Competition between acidic sites and hydrogenation sites in Cu/ZrO_(2) catalysts with different crystal phases for conversion of biomass-derived organics

Oxides with different crystal phases can have important effects on the configuration of surface atoms,which can further affect the distribution of hydrogenation sites and acidic sites as well as the competitions of these varied types of catalytic sites.This could be potentially used to tailor the distribution of the products.In this study,zirconium oxides with different crystal phases supported copper catalysts were prepared for the hydrogenation of the biomass-derived furfural,vanillin,etc.The results showed that both calcination temperature and Cu species affected the shift of zirconia from tetragonal phase to the monoclinic phase.Monoclinic zirconia supported copper catalyst can effectively catalyze the hydrogenation of furfural to furfuryl alcohol via hydrogenation route due to its low amount of Brønsted acidic sites,although the surface area and the exposed metallic Cu surface area were much lower than the tetragonal zirconia supported copper catalyst.Zirconia with tetragonal or tetragonal/monoclinic phases supported copper catalysts contain abundant acidic sites and especially the Br?nsted acidic sites,which catalyzed mainly the conversion of furfural via the acid-catalyzed routes such as the acetalization,rather than the hydrogenation.The acidic sites over the Cu/ZrO_(2)catalyst played more predominant roles than the hydrogenation sites in determining the conversion of the organics like furfural and vanillin.

Formation Sites and Microscopic Conformation Study on the Konjac Glucomannan Molecular Helices

In this work, the formation sites, helical parameters and hydrogen bond positions of Konjac glucomannan molecular helices were investigated using molecular dynamic simulation method. To our interest, the KGM chain is mainly composed by local left and right helix struetttres. The formation sites of KGM chain might locate at the chain-segments containing acetyl groups, and the left helix is the favorable conformation of KGM. Temperature-dependent molecule conformation study indicates that the right helix is dominant when the temperature is lower than 343 K, above which, however, the left helix is dominating （right helix disappears）. In addition, intramolecular hydrogen bonds in the left helix can be found at the -OH groups on C（2）, C（4） and C（6） of mannose residues; comparably, the intramolecular hydrogen bonds in the right helix can be mainly observed at the -OH groups on C（4） and C（6） of the mannose residues and C（3） of the glucose residues. In conclusion, molecular dynamic simulation is an efficient method for the microscopic conformation study of glucomannan molecular helices.

Influence of Zr, Ce, and La on Co_3O_4 catalyst for CO_2 methanation at low temperature

The Co3O4 and Zr-,Ce-,and La-Co3O4 catalysts were prepared,characterized,and applied to produce CH4 from CO2 catalytic hydrogenation in low temperature as 140–220℃.The results indicated that the addition of Zr,Ce,or La to the Co3O4 decreased the crystallite sizes of Co and the outer-shell electron density of Co^3＋,and increased the specific surface area,which would provide more active sites for the CO2 methanation.Especially,the addition of Zr also changed the reducing state of Co3O4 via an obvious change in the interaction between Co3O4 and ZrO2.Furthermore,Zr doped into the Co3O4 increased the basic intensity of the weak and medium basic sites,as well as the amount of Lewis acid sites,and Bronsted acid sites were also found on the Zr-Co3O4 surface.The introduction of Zr,Ce,or La favored the production of CH4,and the Zr-Co3O4catalyst exhibited the highest CO2 conversion（58.2%）and CH4 selectivity（100%）at 200℃,and 0.5 MPa with a gaseous hourly space velocity of 18,000 ml·g^-1（cat）·h^-1,and the catalytic activity of CO2methanation for the Zr-,Ce-,and La-Co3O4 exhibited more stable than Co3O4 in a 20-h reaction.

Hydrogenation properties of(V_(0.85)Fe_(0.15))_(100-x)M_(x)-Ce BCC solid solution alloys with M=Cr,Mo,Al

The structure and hydrogenation properties of (V_(0.85)Fe_(0.15))_(100-x)M_(x)-Ce(x=0,1,3,5;at%) alloys with M=Cr,Mo,Al were investigated.All the alloys show the same phase composition consisting of BCC matric and CeO_(2)phases which distribute along the grain boundary.The hydrogen capacities of (V_(0.85)Fe_(0.15))_(100-x)M_(x)-Ce change little with M,and none of them exceeds 2.0 wt%.But the plateau pressure shows remarkable linearly variation with the amount of M and the lattice parameter of BCC matric.The additions of Cr,Mo and A1 raise the plateau,but the linear relation of plateau versus BCC lattice parameter of Mo/Al-added alloys is opposite to that of Cr-added alloys and many other conventional hydrogen storage alloys.The radius of hydrogen site is introduced to explain the inconsistent.The plateau pressure of (V_(0.85)Fe_(0.15))_(100-x)M_(x)-Ce with any kind of M added increases with the contraction of the hydrogen site.The plateau pressure of (V_(0.85)Fe_(0.15))_(100-x)M_(x)-Ce can also be reflected by the stability of hydride which is judged by the enthalpy change during the dehydrogenation.