Catalytic behaviour of M1, M2, and M1/M2 physical mixtures of the Mo–V–Nb–Te–oxide system in propane and propene ammoxidation

Essentially pure orthorhombic M1 and pseudo-hexagonal M2 phases were prepared using the precursor method. Consistent with literature the M1 phase was shown to be effective for propane ammoxidation to acrylonitrile while the M2 phase was essentially inert for propane activation. Both phases convert propene efficiently to acrylonitrile. Both phases show a significant selectivity dependence on the ammonia and oxygen concentrations in the feed, revealing thereby additional insights into the reaction mechanism.

Physical mixtures of the two separately prepared phases exhibited symbiosis in the ammoxidation of propane when finally divided (5 μm), thoroughly mixed and brought into intimate contact with each other. Acrylonitrile yields significantly higher than those obtained with the M1 phase alone were demonstrated with a 50 wt.% M1/50 wt.% M2 physical mixture having a corresponding surface area ratio of about 4:1. The phase cooperation effect is particularly large at high propane conversions and non-existent when the particle size of the phases is too large (e.g. >250 μm) and the inter-particle contact is poor.     

Introduction to special issue.

Recent years have witnessed the emergence of two powerful, and seemingly contradictory, visions of what most fundamentally causes change in psychotherapy. One of these visions emphasizes the primacy of therapist technique. According to this viewpoint, it is the specific methods used by the psychotherapist that account for, by far, most of the variance in treatment outcome. This viewpoint is seen most notably in what have been termed the empirically supported treatments (EST) and evidence-based practices (EBP) movements. The second vision instead focuses on the patient-therapist relationship and so-called therapist-offered relationship qualities as the sine qua non of therapeutic effectiveness. Advocates of this viewpoint underscore research on the importance of relational qualities such as the therapeutic working alliance (or cohesion in groups) and therapist-offered conditions. While acknowledging the value of both visions noted above, this special issue of Psychotherapy is based on the notion that what matters most in psychotherapeutic treatments is the interplay of the two, of techniques and the therapeutic relationship. Technical factors and relational factors are indelible elements in each and every psychotherapy encounter, and the articles in this special issue explore and seek to uncover why this is so. The articles, in addition, seek to describe the complex ways in which technique and relationship interact with one another in different treatments, at different points in treatment, and in conjunction with still other variables. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Kinetic analysis of the liquid phase hydrogenation of 2-ethyl-hexenal in the presence of supported Ni,Pd and Ni-S catalysts

The kinetics of the consecutive hydrogenation reactions 2-ethyl-hexenal → 2-ethyl-hexanal → 2-ethyl-hexanol were studied in the liquid phase in presence of commercial Ni, Pd and Ni-S catalysts. The Pd and Ni-S catalysts were extremely selective with respect to the formation of 2-ethyl-hexanal, while the full reaction sequence was readily catalyzed by nickel. A Langmuir-Hinshelwood model with dissociative hydrogen adsorption was found to be the most probable model, for all three catalysts. The proposal of dissociative hydrogen adsorption of the Ni-S catalyst was supported by an independent gas-phase experiment, using the H₂/D₂ exchange reaction as a model reaction for the hydrogen àdsorption process.     

Pd/C催化苯酚氧化羰基化合成碳酸二苯酯反应研究

考察了Pd/C催化苯酚氧化羰基化合成碳酸二苯酯反应,确定了该反应较适宜的反应条件为反应温度80℃、反应压力5MPa、气相反应物进料配比n(CO)/n(O2)=10、反应时间4h。具有较大极性和较强的永久偶极矩的溶剂二氯乙烷的加入可有效提高苯酚转化率和碳酸二苯酯收率。XRD表征表明可能由于水的存在导致催化剂的活性组分Pd发生聚集使晶粒不断增大。     

Fundamentals in the preparation of heterogeneous catalysts

The preparation of heterogeneous catalysts has by now lost all empirical aspects. The approach is scientific and involves a wide number of specific competencies of solid state chemistry, analytical chemistry, physical chemistry, kinetics, rheology, etc. The fundamental aspects in the preparation of heterogeneous catalysts starting from catalyst design up to the catalyst in its final form are briefly reviewed, with focus on the key factors in each preparation step and the main differences between laboratory and industrial scale preparations. The main properties of monolithic catalysts and their preparation methods are also reported, considering their relevance for environmental applications.     

Electronic and geometric effects of alkali promoters in CO hydrogenation over K/Mo2C catalysts

When potassium salts such as K₂CO₃, KOH, CH₃COOK, and K₂S were added to Mo₂C, the promoted catalysts showed high selectivities to alcohols and light olefins in CO hydrogenation at 573 K and 1.0 MPa. However, K₂SO₄ and KCl caused only slight increase in olefin selectivity with negligible alcohol formation. These two groups of promoters showed different physical and chemical states during the reaction as observed by AES, EDS, EPMA, IR and transient reaction behavior. This difference accounted for the observed difference in selectivity.     

简支圆板在冲击荷载作用下的塑性动力响应分析

采用双剪应力强度理论求解了拉压异性材料简支圆板在中等脉冲荷载作用下的动力响应问题，得出了塑性动力极限荷载、内力场和速度场。讨论了静力许可条件和运动许可条件。利用本文的解还得出了简支圆板在静力荷载作用下的极限荷载、内力场和速度场。研究结果表明，材料的拉压强度比对动力解的影响要大于对静力解的影响，所以，根据材料的不同，选择合适的强度理论，对于更好地发挥材料的强度潜力具有重要的意义。     

Investigation of ethylene and styrene copolymerization initiated with dinuclear constrained geometry catalysts holding polymethylene as a bridging ligand and indenyl as a cyclopentadienyl derivative

A series of polymethylene‐bridged dinuclear constrained geometry catalysts (CGC) [Me₂Si(Ind)(N^tBu) TiCl₂]₂[(CH₂)_n] ( 1 , n = 6; 2 , n = 9; 3 , n = 12) were synthesized to study the copolymerization of ethylene and styrene. The experiments display that the polymerization activity of the dinuclear catalysts increased in the order of 1 < 2 < 3 , which indicated that the dinuclear CGC with the longest methylene units as a bridge showed the greatest activity. According to the activity correlation with the monomer ratio, all the catalysts exhibited maximum polymerization activity at the monomer ratio of ([styrene]/[ethylene]) of 2. The dinuclear CGC 2 and 3 represented excellent characteristics of styrene reactivity while catalyst 1 represented considerably low styrene reactivity. The relation between the molecular weights of the polymers and the catalysts used in the polymerization is not straightforward. The steric interference in catalyst 1 , containing just six methylene bridges, can be applied to explain not only the strikingly decreased activity but also the very low styrene content in the copolymer. In contrast, the electronic effect seems to be more pronounced in manipulating the polymerization properties of catalysts 2 and 3 having nine and 12 methylene bridges, respectively. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2469–2474, 2003     

First-principles calculations of phase equilibria and transformation dynamics of Fe-based alloys

Theoretical procedures of first-principles calculations of phase stability and phase equilibria are summarized. The present scheme is shown to be able to reproduce the transition temperatures with surprisingly high accuracy for Fe−Pd and Fe−Pt systems. The main emphasis of the present report is placed on the extension of the first-principles calculation to transition dynamics calculations. This is performed by combining the cluster variation method with the phase-field method via a coarse graining operation. The time evolution process of antiphase boundaries associated with L1₀ ordering for Fe−Pd system is demonstrated. This paper was presented at the International Symposium on User Aspects of Phase Diagrams, Materials Solutions Conference and Exposition, Columbus, Ohio, 18–20 October, 2004.     

Benign oxidants and single-site solid catalysts for the solvent-free selective oxidation of toluene

Two types of single-site heterogeneous catalysts have been designed so as to facilitate either the side-chain oxidation or ring-hydroxylation of toluene in O₂ (solvent-free) or by employing aqueous (H₂O₂) or organic (cumene hydroperoxide) hydroperoxides in high yield. The use of H₂O₂ and cumene hydroperoxide in particular, facilitates the ring-hydroxylation of toluene when zeolite-encapsulated metal complexes, such as perhalogenated or tetra-nitro-substituted phthalocyanines, are used as catalysts. Nanoporous, redox molecular sieves, display a higher tendency for the side-chain oxidation of toluene with air as an oxidant, with benzoic acid as the predominant product.