Vapour treatment

Eormaldehyde vapour treatment has been applied to improve the dimensional stability of medium-density fibreboard (MDF) (Minato elal, 1992) and albizzia waferboard (Yusuf elal, 1995c). 

Present results indicate a regeneration of Bransted sites by in situ water vapour treatment in the IR cell. Reversible transition of non-tetrahedral into tetrahedral Al is also observed with other kinds of hydrothermal treatment. After stirring of calcined MCM-41 in aqueous ammonium exchange solution at 60 to 80°C, the intensity of the BS band at 1450 cm 1 increases distinctly as compared with the ammonia loaded calcined sample. 

This approach has been used extensively for amino acid analysis using low-pressure ion-exchange chromatography and post-column ninhydrin reaction. Spraying, dipping and vapour-treatment techniques are well known as post-separation reactions in TLC, but these are considered only briefly since the majority of them are not quantitative. While the problems of pre-separation techniques are quite similar for TLC and HPLC, they differ considerably for post-separation reactions. 

The selective synthesis of propene has been reported by Fraenkel and Gates [139] using zeolite-entrapped cobalt clusters. The catalysts were prepared by impregnating commercial 5 A zeolites with CoClj solution and subsequent Cd-vapour treatment at 450-500 0. Coo-CdA zeolites gave 90-100 molSJ propene. whereas Co A zeolite and Co -CdY zeolite gave only traces of propene, but mainly methane. The unusual selectivity for propene was claimed to be unchanged, even after 17 hours on stream. 

Demanding process, including moisture control, ammonia vapour treatment and oxidation Extra washing after curing including drying costs... 

The stabilisation of the zeolites using heat treatment under steam (vapour treatment) causes migration of aluminium out of the lattice. The result is the formation of an amorphous compound that can be detected by XRD in the form of a poorly defined scattering back-... 

Figure 10.26 SAXS intensity curves for a zeolite as-synthesised and after vapour treatment.

To prove if an enrichment in phosphorus is the reason for this effect, different catalyst samples were exposed to wet feeds containing different levels of water vapour and, thereafter, the chemical composition of the catalyst surfaces was determined. Figure 2 shows the change in P V ratio as determined by XPS versus the duration of water vapour treatment. 

Figure 6 shows the dependence of P V ratios determined by ISS (uppermost layer) and by XPS (about 50% of the XPS signal intensity stems from first 6 layers) on the temperature of the water vapour treatment. 

Fig. 1. NH3 TPD spectra of the catalyst a) without water vapour treatment b) with water vapour treatment.

In the industrial piactiee the strength of hydrothermally treated concrete is a veiy important feature. Three kinds of water vapour treatments are applied short — not more than 4 h at 80-90 °C medium — 7-8 h at 70 °C long —12-18 h at 40-50°C. 

FIGURE 1. Absorption and CD spectra of protochlorophyll solid films. A Film treated with acetone vapour for 1 min, B the same film after 45 min acetone vapour treatment, C film treated with dioxane vapour for 5 min. 

Snch a treatment is inadequate with polyolefins and some other polymers, although immersion of polyolefins in hot chlorinated solvent vaponrs for a few seconds can lead to great improvements in adhesion. This vapour treatment is discussed in the article Pretreatments of polyolefins. 

Fig. 10A3 Changes in soluble and total tannins during post-harvest treatments for removal of astringenqr in Hiratanenashi persimmon. A Ethanol vapour treatment. B Carbon dioxide gas treatment...

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