No description available.

The aim of the presented Diploma Thesis was to develop a new method for the indirect determination of formaldehyde in wood-based products using gas-diffusion microextraction coupled with electrochemical detection on unmodified screen-printed electrodes (MLEM-SPCE). Formaldehyde released from the sample is derivatized using an acetylacetone reagent present in an acceptor solution. The product of derivatization of formaldehyde with acetylacetone is 3,5-diacetyl-1,4-dihydrolutidine (DDL) which forms a selective oxidation voltammetric peak at a potential of 0.4 V. Detection and quantification limits of 0.57 mg kg−1 and 1.89 mg kg−1 , respectively, were obtained, together with intra- and inter-day precision below 10% (as relative standard deviation, RSD). The developed methodology was applied to determine formaldehyde content in seven samples. Similar results were obtained from the European standard method EN 717-3 with a significant reduction of total analysis time. The developed method MLEM-SPCE, which combines the use of a new sample preparation procedure for volatile compounds with the firstly introduced determination of formaldehyde (as the derivative product DDL) on unmodified SPCEs, proves to be a promising alternative for the determination of formaldehyde in wood-based products and other samples.

Adhesives used for wood composites such as particleboard are conventionally of petrochemical nature with formaldehyde as a base substance and represent a pain point in the industry due their toxic emissions. Consequently, adhesives are subject to an agenda to develop more benign, low-impact alternatives. On the one hand, the issue has been addressed by means of optimisation of composition and amounts, and on the other hand, development of biobased adhesives from different renewable feedstock has been taking place over the past decades. Yet, these bio-adhesives remain a niche segment as renewability or lower toxicity alone is widely not enough despite increasingly strict regulations on formaldehyde emissions. Emphasis on a more comprehensive set of beneficial properties of ‘green’ adhesives is needed for successful adoption in the market. In this context, this study investigates the holistic sustainability potential of a yet untapped bio- adhesive feedstock: macroalgae. Current research on an algae-based adhesive from cultivated biomass in Sweden suggests suitable adhesive properties for particleboard manufacture. Complementing these promising findings on material properties, this study assesses sustainability of using an algae-based adhesive in a particleboard production system as opposed to conventional formaldehyde-based resins. A comparative cradle-to-gate life cycle assessment of different scenarios was conducted, with the specific aim to explore changes in toxicity, climate change impacts and eutrophication due to the known benefits of cultivated macroalgae in these areas. A considerably better performance for algae-based adhesives was found across impact categories (CML baseline method) compared to formaldehyde-based scenarios, as well as a similar pattern with respect to cumulative energy demand. Particularly under a low-impact preservation method for the algal biomass, relative impacts were substantially lower without exception. Furthermore, a potential for carbon sequestration and replacing of fossil with biogenic carbon flows was identified, as well as bioremediation of location eutrophication through nutrient uptake of the biomass during cultivation. Despite the early stage and the need for further research, the results point to a promising potential for macroalgae as a feedstock for biobased wood adhesives which go beyond renewability. / Lim som vanligtvis används för träkomponenter som exempelvis spånskivor är konventionellt från petrokemiska källor med formaldehyd som basämne, och anses vara en utmaning för branschen på grund av dess giftiga utsläpp. Därav är det av intresse för branschen att utveckla bättre alternativ med mindre miljöpåverkan. Utvecklingen har dels skett genom optimering av sammansättning och proportioner, men under det senaste decennierna har även utveckling av biobaserade lim från olika förnyelsebara råvaror tagit fart. Dessa biobaserade lim är dock fortfarande ett nischat område, att enbart arbeta med förnybara råvaror som ger lägre toxicitet verkar inte vara tillräckligt, trots allt striktare bestämmelser om formaldehydutsläpp. Därför krävs det tydliga bevis av miljövinsterna med lim av förnyelsebara råvaror för att denna metod ska bli mer framgångsrik på marknaden. I detta sammanhang undersöker denna uppsats, genom ett holistiskt perspektiv, potentialen med lim gjort på det ännu outnyttjade förnyelsebara materialet makroalger. Aktuell forskning på algbaserat lim från odlad biomassa i Sverige har uppvisat lämpliga limegenskaper för användning inom spånskivetillverkning. Som ett komplement för dessa potentiella fördelaktiga egenskaper, bedömer denna uppsats miljönyttan med användandet av ett algbaserat lim i produktionssystem av spånskivor, i relation till det konventionella formaldehydbaserade limmet. Därmed görs en jämförande livscykelanalys från vaggan till grinden av olika scenarier, med syftet att undersöka förändringar i toxicitet, klimatpåverkan och övergödning, i och med att dessa tre påverkanskategorier redan har visat på kända miljöfördelar. Resultatet visade att det algbaserade limmet hade betydligt bättre miljöprestanda i alla påverkanskategorier undersökt med metoden CML baseline i jämförelse med det formaldehydbaserade limmet, vilket även visades för kategorin kumulativt energibehov. När en konserveringsmetod används för att processa algbiomassan, är skillnaden i miljöpåverkan av dom två limmen lägre inom alla påverkanskategorier. Slutligen identifierades potential för kolbindning och utbyte av biogena och fossila kolflöden, även bioremediering av lokal övergödning genom att biomassan upptog näringsämnen under odling. Trots det tidiga stadiet och behovet av fortsatt forskning så visar dessa resultat en fortsatt potential för makroalger som ett råmaterial för biobaserade trälim som tar förbybarhet ett steg längre.

The current method for estimating wood failure is highly subjective. Various techniques have been proposed to improve the current protocol, but none have succeeded. This research aims to use deep learning/semantic segmentation using SegNet architecture to estimate wood failure in four types of three-ply plywood from mechanical shear strength specimens. We trained and tested our approach on custom and commercial plywood with bio-based and phenol-formaldehyde adhesives. Shear specimens were prepared and tested. Photographs of 255 shear bonded areas were taken. Forty photographs were used to solicit visual estimates from five human evaluators, and the remaining photographs were used to train the machine learning models. Twelve models were trained with the combination of four image sizes and three dataset splits. In comparison to visual estimates, the model trained on 512 × 512 image size with 90/10 dataset split had a mean absolute error (MAE) of 6%, which was the best among the literature.

No description available.

Formaldehyde is a chemical used widely in the manufacture of building materials. A remarkable example is represented by the Lucite two-step Alpha technology for the large scale production of methyl methacrylate (MMA), the essential building block of all acrylic-based products. Esters and ketones are important intermediates in the manufacture of acrylate esters therefore α-hydroxymethylenation of carbonyl compounds using formaldehyde as a one carbon alkylating agent and subsequent dehydration to the corresponding methylenated derivatives has been explored in the current work. We report a novel catalytic approach for the synthesis of methyl methacrylate (MMA) via one-pot α-methylenation of methyl propanoate (a chemical intermediate of the ALPHA process) with formaldehyde, generated in situ by Ru-catalysed dehydrogenation of methanol. Elucidation of the mechanism involved in the catalytic dehydrogenation of methanol along with the collateral alcohol decarbonylation reaction was gained through a combined experimental and DFT study. The development of an alternative process where anhydrous formaldehyde is produced in situ would provide a simplification over the current second step of the ALPHA technology where the formaldehyde is initially produced as formalin, subsequently dehydrated to afford anhydrous formaldehyde in order to ensure high selectivity to MMA. As an alternative approach, ketones, in particular 3-pentanone and 2-butanone, were targeted as potential substrates in order to overcome some of the problems related to competing reactions that occur at the ester group. Hydroxymethylenation, followed by dehydration and Baeyer-Villager oxidation, possibly catalysed by enzymes to reverse the normal selectivity, leads to the formation of acrylate esters. The catalytic reaction is enabled by a gold carbene hydroxide complex in such a way that the substrate undergoes C-H activation and the nascent metal alkyl acts as a nucleophile towards the electrophilic formaldehyde, supplied in the form of alcoform* (solution of paraformaldehyde in methanol).

De l'observation des transitions à 140 et 150 GHz de l'ortho formaldéhyde et à 72 et 145 GHz du para formaldéhyde se déduit un rapport d'abondances ortho/ para voisin de 3 dans le nuage moléculaire interstellaire Orion A et apparemment plus faible dans les nuages sombres TMC1 et L183. L'étude des mécanismes chimiques en phase gazeuse succeptibles de régir les abondances des deux espèces conduit à un rapport théorique de 3 dans les nuages chauds et denses connue Orion; ce rapport reste indéterminé mais pourrait être plus faible dans les nuages froids connue TMC1 et L183. Quatre nuages moléculaires géants (S147/S153, S184, S158/S159(NGC7538) et W3) ont été cartographiés avec l'antenne de 2,50 m de l'Observatoire de Bordeaux en émissions 13C0 (J=1-0) et HC0+ (J=1-0), dont les étendues se révèlent tout à fait comparables. Quelques caractéristiques des nuages (dimensions, masse, dynamique ...) sont déduites des observations 13 CO *

Graphene has been shown to be very powerful as a transducer in many biosensor applications due to its high sensitivity. This enables smaller surfaces and therefore less material consumption when producing sensors and concequently cheaper and more portable sensors compared to the commercially available sensors today. The electrical properties of graphene are very sensitive to gas exposure why presence of molecules or small changes in concentration could easily be detected when using graphene as a sensing layer. Graphene is sensitive towards many molecules and in order to detect and possibly identify gas molecules the surface needs to be functionalized. The intention of this project was to use nanoparticles (NPs) to further increase sensitivity and specificity towards selected molecules and also enable biofunctionalization of the NPs, and by that tune the electrical properties of the graphene. This study proposes the use of Fe3O4 and TiO2 NPs to enable sensitive detection of volatile gases and possibly further functionalization of the NPs using biomolecules as a detecting agent in a liquid-phasebiosensor application. The interaction between graphene and NPs have been investigated using several surface charactarization methods and electrical measurements for detection of gaseous molecules and also molecules in a liquid solution. The characterizing methods used are XPS, AFM with surface-potential mapping and Raman spectroscopy with reflectance mapping in order to investigate the NPs interaction with the graphene surface. Sensors where manufactured for gas-phase detection of CO, formaldehyde, benzene and NH3 specifically and display differences in sensitivity and behavior of the Fe3O4 and TiO2 NPs respectively. For liquid measurements the difference in behavior in two buffers was investigated using an in-house flow-cell setup. The surface charecterizing measurements indicated that just a small difference could be found between the two NPs, however a significant change in sensor response could be detected as a function of coverage. The liquid and gas-phase measurements rendered information on differences in sensitivity between the NPs and between analytes where TiO2 showed a higher level of sensitivity towards most of the gases investigated. Both Fe3O4 and TiO2 NP coated graphene showed capability to detect formaldehyde and benzene down to 50 ppb and 5 ppb respectively. The sensitive gas detection could help protecting individuals being exposed to a hazardous level of volatile gases if concentrations increase rapidly or at a long term exposure with lower concentrations, improving saftey and health where these gases are present.

Ce travail de thèse se focalise sur l'impact des propriétés acido-basiques des catalyseurs (quantité et force des sites) dans la production d’acroléine par couplage oxydant d’alcools en phase gazeuse. L'influence du rapport entre site acides et sites basiques des catalyseurs a été étudiée dans la condensation aldolique de l'acétaldéhyde et du formaldéhyde en acroléine, réalisée en conditions oxydantes. Les données et corrélations obtenues ont donné des informations indispensables à l’identification des paramètres qui doivent être modifiés afin d'améliorer la sélectivité en acroléine. La première réaction du procédé implique l'oxydation du méthanol et de l'éthanol respectivement en formaldéhyde et acétaldéhyde sur un catalyseur rédox de type FeMoOx.Ensuite, l'aldolisation croisée des deux aldéhydes et la déshydratation en acroléine sont effectuées sur des catalyseurs acido-basiques.Les alcools impliqués dans ce procédé pouvant dériver de la biomasse, cette nouvelle voie de production d'acroléine présente un intérêt élevé puisqu'elle peut remplacer la production actuelle d'acroléine basée sur des ressources fossiles (aujourd'hui l’acroléine est produite industriellement par oxydation du propylène).Le catalyseur optimal doit présenter des caractéristiques amphotères avec une quantité similaire de sites basiques et acides. Une présence modérée et équilibrée de sites acides et basiques améliore le rendement en acroléine et déplace à plus haute température la production des oxydes de carbone. Parmi tous les catalyseurs étudiés, et grâce à ses propriétés acido-basiques spécifiques, MgO supporté sur silice a été identifié comme étant le meilleur catalyseur pour la condensation aldolique des aldéhydes en acroléine en conditions oxydantes / The present work focuses on the impact of the amount and strength of acidic and/or basic sites on the yield of acrolein produced by alcohols oxidative coupling in gas phase. The influence of acid/base ratio of catalytic sites has been studied in the aldol condensation of acetaldehyde and formaldehyde to acrolein performed in oxidizing conditions. The obtained data and correlations supplied valuable information to understand which parameters have to be modified to improve the acrolein selectivity. The first reaction of the process implies methanol and ethanol oxidation respectively to formaldehyde and acetaldehyde on a FeMoOx redox catalyst. Then the cross-aldolization of the two aldehydes and the dehydration to acrolein is performed on acid/base catalysts. Because the alcohols involved in this process can be bio-sourced, this new route to produce acrolein presents a very high interest, since it can replace the current fossil-based acrolein production (nowadays industrially produced by oxidation of propylene). The optimal catalyst should present amphoteric features with a similar amount of both basic and acidic sites. A moderate and balanced presence of acidic and basic sites improves the acrolein yield and the production of carbon oxides is significantly increased only at high temperature. Among all studied catalysts, MgO supported on silica has been identified as the best catalyst for aldol-condensation of aldehydes to acrolein in oxidizing conditions thanks to a given ratio of basic to acidic sites

Submitted by Ana Laura Soler Cunha Buzo (analaurasolercunha@gmail.com) on 2018-09-28T22:21:33Z No. of bitstreams: 1 DISSERTAÇÃO FINAL .pdf: 3047917 bytes, checksum: 4b9d9190322307f4e23c7de4f21936e9 (MD5) / Approved for entry into archive by Cristina Alexandra de Godoy null (cristina@adm.feis.unesp.br) on 2018-10-01T13:05:23Z (GMT) No. of bitstreams: 1 buzo_alsc_me_ilha.pdf: 3047917 bytes, checksum: 4b9d9190322307f4e23c7de4f21936e9 (MD5) / Made available in DSpace on 2018-10-01T13:05:23Z (GMT). No. of bitstreams: 1 buzo_alsc_me_ilha.pdf: 3047917 bytes, checksum: 4b9d9190322307f4e23c7de4f21936e9 (MD5) Previous issue date: 2018-07-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O desenvolvimento de estudos para produção de derivados de madeira tem representado uma real alternativa para contribuir as políticas de sustentabilidade, principalmente de espécies arbóreas nativas. Nesse contexto, o reaproveitamento de resíduos lignocelulósicos tem contribuído como uma alternativa para a produção industrial de painéis de madeira. Dentro desse contexto este trabalho se constitui do estudo para produção e avaliação de painéis aglomerados, empregando-se partículas de bagaço de cana-de-açúcar (Saccharum officinarum) e partículas de madeira de pinus (Pinus taeda; Pinus elliottii) e utilizando-se dois tipos de aglutinantes, o Poliuretano derivado do óleo de mamona (PU-M) e a Resina Ureia-formaldeído (UF). Para produção dos painéis foram propostos diferentes tratamentos com variações entre as proporções de massas das partículas, densidade nominal dos painéis de 0,80 g/cm3 e pressão de prensagem de 50 kgf/cm2 durante 10 min. As misturas de partículas foram utilizadas com 10% de umidade para o adesivo PU-M e 3% de umidade para a resina UF ambos com um conteúdo de 10% em relação à massa seca das partículas. Para prensagem dos painéis com PU-M empregou-se 100 ºC e para os painéis com UF 130 ºC. Os painéis foram submetidos a ensaios para avaliação das propriedades físicas (densidade, umidade e inchamento) e mecânicas (módulo de elasticidade, módulo de ruptura à flexão e tração perpendicular) de acordo com a ABNT NBR 14810-1 e 2 (2013). Os resultados obtidos evidenciaram ser possível a utilização das partículas provenientes do bagaço de cana e de pinus para a produção de painéis aglomerados de alta densidade. Verificou-se que os painéis produzidos com o poliuretano apresentaram maior eficiência e suas propriedades físicas e mecânicas encontram-se compatíveis com os requisitos da Norma Brasileira para painéis do tipo P6 - Painéis estruturais para uso em condições severas de carga, em condições secas. Entretanto, verificou-se que os painéis produzidos com UF podem ser classificados como painéis do Tipo P2 - Painéis não estruturais para uso em condições secas. / The development of studies for the production of wood derivatives has represented a real alternative to improve sustainability policies, mainly of native tree species. In this context, the reuse of lignocellulosic waste has contributed as an alternative to the industrial production of wood panels. This way, this work aims to produce and evaluate chipboards using particles of sugarcane bagasse (Saccharum officinarum) and particles of pine wood (Pinus taeda; Pinus elliottii) and using two types of binders, the Polyurethane derived from castor oil (PU-Castor) and Urea formaldehyde resin (UF). Different treatments were proposed for the production of boards with variations between the particle mass ratios, panels’ nominal density of 0.80 g/cm3 and pressing pressure of 50 kgf/cm2 for 10 minutes. Particle mixtures were used at 10% moisture for the PU-Castor adhesive and 3% moisture for the UF resin both with a content of 10% relative to the dry mass of the particles. For the pressing of panels with PU-Castor was used 100 °C and of panels with UF was used 130 °C. The boards were submitted to tests to evaluate the physical properties (density, moisture and swelling after 24 hours) and mechanical (modulus of elasticity, modulus of resistance to bending and perpendicular traction) according to the ABNT NBR 14810-1 and 2 (2013). The results showed that it is possible to use particles from sugarcane bagasse and pine wood for high density chipboards production. It was found that the boards produced with polyurethane presented higher efficiency and their physical and mechanical properties are compatible with the requirements of Brazilian Standard Regulations for P6 boards (Structural boards for use under severe load conditions for dry conditions use). However, it has been found that panels made with UF can be classified as type P2 panels – Non-structural boards for dry conditions use. / CAPES - DS