Temperature-programmed Pyrolysis Research Articles

Comparative study of temperature-programmed pyrolysis and two-step fast pyrolysis of oily sludge

Oily sludge (OS) is the main waste produced in the process of crude oil extraction, transportation, and refining. As a promising technology of OS treatment, pyrolysis can reduce pollutant emissions and fully recover resources. In this study, the pyrolysis characteristics and product quality of temperature-programmed pyrolysis (TPP) and two-step fast pyrolysis (TSFP) were investigated. For the TG analysis, the faster heating rate could promote the pyrolysis of OS and increase its weight loss rate. In TPP, the higher final pyrolysis temperature provided more energy, which made the CH bond and CC bond break, increased the gas yield and oil yield, and also increased the hydrogen component in the gas, but reduced the char yield. However, the lower final pyrolysis temperature could improve the calorific value of oil. In TSFP, the oil yield was mainly affected by the first step pyrolysis temperature (T1), and the oil yield was 30.9 % at T1 of 500 ℃. The gas yield was both affected by T1 and the second step pyrolysis temperature (T2), and the gas yield could reach a maximum of 32.5 % at 550 ℃ (T1) × 800 ℃ (T2), which was 46.9 % higher than that of TPP (700 ℃, 22.1 %). This was due to the fact that as the T2 rose, the macromolecular components broke down, promoting the generation of gas. In TSFP, the hydrogen component in the gas was the most at 500 ℃ (T1) × 800 ℃ (T2). Compared with TPP, the total calorific value of the available products (oil and hydrogen) could be increased by TSFP, which increased the energy utilization efficiency. This study is expected to provide a theoretical basis for the industrial application of TSFP.

Solid phase microextraction of benzenes in river water by pomelo peel biochar

Pomelo peel, as a by-product of pomelo consumption, is rich in various fiber and functional compounds. The utilization of the valuable components found in pomelo peel may mitigate environmental concerns. In this study, pomelo peel rich in lignin and oxygen-containing functional groups was used to prepare pomelo peel biochar (PPB) via temperature-programmed pyrolysis at different temperatures (800 ℃ and 1000 ℃). Their structures were investigated by N2 adsorption-desorption isotherms and BJH pore size distribution. The results showed that PPB1000 (pomelo peel biochar prepared at 1000 ℃) had a higher specific surface area (749.9 m2/g), larger pore volume (0.42 cm3/g), more concentrated pore size distribution (2-3 nm), and better adsorption performance than commercial activated carbon. PPB1000 exhibited excellent capability to capture benzenes (BTEX, including benzene (B), toluene (T), ethylbenzene (E), and xylene (X)) through hydrogen bonds, π-π, and electrostatic interactions. Additionally, their honeycomb porous structure could provide additional adsorption sites and material transport paths. PPB1000 was coated on iron wire using the sol-gel method to prepare chemically and mechanically stable solid phase microextraction (SPME) fibers. By combining PPB1000-based SPME analysis with gas chromatography-flame ionization detection (GC-FID), an effective method was developed for the extraction and determination of BTEX. The optimized method had low LODs (0.004-0.032 μg/L), wide linear range (1-100 μg/L), and good linear relationship (determination coefficients, r2≥0.9919). The RSDs of the intra-batch (n=6) and inter-batch (n=5) precisions were 1.04%-6.56% and 1.03%-12.42%, respectively. The method validation results showed that PPB1000 had good stability. Compared with the commercial reagent polydimethylsiloxane (7 μm), PPB1000 had a higher extraction efficiency. When applied to the analysis of BTEX in natural water samples, trace levels of ethylbenzene (4.80 μg/L), o-xylene (3. 00 μg/L), and m-xylene and p-xylene (2.46 μg/L) were detected. Recovery tests were performed to validate the reliability of the method, and recoveries were between 75.7% and 117.6%. This effective pretreatment process combined with GC-FID could realize the rapid detection of BTEX and is promising for the analysis of BTEX in complex matrixes in the future.

Petroleum pitch-derived porous carbon as a metal-free catalyst for direct propane dehydrogenation to propylene

Propane dehydrogenation (PDH), as one of the most promising strategies for propylene synthesis, has attracted tremendous attention with the increase of shale gas exploitation. The exploration of green and sustainable catalytic materials to replace the high-price (Pt-Sn/Al2O3) and environmentally unfavorable (Cr2O3/Al2O3) catalysts will drive the rapid development of PDH technology. Porous carbon-based materials have been proposed as ideal PDH catalysts due to their abundant surface quinone/ketone CO groups for C-H bond activation and well-developed pore structures for mass transfer. However, the facile preparation of carbon-based catalysts with controllable surface properties and unique architectures remains a challenge. And the structure-function relationship of carbon-based catalysts in PDH is also under debate. Herein, we report a simple and efficient synthetic method to prepare the porous carbon-based PDH catalysts with cheap and readily available petroleum pitch as carbon source. The surface chemical properties and architectures of the porous carbon-based catalysts can be precisely tailored by varying the activation temperature during the synthesis process. Various characterizations including X-ray photoelectron spectra, temperature-programmed pyrolysis curves, thermogravimetric analysis and morphology observations clarify that the plentiful surface quinone/ketone CO groups and appropriate adsorption/desorption strengths of reactant/products derived from the great specific surface area are vital factors that guarantee the excellent C-H bond activation capability (propane conversion 45.6%) and alkenes selectivity (73.9%, propylene and ethylene) of the petroleum pitch-derived porous carbon catalyst. This work not only provides a promising alternative catalyst for the PDH process but also enriches the application fields of the carbon-based catalysts.

Effect of Fe impregnation on CO2-assisted pyrolysis of hazelnut shell

To find an economical and efficient way for mitigating CO2 emission, this study utilized CO2 as a reaction medium and investigated its influence on biomass pyrolysis. To this end, CO2-assisted pyrolysis of hazelnut shell (HS) and Fe-loaded HS (HSFe) was conducted using a thermogravimetric analysis (TGA) unit and a fixed-bed reactor. The temperature-programmed TGA tests demonstrated that there was no occurrence of the heterogeneous reaction between the solid char and CO2 at temperatures below 700 °C. However, the gaseous effluents evolved from the temperature-programmed pyrolysis of HS and HSFe in a fixed-bed reactor proved that CO2 played a mechanistic role in enhancing CO generation via the gas phase reactions (GPRs) between CO2 and volatile organic compounds (VOCs). Through the quantitative analysis of gas evolution rates, the CO production and the CO2 consumption in the GPRs always followed a stoichiometric relationship of about 2:1. A possible mechanism of the GPRs between CO2 and VOCs was proposed. Besides, Fe addition reduced the reaction temperatures of the GPRs between CO2 and VOCs by 120–160 °C, and significantly enhanced the reaction rate of these GPRs. As a result, the enhanced CO generation and the net CO2 consumption of HS loaded with 5 wt% Fe (HS5%Fe) in CO2 atmosphere were more than twice those of raw HS at temperatures above 500 °C. The XRD results revealed that Fe3O4 was the major chemical form of Fe species in HS5%Fe chars generated at temperatures ≥ 500 °C in CO2 atmosphere, which played a catalytic role in the GPRs between CO2 and VOCs.

Temperature-programmed pyrolysis of sunflower seed husks: application of reaction models for the kinetic and thermodynamic calculation

Temperature-programmed pyrolysis of sunflower seed husks: application of reaction models for the kinetic and thermodynamic calculation

Release characteristics of mercury in fly ashes collected from coal-fired CFB power units during thermal treatment

In order to investigate release characteristics of mercury in fly ashes collected from a coal-fired CFB power unit, the effect of temperature and time on mercury release characteristics of fly ash samples as well as release rules of mercury in fly ash samples were analyzed through the heat treatment experiments and temperature-programmed pyrolysis experiments. Moreover, the mechanism of mercury adsorption was examined based on the fitting results of first order kinetic model, Elovich kinetic model, Freundlich kinetic model and parabolic diffusion kinetic model. The results of heat treatment experiments showed that mercury release rate of the CFB fly ash was closely related to the heating temperature and time. The release rate of mercury in the CFB fly ash was lower than 0.2 at temperature below 200 ℃, while the release rate of mercury in the CFB fly ash was no less than 0.935 at the temperature over 300 ℃. The results of temperature-programmed pyrolysis experiments suggested that Mercury species present in the fly ash include HgCl2, Hg2Cl2, HgO, HgSO4, HgS (black) and HgS (red). HgS (black) and HgS (red) were the main mercury species present in the fly ash. The fitting results of kinetic equation showed that Elovich kinetic model was more applicable to reflect the Hg release from the fly ash, while the correlation coefficient R2 between the experimental and calculated data was greater than 0.95. It is indicated that this process controlled by multiple reaction mechanisms, and the activation energy changes greatly.

Fractionation of biomass and plastic wastes to value-added products via stepwise pyrolysis: a state-of-art review

Abstract Pyrolysis has been considered as a promising thermochemical process that can convert biomass in nonoxidizing atmospheres to value-added liquid bio-oil, solid biochar, and noncondensable gas products. Fast pyrolysis has a better economic return because of the valuable biofuel production (e.g. bio-oil, syngas). Because of the complexity and heterogeneity of the feedstocks, the one-step pyrolysis often leads to the mixed, acidic, and highly oxygenated liquid products. Moreover, the downstream processes (e.g. deoxygenation) for the desired fuels require high costs on energy and catalysts consumption. Stepwise pyrolysis is defined as a temperature-programmed pyrolysis that can separately obtain the products from each temperature step. It is a feasible approach to accomplish the fractionation by optimizing the pyrolysis process based on the decomposition temperature ranges and products among the biomass constituents. In recent years, the stepwise pyrolysis technology has gained attentions in thermochemical conversion of complex organic solid wastes. Through the stepwise pyrolysis of a real waste, oxygenated and acidic products were concentrated in the first-step liquid product, whereas the second-step product normally contained a high portion of hydrocarbon with low acidity. The stepwise pyrolysis of biomass, plastics, and their mixtures is comprehensively reviewed with the objective of fully understanding the related mechanisms, influence factors, and challenges.

Determination of mercury occurrence and thermal stability in high ash bituminous coal based on sink-float and sequential chemical extraction method

The high-ash coals have gradually become essential energy resources due to their availability, and the occurrence of Hg in coals and its thermal stability could be significantly influenced by ash-forming minerals. In this work, a high-ash bituminous coal was divided into 4 density fractions using sink-float procedure. The sequential chemical extraction procedures, temperature-programmed pyrolysis and TG/DTG experiments were carried to investigate the Hg occurrence and thermal stability in different samples. The results showed that the Hg contents in samples has a positive relation with the ash, sulfate and sulfide contents, and the correlation coefficients were 0.868, 0.535 and 0.924, respectively. However, the negative value with correlation coefficient of 0.751 between the Hg and organic sulfur content was obtained. The Hg species in different samples were quite distinct, the organic matrix-bound Hg was the dominate form in SG1 with the content of 76.14%, the SG2 and SG3 were mainly composed of HCl soluble Hg and Hg(NO3)2·xH2O, and the Hg species occurred in SG4 were mainly HCl soluble Hg and pyrite-bound Hg. In the process of pyrolysis, the matrix-bound Hg, HCl soluble Hg, HgS and Hg(NO3)2·xH2O were thermally unstable and could be released into gas in the drying and desorption stage of 30–400 °C, while the pyrite-bound Hg mainly released with the decomposition of pyrite in the temperature range of 400–600 °C. There was only little Hg released in the temperature range of 600–850 °C, indicating the negligible relationship of Hg with carbonate and silicate minerals.

Physicochemical Characteristics of Mauritia arabica Shell with High Temperature Calcination

Mauritia arabica shell (MAS), is widely applied as a Chinese tradition medicine after thermal decomposition. However, it is still uncertain how the thermal decomposition process affects the physicochemical properties of MAS. Moreover, the influences of these properties on the bioavailability have not been well understood. In this investigation, a temperature-programmed pyrolysis process is applied to calcine MAS to achieve the desired MAS with different physicochemical properties. The results showed that a weight loss of 43.27% - 44.73% was detected after MAS was calcined at 900°C, which was mainly attributed to the decomposition of protein, the phase transition of calcium carbonate from aragonite to calcite, and the decomposition of calcium carbonate. The activation energy in the heating duration was calculated by applying the Kissinger-Akahira-Sunose model (KAS), which was 58.13 kJ/mol for crystalline transformation and 181.27 kJ/mol for decomposition. Besides,according to the analyses from Fourier transform infrared (FTIR) and X-ray powder diffraction (XRD) tests, the crystalline of calcium carbonate in MAS was aragonite. These results provide beneficial temperature parameters for the pretreatments of MAS for pharmaceutical usages.

Pyrolysis and Oxidation of Asphaltene-Born Coke-like Residue Formed onto in Situ Prepared NiO Nanoparticles toward Advanced in Situ Combustion Enhanced Oil Recovery Processes

Pyrolysis and oxidation of asphaltene-born coke-like residue formed onto ex situ and in situ prepared NiO nanoparticles as initial steps toward developing advanced in situ combustion enhanced oil recovery (EOR) processes were studied. The in situ synthesized NiO nanoparticles in heavy oil matrix, containing coke-like residue, were characterized by X-ray diffraction, Brunauer–Emmett–Teller, field-emission scanning electron microscopy, and energy-dispersive X-ray mapping techniques. The pyrolysis and postpyrolysis oxidation of the coke residue were investigated by temperature-programmed pyrolysis (TPP) and temperature-programmed oxidation (TPO) methods, respectively. Oxidation kinetics of the coke residue was described by the Kissinger–Akahira–Sunose isoconversional method. The results showed a higher percentage of coke residue on the in situ prepared nanoparticles than the ex situ employed ones. Eventually, during the TPP of the coke residue, the amount of carbon oxides released per total amount of the cok...

The influence of calcination temperature on the physicochemical characteristics of Pteria martensii

Through temperature-programmed pyrolysis, the physicochemical properties of Pteria martensii (PM) before and after calcination are investigated. Our results show that the mass loss is 11.02% from room temperature to 600 °C with an average mass loss rate of 0.19% per min. The decomposition of organics coupling with the phase transition of calcium carbonate from aragonite to calcite occurs in the range of 367.4–423.0 °C, as confirmed by X-ray diffraction and Fourier transform infrared spectroscopy analyses. The decomposition pores and channels are changed forming complex porous structures. The surface of sample shows a much rougher fracture, with higher C, O and N element concentrations. At the stage of decomposition and phase transition of organics, the average activation energy value is 118.78 kJ mol−1. This study provides valuable information on the calcination process and calcined PM for use in medicines.

The oxygen evolution during pyrolysis of HunlunBuir lignite under different heating modes

HulunBuir lignite pyrolysis at low temperatures with different coal particle sizes, and different heating modes were studied on a fixed-bed reactor in order to investigate the oxygen evolution characteristics. The results show that pyrolysis temperature heavily influences the oxygen evolution. Almost 70.69wt% of oxygen in lignite transferred into volatile products at 700°C. With an increase of temperature, the proportion of oxygen transferred into pyrolysis water (water-O) and gas (gas-O), while the proportion of oxygen in tar (tar-O) reached a maximum of 2.26wt% at 700°C. The amount of carbonyl groups and ether linkages reached their maxima in char at 600°C and 650°C, respectively. After temperature-programmed pyrolysis and isothermal pyrolysis, there was more oxygen in the chars collected from the smaller coal particles, while after solid heat carrier pyrolysis, the coal particle size had little impact on the oxygen amount in chars (Char-O). At the same pyrolysis temperature, heating rate was determined to be one of the main factors that affecting the oxygen evolution.

Online analysis of initial volatile products of Shenhua coal and its macerals with pyrolysis vacuum ultraviolet photoionization mass spectrometry

Initial volatile products from pyrolysis of Shenhua coal and its macerals were investigated by using online pyrolysis-vacuum ultraviolet photoionization mass spectrometry (Py-VUVPI-MS). The fragment-free spectra of initial volatile products were measured during the temperature-programmed pyrolysis of the samples, and the intensity profiles of the initial volatile products as the function of temperature were detected. Mononuclear aromatics and phenols are the primary constituents of initial volatile products along with alkenes, n-alkyl naphthalene, n-alkyl naphthol, etc. The relative content of phenols evolved from coal macerals shows the order of vitrinite>raw coal>inertinite and that of polycyclic aromatic hydrocarbons (PAHs) exhibits the opposite trends. The different relative content in initial volatile products can be attributed to the different structures of coal macerals. The main source of phenols is the thermal decomposition of the oxygen-containing functional groups. PAHs come from two parts: thermal decomposition of coal macromolecular and free PAHs in mobile phase. This work provides a method for online analysis of initial pyrolytic products from coal by Py-VUVPI-MS.

Coprocessing of Pyrolytic Nitrogen Removal of Low-Rank Coals and Reduction of Limonite Ore

Temperature-programmed pyrolysis of low-rank coals physically mixed with goethite-rich limonite ore has been studied with a fixed-bed quartz reactor for the purpose of developing a novel coprocessing method for the removal of coal-bound nitrogen and the reduction of goethite. Limonite at loadings of 5–40 mass % promotes the formation of N2 from brown coal at 650–1000 °C and the consequent nitrogen removal, although the effect levels off beyond 20 mass % and thus seems to be limited. X-ray diffraction (XRD) measurements after pyrolysis showed that goethite can readily be reduced to metallic iron (α-Fe), irrespective of the limonite loading and the type of coexisting coal, and that part of the α-Fe reacts with a small amount of carbon to form cementite, a solid solution of iron and carbon. This method might have potential for the simultaneous production of low-nitrogen chars and reduced iron materials by utilizing low-value coals and limonite ores.

Temperature-programmed pyrolysis of magnesium ammonium phosphate and removal of ammonia-nitrogen by its pyrolysate

In order to achieve the dual goals of complete deamination of magnesium ammonium phosphate (MAP) and ensure the pyrolysate's good removal properties towards ammonia-nitrogen, a temperature-programmed method for the pyrolysis of MAP was studied, as well as the thermodynamic and kinetic processes involved in the removal reaction system between MAP pyrolysate and aqueous ammonium. It was found that the pyrolysis method and pyrolysis final temperature had significant effects on the MAP pyrolysate's removal properties towards aqueous ammonium, and the following conditions were deemed to be more appropriate: pyrolysis final temperature and heating rate at 180 °C and 5 °C/min, respectively, and a pH level of 9.5 for the removal reaction system. The resultant ammonium removal capacity by the MAP pyrolysate was 95.62 mg/g. After 120 min, the removal rate with an initial concentration of 1000 mg/L was 82%. The kinetic and thermodynamic results indicated that the removal of aqueous ammonium by MAP pyrolysate was the exchange process between H+ and NH4+ via MAP precipitation. The kinetics complied with the Lagergren quasi second-order model with an equilibrium time of 120 min, while the isothermal curves complied with the Freundlich model.

Influence of Hg occurrence in coal on accuracy of Hg direct measurement based on thermal decomposition

To better monitor and control Hg emissions from coal-fired power plants, quantification of Hg contents in coal is essential. Thermal decomposition is widely used to pretreat solid samples. The complete thermal release of Hg in coal samples is a premise for obtaining accurate results of measured Hg contents. The recommended heating temperature is 800°C for coal samples. The research work in this paper has verified the existence of an abnormal phenomenon, where some Hg occurrences in typical coal at 800°C could not fully decompose. The temperature-programmed pyrolysis was designed to validate the assumption and determine the optimum decomposition temperature. The results demonstrate that Hg combined with montmorillonite mineral fully decomposes at temperatures above 800°C. The obtained results help to clarify the relationship between the decomposition temperature and Hg occurrence. The study offers good guidance to improve the accuracy of measured Hg contents by thermal decomposition, thus expanding the laboratory and industrial application.

Following the structure and reactivity of Tuncbilek lignite during pyrolysis and hydrogenation

Combustion, pyrolysis and hydropyrolysis reactivity of Tuncbilek lignite was monitored by temperature programmed pyrolysis (TPP) under pure nitrogen flow, temperature programmed oxidation (TPO) under air flow and temperature programmed hydrogenation (TPH) under hydrogen flow at atmospheric pressure in a packed bed reactor.The structures of the organic and inorganic components were analyzed by NMR spectroscopy and XRD. Only methane and hydrogen were the main products of TPP while small amounts of CO and CO2 were also observed. Solid-state 1H and 13C CPMAS and 1H liquid Nuclear Magnetic Resonance (NMR) Spectroscopy of the pristine lignite, as well as tar and char products of pyrolysis and hydrogenation (hydropyrolysis), revealed similar tar compositions. TGA of pyrolysis chars indicated that there were more residual volatiles in hydropyrolysis char in comparison to pyrolysis char. Elemental analysis of pyrolysis and hydropyrolysis chars revealed that 25% of sulfur was lost during pyrolysis, whereas >90% of sulfur was lost during hydropyrolysis indicating efficiency of atmospheric pressure hydropyrolysis for both desulfurization and tar production. Volatile matter and fixed carbon, mostly aromatic, gave rise to distinct oxidation peaks during TPO. The oxidation peak due to volatiles was missing from TPO of pyrolysis char as well as from organic contents determined by NMR spectroscopy.

Effect of temperature-programmed pyrolysis pre-treatment on desulfurization performance of Zn-based sorbent prepared by lignite as support

A series of Zn-based sorbents were prepared by high-pressure impregnation with lignite as precursor of support and zinc nitrate as the precursor of active component, followed by temperature-programmed pyrolysis of the impregnated lignite sample in a fixed-bed quartz reactor. The H2S removal performances of sorbents prepared under different pyrolysis conditions such as temperatures, holding time as well as heating rates were evaluated. The physical and chemical properties of sorbents were characterized by atomic absorption spectroscopy (AAS), X-ray diffraction (XRD), transmission electron microscope (TEM) and nitrogen adsorption techniques. The results show that the process of pyrolysis can improve the pore structure dramatically, which lead to the high specific surface area and large pore volume. The good desulfurization performance of sorbent was attributed to both of the proper porous structure of sorbents, the content and distribution of active component. The optimal operating conditions of temperature-programmed pyrolysis for the impregnated lignite sample were the heating rate of 10°C/min, holding time of 180min in N2 atmosphere and pyrolysis temperature of 550°C. The sulfidation time could hold for over 720min before reaching 1ppm H2S in outlet gases and the sulfur capacity was up to 25.91g S/100g ZnO for sorbent prepared under this optimized condition.

In-situ analysis of volatile products from lignite pyrolysis with pyrolysis-vacuum ultraviolet photoionization and electron impact mass spectrometry

Pyrolytic species of two kinds of lignites (samples A and B) are investigated in-situ with pyrolysis-vacuum ultraviolet photoionization/electron impact mass spectrometry (PVUVPI/EIMS). Mass spectra of pyrolytic fragments are measured during temperature-programmed pyrolysis process of two lignite samples and the intensity profiles of the pyrolytic species are estimated in different temperatures. Experimental results show that H2, H2O, CO, and CO2 are dominant inorganic gaseous products and their characteristic temperatures are in accord with the temperatures of related chemical bonds cleavage. Mononuclear aromatics are dominant organic pyrolysis products, and many olefin species are also identified. The differences between samples A and B on macromolecular structures make the distribution of pyrolytic products different. In addition, the peak of H2S and CH3SH are both clearly observed in mass spectra of sample B, which could come from thioether bonds decomposition. This work also illustrates that the PVUVPI/EIMS performs very well in in-situ analysis pyrolytic products.

Effect of Demineralization on Shale Oil Yield by Bioleaching Process of Huadian (China) Oil Shale

In this study, the effect of the mineral matter of Huadian (China) Oil Shale on the conversion of organic carbon of oil shale to shale oil. The bioleaching process is taken in a mixed culture of the lithotrophic bacteria Thiobacillus ferrooxidans(Tf). The aim of bioleaching process was to dissolve the inorganic matters and improve the shale oil yield. A series of temperature-programmed pyrolysis operation was performed with raw and bioleached oil shale to find the best retorting temperature, 500oC is the best temperature to retort the oil shale. The oil shale samples were detected by SEM, DG, Fischer assay test, the results show that the surface structure was significantly different from the raw sample, and the shale oil yield improved from 8.9% to 11.7%.