Catalyst Development

Graphitic carbon nitride was synthesized via thermolysis of urea and then ultrasonic exfoliated from colloidal solution to obtain phase pure ultrafine powder of g-C 3 N 4 . It was shown that ultrasonic-assisted exfoliation of the initial graphitic carbon nitride powder leads to an increase in its phase purity (PXRD), a change in the morphology (SEM), a decrease in the band gap from 2.93 eV to 2.85 eV (DRS) and an increase in the specific surface from 58.6 m 2 /g to 136.7 m 2 /g (BET). In addition, it was found that the exfoliated g-C 3 N 4 is an effective catalyst for the process of electrocatalytic reforming -the hydrogen evolution from the water-alcohol solution. Based on volamperometry, it was found that the hydrogen overpotential of graphitic carbon nitride is equal to 249 mV (at 10 mA/cm 2 ), and the Taffel slope is 112 mV/dec. The results of cyclic voltammetry of the electrode based on exfoliated g-C 3 N 4 indicate its high stability, which allows us to consider the exfoliated graphitic carbon nitride as a promising basis of materials for electrocatalytic reforming of alcohols.

2018 Summer.Includes bibliographical references.Lean burn two stroke engines are used extensively for stationary applications including power generation, cogeneration and compression. Natural gas is abundant, relatively inexpensive, and combustion produces less CO2, particulate matter, and SOx than gasoline and diesel. However, the Natural gas industry continues to be impacted by increasingly stricter emissions limits. One approach to comply with these emission limits is outfitting engines with an oxidation catalyst. Oxidation catalysts are proven to reduce hydrocarbon and carbon monoxide emissions, but surface poisoning due to lube oil carry over diminishes performance. Zinc, phosphorus, and sulfur found in oil additives poison the catalysts surface, and readily leach into an acidic environment. Two commercial catalyst modules were aged at a field site on a slipstream of a GMVH-12 engine until they no longer met the National Emissions Standards for Hazardous Air Pollutants (NESHAP)...

The thermochemical process converts almost any kind of biomass to a desired final product, i.e. gaseous or liquid transportation fuels and chemicals. The transportation fuels obtained in this way are renewable biofuels, which are alternatives to fossil fuels. During the last few years, thermochemical plants for the production of bioethanol have been launched and another is under construction. A total of about 290 million liters of ethanol are expected to be processed per year, mostly using municipal solid waste. Considerable efforts have been made in order to find a more selective catalyst for the conversion of biomass-derived syngas to ethanol. use of mesoporous catalyst have been found over a Cu/MCM-41 catalyst, shown in Paper V. Also in Paper V, the effect of metal promoters (Fe and K) has been studied; a noticeable increase of ethanol reaction rate was found over Cu-Fe-K/MCM-41 catalyst as compared to Cu/MCM-41.

Hydroxyapatite, a bioceramic material, possesses sufficient stability in aqueous and organic medium and it is mainly known for its role in tooth and bone structure. However, it is less-known that, in certain conditions, the HA can be used as a catalyst in its free, metal-doped and composite forms. HA as a catalyst is generally prepared by i mpregnation or co-precipitation methods, sometimes from natural P-containing wastes. HA can be doped with mono-or polymetallic ions or nanoparticles and can contain other admixtures or supports (i.e., carbon). Different Ca/P ratios (ideal 1.67; the ranges are 1.5e1.7 in synthetic and 1.5e1.8 in biologic forms) can be revealed for the HA. Nanosized HA forms are frequent in several applications. A variety of distinct processes can be HA-catalyzed, such as oxidation of alcohols, dehydrogenation, hydrogenation and hydrogenolysis, CC bond formation, among other important existing low-and large-scale organic processes. The HA can be also used for catalytic environmental remediation, CO 2 fixation, and N 2 O decomposition. In this review, we emphasize most recent advances (mainly last decade) on the catalytic HA applications, except for biomedical ones.

This paper presented the kinetic study of molybdenum borides via the Volmer-Heyrovsky-Tafel (V-H-T) mechanistic steps for hydrogen evolution reaction (HER). A theoretical approach was carried out to investigate the kinetic properties of several molybdenum boride materials for HER in 0.5 M H2SO4. Our findings offer definitive proof that the simulated results show that B, Mo, Mo2B, and α-MoB, proceed through V-H mechanistic steps (slower kinetics) while β-MoB and MoB2 exhibit V-H-T mechanistic steps with higher kinetics. The kinetic parameters were determined in terms of the standard rate constant parameters for the Volmer step (kV, k-V), Heyrovsky step (kH, k-H), and rate constant for the Tafel step (kT, k-T). The simulation was able to predict the overpotential at 10 mA/cm2, η10 recorded at approximately 780, 585, 480, 350, 310, and 300 mV for B, Mo, Mo2B, α-MoB, β-MoB, and MoB2 respectively. Based on these findings, the adopted mathematical model shows good coherency to the experimental findings. The simulation work provides a good numerical estimation of the characteristics of the electrocatalyst for HER. This paper successfully elucidated the reaction mechanisms (V-H-T steps) and understood the rate-limiting steps involved in the HER process on Mo-B materials.

Biomass gasification as a thermochemical treatment method is typically used for heat and power production. Instead of burning the producer gas, it can be converted to added-value products, i.e to fuels and chemicals. One such conversion is the catalytic Fischer-Tropsch synthesis (FTS) which converts synthesis gas to a chain of aliphatic hydrocarbons (FT diesel) as studied in this thesis. This requires, however, proper cleaning steps of producer gas, such as the removal of tar compounds and other impurities. These cleaning steps are not considered in this thesis. The first goal of the thesis was to determine the tar content in the producer gas from a small scale biomass gasifier. This subject is discussed in Paper I. The second and main goal of the thesis was the preparation and characterization of cobalt (or iron) catalysts for catalytic conversion of a gas mixture close to the synthesis as discussed in Papers II-V. The overall aim of the second part was to study the effects of promoters on the reducibility of cobalt and the effects of different calcination conditions on the degree of reduction and size of the metallic cobalt particles. In this later part different catalytic supports were used. According to the results of the thesis, naphthalene and toluene were the main tar compounds in the producer gas representing almost 80 % of the GC detected tar compounds. Only traces of polycyclic aromatic compounds were detected and no phenolic compounds were found in the gas. Further, a number of supported heterogeneous catalysts for FTS using cobalt (Co) or in some cases iron (Fe) as the active metal were prepared and characterized. These catalysts were supported on alumina (Al 2 O 3), titanium dioxide (TiO 2) or silicon carbide (SiC). Catalysts were promoted with Ru, Re or Rh in the concentrations of 0, 0.2, 0.5, and 1.0 mass-%. Several characterization methods (such as H 2-TPR, catalytic activity measurements, N 2 physisorption, CO chemisorption, X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD)) were used to find answers to the behaviour of these catalysts under selected conditions and in the model reaction of FTS. Based on the results, there are significant differences in the characteristics of the catalysts, the differences are dependent of the supports used, promoters added and calcination conditions used. The properties of the support, especially the pore size distribution will effect the distribution of products formed in the Fischer-Tropsch synthesis. Addition of promoters and variatons in calcination conditions will effect the dispersion and the particle size of the active metal.

A carbonization-sulfonation method was utilized in synthesizing sulfonated mesoporous catalysts from palm tree biomass. Brunauer-Emmet-Teller (BET), powder X-ray diffraction (XRD), energy dispersive X-ray (EDX), and field emission scanning emission microscopy (FE-SEM) analyses were used to evaluate the structural and textural properties of the catalysts. Further, Fourier transform infrared (FT-IR) spectroscopy and titrimetric analyses measured the strong acid value and acidity distribution of the materials. These analyses indicated that the catalysts had large mesopore volume, large surface area, uniform pore size, and high acid density. The catalytic activity exhibited by esterifying used frying oil (UFO) containing high (48%) free fatty acid (FFA) content further indicated these properties. All catalysts exhibited high activity, with sPTS/400 converting more than 98% FFA into fatty acid methyl esters (FAMEs). The catalyst exhibited the highest acid density, 1.2974 mmol/g, determined by NaOH titration. This is outstanding considering the lower reaction parameters of 5 h, 5:1 methanol-to-oil ratio, and a moderate temperature range between 100 and 200 °C. The study further illustrates the prospect of converting wastes into highly efficient, benign, and recyclable solid acid catalysts.

Double promoted γ-alumina heterogeneous base catalyst (CaO/KI/γ-alumina) was firstly developed for the production of biodiesel from palm oil in refluxed methanol. This study have been conducted in order to improve the activity of single promoted catalyst (CaO/γ-alumina) and to enhance the efficiency of biodiesel production that have been done in the previous work. The CaO/KI/γ-alumina catalyst was prepared by precipitation and impregnation methods. Engineering catalyst done with some parameters that effect on the activity of a catalyst among other: % CaO loading (wt. % against alumina), temperature and time of calcinations. The catalyst was characterized by mean of XRD, and BET methods. The activity of catalyst has been tested by introduced to the transesterification reaction of palm oil. The reaction was carried out in the batch type of reactor (three-neck glass flask with 500 ml capacity) equipped with reflux condenser, thermometer and magnetic stirrer. The result showed that the optimum condition of preparation catalyst (% of CaO loading, temperature and time of calcinations) were 30%, 650°C and 4.5 h, respectively. Under the optimum condition of catalyst, reaction temperature 65°C, reaction time 5 h and oil to methanol molar ratio of 1:42 the biodiesel yield was almost 95%. Therefore, it can be proved that the activity of double promoted catalyst (CaO/KI/γ-alumina) much higher than that the single promoted (CaO/γ-alumina) catalyst.

Catalysis of the hydrogen evolution reaction (HER) is important in the development of an energy economy based on clean hydrogen gas. In this work, we report a new catalyst material for the generation of hydrogen via hydronium reduction. The new material, which consists of MoO 2 , sulfur, and graphene, was prepared by co-reduction of molybdenum salt and graphite oxide in air in the presence of focused solar radiation. The potential utility of this material for HER catalysis was evaluated by cyclic and linear-sweep voltammograms and compared against a Pt/C commercial catalyst. The MoO 2 /graphene hybrid nanocomposite exhibits a Tafel slope of 47 mV/dec and hydrogen evolution at a potential onlỹ 120 mV more negative than the standard Pt/Carbon catalyst at 10 mA/cm 2 current density. The hydrogen gas generated by the catalytic material was measured using gas chromatography. The simple synthesis and low overpotential suggests that this hybrid composite has potential as an HER catalyst.

Highlights  Few-layered MoS2 are deposited onto 3D interconnected porous carbon nanosheets to increase the exposure of active edges.  The few-layered MoS2 are vertically aligned on the 3D interconnected porous carbon nanosheets through a simple solvothermal reduction method.  The obtained nanocomposite shows an excellent catalytic activity in HER.

Extraction of neutral nitrogen-containing compounds (N-compounds) has been investigated with chloride based ionic liquids (ILs) with varying cation classes (imidazolium, pyridinium). ILs were first discriminated by their mutual solubility of ILs and model fuel. Low solubility of 1-butyl-3-methylimidazolinium chloride (BMImCl) and 1-octylpyridinium chloride (OcPyCl) in the model fuel was observed. The ILs were then evaluated using a synthetic solution with dibenzothiophene and carbazole as model compounds, and a high selectivity for N-compounds was found. BMImCl and OcPyCl were then evaluated using straight-run diesel feed, containing 13 400 ppm S and 105 ppm N. An extraction of up to 50% of the N-compounds was obtained in one step whereas the sulfur concentration reduction was only 5%. Both ILs can be regenerated using small amount of water. Extracted compounds could be then extracted using toluene. The major constituents were identified by GC-MS. Analysis of the extracted compounds emphasized the selectivity of the extraction process. Furthermore, refractory sulfur-containing compounds (S-compounds) and polyaromatics were also identified in the extract.

Aluminum chloride-urea ionic liquid was investigated for its active species concentration with the aide of electronic spectroscopy by Lewis acid-base titration with chloride ions. A coordination bonds between aluminum cationic species of the ionic liquid and the aromatic ring of toluene or benzene was assumed to be responsible for new formed bands in visible and ultraviolet regions. Upon Lewis acid-base titration these bands disappeared and the concentration of the acidic species were elucidated to be around 75 mole% of the initial aluminum chloride used to prepare a 1.5 mole aluminum chloride to 1 mole urea ionic liquid. The product of this reaction assumed to be between 1 acidic species to 1 chloride ion according to the mole fraction elucidated graph.

A CuO-ZnO-Al 2 O 3 catalyst was synthesized by an ultrasound assisted co-precipitation method and compared with the one synthesized by a conventional co-precipitation method. The characterization results of XRD, BET, FESEM and FTIR indicated that the physicochemical properties of the catalysts are strongly influenced by the formulated precursor and the synthesis method. The morphology of the catalyst precipitated under ultrasound irradiation was well-defined and agglomoration-free with average size particle of 32.3 nm. The dispersion of CuO and the surface area of the catalyst exhibited an improvement in acetate based catalyst. The high degree of synergism effect between CuO and other components in CuO-ZnO-Al 2 O 3 catalyst was expected in the acetate-based catalyst synthesized with ultrasound assisted co-precipitation method due to low crystallinity and small size of copper species. The catalytic performance for the synthesis of methanol was examined at 200-300°C and 10-40 bar in a stainless steel reactor. The CuO-ZnO-Al 2 O 3 catalyst synthesized from acetate precursor precipitated under ultrasound irradiation exhibited a supreme catalytic activity at 275°C, 40 bar, 18,000 cm 3 /g h and H 2 /CO = 2 in terms of CO conversion and methanol yield.

Fischer-Tropsch (FT) synthesis activity and the stability of a Co/SiO 2 catalyst modified with Mn-and Zr were examined under various practical conditions. Dependence of FT synthesis on reaction pressure and benchscale FT synthesis were investigated. Evaluating catalyst lifetime during continuous FT reactions was conducted. The Co + Mn + Zr/SiO 2 catalyst exhibited relatively greater activity and stable reactivity for 168 h. Sulfur resistance of catalysts were investigated and results showed that the presence of 4 ppm H 2 S drastically affected catalytic activity. The Co + Mn + Zr/SiO 2 catalyst exhibited greater activity even with H 2 presence and the sulfur poisoning rate was almost similar on both Co + Mn + Zr/SiO 2 and Co/SiO 2 catalysts.

The Fischer-Tropsch synthesis (FTS) for the conversion of carbon monoxide and hydrogen to higher hydrocarbons was investigated over a supported Cu/Co catalyst promoted by dielectric-barrier discharges (DBDs) at relatively low temperatures and ambient pressure. The effect of plasma power, operation pressure, and H 2 /CO molar ratio on the activity and selectivity of the catalyst in a DBD reactor were studied. The fresh and used catalyst samples were characterized by scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray, and X-ray diffraction. We also used DBDs in catalyst preparation as a technique to enhance metal distribution on the catalyst support. The present study reveals that plasma can promote the FTS over a Cu/Co-based catalyst at low temperatures and ambient pressure. The formation of methane was strongly suppressed in plasma. In contrast to conventional FTS, CO conversion was higher at low operating pressure than that at higher pressure in the DBD-promoted FTS, which indicates the presence of a new reaction path for FTS.

Exploring efficient noble-metal-free water splitting electrocatalysts from earth-abundant elements is of great importance to realize wide applications in the generation of hydrogen fuel for clean energy. Here we reported a facile route to synthesize ε-Fe 3 N single-phase nanoparticles by thermal ammonolysis of Fe precursors. The roles of nitrogen atoms in tailoring the hydrogen evolution reaction (HER) activities of ε-Fe 3 N have been systematically investigated. HER activity is enhanced by reducing the effective coordination number of nitrogen atoms from 2.61 to 1.67, where the standard coordination number in ε-Fe 3 N is 2. Density functional theory (DFT) calculations reveal that the reduction of nitrogen content lowers the energy of the Tafel process on the (̅ 100)-FeN exposed and (11 ̅ 0) N-exposed surfaces. Both surfaces are thermodynamically favored for the HER. Furthermore, the active sites of the Tafel process changes from the kinetically less favored hollow sites of Fe atoms to the kinetic more favored top site of N atoms and the bridge site of Fe atoms on both (̅ 100)-FeN and (11 ̅ 0) N-exposed surfaces. Our findings propose a novel strategy to enhance This article is protected by copyright. All rights reserved. 3 HER activity by utilizing nitrogen deficiency, which is of great importance for the development of highly active transition metal based electrocatalysts.

This review aims to provide an overview of the main catalytic studies of H 2 production by ethanol steam reforming (ESR). The reaction is endothermic and produces H 2 , CO 2 , CH 4 , CO and coke. The conversion and H 2 selectivity of these products depended greatly of the physicochemical properties of the catalysts, active metal, promoters, temperature, longterm reaction, water/ethanol ratio, space velocity, contact time, and presence of O 2. Initial total conversion has been reported in all catalysts evaluated between 300 and 850 C. The noble catalysts with high selectivity to H 2 (more than 80%) were: Rh, Ru, Pd and Ir and non-noble metal catalysts were: Ni, Co and Cu. The support materials include CeO 2 , ZnO, MgO, Al 2 O 3 , zeolites-Y, TiO 2 , SiO 2 , La 2 O 2 CO 3 , CeO 2 eZrO 2 and hydrotalcites. The impregnation method produced the best noble metal catalysts in terms of selectivity and conversion. The decrease of coke was related with the presence of basic sites on the support.

The advantages of homogeneous transition catalysts are to some extend damped by the necessity to separate, and if possible recycle, the catalyst from the solution. Immobilization of catalysts on a solid support is a frequently used strategy, but the general drawback is a lower catalyst activity and selectivity. We now report a new strategy to monitor catalyst immobilization by imaging with two-photon fluorescence microscopy at sub-micrometer level. To this end a diphosphine ligand with intrinsic fluorescent properties, which gives rise to active and selective rhodium hydroformylation catalysts was immobilized on a glass surface using traditional methods. The imaging of the immobilized ligand uncovered clustering of the ligands and therefore of the catalyst particles, explaining part of the deterioration of the catalyst performance compared to the homogeneous phase system. Based on these results a simple new immobilization process was developed that did not give rise to clustering and the supported rhodium catalysts gave activities and selectivities that are close to the homogeneous catalyst, with the advantage that separation and recycling can be done by simple filtration processes.. Catalyst recovery is an important topic in the area of homogeneous catalysis since the product-catalyst separation is one of the main obstacles towards application of these classes of catalysts. So far, several strategies for catalyst recycling have been explored, 1 but a general strategy remains elusive. A widely studied approach to facilitate catalyst-product separation is the attachment of homogeneous catalysts to polymeric organic, inorganic, hybrid, or dendrimeric supports. 2-5 Inorganic materials have shown to be particularly suited as solid support for homogeneous catalysts because of their physical strength and chemical inertness and many of such immobilized catalytic systems have been reported. A common drawback, however, remains the generally lower activity and selectivity compared to the homogeneous counterpart. It is known that the properties of the solid support affects the catalytic reaction to a certain extend. Surprisingly, an in-depth investigation of the effect of the immobilization process on the

From the past decades, microbial fuel cells (MFCs) have evolved as a green alternative to produce electrical energy from organic matter degradation. Cathode modification significantly enhances the overall MFC performance. In this work, we report on ZIF-8 and carbon nanotubes (CNTs) derived catalyst materials as cathode for MFC. The catalysts were prepared via high-temperature pyrolysis at 900 • C and were physically characterized by various analytical techniques. All the catalyst materials carry tubular arrangements of CNTs covering the ZIF-8 crystals and exhibit highly micro-mesoporous texture. The electrocatalytic activity for oxygen reduction reaction (ORR) was studied in 0.1 M phosphate buffer at a catalyst loading of 0.2 mg cm − 2. The FeCo-N-C@900 catalyst showed the highest ORR activity with half-wave potential of 0.71 V vs RHE and limiting current density of − 5.62 mA cm − 2 at 1900 rpm. When tested in MFC, FeCo-N-C@900 coated cathode delivered the maximum power density of 1557 mW m − 2 (comparable to Pt/C catalyst reaching P max of 1681 mW m − 2) with chemical oxygen demand (COD) removal efficiency of 87.3%. The Next generation DNA sequencing analysis revealed the accumulation of various exoelectrogenic bacterial strains i.e., Bacillus, Desulfovibrio, Comamonadaceae sp. etc. commonly found in anaerobic biomass and showing the successful enrichment of the biofilm responsible for oxidizing organic matter at the anode. The present study illustrates the potential of transitional metal-doped ZIF-8 and CNTs composite electrocatalysts for enhancing the power output of MFC with generating promising power and current densities.

Promotion par les métaux nobles de catalyseurs Fischer-Tropsch à base de cobalt : une revue-La synthèse Fischer-Tropsch est une part essentielle du procédé XTL (X-To-Liquids, avec X = Gaz, Biomasse ou Charbon) qui convertit du gaz de synthèse en hydrocarbures pour carburants propres. Les catalyseurs à base de cobalt supportés sur des oxydes inorganiques constituent le meilleur compromis pour la production de paraffines à longues chaînes carbonées et de cires. L'efficacité du procédé Fischer-Tropsch dépend très fortement de la performance du catalyseur à base de cobalt. La promotion de ce catalyseur par des métaux précieux peut très fortement améliorer ses performances. Cet article fait la revue des différents effets des métaux nobles sur la structure et la performance de catalyseurs à base de cobalt. Les impacts sur le coût et l'activité des catalyseurs apparaissent comme des éléments incontournables dans le design de catalyseurs performants pour la synthèse Fischer-Tropsch.

Telah dilakukan sintesis katalis Pd/Ce/Zeolit, sintesis dilakukan dengan cara impregnasi larutan garam palladium dan serium pada zeolit , kalsinasi dilakukan pada suhu 600 ºC dengan dialiri N2 selama 4 jam kemudian O2 selama 1 jam selanjutnya direduksi dengan H2 pada 900 ºC selama 5 jam. Karakterisasi katalis dilakukan dengan menggunakan difraktometer sinar-X dan uji katalitik dilakukan terhadap umpan gas CO, banyaknya CO yang terkonversi ditentukan dengan kromatografi gas. Disimpulkan bahwa spesies logam yang terbentuk adalah Pd(0), PdO, PdO2, Ce2O3,dan Ce6O11. Katalis Pd/Ce/zeolit pada konsentrasi Ce 3 % adalah yang terbaik mempunyai ukuran partikel PdO/ Ce2O3 279,09/263,69 dengan kemampuan konversi terhadap gas CO 78,789 % pada suhu 700 ºC.

In heterogeneous catalysis, the interface between active metal and support plays a key role in catalyzing various reactions. Specially, the synergistic effect between active metals and oxygen vacancies on support can greatly promote catalytic efficiency. However, the construction of high-density metal-vacancy synergistic sites on catalyst surface is very challenging. In this work, isolated Pt atoms were first deposited onto a very thin-layer of MoO3 surface stabilized on γ-Mo2N. Subsequently, the Pt-MoOx/γ-Mo2N catalyst, containing abundant Pt cluster-oxygen vacancy (Ptn-Ov) sites, was in situ constructed. This catalyst exhibited an unmatched activity and excellent stability in the reverse water-gas shift (RWGS) reaction at low temperature (300 ºC). Systematic in situ characterizations illustrated that the MoO3 structure on the γ-Mo2N surface could easily deoxidize into MoOx (2

Artykuł wyjaśnia, czym są i jaką rolę odgrywają katalizatory. Obrazowo działanie katalizatora przyrównano do estakady na rondzie, która przyspiesza ruch i kieruje go na właściwe tory. Katalizator także przyspiesza reakcję chemiczną i kieruje ją na właściwe tory - nie ulegając przy tym zużyciu.

A series of copper ion substituted MAl2O4 (M= Mg, Mn, Fe and Zn) spinels is prepared by a single step solution combustion synthesis (SCS) and tested for methanol steam reforming (MSR). The copper ion substituted Cu0.1Fe0.9Al2O4 appears to be the most active, showing ~98% methanol conversion at 300 °C with ~5% CO selectivity at GHSV= 30000 h-1 and H2O:CH3OH= 1.1. The analogous impregnated catalyst, CuO (10 at.%)/FeAl2O4, is found to be much less active. These materials are characterized by XRD, H2-TPR, BET, HRTEM, XPS and XANES analyses. Spinel phase formation is highly facilitated upon Cu-ion substitution, and Cu loading beyond 10 at.% leads to the formation of CuO as an additional phase. The ionic substitution of copper in FeAl2O4 leads to the highly crystalline SCS catalyst containing Cu 2+ ion sites that are shown to be more active than the dispersed CuO nano-crystallites on the FeAl2O4 impregnated catalyst, despite its lower surface area. The as prepared SCS catalyst contains also a portion of copper as Cu 1+ that increases when subjected to reforming atmosphere. The MSR activity of the SCS catalyst decreases with time-on-stream due to the sintering of catalyst crystallites as established from XPS and HRTEM analyses.

Direct hydrothermal synthesis of mordenite without the addition of both seed and organic template is reported in this work. The role of inorganic cations in the crystal purity and directing the mordenite structure were studied. It was observed that higher Si/Al ratio requires higher alkalinity of the gel. Pure mordenite was obtained using silica gel, colloidal silica and fumed silica. Amorphous material was obtained using tetraethyl orthosilicate (TEOS) due to dissolution problem of TEOS in water. It was also observed that crystal size decrease with decrease in crystallization temperature. The Si/Al ratio can be raised to as high as 50 using silica gel in template-free process. At fixed Na/Si ratio of 0.52, pure mordenite with ratios Si/Al of 15 and 25 could be obtained. fumed silica favours the formation of rod-like crystals.

Lewis acidic ionic liquid (IL) of 1-octyl-3-methylimidazolium tetrachloroferrates ([Omim]FeCl 4) with an interesting structure, was synthesized and introduced as a highly effective catalyst and also as extractive solvent in oxidative desulfurization (ODS) of model and real diesel fuels with H 2 O 2 oxidant. FT-IR, H-NMR and TG-DSC analysis were used for characterization of the prepared ILs. GC-FID, GC-PFPD and GC-MS measurements were also employed to investigate the ODS yields and mechanism. The adequate structure and acidic properties of [Omim]FeCl 4 allowed removal of thiophenic compounds with high efficiency in an extraction and then oxidation process. The effects of the major processing variables on ODS performance of [Omim]FeCl 4 were studied in detail. At the optimal conditions of V IL /V oil of 1/10, O/S molar ratio of 5, reaction time of 15 min and room temperature, BT and DBT were totally eliminated, and 4,6-DMDBT was removed by 99% from the model diesel. Moreover, [Omim]FeCl 4 was able to desulfurize two real diesel fuels containing 590 and 2573 ppmw of sulfur with the efficiency of 85% and 61.2%, respectively, at a short time of 15 min. The experimental results also showed a remarkable selectivity of 0.919 for elimination of thiophenic compounds in competition with nonsulfur aromatic model of 2-methyl naphthalene. [Omim]FeCl 4 exhibited an excellent recyclability with no significant decline in activity after use in 7 reaction cycles. An overall mechanism was also suggested for desulfurization by the proposed system.

Graphene oxide (GO) was deposited on the surface of a MnO2 air cathode by thermal evaporation at 50°C from a GO colloidal suspension. Fourier transformed infrared spectroscopy and field emission scanning electron microscopy confirmed the presence of GO on the MnO2 air cathode (GO-MnO2). Voltammetry and chrono-amperometry showed increased currents for the oxygen reduction reaction (ORR) in 6 M KOH solution for GO-MnO2 compared to the MnO2 cathode. The GO-MnO2 was used as an air cathode in an alkaline tin-air cell and produced a maximum power density of 13 mW cm−2, in contrast to MnO2, which produced a maximum power density of 9.2 mW cm−2. The electrochemical impedance spectroscopy results suggest that the chemical step for the ORR is the rate determining step, as proposed earlier by different researchers. It is suggested that the presence of GO and electrochemically reduced graphene oxide (ERGO) on the MnO2 surface are responsible for the increased rate of this step, whereby GO and E...

Long, highly oriented, semiconducting graphene nanoribbons (GNRs) are fabricated by chemical vapor deposition (CVD) on Ge(001) substrate. However, these anisotropic nanoribbons are apt to randomly distribute on Ge surface, which hinders their scalable applications in high‐performance graphene electronic devices. In this work, it is proved that the alignment of GNRs is closely related to the miscut angle of vicinal Ge(001) substrate. By investigating the growth behaviors of the GNRs on vicinal Ge(001) substrates with 0°, 4°, 8°, and 12° miscut toward Ge[111], it can be found that GNRs tend to nucleate along the orientation perpendicular to the miscut direction with the increase of miscut angle, and unidirectional GNRs are successfully synthesized on 12° miscut Ge(001) surface. Moreover, the shape of GNRs is also tuned by the miscut angle, which undoubtedly affects the aspect ratio of these GNRs. These promising results demonstrate that synthesizing unidirectional GNRs by the proposed...

Structuring of different types of catalytic active centers at a single-pellet level appears to be a promising and powerful tool for integration and intensification of multistep solid-catalyzed chemical reactions. However, the enhancement in the product yield and selectivity strongly depends on the proper choice of the distribution of different catalysts within the pellet. To demonstrate potential benefits from properly designed catalyst pellet, numerical studies were conducted with the aid of the mathematical model of a single spherical bifunctional catalyst pellet. The analysis was performed both for a system of two generic chemical reactions and for a real process, i.e., direct synthesis of dimethyl ether (DME) from synthesis gas via methanol. Evaluation of the pellet performance was done for three arrangements of the catalytic active sites within the pellet, i.e., a uniform distribution of two types of catalytic active centers in the entire volume of the pellet, and two core–shel...

Controlling the selectivity in single step conversion of syngas to single aromatic hydrocarbon to enhance the CO utilization is a big challenge. By adapting the reaction coupling methodology, which allows the precise control of CC coupling reaction, we obtained a high selectivity ~70% of a single product, tetramethylbenzene (TeMB), in hydrocarbons, at total CO conversion of 37%. This was enabled by the reaction of H 2deficient syngas over a composite catalyst of physically mixed nano-sized ZnCr 2 O 4 and H-ZSM-5. The H-ZSM-5 employed in this work appeared as coffin shape with short straight channels [010] along b-axis which exhibit low molecular diffusion resistance, results in high selectivity of aromatics particularly TeMB. Due to selective methanol Page 2 of 43 ACS Paragon Plus Environment ACS Catalysis 3 formation and enhanced molecular diffusion, we observed an aromatic vacancy created inside H-ZSM-5 pores, which boost the transformation of olefins into aromatics, thus making the aromatic cycle dominant in a dual cycle mechanism and gave high yield of aromatics and TeMB. Furthermore, no catalyst deactivation was observed within 600hr of reaction time using hydrogen deficient syngas. Therefore, by rejecting the need of extra H 2 addition into the STA reaction system, direct conversion of H 2-deficient syngas derived from coal/biomass into TeMB makes an attractive industrial process.

the processes to valorize biomass is via biomass to liquids (BTL), in which the biomass is transformed to synthesis gas and subsequently to liquid fuels. Synthesis gas can be converted to chemicals or fuels via a range of different processes. An interesting alternative is Fischer-Tropsch synthesis (FTS), a catalytic reaction by which syngas is transformed into a wide range of hydrocarbons. The reaction can be catalyzed by group VIII elements, but in commercial applications only Fe and Co are currently employed. Cobalt is interesting due to its high activity at low temperature (200 − 300 ºC), high selectivity towards long chain hydrocarbons, low production of oxygenates and alkenes and high durability. However, by optimizing the synthesis method and operation conditions, it is possible to tune the selectivity towards different products. To increase the profitability of the BTL and FT process, it is possible to adjust the product distribution to more valuable products. Among the FT products, light olefins represent added value compared to fuels, which always will be the main product [2]. The demand for these products has been increasing every year. Ethylene, propylene and olefinic C 4 fractions, mostly produced by steam cracking or recovered from oil refineries, are key building blocks in the petrochemical industry. In the case of propylene, the gap between the

Melting/freezing points of AlCl 3 in saturated chloroaluminate ionic liquids [molar ratio 2:1 AlCl 3 : 1-ethyl-3-methyl imidazolium chloride (EMIC)] are measured by differential scanning calorimetry (DSC). A critical range of temperature data (50-130°C) for AlCl 3 dissolution and precipitation from saturated chloroaluminate ionic liquids is obtained. This range of temperature data is of significance to control phase transition of AlCl 3 in saturated chloroaluminate ionic liquids. By applying the chloroaluminate ionic liquids to electrolytes for energy storage usage, solid AlCl 3 can be partially dissolved and precipitated out during the charging/discharging cycle of energy storage equipment. Therefore, the energy density of the electrolytes is expected to be greatly improved.

Direct hydrothermal synthesis of mordenite without the addition of both seed and organic template is reported in this work. The role of inorganic cations in the crystal purity and directing the mordenite structure were studied. It was observed that higher Si/Al ratio requires higher alkalinity of the gel. Pure mordenite was obtained using silica gel, colloidal silica and fumed silica. Amorphous material was obtained using tetraethyl orthosilicate (TEOS) due to dissolution problem of TEOS in water. It was also observed that crystal size decrease with decrease in crystallization temperature. The Si/Al ratio can be raised to as high as 50 using silica gel in template-free process. At fixed Na/Si ratio of 0.52, pure mordenite with ratios Si/Al of 15 and 25 could be obtained. fumed silica favours the formation of rod-like crystals.

In this work, we synthesized the metal-organic framework ZIF-67 (MOF) by the hydrothermal method. The XRD spectrum of this MOF was consistent with the spectrum given in the literature, which indicated the successful synthesis of ZIF-67. Following the calcination process of the MOF, ruthenium metal was added to the catalyst as a promoter by impregnation method to synthesize Co-Ru@NC composite catalyst. In addition, we synthesized the Co-Ru@ZSM-5 and Co-Ru@ɤ-Al2O3 catalysts by the impregnation method. We performed the characterization tests such as atomic absorption, EDX, ESEM, TEM, BET, XRD, and H2-TPR to find out the surface and volume of the catalysts, formed phase, reduction temperature, hydrogen consumption, and catalyst morphology. Moreover, we carried out Fischer-Tropsch Synthesis (FTS) to obtain the CO conversion, hydrocarbon product selectivity, hydrocarbon chain growth probability, and reaction yield using the synthesized catalysts. The results of using three catalysts showe...

Ethanol and higher alcohols are one of the most interesting alternatives to replace fossil fuels in the transportation sector. Nickel-modified alkali-doped molybdenum sulfide is a potential catalyst for the conversion of syngas to mixed alcohols. In this work, K-Ni-MoS 2 catalysts were synthetized by coprecipitation in aqueous solution or in microemulsions, followed by alkali doping. The influence of the preparation route in CO hydrogenation was investigated at 91 bar, 340/370 • C and GHSV = 2000-14,000 NmL/h g catalyst. The catalysts were also characterized by TGA, ICP, XPS, nitrogen adsorption, XRD, SEM-EDX and TEM. The novel microemulsion catalyst outperformed the conventional one, resulting in higher yields of ethanol and higher alcohols. The higher activity and selectivity was attributed to a higher concentration of promoters on the microemulsion catalyst surface, together with a lower degree of crystallinity.

 methane catalytic conversion is conducted over biomass char to produce H2  deposited pyrolytic carbon is regenerated by steam gasification  regeneration of char is effective  effect of minerals on char organisation and reactivity isA c c e p t e d M a n u s c r i p t 3/3

Different amount of boron-modified Ni/Mo 2 C were synthesized, characterized and tested during the hydrogenation of alkali lignin, to evaluate the effect of boron on the Ni promoted behavior. xB-Ni/Mo 2 C (x = 0.5, 1, 3, 5) is found to enhance the lignin conversion and bio-oil yield at the same time, and the highest bio-oil yield was obtained with 1B-Ni/Mo 2 C (63.8%), under the optimum reaction condition (2 MPa H 2 , 290 °C and 2 h). Characteristic results of BET method, ICP-OES, XRD, Raman, SEM, TEM, XPS, H 2-TPR and NH 3 /CO 2 /CO-TPD indicate the improved catalytic performance comes from strong interaction between boron and nickel species, which results in improved surace area, highly dispersed Ni particles, increased acidic sites, thus favors cleavage of the CO and CC bonds. A possible reaction mechanism was also present based on the catalytic system.

CQDs were synthesized by facile and one-step electrochemical method. One-step electrochemical method was employed for deposition of CQDs. A green, low-cost and electrochemically-synthesized electrocatalyst was introduced. Enhancement of hydrogen evolution reaction was evaluated. The Ni-Cu/RCQD nanocomposite, offers promising option as cathodic electrode for HER.

Platinum–dysprosium (Pt–Dy) alloys prepared by the arc melting technique are assessed as potential electrodes for the oxygen reduction reaction (ORR) using voltammetry and chronoamperometry in alkaline media. A relatively small change (10 at.%) in the alloy composition brought a notable difference in the alloys’ performance for the ORR. Pt40Dy60 electrode, i.e., the electrode with a lower amount of Pt, was identified to have a higher activity towards ORR as evidenced by lower overpotential and higher current densities under identical experimental conditions. Furthermore, DFT calculations point out the unique single-atom-like coordination and electronic structure of Pt atoms in the Pt40Dy60 surface as responsible for enhanced ORR activity compared to the alloy with a higher Pt content. Additionally, Pt–Dy alloys showed activity in the oxygen evolution reaction (OER), with the OER current density lower than that of pure Pt.

NiAl 2 O 4 with high surface area was synthesized by the combustion method, evaluating the effect of urea/nitrate (U/N) ratio. The use of a stoichiometric U/N ratio resulted in a material with high surface area and homogeneous nanocrystallites, while the excess of fuel resulted in a non-porous material with low surface area. The formation of superficial Ni nanoparticles resulted in excellent stability on CO 2 methane reforming. This can be attributed to the rearrangement of nickel in the aluminate matrix and the migration of nickel particles through carbon filaments at the surface during the activation process.

I, Ahmed Umar, hereby certify that this thesis, which is approximately 80,400 words in length, has been written by me, and that it is the record of work carried out by me, or principally by myself in collaboration with others as acknowledged, and that it has not been submitted in any previous application for a higher degree. I was admitted as a research student in November, 2011 and as a candidate for the degree of PhD in September, 2012; the higher study for which this is a record was carried out in the University of St Andrews between 2011 and 2015. Date: 14 th June, 2016 signature of candidate …….……………….……… I hereby certify that the candidate has fulfilled the conditions of the Resolution and Regulations appropriate for the degree of PhD in the University of St Andrews and that the candidate is qualified to submit this thesis in application for that degree. Date: 14 th June, 2016 signature of supervisor ……..……………….……… In submitting this thesis to the University of St Andrews I understand that I am giving permission for it to be made available for use in accordance with the regulations of the University Library for the time being in force, subject to any copyright vested in the work not being affected thereby. I also understand that the title and the abstract will be published, and that a copy of the work may be made and supplied to any bona fide library or research worker, that my thesis will be electronically accessible for personal or research use unless exempt by award of an embargo as requested below, and that the library has the right to migrate my thesis into new electronic forms as required to ensure continued access to the thesis. I have obtained any third-party copyright permissions that may be required in order to allow such access and migration, or have requested the appropriate embargo below. The following is an agreed request by candidate and supervisor regarding the publication of this thesis: Embargo on electronic publication of thesis for a period of one year but access to printed copy on the following reason: Publication would preclude future publication. Date 14 th June, 2016 signature of candidate ….………..signature of supervisor……………… 5.2 Glycerol steam reforming over Ni/γ-Al 2 O 3 for hydrogen production………………………………………………………………………………………………163 5.

In this work, we used a dissociative mechanism to perform calculations based on Density Functional Theory, DFT, and electronic structure in order to study the oxygen reduction reaction on graphene doped with iron. The model takes into account some of the operating conditions of a proton exchange membrane fuel cell such as the equilibrium of hydrogen oxidation reaction, electrode potential of 1.23 V and 0 V, solvation effects, and corrections to the energy at the zero point (ZPE) and the entropic one. However, in this approach, we neglect the effects on the free energy of the interaction of the adsorbed species with the electric field due to the double electrochemical layer, the pH of the acid medium, and the oxygen coverage. The free energy diagrams for different intermediate steps of the oxygen reduction reaction, ORR, the oxygen adsorption energy on sites close to those occupied by the Fe-atoms, as well as the activity calculations indicated that Fe-Graphene (Fe-G) system, may possess catalytic properties close to either Pt, as catalyst, as its alloys since they can favor the ORR in a fuel cell proton exchange membrane. The results have been compared with other theoretical studies which use graphene as a central element as will be established in the present manuscript.

Because of the energy shortage and global warming effects, renewable and clean energies have received great attention [1-4]. Among them, bio-energy has a potential to offer a significant portion of the projected renewable energy provisions of the future. For example, ethanol (EtOH) has been widely used, serving as a good additive for improving the gasoline octane value and burning efficiency [5-7]. Currently, ethanol is mainly produced by two major classes of processes: (1) biological processes via fermentation of sugars derived from corn, sugar cane or sorghum [8], and (2) chemical transformation via hydrogenation of carbon (C) and oxygen (O) contained materials, such as carbon monoxide (CO) and fructose [9]. In the hydrogenation of synthesis gas (syngas), molybdenumbased carbides (b-Mo 2 C) have been greatly tested, especially for those of alkali-modified b-Mo 2 C [10,11]. As the previous study described [12], molybdenum carbide mainly produced light alkanes, whereas its modification with potassium (K) was found to significantly enhance the selectivity to alcohols composed of linear alcohols of C 1-C 7 (C 1-C 7 OH). The addition of K to b-Mo 2 C catalyst led a remarkable shift of the products from hydrocarbons (HCs) to alcohols, and further exhibited highly active and excellent promotion effect to enhance the selectivity to C 2 + OH [13-15]. Vanadium (V) used as a promoter can be easily reduced into low

Effects of reaction conditions on the production of alcohols (AOHs) and alkanes (Alk) from CO and H 2 , which can be obtained from the gasification of biomass, using a molybdenum sulfide (MoS 2)-based catalyst of MoS 2 /γ-Al 2 O 3 were studied. A high-pressure fixed packed bed (HPFPB) was employed to carry out the reaction. The results indicate that the conversion of CO (X CO) and specific production rates of alcohol (SPR AOH) and alkane (SPR Alk) are highly depended on temperature (T). In T = 423-573 K, maximum yield of alcohols (Y AOH) and SPR AOH occur at T = 523 K. In the meantime, well performance gives the selectivity of ethanol (S EtOH) of 52.0 C%. For the studies on varying H 2 /CO mole ratio (M H/C) from 1 to 4 at 523 K, the appropriate M H/C to produce EtOH is 2, giving higher ratios of SPR AOH /SPR Alk and Y AOH /Y Alk than those with other M H/C. As for varying the total gas flow rates (Q G) of 300, 450, 600 to 900 cm 3 min −1 tested at T = 523 K and M H/C = 2, the lower Q G provides longer reaction time (or gaseous retention time, t R) thus

Nowadays, plasmonic nanomaterials have become more attractive owing to their enhanced surface sensitivity towards species adsorption. Here we report on Ag-decorated MoO 3 nanotubes (Ag-MNTs) were obtained via a straightforward two-step process, involving anodizing synthesis of blue MoO x nanosheets in water, followed by adding an AgNO 3 complex. It was observed that, depending on the Ag:Mo molar ratio, the solution bleached to light green or brown colors. Based on TEM, XRD, UV-Vis, Raman spectroscopy, and XPS, we found that this is due to a process in which MoO x nanosheets transform into MoO 3 nanotubes (MNTs), and formation of Ag NPs decorated on those nanotubes. The Ag-MoO 3 colloidal solutions achieved were sensitive to hydrogen injection as the color return to a light green/blue color. Our data show that the Mo oxide stoichiometry is reversible in a hydrogenation/dehydrogenation cycle. But the structure of MNTs collapses due to the interaction with hydrogen. However, the real-time hydrogen doping was studied by UV-Vis spectrometry on sealed hydrogenated solutions. This process led to a spectral shift in Ag plasmonic peak, and change in the absorption strength with a correlation to Ag:Mo molar ratio, and MoO x LSPR absorption, which was assumed to be proportional to the hydrogen doping level.