n-Hexadecane hydrocracking Single-Event MicroKinetics on Pt/H-beta

[EN] The Single-Event MicroKinetic (SEMK) model constructed for gas-phase hydroconversion of light n-alkanes on large-pore USY zeolites was applied, for the first time, to the hydrocracking of n-hexadecane on a Pt/H-Beta catalyst. Despite the 12-ringed pore channels, shape selectivity was observed in the formation of ethyl side chains. Additionally, heavy feed molecules such as n-hexadecane lead to physisorption saturation of the catalyst pores by strong Van der Waals interactions of the long alkyl chains with the zeolite framework. Intermolecular interactions and packing efficiencies in the pores induce deviations from typical Henry-regime physisorption characteristics as the physisorption selectivity, which is expected to increase with increasing carbon number, appeared to be independent of the latter. Micropore saturation effects were described by the 'size entropy' which quantifies the difference in standard entropy loss between physisorption in the Henry regime and hindered physisorption on a saturated surface. The size entropy is proportional to the catalyst loading with physisorbed species and the adsorbate carbon number. The addition of a size entropy term in the SEMK model, amounting to 102J mol(-1) K-1 for a hexadecane molecule at full saturation, allowed accurately reproducing the contribution of secondary isomerization and cracking reactions, as quantified by means of a contribution analysis. (C) 2012 Elsevier B.V. All rights reserved.This work was funded by the European Research Institute of Catalysis and the European Community’s Sixth Framework Programme. This work was also supported by the Research Board of Ghent University (BOF), the Interuniversity Attraction Poles Programme–Belgian State–Belgian Science Policy and the Long Term Structural Methusalem Funding by the Flemish Government. Financial support by the Comisión Interministerial de Ciencia y Tecnología (CICYT) of Spain through the Project CTQ2010-17988/PPQ is also gratefully acknowledged.Vandegehuchte, BD.; Thybaut, JW.; Martinez Feliu, A.; Arribas Viana, MDLD.; Marin, GB. (2012). n-Hexadecane hydrocracking Single-Event MicroKinetics on Pt/H-beta. Applied Catalysis A General. 441:10-20. doi:10.1016/j.apcata.2012.06.054S102044

Steady State Simulation of a Multi-Bed Adiabatic Reactor for Methanol Production

A one dimensional heterogeneous model accounting for intraparticle diffusion limitations is developed for methanol production from carbon oxides and hydrogen. The model and the kinetics used fit very will industrial data. The effect of the CO2/CO, (C02 + CO)/H2 mole ratios, inlet temperature, reaction pressure, size of the catalyst particle and the tortuosity factor on the reactor performance are investigated. The study indicates that the methanol reactor operation is highly sensitive to variations in the temperature

Successive annual applications of organic manures for cut grass: short-term observations on utilisation of manure nitrogen

The recovery of nitrogen (N) from, and the fertilizer‐N value of, low dry‐matter (DM) cattle slurry and farm yard manure (FYM), applied annually to perennial ryegrass swards grown at two sites, on sandy loam and shallow calcareous silty clay loam soils, were studied over a 4‐year period. Slurry or FYM, applied at target rates of either 150 kg N ha−1 or 300 kg N ha−1 in either October, February or May/June, in combination with 150 kg N ha−1 inorganic fertilizer‐N (applied as split dressings before the first and second grass cut), were compared with a set of inorganic fertilizer‐N response treatments. DM yield, N offtake, apparent manure‐N recovery (in herbage) and manure‐N efficiency (compared with inorganic fertilizer‐N) were determined at two silage cuts each summer. Soil mineral nitrogen (SMN) measurements in autumn and spring were used to assess potential N leaching loss over winter and to quantify available N residues in the soil in spring. Apparent manure‐N recovery and manure‐N efficiency were usually greater from slurry applications in February than from those in October, but the timing of the application of FYM had a much smaller effect, compared with the timings of the application of slurry, on the utilization of N from manure by grass. Spring assessment of SMN was useful in quantifying available N residues from October slurry applications. Manure‐N recovery for all application timings was, on average, higher from the sandy loam than the shallow calcareous clay loam. The application of slurry to grass in early spring, at a rate of 150 kg total N ha−1, with the addition of a supplementary 50 kg inorganic fertilizer‐N ha−1, was the most suitable strategy for utilizing slurry‐N effectively and for supplying the N requirement for first‐cut silage

Effects of nitrification inhibitor and acid addition to cattle slurry on nitrogen losses and herbage yields

Cattle slurry was applied to grassland on two contrasting soils in autumn and spring between 1987 and 1990. Slurry was applied with or without the addition of acid, to lower the pH to 5.5, and, in autumn only, with or without a nitrification inhibitor. Ammonia volatilization, denitrification and apparent recovery of N by the cut herbage accounted for 61-86% of the ammonium nitrogen (NH4+-N) applied in slurry. Estimates from lysimeter experiments indicated that nitrate leaching from autumn application may have accounted for an additional 1-2% only. Acidifying slurry reduced volatilization losses to 1-12% of the NH4+-N applied, and the nitrification inhibitor halved denitrification losses from autumn applications. Reductions in nitrogen losses were reflected in significant increases in first-cut herbage yields which, for slurry applied in the autumn with acid and the nitrification inhibitor, were generally greater than those from 120 kg ha-1 N as ammonium nitrate applied in the spring. There were no significant differences between treatments at subsequent cuts in each season but, owing to the large increases at first cut, total yields were significantly higher for autumn-applied slurry with acid and nitrification inhibitor