Catalysts analysis

In all tests, there was no sign of carbon black formation. Pressure drop over the reactor remained constant during the whole operating period, and there was no accumulation of free carbon on the catalyst. Analysis of the discharged catalyst for free carbon revealed that the carbon content was lower than the amount of carbon added to the catalyst as a pelletizing aid. 

Special attention was paid to the detection of residual Cu-fl quantities accompanying the metallic Cu. The relative amounts of Cu+1 and Cu were determined by curve-fitting the Cu (LMM) spectra using the Physical Electronics Version 6 curve-fitting program. The catalyst showed reduction of Cu+2 Into a mixture of Cu+1 and Cu after reduction In H2 at 250 C for one hour (Figure 6) as evidenced by the two resolved peaks In the Cu (LMM) spectrum at 568.0 and 570.3 eV which are characteristic of Cu and Cu+1, respectively, and by the disappearance of the Cu+2 2p satellite structure. It could be shown that less than 2%, If any, of the total Cu could be present In the +1 oxidation state during methanol formation. However, when the catalyst was briefly exposed to air (1 minute), a few percent of Cu+1 readily formed (7). Thus, any kind of oxidation environment has to be avoided between methanol synthesis and catalyst analysis. Otherwise, appreciable amounts of Cu+1 will be detected. 

In 2008, Xiuyang et al. made an in-depth experimental study on the glucose decomposition in High Temperature Liquid Water (HTLW) from 180 to 220°C [73]. Interestingly, at 220°C, 100% of glucose was consumed within 90 min without addition of any catalyst. Analysis of the crude revealed that the main products of the reaction were HMF, levulinic acid, humic matter, and two unidentified soluble compounds. The maximum yield of HMF was obtained after 30 min of reaction (32%). 

Figure 9. Desulfurization catalyst analysis after pilot plant test...

In heterogeneous catalysis, the term active site is also used extensively [7,8], The density of active sites per unit surface area of the catalyst is an important parameter in catalyst analysis and development [9], However, whereas the surface area is relatively easily determined experimentally [10], the number of active sites in heterogeneous catalysts is not easily estimated. Therefore, although both fields use turnover numbers (reactant converted per unit time per active site) to describe activity, only the enzymologists can be sure that the quantitation of this parameter is adequate. 

No precise information about the olefin polymerisation mechanism has been obtained from kinetic measurements in systems with heterogeneous catalysts analysis of kinetic data has not yet afforded consistent indications either concerning monomer adsorption on the catalyst surface or concerning the existence of two steps, i.e. monomer coordination and insertion of the coordinated monomer, in the polymerisation [scheme (2) in chapter 2], Note that, under suitable conditions, each step can be, in principle, the polymerisation rate determining step [241]. Furthermore, no % complexes have been directly identified in the polymerisation process. Indirect indications, however, may favour particular steps [242]. Actually, no general olefin polymerisation mechanism that may be operating in the presence of Ziegler-Natta catalysts exists, but rather the reaction pathway depends on the type of catalyst, the kind of monomer and the polymerisation conditions. 

Initial sulfur (Catalyst analysis) (Solution analysis)... 

Catalyst analysis by XRD, [6] area and pore volume measurements and C and S elemental analysis was performed on the samples before and after use in the laboratory micro reactors. 

For a long time practical catalysis remained an empirical art rather than a scientific discipline, mainly because the complexity of the catalytic systems obscured the molecular insights needed for their control in a predictive manner. The modern spectroscopic techniques available to the analytical laboratory enable detailed catalyst analysis and in-situ studies. Advanced inorganic and organometallic chemistry and catalyst synthesis (e.g. zeolite synthesis) are also significant. This has changed catalytic practice and has resulted in a considerable reduction of catalyst development times. Nonetheless, in catalysis, accidental discovery and high risk exploratory research are still important factors in innovation. 

To obtain the coking mechanism of zeolite catalyst for SCFP alkylation of benzene, two kinds of the zeolite used in LP and SCFP alkylation processes were analyzed by using the conventional catalyst analysis methods. Fresh zeolite is also analyzed for comparison. 

For the purpose of catalyst analysis, the weaknesses of ESCA turn into strengths as it is the chemical bonding of the outer surface of a solid that is of interest and only to a lesser extent its bulk chemical structure. Most of our theoretical understanding of chemical bonding refers, however, to the bulk state (crystal structures)... 

Typical performance levels of an electron microprobe for quantitative analysis of a solid material correspond to a precision of around 1% for major elements and detection limits of approximately 100 to 500 ppm. Catalyst analysis poses specific problems because of the nature of the supports insulating, hydrated and porous. The precision of analysis for a catalyst is limited by the counting statistics to which is added an error due to the porous nature of the material (the signals measured on a porous alumina are, generally speaking, between 5 and 30% lower than those measured on a solid alumina). 

The electron microprobe is well adapted to catalyst analysis in general and in particular to the study of the distribution of active elements. The detection thresholds arc compatible with the (generally extremely low) concentration levels used for these elements. 

The techniques developed cover various fields, including textural characterisation, elementary and structural analysis and the analysis of composition and surface sites. The book describes the major phases of the technique s development and industrial application, presents its basic concepts and provides a general deKription of industrial equipment, all in a manner that is fully accessible to the non specialist. There is a particular focus on measurement (sample handling, test duration, calibration procedures, etc.) and performance (precision, application limits, possible errors and artefacts), illustrated by concrete examples of catalyst analysis. 

Initial deactivation is almost certainly due to adsorption of asphaltenes on acidic sites on the catalyst. Analysis of the catalyst shows that the initial deposits block smaller pores to cause up to a 50% loss of surface area. 

Increased propylene ammoxidation activity of each phase upon alterion doping is due to the juxtaposition of all necessary elements for oxidation catalysis in a single phase. The requirements of a good oxidation catalyst are a) activation of the substrate molecule, b) oxidation activity (oxygen inserting) and c) facile redox capabilities to ease electron conduction and site reconstruction. For reasons discussed extensively in the literature (7 ), we assign these roles to Bi, Mo, and Ce ion sites respectively in the catalysts described here. The solid solution formation observed in these materials enables all of these functions to be represented in one phase and on one surface of the catalyst. Analysis of the Multiphase Catalyst... 

The reaction was carried out using the same unit as with dimerization of ethylene. The conditions of the reaction were pressure - 0,2 MPa temperature - 313 K molar ratio Al/Ni -10. CEP-PMAA-NCb bHaO-SCEA was used as a catalyst. Analysis of the reaction products has shown that there was 46.0% mass of 4-methyl-l-pentene 41,0%mass of 4-methyl-2-pentene and 13,0% mass of other isomers in the mixture. Thus, using gel-immobilized nickel... 

Catalyst Analysis T/°C Conv. /% Concentrations/mol% Selectivity/% Yield/%... 

Carbon formation has been observed to occur both in the partial oxidation/steam reforming catalyst and in the reformate after it exits the catalyst. Analysis of carbon formed in the steam reformer catalyst found that the carbon was mostly carbonaceous carbon with an approximate H/C ratio of 0.2 - thus about 97% carbon. Carbon that formed in the reformate after it exited the catalyst (probably from unconverted hydrocarbons) has been analyzed to contain 30% by weight solidified hydrocarbons. 

Spent Catalyst Analysis. Analysis of catalysts subjected to car and engine testing by x-ray fluorescence (XRF) revealed the expected con-... 

The analyses of the Auger spectra suggest the relative insensitivity of sulfur adsorption to temperature similar to the observations noted with the ceria-only model catalyst analysis. As previously indicated, the lack of discernible temperature dependencies may be attributed to the minimum reduction and oxidation temperatures for cerium oxides [15]. Because of the lack of discemable temperature dependencies, the data were averaged as a function of temperature and considered for pressure dependence. The pressure dependence on the extent of sulfur adsorption is clearly evident as a function of model catalyst composition. 

Resin-bound diazoimides 190 were subsequently reacted with different electron deficient acetylenes 191 in benzene at 80°C for 2 hours in the presence of Rh2(OAc)4 as a catalyst. Analysis of the crude products showed exclusively the presence of the desired furans 192 and excess unreacted acetylene, which, when sufficiently volatile (e.g propiolate esters), were eliminated in vacuo to provide furans of high purity. To avoid contamination of the desired furan product with residual, non-volatile acetylene, a two step sequence was implemented for the cycloaddition reaction. Thus, C-labelled diazoimide 193 was allowed to react with a large excess (10 eq) of dimethyl acetylenedicarboxylate (DMAD) 194 in the presence of Rhj(OAc)4 at room temperature in anticipation of trapping the bicyclic intermediate 196 on the polymeric support. After washing the... 

The kinetics of heterogeneous-catalytic epoxidation of cycloh cene (CH) by tert-butyl hydroperoxide (TBHP) was investigated [202]. Catalysts were prepared by impregnating the ion-exchange resin, Amberlite IRS-84 in H-form, with the acidic solution of ammonium molybdate. The concentration of Mo was 0.35 mmole/g resin. The reaction kinetics were studied in the absence of solvent and at high molecular ratios of CH and TBHP. The reaction proceeded by pseudo-zero-order in respect of CH. Reaction selectivity was 90- 95 7o U. the initial rate could be determined from the rate of TBHP consumption. It was found that the reaction order was 1.8 for TBHP and 1 for the catalyst. Analysis of EPR spectra of catalysts before and after the reaction showed partial oxidation of Mo to Mo. The authors supposed a stepwise reaction mechanism in which the interaction between CH and a complex of Mo and TBHP is considered to be the slow and irreversible step. In this complex. Mo was present in the oxidized state. 

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