Support spray drying

Figure 12. SEM micrographs of a metallocene/MAO-supported spray-dried silica gel after a polymerization time of 5 and 22 min. The enlarged polymer morphology is shown in a magnification on the right side.

For example, amorphous clarithromycin was prepared by grind and spray-drying processes, and XRPD was used to follow changes in crystallinity upon exposure to elevated temperature and relative humidity [59]. Exposure of either substance to a 40°C/82% RH environment for seven days led to the formation of the crystalline form, but the spray-dried material yielded more crystalline product than did the ground material. This finding, when supported with thermal analysis studies, led to the conclusion that the amorphous substances produced by the different processing methods were not equivalent. 

Thin layer chromatography was carried out on 20x20cm glass plates coated 0.25mm thick with a suitable support and dried overnight. Silica gel G, silica gel H and cellulose were examined as the solid phases for chromatography of methanearsonate, arsenite and arsenate. Several sprays for the visualization of the arsenicals on plates were tested. Three of the more successful reagents and the colour produced with final product are shown in Table 13.2. 

A significant recent advance has been the development of microfiltration and ultrafiltration membranes composed of inorganic oxide materials. These are presently produced by two main techniques (a) deposition of colloidal metal oxide on to a supporting material such as carbon, and (b) as purely ceramic materials by high temperature sintering of spray-dried oxide microspheres. Other innovative production techniques lead to the... 

While there is no direct data to support this statement, we have found vastly different shelf-lives for products which contain essentially similiar trace metal levels, surface oils, and absolute densities. We can find no other explanation for the differences in shelf-life other than matrix porosity. This area needs to be further studied in order to confirm this hypothesis and then take advantage of it to improve the shelf-life of spray dried flavorings. 

The extractable surface oil results of the spray dried powders are listed in Table IV. The extractable surface oil decreased as the emulsion size decreased. Based on previous knowledge, one would anticipate that less surface oil would result in a better shelf-life. The results of this study do not support that theory especially when you consider the third set of samples in which the coarse emulsion had the greatest amount of extractable surface oil yet also had the longest shelf-life. 

Suspensions of these spherical particles are used for spray drying to produce large agglomerates which are used as packings for various separation techniques such as High Performance Liquid Chromatography (HPLC) or Supercritical Fluid Chromatography (SFC). They also serve as supports for catalysts. 

Polymer-supported tetraphenylphosphonium bromide is a recyclable catalyst for halogen-exchange reactions. The reaction of 1 equivalent of chloro-2,4-dimtrobenzene with 1 5 equivalents of spray-dried potassium fluoride and 0.1 equivalent of this catalyst in acetonitrile at 80 °C for 12 h gives 2,4-dmitro-fluorobenzene in 98% yield An 11% yield is obtained without the catalyst [3 /]. 

Foams can also be involved in the drying of food products. A wide variety of foods, including fruits and vegetables, can be foamed and then spread out in thin layers on a support for foam-mat drying [633,845], Other foods, such as milk, cream, and cheese can be dried by foaming them, then injecting the foam into a spray-drier. This process is called foam spray drying [633],... 

The chapters in Characterization and Catalyst Development An Interactive Approach, assembled from both academic and industrial contributors, give a unique perspective on catalyst development Some chapters thoroughly characterize the catalyst prior to plant evaluation, whereas others utilize characterization to explain performance variances. Some new types of catalysts incorporated into this volume include the preparation of novel catalyst supports based on alumina and hydrous titanates. Attrition-resistant catalysts and ultrafine ceramics were prepared by modified spray-drying methods. New catalyst compositions based on vanadium-containing anionic clays were proposed for oxidation. A recently commercialized catalyst based on magnesium spinel was proposed for use in the abatement of sulfur oxide pollutants in fluid... 

Vanadyl phosphates (VPO) and multiple component molybdate (MCM) are good examples of catalysts, and alpha alumina, amorphous silica and alumino-silicates are good examples of catalyst supports that can be fabricated in the form of 45 to 150 im diameter spray dried porous spheres with attrition resistance improved by a relatively thin peripheral layer rich in amorphous silica, amorphous alumina, or phosphorus oxides. The hard phase component or precursor is selected in each case so that it will not interfere with the catalytic performance of the catalyst. 

Catalysts are manufactured by various methods (such as precipitation, extrusion and spray drying) in the form of cylinders, rings, multi-lobed extru-dates and other shapes. They range in size from a few millimetres to several centimetres small spheres are used in fluidized bed reactors. Active phases can be dispersed on the pre-shaped support by several methods such as by impregnation of a solution of the active components. Alternatively the catalysts can be made by the extrusion of mixtures of solid components the support, active phase, and binder. For some reactions that are diffusion limited, the catalyt-ically active species are not uniformly distributed instead they are deposited on the outer shell of the catalyst particle (egg-shell catalysts), since those inside the particle cannot be involved in the reaction. 

Table 12-43 shows some of the operational parameters associated with specific and typical products. For each of these product groups and any other product, successful drying depends on the proper selection of a plant concept and proper selection of operational parameters, in particular inlet and outlet temperatures and the atomization method. These parameters are traditionally established through pilot-scale test work, and leading suppliers on the spray drying market often have extensive test stations to support their sales efforts. 

Particulate titanium dioxide (Degussa P25 (trademark)) support was calcined at 650 C for 16 hours, spray dried and classified to 75-150 micron. The support had a rutile content of 80% and a surface area of 27m /g. 

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