Inês Matos

Activated carbons from sisal waste by chemical activation with K2CO3: Kinetics of paracetamol and ibuprofen removal from aqueous solution

Sisal waste was used as precursor to prepare carbons by chemical activation. The influence of the K(2)CO(3) amount and activation temperature on the materials textural properties were studied through N(2) and CO(2) adsorption assays. As the severity of the treatment increases there is a development of supermicropores, and the micropore size distribution changes from mono to bimodal. A carbon with an apparent surface area of 1,038 m(2)g(-1) and pore volume of 0.49 cm(3)g(-1) was obtained. TPD results showed the incidence in acidic type groups although the pH(PZC) reveals an almost neutral character of the surface. Adsorption kinetic data of ibuprofen and paracetamol show that the processes obey to a pseudo-second order kinetic equation. Regarding the removal efficiency the prepared samples attained values comparable to a commercial carbon (>65%), revealing that chemical activation of sisal wastes with K(2)CO(3) allows obtaining samples suitable for pharmaceutical compounds removal from liquid phase.

Acid-activated carbon materials: Cheaper alternative catalysts for the synthesis of substituted quinolines

We describe the first examples of Friedländer reactions efficiently catalyzed by carbon materials. We report herein a series of acidic activated carbon materials, which can be considered as an environmentally friendly, cheaper alternative to the traditional acidic mesoporous silicates or even zeolites for the synthesis of quinolines/quinolones. Textural parameters of the acidic activated carbon materials together with their acidic properties are important factors that affect the reaction selectivity. Some mechanistic details have been addressed by computational calculations.

Zeolites Efficiently Promote the Cyclization of Nonactivated Unsaturated Alcohols

Tetrahydrofurans are an important class of five-membered oxygen heterocycles often present in a great variety of natural products and as synthetic compounds exhibit biological activity. Among their industrial applications they are widely used in cosmetic formulations, perfumes and flavors. As examples, mucoxin is a natural product with high potential as specific antitumor agent against breast carcinoma. Furans 1 a, 1 b and 1 c are known as flavors and show insecticidal activity (Scheme 1).

Intramolecular Hydroalkoxylation of Non‐Activated CC Bonds Catalysed by Zeolites: An Experimental and Theoretical Study

The high activity and selectivity of zeolites in the cyclisation of unsaturated alcohols is reported for the first time; the details of a reaction mechanism based on quantum chemical calculations are also provided. The high efficiency of zeolites MFI, BEA and FAU in the cyclisation of unsaturated alcohols (cis-decen-1-ol, 6-methylhept-5-en-2-ol and 2-allylphenol) to afford oxygen-containing heterocyclic rings is demonstrated. The best catalytic performance is found for zeolites with the optimum concentration of Brønsted acid sites (ca. 0.2 mmol g(-1)) and the minimum number of Lewis acid sites. It is proposed that the efficiency of the catalysts is reduced by the existence of the so-called dual site, at which a molecule of unsaturated alcohol can simultaneously interact with two acid sites (an OH group with one and the double bond with the other Brønsted site), which increases the interaction strength. The formation of such adsorption complexes leads to a decrease in the catalyst activity because of (i) an increase in the reaction barrier, (ii) an unfavourable conformation and (iii) diffusion limitations. A new procedure for the preparation of tetrahydrofurans and pyrans over zeolite catalysts provides important oxygen-containing heterocycles with numerous applications.

Biodiesel production waste as promising biomass precursor of reusable activated carbons for caffeine removal

Biodiesel production generates low particle size rapeseed waste (recovered from warehouse air filtration systems) that was herein explored as promising biomass precursor of chemically activated carbons. The influence of several experimental parameters on the porosity development was investigated. No benefit was observed when solution impregnation was made nor a significant dependence of the biomass : K2CO3 ratio was observed and, as expected, high porosity development was obtained only for treatments at 700 °C. Microporous materials with apparent surface area around 1000 m2 g−1 were obtained comparing favorably with literature data regarding activated carbons from rapeseed processing by-products. A selected lab-made sample and two commercial carbons were tested as adsorbents of caffeine from aqueous solution. Although commercial materials present a quicker adsorption rate, regarding adsorption capacity the lab-made sample reaches the same value attained by a benchmark material. The regeneration tests made over the rapeseed derived carbon through heat treatments at 600 °C for 1 hour under N2 flow proved that at least two exhaustion–regeneration cycles can be made since the material retains a caffeine adsorption capacity similar to that of the fresh carbon. Therefore, a waste management problem of biodiesel industry – rapeseed residue – can be transformed in a valuable material with promising properties for environmental remediation processes.

Asma e a nova lei do tabaco. O que mudou

January 2008 saw new legislation implanted in Portugal restricting smoking in closed public spaces. As second-hand smoke worsens asthma symptoms, it is important to understand how asthma patients feel this new legislation impacts on their well-being. A descriptive cross-sectional study was conducted in a convenience sample formed of 96 asthma patients who had Pulmonology appointments at the Pulido Valente and Santa Marta Hospitals. All data was collected from a standardised questionnaire with volunteer, anonymous and confidential answers. Epi InfoTM software was used for statistical processing purposes, and the results analysed using the chi-squared test (α = 5%). 67.7% of the patients polled were exposed to second-hand smoke until December 2007, with a higher percentage in those currently in work. A considerable percentage (39.6%) described positive changes (measured by improved performance of daily life activities, decrease in symptoms or lesser recourse to SOS medication), even though the majority did not recognise any improvement. 81.6% of those who noted positive changes said they were no longer exposed to second-hand smoke with the passing of the new legislation, and 65.8% stated that the smoking ban was the factor responsible for those changes. These results, only two months after the implementation of the legislative ban on smoking in public spaces, underline the importance of approving effective measures to create and enforce smoke-free environments, reducing worsening of symptoms and improving asthma patients’ well-being. Rev Port Pneumol 2009; XV (1): 27-42

Heterogeneization of alpha diimines nickel catalysts for the polymerization of ethylene and methylmethacrylate

Abstract In this paper we present two different techniques for the preparation of single site heterogeneous catalyst. The first method consists in the impregnation of a solution of the organometallic compound in MCM41. The second method intends to establish the in situ synthesis of the complex within the solid’s pores by the reaction of the organic ligand with the metal cation previously introduced in the support. The direct deposition of the organometallic complex in the support resulted in an active catalyst which gives polyethylene with the same microstructure as the one obtained with the related homogeneous systems. The heterogeneous catalysts obtained by reaction of the ligand with the metal already present in the support showed a lower catalytic activity.

Recovery of phenolic compounds from multi-component solution by a synthesized activated carbon using resorcinol and formaldehyde

The adsorption of four phenolic compounds (gallic acid, protocatechuic acid, vanillic acid and syringic acid) is investigated using a synthesized mesoporous carbon on both single and multi-component synthetic solutions. Some correlation of the adsorption capacity of the carbon and the nature of adsorbate could be made, except for gallic acid whose concentration decrease seems to be not exclusively due to adsorption but also to polymerization reaction. In the multi-component mixture, negative effects in the adsorption capacity are observed probably due to competition for the active centers of the adsorbent surface. In desorption studies, ethanol presents better performance than water and acetonitrile. Vanillic acid is the compound with the higher adsorption and interestingly it is then possible to desorb a relatively high amount of it from the adsorbent, which may represent a possibility for a selective recovery of vanillic acid. These results present a potential way to treat the wastewater from the cork industry.

Enhanced catalytic properties of carbons supported zirconia (Zr) and sulfated zirconia (SZr) in the green synthesis of benzodiazepines

This work reports for the first time a new series of promising porous catalytic carbon materials, functionalized with Lewis and Brønsted acid sites useful in the green synthesis of 2,3‐dihydro‐1H‐1,5‐benzodiazepine – nitrogen heterocyclic compounds. Benzodiazepines and derivatives are fine chemicals exhibiting interesting therapeutic properties. Carbon materials have been barely investigated in the synthesis of this type of compounds. Two commercial carbon materials were selected exhibiting different textural properties: i) Norit RX3 (N) as microporous sample and ii) mesoporous xerogel (X), both used as supports of ZrO2 (Zr) and ZrO2/SO42− (SZr). The supported SZr led to higher conversion values and selectivities to the target benzodiazepine. Both chemical and textural properties influenced significantly the catalytic performance. Particularly relevant are the results concerning the non‐sulfated samples, NZr and XZr, that were able to catalyze the reaction leading to the target benzodiazepine with high selectivity (up to 80 %; 2 h). These results indicated an important role of the carbon own surface functional groups, avoiding the use of H2SO4. Even very low amounts of SZr supported on carbon reveal high activity and selectivity. Therefore, the carbon materials herein reported can be considered an efficient and sustainable alternative bifunctional catalysts for the benzodiazepine synthesis.

Cr(III) removal from synthetic and industrial wastewaters by using co-gasification chars of rice waste streams

Blends of rice waste streams were submitted to co-gasification assays. The resulting chars (G1C and G2C) were characterized and used in Cr(III) removal assays from a synthetic solution. A Commercial Activated Carbon (CAC) was used for comparison purposes. The chars were non-porous materials mainly composed by ashes (68.3-92.6% w/w). The influences of adsorbent loading (solid/liquid ratio - S/L) and initial pH in Cr(III) removal were tested. G2C at a S/L of 5 mg L-1 and an initial pH of 4.50 presented an uptake capacity significantly higher than CAC (7.29 and 2.59 mg g-1, respectively). G2C was used in Cr(III) removal assays from an industrial wastewater with Cr(III) concentrations of 50, 100 and 200 mg L-1. Cr(III) removal by precipitation (uptake capacity ranging from 11.1 to 14.9 mg g-1) was more effective in G2C, while adsorption (uptake capacity of 16.1 mg g-1) was the main removal mechanism in CAC.