Pellets, preparation stages

The most frequently used methods to produce catalysts are precipitation and impregnation. In both processes the catalyst precursors are usu ly converted to oxides by heating and the powders converted to solid granules or pellets. Catalysts often contain promoters that are added during the preparation stages. If... 

Stage 4 Preparation of 1-l2-Phenyi-2-Methoxyl -Ethyi-4-[3-Phenyl-3-Hydroxypropyl] -Piperazine Dihydrochioride - In a double-neck flask equipped with a thermometer and a mechanical stirrer, there is placed in suspension in 800 ml of methanol, 233 grams of 1-[2-phenyl-2-methoxy]-ethyl-4-[2-benzoyl-ethyl]-piperazine dihydrochioride (0.55 mol). It is cooled to approximately 5°C, and 46 grams of NaOH pellets dissolved in 80 ml of HjO are added. When the temperature is about 5°C, one addition of 29,2 grams of sodium borohydride in 40 ml HjO is made. The ice-bath is then removed and stirring continued at ambient temperature for 6 hours. 

Diazomethane was prepared by the method of Moore and Reed,3 using 10% extra 2-(2-ethoxyethoxy)ethanol and an extra 100 ml. of water over that recommended to prevent stirring difficulties in the later stages of the distillation. The ethereal diazomethane solution was dried at 0° over KOH pellets, and the concentration was determined by reaction of an aliquot with henzoic acid and determining the resulting methyl benzoate by vapor phase chromatography. 

The GPPS and HIPS reactor sections each contain several polymerization reactors in series, two-stage devolatilization and a pelletizing line. The devolatilization equipment is designed to deliver polystyrene product with a concentration of residual total volatile material (TVM) of less than 100 wt-ppm. Common equipment includes sections for feed preparation, SM recovery, water removal and bulk-resin handling. 

Matrix minitablets based on starch/microcrystalline wax mixtures were prepared by melt granulation in a hot-stage screw extruder, followed by milling and compression.f This technique was preferred over the production of pellets. 

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