Catalytic oxidation of CO,hydrocarbons, and ethyl acetate over perovskite-type complex oxides

The catalytic activity of M^IM^IIO₃] perovskite-type complex oxides (M^I = La, Y, Nd, Yb; M^II = Co, Mn, Ni) in the oxidation of CO, propylene, benzene, ethylbenzene,o-xylene, and ethyl acetate was investigated. The Co-containing catalysts were shown to be more active in the oxidation than the Mn-containing catalysts. A relationship between the catalytic and adsorption properties was established.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 602–605, April, 1994.     

A study of methylation of inorganic tin by iodomethane in an aquatic environment with 13C carbon isotope tracer technique

The methylation of tin(II) [Sn(II)] by iodomethane (CH₃I) under environmental conditions has been further demonstrated by a ¹³C carbon isotope tracer method. Methylation products are mainly monomethyltin, and very small amounts of dimethyltin. The reaction of Sn(II) and CH₃I was investigated at pH 2, 4, 6, 8, 10 and salinity (S) 8, 15, 22, 28, 35%; it has been found the reaction was affected by pH and salinity, the tin methylation activity being highest at about pH 6 and S = 28% . The methylation reaction is first-order for both CH₃I and Sn(II), and the rate equation has been obtained as follows: .     

Inorganic—Organic Hybrid 18—Molybdodiphosphate Nanoparticles Bullk—modified Carbon Paste Electrode and Its Electrocatalysis

A kind of inorganic‐organic hybrid 18‐molybdodiphosphate nanoparticles ([(C₄H₉)₄N]₆P₂Mo₁₈Q₆₂·4H₂O) was firstly used as a bulk‐modifier to fabricate a three‐dimensional chemically modified carbon paste electrode (CPE) by direct mixing. The electrochemical behavior of the solid nanoparticles dispersed in the CPE in acidic aqueous solution was characterized by cyclic and square‐wave voltammetry. The hybrid 18‐molybdodiphosphate nanoparticles bulk‐modified CPE (MNP‐CPE) displayed a high electrocatalytic activity towards the reduction of nitrite, bromate and hydrogen peroxide. The remarkable advantages of the MNP‐CPE over the traditional polyoxometalates‐modified electrodes are their excellent reproducibility of surface‐renewal and high stability owing to the insolubility of the hybrid 18‐molybdodiphosphate nanoparticles.     

Study of Factors Affecting the Performance of Voltammetric Copper Sensors Based on Gly‐Gly‐His Modified Glassy Carbon and Gold Electrodes

This paper reports a study of the factors affecting the analytical performance of gold and glassy carbon electrodes modified with the tripeptide Gly‐Gly‐His for the detection of copper ions. Gly‐Gly‐His is attached to a glassy carbon (GC) surface modified with 4‐carboxyphenyl moieties or a gold surface modified with 3‐mercaptopropionic acid by the reaction of the N‐terminal amine group of the peptide with the carboxylic acid groups of the monolayer via carbodiimide activation. X‐ray photoelectron spectroscopy was used to characterize the steps in the biosensor fabrication. It was found that the analytical performance of a sensor prepared with Gly‐Gly‐His on a GC electrode was similar to that on a gold electrode under the same conditions. The performance was greatly enhanced at higher temperature, no added salt during copper accumulation and longer accumulation time within a pH range of 7–9. Interference studies and investigations of stability of the Gly‐Gly‐His sensor are reported. Analysis of natural water samples show that the sensors measure only copper ions that can complex at the sensor surface. Strongly complexed copper in natural water is not measured. Despite greater stability of diazonium salt derived monolayers on carbon surfaces compared with alkanethiols self‐assembled monolayers on gold, the stability of the sensors was essentially the same regardless of the modification procedure.     

COMBINED PARTIAL OXIDATION AND CARBONDIOXIDE REFORMING OF METHANE PROCESS TO SYNTHESIS GAS

IntroductionIthasbccndcmonstratcdthatmcthancrcformingt"ithcarbondioxidcpr0ducessynthcsisgasrichincarbonmonoxidc-x"hichisuscfulforthcs}nthcsisofaccticacid'dimcthylcthcrando.o-alcoholsll'2].Carbondioxidcref0rmingismorccndothcrmicthanstcamrcformingfCH4 CO2,'2CO 2H2Ai/'2,,=2473kJ..ol-1(l)Accordingl\"thisrcact1onnccdshighcrtcmpcraturcandlimitsspaccvclocityoffccdgas,Wehavcprct'ious1\studicdmcthancrcformingt"lthC02inthcmonotubcproccssl3J.Inordertoconvcrtmcthancinfccdgascomplctcl}',thcspaccvcloci…     

纳米级碳导电剂的种类对licoo2电化学性能的影响

碳纳米管;锂离子电池;正极;倍率容量;导电剂     

Mechanistic Aspects of Carbon Nanotube Nucleation and Growth

The discovery, synthesis, characterization, and applicability of carbon nanotubes have produced tremendous excitement and interest among scientists and engineers. In particular, the use of these unique tubular nanostructures for new strong lightweight materials, nanoelectronics, fuel storage and cells, electron emitters and bio, scanning probe microscopy, and chemical sensing devices has created an intense effort to advance the synthesis so as to mass produce carbon nanotubes with control over diameter and helicity. The massive and controlled synthesis of this heralded nanostructure has been a great challenge. Although significant progress has advanced the preparation, more synthetic development is required. The syntheses have so far involved three main approaches: arc discharge vaporization, laser vaporization, and catalytic chemical vapor deposition. The synthetic trend has progressed to a point where further advancement with these techniques will require a better understanding of the mechanism of nucleation and growth. The mechanics of carbon nanotube nucleation and growth involve very complex and diverse phenomena occurring under extreme conditions and on the mesoscopic scale. As yet the detail mechanism is unknown. Difficulties with experimental probing and computational simulation have increased the mystery of this mechanism. This review presents an account of research on the synthesis of carbon nanotubes and the mechanism of formation. This overview includes all three mentioned synthetic approaches and hybrids thereof. On the basis of this broad account a comprehensive mechanism for carbon nanotube nucleation and growth naturally arises. This mechanism is qualitative and it hopes to inspire more quantitative exploration and synthetic advancement.     

Anodic stripping voltammetry of sulphide at a nickel film: towards the development of a reagentless sensor

The determination of sulphide at an electrochemically generated nickel oxide layer at glassy carbon and screen-printed electrodes in acidic media has been examined and appraised. The NiO layer was found to produce a stripping-like signal to sulphide and gave a linear peak current response from 20 to 90 μM. The response was further enhanced by repetitive cycling allowing accumulation of nickel sulphide at the electrode surface such that lower micromolar levels of sulphide (i.e. 5 μM) can be determined. The response at the NiO layer to sulphide is shown to be reproducible over a period of 24 h, thereby offering the development of a disposable amperometric sensor for sulphide.     

Optimisation of Supercritical Carbon Dioxide Systems for Complexation of Naproxen : Beta-Cyclodextrin

Supercritical carbon dioxide (scCO₂)offers several attractive scenarios for thepharmaceutical processing as an alternativeto aqueous and organic solvents. In thiswork naproxen, a widely used non steroidalanti-inflammatory drug with analgesic andanti-inflammatory properties, was chosenas a model drug. Its complexation with cyclodextrinsimproves the rate and extent of dissolutionof the drug, increase its rate of absorption and mayreduce the unpleasant side-effects of the drug.The interest in using this supercritical technologyled us to develop an experimental unit for the useof supercritical CO₂ as a processing medium forthe complexation of naproxen with beta cyclodextrin (CD).     

共沉淀浸渍法制备由合成气直接合成二甲醚的Cu-Mn催化剂

采用共沉淀浸渍法,制备了直接合成二甲醚的Cu-Mn-Zn催化剂,通过对组成成分及其配比的研究,发现Cu含量一定的条件下,n(Zn)/n(Mn)摩尔比对催化剂性能有较大的影响,当n(Zn)/n(Mn)=1/3～1/2时,催化剂对CO的转化率和对二甲醚的选择性达到最佳,分别为53.6%和63.5%；如锰添加比例过大,对催化剂催化合成二甲醚有微弱抑制；添加锌比例过大,会大大降低CO的转化率。载体Y分子筛的含量对催化剂性能也有影响,用量过大将降低催化剂的活性和对二甲醚的选择性,当其含量为33%时,催化剂上CO转化率和选择性可分别达到66%和68%,且催化剂活性随分子筛含量减少不再有明显的变化。