Hydrogenation solubility, reaction product effects

We have now found that replacing water in the melt by methanol leads to large increases in pyridine solubility of product from the treatment, even without tetralin addition. In this paper we characterize the effects of temperature, time, hydrogen pressure, reaction stoichiometry, and addition of various inorganic and organic additives. Because oxygen removal Present Address Chevron Research Co., Box 1627, Richmond, CA 94804. 

The effect of trace contaminants on the reaction has been investigated carefully. All uncondensed effiuent gases were recycled to the reactor, except for the amounts present in the streams taken off for analysis or flashed upon depressuring of the organic phase. Aqueous phase from the separator containing the water soluble by-products has been used as the water feed to the reactor. Hydrogen chloride containing chlorinated hydrocarbons and acetylene was used in all operations. In addition, certain possible impurities were tested for their effect on the kinetics and selectivity of the process. Paraffins, carbon monoxide, sulfide, carbon dioxide, alkali, and alkaline earth metals were found to be chemically inert. Olefins, diolefins and acetylenic compounds are chlorinated to the expected products. No deleterious effects of by-product recycle were observed even when some of the main by-products were added extraneously. 

A special situation may arise if reaction products considerably affect the hydrogen solubility, which then varies during the reaction. Such a phenomenon occurs most often in the hydrogenation of the substrate in bulk, without solvent, mainly where the chemical character of the hydrogenation product markedly differs from that of the initial compound [e.g., hydrogenation of nitrobenzene to aniline and water (72)]. In such a case the hydrogen concentration cannot be drawn into the constant, because its varying concentration in the liquid phase is reflected in the form of the kinetic equation. In many such cases the effect of reaction products is also reflected in the kinetic equation. 

A steady-state flow apparatus has been used to determine the pressure dependence of the relative quasi-bimolecular rate constants for the reactant pairs NH3 + McgN and Me2HN + McaN in their reaction with BFg. The reactions between NH3 and the amalgams of Mn, U, Ti, and A1 produce MngHgN, UNi.sa, TiN, and AIN, respectively. Orders of reaction were determined for the above cases but for Fe and Or, which have very low solubility in Hg, reaction was so slow that no reaction products could be isolated or identified. An investigation of the photolysis of NH3 and ND3 has revealed an important isotope effect. The ratio of molecular and atomic hydrogen produced by photolysis at 147 and 123.6 nm was h,/ > while at 185 nm Th dissociation ... 

Cupric chloride or copper(II) chloride [7447-39 ], CUCI2, is usually prepared by dehydration of the dihydrate at 120°C. The anhydrous product is a dehquescent, monoclinic yellow crystal that forms the blue-green orthohombic, bipyramidal dihydrate in moist air. Both products are available commercially. The dihydrate can be prepared by reaction of copper carbonate, hydroxide, or oxide and hydrochloric acid followed by crystallization. The commercial preparation uses a tower packed with copper. An aqueous solution of copper(II) chloride is circulated through the tower and chlorine gas is sparged into the bottom of the tower to effect oxidation of the copper metal. Hydrochloric acid or hydrogen chloride is used to prevent hydrolysis of the copper(II) (11,12). Copper(II) chloride is very soluble in water and soluble in methanol, ethanol, and acetone. 

Both reactions were carried out under two-phase conditions with the help of an additional organic solvent (such as iPrOH). The catalyst could be reused with the same activity and enantioselectivity after decantation of the hydrogenation products. A more recent example, again by de Souza and Dupont, has been reported. They made a detailed study of the asymmetric hydrogenation of a-acetamidocin-namic acid and the kinetic resolution of methyl ( )-3-hydroxy-2-methylenebu-tanoate with chiral Rh(I) and Ru(II) complexes in [BMIM][BF4] and [BMIM][PFg] [55]. The authors described the remarkable effects of the molecular hydrogen concentration in the ionic catalyst layer on the conversion and enantioselectivity of these reactions. The solubility of hydrogen in [BMIM][BF4] was found to be almost four times higher than in [BMIM][PFg]. 

Figure 12 clearly shows the effect of iron sulfide content of the coal on total conversion and liquid product yield during hydrogenation. The conversion increased from about 52 per cent to 70 per cent using the hot-rod reactor with no added catalyst. The yield of toluene soluble product (oil plus asphaltene) increased from about 30 to 44 per cent with total sulfur increase from 1 to 6.5 per cent. Thus it would appear that iron sulfide can act catalytically in the dry hydrogenation reaction as well as in slurried reactions (15). 

In this paper we have looked firstly at the effect that the catalyst concentration, secondly at the effect that the reactor temperature and finally at the effect that the residence time at temperature have on the chemical structure of the oils (hexane soluble product) produced on hydropyrolysis (dry hydrogenation) of a high volatile bituminous coal. Generally, the hydropyrolysis conditions used in this study resulted in oil yields that were considerably higher than the asphaltene yields and this study has been limited to the effects that the three reaction conditions have on the chemical nature of the oils produced. 

Water-soluble complexes constitute an important class of rhodium catalysts as they permit hydrogenation using either molecular hydrogen or transfer hydrogenation with formic acid or propan-2-ol. The advantages of these catalysts are that they combine high reactivity and selectivity with an ability to perform the reactions in a biphasic system. This allows the product to be kept separate from the catalyst and allows for an ease of work-up and cost-effective catalyst recycling. The water-soluble Rh-TPPTS catalysts can easily be prepared in situ from the reaction of [RhCl(COD)]2 with the sulfonated phosphine (Fig. 15.4) in water [17]. 

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