Second-stage Reaction Research Articles

Molecular-level kinetic modelling for the pyrolysis of high-density polyethylene in a two-stage process

A two-stage process has been developed for the pyrolysis of high-density polyethylene to obtain light olefins, where probable mechanisms for each stage pyrolysis were proposed in our previous study. This work aims to establish molecular-level kinetic models for the first-stage pyrolysis at a lower temperature and for the second-stage pyrolysis at a higher temperature, respectively, to predict the overall reaction performances in accordance to the role of detailed mechanisms. A structure-oriented lumping (SOL) method based molecular-level kinetic model can effectively describe the first-stage pyrolysis, while a detailed molecular-level kinetic model is developed for the second-stage pyrolysis to track the evolutions of all alkanes, olefins, and diolefins, with special focus on the formation of light olefins. The established separate models can achieve the automatic generation of complex reaction networks and present good agreement with experimental data obtained from the first- and second-stage. In addition, the first-stage model indicates that the random scission plays an important role in the pyrolysis process at lower temperatures, while the chain-end scission mechanism dominates the second-stage reaction to produce light olefins at higher temperatures. As a whole, the molecular-level modelling scheme behaves excellently at a wide range of temperature, which provides guidance for upgrading the pyrolysis process.

Self-actuated microfluidic chiplet for two-stage multiplex nucleic acid amplification assay.

Effective diagnosis of comorbidities and infectious diseases that present similar symptoms requires point-of-need assays capable of co-detecting and differentiating among multiple co-endemic pathogens to enable timely, precision medicine and effective control measures. We previously developed a two-stage isothermal amplification assay dubbed Penn-RAMP to address this need. Penn-RAMP's first stage comprises a recombinase polymerase amplification (RPA), which amplifies all targets of interest in a single reaction chamber for a short duration. The RPA amplicons are then aliquoted into multiple loop-mediated isothermal amplification (LAMP) reaction chambers, each customized with pre-dried primers to amplify a single target or a group of targets. To enable Penn-RAMP at the point of need, we describe here a self-actuated Penn-RAMP chiplet that accommodates the Penn-RAMP assay. Our chiplet employs temperature-controlled phase change valves and capillary valves to self-aliquot first-stage amplicons into multiple (five) second-stage reaction chambers and to seal these chambers. The functionality of our device is demonstrated by co-detecting plant pathogens. The analytical performance of our chiplet is comparable to that of the benchtop Penn-RAMP assay and surpasses that of standalone LAMP assays. Our self-actuated chiplet can be operated standalone with purified nucleic acids or as the downstream amplification module of a sample preparation cassette.

Precursor decomposition mechanism of In2O3 powder for oxide ceramic targets

In this study, precursor decomposition as well as nucleation and growth processes during the preparation of In2O3 powders via chemical precipitation were investigated. This is to provide guidance for the preparation of high-quality In-based oxide target powders. In-situ phase and microstructure evolution during thermal decomposition of precursors were analyzed. In addition, decomposition behavior of precursors at different heating rates was explored. Results show that amorphous In(OH)3 precursor powder gradually decomposes and transforms into crystalline In2O3 powder during heating process. Its degree of crystallinity increases with the increase in temperature. Fine and homogeneous In2O3 powder with average grain size of 54.46 nm was obtained by holding the powder at 770 °C for 3 h. The decomposition of precursors at any given heating rate can be divided into two stages: (i) dehydration and (ii) nucleation and crystallization. However, higher heating rate clearly results in temperature hysteresis effect, the occurrence of decomposition reaction at higher temperature, and an increase in the maximum reaction rate of decomposition reaction. Moreover, activation energy of thermal decomposition was obtained using model-free transformation method. Decomposition reaction model of In(OH)3 precursor was established using model-fitting method. It was deduced that first-stage reaction mechanism is three-dimensional diffusion. Reaction rate in this stage is controlled by product layer diffusion. Furthermore, second-stage reaction mechanism is random nucleation and subsequent growth. Reaction rate in this stage is controlled by nucleation and growth rates.

Enhanced oxidation of urea by pH swing during chlorination: pH-dependent reaction mechanism

Urea reacts with chlorine to form chlorinated ureas (chloroureas), and fully chlorinated urea (tetrachlorourea) is further hydrolyzed into CO2 and chloramines. This study found that the oxidative degradation of urea by chlorination was enhanced by the pH swing, wherein the reaction proceeded under an acidic pH (e.g., pH = 3) in the first stage, and the solution pH was subsequently increased to a neutral or alkaline value (e.g., pH > 7) in the second-stage reaction. The degradation rate of urea by pH-swing chlorination increased with increasing chlorine dose and pH during the second-stage reaction. The pH-swing chlorination was based on the opposite pH dependence of sub-processes comprising urea chlorination. The formation of monochlorourea was favored under acidic pH conditions; however, the subsequent conversion into di- and trichloroureas was favored under neutral or alkaline pH conditions. The deprotonation of monochlorourea (pKa = 9.7 ± 1.1) and dichlorourea (pKa = 5.1 ± 1.4) was suggested to be responsible for the accelerated reaction in the second stage under increased pH conditions. pH-swing chlorination was also effective in degrading urea at low concentrations (micromolar levels). In addition, the total nitrogen concentration significantly decreased during the degradation of urea because of the volatilization of chloramines and the release of other gaseous nitrogen compounds.

Interaction of metallic magnesium with ammonia: Mechanochemical synthesis of Mg(NH2)2 for hydrogen storage

Mg(NH2)2-2LiH is one of the most promising hydrogen storage systems to be applied in hydrogen powered vehicles as hydrogen source. However, the synthesis of the main raw material Mg(NH2)2 is high-cost and time-consuming for the present technologies. Herein, we report a low-cost, time-saving and low-carbon method to synthesize Mg(NH2)2 by mechanochemical reaction of metallic Mg with ammonia. After 72 h of mechanochemical reaction, amorphous Mg(NH2)2 is successfully synthesized by milling metallic Mg and ammonia at room temperature. A two-stage reaction is demonstrated to be responsible for the conversion of Mg and ammonia into Mg(NH2)2. In the initial process of ball milling, Mg particles tend to clump and agglomerate because of the ductility of metallic Mg. The first reaction stage between metallic Mg and ammonia occurs at the surfaces and interfaces of bulk Mg to form MgH2 and Mg(NH2)2 powders. With prolonged milling time, the size of bulk Mg decreases with milling time due to the continuous occurrence of the first-stage reaction. The second-stage reaction is confirmed to be the reaction of MgH2, developed in the first reaction stage, with ammonia to produce Mg(NH2)2. The as-synthesized Mg(NH2)2 is used as raw material for synthesizing Mg(NH2)2-2LiH material, showing almost the same hydrogen storage performance as the Mg(NH2)2 synthesized by heating Mg and ammonia. This study provides a new method to synthesize Mg(NH2)2 for hydrogen storage on a large scale.

Study of high-pressure air jet controlled compression ignition with compound thermodynamic cycle for combustion and emission formation process

A novel method called high-pressure air (HPA) jet controlled compression ignition (JCCI) based on the compound thermodynamic cycle was investigated in this work. The combustion process of premixed mixture can be controlled flexibly by the high-pressure air jet compression, and it characterizes the intensified low-temperature reaction and two-stage high-temperature reaction. The three-dimensional (3D) computational fluid dynamics (CFD) numerical simulation was employed to study the emission formation process and mechanism, and the effects of high-pressure air jet temperature and duration on emissions were also investigated. The simulation results showed that the NOx formation is mainly affected by the first-stage high-temperature reaction due to the higher reaction temperature. Overall, this combustion mode can obtain ultra-low NOx emission. The second-stage high-temperature reaction plays an important role in the CO and THC formation caused by the mixing effect of the high-pressure air and original in-cylinder mixture. The increasing air jet temperature leads to a larger high-temperature in-cylinder region and more fuel in the first-stage reaction, and therefore resulting in higher NOx emission. However, the increasing air jet temperature can significantly reduce the CO and THC emissions. For the air jet duration comparisons, both too short and too long air jet durations could induce higher NOx emission. A higher air jet duration would result in higher CO emission due to the more high-pressure air jet with relatively low temperature.

Thermal Metamorphosis in (Meth)acrylate Photopolymers: Stress Relaxation, Reshaping, and Second-Stage Reaction

Thermally transformable/responsive (meth)acrylate photopolymer networks were constructed from commercial (meth)acrylate esters and synthetic di- and mono(meth)acylate monomers bearing thioester functionalities. The thermal responsiveness, here self-limited exchange, relied on the catalytic metamorphosis of thioesters into esters with the concomitant depletion of hydroxyls and subsequent generation of free thiols. The thioester–hydroxyl cross-exchange was demonstrated in network systems with interchain thioesters as well as in networks with side-chain pendant thioacetyls. The interchain metamorphosis resulted in close to 80% conversion of thioesters into esters when 2 equiv of hydroxyl groups was initially present. In practical terms, such an outcome enabled efficient stress relaxation (60%) and good shape adaptation (90% shape fixity) in 1 h at 105 °C. On the other hand, side-chain S → O acyl transfer reactions were found to vary in efficiency depending on the vicinity of thioesters and hydroxyls. When in close vicinity, efficient noncatalytic exchange was observed in materials with 1-to-1 thioester-to-hydroxyl ratios nearing 60%. The benefits of generating free thiols postpolymerization were further explored in enhanced two-stage curing systems where a subsequent thiol–ene photopolymerization was demonstrated at ambient as well as at elevated temperatures.

High Molecular Weight Unsaturated Copolyesters Derived from Fully Biobased trans-β-Hydromuconic Acid and Fumaric Acid with 1,4-Butanediol: Synthesis and Thermomechanical Properties

This work describes the synthesis, structure, and physical and thermomechanical properties of fully biobased unsaturated copolyesters via melt-polycondensation of renewable monomers trans-β-hydromuconic acid and fumaric acid with 1,4-butanediol conducted by a two-step polymerization employing stannous octoate as a catalyst and 4-methoxyphenol as a radical inhibitor. The polymerization conditions, including catalyst amount, second-stage reaction temperature, and time, were optimized to prepare high molecular mass unsaturated copolyesters without isomerization and saturation reaction in the unsaturated double bonds. Consequently, a series of poly(butylene hydromuconoate-co-butylene fumarate) (PBHBF) samples with weight-average molecular weight over 80 kg/mol were obtained. The chemical structures identified by 1H and 13C NMR indicated that the notorious side reactions of isomerization and saturation of C═C bonds in unsaturated polyesters were eliminated in the obtained PBHBF copolyesters. From the physical ...

Influence of Ag replacement on the formation and heating-induced phase decomposition of Zr65Al7.5Co27.5-xAgx (x=5 to 20 at%) glassy alloys

A glass-type alloy with glass transition (GT) and supercooled liquid region was formed at a limited Ag/Co content ratio around 1.2 in melt-spun Zr65Al7.5Co27.5-xAgx (x = 5–20 at%) alloys. This alloy crystallized through two-stage exothermic reactions where an icosahedral (I) phase appears as a primary precipitation phase, followed by the second-stage reaction from glass + I-phase to four crystalline phases. The I-phase has a spherical morphology and its size is about 8 nm. The Zr65Al7.5Co17.5Ag10 alloy without GT keeps a glass-like structure even after heating for 3.6 ks at 750 K above the first exothermic peak, indicating the formation of a cluster-like glassy phase. The Zr65Al7.5Co17.5Ag10 alloy rod keeps a glassy phase in the diameter up to 1.7 mm, though the rod does not show the first-stage exothermic reaction. These features are the same as those for the annealed ribbons, indicating that a clustered glassy phase is also formed for the bulk alloy. This alloy satisfies with the formation criterion of the clustered glassy phase, i.e., large atomic size mismatch and positive heat of mixing for solute elements. The high stability of glassy phase leading to the formation of the clustered glassy phase is due to the resistance to atomic rearrangement of unlike Co and Ag elements. The Zr65Al7.5Co12.5Ag15 alloy exhibits the lowest decomposition temperature (Tx) and the highest hardness, being opposite to the previous relation for hardness to increase with increasing Tx. The relationship between GT and I-phase precipitation suggests that the GT is attributed to the development of I-like medium-range ordered structure.

The effects of hydrogen addition on the auto-ignition delay of homogeneous primary reference fuel/air mixtures in a rapid compression machine

The ignition delay time with mixtures of primary reference fuels (PRFs) and hydrogen were measured using a rapid compression machine (RCM), where the concentration of hydrogen was systematically varied. The experiments were performed for compressed temperatures in the range 735–847 K. The fuel/air equivalence ratio was varied to investigate its effects on the ignition delay of n-heptane and iso-octane. Hydrogen was added with hydrogen-energy-share ratios in the range of 0–10%, meaning that the energy of the hydrogen replaced 0–10% of that of either n-heptane or iso-octane. When hydrogen was added to n-heptane, there was a significant increase in the ignition delay, especially during the first-stage reaction region. This was explained using the chemical kinetic analysis software package CHEMKIN PRO; hydrogen consumed radical species related to the ignition of hydrocarbon fuels. With iso-octane, there was a significant increase in the ignition delay not only in the fist-stage reaction region, but also in second-stage reaction region. The effects of the hydrogen concentration were found to depend on the equivalence ratio and temperature for both fuels.

High-yield production of vanillin from ferulic acid by a coenzyme-independent decarboxylase/oxygenase two-stage process

Vanillin is one of the world's most important flavor and fragrance compounds in foods and cosmetics. Recently, we demonstrated that vanillin could be produced from ferulic acid via 4-vinylguaiacol in a coenzyme-independent manner using the decarboxylase Fdc and the oxygenase Cso2. In this study, we investigated a new two-pot bioprocess for vanillin production using the whole-cell catalyst of Escherichia coli expressing Fdc in the first stage and that of E. coli expressing Cso2 in the second stage. We first optimized the second-step Cso2 reaction from 4-vinylguaiacol to vanillin, a rate-determining step for the production of vanillin. Addition of FeCl2 to the cultivation medium enhanced the activity of the resulting E. coli cells expressing Cso2, an iron protein belonging to the carotenoid cleavage oxygenase family. Furthermore, a butyl acetate-water biphasic system was effective in improving the production of vanillin. Under the optimized conditions, we attempted to produce vanillin from ferulic acid by a two-pot bioprocess on a flask scale. In the first stage, E. coli cells expressing Fdc rapidly decarboxylated ferulic acid and completely converted 75 mM of this substrate to 4-vinylguaiacol within 2 h at pH 9.0. After the first-stage reaction, cells were removed from the reaction mixture by centrifugation, and the pH of the resulting supernatant was adjusted to 10.5, the optimal pH for Cso2. This solution was subjected to the second-stage reaction. In the second stage, E. coli cells expressing Cso2 efficiently oxidized 4-vinylguaiacol to vanillin. The concentration of vanillin reached 52 mM (7.8 g L(-1)) in 24 h, which is the highest level attained to date for the biotechnological production of vanillin using recombinant cells.

Pyrolysis Reaction Pathways of Waste Epoxy-Printed Circuit Board

Abstract This article elucidates pyrolysis reaction pathways of waste epoxy-printed circuit boards (e-PCBs). Non-isothermal thermogravimetric analyses showed that waste e-PCBs decomposed via a series of reactions distinguished by three apparent reaction regions. The first-stage reaction (<250°C) can be accounted for by the cleavage reaction of N-containing cross-linkage between brominated epoxy resin (BER) and non-brominated epoxy resin (NBER). Evolved gas analysis-mass spectrometry (EGA-MS) showed that the second-stage reaction (250–500°C) can be represented by two independent decomposition reactions of BERs and NBERs to yield thermally stable intermediates. BERs decomposed more rapidly (250–350°C), whereas NBERs decomposed over broader temperature regions (250–500°C) with slower decomposition rates. Multi-shot gas chromatography/mass spectrometry also indicated that brominated compounds, brominated phenol and brominated bisphenol A, are generated mainly at lower temperature zones of the second-stage reg...

Polymers from Fatty Acids: Poly(ω-hydroxyl tetradecanoic acid) Synthesis and Physico-Mechanical Studies

This Article describes the synthesis and physicomechanical properties of bioplastics prepared from methyl ω-hydroxytetradecanoic acid (Me-ω-OHC14), a new monomer available by a fermentation process using an engineered Candida tropicalis strain. Melt-condensation experiments were conducted using titanium tetraisopropoxide (Ti[OiPr](4)) as a catalyst in a two-stage polymerization (2 h at 200 °C under N(2), 4 h at 220 °C under 0.1 mmHg). Poly(ω-hydroxytetradecanoate), P(ω-OHC14), M(w), determined by SEC-MALLS, increased from 53K to 110K as the Ti(OiPr)(4) concentration increased from 50 to 300 ppm. By varying the polymerization conditions (catalyst concentration, reaction time, second-stage reaction temperature) a series of P(ω-OHC14) samples were prepared with M(w) values from 53K to 140K. The synthesized polyesters with M(w) ranging from 53K to 140K were subjected to characterization by DSC, TGA, DMTA, and tensile testing. Influences of P(ω-OHC14) molecular weight, melting point, and enthalpies of melting/crystallization on material tensile properties were explored. Cold-drawing tensile tests at room temperature for P(ω-OHC14) with M(w) 53K-78K showed a brittle-to-ductile transition. In contrast, P(ω-OHC14) with M(w) 53K undergoes brittle fracture. Increasing P(ω-OHC14) M(w) above 78K resulted in a strain-hardening phenomena and tough properties with elongation at break ~700% and true tensile strength of ~50 MPa. Comparisons between high density polyethylene and P(ω-OHC14) mechanical and thermal properties as a function of their respective molecular weights are discussed.

Pyrolysis of scrap printed circuit board plastic particles in a fluidized bed

Pyrolysis behavior and corresponding pyrolysis products of printed circuit board plastic particles (PCBP particles) were investigated in a fluidized bed using TG-FTIR analysis system. PCBP particles were separated from crashed printed circuit boards using fluidized beds, 354 μm crashed plastic particles were pyrolyzed at the temperature ranging from 20 to 900 °C by a thermogravimetric analyzer. Two stages of decomposition were identified for PCBP particles under nitrogen conditions. The activation energy was 90.49 kJ/mol for the first-stage reaction and 137.80 kJ/mol for the second-stage reaction. Further, gas products, liquid products, and solid residues yielded in the fluidized bed were analyzed using an elemental analyzer and FTIR. It has been found that the liquid yields increased with an increase in pyrolysis temperature, and with an increase in superficial gas velocity. The main compositions of liquid products were aromatic compounds including substituted benzenes. Whereas, the solid products mainly contained char and fiberglass. A fluidized bed, made of a stainless steel cylinder with 27 mm i.d. and a height of 1600 mm, was used to pyrolyse the printed circuit board plastic (PCBP) particles at bed temperature ranging from 400 to 600 °C. The gas and liquid products and solid residues yielded in the fluidized bed were analyzed.

Selective separation of phosphate and fluoride from semiconductor wastewater

Hydrofluoric acid (HF) and phosphoric acid (H(3)PO(4)) are widely used in semiconductor industry for etching and rinsing purposes. Consequently, significant amount of wastewater containing phosphate and fluoride is generated. Selective separation of phosphate and fluoride from the semiconductor wastewater, containing 936 mg/L of fluoride, 118 mg/L of phosphate, 640 mg/L of sulfate, and 26.7 mg/L of ammonia, was studied. Chemical precipitation and flotation reactions were utilized in the two-stage treatment processes. The first-stage reaction involved the addition of magnesium chloride (MgCl(2)) to induce selective precipitation of magnesium phosphate. The optimal condition was pH 10 and molar ratio, [Mg(2 + )]/[(PO(4) (3-))], of 3:1, and 66.2% of phosphate was removed and recovered as bobierrite (Mg(3)(PO(4))(2).8H(2)O). No reaction was found between MgCl(2) and fluoride. Calcium chloride (CaCl(2)) was used in the second-stage reaction to induce precipitation of calcium fluoride and calcium phosphate. The optimum molar ratio, [Ca(2 + )]/[F(-)], was 0.7 at pH 10, and residual fluoride concentration of 10.7 mg/L and phosphate concentration of lower than 0.5 mg/L was obtained. Thermodynamic equilibrium was modeled with PHREEQC and compared with experimental results. Sodium dodecylsulfate (SDS) was an effective collector for subsequent solid-liquid removal via dispersed air flotation (DiAF). The study demonstrated that phosphate can be selectively recovered from the wastewater. Potential benefits include recovery of phosphate for reuse, lower required dosage of calcium for fluoride removal, and less amount of CaF(2) sludge.

The thermal decomposition of N,N-dimethyl-3-oxaglutaramic acid and the kinetics of its second-stage thermal decomposition reaction

N,N-dimethyl-3-oxa-glutaramic acid was purified and characterized by 1H-NMR, Fourier transform infrared spectroscopy (FT-IR) and elemental analysis. The thermal decomposition of the title compound was studied by means of thermogravimetry differential thermogravimetry (TG-DTG) and FT-IR. The kinetic parameters of its second-stage decomposition reaction were calculated and the decomposition mechanism was discussed. The kinetic model function in a differential form, apparent activation energy and pre-exponential constant of the reaction are 3/2 [(1−α)1/3−1]−1, 203.75 kJ·mol−1 and 1017.95s−1, respectively. The values of ΔS≠, ΔH≠ and ΔG≠ of the reaction are 94.28 J·mol−1·K−1, 203.75 kJ·mol−1 and 155.75 kJ·mol−1, respectively.

Thermally triggered two-stage reaction of carbonates and clay during ceramic firing — A case study on Bronze Age Cypriot ceramics

Cypriot Bronze-age Plain White Wheelmade ware samples were investigated in order to examine their chemical and mineralogical features, their manufacturing procedures and associated firing temperature controlled mineral reactions. Beside the geochemical characterisation of the ware group, the main focus of the study was to determine phase transformations (especially the reaction of calcareous inclusions in phyllosilicatic matrices) via petrographical, mineralogical, microtextural and phase-geochemical methods. Three groups of pottery, fired at increasing temperatures (group I: < 600 °C, group II: 650–800 °C and group III: 850–1000 °C), could be distinguished taking their individual states of carbonate decomposition together with accompanying mineral reactions into account. In group I, no mineral transformations occur, whereas in group II and III, two conspicuous and temperature-indicative stages of carbonate reactions are observable. The first reaction stage takes place in group II samples and is characterized by the development of spherical reaction domains around paste matrix included calcareous grains by means of Ca-dispersion from the grains into the surrounding clayish matrix. This process provides the initial position for partial melting and blastesis of new mineral phases that follow. In the second-stage reaction, designative for group III, advanced carbonate decomposition takes place. Temperature triggered melts evolve from breakdown products of sufficiently heated clay minerals and build up glassy Al–Si rims at the interface of carbonates and the surrounding clay paste. At the same time, Ca-silicates grow in the domain of the Ca-affected matrix that indeed already evolved at lower temperatures (first-stage reaction) but only now reaches the sufficient heat for mineral blastesis. We assume that the carbonate-tempered ceramics were deliberately fired up to temperatures that are represented by group II but due to heterogeneous firing conditions parts of the vessels were unintentionally under- and overfired respectively.

Facile synthesis of silica/polymer hybrid microspheres and hollow polymer microspheres

Monodisperse silica/polydivinylbenzene (SiO2/PDVB) and silica/poly(ethyleneglycol dimethacrylate) (SiO2/PEGDMA) core–shell hybrid microspheres were prepared by a two-stage reaction with silica particles' grafting of 3-(methacryloxy)propyltrimethoxysilane (MPS) as core and PDVB or PEGDMA as shell, in which the MPS-modified silica core with diameter of 238nm was synthesized by Stöber method and subsequently grafted with MPS as the first-stage reaction. The PDVB or PEGDMA shell was then encapsulated over the MPS-modified silica core by distillation precipitation polymerization of divinylbenzene (DVB) or ethyleneglycol dimethacrylate (EGDMA) in neat acetonitrile with 2,2′-azobisisobutyronitrile (AIBN) initiator as the second-stage reaction. The encapsulation of PDVB and PEGDMA on modified silica core particles was driven by the capture of DVB or EGDMA oligomer radicals via the vinyl groups on the surface of the modified silica cores during the second-stage polymerization in the absence of any stabilizer or surfactant. The shell thickness of the core–shell hybrid particles was controlled by the feed of DVB or EGDMA monomer during the polymerization. Hollow PDVB or PEGDMA microspheres with various shell thickness were further developed after selective removal of the modified silica cores with hydrofluoric acid. The resultant core–shell hybrid materials and hollow microspheres were characterized by transmission electron microscopy (TEM), and Fourier transform infrared spectra (FT-IR).

Pyrolysis characteristics of integrated circuit boards at various particle sizes and temperatures

A pyrolysis method was employed to recycle the metals and brominated compounds blended into printed circuit boards. This research investigated the effect of particle size and process temperature on the element composition of IC boards and pyrolytic residues, liquid products, and water-soluble ionic species in the exhaust, with the overall goal being to identify the pyrolysis conditions that will have the least impact on the environment. Integrated circuit (IC) boards were crushed into 5–40 mesh (0.71–4.4 mm), and the crushed particles were pyrolyzed at temperatures ranging from 200 to 500 °C. The thermal decomposition kinetics were measured by a thermogravimetric (TG) analyzer. The composition of pyrolytic residues was analyzed by Energy Dispersive X-ray Spectrometer (EDS), Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-AES) and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). In addition, the element compositions of liquid products were analyzed by ICP-AES and ICP-MS. Pyrolytic exhaust was collected by a water-absorption system in an ice-bath cooler, and IC analysis showed that the absorbed solution comprised 11 ionic species. Based on the pyrolytic kinetic parameters of TG analysis and pyrolytic residues at various temperatures for 30 min, the effect of particle size was insignificant in this study, and temperature was the key factor for the IC board pyrolysis. Two stages of decomposition were found for IC board pyrolysis under nitrogen atmosphere. The activation energy was 38–47 kcal/mol for the first-stage reaction and 5.2–9.4 kcal/mol for the second-stage reaction. Metal content was low in the liquid by-product of the IC board pyrolysis process, which is an advantage in that the liquid product could be used as a fuel. Brominate and ammonium were the main water-soluble ionic species of the pyrolytic exhaust. A plan for their safe and effective disposal must be developed if the pyrolytic recycling process is to be applied to IC boards.

Selective Synthesis of Middle Isoparaffins via a Two-Stage Fischer−Tropsch Reaction: Activity Investigation for a Hybrid Catalyst

The activity of hybrid catalysts for the direct isoparaffin synthesis, especially C4−C6 with a very high octane number, from Fischer−Tropsch synthesis (FTS) in a two-stage reactor was investigated. The hybrid of Co/SiO2 and H-ZSM-5 was used as the first-stage reaction catalyst, and different types of H zeolites alone or their hybrid with Pd/SiO2 were used as the second-stage reaction catalysts. The obtained results demonstrated that the carbon number of products could terminate at 6 and isoparaffin hydrocarbons could be synthesized in very high selectivity from synthesis gas compared with that in a single-stage reaction using a physically mixed Co/SiO2 and H-ZSM-5 catalyst. The first-stage Co/SiO2 + H-ZSM-5 catalyst made the products mainly distribute in the C1−C11 range and considerably increase in the corresponding isoparaffins because of successive cracking, as well as isomerization, of the primary FTS products on H-ZSM-5. The selectivities of isoparaffins with much lower carbon number were further rai...