High purity H2 by sorption-enhanced chemical looping reforming of waste cooking oil in a packed bed reactor.

High purity hydrogen (>95%) was produced at 600 degrees C and 1 atm by steam reforming of waste cooking oil at a molar steam to carbon ratio of 4 using chemical looping, a process that features redox cycles of a Ni catalyst with the in-situ carbonation/calcination of a CO(2) sorbent (dolomite) in a packed bed reactor under alternated feedstreams of fuel-steam and air. The fuel and steam conversion were higher with the sorbent present than without it. Initially, the dolomite carbonation was very efficient (100%), and 98% purity hydrogen was produced, but the carbonation decreased to around 56% with a purity of 95% respectively in the following cycles. Reduction of the nickel catalyst occurred alongside steam reforming, water gas shift and carbonation, with H(2) produced continuously under fuel-steam feeds. Catalyst and CO(2)-sorbent regeneration was observed, and long periods of autothermal operation within each cycle were demonstrated

High hydrogen yield and purity from palm empty fruit bunch and pine pyrolysis oils

The benefits of CO 2 sorption enhanced steam reforming using calcined dolomite were demonstrated for the production of hydrogen from highly oxygenated pyrolysis oils of the agricultural waste palm empty fruit bunches (PEFB) and pine wood. At 1 atm in a down-flow packed bed reactor at 600 °C, the best molar steam to carbon ratios were between 2 and 3 using a Ni catalyst. After incorporating steam-activated calcined dolomite as the CO 2 sorbent in the reactor bed, the H 2 yield from the moisture free PEFB oil increased from 9.5 to 10.4 wt.% while that of the pine oil increased from 9.9 to 13.9 wt.%. The hydrogen purity also rose from 68 to 96% and from 54 to 87% for the PEFB and pine oils respectively, demonstrating very substantial sorption enhancement effects

Temperature-programmed reduction of nickel steam reforming catalyst with glucose

Temperature-programmed reduction (TPR) of a NiO/α-Al2O3 steam reforming catalyst with glucose under a N2 flow was investigated using TGA-FTIR technique. A series of catalyst samples obtained at different temperatures during the TPR were characterised by XRD, CHN elemental analysis, SEM-EDX and TPO. Results showed that the whole TPR covering from room temperature to 900 °C consisted of two reactive processes. They were glucose pyrolysis producing carbonaceous materials (char), and NiO reduction by the char resulting in CO2 as a main product. When the initial mass ratio of glucose to the catalyst was 1:10, the catalyst could be completely reduced without carbon remaining. Moreover, two mass loss peaks were observed at around 440 °C and 670 °C, respectively, during the reduction. Based on the experiments of char characterisation, H2 TPR and excess glucose TPR, a two-stage reduction mechanism was proposed. The first reduction stage was attributed to a solid reaction between NiO and char. The second stage was assigned to NiO being reduced by the CO produced by char gasification with CO2. Their apparent activation energies were 197 ± 19 kJ/mol and 316 ± 17 kJ/mol, respectively, estimated using the Kissinger method

Hydrogen via reforming aqueous ammonia and biomethane co-products of wastewater treatment: environmental and economic sustainability

Green H2 is increasingly viewed as a key energy carrier for the fight against climate change. Wastewater treatment plants (WWTPs) have the unique potential to be centres of renewable H2 generation with the growing availability of two attractive feedstocks: biomethane and ammonia. An innovative and novel method of ammonia recovery from digestate liquor followed by a state-of-the-art H2 production process named NWaste2H2 is demonstrated for a case-study WWTP. The recovered ammonia is used alongside biomethane for H2 production and its diversion from conventional biological treatment has two other crucial benefits, with reductions in both associated electricity demand and emissions of nitrous oxide, an extremely potent greenhouse gas. Process modelling, supported by extensive experiments in a packed-bed reactor at bench-scale, demonstrate the prized capability of simultaneously performing steam methane reforming and ammonia decomposition to generate a H2-rich syngas with yields close to equilibrium values. Greenhouse gas emission abatement from the replacement of diesel buses and reduced N2O emissions from biological treatment could save up to 17.2 kg CO2 equivalent (CO2e) per year for each person served by the WWTP. An in-depth economic study illustrates the ability to achieve a positive net present value with a 10% discount factor as early as 5.8 years when the H2 is prepared and sold to power fuel cell electric buses

Direct reduction of nickel catalyst with model bio-compounds

The effects of temperature and S/C on the reduction extent and kinetics of a steam reforming NiO/α-Al₂O₃ catalyst were systematically investigated using five bio-compounds commonly produced during the fermentation, pyrolysis and gasification processes of biomass (acetic acid, ethanol, acetone, furfural and glucose). Reduction was also performed with methane and hydrogen for comparison. Kinetic modelling was applied to the NiO conversion range of 0–50% using the Handcock and Sharp method. The two-dimensional nuclei growth model (A2) was found to fit very well except for glucose. For all the bio-compounds, the apparent activation energy of NiO reduction was between 30 and 40 kJ/mol. Their pre-exponential factors decreased in this order: CH₄ > ethanol ≈ acetone > acetic acid > furfural > glucose, probably due to the different activities of reducing species they produced. Optimal molar steam to carbon ratios for reduction kinetics were found between 1 and 2

Thermodynamics of hydrogen production from urea by steam reforming with and without in situ carbon dioxide sorption

The thermodynamic effects of molar steam to carbon ratio (S:C), of pressure, and of having CaO present on the H2 yield and enthalpy balance of urea steam reforming were investigated. At a S:C of 3 the presence of CaO increased the H2 yield from 2.6 mol H2/mol urea feed at 940 K to 2.9 at 890 K, and decreased the enthalpy of bringing the system to equilibrium. A minimum enthalpy of 180.4 kJ was required to produce 1 mol of H2 at 880 K. This decreased to 94.0 kJ at 660 K with CaO-based CO2 sorption and, when including a regeneration step of the CaCO3 at 1170 K, to 173 kJ at 720 K. The presence of CaO allowed widening the range of viable operation at lower temperature and significantly inhibited carbon formation. The feasibility of producing H2 from renewable urea in a low carbon future is discussed

Feasibility of hydrogen production from steam reforming of biodiesel (FAME) feedstock on Ni-supported catalysts

The catalytic steam reforming of biodiesel was examined over Ni-alumina and Ni-ceria-zirconia catalysts at atmospheric pressure. Effects of temperatures of biodiesel preheating/ vapourising (190-365 °C) and reforming (600-800 °C), molar steam to carbon ratio (S/C=2-3), , and residence time in the reformer, represented by the weight hourly space velocity ‘WHSV’ of around 3 were examined for 2h. Ni supported on calcium aluminate and on Ceria-zirconia supports achieved steady state hydrogen product stream within 90% of the equilibrium yields, although 4% and 1% of the carbon feed had deposited on the catalysts, respectively, during the combined conditions of start-up and steady state. Addition of dopants to ceria-zirconia supported catalyst decreased the performance of the catalyst. Increase in S/C ratio had the expected positive effects of higher H2 yield and lower carbon deposition