Steam Reforming Of Phenol Research Articles

Co–Fe/Al2O3 catalyst for low-temperature steam reforming of phenol for hydrogen production

In this study, a series of high-efficient catalyst, Co–Fe/Al2O3, were synthesized via the sol-gel method for low-temperature phenol steam reforming (PSR). The optimized catalyst, 15Co–2Fe/Al2O3, exhibited a remarkable phenol conversion of 95.3%, a H2 yield of 92.1% at 450 °C, GHSV = 7500 h−1 and a steam-to-carbon (S/C) ratio of 10. Furthermore, the catalyst activity was maintained for 660 min before a gradual decline was observed. The NH3-TPD analysis revealed that the addition of Fe enhanced the surface acidity of the catalyst, providing more active sites for phenol adsorption and activation. This study aims to address the challenges associated with high reaction temperatures and poor catalyst stability in PSR. Various characterization techniques have been employed to investigate the reaction mechanisms of bimetallic catalysts in low-temperature PSR.

The kinetic and experimental study of the phenol steam reforming towards hydrogen production over Ni-Rh/MgO catalyst

To study the kinetic implied on the Langmuir-Freundlich (LF) adsorption isotherm, the experimental tests of phenol steam reforming (PSR) reaction in the presence of Ni-Rh/MgO catalyst were performed in the temperature range of 500 °C-800 °C and flow rate of 10 mL/h to 30 mL/h in a fixed bed reactor. LF model accurately fitted the experimental responses with assuming CO and CO2 formation reactions as the kinetic limitations. By comparing two experimental and calculated values, the deviation of kinetic model in calculating experimental H2 yield was lower (2.58 %) compared to phenol conversion, CO and CO2 yields. The stability analysis revealed that conversion and yields were almost fixed without obvious deactivation up to 55 h initial time on stream, however, activity was declined over time on stream in the range of 55 h to 70 h because of coke deposition. The characterization results demonstrated that the deposited coke on the catalyst surface after the stability test was more aromatic and less aliphatic and included carboxylic group, methyl group and aromatic structure. The phenol conversion near to 90 % was attained at 800 °C and flow rate of 10 mL/h. The temperature had a positive effect on the catalytic activity regarding to phenol conversion, H2 and CO yields. However, temperature variable had a negative impact on CO2 yield. The changes of phenol conversion, H2 and CO2 yields showed descending trends with flow rate in the range of 10 mL/h to 30 mL/h. In the range of 500 °C-600 °C, CO yield was approximately constant by altering flow rate from 10 mL/h to 30 mL/h.

Optimized Ni/Al2O3–SiO2 Catalyst for Steam Reforming of Phenol with Enhanced Hydrogen Production and Stability

Abstract Well-designed Ni/Al2O3–SiO2 catalysts synthesized with nickel as the active metal and alumina–silica as the catalyst mixture support were investigated for steam reforming of phenol with enhanced hydrogen production and stability. The prepared catalysts were characterized using x-ray diffraction, field emission scanning electron microscopy, Brunauer–Emmett–Teller (BET), Fourier transform infrared, hydrogen temperature-programmed reduction, pyridine diffuse reflectance infrared Fourier transform spectroscopy (Py-IR), and thermal gravimetric-differential scanning calorimetry (TG-DSC) techniques in detail. The BET results show that their specific surface areas ranged from 29.832 to 220.330 m2·g–1. The Py-IR results indicate the existence of large Lewis acid regions in the pure C-Ni (“C-Nix-Siy” means the Ni/Al2O3-to-SiO2 catalyst prepared with Ni(CH3COO)2 · 4H2O with SiO2 support mass ratios of y/(x + y).) and C-Ni4-Si1. The effects of the Ni/Al2O3-to-SiO2 mass ratio, reaction temperature, and active metal salt anion species on catalytic activity were studied. The results show that the C-Ni4-Si1 catalyst using nickel acetate tetrahydrate as the active metal salt with an SiO2 mass ratio of 20 wt% achieves a maximum phenol conversion of 97.3 % and hydrogen production of 92.7 % at 550°C. The stability of C-Ni4-Si1 was further investigated, and it was shown to react continuously and stably for more than 800 min at 550°C with excellent catalytic reaction stability. A final weight loss of only 9.31 % shown in the TG-DSC result of the spent C-Ni4-Si1 catalyst confirmed the excellent thermal stability and low coking rate of C-Ni4-Si1.

Low-temperature steam reforming of phenol for hydrogen production over Co/Al2O3–ash catalysts

A low-cost, high-performance catalyst for phenol steam reforming (PSR) at low temperature was prepared by introducing waste coal ash into Co/Al2O3. The optimized content of coal ash in the catalyst were ranged from 50 to 65 wt%, presenting over 97% phenol conversion and 92% H2 yield at low temperature of 450 °C. The stability for the best catalyst with an ash content of 50 wt% exceeded 85 h. Two-step reduction of Co3O4 to Co0 via CoO was identified by in-situ XRD. DFT calculations showed that phenol adsorption and decomposition were preferred on the FeCo bimetal surface rather than the single Co surface. H2O adsorption and dissociation fascinated on the CaO incorporated Al2O3 surface. Both Fe and Ca in the coal ash improved the catalyst performance in PSR at low temperature. This work gives an opportunity to solve the drawbacks of high reaction-temperature and low catalyst-stability in PSR, and furthermore benefits to get a deep insight into the reaction mechanism of PSR over the catalyst.

Production of hydrogen by steam reforming of phenol over Ni/Al2O3-ash catalysts

An improved method for hydrogen production by the steam reforming of phenol over novel fly ash-based catalysts is investigated. The Ni/Al 2 O 3 -ash catalysts are prepared by an equal-volume impregnation method and characterized by XRD, FESEM, BET and H 2 -TPR techniques. The effects of various process parameters including mixing ratio of fly ash, temperature, support, gas hourly space velocity (GHSV) and steam-to-carbon molar ratio (S/C) on the catalytic activity are investigated. The results show that fly ash mixing at 50 wt% and choosing γ-Al 2 O 3 as the support own the best performance. A maximum hydrogen yield of 83.8% is achieved at 450 °C with a S/C of 10 and a GHSV of 4968 h −1 with a maximum phenol conversion of 98.6%. The stability of the Ni-ash1-γA1 catalyst is further investigated and it is shown to continuously and stably react for more than 20 h at 450 °C with excellent catalytic reaction stability. • Ni/Al 2 O 3 -ash catalysts are prepared for phenol steam reforming to produce hydrogen. • Fly ash mixing at 50 wt% on the oxide support γ-Al 2 O 3 exhibits good performance. • An optimum hydrogen yield of 83.8% is produced at 450 °C. • A phenol conversion of 98.6% is achieved with a S/C of 10 and GHSV of 4968 h −1 . • Ni-ash1-γA1 catalysts react stably for more than 20 h at 450 °C.

Upgrading syngas from wood gasification through steam reforming of tars over highly active Ni-perovskite catalysts at relatively low temperature

Tar formation during biomass gasification causes several operational problems, besides limiting the downstream application of the syngas produced. The development of an efficient catalyst for tar reforming at mild temperature is targeted. In this study, La-based perovskite (La0.6Sr0.4Co0.2Fe0.8O3-δ)-supported Ni materials have been synthesized through wetness impregnation (Ni/LSCF) and one-pot sol-gel method (Ni-LSCF). As-prepared catalysts have been characterized by N2 physisorption, XRD, TPR, H2-TPD and XPS. The impact of the synthesis path and the effect of Ru have been evaluated in steam reforming of toluene and phenol at low temperature (550 °C) under a model syngas. Regardless the tar model molecule, similar catalytic stability and activity toward tar reforming were attained for both Ni/LSCF and Ni-LSCF. However, a better catalytic performance toward WGS and higher resistance to coke formation were evidenced for Ni-LSCF than for Ni/LSCF. This better behavior has been mainly ascribed to the high Sr content at its surface, pointing out the key role of the basic elements at the catalytic surface in the activity and stability in steam reforming of tars. The addition of Ru led to an enhancement in the catalytic activity for toluene reforming, while no noticeable improvement was attained for phenol reforming.

Steam reforming of phenol toward cleaner hydrogen production over bimetallic Ni/Ti modified zinc titanate perovskite in tandem with a kinetic model development

Hydrogen as a clean energy carrier with high heat combustion and zero environmental impacts is an attractive alternative to fossil fuels. In this study, NiO/TiO2 modified ZnTiO3 perovskite (NTZ) with high reducibility catalyst was designated by co-precipitation method and examined in the reaction of steam reforming of phenol (SRP) for H2 production. The activity tests for SRP were carried out in a fixed bed reactor (FBR) under different operating conditions. The NTZ-composite consisting of NiO/TiO2 loaded ZnTiO3 perovskite achieved the highest yield of H2 and phenol conversion of ~76 and 90%, respectively, with excellent durability and time on stream (50 h) stability without obvious deactivation. The high exposed active sites of NiO/TiO2 metals over the bi-metal support (ZnTiO3) and the metal-support interaction significantly improved the catalytic performance. The products distribution of H2, CO2, and CO as a measure of the dominant reactions; SRP, water gas shift (WGS), and reverse water gas shift (RWGS) were correlated to kinetic models and developed according to Langmuir-Hinshelwood-Hougen-Watson (LHHW) expressions. LHHW model accurately fitting the experimental results with surface reactions as the kinetic limitations. SRP reaction revealed the highest rate constant of 21.70 mol g-cat−1 h−1 atm−1 with 39.96 kJ mol-1 activation energy. NTZ is a promising catalyst for the SRP reaction toward H2 production with minimum kinetic limitations and would be promising in the clean energy production and other environmental applications.

Tri-metallic Ni–Co modified reducible TiO2 nanocomposite for boosting H2 production through steam reforming of phenol

Well-designed Co3O4 nanocubes (NCs) dispersed NiO/TiO2 to construct tri-metallic reducible NiO/TiO2/Co3O4 NCs structured catalyst for steam-reforming of phenol (SRP) with enhanced hydrogen production has been investigated. The controlled morphology with good dispersion was obtained, enabling efficient SRP toward selective H2 production. Using 10% NiO- 5% Co3O4 NCs/TiO2 composite, H2 yield of 69.91% and phenol conversion of 78.4% was achieved, significantly higher than using NiO/TiO2 and TiO2 samples. The cubical structured Co3O4 dispersed NiO/TiO2 composite showed significantly improved H2 yield and phenol conversion due to strong metal-support interaction with reducible support for providing more active sites. The H2 production was further increased by increasing reaction temperature, phenol concentration, feed flow rate and catalysts loading, however, they have adverse effect on the selectivity due to more CO formation. The composite catalyst possesses excellent activity and stability due to strong tri-metallic interaction and exceptional electronic interfaces. The spent catalyst analysis confirms the formation of graphene and carbon nanotubes over the reducible support. This study reveals that Co3O4 NCs are able to increase NiO/TiO2 activity for H2 production by inhibiting carbon monoxide formation and would be beneficial in other reforming applications.

Hydrogen Production from Catalytic Polyethylene Terephthalate Waste Reforming Reaction, an overview

AbstractAs a sustainable and renewable energy carrier for transition, hydrogen is considered as a key future fuel for the low carbon energy systems. During the past few decades, attention has been given to the conversion of waste materials, including plastics to the production of hydrogen. Studies in this field are of great importance because they resolve numerous problems brought about by plastic waste with other forms of waste. Polyethylene terephthalate (PET) is one of the major products of plastic waste which constitutes a major threat to environmental conservation efforts and harms living organism. Phenol has been chosen in this study as a solvent for PET to produce hydrogen because of unwanted liquid product in the bio-oil. This research investigates catalytic steam reforming of phenol with dissolved PET for hydrogen production. The aim of this study was the review of a highly active and stable catalyst for hydrogen production from steam reforming waste products. The analysis of product composition indicated that steam reforming of PET-phenol generally produced a high amount of aliphatic branched-chain compounds, together with a moderate amount of cyclic compounds. The reaction conditions also led to the alkylation of phenol by the reforming products from the PET-phenol solution with and without the catalyst. In conclusion, this study explored new ways to use l product derived from waste plastic materials. It provides a promising clean technology, which employed polyethylene terephthalate waste dissolved in phenol (as a solvent) for hydrogen production.

Hydrogen Production from Sorption-Enhanced Steam Reforming of Phenol over a Ni–Ca–Al–O Bifunctional Catalyst

Phenol is one of the major products of bio-oil derived from biomass pyrolysis. Sorption-enhanced steam reforming of phenol (SESRP) aiming to produce high-purity H2 has been carried out over Ni–Ca–A...

CO2 sorption-enhanced steam reforming of phenol using Ni–M/CaO–Ca12Al14O33 (M = Cu, Co, and Ce) as catalytic sorbents

Abstract In this study, two kinds of Ni/CaO–Ca12Al14O33 catalytic sorbents were synthesized by wet impregnation using different CaO–Ca12Al14O33 as supports, which were prepared via calcination hydration (CH) and sol–gel/loading (SL) methods. Sorption-enhanced steam reforming (SESR) for hydrogen production was investigated using phenol as a tar model compound in a laboratory-scale fixed bed reactor. The Ni/CaO–Ca12Al14O33(CH) exhibited a higher hydrogen production activity compared to Ni/CaO–Ca12Al14O33(SL). The optimum operation condition for SESR process was obtained as temperature of 650 °C with S/C ratio of 3.0. Under this condition, the maximum H2 concentrations of 69.75% and 67.68% were achieved for Ni/CaO–Ca12Al14O33(CH) and Ni/CaO–Ca12Al14O33(SL), respectively. The corresponding H2 yields were 1.61 L/g and 1.45 L/g. However, a rapid deactivation of the Ni/CaO–Ca12Al14O33 catalytic sorbents occurred during the cyclic tests. Thus, bimetallic catalytic sorbents, Ni–M/CaO–Ca12Al14O33 (M = Cu, Co, and Ce), were developed by introducing the guest metal oxides. Among the three bimetallic catalytic sorbents, Ni–Co/CaO–Ca12Al14O33(CH) had the greatest potential for hydrogen production due to the synergistic catalytic effect of Co and Ni. The maximum H2 concentration of 82.23% and the maximum H2 yield of 2.31 L/g at 650 °C with S/C = 3.0 were observed for Ni–Co/CaO–Ca12Al14O33(CH). During the cyclic tests, the slight decrease in the H2 yield of Ni–Co/CaO–Ca12Al14O33(CH) was attributed to the decrease in the CO2 sorption capacity. The Ni–Ce/CaO–Ca12Al14O33(CH) showed a stable CO2 sorption/desorption ability, but the H2 yield decreased sharply due to the sintering of Ni particles and carbon deposition. Although the CO2 sorption capacity of Ni–Cu/CaO–Ca12Al14O33(CH) was well below the other two, it exhibited excellent stability. The results suggest that Ni–Co/CaO–Ca12Al14O33 and Ni–Cu/CaO–Ca12Al14O33 catalytic sorbents have great potential for the steam reforming of tar.

Conversion of polyethylene terephthalate plastic waste and phenol steam reforming to hydrogen and valuable liquid fuel: Synthesis effect of Ni–Co/ZrO2 nanostructured catalysts

Ni–Co/ZrO2 (NCZ) nano-structure catalysts prepared by the hydrothermal method (NCZ-hyd) and conventional impregnation (NCZ-imp) method. The comparative catalytic activity and coke resistance for each prepared catalyst were examined in steam reforming of phenol and polyethylene terephthalate (PET) plastic waste. The Physico-chemical catalysts properties were characterized by N2-adsorption, XRD, FTIR, TEM, SEM, EDX, H2-TPR, CO2-TPD, and TGA. The effects of preparation methods of NCZ nano-structure catalyst on the catalytic performances in PET-phenol steam reforming were investigated. The NCZ-hyd nanostructure catalyst exposed more outstanding catalytic activity and more excellent coke resistance in comparison with the NCZ-imp. The experimental findings exhibited that catalyst synthesized by hydrothermal method were uniform with the size of 8.8 nm, while NCZ particles prepared by conventional impregnation method were un-uniform, unshaped, and agglomerated, and the size distribution of its particles was from 25 to 50 nm. PET-Phenol conversion and hydrogen yield of 56.5% and 52.5% for the NCZ-imp while 67.6% and 64.8% for the NCZ-hyd catalyst were achieved, respectively. The kinetic study of steam reforming of PET-phenol was also implemented. The activation energy was found to be 69.03 J/mol for NCZ-imp while 107.3 J/mol for the NCZ-hyd nanostructured catalysts. The PET-phenol steam reforming produced valuable liquid products such as benzene, 2-methyl phenol, and dibenzofuran which is one of the crucial keys to solving the waste plastic recycling problem.

Effect of support size for stimulating hydrogen production in phenol steam reforming using Ni-embedded TiO2 nanocatalyst

Fabrication of reducible titanium dioxide (TiO2) loaded with nickel (Ni) to maximize metal-support interaction for stimulating hydrogen (H2) production via phenol steam reforming (PSR) has been investigated. Catalysts, synthesized by sol-gel assisted impregnation method, were characterized by XRD, FE-SEM, EDX, BET, H2-TPR and TEM techniques. The effects of three different catalyst sizes namely Ni/TiO2-A (11−49 nm), Ni/TiO2-B (22−196 nm) and Ni/TiO2-C (69−205 nm) for their mass transfer limitation, catalytic activity and coke formations were evaluated. Using smaller particle sizes of TiO2 higher BET surface area with good morphology and Ni dispersion was achieved. The Ni/TiO2-A sample shows highest phenol reforming activity with phenol conversion and H2 yield of 98.3 and 76.9 %, respectively. When large sizes TiO2 particles in Ni/TiO2-B and Ni/TiO2-C samples were employed, phenol conversion of 93.7 and 73.1 % and H2 yield of 71.2 and 55.6%, respectively, were achieved. This reveals that smaller support particle sizes have higher conversion and yields, and activity was declined when support size was increased to larger particle sizes. This was obviously small particle sizes resulted in larger surface area, higher metal dispersion and efficient surface reactions with minimum internal diffusion effects. Furthermore, stability analysis reveals continuous H2 production over smaller particles without obvious deactivation, however, activity was declined over time on stream using large support size due to obvious coke depositions. Thus, supports sizes and interaction of metal and support has significant contribution to maximize activity and stability and can be further employed in reforming systems for renewable hydrogen production.

Ni-embedded TiO2-ZnTiO3 reducible perovskite composite with synergistic effect of metal/support towards enhanced H2 production via phenol steam reforming

Highly reducible Ni-dispersed TiO2-ZnTiO3 perovskite nanocomposite with different anatase/rutile contents of TiO2 for enhanced phenol steam reforming (PSR) towards selective H2 production has been investigated. In-situ growth of TiO2 nanoparticles (NPs) over ZnTiO3 cubic perovskite was obtained through hydrothermal assisted impregnation method. TiO2-ZnTiO3 composite performance was entirely dependent on the Zn/Ti molar ratios. With Zn/Ti molar ratio of 2, 19.80% TiO2 rutile phase in TiO2-ZnTiO3 composite was obtained, giving highest catalytic activity for H2 production. Using 10% Ni supported TiO2-ZnTiO3, phenol conversion and H2 yield of 89.10% and 75.60%, respectively were attained, while it was only 44.60% and 63.32% with 10% Ni/TiO2 NPs. This was obviously due to strong metal-support interaction with higher Ni-dispersion. More importantly, CO yield with Ni/TiO2 was 9.68%, decreased to 6.49% using 10% Ni/TiO2-ZnTiO3 perovskite composite, resulting in lower CO/CO2 ratio and trivial coke formation. Besides, Ni/TiO2-ZnTiO3 composite gave stability for more than 50 h without obvious deactivation, while it was only 6 h over Ni/TiO2 NPs. The effect of operating parameters reveals that reaction temperature 700 °C, catalyst loading 0.3 g and phenol/water ratio 5/95 wt% gave the highest catalyst activity. Besides, activity was also enhanced with increasing GHSV (mL.g−1.h−1), which confirms external mass transfer limitation. In conclusion, strong metal-supports interactions in Ni/TiO2-ZnTiO3 composite provide higher Ni-dispersion for stimulating catalytic activity and can be considered as a promising material for hydrogen production applications.

Steam Reforming of Model Bio-Oil Aqueous Fraction Using Ni-(Cu, Co, Cr)/SBA-15 Catalysts.

Hydrogen obtained from biomass derivatives is considered a promising alternative to fossil fuels. The aim of this work is to test the viability of Ni-M/SBA-15 (M: Co, Cu, Cr) catalysts for the hydrogen production from bio-oil aqueous fraction reforming. Tests were performed in a fixed-bed reactor at 600 °C and atmospheric pressure. Firstly, the steam reforming (SR) of acetic acid, hydroxyacetone, furfural and phenol, as representative constituents of the bio-oil aqueous fraction, was carried out. Lower reactivity with increasing carbon number and decreasing steam-to-carbon ratio was observed. Coking rate during SR is a consequence of carbon number and aromaticity of the reactant, as well as the steam-to-carbon ratio. However, deactivation also depends on the graphitization degree of carbon filaments, higher in the case of coke formed from phenol. Then, the performance of the Ni-M/SBA-15 catalysts was studied in the reforming of a bio-oil aqueous fraction surrogate containing the four model compounds. Ni-Co/SBA-15 and Ni-Cr/SBA-15 samples were the most active because Co also catalyze the steam reforming reactions and Cr promotes the formation of very small Ni crystallites accounting for high conversion and the low coke deposition (~8 times lower than Ni/SBA-15) in the form of poorly condensed carbon filaments.

Steam reforming and carbon deposition evaluation of phenol and naphthalene used as tar model compounds over Ni and Fe olivine-supported catalysts

Iron and nickel-based catalysts over an olivine support were prepared by different methods (thermal fusion (TF) and wetness impregnation (WI)), and the effect of steam reforming of phenol and naphthalene on those catalysts was tested. The structure of catalysts synthesized by the TF method exhibited obvious differences compared with the WI method. During the thermal fusion process, part of Fe and Ni was migrated into the olivine framework to form (Mg,Fe) Fe2O4 and Ni2SiO4(NiFe2O4), respectively. In this structure, Fe and Ni acted as active metal, and Si, Mg, O acted as dispersed phases, so Fe and Ni can be dispersed more uniformly and exhibit more stable catalytic activity. However, The Fe and Ni presented as Fe2O3 and NiO–MgO in the wetness impregnation process which was easily sintered and consumed duo to attrition during the catalytic reaction. The catalysts prepared by the two methods both performed well for phenol steam reforming (Fe-containing catalysts reached more than 93% and Ni-containing catalysts reached more than 99%) and carbon deposition resistance (carbon deposition rates were both lower than 7%), while the carbon deposits from the steam reforming of naphthalene were difficult to eliminate by steam. After analysis, it was found that the carbon deposits from phenol catalytic cracking was mainly Cα which was easy to react with steam, and that those from naphthalene were mainly Cβ and Cγ which had poor reactivity.

Thermodynamic investigation and experimental analysis on phenol steam reforming towards enhanced H2 production over structured Ni/ZnTiO3 nanocatalyst

Thermodynamic analysis incorporated with experiments for H2 production from phenol steam reforming (PSR) over structured Ni/ZnTiO3 nanocatalyst has been investigated. Catalyst samples, prepared via hydrothermal and impregnation methods, were characterized by XRD, FE-SEM, EDX and TGA spectroscopy techniques. First, thermodynamic analysis was applied to investigate the influence of experimental parameters on the products distribution. The optimum operating conditions of PSR based on the thermodynamic analysis were found to be; temperatures 500–700 °C, 5 wt% phenol concentration and atmospheric pressure, where higher H2 yield can be obtained with minimal coke depositions. Next, catalytic performance of Ni/ZnTiO3 for promoting PSR towards H2 production was conducted in a fixed bed reactor at 700 °C and 1 atm. Observably, Ni promoted ZnTiO3 catalyst found very efficient for H2 yield and selectivity. Utilizing 10% Ni/ZnTiO3 catalyst, phenol conversion of 88.3% with H2 yield and selectivity of 75.6 and 68.52%, respectively were attained. The stability test exhibited that Ni/ZnTiO3 catalyst kept active over 100 h without obvious deactivation. According to a comparison between thermodynamic analysis and experimental results, it was possible to illustrate deviations regarding the phenol conversion and selective H2 production. In general, Ni/ZnTiO3 catalyst revealed excellent activity in PSR as a promising material for H2 production.

Enhanced Metal–Support Interaction in Ni/Co3O4/TiO2 Nanorods toward Stable and Dynamic Hydrogen Production from Phenol Steam Reforming

The fabrication of highly stable Ni and Co3O4 nanocube-supported TiO2 nanorods (NRs) catalysts with improved metal–support interaction for steam reforming of phenol (SRP) has been investigated. An enhanced catalytic performance of Ni/Co3O4/TiO2 NRs with H2-rich gas and hardly formed coke was achieved and rationalized with spectroscopic results and structural assessments. Over 10% Ni/5% Co3O4/TiO2 NRs, SRP and water gas shift reactions dominate, producing mostly H2 and CO2, yet Ni/TiO2 microparticles promoted CO. With catalyst loading, steam-to-carbon ratio, and gas hourly space velocity, the H2 yield was improved with higher CO2/CO ratio and low CO yield. A Ni/Co3O4/TiO2 NRs catalyst possesses excellent stability, which prevailed for more than 100 h without obvious deactivation. The high performance was due to a 1D TiO2 NRs/Co3O4 nanocubes heterojunction, good metal dispersion, and higher reducibility, thereby providing a strong interaction of bimetallic active sites. This study reveals that Co3O4 promote...

Comparative study on phenol and naphthalene steam reforming over Ni-Fe alloy catalysts supported on olivine synthesized by different methods

Ni/Fe bimetallic catalysts were synthesized on an olivine support using the wetness impregnation (WI) and thermal fusion (TF) methods, and catalytic cracking and steam reforming on different tar model compounds (phenol and naphthalene) were investigated in a fixed bed reactor. The effects of the reaction temperature and space-time on the catalytic cracking activity of phenol and naphthalene were tested, and the influences of steam on the carbon molar ratio (S/C) and different synthesized methods on the steam reforming of phenol and naphthalene were also studied. In addition, the carbon deposited on the catalyst was analysed using temperature program oxidation (TPO), Raman spectroscopy and transmission electron microscopy (TEM) methods. The elemental composition of the catalyst was analysed by X-ray fluorescence (XRF), and the physiochemical properties of the catalysts were characterized via X-ray diffraction (XRD), the BET surface area, scanning electron microscopy (SEM), TEM, Raman spectroscopy, temperature program reduction (TPR), and X-ray photoelectron spectroscopy (XPS). The results showed that the structure of TF-Ni/Fe/olivine changed considerably compared with that of calcined olivine (mainly the Mg2SiO4 phase) and that a portion of Fe was fused into the olivine structure and reorganized into a new (Mg, Fe) Fe2O4 phase. After reduction, the Ni-Fe alloy was detected on both catalysts, and the particle size of the Ni-Fe alloy on TF-Ni/Fe/olivine was smaller than that of WI-Ni/Fe/olivine. The TF-Ni/Fe/olivine cracked phenol into small-molecule gas (CO and H2) and a small quantity of olefin. By contrast, phenol was polymerized to naphthalene in the absence of a catalyst. The phenol and naphthalene steam reforming conversion on WI-Ni/Fe/olivine were both higher than that of TF-Ni/Fe/olivine. A 100-h stability test of phenol steam reforming on TF-Ni/Fe/olivine and WI-Ni/Fe/olivine was conducted, and TF-Ni/Fe/olivine showed higher stability in the early stages of the experiment due to stronger interactions between the active sites and olivine support. The deposited carbon from naphthalene steam reforming was more difficult to eliminate because it contained more Cβ and Cγ, which had higher degrees of graphitization.

Steam reforming of simulated bio-oil on K-Ni-Cu-Mg-Ce-O/Al2O3: The effect of K

Steam reforming of simulated bio-oil (ethanol, acetone, phenol, and acetic acid) and phenol has been studied on K-Ni-Cu-Mg-Ce-O/Al2O3 composite catalysts. Complementary characterization techniques, such as nitrogen sorption, XRD, H2-TPR, H2-TPD, CO-TPD, CO-DRIFTS, and in situ XPS, were used to correlate surface structure and functionality to catalytic performance of potassium (K) doped catalysts. K doping of the Ni-Cu-Mg-Ce-O/Al2O3 catalyst created a Ni°/Ni2+ mixed active phase, which not only enhanced steam reforming activity, but also suppressed the methanation reaction. In addition, K doping changed the surface acid-basic properties of the catalyst, which instead favor the gasifcation and water-gas shift reactions. With the combination of these effects, K doping of Ni-Cu-Mg-Ce-O/Al2O3 catalysts led to higher C1 yield and much lower methane formation, favoring hydrogen production in steam reforming of both phenol and simulated bio-oil.