Self-immobilized catalysts for ethylene polymerization: neutral, single-component salicylaldiminato phenyl nickel(II) complexes bearing allyl substituents

A new family of self-immobilized ethylene polymerization catalysts, derived from neutral, single-component salicylaldiminato phenyl nickel complexes, is described.

Chiral synthesis on catalysts immobilized in microporous and mesoporous materials

This paper reviews the recent progress made in the asymmetric synthesis on chiral catalysts in porous materials and discusses the effects of surface and pores on enantio-selectivity (confinement effect). This paper also summarizes various approaches of immobilization of the chiral catalysts onto surfaces and into pores of solid inorganic supports such as microporous and mesoporous materials. The most important reactions surveyed for the chiral synthesis in porous materials include epoxidation. hydrogenation, hydroformylation, Aldol and Diels-Alder reactions, etc. The confinement effect originated from the surfaces and the pores turns out to be a general phenomenon. which may make the enantioselectivity increase (positive effect) or decrease (negative effect). The confinement effect becomes more pronounced particularly when the bonding between the catalyst and the surface is more rigid and the pore size is tuned to a suitable range. It is proposed that the confinement in chiral synthesis is essentially a consequence of subtle change in transition states induced by weak-interaction in pores or on surfaces. It is also anticipated that the enantioselectivity could be improved by tuning the confinement effect based on the molecular designing of the pore/surface and the immobilized catalysts according to the requirements of chiral reactions.

Self-immobilized metallocene catalysts bearing an allyl group for ethylene polymerization, X-ray crystal structure of [(CH2=CHCH2)CH3Si(C13H8)(2)]ZrCl2

A series of ansa-metallocene complexes with an allyl substituted silane bridge [(CH =CHCH2)CH3Si(C5H4)(2)]TiCl2 (1), [(CH2=CHCH2)CH3Si(C9H6)(2)]MCl2 [M = Ti (2), Zr (3), Hf (4)] and [(CH2=CHCH2)CH3Si(C13H8)(2)]ZrCl2 (6) have been synthesized and characterized. The molecular structure of 6 has been determined by X-ray crystallographic analysis. Complexes 1-4, 6 bearing allyl groups have been investigated as self-immobilized catalysts for ethylene polymerization in the presence of MMAO. The results showed that the self-immobilized catalysts 1-4, 6 kept high ethylene polymerization activities of ca. 10(6) g PE mol(-1) M h(-1) and high molecular weight (M-w approximate to 10(5)) of polyethylene.

Ethylene polymerization by self-immobilized neutral nickel catalysts bearing allyl groups

[Ni(Ph)(PPh3)(N,O)] complexes containing phenyliminophenolato ligands (N,O) (1: N,O = A; 2: N,O = B; 3: N,O = Q 4: N,O = D; 5: N,O = E) have been synthesized and characterized. The molecular structure of 4 was determined by single-crystal X-ray analysis. Complexes 2-5 bearing allyl groups have been investigated as self-immobilized catalysts for ethylene polymerization without the use of co-catalysts. The high ethylene polymerization activities of ca. 10(5) g.PE mol(-1) Ni.h(-1) and high molecular weight (M-w approximate to 10(5)) of polyethylene could be accomplished by changing the ligand structures and reaction conditions. The self-immobilization of catalysts brings about a dramatic increase in the catalytic activities of ethylene polymerization.

Heterogeneous catalysts for biodiesel production

The production of biodiesel is greatly increasing due to its enviromental benefits. However, production costs are still rather high, compared to petroleum-based diesel fuel. The introduction of a solid heterogeneous catalyst in biodiesel production could reduce its price, becoming competitive with diesel also from a financial point of view. Therefore, great research efforts have been underway recently to find the right catalysts. This paper will be concerned with reviewing acid and basic heterogeneous catalyst performances for biodiesel production, examining both scientific and patent literature.

Self-immobilized titanium and zirconium catalysts with phenoxy-imine ligands for ethylene polymerization. X-ray crystal structure of bis(N-(3-tert-butylsalicylidene)-4 '-allyloxyanilinato) zirconium(IV) dichloride

Four self-immobilized FI catalysts with allyl substituted phenoxy-imine ligands [{4-(CH2=CHCH2O)C6H5N=CH-C6H3(3-tert-C4H9)O}(2) MCl2] (1: M = Ti: 2: M = Zr), [{3-(CH2=CHCH2O)C6H5N=CH-C6H3(3-tert-C4H9)O}(2)MCl2] (3: M = Zr), [{4-(CH2=CHCH2-2,6-(iso-C3H7)(2))C6H5N=CH-C6H3(3,5-(NO2)(2))O}(2)MCl2] (4: M = Zr) have been synthesized and characterized. The molecular structure of 2 has been determined by X-ray crystallographic analysis. The results of ethylene polymerization showed that the self-immobilized titanium (IV) and zirconium (IV) catalysts 1-3 kept high activity for ethylene polymerization and 4 showed no activity. SEM showed the immobilization effect could greatly improve the morphology of polymer particles to afford micron-granula polyolefin as supported catalysts.

Micron-granula polyolefin with self-immobilized nickel and iron diimine catalysts bearing one or two allyl groups

Self-immobilized nickel and iron diimine catalysts bearing one or two allyl groups of [ArN=C](2)(C10H6)NiBr2 [Ar = 4-allyl-2,6-(i-Pr)(2)C6H2] (1), [ArN=C(Me)[Ar'N=C(Me)]C5H3NFeCl2 [Ar = Ar' = 4-allyl-2,6-(i-Pr)(2)C6H3, Ar = 2,6-(i-Pr)(2)C6H3, and Ar' = 4-allyl-2,6-(i-Pr)(2)C6H3] were synthesized and characterized. All three catalysts were investigated for olefin polymerization. As a result, these catalysts not only showed high activities as the catalyst free from the allyl group, such as [ArN=C](2)C10H6,NiBr2 (Ar = 2,6-(i-Pr)(2)C6H2)], but also greatly improved the morphology of polymer particles to afford micron-granula polyolefin. The self-immobilization of catalysts, the formation mechanism of microspherical. polymer, and the influence on the size of the particles are discussed. The molecular structure of self-immobilized nickel catalyst 1 was also characterized by crystallographic analysis.

Polymer immobilized silane bridged metallocene catalysts for ethylene polymerization

Ansa-zirconocene complex with an allyl substituted silane bridge [(CH2=CHCH2)CH3Si(C5H4)(2)]ZrCl2 (1a) has been synthesized and characterized. The molecular structure of la has been determined by X-ray crystallographic analysis. The polymer immobilized metallocene catalyst 1b is prepared by the co-polymerization of la with styrene in the presence of radical initiator. The result of ethylene polymerization showed that the polymer immobilized metallocene catalyst kept high activity for ethylene polymerization and was a potential supported catalyst for olefin polymerization.

Polyethylene glycol-stabilized platinum nanoparticles: The efficient and recyclable catalysts for selective hydrogenation of o-chloronitrobenzene to o-chloroaniline

In the present work, platinum nanoparticles were prepared by in situ reduction with polyethylene glycols (PEGs). The catalytic performance of Pt nanoparticles immobilized in PEGs (Pt-PEGs) is discussed for the hydrogenation of o-chloronitrobenzene (o-CNB). A high selectivity to o-chloroaniline (o-CAN) of about 99.7% was obtained with the Pt-PEGs catalysts at the complete conversion of o-CNB, which is much higher than that (83.4%) obtained over the conventional catalyst of Pt/C. The Pt nanoparticies could be immobilized in PEGs stably and recycled for four times with the same activity and selectivity. It presents a promising performance in the hydrogenation and its wide application in catalytic reactions is expected.

Preparation of methyl tert-butyl ether (MTBE) over heteropoly acids immobilized on activated carbon (HPA/C) in the vapor phase

Heteropolyacids (HPAs) supported on the activated carbon (SiW12/C and PW12/C) have been used to study the formation of methyl tert-butyl ether (MTBE). Compared to the conventional commercial catalysts, Amberlyst-15 resin and HZSM-5, HPAs supported catalysts have been proved to have much higher catalytic activity under lower temperature, especially selectivity to MTBE is up to 100%. It may be due to the high acid strength of HPAs as well as the specialty of heteropolyanion.

Quantifying Cell Binding Kinetics Mediated By Surface-Bound Blood Type B Antigen To Immobilized Antibodies

Cell adhesion is crucial to many biological processes, such as inflammatory responses, tumor metastasis and thrombosis formation. Recently a commercial surface plasmon resonance (SPR)-based BIAcore biosensor has been extended to determine cell binding mediated by surface-bound biomolecular interactions. How such cell binding is quantitatively governed by kinetic rates and regulating factors, however, has been poorly understood. Here we developed a novel assay to determine the binding kinetics of surface-bound biomolecular interactions using a commercial BIAcore 3000 biosensor. Human red blood cells (RBCs) presenting blood group B antigen and CM5 chip bearing immobilized anti-B monoclonal antibody (mAb) were used to obtain the time courses of response unit, or sensorgrams, when flowing RBCs over the chip surface. A cellular kinetic model was proposed to correlate the sensorgrams with kinetic rates. Impacts of regulating factors, such as cell concentration, flow duration and rate, antibody-presenting level, as well as pH value and osmotic pressure of suspending medium were tested systematically, which imparted the confidence that the approach can be applied to kinetic measurements of cell adhesion mediated by surface-bound biomolecular interactions. These results provided a new insight into quantifying cell binding using a commercial SPR-based BIAcore biosensor.