Flash pyrolysis of Silopi asphaltite in a free-fall reactor under vacuum

Flash pyrolysis experiments on asphaltite samples were performed in a free-fall reactor under vacuum to determine the effects of pyrolysis temperature, feed rate and particle size. Maximum liquid yield of 13 wt.% was obtained in free-fall reactor under vacuum when the pyrolysis temperature was 700 °C, feed rate was 0.4 g min⁻¹ and particle sizes were between 0.075 and 0.250 mm. The liquid products obtained at various pyrolysis conditions were analyzed by gas chromatography/mass spectrometer (GC/MS) and liquid products were classified as following: C5–C10, C11–C15, C16–C20 and C20+. The amount of saturated hydrocarbons decreased while the amount of unsaturated hydrocarbons increased with increase of temperature. While percent of C5–C10 unsaturated hydrocarbons continuously increased with increase of temperature, the percent of C11–C15 unsaturated hydrocarbons increased up to 750 °C and then started to diminish. Functional group analysis of solid residue was carried out using Fourier transform infrared spectrometry (FT-IR). The proximate analysis of solid residue indicated that percent of fixed carbon and ash increased with temperature.     

Pyrolysis of textile wastes: I. Kinetics and yields

Thermal behavior of textile waste was studied by thermogravimetry at different heating rates and also by semi-batch pyrolysis. It was shown that the onset temperature of mass loss is within 104–156 °C and the final reaction temperature is within 423–500 °C. The average mass loss is 89.5%. There are three DTG peaks located at the temperature ranges of 135–309, 276–394 and 374–500 °C, respectively. The first two might be associated with either with decomposition of the hemicellulose and cellulose or with different processes of cellulose decomposition. The third peak is possibly associated to a synthetic polymer. At a temperature of 460 °C, the expected amount of volatiles of this waste is within 85–89%. The kinetic parameters of the individual degradation processes were determined by using a parallel model. Their dependence on the heating rate was also established. The pyrolysis rate is considered as the sum of the three reaction rates. The pyrolysis in a batch reactor at 700 °C and nitrogen flow of 60 ml/min produces 72 wt.% of oil, 13.5 wt.% of gas and 12.5 wt.% of char. The kinetic parameters of the first peak do not vary with heating rate, while those of the second and the third peak increase and decrease, respectively, with an increasing heating rate, proving the existence of complex reaction mechanisms for both cases.     

Step-wise and one-step vacuum pyrolysis of birch-derived biomass to monitor the evolution of phenols

One-step and stepwise laboratory batch vacuum pyrolysis of a mixture of birch bark (ca. 46%) and birch sapwood (ca. 54%) was carried out in the temperature range 25–550°C. The pyrolysis oil (defined as the total condensates, including water and organics) was analyzed by GC–MSD and the quantity of phenols (referred to monolignols in this paper) was determined as a function of temperature. The active zone of decomposition and the maximum recovery of phenols were found to be in the temperature range 275–350°C. Distribution of phenols, charcoal and water as a function of temperature was investigated. Stepwise and one-step pyrolysis yielded total phenols of 4.43 and 2.51 wt.% (anhydrous feed basis), respectively. The yields of pyrolysis oil (62.39 wt.%), wood charcoal (23.25 wt.%) and gas ( 14.36 wt.%) produced by both methods were approximately similar, on an anhydrous feed basis.     

Liquid phase mononitration of chlorobenzene over WOx/ZrO2: A study of catalyst and reaction parameters

To study the effect of W concentration and activation temperature of the catalysts a series of WO_x/ZrO₂ samples with varying concentration of W (10–25 wt.%) were prepared and activated at 650/750 °C. XRD of sample shows 15 wt.% W stabilizes the tetragonal phase of zirconia up to 750 °C. Above and less than 15 wt.% shows peaks corresponding to monoclinic WO₃ and monoclinic ZrO₂, respectively. Further, the tungsten modification stabilizes the specific surface area of ZrO₂. There is an increase in the surface area observed up to 15 wt.% W, which declines on further increase in the concentration. The NH₃ TPD confirms the presence of acid sites with varying strength from the broad desorption profile. The 15 wt.% W and activated at 750 °C shows maximum acidity. The results of the nitration reaction of chlorobezene imply the 15 wt.% W and activation at 750 °C shows maximum activity. Not only yield, a better para-selectivity is also achieved with WO_x/ZrO₂ samples. Effect of activation temperature, W concentration and reaction parameters such as reaction temperature, reaction time, the presence of solvent and solvent free medium on activity and selectivity are studied in details.     

Thermal behaviour of lyocell fibres

Fourier-transform infrared (FTIR) spectroscopy has been applied in combination with wide-angle X-ray diffraction and measurements of strength, fluidity, yellowness, birefringence, and moisture regain to detect microstructural changes in lyocell fibres, a regenerated cellulose fibre, subjected to direct heat and annealing treatments. TMA, and SEM were used to show the effect of direct heat and annealing on lyocell fibres. The FTIR spectroscopy results show that a decrease in intermolecular hydrogen bonding occurs at 70 and 80 °C for annealed and directly heated samples, respectively. The results demonstrate increase of the intensity of O–H stretching vibrations, this associated with hydrogen bonds reforming around 130 °C. Lyocell fibres shrink with direct heating in the temperature range 130–160 °C. The crystallinity decreases gradually with increasing temperature. There is no significant change in colour of the samples annealed up to 150 °C. A continuous increase in the fluidity occurs for the annealed samples in the range 150–230 °C. The tenacity and breaking extension of heated samples decrease with increasing temperature. The lower annealing temperatures cause no observable change in the smooth and void-free surface, but in the annealing temperature range 170–230 °C, substantial non-uniformity is apparent on the surface of the fibres.     

Sinterability enhancement in semicokes obtained by controlled pyrolysis of a petroleum residue

Self-sintering semicokes were prepared by pyrolysis of an aromatic petroleum residue at 460–480 °C and pressures of 0.1–1.0 MPa. The evolution of gases and thermoplasticity from resultant semicokes were monitored by TGA and TMA, respectively. Sintering behaviour of the semicokes is extremely sensitive to pyrolysis conditions which determine contents of volatile matter and binder phase. Semicokes produced at 1.0 MPa have high volatile contents with excessive plasticity. Changes of temperature and soak time, used to reduce volatile matter contents induce reductions to the plasticity and sintering. A lower pyrolysis pressure has a similar effect. Although the operational window is narrow, heat-treated compacts (2500 °C) can be made with high density (1.9 g cm⁻³) and bending strengths >75 MPa. Using high-temperature pyrolysis (460 °C) with a post-treatment at 350–400 °C eliminates light components, without decreasing sintering properties. Compacts from these powders also exhibit high density (1.9 g cm⁻³) with higher bending strengths >90 MPa, comparable or superior to mesocarbon microbeads (MCMB) obtained from the same precursor.     

Thermochemical conversion of cellulose in polar solvent (sulfolane) into levoglucosan and other low molecular-weight substances

Pyrolysis of cellulose in sulfolane, an aprotic polar solvent, was conducted at the temperature between 200 and 330 °C. Sulfolane was used as a good solvent for levoglucosan, the major anhydromonosaccharide formed from cellulose pyrolysis, for prevention of the polymerization reaction. Cellulose was observed completely decomposed into soluble products in sulfolane within 3, 10, 60 and 480 min at 330, 280, 240 and 200 °C, respectively. The soluble products had molecular weights less than 500 after acetylation (GPC analysis) and similar product composition to that from cellulose pyrolysis under nitrogen (levoglucosan, levoglucosenone, furfural and 5-hydroxymethylfurfural by HPLC analysis). Pyrolysis of cellulose in polar solvent, which can solubilize anhydromonosaccharides, is proposed as a method for selective formation of levoglucosan and other low molecular-weight (MW) substances. As well, the cellulose pyrolysis in sulfolane did not suffer from carbonization reactions (microscopic and IR spectroscopic analysis) as did cellulose pyrolysis under nitrogen or in dioctyl phthalate (a poor solvent for levoglucosan) which gave brown/black solids. The residues obtained from the pyrolysis in sulfolane were colorless and gave similar IR spectra to that of the original cellulose. Based on these results, a ‘surface-peeling mechanism’ is proposed, and the role of the solvent in the mechanism is discussed.     

The direct synthesis of dimethyl ether from syngas over hybrid catalysts with sulfate-modified γ-alumina as methanol dehydration components

A series of γ-Al₂O₃ samples modified with various contents of sulfate (0–15 wt.%) and calcined at different temperatures (350–750 °C) were prepared by an impregnation method and physically admixed with CuO–ZnO–Al₂O₃ methanol synthesis catalyst to form hybrid catalysts. The direct synthesis of dimethyl ether (DME) from syngas was carried out over the prepared hybrid catalysts under pressurized fixed-bed continuous flow conditions. The results revealed that the catalytic activity of SO₄²⁻/γ-Al₂O₃ for methanol dehydration increased significantly when the content of sulfate increased to 10 wt.%, resulting in the increase in both DME selectivity and CO conversion. However, when the content of sulfate of SO₄²⁻/γ-Al₂O₃ was further increased to 15 wt.%, the activity for methanol dehydration was increased, and the selectivity for DME decreased slightly as reflected in the increased formation of byproducts like hydrocarbons and CO₂. On the other hand, when the calcination temperature of SO₄²⁻/γ-Al₂O₃ increased from 350 °C to 550 °C, both the CO conversion and the DME selectivity increased gradually, accompanied with the decreased formation of CO₂. Nevertheless, a further increase in calcination temperature to 750 °C remarkably decreased the catalytic activity of SO₄²⁻/γ-Al₂O₃ for methanol dehydration, resulting in the significant decline in both DME selectivity and CO conversion. The hybrid catalyst containing the SO₄²⁻/γ-Al₂O₃ with 10 wt.% sulfate and calcined at 550 °C exhibited the highest selectivity and yield for the synthesis of DME.     

Liquid-phase alkylation of phenol with long-chain olefins over WOx/ZrO2 solid acid catalysts

The liquid-phase alkylation of phenol with 1-dodecene was carried out over WO_x/ZrO₂ solid acid catalysts. The catalysts were prepared by wet impregnation method using zirconium oxyhydroxide and ammonium metatungstate. Catalysts with different WO₃ loading (5–30 wt.%) were prepared and calcined at 800 °C and catalyst with 15% WO₃ was calcined from 700–850 °C. All the catalysts were characterized by surface area, XRD, and FTIR. The catalyst with 15% WO₃ calcined at 800 °C (15 WZ-800) was found to be the most active in the reaction. The effect of temperature, molar ratio and catalyst weight on dodecene conversion and products selectivity was studied in detail. Under the optimized reaction conditions of 120 °C, phenol/1-dodecene molar ratio 2 and time 2 h, the catalyst 15 WZ-800 gave >99% dodecene conversion with 90% dodecylphenol selectivity. Comparison of the catalytic activity of 15 WZ-800 with sulfated zirconia calcined at 500 °C (SZ-500) and Hβ zeolite showed that activity of SZ-500 was lower than that of 15 WZ-800, while Hβ zeolite showed negligible activity. It is observed that the presence of water in the reaction mixture was detrimental to the catalytic activity of WO_x/ZrO₂. The catalyst 15 WZ-800 also found to be an efficient catalyst for alkylation of phenol with long-chain olefins like 1-octene and 1-decene.     

Zirconia-supported phosphotungstic acid as catalyst for alkylation of phenol with benzyl alcohol

The liquid-phase alkylation of phenol with benzyl alcohol was carried out using zirconia-supported phosphotungstic acid (PTA) as catalyst. The catalysts with different PTA loadings (5–20 wt.% calcined at 750 °C) and calcination temperature (15 wt.% calcined from 650 to 850 °C) were prepared and characterized by ³¹P MAS NMR and FT-IR pyridine adsorption spectroscopy. The catalyst with optimum PTA loading (15%) and calcination temperature (750 °C) was prepared in different solvents. ³¹P MAS NMR spectra of the catalysts showed two types of phosphorous species, one is the Keggin unit and the other is the decomposition product of PTA and the relative amount of each depends on PTA loading, calcination temperature and the solvent used for the catalyst preparation. The catalysts with 15% PTA on zirconia calcined at 750 °C showed the highest Brönsted acidity. At 130 °C and phenol/benzyl alcohol molar ratio of 2 (time, 1 h), the most active catalyst, 15% PTA calcined at 750 °C gave 98% benzyl alcohol conversion with 83% benzyl phenol selectivity.     

Pyrolysis of carbonaceous foundry sand additives: Seacoal and gilsonite

Seacoal and gilsonite are used by the foundry industry as carbonaceous additives in green molding sands. In this study, pyrolysis was used to simulate the heating conditions that the carbonaceous additives would experience during metal casting. Gas chromatography–mass spectrometry was used to tentatively identify major organic products generated during their pyrolysis at 500, 750, and 1000 °C. A number of compounds of environmental concern were identified during the pyrolysis of seacoal and gilsonite, including substituted benzenes, phenolics, and polycyclic aromatic hydrocarbons (PAHs). These thermal decomposition products, and especially PAHs, were generated at each pyrolysis temperature in all foundry sands containing seacoal. In gilsonite-amended sand, however, mainly alkanes and alkenes were identified at 500 and 750 °C and PAHs at 1000 °C. Compared to seacoal, the most intense peaks occurred during the pyrolysis of sand containing gilsonite. The greatest loss of pyrolyzable material also occurred during heating of gilsonite-amended sand from ambient temperature to 1000 °C in a thermogravimetric analyzer. The results obtained from this study will be useful to green sand foundries looking to reduce volatile hydrocarbon emissions.     

Use of a MDI-functionalized reactive polymer for the manufacture of modified bitumen with enhanced properties for roofing applications

In this study, the suitability of a reactive polymer, synthesized by reaction of 4,4′-diphenylmethane diisocyanate (MDI) with a low molecular weight polyethylene-glycol (PEG), as a modifying agent for the manufacture of bitumen-based waterproof membranes, was evaluated. With that purpose, rheological and thermal analysis tests, and microstructural observations by AFM were carried out on different samples of modified bitumen having a MDI–PEG content ranging from 0 to 10 wt.%, cured at room temperature for a period of time within 0–30 days. The results obtained demonstrate that the addition of the reactive polymer proposed in this work to bitumen is very suitable at high in-service temperatures, because a noticeable increase in the values of viscosity, at 60 °C, of the resulting modified bitumen samples is observed on a time-scale of days. AFM observations, carried out at 50 °C, evidenced that the reactive polymer MDI–PEG leads to a new microstructure, displaying a higher level of stiffness. Therefore, this polymer should be seriously taken into consideration as a modifier of bituminous coatings for the waterproofing industry.     

Thermal solid–solid interactions and physicochemical properties of NiO/Fe2O3 system doped with K2O

The effects of calcination temperature and doping with K₂O on solid–solid interactions and physicochemical properties of NiO/Fe₂O₃ system were investigated using TG, DTA and XRD techniques. The amounts of potassium, expressed as mol% K₂O were 0.62, 1.23, 2.44 and 4.26. The pure and variously doped mixed solids were thermally treated at 300, 500, 750, 900 and 1000 °C. The catalytic activity was determined for each solid in H₂O₂ decomposition reaction at 30–50 °C. The results obtained showed that the doping process much affected the degree of crystallinity of both NiO and Fe₂O₃ phases detected for all solids calcined at 300 and 500 °C. Fe₂O₃ interacted readily with NiO at temperature starting from 700 °C producing crystalline NiFe₂O₄ phase. The degree of reaction propagation increased with increasing calcination temperature. The completion of this reaction required a prolonged heating at temperature >900 °C. K₂O-doping stimulates the ferrite formation to an extent proportional to its amount added. The stimulation effect of potassium was evidenced by following up the change in the peak height of certain diffraction lines characteristic NiO, Fe₂O₃, NiFe₂O₄ phases located at “d” spacing 2.08, 2.69 and 2.95 Å, respectively. The change of peak height of the diffraction lines at 2.95 Å as a function of firing temperature of pure and doped mixed solids enabled the calculation of the activation energy (ΔE) of the ferrite formation. The computed ΔE values were 120, 80, 49, 36 and 25 kJ mol⁻¹ for pure and variously doped solids, respectively. The decrease in ΔE value of NiFe₂O₄ formation as a function of dopant added was not only attributed to an effective increase in the mobility of reacting cations but also to the formation of potassium ferrite. The calcination temperature and doping with K₂O much affected the catalytic activity of the system under investigation.     

The fate of As, Pb, Cd, Cr and Mn in a coal during pyrolysis

Transformation of As, Pb, Cd, Cr, and Mn in Chinese Datong coal during pyrolysis was studied. Experiments were carried out in a fixed-bed quartz reactor with a heating rate of 20 °C min⁻¹. Effects of the final temperature (300–1000 °C) and atmosphere (N₂ and H₂ at 0.1 MPa) were examined. Chemical form distribution of the elements in the coal and coal-derived chars (obtained at 1000 °C under N₂ and H₂) was investigated. As, Pb, Cr, Cd, and Mn in the coal and the chars were classified into five chemical forms (ion exchangeable, bound to carbonates, bound to Fe–Mn oxides, bound to organic matter, and in the residue) by a sequential dissolution method. Results show that As, Pb, and Cd are more volatile and tend to enrich in the volatile phase in the pyrolysis. Cr and Mn are relative non-volatile and tend to enrich in the solid phase. H₂ atmosphere promotes the release of the elements. The elements in all the five chemical forms undergo transformation in pyrolysis, and As, Pb, Cr and Cd show similar behavior.     

Measurements and particle resolved modelling of the thermo- and fluid dynamics of a packed bed

The objective of this study is to investigate experimentally and numerically into heat-up, drying and pyrolysis of a packed bed consisting of large single particles. The novelty of the current approach is that the numerical model contrary to continuum mechanic approaches considers a packed bed as an ensemble of a finite number of particles, which may have different material properties or sizes. The heat-up, drying and pyrolysis process of each particle is described sufficiently accurate by a set of one-dimensional and transient differential conservation equations for mass and energy. Applying this model to all particles, including interactions between them, of a packed bed forms the entire backed bed process as a sum of individual particle processes. The arrangement of particles within a bed defines a void space between the particles. The flow through the void space of a packed bed is modelled as a flow through a porous media taking into account interaction between the solid and the gaseous phase by heat and mass transfer. Experiments for drying and pyrolysis of a packed bed were carried out for validation in a temperature range of T=120–530 °C. The temperatures and the mass loss due to drying and pyrolysis were recorded during the experiments. The measured mass loss of the packed bed due to drying were well predicted by the constant evaporation temperature model of the particles and thus, indicating, that the drying process is transport limited by heat transfer for large wood particles in a temperature range of T=120–530 °C. A comparison between experiments and predictions of pyrolysis yielded reasonable agreement for temperatures above T=300 °C. For temperatures of T≈200 °C the deviations were not acceptable. However, the results show, that a particle resolved approach is well suited to describe packed bed processes.     

Synthesis of industrial scale NaY zeolite membranes and ethanol permeating performance in pervaporation and vapor permeation up to 130 °C and 570 kPa

NaY zeolite tubular membranes in an industrial scale of 80 cm long were synthesized on monolayer and asymmetric porous supports. The quality of synthesized membranes were evaluated by pervaporation (PV) experiments in 80 cm long at 75 °C in a mixture of water (10 wt.%)/ethanol (90 wt.%), resulting in higher permeation fluxes of 5.1 kg m⁻² h⁻¹ in the monolayer type membrane and of 9.1–10.1 kg m⁻² h⁻¹ in the asymmetric-type membranes, respectively. The uniformity with small performance fluctuation in longitudinal direction of the membranes were observed by PV for 10–12 cm long samples at 50 °C in a mixture of methanol (10 wt.%)/MTBE (90 wt.%). The ethanol single component permeation experiments in PV and vapor permeation (VP) up to 130 °C and 570 kPa were performed to determine the relations between the ethanol flux and the ethanol pressure difference across the membrane which is represented by permeance (Π, mol m⁻² s⁻¹ Pa⁻¹) for estimate of potential of ethanol extraction through the present NaY zeolite membranes applying feasible studies. Results indicate that (1) the permeation fluxes are linearly proportional to the driving force of vapor pressure for each sample in VP and PV. The permeances through an asymmetric support type membrane were rather constant of 0.6–1.2 × 10⁻⁷ mol m⁻² s⁻¹ Pa⁻¹ in the wide temperature range of 90–130 °C in PV and VP, indicating that the ethanol permeances have weak temperature dependency with the feed at the saturated vapor pressure.

The results of superheating VP experiments showed that ethanol permeation fluxes are increased with increasing of the degree of superheating at a given constant feed vapor pressure. The ethanol permeances are increased with increasing of temperature at a given feed vapor pressure. The superheating VP could be a feasible process in industry.     

Production of liquid fuels and chemicals from pyrolysis of Bangladeshi bicycle/rickshaw tire wastes

Tire wastes in the form of used bicycle/rickshaw tires available in Bangladesh were pyrolyzed in a fixed-bed fire-tube heating reactor under different pyrolysis conditions to determine the role of final temperature, sweeping gas flow rate and feed size on the product yields and liquid product composition. Final temperature range studied was between 375 and 575 °C and the highest liquid product yield was obtained at 475 °C. Liquid products obtained under the most suitable conditions were characterized by elemental analyses, FT-IR, ¹H NMR and GC–MS techniques. The results show that it is possible to obtain liquid products that are comparable to petroleum fuels and valuable chemical feedstock from bicycle/rickshaw tire wastes if the pyrolysis conditions are chosen accordingly.     

Measurement of glass transition temperature by mechanical (DMTA), thermal (DSC and MDSC), water diffusion and density methods: A comparison study

Glass transition measured by DMTA from the change in slope in storage modulus was 55 °C, which was 10.5 °C lower than the value measured by tan δ peak. Initial glass transition measured by DSC, increased exponentially and reached a constant value of 55 °C at or higher heating rate of 30 °C/min. Transition temperature, measured by MDSC, remained constant up to heating rate 15 °C/min and then decreased. The glass transition values determined from reversible heat flow was 60 °C. The break in diffusivity and density (i.e. volume) was observed at 50 °C below the glass transition temperature measured by thermal and mechanical methods.     

Pyrolytic synthesis of long strands of large diameter single-walled carbon nanotubes at atmospheric pressure in the absence of sulphur and hydrogen

We describe the synthesis of cm-long strands consisting of single-walled carbon nanotube ropes. The method involves the thermolysis of ferrocene (FeCp₂)–alcohol solutions under an Ar atmosphere at 800–950 °C. The tubes within strands could exhibit large diameters (2–3.5 nm OD) in high yields by either increasing the ferrocene concentration in the alcohol solution or by increasing the pyrolysis temperature. We noted that the nanotube material with the highest degree of crystallinity was produced at 950 °C, and as the ferrocene concentration in the alcohol solution increases (e.g., 1.2 wt%), the tubes tend to be metallic. This method appears to be simple, safer and more efficient than others reported in the literature because it does not require vacuum, sulphur agents, relatively high temperatures or large amounts of H₂.     

Catalytic effect of zinc oxide on the reduction of barium sulfate by methane

Reduction of barium sulfate by methane was investigated in this work. The thermogravimetric method was used to obtain kinetic parameters of the reaction in the temperature range of 900–975 °C at atmospheric pressure. The kinetics of the reaction has been studied both in the absence and presence of zinc oxide as a catalyst. The conversion–time data have been interpreted by using the grain model, and the effect of catalyst on the kinetic parameters has been elucidated. It was found that zinc oxide acted as fairly strong catalyst for the reaction, especially at higher temperatures. At about 975 °C the reaction rate constant was increased more than 7 times by using 2% of zinc oxide. This enhancement in the rate constant is valuable for industries.