US 3450776 A
Description (OCR text may contain errors)
United States Patent 3,450,776 PROCESS FOR THE HYDROGENATION OF WATER-MISCIBLE A CETYLEN E C OM- POUNDS INTO OLEFIN COMPOUNDS Alessandro Di Cio and Marcello Massi Mauri, Milan, Italy, assignors to Snam Progetti S.p.A., Milan, Italy, a. corporation of Italy N 0 Drawing. Continuation-impart of application Ser. No. 364,759, May 4, 1964. This application Feb. 16, 1968, Ser. No. 705,930
Int. Cl. C07c 29/00, 31/12, 31/18 US. Cl. 260-635 4 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to a process for the selective hydrogenation of water-miscible acetylene compounds. This application is a continuation-in-part of our pending application, Ser. No. 364,759, filed May 4, 1964, and now abandoned.
It is already known that it is possible selectively to hydrogenate acetylene compounds to form olefin compounds in the presence of palladium-based catalysts. In prior cases, however, there has always been production of at least 2%3% of saturated compounds. Selectivity, as a matter of fact, never exceeds, by operating this way, 97%98%. In order that higher selectivity ratings may be achieved, it has been suggested partially to deactivate the palladium catalyst by impregnation or co-precipitation with salts of Pb, Zn, Hg, Cd, Th, Sn and others.
In the known processes, however, it is necessary first to prepare the catalyst by treating the catalyst wtih the zinc or other poisoning salt. Only then could such a hydrogenation process be carried out.
These known impregnation or co-precipitation methods, moreover, can be performed, in practice, only with difficulty, in that the de-activation conditions of the catalyst (temperature, concentration of the de-activating salt, duration of the operation) are extremely critical; and it is difficult to obtain uniformity in preparation of the poisoned catalyst.
It is likewise known that, in order that a highly selective catalyst may be produced, it is necessary that the impregnation or de-activation step be carried out at somewhat high temperatures (from 80 C. to 100 C.) and this, inter alia, is an unfavorable circumstance, particularly if supported catalysts are concerned.
Such difliculties are particularly serious when the hydrogenation process is to be continuous.
We have discovered that, in the hydrogenation of watermisci-ble acetylene compounds through the use of a palladium-based catalyst, it is possible to condition the catalyst, which may be furnished with a conventional supporting mass such as calcium carbonate or barium sulfate, to attain a 100% selectivity even in the cold or at least at temperatures in the range 20 C.-60 C. and to maintain the catalyst in condition to attain that selectivity over an extended period, by feeding thereto a reaction mixture which includes, in aqueous solution, 0.01% to 3,450,776 Patented June 17, 1969 ice 5.0%, based on the weight of the acetylene compound, of a zinc salt. In the practice of our invention the salt employed is a member of the group consisting of zinc acetate, zinc sulfate, zinc nitrate, zinc chloride and zinc oxalate; and hydrogenation occurs at a pressure between 1 and 20 atmospheres, preferably in the presence of about 0.5% (by weight of the acetylene compound) of an amine compound. Through the practice of our invention, the difiiculties inherent in prior methods, which have been referred to above, are avoided and good uniformity in the poisoning of the catalyst is insured.
By operating according to the present invention it is not at all necessary, in order to have selectivity, to subject the palladium catalyst to impregnation in hot condition or to co-precipitation steps which are burdensome and complicated, since the zinc is continually added, in the form of a soluble compound, with the hydro genation mixture.
In addition to this paramount operational and economical advantage, the present invention represents a further advancement in that the lifetime of the catalysts employed according to the invention is longer than that of the conventional de-activated catalysts, the respective selectivities being equal.
According to our invention, it is possible to cause the material to be hydrogenated and the zinc salt to pass over the catalyst several tens of times during continuous test runs, obtaining in any case a maximum selectivity rating.
The anion moiety of the zinc salt is immaterial to the ends of selectivity, it being preferable, however, that the salt itself be at least fairly water-soluble. Chlorides, sulfates, nitrates, acetates and oxalates lend themselves very well to this purpose.
The amount of salt may be varied between 0.01% and 5% and preferably from 0.01% to 2% on a weight basis with respect to the acetylene compound.
The invention can also be applied to diluted aqueous solutions of the acetylene compound, in that the presence of large amounts of water does not impair in the slightest the reaction selectivity.
It is preferable to add to the reaction mixture an amine compound, generally ammonia, in very slight amounts, preferably less than 0.5 on a. weight basis with respect to the acetylene compound. Larger amounts, up to 20%- '30%, do not produce, however, any detrimental effect upon the reaction. The salient feature of the present invention, however, is not the use of amines, nor is it the composition of the hydrogenation catalyst. It is, rather, the carrying out of the hydogenation simultaneously with the poiosning, and, if desired, in a continuous manner by feeding onto the catalyst, not in itself selective, both the solution of the compound to be hydrogenated and the solution of the zinc or other poisoning salt.
The present invention can be applied both to continuous or batch processes within a wide temperature range e.g. between 20 C. and 60 C. and within a Wide pressure range eg from 1 to 20 atmospheres.
It should be noted that the amount of salt to be added to the reaction mixture is a function, within the above indicated limits, of the reaction velocity, i.e. of the hydrogen pressure and temperature, as will be explained more in detail in the examples to follow.
By operating according to the present invention, the absorption of hydrogen by the reacting mixture ceases once the triple bond is hydrogenated in a double bond, after which, even though the reacted mixture be allowed to stay in the reaction mixture even for a relatively long time, no further hydrogenation takes place.
The present disclosure will be better illustrated by the following operative examples.
3 EXAMPLE 1 By hydrogenating 2-methyl-3-butyn-2-ol in the form of an azeotropic mixture with water (26% water by weight), in the presence of 1% by weight of a catalyst consisting of palladium on a calcium carbonate support Pd) and of 0.1% by weight of ammonia with respect to the methylbutynol, in an autoclave with stirring and under the above-described temperature and pressure conditions, 100% selectivity has always been attained, along with the stoppage of the reaction after the absorption of the hydrogen amount theoretically corresponding to the quantity which is necessary for the hydrogenation of the triple bond only, by adding the weight percentages of Zinc acetate indicated in the table below.
Temperature, Pressure Percent Zn C. atmospheres acetate EXAMPLE 2 2-methyl-3-butyn-2-ol has been hydrogenated, in the form of an azeotropic mixture with water, at 1 atmosphere and at 50 C. with several salts, as specified in the table below, always obtaining 100% selectivity.
In order to test the catalyst lifetime, an autoclave fitted with a stirrer has been charged with 100 grs. of an azeotropic mixture of 2-methyl-3-butyn-2-ol and water, 1 gram of Pd (CaCO -supported, 5% Pd), 0.1 gram zinc acetate and 0.1 gram ammonia: hydrogen has been allowed to be absorbed at 1 atmosphere and 60 C. temperature until the reaction was over. The liquid fraction has been removed by decantation and, on the catalyst left on the bottom of the autoclave, there have been introduced 100 grs. of an azeotropic mixture of methylbutynol and water, 0.02 gr. zinc acetate and 0.1 gr. ammonia, causing hydrogen to be absorbed. This operational sequence has been repeated 50 times. The reaction stops after absorption of the hydrogen amount necessary according to theory for the formation of methylbutenol. A selectivity of virtually 100% is achieved and the same reaction velocity throughout all the tests, has been ascertained.
EXAMPLE 4 An autoclave equipped with stirrer, kept at 1 atmosphere and C., has been charged with 500 grs. 2-butyn- 1,4-diol, 20 grs. water, 0.5 gr. Zn(COOCH 5 grs. Pd/
CaCO (5 Pd) and 0.1 gr. NH Once the theoretical amount of hydrogen has been absorbed, the reaction has ceased and a quantitative yield of 2-buten-1,4-dio1 has been obtained.
EXAMPLE 5 A tubular reactor, thermostatically kept at C., is continually fed in uniflow conditions, with 30 liters an hour of an azeotropic mixture of methylbutynol and water containing 1% of Pd/CaCO (5% Pd), 0.2%
0.02% NH and 5 normal cubic meters of hydrogen. By working at a pressure of 6 atmospheres a product is obtained which contains no saturated compounds but only a slight trace of acetylenic alcohol.
What is claimed is:
1. A process for the selective hydrogenation of an acetylenic compound selected from the group consisting of 2-methyl-3-butyn-2-ol and 2-butyn-1,4-diol into the corresponding olefin compound which comprises feeding the acetylene compound, mixed with water and an aqueous solution of a zinc salt selected from the group consisting of zinc acetate, zinc sulfate, zinc nitrate, zinc chloride and zinc oxalate, onto a palladium-based catalyst, the selective hydrogenation being effected at a temperature between 20 C. and C. and at a pressure between 1 and 20 atmospheres, the weight of the zinc salt being between 0.01% and 5% of the weight of the acetylene compound.
2. The process according to claim 1 wherein the Weight of the zinc salt is between 0.01% and 2% of the weight of the acetylene compound.
3. The process according to claim 1 wherein the reaction is carried out in the presence of an amine compound.
4. The process according to claim 3 wherein the amine compound is ammonia in an amount about 0.5% by weight of the acetylene compound.
References Cited UNITED STATES PATENTS 2,207,070 7/1940 Reppe et al. 2,267,749 12/1941 Reppe et al. 2,335,795 11/1943 Reppe et al. 2,516,826 7/ 1950 Smith.
FOREIGN PATENTS 1,190,949 4/1959 France.
658,801 3/1963 Canada.
LEON ZITVER, Primary Examiner.
J. E. EVANS, Assistant Examiner.
US. Cl. X.R. 252-473; 260-642