Oxalic acid, from sucrose

Although many workers have been interested in the production of oxalic acid from sucrose, it is probably true that sucrose cannot compete with other raw materials as a source of this acid. For example, sawdust has been found to be an excellent source of oxalic acid. It is possible, however, to arrest the oxidation of sucrose before the oxalic acid stage is reached and the much more valuable tartaric acid has been obtained in this way. Tartaric acid, at the moment manufactured from waste... 

The mechanism of the formation of levulinic acid probably involves the substance 5-hydroxymethylfurfural (XXVIII), which may also be obtained from sucrose by treatment with dilute oxalic acid. This... 

In 1895 Dull,9 who was studying inulin and its products of hydrolysis, found that when either fructose or sorbose was treated with an aqueous solution of oxalic acid under pressure, a substance was obtained which had the formula CeHeOa and resembled furfural in its properties. This substance was further investigated by Kiermayer4 who found that fructose and sucrose were the best sources when they were heated with 0.3% aqueous oxalic acid at 120°. It was however only the fructose portion of the sucrose molecule which was transformed since the glucose moiety was recovered unchanged. Kiermayer prepared several derivatives of CeH Os and from its reactions concluded that its structure was probably /3-hydroxy-S-methylfurfural (III). Van Ekenstein and... 

Blanksma5 continued the investigation of the formation of hydroxy-methylfurfural and confirmed Kiermayer s results that it was formed from hexoses by elimination of three molecules of water on acidic degradation and showed that ketoses reacted more readily than aldoses, a fact which was observed by Kiermayer when sucrose was treated with aqueous oxalic acid. Kiermayer had observed also that levulinic acid was obtained when hydroxymethylfurfural was treated with aqueous oxalic acid under pressure and this received further confirmation by Van Ekenstein and Blanksma.6 It was these authors who first pointed out that the complete degradation of hexoses to levulinic acid took place through the intermediate formation of hydroxymethylfurfural. 

Traditionally, oxalic acid has been extracted from natural products by treating them with an alkaline solution, followed by crystallization of the acid. Sodium hydroxide is the alkaline material most commonly used for this procedure. Today, a number of methods are available for the commercial preparation of oxalic acid. In one procedure, carbon monoxide gas is bubbled through a concentrated solution of sodium hydroxide to produce oxalic acid. Alternatively, sodium formate (COONa) is heated in the presence of sodium hydroxide or sodium carbonate to obtain the acid. Another popular method of preparing oxalic acid involves the oxidation of sucrose (common table sugar) or more complex carbohydrates using nitric acid as a catalyst. The reaction results in the formation of oxalic acid and water as the primary products. 

For the determination of AA, two non-enz3miatic sensors based on PANI-CNT composites were developed that differ from each other in the electrode composition. The catal ftic effect of copper nanoparticles (CuNPs] was utilized in one of the approaches [47] and the other was based on an electropolymerized poly(2,5-dimethoxyaniline]-NH2-MWCNT film [48]. Both sensors showed selective oxidation of AA in the presence of DA and UA at 0.4 and 0.28 V, respectively. The interference from 10 pM glucose, oxalic acid, fructose, lactose, NaCl, sucrose, and tartaric acid was negligible in 0.1MAA[47]. 

The formation of furfural is an acid-catalyzed dehydration reaction in which 3 moles of water are removed from 1 mole of hexose or pentose. The reactions are shown in Fig. 3.8. A common method for producing 5-(hydroxymethyl) furfural is the reaction of sucrose described by Haworth and Jones [8] in which a 30% solution of sucrose in water is heated to 120-140°C under pressure for 2-3 hr with 0.3% oxalic acid. In this process, the 5-(hydroxymethyl) furfural is formed primarily from the fructose part of sucrose and results in a 57% yield. 

The yield of citric acid on sugar varies from process to process and from manufacturer to manufacturer. The theoretical maximum is 112 percent on sucrose. The liquid surface fermentation has a yield of 90 to 95 percent, and the submerged culture fermentation 75 to 85 percent. Improvements have been made by reducing the formation of by-products, mainly oxalic acid, and yields of the submerged culture process are reaching those of the surface culture process. 

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