Novel, environmentally-benign catalysts for selective catalytic reduction of NOx were prepared by citric method through introducing transition metal elements (Ce, Cu and Co) into iron oxide. The physical-chemical properties of different catalysts were investigated by the characterization technologies like N2-physisorption, XRD, NH3/NOTPD and H2-TPR. The results indicated that the introduction of transition metal elements increased the specific surface area and adsorption ability for reactants (NH3 and NOx). The redox capacity for the doped catalysts was improved at the same time. These characteristics all contributed to the improvement of catalytic performance. The CoFeOx catalyst exhibited the widest temperature window for SCR reaction, and the CeFeOx catalyst showed the most obvious decline of NOx conversion with the elevation of temperature above 250 °C. Water vapor inhibited the SCR activity at low temperatures and relieved the decline of NOx conversion at higher temperatures. Meanwhile, the formation of N2O was inhibited. The pretreatment of SO2 leaded to the sulfation of the active species for different catalysts. The decline of redox capacity and the reduction of active nitrate adsorbed species accounted for the serious loss of SCR activity at low temperatures. The abundant surface acid sites brought by the sulfation process might be the main reason for good SCR activity in the medium temperature range.

The selective catalytic reduction (SCR) activities of the MoO3 doped V/WTi catalysts prepared by the incipient wetness impregnation method at low temperature were investigated. The results showed that the addition of MoO3 could enhance the NOx conversion at low temperature and the best SCR activity was obtained when the dosage of MoO3 reached 5 wt.%. The NH3-TPD and DRIFTS experiments indicated that the addition of MoO3 changed the type and number of acid sites on the surface of catalysts and reaction activities of acid sites were altered at the same time. The redox capacity and amount of active oxygen species got improved for V3Mo5/WTi catalyst, which could be confirmed by the H2-TPR and transient response experiments. Water vapor inhibited the NOx conversion at low temperature. Deposition of ammonium sulfate or bisulfate might be main reason for the loss of catalytic activity in the presence of SO2 at low temperature. Choosing the suitable NH3/NO ratio and elevation of reaction temperature both could weaken the influence of SO2 on the SCR activity of the V3Mo5/WTi catalyst. Thermal treatment of the deactivated catalyst at 350°C could get the low temperature activity recovered. The decrease of GHSV improved the deNOx efficiency at low temperature and we speculated that the rational technological process and operation parameters could contribute to the application of this kind of catalysts in real industrial environment.A suitable addition of MoO3 improved the SCR activity of V2O5/WO3–TiO2 catalyst at low temperature.Download high-res image (248KB)Download full-size image

•Hierarchical porous HZSM-5 zeolites had been prepared by alkaline treatment.•The performance of alkali-treated zeolites were tested in CFP of waste cardboard.•Carbon yield of aromatics increased dramatically, especially BTX compounds.•Coke yield was decreased by mildly alkali-treated HZSM-5 zeolites.The effects of hierarchical porous HZSM-5 zeolites on improving the yield of aromatic hydrocarbons during catalytic fast pyrolysis (CFP) of waste cardboard (WCB) were investigated. Desilicated HZSM-5 zeolites were successfully prepared by alkaline treatment using NaOH solution with different concentrations (0.1 M–0.7 M). A Py-GC/MS apparatus was adopted to carry out the CFP experiments. Results showed that under mild alkaline treatment (NaOH concentration ≤ 0.3 M), the micropores and crystallinity of HZSM-5 were preserved, while the mesopores and weak acid sites increased. The desilicated HZSM-5 zeolites increased the total yield of pyrolytic products from WCB. With regard to the product distribution, carbon yield of aromatics increased dramatically, while that of sugars, carbonyl compounds and other oxygenates decreased obviously. Specifically, HZSM-5 treated by 0.3 M NaOH solution (HZ-0.3 M) was proved to be the most effective catalyst, resulting in a 44% increase of carbon yield of aromatics and an 82% increase of carbon yield of BTX (benzene, toluene and xylenes) comparing to the parent HZSM-5. In addition, the amount of coke deposited on HZ-0.3 M decreased by 29% compared to that on the parent HZSM-5. The retained micropores and the created mesopores of desilicated HZSM-5 zeolites contributed to the enhancement of catalytic performance. However, harsh alkaline treatment of HZSM-5 zeolites (NaOH concentration ≥0.5 M) resulted in the grave collapse of zeolitic crystallinity and the obvious loss of micropores. As a result, the catalytic activities of HZSM-5 zeolites had been weakened.

•Catalytic fast co-pyrolysis showed great promise for upgrading bio-oil production.•An optimal co-pyrolysis temperature of 600 °C was beneficial for aromatics and olefins.•Carbon yields of aromatics and olefins increased with increasing of H/C molar ratio.•A significant synergistic effect during co-CFP of WCO and TR was investigated.Catalytic fast co-pyrolysis (co-CFP) offers a concise and effective process to achieve an upgraded bio-oil production. In this paper, co-CFP experiments of waste cooking oil (WCO) and tea residual (TR) with HZSM-5 zeolites were carried out. The influences of pyrolysis reaction temperature and H/C ratio on pyrolytic products distribution and selectivities of aromatics were performed. Furthermore, the prevailing synergetic effect of target products during co-CFP process was investigated. Experimental results indicated that H/C ratio played a pivotal role in carbon yields of aromatics and olefins, and with H/C ratio increasing, the synergetic coefficient tended to increase, thus led to a dramatic growth of aromatics and olefins yields. Besides, the pyrolysis temperature made a significant contribution to carbon yields, and the yields of aromatics and olefins increased at first and then decreased at the researched temperature region. Note that 600 °C was an optimum temperature as the maximum yields of aromatics and olefins could be achieved. Concerning the transportation fuel dependence and security on fossil fuels, co-CFP of WCO and TR provides a novel way to improve the quality and quantity of pyrolysis bio-oil, and thus contributes bioenergy accepted as a cost-competitive and promising alternative energy.

•Explore the use of catkins as an additive to the CBPs fuel and assess its utilization.•Combustion of CBPs is a first-order reaction, and it is divided into three stages.•Combustion of CBPs is mainly focused on the stage of volatile-release.This work presents studies on the combustion of Composite Biomass Pellets (CBPS) in fluidized bed using bauxite particles as the bed material. Prior to the combustion experiment, cold-flow characterization and thermogravimetric analysis are performed to investigate the effect of air velocity and combustion mechanism of CBPS. The cold-state test shows that CBPs and bauxite particles fluidize well in the fluidized bed. However, because of the presence of large CBPs, optimization of the fluidization velocity is rather challenging. CBPs can gather at the bottom of the fluidized bed at lower gas velocities. On the contrary, when the velocity is too high, they accumulate in the upper section of the fluidized bed. The suitable fluidization velocity for the system in this study was found to be between 1.5–2.0 m/s. At the same time, it is found that the critical fluidization velocity and the pressure fluctuation of the two-component system increase with the increase of CBPs mass concentration. The thermogravimetric experiment verifies that the combustion of CBPs is a first-order reaction, and it is divided into three stages: (i) dehydration, (ii) release and combustion of the volatile and (iii) the coke combustion. The combustion of CBPs is mainly based on the stage of volatile combustion, and its activation energy is greater than that of char combustion. During the combustion test, CBPS are burned at a 10 kg/h feed rate, while the excess air is varied from 25% to 100%. Temperatures of the bed and flue gas concentrations (O2, CO, SO2 and NO) are recorded. CBPs can be burnt stably, and the temperature of dense phase is maintained at 765–780 °C. With the increase of the air velocity, the main combustion region has a tendency to move up. While the combustion is stable, O2 and CO2 concentrations are maintained at about 7%, and 12%, respectively. The concentration of SO2 in the flue gas after the initial stage of combustion is nearly zero. Furthermore, NO concentration is found to be closely related to O2: the NO reaches its peak value after initial stage and later decreases with the continued depletion of O2. Towards the end of combustion, NO increases with the increase of O2.This work presents studies on the combustion of Composite Biomass Pellets in fluidized bed. The use of catkins as an additive to the CBPs fuel is first time and proved well.Download high-res image (380KB)Download full-size image

•Co-pyrolysis of bamboo residual and waste tire over CaO and HZSM-5 was conducted.•Co-modification of HZSM-5 by NaOH leaching and hydrothermal process was proposed.•A dual catalytic stage bed of CaO and HZSM-5 facilitated the yield of aromatics.•Co-modified HZSM-5 zeolites showed significant selectivity towards aromatics.Experiments for an upgraded liquid oil production via fast co-pyrolysis of bamboo residual and waste tire over two catalytic beds of CaO and HZSM-5 were conducted, and the effect of CaO to HZSM-5 mass ratio on pyrolytic products distribution was investigated and analyzed. Furthermore, a novel modification method for enhancing the catalytic performance of HZSM-5 by an integrated alkali treatment and hydrothermal process was carried out, and the influence of co-modified HZSM-5 on products distribution was also studied. Experimental results revealed that the catalytic fast co-pyrolysis of bamboo residual and waste tire increased the relative contents of aromatics and olefins. Simultaneously, a use of dual catalytic stage of CaO and HZSM-5 further facilitated the relative contents of aromatics and olefins significantly, and inhibited the formation of undesirables like acids. A maximum yield of hydrocarbons could be reached at HZSM-5 to CaO mass ratio of 3:2. Furthermore, the co-modified HZSM-5 promoted the relative contents of aromatics and olefins compared with the fresh ones, which showed great promise for upgrading the quality of liquid oil.

•HZSM-5 was modified by sequential NaOH leaching and hydrothermal treatment.•Micro-mesopore hierarchical system was created and acidic properties were improved.•Co-modified HZSM-5 was used to conduct catalytic fast pyrolysis of waste cooking oil.•A moderate alkali treatment time of 4 h was beneficial for promoting the aromatics.An integrated modified HZSM-5 was prepared by sodium hydroxide leaching and followed by hydrothermal process in series, and the co-modified zeolites were then used to conduct the catalytic fast pyrolysis of waste cooking oil to investigate whether an enhanced production of aromatics could be obtained. X-ray diffraction, N2 adsorption–desorption, TEM and NH3-TPD were utilized to characterize the modified zeolites. Experimental results indicated that the crystal structure of HZSM-5 was damaged as alkali treatment time was beyond 4 h, and a micro-mesopore hierarchical system was created inside the zeolites. Simultaneously, the strong acid sites decreased with the increment of modification time, while the weak acid sites performed an opposite inclination. The relative yields of aromatics and olefins presented deviation when alkali treatment time exceeded the specific limitation, and a moderate alkali treatment time of 4 h was beneficial for promoting the yield of aromatics.Download high-res image (225KB)Download full-size image

In this paper, a series of Cu-Fe-Ti and Co-Fe-Ti oxide catalysts were prepared by sol gel method. Cu-Fe-Ti and Co-Fe-Ti oxide catalysts showed the moderate catalytic activity for selective catalytic reduction (SCR) of NO with NH3 at low temperature. The catalysts with the molar ratio as 4:1:10 (M:Fe:Ti) were selected as the representatives for comparison of reaction properties and H2O resistance, which were denoted as Cu-Fe/TiO2 and Co-Fe/TiO2 respectively. The characterization results manifested Co-Fe/TiO2 owned more adsorption capacity of the reactants and Cu-Fe/TiO2 had better redox ability. The in situ DRIFTS experiments indicated that adsorbed NH3 species and nitrate species both exhibited reaction activity for Co-Fe/TiO2, while nitric oxide was only be reduced by adsorbed NH3 species through Eley-Rideal mechanism for Cu-Fe/TiO2 at 150 °C. Co-Fe/TiO2 exhibited the better resistance to H2O and its temperature window shifted towards the higher temperature in presence of 10 vol% H2O, while the SCR activity of Cu-Fe/TiO2 was inhibited significantly in the whole temperature range investigated. The suppression of adsorption and activation for NH3 and NOx might be the reasons for the reversible inactivation, which was confirmed by the inhibitation of catalytic activities for separation NH3 and NO oxidation under the wet condition. We speculated that different thermal stability of adsorbed species and redox capacity of catalysts leaded to the different SCR behavior in absence and presence of H2O.

Flow regime identification is important in the application of fluidized beds. This paper provides a method for deciding flow regime number by objective criterion. The optimized fuzzy c-means clustering algorithm was used to cluster the flow regime classification of two-component particles in a fluidized bed. The genetic algorithm was applied to optimize the initial center clusters of fuzzy c-means clustering. Hilbert-Huang transform was applied to analyze pressure fluctuation signals and extract the characteristic parameters. Three clusters were found and respectively ascribed to three flow regimes: bubbling bed, slugging bed, and turbulent bed. A multilayer neural network was used to train and test the identification system of the flow regimes. The identification accuracies of bubbling bed, slugging bed, and turbulent bed can reach 91.67%, 92.85%, and 91.30%, respectively.

In order to recover valuable pyrolytic oils, mixed municipal solid waste was pyrolyzed in a fluidized bed reactor. Results showed that liquid products yielded among 38.4–56.5 wt% and separated into water-soluble phases and organic phases. Moisture was concentrated in the water-soluble phases (39.4–57.3 wt%), making them low in carbon content and heating value. On the other hand, the higher carbon content and lower oxygen content of organic phases make their heating value (27.5–32.1 MJ/kg) and quality higher than bio-oils. Water-soluble phases mainly included acids, carboxylics, phenols, and sugars, which could be used as chemical feedstocks and substantial fuel. Organic phases mostly contained aromatics and phenols and could be used as fossil fuels directly or as chemical materials. Heavy metals of Cd and Pb were proved to be poor in both water-soluble phases and organic phases. As for Zn, it was found to be higher in the water-soluble phases at 450 and 550 °C with quartz sand as bed material than that in crude oils. However, Zn content in organic phases was comparable to crude oils. High-aluminum bauxite and attapulgite as bed materials increased heating value of water-soluble phases and organic phases respectively, and both performed well in reducing the Zn content of water-soluble phases. This work proved that it was an operative way to produce valuable pyrolytic oils by pyrolysis of mixed municipal solid waste.

Mn-Fe/TiO2 catalysts synthesized by sol-gel and co-precipitation methods were used for the selective catalytic reduction (SCR) of NO with NH3. The catalysts were characterized by N2 physisorption, XRD, NH3/NOx-TPD, and H2-TPR. The catalytic activities for SCR and NH3/NO oxidation were investigated in the absence and presence of water. In this study, Mn-Fe/TiO2(S) catalyst exhibited better catalytic activity at low temperature below 175 °C in the absence of H2O. However, more by-product of N2O was observed in this case in contrast with Mn-Fe/TiO2(C). The similar phenomenon was observed during the process of NH3 catalytic oxidation. The excellent redox capability and abundant active adsorbed species on the catalyst surface accounted for higher NOx conversion and more N2O formation for Mn-Fe/TiO2(S). It was found that water vapor hindered the activation of NH3 and adsorption-oxidation of NO, and thus, impeded catalytic activity of Mn-Fe/TiO2 during standard SCR process at low temperature, even though it reduced the formation of N2O. The inhibition for over dehydrogenation of amide adsorbed species and the deceleration for decomposition of ammonium nitrate species might be two reasons accounting for the decrease of N2O concentration in the presence of H2O. The different catalysts exhibited the different poisoning resistance to SO2 and the SO2 resistance of manganese-based catalyst at low temperature still needed the further improvement.

To investigate the pyrolysis characteristics of waste tire, an analytical pyrolyzer coupled with gas chromatography/mass spectrometry (Py–GC/MS) setup had been proposed. Waste tire was pyrolyzed under different temperatures. Results showed that the primary pyrolysis products of waste tire at 600 °C were alkenes rather than alkanes or aromatics. Isoprene (18.7%) and d-limonene (22.9%) represented the main compounds of chain alkenes and cyclic alkenes, respectively. The degradation procedure of d-limonene was also investigated. It could be indicated that, when the temperature was 500 °C and below, isomerized alkenes of d-limonene were the main products. With the temperature increasing to 600 °C and above, aromatics began to raise. According to the product distribution, eight pyrolysis reaction pathways of d-limonene were proposed. Pyrolysis of waste tire under different temperatures proved that the reaction pathways of d-limonene were reliable. Moreover, a thermogravimetric analyzer coupled with Fourier transform infrared spectroscopy (TG-FTIR) investigation also consolidated the main processes proposed by Py–GC/MS. These findings provide some references for the pyrolysis mechanism of waste tires.

In order to reduce coke yield during catalytic fast pyrolysis of biomass, MgO and 2,4-dimethylquinoline (2,4-DMQ) were selected to reduce the number of external acid sites of HZSM-5. Both MgO and 2,4-DMQ deposition could cause a reduction in total acid sites (both weak acid sites and strong acid sites) and external acid sites of HZSM-5. The modified catalysts were used for the catalytic conversion of bio-derived furan. For the MgO/HZSM-5 catalyst, the effects of amount of MgO deposited and deposition time were studied. The carbon yields of aromatics, C2–C5 olefins, total chemicals, CO2 and CO increased at first and then decreased slightly when the deposited amount increased, while the carbon yield of coke decreased first and then increased gradually. Furthermore, as the deposited time increased, the carbon yields of petrochemicals, CO2 and CO increased greatly, whereas that of coke decreased. For the 2,4-DMQ/HZSM-5 catalyst, the effects of 2,4-DMQ treatment amount and treatment time were investigated. The experimental results showed that an increase in 2,4-DMQ treatment amount or treatment time could retard the generation of the target products, CO2 and CO but promote coke formation.

Hilbert-Huang transformation was used to investigate the nonlinear characteristics of two-component (biomass particles and quartz sand) mixing flow by analyzing the pressure fluctuation signals in fluidized bed. Based on empirical mode decomposition (EMD), the Hilbert-Huang spectra in bubbling and slugging flow patterns were obtained and analyzed. In bubbling flow pattern, compared with one-component (quartz sand) flow, the energy of two-component mixing flow is lower in 0-5 Hz and higher in 40–50 Hz. In slugging flow pattern, the energy in pressure fluctuation mainly lies in 0–5 Hz. and the effect of biomass particles on the Hilbert-Huang spectrum is not very obvious. Compared with traditional power spectral density (PSD), HHT is much more suitable for investigating pressure fluctuation signals in fluidized beds.

Nitric oxide (NO) from flue gas is hard to remove because of low solubility and reactivity. A new technology for photocatalytic oxidation of NO using ultraviolet (UV)/TiO2/H2O2 process is studied in an efficient laboratory-scale reactor. Effects of several key operational parameters on NO removal efficiency are studied, including TiO2 content, H2O2 initial concentration, UV lamp power, NO initial content, oxygen volume fraction and TiO2/H2O2 solution volume. The results illustrate that the NO removal efficiency increases with the increasing of H2O2 initial concentration or UV lamp power. Meanwhile, a lower NO initial content or a higher TiO2/H2O2 solution volume will result in higher NO removal efficiency. In addition, oxygen volume fraction has a little effect. The highest NO removal efficiency is achieved at the TiO2 content of 0.75 g/L, H2O2 initial concentration of 2.5 mol/L, UV lamp power of 36 W, NO initial content of 206×10−6 and TiO2/H2O2 solution volume of 600 mL. It is beneficial for the development and application of NO removal from coal-fired flue gas with UV/TiO2/H2O2 process.

Sequential and single extraction procedures were applied to both fresh and dried Sedum Plumbizincicola leaves and stems. The extractants, different from those of soil, sediment or sewage sludge metal fractions, were water, 80% (v/v) ethanol, 1 mol/L NaCl, 2% HAc and 0.6 mol/L HCl. Zn, Cd and Cu in the extracts and samples were measured by flame atomic adsorption spectrometry. In sequential extraction procedures, water soluble form and ethanol soluble form are the main fractions for Zn, while water soluble form and NaCl soluble form for Cd, and comparatively uniform distribution for Cu with the residue form most and HCl soluble form second. Single extraction procedures are used to compare the extraction efficiencies of the five reagents to screen appropriate extractants and operating conditions for liquid extraction to deal with large amount of harvested metal-contained biomass, which will pose a threat to the environment if treated improperly. The sequences of extraction efficiencies are HCl>NaCl≈HAc>Water≈Ethanol for Zn and HCl≈NaCl≈HAc>Water>Ethanol for Cd. As for Cu, all the five extractants cannot effectively extract Cu, but HCl achieves a higher efficiency (>70% in fresh samples, and 45%–60% in dried samples). Besides, extraction efficiencies for most extractants in fresh samples are higher than those in dried samples, and extraction efficiencies of stems and leaves for the five extractants are close. The two extraction procedures can obtain high degree of accuracy with the relative standard deviation (RSD) lower than 10%, and metal recoveries are controlled between 80%–120% with most of 90%–110%.

Fresh HZSM-5 catalyst was hydrothermally treated with 20% steam partial pressure at 450, 500, and 550 °C. Catalytic upgrading of corn stalk fast pyrolysis vapors with fresh and hydrothermally treated HZSM-5 catalysts was studied by means of analytical Py-GC/MS. Hydrothermal treatment caused a reduction in the surface area, micropore surface area, pore volume, micropore volume, pore size, total acid sites (both weak acid sites and strong acid sites), and coke yield of the HZSM-5 catalyst. The product distribution and the quality of the pyrolysis vapors were also affected. HZSM-5 catalyst with higher hydrothermal treatment temperature resulted in a higher relative content of hydrocarbons and lower relative contents of acids, esters, sugars, and furans. Esters, sugars, and furans were completely converted when HZSM-5 catalyst with 550 °C hydrothermal treatment was used. The relative contents of alcohols, carbonyls, and phenols first increased and then decreased sharply with a rise of hydrothermal treatment temperature. The increase of hydrothermal treatment temperature was also conducive to the decrease of oxygen content in the organic pyrolysis vapors.

Element mercury (Hg0) from flue gas is difficult to remove because of its low solubility in water and high volatility. A new technology for photooxidative removal of Hg0 with an ultraviolet (UV)/H2O2 advanced oxidation process is studied in an efficient laboratory-scale bubble column reactor. Influence of several key operational parameters on Hg0 removal efficiency is investigated. The results show that an increase in the UV light power, H2O2 initial concentration or H2O2 solution volume will enhance Hg0 removal. The Hg0 removal is inhibited by an increase of the Hg0 initial concentration. The solution initial pH and pH conditioning agent have a remarkable synergistic effect. The highest Hg0 removal efficiencies are achieved at the UV light power of 36W, H2O2 initial concentration of 0.125 mol/L, Hg0 initial concentration of 25.3 μg/Nm3, solution initial pH of 5, H2O2 solution volume of 600 ml, respectively. In addition, the O2 percentage has little effect on the Hg0 removal efficiency. This study is beneficial for the potential practical application of Hg0 removal from coal-fired flue gas with UV/H2O2 advanced oxidation process.

Recurrence plot and recurrence quantification analysis was applied into the analysis of the pressure fluctuation signals in spouted bed, and some parameters including recurrence rate, determinism, laminarity, averaged diagonal line length, trapping time and entropy were extracted from recurrence plots. Based on these characteristic parameters, least square support vector machine was applied to recognize the flow regimes, and parameters in least square support vector machine were optimized by adaptive genetic optimization algorithm. The recognition accuracies of packed bed, stable spouting, bubbly fluidized bed and slugging bed could reach 85%, 85%, 80% and 90% respectively.Recurrence plot method was used to extract the characteristic parameters from the pressure fluctuation signals in the spouted bed. Based on these characteristic parameters, least square support vector machine was applied to recognize the flow regimes, and adaptive genetic algorithm was used to optimize the parameters in support vector machine.Highlights► Nonlinear phenomenon in spouted bed was presented by recurrence plot. ► Recurrence quantification analysis was used for pressure fluctuation signals. ► Least square support vector machine was used to recognize the flow regimes.

A large abundance of biomass waste is generated from harmful algal blooms (HABs) which dramatically damages the environment. Algae from lake blooms was pyrolyzed in a fixed-bed reactor at 300–700 °C in order to evaluate the effect of temperature on the product distribution and bio-oil quality. Yields and compositions of bio-oil, char, and gases were analyzed. The results demonstrated that the maximum yield (59%) of algal bio-oil was obtained at 500 °C. The bio-oil from algal blooms was characterized with higher heating value (about 21 MJ/kg) and nitrogen content (2.68%) when compared with pine sawdust. Elevated temperatures improved the bio-oil quality by increasing its heating value and hydrocarbon content. However, excessively higher temperatures also lead to the formation of undesired products such as nitrogenous compounds and polycyclic aromatic hydrocarbons (PAHs).

The characteristics of a fluidized bed electrode applied as a direct carbon fuel cell anode, which has an inner diameter of 35 mm and height of 520 mm and employed bamboo-based activated carbon (BB-AC) as a feedstock, are vigorously studied under various experimental conditions. The optimal performance of the fluidized bed electrode direct carbon fuel cell (FEBDCFC) anode with the BB-AC as a fuel is obtained under the following conditions with a limiting current density of 95.9 mA cm−2: reaction temperature, 923 K; N2 flow rate, 385 ml min−1; O2/CO2 flow rate, 10/20 ml min−1; nickel particle content, 30 g; and a cylindrically curved nickel plate as a current collector. Under the same optimal conditions, the limiting current density of the FEBDCFC anode with oak wood-based activated carbon and activated carbon fiber as the fuel is determined to be 94.5 and 88.4 mA cm−2, which is lower than that determined for BB-AC as the fuel. Comparatively, the limiting current density for graphite, which is utilized as the carbon fuel for this fuel cell system, could not be unequivocally determined because no plateau of the limiting current density against the overpotential is observed.Research highlights▶ Limiting current density increases with N2 flow rate. ▶ Limiting current density increases with nickel particle content. ▶ Larger current collector surface area gives higher current density. ▶ The FBEDCFC anode fed with BB-AC shows the best performance.

A biomass-based activated carbon, utilized for direct carbon fuel cells (DCFCs), is prepared from bamboo scraps under different activation temperatures, activation times, and impregnation ratios. The K2CO3 is employed as the activating agent, while the activated carbon is treated in HNO3 solution for the purpose of surface modification and ash removal. The applicability of the prepared activated carbon for DCFCs is evaluated by a fluidized bed electrode direct carbon fuel cell anode. It is found that the BET surface area of the activated carbon could reach 1264 m2 g–1 under the following conditions: activation temperature, 1173 K; activation time, 2 h; impregnation ratio, 1. The content and diversity of the surface oxygen functional groups of the activated carbon could be well improved through the HNO3 treatment, and the ash content is notably reduced. Differently, the BET surface area is slightly reduced while the electrical resistivity is remarkably increased. The optimal HNO3 solution concentration is estimated to be 2 mol L–1, giving the treated bamboo-based activated carbon outstanding polarization performance among the tested carbon fuels.

A fluidized bed electrode could lower concentration polarization and activation polarization because of its high mass and heat transfer coefficient. The polarization characteristics of the fluidized bed electrode are systematically investigated in a molten carbonate fuel cell anode with an O2/CO2/gold reference electrode. The results show that polarization performance of the anode is improved by selecting proper flow rates of H2, O2 and CO2, choosing suitable nickel particle content together with appropriate O2/CO2 ratio, and increasing reaction temperature as well as the area of the current collector. Limiting current density of 115.56 mA·cm−2 is achieved under optimum performance as follows: a cylindrically curved nickel plate current collector, nickel particle content of 7.89%, the reaction temperature of 923 K, H2 flow rate of 275 mL·min−1, O2/CO2 flow rate of 10/20 mL·min−1 and O2/CO2 ratio of 1 : 2.

Fast pyrolysis is a promising technology that can convert biomass into liquid. Bio-oil is one such product, known not only as a greenhouse gas-neutral energy source, but also an opportunity to reduce reliance on fossil fuels. Pyrolytic lignin, a fine homogeneous powder, is the water-insoluble fraction of bio-oil and it contributes to the instability of bio-oil. Additionally, pyrolytic lignin can be used in commercial materials such as adhesives in the wood-based panel industry. This paper presents the structural characterization of pyrolytic lignin extracted from aged bio-oil and the relationship between its properties and the treatment temperature of the aged bio-oil. Pyrolytic lignin samples were characterized by Fourier transform infrared spectroscopy, gel permeation chromatography, differential scanning calorimetry, thermogravimetric analysis and proton nuclear magnetic resonance spectroscopy. The average molecular weight of pyrolytic lignin increased from 700 to 1000 g/mol with increasing aging temperature (6–50°C). Differential scanning calorimetry showed that the glass transition temperature of pyrolytic lignin increases with lower heating rate and higher treatment temperature of bio-oil. An increase in the initial decomposition temperature and the temperature at 95 wt% weight loss of the aged pyrolytic lignin in thermogravimetry were observed for the bio-oil aged at higher temperature. An increase in residue weight of aged pyrolytic lignin was found in bio-oil aged at higher temperatures.

There has been an increasing interest in alternative fuels made from biomass which is abundant and renewable. Bio-oil and bio-diesel seem to be such promising liquid fuels. Bio-oil produced by fast pyrolysis of biomass is highly viscous, acidic, and has high water content. To overcome these problems as a fuel, a method of emulsifying bio-oil with bio-diesel was performed in the previous paper, and a stable mixture of bio-oil and bio-diesel was successfully prepared. In this paper, several properties of the mixture are discussed by using TG, FTIR and 1H NMR. The results show us that, compared with crude bio-oil, some properties of bio-oil/bio-diesel mixture such as water content, acid number, viscosity are much improved. The thermal decomposition of the mixture under air/nitrogen is shown using a thermogravimetric analyzer (TGA). Further information about the functional groups is exhibited through Fourier Transform infrared spectrometer (FTIR) and nuclear magnetic spectroscopy (NMR).

•Waste tire was pyrolyzed in Py-GC/MS with three different catalysts, as well as d-limonene and polybutadiene rubber.•Catalytic pyrolysis pathways of d-limonene were proposed.•Catalytic pyrolysis features of polybutadiene rubber were investigated.•Catalytic degrading processes of waste tire were illustrated by the catalytic converting routes of d-limonene and polybutadiene rubber.Pyrolysis of waste tire with HY, HZSM-5 (HZ) and purified attapulgite (PA) catalysts to produce valuable aromatic hydrocarbons has been carried out in a Pyrolyzer- Gas Chromatograph/Mass Spectrum (Py-GC/MS) reactor. Likewise, d-limonene and polybutadiene rubber (BR), which played important roles in the pyrolysis process of waste tire, has also been pyrolyzed in the Py-GC/MS reactor with these catalysts. Based on the product distribution, the catalytic pyrolysis mechanisms of d-limonene were proposed, while those of BR were extended. With these mechanisms, the catalytic pyrolysis characteristics of waste tire could be explained reasonably. Results showed that HY promoted a dramatic increase of aromatics from pyrolysis of d-limonene and BR, leading to the considerable growth of aromatics in the degraded products of waste tire. The shape selectivity of HZ to mono-cyclic aromatics performed effectively in the pyrolysis of BR, yet it exhibited a weak performance in the pyrolysis of d-limonene. As a result, upon the catalytic pyrolysis of waste tire, HZ was inferior to HY in the aromatization ability. However, the selectivity of HZ to BTXE (benzene, toluene, xylene and ethylbenzene) was superior to that of HY. PA performed a weaker catalytic ability in promoting the production of aromatics during the pyrolysis of d-limonene, BR and waste tire.

A novel technology of two-step fast microwave-assisted pyrolysis (fMAP) of corn stover for bio-oil production was investigated in the presence of microwave absorbent (SiC) and HZSM-5 catalyst. Effects of fMAP temperature and catalyst-to-biomass ratio on bio-oil yield and chemical components were examined. The results showed that this technology, employing microwave, microwave absorbent and HZSM-5 catalyst, was effective and promising for biomass fast pyrolysis. The fMAP temperature of 500°C was considered the optimum condition for maximum yield and best quality of bio-oil. Besides, the bio-oil yield decreased linearly and the chemical components in bio-oil were improved sequentially with the increase of catalyst-to-biomass ratio from 1:100 to 1:20. The elemental compositions of bio-char were also determined. Additionally, compared to one-step fMAP process, two-step fMAP could promote the bio-oil quality with a smaller catalyst-to-biomass ratio.Download full-size image

Bio-oil is a new liquid fuel produced by fast pyrolysis, which is a promising technology to convert biomass into liquid. Pyrolytic lignin extracted from bio-oil, a fine powder, contributes to the instability of bio-oil. The paper presents the structural features of three kinds of pyrolytic lignin extracted from bio-oil with different methods (WIF, HMM, and LMM). The pyrolytic lignin samples are characterized by Fourier transform infrared spectrometer (FTIR) and X-ray photoelectron spectroscopy (XPS). FTIR data indicate that the three pyrolytic lignin samples have similar functional groups, while the absorption intensity is different, and show characteristic vibrations of typical lignocellulosic material groups OH (3340–3380 cm−1), CH (2912–2929 cm−1) and CO (1652–1725 cm−1). Comparison in the region (3340–3380 cm−1) indicates that WIF has more OH stretch groups than HMM and LMM. The carbon spectra are fitted to four peaks: C1, CC or CH, BE = 283.5 eV; C2, COR or COH, BE = 284.5–285.8 eV; C3, CO or HOCOR, BE = 286.10–287.10 eV; C4, OCO, BE = 287.5–287.7 eV. The absence of C1, CC or CH indicates the dominant polymerization structure of aromatic carbon in pyrolytic lignin samples. For HMM and WIF, C2a and C2b can not be separated, so there is no free hydroxyl group in the samples. The oxygen peaks are also fitted to four peaks: O1, OH, BE = 530.3 eV; O2, RCO, BE = 531.45–531.72 eV; O3, OCO, BE = 532.73–533.74 eV; O4, H2O, BE = 535 eV. The absence of O1 and O4 indicates that little hydroxyl groups and adsorbed water are present in the samples.