Band 6, Heft 4

As the major composite of biomass, lignin can be utilized as feedstock for valuable chemicals, especially phenols. Catalysis hydrogenation of lignin is an attractive route for the conversion. However, most of them require hydrogen gas under high pressure which is dangerous. Hydrogen transfer reaction provides an alternative route to degrade and hydrogenate lignin or its units to small molecular compounds. Here, a two-step method has been employed using Raney Ni and Pd/C catalysts consecutively for hydrogen transfer catalysis for lignin. The results reveal that lignin can be degraded efficiently about 90% during conversion, and the major products are phenols with ~30% in yield. It provides a new green method for converting natural lignin to valuable chemicals.

An efficient one-pot multicomponent reaction of 2-aminopyridine with aromatic aldehydes and either benzoyl cyanide or cyanamide in pyridine under controlled microwave heating afforded N-aryldene-2-arylimidazo[1,2-a]-pyridine-3-ylamine derivatives. The reaction is catalyst free and is of high atom economy.

The effect of the urease immobilization method was studied on magnetic supports for the Biginelli/Hantzsch reaction. For this purpose, Fe 3 O 4 /SiO 2 was modified with 3-aminopropyl-triethoxysilane and then activated with glutaraldehyde. A ratio of 500 mg of enzyme per gram of support at 4°C and 18 h were sufficient for the physical adsorption, while 24 h were required for covalent bonding. The Biginelli and Hantzsch reactions were used to evaluate urease application in multicomponent reactions (MCRs). The synthesis of 1,4-dihydropyrimidines was successfully performed using immobilized urease favoring the Hantzsch product. The magnetic properties of the supports allow easy separation, and the urease immobilized by both methods improved the enzymatic activity compared to that of free urease.

A series of organic-inorganic composite catalysts were prepared by modifying tungstophosphoric acid (H 3 PW 12 O 40 ) and propyl sulfonic acid-functionalized ionic complex. The obtained water-soluble catalysts were well characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and nuclear magnetic resonance, and investigated for their performance as homogeneous catalysts for selective oxidation of benzyl alcohol (BzOH) with hydrogen peroxide (H 2 O 2 ) in water. Among them, the [DMBPSH]H 2 PW 12 O 40 catalyst exhibited the best oxidative activity with a desirable benzaldehyde (BzH) selectivity of 97.0% and an excellent BzOH conversion of 98.5%. Further kinetic studies and model analysis by response surface methodology revealed that alcohols’ oxidation reaction followed an apparent order of 2.2 with an activation energy of 36.18 kJ/mol. And the optimal reaction conditions were established as follows: BzOH/H 2 O 2 molar ratio of 1:1.7, amount of catalyst 5.4 wt%, reaction time 3.9 h, amount of water 24 ml, and a maximum yield of BzH of 95.8%. Under optimum conditions, [DMBPSH]H 2 PW 12 O 40 catalyst showed a superior catalytic efficiency and reusability due to strong acidity and excellent surface activity.

Fe-carbon nanoreactors were prepared by the impregnation of carbon cages with iron nitrate. Carbon cages were obtained using molasses as a carbon precursor and silica spheres as a template. The porous structure of the carbon cages allows for uniform dispersion of Fe. Fe concentration was equal to 0.68, 1.32, and 2.64 wt% as Fe 3 O 4 . Obtained materials were characterized by nitrogen adsorption at 77 K, X-ray powder diffraction (XRD), and scanning electron microscope (SEM) method. Fe-carbon nanoreactors were very active in limonene oxidation. Fe-carbon nanoreactors were used as a catalyst in limonene oxidation by t-butyl hydroperoxide.

In this work, a falling film micro reactor was investigated regarding its ability to continuously eliminate tetrahydrofuran (THF) out of a THF-water mixture via nitrogen stripping. Mass transfer measurements were performed at different temperatures and flow rates. The residual content of THF in the eluate was quantified with high precision (<0.1%) via density measurements. Remarkably, complete elimination of THF could be achieved for liquid volume flow rates smaller than 2 ml/min and nitrogen volume flow rates larger than 400 ml/min at all three investigated temperatures (55°C, 60°C, and 65°C). In order to assist future design processes of such binary microstripping systems, we further developed a mass transfer model for this separation process extending an existing model for evaporation of a pure liquid. The good agreement of experimental data and calculations in the overall investigated parameter range (≤20%, for gas flow rates below 500 ml/min ≤11%) shows the potential of the model for the prediction of alternative operational parameter settings, e.g. at different THF entrance concentrations.

We report a facile approach used for the simultaneous reduction and synthesis of a well dispersed magnetically separable palladium nanoparticle supported on magnetite (Pd/Fe 3 O 4 nanoparticles) via continuous flow synthesis under microwave irradiation conditions, using a Wave Craft’s microwave flow reactor commercially known as ArrheniusOne, which can act as a unique process for the synthesis of highly active catalysts for carbon monoxide (CO) oxidation catalysis. The prepared catalysts are magnetic, which is an advantage in the separation process of the catalyst from the reaction medium. The separation process is achieved by applying a strong external magnetic field which makes the separation process easy, reliable, and environmentally friendly. Hydrazine hydrate was used as the reducing agent under continuous flow reaction conditions. The investigated catalysis data revealed that palladium supported on iron oxide catalyst synthesized by continuous flow microwave irradiation conditions showed remarkable high catalytic activity towards CO oxidation compared to the ones that were prepared by batch reaction conditions under the same experimental conditions. This could be attributed to the high degree of dispersion and concentration ratio of the Pd nanoparticles dispersed on the surface of magnetite (Fe 3 O 4 ) with a small particle size of 5–8 nm due to the effective microwave-assisted reduction method under continuous flow conditions. These nanoparticles were further characterized by a variety of spectroscopic techniques including X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and transmission electron microscopy (TEM).

Apart from being a component of some animal feed products, the main industrial use of recycled waste frying oils is biodiesel preparation. With the aim of finding a suitable technology for a cost-effective valorization of used cooking oil, we investigated some oxidative treatments under hydrodynamic cavitation with air flow. This process enabled the preparation of a useful precursor of fatliquor used in the leather industry through the efficient oxidation/polymerization of waste oils at 90°C. The same technique enabled a stable dispersion/emulsification in water without surfactants. Thanks to the use of these innovative techniques, a four-fold reduction of the oxidation time of waste oil was achieved. All the results indicate that the use of a highly efficient rotor-stator generator of hydrodynamic cavitation is compatible with a process scaling up for potential industrial applications.

Recently, printing ink ingredients have been provided from vegetable oils as a renewable, non-toxic, and biodegradable resource. In this work, to produce bio-based polymer potentially exploitable in printing ink vehicles, tris(ethylenediamine)nickel(II) nitrate and bis(ethylenediamine)copper(II) nitrate complexes were synthesized, characterized, and then used as heterogeneous catalysts for polymerization of soybean oil. Also, nickel and copper oxide catalysts were fabricated through thermolysis of the mentioned complexes and, after characterization, were employed for the polymerization reaction. The results showed that the presence of nickel and copper complex catalysts favored the reaction progress as the viscosity of the reaction product was increased 4 and 1.3 times, respectively, compared with polymerization without a catalyst. Also, the results obtained from using nickel and copper oxides indicated that these metal oxides do not have a significant effect on the reaction process.

An extractive fermentation approach in an aqueous two-phase system (ATPS) with wheat bran as a main substrate was used in this study to intensify the production of β-glucosidase enzyme (EC 3.2.1.21) from Aspergillus niger NRRL 322. Possible parameters, such as phase concentration and incubation period, were evaluated based on enzyme production. The fungus expressed high enzyme production, i.e. 948 U/ml after 96 h at 180 RPM when PEG4000 (12% w/w) and potassium phosphate (14% w/w) were used. This strategy of extractive fermentation with ATPS shows an increase in β-glucosidase enzyme yield of 948 U/ml compared with submerged fermentation, which gives a yield of 790 U/ml. β-Glucosidase yield in salt phase also increased by 1.2-fold compared with the submerged fermentation under the same conditions.