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[Display omitted] • Lewis number deviates from one in the entrance length. • The catalyst activity do not modify the initial Nu and Sh inside of the channels. • Re modifies the thermal entrance length because of the reduction of the flow area. This paper is devoted to the multi-scale model of the heat and mass transfer inside of a honeycomb monolith substrate. Due to computational limitations, monoliths are modelled as a continuum in full-scale catalytic reactors models. That makes it necessary to use correlations or sub-models derived from channel scale results to account for a physically consistent heat and mass transfer inside of the substrate. In this paper detailed computational models at a channel and reactor scales are analyzed. Catalytic oxidation of CO is used as a reaction and the fluid properties are considered to be temperature-dependent. First, a channel scale model is used to analyze Nusselt, Sherwood, Lewis, and Damköhler numbers inside of the monolith channels. Secondly, sub-models obtained at a channel level are implemented in a full-scale reactor model using the continuum approach, to evaluate the impact of using detailed vs. highly simplified correlations for heat and mass transfer. The reactor scale model accounts for the transitions of the flow regime, entrance length effects, an-isotropic substrate thermal conductivity and temperature-dependent fluid properties. According to the results, the Lewis number can deviate significantly from one in the entrance length, however, it approaches asymptotically to unity as the flow develops. Regarding Nusselt and Sherwood, current interpolating methodologies are not able to predict the correct value in the entrance region when Damköhler is low, nonetheless, are reasonably accurate for the asymptotic one. [ABSTRACT FROM AUTHOR]

[Display omitted] • NiO-Al 2 O 3 based structured catalysts were tested in the ODH of ethane. • Three ceramic structures were used as substrates: a monolith, a foam and a paper. • Different NiO physicochemical properties were obtained within the substrates. • The systems with the stronger NiO-Al 2 O 3 interactions were the most selective. • The addition of Ce generated a marked productivity increment. Structured catalysts have important advantages compared to powder formulations and they are required for processes intensification. In this work, three different ceramic structures: a cordierite monolith, an alumina foam and an alumina-silica paper were used as substrates for the deposition of a NiO-Al 2 O 3 coating and tested in the oxidative dehydrogenation of ethane to produce ethylene. For comparison, a NiO-Al 2 O 3 powder catalyst was also prepared. Nickel oxide species with different physicochemical features were obtained over each structure, evidenced by morphological (SEM-EDX) and physicochemical characterization (XRD, LRS and XPS). The best distributions of the catalytic coatings and NiO physicochemical properties were obtained when the monolith and the foam were used as substrates. These led to higher NiO-Al 2 O 3 interactions and consequently to high ethylene selectivity values, 70–90 %, corresponding to the former an ethane conversion of 22 % and to the latter a 5 %. The distribution of the active phase on the ceramic paper was heterogeneous, with NiO agglomerations and poor NiO-support interaction thus achieving low olefin selectivity (∼ 30 %). The addition of a second element such as cerium was also studied in those structured catalysts with high selectivity, resulting in both cases in an increment of ethane conversion but a decrease in ethylene selectivity. This behavior was attributed to the generation of electrophilic oxygen species. [ABSTRACT FROM AUTHOR]

[Display omitted] • Wall-flow channeled monoliths with trimodal pore-size distribution. • SiC monoliths with core-skin hierarchical macroporosity allow membrane coating. • Homogeneous loading of SiO 2 or Al 2 O 3 nanoparticles into the SiC macropores. • Texture defined by SiC porosity, nanoparticle composition, size and load, and calcination temperature. • Efficient Rh-catalyst immobilization, hydroformylation integrated membrane reactor feasible. Monolithic support materials with the mechanical resistance and thermal conductivity of SiC as well as tunable surface chemistry and textural properties were developed for their use in catalytic membrane reactors. After heat treatment, the extruded SiC monoliths have a monomodal distribution of macropores of a few μm in diameter depending on the particle size of the starting material. A macroporous, defect-free, smoother skin was applied onto the external wall using a solution of sub-micrometer SiC particles. These monoliths with skin could be coated successfully with molecularly selective membranes, and thus have application in membrane reactor processes. Finally, metal oxide nanoparticles were infiltrated into the macropores to modify the surface texture and chemistry, allowing the immobilization of liquid phase catalysts. The resulting multimodal distribution of pore sizes could be tuned by the choice of SiC and oxide particle sizes, number of wash-coats and calcination temperature. Mesopores created between nanoparticles had diameters of roughly 40 % of those of the nanoparticles. Small macropores, between 10−1000 nm, were also created, with bigger size and volume at higher calcination temperatures due to the metal oxide particles contraction. The developed materials were validated as support for PDMS membranes and for continuous gas-phase hydroformylation of 1-butene using Rh-diphosphite catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ordered ceramic monoliths are formed by casting using 3D printed resin templates. • Coating with a MFI zeolite layer increases porosity of monolith walls. • Various amounts of Co 3 O 4 are deposited by ion-exchange or impregnation technique. • Catalytic activity of Co 3 O 4 -modified monolith is higher than that of reference Co-BEA. • Co 3 O 4 -containing monoliths show very high stability and selectivity to CO 2. A facile method of fabrication of ceramic monoliths assisted by 3D printing was developed for preparation of Co 3 O 4 -based catalysts of total oxidation of volatile organic compounds. The proposed approach was based on the production of a resin template, which was subsequently used at a casting step for the construction of corundum monolith. The walls of this material were additionally coated with a MFI zeolite layer providing the possibility of modification with a Co 3 O 4 precursor using ion-exchange and impregnation techniques. The parent and Co 3 O 4 -modified monoliths with varying active phase content were characterized by SEM/EDS, XRD, XRF, XPS, UV–vis-DR and H 2 -TPR. Their catalytic performance in the toluene combustion was also tested. It was shown that the formation of Co 3 O 4 spinel particles highly dispersed on the zeolite-coated monolith resulted in excellent catalytic activity measured by very high TOF values. Furthermore, stability tests confirmed that the obtained monolith catalysts can work for prolonged reaction time without noticeable changes in the toluene conversion and selectivity to CO 2. [ABSTRACT FROM AUTHOR]

• Synthesis of silica monoliths with uniform macro-mesoporous structures, high porosity, and high surface area. • Laccase from Trametes versicolor immobilized in monoliths by covalent grafting. • Enzymatic monoliths applied for tetracycline depletion in aqueous solutions with flow through reactor configuration in sequential operation. • Modelling and simulation of tetracycline degradation efficiency with computational fluid dynamics model coupled with bio-reaction kinetics. Silica monoliths with uniform macro-/mesoporous structures (20 μm and 20 nm macro- and mesopores diameters, respectively), high porosity (83 %) and high surface area (370 m2 g−1) were prepared. The monoliths were grafted with amino groups (0.9 mmol NH 2 g−1) and used to immobilize laccase from Trametes versicolor by covalent grafting with glutaraldehyde (GLU) (1.0 mmol GLU g−1) leading to an ABTS activity of 20 U g−1. Immobilization yield was 80 %, based on the difference of initial and final activity of enzymatic solution used for immobilization. Enzymatic monoliths were used for the degradation of tetracycline (TC) in aqueous solution (20 mg L−1) in continuous flow with recycling configuration. TC degradation efficiency was found to be 40–50 % after 5 h of reaction at pH 7. Enzymatic monoliths were used during 75 h of sequential operation without losing activity. A Steady-state computational fluid dynamics (CFD) model based on Michaelis Menten reaction kinetics, allowed computing TC degradation efficiency. [ABSTRACT FROM AUTHOR]

• Activity evaluation of graphene-based nanopowders in the CWPO of phenol. • Graphene-based nanoplatelets stand out as remarkable catalysts for CWPO process. • 3D printed pure graphene-based monoliths are manufactured by direct ink writing. • Graphene monoliths are catalytically active and maintain their physical integrity. • Deactivation of monoliths by fouling, and regeneration by thermal treatment. This paper explores the catalytic behaviour of different graphene-based nanostructures for the treatment of wastewater using Catalytic Wet Peroxide Oxidation (CWPO) processes. In a first stage, graphene-based nanopowders with distinct physical-chemical characteristics are tested in the CWPO of phenol using the following standard operating conditions: [Phenol] 0 = 1 g·L−1, [H 2 O 2 0 = 5 g L−1 and 80 °C. Graphene nanoplatelets with the lowest oxygen content exhibit the highest catalytic activity. The typical phenol oxidation by-products are detected in the liquid phase while CO and CO 2 appear in the gas phase. Afterwards, three dimensional (3D) porous graphene monoliths (D ∼ 11.5 mm, H ∼ 4 mm, D open ∼ 0.68 mm and δ w =0.36 cm, 75 cells·cm−2, ε graphene skeleton = 41%) based on those nanoplatelets are additive manufactured using a direct ink writing technique and, then, tested under similar CWPO conditions. The results evidence that the 3D graphene-based structures are catalytically active, though they undergo a progressive deactivation due to the deposition of organic matter. The graphene-based monoliths can be regenerated by thermal treatments, allowing their use at industrial scale by means of reaction-thermal regeneration cycles. [ABSTRACT FROM AUTHOR]

Present work prepared a series of dip-coating M(Fe, Co)-BEA monolith catalyst using honeycomb cordierite as the substrate for N 2 O direct decomposition. The M(Fe, Co)-BEA (M = 1 wt%) powder zeolites were prepared by the ion exchange method, which were then washcoated on the cordierite substrate by silica-gel or alumina-gel as a binder (5 and 10 wt%). The morphologies of the prepared monolithic samples were analyzed by the scanning electron microscopy (SEM), suggesting that the powder of M(Fe, Co)-BEA zeolites can be well dip-coated on the cordierite support by silica-gel or alumina-gel with a relatively lower content (5 wt%). Through the catalytic activity evaluations, it is interestingly found that (I) the alumina-gel has an obvious promotion effect on N 2 O decomposition for the Fe-BEA monolith samples, while silica-gel can improve the decomposition activity of the Co-BEA monolith samples; (II) the low binder content (5 wt%) is more preferable to the high binder content (10 wt%) for preparation of the monolith catalysts. Computational fluid dynamics (CFD) was also employed to simulate the N 2 O direct decomposition over M(Fe, Co)-BEA monolith, wherein the fluid dynamics (mass distribution, pressure drop) were thereafter analyzed. [ABSTRACT FROM AUTHOR]

Highlights: [•] The preparation method of Cu-zeolite/cordierite monolith catalysts is optimized. [•] Zeolite washcoating followed by Cu ion-exchange is compared to washcoating with Cu-zeolite. [•] Washcoating with Cu ion-exchanged powder zeolite led to most active SCR catalyst. [•] Cu exchanged home-extruded BETA zeolite monolith achieved high SCR activity. [ABSTRACT FROM AUTHOR]

Highlights: [•] FIB-SEM technique is used for characterization of washcoated monolith catalysts. [•] Barium was evenly distributed along the washcoat surface. [•] Pt particles around 1–2nm were identified in the alumina washcoat. [•] NSR conversion is enhanced by Pt–Ba interaction in the whole washcoat depth. [ABSTRACT FROM AUTHOR]

Abstract: Spatially 1D simulations of exhaust gas catalysts are often used in the automotive industry because of short computation times. In fully 3D CFD-based model, the computational requirements increase by several orders of magnitude. A novel approach to 3D simulations of complete exhaust gas aftertreatment systems is proposed in this paper. It is based on a modular combination of standard CFD tool with a user-defined 1D channel model. The employment of external 1D channel model enables more effective computations and gives maximum freedom in definition of realistic reaction kinetics, including non-linear rate laws and fully transient solution of adsorbed components. The approach is validated by comparison of the results from the stand-alone 1D model and single channel CFD simulation. Dynamic simulations of CO oxidation light-off and lean/rich operation of NO x storage catalyst (NSRC, LNT) are then conducted in a test geometry with 10 representative channels and skewed inlet/outlet pipes. Finally, a complex system including bent pipes and conical expansion/constriction parts is simulated with 80 representative channels. It is demonstrated that relatively large deviations can exist between the individual channels. Non-uniform inlet flow distribution affects light-off behaviour as well as breakthrough of adsorbed components, and it may also lead to a different extent of catalyst ageing in individual channels. The combined 3D CFD and 1D channels simulation approach represents an effective tool for analysis of such problems and can help with the design of more efficient exhaust gas aftertreatment systems. [Copyright &y& Elsevier]

Abstract: This paper describes a computational study of a full size catalytic converter. The simulations are validated against experimental data obtained from the literature. It is seen that the flow distribution under both reacting and non-reacting conditions is a strong function of the converter properties, including such factors as the monolith cell density, the diffuser angle and the aspect ratio. The mass flow rate of the feed also has a strong influence. Monolith substrates with a high cell density showed faster light-off for a model reaction. A dual zone monolith consisting of a high cell density core and a low cell density outer annulus showed worse performance in the light-off compared to all other configurations tested. The overall execution time required for a two dimensional simulation required anything from under a minute for a steady state cold flow test, to 2h for a transient light-off with reaction. [Copyright &y& Elsevier]

Abstract: A detailed analysis of the catalytic behavior in the storage and reduction of NO x of a homemade Pt–BaO/Al2O3 NSR monolith catalyst determining the N2/NH3 production surface in response to operational variables, namely temperature and hydrogen concentration during rich conditions was obtained. The production response curves are used to design the optimal operation, with high NO x removal efficiency and maximum production of nitrogen, when running the single NSR catalyst and the combined NSR–SCR configuration with Fe-beta zeolite catalyst placed downstream the Pt–BaO/Al2O3 monolith. Optimal operation of the single NSR monolith was attained at 300°C and 1% H2, which showed NO x removal of 74% with 64% of nitrogen production (both related to the total amount of NO in the feedstream, difference was mainly ammonia). The double NSR–SCR configuration allowed the Fe-beta catalyst storing ammonia to react with NO x leaving the NSR during the subsequent lean phase. This has a benefit on both the NO x removal efficiency and the N2 production. The amount of ammonia needed for total NO x removal efficiency and N2 production can be supplied by tuning temperature and H2 concentration. Temperature of 300°C and 3% H2 during rich conditions, produced 23% of ammonia at the exit of NSR. The SCR reaction between this amount of ammonia adsorbed on Fe-beta and the untrapped NO in NSR, resulted in practical total NO x removal efficiency (98%) and N2 production of 97% when the double NSR–SCR system is operated. [Copyright &y& Elsevier]

Abstract: The development of the catalyst suitable for the catalytic partial oxidation (CPOX) of natural gas was investigated for the efficient production of synthesis gas. The catalyst of Rh/CeO2 +ZrO2 +MgO was found to show higher catalytic performance than Rh/MgO. The additional effect of CeO2 and ZrO2 to Rh/MgO on catalytic property was studied by H2-TPR, isotopic oxygen exchange reaction and DRIFT spectroscopy. And it was revealed that the state of Rh can maintain metallic phase during the CPOX reaction, and that oxygen can be supplied from lattice oxygen, and that adsorbed CO can desorb easily. The application of foam monolith catalyst coated with developed support materials to high pressure and short contact time CPOX reaction has been investigated, and we have succeeded in demonstrating the stable catalytic performance for 2000h at 1.0MPa and 500,000h−1 GHSV. [Copyright &y& Elsevier]

Abstract: In this work photo-Fenton oxidation of acetic acid, was carried out on perovskites based structured catalysts, in the presence or in the absence of low amounts of Pt. Homogeneous photo-Fenton reaction by ferrioxalate complex has been also performed. The comparison of homogeneous and heterogeneous photo-Fenton oxidation indicates that the use of a heterogeneous structured catalyst greatly improves the total organic carbon (TOC) removal and leads to a more effective use of H2O2. The rate of TOC removal during the runtime decreased because of the occurring side H2O2 decomposition to O2 that subtracts the oxidant to the photo-Fenton reaction. Moreover it allows enlarging the pH range of operation without the formation of sludge or significant metal leaching. LaFeO3 and Pt/LaMnO3 resulted the best catalysts for this process in terms of reaction rate. [Copyright &y& Elsevier]

Abstract: Catalytic combustion of CH4 or other gaseous HCs in microscale channels is becoming the key technology for various portable power generation devices that could replace current batteries to meet the increasing demand for more efficient, longer lasting and more environmentally friendly energy-consuming utilizations. New type of catalysts for the CH4/H2/air lean mixtures oxidation in drastic conditions were proposed and investigated; they were lined on SiC monoliths (dimensions 6mm×6mm×22mm) and tested into a lab-microreactor able to reach high power density (7.6MWth m−3). The catalysts were directly deposited on the monoliths via in situ solution combustion synthesis. The most interesting performance on the oxidation of CH4/H2/air lean mixtures was obtained with the monolith 2% Pt/(5% Al2O3), 2% Pd/(5% NiCrO4), followed by 2% Pd/(5% CeO2·ZrO2) and 2% Pd/(5% LaMnO3·ZrO2); the monolith 2% Pt/(5% Al2O3) behave better by burning CH4 or H2 alone. For the Pd-based catalysts, the addition of H2 to the reactive mixture led to an improvement of the CH4 combustion, whereas this did not happen for the Pt-based one. The addition of H2 to the gas mixture allowed to a decrease of the CH4-T50 and CH4-T100 compared to the combustion of CH4 alone, and the conversion curves slope becomes steeper: the higher the H2 concentration, the higher the mixture reactivity towards CH4 oxidation, probably due to the larger production of H2 reactive radicals (OHmple-para> [ABSTRACT FROM AUTHOR]

Abstract: Structured ceramic honeycomb monolith and open cell foams were employed as Ni catalyst carrier for methane autothermal reforming (CH4-ATR). The catalysts were prepared through washcoating of the supports with a commercial CeO2–Al2O3-based slurry and further impregnation into aqueous solution of nickel acetate tetrahydrate. A quite good reproducible preparation procedure was individuated in terms of both washcoat loading and resistance to ultrasonic vibrations and thermal shock tests. The catalysts were characterized by means of several techniques such as XRD, SEM, N2 adsorption at −196°C, Hg porosimetry and H2-TPR. The catalytic activity towards CH4-ATR was tested in kW-scale autothermal reforming reactor which is able to produce up to 5m3(stp)/h of H2. The reactor is thermally integrated with two heat exchangers for the preheating of the air and liquid water fed to the system, thus being completely self-sustained and able to perform without any external heat source. The tests carried out aiming to evaluate the influence of the O2/CH4 ratio on catalytic performance showed the higher activity of foam structured samples which can provide a lower average temperature in the catalytic bed. [ABSTRACT FROM AUTHOR]

Abstract: Ethanol steam reforming (S/C =3) was effectively performed at low temperature over catalytic wall reactors comprising a wide range of channel dimensions, ranging from conventional monoliths (channel width of 0.9mm) to semicylindrical microchannels (0.35mm radius) and to silicon micromonoliths (channel diameter of 3–4μm). Co3O4 catalyst coatings were successfully prepared inside the channels from in situ thermal decomposition of two-dimensional layered cobalt hydroxide salts and showed a remarkable high homogeneity and mechanical stability. The Si-micromonolithic reactor proved extremely promising for hydrogen production for micro-fuel cell operation. Specific H2 production rates exceeding 50LN of H2 per mL of liquid and cm3 of reactor were measured for ca. 42% ethanol conversion and residence times in the order of milliseconds. [Copyright &y& Elsevier]

Abstract: This paper reports recent research results about the impact of different catalyst bed configurations on Fischer–Tropsch (FT) synthesis product distributions. A powdered CoRe/γ-alumina catalyst with a particle size ranging from 60 to 100mesh was prepared and tested in a packed bed reactor. The same catalyst was ball milled and coated on a ceramic monolith support structure of channel size about 1mm. The monolith catalyst module was tested in two different ways, as a whole piece and as well-defined channels. Steady-state reaction conversion was measured at various temperatures under a constant H2/CO feed ratio of 2 and a reactor pressure of 25bar. Detailed product analysis was performed. Significant formation of wax was evident with the packed particle bed and with the monolith catalyst that was improperly packed. By contrast, wax formation was not detected in the liquid product by confining the reactions inside the monolith channel. This study presents an important finding about the structured catalyst/reactor system, in that the product distribution highly depends on how the structured reactor is set up. Even if a catalyst is tested under identical reaction conditions (T, P, H2/CO ratio), hydrodynamics (or flow conditions) inside a structured channel may have a significant impact on the product distribution. [Copyright &y& Elsevier]

Abstract: Cobalt–silica (Co–SiO2) aerogel coatings were successfully grown on the walls of ceramic monolith channels, thus resulting in structured catalytic wall materials useful for gas–solid reactions. The preparation involved the synthesis in situ of SiO2 gels by the sol–gel hydrolysis and condensation of tetraethylorthosilicate (TEOS), quenching at the gelation point, incorporation of Co by impregnation, and extraction of the solvent by supercritical drying. Characterization of the aerogel-coated monoliths revealed an excellent dispersion and homogeneity of the aerogel and good adherence properties. The catalytic performance of these materials in the ethanol steam reforming reaction addressed to obtain hydrogen was studied at atmospheric pressure by carrying out consecutive cycles at 473–773–473K with a C2H5OH:H2O∼1:3 (molar) mixture and stability tests, and the results were compared with those obtained over monoliths prepared by conventional washcoating methods from Co–SiO2 xerogel. Co–SiO2 aerogel catalytic walls were about four times more active for hydrogen generation at 623K than conventional monoliths. An unusual rapid activation of aerogel-coated monoliths was attained at 580–590K, even after several cycles and oxidation treatments at 563–613K, which was attributed to highly dispersed cobalt particles and higher effective diffusivity of reaction species due to high porosity and larger average pore size. The reproducible low-temperature activation of Co–SiO2 aerogels supported on ceramic monoliths may be useful for the practical application of fuel reformers to the on-site generation of hydrogen from ethanol. [Copyright &y& Elsevier]

Abstract: Cordierite monoliths coated with Co/ZnO catalysts were prepared by washcoating, urea, and sol–gel techniques and characterized by confocal microscopy, scanning electron microscopy (SEM), transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), and adherence tests. The performance of the catalytic monoliths for practical application in the production of hydrogen through ethanol steam reforming (ESR) and water gas shift (WGS) reactions was evaluated. Monoliths prepared by the urea method exhibited excellent dispersion and adherence of catalyst coatings and performed better for the reforming of ethanol. 5.6mol H2/mol C2H5OH were obtained from a C2H5OH:H2O=1:6 gaseous mixture at 723K and 0.33mLmin−1 of C2H5OH. Under these conditions and total ethanol conversion the composition of the effluent stream was 73.9% H2, 23.7% CO2, 1.2% CO, and 1.0% CH4. The amount of CO was kept low due to the activity of monoliths for the WGS reaction under ethanol steam reforming conditions. [Copyright &y& Elsevier]

Abstract: Several nitrogen compounds can be produced during the regeneration phase in periodically operated NO x storage and reduction catalyst (NSRC) for conversion of automobile exhaust gases. Besides the main product N2, also NO, N2O, and NH3 can be formed, depending on the regeneration phase length, temperature, and gas composition. This contribution focuses on experimental evaluation of the NO x reduction dynamics and selectivity towards the main products (NO, N2 and NH3) within the short rich phase, and consequent development of the corresponding global reaction-kinetic model. An industrial NSRC monolith sample of PtRh/Ba/CeO2/ -Al2O3 type is employed in nearly isothermal laboratory micro-reactor. The oxygen and NO x storage/reduction experiments are performed in the temperature range 100–500 °C in the presence of CO2 and H2O, using H2, CO and C3H6 as the reducing agents. The spatially distributed NSRC model developed earlier is extended by the following reactions: NH3 is formed by the reaction of H2 with NO x and it can further react with oxygen and NO x deposited on the catalyst surface, producing N2. Considering this scheme with ammonia as an active intermediate of the NO x reduction, a good agreement with experiments is obtained in terms of the NO x reduction dynamics and selectivity. A reduction front travelling in the flow direction along the reactor is predicted, with the NH3 maximum on the moving boundary. When the front reaches the reactor outlet, the NH3 peak is observed in the exhaust gas. It is assumed that the ammonia formation during the NO x reduction by CO and HCs at higher temperatures proceed via the water gas shift and steam reforming reactions producing hydrogen. It is further demonstrated that oxygen storage effects influence the dynamics of the stored NO x reduction. The temperature dependences of the outlet ammonia peak delay and the selectivity towards NH3 are correlated with the effective oxygen and NO x storage capacity. [Copyright &y& Elsevier]

Abstract: The conversion of biomass-derived crude oil towards H2 production was investigated using continuous catalytic steam reforming and sequential cracking/reforming processes. The performances of Pt/Ce0.5Zr0.5O2 and Rh/Ce0.5Zr0.5O2 catalysts deposited on cordierite monoliths were comparatively studied. The Pt-based catalyst showed better catalytic activity than Rh for steam reforming in the whole range of steam-to-carbon molar ratios (S/C) studied, the amount of added water determining the H2 yield for both noble metals. The best H2 yield (70%, corresponding to ∼49mmol of H2/g of bio-oil) was obtained with the Pt catalyst at S/C ratio of 10 at 780°C, with CH4 concentrations below 1%. In the case of sequential cracking, the process alternated cracking steps, during which the bio-oil is converted into H2, CO, CO2, CH4 and carbon stored on the catalyst, with regeneration steps where the deposited coke was burnt under O2. Comparison with thermal bio-oil cracking showed that the catalyst plays a major role in enhancing the H2 productivity up to 18mmol of H2/g of bio-oil (∼50% of H2 in gaseous products stream) and lowering the CH4 formation. The steam reforming offers high yields towards H2 but is highly endothermic, whereas the sequential cracking, despite lower H2 yields, offers a better control of coke formation and catalyst stability, and due to lower energy input can theoretically run auto-thermally. [Copyright &y& Elsevier]

Abstract: The growth of carbon nanofibers (CNF) was studied over a cordierite monolith previously coated with mordenite synthesized by a hydrothermal route. The zeolitic layer was deposited in order to have the sufficient number of cationic exchange sites to anchor the metallic particles responsible for the CNF formation. To produce the carbon nanofibers, cobalt was the active metal and acetylene, the source of carbon. The amount and type of nanocarbonaceous material obtained were studied as a function of the following operating conditions: (i) the reduction temperature of the metallic phase, (ii) the presence or absence of H2 in the feed and (iii) the orientation of the monolith channels with respect to the flow direction. The results obtained indicate that under specific operating conditions, large amounts of fibers grow over the whole internal surface of the channels. These fibers provide a large specific surface, which indicates that this type of structured catalysts could be used as three-phase reactors. [Copyright &y& Elsevier]

Abstract: Monolith reactors offer several advantages over traditional random fixed beds or slurry reactors, such as better mass transfer characteristics, higher volumetric productivity for a smaller amount of catalyst, elimination of filtration step and lower pressure drop. However, achieving an even gas–liquid distribution across the monolith is difficult. The cocurrent downflow contactor (CDC) reactor presents an elegant solution to this problem by establishing a stable two-phase dispersion. When comparing the CDC reactor with traditional stirred tank and trickle bed reactors for the hydrogenation of 2-butyne-1,4-diol, greater selectivity towards the alkene intermediate is observed in the CDC for a range of solvents. This is partly due to a high dispersion (67%) of Pd on the washcoat support of the monolith and also to the optimisation of the surface species concentrations as a result of greater mass transfer of hydrogen to the catalyst surface compared with alternative reactor designs. Furthermore, when considering the effect of scale-out on the monolith by comparing a single capillary with 1256 and 5026 channel monoliths, initial reaction rates and selectivity were maintained. This supports the use of the CDC as a suitable method for dispersing gas–liquid mixtures through a monolith. [Copyright &y& Elsevier]

Abstract: Fe-ZSM5 was prepared with high iron content by solid-state ion exchange and characterized by ICP-AES, BET surface measurements, TEM, UV–vis, EPR and DRIFT spectroscopy as well as supplementing catalytic tests in order to clear up its functionality in urea-SCR. Due to the over-exchange with iron small Fe2O3 particles were formed, identified by UV–vis, EPR and TEM measurements, which were proved to be not active for the SCR reaction. However, the oxidation of NO to NO2 over Fe3+ ions in the catalyst was realized to be a pre-requisite for the SCR reaction and the rate-determining step. DRIFT investigations under SCR conditions showed adsorbates on Fe2+ up to 300°C. The high SCR activity above 300°C can be explained by the faster reoxidation of Fe2+ to Fe3+ sites at high temperatures. The observed inhibition of the SCR reaction by excess ammonia at low and intermediate temperatures can be explained in this context by the reducing properties of ammonia converting Fe3+ to Fe2+ or by preventing the reoxidation of Fe2+. [Copyright &y& Elsevier]

Abstract: Transient behaviour of catalytic monolith converter with NO x storage is studied under conditions typical for automobiles with lean-burn engines (i.e., diesel and advanced gasoline ones). Periodical alternation of inlet concentrations is applied—NO x are adsorbed on the catalyst surface during a long reductant-lean phase (2–3min) and then reduced to N2 within a short reductant-rich phase (2–6s). Samples of industrial NO x storage and reduction catalyst of NM/Ba/CeO2/γ-Al2O3 type (NM=noble metal), washcoated on 400cpsi cordierite substrate, are used in the study. Effects of the rich-phase length and composition on the overall NO x conversions are examined experimentally. Reduction of NO x by CO, H2 and unburned hydrocarbons (represented by C3H6) in the presence of CO2 and H2O is considered. Effective, spatially 1D, heterogeneous mathematical model of catalytic monolith with NO x and oxygen storage capacity is described. The minimum set of experiments needed for the evaluation of relevant reaction kinetic parameters is discussed: (i) CO, H2 and HC oxidation light-off under both lean and rich conditions, including inhibition effects, (ii) NO/NO2 transformation, (iii) NO x storage, including temperature dependence of effective NO x storage capacity, (iv) water gas shift and steam reforming under rich conditions, i.e., in situ production of hydrogen, (v) oxygen storage and reduction, including temperature dependence of effective oxygen storage capacity, and (vi) NO x desorption and reduction under rich conditions. The experimental data are compared with the simulation results. [Copyright &y& Elsevier]

Abstract: This paper presents experimental and modelling results for the oxidation of mixtures of hydrogen and carbon monoxide in a lean atmosphere. Transient light-off experiments over a platinum catalyst (80g/ft3 loading) supported on a washcoated ceramic monolith were performed with a slow inlet temperature ramp. Results for CO alone agree with earlier results that predict self-inhibition of CO; that is an increasing light-off temperature with increasing CO concentration. Addition of hydrogen to the feed causes a reduction in light-off temperature for all concentrations of CO studied. The most significant shift in light-off temperature occurs with the addition of small amounts of hydrogen (500ppm, v/v) with only minor marginal enhancement occurring at higher hydrogen concentrations. Hydrogen alone in a lean atmosphere will oxidise at room temperature. In mixtures of hydrogen and CO, the CO was observed to react first until a conversion of about 50% was observed, at which point the conversion of hydrogen rapidly went from 0 to 100%. Simulations performed using literature mechanistic models for the oxidation of these mixtures predicted that hydrogen ignites first, followed by CO, a direct contradiction of the experimental evidence. Upon changing the activation energy between adsorbed hydrogen and oxygen, the CO was observed to oxidise first, however, no enhancement of light-off was predicted. The effect cannot be explained by the mechanistic model currently under discussion. [Copyright &y& Elsevier]

Abstract: Understanding how a reductant evolves and is utilized during regeneration of NO x storage-reduction catalyst can lead to predictive kinetic models, improved catalysts and energy-efficient engine-catalyst systems. We performed practically relevant NO x storage/regeneration cycling (56s/4s) experiments over a monolithic Pt/K/Al2O3 catalyst in a bench-flow reactor and resolved multiple transient reactions and exotherms. Carbon monoxide was the reductant and intra-channel speciation and temperature measurements were instrumental in resolving CO chemistry. Gas-phase O2 reacted with CO very fast over the entire regeneration time, and was depleted at the catalyst front. The resulting exotherm was significant and dissipated slowly over time raising the subsequent storage temperature considerably. NO x release/reduction by CO was also vigorous and primary NO x removal occurred at early regeneration times. The NO x -attributable exotherm was smaller than that of the O2–CO reaction, but extended deeper into the front portion of catalyst due to axially distributed NO x storage. Secondary NO x release/reduction occurred after the primary and produced NH3 as the main product. Hydrogen appeared when and where both the O2 consumption and major NO x release/reduction were near complete. We proposed that H2 produced via water–gas shift (WGS) reaction had little impact on O2 depletion and primary NO x release/reduction under the conditions studied. Further study is necessary to assess the impact of WGS reaction on secondary NO x release/reduction. [Copyright &y& Elsevier]

Abstract: Selective catalytic reduction (SCR) among the approaches for alleviating NOx emission was much attracted. Zeolites have the advantage for adsorption of propene, and noble metal catalyst has the advantage for oxidation of NO to NO2. Pt (or Au)/Al2O3 (or SiO2) were used as the lower layer of double wash-coated monolith catalysts. Zeolites (H-mordenite or ZSM-5) were coated as the upper layer. The catalytic performance of the double wash-coated catalyst was, remarkably, improved. Also, temperature window was shifted to lower temperature and broadened. It was known that the combined noble metal monolith catalyst with zeolite was very effective in removing NOx by SCR with hydrocarbons. [Copyright &y& Elsevier]

Abstract: Potential application of monolith reactors in a biological process was investigated experimentally. A possible problem when using monolith reactors in biological applications is clogging due to biofilm formation. An interesting phenomenon is the pattern in which biofilms develop inside the monolith channels. Rather unexpectedly at a first glance, it was repeatedly observed that biofilm formation started in the middle of a side of the square-section monolith channels, instead of colonizing first the low-shear areas in the corners. To explain this biofilm formation pattern, a two-dimensional mechanistic model based on substrate diffusion and consumption accompanied by microbial growth and detachment was developed in this study. Simulation results suggest that the unexpected biofilm patterns are generated by the balance between biofilm growth and biofilm detachment due to shear stress induced erosion. In the early stages, the biofilm growth in the corners is strongly limited by the external resistance to substrate transfer. As time passes and the biofilm grows in thickness, mechanical forces due to passing gas bubbles will lead to a more regular biofilm shape, including the channel corners. [Copyright &y& Elsevier]

Abstract: Flow distribution characteristics in a 0.05m diameter monolith reactor, operated co-current downward in the Taylor flow regime, was investigated and quantified using gamma ray computed tomography (CT). The results indicate that the flow distribution is a strong function of liquid distributor design, and gas and liquid superficial velocities. Additionally, within the range of gas and liquid superficial velocities investigated, a window of operating condition (gas and liquid velocities) was identified which resulted in a close to uniform phase distribution. [Copyright &y& Elsevier]

Abstract: The performance of a liquid-phase hydrogenation carried out in a monolithic reactor on an industrial scale has been studied by measuring temperature differences accurately. The process studied is the hydrogenator in the autoxidation process for large-scale production of hydrogen peroxide by Eka Chemicals, Akzo Nobel. Temperature differences are primarily caused by the exothermic reaction and can be used to measure variations in local reaction rates. Non-uniformities in liquid flow distribution can also be detected. One important finding was the existence of multiple steady states that can be attributed to the stop/startup procedure. [Copyright &y& Elsevier]

Abstract: Square channel cordierite monoliths have been loaded with alumina washcoat layers of various thicknesses (20–110μm) and loaded with rhenium and cobalt resulting in a 0.1wt.% Re/17wt.% Co/Al2O3 catalyst. These monolithic catalysts have been tested in the Fischer–Tropsch synthesis in a temperature window (180–225°C) under synthesis gas compositions ranging from stoichiometrically excess carbon monoxide to excess hydrogen (H2/CO=1–3). The results include data on the activity and selectivity of CoRe/Al2O3 monolithic catalysts for FTS under these process conditions. Washcoat layers thicker than about 50μm appear to lead to internal diffusion limitations. Thinner washcoat layers yield, depending on the conditions, to larger amounts of α-olefins than alkanes for chain lengths below 10 carbon atoms. ASF and non-ASF chain length distributions are obtained for thin washcoats, whereby the chain growth probability increases from 0.83 to 0.93. Under certain conditions the amounts of alkanes even increase with chain length. These experimental results with different diffusion lengths have been used to analyze the effects of secondary reactions on FTS selectivity. [Copyright &y& Elsevier]

Abstract: The study of permeable composite monolith (PCM) membranes for the Fischer–Tropsch synthesis is continued. On the scale of membranes with outer diameter of 42mm, it is proved that PCM can combine high productivity of hydrocarbons (>55 ( h)−1 at 0.6MPa, 484K), high selectivity towards heavy hydrocarbons (α ASF >0.85, C5+ upto 0.9) as well as high heat-conductivity and high mechanical strength. [Copyright &y& Elsevier]

The present study was carried out to asses performance of a Pd-monolith downflow bubble column (DBC) reactor, and compare it with that of the slurry and the fixed bed DBC. The selective hydrogenation of butyne-1,4-diol to cis-2-butene-1,4-diol over palladium catalyst was chosen as a model reaction. In principle, the monolith DBC allowed the reaction to take place under kinetic control regime. Comparison with DBC employing 5% Pd/C powder and 1% Pd-on-Raschig ring catalysts revealed a better performance of the monolith DBC (1% Pd loading) with advantage of smaller reaction volume and intensified reaction rate. In the monolith DBC, improved hydrogen transport was possible, as the interface between bubbles and the channel wall was very thin, thus, the length of the diffusion path was very short. In addition, the interfacial surface area at both gas–liquid and liquid–solid interface in the monolith was also very high. The reaction kinetics was well represented by the Langmuir–Hinshelwood mechanism. As an alternative to conventional three-phase reactors, the monolith DBC was simple due to its inherent characteristic operation and no specially designed device. [Copyright &y& Elsevier]

Spatio-temporal temperature profiles experimentally observed during the operation of a structured perovskite-based catalytic monolith for the combustion of methane were simulated by means of a transient heterogeneous one-dimensional model which accounts for heat losses to the surroundings and thermal conductivity inside the monolith substrate. In fact it is shown that such thermal phenomena are essential to correctly reproduce the slow warm-up transients and the wrong-way behaviour observed in a low conductivity ceramic monolith. Model simulations reveal that at higher values of solid conductivity the catalyst does not exhibit hot spot both in time and space, but needs higher inlet gas temperatures to reach complete methane conversion. Bifurcation analysis of the catalytic monolith reactor model were carried out to study steady-state multiplicity. We show that the origin of multiplicity is purely thermal as it is mainly ruled by the heat transfer through the external surface. [Copyright &y& Elsevier]

A new reactor concept to replace slurry bed catalysts with monolithic catalysts is described. Different configurations are presented, all requiring minimal hardware modifications for revamp. One key feature of the new concept is that no troublesome filtration step is required, while maintaining the benefits of high catalyst effectiveness and selectivity. Furthermore, higher catalyst loads per reactor volume can be achieved with the monolith. Cold flow experiments are used to demonstrate the feasibility of the concept and to determine some empirical parameters for a simple hydrodynamic model. Characteristic performance data for the monolith reactor, such as mass transfer, heat transfer, and reactive performance, as well as their dependence on the type of monolith used are discussed on the basis of model calculations. [Copyright &y& Elsevier]

Washcoats with improved mass transfer properties are necessary to circumvent concentration gradients in case of fast reactions in liquid phase, e.g. nitrate hydrogenation. A highly porous, high surface area (180 m2/g) and thin washcoat of carbon fibers, was produced on a monolith support by methane decomposition over small nickel particles. Carbon fibers form a homogeneous layer less then 1 μm thin, covering the surface of the channels in the monolith. The fibers penetrated into the cordierite, which is suggested to cause a remarkable stability of the fibers against ultrasound maltreatment. The texture of the fibers is independent of both the thickness of the γ-alumina washcoat as well as the time to grow carbon fibers. [Copyright &y& Elsevier]