Design of Reduction Process of SnO2 by CH4 for Efficient Sn Recovery

Role of support bio-templating in Ni/Al2O3 catalysts for hydrogen production via dry reforming of methane

Bio-templating, a synthetic approach inspired by nature, is an emerging area in material engineering. In this study, waste leaves of Sycamore were utilized as a bio-template for producing alumina support to prepare catalyst. The performance of Ni and Ce impregnated on bio-templated alumina support was investigated in dry reforming of methane for the first time. The effect of process and catalytic variables were examined in detail. The results showed that impregnation of 20% Ni and 3% Ce on the bio-templated alumina led to improved Ni dispersion and achieving the maximum CH4 conversion of 88.7%, CO2 conversion of 78.5%, and H2 yield of 85.3%, compared to 84.4%, 75.6% and 83.4% for the non-templated catalyst at 700 °C, respectively. Detailed characterization of the catalysts revealed that the enhanced performance in the bio-templated catalyst could be attributed to smaller Ni particles, superior dispersion of Ni on the support, the mesoporous structure of alumina, and the larger surface area of support. Furthermore, analysis of the used catalyst showed reduced coke formation on the catalyst surface and high stability of bio-templated catalysts, highlighting the main advantage of bio-templated catalysts over non-templated ones. The findings presented in this study contribute to the potential future applications of bio-templating materials and shed light on the rational design of bio-templating materials.

Formation of spherical Sn particles by reducing SnO2 film in floating wire-assisted H2/Ar plasma at atmospheric pressure

A green method to synthesize spherical Sn particles by reducing SnO₂ film in atmospheric-pressure H₂/Ar plasma at low temperatures for various applications is presented. The floating wire-assisted remotely-generated plasma with a mixture of 0.05% H₂/Ar gas formed spherical metallic Sn particles by reducing a SnO₂ layer on glass substrate. During the reduction process, H radical density was measured by using vacuum ultraviolet absorption spectroscopy, and plasma properties including electron density and gas temperature were diagnosed by optical emission spectroscopy. The inductively coupled generated plasma with a high electron density of 10¹⁴ cm⁻³, a hydrogen atom density of 10¹⁴ cm⁻³, and a gas temperature of 940 K was obtained at a remote region distance of 150 mm where the SnO₂/glass substrate was placed for plasma treatment. The process has been modeled on the spherical Sn formation based on the reduction of SnO₂ films using H radicals. Depending on the treatment condition, the total reduction area, where spherical Sn particles formed, was enlarged and could reach 300 mm² after 2 min. The substrate temperature affected the expansion rate of the total reduction area and the growth of the Sn spheres.

Effect of Pd/Ce loading on the performance of Pd-Ce/γ-Al2O3 catalysts for toluene abatement

A single metal Pd/γ-Al₂O₃ catalyst and a bimetallic Pd-Ce/γ-Al₂O₃ catalyst were prepared by the equal-volume impregnation method to investigate the effect of CeO₂ loading on the catalytic oxidation of toluene. The specific surface area, surface morphology, and redox performance of the catalyst were characterized by N₂ desorption, scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), H₂-TPR, O₂-TPD, and electron paramagnetic resonance (EPR). The results showed that bimetal catalysts loaded CeO₂ had smaller nano-PdO particles than those of the Pd/γ-Al₂O₃ catalyst. Compared with the catalyst of 0.2Pd/γ-Al₂O₃ (percentage of mass, the same as below), the catalyst doped with 0.3CeO₂ had a stronger reduction peak, which was shifted to the low-temperature zone by more than 80 °C. The results of XPS and O₂-TPD showed that the introduction of CeO₂ provided more surface oxygen vacancy for the catalyst and enhanced its catalytic oxidation ability, and the amount of desorbed O₂ increased from 3.55 μmol/g to 8.54 μmol/g. The results of EPR were that the addition of CeO₂ increased the content of active oxygen species and oxygen vacancies on the surface of the catalysts, which might be due to the supply of electrons to the O₂ and PdO during the Ce³⁺toCe⁴⁺ conversion process. That could have accelerated the catalytic reaction process. Compared with the single precious metal catalyst, the T₁₀ and T₉₀ of the Pd-Ce/γ-Al₂O₃ catalyst were decreased by 22 °C and 40 °C, respectively.

Efficient Sn Recovery from SnO2 by Alkane (CxHy=2x+2, 0 ≤ x ≤ 4) Reduction

We study the mechanism of alkane reduction of SnO2 for efficient low-temperature recovery of Sn from SnO2. Based on thermodynamic simulation results, we comparatively analyze the reduction behavior and the efficiency of SnO2 reduction by H2 and alkanes (CxHy=2x+2, 0 ≤ x ≤ 4). We found that alkanes (n·CxHy) with the higher nx generally complete the reduction of SnO2 (T100) at the lower temperature. Moreover, the T100 of the SnO2 reduction by alkanes (n·CxHy) was decreased from the T100 of pure hydrogen with the same amount of hydrogen atoms (n·Hy). We found that the concentration of a gas phase product mixture, the amount of the produced solid carbon, and the T100 complementary vary as a function of the nx and ny, the total amount of carbon and hydrogen atoms in the reducing gas phase molecules. Our results demonstrate a viability of the low temperature reduction method of SnO2 by alkanes for efficient recovery of Sn from SnO2, which can be applied for Sn recovery from Sn containing industrial wastes or Sn ores with economic value added that is held by the co-produced H2.

A value-added multistage utilization process for the gradient-recovery tin, iron and preparing composite phase change materials (C-PCMs) from tailings

Tin-, iron-bearing tailing is a typically hazardous solid waste in China, which contains plenty of valuable tin, iron elements and is not utilized effectively. In this study, a multistage utilization process was put forward to get the utmost out of the valuable elements (tin and iron) from the tailings, and a gradient-recovery method with three procedures was demonstrated: (1) An activated roasting followed by magnetic separation process was conducted under CO-CO2 atmosphere, tin and iron were efficiently separated during magnetic separation process, and 90.8 wt% iron was enriched in magnetic materials while tin entered into non-magnetic materials; (2) The tin-enriched non-magnetic materials were briquetted with CaCl2 and anthracite and roasted, then tin-rich dusts were collected during the chloridizing roasting process; (3) The roasted briquettes were infiltrated in melting NaNO3 to prepare NaNO3/C-PCMs by a infiltration method. Three kinds of products were obtained from the tailings by the novel process: magnetic concentrates containing 64.53 wt.% TFe, tin-rich dusts containg 52.4 wt.% TSn and NaNO3/C-PCMs for high temperature heat storage. Such a comprehensive and clean utilization method for tin-, iron-bearing tailings produced no secondary hazardous solid wastes, and had great potential for practical application.