Aluminum phosphate catalyst

Direct ammonolysis involving dehydratioa catalysts is geaerahy ma at higher temperatures (300—500°C) and at about the same pressure as reductive ammonolysis. Many catalysts are active, including aluminas, siUca, titanium dioxide [13463-67-7], and aluminum phosphate [7784-30-7] (41—43). Yields are acceptable (>80%), and coking and nitrile formation are negligible. However, Htfle control is possible over the composition of the mixture of primary and secondary amines that can be obtained. 

The iron aluminum phosphate catalyst used in this study was prepared by a sol-gel... 

Walker A process for partially oxidizing natural gas or LPG, forming a mixture of methanol, formaldehyde, and acetaldehyde. Air is the oxidant and aluminum phosphate the catalyst. Invented by J. C. Walker in the 1920s and operated by the Cities Service Corporation, OK, in the 1950s. 

Title Aluminum Phosphate-Supported Group VI Metal Amide Catalysts for Oligomerization of Ethylene... 

Zeolites, which are aluminosilicates that can be regarded as being derived from AI2O3 and SiC>2, function as acidic catalysts in much the same way (Section 7.3). In addition, they catalyze isomerization, cracking, alkylation, and other organic reactions. A structurally related class of micro-porous materials based on aluminum phosphate (AIPO4) has also been developed (Section 7.7) like zeolites, they have cavities and channels at the molecular level and can function as shape-selective catalysts. 

Silica and aluminum phosphate have much in common. They are isoelec-tronic and isostructural, the phase diagrams being nearly identical even down to the transition temperatures. Therefore, aluminum phosphate can replace silica as a support to form an active polymerization catalyst (79,80). However, their catalytic properties are quite different, because on the surface the two supports exhibit quite different chemistries. Hydroxyl groups on A1P04 are more varied (P—OH and A1—OH) and more acidic, and of course the P=0 species has no equivalent on silica. The presence of this third species seems to reduce the hydroxyl population, as can be seen in Fig. 21, so that Cr/AP04 is somewhat more active than Cr/silica at the low calcining temperatures, and it is considerably more active than Cr/alumina. 

Methanol plus aluminum phosphate catalyst yields monomethylamine (CH3NH2), dimethylamine [(CH3)2NH], and trimethylamine [(CH3)3N]... 

If catalysts are prepared by coprecipitation, the composition of the solutions determine the composition of the final product. Often the composition of the precipitate will reflect the solution concentrations, as was shown for CuO/ZnO catalysts for methanol synthesis [18], but this is not necessarily the case. For al-minum phosphates it was found that at low P A1 ratios the precipitate composition is identical to the solution composition, but if the P A1 ratio in the solution comes close to and exceeds unity, the precipitate composition asymptotically approaches a P A1 ratio of 1 [19]. Deviations from solution composition in coprecipitation processes will generally occur if solubilities of the different compounds differ strongly and precipitation is not complete or, if in addition to stoichiometric compounds, only one component forms an insoluble precipitate this the case for the aluminum phosphate. 

Figure 10.13. solid-state NMR chemical shift data from the same taxi-cab aged catalyst as shown in Fig. 10.12. In this case, the peak on the left near 0 ppm corresponds to Zn3(P04)2 as well as mixed Zn, Ca, and Mg phosphates, while the peak on the right (-30 ppm) corresponds to aluminum phosphate. [30]...

The neutral molecular sieve, aluminum phosphate (ALPO, Chapter 10) can also serve as a shape selective support for metal catalysts. These catalysts are normally prepared by the incipient wetness process followed by appropriate drying and reduction procedures. Fig. 13.19 illustrates the selectivity observed using a Ni/ALPO catalyst to hydrogenate a mixture of styrene and a methyl styrene (Eqn. 13.13). The rates of hydrogenation of cyclic alkenes over a Rh/ALPO catalyst decreased in the order cyclopentene cyclohexene > cycloheptene > cyclooctene but no selectivity was observed in a competitive hydrogenation of a mixture of cyclohexene and cyclooctene. 75... 

The alkylation of toluene with methtmol at 400°C over H-ZSM-5 gave, at 36% conversion, a 69% selectivity for xylene formation, of which 27% was the para isomer. 2 Aluminum phosphate based molecular sieve catalysts such as CoAPO gave a lower conversion but higher selectivities for p-xylene formation. 2 Metallosilicates such as As-silicate having a ZSM-5 structure produced an 82% selectivity for p-xylene at 21% conversion. 

A series of CoMo/Alumina-Aluminum Phosphate catalysts with various pore diameters was prepared. These catalysts have a narrow pore size distribution and, therefore, are suitable for studying the effect of pore structure on the deactivation of reaction. Hydrodesulfurization of res id oils over these catalysts was carried out in a trickle bed reactor- The results show that the deactivation of reaction can be masked by pore diffusion in catalyst particle leading to erro neous measurements of deactivation rate constants from experimental data. A theoretical model is developed to calculate the intrinsic rate constant of major reaction. A method developed by Nojcik (1986) was then used to determine the intrinsic deactivation rate constant and deactivation effectiveness factor- The results indicate that the deactivation effectiveness factor is decreased with decreasing pore diameter of the catalyst, indicating that the pore diffusion plays a dominant role in deactivation of catalyst. 

Cabello, J. A., Campelo, J. M., Garcia, A., Luna, D., Marinas, J. M. Knoevenagei condensation in the heterogeneous phase using aluminum phosphate-aluminum oxide as a new catalyst. J. Org. Chem. 1984,49, 5195-5197. 

Figure 10.12. AI solid-state NMR chemical shift data from a fresh Pd-only catalyst and from inlet, middle, and outlet sections of a high-mileage taxi-cab aged catalyst of the same formulation. Note the strong feature at 40 ppm in the vehicle-aged catalyst corresponding to hydrated aluminum phosphate. The broad features near 5 and 60 ppm are associated with octahedrally and tetrahedrally coordinated aluminum cations in the alumina washcoat. [30]...

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