Organic compounds -- part of the class 532-570 series – Organic compounds – Oxygen containing
Reexamination Certificate
1999-08-25
2002-01-29
O'Sullivan, Peter (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Oxygen containing
Reexamination Certificate
active
06342646
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an improved process for the production of 1,3-propanediol by catalytic hydrogenation of 3-hydroxypropanal (HPA).
TECHNICAL BACKGROUND
1,3-Propanediol is used as a monomer unit for polyesters and polyurethanes and as a starting material for synthesizing cyclic compounds.
Various processes are known for the production of 1,3-propanediol via 3-hydroxypropanal (HPA) which start either from C2 and C1 structural units or from a C3 structural unit, such as, for example, acrolein. When acrolein is used, it is first hydrated in aqueous phase in the presence of an acidic catalyst to form HPA. After removing the unreacted acrolein, the aqueous reaction mixture formed during hydration still contains, in addition to 85 wt % based on total organics of 3-hydroxypropanal, approximately 8 wt % 4-oxaheptane-1,7-dial and further organic components in smaller proportions by weight. This reaction mixture is hydrogenated in the presence of hydrogenation catalysts to produce 1,3-propanediol. The 1,3-propanediol is recovered from the reaction mixture by distillation and/or extraction based methods known to those skilled in the art.
U.S. Pat. No. 5,334,778 discloses a two stage process for hydrogenating 3-hydroxypropanal which yields 1,3-propanediol having a residual carbonyl content, expressed as propanal, of below 500 ppm. The hydrogenation is carried out at 30° C. to 80° C. to a 3-hydroxypropanal conversion of 50 to 95% and then is continued at 100° C. to 180° C. to a 3-hydroxypropanal conversion of substantially 100%. Suitable hydrogenation catalysts therein include Raney nickel suspension catalysts, and supported catalysts based on platinum or ruthenium on activated carbon, Al203, SiO2, or TiO2 as well as nickel on oxide- or silicate-containing supports.
According to U.S. Pat. No. 5,015,789, very active nickel catalysts exhibit inadequate long-term stability, with a rapid drop in hydrogenation conversion and reaction speed upon repeated use of the catalyst. This results in frequent replacement of the entire catalyst packing, which is associated with known problems in the disposal and working up of compounds containing nickel. In addition, soluble nickel compounds can form in the process and are released into the product stream, requiring further steps to separate the resulting contaminants.
Copending patent application, Ser. No. 60/099,235 discloses a two-stage process for the production of 1,3-propanediol which comprises hydrogenating an aqueous solution of 3-hydroxypropanal using an oxide-supported metal hydrogenation catalyst in a first, low temperature, stage and continuing hydrogenation in a second, high temperature, stage using an activated carbon-supported metal hydrogenation catalyst.
Hydrogenation processes may be characterized by the conversions, selectivities, and space-time yields achievable therewith. Percent conversion of 3-hydroxypropanal is defined by:
X
=
%
Conversion
of
HPA
=
moles
of
HPA
converted
moles
of
HPA
supplied
×
100
Selectivity of the hydrogenation process is a measure of the amount of converted 3-hydroxypropanal which is converted into the desired product:
%
Selectivity
=
moles
of
1
,
3
-
propanediol
moles
of
HPA
converted
×
100
The space-time yield is another important characteristic for continuous hydrogenation processes, stating the achievable quantity of product per unit time and reaction volume.
When hydrogenating 3-hydroxypropanal to 1,3-propanediol on a large industrial scale, it is vital, with regard to the economic viability of the hydrogenation process and the quality of the product, for conversion and selectivity to be as close as possible to 100%. The 1,3-propanediol may be separated from the water as well as remaining 3-hydroxypropanal and secondary products contained in the product stream by distillation after the hydrogenation. However, this distillative separation is rendered very difficult by residual 3-hydroxypropanal and secondary products and may even become impossible due to reactions between the residual 3-hydroxypropanal and 1,3-propanediol to yield acetals such as 2-(2′-hydroxyethyl)-1,3-dioxane (HED), which have a boiling point close to the boiling point of 1,3-propanediol. Thus, the lower the conversion and selectivity, the poorer the achievable product quality.
In order to produce 1,3-propanediol economically, it is also important for the catalyst to exhibit high activity for the hydrogenation of 3-hydroxypropanal. The objective should thus be to find a process in which the smallest possible quantity of catalyst is necessary for the production of 1,3-propanediol; i.e., it is desirable to achieve the greatest possible conversion of 3-hydroxypropanal to 1,3-propanediol with a small volume of catalyst.
Another important quality criterion for hydrogenation catalysts is their operational service life. Good catalysts should ensure high conversion and selectivity in the hydrogenation of 3-hydroxypropanal to 1,3-propanediol over the course of their service life.
It is an object of the present invention to provide an improved process for the preparation of 1,3-propanediol via the hydrogenation of 3-hydroxypropanal whereby the service life of the hydrogenation catalyst is extended.
SUMMARY OF THE INVENTION
The present invention provides an improved process for the hydrogenation of 3-hydroxypropanal to 1,3-propanediol which comprises purifying an aqueous solution of 3-hydroxypropanal by contacting said aqueous solution with a purifying agent prior to hydrogenation.
The present invention further provides a process for the preparation of 1,3-propanediol which comprises: a) contacting an aqueous solution of 3-hydroxypropanal with a purifying agent; and b) hydrogenating said aqueous solution of 3-hydroxypropanal to 1,3-propanediol.
DETAILED DESCRIPTION OF THE INVENTION
The process of the current invention comprises an improved process for the hydrogenation of 3-hydroxypropanal (HPA). In the first stage, an aqueous HPA solution is contacted with a purifying agent; in the subsequent stage (or multiple stages), the contacted HPA solution is hydrogenated to 1,3-propanediol (PDO).
There are various hydrogenation processes known for the conversion of HPA to PDO that utilize aqueous HPA feeds. The purification stage of the present invention is applicable to, and combinable with, all said processes. Most preferably, the purification stage of the present invention is applied to the hydrogenation processes disclosed in U.S. Pat. No. 5,334,778 and in copending patent application, Ser. No. 60/099,235.
It has been found that hydrogenation catalysts are deactivated more rapidly than desired in the preparation of PDO via the hydrogenation of HPA. The deactivation of the catalysts is believed to be due to the adverse interaction between impurities in the aqueous HPA feed and the hydrogenation catalysts employed.
It has been found that treatment of the aqueous HPA feed with a purifying agent prior to hydrogenation improves performance and lifetime of the hydrogenation catalysts. Surprisingly, the initial activity of the hydrogenation catalyst is particularly enhanced. Purifying agents useful in the process of the present invention comprise purifying carbons, purifying silica compositions, diatomaceous earths and zeolites.
The most preferred purifying agents useful in the process of the present invention comprise purifying carbons.
When the purifying agents employed in the process of the present invention are purifying carbons, the carbons are those typically employed as decolorizing carbons. Typically they are activated carbons commercially available from various vendors.
After the purifying agent contacting stage of the process is carried out, the hydrogenation may be carried out using the methods disclosed in U.S. Pat. No. 5,334,778, incorpor
Haas Thomas
Hofen Willi
Jaeger Bernd
Vanheertum Rudolf
E. I. du Pont de Nemours and Company
O'Sullivan Peter
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