Oxidative methanol dehydrogenation

Diakov, V., Lafarga, D. and Varma, A., 2001. Methanol Oxidative Dehydrogenation in a Catalytic Packed-Bed Membrane Reactor. Catalysis Today, 67(1-3) 159-167. 

Diakov, V. and Varma, A., 2004. Optimal Feed Distribution in a Packed-Bed Membrane Reactor The Case of Methanol Oxidative Dehydrogenation. Industrial Engineering Chemistry Research, 43(2) 309-314. 

Diakov, V., Blackwell, B. and Varma, A. (2002) Methanol oxidative dehydrogenation in a catalytic packed-bed membrane reactor Experiments and model. Chemical Engineering Science, 57, 1563—1569. 

Methanol undergoes reactions that are typical of alcohols as a chemical class (3). Dehydrogenation and oxidative dehydrogenation to formaldehyde over silver or molybdenum oxide catalysts are of particular industrial importance. 

Methane oxidation and partial oxidation, electrochemical promotion of, 308 dimerization, 470 reforming, 410 Methanol dehydrogenation electrochemical promotion of, 403 selectivity modification, 404 Methanol oxidation electrochemical promotion of 398 selectivity modification, 400 Microscopy... 

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

The same samples, after a pretreatment in flowing oxygen (10%) at 625 K, were used as catalysts for the oxidative dehydrogenation of ethanol and methanol in the same reactor. The reaction mixture consisted of O2 (3 or 5%), methanol vapor (3%) or ethanol vapor (5%) and He (balance), all delivered by Tylan mass flow controllers or vaporizer flow controllers. Products were analyzed by gas chromatography. The catalysts exhibited no induction period and their activities were stable over many days and over repeated temperature cycles. 

Selectivity may also come from reducing the contribution of a side reaction, e.g. the reaction of a labile moiety on a molecule which itself undergoes a reaction. Here, control over the temperature, i.e. the avoidance of hot spots, is the key to increasing selectivity. In this respect, the oxidative dehydrogenation of an undisclosed methanol derivative to the corresponding aldehyde was investigated in the framework of the development of a large-scale chemical production process. A selectivity of 96% at 55% conversion was found for the micro reactor (390 °C), which exceeds the performance of laboratory pan-like (40% 50% 550 °C) and short shell-and-tube (85% 50% 450 °C) reactors [73,110,112,153,154]. 

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%. 

Both processes - referring to the non-substituted and substituted methanol reactant- utilize elemental silver catalyst by means of oxidative dehydrogenation. Production is carried out in a pan-like reactor with a 2 cm thick catalyst layer placed on a gas-permeable plate. A selectivity of 95% is obtained at nearly complete conversion. This performance is achieved independent of the size of the reactor, so both at laboratory and production scale, with diameters of 5 cm and 7 m respectively. 

Vanadia catalysts exhibit high activity and selectivity for numerous oxidation reactions. The reactions are partial oxidation of methane and methanol to formaldehyde, and oxidative dehydrogenation of propane to propene and ethane to ethcnc.62 62 The catalytic activity and selectivity of... 

Skeletal catalysts are usually employed in slurry-phase reactors or fixed-bed reactors. Hydrogenation of cottonseed oil, oxidative dehydrogenation of alcohols, and several other reactions are performed in sluny phase, where the catalysts are charged into the liquid and optionally stirred (often by action of the gases involved) to achieve intimate mixing. Fixed-bed designs suit methanol synthesis from syngas and catalysis of the water gas shift reaction, and are usually preferred because they obviate the need to separate product from catalyst and are simple in terms of a continuous process. 

The extra oxygen decreased the activation energy of C-H bond scission of the methoxy, which is the rate-limiting step of the selective methanol oxidation. TPD spectra of CO indicate that extra oxygen species reduce the electron density of Mo atoms in MoNC rows. This modification causes the decrease of the activation energy for the methoxy dehydrogenation. The extra oxygen is... 

The concentration of acid should affect interfacial reactions in various ways such as through the hydrogen ion concentration, water activity, and behavior of anions. Hydrogen ion concentration may play a minor role because the dehydrogenation can be considered as relatively fast steps in the methanol oxidation. Therefore, the other two elements will be considered here. 

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... 

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