Pyrolysis-gas Chromatography-mass Spectrometer Research Articles

Properties of Ramie (Boehmeria nivea (L.) Gaudich) Fibers Impregnated with Non-Isocyanate Polyurethane Resins Derived from Lignin.

The textile industries need an alternative to cotton since its supply is unable to keep up with the growing global demand. The ramie (Boehmeria nivea (L.) Gaudich) fiber has a lot of potential as a renewable raw material but has low fire-resistance, which should be improved. In this work, the objectives were to investigate the characteristics of lignin derived from black liquor of kraft pulping, as well as the properties of the developed lignin-based non-isocyanate-polyurethane (L-NIPU), and to analyze ramie fiber before and after impregnation with L-NIPU. Two different formulations of L-NIPU were impregnated into ramie fiber for 30, 60, and 90 min at 25 × 2 °C under 50 kPa. The calculation of the Weight Percent Gain (WPG), Fourier Transform Infrared Spectrometer (FTIR), Rotational Rheometer, Dynamic Mechanical Analyzer (DMA), Pyrolysis Gas Chromatography Mass Spectrometer (Py-GCMS), Universal Testing Machine (UTM), and hydrolysis test were used to evaluate the properties of ramie fibers. The result showed that ramie fiber impregnated with L-NIPU produced higher mechanical property values and WPG than non-impregnated ramie fiber. There is a tendency that the longer impregnation time results in better WPG values, FTIR intensity of the urethane group, thermomechanical properties, crystallinity, and mechanical properties of ramie fiber. However, the use of DMC and HMT cannot replace the role of isocyanates in the synthesis of L-NIPU because it produces lower heat resistance than ramie impregnated using pMDI. Based on the results obtained, the impregnation of ramie fiber with L-NIPU represents a promising approach to increase its wider industrial application as a functional material.

A study on self-shielding effect of CaCO3 in cable pyrolysis using gas product analysis and PSO optimization

This paper investigates the self-shielding mechanism of CaCO3 during the pyrolysis of PVC-CaCO3 based cable. Previous studies have focused on HCl adsorption by CaCO3, neglecting the self-shielding effect. In this paper, thermogravimetric-infrared analyzer, pyrolysis gas chromatography-mass spectrometer and particle swarm optimization (PSO) algorithm are used to investigate the self-shielding mechanism. The results show a three-stage pyrolysis process. In the first stage, CaCO3 weakens the autocatalytic decomposition of PVC by absorbing HCl in the solid phase. The 3rd Avrami Erofeev model was obtained by PSO, representing the production of CaCl2 crystals. The second stage demonstrates self-shielding due to a reduction in solid-phase porosity. CaCO3 encapsulation inhibits the pyrolysis of PVC resulting in macromolecular intermediates. The 3rd order-based model was obtained by PSO, with a lower pyrolysis reaction rate compared to pure PVC. In the third stage, the stability of Cl in the solid phase is weakened at high temperatures, which converts the Cl to the gas phase in the form of chlorinated hydrocarbons, leading to the failure of self-shielding effect of CaCO3. The 2nd order-based model was obtained by PSO, which is considered as a result of the solid phase reactions instead of pyrolysis.

Low-carbon conversion of crude oil to C2-C4 olefins by micro Py-GC/MS and a small-scale fluidized-bed reactor

Green utilization of crude oil has become an important way for energy transformation in the petrochemical industry. Crude oil to aimed low-carbon (C2-C4) olefins had been conducted by micro pyrolysis-gas chromatograph/mass spectrometer (Py-GC/MS) and a small-scale fluidized-bed reactor. Fe-modified Al2O3/USY catalysts were used in the catalytic pyrolysis of crude oil. The results showed that product distribution altered hugely after Fe incorporation. Suitable incorporation of Fe can promote the conversion of crude oil, while excessive Fe incorporation could reduce the yield of light olefins. Bifunctional 1%Fe/USY catalyst showed good catalytic dehydrogenation pyrolysis activity in light olefin production, which could guide the clean and low-carbon conversion of crude oil.

Role of Pseudomonas fluorescens FSYZ01 on the corrosion behavior of Q235B carbon steel in oilfield produced water.

The corrosion behavior of Q235B carbon steel is investigated in water, LB medium, and oilfield produced water adding Pseudomonas fluorescens FSYZ01. After immersion at 30°C for 13days, the weight loss of carbon steel with this strain decreased by 32.23%, 54.07%, and 78.34%, respectively. X-ray diffraction (XRD) results show that P. fluorescens FSYZ01 inhibited conversion of iron oxides by hindering oxygen from approaching metal surface. Fourier transform infrared (FT-IR) and X-ray photoelectron spectrometer (XPS) results show that specific functional groups and bonds reacted with Fe(II/III) to form a dense and stable chelate-oxide protective layer, thereby inhibiting corrosion. Pyrolysis gas chromatography-mass spectrometer (Py-GCMS) results demonstrate the bacteria degraded C12 to C20 alkanes in oil. The inhibitory mechanism of crude oil-degrading bacteria P. fluorescens FSYZ01 on the carbon steel corrosion was proposed, so as to slow corrosion of oilfield produced water system pipeline and prolong its service life, helping to comprehend the microbial corrosion in the actual environment.

The estimation of DBPs formation potential depending on the molecular structure of natural organic matter

Objectives:Since natural organic matter(NOM) is generated from an ecosystem, it has various characteristics depending on its origin. Especially, aquatic NOM reduces an efficiency of water treatment system and forms disinfection-by-products(DBPs) as a precursor. In this study, DBP formation potential was estimated according to the molecular structure of NOMs resulted by pyrolysis-gas chromatography-mass spectrometer(py-GC-MS). Methods:Five NOM samples were characterized: Suwannee River NOM(SRNOM), Mississippi River NOM(MRNOM), Nakdong River NOM(NR), NOM in effluent of Jinhae wastewater treatment plant(WP), and NOM in a small stream(SG) in Changwon city. The various analytical instruments were used including TOC analyzer, UV spectrometer, fluorescence spectrometer, and size-exclusion chromatography. After freeze drying of NOMs, molecular structure of samples was identified by py-GC-MS. Results and Discussion:Molecular weights of SRNOM and MRNOM were similar each other (~1400Da). The others(NR,WP,SG) were larger than the SRNOM and MRNOM. Hydrophobicity of the samples followed the order: SRNOM≒MRNOM > NR > WP > SG. Py-GC-MS results showed that SRNOM and MRNOM contain high portion of humic components. Otherwise, NR, WP, SG have protein which is originated from microbials. The DBP formation potential of SRNOM and MRNOM were the highest.Conclusion:This research shows the different characteristics of NOMs originated from different source. The results confirmed that NOM contained high portion of humic components results in the formation of high concentration of DBPs.

Catalytic process toward green recycling of polyvinyl chloride: A study on thermodynamic, kinetic and pyrolysis characteristics

Municipal solid wastes (MSW) include a considerable amount of polyvinyl chloride (PVC). How to quickly and harmlessly dispose of the PVC-containing MSW and convert them into a valuable resource is an urgent issue at present. The application of catalysts has yet been proven to be effective in mitigating organic pollutant production. In the present study, a thermogravimetric analyzer (TGA) and pyrolysis-gas chromatography-mass spectrometer (Py-GC/MS) were utilized to investigate the thermodynamic properties, kinetic parameters and pyrolysis characteristics of PVC with different zeolites including HZSM-5 with the Si/Al of 80 and 280, ferrierite, HY and MCM-41 zeolite. It turned out that the introduction of different catalysts with different pore structures and acid site concentrations made different catalytic effects on the cracking mechanism of PVC. Among the five zeolites, MCM-41 decreased temperature at the 50 % conversion to 296 °C, increased weight loss mate at a maximum of 25 %/min and generated fewer PAHs (whose changing amplitude decreased by 94 % in ex-situ catalytic mode in comparison to non-catalytic mode), indicative of its higher catalytic activity in PVC polymer degradation. Under the consideration of maximizing catalytic cracking activity and minimizing secondary pollutants production, non-catalytic dechlorination at approximately 300 °C followed by catalytic degradation in ex-situ mode over mesoporous MCM-41 at higher temperatures was the best recommendation.

Mechanism of catalytic conversion of kerosene co-refining heavy oil to BTEXN by Py-GC/MS based on “point-line-surface-body” step by step research strategy

Kerosene co-refining heavy oil (KCR-H), KCR-H six group components (KCR-HS), six typical model compounds representing the KCR-HS and its mixed model compound were selected as raw materials. The effects of the physicochemical properties of single and bi-metallic modified HZSM-5 (Me/Z-5) on the selectivity and yield of benzene (B), toluene (T), ethylbenzene (E), xylene (X), naphthalene (N) in cracking products were investigated by pyrolysis–gas chromatograph/mass spectrometer (Py-GC/MS). The results show that Ni-Mo/Z-5 exhibits superior selectivity for light aromatic in the catalytic conversion of tetradecane, benzofuran, and KCR-H, compared with Z-5. Additionally, oxygenated and aliphatic compounds are more easily converted to light aromatics than PAHs and nitrogen-containing compounds. Using Ni-Mo/Z-5 catalytic conversion benzofuran, the selectivity of BTEXN in the cracking product is 65.01 %, which is 23.44 times higher than pyrene (2.66 %). Due to the preferential cracking of benzofuran, small molecular fragments prepared by tetradecane and methyl naphthalene promote the catalytic conversion of methyl phenol, quinoline, and pyrene. Compared with the theoretical BTEXN yield (1338.39 mg/kg), the experimental BTEXN yield obtained from mixed model compounds (MCs) increasing by 37.95 %, which is 1846.40 mg/kg. In addition, the BTEXN selectivity of saturates (Satur) over Ni-Mo/Z-5 is 62.97 %, increases by 12.97 % compared with tetradecane, which represents the components of this group, indicating that the synergistic effect between oxygenated compounds and aliphatic compounds is conducive to produce light aromatics. Furthermore, based on the structural characteristics and catalytic properties of metalmodified Z-5 and the conformational relationships between points, lines, surfaces, and bodies, possible catalytic conversion mechanisms and pathways for KCR-H and KCR-HS were proposed.

Accurately quantifying carbon structural types and predicting pyrolysis behavior of coal using solid 13C NMR Cp/MAS spectra

Coal conversion to material or chemical by pyrolysis is the main methods for achieving carbon neutrality. To predict correct pyrolysis behavior, accurately quantifying carbon structural types of complex coal discussed in this study is significative. Carbon structural types in coal based on 13C NMR Cp/MAS TOSS spectra were accurately quantified by coupling standard curve and peak-fitting method to reduce nuclear overhauser effect (NOE). The H/C atomic ratio and aromaticity is used to verify the accuracy of this method. The pyrolysis behavior was predicted by pyrolysis Gas Chromatography-Mass Spectrometer (Py-GC-MS), thermogravimetric analysis (TG), and fix-bed slow pyrolysis according to correction carbon structure. The results show that the H/C atomic ratio calculated by correction carbon structure is agreed with that from ultimate analysis, as well as aromaticity. Their correction relative deviations are below 10%, farther lower than experimental value, increasing with the increment of Cdaf%. The correction carbon structure evolution during pyrolysis is coincided with general conclusion and Py-GC-MS analysis. The mono-aromatics and phenolics are evaluated by correction carbon structure. It is significantly fundamental study for carbon material to chemicals from micro-angle. These results are also a guide for accurate calculation and simulations of quantum chemistry.

Thermal degradation and pyrolysis behavior of wholly aromatic phosphorus-containing thermotropic liquid crystal copolyesters

In this study, the thermal degradation and pyrolysis behavior of three wholly aromatic phosphorus-containing thermotropic liquid crystal copolyesters (TLCP) were investigated. The non-isothermal degradation kinetic parameters were determined using the Kissinger and Friedman method. The copolyesters exhibited two degradation stages in air but only one in N2, and better thermal stability was observed for those containing more 10-(2,5-Dihydroxypheny)-10 h-9-oxa-10-phospha-phe-nanthrene-10-oxide (DOPO-HQ) units, which could be reflected by the thermogravimetric analyzer (TGA) data and E values. The TGA coupled with Fourier transform infrared spectroscopy (TG-FTIR) and pyrolysis-gas chromatograph-mass spectrometer (Py-GC-MS) results showed that DOPO-HQ decomposed first in the early stage of degradation, generating gaseous pyrolysis products and forming phosphorus-containing char residue in the later stages of degradation. However, the copolyesters produced more CO2 and less organic volatiles during thermal oxidative degradation. The morphology and FTIR spectra of the char residue obtained after TGA experiments showed a continuous and dense structure due to the presence of phosphorus moieties. The microscale combustion calorimeter (MCC) and limiting oxygen index (LOI) results showed that the copolyesters have excellent flame retardant properties, and the LOI value increases monotonically with increasing of DOPO-HQ content, having a maximum value up to 73.8%, due to its excellent gas-phase and condensed-phase fire inhibition mechanisms. Overall, the resulted phosphorus-containing thermotropic liquid crystal copolyesters exhibited excellent thermal stability and flame retardancy, the thermal degradation and pyrolysis research would be a good guidance for its processing and application.

Investigation of the (catalytic) co-pyrolysis of Shendong coal and coal tar based on rapid pyrolysis and ANN modelling

The catalytic co-pyrolysis of coal and hydrogen-rich substances is an effective way to improve the yield and quality of coal tar. In this paper, the co-pyrolysis experiments of Shendong low rank coal (SD) and low temperature coal tar (HCT) catalyzed by hematite, chalcopyrite, nickel laterite, and molybdenite were carried out respectively. The catalytic co-pyrolysis characteristics and product distribution of coal-tar slurry with different coal-tar ratios were investigated by the thermogravimetric analyzer (TGA), pyrolysis-gas chromatography/mass spectrometer (Py-GC/MS), and fixed bed rapid pyrolysis reactor (FBR). In addition, the response surface design method and artificial neural network (ANN) were introduced to optimize catalyst ratios. The analysis results show that the experimental value of the maximum weight loss rate in the high temperature pyrolysis stage with a coal-tar ratio of 5: 5 is greater than the estimated value. Besides, the coal-tar co-pyrolysis has a synergistic effect, which strongly reduces the apparent activation energy of the pyrolysis process. The addition of HCT promotes the generation of oxygen-containing compounds and aromatics. The presence of natural minerals promotes the formation of light tar, especially mono-aromatics, aliphatics, and phenol in the pyrolysis tar. After optimizing and verifying the catalyst ratio by ANN, the pyrolysis tar yield, light component content, and light tar yield are 50.49 wt%, 46.14%, and 21.14 wt%, respectively.

Gas evolution characteristics of three kinds of no-bake resin-bonded sands for foundry in production

No-bake resin-bonded sand is commonly used in casting production. However, its air pollution is relatively serious, especially in the molding and pouring process. For this reason, it is necessary to study the gas evolution characteristics of no-bake resin-bonded sand from room temperature to high temperatures, and not only the amount of gaseous products, but also the composition of the gaseous products. No-bake furan resin-bonded sand (#1), phenolic urethane no-bake resin-bonded sand (#2), and alkaline phenolic no-bake resin-bonded sand (#3) are the three most common no-bake resin-bonded sands in casting. The gas evolution volume and rate of these three no-bake resin-bonded sands were studied. Thermogravimetry-mass spectrometer (TG-MS), headspace-gas chromatography/mass spectrometer (HS-GC/MS), and pyrolysis-gas chromatography/mass spectrometer (PY-GC/MS) were used to measure the composition of the gaseous products emitted from binders at room temperature and high temperatures. The differences between formaldehyde, heterocyclic aromatic compounds (HAC), monocyclic aromatic hydrocarbons (MAH), and polycyclic aromatic hydrocarbons (PAHs) gaseous products from the three types of no-bake resin-bonded sands during the molding and casting process were compared. From the perspective of environmental protection, alkaline phenolic no-bake resin-bonded sand and no-bake furan resin-bonded sand are better than phenolic urethane no-bake resin-bonded sand.

Experimental Study on Pyrolysis of Rice Straw Catalyzed by CaO/Al2O3-Phosphate Mixture

CaO and phosphates showed synergistic effects in the regulation of pyrolysis products in the pyrolysis of when they were directly mixed with camphor wood. The alkyl phenol yield increased during the pyrolysis process of corn straw fermentation residue directly mixed with KH2PO4 supported by γ-Al2O3. Rice stalks from agricultural crops are often disposed as waste. However, the potassium phosphate impregnated raw straw pyrolysis with CaO and Al2O3 has not been reported. This paper studied the synergistic effects of CaO or Al2O3 and three potassium phosphates (i.e., KH2PO4, K2HPO4·3H2O, and K3PO4·3H2O) in the rice straw pyrolysis through pyrolysis–gas chromatography-mass spectrometer (Py-GC/MS) experiments. The results showed that CaO/Al2O3 and potassium phosphates showed synergistic effects in the regulation of the types or contents of phenols, ketones, aldehydes, etc. and increased the contents of phenols, aldehydes, acids, and levoglucosan (LG) from most samples and increased those of ketones compared with those catalyzed by potassium phosphates alone. They were suitable for the production of ketone-rich and acid-low bio-oil, which is an important precursor for the preparation of power or jet fuel. The highest contents of ketones (HCK) reached 56.65% and 56.02% in the pyrolysis of K3PO4·3H2O impregnated rice straw with CaO or Al2O3, respectively. The lowest contents of acids and acetic acid (LCA) were nearly or equal to 0, respectively. HCK and LCA were respectively significantly higher and lower than the values reported in the literatures for biomass catalytic pyrolysis using CaO/Al2O3 and potassium phosphates alone or in combination. Dehydration reactions, etc. were further promoted under the co-catalysis of the two catalysts, and some phenols could be converted to benzene products, etc. For 50% K3PO4·3H2O impregnated sample, the yields of furans reduced sharply after CaO addition. For most impregnated samples except 50% K2HPO4·3H2O and 30% and 50% K3PO4·3H2O samples, the contents of total furans and furfural increased after Al2O3 addition.

An Ancient Egyptian Multilayered Polychrome Wooden Sculpture Belonging to the Museo Egizio of Torino: Characterization of Painting Materials and Design of Cleaning Processes by Means of Highly Retentive Hydrogels

This contribution focuses on the conservation of an Egyptian wooden sculpture (Inventory Number Cat. 745) belonging to the Museo Egizio of Torino in northwest Italy. A preliminary and interdisciplinary study of constituent painting materials and their layering is here provided. It was conducted by means of a multi-technique approach starting from non-invasive multispectral analysis on the whole object, and subsequently, on selected micro-samples. In particular, visible fluorescence induced by ultraviolet radiation (UVF), infrared reflectography (IRR) and visible--induced infrared luminescence were used on the whole object. The micro-samples were analysed by means of an optical microscope with visible and UV light sources, a scanning electron microscope (SEM) with an energy-dispersive X-ray spectrometer (EDX), Fourier transform infrared (FT-IR) spectrometer, pyrolysis-gas chromatography/mass spectrometer (Py-GC/MS) and micro-particle induced X-ray emission (PIXE). The characterization of the painting materials allowed the detection of Egyptian blue and Egyptian green, and also confirmed the pertinence of the top brown layer to the original materials, which is a key point to design a suitable surface treatment. In fact, due to the water sensitiveness of the original materials, only few options were available to perform cleaning operations on this artwork. To setup the cleaning procedure, we performed several preliminary tests on mockups using dry cleaning materials, commonly used to treat reactive surfaces, and innovative highly water retentive hydrogels, which can potentially limit the mechanical action on the original surface while proving excellent cleaning results. Overall, this study has proved fundamental to increase our knowledge on ancient Egyptian artistic techniques and contribute to hypothesize the possible provenance of the artefact. It also demonstrated that polyvinyl alcohol-based retentive gels allow for the safe and efficient cleaning of extremely water sensitive painted surfaces, as those typical of ancient Egyptian artefacts.

Fast pyrolysis of holocellulose for the preparation of long-chain ether fuel precursors: Effect of holocellulose types

The pyrolysis behaviors of nine biomass-derived holocelluloses (from seven agricultural and two forestry residues) were studied on a thermogravimetric analyzer (TGA) and pyrolysis–gas chromatography/mass spectrometer (Py-GC/MS). The results illustrated that compared with forestry holocellulose, agricultural holocellulose had quite high ash and hemicellulose contents. Moreover, agricultural holocellulose presented lower initial temperature and maximum mass loss rate. The results of GC/MS revealed that agricultural holocellulose produced more acids, ketones, aldehydes and furans and corn stalk holocellulose led to the highest targeted compounds (ketones, aldehydes and furans with carbonyl group) content of 51.4%. Woody holocellulose was suitable for the production of sugars, particularly levoglucosan, and pine sawdust holocellulose afforded the highest levoglucosan content of 46.55%. Intriguingly, the correlation of sugars/levoglucosan content with a mass ratio of cellulose to hemicellulose (CE/HCE) was put forward.

Thermal Decomposition Characteristics of Poly((4-Vinylbenzyl) Trimethylammonium Bis (Trifluoromethanesulfonimide)) Studied by Pyrolysis-GS / MS

Over the past decades, significant advances have been made in the development and research of gas separation membranes based on ionic liquids (IL) and their polymer analogs (PIL) for membrane separation of "acid gases" such as CO2 and H2S from gas mixtures. Polymers containing various amino groups are of great interest for the selective separation of acid gases from gas mixtures, since ammonia and its derivatives are used in conventional purification. In this work, we have synthesized a monomeric ionic liquid based on 4 vinylbenzyl chloride with included triethylamine by the Menshutkin reaction. Further, on its basis, polymer ionic liquids were obtained by the method of free radical polymerization, then an anion exchange reaction was carried out to replace the Cl anion with Tf2N. To analyze the process of thermal pyrolysis of poly [VBTEA-Tf2N] a pyrolysis-gas chromatography/mass spectrometer (Py-GC/MS) was employed in this research. The obtained materials, which are high molecular weight compounds, can be used to obtain polymer membranes of various architectures by traditional methods: both non-porous symmetric membranes and microporous asymmetric membranes.

Catalytic Conversion of a ≥ 200 °C Fraction Separated from Low-Temperature Coal Tar into Light Aromatic Hydrocarbons.

A ≥ 200 °C fraction (CT200F) of low-temperature coal tar was prepared by a rotary film evaporator. The catalytic conversion experiments of CT200F and six model compounds were conducted on the pyrolysis gas chromatography–mass spectrometer. The yields of catalytic conversion products benzene, toluene, xylene, and naphthalene (BTXN) were analyzed by semi-quantitative analysis according to the chromatographic peak areas. Additionally, the possible formation pathways and mechanisms of the target products BTXN generated over different catalysts were investigated. The results show that the yield of aromatic hydrocarbons increases and the yield of acid compounds decreases during CT200F pyrolysis over ZSM-5, HY, USY, and β-zeolite compared with that of its non-catalytic pyrolysis, especially the yields of BTXN obtained over USY and β-zeolite increase by 128 and 108%, respectively. The pore structure of ZSM-5 is suitable to produce BTX, while the suitable acidity and pore structure of USY, HY, and β-zeolite are more beneficial for the selective preparation of naphthalene than that of ZSM-5. The conversion pathways of six model compounds into BTXN over zeolites were obtained, and the following conclusions can be drawn: The dehydroxylation effect of zeolites shows the order of ZSM-5 > HY > USY > β-zeolite. The catalytic effect of zeolites on the cracking and ring opening of PAHs in CT200F shows the order of β-zeolite > USY > HY > ZSM-5. The catalytic effect of catalysts on the cracking and aromatization of aliphatic compounds shows the order of ZSM-5 > β-zeolite > USY > HY. β-zeolite has an outstanding catalytic performance in the conversion of PAHs into naphthalene. ZSM-5 and HY can effectively remove phenolic hydroxyl groups in phenol and naphthol. During the catalytic conversion processes of the coal tar fraction and model compounds, the catalytic effect of the pore constructions of zeolites is more important than their acidities, which determines whether large molecules can enter and whether acid sites in non-micropores can be effectively utilized.

Preparation and properties of poly(MMA-co-TMPTA)/fragrance microcapsules

In order to improve the encapsulation efficiency and shell properties of PMMA capsules, poly(MMA-co-TMPTA)/fragrance microcapsules were fabricated by in-situ polymerization with Trimethylolpropane Triacrylate (TMPTA) as the co-monomer. The poly (MMA-co-TMPTA)/fragrance microcapsules were characterized by scanning electron microscopy (SEM), thermogravimetric analyzer (TGA), pyrolysis gas chromatography-mass spectrometer (PGC-MS) and electronic nose (PEN-3). The results indicate that the poly(MMA-co-TMPTA)/fragrance microcapsules present pomegranate shape with rough and sunk surface and have the particle size in the range of 10−20 μm. poly(MMA-co-TMPTA)/fragrance microcapsules has good thermal stability, high encapsulation efficiency of 91.6 % and good slow-release property, and the fragrance on the fabric can be retained for more than 3 months.

Influence of temperature on accessible pyrolysis pathways of homopolymerized bisphenol A/F epoxies and copolymers

Understanding the thermal pyrolysis of epoxies and their copolymers is important for identifying structural changes resultant from thermal transients, enabling identification of failure modes of high-performance composite materials. This work expands our understanding of the thermal pyrolysis of cured epoxies and the role of temperature and composition on products, pathways, and relative rates. Numerous researchers have explored the pyrolysis of bisphenol A (BPA) epoxy. Significantly fewer have studied bisphenol F (BPF), and copolymers of BPA and BPF have been neglected. In this work, a pyrolysis gas chromatography mass spectrometer (PY-GC-MS) was used to investigate the degradation mechanism of homopolymerized BPA, BPF epoxies and their copolymers. For polymer identification, pyrolysis >450 °C resulted in the most extensive fragmentation and is useful for material identification, though lower temperatures show different degradation product profiles that provide mechanistic insight into thermal degradation pathways. Temperature greatly influences the accessible pyrolysis pathways of BPA, revealing dual mechanisms of formation for products p-isopropylphenol and p-isopropenylphenol. For BPF at low pyrolysis temperature the p,p-bisphenol F isomer is produced at significantly lower relative abundance compared to the abundance at higher temperatures tested, but production of the other two isomers changes little with respect to temperature. This suggests the epoxy components consisting of the p,p-bisphenol F isomer have higher thermal stability. Overall, the copolymer epoxies were found to have similar degradation products in stoichiometric distributions. The major exception was the formation of the p,p-bisphenol F isomer, which shows evidence of thermal stabilizing effects from addition of BPA epoxy.

Experimental study on pyrolysis of camphor wood catalyzed by CaO-calcined phosphate mixture

Pyrolysis-gas chromatography-mass spectrometer (Py-GC/MS) was used to investigate the catalytic pyrolysis of camphor wood with the mixture of CaO and four types of calcined phosphates (K3PO4·3H2O, K2HPO4·3H2O, KH2PO4, and Zn3(PO4)2·4H2O). The results show that after CaO and calcined K3PO4·3H2O addition, the relative yields of 3-methoxy-1,2-benzenediol, 3-methoxy-2,5,6-trimethylphenol decrease significantly, while those of isoeugenol, trans-isoeugenol, and furfural are obviously enhanced. CaO and calcined K3PO4·3H2O exhibit strong synergistic effects and can regulate the composition distributions of products such as phenols. The relative yields of cyclopentanones and phenols are enhanced after the mixture of CaO and calcined K2HPO4·3H2O addition compared with those with single CaO or calcined K2HPO4·3H2O addition. The relative yields of acetic acid fluctuate in the range of 8.90–9.56% after calcined KH2PO4 addition. After adding the mixture of CaO and calcined KH2PO4, the relative yields of acetic acid decrease from 9.11% to 4.65% and those of propionaldehyde and 2, 6-dimethoxy-phenylpropionic acid compounds are improved compared with those after single catalyst addition. CaO and calcined Zn3(PO4)2·4H2O have strong synergistic effects on the formation of chain alkanes. They also enhance the relative contents of phenol and further decrease those of resorcinol, 3-methoxy-1,2-benzenediol, 4-methyl-1,2-benzenediol, indicating they exhibit strong synergistic effects and can further catalyze the cleavage of hydroxyl, methyl and methoxy groups.

Effects of transition metal oxides on pyrolysis properties of PVC

Polyvinyl chloride (PVC) produces a large amount of solid wastes because of its wide use. How to dispose quickly and harmlessly of the PVC solid wastes and turn into a resource is currently a major problem. In this paper, the experimental material was PVC. Thermogravimetric analyzer (TG) and pyrolysis-gas chromatography-mass spectrometer (Py-GC–MS) were used to study the pyrolysis characteristics of PVC with transition metal oxide. The effect of in-situ pyrolysis of PVC in N2 on transition metal oxides was studied in a SX3−4-10A muffle furnace. The composition of tars captured by the cold trap was analyzed by GC–MS. The residual carbon after pyrolysis was analyed by scanning electron microscope (SEM) and XRD. The results of PY-GC–MS and GC–MS showed that the two stages of PVC pyrolysis were advanced with the transition metal oxide.The decomposition peak temperature increased to make PVC pyrolysis more complete. The transition metal oxide reduced significantly the production of benzene, toluene, indene, naphthalene, anthracene and other compounds during the pyrolysis of PVC. The results of SEM and XRD showed that transition metal oxides absorbed HCl produced by pyrolysis and increased the amount of residual carbon in the system. These studies provided a theoretical basis for the pyrolysis rapidly of PVC.