Methanol conversion

The subject has been reviewed (37,38). Water may be added to the feed to suppress methyl acetate formation, but is probably not when operating on an industrial scale. Water increase methanol conversion, but it is involved in the unavoidable loss of carbon monoxide. A typical methanol carbonylation flow sheet is given in Figure 2. 

With increasing energy costs, maximum methanol conversion is desirable, eliminating the need for the energy-intensive distillation for methanol... 

In contrast to the silver process, all of the formaldehyde is made by the exothermic reaction (eq. 23) at essentially atmospheric pressure and at 300—400°C. By proper temperature control, a methanol conversion greater than 99% can be maintained. By-products are carbon monoxide and dimethyl ether, in addition to small amounts of carbon dioxide and formic acid. Overall plant yields are 88—92%. 

The carboaylatioa of methanol to give formic acid is carried out ia the Hquid phase with the aid of a basic catalyst such as sodium methoxide. It is important to minimi2e the presence of water and carbon dioxide ia the startiag materials, as these cause deactivatioa of the catalyst. The reactioa is an equHibrium, and elevated pressures are necessary to give good conversions. Typical reaction conditions appear to be 80°C, 4.5 MPa (44 atm) pressure and 2.5% w/w of catalyst. Under these conditions the methanol conversion is around 30% (25). 

S. Yurchak and S. S. Wong, "Mobil Methanol Conversion Technology," Proceedings IGT Asian Natural Gas Seminar, Singapore, 1992, pp. 593—618. 

A Belgian patent (178) claims improved ethanol selectivity of over 62%, starting with methanol and synthesis gas and using a cobalt catalyst with a hahde promoter and a tertiary phosphine. At 195°C, and initial carbon monoxide pressure of 7.1 MPa (70 atm) and hydrogen pressure of 7.1 MPa, methanol conversions of 30% were indicated, but the selectivity for acetic acid and methyl acetate, usehil by-products from this reaction, was only 7%. Ruthenium and osmium catalysts (179,180) have also been employed for this reaction. The addition of a bicycHc trialkyl phosphine is claimed to increase methanol conversion from 24% to 89% (181). 

M. G. Block, R. B. Callen and J. H. Stockinger, The analysis of hydrocar bon products obtained from methanol conversion to gasoline using open tubular GC columns and selective olefin absorption , ]. Chromatogr. Sci. 15 504-512 (1977). 

Methanol conversion to hydrocarbons over various zeolites (370X, 1 atm, 1 LHSV)... 

Detergent manufacturing Catalytic cracking and hydrocracking Xylene isomerization, benzene alkylation, catalytic cracking, catalyst dewaxing, and methanol conversion. 

Methanol oxidation on Pt has been investigated at temperatures 350° to 650°C, CH3OH partial pressures, pM, between 5-10"2 and 1 kPa and oxygen partial pressures, po2, between 1 and 20 kPa.50 Formaldehyde and C02 were the only products detected in measurable concentrations. The open-circuit selectivity to H2CO is of the order of 0.5 and is practically unaffected by gas residence time over the above conditions for methanol conversions below 30%. Consequently the reactions of H2CO and C02 formation can be considered kinetically as two parallel reactions. 

In this work, the MeOH kinetic model of Lee et al. [9] is adopted for the micro-channel fluid dynamics analysis. Pressure and concentration distributions are investigated and represented to provide the physico-chemical insight on the transport phenomena in the microscale flow chamber. The mass, momentum, and species equations were employed with kinetic equations that describe the chemical reaction characteristics to solve flow-field, methanol conversion rate, and species concentration variations along the micro-reformer channel. 

A complete methanol reforming system was constructed by coimecting the integrated reformer with a PROX reactor. Fig. 5 shows the evolution of temperature at the gas outlet of the evaporator, reformer and PROX reactor during the start-up. Temperature of the reformer became stable in 5 min after introduction of the reactant. The reformer produced hydrogen up to 1.5L/min with methanol conversion higher than 95%, enough to run a lOOW PEMFC. 

Fig.4. Effect of thermal Peclet number on maximum reactor temperature and methanol conversion.

Methane-to-methanol conversion by gas-phase transition metal oxide cations has been extensively studied by experiment and theory see reviews by Schroder, Schwarz, and co-workers [18, 23, 134, 135] and by Metz [25, 136]. We have used photofragment spectroscopy to study the electronic spectroscopy of FeO" " [47, 137], NiO [25], and PtO [68], as well as the electronic and vibrational spectroscopy of intermediates of the FeO - - CH4 reaction. [45, 136] We have also used photoionization of FeO to characterize low lying, low spin electronic states of FeO [39]. Our results on the iron-containing molecules are presented in this section. 

The results in Table 3 show that H-mordenite has a high selectivity and activity for dehydration of methanol to dimethylether. At 150°C, 1.66 mol/kg catal/hr or 95% of the methanol had been converted to dimethylether. This rate is consistent with that foimd by Bandiera and Naccache [10] for dehydration of methanol only over H-mordenite, 1.4 mol/kg catal/hr, when extrt lat to 150°C. At the same time, only 0.076 mol/kg catal/hr or 4% of the isobutanol present has been converted. In contrast, over the HZSM-5 zeolite, both methanol and isobutanol are converted. In fact, at 175 X, isobutanol conversion was higher than methanol conversion over HZSM-5. This presents a seemingly paradoxical case of shape selectivity. H-Mordenite, the zeolite with the larger channels, selectively dehydrates the smaller alcohol in the 1/1 methanol/ isobutanol mixture. HZSM-5, with smaller diameter pores, shows no such selectivity. In the absence of methanol, under the same conditions at 15(fC, isobutanol reacted over H-mordenite at the rate of 0.13 mol/kg catal/hr, higher than in the presence of methanol, but still far less than over H M-5 or other catalysts in this study. 

GP 4] [R 11] For methanol conversion over sputtered silver catalyst, variation in oxygen content from 10% to more than 90% of the gas mixtare results in a slight decrease of conversion from 75 to 70% and of selectivity from 91 to 89% (8.5 vol.-% methanol balance helium 510 °C 10 ms slightly > 1 atm) [72]. 

Gao L, Huang H, Korzeniewski C. 2004. The efficiency of methanol conversion to CO2 on thin films of Pt and PtRu fuel cell catalysts. Electrochim Acta 49 1281-1287. 

Basch, H., Mogi, K., Musaev, D. G., Morokuma, K., 1999, Mechanism of the Methane —> Methanol Conversion Reaction Catalyzed by Methane Monooxygenase A Density Functional Study , J. Am. Chem. Soc., 121, 7249. 

Figure 1. Radio-signals of UC- products in nC-methanol conversion (a) at 300 °C and nC-methanol conversion with non-radioactive CH3I (b) at 350 °C.

Figure 2. The influence of both BAS (Bronsted acid sites) and LAS (Lewis acid sites) acidity (in pmol/g) on selectivities of methanol conversion products on Fe-Beta-300(a) as well as co-reaction products (b) of methanol with methyl iodide on Fe-Beta-300 as a function of catalyst temperature.

Pannetier et al. (8) observed that the presence of chelating ligands on the rhodium gave a much poorer methanol conversion over a limited reaction period than did reactions using rhodium complexes with mono-dentate ligands. This may reflect the slower removal and subsequent quatemization of the chelating ligands. 

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