Aqueous Phase Reforming Research Articles

Global warming potential analysis of bio-jet fuel based on life cycle assessment

Due to the large amount of greenhouse gas (GHG) emissions and the high dependence on fossil energy, the aviation industry has attracted a lot of attention for emission reduction and sustainable development. Biomass is a green and sustainable renewable resource, and its chemical conversion to produce bio-jet fuel is considered to be an effective way to replace fossil jet fuel and achieve emission reduction. In this study, the cradle-to-grave life cycle analysis is conducted for three bio-jet fuel conversion pathways, including biomass aqueous phase reforming (APR), hydrogenated esters and fatty acids (HEFA), and hydrothermal liquefaction (HTL). Compared with fossil jet fuels, the three bio-jet fuels have a great advantage on global warming potential (GWP), contributing 29.2, 43.6 and 51.2 g CO2-eq/MJ respectively. In general, as a relatively new bio-jet fuel conversion technology, the technology of aqueous phase reforming has minimal environmental impact. If the barriers of raw material availability and economy could be broken down, bio-jet fuel will have great development potential in replacing fossil jet fuel and realizing sustainable development.

Aqueous-Phase Glycerol Conversion over Ni-Based Catalysts Synthesized by Nanocasting

A morphological strategy consisting of nanocasting synthesis of nickel aluminate spinel precursor was addressed. Two nanocasted catalysts were synthesized involving different template-removal procedures (i.e., Teflon-assisted calcination vs. NaOH washing) for spinel recovery. As a reference, spinel NiAl2O4 supported by SBA-15 and bare nickel aluminate spinel were selected. The obtained solids were characterized in detail, examining their textural, acid–base, structural and compositional characteristics, either in the calcined or reduced forms. The as-obtained catalysts’ performance was evaluated in the aqueous-phase reforming of glycerol at 235 °C and 35 bar. Exhausted samples were also characterized to enlighten changes in catalyst properties during the aqueous-phase reaction. NiAl/SBA-15 and NiAl-NCF catalyst showed very poor catalytic performance for the glycerol transformation. NiAl-NCN catalyst presented improved activity with respect to NiAl, with a 20% higher hydrogen production rate but, as a drawback, higher methane formation for a whole range of glycerol conversions. Exhausted catalyst indicated nickel oxidized in liquid phase reaction.

High-loaded sub-6 nm Cu catalyst with superior hydrothermal-stability and efficiency for aqueous phase reforming of methanol to hydrogen

Developing an efficient, hydrothermally stable and non-noble metal catalyst is a key for application of aqueous-phase reforming of methanol (APRM) to produce hydrogen in situ. Herein, a Cu@NC catalyst with high metal loading (44.9 wt %) and sub-6 nm Cu nanoparticle size was synthesized by pyrolyzing Cu-chitosan chelates. The coordination between metal ions (Cu2+) and amine functional groups in chitosan enabled high metallic dispersion in Cu-chitosan chelates. After pyrolysis, the Cu nanoparticles were embedded in N-doped carbon (NC) matrix. This confinement effect ensured remarkable hydrothermal stability for the Cu@NC catalyst. As a result, a high hydrogen production rate of 34.0 μmol·gcat−1·s−1 was obtained over Cu@NC-200 catalyst, about 12.6 times higher than that of a traditionally impregnated Cu/C catalyst. Notably, no deactivation and aggregation of Cu nanoparticle were observed after 200 h’ running in APRM, indicating excellent hydrothermal stability of the Cu@NC catalyst. Thus, this work developed a simple strategy to prepare an efficient and robust catalyst that could work well under hash hydrothermal conditions for application of APRM on the compact mobile devices.

Lignin depolymerization and monomeric evolution during fast pyrolysis oil upgrading with hydrogen from glycerol aqueous phase reforming

• Upgrading of Bio-oil with hydrogen from glycerol aqueous phase reforming. • 34.6% of lignin derived compounds were converted to hydrocarbon. • Pt/C and H-ZSM-5 catalysts were effective for hydrodeoxygenation reaction. • n-Decane as a co-solvent prevents condensation reaction. • Series of demethoxylation, hydrogenation, and hydrodeoxygenation were observed. A novel approach to Fast Pyrolysis Oil (FPO) upgrading with hydrogen from glycerol aqueous phase reforming (APR) was conducted in a biphasic solution. FPO contains both monomer and polymer compounds which rich in oxygen, giving high acidity and low stability. Hydrogen demanding reaction of depolymerization and hydrodeoxygenation (HDO), often called upgrading, is required to improve FPO properties by converting these compounds to hydrocarbon monomers. APR reaction of glycerol where glycerol is reacted with water to produce hydrogen is one of the renewable choices to obtain hydrogen. Prior to upgrading of FPO, catalyst screening and reaction optimization were studied using phenol as a model compound. Upgrading of FPO with in situ glycerol APR was conducted with Pt/C, facilitating hydrogen production (APR) and utilization (hydrogenation), and H-ZSM-5, facilitating dehydration reaction. n-Decane was added to the reaction as a co-solvent to prevent the condensation of the non-polar fragments of FPO which led to coke formation. Upon upgrading the weight average molecular weight (Mw), polydispersity index (PDI), and oxygen to carbon (O/C) ratio of FPO decreased. The highest hydrocarbon yield (7.7% FPO basis or 34.6% lignin basis) was obtained by combining Pt/C and H-ZSM-5 catalysts with n-decane as a co-solvent. Evidence of progressive depolymerization and sequential demethoxylation, hydrogenation, and deoxygenation during upgrading were observed in the products.

Synergetic photocatalytic and thermocatalytic aqueous phase reforming of methanol for hydrogen production based on noble metal/photosensitive supports catalysts

To overcome high Gibbs free energy and low reaction rate of thermal catalytic and photocatalytic hydrogen production from methanol-H2O mixture, photo-thermal synergistic catalysis (PC-TC) reforming has proved to be an effective strategy owing to the photo-assited thermal synergistic effect to accelerate the step controlling kinetic behavior. In order to efficiently produce H2, proper photosensitive catalysts which absorb light energy and also show efficient thermal catalytic (TC) performance need to be developed. To study the designing principle for catalysts, herein we incorporate Pt/Pd and three different supports which show similar band gaps (ZnO, CeO2, and P25) through the in-situ photo-deposition, which act as catalysts for PC-TC methanol aqueous reforming. The resultant 0.1%Pt/P25 catalyst exhibits H2 evolution activity ∼3.1 times than that of the TC condition and ∼5.5 times than that of the photocatalytic reforming (PC) condition in the proposed PC-TC process; meanwhile 0.1%Pt/ZnO and 01%Pt/CeO2 under PC-TC condition show ∼1.3 times and ∼2.0 times than that of the catalytic performance under TC condition. The physical characterizations prove that the metal-support interaction and the supports may be key factors for the catalytic performance. The active intermediate trapping experiments demonstrate possible intermediates in the PC-TC process and established reaction mechanisms to explain the synergetic effect for improved efficiency of hydrogen production. These findings may open up a new avenue of designing catalysts based on semiconductors for the PC-TC reforming of methanol-water to produce hydrogen in a high-efficiency and low-cost way, serving the needs of the future hydrogen economy.

Study on the promotion of FeOx species on water-gas shift reaction in methanol aqueous phase reforming over PtFe/Al2O3 catalyst

Hydrogen production by catalytic aqueous phase reforming (APR) of biomass-derived oxygenates is a promising route to produce hydrogen in a renewable way. As the typical APR catalyst, Pt/Al2O3 is confronted with high methanation activity that consumes H2 and produces undesired CH4 during the treatment of methanol solution. In contrast, WGS reaction is the main pathway to boost H2 generation during APR process. In this work, a series of PtFe/Al2O3 catalyst with different Fe contents were prepared, characterized and tested for the methanol APR reaction. XRD, TEM, XPS and H2-TPR technologies were applied to study the change of physicochemical properties with the addition of iron. The restriction on methanation and promotion on WGS reaction were proved as well. With the increase of Fe content, the interaction between Pt and FeOx species have both positive and negative effects on APR reactivity while the CH4 selectivity descending continuously from 9.25% to as low as 0.60%. Besides, the effects of reduction temperatures (250–350 °C) of Pt0.5Fe/Al2O3 catalyst on APR performances were also investigated. An “Oxygen dynamic transfer cycle” between H2O/CO∗ and FeOx species with oxygen vacancies is proposed and verified. This indirect WGS reaction through lattice oxygen on FeOx species that boosting WGS reactivity helps improving H2 selectivity in the gas products of methanol APR.

Identifying the realistic catalyst for aqueous phase reforming of methanol over Pt supported by lanthanum nickel perovskite catalyst

In-situ supply of H2 by aqueous phase reforming (APR) of methanol is promising but still challenging due to the unsatisfied activity and stability of catalyst. Herein, we prepared lanthanum nickel perovskite supporting Pt catalysts and evaluated their performance in methanol APR. A transformation from lanthanum nickel perovskite into LaCO3OH happened after APR. The characterizations results reveal that these two perovskite catalysts transformed into LaCO3OH supporting Pt and NiOx structure. We further prepared Pt-NiOx/LaCO3OH catalyst to verify it. Combining with temperature programmed surface reaction, a possible mechanism is proposed. The transformed catalyst possessed more metallic Pt sites and more abundant active OH groups, which are beneficial for methanol decomposition and CO shift, respectively. In addition, although the structure transformation happened for perovskite supporting Pt catalyst, it presented extremely excellent stability with only 7% loss of its highest rate of hydrogen production after 315 h on stream.

Integration of hydrothermal carbonization and aqueous phase reforming for energy recovery from sewage sludge

This study investigates the energy recovery from sewage sludge by combining hydrothermal carbonization and aqueous phase reforming of the generated process water. The hydrothermal treatment was carried out at 170 °C and 230 °C for 1 h, and produced a hydrochar with adequate physicochemical properties, such as a higher heating value (20–24 MJ kg−1) than sludge, improved fuel ratio (0.2–0.5) and a broad comprehensive combustion index (5.8 × 10−7 to 10.0 × 10−7 min−2 °C−3). Aqueous phase reforming of the process water was carried out at 220 °C and 25–29 bar for 4 h. A maximum H2 yield of 98.7 mmol H2 gTOC−1 was achieved using a bimetallic Pt/Rh catalyst supported on carbon black and for the process water obtained at the lowest carbonization temperature. The integration of hydrothermal carbonization and aqueous phase reforming processes is an interesting alternative for the management and energy recovery of sewage sludge, which allows reaching a potential energy recovery of 17.3 MJ per kg of dry sewage sludge, equivalent to 93.5 % gross energy recovery, under optimized conditions.

Hydrogen production via aqueous-phase reforming for high-temperature proton exchange membrane fuel cells - a review.

Aqueous-phase reforming (APR) can convert methanol and other oxygenated hydrocarbons to hydrogen and carbon dioxide at lower temperatures when compared with the corresponding gas phase process. APR favours the water-gas shift (WGS) reaction and inhibits alkane formation; moreover, it is a simpler and more energy efficient process compared to gas-phase steam reforming. For example, Pt-based catalysts supported on alumina are typically selected for methanol APR, due to their high activity at temperatures of circa 200°C. However, non-noble catalysts such as nickel (Ni) supported on metal-oxides or zeolites are being investigated with promising results in terms of catalytic activity and stability. The development of APR kinetic models and reactor designs is also being addressed to make APR a more attractive process for producing in situ hydrogen.This can also lead to the possibility of APR integration with high-temperature proton exchange membrane fuel cells. The integration can result into increased overall system efficiency and avoiding critical issues faced in the state-of-the-art fuel cells integrated with methanol steam reforming.

Ce-doped cobalt aluminate catalysts for the glycerol hydrodeoxygenation (HDO) with in-situ produced hydrogen

In this study, the hydrodeoxygenation (HDO) of glycerol with in-situ produced H2, via aqueous-phase reforming, was investigated over Ce-doped CoAl2O4 catalysts synthesized by coprecipitation. The catalytic runs were performed at 50 bar/260 ºC for 3 h TOS in a fixed bed reactor. The synthesized catalysts were extensively characterized to better understand the effect of physicochemical and surface characteristics on the catalytic performance. The results revealed that doping with Ce increases the population and strength of acid centers, which results in a higher selectivity towards deoxygenated liquid products. Ce-doped catalysts exhibited higher yield to hydroxyacetone and 1,2-propanediol. Post-reaction characterization revealed a decrease of the metallic surface area, mainly due to alumina coating, and to a lesser extent, due to the oxidation and leaching of the cobalt.

Coupling hydrothermal liquefaction and aqueous phase reforming for integrated production of biocrude and renewable H2

AbstractLignin‐rich stream from lignocellulosic ethanol production was converted into biocrude by continuous hydrothermal liquefaction (HTL) while hydrogen was produced by aqueous phase reforming (APR) of the HTL aqueous by‐product. The effects of Na2CO3 and NaOH were investigated both in terms of processability of the feedstock as well as yield and composition of the obtained products. A maximum biocrude yield of 27 wt% was reached in the NaOH‐catalyzed runs. A relevant amount of dissolved phenolics were detected in the co‐produced aqueous phase (AP), and removed by liquid–liquid extraction using butyl acetate or diethyl ether, preserving the APR catalyst stability and reaching an hydrogen yield up to 146 mmol H2 L−1 AP. Preliminary mass balances integrating HTL and APR showed that the hydrogen provided by APR may account for up to 46% of the hydrogen amount theoretically required for upgrading the HTL biocrude, thus significantly improving the process performance and sustainability.

Aqueous-phase reforming of glycerol over Pt-Co catalyst: Effect of process variables

This study examined the influence of process variables (glycerol concentration in feed, coupled temperature/pressure and space velocity) in the catalytic performance in the APR of glycerol over 0.3Pt/CoAl catalyst in a continuous fixed-bed reactor in order to maximize the production of H2. The effect of glycerol concentration in the feed was studied from 5 to 20 wt%, the coupled temperature/pressure varied from 225 °C/25 bar to 260 °C/50 bar and the spatial velocity was changed from 0.68 to 17 h-1. Our results reflected that H2 production was favored at higher reaction temperature/pressure (3.62 vs. 2.49 molH2/molGly-converted, at the most severe and mild conditions, respectively), lower WHSV (3.89 vs. 1.27 molH2/molGly-converted, at the lowest and highest space velocity, respectively) and more diluted feedstocks (3.95 vs. 1.44 molH2/molGly-converted, at the most diluted and concentrated freestreams, respectively). A threshold value at 10 wt% glycerol was found for the ratio of dehydrogenation to dehydration liquid products. The post-reaction catalyst was also characterized by several techniques, showing that Co leaching was the major drawback, especially at the mildest operation conditions, while carbonaceous deposits are negligible.

Aqueous phase reforming of birch and pine hemicellulose hydrolysates

The current work focuses on studying the aqueous phase reforming (APR) of pine and birch hydrolysate obtained from waste wood by using organic acids available from biorefineries. Processing of representative synthetic mixtures was utilized in the work in order to support data interpretation related to the influence of different chemical compound and processing parameters on the APR of the actual hydrolysates. It was shown, that hydrogenation of the hydrolysates prior to APR was not feasible in the presence of formic acid, which ruled out one potential processing route. However, it was successfully demonstrated that birch and pine hydrolysates could be directly processed obtaining close to full conversion. The best results were obtained with tailored bimetallic Pd-Pt/sibunit catalyst in a trickle bed reactor system in the temperature range 175 °C–225 °C.

Catalytic Production of Renewable Hydrogen for Use in Fuel Cells: A Review Study

Hydrogen production from renewable sources is gaining increasing importance for application as fuel, in particular with high efficiency and low impact devices such as fuel cells. In addition, the possibility to produce more sustainable hydrogen for industrial application is also of interest for fundamental industrial processes, such as ammonia and methanol synthesis. Catalytic processes are used in most options for the production of hydrogen from renewable sources. Catalysts are directly involved in the main transformation, as in the case of reforming and of electro-/photo-catalytic water splitting, or in the upgrade and refining of the main reaction products, as in the case of tar reforming. In every case, for the main processes that reached a sufficiently mature development stage, attempts of process design, economic and environmental impact assessment are presented, on one hand to finalise the demonstration of the technology, on the other hand to highlight the challenges and bottlenecks. Selected examples are described, highlighting whenever possible the role of catalysis and the open issues, e.g. for the H2 production from reforming, aqueous phase reforming, biomass pyrolysis and gasification, photo- and electro-catalytic processes, enzymatic catalysis. The case history of hydrogen production from bioethanol for use in fuel cells is detailed from the point of view of process design and techno-economic validation. Examples of steady state or dynamic simulation of a centralised or distributed H2 production unit are presented to demonstrate the feasibility of this technology, that appears as one of the nearest to market. The economic feasibility seems demonstrated when producing hydrogen starting from diluted bioethanol.

Influence of Catalyst Reduction Temperature on Autogenous Glycerol Hydrogenolysis over NiAl Catalyst

AbstractAutogenous glycerol hydrogenolysis to 1,2‐propanediol by aqueous phase reforming (APR) was investigated over supported nickel catalysts. Effect of reduction temperature on physico‐chemical properties of catalysts played a significant role in tuning conversion and product selectivities. The formation of nickel aluminate (NiAl2O4) spinel phase during catalyst reduction led to rearrangement of Ni species to obtain small and stable Ni particles. The catalyst activation temperature alters the extent of reduction of multivalent Ni species (Ni0, Ni+2/+3) which facilitated glycerol dehydration and hydrogenation while suppressing C−C cleavage and thus avoiding undesirable side products. Additionally, presence of moderate BrØnsted/Lewis acid ratio of the catalyst promoted higher 1,2‐PDO selectivity. In‐situ glycerol hydrogenolysis involves glycerol dehydration to acetol with simultaneous reforming to H2 and CO2 and this hydrogen converts acetol to 1,2‐PDO.

Hydrogen production from aqueous phase reforming of glycerol over attapulgite-supported nickel catalysts: Effect of acid/base treatment and Fe additive

In this paper, a series of nickel-based catalysts supported on modified attapulgite (ATP) by acid (citric acid and EDTA) and base (NaOH) were prepared and applied to the aqueous phase reforming of glycerol (APRG). The modified ATP (MA) and as-prepared catalysts were detected using N2 adsorption-desorption, ICP-OES, XRD, FT-IR, SEM-EDS, HRTEM, XPS, H2-TPR, NH3-TPD. The results manifested that the acid/base treatment of ATP significantly increased the surface area and pore volume, enhanced the metal-support interaction (MSI) and decreased the Ni particle size, resulting in the better glycerol conversion and H2 selectivity, especially for Ni/MA-E catalyst, where the ATP was pretreated using EDTA. In addition, the bimetallic NiFe/MA-E catalyst exhibited the highest conversion of glycerol to gas product (54.4%) and H2 selectivity (84.6%) at very low temperature (280 °C). These results were attributed to the strongest the interplay of active metal with support by the formation of Ni–Fe alloy, resulting in the highest active metal dispersion, smallest metal particle size, lowest the reducibility of active metal and most surface Ni0 content. According to the characterizations of spent catalysts, it demonstrated that monometallic Ni catalysts presented obvious sintering of Ni metal particle and larger accumulation of carbon deposition, which led to the deactivation of the catalyst. While NiFe/MA-E catalyst showed less particle agglomeration and coke formation attributed to the lower content of surface acid site. Apart from that, another cause of catalyst deactivation might be the destruction of ATP skeleton during APRG.

Comparison of gelatinous and calcined magnesia supported Ni or/and Co-based catalysts for aqueous phase reforming of glycerol

In this work, two different types of catalysts with MgO support for aqueous phase reforming of glycerol were prepared by the sol-gel method and calcining method, respectively, and the active metals (nickel or/and cobalt) were added by the initial wet impregnation (IWI) method. It is found that the catalyst supported by gelatinous MgO presents better dispersion and the amount of hydrogen produced by the catalyst containing gelatinous MgO support is more than 1.5 times compared with other catalysts. For the Ni–Co bimetallic catalysts, the higher reaction temperature is beneficial to hydrogen yield, but decreases hydrogen selectivity. A high concentration of glycerol increases hydrogen yield and selectivity. Introducing CaO as an absorbent in aqueous phase reforming can improve WGS reaction and reduce methanation reaction through in-situ CO2 removal and capture. The gelatinous Ni–Co/MgO catalyst presents superior activity and multi-cycle stability.

Lignin Depolymerization and Monomeric Evolution During Fast Pyrolysis Oil Upgrading with Hydrogen from Glycerol Aqueous Phase Reforming

Lignin Depolymerization and Monomeric Evolution During Fast Pyrolysis Oil Upgrading with Hydrogen from Glycerol Aqueous Phase Reforming

Aqueous-Phase Reforming of Hydroxyacetone Solution to Bio-Based H2 Over Supported Pt Catalysts

Aqueous-Phase Reforming of Hydroxyacetone Solution to Bio-Based H2 Over Supported Pt Catalysts

Monitoring Molecular Weight Changes during Technical Lignin Depolymerization by Operando Attenuated Total Reflectance Infrared Spectroscopy and Chemometrics.

Technical lignins are increasingly available at industrial scale, offering opportunities for valorization, such as by (partial) depolymerization. Any downstream lignin application requires careful tailoring of structural properties, such as molecular weight or functional group density, properties that are difficult to control or predict given the structure variability and recalcitrance of technical lignins. Online insight into changes in molecular weight (M w), to gauge the extent of lignin depolymerization and repolymerization, would be highly desired to improve such control, but cannot be readily provided by the standard ex‐situ techniques, such as size exclusion chromatography (SEC). Herein, operando attenuated total reflectance infrared (ATR‐IR) spectroscopy combined with chemometrics provided temporal changes in M w during lignin depolymerization with high resolution. More specifically, ex‐situ SEC‐derived M w and polydispersity data of kraft lignin subjected to aqueous phase reforming conditions could be well correlated with ATR‐IR spectra of the reaction mixture as a function of time. The developed method showed excellent regression results and relative error, comparable to the standard SEC method. The method developed has the potential to be translated to other lignin depolymerization processes.