Slurry, solvent-free

Innovation process Water-based low-solvent dipping coatings have been state-of-the-art for some time as primers. In the mid 1980s the development of water-based fillers and topcoats was advanced by VW. These have become estabhshed extensively in Germany. Solvent-free powder clear coatings have been used by DaimlerCluysler (as powder slurry suspended in water) and by BMW since 1997. 

Catalytic systems based on various metal oxides under MW-assisted, solvent-free, aerobic conditions were compared for benzyl alcohol oxidation (Table 18.6) [23]. The manganese oxides were prepared by solution-based or solid-state reaction procedures [24], while V2O5, CuO, Fe Og, C02O3, and NiO were obtained via sol-gel or precipitation methods [25]. The benzyl alcohol oxidation was performed in a glass reactor where the slurry of catalyst with alcohol was stirred under dioxygen pressure and MW irradiation (Scheme 18.10, Table 18.6). 

LPME proved to be an extremely simple, low cost, and virtually solvent-free sample-preparation technique, which provides a high degree of selectivity and enrichment by additionally eliminating the possibility of carryover between runs [219-225]. LPME overcomes the drawback of the droplet fall. An alternative LPME was performed in a hollow fiber of 2 cm, which is sealed and immersed in the sample to extract the analytes. With this approach, higher enrichment factors are obtained for penta- and hexachloro-benzene and can be used for slurry, real environmental, and biological samples [226]. 

The concentration of insoluble solid B in any mixture or slurry will be expressed as N mass B/mass (A + C), whether the solid is wet with liquid solution or not. Solute C compositions will be expressed as weight fractions on a B-free basis jc = wt fraction C in the effluent solution from a stage (B-free basis), andy wt fraction C in the solid or slurry (B-free basis). The value of y must include all solute C associated with the mixture, including that dissolved in adhering solution as well as undissolved or adsorbed solute. If the solid is dry, as it may be before leaching operations begin, N is the ratio of weights of insoluble to soluble substance, andy = l.O. For pure solvent A, N = 0,x —0. 

Suspension polymerization of VDE in water are batch processes in autoclaves designed to limit scale formation (91). Most systems operate from 30 to 100°C and are initiated with monomer-soluble organic free-radical initiators such as diisopropyl peroxydicarbonate (92—96), tert-huty peroxypivalate (97), or / fZ-amyl peroxypivalate (98). Usually water-soluble polymers, eg, cellulose derivatives or poly(vinyl alcohol), are used as suspending agents to reduce coalescence of polymer particles. Organic solvents that may act as a reaction accelerator or chain-transfer agent are often employed. The reactor product is a slurry of suspended polymer particles, usually spheres of 30—100 pm in diameter they are separated from the water phase thoroughly washed and dried. Size and internal stmcture of beads, ie, porosity, and dispersant residues affect how the resin performs in appHcations. 

There are two commercial solvent crystaUi2ation processes. The Emersol Process, patented in 1942 by Emery Industries, uses methanol as solvent and the Armour-Texaco Process, patented in 1948, uses acetone as solvent. The fatty acids to be separated are dissolved in the solvent and cooled, usually in a double-pipe chiller. Internal scrapers rotating at low rpm remove the crystals from the chilled surface. The slurry is then separated by means of a rotary vacuum filter. The filter cake is sprayed with cold solvent to remove free Hquid acids, and the solvents are removed by flash evaporation and steam stripping and recovered for reuse (10). 

Direct Liquefaction Kinetics Hydrogenation of coal in a slurry is a complex process, the mechanism of which is not fully understood. It is generaly believed that coal first decomposes in the solvent to form free raclicals which are then stabilized by extraction of hydrogen from hydroaromatic solvent molecules, such as tetralin. If the solvent does not possess sufficient hydrogen transfer capability, the free radicals can recombine (undergo retrograde reactions) to form heavy, nonliquid molecules. A greatly simplified model of the liquefaction process is shown below. 

This procedure can be varied widely with respect to temperature, pressure, and solvent. Highest yields were obtained in isopropyl alcohol and with low pressures. For larger runs less catalyst and longer times may be used. A 20-25% slurry of the less soluble a-acylamidocinnamics may be used without detriment. Care must be taken to purge these slurries thoroughly since oxygen destroys the catalyst. The solvent must be free of peroxides. 

Three processes are used commercially to make linear polyethylene-solution, slurry, and gas phase. All are called low-pressure processes (< 50 atm) to distinguish them from the free radical or high-pressure process that makes highly branched polyethylene. In the solution mode a hydrocarbon solvent at 125-170°C dissolves the polymer as it forms. The reaction usually slows as the solution becomes viscous because it becomes difficult to stir ethylene into the liquid phase. In contrast, The slurry process uses a poor solvent and low temperature (60-110°C) to prevent dissolving or even swelling of the polymer. Each catalyst particle creates a polymer particle several thousand times larger than itself. There is no viscosity limitation in the slurry method the diluent serves to transfer heat and to keep the catalyst in contact with ethylene and other reactants. Finally, the gas-phase process is much like the slurry method in that polymer particles are formed at similar temperatures. A bed of catalyst/polymer is fluidized by circulating ethylene, which also serves as a coolant. 

Citronellol 1 (3.2 mmol, 0.500 g), Se02 (1.6 mmol, 0.176 g) and t-BuOOH (70%, 4.48 mmol, 0.576 g) were dissolved in a small amount of dichloro-methane. Silica (1 g) was then added to form a slurry and excess solvent was evaporated off to obtain free flowing silica which was then exposed to micro-wave irradiation at power level 9 (640 W) for 10 min. Diethyl ether was then added and the mixture filtered. The filtrate was then washed (10% KOH, brine) and then dried (anhydrous Na2S04). The solvent was evaporated to furnish the pure product in 83% yield. 

As a rough guide the amount of adsorbent used should normally be 25-50 times the weight of the material to be separated. A slurry of the adsorbent in the solvent (approximately 1 10) is poured through a funnel into a clean dry column clamped vertically, in a position away from draughts or warm air currents from a radiator or electric oven, etc. The adsorbent will settle evenly and free of air bubbles if assisted by gentle tapping of the tube with a wooden rod. For... 

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