrete metallic 
cadmium or silver was observed. Lines were observed at 2.41, 2.36, 2.08, 
A, and a sharp line characteristic of .gamma. at 1.67. The back reflection 
was weak. Bulk chemical analysis indicated that these alloys had an 
average composition of 29.8% Ag and 70.2% Cd. 
TABLE IV 
__________________________________________________________________________ 
Mole Weight 
Weight Percent 
Percent Reactor 
Contact 
Percent 
Product Selectivity 
Acrolein 
Catalyst 
Pressure 
Time Acrolein 
Allyl 
In Feed 
Temp. .degree. C 
psig sec. Conversion 
Alcohol 
Propanal 
Propanol 
__________________________________________________________________________ 
2.30 125 197 6.1 12 73 21 1 
2.30 150 198 6.1 14 74 26 0 
2.20 175 201 6.2 8 74 26 0 
0.89 125 505 7.8 7 77 23 0 
0.89 150 506 7.8 11 77 22 0 
0.88 175 512 7.9 33 77 17 2 
0.87 185 516 8.0 54 73 21 3 
__________________________________________________________________________ 
EXAMPLE V 
A solution of 34.1 grams AgNO.sub.3 (0.20 mole) and 60.2 grams 
Cd(NO.sub.3).sub.2.sup.. 2H.sub.2 O (0.195 mole) in 200 milliliters of 
water was added simultaneously with a solution of 34.95 grams of 87.4% 
analytical reagent grade KOH (0.591 mole) in 200 milliliters of water to 
400 milliliters of rapidly stirred distilled water. The pH of the 
supernatant phase after addition was 6.0. The volume of the suspension was 
increased to 1500 milliliters, and 1000 milliliters of Cab-O-Sil M-5 were 
added with vigorous stirring. The total volume was adjusted to 2000 
milliliters and the slurry was filtered. The filter cake was washed with 
3000 milliliters of distilled water, calcined in air at 250.degree. C for 
215 hours, and the resulting catalyst precursor was crushed and screened 
to yield a 50-80 mesh fraction. Chemical analysis indicated that the 
composition contained 49.6% SiO.sub.2, 25.9% Ag, 18.6% Cd, and 0.4% K. 
Powder X-ray diffraction indicated that metallic silver and cadmium oxide, 
CdO, both of medium order were present at this stage, besides the 
amorphous SiO.sub.2 which did not contribute detectable X-ray diffraction 
lines. 
A 7.35 grams quantity of this catalyst precursor were placed in a 0.925 cm 
i.d. by 28 cm reactor tube. Under 499 psig hydrogen flowing at 1500 SCCM, 
the reactor was heated to 200.degree. C from 18.degree. C, maintained at 
200.degree. C for 15 minutes, and cooled to 125.degree. C over a total 
period of one hour. The hydrogen was then replaced by 1 part acrolein in 
111 parts hydrogen. Table V summarizes the results based on the analysis 
of liquid products collected at -78.degree. C under reactor pressure. 
A 2.71 gram quantity of the catalyst precursor was placed in a 0.55 cm i.d. 
by 28 cm reactor tube, and under 620 psig hydrogen flowing at 1500 SCCM 
the material was heated from 10.degree. C to 200.degree. C over a period 
of 1 hour. The catalyst was maintained at 200.degree. C for 15 minutes and 
then cooled rapidly to 125.degree. C, at which time an acrolein/hydrogen 
stream replaced the pure hydrogen. Table V summarizes various reactor 
conditions and the composition of the liquid products collected in a trap 
held at -78.degree. C and reactor pressure. 
X-ray diffraction analysis of the used catalyst indicated that the 
principal AgCd alloy was the .alpha.-phase with some .gamma.-phase also 
present. Bulk chemical analysis indicated that the average composition of 
the silver cadmium alloy on silica was 58.2% Ag and 41.8% Cd. 
TABLE V 
__________________________________________________________________________ 
Mole Weight 
Weight Percent 
Percent Reactor 
Contact 
Percent 
Product Selectivity 
Acrolein 
Catalyst 
Pressure 
Time Acrolein 
Allyl 
In Feed 
Temp. .degree. C 
psig sec. Conversion 
Alcohol 
Propanal 
Propanol 
__________________________________________________________________________ 
0.90 125 502 18.7 61.0 72 15 11 
0.89 150 504 18.8 82.0 76 14 8 
0.89 175 501 18.7 99.4 66 3 31 
0.90 180 502 18.7 99.7 68 1 31 
__________________________________________________________________________ 
TABLE V-A 
__________________________________________________________________________ 
Mole Weight 
Weight Percent 
Percent Reactor 
Contact 
Percent 
Product Selectivity 
Acrolein 
Catalyst 
Pressure 
Time Acrolein 
Allyl 
In Feed 
Temp. .degree. C 
psig sec. Conversion 
Alcohol 
Propanal 
Propanol 
__________________________________________________________________________ 
3.00 150 999 6.7 11.1 78.9.sup.(1) 
21.1 0.0 
3.00 175 999 6.7 91.3 74.2.sup.(2) 
15.5 10.3 
__________________________________________________________________________ 
Sty (Grams Allyl Alcohol/Liter Hour)? 
.sup.(1) 103 
.sup.(2) 958 
EXAMPLE VI 
A 28.77 gram quantity of analytical reagent grade KOH (0.446 mole) was 
added to 200 milliliters of distilled water, and the resultant solution 
was warmed to 100.degree. C. With rapid stirring a solution of 25.26 grams 
AgNO.sub.3 (0.149 mole) and 45.85 grams Cd(NO.sub.3).sub.2.sup.. 4H.sub.2 
O (0.149 mole) in 100 milliliters of distilled water was added. The 
suspension was cooled and diluted by the addition of 1000 milliliters of 
2.degree. C distilled water followed by 100 milliliters of Cab-O-Sil M-5. 
Additional distilled water was added to adjust the total volume to 1800 
milliliters. The pH of the supernatant phase was 6.5. 
The suspension was vacuum filtered, and the filter cake was washed with 
2000 milliliters of distilled water and calcined in air at 250.degree. C 
for 20 hours. The catalyst precursor was then crushed and screened to 
provide a 50-80 mesh fraction. X-ray diffraction examination revealed 
principally CdO of medium order, and no detectable silver lines. 
A 4.04 gram quantity of this material was placed in a 0.55 cm i.d. by 28 cm 
reactor tube. The reactor under 490 psig hydrogen flowing at 1500 SCCM was 
heated from 20.degree. C to 200.degree. C, held at 200.degree. C for 15 
minutes and cooled to 125.degree. C over the course of 1.6 hours. At this 
time, the hydrogen was replaced by 1 part acrolein in 109 parts hydrogen. 
Table VI summarizes various reactor conditions, and the resultant 
composition of liquid products collected in a trap held at -78.degree. C 
and reactor pressure. The used catalyst, 5.7% silica with 65.7% alloys, 
consisted of well ordered .alpha.,.gamma. and some .epsilon.-phase AgCd 
alloy on SiO.sub.2. The average alloy composition was 52.4% Ag and 46.6% 
Cd. 
TABLE VI 
__________________________________________________________________________ 
Mole Weight 
Weight Percent 
Percent Reactor 
Contact 
Percent 
Product Selectivity 
Acrolein 
Catalyst 
Pressure 
Time Acrolein 
Allyl 
In Feed 
Temp. .degree. C 
psig sec. Conversion 
Alcohol 
Propanal 
Propanol 
__________________________________________________________________________ 
0.91 125 494 7.9 8.95 69.2 18.0 4.4 
0.89 150 503 8.1 10.80 77.7 19.3 1.0 
0.89 175 506 8.1 55.00 78.7 12.8 9.8 
0.89 190 506 8.1 97.60 70.9 5.1 23.1 
0.91 200 496 7.9 99.10 61.2 2.7 35.7 
__________________________________________________________________________ 
EXAMPLE VII 
Allyl alcohol (10 grams), benzene (40 grams), triphenyl phosphine (30 
grams) and hexarhodium hexadecyl carbonyl (0.05 grams) were sealed in a 
300 ml "Magnadrive" autoclave. The vessel was pressured with carbon 
monoxide to 90 psig and depressurized twice then heated to 80.degree. C. A 
mixture of carbon monoxide and hydrogen (1:1 mole ratio) was admitted to 
the vessel until the pressure reached 90 psig. Constant gas pressure was 
maintained on the reaction vessel by means of a pressure regulator 
attached to a one liter storage vessel also containing a mixture of carbon 
monoxide and hydrogen (1:1 mole ratio). Gas absorption ceased after 40 
minutes. The reactor was cooled to room temperature and the liquid 
contents analyzed by gas chromatography. The allyl alcohol conversion was 
found to be 99% to 4-hydroxybutanal (87 wt%), 2-methyl-3-hydroxypropanal 
(12 wt%) and propanal (1 wt%). 
EXAMPLE VIII 
The liquid contents from Example VII were extracted with two 25 ml portions 
of water. A gas chromatograph of the benzene/triphenyl phosphine/rhodium 
carbonyl showed only traces of aldehydes indicating quantitative 
extraction of the products by water. These aqueous extracts were combined 
(59 grams) and hydrogenated with Raney nickel (1.0 gram) at 110.degree. C 
for 2 hours under 1000 psig hydrogen pressure in a "Magnadrive" autoclave. 
Gas chromatographic analysis of the resulting liquid showed 99% conversion 
to a mixture of 1,4-butanediol and 2-methyl-1,3-propanediol. 
EXAMPLE IX 
In the same manner Example VII, allyl alcohol (10 grams) benzene (40 
grams), tributyl phosphine (50 grams) and dicobalt octa carbonyl (0.1 
gram) are sealed in a 300 ml "Magnadrive" autoclave. The vessel is 
pressurized to 300 psig with a mixture of carbon monoxide and hydrogen 
(1:1 mole ratio), and the gas pressure is held constant while the 
hydroformylation reaction medium is maintained at a temperature of 
100.degree. C for 1 hour. 
The temperature is then increased to 200.degree. C and maintained until the 
conversion of the 4-hydroxybutanal intermediate to 1,4-butanediol is 
completed. 
Similar results are obtained for conversion of acrolein to 1,4-butanediol 
when a silver-cadium-zinc alloy is employed in place of silver-cadmium 
alloy as a hydrogenation catalyst in step (1) of the invention process.