ALUMINUM HYDROXYNITRATES THERMOLYSIS

The thermolysis of various aluminum hydroxynitrates obtained by fresh precipitated Al hydroxide dissolution in a stoichiometric quantity of nitric acid has been studied. Under heating their multistage decomposition occurs including a gradual removal of chemically bonded water and denitration. According to thermal analysis data the composition of AlOH(NO3)2·mH2O, Al(OH)2NO3·nH2O and Al2(OH)5NO3·kH2O decomposition products at temperatures of 40-800 °С has been determined. It was ascertained that crystalline hydrate water segrerates under 157 °С (double stage). In the course of the primary dehydration the most loosely coupled crystal water (0.5-0.8 water molecules) escapes. Then the secondary dehydration – the remaining crystal water removal – takes place. This process becomes easier with increasing hydroxygroups quantity; it is confirmed by a proper temperature interval shift to lower temperatures. At 190-241 °С nitrate turns into nitrite (at approximately the same temperature for all studied compounds). Afterwards (249-376 °С) the denitration and chemically bonded water removal from salts anions take place. At that boehmite AlOOH is formed. The latter gives alumina transitional forms. In the time of Al(OH)2NO3·nH2O and Al2(OH)5NO3·kH2O thermolysis the partial removal of chemically bonded water overlaps on the denitration; so thermogravimetric curves have the most complex form. As a result all hydroxynitrates in contrast with aluminum nitrate are transformed into boehmite AlOOH that is confirmed by X-ray phase analysis. In addition, the composition of thermal decomposition products is confirmed by elemental analysis data.Forcitation:Kosenko N.F., Filatova N.V., Lipina E.A. Aluminum hydroxynitrates thermolysis. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 8. P. 31-36.

Structural interrelationships between the bis(pentamethylcyclopentadienyl)arsenic(III) and antimony(III) cations and their precursor chlorides

The chloropnictines (η-C5Me5)2AsCl (1), (η-C5Me5)2SbCl (2), and (η-C5Me5)2BiCl (3) have been prepared by treatment of the appropriate element trichloride with LiC5Me5. X-ray crystallographic assays establish that in the case of 1, both C5Me5 rings are attached to As in an η1(σ) fashion. In 2 and 3, the C5Me5 rings are π delocalized and feature tri- and pentahapto ring binding, respectively, to the group 15 element. Conversion of 1 and 2 to the salts [As(η-C5Me5)2][AlCl4] (4) and [Sb(η-C5Me5)2][AlCl4] (5) was effected by reaction with the stoichiometric quantity of Al2Cl6. The X-ray crystal structure of 4 is surprisingly complex and features four independent ion pairs in the asymmetric unit with a variety of hapticities for the π-bonded C5Me5 rings. The structure of the stibocenium cation of 5 involves bis(η4) attachment of the π-bonded C5Me5 rings.Key words: main group metallocenes, arsocenium cations, stibocenium cations, group 15 pentamethylcyclopentadienyl chlorides.

Effects of Regeneration Procedures on the Performance of Reverse-Cycle Ion Exchange in the Purification of Sugarcane Juices

Investigations of the chemical requirements for regeneration of the first-anion and the cation-exchanger beds of the reverse-cycle system were undertaken in these studies, but no attempt was made to establish the requirements for the second-anion exchanger bed. A large dosage of NaOH to provide superior exchanger capacity was used for the highly basic anion resin in first position, and by recycling usable portions of the waste regenerant in a subsequent test, an average of 114 percent of the stoichiometric quantity of NaOH was consumed per test. No change in performance of the exchanger system was detected following adoption of such a regenerant recycling procedure. Efforts to obtain satisfactory regeneration of the weakly acid cation exchanger with H2SO4 were discouraging. The quantity of material which could be processed per test was less, the percentage removals of ash and protein were less, and the ash-percent-dry solids remaining in the product juices was 79-percent greater than when HCl was employed as regenerant. Juice purities following ion-exchange processing were found to have increased by approximately one-half as much with H2SO4 regeneration as with HC1. Examination of the product juices revealed that their potassiumion contents were much greater during H2SO4 regeneration tests than while HC1 was used. Apparently the large quantities of calcium and magnesium ions found in cane juices were not efficiently regenerated from the exchanger resin by H2SO4 , and that part which remained in the resin during subsequent juice deionization increased the leakage of potassium ions into the product juices. Although HC1 was much more expensive than H2SO4, the recycling of excess regenerant to reduce the quantity consumed to approximately 105 percent of the necessary stoichiometric requirement would make the use of this more costly acid economically attractive. Information was obtained in these tests which showed the importance of efficient backwashing of the highly basic first anion bed in order to eliminate significant quantities of Mg(OH)2, and organic materials precipitated on the resin particles during passage of juices through the bed. The effective backwashing obtained in the semipilot-plant column was not always attained in the smaller laboratory column and some insoluble materials remained following backwashing and regeneration.