Enhancement of hydrogen production in a novel fluidized-bed membrane reactor for naphtha reforming

In this work, a novel fluidized-bed membrane reactor (FBMR) for naphtha reforming in the presence of catalyst deactivation has been proposed. In this reactor configuration, a fluidized-bed reactor with perm-selective Pd–Ag (23 wt% Ag) wall to hydrogen has been used. The reactants are flowing through the tube side which is a fluidized-bed membrane reactor while hydrogen is flowing through the shell side which contains carrier gas. Hydrogen penetrates from fluidized-bed side into the carrier gas due to the hydrogen partial pressure driving force. Hydrogen permeation through membrane leads to shift the reaction toward the product according to the thermodynamic equilibrium. This membrane-assisted fluidized-bed reactor configuration solves some drawbacks of conventional naphtha reforming reactors such as pressure drop, internal mass transfer limitations and radial gradient of concentration and temperature. In FBMR the hydrogen which is produced in shell side is a valuable gas and can be used for different purposes. The two-phase theory of fluidization is used to model and simulate the FBMR. Industrial packed bed reactor (PBR) for naphtha reforming is used as a basis for comparison. This comparison shows enhancement in the yield of aromatic production in FBMR for naphtha reforming. Although using FBMR reduces hydrogen mole fraction in reaction side and enhances catalyst deactivation due to coking, but this effect can be compensated using advantages of FBMR such as suitable hydrogen to hydrocarbon molar ratio, lowering deactivation rate due to lower temperature, control of permeation rate by adjusting shell side pressure and shifting the equilibrium reactions. The impacts of hydrogen to hydrocarbon molar ratio, pressure, membrane thickness, flow rate and temperature have been investigated in this work.     

Modeling & optimization of renewable hydrogen production from biomass via anaerobic digestion & dry reformation

There is a growing interest in the usage of hydrogen as an environmentally cleaner form of energy for end users. However, hydrogen does not occur naturally and needs to be produced through energy intensive processes, such as steam reformation. In order to be truly renewable, hydrogen must be produced through processes that do not lead to direct or indirect carbon dioxide emissions. Dry reformation of methane is a route that consumes carbon dioxide to produce hydrogen. This work describes the production of hydrogen from biomass via anaerobic digestion of waste biomass and dry reformation of biogas. This process consumes carbon dioxide instead of releasing it and uses only renewable feed materials for hydrogen production. An end-to-end simulation of this process is developed primarily using Aspen HYSYS® and consists of steady state models for anaerobic digestion of biomass, dry reformation of biogas in a fixed-bed catalytic reactor containing Ni–Co/Al₂O₃ catalyst, and a custom-model for hydrogen separation using a hollow fibre membrane separator. A mixture-process variable design is used to simultaneously optimize feed composition and process conditions for the process. It is identified that if biogas containing 52 mol% methane, 38 mol% carbon dioxide, and 10 mol% water (or steam) is used for hydrogen production by dry reformation at a temperature of 837.5 °C and a pressure of 101.3 kPa; optimal values of 89.9% methane conversion, 99.99% carbon dioxide conversion and hydrogen selectivity 1.21 can be obtained.     

Noncatalytic gasification of isooctane in supercritical water: A Strategy for high-yield hydrogen production

Continuous supercritical water gasification of isooctane, a model gasoline compound, is investigated using an updraft gasification system. A new reactor material, Haynes^® 230^® alloy, is employed to run gasification reactions at high temperature and pressure (763 ± 2 °C; 25 MPa). A large-volume reactor is used (170 mL) to enable the gasification to be run at a long residence time, up to 120 s. Various gasification experiments are performed by changing the residence time (60-120 s), the isooctane concentration (6.3-14.7 wt%), and the oxidant concentration (equivalent oxidant ratio 0-0.3). The total gas yield and the hydrogen gas yield increase with increasing residence time. At 106 s and an isooctane concentration of 6.3 wt%, a very high hydrogen gas yield of 12.4 mol/mol isooctane, which is 50% of the theoretical maximum hydrogen gas yield and 92% of the equilibrium hydrogen gas yield under the given conditions, is achieved. Under these conditions, supercritical water partial oxidation does not increase the hydrogen gas yield significantly. The produced gases are hydrogen (68 mol%), carbon dioxide (20 mol%), methane (9.8 mol%), carbon monoxide (1.3 mol%), and ethane (0.9 mol%). The carbon gasification efficiency is in the range 75-91%, depending on the oxidant concentration. A comparison of supercritical water gasification with other conventional methods, including steam reforming, autothermal reforming, and partial oxidation, is also presented.     

A novel tubular membrane reactor for pure hydrogen production in the synthesis of formaldehyde by the silver catalyst process

Formaldehyde-based chemistry plays a significant role in the production of different materials. In this work, attempts have been made to revamp a silver catalyzed formaldehyde plant by applying membrane technology. The conventional silver catalyst packed bed reactor was replaced by a shell and tube membrane reactor. A steady-state one-dimensional model was applied to evaluate the performance of the proposed membrane process. The model was validated with experimental results from the plant.The effects of various parameters including reactor pressure, feed temperature, and membrane thickness on the membrane reactor were investigated. Results showed that the effect of feed temperature on production rates was negligible. The increase in pressure and decrease in membrane thickness, however, leads to increase products. The simultaneous production of 100 tonnes/day of formalin 37% (37 wt% formaldehyde in water) and 500 kg/day pure hydrogen achieved by the proposed process. Furthermore, the exiting reactor temperature can be reduced to 420 °C which is significantly lower than the conventional method (650 °C).     

Catalytic dehydrogenation of cyclohexane over Ag-M/ACC catalysts for hydrogen supply

Dehydrogenation of cyclohexane to benzene has been carried out over Ag supported on activated carbon cloth (Ag/ACC) catalysts using a spray- pulse reactor. Hydrogen evolution was studied for hydrogen storage and supply system applications. The maximum rate of hydrogen evolution rate using monometallic Ag/ACC catalysts was 6.9 mmol/g_met/min for Ag loading of 10 wt%. An enhanced hydrogen evolution was observed by adding a small amount of noble metal (1 wt% Pt, Pd, Rh) to the Ag based catalysts. A synergistic effect was observed in the case of the Pt promoted catalysts on the hydrogen production were twice as compared to 10 wt% Ag catalyst only.     

Dynamic optimization of a multi-stage spherical,radial flow reactor for the naphtha reforming process in the presence of catalyst deactivation using differential evolution (DE) method

In the present research, differential evolution (DE) method has been used to optimize the operating conditions of a radial flow spherical reactor containing the naphtha reforming reactions. In this reactor configuration, the space between the two concentric spheres is filled by catalyst. The dynamic behavior of the reactor has been taken into account in the optimization process. The achieved mass and energy balance equations in the model are solved by orthogonal collocation method. The goal of this optimization is to maximize the hydrogen and aromatic production which leads to the maximum consumption of the paraffins and naphthenes. In order to reach this end, the inlet temperature of the gas at the entrance of each reactor, the total pressure of the process, as well as the catalyst distribution in each reactor have been optimized using the differential evolution (DE) method. The results of the optimization of the spherical reactor have been compared with the non-optimized spherical reactor. The comparison shows acceptable enhancement in the performance of the reactor.     

Steam reforming of simulated pre-reformed naphtha in a PdAu membrane reactor

Process intensification in a membrane reactor is an efficient and compact way to produce hydrogen. A methane-rich gas mixture that simulated the composition of pre-reformed naphtha (PRN; with a steam-to-carbon ratio of 2.7) was reformed at temperatures of 550 °C–625 °C and pressures up to 40 barg. The reactor contained commercial steam reforming catalyst and a 14.8 cm long, 2.6 μm thick Pd-1.8Au (wt. %) membrane on a porous alumina support. Methane conversions approaching 90% were obtained in the membrane reactor at a gas-hourly space velocity of 676 h^?1, compared to ≤30% conversion at the same conditions in conventional reactor mode (CM) without withdrawing hydrogen through the membrane. The results were compared to steam methane reforming (SMR) in the membrane reactor at similar conditions. The nitrogen leak through the membrane increased slowly during the testing, because of both pinhole formation and some leakage through the end seals.     

Hydrogen production from carbon dioxide reforming of methane over Ni-Co/MgO-ZrO2 catalyst: Process optimization

Greenhouse gases, carbon dioxide and methane are utilized in the production of hydrogen through carbon dioxide reforming of methane catalyzed by Ni-Co/MgO-ZrO₂ catalyst. Design of Experiments (DOE) was used to study the effects of process variables such as, carbon dioxide to methane ratios (1-5), gas hourly space velocity (8400-200,000 mL/g/h), oxygen concentration in the feed (3-8 mol%) and reaction temperature (700-800 °C) over methane conversion and yield of hydrogen. The ANOVA analysis indicated that the effect of each process variable was significant to its respective responses in the proposed quadratic model. The response surface methodology (RSM) was used to find the optimum value of the process variables by maximizing the hydrogen yield in the process model. The optimum space velocity as 145,190 mL/g/h at reaction temperature 749 °C with carbon dioxide to methane ratio of 3 and 7 mol% of oxygen in the feed gave 88 mol% of CH₄ conversion and 86 mol% of hydrogen yield, respectively. The experiments were run at the optimum condition gave 87.7 mol% methane conversion and 85.5 mol% of hydrogen yield, which were in good agreement with the simulated values obtained from the model. The catalyst stability and its regeneration characteristics were studied at the optimum condition by monitoring methane conversion and hydrogen yield with time on stream.     

Underwater vehicle hydrogen production from methanol steam reforming using hydrogen peroxide

Methanol steam reforming (MSR) can supply hydrogen (H₂) to underwater vehicles equipped with a fuel cell. Low reaction temperatures ensure the composition of the reformed gas suitable for the H₂ purification unit and increase the design freedom of a reforming plant. However, such temperatures decrease the catalyst activity and thereby the methanol (MeOH) conversion and H₂ production. Herein, hydrogen peroxide (H₂O₂) was supplied with MeOH and water (H₂O) to ensure sufficient MeOH conversion and H₂ production at low temperatures. A tube reactor loaded with a commercial Cu/Zn catalyst was installed in an electric furnace maintained at 200–250 °C, and MeOH and 0 wt%, 11.88 wt%, 22.51 wt%, and 32.07 wt% H₂O₂ were supplied. When the furnace temperature was 200 °C, the MeOH conversion was 49.3% at 0 wt% H₂O₂ but 93.5% at 32.07 wt% H₂O₂. The effect of adding H₂O₂ was greater under the temperature conditions where the MeOH conversion was 100% or less. To analyze the effect of H₂O₂ addition on catalyst durability, the furnace was maintained at 200 °C, and the reactor was continuously operated for 110 h with 0 wt% and 32.07 wt% H₂O₂. The addition of H₂O₂ did not significantly decrease the Cu/Zn catalyst durability.     

Ni–Mo nanoparticles stabilized by ether functionalized ionic polymer: A novel and efficient catalyst for hydrodeoxygenation of 4-methylanisole as a representative of lignin-derived pyrolysis bio-oils

In the present study, nickel-molybdenum nanoparticles stabilized with ether functionalized ionic polymer were synthesized and utilized as a novel and efficient catalyst for hydrodeoxygenation of 4-methylanisole as a representative of lignin-derived bio-oil. The catalytic upgrading process was performed in the presence of hydrogen with a batch reactor at temperature of 80–200 °C, hydrogen pressure of 10–50 bar, reaction time of 0.5–15 h and catalyst loading of 1–5 mol%. The major reaction classes during 4-methylanisole upgrading were hydrodeoxygenation and hydrogenolysis which resulted in production of 4-methylphenol, toluene, phenol and benzene as the main products. The experimental results indicated that the catalytic activity of Ni–Mo (20%–80%) nanoparticles stabilized with ionic polymer is superior to that with low Mo content. Also, it is observed that the selectivity of deoxygenated products including toluene and benzene improves with increasing the Mo content of the catalyst. Finally, regarding to the excellent catalytic activity of synthesized nanocatalyst during upgrading process of bio-oil at mild operating condition, ether functionalized ionic polymer was introduced as an applicable and effective stabilizers for nickel-molybdenum nanoparticles.     

Optimal design of a radial-flow membrane reactor as a novel configuration for continuous catalytic regenerative naphtha reforming process considering a detailed kinetic model

The significance of the catalytic naphtha reforming process in the petroleum refining and petrochemical industry generates continuous evolution of the technology. These improvements would be observed in presenting more efficient reactor setups in order to improve production yield and operating conditions, as well as elucidating better kinetic and deactivation models with higher predicting ability. Both of these items have been considered in this work. An optimized radial-flow moving bed membrane reactor has been proposed as a novel configuration for naphtha reforming process. Optimization has been carried out by differential evolution (DE) method considering 40 decision variables. A detailed kinetic model has also been presented. The proposed kinetic model consists of 32 lumped pseudo-components and 84 reactions. Deactivation rate of catalyst has also been taken into account by considering coke deposition on both acidic and metallic sites. Plant data have been used to validate the modeling results. In order to assess the performance of the proposed configuration, the obtained modeling results have been compared with those of conventional configuration, which shows the superiority of the presented one.     

Optimization of Liquid Organic Hydrogen Carrier (LOHC) dehydrogenation system

In this paper, the perhydrodibenzyltoluene dehydrogenation flowsheet has been simulated. Modelling of the dehydrogenation reactor has been performed using the 1-D model. External and internal mass transfer resistances are also considered. Non-isothermal pellet condition has been considered for simulating the dehydrogenation reactor. The flowsheet simulation has been carried out in DW-Sim v 6.5.2 integrated with the reactor model coded in Python. NET. The dehydrogenation reactor is operated at a feed temperature between 523 K ?613 K, a wall temperature of 623 K and 653 K, and a reactor pressure maintained at 1.2 atm. The amount of catalyst required for the perhydrodibenzyltoluene (PDBT) dehydrogenation reactor is evaluated such that the conversion reaches 99%. The process flowsheet has been simulated to produce 10 Nm³/hr of industrial-grade hydrogen. The effects of feed temperature, wall temperature, and hydrogen burner efficiency on various system requirements, including catalyst weight, energy supplied to the dehydrogenation reactor, areas of the heat exchanger, and hydrogen production from the reactor, have been discussed. Preliminary cost optimization based on the heat exchangers and catalyst at various feed temperatures, reactor wall temperature, and hydrogen burner efficiency has been carried out.     

Efficiency assessment of a photo electrochemical chloralkali process for hydrogen and sodium hydroxide production

In present study, a new reactor configuration is developed which integrates photochemical hydrogen production with an electrochemical chloralkali process. The effects of different parameters on rate of hydrogen, chlorine and sodium hydroxide production are experimentally examined and discussed. The parameters include applied voltage, varied from 4 V to 5 V, amount of catalyst, varied from 1 g/425 mL to 4 g/425 mL, and light intensity, varied from 20 W/m² to 55 W/m². Factorial design of experiments is applied and an analysis of variance (ANOVA) is used to analyze the experimental results. Energy and exergy efficiencies are also examined. An optimization study is performed to find the optimal catalyst concentration. An optimized catalyst concentration in salty water is used to examine its effect on the rate of hydrogen production.     

Influence of catalyst and temperature on gasification performance of pig compost for hydrogen-rich gas production

The catalytic steam gasification of pig compost (PC) for hydrogen-rich gas production was conducted in a fixed-bed reactor. The influence of the catalyst and reactor temperature on yield and product composition was studied at the temperature range of 700–850 °C, for weight hourly space velocity (WHSV) in the range of 0.30–0.60 h⁻¹. The results indicate that the developed NiO on modified dolomite (NiO/MD) catalyst reveals better catalytic performance on the tar elimination and hydrogen yield than calcined MD or NiO/γ-Al₂O₃ catalyst. Meanwhile, the lower WHSV and higher reactor temperature can contribute to more hydrogen production and gas yield. Moreover, the char from catalytic steam gasification of PC has a highest ash content of 75.84% at 850 °C. In conclusion, pig compost is a potential candidate for hydrogen gas production through catalytic steam gasification technology.     

Hydrogen production from dairy wastewater using catalytic supercritical water gasification: Mechanism and reaction pathway

The supercritical water gasification (SCWG) of real dairy wastewater (cheese-based or whey) was performed in a batch reactor in presence of two catalysts (MnO₂, MgO) and one additive (formic acid). The operational conditions of this work were at a temperature range of 350–400 C and the residence time of 30–60 min. The catalysts and formic acid were applied in 1 wt%, 3 wt%, and 5 wt% to determine their effect on hydrogen production. The concentrations of catalysts and formic acid were calculated based on the weight of feedstock without ash. The results showed that increased temperature and prolonged residence time contributed to the hydrogen production (HP) and gasification efficiency (GE). The gas yield of hydrogen in the optimum condition (400 C and 60 min) was achieved as 1.36 mmol/gr DAF (dry ash free). Formic acid addition was favored towards enhancing hydrogen content while the addition of metal oxides (MnO₂ and MgO) had an apex in their hydrogen production and they reached the highest hydrogen in 1 wt% concentration then ebbed. Moreover, GE was increased by the addition of the catalysts and formic acid concentrations. The highest hydrogen content (35.4%) was obtained in 1 wt% MnO₂ and the highest GE (32.22%) was attained in the 5 wt% formic acid concentration. A reaction pathway was proposed based on the GC-MS data of feedstock and produced liquid phase at different condition as well as similar studies.     

Hydrogen production on-demand by hydride salt and water two-phase generator

This research focuses on novel designs of powder-to-water hydrogen generators for “on-demand” use, with hydrogen-based fuel cells. Hydrogen is produced in a chemical reaction between water and hydride sodium with the assistance of a catalyst. This configuration allows high energy density, together with portability, and easy to use, refill or clean. We describe our experience in implementing powder-to-water generators for a portable integrated power system. Five different prototype designs were developed, built, examined and characterized. Tests have been carried out in order to monitor hydrogen production, operation, and reaction conditions (i.e., hydrogen flow, motor power, reactor temperature, and pressure) and to evaluate the prototypes feasibility, efficiency and performance. We show relatively constant on-demand hydrogen flow (of about 400 mL/min) for extended durations (5–7 h), with short (<15 min) operation breaks, with a hydrogen density of 4.5 wt% (out of reactants) and estimated energy density of 1400 Wh/kg.     

Modeling of an axial flow,spherical packed-bed reactor for naphtha reforming process in the presence of the catalyst deactivation

Improving the octane number of the aromatics’ compounds has always been an important matter in refineries and lots of investigations have been made concerning this issue. In this study, an axial-flow spherical packed-bed reactor (AF-SPBR) is considered for naphtha reforming process in the presence of catalyst deactivation. Model equations are solved by the orthogonal collocation method. The AF-SPBR results are compared with the plant data of a conventional tubular packed-bed reactor (TR). The effects of some important parameters such as pressure and temperature on aromatic and hydrogen production rates and catalyst activity have been investigated. Higher production rates of aromatics can successfully be achieved in this novel reactor. Moreover, results show the capability of flow augmentation in the proposed configuration in comparison with the TR. This study shows the superiority of AF-SPBR configuration to the conventional types.     

Screening,optimization and kinetics of Jatropha curcas oil transesterification with heterogeneous catalysts

This work investigates the production of fatty acid methyl esters (FAME) from Jatropha curcas oil using a variety of heterogeneous catalysts: resins, zeolites, clays, hydrotalcites, aluminas and niobium oxide. For this purpose, a catalyst screening was first conducted in a batch reactor at the following operating conditions: oil to methanol molar ratio of 1:9, 6 h of reaction, 5 wt% catalyst, at 333 and 393 K. From the screening step, KSF clay and Amberlyst 15 catalysts were selected to carry out a 2³ full factorial central composite rotatable design so as to elucidate the effects of process variables on FAME yield. The optimum reaction conditions for both catalysts were found to be oil to methanol molar ratio of 1:12, 5 wt% of catalyst, 433 K and 6 h of reaction with a FAME yield of about 70 wt%. A kinetic study was then experimentally performed and a semi-empirical model was built to represent the experimental data. Finally, catalyst re-utilization in five successive batch experiments was evaluated at the optimized conditions.     

CFD modelling of supercritical water reforming of glycerol for hydrogen production

Glycerol, as a main by-product of biodiesel synthesis, can be used in a large variety of applications including food, personal care, pharmaceutical and chemical industries However, due to the large production of biodiesel, the glycerol market was depressed. The conversion of glycerol into an energy carrier (syngas or hydrogen) could be a very interesting route to providing value as a renewable energy source. The reforming of glycerol leads to an almost complete conversion and very high carbon-to-gas efficiency with short residence time.In this work, the performances of packed bed reactor for hydrogen production from glycerol in supercritical conditions, by using a Ni-based catalyst supported on Al₂O₃ and SiO₂, through CFD modelling in three-dimensions were studied. The parameters of kinetic model were determined by using an optimization method to fit the experimental data. The developed model was been validated based on experimental results published in literature for three different feed concentration of glycerol of 5, 10 and 20 wt% (R² = 0.969).Varying the reaction temperature, between 500 and 800 °C, and residence time, between 1.5 and 10 s, the concentration of hydrogen increased with increasing the temperature and decreasing the residence time. At high temperature, the hydrogen can achieve a concentration of 65% and the present of methane is less than 5% and carbon monoxide maintain lower concentration. The simulation results show that high hydrogen yield can be obtained in short residence time with conversion of glycerol almost completed.     

Effective and facile conversion of bamboo into platform chemicals over SnCl4 in a sulfolane/water solution

Thermochemical conversion of lignocellulosic biomass into value-added chemicals has attracted great interest worldwide. Herein, we report an effective and facile process to transform bamboo into 5-hydroxymethylfurfural (5-HMF), furfural (FF) and levulinic acid (LA) using metal chlorides as catalysts. The effects of the reaction parameters, such as the reaction time, temperature, initial pressure and catalyst loading on the bamboo conversion and product yields were investigated. Notably, the optimum reaction conditions were heating 200 °C for 2 h using 0.75 g of SnCl₄ as catalyst in a 90.0 wt% aqueous sulfolane solution, where the conversion of bamboo was 90.0 wt% forming 41.2 mol% of 5-HMF, 20.1 mol% of FF and 24.6 mol% of LA. The synergistic effect of [Sn(OH)₃(aq)]⁺ and cation polarization has an important role in the outstanding efficiency and specificity of our selective liquefaction system. Moreover, the water/sulfolane system displays excellent performance for maintaining the Lewis acid active sites in [Sn(OH)₃(aq)]⁺. In the process, sulfolane regulates the hydrolysis of SnCl₄ to provide an effective Lewis acid strength. This study sheds light on the remarkable potential of the process for future industrial application.