Methane Reforming with H2S and Sulfur for Hydrogen Production: Thermodynamic Assessment

Nowadays, most ofthe hydrogen is obtained from fossil fuels. Atthe same time, the effort and resources dedicated to the developmentof sustainable hydrogen manufacturing processes are rapidly increasingto promote the energy transition toward renewable sources. In thisdirection, a potential source of hydrogen could be hydrogen sulfide,produced as a byproduct in several processes, and in particular inthe oil extraction and refinery operations. Methane reforming usingH(2)S has recently attracted much interest for its economicand environmental implications. Its conversion, in fact, providesa viable way for the elimination of a hazardous molecule, producinga high-added value product like hydrogen. At the same time, some ofthe still open key aspects of this process are the coke depositiondue to thermal pyrolysis of methane and the process endothermicity.In this work, the methane reforming with H2S by co-feedingsulfur is investigated through a detailed thermodynamic analysis asa way to alleviate the critical aspects highlighted for the process.A parametric analysis was conducted to assess the best thermodynamicconditions in terms of pressure, temperature, and feed composition.Changing the sulfur, H2S, and methane feed compositioncan enhance the system by improving the hydrogen production yield,reducing the carbon and sulfur deposition, increasing the H2S removal efficiency, and reducing the necessary thermal duty

Hydrocracking of long chain linear paraffins

The hydrocracking reactivity of two model compounds, namely n-C(16)H(34) (n-C16) and n-C(28)H(58) (n-C28), was investigated on a Pt/SiO(2)-Al(2)O(3) catalyst. Conversion and products distribution have been determined under a wide range of operating conditions (i.e. pressure: 20-80 bar; temperature: 270-330 degrees C; weight hourly space velocity: 0.33-1.0 h(-1): H(2)/n-paraffin feeding ratio 0.05-0.15 wt/wt). The latter were changed according to a central composite design. The present paper summarises the results obtained on both the model paraffins, depending on the reaction conditions. A first, simple kinetic elaboration is also presented, based on an ideal PFR model and a first order kinetics. The reaction confirmed to be first order with respect to the n-paraffin. Experimental data showed that for both n-C16 and n-C28 conversion was affected by H(2)/n-paraffin ratio. The change of conversion was explained in terms of vapour liquid equilibrium (VLE), which in turn is affected by the H(2)/n-paraffin ratio, so leading to a different vaporisation degree of reactant. In agreement with the VLE data, the effect of H(2)/n-paraffin on conversion was lower for n-C28. VLE calculations have been carried out to estimate the H(2) partial pressure and degree of vaporisation of the normal paraffin. The reaction order for hydrogen was -1 and -0.5 for n-C16 an n-C28, respectively. However, in the case of n-C16 the data obtained at the lower bound of the pressure range examined displayed an increase of the reaction order. The apparent activation energy was calculated after correction of the contact time taking into account the liquid-vapour equilibrium: similar values have been estimated for n-C16 and n-C28, ca. 32 and 31 kcal/mol, respectively

Liquid fuels from Fischer-Tropsch wax hydrocracking: Isomer distribution

Considering the current need of low emission fuels for the automotive market and the need of renewable fuels that will emerge in the very next future, Fischer-Tropsch (FT) based technologies should be considered a valid option to accomplish both low emission and renewable fuel production targets. A hydrocracking step is necessary for obtaining high quality fuels from FT wax. Isomerisation is an important reaction that takes place during the hydroconversion process. The amount and the type of the isomers in the produced fuels heavily influence both cold flow properties and cetane number. In this paper the results of a detailed method of analysis which allows the distinction between mono-branched and multi-branched isomers in fuels obtained from an FT wax hydrocracking process, are presented and discussed. In particular the influence of the operating conditions and the wax conversion on the isomer distribution is pointed out

Introduction of a Breakage Probability Function in the Hydrocracking Reactor Model

This paper shows how a breakage probability function for the C-C bonds, elaborated from experimental evidence reported in literature, is introduced in the reactor model for the hydrocracking of Fischer-Tropsch waxes. The results demonstrate a better response to the variation of the operating conditions (especially as concerns temperature) and show product distributions closer to the experimental ones than those predicted by the previous model [Pellegrini, L. A. et al. Chem. Eng. Sci. 2008, 63, 4285]. The agreement with the experimental data has also been enhanced introducing a dependence on temperature (in addition to the dependence on the number of carbon atoms) in the expressions for the Langmuir constants and giving the equilibrium constants for isomerization reactions a new function derived from a thermodynamic study