NH3 Temperature-programmed Desorption Research Articles

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

Abstract 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.

Rapid green synthesis of ZSM-5 zeolite from leached illite clay

Abstract A seed-induced rapid synthesis of submicron ZSM-5 zeolites from acid-leached illite clay was achieved via solid-like state conversion. The optimal synthesis conditions and crystallization mechanism were investigated. The synthesized ZSM-5 zeolites were characterized using X-ray diffraction, scanning electron microscopy, N2 adsorption–desorption, X-ray fluorescence, NH3 temperature-programmed desorption, and 27Al MAS NMR. The results clearly indicated that well-dispersed submicron-size ZSM-5 zeolites were synthesized in the relatively short period of 6 h. In the solid-like state conversion synthesis system induced by crystal seeds, the sample gradually transformed from amorphous to well-dispersed submicron ZSM-5 as the crystallization time increased. Aluminum entered the ZSM-5 zeolites framework to provide acidic sites. The obtained ZSM-5 zeolites showed slightly better catalytic performance in toluene disproportionation than ZSM-5 seeds.

Synthesis of Mo-MCM-48 and their isomerization performances of n-heptane

A series of Mo-MCM-48 molecular sieves were prepared by in-situ doping method and used as the catalyst for isomerization of n-heptane. The samples were characterized by X-ray powder diffraction, scanning electron microscope, transmission electron microscope, Nitrogen adsorption desorption isotherms (N2 adsorption–desorption), NH3 temperature programmed desorption (NH3-TPD), and Fourier Transform infrared spectroscopy (FT-IR). The results showed that Mo-MCM-48 samples modified by Mo species still had the typical cubic mesoporous structure of MCM-48. The results of n-heptane isomerization showed that when the doping amount of Mo species was 0.02, the reaction temperature was 250 °C, and the reaction time was 150 min, the conversion of n-heptane and the selectivity of isoheptane of Mo-MCM-48 were up to 36.71% and 52.41%, respectively. There were no obvious decline of the catalytic activity of Mo-MCM-48 after reaction for 190 min.

Promotion effect of S and N co-addition on the catalytic performance of V2O5/TiO2 for NH3-SCR of NOX

Abstract The influence of S and N in the V2O5/TiO2 catalyst system on the activity was evaluated for the selective catalytic reduction (SCR) of NOX. The VTi1 (S/N/Ti = 3:1:100) with wide temperature window has the highest catalytic activity. The properties of the catalysts were characterized by physicochemical measurements, including X-ray diffraction, BET surface area, NH3 temperature-programmed desorption, H2 temperature-programmed reduction and O2 temperature-programmed desorption, and so on. The structure, surface area, Lewis acidity, reducibility and active sites of the catalyst were significantly influenced by adding S and N. The results of ultraviolet–visible spectroscopy and electron paramagnetic resonance indicated that the presence of the strong electron interactions between dispersed vanadia and TiO2 species and more active oxygen species on the surface of catalyst. This work provides new insights into the effect of active oxygen species on the catalytic conversion of the nitrogen oxides.

Catalytic hydrodeoxygenation of jojoba oil to the green-fuel application on Ni-MoS/Mesoporous zirconia-silica catalysts

Abstract Zirconia modified mesoporous silica such as Zr-SBA-15, Zr-KIT-6, Zr-SiO2, and Zr-FSM-16 with Si/Zr = 10 ratio over Ni-MoS catalysts were prepared under the hydrothermal condition and compared with Ni-MoS/Zr-Al (10). The prepared materials were characterized by various techniques like X-ray diffraction analysis (XRD), N2-sorption studies, diffuse reflectance measurement–UV-Vis spectrophotometers (DR-UV-vis), NH3-temperature-programmed desorption (NH3-TPD)/H2-Temperature programmed reduction (H2-TPR), Laser-Raman, high resolution transmission electron microscopy (HRTEM) and fourier-transform infrared spectroscopy (FT-IR) techniques. The activity of materials was investigated in hydrodeoxygenation (HDO) of jojoba oil to produce long-chain hydrocarbons at 225–375 °C under 10–40 bar H2 pressure in a stainless steel fixed bed reactor. Among the catalysts tested, Ni-MoS/Zr-K (10) exhibited the highest catalytic activity of 90% conversion and 79% yield of C18–C22 hydrocarbon. The structure-activity relationships and product distributions were also discussed in detail.

Sc2O3-promoted composite of In2O3 and Beta zeolite for direct conversion of bio-ethanol to propylene

Abstract A series of Sc 2 O 3 -modified (1–5%) In 2 O 3 /Beta composites were prepared by the deposition-precipitation method. These catalysts were characterized by X-ray diffraction, N 2 adsorption, temperature-programmed desorption of NH 3 and CO 2 , temperature-programmed reduction, X-ray photoelectron spectroscopy and 27 Al magic-angle spinning nuclear magnetic resonance. The incorporation of Sc 2 O 3 into In 2 O 3 /Beta results in enhanced catalyst stability for the conversion of ethanol to propylene, which is due to inhibition of the reduction of In 3+ to In 0 upon Sc 2 O 3 modification.

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.

Decomposition reaction of methylcyclohexane using H-ZSM-5 supported on NiCrAl metal foam

The endothermic reaction of the fuel is used as a cooling system for hypersonic aircraft. At this time, the zeolite catalyst is used for an effective endothermic reaction. In this work, the effect of metal foam catalyst on the composition of the product was investigated by using zeolite with a metal foam support as a catalyst for the endothermic reaction. The metal foam support was made with NiCrAl alloy. The characteristics of the zeolite catalyst were confirmed by X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FT-IR) analysis and NH3-Temperature programmed desorption (NH3-TPD) analysis. The composition of the product of the endothermic reaction was analyzed by GC–MS. In experiments of H-ZSM-5 catalyst pellet, the conversion of methylcyclohexane (MCH) was about 82%. While, in the case of the H-ZSM-5 catalyst supported with the metal foam, the conversion of MCH was about 93% and the conversion was 11% higher than that of the zeolite catalyst itself. In addition, experimental results with different temperatures showed that MCH conversion and aromatic hydrocarbon increased with increasing temperature. On the other hand, low hydrocarbons increased when increasing from 598 to 633 K, but decreased when increasing to 673 K.

3D-printed ZSM-5 monoliths with metal dopants for methanol conversion in the presence and absence of carbon dioxide

Abstract The development of effective strategies to utilize CO2 as a renewable feedstock for producing commercially-viable products is an interesting challenge to explore new concepts and opportunities in catalysis and industrial chemistry. In this study, 3D-printed ZSM-5 monoliths doped with Ga2O3, Cr2O3, CuO, ZnO, MoO3, and Y2O3were synthesized using the state-of-art 3D printing technique. The physicochemical properties of the catalysts were characterized by X-ray diffraction, N2 physisorption, NH3 and CO2 temperature-programed desorption and H2 temperature-programmed reduction. The promotional effect of doped metals on catalytic performance of 3D-printed ZSM-5 monoliths in methanol to hydrocarbon (MTH) reaction in the presence and absence of CO2 was investigated. Results indicated that both metal dopants type and reaction atmosphere greatly influence catalyst stability and product distribution. The yield of light olefins was enhanced over all metal-doped 3D-printed ZSM-5 monoliths in N2 atmosphere (absence of CO2), however, CO2 atmosphere did not favor the production of light olefins. Although selectivity toward ethylene slightly decreased, the propylene yield was almost constant after switching N2 to CO2 in MTH reaction at 400 °C. Furthermore, it was found that Y- and Zn-doped ZSM-5 monoliths exhibited higher yield of light olefins and BTX compounds in the in the absence and presence of CO2, respectively.

Temperature-dependent dynamics of NH3-derived Cu species in the Cu-CHA SCR catalyst

In situ XAS and UV-vis–NIR spectroscopy shed light on Cu-speciation during NH3 temperature-programmed desorption and surface reaction (TPSR) over a commercial Cu-chabazite deNOx catalyst, expanding the fundamental knowledge required to unravel the NH3-SCR mechanism across the whole operation-relevant temperature range.

Influence of the addition of vanadium to Pt/TiO2 catalyst on the selective catalytic oxidation of NH3 to N2

ABSTRACTIn this work, the effect of the addition of vanadium to the Pt/TiO2 catalyst on the selective catalytic oxidation (SCO) of NH3 to N2 was investigated. It was found that the addition of vanadium significantly enhanced catalytic activity at all tested temperatures. The Pt/V/TiO2 catalyst exhibited the highest NH3 conversion (∼100%) and NH3 to N2 conversion (∼81%) at 250°C. The physicochemical characteristics of the catalysts were investigated via Brunauer-Emmett-Teller (BET) analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), NH3 temperature-programmed desorption (TPD), NH3 temperature-programmed oxidation (TPO), and in situ Fourier-transform infrared (FTIR) spectroscopy. It was found that the addition of V to the catalyst enhanced the conversion of NH3 as a result of the formation of new acid sites. The increase in the number of acid sites resulted in increased NH3 to N2 conversion via the internal selective catalytic reduction (i-SCR) mechanism. This mechanism involves the SCR of NOx, which are formed by the oxidation of NH3. Based on experimental results and analyses of the catalysts modified by the addition of V, it was shown that there was a close relation between reaction selectivity and the surface oxygen species of the catalyst and N2 yield. Furthermore, the addition of V increased the durability of SO2 by inhibiting the formation of ammonium bisulfate (ABS).

Sulphated Zr–Al2O3 catalysts through jatropha oil to green-diesel production

Abstract Composite materials of zirconia–alumina (Zr–Al2O3) with Al/Zr 10 ratio was successfully synthesized by sol–gel method and followed by different sulfiding methods. The synthesized catalysts were characterized by various techniques such as X-ray powder diffraction (XRD), N2-sorption, NH3-Temperature Programmed Desorption (NH3-TPD), Diffuse Reflectance UV–Vis Spectrophotometers (DR UV–Vis), Scanning Electron Microscopy (SEM), and the biodiesel was analyzed by Gel permeation chromatography (GPC) and Gas chromatography–mass spectrometry (GC–MS). The jatropha oil conversion of above 96% was obtained at optimized conditions of 110 °C, 1:20 jatropha oil to methanol ratio, 1.5 g of catalysts and 3 h reaction time. The catalysts reusability study was performed for 6th cycles using sulphated Zr–Al2O3 under hydrothermal (H) method, denoted as SO42−/Zr–Al2O3 (10)–H and the activity is correlated with physico-chemical properties.

Effect of Crystallization on the Catalytic Cracking Performance of Zeolite Socony Mobil-5.

In the research, zeolite socony mobil-5 (ZSM-5) catalyst was prepared by hydrothermal method and characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), NH3-temperature programmed desorption (NH3-TPD) and Brunauer- Emmett-Teller (BET). The catalytic products from Jatropha carcass L. oil were analyzed by gas chromatography-mass spectrometer (GC-MS). The effects of crystallization time and crystallization temperature on catalytic cracking performance of ZSM-5 were investigated. According to the results, the catalytic cracking performance of ZSM-5 was closely associated with its pore structure. When the crystallization time was 60 h and the crystallization temperature was 170 °C, ZSM-5 with optimal catalytic cracking performance was synthesized. Catalyzed by the optimal ZSM-5, Jatropha carcass L. oil showed the liquid conversion rate of 26.60% and the acid value of 1.24 mg KOH·g-1. The main catalytic products from Jatropha carcass L. oil included benzene (10.02%), methylbenzene (20.52%), o-xylene (14.45%) and p-xylene (6.59%).

Influence of Sulfur-Containing Sodium Salt Poisoned V2O5–WO3/TiO2 Catalysts on SO2–SO3 Conversion and NO Removal

A series of poisoned catalysts with various forms and contents of sodium salts (Na2SO4 and Na2S2O7) were prepared using the wet impregnation method. The influence of sodium salts poisoned catalysts on SO2 oxidation and NO reduction was investigated. The chemical and physical features of the catalysts were characterized via NH3-temperature programmed desorption (NH3-TPD), H2-temperature programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FT-IR). The results showed that sodium salts poisoned catalysts led to a decrease in the denitration efficiency. The 3.6% Na2SO4 poisoned catalyst was the most severely deactivated with denitration efficiency of only 50.97% at 350 °C. The introduction of SO42− and S2O72− created new Brønsted acid sites, which facilitated the adsorption of NH3 and NO reduction. The sodium salts poisoned catalysts significantly increased the conversion of SO2–SO3. 3.6%Na2S2O7 poisoned catalyst had the strongest effect on SO2 oxidation and the catalyst achieved a maximum SO2–SO3-conversion of 1.44% at 410 °C. Characterization results showed sodium salts poisoned catalysts consumed the active ingredient and lowered the V4+/V5+ ratio, which suppressed catalytic performance. However, they increased the content of chemically adsorbed oxygen and the strength of V5+=O bonds, which promoted SO2 oxidation.

Acylation of Anisole Catalyzed by Hierarchical Porous Hβ Zeolite Modified with Cr

Modified hierarchical porous Hβ zeolite was obtained by metal modification of Hβ zeolite, which was treated with alkaline solution, and the catalysts before and after modification were characterized by means of X-ray diffraction(XRD), nitrogen adsorption-desorption, scanning electron microscopy(SEM), X-ray fluorescence(XRF), NH3 temperature-programmed desorption and Fourier-transform infrared spectroscopy(FTIR). The activities of acylation of anisole with acetic anhydride were also investigated. The results show that the Hβ zeolite, which was treated with alkaline solution has microporous and mesoporous structures that could improve the diffusion performance of chemical reaction. The amount of acid was modulated with metal modification. The Hβ zeolite modified by 5%(mass fraction) metal chromium had the best catalytic performance. The conversion of acetic anhydride acylation was 93.01% under the optimal conditions, which was higher than that of other catalysts. The catalyst not only showed good activity, but also exhibited a stable performance in regeneration tests.

Vanadium oxide modified H-beta zeolite for the synthesis of polyoxymethylene dimethyl ethers from dimethyl ether direct oxidation

Abstract The bifunctional H-beta zeolite supported vanadium oxide catalysts were prepared at different calcination temperatures and investigated for dimethyl ether (DME) direct oxidation to polyoxymethylene dimethyl ethers (DMMx). The impact of the nature of VOx species and the acid properties controlled by the calcination temperature on the DMMx formation has been studied in detail. Vanadium oxide species dispersing well on the H-beta zeolite offer suitable redox sites. Meanwhile, the acid strength and distribution of H-beta zeolite are modulated by the interaction between VOx species and zeolite framework. The acid properties of the catalysts with different calcination temperatures are analyzed by pyridine-Fourier transform infrared spectra and NH3 temperature-programmed desorption measurements, and the selectivity to DMMx shows a linear relationship with the Bronsted/Lewis acid sites ratio, indicating that the catalysts with higher B/L ratio are effective for the DMMx formation. In addition, the NH3-TPD results confirm that more acid sites with strong strength for the catalysts are in favor of the C–O chain growth to synthesize larger DMMx molecules. These results above are helpful for us to well understand the active sites and design the effective catalysts to synthesize DMMx with longer C–O chain.

Influence of various aluminum distributions on modification of ZSM-5 zeolite framework with cobalt ions in alkane catalytic cracking

HZSM-5 (HZ(1) and HZ(2)) zeolites synthesized with various framework aluminum distributions and also cobalt-modified H-form zeolites (Co/HZ(1) and Co/HZ(2)) were used to evaluate the production of light olefins in catalytic cracking of liquefied petroleum gas (LPG). The characterization of catalysts was carried out by X-ray diffraction (XRD), field-emission scanning electron microscopic (FE-SEM), Brunauer–Emmett–Teller (BET), X-ray fluorescence (XRF), Barrett–Joyner–Halenda (BJH), Thermal Gravimetric Analyzer (TGA), diffuse reflectance (DR) UV–visible and NH3-Temperature-Programmed Desorption (NH3-TPD) analyses. The results showed that the highest single aluminum proportion was 89.3% for NaZSM-5(1) synthesized with aluminum nitrate. The catalytic results indicated that the olefin yield increased from 30.8% to 39.3% and 24.7% to 41.4% after HZ(1) and HZ(2) modification with cobalt ions, respectively. After 240 min of time on stream (TOS), the olefin yield decreased 33.92, 23.37, 48.24 and 21.39% for HZ(1), Co/HZ(1), HZ(2) and Co/HZ(2), respectively. The amount of coke deposited on catalyst decreased from 15.28% to 4.97% after modification of HZ(2). The highest stability and the highest ratio of propylene to ethylene (P/E) was found for Co/HZ(2). Consequently, the effect of HZ(2) (with higher close Al atoms) modification with cobalt ions on the olefin production and catalytic stability was greater than HZ(1) modification.

Conversion of Ethanol and Acetaldehyde to 1, 3-Butadiene Catalyzed by Zr–Si Materials

Series of ZrO2 supported on the different kinds of SiO2 carriers were applied in the reaction of 1, 3-butadiene formation from ethanol and acetaldehyde. ZrO2/Nano-SiO2 performed the best performance with the 1, 3-butadiene selectivity 91.43% and the total conversation 52.39%. Prepared catalysts were characterized by N2 adsorption–desorption, TEM, XRD, temperature-programmed desorption of NH3 and CO2, FTIR spectroscopy of adsorbed pyridine and CO2, Raman XPS. The results show that the weak Lewis acid and basic sites are appropriate for BD formation. Furthermore, more and balance acid-basic sites are rather important for the reaction of ethanol and acetaldehyde conversion to BD.

Study of Chemical and Morphological Transformations during Ni2Mo3N Synthesis via an Oxide Precursor Nitration Route

Chemical and morphological transformations during Ni2Mo3N synthesis were studied in this work. Nitride samples were synthesized from oxide precursors in H2/N2 flow and were analyzed by thermogravimetry, X-ray diffraction analysis, scanning electron microscopy, and energy dispersive X-ray spectroscopy methods. In addition, physical and chemical adsorption properties were studied using low-temperature N2 physisorption and NH3 temperature-programmed desorption. It was shown that nitride formation proceeds through a sequence of phase transformations: NiMoO4 + MoO3 → Ni + NiMo + MoO2 → Ni + NiMo + Mo2N → Ni2Mo3N. The weight changes that were calculated from the proposed reactions were in agreement with the experimental data from thermogravimetry. The morphology of the powder changed from platelets and spheres for the oxide sample, to aggregates of needle-like particles for the intermediate product, to porous particles with an extended surface area for the nitride final product. The obtained results should prove useful for subsequent Ni2Mo3N based catalysts production process optimization.