Analysis of low levels of oxygen, carbon monoxide, and carbon dioxide in polyolefin feed streams using a pulsed discharge detector and two PLOT columns

A gas chromatography (GC) method is developed for rapid analysis of polyolefin feed streams for the catalyst poisons CO, CO(2), and O(2). The method uses an HP MoleSieve column in parallel with a CP-PoraPLOT Q column and a pulsed discharge detector (PDD). Detection limits for each of the potential poisons are between 50 and 250 ppb. For a 10-ppm standard, the precision of the method was +/- 4.2% for oxygen, +/- 7.8% for carbon dioxide, and +/- 2.0% for carbon monoxide. In addition to the polyolefin feed stream, nitrogen and hydrogen feed streams are also analyzed. In each case, sampling is observed to be a critical issue, with air contamination of the sample cylinder often the limiting step in determining the true level of oxygen. It is also noted that large amounts of argon are present in the standards when nitrogen is used as a balance gas. Because the trace oxygen peak partly coelutes with the larger argon peak, it is suggested that helium be used as the balance gas for all standards. This general experimental arrangement should be effective when applied to feed streams for other polymers as well.     

常温高压下移动颗粒层除尘试验研究

介绍了用于整体煤气化联合循环（IGCC）热煤气和增压流化床燃烧联合循环（PFBC-CC）高温烟气除尘的移动颗粒层试验台。调试阶段进行了一系列的条件试验。改进后的常温下进行了试验,结果表明在高压下能够实现颗粒层过滤和气力循环清灰的一体化稳定运动。研究发现移动颗粒层过滤时,气流之间的压力平衡是一个关键因素,运行中必须严格控制过滤气体和输送气体的压力。移动颗粒层过滤器和循环清灰系统的结构对过滤性能有较大的影响。     

On-line multidimensional supercritical fluid chromatography/capillary gas chromatography

A new analytical technique combining on-line supercritical fluid chromatography with capillary gas chromatography has been developed. The supercritical fluid sample effluent is decompressed through a restrictor directly into a conventional capillary gas chromatographic injection port. This technique allows for not only direct (100%) sample transfer from the supercritical fluid chromatograph to the gas chromatograph but also for selective or multi-step heartcutting of various sample peaks as they elute from the supercritical fluid chromatograph. Heartcut times are determined by monitoring the responses from the flame ionization or ultraviolet absorbance detectors on the supercritical fluid chromatograph. This report describes the operational setup and provides the results of heartcut reproducibility experiments using normal hydrocarbon and aromatic test mixtures. Results from studies where operational parameters were varied, such as GC injector temperature, will also be provided. The potential usefulness of this new technique for selective heartcutting will also be demonstrated using complex hydrocarbon streams.     

The composition-explicit distillation curve technique: Relating chemical analysis and physical properties of complex fluids

The analysis of complex fluids such as crude oils, fuels, vegetable oils and mixed waste streams poses significant challenges arising primarily from the multiplicity of components, the different properties of the components (polarity, polarizability, etc.) and matrix properties. We have recently introduced an analytical strategy that simplifies many of these analyses, and provides the added potential of linking compositional information with physical property information. This aspect can be used to facilitate equation of state development for the complex fluids. In addition to chemical characterization, the approach provides the ability to calculate thermodynamic properties for such complex heterogeneous streams. The technique is based on the advanced distillation curve (ADC) metrology, which separates a complex fluid by distillation into fractions that are sampled, and for which thermodynamically consistent temperatures are measured at atmospheric pressure. The collected sample fractions can be analyzed by any method that is appropriate. The analytical methods we have applied include gas chromatography (with flame ionization, mass spectrometric and sulfur chemiluminescence detection), thin layer chromatography, FTIR, corrosivity analysis, neutron activation analysis and cold neutron prompt gamma activation analysis. By far, the most widely used analytical technique we have used with the ADC is gas chromatography. This has enabled us to study finished fuels (gasoline, diesel fuels, aviation fuels, rocket propellants), crude oils (including a crude oil made from swine manure) and waste oils streams (used automotive and transformer oils). In this special issue of the Journal of Chromatography, specifically dedicated to extraction technologies, we describe the essential features of the advanced distillation curve metrology as an analytical strategy for complex fluids.     

Removal of SO2 and the simultaneous removal of SO2 and NO from simulated flue gas streams using dielectric barrier discharge plasmas

A gas-phase oxidation method using dielectric barrier discharges (DBDs) has been developed to remove SO₂ and to simultaneously remove SO₂ and NO from gas streams that are similar to gas streams generated by the combustion of fossil fuels. SO₂ and NO removal efficiencies are evaluated as a function of applied voltage, temperature, and concentrations of SO₂, NO, H₂O_(g), and NH3. With constant H₂O_(g) concentration, both SO₂ and NO removal efficiencies increase with increasing temperature from 100 to 160°C. At 160°C with 15% by volume H₂0_(g), more than 95% of the NO and 32% of the S0₂ are simultaneously removed from the gas stream. Injection of NH₃ into the gas stream caused an increase in S0₂ removal efficiency to essentially 100%. These results indicate that DBD plasmas have the potential to simultaneously remove SO₂ and NO from gas streams generated by large-scale fossil fuel combustors.     

Thermodynamic properties of a shell molecule-gas particles system

A Lennard-Jones potential is used to derive formulaefor the potential of interaction between shell macromolecules and gas atoms. Calculations are carried as far as thespherical symmetry approximation. The potential of interaction determines the stability of a shell topological compound. When the distance R between a shell molecule and a gas atom is equal the radius 1 of the outer shell, the potential is the highest and determines a barrier, which must be lower than an energy of the trapped/by the shell molecule/atom to be released.     

Identifying hazardous chemical reactivity

Hazardous chemical reactivity is chemical reaction that can produce detonation, deflagration or runaway reaction, which can possibly lead to thermal explosion. In the course of the development of a chemical manufacturing process, the raw materials, process streams, isolated intermediates, final product (and the variations of these that are likely to be caused by some process upset) must all be evaluated to determine the potential of each for hazardous chemical reactivity. Although toxic, ecotoxic and flammability hazards may also result from reactivity, this short article is limited to a review of the general strategy and thermal analytical methods used to identify hazards due to the rapid and uncontrolled release of energy by reaction. It is intended as an introduction to the field, and so provides numerous references to the basic sources.     

Determination of gas flow distribution in a SO2-oxidation industrial reactor by radiotracer technique

Two independent experiments carried out with⁸⁵Kr under the same production conditions have shown that the gas flow is not uniformly distributed over the cross-sectional area of the reactor, thus a simple model for two parallel streams was adopted to evaluate the influence of this maldistribution upon the SO₂ conversion. Calculations have shown a diminution of 0.8% in the range of a total conversion of 97%, thus special attention must be paid to the reconstruction of the gas distribution device.     

High-throughput parallel reactor system for propylene oxidation catalyst investigation

A high-throughput reactor system was designed for catalyst testing, which includes two important sections: the gas flow splitters and the parallel reactor. Each gas flow splitter could split one gas stream to 64 streams (8 x 8). The current system has two gas splitters that could feed two kinds of gases (from mass flow controllers) to a 64-channel (8 x 8) parallel fixed-bed reactor. The reactor is composed of tube connectors, a reactor tube array, a heating block, a product collector, and a temperature controller. The reactor system could test 64 catalysts simultaneously and give results, which are comparable with a regular single-channel microreactor. For the purpose of verifying the validity of the reactor system, propylene oxidation to prepare acrolein was used as the probing reaction. In order to analyze the reaction products, a high-throughput colorimetric diffusion-reflection imaging method was developed for the analysis of acrolein. By comparing the results from colorimetric diffusion-reflection imaging analysis with that from the traditional gas chromatography spectrometer with thermal conductivity detectors, a colorimetric diffusion-reflection imaging method was confirmed to be reliable and accurate in acrolein analysis.     

Interaction of water with titania: implications for high-temperature gas sensing

High-temperature gas sensors based on semiconducting metal oxides show potential for optimization of combustion processes, resulting in efficient energy use and minimization of emissions. Such metal oxides can function as gas sensors because of the reaction of the sensing gas (e.g., CO) with ionosorbed oxygen species on the oxide surface with the resulting increase in conductivity. A limitation of metal oxide sensors is their difficulty of distinguishing between different gases. Designing selectivity into sensors necessitates a better understanding of the chemistry of gas-solid interactions at high temperatures. In this paper, we have used in situ infrared spectroscopy to monitor the dehydration of a hydrated anatase surface up to 600 degrees C and also to examine the hydration/dehydration of anatase held at 400 degrees C. When the O-H stretching region (3000-3800 cm(-1)) was primarily focused on, it was found that water loss from the titania surface proceeded at lower temperatures (<200 degrees C) through desorption, whereas at higher temperatures, water dissociation to terminal (approximately 3710 cm(-1)) and bridged (approximately 3660 cm(-1)) hydroxyl groups was noted. With a further increase in temperature to 600 degrees C, the bridged hydroxyl groups disappeared faster than the terminal ones. The electrical resistance of anatase at 600 degrees C was measured in the presence of moist gas streams and resulted in an increase in conductivity in the presence of water. In situ vibrational spectroscopy indicated a temporal correlation between the appearance of the bridging hydroxyl group and the change in electrical resistance. Several possible mechanisms are discussed. The chemical reaction of water with anatase at high temperatures necessitates that water be removed from the gas stream to avoid interference. A strategy involving the use of a hydrophobic microporous filter that can reject water and let gases such as CO pass unimpeded is examined. Successful use of such a concept has been demonstrated with a silicalite filter using moist CO gas streams.     

Reduction of nitric oxide to elemental nitrogen byThiobacillus Denitrificans

A need exists for new technology for the disposal of concentrated NO_x streams obtained from certain regenerable, dry scrubbing processes, such as the NOXSO process, and the removal and disposal of NO_x from more dilute gas streams produced by nitric acid plants. It has been demonstrated that the facultative anaerobe and autotroph, Thiobacillus denitrificans, may be cultured anaerobically in batch reactors using NO (g) as a terminal electron acceptor. Thiosulfate served as an energy source, CO₂ (g) as a carbon source, and ammonium ion as a source of reduced nitrogen. The growth of T.denitrificans was indicated by depletion of thiosulfate and ammonium ion and the accumulation of biomass. The feed gas consisted of 5000 ppmv NO, 5%, CO₂, and balance nitrogen. The NO concentration in the outlet gas was typically 200 ppmv.     

The Possibility of Wax Formation in Gas Fields： a Case Study

Natural gas production from a gas reservoir(Reservoir A)located in the south of Iran,presents solids deposition during processing because the condensate contains suspended and dissolved solids.Solids deposition occurs not only in the transportation lines from the wells to the separators but also in the various operating units of gas streams and condensate stream.In this study,the multisolid-phase model has been used to predict the wax precipitation from gas and gas condensate fluids.The properties of gas and liquid phases are described using the Soave-Redlich-Kwong(SRK)equation of state.The model is then used to predict the possibility of the wax formation in Reservoir A gas facilities,located at the south of Iran.Solid deposition which occurred in the various streams of that facility confirmed the calculated results.Finally,the wax appearance temperature(WAT),the weight percent of wax formation and the effects of pressure and temperature on the wax formation were also predicted.     

Abatement of Gas-phase p-Xylene via Dielectric Barrier Discharges

The effectiveness of applying dielectric barrier discharges (DBDs) to remove p-xylene from gas streams was experimentally investigated in this study. Parameters investigated include applied voltage, gas flow rate, gas temperature and gas composition. Experimental results indicate that as high as 100% p-xylene removal efficiency is achieved for the gas stream containing low p-xylene concentration of 26 ppmv. Removal efficiency of p-xylene achieved with DBDs increases with increasing applied voltage. However, energy consumption is also increased with increasing applied voltage. The best energy efficiency of 7.1 g/kWh is achieved for the gas streams containing 500 ppmv p-xylene, 5% O₂, 1.6% H₂O_(g), and balanced N₂ at the applied voltage of 18 kV. Product analysis indicates that around 70 or 95% of the carbons in p-xylene molecules are transformed into carbon dioxide for the gas streams without or with water vapor, respectively.     

Pharmaceutical modulation of diffusion potentials at aqueous-aqueous boundaries under laminar flow conditions

In this work, the modulation of the diffusion potential formed at the microfluidic aqueous-aqueous boundary by a pharmaceutical substance is presented. Co-flowing aqueous streams in a microchannel were used to form the stable boundary between the streams. Measurement of the open circuit potential between two silver/silver chloride electrodes enabled the diffusion potential at the boundary to be determined, which is concentration dependent. Experimental results for protonated propranolol as well as tetrapropylammonium are presented. This concept may be useful as a strategy for the detection of drug substances.     

An apparatus for the determination of volatile analytes by stopped-flow injection analysis using an integrated fiber optic detector

A new method for the analysis of volatile analytes using a stopped-flow injection system originating from either a gas or liquid phase has been developed. It uses an integrated fiber optic detector which also serves as a reactor. This system combines the advantages of gas diffusion and stopped-flow, making the overall assay very sensitive. Both gas streams and aqueous solutions containing ammonia were analyzed. The limits of detection are 40 ppb for gas phase analysis and 1.0 ppm for aqueous phase analysis.     

Determination of arsenic in petroleum refinery streams by electrothermal atomic absorption spectrometry after multivariate optimization based on Doehlert design

This paper reports the development of a methodology for the determination of arsenic in petroleum refinery aqueous streams containing large amounts of unknown volatile organic compounds, employing electrothermal atomic absorption spectrometry with polarized Zeeman-effect background correction. In order to make the procedure applicable, the influence of chemical modification and the drying step was examined. Also, pyrolysis and atomization temperatures and the amount of nitric acid added to the sample were optimized using a multivariate approach based on Doehlert matrix. Obtained results indicate that, in this kind of sample, arsenic must be determined by standard addition procedure with a careful control of the drying step temperature and ramp pattern. In order to evaluate the accuracy of the procedure, a test was performed in six spiked samples of petroleum refinery aqueous streams and the relative errors verified in the analysis of such samples (added As between 12.5 and 190 μg l⁻¹) ranged from −7.2 to +16.7%. The detection limit and the relative standard deviation were also calculated and the values are 68 pg and 7.5% (at 12.5 μg l⁻¹ level), respectively.     

Development of heterogeneous catalysts for transesterification of triglycerides

This paper describes a preliminary work done towards the development of new metallic heterogeneous catalysts to be used in the transesterification reaction of triglycerides, which is of considerable interest in the production of biodiesel. Biodiesel is a mixture of mono-alkyl esters of fatty acids, and is currently manufactured by transesterification of triglycerides with methanol using NaOH or KOH as liquid base catalyst. Catalysts as such are corrosive to the equipment, and as these catalysts are present in the liquid phase, must be neutralized after the completion of the reaction, typically using HCl, thus producing salt streams. Moreover, due to the presence of free fatty acids, it reacts to form soaps as unwanted by-products, hence requiring more expensive separation processes. Therefore, there is a great need for the development of industrial processes for biodiesel production using solid acid catalysts. The key benefit of using solid acid catalysts is that no polluting by-products are formed, and the catalysts do not have to be removed since they do not mix with the biodiesel product.     

超临界流体萃取分离离子液体与有机物及其相平衡的研究

离子液体具有一些优良的物理和化学性质,非常有希望成为传统有机溶剂的替代溶剂.但是如何从过程物流中分离和回收离子液体将是其工业化应用的一个很大挑战.蒸馏、液液萃取和超临界萃取是目前已知的三个可行的方法.其中超临界萃取可应用于离子液体与挥发的或相对不挥发的有机物的分离,而且不存在相间交叉污染.本文从二元体系相平衡、三元体系相平衡、模型化研究和萃取实验结果方面介绍了超临界萃取方法的最新研究进展,在此基础上提出了用超临界丙烷替代超临界二氧化碳作为萃取溶剂的新思路,并探讨了该领域今后的研究方向和工业化前景.     

Potentiometric investigation of protonation reactions at aqueous-aqueous boundaries within a dual-stream microfluidic structure

The laminar flow regime prevailing in pressure-driven flow through a Y-shaped microfluidic channel was utilized to create a stable boundary between two aqueous liquids. Transverse transport of ions between these two liquids gave rise to a diffusion potential, which was monitored by measurement of the open circuit potential. In this report, the influence on the cross-channel potential distribution of protonation reactions occurring in the boundary zone between the two co-flowing liquids is presented. The proton source was present in one of the co-flowing streams, and an uncharged proton acceptor was present in the other aqueous stream. The time-dependent transport equation for diffusion and migration was augmented by chemical reaction terms and was solved for all species present in both streams as a theoretical basis for the analysis. Within this model, the system was assumed to be homogeneous along the channel height, and effects of nonuniform velocity profiles were neglected. A reduction in potential by several millivolts was predicted for a protonation reaction occurring close to the boundary between the two aqueous streams, provided that the mobility of the protonated species was lower than the mobility of the co-cation in the background electrolyte (alkali metal cation in this case). The magnitude of the decrease in the potential was greater for protonated molecules with lower mobility or if the mobility of the background electrolyte cation was increased. Experimental results are presented for imidazole and D-histidine as proton acceptors present in 10 mM KCl, 10 mM NaCl, or 10 mM CsCl solution and co-flowing with a stream of 10 mM hydrochloric acid, which served as the proton source. Decreases in measured potential, in line with the predicted diminished potential, were obtained.