Influence of temperature and steam on the products from the flash pyrolysis of Jordan oil shale

Oil shale samples from the Sultani deposit in the south of Jordan, were pyrolysed in a semi‐continuous fluidized bed reactor under nitrogen and nitrogen/steam atmosphere. The pyrolysis temperature between 400 and 650°C were investigated. Increasing the pyrolysis temperature from 400 to 520°C caused a large increase in the oil yield. Further increase of the pyrolysis temperature resulted in a decrease in oil yield and a large increase in the evolved gases. This increase in the hydrocarbon gas yield was attributed to oil thermal cracking reactions. The evolved gases were composed of H₂, CO, CO₂, and hydrocarbons from C₁ to C₄. The presence of steam improved the oil yield which may be a result of reducing the degree of decomposition. The derived oils were fractionated into chemical classes using mini‐column liquid chromatography. Copyright © 2002 John Wiley & Sons, Ltd.     

Chemical structure and pyrolysis characteristics of demineralized Zhundong Coal

To investigate the effects of acid treatments on the chemical structure and pyrolysis behavior of coal, we examined the low-rank Zhundong coal pretreated by four single acids (HCl, HF, H₂SO₄, HNO₃) and a combined acid (HCl-HF-HCl). Our results indicated that the carboxylic and phenolic hydroxyl contents of the coal increased, while the aliphatic and aromatic hydrogen contents decreased after leaching. Nitric acid destroyed long aliphatic chains in coal, which caused the key pyrolysis stage to occur at lower temperature, the number of volatiles increased, and the pyrolysis rate improved.     

Quantitative comparison of different chemical pretreatment methods on chemical structure and pyrolysis characteristics of corncobs

In order to identify the effects of different chemical pretreatment methods on structure changes of corncobs and their subsequent pyrolysis characteristics, the chemical pretreatment of corncobs was performed using different concentrations of sodium hydroxide (NaOH), sulfuric acid (H₂SO₄), and hydrogen peroxide (H₂O₂) solutions. The structure changes of corncobs were characterized by elemental analysis, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD). The pyrolysis characteristics of raw and pretreated corncobs were conducted on thermogravimetric analyzer (TGA) and pyrolysis–gas chromatography/mass spectrometry (Py–GC/MS). TG/DTG analysis of raw and pretreated corncobs demonstrated that the rank order for the ease of pyrolysis was untreated < 1% NaOH < 1% H₂O₂ < 2% NaOH < 2% H₂SO₄ < 1% H₂SO_4. Py–GC/MS analysis showed that chemical pretreatment can effectively promote the production of furans and levoglucosan (LG) and inhibit the formation of acetic acid, ketones and phenols. The rank order of LG yields from untreated and pretreated corncobs was untreated < 1% NaOH < 2% NaOH < 1% H₂O₂ < 1% H₂SO₄ < 2% H₂SO_4. The maximum yield of LG (15.01%) was obtained by fast pyrolysis of corncobs pretreated using 2% H₂SO₄. It was 18.53 times the yield of LG from untreated corncobs. The results could be mainly attributed to the passivation of alkali metal and alkali earth metal and the removal of hemicellulose and lignin fractions during pretreatment.     

The effect of various acids treatment on the purification and electrochemical hydrogen storage of multi-walled carbon nanotubes

The effects of HCl, HNO₃, H₂SO₄ and HF acids on the purification and the electrochemical hydrogen storage of multi-walled carbon nanotubes (MWCNTs) were studied. The MWCNTs were synthesized on Fe–Ni catalyst by thermal chemical vapor deposition method. The X-ray diffraction and thermal gravimetric analysis results indicated that the MWCNTs purified by HF acid had the highest impurities as compared with the other acids. The N₂ adsorption results at 77 K indicated that all the samples were mainly mesoporous and the purified MWCNTs by HF acid had the highest surface area as compared with the other acids. The hydrogen storage capacities of the purified MWCNTs by the following acids were in ascending order as: H₂SO₄, HCl, HNO₃ and HF. It was found that the 1–2 nm micropores in the MWCNTs are very important for hydrogen storage. Further, the presences of catalyst and defective sites in MWCNTs influence the hydrogen storage capacity.     

The chemistry of minerals obtained from the combustion of Jordanian oil shale

A characterization study was performed on the spent oil shale (oil shale ash) obtained from the combustion of Jordanian oil shale. This characterization utilized different analytical techniques. These include scanning electron microscope with energy dispersive spectrum analysis, X-ray fluorescence, X-ray diffraction and Qemscan. During the combustion process, minimal fragmentation was encountered since Jordanian oil shale contains large proportions of ash which maintain the original structure of the oil shale particle. Different analytical techniques confirmed that the dominant phase of minerals in the oil shale is calcite, which transforms, in parts, into anhydrite during combustion. Sulphur was found to be mainly of an organic source. This sulphur is combusted to produce SO₂ and then SO₃, which controls the sulphation reaction of the calcite. The dominant phase in the ash was the anhydrite in addition to the calcite, clays and calcium phosphate.     

Experimental study of the pyrolysis of waste bitumen for oil production

This work focuses on bitumen slow pyrolysis. Mass and energy yields of oil, solid and gas were obtained from pyrolysis experiments using a semi-batch reactor in a nitrogen atmosphere, under three non-isothermal conditions (maximum temperature: 450 °C, 500 °C and 550 °C). The effect of temperature on the product yields was discussed. The gas compositions were analysed using gas chromatography (GC) and the heating value of oil and solid residue was also measured. Using a thermo-gravimetric analyser, kinetic parameters were evaluated through Ozawa-Flynn-Wall (OFW) method. Results showed that oil yield is maximum at 500 °C (50%). Moreover, gas yield increased with increasing pyrolysis temperature from 18% to 36%. On the other hand, solid yield showed an opposite trend: it decreased from 39% to 32%. As regard energy yields, they showed a similar trend with the mass ones. H_2, CH₄, C₂H₄, C₂H₆ and C₃H₈ are the main components of the produced gas phase. It has been noticed that the recovery of bitumen to liquid oil through pyrolysis process had a great potential since the oil produced had high calorific value comparable with commercial fuels.     

Comparing product distribution and desulfurization during direct pyrolysis and hydropyrolysis of Longkou oil shale kerogen using reactive MD simulations

The product distribution and organic sulfur removal during direct pyrolysis and hydropyrolysis of oil shale kerogen were investigated via reactive molecular dynamics (RMD) simulations with reactive force field (ReaxFF). Two structural models for direct pyrolysis and hydropyrolysis of kerogen were constructed about kerogen extracted from Longkou oil shale to investigate the impact of H₂ at different temperatures on the product distribution and reaction processes of oil shale. The experimental results show that hydropyrolysis could increase light shale oil (the most important product in shale oil industry), and improve the removal rate of organic sulfur simultaneously. It was found that comparing to the direct pyrolysis, hydropyrolysis can provide more H free radicals to participate in the reaction and therefore promoting the pyrolytic reaction of kerogen. In addition, hydropyrolysis greatly promoted the desulfurization due to the contribution to the production of H₂O molecules, and the transfer of sulfur to the gas products requires the participation of H₂O molecules. This work is an intensive study on hydropyrolysis mechanism at different temperatures at the atomic level. These conclusions could be helpful for the clean utilization technology of oil shale industry.     

Structural model of Longkou oil shale kerogen and the evolution process under steam pyrolysis based on ReaxFF molecular dynamics simulation

ABSTRACT

The product distribution and reaction mechanism of steam pyrolysis of Longkou oil shale kerogen was researched by molecular dynamics simulation. Molecule structural model used in the simulation was constructed according to the analysis results of a series of detection about kerogen extracted from Longkou oil shale. Reactive force field molecular dynamics (ReaxFF MD) was used to simulate both steam pyrolysis and direct pyrolysis process of the kerogen at the temperature of 1600, 2000, 2400 and 2800 K. The results show that temperature is a critical factor affecting product distribution in steam pyrolysis, and 2000 K is a proper set temperature for studying steam pyrolysis via molecular simulation method. Besides that, adding the H₂O molecules during steam pyrolysis can form complexes with heterogeneous atoms, thus destroying the intermolecular interactions in kerogen. Moreover, as the hydrogen radicals come from H₂O molecules can inhibit cross-linking reactions between small fractions, it can reduce the average molecular weight of organic molecules product. These conclusions could be helpful for rational use of oil shale.     

Extracting oil from shale using solar energy

We used two solar receiver reactors, one fixed and the other fluidized, to study, on a laboratory scale, the pyrolysis of oil shale and the recovery of the volatile product. We observed the distribution of the products in a series of traps as well as the overall oil yield. Yields greater than the Fischer Assays can be obtained. The high temperatures obtainable with solar energy can also be used to pyrolize the substrate and remove CO₂.     

Mineral Matter Identification in Nallıhan Lignite by Leaching with Mineral Acids

Abstract

Coals are heterogeneous, complex noncrystalline macromolecules having both organic and inorganic materials that contain some inorganic constituents. Some techniques have been applied to this fossil fuel in order to remove these undesired inorganic parts from the organic part. Chemical demineralization is one of the suitable methods for removal of inorganic elements although it is an expensive way. But by this method, many elements are leached effectively from the lignite body from the point of economic view because these inorganic parts may cause some undesired deleterious effects. In this study, the demineralization effect of some aqueous acids of 5% such as HCl, H₂SO₄, HNO₃, and HF was studied. The effect of these mineral acids was shown by X-ray spectroscopy.     

CO2 gasification characteristics of nascent pyrolyzed particles from coals and oil shale

In this work, the co‐pyrolysis characteristics of oil shale with two typical coals, bitumite and lignite, and the co‐gasification characteristics of the mixture pyrolyzed fuels were studied via thermo‐gravimetric analysis. The individual fuels and mixture fuels were first pyrolysis in N₂ atmosphere to specified temperature (450, 550, and 620 °C) at the heating rate of 20, 30 and 40 °C/min, respectively, and then maintained at the given temperature for 20 min before converted to CO₂ ambient to conduct the CO₂ gasification tests. The kinetic behavior and effects of both fuel types and pyrolysis temperature were investigated. The shoulder peak at around 550 °C observed in the derivative of weight loss derivative thermogravimetry analysis (DTG) curve during the pyrolysis of oil shale has confirmed the existence of specific reactions of oil shale at around 550 °C that leads to a sharp trough in the differential curves of co‐pyrolysis with coals and the unusual change in activation energies of gasification. In isothermal pyrolysis stage, oil shale lost its vast majority of organic matters at the temperature lower than 550 °C. The escape of pyrolysis gas and liquids in the coals is much harder than that in oil shale. The interaction between oil shale and bitumite was too weak to discriminate both in the pyrolysis and CO₂ gasification process. The variation of the particle surface structure caused by the releasing of volatile gases is strongly affected by the reaction rate and temperature. Quick volatile decomposition and gas releasing lead to the increase of surface area, decrease of the average pore diameter as well as the uniformization of the pore structure, while the higher temperature results in the blockade and merging of fine pores. The two factors lead to the greatest mass loss rate in the pyrolyzed particles obtained at 550 °C in temperature programmed CO₂ gasification stage. Two model‐free methods, Friedman method and Flynn–Wall–Ozawa method, were used to extract kinetic parameters from the experimentally determined pyrolyzed fuel conversions. The volatile contend has a significant influence on the fixed carbon conversion during the partially pyrolyzed particles' CO₂ gasification. In this study, significant interactions existed in co‐thermal utilization, both pyrolysis and CO₂ gasification, of oil shale and lignite. It is therefore surmised that co‐gasification of pyrolyzed lignite and oil shale may represent a feasible, practical route to high‐efficiency utilization of these fuels. Copyright © 2017 John Wiley & Sons, Ltd.     

Impact of fast and slow pyrolysis on the degradation of mixed plastic waste: Product yield analysis and their characterization

This work primarily investigated the pyrolysis of post-consumer mixed plastic wastes during slow pyrolysis (non-isothermal) in a batch reactor to assess the effect of different heating rates on the product yield and its composition. The effect of residence time during fast pyrolysis (Isothermal) in Pyro-GC was also investigated. Initially, TG analysis was performed to investigate the degradation temperature range at different heating rates of 5, 10, 20 and 40 °C/min. Two different heating rates of 10 and 20 °C/min were selected for examining the effect on products such as oil and gases (H₂, CO, CO₂ and C₁-C₆ hydrocarbons) during slow pyrolysis. The oil obtained at higher heating rate had higher density (0.743 kg/m³) while the amount of residue decreased with the increase in heating rate. Also, the effect of residence time during fast pyrolysis was investigated using Pyro-GC at 500 °C for the product formation. It was observed that an optimum residence time of 10sec was favourable for the higher production of lower hydrocarbons (C₁-C₃) and less production of heavier hydrocarbons (C₆). This work represents the combined analysis of fast and slow pyrolysis and their impact on the product yield. Also, the effect of heating rate on non-isothermal condition and the effect of the residence time of volatiles in isothermal condition was analysed and reported.     

Effect of acid treatment on the physico-chemical properties of Nafion 117 membrane

In this work, the effect on the physico-chemical properties of Nafion 117 membrane due to the treatment with HCl, H₂SO₄ and HNO₃ was studied. Water uptake, crystallinity, proton conductivity and water dynamics were evaluated on treated and non-treated membranes. An increase in the water uptake and conductivity and a decrease in the crystallinity were observed in treated membranes in comparison with the untreated one. The water dynamics, studied by spin-spin NMR relaxometry, suggests that treated membranes have a more uniform channel size distribution. The treatment with HCl and HNO₃ showed higher conductivity and water uptake than H₂SO₄.     

Study of breakage of main covalent bonds during co-pyrolysis of oil shale and alkaline lignin by TG-FTIR integrated analysis

Pyrolytic vapor generated over different temperature ranges can be correlated with breaking of different groups of covalent bonds. In the present study, pyrolysis of oil shale and alkaline lignin was studied by thermogravimetry coupled with fourier transform infrared spectroscopy (TG-FTIR) analysis. As the dominant fraction of pyrolytic gaseous products, methane (CH₄) was selected as an entry point to track the breakage of main covalent bonds during pyrolysis of oil shale and alkaline lignin. Through applying the deconvolution method, overall CH₄ evolution and differential thermogravimetric (DTG) curves of pyrolysis of oil shale and alkaline lignin could be fitted by a series of sub-curves assigned to different groups of covalent bonds. This indicated that the mass loss of oil shale was mainly caused by the fracture of three groups of covalent bonds. In contrast, mass loss of alkaline lignin was mainly caused by the fracture of two groups of covalent bonds. Furthermore, detailed influence of co-pyrolysis on the cleavage of covalent bonds was also analyzed for different blending ratios of oil shale and alkaline lignin. The results revealed that co-pyrolysis of alkaline lignin and oil shale led to the enhancement in CH₄ yield by promoting the breakage of linkages. It was also found that among three groups of covalent bonds, the third was most significantly influenced due to reduction in its bond energy.     

Entrained flow gasification of straw- and wood-derived pyrolysis oil in a pressurized oxygen blown gasifier

Fast pyrolysis oil can be used as a feedstock for syngas production. This approach can have certain advantages over direct biomass gasification. Pilot scale tests were performed to investigate the route from biomass via fast pyrolysis and entrained flow gasification to syngas. Wheat straw and clean pine wood were used as feedstocks; both were converted into homogeneous pyrolysis oils with very similar properties using in-situ water removal. These pyrolysis oils were subsequently gasified in a pressurized, oxygen blown entrained flow gasifier using a thermal load of 0.4 MW. At a pressure of 0.4 MPa and a lambda value of 0.4, temperatures around 1250 °C were obtained. Syngas volume fractions of 46% CO, 30% H₂ and 23% CO₂ were obtained for both pyrolysis oils. 2% of CH₄ remained in the product gas, along with 0.1% of both C₂H₂ and C₂H₄. Minor quantities of H₂S (3 vs. 23) cm³ m⁻³, COS (22 vs. 94) cm³ m⁻³ and benzene (310 vs. 532) cm³ m⁻³ were measured for wood- and straw derived pyrolysis oils respectively. A continuous 2-day gasification run with wood derived pyrolysis oil demonstrated full steady state operation. The experimental results show that pyrolysis oils from different biomass feedstocks can be processed in the same gasifier, and issues with ash composition and melting behaviour of the feedstocks are avoided by applying fast pyrolysis pre-treatment.     

Effects of surface modification on the PEC performance of electrochemically deposited n-CdTe films

CdTe thin films were electrodeposited on Ni substrates from aqueous solutions containing CdSO₄, TeO₂ and H₂SO₄ with an interchangeable rotating disk electrode. The variations in the composition of the CdTe films with cathodic potentials and heat treatment temperatures were studied by the polarographic method. The deposition and annealing parameters had been optimized to yield a good photoelectrochemical performance. After surface modification, the conversion efficiencies were 0.61% and 5.3% for the cells p-CdTe/SnCl₂ (sat.), 0.2M HCl/C and n-CdTe/1 M Na₂S, 1 M S, 1 M NaOH/C, respectively.     

Thermogravimetric-Mass Spectrometric Study of the Pyrolysis Behavior of Shenmu Macerals Under Hydrogen and Argon

The pyrolysis characteristics of macerals separated from Chinese Shenmu coal were systematically investigated using TG-151 pressurized thermobalance coupling with mass spectrometer under 0.1 MPa of Ar and H₂, heating rate of 10°C/min and final temperature of 900°C. The TG/DTG results showed that vitrinite always had a higher volatile matter yield, larger maximum rate of weight loss, lower temperature of the maximum rate of weight loss than inertinite. Inertinite showed high response to the external hydrogen, especially at a higher temperature. The gases evolved during thermogravimetric analysis of macerals were analyzed on-line by mass spectrometer for the relative intensity of H₂O, C₁–C₄, and C₆H₆. An obvious difference in evolution curves could be observed. The content of all gases evolved from vitrinite was higher than those from inertinite in both atmospheres. The amount of H₂O and light hydrocarbons was higher in H₂ than that in Ar, indicating the hydrogenation of oxygen-containing functional groups and free radicals formed during pyrolysis. The evolution curves of H₂O and CH₄ had different peak distributions and evolution temperatures under H₂ and Ar, suggesting the different reaction mechanism during pyrolysis in different atmosphere. The evolution curves also revealed the different structural characteristics among vitrinite, inertinite and the parent coal.     

The effect of minerals on the pyrolysis and the combustion of oil shale

Oil shale (OS) is a particularly promising alternative fossil fuel source. However, very different from coal, its inorganic mineral content is very high. The organic matters (mainly kerogen) are finely distributed in the inorganic minerals. Therefore, the minerals may affect the processing of OS, whose elucidation is critical to the choice of processing conditions. In this work, different minerals (SiO₂, CaCO₃, and Al₂O₃) were added to OS with different mass ratios of OS to mineral, respectively. Then, the thermogravimetric (TG) technique was employed to analyze the reaction behavior of these different OS/mineral mixtures in N₂ and in air for studying the influence of minerals on the OS pyrolysis in N₂ (i.e., retorting) and on the OS combustion in air. The results show that CaCO₃ and Al₂O₃ have a promoting effect on both pyrolysis and combustion of OS, and they can decrease the reaction activation energy of both kinds of processes. However, SiO₂ has an inhibitive effect and can increase the reaction activation energy for both kinds of processes. It is hoped that the present study can further increase the understanding toward the effect of different minerals on the OS reactions.     

A comparative study of vegetable oil methyl esters (biodiesels)

In the present study, rubber seed oil, coconut oil and palm kernel oil, which are locally available especially in Kerala (India), are chosen and their transesterification processes have been investigated. The various process variables like temperature, catalyst concentration, amount of methanol and reaction time were optimized. Biodiesel from rubber seed oil (with high free fatty acid) was produced by employing two-step pretreatment process (acid esterification) to reduce acid value from 48 to 1.72 mg KOH/g with 0.40 and 0.35 v/v methanol-oil ratio and 1.0% v/v H₂SO₄ as catalyst at a temperature of 63(±2) °C with 1 h reaction time followed by transesterification using methanol-oil ratio of 0.30 v/v, 0.5 w/v KOH as alkaline catalyst at 55(±2) °C with 40 min reaction time to yield 98-99% biodiesel. Coconut oil and palm oil, being edible oils, transesterification with 0.25 v/v methanol-oil ratio, 0.50% w/v KOH as at 58(±2) °C, 20 min reaction time for coconut oil and 0.25% v/v methanol-oil ratio, 0.50% w/v KOH as alkaline catalyst at 60(±2) °C for palm kernel oil will convert them to 98-99% biodiesel. The brake thermal efficiency of palm oil biodiesel was higher with lower brake specific fuel consumption, but rubber seed oil biodiesel(ROB) showed less emission (CO and NO_x) compared to other biodiesels.     

In situ reactive extraction of Jatropha curcas L. seeds assisted by ultrasound: Preliminary studies

Esterification is required to reduce the high free fatty acid (FFA) content of crude Jatropha oil to below 3% prior to transesterification. In this study, raw decorticated Jatropha seeds were employed as the feedstock in in situ reactive extraction assisted by ultrasound in the presence of sulfuric acid (H₂SO₄) as a catalyst. Extraction efficiency, esterification efficiency, and fatty acid methyl ester (FAME) yield were optimized as a function of ultrasonic pulse mode, amplitude, and H₂SO₄ amount. The optimum extraction efficiency of 83.96%, esterification efficiency of 71.10%, and FAME yield of 38.58% were achieved at a pulse mode of 5 s on/2 s off, an ultrasonic amplitude of 60%, and an H₂SO₄ amount of 5 mL in reaction time of 150 min.