TG-FTIR Analysis Research Articles

Effect of starch-based flame retardant on the thermal degradation and combustion properties of reconstituted tobacco sheet

In this paper, starch, distarch phosphate (DSP) and hydroxypropyl distarch phosphate (HPDSP) were used as “green” carbon sources with ammonium polyphosphate (APP) to prepare flame retardant reconstituted tobacco sheet (RTS) by paper-making process and the effect of these starch-based flame retardants on their thermal degradation and combustion properties was preliminarily investigated. Micro-scale combustion calorimetry results showed the value of the heat release of modified RTS was lower than that of pure RTS, demonstrating the restrained combustion behavior of modified RTS. TG-FTIR and TG-MS analysis indicated that the starch-based flame retardant coating promoted the char formation, inhibited char combustion and release of gaseous products except for NH3, with the relative best comprehensive performance of APP-DSP. Cigarette burning cone analysis also confirmed that the modified RTS had lower temperature and smaller burning cone volume than that of pure RTS, especially APP-HPDSP-RTS. This work could highly expand the application of starch and its derivatives in flame retardant and tobacco industry.

Comparative study on the two-step pyrolysis of different lignocellulosic biomass: Effects of components

To investigate the effects of components on the two-step pyrolysis (TSP) of lignocellulosic biomass, the comparative study on TSP of walnut shell (WS), cotton stalk (CS), corncob (CC) and their acid washed samples (AWS, ACS, ACC) was conducted by TG-FTIR and Py-GC/MS. TG-FTIR analysis showed that the higher lignin content of WS lead to the lowest weight loss. CS and CC had higher content of holocellulose and generated more CO2 and carbonyl compounds. The inorganic component increased pyrolysis residue. CC and CS released most holocellulose derivatives in the first step (S1), and WS produced more phenols in the second step (S2). The removal of inorganic component increased the contents of sugars and furans in TSP. Higher selectivities of different value-added compounds could be achieved by different lignocellulosic biomass in TSP due to the fractionated conversion of components and different component proportions, such as acids (23.10 %, WS, S1), furans (12.11 %, ACS, S1), ketones (12.97 %, CC, S1) and sugars (54.81 %, ACC, S2), etc. TSP could facilitate the utilization of lignocellulose biomass in fine chemical or fuel.

Structural changes and sodium species redistribution of a typical sodium-rich coal during thermal dissolution with aromatic solvents

Sodium-rich coals are widely distributed all over the world and they are considered as suitable materials for thermal dissolution of coals. In this work, to better understand structural changes of sodium-rich coals during thermal dissolution process, TG-FTIR was used to characterize weight loss and evolution of gases released from pyrolysis of a typical sodium-rich coal and extraction residues. Additionally, the occurrence mode of sodium species was determined by sequential chemical extraction method in order to examine sodium species redistribution. The results show that the organic oxygen content of coal was reduced by thermal treatment, which implied that thermal dissolution tended to remove oxygen and upgrade coal. TG-FTIR analysis also revealed that the CO2 content released from pyrolysis of extraction residues was on a lower level than that released from pyrolysis of raw coal. During thermal dissolution, the chemical structures of raw coal got more compact. It suggests that coal reactivity toward further thermal conversion would be weakened. In pyrolysis process, weight loss of samples treated by tetralin was higher compared with those treated by 1-methylnaphthalene, especially at 300 °C. This difference proves that raw coal had been pre-hydrogenated by tetralin even as low as 200–300 °C. Furthermore, tar produced in pyrolysis of samples treated by tetralin was deoxygenated by the residual tetralin and it leaded to decrease of tar-O structures, which influenced release of CO. Besides, it was observed that most sodium species were reserved in the extraction residue, as retention ratios were significantly high. At the same temperature, more exchangeable sodium species were promoted to be transformed into water-soluble ones when tetralin was used, which demonstrated that tetralin had better promotive effects on decomposition of –COO−. Along with decomposition of –COO−, exchangeable sodium species were detached from coal matrix and transformed into other chemical forms.

Thermal stability and pyrolysis characteristics of MTMS aerogels prepared in pure water

Silica aerogel (SA) is a nanoporous material and has attracted increasing attention in the field of thermal insulation in recent years. In this work, the thermal stability and pyrolysis characteristics of the methyltrimethoxysilane (MTMS) silica aerogel (MSA) prepared in pure water were investigated experimentally. The MSA shows a high thermal stability with the onset and peak temperature (Tonset and Tpeak) about 417 °C and 476 °C, respectively, in the pyrolysis process. The oxidation kinetics reveals that the pyrolysis of MSA can be divided into three stages with the average apparent activation energy (E) of each stage being 382.8 kJ/mol, 364.4 kJ/mol, and 328.9 kJ/mol, respectively. The pre-exponential factor (A) has the same tendency with the E. The TG-FTIR analysis demonstrates that the CO2 and H2O are the main volatiles during the pyrolysis process and all of them increase against the temperature. It is further observed that the production of CO2 presents a linear increase, and the H2O shows an obvious two-stage form along with the temperature. Compared with other hydrophobic SAs, the MSA has a larger Tonset and Tpeak and much larger E, indicating better thermal safety. The research outcomes provide a technical guide to analyze the thermal pyrolysis of hydrophobic SA and put a new insight to reduce their thermal hazards, which is beneficial to the development of higher-performance nanoporous silica aerogels for the thermal insulation field.

Methane decomposition over Fe-based catalysts

Catalytic approach for methane decomposition can be seriously considered as a promising process for COx free hydrogen generation. In this study, catalytic methane decomposition was performed using Fe-based catalysts, and catalytic performance tests were carried out in a CH4:N2 flow at 750 and 800 °C. The analyses of reaction products were carried out by a mass spectrometer. For the preparation of Fe-based catalysts, sol-gel method was utilized. Yttria (Y2O3) and alumina (Al2O3) were used as support materials. Theoretical molar ratios (Fe2O3/Y2O3/Al2O3) of the samples C1–C5 were 1:0:0, 1:1:0, 1:1:5, 2:1:4 and 3:1:6, respectively. The characterization analyses of fresh and spent catalysts were performed with XRD, SEM, TPR, TG-FTIR and BET surface analysis techniques. Surface basicity of catalysts was determined via CO2-TPD measurements. In the presence of Fe2O3/Y2O3 and Fe2O3/Y2O3/Al2O3 catalysts, methane conversions of 29% and 4% were achieved at 750 °C. Adding alumina into Fe2O3/Y2O3 catalyst leads to the formation of garnet type crystal structure which reduces catalytic activity.

Comparative chemical analysis of pyrolyzed bio oil using online TGA-FTIR and GC-MS

The present study proposed successfully TG-FTIR as a novel technique for high quality bio oil production having desirable concentration of targeted products especially phenols and acids. TG-FTIR analysis of pine waste was performed to calculate yield of desirable chemical compounds at different temperature ranged 350−600 °C. While, bio oil was produced at each corresponded temperatures and GC–MS analysis was carried out to support TG-FTIR analysis which showed high consistency. Additionally, efficient extraction of phenolic compounds was performed via complex method using Ca2+ as a complex agent under alkaline conditions which showed that 95 % phenols were extracted successfully. Meanwhile, production of calcium acetate in residue bio oil turns this study highly valuable for future scientific research.

Heterometallic di- and trinuclear CuIILnIII (LnIII = La, Ce, Pr, Nd) complexes with an alcohol-functionalized compartmental Schiff base ligand: Syntheses, crystal structures, thermal and magnetic studies

The reaction of the multi-site Schiff base ligand 2,2′-{(2-hydroxypropane-1,3-diyl)bis[nitrilomethylidene]}bis(4-bromo-6-methoxyphenol) (H3L) with copper(II) acetate, followed by the addition of lanthanide(III) nitrate afforded the new heterotri- and heterodinuclear compounds [Cu2La(HL)2(NO3)2(MeOH)2]NO3·2MeOH·2H2O (1), [Cu2Ce(HL)2(NO3)2(MeOH)2]NO3·MeOH·2H2O (2), [Cu2Pr(HL)2(NO3)2H2O]NO3·H2O (3), and [CuNd(HL)(NO3)3H2O(MeOH)]·1.5MeOH (4). The single-crystal X-ray crystallography results show that in all reported complexes the LnIII and CuII ions are connected through double phenoxido bridges and trinuclear complexes 1–3 are not linear entities. Compounds 1–4 are stable at room temperature and their decomposition processes proceed in a similar way. During heating in an air or nitrogen atmosphere, in the first step a desolvation process is observed. TG-FTIR analysis shows that the main gaseous products released over the whole decomposition process are water, methanol, ammonia, carbon dioxide and carbon monoxide. The final solid products for the decomposition of 1–4 in air are principally mixtures of CuO and Ln2CuO4. The temperature dependence of the magnetic susceptibility indicated that in the reported heteronuclear complexes the interaction between the CuII and CeIII/PrIII/NdIII ions is antiferromagnetic.

Non-isothermal TG/DTG-FTIR kinetic study for devolatilization of Dalbergia sissoo wood under nitrogen atmosphere

The present study deals with chemical characterization and pyrolysis kinetics of Dalbergia sissoo wood (DSW). The characterization of DSW, in terms of proximate, ultimate, biochemical compositions, and TG-FTIR analysis are carried out. FTIR, coupled with TG system, identified the traces of various volatiles such as H2O, CH4, CO2, CO, CH3CHO, HCHO, CH3COCH3, CH3COOH, HCOOH, and R–OH during pyrolysis. Further, a non-isothermal TG for the pyrolysis of DSW has been performed in a nitrogen atmosphere. The integral isoconversional model-free methods are applied on TG data of DSW to evaluate activation energies at five different heating rates from 5 to 30 °C min−1. The variations in pyrolysis behavior as reflected by the activation energies have been explained based on type of volatiles that gets released with time during the degradation process. The full range of solid-state kinetic models purposed by Malek method produced best fits with TG results, with the 3-D diffusion model followed by random nucleation with three nuclei on the individual particle.

Kinetics and mechanism of thermal degradation of aldehyde tanned leather

The thermal degradation of hides before and after tanning with formaldehyde and glutaraldehyde were studied using thermogravimetric analyzer (TGA) and TGA coupled with Fourier transform infrared spectrometry (TGA-FTIR). TG-FTIR analysis indicated that the pyrolysis products of both untanned hides and tanned leathers are mainly CO2, NH3, and CO contained organic components with some HNCO, CH4 and H2O. Compared to that of untanned hides, the peak intensity of evolved NH3 from formaldehyde tanned one is enhanced, while the evolved temperature decreases from 220 °C to 200 °C. The evolution of CO contained organic components is increased due to the introduction of carbonyl groups after formaldehyde tanning. However, for the glutaraldehyde-tanned leather, the evolution peak intensity of CO contained organic components decreases with more CO2 yield, suggesting that the carbonyl groups introduced by glutaraldehyde-tanning is mainly changed to CO2 rather than CO contained organic components. The kinetic analysis of thermal degradation process of the hides and tanned leathers are also investigated by using the methods of Flynn-Wall-Ozawa, Friedman and Criado. Results indicated that the thermal degradation process can be described by the three-dimensional diffusion model (D3) at the conversion below 0.5. Whereas, at the conversion above 0.5, this process turns to comply random nucleation model (F3).

Influence of polypropylene and nanoclay on thermal and thermo-oxidative degradation of poly(lactide acid): TG-FTIR, TG-DSC studies and kinetic analysis

Compatibilized poly(lactic acid)/polypropylene (PLA/PP) blends with a drop-matrix morphology containing 25 wt.% PP, 5 wt.% ethylene/n-butyl acrylate/glycidyl methacrylate terpolymer (PTW) as compatibilizer, and 5 wt.% nanoclay were prepared by one-step mixing process in a twin-screw extruder. TEM analysis revealed that the clay particles were mainly localized in the PLA matrix phase in the absence of PTW; by contrast, the addition of compatibilizer changed the location to the blend interface. Multiple rate thermogravimetric analysis revealed two-stage and single-stage weight losses under neutral and air atmospheres, respectively. To reveal the influence of blending, nanoclay inclusion and compatibilization process on the PLA degradation process, a systematic quantitative evaluation of degradation processes was carried out based on kinetic parameters derived from model-free and model-fitting analyses. The results revealed that the activation energy of the thermo-oxidative process, being significantly lower than that of the thermal pyrolysis, greatly increases in the presence of nanoclay, indicating the accelerating role of oxygen in the degradation process and the barrier effect of nanoclay against oxygen diffusion. The combined TG-DSC analysis in the nitrogen environment confirmed the appearance of endothermic signals being proportional to the sample weight loss, which is characteristic of thermal pyrolysis. Subsequently, in an oxygen-containing environment, initial exothermic peaks were formed, which was attributed to the oxidative degradation of the sample. As the reaction progressed, secondary peaks were observed due to the degradation of residuals formed in the first stage of the degradation process. Also, for chemical analysis of volatiles, simultaneous TG-FTIR analysis was employed in a neutral atmosphere at the maximum degradation temperature. Lactide, acetaldehyde, carbon dioxide (CO2) and carbon monoxide (CO) were the products obtained from the degradation process of the PLA phase.

The use of metallurgical waste for heterogeneous photo Fenton-Like treatment of cosmetic effluent

Abstract Cosmetic industry wastewater has undesirable features such as low biodegradability, high levels of suspended solids, fats and oils, and high load of organic matter. The heterogeneous photo Fenton-Like degradation process is an alternative means of treating this wastewater since it has the ability to mineralize organic matter. In addition, waste from the steel/metallurgical industry can be used as a source of iron, by generating less solid waste (sludge) and involving a more cost-effective technology. This study aims to evaluate the heterogeneous photo Fenton-Like treatment before and after the adsorption-desorption equilibrium, by using the metallurgical residue as a catalyst, as well as determining possible organic compounds adsorbed by the generated chemical sludge. The treatment was carried out with metallurgical waste, as a source of iron, in concentrations of 8.0 g L−1, H2O2 0.05 g L−1 and initial pH 3.0 in 6 min of treatment. Under these conditions, it was possible to obtain removals of above 75 % for total organic carbon and 99 % for chemical oxygen demand. The analysis of the residue of the treatment was submitted to TG-FTIR analyses and was determined that at the end of the photo Fenton-Like process after the adsorption process, approximately 10.8 % of the mass of organic matter remained adsorbed onto the residue, which suggested that most of what was present in the cosmetic matrix, had been oxidized. FTIR analyses of the solid sample also revealed that the adsorbed organic compound is possibly paraffin, which corresponds to the type of effluent discharged by the cosmetics industry.

Evaluation of models to predict the influence of chemical pretreatment on the peels of Nephelium lappaceum L. based on pyrolysis kinetic parameters obtained using a combined Fraser-Suzuki function and Friedman’s isoconversional method

In the present work, two chemometric strategies were evaluated to assess the influence of the chemical pretreatment: a Kohonen self-organizing map neural network and a Support Vector Machine Learning algorithm. Kohonen ANN was able to predict the influence of chemical treatment mainly on pseudo-component lignin, since cellulose and hemicellulose have similar structures; presenting a topological error of 0.044 and a quantification error of 0.193, while the Vector Supporting Machine (SVM) algorithm was able to predict the classes with accuracy of 0.956, area under the ROC curve (AUC) of 0.992 and F1 score of 0.956, proving to be a more effective strategy in predicting the influence of the chemical treatment on the rambutan shells based on the kinetic parameters. It was also observed an increase in the activation energy for the cellulose pretreated with sodium hydroxide and with phosphoric acid, mainly due to the partial conversion of type I cellulose into type II cellulose, ranging from 152 to 155 kJ/mol versus 124 kJ/mol for the untreated sample. The thermal decomposition mechanism did not change significantly, being estimated as pseudo-zero order, using the Master-Plot method. TG-FTIR analysis reveals that the main gases emitted during pyrolysis are CO2, H2O and CO, being the carbon dioxide-related band an indicator of the influence of the chemical treatment. This analysis also reveals the release of sulfur compounds from the sample treated with sulfuric acid, indicating that the environmental point of view of this sample shows no viability as use as pyrolysis feedstock.

Catalytic conversion of triglycerides by metal-based catalysts and subsequent modification of molecular structure by ZSM-5 and Raney Ni for the production of high-value biofuel

We report herein a catalytic deoxygenation strategy that allows the direct removal of oxygen atoms from triglycerides by lowering the activation energy through the use of metal-based catalysts. Activation energies were investigated by TG analysis, employing fatty acid salts as model compounds. Introducing different metal atoms into carboxyl groups has a substantial effect on the dynamic pyrolytic behavior, and decomposition activation energies varied in the range 80–260 kJ/mol. The catalytic cracking of soybean oil using SnO as a representative catalyst has been investigated in a 5 L reactor, whereby the catalyst lowered the decomposition temperature by approximately 40 °C and gave a conversion rate of approximately 66 wt%. A catalytic conversion mechanism has been proposed based on the results of TG-FTIR, GC, and GC-MS analyses. The pyrolysis products from the deoxygenation process had a high alkene content, endowing them with great potential for conversion into cyclic hydrocarbons used in real aviation fuels. Such conversion through aromatization and hydrogenation over ZSM-5 and Raney Ni catalyst has been investigated. Overall, a new refining process, including conversion of triglycerides to alkanes and terminal alkenes catalyzed by metal compounds, furnishing viable aviation and diesel fuels, is reported.

Organic tin, calcium–zinc and titanium composites as reinforcing agents and its effects on the thermal stability of polyvinyl chloride

In view of the polyvinyl chloride (PVC) in the processing and molding easy degradation, the stability effect of different components is not good when used alone, and PVC in thermal degradation with the release of hydrogen chloride will lead to the formation of toxic gas dioxins to the environment and human problems. For this purpose, the nanosized titanium dioxide (NT), calcium–zinc (Ca-Zn)*, dipentaerythritol (Dip) and organotin (OT) were modified with butyl titanate (BT), coupling agent to synthesize the composite material and used as the strengthening agent for PVC. The composites and PVC were characterized, and their properties were determined using Raman, XRD, TG, TG-IR, Congo red and DMA. The results showed that the BT/NT/Dip/OT/(Ca-Zn)* complex not only kept the basic configuration of NT particles, but also had strong interaction between components due to BT coupling, which had synergistic effect on PVC. Similarly, BT was involved in the coupling between PVC and Dip/OT, resulting in prolonged initial discoloration time. When 3.8mass%BT/NT, 0.32mass%OT, 0.32mass%(Ca-Zn)* and 0.63mass% Dip were added to the PVC film, compared with blank sample and only 1phr of OT stabilizer, the new composite material was formed. The longest initial discoloration time was observed by Congo red, and the temperature was improved when TG was used to analyze the maximum mass loss rate, and the maximum mass loss rate was reduced by 115%. As the conversion rate reached 1%, the decomposition temperatures of PVC composite film and blank sample were 234.7 °C and 175.2 °C, respectively, indicating that the formed PVC film had excellent thermal stability. TG-FTIR analysis showed that after adding OT at 0.5 phr, (Ca-Zn)* at 0.5 phr and Dip at 1.0 phr, the composite film was around 331.1 °C and 476.6 °C, and the peak strength of CH4 gas released by thermal degradation was 114.0 and 262.0% higher than that of blank sample, respectively. It can be seen that pentaerythritol has a promoting effect on CH4 release of PVC, and the peak strength of CO2 is shifted to the high temperature zone, contrary to the blank sample, there is no formation of hydroxyl or water, which means that the thermal degradation pathway of PVC has changed, and it is possible to inhibit the generation of aromatic hydrocarbons and dioxins. By introducing 3.8 mass% BT/NT composite reinforcement, compared with the blank sample, the observed storage modulus increased by 22.4%, and the mechanical properties of PVC composite material were improved.

Halogen-free and phosphorus-free flame-retarded polycarbonate using cyclic polyphenylsilsesquioxanes

Organic–inorganic hybrid macrocyclic compounds, polyphenylsilsesquioxanes (cyc-PPSQ), have been synthesized through hydrolysis and condensation reactions of phenyl trichlorosilane. PC/cyc-PPSQ flame retardant materials were obtained by melt blending cyc-PPSQ and PC using a twin-screw extruder. The combustion and thermal decomposition behavior of PC/cyc-PPSQ composites were studied using UL-94, LOI, CONE, TG–FTIR and Py–GC/MS, which showed that the presence of cyc-PPSQ could improve flame retardancy and reduce the heat release and smoke release during combustion of PC. Incorporation of 2 wt% cyc-PPSQ produced a PC/cyc-PPSQ-2 composite which displayed LOI 37.5% and UL-94 V-0 (1.6 mm). The presence of cyc-PPSQ not only improved the flame retardancy of PC, but also did not diminish the glass transition temperature, good mechanical properties and transparency of PC. These results combined with those from TG–FTIR analysis suggest that cyc-PPSQ can promote the initial thermal induced chain-breaking reaction of PC, promote the cross-linking and charring of PC, and facilitate the formation of a dense carbon layer and external SiO2 inorganic barrier layer during combustion. Results from Py–GC/MS indicate that the presence of cyc-PPSQ promotes the generation of phenolic compounds when the composites are pyrolyzed at high temperature.

Preparation and characterization of nano silver immobilized hydrochar derived from hydrothermal carbonization of tobacco stem

In this present study, silver nanoparticles (AgNPs) immobilized hydrochar was prepared through a facile one-pot co-hydrothermal carbonization of tobacco stem and silver nitrate. The effect of concentration of silver precursor, hydrothermal temperature and reaction time on the chemical compositions, structural property, combustion performance, as well as gaseous products release behavior of the resultant AgNPs immobilized hydrochar were evaluated. The co-hydrothermal treatment decreased the volatile matter while increased the ash content of hydrochar. Single-phase AgNPs were successfully generated and evenly immobilized onto the hydrochar during the hydrothermal process. The immobilized AgNPs played a notable catalytic role during the char combustion stage, thereby decreased the ignition temperature, burnout temperature and maximum rate temperature for char combustion. Meanwhile, TG-FTIR analysis suggested that the emission amount of harmful gas CO during hydrochar combustion was reduced due to the catalytic effect of AgNPs. This phenomenon may indicate the appropriate amount of nanoparticles immobilization could enhance the combustion behavior of hydrochar fuel.

Insights into microwave heating response and thermal decomposition behavior of deep eutectic solvents

The development of microwave (MW) assisted processes involving the use of deep eutectic solvents (DESs) is a fast-expanding research topic. However, there is a lack of information about the heating behavior of DESs under MW irradiation. In this work, a family of DESs composed by choline chloride and two types of hydrogen bond donors (carboxylic acids or polyols) was prepared and its MW heating response and thermal heating behavior were investigated as well as compared to that of the single components. The MW absorption properties were explored using different MW applied power at fixed MW irradiation times. The thermal behavior and the analysis of the evolved gases during the DESs thermal decomposition were assessed by TG-FTIR analysis. A strong interaction of DESs with MWs was found in all cases. Polyol-based DESs showed the highest MW response, ChCl-glycerol being the best MW absorbing system. The thermal heating behavior revealed that a decomposition process of entire DES occurred rather than a sum of evaporation steps of their single components. This decomposition can be ascribed to a synergy effect of heating and H-bond acidity strength in DESs network. Different thermal decomposition pathways for all DESs were thus proposed. All studied DESs showed thermal decomposition behavior and MW absorption properties more similar to ionic liquids (ILs) than molecular solvents. These unique properties make DESs suitable green solvents for the development of MW assisted chemical processes.

Thermal behavior and smoke characteristics of glass/epoxy laminate and its foam core sandwich composite

Thermal behavior and smoke characteristics of glass/epoxy laminate and its foam core sandwich composite were comprehensively investigated using thermogravimetric analysis, TG–FTIR analysis, smoke density test and cone calorimeter test. The thermal decomposition, thermal interpretation of gas release, smoke density, smoke release, carbon monoxide and carbon dioxide productions were analyzed and compared for glass/epoxy laminate and its foam core sandwich composite. Their kinetic and thermodynamic models were obtained, and the apparent activation energy, pre-exponential factor and thermodynamic parameters were determined correspondingly. The results show that there are significant differences in the thermal behavior and smoke characteristics between these two composites. Compared with glass/epoxy laminate, foam core sandwich composite demonstrates a higher propensity of pyrolysis and combustions and greater hazards to life and property.

A TG-FTIR investigation on the co-pyrolysis of the waste HDPE, PP, PS and PET under high heating conditions

The present study relates to the investigation of degradation of polymers such as HDPE, PP, PS and PET individually and in mixed forms. Eleven different mixture combinations were analyzed via TG Analysis to determine their degradation behavior individually and in mixed forms. FTIR analysis of the raw polymers was performed to investigate the presence of different functional groups in the sample. Online TG-FTIR analysis was performed to investigate the functional groups present in the volatiles fractions during single component pyrolysis and the interaction of polymers during co-pyrolysis was analyzed, compared and reported. Also, a real-world post consumer mixed waste was also analyzed and compared. During the co-pyrolysis of HDPE with PP and PS, the degradation of PP was delayed whereas PS reduced the degradation temperature of HDPE. In the case of degradation of PS with PP and PET, the increase in degradation temperature was reported whereas, in the case of PET and HDPE mixture, the degradation temperature of HDPE was reduced. During the interaction of PP and PET mixed degradation, PET degradation temperature was delayed. During the FTIR analysis a large amount of alkanes, alkenes, aromatics groups were observed during the degradation of HDPE, PP and PS whereas in case of PET the presence of oxygenated groups is observed. During the mixed degradation, the presence of PET in the sample caused the formation of oxygenated groups by reducing the absorption intensity of other groups or by disappearing the groups. Compounds such as benzoic acid, CO and CO2 was detected during the degradation of PET whereas in other polymers a large amount of methane or methylene group is observed. Overall during the degradation of mixed polymer mixture presence of PET played a vital role in the formation of light gas fractions. Even though a numerous investigation on co-pyrolysis of polymers were available, there is still not sufficient information of interaction of polymers with each other, especially with PET. This article attempts to fill this gap.

Structural transformation of vanadate nanotubes into vanadate oxides nanostructures during the dry reforming of methane

The metal-containing vanadate nanotubes namely MeVO-NT (Me = Ni, Co or Pt) were in situ transformed into vanadate oxides nanostructures i.e., MeVxOy, during the methane dry reforming. All the experimental observations through Raman, HRTEM, XRD, XPS, SEM-EDS, TG-FTIR and elemental analysis, strongly suggested that the VOx (MeV2O7, V2O5 and VO2) support contained the metal species that were involved in the dry reforming of methane (DRM) reaction. The pristine VO-NT catalyst exhibited a fairly low activity in DRM due to its degradation. In the case of CoVO-NT, the Co3O4/VO2, Co3O4/Co2V2O7 and Co3O4/V2O5 phases were deactivated by oxidation of the Co particles, instead of being deactivated by sintering and coking, as well. In contrast to CoVO-NT, PtVO-NT having PtOx/V2O5, PtOx/VO2 or even PtOx/V2O7 phases inhibited heavy carbonaceous deposition on surface, but sintering was not avoided. The NiVO-NT was active due to the stability of the Ni°/Ni2V2O7 active phase in hindering heavy whisker and filamentous carbonaceous deposits on such catalyst. Using Halgren-Lipscomb algorithm in the frame of density functional theory (DFT), transition states energy for all three catalysts were obtained. It was found that PtVO-NT energy profile was lower than CoVO-NT and NiVO-NT counterparts. This suggested that the Pt sites dispersed on VOx structure was catalytic active during the methane activation in DRM whereas the CoVO-NT and CoVO-NT solids were prone to perform side reactions.