Silicon-aluminum ratio

Molecular sieving, 18 269-272 effect of temperature, 18 271, 272 sorbate structure, 18 270, 271 molecular dimensions, 18 270, 271 polarity, 18 271 zeolitic, 39 352 structure, 18 269, 270 effect of cation, 18 269, 270 of solvation, 18 270 ring shape, 18 269 ring size, 18 269 silicon aluminum ratio, 18 270... 

B., and Hunger, M. (1992) Mordenite acidity dependence on the silicon/ aluminum ratio and the framework aluminum topology. 1. Sample preparation and physicochemical characterization. /. Phys. Chem., 96 (21), 8473-8479. 

When 1,2-dichlorobenzene in hydrogen-saturated deionized water was exposed to a slurry of palladium catalyst (1%) at room temperature, benzene formed via the intermediate chlorobenzene. The reaction rate decreased in the order of MCM-41 (mesoporous oxide having a silicon aluminum ratio of 35) > alumina > Y (dealuminated zeolite having a silicon aluminum ratio of 15). It appeared the reaction rate was directly proportional to the surface area of the support catalyst used (Schiith and Reinhard, 1997). 

Tn the past four years there has been great interest in how the variation A of the silicon aluminum ratio of zeolites affects their catalytic and sorptive properties. Ward (1) and Tsutsumi et al. (2) found that catalytic activity increased with increase in the silicon aluminum ratio of X and Y zeolites. As the Al content decreases, the interaluminum distance increases, and the cations or protons present experience weaker electrostatic shielding and form strong Bronsted acids (3). 

We report here a novel method of increasing the silicon-aluminum ratio of HY zeolite by reaction with the organosilicon compound, tetra-... 

In this section, a hydrothermal treatment that produces phase transformations in clinoptilolite and allows us to synthesize zeolites X and Y is described. Zeolites X and Y have the FAU-type framework however, the zeolite X has a silicon/aluminum ratio in the range 1 < Si/Al < 1.5 and zeolite Y has a silicon/aluminum ratio in the range 1.5 < Si/Al < =7.0. 

HEAT OF ADSORPTION CONSTANTS, INITIAL HEATS AND SILICON ALUMINUM RATIOS... 

The 1 1 silicon/aluminum ratio in Lot C persists even after methanol cleaning. This would siq>port the earlier observation that a portion of the grinding media, in particular AI2O2, be firmly embedded in the surface during polishing. 

Zeolites with a silicon/aluminum ratio of 1, because of their low water content, have the highest possible ion-exchange capacity, when computed on this basis. Linde 4A and Linde 13-X exhibit selectivity patterns characteristic of high-field-strength exchangers despite their open structure and higher water content. 

J. Turkevich (Princeton University, Princeton, N. J. 08540) In connection with Figure 3, I would like to know how the silicon-aluminum ratio is determined. The synthetic zeolites and maybe natural ones are obtained from silica-rich gels which increase in silica-alumina ratio in the mother liquid as the silicon-aluminum ratio increases in the crystals. Silica may be occluded and adsorbed as a colloidal gel on the zeolite and difficult to wash off. The silica ratio as measured will be higher and the lines asymetrically lower. 

In material science applications solid state NMR often employs a 200—750 MHz NMR spectrometer (Table 7.1) with a wide-bore magnet and high-power RF amplifiers and matching NMR probes [10—12]. This equipment is especially useful for analysis of polymer structures with and NMR and for analysis of zeolites with and Si NMR. In polymers, local dynamics can be studied with time scales ranging from seconds to picoseconds phase separations can be studied with domain sizes from nanometers to micrometers. For zeolites, the structures are characterized in terms of silicon/aluminum ratios, aluminum—hydrogen distances, and the chemistry of catalytic sites. 

---