Unpredicted Concentration-Dependent Sensory Properties of Pyrene-Containing NBN-Doped Polycyclic Aromatic Hydrocarbons

Pyrene molecules containing NBN-doped polycyclic aromatic hydrocarbons (PAHs) have been synthesized by a simple and efficient intermolecular dehydration reaction between 1-pyrenylboronic acid and aromatic diamine. Pyrene-B (o-phenylenediamine) with a five-membered NBN ring and pyrene-B (1,8-diaminonaphthalene) with a six-membered NBN ring show differing luminescence. Pyrene-B (o-phenylenediamine) shows concentration-dependent luminescence and enhanced emission after grinding at solid state. Pyrene-B (1,8-diaminonaphthalene) exhibits a turn-on type luminescence upon fluoride ion addition at lower concentration, as well as concentration-dependent stability. Further potential applications of Pyrene-B (o-phenylenediamine) on artificial light-harvesting film were demonstrated by using commercial NiR dye as acceptor.

Effectively Synthesizing SO4/TiO2 Catalyst and Its Performance for Converting Ethanol into Diethyl Ether (DEE)

This SO4/TiO2 catalyst as a heterogeneous acidic catalyst was synthesized in various concentrations of H2SO4. The activity and selectivity of the SO4/TiO2 catalyst on the dehydration reaction of ethanol to diethyl ether were studied as well. The SO4/TiO2 was prepared from TiO2 powder by wet impregnation method with a various aqueous solution of H2SO4 (1; 2; 3 M H2SO4) and calcination temperature (400, 500, and 600 °C) to obtain a catalyst with optimum acidity. The catalysts were characterized using FTIR, XRD, SEM-EDX, SAA, TGA/DSC, and acidity test gravimetrically with ammonia. The liquid product of DEE was analyzed by gas chromatography (GC) to analyze the selectivity of the catalyst. The catalyst TS-3-400 had the highest activity and selectivity in the dehydration reaction of ethanol to diethyl ether at a temperature of 225 °C, with a conversion of 51.83% and a DEE selectivity of 1.72%.

Influence of Crystallite Size of Nickel and Cobalt Ferrites on the Catalytic Pyrolysis of Buckwheat Straw by Using TGA-FTIR Method

Pyrolysis of buckwheat straw with or without catalysts was investigated using the TGA-FTIR method to determine the influence of nickel and cobalt ferrites on the distribution of pyrolysis products. According to the obtained results, the overall shape of the thermogravimetric and derivative thermogravimetric curves is unchanged in the presence of nickel and cobalt ferrites but different weight losses were observed. All catalysts contribute to the formation of solid residue from BWS pyrolysis. The presence of cobalt ferrites exhibited the highest bio-oil yields, whereas the highest non-condensable gas yield and the lowest bio-oil yield was obtained with the addition of NiFe2O4 (1) catalyst. According to the obtained results, the ability of nickel and cobalt ferrites to catalyze deoxygenation reactions depends on the crystallite size. The nickel or cobalt ferrites with smaller crystallite size (15-22 nm) show a higher ability to catalyzed dehydration reaction than catalysts with larger crystallite size (45-54 nm).

Study on the Synthesis of 6-Hydroxyhexyl 5-(Hydroxymethyl) Furan-2-Carboxylate from 5-Hydroxymethylfurfural (HMF) and Alkanediols

Nowadays, due to the fact that the term ‘sustainable development’ has caught everyone’s attention, chemists have been researching substances which obtainable via synthesizing biocompounds. Recently, scientists found out that 5-hydroxylmethylfurfural (HMF), which can be synthesized via dehydration reaction of common biocompounds like polysaccharides, has a great potential of forming novel derivatives to utilize in the biopolymer manufacturing field. HMF oxidative esterification is one of the notable reactions of which the outcome seems promising and applicable. In this research, the esterification of HMF and hexane-1,6-diol took place directly in DMSO or TEA solvent using Ru/C, Co3O4-N@C as catalysts, base K3PO4; with oxygen 1 bar as an oxidant. LC-MS/MS analysis was used to detect the presence of the ester products; however, due to the low conversion and selectivity, the content of desired product is not enough to isolate and confirm its structure.

MODIFIED ZSM-5 ZEOLITES IN THE PROCESS OF MONOSACCHARIDE DEHYDRATION

В данном исследовании была разработана методика синтеза катализаторов на основе цеолитов типа ZSM-5 с различным соотношением Si/Al и количеством кислотных центров, модифицированных оксидом вольфрама (VI). Синтезированные катализаторы были охарактеризованы и протестированы в реакции превращения моносахаридов (фруктозы и глюкозы) в 5-гидроксиметилфурфурол и левулиновую кислоту. Было показано, что введение в состав цеолитов ZSM-5 частиц оксида вольфрама приводит к заметному увеличению количества активных кислотных центров на поверхности катализатора, играющих важную роль в реакции дегидратации моносахаридов. В результате модификации заметно возросла каталитическая активность цеолитов. Результаты исследования показывают перспективность использования цеолитов типа ZSM-5, модифицированных оксидом вольфрама (VI), для конверсии биомассы в платформенные химические соединения. In this study, a method was developed for the synthesis of catalysts based on zeolites of the ZSM-5 type with different Si/Al ratios and the number of acid sites modified with tungsten (VI) oxide. The synthesized catalysts were characterized and tested in the reaction of converting monosaccharides (fructose and glucose) into 5-hydroxymethylfurfural and levulinic acid. It was shown that the introduction of tungsten oxide particles into the composition of ZSM-5 zeolites leads to a noticeable increase in the number of active acid sites on the catalyst surface, which play an important role in the dehydration reaction of monosaccharides. As a result of the modification, the catalytic activity of zeolites has noticeably increased. The results of the study show that the use of zeolites of the ZSM-5 type, modified with tungsten (VI) oxide, is promising for the conversion of biomass into platform chemical compounds.

Adsorption and Dehydration Reaction of Ethanol to Ethylene on Isomorphous B, Al, and Ga Substitution of H-ZSM-5 Zeolite: An Embedded ONIOM Study

Dehydration reactions are important in the petroleum and petrochemical industries, especially for the feedstock production. In this work, the catalytic activity of zeolites with different acidities for the dehydration of ethanol to ethylene was investigated by calculations on cluster models of three isomorphous B, Al, and Ga substitution of H-ZSM-5 zeolites. Detailed reaction profiles for the dehydration reaction, assuming either a stepwise or a concerted mechanism, were calculated by using the ONIOM(MP2:M06-2X) + SCREEP method. The adsorption energies of ethanol are -21.6, -28.1 and -27.7 kcal/mol on H-[B]-ZSM-5, H-[Al]-ZSM-5, H-[Ga]-ZSM-5 zeolites, respectively. The stepwise mechanism was preferred on all isomorphous zeolites. The activation energies for the ethoxy formation as the rate-determining step are in range of 40.0 to 42.3 kcal/mol. The results indicated that the order of catalytic activity were H-[Al]-ZSM-5 > H-[Ga]-ZSM-5 > H-[B]-ZSM-5 for catalyzing the dehydration of ethanol to ethylene. Besides the acid strength, the zeolite framework affected the reaction by stabilizing the reaction intermediates leading to more stable adsorption complexes and lower activation barriers.