Reaction Kinetics of Steam Reforming of n‐Butanol over a Ni/Hydrotalcite Catalyst

Pyrolytic lignin can be transformed to liquid transportation fuels by hydrotreatment, which requires hydrogen (H₂). Bio‐oil is a suitable renewable feedstock for H₂ production. Here, n‐butanol was chosen as a model compound representing alcohols in the bio‐oil aqueous fraction. H₂ production from steam reforming of n‐butanol was investigated in a fixed‐bed reactor using a commercial Ni/hydrotalcite catalyst. A plausible reaction pathway in the presence of Ni was discussed. An increase in reforming temperature, space time, and steam/carbon ratio in the feed enhanced the n‐butanol conversion and H₂ yield. Reaction kinetics was studied in the defined chemical control regime. The reaction order with respect to n‐butanol (one) and the activation energy were determined.     

Hydrogen production from partial oxidation and reforming of DME

Hydrogen production from partial oxidation and reforming of dimethyl ether (DME) was investigated with a fixed bed continuous-flow reactor. H₂ yield of over 90% was obtained with 100% DME conversion at 700 °C over Pt/Al₂O₃+Ni–MgO dual catalyst bed, while keeping CH₄ yield at low level. Such results indicated that partial oxidation and reforming of DME to produce hydrogen at high temperature is possible and effective.     

Achieving 360 NL h−1 Hydrogen Production Rate Through 30‐Cell Solid Oxide Electrolysis Stack with LSCF–GDC Composite Oxygen Electrode

A 30‐cell solid oxide electrolysis (SOE) stack consisting of 30‐cell planar Ni–YSZ hydrogen electrode‐supported single cell with La_0.6Sr_0.4Co_0.2Fe_0.8O_3–δ–Ce_0.9Gd_0.1O_1.95 (LSCF–GDC) composite oxygen electrodes, interconnects, and sealing materials was tested at 750 °C in steam electrolysis mode for hydrogen production. The direction of gas flow in the stack was a cross‐flow configuration, and the stack configuration was designed to open gas flow channels at the air outlet. The electrolysis efficiency of the stack was higher than 100% at 90/10H₂O/H₂ ratio under <0.5 A cm⁻² current density. During hydrogen production, the stack was operated at 750 °C under 0.5 A cm⁻² constant current density for more than 500 h with 4.06% k h⁻¹ degradation rate. Up to 73% steam conversion rate and 91.6% current efficiency were obtained; the net hydrogen production rate reached as high as 361.4 NL h⁻¹. Our results suggested that the SOE stack that was designed with LSCF–GDC composite oxygen electrode could be used to conduct large‐scale hydrogen production.     

Pt–calcium cobaltate enables sorption-enhanced steam reforming of glycerol coupled with chemical-looping CH4 combustion

Sorption-enhanced steam reforming (SESR) process is usually highly energy intensive in producing high-purity hydrogen. Herein, the sorbent decarbonation was conducted in the presence of O₂ to enable the exothermic reaction between CaO and CoO_x to form calcium cobaltate (CCO). By utilizing CCO as oxygen carrier (OC), the chemical-looping methane combustion was employed prior to the SESR of glycerol (SESRG), by which CCO was prereduced to Co catalysts and CaO sorbent, thereby significantly improving the H₂ yield from SESRG. With a Pt-doped CCO acting as precatalyst, CO₂ sorbent, and OC, we realized 70% CH₄ conversion and 96 vol% H₂ with 120% yield (based on glycerol) for 20 cycles, and the excess H₂ was due to steam gasification of coke. The promoting effects of Pt toward CH₄ conversion and H₂ production were rationalized by CH₄ temperature-programmed reduction, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. Our results demonstrate the feasibility of process integration enabled by multifunctional materials.     

Comparative Study on Thermodynamic Analysis of CO2 Utilization Reactions

Thermodynamic analysis of dimethyl ether (DME) and methane synthesis from CO₂ hydrogenation, and dry reforming of methane was performed using Gibbs free energy minimization. The effects of temperature, pressure, and feed composition on conversion, selectivity, and yield were investigated for each process. High pressure, high H₂/CO₂ ratio, and low temperature favored DME production. The yield of methane during CO₂ methanation increased at lower temperature, higher pressure, and H₂/CO₂ ratio. The yield of synthesis gas improved at higher temperature. Comparison of the three processes demonstrated that the CO₂ conversion was highest during CO₂ methanation reaction if the fraction of CO₂ mol in the feed was less than 0.3. Above this value in the feed, dry reforming allowed the highest CO₂ conversion.     

On-board plasma-assisted conversion of heavy hydrocarbons into synthesis gas

The fuel conversion performance of two gliding arc plasma reformers is investigated with the goal of syn-gas production on-board vehicles. In both systems, n-tetradecane (C₁₄H₃₀) fuel was reformed with plasma under partial oxidation conditions in the absence of metal catalysts and steam. A comparison of the performance of each device is made with regard to the hydrogen yield and energy conversion efficiency. The results show that gliding arc systems are capable of reforming heavy hydrocarbon fuels with high conversion efficiency and are an important piece of technology for on-board vehicular reforming systems that should be further developed and optimized.     

Hydrogen Production from Ethanol Steam Reforming Over Supported Cobalt Catalysts

Hydrogen production was carried out via ethanol steam reforming over supported cobalt catalysts. Wet incipient impregnation method was used to support cobalt on ZrO₂, CeO₂ and CeZrO₄ followed by pre-reduction with H₂ up to 677 °C to attain supported cobalt catalysts. It was found that the non-noble metal based 10 wt.% Co/CeZrO₄ is an efficient catalyst to achieve ethanol conversion of 100% and hydrogen yield of 82% (4.9 mol H₂/mol ethanol) at 450 °C, which is superior to 0.5 wt.% Rh/Al₂O₃. The pre-reduction process is required to activate supported cobalt catalysts for high H₂ yield of ethanol steam reforming. In addition, support effect is found significant for cobalt during ethanol steam reforming. 10% Co/CeO₂ gave high H₂ selectivity while suffered low conversion due to the poor thermal stability. In contrast to CeO₂, 10 wt.% Co/ZrO₂ achieved high conversion while suffered lower H₂ yield due to the production of methane. The synergistic effect of ZrO₂ and CeO₂ to promote high ethanol conversion while suppress methanation was observed when CeZrO₄ was used as a support for cobalt. This synergistic effect of CeZrO₄ support leads to a high hydrogen yield at low temperature for 10 wt.% Co/CeZrO₄ catalyst. Under the high weight hourly space velocity (WHSV) of ethanol (2.5 h⁻¹), the hydrogen yield over 10 wt.% Co/CeZrO₄ was found to gradually decrease to 70% of its initial value in 6 h possibly due to the coke formation on the catalyst.     

CO2 Reduction to Substitute Natural Gas: Toward a Global Low Carbon Energy System

Methane has proven to be an outstanding energy carrier and is the main component of natural gas and substitute natural gas (SNG). SNG may be synthesized from the CO₂ and hydrogen available from various sources and may be introduced into the existing infrastructure used by the natural gas sector for transport and distribution to power plants, industry, and households. Renewable SNG may be generated when H₂ is produced from renewable energy sources, such as solar, wind, and hydro. In parallel, the use of CO₂-containing feed streams from fossil origin or preferably, from biomass, permits the avoidance of CO₂ emissions. In particular, the biomass-to-SNG conversion, combined with the use of renewable H₂ obtained by electrolysis, appears a promising way to reduce CO₂ emissions considerably, while avoiding energy intensive CO₂ separation from the bio feed streams. The existing technologies for the production of SNG are described in this short review, along with the need for renewed research and development efforts to improve the energy efficiency of the renewables-to-SNG conversion chain. Innovative technologies aiming at a more efficient management of the heat delivered in the exothermic methanation process are therefore highly desirable. The production of renewable SNG through the Sabatier process is a key process to the transition towards a global sustainable energy system, and is complementary to other renewable energy carriers such as methanol, dimethyl ether, formic acid, and Fischer-Tropsch fuels.     

Catalytic Steam Reforming of Fast Pyrolysis Bio‐Oil in Fixed Bed and Fluidized Bed Reactors

Catalytic steam reforming of bio‐oil is an economically‐feasible route which produces renewable hydrogen. The Ni/MgO‐La₂O₃‐Al₂O₃ catalyst was prepared with Ni as active agent, Al₂O₃ as support, and MgO and La₂O₃ as promoters. The experiments were conducted in fixed bed and fluidized bed reactors, respectively. Temperature, steam‐to‐carbon mole ratio (S/C), and liquid hourly space velocity (LHSV) were investigated with hydrogen yield as index. For the fluidized bed reactor, maximum hydrogen yield was obtained under temperatures 700–800 °C, S/C 15–20, LHSV 0.5–1.0 h^–1, and the maximum H₂ yield was 75.88 %. The carbon deposition content obtained from the fluidized bed was lower than that from the fixed bed. The maximum H₂ yield obtained in the fluidized bed was 7 % higher than that of the fixed bed. The carbon deposition contents obtained from the fluidized bed was lower than that of the fixed bed at the same reaction temperature.     

Manganese‐containing redox catalysts for selective hydrogen combustion under a cyclic redox scheme

Selective hydrogen combustion (SHC) in the presence of light hydrocarbons was demonstrated with a series of Mn‐containing mixed oxide redox catalysts in the context of a chemical looping‐oxidative dehydrogenation scheme. Unpromoted and 20 wt % Na₂WO₄‐promoted Mg₆MnO₈, SrMnO₃, and CaMnO₃ exhibited varying SHC capabilities at temperatures between 550 and 850°C. Reduction temperature of unpromoted redox catalysts increased in the order Mg₆MnO₈ < SrMnO₃ < CaMnO₃. Promotion with 20 wt % Na₂WO₄ resulted in more selective redox catalysts capable of high‐temperature SHC. XPS analysis revealed a correlation between suppression of near‐surface Mn and SHC selectivity. Na₂WO₄/CaMnO₃ showed steady SHC performance (89% H₂ conversion, 88% selectivity) at 850°C over 50 redox cycles. In series with a Cr₂O₃/Al₂O₃ ethane dehydrogenation catalyst, Na₂WO₄/CaMnO₃ combusted 84% of H₂ produced while limiting CO_x yield below 2%. The redox catalysts reported can be suitable for SHC in a cyclic redox scheme for the production of light olefins from alkanes. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3141–3150, 2018     

Autothermal Reforming of Methane with Integrated CO2 Capture in a Novel Fluidized Bed Membrane Reactor. Part 1: Experimental Demonstration

Two fluidized bed membrane reactor concepts for hydrogen production via autothermal reforming of methane with integrated CO₂ capture are proposed. Ultra-pure hydrogen is obtained via hydrogen perm-selective Pd-based membranes, while the required reaction energy is supplied by oxidizing part of the CH₄ in situ in the methane combustion configuration or by combusting part of the permeated H₂ in the hydrogen combustion configuration (oxidative sweeping). In this first part, the technical feasibility of the two concepts has been studied experimentally, investigating the reactor performance (CH₄ conversion, CO selectivity, H₂ production and H₂ yield) at different operating conditions. A more detailed comparison of the performance of the two proposed reactor concepts is carried out with a simulation study and is presented in the second part of this work.     

Superbase‐Catalyzed [4+2] Cycloaddition of Acetylenes to 3,6‐Di(pyrrol‐2‐yl)‐1,2,4,5‐tetrazine: A Facile Synthesis of 3,6‐Di(pyrrol‐2‐yl)pyridazines

Acetylenes undergo the [4+2] cycloaddition to 3,6‐di(pyrrol‐2‐yl)‐1,2,4,5‐tetrazine in the potassium hydroxide/dimethyl sulfoxide or potassium tert‐butoxide/dimethyl sulfoxide systems (80 °C, 2.5–4 h) to afford (after extrusion of the nitrogen molecule from the intermediate) 3,6‐di(pyrrol‐2‐yl)pyridazines in up to 73% yield, while under non‐catalytic conditions this reaction does not take place. This unusual result substantially extends the scope of synthetic application and mechanistic diversity of the Diels–Alder reaction. The step‐wise mechanisms involving the formation of [OH/tetrazine]⁻ or [t‐BuO/tetrazine]⁻ anionic intermediate complexes or cycloaddition of tetrazine to the acetylide anion are considered.     

Synthesis and characterization of mono‐acylglycerols through the glycerolysis of methyl esters obtained from linseed oil

Here we investigate the production and characterization of mono‐acylglycerols through the glycerolysis of biodiesel, a methyl ester mixture, obtained from linseed oil. The biodiesel employed was derived from linseed oil through transesterification according to transesterification double step process 1 . The efficiency of H₂SO₄, CaO, and NaOH as catalysts was evaluated for the production of mono‐acylglycerols. The glycerolysis reactions were performed by varying the molar ratio of the reagents (biodiesel:glycerol), the type and amount of catalyst, reaction time and temperature. Systematic evaluation of reaction yield is shown as a function of these parameters. Reaction products were characterized through IR spectroscopy, hydrogen NMR, and the GC techniques. The study of three different catalysts indicated that the most efficient was 5% NaOH in a 1:5 biodiesel–glycerol molar ratio with 10 h reaction time. The reaction reached a maximum of 85% biodiesel conversion with a mono‐acylglycerol yield of 72% at 130°C.     

Efficiency of hydrogen recovery from reformate with a polymer electrolyte hydrogen pump

The energy efficiency of hydrogen recovery from mixtures of CO₂, H₂O, and H₂ by a polymer electrolyte hydrogen pump (PEHP) has been evaluated. The PEHP pumps protons across the polymer electrolyte, producing >99.99% pure H₂ and a concentrated CO₂ stream. Single stage PEHP experiments recovered 65% of the hydrogen with an energy efficiency of 50%. The energy efficiency is limited by hydrogen mass transport across the porous gas diffusion electrode. The mass transport resistance for hydrogen increases as H₂ is depleted from the CO₂/H₂ mixture by the PEHP. Analysis shows that a multistage PEHP with fixed applied potential difference can recover >90% of the hydrogen with an energy efficiency of 75%, whereas a novel multistage PEHP design with a programmed voltage profile can achieve >90% energy efficiency with >98% hydrogen recovery. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

DFT study on pathways of partial oxidation of DME under cold plasma conditions

Pathways of partial oxidation of dimethyl ether under cold plasma conditions have been studied by density functional theory method in this work. Total energies, energy barriers and reaction enthalpies at 0 K or 298.15 K have been calculated at GGA/PW91/DNP level. The calculation shows that, with the presence of O₂, the energy barrier of dimethyl ether conversion is reduced and the conversion from dimethyl ether to H₂ and CO is promoted under cold plasma conditions. The formation of syngas is through a multi-step pathway via the conversions of methoxymethyl radical (CH₃OCH₂·), formaldehyde, HCO·, CH₃·, CH₃O·, while the recombination of H generates extra hydrogen. The formation and effect of dimethyl ether anions have been also investigated in this work.     

Aggregation behavior of 3,6‐O‐carboxymethylated chitin in aqueous solutions

The aggregation behavior of 3,6‐O‐carboxymethylated chitin (3,6‐O‐CM‐chitin) in aqueous solutions was investigated by viscometry, gel permeation chromatography (GPC), and GPC combined with laser light scattering (GPC‐LLS) techniques. 3,6‐O‐CM‐chitin has a strong tendency to form aggregates in NaCl aqueous solutions with the apparent aggregation number (N_ap) of about 27. There were three kinds of aggregates corresponding to different cohesive energies, the aggregates with low cohesive energy were first dissociated at 60°C, the aggregates with middle cohesive energy were then dissociated at 80 to 90°C, and the aggregates with high cohesive energy were difficult to be disrupted by heating. Decreasing polysaccharide concentration (c_p) or increasing NaCl concentration (c_s) reduced the content of the aggregates. At the critical c_p of 2.5 × 10^?5 g/mL, the aggregates were dissociated into single chains completely. The change of aggregation and disaggregation of 3,6‐O‐CM‐chitin in water–cadoxen mixtures occurred from 0.1 to 0.4 of v_cad, and were irreversible. Intermolecular hydrogen bonding can be ascribed as main driving force for aggregation. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1838–1843, 2002     

Improved energy recovery from dark fermented cane molasses using microbial fuel cells

A major limitation associated with fermentative hydrogen production is the low substrate conversion efficiency. This limitation can be overcome by integrating the process with a microbial fuel cell (MFC) which converts the residual energy of the substrate to electricity. Studies were carried out to check the feasibility of this integration. Biohydrogen was produced from the fermentation of cane molasses in both batch and continuous modes. A maximum yield of about 8.23 mol H₂/kg COD_removed was observed in the batch process compared to 11.6 mol H₂/kg COD_removed in the continuous process. The spent fermentation media was then used as a substrate in an MFC for electricity generation. The MFC parameters such as the initial anolyte pH, the substrate concentration and the effect of pre-treatment were studied and optimized to maximize coulombic efficiency. Reductions in COD and total carbohydrates were about 85% and 88% respectively. A power output of 3.02 W/m³ was obtained with an anolyte pH of 7.5 using alkali pre-treated spent media. The results show that integrating a MFC with dark fermentation is a promising way to utilize the substrate energy.     

The photosynthetic efficiency of Chlorella biomass growth with reference to solar energy utilisation

The photosynthetic efficiency (PE) of a growing algal culture was determined from the growth yield (Y), that is, biomass produced/light absorbed and the calorific value of the biomass (k); PE = kY. To obtain the maximum photosynthetic efficiency the algae were grown in light-limited chemostat cultures in urea-mineral salts media plus CO₂ and steady-states were obtained at different specific growth rates. With a given light input the biomass output rate was independent of the specific growth rate up to at least 70% of the maximum specific growth rate. The photosynthetic efficiency was independent of the incident light intensity over the range studied, 5.3–21.3 W m^?2. The light source had a spectral range of 400–700 nm and its mean wavelength was assumed to be 575 nm. The values of the maximum growth yields (YG , g dry weight kJ^?1) were 0.0153 for the Sorokin Chlorella strain 211/8k and 0.0206 for a newly selected mixed culture MA003 which consisted of an alga and three species of heterotrophic bacteria. The maintenance energy (m) of the mixed culture MA003 was in the range 0–0.32 kJ g^?1 dry weight h^?1 and the specific maintenance rate (mYG ) was in the range 0–0.0066 h^?1. In Chlorella strain 211/8k the maximum PE was 34.7% which corresponds to a quantum demand (n) of 6.6 per O₂ molecule evolved. In the mixed culture MA003 the maximum PE was 46.8% with 95% confidence limits, 42.7–51.5. This PE value corresponds to a quantum demand (n) of 4.8 per O₂ molecule evolved. These results call in question the current model of photosynthesis which predicts that the maximum PE with absorbed light of mean wavelength 575 nm should not exceed 29% and the minimum quantum demand, n = 8. From our results with culture MA003 it is deduced that the maximum practicable storage of total solar energy by algal biomass growth in vitro is 18%.     

Epoxidation of a Series of C2–C6 Olefins in the Gas Phase

Epoxidation of ethylene, propylene, 2‐methylpropene, trans‐2‐butene, 2‐methyl‐2‐butene, and 2,3‐dimethyl‐2‐butene were carried out in a flow‐through reactor in the homogeneous gas phase at pressures of 0.25–1.0 bar in the temperature range of 250–375 °C. Residence times in the reactor varied from 8.3 to 38 ms. The oxidizing agent needed in the feed gas is ozone. The O₃ efficiency (reacted olefin/initial O₃) was found to be strongly dependent on the reactivity of the olefin used. For C₄–C₆ olefins, the O₃ efficiency was better than 75 % in each case. For 2‐methyl‐2‐butene and 2,3‐dimethyl‐2‐butene, the O₃ efficiency exceeded the theoretical value of 100 % considerably. The selectivity to epoxide was about 90 % independent of the olefin used. Under conditions of nearly total olefin conversion, the high selectivity to the epoxide has been retained as unchanged. There were no indications for consecutive reactions of the epoxides.     

Novel fluorescent porous hyperbranched aromatic polyamide containing 1,3,5‐triphenylbenzene moieties: Synthesis and characterization

In this thesis, two novel porous hyperbranched poly(1,3,5‐tris(4‐carboxyphenyl) benzene p ‐phenylenediamine) amides with different terminal functional groups are synthesized through an A₂ + B₃ approach using 1,3,5‐tri(4‐carboxyl phenyl) benzene (H₃BTB) and p ‐phenylenediamine as raw material, N ‐methyl‐pyrrolidone as solvent, triphenyl phosphite and pyridine as dehydrating agent, by means of regulating the mole ratio of the monomers. The chemical structures of the prepared hyperbranched polymers are characterized by Fourier transform infrared spectroscopy and nuclear magnetic resonance (¹H‐NMR and ¹³C‐NMR) analysis. These two polymers can be soluble in dimethyl sulfoxide (DMSO) and N ,N ‐dimethyl formamide (DMF). Their DMSO solutions exhibit strong blue fluorescence, especially for the amino terminated polymer HP‐NH₂. While in DMF solution, the two polymers emit strong green fluorescence. These two polymers are porous polymers with the Brunauer?Emmett?Teller surface areas of 4.53 and 24.52 m²/g for HP‐COOH and HP‐NH₂, respectively. They are potential useful in the areas of storage, separation, catalysis, and light emitting. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44505.