Acid Properties Of Catalysts Research Articles

Effect of the reorganization of acid sites induced by metal species on TiO2 supports on the conversion of furfural to acetals and ethers

For the catalytic hydrogenation of furfural (FFR) over supported metal catalysts, acetals and ethers were often observed as by-products when alcohols were used as solvents. The presence of specific acid sites on the catalyst led to the conversion of FFR to acetals and ethers. To understand the effect of the interaction between metal species and oxide supports on the acid properties of catalysts and the conversion of FFR to acetals and ethers, anatase TiO2 (TiO2-A), rutile TiO2 (TiO2-R) and these TiO2 supported Ni catalysts were studied as models. The relationship between the acid properties of these samples and FFR conversion pathways in isopropanol was revealed. The interaction between Ni species and TiO2 supports was found to selectively remove Brønsted acid sites on the TiO2 supports in the absence of H2, thereby inhibiting the conversion of FFR to acetals and ethers in N2. However, the presence of high-pressure H2 during the reaction induced the formation of new Brønsted acid sites on Ni/TiO2 catalysts via hydrogen spillover, promoting the acetalization of FFR to acetals and the hydrogenolysis of acetals to ethers. The Ni/TiO2-A catalyst exhibited higher activity in catalyzing the conversion of FFR to acetals and ethers compared to the Ni/TiO2-R catalyst. This work provides reference information for the selective regulation of acid-catalyzed reaction pathways of FFR in alcohols.

Enhancing reductive conversion of levulinic acid and levulinates to γ-valerolactone: Role of oxygen vacancy in MnOx catalysts

Oxygen vacancies (Ov) in metal oxides play a crucial role in modifying the electronic and acidic properties of catalysts, thereby influencing their catalytic activity. This study explores the impact of Ov in MnOx catalysts on their acidic and catalytic properties for the Meerwein–Ponndorf–Verley reduction of levulinic acid (LA) and levulinate to γ-valerolactone (GVL). Various characterization techniques demonstrate that surface Ov significantly modulate the acidic properties of MnOx catalysts, positively correlating with Lewis/Brønsted acid ratio and GVL yield. In situ DRIFTS and DFT calculations further unveil the reaction mechanism, revealing that Ov facilitate the activation and dehydrogenation of isopropanol and subsequent hydrogen transfer and hydrogenation of LA, leading to enhanced GVL production. These insights underscore the pivotal role of Ov in MnOx catalysts for the efficient conversion of LA to GVL, highlighting their importance in improving catalytic performance.

Highly efficient hydrolysis of cellulose to sugars using supercritical CO2 as a green acid catalyst and solvent

Rapid depolymerization of cellulose into processable monomers (e.g., sugars) using solid acid catalysts is an important step for cost-effective biofuel and biochemical production, but has not yet been achieved due to the limited contact between solid cellulose and solid catalysts. Herein, the unique roles of supercritical CO2 (i.e., scCO2) as an in-situ acid catalyst and reaction solvent in achieving the ultra-fast full solid catalytic hydrolysis of cellulose are disclosed for the first time. When the ball-milling pretreated cellulose was hydrolyzed using oxidized carbon catalysts at 150 °C and 100–300 bar-CO2, the hydrolysis kinetics remarkably increased by 3× for conversion and 5× for glucose, resulting in ∼90% conversion and ∼85% total sugar selectivity at 20 min. The hydrolysis rate obtained with scCO2 here was higher than conventional ones with toxic and unrecyclable homogeneous catalysts (e.g., HCl) under harsh reaction conditions (i.e., 180–220 °C and pH of 1–2). A comprehensive reaction engineering study (e.g., temperature, CO2 pressure, stirring speed, catalyst acid properties) combined with the estimation of the solution pH by the CO2 phase equilibrium model and the in-situ and ex-situ monitoring of the phase behavior of the H2O/scCO2 solution were conducted to quantify the activity promotion by scCO2 and understand the acid-solvent roles of scCO2 toward the enhanced hydrolysis of cellulose. Specifically, the formation of the Pickering emulsions at the interface between scCO2 and water and their impact on the enhancement of the cellulose-carbon contact were proposed and verified in detail.

A catalyst acid property-included stoichiometric coefficient model for catalytic pyrolysis of hydrocarbon mixtures

Process modeling is considered an effective way to achieve refined management in the petrochemical industry, and is also the foundation and necessary link of intelligent chemical platform construction. This study aims to the simulation of the formation of gaseous products for the catalytic pyrolysis of representative naphtha compositions using a stoichiometric coefficient model. Firstly, the interaction mechanism of n/cyclo-paraffins was investigated using a pseudo-first-order kinetic model, and the cracking activity of hydrocarbon mixtures was quantified using the carbon number and cyclo-paraffin content. Subsequently, a database of the stoichiometric coefficients of the gaseous products was constructed. Considering the acid properties of the catalysts, a catalyst acid property-included stoichiometric coefficient model was developed to adapt to varying feedstock composition and catalyst systems, which could reflect gaseous production in the catalytic pyrolysis of multi-component mixed hydrocarbons. Moreover, the simulation using the present model shows that the production of light olefins in the catalytic pyrolysis of mixed hydrocarbons can be increased under the optimized catalyst acid properties. Hence, this study aims to provides theoretical guidance for the prediction of product distribution as well as the design and selection of catalysts used in the catalytic pyrolysis processes for multi-component mixed hydrocarbon.

WO3-based porous MCM-48 catalysts for renewable acrolein synthesis by the dehydration of glycerol

The gas-phase selective dehydration of glycerol to acrolein was studied over x%W (x: 5, 15, 25, and 35 %, w/w) supported on MCM-48. Microporous silica MCM-48 was synthesized to produce three-dimensional cubic crystals with a high surface area and resistance to hydrolytic pressure. Tungsten oxide (WO3) based solid acid catalysts supported on MCM-48 were prepared by two distinct synthesis methods, namely, oxalic acid added sol–gel (HSG) and nonhydrolytic sol–gel (NHSG) methods. The morphological and textural properties of catalysts were characterized by XRD, BET, SEM, Raman, XPS, and FT-IR techniques. The acidic properties of catalysts were elucidated by FTIR pyridine-adsorption and NH3-Temperature Programmed Desorption (NH3-TPD). The total surface acid sites’ concentration, Brønsted (B) and Lewis (L) acid concentrations, and B/(B+L) ratios were calculated from NH3-TPD and pyridine-FTIR. The steady acrolein yields were obtained with the optimal catalysts (15 %W and 25 %W loaded MCM-48 for HSG and NHSG, respectively). This study demonstrated that the medium-strength surface acidity and B/(B+L) ratios for glycerol dehydration to acrolein were correlated with both the activity and the selectivity of acrolein.

Experiment and a catalyst acid property‐included global reaction modeling for catalytic pyrolysis of 1‐pentene

AbstractThe acid property of the catalyst is usually one of the most important parameters for the selection and design of catalysts for catalytic pyrolysis of 1‐pentene. Here, seven catalysts with similar pore properties and different acid properties were evaluated and characterized in terms of three key properties: Total acid amount (TA), Brønsted to Lewis acid ratio (B/L), and strong to weak acid ratio (S/W). A database of the stoichiometric coefficients of 26 pyrolysis products was constructed. Then, a novel catalyst acid property‐included global reaction modeling method was developed, which was used to predict the yields of the 26 pyrolysis products. Besides, a suitable range of TA, B/L, and S/W was obtained for enhancing ethylene and propylene. The model thus can predict the product composition, and be used for the design and selection of the acid properties of catalysts. This simulation method can also be extended to other hydrocarbon systems.

Synthesis and consequence of Zn modified ZSM-5 zeolite supported Ni catalyst for catalytic aromatization of olefin/paraffin

Zn modified ZSM-5 zeolite supported Ni bifunctional catalysts were prepared by in-situ hydrothermal synthesis (Zn-Ni-ZSM-5), co-impregnation method (Zn-Ni/ZSM-5) as well as combining in-situ hydrothermal synthesis of Zn-ZSM-5 and sequential impregnation of Ni (Ni/Zn-ZSM-5) and used for the selective converting olefin to aromatics applicable for FCC gasoline hydro-upgrading. The Lewis (L) acid sites generated by ZnOH+ species and hydrogenation active sites from Ni0 species were varied with preparation method, in which their locations at the external surface or micropores of zeolite changed the acid properties of catalysts. Comparing to the Zn-Ni/ZSM-5 from the co-impregnation method, direct in-situ hydrothermal method could incorporate Zn and Ni species within zeolite, which makes the strong interaction between the metal species and the framework Al to form medium-strong L acids (ZnOH+/NiOH+). This leads to the decrease of ratio of Brønsted acid sites to L acid sites (B/L) from 0.40 to 0.12 and the difficulty in reducing of Ni cations to Ni0 from 57% to 30% Ni0 percent. Ni/Zn-ZSM-5 sample prepared by incorporating Zn species into micropores and sequential depositing Ni species at the external surface of zeolite possesses a low B/L ratio similar to Zn-Ni-ZSM-5 (0.20 versus 0.12) but a much higher Ni0 percent (52% versus 30%). Zn-Ni-ZSM-5 shows closer intimacy between Zn and Ni species comparing to Zn-Ni/ZSM-5 and Ni/Zn-ZSM-5. For the 1-hexene aromatization, the formed iso-alkene at acid sites was quickly saturated to iso-alkanes by the adjacent Ni0 particles over Ni-Zn-ZSM-5 catalyst in hydrogen steam. However, the location of aromatization active sites (ZnOH+, L acid sites) in micropores and hydrogenation active sites (Ni0 species) on external surface of Ni/Zn-ZSM-5 makes the tandem conversion of n-alkene → iso-alkene → aromatics, rather than the n-alkene → iso-alkene → iso-alkane. Thus, Zn-Ni-ZSM-5 with close intimacy of ZnOH+ and Ni0 particles shows a high iso-alkane selectivity (27.9% iC4+), while Ni/Zn-ZSM-5 exhibits a high aromatics selectivity (39.6 %) in the conversion of 1-hexene in hydrogen steam. Similar results have also found in the conversion of n-heptane. Here, the control of the intimacy of Zn and Ni in ZSM-5 zeolites has been realized to be a good protocol to adjust the selective conversion of olefins/alkanes to aromatics versus iso-alkanes.

Insight into reaction path and mechanism of catalytic cracking of n-hexane in HZSM-5 zeolites

The n-hexane was used as a model compound to study the catalytic cracking behavior of light hydrocarbon in HZSM-5 zeolites, and the law of product selectivity of real acid-catalyzed reaction was investigated by analyzing the product distributions. The results showed that no pyrolysis reaction was found at 300°C. Only the acid catalytic reaction took place by the mechanism of carbocation, whose activity was positively correlated to the amount of Brønsted (B) acid sites. The selectivity of ethane, ethylene and propane was negatively correlated, while that of propylene was positively correlated with the Si/Al ratios and catalyst to oil ratios, suggesting that low acid density might be more favorable for monomolecular cracking reactions. It was worth nothing that the total selectivity of C4 products was much higher than that of C2 products. Combined with the quantum chemistry calculation results, it could be confirmed that the super-stability of C2H+ 5 carbenium ion from the monomolecular cracking of n-hexane made it difficult to produce ethylene and ethane through hydrogen transfer reaction. It’s easier to form a C8 carbenium ion (C8H+ 19) with another n-hexane molecule, and then to generate more C4 products. These results revealed the nature of the low selectivity of ethylene in light hydrocarbon catalytic cracking products. It could be concluded that the product selectivity of catalytic cracking of light hydrocarbons could be modulated by controlling reaction paths depending on the catalyst acid properties and the catalyst to oil ratios. This work will provide important theoretical support for the catalyst design and process development of naphtha catalytic cracking.

Enhanced catalytic performance of isobutane direct dehydrogenation over Pt-In catalysts: Effect of different fluorides modified hydrotalcite-like derivatives

A series of MgF2-modified hydrotalcite-like (HT) derivatives supported Pt-In catalysts PtInHTR-X (X = NH4F, NaF and KF, R = reduced catalyst) were prepared by combination of hydrothermal method, alkali-etching and impregnation strategy and applied to direct dehydrogenation of isobutane to isobutene. The catalysts and precursors were characterized by XRD, SEM, TEM, XPS, TG, O2-TPO and low temperature N2 adsorption-desorption isotherms. The formation of MgF2 phase as dopant to modify the catalyst can influence the pore structure and even the surface acid properties of catalysts. Especially, compared with the three catalysts, PtInHTR-KF catalyst had better stability of isobutene selectivity of over 95% after 9 h reaction, and PtInHTR-NH4F and PtInHTR-NaF catalysts exhibited more stable isobutane activity of 60%. One of the reasons for this catalytic performance is that small particles of MgF2 and unsaturated MgF2 can provide weak acidic sites which can inhibit coke deposition. And it was found the improved catalytic performance was also related to the appropriate In3+/In0 ratio, well-dispersed Pt species and the excellent anti-sintering ability of catalysts modified MgF2.

New approach to determine the surface and interface thermodynamic properties of H-\u03b2-zeolite/rhodium catalysts by inverse gas chromatography at infinite dilution

The thermodynamic surface properties and Lewis acid–base constants of H-β-zeolite supported rhodium catalysts were determined by using the inverse gas chromatography technique at infinite dilution. The effect of the temperature and the rhodium percentage supported by zeolite on the acid base properties in Lewis terms of the various catalysts were studied. The dispersive component of the surface energy of Rh/H-β-zeolite was calculated by using both the Dorris and Gray method and the straight-line method. We highlighted the role of the surface areas of n-alkanes on the determination of the surface energy of catalysts. To this aim various molecular models of n-alkanes were tested, namely Kiselev, cylindrical, Van der Waals, Redlich–Kwong, geometric and spherical models. An important deviation in the values of the dispersive component of the surface energy {gamma }_{s}^{d} determined by the classical and new methods was emphasized. A non-linear dependency of {gamma }_{s}^{d} with the specific surface area of catalysts was highlighted showing a local maximum at 1%Rh. The study of RTlnVn and the specific free energy ∆Gsp(T) of n-alkanes and polar solvents adsorbed on the various catalysts revealed the important change in the acid properties of catalysts with both the temperature and the rhodium percentage. The results proved strong amphoteric behavior of all catalysts of the rhodium supported by H-β-zeolite that actively react with the amphoteric solvents (methanol, acetone, tri-CE and tetra-CE), acid (chloroform) and base (ether) molecules. It was shown that the Guttmann method generally used to determine the acid base constants KA and KD revealed some irregularities with a linear regression coefficient not very satisfactory. The accurate determination of the acid–base constants KA, KD and K of the various catalysts was obtained by applying Hamieh’s model (linear regression coefficients approaching r2 ≈ 1.000). It was proved that all acid base constants determined by this model strongly depends on the rhodium percentage and the specific surface area of the catalysts.

Citric acid-modified beta zeolite for polyoxymethylene dimethyl ethers synthesis: The textural and acidic properties regulation

Beta zeolite exhibits satisfactory catalytic activity in the synthesis of polyoxymethylene dimethyl ethers. However, the microporous channels of beta zeolite have adverse effects on mass transfer of macromolecules. In this work, it was found that the textural and acidic properties of catalysts could be improved by citric acid treatment. Extensive characterization confirmed that citric acid induced significant pore-expanding on catalysts, and its dealumination and realumination effect could lead to reduced amount of total acid sites and increased amount of Brønsted acid sites (BAS). Meanwhile, a good positive correlation was found between amount of external weak BAS and initial reaction rate. It was speculated that BAS with relatively weak acid strength might be the primary active sites in this reaction. Compared with the blank sample, the initial reaction rate of optimal catalyst was increased by 100 %, and the conversion of trioxane was increased by 86.5 %, indicating a significantly improved catalytic activity.

Facile moderate-temperature hydrothermal design of nanocrystalline coffin-shaped ZSM-5 catalyst for transformation of CH3OH to C2H4/C3H6

Different crystallization times were studied during hydrothermally synthesis of ZSM-5 framework at moderate temperature to investigate the physicochemical properties and MTO catalytic behavior. The ZSM-5 samples were synthesized at moderate temperature (250 °C) and different crystallization times (24, 18, 12, 6, and 3 h). The synthesized samples were analyzed by XRD, FESEM, EDX, BET-BJH, FTIR, and TPD-NH3 experimental approaches. The results revealed that the purity of crystalline phase, nucleation rate, crystallinity, morphology, porosity, and acidic properties of catalysts depended on the condition of moderate temperature synthesis with strong dependence on crystallization time. This was indicative of the ZSM-5 zeolite prepared at short crystallization time (3 h) facilitated facile design of coffin-shaped ZSM-5 particles which were capable of producing improved properties could provide some useful indication for MTO reaction. So, the MTO catalytic process was carried out using the specific MTO reaction condition of T = 460 °C, CH3OH: H2O = 1:1 (vol:vol) and the feed gas hourly space velocity (GHSV) = 10500 cm3/gcat.h). The ZSM-5(250-3) catalyst showed an enhanced selectivity toward desired olefins, whereas it presented 65% selectivity to propylene and 9% selectivity to ethylene after 35 h on stream. The possible reaction pathway for facile design synthesis of ZSM-5 catalyst via moderate temperature was proposed.

Catalytic Oxidation of Trichloroethylene over RuO2 Supported on Ceria-zirconia Mixed Oxide

Ru/Ce-Zr catalysts were prepared by impregnation of Ru on the hydrothermally synthesized Ce-Zr mixed oxide with different molar ratio of Ce/Zr. The resultant products were systematically characterized by inductively coupled plasma(ICP), X-ray diffraction(XRD), scanning electron microscopy(SEM)/energy dispersive spectrometry(EDS), H2-temperature programmed reduction(H2-TPR), NH3-temperature programmed desorption(NH3-TPD) and X-ray photoelectron spectroscopy(XPS). It was proved by H2-TPR and NH3-TPD that the introduction of Ru can improve the activity of oxygen of catalysts and the presence of Zr contributes to the increments of acid properties of catalysts. When the molar ratio of Ce-Zr was 8:4, the quantity of Ru was 0.9%(mass ratio), and the calcined temperature of catalysts was at 400 °C, the removal rate of 90% for trichloroethylene(TCE) was reached at 250 °C for 5360 mg/m3 TCE and the stability of the catalysts was investigated under the condition. The results showed that the high removal rate can be maintained for at least 90 h, which is promising for industrial application.

Preparation of 2-Methylnaphthalene from 1-Methylnaphthalene via Catalytic Isomerization and Crystallization

Large amounts of residual 1-methylnaphthalene are generated when 2-methylnaphthalene is extracted from alkyl naphthalene. In order to transform waste into assets, this study proposes a feasible process for preparing 2-methylnaphthalene from 1-methylnaphthalene through isomerization and crystallization. The 1-methylnaphthalene isomerization was carried out in a fixed-bed reactor over mixed acids-treated HBEA zeolite. The results showed that acidic properties of catalysts and reaction temperature were associated with the 2-methylnaphthalene selectivity, yield and catalytic stability. At a high reaction temperature of 623 K, the 2-methylnaphthalene yield was 65.84 %, and the deactivation rate was much lower. The separation of reaction products was then investigated by two consecutive crystallization processes. Under optimal conditions, the 2-methylnaphthalene purity attained 96.67 % in the product, while the yield was 87.48 % in the refining process.

Continuous Production of 5‐Hydroxymethylfurfural from Monosaccharide over Zirconium Phosphates

Abstract5‐hydroxymethylfurfural (HMF), an important platform compound produced from lignocellulosic biomass, is widely applied in petrochemical industry for downstream synthesis of medical supplies or intermediate of the other important chemicals by the typical catalytic processes. A continuous production route was developed to yield HMF from monosaccharides by using zirconium phosphate (ZrP) with different Zr/P ratios as catalysts. Its physicochemical properties were then characterized by Brunauer‐Emmett‐Teller (BET), X‐ray powder diffraction (XRD), X‐ray photoelectron spectra (XPS), Fourier transform infrared spectroscopy (FT‐IR), pyridine adsorbed Fourier transform infrared spectroscopy (Py‐FT‐IR), X‐ray fluorescence (XRF) and temperature programmed desorption of ammonia (NH3‐TPD) techniques. A mixed phase containing monosaccharide in aqueous and dimethyl sulfoxide (DMSO) phase was applied in the fixed bed to keep the continuous production. The optimized reaction conditions were applied to maximized HMF yield by varying the processing parameters. The highest HMF yield of 56.3% was obtained when using fructose as the feedstock under the reaction condition of 120 °C, 180 min, N2 pressure 2 MPa and DMSO: fructose solution of 9:1 over ZrP with the P/Zr with molar ratio of 2. Comparatively, the glucose conversion of 72% with the HMF yield of 32% were gained under the same conditions using glucose as the feedstock. It is deduced that the ZrP catalysts simultaneously possessing Brönsted/Lewis acid showed synergy in glucose dehydration to HMF. The ZrP catalyst showed good stability and no obvious deactivation was observed after 30 h of time‐on‐stream, due to the primary structure and acidic properties of catalyst can be kept during the reaction. Finally, it is generally efficient for some C6 sugars dehydration to HMF with the Brönsted/Lewis acid synergy of ZrP.

Catalytic oxidation performances of typical oxygenated volatile organic compounds (acetone and acetaldehyde) over MAlO (M = Mn, Co, Ni, Fe) hydrotalcite-derived oxides

In this study, a series of hydrotalcite-derived oxides MAlO (M = Mn, Co, Ni, Fe) were prepared by calcinating of hydrotalcite for acetone and acetaldehyde total oxidation. Detailed results confirmed that the highest of CO2 yield and the lowest amount of by-product was observed over MnAlO catalyst. In particular, the MnAlO catalyst appeared to have the best catalytic performance for acetone and acetaldehyde oxidation with T100 about 170 °C and 150 °C at a high space velocity, respectively. Catalytic activity was significantly governed by the excellent reducibility (Mn4+/Mn3+) and abundant chemical adsorption oxygen species (Oadsorbe/Olattice) of the catalysts. Besides, acid property of catalysts was beneficial to catalytic oxidation process. Interestingly, the lower amounts of by-product (acetaldehyde) were generated for acetone oxidation over MnAlO than those of other catalysts, it did not influence on the total oxidation of acetone due to its superior catalytic activity, it was investigated and analyzed the reaction mechanism of acetone oxidation and the formation of by-product over MnAlO catalyst, the result confirmed that desorption of reactant molecule and negative effect of water vapor play a vital role in the by-product generation and catalytic performances.

Production of γ-valerolactone from furfural by a single-step process using Sn-Al-Beta zeolites: Optimizing the catalyst acid properties and process conditions

A bifunctional Sn-Al-Beta zeolite which possesses isolated Lewis and Brønsted acid sites was prepared by a post-synthesis procedure and applied to the one-pot conversion of furfural to γ-valerolactone (GVL), a value-added chemical. Sn-Al-Beta was capable of catalyzing a cascade of the transfer hydrogenation and hydrolysis of furfural to GVL by the interplay of Lewis and Brønsted acid sites. The degree of dealumination and the tin-incorporation method largely influence the acid properties of the catalyst and the catalyst selectivity. A high yield of GVL up to 60% was obtained with Sn-Al-Beta 7 (Si/Sn=63 and Si/Al=473) at 180°C in 2-butanol.

Effect of the aging time of the precipitate on the activity of Cu/ZnO catalysts for alcohol-assisted low temperature methanol synthesis

Cu/ZnO_X catalysts were prepared by a co-precipitation method with various aging times of the precipitate (X=10min–10h). All prepared catalysts were evaluated in alcohol-assisted methanol synthesis through a low temperature liquid phase reaction using a batch type reactor under a reaction pressure of 50bar at a temperature of 150°C. Unlike the conventional low temperature methanol synthesis, ethanol was adopted as both the solvent and the reaction intermediate in this study. Variation of the aging time of the precipitate led to numerous changes in the surface properties of catalysts, resulting in the different catalytic activity in this reaction. This means that aging time of the precipitate should be precisely controlled for obtaining an efficient Cu/ZnO catalyst by a co-precipitation method. The results of catalytic activities and catalyst characterizations clearly demonstrated that the copper particle size, the morphology, and the strong acidity of the Cu/ZnO catalysts played key roles in this reaction. Small copper particle size, plate-like morphology, and high strong acidity of the catalysts were favorable for efficiently producing methanol in this reaction. Among the Cu/ZnO_X catalysts, the Cu/ZnO_5h catalyst showed the best catalytic activity. According to the proposed reaction pathway, not only the intrinsic activity of metallic copper but also the acid properties of catalysts were important factors to determine the activity of Cu/ZnO catalysts in this reaction.

Effect of Mo-Doped Mesoporous Al-SSP Catalysts for the Catalytic Dehydration of Ethanol to Ethylene

The catalytic dehydration of ethanol to ethylene over the mesoporous Al-SSP and Mo-doped Al-SSP catalysts was investigated. The Al-SSP catalyst was first synthesized by the modified sol-gel method and then doped with Mo by impregnation to obtain 1% Mo/Al-SSP and 5% Mo/Al-SSP catalysts (1 and 5 wt% of Mo). The final catalysts were characterized using various techniques such as XRD, N2physisorption, SEM/EDX, TEM, and NH3-TPD. The catalytic activity for all catalysts in gas-phase ethanol dehydration reaction was determined at temperature range of 200°C to 400°C. It was found that the most crucial factor influencing the catalytic activities appears to be the acidity. The acid property of catalysts depended on the amount of Mo loading. Increased Mo loading in Al-SSP resulted in increased weak acid sites, which enhanced the catalytic activity. Besides acidity, the high concentration of Al at surface of catalyst is also essential to obtain high activity. Based on the results, the most suitable catalyst in this study is 1% Mo/Al-SSP catalyst, which can produce ethylene yield of ca. 90% at 300°C with slight amounts of diethyl ether (DEE) and acetaldehyde.

Saccharification of cellulosic biomass using sulfonated mesoporous carbon‐based catalysts

A series of sulfonated mesoporous carbon‐based catalysts with intact silica template (MC) were prepared through incomplete carbonization of sucrose followed by sulfonation. The MC catalysts were characterized by use of Fourier Transform‐infrared spectra, N2 adsorption–desorption, and titration method. The effects of preparation conditions such as carbonization temperature, amount of carbon precursor, sulfonation time, and temperature on the structural and acidic properties of the catalysts were investigated. Preparation conditions such as amount of carbon precursor, sulfonation time, and temperature significantly influenced the surface area and acidic properties of MC catalysts. The activity of prepared catalysts in saccharification was tested using cellulose and rice straw as substrates and high saccharification yield can be obtained using these catalysts. In saccharification of cellulose without pretreatment, the highest yield of 25.2% of C6 monosaccharide can be attained after reaction at 180°C for 3 h. In saccharification of rice straw, the total monosaccharide yield of 43.4% can be achieved after reaction at 150°C for 1 h. In addition, it was found that despite the versatility of mesoporous structure in varied chemical reactions has been confirmed, acid amount was the most important property that determined the effectivity of cellulose saccharification. © 2015 American Institute of Chemical Engineers Environ Prog, 35: 574–581, 2016