a fourth-generation ziegler-natta catalyst was prepared to synthesize polypropylene (pp), which was stabilized by in situ polymerization employing lignin as antioxidant. the antioxidant properties of lignin were compared with those of the commercial antioxidant irganox 1010. the presence of lignin in the reaction medium slightly decreased the catalytic activity of the reaction. the isotacticity...

Protein functions have evolved in part via domain recombination events. Such events, for example, recombine structurally independent functional domains and shuffle targeting, regulatory, and/or catalytic functions. Domain recombination, however, can generate new functions, as implied by the observation of catalytic sites at interfaces of distinct folding domains. If useful to an evolving organi...

The replacement of hazardous solvents and the utilization of catalytic processes are two key points of the green chemistry movement, so aqueous organometallic catalytic processes are of great interest in this context. Nevertheless, these processes require not only the use of water-soluble ligands such as phosphanes to solubilise the transition metals in water, but also the use of mass transfer ...

La3+ and Sm3+ - doped Bi2Mn2O7 nanocatalysts were synthesized in 1 M NaOH aqueous solution, via a stoichiometric 1:1 Bi:Mn molar ratio hydrothermal method at 180 °C for 48 h. Bi(NO3)3, MnO2, La(NO3)3 and Sm2O3 were used as raw materials. The synthesized nanomaterials were characterized by powder X-ray diffraction (PXRD) technique. Both of the La3+ and Sm3+ - doped Bi2Mn2O7 nanomaterials were cr...

We study equilibrium properties of a catalytically activated annihilation A+A-->0 reaction taking place on a one-dimensional chain of length N (N--> infinity ) in which some segments (placed at random, with mean concentration p) possess special, catalytic properties. Annihilation reaction takes place as soon as any two A particles land onto two vacant sites at the extremities of the catalytic s...

Iron–nickel spinel oxide NiFe2O4 nanoparticles have been prepared by the combination of chemical precipitation and subsequent mechanical milling. For comparison, their analogue obtained by thermal synthesis is also studied. Phase composition and structural properties of iron–nickel oxides are investigated by X-ray diffraction and Mössbauer spectroscopy. Their catalytic behavior in methanol deco...

An overview on the developments of zirconium phosphate (ZrP) and its organic derivatives in heterogeneous catalysis in recent years is reported in the present review. Two basic aspects have been emphasized: first, the catalytic properties of zirconium phosphates were discussed, with particular attention to the effect of surface acidity and hydrophobic/hydrophilic character, textural properties,...

We investigate the search properties of pre-evolutionary random catalytic reaction networks, where reactions might be reversible, and replication is not taken for granted. Since it counts only on slow growth rates and weak selective pressure to steer the search process, catalytic search is an inherently slow process. However it presents interesting properties worth exploring, such as the potent...

Micro/mesoporous zeolitic composites (MZCs) represent an important class of hierarchical zeolitic materials that have attracted increasing attention in recent years. By introducing an additional mesoporous phase interconnected with the microporosity of zeolites, a hierarchical porous system of MZCs is formed which facilitates molecular transport while preserving the intrinsic catalytic properti...

We demonstrate that human placenta is a convenient source of creatine kinase isoenzyme BB. We compare the physicochemical and catalytic properties with those of other creatine kinase isoenzymes: purified human abdominal muscle MM and brain BB. We also describe a stabilizing medium for creatine kinase BB. Human placental and brain BB have similar catalytic properties, the respective Km values fo...