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•Model-free integral kinetics method and analytical TGA–FTIR were conducted on pyrolysis process of PKS.•The pyrolysis mechanism of PKS was elaborated.•Thermal stability was ...established: lignin>cellulose>xylan.•Detailed compositions in the volatiles of PKS pyrolysis were determinated.•The interaction of biomass three components led to the fluctuation of activation energy in PKS pyrolysis.
Palm kernel shell (PKS) from palm oil production is a potential biomass source for bio-energy production. A fundamental understanding of PKS pyrolysis behavior and kinetics is essential to its efficient thermochemical conversion. The thermal degradation profile in derivative thermogravimetry (DTG) analysis shown two significant mass-loss peaks mainly related to the decomposition of hemicellulose and cellulose respectively. This characteristic differentiated with other biomass (e.g. wheat straw and corn stover) presented just one peak or accompanied with an extra “shoulder” peak (e.g. wheat straw). According to the Fourier transform infrared spectrometry (FTIR) analysis, the prominent volatile components generated by the pyrolysis of PKS were CO2 (2400–2250cm−1 and 586–726cm−1), aldehydes, ketones, organic acids (1900–1650cm−1), and alkanes, phenols (1475–1000cm−1). The activation energy dependent on the conversion rate was estimated by two model-free integral methods: Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS) method at different heating rates. The fluctuation of activation energy can be interpreted as a result of interactive reactions related to cellulose, hemicellulose and lignin degradation, occurred in the pyrolysis process. Based on TGA–FTIR analysis and model free integral kinetics method, the pyrolysis mechanism of PKS was elaborated in this paper.
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•Properties of solid, liquid and gaseous products of biomass torrefaction are studied.•Torrefaction characteristics of three biomass components are significantly ...different.•Dehydration and oxygen-containing gas are the two dominant deoxygenation pathways.•About 19.76–71.11% of oxygen is removed from hemicellulose torrefied at 210–300 °C.•Solid products of torrefaction retain most of the energy in the original samples.
In this work, torrefaction of hemicellulose, cellulose, and lignin were studied at a series of torrefaction temperatures (210, 240, 270, and 300 °C) based on the properties of their three-phase products, namely solid, liquid (water and tar), and gaseous products. Among the three biomass components, significant difference of torrefaction characteristics was found due to their different molecular structures. For the solid product, hemicellulose presented lowest yield from 85.65% to 41.54% as the temperature increased because of the poor thermostability, thereby showing obvious variations in carbon and oxygen contents. For the gaseous product, CO2, followed by CO, were the dominant gaseous components in all torrefaction conditions including different feedstock and temperatures; also a small number of other components (H2 and CH4) were produced during torrefaction of lignin. The liquid product was composed of water and a small amount of tar. For the tar product, acids and ketones were the dominant components in the torrefaction of hemicellulose, while anhydrosugar in the torrefaction of cellulose, and phenols in the torrefaction of lignin. As the temperature increased from 210 °C to 300 °C, about 19.76–71.11%, 5.85–33.27%, and 16.28–44.89% of oxygen from hemicellulose, cellulose, and lignin, respectively, was transformed into the liquid and gaseous products. Dehydration reaction and volatilization of the oxygenated gaseous product were the two dominant deoxygenation pathways, and the water, CO2, and CO were the dominant carriers of oxygen migration. In contrast to oxygen, only a small amount of carbon was transferred into tar product, followed by gaseous product, consequently the solid samples still retained most of the energy.
•Biochar and bio-oil decrease while gas yield increases with increasing heating rate.•Activation energy values for bamboo pyrolysis increase with increasing heating rate.•Increasing heating rate ...improves phenolics production while reduces water in bio-oil.•Temperature gradient and secondary decomposition are noticeable in fixed bed reactor.•Increasing heating rate improves the specific surface area of the biochar.
Effects of heating rate on slow pyrolysis behaviors, kinetic parameters, and products properties of moso bamboo were investigated in this study. Pyrolysis experiments were performed up to 700°C at heating rates of 5, 10, 20, and 30°C/min using thermogravimetric analysis (TGA) and a lab-scale fixed bed pyrolysis reactor. The results show that the onset and offset temperatures of the main devolatilization stage of thermogravimetry/derivative thermogravimetry (TG/DTG) curves obviously shift toward the high-temperature range, and the activation energy values increase with increasing heating rate. The heating rate has different effects on the pyrolysis products properties, including biochar (element content, proximate analysis, specific surface area, heating value), bio-oil (water content, chemical composition), and non-condensable gas. The solid yields from the fixed bed pyrolysis reactor are noticeably different from those of TGA mainly because the thermal hysteresis of the sample in the fixed bed pyrolysis reactor is more thorough.
Bio-oil is the liquid product of the fast pyrolysis of biomass. Recently, bio-oil has gained increasing attention for its direct use in combustion within boilers and furnaces as well as its use in ...automobiles and chemical materials after refining. Unfortunately, the composition of bio-oil is very complex. Aging occurs during storage, which leads to obvious changes in the physical and chemical properties of the oil. The poor storage stability of bio-oil restricts its extensive applications as a key renewable energy alternative. Viscosity and average molecular weight, as well as water and solid content can measured to determine changes in bio-oil. In this article, the testing parameters and technologies used for examining bio-oil stability and research progress in the field of bio-oil stability are reviewed. Emphasis is placed on thermal and oxidation stability. Scientific and technical developments towards improving bio-oil stability are also discussed. Furthermore, important aspects for consideration when developing experimental plans for bio-oil upgrades are examined. It also points out challenges to success with bio-oil upgrading in the future.
The properties of biomass directly result in the quality of bio-oil. Torrefaction pretreatment is an alternative and promising approach for biomass updating to produce high-quality bio-oil. The ...effects of torrefaction on the pyrolysis of rice husk were investigated using thermogravimetry–Fourier transform infrared spectroscopy (TG-FTIR), a pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), and a fast pyrolysis device. The results show that with increasing torrefaction temperature, the weight loss decreases and the shoulder peaks of torrefied rice husk in DTG curves fade away. The pyrolysis characteristics and kinetics analysis of torrefied rice husk at 290 °C are unique. Three-dimensional FTIR analysis of the evolved gases clearly shows the generation properties of individual volatile components. Fast pyrolysis of torrefied rice husk produces improved bio-oil low moisture content and high heat value. Py-GC/MS analysis shows that the acidic content does not increase, while the content of many highly valued products (e.g., levoglucose) increases greatly.
•A novel approach was performed to upgrade the quality of biomass pyrolysis products.•Aqueous phase bio-oil washing pretreatment removed metals from the sample.•Torrefaction reduced the oxygen but ...increased the metal content of cotton stalk.•3D FTIR results were consistent with the pyrolysis stages of the TG/DTG curve.•Combined pretreatment reduced water and acid and increased phenol content of bio-oil.
Bio-oil undergoes phase separation because of poor stability. Practical application of aqueous phase bio-oil is challenging. In this study, a novel approach that combines aqueous phase bio-oil washing and torrefaction pretreatment was used to upgrade the biomass and pyrolysis product quality. The effects of individual and combined pretreatments on cotton stalk pyrolysis were studied using TG-FTIR and a fixed bed reactor. The results showed that the aqueous phase bio-oil washing pretreatment removed metals and resolved the two pyrolysis peaks in the DTG curve. Importantly, it increased the bio-oil yield and improved the pyrolysis product quality. For example, the water and acid content of bio-oil decreased significantly along with an increase in phenol formation, and the heating value of non-condensable gases improved, and these were more pronounced when combined with torrefaction pretreatment. Therefore, the combined pretreatment is a promising method, which would contribute to the development of polygeneration pyrolysis technology.
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•Removal rate of AAEMs are remarkably improved by using aqueous phase bio-oil.•Furfural, hydroxyacetone, ethylene glycol, phenol and guaiacol are used for leaching.•Acetic acid is the ...key component in bio-oil to leach AAEMs from biomass.•Synergistic leaching effect occurred between acetic acid and non-acidic components.•Non-acidic compounds in bio-oil play an important role in leaching of AAEMs.
In this study, six dominant organic compounds in biomass pyrolyzed bio-oil, composed of acidic compound (acetic acid) and non-acidic compound (furfural, hydroxyacetone, ethylene glycol, phenol, and guaiacol) were used to remove AAEMs from different lignocellulosic biomass (rice husk, cotton stalk, and fir sawdust) by leaching pretreatment. Other four conventional solutions (deionized water, hydrochloric acid solution, aqueous phase bio-oil, and simulated bio-oil) were selected as control eluents. Results showed that the removal rate of AAEMs was highly affected by the types of immersion solutions, pH values, and the species of biomass. Majority of K in biomass could be removed by leaching of acetic acid. Ca was more difficult to be removed by leaching of water and acetic acid, but could be removed by leaching of HCl. In general, the removal rate of K was highest among the four species of AAMEs by using five non-acidic components, followed by Na, Mg, and Ca. The use of five non-acidic solutions was significantly benefit for the remove of K, Mg, and Na, but, was less useful in removal of Ca in rice husk and fir sawdust. However, the removal rates of Ca in cotton stalk by leaching of phenol, guaiacol, and hydroxyacetone were increased to nearly three times than water leaching. A synergistic effect for removing AAEMs occurred between acetic acid and non-acidic components in bio-oil, indicating that the non-acidic compounds also play an important role in leaching of AAEMs.
► Two different stages were shown in the pyrolysis process of biomass. ► Nonisothermal Page model is the best model for describing the drying kinetics. ► DAEM is not adequate for kinetics analysis in ...the first stage of biomass pyrolysis. ► Three ranges of activation energy are identified for the whole pyrolysis process.
An in-depth investigation was conducted on the kinetic analysis of raw biomass using thermogravimetric analysis (TGA), from which the activation energy distribution of the whole pyrolysis process was obtained. Two different stages, namely, drying stage (Stage I) and devolatilization stage (Stage II), were shown in the pyrolysis process in which the activation energy values changed with conversion. The activation energy at low conversions (below 0.15) in the drying stage ranged from 10 to 30kJ/mol. Such energy was calculated using the nonisothermal Page model, known as the best model to describe the drying kinetics. Kinetic analysis was performed using the distributed activation energy model in a wide range of conversions (0.15–0.95) in the devolatilization stage. The activation energy first ranged from 178.23 to 245.58kJ/mol and from 159.66 to 210.76kJ/mol for corn straw and wheat straw, respectively, then increasing remarkably with an irregular trend.
Salmonella typhimurium is a pathogenic gram-negative bacterium, which is found primarily in the intestinal lumen. It often causes diarrhea in infants and young children and leads to food poisoning. ...Drug resistance of Salmonella typhimurium presented serious complications in clinical patients. In this study, we investigated the antibiotic susceptibility of Salmonella typhimurium standard strain L forms to the third and forth generation cephalosporins, in order to control and eliminate Salmonella typhimurium L forms in infection treatment. Salmonella typhimurium L forms were induced by β-lactam antibiotic cefazolin in the culture medium of bacterial L forms. The antibiotic susceptibility of Salmonella typhimurium L forms was analyzed by K-B drug susceptibility testing. The change trend of drug susceptibility and resistance of Salmonella typhimurium L forms was obtained in accordance with USA clinical and laboratory standards institute (CLSI) evaluation data and statistical analysis. Drug resistance of Salmonella typhimurium L forms showed little increasing trend compared with their parent bacteria. The L form inhibition zone was smaller than in the parent bacteria. However, the drug susceptibility of L forms of Salmonella typhimurium to the third and forth generation cephalosporins remained sensitive.The antibiotic susceptibility of Salmonella typhimurium L forms to the third and forth generation cephalosporins remains sensitive, and the combined use of multi-antibiotics is a convenient and effective method to reduce Salmonella typhimurium L forms occurrence.
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