Physicochemical characteristics samples

MCM-22 with Si/AM 5 was synthesized according to the method reported by Corma et al. [12]]. The physicochemical characteristics and the acidity of this MCM-22 sample are reported in a previous study [13], Platinum was introduced via three different ways ion exchange with a solution of Pt(NH3)4.Cl2 (sample E), incipient wetness impregnation with H2PtCl6.xH20 (I) and mechanical mixture with 0.45 wt.% Pt/Al203 (M). The Pt contents of all the samples are 1 wt.% with respect to the zeolite. 

An analysis of the extensive literature data and the data of the authors of this book [1640, 1642, 1655] permits a conclusion that the variations in the physicochemical characteristics of Al(OR)3 are caused by the existence of different types of aggregates and the possibility oftheir mutual transformations. The molecular composition depends on the conditions in the course of sample preparation — temperature, nature ofthe solvent applied, and the age ofthe sample. An important role is also played by the presence in the samples of microamounts of oxocomplexes, which are always formed on sublimation, distillation, and any other thermal treatments. 

As many physicochemical characteristics as possible of reactants, possible intermediates and products should be considered. These might include spectral features (IR, UV-vis, NMR), ion conductivities (if ions participate in the reaction), optical activity, etc. If such data are not available in the literature, they should be investigated early on as they may lead to a monitoring procedure for the kinetic study. Although physicochemical properties which are directly proportional to concentration are most convenient, others such as pH or electrode potentials may be used as their relationship to concentration is well understood. When the relationship between an observed property or measured signal and concentration of a component in the reaction mixture is not theoretically derived, e.g. GLC signals from analysed samples of the reaction mixture, calibration curves may be used. These are constructed by analysis of standard solutions of a reaction component (see Chapter 2). 

The physicochemical characteristics of the HZSM5 samples studied are summarized in Table 1. In none of the samples studied extra lattice alumina was detected by 27AL-MAS-NMR, The parent zeolites were modified by treatment with SifOEt). These silylated samples were prepared by suspending the zeolite powder in dry n-hexane in which a calculated amount of tetraethyl orthosilicate was added [15]. The concentration of acid sites hardly changed by this modification (only the sites at the external surface were blocked), but the rate of transport of the molecules in the pores was drastically lower than with the untreated samples indicating a decrease in the effective pore diameter... 

In contrast to GC, liquid chromatography hyphenated with mass spectrometry (LC-MS) does not require a derivatization step before sample analysis. Separation of metabolite from sample matrix is achieved using chromatography columns with various stationary phases of different physicochemical characteristics. LC-MS is more often used than GC-MS because it is more suitable for unstable compounds, compounds difficult to derivatize, and nonvolatile compounds [6, 7]. Therefore, a wider range of metabolites with various physicochemical properties can be determined using LC-MS. Moreover, the sample pretreatment procedure is much simpler, which can have a great impact on minimization of analytical variability. 

Model NOM included polymaleic acid (PMA), a fiilvic acid surrogate natural humic (LaHA) and fiilvic acids (LaFA) extracted from Laurentian soil and Aldrich humic acid (AHA) purified to remove ash components. Physicochemical characteristics of these compounds have been reported in one of our previous publications [23]. Surface water samples were collected from the Edisto River, Charleston, S.C the Intercoastal Waterway, Myrtle Beach, S.C. and the Tomhannock Reservoir, Troy, NY. Physicochemical characteristics of these compounds have been reported previously [20]. 

Solid-waste sampling and characterization is difficult because solid waste presents in varying quantities, components composition, and physicochemical characteristics. The difficulty is more intensive for municipal solid waste, because these parameters are highly dependent on the site and period of waste generation. 

Table 1 - Physicochemical characteristics of the catalyst samples. The number following USY refers to the temperature of the hydrothermal treatment 3T means three consecutive hydro-thermal treatments.

The samples of leachate from the regional landfill for solid wastes before wastewater treatment plant were collected and analyzed for common physicochemical characteristics during three years period (2002-2004). 

TABLE 10. Physicochemical characteristics of the USY samples before and after (NH4)2SiF6 treatment. 

Whatever the investigation to be performed on whichever sample, it must be kept in mind that every step of the protocol should be designed to avoid modifications of the native physicochemical characteristics of the sample (e.g., precipitation/coagulat-ion/dissolution due to shifts in particle concentration, ionic strength, pH, redox potential, temperature or uncontrolled dehydration of sample). 

Obviously, the bulk composition of these solid standards should ideally be as similar as possible to that of the samples of interest, because the ablation yield, the transport efficiency of the particles produced, and the generation of the signals in the ICPMS instrument will most probably be influenced by the physicochemical characteristics of the matrix. Unfortunately, perfectly matrix-matched standards are not often available, with the possible exception of the analysis of glass and, particularly, of metals, for which a large number of reference materials are accessible. Some research papers on coins and metallic artifacts have used commercially available reference materials for calibration, generally with satisfactory results [26,39,48,49,63,64,72,73]. 

Because the properties of chitin straightforwardly and inherently depend on the source of chitin, it is necessary to characterize the properties of chitin before it is further utilized for a specific application. In fact, not every chitin or chitosan sample can be used for the same applications. That is why a complete characterization of the samples is mandatory. The physicochemical characteristics of chitin and chitosan and the determination methods are summarized in Table 8. 

In the case of the hydrodesulfurization (h.d.s.) processes the W( i)/Y-Al203 specimens are mainly used as precursor solids for preparing Ni-W/Y-Al203 catalysts. It is therefore necessary for us to examine whether the better physicochemical characteristics achieved by the use of EDF are maintained after the Ni(") deposition, by Dl, on the W(vi)/Y-Al203 samples. Table 8 shows that this is, in effect, the case. 

This paper describes preparation, physicochemical characterization and catalytic properties of a series of vanadium-doped alumina- and titania-pillared montmorillonites obtained by various methods The aim of this work was to investigate the influence of the preparation procedure and pretreatment on location of vanadium dopant within the PILC structure and to correlate the physicochemical characteristics of tiie samples with their catalytic activity in ammoxidation of m-xylene. 

As in LC, both destructive and nondestructive detectors are used in SFC. The detector most commonly used for this technique is the flame ionization detector. It is a destructive, sensitive, and universal detector, which is well known from gas chromatography. Even though Richter et al. [151] described, in 1989, a new FID detector with a detection limit (5 pg of carbon per second) and a linear dynamic range (10 ) very similar to that achieved in FID-GC systems, the ordinary FID-SFC system is still a factor of 10- 1000 poorer in sensitivity, which consequently calls for relatively concentrated sample solutions. If very. sensitive detection is essential, the FID-SFC detection limit can be increased by a factor of ca. 1000 by replacing carbon dioxide with nitrous oxide, which has similar physicochemical characteristics (see Table 9). However, one should be aware of the fact that N2O can explode under higher pressure and temperature. 

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