Hey Antoncho, it's nice when aurelius actually has time to do work. here's your patent- in text (the pertinent parts anyway)
US Patent 2259895
Process for the manufacture of aliphatic carboxylic acid anhydrides
(Antoncho: Post # 392044)
The present inverntion related to the production of organic carboxylic acid anhydrides such as acetic anhydride and other simple aliphatic anhydrides. (listed through butyric)
It is known that in the oxidation of aldehydes the corresponding carboxylic acid anhydrides are formed over the intermediate existence of per-compounds. These anhydrides are obtained by known measures such as distillation in vacuo, whereby the anhydrides are preserved from the saponifying influence of the water formed at the oxidation. Generally metal salts, especially the acetates of copper, cobalt, or manganese are used in the dissolved or suspended form. The yields and the reactions velocity are very unsatisfying so that a technical process is nearly impossible.
It is an object of my invention to provide such catalysts as accelerate the reactions so that the process may be well practiced.
My invention consists in carrying through the said process with catalysts to which stronger acids, or those acids which are able to form complex compounds or other acidic substances are added. Te catalysts to which these substances according to my invention are added are the salts of the metals with organic acids.
I prefer to employ polyvalent metals salts and to use the free organic acids of the salt as solvent or suspending agent. The salts of copper, silver, cobalt, nickel, iron chromium and the like are used, preferably I the presence of substances with large surface such as silica gel, active-carbon, or cellulose.
As strong acids I use sulphuric acids, alkali bisulfates, perchloric acid, phosphoric acid, acid phosphates, sulpho-acetic acid, benzene sulphonic acid, chlorinated carboxylic acids and so on.
In the same way, weaker acidic substances which form strong acidic comples compounds by reactions with a corresponding carboxylic acids, such as boric acid, zinc chloride, vanadium acid, molybdic acid and the like my be employed.
The effect obtainable by my invention is quite surprising. One would have supposed that in the presence of such strong acids, which are well known hydrating catalysts, that the acetic anhydride would hydrolyze to the respective acid.
Copper sulphate is not a great catalyst for the reaction. owever, have shown to me, that by using a catalyst which was obtained by adding sulphuric acid to a solution of copper acetate the yields and the velocity of reaction are much improved.
Oxygen containing gas (such as air) is bubbled through the reaction mixture to keep the solution at a maintainable heat level. Adding esters of such acid/anhydride will also increase the velocity of the reaction. This process can be carried out as a continuous process by removing ½ the reaction volume and distilling out the product. The remaining substances are reintroduced to the reaction flask with additional catalyst.
Example 1:
In a stirring vessel, which is provided with a good cooling system and which enables the reaction liquid to circulate 30 parts of glacial acetic acid, 0.15 parts of cobalt acetate, and 0.2 parts of copper acetate are introduced. At 44-45*C, 34.5kg of acetaldehyde are treated with the equivalent of quantity of oxygen, within 2-1/2 hours. After one hour the reaction liquid contained 26% acetic anhydride and from that time the liquid was removed gradually in the rate as acetaldehyde was introduced. 55% of the reacted acetaldehyde was turned to acetic anhydride.
Example 2:
In the same way as in Ex. 1, by using 0.15parts cobalt acetate and 0.2 copper sulfate within 2 hours, 17.6 parts acetaldehyde entered into the reaction, whereby a yield of 52% acetic anhydride was obtained.
Example 3:
I used 0.15 parts of cobalt acetate, 0.2 copper acetate and 0.02 part sulfuric acid. Within one hour 17.5 parts of acetaldehyde are reacted with a yield of 63% acetic anhydride.
Example 4:
I used 0.15part of cobalt acetate, 0.2 part of copper acetate and 0.03 parts benzene sulfonic acid. Within one hour, 18.8kg acetaldehyde are reacted, whereby a 61% yield of 3kg of acetic anhydride) is obtained.
Example 5:
when using 0.15part of cobalt acetate, 0.2 part copper acetate and 0.03part boric acid, 18.2 parts acetaldehyde were reacted per hour and 13.1kg AA/hour were formed. 61% yield.
Example 7:
In a stirring vessel as in Example 1 to a solution of 30 parts of ethyl acetate, 0.15 part cobalt acetate, 0.1 part copper acetate and 0.3 part boric acid in 500ml GAA pure acetaldehyde was introduced with the equivalent quantity of oxygen at a rate corresponding to the velocity of the oxidation. 18.4 kg acetaldehyde were reacted/ hour and 15.4 kg of AA were obtained. yielded 72% !!!! The reaction liquid had a content of 32% AA, the reaction temperature was kept at 44-45*C
There are more examples, only one with higher yields (73% AA, but more reactants needed)
eatly advised not to use Manganese catalysts as they reduce the yield to consistant 20% ranges.
Other simple aliphatic acids may be used to obtain their respective anhydrides.
