No abstract

A citric acid ligand assisted self-assembly method is used for the synthesis of ternary mesoporous cerium lanthanum solid solution doped with metal elements (Co, Zr, Mg). Their textural property was characterized by X-ray diffraction, transmission electron microscopy, N2 adsorption-desorption, X-ray photoelectron spectroscopy and TPD techniques, and so on. The results of catalytic testing for synthesis of dimethyl carbonate (DMC) from CH3OH and CO2 indicated that the DMC yield reached 316 mmol/g on Ce-La-Co solid solution when the reaction temperature was 413 K and the reaction pressure was 8.0 MPa. It was found that Co had synergistic effect with La and Ce, doping of Co on the mesoporous Ce-La solid solution was helpful to increase the surface area of the catalyst, promote CO2 adsorption and activation, and improve the redox performance of solid solution catalyst. The conversion of Co2+ to Co3+ resulted in the continuous redox cycle between Ce4+ and Ce3+, and the oxygen vacancy content of the catalyst was increased. Studies have shown that the catalytic performance of Ce-La-Co solid solution is positively correlated with oxygen vacancy content. On this basis, the reaction mechanism of DMC synthesis from CO2 and CH3OH on the catalyst was speculated.

Several alkylammonium salts were used in the study of α-titanium phosphate (α-TiP) intercalation chemistry. The characterization results demonstrated that the expected intercalation by direct ion exchange could be successfully achieved without any addition of an extra amine substance. Our findings are different from the current opinion that by the ion-exchange method, without the assistance of bases, large cations are difficult to exchange into the narrow interlayer space of α-tetravalent metal phosphate directly because of the small interlayer distance. Studies found that alkylammonium cations, for example, n-butylammonium cation, could be directly exchanged into the interlayer space merely by choosing salts with appropriate anions such as phosphate, phosphite, sulfite, citrate, and malate ions. In the case of phosphates, besides n-butylammonium, the exchange of n-hexylammonium, cyclohexylammonium, and pyridinium with interlayer protons was investigated and successfully accomplished as well. The uptake values for these four cations were 0.420, 0.595, 0.571, and 0.335 g/g, respectively. A mechanism study revealed that although the relevant exchange reaction seemed only to involve the proton of α-TiP and the alkylammonium cation of the salt, the strength of the conjugate acid of the anion from the salt-the counterion-was proven to be the key factor in this process.

A new noble metal-free Ni–Co–P/HAP amorphous alloy catalyst was developed, and it showed excellent catalytic activity for in situ hydrodeoxygenation of vanillin to 2-methoxy-4-methylphenol with formic acid as a hydrogen source.