NH3 Temperature-programmed Desorption Research Articles

Acylation of anisole with carboxylic acids catalyzed by tungsten oxide supported on titanium dioxide

Friedel-Crafts (F-C) acylation of anisole with octanoic acid was carried out on tungsten oxide (WO3) supported on various types of oxide supports. We have found that the highest activity was obtained when TiO2 was used as the support. WO3/TiO2 was found to be active in the acylation of anisole with carboxylic acids of varying alkyl chain lengths (C6–C10). It was possible to recycle the WO3/TiO2 catalyst for up to 5 times without deactivation. The turnover frequency (TOF) of the catalyst was closely correlated with the electronegativity of the cation of the support used for WO3. When a strong basic oxide such as CeO2 was used as a support, the acid strength of WO3 was diminished, while the strong acidity of WO3 was retained on a weak basic support like TiO2. This explains why the acid strength and consequently, the activity, were found to be the highest for the WO3/TiO2 catalyst. The trend of the catalytic performance was consistent with the order of acid strength of WO3 on different supports measured by temperature-programmed desorption of NH3.

Morphology-Oriented ZrO2-Supported Vanadium Oxide for the NH3-SCR Process: Importance of Structural and Textural Properties.

ZrO2 supports, with diverse morphologies (hollow sphere, star, rod, mesoporous), were produced using hydrothermal and evaporation-induced self-assembly methods. Zirconia-supported vanadium oxide catalysts were prepared by wet impregnation and used for the low-temperature selective catalytic reduction (SCR) of NO with ammonia. Characterization of catalysts includes N2 physisorption, elementary analysis, X-ray diffraction, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, temperature-programmed reduction by H2, and temperature-programmed desorption of NH3. Significant differences in terms of activity are measured. 3 wt % V2O5 supported on mesoporous ZrO2 (V/MZ) presents excellent N2 yields (>90%, in the 200-400 °C interval), with a wide operating temperature window (NO conversion > 95%, in the 225-425 °C interval), and less interesting performances were obtained when vanadium oxide is supported over stars, hollow spheres, and rods. Surface characterization showed a content of tetravalent vanadium ion, when supported, decreasing in the order of mesoporous > hollow sphere > star > rod. This order is in perfect agreement with the order of performance of the catalyst in the NH3-SCR reaction. The impact of tetravalent ion's presence on the surface is confirmed by diffuse reflectance infrared Fourier transform spectroscopy analysis, Brønsted acid sites generated on the surface, and the V4+-OH species involved in the reaction. The production of more important nitrite species over the tetragonal supported vanadium oxide catalyst could be another reason for the excellent NH3-SCR performance displayed by the V/MZ catalyst. When supported over monoclinic zirconia, like vanadium oxide over star-type morphology, the adsorbed NH3 species (NH4+ and coordinated NH3) reacted with NO x adsorption species (nitrate) to form ammonium nitrate. Ammonium nitrate can be decomposed to N2 and N2O (or NO2). Thus, NO conversion curves and N2 yield curves over tetragonal zirconia (MZ) at lower temperature were ahead of those over V/star ZrO2 because of the higher V4+ surface content and more active B acid sites associated with an easy formation of the nitrito intermediate.

Esterification of Palm Fatty Acid Distillate for Biodiesel Production Catalyzed by Synthesized Kenaf Seed Cake-Based Sulfonated Catalyst

Sulfonated kenaf seed cake (SO3H-KSC) catalyst, was synthesized to aid biodiesel production from palm fatty acid distillate (PFAD). It was chemically activated with phosphoric acid for an impregnation period of 24 h in order to enhance the porosity and the specific surface area of kenaf seed cake (KSC). After the carbonization and sulfonation, the resultant catalyst was characterized with powder X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscope (FESEM), NH3-temperature programmed desorption (NH3-TPD) and thermogravimetric analysis (TGA). The SO3H-KSC catalyst was amorphous in nature and had an acid density of 14.32 mmol/g, specific surface area of 365.63 m2/g, pore volume of 0.31 cm3/g and pore diameter of 2.89 nm. At optimum esterification conditions--reaction time 90 mins, temperature of 338 K, methanol:PFAD molar ratio of 10:1 and catalyst concentration of 2 wt.%—a free fatty acid (FFA) conversion of 98.7% and fatty acid methyl esters (FAME) yield of 97.9% was achieved. The synthesized SO3H-KSC catalyst underwent five reaction cycles while maintaining a fatty acid methyl esters (FAME) yield and free fatty acid (FFA) conversion of >90%. Thus, the SO3H-KSC catalyst was shown to be an excellent application of bio-based material as a precursor for catalyst synthesis for esterification of PFAD.

Improving hydrothermal stability of acid sites in MFI type aluminosilicate zeolite (ZSM-5) by coating MFI type all silica zeolite (silicalite-1) shell layer

Abstract Zeolites have been applied in various chemical processes due to their multi-functionality. In practical use of zeolites, their hydrothermal stability is one of the important factors. We focused on the coating with hydrophobic silicalite-1, which is all silica MFI zeolite. In this work, we investigated the hydrothermal stability of ZSM-5 (MFI type aluminosilicate zeolite) coated with silicalite-1 (all silica MFI zeolite) by the combination of steam treatment and NH3 temperature programed desorption (NH3-TPD). The peak area at higher temperature (h-peak area) in NH3-TPD profiles for core-shell MFI zeolite (ZSM-5/s-1) was unchanged even after steam treatment for 8 h in contrast to uncoated ZSM-5. These results strongly indicate that extremely high Si/Al ratio on the external surface coated with silicalite-1 is highly effective for improving the hydrothermal stability; the hydrophobicity of silicalite-1 probably prevents the penetration of steam into Al sites of ZSM-5. This work opens up a new function of the silicalite-1 layer on ZSM-5 other than improvement of shape selectivity.

Optimization of Cu-Ni-Mn-catalysts for the conversion of ethanol to butanol

In the present study, the catalytic coupling of ethanol into 1-butanol through the Guerbet reaction was studied in a fixed bed reactor over different catalytic systems based on Cu and/or Ni as a hydrogenating/dehydrogenating components, and manganese oxide incorporating acid/base properties over a carbonaceous support, high surface area graphite (HSAG). The catalysts were prepared by wetness impregnation of the support with the corresponding metal nitrates and the resulting material was then reduced in-situ with hydrogen at 573 K for 1 h before reaction. The catalysts were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), specific surface area, NH3 temperature-programmed desorption, CO2 chemisorption, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). From all these techniques it can be deduced that the dimensions of the catalytic ingredients (Cu, Ni, Mn) are in the nanometric scale and homogeneously dispersed on the support. The reactions were performed in a continuous-flow fixed-bed reactor in gas phase with these bifunctional catalysts at 503 K and 50 bar using a stream of helium and ethanol. The bimetallic catalyst 2.5Cu2.5Ni-Mn/HSAG, treated in helium at 723 K prior reduction with hydrogen, exhibited the best catalytic performance in terms of 1-butanol selectivity (39%), presumably due to the synergetic effect of the weak strength acid sites and the strong base sites related to manganese oxide and the Cu-Ni nanoparticles.

Scaling-Up of Bio-Oil Upgrading during Biomass Pyrolysis over ZrO2 /ZSM-5-Attapulgite.

Ex situ catalytic biomass pyrolysis was investigated at both laboratory and bench scale by using a zeolite ZSM-5-based catalyst for selectively upgrading the bio-oil vapors. The catalyst consisted of nanocrystalline ZSM-5, modified by incorporation of ZrO2 and agglomerated with attapulgite (ZrO2 /n-ZSM-5-ATP). Characterization of this material by means of different techniques, including CO2 and NH3 temperature-programmed desorption (TPD), NMR spectroscopy, UV/Vis microspectroscopy, and fluorescence microscopy, showed that it possessed the right combination of accessibility and acid-base properties for promoting the conversion of the bulky molecules formed by lignocellulose pyrolysis and their subsequent deoxygenation to upgraded liquid organic fractions (bio-oil). The results obtained at the laboratory scale by varying the catalyst-to-biomass ratio (C/B) indicated that the ZrO2 /n-ZSM-5-ATP catalyst was more efficient for bio-oil deoxygenation than the parent zeolite n-ZSM-5, producing upgraded bio-oils with better combinations of mass and energy yields with respect to the oxygen content. The excellent performance of the ZrO2 /n-ZSM-5-ATP system was confirmed by working with a continuous bench-scale plant. The scale-up of the process, even with different raw biomasses as the feedstock, reaction conditions, and operation modes, was in line with the laboratory-scale results, leading to deoxygenation degrees of approximately 60 % with energy yields of approximately 70 % with respect to those of the thermal bio-oil.

Composition and kinetic study on template- and solvent-free synthesis of ZSM-5 using leached illite clay

Abstract ZSM-5 was synthesized by using leached illite clay in a template- and solvent-free method, which involves grinding and heating the raw materials without adding solvent water or an organic template. The physicochemical properties of the obtained samples were characterized by X-ray fluorescence, X-ray diffraction, FT-IR spectroscopy, 27Al MAS NMR spectroscopy, scanning electron microscope, energy dispersive X-ray spectroscopy, Py-IR spectroscopy, NH3-temperature-programmed desorption (NH3-TPD) analysis and N2 adsorption-desorption analysis. According to the results, highly crystalline ZSM-5 was obtained at 473 K after 24 h. The kinetic study based on 6.7Na2O–40SiO2–Al2O3 was conducted at 453, 463, and 473 K, and the results suggested that the apparent activation energies for nucleation and growth were 61.0 kJ/mol and 70.9 kJ/mol, respectively Furthermore, the mechanism for template- and solvent-free synthesis of ZSM-5 using leached illite as the silica source was discussed. The catalytic activity of the synthesized ZSM-5 towards toluene disproportionation was comparable to that of commercial ZSM-5.

Isobutane alkylation with 2-butene in novel ionic liquid/solid acid catalysts

For upgrading of petroleum, the alkylation reaction between isobutane and 2-butene can produce a premium blending stock for gasoline. The novel ionic liquid/solid acid catalysts that combined the advantages of ionic liquids (IL) and solid acids (SA) were used to catalyze the C4 alkylation. These catalysts were prepared by dispersion of SO42−/ZrO2 (SZ) into the mesopores MCM-41 and by immobilization of IL on solid supports. The materials have been characterized by X-ray diffraction, nitrogen adsorption isotherms, infrared spectroscopy, magic-angle spinning solid state NMR (29Si/31P MAS NMR), and temperature-programmed desorption of NH3. Results showed that SZ was loaded into the inner pores of MCM-41 mesopores, and the IL played an important role in maintaining the activity of the as-synthesized catalyst. The catalytic behavior of the novel IL/SA catalyst has been investigated in a batch reactor and a continuously stirred tank reactor (CSTR) at 25 °C, respectively. It is found that 5 g IL/SZ-Zn@MCM-41 in the CSTR could continuously catalyze the alkylation reaction more than 240 min. The amount of trimethylpentanes (TMP) and the research octane number (RON) of the obtained alkylate reached up to 83.3 wt% and 98.5, respectively.

An Unusually Acidic and Thermally Stable Cesium Titanate Cs xTi2- yM yO4 ( x = 0.67 or 0.70; M = vacancy or Zn).

Proton-free, alkali-containing layered metal oxides are thermally stable compared to their protonic counterparts, potentially allowing catalysis by Lewis acid sites at elevated temperatures. However, the Lewis acidic nature of these materials has not been well explored, as alkali ions are generally considered to promote basic but to suppress acidic character. Here, we report a rare example of an unusually acidic cesium-containing oxide Cs xTi2- yM yO4 ( x = 0.67 or 0.70; M = Ti vacancy □ or Zn). These lepidocrocite-type microcrystals desorbed NH3 at >400 °C with a total acidity of ≲410 μmol g-1 at a specific surface area of only 5 m2 g-1, without the need for lengthy proton-ion exchange, pillaring, delamination, or restacking. The soft and easily polarized Cs+ ion essentially drives the formation of the Lewis acidic site on the surfaces as suggested by IR of sorbed pyridine. The two-dimensional layered structure was preserved after the oxide was employed in the ethanol conversion at 380 °C, the temperature at which the protonic form could have converted to anatase. The structure was also retained after the NH3 temperature-programmed desorption measurement up to 700 °C. The production of ethylene from ethanol, well-known to occur over acid sites, unambiguously confirmed the acidic nature of this cesium titanate.

N-Dodecane Hydroisomerization over Hierarchical ZSM-22 Prepared by a Dual-Protected Alkali Treatment

In this work, a series of hierarchical ZSM-22 zeolites are prepared by a dual-protected alkali treatment route in the presence of microporous and mesoporous templates. The pore structure and acidity of hierarchical ZSM-22 zeolites are tailored by partial detemplation and addition of cetyltrimethylammonium bromide (CTAB), which are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, inductively coupled plasma, N2 adsorption–desorption, temperature-programmed desorption of NH3, Py-IR, Lu-IR, and 27Al magic-angle spinning nuclear magnetic resonance. The retained microporous templates after partial detemplation keep the ZSM-22 rod-like morphology in the alkali treatment. CTAB effectively introduces uniform mesoporosity centered at ca. 3.2 nm. As a result, as-prepared hierarchical ZSM-22 (430ATC) contains a large amount of small mesopores and pore-mouths, and higher desilication efficiency is achieved. After loading 0.5 wt % Pt, this hierarchical ZSM-22 supported...

Poisoning effects of lead species on the V2O5‐WO3/TiO2 type NH3‐selective catalytic reduction catalyst

AbstractHeavy metal Pb is an inevitable ingredient of coal‐fired flue gas and has been proven to be a source of inhibiting effect on the selective catalytic reduction (SCR) catalyst. In this paper, two types of Pb‐poisoned catalyst, prepared by the incipient wetness impregnation and solid diffusion methods, are studied to unveil the poisoning effects of lead species on the V2O5‐WO3/TiO2 catalyst. The activity test results showed that lead species loaded by the incipient wetness impregnation method exhibited a significant inhibiting effect on the denitrification efficiency of the catalyst although a negligible activity loss was observed on the samples from the solid diffusion method. Characterizations of fresh and Pb‐poisoned catalysts from incipient wetness impregnation method were applied using comprehensive techniques such as X‐Ray diffraction (XRD), field emission scanning electron microscopy (FE‐SEM), X‐ray fluorescence (XRF), NH3‐temperature programmed desorption (NH3‐TPD), X‐Ray photoelectron spectroscopy (XPS), and so forth. The analytical results indicated that a phase transformation occurred in tungsten species and the amorphous WO3 converted into PbWO4, causing the accumulation and valence imbalance of active vanadium phase, which further decreased the surface acidity and activity of the V2O5‐WO3/TiO2 catalyst.

Simultaneous removal of NOx and Hg0 from simulated flue gas over CuaCebZrcO3/r-Al2O3 catalysts at low temperatures: performance, characterization, and mechanism.

To optimize the simultaneous removal of NOx and Hg0, a series of CuaCebZrcO3/γ-Al2O3 catalysts prepared by the impregnation method were explored and their physical and chemical properties were analyzed by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) analysis, X-ray photoelectron spectroscopy (XPS), NH3-temperature-programmed desorption (NH3-TPD), H2-temperature-programmed reduction (H2-TPR), in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFT), and Fourier transform infrared spectroscopy (FT-IR). The results showed that 15% Cu1.4Ce0.55Zr0.25O3/γ-Al2O3 resulted in the highest conversion efficiency for the simultaneous removal of NOx (93%) and Hg0 (85%) at low temperatures (200 to 300°C). Meanwhile, 15% Cu1.4Ce0.55Zr0.25O3/γ-Al2O3 showed good stability and resistance to SO2 and H2O, which is due to its low crystallinity, good textural performance, and strong redox ability. According to the TPD, TPR, and XPS results, the strong acidic character of 15% Cu1.4Ce0.55Zr0.25O3/γ-Al2O3 promoted the removal of NOx and Hg0. The synergistic effect between CuO and CeO2 in 15% Cu1.4Ce0.55Zr0.25O3/γ-Al2O3 can increase the mobility of chemically adsorbed oxygen and activates lattice oxygen, leading to an excellent performance. The DRIFT results showed that NH3, NH4+, nitrate, and nitrite participated in the selective catalytic reduction (SCR) reaction. On the basis of our experimental results, Hg0 and NOx removal mechanisms were proposed as Hg (ad) + O* → HgO (ad) and 2NH3/NH4+ (ad) + NO2/NO3- (ad) + NO→2N2 + 3H2O/2H+, respectively.

Direct catalytic decomposition of N2O over Co(x)/RPSA catalysts

As one of the main greenhouse gases, reducing emissions of N2O is imperative, for which catalytic decomposition is one of the most effective methods. A series of cobalt catalysts supported on RPSA zeolite, denoted as Co(x)/RPSA-T, were prepared using the impregnation method and characterized by X-ray diffraction (XRD) analysis, Brunauer–Emmett–Teller (BET) measurements, thermogravimetric mass spectrometry (TG–MS), H2 temperature-programmed reduction (TPR), NH3 temperature-programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS), X-ray fluorescence (XRF) spectroscopy, and in situ diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS). Catalytic activity tests for N2O decomposition were carried out in a fixed-bed microreactor. The results showed that the redox properties of the catalysts remarkably influenced their catalytic performance. The catalytic activity results for the Co(10)/RPSA-600 catalyst showed the best performance under the conditions of 0.65 vol% N2O, 0.88 vol% O2, with Ar as balance gas, achieving conversions of 10 % and 90 % of N2O at temperature of 348 °C and 438 °C, respectively.

Spatial Confinement Effects of Microcapsule Catalyst for Improved Coking‐ and Sintering‐Resistant Behaviors Toward CO2 Reforming of Methane Reaction

The CO2 dry reforming of methane (DRM) reaction is an important technology with high prospects to reduce greenhouse gas emissions while simultaneously producing syngas for industrial usage. To date, the lack of an effective catalyst for the reaction has inhibited its commercialization. The coking and sintering behaviors of the catalysts are key factors for commercial production of syngas from DRM reaction. A microcapsule catalyst prepared by sol–gel method with Ni/ZSM‐5 as core and amorphous SiO2 as shell is successfully synthesized. The characterizations of the catalysts are analyzed using X‐ray powder diffraction (XRD), transmission electron microscopy (TEM), H2 temperature programmed reduction (H2‐TPR), NH3 temperature programmed desorption (NH3‐TPD), and thermogravimetry & differential scanning calorimetry (TGA‐DSC). The spatial confinement of the Ni metal particles between the SiO2 shell and ZSM‐5 suppresses Ni particles aggregation by strengthening the interaction between Ni particles and ZSM‐5 core. The coking‐resistant ability is equally improved. The capsule catalysts isolate the contact between the carbon deposits and the nickel active centre, thus improving the activity of the catalysts. 10Ni/ZSM‐5@SiO2 emerged superior in activity in comparison to other catalysts.

Synthesis of solketal over zirconia based acid catalysts

Microwave assisted synthesis of ‘solketal’ over zirconia (ZrO2) and its modified forms (Mo(VI)/ZrO2, W(VI)/ZrO2 and V(V)/ZrO2) coated on honeycomb monoliths is reported. The solid acids were coated on honeycomb monoliths by ‘dip and dry’ method and characterized for their surface acidity, crystalinity, functionality, morphology and elemental analysis by using techniques such as NH3-Temperature programmed desorption (NH3-TPD), powder X-ray diffraction (PXRD), Fourier transform-infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) and Inductively coupled plasma-optical emission spectroscopy (ICP-OES). The honeycomb monoliths coated with solid acids were employed as catalysts in the condensation of glycerol with acetone to synthesize solketal under microwave irradiation conditions. The reaction conditions such as molar ratio of the reactants (glycerol: acetone), reaction temperature, reaction time were studied to obtain highest possible yield of solketal with greater selectivity. The catalytic activity of honeycomb catalytic material was compared with the powder forms of the catalysts. 98% yield of solketal with 98% selectivity was achieved over Mo(VI)/ZrO2 coated on a honeycomb monolith in a very shorter reaction time of 8 min at 60 oC under microwave heating. These honeycomb catalytic material were found to be easily reactivable and reusable atleast for 6 reaction cycles. Hence, honeycomb catalysts were found to be efficient, economical and effective in the synthesis of value added chemical such as solketal. A possible mechanism for the formation of solketal is proposed.
 Bangladesh J. Sci. Ind. Res.54(1), 31-38, 2019

The role of molybdenum on the enhanced performance and SO2 resistance of V/Mo-Ti catalysts for NH3-SCR

The influence of molybdenum on the selective catalytic reduction (SCR) performance and SO2 durability of V/Mo-Ti catalysts was investigated. The characteristics of the catalysts were investigated by Brunauer-Emmett-Teller (BET) surface area analysis, field-emission transmission electron microscopy (FE-TEM), Raman spectroscopy, NH3-temperature programmed desorption (NH3-TPD), in-situ diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTs), SO2 temperature-programmed desorption (SO2-TPD), and X-ray photoelectron spectroscopy (XPS). The V/Mo-Ti catalysts exhibited improved SCR performances and SO2 resistances at 250 °C compared to those of V/W/Ti catalysts. The improved catalytic activity was shown to be imparted by amorphous MoOx. The formation of amorphous MoOx species with the addition of molybdenum to titanic acid was found to be more significant than that by the addition of molybdenum to crystalline TiO2. The increased density of NH3-adsorption and Brønsted-acid sites by addition of molybdenum was found to have a positive effect on catalyst performance. Since the reaction between SO2 and VOx was suppressed by the addition of molybdenum, the area of the SO2-TPD peak due to desorption of adsorbed SO2 from the catalyst surface was reduced. This decrease in the amount of adsorbed SO2 improved the SO2 resistances of the catalysts. The V/Mo-Ti catalysts exhibited increasing activities and SO2 resistances with increasing Mo6+ ratio (and Mo6+ atoms/cm3). Furthermore, they exhibited suppressed formation of ammonium sulfate salts due to decreased SO2 adsorption, as the reaction of terminal VO groups and adsorbed SO2 is inhibited by the addition of molybdenum. Thus, the V/Mo-Ti catalysts exhibited better catalytic activities and SO2 durability than those of V/W/Ti catalysts.

Effect of preferential exposure of anatase TiO2 {0 0 1} facets on the performance of Mn-Ce/TiO2 catalysts for low-temperature selective catalytic reduction of NOx with NH3

Titanium dioxide with preferentially exposed {001} facets (TiO2-NS) was synthesized by hydrothermal method using HF as a crystal plane regulator. The obtained TiO2-NS was used as the carrier of the low temperature SCR catalysts Mn-Ce/TiO2-NS which was prepared by impregnation method. Meanwhile, Mn-Ce/TiO2-NP catalyst was prepared as a comparison by the same method using titanium dioxide with priority to {101} facets (TiO2-NP) as the carrier. The effect of preferential exposure of anatase TiO2 {001} facets on the low-temperature selective catalytic reduction performance of Mn-Ce/TiO2 was studied. The support TiO2 (TiO2-NS and TiO2-NP) and the SCR catalysts were characterized by means of Scanning electron microscopy (SEM), Transmission electron microscope (TEM), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface measurement, X-ray photoelectron spectroscopy (XPS), Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) and NH3-temperature programmed desorption (NH3-TPD). The results showed that the preferentially exposed {001} facets of TiO2 could increase the specific surface area and the concentration of surface adsorbed oxygen of the catalyst, and enhance the surface acidity. The denitration test indicated that Mn-Ce/TiO2-NS catalyst showed excellent NO conversion. In particular, the catalytic efficiency of Mn-Ce/TiO2-NS was about 30% higher than that of Mn-Ce/TiO2-NP in the low temperature window within 100–160 °C.

Dealumination and desilication for Al-rich HZSM-5 zeolite via steam-alkaline treatment and its application in methanol aromatization

The hierarchical HZSM-5 was prepared via dealumination and desilication of commercial Al-rich HZSM-5, and characterized by X-ray diffraction, 27Al magic-angle spinning nuclear magnetic resonance, inductively coupled plasma mass spectrometry, scanning electron microscope, transmission electron microscope, N2 adsorption-desorption, NH3 temperature-programmed desorption, performed thermogravimetric and Raman spectrum. The results showed that partial framework of HZSM-5 was removed after steam treatment at 0.15 MPa, 500°C for 3 h. HZSM-5 with high specific surface area and much mesoporosity was obtained by the subsequent alkaline treatment. The regulation of acid quantity was achieved by altering the concentration of alkaline. Dealumination and desilication of Al-rich HZSM-5 zeolites became more effective using a combination of steam and alkaline treatments than using alkaline treatment alone. Methanol aromatization reaction was employed to evaluate the catalytic performance of treated HZSM-5 at 0.15 MPa, 450°C and MHSV of 1.5 h–1. The results indicated that after steam treatment, HZSM-5 further treated with 0.2 mol/L NaOH exhibits the best catalytic performance: the selectivity of aromatics reached 42.1% and the lifetime of catalyst attained 212 h, which are much better than untreated HZSM-5.

Designing a hierarchical nanosheet ZSM-35 zeolite to realize more efficient ethanol synthesis from dimethyl ether and syngas

Abstract In this work, a dual-catalyst bed reactor packed with the combination of hierarchical nanosheet HZSM-35 (Hi-NZ35) zeolite and CuZnAl catalyst was proposed to realize more efficient ethanol synthesis from dimethyl ether (DME) and syngas (CO+H2). The nanosheet ZSM-35 (NZ35) zeolite was prepared via a direct hydrothermal synthesis route and the CuZnAl catalyst was prepared by co-precipitation method. Moreover, a series of Hi-NZ35x zeolites were obtained from NZ35 zeolite by further treatment with varied NaOH aqueous solution using hydrothermal process (“x” means the NaOH solution concentration of 0.2-0.6 M). The catalysts properties, such as crystallinity, porosity, acidity, morphology and composition, were characterized by X-ray diffraction (XRD), N2 adsorption-desorption, NH3 temperature-programmed desorption (NH3-TPD), H2 temperature-programmed reduction (H2-TPR), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). It was found that Hi-NZ350.4 zeolite was more effective to obtain hierarchical porosity with mesopore volume up to 0.131 cm3 g−1. For single DME carbonylation reaction, the NZ35 zeolite exhibited superior catalytic activity (32.2%) and stability compared with conventional ZSM-35 (CZ35) zeolite. Furthermore, improved catalytic activity (42.0%) was observed on Hi-NZ350.4 zeolite owing to its abundant mesoporous structure. This result revealed that the hierarchical porosity of zeolite could effectively promote the catalytic performance of zeolite for DME carbonylation reaction. For the ethanol synthesis using the optimized catalysts combination of Hi-NZ350.4 zeolite and CuZnAl catalyst, the DME conversion was about 47.2% with higher ethanol productivity of 840.2 mmol kg−1 h−1.

Effect of acidity of oxide support on the activity and stability of μ-nitrido diiron phthalocyanine complex

Various oxides, including Al2O3, Fe2O3, SiO2, and ZrO2, were employed as catalyst supports for the oxidation of cyclohexane by a μ-nitrido-bis[tetra(tert-butyl)phthalocyaninatoiron] complex. These oxide supports were characterized by Brunauer–Emmett–Teller surface area measurements and NH3 temperature-programmed desorption analyses. The catalyst supported on Al2O3, which has the highest acidity among the oxides considered here, showed the best activity with a turnover number (TON) of ˜108.8, without any co-catalyst. Furthermore, recycle tests of the catalysts revealed a TON of 69.3 for the Al2O3-supported catalyst after the third run. The strongly acidic sites in the Al2O3 support could be responsible for the strong adsorption of μ-nitrido diiron phthalocyanine, resulting in enhanced catalytic activity and stability.