thermogravimetry-Fourier Transform Infrared Spectroscopy Research Articles

Liquid crystalline polyurethane/POSS hybrid nanocomposites pyrolysis studies by Py-GC/MS and TG/FTIR techniques

The process of pyrolysis of liquid crystalline polyurethane (LCPU) composites with polyhedral oligomeric silsesquioxanes (POSS) has been studied using pyrolysis - gas chromatography/mass spectrometry (Py-GC/MS) and thermogravimetry/Fourier transform infrared spectroscopy (TG/FTIR) coupled thermoanalytical techniques. LCPU elastomers modified with POSS molecules with different architectures, bearing aromatic, isobutyl and cycloaliphatic moieties, yield various volatile products of pyrolysis that were collected and characterized. The TG study showed significant differences in the thermal behavior of composites studied, evidencing the influence of the silsesquioxane type on the polyurethane pyrolysis paths. FTIR study of volatile products of thermal decomposition showed the presence of characteristic bands originated from carbonyl, amine, ether, methylene, and unsaturated hydrocarbon linkages. GC/MS investigation confirmed the existence of compounds identified by the IR method. The application of both thermoanalytical methods made it possible to postulate the thermal decomposition routes of PU/POSS hybrids and to point out the main factors responsible for changes in the thermal stability.

Flame retardance and fume inhibition of bio-based composite flame retardant on bituminous combustion and its numerical models

To investigate the effects of sustainable bio-based composite flame retardant (BCFR) on flame retardance and fume suppression of bitumen and establish unified combustion models of bitumen and BCFR bitumen, the mass loss and fume release during bituminous and BCFR bituminous combustion processes were studied using thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR) tests. Results show that when bitumen burns out, BCFR bitumen remains the residue rates of 33%, 28% and 21% at 5, 10 and 15 °C/min, respectively. BCFR dilutes active free radicals involved in combustion at early bituminous combustion stage, thus reducing the reaction rate, and then inhibits bituminous combustion by forming intumescent char layer, increasing the char yield of bitumen, strengthening the thermal stability of char produced from bituminous combustion. BCFR does not reduce the kinds of fume constituents released from bituminous combustion but inhibits the release of aldehydes and phenols mainly by suppressing the oxidation reaction at early bituminous combustion stage. BCFR can effectively suppress the fumes release amount during bituminous combustion at lower heating rates. The proportions of alkanes and ketones released at the second and third stages of BCFR bituminous combustion are larger than those of bituminous combustion by 9.27% and 5.8% at 15 °C/min, respectively. Although BCFR has limited inhibitory effects on fume release amount at a larger heating rate, it inhibits the volatilization and combustion of alkanes in bitumen. Meanwhile, the combustion models of bitumen and BCFR bitumen established can better reproduce TG test results. This study develops a cleaner and more efficient bio-based flame retardant, and provides a reliable bituminous combustion model for large-scale fire simulation.

Co-pyrolytic interactions and products of brominated epoxy resin and polyethylene terephthalate: TG-FTIR analysis and machine learning prediction

Pyrolysis is an effective approach for organic waste utilization, and the co-pyrolysis of multiple materials holds potential for both environmental and economic benefits. Brominated epoxy resin (BER) and polyethylene terephthalate (PET) are widely used organic materials in modern society, and the productions of their corresponding wastes are increasing annually. However, limited research has been conducted on the co-pyrolysis of BER and PET. In this study, mixtures of BER and PET were prepared in various proportions, and thermogravimetry (TG) and thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR) analyses were employed to investigate the reaction characteristics, volatile product compositions, and evolution during co-pyrolysis. Synergistic effects were observed at lower temperatures in the major reaction stage for mixtures with PET content below 40%, while inhibitory effects were noted at higher temperatures. For mixtures with PET content over 40%, the antagonistic effect was more prominent. The main volatile products during co-pyrolysis were identified as CO2, benzoic acid, and alcohols, and their evolutions exhibited complex changes due to interactions. In addition, machine learning algorithms successfully predicted real-time volatile emissions, with the random forest model proving accurate. This study enhanced understanding of organics interactions during thermal treatment and would contribute to the reduction of environmental pollution.

Research on the Characteristics and Kinetics of the Pyrolysis Process and Products Generation of Jimsar (China) Oil Shale Using TG-FTIR

The characteristics and kinetics of the pyrolysis process and product generation from Jimsar oil shale were investigated using the thermogravimetry–Fourier transform infrared spectroscopy (TG-FTIR) coupling technique. The results showed that the pyrolysis of oil shale had different reaction mechanisms in different conversion rate ranges (αP = 0–0.2, 0.2–0.6, 0.6–1). The pyrolyzed heating rate mainly affected the reaction mechanism in the range αP = 0.6–1. The released gaseous products were mainly composed of small-molecule compounds (CO2, SO2, CO, CH4), aliphatic (–CH2, –CH3), aromatic (C=C), and O–H functional groups. The generation models of C=C, –CH2, –CH3, CH4, CO, and CO2 derived in the temperature range of 573.15–873.15 K are all chemical reaction models, while the generation models of CO and CO2 derived in the range of 873.15–1073.15 K are both diffusion models. The relative values and variation in the thermodynamic parameters corresponded with that of the activation energy for the evolved components, representing the energy requirement during the generation process.

Synergistic Adenosine Triphosphate/Chitosan Bio-coatings on Polyurethane Foam for Simultaneously Improved Flame Retardancy and Smoke Suppression

Considering that fire safety is a persistent problem for most polymeric materials, including polyurethane (PU) foam, the demand for flame retardants (FRs) is growing. However, the use of conventional FRs containing halogenated and brominated chemicals has been continuously regulated owing to their toxicity. Here, we demonstrate the layer-by-layer (LbL) coating of negatively charged adenosine triphosphate (ATP) and positively charged chitosan (CS) as the synergistic FR on PU foam, a model flammable polymer material. The FR performance of the PU coated with LbL-assembled ATP and CS (ATP/CS-PU) was tested, and the results suggested that the ATP/CS layers were finely deposited on the surface of the PU without damaging the structure. Only five bilayers (5BL) were sufficient to impart excellent fire retardancy, which exhibited a limiting oxygen index value of 35% and the HF-1 rating in the UL94 foamed material horizontal burning test. In addition, ATP/CS(5BL)-PU showed a significant reduction in the peak heat release rate of 42.0% and in the total smoke release of 30.6% compared to that of bare PU (b-PU). Furthermore, the ATP/CS coatings did not deteriorate the mechanical properties of b-PU. Finally, combined thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR) showed that ATP/CS(5BL)-PU was safe because it suppresses hazardous gases, which is the main problem with conventional FRs.

An Analysis of the Influence of Low Density Polyethylene, Novolac, and Coal Tar Pitch Additives on the Decrease in Content of Impurities Emitted from Densified Pea Husks during the Process of Their Pyrolysis

The course of pyrolysis of pea husks was studied. It was stated that the compaction of a sample during its pyrolysis causes an almost two-fold increase in the content of hydrocarbons in the composition of volatile products in the temperature range of 350–470 °C. Low density polyethylene (LDPE), novolac, and coal tar pitch (CTP) wastes were added to feedstocks in the amount of 2 wt% in order to decrease the contribution of saturated and unsaturated hydrocarbons along with oxygen-containing compounds in volatile products. The analysis of the obtained products of pyrolysis was conducted using the techniques of thermogravimetry/Fourier transform infrared spectroscopy (TG/FT-IR), attenuated total reflectance (ATR) and ultraviolet (UV)-spectroscopies, gas chromatography-mass spectrometry (GCMS), X-ray diffractions (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray analysis (EDX). It was determined that pitch took the first place in a series of effectiveness in decreasing the content of harmful compounds in pyrolysis products; novolac was the second. A temperature of 370 °C (CTP) lowers the contribution of compounds with carbonyl groups (by approx. 2.7 times) and the contribution of alcohols, phenols, and esters (by approx. 4.4 times). At a temperature of 465 °C, this additive reduces the contribution of saturated and unsaturated hydrocarbons in the composition of volatiles (by approx. 5.8 times) and at a temperature of 520 °C, a more substantial decrease is observed (by approx. 14.3 times). During the pyrolysis in the temperature range of 420–520 °C, LDPE actively emits its own products of decomposition in the form of aliphatic hydrocarbons that negatively affect the environment. The composition of condensed pyrolysis products changes under the influence of additives. In water condensates, the concentration of determined phenols and anhydrosugars increases slightly under the influence of additives. The SEM and XRD investigations proved that inorganics interact with volatile pyrolysis products from the blends of pea husks with additives and change their composition. After the transformation of chemical composition, inorganics catalyse secondary reactions that take place in the pyrolysis products of blends.

Influence of Oxygen Concentration on Combustion Kinetics and Gas Products of a Polyurethane–Coal Mixture

Polyurethane materials are often used in mines to fill the geological structural areas for pretreatment and plugging. These areas are primarily high-incidence areas of coal spontaneous combustion (CSC). Polyurethane will promote the spontaneous combustion of the remaining coal because of its superior thermal insulation performance. Previous studies have focused on the effect of polyurethane on the spontaneous combustion of coal in air atmosphere, without considering the variation of oxygen concentration in the mining area. The paper investigates the effect of polyurethane on the spontaneous combustion of coal in the mining area under different oxygen concentration conditions according to the variation law of oxygen concentration in the mining area. Herein, thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR) coupled methods were used to study the kinetics and gas release laws of a polyurethane–coal mixture. The critical temperature of coal increases with the decrease of oxygen concentration. When the oxygen concentration exceeds 10%, the shift of the thermogravimetric curve to the right is smaller, indicating that the oxygen concentration has less influence on the combustion of a polyurethane–coal mixture. When the oxygen concentration is less than 10%, the shift of the thermogravimetric curve toward a higher temperature is more prominent, indicating that the oxygen concentration has a greater influence on the thermogravimetric curve. Simultaneously, the maximum value of DTG increases with the increasing oxygen concentration. The main gas products of coal pyrolysis are CO2, CH4, and H2O, while those of polyurethane pyrolysis are mainly CO2, CO, CH4, and H2O during the pyrolysis process. The amount of CO2 during the pyrolysis of various proportions of coal and polyurethane is the main difference in the gas products. Coal can promote the pyrolysis of polyurethane to some extent. The characteristic temperature rises and falls as the proportion of polyurethane in the polyurethane–coal mixture changes. In the actual monitoring, small amounts of H2O, CO2, and CO gases appear in the starting phase, then a large increase in the amount of gases can be considered that polyurethane is involved in the relevant combustion reactions, which can avoid misjudgment of the spontaneous combustion of coal in the mining area.

Investigation of pyrolysis kinetics, mechanism and thermal stability of tert-butyl peroxy-2-ethyl hexanoate

Tert-butyl peroxy-2-ethyl hexanoate (TBPO), an important organic peroxide, is widely used as a polymerization initiator and curing agent in the chemical industry. Its thermal instability due to the presence of the peroxide bond may incur a decomposition reaction and cause further thermal runaway. The pyrolysis characteristics of TBPO were assessed by three advanced calorimetry techniques. The apparent activation energies under dynamic and adiabatic conditions were calculated, and critical thermal safety parameters were determined. The specific distribution of the pyrolysis products of TBPO were identified by combining thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR) and gas chromatography/mass spectrometry (GC/MS), and the most likely pyrolysis mechanism was proposed. In addition, density functional theory (DFT) was used to evaluate the activation free energy and activation free enthalpy for each step of the pyrolysis process at the B3LYP/def2-TZVP calculation level, and kinetic calculations at different temperatures were performed by using the conventional transition state theory. The theoretical simulation results were found to be in good agreement with the experimental data. The findings of this study can provide a favorable reference to forestall thermal safety accidents in the actual storage, transportation, and operation of TBPO.

Effect of the oxygen concentration on the combustion of asphalt binder

The combustion mechanism and gaseous products of asphalt binder at five different oxygen concentrations (21%, 18%, 15%, 12%, and 10%) were studied by thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR). The evolution of the functional groups and microscopic morphology of condensed phase were also analyzed by infrared spectroscopy (IR) and scanning electron microscopy (SEM). The semi quantitative research was realized by calculating the absorption peak area of IR, proximate and ultimate analyses. Results show that the oxygen concentration influences both the pyrolysis and combustion stages of asphalt, and the influence on the combustion of heavy components is more significant. With the decrease of oxygen concentration, the residual mass after the combustion of asphalt binder increases. Additionally, the temperature zone of combustion shifts higher, and a thermal reaction lag effect becomes more obvious. The concentration of oxygen only changes the concentration of gaseous products, instead of the types. Moreover, the concentrations of CO2, CO, H2O, SO2, etc. all decrease, and there is the biggest drop in CO2. The low oxygen concentration inhibits the dehydrogenation reaction of asphalt in the aerobic pyrolysis stage, while the complete combustion of asphalt residues is inhibited in the combustion of heavy components stage. These will all provide more scientific basis for the analysis of asphalt combustion under low oxygen conditions in tunnel fires.

Thermal degradation of cyanidin-3-O-glucoside: Mechanism and toxicity of products

The thermal degradation behavior of cyanidin-3-O-gluoside (Cy3G) in nitrogen and air was studied using thermogravimetric analysis (TGA), thermogravimetry–Fourier transform infrared spectroscopy (TG-FTIR) and pyrolysis–gas chromatography/mass spectrometry (Py-GCMS). The results show that the thermal degradation of Cy3G in nitrogen and in air can be divided into three steps. The total degradation rate was 63.09% in nitrogen and 99.42% in air, and the total activation energy (Ea) was 65.85 and 80.98 kJ·mol−1, respectively. The TG-FTIR analysis showed that Cy3G is significantly decomposed at 200–300 °C. The Py-GCMS analysis shows that the first step in the thermal degradation of Cy3G in nitrogen is the cleavage of glycosidic bonds to give cyanidin and glucoside. The glucoside and cyanidin then degrade further to give mainly low molecular weight compounds, together with furan derivatives, pyran derivatives and aromatic compounds. The phenols and furans found in the pyrolysis products are known to have a degree of toxicity.

Inhibitory action of halogen-free fire retardants on combustion and volatile emission of bituminous components.

The objective of this study is to quantitatively evaluate inhibitory action of halogen-free fire retardants (HFR) on combustion properties and volatile emission of such bituminous components as saturates, aromatics, resins, and asphaltenes (SARA). Thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR) tests were performed on SARA fractions containing matched fire retardants, respectively, and thermal kinetics parameters based on TG curves and functional and structural indices from FTIR spectra were calculated, respectively. The selected fire retardants have not affected the combustion process of SARA fractions, but the combustion temperature intervals are elevated and combustion progresses are retarded. Also, the char yields of SARA fractions are obviously increased by the matched fire retardants, improving their heat stability. The activation energy is elevated because of the added fire retardants, indicating combustion resistance of SARA fractions become larger. Additionally, the matched fire retardants inhibit the toxic gas emission in the combustion process of SARA fractions, but have few effects on gaseous product constituents. H2O and CO2 are identified as two typical released gases in various combustion phases of each SARA fraction. Finally, the added hydroxide play a role of fire retardants through cooling, dilution, adsorption, and neutralization, and the generated active oxide facilitates the expandable graphite (EG) and matrix to form densified and thick carbon layer. These suppress the volatile emission, and hinder the heat conduction and oxygen supply. Fire retardant composite exhibits the synergistic effect of fire retardancy and smoke inhibition in the combustion process of SARA fractions.

Experimental thermal hazard investigation on carbonate electrolytes using a cone calorimeter

During the thermal runaway (TR) processing of lithium-ion batteries (LIBs), electrolyte would release most of the heat as the main component. Thus, study on the fire risk of electrolyte is conductive to quantitatively evaluate the safety of LIBs. In this work, the combustion characteristics of three kinds of carbonate mixture electrolytes and the composition of residue were investigated. The significant parameters from the cone calorimeter tests reflecting the thermal hazards such as heat release rate (HRR), mass loss rate (MLR) and open cup flash point were measured. The HRR curves at the radiant power of 15 and 25 kW/m2 were more gradual than those at 35 kW/m2 which had one or two apparent peaks. The addition of diethyl carbonate (DEC) increased the HRRs significantly. The applicability of thermal chemistry (TC) theory used to calculate HRR in previous works was studied. The results of TC technique had a disparity with those from the cone calorimeter called oxygen consumption (OC) calorimetry especially for the electrolyte containing DEC, which was proved by thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR) experimental results, while it is different from the conclusion reported in previous study. The constituent of carbonate electrolytes residue was analyzed by the X-ray Fluorescence (XRF). Element fluorine (F) accounted for over 90% of the residue. The open cup flash point and ignition temperature were determined by the open cup flash point apparatus. The results showed that the fire point was very close to the open cup flash point, and the difference was within 0.1 K.

Surface Characterization of Composite Catalysts Prepared by Sol‐Gel Route

AbstractThe aim of this work is to synthesize Nb‐V oxide catalysts by sol gel route starting from metal alkoxides using different H2O/V ratios. Dried samples are characterized by X‐ray diffraction (XRD), atomic absorption, and Brunauer‐Emmett‐Teller (BET) analysis. Calcination of dried materials up to 600°C in flowing air has been followed with Thermogravimetry‐Fourier‐transform infrared spectroscopy (TG‐FTIR) spectroscopic analysis. The catalytic properties of calcined materials are tested in the oxidative dehydrogenation of ethane at 600°C. An improvement of the catalytic performances of vanadium for the gel prepared with the higher H2O/V ratio is found with respect to those of the supported catalyst due to the better interaction between vanadium and niobium.

Effect of Mixed Isocyanate Curing Agents on the Performance of In Situ‐Prepared HTPE Binder Applied in Propellant

AbstractA novel hydroxyl‐terminated block copolymer (HTPE) binder was prepared through an in situ preparation method to replace the traditional HTPE binder. The preparation method is less costly and bypasses the preparation of the HTPE prepolymer intermediate, thus avoiding the complicated prepolymer synthesis process. Uniaxial tensile testing, low‐field nuclear magnetic resonance, and infrared spectroscopy were used to investigate the mechanical properties, curing networks, and hydrogen bonding (H‐bonds) of the binder. The crosslink density (Ve) decreased with an increase in the ratio of −NCO in the IPDI to the total −NCO in the IPDI and N100 (χ). The proportion of H‐bonds formed by the imino groups increased with the IPDI content and reached 86.53 % at a χ value of 90 %, indicating a positive correlation between the H‐bonds and σm. Additionally, to study the pot life of the in situ‐prepared HTPE binder, the rheological properties of the curing reactions were studied. When the χ value was in the range of 50 %–90 %, the pot life of the binder met the composite propellant requirements for military applications. The thermal decomposition behaviors of the in situ‐prepared HTPE binder and the traditional HTPE binder were investigated by the coupling analysis of thermogravimetry‐Fourier transform infrared spectroscopy (TG‐FTIR), and the novel in situ‐prepared HTPE binder exhibited good thermal stability and superior energetic performance. Compared with the traditional HTPE‐based propellant, the mechanical properties of the in situ‐prepared‐HTPE‐based propellants were greatly improved. With these data, the in situ‐prepared HTPE binder has great potential for application in rocket propellant formulations.

The Influence of Freezing on the Course of Carbonization and Pyrolysis of a Bituminous High-Volatile Coal

The course of thermal behavior of a fresh bituminous high-volatile coal during carbonization and pyrolysis was compared to that of this coal thawed after storage. The research was carried out using the following techniques: X-raying, thermogravimetry/Fourier transform-infrared spectroscopy (TG/FT-IR), extraction, Diffuse Reflectance Infrared Fourier Transform Spectroscopes (DRIFT), Attenuated Total Reflectance (ATR), and SEM. The increase in range of the viscous-liquid state and a decrease in temperature of its appearance were stated along with the formation of a more compact residue at the re-solidification stagtablee for the thawed coal during its carbonization. There is a fourfold reduction in the charge volume. The leakage of bitumen that contains 87 At % of C atoms from swollen grains and a fourfold increase in the yield of the material extracted from these grains are the proof of a greater plasticization of thawed coal. During the pyrolysis of thawed coal, the yield in volatile products of pyrolysis increases, and the composition of these products changes. The contribution ratio of saturated and unsaturated hydrocarbons, CO2, alcohols, and phenols decreases in the composition of volatile products of thawed coal. It is suggested that the use of freezing during the storage of a freshly mined coal that has a poorer caking ability can improve its plasticization during carbonization.

Pyrolysis characteristics, artificial neural network modeling and environmental impact of coal gangue and biomass by TG-FTIR

The harm done to the environment by coal gangue was very serious, and it is urgent to adopt effective methods to dispose of coal gangue in order to prevent further environmental damage. Co-pyrolysis experiments of coal gangue (CG) and peanut shell (PS) were carried out using thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR) under nitrogen atmosphere. The heavy metal was detected using the inductively coupled plasma-optical emission spectroscopy (ICP-OES). CG and PS were mixed according to the mass ratio of 1:0, 3:1, 1:1, 1:3 and 0:1. The samples were heated to 1000 °C at the heating rate of 10 °C/min, 20 °C/min and 30 °C/min. The comprehensive pyrolysis index (CPI) of CG, C3P1, C1P1, C1P3 and PS is 0.17 × 10−8, 9.75 × 10−8, 35.47 × 10−8, 100.94 × 10−8 and 192.72 × 10−8%2 ·min−2·°C−3. The kinetic parameters were calculated by model-free methods (Flynn–Wall–Ozawa and Kissinger–Akahira–Sunose). The gas products generated at different temperatures during the pyrolysis experiment were detected by Fourier transform infrared spectrometer. The heating rate, temperature and mixing ratio are the input parameters of artificial neural network (ANN), and the remaining mass percentage of sample during the pyrolysis is the output parameter. The ANN model was established and used to predict thermogravimetric experimental data. The ANN18 model is the best model for predicting the co-pyrolysis of CG and PS.

Combustion behavior, kinetics, gas emission characteristics and artificial neural network modeling of coal gangue and biomass via TG-FTIR

The combustion behavior and gas product characteristics of coal gangue (CG) and peanut shell (PS) in air atmosphere were studied by thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR). Artificial neural network (ANN) method was used to establish the optimal prediction model of CG and PS co-combustion. The heating rate of TG-FTIR experiment was set to 10 °C/min, 20 °C/min and 30 °C/min. The mass fractions of PS in the experimental samples were 0%, 25%, 50%, 75% and 100%. Some functional groups in the gas products were detected by Fourier transform infrared spectrometer. Moreover, the apparent activation energy (E) was calculated by Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS). The activation energies of CG and PS mixture combustion are significantly lower than that of pure substance. ANN models have been established to predict the relationship between mass loss and experimental conditions. By comparing errors and correlation coefficients, it is found that the ANN20 model is optimal.

Analyses on thermal stability of lignites and its derived humic acids

ABSTRACT The thermal stabilities of humic acids (HAs) are critical for its effective utilization and relate closely with raw lignites. Thus, this work is to study the relationship of thermal stability between lignites and its derived HAs using Thermogravimetry – Fourier Transform Infrared Spectroscopy (TG-FTIR) and Differential Scanning Calorimetry Measurement (DSC) techniques. The TG-FTIR results indicated that the intensities of peaks from the evolution gases (H2O, CO2, CO, CH4) during thermal treatment of Zhaotong lignite (ZL) and its derived HAs (denoted as ZLHA) are higher compared with the Mile lignite (ML) and its derived HA (denoted as MLHA). TG-FTIR and DSC measurements of lignites showed that the thermal stability of ML is better than that of ZL, and the more oxygen containing functional groups existed in ZL. Similarly, the results indicated that the contents of oxygen containing functional groups of ZLHA are higher than that of MLHA. On the other hand, DSC experimental data showed that the MLHA has smaller peaks on the DSC profiles, which showed that MLHA has longer aliphatic chain and less oxygen containing functional groups. Briefly, the results obtained from TG-FTIR and DSC measurement are consistent. The thermal stabilities of HAs are highly associated with the physicochemical property of raw lignites.

On the mechanism of xylan pyrolysis by combined experimental and computational approaches

Pyrolysis is the initial stage of biomass combustion, whereas, the pyrolysis mechanism of biomass, especially the hemicellulose component, is still not well elucidated. Herein, a common hemicellulose polysaccharide, xylan, was investigated to reveal the evolution of volatiles and solid residue through combined thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR) and in-situ diffuse reflectance infrared Fourier transform spectroscopy (in-situ DRIFT) techniques. Quantum chemistry calculation was also conducted to analyze the primary xylan pyrolysis mechanism by using a long-chain xylan model which was built based on the structural characterization of xylan. The experimental results indicated that the functional groups in solid-phase evolved intensively during the main weight loss zone (200–350 °C), leading to the violent release of volatiles. The decomposition of branches, especially the arabinose unit, was prior to that of the backbone, with relatively low energy barriers and high rate constants. The initial enhancement of CO vibration in solid-phase above 200 °C derived from the formation of the furanose unit. Both dehydration and breakage of glycosidic bonds were responsible for the formation of CC bond in solid-phase from 300 °C. The cracking of the 4-O-Me group resulted in the release of aldehydes to gas-phase in the main weight loss zone (200–350 °C). The scission of the whole 4-O-MeGlc unit and/or the rupture of the uronic acid group led to the gas-phase CO bond formation.

Investigation of a Ni-Modified MCM-41 Catalyst for the Reduction of Oxygenates and Carbon Deposits during the Co-Pyrolysis of Cellulose and Polypropylene.

Catalytic fast co-pyrolysis of biomass and plastic is an effective method to achieve high-quality bio-oil production. In this work, (Ni)-MCM-41 catalysts with different Ni loadings were prepared and characterized in detail by using a variety of advanced analytical techniques, and the effects on the catalytic performance were analyzed by micropyrolysis with gas chromatography mass spectrometry (Py-GC/MS) and thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR) methods. The results showed that an appropriate amount of Ni addition can effectively modulate the physicochemical properties of MCM-41. For a Ni loading of 25.1 wt % (Cat-C), the catalyst showed an optimal catalytic performance, a decrease in the proportion of oxygenated compounds in the product from 35.6 (MCM-41) to 13.4%, and an increase in the relative total amount of olefins plus aromatics from 62.2 (MCM-41) to 84.6%. The excellent catalytic performance of Cat-C can be ascribed to a balancing of its proper physical structural properties, appropriate acidity, strong metal–carrier interaction, high metal dispersion, and excellent compatibility balance between active and acidic sites.