Aqueous-phase Reforming Of Methanol Research Articles

Size-modulated Pt nanoparticles for low-temperature plasmon-enhanced hydrogen production from aqueous phase reforming of methanol

Al2O3 supported Pt nanoparticles photocatalyst enables efficient hydrogen production (115.2 μmol min−1 gcat−1) through aqueous phase reforming of methanol (APRM) reaction under light irradiation at low temperatures of 150 °C, which is 6 times higher than that of APRM reaction conducted in the dark. We demonstrate that the particle size of Pt nanoparticles greatly affected the light absorption ability, which is of great importance for light utilization of the photocatalyst. The medium particle size of Pt nanoparticles enables the lower electron density states, which is benefit for the dehydrogenation of methanol and the sequential water–gas shift (WGS) reaction and eventually promoted the photocatalytic performance for hydrogen production.

Oxygen vacancies promoted hydrogen production from methanol aqueous phase reforming over MgAl−LDHs supported plasmonic Ru nanoparticles catalyst

Catalytic aqueous phase reforming of methanol is a promising process for the sustainable hydrogen production. The search for highly efficient heterogeneous catalyst is a topic of interest. Herein, we report oxygen vacancies enriched MgAl−LDHs supported plasmonic Ru nanoparticles catalyst exhibit excellent photocatalytic performance for efficient hydrogen production at 150 ºC under light irradiation. Characterizations demonstrate abundant oxygen vacancies are introduced into MgAl−LDHs via “memory effect”. The local electron transfer from oxygen vacancies of the MgAl−LDHs to the Ru nanoparticles leading the formation of electron-rich Ru species, which promote the dehydrogenation of methanol under light irradiation. In situ DRIFTS demonstrated a redox mechanism of water-gas shift reaction due to the existence of oxygen vacancies, which resulted a faster hydrogen production rate. This work displays a facile strategy for synthesis of oxygen vacancies rich LDH supported metal nanoparticles catalysts and deep understanding into the pathway and mechanism toward the effective hydrogen production.

Synthesis of γ-Valerolactone through coupling of methyl levulinate hydrogenation with aqueous phase reforming of methanol over Pt/CoxAl catalyst

The synthesis of high-value γ-valerolactone (GVL) from biomass-derived methyl levulinate (ML) conventionally requires a high-pressure hydrogen, which incurs significant costs and safety concerns. This study proposes an innovative approach to produce GVL by integrating ML hydrogenation with aqueous phase reforming of methanol (APRM) using Pt/CoxAl catalysts, thereby eliminating the need for an external hydrogen source. The influence of catalyst composition, methanol concentration, and reaction temperature on catalytic performance has been carefully examined. The results suggest that Pt/Co1Al demonstrated exceptional activity, yielding up to 98.2% GVL, and maintaining stable performance over multiple cycles. Characterization results revealed that Pt0 facilitates both APRM and ML hydrogenation, while Brønsted acid sites catalyze the hydrolysis of ML and lactonization of intermediates. The synergy between Pt0 and Brønsted acid sites is essential for GVL formation. The appropriate amount of Co not only enhances Pt dispersion but also increases Brønsted acid sites, thereby boosting catalytic efficiency. This work offers a sustainable and economically feasible strategy for transforming biomass derivatives into valuable fuels and chemicals.

Aqueous phase reforming of methanol for hydrogen production over highly-dispersed PtLa/CeO2 catalyst prepared by photochemical reduction method

Hydrogen production by catalytic aqueous phase reforming (APR) of biomass oxygenated derivatives in relatively mild conditions is a promising way to produce hydrogen. In this work, Pt/CeO2-HT, Pt/La–CeO2-HT and PtLa/CeO2 catalysts were synthesized by a novel photochemical reduction method and applied to the methanol APR. Extensive characterizations have proved that the mild catalyst preparation method gave it a high dispersion of Pt species and the addition of La modified the metal-support interaction. The results showed that La-modified Pt/La–CeO2-HT and PtLa/CeO2 catalysts exhibited better catalytic performance than the Pt/CeO2-HT catalyst, among which the hydrogen yield was the highest for the surface La-modified PtLa/CeO2 catalyst (177.7 mmol/gcat). This was mainly attributed to the surface modification of La resulted in a significant increase in the number of moderately strong basic sites and surface oxygen vacancies in the PtLa/CeO2 catalyst. The enhancement of catalyst basicity effectively promoted the dissociation of H2O to produce hydroxyl groups, while a large number of surface oxygen vacancies provided more active sites for the adsorption and dissociation of H2O. And their synergistic behavior efficiently facilitated the water gas shift (WGS) reaction, resulting in a significant increase in hydrogen yield of methanol APR. Associated with the in situ DRIFTS analyzes and the results indicated by WGS reaction, possible promotion mechanism was proposed.

High density ultra-small Cu nanoparticles with abundant oxygen vacancies for efficient hydrogen evolution from MeOH/H2O

Efficient release of H2 with negligible CO impurities from sustainable MeOH/H2O has become a promising goal for on-board hydrogen generator. However, hydrogen release kinetics still face challenges. In this work, the Cu/ZnO/CeO2 catalyst with high density ultra-small Cu nanoparticles and abundant oxygen vacancies were prepared for intensifying hydrogen evolution in aqueous phase reforming of methanol (APRM). The optimized 55% Cu/ZnO/CeO2 catalyst (Cu NPs of 3.8 nm, Cu loading of 55.89 wt%, oxygen vacancies of 2.316 × 1015 spins g−1) exhibited an excellent H2 evolution rate of 58.39 μmolgcat−1 s−1 even at low temperature of 210 °C, which was 2.1-fold enhancement than that of commercial Cu/ZnO/Al2O3 catalyst. Characterizations and experiments revealed that ZnO/CeO2 intensified the strong metal-support interaction (SMSI), which anchored the Cu NPs, generated abundant oxygen vacancies and adjusted electronic structure to form Cu0-Cu+-Ov active sites for facilitating the kinetics of APRM.

Oxygen vacancy of Pt/CeO2 enabled low-temperature hydrogen generation from methanol and water

Aqueous-phase reforming of methanol (APRM) represents an alternative approach to achieve a sustainable hydrogen generation and safe storage. Nonetheless, the limitations imposed by the high operating temperatures of heterogeneous catalysts serve as a bottleneck for the widespread adoption of this system. Herein, we demonstrated that the Pt nanoparticles supported on porous nanorods of CeO2 with abundant oxygen vacancies (Pt/PN-CeO2) enabled the efficient H2 generation through low-temperature (<60 °C) APRM reaction. The presence of oxygen vacancies on PN-CeO2 could enhance the electronic density of supported Pt nanoparticles through strong metal-support interaction, thereby promoting the activation of methanol. Meanwhile, the oxygen vacancies could further promote the H2O activation. Consequently, the interface between Pt and PN-CeO2 enabled efficient H2 generation at 60 °C with a TOF values of 173.5 h−1 and suppress CO generation. This finding provides a promising pathway towards the low-temperature APRM reaction.

Hydrogen production by aqueous phase reforming of methanol over stable C-modified NiMgAl hydrotalcite catalyst

Enhanced methanol conversion and hydrogen yield are achieved over carbon modified hydrotalcite catalyst with high stability.

Improved Low-temperature Hydrogen Production from Aqueous Methanol Based on Synergism Between Cationic Pt and Interfacial Basic LaO x.

Aqueous phase reforming of methanol (APRM) is simple, inexpensive and provides a high hydrogen gravimetric density of 18.8 wt%, and so is superior to traditional gas-phase reactions performed at relatively high temperatures. In the present work, the interface between Pt nanoparticles and a TiN support was modified using a highly dispersed amorphous LaO x phase. The resulting Pt/LaO x /TiO(N) exhibited enhanced activity and long-term stability during the APRM reaction under base-free conditions compared with Pt catalysts supported on unmodified TiN or crystalline La2O3. The interfacial amorphous LaO x phase promoted the deposition of small Pt nanoparticles having a narrow size distribution, and also generated electron-deficient Pt. An assessment of kinetic isotope data and theoretical investigations demonstrated that the cationic Pt nanoparticles facilitated the cleavage of O-H and C-H bonds in methanol while the amorphous LaO x enhanced the dissociation of water, thus enabling the water-gas shift reaction under mild conditions.

Stabilized *OH species by K+-doped Pt for H2 generation with ultra-low levels of CO through aqueous-phase reforming of methanol at low temperature

Aqueous-phase reforming of methanol (APRM) represents an attractive approach for H2 storage and transportation. However, metals with high capacity of methanol activation generally exhibit poor capability for water dissociation and/or weak stabilization of *OH intermediates, leading to the unsatisfactory activity and unavoidable CO generation. Herein, we demonstrated that K+-doped Pt nanoparticles on γ-Al2O3 (PtKx/Al2O3) stabilized the *OH intermediates on Pt surface, thereby achieving efficient H2 generation with ultra-low levels of CO through APRM at 120 °C. Mechanism investigations illustrated that K+ in Pt nanoparticles shifted the d-band center to stabilize the critical *OH generated from water dissociation without interference on methanol dissociation. Consequently, the PtKx/Al2O3 catalysts delivered a TOF of 142.3 h−1 with undetectable CO by gas chromatograph equipped with FID (detection limit: 5 ppm) at 120 °C. These findings are anticipated to promote methanol as a practical H2 carrier for the delivery of hydrogen with high purity.

High-performance metal-base bifunctional catalysts (NixMgy-MMO) for aqueous phase reforming of methanol to hydrogen

Reforming methanol in an aqueous phase is of great interest, including the water–gas shift (WGS) reaction for converting the CO formed from the dehydrogenation of methanol (DM) to CO2 and promoting hydrogen gas production by 50%. Ni-based catalysts are highly active for catalyzing the involved dehydrogenation reaction but perform poorly at the low temperature range for the WGS reaction. In this work, metallic Ni-catalytic sites supported on basic mixed metal oxides (NixMgy-MMO), prepared from NiMgAl layered double hydroxide (LDH) precursors, were applied for the first time in the aqueous phase reforming of methanol (APRM). The Ni3Mg1-MMO catalyst demonstrated outstanding catalytic performance with a high hydrogen production rate of 167.2 μmolH2/gcat./s and a low CO selectivity of 1.9% at the temperature of 240 °C. These are among the best literature results for the APRM catalyzed by Ni-based catalysts. Compared to the neutral Ni@NC catalyst, the metal-base bifunctional Ni3Mg1-MMO catalyst significantly boosts the WGS process, reducing the CO selectivity and enhancing the APRM. The structure-performance studies of the NixMgy-MMO catalysts in the reactions of DM, WGS, and APRM showed that the intrinsic activity for DM increases significantly as the Ni particle size decreases, while WGS and APRM reactions are dominantly improved by the medium basic property that originated from Mg-O pairs. As a result, the intrinsic activity of the catalysts in APRM also decreases as the Ni particle size increases. These new findings are transferable to the design of efficient metal-base bifunctional catalysts for reactions similar to WGS and APRM.

Highly efficient releasing of hydrogen from aqueous-phase reforming of methanol over Cu-SP/Al2O3–ZnO catalyst by carbon layer encapsulated hierarchical porous microsphere strategy

Highly efficient releasing of hydrogen by aqueous-phase reforming of methanol (APRM) is of great significance to promote the development of stationary and mobile H2 power supply for polymer electrolyte membrane fuel cells (PEMFCs). However, highly active catalysts with excellent performance of in situ releasing H2 from APRM still face challenges. Herein, we report a Cu-SP/Al2O3–ZnO (Cu-SP/AZ) catalyst prepared by carbon layer encapsulated hierarchical porous microsphere strategy, which enhanced Cu dispersion (52.8 wt% loading, ∼5 nm particle size) on Al2O3–ZnO (AZ) microsphere. The proposed catalyst exhibited high H2 production rate (base-free) of 64.23 μmolH2/gcat/s at 210 °C, which was nearly the same as that of 20% Pt/C catalyst (63.86 μmolH2/gcat/s) and 2.6-fold higher than that of commercial CuO/ZnO/Al2O3 catalyst (24.62 μmolH2/gcat/s). The characterization results demonstrated that its high activity in APRM could be ascribed to the strategy of carbon layer encapsulated hierarchical porous microsphere as well as coordination of hydroxyl functional group of SP with Cu2+.

Engineering of the Cu+/Cu0 interface by chitosan-glucose complex for aqueous phase reforming of methanol into hydrogen

The aqueous-phase reforming of methanol(APRM)via non-precious metal heterogeneous catalysts is highly desirable, but challenging. Herein, we report a highly efficient copper catalyst encapsulated by chitosan-glucose (CS-G) conjugate with high metal loading of 35 wt% for H2 generation from APRM. The optimized Cu@CS19-G1-300 catalyst exhibited exceptional activity of 1.39 × 105 μmolH2/gcat/h at low temperature of 210 °C, which was ∼4.5 times higher than that of commercial CuZrAl catalysts (2.88 × 104 μmolH2gcat−1h−1). The chitosan-glucose conjugate acted not only as the main carbon support for Cu dispersion, but also as adsorbent to stablize as many Cu ions as possible. And meanwhile, with abundant Cu+/Cu0 interface sites due to the reducing effect of glucose, the water gas shift reaction (WGSR) was intensified and thus displayed excellent selectivity toward CO by-product. This specific catalyst construction for H2 production from APRM exhibits great potential of on-site H2 supply for polymer membrane fuel cells.

Confinement of Cu2O by in-situ derived NH2-MIL-125@TiO2 for synergetic photothermal-driven hydrogen evolution from aqueous-phase methanol reforming

Photothermal synergism can effectively activate methanol at low operating temperature and significantly reduce the activation energy of the reaction, achieving more efficiently H2 release from methanol reforming. Here, a novel hierarchical heterojunction that integrating photo- and thermal-active Cu2O catalytic species with in-situ derived NH2-MIL-125@TiO2 framework was specifically designed for photothermal-driven aqueous phase reforming of methanol into H2. The afforded Cu2O/NH2-MIL-125@TiO2 realized an outstanding photothermal H2 production activity (apparent quantum efficiency of 22.3 % at 365 nm), ca. 13-times higher than that of thermocatalytic condition. Interestingly, the photothermal effect did confer the Cu2O/NH2-MIL-125@TiO2 with unexpected activity at low temperature subsided to 100 °C and accelerated the activation of MeOH/H2O with an obvious reduction of activation energy from 82.62 kJ·mol−1 to 52.40 kJ·mol−1.The improvement of catalyst stability and the promotion of charge separation also contributed to a long-term photothermal H2 evolution activity with average rate of 1.49x106 μmolgCu-1h−1 and a total turnover number (TON) up to 5971 in 63 h, almost 125-fold promotion compared with Cu2O.

Metal‐organic framework stabilizes Cu7S4‐wrapped Cu2O heterostructure for photothermal‐promoted methanol/water reforming into hydrogen

AbstractTo realize highly efficient in situ release of hydrogen energy from methanol reforming at lower operation temperature, the introduction of solar energy can effectively activate the methanol and significantly reduce activation energy of reaction. Herein, the hierarchical integration of photoactive Cu2O/Cu7S4 core‐shell nanospheres stabilized by MIL‐101(Cr) support for H2 evolution from photothermal‐driven aqueous phase reforming of methanol afforded nearly sixfold enhanced performance compared with thermocatalytic process. Impressively, the photothermal effect conferred the Cu2O/Cu7S4@MIL‐101(Cr) with unprecedented activity at low temperature subside to 100°C and accelerated the activation of water and methanol with distinctly decreased activation energy from 103.9 to 66.6 kJ·mol−1. Meanwhile, the enhanced catalyst stability and facilitated charge separation between Cu2O/Cu7S4 and MIL‐101(Cr) also contribute to the extraordinary photothermal‐enhanced H2 evolution with an overall turnover number of up to 14,266 in 60 h (apparent quantum efficiency of 25.08% at 365 nm), almost 10,000 times higher than that of Cu2O/Cu7S4.

Improving the hydrothermal stability and hydrogen selectivity of Ni-Cu based catalysts for the aqueous-phase reforming of methanol

Non-precious metal catalysts suitable for hydrogen production via aqueous phase reforming (APR) of methanol show important technical and commercial value in the development of distributed, small/micro-scale on-site hydrogen production systems. They still face the challenges of reduced activity and stability due to sintering and oxidation of active metal nanoparticles, change of the surface state and collapse of the pore structure of used supports under hydrothermal conditions. To solve these problems, a series of ZnO/Ni-xCu/Al2O3 (x = 0, 2, 4, 6, 8, 10) catalysts were prepared by a simple impregnation method in this work. The addition of Cu improved the reducibility of NiO, and promoted the formation of smaller and more dispersed metal particles on the surface of Al2O3, facilitating hydrogen production and hindering methane formation. Among them, the highest average hydrogen production rate (362.1 μmol‧min−1‧gcat−1) and the highest hydrogen selectivity (99%) were reached using ZnO/Ni-8Cu/Al2O3 catalyst, which were 1.6 times and 20.7% higher than those obtained on the mono-metallic ZnO/Ni/Al2O3 catalyst, respectively. On the other hand, the modification of Ni-8Cu/Al2O3 with ZnO prevented effectively the reaction of surface water with Al2O3 and inhibited the formation of boehmite phase, leading to dramatical improvement of its stability during APR of methanol with a prolonged lifetime (72 h) by 6 times. This new developed ZnO/Ni-xCu/Al2O3 catalysts offer great potential for the development of commercial catalysts to produce hydrogen from APR of methanol.

Bio‑hydrogen and valuable chemicals from industrial waste glycerol via catalytic aqueous-phase transformation

Waste glycerol obtained as by-product of biodiesel production has been submitted to a sequential physico-chemical treatment in order to make it suitable for continuous Aqueous-Phase Reforming (APR) in a tubular reactor. Special focus was given to the impact of impurities. APR was performed using 0.3%Pt/CoAl2O4 catalyst, at 260 °C and 50 bar within WHSV range 6–55 h−1 to cover whole conversion ranges. Glycerol conversion and yield to hydrogen reached 99.7% and 45.4%, respectively at WHSV = 6 h−1. The liquid product distribution strongly varied with glycerol conversion, maximum C-yield to 1,2-propylene glycol was attained in the 60–90% glycerol conversion range. APR of methanol and acetic acid aqueous feedstreams were investigated independently. It was concluded that acetic acid exerts a negative influence on catalyst stability since glycerol conversion decreased by 41% after 5 h TOS. Extensive characterization of fresh and exhausted catalysts revealed strong Co leaching, especially for acetic acid APR, oxidation of metals, and carbonaceous deposits. The basis for the regeneration of the spent catalyst, consisting of a reductive treatment at 500 °C, has been established. This work is expected to have significant implications for the development of APR technology for crude glycerol from biodiesel industry.

Promoting mechanism of alkali for aqueous phase reforming of bio-methanol towards highly efficient production of COx-free hydrogen

Transforming the poisonous CO generated on the active metal sites promptly is essential for Ni-based catalyst applying in aqueous-phase reforming (APR) of biomass-derived oxygenated hydrocarbons, e.g. methanol, due to its low water-gas-shift (WGS) activity. Here, we used alkali modifier in the APR of methanol (APRM) with a Ni@NC catalyst and explored the promotion mechanism of alkali in depth. Compared with the performance of APRM over the Ni@NC catalyst without using any alkali, the hydrogen production rate increased to 8 times higher (from 33.4 to 265.4 μmolH2/gcat./s), while the CO selectivity decreased drastically (from 26.8% to 0.1%) after adding KOH at 220 °C. Through IR and XRD analysis of the produced potassium salts, it was found that the KOH mainly directly reacted with the CO produced from methanol dehydrogenation forming HCOOK, which eliminated the poisonous effect of CO on the active Ni sites and promoted methanol dehydrogenation remarkably. Besides, a small amount of KOH reacted with CO2 and promoted the WGS, by which in situ stabilization of CO2 was realized, reducing carbon emission. As a result, COx-free hydrogen at a high production rate was achieved, with HCOOK, the precursor for the important hydrogen carrier formic acid, as a side product.

Novel Pt/MoS2 nanosheet catalyst for hydrogen production via aqueous-phase reforming of methanol

Novel Pt/MoS2 nanosheet catalyst for hydrogen production via aqueous-phase reforming of methanol

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.

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.