Methyl and ethyl chloride synthesis in microreactors

Methyl chloride is an important chemical intermediate with a variety of applications. It is produced today in large units and shipped to the endusers. Most of the derived products are harmless, as silicones, butyl rubber and methyl cellulose. However, methyl chloride is highly toxic and flammable. On-site production in the required quantities is desirable to reduce the risks involved in transportation and storage. Ethyl chloride is a smaller-scale chemical intermediate that is mainly used in the production of cellulose derivatives. Thus, the combination of onsite production of methyl and ethyl chloride is attractive for the cellulose processing industry, e.g. current and future biorefineries. Both alkyl chlorides can be produced by hydrochlorination of the corresponding alcohol, ethanol or methanol. Microreactors are attractive for the on-site production as the reactions are very fast and involve toxic chemicals. In microreactors, the diffusion limitations can be suppressed and the process safety can be improved. The modular setup of microreactors is flexible to adjust the production capacity as needed. Although methyl and ethyl chloride are important chemical intermediates, the literature available on potential catalysts and reaction kinetics is limited. Thus the thesis includes an extensive catalyst screening and characterization, along with kinetic studies and engineering the hydrochlorination process in microreactors. A range of zeolite and alumina based catalysts, neat and impregnated with ZnCl2, were screened for the methanol hydrochlorination. The influence of zinc loading, support, zinc precursor and pH was investigated. The catalysts were characterized with FTIR, TEM, XPS, nitrogen physisorption, XRD and EDX to identify the relationship between the catalyst characteristics and the activity and selectivity in the methyl chloride synthesis. The acidic properties of the catalyst were strongly influenced upon the ZnCl2 modification. In both cases, alumina and zeolite supports, zinc reacted to a certain amount with specific surface sites, which resulted in a decrease of strong and medium Brønsted and Lewis acid sites and the formation of zinc-based weak Lewis acid sites. The latter are highly active and selective in methanol hydrochlorination. Along with the molecular zinc sites, bulk zinc species are present on the support material. Zinc modified zeolite catalysts exhibited the highest activity also at low temperatures (ca 200 °C), however, showing deactivation with time-onstream. Zn/H-ZSM-5 zeolite catalysts had a higher stability than ZnCl2 modified H-Beta and they could be regenerated by burning the coke in air at 400 °C. Neat alumina and zinc modified alumina catalysts were active and selective at 300 °C and higher temperatures. However, zeolite catalysts can be suitable for methyl chloride synthesis at lower temperatures, i.e. 200 °C. Neat γ-alumina was found to be the most stable catalyst when coated in a microreactor channel and it was thus used as the catalyst for systematic kinetic studies in the microreactor. A binder-free and reproducible catalyst coating technique was developed. The uniformity, thickness and stability of the coatings were extensively characterized by SEM, confocal microscopy and EDX analysis. A stable coating could be obtained by thermally pretreating the microreactor platelets and ball milling the alumina to obtain a small particle size. Slurry aging and slow drying improved the coating uniformity. Methyl chloride synthesis from methanol and hydrochloric acid was performed in an alumina-coated microreactor. Conversions from 4% to 83% were achieved in the investigated temperature range of 280-340 °C. This demonstrated that the reaction is fast enough to be successfully performed in a microreactor system. The performance of the microreactor was compared with a tubular fixed bed reactor. The results obtained with both reactors were comparable, but the microreactor allows a rapid catalytic screening with low consumption of chemicals. As a complete conversion of methanol could not be reached in a single microreactor, a second microreactor was coupled in series. A maximum conversion of 97.6 % and a selectivity of 98.8 % were reached at 340°C, which is close to the calculated values at a thermodynamic equilibrium. A kinetic model based on kinetic experiments and thermodynamic calculations was developed. The model was based on a Langmuir Hinshelwood-type mechanism and a plug flow model for the microreactor. The influence of the reactant adsorption on the catalyst surface was investigated by performing transient experiments and comparing different kinetic models. The obtained activation energy for methyl chloride was ca. two fold higher than the previously published, indicating diffusion limitations in the previous studies. A detailed modeling of the diffusion in the porous catalyst layer revealed that severe diffusion limitations occur starting from catalyst coating thicknesses of 50 μm. At a catalyst coating thickness of ca 15 μm as in the microreactor, the conditions of intrinsic kinetics prevail. Ethanol hydrochlorination was performed successfully in the microreactor system. The reaction temperature was 240-340°C. An almost complete conversion of ethanol was achieved at 340°C. The product distribution was broader than for methanol hydrochlorination. Ethylene, diethyl ether and acetaldehyde were detected as by-products, ethylene being the most dominant by-product. A kinetic model including a thorough thermodynamic analysis was developed and the influence of adsorbed HCl on the reaction rate of ethanol dehydration reactions was demonstrated. The separation of methyl chloride using condensers was investigated. The proposed microreactor-condenser concept enables the production of methyl chloride with a high purity of 99%.

Enzymatic Synthesis, Recovery, and Purification of Ethyl β-ᴅ-glucopyranoside

A method to synthesize ethyl β-ᴅ-glucopyranoside (BEG) was searched. Feasibility of different ion exchange resins was examined to purify the product from the synthetic binary solution of BEG and glucose. The target was to produce at least 50 grams of 99 % pure BEG with a scaled up process. Another target was to transfer the batch process into steady-state recycle chromatography process (SSR). BEG was synthesized enzymatically with reverse hydrolysis utilizing β-glucosidase as a catalyst. 65 % of glucose reacted with ethanol into BEG during the synthesis. Different ion exchanger based resins were examined to separate BEG from glucose. Based on batch chromatography experiments the best adsorbent was chosen between styrene based strong acid cation exchange resins (SAC) and acryl based weak acid cation exchange resins (WAC). CA10GC WAC resin in Na+ form was chosen for the further separation studies. To produce greater amounts of the product the batch process was scaled up. The adsorption isotherms for the components were linear. The target purity was possible to reach already in batch without recycle with flowrate and injection size small enough. 99 % pure product was produced with scaled-up batch process. Batch process was transferred to SSR process utilizing the data from design pulse chromatograms and Matlab simulations. The optimal operating conditions for the system were determined. Batch and SSR separation results were compared and by using SSR 98 % pure products were gained with 40 % higher productivity and 40 % lower eluent consumption compared to batch process producing as pure products.

Organofosforiyhdisteille (TBEP ja TEHP) altistuminen työpaikoilla

Työssä mitattiin työilman TBEP- ja TEHP-pitoisuuksia siivousalalla (3 kohdetta) ja muovituoteteollisuudessa (2 kohdetta). Pitoisuutta ilmassa verrattiin työntekijöidenbiomonitorointinäytteistä analysoitujen 2-butoksietikkahapon (2-BAA) ja 2-etyyliheksaanihapon (2-EHA) pitoisuuteen. Tavoitteena oli biomonitoroin-timenetelmän soveltuvuuden selvittäminen altistumisen arvioinnissa sekä tarvittavien lisäsuojaus- ja torjunta-tarpeiden selvittäminen. Biomonitorointia sekoittavien tekijöiden (2-butoksietanoli ja 2-etyyli-1-heksanoli) pitoisuus mitattiin työntekijöidenhengitysilmasta kerätystä VOC-näytteestä. OVS-keräimiin kerätyt TBEP- ja TEHP-näytteet uutettiin ultraäänellä sopivalla liuottimella ja analysoitiin kaasukromatografisesti (GC). VOC-näytteet kerättiin Tenax GR ¿adsorbenttiin, irrotettiin keräimestä termodesorptiolla ja analysoitiin GC:lla. Biomonitorointinäytteiden (virtsa) 2-BAA- ja 2-EHA -pitoisuus analysoitiin myös GC:lla. Lattianvahauksen aikana siivoojien hengitysilmasta mitatuissa TBEP-näytteissä pitoisuudet vaihtelivat välillä 70 - 860 ng/m3 sekä VOC-näytteistä 88 %:sta löytyi2-butoksietanolia, jonka pitoisuus vaihteli välillä 3 - 1800 µg/m3. Virtsan 2-BAA:n pitoisuudet vaihtelivat välillä <0,3 - 26 mmol/mol kreatiniinia ollen korkeimmillaan 43 % toimenpiderajasta. Raskaana olevien toimenpideraja ylitettiin 30 % näytteistä. Muovituotetehtaissa TEHP-pitoisuus työntekijöiden hengitysilmassa oli alle määritysrajan (eli < 1 - < 3 ng/m3). Muovituotetehtaissa kerätyistä VOC-näytteistä 16 %:sta löydettiin 2-etyyli-1-heksanolia, jonka pitoisuus vaihteli välillä 90 - 100 µg/m3. Virtsan 2-EHA-pitoisuudet olivat välillä <0,1 - 0,2 mmol/mol kreatiniinia. Tulosten perusteella siivoojat altistuvat TBEP:lle ja 2-butoksietanolille lattianvahauksen yhteydessä, muttaaltistuminen ei ilman pitoisuuksien ja biomonitoroinnin tulosten mukaan aiheutaterveyshaittaa ainakaan yhden mahdollisen metaboliitin 2-BAA:n kautta. Pois lukien raskaana olevat työntekijät, joille 2-butoksietanolia sisältävän vahanpoistotuotteen käsitteleminen aiheuttaa mahdollista terveyshaittaa. Käytetyillä biomonitorointimenetelmillä ei voitu osoittaa altistumista tapahtuneen mitatuilla TBEP:n ja TEHP:n pitoi-suustasoilla. Metaboliareittien varmistamisen jälkeen on mahdollista tutkia toimivampaa menetelmää altistumisen arviointiin biomonitoroinnin avulla. Työntekijöiden suojautuminen niin muovituotetehtaissa kuin siivoustyössäkin mitattujen yhdisteiden osalta oli pääosin riittävää. Ainoastaan raskaana olevien työntekijöiden, jotka siivoustyössään altistuvat 2-butoksietanolille, suojaukseen tulisi kiinnittää huomiota.

Muurahaishapon käyttö etikkahapon ja propionihapon sovelluksissa

Työssä tutkittiin muurahais-, etikka- ja propionihapon sekä näiden johdannaisten teollisia sovelluskohteita. Työn tarkoituksena oli löytää muurahaishapolle tai sen johdannaisille potentiaalisia käyttökohteita etikka- ja propionihapon sekä näiden johdannaisten teollisista sovelluskohteista. Työssä on laaja kirjallisuuskatsaus, jossa käsitellään muurahais-, etikka- ja propionihapon kemiallisia ja fysikaalisia ominaisuuksia, ekologisia ja korroosiovaikutuksia sekä yleensä orgaanisten happojen antimikrobisia ominaisuuksia. Tämän lisäksi työssä esitellään tarkasteltavien happojen sekä happojohdannaisten markkinat teollisissa sovelluksissa Yhdysvalloissa, Länsi-Euroopassa ja Japanissa. Korvaavuuksien syventävän analyysin avulla pyrittiin löytämään ne sovelluskohteet muurahaishapolle tai sen johdannaisille, joissa ne voisivat olla hinnaltaan kilpailukykyisiä vastaavien etikka-ja propionihapposovellusten kanssa. Mahdollisen korvaavuuden rajaksi asetettiin5 000 tonnia sovelluskohdetta kohti. Kirjallisuustutkimuksen perusteella etikkahapon estereiden (asetaattiestereiden) käyttökohde liuottimien komponentteinavoisi olla potentiaalisin käyttökohde vastaaville muurahaishapon estereille (formiaattiestereille). Asetaattiestereitä on ennustettu käytettävän maailmalla 2 808 000 tonnia vuonna 2006. Niiden pääkäyttöalueet ovat liuottimina pintapäällysteissä kuten maaleissa, lakoissa sekä painomusteissa ja -väreissä. Toistaiseksi formiaattiestereitä on hyödynnetty vain muutamia satoja tonneja lähinnä lääketeollisuuden sovelluksissa välituotteena. Työssä tehtyjen alustavien laskelmien perusteella muurahaishapon esterit ovat hintatasoltaan kilpailukykyinen vaihtoehto vastaaville asetaattiestereille. Diplomityön kokeellisessa osassa etyyliformiaattia valmistettiin menestyksekkäästi laboratoriomittakaavassa. Toinen potentiaalinen uusi tuote on selluloosaformiaattikuitu (SF-kuitu). Selluloosa-asetaattikuitua käytettiin vuonna 2001 845 000 tonnia, josta 79 % kului savukefilttereiden valmistukseen. SF-kuitu on kirjallisuuden mukaan vaihtoehtoinen raaka-aine savukefilttereiden valmistukseen.

Ion-exchange resins as stationary phase in reactive chromatography

Dynamic behavior of bothisothermal and non-isothermal single-column chromatographic reactors with an ion-exchange resin as the stationary phase was investigated. The reactor performance was interpreted by using results obtained when studying the effect of the resin properties on the equilibrium and kinetic phenomena occurring simultaneously in the reactor. Mathematical models were derived for each phenomenon and combined to simulate the chromatographic reactor. The phenomena studied includes phase equilibria in multicomponent liquid mixture¿ion-exchange resin systems, chemicalequilibrium in the presence of a resin catalyst, diffusion of liquids in gel-type and macroporous resins, and chemical reaction kinetics. Above all, attention was paid to the swelling behavior of the resins and how it affects the kinetic phenomena. Several poly(styrene-co-divinylbenzene) resins with different cross-link densities and internal porosities were used. Esterification of acetic acid with ethanol to produce ethyl acetate and water was used as a model reaction system. Choosing an ion-exchange resin with a low cross-link density is beneficial inthe case of the present reaction system: the amount of ethyl acetate as well the ethyl acetate to water mole ratio in the effluent stream increase with decreasing cross-link density. The enhanced performance of the reactor is mainly attributed to increasing reaction rate, which in turn originates from the phase equilibrium behavior of the system. Also mass transfer considerations favor the use ofresins with low cross-link density. The diffusion coefficients of liquids in the gel-type ion-exchange resins were found to fall rapidly when the extent of swelling became low. Glass transition of the polymer was not found to significantlyretard the diffusion in sulfonated PS¿DVB ion-exchange resins. It was also shown that non-isothermal operation of a chromatographic reactor could be used to significantly enhance the reactor performance. In the case of the exothermic modelreaction system and a near-adiabatic column, a positive thermal wave (higher temperature than in the initial state) was found to travel together with the reactive front. This further increased the conversion of the reactants. Diffusion-induced volume changes of the ion-exchange resins were studied in a flow-through cell. It was shown that describing the swelling and shrinking kinetics of the particles calls for a mass transfer model that explicitly includes the limited expansibility of the polymer network. A good description of the process was obtained by combining the generalized Maxwell-Stefan approach and an activity model that was derived from the thermodynamics of polymer solutions and gels. The swelling pressure in the resin phase was evaluated by using a non-Gaussian expression forthe polymer chain length distribution. Dimensional changes of the resin particles necessitate the use of non-standard mathematical tools for dynamic simulations. A transformed coordinate system, where the mass of the polymer was used as a spatial variable, was applied when simulating the chromatographic reactor columns as well as the swelling and shrinking kinetics of the resin particles. Shrinking of the particles in a column leads to formation of dead volume on top of the resin bed. In ordinary Eulerian coordinates, this results in a moving discontinuity that in turn causes numerical difficulties in the solution of the PDE system. The motion of the discontinuity was eliminated by spanning two calculation grids in the column that overlapped at the top of the resin bed. The reactive and non-reactive phase equilibrium data were correlated with a model derived from thethermodynamics of polymer solution and gels. The thermodynamic approach used inthis work is best suited at high degrees of swelling because the polymer matrixmay be in the glassy state when the extent of swelling is low.

Gas-phase photocatalytic oxidation of volatile organic compounds

Substances emitted into the atmosphere by human activities in urban and industrial areas cause environmental problems such as air quality degradation, respiratory diseases, climate change, global warming, and stratospheric ozone depletion. Volatile organic compounds (VOCs) are major air pollutants, emitted largely by industry, transportation and households. Many VOCs are toxic, and some are considered to be carcinogenic, mutagenic, or teratogenic. A wide spectrum of VOCs is readily oxidized photocatalytically. Photocatalytic oxidation (PCO) over titanium dioxide may present a potential alternative to air treatment strategies currently in use, such as adsorption and thermal treatment, due to its advantageous activity under ambient conditions, although higher but still mild temperatures may also be applied. The objective of the present research was to disclose routes of chemical reactions, estimate the kinetics and the sensitivity of gas-phase PCO to reaction conditions in respect of air pollutants containing heteroatoms in their molecules. Deactivation of the photocatalyst and restoration of its activity was also taken under consideration to assess the practical possibility of the application of PCO to the treatment of air polluted with VOCs. UV-irradiated titanium dioxide was selected as a photocatalyst for its chemical inertness, non-toxic character and low cost. In the present work Degussa P25 TiO2 photocatalyst was mostly used. In transient studies platinized TiO2 was also studied. The experimental research into PCO of following VOCs was undertaken: - methyl tert-butyl ether (MTBE) as the basic oxygenated motor fuel additive and, thus, a major non-biodegradable pollutant of groundwater; - tert-butyl alcohol (TBA) as the primary product of MTBE hydrolysis and PCO; - ethyl mercaptan (ethanethiol) as one of the reduced sulphur pungent air pollutants in the pulp-and-paper industry; - methylamine (MA) and dimethylamine (DMA) as the amino compounds often emitted by various industries. The PCO of VOCs was studied using a continuous-flow mode. The PCO of MTBE and TBA was also studied by transient mode, in which carbon dioxide, water, and acetone were identified as the main gas-phase products. The volatile products of thermal catalytic oxidation (TCO) of MTBE included 2-methyl-1-propene (2-MP), carbon monoxide, carbon dioxide and water; TBA decomposed to 2-MP and water. Continuous PCO of 4 TBA proceeded faster in humid air than dry air. MTBE oxidation, however, was less sensitive to humidity. The TiO2 catalyst was stable during continuous PCO of MTBE and TBA above 373 K, but gradually lost activity below 373 K; the catalyst could be regenerated by UV irradiation in the absence of gas-phase VOCs. Sulphur dioxide, carbon monoxide, carbon dioxide and water were identified as ultimate products of PCO of ethanethiol. Acetic acid was identified as a photocatalytic oxidation by-product. The limits of ethanethiol concentration and temperature, at which the reactor performance was stable for indefinite time, were established. The apparent reaction kinetics appeared to be independent of the reaction temperature within the studied limits, 373 to 453 K. The catalyst was completely and irreversibly deactivated with ethanethiol TCO. Volatile PCO products of MA included ammonia, nitrogen dioxide, nitrous oxide, carbon dioxide and water. Formamide was observed among DMA PCO products together with others similar to the ones of MA. TCO for both substances resulted in the formation of ammonia, hydrogen cyanide, carbon monoxide, carbon dioxide and water. No deactivation of the photocatalyst during the multiple long-run experiments was observed at the concentrations and temperatures used in the study. PCO of MA was also studied in the aqueous phase. Maximum efficiency was achieved in an alkaline media, where MA exhibited high fugitivity. Two mechanisms of aqueous PCO – decomposition to formate and ammonia, and oxidation of organic nitrogen directly to nitrite - lead ultimately to carbon dioxide, water, ammonia and nitrate: formate and nitrite were observed as intermediates. A part of the ammonia formed in the reaction was oxidized to nitrite and nitrate. This finding helped in better understanding of the gasphase PCO pathways. The PCO kinetic data for VOCs fitted well to the monomolecular Langmuir- Hinshelwood (L-H) model, whereas TCO kinetic behaviour matched the first order process for volatile amines and the L-H model for others. It should be noted that both LH and the first order equations were only the data fit, not the real description of the reaction kinetics. The dependence of the kinetic constants on temperature was established in the form of an Arrhenius equation.

Hiilidioksidin talteenottoon soveltuvan anioninvaihtohartsin valmistus ja karakterisointi

Tämän työn tarkoituksena oli tutkia hiilidioksidin talteenottoon soveltuvan anioninvaihtohartsin valmistusmenetelmiä, kokeilla eri menetelmiä käytännössä ja tutkia sekä itse valmistettujen että valmiina saatujen hartsien adsorptiokykyä ja muita ominaisuuksia. Kemiallinen adsorptio amiiniryhmän omaavien hartsien avulla on yksi tapa sitoa hiilidioksidia ilmasta. Primäärinen amiiniryhmä sitoo hiilidioksidia parhaiten. Primäärisen amiiniryhmän omaava anioninvaihtohartsi voidaan valmistaa pohjapolymeeristä halogeenialkyloimalla ja aminoimalla, aminoalkyloimalla tai suoraan aminoimalla. Aminoalkylointi voidaan suorittaa erilaisilla reagensseilla ja katalyyteillä. Tässä työssä hartseja valmistettiin aminoimalla polymetyyliakrylaattidivinyylibentseenipohjaista polymeeriä etyylidiamiinilla ja propyylidiamiinilla. Lisäksi suoritettiin polystyreeni-divinyylibentseenipohjaisen polymeerin aminoalkylointi bis(ftaali-imidometyyli)eetterin avulla. Reaktio tehtiin kahdella eri katalyytillä; rikkitrioksidilla ja rautakloridilla. Aminoalkylointireaktioissa tarvittava eetteri piti ennen varsinaista reaktiota valmistaa N-hydroksymetyyliftaali-imidistä. Myös tämän reagenssin syntetisointia ftaali-imidistä kokeiltiin. Kaikki synteesit onnistuivat melko hyvin, paitsi aminoalkylointi rautakloridikatalyytillä. Hartsien valmistuksen lisäksi itse valmistettuja primäärisen amiiniryhmän omaavia hartseja sekä erilaisia amiiniryhmiä omaavia valmiita hartseja karakterisoitiin eri tavoin. Erityisesti haluttiin tutkia hiilidioksidin adsorptiokapasiteettia ja hartsien termistä kestävyyttä. Kaikista tutkituista hartseista lähimpänä haluttuja ominaisuuksia olivat kaksi kaupallista primäärisen amiiniryhmän omaavaa PS-DVBpohjaista makrohuokoista hartsia. Rakenteeltaan samanlainen itse valmistettu hartsi (rikkitrioksidikatalyytin läsnä ollessa aminoalkyloitu) oli myös ominaisuuksiltaan lupaava. Valmistusmenetelmää pitää kuitenkin tutkia ja kehittää lisää vielä parempien tulosten aikaansaamiseksi. Myös kaupallinen polyetyleeni-imiinirakenteen omaava silikapohjainen hartsi oli ominaisuuksiltaan hyvä.

Lipase-catalyzed Approaches towards Secondary Alcohols: Intermediates for Enantiopure Drugs

The use of enantiopure intermediates for drug synthesis is a trend in pharmaceutical industry. Different physiological effects are associated with the enantiomers of chiral molecules. Thus, the safety profile of a drug based on an enantiopure active pharmaceutical ingredient is more reliable. Biocatalysis is an important tool to access enantiopure molecules. In biocatalysis, the advantage of selectivity (chemo-, regio- and stereoselectivity) is combined with the benefits of a green synthesis strategy. Chemoenzymatic syntheses of drug molecules, obtained by combining biocatalysis with modern chemical synthesis steps usually consists of fewer reaction steps, reduced waste production and improved overall synthetic efficiency both in yields and enantio- and/or diastereoselectivities compared with classical chemical synthesis. The experimental work together with the literature review clearly indicates that lipase catalysis is highly applicable in the synthesis of enantiopure intermediates of drug molecules as the basis to infer the correct stereochemistry. By lipase catalysis, enantiopure secondary alcohols used as intermediates in the synthesis of Dorzolamide, an antiglaucoma drug, were obtained. Enantiopure _-hydroxy nitriles as potential intermediates for the synthesis of antidepressant drugs with 1-aryl-3- methylaminopropan-1-ol structure were also obtained with lipases. Kinetic resolution of racemates was the main biocatalytic approach applied. Candida Antarctica lipase B, Burkholderia cepacia lipase and Thermomyces lanuginosus lipase were applied for the acylation of alcohols and the alcoholysis of their esters in organic solvents, such as in diisopropyl ether and tert-butyl methyl ether. Candida Antarctica lipase B was used under solvent free conditions for the acylation of ethyl 3-hydroxybutanoate.

Rigid Rod Polymer Fillers in Acrylic Denture and Dental Adhesive Resin Systems

Polymeric materials have been used in dental applications for decades. Adhesion of polymeric materials to each other and to the tooth substrate is essential to their successful use. The aim of this series of studies was two-folded. First, to improve adhesion of poly(paraphenylene) based rigid rod polymer (RRP) to other dental polymers, and secondly, to evaluate the usability of a new dentin primer system based on RRP fillers. Poly(paraphenylene) based RRP would be a tempting material for dental applications because of its good mechanical properties. To be used in dental applications, reliable adhesion between RRP and other dental polymers is required. In this series of studies, the adhesion of RRP to denture base polymer and the mechanical properties of RRP-denture base polymer-material combination were evaluated. Also adhesion of BisGMA-TEGDMA-resin to RRP was determined. Different surface treatments were tested to improve the adhesion of BisGMA-TEGDMA-resin to RRP. Results were based on three-point bending testing, Vickers surface hardness test and scanning electron microscope analysis (SEM), which showed that no reliable adhesion between RRP and denture base polymer was formed. Addition of RRP filler to denture base polymer increased surface hardness and flexural modulus but flexural strength decreased. Results from the shear bond strength test and SEM revealed that adhesion between resin and RRP was possible to improve by surface treatment with dichloromethane (DCM) based primer and a new kind of adhesive surface can be designed. The current dentin bonding agents have good immediate bond strength, but in long term the bond strength may decrease due to the detrimental effect of water and perhaps by matrix metalloproteinases. This leads to problems in longevity of restorations. Current bonding agents use organic monomers. In this series of studies, RRP filled dentin primer was tested in order to decrease the water sorption of the monomer system of the primers. The properties of new dentin primer system were evaluated in vitro by comparing it to commercial etch and rinse adhesive system. The results from the contact angle measurements and SEM showed that experimental primer with RRP reinforcement provided similar resin infiltration to dentin collagen and formed the resin-dentin interface as the control primer. Microtensile bond strength test and SEM revealed that in short term water storing, RRP increased bond strength and primer with BMEP-monomer (bis[2-(methacryloyloxy)-ethyl]phosphate) and high solvent concentration provided comparable bonding properties to the commercial control primers. In long term water storing, the high solvent-monomer concentration of the experimental primers decreased bond strength. However, in low solvent-monomer concentration groups, the long-term water storing did not decrease the bond strength despite the existence of hydrophilic monomers which were used in the system. These studies demonstrated that new dentin primer system reached the mechanical properties of current traditional etch and rinse adhesive system in short time water storing. Improved properties can be achieved by further modifications of the monomer system. Studies of the adhesion of RRP to other polymers suggest that adhesion between RRP and other dental polymers is possible to obtain by certain surface treatments.

Determination of decomposition products of flotation collector chemicals using capillary electrophoresis

Vaahdotusta käytetään yleisesti erottamaan eri mineraaleja malmista. Tässä menetelmässä käytetään erityisiä pinta-aktiivisia aineita, joita kutsutaan kokoojakemikaaleiksi, muuntamaan halutut mineraalit hydrofobisiksi ja erottamaan ne hydrofiilisistä partikkeleista ilmakuplien avulla. Eräs tärkeimmistä kokoojakemikaalien ryhmistä on ksantaatit. Ksantaateilla on havaittu taipumusta hajota useiksi erilaisiksi hajoamistuotteiksi vaahdotusprosessin aikana. Näillä hajoamistuotteilla voi olla monia haitallisia vaikutuksia vaahdotuksen tuloksiin. Näiden tuotteiden tunnistaminen ja määrittäminen on tärkeää vaahdotusprosessin paremman ymmärtämisen kannalta. Työn kirjallisuusosassa vaahdotusprosessi, ksantaatit ja niiden yleisimmät hajoamistuotteet on esitelty, kuten myös käytetty analyysimenetelmä, kapillaarielektroforeesi. Työn kokeellisessa osassa etsittiin sopivaa erotusmenetelmää etyyliksantaatin, etyylitiokarbonaatin, etyyliperksantaatin ja etyyliksantyylitiosulfaatin erottamiseksi kapillaarilelektroforeesilla. Pääasiassa keskityttiin kahteen eri erotusmenetelmään. Ensimmäinen menetelmä kykeni erottamaan kaikki tutkitut tuotteet puhdasvesinäytteissä, ja toinen menetelmä oli sopiva näiden tuotteiden erottamiseen prosessivesinäytteissä. Jälkimmäistä menetelmää kokeiltiin käytännössä rikastamolla, jossa sillä kyettiin erottamaan isobutyyliksantaatti, isobutyylitiokarbonaatti, ja suurella todennäköisyydellä myös isobutyyliperksantaatti.

Determination of collector chemicals from flotation process waters using capillary electrophoresis

Vaahdotusprosessia käytetään yleisesti erottamaan arvokkaita mineraaleja malmeista. Toimiakseen tehokkaasti prosessi tarvitsee kokoojakemikaaleja, joiden tehtävänä on sitoa halutut mineraalit ilmakupliin. Jotta näiden kemikaalien käyttäytymistä prosessissa voitaisiin ymmärtää paremmin ja prosessin ohjausta tehostaa, pitää kokoojia pystyä analysoimaan prosessivesistä. Työn kirjallisuusosassa on koottu ja vertailtu erilaisia kirjallisuudesta löytyneitä analyysimenetelmiä kokoojakemikaaleille. Kokeellisessaosassa on kehitetty kaksi kapillaarielektroforeesimenetelmää näiden kemikaalien tutkimiseen. Menetelmien toteamisrajat tutkituille kemikaaleille olivat seuraavanlaiset: natrium diiosobutylditiofosfaattille (DTP) 2,7 mg/L puhtaassa vedessä ja 6,7 mg/L prosessivedessä; natrium diisobutyldithiofosfinaatille (DTPI) vastaavasti 4,5 mg/L ja 6,7 mg/L; etyyli ksantaatille 0,025 mg/L ja 0,16 mg/L; ja isobutyyli ksantaatille 0,41 mg/L ja 0,62 mg/L. Näitä menetelmiä voidaan tulevaisuudessa kehittää kokoojien hajoamistuotteiden analysointia varten sekä prosessien on-line mittauksiin.

Novel technology for preparation of optically active chemicals

Asymmetric synthesis using modified heterogeneous catalysts has gained lots of interest in the production of optically pure chemicals, such as pharmaceuticals, nutraceuticals, fragrances and agrochemicals. Heterogeneous modified catalysts capable of inducing high enantioselectivities are preferred in industrial scale due to their superior separation and handling properties. The topic has been intensively investigated both in industry and academia. The enantioselective hydrogenation of ethyl benzoylformate (EBF) to (R)-ethyl mandelate over (-)-cinchonidine (CD)-modified Pt/Al2O3 catalyst in a laboratory-scale semi-batch reactor was studied as a function of modifier concentration, reaction temperature, stirring rate and catalyst particle size. The main product was always (R)-ethyl mandelate while small amounts of (S)-ethyl mandelate were obtained as by product. The kinetic results showed higher enantioselectivity and lower initial rates approaching asymptotically to a constant value as the amount of modifier was increased. Additionally, catalyst deactivation due to presence of impurities in the feed was prominent in some cases; therefore activated carbon was used as a cleaning agent of the raw material to remove impurities prior to catalyst addition. Detailed characterizations methods (SEM, EDX, TPR, BET, chemisorption, particle size distribution) of the catalysts were carried out. Solvent effects were also studied in the semi-batch reactor. Solvents with dielectric constant (e) between 2 and 25 were applied. The enantiomeric excess (ee) increased with an increase of the dielectric coefficient up to a maximum followed by a nonlinear decrease. A kinetic model was proposed for the enantioselectivity dependence on the dielectric constant based on the Kirkwood treatment. The non-linear dependence of ee on (e) successfully described the variation of ee in different solvents. Systematic kinetic experiments were carried out in the semi-batch reactor. Toluene was used as a solvent. Based on these results, a kinetic model based on the assumption of different number of sites was developed. Density functional theory calculations were applied to study the energetics of the EBF adsorption on pure Pt(1 1 1). The hydrogenation rate constants were determined along with the adsorption parameters by non-linear regression analysis. A comparison between the model and the experimental data revealed a very good correspondence. Transient experiments in a fixed-bed reactor were also carried out in this work. The results demonstrated that continuous enantioselective hydrogenation of EBF in hexane/2-propanol 90/10 (v/v) is possible and that continuous feeding of (-)-cinchonidine is needed to maintain a high steady-state enantioselectivity. The catalyst showed a good stability and high enantioselectivity was achieved in the fixed-bed reactor. Chromatographic separation of (R)- and (S)-ethyl mandelate originating from the continuous reactor was investigated. A commercial column filled with a chiral resin was chosen as a perspective preparative-scale adsorbent. Since the adsorption equilibrium isotherms were linear within the entire investigated range of concentrations, they were determined by pulse experiments for the isomers present in a post-reaction mixture. Breakthrough curves were measured and described successfully by the dispersive plug flow model with a linear driving force approximation. The focus of this research project was the development of a new integrated production concept of optically active chemicals by combining heterogeneous catalysis and chromatographic separation technology. The proposed work is fundamental research in advanced process technology aiming to improve efficiency and enable clean and environmentally benign production of enantiomeric pure chemicals.

Bio-ethanol valorization towards C4s including 1-butanol over metal modified alumina and zeolite catalysts

Bio-ethanol has been used as a fuel additive in modern society aimed at reducing CO2-emissions and dependence on oil. However, ethanol is unsuitable as fuel supplement in higher proportions due to its physico-chemical properties. One option to counteract the negative effects is to upgrade ethanol in a continuous fixed bed reactor to more valuable C4 products such as 1-butanol providing chemical similarity with traditional gasoline components. Bio-ethanol based valorization products also have other end-uses than just fuel additives. E.g. 1-butanol and ethyl acetate are well characterised industrial solvents and platform chemicals providing greener alternatives. The modern approach is to apply heterogeneous catalysts in the investigated reactions. The research was concentrated on aluminium oxide (Al2O3) and zeolites that were used as catalysts and catalyst supports. The metals supported (Cu, Ni, Co) gave very different product profiles and, thus, a profound view of different catalyst preparation methods and characterisation techniques was necessary. Additionally, acidity and basicity of the catalyst surface have an important role in determining the product profile. It was observed that ordinary determination of acid strength was not enough to explain all the phenomena e.g. the reaction mechanism. One of the main findings of the thesis is based on the catalytically active site which originates from crystallite structure. As a consequence, the overall evaluation of different by-products and intermediates was carried out by combining the information. Further kinetic analysis was carried out on metal (Cu, Ni, Co) supported self-prepared alumina catalysts. The thesis gives information for further catalyst developments aimed to scale-up towards industrially feasible operations.

On-line determination of residual collector concentration in flotation process

Valuable minerals can be recovered by using froth flotation. This is a widely used separation technique in mineral processing. In a flotation cell hydrophobic particles attach on air bubbles dispersed in the slurry and rise on the top of the cell. Valuable particles are made hydrophobic by adding collector chemicals in the slurry. With the help of a frother reagent a stable froth forms on the top of the cell and the froth with valuable minerals, i.e. the concentrate, can be removed for further processing. Normally the collector is dosed on the basis of the feed rate of the flotation circuit and the head grade of the valuable metal. However, also the mineral composition of the ore affects the consumption of the collector, i.e. how much is adsorbed on the mineral surfaces. Therefore it is worth monitoring the residual collector concentration in the flotation tailings. Excess usage of collector causes unnecessary costs and may even disturb the process. In the literature part of the Master’s thesis the basics of flotation process and collector chemicals are introduced. Capillary electrophoresis (CE), an analytical technique suitable for detecting collector chemicals, is also reviewed. In the experimental part of the thesis the development of an on-line CE method for monitoring the concentration of collector chemicals in a flotation process and the results of a measurement campaign are presented. It was possible to determine the quality and quantity of collector chemicals in nickel flotation tailings at a concentrator plant with the developed on-line CE method. Sodium ethyl xanthate and sodium isopropyl xanthate residuals were found in the tailings and slight correlation between the measured concentrations and the dosage amounts could be seen.

Ionic liquid mediated biomass deconstruction: from analysis challenges to fermentable sugars

Ionic liquids, ILs, have recently been studied with accelerating interest to be used for a deconstruction/fractionation, dissolution or pretreatment processing method of lignocellulosic biomass. ILs are usually utilized combined with heat. Regarding lignocellulosic recalcitrance toward fractionation and IL utilization, most of the studies concern IL utilization in the biomass fermentation process prior to the enzymatic hydrolysis step. It has been demonstrated that IL-pretreatment gives more efficient hydrolysis of the biomass polysaccharides than enzymatic hydrolysis alone. Both cellulose (especially cellulose) and lignin are very resistant towards fractionation and even dissolution methods. As an example, it can be mentioned that softwood, hardwood and grass-type plant species have different types of lignin structures leading to the fact that softwood lignin (guaiacyl lignin dominates) is the most difficult to solubilize or chemically disrupt. In addition to the known conventional biomass processing methods, several ILs have also been found to efficiently dissolve either cellulose and/or wood samples – different ILs are suitable for different purposes. An IL treatment of wood usually results in non-fibrous pulp, where lignin is not efficiently separated and wood components are selectively precipitated, as cellulose is not soluble or degradable in ionic liquids under mild conditions. Nevertheless, new ILs capable of rather good fractionation performance have recently emerged. The capability of the IL to dissolve or deconstruct wood or cellulose depends on several factors, (e.g. sample origin, the particle size of the biomass, mechanical treatments as pulverization, initial biomassto-IL ratio, water content of the biomass, possible impurities of IL, reaction conditions, temperature etc). The aim of this study was to obtain (fermentable) saccharides and other valuable chemicals from wood by a combined heat and IL-treatment. Thermal treatments alone contribute to the degradation of polysaccharides (e.g. 150 °C alone is said to cause the degradation of polysaccharides), thus temperatures below that should be used, if the research interest lies on the IL effectiveness. On the other hand, the efficiency of the IL-treatment can also be enhanced to combine other treatment methods, (e.g. microwave heating). The samples of spruce, pine and birch sawdust were treated with either 1-Ethyl-3-methylimidazolium chloride, Emim Cl, or 1-Ethyl-3-methylimidazolium acetate, Emim Ac, (or with ionized water for comparison) at various temperatures (where focus was between 80 and 120 °C). The samples were withdrawn at fixed time intervals (the main interest treatment time area lied between 0 and 100 hours). Double experiments were executed. The selected mono- and disaccharides, as well as their known degradation products, 5-hydroxymethylfurfural, 5-HMF, and furfural were analyzed with capillary electrophoresis, CE, and high-performance liquid chromatography, HPLC. Initially, even GC and GC-MS were utilized. Galactose, glucose, mannose and xylose were the main monosaccharides that were present in the wood samples exposed to ILs at elevated temperatures; in addition, furfural and 5-HMF were detected; moreover, the quantitative amount of the two latter ones were naturally increasing in line with the heating time or the IL:wood ratio.