Slurry packing apparatus

Figure 4.9 Up-fill slurry packing apparatus. (Reproduced with perslssion from Micromeritics Instruments Coirp.)...

Columns consisting of particles of less than 30-50 jum in diameter are prepared most efAciently by slurry packing. Balanced-density slurry packing [11,12] is the most successful of such methods. In this technique, a supporting liquid is used which has the same density as that of the particles. This eliminates sedimentation problems. A typical balanced-density slurry-packing apparatus is shown in Fig.3.42. For the preparation of a... 

Fig. 3.42. Balanced-density slurry-packing apparatus. A, Whitey ball valve B, stainless-steel tubing (0.25 in. O.D. X 0.094 in. I.D.), the lower portion of which is machined to allow it to fit through the body of the Swagelok tee C, small hole in the side of B to allow access of eluting solvent ...

HPLC columns are much more difficult to pack correctly than GLC columns, because they must be packed under high pressure. Ideally, this is at the pressure limit of the chromatograph s pump, usually 6000 p.s.i.g. Because of the high cost of HPLC columns, some investigators prefer to pack their own. If a high pressure compressed air line (100 -150 p.s.i.g.) is available, then a slurry-packing apparatus like that shown in Figure 19-33 can be used. It has an "air amplification pump" and can be used to repack a column. 

Figure 19-33. A slurry packing apparatus. (Courtesy - Alltech Associates Inc., Deerfield, IL)...

Slurry packing techniques are required for the preparation of efficient columns with rigid particles of less than 20 micrometers in diameter. The same general packing apparatus. Figure 4.8, can be used to pack columns by the balanced-density slurry, liquid slurry, or the viscous slurry techniques. Down-fill slurry packing is the method of choice for small bore columns and packed capillary columns. 

A number of commercial column packing apparatuses are available. One type, the ascending type, is a stirred can that pumps slurry upward into the pressure line and then down into the column. The descending type of packer is simply a slurry reservoir that attaches in place of the inlet end-cap and frit and is equipped with a pump connection at the top (Fig. 5.3). Manufacturers use 20,000-psi pumps to drive slurry into the column, but most laboratory packing apparatuses rely on pumps that reach a maximum of only 6,000-10,000psi. The pumps are run fully open until the pressure stabilizes. 

Reversed-phase silica gel column Place a cotton wool plug at the bottom of a glass chromatography column. Pack 5 g of reversed-phase silica gel slurried with a solvent mixture of n-hexane-benzene-methanol (80 20 0.4, v/v/v) into the glass column. Place an anhydrous sodium sulfate layer about 1 -cm thick above and below the silica gel bed Bell jar-type filtering apparatus Buchner funnel, 11-cm i.d. 

Fig. 9. Apparatus for sluijy packing of columns. After the properly fittul column tube is attached to the bottom of the reservoir, both are filled up with the slurry ofthe micropartic-ulate stationary phase. Thereafter a displacement liquid is pumped into the reservoir by the constant pressure pump, e.g., Haskel Model DST>I00, which is driven by preuurized air. Upon displacement, the slurry from the reservoir is filtered over the porous etal frit at the bottom of the column tubing which becomes densely packed with the partic s. By intermit-tently operating the liquid shut-off valve between the pump and the reservoirpressure waves can te generated in order to flirther compact the column packing. Reprinted from Bakalyar et at. U05) with permission from Spectra-Physics.

Apparatus Pack a 2.5- x 45-cm glass column with approximately 20 g of cellulose (Whatman CF-11 grade, or equivalent) that has been slurried in the eluant and from which the fines have been removed by decantation. Equilibrate the column thoroughly with the eluant, 35% ammonium sulfate. 

The activity tests of liquid-phase oxidation of aqueous phenol solution were conducted in a semibatch slurry reactor at operating conditions given in the caption of Figure 1. The experimental apparatus, the procedure of these measurements and the analysis of the reaction samples are described in detail in a preceding paper [6]. Additional kinetic and mechanistic investigations were carried out in an isothermal, differentially operated "liquid-saturated" fixed-bed reactor [8, 9] which was packed with a pretreated EX-1144.3 catalyst (Sfld-Chemie... 

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