Add sites

Consider the simplest type of L-system namely, a deterministic context-free L-system, also called a DOL-Systeni. As the name implies, the production rules of such systems are allowed to transform only single symbols i.e. the dynamics is independent of all neighboring symbol values. DOL-Systems are thus generalized CA systems that are allowed to add sites but whose local rule depends only on a given site itself and none of its neighbors. 

When H-EDTA-MOR was exposed to 0.3 kPa of NH3 at 473 K and evacuated at 473 K (Figure 6E), only protonated ammonia (NH4 ) was observed. The NH4" deformation band builds up at 1443 cm- together with a small amount of coordinated NH3 bonds (deformation) that attached to Lewis add sites at 1624 cm L... 

The major addic sites on H-MOR are Bronsted sites determined by pyridine adsorption studies above 80 % of addic sites are Br0nsted sites and the rest are Lewis add sites [4,5]. After adsorption of NH3, 0.3 kPa of EA are admitted on H-EDTA-MOR at 473 K (Figure 6F) adsorbed NH3 is easily replaced by EA to produce deformation bands of NH3+ (1597 cm-i, 1497 cm-t), CH2 (1460 cm-i). This spectrum is quite the same as the spectrum in Figure 6A. The results suggest that adsorption of EA is much stronger than that of NH3. When adsorbed EA is heated up to 573 K (Figure 6G-6H), the spectra are almost the same as the spectra in Figure 6B and 6C. 

For presulfided Co.Mo/Si02-Al203, the formation and elimination of the add sites were almost the same as those observed for non-sulfided Ck>.Mo/Si02-Al203. Presufidation with hydrogen sulfide did not affect much the conversion of the acid sites caused by gas phase hydrogen. 

For C0.M0/AI2O3 catalyst, no IR bands ascribed to pyridine were appreciable after outgassing at 423K. The add sites on C0.M0/AI2O3 are much weaker than those on Co.Mo/Si02-Al203. 

The recovery of the Lewis add sites and the decrease in the protonic acid sites to the original values by outgassing gas phase hydrogen are rather slow and require a high temperature. The addition of Pt/Si02 did not affect much the restoration of Ae Lewis add sites of H-ZSM-5 by outgassing gas phase hydrogen. 

Sulfate-doped zirconia was found to have both Lewis and Brdnsted add sites on the surface, where the sulfate groups were the carrier of the protonic site. The ratio of Lewis to Br0nsted sites was found to vary depending on heat treatment, but the percentage of sulfate groups associated with a proton was found to be constant at 12-17%. 

A very convenient method to quantitatively determined the number of Bronsted add sites in the often used photochemical nano-vessels, zeolites X and Y, is available.28 This method take advantage of indicator/probe molecules which undergo an intense color change upon protonation within the zeolite pore network. The amount of a base necessary to quench the color change gives a direct measure of the concentration of acidic sites. The base used to titrate the Bronsted sites must be more basic than the probe molecule and sufficiently basic to be completely protonated. 

In general, the associated acid sites of -OH(a) and the dissociated (ionized) base sites of -OH2 (b) predominate in acidic solutions, while the associated base sites of -OH(b) and the dissociated add sites of -0 (a) predominate in basic solutions. It then follows that the hydroxsdated solid interface of semiconductor electrodes is positively charged in acidic solutions and negatively charged in basic solutions. 

S. (2005) Probing the add sites in confined spaces of microporous materials by vibrational spectroscopy. Phys. Chem. Chem. Phys., 7,1627-1642. 

Martin, A., Wolf, U., Bemdt, H., and Lucke, B. (1993) Nature, strength, and concentration of add sites of erioite-rich zeolite T determined by ammonia-i.r. 

Nesterenko, N.S., Thibault-Starzyk, F., MontouiUout, V., Yusdienko, V.V., Fernandez, C., Gilson, J.-P., Fajula, F., and Ivanova, 1.1. (2004) Accessibility of the add sites in dealuminated small-port mordenites smdied by FTIR of co-adsorbed alkylpyridines and CO. Micropor. Mesopor. Mater., 71 (1-3), 157-166. 

Tessonnier, J.-P., Louis, B., Rigolet, S., Ledoux, M.J., and Pham-Huu, C. (2008) Methane dehydroaromatization on Mo/ ZSM-5 about the hidden role of Bronsted add sites. Appl. Catal. A,... 

Periodic density functional investigation of lewis add sites in zeolites relative strength order as... 

Ligands Susceptible to Reaction with Lewis Add Sites of Inorganic Oxides... 

Method Basis sets Hydroxamic acids Add site Reference... 

The role of surfactant molecules in the synthesis of Fe-Zn DMC is probably to increase the surface area and add sites density, thereby enhancing the catalytic... 

Bruyere.V.I.E. Blesa, M.A. (1985) Acidic and reductive dissolution of magnetite in aqueous sulphuric add. Site-binding model and experimental results. J. Electroanal. Chem. 182 141-156... 

String username = rs.getString( username ) sites.add(site) ... 

Considerable efforts have been made to understand ZSM-5-based catalysts for the selective oxidation of benzene to phenol by nitrous oxide. However, the nature of the active species remains unclear. The most important proposals for the active species are extraframework Fe species [101], Bronsted add sites [102] and Lewis and A1 sites [103, 104]. The activity is usually interpreted in terms of very small, possibly... 

---