Aidan M. Doyle

Investigation of nickel supported catalysts for the upgrading of brown peat derived gasification products

Abstract A gasification test rig was designed in which peat was gasified under nitrogen over a temperature range 25–550°C at 5° C min −1 . The gasification unit resulted in 35.5 wt% of the carbon present in the peat being converted to a volatile fraction. The volatile fraction was transferred to a secondary catalytic reforming reactor at 800°C. The thermal effect of the second reactor resulted in an increase in the CO, CO2 and CH4 content of the volatile fraction, a syngas ratio of 0.75 and a higher heating value (HHV) of 26.5 MJ kg −1 . Several nickel-supported catalysts were investigated with the intention that they should give an increase in the conversion of the condensable hydrocarbons in the volatile fraction to CO, CO2 and CH4, and a resultant gas stream suitable for use in an integrated gasification combined cycle plant (IGCC) (i.e. syngas ratio 2:1, low methane content and better HHV). Alumina-supported nickel catalysts investigated gave the highest activities and co-precipitated Ni/Al catalysts were most active. A Ni/Al 3:17 catalyst increased the conversion of the hydrocarbons to 91.5%, gave a syngas ratio of 1.81:1, increased the HHV by a factor of 5.3 and completely eliminated methane from the gas stream.

Synthesis of 2-cyanoethyl-modified MCM-48 stable to surfactant removal by solvent extraction: Influence of organic modifier, base and surfactant

Abstract A 2-cyanoethyl grafted MCM-48 mesoporous silicate, which was stable to surfactant removal by solvent extraction, was synthesised by co-condensation of 2-cyanoethyltriethoxysilane and tetraethyl orthosilicate in basic conditions using cetyltrimethylammonium bromide as surfactant. The presence of the organic group was verified by infrared analysis. Additional studies confirmed that the concentration of sodium hydroxide used for this synthesis influenced the mesopore properties. MCM-41 and MCM-48 were formed using a narrow range of base concentrations while preparations outside this range gave disordered materials with reduced porosity. Materials synthesised using various quantities of cetyltrimethylammonium bromide showed that MCM-48 was formed over a range of surfactant concentrations although the order varied considerably. The mesopore phase was further adjusted by altering the concentration of 2-cyanoethyltriethoxysilane modifier. Preparations using 0–10 and 20 mol% organic modifier (of total silica) produced MCM-48 and MCM-41, respectively, while greater modifier concentrations gave disordered materials with significantly diminished porosity characteristics.

Shape-Selective Adsorption of Substituted Aniline Pollutants from Wastewater:

ZSM-5 zeolite was used to treat wastewater containing aniline, 2-nitroaniline (2-NA), 3-nitroaniline (3-NA) and 4-nitroaniline (4-NA). Each molecule was removed from aqueous solution by Type I Langmuir adsorption onto ZSM-5. The quantities adsorbed varied greatly due to their shape-selective adsorption within the pores of ZSM-5. Aniline and 4-NA had maximum adsorption amounts of 161 and 265 mg g−1, respectively, while the maximum amounts of 3-NA and 2-NA were 94.3 and 37.2 mg g−1, corresponding to reductions of 64% and 86%, respectively, relative to 4-NA. This outcome was caused by the increase in the effective diameter for adsorption when the nitro group was located at the 2- and 3- positions of the molecule. This significantly reduced their ability to enter into, and diffuse through, the pores of ZSM-5. These findings underpin the importance of choosing the correct substrate when using such materials for water purification.

Indirect Observation of Structured Incipient Zeolite Nanoparticles in Clear Precursor Solutions

The structure of the zeolite precursor particles present in clear synthesis solutions yielding colloidal silicalite-1 (purely siliceous zeolite with MFI-type structure) is one of the most controversial issues in modern zeolite science. Owing to the nature of the synthesis and the absence of Al, these systems are widely used as models to study the mechanism of zeolite crystallization in general. Ever since the “nanoslab” hypothesis was proposed byMartens et al. it has been the subject of a lot of criticism. The major disagreement is about the structure of the subcolloidal precursor particles present in the initial clear mixtures. Whereas Martens et al. suggest that these particles have MFI structural features, an amorphous nature of the particles has been proposed in numerous other studies. In some cases, the nanoparticles were extracted from the synthesis solutions, and concerns have been raised about possible changes in their structure or interference from the extraction procedure. 5] Other authors base their arguments against the crystalline nature of the precursor particles on the results of solid-state NMR analysis after Si enrichment. A recent NMR study on aqueous silicate solutions revealed the presence of structural units typical of the MFI structure. Other complementary techniques such as dynamic light scattering have also been used to further characterize the species present in the precursor solutions. Thus, despite the fact that a remarkable number of papers discussing the structure of the silicalite-1 precursor particles have already been published, the discussion is still ongoing and new publications regularly appear. Infrared spectroscopy has also extensively been used to study the structure of the silicalite-1 precursor particles. 7,12, 13] Based on the presence of a band near 550 cm , which is widely accepted to be characteristic of the MFI structure, either crystalline or amorphous character of the precursor particles has been suggested. These IR studies were performed on freeze-dried samples, extracted precursor particles, and original sols. However, the IR spectra published so far showed substantial differences in the 1000–1300 cm 1 spectral range which indicate that specific sampling affects the structural features of the nanoparticles. Recently, IR spectroscopy with synchrotron radiation was used for the first time to study in situ catalytic reactions in zeolite crystals. On the basis of synchrotron-based grazing-incidence reflection-absorption infrared (RAIR) spectra of ultrathin zeolite films on Au surfaces, we give unambiguous evidence for the existence of incipient zeolite nanoparticles in clear precursor solutions: these are subcolloidal particles having all the structural features of the zeolite framework but a size of only a few unit cells which is insufficient to generate a diffraction pattern. The novelty in our study is twofold: sample preparation and method of characterization. First, to separate the subnanoparticles from the solution, we used the Langmuir–Blodgett (LB) method to deposit them on Au substrates. The LB method allows concentration of the subcolloidal particles at the air/water interface as floating films and transfer of these films to the solid supports, which ensures preservation of the native particle structure. Second, we prepared the LB films on Au surfaces in order to characterize the samples by RAIR spectroscopy, which is the most efficient spectroscopic method for structural analysis of ultrathin films. Vibrational spectroscopy has great advantages over diffraction methods in detecting crystalline particles with a size of just 2–3 unit cells, because such particles are large enough to generate phonon modes of the corresponding crystal lattice but too small to give rise to detectible Bragg reflections even when synchrotron X-ray radiation is used. In addition, the vibrational spectra are easy to interpret and can unambiguously distinguish between amorphous and crystalline features, which is sometimes a problem for other surface-sensitive spectroscopic methods. Enhancement of the IR absorption due to the presence of a strongly reflecting noble metal surface allows the detection of even monomolecular layers when grazing-incident RAIR spectroscopy is [*] Dr. L. Tosheva, L. H. Wee, Dr. A. M. Doyle Division of Chemistry and Materials Manchester Metropolitan University Chester St., Manchester M15GD (UK) Fax: (+44)161-247-6357 E-mail: l.tosheva@mmu.ac.uk a.m.doyle@mmu.ac.uk

Modified colloidal silicalite-1 crystals and their use for preparation of Langmuir-Blodgett films

Purified colloidal Silicalite-1 crystals with a size of 100 nm were modified by centrifugation and re-dispersion in methanol, ethanol, 2-propanol or 1-butanol followed by sonication for two hours. After centrifugation and re-dispersion in fresh solvents, the alcohol suspensions of modified hydrophobic Silicalite-1 were spread at the air-water interface in a Langmuir-Blodgett trough and pressure-area isotherms were recorded. The floating monolayers were successfully transferred to Si wafers. The interaction between Silicalite-1 and methanol was studied in detail by collecting ATR-IR spectra of a Silicalite-1 suspension in methanol upon in situ methanol evaporation and during exposure to air. The increased hydrophobicity of the methanol modified Silicalite-1 was attributed to esterification of the surface of the zeolite nanocrystals. The modification procedure was also applied to micron-sized Silicalite-1 and corresponding Langmuir-Blodgett films were prepared.

Heterogeneous Alkane Reactions over Nanoporous Catalysts

Pt-USY-712 (Si/Al = 6) and three SBA-15 catalysts (metal-loaded with 1 wt% Pt, 1 wt% Ni or 0.5 wt% Pt and 0.5 wt% Ni) were prepared and characterised using scanning electron microscopy (SEM), X-ray diffraction (XRD), N

An Investigation into the Adsorption Characteristics of Grafted Mesoporous Silicates for the Removal of Tetramethyl Ammonium Hydroxide from Aqueous Solution

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Utilisation of a Mesoporous Silicate Material for the Removal of Quaternary Ammonium Hydroxides (QAHs) from Aqueous Solution

2 adsorption porosimetry / BET and transmission electron microscopy (TEM). The catalysts were then tested in the hydroisomerisation and hydrocracking of