Preparation of 2,2'-oxydisuccinate

There is disclosed herein an improved processes for the preparation of oxydisuccinate by reacting in an alkaline reaction medium the salts of maleic acid and malic acid in the presence of a calcium ion catalyst wherein unreacted maleic acid salts are recovered from the reaction medium as sodium hydrogen maleate by lowering the pH of the reaction product to a range of from about 4 to 6. The precipitated sodium hydrogen maleate salts are recycled to the synthesis reaction as salts of malic acid by hydration in the presence of a hydration catalyst to prepare additional amounts of product.

This invention relates to a process for making ether carboxylic acids and 
more particularly to processes for making ether carboxylates prepared by a 
calcium ion catalyzed reaction in alkaline medium of maleic and malic acid 
salts. Such reactions are of the type typically referred to as Michael 
condensation reactions. 
Polycarboxylic acids have long been known to be useful, usually in the salt 
form, as detergent builders or sequestrants. Also, ether carboxylates 
useful as metal sequestering and detergent builders have been known and 
are most desirable for their beneficial effects in laundering 
applications. 
Because ether carboxylates have such effective sequestering ability they 
have become attractive in recent times for the replacement of sodium 
tripolyphosphate which has long been the leading detergent builder or 
sequesterant. Examples of prior art efforts to provide ether carboxylate 
detergent builders or sequesterants are found in U.S. Pat. Nos. 3,635,830; 
3,692,685 which relate to the use of oxydisuccinic acid salts particularly 
2,2'-oxydisuccinate salts (ODS) as detergent builders. Another example of 
an ether polycarboxylate detergent builder or sequesterant is found in 
U.S. Pat. No. 3,914,927 which relates to carboxymethyl oxysuccinates. 
While many carboxylate compounds in the prior art have utility as a builder 
or sequesterant in laundry detergent formulations, it has been found that 
certain ether carboxylates are more attractive and cost effective for such 
utility. In the field of detergent builders and sequesterants for laundry 
detergent formulations low cost of the components is extremely important 
because it is in a very competitive market. While many ether carboxylate 
compounds have been found to be useful there is needed more economical 
manufacturing processes whereby such compounds can be economically 
produced in large volume. 
The synthesis of many ether carboxylates, including the oxydisuccinates, is 
achieved in an equilibrium reaction wherein starting materials, tartrate 
or malate and maleate salts, remain in solution at the end of the 
reaction. In many cases these starting materials are removed only by 
solvent extraction which is expensive and not ecologically attractive. 
Large scale production of such ether carboxylates incur large costs for 
recovery of reactants and an ecologically and environmentally acceptable 
means for recovering unreacted starting material is practically a 
requirement for industrial production of commercial quantities of these 
ether carboxylates. 
There has previously been discovered a process for preparing ether 
carboxylates by the reaction of the salts of malic acid and maleic acid, 
said reaction catalyzed by calcium ions and conducted under alkaline 
conditions wherein unreacted salts are conveniently recovered in such 
manner that they may be recycled to the synthesis reaction to produce 
additional ether carboxylate. It was discovered that at a limited range of 
acidity certain unreacted salts are conveniently recovered from the 
reaction mixture at the conclusion of the reaction. By reducing the pH of 
the reaction mixture to a range within about 4 to about 6 by combining a 
suitable acid with the reaction mixture, the insoluble salts of starting 
acids precipitate while the desired ether carboxylate product remains in 
solution. The precipitate is removed by known means such as filtration 
thereby allowing further processing of the ether carboxylate solution. 
Such further processing will depend, of course, upon the particular ether 
carboxylate produced. 
To conduct the above mentioned process for preparing ODS in an efficient 
manner the insoluble salts of maleic and malic acids are recycled to 
provide further ODS product. When the acidification of the reaction 
mixture to a pH in the range of from about 4 to about 6 is performed with 
maleic acid one of the insoluble precipitates formed is sodium hydrogen 
maleate derived from the unreacted salt of maleic acid. While such salt 
may be recycled directly or indirectly as the calcium salt to the reactor 
as described in U.S. Pat. No. 4,959,496 to Crutchfield et al., a more 
efficient recycle route of the sodium hydrogen maleate has been 
discovered. 
SUMMARY OF THE INVENTION 
It has now been discovered that sodium hydrogen maleate recovered from the 
reaction product in the production of ODS by precipitation with maleic 
acid can be employed to efficiently provide malic acid salt by hydration 
either alone or together with maleic anhydride. The malic acid salt is 
then introduced into the reactor together with maleic acid salt to provide 
additional amounts of ODS. 
Catalysts are optionally employed to increase the rate of conversion to 
malic acid salt. Such catalyst is usually a mineral acid such as sulfuric 
or hydrochloric acid or an acid salt such as calcium nitrate. 
The hydration reaction takes place at elevated temperatures in the range of 
from about 100.degree. C. to about 175.degree. C. and usually about 
150.degree. C. With sufficient catalyst present the hydrolysis reaction 
takes place at about the same rate as when only the maleic anhydride is 
present. The reaction rate for the hydration of maleate to malate is 
favored or increased by employing elevated temperatures. Thus, the 
hydration reaction rate is somewhat higher at temperatures in the range of 
from about 150.degree. C. to about 160.degree. C. 
DETAILED DESCRIPTION OF THE INVENTION 
Calcium catalyzed reactions for the production of ether carboxylates are 
known. A typical prior 
art example of such a process is disclosed in U.S. Pat. No. 4,798,907 
MacBriar et al and such patent is hereby incorporated by reference. 
ETHER CARBOXYLATE SYNTHESIS 
It is typical of the Michael condensation reactions to provide the most 
effective equilibrium state for the production of the desired compound or 
mixture by control of the reactant ratio. For example, high ratios of 
maleic acid salts to malate acid salt in the range of 2 to 1 or greater 
respectively provide the more optimum production of ODS in the calcium ion 
catalyzed reaction disclosed in the European publication referred to 
above. However, a significant amount of unreacted maleate salt remains in 
solution at the end of the reaction together with the desired ODS. 
The recovery of unreacted maleate salts from calcium catalyzed reactions of 
maleic acid salts with salt of malic acid in alkaline medium is 
conveniently achieved by acidifying the reaction product so as to reduce 
the pH to within the range of about 4 to about 6. However it has been 
found that the salts of malic acid in the reaction mixture are least 
soluble at a pH in the range of from about 7 to about 8.5 and such salts 
become increasingly soluble as the pH is reduced further to the above 
mentioned range of from about 4 to about 6. Preferably, the acid addition 
to the reaction mixture is interrupted when the pH of the reaction mixture 
reaches slightly below 8. The precipitated salts are then removed before 
reducing the pH to the desired lower level of from about 4 to about 6. The 
lower range is optimum for precipitation and removal of the maleic acid 
salts in the form of sodium hydrogen maleate. The lower pH range also 
provides removal of a majority of the malic acid salts but it has now been 
discovered that the malic acid salts which have precipitated during acid 
addition for the purpose of lowering the pH to a range between about 4 and 
about 6 begin to redissolve into the reaction mixture before completion of 
the process of acid addition and removal of the precipitate. To remove the 
maximum amount of malic acid salts it is necessary to interrupt acid 
addition at the higher pH range and remove precipitated acid salts. Even 
though malic salts are removed at the higher pH range, it has been found 
that the precipitation and removal of further amounts of malic acid salts 
still occurs together with the precipitation of the sodium hydrogen 
maleate salt at the lower pH range of from about 4 to about 6. 
A particular advantage of the process of this invention, whereby unreacted 
maleate salt is recovered, is the ability to regulate the reactant ratios 
more freely since convenient recovery and recycle is possible. Loss of 
unreacted maleate salt is insignificant and its recovery economical, 
particularly when maleic acid is employed to reduce the pH of the reaction 
product of the condensation reaction. High maleate to malate ratios such 
as in excess of 1 to 1 respectively have been found to result in the 
reduction or even elimination of the maturation step usually required in 
the production of ODS. Therefore, a preferred embodiment of this invention 
is the calcium catalyzed reaction of maleate and malate salts in alkaline 
medium wherein the ratio of maleate to malate salt is in excess of 1. 
Small amounts of by-products such as fumarate and residual amounts of ODS 
trapped in the precipitate are not deleterious to the use of this recycled 
precipitate in subsequent condensation synthesis reaction. 
Sodium hydrogen maleate may be recycled to the hydration reactor alone or 
in admixture with additional maleic acid (or anhydride +H.sub.2 O) to 
provide the amount of substrate required to produce the needed amount of 
malic acid. If the amount of sodium hydrogen maleate is greater than that 
needed for hydration to malic acid, the excess sodium hydrogen maleate may 
be recycled to the ODS synthesis reaction, preferably in accordance with 
the procedure described in U.S. Pat. No. 4,959,496 referred to above and 
hereby incorporated by reference. 
Hydration of maleic acid to form fumaric and malic acid is well known, Kirk 
Othmer Encyclopedia of Chemical Technology, 3rd Ed., Vol. 13, p. 103-120. 
However, the recycle of sodium hydrogen maleate in the manufacture of ODS 
has heretofore been known only for its use as a maleic acid salt. 
It has been found that the use of catalyst in the hydration reaction is 
advantageous because it results in higher conversion of maleate to malic 
acid. Inorganic, mineral acids and salts are the usual catalysts, for 
example, sulfuric acid, hydrochloric acid, nitric acid, and preferably 
calcium nitrate. As will be shown by the following examples, the amount of 
sulfuric acid required to provide desirable conversion rates is higher in 
the process of this invention than would be expected from prior experience 
with maleic anhydride alone. 
FORMATION OF ODS 
As noted above there has been previously disclosed an ether-bond forming 
reaction using the combination of sodium and calcium salts in aqueous 
alkaline ether-bond forming reactions to provide in high yield ether 
carboxylates. One such disclosure is EPO 0 236 007. The ether carboxylate 
is formed in a reaction mixture containing sodium and calcium salts of 
maleic acid and malic acid which react to form the sodium and calcium 
salts of ODS. The reaction takes place at temperatures below about 
120.degree. C. in aqueous medium wherein one component is the maleate salt 
and the other is the malate salt. The reaction mixture also contains an 
inorganic reactant component consisting essentially of at least one 
inorganic base or mixture thereof. The reaction mixture is held at a 
temperature of at least about 60.degree. C. for a period sufficient to 
permit a major portion of the ether-bond formation between the maleate and 
malate present in the reaction mixture. According to previously known 
reactions the malate to maleate molar ratios range from about 1:0.7 to 
about 1:2, more preferably from about 1:1.05 to about 1:1.4 at the initial 
time of combination. 
The molar ratio of calcium to maleate plus malate is disclosed in the prior 
art to be in the range of from about 0.1:1 to about 0.75:1, more 
preferably from about 0.31:1 to about 0.57:1. Also present in the reaction 
mixture is sodium which is present at a molar ratio of sodium to maleate 
plus malate of from about 0.5:1 to about 2.2:1. Ratios of sodium to malate 
and maleate are adjusted in the event the acid form of these compounds are 
employed and no organic salts are used. When the acid form of maleate and 
malate are employed the sodium to maleate plus malate molar ratio is 
generally in the range of from about 0.9:1 to about 1.48:1. As noted 
above, the reaction mixture is alkaline generally by the addition of an 
inorganic base so as to provide from about 0.01 to about 0.4 moles of free 
hydroxide per mole of combined maleate and malate. Preferably the free 
hydroxide is present in the range from about 0.04:1 to about 0.2:1 per 
mole of combined maleate and malate, preferably from 0.04:1 to 0.1:1 
respectively. The reaction is reported to have been performed at a pH in 
the range of from about 9 to about 13 measured by cooling the reaction 
mixture sample to 25.degree. C. and diluting to about 5% dissolved solids 
prior to pH measurement. 
In accordance with this invention the malate/maleate ratio is reversed such 
that it is now convenient and economical to operate the reaction to 
produce ODS with an excess of maleate in the reaction mixture. In general 
the malate to maleate molar ratios in accordance with the process of this 
invention can range from about 1:1.5 to 1:3 respectively or even higher. 
Of course, the excess maleate does not react but is recovered in 
accordance with this invention for reuse in a convenient manner as will be 
more fully described below. Calcium hydroxide level is typically in the 
range of, on a molar basis of malate to calcium hydroxide, from 1:1 to 
1:2. Calcium levels affect the reaction rate but have little effect on the 
ability to recover unreacted starting material in the form of sodium 
hydrogen maleate. An excess of base has been discovered to increase the 
speed of the reaction but also it increases the speed of the reversion of 
the desired ODS product to fumarate. In general, the reactant ratios in 
the reaction mixture in accordance with this invention in terms of malic 
acid/ maleic acid/calcium hydroxide/sodium hydroxide mole ratio is 
typically in the range of 1/2.2/1.6/3.4. These ratios are the usual 
mid-point of ranges commonly employed and found to provide optimum results 
in accordance with this invention and can vary widely. 
The reaction temperature of the process of this invention appears to 
control the rate of reaction and thus the amount of time required to 
produce optimum results. Typically, at 80.degree. C. the reaction proceeds 
to completion in from about 1 to 3 hours for maximum malate conversion 
utilizing the abovementioned reactant ratios. When the reaction is run at 
about 70.degree. C. maximum malate conversion occurs in from 2 to 6 hours 
and such conversion is slightly higher than is found at a reaction 
temperature of 80.degree. C. Acceptable results have been obtained at 
higher temperatures (90.degree./100.degree. C.) with reaction times of 1 
hour or less; however, the amount of fumarate formed increases rapidly. 
The aqueous reaction mixtures forming ether carboxylates by the reaction of 
maleate and malate according to prior art methods contain from about 31% 
to about 41% by weight, more preferably 36% to about 40% by weight maleate 
and malate. The reaction mixture in accordance with this invention may 
contain from about 40% to 75%, by weight of the maleate and maleate salts. 
The progress of the reaction is typically determined by applying 
techniques such as High Performance Liquid Chromatography (HPLC) whereby 
the yield of ODS and the levels of maleate and malate reactants and of 
fumarate by-products and other individual reaction product can be 
monitored. The reaction is terminated by cooling typically to below 
50.degree. C. and preferably to ambient temperature. In prior art 
reactions, yields of at least 50% of the ODS based upon malate were 
obtained. However, in accordance with the process of the present invention 
the yields can be higher and product processing shorter due to adjustment 
of reactant ratios and to the convenient recovery of unreacted starting 
materials. Because starting materials are conveniently recovered, greater 
freedom of reactant ratios in the initial reaction mixture are obtained to 
the benefit of greater conversion and shorter processing time to provide a 
final product. It is reported that the complex sodium/calcium salts of the 
maleate and malate reactants as well as the ODS product formed in situ 
provide much higher solubilities of the reaction product than when 
single-metal calcium salts are employed. Such solubility is advantageous 
because it allows convenient high-concentration processes, easier pumping 
and handling properties. 
In accordance with this invention sodium hydrogen maleate is easily 
recovered from the reaction product by reducing the pH of the reaction 
product with maleic acid to a range of from about 4 to about 6 whereby the 
unreacted maleic acid salt precipitates as sodium hydrogen maleate and is 
easily recovered for recycle to the synthesis reaction. Such process will 
be more fully described below. 
The recovery of maleate and malic salt is achieved by lowering the pH of 
the reaction mixture whereby sodium hydrogen maleate precipitates. In the 
preferred embodiment the reaction mixture is also cooled and diluted with 
water. Maleic acid is added so as to bring the combined synthesis mass and 
acid to a final pH in the range of from about 4.5 to 5.5, preferably 
slightly below 5.2. 
In the process of this invention, the acid substance may be added to the 
crude reaction mass. Alternately, the reaction mass may be added to a heel 
containing the acid substance. In a further process of this invention, the 
acid substance and the reaction mass may be added concurrently into a 
mixing vessel. Sufficient water is added to the reaction mass and/or acid 
material so that the final concentration of desired ether carboxylate in 
the completed mixture is from about 40% to about 55%, by weight. 
Sufficient acid is added t reach the preferred pH range of from about 4.5 
to about 5.5 and the precipitated reaction mass is cooled to below 
50.degree. C. Preferably the reaction mass is cooled to a range of from 
just above the freezing point of the mixture to about 40.degree. C., most 
practically to about 20.degree. C. to about 30.degree. C. Satisfactory 
filtration rates are thus obtained in large scale production. In a 
preferred mode, cooling the reaction product from the 80.degree. C. 
reaction temperature to 65.degree. C. over 30 minutes is followed by slow 
cooling to from about 30.degree. C. to about 40.degree. C. The suspension 
is then allowed to rest for about 30 minutes. The slurry is preferably 
cooled slowly with mild or slow agitation so as to grow particles which 
can be filtered in an appropriately short time. Other methods of acid 
addition such as are noted above can also be employed with appropriate 
adjustment of precipitation conditions. 
Removal of the precipitated acid salt may take any form practical and 
typically is performed by continuously drawing the slurry from the 
precipitator to a belt or drum filter or centrifuge. Other forms of 
removal such as decantation, etc. may also be employed. The filtrate 
contains the ether carboxylate in salt form. In a preferred embodiment the 
filtrate is transferred to another precipitator for removal of the calcium 
cations in the form of calcium carbonate. 
Throughout pH reduction, cooling is required to maintain the temperature of 
the reaction mixture in the desired range of about 35.degree. C. As noted 
above, the reaction mixture is held for about 30 to about 40 minutes after 
final pH reduction to allow crystal formation. The larger agglomerates are 
more easily separated from the reaction mixture. 
CALCIUM CARBONATE PRECIPITATION 
After removal of the insoluble acid salt or salts as described above, the 
filtrate from such operation is recovered and purified for use as 
detergent builder. In a preferred embodiment, calcium is removed either 
batchwise or preferably continuously. Typically, the filtrate from the 
above-mentioned step is pH adjusted with a base, preferably sodium 
hydroxide, as it is being fed into a calcium carbonate precipitator to 
bring the pH of the solution into a range of from about 10 to about 12, 
preferably from about 10 to about 10.5. The pH adjustment may be performed 
either in the precipitator or in a separate vessel if desired. The pH 
adjusted material is maintained in the range of from about 75.degree. C. 
to about 110.degree. C., preferably at about 90.degree. C. to 100.degree. 
C. Concurrently a solution of a basic carbonate, preferably sodium 
carbonate, preferably at a concentration of about 25%, is added to the 
precipitator to provide an overall mole ratio of carbonate to calcium of 
1.3:1. 
Alternatively, calcium carbonate is removed by increasing the mole ratio of 
carbonate ion to calcium ion without change in pH. 
Although this invention is described with respect to carbonate 
precipitation using the preferred sodium cation, it is to be understood 
that other suitable cations may also be employed to obtain precipitation 
of calcium carbonate. Other cations useful in the process of this 
invention include potassium, ammonium or organo substituted ammonium. 
Other salts may be employed to obtain the calcium carbonate precipitate 
and includes sodium bicarbonate and mixtures of carbonates and 
bicarbonates. 
During the precipitation of calcium carbonate it is preferred that water is 
continuously removed from the slurry to maintain the concentration of the 
organic acid salts in the range of from about 30% to about 50% by weight. 
Filtration of the precipitated calcium carbonate may take any form 
practical and typically is performed by continuously drawing the slurry 
from the precipitator to a centrifuge or to a belt or drum filter. The 
filtrate contains the desired ether carboxylate mostly as the alkaline 
salt along with minor amounts of raw material and by-products. 
The wet cake from the separation is mechanically reslurried with water to 
form an approximately 50% calcium carbonate slurry for recycle to the 
synthesis reaction. The recovered carbonate may be added directly to the 
ether carboxylate synthesis reactor or together with recovered, unreacted 
tartrate and maleate. Preferably, the recovered calcium carbonate is 
converted to calcium maleate in a separate vessel before return to the 
synthesis reaction. 
To further illustrate the process of the present invention there is 
described below nonlimiting preferred embodiments. Unless otherwise noted 
all percentages are by weight.

EXAMPLE 1 
Into a 1 liter Ace reactor equipped with a thermometer, mechanical stirrer, 
condenser and a sample port there is placed 156.5g of water. Then 240g of 
50% sodium hydroxide solution (3.0 moles) were added. D,L-malic acid 
(134.Og, 1.0 mole) Was added slowly to this mixture. At the end of the 
addition, the temperature had risen to ca. 85-90.degree. C. Calcium 
hydroxide (118.4g, 1.6 mole) was added as a solid to the solution and the 
slurry stirred vigorously. Maleic anhydride (196.0g, 2.0 moles) was added 
as a solid at such a rate that the temperature was maintained between 
80.degree. and 95.degree. C. (ca. 15 min.) On completion of this addition, 
the reaction mass comprised about 60% solids, 40% water. The partially 
cleared (translucent) mass was stirred and held at 80.degree.-85.degree. 
C. for three hours. At the end of the reaction period a solution of maleic 
acid, prepared by dissolving 98g (1.0 mole) of maleic anhydride in 200g 
water at 65.degree.-70.degree. C. was added to the hot reaction mixture. 
The pH after the addition of maleic acid was measured at 4.94. The 
reaction mass was cooled to about 30.degree. C. and filtered. The crystals 
of sodium hydrogen maleate were washed with about 150 ml water and air 
dried. The filter cake weighed 432.3g and the filtrate weighed 560.6g. 
Both were sampled for analysis. 
A solution of 220.5g (2.08 moles) of sodium carbonate in 600 ml water was 
prepared and heated to about 80.degree. C. The filtrate from above was 
slowly added to the sodium carbonate solution at 80.degree. C. to 
precipitate calcium carbonate from the reaction mixture. The resulting 
slurry was heated at 80.degree.-85.degree. C. for one hour and then 
filtered hot. The calcium carbonate filter cake was washed with about 50 
ml water. The filtrate, containing the desired ODS as the tetrasodium salt 
was analysed. Analysis by x-ray fluorescence indicates only 0.056% calcium 
present in the filtrate. Analytical results of the reaction mixture 
(normalized weight %) appear in Table XVII below. 
TABLE XVII 
______________________________________ 
AFTER 
AFTER CAR- 
SAMPLE: END OF MALEATE BONATE 
COMPONENT REACTION REMOVAL REMOVAL 
______________________________________ 
Disodium Malate 
6.22 8.34 8.41 
Disodium Maleate 
28.75 2.18 2.37 
Disodium Fumarate 
5.07 7.15 7.11 
Tetrasodium 59.96 82.33 82.11 
Oxydisuccinate 
Malate Conversion 
83.54 83.87 83.72 
(Mole %) 
______________________________________ 
This example shows that maleic acid can be used to remove sodium hydrogen 
maleate from the reaction and still maintain acceptably low residual 
levels of maleate in the final product. 
EXAMPLE 2 
Tests were conducted to determine the characteristics of maleate hydration 
with and Without the presence of sodium hydrogen maleate. Hydration 
reactions were conducted at 120.degree. C. for times noted in the table. 
In Part A maleic anhydride alone was added to water. In Part B maleic 
anhydride and sodium hydrogen maleate as recovered in the procedure of 
Example 1 were combined and in Part C maleic anhydride, sodium hydrogen 
maleate and fumaric acid were combined. In the table below the amount of 
feed material is expressed in grams. The results shown in Table I below 
indicates that a higher ratio of sulfuric acid is required to provide 
equivalent conversion to malate when sodium hydrogen maleate is present, 
Part C. 
TABLE I 
__________________________________________________________________________ 
Part A 
Mole % 
Rxn. Maleic Conv. 
Mole % 
Maleic 
Feed Catalyst 
Maleic/Cat. 
Time to to Unconv. 
Acid 
H.sub.2 O 
Cat 
Type Mole Ratio 
(hrs.) 
Malate 
Fumarate 
Maleate 
__________________________________________________________________________ 
1.240 
1.240 
-- none -- 20 19.6 29.1 51.3 
1.130 
1.130 
0.260 
H.sub.2 SO.sub.4 
3.67 20 65.1 24.3 10.6 
1.095 
1.579 
0.146 
Ca(NO.sub.3).sub.2 
10.61 20 29.6 64.8 5.6 
1.160 
1.160 
-- none -- 94 49.4 41.1 9.4 
1.225 
1.225 
0.290 
H.sub.2 SO.sub.4 
3.57 94 81.0 18.6 0.4 
1.195 
1.648 
0.137 
Ca(NO.sub.3).sub.2 
12.36 94 62.0 36.2 1.8 
__________________________________________________________________________ 
Part B 
Mole % 
Feed Total Rxn. Maleic Conv. 
Maleic 
NaH Catalyst 
Maleic/Cat. 
Time To To 
Acid 
Maleate 
H.sub.2 O 
Cat. 
type Mole Ratio 
(hrs.) 
Malate 
Fumarate 
__________________________________________________________________________ 
0.344 
0.410 1.396 
-- none -- 20 14.7 
47.1 
0.351 
0.417 1.422 
0.280 
H.sub.2 SO.sub.4 
2.11 20 26.4 
50.2 
0.360 
0.429 1.931 
0.137 
Ca(NO.sub.3).sub.2 
7.44 20 21.8 
52.5 
0.372 
0.442 1.506 
-- none -- 94 54.9 
40.2 
0.380 
0.452 1.538 
0.250 
H.sub.2 SO.sub.4 
2.57 94 47.1 
51.9 
0.369 
0.438 1.953 
0.140 
Ca(NO.sub.3).sub.2 
7.44 94 62.8 
32.5 
__________________________________________________________________________ 
Part C 
Mole % Conv. 
Feed Total Rxn. 
of Maleic & 
Maleic 
NaH Fumaric Catalyst 
Maleic/Cat. 
Time 
Fumaric to 
Acid 
Maleate 
Acid H.sub.2 O 
Cat 
type Mole Ratio 
(hrs.) 
Malate 
Fumarate 
__________________________________________________________________________ 
0.148 
0.440 
0.074 
1.788 
-- none -- 16 3.2 
26.7 
0.146 
0.435 
0.073 
1.766 
0.630 
H.sub.2 SO.sub.4 
0.78 16 22.2 
17.6 
0.145 
0.431 
0.073 
1.751 
-- none -- 90 16.2 
57.5 
0.144 
0.430 
0.072 
1.744 
0.600 
H.sub.2 SO.sub.4 
0.81 90 71.5 
21.0 
__________________________________________________________________________ 
EXAMPLE 3 
The conversion of sodium hydrogen maleate to malic acid was provided under 
different catalyst conditions. From the results, presented in Table II 
below it is shown that hydrochloric acid provides greater conversion to 
malate than sulfuric acid but that sulfuric acid, at higher ratio to 
maleate improves conversion to malate. As in Example 1, the hydration 
reaction was conducted at 120.degree. C. The feed material is listed in 
weight percent of the reaction mixture. In the first test, Part A, no 
catalyst was employed. In the second test, Part B, sulfuric acid was 
employed at a higher ratio than reported above and in the third test, Part 
C hydrochloric acid was employed as the catalyst in place of sulfuric 
acid. 
TABLE II 
__________________________________________________________________________ 
Mole % 
Normalized Wt. % 
Maleic Conv. 
as (Na salt) To To Feed 
Reaction Time 
Malate 
Maleate 
Fumarate 
Malate 
Fumarate 
Material (Wt. %) 
__________________________________________________________________________ 
Part A 
0 0.00 
100.00 
0.00 0.00 
0.00 NaH Maleate 
22.74% 
4 0.00 
99.71 
0.29 0.00 
0.29 Water 77.26 
101/2 0.00 
99.58 
0.42 0.00 
0.42 
22 0.00 
99.27 
0.73 0.00 
0.73 
47 0.00 
98.01 
1.99 0.00 
1.99 
Part B 
0 0.00 
100.00 
0.00 0.00 
0.00 NaH Maleate 
22.74% 
4 2.99 
90.52 
6.49 2.70 
6.51 Water 77.26 
101/2 8.76 
72.78 
18.46 
7.94 
18.62 
H.sub.2 SO.sub.4 catalyst 
22 15.37 
59.71 
24.92 
14.03 
25.31 
Mole Ratio 
47 24.38 
29.14 
46.48 
24.47 
47.65 
Diacid/H.sub.2 SO.sub.4 = 1.33 
Part C 
0 0.00 
100.00 
0.00 0.00 
0.00 NaH Maleate 
22.74% 
4 9.07 
30.44 
60.49 
8.23 
61.05 
Water 77.26 
101/2 17.11 
14.26 
68.73 
15.65 
69.94 
HCl catalyst 
22 25.84 
1.30 72.86 
23.85 
74.81 
Mole Ratio 
47 42.13 
1.03 56.85 
39.55 
59.38 
Diacid/HCl = 0.71 
__________________________________________________________________________ 
There has been described a novel process of general application to the 
production ODS. While the process has been described with reference to 
specific compounds, no intention is made by such reference to limit the 
scope of this invention unless expressly stated. Various modifications may 
be made in the materials and sequence of process steps as well as process 
combinations which are adapted to suit the various reactants and products 
without departing from this invention.