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Ni/SiO 2 catalysts prepared by a sol–gel method have been investigated for hydrogen production via steam reforming of ethanol using a continuous flow, fixed bed reactor system. Chemical equilibrium calculations were also performed to determine the effects of temperature and molar steam to carbon ratio on hydrogen production. The acidity of the preparation solution (modified by nitric acid and ammonia) and calcination atmosphere (air and N 2 ) were investigated in the preparation of the catalysts. BET surface area and porosity, temperature-programmed oxidation (TPO), X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to characterise the prepared catalysts. The BET surface area was reduced when the solution acidity was lowered during the sol–gel preparation process. A pH value less than 2.0 was necessary to achieve high metal dispersion in the catalyst. Smaller NiO particles were obtained when the catalyst was calcined in N 2 . Material balances on ethanol steam reforming at 600 °C using the prepared Ni/SiO 2 catalysts were determined, and higher hydrogen production with lower coke deposition on the reacted catalysts were also obtained from the catalysts calcined in N 2 atmosphere. [ABSTRACT FROM AUTHOR]

Syngas production (H 2 and CO) from carbon dioxide reforming of high density polyethylene (HDPE) over Ni–Al catalyst was evaluated in a two-stage fixed bed reactor. Syngas production was favoured by CO 2 addition, with the highest production of 138.81 mmol syngas g − 1 HDPE , which was about six times higher than non-catalytic, non-CO 2 addition. The catalytic performances of nickel-based catalysts with different promoter metals (Cu, Mg and Co) in the CO 2 reforming of HDPE were also studied. It was found that Ni–Co–Al had an excellent anti-coking performance, with no detectable formation of coke on the catalyst surface. Moreover, the syngas production was significantly improved by the addition of Co compared to the Cu and Mg metal promoters. The CO 2 conversion for Ni–Co–Al catalyst was also the highest at 57.62%. Further investigation of the effect of Co concentration on CO 2 reforming of HDPE showed that the higher Co content, the higher the syngas production and CO 2 conversion. [ABSTRACT FROM AUTHOR]

This paper investigates the co-production of hydrogen and carbon nanotubes from the pyrolysis–catalytic gasification of waste plastics (polypropylene). We report on the influence of a range of metal additions to a nickel based catalyst based on ternary mixed oxide types Ni–Metal–Al, where the metal was Zn, Mg, Ca, Ce or Mn. The results showed that of the different metal–nickel catalysts investigated, the Ni–Mn–Al catalyst was the most promising catalyst in relation to the co-production of hydrogen and CNT. For example, the Ni–Mn–Al catalyst produced 71.4 mmol hydrogen g − 1 plastic, while the hydrogen production using Ni–Ca–Al, Ni–Ce–Al and Ni–Zn–Al catalysts were 68.5 mmol g − 1 , 63.1 mmol g − 1 and 45.9 mmol hydrogen g − 1 plastic respectively. In addition, carbon deposition on the catalyst was highest in the order of: Ni–Mn–Al > Ni–Ca–Al > Ni–Zn–Al > Ni–Ce–Al > Ni–Mg–Al. The carbon deposition for the Ni–Mn–Al catalyst was found to consist of mostly carbon nanotubes. Further investigation of the Ni–Mn–Al catalyst demonstrated that the interaction between Ni and catalyst support plays a significant role in the gasification process; weak metal support interaction (for the Ni–Mn–Al catalyst calcined at 300 °C) resulted in a lower hydrogen production and much higher yield of carbon products. In addition, the influence of steam injection rate on hydrogen and carbon nanotube production was investigated for the Ni–Mn–Al catalyst. Increasing the steam injection rate significantly increased hydrogen production and decreased carbon deposition. However, at lower steam injection rates, the quality of the product carbon nanotubes was improved. [ABSTRACT FROM AUTHOR]