A catalytic hollow fibre membrane reactor for combined steam methane reforming and water gas shift reaction

A catalytic hollow fibre membrane reactor (CHFMR) was developed in this study for combined steam methane reforming (SMR) and water gas shift (WGS) reaction. This is achieved by incorporating a Ni/SBA-15 catalyst into a plurality of micro-channels with open entrance from inner surface of Al2O3 hollow fibres, followed by coating of a 3.3μm Pd membrane on the outer surface of the hollow fibre using an electroless plating method. In addition to systematic characterizations of each reactor component, i.e. Ni/SBA-15 catalyst, micro-structured ceramic hollow fibre and Pd separating layer, the effect of how the reactor was assembled or fabricated on the catalytic performance was evaluated. Electroless plating of the Pd membrane impaired the catalytic performance of the deposited Ni/SBA-15 catalyst. Also, the over-removal of hydrogen from the reaction zone was considered as the main reason for the deactivation of the Ni-based catalyst. Instead of mitigating such deactivation using "compensating" hydrogen, starting the reaction at higher temperatures was found more efficient in improving the reactor performance, due to a better match between hydrogen production (from the reaction) and hydrogen removal (from the Pd membrane). An effective methane conversion of approximately 53%, a CO2 selectivity of 94% and a H2 recovery of 43% can be achieved at 560°C. In order for a more significant "shift" phenomenon, alternative methodology of fabricating the reactor and more coke resistant catalysts are recommended

Microstructured catalytic hollow fiber reactor for methane steam reforming

Microstructured alumina hollow fibers, which contain a plurality of radial microchannels with significant openings on the inner surface, have been fabricated in this study and used to develop an efficient catalytic hollow fiber reactor. Apart from low mass-transfer resistance, a unique structure of this type facilitates the incorporation of Ni-based catalysts, which can be with or without the aged secondary support, SBA-15. In contrast to a fixed bed reactor, the catalytic hollow fiber reactor shows similar methane conversion, with a gas hourly space velocity that is approximately 6.5 times higher, a significantly greater CO2 selectivity, and better productivity rates. These results demonstrate the advantages of dispersing the catalyst inside the microstructured hollow fiber as well as the potential to reduce the required quantity of catalyst

Autothermal reforming of palm empty fruit bunch bio-oil: thermodynamic modelling

This work focuses on thermodynamic analysis of the autothermal reforming of palm empty fruit bunch (PEFB) bio-oil for the production of hydrogen and syngas. PEFB bio-oil composition was simulated using bio-oil surrogates generated from a mixture of acetic acid, phenol, levoglucosan, palmitic acid and furfural. A sensitivity analysis revealed that the hydrogen and syngas yields were not sensitive to actual bio-oil composition, but were determined by a good match of molar elemental composition between real bio-oil and surrogate mixture. The maximum hydrogen yield obtained under constant reaction enthalpy and pressure was about 12 wt% at S/C = 1 and increased to about 18 wt% at S/C = 4; both yields occurring at equivalence ratio Φ of 0.31. The possibility of generating syngas with varying H2 and CO content using autothermal reforming was analysed and application of this process to fuel cells and Fischer-Tropsch synthesis is discussed. Using a novel simple modelling methodology, reaction mechanisms were proposed which were able to account for equilibrium product distribution. It was evident that different combinations of reactions could be used to obtain the same equilibrium product concentrations. One proposed reaction mechanism, referred to as the ‘partial oxidation based mechanism’ involved the partial oxidation reaction of the bio-oil to produce hydrogen, with the extent of steam reforming and water gas shift reactions varying depending on the amount of oxygen used. Another proposed mechanism, referred to as the ‘complete oxidation based mechanism’ was represented by thermal decomposition of about 30% of bio-oil and hydrogen production obtained by decomposition, steam reforming, water gas shift and carbon gasification reactions. The importance of these mechanisms in assisting in the eventual choice of catalyst to be used in a real ATR of PEFB bio-oil process was discussed

Investigations on hydrogenation of selected organic sulfur compounds on the Ni-Mo/Al2O3 catalyst in terms of natural gas desulfurization

Technological problems of natural gas desulfurization in syngases manufacturing plants have been discussed and the results of investigations on the activity of the model Ni-Mo/Al$\text{}_{2}$O$\text{}_{3}$ catalyst in hydrogenation of selected sulfur compounds have been presented. The HDS reaction rate is dependent on a compound structure. The hydrogenation rate on the Ni-Mo/Al$\text{}_{2}$O$\text{}_{3}$ catalyst for the given sulfur compound increases in the order: CS$\text{}_{2}$(CH$\text{}_{3}$)$\text{}_{2}$S>C$\text{}_{4}$H$\text{}_{10}$S>C$\text{}_{2}$H$\text{}_{6}$S$\text{}_{2}$C$\text{}_{4}$H$\text{}_{4}$S