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Ni/SiO 2 catalysts prepared by a sol–gel method have been investigated for hydrogen production via steam reforming of ethanol using a continuous flow, fixed bed reactor system. Chemical equilibrium calculations were also performed to determine the effects of temperature and molar steam to carbon ratio on hydrogen production. The acidity of the preparation solution (modified by nitric acid and ammonia) and calcination atmosphere (air and N 2 ) were investigated in the preparation of the catalysts. BET surface area and porosity, temperature-programmed oxidation (TPO), X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to characterise the prepared catalysts. The BET surface area was reduced when the solution acidity was lowered during the sol–gel preparation process. A pH value less than 2.0 was necessary to achieve high metal dispersion in the catalyst. Smaller NiO particles were obtained when the catalyst was calcined in N 2 . Material balances on ethanol steam reforming at 600 °C using the prepared Ni/SiO 2 catalysts were determined, and higher hydrogen production with lower coke deposition on the reacted catalysts were also obtained from the catalysts calcined in N 2 atmosphere. [ABSTRACT FROM AUTHOR]

Highlights: [•] Ni–Cu–Al catalyst for hydrogen production was synthesized by rising pH technique. [•] Experimental data were analyzed with non-stoichiometric thermodynamic calculation. [•] Catalyst deactivation due to carbon deposits in glycerol steam reforming was found. [•] Carbon removal was analyzed by TGA experiment during medium temperature oxidation. [•] Reforming was tested by separability kinetics of rate law and catalyst deactivation. [Copyright &y& Elsevier]

Abstract: The objective of this review is to analyze potential technologies and their baseline performance of producing hydrogen from catalytic steam reforming of biodiesel byproduct glycerol. High oxygen content and high impurity level of biodiesel byproduct glycerol, as well as the complex intermediates and high coking potential in its thermal degradation, make the modeling, design, and operation of glycerol steam reforming a challenge. Thermal decomposition characterization of biodiesel byproduct glycerol was covered, and the recent developments and methods for high-purity hydrogen production from glycerol steam reforming were illustrated. The thermodynamics constraint of water gas shift reaction can be overcome by the sorption-enhanced steam reforming process, which integrated catalytic steam reforming, water gas shift reaction and in-situ CO2 removal at high temperatures in a single stage reactor. The effectiveness of both the enhanced H2 production and the use of CO2 sorbents have been demonstrated and discussed. The technical challenges to achieve a stable high-purity hydrogen production by the sorption-enhanced steam reforming process included extending operation time, selecting suitable sorbents, finding a way for continuous reaction-regeneration of catalyst and sorbent mixture and improving process efficiencies. The continuous sorption-enhanced steam reforming of glycerol was designed by a simultaneous flow concept of catalyst and sorbent for continuous reaction-regeneration using two slow moving-bed reactors for high-purity hydrogen production and CO2 capture, and in this process, catalyst and sorbent were run in nearly fresh state for H2 production. The sorption-enhanced chemical-looping reforming was also demonstrated. The paper discusses some issues and challenges, along with the possible solutions in order to help in efficient production of hydrogen from catalytic steam reforming of biodiesel byproduct glycerol. [Copyright &y& Elsevier]

Abstract: H2 production from glycerol steam reforming by the Ni–Cu–Al, Ni–Cu–Mg, Ni–Mg catalysts was evaluated experimentally in a continuous flow fixed-bed reactor under atmospheric pressure within a temperature range from 450 to 650 °C. The catalysts were synthesized by the co-precipitation methods, and characterized by the elemental analysis, BET, XRD and SEM. The GC and FTIR were applied to analyze the products from steam reforming of glycerol. The coke deposited on the catalysts was measured by TGA experiments during medium temperature oxidation. The results showed that glycerol conversion and H2 production were increased with increasing temperatures, and glycerol decomposition was favored over its steam reforming at low temperatures. The Ni–Cu–Al catalyst containing NiO of 29.2 wt%, CuO of 31.1 wt%, Al2O3 of 39.7 wt% performed high catalytic activity, and the H2 selectivity was found to be 92.9% and conversion of glycerol was up to 90.9% at 650 °C. The deactivation of catalysts due to the formation and deposition of coke was observed. An improved iterative Coats–Redfern method was used to evaluate the non-isothermal kinetic parameters of coke removal from catalysts, and the results showed the reaction order of n = 1 and 2 in the Fn nth order reaction model predicted accurately the main phase in the coke removal for the regeneration of Ni–Mg and Ni–Cu–Al catalysts, respectively. [Copyright &y& Elsevier]

Abstract: Steam reforming of the crude glycerol by-product of a biodiesel production plant has been evaluated experimentally at atmospheric pressure, with and without in situ CO2 sorption, in a continuous flow fixed-bed reactor between 400°C and 700°C. The process outputs were compared to those using pure glycerol. Thermodynamic equilibrium calculations were used to assess the effect on the steam reforming process of the main crude impurities (methanol and four fatty acid methyl esters). The crude glycerol and steam conversions and the H2 purity reached 100%, 11% and 68%, respectively at 600°C. No CH4 was found at and above 600°C. Steam reforming of crude glycerol with in situ CO2 removal is shown to be an effective means of achieving hydrogen purity above 88% in pre-CO2 breakthrough conditions. [Copyright &y& Elsevier]

Abstract: Five catalysts were evaluated for removal of tar components in high temperature fuel gas cleaning. 1-Methylnaphthalene was chosen as a model of the tar components. The NiMo catalyst having the highest surface area exhibited the highest activity of tar removal among the five catalysts. The effects of reaction temperature and space velocity on tar removal were studied in the range of 250–650°C and 3000–9000h−1, respectively. A lumped kinetic model was developed to describe the removal process. A sequential method to estimate the rate constants in the lumped kinetic model was adopted, which greatly simplifies the data treatments. Kinetic constants and activation energies were determined by a nonlinear regression program. The results showed that the predicted yields were very close to the experimental ones. [Copyright &y& Elsevier]