Analysis of External and Internal Mass Transfer at Low Reynolds Numbers in a Multiple-Slit Packed Bed Microstructured Reactor for Synthesis of Methanol from Syngas

Abstract

The possibility of mass transfer limitations in an integrated micro packed bed reactor−heat exchanger (IMPBRHE) for methanol synthesis was experimentally investigated. Experiments were performed with three different particle size distributions (50−200 μm) of a Cu-based catalyst at 80 bar and 215−270 °C. Negligible effects of pore diffusion limitations on the performance of the reactor under methanol synthesis conditions for catalyst particle diameters up to 125 μm were found. Due to a very low Reynolds numbers (∼1) and dominance of molecular diffusion, variation of the total pressure was applied as a suitable technique to alter the diffusivities of reactants in the gas mixture by dilution, while keeping the reactant flow and partial pressure constant. No significant change in the CO conversion was observed in the temperature range 235−255 °C, pressure range 50−90 bar, and for reactant contact times of 105−308 ms•g/mL. The same procedure was applied to a laboratory fixed bed reactor with similar results. Possible heat transfer effects associated with the dilution were shown to be negligible. We therefore conclude that both reactor systems operate in the absence of external mass transfer limitations.

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

“…Cu(NO 3 ) 2 , Zn(NO 3 ) 2 and Al(NO 3 ) 3 , with sodium carbonate in a sodium acetate solution at 50°C and pH 7.0. Precipitates were then filtered, washed throughly with deionized water, dried overnight and calcined at 400°C for 2 h [21]. The resulting homemade catalyst has Cu/Zn/Al molar ratio of 22/57/21 as determined by ICP.…”

“…The reactor consists of a 6 cm long reaction slit with rectangular cross section of 8.8 × 1.5 mm 2 , sandwiched between cross flow channels for circulation of a heat transfer oil. Such reactors have been studied earlier under similar operating conditions for the methanol [21][22][23] and the direct DME [24][25][26] syntheses, and established as practically isothermal, isobaric, free from mass transfer limitations, and with a narrow residence time distribution. Premixed synthesis gas with H 2 to CO molar ratio of either 1 (Syngas-1) or 2 (Syngas-2) was used as feed.…”

“…The methanol and DME syntheses from the standard synthesis gases applied, are considered free from mass transfer limitations based on our previous studies [21,24]. However, changes in gas composition and pressure, alter the diffusivities of the components in a gas mixture.…”

“…Manipulation of the reactants' diffusivities by syngas dilution with He or Ar was performed earlier in our group [21,24] to demonstrate that both methanol and direct DME syntheses in similar microchannel reactors and under an identical range of operating conditions are free from mass transfer limitations. A summary of the results is also presented in Figure 9.…”

Preliminary Study Of Local Catalyst For Low Cost Methanol Synthesis As Subsequence Process Of A Model System Of Biomass Fluidized Bed Catalytic Gasification

“…Micro process technology is one of the promising breakthroughs involving Cu/ZnO-support catalyst in the Integrated micro packed bed reactor-heat exchanger (IMPBRHE) [4][5][6]. In this process, CO which is one of the pollutants will act as reactant together with H 2 and converted to methanol through a catalyzed process in the fixed bed reactor.…”