Thesis (Ph. D.)--Institute of Paper Chemistry, 1976. / Bibliography: leaves 110-114.

Microporous organic polymers (MOPs) are porous materials. Owing to their high surface area, tunable pore sizes and high physicochemical stability, they are studied for applications including gas capture and separation and heterogeneous catalysis. In this thesis, a series of imine/azo-linked MOPs were synthesized. The MOPs were examined as potential CO2 sorbents and as supports for heterogeneous catalysis. The MOPs were synthesized by Schiff base polycondensations and oxidative couplings. The porosities of the imine-linked MOPs were tunable and affected by a range of factors, such as the synthesis conditions, monomer lengths, monomer ratios. All the MOPs had ultramicropores and displayed relatively high CO2 uptakes and CO2-over-N2 selectivities at the CO2 concentrations relevant for post-combustion capture of CO2. Moreover, the ketimine-linked MOPs were moderately hydrophobic, which might increase their efficiency for CO2 capture and separation. The diverse synthesis routes and rich functionalities of MOPs allowed further post-modification to improve their performance in CO2 capture. A micro-/mesoporous polymer PP1-2, rich in aldehyde end groups, was post-synthetically modified by the alkyl amine tris(2-aminoethyl)amine (tren). The tethered amine moieties induced chemisorption of CO2 on the polymer, which was confirmed by the study of in situ infrared (IR) and solid-state 13C nuclear magnetic resonance (NMR) spectroscopy. As a result, the modified polymer PP1-2-tren had a large CO2 capacity and very high CO2-over-N2 selectivity at low partial pressures of CO2. Pd(II) species were incorporated in the selected MOPs by means of complexation or chemical bonding with the imine or azo groups. The Pd(II)-rich MOPs were tested as heterogeneous catalysts for various organic reactions. The porous Pd(II)-polyimine (Pd2+/PP-1) was an excellent co-catalyst in combination with chiral amine for cooperatively catalyzed and enantioselective cascade reactions. In addition, the cyclopalladated azo-linked MOP (Pd(II)/PP-2) catalyzed Suzuki and Heck coupling reactions highly efficiently. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Accepted. Paper 7: Manuscript.</p>

Utilizando a Teoria do Funcional da Densidade junto com o formalismo do pseudopotencial de primeiros princípios, realizamos um estudo sistemático do processo de adsorção da molécula de oxigênio sobre a superfície livre de CdTe (110) nas reconstruções 1x1, 1x2 e 2x1. Este estudo consistiu na determinação das adsorções energeticamente favoráveis e na viabilidade de suas formações através da análise das barreiras de ativação. Nossas análises indicam que apenas uma molécula de oxigênio adsorve sobre a superfície livre em uma reconstrução 1x1 e que não ocorre a quebra da molécula durante o processo de adsorção. As estruturas formadas foram divididas nos regimes de baixas e altas temperaturas. Do estudo das barreiras de ativação verificamos que no regime de baixas temperaturas a molécula de oxigênio liga-se exclusivamente ao Cd da primeira camada através de ligações Cd-O-O ou Cd-O2. A configuração da superfície de CdTe com a molécula adsorvida, se assemelha a configuração do cristal. As estruturas de faixas de energia neste regime apresentam um estado característico de defeito duplo aceitador. Para o regime de altas temperaturas, a molécula adsorve entre o Cd da primeira camada e o Te da segunda camada, quebrando esta ligação Cd-Te e também quebrando a ligação que o Cd da segunda camada realiza com o Te da terceira camada. O complexo formado apresenta ligações Cd-O, Cd-O2, Te-O e O-O e as estruturas de faixas de energia apresentam um gap indireto entre os pontos gama e X de 1.30 eV. / Density Functional Theory with first-principles pseudopotential formalism have been used to a systematic research of the oxygen molecule adsorption on the free surface of CdTe(110) in the 1x1, 1x2 and 2x1 reconstructions. This research was based on the determination of the adsorptions energetically favorables and the viability of each formation through their activation barriers analysis. This analysis indicates that only one oxygen molecule adsorbs over the free surface of the CdTe(110) in the 1x1 reconstruction and that the dissociation of the molecule does not occur during the adsorption process. The structures were divided on the high and low temperature regimes. From the activation barriers study it was verified that on the regime of low temperatures the oxygen molecule bind exclusively to the Cd of the first layer through the Cd-O-O or Cd-O$_2$ bonds. The CdTe surface configuration with the adsorbed molecule looks like a crystal configuration. The energy band structure, on this regime, shows a characteristic state of double acceptor defect. For the high temperature regime the molecule adsorbs between the Cd of the first layer and the Te of second layer, breaking the Cd-Te bond between them and also breaking the bonds that the Cd of the second layer does with the third layer. The complex shows Cd-O, Cd-O2, Te-O and O-O bonds and the energy band structure shows an indirect gap between the gamma and X points of 1.30eV.

No description available.

Well-defined silica supported bimetallic catalysts Pt100-x Pdx (where x is the molar ratio of Pd) are prepared by Surface Organometallic Chemistry (SOMC) via controlled decomposition of Pd2(allyl)2Cl2 on Pt/SiO2. For comparison purposes, Pt100-x Pdx bimetallic catalysts is also prepared by ion-exchange (IE). According to the results of STEM, XAS and H2 chemisorption, all bimetallic nanoparticles, prepared using neither SOMC nor IE, produce discrete formation of monometallic species (either Pt or Pd). Most catalysts exhibit a narrow particle size distribution with an average diameter ranging from 1 to 3 nm for samples prepared by IE and from 2 to 5 nm for the ones synthesized by SOMC. For all catalysts investigated in the present work, iso-butane reaction with hydrogen under differential conditions (conversions below 5%) leads to the formation of methane and propane (hydrogenolysis), n-butane (isomerization), and traces of iso-butylene (dehydrogenation). The total rate of reaction decreases with increasing the Pd loading for both catalysts series as a result of decreasing turnover rate (expressed as moles converted per total surface metal per second) of both isomerization and hydrogenolysis. In the case of Pt100-x Pdx(SOMC) catalysts, the results suggest a selective coverage of Pt (100) surface by a Pd layer, followed by a buildup of Pd overcoat onto a Pd layer assuming that each metal keeps its intrinsic catalytic properties. There is no mutual electronic charge transfer between the two metals (DFT). For the PtPd catalysts prepared by IE, the catalytic behavior cannot simply be explained by a surface coverage of highly active Pt metal by less active Pd (not observed), suggesting there is formation of a surface alloy between Pt and Pd collaborated by EXAFS and DFT. The catalytic results are explained by a simple structure activity relationship based on the previously proposed mechanism of C-H bond and C-C Bond activation and cleavage for iso-butane hydrogenolysis, isomerization, cracking and dehydrogenation.

<p>Space and water heating contribute over 50% of all the residential building energy consumption and are especially major energy consumers in the cold climates. Meanwhile, conventional furnaces and boilers with energy efficiency limited to below 100% dominate the residential heating in the cold climate, and the electric vapor-compression heat pump capacity and efficiency decline drastically at low ambient temperatures. Thermally driven ammonia-based chemical adsorption (chemisorption) heat pump (CSHP) systems utilize the reversible chemical reaction between the ammonia vapor and solid sorbent to generate heat pumping effect, which can provide heating with much higher energy efficiency than existing cold-climate heating technologies. Despite the significant potential of energy efficiency improvement from existing technologies, most studies in the literature on chemisorption heat pump systems focus on adopting the technology for refrigeration and energy storage applications, with very limited investigations available for using the technology for producing heating in cold climates. </p> This thesis study is thus conducted to characterize the operation behavior and performance of a CSHP system under cold ambient conditions and further identify optimal design and control for such systems to achieve high performance. In this study, both experimental and modelling approaches are pursued to investigate a CSHP heating system from the perspective of the sorption material using the multiple-stage LiCl-ammonia reactions, to the novel adsorber component with hybrid heat pipe heat exchanger, and finally to the performance of the complete heat pump system. The experimental studies are based on a prototype CSHP system tested to identify the chemical kinetics of the sorption material, as well as the transient performance of the adsorber and the system. The calibrated chemical kinetics are then used in the development of a transient adsorber model to analyze the operation and improve design of the adsorber. The heating COP of the prototype system was measured to be 0.75-1.16 under ambient temperatures of 8-20 C. Finally, a dynamic system model is developed based on the dynamic models of the adsorber and other components in the system. The system model is validated against the experimental data and used to analyze the detailed energy flow and operation dynamic. Based on the inefficiencies revealed by the simulation of the current prototype system, an improved system design with reduced thermal mass and heat loss is introduced. Simulation of the improved system results in heating COP of 1.17 to 1.23 under -13.9 C to 8.3 C ambient, respectively.

The Diesel Oxidation Catalyst (DOC) is subjected to harsh conditions, causing its performance to diminish over time as the result of different aging mechanisms, which either decreases or lowers the accessibility to the catalyst’s active sites. Previous work using chemisorption to quantify aging progression has resulted in a reproducibility of 17%. In this study it has been attempted to lower this, while also performing performance evaluations to see if correlations exist between dispersion and Light-Off Temperature (LOT). Two catalysts have been investigated, LLC (Low Loading Catalyst) and HLC (High Loading Catalyst). These were hydrothermally aged at 600 C, 700 C and 800 C. In addition to these, two HLC engine cell samples were also investigated. To ensure sample homogeneity, different sample preparation methods were investigated. Catalyst samples were crushed, or had their washcoat layer removed, or were milled and then sieved. A total of 5 runs were done using fresh catalysts of LLC and HLC to calculate the standard deviation. Evaluation of performance was done on all samples using Synthetic Catalyst Activity Testing (SCAT). It was deemed that the only viable sample preparation method was to mill and sieve as other methods would be hard to reproduce. The results showed that the reproducibility for LLC was %STD = 4% and for HLC %STD = 2%. For LLC, a correlation between catalytic activity and dispersion was found. The activity dropped with respect to the dispersion in a close to linear fashion without a large effect on BET surface area. For HLC the dispersion decreased largely upon hydrothermal aging, however no correlation was found with the activity; only when aged at 800 C a significant change in LOT was noted. The BET surface area measurements were inconsistent. Lower dispersion sometimes resulted in higher surface area. Engine cell samples exhibited notable decrease in dispersion, but not in surface area, and did not correlate to the hydrothermally aged catalysts, which might be due to other effects inhibiting CO chemisorption during measurements. / Dieseloxidationskatalysatorn (DOC) utsätts för tuffa förhållanden, vilket medför att dess prestanda minskar med tiden på grund av olika åldringsmekanismer, vilka antingen minskar dess aktiva säten eller minskar tillgängligheten till dessa. Tidigare studier då kemisorption använts för att kvantifiera vilken utsträckning katalysatorn har blivit deaktiverad har resulterat i en reproducerbarhet på 17%. Denna studie har syftat till att minska detta, men även till att utföra prestandamätningar för att se om det existerar korrelationer mellan dispersion och tändtemperatur (LOT). Två katalysatorer undersöktes, LLC (lågladdad katalysator) och HLC (högladdad katalysator), både som färska, men även som hydrotermiskt åldrade i 600 C, 700 C and 800 C. Dessutom undersöktes två motorcellsprover av HLC. För att säkerställa provhomogenitet undersöktes olika provprepareringsmetoder. Katalysatorprover krossades, eller fick washcoat avlägsnat eller maldes samt siktades. Totalt fem körningar gjordes på färska katalysatorer (LLC och HLC). Prestandamätningar gjordes på samtliga prov i Synthetic Catalyst Activity Testing (SCAT). Det bedömdes att den enda gångbara provprepareringsmetoden var att mala samt sikta katalysatorn då de andra metoderna skulle bli svåra att upprepa på ett reproducerbart sätt. Resultaten visade att reproducerbarheten för LLC var %STD = 4% och för HLC %STD = 2%. LLC visade på korrelation mellan katalytisk aktivitet och dispersion. Aktiviteten minskade linjärt utan större förluster i BETytarea. För HLC minskade dispersionen i hög grad med ökad åldringstemperatur, däremot kunde ingen korrelation med katalytisk aktivitet påvisas; enbart då katalysatorn åldrades vid 800 C ändrades LOT signifikant. Förändringarna i BET-ytarean var inte beroende av åldringstemperatur då lägre dispersion ibland resulterade i högre ytarea. För motorcellsproverna uppmättes en märkbart låg dispersion, medan ytarean var relativt oförändrad. Dessa resultat kunde inte korreleras till de hydrotermiskt åldrade proverna, vilket kan bero på att andra effekter inhiberat CO kemisorptionen.

M. Tech. (Chemistry, Faculty of Applied and Computer Science), Vaal University of Technology / The abundance of agricultural waste materials has led to its use as adsorbents for trace metal adsorption. The raw Macadamia nutshell (RMN) powder was treated with a hydrochloric acid solution to obtain acid modified Macadamia nutshells (AMM), and with sodium hydroxide solution to obtain base modified Macadamia nutshells (BMM). Then, the AMM and BMM materials were grafted with 0.5 M, 1 M, and 2 M acrylic acid. The different AMM grafted materials were labelled 0.5 GAM, 1 GAM and 2 GAM representing the different grafting ratios. The same naming order was followed for the BMM grafted materials, that is, 0.5 GBM, 1 GBM and 2 GBM corresponding to different concentrations used. The prepared Macadamia based adsorbents were characterized using Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), carbon, hydrogen, nitrogen and sulphur (CHNS) analysis, powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) analysis. The determination of surface properties such as the point of zero charge (pHPZC), bulk density and the surface negative charge was accomplished with appropriate wet chemistry methods. The adsorption of selected trace metals (Cu(II), Cd(II), Co(II), and Cr(VI)) was done in batch experiments. Atomic absorption spectroscopy (AAS) was used for the determination of metal ions concentrations and total Cr. The ultraviolet-visible (UV–Vis) spectroscopy was used for the determination of Cr(VI) concentration remaining in solution after adsorption. The RMN, AMM, and BMM adsorbents showed potential in removing more than 45% Cu(II) ions, but less than 30% for both Cd(II) and Co(II) ions. However, more than 90% removal of Cr(VI) ions was achieved with the same adsorbents. Consequently, only the adsorption of Cr(VI) was further investigated in the study due to the higher removal efficiency displayed by the Macadamia based biosorbents. The optimum adsorption conditions for the RMN, AMM, and BMM materials were found to be pH 2, 100 mg/L initial concentration of Cr(VI), 600 min contact time and 0.2 g adsorbent mass. The ideal conditions for the 0.5 GAM and 0.5 GBM were found to be pH 2, 25 mg/L initial concentration of Cr(VI), 180 min contact time, and 0.15 g adsorbent mass. The optimum temperature was found to be 40℃ for all materials. A volume of 20 mL was used for all batch experiments. The RMN, AMM, BMM, 0.5 GBM, and 0.5 GAM adsorption mechanisms were better described by the Langmuir isotherm which predicted a monolayer sorption process. The kinetic data fitted better to the pseudo second-order rate model which signified a chemisorption type of interaction. The thermodynamic parameters showed that the adsorption reaction was feasible, spontaneous and endothermic. The Macadamia based materials showed greater potential as adsorbents for the adsorption of Cr(VI) ions from aqueous solution compared to the other selected trace metal ions [Cd(II), Cu(II) and Co(II)].

Density functional theory calculations were performed to study the dissociative chemisorption of methane over Pt(111) with the idea of finding the minimum energy path for the reaction and its dependence on surface coverage. Two approaches were used to evaluate this problem; first, we used different sizes of supercells (2x2, 3x3, 4x4) in order to decrease surface coverage in the absence of pre-adsorbed H and CH3 fragments to calculate the energy barriers of dissociation. The second approach uses a 4x4 unit cell and surface coverage is simulated by adding pre-absorbed H and CH3 fragments. Results for both approaches show that in general the height of the dissociation barriers increases as the surface coverage increases, although, the first approach yields slightly lower barriers due to the fact that all repeatable images of the incident molecule are approaching the surface simultaneously. Using the reaction path formulation we were able to compute the potential energy surface for CH4 dissociation. Our results suggest that excitation of the symmetric stretch and bend modes will likely increase the probability for reaction.

No description available.