Ethanol steam reforming over Ni/ZSM-5 nanosheet for hydrogen production

Compared to reforming reactions using hydrocarbons,ethanol steam reforming(ESR)is a sustainable alternative for hydrogen(H_(2))production since ethanol can be produced sustainably using biomass.This work explores the catalyst design strategies for preparing the Ni supported on ZSM-5 zeolite catalysts to promote ESR.Specifically,two-dimensional ZSM-5 nanosheet and conventional ZSM-5 crystal were used as the catalyst carriers and two synthesis strategies,i.e.,in situ encapsulation and wet impregnation method,were employed to prepare the catalysts.Based on the comparative characterization of the catalysts and comparative catalytic assessments,it was found that the combination of the in situ encapsulation synthesis and the ZSM-5 nanosheet carrier was the effective strategy to develop catalysts for promoting H_(2) production via ESR due to the improved mass transfer(through the 2-D structure of ZSM-5 nanosheet)and formation of confined small Ni nanoparticles(resulted via the in situ encapsulation synthesis).In addition,the resulting ZSM-5 nanosheet supported Ni catalyst also showed high Ni dispersion and high accessibility to Ni sites by the reactants,being able to improve the activity and stability of catalysts and suppress metal sintering and coking during ESR at high reaction temperatures.Thus,the Ni supported on ZSM-5 nanosheet catalyst prepared by encapsulation showed the stable performance with~88% ethanol conversion and~65% H_(2) yield achieved during a 48-h longevity test at 550-C.

Pt nanoclusters modified porous g-C_(3)N_(4)nanosheets to significantly enhance hydrogen production by photocatalytic water reforming of methanol

For the use of green hydrogen energy,it is crucial to have efficient photocatalytic activity for hydrogen generation by water reforming of methanol under mild conditions.Much attention has been paid to gC_(3)N_(4)as a promising photocatalyst for the generation of hydrogen.To improve the separation of photogenerated charge,porous nanosheet g-C_(3)N_(4)was modified with Pt nanoclusters(Pt/g-C_(3)N_(4))through impregnation and following photo-induced reduction.This catalyst showed excellent photocatalytic activity of water reforming of methanol fo r hydrogen production with a 17.12 mmol·g^(-1)·h^(-1)rate at room temperature,which was 311 times higher than that of the unmodified g-C_(3)N_(4).The strong interactions of Pt-N in Pt/g-C_(3)N_(4)constructed effective electron transfer channels to promote the separation of photogenerated electrons and holes effectively.In addition,in-situ infrared spectroscopy was used to investigate the intermediates of the hydrogen production reaction,which proved that methanol and water eventually turn into H_(2)and CO_(2)via formaldehyde and formate.This study provides insights for understanding the photocatalytic hydrogen production in the water reforming of methanol.

High H_(2) selective performance of Ni-Fe-Ca/H-Al catalysts for steam reforming of biomass and plastic

The development of a selective catalyst for the conversion of biomass and plastics into H2by steam reforming can combat the energy crisis and global warming.In this work,support Ni-Fe-Ca/H-Al bifunctional catalysts were prepared by loading Ni and Fe into pretreatment CaO/Al_(2)O_(3)(Ca/H-Al)carriers and showed high catalytic activity for the steam reforming of biomass and plastic.Moreover,the idea of bidirectional degradation was exploited to strengthen the pyrolysis of plastic with a high H/C and biomass with a high O/C.Interestingly,the products presented high H2selective(1302.10 m L/g)and low CO_(2)yield(120.23 m L/g)in 7Ni-5Fe-Ca/H-Al(2:4)catalyst compared with current reports.Here,the abundant oxygen vacancies(Ov)in the H-Al carrier exhibited an electron-deficient nature,providing active sites for anchoring Ni O.Meanwhile,Ni O interacted with Ca_(2)Fe_(2)O_(5)to produce more defective Ovsites,which stabilized the NiO particles in the 7Ni-5Fe-Ca/H-Al(2:4)catalyst,and the interaction between the catalyst and the carrier was enhanced,leading to the reduction of weakly basic sites,this property promoted the strong adsorption of CO_(2)and H2O by the catalyst,contributing to the enhancement of efficient steam conversion and the promotion of conversion of by-products to H2.Notably,7Ni-5Fe-Ca/H-Al(2:4)catalysts maintained structural integrity after regeneration and exhibited excellent regenerability in H2selection and CO_(2)adsorption.The work provides a new idea for the study of efficient H2production from steam reforming of biomass and plastics.

Probing deactivation by coking in catalyst pellets for dry reforming of methane using a pore network model

Dry reforming of methane(DRM) is an attractive technology for utilizing the greenhouse gases(CO_(2) and CH_(4)) to produce syngas. However, the catalyst pellets for DRM are heavily plagued by deactivation by coking, which prevents this technology from commercialization. In this work, a pore network model is developed to probe the catalyst deactivation by coking in a Ni/Al_(2)O_(3) catalyst pellet for DRM. The reaction conditions can significantly change the coking rate and then affect the catalyst deactivation. The catalyst lifetime is higher under lower temperature, pressure, and CH_(4)/CO_(2) molar ratio, but the maximum coke content in a catalyst pellet is independent of these reaction conditions. The catalyst pellet with larger pore diameter, narrower pore size distribution and higher pore connectivity is more robust against catalyst deactivation by coking, as the pores in this pellet are more difficult to be plugged or inaccessible.The maximum coke content is also higher for narrower pore size distribution and higher pore connectivity, as the number of inaccessible pores is lower. Besides, the catalyst pellet radius only slightly affects the coke content, although the diffusion limitation increases with the pellet radius. These results should serve to guide the rational design of robust DRM catalyst pellets against deactivation by coking.

Improvement strategies for Ni-based alcohol steam reforming catalysts

Steam reforming(SR)of fossil methane is already a well-known,documented and established expertise in the industrial sector as it accounts for the vast majority of global hydrogen production.From a sustainable development perspective,hydrogen production by SR of biomass-derived feedstock represents a promising alternative that could help to lower the carbon footprint of the traditional process.In this regard,bio-alcohols such as methanol,ethanol or glycerol are among the attractive candidates that could serve as green hydrogen carriers as they decompose at relatively low temperatures in the presence of water compared to methane,allowing for improved H_(2)yields.However,significant challenges remain regarding the activity and stability of nickel-based catalysts,which are most widely used in alcohol SR processes due to their affordability and ability to break C–C,O–H and C–H bonds,yet are prone to rapid deactivation primarily caused by coke deposition and metal particle sintering.In this state-of-the-art review,a portfolio of strategies to improve the performance of Ni-based catalysts used in alcohol SR processes is unfolded with the intent of pinpointing the critical issues in catalyst development.Close examination of the literature reveals that the efforts tackling these recurring issues can be directed at the active metal,either by tuning Ni dispersion and Ni-support interactions or by targeting synergistic effects in bimetallic systems,while others focus on the support,either by modifying acid-base character,oxygen mobility,or by embedding Ni in specific crystallographic structures.This review provides a very useful tool to orient future work in catalyst development.

The Joule–Thomson effect of (CO_(2)+H_(2)) binary system relevant to gas switching reforming with carbon capture and storage(CCS)

The Joule-Thomson effect is one of the important thermodynamic properties in the system relevant to gas switching reforming with carbon capture and storage(CCS). In this work, a set of apparatus was set up to determine the Joule-Thomson effect of binary mixtures(CO_(2)+ H_(2)). The accuracy of the apparatus was verified by comparing with the experimental data of carbon dioxide. The Joule-Thomson coefficients(μ_(JT)) for(CO_(2)+ H_(2)) binary mixtures with mole fractions of carbon dioxide(x_(CO_(2))= 0.1, 0.26, 0.5,0.86, 0.94) along six isotherms at various pressures were measured. Five equations of state EOSs(PR,SRK, PR, BWR and GERG-2008 equation) were used to calculate the μ_(JT)for both pure systems and binary systems, among which the GERG-2008 predicted best with a wide range of pressure and temperature.Moreover, the Joule-Thomson inversion curves(JTIC) were calculated with five equations of state. A comparison was made between experimental data and predicted data for the inversion curve of CO_(2). The investigated EOSs show a similar prediction of the low-temperature branch of the JTIC for both pure and binary systems, except for the BWRS equation of state. Among all the equations, SRK has the most similar result to GERG-2008 for predicting JTIC.

Study on the Catalytic Reforming Law of Solid-Phase Carbon and Nitrogen Sources Loaded with MnO_(2)at Low Temperatures in Tahe Heavy Oil

MnO_(2)/Melem composites were synthesized with MnO_(2)nanoparticles loaded onto the Melem using the hydrothermal method.As raw materials for C and N carriers,Melem was prepared from melamine roasted at 354℃,and KMnO_(4)as a raw material for Mn,MnO_(2)nanoparticles were prepared using the hydrothermal synthesis of KMnO_(4).Scanning electron microscopy(SEM),transmission electron microscopy(TEM),X-ray diffraction(XRD),and a laser particle size analyzer were used for structural characterization,and the catalytic oxidation performance of the heavy oil was investigated at different reaction temperatures(100℃to 180℃)using MnO_(2)/Melem with an oxidant and donor protonic acid.The results showed that the synthesizedβ-MnO_(2)nanoparticles were successfully loaded onto the Melem surface;the oil samples before and after the reaction at different temperatures were subjected to SARA analysis using Fourier transform infrared(FT-IR),elemental analysis,gas chromatography-mass spectrometry(GC-MS)and viscosity tests,respectively.It was determined that the hydrocarbons in the crude oil were converted to heavy mass by oxidation reactions with the oxidant mainly through a low-temperature oxidation process below 140℃in the heavy oil when the temperature exceeds 140℃,in addition to the oxidation reaction with the oxidant,a cleavage reaction in the carbon chain occurs to form hydrocarbon substances with lower molecular weights.

An Energy Production System Powered by Solar Heat with Biogas Dry Reforming Reactor and Solid Oxide Fuel Cell

In this paper, an energy system consisting of solar collector, biogas dry reforming reactor and solid oxide fuel cell (SOFC) has been proposed. The heat produced from the concentrating solar collector is used to drive a biogas dry reforming reactor in order to produce H2 as a fuel for SOFC, in such as system. The aim of this study is to clarify the impact of climate data on the performance of solar collector with various sizes/designs. The temperature of heat transfer fluid produced by the solar collector is calculated by adopting the climate data for Nagoya city in Japan in 2021. The amount of H2 produced from the biogas dry reforming reactor and the power generated by SOFC were simulated. The results show the temperature of heat transfer fluid (Tfb) and Tfb ratio (a) based on the length of absorber (dx) = 1 m have a peak near the noon following the trend of solar intensity (I). Results also revealed that a increases with increase in dx. It is found that the differences of Tfb and a between dx = 2 m and dx = 3 m are larger than those between dx = 1 m and dx = 2 m. It is revealed that Tfb and a are higher in spring and summer. dx = 4 m is the optimum length of solar absorber. The amount of H2 produced from the biogas dry reforming reactor as well as the power generated by SOFC is the highest in August, resulting that it is prefer to produce H2 and to generate SOFC in summer.

Thermodynamic analysis of mixed and dry reforming of methane for solar thermal applications

Thermodynamic analysis of the reforming of methane with carbon dioxide alone （＂dry reforming＂） and with carbon dioxide and steam together （＂mixed reforming＂） is performed as part of a project which investigates the suitability of these endothermic reactions for the storage of solar thermal energy. The Gibbs free energy minimization method was employed to identify thermodynamically optimal operating conditions for dry reforming as well as mixed reforming with a desired H2/CO molar ratio of 2. The non-stoichiometric equilibrium model was developed using FactSage software to conduct the thermodynamic calculations for carbon formation, H2/CO ratio, CH4 conversion and H2 yield as a function of reaction temperature, pressure and reactant molar ratios. Thermodynamic calculations demonstrate that in the mixed reforming process, optimal operating conditions in a carbon-free zone are under H2O/CH4 /CO2 =1.0/1.0/0.5, p = 1 to 10 bar and T = 800 to 850℃ for the production of syngas with a H2 /CO molar ratio of 2. Under the optimal conditions, the maximum H2 yield of 88.0% is achieved at 1 bar and 850℃ with a maximum CH4 conversion of 99.3%. In the dry reforming process, a carbon formation regime is always present at a CO2/CH4 molar ratio of 1 for T = 700 1000℃ and p = 1-30 bar, whereas a carbon-free regime can be obtained at a CO2/CH4 molar ratio greater than 1.5 and T≥800℃.

Review on Innovative Catalytic Reforming of Natural Gas to Syngas

Decreasing supplies of high quality crude oil and increasing demand for high quality distillates have motivated the interest in converting natural gas to liquid fuels, especially with the present boom in natural gas proven reserves. Nevertheless, one major issue is the curtailment of costs incurred in producing synthesis gas from natural gas, which account for approximately 60% of the costs used in producing liquid fuels. While there are three main routes to convert natural gas to syngas: steam reforming (SMR), partial Oxidation (POX) and auto-thermal reforming (ATR). Significant new developments and improvements in these technologies, established innovative processes to minimize greenhouse gases emission, minimize energy consumption, enhance syngas processes, adjust the desired H2/CO ratio and change the baseline economics. This article reviews the state of the art for the reforming of natural gas to synthesis gas taking into consideration all the new innovations in both processes and catalysis.

Low-temperature dry reforming of methane tuned by chemical speciations of active sites on the SiO_(2) and γ-Al_(2)O_(3) supported Ni and Ni-Ce catalysts

The cognition of active sites in the Ni-based catalysts plays a vital role and remains a huge challenge in improving catalytic performance of low temperature CO_(2) dry reforming of methane(LTDRM).In this work,typical catalysts of SiO_(2) and γ-Al_(2)O_(3) supported Ni and Ni-Ce were designed and prepared.Importantly,the difference in the chemical speciations of active sites on the Ni-based catalysts is revealed by advanced characterizations and further estimates respective catalytic performance for LTDRM.Results show that larger[Ni0-]particles mixed with[Ni-O-Sin])species on the Ni/SiO_(2)(R)make CH_(4) excessive decomposition,leading to poor activity and stability.Once the Ce species is doped,however,superior activity(59.0%CH_(4) and 59.8%CO_(2) conversions),stability and high H_(2)/CO ratio(0.96)at 600℃ can be achieved on the Ni-Ce/SiO_(2)(R),in comparison with other catalysts and even reported studies.The improved performance can be ascribed to the formation of integral([Ni0_(n))]-[CeⅢ-□-CeⅢ])species on the Ni-Ce/SiO_(2)(R)catalyst,containing highly dispersed[Ni]particles and rich oxygen vacancies,which can synergistically establish a new stable balance between gasification of carbon species and CO_(2) dissocia-tion.With respect to Ni-Ce/γ-Al_(2)O_(3)(R),the Ni and Ce precursors are easily captured by extra-framework Al_(n)-OH groups and further form stable isolated([Ni0_(n))]-[Ni-O-Al_(n)])and[CeⅢ-O-Al_(n)]species.In such a case,both of them preferentially accelerate CO_(2) adsorption and dissociation,causing more car-bon deposition due to the disproportionation of superfuous CO product.This deep distinguishment of chemical speciations of active sites can guide us to further develop new efficient Ni-based catalysts for LTDRM in the future.

Profitability Analysis of Selected Steam Methane Reforming Methods for Hydrogen Production

One of the matured methods for producing hydrogen in bulk is steam methane reforming (SMR). The two commercial aspects of producing hydrogen from SMR are SMR with shift reactor (SR) and SMR with dry methane reforming (DRM). Although SMR with SR produces high hydrogen yield, it emits a large quantity of carbon dioxide (CO2). On the contrary, SMR and DRM produce low hydrogen yield but favorably emit a low quantity of CO2. However, it is not obvious which of these methods is more favourable economically. Consequently, using UNISIM Software Package, this study investigates three SMR methods namely SMR with SR, SMR with DRM and SMR with the combination of DRM and SR for the purpose of determining the most favourable route for producing hydrogen. This was done on the basis of feedstock rate of 100 kmol/hr of methane which reacted with 250 kmol/hr of steam for 8000 hrs annually using the rate of CO2 and CO emissions (COx) and the plant net profit percentage as performance indices. The profitability analysis shows that SMR/SR process is the most profitable process with a net profit percentage of 41.3%. Moreover, SMR/SR process has the highest yield and interestingly lowest COx emission rate. It is therefore concluded that the most favourable process route, technically and economically, is SMR/SR for the production of hydrogen using methane as feedstock.

Autothermal Reforming of Methane over Ni Catalysts Supported on CuO-ZrO_2-CeO_2-Al_2O_3

Ni catalysts supported on various mixed oxides of Al2O3 with rare earth oxide and transitional metal oxides were synthesized. The studies focused on the measurement of the autothermal reforming of methane to hydrogen over Ni catalysts supported on the mixed oxide ZrxCe30-xAl70Oδ （x-=5, 10, 15）. The catalytic performance of Ni/Zr10Ce20Al70Oδ was better than that of other catalysts. XRD results showed that the addition of Zr to Ni/Ce30Al70Oδ prevented the formation of NiAl2O4 and facilitated the dispersion of NiO. Effects of CuO addition to Zr10Ce20Al70Oδ were also investigated. The activity of Ni catalyst supported on CuO-ZrO2-CeO2-Al2O3 was somewhat affected and the Ni/Cu5Zr10Ce20Al65Oδ showed the best catalytic performance with the highest CH4 conversion, yield of H2, selectivity for H2 and H2/CO production ratio in operation temperatures ranging from 650 to 750 ℃.

Ni-Co/Mg-Al catalyst derived from hydrotalcite-like compound prepared by plasma for dry reforming of methane

Ni-Co bimetallic catalysts with different Ni/Co content were derived from cold plasma jet decomposition and reduction of hydrotalcite-like compounds containing Ni,Co,Mg and Al,and their catalytic performance was investigated with dry reforming of methane.Experimental results showed that the hydrotalcite-like precursors could be completely decomposed and partly reduced by cold plasma jet,and the Nicontained catalysts exhibited much higher activity than the catalyst without Ni.Especially,the catalyst with Ni/Co ratio of 8/2 achieved not only the highest conversions of 80.3%and 69.3%for CH4 and CO2,respectively,but also the best stability in 100 h testing.The catalysts were characterized by XRD,XPS,TEM and N2 adsorption techniques,and the results showed that the better performance of the 8Ni2Co bimetallic catalyst was attributed to its higher metal dispersion,smaller metal particle size,as well as the interaction effect between Ni and Co,which were brought by the special catalyst preparation method.

Hydrogen production from steam reforming of methanol over CuO/ZnO/Al_2O_3 catalysts: Catalytic performance and kinetic modeling

A series of CuO/ZnO/Al_2O_3, CuO/ZnO/ZrO_2/Al_2O_3 and CuO/ZnO/CeO_2/Al_2O_3 catalysts were prepared by coprecipitation and characterized by N_2 adsorption, XRD, TPR, N_2O titration and HRTEM. The catalytic performances of these catalysts for the steam reforming of methanol were evaluated in a laboratory-scale fixed-bed reactor at 0.1 MPa and temperatures between 473 and 543 K. The results showed that the catalytic activity depended greatly on the catalyst reducibility and the specific surface area of Cu. An approximate linear correlation between the catalytic activity and the Cu surface area was found for all catalysts investigated in this study.Compared to CuO/ZnO/Al_2O_3, the ZrO_2-doped CuO/ZnO/Al_2O_3 exhibited higher activity and selectivity to CO,while the CeO_2-doped catalyst displayed lower activity and selectivity. Finally, an intrinsic kinetic study was carried out over a screened CuO/ZnO/CeO_2/Al_2O_3 catalyst in the absence of internal and external mass transfer effects. A good agreement was observed between the model-derived effluent concentrations of CO(CO_2) and the experimental data. The activation energies for the reactions of methanol-steam reforming, water-gas shift and methanol decomposition over CuO/ZnO/CeO_2/Al_2O_3 were 93.1, 85.1 and 116.5 k J·mol^(-1), respectively.

Removal of biomass tar by steam reforming over calcined scallop shell supported Cu catalysts

In this study, the main purpose is to develop low-cost catalysts with high activity and stability for high quality syngas production via steam reforming of biomass tar in biomass gasification process. The calcined waste scallop shell（CS） supported copper（Cu） catalysts are prepared for steam reforming of biomass tar. The prepared Cu supported on CS catalysts exhibit higher catalytic activity than those on commercial CaO and Al;O;. Characterization results indicate that Cu/CS has a strong interaction between Cu and CaO in CS support, resulting in the formation of calcium copper oxide phase which could stabilize Cu species and provide new active sites for the tar reforming. In addition, the strong basicity of CS support and other inorganic elements contained in CS support could enhance the activity of Cu/CS. The addition of a small amount of Co is found to be able to stabilize the catalytic activity of Cu/CS catalysts,making them reusable after regeneration without any loss of their activities.

Effect of Ni loadings on the activity and coke formation of MgO-modified Ni/Al_2O_3 nanocatalyst in dry reforming of methane

MgO-modified Ni/Al2O3 catalysts with different Ni loadings were prepared and employed in dry reforming of methane （DRM）. The effect of Ni loadings on the activity and coke formation of Ni/MgO-A1203 catalysts were investigated. The synthesized catalysts were characterized by XRD, N2 adsorption-desorption, SEM, TPO and TPR techniques. The obtained results showed that increasing nickel loading decreased the BET surface area and increased the catalytic activity and amount of deposited carbon. In addition, the effect of gas hourly space velocity （GHSV） and feed ratio were studied.

Hydrogen generation from steam reforming of ethanol in dielectric barrier discharge

Dielectric barrier discharge （DBD） was used for the generation of hydrogen from ethanol reforming. Effects of reaction conditions, such as vaporization temperature, ethanol flow rate, water/ethanol ratio, and addition of oxygen, on the ethanol conversion and hydrogen yield, were studied. The results showed that the increase of ethanol flow rate decreased ethanol conversion and hydrogen yield, and high water/ethanol ratio and addition of oxygen were advantageous. Ethanol conversion and hydrogen yield increased with the vaporization room temperature up to the maximum at first, and then decreased slightly. The maximum hydrogen yield of 31.8% was obtained at an ethanol conversion of 88.4% under the optimum operation conditions of vaporization room temperature of 120 ？C, ethanol flux of 0.18 mL/min, water/ethanol ratio of 7.7 and oxygen volume concentration of 13.3%.

Effect of Transition Metals (Cu, Co and Fe) on the Autothermal Reforming of Methane over Ni/Ce_(0.2)Zr_(0.1)Al_(0.7)O_δ Catalyst

The transition metals （Cu, Co, and Fe） were applied to modify Ni/Ce0.2Zr0.1Al0.7Oδ catalyst. The effects of transition metals on the catalytic properties of Ni/Ce0.2Zr0.1Al0.7Oδ autothermal reforming of methane were investigated. The Ni-supported catalysts were characterized by XRD, TPR and XPS. Tests in autothermal reforming of methane to hydrogen showed that the addition of transition metals （Cu and Co） significantly increased the activity of catalyst under the conditions of lower reaction temperature, and Ni/Cu0.05Ce0.2Zr0.1Al0.65Oδ was found to have the highest conversion of CH4 among all catalysts in the operation temperatures ranging from 923 K to 1023 K. TPR, XRD and XPS measurements indicated that the cubic phases of CexZr1-xO2 solid solution were formed in the preparation process of catalysts. Strong interaction was found to exist between NiO and CexZr1-xO2 solid solution. The addition of Cu improved the dispersion of NiO, inhibited the formation of NiAl2O4, and thus significantly promoted the activity of the catalyst Ni/Cu0.05Ce0.2Zr0.1Al0.65Oδ

Effect of Ni Loading and Ce_(x)Zr_(1-x)O_(2) Promoter on Ni-Based SBA-15 Catalysts for Steam Reforming of Methane

A series of Ni/SBA-15 catalysts with Ni contents ranging from 5wt% to 20wt% as well as 10wt%Ni/10wt%CexZr1-xO2/SBA-15 （x=0, 0.5, 1） were prepared. The structures of the catalysts were characterized using XRD, TPR, TEM and BET techniques. The catalytic activities of the catalysts for steam reforming of methane were evaluated in a continuous flow microreactor. The results indicated that both the Ni/SBA-15 and the Ni/CexZr1-xO2/SBA-15 catalysts had good catalytic activities at at- mospheric pressure. The 10wt%Ni/SBA-15 catalyst exhibited excellent stability at 800 ℃ for time on stream of 740 h. After the reaction, carbon deposits were not formed on the surface of the catalyst. There existed a regular hexagonal mesoporous structure in the Ni/SBA-15 and the Ni/CexZr1-xO2/SBA-15 catalysts. The nickel species and the CexZr1-xO2 component were all confined in the SBA-15 mesopores. The CexZr1-xO2 could promote dispersion of the nickel species in the Ni/CexZr1-xO2/SBA-15 catalysts.