Effect water vapor

Three series of LaCoi. CuxOs, LaMni.xCuxOs, LaFei x(Cu, Pd)x03 perovskites prepared by reactive grinding were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), temperature programmed desorption (TPD) of O2, NO + O2, and CsHg in the absence or presence of H2O, Fourier transform infrared (FTIR) spectroscopy as well as activity evaluations without or with 10% steam in the feed. This research was carried out with the objective to investigate the water vapor effect on the catalytic behavior of the tested perovskites. An attempt to propose a steam deactivation mechanism and to correlate the water resistance of perovskites with their properties has also been done. 

Tphe excellent catalytic activity of lanthanum exchanged faujasite zeo-A lites in reactions involving carbonium ions has been reported previously (1—10). Studies deal with isomerization (o-xylene (1), 1-methy 1-2-ethylbenzene (2)), alkylation (ethylene-benzene (3) propylene-benzene (4), propylene-toluene (5)), and cracking reactions (n-butane (5), n-hexane, n-heptane, ethylbenzene (6), cumene (7, 8, 10)). The catalytic activity of LaY zeolites is equivalent to that of HY zeolites (5 7). The stability of activity for LaY was studied after thermal treatment up to 750° C. However, discrepancies arise in the determination of the optimal temperatures of pretreatment. For the same kind of reaction (alkylation), the activity increases (4), remains constant (5), or decreases (3) with increasing temperatures. These results may be attributed to experimental conditions (5) and to differences in the nature of the active sites involved. Other factors, such as the introduction of cations (11) and rehydration treatments (6), may influence the catalytic activity. Water vapor effects are easily... 

Other inert materials that can be used include water vapor and carbon dioxide, which are somewhat more effective than nitrogen because they have higher heat capacities. To use water vapor effectively as an inerting agent at atmospheric pressure, the temperature should be 90-95°C. Carbon dioxide is an effective inerting agent, but it has significant solubility in water and other materials and is reactive with alkaline substances. 

Yes. In fact, in some of the studies of the water vapor effect there is a... 

Elucidation of control of water vapor effects Disturbances by water vapor have been a major origin of errors in gas response. Elimination of them upgrades the quality of gas sensing. 

M. C. Maris-Sida, G. H. Meier and F. S. Pettit, Some water vapor effects dining the oxidation of alloys that are a-A Os formers,... 

Gordon Israelson PE (2008) Water vapor effects on fuel ceU desulfurizer performance—a decade of field experience. In Proceedings of Fuel CeU 200 Sixth Int Fuel Cell Sdaioe Eng Tech Conference Denver, Colorado, USA... 

Holstein, W. and Machiels, C. (1996). Inhibitionof Methanol Oxidation by Water Vapor—Effect on Measured Kinetics and Relevance to the Mechanism, J. Catal., 162, pp. 118—124. 

Holstein, W.L. and Machiels, C.J. Inhibition of methanol oxidation by water vapor-effect on measnred kinetics and relevance to the mechanism. J. Catal. 1996,162, 118-124. 

Butkovskaya, N., Rayez, M.-T., Rayez, J.-C., Kukui, A., Le Bras, G. Water vapor effect on the HNO3 yield in the H02-hNO reaction experimental and theoretical evidence. J. Phys. Chem. A 113, 11327-11342(2009)... 

Acetic acid is having a great demand in plastics, textiles, paper, paints, and adhesives industries. At present, it is the produced by the Monsanto process. Alternative route for the synthesis of aeetie acid is by using CO and methane. A South African patent by Freund and Wambach [309] claimed that with one or more metals of group VIA, VIIA, and VIIIA on alumina, the direet synthesis of acetic acid from CO and CH at 100-600°C and 0.1-20 MPa, a selectivity of 70-95% is obtained. Cu-Co oxides [310] and Pd or Pt-based eatalysts [311] are foimd to be effective for the activation of C-H bond in methane. Introduction of oxygen to the reactant system is another way to overeome thermodynamic limitations. Huang et al. [312] explored the eatalytie aetivity of VjOj-PdCyAl OjOn the direct synthesis of acetic acid from CH and CO in the presence of and showed the water-vapor effect on the rate of formation of acetic acid. 

FIG. 4.23. Hydrogen-water vapor effective diffusivity derived from data for the reduction of hematite to iron compared with that obtained by direct measurements and calculated from pore structure. From the work of Turkdogan et al. [62]. V, previous work A, present work (both direct measurements) , calculated from pore structure 0, derived from reduction data. 

In addition to the temperature limitation, chromia-forming alloys suffer problems at lower temperatures due to the presence of water vapor in the environment (i.e. steam or combustion gas) (Opila, 2004). This is a significant issue as many high temperature applications involve these environments. The study of water vapor effects has been ongoing for many years (e.g. Caplan and Cohen, 1959 Fujii and Meussner, 1964) and is a very active area of current research (Otsuka et al., 1989 Shen et al 1997 Nickel et al.. 

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