Pellets starting material

An intimate mixture of the starting materials is pelleted and placed in a crucible and heated to 1500-2000°C under vacuum or in a vented furnace, i. Borothermic Reduction of a Metal Oxide. 

The resulting styrene/maleic acid copolymer is soluble in hot water, in contrast to the starting material the aqueous solution of the product gives a distinctly acid reaction. The disappearance of the anhydride moiety can be verified by IR or C-NMR spectroscopic methods.The IR spectra of polymers should be recorded from a film of the sample prepared on a KBr pellet (freshly made from KBr powder). For this, a drop of a solution of the polymer in a low-boiling solvent (e.g.,THF, methylene chloride) is placed on the pellet.The residual solvent can often be removed directly in the IR beam.The resulting spectra are characterized by their sharp bands. 

The effects of non-uniform distribution of the catalytic material within the support in the performance of catalyst pellets started receiving attention in the late 60 s (cf 1-4). These, as well as later studies, both theoretical and experimental, demonstrated that non-uniformly distributed catalysts can offer superior conversion, selectivity, durability, and thermal sensitivity characteristics over those wherein the activity is uniform. Work in this area has been reviewed by Gavriilidis et al. (5). Recently, Wu et al. (6) showed that for any catalyst performance index (i.e. conversion, selectivity or yield) and for the most general case of an arbitrary number of reactions, following arbitrary kinetics, occurring in a non-isothermal pellet, with finite external mass and heat transfer resistances, the optimal catalyst distribution remains a Dirac-delta function. 

Different possible paths of glauconitization are Indicated in Figure 17. These paths indicate the variation in bulk composition of the pellet, as a function of K-Fe-Al variables. Depending upon the mineral (and chemical) composition of the starting material, different assemblages will be found in the pellets. 

LaNiSb was found to crystallize with the ZrBeSi type with lattice parameters of a = 0.4404, c = 0.8403 (Hartjes and Jeitschko, 1995 X-ray powder diffraction). Cold-pressed pellets of the ideal composition were arc melted in an atmosphere of argon and annealed at 1120 K for one week. Purities of starting materials were better than 99.9%. 

To a solution of 27.3 g (1 mole) of 3-amino-4-carbomethoxy-2,5-dihydro-2-thiophenevaleric acid methyl ester in 250 ml dry methanol was added 4.0 g (0.1 mole) of sodium hydroxide pellets. The reaction mixture was refluxed 4.0 hrs, cooled and concentrated to a volume of 50 ml. The residue was taken up in 80 ml dichloromethane and transfered to a separatory funnel. After the addition of 150 ml of 10% by weight aqueous sodium bicarbonate solution, the aqueous layer was extracted twice with 50 ml portions of dichloromethane. The organic phases were combined, dried over anhydrous sodium sulfate, and evaporated to yield 6.4 g (0.0234 mole) of recovered starting material. The aqueous phase was adjusted to pH 1 with 6 N hydrochloric acid and extracted three times with 75 ml portions of dichloromethane. The organic phases were pooled, dried over anhydrous sodium sulfate, and evaporated to yield 18.3 g (0.071 mole, 71%) of 3-amino-4-carbomethoxy-2,5-dihydro-2-thiophenevaleric acid as a tan solid, upon trituration with pet. ether. 

The p-chlorophenoxyisobutyric acid used as starting material may be obtained as follows. A mixture of 200 parts of p-chlorophenol, 1,000 parts of acetone and 360 parts of sodium hydroxide pellets is heated under reflux and 240 parts of chloroform are gradually added at such a rate that the mixture continues to reflux without further application of heat. 

Procedure A To 5-nitrosalicylic acid potassium salt (55 g, 246 mmol) dissolved in water (200 mL) was added potassium hydroxide pellets to reach pH 11.5. To this solution 2 g of Raney nickel were added. The mixture was heated-up to reflux and hydrazine hydrate (40 mL, 80% in water, 64 mmol) was added dropwise during 3-4 hrs. The reflux was maintened until HPLC showed the disappearance of the starting material and the complete reduction of 5-nitrosalicylic acid (3-4 hrs). The hot mixture was filtered under nitrogen and the solution was collected. The solution was cooled to 40°C and the pH was adjusted to 2.3 by addition of 35% HCI aqueous solution. The precipitation of 5-aminosalicylic acid occurred. The solution was cooled at 0°C, and after standing at this temperature for 2 hr, the precipitate was filtered, washed with water, and dried at 60-70°C. 5-Aminosalicylic acid was obtained in 89% yield. 

For commercial processes, formed supports are more useful. Compared with other supports, fumed oxide supports showed new catalytic effects [41]. Some intensively investigated applications for these supports are abstracted in the following. SiC>2 pellets have been successfully introduced in a new generation of precious metal supports in vinylacetate monomer production [42]. This resulted in better selcctivities and an up to 50% higher space-time yield compared with supports based on natural alumo-silicates. In alkene hydration fumed silica pellets serve as a support for phosphoric acid. In this case, an increased catalyst lifetime and a higher space-time yield were observed [43]. Pyrogenic TiC>2 powder can be used as a starting material for the manufacture of monolithic catalysts [44] for the selective reduction of NOv with ammonia. 

Catalysts are formed by a variety of methods depending on the rheology of the materials. The products of different processes have been compared in general terms in Table 3.2. The choice of the method depends on the size, shape and density of the catalyst particle required, on the strength required and on the properties of the starting material. The three main processes used in catalyst manufacture to make conveniently sized particles from powders are pelletizing, extrusion and granulation. 

BaLnjMnjOy (Ln= Nd, Sm and Eu) were prepared from the conventional solid state reaction method. The starting materials, BaCOs, LnjOj and MnjOj, were mixed with an appropriate molar ratio and pressed into pellets followed by heating finally at 1623 K in purified Ar. 

General All starting materials were of analytical grade. Elemental analyses (C, H, N) were performed on a Perkin-Elmer 240 analyser. IR spectra were recorded on a Shimadzu IR-408 spectrometer as KBr pellets. Variable-temperature magnetic susceptibilities were measured on a Quantum Design MPMS-7 SQUID magnetometer. Diamagnetic corrections were made with Pascal s constants for all the constituent atoms. 

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