The objective of this work is to study the effect of combining methanol synthesis and methanol dehydration in a single reactor, on the catalytic performance. For this, the influence of operating conditions (space velocity, temperature, pressure, time on stream and syngas composition) on the activity, selectivity and stability was studied for the methanol synthesis, methanol dehydration and direct DME synthesis. The experiments were conducted in a micro packed bed reactor-heat exchanger. Catalyst, either Cu-ZnO-based methanol synthesis catalysts, H-ZSM-5 or γ-alumina methanol dehydration catalysts, or a physical mixture of these, was used. Experiments were conducted at temperature, pressure and space velocity ranges of, 210-270oC, 10-50 bar and 100-700 nml/(min×gr catalyst), respectively. Figure 1 illustrates the product yields for methanol synthesis and direct DME synthesis reactions under identical operating conditions. The direct synthesis was controlled by methanol formation, and the space velocity is based on the methanol synthesis catalyst accordingly. The results suggest that combining methanol synthesis and dehydration has a negative effect on the methanol formation kinetics, which can be observed at lower temperatures where the effect of the reverse reaction on methanol synthesis is negligible. Similar conclusions can be drawn using a syngas with H2/CO molar ratio of 1. It is also found that the dehydration reaction introduces a negative effect on the stability of the methanol synthesis catalyst. The same trend was also seen using γ-alumina as a dehydration catalyst. The origin of the observed phenomena will be further discussed and investigated, including the possible inhibition by the dehydration products (DME and H2O).

Direct dimethyl ether synthesis from synthesis gas: The influence of methanol dehydration on methanol synthesis reaction

249th National Meeting (2015)

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