The gasification of biomass produces a syngas that can be used for electricity generation and fuels/chemicals production. However, tar is generated along with the syngas as a by-product which causes ...problematic issues in the end-use of the syngas, such as blockages, plugging and corrosion. Catalytic steam reforming is a suitable option to convert tar into more syngas in the presence of nickel-based catalysts, as the preferred catalyst, mainly due to their activity and low cost. There has been considerable research reported in the literature on modified nickel-based catalysts for steam tar reforming. These modifications have been carried out in order to improve the performance of the Ni-based catalysts for tar reforming, mainly in terms of catalyst stability and activity. Such improvements are achieved by manipulating the properties of the catalyst. This paper therefore presents a critical assessment of these modifications on Ni-based catalysts available in the literature for improved tar reforming. The modifications considered in this review were categorised as: the addition of secondary metal (Fe, Co, Cu, Cr), the addition of noble metals (Pt, Pd, Rh, Au, Rh, Ir), addition of rare earth metals as promoters (Ce, La), alkali and alkaline earth metals (Sr, Ba, Ca, Mg,Ba) and modification of the support material. The paper aims at understanding the properties responsible for the improved performance of the modified Ni-based catalysts in comparison with unmodified Ni-based catalysts. The review paper will serve as a guide for further improvement of Ni-based catalysts for biomass tar reforming.
•Gasification of biomass produces a problematic tar which is a barrier to deployment.•Catalytic steam reforming with Ni-catalysts converts tar to useful gas products.•Modification of Ni-based catalysts can reduced catalyst coking and sintering.•A wide range of catalysts used as Ni-catalyst modifiers are reviewed.•The underlying reasons for enhanced catalyst performance are reviewed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Summary
Activated carbon is a promising material that has a broad application prospect. In this work, biomass (tea seed shell) was used to prepare activated carbon with KOH activation (referred to as ...AC), and nitrogen was doped in activated carbon using melamine as the nitrogen source (referred to as NAC‐x, where x is the mass ratio of melamine and activated carbon). The obtained activated biomass carbon (activated bio‐carbon) samples were characterized by Brunauer–Emmett–Teller (BET)‐specific surface area analysis, ultimate analysis, X‐ray photoelectron spectroscopy (XPS) analysis, Raman spectrum analysis, and X‐ray diffraction (XRD) patterns. The specific surface areas of activated bio‐carbons were 1503.20 m2/g (AC), 1064.54 m2/g (NAC‐1), 1187.93 m2/g (NAC‐2), 1055.32 m2/g (NAC‐3), and 706.22 m2/g (NAC‐4), revealing that nitrogen‐doping process leads to decrease in specific surface area. XPS analysis revealed that the main nitrogen‐containing functional groups were pyrrolic‐N and pyridinic‐N. The capacity of CO2 capture and electrochemical performance of activated bio‐carbon samples were investigated. The CO2 capturing capacity followed this order: AC (3.15 mmol/g) > NAC‐2 (2.75 mmol/g) > NAC‐1 (2.69 mmol/g) > NAC‐3 (2.44 mmol/g) > NAC‐4 (1.95 mmol/g) at 298 K at 1 bar, which is consistent with the order of specific surface area. The specific surface area played a dominant role in CO2 capturing capacity. As for supercapacitor, AC‐4 showed the highest specific capacitance (168 F/g) at the current density of 0.5 A/g, but NAC‐2 showed the best electrochemical performance (89 F/g) at 2 A/g. Nitrogen‐containing functional groups and specific surface area both had an important impact on electrochemical performance. In general, NAC‐3 and NAC‐2 produced excellent electrochemical performance. Compared with NAC‐3, less melamine was used to prepare NAC‐2; therefore, NAC‐2 was considered as the best activated bio‐carbon for supercapacitor for 141 F/g (at 0.5 A/g), 108 F/g (at 1 A/g), and 89 F/g (at 2 A/g) in this work.
Activated carbon was prepared from tea shell, and nitrogen was doped with melamine.
Disordered carbon structure was showed. Pyrrolic‐N and pyrridinic‐N were main functional groups.
Specific surface area and pore structure were key factors for CO2 capturing capacity.
Nitrogen‐containing functional groups played an important role for supercapacitor.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The increasing levels of sewage sludge production demands research and development to introduce more commercially feasible options for reducing socio-economic and environmental problems associated ...with its current treatment. Sewage sludge may be processed to produce useful products or as a feedstock for energy generation. Initially, the characteristics of sewage sludge are discussed in terms of composition and the current options for its treatment with the associated environmental impacts. Processes to valorize sewage sludge are discussed, including heavy metal removal from sewage sludge, production of bio-char, production and use of activated carbon and use of sewage sludge combustion ash in cement and concrete. Thermochemical processes i.e., pyrolysis, co-pyrolysis and catalytic pyrolysis, also gasification and combustion for process intensification, energy and resource recovery from sewage sludge are then critically reviewed in detail. The pyrolysis of sewage sludge to produce a bio-oil is covered in relation to product bio-oil composition, reactor type and the use of catalysts. Gasification of sewage sludge focusses on the characteristics of the different available reactor types and the influence of a range of process parameters and catalysts on gas yield and composition. The selection and design of catalysts are of vital importance to enhance the selectivity of the selected thermochemical pyrolysis or gasification process. The catalysts used for sewage sludge treatment need more research to enable selectivity towards the targeted desired end-products along with optimization of parametric conditions and development of innovative reactor technologies. The combustion of sewage sludge is reviewed in terms of reactor technologies, flue gas cleaning systems and pollutant emissions. In addition, reactor technologies in terms of technological strength and market competitiveness with the particular application to sewage sludge are compared for the first time for thermochemical conversion. A critical comparison is made of the drying techniques, co-feedstocks and catalytic processes, reaction kinetics, reactor technologies, operating conditions to be optimized, removal of impurities, fuel properties, their constraints and required improvements. The emphasis of this review is to promote environmental sustainability for process intensification, energy and resource recovery from pyrolysis, gasification and combustion involving the use of catalysts.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Summary
Biomass based carbon has captured more and more attention because it is environmentally friendly and has properties of low cost and ideal sustainability. In this study, three kinds of ...activated biomass carbons (ie, ABC‐700, ABC‐800 and ABC‐900) were first carbonized through pine sawdust pyrolysis and then activated using KOH under three different activation temperatures (ie, 700°C, 800°C and 900°C). The structure properties of the prepared activated biomass carbons were characterized by N2‐adsorption/desorption, SEM, TEM, XRD, Raman, XPS, TG and ultimate analysis. To clarify the activation mechanism, the gas products produced during KOH activation process were measured online with an ETG gas analyzer. The performance of the activated biomass carbons derived from pine sawdust for supercapacitor and CO2 capture was then evaluated. The predominant gas products during the activation process are H2 and CO. It indicates that the porous structure was created by using an enhanced etching reaction between carbon atoms and KOH. An increment of the activation temperature from 700 to 900°C results in the increase of surface area (from 1728.66 to 2330.89 m2/g) and total pore volume (from 0.671 to 1.914 cm3/g). Among the three samples, ABC‐900 exhibits the maximal specific capacitance of 175.6 F·g−1 and high energy density of 24.39 Wh·kg−1 at the 0.5 A·g−1. And the ABC‐700 shows the maximal CO2 capture capacity of 4.21 mmol/g and high selectivity of CO2 over N2 at 298 K and 1 bar. In addition, ABC‐700 also has excellent stability and reproducibility after 15 times adsorption‐desorption cycles. The unexceptionable electrochemical performance and adsorption capacity of the biomass‐carbons show its broad application prospects in the field of supercapacitors and CO2 capture.
Activated biomass carbon (ABC) was successfully fabricated from pine sawdust.
ABC exhibited an excellent specific capacitance of 175 F g−1 0.5 A g−1.
The CO2 capture capacity of the ABC reaches 4.21 mmol/g at 298 K, 1 bar.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Concerns in the last few decades regarding the environmental and socioeconomic impacts of the dependence on fossil fuels have resulted in calls for more renewable and alternative energy sources. This ...has led to recent interest in copyrolysis of biomass and coal. Numerous reviews have been found related to individual pyrolysis of coal and biomass. This review deals mainly with the copyrolysis of coal and biomass and then compares their results with those obtained using coal and biomass pyrolysis in detail. It is controversial whether there are synergistic or additive behaviours when coal and biomass are blended during copyrolysis. In this review, the effects of reaction parameters such as feedstock types, blending ratio, heating rate, temperature, and reactor types on the occurrence of synergy are discussed. Also, the main properties of the copyrolytic products are pointed out. Some possible synergistic mechanisms are also suggested. Additionally, several outlooks based on studies in the literature are also presented in this paper.
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DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK, VSZLJ
Summary
Catalytic steam reforming of tar is considered to be an attractive pathway for tar removal and H2 production in the modern world. In this study, activation of biochar (B) from pine wood ...pyrolysis was performed to boost its specific surface area and pore structure. The activated biochar (AB) was used as a catalyst support with the aim to enhance the catalytic activity. The catalytic reforming performance of toluene over Ni/AB catalyst was investigated, and the catalytic behavior of Ni/AB catalysts was compared with Ni/Al2O3 and Ni/B. The effect of potassium hydroxide (KOH) to biochar ratio, Ni loading, reforming temperature, weight hourly space velocity and steam to carbon ratio(S/C) on the performance of Ni/AB catalysts were studied. The results showed that Ni/AB catalysts exhibited a superior catalytic activity for carbon conversion and H2 production to Ni/B and Ni/Al2O3 catalysts. In addition, high carbon conversion (86.2%) and H2 production (64.3%) can be achieved with Ni/AB catalyst under the optimal operating conditions. Furthermore, in order to improve the stability of the Ni/AB catalyst, Ce was introduced to Ni/AB catalyst. According to stability tests, the H2 concentration of Ni‐Ce/AB catalysts was still higher than 2.24 mmol/min even after 20 hours reaction.
Carbon‐based nickel catalyst shows a superior catalytic activity to the Ni/Al2O3 catalyst.
The catalytic performance of biochar can be enhanced significantly after activation by KOH.
The introduction of Ce can markedly prolong the lifetime of char‐based Ni catalyst.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Superhydrophobic surfaces have great potential for application in self-cleaning and oil/water separation. However, the large-scale practical applications of superhydrophobic coating surfaces are ...impeded by many factors, such as complicated fabrication processes, the use of fluorinated reagents and noxious organic solvents and poor mechanical stability. Herein, we describe the successful preparation of a fluorine-free multifunctional coating without noxious organic solvents that was brushed, dipped or sprayed onto glass slides and stainless-steel meshes as substrates. The obtained multifunctional superhydrophobic and superoleophilic surfaces (MSHOs) demonstrated self-cleaning abilities even when contaminated with or immersed in oil. The superhydrophobic surfaces were robust and maintained their water repellency after being scratched with a knife or abraded with sandpaper for 50 cycles. In addition, stainless-steel meshes sprayed with the coating quickly separated various oil/water mixtures with a high separation efficiency (>93%). Furthermore, the coated mesh maintained a high separation efficiency above 95% over 20 cycles of separation. This simple and effective strategy will inspire the large-scale fabrication of multifunctional surfaces for practical applications in self-cleaning and oil/water separation.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
► Pyrolysis and combustion of pine sawdust were investigated with TG–FTIR and Py–GC/MS analysis. ► Kinetic parameters for pine sawdust pyrolysis and combustion process were obtained. ► The gaseous ...species were identified by the spectra: H2O, CO2, CO, CH4, phenols, and paraffin gas. ► The main compounds of pine sawdust thermal decomposing were organic acid, aldehyde and acid anhydride group.
Pyrolysis and combustion of pine sawdust have been investigated by using thermogravimetric analyzer coupled with Fourier transform infrared spectrometry (TG–FTIR) analysis in this paper. Pyrolysis–gas chromatography and mass spectrometry (Py–GC/MS) analysis was employed to characterize subsequently the structure and composition of evolving gas in pine sawdust pyrolysis process. TG results showed that both pyrolysis and combustion of pine sawdust presented three weight loss stages, respectively. The apparent activation energy of pyrolysis reaction is 108.18kJmol−1 in temperature of 239–394°C, while under combustion process which is 128.43kJmol−1 and 98.338kJmol−1 in 226–329°C and 349–486°C, respectively. The evolving gaseous products during the pyrolysis and combustion infrared spectrums such as H2O, CH4, CO, CO2, phenol and alkane were found. Py–GC/MS results indicated that the main compounds of pine sawdust thermal decomposition were small molar gases, acetaldehyde, acetic acid, anhydride with formic and acetic anhydride. And possible formation pathways for main pyrolysis products were tentatively presented.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Carbon Balance And Management makes the readers familiar with the global carbon cycle and the carbon sequestration potential on agricultural lands. It talks about understanding the balance of carbon ...and greenhouse gases. It provides the insights into the various aspects related to the balance of carbon in the ecosystem and its management so that the readers can know more about the carbon balance and related things. This book also discusses about measuring and managing carbon emissions of the European chemical transport, the balance of carbon in Africa, the climate change resulting from the carbon emission, the effects of carbon tax on the environment and economy and the chemistry of carbon cycle.
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