Hydrogen production by steam reforming of bio-alcohols:the use of conventional and membrane-assisted catalytic reactors

Abstract The energy consumption around the globe is on the rise due to the exponential population growth and urbanization. There is a need for alternative and non-conventional energy sources, which are CO2-neutral, and a need to produce less or no environmental pollutants and to have high energy efficiency. One of the alternative approaches is hydrogen economy with the fuel cell (FC) technology which is forecasted to lead to a sustainable society. Hydrogen (H2) is recognized as a potential fuel and clean energy carrier being at the same time a carbon-free element. Moreover, H2 is utilized in many processes in chemical, food, metallurgical, and pharmaceutical industry and it is also a valuable chemical in many reactions (e.g. refineries). Non-renewable resources have been the major feedstock for H2 production for many years. At present, ~50% of H2 is produced via catalytic steam reforming of natural gas followed by various down-stream purification steps to produce ~99.99% H2, the process being highly energy intensive. Henceforth, bio-fuels like biomass derived alcohols (e.g. bio-ethanol and bio-glycerol), can be viable raw materials for the H2 production. In a membrane based reactor, the reaction and selective separation of H2 occur simultaneously in one unit, thus improving the overall reactor efficiency. The main motivation of this work is to produce H2 more efficiently and in an environmentally friendly way from bio-alcohols with a high H2 selectivity, purity and yield. In this thesis, the work was divided into two research areas, the first being the catalytic studies using metal decorated carbon nanotube (CNT) based catalysts in steam reforming of ethanol (SRE) at low temperatures (<450 °C). The second part was the study of steam reforming (SR) and the water-gas-shift (WGS) reactions in a membrane reactor (MR) using dense and composite Pd-based membranes to produce high purity H2. CNTs were found to be promising support materials for the low temperature reforming compared to conventional catalyst supports, e.g. Al2O3. The metal/metal oxide decorated CNTs presented active particles with narrow size distribution and small size (~2–5 nm). The ZnO promoted Ni/CNT based catalysts showed the highest H2 selectivity of ~76% with very low CO selectivity <1%. Ethanol was shown to be a more suitable and viable source for H2 than glycerol. The dense Pd-Ag membrane had higher selectivity but a lower permeating flux than the composite membrane. The MR performance is also dependent on the active catalyst materials and thus, both the catalyst and membrane play an important role. Overall, the membrane–assisted reformer outperforms the conventional reformer and it is a potential technology in pure H2 production. The high purity of H2 gas with a CO-free reformate for fuel cell applications can be gained using the MR system.Tiivistelmä Maailman energiankulutus on kasvussa räjähdysmäisen väestönkasvun ja voimakkaan kaupungistumisen myötä. Tällä hetkellä energian tuottamisen aiheuttamat ympäristöongelmat ja taloudellinen epävarmuus ovat seikkoja, joiden ratkaisemiseksi tarvitaan vaihtoehtoisia ja ei-perinteisiä energialähteitä, joilla on korkea energiasisältö ja jotka tuottavat vähän hiilidioksidipäästöjä. Eräs vaihtoehtoisista lähestymistavoista on vetytalous yhdistettynä polttokennotekniikkaan, minkä on esitetty helpottavan siirtymistä kestävään yhteiskuntaan. Vety on puhdas ja hiilivapaa polttoaine ja energian kantaja. Lisäksi vetyä käytetään monissa prosesseissa kemian-, elintarvike-, metalli- ja lääketeollisuudessa ja se on arvokas kemikaali monissa prosesseissa (mm. öljynjalostamoissa). Uusiutumattomat luonnonvarat ovat olleet tähän saakka merkittävin vedyn tuotannon raaka-aine. Tällä hetkellä noin 50 % vedystä tuotetaan maakaasun katalyyttisellä höyryreformoinilla. Puhtaan (yli 99,99 %) vedyn tuotanto vaatii kuitenkin useita puhdistusvaiheita, jotka ovat erittäin energiaintensiivisiä. Integroimalla reaktio- ja puhdistusvaihe samaan yksikköön (membraanireaktori) saavutetaan huomattavia kustannussäästöjä. Biopolttoaineet, kuten biomassapohjaiset alkoholit (bioetanoli ja bioglyseroli), ovat vaihtoehtoisia lähtöaineita vedyn valmistuksessa. Tämän työn tavoitteena on tuottaa vetyä bioalkoholeista tehokkaasti (korkea selektiivisyys ja saanto) ja ympäristöystävällisesti. Tutkimus on jaettu kahteen osaan, joista ensimmäisessä tutkittiin etanolin katalyyttistä höyryreformointia matalissa lämpötiloissa (<450 °C) hyödyntämällä metallipinnoitettuja hiilinanoputkia. Työn toisessa osassa höyryreformointia ja vesikaasun siirtoreaktioa tutkittiin membraanireaktorissa käyttämällä vedyn tuotantoon tiheitä palladiumpohjaisia kalvoja sekä huokoisia palladiumkomposiittikalvoja. Hiilinanoputket (CNT) havaittiin lupaaviksi katalyyttien tukimateriaaleiksi verrattuna tavanomaisesti valmistettuihin tukiaineisiin, kuten Al2O3. CNT-tukiaineelle pinnoitetuilla aktiivisilla aineilla (metalli-/metallioksidit) todettiin olevan pieni partikkelikoko (~2–5 nm) ja kapea partikkelikokojakauma. Sinkkioksidin (ZnO) lisäyksellä Ni/CNT-katalyytteihin saavutettiin korkea vetyselektiivisyys (~76 %) ja erittäin alhainen hiilimoksidiselektiivisyys (<1 %). Etanolin todettiin olevan parempi vedyn raaka-aine kuin glyserolin. Tiheillä Pd-Ag-kalvoilla havaittiin olevan vedyn suhteen korkeampi selektiivisyys mutta matalampi vuo verrattuna palladiumkomposiittikalvoihin. Membraanireaktorin suorituskyky oli riippuvainen myös katalyytin aktiivisuudesta, joten sekä kalvolla että katalyyttimateriaalilla oli merkittävä rooli kyseisessä reaktorirakenteessa. Yhteenvetona voidaan todeta, että membraanierotukseen perustuva reformointiyksikkö on huomattavasti perinteistä reformeriyksikköä suorituskykyisempi mahdollistaen tehokkaan teknologian puhtaan vedyn tuottamiseksi. Membraanitekniikalla tuotettua puhdasta vetyä voidaan hyödyntää mm. polttokennojen polttoaineena

Measuring Coping in Parents of Children with Disabilities: A Rasch Model Approach

<div><p>Background</p><p>Parents of a child with disability must cope with greater demands than those living with a healthy child. Coping refers to a person’s cognitive or behavioral efforts to manage the demands of a stressful situation. The Coping Health Inventory for Parents (CHIP) is a well-recognized measure of coping among parents of chronically ill children and assesses different coping patterns using its three subscales. The purpose of this study was to provide further insights into the psychometric properties of the CHIP subscales in a sample of parents of children with disabilities.</p><p>Methods</p><p>In this cross-sectional study, 220 parents (mean age, 33.4 years; 85% mothers) caring for a child with disability enrolled in special schools as well as in mainstream schools completed the 45-item CHIP. Rasch analysis was applied to the CHIP data and the psychometric performance of each of the three subscales was tested. Subscale revision was performed in the context of Rasch analysis statistics.</p><p>Results</p><p>Response categories were not used as intended, necessitating combining categories, thereby reducing the number from 4 to 3. The subscale – ‘maintaining social support’ satisfied all the Rasch model expectations. Four item misfit the Rasch model in the subscale –maintaining family integration’, but their deletion resulted in a 15-item scale with items that fit the Rasch model well. The remaining subscale – ‘understanding the healthcare situation’ lacked adequate measurement precision (<2.0 logits).</p><p>Conclusions</p><p>The current Rasch analyses add to the evidence of measurement properties of the CHIP and show that the two of its subscales (one original and the other revised) have good psychometric properties and work well to measure coping patterns in parents of children with disabilities. However the third subscale is limited by its inadequate measurement precision and requires more items.</p></div

CNT-based catalysts for H2 production by ethanol reforming

Hydrogen production by steam reforming of ethanol (SRE) was studied using steam to ethanol ratio of 3 1 between the temperature range of 150-450 degrees C over metal and metal oxide nanoparticle catalysts (Ni, Co, Pt and Rh) supported on carbon nanotubes (CNTs) and compared to a commercial catalyst (Ni/Al2O3) The aim was to find out the suitability of CNTs supports with metal nanoparticles for the SRE reactions at low temperatures The idea to develop CNT based catalysts that have high selectivity for H-2 is one of the driving forces for this study The catalytic performance was evaluated in terms of ethanol conversion product gas composition hydrogen yield and selectivity to hydrogen The Co/CNT and Ni/CNT catalysts were found to have the highest activity and selectivity towards hydrogen formation among the catalysts studied Almost complete ethanol conversion is achieved over the Ni/CNT catalyst at 400 °C The highest hydrogen yield of 2 5 is however obtained over the Co/CNT catalyst at 450 °C The formation of CO and CH4 was very low over the Co/CNT catalyst compared to all the other tested catalysts The Pt and Rh CNT based catalysts were found to have low activity and selectivity in the SRE reaction Hydrogen production via steam reforming of ethanol at low temperatures using especially Co/CNT catalyst has thus potential in the future in e.g. the fuel cell applications

The patient health questionnaire-9: validation among patients with glaucoma.

BACKGROUND: Depression and anxiety are two common normal responses to a chronic disease such as glaucoma. This study analysed the measurement properties of the depression screening instrument - Patient Health Questionnaire-9 (PHQ-9) using Rasch analysis to determine if it can be used as a measure. METHODS: In this hospital-based cross-sectional study, the PHQ-9 was administered to primary glaucoma adults attending a glaucoma clinic of a tertiary eye care centre, South India. All patients underwent a comprehensive clinical evaluation. Patient demographics and sub-type of glaucoma were abstracted from the medical record. Rasch analysis was used to investigate the following properties of the PHQ-9: behaviour of the response categories, measurement precision (assessed using person separation reliability, PSR; minimum recommended value 0.80), unidimensionality (assessed using item fit [0.7-1.3] and principal components analysis of residuals), and targeting. RESULTS: 198 patients (mean age ± standard deviation  = 59.83±12.34 years; 67% male) were included. The native PHQ-9 did not fit the Rasch model. The response categories showed disordered thresholds which became ordered after category reorganization. Measurement precision was below acceptable limits (0.62) and targeting was sub-optimal (-1.27 logits). Four items misfit that were deleted iteratively following which a set of five items fit the Rasch model. However measurement precision failed to improve and targeting worsened further (-1.62 logits). CONCLUSIONS: The PHQ-9, in its present form, provides suboptimal assessment of depression in patients with glaucoma in India. Therefore, there is a need to develop a new depression instrument for our glaucoma population. A superior strategy would be to use the item bank for depression but this will also need to be validated in glaucoma patients before deciding its utility

Longshore currents on a meso-tidal beach of Goa, India - Measurements and improved formulae

867-877Field experiments in the surfzone were conducted on a meso-tidal beach stretch between Sinquerim and Baga off Goa on India's central west coast. Surfzone waves and currents were measured using an array of seabird wave and tide gauges and Aanderaa RCM9 current meters. Rip currents were observed prominently in this stretch with increased intensity during the ebb tide. Six longshore current prediction equations are tested for their suitability in this region. The Longshore Current (LSC) estimated using these equations showed a wide range of Mean Absolute Percentage Error (MAPE) and Scatter Index, and the correlation coefficients were also found to be less than 50 %. Hence, these equations are further modified by including the alongshore wind shear component, and the LSC was re-estimated to study the variations in current along the Candolim beach. It was observed that the correlation coefficients improved up to 64 % for most of the equations

Overall performance of the CHIP Subscales in parents of children with disabilities.

<p>CHIP- Coping Health Inventory for Parents.</p><p>* Misfitting items were deleted iteratively and the final 15-item revised version is only shown here. See text for details (results section).</p><p>Overall performance of the CHIP Subscales in parents of children with disabilities.</p

Person-item map for the Rasch-revised 15-item ‘maintaining family integration, co-operation, and an optimistic definition of the situation’ subscale of the Coping Health Inventory for Parents (n = 220).

<p>Participants are located on the left of the dashed line (represented by ‘x’) and participants with better coping ability are located at the top of the map. Items (i.e., coping patterns) are on the right of the dashed line with those considered to be least helpful located toward the top of the map. Each ‘x’ and “.” represent two and one participants respectively. Alongside each item is also indicated its abridged description and number as in the 45-item original CHIP. The complete description of items can be found in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0118189#pone.0118189.t002" target="_blank">Table 2</a> in the text. M, mean; S, 1 SD from the mean; T, 2 SD from the mean.</p

CNT-based catalysts for H-2 production by ethanol reforming

Hydrogen production by steam reforming of ethanol (SRE) was studied using steam to ethanol ratio of 3 1 between the temperature range of 150-450 degrees C over metal and metal oxide nanoparticle catalysts (Ni, Co, Pt and Rh) supported on carbon nanotubes (CNTs) and compared to a commercial catalyst (Ni/Al2O3) The aim was to find out the suitability of CNTs supports with metal nanoparticles for the SRE reactions at low temperatures The idea to develop CNT based catalysts that have high selectivity for H-2 is one of the driving forces for this study The catalytic performance was evaluated in terms of ethanol conversion product gas composition hydrogen yield and selectivity to hydrogen The Co/CNT and Ni/CNT catalysts were found to have the highest activity and selectivity towards hydrogen formation among the catalysts studied Almost complete ethanol conversion is achieved over the Ni/CNT catalyst at 400 degrees C The highest hydrogen yield of 2 5 is however obtained over the Co/CNT catalyst at 450 degrees C The formation of CO and CH4 was very low over the Co/CNT catalyst compared to all the other tested catalysts The Pt and Rh CNT based catalysts were found to have low activity and selectivity in the SRE reaction Hydrogen production via steam reforming of ethanol at low temperatures using especially Co/CNT catalyst has thus potential in the future in e g the fuel cell applications (C) 2010 Professor T Nejat Veziroglu Published by Elsevier Ltd All rights reserve

Item content of the Patient-Health Questionnaire-9.

<p>^*Framing question for all above items – “Over the last 2 weeks, how often have you been bothered by any of the following”.</p><p>Response options for all the above items: not at all (0), several days (1), more than half the days (2), nearly every day (3).</p