Activity measurements catalysts

High purity oxygen from lOL,India and CO (99.5 %) from Air Products Ltd, UK were used for the activity measurement. Catalyst activity was evaluated in the temperature range 150-250 °C in a tubular reactor loaded with 3 cc of the catalyst. The reactant flow used was a mixture of 130 ml/minute oxygen and 20 ml/minute carbon monoxide. The inlet and outlet concentrations of carbon monoxide and carbon dioxide formed during reaction were analysed in a GC with FID detector. Carbon monoxide and carbon dioxide were converted to methane using a microcatalytic methanator connected after Poropak Q column. 

Because the chemiluminescence intensity can be used to monitor the concentration of peroxyl radicals, factors that influence the rate of autooxidation can easily be measured. Included are the rate and activation energy of initiation, rates of chain transfer in cooxidations, the activities of catalysts such as cobalt salts, and the activities of inhibitors (128). 

The hterature consists of patents, books, journals, and trade Hterature. The examples in patents may be especially valuable. The primary Hterature provides much catalyst performance data, but there is a lack of quantitative results characterizing the performance of industrial catalysts under industrially reaHstic conditions. Characterizations of industrial catalysts are often restricted to physical characterizations and perhaps activity measurements with pure component feeds, but it is extremely rare to find data characterizing long-term catalyst performance with impure, multicomponent industrial feedstocks. Catalyst regeneration procedures are scarcely reported. Those who have proprietary technology are normally reluctant to make it known. Readers should be critical in assessing published work that claims a relevance to technology. 

The amount of fresh catalyst added is usually a balance between catalyst cost and desired activity. Most refiners monitor the MAT data from the catalyst vendor s equilibrium data sheet to adjust the fresh catalyst addition rate. It should be noted that MAT numbers are based on a fixed-bed reactor system and, therefore, do not truly reflect the dynamics of an FCC unit. A catalyst with a high MAT number may or may not produce the desired yields. An alternate method of measuring catalyst performance is dynamic activity. Dynamic activity is calculated as shown below ... 

The reducibility of the catalyst is demonstrated in Figure 6 which shows the activity of catalysts, measured as described above, after reduction to constant activity at temperatures of 280°-350°C (536°-662°F). It will be seen that ICI catalyst 11-3 compares favorably with other catalysts which contain larger amounts of alumina and consequently are more difficult to reduce at acceptable temperatures. 

In addition to actual synthesis tests, fresh and used catalysts were investigated extensively in order to determine the effect of steam on catalyst activity and catalyst stability. This was done by measurement of surface areas. Whereas the Brunauer-Emmett-Teller (BET) area (4) is a measure of the total surface area, the volume of chemisorbed hydrogen is a measure only of the exposed metallic nickel area and therefore should be a truer measure of the catalytically active area. The H2 chemisorption measurement data are summarized in Table III. For fresh reduced catalyst, activity was equivalent to 11.2 ml/g. When this reduced catalyst was treated with a mixture of hydrogen and steam, it lost 27% of its activity. This activity loss is definitely caused by steam since a... 

These models indicate that propylene gas phase polymerization with a highly active TiCil3 catalyst shifts from kinetic control at short reaction times to diffusion control at longer times as the catalyst yield exceeds about 4000 g.PP/g.TiCil3. Measures to reduce this limitation would significantly benefit the process. 

While the control resins were deep red in color due to the presence of soluble porphyrin complexes, the methacrylate resins obtained after removal of the polyethylene-supported catalysts varied from light yellow to nearly water-white (APHA < 25). UV-Vis spectrophotometric analysis of the yellow resins indicated an absorption signal for the cobalt porphyrin complex Soret band (wavelength of cobalt(ll) porphyrin species appears at -415 nm free porphyrin ligand is formd at -423 tun). Resin samples that visttally appear as water-white show little or no porphyrin species present in the spectrum. Measured catalyst activity and PDl of the polyethylene-supported porphyrin complexes are in the expected range for soluble porphyrin CCT catalysts (PDl = M /Mn - 1.2- 2.0)." The screening resrrlts clearly... 

We are applying the principles of enzyme mechanism to organometallic catalysis of the reactions of nonpolar and polar molecules for our early work using heterocyclic phosphines, please see ref. 1.(1) Here we report that whereas uncatalyzed alkyne hydration by water has a half-life measured in thousands of years, we have created improved catalysts which reduce the half-life to minutes, even at neutral pH. These data correspond to enzyme-like rate accelerations of >3.4 x 109, which is 12.8 times faster than our previously reported catalyst and 1170 times faster than the best catalyst known in the literature without a heterocyclic phosphine. In some cases, practical hydration can now be conducted at room temperature. Moreover, our improved catalysts favor anti-Markovnikov hydration over traditional Markovnikov hydration in ratios of over 1000 to 1, with aldehyde yields above 99% in many cases. In addition, we find that very active hydration catalysts can be created in situ by adding heterocyclic phosphines to otherwise inactive catalysts. The scope, limitations, and development of these reactions will be described in detail. 

Dendrimer encapsulated Pt nanoparticles (DENs) were prepared via literature methods (1, 11). PtCl42 and dendrimer solutions (20 1 Pt2+ dendrimer molar ratio) were mixed and stirred under N2 at room temperature for 3 days. After reduction with 30 equivalents of BH4 overnight, dialysis of the resulted light brown solution (2 days) yielded Pt2o nanoparticle stock solution. The stock solution was filtered through a fine frit and Pt concentration was determined with Atomic Absorption Spectroscopy (11). Details on catalyst characterization and activity measurements have been published previously (11). 

Recent work done by Xiong et al.84 on Co/AC (activated carbon) catalysts showed that a Co2C species formed during the catalyst reduction in hydrogen at 500°C. Evidence for the carbide in the Co/AC catalysts was obtained by x-ray diffraction and XPS measurements, and the formation of this Co2C species reduced the FTS activity over the Co-based catalysts. The presence of bulk carbide also seems to enhance alcohol selectivity.85... 

This enantioselective mechanism is also in accordance with the elegant analysis and optical activity measurements by Pino et al.44,45 on the saturated propene oligomers obtained under suitable conditions with this kind of catalysts, proving that the re insertion of the monomer is favored in case of (R, R) chirality of coordination of the C2H4(1-Ind)2 ligand. 

Samples 1-4 correspond to VPO treated in steam for 92, 312h, in N2 and activated base catalysts, respectively, k, are pseudo-first-order rate constants for the disappearance of butane. The constants are measured in a microreactor on a larger amount ( 1 g) of catalyst at 633 K. k (intrinsic) are based on the BET surface area. 

Table 120 Activity comparison of Au/a-Fe203 (coprecipitation) with reference Au/A1203 (coprecipitation) and Cu/Zn/Al catalysts using a feed containing 4.88%CO in Ar, a SV = 4000 h 1, and a partial pressure of H20 of 223 Torr. Atomic ratios of Au Fe and Au Al were 1 22. Activity measurements are in mol CO per m2 per hour516...

Catalyst Activity Measurements. Activity measurements for thiophene HDS and the consecutive hydrogenation of butene were carried out in a Pyrex-glass, fixed-bed reactor at 625 K and at atmospheric pressure as described in Ref. (9). Before the measurements the catalysts were presulfided in 2% H2S in H2 at 675 K. For each catalyst conversions were measured at different space velocities of the thiophene/H2 mixture (2.5 thiophene) and the catalytic activities are here expressed as pseudo first-order rate constants as-... 

Ab initio methods, 147-49 Acetate ion, decomposition, 135 Acetylene, interaction with palladium, tunneling spectroscopy, 435,437f Acid-dealuminated Y zeolites catalytical properties, 183 sorption, 175-78 Acid sites, on zeolites, 254 acidification effects, 266 Acoustic ringing, in NMR, elimination, 386 Active sites, nature, 104 Activity measurements, Co-Mo catalysts, 74 Adsorbed molecules,... 

Because the composition and nano-scale structure of a catalyst depend on the temperature and the gas environment, it is important to measure catalyst activity under conditions experienced in the industrial converters. For the sulphuric acid catalysts, the activity for conversion of S02 to S03 was measured in the set-up shown in Fig. 9. 

Normally, the best activities observed during the development process are found for catalysts prepared in the laboratory where special attention is paid to each preparation step and where better control of e.g. impregnation and calcination temperature history can be achieved. This should be kept in mind when comparing activities of new lab-prepared catalysts with standard products from a production facility. As a consequence, it is seldom worth the effort to continue with a test production if the activity of the lab-prepared catalyst fails to meet the requirements. Important results for the test-produced catalysts are activity measurements covering the full range of operating conditions in the industrial converter and the mechanical strength. 

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