Surface Basicity Research Articles

K2SO4-promoted TiO2 for the efficient oxidative coupling of methane

The oxidative coupling of methane (OCM) into C2−3 hydrocarbons is still limited to a few types of catalysts with low product yield. Herein, we reported our discovery that a K2SO4-promoted TiO2 catalyst can effectively catalyze the OCM reactions with a C2−3 yield of up to 26 %, which is comparable to the classical Mn-NaWOx/SiO2 catalyst. Besides, this catalyst not only exhibits promising stability for at least 200 h without signs of deactivation under typical OCM conditions but also demonstrates high sulfur-resistance performance, outperforming most reported catalysts. We have evidenced that K+ ions are responsible for increasing the surface basicity of rutile TiO2, thus benefiting C2−3 selectivity. The presence of SO42− can prevent the formation of potassium titanates, which catalyze the over-oxidation of CH4. The surface lattice oxygen species are confirmed to be the active sites for selective CH4 activation, while the chemisorbed oxygen species catalyze the combustion of CH4 to CO2.

Efficient Catalytic Synthesis of Glycerol Carbonate Using Optimized Na and K Titanate Nanotubes Catalysts

The synthesis of glycerol carbonate from glycerol has garnered significant research attention because of its wide application in the lithium-ion battery and pharmaceutical industries. This study summarizes the catalytic transformation of glycerol to glycerol carbonate using Na and K titanate nanotubes as catalysts. We report the synthesis of Na and K titanate nanotubes catalyst by a simple co-precipitation route and investigate their catalytic activity in the transesterification of glycerol. The physicochemical properties of the Na and K titanate nanotubes catalyst were successfully studied by CO2-TPD and XRD. The designed catalyst possesses high catalytic efficiency and stability in the transesterification reaction of glycerol. Based on its surface area and basicity, several experiments were performed, and it was observed that under optimized conditions (i.e., 5 wt.% catalyst loading, 5:1 molar ratio of DMC to glycerol, 90 °C, and 90 min), the highest conversion of glycerol was achieved, 92.6% glycerol carbonate. The high thermal stability and recyclability make it an efficient heterogeneous catalyst for the synthesis of glycerol carbonate.

Enhancing Ammonia Synthesis on Co3Mo3N via Metal Support Interactions on a Single‐crystalline MgO Support

AbstractCo3Mo3N has been reported to have activity for the synthesis of ammonia surpassing that of industrial Fe catalysts under certain conditions. However, so far the research has largely focused on unsupported Co3Mo3N. We report a comprehensive study on the catalytic activity of Co3Mo3N when supported on two distinct MgO substrates. Our findings reveal that the method of MgO preparation plays a crucial role in influencing surface basicity. Remarkably, Co3Mo3N supported on single‐crystalline MgO demonstrates significantly enhanced catalytic activity, achieving a 162.0 mmol g−1metal h−1 rate. This surpasses the performance on commercial MgO support (41.2 mmol g−1metal h−1) and unsupported Co3Mo3N (15.0 mmol g−1metal h−1). While kinetic analyses show no substantial differences between the two supported catalysts, spectroscopic studies employing CO2 and N2 temperature‐programmed desorption (TPD) reveal a richer array of basic sites and adsorption/desorption phenomena on the single‐crystalline MgO support. These catalysts exhibit exceptional stability. The drastically reduced Co/Mo loading amounts in comparison to the bulk form, make the commercialization of Co3Mo3N catalysts more practical.

Active metal-free CaO-based dual-function materials for integrated CO2 capture and reverse water–gas shift

Integrated CO2 capture and conversion into CO via the reverse water–gas shift reaction (ICCC-RWGS) using CaO-based dual-function materials (DFMs) offers an attractive avenue for mitigating anthropogenic CO2 emissions. Active metal-free CaO-based DFMs have advantages such as no CO formation at the CO2 capture stage and high CO selectivity across a broad temperature range at the CO2 conversion stage, yet they face challenges with low CO yield. Herein, we report the enhanced performance of CaO-based DFMs co-doped with gallium (Ga) and zirconium (Zr) oxides in the ICCC-RWGS process. This improvement can be attributed to the synergistic interaction among Ca, Ga and Zr oxides, resulting in reduced CaO crystallites, enhanced surface basicity, and increased concentration of oxygen vacancies. The most promising DFM consists of 90 wt% CaO, 4.5 wt% Ca3Ga4O9 and 5.5 wt% CaZrO3 (with a Ga/Zr molar ratio of 1). When exposed to a simulated flue gas (5 % O2, 10 % H2O, 15 % CO2, and 70 % N2), this DFM exhibits a stable CO2 capture capacity of 11.90 mmol/gDFM over 20 consecutive isothermal ICCC-RWGS cycles at 650 °C. Meanwhile, its CO2 conversion and CO yield are maintained at 83.4 % and 10.26 mmol/gDFM, respectively. This study highlights the significance of a multi-metal oxide synergistic strategy in CaO-based DFMs to achieve superior performance in the ICCC-RWGS process.

Surface Basicity and Hydrophilic Character of Coal Ash-Derived Zeolite NaP1 Modified by Fatty Acids.

Zeolite NaP1 was found to display the highest affinity for CO2 in preliminary modifications of coal fly ash-derived zeolites (4A, Y, NaP1 and X) by four amines (1,3-diaminopropane, N,N,N',N'-tetramethylethylenediamine, Tris(2-aminoethyl)amine and ethylenediamine). In the second step, different fatty acid loaded NaP1 samples were prepared using palmitic, oleic and lauric acids. CO2 and H2O thermal programmed desorption (TPD) revealed changes in intrinsic basicity and hydrophilic character, expressed in terms of CO2 and H2O retention capacity (CRC and WRC, respectively). Infrared spectroscopy (IR), N2 adsorption-desorption isotherms and scanning electron microscopy allowed for correlating these changes with the type of interactions between the incorporated species and the zeolite surface. The highest CRC values and the lowest CO2 desorption temperatures were registered for NaP1 with the optimum content in palmitic acid (PA) and were explained in terms of the shading effect of surface acidity by the rise of basic Na+-palmitate salt upon cation exchange. The amine/fatty acid combination was found to paradoxically mitigate this beneficial effect of PA incorporation. These results are of great interest because they demonstrate that fatty acid incorporation is an interesting strategy for reversible CO2 capture.

ZnO–Doped CaO Binary Core–Shell Catalysts for Biodiesel Production via Mexican Palm Oil Transesterification

This work investigates biodiesel production via transesterification of Mexican palm oil with methanol catalyzed by binary solid base core–shell catalysts with improved catalytic stability. A series of CaO–ZnO mixed solids were prepared using an inexpensive co–precipitation method by varying ZnO content from 5 to 20 mol%. Several factors, such as surface basicity, ZnO content, phase compositions, and thermal treatment of the catalysts, were all proven to be crucial for the production of biodiesel with good quality. Thermal treatment could effectively remove the surface adsorbed water and impurities and improved the catalytic activity. The addition of ZnO to CaO significantly enhanced the catalysts’ stability; however, it led to lower surface basicity and slightly diminished catalytic activity. ZnO doping inhibited the formation of surface Ca(OH)2 and promoted the formation of Ca–Zn–O or CaZn2(OH)6 phase as the core and a surface CaCO3 shell, which effectively decreased Ca2+ leaching by approximately 74% in methanol and 65% in a methanol–glycerol (4:1) mixture. A combined method of separation and purification for obtaining clean biodiesel with high quality was proposed. The biodiesel obtained under the control conditions exhibited properties which satisfied the corresponding standards well.

Elucidating the role of potassium addition on the surface chemistry and catalytic properties of cobalt catalysts for ammonia synthesis.

The ammonia synthesis process produces millions of tons of ammonia annually needed for the production of fertilisers, making it the second most produced chemical worldwide. Although this process has been optimised extensively, it still consumes large amounts of energy (around 2% of global energy consumption), making it essential to improve its efficiency. To accelerate this improvement, research on catalysts is necessary. Here, we studied the role of potassium in ammonia synthesis on cobalt catalysts and found that it was detrimental to the catalytic activity. It was shown that, regardless of the amount of introduced K, the activity of the K-modified catalysts was much lower than that of the undoped catalyst. K was found to be in the form of oxide; however, it was unstable and reducible to metallic K, which easily volatilised from the catalyst surface under activation conditions. In addition, potassium doping resulted in the sintering of the catalyst, the decrease in the surface basicity, and contributed to the loss of the active sites, mainly due to the coverage of Co surface by residual K species.

Development of Ni-doped A-site lanthanides-based perovskite-type oxide catalysts for CO2 methanation by auto-combustion method.

Engineering the interfacial interaction between the active metal element and support material is a promising strategy for improving the performance of catalysts toward CO2 methanation. Herein, the Ni-doped rare-earth metal-based A-site substituted perovskite-type oxide catalysts (Ni/AMnO3; A = Sm, La, Nd, Ce, Pr) were synthesized by auto-combustion method, thoroughly characterized, and evaluated for CO2 methanation reaction. The XRD analysis confirmed the perovskite structure and the formation of nano-size particles with crystallite sizes ranging from 18 to 47 nm. The Ni/CeMnO3 catalyst exhibited a higher CO2 conversion rate of 6.6 × 10-5 molCO2 gcat -1 s-1 and high selectivity towards CH4 formation due to the surface composition of the active sites and capability to activate CO2 molecules under redox property adopted associative and dissociative mechanisms. The higher activity of the catalyst could be attributed to the strong metal-support interface, available active sites, surface basicity, and higher surface area. XRD analysis of spent catalysts showed enlarged crystallite size, indicating particle aggregation during the reaction; nevertheless, the cerium-containing catalyst displayed the least increase, demonstrating resilience, structural stability, and potential for CO2 methanation reaction.

Improving the catalytic performance of Co/BaCeO3 catalyst for ammonia synthesis by Y-modification of the perovskite-type support.

Y-modified perovskite-type oxides BaCe1-x Y x O3-δ (x = 0-0.30) were synthesised and used as supports for cobalt catalysts. The influence of yttrium content on the properties of the support and catalyst performance in the ammonia synthesis reaction was examined using PXRD, STEM-EDX, and sorption techniques (N2 physisorption, H2-TPD, CO2-TPD). The studies revealed that the incorporation of a small amount of yttrium into barium cerate (up to 10 mol%) increased specific surface area and basicity. The catalyst testing under conditions close to the industrial ones (T = 400-470 °C, p = 6.3 MPa, H2/N2 = 3) showed that the most active catalyst was deposited on a support containing 10 mol% Y. The NH3 synthesis reaction rate was 15-20% higher than that of the undoped Co/BaCeO3 catalyst. The activity of the catalysts decreased with further increasing Y content in the support (up to 30 mol%). However, all the studied Co/BaCe1-x Y x O3-δ catalysts exhibited excellent thermal stability, over 240 h of operation. The particularly beneficial properties of the catalyst containing 10 mol% of Y were associated with the highest basicity of the support surface, favourable adsorption properties (suitable proportion of weakly and strongly hydrogen-binding sites), and preferred size of cobalt particles (60 nm). The Co/BaCe0.90Y0.10O3-δ catalyst showed better ammonia synthesis performance compared to the commercial iron catalyst (ZA-5), giving prospects for process reorganisation towards energy-efficient ammonia production.

Optimizing CO2 methanation: effect of surface basicity and active phase reducibility on Ni-based catalysts

CO2 methanation presents an intriguing avenue for utilizing carbon dioxide and generating methane as synthetic natural gas. Both reducibility and basicity of catalysts play a major role in catalytic performances improvement.

Effect of surface modification of Fe/g-C3N4 catalyst on the product distribution in CO hydrogenation

Carbon nitride (g-C3N4) prepared using thermal condensation of urea was pretreated by H2O2/NH3·H2O and used as support to obtain Fe/g-C3N4 catalyst via impregnation method. The catalytic performance of the catalysts both before and after modification was investigated in CO hydrogenation. Combining detailed characterizations, such as XRD, SEM, TEM, FT-IR, TG, CO2-TPD, CO-TPD, H2-TPR, contact angle measurement, and N2 physical adsorption and desorption, we investigated the effects of surface pretreatment on the texture properties of Fe/g-C3N4 catalysts and the product distribution of CO hydrogenation. The results demonstrate that various pretreatment techniques have significant influences on the textural properties and catalytic performance of the catalysts. The prepared g-C3N4 with a typical honeycomb structure has strong interaction with highly dispersed Fe. Both before and after modification, the materials are hydrophilic, and the hydrophilicity is increased after treatment with H2O2 and NH3·H2O. Treatment with H2O2 enhances surface hydroxyl groups. NH3·H2O treatment improves surface amino groups, promotes CO adsorption, and facilitates the formation of Fe(NCN) phase. The surface basicity of all pretreated catalysts is enhanced. The water gas shift (WGS) reaction activity of the two-step modified catalyst Fe/AM-g-C3N4 was lower, and the CO2 selectivity in CO hydrogenation was reduced to 11.61%. Due to the enhanced basicity of Fe/AM-g-C3N4, the secondary hydrogenation ability of olefins was inhibited to obtain higher olefin selectivity with C= 2–C= 4 of 32.37% and an O/P value of 3.23.

Propylene Production via Oxidative Dehydrogenation of Propane with Carbon Dioxide over Composite MxOy-TiO2 Catalysts.

The CO2-assisted oxidative dehydrogenation of propane (ODP) was investigated over titania based composite metal oxides, 10% MxOy-TiO2 (M: Zr, Ce, Ca, Cr, Ga). It was found that the surface basicity of composite metal oxides was significantly higher than that of bare TiO2 and varied in a manner which depended strongly on the nature of the MxOy modifier. The addition of metal oxides on the TiO2 surface resulted in a significant improvement of catalytic performance induced by a synergetic interaction between MxOy and TiO2 support. Propane conversion and propylene yield were strongly influenced by the nature of the metal oxide additive and were found to be superior for the Cr2O3-TiO2 and Ga2O3-TiO2 catalysts characterized by moderate basicity. The reducibility of the latter catalysts was significantly increased, contributing to the improved catalytic performance. This was also the case for the surface acidity of Ga2O3-TiO2 which was found to be higher compared with Cr2O3-TiO2 and TiO2. A general trend was observed whereby catalytic performance increased significantly with decreasing the primary crystallite size of TiO2. DRIFTS studies conducted under reaction conditions showed that the adsorption/activation of CO2 was favored on the surface of composite metal oxides. This may be induced by the improved surface basicity observed with the MxOy addition on the TiO2 surface. The Ga2O3 containing sample exhibited sufficient stability for about 30 h on stream, indicating that it is suitable for the production of propylene through ODP with CO2 reaction.

Synthesis of highly basic, low-cost iron oxides from tin can waste as valorization of municipal solid waste and study of their catalytic efficiency as potent catalysts for MEK production

In the present study, low-cost iron oxide catalysts have been prepared by a simple precipitation method using tin food can waste as a source of iron and sodium hydroxide or ammonium hydroxide solution as a precipitating agent. The prepared catalysts were characterized by thermogravimetric analysis (TGA), differential thermal analysis (DTA), X-ray diffraction (XRD), FT-IR spectra, scanning electron microscopy (SEM), EDAX quantitative elemental analysis, and BET surface area measurements. Surface basicity of iron oxide catalysts was measured by adsorption of carbon dioxide as an acidic probe molecule, followed by desorption measurements using the TGA technique. The prepared iron oxide catalysts were tested by dehydrogenation of 2-butanol to methyl ethyl ketone (MEK) at a temperature range of 275–375 °C. Commercial iron oxide was tested under identical reaction conditions for comparison with the prepared catalysts. The results indicated the superiority of the prepared catalysts over the commercial one and the superiority of the catalyst prepared using NaOH over that prepared using NH4OH as precipitating agents. The use of different precipitating agents affects the surface morphology and, consequently, the catalytic activity of the produced iron oxide catalysts.Graphical abstract

The Relevance of Carbon for Energy Transition: Ways to Assess Its Surface Properties and Standardize Their Characterization

Technical carbon blacks (CB) are well-established materials that gain increasing attraction in the context of electrification and transition towards renewable energy sources. Their availability, low price, and favorable properties (e.g., conductivity, specific surface area) make them ideal candidates as additives in batteries or as support material for electrocatalysts, e.g., in fuel cells [1]. However, due to the vast number of producers and manufacturing processes large variations in their properties can be observed making product quality control difficult.To this end, we report on ways and methods to standardize the characterization of CB materials that are specifically designed for fuel cell and battery applications. By applying analytical centrifugation (AC) and combining it with complementary methods (e.g., electrical conductivity measurements, Boehm titration), we identify parameters like particle size, morphology, and surface properties that are influential for the overall value chain in electrode manufacturing. This helps to minimize the effects of material inherent property fluctuations as well as process-related fluctuations on the final electrochemical performance.Four different CBs were investigated, and their various properties were assessed. Our results show that the degree of graphitization and hence the electrical conductivity in a CB can be correlated with the overall surface basicity. Moreover, these properties can be linked with their dispersibility features on the ink formulation level and studied via liquid phase characterization using Hansen Parameters (Fig. 1) [2]. In brief, the higher the basicity of a CB surface is, the better the interaction with non-polar/mildly polar aprotic solvents becomes. This is especially true when oxygen-containing surface functional groups that cause a higher overall polarity of the material are missing.Figure 1: Hansen interaction space (for polar, disperse and hydrogen bonding interactions) showing the location of various solvents that are used as probe liquids for determining the Hansen Similarity Parameters of the respective CBs in 3D space (a) and 2D representations (b-d).To conclude, we were able to identify differences in CB materials by applying AC-based characterization techniques. Those differences can have a huge impact on the overall process chain of electrode production as they are decisive not only in formulation considerations but also in the subsequent processing steps. In the future, we will focus on closing the process chain and try to apply our characterization routines for an efficient identification of decisive process parameters at every stage of production. Additionally, we want to transfer knowledge gained from lab-scale techniques (e.g., sonication methods) to industrially relevant mixing procedures. By this, we will give electrode manufacturers tools at hand for a fast characterization of feed materials to save costly and lengthy adjustments of processes due to quality fluctuations. An accelerated implementation of green energy solutions is sought by this approach.

Tailoring the microenvironment of MOF-derived Co nanoparticles for efficient higher alcohol production via Fischer-Tropsch synthesis

Alcohols are considered as high value-added products from Fischer–Tropsch synthesis (FTS). Efficient conversion of syngas into higher alcohols (C2+OH, HA) is of great significance but poses grand challenges. Herein, a series of nitrogen-doped carbon confined Co catalysts (Co@NC and K-Co@NC) have been prepared via pyrolysis of different Co-containing ZIF-67 and K addition by ball milling. After K addition for modulation of the microenvironment of Co-containing catalysts, the K-Co@NC catalysts display an enhanced HA selectivity in FTS, with a maximum HA selectivity up to ∼30 % and a space time yield of HA (STYC2+OH) of 58 mg·gcat−1·h−1, reflecting the highest HA productivities for Co-based heterogeneous catalysts under similar FTS conditions. Comprehensive characterization studies reveal that K addition, could not only modulate the surface basicity for suppressing the side reactions, but also act as electron donors for promoting the formation of Co2C species during the FTS process, facilitating CO non-dissociative adsorption and CO insertion for improving alcohol formation in FTS. This work provides a feasible strategy for the design of highly efficient Co-based FTS catalysts for production of HA by utilizing MOF materials as the scaffolds.

Dry Reforming of Methane over Li-Doped Ni/TiO2 Catalysts: Effect of Support Basicity

In this research, we investigate the impact of Li doping on a TiO2 support, synthesized through the sol-gel method, with a focus on varying the aging time. Our objective is to elucidate how aging duration and doping influence the surface basicity, thereby mitigating carbon formation and amplifying the catalytic efficacy of Ni-loaded catalysts (15 wt.%). Essential characterization techniques encompass X-ray diffraction, H2-TPR, FE-SEM, N2-physisorption, DLS, FTIR, and Raman spectroscopies. Our findings reveal that extended aging periods promote the development of a basic character, attributable to oxygen defects within TiO2. This inherent trait bears significant implications for catalyst performance, stability, and carbon formation during the reaction. Remarkably, the catalyst with the highest catalytic activity and stability boasts an 85% relative basicity, a property also induced by incorporating lithium into the TiO2 support.

Optimization of nitrogen-doped sludge char preparation and mechanism study for catalytic oxidation of NO at room temperature

Catalytic oxidation of NO at room temperature was carried out over nitrogen (N)-doped sludge char (SC) prepared from pyrolysis of municipal sewage sludge, and urea was adopted as nitrogen source. The effects of different N-doping methods (one-step and two-step method), dried sludge (DS)/urea mass ratios (5:1, 4:1, 3:1, 2:1, and 1:1), SC preparation procedures (pyrolysis only, pyrolysis with acid washing, and pyrolysis with KOH activation and acid washing), and different pyrolysis temperatures (500, 600, 700, and 800°C) on the catalytic oxidation of NO were compared to optimize the procedure for SC preparation. The results indicated that N-doping could obviously promote the catalytic performance of SC. The one-step method with simultaneous sludge pyrolysis (at 700°C), KOH activation, and N-doping (DS/urea of 3:1) was the optimal procedure for preparing the N-doped SC with the NO conversion rate of 54.7%, whereas the optimal NO conversion rate of SC without N-doping was only 47.3%. Urea worked both as carbon and nitrogen source, which could increase about 2.9%-16.5% of carbon and 24.8%-42.7% of nitrogen content in SC pyrolyzed at 700°C. N-doping significantly promoted microporosity of SC. The optimal N-doped SC showed specific surface areas of 571.38 m2/g, much higher than 374.34 m2/g of the optimal SC without N-doping. In addition, N-doping also increased amorphousness and surface basicity of SC through the formation of N-containing groups. Finally, three reaction paths, i.e. microporous reactor, active sites, and basic site control path, were proposed to explain the mechanism of N-doping on promoting the catalytic performance of NO.

Sr Promoted Ni/W-Zr Catalysts for Highly Efficient CO2 Methanation: Unveiling the Role of Surface Basicity.

This study explores the employment of CO2 methanation for carbon dioxide utilization and global warming mitigation. For the first time, in this work, we combine the interesting properties of the WO3-ZrO2 support and the benefits of Sr to improve the performance of Ni-based catalysts in this reaction. Sr loading on 5Ni/W-Zr samples is increased to 3 wt %, resulting in improved surface basicity through strong basic site formation. After 300 min, the 5Ni + 3Sr/W-Zr catalyst exhibits high activity and stability, achieving 90% CO2 conversion and 82% CH4 yield compared to 62 and 57% on 5Ni/W-Zr. Limited sintering and absence of carbon deposits are confirmed by temperature-programmed oxidation, XRD, Raman, and TEM analyses at 350 °C for 300 min. Sr promotion creates additional CO2 adsorption and conversion sites, enhancing the catalytic performance.

Pt-Nb2O5-TiO2 based semiconductors for photo-reforming of glucose and fructose aqueous solutions

The conversion of biomass derivatives into fuels and valuable compounds under green conditions is increasingly attracting the attention of the scientific community. In this study, the photo-reforming of aqueous glucose and fructose solutions in the presence of 0.5 wt% Pt-loaded homemade bare and Nb2O5-TiO2 catalysts was investigated to maximize the activity of titania for both hydrogen production and valuable chemical production. The most efficient sample was the home-prepared Pt-4 %Nb2O5-HP, for both glucose and fructose conversion, with the highest H2 productivity and the highest selectivity towards partially oxidized compounds. The behaviour of the Pt-4 %Nb2O5-HP derives from a favourable compromise of some surface and intrinsic electronic properties as, for instance, photoluminescence, zeta potential and surface acidity. The presence of Nb2O5 decreased the recombination rate of photoproduced charges. Photo-deposition of Pt was essential for H2 production and, surprisingly, also increased the basicity of the TiO2 surface; an increase in surface acidity was measured when only niobium oxide was added, whereas stronger basic sites were observed in the simultaneous presence of Pt and niobium oxide.

Biodiesel production from transesterified yellow grease by ZSM-5 zeolite-supported BaO catalyst: process optimization by Taguchi’s experimental design approach

Methanolysis of yellow grease (YG) was performed to synthesize its corresponding methyl ester (YGME) using BaO loaded on ZSM-5 (BaO/ZSM-5) as a heterogeneous base catalyst that was prepared via metallic solution hydrolysis method and characterized using N2 adsorption–desorption (BET), surface basicity, XRD, TGA/DTA, SEM, FTIR and Raman techniques.### The Taguchi design approach was utilized to optimize the transesterification process factors, and among the parameters studied, calcination temperature was found to have a significant influence on YGME yield. At 70 ℃ for 3 h, a YGME yield of 95.9 ±0.94\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\pm 0.94$$\\end{document}% was obtained using a methanol/YG molar ratio of 15:1 and 1 g (2 wt.% of YG used) of BaO/ZSM-5 sample calcined at 700 ℃. The BaO/ZSM-5 catalyst was reused six times with only a 15% decrease in activity.