Nitrogen Physisorption Research Articles

Thermal stability of MxOy‐doped zirconia aerogels (M = Y, Yb, Gd, Ce, Ca) studied through 1200°C

AbstractThe high porosities and low densities of ceramic aerogels offer outstanding insulative performance in applications where weight is a critical factor. The high surface area‐to‐volume ratios and specific surface areas provide extremely low thermal conductivity, but also contribute to rapid densification of the pore structure at elevated temperatures. This densification diminishes their favorable properties and inhibits use of aerogels in high‐temperature applications. This work contributes to a design framework for thermally stable aerogels via the study of dopant chemistry (Y, Yb, Gd, Ca, Ce) in zirconia aerogels. The structural evolution was studied through 1200°C using nitrogen physisorption, scanning electron microscopy, and X‐ray diffraction. The role of dopant identity and concentration in thermal stability was elucidated. In the context of the design framework, dopant chemistry is an aggregate for many closely related material properties, each of which may contribute to aerogel structural evolution. To develop a truly predictive design framework for ceramic‐based aerogels, systematic and comprehensive evaluation of thermodynamic and kinetic properties must be performed in conjunction with studies on structural evolution.

Regulating the physical properties of silica immobilized Fe(II), Ni(II) and Co(II) catalysts towards ethylene oligomerization reactions

Immobilization of the phenol((triethoxysilyl)propylimino) ligand (LH) on SBA15 and MCM41 afforded the ligands LH-SBA15 and LH-MCM41 respectively. The reactions of LH-SBA15 and LH-MCM41 with NiCl2, CoCl2 and FeCl2 salts produced the respective materials [Ni(LH-SBA15)2Cl2], (Ni-SBA15), [Co(LHSBA15)2Cl2], (Co-SBA15), [Fe(LH-SBA15)2Cl2], (Fe-SBA15) and [Ni(LH-MCM41)2Cl2], (Ni-MCM41) in good yields. The functional group determination, morphology, physical and surfaced properties of the materials containing immobilized ligands and complexes were established from FT-IR, TGA, TEM, SEM-EDX, PXRD, ICP-AES, and nitrogen physisorption measurement techniques. Activation of the complexes on the surface with EtAlCl2 as co-catalyst formed active catalysts for the oligomerization of ethylene affording mainly C6 oligomers. The SBA-15 immobilized catalysts were more active than the corresponding MCM-41 materials, while Ni(II) catalysts performed better than the corresponding Co(II) and Fe(II) systems. The immobilized catalysts could be used in three cycles without significant loss of catalytic activity and selectivity.

Kinetic study of glycerol hydrodeoxygenation on Al2O3 and NiMo2C/Al2O3 catalysts

A kinetic study of glycerol hydrodeoxygenation (HDO) on NiMo2C/Al2O3 and Al2O3, prepared by sol-gel technique, was carried out in a batch reactor, from 250 °C to 285 °C, at high glycerol concentration (95wt%). Structural and surface properties of the catalysts were determined by XRD, nitrogen physisorption, TEM and NH3-TPD. Impregnation of alumina with Ni and Mo and subsequent carburization at 730 °C increased crystallite sizes and reduced total acidity of the catalyst to 1/3 that of pure alumina. All reactions were well fitted to a zeroth order model. Estimation of reagents mass transport rates suggests no diffusion limitation. Main products were propanediols, ethylene glycol and long-chain molecules from oligomerization reactions, as well as methane, ethane and propane. At this temperature range, long-chain compounds have the highest yields, mainly on alumina.

Thermochemical heat storage through CaO-Mayenite/CaCO3 system: Thermal performances comparison for two synthesis methods

ThermoChemical Storage systems (TCS) are gaining attention for long term-thermal energy storage applications. Those systems can successfully increase the electricity generation flexibility in CSP (Concentrated Solar Power) plants or optimize the heat recovery and storage in energy-intensive industries (EII) as well. CaO/CaCO3 based systems are currently broadly investigated for thermochemical storage, either natural or synthetic materials. Among these, CaO/Mayenite (Ca12Al14O33) sorbents are considered very promising. CaO/Mayenite (Ca12Al14O33) based material was developed according to two different synthesis methods. The first one consisted in a one-step sol-gel method where aluminium precursor and pure CaO are weighted to obtain the exact weight ratio of 75/25 (CaO/Ca12Al14O33). In the second one, a two-step method was adopted: pure Mayenite was preliminarily synthetized by one step sol-gel method and CaO/Mayenite was obtained by direct wet mixing with pure CaO. Samples obtained were characterized by XRD, SEM, TGA, nitrogen physisorption, Raman spectroscopy and thermal stability was tested over 40 charging/discharging cycles in TGA. Raman spectra revealed free oxygen O2− presence in the structure of Mayenite and in CaO-Mayenite samples as well, lying at 1128 cm-1. Thermal properties such as thermal conductivity, heat capacity and volumetric energy density storage have been determined. The thermal conductivity found were 0.377 ± 0.004 (W/mK) for A; 0.101 ± 0.006 (W/mK) for B and for Mayenite 1.16 ± 2.7 10−4 (W/mK). It was found that two step method led to a better performing material in terms of carbonation reaction reactivity, and hence thermal storage. This material showed 50 % carbonation reaction conversion value at 40th cycle, corresponding to 0.250 g CO2/g dry sample, which is 4 times higher than CaO conversion. At 40th cycle, moderate sintering effect is remarked, with 2.3 % conversion drop, indicating that Mayenite insertion effectively acts as spacer. Volumetric storage energy density Sd has been determined for both samples and compared to CaO at increasing cycle number. Sample B storage density was effectively even at 40th cycle with 0.69 GJ/m3, thus about 3.5 times higher than CaO.

Evaluating the pre-treatment protocol required to produce an effective carbonized waste adsorbent for organic pollution control

With the goal of fostering the circular economy, the present work was devised to minimize and manage agricultural waste by transforming it into biochar; a versatile dye removal adsorbent. Waterways across the globe are frequently fouled and contaminated with organic materials, especially via unregulated industrial effluents, producing toxic water supplies. Rhodamine B (RhB) and Methylene blue (MB) dyes were used as model organic pollutants in water. The contaminants were then readily extracted from environmental samples using sustainable wheat straw derived biochars. These materials were utilized in an effort to link the circular economy directly to environmental protection, reducing organic contamination by using a low carbon solution. Herein, two methods were adopted to refine a low temperature carbonized material, dependent on initial pre-treatment; leaching followed by milling (method-I) and milling followed by leaching (method-II). Scanning Electron Microscopy (SEM), nitrogen physisorption, proximate and ultimate analysis and Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR) were used to examine the properties of the synthesized materials. It was found that by altering the process of initial waste pre-treatment, an increase in available surface area (6.284 m2g−1–20.754 m2g−1) and pore structure can be found post feedstock pyrolysis. Additionally, FTIR of the biochar post extraction supported the adsorption process of both dyes, demonstrating a change in dye-adsorbent bonding, depending on the initial waste pre-treatment for the biochar. In batch mode, several operating parameters including pH, concentration, duration, and dose were optimized. Kinetics and adsorption isotherm studies for biochar synthesized by method-II pre-treatment (BC-II) revealed that the system follows Pseudo-first-order kinetics and Freundlich adsorption isotherm model with the relative R2 of 0.9989 and 0.9880 for RhB, comparing with 0.9933 and 0.9932 for MB. The optimal produced biochar, BC-II effectively removed 91.06% of RhB from solution at pH 4 and 92.43% for MB at pH 8. This study brings forth a solution to enhance waste management by creating a circular scenario and alleviate environmental contamination by utilizing wheat straw as a biochar adsorbent, produced under controlled and low temperature conditions.

Study of Fe-Doped Ordered Mesoporous Titanium Dioxide Synthesis

Titanium dioxide is often designed as an excellent catalyst carrier and photocatalyst due to its tunable structure. In this paper, iron-doped ordered mesoporous titanium dioxide was prepared. These powders were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and nitrogen physisorption (BET). It was found that mesoporous titanium dioxide powders containing 1% Fe doping were roasted at 350 °C to favor the formation of ordered mesoporous titanium dioxide. This is due to the fact that Fe doping can enhance the pore structure and improve the orderliness of pores, while the increase in temperature can accelerate the growth of grains.

The titania-catalyzed oxidative dehydrogenation of methanol to formaldehyde

Formaldehyde is one of the most important intermediates in today’s chemical industry and mainly produced via the silver or Formox process. In this study, we introduce titania as a new catalyst for the oxidative dehydrogenation (ODH) of methanol to formaldehyde. Bulk titania catalysts were tested under methanol ODH conditions and the influence of reaction temperature, residence time and feed composition was investigated. The highest formaldehyde yield exhibited in the titania-catalyzed methanol ODH was around 70 % at 600 °C, 1.6 gCatalyst h molMethanol−1 and 2.0 molMethanol molOxygen−1. Long-term experiments were performed to get insights on the catalyst stability. While catalyst deactivation was observed at 600 °C (90–60 % methanol conversion after 72 h) and 550 °C (90–85 % methanol conversion after 72 h), methanol conversion (85 %) was stable and no deactivation occurred at 500 °C. Characterization of the used catalysts by nitrogen physisorption, powder X-ray diffraction and thermogravimetric analysis revealed deposition of carbon species as the main cause of catalyst deactivation. By alternating reaction and regeneration with oxygen, constant methanol conversions (90 %) and formaldehyde yields (70 %) were achieved at 600 °C.

Utilization Perspectives of Lignin Biochar from Industrial Biomass Residue.

The present study aimed at utilizing technically hydrolyzed lignin (THL), industrial biomass residue, derived in high-temperature diluted sulfuric acid hydrolysis of softwood and hardwood chips to sugars. The THL was carbonized in a horizontal tube furnace at atmospheric pressure, in inert atmosphere and at three different temperatures (500, 600, and 700 °C). Biochar chemical composition was investigated along with its HHV, thermal stability (thermogravimetric analysis), and textural properties. Surface area and pore volume were measured with nitrogen physisorption analysis often named upon Brunauer-Emmett-Teller (BET). Increasing the carbonization temperature reduced volatile organic compounds (40 ÷ 96 wt. %), increased fixed carbon (2.11 to 3.68 times the wt. % of fixed carbon in THL), ash, and C-content. Moreover, H and O were reduced, while N- and S-content were below the detection limit. This suggested biochar application as solid biofuel. The biochar Fourier-transform infrared (FTIR) spectra revealed that the functional groups were gradually lost, thus forming materials having merely polycyclic aromatic structures and high condensation rate. The biochar obtained at 600 and 700 °C proved having properties typical for microporous adsorbents, suitable for selective adsorption purposes. Based on the latest observations, another biochar application was proposed-as a catalyst.

Reducing toxic element leaching in mine tailings with natural zeolite clinoptilolite.

The use of natural zeolite clinoptilolite to reduce the leaching rate of potentially toxic elements such as Cd, Pb, and Mn in soil from mine tailings was studied. Soil from the surroundings of the mine El Bote in Zacatecas, Mexico, was analyzed, and the zeolite was characterized by X-ray diffraction, Fourier-transform infrared spectroscopy, and nitrogen physisorption. An ammonium-exchange method for the zeolite was employed. Leaching experiments using packed columns with polluted soil and zeolite mixtures were carried out and the effect of the pH of the carrier solutions was studied. Incorporation of zeolite in the soil achieved a beneficial increase in pH, from 5.03 to 6.95. The concentration of Cd and Mn was reduced when zeolite was present in the column and the ammonium-modified zeolite with ammonia also enhanced the concentration reduction of metallic species in leachates in a range of 28 to 68%. The first-order model best fits the experimental data, suggesting that the leaching rate is controlled by concentration difference between the liquid and the soil matrix. These results demonstrate the potential for using natural zeolite clinoptilolite to reduce the leaching rate of potentially toxic elements in soil from mine tailings.

Engineering of Silica Mesoporous Materials for CO2 Adsorption.

Adsorption methods for CO2 capture are characterized by high selectivity and low energy consumption. Therefore, the engineering of solid supports for efficient CO2 adsorption attracts research attention. Modification of mesoporous silica materials with tailor-made organic molecules can greatly improve silica's performance in CO2 capture and separation. In that context, a new derivative of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, possessing an electron-rich condensed aromatic structure and also known for its anti-oxidative properties, was synthesized and applied as a modifying agent of 2D SBA-15, 3D SBA-16, and KIT-6 silicates. The physicochemical properties of the initial and modified materials were studied using nitrogen physisorption and temperature-gravimetric analysis. The adsorption capacity of CO2 was measured in a dynamic CO2 adsorption regime. The three modified materials displayed a higher capacity for CO2 adsorption than the initial ones. Among the studied sorbents, the modified mesoporous SBA-15 silica showed the highest adsorption capacity for CO2 (3.9 mmol/g). In the presence of 1 vol.% water vapor, the adsorption capacities of the modified materials were enhanced. Total CO2 desorption from the modified materials was achieved at 80 °C. The obtained silica materials displayed stable performance in five CO2 adsorption/desorption cycles. The experimental data can be appropriately described by the Yoon-Nelson kinetic model.

Boron adsorption on modified zeolites: Effect of modifier and source of water

The removal of boron from drinking water is a concern in various parts of the world due to the toxic effects of this metalloid in high concentrations. In this paper, zeolites LTL and FAU X were synthesized and modified with salts of nickel (NiCl2), iron (FeCl3), and aminopropyltriethoxysilane (APS) in order to promote their affinity for boron species present in aqueous systems. The adsorption capacity of modified zeolites for boron was evaluated in a synthetic boron solution and with groundwater samples for human use. The effect of the pH and zeolite dose was studied in adsorption tests using groundwater. The modified zeolites were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, nitrogen physisorption, and Fourier-transform infrared spectroscopy. Results indicated that the modification of zeolites favors affinity for boron species. The highest adsorption capacity of boron on zeolites was achieved in the synthetic solution. The adsorption capacity of the modified zeolites depended on the pH, the electrical conductivity, the modifying agent, the zeolitic structure, and the dose of adsorbent. The zeolitic structure-modifying agent interaction was decisive for boron adsorption capacity, with LTL-Ni zeolite being the best-performing adsorbent, thanks to its textural properties and nickel’s ability to form complexes with boron species.

Direct Valorization of Recycled Palladium as Heterogeneous Catalysts for Total Oxidation of Methane

Electronic waste as an alternative source of palladium is used for the preparation of heterogeneous catalysts for methane oxidation. The strategy developed in this paper involves two steps: optimization of the leaching protocol to recover the Pd from the waste, and development of a suitable impregnation protocol directly from the leachate, which is a strongly acidic solution. The precipitation-deposition technique is particularly suitable for the preparation of catalysts from acidic media. The impact of Ba, Bi, and Ag impurities on the catalytic performance is studied on model catalysts. The presence of these elements and their impact on the catalytic properties are analyzed and discussed using X-ray diffraction, nitrogen physisorption, scanning and transmission electron microscopy. Through variation of the pH, the impurities co-deposited with Pd can be limited and the catalytic performance of catalysts derived from real waste can be greatly enhanced.

Issue Information

Journal of the American Ceramic SocietyVolume 106, Issue 8 p. 4515-4518 ISSUE INFORMATIONFree Access Issue Information First published: 31 May 2023 https://doi.org/10.1111/jace.18565AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Graphical Abstract Cover Photograph: Solvent effect on the gelation step during the synthesis of polymer-derived ceramic aerogels can be exploited to tailor their pore and particle size distributions. The image shows FE-SEM micrographs and nitrogen physisorption isotherms at 77 K of polymer-derived SiC/C aerogels prepared with different solvents: (top) n-Hexane; (middle) acetone; (bottom) cyclohexane. Insets: comparison of density functional theory (DFT) cumulative pore volumes of preceramic and ceramic aerogels. Credits: All authors of this article. Volume106, Issue8August 2023Pages 4515-4518 RelatedInformation

Mesoporous colloidal silica cubes with catalytically active cores

Preparation methods of cubic core-shell particles with specific functionality are limited. Here we demonstrate the possibility to transform cuprous oxide cubes coated with mesoporous silica into functional core-shell particles, while retaining their cubic shape. Cuprous oxide nanocubes are coated with mesoporous silica using cetyltrimethylammonium bromide as a template, after which the cuprous oxide core is transformed using liquid phase calcination and galvanic replacement. Nitrogen physisorption and electron microscopy confirm that mesoporous silica coatings are obtained with tuneable thickness. The successful transformation of cuprous oxide into gold and silver is assessed via UV–VIS spectroscopy and energy dispersive X-ray spectroscopy. Particles with a silver core and a cubic mesoporous silica shell are demonstrated to be catalytically active in the degradation of the dye Congo red.Graphical abstract

Support Effect of Ga-Based Catalysts in the CO2-Assisted Oxidative Dehydrogenation of Propane

Carbon dioxide (CO2) assisted oxidative dehydrogenation of propane over Ga-modified catalysts is highly sensitive to the identity of support, but the underlying cause of support effects has not been well established. In this article, SSZ-13, SSZ-39, ZSM-5, silica and γ-Al2O3 were used to load Ga species by incipient wet impregnation. The structure, textural properties, acidity of the Ga-based catalysts and the process of CO2-assisted oxidative dehydrogenation of propane were examined by X-ray diffraction (XRD), nitrogen physisorption (N2 physisorption), ammonia temperature-programmed desorption (NH3-TPD), pyridine chemisorbed Fourier transform infrared spectra (Py-FTIR), OH-FTIR and in situ FTIR. Evaluation of the catalytic performance combined with detailed catalyst characterization suggests that their dehydrogenation activity is positively associated with the number of acid sites in middle strength, confirming that the Lewis acid sites generated by Ga cations are the active species in the reaction. Ga/Na-SSZ-39(9) also has feasible acidic strength and a unique channel structure, which is conducive to the dissociative adsorption of propane and desorption of olefins. The Ga/Na-SSZ-39(9) catalysts showed superior olefins selectivity and catalytic stability at 600 ℃ compared to any other catalysts. This approach to quantifying support acid strength, and channel structure and applying it as a key catalytic descriptor of support effects is a useful tool to enable the rational design of next-generation CO2-assisted oxidative dehydrogenation catalysts.

Selective catalytic reduction of nitric oxide with a novel Mn–Ti–Ce oxide core-shell catalyst having improved low-temperature activity and water tolerance

A novel core-shell-shell Mn–Ti–Ce oxide catalyst (MnOx@TiO2@CeO2) was synthesized by a three-step method and applied for the selective catalytic reduction of NOx with ammonia (NH3-SCR). The catalyst exhibited an excellent low-temperature activity with NOx conversion >80% in a broad temperature range under both dry (120–260 °C) and wet (180–255 °C) conditions with a weight hourly space velocity (WHSV) of 240,000 mL/(g·h). Nitrogen physisorption and X-ray photoelectron spectroscopy (XPS) results showed that the formation of the inner TiO2 shell significantly increased the specific surface area, surface Mn4+/Mn ratio and chemisorbed oxygen, which could provide more active sites and promote the oxidation of NO to NO2. Ammonia temperature-programmed desorption (NH3-TPD) results indicated that the formation of the outer CeO2 shell not only extensively increased the surface acid sites but also enhanced the acid strength, beneficial for the ammonia adsorption and resulting in a good water tolerance.

Ruthenium Catalysts Supported on Hydrothermally Treated Carbon from Rice Husk: The Effect of Reduction Temperature on the Hydrogenation Reaction of Levulinic Acid to γ-Valerolactone

Ru catalysts supported on activated carbon obtained by hydrothermal treatment of rice husk were evaluated in the hydrogenation reaction of levulinic acid to γ-valerolactone. The hydrothermally treated carbon was characterized by nitrogen physisorption, elemental analysis, and thermogravimetric analysis, and the catalysts were characterized by FTIR spectroscopy, X-ray photoelectron spectroscopy, temperature-programmed reduction, and temperature-programmed desorption of pyridine (acidic properties). Prior to the reaction, the catalysts were reduced at different temperatures in the range of 100–350 °C to evaluate the effect of the reduction temperature on the performance in the hydrogenation of levulinic acid. The reaction was carried out in a batch reactor at 70 °C and 1.5 MPa. The results of conversion and selectivity to γ-valerolactone showed that the catalyst with the best performance was the sample reduced at 200 °C. After 2 h of reaction, a γ-valerolactone yield of 74% was achieved. This catalyst presented the lowest acidity value, and the ruthenium-containing phase consisted mainly of RuO2, with a small portion of Ru0. The solid catalyst can be recovered and successfully reused for three runs with the GVL yield at 56%.

Low temperature synthesis of MCM-48 and its adsorbent capacity for the removal of basic red 29 dye from model solutions

The low temperature synthesis of MCM-48 was performed and its adsorptive properties were investigated for the first time in literature by studying Basic Red 29 (BR29) dye adsorption from model solutions. The modification of the surface properties and pore structure of silica-based material MCM-48 induced by BR29 adsorption were characterized using XRD, nitrogen physisorption, and SEM methods before and after dye adsorption.The effects of contact time, solution pH, dye concentration, and temperature on the adsorption capacity of MCM-48 were investigated. Different adsorption models and different kinetic models were used, respectively to define the equilibrium data and the kinetics of adsorption. Adsorption data was seen to fit the Langmuir isotherm and the pseudo-second-order kinetic model. In addition, MCM-48 was found to be very successful for the removal of the BR29 dye model solutions, even at an initial dye concentration of 500 mg/L for which the removal efficiency was above 97%.

Photocatalytic Degradation of Diclofenac by Nitrogen-Doped Carbon Quantum Dot-Graphitic Carbon Nitride (CNQD)

In this study nitrogen-doped carbon quantum dots/graphitic carbon nitride nanosheet (CNQD) composites with different contents of nitrogen-doped carbon quantum dots (NCQDs; 2, 4, 6, and 8 wt%) were synthesized. The morphological, physicochemical, and photoelectrochemical properties were investigated using complementary methods such as scanning electron microscopy (SEM), powder X-ray diffraction (pXRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), UV/Vis spectroscopy in diffuse reflectance (DRS), photoluminescence (PL), nitrogen physisorption (BET), photocurrent response, and electrochemical impedance spectroscopy (EIS). The photocatalytic activity of the synthesized materials was assessed during diclofenac (DCF) degradation in an aqueous solution under visible light irradiation. As a result, improved photocatalytic efficiency in DCF degradation was observed for all the CNQD composites compared with bulk graphitic carbon nitride (bCN) and nanosheet g-C3N4 (CNS). The fastest DCF degradation was observed for the 6 wt% NCQD on the surface of CNS (CNQD-6), which removed 62% of DCF in 3 h, with an associated k value of 5.41 × 10−3 min−1. The performance test results confirmed the contribution of NCQDs to enhancing photocatalytic activity, leading to an improvement factor of 1.24 over bCN. The morphology of the CNS and the synergistic interaction between NCQDs and CNS were essential elements for enhancing photocatalytic activity. The photoelectrochemical data and photoluminescence analyses showed the efficient migration of photoexcited electrons from NCQDs to the CNS. The reduced charge recombination rates in CNQD photocatalysts might be due to the synergistic interaction between NCQDs and CNS and the unique up-conversion photoluminescence properties of NCQDs. Further investigations revealed that the photogenerated superoxide radicals (•O2−) predominated in the degradation of DCF, and this photocatalyst had good reusability and toxicity reduction abilities. This work provides insight into the effects of NCQDs on the CNS surface to enhance its potential to remove emerging organic pollutants from water and wastewater.

The effect of the acid pre-treatment temperature of natural diatomaceous earth on the Si/Al ratio of ZSM-5 zeolite

Bolivian diatomaceous earth is a potentially lower cost silica source than conventional high purity reagents used in zeolite synthesis. Due to its complex composition, it is necessary to pre-treat it with sulfuric acid in order to reduce impurities and regulate the aluminum content. In the present work several experiments were carried out with natural Bolivian diatomaceous earth in the pre-treatment stage. In order to determine the effect on the final Si/Al ratio, the temperature of the acid pre-treatment was varied between 50 to 155 °C. The results show that the Si/Al ratio can be modulated from 6.2 up to 38.1. These treated diatomaceous earth samples were used to synthetise ZSM-5 zeolite. The obtained ZSM-5 zeolites have a Si/Al ratio in the following range: 9.6 to 40.2. XRD, NH3-TPD and Nitrogen Physisorption techniques were used to characterise the properties of the obtained zeolites. The degree of crystallisation and the specific surface area are directly related to the Si/Al ratio, resulting in high values at high Si/Al ratios. The acid sites are composed of strong Brönsted acid sites and, strong and weak Lewis acid sites. For the zeolite with a low Si/Al ratio a high total acidity was found (>0.51 molNH3/Kgzeolite), while at high Si/Al ratios the total acidity is reduced (<0.38 molNH3/Kgzeolite).