Filtration, continuous procedure

Procedure 1 96 % ethanol was added to the culture medium (3 1), while continuously stirring. The precipitated polysaccharide was kept overnight at -4°C and then separated by filtration. It was washed with 70 % hydrochloric acid ethanol, then with 70 % ethanol to a neutral pH. In the end it was washed with 96 % ethanol and dried at 50°C (Sample 1). 

While the emphasis here has been on the reduction of the amount of waste sludges, it is also equally important to address the problem of regulating the effluents and emissions. In this context, special mention may be made of ammonia which must be carefully regulated. The procedure for processing ammonium fluoride or ammonium sulfate containing solutions begins with lime treatment. The filtrates are fed continuously into a column and stripped with live steam and upgraded. In this way it is possible (with improved equipment and carefully controlled operation) to attain ammonia contents of less than 50 ppm in the effluent. 

The objective of the present study is to develop a cross-flow filtration module operated under low transmembrane pressure drop that can result in high permeate flux, and also to demonstrate the efficient use of such a module to continuously separate wax from ultrafine iron catalyst particles from simulated FTS catalyst/ wax slurry products from an SBCR pilot plant unit. An important goal of this research was to monitor and record cross-flow flux measurements over a longterm time-on-stream (TOS) period (500+ h). Two types (active and passive) of permeate flux maintenance procedures were developed and tested during this study. Depending on the efficiency of different flux maintenance or filter media cleaning procedures employed over the long-term test to stabilize the flux over time, the most efficient procedure can be selected for further development and cost optimization. The effect of mono-olefins and aliphatic alcohols on permeate flux and on the efficiency of the filter membrane for catalyst/wax separation was also studied. 

In order to develop a continuous flux maintenance procedure, the present study examined the transmembrane flux values from the cross-flow filtration module with a filtration media area of 0.0198 m2 (0.213 ft2), a slurry density of approximately 0.69 g/cm3 at 200°C, 17 kg of simulated FT wax with a catalyst loading of 0.26 wt%, and a TMP between 0.68 and 1.72 bar (10-25 psig). The filtration process was run in a recycle mode, whereas clean permeate was added back to the slurry mixture, thus allowing the catalyst concentration to remain approximately constant over the course of the run (given minor adjustments for about 5 ml permeate and slurry samples collected throughout the test). 

The solid is suspended in 300 ml. of 5% sodium hydroxide at 15° (Note 5). The mixture is stirred for 30 minutes, and the solid is filtered by suction and washed with water until the filtrates are no longer alkaline. The procedure is repeated, but stirring is continued for 0.75-1.0 hour. After the solid has been filtered by suction, washed, and pressed as dry as possible, it is dried under reduced pressure over phosphorus pentoxide for 12-16 hours. 

Membrane absorbers are continuous chromatographic supports, which circumvent some of the above-mentioned problems of particulate stationary phases. They were originally derived from membrane (filtration) technology. The immobilization of interactive (ionic, hydrophobic, or biospecific) groups on the surface of microfiltration membranes was found to increase the selectivity of certain separation procedure. Ideally such activated membranes, or membrane adsorbers, allow the selective adsorption of certain substances and substance classes, which may subsequently be eluted by means of a stepwise change of the mobile phase (elution buffer). More complete information on the various types of modern membrane technology can be found in some recent reviews [e.g., 31-33]. 

General Procedure for the Preparation of Oligomers 4. BTDA (0.25 mol) was dissolved in NMP (20% solids) contained in a dry 100-mL, 3-necked flask equipped with a thermometer, a N2 inlet and a short-path distillation apparatus. After the appropriate amount of amine was added in a single portion the solution was stirred at room temperature for 2 h. The appropriate amount of APA was added, and the reaction mixture was stirred for an additional 2 h. The temperature of the flask was then Increased until distillation commenced. The oligomer concentration was maintained at approximately 20% by continually replacing the distillate with fresh NMP. The distillation-addition cycle was carried out for 2 h. The mixture was then poured into ethanol. The precipitate that formed was collected by filtration, washed several times with ethanol, and dried under reduced pressure. 

Typical procedure A solution of (dodecane thiol, = Me(CH2) , 1 mL, 4.17 nunol), trimethyl phosphite (591 pL, 5.01 mmol) and terf-amine (lutidine 681 pL, 5.84 nunol) or calcium carbonate (1.4 mol equiv based on the thiol) in CH2CI2 (20 mL) was cooled to -42°C in an MeCN-solid CO2 bath, and TeCl4 (0.8 equiv) was added. The mixture was stirred at the same temperature for 5-10 min and then, after removal of the bath, stirring was continued at room temperature (1.5-3 h). Precipitates were filtered off and the filtrate was washed with water and dried (MgS04). The solvent was removed under reduced pressure and the phos-phorothioate (1.24 g, 96% yield) were isolated by column chromatography on silica gel. 

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