Liquid Reaction Products Research Articles

Oxidation of ZrB2–SiC: Influence of SiC Content on Solid and Liquid Oxide Phase Formation

The effect of SiC concentration on the liquid and solid oxide phases formed during oxidation of ZrB2–SiC composites is investigated. Oxide‐scale features called convection cells are formed from liquid and solid oxide reaction products upon oxidation of the ZrB2–SiC composites. These convection cells form in the outermost borosilicate oxide film of the oxide scale formed on the ZrB2–SiC during oxidation at high temperatures (≥1500°C). In this study, three ZrB2–SiC composites with different amounts of SiC were tested at 1550°C for various durations of time to study the effect of the SiC concentration particularly on the formation of the convection cell features. A calculated ternary phase diagram of a ZrO2–SiO2–B2O3 (BSZ) system was used for interpretation of the results. The convection cells formed during oxidation were fewer and less uniformly distributed for composites with a higher SiC concentration. This is because the convection cells are formed from ZrO2 precipitates from a BSZ oxide liquid that forms upon oxidation of the composite at 1550°C. Higher SiC‐containing composites will have less dissolved ZrO2 because they have less B2O3, which results in a smaller amount of precipitated ZrO2 and consequently fewer convection cells.

Activity of Oxalic Acid Treated ZnO/CuO/HZSM-5 Catalyst for the Transformation of Methanol to Gasoline Range Hydrocarbons

The present study describes the stability of oxalic acid treated ZnO/CuO/HZSM-5 catalyst for the conversion of methanol to gasoline range hydrocarbons. A 0.5 wt % ZnO/7 wt % CuO/HZSM-5 catalyst was prepared by the wet impregnation method followed by dealumination using oxalic acid. Fresh and used catalysts were characterized by X-ray diffraction, scanning electron microscopy, surface area analysis, pore size analysis, thermogravimetric analysis, NH3 temperature programmed desorption, and X-ray photoelectron spectroscopy. All the kinetic experiments were carried out in an isothermal fixed bed reactor at 673 K. The major liquid reaction products were cyclopentene, n-hexane, 1-octene, cycloheptane, 2,5-dimethylhexane, n-nonane, cyclohexane, ethylbenzene, xylene, toluene, isopropylbenzene, trimethylbenzene, and tetramethylbenzene. The effect of run time was also studied to investigate the effect of oxalic acid treatment on catalyst stability. The oxalic acid treated catalyst was more resistant to deactivation...

Gas-phase nitration of toluene with zeolite beta

Abstract The gas-phase nitration of toluene was studied over a solid-acid zeolite beta catalyst with two different nitrating agents, HNO 3 and N 2 O 4 , in a setup for continuous nitration. The selectivity of the reactions to 4-nitrotoluene was good, but the catalysts deactivated within a few hours. HNO 3 gave higher yields than N 2 O 4 , but both HNO 3 and N 2 O 4 required a temperature lower than 160 °C to obtain acceptable yields and less oxidation products. At higher temperatures, catalyst deactivation was accelerated and the yield of nitrotoluene decreased. Lowering the feed rate of toluene led to a slower deactivation of catalyst. The deactivation of the catalyst was caused by pore blocking due to liquid reaction products as well as coke formation. Unlike in liquid-phase nitration, dealumination did not play a role in the deactivation of the catalyst, which could be regenerated by calcination in air.

Ionic Liquids: Synthesis and Characterisation of Triphenylphosphonium Tosylates

AbstractIonic liquids are currently attracting considerable interest from chemists, partly due to their potential as “green” alternatives to volatile molecular organic solvents. Phosphonium ionic liquids have received much less attention than ammonium salts in the past, but the situation is changing. The salts are applied in the liquid state but in this work, salts with higher melting points than is generally the case are investigated. They are solid at room temperature, thus enabling facile separation of liquid reaction products. Nine triphenylphosphonium tosylates have been prepared and characterised; their crystal structures have been determined and their melting points have been scrutinized, showing some sensitivity to the duration of drying. The structural information is expected to be invaluable in the understanding of the properties of the molten state.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Interaction of alumina inclusions in steel with calcium-containing materials

Clogging of tundish and submerged entry nozzles (SENs) adversely impacts productivity and quality in the continuous casting of aluminum-killed steels. Clogging results from an accretion layer that develops on the inside surface of the nozzle and restricts steel flow. Current nozzle refractories often react with molten steel to form solid by products that promote clogging. Nozzle materials that are inert with the liquid steel or react with accretions to form liquid reaction products could inhibit or eliminate clogging. Static experiments were conducted to investigate the stability between calcium-based materials and aluminum-killed steel. The results indicate that both calcium titanate and calcium zirconate react with alumina to form calcium aluminates. However, only the reaction between alumina and calcium titanate yielded calcium aluminate chemistries that were molten at steel casting temperatures. Liquid reaction products are preferred since they would be removed from the nozzle by the steel flow, thereby preventing accretion formation and clogging.

Hydrothermal upgrading of biomass to biofuel; studies on some monosaccharide model compounds

During the hydrothermal upgrading of biomass, hydrolysis to glucose is an important step. To elucidate some of the reaction pathways that follow this initial hydrolysis, the hydrothermal treatment (340 °C, 27.5 MPa, 25–204 s) of dilute (50 mM) solutions of d-glucose and some other monosaccharides were studied. As a result of the increase of K w under subcritical conditions, both acid and base catalysed reactions occur. The acid catalysed reactions are mainly dehydrations leading initially to 5-hydroxymethylfurfural. Important base catalysed reactions result in glycolaldehyde and glyceraldehyde. Further fragmentations and dehydrations lead to a variety of low molecular weight compounds such as formic acid, acetic acid, lactic acid, acrylic acid, 2-furaldehyde and 1,2,4-benzenetriol. Important pathways leading to a decrease of the O-content of the liquid reaction products start from the intermediate glyceraldehyde, which forms pyruvaldehyde, which in its turn is converted into formic acid and acetaldehyde. The latter compound can also be formed via isomerisation of glyceraldehyde into lactic acid followed by decarbonylation.

Hydrocarbon Mixtures from Waste Polymer Degradation

The degradation of waste polymers is one of the possible routes of utilization. Various cracking processes are suggested for different waste polymers, when long alkyl chains are degraded and transformed into lighter hydrocarbons. Yields of the liquid and gas reaction products can be increased and composition thereof can be modified by catalysts. Catalytic cracking of polyolefin waste polymers was studied in a batch reactor without and with Y, FAU (FCC), H-ZSM5 and natural clinoptilolite zeolite catalysts. The additives of the feed polymers did not significantly affect the yields and properties of the products but the type of the catalysts did. Both the gas and liquid yields increased with the catalyst concentration. The activity of the catalysts influenced the yields and the molecular weight of the volatile compounds. In the presence of catalysts both double bond and carbon chain isomerization were observed, but the latter was less significant than the former. The minimum temperature of cracking is lower with catalyst than without catalyst. The grain size of catalyst affects the yields, but less significantly the composition of products.

Hydrothermal conversion of municipal organic waste into resources

Sub- and supercritical water have been focused on as an environmentally attractive reaction media where organic materials can be decomposed into smaller molecules. We applied a hydrothermal reaction in subcritical water to the treatment of rabbit food as a model municipal solid waste. The reaction was carried out in a batch reactor at the temperature range of 473–623 K or in a semi-continuous reactor with the temperature profile from 473 to 573 K. The liquid reaction products were separated into water-soluble and water-insoluble parts. The water-soluble part was analyzed in terms of glucose and organic acids. For the batch reactor, the largest amount of water-soluble component was approximately 50%. Major organic acids detected were acetic acid and lactic acid. The largest yields were 2.6% for acetic acid and 3.2% for lactic acid. The largest yield of glucose was 33% at 523 K. For the semi-continuous reactor, the glucose yields were 11.5%, 3.9% and 8.7% in each fraction obtained at 473, 523, and 573 K, respectively.

Validation study of computer code sphincs for sodium fire safety evaluation of fast reactor

A computer code sphincs solves coupled phenomena of thermal hydraulics and sodium fire based on a multi-zone model. It deals with an arbitrary number of rooms, each of which is connected mutually by doorways and penetrations. With regard to the combustion phenomena, a flame sheet model and a liquid droplet combustion model are used for pool and spray fires, respectively, with the chemical equilibrium model based on the Gibbs free energy minimization method. The chemical reaction and mass and heat transfer are solved interactively. A specific feature of sphincs is detailed representation of thermalhydraulics of a sodium pool and a steel liner, which is placed on the floor to prevent sodium–concrete contact. The authors analyzed a series of pool combustion experiments, in which gas and liner temperatures are measured in detail. It has been found that good agreement is obtained and the sphincs code has been validated with regard to pool combustion phenomena. Further research needs are identified for pool spreading modeling considering thermal deformation of steel liner and measurement of pool fluidity property as a mixture of liquid sodium and reaction products. The sphincs code is to be used mainly in the safety evaluation of the consequence of a sodium fire accident in a liquid metal cooled fast reactor as well as fire safety analysis in general.

Supercritical Water Oxidation of a Model Municipal Solid Waste

Supercritical water oxidation has been focused on as an environmentally attractive technology by which organic materials can be oxidized to carbon dioxide, water, and nitrogen gas. We applied supercritical water oxidation to the treatment of dog food as a model municipal solid waste. The reaction was carried out in a batch reactor with hydrogen peroxide as the oxidant over the temperature range of 673−823 K. The liquid reaction products were analyzed to determine the total organic carbon (TOC), organic acid, and ammonium ion contents. When the oxidant was stoichiometrically insufficient, TOC decreased with an increasing temperature and amount of oxidant. Acetic acid and ammonium ion were detected as major refractory intermediates. Ammonium ion was completely decomposed more easily than in sewage sludge, presumably because hydrochloric acid produced Cr ion by corrosion of the wall of the reactor. The activation energy was 97.2 kJ/mol for the reduction of TOC and 130.8 kJ/mol for the reduction of ammonium i...

Interdiffusion involved in SHS welding of SiC ceramic to itself and to Ni-based superalloy

In order to reach a better understanding of the mechanism of joining of SiC ceramic to itself and to Ni-based superalloy by pressure-aided self-propagating high-temperature synthesis (SHS) welding process, microstructural study and energy dispersive X-ray microanalysis (EDX) were carried out with the welded samples. The wettability between SiC ceramic and the liquid reaction products of the filler is very good. A composition transition layer forms at the SiC/filler interface mainly due to the diffusion of Ti from the filler to the ceramic. The affinity between Ti and SiC is better than that between Ni and SiC. The components of the Ni-based superalloy remarkably diffuse into the reaction products of the filler. The microstructure shows an excellent bonding at the interfaces.

99/00359 A pressurized reactor with integrated load cell for measuring the activities of Fischer-Tropsch-catalysts and their loadings with liquid reaction products (wax)

99/00359 A pressurized reactor with integrated load cell for measuring the activities of Fischer-Tropsch-catalysts and their loadings with liquid reaction products (wax)

Catalytic coprocessing of LDPE with coal and petroleum resid using different catalysts

Catalytic coprocessing of low density polyethylene (LDPE) with coal and heavy petroleum resid was investigated using four different catalysts that included both hydrotreating and hydrocracking catalysts. Reaction systems that were evaluated included LDPE alone; LDPE with coal; and LDPE, coal, and resid. The catalysts used were NiMo/Al 2O 3, a hydrotreating catalyst with some hydrocracking activity, and the hydrocracking catalysts Zeolyst 753, NiMo/zeolite, and HZSM-5. These catalysts were reacted individually or in combinations of 10 wt.% of each hydrocracking catalyst in NiMo/Al 2O 3. The catalytic reactions were performed at two temperatures, 400 and 430°C, using 1 wt.% of each catalyst or a combination of catalysts on a total feed basis. The effects of the different catalysts on the reaction products were measured in terms of solvent fractionation and total boiling point distribution. Reactions at the higher reaction temperature of 430°C resulted in substantially higher conversion and production of lighter products than the reactions at 400°C. The LDPE reaction system was sensitive to the catalyst type, and yielded increased conversion and lighter products when Zeolyst 753 and NiMo/zeolite were used. By contrast, the conversion and product slate obtained from the LDPE and coal systems were low and showed no effect due to the different types of catalyst. Introduction of resid to the LDPE/coal system increased the reactivity of the system and allowed the catalysts to have a larger effect. The hydrocracking catalysts were the most active in producing more conversion and hexane soluble material. Comparison of the effect of increasing the reaction time up to 5 h with 1 wt.% catalyst loading to the effect of increasing the catalyst loading from 1 wt.% to 10 wt.% for a reaction time of 1 h showed that increased reaction time was much more effective than catalyst loading in converting the solid LDPE to liquid reaction products.

Chemistry and kinetics of chemical vapor deposition of pyrocarbon — III pyrocarbon deposition from propylene and benzene in the low temperature regime

Pyrocarbon deposition from propylene and benzene was studied at ambient pressure and 1000 °C using a vertical hot-wall reactor. Initial partial pressures of the hydrocarbons and residence time were varied; the influence of hydrogen in the feed gas was additionally studied. Gaseous and liquid reaction products were analyzed by on-line gas chromatography. The results are discussed in terms of homogeneous gas-phase and heterogeneous pyrocarbon deposition reactions. Reactions models have been derived and used for simulation of pyrocarbon deposition rates and their inhibition by hydrogen. Pyrocarbon deposition from propylene is shown to be controlled by complex pyrolysis reactions in the gas-phase, whereas benzene forms pyrocarbon directly i.e. without significant formation of intermediate products in the gas-phase.

5550278 Process for working up the liquid reaction products from the cu-catalysed preparation of dimethyl carbonate : Rechner Johann; Wagner Paul; Buysch Hans-Jose; Klausner Alexander Krefeld, Germany assigned to Bayer Aktiengesellschaft

5550278 Process for working up the liquid reaction products from the cu-catalysed preparation of dimethyl carbonate : Rechner Johann; Wagner Paul; Buysch Hans-Jose; Klausner Alexander Krefeld, Germany assigned to Bayer Aktiengesellschaft

Sequential injection analysis system for the determination of hydride-forming elements by direct current plasma atomic emission spectrometry

A method for the determination of volatile hydride-forming elements with direct current plasma atomic emission spectrometry (DCP-AES) based on a modified version of the sequential injection analyser has been developed. The sequential injection (SI) hydride generator consists of two multi-port valves and a piston burette. The burette is also used as a dynamic reaction chamber the volume of which can be changed by the piston movement. This arrangement allows isobaric reaction. The burette also functions as a gas–liquid separator where the liquid reaction products are drained via a channel through the piston head. The hydride gases are pumped by the piston into the plasma through a thin quarts capillary, which is also used to position the direction of gas flow to the centre of the plasma. All functional parts in this system are computer controlled. The performance of the SI hydride generation DCP-AES system has been tested in the determination of arsenic, bismuth and germanium. The detection limits (3s) were 0.15, 0.08 and 0.03 µg l–1, respectively. The calibration graphs were linear (r >0.999) in the concentration ranges studied: 0–50 µg l–1 for arsenic and 0–10 µg l–1 for bismuth and germanium. The relative standard deviation for all three elements was less than 10% at a concentration level of 1 µg l–1 and ≈3% at the 10 µg l–1 level. The accuracy of the method was tested in the determination of arsenic in the National Institute of Standards and Technology (NIST) Standard Reference Materials, NIST SRM 1573 Tomato Leaves and NIST SRM 1575 Pine Needles.

Synthesis of mixtures of aromatic and aliphatic hydrocarbons from CO and H2 over Fe catalysts

It was determined that 8.2% Fe-1–4.5% K/Al2O3 catalysts are active in the synthesis of C1-C6 aliphatic and C6-C8 aromatic hydrocarbons (AH) from mixtures of CO:H2=1:2–2:1. The AH content in the liquid reaction products is 90%. A discussion of the synthesis schemes for AH is presented.

LWR fuel rod behavior during severe accidents

Chemical interactions between UO 2 fuel and Zircaloy cladding up to 2350°C are described. UO 2/Zircaloy single effects tests have been performed with short LWR fuel rod segments in inert gas and under oxidizing conditions. The reaction kinetics of molten Zircaloy cladding with solid UO 2 fuel has been investigated with UO 2 crucibles containing molten Zircaloy. The UO 2/Zircaloy reactions obey parabolic rate laws. The oxygen uptake by solid Zircaloy due to chemical interaction with UO 2 occurs nearly as quickly as that from the reaction with steam or oxygen. To study the competing effects of the external and internal cladding oxidation under realistic boundary conditions and the influence of the uncontrolled temperature escalation due to the exothermic steam/Zircaloy reaction on the maximum cladding temperature, single rod and bundle experiments have been performed. Electrically heated fuel rod simulators, including absorber rod material (Ag, In, Cd alloy), guide tubes and grid spacers are used. The maximum measured cladding temperature during the temperature escalation was about 2200°C. The failure temperature of the absorber rods and the extent of bundle damage depends on the guide tube material (Zircaloy or stainless steel) and varies between 1200 and 1350°C. The molten materials and liquid reaction products can relocate and form large coherent lumps on solidification, which may result in complete blockage of the fuel rod bundle cross section. In the future, 7 × 7 bundle experiments of 2 m overall length will be performed in the new CORA facility to study, in addition, the influence of quenching on fuel rod integrity.

Zur Pyrolyse unsubstituierter Cyclane – Produktbildungsselektivitäten, kinetische Parameter, mechanistische Interpretationen

On the Pyrolysis of Unsubstituted Cyclanes – Selectivity of the Formation of Reaction Products, Kinetic Parameters, Mechanistic InterpretationsThe thermal decompostion of cyclopentane (1), cyclohexane (2), cycloheptane (3), cyclooctane (4), cyclodecane (5), and cyclododecane (6) was studied in a laboratoryscale metallic tubular reactor at 650 to 850°C in the presence of steam. The kinetic parameters for the overall reactions were determined and the gaseous as well as the liquid reaction products were analyzed and identified by gas chromatography or by the coupling of gas chromatography and mass spectrometry, respectively. It could be shown that from all cyclanes the isomeric α‐olefines are formed, if the conversion of the starting cyclanes is small. This supports the view that the cyclane → α‐olefin isomerization is an important initial reaction in pyrolysis of 1 up to 6. The results also demonstrate that the main pathway of degradation is a radical chain mechanism via cyclanyl radicals with β(CC) bond scission and 1.4 or 1.5‐H‐isomerization of alkenyl radicals as the most important reaction steps.

Tubing bomb coal liquefaction technique

An experimental coal liquefaction test procedure is described in which coal, solvent, and hydrogen are reacted in a small, agitated batch reactor (tubing bomb) that is rapidly heated in a sand bath. After completion of the desired reaction time, the reactor is quench-cooled, and solid and liquid reaction products are removed using cyclohexane as a wash medium. Conversion of coal to cyclohexane soluble material is reproducible and correlates well with the conversion to 538/sup 0/C (1000/sup 0/F) minus boiling point liquids obtained by larger scale process units. The principal data obtained with the tubing bomb technique are: hydrogen consumption (molecular hydrogen and hydrogen transferred from the solvent), gas make (H/sub 2/S, CO /SUB x/, and hydrocarbon gases), water make, liquid yields, solid residue (cyclohexane insolubles), and conversion. Details of the apparatus, experimental procedure, sample analysis procedures, and data workup are described. Experimental results for a bituminous, a subbituminous coal and a lignite are shown to illustrate the technique.