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This study examined the effects of microwave (MW) and ultrasonic (US) waves on an heavy crude oil sample from a reservoir in southwest Iran. The waves irradiated the sample from two to 10 min at two-minute steps. MW caused the temperature of the crude-oil sample to rise by selective heating of polar components and creation of hot zones; under US, heating was accompanied by a cavitation effect. MW at 2 and 4 min reduced the sample’s viscosity by inducing hot zones. At 2 min, the viscosity declined 16% due to cracking of heavy components such as asphaltenes, which have a higher capacity to absorb MW. As the radiation time increased after 4 min, the viscosity increased because light components escaped from the sample. However, US reduced the viscosity of the heavy crude oil sample at all time durations. The greatest reduction of viscosity was around 19%, at 4 min. The viscosity increased with irradiation time and then remained constant. Ultrasonic waves altered the viscosity by creating bubbles, which disintegrated the resin intermolecular bonds and cracked the large molecular particles of the asphaltene. The reduction in sulfur content under US was much greater than under MW. At all time durations, sulfur content fell as radiation time increased. Due to its high potential to absorb MW, creates active sulfur that can be emitted from the crude oil as sulfide and hydrogen sulfide, with the sulfur level falling to 0.39%. Furthermore, US waves also reduced sulfur content to around 0.46% as the asphaltene flocks disintegrated. Reduction of sulfur content from asphaltene agglomerates under MW and US was observed using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). In addition to reducing the effect of sulfur by affecting its nitrogen and oxygen elements, irradiation also reduced the polarity of the asphaltene particles and prevented reaggregation of cracked particles. Results of SARA (saturation, aromatic, resin and asphaltene) analysis showed that asphaltene particles have a higher capacity to absorb MW than resin components, as after the amount of asphaltene components declined in the early stages of irradiation, resin components began to change, falling to 34% at 10 min. The decrease in asphaltene content in samples under US was more evident, reaching 34% at 8 min. According to Fourier transform infrared (FTIR) spectra results, MW irradiation caused cracking of large-chain molecules and drove light components from heavy crude sample. These two phenomena are a function of radiation time. The rate of cracking of heavy components was continuously greater than the rate of light components leaving the sample at early time intervals; ultimately, this resulted in an upgraded heavy oil. In some cases, despite cracking of large-chain molecules and creation of light components, the output values of light components were higher. Under US, the cracking of large-chain molecules occurred, but due to the departure of heavy components from the crude oil, peak intensities increased and the resulting crude oil had purer components. [ABSTRACT FROM AUTHOR]

A detailed kinetic model consisting of 833 reactions has been developed to describe the thermal cracking of n -butylcyclohexane at high pressure (100 bar). A primary mechanism was written in an exhaustive manner whereas a partial secondary mechanism was considered to describe the formation and the consumption reactions of aromatic compounds. The model was tested against our experimental data for BCH pyrolysis at 100 bar in the temperature range 375–425 °C. A global agreement was reached for BCH conversion up to 50% for both conversion and product yields e.g. propane, cyclohexane and toluene. Flow analysis of the proposed mechanism at a conversion of 35% shows that both alkanes (i.e. methane, ethane, propane and n -butane) and cycloalkanes (i.e. cyclohexane, methylcyclohexane and ethylcyclohexane) mainly come from the breaking of the side alkyl chain. The production of butylbenzene is due to the direct dehydrogenation of BCH whereas other alkylaromatic compounds i.e. benzene, toluene and ethylbenzene seem to come from the breaking of the side alkyl chain of butylbenzene rather than aromatization of cycloalkanes or alkylcyclohexenes. At 100 bar and around 400 °C, breaking of alkyl side chain reactions prevail on dehydrogenation reactions and ring opening. [ABSTRACT FROM AUTHOR]

Two-step hydrotreatment experiments were performed using three completely different bio-oil fractions namely: whole bio-oil, heavy bio-oil obtained after fractional condensation of pyrolysis vapours and pyrolytic lignin obtained by cold water precipitation of the bio-oil. The aim is to study the de-oxygenation and in addition SEC and UV-fluorescence analysis was used to identify the importance of cracking, polymerization and hydrogenation reactions of the three different bio-oil feedstocks. In the first step hydrotreatment, Ru/C was used at 250 or 300 °C with reaction time of 2 h. In the second step hydrotreatment, Ni-Mo/Al 2 O 3 catalyst was used at 375 or 400 °C, with reaction time of 2 or 4 h. During stabilization in the first step, pyrolytic lignin was hydrogenated to a large extent accompanied by cracking reactions. In the second step, unsulphided Ni-Mo/Al 2 O 3 catalyst was active enough to effectively crack pyrolytic lignin into smaller molecules. High molecular weight compounds including large aromatic ring structures were formed from the reactive sugar rich fraction in both first step stabilization and second step hydrotreatment. The newly formed polymerization products were difficult to crack even at extended reaction times of 4 h at 400 °C. Importantly, the presence of water (and light oxygenates) could significantly supress the polymerization reactions. [ABSTRACT FROM AUTHOR]

Cracking–Deoxygenation process is one of the important reaction pathways for the production of biofuel with desirable n- C 17 hydrocarbon chain via removal of oxygen compounds. Calcium-based catalyst has attracted much attention in deoxygenation process due its relatively high capacity in removing oxygenated compounds in the form of CO 2 and CO under decarboxylation and decarbonylation reaction, respectively. In the present study, deoxygenation of triolein was investigated using Ca(OH) 2 nanocatalyst derived from low cost natural waste shells. The Ca(OH) 2 nanocatalyst was prepared via integration techniques between surfactant treatment (anionic and non-ionic) and wet sonochemical effect. Results showed that sonochemically assisted surfactant treatment has successfully enhanced the physicochemical properties of Ca(OH) 2 nanocatalyst in terms of nano-particle sizes (∼50 nm), high surface area (∼130 m 2 g−1), large porosity (∼18.6 nm) and strong basic strength. The presence of superior properties from surfactant treated Ca(OH) 2 nanocatalysts rendered high deoxygenation degree, which are capable of producing high alkane and alkene selectivity in chain length of n-C 17 (high value of C 17 /( n -C 17 + n -C 18 ) ratio = 0.88). Furthermore, both Ca(OH) 2 –EG and Ca(OH) 2 –CTAB nanocatalysts showed high reactivity with 47.37% and 44.50%, respectively in total liquid hydrocarbon content of triolein conversion with high H/C and low O/C ratio. [ABSTRACT FROM AUTHOR]

Underground coal gasification (UCG) allows in situ conversion of unmineable coal deposits into a combustible gas. UCG involves a number of steps, including combustion, oxidation–reduction (REDOX) reactions, pyrolysis, and drying, within the gasification channel at high temperatures. Pyrolysis, in particular, plays a vital role in UCG. We herein investigated the pyrolysis behavior of lump lignite from Inner Mongolia, China, and investigated the influence of pyrolysis on the swelling behavior of the lump lignite. The samples (50 × 40 × 40 mm 3 ) were studied at a heating rate of 3 °C/min. The resulting chars were analyzed by scanning electron microscopy and Fourier transform infrared spectroscopy. In addition, the composition of the pyrolysis gas released from lump lignite was compared with that released from particle lignite (particle diameter = 1 mm). The results showed that obvious swelling between 100 and 600 °C, followed by subtle swelling events between 600 and 900 °C. The concentrations of H 2 and CO gases in lump lignite were higher than those in particle lignite when exposed to elevated temperatures, and the main functional groups disappeared at high temperatures due to thermal cracking. Consequently, pyrolysis occurring in the gasification channel converted the coal around the channel into a highly porous char whose permeability aided the transport of gasification agents and product gases in coal seam. [ABSTRACT FROM AUTHOR]

Hydrocarbon pyrolysis concerns many different fields (petroleum geochemistry, refinery, fuel thermal stability, pyrocarbon deposition, etc.). It is therefore studied in a wide variety of temperature–pressure experimental conditions, which strongly affect the chemistry of hydrocarbons cracking. An experimental study of the pyrolysis of n -octane has been performed at very low reactant concentration (1 mbar diluted in inert gas − total pressure 1500 mbar − molar fraction 0.07%) in a closed reactor, at temperatures ranging between 350 °C and 450 °C, and reaction time from 1 h to 70 h. The major products of the reaction are 1-alkenes (C 2 H 4 to C 7 H 14 ), methane and ethane; other alkanes (C 3 H 8 to C 6 H 14 ) are minor products. At 450 °C and 4 h, the conversion is close to 9% and we observe, in terms of molar fractions: C 2 H 4 > C 3 H 6 ≈ CH 4 > C 4 H 8 > C 5 H 10 > C 6 H 12 ≈ C 2 H 6 > C 7 H 14 These experimental results are very different from those of the thermal decomposition of n -alkanes at the same low temperature but at high pressure. In particular, the cracking stoichiometric equations (for example: C 8 H 18 = C 6 H 14 + C 2 H 4 ) are not observed since alkanes (except methane and ethane) are in very low quantities. This can be explained by the very low concentration of reactant which limits the bimolecular reactions. In our conditions, the radicals decompose several times by beta-scissions of CC bonds when it is possible (unimolecular reaction), rather than react by H-transfers (metathesis) with the reactant (bimolecular reaction) which produce alkanes. A detailed free radical mechanism (184 reactions, 16 molecules and 18 radicals— mechanism available as Supplementary material) allows modeling the experimental results. [ABSTRACT FROM AUTHOR]

We studied the pyrolysis of n -butylcyclohexane at high pressure (100 bar) in a gold sealed tube reactor between 300 and 425 °C. The conversion obtained was between 3% and 99%. Pyrolysis led to 3 main chemical classes of products: (a) n -alkanes (methane, ethane, propane and butane), (b) naphthenes (cyclohexane, methylcyclohexane, methylcyclopentane) and (c) alkylbenzenes (benzene, toluene, butylbenzene). This distribution of major products does not suggest any ring opening during thermal cracking, but rather breaking of alkyl side chains along with aromatization. The early production of butylbenzene at low conversion indicates that aromatization occurred first. We proposed pathways mainly based on free-radical reactions to account for the formation of major pyrolysis products i.e., propane, cyclohexane, methylcyclopentane and butylbenzene. Experimental data enabled us to determine apparent global kinetic parameters under the assumption of a first-order rate: frequency factor A = 6.7 × 10 16 s −1 and activation energy E a = 69 kcal/mol. We made several comparisons between n -alkanes, aromatic compounds and naphthenes, to observe the relative thermal stability of different classes and the influence of the length of an alkyl side chain. Data from the literature at high pressure or simulations from validated kinetic models were used. For the same carbon number, thermal stabilities of naphthene and n -alkane are similar, whereas the equivalent aromatic compound is less stable. This observation only seems valid for long alkyl side chains, as methylated compounds are much more stable than other alkylated ones, whether these are aromatic or naphthenic. [ABSTRACT FROM AUTHOR]

A typical petroleum refinery makes use of vacuum gas oil by cracking the large molecular weight compounds into light fuel hydrocarbons. For various types of fast pyrolysis bio-oil, successful analogous methods for processing heavy fractions could expedite integration into a petroleum refinery for fuel production. This paper investigated the applicability of bio-oil distillation residues (i.e., ‘bottoms’) toward end-use and/or post-processing through the use of various physical and chemical characterization methods, including FTIR, NMR and their decomposition in a micropyrolyzer (Py–GC–MS). We compared distillate bottoms from both the recently developed tail-gas reactive pyrolysis (TGRP) and traditional pyrolysis bio-oils, emanating from switchgrass and horse manure feedstocks. Based on the FTIR and NMR measurements, we found the traditional bio-oil bottoms to contain more reactive functional groups, whereas TGRP bottoms are highly aromatic and exhibit a lack of functional groups. Manure-based bottoms consistently contained more aliphatic carbons than those of switchgrass origin. However, irrespective of the origin of the feedstock, all bottoms samples possessed high HHVs making them suitable for solid fuel application, such as direct combustion (30 MJ/kg for traditional bio-oil bottoms; 37 MJ/kg for TGRP bottoms). A preliminary evaluation using Py–GC–MS to test their suitability for use in refinery cracking processes revealed that the TGRP-based bottoms all produced significant yields of pyrolyzate (20–50%), with nearly all detected compounds comprising alkyl benzenes and alkyl phenols. However, the manure-based TGRP bottoms produced a higher proportion of C 8 –C 18 paraffin compounds. [ABSTRACT FROM AUTHOR]

Abstract: A combination of pyrolysis-GC/MS and TLC–FID techniques were used for whole sample analysis of bio-oil samples obtained from different liginocellulosic biomasses, (i.e., birch wood, pine wood, barley straw and forest residue and thermal-cracking fractions). Both techniques showed the ability to analyze the whole sample without cleanup or fractionation and to distinguish among the bio-oils based on their feedstock sources. The TLC–FID is a chromatographic method whereby the oil solution is spotted on a TLC rod, developed by a two solvent system and the chromatographic bands measured by flame ionization detection (FID). The Py-GC/MS instrument uses a sample cup and a vertical microfurnace to analysis bio-oils. The non-volatiles fraction remaining in the cup were weighed after thermal evaporation-GC/MS. The hardwood birch bio-oil was shown to have syringol and its derivatives compared to pine wood and barley straw bio-oils that were shown to have methoxyphenolic and non-methoxy-phenolic compounds, respectively. TLC–FID shows clear differences in the peak areas and shapes for the bio-oils fractions by solvent development on chromarods and are in agreement with the results obtained by Py-GC/MS. Furthermore, forest residue bio-oil and its thermal cracking fractions could be effectively characterized by TLC–FID (and Py-GC/MS) whereby the light fraction was composed of a wide range of lower polarity compounds while middle and heavy fraction had higher polarity compounds. [Copyright &y& Elsevier]

Abstract: Batch-mode pyrolysis of 200.0g samples of polymers was studied at low temperature. The cracking reaction was carried out in a stainless-steel autoclave with reaction temperatures of 360, 380, 400 and 420°C, initial pressure of 6.325kPa (absolute pressure) and reaction times of 0–240min. Based on the experimental results, a four-lump kinetic model has been developed to describe the production distribution of the light fractions, middle distillates and heavy fraction. This model reasonably fitted the results in each reaction of operation conditions. It was also found that the pyrolysis kinetics of separated plastic, mixed plastic and mixed plastic containing additives can be described by the same kinetic model. The plastic additives have not had a great influence on the product distribution and kinetics of the mixed plastic pyrolysis. Finally, the optimum conditions of low-temperature conversion of plastic mixtures to value-added products were established. The formation of heavy fractions from HDPE was as high as 70wt% at 380°C at a reaction time of 250min. During the thermal degradation of plastic mixtures, the heavy fractions yielded up 50wt% for 30min reaction time at 400°C. The total activation energies for the conversion of HDPE and the plastic mixtures were estimated to be 217.66kJmol−1 and 178.49kJmol−1, respectively. [Copyright &y& Elsevier]

Abstract: Thermolysis of tetrafluoroethylene at ≤500°C is well-known to lead to equilibration with octafluorocyclobutane; at ≈600°C this mixture forms hexafluoropropylene; and at slightly more forcing conditions the latter is converted to octafluoroisobutylene (and/or octafluoro-2-butene). This chain-elongation behavior contrasts with the familiar cracking of non-fluorinated olefins and the thermodynamic rationale is provided herein. Several mechanisms have been proposed in the literature without a clear choice. Kinetic modeling herein of available product/kinetic data with use of current thermochemical and kinetic parameters supports a key role for difluorocarbene formed from dissociation of tetrafluoroethylene. Arbitrary selection between unfortunately inconsistent available measurements and/or computations of elementary rate constants, with modest adjustments, allowed data matches with either a direct insertion into an olefinic C–F bond or an addition to the olefin to give a 1,3-biradical followed by a 1,2-fluorine shift. In contrast, a 1,2-fluorine shift in the starting olefin to generate a carbene, followed by carbene combination, seems unlikely. However, the modeling was only partially successful, especially for hexafluoropropylene as feed which seems a comparatively inefficient source of difluorocarbene. This highlights the need for improved experimental thermolysis data at low conversion, independent elementary rate constants for key steps, and enthalpies of formation of fluorocarbons and their reactive intermediates, especially C3F6. [Copyright &y& Elsevier]

Abstract: On the basis of development in the laboratory, the SiO2/S coating was prepared on the internal surface of HK40 alloy tube in a pilot plant setup. The coating sampled on the outlet of furnace tube was characterized by scanning electron microscope (SEM). The anti-coking property of the SiO2/S coating was evaluated with light naphtha according to pressure changes. The morphologies and chemical components of cokes on the outlet of the coated and blank tubes were characterized by SEM and energy dispersive spectroscopy (EDS), respectively. The main product yields of light naphtha steam cracking were analyzed by gas chromatography–mass spectrometry (GC–MS). The results show that the SiO2/S coating is compact and has a thickness of 15μm on the outlet of furnace tube. The SiO2/S coating reduces coke yield by 60% compared to that observed in the blank tube during 8h cracking run. However, the coke reductions of the SiO2/S coating are both about 40% when the cracking time is 26h and 66h, respectively. The outlet of the coated tube has the exfoliated coke with a thickness of about 30μm. The coke on the process side has many irregular particles, and the coke on the metal side is not filamentous coke but amorphous coke particles after the exfoliated coke is taken away. The yield of C2H4 has a slight increase in the coated tube, and the yield of C4H8 has a decrease. However, the SiO2/S coating has little influence on the total yield of olefin. [ABSTRACT FROM AUTHOR]

Abstract: The effect of temperature, steam-to-naphtha ratio, and residence time and their quadratic and cubic interactions on the yield of light olefins (ethylene and propylene) in naphtha steam cracking has been investigated. The temperature, steam-to-naphtha ratio, and residence time were varied in the range 1053–1153K, 0.5–0.9g/g, and 0.15–0.4s, respectively. Based on the experimental results, naphtha steam cracking was modeled by use of statistical design of experiments (DoE). The results for the successful multiobjective optimization (MOO) of the naphtha steam cracking have also been reported. The new developed model is employed for the optimization purposes. Two MOO problems are solved; these problems involved maximization of ethylene, propylene and selectivity and minimization of severity. The response defined by the three most significant parameters was obtained from full factorial design and the optimal parameter set was found. The superiority of the DoE method over the conventional change one separate factor at a time approach is shown by the fact that we were able to study the higher interactions and optimize three individual factors with only 27 runs. [Copyright &y& Elsevier]

Abstract: The thermal cracking and the thermal catalytic cracking of soybean oil were evaluated for the production of biofuels as an alternative to fossil fuels. The catalyst proposed for the cracking reaction was bauxite, a high-acidity and low-cost catalyst. The chromatographic profile of the biofuels obtained by cracking showed hydrocarbon compounds such as alkanes, alkenes and aromatics, as well as some oxygenated compounds such as carboxylic acids, ketones and alcohols. The products generated by the thermal catalytic cracking process showed better results than the thermal cracking products because of the low quantity of acids present. The catalyst used was thus shown to act in the secondary cracking process, in which the fatty acids decompose and generate hydrocarbons. [Copyright &y& Elsevier]

Abstract: Thermal cracking of kerosene for producing ethylene and propylene has been studied in an experimental setup. A set of experiments were designed using Response Surface Design (Box Behnken) method. In these experiments, the coil outlet temperature (COT), residence time and steam ratio varied from 795°C, 0.13s and 0.6 to 838°C, 0.27s and 1.0, respectively. Obtained maximum ethylene and propylene yield in these experiments were 32 and 16.9wt.%, respectively. In next step of studies, we tried to develop an applicable kinetic model to predict yield distribution of products of the kerosene thermal cracking. Therefore, a reaction mechanism is generated on the basis of major reactions classes in the pyrolysis and feed compounds using some simplification assumptions in the model. This semi-mechanistic kinetic model contains 172 reactions, 22 molecular and 29 radical species. A sensitivity analysis was done on kinetic model and controlling reactions identified. An objective function was defined and used to tune the model with experimental data. Finally, the calculated model results were compared with the experimental data. Scatter diagrams showed good agreement between model and experimental data. [Copyright &y& Elsevier]

Abstract: The steam cracking (copyrolysis) of naphtha with oils/waxes from thermal decomposition of polyalkenes has been investigated as a process for chemical recycling of plastic wastes. High-density polyethylene (HDPE), two-component mixture (LDPE/PP) and three-component mixture (HDPE/LDPE/PP) were thermally decomposed in a batch reactor at 450°C, thus forming oil/wax products. Subsequently, these products were dissolved in heavy naphtha in the amount of 10 mass% to obtain steam cracking feedstock. The composition of gaseous and liquid products during copyrolysis was studied at 780°C and 820°C in dependence on residence time from 0.08s to 0.51s. The obtained results were compared with the product composition from steam cracking of naphtha at identical experimental conditions. The decomposition of polyalkene oils/waxes during copyrolysis was confirmed on the basis of analysis of liquid products. It was shown that more ethene and propene was formed during copyrolysis of oil/wax from HDPE in comparison with naphtha and both mixtures and so oil/wax from HDPE seems to be favourable component of steam cracking feedstock. There were slight differences between product compositions from copyrolysis of two- and three-component mixtures. The presence of HDPE in three-component mixture supported formation of gas and ethene. The presence of oil/wax form PP enhanced formation of propene and branched alkenes. For both type of polyalkenic mixtures the yields of desired low molecular alkenes and alkanes were higher or approximately the same as from naphtha. The results confirm suitability of oils/waxes from polyalkenes as a co-feed for steam cracking units. [Copyright &y& Elsevier]

The present paper shows that it is possible to carry out the thermal decomposition of solid particles followed, by the partial cracking of the evolved vapours, inside a cyclone rector heated at its walls. The results obtained with isocyanuric acid and with biomass particles are reported. From a mathematical model, it is possible to derive the kinetic constants of the gas phase cracking reactions. The results obtained with both solids are very similar. It is concluded that the thermal reaction of isocyanuric acid can be used as a model reaction for simulating the thermal cracking of the vapours formed during the fast pyrolysis of biomass. [Copyright &y& Elsevier]