Continuous process for the preparation of 2-ethyl-2-(hydroxymethyl) hexanal and 2-butyl-2-theyl-1,3-propanediol

Disclosed is a continuous process for the manufacture of 2-ethyl-2-(hydroxymethyl)hexanal wherein 2-ethylhexanal, formaldehyde and a tertiary amine are continuously fed to a reaction zone and crude product comprising an aqueous phase and an organic phase containing 2-ethyl-2-(hydroxymethyl)hexanal and 2-ethylhexanal is continuously removed from the reaction zone. Also disclosed are processes for (1) the azeotropic distillation of the organic phase of the crude product whereby unreacted 2-ethylhexanal is recovered and (2) the catalytic hydrogenation of the refined, organic phase of the crude product to produce 2-butyl-2-ethyl-1,3-propanediol.

This invention pertains to an improved process for the preparation of 
2-ethyl-2-(hydroxymethyl)hexanal by the condensation of 2-ethylhexanal and 
formaldehyde in the presence of a trialkylamine catalyst. More 
specifically, this invention pertains to a continuous process for the 
manufacture of 2-ethyl-2-(hydroxymethyl)hexanal wherein 2-ethylhexanal, 
formaldehyde and a tertiary amine are continuously fed to a reaction zone, 
crude product comprising an aqueous phase and an organic phase containing 
2-ethyl-2-(hydroxymethyl)hexanal and 2-ethylhexanal is continuously 
removed from the reaction zone. This invention also concerns the 
azeotropic distillation of the organic phase of the crude product whereby 
unreacted 2-ethylhexanal is recovered. Finally, this invention provides 
for the catalytic hydrogenation of the refined, organic phase of the crude 
product to produce 2-butyl-2-ethyl1,3-propanediol. 
Japanese Patent Publication 73 43,085 describes the preparation of 
2-ethyl-2-(hydroxymethyl)hexanal (EHMH) by the reaction of 2-ethylhexanal 
and formaldehyde in the presence of alkali metal hydroxides at a pH of 8.0 
to 11.0. The EHMH is converted to 2-butyl-2-ethyl-1,3-propanediol (BEPD) 
by the Cannizzaro reaction using a second equivalent of formaldehyde and 
alkali metal hydroxide. This process generates one equivalent of sodium 
formate for each equivalent of BEPD. Purification of the aqueous sodium 
formate stream or disposal of this stream is the major disadvantage of 
this process. Another disadvantage is the added raw material cost 
occasioned by the use of an extra equivalent of formaldehyde to convert 
the BHMH to BEPD. British Patent 1,320,387 discloses the preparation of 
2-ethyl-2-(hydroxymethyl)hexanal by heating with vigorous agitation a 
mixture of 2-ethylhexanal, formaldehyde and triethylamine at 
90.degree.-93.degree. C. for eight hours. A slight stoichiometric excess 
of formaldehyde was used and the amount of triethylamine employed was 4.6 
weight percent based on the total weight of the materials. Despite the 
eight hour reaction time and vigorous agitation of the batch reaction 
mixture, the percent conversion of 2-ethylhexanal reported was 
approximately 81.2. Thus, the product obtained contained a substantial 
amount of unreacted formaldehyde which can detrimentally affect the 
performance of catalysts, especially nickel catalysts, used to hydrogenate 
EHMH to BEPD. The presence of such substantial amounts of formaldehyde 
also is undesirable due to the formation of formaldehyde polymers which 
can foul or plug processing equipment such as piping used to transport 
effluents from distillation columns. 
We have found that 2-ethyl-2-(hydroxymethyl)hexanal may be produced at 
improved rates by reacting aqueous formaldehyde with a stoichiometric 
excess of 2-ethylhexanal in the presence of a tertiary amine wherein the 
tertiary amine functions both as a catalyst and a co-solvent. Thus, one 
embodiment of the present invention is a continuous process for the 
preparation of 2-ethyl-2-(hydroxymethyl)hexanal by the condensation of 
2-ethylhexanal and formaldehyde in the presence of a tertiary amine by the 
steps comprising: 
(1) continuously feeding to a reaction zone 2-ethylhexanal, aqueous 
formaldehyde and a tertiary amine, wherein (i) a stoichiometric excess of 
2-ethylhexanal is fed and (ii) the feed rates of tertiary amine and 
2-ethylhexanal maintain in the reaction zone a tertiary 
amine:2-ethylhexanal weight ratio of at least 0.2; and 
(2) continuously removing from the reaction zone a crude product mixture 
comprising (i) an aqueous phase and (ii) an organic phase containing 
2-ethyl-2-(hydroxymethyl)hexanal and 2-ethylhexanal. 
We have found that when the weight ratio of tertiary amine:2-ethylhexanal 
is maintained at a value of at least 0.2, the tertiary amine functions 
both as a catalyst for the condensation reaction and as a co-solvent for 
the 2-ethylhexanal and the aqueous formaldehyde, thereby permitting more 
intimate contact of the reactants and an improved reaction rate. British 
Patent 1,320,387 referred to above proposes the use of alkanols and cyclic 
ethers as solubilizers to improve mixing and accelerate the reaction. We 
have found that the use of methanol in the process gives little 
improvement in reaction rate. Furthermore, the use of the proposed 
extraneous materials presents recovery and recycle problems including 
toxicological and environmental considerations. The use of alkanols or 
cyclic ethers also can be detrimental to the efficient separation of the 
aqueous and organic phases recovered from the reaction zone. 
The 2-ethylhexanal is fed to the reaction zone in a stoichiometric excess 
relative to the formaldehyde fed. Generally, the 2-ethylhexanal excess is 
at least 0.1 mole percent, preferably about 0.3 to 0.6 mole excess 
relative to the stoichiometric amount. The aqueous formaldehyde solution 
used in our novel process may contain from about 20 to 80 weight percent 
formaldehyde and a minor amount, e.g., up to 1 weight percent, of methanol 
as a stabilizer. The aqueous formaldehyde preferably contains about 30 to 
50 weight percent formaldehyde. 
The tertiary amine catalyst/co-solvent preferably is a trialkyl amine 
having a total carbon content of up to about 12 such as trimethylamine, 
triethylamine, tripropylamine and the like. As stated above, the tertiary 
amine and 2-ethylhexanal are fed to the reaction zone at rates which 
maintain a tertiary amine:2-hexanal weight ratio of at least 0.2 in the 
reaction zone. Although the weight ratio of tertiary amine:2-ethylhexanal 
may be as high as about 0.5, we have found that good production rates may 
be achieved by maintaining the ratio in the range of about 0.3 to 0.4. 
The condensation reaction may be carried out at a temperature of about 
90.degree. to 140.degree. C. and a pressure of about 1 to 10 bars 
absolute. Preferred reaction conditions are a temperature of about 
100.degree. to 125.degree. C. and a pressure of about 1 to 3 bars 
absolute. 
The practice of the condensation process provided by the present invention 
permits the preparation of EHMH at improved production rates even though 
the degree of agitation which may be achieved in continuous operation 
typically is substantially less than the agitation which is possible when 
operating a batch process. The formation of by products such as 
2-ethylhexanol, formate salts, and high molecular weight esters resulting 
from the Tischenko reaction of EHMH is minimized. Normally, the production 
rate (the space time yield) is at least 100 grams EHMH per liter hour 
wherein liter refers to the total volume (in liters) of the mixture in the 
reaction zone. At space time yields of 100 g/L hour, the process typically 
gives a formaldehyde conversion of at least 90 mole percent which results 
in the organic phase of the crude reaction product having a formaldehyde 
content of less than 1.7 weight percent based on the weight of the organic 
phase. It is preferred to operate the process in a manner to achieve space 
time yields of EHMH in the range of about 100 to 500 g/L hour while 
obtaining a formaldehyde conversion of greater than about 90 to 95 mole 
percent and a formaldehyde concentration of less than 1.7 weight percent 
in the organic phase of the crude product. 
The continuous condensation process may be carried out by continuously 
feeding 2-ethylhexanal, aqueous formaldehyde and a tertiary amine, 
including recycle 2-ethylhexanal and tertiary amine, to a reaction zone 
and continuously removing a crude product stream comprising an aqueous 
phase and an organic phase. The reaction zone may comprise one or more 
reactors designed to provide agitation of the reaction mixture, e.g., 
reactors equipped with agitators, a tube reactor containing packing 
material, recirculating reactors and the like. To obtain formaldehyde 
conversions of at least 90 mole percent, the residence time in the 
reaction zone typically is about 3.5 to 6 hours. The effluent from the 
reaction zone is fed to a decanter wherein all, or a substantial portion 
of, the aqueous phase is separated from the organic phase which contains 
EHMH product, tertiary amine, unreacted 2-ethylhexanal, BEPD and minor 
amounts of formaldehyde, the ammonium formate salt of the tertiary amine, 
methanol and higher molecular weight organics such as formaldehyde 
condensation products and C-17 and C-18 esters [2-ethylhexanoate and 
2-ethyl-2-(hydroxymethyl)hexanoate esters of 
2-butyl-2-ethyl-1,3-propanediol]. The aqueous phase contains the ammonium 
formate salt of the tertiary amine which may be recovered by treating the 
aqueous phase with an alkali metal hydroxide. For example, the aqueous 
phase may be contacted with sodium hydroxide to produce sodium formate and 
the tertiary amine which is recovered from the resulting mixture by 
distillation. 
In a second embodiment of the present invention, the crude organic phase 
obtained in accordance with the condensation process described hereinabove 
is fed continuously to an extractive, azeotropic distillation zone to 
recover the tertiary amine and unreacted 2-ethylhexanal. This embodiment 
of our invention provides a continuous process for the recovery of 
2-ethylhexanal and tertiary amine from a mixture comprising 
2-ethyl-2-(hydroxymethyl)hexanal, 2-ethylhexanal, tertiary amine and water 
by the steps of: 
(1) continuously feeding the mixture to the mid section of a distillation 
column; 
(2) continuously feeding water to the middle or upper section of the 
distillation column; 
(3) continuously removing from the distillation column a vapor stream 
comprising 2-ethylhexanal, tertiary amine and water; 
(4) condensing the vapor stream of step (3) to obtain a two phase liquid 
and separating the organic phase rich in 2-ethylhexanal and tertiary 
amine; and 
(5) continuously removing from the lower section of the distillation column 
a two phase mixture depleted in 2-ethylhexanal and tertiary amine. 
The extractive, azeotropic distillation zone comprises a distillation 
column and decanters for separation of the aqueous and organic effluents 
of the distillation column. The crude organic phase obtained from the 
condensation process is fed continuously to the midsection of the 
distillation column. Water also is fed to the distillation at or near the 
top and/or to the mid section of the column. The distillation column is 
operated at approximately atmospheric pressure, a base temperature of 
about 100.degree. to 110.degree. C. and a head temperature of about 
96.degree. to 98.degree. C. to minimize decomposition of the EHMH and 
formation of esters via the Tischenko reaction. Maintaining the column 
head temperature at about 96.degree. to 98.degree. C. maximizes the amount 
of 2-ethylhexanal removed as vapor from the distillation column. 
A vapor stream comprising tertiary amine and a constant boiling mixture 
(binary azeotrope) consisting of 48.4 weight percent 2-ethylhexanal and 
51.6 weight percent water and having a boiling point of 96.4.degree. C. is 
removed continuously at or near the top of the column. The vapor stream is 
condensed and the organic phase comprising 2-ethylhexanal and tertiary 
amine is separated, e.g., by means of a decanter, from the resulting two 
phase liquid and recycled to the condensation reaction zone. The aqueous 
phase of the two phase liquid may be recycled to the upper portion of the 
distillation column. 
A liquid stream comprised of all, or essentially all, of the EHMH fed to 
the distillation column, water, BEPD and minor amounts of formaldehyde, 
2-ethylhexanal, and C-17 and C-18 esters is removed continuously from the 
base of the distillation column and fed to a decanter wherein the aqueous 
and organic phases of the column underflow are separated. The aqueous 
phase of the underflow stream containing minor amounts of the formate salt 
of the tertiary amine and EHMH may be treated with an alkali metal 
hydroxide to recover the tertiary amine for recycle to the condensation 
reaction zone. The organic phases comprises a major amount of EHMH and 
minor amounts of water, formaldehyde, 2-ethylhexanal, and C-17 and C-18 
esters. The refined organic phase obtained from the extractive, azeotropic 
distillation zone preferably is comprised of at least 80 weight percent 
EHMH and less than about 2 weight percent formaldehyde. 
In another embodiment of the present invention, the refined organic phase 
is fed continuously to a hydrogenation zone wherein the EHMH component of 
the refined organic phase is catalytically hydrogenated at elevated 
temperatures and pressures, according to known means, to produce BEPD. For 
example, the catalysts and/or processes described in U.S. Pat. Nos. 
4,097,540, 4,181,810, 4,250,337, 4,386,219, 4,393,251, 4851,592 and 
4,855,515 may be used to convert the EHMH to BEPD. This embodiment 
involves a process for the preparation of BEPD by the condensation and 
recovery processes described hereinabove in combination the hydrogenation 
of the EHMH to BEPD. Thus, our invention includes a process for the 
continuous preparation of 2-butyl-2-ethyl-1,3-propanediol which comprises 
the steps of: 
(1) continuously feeding to a reaction zone 2-ethylhexanal, aqueous 
formaldehyde and a tertiary amine, wherein (i) a stoichiometric excess of 
2-ethylhexanal is fed and (ii) the feed rates of tertiary amine and 
2-ethylhexanal maintain in the reaction zone a tertiary 
amine:2-ethylhexanal weight ratio of at least 0.2; 
(2) continuously removing from the reaction zone a crude product mixture 
comprising (i) an aqueous phase and (ii) an organic phase containing 
2-ethyl-2-(hydroxymethyl)hexanal, 2-ethylhexanal and tertiary amine; 
(3) continuously feeding the organic phase of step (2) to the mid section 
of a distillation column; 
(4) continuously feeding water to the middle or upper section of the 
distillation column; 
(5) continuously removing from the distillation column a vapor stream 
comprising 2-ethylhexanal, tertiary amine and water; 
(6) condensing the vapor stream of step (5) to obtain a two phase liquid, 
separating the organic phase rich in 2-ethylhexanal and tertiary amine, 
and recycling the organic phase to the reaction zone; 
(7) continuously removing from the lower section of the distillation column 
a two phase mixture depleted in 2-ethylhexanal and tertiary amine; 
(8) continuously separating the two phase mixture of step (5) into (i) an 
aqueous phase and (ii) an organic phase rich in 2-ethyl-2-(hydroxymethyl) 
hexanal; and 
(9) continuously feeding the organic phase of step (8) to a hydrogenation 
zone wherein the 2-ethyl2-(hydroxymethyl)hexanal is hydrogenated to 
2-butyl-2-ethyl-1,3-propanediol in the presence of a hydrogenation 
catalyst. 
The hydrogenation zone comprises a pressure vessel containing one or more 
fixed beds of a suitable hydrogenation catalyst. The product of the 
hydrogenation zone may be recycled to dissipate the heat of hydrogenation. 
The hydrogenation preferably is carried out by passing the refined organic 
phase over one or more fixed beds of a supported nickel catalyst at a 
total pressure of about 21 to 36 bars absolute and at a hydrogenation zone 
exit temperature of about 150.degree. to 170.degree. C. The catalyst may 
comprise nickel deposited on a catalyst support material such as silica, 
alumina, carbon, titanium dioxide, molecular sieves, zeolites, kieselguhr, 
etc. Normally, the supported nickel catalysts are comprised of about 1 to 
90 weight percent nickel, calculated as [Ni], based on the total weight of 
the catalyst. Preferred nickel catalysts comprise about 1 to 70 weight 
percent nickel on silica/alumina. 
The conversion of EHMH to BEPD in the hydrogenation zone typically is 
greater than 99%, e.g., 99.7% or greater. The product of the hydrogenation 
zone normally comprises at least 75 weight percent BEPD and minor amounts 
of water, methanol, 2-ethylhexanol, BEPD 2-ethylhexanoate and BEPD 
2-ethyl-2-(hydroxymethyl)hexanoate, We have found that the activity of the 
nickel hydrogenation catalyst does not decline measurably over 60 days of 
continuous operation. 
The hydrogenation product may be refined according to known purification 
techniques to obtain BEPD having a purity of 99.5% or greater. Thus, the 
effluent from the hydrogenation vessel may be fed to a flash pot wherein 
the pressure is reduced and essentially all of the material, except for 
any high boiling components present, is flashed to the mid section of a 
first distillation column operated at about 200.degree. C. under reduced 
pressure. Low boiling components comprising water and 2-ethylhexanol are 
removed from the top of the column and remainder is removed from the base 
of the column and fed to the mid-section of a second distillation column, 
also operated at 200.degree. C. and at reduced pressure. The ester 
impurities are underflowed from the second column and purified BEPD, 
typically containing less than 50 ppm nitrogen, is removed from the top, 
of the column.

Referring to the FIGURE, fresh 2-ethylhexanal, aqueous formaldehyde and 
tertiary amine are fed continuously by means of conduits 2, 4, 6, 8, and 
10 to condensation reaction zone 12 along with reaction mixture recycle, 
fed via conduits 14, 8 and 10, and recycle 2-ethylhexanal and tertiary 
amine, fed via conduits 16 and 10. The 2-ethylhexanal:formaldehyde mole 
ratio fed by conduit 10 normally is in the range of about 1.1:1 to about 
1.6:1. The residence time of the reaction mixture within zone 12 is about 
3.5 to 6 hours. Crude product comprising (i) an aqueous phase and (ii) an 
organic phase containing 2-ethyl-2-(hydroxymethyl)hexanal and 
2-ethylhexanal is removed continuously from reaction zone 12 and 
transported by conduit 18 to decanter 20. 
The crude organic phase comprising EHMH, 2-ethylhexanal and tertiary amine 
is transported by conduits 22 and 23 from decanter 20 to the mid section 
of extractive, azeotropic distillation column 24. Fresh water is supplied 
to column 24 by conduits 26 and 23 as a mixture with the crude organic 
phase and/or by conduit 28. Alternatively, a portion or all of the fresh 
water may be provided to column 24 by means of conduit 28. The base of 
column 24 is maintained at about 100.degree. to 110.degree. C. by 
recirculating a liquid phase from the base of column 24 through lines 30 
and 32, reboiler 34 and line 36. Vapor comprising water, 2-ethylhexanal 
and tertiary amine is removed continuously from column 24 via conduit 38, 
condensed in condenser 40 and fed by conduit 42 to decanter 44. The 
temperature of the vapor phase exiting column 24 normally is in the range 
of about 96.degree. to 98.degree. C. The organic phase comprising 
2-ethylhexanal and tertiary amine is recycled via conduits 16 and 10 to 
reaction zone 12. The aqueous phase is returned to the upper portion of 
distillation column 24 by conduit 46. 
A liquid phase comprising all, or essentially all, of the EHMH fed to 
distillation column 24, water and minor amounts of formaldehyde, 
2-ethylhexanal, and 2-ethylhexanoate and 
2-ethyl-2-(hydroxymethyl)hexanoate esters of 
2-butyl2-ethyl-1,3-propanediol is removed continuously from the base of 
column 24 by conduit 30 and fed via conduit 48 to decanter 50. The refined 
organic phase separated in decanter 50 is fed via conduit 52 to 
hydrogenation zone 54 wherein the EHMH is catalytically hydrogenated to 
BEPD as described hereinabove. The hydrogenation zone may comprise one or 
more pressure vessels containing a supported hydrogen ation catalyst. The 
hydrogenation preferably is carried out at a temperature of about 
150.degree. to 170.degree. C. and a pressure of about 28 to 36 bars 
absolute in the presence of a supported nickel catalyst, e.g., about 50 
weight percent nickel on alumina. 
An important feature of the present invention is the provision of the 
EHMH-containing, refined organic phase which contains less than (i) 2.0 
weight percent formaldehyde and (ii) 1.0 weight percent 2-ethylhexanal. 
The upper limits of formaldehyde and 2-ethylhexanal preferably are 3.0 and 
5.0 weight percent, respectively. The low formaldehyde concentration 
permits the use of nickel catalysts and relatively low hydrogenation 
pressures in hydrogenation zone 54. Nickel hydrogenation catalysts 
normally are rapidly deactivated by the presence of significant amounts of 
formaldehyde, e.g., formaldehyde concentrations of about 3.0 weight 
percent or higher, in hydrogenation feed mixtures. The low concentrations 
of 2-ethylhexanal results in the production of BEPD at high yields e.g., 
85% or greater, based on the 2-ethylhexanal fed to reaction zone 12. 
Hydrogenation product is removed continuously from hydrogenation zone 54 
through conduit 56 and transported to a BEPD refining zone (not shown) 
comprising a distillation train wherein high and low boilers are separated 
from the BEPD according to conventional purification techniques. The 
refined BEPD thus obtained typically has a purity of 99.5% or greater and 
a nitrogen content of less than 50 ppm. 
The aqueous phases, containing the formate salt of the tertiary amine, 
collected in decanters 20 and 54 are combined by means of conduits 58, 60 
and 62 and fed via conduit 63 to amine recovery zone 64. The tertiary 
amine is liberated from the formate salt of the amine by treating the 
aqueous phases with an alkali metal hydroxide, supplied via line 66, and 
the tertiary amine thus recovered is returned to reaction zone 12 by 
conduits 68, 8 and 10. An aqueous waste stream containing alkali metal 
formate is removed from amine recovery zone 64 for disposal in a 
conventional waste water treatment plant. 
The processes provided by the present invention are further illustrated by 
the following examples. 
EXAMPLES 1-3 AND COMATIVE EXAMPLES 1 AND 2 
A one liter Parr autoclave was charged with 2-ethylhexanal (334 g, 406 mL, 
2.6 mole), 44% aqueous formaldehyde (136.4 g, 122 mL, 2.0 mole) and 
varying amounts of triethylamine to determine the effect of increasing 
triethylamine concentration on reaction rate. After purging with nitrogen, 
the autoclave was sealed and heated at 100.degree. C. for one hour. The 
autoclave was cooled and the contents were analyzed for formaldehyde 
(HCHO) by calorimetric analysis and for 2-ethyl2-(hydroxymethyl)hexanal 
(EHMH) by gas chromatography analysis. The yield of EHMH was calculated 
based on the 2-ethylhexanal consumed which was determined after correcting 
the gas chromatograph area for methanol and excess 2-ethylhexanal. Table I 
sets forth the amount of triethylamine (TEA, g/mL), the concentration by 
weight of triethylamine based on the total weight of the materials charged 
(TEA, %), the mole percent of formaldehyde converted (HCHO Conv.) and the 
percent yield of EHMH obtained. 
TABLE I 
______________________________________ 
TEA HCHO Yield 
Example g/mL % Conv. EHMH 
______________________________________ 
1 47.0/65.4 10 86 68.2 
2 70.6/98.0 15 92 83.4 
3 94.0/130.6 
20 95 88.0 
C-1 9.4/13.0 2 40 35.2 
C-2 23.6/32.6 5 74 48.9 
______________________________________ 
The data presented in Table I establish the beneficial effects obtained by 
the use of larger amount of triethylamine. The weight ratios of the 
triethylamine to 2-ethylhexanal initially fed in these batch experiments 
vary from the ratios resulting from continuous operation wherein the 
triethylamine and reactants are continuously consumed. 
EXAMPLES 4-6 AND COMATIVE EXAMPLES 3 AND 4 
To determine the effect of carrying out the condensation reaction in the 
presence of methanol as a co-solvent, Examples 1-3 and Comparative 
Examples 1 and 2 were repeated except that the reactions were carried out 
in the presence of 30 weight percent methanol based on the total weight of 
materials charged to the autoclave. The amounts of methanol used (MeOH, g) 
in each example and the triethylamine concentration, the formaldehyde 
conversion and yield of EHMH, as described in the preceding examples, are 
set forth in Table II. 
TABLE II 
______________________________________ 
TEA HCHO Yield 
Example % MeOH Conv. EHMH 
______________________________________ 
4 10 156 81.0 81.3 
5 15 162 84.0 87.0 
6 20 170 90.0 85.0 
C-3 2 144 72.8 65.0 
C-4 5 148 78.8 72.8 
______________________________________ 
The results reported in Table II establish that the presence of methanol 
improves formaldehyde conversion and yield of 
2-ethyl-2-(hydroxymethyl)hexanal when used in combination with low 
concentrations of triethylamine. However, superior results are achieved 
only when triethylamine is used in initial concentrations of 10 to 20 
weight percent. 
EXAMPLE 7 
This example illustrates the continuous operation of the processes of our 
invention employing the production system depicted in the FIGURE. All 
parts given are by weight unless stated otherwise. 
Fresh 2-ethylhexanal, 44% aqueous formaldehyde and triethylamine are fed at 
406.0, 271.0 and 1.66 parts per hour, respectively, to reaction zone 12 
via conduits 2, 4, 6, 8 and 10 along with 257.0 parts per hour 
2-ethylhexanal, 1.4 parts per hour formaldehyde and 132.9 parts per hour 
triethylamine supplied by recycle conduits 16 and 68. Reaction zone 12 
comprises a plurality of recirculating reactors maintained at about 
110.degree. C. and about 4.5 bars absolute. The residence time of the 
reaction mixture in the reaction zone is about 3.7 hours. Crude 
condensation reaction mixture comprising EHMH is removed continuously from 
reaction zone 12 at a rate of 1085.0 parts per hour and fed to decanter 20 
wherein the crude organic phase is separated from the aqueous phase. The 
space time yield of EHMH averages 117 g/liter hour. 
Crude organic phase is removed from decanter 20 at a rate of 920.3 parts 
per hour and fed to distillation column 24 via lines 22 and 23 along with 
water which is added at 150.0 parts per hour through conduit 26. No water 
is fed through conduit 28. The base of column 24 is maintained at about 
105.degree. C., as described hereinabove, to produce an overhead vapor 
stream which is removed continuously via conduit 38, condensed in 
condenser 40 and fed by conduit 42 to decanter 44. The organic phase from 
decanter 44 comprising 2-ethylhexanal and tertiary amine is recycled via 
conduits 16 and 10 to reaction zone 12 at the rate of 364.0 parts per 
hour. The aqueous phase from decanter 44 is returned to the upper portion 
of column 24 by conduit 46. 
A liquid phase stream is removed continuously from column 24 and 
transported by conduits 30 and 48 to decanter 50 at a rate of 692.5 parts 
per hour. The refined organic phase separated in decanter 50 is fed via 
conduit 52 at 541.7 parts per hour to hydrogenation zone 54 wherein the 
EHMH is catalytically hydrogenated to BEPD using a 50% nickel on alumina 
catalyst. The hydrogenation is carried out in the liquid phase at a 
pressure of 35.5 bars absolute and a catalyst bed exit temperature of 
160.degree. C. using a trickle bed reactor. Hydrogenation zone 54 included 
means for recycling effluent from the hydrogenation reactor to the reactor 
feed at a volume ratio of 10 parts effluent per part fresh feed. 
The hydrogenation product of conduit 56 is flash distilled at 50 torr to 
remove most of the high boiling impurities. The top takeoff of the flash 
column is fed to a second column which removes all low boiling impurities. 
This column is operated at 6.5 bars absolute with a base temperature of 
200.degree. C. The base overflow from this column is fed to the refining 
column. This column is operated at 20 torr with a base temperature of 
210.degree. C. BEPD of 99.7 percent purity is removed from the top of the 
column and a small amount of high boiling esters is removed from the base 
of the column. 
The yield of BEPD is 85 percent based on the 2-ethylhexanal, and 68 percent 
based on the formaldehyde, fed to the reaction zone 12. Utilization of the 
triethylamine catalyst is very efficient with an average usage of 1 part 
by weight triethylamine per 200 parts by weight BEPD. 
The compositions, by weight percent, of the mixtures present in conduits 
10, 16, 18, 22, 23, 42, 48, 52 and 56 during the operation of the 
processes described in Example 4 are set forth in Table III wherein HCHO 
is formaldehyde, HEH is 2-ethylhexanal, TEA is triethylamine, EHMH is 
2-ethyl-2-(hydroxymethyl)hexanal. Esters are 2-ethylhexanoate and 
2-ethyl2-(hydroxymethyl)hexanoate esters of 
2-butyl-2-ethyl-1,3-propanediol and BEPD is 
2-butyl-2-ethyl-1,3-propanediol. These mixtures also contain varying 
amounts of additional components such as methanol, ethanol, TEA formate 
and formaldehyde condensation products, depending on the particular 
mixture. 
TABLE III 
__________________________________________________________________________ 
Conduit 
Water 
HCHO 
HEH TEA EHMH Esters 
BEPD 
Other 
__________________________________________________________________________ 
10 14.0 
2.2 34.5 
12.4 
28.5 1.9 3.4 3.1 
16 1.9 0.4 70.3 
24.0 
1.9 -- -- 1.5 
18 13.7 
0.8 23.7 
8.1 33.2 2.9 6.7 10.9 
22 2.7 0.9 27.9 
9.5 39.1 3.4 7.9 8.6 
23 16.4 
0.7 24.0 
8.2 33.6 2.9 6.8 7.4 
42 49.5 
0.1 22.4 
10.7 
0.7 -- -- 16.6 
48 22.9 
0.9 1.2 0.2 50.8 5.6 10.6 
7.8 
52 8.2 1.1 1.5 0.3 65.0 7.2 13.5 
3.2 
56 8.1 -- Trace 
Trace 
-- 7.1 78.6 
6.2 
__________________________________________________________________________ 
The invention has been described in detail with particular reference to 
preferred embodiments thereof, but it will be understood that variations 
and modification can be effected within the spirit and scope of the 
invention.