Mass-spectrometric study of single-walled carbon nanotubes modified by aliphatic amines

The gas-phase derivatization procedure was employed for direct (i.e., without chemical activation of terminal carboxylic groups) amidization of oxidized single-walled carbon nanotubes (SWNTs) with simple aliphatic amines. The procedure includes treatment of SWNTs with amine vapors under reduced pressure and temperature of 160-170ºC. Applicability of temperature-programmed desorption mass spectrometry for chemical characterization of the derivatized SWNTs was analyzed. Heating of the amine-treated SWNTs at temperature >200ºC causes cleavage of alkenes from the amine residues: nonene and pentene are formed in the case of nonylamine and dipentylamine, respectively

Design of functionalized polysiloxanes: synthesis and study on sulfur-containing xerogels with mono- and bifunctional surface layer

Urea- and thiourea-containing trialkoxysilanes were prepared with a high yield and purity. By sol-gel processing of these precursors the new functionalized xerogels were synthesized and characterized by FTIR, elemental analysis, thermal analysis and adsorption method. Mono- and bifunctionalized xerogels were easily prepared by mixing of precursors in the desired ratios together with tetraethyl orthosilicate. Obtained functional polysiloxanes are perspective materials for metal sorption and hybrid catalysis applications

Adsorption of polyvinylpyrrolidone and polyoxyethylene by pure and mixed silicon, aluminium and titanium oxides

Adsorption of polyvinylpyrrolidone (PVP) and polyoxyethylene (POE) from the aqueous solutions onto surfaces of individual and mixed silicon, titanium and aluminium oxides was studied. It was found that the values of polymer adsorption depend on composition of oxides. It was shown with IR spectroscopy that the surface of the oxides studied is fully accessible to interaction with PVP and POE

Investigation of the Nature of Acid Centres on a Pyrogenic γ-Aluminium Oxide Surface Using Pyridine and n-Butylamine

The process of pyridine and n-butylamine adsorption and desorption at a pyrogenic aluminium oxide surface has been studied using IR spectroscopy. It has been found that both Lewis and Brönsted acid centres are present on an Al 2 O 3 surface annealed in vacuum at 200°C, with coordination-bonded water possessing stronger proton-donor properties than hydroxy groups. Dehydroxylation of the surface gave rise to new types of strong electron-acceptor centres. The surface hydroxy groups did not exhibit acidic properties at room temperature and formed a hydrogen bond with pyridine, whilst for desorption at elevated temperatures the IR bands observed indicated the formation of a pyridinium ion, i.e. proton transport to the adsorbed base became possible

A Study of the Brönsted Site Acidity of Crystalline and Amorphous Aluminosilicates: 1. Desorption of Ammonia, Dehydration of 2-Propanol and Cracking of Cumene

The acidity of the H-form aluminosilicates, which include ZSM-5, mordenite, Y-faujasite, Al-containing aerosils and silica gels, and the layering of aluminosilicate compounds on an aerosil surface was measured by temperature-programmed mass spectrometry desorption (TPD) of NH 3 . It was found that the desorption energies of NH 3 decrease in the order: H-M > H-ZSM-5 > Al-aerosils> H-Y > CVD Al-silicates> Al-silica gels. The catalytic activities of the studied samples in 2-propanol dehydration and cumene cracking have been shown to decrease in the same order

Single-step template synthesis of mesoporous silicas containing thiourea functional groups

Mesopo rous adsorbents co ntaining mono-(-(CH₂)₃NHC(=S)NHC₂H₅) or bi-(-(CH₂)₃NHC(=S)NHC₂H₅ / amino) functional surface layer have been synthesized in a single-step process using bi- or tricomponent (with respect to alkoxysilanes) systems and 1-dodecylamine as a template. The studied systems have been shown to have a disordered lattice similar to hexagonal one, a developed porous structure (Sₛₚ 409 to 718 m²/g; Vₛ 0.26 to 0.82 сm³/g; d 2.4 to 2.5 nm) and a relatively high content of functional groups (Cc=s from 0.7 mmol/g to 2.2 mmol/g). It has been found that hydrothermal treatment of mesophases in a mother liquor for 24 hours at 80 ℃ does not result in an enhanced structure ordering but even in worsened structure-adsorption characteristic of the final products.Мезопористi а Д сорбенти, що мiстять моно-((CH₂)₃NHC(=S)NHC₂H₅) чи бi- (- NНС(=S)NНC₂H₅/амiн) функцiональний поверхневий шар, одностадiйно синтезовано з використанням дво- чи трикомпонентних (за алкоксисиланами) систем i 1-додециламiна як темплату. Показано, що вони мають неупорядковану гратку, близьку до гексагональної, розвинуту порувату структуру (Sₙᵤₘ - 409-718 м²/Г, V = 0.26-0.82 см³/Г, d = 2.4-2.5 нм) та вiдносно високий вмiст функцiональних груп (Сc=s вiд 0.7 ммоль/Г до 2.2 ммоль/Г). Встановлено, що гiдротермальна обробка мезофаз у маточному розчинi протягом 24 годин при 80 ℃ не тiльки не веде до бiльш впорядкованої структури, а навiть дещо погiршуе структурно-адсорбцiйнi характеристики кiнцевих продуктiв.Мезопористые адсорбенты, содержащие моно-(-(CH₂)₃NHC(=S)NHC₂H₅) или би-(-(CH₂)₃NHC(=S)NHC₂H₅)/амин) функциональный поверхностный слой, одностадийно синтезированы с использованием двух- или трёхкомпонентных (по алкоксисиланам) систем и 1-додециламина как темплата. Показано, что они имеют неупорядоченную решётку, близкую к гексагональной, развитую пористую структуру (Sуд 409-718 м²/г, Vc 0.26-0.82 см³/г, d 2.4-2.5 нм) и относительно высокое содержание функциональных групп (Сc=s - от 0.7 ммоль/г до 2.2 ммоль/г). Установлено, что гидротермальная обработка мезофаз в маточном растворе в течение 24 ч при 80 ℃ не только не ведёт к более упорядоченной структуре, но даже несколько ухудшает структурно-адсорбционные характеристики конечных продуктов

Novel polyorganosiloxane xerogels with bifunctional ≡Si(CH₂)₃H/≡Si(CH₂)₃NH₂ surface layer

Novel polyorganosiloxanes gels with bifunctional (≡Si(CH₂)₃H/≡Si(CH₂)₃NH₂) surface layer have been prepared by a sol-gel technique using silane-ternary systems. The surface properties of the obtained gels are highly reproducible. The effect of the addition of a catalyst was investigated, and it is shown that the addition of fluoride ion has a highly beneficial effect on the porous properties of the materials. The synthesized samples have specific surface areas up to 250 m²/g, and have a high potential as selective sorbents for heavy and noble metals (Hg²⁺, Ag⁺, Au³⁺ etc.)