Roles of Ceria on Base Metal Oxide Catalysts——NO+CO Reaction

A microreactor system was used to study the catalytic reaction of NO+CO→1/2 N_2+CO_2 over Cu,Fe, Mn,Cr,and Ce oxides supported on alumina,and the effect of adding Ce in supported Cu-M-O(M=Mn,Fe and Cr) catalysts on their catalytic activities for the topic reaction and the concentration of N_2O produced.It was found that the catalytic activity order of the single-element oxide is:CuO>Fe_2O_3≈Cr_2O_3> MnO_2>CeO_2>NiO.Cu-Mn-O is more active than CuO,and Cu-Fe-O is more active than Cu-Mn-O and Cu-Cr-O for NO+CO reaction.This study shows that the addition of Ce in supported Cu-M-O can promote their catalytic activities Jot the topic reaction,which makes the reaction of 2NO+CO→N_2O+CO_2 fast,and N_2O is an intermediate compound produced during NO+CO reaction.

Roles of Ceria on Copper and Manganese Oxides Catalyst——Adsorption of NO and CO

A microreactor system and TPD techniques were used to study the reaction kinetics of the CO+ NO reaction and the adsorption of CO,NO,CO_2 and N_2O over Cu-Mn-O(Ⅰ)and Cu-Mn-Ce-O(Ⅱ) catalysts.The results show that the catalytic activity of(Ⅱ)is higher than that of(Ⅰ)for the CO+NO reac- tion,and the higher the conversion of NO,the larger was the activity difference between(Ⅰ)and(Ⅱ).For (Ⅰ)the rate of NO elimination is dependent on the partial pressures of NO,CO,CO_2 with the kinetics or- ders of 0.48,0.56,0.08,respectively.The TPD study shows that the presence of Ce in(Ⅱ)may promote the adsorption of NO,CO on the surface,i.e.an increase of the coverage θ_(NO),θ_(CO),which result in a decrease of the hindrance of the reaction products.For CO_2 and N_2O the situation is in the opposite,the presence of Ce makes the θ_(CO)_2)and θ_(NO)on(Ⅱ)decrease,which weakens the inhibition of CO_2 for the reaction.

KINETICS OF METHANOL SYNTHESIS IN THE PRESENCE OF C301 Cu-BASED CATALYST (Ⅰ) INTRINSIC AND GLOBAL KINETICS*

The intrinsic and global kinetics of methanol synthesis from carbon monoxide, carbon dioxide and hydrogen in the presence of C301 commercial catalyst is studied. The investigation is performed under typical commercial conditions in an isothermal plug-flow integral reactor and

KINETICS OF METHANOL SYNTHESIS IN THE PRESENCE OF C301 Cu-BASED CATALYST (Ⅱ) EFFECTIVENESS FACTORS OF PARALLEL REACTIONS*

For multiple reaction system of methanol synthesis in the presence of Cu-based catalyst, hydrogenation reactions of CO and CO2 are selected as key reactions. A diffusion model, taking CO and CO2 as key components, is presented for the calculation of the intraparticle effectiveness factors of the two parallel key reactions over C301 Cu-based catalyst. Numerical solutions of the effectiveness

KINETICS OF FAST URETHANE POLYMERIZATION IN REACTION INJECTION MOULDING

The kinetics of dibutyltin dilaurate(DBTDL) catalyzed fast urethane polymerization of polyoxypropylenepolyoxyethlene triol with uretonimine modified 4, 4’-diphenylmethane diisocyanate (l-MDI) in RIM was studied by infrared spectroscopy and adiabatic temperature rise. For isothermal reaction, the overall reaction order was found to change from 3/2 to 2 with increasing reaction temperature. For adiabatic reaction, the overall reaction order was found to change from 3/2 to 2 with increasing catalyst concentration and hard segment content. The phase separation occured during the RIM urethane polymerization leads to a deviation of the kinetics relationships for higher conversion from those for lower.

A Study on the Thermal Stability of La_2O_3-TiO_2 Supports

In this paper,various techniques including BET,XRD,SEM and XPS were used to study the sintering of pure and La_2O_3-doped titania.The experimental results show that sintering of titania proceeds via volume diffu- sion.Adding of lanthanum oxide decreases the rate of sintering and hinders the phase transition from anatase to rutile crystal by strong surface interaction between the mixed crystals(La_4Ti_9O_(24),La_(0.66)TiO_(2.99))and TiO_2.

THE RELATION OF SEQUENCE DISTRIBUTIONS OF S-SBR TO ITS MOLECULAR WEIGHT DISTRIBUTIONS

The relationship between sequence distributions and molecular weight distributions of S-SBR, obtained from styrene and butadiene anionic copolymerization at various conversions with THF/Li^+ as an initiator has been studied by ^(13)C-NMR,GPC. The results showed that the molecular weight distributions of the copolymer couldbe correlated sophisticatedly to the binary sequcne distributions or the monomer unit distributions of the copolymer in a corrected Poisson's distribution from.

Behavior of 2-ethylhexanoic Acid in Organic Phase of Gallium Extraction

The rate of batch extraction of gallium from alkaline aqueous solution was studied by adding 2-ethylhexanoic acid in organic phase containing 7-substituted-8-hydroxyquinoline(extractant N601), n-decanol and kerosene.The extraction of Ga can be considered as a pseudo-homogeneous first-order reac- tion.The neutralization and distribution of organic acid between phases during the extraction were studied. The effect of 2-ethylhexanoic acid on the protonation of N601 is insignificant.The extraction of HCl during the stripping of gallium is mainly dependent on the concentration of aqueous hydrochloric acid and the con- tent of N601.Under the given conditions of temperature and N601 content,the acidity of organic phase is a linear function of the concentration of carboxylic acid in organic phase and the concentration of hydrochloric acid in equilibrium aqueous phase,if the latter is 1.9～5.6 mol/L.

PHASE SEPARATION AND CRYSTALLIZATION OF CHALCOGENIDE GLASSES

In this paper the experimental results associated until the phase separation and nucleation and crystallization of chalcogenidc glasses are described. Experi-ments demonstrate that the phas separation may be affected by small amount of additives. It has been found that some chalcogenide glasses could be converted into glass-ceramics without phase separation. The different mechanisms of nucleated crystallization of chalcogenide glasses are discussed and propossed.

WORMHOLE AND THE DIMENSIONALITY OF SPACETIME IN EINSTEIN-GAUGE THEORIES

The wormhole effect is discussed in the d-dimensional Einstein-Yang-Mills theory.We show that the peak of the probability function leads to the explanation of the spontaneous compactification down to a four-dimensional spacetime and vanishing four-dimensional cosmological constant,i.e.,the observable spacetime must be four-dimensional and flat.

A NEWLY DEVELOPED LIQUID-LIQUID EXTRACTION COLUMN——The Open Turbine Rotating Disc Contactor(OTRDC)

The experimental study on hydrodynamics,axial mixing and mass transfer has been carried out in anewly developed liquid-liquid contactor,the open turbine rotating disc contactor(OTRDC).It has been foundthat the OTRDC is possible to be operated with higher hold-up of dispersed phase,larger interface and hencehigher efficiency of mass transfer comparing with the ordinary RDC.In correlating axial mixing data,a combinedmodel has been used in which both forward mixing due to the drop size distribution and backmixingof droplets are taken into account.The RTD curves of dispersed phase predicted by the model were fit wellwith the experimental data.The comparison of the experimental mass transfer data with thosc predicted by theaxial mixing model and theoretical single drop models shown they are in good agreement.

RESIDENCE TIME DISTRIBUTION IN A SCREW EXTRUDER

It has been studied that the residence time distribution(RTD)function in a screw extruder in relation to that in thescrew and that in the die.For a complex flow field such as that between screw and die,it was supposed that the RTDfunction in the screw and that in the die were almost independent on each other.Therefore,a probabilistic method wasused to predict the RTD function in a complete extruder from that in the screw and that in the die.The experiments fordetermining the RTD were based on a stimulus-response technique.The results predicted,both in single-screw extruderand in twin-screw extruder,were in good agreement with those experimentally obtained.

Mssbauer Study of Coal Desulfurization by Microwave Irradiation Combined With Manetic-Separation and Chemical Acid-Leaching

^(57)Fe Mssbauer spectroscopy was used to study the mechanism and regularity of coal desulfurization by microwave irradiation combined with magnetic-separation and with chemical acid-leaching. The results of phase analyses show that the decomposing reaction of pyrite intrinsic in coal, caused by the selective dielectric heating of microwave electromagnetic energy, FeS_2→Fe_(1-x)S→FeS, consecutively progresses towards the right-hand side with increased irradiation time. The whole process of microwave desulfurization of raw coal consists of the initiation, the promotion, and the saturation stages. The optimum desulfurization efficiency for microwave irradiation combined with magnetic-separation treatment and with chemical acid-leaching treatment can be attained by appropriately controlling the irradiation time to enable the corresponding microwave treatment to lie in the promotion stage and the saturation stage, respectively.

NEW TRITERPENOIDAL SAPONINS FROM MUSSAENDA PUBESECUS

A cyclolanostene-type triterpene and two saponins derived thereform, namely MP-C,D and F,were isolated from the acid-hydrolyzate of the mixture of saponins of Mussaenda pubesecus.Their structures were elucidated on the basis of chemical and UV,IR,~1H,^(13)C NMR and MS spectral evidence.The two new saponins MP-D and F were named Mussaendoside A and C,respectively.

STOPPED PROCESSES OF TEMPORALLY HOMOGENEOUS MARKOV JUMP PROCESSES

Let X=（X, （ω））(t≥0 be a jump process defined on a complete probability space （Ω, F, P）:

A Standard Model-Theoretic Approach to Operational Semantics of Recursive Programs

In this paper we try to introduce a new approach to operational semantics of recursive programs by using ideas in the“priority method”which is a fundamental tool in Recursion Theory.In lieu of modelling partial functions by introducing undefined values in a traditional approach,we shall define a priority derivation tree for every term,and by respecting the rule“attacking the subterm of the highest priority first”we define transition relations,computation sequences etc.directly based on a standard interpretation which includes no undefined value in its domain.Finally,we prove that our new approach generates the same operational semantics as the traditional one.It is also pointed out that we can use our strategy to refute a claim of Loeckx and Sieber that the opperational semantics of recursive programs cannot be built based on predicate logic.

INFLUENCE OF IRRADIATION TIME ON THE MICROWAVE DESULFURIZATION OF COAL

The microwave desulfurization is a novel and attractive physical method for coal cleaning, which is divided into two types: with and without leachant. The latter at first was proposed by Zavitsanos et al., they selected air or reducing gas as reacting atmosphere, and the desulfufization rates of 26.8—53.5% were obtained. It has substantial advantages

CONFORMATION AND STERIC ENERGY OF MACROMOLECULES CALCULATED BY THE METHOD OF MOLECULAR MECHANICS

Ⅰ. INTRODUCTIONMolecular mechanics (MM) is one of the methods used to theoretically study the compound structure and conformation in chemistry. It has been proved by experiments that the calculations of the formation heat and configuration of organic compounds are very successful. However, it is difficult to calculate the steric energy of macromolecules

THE INVESTIGATION OF DOPING OF POLYPHENYLENE SULFIDE WITH ANTIMONY PENTACHLORIDE

I. INTRODUCTION Electrical conductive polymers have attracted considerable attention since the metallic conducting polyacetylene was reported. A relatively large number of conjugated polymers are now known which can be doped with either strong electron acceptors or donors to yield conducting complexes. The preparation of conducting polymer is usually

ENDOR AND ESR STUDIES OF RADICALS FORMED IN FRIEDEL-CRAFTS REACTIONS

The present study deals with the study of some Friedel-Crafts alkylating system and the accurate measurement of hyperfine coupling constants by ESR and ENDOR techniques. The results indicate that the observed ESR spectra are due to polycyclic aromatic radical cations formed from their parent hydrocarbons.It is suggested that benzyl halides produced in the Friedel-Crafts alkylating reaction undergo Scholl condensation reaction to give polycyclic aromatic hydrocarbons, which were converted into the corresponding polycyclic aromatic radical cations in the presence of aluminum chloride.