Product Yield Distribution Research Articles

Effects of mineral matter on products and sulfur distributions in hydropyrolysis

The effects of the mineral matter on the product yield and sulfur distribution in hydropyrolysis and pyrolysis of Chinese Hongmiao lignite were investigated using a fixed-bed reactor. The volatile sulfur-containing gases (H 2S,COS,CH 3SH) were also analyzed as a function of pyrolysis temperature. Coal samples were treated with HCl/HF or HCl/HF and CrCl 2 solution to eliminate minerals and pyrite respectively. In hydropyrolysis, demineralized Hongmiao lignite showed lower yields of tar and water than the raw coal. Demineralization cannot only minimize the fixation effect of basic mineral matter on sulfur-containing gases, but also increase the sulfur distribution of the tar. Further, from the evolution profiles of sulfur-containing gases, it is possible to elucidate the contribution of minerals, pyrite and organic sulfur to the sulfur evolution. Pyrite may not be the only source of COS formation.

A high-fluence 0.6 GEV proton irradiation experiment with thin uranium and thorium targets

High-fluence proton irradiation eperiments with thin actinide targets are part of PSI's programme related to accelerator-based transmutation studies. The aim is to provide experimental data for the validation of theoretical models in nucleon-meson transport codes, with emphasis on the mass yield distribution of spallation and fission products. The paper presents results of an irradiation experiment carried out with 238UO 2 and 232ThO 2. Based on mass spectrometric measurements, isobaric production cross-sections for fission and spallation products, as well as total fission cross-sections of the target nuclides, are reported. The experimentally deduced total fission cross-sections for both target nuclides are found to be approximately twice as large as values reported in certain earlier experiments, as well as with respect to calculational results obtained using the HETC code and the RAL high-energy fission model.

Experimental and numerical study of the thermal destruction of hexachlorobenzene

Hexachlorobenzene (HCB) was used as a model chlorocarbon molecule to investigate the thermal decomposition process of a polychlorinated aromatic compound in pyrolytic environments. The thermal decomposition of 1.07% HCB in nitrogen atmosphere was studied to determine important chlorocarbon pyrolysis reaction pathways. Reactions were carried out at 1 atm pressure in a tubular flow reactor 1.0 cm i.d.. The degradation of HCB plus intermediate and final product formation was analyzed from 900 to 1200°C, with a mean residence time of 2.0 s. The product yield distributions are reported. Initial decomposition was observed at 900°C with formation of Cl 2 and C 12Cl 10(cy). Pronounced decomposition and molecular growth were observed at higher temperatures as evidenced by the formation of CCl 4, C 2Cl 4, C 2Cl 6, C 4Cl 6, C 8Cl 8(cy), C 10Cl 8(cy), C 12Cl 8 (cy), C 18Cl 10 (cy) and soot. A detailed kinetic reaction mechanism based upon fundamental thermochemical principles and transition state theory was developed and used to model our experimental results. Sensitivity analysis was used to determine important reactions pathways responsible for the formation and destruction of species. The computed results agree qualitatively with all the experimental trends and quantitative agreement is obtained with several of the composition profiles. Important radical-molecule addition reactions leading to molecular growth are identified using sensitivity analysis and production rate calculations.

Yield and Pore-size Distribution of Pyrolysis Products of Organic Compounds as Chemical Modifiers in Electrothermal Graphite Furnace Atomic Absorption Spectrometry†

Yields of pyrolysis products and pore-size distribution of amorphous carbon produced from organic chemical modifiers, such as ascorbic acid, glucose and sucrose, for electrothermal atomization atomic absorption spectrometry were examined: the pyrolysis yield (for which ascorbic acid>glucose>sucrose) and the pore-size distribution are independent of the modifier used.

Isotopic product distributions in the near symmetric mass region in proton induced fission of 238U.

We have studied fission product yields using 19.8 MeV proton induced fission of a thin $^{238}\mathrm{U}$ target and the on-line mass separator IGISOL. The nonselectivity of the separation method used with respect to Z has allowed accurate determination of the yields of symmetric fission for the first time. The cumulative yields for the elements from Z=40 (Zr) up to Z=47 (Ag) have been determined from the beta- and gamma-radioactivity measurements. The independent fission product yield distributions for elements Tc, Ru, and Rh are obtained from the experimental data. An improved theoretical model for calculating mass and independent yields is described and applied. It is found that the charge splitting for the primary fragments differs from that obtained with the unchanged charge division model at moderate excitation energies of compound nuclei. A comparison of the calculated and experimental fission product yields shows that the model presented can be applied for predictions of cross sections for very neutron-rich nuclei in the light particle induced fission.

Microactivity test (MAT) study of the ZSM-5 addition effects on FCC product yields and gasoline composition

A commercial ZSM-5 containing additive was tested at a MAT unit and the derived results concerning product distribution as well as gasoline composition shifts have been interpreted by means of changes in the rates of certain secondary reactions occurring during catalytic cracking. The most important resulte of the ZSM-5 addition are gasoline yield decrease, LPG alkenes increase and RON gain. The gasoline composition changes include a significant decrease of the C 6-C 9 alkanes yield, lighter gasoline formation through increase of the C 5 hydrocarbons yields, increased branching in the light alkenes and a small decrease in the naphthenes and aromatics yields. Most of the above effects have been interpreted by taking into account the enhanced alkenes reactivity on ZSM-5. A comparison of the present results with those from pilot plants and commercial units reveal that the shifts imposed by ZSM-5 either to the product yield distribution or to gasoline composition are in very good agreement, despite the significant differences of the absolute yields.

Prediction of product yield distributions from wafer parametric measurements of CMOS circuits : Leonid Mizrukhin and Jim Huey and Sunil Mehta. IEEE Trans. Semicond. mfg5, 88 (1992)

By applying an external uniaxial mechanical stress, we have extracted, for the first time, the piezoresistance coefficients of biaxially strained and unstrained fully-depleted silicon-on-insulator (FD-SOI) nMOS transistors that integrate a HfO2/TiN gate stack. We have shown that when a uniaxial stress is added to a biaxial stress, the resulting piezoresistance effect is not a linear superposition of the individual influences of these stresses. Indeed, the measured piezoresistance coefficients were dependent on the initial level of biaxial stress. This contrasts with previous results showing for instance linear behaviour in the case of pure uniaxial stress along a 〈1 1 0〉 crystallographic direction. In addition, we have demonstrated that electron mobility can still be enhanced on biaxially strained FD-SOI devices, even for SOI films as thin as 10 nm, provided that channel stress includes a shear component. These results were explained by the effect of shear stress on the electron conduction effective mass. Such a shear stress can be generated for instance by applying uniaxial tensile (compressive) stress parallel (perpendicular) to the channel along a 〈1 1 0〉 crystallographic direction.

Prediction of product yield distributions from wafer parametric measurements of CMOS circuits

A technique for predicting the yield distribution of CMOS circuits based on electrical parameter distributions is presented. This technique uses the mean and standard deviation of the measured threshold voltage and mobility of NMOS and PMOS transistors to project the yield of the circuit in a specified design window. The method thus provides a quantitative means of carrying out tradeoffs between design windows and final product yield. >

Effect of temperature, carrier gas and precursor structure on PCDD and PCDF formed from precursors by catalytic activity of MSW incinerator fly ash

The difference in products formed from precursors by catalytic activity of fly ash under an inert atmosphere of nitrogen and an oxygen-rich atmosphere of high purity air were examined. Replacement of nitrogen with air affected a shift to the higher chlorinated isomers being formed and also resulted in a greater overall yield of both PCDD and PCDF. A series of diphenylethers with different levels of chlorine substitution at varying positions were studied in the catalytic formation of PCDD and PCDF. All the precursors formed at least some PCDD and PCDF congeners, but the yields and isomer distributions varied with the structure of the precursor. The temperature dependance of product yield and congener distribution at low temperatures (200–350°C) is also presented.

Kinetics and product yield distributions in the [formula omitted] catalysed hydrocracking of Athabasca bitumen

Hydrocracking of Athabasca bitumen was studied in a batch reactor at 620–693 K and at an initial hydrogen pressure of 7.2 MPa (at 293 K). The reaction products were separated into coke, asphaltenes, resins, aromatics, saturates and gases. The reaction time versus product yield curves were obtained for the above six product groups. Three kinetic models were developed to provide insight into the reaction mechanism. Separated bitumen fractions and lumped fractions (heavy ends = coke + asphaltenes + resins; light oils = saturates + aromatics; asphaltics = coke + asphaltenes; and maltenes = resins + aromatics + saturates) were used as pseudo-components in the kinetic models. The proposed models are: bitumen → gases; heavy ends → light oils → gases, asphaltics → maltenes → gases. The mathematical model was chosen to be power law because of the complexity of the reaction system. Hydrocracking reactions were assumed to be first order with respect to hydrocarbons and zero order with respect to hydrogen. The reaction rate constants were represented by an Arrhenius type expression. Activation energies and the frequency factors were determined for each reaction model proposed.

Ethanol production from xylose by Thermoanaerobacter ethanolicus in batch and continuous culture

The fermentation of xylose by Thermoanaerobacter ethanolicus ATCC 31938 was studied in pH-controlled batch and continuous cultures. In batch culture, a dependency of growth rate, product yield, and product distribution upon xylose concentration was observed. With 27 mM xylose media, an ethanol yield of 1.3 mol ethanol/mol xylose (78% of maximum theoretical yield) was typically obtained. With the same media, xylose-limited growth in continuous culture could be achieved with a volumetric productivity of 0.50 g ethanol/liter h and a yield of 0.42 g ethanol/g xylose (1.37 mol ethanol/mol xylose). With extended operation of the chemostat, variation in xylose uptake and a decline in ethanol yield was seen. Instability with respect to fermentation performance was attributed to a selection for mutant populations with different metabolic characteristics. Ethanol production in these T. ethanolicus systems was compared with xylose-to-ethanol conversions of other organisms. Relative to the other systems, T. ethanolicus offers the advantages of a high ethanol yield at low xylose concentrations in batch culture and of a rapid growth rate. Its disadvantages include a lower ethanol yield at higher xylose concentrations in batch culture and an instability of fermentation characteristics in continuous culture.

Fission and particle evaporation following stopped-negative-pion absorption in 209Bi

Fission and particle evaporation following stopped- π − absorption were measured for 209Bi. The fission probability per captured π − was obtained as W f = (3.01 ± 0.34) × 10 −3 from the number of fission tracks observed in the mica track detector and that of π − stopped in the Bi target. The latter was derived from the observed absolute intensities of pionic Bi X-rays. The isotopic yield distributions for the ( π −, xn) and ( π −, pxn) reactions were also determined by in-beam and activation γ-ray measurements. From the analysis of the fission probability and the product-yield distribution, it was concluded that the thermally equilibrated nuclear states have a wide energy distribution and rather low excitation energies (∼50 MeV) compared to the initially involved energy of 140 MeV. A model was proposed for the formation and decay of 209Bi nuclei excited by the capture of the stopped π −. The model well reproduces the experimental results.

Comparative kinetic study of ethylbenzene isomerisation on acidic and non‐acidic Pt/Al2O3 catalysts

AbstractEthylbenzene (EB) isomerisation to o‐, m‐ and p‐xylene was investigated in a microcatalytic reactor on acidic and non‐acidic Pt/Al2O3 catalysts. Total conversion and product yield distribution data were determined on both catalysts for EB and the xylenes in the temperature range 513–673 K and 1.8 atm. Total conversion of each of the C8 isomers went through a maximum as the temperature was increased. The onset of reaction occurred at a lower temperature, and the initial rates were higher on the acidic catalyst. Furthermore, the acidic catalyst was found to be very selective in the production of p‐xylene at temperatures less than 563 K, and of p‐ and o‐xylene at temperatures less between 563 and 593 K. The Wei‐Prater method was used for the calculation of absolute rate constants for EB isomerisation on both catalysts. Generally, the rate constants were higher on acidic Pt/Al2O3.

Products of rapidly heated oil sand

Previous work on direct oil sand heating showed that hydrocarbon removal of ≈90% could be achieved below a temperature of ≈550 °C. It was also found that the rate of heat-up did not affect the total yield. In the present work, the influence of various parameters, including heating rate, on the yield distribution of products from directly heated oil sand and separated bitumen was examined using gas chromatography. It is found that the heating rate has a very dramatic influence on the distribution of products. Fast heating rates cause a strong shift to lighter species in either inert or chemically reactive atmospheres. It is possible to achieve a very wide range of distribution of products by employing suitable values of heating rate and final temperature. Increasing hydrogen pressure is found to have a significant influence on the yield distribution up to ≈3 MPa, after which point, little further change is observed.

Fluoro-ketones. II Reactions of fluorocarbon grignards and copper compounds with perfluoroalkylacid fluorides

The reactions between C 6F 5MgBr (I), p-BrC 6F 4MgBr (X), C 6F 5Cu (XXI), p-HC 6F 4Cu (XXII) and p-BrC 6F 4Cu (XV) with primary and secondary perfluoroalkylether acid fluorides were studied. The Grignard compounds react very slowly with the secondary acid halides (R fCF(CF 3C(O)F) whereby competing reactions cause undesirable by-products and reduction of ketone yields. Primary acid halides (R fCF 2C(O)F) react much faster with C 6F 5MgBr to give the ketone in improved yields. The organocopper compound react with either primary or secondary acid halides to give the ketone in excellent yields with no by-product formation from competing secondary reactions. Solvent, type of organometallic reagent and primary versus secondary acid fluoride are variables that influence product yield and product distribution.

Effect of Inorganic Additives on the Reactions of Isomeric Transition-Activated 80Br and 82Br in the Gaseous HBr–CH4 System

Abstract The effects of various inorganic additives with and without dipole moments on the product yield distributions have been examined in the CH4–H80mBr and CH4-H82mBr systems. Indications were that the ion-clusters formed in the reactions of IT-activated 80Br and 82Br play an important role in determining individual product yield distributions.

Nine MeV bremsstrahlung fission of 238U

The mass yield distribution of fission products produced in the photofission of 238U using 9 MeV bremsstrahlung have been radiochemically measured for 21 mass chains. The absolute activities of the nuclides measured were determined from gross β counting and total chain yields were measured relative to 99Mo. The peak to valley ratio was found to be about 310, which is comparable with previous results measured at 10 MeV. Fine structure was found to be a prominent feature and occurred around mass number 133, although mass number 134 could not be measured in the present investigation. The fission yields measured in this work have been compared to all known existing values for work in photon energy range of 9 ± 1 MeV.

Investigation of the reported mass distribution curves in the fission of 233U with 14·8 MeV neutrons

The mass yield distribution of fission products produced in the fission of 233U with 14·8 MeV neutrons has been measured for eight mass chains in the symmetric region. This investigation was initiated to resolve existing discrepancies in published data with respect to the fission yields in the valley region and the peak-to-valley ratio. The absolute activities of the nuclides measured were determined from gross beta counting and total yields were measured relative to 132Te or 99Mo. The standard yields were chosen due to the close agreement of previous data for those mass chains. The peak-to-valley ratio calculated was about 3·5. The fission yields measured in this work have been compared to known existing values for 14·8 MeV neutron-induced fission of 233U.

Description of the Thermal Decomposition of Naphthas

In laboratory tubular reactor at atmospheric pressure and in a temperature range of 580-830 °C the pyrolysis of a straight-run Romashkino naphtha cut with a boiling range of 40-160 °C was investigated. New characteristics were introduced to characterize the degree of the decomposition of the naphthas. Substituting the conversion in kinetic equations developed for flow reactors by the decomposition grade, appropriate correlation were derived for describing the overall decomposition rate of the naphthas. It was demonstrated that in the temperature and residence time ranges of industrial pyrolysis processes, the expansion and the yield distribution of the main reaction products depend only on the decomposition grade. For the predicting the product distribution in naphtha pyrolysis a simplified kinetic model was elaborated.

Dry Distillation and Decomposition of Asphalts

Fundamental studies have been made to get low-sulfur fuels from petroleum residue. Asphalts were decomposed to gases, oil and coke by dry distillation.The data concerning on product yield and sulfur distribution were obtained in temperature range 400-1000°C. As raising temperature, cracking proceeded up to 700°C and dehydrogenation of coke followed in higher temperature. Sulfur content of oil was 2. 4-3.4wt.%, and H2S was 2. 0-8. 0vol.% of gas produced. More than 40wt.% of feed sulfur remained in coke.Coke was converted to carbon oxides and hydrogen by steam. CaO, BaCO3, MgO, Na2CO3 and K2CO3 catalyzed these reactions, and CaO accepted sulfur by the reaction CaO+H2S=CaS+H2O.Hydrogen had little effects on product yield and sulfur distribution.