Selective catalytic reduction of NOx by low-temperature NH3 over MnxZr1 mixed-oxide catalysts

MnxZr1 series catalysts were prepared by a coprecipitation method.

Preparation and Flame Retardant Properties of Calcium–Aluminium Hydrotalcite with Root Cutting Silicate Layers as Bamboo Flame Retardants

Bamboo has been widely used in architecture, decoration and other fields because of its advantages of short growth period, high strength and degradability. However, bamboo, as a combustible material like wood, are easy to burn and cause building fires. However, the existing bamboo water-based flame retardants have some shortcomings, such as strong hygroscopicity and easy loss, which limits the application of bamboo products. In order to improve the flame retardant performance of bamboo, CaAl-SiO2 layered double hydroxide (LDH) as bamboo flame retardant was synthesised by coprecipitation method. The influence of preparation technology on CaAl–SiO3–LDH structures and properties as well as the flame retardant and smoke suppression characteristics of flame retardant-treated bamboo was discussed. The results revealed that the crystallisation temperature, crystallisation time and crystallisation concentration of CaAl–SiO3–LDHs considerably affected its structure and properties. The optimum technological parameters for preparing CaAl–SiO3–LDHs by using the coprecipitation method are as follows: crystallisation temperature of 100 °C, crystallisation time of 9 h and Ca2+ solution molar concentration of 0.33 mol/L. Compared with nonflame-retardant wood, CaAl–SiO3–LDH flame retardant treatment delayed the peak time of the heat release rate by 20 s and the ignition time by 77.78% and increased the carbon residue rate by 9.54%. This study can provide reference for the research of new flame retardant for bamboo products.

Synthesis of TiO2-NiFe2O4 nanocomposites using coprecipitation method as photocatalyst for methylene blue removal

Methylene blue, a basic dye that is important in the coloring process in the textile industry. However, the use of the dye Methylene blue is hazardous for the skin, the eyes, and swallowed. Three composition types of TiO2-NiFe2O4 nanocomposites (75:25, 50:50, and 25:75) had been synthesized using a simple coprecipitation method. The photodegradation and adsorption performance of the nanocomposites were also evaluated. Based on X-ray diffraction analysis, both the titania anatase and nickel ferrite spinel phases appeared in each nanocomposite’s diffraction pattern. The average crystallite size of the nanocomposites was 38 nm, 33 nm, and 41 nm for compositions 75:25, 50:50, and 25:75, respectively. The optimum photodegradation activity of TiO2-NiFe2O4 nanocomposites was achieved at composition 75:25 %mol with >99% methylene blue degraded during 120 minutes of UV irradiation time. However, all nanocomposites also have adsorption capability toward methylene blue with an optimum percentage of 98%. Therefore, TiO2-NiFe2O4 nanocomposites can be used either as photocatalysts or adsorbents for methylene blue removal in an aqueous solution.

Biosynthesis and characterization of zinc ferrite (ZnFe2O4) via Antidesma bunius L. fruit extract

Biosynthesis of ZnFe2O4 via Antidesma bunius L fruit extract has been carried out. In this synthesis, Zn(NO3)2.6H2O and Fe(NO3)3.9H2O were used which act as precursors of Zn2+ and Fe3+ ions with a coefficient ratio of 1:2 using the coprecipitation method with variations in calcination temperatures of 500 °C, 600 °C and 700 °C. The precursor used is NaOH. XRD data showed that there are diffraction peaks of ZnFe2O4 in all samples but at a calcination temperature of 700,°C the diffraction peaks of ZnFe2O4 with high intensity are more visible at 2Θ = 31.78°, 34.42°, 35.2°, 36.22°, 56.61° this peak corresponds to the peak ZnFe2O4 diffraction (JCPDS 22-1012) in addition there is also a peak of ZnO at 2Θ = 31.7°, 34.4°, 36.2°, 47.5°, 62.8°, 66.5° and 69.2° (JCPDS 36-1451). FTIR analysis showed that the Zn-O stretching group was at wave numbers 837 cm-1, 870 cm-1, 1058 cm-1, 1065 cm-1, and 1350 cm-1. The Zn-O-Zn strain is found at wave numbers 1350 cm-1, 1633 cm-1, and 1634 cm-1, respectively. The appearance of these bonding groups proves that the synthesis of ZnFe2O4 has been formed.

Development of Synthesis and Fabrication Process for Mn-CeO2 Foam via Two-Step Water-Splitting Cycle Hydrogen Production

The effects of doping manganese ions into a cerium oxide lattice for a thermochemical two-step water-splitting cycle to produce oxygen and hydrogen and new synthesis methods were experimentally investigated. In order to comparison of oxygen/hydrogen producing performance, pristine CeO2, a coprecipitation method for Mn-CeO2, and a direct depositing method for Mn-CeO2 with different particle sizes (50~75, 100–212, over 212 μm) and doping extents (0, 5, 15 mol%) were tested in the context of synthesis and fabrication processes of reactive metal oxide coated ceramic foam devices. Sample powders were coated onto zirconia (magnesium partially stabilized zirconia oxide, MPSZ) porous foam at 30 weight percent using spin coating or a direct depositing method, tested using a solar reactor at 1400 °C as a thermal reduction step and at 1200 °C as a water decomposition step for five repeated cycles. The sample foam devices were irradiated using a 3-kWth sun-simulator, and all reactive foam devices recorded successful oxygen/hydrogen production using the two-step water-splitting cycles. Among the seven sample devices, the 5 mol% Mn-CeO2 foam device, that synthesized using the coprecipitation method, showed the greatest hydrogen production. The newly suggested direct depositing method, with its contemporaneous synthesis and coating of the Mn-CeO2 foam device, showed successful oxygen/hydrogen production with a reduction in the manufacturing time and reactants, which was lossless compared to conventional spin coating processes. However, proposed direct depositing method still needs further investigation to improve its stability and long-term device durability.

Enhanced Reforming of Tar Based on Double-Effect Ni/CaO–Ca12Al14O33 Catalysts: Modified by Ce, Mg, and Fe

The double-effect Ni-based catalysts, modified with Ce, Mg, and Fe and synthesized by the coprecipitation method, were applied into the enhanced steam reforming process of real tar. The effects of the catalysts with different doping mass proportions (3, 6, 9, and 12%) of Ce, Mg, and Fe on the H2 yield, and H2 and CO2 concentrations were studied. The results revealed that the tar reforming efficiency was improved with appropriate proportions of the additives added. The Ce- or Mg-doped catalyst could change the distribution or morphology of the active component Ni. The modified catalyst with 6% Ce or 3% Mg doping showed the best catalytic activity in the reforming experiment, with the H2 yield reaching 86.84% or 85.22%, respectively. The Fe-doped catalyst could form an Ni–Fe alloy and improve the stability of the catalyst, and the better catalytic activity can be obtained at 9 and 12% Fe doping, with the H2 yield reaching 85.54 and 85.80%, respectively.

Structural evolution and synthesis mechanism of ytterbium disilicate powders prepared by cocurrent chemical coprecipitation method

Ytterbium disilicate powders were synthesized by cocurrent chemical coprecipitation method. The influence of Si/Yb molar ratio and calcination temperature on compositions and structures of Yb2Si2O7 products were investigated. The formation mechanism and thermal behavior of precursor as well as the phase evolution of Yb2Si2O7 were also discussed in depth. Results show that pure β-Yb2Si2O7 powders with nanoscale size can be obtained from the precursor with Si/Yb molar ratio of 1.1 after being calcinated at temperatures above 1200 ℃. The Yb2Si2O7 precursor is an amorphous polymer cross-linked with -[Si-O-Yb]- chain segments which are formed though Yb atoms embedding in the -[Si-O-Si]- network. After a continuous dihydroxylation and structural ordering, the amorphous precursor transformed to α-Yb2Si2O7 crystals by atomic rearrangement. Elevated calcination temperature can induce to the coordination structures and environment evolutions of structural units and then converted to stable (Si2O7) groups and (YbO6) polyhedrons, which results in the formation of β-Yb2Si2O7.