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This paper provides a review of progress in catalytic conversion of JP-8 fuel and its surrogates made over the last decade. The effect of different types of catalyst and support materials, as well as different preparation methods, is discussed in detail. The derivation of kinetic models for computational studies is also examined. Particular attention is given to the development of sulfur tolerant catalysts and the mechanisms by which catalyst poisoning occurs, as this is an important obstacle to overcome for systems using sulfur-laden fuel. Suggestions for further research are offered. [ABSTRACT FROM AUTHOR]

The results obtained from the combustion behavior of propane over platinum and rhodium catalysts in a meso-scale heat recirculating combustor are presented. The extinction limits, conversion, product selectivity/yield, and activation energy using the two catalysts were compared in an effort to predict their performance using a liquid fuel. The extinction limits were also compared to those of non-catalytic combustion in the same combustor. The results showed that the use of a catalyst greatly expanded the range of stable operating conditions, in terms of both extinction limits and flow rates supported. The Rh catalyst was found to exhibit a higher propane conversion rate, reaching a maximum of 90.4% at stoichiometric conditions (as compared to only 61.4% offered by the Pt catalyst under lean conditions), but the Pt catalyst had superior CO 2 selectivity for most of the examined conditions, indicating more of the heat released being used for product formation as opposed to being lost to the environment. However, despite having a higher rate of heat loss, the combustion with the Rh catalyst produced an overall higher amount of enthalpy than the Pt due to its superior fuel conversion. The Pt catalyst also had a significantly smaller activation energy (13.8 kJ/mol) than the Rh catalyst (74.7 kJ/mol), except at equivalence ratios richer than Φ = 1.75 (corresponding to catalyst temperatures below 500 °C), where it abruptly changed to 211.4 kJ/mol, signifying a transition from diffusion-limited reactions to kinetically limited reactions at this point. The results reveal that Rh would be a more suitable catalyst for use in liquid-fueled meso-scale combustors, as fuel conversion has been found to be a limiting factor for combustion stability in these systems, and as its higher output energy allows for greater flexibility of use. [ABSTRACT FROM AUTHOR]

The pillared MWW (PMWW or MCM-36) and pillared MFI (PMFI) zeolites are 2-dimensional (2D) catalytically active materials made by pillaring of layered MCM-22(P) and multilamellar MFI precursors, respectively. The single- or near single-unit-cell thick 2D microporous layers in PMWW and PMFI expose comparable number of external surface acid sites ( i.e. , acid sites enclosed in mesopores between zeolitic layers) to those in micropores, which become important or dominant contributor to the catalytic properties. Although the acidity and catalytic activities of PMWW and PMFI have been studied, modification of their external surfaces and its implications on catalytic reactions are not available. In the present study, we report the tailoring of external surfaces of PMWW and PMFI zeolites by atomic layer deposition (ALD) of silicon (ALD-Si) and aluminum (ALD-Al), respectively. The textural, acidic and catalytic properties of the ALD modified pillared zeolites were investigated using a variety of characterization methods. ALD-Al and ALD-Si modifications kept micropore almost intact, but resulted in significant reduction in mesopore volume and considerable changes in external surface composition and acidity. The catalytic tests showed that intrinsic catalytic behavior of Brønsted acid sites in ALD modified pillared zeolites was similar to their parent counterparts. In diffusion constrained parallel reactions, ALD of Al- or Si-species altered catalyst selectivity. In addition, ALD of Si-species on PMFI zeolite deactivated surface active sites, which resulted in improved catalytic activity in direct methane aromatization reactions under optimal ALD cycles. The study exemplified for the first time that ALD is an effective tool for tuning the surface properties of 2D unit-cell thick zeolites. [ABSTRACT FROM AUTHOR]