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In commercial methanol production from syngas, the conversion is thermodynamically limited to 0.3-0.7 leading to large recycles of non-converted syngas. This problem can be overcome to a significant extent by in situ condensation of methanol during its synthesis which is possible nowadays due to the availability of highly active catalysts allowing for lower reactor temperatures. For the first time, in situ methanol condensation at 20 MPa and 473 K was demonstrated visually in a view cell. The condensation of reaction products (mainly methanol and water) drives the equilibrium reactions nearly to completion, as is demonstrated experimentally in a packed bed reactor and supported by thermodynamic calculations. Contrary to conventional methanol synthesis, once-through operation becomes possible avoiding recycling of unconverted syngas, which can be economically beneficial for industrial stakeholders. (C) 2012 Elsevier Ltd. All rights reserved.

An explorative screening study with Pt/CeZrO2, Ni/ZrO2. Ni/CaO-6Al(2)O(3), NiCu/CeZrO2, and a CuZn alloy was carried out to investigate the influence of different catalysts on the carbon-to-gas efficiency and gas composition in the reforming of glycerol in supercritical water. Experiments were conducted at 255-270 bar in a continuous set-up, with temperatures ranging from 375 to 700 degrees C. a feed concentration of 10 wt%, and a residence time of 8-87 s. The catalysts promoted the decomposition of glycerol significantly. At 674 degrees C the conversion of glycerol without catalyst was approximately 40%, while in the presence of catalysts (almost) complete conversion was obtained. All catalysts promoted the water-gas shift reaction, while the ones based on Ni also promoted methanation. Visual coke formation was significant for Ni/ZrO2 and Pt/CeZrO2, which might be responsible for the observed reduction in activity at longer runtimes for these two catalysts. The specific surface area of all catalysts, apart from CuZn, decreased after contact with water at supercritical conditions. Except for NiCu/CeZrO2, XRD analysis indicated only minor changes in crystal structure of the supports, confirming the stability and suitability of these supports in supercritical water. (C) 2012 Elsevier B.V. All rights reserved.

An integrated process for the synthesis of methanol from aqueous glycerol involving reforming of the feed to syngas followed by methanol synthesis is successfully demonstrated in a continuous bench scale unit. Glycerol reforming was carried out at pressures of 24-27 MPa and temperatures of 948-998 K with a throughput of approximately 1 kg aqueous feed/h (3-10 wt.% glycerol) leading to high glycerol conversions of (95.0-99.9%) and syngas with a composition range of H-2/CO/CO2/CxHy = 44-67/1-21/16-34/2-18 vol.%. The effluent water of the process was recycled at high pressure, reducing the water consumption of the process significantly. Subsequent syngas conversion to methanol was carried out in a packed bed reactor at temperatures between 468 and 518 K and pressures between 24 and 27 MPa using a commercial methanol catalyst (Cu/ZnO/Al2O3). The maximum yield of methanol based on glycerol intake was 0.62 kg methanol/kg glycerol for an experiment with a time on stream of 16 h, which corresponds to a carbon conversion (carbon in methanol over carbon in glycerol) of 60%. This value is close to the maximum theoretical yield of 78% based on stoichiometric considerations. (C) 2012 Elsevier B.V. All rights reserved.

Reforming of pure glycerol, crude glycerin, and methanol (pure and in the presence of Na(2)CO(3)) in supercritical water was investigated. Continuous experiments were carried out at temperatures between 450 and 650 degrees C, residence times between 6 and 173 s, and feed concentrations of 3-20 wt%. For methanol the gas products are mainly H(2), CO(2), and CO. The carbon-to-gas efficiency and the observed activation energy for pure methanol are higher than for methanol with Na(2)CO(3). This can be explained by assuming different decomposition mechanisms for pure methanol and methanol with Na(2)CO(3). For glycerol, H(2), CO, CO(2), CH(4), and higher hydrocarbons are produced. The carbon-to-gas efficiencies of crude glycerin and pure glycerol are comparable. Overall, 2 of the 3 carbon atoms present in glycerol end up in carbon oxides, while 1 carbon atom becomes C(x)H(y). The overall mechanism of glycerol decomposition involves the dehydration of 1 mole of H(2)O/mole glycerol. For both, methanol and glycerol at carbon-to-gas efficiencies below 70%, the gas yields (mole/mole feed) and carbon-to-gas efficiency correlate well. (C) 2011 Elsevier B.V. All rights reserved.