Optimization of VPSA-EHP/C process for high-pressure hydrogen recovery from Coke Oven Gas using CO selective adsorbent

The production of hydrogen through conventional pathways and recovery from by-products typically utilize pressure swing adsorption (PSA) technology as final purification step. Dual-layered PSA columns packed with conventional activated carbon and molecular sieve 5A material exhibit relatively low selectivity for O₂, N₂ and CO in particular. Therefore, eliminating CO (and other poisons) using conventional PSA to acceptable concentrations for EHP/C is only achievable with lower recovery rates. To improve recovery rates, there is a need for a highly efficient purification process that is highly selective for these hydrogen contaminants without compromising the product quality. Here we report an optimization study where vacuum PSA (VPSA) and electrochemical hydrogen purification and compression (EHP/C) technology is utilized for purification and compression of hydrogen from Coke Oven Gas (COG). The VPSA columns were packed with activated carbon and CuCl(7.0)-activated carbon to selectively retain poisonous CO₂ and CO, respectively. The optimal operating conditions were determined with surrogate models produced via non-linear regression of known sample input-output data points, by varying the adsorbent layering ratio (0.30–0.84), adsorption pressure (0.38–0.78 MPa), purge to feed ratio (P/F-ratio) (1–10%), adsorption step time (100–1500 s) and the EHP/C stack current per cell (37–52 A) in the original models. The two-bed VPSA system obtained 90.5% recovery and retained CO and CO₂ below their thresholds at 0.84 layering ratio, 0.78 MPa adsorption pressure, 840s adsorption time and 5.3% P/F-ratio, at the expense of H₂ purity (77.1%) by breakthrough of CH₄, N₂ and O₂. Hydrogen purity was upgraded to >99.999% by EHP/C, which recovered 90.0% of hydrogen and simultaneously compressed to 20 MPa, which required 3.2 kWh/kg H₂. The overall VPSA-EHP/C recovery rate in this configuration was 81.5%. By utilizing the EHP/C retentate gas as VPSA purge gas, overall VPSA-EHP/C recovery rates may reach 87.3% and consume less energy due to a decrease in adsorption pressure. We show that adsorption columns designed to function as poisonous component eliminator are an effective strategy to pre-condition hydrogen synthesis gases prior to further processing with EHP/C. Although the EHP/C was exposed to significant concentrations of methane, nitrogen and oxygen by their advancement through VPSA, the performance was only slightly affected. The VPSA-EHP/C method is applicable to a wide range of hydrogen gas mixtures that require further purification and compression. Traditional PSA for purification from primary and by-product (COG, annealing, chlor-alkali and flat/float glass manufacturing) hydrogen sources can be changed to a VPSA-EHP/C systems for hydrogen purification and simultaneous compression.     

Modeling study on a two-stage hydrogen purification process of pressure swing adsorption and carbon monoxide selective methanation for proton exchange membrane fuel cells

A two-stage hydrogen purification process based on pressure swing adsorption (PSA) and CO selective methanation (CO-SMET) is proposed to meet the stringent requirements of H₂-rich fuel for kW-scale skid-mounted or distributed proton exchange membrane fuel cell systems. The reforming gas is purified using dynamic adsorption model of PSA with activated carbon for initial purification and then kinetic model of CO-SMET with 50 wt% Ni/Al₂O₃ for CO deep removal. Sensitive analyses of the gas hourly space velocity, adsorption time and adsorption pressure etc. are studied. The results show that excellent H₂ purity and CO concentration below 1000 ppm for the initial target using the three-bed and four-bed PSA system at shorter adsorption time and higher pressure, and then CO concentration below 10 ppm with H₂ purity over 99.94% on CO-SMET. This work provides a small-scale and hydrogen-saving process for hydrogen purification can be achieved by the two-stage process.     

H2 PSA purifier for CO removal from hydrogen mixtures

A two-bed PSA purifier was developed to produce high purity hydrogen for fuel cell applications. Two types of hydrogen-rich mixtures produced from coal off-gas were used. Feed 1 consisted of a 99% H₂ mixture (H₂:CO:CO₂:N₂ = 99:0.1:0.05:0.85 vol.%) containing 0.1% CO while Feed 2 was a 95% H₂ mixture (H₂:CO:CO₂:CH₄:N₂ = 95:0.3:0.1:0.05:4.55 vol.%) containing 0.3% CO. An increase in the P/F ratio and adsorption pressure led to an almost linear decrease in H₂ recovery with increasing purity. However, a sharp drop in CO concentration occurred at a specific operating range in both feeds. The feed was purified to 1.1 ppm CO with 99.99+% H₂ purity and 80.0% recovery under 6.5 bar and 0.15 P/F ratio while CO in Feed 2 could be reduced to 6.7 ppm with 99.96% H₂ purity and 78.4% recovery. The PVSA process, which combined vacuum and purge steps, could improve recovery by about 10% compared to the PSA process.     

Single- and double-bed pressure swing adsorption processes for H2/CO syngas separation

Pressure swing adsorption (PSA) technology is an effective method to extract hydrogen from synthesis gas (syngas) and purify the produced hydrogen. The dynamic adsorption models for syngas (H₂/CO 70/30 mol%) treatment by single- and double-bed PSA systems with zeolite 5A were developed. The breakthrough curves of the single-bed hydrogen purification PSA system were studied. Subsequently, the performance of the single- and double-bed PSA cycles was studied. The models were built and implemented using the Aspen Adsorption platform. After model validation and successful simulation of the breakthrough curves in the single-bed model, the simulation of five- and six-step PSA cycles in the single-bed and double-bed models, respectively, were carried out. A parametric study of both single- and double-bed models was then carried out. The results reveal that the simulated breakthrough curves agree with the experimental curves very well. The parametric study shows that, with certain range of 1.38 × 10⁻⁶ to 2.08 × 10⁻⁶ kmol/s for feed flow rate, the adsorption time of 240–360 s for single-bed and 180–300 s for double-bed, a lower feed flow rate and shorter adsorption time leads to higher purity, lower recovery, and lower productivity. For the double-bed PSA model, the influence of the pressure equalization time, with the range of 5–40 s, on the PSA process was also studied. It can be found that, as the pressure equalization time increased, better purity and recovery but lower productivity were obtained. The results show that, at a feed flow rate of 1.58 × 10⁻⁶ kmol/s, the recovery and productivity of the double bed are higher by 11% and 1 mol/kg/h, respectively, than those of the single bed.     

Hydrogen purification using compact pressure swing adsorption system for fuel cell

Adsorption of CO and CO₂ in mixtures of H₂/CO/CO₂ was achieved using compact pressure swing adsorption (CPSA) system to produce purified hydrogen for use in fuel cell. A CPSA system was designed by combining four adsorption beds that simultaneously operate at different processes in the pressure swing adsorption (PSA) process cycle. The overall diameter of the cylindrical shell of the CPSA is 35 cm and its height is 40 cm. Several suitable adsorbent materials for CO and CO₂ adsorption in a hydrogen stream were identified and their adsorption properties were tested. Activated carbon from Sigma–Aldrich was the adsorbent chosen. It has a surface area of 695.07 m²/g. CO adsorption capacity (STP) of 0.55 mmol/g and CO₂ at 2.05 mmol/g were obtained. The CPSA system has a rapid process cycle that can supply hydrogen continuously without disruption by the regeneration process of the adsorbent. The process cycle in each column of the CPSA consists of pressurization, adsorption, blowdown and purging processes. CPSA is capable of reducing the CO concentration in a H₂/CO/CO₂ mixture from 4000 ppm to 1.4 ppm and the CO₂ concentration from 5% to 7.0 ppm CO₂ in 60 cycles and 3600 s. Based on the mixture used in the experimental work, the H₂ purity obtained was 99.999%, product throughput of 0.04 kg H₂/kg adsorbent with purge/feed ratio was 0.001 and vent loss/feed ratio was 0.02. It is therefore concluded that the CPSA system met the required specifications of hydrogen purity for fuel cell applications.     

Machine learning–based optimization for hydrogen purification performance of layered bed pressure swing adsorption

An adsorption, heat and mass transfer model for the five-component gas from coal gas (H₂/CO₂/CH₄/CO/N₂ = 38/50/1/1/10 vol%) in a layered bed packed with activated carbon and zeolite was established by Aspen Adsorption software. Compared with published experimental results, the hydrogen purification performance by pressure swing adsorption (PSA) in a layered bed was numerically studied. The results show that there is a contradiction between the hydrogen purity and recovery, so the multi-objective optimization algorithms are needed to optimize the PSA process. Machine learning methods can be used for data analysis and prediction; the polynomial regression (PNR) and artificial neural network (ANN) were used to predict the purification performance of two-bed six-step process. Finally, two ANN models combined with sequence quadratic program (SQP) algorithm were used to achieve multi-objective optimization of hydrogen purification performance. According to the analysis of the optimization results, the ANN models are more suitable for optimizing the purification performance of hydrogen than the PNR model.     

Simulation of 12-bed vacuum pressure-swing adsorption for hydrogen separation from methanol-steam reforming off-gas

This study focuses on analysis of a 12-bed vacuum pressure-swing adsorption (VPSA) process capable of purifying hydrogen from a ternary mixture (H₂/CO₂/CO 75/24/1 mol%) derived from methanol-steam reforming. The process produces 9 kmol H₂/h with less than 2 ppm and 0.2 ppm of CO2 and CO, respectively, to supply a polymer electrolyte membrane fuel cell. The process model is developed in Aspen Adsorption® using the “uni-bed” approach. A parametric study of H₂ purity and recovery with respect to adsorption pressure, adsorbent height, activated carbon:zeolite ratio, feed composition, and number of beds is performed. Results show 12-bed VPSA can meet the H₂ purity goals, with H₂ recovery as high as 75.75%. Adsorption occurs at 7 bar, the column height is 1.2 m, and the adsorbent ratio is 70%:30%. A 4-bed VPSA can achieve the same purity goals as the 12-bed process, but H₂ recovery decreases to 61.34%.     

The ReSER-COG process for hydrogen production on a Ni–CaO/Al2O3 complex catalyst

The reactive sorption-enhanced reforming process of simulated coke oven gas (ReSER-COG) was investigated in a laboratory-scale fixed-bed reactor with Ni–CaO/Al₂O₃ complex catalyst. Simulated coke oven gases that are free of or contain C2+ hydrocarbons (C₂H₄, C₂H₆, C₃H₆, C₃H₈) have been studied as feed materials of the ReSER process for hydrogen production. The effects of temperature, steam to methane molar ratio (S/CH₄) and carbon space velocity on the characteristics of ReSER-COG were studied. The results showed that the hydrogen concentration reaches up to 95.8% at a reaction temperature of 600 °C and a S/CH₄ of 5.8 under normal atmospheric pressure conditions. This reaction temperature was approximately 200 °C lower than that of the coke oven gas steam reforming (COGSR) processes used for the hydrogen production. The amount of H₂ generated by ReSER-COG was approximately 4.4 times more than that produced by the pressure-swing adsorption (PSA) method per unit volume of COG. The reaction temperature was 50 °C lower when simulated COG with C2+ was used, as opposed to when COG without C2+ was used. The complex catalyst has a better resistance of coking during the ReSER-COG process when C2+ gas is present.     

Artificial neural network based optimization for hydrogen purification performance of pressure swing adsorption

A pressure swing adsorption (PSA) cycle model is implemented on Aspen Adsorption platform and is applied for simulating the PSA procedures of ternary-component gas mixture with molar fraction of H₂/CO₂/CO = 0.68/0.27/0.05 on Cu-BTC adsorbent bed. The simulation results of breakthrough curves and PSA cycle performance fit well with the experimental data from literature. The effects of adsorption pressure, product flow rate and adsorption time on the PSA system performance are further studied. Increasing adsorption pressure increases hydrogen purity and decreases hydrogen recovery, while prolonging adsorption time and reducing product flow rate raise hydrogen recovery and lower hydrogen purity. Then an artificial neural network (ANN) model is built for predicting PSA system performance and further optimizing the operation parameters of the PSA cycle. The performance data obtained from the Aspen model is used to train ANN model. The trained ANN model has good capability to predict the hydrogen purification performance of PSA cycle with reasonable accuracy and considerable speed. Based on the ANN model, an optimization is realized for finding optimal parameters of PSA cycle. This research shows that it is feasible to find optimal operation parameters of PSA cycle by the optimization algorithm based on the ANN model which was trained on the data produced from Aspen model.     

Optimization of pressure swing adsorption for hydrogen purification based on Box-Behnken design method

Pressure swing adsorption (PSA) is an important technology for mixture gas separation and purification. In this work, a dynamic model for a layered adsorption bed packed with activated carbon and zeolite 5A was developed and validated to study the PSA process. The model was validated by calculating breakthrough curves of a five-component gas mixture (H₂/CH₄/CO/N₂/CO₂ = 56.4/26.6/8.4/5.5/3.1 mol%) and comparing the results with available experimental data. The purification performance of six-step layered bed PSA cycle was studied using the model. In order to optimize the cycle, the Box-Behnken design (BBD) method was used, as implemented in Design Expert?. The parametric study showed that, for adsorption step durations ranging from 160 to 200 s, as the adsorption time increased, the purity decreased, whereas the recovery and productivity increased. During the pressure equalization step, the purity increased as the pressure equalization time increased, but the recovery and productivity decreased for step durations ranging from 10 to 30 s. As the P/F ratio (hydrogen used in purge step to hydrogen fed in adsorption step) increased from 0.05 to 0.125, the purity increased, whereas the recovery and productivity decreased. The optimization of the layered bed PSA process by the BBD method was then performed. In addition to the adsorption time, the pressure equalization time and the P/F ratio were considered as independent optimization parameters. Quadratic regression equations were then obtained for three responses of the system, namely purity, recovery, and productivity. When purity is set as the main performance indicator, the following values were obtained for the optimization parameters: an adsorption time of 168 s, a pressure equalization time of 14 s, and a P/F ratio of 0.11. Under those conditions, the system achieved a purity of 99.99%, a recovery of 57.76%, and a productivity of 6.41 mol/(kg·h).     

Investigation of a novel & integrated simulation model for hydrogen production from lignocellulosic biomass

Process simulation and modeling works are very important to determine novel design and operation conditions. In this study; hydrogen production from synthesis gas obtained by gasification of lignocellulosic biomass is investigated. The main motivation of this work is to understand how biomass is converted to hydrogen rich synthesis gas and its environmentally friendly impact. Hydrogen market development in several energy production units such as fuel cells is another motivation to realize these kinds of activities. The initial results can help to contribute to the literature and widen our experience on utilization of the CO₂ neutral biomass sources and gasification technology which can develop the design of hydrogen production processes. The raw syngas is obtained via staged gasification of biomass, using bubbling fluidized bed technology with secondary agents; then it is cleaned, its hydrocarbon content is reformed, CO content is shifted (WGS) and finally H₂ content is separated by the PSA (Pressure Swing Adsorption) unit. According to the preliminary results of the ASPEN HYSYS conceptual process simulation model; the composition of hydrogen rich gas (0.62% H₂O, 38.83% H₂, 1.65% CO, 26.13% CO₂, 0.08% CH₄, and 32.69% N₂) has been determined. The first simulation results show that the hydrogen purity of the product gas after PSA unit is 99.999% approximately. The mass lower heating value (LHV_mass) of the product gas before PSA unit is expected to be about 4500 kJ/kg and the overall fuel processor efficiency has been calculated as ～93%.     

Experimental optimization analysis on operating conditions of CO removal process from hydrogen-rich reformate

The catalytic effects of CO preferential oxidation and methanation catalysts for deep CO removal under different operating conditions (temperature, space velocity, water content, etc.) are systematically studied from the aspects of CO content, CO selectivity, and hydrogen loss index. Results indicate that the 3 wt% Ru/Al₂O₃ preferential oxidation catalysts reduce CO content to below 10 ppm with a high hydrogen consumption of 11.6–15.7%. And methanation catalysts with 0.7 wt% Ru/Al₂O₃ also exhibit excellent CO removal performance at 220–240 °C without hydrogen loss. Besides, NiCl_x/CeO₂ methanation catalysts possess the characteristics of high space velocity, high activity, and high water-gas resistance, and can maintain the CO content at close to 20 ppm. Based on these experimental results, the coupling scheme of combining NiCl_x/CeO₂ methanation catalysts (low cost and high reaction space velocity) with 0.7 wt% Ru/Al₂O₃ methanation catalysts (high activity) to reduce CO content to below10 ppm is proposed.     

Lowering risk of methanation of carbon support in Ru/carbon catalysts for CO methanation by adding lanthanum

Two series of Ru/C catalysts doped with lanthanum ions are prepared and studied in CO methanation in the H₂-rich gas. The samples are characterized by N₂ physisorption, TG-MS studies, XRD, XPS, TEM/STEM and CO chemisorption. Two graphitized carbons differing in surface area (115 and 80.6 m²/g) are used as supports. The average sizes of ruthenium crystallites deposited on their surfaces are 4.33 and 5.95 nm, respectively. The addition of the proper amount of La to the Ru/carbon catalysts leads to an above 20% increase in the catalytic activity along with stable CH₄ selectivity higher than 99% at all temperatures. Simultaneously, lanthanum acts as the inhibitor of methanation of the carbon support under conditions of high temperature and hydrogen atmosphere. Such positive effects are achieved at a very low concentration of La in the prepared samples, a maximum 0.04 La/Ru (molar ratio). 0.01 mmol La introduced to the Ru/C system leads to 98% CO conversion at 270 °C.     

Continuous sorption-enhanced steam reforming of glycerol to high-purity hydrogen production

In this study, the continuous sorption-enhanced steam reforming of glycerol to high-purity hydrogen production by a simultaneous flow concept of catalyst and sorbent for reaction and regeneration using two moving-bed reactors has been evaluated experimentally. A Ni-based catalyst (NiO/NiAl₂O₄) and a lime sorbent (CaO) were used for glycerol steam reforming with and without in-situ CO₂ removal at 500 °C and 600 °C. The simultaneous regeneration of catalyst and sorbent was carried out with the mixture gas of N₂ and steam at 900 °C. The product gases were measured by a GC gas analyzer. It is obvious that the amounts of CO₂, CO and CH₄ were reduced in the sorption-enhanced steam reforming of glycerol, and the H₂ concentration is greatly increased in the pre-CO₂ breakthrough periods within 10 min both 500 °C and 600 °C. The extended time of operation for high-purity hydrogen production and CO₂ capture was obtained by the continuous sorption-enhanced steam reforming of glycerol. High-purity H₂ products of 93.9% and 96.1% were produced at 500 °C and 600 °C and very small amounts of CO₂, CH₄ and CO were formed. The decay in activity during the continuous reaction-regeneration of catalyst and sorbent was not observed.     

Optimization of hydrogen production from three reforming approaches of glycerol via using supercritical water with in situ CO2 separation

A pathway for hydrogen production from supercritical water reforming of glycerol integrated with in situ CO₂ removal was proposed and analyzed. The thermodynamic analysis carried out by the minimizing Gibbs free energy method of three glycerol reforming processes for hydrogen production was investigated in terms of equilibrium compositions and energy consumption using AspenPlus™ simulator. The effect of operating condition, i.e., temperature, pressure, steam to glycerol (S/G) ratio, calcium oxide to glycerol (CaO/G) ratio, air to glycerol (A/G) ratio, and nickel oxide to glycerol (NiO/G) ratio on the hydrogen production was investigated. The optimum operating conditions under maximum H₂ production were predicted at 450 °C (only steam reforming), 400 °C (for autothermal reforming and chemical looping reforming), 240 atm, S/G ratio of 40, CaO/G ratio of 2.5, A/G ratio of 1 (for autothermal reforming), and NiO/G ratio of 1 (for chemical looping reforming). Compared to three reforming processes, the steam reforming obtained the highest hydrogen purity and yield. Moreover, it was found that only autothermal reforming and chemical looping reforming were possible to operate under the thermal self-sufficient condition, which the hydrogen purity of chemical looping reforming (92.14%) was higher than that of autothermal reforming (52.98%). Under both the maximum H₂ production and thermal self-sufficient conditions, the amount of CO was found below 50 ppm for all reforming processes.     

Hydrogen production via steam reforming of coke oven gas enhanced by steel slag-derived CaO

Steel slag, a waste from steelmaking plant, has been proven to be good candidate resources for low-cost calcium-based CO₂ sorbent derivation. In this work, a cheap and sintering-resistance CaO-based sorbent (CaO (SS)) was prepared from low cost waste steel slag and was applied to enhance catalytic steam reforming of coke oven gas for production of high-purity hydrogen. This steel slag-derived CaO possessed a high and stable CO₂ capture capacity of about 0.48 g CO₂/g sorbent after 35 adsorption/desorption cycles, which was mainly ascribed to the mesoporous structure and the presence of MgO and Fe₂O₃. Product gas containing 95.8 vol% H₂ and 1.4 vol% CO, with a CH₄ conversion of 91.3% was achieved at 600 °C by steam reforming of COG enhanced by CaO (SS). Although high temperature was beneficial for methane conversion, CH₄ conversion was remarkably increased at lower operation temperatures with the promotion effects from CaO (SS), and CO selectivity has been also greatly decreased. Reducing WHSV could increase methane conversion and reduce CO selectivity due to longer reactants residence time. Reducing C/A could increase methane conversion and hydrogen recovery factor, and also decrease CO selectivity. When being mixed with catalyst during SE-SRCOG, CaO (SS) with a uniform size distribution favored methane conversion due to the high utilization efficiency of catalyst. Promising stability of CaO (SS) in cyclic reforming/calcination tests was evidenced with a hydrogen recovery factor >2.1 and CH₄ conversion of 82.5% at 600 °C after 10 cycles using CaO (SS) as sorbent.     

PEFC-type impurity sensors for hydrogen fuels

Hydrogen purity sensor cells were newly developed with the principle of PEFC. By using the phenomena of PEFC's voltage drop seen in the presence of impurities and further minimizing the amount of Pt to make the cells more sensitive to impurities, the sensor cells were prepared. This unique sensing principle was applied to typical impurities in practical hydrogen gases, including CO, H₂S, and NH₃. Sensor responses were derived by analyzing various kinds of dependency on Pt loading, current density, impurity concentration, and operational temperature. Possibility of recovery from impurity poisoning was also studied by varying impurities' supply and potential charge. Consequently, our simple PEFC-type hydrogen purity sensors were verified to have ability to sense ppm-level impurities within 10 min.     

Methanol steam reforming in an Al2O3 supported thin Pd-layer membrane reactor over Cu/ZnO/Al2O3 catalyst

In this experimental study, a membrane reactor housing a composite membrane constituted by a thin Pd-layer supported onto Al₂O₃ is utilized to perform methanol steam reforming reaction to produce high-grade hydrogen for PEM fuel cell applications. The influence of various parameters such as temperature, from 280 to 330 °C, and pressure, from 1.5 to 2.5 bar, is analyzed. A commercial Cu/Zn-based catalyst is packed in the annulus of the membrane reactor and the experimental tests are performed at space velocity equal to 18,500 h⁻¹ and H₂O:CH₃OH feed molar ratio equal to 2.5:1. Results in terms of methanol conversion, hydrogen recovery, hydrogen yield and products selectivities are given. As a best result of this work, 85% of methanol conversion and a highly pure hydrogen stream permeated through the membrane with a CO content lower than 10 ppm were reached at 330 °C and 2.5 bar. Furthermore, a comparison between the experimental results obtained in this work and literature data is proposed and discussed.     

Hydrogen permeation studies of composite supported alumina-carbon molecular sieves membranes: Separation of diluted hydrogen from mixtures with methane

One alternative for the storage and transport of hydrogen is blending a low amount of hydrogen (up to 15 or 20%) into existing natural gas grids. When demanded, hydrogen can be then separated, close to the end users using membranes. In this work, composite alumina carbon molecular sieves membranes (Al-CMSM) supported on tubular porous alumina have been prepared and characterized. Single gas permeation studies showed that the H₂/CH₄ separation properties at 30 °C are well above the Robeson limit of polymeric membranes. H₂ permeation studies of the H₂–CH₄ mixture gases, containing 5–20% of H₂ show that the H₂ purity depends on the H₂ content in the feed and the operating temperature. In the best scenario investigated in this work, for samples containing 10% of H₂ with an inlet pressure of 7.5 bar and permeated pressure of 0.01 bar at 30 °C, the H₂ purity obtained was 99.4%.     

Production of high purity hydrogen by sorption enhanced steam reforming of crude glycerol

Here we report effective production of pure hydrogen from crude glycerol by the one-stage sorption enhanced steam reforming (SESR) process. This process yielded H₂ up to 88% with a very high purity (99.7 vol%) at atmospheric pressure and at 550–600 °C with a steam/C = 3 in a fixed-bed reactor over a mixture of Ni/Co catalyst derived from hydrotalcite-like material (HT) and dolomite as CO₂ sorbent. The concentration of methane is lowest at 575 °C, while the CO concentration increases concurrently with increasing temperature from 525 to 600 °C. The high coking potential of glycerol and fatty acid methyl esters (C₁₇–C₁₉) resulted in the increased formation of coke, thus lower hydrogen yield. The reaction rates of methane reforming and water–gas shift reactions are much higher than the steam reforming of crude glycerol on Co–Ni catalysts. The high purity of hydrogen can be obtained even at low spatial times with low crude glycerol conversions. Our work reveals a great potential to directly convert biomass derived complex mixtures to the most clean energy carrier of hydrogen with high yield and purity.