Effect of thermal preoxidation and the addition of ammonium molybdate on the thermal conversion of cellulose and cellulose compositions

As found by thermogravimetric and differential thermal analysis and gas chromatography, the thermal oxidative pretreatment of cellulose and cellulose compositions with high-molecular-weight polycondensed aromatic systems of natural origin resulted in a shift of peaks due to intense thermal degradation to the region of lower temperatures and changes in the yields of carbon residues and in the quantitative composition of the main gaseous products of pyrolysis. In the presence of ammonium molybdate, which is a catalyst for cellulose oxidation and carbonization, the effect of the thermal oxidative treatment was even more enhanced. This was reflected in an increase in the low-temperature shifts of intense degradation processes and a considerable increase in the yields of carbon residues of cellulose and cellulose compositions.     

Thermogravimetric and differential thermal analysis of cellulose,hemicellulose, and lignin

The thermal degradation of samples of cellulose, hemicellulose, and lignin have been investigated using the techniques of thermogravimetric analysis (TGA) and differential thermal analysis (DTA) between room temperature and 600°C. The results calculated from static and dynamic TGA indicated that the activation energy E for thermal degradation for different cellulosic, hemicellulose, and lignin samples is in the range 36–60, 15–26, and 13–19 kcal/mole, respectively. DTA of all the wood components studied showed an endothermic tendency around 100°C in an atmosphere of flowing nitrogen and stationary air. However, in the presence of flowing oxygen this endothermic effect was absent. In the active pyrolysis temperature range in flowing nitrogen and stationary air atmospheres, thermal degradation of Avicel cellulose occurred via a sharp endothermic and a sharp exothermic process, the endothermic nadir and exothermic peak being at 320° and 360°C, respectively. In the presence of oxygen, combustion of Avicel cellulose occurred via two sharp exothermic processes. DTA studies of different cellulose samples in the presence of air showed that the shape of the curve depends on the sources from which the samples were prepared as well as on the presence of noncellulosic impurities. Potassium xylan recorded a sharp exothermic peak at 290°C in a nitrogen atmosphere, and in a stationary air atmosphere it yielded an additional peak at 410°C, while in the presence of oxygen the curve showed two sharp exothermic peaks. DTA traces of periodate lignin in flowing nitrogen and air were the same and showed two exothermic peaks at 320° and 410°C, while in the presence of oxygen there were two exothermic peaks in the temperature range 200°–500°C.     

纤维素热解动力学分析方法研究

以微晶纤维素为原料,在氮气气氛中利用热重分析仪考察了不同升温速率条件下纤维素的热解实验,分析了纤维素的热解动力学特性。采用双等双步法和Popescu法从热分析动力学的41种机理函数中选取最概然反应机理函数,同时运用Freeman-Carroll法、Coats-Redfern法、Starink法和双等双步法4种热分析方法计算热解反应活化能（E）、指前因子（A）,并对结果进行了分析比较。结果表明,随着升温速率提高,纤维素热解起始温度增加,热失重速率升高;纤维素的热解过程可分为4个阶段：脱水预热（40~120℃）、热解初期（120~260℃）、主要热解失重（260~400℃）和炭化（400~900℃）。纤维素主要热解段分两个阶段进行,其活化能在低温段（260~350℃）时,为166~176 kJ/mol,高温段（350~400℃）时,为171~216 kJ/mol;采用反Jander动力学模型能较好地描述主要热解反应过程;采用单一扫描速率法（Freeman-Carroll法和Coats-Redfern法）分析结果与实际值有较大偏差,多重扫描速率法（Starink法和双等双步法）得到的结果更具可靠性。     

Pyrolysis properties and kinetics of mandarin peel

The thermal property of the pyrolysis reaction of mandarin peel was studied using thermogravimetric analysis (TGA). Thermogravimetric analyses with temperature increases of 10, 20 and 40 °C/min showed large weight losses within the temperature range 150–590 °C. Differential thermogravimetric (DTG) analysis curves illustrated that the pyrolysis of mandarin peel was a multi-step process, consisting of water desorption, the decomposition of pectin, hemicellulose, cellulose and lignin, and devolatilization of the residual char. The apparent activation energies ranged between 119 and 406 kJ/mol, depending on the pyrolytic conversion. The pyrolysis products were analyzed, using pyrolyzergas chromatography/mass spectrometry (Py-GC/MS), to evaluate mandarin peel as a renewable source of valuable industrial chemicals. The pyrolysis products of mandarin peel contained high portions of methanol and acetic acid, as well as valuable compounds, such as limonene and vitamin E.     

Thermal degradation of celluloses and their vinylic copolymers by thermogravimetric analysis

Thermal degradation of unmercerized and mercerized cotton cellulose with different % NaOH solutions and grafted vinylic copolymers with different mixtures of vinyl acetate‐methylacrylate¹ have been studied by thermogravimetric analysis (TGA) in nitrogen between 25 and 600°C at different heating rates. The differences between unmercerized and mercerized samples are related to structural differences between cellulose‐I (native) and cellulose‐II. The grafted cellulosic vinylic copolymers have shown that their thermal stability depends upon the cellulosic substrate and the grafting percentage. From our results, it can be deduced that it is possible to prepare the cellulosic materials with good thermal stability, short degradation temperature interval, and various residues at the end of degradation. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 201–209, 1999     

Office waste paper as cellulose nanocrystal source

Cellulose nanocrystals (CNC) are isolated from office waste paper using an alkali solution and a subsequent acid hydrolysis process. The Fourier transform infrared spectroscopy and X‐ray diffraction (XRD) results demonstrate that ink and fillers used in the papermaking industry are almost totally removed after alkali treatments. The XRD results show that CNCs obtained after 2 wt % NaOH solution treatment and a subsequent hydrolysis process exhibit only a cellulose I crystalline structure, and the crystallinity index value increases around 42% with respect to initial office waste paper. Nevertheless, CNCs obtained after 7.5 wt % NaOH solution treatment and a subsequent acid hydrolysis process show a mixture of cellulose I and cellulose II polymorphs. The thermal analysis shows that the CNCs obtained after 7.5 wt % NaOH solution treatment and a subsequent acid hydrolysis process are thermally less stable than other samples, suggesting that the cellulose chains could depolymerize into low molecular weight sugar compounds. Even though the atomic force microscopy images confirm the presence of CNCs, the optical images show that some cellulose microfibers still maintain their structure. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45257.     

Extraction of cellulose nanocrystals and fabrication of high alumina refractory bricks using pencil chips as a waste biomass source

Extraction of “green” cellulose nanocrystals (CNCs) from waste biomass is a sustainable strategy for high valued valorization in the view of socio-economic and environmental issues. Herein, for the first time, waste pencil chips (PC) as a potential source of cellulose, were used for the extraction of CNCs. CNCs were successfully extracted from PC wastes using alkali and bleaching chemical treatments to remove hemicellulose and lignin followed by acid hydrolysis using concentrated sulfuric acid. The products after each step were characterized in terms of crystallinity, chemical structures, thermal properties, and morphologies. The XRD results showed that the crystalline index increased about 16% from PC (75%) to CNCs (91%). The FTIR analysis confirmed the removal of the hemicellulose and lignin from PC after alkali and bleaching treatments. The TGA analysis showed that the thermal stability of the CNCs is affected mainly by the dehydration reaction caused by sulfate groups. The SEM and FE-SEM images showed that after chemical treatments, defibrillation of fibers occurs and CNCs have a needle/rod like structure. Also, the specific surface aera was greatly increased from 0.495 for PC to 486.430 m²/g for CNCs. Herein, for the first time, lignin-containing cellulose extracted from PC was replaced with sawdust (SRB) in the production of alumina refractory bricks (RBs), as a pore former/binder. Interestingly, the prepared RBs (PC–NaOH/RB) had a greater amount of alumina (83%) and a lower density (0.75 g/cm³) than SRB. The classification temperature increased from 1650 for SRB to 1717 °C for PC-NaOH/RB.     

Thermal degradation of partially carboxymethylated cellulose grafted with 4-vinylpyridine

Partially carboxymethylated cellulose (PCMC) was grafted with 4-vinylpyridine (4-VP) using ceric ammonium nitrate (CAN) as initiator and the thermal behaviour of the grafted samples having different grafting yields was studied by means of thermogravimetric dynamic analysis (TGA). For comparison, the thermal behaviour of poly(4-vinylpyridine), P(4-VP), and the ungrafted cellulosic substrate were also examined. The activation energies were determined according to the Broido method. From the thermogravimetric curves the temperature range at which the main decomposition occurred was determined and showed that the thermal degradation of grafted samples was initiated at lower temperature than both PCMC and P(4-VP).     

Comparison of cellulose and chitin nanocrystals for reinforcing regenerated cellulose fibers

In this study, regenerated cellulose fibers reinforced by cellulose nanocrystals (CENC) and chitin nanocrystals (CHNC) were prepared by blending the nanocrystals suspensions with the cellulose solution in NaOH/urea/water solvent at room temperature. The effect of nanocrystals' addition on the properties of spinning dopes and regenerated fibers were investigated and compared. Results showed that the obtained CENC and CHNC had different dimensions, and both of them increased the viscosity and decreased the transparency of the spinning dopes. However, the dissolution state of cellulose was not changed. CHNC had a greater influence on the properties of spinning dopes, while CENC had more obvious effect on the performance of regenerated fibers. The CENC reinforced fibers showed a higher crystallinity index as compared to the CHNC reinforced fibers. The tensile strength of the regenerated fibers was evidently improved when 3 wt % CENC or 2 wt % CHNC were added, while the elongation at break of the fibers was slightly decreased with the increase of nanocrystals content. The morphology and thermal stability of the regenerated fibers was not affected by the addition of nanocrystals. This study suggested that the dimension, group and content of nanocrystals were important factors for the reinforcement of regenerated cellulose fibers. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44880.     

油茶果蒲与聚丙烯共热解特性及动力学分析

为了研究油茶果蒲(CS)与聚丙烯(PP)混合比例(质量比)对两者共热解特性及动力学参数的影响,将CS与PP按不同比例(3∶7、 5∶5和7∶3)混合,分别在5、 10、 15和20℃/min的升温速率下,由50℃升温至800℃进行热重实验及动力学分析。热重实验结果表明：混合样品的共热解可以分为两个阶段,当温度低于352℃时,在混合样品热解中CS热解占主导作用,混合样品中的PP促进了CS的热解;温度高于352℃时,PP的热解占主导作用,CS对PP热解起抑制作用。动力学分析结果表明：FWO法适合CS与PP单独热解及共热解动力学分析,m(CS)∶m(PP)为3∶7的混合样品平均表观活化能(217.04 kJ/mol)最低,相比于CS单独热解的平均表观活化能(474.94 kJ/mol)降低了54.3%。     

TGA and macro-TGA characterisation of biomass fuels and fuel mixtures

The thermal behaviour of selected biomass fuels and mixtures as wood, demolition wood, coffee waste and glossy paper was investigated using a thermogravimetric analyzer (TGA) and a macro-thermobalance (macro-TGA). A kinetic model, involving first-order independent parallel reactions, was applied to results obtained from pyrolysis TGA experiments. The pyrolysis rate was considered as the sum of the main biomass pseudo-components, namely cellulose, hemicellulose and lignin. Additionally, the thermal behaviour of the same fuels was investigated at combustion conditions in the TGA, including ignition behaviour. The thermogravimetric analysis showed that each single fuel had pyrolysis and combustion characteristics based on its own main pseudo-components (hemicellulose, cellulose and lignin). The pyrolysis and combustion characteristics of selected fuel mixtures and the gas composition analysis from macro-TGA experiments showed respectively quantitative and qualitative summative behaviour based on the single fuels.     

Flame Retardant Functionalization of Microcrystalline Cellulose by Phosphorylation Reaction with Phytic Acid

The functionalization of microcrystalline cellulose (MCC) is an important strategy for broadening its application fields. In the present work, MCC was functionalized by phosphorylation reaction with phytic acid (PA) for enhanced flame retardancy. The conditions of phosphorylation reaction including PA concentration, MCC/PA weight ratio and temperature were discussed, and the thermal degradation, heat release and char-forming properties of the resulting PA modified MCC were studied by thermogravimetric analysis and pyrolysis combustion flow calorimetry. The PA modified MCC, which was prepared at 90 °C, 50%PA and 1:3 weight ratio of MCC to PA, exhibited early thermal dehydration with rapid char formation as well as low heat release capability. This work suggests a novel strategy for the phosphorylation of cellulose using PA and reveals that the PA phosphorylated MCC can act as a promising flame retardant material.     

基于离子液体再生的纤维素热解特性

利用离子液体1-丁基-3-甲基咪唑氯([Bmim]Cl)溶解PH-101微晶纤维素,通过不同的再生方法获得两种再生的纤维素,并利用XRD确定其结晶度,场发射扫描电镜(SEM)获得其形貌特征,热重(TG)分析表征其热稳定性.采用Py-GC/MS 对不同结晶度纤维素进行快速热解,并对热解挥发分进行在线分析,观察结晶度对纤维素热解特性的影响.研究表明左旋葡聚糖产率随结晶度降低而减少,而小分子产物随结晶度降低而增多.     

On the use of cellulose nanowhisker as reinforcement in all-cellulose composite membrane from corn stalk

All-cellulose composite (ACC) membranes were prepared with cellulose and cellulose nano whisker (CNW) extracted from corn stalk by using NaOH/thiourea as solvent. CNW was isolated via acid hydrolysis method and the yield, size distribution and morphology of CNW were investigated. ACC Membranes were characterized via SEM, XRD, TGA as well as water flux and were further plasticized with glycerol aqueous solution. The mechanical property and transparency of ACC membranes before and after plasticization were compared. CNW prepared with 63% sulfuric acid for 60 min of hydrolysis time had the biggest ratio of length to diameter and moderate yield. ACC membrane with 5% CNW content had the highest tensile strength and the structure of ACC membranes was observed clearly in SEM images. TGA testing indicated that the initial degradation temperature tended to lower after CNW was introduced into membrane. ACC membrane had good optical transmittance and good flexibility after plasticization.     

Influence of particle size on the analytical and chemical properties of two energy crops

Two energy crops (switchgrass and reed canary grass) have been processed using ball mills and divided into two size fractions (<90 μm and 90–600 μm) and analysed using an array of analytical techniques including proximate and ultimate analysis, metal analysis, calorific value determination, and plant component analysis (cellulose, lignin and hemicellulose contents). The results indicate that smaller particles of the two grasses have a significantly higher concentration of inorganic matter and moisture content than larger particles. In contrast the larger size fractions had a higher carbon content, and lower nitrogen content, with a resulting higher calorific value. The volatile content was also higher in the larger size fraction. The composition of the organic content varied between the two size fractions, most noticeable was the difference in cellulose concentration which was approximately 50% higher in the >90 μm sample. Two laboratory scale techniques, thermogravimetric analysis (TGA) and pyrolysis–GC–MS (py–GC–MS), were used to study the significance of these differences in thermal conversion. In py–GC–MS of reed canary grass, and switchgrass to a lesser extent, the amounts of cellulose and lignin decomposition products were higher for the larger particle size fraction. The differences in cellulose contents were also apparent from the TGA studies, where different mass losses were seen in the cellulose decomposition region of the two size fractions. From the results of these two techniques it was concluded that the differences in ash, and therefore catalytic metal contents, between the two size fractions, resulted in lower pyrolysis temperatures, lower char combustion temperatures, and higher yields of catalytic pyrolysis decomposition products for the smaller size fractions. The implications of the results are discussed in terms of the bio-oil quality in fast pyrolysis and the predicted behaviour of the ash in combustion. It is suggested that pre-treatment by milling is one route that might be used routinely as a feedstock quality improvement strategy in integrated biomass conversion processes.     

可燃固体废弃物的热解动力学

研究了垃圾中各种可燃物的热解特性 ,得出了各自的热解动力学参数 ,并对各种可燃物的热解特性进行了评价 .     

纤维素与木质素共热解试验及动力学分析

采用热重分析仪（TGA）对木质素与纤维素单独热解和共热解基本特性及热解动力学进行了研究。热重分析曲线表明,木质素热解过程是由两个位于不同温度段的热解过程组成,纤维素则仅在300～380 ℃的温区内迅速热解,在纤维素含量较低（≤40%）共热解时,二者表现为相互抑制作用,但随着纤维素含量增大,二者关系转变为相互促进作用。热解动力学研究表明,纤维素与木质素单独热解和共热解过程都可用一级反应动力学模型来描述,且随着纤维素含量增加,反应活化能（E）也随之增加,但其值总小于活化能线性加和值（Ec）,据此可推测共热解过程存在着一定的协同作用。     

PYROLYTIC KINETICS OF COMBUSTIBLE OF MSW

研究了垃圾中各种可燃物的热解特性 ,得出了各自的热解动力学参数 ,并对各种可燃物的热解特性进行了评价 .     

Effect of high temperature alkali cooking on the constituents,structure and thermal degradation of hemp fiber

Degumming of hemp fiber by high temperature alkali cooking was investigated, and the effect of temperature and dosage of alkali on the constituents, structure, and thermal degradation of hemp fiber was also discussed in this work. The morphology, structure, and thermal degradation of hemp fiber after high temperature cooking were investigated through SEM, FTIR, WAXD, and TG analysis. The results indicated that the high temperature cooking process was effective for removing hemicelluloses and lignin and could also improve the thermal stability of cellulose. Crystallinity index of the treated hemp fiber was increased, which was related to the cooking temperature and NaOH dosage. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

聚糠醇薄膜的热解动力学研究

采用热重法分析了聚糠醇薄膜在氮气氛围下的热解过程。结果表明，聚糠醇薄膜热解过程分为三个阶段，其中第二个阶段（160℃～480℃）为主要热分解阶段，同时也对聚糠醇薄膜在主要热解区间的热解反应动力学进行研究，显示聚糠醇薄膜在主要热解区间内的热解反应是分段进行的，均为一级反应，在不同热解阶段发生的热解反应分别具有不同的活化能和频率因子。