Steam adsorbed

Carr, R.G., and Somorjai, G.A., Hydrogen production from photolysis of steam adsorbed onto platinized SrTiOj, Nature, 290, 576, 1981. 

This observation is surprising given literature reports that steam adsorbs strongly on Pd membranes [17] and also causes inhibition of the Ha flux when present in the feed gas stream at lower temperatures. The enhancement due to the steam sweep stream could be due to a cleaning effect where the steam reacts with CO or carbon present on the permeate side of the membrane to form CO2 as we have observed that the Pd-Cu membrane is a catalyst for the WGS reaction. Carbon dioxide is less strongly bound to the surface of the membrane than CO that would free additional sites for the formation of molecular hydrogen. The He sweep could have a similar... 

After the adsorber has been steamed, the outlet valve is switched over. The steamed adsorber is then dried with solvent-free air taken from the laden adsorber. A feature of this process is that the steamed adsorber is always dried with solvent-free air. An advantage of this two-stage process is that the laden adsorber can be loaded beyond the breakthrough capacity since the second adsorber is unladen and can therefore accept any excess solvent. 

When the bed is saturated, regeneration of the adsorbent is necessary. Carbon beds are typically regenerated with steam, hot air, or a combination of vacuum and hot gas. 

Although it is hard to draw a sharp distinction, emulsions and foams are somewhat different from systems normally referred to as colloidal. Thus, whereas ordinary cream is an oil-in-water emulsion, the very fine aqueous suspension of oil droplets that results from the condensation of oily steam is essentially colloidal and is called an oil hydrosol. In this case the oil occupies only a small fraction of the volume of the system, and the particles of oil are small enough that their natural sedimentation rate is so slow that even small thermal convection currents suffice to keep them suspended for a cream, on the other hand, as also is the case for foams, the inner phase constitutes a sizable fraction of the total volume, and the system consists of a network of interfaces that are prevented from collapsing or coalescing by virtue of adsorbed films or electrical repulsions. 

The removal of volatile organic compounds (VOC) from air is most often accompHshed by TSA. Air streams needing treatment can be found in most chemical and manufacturing plants, especially those using solvents. At concentrations from 500 to 15,000 ppm, recovery of the VOC from steam used to regenerate activated carbon adsorbent thermally is economically justified. Concentrations above 15,000 ppm ate typically in the explosive range and... 

Stea.ming Retjuirements. The steaming of fixed beds of activated carbon is a combination of thermal swing and displacement purge swing. The exothermic heat released when the water adsorbs from the vapor phase is much higher than is possible with heated gas purging. This cycle has been successhiUy modeled by equiUbrium theory (128). 

Naphtha desulfurization is conducted in the vapor phase as described for natural gas. Raw naphtha is preheated and vaporized in a separate furnace. If the sulfur content of the naphtha is very high, after Co—Mo hydrotreating, the naphtha is condensed, H2S is stripped out, and the residual H2S is adsorbed on ZnO. The primary reformer operates at conditions similar to those used with natural gas feed. The nickel catalyst, however, requires a promoter such as potassium in order to avoid carbon deposition at the practical levels of steam-to-carbon ratios of 3.5—5.0. Deposition of carbon from hydrocarbons cracking on the particles of the catalyst reduces the activity of the catalyst for the reforming and results in local uneven heating of the reformer tubes because the firing heat is not removed by the reforming reaction. 

Do not regenerate molecular sieves by steaming water typically is strongly adsorbed and may not be easily displaced by adsorbent in next adsorption cycle. 

The refining process most commonly used involves treatment with hot aqueous alkaH to convert free fatty acids to soaps, followed by bleaching, usually with hydrogen peroxide, although sodium chlorite, sodium hypochlorite, and ozone have also been used. Other techniques include distillation, steam stripping, neutralization by alkaH, Hquid thermal diffusion, and the use of active adsorbents, eg, charcoal and bentonite, and solvent fractionation... 

The low autoignition temperature of benzaldehyde (192°C) presents safety problems since benzaldehyde can be ignited by exposure to low pressure steam piping, for example. Benzaldehyde may also spontaneously ignite when soaked into rags or clothing or adsorbed onto activated carbon (13). 

Other types of regenerators designed for specific adsorption systems may use solvents and chemicals to remove susceptible adsorbates (51), steam or heated inert gas to recover volatile organic solvents (52), and biological systems in which organics adsorbed on the activated carbon during water treatment are continuously degraded (53). 

Hydrogen Liquefaction. Hydrogen can be produced from caustic—chlorine electrolytic cells, by decomposition of ammonia or methanol, or by steam—methane reforming. Hydrogen recovered by these methods must be further purified prior to Hquefaction. This is generally achieved by utilizing pressure swing adsorption methods whereby impurities are adsorbed on a soHd adsorbent. 

Adsorbent regeneration requiring a steam or vacuum source... 

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