Methanol, production temperature effect

The solvent and temperature effects for the Michael addition of amidoxime 7 to DMAD were probed because the reaction itself occurs without any other catalysts. As shown in Table 6.2, the reaction gave a high ratio of 8E in strongly aprotic polar solvents such as DMF and DMSO (entry 1 and 2). 8E was also found as the major product in MeCN (entry 3), dichloromethane (entry 4), and xylenes (entry 5). To our delight, the desired 8Z was obtained as the major component in methanol (entry 6). The stereoselectivity of 8Z versus 8E was better at low temperature (entry 7). A similar result was observed when the reaction was run in THF or dichlo-roethane in the presence of a catalytic amount of DABCO (entries 9 and 10). 

Hirano, A., Hon-Nami, K., Kunito, S., Hada, M., and Ogushi, T. (1998). Temperature Effect on Continuous Gasification of Microalgal Biomass Theoretical Yield of Methanol Production and its Energy Balance, Catalysis Today 45. pp. 399-404. 

Again consider the modified system configuration described in the previous problem and estimate the effects of temperature and pressure on conversion. Do this by calculating CO and H conversions and methanol production for the following conditions ... 

Fig. 6 shows the results for an operatir>g pressure of 5.27 MPa., an initial operating temperature of 498 K, and three different space velocities. At the right-hand terminus of each of the three lines in Rg. 6, temperature programming can no longer maintain a constant production rate. An increase in temperature beyond the terminal point increases the rate constant, k. but this effect Is exactly counterbalanced by a decrease of the equilibrium constant, K q. At these conditions, which are representative of commercial reactor designs, temperature programming cannot be used to maintain constant methanol production because the production rate cannot be held constant for a sufficiently-long period of time. 

The kinetic theory model was extended to include the effect of the mass transfer coefficient between the liquid and the gas and the water gas shift reaction in the slurry bubble column reactor. The computed granular temperature was around 30 cm /sec and the computed catalyst viscosity was closed to 1.0 cp. The volumetric mass transfer coefficient estimated by the simulation has a good agreement with experimental values shown in the literature. The optimum particle size was determined for maximum methanol production in a SBCR. The size was about 60 - 70 microns, found for maximum granular temperature. This particle size is similar to FCC particle used in petroleum refining. 

Fig. 5.2 Temperature dependence of the equilibrium yield and reaction kinetics of an exothermic, reversible reaction (e.g. methanol synthesis). The effective yield corresponding to the real production of the sought products is a compromise of both relations, giving an optimum temperature Topt.

Figure 4. The effect of co-feeding methanol with wood. Selected product ratios for wood alone, methanol alone, and wood co-fed with methanol with the methanol products subtracted. The ratios are light aromatics/ H2O + CO + COo, (arom/inorg) COo/water and trimethylbenzene/toluene (TMB/TOO. Temperature = 500 C wood WHSV= 2.9 methanol WHSV= 2.8.

The higher conversion of methanol synthesis was obtained by applying more effective heat removal to keep reaction temperature as low as possible [17]. The removal of methanol product during the reaction also shifts the equilibrimn to higher conversion. Consequently, the higher total carbon conversion in SC-Ce can be illustrated in terms of both more effective heat transfer and high molecular diffusion efficiency. The more effective heat transfer resulted from the higher thermal conductivity of the SC phase which... 

CO2 is the most common product. Other products and by-products such as acetaldehyde and acetic acid will inevitably decrease flie fuel efficiency. The electrooxidative removal of CO-like intermediates and flie cleavage of the C-C bond are the two main obstacles and rate determining steps. It is elear fliat ethanol eleetrooxidation involves more intermediates and produets than that of methanol, and thus more active electrocatalysts are needed to promote eflianol eleetrooxidation at tower temperatures [102]. Although fliere are some similarities in the oxidation of low molecular weight alcohols on Pt (e.g., CO is produced as intermediate), the best catalyst is not the same for all situations. Contrary to what was found for the oxidation of methanol, the more effective catalyst for flie oxidation of ethanol is not necessarily a Pt-Ru alloy [104]. 

The rate expression for a chemical reaction is in general a function of the concentrations of reactants and products, temperature and pressure. The transport restrictions against mass and heat transport in a single catalyst particle cause a variation in these properties, and hence a variation in the reaction rate. The pressure variation in the catalyst particle is not taken into account, however, because practical experience has shown this effect to be negligible for reactions in ammonia, methanol and hydrogen plants. 

Ethanol has also been utilized for oil extraction. Oil solubility in ethanol varies with temperature and water content. Soybean oil is completely miscible with absolute ethanol above 70 °C (Johnson and Lusas, 1983). As ethanol concentration decreases and water content increases, oil solubility is significantly reduced in the mixture. The higher cost and latent heat of vaporization are the major disadvantages of ethanol as a solvent for oilseed extraction. Recent developments in bioethanol production may reduce the cost of ethanol, making it a viable alternative to hexane. Solvent mixtures can also be used to extract oil. Hexane/alcohol azeotropes have been used for extraction of residual lipids from hexane-extracted meals to improve flavor and odor, specifically from soybean and peanuts. Grassy and beany flavors in oilseeds are associated with the presence of phosphatides, which can be easily extracted with hexane/alcohol mixtures. Similarly, hexane/alcohol azeotropes, specifically hexane/methanol, are very effective in extracting aflatoxin from meal. 

The mixture is decanted into an Erlenmeyer flask, the residual green salts are washed with two 15-ml portions of acetone, and the washings are added to the main acetone solution. Cautiously, sodium bicarbonate (approx. 13 g) is added to the solution with swirling until the pH of the reaction mixture is neutral. The suspension is filtered, and the residue is washed with 10-15 ml of acetone. The filtrate is transferred to a round-bottom flask and concentrated on a rotary evaporator under an aspirator while the flask temperature is maintained at about 50°. The flask is cooled and the residue transferred to a separatory funnel, (If solidification occurs, the residue may be dissolved in ether to effect the transfer.) To the funnel is added 100 ml of saturated sodium chloride solution, and the mixture is extracted with two 50-ml portions of ether. The ether extracts are combined, washed with several 5-ml portions of water, dried over anhydrous magnesium sulfate, and filtered into a round-bottom flask. The ether may be distilled away at atmospheric pressure (steam bath) or evaporated on a rotary evaporator. On cooling, the residue should crystallize. If it does not, it may be treated with 5 ml of 30-60° petroleum ether, and crystallization may be induced by cooling and scratching. The crystalline product is collected by filtration and recrystallized from aqueous methanol. 4-r-Butylcyclohexanone has mp 48-49° (yield 60-90 %). 

The mixture was stirred at ice bath temperature for 2 hours, 1 ml of methanol was added and the mixture was filtered to remove insoluble impurities. Two milliliters of water were added to the filtrate and the pH was adjusted momentarily to pH 1.5, to effect removal of theenamine block, and then to pH 4.5 with triethylamine. After stirring for an additional hour at ice bath temperature the reaction product,7-(D-0 -phenylglycylamido)-3-chloro-3-cephem-4-carboxylic acid (zwitterion) precipitated from the reaction mixture as a crystalline solid. 

The oxidation of n-butane represents a good example illustrating the effect of a catalyst on the selectivity for a certain product. The noncatalytic oxidation of n-butane is nonselective and produces a mixture of oxygenated compounds including formaldehyde, acetic acid, acetone, and alcohols. Typical weight % yields when n-butane is oxidized in the vapor phase at a temperature range of 360-450°C and approximately 7 atmospheres are formaldehyde 33%, acetaldehyde 31%, methanol 20%, acetone 4%, and mixed solvents 12%. 

Complete reduction of the azepine ring to hexahydroazepine has been effected with hydrogen and palladium,40 or platinum,135 239 catalysts. For example, ethyl 1 f/-azepine-l-carboxylate is reduced quantitatively at room temperature to ethyl hexahydroazepine-l-carboxylate (92% bp 118 —120 3C).134 136 TV-Phenyl-S/Z-azepin -amine (1), however, with platinum(IV) oxide and hydrogen in methanol yields the hexahydroazepine 2 in which the amidine unit is preserved in the final product.34 The same result is obtained using 5% palladium/barium carbonate, or 2 % palladium/Raney nickel, as catalyst. 

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