pyrolysis

摘要： Biomass-derived residue carbonization has been an important issue for"carbon fixation"and"zero emission",and the carbonized products have multiple application potentials.However,there have been no specific research to study the differences in macro-and micro-morphology,electrical properties and many other aspects of the products obtained from carbonization of pure cellulose,pure lignin or their complex,lignocellulose.In this work,lignocellulose with cellulose to lignin mass ratio of 10:1 is obtained using p-toluenesulfonic acid hydrolysis followed by homogenization process at a controlled condition.Then,carbon heterostructure with fibers and sheets(CH-10)are obtained by pyrolysis at 1500°C.Detailed results imply that the fiber-like carbon structure possesses high crystallinity and low defect density,coming from carbonization of the cellulose content in lignocellulose(LC)nanofibers.Correspondingly,the graphite-like carbon sheet with high defect density and low crystallinity comes from carbonization of the lignin content in LCs.Further investigation indicates CH-10 possesses enhanced polarization and moderate impedance matching which makes it an ideal candidate for electromagnetic wave(EMW)absorption.CH-10 exhibits an excellent EMW absorption performance with a minimum RL value of-50.05 dB and a broadest absorption bandwidth of 4.16 GHz at a coating thickness as thin as 1.3 mm.

摘要： Induced BVOC emissions from pyrolyzed plants that may accumulate in confined topographies have been a controversy for their role in wildfire eruptions or flashovers. α-pinene (C10H16) is one of the most abundant monoterpenes emitted from pyrolyzed Mediterranean vegetation in wildfires. Its thermal degradation under fire thermal stresses produces a range of highly flammable gases. In order to identify these products, thermal degradation experiments were performed on α-pinene in a tubular furnace in an inert atmosphere and a high-temperature range (300°C - 900°C). The pyrolysis products were identified using gas chromatography (GC) linked to a tubular furnace outlet by which their retention times were compared with those of reference standards. The degradation products were mainly terpenoids, aliphatic hydrocarbons (methane, ethane, ethene, propane, propene, 1,3-butadiene, isoprene), and aromatics (benzene, toluene) in addition to hydrogen. The radical mechanisms of the chemical reactions associated with the formation of the products at different experimental temperatures were addressed and compared with the literature. Monoterpenes, butadiene, isoprene, aliphatic hydrocarbons, and aromatics formations from α-pinene were consistent with the literature. However, even if benzene has been identified in our experiments, we cannot support with certainty the mechanisms of its formation described in the literature since acetylene was not observed.

摘要： The main source of energy for most African families remains firewood. The exploitation of this resource is the main cause of accelerated environmental degradation with its consequences which are climate change and soil impoverishment. However, agricultural residues are often available and even abandoned in fields after harvest. In this regard, we have characterized three biomass with no economic value in order to use them for the production of biochar to improve soil quality while providing the energy necessary for household cooking. Our research was based on the following biomasses: cotton stalks, maize rachis and rice husks. The study made it possible to characterize the biomasses which could be used for combustion and/or pyrolysis. From the results obtained, we could observe a high ash content in the rice husk (24.21%) against 2.41% for cotton stalks and 2.00% for maize rachis. These results influence the calorific value of the rice husk, thus allowing it to be used matter in pyrolysis and not in combustion. In addition, cotton stalks and corn rachis can be used both as fuel and as biomass to be pyrolyzed.

摘要： Recycle of plastic waste is an indisputable means to alleviate both environment and energy crisis.In this work,effects of heating condition on polyethylene behaviors in nitrogen and air were studied.It was observed that polyethylene behavior was a single step in nitrogen,while the multiple steps occurred in air.According to the weight loss and heat flow curves,polyethylene behaviors in air were divided into three regions:low-temperature( 380 °C) regions.Kinetic analysis revealed that the partial oxidization took the dominance in the low-temperature region,which seldom formed CO and CO_(2);the combustion took the dominance in the middle-temperature region,which was positive to the formation of CO and CO_(2);the pyrolysis was initiated and enhanced in the high-temperature region,which inhibited the formation of CO and CO;.According to the kinetic simulation,a synergistic effect between the pyrolysis and combustion was proposed to account for the acceleration of polyethylene conversion.This work may provide useful information about polyethylene behaviors under heating condition,and help to design and optimize plastic waste incineration process.

摘要： Due to the complexity of feedstock,it is challenging to build a general model for light olefins production.This work was intended to simulate the formation of ethylene,propene and 1,3-butadiene in alkanes pyrolysis by referring the effects of normal/cyclo-structures.First,the pyrolysis of n-pentane,n-hexane,n-heptane,n-octane,n-nonane,n-decane,cyclohexane,methylcyclohexane,n-hexane and cyclohexane mixtures,and n-heptane and methylcyclohexane mixtures were carried out at 650–800°C,and a particular attention was paid to the measurement of ethylene,propene and 1,3-butadiene.Then,pseudo-first order kinetics was taken to characterize the pyrolysis process,and the effects of feedstock composition were studied.It was found that chain length and cyclo-alkane content can be qualitatively and quantitively represented by carbon atom number and pseudo-cyclohexane content,which made a significant difference on light olefins formation.Furthermore,the inverse proportional/quadratic function,linear function and exponential function were proposed to simulate the effects of chain length,cycloalkane content and reaction temperature on light olefins formation,respectively.Although the obtained empirical model well reproduced feedstock conversion,ethylene yield and propene yield in normal/cycloalkanes pyrolysis,it exhibited limitations in simulating 1,3-butadiene formation.Finally,the accuracy and flexibility of the present model was validated by predicting light olefins formation in the pyrolysis of multiple hydrocarbon mixtures.The prediction data well agreed with the experiment data for feedstock conversion,ethylene yield and propene yield,and overall characterized the changing trend of 1,3-butadiene yield along with reaction temperature,indicating that the present model could basically reflect light olefins production in the pyrolysis process even for complex feedstock.

摘要： Plastic is a basic need for humans,but it has also caused big problems for the environment.Then,the purpose of this study was to determine the effect of the type of plastic and the addition of a zeolite catalyst on the oil yield from the pyrolysis of plastic waste.The research stages were natural zeolite activation,pyrolysis reactor settings,pyrolysis of plastic waste(PP and LDPE types),and characterization.The results showed that the used natural zeolite had a mordenite phase and activated natural zeolite had a higher Si/Al ratio than the inactivated one.The addition of a zeolite catalyst had an effect on the produced yield.The yields of oil from plastic waste pyrolysis with zeolite catalyst for PP and LDPE plastics were about 75.9 and 76.9 w/w,respectively.The results of the GCMS analysis showed that the compounds of the pyrolysis oil were thought to be from the alkanes,cycloalkanes,alkenes,carboxylic acids with aromatic rings,and ketones.The results of the GC-MS test showed that the uncatalyzed pyrolysis product consists of compounds with a range of C5-C11 carbon chains.Meanwhile,the ranges of pyrolysis products with active zeolite catalyst were C6-C24 carbon chains.

摘要： In this work,the thermal degradation and drying of bio-hardeners are investigated.Four bio-hardeners based on exudates of Senegalia senegal,Vachellia nilotica,Vachellia seyal,and Acacia siebteriana were analyzed by FTIR and thermogravimetric analysis,and a desorption study was also conducted.The analysis by infrared spectroscopy indicates the existence of oligomers of different types all giving 5-hydroxy-2-hydroxymethylfuran and 2,5-dihydroxymethylfuran which are then the real hardening molecules.The pyrolysis of these extracts reveals three main regions of mass loss,a first region is located between 25°Cand 110°Creflecting the loss of water from the adhesive and the formation of some traces of volatile organic compounds such as CO_(2)and CO,a second zone characterized by the release of CO,CO_(2)and CH4 gases with peaks between 110°and 798.8°C.At the end of the analysis,about 22%of the initial mass remains undecomposed,this mass corresponds to the rigid segments of the bio-hardener which are not completely decomposed.

摘要： This study deals with the valorization of natural residues into activated carbon prepared from waste“Baobab fruit shell”from the Fatick Region,Senegal.Thus,after the preparation of the baobab shell,a chemical activation with orthophosphoric acid H3PO4(85%)was performed followed by pyrolysis at 530°C.To eliminate possible carbonization residues,the activated carbons were impregnated in 0.1 M hydrochloric acid and/or soda solutions and then washed thoroughly with distilled water to obtain a pH between 6.5 and 7.The latter were then dried in an oven at 105°C for 24 h.A characterization was carried out to determine the moisture content,the ash content,the iodine and methylene blue indices,the surface functions and the pH at zero charge point(pHpzc).The moisture and ash contents were 1.87%and 0.72%,respectively.The iodine and peroxide indices obtained were 939,09 mg/g and 575.73 mg/g,respectively.Surface function analysis by Boehm’s method showed that the acidic functions were higher than the basic functions and their pHpzc was lower than neutrality.The best efficiency of methylene blue removal was 99.75%and was obtained with a mass of 0.150 g of activated carbon,pH equal to 10,an initial concentration of methylene blue of 200 mg/L and a contact time of 35 min.

摘要： HZSM-5 zeolites with Si/Al ratios of 20,35,50 and 65 were prepared by the directing crystallization process of silicalite-1 seeds.The influence of Si/Al ratios on the production of benzene,toluene,xylene and naphthalene(BTXN)originated from asphaltenes catalytic pyrolysis was explored by adopting Py-GC/MS.Modified Z5-50 zeolites were prepared by various metal ions(Ni^(2+),Mo^(6+),Fe^(3+),and Co^(2+))with different loading rates(3%(mass),5%(mass),7%(mass),and 9%(mass))and the physical and chemical properties of these zeolites were characterized by XRD,SEM,ICP-OES,XPS,NH_(3)-TPD,FTIR,Py-IR and N_(2)adsorption-desorption isotherm.In addition,they were employed to catalyze the conversion of asphaltenes pyrolysis production to BTXN using Py-GC/MS.Results show that the highest relative content of aromatics has been obtained over HZSM-5 with Si/Al ratio of 50(Z5-50),reaching 61.87%.Besides,the loading of Ni,Mo,Fe,and Co on Z5-50 leads to an increase of acid strength and provides new active sites.The relative content of BTXN increases by 3.17%over 3Ni-Z5,which may be ascribed to that Ni promoted the conversion of polycyclic aromatic hydrocarbons(PAHs)to monocyclic aromatics due to the cracking of aliphatic side chains of PAHs and the decrease of phenolic activation energy.While under the catalysis of 5Mo-Z5,the relative content of aromatics and BTXN augmented by 5.75%and 4.02%,respectively.In addition,the highest relative content of aromatics reaches 70.09%when the loading rate of Fe was 7%(mass),and the relative content of BTXN increases from 25.87%to 29.42%.The results demonstrate that the active sites provided by different metal species expressed diverse effects on BTXN.Although the Bronsted/Lewis acid ratios of HZSM-5 modified by metal decreased,the acid strength and the relative content of BTXN both increased,which illustrated that there is a synergistic catalysis with the Bronsted acid sites and Lewis acid sites provided by metal species.In general,the performance of the catalyst is affected by the pore structure,acidity and metal active sites.Moreover,the possible formation mechanism of BTXN derived from asphaltenes catalytic pyrolysis was proposed on the basis of structural features and catalytic performances of a series of zeolites.

摘要： Pyrolysis experiments were conducted on lacustrine organic-rich shale from Cangdong Sag in Bohai Bay Basin,China,to investigate the impact of hydrocarbon generation on shale pore structure evolution.Thermal evolution is found to control the transformation of organic matter,hydrocarbon products characteristics,and pore structure changes.Furthermore,pore volume and specific surface area increase with increasing maturity.In low-mature stage,the retained oil content begins to increase,pore volumes show slight changes,and primary pores are occluded by the generated crude oil of high molecular weight and density.In the oil-window stage,the retained oil content rapidly increases and reaches maximum,and pore volumes gradually increase with increasing thermal maturity.At high mature stage,the retained oil content begins to decrease,and the pore volume increases considerably owing to the expulsion of liquid hydrocarbon.In over mature stage,natural gas content significantly increases and kerogen transforms to asphalt.Numerous organic pores are formed and the pore size gradually increases,resulting from the connection of organic pores caused the increasing thermal stress.This study lays a foundation for understanding variation of hydrocarbon products during the thermal evolution of lacustrine shales and its relationship with the evolution of shale reservoirs.

摘要： Non-isothermal Pyrolysis kinetics phenol-formaldehyde（PF) resin is investigated using thermogravimetry（TG). The TG experiments at controlled heating rates were used for obtaining the kinetic parameters of the reactive system. The research indicates that the pyrolysis process consists of four consecutive distinct stages. The anterior two stages are named as one-dimensional diffusion and three-dimensional reaction regions，while the third stage is characterized as a random nucleation and its subsequent growth，and the latest one can be defined as a chemical reaction region. According to the calculation results of the apparent activation energy Ea，the changes of entropy △S≠，enthalpy △H≠and Gibbs free energy △G≠，the anterior three stages are non-spontaneous processes. While the fourth stage proceeds spontaneously.