Modeling and simulation of steam methane reforming and methane combustion over continuous and segmented catalyst beds in autothermal reactor

In this paper, a numerical analysis of the production of hydrogen via autothermal (ATR) steam methane reforming (SMR) is presented. The combustion reaction occurs over a Pt/Al₂O₃ catalyst, and the reforming reaction is operated using a Ni/Al₂O₃ catalyst inside the same cylindrical channel. A novel configuration with18 catalytic-bed macro-patterns alternately mounted, referred to as SDB, is designed and compared with the catalytic dual-bed reactor (conventional configuration), referred to as CDB, at the same operating temperature and pressure conditions of 900 °C and 14 bars, respectively. The results showed that hydrogen yield was improved by 4.5% compared to the conventional configuration, while a decrease of 67 °C of the highest temperature was noticed. Meanwhile, the methane conversion was 63.73% and 65.44% for the CDB and SDB configurations, respectively. Furthermore, the length of the reactor can be decreased by 27%, keeping the same hydrogen yield at the outlet of the conventional reactor, indicating a potential reduction in hydrogen cost.     

Preparation,characterization, and properties of Pt/Al2O3/cordierite monolith catalyst for hydrogen generation from hydrolysis of sodium borohydride in a flow reactor

High-purity hydrogen can be generated by hydrolysis of sodium borohydride and used for operating portable proton exchange membrane fuel cells. The monolith supported catalyst is suitable for practical NaBH₄-based hydrogen generation system due to its simple reactor structure miniaturizing for small size applications and easy separation from the spent solution. In the present study, a structured catalyst was prepared by wash-coating the Al₂O₃ sol over the wall of cordierite monolith followed by depositing Pt using incipient wet impregnation method; then the monolithic catalysts were characterized by XRF, XRD, SEM, HRTEM and XPS. The catalytic activity of the Pt-based monolithic catalyst towards hydrolysis of NaBH₄ was tested using a flow reactor under ambient conditions in an autothermal manner. The characterization results show that Pt nanoparticles are highly dispersed on the surface of the Al₂O₃-coated layer. A continuous and stable hydrogen generation can be obtained by feeding the reactant (10 wt% NaBH₄–5 wt % NaOH) into the tube reactor loaded with the monolithic catalyst at feed rates of 0.5–2.0 mL min⁻¹.     

Ce promoting effect on the activity and coke formation of Ni catalysts supported on mesoporous nanocrystalline γ-Al2O3 in autothermal reforming of methane

In this study methane autothermal reforming (ATR) was investigated over Ni/Al₂O₃ and Ni/Al₂O₃–CeO₂ catalysts. The catalyst carriers were prepared through a facile one-step method, which produced mesoporous nanocrystalline carriers for Ni catalysts. The samples were characterized by XRD, TPR, BET, TPO and SEM characterization techniques and the catalytic activity and stability were also studied at different conditions (GHSV and feed ratio) in methane ATR. It was found that the nickel catalyst supported on 3 wt.% Ce–Al₂O₃ exhibited higher activity compared to the catalysts supported on the Al₂O₃ and promoted Al₂O₃ with 1 and 6 wt.% Ce. The results also showed that the nickel catalyst supported on 3 wt.% Ce–Al₂O₃ possessed the highest resistance against carbon deposition in ATR reaction.     

Hydrogen production from glycerol dry reforming over Ag-promoted Ni/Al2O3

In recent times, glycerol has been employed as feedstock for the production of syngas (H₂ and CO) with H₂ as its main constituent. This study centers on dry reforming of glycerol over Ag-promoted Ni/Al₂O₃ catalysts. Prior to characterization, the catalysts were synthesized using the wet impregnation method. The reforming process was carried out using a fixed bed reactor at reactor operating conditions; 873–1173 K, carbon dioxide to glycerol ratio of 0.5 and gas hourly space velocity (WHSV) in the range of 14.4 ≤ 72 L g_cat⁻¹ h⁻¹). Ag (3)-Ni/Al₂O₃ gave highest glycerol conversion and hydrogen yield of 40.7% and 32%, respectively. The optimum conditions which gave highest H₂ production, minimized methane production and carbon deposition were reaction temperature of 1073 K and carbon dioxide to glycerol ratio of 1:1. This result can attributed to the small metal crystallite size characteristics possessed by Ag (3)–Ni/Al₂O₃, which enhanced metal dispersion in the catalyst matrix. Characterization of the spent catalyst revealed the formation of two types of carbon species; encapsulating and filamentous carbon which can be oxidized by O₂.     

Methanol steam reforming over PdZn/ZnAl2O4/Al2O3 in a catalytic membrane reactor: An experimental and modelling study

A catalytic membrane reactor equipped with Pd–Ag metallic membranes and loaded with PdZn/ZnAl₂O₄/Al₂O₃ catalytic pellets was tested for the methanol steam reforming reaction (S/C = 1) aimed at producing a pure hydrogen stream for PEM fuel cell feeding. The catalyst was prepared in two steps. First, commercial γ-Al₂O₃ pellets were impregnated with ZnCl₂ and calcined at 700 °C to obtain a ZnAl₂O₄ shell, and subsequently impregnated with PdCl₂ and reduced at 600 °C to obtain PdZn alloy nanoparticles. The catalyst was tested both in a conventional packed bed reactor and in a catalytic membrane reactor. A 3D CFD non-isothermal model with mass transfer limitations was developed and validated with experimental data. The reactions of methanol steam reforming, reverse water-gas shift and methanation were modeled under different pressure, temperature and feed load values. The model was used to study and simulate the CMR under different operation conditions.     

Hydrogen production via catalytic pulsed plasma conversion of methane: Effect of Ni–K2O/Al2O3 loading,applied voltage,and argon flow rate

Despite industrial application of methane as an energy source and raw material for chemical manufacturing, it is a potent heat absorber and a strong greenhouse gas. Evidently reduction of methane emission especially in the natural gas sector is essential. Methane to hydrogen conversion through non-thermal plasma technologies has received increasing attention. In this paper, catalytic methane conversion into hydrogen is experimentally studied via nano-second pulsed DBD plasma reactor. The effect of carrier gas flow, applied voltage, and commercial Ni–K₂O/Al₂O₃ catalyst loading on methane conversion, hydrogen production, hydrogen selectivity, discharge power, and energy efficiency are studied. The results showed that in the plasma alone system, the highest methane conversion and hydrogen production occurs at argon flow rate of 70 mL/min. Increase in the applied voltage increases the methane conversion and hydrogen production while it decreases the energy efficiency. Presence of 1 g Ni–K₂O/Al₂O₃ catalyst shifts the optimum voltage for methane conversion and hydrogen production to 8 kV, reduces the required power, and increases the energy efficiency of the process. Finally in the catalytic plasma mode the optimum process condition occurs at the argon flow rate of 70 mL/min, applied voltage of 8 kV, and catalyst loading of 6 g. Compared with the optimum condition in the absence of catalyst, presence of 6 g Ni–K₂O/Al₂O₃ catalyst increased the methane conversion, hydrogen production, hydrogen selectivity and energy efficiency by 15.7, 22.5, 7.1, and 40% respectively.     

Hydrogen production by steam reforming of methanol in a micro-channel reactor coated with Cu/ZnO/ZrO2/Al2O3 catalyst

Hydrogen production by steam reforming of methanol is studied over Cu/Zn-based catalysts (Cu/ZnO, Cu/ZnO/Al₂O₃, Cu/ZnO/ZrO₂/Al₂O₃). Cu/Zn-based catalysts are derived from hydrotalcite-like precursors prepared by a co-precipitation method. The catalysts are characterized by N₂O chemisorption, XRD, and BET surface area measurements. ZrO₂ added to the Cu/Zn-based catalyst enhances copper dispersion on the catalyst surface. Among the catalysts tested, Cu/ZnO/ZrO₂/Al₂O₃ exhibits the highest methanol conversion and the lowest CO concentration in the outlet gas. A micro-channel reactor coated with a Cu/ZnO/ZrO₂/Al₂O₃ catalyst in the presence of an undercoated Al₂O₃ buffer layer exhibits higher methanol conversion and lower CO concentration in the outlet gas than in the absence of an undercoated Al₂O₃ buffer layer. The micro-channel reactor with a undercoated Al₂O₃ buffer layer produces large amounts of hydrogen compared with one without a buffer layer. The undercoated Al₂O₃ buffer layer enhances the adhesion between catalysts and micro-channel walls, which leads to improvement in reactor performance.     

Hydrogen production by thermo-catalytic conversion of methane over lanthanum strontium cobalt ferrite (LSCF) and αAl2O3 supported Ni catalysts

This study investigates hydrogen production by thermo-catalytic steam methane reforming over lanthanum strontium cobalt ferrite supported Nickel (Ni/LSCF) and commercial Ni/$\alpha$Al₂O₃ catalysts. The Ni/LSCF catalyst was synthesized using wet impregnation method and characterized by XRD, TEM, SEM, EDX, N₂-physisorption analysis, and H₂-TPR. The characterization analyses show that Ni/LSCF and Ni/$\alpha$Al₂O₃ possess the required physicochemical properties to catalyze the steam methane reforming reaction. The activity of the Ni/LSCF catalyst in steam methane reforming at 750 °C, 800 °C, and 850 °C resulted in CH₄ conversions of 73.46%, 78.67%, and 87.56%, respectively. In addition, hydrogen (H₂) yields of 64.34%, 72.57%, and 82.56% were obtained from the steam methane reforming at 750 °C, 800 °C, and 850 °C, respectively over the Ni/LSCF catalyst. The Ni/LSCF catalyst was found to have higher activities in term of CH₄ conversion and H₂ yield compare to the commercial Ni/$\alpha$Al₂O₃. However, the stability test conducted at 480 min time on stream (TOS) revealed that the commercial Ni-αAl₂O₃ was more stable in the steam methane reforming than the Ni/LSCF catalyst. The characterization of the used catalysts by TEM, XRD and TGA shows evidence of carbon deposition mostly on the used Ni/LSCF catalyst.     

Synthetic gas production by dry reforming of methane over Ni/Al2O3–ZrO2 catalysts: High H2/CO ratio

Alumina prepared by the sol-gel method, was impregnated with zirconia (5, 15 and 30 wt.%). Subsequently, the resulting Al₂O₃–ZrO₂ supports were impregnated with 15% Ni to obtain the Ni/Al₂O₃–ZrO₂ catalysts. The obtained catalysts were characterized by BET, SEM, XRD, H₂-TPR and TPD- CO₂. The catalytic activity was studied by means of dry reforming of methane (DRM) for syngas production. The catalysts displayed different physicochemical properties and trends of their catalytic activity as a function of the ZrO₂ content in the mixed oxide supports. For instance, ZrO₂ (5 wt %) in the catalyst, led to enhanced concentration of the medium strength basic sites and increased specific surface area, yielding thus the best performance in the DRM, with low carbon deposition after 36 h of reaction, compared with the other catalysts. This indicates that during the DRM reaction, this catalyst can provide more surface oxygen to prevent carbon deposits that could deactivate the catalyst.     

Optimization of a fluidized bed reactor for methane decomposition over Fe/Al2O3 catalysts: Activity and regeneration studies

Catalytic methane decomposition was investigated over 40 wt% Fe/Al₂O₃ catalyst in fluidized bed reactor (FLBR). After optimization of FLBR conditions in terms of catalyst bulk density, particle size, minimum fluidization velocity, and the catalyst bed height, the catalyst activity and stability tests were conducted by comparison with a fixed bed reactor (FBR). Although a similar stable methane conversion was obtained over both reactors, the pressure drop during 35 min operation of FBR was 9 times higher than that of FLBR, which indicated the possibility of continuous operation of methane decomposition process over FLBR. Further, the influence of the space velocity, feed dilution and regeneration on catalysts reactivity was studied in FLBR to conclude that a reaction condition of 12 L/g_cat∙h, feed of 20%H₂–80%CH₄ and CO₂-regeneration of deactivated catalysts may be favourable for operating methane decomposition in FLBR continually and effectively to provide stable hydrogen.     

Improved performance of Ni/Al2O3 catalyst deriving from the hydrotalcite precursor synthesized on Al2O3 support for dry reforming of methane

Exploiting Ni-based catalysts with excellent catalytic activity and anti-coking ability is significant for dry reforming of CH₄ with CO₂ (DRM) which is a promising route to CO₂ utilization. In this work, the Ni/Al₂O₃ catalyst with hydrotalcite precursor (NiAl-LDH) was synthesized by a facile in-situ growth method. And the effect of the NiAl-LDH structure on the catalytic activity and anti-coking ability of Ni/Al₂O₃ catalyst was revealed. The H₂-temperature programmed desorption (H₂-TPD) revealed that better Ni dispersion and more Ni–Al₂O₃ interface could be obtained by the NiAl-LDH precursor, which were vital for the activation of CH₄ and CO₂. Moreover, the NiAl-LDH precursor with non-LDH phase or turbostratic structure was also created by insufficient or extra amount of urea, and the obtained catalysts exhibited a poor catalytic stability, further confirming the importance of the LDH structure. In comparison with the Ni-IMP catalyst prepared by the conventional impregnation method, the CH₄ conversion increased by 16% and the carbon deposition decreased by 75% over Ni-6 catalyst with well-organized LDH precursor under the same reaction conditions. Hence, this work represents an important step toward developing Ni-based catalysts with excellent catalytic activity and anti-coking ability for DRM with the LDH precursor.     

Non-oxidative decomposition of methane/methanol mixture over mesoporous Ni-Cu/Al2O3 Co-doped catalysts

Thermocatalytic decomposition of methane (TCD) is reported to be a promising and green route of hydrogen generation, however, the relatively fast catalyst deactivation is the main drawback of this technology. This article reports an attempt to increase the catalyst deactivation time by using Cu promoted Ni-based catalyst, and methanol premixed methane gas as a feedstock. The catalysts were prepared by wet impregnation method and characterized by TGA, BET, XRD, TPR, FESEM, Raman and TEM. An inevitable decline in surface area from 5.15 to 4.52 m²g^-1 due to the addition of 15%Cu on 50%Ni/Al₂O₃ was due to the agglomeration of particles and pore blockage of γ -Al₂O₃ support. Moreover, the reduction of NiO was shifted towards lower temperature by successful impregnation of Cu promoter. The overlapping peaks of NiO and CuO confirmed the formation of mixed oxides Ni_x Cu _(1-x) O via XRD analysis. The catalytic activity of both catalysts showed that 50%Ni-15%Cu/Al₂O₃ resulted in better methane conversion 75% at 1023 K TOS for 6 h. The post reaction analysis of the catalysts revealed that carbon in the form of CNF got deposited on the surface of the catalyst having amorphous and crystalline morphology. Finally, TEM also revealed that GF, CNF, and MWCNF were encapsulated over the surface of 50%Ni-15%Cu/Al₂O_3.     

Mo-promoted Ni/Al2O3 catalyst for dry reforming of methane

Mo-promoted alumina supported Ni catalysts were prepared through a conventional impregnation method and tested in dry reforming of methane (DRM) at temperatures from 550 to 850 °C. The catalysts were characterized by means of H₂-temperature programmed reduction (H₂-TPR), CO₂-temperature programmed desorption (CO₂-TPD), X-ray diffraction (XRD), N₂ physisorption and Raman spectroscopy. Mo-promotion caused a reduction in the DRM catalytic activity. The weaker interaction between NiO species and the alumina support, the formation of a MoNi₄ phase, and the lower basicity of this Ni-Mo/Al₂O₃ catalyst were identified as the main causes for its lower activity. However, pre-reducing the Ni-Mo/Al₂O₃ catalyst at temperatures lower than 700 °C, instead of 900 °C, resulted in a considerable increase of its catalytic activity. This was mainly due to the formation of a separate Ni⁰ phase that did not interact with Mo and to an increase in medium strength basicity.     

Structure-dependent activity and stability of Al2O3 supported Rh catalysts for the steam reforming of n-dodecane

Steam reforming of liquid hydrocarbon fuels is an appealing way for the production of hydrogen. In this work, the Rh/Al₂O₃ catalysts with nanorod (NR), nanofiber (NF) and sponge-shaped (SP) alumina supports were successfully designed for the steam reforming of n-dodecane as a surrogate compound for diesel/jet fuels. The catalysts before and after reaction were well characterized by using ICP, XRD, N₂ adsorption, TEM, HAADF-STEM, H₂-TPR, CO chemisorption, NH₃-TPD, CO₂-TPD, XPS, Al²⁷ NMR and TG. The results confirmed that the dispersion and surface structure of Rh species is quite dependent on the enclosed various morphologies. Rh/Al₂O₃-NR possesses highly dispersed, uniform and accessible Rh particles with the highest percentage of surface electron deficient Rh⁰ active species, which due to the unique properties of Al₂O₃ nanorod including high crystallinity, relatively large alumina particle size, thermal stability, and large pore volume and size. As a consequent, Rh/Al₂O₃-NR catalyst exhibited superior catalytic activity towards steam reforming reactions and hydrogen production rate over other two catalysts. Especially, Rh/Al₂O₃-NR catalyst showed the highest hydrogen production rate of 87,600 mmol g_fuel^?1 g_Rh^?1min^?1 among any Rh-based catalysts and other noble metal-based catalysts to date. After long-term reaction, a significant deactivation occurred on Rh/Al₂O₃–NF and Rh/Al₂O₃-SP catalysts, due to aggregation and sintering of Rh metal particles, coke deposition and poor hydrothermal stability of nanofibrous structure. In contrast, the Rh/Al₂O₃-NR catalyst shows excellent reforming stability with negligible coke formation. No significantly sintering and aggregation of the Rh particles is observed after long-term reaction. Such great catalyst stability can be explained by the role of hydrothermal stable nanorod alumina support, which not only provides a unique environment for the stabilization of uniform and small-size Rh particles but also affords strong surface basic sites.     

Improved catalytic stability and anti-coking ability of Ni/La2O3–Al2O3 catalyst by doping alkaline earth metals for n-decane reforming

In this paper, a series of alkaline earth metals oxides doped Ni/La₂O₃–Al₂O₃ catalysts were synthesized by the coprecipitation method combined with two step impregnation methods. n-decane reforming was used to investigate these catalysts, in order to develop an excellent catalyst with better hydrogen selectivity, activity, stability, as well as lower carbon deposition. Deactivation by carbon deposition, the catalyst regenerability and stability tests were also used to weigh the selected catalyst. These catalysts are characterized by N₂ adsorption-desorption, XRD, NH₃-TPD, Raman, and TEM. The introduction of alkaline earth metals modifiers enhances the activity, stability and anti-coking ability, meanwhile the SrO modified Ni/La₂O₃–Al₂O₃ shows the best catalytic activity. Moreover, the hydrogen selectivity and conversion over regenerative Ni/La₂O₃–Al₂O₃/SrO catalysts were quite close to the results of fresh ones. The enhancements of M oxides doped catalysts (especially Sr) can be due to the improved textural properties, basicity, metal-support interaction and anti-coking ability. As a consequence, loading different metals in different ways helps to gradually improve the stability, activity and coking inhibition of catalysts is an effective approach to obtain a multi-function catalyst.     

Ni/Pd-promoted Al2O3–La2O3 catalyst for hydrogen production from polyethylene terephthalate waste via steam reforming

Ni/Pd-co-promoted Al₂O₃–La₂O₃ catalysts for selective hydrogen production from polyethylene terephthalate (PET) plastic waste via steam reforming process has been investigated. The catalysts were prepared by impregnation method and were characterized using XRD, BET, TPD-CO₂, TPR-H₂, SEM, TGA and DTA. The results showed that Ni-Pd-co-impregnated Al₂O₃–La₂O₃ catalyst has excellent activity for the production of hydrogen with a prolong stability. The feed conversion of 87% was achieved over 10% Ni/Al₂O₃ catalyst which increased to 93.87% in the case of 10% Ni-1% Pd/Al₂O₃–La₂O₃ catalysts with an H₂ fraction of 0.60. The catalyst performance in term of H₂ selectivity and feed conversion was further investigated under various operating parameters, e.g., temperatures, feed flow rates, feed ratios and PET concentrations. It was found that the temperature has positive effects on H₂ selectivity and conversion, yet feed flow rate has the adverse effects. In addition, PET concentrations showed improved in H₂ selectivity in comparison to when only phenol as a solvent was involved. The Ni particles, which are the noble-based active species are more effective, thus offered good hydrogen production in the PET steam reforming process. Incorporation of La₂O₃ as support and Pd as a promoter to the Ni/Al₂O₃ catalyst significantly increased catalyst stability. The Ni–Pd/Al₂O₃–Al₂O₃ catalyst showed remarkable activity even after 36 h along with the production of carbon nanotubes, while H₂ selectivity and feed conversion was only slightly decreased.     

Modeling and simulation of methane steam reforming in a thermally coupled membrane reactor

A distributed mathematical model for thermally coupled membrane reactor that is composed of three channels is developed for methane steam reforming. Methane combustion takes place in the first channel on a Pt/δ–Al₂O₃$\text{Pt}/\delta \text{–}{\text{Al}}_2{\text{O}}_3$ catalyst layer that supplies the necessary heat for the endothermic steam reforming reaction. In the second channel, catalytic steam reforming reactions take place in the presence of Ni/MgO–Al₂O₃ catalyst. The combustion catalyst forms a thin layer next to the reactor wall to minimize the heat transfer resistance. Selective permeation of hydrogen through the palladium membrane is achieved either by co-current or counter-current flow of sweep gas through the third channel. The burner is modeled as a monolith reactor and the reformer is assumed to behave as a pseudo-homogenous reactor. The mass and energy balance equations for the thermally coupled membrane reactor form a set of 22 coupled ordinary differential equations. With the application of appropriate boundary conditions, the distributed reactor model for steady-state operation is solved as a boundary value problem. The model equations are discretized using spline collocation on finite elements. The discretized nonlinear modeling equations, along with the boundary conditions, form a system of algebraic equations that are solved using the trust region dogleg method. The performance of the reactor is numerically investigated for various key operating variables such as inlet fuel concentration, inlet steam/methane ratio, inlet reformer gas temperature and inlet reformer gas velocity. Simulations for both the co-current and the countercurrent flow modes are also performed using different sweep gas flow rates. For each case, the reactor performance is analyzed based on methane conversion and hydrogen recovery yield.     

Preparation of nickel catalysts supported on CaO.2Al2O3 for methane reforming with carbon dioxide

Nanocrystalline calcium aluminate (CaO.2Al₂O₃) was prepared by a simple co-precipitation method using Poly (ethylene glycol)-block-poly(propylene glycol)-block poly(ethylene glycol) (PEG-PPG-PEG, MW:5800) as surfactant and employed as catalyst support for nickel catalysts in methane reforming with carbon dioxide. The prepared samples were characterized by X-ray diffraction (XRD), N₂ adsorption (BET), Temperature programmed reduction and oxidation (TPR-TPO) and Scanning electron microscopy (SEM) techniques. The results showed that the prepared support has a high potential as support for nickel catalysts in methane reforming with carbon dioxide. The results showed high catalytic activity and stability for the prepared catalysts. Among the prepared catalysts 15% Ni/CaO.2Al₂O₃ was the most active catalyst and showed the highest affinity for carbon formation. In addition, 7% Ni/CaO.2Al₂O₃ possessed high catalytic stability during 50 h time on stream. The TPO analysis revealed that increasing in nickel content increased the amount of deposited carbon over the spent catalysts. SEM results detected only whisker type of carbon for all spent catalysts.     

Autothermal reforming of methane for producing high-purity hydrogen in a Pd/Ag membrane reactor

Autothermal reforming of methane includes steam reforming and partial oxidizing methane. Theoretically, the required endothermic heat of steam reforming of methane could be provided by adding oxygen to partially oxidize the methane. Therefore, combining the steam reforming of methane with partial oxidation may help in achieving a heat balance that can obtain better heat efficacy. Membrane reactors offer the possibility of overcoming the equilibrium conversion through selectively removing one of the products from the reaction zone. For instance, only can hydrogen products permeate through a palladium membrane, which shifts the equilibrium toward conversions that are higher than the thermodynamic equilibrium. In this study, autothermal reforming of methane was carried out in a traditional reactor and a Pd/Ag membrane reactor, which were packed with an appropriate amount of commercial Ni/MgO/Al₂O₃ catalyst. A power analyzer was employed to measure the power consumption and to check the autothermicity. The average dense Pd/Ag membrane thickness is 24.3 μm, which was coated on a porous stainless steel tube via the electroless palladium/silver plating procedure. The experimental operating conditions had temperatures that were between 350 °C and 470 °C, pressures that were between 3 atm and 7 atm, and O₂/CH₄ = 0–0.5. The effects of the operating conditions on methane conversion, permeance of hydrogen, H₂/CO, selectivities of CO_x, amount of power supply, and the carbon deposition of the catalyst after the reaction is thoroughly discussed in this paper. The experimental results indicate that an optimum methane conversion of 95%, with a hydrogen production rate of 0.093 mol/m². S, can be obtained from the autothermal reforming of methane at H₂O/CH₄ = 1.3 and O₂/CH₄ near 0.4, at which the reaction does not consume power, and the catalysts are not subject to any carbon deposition.     

Pellet size dependent steam reforming of polyethylene terephthalate waste for hydrogen production over Ni/La promoted Al2O3 catalyst

The effect of different pellet sizes of nickel (Ni) and lanthanum (La) promoted Al₂O₃ support on the catalytic performance for selective hydrogen production from polyethylene terephthalate (PET) plastic waste via steam reforming process has been investigated. The catalysts were prepared by impregnation method and were characterized using XRD, BET, TPD-CO₂, TPR, SEM, EDX, TEM and TGA. The results showed that NiLa-co-impregnated Al₂O₃ catalyst has excellent activity for the production of hydrogen. Feed conversion of 88.53% was achieved over 10% Ni/Al₂O₃ catalyst which increased to 95.83% in the case of 10% Ni-5% La/Al₂O₃ catalysts with a H₂ selectivity of 70.44%. The catalyst performance in term of gas production and feed conversion was further investigated under various operating parameters, e.g., feed flow-rate, and catalyst pellet size. It was found that at 0.4 ml/min feed flow rate, highest feed conversion and H₂ selectivity were achieved. The Ni particles, which are the noble-based active species are highly effective, thus offered good hydrogen production in the phenol-PET steam reforming process. Incorporation of La as a promoter in Ni/Al₂O₃ catalyst has significantly increased the catalyst reusability with prolonged stability. The NiLa/Al₂O₃ catalyst with larger size showed remarkable activity due to the presence of significant temperature gradients inside the pellet compared to smaller size. Additionally, the catalyst showed only slight decrease in H₂ selectivity and feed conversion even after 24 h, although production of carbon nanotubes was evidenced on its surface.