The effects of metallic catalysts on light crude oil oxidation in limestone medium

In this study, 28 experiments were performed to study the effects of metallic additives on light crude oil oxidation in limestone medium. Karakuş and Beykan crude oils from Turkish oil fields were used. The metallic additives were ferric chloride (FeCl₃), copper chloride (CuCl) and magnesium chloride (MgCl₂·6H₂O). The mixture of aqueous solutions of three metallic salts with limestone and the crude oils was subjected to a controlled heating schedule under a constant flow rate of air. The produced gas was analysed for its oxygen and carbon oxides contents.The results of reaction kinetics showed that the molar CO₂/CO ratio values of fuel combustion increased when additives were added. A decrease in the atomic H/C ratio with an increase in temperature was observed for all runs. The reaction order, m in Arrhenius equation increases as concentration of copper and magnesium chloride additive increases but decreases as ferric chloride additive increases in both crude oils. It is observed that the metallic additives except ferric chloride decreased the Arrhenius constant, Ar, for both crude oils.As concentration of ferric chloride increases the activation energy of Karakuş crude oil increases while activation energy of Beykan crude oil decreases. The copper chloride additive shows same trend for both crude oils. The 1.0 mol% concentration decreases the activation energies. The 2.0 mol% magnesium chloride increases the activation energy of Karakuş crude oil while decreases the activation energy of Beykan crude oil more than 1.0 mol% does.For Karakuş crude oil, the oxygen consumption curves of 2.0 mol% of metallic additives show one peak. There is similar behavior between runs with 1.0 mol% of ferric chloride and magnesium chloride and runs with no additive, but the oxidation reaction peaks with metallic salts at both concentrations occurs at lower temperatures. For Beykan crude oil, all the additives lower the peak temperature when they are compared to standard run. The trends of the curves are actually the same. Copper chloride shows one peak with the 1.0 and 2.0 mol% runs for both crude oils.     

Direct Oxidation of Propylene to Propylene Oxide with Molecular Oxygen: A Review

The direct oxidation of propylene to propylene oxide (PO) using molecular oxygen has many advantages over existing chlorohydrin and hydroperoxide process, which produce side products and require complex purification schemes. Recent advances in liquid-phase and gas-phase catalytic oxidation of propylene in the presence of only molecular oxygen as oxidant and in absence of reducing agents are summarized. Liquid-phase PO processes involving soluble or insoluble Mo, W, or V catalysts have been reported which provide moderate conversions and selectivities, but these likely involve autoxidation by homogeneous chain reactions. Gas-phase PO catalysts have been mostly Ag-, Cu-, or TiO₂-based substances, although other compositions such as Au-, MoO₃-, Bi-based catalysts and photocatalysts have also been suggested as possibilities. The Ag catalysts differ from those used for ethylene oxide production in having high Ag contents and numerous additives. The additives are solid-phase alkali metals, alkaline earth metals, and halogens, with the most common substances being NaCl and CaCO₃. Nitrogen oxides in the form of gas-phase species or nitrates have also been found to be effective in enhancing PO production. Direct epoxidation by surface nitrates is a possibility. Titania catalysts supported on silicates have also been reported. These have higher PO selectivities at high conversion than silver catalysts.     

The Effect of Gaseous Diluents on Ozone Generation from Oxygen

Ozone generation in a negative corona discharge has been experimentally investigated using both a pure oxygen and in binary mixtures of oxygen with several gases. The concentration of ozone (O₃) in such mixtures is found to be dependent both on the input energy density η, dissipated in unit volume of gas mixture and on the type and the concentration of the additives. The experimentally measured dependencies of ozone concentration on the input energy density (O₃) = f(η) have been fitted using the Vasiliev–Kobozev–Eremin formula and the specific rate coefficients for ozone formation K_f and ozone decomposition K_d have been calculated. Using Ar, N₂ or CO₂ as admixtures, an increase in the specific rate coefficient for ozone generation was observed for increasing concentrations of added gaseous impurity into oxygen. In contrast, admixtures with SF₆ or CCl₂F₂ caused a substantial reduction of K_f values. The absolute values of ozone concentration at constant input energy density were observed to decrease with decreasing concentrations of oxygen in all mixtures.     

Does lower energy usage mean lower carbon dioxide emissions? — A new perspective on the distillation process

Although fossil fuels play an important role as the primary energy source that currently cannot be replaced easily with other energy sources, their depletion and environmental impact are becoming major concerns. Improvements in energy efficiency are believed to solve both problems simultaneously. We examined the relationships between the improvement in energy efficiency, energy usage and CO₂ emissions in industry, especially in the distillation process. The energy efficiency improvement of dimethyl ether (DME) purification performed with dividing-wall column distillation (DWC) and acetic acid recovery performed with mechanical vapor recompression (MVR) were evaluated by recalculating the amount of fuel burnt and its CO₂ emission. The results showed that the paradigm of lower energy being directly proportional to lower CO₂ emissions is not entirely correct. To avoid this confusion, a tool for examining the uncommon behavior of various systems was developed.     

Flame‐retardant properties of magnesium hydroxystannate and strontium hydroxystannate coated calcium carbonate on soft poly(vinyl chloride)

The flame‐retardant and smoke‐suppressant properties of soft poly(vinyl chloride) (PVC) treated with zinc hydroxystannate (ZHS), calcium carbonate (CaCO₃), magnesium hydroxystannate [MgSn(OH)₆], strontium hydroxystannate [SrSn(OH)₆], ZHS–MgSn(OH)₆, ZHS–SrSn(OH)₆, MgSn(OH)₆‐coated CaCO₃, SrSn(OH)₆‐coated CaCO₃, ZHS–MgSn(OH)₆‐coated CaCO₃, and ZHS–SrSn(OH)₆‐coated CaCO₃ were studied with the limited oxygen index, char yield, and smoke density rating methods; the mechanical properties were also studied. The results showed that, with the equivalent addition of the corresponding hydroxystannate, the soft PVC treated with hydroxystannate‐coated CaCO₃ had a higher limited oxygen index than the corresponding hydroxystannate, and the soft PVC treated with the agents containing magnesium had a higher limited oxygen index than the soft PVC treated with the agents containing strontium, except for ZHS–MgSn(OH)₆‐coated CaCO₃. The improvement in the char formation of the hydroxystannate‐coated CaCO₃ was better than that of the corresponding hydroxystannate in most cases, and the aforementioned agents reduced the smoke density rating, decreased the tensile strength, and increased the elongation and impact strength basically. Thermal analysis showed that the additives promoted the evolution of hydrogen chloride, early crosslinking, and rapid charring through the strong catalyzing effect of Lewis acids. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Using yttrium,tungsten, and niobium-oxide additives to improve the electrical resistance of strontium zirconate ceramics

Conclusions It is possible to increase the electrical resistance of materials with vacancy transfer of oxygen anions by filling some of the oxygen vacancies with oxygen admitted by means of additives forming a solid solution.To bring in additional oxygen the cation of the additive should have a higher degree of oxidation than the cation it is replacing in the strontium zirconate.In terms of the effective influence on enhancing the conductivity of strontium zirconate, the additives are arranged in accordance with the amount of admitted oxygen in the series: Y₂O₃ + Nb₂O₅, SrO + WO₃, Y₂O₃+2 WO₃, 2SrO+ Nb₂O₅, Y₂O₃+2ZrO₂, Y₂O₃.Additions of yttrium, tungsten, and niobium oxides will improve the working properties of ceramics based on strontium zirconate, since they increase its electrical resistance by 10 or more times at room temperature, and 4–7 times at 1500°C, which indicates the preservation, up to quite high temperatures, of the marked influence on conductivity of the transfer of oxygen through the oxygen vacancies.Translated from Ogneupory, No. 8, pp. 11–13, August, 1993.     

Effect of pro-oxidants on the aerobic biodegradation,disintegration, and physio-mechanical properties of compostable polymers

Biodegradable polymers are gaining momentum to resolve the globally acknowledged plastic waste problem. Understanding, characterizing, and developing new generations of biodegradable plastics is crucial to provide industries with alternative green materials that can fully satisfy biodegradation rates and lifetime specifications. This study evaluates the influence of metal pro-oxidant additives on the degradation properties of various biodegradable polymer systems. For this purpose, iron (III) stearate (FeSt₃) and bismuth oxide (Bi₂O₃), as oxidant agents, were incorporated into poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), poly(butylene adipate-co-terephthalate) (PBAT), cellulose acetate (CA), poly(lactic acid) (PLA), and thermoplastic starch (TPS) bioplastics. The material performances and biodegradability properties due to the additives on the resulting bioplastic formulations were investigated. A mechanism was proposed in which both pro-oxidant additives can accelerate the thermo-oxidation processes under composting conditions and cleave the polymer chains into smaller fragments to stimulate the biodegradation rate through microorganisms' activity. The study revealed that both pro-oxidant additives, FeSt₃ and Bi₂O₃, effectively improved the biodegradation process for all tested polymers except TPS, which already had a very high biodegradation rate. The observed change in the barrier and mechanical properties due to the additives were within tolerable limits of corresponding neat polymers.     

Iron Nanoparticle Additives as Burning Rate Enhancers in AP/HTPB Composite Propellants

Burning rate measurements were carried out for ammonium perchlorate/hydroxyl‐terminated polybutadiene (AP/HTPB) composite propellants with iron (Fe) nanoparticles as additives. Experiments were performed in a strand burner at pressures from 0.2 to 10 MPa for propellants containing approximately 80 % AP and Fe nanoparticles (60–80 nm) at concentration from 0 to 3 % by weight. It was found that the addition of 1 % Fe nanoparticles increased burning rate by factors of 1.2–1.6. Because Fe nanoparticles are oxidized on the surface and have high surface‐to‐volume ratio, they provide a large surface area of Fe₂O₃ for AP thermal decomposition catalysis at the burning propellant surface, while also providing added energy release due to the oxidation of nanoparticle sub‐shell Fe. The increase in burning rate due to Fe nanoparticle content is similar to the increase in burning rate caused by the addition of iron oxide (Fe₂O₃) particles observed in prior literature.     

Photosensitized degradation of polyolefins. II

The oxydative photodegradation of polyethylene sensitized by aromatically substituted dienes such as 1,6-diphenyl-1,3,5-hexatriene (DPH) and 1,4-diphenyl-1,3-butadiene (DPB) has been investigated. The rate of degradation has been monitored by following the change of the mechanical properties of the polymer during accelerated indoor aging tests. It was found that both additives are efficient sensitizers of the photodegradation of polyethylene. The mechanism of photo-oxidation has been investigated by ESR and IR spectroscopy and it has been interpreted on the basis of a complex mechanism which includes excited singlet oxygen (¹O₂) and the products of photodegradation of the additives. Singlet oxygen, produced by DPB and DPH and/or by impurities present in the polymer, reacts with the additives themselves and, directly, with polyethylene. In turn, the products of photodegradation of the additives react with the polymer via hydrogen atom abstraction, further promoting the photodegradation. Irradiation carried out in absence of air seems to rule out the possibility of direct hydrogen atom abstraction by DPB and DPH.     

The influence of air and its components on the cathodic stability of N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide

Although water- and air-stable ionic liquids have been in use for some years, experiments found in the literature are still performed in inert gas with ppm levels of oxygen and water. In this study, the influence of different environments (vacuum, argon, nitrogen, air and oxygen and water) on the cathodic electrochemical window of the ionic liquid N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR₁₄TFSI) is reported and compared with investigations and processes found in the literature. The investigation indicates that this ionic liquid is highly stable in a vacuum and under argon flow. However, its cathodic stability is reduced in nitrogen and dry air. The simultaneous presence of water and air strongly affected the useful electrochemical window, as seen previously for imidazolium-based ionic liquids.     

Study of poly(vinyl chloride) interfaces using slow positron beams

Elemental and X‐ray fluorescence analyses were performed to determine the chemical compositions of insulator and jacket poly(vinyl chloride) (PVC) samples. In addition, differential scanning calorimetry (DSC) measurement was performed to determine their glass‐transition temperatures (T_g) and melting points. The effect of additives on the two investigated samples, as well as on a pure PVC sample, was studied using Doppler‐broadening energy spectra coupled with the slow positron beam technique. Significant variation in the S parameter as a function of positron implantation energy and depth from the surface to the bulk was observed in all samples. The S parameter increased at a very low positron energy (< 1 keV), saturated to about 6 keV, and then decreased up to 27 keV. The S parameter (ΔS) changed to the extent of the change in the breadth of the distribution of free‐volume defects, which was larger in the jacket PVC sample, which had more additives, than in the insulator PVC sample. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3789–3793, 2006     

Phase formation in porous liquid phase sintered silicon carbide: Part III: Interaction between Al2O3–Y2O3 and SiC

The structure and phase formation of porous liquid phase sintered silicon carbide (porous LPS-SiC), containing yttria and alumina additives have been studied. The present paper is focused on the system Y–Al–Si–C–O. The systems Al–Si–C–O and Y–Si–C–O have been studied in previous papers [J. Eur. Ceram. Soc. (in press) parts I and II].The reaction products of the interaction of Al₂O₃/Y₂O₃ with SiC and resulting microstructures were analysed by model experiments. The influences of different sintering atmospheres, namely argon and Ar/CO and different temperatures have been investigated. Thermodynamic calculations and sintering experiments reveal that silicides or carbides can be formed in addition to stable oxides. The main parameters controlling the formation of the different reaction products are the free carbon content, the oxygen activity and the temperature.Using CO containing atmospheres, the decomposition of the oxide additives can be effectively suppressed and stable porous LPS-SiC can be produced.     

Recovery,characterization and conceptual modelling of Non-Bituminous organic materials from oil sands

The hot water process has recovered approximately 90% of the bitumen in oil sands, but the remaining 10% of bitumen and naphtha has been lost to the tailings pond. Recovery of bitumen and non-bituminous combustibles (NBC) from centrifuge, scroll and final tailings has been considered. The effects of four sequestering agents, and of chemical additives such as CaCl₂ and FeCl₃ on the flotation behavior of bitumen, NBC and minerals in these tailings have been investigated. A simple method of isolating NBC materials has been developed. The flotation of both bitumen and NBC was enhanced by phosphate treatment and depressed by EDTA. NBC was characterized by its physical properties, energy content, functionality and chemical analysis. A conceptual model explains the interactions between the bitumen, minerals and NBC fractions present in tailings slurries.     

Electrolyte additives for enhanced thermal stability of the graphite anode interface in a Li-ion battery

The influence of electrolyte additives on the thermal stability of graphite anodes in a Li-ion battery has been investigated. The selected additives are: ethyltriacetoxysilane, 1,3-benzoldioxole, tetra(ethylene glycol)dimethylether and vinylene carbonate. These compounds were added in 4% to an electrolyte consisting of 1M LiBF₄ ethylene carbonate (EC)/diethyl carbonate (DEC) solvent mixture. Differential scanning calorimetry (DSC) was used to investigate the thermal stability. The electrochemical performance was investigated by galvanostatic cycling and the formed solid electrolyte interphase (SEI) was characterised by photoelectron spectroscopy (PES) using Al Kα and synchrotron radiation (SR). The onset temperature for the thermally activated reactions was found to increase for all electrodes cycled with additives compared to electrodes cycled without additives. The onset temperature increased in the order: no additive < tetra(ethylene glycol)dimethyl ether < 1,3-benzoldioxole < ethyl-triacetoxysilane < vinylene carbonate. Features in the PES spectra found to be associated with high onset temperatures for thermally activated reactions are: (i) no discernible graphite peak, (ii) small amount of salt species of the type LiF and Li_xBF_yO_z and (iii) larger amounts of organic compounds preferably with a high oxygen content.     

Propane Oxidative Dehydrogenation over Metal Pyrophosphates Catalysts

Metal pyrophosphates (M–P₂O₇, where M is V, Zr, Cr, Mg, Mn, Ni or Ce) have been found to catalyze the oxidative dehydrogenation of propane to propene. The reaction was conducted at 1 atm, 450–550°C and feed flowrate of 75 cm³/min (20 cm³/min propane, 5 cm³/min oxygen and the balance is helium). All catalysts showed increase in degrees of conversion and decrease in olefins selectivity with increase in reaction temperature. At 550°C, MnP₂O₇ exhibited the highest activity (40.7% conversion) and total olefins (C₃H₆ and C₂H₄) yield (29.3%). The other catalysts, indicated by their respective metals, may be ranked (based on olefins yield) as V (16.9%) < Cr (17.5%) < Ce (25.1%) < Zr (26.2%) < Ni (26.8%) < Mg (27.9%). The reactivity of the lattice oxygen was estimated from energy of formation of the corresponding metal oxides. Correlation between the selectivity to propene and the standard energy of formation was attempted. Although there was no clear correlation, the result suggested that the lattice oxygen play a key role in the selectivity-determining step.     

Effects of additives on the stability of electrolytes for all-vanadium redox flow batteries

The stability of the electrolytes for all-vanadium redox flow battery was investigated with ex-situ heating/cooling treatment and in situ flow-battery testing methods. The effects of inorganic and organic additives have been studied. The additives containing the ions of potassium, phosphate, and polyphosphate are not suitable stabilizing agents because of their reactions with V(V) ions, forming precipitates of KVSO₆ or VOPO₄. Of the chemicals studied, polyacrylic acid and its mixture with CH₃SO₃H are the most promising stabilizing candidates which can stabilize all the four vanadium ions (V²⁺, V³⁺, VO²⁺, and VO₂ ⁺) in electrolyte solutions up to 1.8 M. However, further effort is needed to obtain a stable electrolyte solution with >1.8 M V⁵⁺ at temperatures higher than 40 °C.     

Densification,microstructure and mechanical properties of ZrB2–SiCw ceramic composites

ZrB₂–SiCw composites were prepared through hot-pressing at a low temperature of 1800 °C, and Al₂O₃ plus Y₂O₃ were added as sintering aids. Analysis revealed that additives may react with impurities (i.e. surface oxygen impurities and residual metallic impurities) to form a transient liquid phase, thus promote the sintering and densification of ZrB₂–SiCw composites. The content of additives was found to have a significant influence on the sinterability, microstructure and mechanical properties of ZrB₂–SiCw composites. ZrB₂–SiCw composite prepared with a small amount of additives (3 vol.%) provided the optimal combination of microstructure (relative density of 98.3%) and excellent properties, including flexural strength of 783 MPa and fracture toughness of 6.7 MPa m^1/2. With further addition of additives, SiC whiskers were inclined to gather together and be enveloped by excessive liquids to form core-rim-like structures, which lead to little decrease in mechanical properties.     

Catalytic graphitization of novolac resin for refractory applications

This study investigated how to induce graphite generation from the carbonization process of novolac resins using conditions that can be adopted for carbon-containing refractories (CCRs) production. The effect of boron oxide or boric acid (graphitizing agents), cross-linking additive (hexamethylenetetramine) and some processing parameters (mixing technique, vacuum degassing, heating rate and thermal treatments) on carbon graphitization from a commercial novolac resin were evaluated. The X-ray diffraction (XRD) technique was selected to measure the graphitization level and crystal parameters of the prepared samples. Based on the attained results, adding graphitizing agents prior to the pyrolysis of resin resulted in carbon crystallization. The best graphitization level was obtained when the mixtures containing 6 wt% B₂O₃ or 10 wt% H₃BO₃ were fired up to 1000 °C for 5 h using a heating rate of 3 °C/min. Although the reproducibility of the obtained results was ascertained, heterogeneous graphitization could be observed based on the XRD profiles, as well as some discrepancies in the calculated graphitization level values. This phenomenon was attributed to the additives susceptibility to agglomeration, preferential graphitization starting from lower binding energy sites and heat treatment temperature, among others.     

Experimental study of iron-control agents selection for high temperature sour gas and oil wells acidizing process

In acidizing process, the pH of acid increases gradually. When PH is higher than about 2.2, Fe³⁺ forms a black sticky precipitant that decreases well permeability. Therefore, using Ferric ion reducing agent as an additive is a proper way to prevent of precipitant formation. In this study, some materials are introduced as reducing agents and compared with each other. Then the effect of adding catalyst to these materials was investigated and the best mixtures were chosen and compared with commercial ferrotrol 200 from BJ service. These two mixtures include thioglycolic acid as ferric ion reducing agent and potassium iodide as a catalyst, and phosphinic acid salt as ferric ion reducing agent and potassium iodide as a catalyst. The results showed that the proposed additives have better performance at high temperature in contrast to ferrotrol 200. Then these two mixtures and ferrotrol 200 were compared with each other in the presence of H₂S and calcium carbonate (representative of reservoir rock). The result showed that the two chosen mixtures mentioned above have better performances in contrast to ferrotrol 200 owing to better reduction of ferric ion and performing faster than H₂S, also, prevent of FeS and S precipitants formation. After that, a comparison between these two mixtures and ferrotrol 200 has been performed in the presence of crude oil that proved these studied additives do successfully; however, additive including thioglycolic acid is more proper in acidizing process of oil wells.     

Processing,structural characterization and performance of alumina supports used in ceramic membranes

Although there are various commercially available methods for the separation and capture of gas species such as CO₂ and H₂, they are energy expensive and in some cases environmentally unfriendly. The membrane separation process presents advantages such as its relative simplicity, ease of use, low energy consumption, and application in the separation of both liquid and gas mixtures. For these reasons, the membrane technology has achieved in the last years a great commercial and strategic importance. In this work we present a structural characterization of an alumina support, before and after the deposition of a titania film on its surface. The obtained asymmetric membranes are intended to be used in gas separation processes. The alumina supports and titania coatings were prepared by dry-pressing and sol–gel process, respectively. The processed samples were characterized by X-ray diffraction (XRD), nitrogen sorption, scanning electron microscopy (SEM), and X-ray microtomography (μ-CT). In order to evaluate the membranes performance, single-gas permeation experiments were performed at room temperature with nitrogen, helium, and carbon dioxide. We observed that although the alumina supports obtained in this work have not been submitted to any surface finishing procedure, the obtained membranes have potential application in gas separation processes. We observed that increasing the pressure feed leads to improving their separation capacity.