HCl Yield Research Articles

Effects of iron oxide minerals on the pyrolysis of polyvinyl chloride: Catalytic dechlorination, chlorine capture, and carbon sequestration

To reduce the risk of organochlorine contamination during the pyrolysis of chlorine-containing plastics, catalytic pyrolytic dechlorination of polyvinyl chloride (PVC) by iron oxides is a promising strategy. However, differences in the structural properties of various iron oxides mineral phases may lead to different catalysis activity. In this study, various characterization methods and theoretical calculations were integrated to reveal the effects of ferrihydrite (Fhy) and hematite (Hem) on the pyrolysis characteristics of PVC at 400–800 °C. Both Fhy and Hem lower the dechlorination temperature of PVC, consequently retarding the degradation of dechlorination intermediates and mitigating the emission of volatile compounds. Fhy and Hem reduced the release of chlorinated hydrocarbons and immobilized chlorine as Rokuhnite. Specifically, the yield of HCl at 400 °C decreased from 88.8% for pure PVC to 29.9%/55.8% with the additions of 30% Fhy/Hem. The surface catalytic activity of Hem is stronger than that of Fhy, resulting in better catalytic dechlorination; while Fhy has a larger specific surface area (more adsorption sites), which leads to better chlorine fixation. Fhy and Hem also facilitated the dehydroaromatisation reaction of dechlorinated PVC, increasing the residual carbon yield at 400 °C from 45.5% to 65.4% and to 75.8%, respectively. Preferably from the perspective of pollutant emission, Fhy with large specific surface area and weak crystallinity can adsorb more HCl and catalyze dechlorination as well, so the addition of Fhy (>30%) to PVC pyrolysis process can be beneficial to the control of pollutant emission and carbon sequestration.

Torrefaction of combustible construction and demolition waste: Evolution of fuel performance, heavy metal migration and combustion characteristics

Combustible construction solid wastes (CSW) derived from construction and demolition (C&D) wastes is an important part for waste-to-energy system. Torrefaction experiment of five CSW components involving plastic (PL), wood (WD), textile (TX), paper and board (PB), and rubber (RB) were conducted in a fixed-bed reactor at torrefaction temperature of 200–400 °C and holding time of 30 min. Fuel properties and heavy metal migration of CSW components via torrefaction are characterized by proximate analysis, ultimate analysis, caloric value determination, and the determination of heavy metal contents in solid, liquid and gas products. Combustion characteristics of CSW components and their torrefied solid products were evaluated by TG-FTIR method. The obtained results indicated that torrefaction has a significant influence on volatile matter, fixed carbon, calorific value, and H/C and O/C molar ratios of CSW components. The ash content in high ash CSW components increases and energy yield decreases significantly when torrefaction temperature is larger than 250 °C. Heavy metals of Zn, Pb, Cu and Mn in CSW components is partly migrated into the liquid products, but Hg and As are almost entirely present in the liquid products at different torrefaction temperatures. The combustible index and burnout index of PL, WD, PB and RB decrease gradually when torrefaction temperature is more than 250 °C, and the lower yields of SO2, NO, HCl, CH4 and CO of torrefied CSW are achieved at torrefaction temperature of 250 °C. The optimum torrefaction temperature of 250 °C is proposed for improving fuel properties, heavy metal migration and combustion characteristics of CSW components.

Synergies of redox ability and acidity over RuMn/ZSM-5 for catalytic elimination of 1,2-dichloroethane

Ru-Mn bimetallic catalyst supported on HZSM-5 was prepared by impregnation method for catalytic oxidation of 1, 2-dichloroethane (1, 2-DCE). The 0.1Ru1Mn/ZSM-5 catalyst exhibited the lowest T90 of 241 °C and the highest yields of HCl (75%) and CO2 (57%). The products contained a small amount of dichloroethylene, trichloroethylene, and tetrachloroethylene, with a total yield of <5%. By the characterizations of various instruments, it was found that 0.1Ru1Mn/ZSM-5 exhibited the best catalytic activity because of its rich acidity, high redox property, and highly dispersed Ru and Mn nanoparticles on the surface of HZSM-5. Furthermore, due to the synergies of Ru-Mn bimetal and redox ability-acidity, 0.1Ru1Mn/ZSM-5 exhibited excellent chlorine resistance ability and good catalytic activity during long-term test. The reaction mechanism of catalytic oxidation of 1, 2-DCE was investigated using in situ DRIFTS and GC–MS techniques. Vinyl alcohol was the vital intermediates for 1, 2-DCE oxidation to CO2 and H2O. The double synergistic strategy can provide a reference for designing catalysts to remove chlorinated volatile organic compounds.

Molecular Mechanism Study of the Kinetics and Product Yields during Copyrolysis of Biomass and Solid Wastes: ReaxFF-MD Method Approach.

Copyrolysis is a potential method for the collaborative disposal of biomass and plastics. There is an interaction between biomass and plastics during copyrolysis. In this work, a combination of ReaxFF-MD simulation and experimental validation was used to investigate the pyrolysis reaction process of the biomass and plastic, observing the evolution of free radicals at the molecular level and exploring the distribution of pyrolysis products. TG-MS results show that reaction temperature ranges for cellulose and PVC are 296-400 and 267-480 °C, respectively. HCl is the main product of PVC pyrolysis, and mixing with cellulose will reduce the yield of HCl. The ReaxFF method was used to model the pyrolysis of cellulose and PVC. The modeling temperature is much higher than the real reaction temperature, which is attributed to the time scale of picoseconds of ReaxFF-MD modeling. Modeling results show that the yield of HCl of the cellulose/PVC mixture is obviously lower than that of pure PVC. When mixed with cellulose, the HCl release is largely inhibited and more chlorine elements are retained in the pyrolysis hydrocarbon fraction or solid products.

Efficient catalytic combustion of 1,2-dichloroethane with manganese dioxide doped with sulfate

Sulfate was incorporated into MnO2 through an in-situ synthesis method, and various techniques were employed to treat the sulfate-doped MnO2 in order to obtain Mn2O3-S, Mn3O4-S, and MnO-S, respectively. The manganese oxides were used for the catalytic degradation of 1,2-dichloroethane (1,2-DCE). The catalytic degradation efficiency of T90 on MnO2-S was 385 °C. Meanwhile, the yield of HCl was 85%, CO2 was 92%, and organic by-products were less than 3%. Characterized by XRD, nitrogen adsorption and desorption, H2-TPR, and NH3-TPD, it was found that MnO2-S exhibited excellent catalytic degradation of 1,2-DCE due to its highest specific surface area (35 m2/g), strongest redox properties, and most abundant acidity. XPS characterization showed that an abundance of Mn4+ was beneficial in improving the resistance to chlorine poisoning. In situ DRIFTS revealed the reaction route on MnO2-S shortly, while the reaction routes on the other samples were more complex. Therefore, sulfate-doped MnO2 has the potential to be applied in the catalytic degradation of 1,2-DCE.

Hydrolysis and Analysis of Agricultural Wastes Using Mineral Acids for Possible Glucose Synthesis

This work focuses on conversion of agricultural wastes into fermentable sugar via acid hydrolysis. Proximate and ultimate analysis was carried out to ascertain the physiochemical properties of the biomass feedstock and fermentable sugar. Mineral acid such as hydrochloric acid (HCl) and sulfuric acid (H2SO4) was used as the media for the conversion of plantain peels and water yam peels into fermentable sugar. Concentration of glucose was analyzed using DNS techniques. Modelling of the process was done using three established kinetic models to determine the rate determining step. Results showed that untreated plantain peels and water yam peels contained 30.1% and 6.4% cellulose but increased significantly to 55.1% and 10.03% after hydrolysis indicating increase in fermentable sugar. In comparing the same conditions of plantain-HCl, plantain-HS, water yam-HCl and water yam-HS at 80°C with acid concentration/sample ratio of 0.5:2 at time 90 mins, plantain peels with HCl yield highest concentration of 4.09mg/l fermentable sugar while at the same condition water yam produced 2.031mg/l. Second order kinetic model appears to be the best fit for the process with better correlation coefficient R2 &gt;99% with HCl and plantain peels at a reaction temperature of 60oC conforming to the rate determining step. The model demonstrated an increasing rate constant with increase in temperature which agrees with the magnitude of the hydrolysis process. This work will help in solving the energy need of our society if commercialized. Also, it can serve as a viable alternative to environmental cleanliness because wastes will become raw materials. Plantain peels and water yam peels demonstrated good potential as a source of fermentable sugar but plantain peels performed better.

Synergistic effect and chlorine migration behavior in co-pyrolysis of Pingshuo coal and polyvinyl chloride and directional chlorine enrichment using calcium oxide

Co-pyrolysis of waste plastics and low-rank coal is an important way to realize the recycling of plastic wastes and the clean and efficient conversion of coal. However, halogens released would cause equipment corrosion and affect tar quality when halogenated plastics were co-pyrolyzed with coal. For this reason, polyvinyl chloride (PVC), as a representative of halogenated plastic, was co-pyrolyzed with Pingshuo coal (PS) in a two-stage fixed-bed reactor. The synergistic effect between PS and PVC and the migration behavior of chlorine were investigated, and the in-situ removal of chlorine during pyrolysis was explored by adding a CaO bed in the second stage of the reactor. The results showed that the addition of PVC in PS has a positive synergistic effect on tar yield with a maximum tar yield increment of 2.30 wt% at 30 wt% PVC, which is related to the negative synergistic effect on gas yield. Furthermore, the addition of PVC increases the content of 1–3 ring aromatics and decreases the content of aliphatics in the tar. The chlorine content in char and tar increases significantly with the increase of PVC addition. The addition of a CaO bed can significantly reduce the yield of HCl and the chlorine content in the tar. At 700 ℃, the dehydrochlorination efficiency of CaO can reach 78.1%. However, the CO2 produced by PS pyrolysis will reduce the dehydrochlorination efficiency of CaO, and this effect of CO2 can be reduced by increasing the temperature of the CaO bed.

Oxidation of Methanol and Dichloromethane on TiO2-CeO2-CuO, TiO2-CeO2 and TiO2-CuO@VUKOPOR®A Ceramic Foams.

The application-attractive form of TiO2, CeO2 and CuO-based open-cell foam supported catalysts was designed to investigate their catalytic performance in oxidation of two model volatile organic compounds-methanol and dichloromethane. TiO2-CeO2, TiO2-CuO and TiO2-CeO2-CuO catalysts as thin films were deposited on VUKOPOR®A ceramic foam using a reverse micelles-controlled sol-gel method, dip-coating and calcination. Three prepared catalytic foams were investigated via light-off tests in methanol and dichloromethane oxidation in the temperature range of 45-400 °C and 100-500 °C, respectively, at GHSV of 11, 600 h-1, which fits to semi-pilot/industrial conditions. TiO2-CuO@VUKOPOR®A foam showed the best catalytic activity and CO2 yield in methanol oxidation due to its low weak Lewis acidity, high weak basicity and easily reducible CuO species and proved good catalytic stability within 20 h test. TiO2-CeO2-CuO@VUKOPOR®A foam was the best in dichloromethane oxidation. Despite of its lower catalytic activity compared to TiO2-CeO2@VUKOPOR®A foam, its highly-reducible -O-Cu-Ce-O- active surface sites led to the highest CO2 yield and the highest weak Lewis acidity contributed to the highest HCl yield. This foam also showed the lowest amount of chlorine deposits.

Enhanced activity of plasma catalysis for trichloroethylene decomposition via metal-support interaction of Si[sbnd]O[sbnd]Co/Mn bonds over CoMnOX/ZSM-5

Metal-support interaction has a substantial influence on catalyst activity while little attention has been paid to it in the plasma catalytic system. Herein, the effect of support on the activity of CoMnOX-based catalysts was investigated for trichloroethylene removal by plasma catalysis, and CoMnOX/ZSM-5 exhibited the highest mineralization rate (36.93−94.24 %), HCl and Cl2 yield (19.66−94.37 %), energy yield (63.29–29 g/kWh), as well as the lowest export ozone concentration (18.72–108.83 mg/m3) under 6–10 kV. The excellent catalytic activity of CoMnOX/ZSM-5 was ascribed to the formation of abundant defects and oxygen vacancies, which was induced by the SiOCo/Mn hybridization promoting Co/MnO bonds cleavage. CoMnOX/ZSM-5 also exhibited superior adsorption ability, large amount of Co3+, Mn4+ and adsorbed oxygen species, high reducibility and suitable acidity. Moreover, CoMnOX/ZSM-5 maintained superior water-resistant ability and high catalytic activity after 50 h operation. The proposed TCE degradation mechanism suggested that the contribution of plasma active oxygen species was involved in TCE oxidation and oxygen cycle of catalyst. This work provides a novel strategy to design catalysts in plasma catalytic system.

Synthesis and structural characterisation of trivalent halidoantimonates and bismuthates of 2-methyl-2-benzoxazole (box): Reactivity and solid-state structural diversity within the [MX(6 – n)] [boxH](3 – n) series (M = Sb or Bi; X = Cl, Br, I; n = 0 or 1)

The structural characterisation (X-ray diffraction) of a series of anionic antimony (III) and bismuth (III) halide complexes containing protonated 2-methyl-1,3-benzoxazole (boxH) countercations are reported. Treatment of aqueous strong acid (HCl or HBr) or strong acid/additional solvent mixtures of box with MX3 (M = Sb, Bi; X = Cl, Br) leads to the isolation of known compounds BiCl5(boxH)2 (6: 33%) and SbBr5(boxH)2 (7: 31%) and the novel material BiBr5(boxH)2 (8: 57%). In the solid state, 6–8 all display an anionic portion consisting of edge sharing infinite zig-zag chains of the metallic [(MX5)2–]∞ units classified as Type A in structure. In contrast, mixtures of box, conc. HCl and SbCl3 yield, following recrystallization, to small quantities of Sb2OCl6(boxH)2 (2: 0.4%); a hitherto unknown complex containing the less common Sb2OCl62− anion. Hypotheses as to the origin of 2 are presented including its formation by hydrolysis of known SbCl4(boxH). Hydroiodic acid solutions of box treated with SbI3 leads to the isolation of the SbI6(boxH)3·(H2O) (9: 42%) which displays a rare example of the isolated SbI63− anion. The treatment BiI3 under similar conditions leads to the precipitation of previously known Bi2I9(boxH)3 (10: 54%) as a major product. Further evaporation of the reaction mixture from which 10 was obtained yields a second minor product, 11 (3%), identified as the Bi analogue of 9: BiI6(boxH)3·(H2O). The species described herein are further discussed in terms of their general coordination properties and relevance to related complexes under current scrutiny for their solid-state materials properties.

Atmospheric chemistry of (Z)- and (E)-1,2-dichloroethene: kinetics and mechanisms of the reactions with Cl atoms, OH radicals, and O3.

Smog chambers interfaced with in situ FT-IR detection were used to investigate the kinetics and mechanisms of the Cl atom, OH radical, and O3 initiated oxidation of (Z)- and (E)-1,2-dichloroethene (CHClCHCl) under atmospheric conditions. Relative and absolute rate methods were used to measure k(Cl + (Z)-CHClCHCl) = (8.80 ± 1.75) × 10-11, k(Cl + (E)-CHClCHCl) = (8.51 ± 1.69) × 10-11, k(OH + (Z)-CHClCHCl) = (2.02 ± 0.43) × 10-12, k(OH + (E)-CHClCHCl) = (1.94 ± 0.43) × 10-12, k(O3 + (Z)-CHClCHCl) = (4.50 ± 0.45) × 10-21, and k(O3 + (E)-CHClCHCl) = (1.02 ± 0.10) × 10-19 cm3 molecule-1 s-1 in 700 Torr of N2/air diluent at 298 ± 2 K. Pressure dependencies for the Cl atom reaction kinetics were observed for both isomers, consistent with isomerization occurring via Cl atom elimination from the chemically activated CHCl-CHCl-Cl adduct. The observed products from Cl initiated oxidation were HC(O)Cl (117-133%), CHCl2CHO (29-30%), and the corresponding CHClCHCl isomer (11-20%). OH radical initiated oxidation gives HC(O)Cl as a major product. For reaction of OH with (E)-CHClCHCl, (Z)-CHClCHCl was also observed as a product. A significant chlorine atom elimination channel was observed experimentally (HCl yield) and supported by computational results. Photochemical ozone creation potentials of 12 and 11 were estimated for (Z)- and (E)-CHClCHCl, respectively. Finally, an empirical kinetic relationship is explored for the addition of OH radicals or Cl atoms to small alkenes. The results are discussed in the context of the atmospheric chemistry of (Z)- and (E)-CHClCHCl.

A full mechanistic and kinetics analysis of carbon tetrachloride (CCl4) sono-conversion: Liquid temperature effect

In this study, a model of CCl4 sono-pyrolysis inside an acoustic bubble is used to provide a novel mechanistic and kinetics study of CCl4 conversion. The impact of fluid temperature (10–50 °C) on CCl4 conversion and the resulted products is illustrated for various aqueous CCl4 concentrations and acoustic intensities (0.7–1.5 W/cm2). With a concentration less than 3 × 10−3 M, 1 W/cm2 is sufficient for the complete degradation of CCl4 at 20 °C. However, at 10 °C, 1.5 W/cm2 is much than enough to degrade CCl4 completely, regardless of its concentration in solution. The generation of reactive chlorine species (RCS) increased proportionately with the temperature rise when the intensity was 0.7 W/cm2. In contrast, between 1 and 1.5 W/cm2, increasing the liquid temperature from 10° to 40 °C has a beneficial effect on the sonolytic activity of the cavity. However, this positive impact continues to be observed only for·OH radicals when the bulk liquid temperature is greater than 40 °C (the yield of RCS, H·, HCl, and HOCl is amortized). According to the simulation results, it was concluded that the rapid sono-degradation of nonvolatile pollutants in the presence of CCl4 was mainly due to the RCS and·OH radicals generated at the efficient bubble collapse.

Effect of experimental variables on coal catalytic hydrogasification in a pressurized fluidized bed

Catalytic hydrogasification of pulverized coal was performed using a pressurized fluidized bed to investigate the effect of experimental variables including catalyst additives, temperature (600–850 °C) and hydrogen (H2) pressure (0.6–3.0 MPa) on the catalytic behavior of cobalt (Co) and formation profiles of target products, i.e., methane (CH4) and liquid hydrocarbons (HCL). The experimental results suggest that calcium (Ca) as an additive demonstrated a superior promoting effect on Co by mediating the Co-coal interaction, which initiated the catalytic depolymerization and hydrogenation of unreactive carbon. The temperature above 750 °C stimulated the diffusion of Co-Ca catalyst in the coal structure, and enhanced the coal catalytic hydrogasification by lowering the activation energy. However, the elevated temperature decreased the HCL yield due to the intensified hydrocracking. The elevation of H2 pressure strengthened the Co-Ca-Coal-H2 interaction, which conduced to the depolymerization and hydrogenation effect of Co-Ca catalyst, and improved the yield of CH4 and HCL. Based on the experimental results, a two-stage pressurized fluidized bed reactor scheme was proposed to couple the coal catalytic hydropyrolysis with char catalytic hydrogasification. Staged hydrogenation of coal was realized, and a yield of 74.2 wt% for gaseous hydrocarbons (CH4 and C2-C3) and 3.36 wt% of HCL (BTX, PCX, and naphthalene) were obtained.

An elemental and 87Sr/86Sr isotopic restitution of contaminated pore waters from sandy sediments of the Peciko gas field (Mahakam Delta, Indonesia)

Pore waters of hydrocarbon-bearing sand layers from gigantic Peciko gas reservoir located to the South of the Mahakam Delta in Indonesia were reconstructed and studied by applying the restored pore-water technique. The method is based on the Sr isotopic compositions of rock chips leached with de-ionized water aided, here, by the associated contents of major, metal and rare-earth elements (REEs). The soluble minerals were also leached with dilute hydrochloric acid and analyzed for their Sr isotopic compositions. The main founding is that many of the recovered H 2 O leachates were most probably contaminated during coring, which induced abnormally high metal and REE contents. The leachates considered free of pollution yield 87 Sr/ 86 Sr ratios that increase progressively with depth, which suggests a recent supply of surface waters to the upper pore waters. It seems also that only a few sedimentary horizons are interconnected at intermediate depths. Furthermore, the minerals dissolved by dilute HCl yield quite systematically lower 87 Sr/ 86 Sr ratios than the associated pore waters, which suggests a crystallization earlier than the recent flushing of the upper sediments by surface-type waters. • Pore waters of gas-bearing sands from Peciko reservoir in Indonesia were reconstructed. • The method includes the 87 Sr/ 86 Sr ratios and the major, metal and REEs of H 2 O leachates. • The H 2 O leachates with high metal and REE contents were contaminated during coring. • Only a few sand units seem to be connected at intermediate depths. • The minerals dissolved by HCl are older than recent fluid supplies in the upper sediments.

Catalytic oxidation of dichloromethane over Pt-Co/HZSM-5 catalyst: Synergistic effect of single-atom Pt, Co3O4, and HZSM-5

The catalytic degradation of chlorinated volatile organic compounds (CVOCs) at low temperatures is a great challenge. In this work, Pt-Co/HZSM-5 ternary catalysts were synthesized and used for the catalytic oxidation of dichloromethane (DCM). By adding only trace amounts of Pt (0.01 wt. %), Pt-Co/HZSM-5 ternary catalyst exhibits better CO2 yield and lower by-product yield than Co/HZSM-5 catalyst. Besides, it maintained stable activity for at least 45 h without substantial changes. The addition of water vapor to the DCM degradation process on Pt-Co/HZSM-5 ternary catalysts was shown to promote DCM conversion, CO2 yield, and HCl yield. Catalyst characterization shows that Co (in the form of Co3O4) could effectively anchor Pt atoms, thus realizing the single-atom dispersion of Pt. In turn, the formed single-atom Pt increases the proportion of oxygen vacancies on the surface of Co3O4, thereby enhancing the redox properties of Co3O4. In the catalytic oxidation process, DCM first adsorbed and dechlorinated on the surface of HZSM-5 due to abundant acid sites and then completely dissociated under the interaction of Pt and Co. Thanks to the synergies of Pt, Co, and HZSM-5, Pt-Co/HZSM-5 exhibited appropriate redox ability, a suitable distribution of acid sites, and sufficient surface adsorbed oxygen, possibly explaining its lower by-product yields and the more efficient formation and desorption of HCl.

The influence of relative humidity on double dielectric barrier discharge plasma for chlorobenzene removal

The influence of relative humidity on the electrical characteristics, the generation of the active species and the chlorobenzene removal performance was studied. The results show that both the peak-to-peak current and the discharge power decreased with the increase of relative humidity under the same peak-to-peak voltage. A reduction of electron temperature was observed with the addition of water vapour, affecting the electron impact processes. It was observed that excited states of N 2 and O were affected by the water due to the quenching effect. A decrease of chlorobenzene removal efficiency was achieved from 81.7% to 70.7% as the increase of humidity. However, carbon balance analysis depicts the yields of CO 2 in humid air were higher than that in dry air due to the help of radical OH, especially in RH = 40%, and highest energy efficiency with 4.4 g kW −1 h −1 was also achieved at RH = 40%. Chlorine balance indicates that the product HCl is more easily generated in the presence of H 2 O. A difference in the chlorobenzene degradation pathway was revealed. Fewer kinds of benzenoid byproducts were found in dry air, which was in agreement with the plasma diagnostics results. Radicals generated in humid air promoted the total oxidation process, resulting in fewer kinds of ring-open byproducts and higher CO 2 yield. • A novel home-made mini dDBD reactor was used to remove chlorobenzene. • Active species generated in the discharge were affected by relative humidity. • The addition of water was helpful to improve the yield of CO 2 and the yield of HCl. • The removal pathways of chlorobenzene were affected by the water.

Comparison of smoke component yields between room‐scale and bench‐scale experiments

SummaryA standard procedure is needed for obtainingaccurate values of the yields of fire effluent components that are associated with harm to people from a singleacute exposure to the effluent from a fire involving realistic commercial products. We compare yields of toxic gases generated by four bench‐scale apparatus to the yields from previously conducted room‐scale fires. The apparatus is the radiant apparatus in NFPA 269 and ASTM E 1678, the smoke density chamber in ISO 5659‐2, a controlled‐atmosphere version of the cone calorimeter (ASTM E 1354), and the tube furnace specified in ISO/TS 19700. The bench‐scale specimens were cut from the same products that were burned in the room‐scale tests: a sofa, bookcases, and household electric power cable. The yields of CO2 CO, HCl, and HCN were determined. The yields of other toxicants (NO, NO2, formaldehyde, and acrolein) were below the detection limits, but were shown to be of limited importance relative to the four measured gases. We developed a criterion of a factor of two for satisfactoryscale agreement. Using this, the yields from the modified cone calorimeter were the most promising, but still imperfect, match to the room fire yields. The results of this study provide an improved basis for obtainingaccurate combustion product yield data for fire hazard and risk modeling over what currently exists.

Modified geopolymers as promising catalyst supports for abatement of dichloromethane

Geopolymers have not been extensively employed as catalytic materials despite of their zeolite-resembling Si–Al structure. Geopolymerization offers a novel way for preparation of catalysts and possibility to use waste or industrial side-stream derived raw material as a resource for catalyst manufacturing. This work concentrates on metakaolin-based geopolymer materials that were prepared, characterized and tested as alternative environmentally benign catalyst supports for the oxidation of dichloromethane. The geopolymers with the Si/Al ratio of 1.5 were modified with HCl to increase their specific surface area, which is important in catalytic applications. Significant increase in specific surface areas was achieved via leaching of Na and Al from the geopolymer structure. Highest specific surface areas achieved for calcined geopolymers were over 500 m2g-1. Use of acid concentrations higher than 1 M led to the dehydroxylation of the geopolymer. Dehydroxylation decreased the total acidity of geopolymer through the loss of the Brønsted acid sites, which are responsible for the adsorption of dichloromethane in the beginning of the catalytic reaction. Absence of Brønsted acid sites was observed by the formation of CH2O as the only reaction intermediate. The best result in the dichloromethane oxidation was found with the geopolymer treated with 1 M HCl. Without using any additional active sites, the maximum dichloromethane conversion of 90% was reached at 525 °C with the maximum HCl yield of 83%. This result indicates the good potential of modified geopolymers to be used as catalyst supports in environmental applications.

PVC-Based Copper Electric Wires under Various Fire Conditions: Toxicity of Fire Effluents.

Ventilation-controlled fires tend to be the worst for toxicity, because they produce large amounts of fire effluent containing high yields of toxic products. In order to examine the dependence of the amount of chosen few main combustion gases under ventilation-controlled conditions, a PVC-insulated copper electric wire with unknown composition (PVC filled with chalk) was studied by mean of a steady state tube furnace. For the tested wire, lower values of CO2 yields at different ventilation conditions were obtained than for the reference pure polymer unplasticized PVC and additionally tested pure LDPE, the yields were higher three times in the case of PVC and two times in the case of LDPE than those received for wire at the same ventilation conditions, which pointed out decreasing contribution of hyperventilation effect to human during cable fire. In contrast, higher values of toxic CO yields, four times higher, were obtained for the PVC-insulated electric wire rather than for the pure polymers. The maximum value of CO yield (0.57 g/g) was determined in the case of 5 L/min of primary airflow and decreased with increasing ventilation. The measured yields of hydrocarbons were similar to the reference values except for the equivalence ratio ϕ = 0.27, where hydrocarbon yield was equal to 0.45 g/g. The HCl yield of fire effluents from the PVC-insulated wire was shown to be independent of ventilation conditions. The corrosive reaction between copper and the HCl species and the flame-retardant mechanisms of the additives, caused the lower values of HCl in the fire effluent of the PVC-insulated copper wire than for pure polymer.

Catalytic abatement of dichloromethane over transition metal oxide catalysts: Thermodynamic modelling and experimental studies

Dichloromethane (DCM) is a noxious chemical that is widely used in industry. The current work focuses on the catalytic abatement of DCM from industrial effluents to minimize its harmful effects to the environment and human wellbeing. Three transition metal oxide catalysts (V, Cu and Mn) supported on γ-Al2O3 were synthetized for total oxidation of DCM in presence of steam. Thermodynamic modelling was used to reveal information related to the stability of the used transition metal oxides in the abatement conditions. The results showed that with 10 wt-% CuO and 10 wt-% V2O5 containing catalysts 100% conversion of DCM together with 90% HCl yield and insignificant by-product formation can be achieved at temperature around 500 °C. According to modelling, V2O5 should be stable at the conditions of DCM oxidation, while CuO would be more stable at higher temperature level (decomposition of CuCl2 starts at 300 °C). MnCl2 remains stable until 800 °C, which leads to deactivation of MnO2 catalyst. Presence of steam inhibits the poisoning of the materials by chlorine based on thermodynamic calculation. XRF analysis supports the results of thermodynamic modelling – used MnO2 and CuO catalysts contain chlorine, which was not detected in case of V2O5/Al2O3. CuO/γ-Al2O3 seems to be a good alternative to noble metal catalysts for the total oxidation of dichloromethane when used in the presence of steam and the temperatures above 300 °C to minimize Cl-poisoning. The outcomes of this study showed that the prepared metal oxides are promising catalysts to minimize pollution caused by chlorinated volatile organic compounds.