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Biomass, regarded as a renewable energy resource, will play an important role for the sustainable development of society, environment and economics. The presence of tar in the gases produced from biomass gasification limits the application of the gaseous products, since the tar can cause blockages, plugging, corrosion and catalyst deactivation. Nickel-based catalysts are known to be effective in biomass gasification for tar reduction to produce synthesis gases because of their comparative lower cost and effective catalytic reactivity. In this paper, several types of nickel-based catalysts reported for biomass gasification are reviewed in relation to their preparation, reaction conditions and stability for the biomass/tar gasification process.

Hydrogen production from the pyrolysis–gasification of waste tyres has been investigated with a Ni/CeO2/Al2O3 catalyst using a two-stage fixed bed reaction system. The conditions of catalyst preparation such as Ni and CeO2 content and calcination temperature were investigated in relation to product yield and composition. The fresh and reacted catalysts were analysed using thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The results showed that there were small changes in the gas and hydrogen yield by adding 5 wt.% of CeO2 into the Ni/CeO2/Al2O3 catalyst. The gas yield related to the mass of waste tyre and the amount of reacted water were increased with the increase of CeO2 content from 5 to 15 wt.%. However, with the further increase of CeO2 content to 30 wt.%, the gas yield related to the mass of tyre and the amount of reacted water was reduced. Increasing the Ni content of the catalyst showed a positive influence on the gas yield and hydrogen production. The investigation of the calcination temperature of the Ni/CeO2/Al2O3 catalyst showed that the oil yield related to the mass of tyre and reacted water decreased from 28.4 to 23.4 wt.% for the catalyst calcined at 500 °C, and decreased from 24.2 to 17.7 wt.% for the catalyst calcined at 750 °C. When the Ni content of the catalyst was increased from 5 to 20 wt.%. there were only small changes in total gas and hydrogen production from the pyrolysis–gasification of waste tyre. Lower coke deposition on the reacted catalyst was obtained for the Ni/CeO2/Al2O3 catalyst prepared at the calcination temperature of 750 °C compared with the 500 °C calcination temperature.

Steam reforming of ethanol to produce hydrogen was carried out using a two-stage reaction system with several nano-Ni/SiO 2 catalysts prepared at different citric acid (CA) contents using the sol–gel process. The fresh (non-calcined and calcined) catalysts and the reacted catalysts were analysed using surface area and pore size analysis, Fourier-transform infrared (FTIR) spectroscopy, thermo-gravimetry analysis (TGA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed that a meso-structured material was produced at Ni:CA ratios lower than 1:0.5; and the pore volume of the catalyst was increased when more citric acid was used during the sol–gel preparation. Gas and hydrogen yield were observed to be increased when the Ni:CA ratio was reduced from 1:0.5 to 1:3.0; however, gas concentration was slightly changed for the catalysts prepared at different Ni:CA ratios. In addition, coke formation was increased from 0.7 to 7.5 wt.% when the Ni:CA ratio decreased from 1:0.5 to 1:3.0. It was also found that the Ni/SiO 2 catalyst prepared at the low CA content (Ni:CA = 0.5) was non-stable during the ethanol steam reforming process; since sintering was obtained as observed using TEM analysis of the used catalyst.

Polypropylene, polystyrene, high density polyethylene and their mixtures and real-world plastic waste were investigated for the production of hydrogen in a two-stage pyrolysis–gasification reactor. The experiments were carried out at gasification temperatures of 800 or 850 °C with or without a Ni–Mg–Al catalyst. The influence of plastic type on the product distribution and hydrogen production in relation to process conditions were investigated. The reacted Ni–Mg–Al catalysts were analyzed by temperature-programmed oxidation and scanning electron microscopy. The results showed that lower gas yield (11.2 wt.% related to the mass of plastic) was obtained for the non-catalytic non-steam pyrolysis–gasification of polystyrene at the gasification temperature of 800 °C, compared with the polypropylene (59.6 wt.%) and high density polyethylene (53.5 wt.%) and waste plastic (45.5 wt.%). In addition, the largest oil product was observed for the non-catalytic pyrolysis–gasification of polystyrene. The presence of the Ni–Mg–Al catalyst greatly improved the steam pyrolysis–gasification of plastics for hydrogen production. The steam catalytic pyrolysis–gasification of polystyrene presented the lowest hydrogen production of 0.155 and 0.196 (g H 2 /g polystyrene) at the gasification temperatures of 800 and 850 °C, respectively. More coke was deposited on the catalyst for the pyrolysis–gasification of polypropylene and waste plastic compared with steam catalytic pyrolysis–gasification of polystyrene and high density polyethylene. Filamentous carbons were observed for the used Ni–Mg–Al catalysts from the pyrolysis–gasification of polypropylene, high density polyethylene, waste plastic and mixed plastics. However, the formation of filamentous carbons on the coked catalyst from the pyrolysis–gasification of polystyrene was low.

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.

A novel Ni–Mg–Al–CaO catalyst/sorbent has been prepared by integration of the catalytic and CO 2 absorbing properties of the material to maximise the production of hydrogen. The prepared catalyst was tested for hydrogen production from the pyrolysis–gasification of polypropylene by using a two-stage fixed-bed reaction system. X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM)-energy dispersive X-ray spectrometry (EDXS) were used to characterize the prepared Ni–Mg–Al–CaO catalyst/sorbent. Ni–Mg–Al–CaO and calcined dolomite showed a stable carbonation conversion after several cycles of carbonation/calcination, while CaO showed a certain degree of decay. The calcined dolomite showed low efficiency for hydrogen production from pyrolysis–gasification of polypropylene. Increasing the gasification temperature resulted in a decrease of H 2 /CO ratio for the Ni–Mg–Al catalyst mixed with sand; however, a stable H 2 /CO ratio (around 3.0) was obtained for the Ni–Mg–Al–CaO catalyst. An increased Ni–Mg–Al–CaO catalyst/polypropylene ratio promoted the production of hydrogen from the pyrolysis–gasification of polypropylene. Approximately 70 wt.% of the potential H 2 production was obtained, when the Ni–Mg–Al–CaO catalyst/polypropylene ratio and gasification temperature were 5 and 800 °C, respectively.

Hydrogen production from waste tires was investigated using a two-stage pyrolysis-gasification reactor and Ni−Mg−Al (1:1:1) as a catalyst. In addition, the elastomer constituents most commonly used in tires, natural rubber (NR), styrene−butadiene rubber (SBR), and butadiene rubber (BR), were also investigated. Experiments were conducted at a pyrolysis temperature of 500 °C and gasification temperature of 800 °C. The results showed that the gas and hydrogen yield were increased for the tire and elastomer constituents during pyrolysis-gasification. However, there was a dramatic increase in H2 and CO concentrations as well as a consequent decrease in CH4 and C2−C4 concentrations when the Ni−Mg−Al catalyst was applied to the pyrolysis-gasification process. For example, hydrogen production increased from 0.68 to 5.43 wt % for the catalytic steam pyrolysis-gasification of waste tire in the presence of Ni−Mg−Al catalyst. The highest hydrogen production (15.26 wt %) was obtained for the BR feedstock. Reacted cata...

Co-precipitated Ni-Mg-Al catalyst was prepared and investigated in relation to the production of hydrogen from the catalytic steam pyrolysis-gasification of polypropylene using a two-stage reaction system. Coke formation on the Ni-Mg-Al catalyst was investigated by using temperature-programmed oxidation (TPO), X-ray diffraction (XRD), scanning electron microscopy (SEM)/energy dispersive X-ray spectroscopy (EDXS), transmission electron microscopy (TEM) and focused ion beam (FIB)/scanning electron microscopy (SEM). The coke formation mechanism on the Ni-Mg-Al catalyst is proposed. It is suggested that the Ni-Mg-Al catalyst is initially reduced during the gasification process, the reactions of decomposition/reforming of hydrocarbons gases occur on the surface and inside the catalyst; this resulted in partial fragmentation of the catalyst into small particles. Layered carbons, perhaps containing monoatomic carbon, metal carbides, etc., are suggested to be a transition layer for the formation of filamentous carbons. The addition of Mg into the Ni-Al catalyst was found to increase the catalytic activity and the physical stability of catalyst. In addition, increasing the calcination temperature from 750 to 850 °C reduced the surface area of the fresh Ni-Mg-Al catalyst, increased the NiO crystal size, and resulted in a decrease of catalytic activity in the pyrolysis-gasification of polypropylene; however, a more stable catalyst was obtained with higher calcination temperature.

Post-consumer plastic waste derived from municipal solid waste was investigated using a two-stage, catalytic steam pyrolysis–gasification process for the production of hydrogen. The three important process parameters of catalyst:plastic ratio, gasification temperature and water injection rate were investigated. Temperature-programmed oxidation (TPO) and scanning electron microscopy (SEM) methods were used to analyse the reacted catalysts. The results showed that there was little influence of catalyst:plastic ratio between the range 0.5 and 2.0 (g/g) on the mass balance and gas composition for the pyrolysis–gasification of waste plastics; this might be due to the effective catalytic activity of the Ni–Mg–Al catalyst. However, increasing the gasification temperature and the water injection rate resulted in an increase of total gas yield and hydrogen production. The coke formation on the catalyst was reduced with increasing use of catalyst; however, a maximum coke formation (9.6 wt.%) was obtained at the gasification temperature of 700 °C when the influence of gasification temperature was investigated. The maximum coke formation was obtained at the water injection rate of 4.74 g h −1 , and a more reactive form of coke seemed to be formed on the catalyst with an increase of the water injection rate, according to the TPO experiments.

Hydrogen production from the catalytic pyrolysis−gasification of polypropylene using a two-stage reaction system has been investigated. In this paper, three important process conditions: water flow rate, carrier gas flow rate, and gasification temperature were investigated in relation to hydrogen production. It is suggested that the water flow rate and gasification temperature have a significant influence on hydrogen production from pyrolysis−gasification of polypropylene, whereas the carrier gas flow rate shows little influence. With increasing water flow rate, the gas yield related to the mass of polypropylene increased from 123.6 to 213.9 wt % when the water flow rate was increased from 1.90 to 9.49 g h−1, then decreased to 195.5 wt % at the water flow rate of 14.20 g h−1. The hydrogen concentration and the potential hydrogen production also showed the highest yields at the water flow rate of 9.49 g h−1. With increasing gasification temperature, the pyrolysis−gasification of polypropylene seems to be p...

The production of hydrogen from the two-stage pyrolysis–gasification of polypropylene using a Ni/CeO 2 /ZSM-5 catalyst has been investigated. Experiments were conducted on CeO 2 loading, calcination temperature and Ni loading of the Ni/CeO 2 /ZSM-5 catalyst in relation to hydrogen production. The results indicated that with increasing CeO 2 loading from 5 to 30 wt.% for the 10 wt.% Ni/CeO 2 /ZSM-5 catalyst calcined at 750 °C, hydrogen concentration in the gas product and the theoretical potential hydrogen production were decreased from 63.0 to 49.8 vol.% and 50.4 to 21.6 wt.%, respectively. In addition, the amount of coke deposited on the catalyst was reduced from 9.5 to 6.2 wt.%. The calcination temperature had little influence on hydrogen production for the catalyst containing 5 wt.% of CeO 2 . However, for the 10 wt.% Ni/CeO 2 /ZSM-5 catalyst with a CeO 2 content of 10 or 30 wt.%, the catalytic activities reduced when the calcination temperature was increased from 500 to 750 °C. The SEM results showed that large amounts of filamentous carbons were formed on the surface of the catalysts. The investigation of different Ni content indicates that the Ni/CeO 2 /ZSM-5 ((2-10)-5-500) catalyst containing 2 wt.% Ni showed poor catalytic activity in relation to the pyrolysis–gasification of polypropylene according to the theoretical potential H 2 production (7.2 wt.%). Increasing the Ni loading to 5 or 10 wt.% in the Ni/CeO 2 /ZSM-5 ((2-10)-5-500) catalyst, high potential hydrogen production was obtained.

Co-precipitated nickel-based catalysts with different metallic molar ratios and calcination temperature were investigated for the production of hydrogen from the pyrolysis–gasification of polypropylene. The experiments were carried out at a pyrolysis temperature of 500 °C and gasification temperature of 800 °C in the presence of steam using a two-stage reaction system. The results suggest that with increasing Ni content in the Ni-Al or Ni-Mg-Al catalyst, the catalytic activity of the catalyst increased, in relation to hydrogen production. For example, the potential hydrogen production increased from 48.8 to 57.7 wt.%, and the amount of water reacted increased from 1.2 to 1.3 (g water/g polypropylene), when the Ni-Al molar ratio was increased from 1:4 to 1:1. After reaction in the pyrolysis–gasification process, the non-reduced Ni-Al catalyst was reduced into metallic Ni, as observed from XRD and TGA analysis. The introduction of Mg into the Ni-Al catalyst significantly increased the amount of reacted water and improved the performance of the catalyst in relation to coke formation, although the hydrogen production was not significantly improved. For the Ni-Al or Ni-Mg-Al catalyst, a 850 °C calcination temperature resulted in a lower catalytic activity compared to the lower calcination temperature of 750 °C. The substitution of Cu for Mg in the Ni-Mg-Al catalyst significantly reduced the catalytic ability for hydrogen production.

Several nickel-based catalysts (Ni/Al2O3, Ni/MgO, Ni/CeO2, Ni/ZSM-5, Ni-Al, Ni-Mg-Al and Ni/CeO2/Al2O3) have been prepared and investigated for their suitability for the production of hydrogen from the two-stage pyrolysis–gasification of polypropylene. Experiments were conducted at a pyrolysis temperature of 500 °C and gasification temperature was kept constant at 800 °C with a catalyst/polypropylene ratio of 0.5. Fresh and reacted catalysts were characterized using a variety of methods, including, thermogravimetric analysis, scanning electron microscopy with energy dispersive X-ray spectrometry and transmission electron microscopy. The results showed that Ni/Al2O3 was deactivated by two types of carbons (monoatomic carbons and filamentous carbons) with a total coke deposition of 11.2 wt.% after reaction, although it showed to be an effective catalyst for the production of hydrogen with a production of 26.7 wt.% of the theoretical yield of hydrogen from that available in the polypropylene. The Ni/MgO catalyst showed low catalytic activity for H2 production, which might be due to the formation of monoatomic carbons on the surface of the catalyst, blocking the access of gaseous products to the catalyst. Ni-Al (1:2) and Ni-Mg-Al (1:1:2) catalysts prepared by co-precipitation showed good catalytic abilities in terms of both H2 production and prevention of coke formation. The ZSM-5 zeolite with higher surface area was also shown to be a good support for the nickel-based catalyst, since, the Ni/ZSM-5 catalyst showed a high rate of hydrogen production (44.3 wt.% of theoretical) from the pyrolysis–gasification of polypropylene.

A two-stage reaction system was used for the pyrolysis-gasification of polypropylene in the presence of steam and a Ni/CeO2/Al2O3 catalyst. The influence of catalyst ratio (0, 0.25, 0.5, 1.0, and 2.0) and gasification temperature (600, 700, 800, and 900 °C) on the production of hydrogen were investigated. The reacted catalysts were characterized using thermogravimetric analysis and scanning electron microscopy-energy dispersive X-ray spectrometry. The maximum potential hydrogen production was only 5 wt % without the catalyst, however it increased to 52.8 wt % in the presence of the Ni/CeO2/Al2O3 catalyst at a catalyst/polypropylene ration of 1. Increasing the catalyst:polypropylene ratio resulted in an increase in hydrogen production and a decrease of coke deposited on the catalyst surface but showed little influence on the CO and CO2 concentrations. Increasing the gasification temperature resulted in a marked increase in potential hydrogen production from 13.4 to 52.0 wt %, as the gasification temperatur...

The thermodynamic performance of an open cycle intercooled gas turbine power plant with pressure drop irreversibilities is optimised by adjusting the intercooling pressure ratio, the flow rate and the distribution of pressure losses along the flow path in the present paper. When the optimisation is performed with the constraints of a fixed fuel flow rate and the power plant size, the power output and efficiency can be maximised again by properly allocating the fixed overall flow area among the compressor inlet and the turbine outlet.

The performance of an air standard Diesel cycle with heat transfer loss, friction-like term loss and variable specific heats of working fluid is analysed by using finite time thermodynamics. The relationships between the power output and the compression ratio, between the thermal efficiency and the compression ratio, as well as the optimal relationship between the power output and the efficiency of the cycle are derived by detailed numerical examples. Moreover, the effects of temperature dependent specific heats of working fluid on the irreversible cycle performance are analysed. The results show that the effects of temperature dependent specific heats of working fluid on the irreversible cycle performance are obvious, and they should be considered in practice cycle analysis. The results obtained in the present paper may provide guidance for the design of practice Diesel engines.

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.

In this review, we highlight the [FeFe]-hydrogenase, which is capable of catalyzing the splitting of molecular hydrogen to produce electrons and protons or catalyzing the reversible reaction: 2H+ + 2e− = H2↑ as a potential renewable fuel. We have focused on [FeFe]-hydrogenase because of structural studies have shed more light on the hydrogenase activity than the [NiFe]-hydrogenase. Our studies on the [FeFe]-hydrogenase from Chlamydomonas reinhardtii CC-503 (HydA 1) have also been highlighted. There are two factors influencing the multiplexed hydrogenase activity: a single hydrophobic channel of catalytic center, which is known as the H-cluster active site based on site-directed mutagenesis, moreover, some promising results have already been obtained. Modifications of [FeFe]-hydrogenase can improve its stabilization and activity in vitro, increase the efficiency of bioenergy utilization, and promote industrial amplification of biofuel production.

In the present paper, power is optimised for an irreversible closed intercooled regenerated Brayton cycle coupled to constant temperature heat reservoirs in the viewpoint of finite time thermodynamics. The power optimisation is performed by searching the optimal heat conductance distributions among the four heat exchangers, namely the hot and cold side heat exchangers, the intercooler and the regenerator for fixed total heat exchanger inventory and by searching the optimal intercooling pressure ratio. When the optimisation is performed with respect to the total pressure ratio of the cycle, the maximum power is maximised twice and a double maximum power is obtained. During the analysis, the heat resistance losses in the four heat exchangers, the irreversible compression and expansion losses in the compressors and the turbine are taken into account.

The optimal exergy-based ecological performance of an irreversible Carnot refrigerator with the losses of heat-resistance, heat leak and internal irreversibility, in which heat transfer between the working fluid and the heat reservoirs obeys a generalized heat transfer law QΔ(Tn), is derived by considering an ecological optimization criterion as the objective function, which consists of maximizing a function representing the best compromise between the exergy output rate and exergy loss rate (entropy production rate) of the refrigerator. Some special examples are discussed. Numerical examples are given to show the effects of heat transfer law, heat leakage and internal irreversibility on the optimal performance of the generalized irreversible refrigerator. The results can provide some theoretical guidance for the design of practical refrigerators.

On the basis of an endoreversible absorption refrigeration cycle model with Newton's heat transfer law, a real absorption refrigerator model, that is, an irreversible four-heat-reservoir cycle model is established in this paper by taking into account the heat resistance, heat leakage and irreversibilities due to the internal dissipation of the working fluid. The performance limits, that is, the maximum coefficient of performance (COP) and the corresponding cooling load, as well as the maximum cooling load and the corresponding COP of the cycle coupled to constant-temperature heat reservoirs are derived by using finite-time thermodynamics. The optimal distribution relation of the heat-transfer surface areas is also obtained. Moreover, the effects of the cycle parameters on the performance limits of the cycle are studied by detailed numerical examples. The results of this paper include the performance limits of almost all kinds of the refrigeration cycles with Newton's heat transfer law.

The optimal ecological performance of an irreversible Carnot heat pump with the losses of heat resistance, heat leak and internal irreversibility, in which heat transfer between the working fluid and the heat reservoirs obeys a generalized heat transfer law q∝(ΔT)n,is derived by considering an ecological optimization criterion as the objective function, which consists of maximizing a function representing the best compromise between the exergy output rate and exergy loss rate (entropy production rate) of the heat pump. Some special examples are discusses.A numerical example is given to show the effects of heat transfer law, heat leakage and internal irreversibility on the optimal performance of the generalized irreversible heat pump. The results can provide some theoretical guidance for the design of practical heat pumps.

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 anal...

Hydrogen production from renewable resources has received extensive attention recently for a sustainable and renewable future. In this study, hydrogen was produced from catalytic steam reforming of the aqueous fraction of crude bio-oil, which was obtained from pyrolysis of biomass. Five Ni–Al catalysts modified with Ca, Ce, Mg, Mn and Zn were investigated using a fixed-bed reactor. Optimized process conditions were obtained with a steam reforming temperature of 800 °C and a steam to carbon ratio of 3.54. The life time of the catalysts in terms of stability of hydrogen production and prohibition of coke formation on the surface of the catalyst were carried out with continuous feeding of raw materials for 4 h. The results showed that the Ni–Mg–Al catalyst exhibited the highest stability of hydrogen production (56.46%) among the studied catalysts. In addition, the life-time test of catalytic experiments showed that all the catalysts suffered deactivation at the beginning of the experiment (reduction of hydrogen production), except for the Ni–Mg–Al catalyst; it is suggested that the observation of abundant amorphous carbon formed on the surface of reacted catalysts (temperature programmed oxidation results) may be responsible for the initial reduction of hydrogen production. In addition, the Ni–Ca–Al catalyst showed the lowest hydrogen production (46.58%) at both the early and stabilized stage of catalytic steam reforming of bio-oil.

A sample of pinewood sawdust was rapidly pre-processed in a torrefaction-type procedure, separately in subcritical water (neutral) and with added Na2CO3 (alkaline compound) and Nb2O 5 (solid acid) in a batch reactor. The original sawdust and the three friable solid recovered products from the hydrothermal procedure were characterized in detail. The solid recovered products (SRPs) gave higher C/O and C/H ratios, higher calorific values and reduced moisture contents compared to the original sawdust. The four solid samples were then subjected to rapid high temperature pyrolysis in a fixed-bed reactor to investigate the effect of the pre-processing routes on the yields and compositions of the pyrolysis products. With increasing pyrolysis temperature, the pre-processed samples produced more CO and H2, far more char and less tar than the original sawdust. The trends in the composition of gases and the yields of char suggested a combination of Boudouard reaction and CO2 dry reforming as the predominant reactions during pyrolysis. For all samples, increased temperature led to reduced tar production with an increase in the aromatic oxygenates and aromatic hydrocarbon contents of the tar. At 800 °C, the ratio of aromatic hydrocarbons increased dramatically particularly from the sample pre-processed with Nb2O5 indicating possible deoxygenation catalysis.

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 40. wt.% to 70. wt.%. For PS, PET and lignin, PAH may be generated directly from the aromatic structure of the feedstock.

Carbon nanotubes (CNTs) have been proven to be possible as high-value by-products of hydrogen production from gasification of waste plastics. In this work, steam content in the gasification process was investigated to increase the quality of CNTs in terms of purity. Three different plastics—low density polyethylene (LDPE), polypropylene (PP) and polystyrene (PS) were studied in a two stage pyrolysis-gasification reactor. Plastics samples were pyrolysed in nitrogen at 600 °C, before the evolved gases were passed to a second stage where steam was injected and the gases were reformed at 800 °C in the presence of a nickel-alumina catalyst. To investigate the effect that steam plays on CNT production, steam injection rates of 0, 0.25, 1.90 and 4.74 g h −1 were employed. The CNTs produced from all three plastics were multiwalled CNTs with diameters between 10 and 20 nm and several microns in length. For all the plastic samples, raising the steam injection rate led to increased hydrogen production as steam reforming and gasification of deposited carbon increased. High quality CNTs, as observed from TEM, TPO and Raman spectroscopy, were produced by controlling the steam injection rate. The largest yield for LDPE was obtained at 0 g h −1 steam injection rate, whilst PP and PS gave their largest yields at 0.25 g h −1 . Overall the largest CNT yield was obtained for PS at 0.25 g h −1 , with a conversion rate of plastic to CNTs of 32 wt%.

Hydrogen production from the pyrolysis/reforming of refuse derived fuel (RDF) was investigated with a series of Ni/SiO2 catalysts. The catalysts were prepared by homogeneous precipitation derived from a sol–gel method (HPG) and compared to Ni/SiO2 catalysts prepared by adding a phase separation step to the HPG process (B-HPG). All the catalysts had a NiO loading of 10 wt.%, and three different calcination temperatures (500 °C, 700 °C and 900 °C) were used for each method. The prepared Ni/SiO2 catalysts were analysed to determine their surface area, and porosity characteristics; additionally scanning electron microscopy (SEM-EDX), transmission electron microscopy (TEM), infrared spectroscopy (FTIR), and X-Ray diffraction (XRD) analyses were carried out. The results showed that the catalyst prepared by HPG and calcined at 700 °C (HPG700), presented a relatively high surface area (∼347 m2 g−1), large pore diameter (12.50 nm), and also resulted in the highest catalytic activity towards H2 production, attaining ∼60 vol.% hydrogen. The lowest hydrogen concentration of about 42 vol.% was obtained using the catalysts prepared by the combined HPG-phase separation method, and calcined at 900 °C (B-HPG900). It was also observed that at calcination temperatures higher than 700 °C the catalytic activity for hydrogen production was diminished for both preparation methods.

The performance of an air standard Atkinson cycle with heat transfer loss and variable specific heats of working fluid is analysed by using finite time thermodynamics. The relationships between the work output and the compression ratio and between the thermal efficiency and the compression ratio, as well as the optimal relationship between the work output and the efficiency of the cycle, are derived from detailed numerical examples. Moreover, the effects of heat transfer loss and variable specific heats of working fluid on the cycle performance are analysed. The results show that these effects are obvious and they should be considered in practice cycle analysis. The results obtained in the present paper may provide guidance for the design of practical internal combustion engines.

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.

The advanced thermal technologies of pyrolysis and gasification provide important economic and environmental options to convert waste materials into useful and high‐value materials, fuels and chemicals. In this chapter, pyrolysis is described in terms of the production of oils, char and gas, with examples of various reaction systems. Gasification is also reviewed in terms of example process systems, influences of gasification temperature and the presence of catalysts. Commercial examples of both technologies are also described.

Hydrogen and syngas production have been investigated from the pyrolysis/gasification of biomass components (cellulose, xylan and lignin) in the presence of Ni-based catalysts by using a two-stage fixed-bed reaction system. Biomass samples were pyrolysed at the first stage and the derived products were gasified at the second stage. The Ni–Mg–Al and Ni–Ca–Al catalysts, prepared by co-precipitation, were applied in the gasification process. The lignin sample pyrolysed with more difficulty (56.0 wt.% of residue fraction) compared with cellulose and xylan at 500 °C, and therefore resulted in the lowest gas yield (42.7 wt.%) for the pyrolysis/gasification of lignin. However, the highest H 2 concentration from the three types of feedstock (55.1 vol.%) was collected for the lignin sample in the presence of steam and catalyst. Carbon deposition was very low as indicated from the TPO and SEM analyses of the reacted Ni–Mg–Al catalyst. The investigation of reaction conditions showed that water injection rate (0.02 and 0.05 g min −1 ) had little influence on the gas production from the pyrolysis/gasification of lignin in the presence of the Ni–Ca–Al catalyst; however, the increase of gasification temperature from 700 to 900 °C resulted in a higher gas and hydrogen production due to the promotion of secondary reactions during the gasification process. Furthermore, coking was highest for the reacted Ni–Ca–Al catalyst at the gasification temperature of 800 °C (7.27 wt.%), when the temperature was increased from 700 to 900 °C. This work shows that the components of biomass have a significant influence on the catalytic gasification process related to hydrogen and syngas production.

Waste material was pyrolyzed in a horizontal tubular reactor at 530-540°C using different catalysts, such as activated carbon, MCM-41, HZSM-5 and their mixtures. Products were investigated by gas-chromatography, EDXRFS and standardized methods. Catalysts significantly affected the yields of volatiles; e.g. HZSM-5 catalyst increased especially the yield of gaseous hydrocarbons, while MCM-41 catalyst was responsible for increasing the pyrolysis oil yield. Synergistic effects were found using mixtures of different catalysts. Furthermore the catalysts modified the main carbon frame of the products. Pyrolysis oil obtained over HZSM-5 catalyst contained large amounts of aromatics, while MCM-41 catalyst mainly isomerized the carbon frame. Regarding contaminants it was concluded, that the sulphur content could be significantly decreased by activated carbon, however it had only a slight effect to the other properties of the products.

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, which would either slow down the O-U-C interconversion or prevent it going through the denatured state.

A zeolite catalyst of ultrastable Y-type (USY) was investigated in the research of two staged pyrolysis-catalysis of scrap tyres. Scrap 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 investigate the effect of zeolite USY on the yield of products and the composition of derived oil. The influences of several parameters such as pyrolysis temperature, catalytic temperature, catalyst/tyre ratio, heating rate, etc. on the yield of the derived oil, char and gas were investigated. It showed that the increase of catalytic temperature and catalyst/tyre ratio resulted in high yield of gas at the expense of the oil yield. For example, when the catalyst/tyre ratio increased from 0.25 to 1.0, the yield of gas increased from 30.5 to 49.9 wt.%, and the oil yield decreased nearly two-fold from 31.6 to 12.7 wt.%. The concentration of light naphtha (boiling point < 160 degrees C) was also investigated in this study. And the high catalyst/tyre ratio favored to increase the concentration of light naphtha (< 160 degrees C) in oil. In order to study the composition of derived oil, a distilled fraction (< 280 degrees C), which was 92.5 wt.% of the oil obtained from catalytic pyrolysis of scrap tyre at a pyrolysis temperature, catalytic temperature and catalyst/tyre ratio of 500, 400 degrees C and 0.5, respectively, was analyzed with gas chromatography/mass spectrometry (GC/MS). The distillate was found to contain 1.23 wt.% benzene, 9.35 wt.% toluene, 3.68 wt.% ethylbenzene, 12.64 wt.% xylenes, 1.81 wt.% limonene and 13.89 wt.% PAHs, etc., where the single ring aromatics represented a significant potential use as chemicals.

Catalytic gasification of biomass in the presence of CaO is a promising route for CO2 capture and thereby high yield hydrogen production. However, the instability of the CaO sorbent for CO2 adsorption is a challenge for the process. A novel bi-functional Ni–Mg–Al–CaO catalyst has been prepared with different contents of CaO by integration of the catalytic and CO2 adsorbing materials to maximise hydrogen production. The prepared catalysts were tested for hydrogen production via the pyrolysis-gasification of wood biomass using a two-stage fixed-bed reaction system. The carbonation/calcination results using thermogravimetric analysis (TGA), in an atmosphere of N2 or CO2, showed that the reactivity of CaO with CO2 decreased even after several cycles of carbonation/calcination, while the Ni–Mg–Al–CaO catalyst showed a comparatively stable CO2 adsorption even after 20 cycles. Adding CaO to the Ni–Mg–Al catalyst leads to an increase in hydrogen production and selectivity due to the enhancement of the water–gas shift reaction by in situ CO2 adsorption. An optimal content of CaO was suggested to be 20 wt% (weight ratio of CaO/Ni–Mg–Al) which gave the highest hydrogen production (20.2 mmol g−1 biomass) in the presence of the Ni–Mg–Al–CaO catalyst. Temperature-programmed oxidation (TPO) showed that carbon deposition was significantly decreased with the addition of CaO in the Ni–Mg–Al catalyst, and with the increase of CaO content, coke deposition on the reacted catalyst was further decreased.

Maximizing the efficiency and economic benefits of bio-oil is a major challenge for the emerging bio-refining industry. This research has developed a promising route to produce clean-fuel hydrogen with high value carbon nanotubes (CNTs) as a by-product of the process via evaporation/pyrolysis-reforming of crude bio-oil. Since the waste catalyst coke is replaced by high-value CNTs, a potential significant increase of additional economic benefit could be contributed to the bio-refining process. Moreover, CO2 emission to the environment from the current practice of coke oxidation during catalyst regeneration would be reduced.

Gasification provides a promising alternative to thermally recycle waste plastics to produce a synthesis gas. The catalytic gasification process described here can process waste plastics to produce either a high yield, hydrogen-rich synthesis gas or high value, multi-walled carbon nano-tubes; a process that can be altered to produce the desired targeted end-product.