Hydrocarbon impurity

Hydrocarbon impurities can be introduced by contamination of the outer surface of the candle if mold release compounds are used. Candles are sometimes shaved to reduce such contamination. 

Water and sulfur compounds are the principal non-hydrocarbon impurities present in light ends which frequently require removal. The sulfur compounds of concern are concerned with here are hydrogen sulfide and mercaptans, both of which have to be removed almost quantitatively from any light ends cut which is going to be marketed. There are two reasons for this First, they have an objectionable odor, even in minute concentrations. Second, they may cause corrosion either by themselves or through their combustion products. 

Pure M-hexane is widely used in laboratories as an extractant for nonpolar compounds and in calibrating instruments for analyses of volatile organic compounds (VOC) or total petroleum hydrocarbons (TPH) (Kanatharana et al. 1993). Since such analyses may require very high levels of purity, laboratories sometimes carry out their own fractional distillation or other pretreatment-purification procedures to remove petroleum hydrocarbon impurities found in commercially available grades of M-hexane (Kanatharana et al. 1993). See Chapter 6 for more information about testing for -hexane. 

Hydrocarbon impurities y y < 0.6 ppm as hexane Produce ozone at < 3 ppb Nonmethane hydrocarbon at 1 ppb Ambient (high)... 

Hydrocarbon impurities in the product hydrogen usually are not detrimental to the processes where this hydrogen will be used. Thus, a small amount of hydrocarbon is tolerable in the effluent gas. 

The production of COS in the front end reaction furnace presents special problems since sulfur in this form may be difficult to remove in the downstream catalytic beds under conditions that are optimal for the Claus redox reaction between H2S and SO COS (and CS2) were known to be generated from hydrocarbon impurities carried over in the acid gas feed thus the efficiency of the up-stream sweetening process became an important factor. The reaction of CO2, a common constituent of the acid gas feed, with H2S and/or sulfur under furnace temperature conditions has also been shown to be an important source of COS. 

The reaction may be conveniently terminated here, but reaction for two days gives a slightly higher yield at the expense of some hydrocarbon impurity formed from the slow reaction of excess alkyllithium with the alkyl bromide. If this impurity can contaminate the final product, the side reaction may be suppressed by conducting the reaction in the minimum amount of solvent necessary to dissolve the dilithium complex. 

D2 at room temperature. If, however, the Cabosil is impregnated with platinum, the exchange goes rapidly (14). The results of such an exchange are shown in Fig. 18. Spectrum A is due to partially dried Cabosil which is used as a support for 9.2 wt. % platinum. The bands at 2.67 and 2.80 n are due to surface OH groups and adsorbed water. The bands in the 3.4-/ region are due to hydrocarbon impurities on spectrometer windows and the bands near 4.27-ju are due to atmospheric C02. Spectrum B was obtained 10 min. after the sample had been exposed to gaseous D2. The... 

Inflammatory changes consisting of hyperemia and bronchitis were observed in the respiratory system of rabbits exposed to 4-6 mg/m (0.30-0.45 ppm) tributyltin chloride for 95 days (Gohlke et al. 1969). Histopathology, consisting of severe bronchitis and vascular and alveolar edema, was seen in rats exposed to 2 mg tin/m (0.41 ppm) as a mixture of tributyltin dibromide (0.39 ppm), dibutyltin bromide (0.02 ppm) and hydrocarbon impurities for 80 days (Iwamoto 1960). Since these were terminal histopathological evaluations only, it is not known whether the changes were reversible or would have produced functional impairment in the animals if exposure had continued. 

Reaction rate oscillations have been observed during the oxidation reaction of CO over Pt/y-Al203 catalysts. The technique of IR transmission spectroscopy has been utilized to monitor the surface state of the catalyst under both steady-state and oscillatory conditions. The effect of hydrocarbon impurities and catalyst deactivation on the dynamic behavior of the system has also been investigated. 

Carberry et al. [2] have observed a startling effect of hydrocarbon impurities on the oscillatory behavior in their system. Oscillations were observed when an "Impure" O2 was used and disappeared when the "impure" O2 was replaced by an "ultrapure" O2. The only apparent difference between the "ultrapure" and the "impure" O2 is a 30 ppm Impurity of hydrocarbons. 

The Oscillatory Behavior. We have so far focused our attention on three questions (a) Does an oscillatory regime exist for this reaction system (b) What is the effect of hydrocarbon impurities and (c) What is the effect of catalyst deactivation on the dynamic behavior ... 

Neutralized cleavage effluent is first split into separate acetone/ cumene/AMS/water and phenol/heavier fractions (5). Overheads from the splitter are then fractionated to remove aldehydes (6) and cumene/ AMS/water (7) to produce high-purity acetone (99.75+ wt%). Splitter bottoms is fractionated undervacuum to producea crude phenol distillate (8) and a heavy waste hydrocarbon stream. Hydrocarbon impurities are removed from the crude phenol by hydroextractive distillation (9) followed by catalytic phenol treatment (10) and vacuum distillation (11) to produce ultra-high-purity phenol (+99.99 wt%). 

The typical hydrocarbon impurity in acid gas is methane. Methane is lighter than the acid gas components, and thus the density of an acid gas mixture is reduced by the presence of methane. Even in a liquid mixture, the density is reduced by the presence of methane. 

---