Hydrogen production from biomass and plastic mixtures by pyrolysis-gasification

The addition of plastics to the steam pyrolysis/gasification of wood sawdust with and without a Ni/AlO catalyst was investigated in order to increase the production of hydrogen in the gaseous stream. To study the influence of the biomass/plastic ratio in the initial feedstock, 5, 10 and 20 wt.% of polypropylene was introduced with the wood in the pyrolysis reactor. To investigate the effect of plastic type, a blend of 80 wt.% of biomass and 20 wt.% of either polypropylene, high density polyethylene, polystyrene or a mixture of real world plastics was fed into the reactor. The results showed that a higher gas yield (56.9 wt.%) and a higher hydrogen concentration and production (36.1 vol.% and 10.98 mmol H g sample, respectively) were obtained in the gaseous fraction when 20 wt.% of polypropylene was mixed with the biomass. This significant improvement in gas and hydrogen yield was attributed to synergetic effects between intermediate species generated via co-pyrolysis. The Ni/Al O catalyst dramatically improved the gas yield as well as the hydrogen concentration and production due to the enhancement of water gas shift and steam reforming reactions. Very low amounts of coke (less than 1 wt.% in all cases) were formed on the catalyst during reaction, with the deposited carbonaceous material being of the filamentous type. The Ni/AlO catalyst was shown to be effective for hydrogen production in the co-pyrolysis/gasification process of wood sawdust and plastics

Hydrogen and Carbon Nanotubes from Pyrolysis-Catalysis of Waste Plastics: A Review

More than 27 million tonnes of waste plastics are generated in Europe each year representing a considerable potential resource. There has been extensive research into the production of liquid fuels and aromatic chemicals from pyrolysis-catalysis of waste plastics. However, there is less work on the production of hydrogen from waste plastics via pyrolysis coupled with catalytic steam reforming. In this paper, the different reactor designs used for hydrogen production from waste plastics are considered and the influence of different catalysts and process parameters on the yield of hydrogen from different types of waste plastics are reviewed. Waste plastics have also been investigated as a source of hydrocarbons for the generation of carbon nanotubes via the chemical vapour deposition route. The influences on the yield and quality of carbon nanotubes derived from waste plastics are reviewed in relation to the reactor designs used for production, catalyst type used for carbon nanotube growth and the influence of operational parameters

High yield hydrogen from the pyrolysis-catalytic gasification of waste tyres with a nickel/dolomite catalyst

Nickel/dolomite catalysts have been prepared and investigated for their suitability for the production of hydrogen from the two-stage pyrolysis-gasification of waste tyres. Experiments were conducted at a pyrolysis temperature of 500 °C and gasification temperature was kept constant at 800 °C with a catalyst/waste tyres ratio of 0.5. Fresh and reacted catalysts were characterised using a variety of methods, including, BET, X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM)-energy dispersive X-ray spectrometry (EDXS). The results indicated that the gas yield was significantly increased from 30.3 to 49.1 wt.% and the potential H production was doubled with the introduction of 5%Ni into the calcined dolomite catalyst. The results show also a further increase in the gas yield and the potential H production with increasing Ni loading from 5 to 20 wt.%. The coke deposited on the catalyst surface was 3.1, 0.9, 2.8 and 3.7 wt.%, when the Ni loading was 0, 5, 10 and 20 wt.% for the calcined dolomite catalyst, respectively. The results showed that the calcined Ni dolomite catalysts became deactivated by filamentous carbons

Comparison of waste plastics pyrolysis under nitrogen and carbon dioxide atmospheres: A thermogravimetric and kinetic study

It is important to understand the influence of pyrolysis atmosphere on the thermal degradation of waste plastics. In this study, the decomposition of waste plastics; high and low density polyethylene, polypropylene, polystyrene, and polyethylene terephthalate were investigated from ambient temperature to 500 °C within nitrogen or carbon dioxide atmospheres. The thermal degradation characteristics and kinetic parameters of individual plastics and mixed plastics (household packaging, building construction and agricultural waste plastics) from three different waste treatment plants were investigated under N2, CO2 and N2/CO2 atmospheres. In all atmospheres, only one degradation peak temperature was observed between 250−510 °C. The replacement of N2 by CO2 showed different effects on the activation energy. Mixtures of N2/CO2 in the pyrolysis atmosphere resulted to lower activation energy for all plastic samples, with the exception of high density polyethylene, polystyrene and polyethylene terephthalate. The lower activation energy suggested that lower energy was required for the degradation process. However, a mixture of more than 30 % of CO2 may influence the degradation process of plastics due to a higher value of residue obtained after the experiment