High Copper Surface Research Articles

Fabrication and Properties of W-Cu Functionally Graded Material by Tape-Casting

In this paper, the W-Cu functionally graded material (FGM) was prepared by using the non-aqueous tape-casting technique combined with vacuum hot-pressing sintering. The graded composite material with high density, uniform transition and graded component was designed by 7 layers with the copper content range from 40 to 100 wt. %. Then the structures and properties of the composite were characterized. The scanning acoustic microscope (SAM) results for the W-Cu graded material showed that the interface between different layers was of high smoothness and parallel. The SEM-EDS results of cross section show that the W and Cu content changed gradually along the laminating direction after sintering. The equivalent electrical conductivity and the equivalent thermal conductivity of the W-Cu graded material were 0.3976×108 S/m and 323.5 W/(m·K), respectively, which were much higher than that of the W-40 wt. % Cu homogeneous composite. The Vickers hardness of the high tungsten content surface and the high copper surface were 163 HV and 80 HV, respectively, which were same with that of the homogeneous material.

The preparation and properties of coprecipitated Cu–Zr–Y and Cu–Zr–La catalysts used for the steam reforming of methanol

A series of Cu–zirconia catalysts containing various additives (Y 2O 3, La 2O 3, Al 2O 3 and CeO 2) have been prepared by coprecipitation and their activities and stabilities under operating conditions have been obtained for the steam reforming of methanol. It has been found that an yttria-promoted catalyst containing 30 mol% Cu and 20 mol% of Y 2O 3 is not only very active but is also very stable under reaction conditions. The yttria appears to stabilise a high copper surface area and may also have a slight promotional effect on the copper. The results obtained with this material compare very favourably with data for the best catalysts reported in the literature.

Study of iron-promoted Cu/SiO 2 catalyst on high temperature reverse water gas shift reaction

The reverse water gas shift reaction over Cu/SiO 2 catalysts with and without iron promoter was studied by means of CO 2 hydrogenation, temperature programmed reduction (TPR), temperature programmed desorption (TPD) and X-ray diffraction (XRD). By addition of a small amount of iron (0.3% Fe to 10% Cu/SiO 2), the catalytic activity and stability of Cu/SiO 2 at high temperatures were effectively improved. The Cu/SiO 2 catalyst had low copper surface area when it was calcined and reduced at 600 °C. Due to the addition of iron, Cu-Fe catalysts provided high copper surface area, even if these catalysts were pretreated at high temperatures. At 600 °C and atmospheric pressure, the Cu-Fe catalysts exhibited high and constant catalytic activity up to 120 h. In contrast, the 10% Cu/SiO 2 catalysts without Fe additives deactivated rapidly. Loss of copper surface area and oxidation of copper are the main factors causing the decay of catalytic activity of Cu/SiO 2 at high temperatures. The new active species located at the interface between Cu and Fe particles is proposed to be an important factor in enhancing catalytic activity. On the other hand, Fe in Cu-Fe catalysts surprisingly inhibits the sintering and oxidation of Cu and elevates the catalytic stability of Cu-Fe catalysts. The formation of small particles of iron species around Cu particles effectively prevents sintering of Cu at high temperatures. Oxygen releasing from the reaction on Cu can rapidly diffuse to Fe surfaces to form Fe oxides through a spillover process. This keeps Cu in its reduced state. Iron also offers similar promotions in catalytic activity, thermal stability and prevention of copper oxidation for Cu/Al 2O 3 and commercial Cu/Zn/Al catalysts.

Hydrogenolysis of Dimethyl Maleate on Cu/ZnO/Al2O3 Catalysts

The gas-phase hydrogenolysis of dimethyl maleate at 10 bar and 513 K was investigated over a series of co-precipitated Cu/ZnO/Al 2 O 3 catalysts. High copper surface areas were obtained with a molar Al content of 5% in the catalysts. Upon variation of composition at fixed alumina content, copper surface areas increased until the molar ratio exceeded Cu/Zn=2:1. At the given reaction conditions, dimethyl maleate was completely converted to dimethyl succinate, which further reacted to methanol, γ-butyrolactone, tetrahydrofuran, and water over all catalysts. Initial deactivation of catalysts was mainly caused by a loss of copper surface area. The catalyst with a molar Cu/Zn ratio of 1:2 was found to be most active and stable under reaction conditions.