Marta I. Ponzi

Obtaining benzaldehyde via promoted V2O5 catalysts

Catalytic activity was measured for the partial oxidation of toluene to benzaldehyde on potassium-promoted vanadium pentoxide catalysts. In addition, the surface acidity of these solids was inferred from the 2-propanol decomposition reaction, which gives an indication of the acid strength. The results of this work showed that both toluene conversion and selectivity to benzaldehyde are related to the presence of acidic sites in the catalyst.

An in vitro Evaluation of Tagetes minuta Essential Oil for the Control of the Honeybee Pathogens Paenibacillus larvae and Ascosphaera apis, and the Parasitic Mite Varroa destructor

Abstract Biological activity was evaluated of the Tagetes minuta essential oil in different in vitro laboratory experiments on the mite (Varroa destructor), honeybees (Apis mellifera), the bacterium that causes the American Foulbrood (Paenibacillus larvae), and the fungus that produces chalkbrood (Ascosphaera apis). Two methods of complete exposure were used for mite lethality test: by spraying in Burgerjons tower with 10 mg of active ingredient in solution with distilled water and emulsion, and in unmodified Petri dishes (60 x 20 mm) with oil (different concentrations) diluted in 1 mL of ethanol. Ratio selection was obtained as: LD50 of Apis mellifera/LD50 of V. destructor. Determination of Minimal Inhibitory Concentrations (MIC): to P. larvae was tested at concentrations of 25, 50, 100, 150, 200, 250, 350, 450, 500, 600, 650, 700, 800 and 1000 ppm. An A. apis strain was grown on agar MY20 supplemented with variable concentrations (between 0–800 ppm) of T. minuta oil was evaluated. Results obtained in tests of total exposure showed that the concentration was able to kill 50% of mites in 24 h (DL50) and was estimated to be 4.37 mg/cage. The efficacy after spray treatment reached 56%. The ratio selection was 3:11. Against P. larvae, the oil showed MIC values ranging from 700–800 μL/L depending on the tested bacterial strains. Tagetes minuta oil in agar MY20 inhibited mycelial growth of A. apis above concentrations of 200 ppm (p = 0.0001). Oil concentrations of 700 and 800 ppm achieved maximum growth inhibition of A. apis (67% of growth inhibition on average). Tagetes minuta oil demonstrated in vitro antibacterial, antifungical and miticide activity, although this oil shows a moderate inhibitor effect compared with other essential oils of native plants from Argentina. However, this oil presents a ratio selection that would allow it to be used in field conditions with a good safety margin. It is possible that this oil can be used in combination with others, in integrated pest management strategies in bee colonies.

Catalytic combustion of soot with a O2/NO mixture. KNO3/ZrO2 catalysts

Abstract Catalysts containing 0.25–20% KNO3 supported on ZrO2 have been studied for diesel soot combustion. The addition of KNO3 to ZrO2 support enhances its activity due to the increased contact between soot and catalyst and also because the KNO3 acts as catalyst. The combustion temperature has been measured for “loose” and “tight” contact, between soot and catalyst, and the difference was 10 K for KNO3(20)/ZrO2 catalyst. This finding is very important because under practical conditions the contact between soot and catalyst is poor and this contact resembles the contact denoted as “loose contact”.

Antimicrobial activity of Pimpinella anisum and Foeniculum vulgare essential oils against Paenibacillus larvae.

Abstract The essential oil obtained by hydrodistillation from the fruits of Pimpinella anisum L. (green anise) and Foeniculum vulgare Miller (fennel) were analyzed by GC and GC/MS and physicochemical properties. The oils of P. anisum and F. vulgare were found to be especially rich in (E)-anethole, 96.3% and 92.7%, respectively. The MICs were determined by the tube dilution method against Paenibacillus larvae. The oils showed MICs values were 300 µg/mL and 250 μg/mL for P. anisum and F. vulgare, respectively. Both oils presented great similarity in physiochemical properties values and antimicrobial activity.

In Vitro Activity of Essential Oils from San Luis-Argentina Against Ascosphaera apis

Abstract Chalkbrood is an invasive mycosis produced by Ascosphaera apis affecting exclusively the larvae growth of Apis mellifera L. There exists no pharmacological treatment and the chemical products used are not able to control the disease generating resistances and residues in the apicultural production. An ecological alternative is the use of essential oils as natural products to control this mycosis. Eight oils were screened against A. apis for fungicidal activity. The oils of Baccharis coridifolia and Eupatorium patens did not possess any activity while the oils of Tessaria absinthioides, Aloysia gratissima, Heterotheca latifolia, Lippia juneliana, L. integrifolia and L. turbinata exhibited varying levels of fungicidal activity.

Laboratory Evaluations of Syzygium aromaticum (L.) Merr. et Perry Essential Oil Against Varroa destructor

Abstract The oil obtained by hydrodistillation of the foral bottom of Syzygium aromaticum (L.) Merr. et Perry was analyzed by GC and GC/MS. Eugenol was the main constituent in the oil (86.7%). The biological activity of the oil applied to Varroa destructor and Apis mellifera was evaluated in two laboratory tests. Mite lethality was estimated using a complete exposure method test with the oil at different concentrations, and a systemic administration method of oil at different concentrations diluted in syrup was placed in feeders for bees. The LC50 for complete exposure method at 24 h was 0.59 μL/dish. The inferior and superior limits obtained were 0.47 x 10−6 μL/dish and 1.22 μL/dish, respectively. LC50 estimated at 48 h showed a slight decrease as compared to that recorded at 24 h. Ratio selection (LC50 of A. mellifera/LC50 of V. destructor) for complete exposure method was 26.46 and 13.35 for 24 h and 48 h, respectively. Regarding the systemic administration method, mites LC50 at 24 h was 12,300 ppm. The inferior and superior limits calculated were 9,214 ppm and 15,178 ppm, respectively. LC50 estimated at 48 h showed a slight decrease as compared to that recorded at 24 h. Ratio selection for systemic administration method was 3.05 and 2.22 for 24 h and 48 h, respectively. Syzygium aromaticum oil was found to be an attractant for V. destructor at 4.8% (w/w) concentration. The results showed that oil toxicity against V. destructor differed depending upon its administration. Nevertheless, the ratio selection calculated by this oil is expected to enable its application under field conditions with a good safety margin. This oil could also be used in combination with other oils in integrated pest management strategies in bee colonies.

Liquid Phase Isomerization of α-Pinene. Study of the Reaction on Sulfated ZrO2

The α-pinene isomerization reaction was studied on sulfated zirconium oxide catalyst for different experimental conditions. The catalysts are active for producing camphene when they present Brönsted acidity and when zirconium oxide crystallizes in the tetragonal phase. The α-pinene conversion and its selectivity to camphene can be optimised by proper selection of operating conditions such as temperature, catalyst concentration and reaction time. The use of this catalyst in the appropriate conditions can result in selectivity to camphene of about 70%.

Soot combustion. Co and K catalysts supported on different supports

The catalytic combustion of particulate material was studied on cobalt catalysts promoted with potassium using different supports for its preparation. Silica, aluminium oxides and hydroxides, zirconium oxide and hydroxide were used as supports. The catalytic activity for combustion depends on the type of support used, the higher activity corresponding to the supported catalyst on zirconium oxide. TPR studies indicate that the interaction metal/support allows to explain the higher activity of the CoK/SiO2 catalyst with respect to the CoK/Al2O3 but the high activity found in CoK/ZrO2is not explained by this interaction. In all cases the Co and K improved the performance of the catalysts.

OBTENTION OF CAMPHENE WITH H3PW12O40 CATALYSTS SUPPORTED ON TiO2, SiO2 AND ZrO2nH2O

The -pinene isomerization reaction was studied on catalysts based on H3PW12O40 (HPW) supported on TiO2, SiO2 and ZrO2nH2O. Catalysts with a 40% nominal charge of phosphotungstic acid (HPW) were prepared by impregnation of supports with a HPW solution. The study of the isomerization reaction was carried out in liquid phase by using a discontinuous reactor, magnetically stirred and maintaining a constant temperature. The catalyst supported on SiO2 resulted to be the most active while the one supported on ZrO2nH2O was the less active. This behavior correlated with the number and strength of the acid sites. XRD studies revealed the formation of HPW crystals when it was supported on SiO2.

Laboratory Evaluation of Heterothalamus alienus Essential Oil Against Different Pests of Apis mellifera

Abstract The Heterothalamus alienus oil was investigated in laboratory for control of different pests that affect the colonies of bees, Apis mellifera, against Varroa destructor mite, the bacterium that causes the American Foulbrood, Paenibacillus larvae and the fungus that produces the chalkbrood, Ascosphaera apis. The oil composition was analyzed by GC and GC/MS, the main components of the oil were β-pinene (44.4%) and trans-muurola-4(14),5-diene (9.2%). The concentration to kill 50% of the mites in 24 h (LC50) was 0.59 mg/cage. Inferior and superior limits were the following ones: 0.34 mg/cage and 1.01 mg/cage, LC50 was estimated for 48 h, and 72 h showed a slight increase with respect to the record of the 24 h. Paenibacillus larvae strains were Gram positive and catalase negative, the oil presented MIC values of 800–900 mg/L and MBC of 1000–1200 mg/L. Disks of impregnated flter paper with H. alienus oil around colonies of A. apis in growth inhibited the micelial growth signifcantly by 51% in the frst experiment (seven days) and by 31% in the second experiment (eight days).