Structure sensitivity of selective acetylene hydrogenation over the catalysts with shape-controlled palladium nanoparticles

The structure sensitivity of acetylene hydrogenation on catalysts with controlled shape of palladium nanoparticles was studied. Palladium particles of cubic (Pdcub), cuboctahedral (Pdco) and octahedral (Pdoct) shapes were obtained by a colloidal method. Poly(N-vinyl)pyrrolidone (PVP) was used as the stabilizer of colloidal solutions. In order to eliminate the effect of the polymer on the properties of the catalyst, PVP was removed from the surface of the particles after their transfer to the support by simultaneous treatment with ozone and UV radiation. This allowed complete cleaning of the catalyst surface from the organic stabilizer without any change in the morphology of particles. The effectiveness of this treatment method was confirmed by X-ray photoelectron spectroscopy and scanning electron microscopy. It was found experimentally that the shape of nanoparticles does not influence the catalyst selectivity, but the activity decreases in the order Pdoct > Pdco > Pdcub. Since octahedrons consist of (111) faces, the cubes contain only (100) faces, and the cuboctahedrons are composed of faces of both types, Pd111 is more active than Pd100. Calculations with the use of a statistical method showed that the ∼3-nm Pd octahedrons are nanoparticles with optimum shape and size, giving maximum catalyst activit

Structure sensitivity of selective acetylene hydrogenation over the catalysts with shape-controlled palladium nanoparticles

The structure sensitivity of acetylene hydrogenation on catalysts with controlled shape of palladium nanoparticles was studied. Palladium particles of cubic (Pd-cub), cuboctahedral (Pd-co) and octahedral (Pd-oct) shapes were obtained by a colloidal method. Poly(N-vinyl)pyrrolidone (PVP) was used as the stabilizer of colloidal solutions. In order to eliminate the effect of the polymer on the properties of the catalyst, PVP was removed from the surface of the particles after their transfer to the support by simultaneous treatment with ozone and UV radiation. This allowed complete cleaning of the catalyst surface from the organic stabilizer without any change in the morphology of particles. The effectiveness of this treatment method was confirmed by X-ray photoelectron spectroscopy and scanning electron microscopy. It was found experimentally that the shape of nanoparticles does not influence the catalyst selectivity, but the activity decreases in the order Pd-oct > Pd-co > Pd-cub. Since octahedrons consist of (111) faces, the cubes contain only (100) faces, and the cuboctahedrons are composed of faces of both types, Pd-111 is more active than Pd-100. Calculations with the use of a statistical method showed that the similar to 3-nm Pd octahedrons are nanoparticles with optimum shape and size, giving maximum catalyst activity

Global Distribution of Rubella Virus Genotypes

Phylogenetic analysis of a collection of 103 E1 gene sequences from rubella viruses isolated from 17 countries from 1961 to 2000 confirmed the existence of at least two genotypes. Rubella genotype I (RGI) isolates, predominant in Europe, Japan, and the Western Hemisphere, segregated into discrete subgenotypes; intercontinental subgenotypes present in the 1960s and 1970s were replaced by geographically restricted subgenotypes after ~1980. Recently, active subgenotypes include one in the United States and Latin America, one in China, and a third that apparently originated in Asia and spread to Europe and North America, starting in 1997, indicating the recent emergence of an intercontinental subgenotype. A virus that potentially arose as a recombinant between two RGI subgenotypes was discovered. Rubella genotype II (RGII) showed greater genetic diversity than did RGI and may actually consist of multiple genotypes. RGII viruses were limited to Asia and Europe; RGI viruses were also present in most of the countries where RGII viruses were isolated

Computer-aided synthesis of repairs of buildings and the engineering infrastructure Автоматизация синтеза ремонтных работ зданий и инженерной инфраструктуры

The authors present a decision making algorithm applicable in the event of an emergency involving structural elements of a building, as well as the algorithm of synthesis of repair plans (emergency and scheduled repairs) consisting in redistribution of emergency repairs over regular repairs.In the event of an accident, a structural element of a building is damaged. An expert compiles a plan of emergency repairs, according to the previously described algorithm, or using PRR CAD software. The proposed algorithm is employed to analyze the plan of emergency repairs and to reconcile it with a plan of scheduled repairs. If the decision is made to conduct emergency repairs within scheduled repairs by means of their synthesis, emergency repairs are redistributed over scheduled repairs. The algorithm of synthesis of plans of repair works is to help the expert distribute emergency repair works over scheduled repair works, or to save material, human and other resources. Implementation of algorithms in a cluster of buildings and structures requires substantial technological resources. Cloud computing technologies can serve as a platform for the implementation of the proposed solutions.<br>Представлен алгоритм принятия решений в случае возникновения аварийной ситуации на конструктивных элементах здания, алгоритм синтеза планов ремонтных работ (аварийных и плановых), заключающийся в перераспределении аварийных ремонтных работ по планам ремонтных работ

Computer-aided design of repairs of buildings and the engineering infrastructure

The authors argue that the design development procedure and the technology-based preparation for the renovation of buildings and the engineering infrastructure are to be considered as a comprehensive process to be automated. One of the main problems that accompany the process of budgeting and scheduling of renovation projects consists in incidental expenses for extra repairs, as they are difficult to project. The authors suggest developing a specialized computer aided design system capable of simulating the building renovation procedure. This methodology is available in the Russian legislation dealing with the renovation activities; it covers supplementary activities and helps experts make efficient decisions aimed at saving construction materials, time and human resources. The subsystems of the CAD software facility responsible for the planning of renovation works include a database, a database management system, a decision making subsystem, a decision synthesis subsystem, a decision analysis system (decision retrospection), a decision evaluation system and other subsystems

Structure Sensitivity of Alkynol Hydrogenation on Shape- and Size-Controlled Palladium Nanocrystals: Which Sites Are Most Active and Selective?

The activity and selectivity of structure-sensitive reactions are strongly correlated with the shape and size of the nanocrystals present in a catalyst. This correlation can be exploited for rational catalyst design, especially if each type of surface atom displays a different behavior, to attain the highest activity and selectivity. In this work, uniform Pd nanocrystals with cubic (in two different sizes), octahedral, and cuboctahedral shapes were synthesized through a solution-phase method with poly(vinyl pyrrolidone) (PVP) serving as a stabilizer and then tested in the hydrogenation of 2-methyl-3-butyn-2-ol (MBY). The observed activity and selectivity suggested that two types of active sites were involved in the catalysis those on the planes and at edges which differ in their coordination numbers. Specifically, semihydrogenation of MBY to 2-methyl-3-buten-2-ol (MBE) occurred preferentially at the plane sites regardless of their crystallographic orientation, Pd-(111) and/or Pd-(100), whereas overhydrogenation occurred mainly at the edge sites. The experimental data can be fit with a kinetic modeling based on a two-site Langmuir Hinshelwood mechanism. By considering surface statistics for nanocrystals with different shapes and sizes, the optimal catalyst in terms of productivity of the target product MBE was predicted to be cubes of roughly 3-5 nm in edge length. This study is an attempt to close the material and pressure gaps between model single-crystal surfaces tested under ultra-high-vacuum conditions and real catalytic systems, providing a powerful tool for rational catalyst design