Hydrogen methanol charge

Figure 2. Effect of methanol charge and hydrogen pressure on corrected total solubility 273 g ZnCl, 50 g coal 250°C 60 min.

Solubilization increases almost linearly with hydrogen pressure, at constant temperature and methanol charge. There is a strong effect of temperature, leading to complete solubility at 275°C in less than 30 minutes. Incorporation is best limited by using lower methanol ratios and higher hydrogen pressures. 

While some portion of this total charge was consumed to form adsorbates, some was consumed to oxidize methanol to C02- To see the relationship of these charges, the amount of adsorbates was estimated by the difference of the hydrogen desorption charges between "with methanol" and "without methanol" ... 

A complex interplay of elementary surface processes includes (i) molecular adsorption, (ii) surface diffusion, (iii) charge transfer, (iv) recombination of adsorbed species, and (v) desorption of reaction products. These processes determine observable rates of reactions in PEFCs, that is, reduction of oxygen and oxidation of hydrogen, methanol, or carbon dioxide. 

The flask of a Parr hydrogenation apparatus was charged with 10,5 g of 3,3-diphenylpropyl-amine, 7.7 g of cyclohexylacetone, 50 ml methanol and 150 mg of platinum dioxide. Hydrogen at a pressure of 3 atmospheres was introduced and the mixture stirred. Upon absorption of the theoretical amount of hydrogen, stirring is discontinued, the catalyst is filtered off and the solution is evaporated to dryness. The residue is taken up with ether and the hydrochloride is precipitated with HCI in alcoholic solution. The product, as collected on a filter and washed with ether, is recrystallized from isopropanol. Yield 17 g (92.5% of theory). 

A 250-mL, two-necked, round-bottomed flask equipped with a magnetic stirbar, thermometer, and a reflux condenser fitted with a rubber septum and balloon of argon is charged with a solution of methyltrioxorhenium (MTO) (0.013 g, 0.05 mmol, 0.1% mol equiv) in 100 mL of methanol (Note 1). Urea hydrogen peroxide (UHP) (14.3 g, 152 mmol) is added (Notes 1, 2, 3, 4), the flask is cooled in an ice bath, and dibenzylamine (9.7 mL, 50.7 mmol) is then added dropwise via syringe over 10 min (Notes 1, 5). After completion of the addition, the ice bath is removed and the mixture is stirred at room temperature (Note 6). A white precipitate forms after approximately 5 min (Note 7) and the yellow color disappears within 20 min (Note 8). Another four portions of MTO (0.1% mol equiv, 0.013 g each) are added at 30-min intervals (2.5 hr total reaction time). After each addition, the reaction mixture develops a yellow color, which then disappears only after the last addition does the mixture remain pale yellow (Note 9). The reaction flask is cooled in an ice bath and solid sodium thiosulfate pentahydrate (12.6 g, 50.7 mmol) is added in portions over 20 min in order to destroy excess hydrogen peroxide (Note 10). The cooled solution is stirred for 1 hr further, at which point a KI paper assay indicates that the excess oxidant has been completely consumed. The solution is decanted into a 500-mL flask to remove small amounts of undissolved thiosulfate. The solid is washed with 50 mL of MeOH and the methanol extract is added to the reaction solution which is then concentrated under reduced pressure by rotary evaporation. Dichloromethane (250 mL) is added to the residue and the urea is removed by filtration through cotton and celite. Concentration of the filtrate affords 10.3 g (97%) of the nitrone as a yellow solid (Note 11). 

General Experimental Procedures. Charge 1.0 eq. of substrate, 0.005 eq. or less catalyst, 8 volumes of dichloromethane, 8 volume of methanol. Purge the system three times each with nitrogen and hydrogen. Maintain the temperature at 25°C and hydrogen pressure at 45 psig, until the reaction is deemed complete. 

The quaternary methylated diammines (CH3)3N(CH2)pN(CH3)3+ could be obtained from a methanol-water solution also for lower p values, i.e. p > 2. The greater stability of these doubly charged ions can be attributed to the more dispersed charge and to the absence of protic hydrogens. 

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