Ioan Calinescu

Microwave-enhanced dechlorination of chlorobenzene

Abstract- Heterogeneous liquid-phase dechlorination of chlorobenzene over supported palladium-based catalysts to form benzene was examined using microwave and conventional heating methods. The reaction was carried out in a solution of NaOH in 2-propanol at atmospheric pressure and reflux temperature (approx. 83°C). Two types of commercial aluminium-silicate and γ-alumina-supported catalysts have been tested. The results obtained under microwave (MW) and conventional (CH) conditions were compared with respect to the rate enhancement, selectivity and catalyst activity. The sole product of the chlorobenzene dehalogenation was benzene. The effect of the addition of NaOH has been analysed for the neutralisation of HCl.

Microwave assisted extraction of essential oils from enzymatically pretreated lavender (Lavandula angustifolia Miller)

In this study, microwave assisted a hydrodistillation process (MWHD) of essential oils from lavender (Lavandula angustifolia Miller) was investigated. In order to examine any potential differences in essential oil extraction, the lavender flowers underwent enzymatic pretreatment.A 23 factorial design of experiments, combined with statistical methods of data analysis were used to optimize enzymatic pretreatment and to evaluate the influence of major variables (enzyme concentration, temperature and pH) on the performance of the microwave assisted extraction.Under optimal conditions, an extraction yield of 24 mg oil g−1 substrate was achieved (an increase by approximately 25% in comparison with the classic extraction conditions of conventional hydrodistillation).The main compounds of the essential oils obtained were analyzed and identified by gas chromatography coupled to mass spectrometry (GC-MS). Analyzing the data obtained indicated that the content of main compounds (linalool and linalyl acetate − 73%) was greater than that obtained by conventional extraction (67%).

Polymer colloids and silver nanoparticles hybrid materials

The present study presents two different methods to obtain hybrid material formed by the poly [styrene (ST)–poly(ethylene glycol) methyl ether methacrylate (PEGMA) 1100] and silver (Ag0). The aim has been to cover the polymeric particles with Ag0 shell. The first method consisted of mixing Ag0 nanoparticles dispersion with poly (ST-PEGMA 1100) dispersion, while in the second method, the Ag0 nanoparticles have been generated in situ. The hybrid materials have been characterized by MO, dynamic light scattering, scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, X-ray energy dispersive spectrometry, and ultraviolet–visible spectrophotometry. The results confirm the obtaining of two types of morphologies. In the first case, the nanoparticles have been arranged in the interspatial zones of the polymer particles, while in the second method, the Ag0 nanoparticles have covered the polymer particles. Thus, the film obtained using the second method is more suitable for the practical application, as a separation membrane, using the antiseptic properties of Ag0.

Microwave-Assisted Batch Extraction of Polyphenols from Sea Buckthorn Leaves

Extraction of polyphenols from sea buckthorn leaves using microwave-assisted extraction (MAE) is described. The influence of different parameters on the extraction process (reactor type, stirring rate, extraction time, temperature, ethanol/water ratio) was studied. The polyphenolic extracts were analyzed in order to determine the total phenolic content (TPC) either by the Folin–Ciocalteu method or by differential pulse voltammetry (DPV), and the concentration of the main polyphenolic compounds by high-performance liquid chromatography (HPLC). The specific microwave energy was also determined. MAE resulted in a shorter extraction time (7.5 versus 30 min for the conventional method). The best results for MAE were obtained at a temperature of 90°C, using a solvent/plant ratio of 20/1 and 50% ethanol in the extraction solvent. The highest values of antioxidant capacity were obtained for polyphenolic extracts resulted from microwave extraction.

Hybrid technology with microwaves, electron beams and catalysts for VOCs removals.

This work presents a hybrid technology and two hybrid installations (HI-1 and HI-2) for volatile organic compounds (VOCs) removal using successive or simultaneous microwave (MW) irradiation, electron beam (EB) irradiation, and catalytic oxidation. HI-1 is designed for successive EB and MW irradiation with two distinct reactors, both containing a catalyst inside. HI-2 is designed for simultaneous EB and MW irradiation in the same reactor containing a catalyst. Real synergistic effects between non-thermal plasma (NTP) and catalysis were obtained by introducing the catalyst into the irradiation zone, i.e. into the MW reactor, EB reactor or into a reactor in which both EB and MW are injected.

Microwave heating in the hydrogen peroxide oxidation of benzene on zeolite catalysts

In this paper benzene hydroxylation with hydrogen peroxide (H2O2) in the presence of the titan-silicates-zeolites was studied. The initial catalyst, HZSM-5 zeolite type was treated to obtain both cobalt-and titan-silicates—zeolite. These improved catalysts were also used for oxidation. To obtain reaction temperature heating was made by conventional techniques and by microwave treatment. From this research it was concluded that reaction temperature is a very important parameter to keep a proper equilibrium between the decomposition rate of hydrogen peroxide and the oxidation rate ofaromatic compound. It was also found that microwaves affect the reaction selectivity.

Microwave assisted hydro-distillation of essential oils from fresh ginger root (Zingiber officinale Roscoe)

Abstract A solvent free in situ microwave hydro-distillation method for extraction of essential oil from fresh ginger root it presented. Extraction was conducted in a TE10n single-mode microwave cavity and variable power 2 kW generator operating at 2.45GHz. The main extracted components identified by gas chromatography (GC) were Zingiberene, α-Curcumene, β-Sesquiphellandrene and α-Selinene. At energy inputs of 0.40 kWh/kg higher powers and shorter exposure times, crucially did not degrade the highly volatile components (α-Pinene and Camphene) despite providing the highest essential oil yields. Optimum processing conditions were found to be 1000W (0.40kWh/kg) for 5 min, for whole ginger root, where 0.35g oil/100g plant was obtained. This was compared to a yield of 0.2g/100g plant in 150 in using conventional hydro-distillation and 0.3g/100g plant in 90 min using a multi-mode microwave cavity-based hydro-distillation.

Integrating Microwave-Assisted Extraction of Essential Oils and Polyphenols from Rosemary and Thyme Leaves

The extraction of essential oils (EOs) and polyphenols from rosemary and thyme has been done using an integrated process: microwave hydro-diffusion and gravity (MHG) for EOs and microwave-assisted extraction (MAE) for polyphenols. The innovative installation based on the MHG principle allows uniform microwave irradiation field due to a mechanical stirring and experiments done at low pressure. The results of quantitative analysis of the EOs extracted by MHG after 10 min were similar with those obtained by traditional methods (conventional hydro-distillation (CHD) and microwave-assisted hydro-distillation (MHD)) after 150 and 105 min, respectively. The specific energy for MHG was 5–15 times lower compared with these classical methods. The MHG extraction of EOs is also an effective method for plant material pretreatment before polyphenol extraction. Total phenolic content increased from 35 to 55 mg GAE/g DM for rosemary and from 23 to 38 mg GAE/g DM for thyme.

Chemical Composition of the Aerial Part and Fruits of Coreopsis tinctoria

Coreopsis tinctoria Nutt. from the Asteraceae family is an annual plant originating from North America and is widespread all over the world [1]. It is cultivated for both its ornamental and dyeing properties because of its bright yellow daisy-like flowers with maroon centers. Recently, this plant has been used to treat several disorders including diarrhea, internal pain and bleeding, to strengthen blood, to control diabetes, and also as an emetic [2–4]. A critical search of the literature reveals that there are few papers dedicated to the Coreopsis genus, and most of them focused on the chemical composition of the petals [5, 6]. So far, only one paper described a systematic study on the metabolic and biological properties of Coreopsis tinctoria [7]. Considered an alien species in Romania, this plant is cultivated mostly for its decorative value and has been classified among the new and rare plants in Romanian flora [8]. Therefore, because of its interesting properties, Coreopsis tinctoria cultivated in Romania was subjected to a systematic study regarding its chemical composition. Thus, this study reports on the identification of the major volatile compounds found in both the dried fruits and the aerial parts of this plant. Plant Material. Coreopsis tinctoria plants were cultivated in Bucharest and their aerial parts were collected during the flowering period, while fruits were collected at maturity. The plant material was air-dried and further stored in hermetically sealed dark paper bags to protect them from humidity and light. The Coreopsis tinctoria plant was authenticated by botanists from the Bucharest Botanical Garden based on available literature [9]. Headspace GC/MS Analysis. A quantity of 0.5 g of dry plant material (whether aerial part or fruits) was placed in a 20 mL headspace vial sealed with a silicone rubber septum and aluminum cap. Gas chromatography was carried out using a Thermo Electron apparatus fitted with a Triplus headspace automatic sampler. A DB-5MS capillary column (25 m 0.25 mm; 0.25 m film thickness) was used. The GC oven temperature program was: initial temperature 60 C (3 min) followed by an increase of 10 C/min up to 200 C (2 min) and then 12 C/min to the final temperature of 240 C (2 min). The carrier gas (helium) flow rate was 1 mL/min. The headspace temperature was kept at 80 C for 10 min prior to the injection of 500 L of the headspace gas into the column. The source and interface temperatures were 200 and 250 C, respectively. The detector operated in the electron impact mode (70 eV). Detection was performed in the range of m/z 35–300. The mass spectrometer was operated in the full-scan mode. All peaks of the chromatograms were analyzed using Xcalibur® software and the NIST 11 Mass Spectral Library to identify the corresponding compounds. An alkane standard solution for GC (C8–C20 in hexane) was used for retention index (RI) calculations [10]. The relative percent of individual components was calculated based on GC peak areas. GC/MS analysis of both the aerial part of the plant and its fruits revealed the presence of 27 volatile constituents (Table 1). Among them, some compounds were present only in the aerial part of the plant, such as -pinene, cis-ocimene, and trans-ocimene, while others were present only in the fruits, such as myrtenol, cis-carveol, and carvone. The quantitative analysis showed that there were few compounds present at a percentage higher than 10%, while most of them were below 2%.

Saccharomyces cerevisiae yeast immobilized on marrow stem sunflower and polyacrylamide hydrogels

Biocatalysts with microorganisms immobilized on solid carriers could provide the solution for development of continuous industrial processes for ethanol obtaining by fermentation of sugars. In this study, modified polyacrylamide hydrogels and marrow stem sunflower are used as supports for Saccharomyces cerevisiae yeast immobilization. The obtained structures are used for fermentation of molasses in batch systems. The free yeast cells are used as reference. The modification of polyacrilamide matrix with (2-hydroxyethyl)methacrylate has a positive effect on structure pore uniformity and fermentation performance. The mechanical properties of the obtained biocatalysts are compared. The novel natural matrix has net superior compression strength.