Hydrophilic interaction chromatography (HILIC) is important for the separation of highly polar substances including biologically active compounds, such as pharmaceutical drugs, neurotransmitters, ...nucleosides, nucleotides, amino acids, peptides, proteins, oligosaccharides, carbohydrates, etc. In the HILIC mode separation, aqueous organic solvents are used as mobile phases on more polar stationary phases that consist of bare silica, and silica phases modified with amino, amide, zwitterionic functional group, polyols including saccharides and other polar groups. This review discusses the column efficiency of HILIC materials in relation to solute and stationary phase structures, as well as comparisons between particle-packed and monolithic columns. In addition, a literature review consisting of 2006–2007 data is included, as a follow up to the excellent review by Hemström and Irgum.
Hetero-dimeric magnetic nanoparticles of the type Au-Fe.sub.3O.sub.4 have been synthesised from separately prepared, differently shaped (spheres and cubes), monodisperse nanoparticles. This synthesis ...was achieved by the following steps: (a) Mono-functionalising each type of nanoparticles with aldehyde functional groups through a solid support approach, where nanoparticle decorated silica nanoparticles were fabricated as an intermediate step; (b) Derivatising the functional faces with complementary functionalities (e.g. amines and carboxylic acids); (c) Dimerising the two types of particles via amide bond formation. The resulting hetero-dimers were characterised by high-resolution TEM, Fourier transform IR spectroscopy and other appropriate methods.
Silica diagenesis is one of the most important aspects of black shale diagenesis and critically controls the reservoirs properties of black shales. Three stratigraphic sections of the Wufeng and ...Longmaxi Formations in the Sichuan Basin along a proximal to distal transect were investigated to study quartz types and their silica sources, as well as their influences on reservoirs properties including rock mechanical properties and porosity preservation. Six types of quartz including detrital quartz, recrystallized radiolaria, siliceous fossil fragments, microcrystalline quartz, quartz overgrowth, and hydrothermal quartz veins were identified based on their occurrences and morphologies under the petrographic microscope and scanning electron microscope and cathodoluminescence color and intensity. Original biogenic silica now exists as recrystallized radiolaria and microcrystalline silica in the mudstone matrix and follows systematic distribution patterns both laterally and stratigraphically. The biological origin of this silica component is supported by the presence of recrystallized radiolaria with preserved spines, preservation of “ghosts” of the central capsule, serrated edges reflecting the spherical lattices of the outer shell, and in addition preserved sponge spicules. A further source of silica for microcrystalline quartz formation was silica released in the course of clay mineral (smectite to illite) transformation.
The different types of quartz make different contributions to the reservoir properties of shales, with microcrystalline quartz having the most important impact. Microcrystalline quartz enhances the rock mechanical properties of shales and protects initial porosity from mechanical compaction through a rigid framework of interconnected diagenetic silica grains. Pores between microcrystalline quartz grains are shielded from complete mechanical compaction and provide space for accumulation of bitumen and oil later in burial history. Subsequently, these pore-filling organic matter develop secondary organic nanopores at higher thermal maturity.
Although biogenic silica content has been used as a paleoproductivity proxy, the method used to calculate it is based on questionable assumptions, and model parameters need to be fine-tuned for a given shale succession on the basis of petrographic observations. In addition, the commonly observed positive correlation between total organic carbon (TOC) and biogenic silica is invalid for very low sedimentation rates and extremely high concentrations of biogenic silica. From low to extremely high biogenic silica content in organic-rich sediments, a parabolic relationship between TOC and biogenic silica should be common.
•Six types of quartz were identified based on their morphologies and occurrences.•Microcrystalline quartz is primarily sourced from biogenic silica.•Microcrystalline quartz enhances mechanical properties and preserves porosity.•Biogenic silica content (in percent) can't be used as a paleoproductivity proxy.
The eco-friendly and efficient non-noble metal nanocatalysts have extensive applications in the effective conversion of biomass derivatives into high-value chemicals. Herein, a highly dispersed and ...stable layered NiCu/SiO.sub.2 catalyst was successfully prepared by a facile ammonia evaporation (AE) method, and then applied to the aqueous-phase furfural (FFR) selective hydrogenation to cyclopentanone (CPO). Under mild conditions, FFR is almost completely transformed. Moreover, compared with traditional preparation methods, the yield of CPO increases significantly to 95.4% by the AE method. This remarkable performance improvement can be attributed to the high dispersion of metal nanoparticles and the synergistic effect between Ni and Cu. Meanwhile, Cu can adjust the electronic structure of Ni, and change the adsorption configuration of FFR on Ni, thereby improving the yield of CPO. This work provides a facile strategy for designing efficient and stable non-noble metal nanocatalysts for the aqueous-phase FFR selective hydrogenation.
The eco-friendly and efficient non-noble metal nanocatalysts have extensive applications in the effective conversion of biomass derivatives into high-value chemicals. Herein, a highly dispersed and ...stable layered NiCu/SiO.sub.2 catalyst was successfully prepared by a facile ammonia evaporation (AE) method, and then applied to the aqueous-phase furfural (FFR) selective hydrogenation to cyclopentanone (CPO). Under mild conditions, FFR is almost completely transformed. Moreover, compared with traditional preparation methods, the yield of CPO increases significantly to 95.4% by the AE method. This remarkable performance improvement can be attributed to the high dispersion of metal nanoparticles and the synergistic effect between Ni and Cu. Meanwhile, Cu can adjust the electronic structure of Ni, and change the adsorption configuration of FFR on Ni, thereby improving the yield of CPO. This work provides a facile strategy for designing efficient and stable non-noble metal nanocatalysts for the aqueous-phase FFR selective hydrogenation. Graphical
In a mixed solvent composed of acetonitrile and ethanol, tetrabutyl orthotitanate (TBOT) was quickly introduced into the pores of the core-shell silica particles (SiO.sub.2@dSiO.sub.2) using the ...coordination bond formed between N and Ti. Since all the hydrolysis reactions of TBOT occurred in the pores, SiO.sub.2@dSiO.sub.2 spheres coated with TiO.sub.2 (S@S@TiO.sub.2) with an effective loading of TiO.sub.2 as high as 74% were obtained. Because all TiO.sub.2 nanoclusters are located in the pores, their growth is restricted by the pores. So the size of crystalline grains in the pores of the shell slowly increases with the increase in the calcination temperature. Due to the confined growth of TiO.sub.2 nanoclusters, S@S@TiO.sub.2 still maintains the anatase phase when the calcination temperature is as high as 1050 °C, which is significantly higher than the maximum thermal stability temperature of 900 °C reported in the literature. When used as photocatalysts for the degradation of Rhodamine B under UV irradiation, the catalytic activity of S@S@TiO.sub.2 calcined at 950 °C is 2.1 times higher than that of the commercial P25 TiO.sub.2 photocatalyst.
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