Process parameters methanol formation

The reverse-flow chemical reactor (RFR) has been shown to be a potentially effective technique for many industrial chemical processes, including oxidation of volatile organic compounds such as propane, propylene, and carbon monoxide removal of nitrogen oxides sulfur dioxide oxidation or reduction production of synthesis gas methanol formation and ethylbenzene dehydration into styrene. An excellent introductory article in the topic is given by Eigenberger and Nieken on the effect of the kinetic reaction parameters, reactor size, and operating parameters on RFR performance. A detailed review that summarizes the applications and theory of RFR operation is given by Matros and Bunimovich. 

Mixed copper/zinc catalysts with high copper-to-zinc ratios are widely used as catalysts for low-pressure methanol production and for low-temperature shift reaction [2, 31], see also Chapter 15. These catalysts are commonly made by coprecipitating mixed-metal nitrate solutions by addition of alkali. Li and Inui [32] showed that apart from chemical composition, pH and temperature are key process parameters. Catalyst precursors were prepared by mixing aqueous solutions of copper, zinc, and aluminum nitrates (total concentration 1 mol/1) and a solution of sodium carbonate (1 mol/1). pH was kept at the desired level by adjusting the relative flow rate of the two liquids. After precipitation was complete, the slurry was aged for at least 0.5 h. When the precipitation was conducted at pH 7.0, the precipitate consisted of a malachite-like phase (Cu,Zn)C03(0H)2 and the resulting catalysts were very active, while at pH < 6 the formation of hydroxynitrates was favored, which led to catalysts less active than those prepared at pH 7.0 (Figure 7.8). 

However, with increasing duration of the process, accompanied by the growth of the conversion of reactants and the concentration of the products in the reactor, the methanol selectivity dropped to 22%, i.e., a value typical for this pressure range ( 40 atm). After decreasing the pressure from 40 to 5 atm, the selectivity of methanol formation in this initiated radical—chain reaction decreases sharply to 2%, thereby confirming the importance of this parameter for the formation of methanol. Thus, reducing the process temperature by more than 200 °C due to its initiation does not show any advantage in terms of selectivity of methanol. 

Ford used HP-IR to investigate an acyliron migratory insertion intermediate formed by flash photolysis. Thus, flash photolysis of (7 -Cp)Fe(C0)2C(0)GH3 affords coordinatively unsaturated ( -Gp)Fe(C0)C(0)CH3. Trapping of the latter with CO in the reverse reaction was studied, and the second-order rate constant could be determined for this reaction under the high CO pressures employed. Variable-temperature studies allowed calculation of activation parameters for methyl migration. Iron cluster compounds have been studied for the carbonylation of methanol to methyl formate. Consistent kinetics and a first-order dependence on cluster concentration confirmed the HP-IR results which showed that the cluster remained intact through the catalytic process. 

Asymmetric polyimide membranes with an ultrathin defect-free skin layer were fabricated by the dry-wet process [15]. Composition of casting solution used for the preparation of asymmetric membranes was 12 wt.% polyimide, 55 wt.% methylene chloride, 23 wt.% 1,1,2-trichloroethene, and 10 wt.% butanol. In the dry process (solvent evaporation) the evaporation period was changed from 15 to 600 s, while in the wet process (coagulation process) the coagulation media was methanol. It was possible to control the thickness of the skin layer by controlling the evaporation period. From this AFM study, it was observed that the nodule formation was controlled by evaporation time, while the coagulation media controlled the roughness parameter. 

The set of reactions shown in Table 5.1 accounts for the formation of the main oxidation products methanol, formaldehyde, and water, but does not provide for their further transformation, since only the initial stage of the process is considered. Nevertheless, its analysis can explain the main qualitative features of the DMTM process, although its quantitative modeling requires much more complex, open-type models that would take into account the totality of homogeneous and heterogeneous elementary steps important in this range of conditions. This means that the model includes all the relevant elementary steps and, if required, it can be readily extended and that all the kinetic parameters are taken from independent databases. Thus, these parameters can and should be modified based only on the subsequent recommendations of these databases. 

The works [158,185—188] investigated the effect of various parameters on the reaction onset temperature and the yield of the products. At pressures of 1 and 5 atm, the increase of the initial concentration of NO to 1% significantly, by 100 °C, decreased the temperature of the process, although the maximum obtainable conversion of methane was almost the same. However, the increase of the NO concentrations to 1.5% produced practically no effect. At these pressures, the selectivity of formation of oxygenates (methanol, formaldehyde, and nitromethane) reached a maximum at an NO concentration of 0.5%, so this concentration was adopted as optimal. The ethane formation selectivity decreased rapidly with increasing NO concentration, nearly to zero. Diluting the mixture with helium, at least up to 60%, had a moderate effect on the process. Even the CH4/O2 ratio, a key parameter of the... 

Information on the partial oxidation of ethane at high pressures is almost exhausted by that presented in the aforementioned works, which are at odds on the question of whether the main products of the process can be C2-oxygenates formed without rupture of the C—C bond. At least at short reaction times and flow conditions, the main products, as in the oxidation of methane, were methanol and formaldehyde. Since these works are quite different in many experimental parameters, the causes of differences in the formation of products remain unclear. 

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