Autothermal Reforming Reaction Research Articles

Reaction induced Ni/MgTi2O5 interface promotes the resistance to sintering and oxidation in auto-thermal reforming of acetic acid

Hydrogen can be produced from acetic acid (HAc) derived from renewable biomass oil via auto-thermal reforming (ATR), which is conducive to upgrading current energy supply in a carbon-neutral and clean way. However, deactivations caused by carbon deposition, sintering, and oxidation have been long-standing obstacles for nickel-based catalysts. To address these challenges, we synthesized a series of Ni-Mg-Ti-O catalysts by Pechini method and tested in ATR. Characterization results showed that mixed oxide of Ni1-xMgxTiO3±δ perovskite was formed after calcination and transformed into Ni0, MgTiO3 and TiO2 after hydrogen reduction, while the Ti4+/Ti3+ redox cycle promoted formation of oxygen vacancies. In addition, the in-situ evolution of MgTiO3 and TiO2 into MgTi2O5 during the ATR reaction was proved, which suppressed sintering and oxidation of Ni species. Density functional theory (DFT) study confirmed the electron transfer over the Ni/MgTi2O5 interface, as well as the enhanced metal-support interaction, which promoted adsorption and dissociation of acetic acid molecules. Consequently, the Ni0.08Mg0.10Ti0.37O0.92±δ (N10MT) catalyst with Ni/MgTi2O5 interface showed high stability and activity with hydrogen yield at 2.72 mol-H2/mol-HAc.

Hybrid systems design for blue and green hydrogen co-production: Integration of autothermal reforming with solid oxide electrolysis

Hydrogen is a clean and sustainable energy alternative to fossil fuels. Current hydrogen production methods are carbon intensive; hence, developing low-carbon hydrogen production methods is important. Among various production technologies, autothermal reforming (ATR) and solid oxide electrolysis (SOEC) are considered promising in terms of energy efficiency. However, there are several limitations: (i) ATR requires an air separation unit that consumes a large amount of energy, and (ii) SOEC, high-temperature steam electrolysis requires an electric resistance heater. To address these limitations, this study proposes a hybrid system of ATR integrated with SOEC. In the hybrid system, waste steam and heat in the ATR process are provided for the SOEC process, whereas the oxygen by-product in the SOEC process is supplied to the ATR process. In particular, the hybrid system where SOEC-generated oxygen completely satisfies the ATR reaction’s oxygen demand exhibits the best thermodynamic and economic performance. This system represents a 28.6% reduction in power consumption compared to a stand-alone system that independently produces blue and green hydrogen. In addition, it exhibits enhanced economic performance with a levelized cost of hydrogen of 5.28 $/kg, which is 1.22 $/kg lower than that of the stand-alone system.

Hydrogen-rich gas with low-level CO produced with autothermal methanol reforming providing a real-time supply used to drive a kW-scale PEMFC system

An integrated system was developed to produce hydrogen-rich gas with low-level CO via autothermal reforming (ATR) of methanol for the purpose of real-time use in a kW-scale proton exchange membrane fuel cell (PEMFC) system. Methanol was converted into a hydrogen-rich gas through ATR in conjunction with water gas shifting (WGS) and preferential oxidation (PrOX) reactors to reduce the CO concentration. A 29.5% hydrogen-rich gas with a CO concentration of approximately 20 ppm was achieved under the optimal parameter settings (i.e., an H2O/CH3OH ratio = 0.5 and an O2/CH3OH ratio = 0.55 for the ATR reaction, an H2O/CO ratio = 5.6 for the WGS reaction, and an O2/CO ratio = 1.08 for the PrOX reaction). Specifically, the reformer system steadily produced low CO, hydrogen-rich gas after 4 h of durability testing. This system was then combined with 40-cell fuel cell stacks with air bleeding and tested for its durability over a period of 6 h. It was verified that the hydrogen-rich gas produced by the reformer system enabled the fuel cell to steadily generate 1040 W of power. Notably, the hydrogen-rich gas (the actual reformate gas) produced herein could generate better performance than the simulated reformate gas reported in the literature.

Hydrogen production and temperature control for DME autothermal reforming process

This study focuses on the control of dimethyl ether (DME) autothermal reforming (ATR) process integrated with proton exchange membrane fuel cells to provide adequate external power for an on-board reformer hydrogen vehicle. ATR reaction was made over Pd–Zn/γ-Al2O3 catalyst, which provides higher selectivity to the hydrogen due to its good oxidation and reforming activities. Catalyst activity was tested experimentally by varying the temperature. The hydrogen volume fraction is close to 45% at the optimal temperature of 400 °C. The objective of the process control scheme was to control the ATR reactor's temperature and the hydrogen production rate. A combination of the feedforward control and the closed-loop control (based on PID control) was applied wherein the DME, and air flow rates were adjusted automatically, and steam was supplied excessively to promote reactions. Due to its good oxidation and reforming activity, it had a high selectivity to hydrogen. The experimental results showed that the volume fraction of hydrogen in the hydrogen-rich gas is close to 45% at the optimum temperature of 400 °C. The control strategy could ensure that the hydrogen production rate changed with the change of fuel cell load and did not affect the temperature of the autothermal reformer. In this way, the stable operation of the reformer was realized, and the fuel cell had a sufficient supply of hydrogen.

Light Cycle Oil Source for Hydrogen Production through Autothermal Reforming using Ruthenium doped Perovskite Catalysts

As the hydrogen economy is coming soon, the development of an efficient H2 production system is the first issue to focus on. In this study, a first attempt to utilize light cycle oil (LCO) feedstock is introduced for H2 production through autothermal reforming (ATR) using perovskite catalysts. From a careful characterization, it is found that LCO possesses a high content of C–H and S/N compounds with over 3–4 ring bonds. These various compounds can directly cause catalyst deactivations to lower the capability of H2 extraction from LCO. To achieve a heteroatom resistance, two different perovskite micro-tubular catalysts are designed with a Ru substitution at the B-site. The activity and stability of the Ru doped perovskite were controlled by modifying the Ru electronic structure, which also affects the oxygen structures. The perovskite with a B-site of Cr reveals a relatively high portion of active Ru and O, demonstrating an effective catalyst structure with a comparable LCO reforming activity at the harsh ATR reaction conditions. The greater stability due to the Ru in the perovskite is investigated post-characterization, showing the possibility of H2 production by LCO fuel through the perovskite catalysts.

Hydrogen production through hydrocarbon fuel reforming processes over Ni based catalysts

Hydrogen production through autothermal reforming (ATR) of hydrocarbon fuels (ethanol, methane) over Ni-based catalysts was studied with a special focus on the role of metal-support interaction. The strength of Ni-support interaction was regulated by means of tailored modification of cerium oxide and aluminum oxide supports. The electronic, redox and structural properties of pre- and post-reaction Ni/Ce1-xMxOy and Ni/Ce1-xMxOy/Al2O3 (M = Zr, Gd, La, Mg) catalysts were studied in detail by TG-DTA, BET, XRD, HRTEM-EDX, HAADF-STEM, TPR, XPS and UV–vis DRS methods. It was found that the mode of Ni-support interaction controls the state, dispersion, and reducibility of Ni active component, and consequently, catalyst performance in ATR of hydrocarbon fuels. Among the tested modifiers (M = Zr, Gd, La, Mg), La has a more pronounced positive effect on the state and functionality of Ni/Ce1-xMxOy and Ni/Ce1-xMxOy/Al2O3 catalysts. The introduction of La as a modifier in the support composition enhances the metal-support interaction, which leads to a diminution of Nin+ reducibility. On the other hand, the improvement of the Ni dispersion and catalyst stability under the ATR reactions is achieved. The addition of a Pd-promoter makes it possible to optimize the reducibility of Nin+ strongly interacting with the support and provides the ability of Ni catalysts to the self-activation. The optimal support composition for Ni nanoparticles was designed that provides hydrogen yields which are close to the thermodynamic equilibrium values: ∼55% (Ce0.8La0.2O1.9, АTP C2H5OH at 600оC) and ∼65% (30Ce0.2Zr0.2La0.6O1.7/Al2O3, АTP CH4 at 850оC).

Pressurized diesel fuel processing using hydrogen peroxide for the fuel cell power unit in low-oxygen environments

A novel concept for diesel fuel processing utilizing H2O2 is suggested to obtain the high-purity H2 required for air-independent propulsion using polymer electrolyte membrane fuel cells for use in submarines and unmanned underwater vehicles. The core components include 1) a diesel-H2O2 autothermal reforming (ATR) reactor to produce H2-rich gas, 2) a water-gas shift (WGS) reactor to convert CO to H2, and 3) a H2 separation membrane to separate only high-purity H2. Diesel and H2O2 can easily be pressurized as they are liquids. The application of the H2 separation membrane without a compressor in the middle of the process is thus advantageous. In this paper, the characteristics of pressurized ATR and WGS reactions are investigated according to the operating conditions. In both reactors, the methanation reaction is enhanced as the pressure increases. Then, permeation experiments with a H2 separation membrane are performed while varying the temperature, pressure difference, and inlet gas composition. In particular, approximately 90% of the H2 is recovered when the steam-separated rear gas of the WGS reactor is used in the H2 separation membrane. Finally, based on the experimental results, design points are suggested for maximizing the efficiency of the diesel-H2O2 fuel processor.

Development of a robust and efficient biogas processor for hydrogen production. Part 2: Experimental campaign

In this study, a robust and efficient decentralized fuel processor based on the direct autothermal reforming (ATR) of biogas with a nominal production rate of 50 Nm3/h of hydrogen and a plant efficiency of about 65% was developed and tested. The ATR unit is composed of a structured catalyst support for the biogas reforming close coupled to a catalytic wall-flow filter to retain eventual soot particles.The performance of the conventional random foam and homogeneous lattice supports structures for the production of hydrogen from the ATR reaction was investigated. 15–0.05 wt%-Ni-Rh/MgAl2O4-SiSiC structured catalyst and LiFeO2-SiC monolith were selected for the conversion of biogas to hydrogen and for the syngas post-treatment process, respectively. For all the experiments, a model synthetic biogas was used and the catalytic activities were evaluated in three different experimental facilities: lab bench, pilot test rig and demonstration plant. High methane conversions (>95%) and hydrogen yields (>1.8) reached in the lab bench were also achieved in the pilot and demonstration plant operating at different GHSV.Results of duration test using a foam coupled to the filter has demonstrated that the pre-commercial processor is reliable while offering a satisfactory reproducibility and negligible pressure drop. A thermodynamic equilibrium and a cold gas efficiency of 90% were reached for an inlet temperature of 500 °C, O/C: 1.1 and S/C: 2.0, as predicted with the Aspen simulation.

Development of a robust and efficient biogas processor for hydrogen production. Part 1: Modelling and simulation

The present work deals with the modelling and simulation of a biogas Demo-processor for green hydrogen production via Autothermal reforming (ATR) process aimed at covering a wide span of potential applications, from fuel cells feed up to the production of pure hydrogen. The biogas ATR unit is composed of a structured catalyst support close coupled to a wall-flow filter that retain soot particles that can be formed during the ATR reaction. Modelling and simulation (CFD and FEM) were carried out to select the innovative catalyst support with promising results for the fuel processor. 3D digital sample reconstruction was performed for the selection of the appropriate porous structures commercially available for the soot filtration and furthermore, 2D CFD analysis was also used to examine flow uniformity issues due to soot trap integration downstream to the ATR. Moreover, the inherent flexibility of the model performed allowed its application in the assessment of the Demonstration plant operating in real conditions. Besides, Aspen simulation has demonstrated that the ATR process is the most promising process to hydrogen production compared to other types of reforming process.

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.

LCA evaluation for the hydrogen production from biogas through the innovative BioRobur project concept

BioRobur is a project aimed to produce hydrogen from biogas through an auto-thermal reforming (ATR) process, in which innovative catalytic systems are used to promote the ATR reactions involved in the process for the conversion of biogas into syngas. A detailed LCA study of hydrogen production from biogas ATR using the BioRobur technology has been performed. LCA analysis has been also conducted for other two conventional processes for the production of hydrogen from biogas: the steam reforming and water hydrolysis (a biogas-fueled Internal Combustion engine (ICE) followed by an Electrolyser). A comparison between these technologies has been made from both the environmental and the energetic viewpoints. The LCA has demonstrated that BioRobur is the most environmentally friendly of considered processes. Moreover, the ICE plus Electrolyser has resulted to be the because of the very large amount of biogas needed for the least efficient process, due to the low conversion yield of biogas into energy of the ICE.

Autothermal reforming of iso-octane and gasoline over Rh-based catalysts: Influence of CeO2/γ-Al2O3-based mixed oxides on hydrogen production

Autothermal reforming (ATR) of iso-octane in the presence of Rh-based catalysts (0.5 wt% of Rh) supported onto γ-Al2O3, CeO2, and ZrO2 were initially carried out at 700 °C with a S/C ratio of 2.0, an O/C ratio of 0.84, and a gas hourly space velocity (GHSV) of 20,000 h−1. The activity of Rh/γ-Al2O3 was found to be higher than Rh/CeO2 and Rh/ZrO2, with H2 and (H2 + CO) yields of 1.98 and 2.48 mol/mol C, respectively, after 10 h. This Rh/γ-Al2O3 material, however, was potentially susceptible to carbon coking and produced 3.5 wt% of carbon deposits following the reforming reaction, as evidenced by C, H, N, and S elemental analysis. In contrast, Rh/CeO2 catalyst exhibited lower activity but higher stability than Rh/γ-Al2O3, with nearly no carbon being formed within 10 h. To combine the superior activity originated from Rh/γ-Al2O3 with high stability from Rh/CeO2, Rh/CeO2/γ-Al2O3 catalysts with different CeO2 contents were synthesized and examined for the ATR reactions of iso-octane. Compared to Rh/γ-Al2O3, the newly prepared Rh/CeO2/γ-Al2O3 catalysts (0.5 wt% of Rh and 20 wt% of CeO2) showed even enhanced activity during 10 h, and H2 and (H2 + CO) yields were calculated to be 2.08 and 2.62 mol/mol C, respectively. In addition, as observed with Rh/CeO2, the catalyst was further found to be stable with less than 0.3 wt% of carbon deposition after 10 h. The Rh/γ-Al2O3 and Rh/CeO2/γ-Al2O3 catalysts were eventually tested for ATR reactions using commercial gasoline that contained sulfur, aromatics, and other impurities. The Rh/γ-Al2O3 catalyst was significantly deactivated, showing decreased activity after 4 h, while the Rh/CeO2/γ-Al2O3 catalyst proved to be excellent in terms of stability against coke formation as well as activity towards the desired reforming reaction, maintaining its ability for H2 production for 100 h.

Development of a self-sustaining kW e-class integrated diesel fuel processing system for solid oxide fuel cells

Among high temperature fuel cells, solid oxide fuel cells (SOFCs) possess several advantages such as fuel flexibility, high power density, and high-quality waste heat for cogeneration applications. However, if the reformates of hydrocarbon fuel are used to operate SOFCs, sulfur poisoning and carbon deposition is observed. Diesel reformate contains sulfur compounds and residual low-molecular-weight (LMW) hydrocarbons, which are formed on the anode of the SOFC. In this study, a new type of diesel fuel processing system was introduced for the stable operation of SOFCs. The novel diesel fuel processor contains three different reaction stages: autothermal reforming (ATR), adsorptive desulfurization, and post-reforming. For the stable operationfof SOFCs, the desulfurization and post-reforming processes are used to eliminate sulfur compounds and residual light hydrocarbons from the diesel reformate. The proposed fuel processor does not require an additional heat exchanger or electrical equipment for the supply of heat or the vaporization of fuel and water. The integrated reactor can be implemented as a self-sustaining reactor due to the exothermic nature of the ATR reaction. The reaction temperature of desulfurization and post-reforming processes are controlled by the arrangement of the reactors and heat exchange through the integrated reactor. The kW e self-sustaining integrated diesel fuel processor was operated for approximately 1000 h, and a reforming efficiency of 60% was achieved. Moreover, the desulfurizer and post-reforming reactor completely removed H 2S and light hydrocarbons from the diesel reformate.

Hydrogen production through auto-thermal reforming of bio-ethanol over Co-based catalysts: effect of iron in Co/Al 2O 3 catalysts

Auto-thermal reforming (ATR) of bio-ethanol is a promising process for hydrogen production, which can lead to the possibility of directly using low concentration ethanol from fermentation plants without going through the energy-consuming distillation and dehydration processes, saving both energy and cost. Co-based catalysts are active for hydrogen production in ATR, where the hydrogen yield and stability are important factors to be considered. To address the concerns of selectivity and deactivation, iron was introduced into Co-based catalysts via wet-impregnation. The catalysts were characterized with TPR, XRD, XPS, and Raman spectra, and tested in ATR of ethanol. The XPS, XRD, and TPR results show that with iron-promotion, more Co metal is obtained over the catalyst surface, which remains stable during the oxidative atmosphere of ATR. Meanwhile, iron promotes the ethanol dehydrogenation pathway in ATR reactions. This synergic effect contributes to the higher activity and stability of Co-based catalysts in the ATR process: A higher hydrogen yield remains around 3.13 mol H 2/mol EtOH at 600 °C and stays stable in a 30-h test.

Hydrogen production by autothermal reforming of kerosene over MgAlO x-supported Rh catalysts

Autothermal reforming (ATR) of kerosene for hydrogen production was performed on the MgAlO x -supported Rh catalysts at LHSV of 15–25, S/C of 2.5, O/C of 0.5, at 101 kPa. Sphere-shaped supports with high compressive ultimate strength (0.90 MPa) were obtained from MG-30 hydrotalcite core (∼3 mm) by thorough heat treatment before impregnation of rhodium. Rhodium was loaded by pore-filling impregnation selectively to the surface of the sphere-shaped supports, confirmed by electron probe microanalysis. Stability tests on the prepared catalysts were performed, focusing on the small amount of C 2–C 3 hydrocarbons, concentrations of which reflect the catalytic activity and stability; i.e., low rates of C 2–C 3 olefin formation correspond to high activity of the catalysts. The reactor was designed to measure temperature profiles and gas distributions within the reactor (inner diameter ∼21.0 mm) and the catalyst bed (length 100 mm). The ATR reactions occur starting with an exothermic combustion of hydrocarbons, followed by an endothermic reforming. The maximum temperature reached ∼1200 K at the inlet of the catalyst bed and decreased to ∼1020 K towards the end of the catalyst bed. Among investigated catalysts, the catalysts treated in air at 1223 K gave the best performance for ATR of kerosene, giving H 2 production reaching 60% of the exit gas. The concentration of the main byproduct, C 2H 4, over the optimized catalyst was lower than 0.03% at the exit of the reactor for 50 h of the study. The catalyst showed high tolerance to coking and high stability even at LHSV of 25 and daily start-up and shut-down (DSS) cycles, meeting practical requirements for the ATR catalysts.

Development of iso-octane fuel processor system for fuel cell applications

An iso-octane fuel processor system with three different reaction stages, autothermal reforming (ATR) reaction of iso-octane, high temperature shift (HTS) and low temperature shift (LTS) reactions, was developed for applications in a fuel cell system. Catalytic properties of the prepared Ni/Fe/MgO/Al 2O 3 and Pt–Ni/CeO 2 or molybdenum carbide catalysts were compared to those of commercial NiO/CaO/Al 2O 3 and Cu/Zn/Al 2O 3 catalysts for ATR and LTS reaction, respectively. It was found that the prepared catalysts formulations in the fuel processor system were more active than those of the commercial catalysts. As the exit gas of iso-octane ATR over the Ni/Fe/MgO/Al 2O 3 catalyst was passed through Fe 3O 4–Cr 2O 3 catalyst for HTS and Mo 2C or Pt–Ni/CeO 2 catalyst for LTS reaction, the concentration of CO in hydrogen-rich stream was reduced to less than 2400 ppm. The results suggest that the iso-octane fuel processor system with prepared catalysts can be applied to PEMFC system when a preferential partial oxidation reaction is added to KIST iso-octane reformer system.

Paper-structured catalyst with porous fiber-network microstructure for autothermal hydrogen production

Abstract Copper–zinc oxide catalyst powders were supported on a microstructured matrix composed of ceramic fiber-network by a papermaking technique. As-prepared catalyst materials, called paper-structured catalyst, were applied to the autothermal reforming (ATR) of methanol to produce hydrogen for fuel cell applications. The paper-structured catalyst demonstrated higher methanol conversion and lower undesirable carbon monoxide concentration, as compared with commercial catalysts. Besides, excellent catalyst durability was exhibited by the suppression of Cu sintering during the ATR reaction. The paper-structured catalyst showed remarkable superiority in methanol conversion even in the case of using sintered catalysts. Such features were possibly induced by the unique fiber-network microstructure (average pore size: ca. 20 μm and porosity: ca. 50%) of the paper composites, which may allow the effective transfer of heat and reactants to the catalyst surfaces. The porous paper-structured catalyst is expected as a promising catalytic material for improving the practical performances in the catalytic gas-reforming process.

Dodecane reforming over nickel-based monolith catalysts

Autothermal reforming (ATR) of n-dodecane was systematically investigated with O/C = 0.6 and H 2O/C = 2.0 over nickel-based catalysts supported on cordierite monoliths. Both nickel supported on monolith (Ni/monolith) and nickel supported on cerium–zirconium oxide (CZO) loaded on monolith (Ni/CZO/monolith) were tested for ATR activity. The influence of nickel weight loading (0–16 wt%) on ATR product yields was examined. Experimental results showed that 2 wt% Ni/CZO/monolith was an optimal composition for ATR. The roles of Ni and CZO were determined by comparing n-dodecane conversion, oxygen conversion, the extent of reforming, and product yields (i.e., CO, CO 2, and H 2). The reaction studies indicated that nickel catalyzed the conversion of n-dodecane by POX and SR, yielding a hydrogen rich effluent, whereas CZO alone catalyzed the conversion of n-dodecane though catalytic oxidation and cracking, yielding an effluent rich in smaller hydrocarbon species. Nickel supported on CZO showed the greatest hydrogen, carbon monoxide, and carbon dioxide yields of the catalysts studied. ATR, partial oxidation (POX), steam reforming (SR), and the influence of reaction temperature on ATR were studied separately and compared at similar conditions over 2 wt% Ni/monolith and 2 wt% Ni/CZO/monolith to elucidate the primary reforming reactions. An n-dodecane ATR reaction schematic is postulated, and the influences of homogeneous activity and oxygen conversion are discussed. It is proposed that POX, homogeneous cracking, and oxidative cracking are the major routes for n-dodecane conversion during ATR, whereas POX of n-dodecane and SR of smaller hydrocarbons are the primary routes to reforming products (i.e., H 2, CO, and CO 2).

Autothermal reforming of n-dodecane, toluene, and their mixture on mono- and bimetallic noble metal zirconia catalysts

Autothermal reforming (ATR) of higher hydrocarbons and their mixture was studied on zirconia-supported mono- (Rh, Pd, or Pt) and bimetallic (RhPt) catalysts. ATR reactions predominated on Rh-containing catalysts at 700–900 °C, whereas thermal cracking predominated on Pt and the support. The thermal stability of Rh was improved when Rh was combined with Pt in the bimetallic catalyst.

휴대용 연료전지를 위한 부탄 자열개질에 관한 연구

This study discusses about research efforts of hydrogen generation from hydrocarbon(e.g., diesel, gasoline, natural gas, and LPG), especially, butane reforming by using Autothermal Reforming Reaction (ATR) technology. Several catalysts were selected for butane ATR. Thermodynamic reactor conditions (temperature, O₂/C, S/C) are varied and reforming characteristics of 2 catalysts (Pt and Rh on ceramic supports) and 1 commercial catalyst (FCR-HC35) have been examined. To understand reaction behaviors in an ATR reactor comprehensively, temperature profiles of reactor were observed. By mass transfer limitation, fuel conversion decreases when GHSV increases. Significant temperature variation along the reactor was observed and it was mainly due reaction kinetics difference between exothermic oxidation and endothermic reforming reaction.