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In many reactions restricted by water, selective removal of water from the reaction system is critical and usually requires a membrane reactor. We found that a simple physical mixture of hydrophobic poly(divinylbenzene) with cobalt-manganese carbide could modulate a local environment of catalysts for rapidly shipping water product in syngas conversion. We were able to shift the water-sorption equilibrium on the catalyst surface, leading to a greater proportion of free surface that in turn raised the rate of syngas conversion by nearly a factor of 2. The carbon monoxide conversion reached 63.5%, and 71.4% of the hydrocarbon products were light olefins at 250°C, outperforming poly(divinylbenzene)-free catalyst under equivalent reaction conditions. The physically mixed CoMn carbide/poly(divinylbenzene) catalyst was durable in the continuous test for 120 hours.

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Strong metalÀ support interactions (SMSI) could improve the performance of nanoparticle catalysts through the electronic and geometric modulation of the reducible metal oxide supports. Here, SMSI is demonstrated to occur for catalysts with non-oxide carrier, such as NbOPO 4-supported Rh nanoparticles, under reduction treatment at low temperature. During CO 2 hydrogenation, this Rh/NbOPO 4 catalyst with SMSI exhibits impressive CO selectivity at high CO 2 conversion in a wide temperature range with hindered methanation. For example, over 98.9 % CO selectivity was obtained with 39.9 % CO 2 conversion at 500°C. Mechanism investigations demonstrate that the SMSI results in the formation of a metalÀ support interface with weaker CO adsorption than the metallic Rh sites, thus accelerating the CO desorption, which hinders deep hydrogenation. Rh nanoparticles with small diameter of about 1.1 nm is sinter-resistant with unchanged performance during a long-period test. This work might extend the investigation of SMSI from oxides to phosphate supports, which helps optimizing the selectivity and stability of metal nanoparticle catalysts.

This work reports a facile sodium cation (Na+)-mediated approach to synthesize α-calcium sulfate hemihydrate (α-HH) whiskers, with calcium sulfate dihydrate (DH) as the precursor, in ethylene glycol (EG)–water solutions at 95.0 °C and atmospheric pressure. The as-synthesized α-HH whiskers exhibit a width of 3–5 μm and a length of 600–700 μm, showing highly promising applications as reinforcing agents. An EG volume percentage of 22.5 vol % is necessary to drive the conversion of DH to α-HH at 95.0 °C, while the Na+ plays a crucial role in regulating both the conversion kinetics and the whisker quality. The conversion rate presents a volcano-like variation versus Na+ concentration (0.05–0.30 M) with the peak one achieved at 0.10 M Na+. Simultaneous boosting and retarding effects of the metallic cation on the DH-α-HH transformation were reported for the first time in alcohol–water systems. The tuning role of Na+ arises from its effect on the supersaturation for α-HH nucleation, the surface property of precursor DH via Na+ doping, as well as surface precipitate of the solid solution eugsterite (Na4Ca­(SO4)3·2H2O). In shape control, an increased Na+ concentration can elongate the α-HH but simultaneously raise the possibility of whisker agglomeration. The bridging action of Na+ among the crystal interfaces associated with the α-HH nucleation accounts for the morphology evolution of whiskers, and the optimal Na+ concentration is 0.075 M with an average aspect ratio of 105. This work provides a systematical investigation on the cation-mediated crystallization of α-HH whiskers, which should lead to a deeper understanding of whisker formation and advance their scale applications.

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