Steam Pyrolysis Research Articles

Pyrolysis–gasification of post-consumer municipal solid plastic waste for hydrogen production

Post-consumer plastic waste derived from municipal solid waste was investigated using a two-stage, catalytic steam pyrolysis–gasification process for the production of hydrogen. The three important process parameters of catalyst:plastic ratio, gasification temperature and water injection rate were investigated. Temperature-programmed oxidation (TPO) and scanning electron microscopy (SEM) methods were used to analyse the reacted catalysts. The results showed that there was little influence of catalyst:plastic ratio between the range 0.5 and 2.0 (g/g) on the mass balance and gas composition for the pyrolysis–gasification of waste plastics; this might be due to the effective catalytic activity of the Ni–Mg–Al catalyst. However, increasing the gasification temperature and the water injection rate resulted in an increase of total gas yield and hydrogen production. The coke formation on the catalyst was reduced with increasing use of catalyst; however, a maximum coke formation (9.6 wt.%) was obtained at the gasification temperature of 700 °C when the influence of gasification temperature was investigated. The maximum coke formation was obtained at the water injection rate of 4.74 g h −1, and a more reactive form of coke seemed to be formed on the catalyst with an increase of the water injection rate, according to the TPO experiments.

Removal of Pb2+, Cd2+, Fe3+, and Sr2+ from Aqueous Solution by Selected Activated Carbons Derived from Date Pits

Date pits (DP) are a huge solid waste in Egypt and are of little or no economic value and in fact present a disposal problem. The quantity of DP has been estimated at a million tons per year. DP have been used for the preparation of physically and chemically activated carbons. The raw materials were physically activated with steam or chemically by impregnation with 10% ferric chloride or calcium acetate. The present study deals with the factors affecting the uptake of (Pb2+, Cd2+, Fe3+, and Sr2+) as pollutants from aqueous solution using activated carbon developed from locally available material DP, by a one‐step steam pyrolysis in a batch mode. The effect of various factors—carbon type, carbon dosage, pH, initial concentration, and temperature on the adsorption capacity were quantitatively determined. The two equilibrium models, the Langmuir and Freundlich equations, were discussed. In this work, analyses and batch adsorption experiments have been carried out to characterize and understand the adsorption mechanism by modeling the adsorption kinetics. Concurrently removal of these cations from the aqueous medium were found to be affected by the presence of some anions, NO3 −, CO3 −2, SO4 −2 and masking agents, oxalic acid, and EDTA in solution.

Aluminized Steel and Zinc Coating for Reduction of Coke Formation in Thermal Cracking of Naphtha

Rate of coke formation during steam pyrolysis of naphtha has been investigated in a laboratory CSTR reactor both for uncoated SS321 and metal coating constructed with thermal spray method with metal powders of aluminum, aluminum-magnesium and zinc. Rate of coke formation was studied in different temperatures and amount of coke as a function of run time has been studied too. The results of the study show that passivating the surface of SS321 with a coating of aluminum and aluminum-magnesium can significantly reduce the rate of coke deposition during naphtha pyrolysis. The results obtained from zinc coated show decoking carry out during thermal cracking. The scanning electron microscope (SEM) was carried out for morphology studied of coke deposited on the different metal surfaces.

One-Step Steam Pyrolysis Preparation and Characterization of Spherical Carbon Adsorbents Obtained from Ion-Exchange Resins

Using the single-set steam pyrolysis of Dowex 50 WX-2 (a polystyrene-divinylbenzene resin), Spherical Carbon Adsorbents (SCAs) were prepared. The porous structure of the materials obtained was easily controlled by varying the heating rate, allowing carbons having a controlled ratio of micropores to mesopores to be obtained. These materials are promising for the adsorption of phenol from aqueous solutions. Moreover, due to the relatively small amount of irreversibility exhibited in such adsorption, they could find potential use in environmental protection.

Conversion of olive wastes to volatiles and carbon adsorbents

Abstract Investigations for the utilization of olive stones and solvent-extracted olive pulp are carried out. Tar, solid and gas products are obtained by pyrolysis of both precursors under vacuum and atmospheric pressure. Vacuum pyrolysis causes a decrease in the solid yield and an increase in the liquid and gas yields. The identified compounds of the liquid products are predominantly oxygen-containing structures (derivatives of phenol, dihydroxybenzenes, guaiacol, syringol, vanilin, veratrol, furan, acids). Activated carbons with a developed porous structure and alkaline character of the surface are produced by steam activation of the solid product and steam pyrolysis of the raw material. Oxidation treatment with air leads to the formation of a large number of oxygen functional groups with different chemical characters on the carbon surface. Chemical activation with K2CO3 allows the preparing of carbon adsorbents with a high surface area and alkaline character of the surface.

Effects of activation schemes on porous, surface and thermal properties of activated carbons prepared from cotton stalks

Cotton stalks were used to obtain activated carbons by one-step processes using both chemical activation by H 3PO 4 or KOH, and thermal activation by steam pyrolysis. Porosity characteristics were determined from the analysis of N 2 adsorption isotherms using both BET and Langmuir equations as well as α S- and t-method. The results showed that the lignocellulosic content of cotton stalks was carbonized via different suggested mechanisms depending mainly on the activating agent. Highly to good porous carbons were obtained and the porosity increased in the order KOH > H 3PO 4 > steam. For the acid-activated series, the best porous carbon, that having S α of 841 m 2/g, was obtained from the acid-to-stalks ratio of 3:4 by weight. The biggest KOH-ratio of 3:1 gave a carbon with much higher microporosity and the biggest specific surface area among those prepared carbons ( S α = 1307 m 2/g). Cotton stalks showed a good response to single-step steam activation. Steam treatment at 600 °C resulted in a limited developed porosity, whereas an increase in temperature to 700 °C led to a considerable increase in porosity and yielded a carbon of S α 722 m 2/g. Thermogravimetric study showed that acid-treatment shifts the main decomposition of cotton stalks to much higher temperatures indicating an increase in thermal stability and carbon yield. Scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) investigations evidenced that the presence of opened-pore structure and different functionalities on the carbon surfaces based, principally, on the activation scheme. The results also showed that cotton stalks, as low cost, are well suited to produce high quality activated carbons composed of a wide range of porosity that could achieve high removal capacity to a broad range of pollutants.

Adsorption of nitrilotriacetic acid onto activated carbon prepared by steam pyrolysis of sawdust: Kinetic and isotherm studies

Abstract Nitrilotriacetic acid (NTA) adsorption onto sawdust activated carbon was studied. The adsorption process was highly pH dependent and has been explained on the basis of pH zpc and speciation of NTA in aqueous solution. In order to optimize the adsorption process, effect of pH, contact time, adsorbent dose, and ionic strength were studied using batch experiments. Equilibrium studies were performed to evaluate the adsorption capacity and adsorption energy of SDAC for the removal of NTA from aqueous phase. Langmuir model best describes the equilibrium adsorption data than Freundlich model. Ionic strength also played an important role in the process of adsorption and lower ionic strength favoured NTA adsorption. The mechanism of NTA adsorption onto SDAC was explained by inner sphere mechanism.

Conversion of Fuel-N into HCN and NH3 During the Pyrolysis and Gasification in Steam: A Comparative Study of Coal and Biomass

Conversion of fuel-N into HCN and NH3 during the pyrolysis and gasification of coal and biomass in steam were compared using fluidized-bed/fixed-bed and two-stage fluidized-bed/tubular reactors. During the pyrolysis and gasification of coal and biomass in steam, the thermal cracking of volatile-N was the main route for the formation of HCN while a small amount of HCN was formed from the breakdown of relatively unstable N-containing structures in char. Our results indicate that once the fuel-N in both biomass and coal is condensed/polymerized into the solid-phase char-N during the gasification in steam, the main nitrogen-containing gaseous product from char-N would be NH3. However, the thermal-cracking/reforming of volatile-N constitutes an additional important route of NH3 formation during the gasification of biomass (e.g., cane trash) in steam while this route is negligible for the gasification of coal. The selectivity of char-N toward HCN and NH3 is largely controlled by char-N stability and/or the availability of H and/or other radicals during the gasification of coal and biomass.

Adsorption of fluoride in aqueous solutions using KMnO 4-modified activated carbon derived from steam pyrolysis of rice straw

Fluoride in drinking water above permissible levels is responsible for human and skeletal fluorosis. In this study, activated carbons (AC) prepared by one-step steam pyrolysis of rice straw at 550, 650, 750 °C, respectively, were modified by liquid-phase oxidation using HNO 3, H 2O 2 and KMnO 4. Characterization of these 12 carbons was made by their surface area, porosity, acidity, basicity, pH pzc, pH and ability to remove fluoride anion. Based on the data of the latter factor, the RS 2/KMnO 4 carbon was selected. Along with batch adsorption studies, which involve effect of pH, adsorbate concentration, adsorbent dosage, contact time, temperature, and Co-ions (SO 4 2−, Cl −, Br −). The effects of natural organic matter (NOM) were also made to remove the fluoride from natural water. On the basis of kinetic studies, specific rate constants involved in the adsorption process using RS 2/KMnO 4 carbon was calculated and second-order adsorption kinetics was observed. Equation isotherms such as Langmuir (L), Freundlich (F), Langmuir–Freundlich (LF) and Dubinin–Radushkevich (DR) were successfully used to model the experimental data. From the DR isotherm parameters, it was considered that the uptake of F − by RS 2/KMnO 4 carbon proceeds by an ion-exchange mechanism ( E = 10.46 kJ mol −1). The thermodynamic parameters of fluoride sorption were calculated and the sorption process was chemical in nature. The ability of RS 2/KMnO 4 to remove F − from Egyptian crude phosphoric acid (P 2O 5 = 48.42%) was tested and the adsorption capacity of F − in H 3PO 4 was greater than that in distilled water. This is may be due to fluoride adsorption enhanced at lower pH of crude acid.

Improvement of thermal reactivation of activated carbon for the removal of 2-methylisoborneol

Rapid small-scale column tests (RSSCTs) were employed to evaluate the impact of the dissolved oxygen (DO) concentration in the water used to create steam on the reactivation of spent granular activated carbon (GAC) using three novel thermal reactivation procedures: steam-curing, steam-curing with ramped temperature, and steam pyrolysis reactivation. Evaluation of the physical properties of the reactivated carbon showed a change in mass and volume loss with a change in DO. Performance testing of the carbons for removal of the taste- and odor-causing compound 2-methylisoborneol (MIB) showed that MIB uptake generally increased as the DO concentration decreased. Decrease in MIB removal with an increase in surface acidity, a phenomenon found in the literature, may be responsible for the changes in adsorption performance, as the higher DO concentrations yielded carbons with higher total surface acidity. In addition, the steam-curing process, which was implemented at 375 °C (i.e. about 400 °C lower than typical reactivation temperatures) with a low DO concentration (i.e. 3–4 mg/L) had comparable performance to the virgin carbon counterpart, which could manifest cost-savings due to the low temperature associated with this protocol compared to conventional reactivation. Furthermore, since the mass loss associated with this steam-curing protocol was low, less virgin carbon make-up would be required also improving the economic viability of this reactivation protocol.

Comparative analysis of pyrolysis oils and its subfractions under different atmospheric conditions

In this paper comparative analysis of bio-oils and their subfraction from static, sweeping gas and steam pyrolysis of apricot pulp, a food industry waste, was investigated. Experimental studies were conducted in a well-swept fixed-bed reactor with a heating rate of 5 °C min− 1, to a final pyrolysis temperature of 550 °C. The oil yield which was 22.4% at the static atmosphere reached to the value of 23.2% in the sweeping gas atmosphere by using 100 cm3 min− 1 N2 flow rate. The yield of liquid product in steam pyrolysis was higher (27.2%) than the static and inert gas atmosphere.The elemental analyses of the pyrolysis oils were determined, and the chemical compositions of the oils were investigated using chromatographic and spectroscopic techniques. The liquid products were fractionated into pentane solubles and insolubles (asphaltenes). Pentane solubles were then solvent fractionated into pentane, toluene, and methanol subfractions by fractionated column chromatograpy. The aliphatic subfractions of the oils were then analysed by capillary column gas–liquid chromatography and GC/MS. For further structural analysis, the pyrolysis oils' aliphatic, aromatic and polar subfractions were conducted using FTIR and 1H NMR spectra.

Characterization and application of activated carbon produced by H 3PO 4 and water vapor activation

Activated carbons have been prepared from woody biomass birch by using various activation procedures: a) treatment with phosphoric acid and pyrolysis at 600 °C in inert atmosphere, b) the same as in (a) followed by steam activation at the same temperature and c) treatment with phosphoric acid and direct pyrolysis in a stream of water vapor at 700 °C. The surface area and the porosity of the activated carbons were strongly dependent on the treatment after impregnation with H 3PO 4 (pyrolysis in inert atmosphere, steam pyrolysis or combination of both). Activated carbon, prepared by impregnation with phosphoric acid followed by steam pyrolysis (steam activation) had highly developed porous structure and the largest surface area among all prepared carbons (iodine number 1280 mg/g and BET surface area 1360 m 2/g). The adsorption capacity of this sample for Hg(II) from aqueous solution was studied in varying treatment conditions: contact time, metal ion concentration and pH. The adsorption followed Langmuir isotherms and the adsorption capacity for Hg(II) at 293 K was 160 mg/g.

Silica -Titania Glass Fibers from Polytitanosiloxanes: Effect of Polymerization Mechanism on Mechanical Properties

SiO2 -TiO2 glass fibers have been prepared via dry spinning of the viscous solutions of polytitanosiloxanes followed by steam treatment and pyrolysis at 500, 700, and 900 °C for 1 h under ambient condition. The polymer was prepared via polycondensation of partially hydrolyzed tetraethoxysilane (TEOS) and an acetylacetone-chelated titan compound at various H2O/TEOS and Si/Ti ratios. Gel fibers formed shown tensile strength as low as 200 MPa and increased around 3 times after pyrolysis. The higher degree of TEOS hydrolysis the higher tensile strength of the fibers. The polymer with higher Si/Ti ratio also provided stronger fibers due to more extensive siloxane network. Fibers with the highest tensile strength, 610 MPa, was obtained from the polymer synthesized with SiO2/TiO2 mol ratio 20 and pyrolysis temperature 700 °C.

Production of bio-fuels from cottonseed cake by catalytic pyrolysis under steam atmosphere

Abstract The purpose of this study is to evaluate the amounts of catalytic pyrolysis products of cottonseed cake in steam atmosphere and investigate the effects of both zeolite and steam on pyrolysis yields. The effect of steam was investigated by co-feeding steam at various velocities (0.6:1.3:2.7 cm s −1 ) in the presence of zeolite (20 wt% of feed). Liquid pyrolysis products obtained at the most appropriate conditions were fractionated by column chromatography. Elemental analysis and FT-IR were applied on both of these liquid products and their sub-fractions. The H/C ratios obtained from elemental analysis were compared with the petroleum products. The aliphatic sub-fractions of the oils were then analysed by capillary column gas chromatography. Further structural analysis of pyrolysis oil was conducted using 1 H-NMR spectroscopy. The characterization has shown that the bio-oil obtained from catalytic and steam pyrolysis of cottonseed cake was more beneficial than those obtained from non-catalytic and catalytic works under static and nitrogen atmospheres.

Synthesis and characterization of a new nanoporous carbon material with a bimodal pore system

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Effect of Feedstock Hydrocarbon Composition on the Distribution of Products of Initiated Pyrolysis

Thermal steam pyrolysis of hydrocarbon feedstock in tube furnaces is a strategic process all over the world in production of basic semifinished products in petrochemistry — ethylene and propylene, the basic feedstock for production of plastics, synthetic fibres, rubber, detergents, etc. [1]. Its share of ethylene and propylene production is 100 and 67%, respectively [2–4]. In addition to lower olefins, benzene, whose share in world production is 39 wt. %, is also manufactured by this process [5].

Superheated steam pyrolysis of biomass elemental components and Sugi (Japanese cedar) for fuels and chemicals

To develop a novel noncatalytic biomass refinery process that can be used as a portable process, superheated steam pyrolysis was investigated to produce both carbonized solid fuels and chemicals using a large-scale reactor. Individual biomass components and native biomass ( Sugi, Japanese cedar) were pyrolyzed. Between 150 and 400 °C, the vaporizing fractions of cellulose, xylan, and kraft lignin were summarized using a numerical model. Cellulose was converted to glycolaldehyde, furfural, 5-hydroxymethyl furfural and levoglucosan, whereas xylan was converted to glycolaldehyde, furfural, and acetic acid. Kraft lignin produced a slight yield of phenol and guaiacol. The total vaporization fraction of Sugi and its vaporizing rate were explained sufficiently using a numerical model based on the weighted average of the vaporizing properties of the individual components. However, the yields of phenol, guaiacol, and acetic acid were underestimated, while the yields of furfurals and levoglucosan were overestimated. Possible synergetic effects among chemicals in the superheated steam pyrolysis of native biomass were also discussed.

Systematics and modeling representations of naphtha thermal cracking for olefin production

Thermal cracking or steam pyrolysis of hydrocarbons could convert them into valuable raw materials, which can be used in the petrochemical industry for polymer production. The reaction mechanisms of naphtha cracking are generally accepted as free-radical chain reactions. Unfortunately, the absence of a simple predictive applied model of pyrolysis is an obstacle to the development of practical methods of conversion. In an attempt to overcome this problem, the application of an analytical semi-empirical model (ASEM) of pyrolysis to the hydrocarbons thermal cracking results has been examined. The ASEM was developed at the University of Florida for organizing experimental data on pyrolysis products of coal, biomass, and alternative fuels (CBAF). This model has been adapted using industrial data for the pyrolysis yields of naphtha reported by Arak Petrochemical Company (APC) in Iran. The absence of oxygen in the naphtha feedstock minimizes the functional groups represented in the products and greatly simplifies the analysis. It is found that similar regularities of the product yields emerge from this effort as in CBAF cases. The results suggest that the analytical methodology should be useful for organizing pyrolysis yields of other hydrocarbons. Furthermore, the simplifications suggest that further experimental data would be helpful in the development of improved and more general models of solid feedstock pyrolysis for many thermo-chemical engineering applications.

The Influencing Factors of the Catalytic Pyrolysis Processes and Their Product Distribution

: Compared with conventional steam pyrolysis, catalytic pyrolysis has its own particular advantages. It can widen the range of pyrolysis feedstocks, increase the yields and selectivity of light olefins, reduce energy cost, and flexibly adjust product distribution. The influencing factors on catalytic pyrolysis processes and their product distribution, such as pyrolysis equipment, feedstock properties, catalyst types, and operating conditions have been reviewed in this paper. All of these factors have significant effects on the catalytic pyrolysis processes and their product distribution. Among these factors, feedstock properties and catalysts are the two key influencing factors.

Sulphur functionality study of steam pyrolyzed “Mequinenza” lignite using reductive pyrolysis technique coupled with MS and GC/MS detection systems

Atmospheric pressure–temperature programmed reduction (AP-TPR) and its analogous in oxidative atmosphere coupled “on-line” with a mass spectrometer (MS) were used to study the behaviour of organic sulphur forms of “Mequinenza” lignite during their mild steam pyrolysis. The obtained data were confirmed and completed by the AP-TPR-GC/MS “off-line” analysis. Samples under study were pyrolyzed at different processing parameters (temperature and flow gas). Some peculiarities in the distribution of non-thiophenic sulphur forms depending on experimental conditions were found. Namely, their amounts decreased with temperature increase at the steam treatment. The experiment performed at 500 °C in water vapor flow proved the C–S bond splitting in dibenzothiophene with biphenyl formation. Sulphonic acid compounds were also systematically removed. At higher temperature of the steam pyrolyzed treatment, this effect was more pronounced. At the same time, a relative increase in sulphones was found. The following organic sulphur species in demineralised lignite were detected by the “off-line” AP-TPR-GC/MS technique: methyl- and benzenethiols; mono- and disulphides; alkylthiolanes; alkenyl thiophenes; alkylbenzo[ b]thiophenes and alkyldibenzo[ bd]thiophenes. Their relative intensities as a function of temperature were followed. A strong preponderance of benzo[ b]thiophene and its alkylated homologues above 450 °C were observed. Thiophene presence was temperature independent.