Influence of Biochar Addition on Nitrogen Transformation during Copyrolysis of Algae and Lignocellulosic Biomass.

Algae are extremely promising sustainable feedstock for fuels and chemicals, while they contain high nitrogen content, which may cause some serious nitrogen emission during algae pyrolysis utilization. In this study, we proposed a feasible method to control the nitrogen emission during algae pyrolysis by introducing lignocellulosic biomass and biochar addition. Nitrogen transformation mechanism was investigated through quantitative analysis of N-species in the pyrolysis products. Results showed that copyrolysis of algae and lignocellulosic biomass greatly increased nitrogen in solid char with large amount of NH3 and HCN releasing (∼20 wt %), while nitrogen in bio-oil decreased largely. With biochar addition, NH3, HCN, and N-containing intermediates (amines/amides and nitriles) reacted with higher active O-species (O-C═O, -OH, and -COOH) in biochar addition, and formed large amounts of amine/amide-N, pyridinic-N, pyrrolic-N, and quaternary-N on the surface of biochar addition, which led to most nitrogen being enriched in char product and biochar addition (over 75 wt %) at the expense of amines/amides, nitriles, and N-containing gas (only 3 wt % NH3 and HCN emission; decrease of 85%). These results demonstrated that biochar addition showed a positive influence on fixation of N-species during thermochemical conversion of algae and could convert nitrogen to valuable N-doped biochar materials.

Relationship between the mandibular curve of Spee and the maxillary compensating curve with dentoskeletal morphology : A cross-sectional study in Chinese young adults with normal occlusion.

PURPOSE: The purpose of this cross-sectional study was to use multiple regression analysis to evaluate the relationship between the mandibular curve of Spee (COS) and the maxillary compensating curve with dentoskeletal morphology in young Chinese adults with normal occlusion. METHODS: This study comprised 62 young adults (31 males, mean age: 24.1 ± 2.2 years; 31 females, mean age: 23.3 ± 3.3 years) with Angle class I normal occlusion. For every subject, intraoral scan models of the maxillary and mandibular arches and lateral cephalograms were acquired. The depth of the COS and compensating curve were assessed on the intraoral scan models. Multiple dental arch dimensional and cephalometric variables were screened by univariate analysis. Subsequently, a multiple linear regression model (forward stepwise selection) was constructed to determine which variables were significantly correlated with the two curve depths. RESULTS: In the mandible, the COS depth was deepest at the mesiobuccal cusp of the first molar. Overjet, mandibular arch width and mandibular-occlusal plane angle significantly correlated with the COS depth (P < 0.05), accounting for 33.1% of the variation in the mandibular COS. In the maxilla, the deepest point of the compensating curve was at the distobuccal cusp of the first molar. Mandibular arch perimeter and overbite significantly correlated with the maxillary compensating curve (P < 0.05), explaining 23.3% of the variation. CONCLUSIONS: Overjet, overbite, mandibular-occlusal plane angle, mandibular arch width and perimeter should be considered when reconstructing occlusal curves in clinical orthodontic treatment and in prosthetic restoration.

Clinical relevance of distolingual roots and periodontal status in mandibular first molars: a cross-sectional study employing CBCT analysis. / ä¸‹é¢Œç¬¬ä¸€ç£¨ç‰™è¿œèˆŒæ ¹çš„å­˜åœ¨ä¸Žç‰™å‘¨çŠ¶æ€çš„ä¸´åºŠç›¸å ³æ€§åˆ†æžï¼šä¸€é¡¹é‡‡ç”¨é”¥å½¢å°„æŸç”µè„‘æ–­å±‚æ‰«æåˆ†æžçš„æ¨ªæ–­é¢ç ”ç©¶.

OBJECTIVES: Distolingual root of the permanent mandibular first molar (PMFM-DLR) has been frequently reported, which may complicate the treatment of periodontitis. This study aimed to assess the morphological features of PMFM-DLR and investigate the correlation between the morphological features of PMFM-DLR and periodontal status in patients with Eastern Chinese ethnic background. MATERIALS AND METHODS: A total of 836 cone beam computed tomography (CBCT) images with 1497 mandibular first molars were analyzed to observe the prevalence of PMFM-DLR at the patients and tooth levels in Eastern China. Among them, complete periodontal charts were available for 69 Chinese patients with 103 teeth. Correlation and regression analyses were used to evaluate the correlation between the morphological features of DLR, bone loss, and periodontal clinical parameters, including clinical attachment loss (CAL), probing pocket depth (PPD), gingival recession (GR), and furcation involvement (FI). RESULTS: The patient-level prevalence and tooth-level prevalence of DLR in mandibular first molars were 29.4% and 26.3%, respectively. Multiple linear regression analysis suggested that bone loss at the lingual site and CAL were negatively affected by the angle of separation between distolingual and mesial roots in the transverse section, while they were significantly influenced by age and the angle of separation between distobuccal and mesial roots in the coronal section. CONCLUSIONS: The prevalence of PMFM-DLR in Eastern China was relatively high in our cohort. The morphological features of DLR were correlated with the periodontal status of mandibular first molars. This study provides critical information on the morphological features of DLR for improved diagnosis and treatment options of mandibular molars with DLR.

Desulfurization and upgrade of pyrolytic oil and gas during waste tires pyrolysis: The role of metal oxides.

Pyrolysis can effectively convert waste tires into high-value products. However, the sulfur-containing compounds in pyrolysis oil and gas would significantly reduce the environmental and economic feasibility of this technology. Here, the desulfurization and upgrade of waste tire pyrolysis oil and gas were performed by adding different metal oxides (Fe2O3, CuO, and CaO). Results showed that Fe2O3 exhibited the highest removal efficiency of 87.7 % for the sulfur-containing gas at 600 °C with an outstanding removal efficiency of 99.5 % for H2S. CuO and CaO were slightly inferior to Fe2O3, with desulfurization efficiencies of 75.9 % and 45.2 % in the gas when added at 5 %. Fe2O3 also demonstrated a notable efficacy in eliminating benzothiophene, the most abundant sulfur compound in pyrolysis oil, with a removal efficiency of 78.1 %. Molecular dynamics simulations and experiments showed that the desulfurization mechanism of Fe2O3 involved the bonding of Fe-S, the breakage of C-S, dehydrogenation and oxygen migration process, which promoted the conversion of Fe2O3 to FeO, FeS and Fe2(SO4)3. Meanwhile, Fe2O3 enhanced the cyclization and dehydrogenation reaction, facilitating the upgrade of oil and gas (monocyclic aromatics to 57.4 % and H2 to 22.3 %). This study may be helpful for the clean and high-value conversion of waste tires.

Preparation of carbon nanotubes by catalytic pyrolysis of dechlorinated PVC.

Plastic waste is attracting growing interest for its utilization potential as a valuable resource. However, conventional thermochemical methods can hardly achieve high-value utilization of certain plastics, such as polyvinyl chloride (PVC) characterized with high chlorine content. Here, a low-temperature aerobic pretreatment method was introduced to realize high-efficiency dechlorination of PVC, and then the dechlorinated PVC was used to prepare carbon nanotubes (CNTs) by a catalytic pyrolysis. The results demonstrate that oxygen can significantly promote the HCl release in a pretty low-temperature range (260-340 °C). Chlorine was almost completely eliminated at 280 °C under 20 % oxygen concentration. Compared to untreated PVC, using the dechlorinated PVC as raw material, higher carbon deposition was obtained and over 60 % CNTs could be collected from the carbon deposition. This study provides a high-value utilization way for the production of CNTs from waste PVC.

Fast pyrolysis of guaiacyl-syringyl (GS) type milled wood lignin: Product characteristics and CH4 formation mechanism study.

It is anticipated that the insight into the demethylation and mechanism of CH4 formation from natural lignin using in-situ diffuse reflectance infrared Fourier transform spectroscopy (in-situ FTIR) combined with two-dimensional perturbation correlation infrared spectroscopy (2D-PCIS) and density functional theory (DFT) calculation analysis would contribute to a deeper insight of bond cleavage mechanism of lignin pyrolysis. Herein, GS-type lignin (poplar MWL) was characterized by Fourier transform infrared spectroscopy (FTIR) and heteronuclear Single-Quantum Correlation Nuclear Magnetic Resonance (HSQC), and its pyrolysis at different temperatures was performed in a lab-scale fixed-bed reactor. The biochar, gaseous and liquid products were qualitative, and quantitative analysis of gases and bio-oil is demonstrated using gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). The key of CH4 formation is the homolytic cleavage of the methoxyl functional group generating methyl radical and further verified via in-situ FTIR combined with 2D-PCIS and DFT calculation. The study established a new methodology based on multiple factor analysis to evaluate the CH4 formation mechanism in GS-type milled wood lignin at the molecular level, which is of positive significance for increasing lignin valorization and improving the environment.

Pyrolysis of boron-crosslinked lignin: Influence on lignin softening and product properties.

In this study, ammonium borate was used as an additive to inhibit lignin softening during the pyrolysis process, and the influence on the pyrolysis process and product characteristics were investigated with potential mechanism being explored in depth. Results showed that with boron addition, glassy transition temperature and thermal stability of lignin increased, and the yield of gas and liquid decreased, while the content of CO, CO2 and H2 increased. Simultaneously, liquid oil showed higher content of simple phenols, especially the diphenols which the maximum reached 80% with 3%BN at 650 ℃, while the yield of heavy components (300 âˆ¼ 400 Da) decreased. With regard to B-doped char, oxygenic groups and specific surface area (509 m2/g of 5%BN at 650 ℃) increased greatly. Increasing temperature promoted the transformation of B doping form from BC2O to BCO2.

Biomass hydrothermal conversion under CO2 atmosphere: A way to improve the regulation of hydrothermal products.

In this study, batched hydrothermal experiments on corn stalk were conducted at 240-330 °C under CO2 or inert (N2) atmosphere. The distribution and characteristics of gaseous, solid, and liquid products were analyzed in detail to comprehensively investigate the effects of CO2 on the hydrothermal conversion of biomass, especially on the cellulose and lignin in biomass. The results demonstrate that compared with N2, CO2 slightly increased the liquid and gas yields and significantly improved the control effect of temperature on bio-oil components. Under CO2 atmosphere, bio-oil achieved effective enrichment of ketones and phenols at 240 °C and 300 °C, respectively, and their highest relative contents reached 44.8% and 62.0%, respectively. In addition, the hydrochar obtained under CO2 atmosphere showed higher crystallinity, which is conducive to its subsequent utilization. This study explored the feasibility of introducing CO2 into the biomass hydrothermal process to realize the high-value utilization of biomass waste and the reuse of CO2.

High-value products from ex-situ catalytic pyrolysis of polypropylene waste using iron-based catalysts: the influence of support materials.

Catalytic pyrolysis is considered a promising strategy for the utilisation of plastic waste from the economic and environmental perspectives. As such, the supporting materials play a critical role in the properties of the catalyst. This study clarified this influence on the dispersion of the iron (Fe) within an experimental context. Four different types of typical supports with different physical structures were introduced and explored in a two-stage fixed-bed reactor; these included metallic oxides (Al2O3, TiO2), a non-metallic oxide (SiO2), and molecular sieves (ZSM-5). The results show that the liquid products were converted into carbon deposits and lighter gaseous products, such as hydrogen. The Al2O3-supported catalyst with a relatively moderate specific surface areas and average pore diameter exhibited improved metal distribution with higher catalytic activity. In comparison, the relatively low specific surface areas of TiO2 and small average pore diameters of ZSM-5 had a negative impact on metal distribution and the subsequent catalytic reformation process; this was because of the inadequate reaction during the catalytic process. The Fe/Al2O3 catalyst produced a higher yield of carbon deposits (30.2 wt%), including over 65% high-value carbon nanotubes (CNTs) and hydrogen content (58.7 vol%). Additionally, more dispersive and uniform CNTs were obtained from the Fe/SiO2 catalyst. The Fe/TiO2 catalyst promoted the formation of carbon fibre twisted like fried dough twist. Notably, there was interesting correspondence between the size of the reduced Fe nanoparticles and the product distribution. Within certain limits, the smaller Fe particle size facilitates the catalytic activity. The smaller and better dispersed Fe particles over the support materials were observed to be essential for hydrocarbon cracking and the subsequent formation of carbon deposits. The findings from this study may provide specific guidance for the preparation of different forms of carbon materials.

Effects of cellulose, hemicellulose, and lignin on the combustion behaviours of biomass under various oxygen concentrations.

The combustion behaviours of three components, namely hemicellulose, cellulose, and lignin, and four types of biomass, namely rice straw, bamboo, peanut shell, and chestnut shell, were examined in a drop tube furnace set at 1273 K, in O2/N2 atmospheres containing 21-100% O2. Radiant energy analysis technology was employed to infer the temperatures of the samples. The results show that the ignition mechanisms of cellulose and hemicellulose change at 30% and 70% O2, respectively, and the lignin particle ignites homogeneously at 20-30% O2, heterogeneously at 50% O2, and hetero-homogeneously at 70-100% O2, respectively. The changes in the ignition mechanisms of biomass particles with lignin content > 10% and < 10% under a certain oxygen concentration depend considerably on the lignin and cellulose contents in the biomass particle, respectively. The expansion of biomass particles with lignin content > 10% and < 10% during combustion process are caused by lignin and hemicellulose, respectively.

Comparative pyrolysis behaviors of stalk, wood and shell biomass: Correlation of cellulose crystallinity and reaction kinetics.

In this study, the pyrolysis process of 20 kinds of biomass samples in 3 types (stalk-type, wood-type and shell-type) was investigated with thermogravimetric analyzer, and the correlation of biomass pyrolysis property with biomass chemical structure was put forward. The results showed that the pyrolysis of the 20 kinds of biomass can be classified by types as the pyrolysis of stalk-type biomass had an overlapping decomposition peak of hemicellulose and cellulose at 317 °C. However, the pyrolysis of wood-type and shell-type biomass showed two separated peaks at low temperature and the cellulose peak was higher in wood-type biomass (365 °C) compared to shell-type biomass (348 °C). The different pyrolysis process mentioned above could be due to the positive correlation between cellulose crystallinity and the decomposition temperature of cellulose as well as the activation energy at the decomposition stage of cellulose.

Effects of hemicellulose, cellulose and lignin on the ignition behaviors of biomass in a drop tube furnace.

The aim of this work was to investigate the effects of cellulose, hemicellulose and lignin on the ignition behaviors of biomass. The ignition events of three components and five types of single biomass particles were captured by a high-speed camera in a drop tube furnace with a temperature of 1273 K, and the combustion temperatures for the single biomass particles were measured by radiant energy analysis technology. The comparison of the flame images and the temperature evolution of five types of biomass with three components shows that the lignin content in the biomass particle strongly influences the ignition behaviors. The ignition mechanism of the biomass particle depends heavily on the lignin content. After homogeneous ignition, the rate of increase in the flame temperature and the char ignition of biomass are closely related to the lignin content. The ignition temperature of the biomass particle depends mainly on the cellulose component.

Co-pyrolysis of microalgae with low-density polyethylene (LDPE) for deoxygenation and denitrification.

To upgrade the algae pyrolytic oil, the influence of algae components on co-pyrolysis with LDPE were studied, with Spirulina platensis (SP), Nannochloropsis sp. (NS) and Enteromorpha Prolifera (EP) as typical algae samples, as they are enriched with proteins, lipids and carbohydrate, respectively, especially, the N and O transformation behavior during the co-pyrolysis was studied in depth. During co-pyrolysis, the interaction on products depended on the components of algae. EP and SP were prior to form CO2, rather than CO. For pyrolytic oil, co-pyrolysis effectively inhibited the formation of N- and O-compounds, but promoted the generation of long-chain alcohol and formic/acetic ester. And the obvious decrease of N and O content in co-pyrolytic oil was observed. However, the rich lipids in NS resulted in the improvement of N yield in pyrolytic oil during co-pyrolysis.

Bimetallic carbon nanotube encapsulated Fe-Ni catalysts from fast pyrolysis of waste plastics and their oxygen reduction properties.

Carbon-based bimetallic electrocatalysts were obtained by catalytic pyrolysis of waste plastics with Fe-Ni-based catalysts and were used as efficient oxygen reduction reaction (ORR) catalysts in this study. The prepared iron-nickel alloy nanoparticles encapsulated in oxidized carbon nanotubes (FeNi-OCNTs) are solid products with a unique structure. Moreover, the chemical composition and structural features of FeNi-OCNTs were determined. The iron-nickel alloy nanoparticles were wrapped in carbon layers, and the carbon nanotubes had an outer diameter of 20-50 nm and micron-scale lengths. FeNi-OCNT with a Fe/Ni ratio of 1:2 (FeNi-OCNT12) exhibited remarkable electrochemical performance as an ORR catalyst with a positive onset potential of 1.01 V (vs. RHE) and a half-wave potential of 0.87 V (vs. RHE), which were comparable to those of a commercial 20% Pt/C catalyst. Furthermore, FeNi-OCNT12 exhibited promising long-term stability and higher tolerance to methanol than the commercial 20% Pt/C catalyst in an alkaline medium. These properties were attributable to the protective OCNT coating of the iron-nickel alloy nanoparticles.

Co-pyrolysis of microalgae and plastic: Characteristics and interaction effects.

To improve the quality of the oil produced from microalgae, the co-pyrolysis of low-density polyethylene (LDPE) and Nannochloropsis sp. (NS) in a fixed bed reactor was investigated at different mixing ratios. Co-pyrolysis improved the gas yield, and the lower heating value of the gas products increased obviously with an increase in the LDPE amount. Furthermore, co-pyrolysis promoted the generation of CH4 and C2+, especially C2H4, with the maximum C2+ yield (84.86 mL/g) obtained with 75% LDPE. Meanwhile, the amounts of oxygenous and nitrogenous compounds in the liquid products decreased rapidly with LDPE addition. The aliphatic hydrocarbon content of the liquid products increased from 22.63% for NS pyrolysis to 77.4% with 25% LDPE. During co-pyrolysis with LDPE, O tended to evolve as H2O and CO (rather than as CO2 for NS pyrolysis) and N was more likely to be released into gas products, which enhanced the quality of the pyrolysis oil.

Pyrolysis characteristics of lignocellulosic biomass components in the presence of CaO.

In this study, the reaction mechanism for the pyrolysis of cellulose, hemicellulose and lignin in the presence of CaO was examined using TG-FTIR and PY-GC/MS. Results indicated that, at low temperature (400-600 °C), in addition to H2O and CO2, acids and phenols from hemicellulose pyrolysis, sugars from cellulose pyrolysis and phenols from lignin pyrolysis would react with CaO. While, at elevated temperature (600 °C-800 °C), the catalytic effect of CaO was more obvious. In detail, in hemicellulose pyrolysis, CaO promoted the catalytic decarbonylation of ketones to form CO, and meanwhile, the formation of hydrocarbons was enhanced. For cellulose pyrolysis, the presence of CaO enhanced the ring-opening and dehydration reactions of sugars, and thus promoted the formation of light organics. As to the pyrolysis of lignin, CaO addition favored the radical reactions and thus increased the yield of CH4. In addition, those monohydric phenols with lower carbon numbers increased.

Enhancing the production of light olefins and aromatics from catalytic fast pyrolysis of cellulose in a dual-catalyst fixed bed reactor.

In this study, the effects of a macroporous catalyst (CaO), mesoporous catalyst (MCM-41), and microporous catalysts (ZSM-5 and SAPO-34) on the production of light olefins and aromatics from cellulose catalytic fast pyrolysis were investigated in a dual-catalyst fixed bed reactor. Further the fractional catalytic pyrolysis of MCM-41 or CaO with ZSM-5 or SAPO-34 was explored. The results showed that ZSM-5 was the most efficient catalyst for the formation of light olefins and aromatics followed by MCM-41, CaO and SAPO-34, and no aromatics were found with SAPO-34 only. Moreover, 15% CaO combined 85% ZSM-5 produced the highest yield of light olefins (5.59%) and aromatic (13.42%). The addition of CaO and MCM-41 promoted the selectivity of C2H4 and decreased the production of naphthalene.

The densification of bio-char: Effect of pyrolysis temperature on the qualities of pellets.

The densification of bio-chars pyrolyzed at different temperatures were investigated to elucidate the effect of temperature on the properties of bio-char pellets and determine the bonding mechanism of pellets. Optimized process conditions were obtained with 128MPa compressive pressure and 35% water addition content. Results showed that both the volume density and compressive strength of bio-char pellets initially decreased and subsequently increased, while the energy consumption increased first and then decreased, with the increase of pyrolysis temperature. The moisture adsorption of bio-char pellets was noticeably lower than raw woody shavings but had elevated than the corresponding char particles. Hydrophilic functional groups, particle size and binder were the main factors that contributed to the cementation of bio-char particles at different temperatures. The result indicated that pyrolysis of woody shavings at 550-650°C and followed by densification was suitable to form bio-char pellets for application as renewable biofuels.