Delta alumina

Fig. 1 shows the selectivities of the main isomerization products a-pinene, dipentene and camphene during the HDS experiment with carbon I and III. Similar results were obtained with other carbon samples. In fig. 1 these results are compared with the isomerization behaviour of AI2O3 (Rh6ne-Poulenc SCS 79 delta-alumina) and SiC>2 (Rhone-Poulenc DBM 250 silica), which were studied previously [Ref.3,4], Carbon induces profound changes in the spectrum of isomerization products dipentene is the major... 

Motschi, H., and M. Rudin (1984), 27A1 ENDOR Study of V02+ Adsorbed on delta-Alumina, Colloid Polym. Sci. 262, 579-583. 

Table 1 shows metal loadings, remaining carbon, and BET surface areas of the resulting calcined catalyses (ref. 4). In the nomenclature used AC, represents delta-alumina K, presence of potassium and 700, catalysts calcined at 700°C... 

For refractory insulation applications heat treatments of the fiber above 1000°C induce the delta alumina to progressively change into alpha alumina. After 100 hours at 1200°C, or one hour at 1400°C, acicular alpha alumina grains can be seen on the surface of the fiber and mullite is detected. After 2 hours at 1400°C the transformation is complete and the... 

Both head- and tail-type cationic vinyl monomers with long methylene chains in THF or chloroform had the maximum adsorption on colloidal silica on the respective adsorption isotherm. Above the monomer concentration giving maximum adsorption, the monomer formed micelles or clusters in bulk solution with removal of adsorbed water molecules from the silica surface. At the monomer concentration giving maximum adsorption, the adsorbed monomer was spontaneously polymerised on the silica surface in THF or chloroform without an initiator at 40C or 60C. The polymerisation mechanism was discussed. Adsorption of an anion-type monomer with a carboxyl group on delta-alumina which showed a positive zeta potential in neutral aqueous solution was higher than that on colloidal silica, but spontaneous polymerisation did not occur on alumina. 19 refs. lAPAN... 

Rooksby, H.P. and Rooymans, C.J.M. (1961) The formation and structure of delta alumina. Clay Miner. Bull., 4, 234-238. 

Alumina is an amphoteric catalyst, which can difficult to characterize via chemical and physic methods. The transformation of cyclopentanol/cyclohexanone mixture allows us to estimate at the same time the acid-base properties of aluminas. From this transformation, it was shown that aluminas can be classified into two families only basic aluminas, such as theta, which were more basic than MgO, and acido-basic aluminas, eta, gamma and delta, which possess an acidic character less pronounced than dealuminated HMOR zeolite... 

Delivery receipt, 25 330 Delocalized cationic azo dyes, 9 423 Delta-3-carene (A-3-carene), 24 499 8-alumina, 2 404, 406t Delta coke, 22 704 8-damascone, 24 570... 

Developments in the zeolite field in terms of non-framework alumina control, leading to super low delta coke zeolites and the advent of enhanced surface activity zeolites, seem promising for the resid cracking field (3). 

Wu, Yuan and Xu have studied nonuniform pellets in the hydrogenation of CO over Ni on alumina supports.39 Selectivity is directly related to the CO/H2 ratio inside the pellets. The active Ni particles were deposited as a narrow band in order to approximate a Dirac delta distribution. Experimental data followed theoretical predictions of the researchers regarding enhanced selectivity to... 

I = 21 y = 0.394 r = 0.9476 F = 49.8 where log P is the hydrophobicity, bondrefr is the molecular refractivity, delta is the submolecular polarity parameter, ind indicator variable (0 for heterocyclics and 1 for benzene derivatives). Calculations indicated that PBD-coated alumina behaves as an RP stationary phase, the bulkiness and the polarity of the solute significantly influencing the retention. The separation efficiency of PBD-coated alumina was compared with those of other stationary phases for the analysis of Catharanthus alkaloids. It was established that the pH of the mobile phase, the concentration and type of the organic modifier, and the presence of salt simultaneously influence the retention. In this special case, the efficiency of PBD-coated alumina was inferior to that of ODS. The retention characteristics of polyethylene-coated alumina (PE-Alu) have been studied in detail using various nonionic surfactants as model compounds.It was found that PE-Alu behaves as an RP stationary phase and separates the surfactants according to the character of the hydrophobic moiety. The relationship between the physicochemical descriptors of 25 aromatic solutes and their retention on PE-coated silica (PE-Si) and PE-Alu was elucidated by stepwise regression analysis. 

The reasons for the enhanced stability of the product wero then examined. X-ray diffraction patterns showed the presence of gamma, chi, delta and a small amount of kappa alumina, but no obvious reasons for the enhanced stability could be detected ... 

Property Alumina Alumina ISO 6474 Alumina ISO 6474/2 Biolox Biolox forte Biolox delta Bionit ... 

Figure 4.3 Microstructure of Biolox delta. 1, Alumina grains 2, Zirconia reinforcing grains and 3, Chromia elongated platelets as crack arresters. ( With permission of CeramTec GmbH, Plochingen, Germany.)...

Among the numerous transition aluminas (as illustrated in Fig.1),gamma, delta and theta A O are the most used. These disordered spinels can be prepared by dehydration of boehmite. Fig. 2 shows the main ways of producing such aluminas. 

Figure 2. Susceptibility-composition isotherm for chromia impregnated on alumina (upper curve) and relation of delta and magnetic moment to chromium concentration (bottom curve).

The dot on each graph represents the results for a hypothetical new catalyst, and shows our method of making comparative evaluations. Comparison is made at the activity level of the new catalyst. And here the hypothetical catalyst is a very good one. It gives much more gasoline than the standard silica-alumina at the expense of C4 s, dry gas and coke. The differences which we found were referred to as A (delta) values. 

Webster TJ, Hellenmeyer EL, Price RL. Increased osteoblast functions on theta plus delta nanofiber alumina. Biomaterials 2005 26 953-60. 

Despite the above-mentioned advantages of cerium oxide and a-alumina especially for the conversion of alcohols, a wide variety of investigations have dealt with alkene conversion on y-alumina-supported active species [16, 28, 41]. For sol-gel layers, which can also be used as a support for CPO [8], the determination of the aluminum phase is often not reported (e.g. [42]) as calcination temperatures between 300 and 700 °C could result in a considerable contribution of amorphous phases to gamma phases and at 800-1000 °C there is an additional transition to a delta phase [43]. 

---