Silver modified Cu/SiO2 catalyst for the hydrogenation of methyl acetate to ethanol

A series of silver modified Cu/SiO2 catalysts were synthesized with ammonia-evaporation method and applied in vapor-phase hydrogenation of methyl acetate to ethanol.The influence of additive‘Ag’on the structural evolution of catalyst was systematically studied by several characterization techniques,such as N2 adsorption–desorption,N2O titration,PXRD,FTIR,in-situ FTIR,H2-TPR,H2-TPD,XPS and TEM.Results showed that incorporation of a small amount of Ag could enhance the structural stability,and the strong interaction between Cu and Ag species was conducive to increase the dispersion of copper species and create a suitable Cu+/(Cu0+Cu+)ratio,which was proposed to be responsible for the improved catalytic activity.The maximum conversion of MA(94.1%)and selectivity of ethanol(91.3%)over optimized Cu-0.5 Ag/SiO2 and 120 h on stream without deactivation under optimal conditions demonstrates its excellent stability.

Structures and oxygen storage/release capacities of CexZr1-xO2:Effects of Zr content and preparation method

Ceria-zirconia solid solution has been prepared by the urea grind combustion and citric acid sol-gel methods for catalytic applications as oxygen storage/release materials in this study. The properties and oxygen storage/release capacities of samples with different Zr contents were characterized and evaluated by X-ray diffraction（XRD）, Nadsorption, scanning electron microscopy（SEM）, Raman spectroscopy, and insitu CO–COlooping test. The results demonstrate that the samples prepared by two methods are all of excellent lattice [O] release/storage properties and maintain good long-term cycle stability. But the preparation method significantly impacts the homogeneity of samples related to their redox properties and the content of Zr over 20%, which greatly changed the properties of ceria-zirconia solid solutions and caused their changing of crystalline symmetry from cubic to tetragonal. The samples prepared by citric acid solgel method are of more homogeneous particle sizes and higher specific surface areas than that by urea grind combustion method, which is benefit to the oxygen release rather than oxygen storage. The bulk oxygen amount migrated to surface increases with the increasing Zr content, however, the amount of lattice oxygen migration decreases when Zr content is over 20%. When Zr content is 20%, the differences of storage/release capacities from two different preparation methods are reduced at high temperature in the long-term loop reaction.

Extensional tectonics and North China Craton destruction:Insights from the magnetic susceptibility anisotropy(AMS)of granite and metamorphic core complex

The craton is a long-lived stable geologic unit on the Earth’s surface.However,since the Mesozoic,the North China Craton(NCC)experienced large-scale lithospheric removal,the fundamental change of physical and chemical characteristics of the lithospheric mantle,widely distributed crustal deformation,and extensive magmatism.This complex evolution contrary to other cratons is called the NCC destruction.Widespread magmatism in the eastern NCC is an important response to the lithospheric removal at depth and crustal deformation on the surface.The plutons emplace under a tectonic context and therefore record the information of the tectonics;especially,the anisotropy magnetic susceptibility(AMS)pattern of the pluton was acquired with the influence of regional stress.In the past fifteen years,about 22 plutons intruding during the different periods from the Late Triassic to the late stage of the Early Cretaceous have been studied with AMS.The emplacement mechanisms of plutons and the contemporary tectonic setting were discussed to constrain their relationship with the NCC destruction in different stages of magmatism.As a result,the Late Triassic,Early Jurassic,and Late Jurassic plutons exhibit consistent N(E)-S(W)trending magnetic lineations.The early stage of Early Cretaceous plutons display NW-SE trending magnetic lineations,while the late stage of Early Cretaceous plutons show magnetic lineations with various orientations.Combined with previous studies,it is concluded that the emplacements of the plutons intruding in these three stages were controlled by weak N(E)-S(W)trending extension,regional NW-SE trending extension,and weak extension in the shallow crustal level,respectively.The transformation of regional extension from the N(E)-S(W)to the NW-SE direction was accompanied by a strain-increasing tendency.The extensional tectonics in the eastern NCC was interpreted to represent the interaction between Mongol-Okhotsk belt,PaleoPacific plate,and eastern Eurasian continent.