Ni-Based Nanoparticles on Mesoporous Silica Supports for Single-Stage Arsenic and Chlorine Removal during Diesel Fraction Hydrotreating.

As- and Cl-containing impurities are highly detrimental to sulfided catalysts in hydrotreating processes. To prevent the irreversible loss of activity of the main sulfide catalysts by As and Cl contaminants, a protective double-layered guard bed catalyst is applied. Two types of mesoporous silica supports (SBA-15 and MCF) were used to obtain sorption-catalytic materials.

Alkali Earth Catalysts Based on Mesoporous MCM-41 and Al-SBA-15 for Sulfone Removal from Middle Distillates.

Mg, Ca, and Ba catalysts supported on structured mesoporous silica oxides types MCM-41 and Al-SBA-15 were synthesized and investigated in sulfone cracking for sulfur removal from oxidized diesel fuel. Functional materials and catalysts were characterized by low-temperature nitrogen adsorption/desorption, transmission electron microscopy, and inductively coupled plasma atomic emission spectroscopy techniques. Catalytic tests were carried out in fixed-bed and batch reactors with a model compound dibenzothiophene sulfone and oxidized diesel fraction as a feed.

Pd(2+)-mediated base pairing in oligonucleotides.

Two short glycol nucleic acid (GNA) oligonucleotides, having either a terminal or an intrachain nucleobase replaced by the pyridine-2,6-dicarboxamide chelate of Pd(2+), have been synthesized and their hybridization properties studied by melting temperature measurements. In the termini of a double-stranded oligonucleotide, the Pd(2+) chelates provided dramatic stabilization of the duplex relative to its metal-free counterpart, in all likelihood owing to formation of Pd(2+)-mediated base pairs between pyridine-2,6-dicarboxamide and the opposing nucleobase. In contrast, no stabilization was observed when the Pd(2+) chelate was placed in the middle of the chain.

Formation of mixed-ligand complexes of Pd2+ with nucleoside 5'-monophosphates and some metal-ion-binding nucleoside surrogates.

Formation of mixed-ligand Pd2+ complexes between canonical nucleoside 5'-monophosphates and five metal-ion-binding nucleoside analogs has been studied by 1H-NMR spectroscopy to test the ability of these nucleoside surrogates to discriminate between unmodified nucleobases by Pd2+-mediated base pairing. The nucleoside analogs studied included 2,6-bis(3,5-dimethylpyrazol-1-yl)-, 2,6-bis(1-methylhydrazinyl)- and 6-(3,5-dimethylpyrazol-1-yl)-substituted 9-(β-d-ribofuranosyl)purines 1-3, and 2,4-bis(3,5-dimethylpyrazol-1-yl)- and 2,4-bis(1-methylhydrazinyl)-substituted 5-(β-d-ribofuranosyl)-pyrimidines 4-5. Among these, the purine derivatives 1-3 bound Pd2+ much more tightly than the pyrimidine derivatives 4, 5 despite apparently similar structures of the potential coordination sites.

Metal-ion-mediated base pairing between natural nucleobases and bidentate 3,5-dimethylpyrazolyl-substituted purine ligands.

The potential of three modified purine bases, namely, 6-(3,5-dimethylpyrazol-1-yl)purine, 2-(3,5-dimethylpyrazol-1-yl)hypoxanthine, and 2-(3,5-dimethylpyrazol-1-yl)adenine, for metal-ion-mediated base pairing within an oligonucleotide environment has been investigated. The respective modified nucleosides were incorporated in the middle of 9-mer 2'-O-methyl oligonucleotides and the hybridization of these modified oligonucleotides with their unmodified counterparts studied by UV and CD spectrometry in the absence and presence of Cu(2+) or Zn(2+). All of the modified oligonucleotides formed more stable duplexes in the presence of divalent metal ions than in the absence thereof, but with different preferences for the complementary oligonucleotide.