Oxidative Dehydrogenation of Methanol

The synthesis of formaldehyde from selective oxidation of methanol over a thin layer of electrolytic silver catalyst is a well-known industrial process that occurs in the temperature range of 850-923 K at atmospheric pressure. Since the total reaction is highly exothermic and fast, requiring very short contact time (0.01 s or less), the use of a silicon MSR was demonstrated to improve conversion up to 75% and 90% selectivity at safe conditions within the flammability limits [29]. 

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Normalization by Oxygen Uptake of the Rates of Oxidative Dehydrogenation of Methanol and Ethanol... 

The oxidative dehydrogenation of methanol to formaldehyde is a model reaction for performance evaluation of micro reactors (see description in [72]). In the corresponding industrial process, a methanol-air mixture of equimolecular ratio of methanol... 

Figure 3.36 Arrhenius plot for the oxidative dehydrogenation of methanol to formaldehyde performed in a micro reactor [72].

The oxidative dehydrogenation of methanol to formaldehyde was choosen as model reaction by BASF for performance evaluation of micro reactors [1, 49-51, 108]. In the industrial process a methanol-air mixture of equimolecular ratio of methanol and oxygen is guided through a shallow catalyst bed of silver at 150 °C feed temperature, 600-650 °C exit temperature, atmospheric pressure and a contact time of 10 ms or less. Conversion amounts to 60-70% at a selectivity of about 90%. 

Oxidative Dehydrogenation of Methanol Porous AI203 membranes... 

Oxidative dehydrogenation of methanol. Silver catalyst deposited in the pores of the membrane (66 wt% Ag). 

Lefferts, L., J. G, van Ommen and J. R. H. Ross, 1986, The oxidative dehydrogenation of methanol to formaldehyde over silver catalysts in relation to the oxygen-silver interaction. Appl. Catal. 23 385-401... 

It includes the steam reforming of methane over a nickel catalyst to synthesis gas followed by the copper-catalyzed transformation of the latter to methanol (see Section 3.5.1). Finally, formaldehyde is produced by oxidative dehydrogenation of methanol. 

The largest and oldest chemical intermediate use for methanol is formaldehyde. Over half of the methanol currently consumed in the world goes into formaldehyde production. Formaldehyde is produced by the catalytic oxidation or the oxidative dehydrogenation of methanol The major outlet for formaldehyde is amino and phenolic resins. These resins are in turn used in the manufacture of adhesives for wood products, molding compounds, binders for thermal insulation and foundry resins. Formaldehyde is also consumed in the production of acetal resins, pentaerythritol, neopentyl glycol, trimethylolpropane, methylenediphenyldiisocyanate (MDI), and textile treating resins. 

The oxidative dehydrogenation of methanol to methanal is mentioned in Chapter 8. 

Recently Brinkmann et al. [2.295] reported a theoretical and experimental study of the oxidative dehydrogenation of methanol to CO2 and H2 by using a CMR with a Pt impregnated tubular alumina membrane. The authors studied the influence on reactor performance of the transmembrane pressure or the purge stream to feed ratio. Conversion increased as either one of these increased, the reactor conversion reaching as high as 84 %, while the hydrogen selectivity remained near 50 %. 

Bulk metals can be used in traditional engineering forms, more particularly as fine wire woven into gauzes. Such forms are generally used only in high-temperature processes, such as the partially oxidative dehydrogenation of methanol (over Ag) or ammonia oxidation (over Pt-Rh) at about 500-600°C and 850-900°C respectively. Mechanical stability is of greater importance than high surface area. 

A microstructured device consisting of a preheating unit, a mixer, a reactor, and a quenching zone was used for the exothermic oxidative dehydrogenation of methanol to formaldehyde [65]. 

However, besides the high heat exchange coefficients, fluidized beds are also suitable for isothermal operations even if a highly exothermic reaction is occurring. This has been demonstrated a.o. by Deshmukh et al. [46,47], who carried out oxidative dehydrogenation of methanol in laboratory-scale membrane fluidized bed reactors. The authors found virtually isothermal conditions even for very high methanol feed concentrations. This important... 

Cao, E. and Gavriilidis, A. (2005). Oxidative dehydrogenation of methanol in a microstruc-tured reactor. Catalysis Today, Vol. 110, pp. 154-163. 

Formaldehyde is produced by oxidation of methanol or oxidative dehydrogenation of methanol. Oxidation of methanol (route (a) in Topic 5.3.2] is a strongly exothermic reaction (AH = -243 kj mol ) that is carried out in a pressure-less oxidation with air in a multi-tubular reactor. The reaction is catalyzed by an iron/molybde-num oxide contact, with Fe2(Mo04) being the active catalytic species. The oxidation is carried out at 350 °C with quantitative methanol conversion. The main side reaction is the total oxidation of methanol to CO2 and water. 

In contrast to methanol oxidation, oxidative dehydrogenation of methanol [route (b) in Topic 5.3.2] is an endothermic reaction (AH = -F84kJ mol ). Methanol is contacted at normal pressure with a heterogeneous silver at 500-700 °C. Owing to the kinetic instability of the formaldehyde product under the applied reaction conditions, the contact time at the catalyst is very short (t < 0.01 s). This is realized by high flow rates in the reactor and a very effective quenching of the product flow leaving the reactor. The product gas is contacted with water to produce an aqueous... 

Brinkmann, T, Perera, S.P and Thomas, W.J. (2001) An experimental and theoretical investigation of a catalytic membrane reactor for the oxidative dehydrogenation of methanol. Chemical Engineering Science, 56, 2047-2061. 

To demonstrate the validity of the ReaxFF potential for modeling catalytic V/O/C/H interactions, the authors simulated the oxidative dehydrogenation of methanol over the 205(00 ) surface. They conducted a 250 ps NVT-MD simulation of a three-layer oxide slab surrounded by 30 gas-phase methanol molecules in a 20 x 20 x 20 periodic box. A dual temperature constraint was... 

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