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The influence of feeding point in conventional stirred tank reactor and flow characteristics in micro‐reactor on the microstructure of Cu‐ZnO catalyst was studied. Cu‐Zn distribution in co‐precipitate was characterized by EDS and Zn fraction in zincian malachite was estimated from the 20 true1¯ peak shift in XRD pattern. The theory analysis and experimental results, combining with measurement of segregation index, show that the contact pattern and mixing of reactants in precipitation process determine the uniformity of Cu‐Zn distribution in initial co‐precipitates at the micro‐scale. The uniform Cu‐Zn distribution is favorable for the formation of zincian malachite with higher Zn fraction, whereas the uneven distribution could lead to either zincian malachite with lower Zn fraction or aurichalcite‐like nonmalachite. These differences in the precursor structure act on subsequent calcination and reduction, as well as their products. Along this path, mixing affects the evolution of the catalyst microstructure by means of Cu‐Zn distribution. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2647–2654, 2018

Cu/ZnO catalyst was prepared by co-precipitation method inside microchannel reactor and characterized by X-Ray diffraction (XRD), thermo gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HRTEM). The XRD analysis of precursors demonstrates that, compared with the sample prepared by conventional batch reactor, more Zn 2+ are incorporated into malachite structure，which is attributed to the relatively uniform distribution of Cu, Zn elements in initial precipitates caused by the excellent mixing performance of the microchannel reactor. Higher decomposition temperature of carbonate species trapped in the interfaces between CuO and ZnO and higher binding energy of Cu2p 3/2 indicate that sample prepared by the new reactor possess a stronger interface interaction, which derives from the more intimate contact between oxide components. This supposition is confirmed by the HRTEM images and the stronger interface interaction in the final reduced catalyst can improve catalytic performance on methanol synthesis.

A correlation based on an extensive literature database was proposed to estimate the infinite-dilution diffusion coefficients in supercritical fluids. The input parameters required for the correlation are temperature, the solute molar mass, the solute density near ambient temperature, the solvent critical temperature, the solvent critical density, and the solvent reduced density. The total average absolute deviation (AAD%) of the prediction is 6.55% for 153 binary systems and 1968 data points over the solvent reduced temperature range of 1.00-1.78, the solvent reduced density range of 0.21-2.34, the solute molar mass range of 58.08-885.40 g/mol, and the solute ambient-temperature density range of 0.63-2.04 g/cm 3 . Introduction of solute density into this new correlation makes it possible to predict with reasonable accuracy the diffusivities in supercritical fluids over a wide solute density range.

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