Synergy in the hybrid thermochemical–biological processes for liquid fuel production

For a successful large scale implementation of biomass-to-liquid fuel for transportation, it is imperative that production of liquid fuel from biomass be maximized. For this purpose, synergistic processes using energy from sustainable carbon-free energy sources are needed. In this paper, we present such novel integrated processes that, when compared to the known conventional conversion methods, have potential to produce nearly three times more liquid fuel from a given quantity of biomass. The new processes treat biomass predominantly as carbon source and rely on the novel integrations to preserve carbon atoms during biomass conversion to liquid fuel. We have named such approach as hybrid hydrogen–carbon (H₂CAR) process. Furthermore, we propose a novel synergistic integration between H₂CAR and fermentation process where high-level heat from the H₂CAR process is used to supply process heat for the fermentation process and CO₂ produced during the fermentation is converted to liquid fuel using H₂CAR process. This synergy leads to increase in process carbon efficiency (100%) and higher energy efficiency (65.7% vs. 57.2%), significantly decreasing land area requirement to produce liquid fuel compared to fermentation-based processes. Such synergistically integrated processes provide attractive opportunities for process design, operation and control.     

Cationic olefin Pd(II) complexes bearing α-iminoketone N,O-ligands: unprecedented isomerisation of the methoxycyclooctenyl ligand

The reaction of [Pd(η¹,η²-C₈H₁₂OMe)Cl]₂ with α-iminoketone ligands affords cationic η¹,η²-5-methoxycyclooctenyl Pd(II) complexes, the intramolecular and interionic structures of which were investigated in both solution and solid state; such complexes undergo unprecedented isomerisation to η¹,η²-1-methoxycyclooctenyl complexes assisted by weak nucleophiles such as olefins or alkynes.     

Thermodynamic analysis and optimization of RWGS processes for solar syngas production from CO2

Process systems were investigated for syngas production from CO₂ and renewable energy (solar) by the reverse water‐gas shift (RWGS) and the reverse water‐gas shift chemical looping (RWGS‐CL) process. Thermodynamic analysis and optimization was performed to maximize the solar‐to‐syngas (StS) efficiency η_StS. Special emphasis was laid on product gas separation. For RWGS‐CL, maximum StS efficiencies of 14.2 and 14.4% were achieved without and with heat integration, respectively. The StS efficiency is dictated by the low overall efficiency of H₂ production. RWGS‐CL is most beneficial for the production of pure CO, where the StS efficiency is one percent point higher compared to that of the RWGS process with heat integration. Heat integration leads to significant reductions in external heat demand since most of the gas phase process heat can be integrated. The StS efficiencies for RWGS and RWGS‐CL achieve the same level as the reported values for solar thermochemical syngas production. © 2016 American Institute of Chemical Engineers AIChE J, 63: 15–22, 2017     

Partial oxidation reforming of biomass fuel gas over nickel-based monolithic catalyst with naphthalene as model compound

With naphthalene as biomass tar model compound, partial oxidation reforming (with addition of O₂) and dry reforming of biomass fuel gas were investigated over nickel-based monoliths at the same conditions. The results showed that both processes had excellent performance in upgrading biomass raw fuel gas. Above 99% of naphthalene was converted into synthesis gases (H₂+CO). About 2.8 wt% of coke deposition was detected on the catalyst surface for dry reforming process at 750 °C during 108 h lifetime test. However, no coke deposition was detected for partial oxidation reforming process, which indicated that addition of O₂ can effectively prohibit the coke formation. O₂ can also increase the CH₄ conversion and H₂/CO ratio of the producer gas. The average conversion of CH₄ in dry and partial oxidation reforming process was 92% and 95%, respectively. The average H₂/CO ratio increased from 0.95 to 1.1 with the addition of O₂, which was suitable to be used as synthesis gas for dimethyl ether (DME) synthesis.     

Energy conversion and temperature dependence in ozone generator fed by synthetic air

A homogenous chemical kinetic model consisting of 21 species and 118 reactions is applied to investigate energy conversion and its temperature dependence in ozone generator fed by synthetic air. The portion of electric energy converted into reaction heat, gas heating and heat loss to surroundings (by convection) in terms of the total electric energy input, the conversion ratios η_reaction, η_gas, and η_loss, are obtained. The detailed reaction pathway including the degree of transformation among species for ozone production is also obtained via simulation of the reaction kinetics. In addition, sensitivity analysis and rate-of-production analysis for the three foremost species O₃, O, and N₂(A) are performed to understand quantitatively the temperature dependence of sensitivity coefficient and production rate for each individual reaction. η_reaction shows a steep rise at low specific energy, but then suffers a gradual decrease at high specific energy. η_loss has a contrary behavior. And η_gas increases steadily with the increase of specific energy. The η_reaction peak of 35.1% is achieved at specific energy of 0.17 J/cm³ at the conditions under investigation. Additionally, inlet gas temperature only has a small effect on energy conversion. Moreover, high gas temperature in discharge gap is confirmed to be not favorable for ozone formation from the view of reaction heat. The sensitivity coefficients of reactions with electron participation are sensitive to gas temperature. O+O₂+O₂→O₂+O₃ and O+O₂+N₂→N₂+O₃ account for about 70% and 30% of generated ozone respectively at the given conditions. And e+O₂→e+O+O, N₂(A)+O₂→N₂O+O, and N₂(A)+O₂→O+O+N₂ are responsible for about 51.3%, 14.7%, and 32.0% of oxygen atom, respectively.     

Energy Conversion and Temperature Dependence in Ozone Generator Using Pulsed Discharge in Oxygen

A detailed reaction kinetic model consisting of 10 species and 63 reactions is developed to investigate the energy conversion and temperature dependence in an ozone generator using oxygen pulsed discharge. The energy conversion ratios of total electric energy converted into reaction heat, heat carried by gas and heat loss to ambient, namely η_reaction, η_gas and η_loss, are obtained for the first time. The ratio of reaction heat η_reaction decreases substantially with increasing specific energy and inlet gas temperature, which represents how much energy is utilized effectively to synthesize ozone. Correspondingly, η_loss and η_gas increase gradually. η_reaction declines from 55.4% to 27.7% at inlet gas temperature of 298 K when specific energy changes from 0.06 J/cm³ to 0.78 J/cm³. The detailed reaction pathway including the degree of transformation among species for ozone formation is also obtained via kinetics simulation. Meanwhile, sensitivity analysis and rate-of-production analysis for the four most important species O₃, O, O(1D) and O₂(b¹∑) obtained from the reaction pathway are executed to understand quantitatively the temperature dependence of sensitivity coefficient and production rate for each individual reaction. The production rate of ozone via the most important ozone generation reaction O+O₂+O₂ = > O₃+O₂ increases linearly with the increase of gas temperature, as well as the destruction rates of ozone via the most important ozone decomposition reactions O₃+O₃ = > O₂+O₂+O₂ and O₃ + O = > O₂(b¹∑)+O₂.     

Semi-transparent thin film solar cells by a solution process

Easily processed, low cost, and highly efficient solar cells are desirable for photovoltaic conversion of solar energy to electricity. We present the fabrication of precursor solution processed CuInGaS2 (CIGS) thin film solar cells on transparent indium tin oxide (ITO) substrates. The CIGS absorber film was prepared by a spin-coating method, followed by two successive heat treatment processes. The first annealing process was on a hot plate at 300 °C for 30 min in air to remove carbon impurities in the film; this was followed by a sulfurization process at 500 °C in an H₂S(1%)/Ar environment to form a polycrystalline CIGS film. The absorber film with an optical band-gap of 1.52 eV and a thickness of about 1.1 µm was successfully synthesized. Because of the usage of a transparent glass substrate, a bifacial CIGS thin film device could be achieved; its power conversion efficiency was measured to be 6.64% and 0.96% for front and rear illumination, respectively, under standard irradiation conditions.     

Experimental investigation of a packed-bed solar reactor for the steam-gasification of carbonaceous feedstocks

Steam-gasification of coal, biomass, and carbonaceous waste feedstocks for syngas production is performed using concentrated solar energy as the source of high-temperature process heat. The solar reactor consists of two cavities separated by a SiC-coated graphite plate, with the upper one serving as the radiative absorber and the lower one containing the reacting packed bed that shrinks as the reaction progresses. The carbonaceous feedstocks tested were industrial and sewage sludges, scrap tire powder, fluff, South African coal, and beech charcoal, and are characterized by having a wide range of volatile, ash, and fixed carbon contents, elemental compositions, and physical properties. A 5 kW solar reactor prototype, subjected to radiative flux concentrations up to 2953 suns and operated at temperatures up to 1490 K, yielded high-quality syngas of typical molar ratios H₂/CO = 1.5 and CO₂/CO = 0.2, and with a calorific content up to 30% upgraded over that of the input feedstock. Solar-to-chemical energy conversion efficiencies varied between 17.3% and 29%. Pyrolysis was evident through the evolution of higher gaseous hydrocarbons and liquid tars during heating of the packed bed. The engineering design, fabrication, and testing of the solar reactor are described.     

Improved Energy Efficiency of Power-to-X Processes Using Heat Pumps Towards Mobility Sector Defossilization

Combining Power-to-X (PtX) processes with high temperature heat pumps (HTHP) can significantly increase their energy efficiency. Evaluating the example of oxymethylene ethers (OME) production from H₂ via H₂O electrolysis and captured CO₂ from air shows that by upgrading waste heat streams using HTHP, a process overall energy efficiency of higher than 61 % can be achieved compared to 30 % in conventional integrated processes. Thereby, the waste heat stream from H₂O electrolysis already covers the low temperature heat demand for CO₂ capture via direct air capture, not only for OME but also for various PtX products. Importantly, a significant lever for the energy efficiency enhancement is the consideration of other low temperature heat-demanding sectors. High overall process energy efficiencies and the electrification of the industry are key aspects towards a sustainable mobility sector.     

Gasification of pelletized renewable fuel for clean energy production

The main aim of the study was to develop and investigate a small-scale experimental gasification technique for the effective thermal decomposition of pelletized renewable fuels (wood sawdust, wheat straw). The technical solution of the biomass gasifier for gasification of renewable fuels presents a downdraft gasifier with controllable additional heat energy supply to the biomass using the radial propane flame injection into the bottom part of the biomass layer. From the kinetic study of the mass conversion rate of pelletized biomass and variations of the composition of produced gas it is concluded that the process of biomass gasification is strongly influenced by the amount of additional heat energy and air supply into the biomass. The results of experimental measurements of the composition of produced gas have shown that under the conditions of the sub-stoichiometric air supply into the layer of pelletized wood biomass (α < 0.3) increasing additional heat energy supply in a range from 60 kJ up to 130 kJ leads to an enhanced mass loss of pelletized biomass and enhanced formation of volatiles (CO, H₂) in the flaming pyrolysis zone. For the wood biomass the average content of CO in the products can be increased from 73 g/m³ up to 97 g/m³, while the average content of H₂ increases from 4.7 g/m³ up to 6.2 g/m³. Similar variations of the composition of products are observed during the enhanced gasification of the wheat straw. At constant rate of additional heat energy supply and the sub-stoichiometric combustion conditions (α ≈ 0.17 − 0.30), a faster thermal decomposition of the pelletized biomass and larger average amount of the produced volatiles (CO, H₂) can be obtained by increasing the air supply rate from 0.27 to 0.43 g/s, determining the variations of air-to-fuel ratio in a range from 1.3 up to 1.6.     

Ru4(μ-CO)(CO)9(η4-μ4-C6H4)(η2-μ1,μ4-PPhCH2CH2PPh2): an unusual pyrolysis product of Ru3(CO)10(dppe) containing a benzyne ligand

The thermal decomposition of Ru₃(CO)₁₀(dppe) in refluxing benzene gives, in contrast to the pyrolysis of the dppm analogue, the tetranuclear cluster Ru₄(μ-CO)(CO)₉(η⁴-μ₄-C₆H₄)(η²-μ₁,μ₄-PCH₂CH₂PPh₂) (1) along with Ru₃(CO)₉(η²-μ₁,μ₂-C₆H₅)(η³-μ₁,μ₂-PPhCH₂CH₂PPh₂) (2). The single-crystal structure analysis of 1 reveals a square-planar tetraruthenium skeleton containing a η⁴-μ₄-benzyne ligand as well as a η²-μ₁,μ₄-phosphinidene–phosphine ligand.     

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.     

Solid-state dye-sensitized hierarchically structured ZnO solar cells

A novel solid-state hierarchically structured ZnO dye-sensitized solar cell (DSC) was assembled by using TiO₂ as filler in polyethylene oxide (PEO)/polyethylene glycol (PEG) electrolytes and ZnO nanocrystalline aggregates as photoanode film. Under optimized composite polyelectrolyte containing PEO/oligo-PEG/TiO₂/LiI/I₂ the photovoltaic performance of the solid-state ZnO DSCs was significantly better, with an overall conversion efficiency (η) of 1.8% under irradiation of 100 mW/cm², which was higher than those of the cells with PEO/TiO₂/LiI/I₂ (η = 1.1%) or PEO/oligo-PEG/LiI/I₂ electrolyte (η = 1.5%). Further, the hierarchically structured ZnO-based cell showed a higher η value of 2.0% under 60 mW/cm² radiation. The morphologies, ionic conductivity of three different composite electrolytes and their performance to the DSCs were also studied by FESEM, I–V data, IPCE and EIS.     

Rheological behaviors of PVA/H2O solutions of high‐polymer concentration

The dynamic viscoelastic properties of poly(vinyl alcohol) (PVA)/H₂O solutions with concentrations of 10 to 25 wt % have been characterized by controlled‐stress rheometry at 30°C. Parameters relating to the linear and nonlinear viscoelasticities include complex viscosity (η*), storage modulus (G′), loss tangent (tan δ), relaxation time (λ), thixotropy, and creep. Change curves of η*, G′, tanδ, and λ with frequency (ω) have been obtained for the PVA/H₂O solutions. Creep and recovery testing yielded compliance (J′) curves with loading and unloading. Shear stress versus rate profiles of the PVA solutions have been obtained through thixotropic measurements. The PVA concentration has been found to have a profound influence on the rheological properties of the aqueous solutions. Four aqueous solutions of 10, 15, 20, and 25 wt % PVA at 30°C exhibited shear‐thinning and showed different transition behaviors of η* and G′ with frequency, and different degrees of creep under constant stress to recovery with time. The 10 wt % PVA solution was viscous and displayed the lowest η* and G′; the 25 wt % PVA solution was viscoelastic and displayed the highest η* and G′; the 15 and 20 wt % PVA solutions showed η* and G′ values and creep to recovery behaviors intermediate between those of the 10 wt % and 25 wt % PVA solutions. The different rheological properties of these PVA/H₂O solutions are considered to correlate with interchain hydrogen bonds and shear‐induced orientation in the solutions. Shearing is able to break the intrachain and interchain hydrogen bonds, and, at the same time, the orientation creates new interchain hydrogen bonding. The reorganization of hydrogen‐bonding mode contributes to the transitions of the macroscopic viscoelasticity with frequency. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Use of Etching to Improve Efficiency of the Multicrystalline Silicon Solar Cell by Using an Acidic Solution

Surface texturing methods using an alkaline solution for monocrystalline Si (c-Si) solar cells have been widely accepted to improve cell performance. However, multicrystalline Si (mc-Si) cells are difficult to be texturized by alkaline etching, because the grains in the substrates are randomly oriented. In this study, we considered a HF/HNO ₃/H ₂O acid solution for texturing the mc-Si cells. The conversion efficiency of mc-Si solar cells textured with the solution (HF/HNO ₃/H ₂O = 30:1:2.5) has relatively high values. In our study, sufficient light confinement is achieved, which contributes to the improvement of both the short circuit current and the conversion efficiency of the acid textured cells. The optimal acid etching ratio HF:HNO ₃:H ₂O = 30:1:2.5 with etching time of 60 s and lowering 41.9 % of the R value can improve 111.8 % of the conversion efficiency (η) of the developed solar cell. More detailed information is used to measure the internal quantum efficiency (IQE) and the lifetime of minority carriers. Thus, the acid texturing approach is instrumental to achieve high efficiency in mass production using relatively low-cost mc-Si as the starting material with proper optimization of the fabrication steps.     

An approach to laminated flexible Dye sensitized solar cells

We have built TiO₂ Dye sensitized solar cells (DSSCs) that combined flexible TiO₂ photoanodes coated on ITO/PET substrates with a gel electrolyte based on PVDF-HFP-SiO₂ films. Titanium isopropoxide (TiP₄) was used as additive to TiO₂ nanoparticles for increasing power conversion efficiency in Dye sensitized solar cell electrodes prepared at low-temperature (130 °C). An efficiency η_AM1.5G = 3.55% on ITO/PET substrates is obtained at 48 mW/cm² illumination with a standard liquid electrolyte based on methoxypropionitrile. Among several solvents forming gels with PVDF-HFP-SiO₂, N-methyl (pyrrolidone) (NMP) was found to enable the most stable devices. A power conversion efficiency η_AM1.5G = 2% was obtained under 10 mW/cm² with flexible TiO₂-ITO-PET photoanodes and the PVDF-HFP-SiO₂ + NMP gel electrolyte.     

Oxidation of Propylene Glycol Methyl Ether Acetate Using Ozone-Based Advanced Oxidation Processes

The present study investigates the degradation of PGMEA and its TOC removal using O₃, UV/O₃, O₃/H₂O₂, and UV/H₂O₂ processes under various experimental conditions. Ozonation of PGMEA was substantially enhanced in the presence of UV light and H₂O₂. Approximately 33% of TOC enhancement was noted in UV/O₃ process over ozonation process. A linear relationship between PGMEA and H₂O₂ decomposition was observed in O₃/H₂O₂ and UV/H₂O₂ processes. The influence of solution pH on the decomposition of PGMEA was investigated and found that basic medium was the most efficient in all AOPs. After 60 minutes 62.4%, 100%, 90% and 54% of PGMEA decomposition at pH 10.0 was observed in O₃, UV/O₃, O₃/H₂O₂, and UV/H₂O₂ processes, respectively. It is concluded that UV/O₃ process is a promising approach for the oxidation and removal of PGMEA.     

Dynamic rheological properties of polyetherimide/polyetheretherketone/liquid crystalline polymer ternary blends

The dynamic rheological properties of poly(etherimide)/poly(etheretherketone)/liquid crystalline polymer (LCP) ternary blends were measured in order to correlate these properties with the morphology obtained after extrusion. The viscosity radio, η_d/η_m, where η_d = disperse phase viscosity and η_m = matrix viscosity, had to be redefined. Below 50 wt% LCP, η_d = η_LCP, η_m = η_PEEK+PEI and η_d/η_m < 1. Above 50 wt% LCP, η_d = η_PEEK+PEI, η_m = η_LCP and η_d/η_m > 1. Fibrillar morphologies were obtained in both cases, except below a concentration of 20 wt% LCP. At low concentrations of LCP the ternary blends had lower viscosities than the component polymers, showing a flow promotion effect of the LCP on the PEI- and PEEK-rich phases.     

Non-equilibrium thermodynamic studies of electro—kinetic effects—XI. Studies with aqueous dioxane

Experimental results for the measurements of electro—osmosis, electro—osmotic pressure difference, streaming potential for dioxane—water (DH₂O) mixtures (30%, 40%, 50% and 60% by mass of dioxane) using Pyrex sintered disc (G₃) at 25° and at voltages of 40 V to 300 V are reported. The data are analysed in the light of the theory of non-equilibrium thermodynamics. It has been found that the validity of the phenomenological relations describing electro—kinetic effects increases with the decrease in the dielectric constant of the mixture. Second-order coefficients estimated from the electro—osmosis and electro—osmotic pressure difference are reported. Onsager's reciprocity relations have been found to hold good for all the mixtures. It has been found that the concentration dependence of L₂₂ and L₂₁ do not conform to the Spiegler's frictional model. Efficiency of electro—kinetic energy conversion (η_e) for electro—osmotic flows has been calculated and it is found that for different composition of dioxane—water mixtures η_max was obtained at half the value of the electro—osmotic pressure difference.     

An empirical thermodynamic model for the ammonia—water—carbon dioxide system at urea synthesis conditions

An empirical thermodynamic model for the NH₃–H₂O? CO₂ system at equilibrium at urea synthesis conditions (140 ≤ T ≤ 200 °C, 50 ≤ P ≤ 250 atm, 2.4 ≤ NH₃/CO₂ ≤ 6, H₂O/CO₂ ≤ 0.5) is presented. This model can quantitatively or semi-quantitatively describe a number of important phenomena in the urea synthesis, such as the bubble-point and gas—liquid equilibrium conditions and the effect of excess ammonia and water on the conversion to urea in the liquid phase. The model also sheds light on the problem of the conversion to urea at high temperatures (T > 190–200 °C).