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Thermo-chemical conversion of plastics provides an economic flexible and environmentally friendly method to recycle waste plastics, and generates valuable materials, such as carbon nanotubes (CNTs) and syngas. The development of catalysts is a key challenge for improving the quantity and quality of CNTs. In this study, spherical catalysts loaded with Ni were studied to control CNTs growth using waste plastic as the feedstock. Three parameters were studied, including catalytic temperature, Ni content and plastics/catalysts ratio. A fixed two-stage reactor was used for thermal pyrolysis of plastic waste and the materials were characterized with various methods including scanning electronic microscopy (SEM), temperature programme oxidation (TPO) and X-ray diffraction (XRD). The results showed that different contents of Ni loaded on sphere results in the formation of metal particles with various sizes, thus leading to CNTs production with different quantity and quality. In addition, an optimal catalytic temperature at 800 °C is suggested for CNTs formation with the Ni/sphere catalyst, as the catalyst might not be activated at 600 °C and 700 °C.

In the present study, the coked catalysts derived from catalytic reforming of the pyrolysis volatiles of polyethylene (PE), lignin (LG) and their mixture were developed as low-cost and environmentally-friendly carbon materials-containing composites to remove heavy metal ions from aqueous solution. The composites were thoroughly characterized by SEM, TEM, XRD, TGA and FT-IR and then their adsorption capability towards Pb(ii) was investigated. It is found that curved cone-shape carbon nanotubes (CNTs) with abundant structural defects and O-containing surface functional groups, such as C-O, CO and -OH, can be obtained from the catalytic reforming of the mixture of PE and LG. The CNT-containing catalyst composite presents a superior adsorption capability towards Pb(ii) when it is employed in Pb(ii) removal. Adsorption isotherm and adsorption kinetics studies show that the adsorption process can be well simulated by the Langmuir isotherm and pseudo-second-order model, demonstrating that the adsorption is subjected to a homogeneous and chemical process. The calculated maximum adsorption capacity is as high as 146.08 mg g-1, which is much higher than most of the adsorbents reported. Moreover, thermodynamic analysis reveals that the adsorption is spontaneous and endothermic. Accordingly, the used catalyst from the catalytic reforming can be developed as a low-cost and highly-efficient adsorbent.

Perovskites are good candidates as a catalyst support to enhance the catalytic performance of Ni catalysts in steam methane reforming for hydrogen production. To obtain a Ni/perovskite catalyst with a high activity and stability, different LaBO3 (B = Al, Fe, Mn), La0.7A0.3AlO3−δ (A = Ca, Ba, Ce, Zn, Sr, Mg) and La1−xMgxAlO3−δ perovskites were prepared and their role in supporting Ni catalysts was comprehensively investigated in the current work. Catalyst characterization methods, including XRD, H2-TPR, H2-TPD, XPS, TG and Raman spectroscopy, were also used to understand the underlying mechanisms. The results show that the doping of Ca, Ba, Ce and Zn in the A site of the perovskite lowers the catalytic activity, while the partial substitution of Mg and Sr could improve the activity of Ni/LaAlO3. More importantly, it is suggested that the Ni/La0.7Mg0.3AlO3−δ catalyst has an outstanding catalytic activity and resistance to carbon deposition, and there is some carbon deposited after a stability test lasting for 35 h. The excellent catalytic performance is determined to be due to the higher dispersion of active Ni, the greater the amount of surface oxygen, the stronger the interaction between the active metal and support due to the partial doping of Mg.

Carbon quantum dots (CQDs), as a novel fluorescent carbon nanomaterial, have raised worldwide concern on account of their remarkable biocompatibility, water solubility, chemical stability, nontoxic...

The production of carbon nanotubes (CNTs) by catalytic pyrolysis of plastics is an environmentally friendly and promising method of waste treatment and energy/materials production. Three types of metal catalysts (Fe/cordierite, Ni/cordierite and Ni-Mg/cordierite) were utilized during the catalytic pyrolysis process of polypropylene in this work. Meanwhile, the influence of reaction pressure (0.5–1.25 MPa) on the synthesis of CNTs was investigated. Carbon formation, especially CNTs, through catalytic pyrolysis of plastics has been tested in a fixed bed reactor, and the materials have been analyzed by temperature program oxidation (TPO), scanning electron microscopy (SEM), high resolution transmission electron microscopy (TEM) and Raman spectroscopy. The highest yield around 93 wt.% filamentous carbon was obtained using the Ni-based catalyst. The strong metal-support interaction within the Ni-Mg-based catalyst suppressed CNTs growth and resulted in shorter and irregular cylindrical carbon tubes. The yield of more uniform and thick CNTs increased with the additional of appropriate reaction pressure, especially at 1.0 MPa (198 mg/gPP). However, an excessive reaction pressure weakened CNTs growth and produced shorter length and larger diameters (around 30–50 nm) CNTs. The fraction of CNTs decreased when the reaction pressure was higher than 0.5 MPa.

Excessive atmospheric CO2 emission is regarded as one of the main factors causing global climate change. Thus, there is an urgent need to explore the possibility of CO2 capture and converting the captured CO2 to fuels or value-added products. Recently, an integrated carbon capture and utilization (ICCU) process performed in a single reactor under isothermal conditions draws intensive attentions due to the reduction of energy requirement for sorbent regeneration. However, from literature, normally a low loading of sorbent in dual functional materials (DFMs) was applied resulting in a very low CO2 capture capacity and consequent low CH4 yield in the ICCU process. Herein, we demonstrate the intermediate-temperature DFMs using inexpensive high-capacity MgO sorbent. The synthesized DFMs are a physical mixture of sorbent and Ru/CeO2 catalyst by the mass ratio of 2:1 allowing simultaneous regeneration of sorbent and conversion of CO2 in a single reactor at 300 °C. During the 1st cycle of ICCU process, 10Ru/CeO2-MgO exhibits the best ICCU performance with the highest CH4 yield of 7.07 mmol g−1 and CO2 conversion of 89 %. However, after 10 cycles of ICCU process, 5Ru/CeO2-MgO exhibits the highest CH4 yield (3.36 mmol g−1) and CO2 conversion (79 %), which are much higher than that of 2.5Ru/CeO2-MgO (1.13 mmol g−1 and 39 %) and 10Ru/CeO2-MgO (2.31 mmol g−1 and 69 %). It is mainly attributed to that more oxygen vacancies are remained in 5Ru/CeO2-MgO resulted from the metal-support interaction.

CaO is a promising material as an alternative CO2 capture material which can be used at high temperature. However, CaO sinters to form large particles under long-term high temperature conditions, resulting in a rapid decrease of its surface area and the capacity of CO2 capture. Incorporating CaO into inert materials is a promising strategy to enhance the performance of CO2 capture. This work investigated a novel composite material called mesocellular siliceous foam (MCF)-supported CaO to enhance the stability and capacity of CaO-based materials for CO2 capture. The crystal structure, surface morphology and porosity property of the developed composite materials were investigated. Thermogravimetric measurements were carried out to study the cyclic CO2 capture performance of the MCF-supported CaO composites. The results showed that a part of CaO reacted with the silica wall, and the formation of Ca2SiO4 within the MCF framework limited the presence of CaO in the mesopores, thus inhibited the sintering of CaO. The sample of MCF-3CaO exhibited a better performance of CO2 capture and long-term stability, compared with the materials prepared with lower CaO loading. This work contributes to the development of high temperature CO2 capture adsorbents, which can be applied for decarbonizing major industrials e.g. power plant.

In this study, a novel nanoscale iron oxide (FeOx) modified carbon nanotubes composite (FeOx@CNTs) was synthesized through a combined ball milling–hydrothermal two-step method and tested for aqueous Sb(III) removal efficiency and mechanisms. FeOx nanoparticles was successfully loaded on the surface of CNTs through functional groups such as hydroxyl (–OH), C–H, and C–O to enhance the removal efficiency of Sb(III) through adsorption and surface complexation. At a dosage of 0.02 g, a FeCl3·6H2O-to-CNTs mass ratio of 3:1, and an initial solution pH of 6.3, the amount of Sb(III) removed by the prepared FeOx@CNTs reached 172 mg/g, which was 42.9 times higher than that of the pristine CNTs (4.01 mg/g). Chemical adsorption and oxidation were the main removal mechanisms. At the equilibrium Sb(III) concentration of 6.08 mg/L, 6.56% of initial Sb(III) was adsorbed onto the surface of FeOx@CNTs, and 81.3% of initial Sb(III) was oxidized to Sb(V) with lower toxicity. The pseudo-second-order kinetic model could better describe the adsorption of Sb(III) onto the FeOx@CNTs composite, indicating that adsorption was mainly controlled by chemical sorption. In the adsorption isotherm equation, the Redlich–Peterson model provided a better fit of Sb(III) adsorption onto the FeOx@CNTs composite than the Langmuir and Freundlich models, which further indicated that the adsorption process was a hybrid removal process dominated by chemical sorption. The presence of CO32− slightly promoted the removal of Sb(III) from aqueous solution. The synthesized composite was magnetic and could be easily separated from the solution by an external magnetic field at the end of the sorption experiment. Based on these findings, the FeOx@CNTs nanocomposite is expected to provide an environmentally-friendly adsorbent with a strong sorption capacity for remediating Sb(III) in water environments.

Excessive anthropogenic CO2 emission in the atmosphere is considered as one of the main contributions to the serious climate changes. However, with the growth of global economics, more fossil fuels will be consumed to feed the global activity, especially in developing countries. Thus, CO2 needs to be captured for storage or converted to fuels or value-added chemicals. Herein, we propose and demonstrate a one-pot method synthesized dual functional materials (DFMs), which contain a sorbent coupled with a catalyst component, allowing the sorbent regeneration and CO2 conversion to CO are performed simultaneously in a single reactor. This process requires no additional thermal energy for the regeneration of sorbents. In addition, CeO2 is incorporated into the DFMs to largely enhance the stability of the materials for the process, and the influence of different Ce loadings on the performance of integrated CO2 capture and conversion is studied. It is found that the DFMs with a Ca/Ni/Ce molar ratio of 1:0.1:0.033 displays almost 100% CO selectivity and 51.8% CO2 conversion in the reverse water-gas shift (RWGS) reaction and a remarkable cyclic stability after 20 cycles of integrated CO2 capture and conversion. Therefore, the incorporation of Ce into DFMs has two profits, for one thing, the oxygen vacancies generated by CeO2 directly reduces the dissociated CO2 regenerated from the DFMs, demonstrating the high CO yield; for another, the well-dispersed CeO2, which could act as a physical barrier, effectively prevents the growth and agglomeration of CaO crystallite and NiO species.

Biomass pyrolysis is a promising thermal chemical processing technology to produce renewable and sustainable energy materials. However, the interaction between biomass components (cellulose, hemicellulose and lignin) during pyrolysis process needed further investigation. In this work, an in-situ Reflectance Infrared Fourier Transform Spectroscopy (in-situ DRIFTS) reactor was introduced to investigate the interactions assisted with Thermogravimetric Analysis (TGA). The experiments demonstrate that there exist complicated interactions between the main components of biomass during pyrolysis. The results from TGA/DTG indicate that the interactions between cellulose and xylan introduce higher pyrolysis temperature, while the interactions between cellulose and lignin, xylan and lignin, resulte less weight loss. The increase of compression pressure for the mixture of main components changes the weight loss of the mixture. The results from in-situ DRIFTS show that the decomposition and aromatization of xylan are promoted when the cellulose is added. Cellulose will also hinder the accumulation of the benzene rings of the lignin. The in-situ DRIFTS experiment results also suggest that the contact pressure between the components conduct more residue solid, mainly because the dehydration reaction of the mixture samples was inhibited and the charring process was promoted, especially the reaction between cellulose and lignin.

Hydrogen sorption and storage in a solid matrix can greatly improve its safety and efficiency when compared to the compressed gas or liquid hydrogen storage system, and kinetics mechanisms are of interest towards the development of such materials. In this study, the composites of Mg-Ni-Cu doped with singe-walled carbon nanotubes (Mg-Ni-Cu/CNTs) were synthetized. The activation performance, isothermal hydrogen sorption and desorption were systematically tested, and the experimental data were analyzed using the shrinking core model. The results show that three cycles of hydrogen sorption and desorption may be enough to fully activate Mg-Ni-Cu/CNTs and the stability can be kept for 150 cycles. A 10.1 wt% of Cu and 50.3 wt% of Ni in Mg-Ni-Cu/CNTs facilitates the hydrogen sorption and a reversible hydrogen capacity of ∼3.35 wt% can be achieved at 310 °C and 3.0 atm, and hydrogen capacity and kinetics shows significant decline during contact with 1.0 vol% CO impurity. Considering desorption at 600 °C, the kinetic profiles are about linear and desorption is completed within minutes. The gas-solid reaction processes for hydrogen sorption undergo three different rate-limiting stages, and hydrogen desorption can only be divided into two stages of surface chemical reaction and product layer diffusion.

Carbon dioxide (CO2) capture using CaO-based adsorbents has recently attracted intense attention from both academic and industrial sectors in the last decade due to the high theoretical capacity of CO2 capture, low cost, and potential use in large scale. However, the successful development of CaO-based adsorbents is limited by significant sintering of adsorbent particles over a number of cycles of CaO carbonation/calcination. In this work, a systematic understanding of fundamental aspects of the cyclic carbonation/calcination of CaO-based materials is reviewed. A number of efforts have been discussed to improve the sintering-resistant properties of CaO-based adsorbents, such as decreasing the particle size and increasing the surface area, dispersing CaO on inert support, as well as surface modification. In particular, severe process conditions such as carrying out material calcination under pure CO2 atmosphere were considered for the development of CaO-based materials. In addition, important process parameters for CaO-based carbon capture such as CO2 partial pressure, carbonation temperature, carbonation time and the presence of contaminants have been reviewed, as well as the reactivation of spent sorbents. Synthetic CaO-based adsorbents have better performance than natural adsorbents due to the improved porosity and the presence of nanosized particles. The promising capacity and stability of CO2 capture can be obtained when the synthetic adsorbents have high surface area and mesopores and/or CaO particles are stabilized using inert materials such as Ca12Al14O33. With an increase of steam concentration in the process, the decay of CO2 capture capacity was mitigated due to the formation of a stable pore structure. The calcium looping technology has been demonstrated in pilot scale combining with catalytic reforming or gasification process. However, the reduction of sorbent costs and the optimization of process conditions (e.g. carbonation and calcination time) still need to be tested in larger scale to reduce the overall costs and enhance the overall energy efficiency. Material attrition is a key challenge in large-scale demonstration of calcium looping process. Novel technology could be developed to avoid the transportation of solid sorbents. For example, by integrating with CO2 conversion to methane, the capture of CO2 and the regeneration of bifunctional sorbents can be carried out at the same temperature in a fixed bed reactor. This can be fulfilled by introducing hydrogen to the stage of sorbent regeneration. However, much more fundamental understanding is required in this area, such as the exploration of synergies between sorbent regeneration and catalytic conversion of CO2.

Biomass gasification is one of the most promising technologies to convert renewable biomass feedstock to useful energy and chemicals for decarbonizing the current industrial activities. However, complex tar compounds are formed in the produced syngas. The presence of tar in syngas is undesirable due to a series problems caused, such as the decrease of overall efficiency and the clogging and contamination of downstream equipment. Until now, catalytic steam reforming has been widely studied for the efficient removal of tar. Previous review articles have focused on the catalytic reforming of tar by categorizing various catalysts as basic catalysts, nickel-based catalysts, non-nickel based catalysts, alkali metal catalysts, zeolite catalysts, and carbon-supported catalysts, etc. Ni-based steam-reforming catalysts have attracted much attention due to their high activity for tar reduction, low-cost and easy regeneration. However, the deactivation caused by the coke deposition and metal sintering remains the greatest challenge for the deployment of the technology. Therefore, modified Ni-based catalysts are now most frequently used for catalytic reforming of tar. At present, few review articles reported the modification of Ni-based catalysts for catalytic reforming of tar compounds. Based on this, the preparation, modification and development methods of Ni-based catalysts for catalytic reforming of tar are reviewed in this paper, aiming at promoting the catalytic performance of conventional Ni-based catalysts, in terms of high catalytic activity, long-term stability and better selectivity towards low molecular weight compounds.

The distance between catalytic sites (Ni) and sorbents (CaO) on the performance of integrated CO2 capture and utilization (ICCU) process is crucial important because the sorbents demonstrate a dramatic volume increase during carbonation reaction (1st stage of ICCU) and sequentially cover the catalytic sites and retard the CO2 conversion (2nd stage of ICCU). Herein, we synthesized various Ni/CaO-based dual functional materials (DFMs) with different distances between active sites and sorbents to provide different volume spaces for the growth of CaCO3 during the carbonation reaction. It is found that both 1%NiCaO and 10%NiCaO synthesized by a one-pot method exhibited a low CO2 conversion (38% and 45%, respectively) and CH4 selectivity (58% and 69%, respectively) as the distance between catalytic sites and sorbents was so close that the Ni active sites were covered by the formed CaCO3 during carbonation reaction. With the increase of the distance by physical mixing method, the CO2 conversion and CH4 selectivity of 1%Ni/CeO2-CaO-phy were largely increased to 62% and 84%, respectively at 550 °C and atmospheric pressure when captured CO2 from 15% CO2/N2. This is attributed to the fact that the Ni active sites were still well dispersed on the surface of CeO2 nanorods instead of being covered by the newly formed CaCO3.

[EN]The activity and stability of a 10 wt%NiO/CaO catalyst were tested in the sorption enhanced ethanol steam reforming (SEESR) in a fluidized bed reactor. The effect of temperature in the 600-750 degrees C range was analyzed and the performance of the catalyst at 700 degrees C was assessed by conducting cycles of SEESR reaction and CO2 desorption. At zero time on stream, an increase in temperature enhanced ethanol steam reforming reactions, and therefore H-2 production increased from a yield of 20.3 wt% at 600 degrees C to 22 wt% at 750 degrees C. However, high temperatures hindered the catalyst sorption performance, i.e., CO2 capture declined from 7.9 to 2.1 mmol(CO2) g(cat)(-1). In order to evaluate the catalyst performance throughout the cycles and relate it with its features, both fresh and deactivated catalysts were characterized in detail by N-2 adsorption-desorption, X-ray fluorescence (XRF), X-ray diffraction (XRD), temperature programmed reduction (TPR) and oxidation (TPO) and transmission electron microscopy (TEM). Subsequent to 12 cycles, the catalyst CO2 capture performance was slightly lower than that of the fresh one (approximately 7%) and hardly changed in the next cycles. Furthermore, the use of the same temperature for SEESR reaction and CO2 desorption led to the highest adsorption capacity of the catalyst over multiple cycles. This work was carried out with financial support from the Spain's Ministries of Science, Innovation and Universities (RTI2018-098283-J-I00 (MCIU/AEI/FEDER, UE) and (RTI2018-101678-BI00 MCIU/AEI/FEDER, UE) and Science and Innovation (PID2019-107357RB-I00 (MCI/AEI/FEDER, UE) , the Basque Government (IT1218-19 and KK-2020/00107) . This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 823745. Maria Cortazar also thanks the Basque Government for her research training grant.

In order to cope with the global energy crisis and environmental pollution problems, there are urgent needs for clean energy such as biomass-derived hydrogen. CaO is effective to promote hydrogen production from biomass gasification due to its high capacity of in-situ CO2 capture. In this work, a two-stage fixed bed reactor was used to produce hydrogen by catalytic conversion of biomass with and without in-situ CO2 capture. In addition, three Ni loadings (5 wt%, 10 wt%, and 20 wt%) supported by Al2O3 and sol-gel CaO have been prepared and tested. The BET analysis shows the surface area of the catalysts increases first and then decreases with the increase of Ni loading. Results from high-resolution transmission electron microscopy (HRTEM) images reveals that NiO particles are well distributed over the porous CaO. The X-ray diffraction (XRD) analysis indicates the NiO nanocrystalline size is increased with increasing Ni loading on Ni/Al2O3, and the most homogeneous dispersion was shown by 10 wt% Ni/CaO. Around 666 mgCO2/gCaO of CO2 adsorption capacity and 850 min stability were obtained using the sol-gel CaO sorbent. Compared to the reference Ni/Al2O3 catalysts, the resistance of carbon deposition on the Ni/CaO results in a lower coke deposition, which is attributed to the basicity of the catalysts. In addition, the increase of loading promotes the decomposition of biomass-derived oxygenated compounds. Much more hydrogen is obtained using the Ni/CaO catalysts compared with Ni/Al2O3 due to in-situ CO2 capture. However, the sintering and particle agglomeration using the 20 wt% Ni-catalyst might be responsible for the reduction of hydrogen production. The highest H2 concentration of 19.32 vol% at 424 °C was obtained when the 10 wt% Ni/CaO catalyst was used.

The influence of complementary macropores, present in hierarchical macroporous mesoporous SBA-15, on the performance of supported Ni nanoparticles for ethanol steam reforming has been investigated. The increased open nature of the architecture, afforded through the incorporation of the secondary macropore network, enables superior metal dispersion. This, in turn, enhances catalytic hydrogen production performance through the generation of a greater density of active sites.

ZSM-5 zeolite coating supported on SiC foams was prepared by a precursor dispersion-secondary growth method and the resulting structured ZSM-5/SiC foam catalyst was used for the proof-of-concept study of catalytic bio-oils upgrading (i.e. deoxygenation of the model compounds of methanol and anisole) in reference to ZSM-5 catalyst pellets. A layer of ZSM-5 coating with inter-crystal porosity on SiC foams was produced by curing the zeolite precursor thermally at 80 °C. The use of SiC foam as the zeolite support significantly improved transport phenomena compared to the packed-bed using ZSM-5 pellets, explaining the comparatively good catalytic performance achieved by the structured ZSM-5/SiC foam catalyst. In comparison with the ZSM-5 pellets, the ZSM-5/SiC foam catalyst showed 100.0% methanol conversion (at the weight hourly space velocity, WHSV, of 8 h–1) and 100.0% anisole conversion (at WHSV =5 h−1) at the initial stage of the processes, while only about 3% were obtained for the ZSM-5 pellets, under the same conditions. Based on the comparative analysis of the characterisation data on the fresh and spent catalysts, the deactivation mechanisms of the ZSM-5/SiC and the ZSM-5 pellet catalysts were explained. The process intensification using SiC foam to support ZSM-5 improved the global gas-to-solid mass transfer notably, and hence mitigating the pore blocking due to the carbon deposition on the external surface of supported ZSM-5.

Catalytic steam gasification of biomass can produce clean and renewable hydrogen. In this study, Ce/Fe bimetallic catalysts were used to promote hydrogen production from cellulose steam catalytic reforming at 500–900 °C. The effect of different Ce/Fe ratios on the catalytic performance of hydrogen production was studied. The distribution of products, gas composition, carbon deposition and the stability of the catalyst were analyzed with variant approaches. The results show that the catalytic performance of the CeO2/Fe2O3 catalyst in relation to hydrogen production was much better than pure CeO2 or Fe2O3. When the ratio of Ce:Fe was 3:7, the maximum yield of the H2 was 28.58 mmol at 800 °C. CeFeO3 could be generated at 800 °C or higher temperature after redox reactions without forming CeO2/Fe2O3 clathrate. And the existence of CeFeO3 enhanced the thermal stability of Ce/Fe catalyst. The presence of CeO2 not only improved the oxidative ability of the iron catalysts, but also was in favour of the oxidation of possible deposited carbon on the surface of the used catalysts.

Catalytic steam reforming for producing high quality syngas from biomass fuel gas was studied over monolithic NiO/porous ceramic catalysts in a fixed-bed reactor. Effects of reaction temperature, steam to carbon (S/C) ratio, and nickel loading content on catalyst performance were investigated. Results indicated that the NiO/porous ceramic monolith catalyst had a good ability to improve bio-fuel gas quality. H 2 yield, H 2 + CO content, and H 2 /CO ratio in produced gas were increased when reaction temperature was increased from 550 to 700 °C. H 2 yield was increased from 28.1% to 40.2% with S/C ratio increased from 1 to 2. And the yield of hydrogen was stabilized with the further increase of S/C ratio. Catalyst activity was not always enhanced with increased nickel content, when NiO loading content reaches 5.96%, serious aggregation and sintering of active composition on catalyst surface occur. The best performance, in terms of H 2 yield, is obtained with 2.50% NiO content at reaction temperature of 700 °C and S/C ratio of 2.

Oil sludge is one of solid wastes that produced in the oil industry. Pyrolysis has been considered as an attractive technology for oil recovery. However, solid fine particles could be generated during process of oil sludge pyrolysis that could cause fouling and blockage in downstream equipment and connections. In this work, a ceramic membrane was used in the reactor to filter the fine particles in the product gas. The influence of temperatures on the component of pyrolysis gas and oil were also investigated by GC–MS and FT-IR. The results showed that the ceramic membrane can trap different ranges of particles. For the particle size less than 38 mm and 38–75 mm, the mass fraction obtained in the presence of the ceramic membrane is higher than that collected without the membrane (from 1.62 to 3.07% and from 20.84 to 22.85%). A maximum oil yield of 10.47% and oil recovery ratio of 52.95% were obtained at 500 °C. The GC–MS analysis of the pyrolysis oil showed that the oil was composed of long-chain aliphatic compounds with a number of carbons ranging from C10 − C27.

In order to facilitate the further processing and utilization of biomass pyrolysis oil, the chemical composition and thermal properties of biomass pyrolysis oil from pyrolysis of rice husk were investigated. The chemical composition analysis revealed that the pyrolysis oil contained a large amount of oxygenated compounds, i.e., acid, ketones, and phenols. Thermal degradation behaviors and kinetics of pyrolysis oil were investigated at different heating rates (5, 20, 35, and 50 °C min–1) under N2 and air atmospheres by TG. Pyrolysis oil decomposition mainly experienced three stages in either N2 or air atmosphere, and the corresponding activation energies vary with the degree of conversion. Py-GC/MS analysis of the pyrolysis oil reveals that ketones and aromatics are the main pyrolysis products of biomass pyrolysis oil. When the temperature increased from 600 to 700 °C during Py-GC/MS analysis, the content of ketones increased while the content of aromatics decreased. Subsequently, the feasibility of cataly...

Biomass transformation into high-value carbon nanomaterials plays a dual role of easing the energy material crisis and reasonable disposal of waste. Here, we employed biomass lignin as carbon source to synthesize fluorescent carbon quantum dots (CQDs) through a facile two-step method. The preparation condition is optimized at 0.3 g of acid additive and 200 ℃, 16 h of hydrothermal treatment. The resultant CQDs with the average diameter of 4.86 nm and high quantum yield of 23.68% are composed of carbon cores and surface functional groups, exhibiting the maximum green emission wavelength of 476 nm. The formation mechanism involves acid dissociation of lignin in the first step, and then the aromatic refusion of lignin fragments. The CQDs show great advantages as fluorescent nanoprobe for metal ion detection, which present an apparent and selective fluorescence quenching effect on Fe3+. This CQD nanoprobe has a highly sensitive response to Fe3+ ions in the concentration of 0 ~ 300 μM with detection limit of 0.77 μM. The utilization of renewable biomass lignin in this study not only opens the avenue of the sustainable, cost-effective and mass production of CQDs, but also provides a novel alternative nanoprobe for sensing field.

In this work, the production of carbon nanotubes (CNTs) from waste plastics was investigated to reduce the cost of CNTs production, as well as providing alternative management for waste plastics. A template-based catalyst (Ni/anodic anodic aluminium oxide-AAO) was studied herein to control the growth of CNTs with uniform distribution of diameters. The addition of a conditioning catalyst (for modifying carbon sources) was studied for their influences on the formation of CNTs on Ni/AAO. A two-stage reactor was used to test the prepared catalysts which were also characterized with various methods e.g. scanning electronic microscopy (SEM) and temperature programmed oxidation (TPO). The results show that the introduction of a conditioning catalyst (Ni/Al2O3) positively affected the growth of CNTs with more uniform distribution of diameters of CNTs.

Catalytic reforming of real biomass pyrolysis oil (BPO) was carried out with a nano-Ni/ceramic foam catalyst using a fixed bed reactor. XRD, TPR, SEM/EDX and BET were used to characterize the synthesized catalysts. The analysis results showed that nickel oxide was in-situ reduced to active nickel metal during the steam reforming process and the size of NiO particles loaded on the surface of ceramic foam was in the range of 30–40 nm. NiO nanoparticles showed a homogeneous multilayer deposition on the surface of the catalyst and the BET surface area of the fresh catalyst was increased with the increase of Ni loading. The effects of calcination temperature, reaction temperature and weight hourly space velocity (WHSV) on hydrogen production were studied. The results showed that the yields of hydrogen and gas were decreased with the calcination temperature increasing from 400 to 700 °C. The yield of H 2 were in the range of 44.41–89.17 g H 2 kg −1 BPO when the reaction temperatures varied from 500 to 800 °C. The hydrogen yield was decreased with the increase of WHSV, and a low activation energy (25.34 kJ mol −1 ) was obtained from kinetic studies, indicating the effectiveness of the nano-Ni/ceramic foam catalyst.

The evaluation of thermochemical characteristics and the development of kinetic model for pyrolysis of waste biomass are more challenging. In this study, the mass losses, intermediates evolved and products formed during pyrolysis of waste wood biomass were determined by coupling DSC/TGA-DTG/GC-MS/FTIR to improve the understanding of conversion processes and decomposition characteristics. The improved non-isothermal kinetics method was proposed by introducing the function of mechanisms, the activation energies and pre-exponential factors were estimated iteratively by regression to enhance modeling accuracy. The results indicated the gases of CO, CO2, CH4, H2 and the liquids of N-containing organics, esters, ketons and carboxylic acids were the most dominated products evolved. The pyrolysis of waste wood biomass could be divided into three phases, and with the increase of heating rates, the caloric requirement for pyrolysis was greatly increased. The random nucleation and one-dimensional diffusion predicted accurately the main (second) and third phases in the pyrolysis of waste wood biomass and waste camphor presented lower activation energies than waste bamboo.

Hypercrosslinked polymers (HCPs) are very promising for large-scale applications due to their easy preparation, high thermal stability, and good capability of CO2 capture. Currently, many amine-functionalized porous materials are prepared through two steps. In this paper, the amine-functionalized HCPs was obtained with a one-step method and it showed a high CO2 adsorption up to 4.24 mmol/g at 273.15 K. In addition, since the azo-functionalized porous materials have many potential applications like the photoresponsive ‘smart’ materials, azobenzene is an attracting functional group for the development of porous materials. Herein, the azo-functionalized HCPs is firstly reported, and it is used as CO2 adsorbents (3.02 mmol/g at 273.15 K) performing good CO2/N2 selectivity (34.52 at 298.15 K).

To explore the mechanism of the influence of Ni-Fe bimetallic catalyst for the producing high-value carbon nanotubes (CNTs) with clean hydrogen from waste plastic pyrolysis, the pyrolysis-catalysis of plastics were performed using a two stage fixed bed reaction system with Ni and Fe loading at variant molar ratios. The catalysts and produced carbon were analysed with various characterization method, including temperature-programed reduction/oxidation, X-ray diffraction, scanning electron microscopy or/and Raman spectroscopy. Both the H2 concentration and H2 yield reached maximum values of 73.93 vol.% and 84.72 mg g−1 plastic, respectively, as the ratio of Ni:Fe at 1:3. The amount and quality of CNTs were greatly influenced by the catalyst composition, and Ni and Fe display different roles to the overall reactivity of Ni-Fe catalyst for the pyrolysis-catalysis of waste plastics. Catalyst with more Fe loading produced more hydrogen and deposited carbon, due to higher cracking ability and the relatively lower interaction between active sites and support. The presence of Ni in Ni-Fe bimetallic catalyst enhanced the thermal stability and graphitization degree of produced carbons. The thermal quality of filamentous carbons might be associated with carbon defects.

Ni/SiO2 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 N2) 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 N2. Material balances on ethanol steam reforming at 600 °C using the prepared Ni/SiO2 catalysts were determined, and higher hydrogen production with lower coke deposition on the reacted catalysts were also obtained from the catalysts calcined in N2 atmosphere.

Mesoporous silica supported Ni nanoparticles have been investigated for hydrogen production from ethanol steam reforming. Ethanol reforming is structure-sensitive over Ni, and also dependent on support mesostructure; three-dimensional KIT-6 possessing interconnected mesopores offers superior metal dispersion, steam reforming activity, and on-stream stability against deactivation compared with a two-dimensional SBA-15 support.

A stainless-steel mesh loaded with nickel catalyst was produced and used for the pyrolysis–catalysis of waste high-density polyethylene with the aim of producing high-value carbon products, including carbon nanotubes (CNTs). The catalysis temperature and plastic-to-catalyst ratio were investigated to determine the influence on the formation of different types of carbon deposited on the nickel–stainless-steel mesh catalyst. Increasing temperature from 700 to 900°C resulted in an increase in the carbon deposited on the nickel-loaded stainless-steel mesh catalyst from 32.5 to 38.0 wt%. The increase in sample-to-catalyst ratio reduced the amount of carbon deposited on the mesh catalyst in terms of g carbon g−1 plastic. The carbons were found to be largely composed of filamentous carbons, with negligible disordered (amorphous) carbons. Transmission electron microscopy analysis of the filamentous carbons revealed them to be composed of a large proportion (estimated at ∼40%) multi-walled carbon nanotubes...

Methanation of syngas (H 2 /CO) in a fixed-bed down-flow reactor under atmospheric atmosphere was investigated over a series of Ni-based catalysts with Fe and TiO 2 as the support. The prepared catalysts (Ni/Al 2 O 3 , Ni-Fe/Al 2 O 3 , and Ni-Fe/TiO 2 -Al 2 O 3 ) were characterized by N 2 adsorption-desorption, X-ray diffraction (XRD), temperature-programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS). The characteristics of the catalysts for the methanation process were investigated with the ratio of H 2 /CO as 3:1 under an atmospheric pressure. The addition of Fe in the Ni/Al 2 O 3 catalyst could promote the dispersion of Ni species and decrease the reduction temperature of catalyst. The optimal ratio for Ni-Fe/Al 2 O 3 catalyst was estimated to be 1 due to the small-sized Ni particles and easily reducible β-type NiO species, giving the CO conversion of 97% and CH 4 selectivity of 94% at 262 °C. The addition of TiO 2 (10 wt%) in Ni-Fe/Al 2 O 3 catalyst promotes the formation of Ni-Fe alloy, facilitating the methanation reaction at low temperatures and suppressing the coke deposition. This also results in the outstanding stability of the Ni-Fe/TiO 2 -Al 2 O 3 catalyst over other Ni-Fe/Al 2 O 3 catalysts.

The production of renewable hydrogen-enriched gas from biomass waste is a promising technology for the development of a sustainable economy and society. Until now, there are still challenges of the technology in terms of the efficiency of hydrogen production. A catalyst is known and has been tested to enhance hydrogen production from biomass gasification, in particular, using Ni-based catalysts, which have high reactivity for hydrogen production and are cost-effective. However, developing a Ni-based catalyst with high thermal stability and resistance of coke deposition on the surface of the catalyst is still a challenging topic. In this work, Ni–Al catalysts doped with low-cost Fe metal were investigated for hydrogen-enriched syngas production from gasification of biomass using a two-stage fixed bed reactor. NiO–Fe2O3–Al2O3 catalysts with various Ni/Fe molar ratios (9:1, 8:2, 6:4, 5:5, 4:6, 2:8, and 1:9) were studied, aiming to understand the influence of Fe addition on the production of hydrogen and the catalyst stability in terms of coke deposition on the surface. X-ray diffraction, temperature-programmed reduction, and transmission electron microscopy (TEM) analysis of the fresh catalysts showed that nanoparticles (mainly NiAl2O4 spinel phase and Al2O3, ∼5 nm) were identified in the catalysts. High dispersion of metal particles was obtained using a co-precipitation method of catalyst preparation. With the increase of Fe addition, hydrogen production was reduced from around 11 to 8 mmol of H2 g–1 of biomass. However, the addition of Fe to the Ni-based catalyst significantly reduced the amount of coke deposited on the surface of the catalyst. The H2/CO molar ratio was maximized to 1.28 when the Ni/Fe molar ratio was 1:1. In addition, sintering of metal particles was not observed through the TEM analysis of the fresh and reacted catalysts.

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 mmol g−1 at 850 °C to 30.62 mmol 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.

Detailed understanding of the mechanisms of the fast stage during CaO carbonation is important for the design of novel efficient CaO materials. This work systematically studies the formation of a CaCO 3 product layer on the outside surface of CaO grains during the fast reaction stage for carbon capture using two types of CaO adsorbents. The carbonation at 400 °C filled the small pores in the commercial CaO grains and no distinct product layer of CaCO 3 was observed. However, a distinct layer of CaCO 3 with a thickness around 90 nm was observed on the outside surface of the commercial CaO grains after the carbonation at 600 °C because the internal pores in the CaO grain had been filled and a layer of CaCO 3 product was deposited on the outside surface of the CaO grain. For sol-gel CaO, the carbonation reaction is limited by the availability of useful porosity for the growth of CaCO 3 product (confinement effect), instead of by the diffusion of ions in the critical layer of the CaCO 3 product. No surface product layer was observed. Therefore, fabricating nano-CaO having dimensions less than the critical thickness of the CaCO 3 layer (∼90 nm) is of potentially great significance if it can be done cheaply and in bulk.

The incorporation of CaO into an inert porous solid support has been identified as an effective approach to improve the stability of adsorbents for CO2 capture. In this work, we focus on enhancing the capacity of carbon capture and cyclic stability of CaO by impregnating CaO particles into a three-dimensional mesoporous silica (KIT-6) support. At a low CaO loading, the three-dimensional mesoporous support was filled with CaO nano-particles. The further increase of CaO loading resulted in the aggregation of CaO particles on the external surface of the support material, as identified by electron microscopy analysis. These CaO/KIT-6 adsorbents show excellent high-temperature CO2 carbonation/calcination stability over multiple cycles of CaO carbonation and calcination. The enhancement of the performance of carbon capture is attributed to the interaction between CaO and the silica skeleton of KIT-6 through the formation of interfacial CaSiO3 and Ca2SiO4 which enhanced the resistance of CaO sintering.

As the amount of waste plastic increases, thermo-chemical conversion of plastics provides an economic flexible and environmental friendly method to manage recycled plastics, and generate valuable materials, such as carbon nanotubes (CNTs). The choice of catalysts and reaction parameters are critical to improving the quantity and quality of CNTs production. In this study, a ceramic membrane catalyst (Ni/Al2O3) was studied to control the CNTs growth, with reaction parameters, including catalytic temperature and Ni content investigated. A fixed two-stage reactor was used for thermal pyrolysis of plastic waste, with the resulting CNTs characterized by various techniques including scanning electronic microscopy (SEM), transmitted electronic microscopy (TEM), temperature programmed oxidation (TPO), and X-ray diffraction (XRD). It is observed that different loadings of Ni resulted in the formation of metal particles with various sizes, which in turn governs CNTs production with varying degrees of quantity and quality, with an optimal catalytic temperature at 700 °C.

Thermogravimetric analysis (TGA) was applied to evaluate the combustion behaviour of combining three feedstocks coal, biomass and polyethylene as a tri-fuel for various blend ratios. The feed materials assessed were bituminous coal (BC), anthracite coal (AC), camphor wood (CW), wheat straw (WS) and polyethylene-terephthalate (PET). The kinetic parameters of the tri-fuel blends were assessed using a Coats-Redfern integral method. The kinetic analysis indicates that the tri-fuel combustion mechanisms follow the diffusion model (D1 & D4) and can be separated in to three distinct stages. TGA analysis demonstrated that an increase in the blend ratio of biomass (CW/WS) and plastic (PET) enhances the combustion properties with respect to lowering the ignition (Ti) and burnout (Th) temperatures, along with an increase in the combustion stability indices (Cs/Csi). This enhancement of the combustion behaviour is more evident for the lower volatile anthracite coal tri-fuel blends. As the blend ratio of the anthracite coal is lowered the overall hydrocarbon-volatile content is increased as a function of increasing the biomass and plastic blend ratios. Laboratory scale analytical analysis of blending biomass, plastic with either bituminous coal or anthracite coal demonstrates a synergistic influence which is observed to benefit the overall combustion behaviour (enhanced mass loss rate and burnout). However, further investigation of tri-fuel blending streams assessing the combustion performance (Ti, Th, Ci, Csi, Ea, flue gas emissions and ash chemistry) is required at pilot and plant scale.

Thermo-chemical conversion is a promising technology for the recycle of waste plastics, as it can produce high-value products such as carbon nanotubes (CNTs) and hydrogen. However, the low yield of CNTs is one of the challenges. In this work, the addition of Mn (0 wt.%, 1 wt.%, 5 wt.%, and 10 wt.%) to Fe-based catalyst to improve the production of CNTs has been investigated. Results show that the increase of Mn content from 0 wt.% to 10 wt.% significantly promotes CNTs yield formed on the catalyst from 23.4 wt.% to 32.9 wt.%. The results show that Fe-particles in the fresh catalysts are between 10−25 nm. And the addition of Mn in the Fe-based catalyst enhanced the metal-support interactions and the dispersion of metal particles, thus leading to the improved catalytic performance in relation to filamentous carbon growth. In addition, the graphitization of CNTs is promoted with the increase of Mn content. Overall, in terms of the quantity and quality of the produced CNTs, 5 wt.% of Mn in Fe-based catalyst shows the best catalytic performance, due to the further increase of Mn content from 5 wt.% to 10 wt.% led to a dramatic decrease of purity by 10 wt.%.

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.

Tar reduction is an important issue for the development of biomass gasification process. In this work, a NiO/ceramic foam catalyst was developed and studied for catalytic steam reforming of tar model compound (benzene) using a fixed-bed reactor. Different reaction temperatures, equivalent ratios (ER), and steam/carbon (S/C) molar ratios were investigated with a space velocity of 5.6 h − 1 . The introduction of the NiO/ceramic foam catalyst showed excellent production of hydrogen and carbon conversion. With the increase of reaction temperature from 700 to 900 °C, the yield of hydrogen increased from 140.67 to 182.06 (g H 2 kg − 1 benzene). The increase of ER resulted in the decrease of the H 2 yield. A stability test (including regeneration of reacted catalyst) showed that the catalyst was deactivated by the deposition of carbons (confirmed from scanning electron microscopy), which could be removed using air oxidation at 750 °C. The catalytic activity of the catalyst in relation to the hydrogen production could be regained after the regeneration process. A kinetic model study of the process showed that the apparent activation energy and the pre-exponential factor were 73.38 kJ/mol and 1.18 × 10 5 (m 3 kg − 1 catalyst h − 1 ), respectively.

Hydrogen production from the catalytic steam gasification of bio-char derived from the pyrolysis of sugar cane bagasse has been investigated in relation to gasification temperature up to 1050 °C, steam flow rate from 6 to 25 ml h−1 and type of Nickel catalyst. The catalysts used were Ni-dolomite, Ni–MgO and Ni–Al2O3, all with 10% nickel loading. The hydrogen yield in the absence of a catalyst at a gasification temperature of 950 °C was 100.97 mmol g−1 of bagasse char. However, the presence of the Ni–MgO and Ni–Al2O3 catalysts produced significantly improved hydrogen yields of 178.75 and 187.25 mmol g−1 of bagasse char respectively at 950 °C. The hydrogen yield from the char with the Ni-dolomite only showed a modest increase in hydrogen yield. The influence of gasification temperature showed that the optimum temperature to obtain the highest hydrogen yield was 950 °C. Increase in gasification temperature from 750 to 950 °C significantly increased hydrogen yield from 45.30 to 187.25 mmol g−1 of bagasse char at 950 °C, but was followed by a decrease in yield at 1050 °C. The influence of steam flow rate showed that with the increase in steam flow rate from 6 to 15 ml h−1 hydrogen yield was increased from 187.25 to 208.41 mmol g−1 of bagasse char. Further increase in steam flow rate resulted in a decrease in hydrogen yield.

Municipal solid waste (MSW) contains significant amounts of polyvinyl chloride (PVC). The reactivity of PVC may form polycyclic aromatic hydrocarbons (PAHs) during the pyrolysis of MSW, which can become a key challenge during the development of pyrolysis technologies. However, there is very limited work in relation to the influence of pyrolysis process conditions in terms of temperature and heating rate on PAHs formation during pyrolysis of PVC. In this work, the formation of 2–4-ring PAHs from the pyrolysis of PVC at temperatures of 500, 600, 700, 800, or 900 °C and at fast and slow heating rates was investigated under a N2 atmosphere in a fixed bed reactor. With the increase of temperature from 500 to 900 °C, HCl yield decreased from 54.7 to 30.2 wt.%, while the yields of gases and PAHs in the tar increased. Slow pyrolysis generated higher HCl yield, and lower gas and tar yield than fast pyrolysis; the PAH yield obtained from the slow pyrolysis was much lower compared to fast pyrolysis. The results suggest that for fast pyrolysis, the dehydrochlorination of the PVC might be incomplete, resulting in the formation of chlorinated aromatic compounds.

The production of hydrogen-enriched syngas from the thermo-chemical conversion of biomass was studied using Ni/CaAlOx catalysts-prepared by co-precipitation method. The effect of Ca addition with different molar ratios of Ca:Al (1:3, 1:2, 1:1, 2:1, 3:1) on the properties and catalytic behavior in relation to syngas production and the coke formation on the surface of the catalysts were investigated. Catalysts were characterized by BET, XRD, TPR, SEM, and TEM. The SEM and TEM results showed that rod-shaped nanoparticles were highly dispersed on the surface of the catalyst. The particle size of NiO was slightly affected with the increase of Ca content in the catalyst. It appeared that the selectivity of CO was increased and the selectivity of CO2 was reduced with the increase of Ca addition to the catalyst. For example, CO2 concentration was reduced from 20 to 12 vol.%, when the molar ratio of Ca/Al was increased from 1:3 to 3:1 for the Ni/CaAlOx catalyst; it is suggested that the water gas shift reaction was inhibited and CO2 reforming reactions were promoted in the presence of the catalyst with higher Ca content. The CO/H-2 molar ratio could be manipulated by changing the Ca content in the catalyst, while the H-2 concentration remaihed almost constant (around 45 vol.%). Thus, using the Ni/CaAlOx catalyst developed in this work could provide a promising route to control the syngas composition, which is an important factor for syngas applications. (C) 2015 Elsevier B.V. All rights reserved.

Nickel, iron, cobalt and copper catalysts were prepared by impregnation and used to produce carbon nanotubes and hydrogen gas from a LDPE feedstock. A two stage catalytic pyrolysis process was used to enable large yields of both products. Plastics samples were pyrolysed in nitrogen at 600 °C, before the evolved gases were passed to a second stage and allowed to deposit carbon onto the catalyst at a temperature of 800 °C. Carbon nanotubes were successfully generated on nickel, iron and cobalt but were barely observed on the copper catalyst. Iron and nickel catalysts gave the largest yield of both hydrogen and carbon nanotubes as a result of metal-support interactions which were neither too strong, like cobalts, nor too weak like copper. These metal support interactions proved a key factor in CNT production. A nickel catalyst with a weaker interaction was prepared using a lower calcination temperature. Yields of both carbon nanotubes and hydrogen gas were lower on the Ni-catalyst prepared at the lower calcination temperature, as a result of sintering of the nickel particles. In addition, the catalyst prepared at a lower calcination temperature produced metal particles which were too large for CNT growth, producing amorphous carbons which deactivate the catalyst instead. Overall the iron catalyst gave the largest yield of CNTs, which is attributed to both its good metal-support interactions and irons large carbon solubility.

Thermo-chemical processing of biomass is a promising alternative to produce renewable hydrogen as a clean fuel or renewable syngas for a sustainable chemical industry. However, the fast deactivation of catalysts due to coke formation and sintering limits the application of catalytic thermo-chemical processing in the emerging bio-refining industry. In this research, Fe–Zn/Al2O3 nanocatalysts have been prepared for the production of hydrogen through pyrolysis catalytic reforming of wood sawdust. Through characterization, it was found that Fe and Zn were well distributed on the surface with a narrow particle size. During the reactions, the yield of hydrogen increased with the increase of Zn content, as Zn is an efficient metal promoter for enhancing the performance of the Fe active site in the reaction. The 20% Fe/Al2O3 catalyst with Zn/Al ratio of 1:1 showed the best performance in the process in relation to the hydrogen production and resistance to coke formation on the surface of the reacted catalyst. All the catalysts showed ultra-high stability during the process and nearly no sintering were observed on the used catalysts. Therefore, the nanocatalysts prepared in this work from natural-abundant and low-cost metals have promising catalytic properties (high metal dispersion and stability) to produce H2-rich syngas with optimal H2/CO ratio from the thermo-chemical processing of biomass.

The non-isothermal characteristics and pyrolysis kinetics of bituminous coal at different heating rates of 10, 20, and 30 ℃/min were studied by coupling TG-MS/DSC techniques. A fixed-bed reactor was used to investigate the coal-CaO-H2O reactions to understand hydrogen production and the effects of CaO under different water feeding rates. The pyrolysis phase, the maximum mass loss rate, the characteristic peak temperature, and the release of the main volatile gases were studied. Based on the improved Coats-Redfern method by introducing the function of Q (E/RT), the activation energies and pre-exponential factors of non-isothermal pyrolysis of bituminous coal were estimated iteratively by regression to enhance their accuracy. The values of E were calculated as 22, 22, 19 kJ/mol in the first stage, 67, 75, 78 kJ/mol in the second stage, 114, 96, 133 kJ/mol in the third stage at the heating rates of 10, 20, and 30 ℃/min. Finally, the concentration and selectivity of gaseous products from the pyrolysis of bituminous coal were studied. The concentrations of H2, CO, and CO2 in the gas products increased with the addition of CaO and the increase of water feeding rate. Besides, the concentration of CH4 increases with the increase of water feeding rate but decreases significantly with the addition of CaO. It is also worth noting that the pyrolysis process was enhanced by CaO addition to in-situ CO2 captured and catalytic cracking reactions at the initial stage of the pyrolysis process.

The management of waste hard plastics is a big challenge in the world. Conventional pyrolysis and gasification of hard plastics have been extensively reported. However, producing high values carbon nanotubes as the main product or byproduct from hard plastics has been rarely reported. In this work, we studied and reported this work by using pyrolysis of phenolic formaldehyde resin producing high value carbon nanotubes to promote the economic competitiveness of the technology. The produced carbon nanotubes were characterized by scanning electronic microscopy, transmission electron microscopy, X-ray diffraction, Raman spectroscopy and temperature programme oxidation. The yield of CNTs using the Ni catalysts is about 24.07 % and its purity is 93.13 %. Compared with the Ni catalysts, the Fe catalysts have higher yield and purity of CNTs, reaching 34.39 % and 97.45 %, respectively. Through transmission electron microscopy and Raman characterization, it is found that the graphitization quality of CNTs produced from Fe catalysts is higher than that of the CNTs produced from Ni catalysts.