Chunfei Wu

Biochar is a promising catalyst/support for biomass gasification. Hydrogen production from biomass steam gasification with biochar or Ni-based biochar has been investigated using a two stage fixed bed reactor. Commercial activated carbon was also studied as a comparison. Catalyst was prepared with an impregnation method and characterized by X-ray diffraction, specific surface and porosity analysis, X-ray fluorescence and scanning electron micrograph. The effects of gasification temperature, steam to biomass ratio, Ni loading and bio-char properties on catalyst activity in terms of hydrogen production were explored. The Ni/AC catalyst showed the best performance at gasification temperature of 800°C, S/B=4, Ni loading of 15wt.%. Texture and composition characterization of the catalysts suggested the interaction between volatiles and biochar promoted the reforming of pyrolysis volatiles. Cotton-char supported Ni exhibited the highest activity of H2 production (64.02vol.%, 92.08mgg(-1) biomass) from biomass gasification, while rice-char showed the lowest H2 production.

ABSTRACT Carbon nanotubes have been produced from a low density polyethylene (LDPE) feedstock via a two stage pyrolysis process. The temperature of the second stage, where carbon deposition on an iron alumina catalyst occurs (growth temperature), was varied using catalyst temperatures of 700, 800 and 900 °C. An increase in catalyst temperature led to a higher yield of both carbon nanotubes and hydrogen, as the rate of carbon deposition increased. Changing the amount of feedstock relative to the catalyst also had an effect on the production of both carbon nanotubes and hydrogen. As more feedstock is used a larger source of carbon gives rise to a larger amount of carbon nanotubes per gram of catalyst. However, in terms of the percentage of feedstock converted into carbon nanotubes and hydrogen gas, a reduction was observed. Conversion of plastic into carbon nanotubes was 29.1 wt.% when 0.5 g LDPE was used, but reduced to 13.1 wt.% with 1.25 g LDPE. This is because the catalyst activity reduces as it becomes overloaded, and much of the hydrocarbon gases are left unreacted. This gives an economic playoff between large conversion of plastics into carbon nanotubes and hydrogen gas, and large yields of carbon nanotubes per gram of catalyst used.

ABSTRACT The influence of process conditions on the production of syngas and H2 from biomass in the form of rice husks was investigated using a two-stage pyrolysis-catalytic reforming reactor. The parameters investigated were, reforming temperature, steam flow rate and biomass particle size and the catalyst used was a 10 wt.% Ni-dolomite catalyst. Biomass was pyrolysed in the first stage, and the product volatiles were reformed in the second stage in the presence of steam and the Ni-dolomite catalyst. Increase in catalyst temperature from 850 °C to 1050 °C marginally improved total syngas yield. However, H2 yield was increased from 20.03 mmoles g-1 at 850 °C to 30.62 mmoles g-1 at 1050 °C and H2 concentration in the product gas increased from 53.95 vol.% to 65.18 vol.%. Raising the steam flow rate increased the H2 yield and H2 gas concentration. A significant increase in H2:CO ratio along with a decrease in CO:CO2 ratio suggested a change in the equilibrium of the water gas shift reaction towards H2 formation with increased steam flow rate. The influence of particle size on H2 yield was small showing an increase in H2 production when the particle size was reduced from 2.8 – 3.3 to 0.2 – 0.5 mm.

ABSTRACT Syngas production (H2 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 CO2 addition, with the highest production of 138.81 mmolsyngas g− 1HDPE, which was about six times higher than non-catalytic, non-CO2 addition. The catalytic performances of nickel-based catalysts with different promoter metals (Cu, Mg and Co) in the CO2 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 CO2 conversion for Ni–Co–Al catalyst was also the highest at 57.62%. Further investigation of the effect of Co concentration on CO2 reforming of HDPE showed that the higher Co content, the higher the syngas production and CO2 conversion.

ABSTRACT A Ni-Mg-Al-Ca catalyst was prepared by a co-precipitation method for hydrogen production from polymeric materials. The prepared catalyst was designed for both the steam cracking of hydrocarbons and for the in situ absorption of CO2 via enhancement of the water-gas shift reaction. The influence of Ca content in the catalyst and catalyst calcination temperature in relation to the pyrolysis-gasification of a wood sawdust/polypropylene mixture was investigated. The highest hydrogen yield of 39.6 mol H2/g Ni with H2/CO ratio of 1.90 was obtained in the presence of the Ca containing catalyst of molar ratio Ni:Mg:Al:Ca = 1:1:1:4, calcined at 500 °C. In addition, thermogravimetric and morphology analyses of the reacted catalysts revealed that Ca introduction into the Ni-Mg-Al catalyst prevented the deposition of filamentous carbon on the catalyst surface. Furthermore, all metals were well dispersed in the catalyst after the pyrolysis-gasification process with 20-30 nm of NiO sized particles observed after the gasification without significant aggregation.

The formation of 2-4 ring polycyclic aromatic hydrocarbons (PAH) from the pyrolysis of nine different municipal solid waste fractions (xylan, cellulose, lignin, pectin, starch, polyethylene (PE), polystyrene (PS), polyvinyl chloride (PVC), and polyethylene terephthalate (PET)) were investigated in a fixed bed furnace at 800°C. The mass distribution of pyrolysis was also reported. The results showed that PS generated the most total PAH, followed by PVC, PET, and lignin. More PAH were detected from the pyrolysis of plastics than the pyrolysis of biomass. In the biomass group, lignin generated more PAH than others. Naphthalene was the most abundant PAH, and the amount of 1-methynaphthalene and 2-methynaphthalene was also notable. Phenanthrene and fluorene were the most abundant 3-ring PAH, while benzo[a]anthracene and chrysene were notable in the tar of PS, PVC, and PET. 2-ring PAH dominated all tar samples, and varied from 40wt.% to 70wt.%. For PS, PET and lignin, PAH may be generated...

The gasification of wastes and biomass is regarded as a viable thermal treatment process to produce syngas composed largely of hydrogen, methane, carbon monoxide and carbon dioxide. However, the process of gasification could be improved if the residual tar could be converted to hydrogen and methane gas and the carbon dioxide could be adsorbed via carbon capture within the process. Thereby the gases would have a much higher calorific value. In this work, a two stage reactor has been used to investigate the catalytic steam pyrolysis-gasification of refuse derived fuel (RDF) derived from municipal solid waste. The first stage involves the pyrolysis of the RDF at 500 °C. The pyrolysis gases are then passed directly to the second stage where gasification of the evolved pyrolysis gases takes place at 800 °C in the presence of steam and a catalyst. A novel Ni-SiO 2 catalyst was used to convert the tar from pyrolysis into methane and hydrogen. The gases from pyrolysis-gasification were anal...

The potential of hydrogen as a fuel source has been increasing as it involves clean combustion compared with the greenhouse gases emissions from the combustion of fossil fuels; additionally hydrogen can be used as fuel in fuel cells or hydrogen powered turbines. The current hydrogen production processes involve the use of fossil fuels by natural gas steam reforming and partial oxidation of coal or heavy hydrocarbons; however there have been investigations into more sustainable sources for hydrogen such as solid wastes. The combination of thermochemical processes such as pyrolysis and catalytic gasification have been suggested as a convenient route to obtain a gas mixture rich in hydrogen. Nickel based catalysts have been proven to be effective to increase the hydrogen content in the syngas during the processing of solid wastes; however their performance is highly influenced by catalyst properties such as the type of support, surface area, metal dispersion, among others; for this rea...

In this report, we introduce a novel and commercially viable method to recover renewable hydrogen and carbon nanotubes from waste glycerol produced in the biodiesel process. Gas-phase catalytic reforming converts glycerol to clean hydrogen fuel and by replacing the problematical coke formed on the catalyst with high value carbon nanotubes, added value can be realised. Additional benefits of around 2.8 kg CNTs from the reforming of 1 tonne of glycerol and the production of 500 Nm(3) H2 could have a considerable impact on the economics of glycerol utilization. Thereby, the contribution of this research will be a significant step forward in solving a current major technical and economic challenge faced by the biofuels industry.

ABSTRACT A two-stage continuous screw-kiln reactor was investigated for the production of synthesis gas (syngas) from the pyrolysis of biomass in the form of waste wood and subsequent catalytic steam reforming of the pyrolysis oils and gases. Four nickel based catalysts; NiO/Al2O3, NiO/CeO2/Al2O3, NiO/SiO2 (prepared by an incipient wetness method) and another NiO/SiO2 (prepared by a sol–gel method), were synthesized and used in the catalytic steam reforming process. Pyrolysis of the biomass at a rapid heating rate of approximately 40 °C/s, was carried out at a pyrolysis temperature of 500 °C and the second stage reforming of the evolved pyrolysis gases was carried out with a catalytic bed kept at a temperature of 760 °C. Gases were analysed using gas chromatography while the fresh and reacted catalyst was analysed by scanning electron microscopy, thermogravimetric analysis, transmission electron microscopy with energy dispersive X-ray and X-ray photoelectron spectroscopy. The reactor design was shown to be effective for the pyrolysis and catalytic steam reforming of biomass with a maximum syngas yield of 54.0 wt.% produced when the sol–gel prepared NiO/SiO2 catalyst was used, which had the highest surface area of 765 m2 g−1. The maximum H2 production of 44.4 vol.% was obtained when the NiO/Al2O3 catalyst was used.

ABSTRACT The use of activated carbon derived from cotton stalk as a potential catalytic support material in the application of NO removal from coal combusted flue gas was experimentally investigated utilizing the SCR-deNOx process. Cotton stalk samples infused with phosphoric acid were chemically activated (CACS) and co-activated (CO-ACS) and impregnated with the metal configuration Mn/Ce (1:2 M ratio) representing 4 wt.% relative to the support material. The CACSx–Mn/Ce and CO-ACSx–Mn/Ce catalysts provided NO conversion efficiencies ranging between ∼10% and 68%. The addition of phosphoric acid significantly increased the BET surface area (m2 g−1) of the respective CACSx–Mn/Ce and CO-ACSx–Mn/Ce catalysts. However based on the experimental and analytical findings this study suggests that the NO conversions efficiencies of the CACSx–Mn/Ce and CO-ACSx–Mn/Ce catalysts are far more dependent on the wt.% of the metal loading than the physical parameters such as the pore size, pore structure and surface area. The relatively lower NO conversion efficiencies may also be further due to the neutralization of the Lewis and Brönsted acid sites of the catalysts by the presence of any alkali metals within the cotton stalk. The cotton stalk derived catalytic support has shown a great potential for possible application within the SCR-deNOx process. It is further suggested that higher NO conversion efficiencies can be realized by an increase in the metal loadings of Mn/Ce for the CACSx–Mn/Ce and CO-ACSx–Mn/Ce catalysts.