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Hydrogen production from waste plastics is an important alternative for managing waste plastics. This work addresses a promising technology for co-producing high value carbon nanotubes (CNTs) in addition to the production of hydrogen; thus significantly increasing the economic feasibility of the process. Catalyst design is a critical factor to control the production of hydrogen and CNTs. NiMnAl catalysts, prepared by a co-precipitation method, with different metal molar ratios were developed and investigated using a two-stage fixed-bed reactor. It was found that the NiMnAl catalyst with the higher Mn content produced a higher yield of carbon (57.7 wt.%). Analysis of the carbon on the NiMnAl catalysts showed it to consist of ~90 wt.% of carbon nanotubes. The CNTs were recovered from the catalyst and added at 2 wt.% to LDPE plastic to form a composite material. The tensile and flexural strength and the tensile and flexural modulus of the CNT composite material were significantly improved by the addition of the recovered CNTs. Thus it is suggested that cost-effective CNTs could be produced from waste plastics as by-product of the production of hydrogen, enhancing the potential applications of CNTs in the composite industry. [ABSTRACT FROM AUTHOR]

Selective catalytic reduction of NOx with NH3 (NH3-SCR) has been widely investigated to reduce NOx emissions from combustion processes, which cause environmental challenges. However, most of the current work on NOx reduction has focused on using feed gas without CO2 or containing small amounts of CO2. In the future, oxy-fuel combustion will play an important role for power generation, and this process generates high concentrations of CO2 in flue gas. Therefore, studies on the SCR process under concentrated CO2 atmosphere conditions are important for future SCR deployment in oxy-fuel combustion processes. In this work, Mn- and Ce-based catalysts using activated carbon as support were used to investigate the effect of CO2 on NO conversion. A N2 atmosphere was used for comparison. Different process conditions such as temperature, SO2 concentration, H2O content in the feed gas and space velocity were studied. Under Mn-Ce/AC conditions, the results suggested that Mn metal could reduce the inhibition effect of CO2 on the NO conversion, while Ce metal increased the inhibition effect of CO2. High space velocity also resulted in a reduction of CO2 inhibition on theNOconversion, although the overall performance of SCR was greatly reduced at high space velocity. Future investigations to design novel Mn-based catalysts are suggested to enhance the SCR performance under concentrated CO2 atmosphere conditions. [ABSTRACT FROM AUTHOR]

Producing both hydrogen and high-value carbon nanotubes (CNTs) derived from waste plastics is reported here using a pyrolysis-reforming technology comprising a two-stage reaction system, in the presence of steam and a Ni–Mn–Al catalyst. The waste plastics consisted of plastics from a motor oil container (MOC), commercial waste high density polyethylene (HDPE) and regranulated HDPE waste containing polyvinyl chloride (PVC). The results show that hydrogen can be produced from the pyrolysis-reforming process, but also carbon nanotubes are formed on the catalyst. However, the content of 0.3 wt.% polyvinyl chloride in the waste HDPE (HDPE/PVC) has been shown to poison the catalyst and significantly reduce the quantity and purity of CNTs. The presence of sulfur has shown less influence on the production of CNTs in terms of quantity and CNT morphologies. Around 94.4 mmol H2 g-1 plastic was obtained for the pyrolysis-reforming of HDPE waste in the presence of the Ni–Mn–Al catalyst and steam at a reforming temperature of 800 °C. The addition of steam in the process results in an increase of hydrogen production and reduction of carbon yield; in addition, the defects of CNTs, for example, edge dislocations were found to be increased with the introduction of steam (from Raman analysis). [ABSTRACT FROM AUTHOR]

Catalytic steam reforming of ethanol has been regarded as a promising way to produce hydrogen. However, catalytic deactivation is a key problem in the process. In this paper, a novel nano-Ni/SiO2 catalyst was prepared by a simple sol—gel method and compared to catalysts prepared by an impregnation method in relation to the steam reforming ethanol process. Good Ni dispersion and high BET surface areas (>700 m² g-1) were obtained for sol—gel catalysts, whereas only 1 m² g-1 surface area was obtained for the Ni/SiO2 impregnation catalyst. The results of catalytic steam reforming of ethanol showed that about twice of the hydrogen production was produced with the Ni/SiO2 catalyst prepared by sol—gel (around 0.2 g h-1) compared with that prepared by impregnation (around 0.1 g h-1). The analysis of the used catalysts showed that 10Ni/SiO2-B and 20Ni/SiO2-B presented the highest stability, while other catalysts were fragmented into small pieces after the reforming process, especially the catalysts prepared by impregnation. A novel catalyst has been produced that has been shown to be effective in the production of hydrogen from the steam reforming of ethanol. [ABSTRACT FROM AUTHOR]

Abstract: Pyrolysis of waste tyres was carried out with a two-stage bed reactor. The waste tyres were first pyrolysed in a fixed bed reactor, and then the evolved pyrolysis gases were passed through a secondary catalytic reactor filled with two types of zeolite catalysts, which were ultrastable Y-type (USY) and ZSM-5 catalyst. The catalytic temperatures were examined to determine their influence on the yield of product from the pyrolysis–catalyst of waste tyres. The results indicated that with the increase of catalytic temperature, the gas yield increased at the expense of oil yield. The light fractions (<220°C) distilled from the derived oils with the two catalyst were analyzed by gas chromatography/mass spectrometry (GC/MS). It showed that there was a dramatic increase in the concentration of single ring aromatic compounds in the light fractions of the derived oils after catalysis. For example, toluene reached a value in the light fraction of 11.62wt%, benzene 1.6wt%, m/p-xylene 12.27wt% and o-xylene 4.42wt%, with the catalysis of USY catalyst, at the pyrolysis temperature, catalysis temperature and catalyst/tyre ratio of 500, 400°C and 0.5, where the light fraction was about 71wt% in the derived oil. The yield of aromatic hydrocarbons in the derived oils were related to the different properties of the two catalysts such as the pore size which influenced the selectivity, and the silica/alumina (Si/Al) ratio which influenced the number of active sites on the catalyst surface. [Copyright &y& Elsevier]

Abstract: In this paper, an ultrastable Y-type (USY) zeolite was investigated with two-staged pyrolysis–catalysis of waste tyres. Waste tyres were pyrolysed in a fixed bed reactor and the evolved pyrolysis gases were passed through a secondary catalytic reactor. The main objective of this paper was to obtain high concentration of certain aromatic hydrocarbons suitable to be used as a chemical feedstock rather than a liquid fuel, and the influence of catalyst/tyre ratio on the product yield and composition of derived oils. The light fraction (boiling point<220°C) was distilled from the derived oil prior to be analyzed with gas chromatography/mass spectrometry (GC/MS). It showed that the increase of catalyst/tyre ratio resulted in high yield of gas at the expense of the oil yield. The high catalyst/tyre ratio favored to increase the concentration of light fraction (<220°C) in oil. Increasing the catalyst/tyre ratio resulted in significant changed in the concentration of benzene, toluene, xylenes and the alkyl aromatic compounds. For benzene and toluene, the highest concentration was obtained at the catalyst/tyre ratio of 0.5. The concentration of xylenes increased with the increasing of catalyst/tyre ratio. [Copyright &y& Elsevier]

Abstract: The influences of alkali and alkali–earth salts on the combustion of municipal solid waste (MSW) have been studied by thermogravimetric analysis (TGA). In the presence of alkali and alkali–earth salts, the combustion of MSW become easier than that of non-catalyzed MSW. By comparing the different temperatures when CRCM (conversion ratio of combustible matter) is 5%, and CRCM when temperature reaches 1123K, the different influences of catalysts on the ignition and burn off of MSW can be obtained. The kinetic model of catalytic combustion has also been investigated in this paper. The catalytic importance sequence to ignition of MSW is described as: CaO–CaCl2>KOH>K2CO3>KCl>Na2CO3>MgO>NaOH>BaCO3>CaO. The catalytic importance sequence to burn off of MSW is described as: Na2CO3>NaOH>CaO–CaCl2>MgO>KCl>K2CO3>KOH=BaCO3>CaO. According to the activation energy of combustion, the catalytic importance sequence for the first combustion process is described asthe catalytic importance sequence for the second combustion process is described as [Copyright &y& Elsevier]

Mn-Ce/FA (M) and Mn-Ce/FA-TiO2 (M), using fly ash (FA) with and without TiO2 as the carriers, were prepared by an integral molding technique. With the increase of TiO2 content, the rates of NO conversion and denitration of Mn-Ce/FA-TiO2 (M) increased, and the NO2 and N2O formation rates decreased. It is found that TiO2 could effectively inhibit the excessive oxidation of NO and the generation of N2O. The effects of space velocity, oxygen concentration and ammonia nitrogen ratio on three types of nitrogen oxides (NO, NO2, N2O) and denitration rates of the Mn-Ce/FA (M) and Mn-Ce/FA-30%TiO2 (M) were further investigated. In addition, it is demonstrated that Mn-Ce/FA (M) and Mn-Ce/FA-30%TiO2 (M) were more suitable to be used in the environment of low sulfur and less water. [ABSTRACT FROM AUTHOR]

Different states of metamorphic proteins can interconvert under physiological conditions to realize corresponding functions. The mechanism behind the conversion is critical for understanding how these proteins work. We report a combined thermodynamic and kinetic study on the folding/unfolding process of the open and closed conformers of mitotic arrest deficient protein 2 (Mad2), a metamorphic protein. It has been observed that open Mad2 (O-Mad2) can convert to closed Mad2 (C-Mad2). Our results show that O-Mad2 and C-Mad2 have similar thermodynamic stability, which explains the presence of metamorphosis. The folding/unfolding kinetics suggest that the conversion between O-Mad2 and C-Mad2 would be much faster than that reported previously if this conversion goes through the denatured state (U) directly, i.e. through an O-Mad2—denatured state (U)—C-Mad2 (O–U–C) pathway. This inconsistency implies that there exist stable intermediates in between the native and denatured states of Mad2, whichwould either slowdown theO–U–C interconversion or prevent it going through the denatured state. [ABSTRACT FROM AUTHOR]

In order to improve the extraction efficiency and reduce the operation time, supersonic energy by means of supersonic bath was used to the modified Tessier sequential extraction for speciation analysis of heavy metals in soils. Extractable contents of Cu, Fe, Mn, Ni, Pb and Zn were measured by flame atomic absorption spectroscopy. The merit of the supersonic extraction (SE) applied to the modified Tessier, method is not only that the operation time for the first 4 fractions was reduced from ca 18 h to 8h, comparing with conventional extraction (CE), but also the extraction efficiency was higher. There were no significant differences between the data obtained by the proposed method using supersonic extraction and the reference values of the standard reference materials of EES-2 and EES-3. The results for both of SE and CE in the soil samples were consistent. The extractable Cu, Ni and Zn in the sample No. 1 were mainly associated with the third fraction (Fe-Mn oxides fraction), and fourth fraction (organic matter fraction) in the sample No. 2. The extractable Fe and Mn were all mainly associated with the third fraction, and Pb the fourth fraction in both of the samples. The effects of varying concentrations of hydroxylamine hydrochloride on the extraction of metals were also studied. [ABSTRACT FROM AUTHOR]

Different transition metals (Ni, Co, Fe, and Mn) at different amounts (0 mmol/g to 1 mmol/g) were introduced into the co-pyrolysis of rice straw and polyethylene. The thermal behavior and the kinetics of rice straw, polyethylene, transition metal-treated rice straw, rice straw/polyethylene, and transition metal-treated rice straw/polyethylene were comparatively investigated via thermogravimetric analysis. The Ni, Co, Fe, and Mn promoted the decomposition of rice straw and polyethylene in mixtures compared with non-transition metal-treated mixtures in terms of the initial decomposition temperature. The presence of these transition metals catalyzed the synergistic interaction between the rice straw and the polyethylene in mixtures, which resulted in a reduction of residue yield from 14.9 wt% for rice straw/polyethylene to 12.6 wt% to 14.5 wt% for transition metal-treated mixtures. Moreover, the difference in weight loss suggested that the negative influence of the softened polyethylene on the rice straw in mixtures could be greatly reduced after the involvement of transition metals. Kinetic analysis revealed that the pyrolysis of rice straw, polyethylene, and transition metal-treated rice straw were well fit by a single first order reaction; two consecutive first order reactions were needed to describe the co-pyrolysis of rice straw/polyethylene with or without transition metals. [ABSTRACT FROM AUTHOR]