Effect of preparative conditions on the surface characteristics of mixed zirconium and titanium oxides

The surface characteristics of mixed zirconium and titanium oxides prepared from different starting materials are investigated. One mode of preparation entailed the use of zirconium sulfate and titanium oxysulfate as starting materials and ammonium hydroxide as precipitating agent. The produced oxides were washed to different extents to obtain samples with different sulfate content. A second preparative mode used zirconium oxychloride and titanous chloride as starting materials also with ammonium hydroxide as precipitating agent. The oxidation of the titanous to the titanic form for these oxides was carried out by means of oxygen gas. Resulting samples were heat treated at 400 °C and 600 °C, and textural characteristics determined from the adsorption of N₂ at 77 K, complemented by infrared and thermal studies. The samples precipitated from the oxychloride and chloride salts of zirconium and titanium, as well as those precipitated from the sulfate and oxysulfate salts and washed free of the sulfate ions displayed quite similar textural characteristics. The unheated samples and those heat-treated at 400 °C were mesoporous, with some microporosity, and relatively large surface areas in the order of 200–300 m²/g. Heat treatment to 600 °C led to a relative decrease in surface area, in the order of 100 m²/g, and to the disappearance of microporosity. The mixed zirconium and titanium oxides with a sulfate content of ≈17% displayed significantly lower surface areas, smaller than 10 m²/g, with a prevalence of micro and mesoporosity. Infrared and thermal studies indicated the presence of differently bounded sulfato groups, which seem to have a blocking effect on the pores, resulting in the observed smaller surface areas.     

Radiation sintering of magnesia: Pore structure studies

Co⁶⁰ γ-ray irradiation of a nonequilibrium surface of magnesium oxide produced tremendous effects on both the extent of the surface area, and on the pore structure. In all cases investigated incompletely decomposed crystals showed appreciable lowering of surface area which indicated activated sintering of the material. The pores present are mainly wide, but with a very narrow distribution of their sizes. Their most probable hydraulic radius is about 10 Å. Upon irradiation sintering is accompanied by widening of pores, and a second group of pores showed its appearance in the pore size distribution curves. These effects seem to be associated with the presence of traces of the volatile component of the parent material, and in particular with the presence of traces of water vapor. Irradiation of the completely decomposed material produced no changes in surface area or pore structure.

The role played by water vapor in accelerating the sintering of magnesia is discussed and possible explanations are given for the effects of irradiation. Dual effects of water vapor might lead to the sintering acceleration of magnesia; chemisorption of OH groups which create cation vacancy on the surface leading to activated surface diffusion, and oxygen bridging between two adjacent/or opposite OH groups particularly in narrow pores, leading to their blocking.     

Antimicrobial Activity of Some Novel Thiourea,Hydrazine, Fused Pyrimidine and 2‐(4‐Substituted)anilinobenzoazole Derivatives Containing Sulfonamido Moieties

Thiophosgenation of sulfonamides 1a‐c in the presence of dilute HCl at room temperature furnished the isothiocyanatosulfonamides 2a‐c and treatment with aromatic amines gave 1,3‐disubstituted thioureas 3a,b . Also, interaction of two molecules of 2c with 1,4‐phenylenediamine yielded the novel bisthiourea 4 . Cyclocondensation of 2 with ortho amino carboxylic acid compounds such as anthranilic acids 8 , 5‐amino‐1‐phenyl‐pyrazol‐4‐carboxylic acid 9 and 4,5,6,7‐tetrahydro‐2‐amino‐benzo[b]thiophene‐3‐carboxylic acid 10 furnished the fused thiopyrimidines 11a‐d, 12 and 13 , respectively. 2‐Anilinobenzoazole derivatives 15a‐c, 16a, b and 17a,b were obtained through cyclocondensation of 2 with 1,2‐dinucleophiles.