Main Gaseous Products Research Articles

Element Transformation and Gaseous Products Distribution for Lignite Gasification in Supercritical Water

Effects of factors on efficiencies of elements (C/H/N/S) and gaseous products were studied for lignite gasification in supercritical water. CO2, CH4and H2are main gaseous products. Temperature plays the most important role. With higher temperature, total efficiencies of lignite and elements have linear increasement, and yields of CO2, CH4and H2rise significantly while CO stays constant almostly. With pressure increasing, total efficiencies of lignite and elements are enhanced, and yields of CO2and CH4rise while change of H2and CO is small. With increasing of equivalence ratio of oxygen, efficiencies of C/H/N and lignite, yields of CO2and H2rise, but yield of CH4reduces. Increasing equivalence ratio of oxygen plays positive role in fixation of S on residues.

Effects of electrode geometry on the performance of dielectric barrier/packed-bed discharge plasmas in benzene degradation

In this study, the effects of electrode geometry on benzene degradation in a dielectric barrier/packed-bed discharge plasma reactor with different electrodes were systematically investigated. Three electrodes were employed in the experiments, these were coil, bolt, and rod geometries. The reactor using the coil electrode showed better performance in reducing the dielectric loss in the barrier compared to that using the bolt or rod electrodes. In the case of the coil electrode, both the benzene degradation efficiency and energy yield were higher than those for the other electrodes, which can be attributed to the increased role of surface mediated reactions. Irrespective of the electrode geometry, the packed-bed discharge plasma was superior to the dielectric barrier discharge plasma in benzene degradation at any specific applied voltage. The main gaseous products of benzene degradation were CO, CO2, H2O, and formic acid. Discharge products such as O3, N2O, N2O5, and HNO3 were also detected in the outlet gas. Moreover, the presence of benzene inhibited the formation of ozone because of the competing reaction of oxygen atoms with benzene. This study is expected to offer an optimized approach combining dielectric barrier discharge and packed-bed discharge to improve the degradation of gaseous pollutants.

Effect of Hydrogen Partial Pressure on Hydrocarbon Production from Deoxygenation of Stearic Acid

The catalytic deoxygenation experiments of stearic acid and hydrogen were performed for 6 hours in the presence of a solvent, dodecane, in a temperature range of 295-305°C and the rotational speed of 100rpm, under a certain hydrogen partial pressure (in argon), using palladium supported on active and mesoporous carbon as a catalyst. The results showed, the main liquid-phase product was n-heptadecane, while the main gaseous products were CO2and CO. When the partial pressure of hydrogen is 3.0MPa, the acid value of primary product is the lowest and the reaction tends to be gentle, conversion rate of stearic acid and selectivity to n-heptadecane is the highest.

Supercritical water gasification of manure: A thermodynamic equilibrium modeling approach

This study aims to investigate for the first time the equilibrium partitioning of elements on the basis of compounds and phases in the supercritical water gasification of mixed pig–cow manure for a temperature interval of 100–580 °C and at a pressure of 24 MPa. The software programs FactSage 5.4.1 and SimuSage 1.12 with user-defined databases have been used for thermodynamic equilibrium calculations. The temperature interval and the weight fraction of water have been chosen as 100 °C–580 °C and 80%, respectively. The effects of pressure and water fraction on main product gases have also been investigated. The results show that three phases are formed for the subcritical region: gas, liquid and solid. In addition to water vapor, CO2, CH4, N2 and H2 are the main gas products of the gas. The liquid phase is composed of an aqueous solution composed of stable ionic compounds such as HCO3−, K+, Na+ and Cl− and dissolved CH4 and N2. The solid phase compounds are mainly composed of C, Ca, Mg and P. Aqueous hydrates exist in the supercritical region but start precipitation at high temperatures. The results show that working above 340 °C would result in good carbon gasification efficiency under equilibrium conditions as the solid carbon completely disappears. In the supercritical region, backward methanation reaction takes place and CH4 decomposes and forms H2. While the water fraction has a significant effect on the amount of main product gases, pressure was found to be less significant.

Production of H2 by Ethanol Photoreforming on Au/TiO2

A deposition‐precipitation method is used to prepare Au/TiO2 solids (0.45–1.7 wt% Au). These materials, consisting of gold nanoparticles (diameter range = 1.5–6.5 nm) supported on the surface of TiO2, are used as photocatalysts for the ethanol photoreforming reaction under either UV‐rich or simulated solar light. The main products of such reactions are H2 in the gas phase and acetaldehyde in the liquid phase according to the reaction CH3CH2OH → CH3CHO ‐ H2. Among the gaseous products, H2 amounts to around or above 99% in all cases; other minor products found in the gas phase are, in decreasing order of molar production: CH4 > CO > C2H4 > CO2 > C2H6 > C3H8. The photoactivity is lower under CO2 atmosphere, as compared to analogous reactions performed under Ar. The H2 production yields are very high (up to a maximum 30 mmol gcat−1 h−1) under UV irradiation, and increase with increasing gold loading. The reactions under simulated solar light also yield significant amounts of H2 (5–6 mmol gcat−1 h−1) as the main gaseous product.

Kinetics of Thermal Decomposition of Ammonium Perchlorate by TG/DSC-MS-FTIR

The method of thermogravimetry/differential scanning calorimetry–mass spectrometry–Fourier transform infrared (TG/DSC-MS-FTIR) simultaneous analysis has been used to study thermal decomposition of ammonium perchlorate (AP). The processing of nonisothermal data at various heating rates was performed using NETZSCH Thermokinetics. The MS-FTIR spectra showed that N2O and NO2 were the main gaseous products of the thermal decomposition of AP, and there was a competition between the formation reaction of N2O and that of NO2 during the process with an iso-concentration point of N2O and NO2. The dependence of the activation energy calculated by Friedman's iso-conversional method on the degree of conversion indicated that the AP decomposition process can be divided into three stages, which are autocatalytic, low-temperature diffusion and high-temperature, stable-phase reaction. The corresponding kinetic parameters were determined by multivariate nonlinear regression and the mechanism of the AP decomposition process was proposed.

Investigation on the thermal degradation of flexible poly(vinyl chloride) filled with ferrites as flame retardant and smoke suppressant using TGA–FTIR and TGA–MS

A series of ferrites (ZnFe2O4, MgFe2O4, NiFe2O4, and CuFe2O4) was prepared by wet air oxidation and their structure and morphology were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses. The prepared ferrites were added to flexible poly(vinyl chloride)(PVC) as flame retardants and smoke suppressants. Subsequently, thermal degradation properties of flexible PVC with ferrite additives were investigated by using TGA–DTG, TGA–FTIR, and TGA–MS. The main mechanism underlying the flame-retarding activity was shown to be caused by the catalyzed the dehydrochlorination of PVC at the first stage and breaking of the char residue at higher temperature. The results showed that addition of ferrites, especially MgFe2O4, at the first stage, not only decreased T5% (defined as the temperature at which 5% of the initial weight has been lost) and increased the weight loss rate, but also promoted cross-linking and stability of char residue. The main gas pyrolysis products were HCl and benzene. When compared with neat PVC, PVC/MgFe2O4 and PVC/CuFe2O4 generated more HCl and less benzene, and consequently retained more carbon in the matrix with respect to the increased flame-retarding and smoke-suppressing. At the second stage, the weight loss of flame-retarding PVC increased obviously, with simultaneous increase in the yield of main gaseous pyrolysis products, CO2 and aliphatic fragments. PVC/CuFe2O4 generated a high yield of CO2, because of the cationic cracking reactions in the presence of Lewis acid, fragmenting of the char residue at higher temperature. Additionally, the inner surface morphology of the char residue derived from PVC/MgFe2O4 was investigated by SEM and EDS, which showed the existence of alveolate and breakable structures, as well as needle-like structures, composed of a mixture of iron chloride and magnesium chloride.

Pyrolysis of poplar wood sawdust by TG-FTIR and Py–GC/MS

Pyrolysis of certain poplar wood sawdust (PWS) was studied by thermogravimetric analyzer coupled with Fourier transform infrared spectroscopy (TG-FTIR). Different heating rates were applied with final temperature of 950°C and about 80% loss weight was observed at the heating rate of 20–80°C/min. The temperature trend of evolving gaseous products of PWS was also investigated. Following experimental research on pyrolysis of PWS was carried out on a pyrolysis–gas-chromatography/mass spectrometry (Py–GC/MS). Associated with the analysis results of TG-FTIR and Py–GC/MS for the pyrolytic products, PWS undergoes in three consecutive stages, corresponding to (1) moisture evaporation, (2) thermal decomposition, and (3) further carbonization. The main pyrolysis sections and the maximum weight loss rates are similar for different heating rates. Carbonyls, including aldehydes and ketones, are the main volatile products, in addition to phenols, furans, benzenes, acids, and so on. As the main gaseous products, CO, CO2, CH4 are released out greatly. Furthermore, possible pyrolysis mechanisms of cellulose, hemicellulose and lignin in biomass including PWS were also proposed. All of the results and findings would help further understanding of thermal behavior of PWS and its thermo-chemical utilization for fuels and chemicals.

Thermal behaviour and kinetic study of some triazoles as potential anti-inflammatory agents

Thermogravimetric (TG), differential thermogravimetric analysis and differential scanning calorimetry had been used to characterize the thermal stability of four new heterocyclic compounds with triazolic structure. The four analysed compounds have similar thermal behaviours, namely the thermal mal curves of these new compounds show three thermal events. These compounds were thermally stable up to 110 °C. Above this temperature, the evolution of hydrochloric acid took place as observed by EGA. Identification and the monitoring of gaseous species released during thermal decomposition of pure triazoles in air atmosphere have been carried out by coupled TG–FTIR. Between 110 and 220 °C the main gaseous product is HCl which was identified on the basis of these FTIR spectra. Arguments for a rapid thermooxidation of the four molecules were brought by EGA by identifying the substances which arise from both the destruction of side chains and of triazolic ring. The kinetic analysis of the destruction process of triazolic structure was investigated using the TG data in air for the substance’s decomposition in non-isothermal conditions. The isoconversional methods, Kissinger–Akahira–Sunose, Flynn–Wall–Ozawa and Friedman, were applied to determine the activation energy from the analysis of four curves measured at different heating rates. In order to obtain realistic kinetic parameters, even if the decomposition process is a complex one, the non-parametric kinetics method was also used. A good agreement between the data obtained from the four applied methods was found.

Torrefaction of Corn Stover in a Macro-thermobalance: Influence of Operating Conditions

The present work is devoted to the experimental study of torrefaction of corn-stover. This biomass was processed in a high capacity thermobalance which can accept a load of approximately 500 g. It allows not only following the weight of the biomass under investigation as a function of time (or temperature) but also to collect and analyze the by-products of the thermal degradation (μ-GC for gas, HPLC for tars). Torrefaction is expected to be of main concern in the preparation of biomass for energy production or for conversion of biomass into liquid fuels. This is one of the reason why this process has been widely studied in the case of wood in the literature. However, so few studies exist on the torrefaction of agricultural residue which could play an important role in the above mentioned fields. The purpose of the present work is to give insights on the transformation of corn stover (which is an important by product of corn) undergoing an operation of torrefaction. To do so, the influence of operational conditions (temperature, residence time, heating rate, weight of sample) on the yield and composition of by-products was studied with a factorial design. It is shown that the main gaseous products are carbon monoxide and dioxide while tars are mainly composed of acetic acid and formaldehyde. It is also shown that the discriminant operating parameter in corn stover conversion is the temperature.

Propeller-like heterotrinuclear CuII–LnIII–CuII compounds – Physicochemical properties

The new heterotrinuclear compounds [Cu2Ln(L)2(NO3)(H2O)2](NO3)2·3H2O (where Ln=Sm (1), Eu (2) and L=C19H18N2O4Br2 is the deprotonated form of N,N′-bis(5-bromo-3-methoxysalicylidene)propylene-1,3-diamine,) have been synthesized and characterized by FTIR, TG-FTIR, TG/DSC and single crystal X-ray analyses. The complexes of 1 and 2 are isostructural. In the trinuclear compounds two terminal copper(II) ions are coordinated by imino and phenolate oxygen atoms, whereas the central lanthanide(III) ion is bound to the phenolate and methoxy oxygen atoms of the Schiff base ligands. The first change in mass estimated from TG curve corresponds to the loss of water molecules. The decomposition of the Schiff base ligand starts above 200°C. The final decomposition solid products are CuO and Ln2CuO4. The TG-FTIR results show that the main gaseous products in whole decomposition process of complexes are water (H2O), carbon dioxide (CO2), carbon monoxide (CO), nitric oxides (NOx) and bromomethane (CH3Br).

Non-catalytic hydropyrolysis of microalgae to produce liquid biofuels

Non-catalytic hydropyrolysis of Chlorella pyrenoidosa was studied by using a stainless-steel batch reactor at different temperature (150–450°C), time (5–120min) and initial hydrogen pressure (1atm–8MPa), aiming to find how these parameters affect the product (oil, gas and solid) yields and properties of the hydropyrolysis oil (HPO). Temperature was the most influential factor to the relative amount of each product and properties of the HPOs. The hydrogen favored the stabilization of the active intermediates but cannot guarantee to produce HPOs in higher hydrogen at its higher initial pressure. The HPO, which showed much difference in component strongly depending on the reaction conditions, mainly consisted of aromatics and straight-chain hydrocarbons, amides, amines, nitriles and carboxylic acids at moderate temperatures. The main gas products detected during the hydropyrolysis were unreacted H2, CO2, CO and CH4. About 85% of energy originally present in the microalgae was recovered as oil under the optimal conditions.

Formation of nanoporous carbon materials in conditions of thermocatalytic synthesis

A study of the volatile products formed in the process of thermocatalytic destruction of a hardwood and the carbonizates on its basis in the presence and absence of acidic (H3PO4) and alkaline (NaOH) activators was performed by thermogravimetry/mass spectrometry (TG/MS) method. Ranges of formation temperatures and the amount of water and the main gaseous products were determined. It is shown that, in the case of activation with alkali, the chemical composition and structure of the precursor have a pronounced effect on the process. Nanoporous carbon materials with high indices of the porous structure were obtained.

Digested sewage sludge gasification in supercritical water

Digested sewage sludge gasification in supercritical water was studied. Influences of main reaction parameters, including temperature (623-698 K), pressure (25-35 Mpa), residence time (10-15 min) and dry matter content (5-25 wt%), were investigated to optimize the gasification process. The main gas products were methane, carbon monoxide, carbon dioxide and traces of ethene, etc. Results showed that 10 wt% dry matter content digested sewage sludge at a temperature of 698 K and residence time of 50 min, with a pressure of 25 MPa, were the most favorable conditions for the sewage sludge gasification and carbon gasification efficiencies. In addition, potassium carbonate (K2CO3) was also employed as the catalyst to make a comparison between gasification with and without catalyst. When 2.6 g K2CO3 was added, a gasification efficiency of 25.26% and a carbon gasification efficiency of 20.02% were achieved, which were almost four times as much as the efficiencies without catalyst. K2CO3 has been proved to be effective in sewage sludge gasification.

Catalytic upgrading of crude algal oil using platinum/gamma alumina in supercritical water

We report herein on the catalytic upgrading of crude oil, produced from the hydrothermal liquefaction of Chlorella pyrenoidosa over platinum on gamma alumina (Pt/γ-Al2O3) in supercritical water (SCW) at 400°C for 1h. We determined the influence of catalyst loading (varied from 0 to 40wt.%), water density (varied from 0 to 0.1g/cm3), and formic acid (HCOOH) loading (varied from 2 to 37mmol) on the product yields and properties of the treated oil. The product yields and properties of the treated oil were largely insensitive to the catalyst loading and sensitive to water density and HCOOH loading. Increasing the catalyst loading or decreasing the water density and formic acid loading produced a lower yield but higher quality treated oil. Moreover, including the Pt/γ-Al2O3 in the reactor led to a product oil that was a freely flowing liquid, as opposed to being the viscous, sticky, and tar-like crude oil material. Compared to SCW+H2, the presence of SCW+HCOOH effectively controls the coke formation. The catalyst experienced a reduction in surface area and micropore volume when used for hydrothermal upgrading. These changes did not influence the catalyst activity, however. Unreacted H2 was the main gaseous product, together with lower yields of CO2 and C1C5 hydrocarbon.

Electrolysis of Alcohols in High Temperature-High Pressure Water

ABSTRACTThe design of clean, efficient and environmentally friendly routes that reduce the waste production and fuel emissions of pollutants into the atmosphere, produce clean, affordable, and renewable energy sources to lessen energy consumption and toxicity on the environment, has become a central issue of chemical research both in industry and academia. One of the approaches being used in green chemistry practices is to use water as a solvent and reaction medium where possible. Much of this work deals with liquid water at temperatures exceeding the normal boiling point which is denoted as sub-critical water.Electrochemical reaction, usually operated at atmospheric condition in water, is generally slow, although it has advantages over chemical reaction such as suppression of side reaction by tuning operating conditions. Since sub-critical water (7 MPa and 250 °C) has remarkable properties such as high ion product and low dielectric constant, it could be a suitable reaction media.We have been studying electrolysis of organic compounds in sub-critical water as waste treatment and molecular degradation technologies. Electrolysis in sub-critical water could degrade harmful and thermally stable organic compounds into innocuous compounds such as hydrogen and water. In this research, we focused on the investigation of the electrochemical reactions of alcohols in sub-critical water to evaluate possibility for the selective production of hydrogen and value-added chemicals.Electrochemical reactions were carried out in sub-critical water using a specially designed autoclave made of SS 316 with a volume of 500 mL. For comparison, thermal degradation experiments of alcohols were also conducted without any direct current loading at identical conditions. Here we employed glycerol and 1-butanol as model compounds of alcohols.As a result of 1-butanol experiments, butanal and butyric acid were produced via partial oxidation at 250 °C and by applying 1-3 A of direct current while no oxidation products were observed at the hydrothermal degradation run. As a gaseous product, hydrogen gas was generated according to the electrochemical reaction mechanism. In the case of glycerol experiments, the main gaseous product was hydrogen gas, whereas glycolaldehyde, lactic acid, and formic acid were generated as the main liquid products at 280 °C. Results indicated that greater than 92% of the glycerol could be decomposed under optimum conditions by hydrothermal electrolysis technique.This presented research will help to degrade stable organic materials in an environmentally friendly way and without need for secondary treatment processes. It will also address the need for novel more efficient techniques for the degradation of stable organic compounds in aqueous conditions and it will advance the use of water as a reaction medium in an efficient way without any organic solvent.

Conversion of Rice Straw to Bio-Fuel by Pyrolysis in Molten KCl-LiCl

The objective of this study was to provide background date on rice straw pyrolysis in molten KCl(40mol%)-LiCl(60mol%). The effects of pyrolysis temperatures and sweep gas flow rates on the pyrolysis products yields and their chemical compositions were studied. The temperatures of pyrolysis and sweep gas flow rates were varied in the range of 380°C -540°C and 60L/h-260L/h, respectively. The compositions of gaseous products were analyzed by gas chromatography, and that of bio-oil obtained was investigated using gas chromatography-mass spectroscopic(GC-MS) technique. The yield of gaseous products increases with the increasing temperature, the char yield has demonstrated a downtrend, and the maximum yield of bio-oil is up to 15.43 wt.% at 460°C. The yield of char decreases with the sweep flow rate, the gaseous has a minimum yield at 100L/h, and the maximum yield of bio-oil is 15.43wt.% at 100L/h .The main gaseous products are CO, CO2 , H2 and CH4. Ketones and phenols are the main compounds in the bio-oil, the presence of molten inhabites their formation, and promotes the production of furfural. The bio-oil attained from pyrolysis is a potential source of renewable fuel and chemical feedstock.

Hydrogen Production from the Decomposition of Ethanol Aqueous Solution Using Glow Discharge Plasma Electrolysis

High-energy electrons play the most important role in the decomposition of ethanol aqueous solutions under glow discharge plasma electrolysis (GDE).The non-Faradaic currents greatly improve,resulting in the actual gas production yield exceeding the theoretical yield.In this paper,we investigated a novel process of hydrogen generation from ethanol decomposition by GDE.The main gaseous products were H2 and CO;in addition to small amounts of C2 H4,CH4,O2,and C2H6.The H2 volume fraction was above 59% and CO was 20%.We conclude that voltages of points C and D (V C and V D) do not change with the electrolyte concentration,but the 'Kellogg area' becomes narrower with increasing electrolyte conductivity and the glow discharge is easier to attain.In addition,with increasing ethanol volume fraction,the H2 volume fraction decreases.The maximum gas production rate occurred for ethanol volume fractions of 30% and 80%.Improving the discharge voltage and raising the electrolyte conductivity had the same effect on glow discharge plasma electrolysis as the voltage load at both ends of the plasma steam sheath increases.The H2 volume fraction remains the same upon varying the discharge voltage or electrolyte conductivity,but increasing the electrolyte conductivity is advantageous to reduce Joule heating effects caused by GDE.

Influence of Atmosphere on the Radiolysis Products of BPC6 under <em>γ</em>-Irradiation

Bis(2-propyloxy)calix[4]crown-6(BPC6) is an effective separation agent for the removal of cesium from high-level liquid wastes,because of its high selectivity and coordination capacity toward cesium ions.BPC6 will be exposed to ionizing radiation generated by radionuclides during the treatment of high-level liquid nuclear wastes,so it is necessary to investigate the radiolysis mechanism of BPC6 under Y-irradiation conditions.In this work,the radiolysis products including the gaseous and solid products of BPC6 solid were systematically assessed using gas chromatography(GC),micro Fourier transform infrared(Micro-FTIR) spectroscopy,and nuclear magnetic resonance spectroscopy.The radiolysis ratio for BPC6 in an O_2 atmosphere(approximately 10.4%) was significantly higher than that in an N_2 atmosphere (approximately 2.5%).The main radiolytic gas products of BPC6 under O_2 were H_2,CH_4,CO,and CO_2, while those under N_2 were H_2,CH_4,CO,CO_2,C_2H_4,C_2H_6,C_3H_6,and C_3H_8.Finally,a mechanism for the radiolysis of BPC6 under different atmospheres was suggested,in terms of the gas and solid radiolytic products.This work will be of significant help in understanding the degradation mechanism of the BPC6 extraction system.

Enhanced hydrogen formation during the catalytic decomposition of H2O2 on metal oxide surfaces in the presence of HO radical scavengers

Presently and for the foreseeable future, hydrogen peroxide and transition metal oxides are important constituents of energy production processes. In this work, the effect of the presence of HO radical scavengers on the product yield from the decomposition of H2O2 on metal oxide surfaces in aqueous solution was examined experimentally. Scavenging the intermediate product HO˙ by means of Tris or TAPS buffer leads to enhanced formation of H2. In parallel, a decrease in the production of the main gaseous product O2 is observed. Under these conditions, H2 formation is a spontaneous process even at room temperature. The yields of both the H2 and O2 depend on the concentration of Tris or TAPS in the reaction media. We observed that TAPS has a higher affinity for the surface of ZrO2 than does Tris. The difference in adsorption of both scavengers is reflected by the difference in their influence on the product yields. The observed sensitivity of the system H2O2-ZrO2 towards the two different scavengers indicates that O2 and H2 are formed at different types of surface sites.