Effect of synthesis condition on the structural features of ni-ce bimetallic catalysts supported on functionalized multi-walled carbon nanotubes

In this paper, screening study in regards to preparation of functionalized multi-walled carbon nanotubes (FMWNT)-supported bi-metallic catalyst is discussed. Functional groups such as hydroxyl and carboxylic acid are introduced on multi-walled carbon nanotubes (MWCNT) surface using acid treatment method with the aid of probe-type ultrasonication. It is done by varying the concentration of nitric acid (HNO3) and sulphuric acid (H2SO4), acid volume ratio and treatment duration. Catalysts with different ratios of cerium and nickel nanoparticles which are either loaded inside or outside of MWCNT were prepared via ultrasonic-assisted co-precipitation method (NiCe/CNT). This is done to study the effect of cerium loadings. The characterization of the FMWNT and catalysts are carried out using transmission electron micrographs (TEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), and Raman spectroscopy. The results showed that the treatment in concentrated HNO3/H2SO4 with volume ratio of 3:1 for 8 h was the most suitable condition to generate large amount of surface oxygen group with minimal defects. The observations for each used condition were discussed thoroughly. Decoration of MWCNT with different metal loadings resulted in different distribution and dispersion of metal on nanotubes surface

Effect of reaction time and catalyst feed rate towards carbon nanotubes yields and purity by using rotary reactor

Continuous production of multi-walled carbon nanotubes (MWCNTs) by chemical vapor deposition (CVD) method was investigated in a rotary reactor. The aim of the study was to investigate the effect of catalyst feeding rate and reaction time on the MWCNTs production yield and purity. Bimetallic Co-Mo supported on MgO was used for the growth of MWCNTs and methane gas was used as the carbon precursor. The results indicated that the highest yield of MWCNTs production was attained at the reaction time of 180 min and catalyst feeding rate of 100 mg/min; this sample also had the highest purity (99.16%). SEM and TEM analyses of the synthesized product confirmed that most of the MWCNTs were sinuous and entangled with a uniform diameter. Raman spectroscopy indicated that the as-produced MWCNTs were mostly graphitic with few disordered carbon and impurities. The results highlighted that synthesized MWCNTs were highly pure which eliminates the need for MWCNTs purification process

Influence of Mechanical Screened Recycled Coarse Aggregates on Properties of Self-Compacting Concrete

The use of recycled coarse aggregates (RA) in concrete is a sustainable alternative to non-renewable natural aggregate (NA) to fabricate concrete products using in concrete structures. However, the adhered mortar on the surface of RA would considerably impact the qualities of concrete products. As a practical treatment procedure, mechanical screening can remove the adhered mortar. This research aims to study the influence of mechanical screening on the fundamental properties of RA and the resulting self-compacting concrete (SCC). The RA were mechanically screened up to four times, and their physical properties including particle size distribution, water absorption, and crushing value were investigated. The properties of RA-SCC including workability, density, compressive and tensile strengths, modulus of elasticity, and microstructure were also examined. The results demonstrated that screening reduced the water absorption of RA from 6.26% to 5.33% and consequently enhanced the workability of RA-SCC. Furthermore, it was shown that increasing the screening up to twice improved the mechanical properties of concrete. In particular, screening increased the compressive strength of concrete by 15–35% compared to the concrete with unscreened RA. Similar improvements were found in tensile strength as well as the elastic modulus results. The microstructure of screened RA-SCC was comparable to that of the control concrete, showing minimal porosity and cracks along the interfacial transition zone. In conclusion, once or twice screening is recommended to the recycling facility plant to remove adequate amount of adhered mortar and fines while preventing damages to the RA. Improving the quality of RA via mechanical screening is one of the promising approaches to increase their potential for use in concrete, thereby reducing extraction of natural resources and promoting a circular economy

A review of carbon-based and non-carbon-based catalyst supports for the selective catalytic reduction of nitric oxide

Various types of carbon-based and non-carbon-based catalyst supports for nitric oxide (NO) removal through selective catalytic reduction (SCR) with ammonia are examined in this review. A number of carbon-based materials, such as carbon nanotubes (CNTs), activated carbon (AC), and graphene (GR) and non-carbon-based materials, such as Zeolite Socony Mobil–5 (ZSM-5), TiO2, and Al2O3 supported materials, were identified as the most up-to-date and recently used catalysts for the removal of NO gas. The main focus of this review is the study of catalyst preparation methods, as this is highly correlated to the behaviour of NO removal. The general mechanisms involved in the system, the Langmuir–Hinshelwood or Eley–Riedeal mechanism, are also discussed. Characterisation analysis affecting the surface and chemical structure of the catalyst is also detailed in this work. Finally, a few major conclusions are drawn and future directions for work on the advancement of the SCR-NH3 catalyst are suggested

Understanding the performance and mechanism of Mg-containing oxides as support catalysts in the thermal dry reforming of methane

Dry reforming of methane (DRM) is one of the more promising methods for syngas (synthetic gas) production and co-utilization of methane and carbon dioxide, which are the main greenhouse gases. Magnesium is commonly applied in a Ni-based catalyst in DRM to improve catalyst performance and inhibit carbon deposition. The aim of this review is to gain better insight into recent developments on the use of Mg as a support or promoter for DRM catalysts. Its high basicity and high thermal stability make Mg suitable for introduction into the highly endothermic reaction of DRM. The introduction of Mg as a support or promoter for Ni-based catalysts allows for good metal dispersion on the catalyst surface, which consequently facilitates high catalytic activity and low catalyst deactivation. The mechanism of DRM and carbon formation and reduction are reviewed. This work further explores how different constraints, such as the synthesis method, metal loading, pretreatment, and operating conditions, influence the dry reforming reactions and product yields. In this review, different strategies for enhancing catalytic activity and the effect of metal dispersion on Mg-containing oxide catalysts are highlighted

Recent trends in graphene materials synthesized by CVD with various carbon precursors

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Co-synthesis of large-area graphene and syngas via CVD method from greenhouse gases

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