MeOH synthesis

Figure 3. Activity of powdered ZnO samples employed in MeOH synthesis (p = 30 bar, T = 573 K, Q = lOmL/min [64% H2, 8% CO2, 6% CO, 22% He]). Particle diameters of the different batches of ZnO decrease from batch A to E. (Reprinted from Reference [39], 2003, with permission from Royal Society of Chemistry).

Haldor-Topsoe MeOH synthesis catalyst (pre-reduced) 0.43 3.3... 

The activity of supported Pt catalysts for methanol synthesis from C0-H2 is considerably enhanced when the metal is supported on oxides which exhibit themselves appreciable activity for MeOH synthesis. Furthermore it is found that the rate of methanol formation on Pt-supported catalyst is increased when Th02, Ce02 were mechanically mixed with the Pt catalyst. Such behaviour is typical for bifunctional catalysts. It has already been reported that Th02, Ce02 adsorb carbon monoxide without dissociation. Such activated CO can be hydrogenated to form a formyl species, the formyl species interacting with lattice oxygen will produce a formate intermediate. 

Figure 1. Effect of Ak Ti and V addition on MeOH synthesis at 1 MPa, 498K. W/F=8 gh/mol (dry base).

Consequently, further development of the MTG process as it is realised in New Zealand should aim at a reduction of the investment. The TIGAS process represents such an effort. In the TIGAS process the two process steps, MeOH synthesis and the MTG process, are integrated into one single synthesis loop without isolation of MeOH as an intermediate (ref. 1), (Fig. 1). 

The basic problem of process integration is that the syntheses involved are preferably carried out at very different pressures, synthesis gas production at 15-20 bar, MeOH synthesis at 50-100 bar, and the MTG process at 15-25 bar. 

The aim of the process development work on the integrated gasoline synthesis has been to arrive at a process scheme in which all three steps of the conversion of natural gas to gasoline are conducted at the same pressure level. This means that operating conditions and catalysts should be modified so that the low pressure processes can operate at relatively high pressure, and efforts should be made to reduce the necessary operating pressure of the MeOH synthesis. 

The simplest way of integrating MeOH synthesis with gasoline synthesis is to operate both processes at the pressure of a conventional MeOH plant, i.e. 

The minimum loop pressure for a MeOH synthesis is determined by the thermodynamics of the reactions taking place. 

Fig. 5. Conversion of synthesis gas versus pressure at 250 C for MeOH synthesis alone and for combined MeOH/DME synthesis.

Reduction of CO to compounds containing C—H and/or C—C bonds has been actively studied because these reductions are important in the conversion of coal-derived CO into fuels and organic chemicals. Reactions in this class include methanation, MeOH synthesis, and Fischer-Tropsch (F-T) synthesis, e.g., equations (b)-(d) equation (d) yields a range of hydrocarbon and oxygenate (ROH and polyol) products. 

Catalyzed reductions of CO by have been long known, beginning with methanation, equation (a), in 1902 . MeOH synthesis, equation (b) in 1923, and Fischer-Tropsch (F-T) synthesis, equation (c) in 1923. ... 

Exchange reactions of methanol/D2 show that the exchange of OH to OD is a very easy process under the conditions of alcohol synthesis so that such a step can be safely postulated in the schemes for MeOH synthesis. 

Fig. 8. TMeOH vs. space time during steady-state MeOH synthesis at 220°C (used to ) 16 ...

Dimethyl ether ((CH3)20, DME) is also expected to be a clean energy source with large calorific value and excellent transportation properties, almost same as LPG Industrially, DME is generally produced in a two-step process namely, MeOH formation and its dehydration. It should be pointed out that its equilibrium yield is far beyond that of MeOH. Therefore the use of a bifiinctional catalytic system that is, a combination of a MeOH synthesis component with a dehydration partner can avoid the equilibrium limit of MeOH. 

AI2O3. Similar tendencies were also observed for the other Cu/ZnO ratios of 4/6 and 5/5. This is explained well by the concept that DME is produced by a series reaction via MeOH synthesis (BF gas -> MeOH -> DME). 

Figure 6 shows XRD (X-ray diffraction) patterns of the Cu-ZnO-AI2O3 catalysts used, in which three substances of Cu, ZnO and ZnAl204 were detected as main peaks. Peaks of A1 or AI2O3 never appeared in spite of our expectation. With increasing AI2O3 from 0 to 14.3 mol%, peaks of Cu and ZnO were broadened and their heights became smaller. In this range, the catalysts became more active for DME and MeOH synthesis with increasing AI2O3 (see Fig. 4). In contrast, 23.1 and 33.0 mol%. 203 catalysts showed ZnAl204 peaks instead of ZnO peaks, however its peak width was very broad. In addition, the Cu peaks of the 33.0 mol% catalyst became very weak.

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