Patent GB-588012-A (GB)
Title: Adsorption of acids
IPC: C08B31/00
Filed: 1945-01-24
Abstract: Mineral acids which are liberated in chemical reactions are adsorbed on a fluoride, preferably sodium fluoride, under substantially anhydrous conditions.  The invention is described with reference to acylation, esterification, etherification, and nitration (see Groups IV and V).  Nitric acid formed as a by-product from nitration with nitrogen pentoxide, dissolved in a non-aqueous inert solvent may be adsorbed either by carrying out the reaction with sodium fluoride present and separating the latter with its adsorbed acid subsequently, or by passing the nitrating solution alternately over the organic material to be nitrated and over the fluoride, fortifying the solutions whenever necessary.  Other fluorides such as those of zinc, magnesium, potassium, and ammonium may be used.  The fouled adsorbent may be heated to release the adsorbed acid.ALSO:Nitration, acylation, esterification and etherification reactions in which a mineral acid is liberated are effected in the presence of a fluoride, preferably sodium fluoride, under substantially anhydrous conditions, when the acid is adsorbed in the fluoride.  Reference is made to the nitrations of carbohydrates and polysaccharides such as cellulose and sugars such as lactose and sucrose; alcohols such as pentaerythritol, mannitol, and glycerol; hydrocarbons such as toluene and paraffins; and amines containing a replaceable hydrogen.  The nitration is carried out by dissolving nitrogen pentoxide in an inert non-aqueous solvent such as one derived from coal tar or petroleum, in particular chloroform, carbon tetrachloride, or propylene dichloride, contacting the solution with the organic material to be nitrated, and then either adding the fluoride to the mixture and subsequently separating it or passing the nitrating solution alternately over the material and the fluoride. The temperature of the process may be kept between - 20 and - 35 DEG  C.  The etherification of carbohydrates such as cellulose may be effected by reacting the carbohydrate with a halogenated acid or halohydrin, for example, chloracetic acid or ethylene chlorhydrin, to produce carbohydrate glycollic acid ether or carbohydrate hydroxy ethyl ether respectively.ALSO:Reactions to give starch derivatives such as nitrostarch, or starch ethers in which a mineral acid is liberated, are carried out in substantially anhydrous conditions in the presence of a fluoride such as sodium fluoride to adsorb the acid.  Nitration is effected by a solution of nitrogen pentoxide in an inert non-aqueous solvent such as one derived from coal tar or petroleum, in particular chloroform, carbon tetrachloride or propylene dichloride which solution is contacted with the starch giving nitric acid as a by-product.  The fluoride may be added to the mixed reactants and subsequently separated or the nitrating solution may be circulated between the starch and the fluoride. Nitrostarch may be obtained with a nitrogen content of 13.91 per cent.  Starch may also be reacted with chloracetic acid to give starch glycollic acid ether or with ethylene chlorhydrin to give starch hydroxy-ethyl ether, hydrochloric acid being liberated in each case and adsorbed on a fluoride.