Phenolic monolithics

Biomass phenolic and furan resins polyimides glassy carbons, binder and matrix carbons" graphite films and monoliths activated carbons ... 

Zhang developed a monolithic poly(styrene-co-divinylbenzene) CEC column in which the EOF is supported by carboxyl groups of polymerized methacrylic acid [ 133]. Using benzene as a probe, column efficiencies of 90,000 -150,000 were observed within a flow velocity range of l-10cm/min (0.2-1.7 mm/s). Different families of compounds such as phenols, anilines, chlorobenzenes, phenylendi-amines, and alkylbenzenes were well separated typically in less than 5 min using 20 cm long columns. 

In contrast, monolithic materials are easily amenable to any format. This has been demonstrated by using short monolithic rods prepared by copolymerization of divinylbenzene and 2-hydroxyethyl methacrylate in the presence of specifically selected porogens [93]. Table 2 compares recoveries of substituted phenols from both the copolymer and poly(divinylbenzene) cartridges and clearly confirms the positive effect of the polar comonomer. 

Table 2. Recovery of phenols from porous poly(divinylbenzene) (DVB) and poly(2-hydrox-ylethyl methacrylate-co-divinylbenzene) (HEMA-DVB) monoliths [93]...

The newly developed monolithic-type column has also found application in the HPLC determination of wine phenolics. Red wine samples were filtered and injected into the column without any other pretreatment. Separations were performed in an ODS monolithic column (100 X 4.6mm i.d.) at 30 1°C. Solvent A was methanol-double-distilled water (2.5 97.5, v/v) at pH 3 with H3P04, and solvent B consisted of methanol-double-distilled water (50 50, v/v) at pH 3 with H3P04. Conditions of gradient elution were as follows 0-lQmin 100... 

M. Castellari, E. Sartini, A. Fabiani, G. Arfelli and A.Amati, Analysis of wine phenolics by high-performance liquid chromatography using a monolithic type column. J. Chromatogr.A 973 (2002) 221-227. 

Hydrophobic monolithic methacrylate capillary columns have been introduced by copolymerization of butyl methacrylate and EDMA as cross-linking agent. The polymerization, however, was not thermally or photochemically but chemically initiated ammonium peroxodisulfate [154]. The resulting monolithic columns were applied to RP separation of small analytes like uracil, phenol, or alkylbenzenes. Reasonable results have been obtained under isocratic conditions, delivering typical values for theoretical plate height ranging between 40 and 50 pm. 

Masumy and Tasomy 28) found that for regularly shaped resol PhFO microspheres it was best to use dilute aqueous solutions with viscosities of 15-50 Pa - sec, water contents of up to 50%, and free phenol contents of 6-9%. The resultant spheres included unexpanded monolithic particles, but these could be eliminated by using a chemical blowing agent such as dinitrosopentamethylenetetramine (DNPMTA) or azodiisobutyronitrile, or a surfactant (0.25 mass %). 

Syntactic materials based on polybenzimidazole and glass or phenolic microspheres (y = 40-500 kg/m3) have been described in the literature109 nl). They have been used as ablation materials that consist of two layers, one of which is a monolithic carbon plastic. Carbon fiber was added to the polyimide binder to improve the mechanical properties of the material. 

Figure 7.14 Chromatogram of (1) uracil, (2) phenol, and (3) benzyl alcohol on C3 porous polymer monolith coated chip [33].

Fig. 6.7. Separation of a mixture of polar and nonpolar aromatic compounds by CEC. Conditions capillary 27 cm x 75 pm i.d.For details on monolith column see Fig. 6.6 mobile phase 1 3 methanol/acetonitrile, 30kV, 25°C, injection 10 kV for 3s UV- detection at 200 nm. (Reprinted with permission of authors from [32]). Peaks pyrene 1, phenanthrene 2, anthracene 3, phenol 4, hydroquinone monomethylether 5, 2-naphtol 6, catechol 7, hydroquinone 8, resorcinol 9.

The most widely applied method is dipcoating (81). The monoliths are dipped in a precursor solution and subsequently dried, carbonized, and (if necessary) activated. Many different carbon precursors have been used, such as saccharides (56,82,83), polyfurfuryl alcohol (84), phenolic resins, and furanic resins (85,86). 

Such a marked variation of dielectric properties does not occur in sorbed (or desorbed) samples of monolithic phenol oligomers. Therefore, for monolithic plastics, sorption of air moisture is a secondary phenomenon, in relation to dielectric properties, whilst for plastic foams it is a primary one. 

Kim et al. [40] made an attempt to oxidize phenol in water solutions using a monolith reactor. Alumina-washcoated cordierite monoliths (62 celLs/cm ) impregnated with copper... 

Crynes et al. [41] continued the study of Kim et al. [40]. The novel monolithic froth reactor, with a monolithic section 0.42 m long and 5 cm in diameter, was used. Cordierite monoliths with a cell density of 62 cells/cm were stacked, one on top of another, to provide a structure 0.33 m long. The monoliths, washcoated with 7-alumina and impregnated with CuO, were tested at 383-423 K and 0.48-1.65 MPa. The liquid flow rate was varied from 0.4 to 3.5 cm sec", and the gas flow rate ranged from 15.8 to 50 cm sec". Phenol in a concentration of 5000 ppm was typically oxidized with air. The reaction rate versus the liquid flow rate showed a distinct maximum of approximately 2 mol g"t sec" at about 1.7 cm sec", while the dependence of the reaction rate on the gas flow rate was rather weak, with a tendency to decrease as the flow rate increased. 

S. Kim, Y.T. Shah, R.L. Cerro, and M.A. Abraham, Aqueous phase oxidation of phenol in a monolithic reactor. Proceedings of AIChE Annual Meeting, Miami Beach, Dec. 1992. 

Crynes et al. [35] have developed what they call a monolith froth reactor. They introduce the gas through a porous glass frit just below the monolith, forming a froth that is fed into the reactor. Oxidation of phenol was studied in a 5-cm-wide and 33-cm-long... 

This coefficient is the stun of the contributions of pore and surface diffusion. The pore diffusivity can be derived from known correlations (see Chapter 5, subsection 5.2.6, e.g., those of Mackie and Meares [89], Satterfield [90], or Brenner and Gaydos [91]). Therefore, this procedme gives the surface diffusion coefficient. It has been used by Miyabe to derive estimates of the surface diffusion coefficients for alkyl benzenes and alkyl phenols on columns packed with Cjg silica [86,92,93] and on monolithic silica columns [93,94]. They were used by Hong et al. to measure the surface diffusion of rubrene on Symmetry Cig [95]. 

Figure 18.10 Two-dimensional separation of a mixture of phenolic and flavone antioxidants [after P. Jandera, University of Pardubice, Czech Republic see also F. Cacciola et a ., J. Chromatogr. A, 1149, 73 (2007)]. Conditions in the first dimension column, 15 cm x 4.6 mm i.d. stationary phase, PEG silica 5 pm mobile phase, 0.3 ml min" water-acetonitrile, gradient 1-55% acetonitrile in 200 min. Interface ten-port valve with two storage columns X-Terra Cl8 2.5 pm, 3 cm x 4.6 mm i.d. which concentrate the eluate. Cycle time, 5 min. Conditions in the second dimension column, 10 cm x 4.6 mm i.d. stationary phase, SpeedROD RP-18e (monolith) mobile phase, 2 ml min" water-acetonitrile, gradient 1-40% acetonitrile in 5min. Diode array detector with 254 + 260 + 280 + 320 nm. Of the numerous identified analytes only the most important ones are specified in the figure.

Phenolic compounds Waters, soils Monolithic minicolumn with polys tyrene-divinylbenzene UV-Vis <1 ng mL 1 Multi-syringe flow system coupled to HPLC minicolumn before the sampling loop [507]... 

H.M. Oliveira, M.A. Segundo, J.L.F.C. Lima, V. Cerda, Multisyringe flow injection system for solid-phase extraction coupled to liquid chromatography using monolithic column for screening of phenolic pollutants, Talanta 77 (2009) 1466. 

Integral-type monolithic structures are produced by extrusion. The extrusion mixture generally includes the following components a type of carbon or carbon precursor such as activated carbon particles, graphite, carbon fibres, etc., a blinder such as phenol resin, hydroxylcellidose, coal tar pitch etc. and extrusion aids/plasticizers such as water or polymers. Typical preparation steps are mixing, extrusion, diying/solidification and carbonization. 

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