α-Al2O3 Support Research Articles

Probing Active Sites on Pd/Pt Alloy Nanoparticles by CO Adsorption.

We studied the adsorption of CO on Pd/Pt nanoparticles (NPs) with varying compositions using polarization-dependent Fourier transform infrared reflection absorption spectroscopy (FT-IRRAS) and theoretical calculations (DFT). We prepared PtPd alloy NPs via physical vapor codeposition on α-Al2O3(0001) supports. Our morphological and structural characterization by scanning electron microscopy and grazing incidence X-ray diffraction revealed well-defined, epitaxial NPs. We used CO as a probe molecule to identify the particles' surface active sites. Polarization-dependent FT-IRRAS enabled us to distinguish CO adsorption on top and side facets of the NPs. The role of the Pd/Pt alloy ratio on CO adsorption was investigated by comparing the experimental CO stretching band frequency for different alloy arrangements to the results for pure Pd and Pt NPs. Moreover, we studied the influence of hydrogen adsorption on the NP surface composition. We determined the dependence of the IR bands on the local atomic arrangement via DFT calculations, revealing that both bulk alloy composition and neighboring atoms influence the wavenumber of the bands.

Preparation and surface hydrophilic modification of MOR zeolite membrane potentially appling for acetic acid aldol condensation reaction system

High-performance MOR zeolite membranes were prepared by loading hydrophilic metal oxides onto the surface of α-Al2O3 support via secondary hydrothermal synthesis method. The effects on the surface morphology and hydrophilicity of MOR zeolite membranes were discussed by means of different metal oxides (TiO2, V2O5, CeO2, ZrO2, WO3) and loadings in combination with SEM, XRD, Raman and Water Contact Angle (WCA) characterization. TiO2-MOR zeolite composite membranes were found that TiO2 could increase interface hydrophilicity. The pervaporation performances of TiO2-MOR zeolite membranes at different temperatures and feed concentrations were investigated. The mass transfer model combining Maxwell-Stefan mechanism, Kundsen diffusion and viscous flow was used to describe the mass transfer process of water molecules through the zeolite layer, and within the α-Al2O3 scaffolds, respectively. The permeation fluxes of water molecules of TiO2-MOR zeolite membranes with the loading of 2 wt% were 0.91 kg m−2 h−1, 1.00 kg m−2 h−1 and the separation factors were up to 10000 at 348 K with 90 wt% AcOH/H2O and 90 wt% AA/H2O solutions. TiO2-MOR zeolite membranes with well acid resistance and high hydrophilicity had promising prospects in the reaction scene where carboxylic acid and water exist simultaneously, such as esterification, ester hydrolysis, acetic acid aldol condensation, etc.

Optimized intermediate layer formation and electroless plating methods to obtain supported dense Pd surfaces.

Dense metallic membranes, especially Pd and Pd alloys, have been intensely investigated to provide an alternative and economical way to obtain H2 with ultrahigh purity. To overcome the high cost of Pd, composite membrane structures that comprise a thin layer of Pd are utilized. However, it is a challenge to obtain a thin, dense, and uniform Pd layer on the support materials. This study investigates the parametric analysis of γ-Al2O3 interlayer formation and the electroless Pd plating (Pd ELP) procedures on α-Al2O3 supports with the aim to achieve a thin, uniform Pd surface without annealing. Adjustments in PEG/PVA concentration, dipping time, and heat treatment enabled creating a thin γ-Al2O3 interlayer on α-Al2O3, minimizing pore size and density. Hydrazine concentration, heat treatment, and bath temperature were adjusted to optimize Pd ELP to achieve maximum yield from the plating bath and a dense, uniform surface without annealing. Pd/γ-Al2O3/α-Al2O3 structures were analyzed using scanning electron microscopy, X-ray diffraction, and thermogravimetric analysis to observe the impact of varied parameters on surface structures. Optimized sample was compared to an annealed Pd/α-Al2O3 prepared in accordance with literature methods and a Pd/graphite/α-Al2O3 sample to validate the use of optimized ELP procedure and the γ-Al2O3 interlayer. Results show that a dense and uniform 13 μm Pd coating was achieved on a γ-Al2O3-coated α-Al2O3 support without annealing, using three fresh ELP baths. This was done using sequential hydrazine addition with a decreased concentration (1 M) into the ELP baths at 30 °C, and applying heat treatment at 120 °C between each fresh ELP bath.

High-Performance FAU Zeolite Membranes Derived from Nano-Seeds for Gas Separation.

In this study, high-performance FAU (NaY type) zeolite membranes were successfully synthesized using small-sized seeds of 50 nm, and their gas separation performance was systematically evaluated. Employing nano-sized NaY seeds and an ultra-dilute reaction solution with a molar composition of 80 Na2O: 1Al2O3: 19 SiO2: 5000H2O, the effects of synthesis temperature, crystallization time, and porous support (α-Al2O3 or mullite) on the formation of FAU membranes were investigated. The results illustrated that further extending the crystallization time or increasing the synthesis temperature led to the formation of a NaP impurity phase on the FAU membrane layer. The most promising FAU membrane with a thickness of 2.7 µm was synthesized on an α-Al2O3 support at 368 K for 8 h and had good reproducibility. The H2 permeance of the membrane was as high as 5.34 × 10-7 mol/(m2 s Pa), and the H2/C3H8 and H2/i-C4H10 selectivities were 183 and 315, respectively. The C3H6/C3H8 selectivity of the membrane was as high as 46, with a remarkably high C3H6 permeance of 1.35 × 10-7 mol/(m2 s Pa). The excellent separation performance of the membrane is mainly attributed to the thin, defect-free membrane layer and the relatively wide pore size (0.74 nm).

Functionalized α-Al2O3 supported gold catalyst for photocatalytic oxidative esterification of benzyl alcohol with methanol to corresponding esters

Alpha-alumina (α-Al2O3) is traditionally considered to be unsuitable as a support for high performance gold-based catalysts because of its small specific surface area. Herein, a highly active α-Al2O3-supported nearly sub-nanometer Au particles photocatalyst for oxidative esterification of benzyl alcohol under visible-light irradiation in a mild condition was synthesized via the electronic interaction between gold precursor and a layer of 3-aminopropyltriethoxysilane (APTES) pre-grafted on the α-Al2O3 called as functionalized α-Al2O3. APTES could serve as a linker to strongly anchor Au nanoparticles (NPs) to α-Al2O3 surface, leading to nearly sub-nanometer Au particles (1.8 ± 0.1 nm). The enhanced metal-support interaction reinforces the interaction of plasmonic hot holes of Au NPs and intermediate molecules, which promote the rate-limiting step of C-H bond cleavage and facilitate the activation of oxygen molecules due to the increased electron cloud density around Au NPs. Meanwhile, α-Al2O3 support can play a synergistic role because of the reactant adsorption can be improved by the acid-base pairs contained.

Oxygen carrier derived from ferric sludge for chemical looping combustion of MSW syngas: Waste derived material performance and carbon footprint assessment

The utilization of water treatment sludge (i.e., ferric sludge) was explored as the oxygen carrier (OC) for chemical looping combustion (CLC) of municipal solid waste (MSW) syngas. The performance of ferric sludge (FS) in CLC and simultaneous HCl removal was evaluated in a bench-scale fluidized bed, and was compared with iron ore (IO) as a benchmarked OC. The results show that FS (92 %) performed better than IO (82 %) in terms of syngas combustion efficiency and FS was able to remove HCl (77 % removal efficiency) while IO was unable to remove any HCl. Comparison of reaction temperature reveals that FS performed better at lower CLC temperature between 800 °C and 850 °C. Agglomeration was observed when FS was used in extended CLC cycles. Thus, investigation of using inert α-Al2O3 support together with FS for extended CLC cycles was investigated. Agglomeration and sintering were drastically reduced and good combustion efficiency of 88 % for H2 and 74 % for CO was attained. Carbon footprint assessment illustrated that FS was superior as a greener material based on global warming potential of 20 and 100 years. Conversion of FS as an OC were characterized with 104.23 and 108.0 kgCO2/t lower than IO for GWP-20 and GWP-100, exhibiting the competitiveness in the usage of waste-derived material in CLC. Hence, FS can be considered as a novel, cost-effective, and greener OC for CLC. The co-utilization of waste-derived material and waste-derived syngas through CLC would be an integrated solution for improved circularity and sustainability.

Highly selective hydrogenation of arenes over Rh nanoparticles immobilized on α-Al2O3 support at room temperature

Selective hydrogenation of arenes is a crucial process not only for the hydrogen storage and transport but also for the synthesis of important pharmaceutical intermediates. Herein, a series of α -Al2O3-supported catalysts prepared using different metals were tested for the arenes hydrogenation of lignin derivatives at room temperature. The kinetic studies reveal that Rh-1/α -Al2O3 exhibits both the highest reaction rate and TOF value for the conversion of diphenyl ether and toluene. The XRD, TEM, XPS and XAS analyses suggest that the distribution of the metal Rh nanoparticles on α -Al2O3 support for Rh-1/ α -Al2O3 catalyst is mainly responsible for the H2 activation/dissociation and subsequent arenes hydrogenation. The density functional theory calculation indicates the stronger adsorption capacity of toluene and guaiacol on Rh (200) than that on Rh (110) and Rh (220). Stable Rh-1/ α -Al2O3 can contribute to the improvement of the arenes hydrogenation of lignin derivatives to produce high-value-added platform chemicals at room temperature.

Orienting of metal-organic framework nanosheets into continuous membranes for fast hydrogen permeation

The extremely thin, porous and crystalline nature endow metal-organic framework nanosheets (MOFNs) to be emerging materials for membrane assembly. However, their reliable manufacturing, especially for the continuous growth in controllable direction, remains a great challenge. Herein, we firstly orient a MOFN (NTU-83, a layered framework) either into vertical or horizontal alignments via one-step bottom-up synthesis on the surface-functionalized α-Al2O3 supports, on which the amide groups promote vertical assembly via the formed COOH⋯NH2 hydrogen bond, while exposed oxygen sites facilitate horizontal growth by Cu⋯O/OH interaction. The H2 permeance of the vertical aligned MOFN membrane (termed VAM) is 2100 ± 7 GPU at 100 °C, and it sharply increases to 8000 ± 40 GPU in horizontal aligned membrane (termed HAM), together with high-steady operation and nearly same H2/CO2 selectivity (varied in range of 6–7). This anti-trade-off performance should be attributed to the relatively short (500 nm) diffusion pathway and nanosized pore (5.4 × 8.2 Å2) of the horizontal-stacked layers when compare with the slightly bent and long (12 μm) interlayer channel (5.1 Å) that connected by eutectic junction points in VAM. Additionally, the universality of this surface functionalization for directional MOF growth was confirmed by producing another set of horizontal and vertical MOFN membranes with 3D structure. Given the rich building blocks of MOFs and various planting groups on the supports, the presented surface functionalization strategy can be extended to the directional assembly of other MOFNs on different supports into highly-efficient membranes.

Experimental and molecular simulation study of a novel benzimidazole-linked polymer membrane for efficient H2/CO2 separation

Developing novel materials for membrane separation is extremely crucial. Benzimidazole-linked polymers (BILPs) show great potential for H2 purification due to their high thermal and chemical stability, while only a few BILPs have been used for membrane-based gas separation. In this work, the BILP-5 composite membranes were prepared via a facile interfacial polymerization. Dense and smooth BILP-5 composite membranes were prepared on α-Al2O3 support and characterized by scanning electron microscope (SEM) and atomic force microscope (AFM). The effects of interfacial polymerization reaction duration, temperature, and pressure on the gas separation performance of BILP-5 membranes were systematically investigated. The resultant BILP-5 membrane shows good stability and a high H2/CO2 selectivity of 16 with a H2 permeance of 362 GPU under mixed gas test at room temperature, which exceeds the 2008 upper bound. Furthermore, the H2/CO2 separation mechanism of BILP-5 membranes was investigated through molecular dynamics simulations. Coupled with the merits of simple preparation, good stability, and excellent gas separation performance, BILP-5 is expected to be one of the most promising membrane materials for H2/CO2 separation.

Pervaporation separation of C6 alkane isomers by Al-bttotb membrane

The metal-organic framework (MOF) membrane has been widely studied in gas separation applications. However, less attention was paid to organic liquids separation, particularly for the separation of straight and branched alkane isomers which is critical to producing high-octane gasoline. Our work is the first example of a dense and defect-free Al-bttotb membrane synthesized on α-Al2O3 support surface through solvothermal in-situ synthesis. The microstructure of the membrane surface was adjusted by controlling the growth rate of the crystal facet through the addition of formic acid during synthesis. The resultant membrane showed great thermal stability, long-term stability, and chemical stability due to the bonding reaction between the ligands and the support surface. The pervaporation test showed that Al-bttotb membrane preferentially permeated straight and mono-branched alkane. The mass fraction of n-hexane (nHEX, straight) and 3-methylpentane (3MP, mono-branched) was accumulated from 66.66% on the feed side to 88.53% on the permeate side after 20 h of the test, while a mass fraction of 2,2-dimethylbutane (22DMB) decreased from 33.33% to 11.47%. This work sheds new light on the separation of organic liquids through MOF polycrystalline membrane.

Thermally rearranged poly(benzoxazole-co-imide) composite membranes on α-Al2O3 support for helium extraction from natural gas

Membrane gas separation is deemed as the most energy-efficient approach to extract the rare He from natural gas. However, the techno-economic feasibility was far from the practical application because of the poor separation performance illustrated by Robeson's upper bound. Herein we reported a high-performance polymeric membrane for He extraction from natural gas. Besides the bulky Cardo segments, the pristine polymeric backbone was featured with reactive ortho-hydroxyl groups, which were thermally rearranged to benzoxazole rings benefitting micropore formation. The polymer was well dissolved in NMP then facilely coated on α-Al2O3 support for further thermal rearrangement. The thin and selective membrane showed He permeance of 40 GPU and He/CH4 mixture selectivity of 74 surpassing the benchmark membranes for helium extraction. Mitigation of physical aging was demonstrated by the long-term (>1000 h) separation in He/N2 and He/CH4 binary mixtures. The excellent He separation performance and anti-aging property endowed the membrane appealing to practical He extraction from natural gas.

Effects of the method of active site characterization for determining structure-sensitivity in Ag-catalyzed ethylene epoxidation

Catalysts have been prepared on a low surface area α-Al2O3 support used commercially for previous generation olefin epoxidation catalysts. Prescreening of the low surface area alumina (0.73 m2/g) indicated the absence of acid catalyzed isomerization of EO at an evaluation temperature of 210 °C. A 0.1 wt% Ag base material synthesized by incipient wetness impregnation of AgNO3 was used as a base material for electroless deposition (ED) of additional Ag to increase particle sizes by controlled reduction of Ag+ directly onto the preexisting Ag surface to form weight loadings between 0.3 and 5.0 wt% metal. A 12 wt% Ag/α-Al2O3 using Ag2C2O₄ as the Ag precursor was also prepared to compare performance of the ED samples with a catalyst more typical of industrial formulations. Characterization by SEM, STEM, and hydrogen titration of oxygen precovered Ag characterized before and after catalytic evaluation indicated that microscopy is required to accurately represent distributions of Ag particle sizes, but H2 titration of O-precovered Ag gives the best representation of active sites since it directly counts the number of Ag surface sites. Larger particles >100 nm are resistant to both Ag sintering and carbon foulant; TOF values were relatively insensitive to particle size with only a 2.2 × difference between the best and worst performing samples. Selectivity, which is not a function of TOF, shows the most significant structure sensitivity effect where particle sizes follow the trend 67 nm ≈ 92 nm (58% EO) < 157 nm (67% EO) < 211–542 nm (73% EO). The lower EO selectivities were also correlated with increased fouling for the smaller Ag sizes, suggesting that more strongly bound EO precursor(s) leads to combustion and CO2/H2O formation.

Vapor/gas separation through carbon molecular sieve membranes: Experimental and theoretical investigation

The separation of H2O vapor from (hydrogen-rich) gaseous streams is a topic of increasing interest in the context of CO2 valorisation, where the in situ water removal increases product yield and catalyst stability. In this work, composite alumina carbon molecular sieve membranes (Al-CMSM) were prepared from phenolic resin solutions loaded with hydrophilic boehmite (γ-AlO(OH)) nanosheets (0.4–1.4 wt. % in solution) which partially transform to γ-Al2O3 nanosheets upon thermal decomposition of the resin, improving the hydrophilicity and thus the adsorption-diffusion contribution of the H2O permeation. The γ-Al2O3 nanosheets showed no influence on the pore size distribution of the membranes in the range of micropores, but they increased the membrane hydrophilicity. In addition, the use of boehmite in the resin solution causes an increase in the viscosity and thus an increase in the carbon layers thickness deposited on the porous α-Al2O3 support (from 1 to 3.3 μm). Furthermore, the alumina sheets introduce defects in the carbon matrix, increasing the tortuosity of the active layer, as concluded via phenomenological modelling and parametric fitting of the experimental results. As a consequence, the water permeability exhibits a maximum (1.3ꞏ10−6 molꞏs−1 Pa−1 m−1 at 150 °C) with boehmite/alumina content of ca. 0.8 wt. %, as the combined effects of increasing hydrophilicity (which favour H2O permeability) and increasing thickness and tortuosity (which hamper permeability) upon increasing boehmite loading. Similarly, the H2O/gas perm-selectivity is optimum at 1.2 wt. % boehmite loading. We further investigated the H2O permeation mechanism by modelling the mono- and multi-layer adsorption and capillary condensation of water in microporous media, which result as the main transport mechanisms in the explored conditions.

Controlled synthesis of α-Al2O3 supported Ag particles with tuning catalytic performance

Herein, α-Al2O3 supported Ag particles with controllable size distribution are prepared successfully by tuning of the calcination conditions through an impregnation method. The size of Ag particles could be adjusted by changing the calcination time and temperature. The catalyst samples were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and other characterization methods under different calcination conditions, and the performance differences of their catalytic reduction of p-nitrophenol (4-NP) were investigated by UV-Vis spectroscopy. The results show that the Ag particles with increased particle size can be obtained on the surface of α-Al2O3 support by increasing the calcination time or calcination temperature. The catalytic performance of the samples obtained by increasing the calcination time decreased, while the catalytic performance of the samples obtained by increasing the calcination temperature increased. This may be due to the interaction between Ag particles and the support, which changes the valence state of Ag species. Also the particle size effect acts on the catalyst and affects its catalytic performance together with the change of valence.

Mixing properties of Al2O3(0001)-supported M 2O3 and MM′O3 monolayers (M, M′ = Ti, V, Cr, Fe)

Considering the importance of sub-monolayer transition metal oxides supported on another oxide in many industrial processes, with the help of a DFT + U approach, we provide information on the structural and electronic properties of pure M 2O3 and mixed MM′O3 oxide monolayers (M, M′ = Ti, V, Cr, Fe) supported on an α-Al2O3(0001) support. With their structure in the prolongation of the alumina corundum lattice, the monolayers have non-equivalent surface and interface cations, which leads to two different cation configurations in the mixed oxides. In all cases, the interfacial charge transfer is weak, but strong cation–cation electron redistributions may take place as in TiVO3, TiFeO3, VFeO3, and TiCrO3 in which actual redox processes lead to cation oxidation states different from the expected +3 value. We show that the tendency to mixing relies on the interplay between two very different driving forces. Cation–cation redox reactions, in most cases, strongly stabilise mixed configurations, but preference for a given cation position in the monolayer, because of surface energy reasons, may strengthen, weaken or even block the mixing tendency. By comparison with results obtained in bulk ilmenite, in free-standing monolayers and in MLs deposited on transition metal substrates, we evidence the flexibility of their electronic structure as a function of size, dimensionality and nature of support, as a lever to tune their properties for specific applications.

Synthesis of silicalite-1 zeolite membranes for vapor-permeation separation of dichlorobenzene Isomers

Silicalite-1 zeolitic membranes have been successfully fabricated on the porous α-Al2O3 support by templated and template-free protocol, respectively, for vapor permeation separation of dichlorobenzene (DCB) isomers. After proving the high quality of the membranes by single gas permeation (He and SF6) performance, the vapor-permeation of DCB isomers over two types of the silicalite-1 membrane was then investigated. The separation results clearly indicated that under the lower partial pressure and higher temperature, the effect of DCB isomer adsorption on the permeance could be kept at a sufficiently low level and sharp selectivity become more important. Thus, high p-DCB selectivity could be achieved. Comparatively, the template-free silicalite-1 zeolite has a much higher p-DCB selectivity due to the relatively fewer inter-crystalline gaps. Under certain separation conditions, the highest selectivity of p-DCB for p-/m-DCB and p-/o-DCB binary systems could reach 165 and 113, respectively.

Synthesis of ZIF-11 Membranes: The Influence of Preparation Technique and Support Type.

Due to its structural features, ZIF-11 is one of the most interesting materials for gas separation applications. Herein, we report a systematic study on the synthesis of ZIF-11 as a supported membrane. For this, we adapted optimized conditions for the ZIF-11 powder synthesis, identified in our previous works, to form ZIF layers on symmetric and asymmetric stainless-steel and asymmetric α-Al2O3 supports. Different techniques were investigated for the challenging layer formation, namely, in situ crystallization (ISC), multiple in situ crystallization (MISC), and the seeding and secondary growth (SSG) method. It was possible to deposit ZIF-11 on different supports by ISC and MISC, although it was difficult to obtain complete layers. SSG, in turn, was more effective in forming dense and well-intergrown ZIF-11 layers. This agrees well with the generally accepted fact that seeding considerably facilitates layer formation. Systematic studies of both individual steps of SSG (seeding and secondary growth) led to a basic understanding of layer formation of ZIF-11 on the different supports. The best membranes prepared by rub seeding and secondary growth achieved Knudsen selectivity. Improved gas separation performance is expected if the formation of defects can be avoided.

Sustainable synthesis of highly water-selective ZSM-5 membrane by wet gel conversion

High-performance zeolite socony mobil five (ZSM-5) membranes were successfully prepared on a cheap, tubular α-Al2O3 support via a proposed wet gel conversion (WGC), aiming at avoiding the competitive zeolite crystals growth in the solution and ensuring the formation of polycrystalline zeolite layer onto the support surface. A small amount of gel was loaded on seeded tubes via dip-coating and then converted to ZSM-5 membranes via direct crystallization without using any additional synthesis solution for membrane growth. By using this method, the amount of synthetic gel was largely reduced as compared with the traditional hydrothermal synthesis. The effects of crystallization temperature, crystallization duration, and synthetic gel silica source dissolution duration on the morphologies, microstructures, and pervaporation performances of ZSM-5 membranes were investigated. Under optimized synthesis conditions, the as-synthesized ZSM-5 membrane showed high separation performance and stability in isopropanol dehydration. During the 104-h pervaporation test, the permeation flux was stable at 2.96 kg m−2 h−1 with a separation coefficient exceeding 10,000. The synthetic route exhibited excellent reproducibility for the fabrication of highly water-selective ZSM-5 membrane. This work provides a novel, feasible method for the preparation of zeolite membranes with high performance, high atom economy, low cost, and reduced waste solution.

Pervaporative Dehydration of Organic Solvents Using High-Silica CHA-Type Zeolite Membrane.

A high-silica chabazite (CHA) type zeolite membrane was prepared on the porous α-Al2O3 support tube by the secondary growth of seed particles. The dehydration performances of the membrane were determined using methanol, ethanol, 2-propanol, acetone, acetic acid, methyl ethyl ketone (MEK), tetrahydrofuran (THF), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and N-methyl-2-pyrolidone (NMP) at 303–373 K. As a result, the dehydration performances of the membrane were categorized to following three types: (1) 2-propanol, acetone, THF, and MEK; (2) ethanol and acetic acid; and (3) methanol, DMF, and DMSO, and NMP. The adsorption isotherms of water, methanol, ethanol, and 2-propanol were determined to discuss the influences of the organic solvents on the permeation and separation performances of the membrane. For 2-propanol, acetone, MEK, and THF solutions, the high permeation fluxes and separation factors were obtained because of the preferential adsorption of water due to molecular sieving. In contrast, the permeation fluxes and separation factors were relatively low for methanol, DMF, and DMSO, and NMP solutions. The lower dehydration performance for the methanol solution was due to the adsorption of methanol. The permeation fluxes for ethanol and acetic acid solution were ca. 1 kg m−2 h−1. The significantly low flux was attributed to the similar molecular diameter to the micropore size of CHA-type zeolite.

Designing tubular composite membranes of polyelectrolyte multilayer on ceramic supports with nanofiltration and reverse osmosis transport properties

Ceramic membranes are relevant for applications, which require mechanical robustness and chemical stability. The preparation of purely ceramic membranes for nanofiltration (NF) and reverse osmosis (RO) is a demanding process. Composite membranes comprise a mechanically stable ceramic support and a functional polymeric separation layer, combining the advantages of both worlds. In this work, we present a molecular strategy to fabricate polyelectrolyte multilayer membranes (PEMM) ranging from dense nanofiltration into the region of reverse osmosis deposited on tubular ceramic supports. A dynamic coating of PAH/PSS on a α-Al2O3 support membrane with pore sizes of 150 nm (MF) and 50 nm (UF) leads to a dense separation layer on the lumen side, with NaCl rejections above 90%. Coating solutions with increased ionic strength, as well as a subsequent covalent crosslinking of the amine groups of the PAH improve long term stability. The substitution of the polyanion PSS by PVSA, having a higher charge density, results in a remarkably low MWCO of 115 Da. This work indicates that balancing the charge density of polymers with the ionic matrix can result in reverse osmosis type selective layers on ceramic support with pore size even as large as 150 nm.