Co/Al2O3 catalyst

A 25.0%Co/Al2O3 catalyst [15] was prepared by a slurry impregnation method, and cobalt nitrate was used as precursor. In this method [1], the ratio of the volume of solution used to the weight of aliunina was 1 1, such that approximately 2.5 times the pore volume of solution served as the loading solution. Two impregnation steps were used, with interval drying, prior to calcination at 400°C. 

The results for the 12.4%Co/Si02 catalyst, the 0.2%Ru-10%TiO2 catalyst, the 0.5%Pt-15%Co/Al2O3 catalyst, and the 25%Co/Al203 catalyst are summarized in Tables 6 - 9 for comparative purposes among the different catalyst systems, and for comparison with the four case studies previously summarized. 

The catalytic tests show that, over the Pt(l 0 0)/Al2O3 catalyst, the formation of CO and NH3 is largely prevented, whereas the yield of N2O increases compared with the Pt(polycrystalline)/Al203 catalyst. These main differences observed should be ascribed to the morphological differences between two catalysts, i.e., the dominant orientation of the crystallographic facets and the average size... 

The capability of NO to reduce nitrates, providing a pathway for the production of ammonium nitrite and thus of nitrogen, has also been demonstrated recently by Weitz and co-workers, mainly on the basis of IR data collected over BaNa-Y zeolite [75] however, according to a parallel additional route NO would also react with NO2 to form N2O3 and then nitrogen [reactions (13.25) and (13.26)], as already discussed. The oxidation of NO by surface nitrates over a Pt-Ba/Al2O3 catalyst has also been reported by Olsson et al. [76], whereas the formation of surface nitrates from NO2 on bare AI2O3 has been reported by Apostolescu et al. [77] and previously observed in our laboratories also [78]. 

Recently, Sederman and co-workers (755) used the DEPT MRI pulse sequence described in Section V.A.2 to investigate 1-octene hydrogenation occurring over a l-wt.% Pd/Al2O3 catalyst in a trickle-bed reactor. The reactor was of inner diameter... 

The effect of that Cs loading was studied by O2 TPD and by ethylene temperature-programmed reaction [3]. The O2 desorption spectrum obtained by Atkins and co-workers for the Cs/Ag/v-AhOa catalyst is shown in Fig. 7.9, lower curve. The upper curve with two peak maxima at 523 K (250 °C) and 573 K (300 °C) is that shown previously for O2 desorption from a fresh, unpromoted Ag/a-Al2O3 catalyst (Fig. 7.1). 

Fig. 6. Deactivation of Ru-promoted and unpromoted 15%Co/Al203 catalysts in a CSTR. Circles CO conversion. Squares H2 conversion. Solid 15%Co/Al203 unpromoted, Open 15%Co-0.5%Ru/Al2O3. (220°C, 275 psig, 5 SL/hg cat).

The process was carried out in flow with a pilot multi-tube reactor at Novocherkassk s plant (Russia). Each tube was combined with a separator and heating trap to collect a mix of liquid and solid products. To produce the suitable hydrocarbon amount for their analysis and to convert to the further industrial scale, 100 g of catalyst was placed into each reactor tube. Three series of 4 samples of 10% C0-M/AI2O3 catalysts with different amounts of the second metal have been parallel tested. The commercial synthesis-gas with CO/H2 = 1/2.2 was used. Temperature and space velocity were increased step by step from 150 until 200°C and from 100 to 300 hr respectively. Pressure was 0.9-1.0 MPa. The duration of each experiment over the bimetallic catalysts was at least 10 days maximum duration of continuous catalyst testing was 3 months. For comparison, also the monometallic 10%Co/Al2O3 has been tested for 100 hours. 

Table 2. The effect of space velocity on selectivity to ceresin over 9.25%Co-0.75%M/Al2O3 catalyst (H2/CO=2.2 P=0.95 MPa, Kco= 53%)...

By TEM studies of the bimetallic catalysts, it has been observed that basically the metal particles are uniformly distributed over the alumina surface. Both metals are dispersed in bimetallic catalysts. In 10% C0/AI2O3 catalyst, the particle size is 3-7 tun (Fig.l). While introdueing the seeond metal to 10%Co/Al2O3, the size of metallie partieles is deereased to 1-2 run depending on the amount of promoter (Fig.2). The further dispersion of metal partieles occurs after using the catalyst in a reaction medium (CO+H2). There is no mierodiffiaction from metal particles in samples used in the Fiseher-Tropseh synthesis. 

The absorption bands in regions of earbonate-earboxylate struetures, carbonyls, CHx, OH adsorbed groups, and physically adsorbed CO2 have been observed by IR-studies of adsorption of CO and mix CO+H2 on a surface of the redueed 10%Co-M/Al2O3 catalysts. In region of adsorbed earbonyls, the bands at 1980-2180 cm assigned to the linear CO adsorbed on high dispersed metal centres probably in different oxidised states have been deteeted at adsorption of (Figure 3). 

Figure 3. IR spectra of CO+H2 adsorption over 10%Co-Pt/Al2O3 catalysts...

A 15.0%Co/Al2O3 [13] catalyst was prepared by a three step IWI of an AI2O3 support (Condea Vista B y-alumina, BET surface area 200 mVg, pore volume 0.51 cm /g, average pore diameter 9.4 nm). The sample was dried under vacuum and although the sample was not calcined between cobalt nitrate loading steps, the final sample was calcined at 400°C. Half was promoted with Pt by IWI of the tetraammineplatinum (II) nitrate salt and calcined at 350°C. 

Figure 3. Fourier transform of the Fourier filtered (M = 1.0-3.2 A ) data of the 20CoRe/y-Al2O3 catalyst (- = FT experiment, = FT theory). The data are fitted using a Co-O and a Co-Co shell.

Bi-Sr-Ca-Fe-CuOx, having a paramagnetic phase, exhibited catalytic activity in the dehydration of tert-BuOH to isobutylene, another ceramic superconductor Bi-Sr-Co-Fe-CuO having a diamagnetic phase, inhibited the reaction. The paramagnetic poly(aniline disulfide), when used as a modifier for LaHY Zeolite (20%)-Al2O3 ( %) catalysts for the cyclohexane isomerization at 350 °C, increased the selectivity for methylcyclopentane and methylcyclopen-tenes [194],... 

Figure 2. Micrographs showing catalyst accumulation in metallic substrates (Fecralloy). Left side 20%Co/Al2O3 on square (700 x 700 pm) microchannels. Right side ZSM-5 deposited on micromonoliths (222 cells/cm ) [30],...

The CO + NO reaction on various kinds of Pd catalysts was investigated by Rainer et al (112). Kinetics data for Pd/A Os and planar model Pcl/Al2O3/Ta(110) catalysts were compared with those for CO ) NO on Pd(lll), (100), and (110) surfaces. Figure 20 is a comparison of the Arrhenius plots measured at partial pressures of about 1 mbar in each reactant tor the model catalysts and at a CO pressure of 5.9 and a NO pressure of 6.8 mbar (in a helium carrier) for the Pd/A Os powder catalyst. 

Then the product gas is fed to a low-temperature reactor where a Cu/Zn-Al2O3 particulate WGS catalyst works at about 200°C. Outlet CO concentration is decreased to <0.5%, while the remaining CO, which can poison downstream ammonia or methanol synthesis catalysts, is removed by pressure swing adsorption (PSA) unit. This method exploits the adsorption capacity of different molecular sieves or active carbon, which selectively permit the crossover of hydrogen but not of the other compounds present in the effluents. This technology has been... 

The bimetallic catalyst was prepared as 5Co-15Ni on 80y-Al2O3 support via multiple impregnation. The support was pre-treated at 1073 K for 6 hours to ensure thermal stability of the alumina phase. It was then mixed with an aqueous solution of Co(N03)2 and stirred at 303 K for 3 hours. The slurry was left to dry overnight in an oven at 393 K. The dried solution was subsequently mixed with calculated amount of Ni(N03)2 solution. Each metal nitrate impregnation was carried out at a constant pH of 2. The final slurry was further dried at 393 K for 12 hours and calcined for 5 hours at a heating rate of 5 K min . The calcined solid was then crushed and sieved to 212-250 pm for further use. 

Of course other alumina films have been used for the preparation of model catalysts and some of them as in the case of Co on 6>-Al2O3/CoAl(100) [188] and Cr on Al2O3/NiAl(001) [189] show a certain template effect, but the resulting layers are in general not as nicely ordered as on Al302/Ni3Al(l 11). 

The effect of space velocity is demonstrated by the example of 10%Co-M (9.25-0.75)/Al2O3. With rising space velocity from 90 to 300 hr, increase in temperature was required from 167 to 195°C to keep the constant degree of carbon monoxide conversion at 53%. At that rate, ceresin yield decreased from 23 to 10% (Table 2). The same behaviour was observed with all the catalysts studied in this woik. 

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