On the stability of carbon nanotube and titania nanowire based catalyst materials:from synthesis to applications

Abstract Degradation of the support and sintering of catalyst nanoparticles inherently leads to a loss of functionality of catalyst materials in converters and sensors. Malfunction in such devices may lead to serious economic and environmental damage. The quest for novel and sustainable catalyst materials with better durability is thus ongoing. In this thesis, one-dimensional nanomaterials such as carbon nanotubes and titanium dioxide nanowires are studied and compared to their conventional zero-dimensional counterparts in regard to their structural and functional stability. With the combination of several catalyst nanomaterials and supporting surfaces, aging properties of more than 70 different materials are assessed by the means of X-ray diffraction, transmission electron microscopy and energy-dispersive X-ray analyses. Although CNTs were shown to be thermally the most stable carbonaceous supports for metal nanoparticles, they are, similar to other carbon supports, more sensitive to high temperatures than metal oxide supports and can suffer deactivation by catalytic oxidation and gasification even at moderate temperatures. In addition, the irradiation of the samples with e-beams caused the most dramatic changes in CNT based materials, where nanosized deformities (voids, channels) were formed when either nanoparticles or defects were present. The prepared nanocompositions have been utilized successfully in three different applications including (i) synthesis of hydrogen from ethanol via a steam reforming reaction, (ii) hydrogenation of citral to form value added chemicals and (iii) the application of advanced electrode materials in electric double-layer capacitors. Both CNT and TiO₂ nanowire based nanomaterials were shown to outperform their conventional nano- and microparticle based counterparts in the studied catalytic reactions, i.e. in citral hydrogenation and steam reforming of ethanol, respectively. Furthermore, nanostructured CNTs obtained by catalytic partial oxidation of the material showed an increased specific surface area, which could be exploited in supercapacitor electrodes with enhanced specific capacitance.Tiivistelmä Katalyyttitukimateriaalin pilaantuminen ja katalyyttinanopartikkelien sintrautuminen johtavat siihen, että muuntajissa ja sensoreissa käytettävät katalyyttiset materiaalit eivät enää toimi, mikä voi aiheuttaa sekä vakavia taloudellisia haittoja että ympäristöhaittoja. Tämän vuoksi kehitetään uusia kestävämpiä katalyyttimateriaaleja. Tässä väitöskirjassa tutkittiin yksiulotteisia nanomateriaaleja, kuten hiilinanoputkia sekä titaanidioksidinanojohtimia ja verrattiin niiden rakenteellista ja toiminnallista stabiiliutta perinteisiin nollaulotteisiin vastineisiin. Erilaisten katalyyttinanomateriaalien ja tukimateriaalien yhdistelmien ikääntymistä arvioitiin röntgendiffraktion, läpäisyelektronimikroskopian ja energiadispersiivisen röntgenanalyysin avulla yli 70 erilaisesta näytteestä. Vaikka hiilinanoputket osoittautuivat termisesti stabiileimmaksi hiilipohjaiseksi tukimateriaaliksi metallinanopartikkeleille, ne ovat kuten kaikki hiilimateriaalit, metallioksiditukimateriaaleja herkempiä korkeille lämpötiloille. Hiilinanoputkipohjaiset katalyytit voivat deaktivoitua katalyyttisen hapettumisen tai kaasuuntumisen vuoksi jo kohtalaisissa lämpötiloissa. Lisäksi elektronisäteellä säteilytetyt nanopartikkelit tai pintavirheitä sisältävät hiilinanoputkipohjaiset katalyytit olivat tutkituista nanomateriaaleista herkimpiä muodostamaan nanorakenteita (koloja, kanavia). Valmistettuja nanokomposiitteja käytettiin onnistuneesti kolmessa eri sovelluksessa: i) vedyn valmistuksessa etanolista höyryreformointireaktiolla, ii) hienokemikaalien valmistuksessa sitraalin hydrauksella sekä iii) elektrodimateriaalina EDLC-kondensaattorissa. Sekä hiilinanoputki- sekä TiO₂-nanojohdinpohjaiset nanomateriaalit toimivat testatuissa katalyyttisissa reaktioissa (etanolin reformointi sekä sitraalin hydraus) paremmin kuin niiden perinteiset vastineet. Lisäksi superkondensaattorin ominaiskapasitanssia onnistuttiin nostamaan lisäämällä hiilinanoputkipohjaisen elektrodin ominaispinta-alaa katalyyttisella hapetusreaktiolla

Biogas drying and purification methods

In August 2020, Biogas2030 statement was made, where the goal for national biogas production and use in 2030 was set to 4 TWh. The goal is approximately four times higher than the current production rate in Finland. In order to reach this not only political decisions must be made but also new technologies and business models have to be created. In Finland, there is large potential for biogas production in agriculture, especially in animal farms, that created suitable biomasses through the year. Although the production of biogas in farms is growing all the time, the energy is often used in the farms as heat and power. The profitgained from the biogas would be better and also the availability of renewable fuels would increase in Finland if the biogas would be purified and sold as fuel. However, in a small scale with current technologies this is not profitable. HABITUS project (Decentralized Biogas Production and liquefaction in Finland, funded by Regional Council of Central Ostrobothnia, European Regional Development Fund) is answering this challenge by creating new technologies suitable for purification and liquefaction of biogas in the small scale. This report was written during summer 2020 for HABITUS project to review the current state and future trends of biogas purification and upgrading technologies

Hevosenlannan energiakäytön edistäminen Keski-Pohjanmaalla

Pääministeri Juha Sipilän hallitus asetti vuonna 2015 yhdeksi kärkihankkeeksi hevosenlannan käytön edistämisen energiantuotannossa. Hieman tämän jälkeen syksyllä 2015 Centria-ammattikorkeakoulu käynnisti Kokkola Industrial Symbiosis System, KISS-hankkeen, jonka yhtenä tavoitteena on ollut vastata hevosalan toimijoiden lannan käsittelyn haasteisiin tuottamalla tietoa hevosenlannan energiakäytön hyödyntämisen mahdollisuuksista. Kokkolassa ja sen lähialueilla on paljon hevosalan yrittäjiä ja hevosen omistajia, jolloin myös syntyvän lannan vuotuinen määrä on suuri. Myös aiemmin mainittu hallituksen kärkihanke hevosenlannan käytön edistämisestä energiantuotannossa oli osaltaan vaikuttamassa siihen, että päätettiin käynnistää selvitystyö hevosenlannan energiakäytön edistämisestä Keski-Pohjanmaalla. Selvityksestä saadun informaation on tarkoitus palvella sekä hevos- että energia-alan toimijoita lisäämällä tietoa hevosenlannan energiakäytön mahdollisuuksista ja lannan kustannustehokkaasta käsittelystä. Selvitystyön ensimmäisessä vaiheessa laadittiin kyselytutkimus Kokkolan ja sen lähialueiden hevosen omistajille ja hevosalan yrittäjille. Kyselytutkimuksessa kerättiin tietoja mm. vuositasolla syntyvistä lantamääristä sekä kustannuksista liittyen kuivikkeiden hankintaan ja lannan käsittelyyn. Toisessa vaiheessa kerättiin näytteitä kuivikkeesta sekä kuivikkeen ja lannan seoksesta alueen talleilta laboratoriotutkimuksia varten. Tavoitteena oli saada mukaan kaikki yleisimmin käytetyt kuiviketyypit kuten kutteri tai sahanpuru, olki ja turve. Selvitystyön kolmannessa vaiheessa tehtiin laboratoriotutkimuksia toisessa vaiheessa kerätyille näytteille. Näytteille tehtiin mm. lämpöarvo- ja alkuainemääritykset sekä okonaistyppipitoisuusmääritykset. Kaikki laboratoriotutkimukset tehtiin Centria-ammattikorkeakoulun laboratoriossa Kokkolassa lukuun ottamatta kokonaistyppipitoisuusmääritystä, joka tehtiin Ahma Ympäristö Oy:n laboratoriossa Oulussa. Selvitys on toteutettu osana Centria-ammattikorkeakoulu Oy:n hallinnoimaa KISS-hanketta (Kokkola Industrial Symbiosis System), joka käynnistyi 1.10.2015. KISS on ELY-keskuksen päärahoittama hanke, jonka tavoitteena on resurssiviisaamman toiminnan ja materiaalikiertojen sulkemisen avulla parantaa Kokkolan seudulla jo olemassa olevan liiketoiminnan kannattavuutta sekä synnyttää uutta teknologia- ja palvelutoimintaa

Portable cyber-physical system for indoor and outdoor gas sensing

Abstract A design, development and testing process for a cyber-physical system capable of versatile gas sensor measurement is described. Two approaches for the system are proposed; a stationary system for calibration and testing in laboratory environments and a portable system with wireless capability. The device utilizes a well-established Arduino microcontroller as well as a Raspberry Pi single board computer. The functionality is realized with C and Python programming languages. The operability is validated by system performance evaluation in the mixture of air and hydrogen gas, using both commercial and experimental Taguchi-type metal oxide semiconductor sensors. The experimental sensors are fabricated by inkjet printing platinum decorated tungsten oxide nanoparticles onto an electrode pattern on a silicon substrate which is then wire bonded to a chip carrier. The measurement platform demonstrated in our paper provides rapid prototyping capabilities for evaluating novel gas sensor materials in realistic measurement scenario

Influence of Metal Precursors and Reduction Protocols on the Chloride-Free Preparation of Catalysts for the Direct Synthesis of Hydrogen Peroxide without Selectivity Enhancers

Different metal precursors and reducing agents were applied in the preparation of 1 wt % Pd catalysts supported on commercial ion-exchange resin (Lewatit K2621) and used in the direct synthesis of H2O2. The catalysts were characterized by using TEM and their performance was evaluated in the direct synthesis of H2O2 (in a batch and semi-batch reactor) to investigate the relationship between the catalyst preparation methods, morphology, and catalytic performance. As expected, both the choice of the Pd precursor and the reduction conditions had a strong influence on the size and size distribution of the resulting supported nanostructured metal nanoparticles and, consequently, on the catalytic performance. The best combination of metal precursor and reduction agent was [Pd(NH3)4]SO4 reduced with hydrogen. This catalyst had the largest average size of the Pd nanoparticles and the broadest size distribution

Three-Dimensional Carbon Nanotube Scaffolds as Particulate Filters and Catalyst Support Membranes

Three-dimensional carbon nanotube scaffolds created using micromachined Si/SiO2 templates are used as nanoparticulate filters and support membranes for gas-phase heterogeneous catalysis. The filtering efficiency of better than 99% is shown for the scaffolds in filtering submicrometer particles from air. In the hydrogenation of propene to propane reaction low activation energy of E-a similar to 27.8 +/- 0.61 kJ . mol(-1), a considerably high turnover rate of similar to 1.1 molecules . Pd site(-1) . s(-1) and durable activity for the reaction are observed with Pd decorated membranes. It is demonstrated that appropriate engineering of macroscopic-ordered nanotube architectures can lead to multifunctional applications

Synthesis and characterization of ceria-supported catalysts for carbon dioxide transformation to diethyl carbonate

Abstract The support materials Al₂O₃, SiO₂ and TiO₂ were modified with 16 wt% CeO₂, using two different preparation methods evaporation-impregnation and precipitation-deposition. The synthesized 16 wt% CeO₂-Al₂O₃, 16 wt% CeO₂-SiO₂ and 16 wt% CeO₂-TiO₂ materials were characterized by means of X-ray powder diffraction for the phase purity, scanning electron microscopy for the morphology, nitrogen physisorption to determine the specific surface area and X-ray photo electron spectroscopy for the oxidation state of the Ce in the TiO₂, Al₂O₃ and SiO₂ matrices. Transmission electron microscopy was used to study the particle size of CeO₂ whereas CO₂-temperature programmed desorption (TPD) was used to determine the basicity of ceria-modified TiO₂, Al₂O₃ and SiO₂ catalysts. Furthermore, the catalytic performance of the as prepared CeO₂-modified catalysts were compared in the synthesis of diethyl carbonate starting from ethanol and CO₂ using butylene oxide as the dehydrating agent. The physico-chemical characterization results were correlated with the catalytic activity results and discussed in detail

2D tungsten chalcogenides:synthesis, properties and applications

Abstract Layered transition metal chalcogenides possess properties that not only open up broad fundamental scientific enquiries but also indicate that a myriad of applications can be developed by using these materials. This is also true for tungsten‐based chalcogenides which can provide an assortment of structural forms with different electronic flairs as well as chemical activity. Such emergence of tungsten based chalcogenides as advanced forms of materials lead several investigators to believe that a tremendous opportunity lies in understanding their fundamental properties, and by utilizing that knowledge the authors may create function specific materials through structural tailoring, defect engineering, chemical modifications as well as by combining them with other layered materials with complementary functionalities. Indeed several current scientific endeavors have indicated that an incredible potential for developing these materials for future applications development in key technology sectors such as energy, electronics, sensors, and catalysis are perhaps viable. This review article is an attempt to capture this essence by providing a summary of key scientific investigations related to various aspects of synthesis, characterization, modifications, and high value applications. Finally, some open questions and a discussion on imminent research needs and directions in developing tungsten based chalcogenide materials for future applications are presented

TiO2 nanoparticles: Vs. TiO2 nanowires as support in hydrogen peroxide direct synthesis: The influence of N and Au doping

The performance of Pd on titania support were evaluated in the direct synthesis of hydrogen peroxide. The equipment used was a high pressure, semi-batch apparatus equipped with a special injection system. Pd (1 wt%) catalysts on TiO2 materials with different nature were prepared by wet impregnation method. Three aspects were investigated: (a) the structure of the support (nanoparticles vs. nanowires); (b) the addition of a second active metal (Au); (c) the influence of N-doping of the support. All samples were characterized by means of XPS, TEM and XRD analyses. TiO2 nanoparticle supported catalyst demonstrated higher H2O2 selectivity and higher turnover frequency (TOF) than the catalysts based on TiO2 nanowires. The addition of Au to the Pd TiO2 nanowire catalyst improved the H2O2 selectivity due to altered particle size and electronic effects. Both N-doped versions of the catalysts gave rise to higher H2O2 selectivity than the parent non-doped ones. The synthetic procedure was the source of this observation: larger mean Pd nanoparticles were present, thus favouring the formation of H2O2 as the primary product. © 2016 Royal Society of Chemistry