Hydrogen production from the aqueous phase derived from fast pyrolysis of biomass

Hydrogen production from the aqueous phase derived from fast pyrolysis of biomass was carried out by catalytic steam reforming in a fluidized bed reactor. The effects of reaction conditions such as reaction temperature, steam-to-carbon ratio (S/C) and weight hourly space velocity of the aqueous phase (WHSV) on the results of hydrogen yield, potential hydrogen yield and carbon selectivity of product gases were investigated. The effect of reaction temperature on the carbon deposition on catalyst was also studied. The hydrogen yield of 64.6%, potential hydrogen yield of 77.6% and the carbon selectivity for product gases of 84.3% can be obtained at the optimized conditions of reaction temperature 800 °C, S/C 10 and WHSV 1.0 h⁻¹.     

Catalytic pyrolysis of Phragmites (reed): Investigation of its potential as a biomass feedstock

In this paper, thermogravimetry, TG, and pyrolysis are used for the thermochemical evaluation of the common reed (Pragmites australis) as a candidate biomass feedstock. The TG analysis indicated that the material loses 4% of its weight below 150 °C through dehydration. The main decomposition reaction occurs between 200 and 390 °C. The rate of weight loss, represented by the derivative thermogravimetric, DTG, signal indicated a multi-step reaction. Kinetic analysis helped in the resolution of the temperature ranges of the overlapping steps. The first step corresponds to the degradation of the hemi-cellulosic fraction and the second to the cellulosic fraction degradation. The TG and DTG signals of reed samples treated with increasing concentration of potassium carbonate (0.6–10 wt%) indicated a catalytic effect of the salt on reed decomposition. The temperature of maximum weight loss rate, DTGmax, exponentially decreased with increasing catalyst content, whilst the initial temperature of the decomposition decreased linearly. The pyrolysis studies were carried out in a Pyrex vertical reactor with sintered glass disc to hold the sample and to aid the fluidization with the nitrogen stream flowing upwards. The reactor was connected to a cyclone and condenser and a gas sampling device. Tar and char are collected and weighed. The gas chromatographic analysis of the evolved gases demonstrated the effect of pyrolysis temperature (400, 450, and 500 °C) on their composition. The temperature increase favors the yields of hydrocarbons, carbon monoxide and hydrogen at the expense of methanol and carbon dioxide. Similarly, reed samples treated with K2CO3 at 10 wt% were pyrolyzed and analyzed. Comparisons for the various parameters (yields, gas composition and carbon–hydrogen recovery) between the untreated and catalyzed reed conversion were also made.     

Synthesis of multi-walled carbon nanotubes catalyzed by substituted ferrocenes

A range of substituted ferrocenes were used as catalysts for the synthesis of multi-walled carbon nanotubes (MWCNTs) and carbon fibers (CFs). These products were obtained in the temperature range 800-1000 °C, in a reducing atmosphere of 5% H₂ by pyrolysis of (CpR)(CpR′)Fe (R and R′ = H, Me, Et and COMe) in toluene solution. The effect of pyrolysis temperature (800-1000 °C), catalyst concentration (5 and 10 wt.% in toluene) and solution injection rate (0.2 and 0.8 ml/min) on the type and yield of carbonaceous product synthesized was investigated. Carbonaceous products formed include graphite film (mostly at high temperature; 900-1000 °C), carbon nanotubes and carbon fibers. The carbonaceous materials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The ferrocene ring substituents influenced both the CNT diameter and the carbon product formed.     

Thermal decomposition study on Jatropha curcas L. waste using TGA and fixed bed reactor

Pyrolysis experiments on Jatropha curcas L. (physic nut) waste were carried out using thermogravimetric analysis (TGA) and a fixed bed quartz reactor to determine suitable degradation model as well as investigate the effect of operating conditions on product distribution. It was found that the main thermal decomposition of physic nut waste generally occurred over the temperature range of 250–450 °C. The three-parallel reactions model was applied for simulating the degradation of this waste. The model agreed relatively well with the experimental data. From the model, the activation energy of hemicelluloses, cellulose and lignin was in the range of 41–68, 187–235, and 97–150 kJ/mol, respectively. Reaction orders of those fractions were in the range of 2.4–3.2. Results from pyrolysis process using fixed bed reactor indicated that increase in temperature and hold time lead to greater production of hydrogen, methane and light hydrocarbons with highest gas production detected at 900 °C. Tar decomposed at higher temperatures resulted in lower liquid yield while gas yield and total conversion increased. Liquid product consists of several fatty acids such as palmitic acid, stearic acid, and oleic acid in the range of 10–23%, 5–12%, and 35–42%, respectively. The amount of char residue decreased with increasing reactor temperature and hold time. Fixed carbon in char increased with temperature with the expense of volatile matter while there was little change on ash content. Generally, pyrolysis of this residue may be applied for the production of value-added products as well as fuels after some upgrading processes.     

Syngas production from pyrolysis–catalytic steam reforming of waste biomass in a continuous screw kiln reactor

A two-stage continuous screw-kiln reactor was investigated for the production of synthesis gas (syngas) from the pyrolysis of biomass in the form of waste wood and subsequent catalytic steam reforming of the pyrolysis oils and gases. Four nickel based catalysts; NiO/Al₂O₃, NiO/CeO₂/Al₂O₃, NiO/SiO₂ (prepared by an incipient wetness method) and another NiO/SiO₂ (prepared by a sol–gel method), were synthesized and used in the catalytic steam reforming process. Pyrolysis of the biomass at a rapid heating rate of approximately 40 °C/s, was carried out at a pyrolysis temperature of 500 °C and the second stage reforming of the evolved pyrolysis gases was carried out with a catalytic bed kept at a temperature of 760 °C. Gases were analysed using gas chromatography while the fresh and reacted catalyst was analysed by scanning electron microscopy, thermogravimetric analysis, transmission electron microscopy with energy dispersive X-ray and X-ray photoelectron spectroscopy. The reactor design was shown to be effective for the pyrolysis and catalytic steam reforming of biomass with a maximum syngas yield of 54.0 wt.% produced when the sol–gel prepared NiO/SiO₂ catalyst was used, which had the highest surface area of 765 m² g⁻¹. The maximum H₂ production of 44.4 vol.% was obtained when the NiO/Al₂O₃ catalyst was used.     

High effects of smoke suppression and char formation of Ni?Mo/Mg(OH)2 for polypropylene

The Ni? Mo/Mg(OH)₂ (NMM) hybrid as an efficient flame retardancy and smoke suppression composite for polypropylene (PP) was synthesized through Ni? Mo co‐precipitation on the surface of Mg(OH)₂ (MH) hexagonal nanosheets. Compared to PP/MH, PP/NMM exhibited excellent smoke suppressing and flame retardancy on the heat release rate, total heat release, smoke production rate, total smoke production, CO production rate and total CO production with the same loading. The reduced hazard of PP/NMM was mainly attributed to the high physical barrier effect of compact char residues on heat, smoke and combustible gas. The mechanism study indicated that multiwalled carbon nanotubes (MWCNTs) generated from the catalytic carbonization of PP by the Ni? Mo compound could play the role of “rebar” to strengthen the char residues, avoid the generation of cracks and form highly compact char layer. Furthermore, MgO could facilitate the production of MWCNTs through changing the pyrolysis process of PP and increasing the reaction time between pyrolysis gas and Ni? Mo compound. Hence, the new Ni? Mo/MH catalyst hybrid may explore the potential for solving the tough problem of the flammability and heavy smoke of the polyolefins system.     

Gas-liquid chromatographic determination of the gaseous products of the two-stage pyrolysis of heavy oils

The two-stage pyrolysis of fuel oil and vacuum residues separated from Egyptian crude oil have been carried out using a batch-type reactor technique. In the first stage, feedstocks undergo catalytic cracking in the presence of platinum as a catalyst at temperatures ranging between 380 and 460 °C and 440 and 520 °C for fuel oil and vacuum residues, respectively. Products are carried by argon gas for subsequent pyrolysis in the second stage at temperatures ranging between 700 and 820 °C and 700 and 800 °C for fuel oil and vacuum residues, respectively. The gas yields are about 94.1 and 82.0 wt% of the total products. The gases comprise saturated (C₁----C₅) and unsaturated hydrocarbons (ethylene, propylene, and butenes). By using platinum wire in the pyrolysis of fuel oil, the ethylene yield increases slightly as the temperature of the first stage increases, while it remains almost unchanged in the pyrolysis of vacuum residue. On the other hand, the propylene yield decreases slightly as the temperature of the first stage increases in the two feedstocks. By using a platinum sheet, the ethylene yield is doubled under the same conditions and increases slightly with an increase of temperature in the second stage. On the other hand, the propylene yield varies inversely with the temperature of the second stage by using platinum, whether as wire or sheet, although the yield is higher when platinum sheet is used under the same conditions.     

Thermal and catalytic degradation of pyrolytic oil from pyrolysis of municipal plastic wastes

Thermal and catalytic degradation of pyrolytic oil obtained from the commercial rotary kiln pyrolysis plant for municipal plastic waste was studied by using fluid catalytic cracking (FCC) catalyst in a bench scale reactor. The characteristics of raw pyrolytic oil and also thermal and catalytic degradation of pyrolytic oil using FCC catalyst (fresh and spent FCC catalyst) under rising temperature programming was examined. The experiments were conducted by temperature programming with 10 °C/min of heating rate up to 420 °C and then holding time of 5 h. During this programming, the sampling of product oil was conducted at a different degradation temperature and also different holding time. The raw pyrolytic oil showed a wide retention time distribution in GC analysis, from 5 of carbon number to about 25, and also different product characteristics with a comparison of those of commercial oils (gasoline, kerosene and diesel). In thermal degradation, the characteristics of product oils obtained were influenced by reaction temperature under temperature programming and holding time in the reactor at 420 °C. The addition of FCC catalyst in degradation process showed the improvement of liquid and gas yield, and also high fraction of heavy hydrocarbons in oil product due to more cracking of residue. Moreover, the characteristic of oil product in catalytic degradation using both spent and fresh FCC catalysts were similar, but a relatively good effect of spent FCC catalyst was observed.     

Gasification of Municipal Solid Wastes in Plasma Arc Medium

Many thermal processes have been developed in order to eliminate the municipal solid wastes or produce energy from them. These processes include a wide range of applications from the simplest burning system to plasma gasification. Plasma gasification is based on re-forming of molecules after all molecules convert to smaller molecules or atoms at high temperatures. In this work, the production of fuel gas is aimed by plasma gasification of municipal solid wastes in high temperatures. Because of this, a plasma reactor of the capacity of 10 kg h^?1 was designed which can gasify municipal solid wastes. Plasma gasification with and without steam and oxygen was performed in temperatures of 600, 800, 1000, 1200, 1400 and 1600 °C in the reactor. A gas mixture containing methane, ethane, hydrogen, carbon dioxide and monoxide, whose content varies with temperature, was obtained. It was found that plasma gasification (or plasma pyrolysis, PG), plasma gasification with oxygen (PGO) and plasma gasification with steam (PGS) were more prone to CO formation. A gas product which was consisted of 95% CO between 1200 and 1400 °C was produced. It was observed that a gas with high energy capacity may be produced by feeding oxygen and steam into the entrance of the high temperature region of the reactor.

     

Floating catalyst CVD synthesis of carbon nanotubes from CpFe(CO)2X (X = Me, I): Poisoning effects of I

Multiwalled carbon nanotubes (MWCNTs), carbon fibers (CFs) and carbon spheres (CSs) were synthesized by an injection chemical vapour deposition (CVD) method using toluene solutions of CpFe(CO)₂Me as catalyst. The effect of pyrolysis temperature (800-1000 °C), catalyst concentration (5 and 10 wt% in toluene) and solution injection rate (0.2 and 0.8 ml/min) on the type and yield of carbonaceous product synthesized was investigated. The carbonaceous materials were characterized by transmission electron microscopy (TEM), thermal gravimetric analysis (TGA) and Raman spectroscopy. The use of CpFe(CO)₂I as catalyst generated only carbon fibres and balls (wide range of conditions). Studies involving the addition of I₂ to catalyst solutions confirmed the poisoning effect of I on CNT production.     

Synthesis of straight and helical carbon nanotubes from catalytic pyrolysis of polyethylene

Straight and helical carbon nanotubes with diameter from 20 to 60 nm have been synthesized through catalytic decomposition of polyethylene in autoclave at 700 °C. The X-ray power diffraction pattern indicates that the products are hexagonal graphite, and transmission electron microscope (TEM) and high resolution transmission electron microscope (HRTEM) images reveal the morphologies and structures of carbon nanotubes. The effects of reaction temperature, catalyst and maleated polypropylene on the growth of the carbon nanotubes were also discussed, and the growth mechanism of the CNTs was proposed. Pyrolysis of polyethylene is a promising green chemical method for economically producing carbon nanotubes.     

Sustainable Diesel from Pyrolysis of Unsaturated Fatty Acid Basic Soaps: The Effect of Temperature on Yield and Product Composition

The production of sustainable diesel without hydrogen addition remains a challenge for low-cost fuel production. In this work, the pyrolysis of unsaturated fatty acid (UFA) basic soaps was studied for the production sustainable diesel (bio-hydrocarbons). UFAs were obtained from palm fatty acids distillate (PFAD), which was purified by the fractional crystallization method. Metal hydroxides were used to make basic soap composed of a Ca, Mg, and Zn mixture with particular composition. The pyrolysis reactions were carried out in a batch reactor at atmospheric pressure and various temperatures from 375 to 475 °C. The liquid products were obtained with the best yield (58.35%) at 425 °C and yield of diesel fraction 53.4%. The fatty acids were not detected in the pyrolysis liquid product. The gas product consisted of carbon dioxide and methane. The liquid products were a mixture of hydrocarbon with carbon chains in the range of C₇ and C₂₀ containing n-alkane, alkene, and iso-alkane.     

Investigation of physicochemical properties of biooils produced from yellow poplar wood (Liriodendron tulipifera) at various temperatures and residence times

Fast pyrolysis of yellow poplar wood (Liriodendron tulipifera) was performed under different temperature ranges and residence times in a fluidized bed reactor to maximize the yield of biooil. In this study, the pyrolysis temperature ranged from 400 °C to 550 °C, and the residence time of pyrolysis products was controlled between 1.2 and 7.7 s by inert nitrogen gas flow. The results revealed that the distribution of thermal degradation products (biooil, biochar, and gas) from the woody biomass was heavily influenced by pyrolysis temperature, as well as residence time. The highest yield of biooil was approximately 68.5 wt% (wet basis), with pyrolysis conditions of 500 °C and 1.9 s of residence time. Water content of the biooils produced at different temperatures was 25-30 wt%, and their higher heating values were estimated to be between 15 MJ/kg and 17 MJ/kg. Using GC/MS analysis, 30 chemical components were identified from the biooil, which were classified into 5 main groups: organic acids, aldehydes, ketones, alcohols, and phenols. In addition, biochar was produced as a co-product of fast pyrolysis of woody biomass, approximately 10 wt%, at temperatures between 450 °C and 550 °C. The physicochemical features of the biochar, including elemental analysis, higher heating values, and morphological properties by SEM, were also determined.     

Effect of carbon nanotubes and their dispersion on thermal curing of polyimide precursors

The process of thermal imidization reaction is significant for temperature and time control in the polyimide industry. Here, we report the effect of carbon nanotubes and their states of dispersion on the thermal imidization of the precursor films of polyimide (poly(amic acid)) for the first time. The curing process was followed by measuring Fourier transform-infrared (FT-IR) spectra, fluorescence spectra, thermogravimetric-differential scanning calorimeter (TG-DSC) properties and the refractive indices of films. It was found that by evenly dispersing 1 wt% of carbon nanotubes assisted by a dispersant in the poly(amic acid),the full imidization temperature of the polyimide can be reduced from 300 °C to 250 °C. Different states of distribution of CNTs were observed by light microscopy and scanning electron microscopy, and proved that a better dispersion of carbon nanotubes dramatically enhanced the speed of imidization. Moreover, the DSC results showed that lower decomposition temperature of poly(amic acid) could be obtained with more uniform distribution of carbon nanotubes, which means the process of cyclodehydration of the poly(amic acid) was accelerated.     

多壁碳纳米管的纯化

用900℃高温氢气处理以及5 mol/L盐酸回流的方法，纯化了一种由甲烷在Ni- Mg-O催化剂上裂解生长的多壁碳纳米管（MWCNTs），考察了不同纯化阶段MWCNTs的 吸水率、比表面积、Ni和Mg残留量以及在不同温度下苯、正己烷、乙醇、丙酮四种 化合物在MWCNTs填充色谱柱上的脱附率的变化，并用透射电镜观察了MWCNTs的形态 。结果表明，高温氢气处理可去除MWCNTs的无定形碳和表面极性基团，使其比表面 积和吸水率减小，同时可打开MWCNTs端口。高温氢气处理后，再用盐酸回流即容易 去除MWCNTs中单用盐酸回流方法无法去除的Ni.经过纯化的MWCNTs的吸水率远小于 活性碳，比Carbopack B稍大，比表面积和Carbopack B相近。苯、正己烷、己醇、 丙酮四种化合物在纯化的MWCNTs填充色谱柱上的脱附率和Carbopack B的相同。经 纯化的MWCNTs的Ni残留量为30 μg/g，Mg残留量低于检测限（10 μg/g）。由于管 腔的存在，纯化的MWCNTs对有机物的保留能力大于Carbopack B。它可以作为气相 色谱固定相和吸附挥发性有机物的吸附剂。     

Catalytical and thermal pyrolysis of polyolefins

Polyolefins have a high potential for alternative oil production since they contain only carbon and hydrogen atoms. By pyrolysis of these materials up to 95% can be obtained as oil and gas. Upgrading the products by catalytic cracking of polyolefins is a subject of growing interest in the last years as less energy is needed for the pyrolysis and more valuable products are formed. Numerous studies have been reported in which a variety of catalysts such as zeolites, silica-alumina, mesoporous MCM-41, solid acids and reaction conditions have been investigated. In our studies we used Lewis acids and mixtures of Ziegler–Natta catalyst such as TiCl₄, AlCl₃ to pyrolyse polypropylene. Experiments were carried out in a batch reactor as well as in a fluidized bed process. The pyrolysis temperature can be decreased by 100 °C compared to runs without catalysts. A drastic increase in the amount of low boiling compounds (C4 hydrocarbons) can be observed by the use of the catalysts instead of longer chained hydrocarbons.     

Influence of MWCNT morphology on dispersion and thermal properties of polyethylene nanocomposites

In this study a series of multi-walled carbon nanotube (MWCNT)/Polyethylene (PE) composites with different kinds and several concentrations of carbon nanotubes (CNTs) were investigated. The morphology and degree of dispersion of the fillers in the polymer matrix at different length scales was investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Both individual and agglomerated MWCNTs were evident but a good dispersion was observed for some of them. TGA measurements were performed on nanocomposites in order to understand if CNTs affect the stabilization mechanism during thermal and oxidative degradation. The analysis demonstrates that MWCNTs presence slightly delays thermal volatilisation (15-20 °C) without modification of thermal degradation mechanism. In contrast, thermal oxidative degradation in air is delayed up to about 100 °C dependently from MWCNTs concentration, in the range used here (0.1-2.0 wt%), and degree of dispersion. The stabilization is due to the formation of a thin protective layer of entangled MWCNTs kept together by carbon char generated on the surface of the nanocomposites as shown by SEM images taken on degradation residues.     

Formation of the main gas compounds during thermal analysis and pyrolysis: Betaine and betaine monohydrate

The thermochemical behaviour of betaine and betaine monohydrate was investigated under two degradation conditions. Betaine was heated up to 700°C at 10°C min^–1 in air and nitrogen flows and the evolved gas was analysed with the combined TG-FTRIR system. The evolved gas from betaine pyrolysis at 350 and 400°C was analysed by gas chromatography using mass-selective detection (Py-GC/MSD). In addition, the electron impact mass spectra of betaine and betaine monohydrate were measured.Esterification is one of the most important pyrolytic processes involving beta- ines. Even glycine betaine can change to dimethylglycine methyl ester via intermolecular transalkylation by heating. Trimethylamine, CO₂, and glycine esters were the main degradation products. Small amounts of ester type compounds evolved both in pyrolysis and with TG-FTIR. The monohydrate lost water between 35 and 260°C while the main decomposition took place at 245-360°C. The residual carbon burnt in air to CO₂ up to a temperature 570°C.This revised version was published online in November 2005 with corrections to the Cover Date.     

The effect of temperature,catalyst, different carrier gases and stirrer on the produced transportation hydrocarbons of LLDPE degradation in a stirred reactor

The pyrolysis of linear low density polyethylene (LLDPE) by used fluid catalytic cracking (FCC) catalyst was studied in a stirred reactor to reach the appropriate transportation hydrocarbons. In this work, the effect of process parameters such as degradation temperature, catalyst/polymer ratio (%), carrier gas type and stirring rate on the condensed yield, product composition and residence time were considered. Product evaluation was performed by GC analyzer and paraffin, naphthene, olefin and aromatic plus carbon number and average molecular weight of the products were measured under different process parameters.Temperature and catalyst as the basic parameters show remarkable effect on the LLDPE cracking. The maximum transportation condensate yield reaches at 450 °C and 20% catalyst respectively although increase of temperature and catalyst content, decrease the residence time patently. Based on the results, molecular weight and reactivity of the carrier gas as mass transfer factor also play a key role in the process. A decrease in molecular weight of the carrier gas led to increase the condensate yield and decrease the residence time. Meanwhile increasing of the carrier gas reactivity could increase the condensate hydrocarbons. Hydrogen as reactive and lower molecular weight carrier gas increases the condensed yield patently. The study showed that stirring rate as a function of heat transfer and temperature homogenizer also affects on the condensate hydrocarbons positively. The maximum condensate yield was found to occur at 50 rpm although the residence time decreases with stirring rate increasing.     

Pyrolysis of wood impregnated with phosphoric acid for the production of activated carbon: Kinetics and porosity development studies

The pyrolysis of impregnated wood for the production of activated carbon is investigated. Laboratory experiments are performed in a TG for heating rates of 10 °C/min and 20 °C/min and a mathematical model for the kinetics of the pyrolysis process is developed and validated. The effect of the temperature and of the time duration of the pyrolysis process on the specific surface of the activated carbon is examined on the basis of experiments conducted in a crossed bed reactor. Results indicate that the temperature and the residence time in the pyrolysis reactor may be optimised. Indeed, it is found that the maximum specific surface of the end product is obtained for pyrolysis processes conducted at a temperature of 400 °C for a time period of 1 h.