NH3 Temperature-programmed Desorption Research Articles

Construction of mesoporous Cu/ZrO2-Al2O3 as a ternary catalyst for efficient synthesis of γ-valerolactone from levulinic acid at low temperature

A ternary base metal catalyst, which contained metallic Cu, oxygen deficiencies derived from ZrO2, and acidic Al2O3, was constructed for the efficient synthesis of γ-valerolactone by levulinic acid hydrogenation under mild conditions. Excellent catalytic performance was obtained by fine tuning the proportion of these three active components. The optimized Cu/Zr-Al-3 catalyst achieved superior catalytic activity with a high mass activity of 220.5 mmol GVL·h−1·g−1 surf. Cu at 130 °C, which was nearly eight times higher than Cu/Al and nine times higher than Cu/Zr. More importantly, Cu/Zr-Al-3 also possessed excellent recycling stability, making it as a potential catalyst for industrial applications. The presence of ZrO2 in the ternary catalysts weakened the Cu–Al2O3 interaction and formed Zr–O–Al interaction in the form of Al2O3–ZrO2 solid solution, which facilitated the reduction of CuO species and in turn enhanced the formation of more Cu0 active sites on the catalyst surface. The existence of a large number of oxygen vacancies and acid sites on the optimized ternary catalysts was also demonstrated by XPS and NH3 temperature-programmed desorption results. Levulinic acid can be adsorbed strongly on oxygen vacancies by its carboxylic or carbonyl groups and then readily attached by active H atoms dissociated on Cu0 sites to form active intermediates, while the acid sites presented on the ternary catalyst surface promote subsequent dehydration and intramolecular esterification of adsorbed active intermediates and consequently facilitate the formation of γ-valerolactone. The adsorption of levulinic acid onto oxygen vacancies also avoided the leaching of active Cu metal via the formation of soluble Cu metal carboxylate complexes, resulting in outstanding recycling stability for the optimized ternary catalysts. The intimate synergies of these ternary active sites mainly accounted for the superior catalytic activity and excellent recycling stability of the Cu/Zr-Al-3 catalyst.

Effect of Metal Oxide–Support Interactions on Ethylene Oligomerization over Nickel Oxide/Silica–Alumina Catalysts

We investigated the interactions between nickel oxide and silica–alumina supports, which were applied to the catalytic oligomerization of ethylene by powder X-ray diffraction, UV diffuse reflectance spectroscopy, H2 temperature-programmed reduction, and X-ray photoelectron spectroscopy. The catalytic activity was also correlated with the acidity of catalysts determined by NH3 temperature-programmed desorption and pyridine FT-IR spectroscopy. Although all the catalysts had similar Ni contents, their catalytic performances were strongly influenced by the strength of the metal oxide–support interaction. Strong interaction promoted the formation of nickel aluminate on the catalyst surface, and resulted in low catalytic activity due to reducing the amount of nickel oxide active sites. However, weak interaction favored the aggregation of nickel oxide species into larger particles, and thus resulted in low ethylene conversion and selectivity to oligomers. Eventually, the optimal activity was realized at the medium interaction strength, preserving a high amount of both active nickel oxides and acid sites.

Synthesis of highly active ETS-10-based titanosilicate for heterogeneously catalyzed transesterification of triglycerides.

In this contribution, the preparation of hierarchically structured ETS-10-based catalysts exhibiting notably higher activity in the conversion of triolein with methanol compared to microporous titanosilicate is presented. Triolein, together with its unsaturated analog trilinolein, represent the most prevalent triglycerides in oils. The introduction of mesopores by post-synthetic treatment with hydrogen peroxide and a subsequent calcination step results in the generation of an additional active surface with Brønsted basic sites becoming accessible for triolein and enhancing the rate of transesterification. The resulting catalyst exhibits a comparable triolein conversion (≈73%) after 4 h of reaction to CaO (≈76%), which is reportedly known to be highly active in the transesterification of triglycerides. In addition, while CaO showed a maximum conversion of 83% after 24 h, the ETS-10-based catalyst reached 100% after 8 h, revealing its higher stability compared to CaO. The following characteristics of the catalysts were experimentally addressed – crystal structure (X-ray diffraction, transmission electron microscopy), crystal shape and size (scanning electron microscopy, laser diffraction), textural properties (N2 sorption, Hg porosimetry), presence of hydroxyl groups and active sites (temperature-programmed desorption of NH3 and CO2, 29Si magic angle spinning nuclear magnetic resonance (NMR)), mesopore accessibility and diffusion coefficient of adsorbed triolein (pulsed field gradient NMR), pore interconnectivity (variable temperature and exchange spectroscopy experiments using hyperpolarized 129Xe NMR) and oxidation state of Ti atoms (electron paramagnetic resonance). The obtained results enabled the detailed understanding of the impact of the post-synthetic treatment applied to the ETS-10 titanosilicate with respect to the catalytic activity in the heterogeneously catalyzed transesterification of triglycerides.

Performance of Catalytic Fast Pyrolysis Using a γ-Al2O3 Catalyst with Compound Modification of ZrO2 and CeO2

To investigate the catalytic pyrolysis performance of complex metal oxide catalysts for biomass, γ-Al2O3 was prepared through the precipitation method, and then ZrO2 and γ-Al2O3 were blended in the proportion of 2:8 using the co-precipitation method. Next, CeO2 was loaded on the surface of the catalyst for further modification. The three catalysts, A, ZA and CZA, were obtained. The specific surface and acidity of the catalysts were characterized by nitrogen adsorption–desorption and NH3-Temperature Programmed Desorption (NH3-TPD) respectively. The catalytic pyrolysis performance of catalysts for bamboo residues was investigated by Pyrolysis gas chromatography mass spectrometry (Py-GC/MS). Chromatograms were analyzed for identification of the pyrolysis products and the relative amounts of each component were calculated. Experimental results indicated that catalyst A had a good catalytic activity for the fast pyrolysis of bamboo residues. The addition of ZrO2 and CeO2 could continuously enhance the acidity of the catalyst and further promote the pyrolysis of macromolecular compounds and deoxidation of oxygen-containing compounds. Finally, catalyst CZA, obtained by compound modification, could not only dramatically reduce the relative content of phenol, acid and aldehyde and other oxygen-containing compounds, but also achieved the maximum hydrocarbon yield of 23.38%. The catalytic performance of catalyst CZA improved significantly compared with catalyst A.

Structural and Electronic Properties of Highly Dispersed Particles of the Active Components of Pd/Al2O3 Catalysts of Butadiene-1,3 Hydrogenation

The effect of the acidic characteristics of an alumina support on the properties of formed palladium particles is studied to improve the activity of catalysts for the hydrogenation of unsaturated hydrocarbons of the pyrogasoline fraction. High catalytic activity is characteristic of highly dispersed palladium particles, but the surfaces of palladium particles are blocked by unsaturated hydrocarbons, due to their electron deficiency. In this work, palladium/alumina catalysts with supports of different acidities due to chemical modification with various reagents are studied via NH3 temperature-programed desorption, transmission electron microscopy, and X-ray photoelectron spectroscopy. The samples are subjected to catalytic tests in the butadiene-1,3 hydrogenation reaction under laboratory conditions. The catalysts on supports with acidic modifiers display low butadiene-1,3 conversion and higher selectivity toward butene-1, relative to an unmodified sample. The catalysts on the supports treated with basic additives displayed high butadiene-1,3 conversion while retaining their selectivities toward butene-1 and butane.

Revisiting effects of alkali metal and alkaline earth co-cation additives to Cu/SSZ-13 selective catalytic reduction catalysts

Cu,M/SSZ-13 (M = Na+, K+ and Ca2+) selective catalytic reduction (SCR) catalysts with Si/Al = 6 and M/Cu ratios varying from 0.1 to 1.0 are prepared by solution ion exchange, followed by slurry drying and hydrothermal aging at 800 °C. The catalysts are characterized with X-ray diffraction and N2 adsorption isotherms to probe their textural properties; 27Al and 29Si nuclear magnetic resonance and NH3 temperature-programmed desorption to probe their acidity properties and levels of dealumination; and electron paramagnetic resonance and H2 temperature-programmed reduction to quantitatively explore the nature of Cu moieties in the catalysts. These studies are followed by density functional theory calculations to elucidate Cu and co-cation interactions at an atomic level and SCR reaction tests to reveal correlations between the chemical and physical properties of the catalysts and their SCR performance. Through these comprehensive investigations, it is discovered that alkali metal co-cation addition can be used for the synthesis of highly stable, and highly active and selective Cu/SSZ-13 catalysts with relatively high Al content. In catalysts with optimal alkali incorporation, dealumination of the SSZ-13 substrate is largely inhibited, allowing high concentrations of SCR-active isolated Cu ions. At the same time, repulsive interactions between Cu ions and alkali metal co-cations preclude excessively high isolated Cu-ion loadings. Interplay between and optimization of these two factors is considered the underlying origin for this successful catalyst synthesis strategy. On the other hand, the alkaline earth co-cation Ca2+ fails to demonstrate any beneficial effects, since it destabilizes isolated Cu ions via site competition.

Valorization of biomass derivatives through the conversion of phenol over silica-supported Mo-Re oxide catalysts

Liquid-phase hydrodeoxygenation of phenol over silica-supported MoOx-ReOx catalysts was investigated at 300 °C and 5 MPa of H2. Mixed-oxides catalysts with similar surface metal density (2.3 atoms of metal per nm2 of SiO2) but different relative Mo and Re loadings were prepared by incipient wetness impregnation. The catalysts were characterized by N2 adsorption, temperature programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), ultraviolet visible diffuse reflectance (UV–vis-DR) spectroscopy, X-ray diffraction (XRD) and temperature programmed desorption of NH3 (TPD-NH3). All the catalysts were highly active and selective towards deoxygenated products. However, MoOx/SiO2 was the most selective towards cyclohexane formation. Higher amount of benzene was produced with the Re-containing catalysts than it was over the MoOx/SiO2 catalyst, indicating that ReOx favored direct deoxygenation over hydrogenation of the aromatic ring. The catalyst containing equimolar amounts of MoOx and ReOx exhibited the highest yield of benzene. This result can be attributed to a synergistic effect that arises from electronic interaction between rhenium and molybdenum oxides which favors the formation of new oxygen vacancy sites. The study reveals that benzene selectivity is mainly influenced by ReOx sites and the activity can be tuned by a balance of MoOx and ReOx sites.

Effect of Zirconia Polymorph on Vapor-Phase Ketonization of Propionic Acid

Vapor-phase ketonization of propionic acid derived from biomass was studied at 300–375 °C over ZrO2 with different zirconia polymorph. The tetragonal ZrO2 (t-ZrO2) are more active than monoclinic ZrO2 (m-ZrO2). The results of characterizations from X-ray diffraction (XRD) and Raman suggest m-ZrO2 and t-ZrO2 are synthesized by the solvothermal method. NH3 and CO2 temperature-programmed desorption (NH3-TPD and CO2-TPD) measurements show that there were more medium-strength Lewis acid base sites with lower coordination exposed on m-ZrO2 relative to t-ZrO2, increasing the adsorption strength of propionic acid. The in situ DRIFTS (Diffuse reflectance infrared Fourier transform spectroscopy) of adsorbed propionic acid under ketonization reaction reveal that as the most abundant surface intermediates, the monodentate propionates are more active than bidentate propionates. In comparison with m-ZrO2, the t-ZrO2 surface favors monodentate adsorption over bidentate adsorption. Additionally, the adsorption strength of monodentate propionate is weaker on t-ZrO2. These differences in adsorption configuration and adsorption strength of propionic acid are affected by the zirconia structure. The higher surface concentration and weaker adsorption strength of monodentate propionates contribute to the higher ketonization rate in the steady state.

Investigation of low-temperature selective catalytic reduction of NOx with ammonia over Cr-promoted Fe/AC catalysts.

Fe/activated coke (AC) and Cr-Fe/AC catalysts with AC as a supporter and Cr and Fe as active components were prepared by an impregnation method for low-temperature selective catalytic reduction (SCR) of NO with NH3. The effects of Cr addition and its concentrations on the deNOx performance of Fe/AC catalysts were studied at low temperature. The Cr addition promotes the low-temperature SCR activity of the 8Fe/AC catalyst and the 8Fe6Cr/AC catalyst has the best low-temperature SCR deNOx performance, which the NOx conversions are greater than 90% at 160-240 °C. The 8Fe6Cr/AC catalyst has good water resistance. However, when 100 ppm SO2 was introduced into the reaction gas, its deNOx efficiency drops to 45% at 180 °C. To clarify the specific effects of Cr addition on the NOx conversions and sulfur poisoning, the Cr-Fe/AC catalysts were characterized by X-ray diffraction, BET, H2 temperature-programmed reduction, NH3 temperature-programmed desorption, X-ray photoelectron spectroscopy, and Fourier infrared spectroscopy. The addition of Cr into Fe/AC catalysts greatly increases the BET surface area and the number of weak and medium-strong acid sites on the catalyst surface and improves the ratio of Fe3+/Fe2+. These factors enhance the NOx conversion of 8Fe/AC catalyst. The formed sulfates and hydrogen sulfates cover the active sites on the catalyst surface, which lead to the sulfur poisoning of the 8Fe6Cr/AC catalyst. Graphical abstract.

Superior activity of iron–manganese supported on kaolin for NO abatement at low temperature

A series of Fe–Mn catalysts was prepared using different supports (kaolin, diatomite, and alumina) and used for NO abatement via low-temperature NH3-selective catalytic reduction (SCR). The results showed that 12Fe–10Mn/Kaolin (with the concentration of Fe and Mn 12 and 10wt.%, respectively) exhibited the highest activity, and more than 95.8% NO conversion could be obtained within the wide temperature range of 120–300°C. The properties of the catalysts were characterized by inductively coupled plasma-atomic emission spectrometry (ICP-AES), thermogravimetry (TG), Brunner–Emmet–Teller (BET) measurements, X-ray diffraction (XRD), H2-temperature programmed reduction (H2-TPR), NH3-temperature programmed desorption (NH3-TPD), X-ray photoelectron spectroscopy (XPS), scanning electron microprobe (SEM) and energy dispersive spectroscopy (EDS) techniques. The support effects resulted in significant differences in the components and structures of catalysts. The 12Fe–10Mn/Kaolin catalyst exhibited better dispersion of active species, optimum low-temperature reduction behavior, the largest amount of normalized Brønsted acid sites, and the highest Mn4+/Mn and Fe3+/(Fe3++Fe2+), all of which may be major reasons for its superior catalytic activity.

Microwave assistant rapid synthesis MCM-41-NH2 from fly ash and Cr(VI) removal performance.

Synthesis of silicon materials from fly ash is an ecologically justified process aimed at the transformation of energy sector waste-fly ash into mesoporous silicon material of broad possible application field. In this study, the MCM-41-NH2 was successfully synthesized from industrial solid waste fly ash via a facile and fast process of alkali fusion method under the assistant of microwave. Due to the employ of microwave, the aging time was controlled within 30min, which was significantly shorter than that of traditional hydrothermal method (48-72h). And, the obtained MCM-41-NH2 was shown an excellent performance to remove Cr(VI) from solution under the investigation of fixed-bed column. The maximum adsorption capacity for Cr(VI) was 53.77mg/g. Additionally, the effect of initial concentration, flow rate, bed height, and pH on Cr(VI) removal were investigated, and the models of Thomas and Adams-Bohart were applied to predict the experiment data; the correlation coefficients (R2) of Thomas model under the investigated conditions were all close to 1. Furthermore, the adsorbent was characterized by N2 adsorption-desorption isotherm, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), zeta potential, ultraviolet-visible spectroscopy (UV-vis), X-ray photoelectron spectroscopy (XPS), and NH3-Temperature Programmed Desorption (NH3-TPD). The results showed that amino groups play an important role in the adsorption process. Cr(VI) was firstly adsorbed on the surface of the MCM-41-NH2, and then some of the adsorbed Cr(VI) were reduced to Cr(III) by the release of the protons of the ammonium. The information showed that MCM-41-NH2 could be an effective and low-cost sorbent for removing Cr(VI) from wastewater. Furthermore, recycling experiments showed that the spent adsorbent had high catalytic performance for methyl mercaptan (CH3SH). Graphical abstract .

Function promotion of SO42−/Al2O3–SnO2 catalyst for biodiesel production from sewage sludge

Catalysts are critical materials for biodiesel production using sewage sludge feedstock. In this research, different SO42−/Al2O3–SnO2 catalysts were prepared and characterized. The catalysts prepared at different conditions were characterized through Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), NH3-temperature-programmed desorption (NH3-TPD), NH3 adsorption FT-IR, and TGA. Then, esterification/transesterification reaction was performed with the lipid extracted from sewage sludge to verify the activity of these catalysts. Results showed that the catalysts with n(Al):n(Sn) = 1:10 prepared by 79 wt% H2SO4 possessed the best physical properties with a large number of active catalytic sites, which led to the biodiesel yield of 73.3% (based on dried extracted crude fat) under the optimized reaction conditions at 130 °C as reaction temperature, 0.8 g as catalyst loading for lipids extracted from 10 g freeze-dried sludge, 4 h as reaction time. Catalysts characterization results showed that acidity, acid sites and Al/Sn molar ratio play an important role in the activity of catalysts. The thermal properties showed that 450 °C was the suitable calcination temperature for catalyst preparation. The optimized SO42−/Al2O3–SnO2 catalyst in this research will have a bright future in the field of sludge production of biodiesel.

Preparation of Au/xCeO2-Al2O3 catalysts with enhanced catalytic properties for the selective acetylene hydrogenation

In this work, Au/Al2O3 and Au/xCeO2-Al2O3 catalysts were prepared by incipient wetness impregnation method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), raman spectroscopy, temperature programmed hydrogen reduction (H2-TPR) and temperature programmed NH3 desorption and C2H2 desorption (NH3-TPD, C2H2-TPD). TEM and XRD results showed that there was no obvious difference for the structures and morphologies compared with Au/Al2O3 and Au/xCeO2-Al2O3. However, enhanced catalytic performance was found in the selective acetylene hydrogenation to ethylene. Raman spectra showed that no coke was obtained for Au/xCeO2-Al2O3. NH3-TPD confirmed that with the increase of CeO2 loading, the surface acidity was decreased and an appropriate CeO2 addition was needed for the improvement of catalytic activity. The charge transfer between metallic Au and CeO2 leads to positively charged Au (Auδ+).The basic character of CeO2 and the positively charged Au may play a positive role in the selective acetylene hydrogenation reaction. A possible reaction mechanism was proposed in this paper.

Effect of preparation method on the Pt-In modified Mg(Al)O catalysts over dehydrogenation of propane

The Pt-In modified Mg(Al)O catalysts were prepared by co-precipitation, co-impregnation, and successive impregnation methods with Pt and In loading at 0.3 and 0.6 wt.%, respectively. The catalysts were tested in the propane dehydrogenation at 550 °C and atmospheric pressure. Pt loading on In-modified Mg(Al)O support prepared by co-precipitation (Pt/Mg(In)(Al)O) exhibited the highest catalytic performances with initial propane conversion and propylene selectivity of 24.2%.and 98.2%, respectively. As revealed by the H2-TPR and XPS results, the Pt/Mg(In)(Al)O exhibited a stronger metal-support interaction and favorable led to more PtIn alloy formation compared to those obtained by the other methods, which greatly enhanced the catalytic performance and stability. Coke formation was significant reduced on all the prepared bimetallic PtIn catalysts, especially coke on the active metal, which diminished the catalytic deactivation. The catalysts were also characterized by CO chemisorption, transmission electron microscopy (TEM), NH3-temperature program desorption (NH3-TPD).

Catalytic Dehydration of Ethanol over WOx Nanoparticles Supported on MFI (Mobile Five) Zeolite Nanosheets

Ethylene can be synthesized in a renewable manner by dehydrating bioethanol over supported metal oxide nanoparticle catalysts. Here, a series of nanoparticulate tungsten oxides supported on MFI (Mobil five) zeolite nanosheets was prepared at different W loadings (1 to 6 mol %) using the incipient wetness method and investigated with respect to the ability to catalyze the dehydration of ethanol. The resulting samples were characterized by X-ray diffraction, electron microscopy, N2 isotherms, X-ray absorption fine structures, and by the temperature-programmed desorption of NH3. The results obtained showed that WOx nanoparticles were homogeneously distributed over the entire void space of nanosheet samples up to a loading of 2 mol %, after which large WOx nanoparticles with needle-like morphology were formed on the surface of the zeolite nanosheet beyond 2mol%. The number of acid sites increased with WOx loading and, as a result, EtOH conversion progressively increased with WOx loading up to 6 mol %. At reaction temperatures of >390 °C, homogeneously distributed WOx nanoparticles showed slightly higher ethylene selectivity than nano-needle structured WOx. However, nano-needle structured WOx exhibited greater catalytic stability. In terms of ethylene yield over 8 h, needle-like WOx nanoparticles were found to be more suitable for the acid-catalyzed dehydration of ethanol than small-sized WOx nanoparticles.

Catalytic Study of Hexadecane Cracking over Novel and Efficient HY/Al-HMS/K10 Hybrid Catalysts

The aim of this study is to provide a new and high-performance catalytic system for the cracking process by combining HY-zeolite, Al-hexagonal mesoporous molecular sieves (HMS) as a new matrix, and montmorillonite K10 as filler components. The Al-HMS molecular sieve was synthesized with different Si/Al molar ratios in the range of 2.5–35 and assembled with various amounts of HY-zeolite and montmorillonite K10 to prepare two- and three-component catalysts. After calcination, their catalytic activities were investigated in a cracking reaction of n-hexadecane at 500 °C and atmospheric pressure as a model reactant. The structure and surface properties of the synthesized catalysts were characterized by X-ray diffraction, scanning electron microscopy, Brunauer–Emmett–Teller, temperature-programmed desorption of NH3, and pyridine-IR techniques. Results indicated that the desired hybrid catalysts were successfully synthesized with the micro-mesoporous structures, high surface area, and suitable pore volume, and t...

Nonoxidative methane activation, coupling, and conversion to ethane, ethylene, and hydrogen over Fe/HZSM‐5, Mo/HZSM‐5, and Fe–Mo/HZSM‐5 catalysts in packed bed reactor

A high abundance of methane and its relatively low price make it an attractive raw feedstock for the production of ethylene, which is in the consumer demand in recent years. Direct catalytic nonoxidative conversion is interesting, because it could be utilized on natural gas well sites. Monometallic and bimetallic Fe and Mo catalysts were prepared for the purpose of the coupling to ethane and ethene. Three supported materials were synthesized with the following loading of metal: 2.5-wt% Fe, 5.0-wt% Fe, and 2.5-wt% Mo on HZSM-5. Process' chemical reactions were also catalyzed with a constant 2.5-wt% Mo/HZSM-5, which had different amounts of Fe, namely, 0.5, 1.0, and 2.5 wt%. Fourier transform infrared (FTIR), N2 adsorption/desorption, NH3 temperature-programmed desorption (TPD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD) were applied for characterization. Coke, accumulated on spent solids, was determined by thermogravimetric analysis (TGA). Activity was evaluated in quartz-packed bed reactor. All surfaces suffered from deactivation due to carbon formation. The addition of Fe to Mo increased CH4 reacted. The highest selectivity for alkenes was achieved over 1.0-wt% Fe to 2.5-wt% Mo/HZSM-5. At the peak of performance, the C-based reactivity was 52% for olefins and 2% for alkanes. Stability was accomplished over 2.5-wt% Fe/HZSM-5, where the rate of C2 synthesis was comparatively stable for 20 hours of the time on stream. The selective C-basis yield for C2H4 and C2H6 was 36% and 23%, respectively. The lowest measured quantity of (carbonaceous) by-products was deposited on 2.5-wt% Fe/HZSM-5 after 26 hours. Propylene was detected very limitedly.

The effect of carrier in KCoMoS-supported catalysts for hydro-upgrading of model FCC gasoline

K-CoMo/Sup (where Sup = Al2O3, SiO2, TiO2 and ZrO2) catalysts were synthesized using H3PMo12O40, CoCO3, KOH and citric acid. The catalysts were characterized by temperature-programmed reduction (TPR), temperature-programmed desorption of NH3, X-ray photoelectron spectroscopy, transmission electron microscopy. Samples were tested in hydrotreating of model fluid catalytic cracking gasoline and in selective hydrogenation of 1,5-hexadiene and n-heptene-1. The type of used carrier significantly affected the morphology of active phase and catalytic properties. Active sites productivity of K-CoMo/Sup catalysts in hydrodesulfurization (HDS) and olefin hydrogenation (HYDO) reactions as well as HDS/HYDO selectivity correlated with active phase morphology excepting TiO2-supported sample. Productivity of active sites in reactions of selective hydrogenation of diolefin depended on maximum peak reduction obtained from TPR, which in turn was a function of acidity of using supports. The highest HDS/HYDO selectivity was obtained at catalyst which possessed the lowest selectivity towards partial hydrogenation of diolefine compared to complete hydrogenation.

Selective Catalytic Reduction of NOx over V2O5-WO3-TiO2 SCR Catalysts—A Study at Elevated Pressure for Maritime Pre-turbine SCR Configuration

The selective catalytic reduction (SCR) of NOx using NH3 was studied at pressures up to 5 bar over a vanadium-based SCR catalyst (~1 wt% V2O5 and 10 wt% WO3/TiO2), relevant for the installation of SCR reactors upstream of the turbocharger at marine engines. Experiments were performed using both granulated catalyst in a lab-scale fixed-bed reactor and a monolith catalyst in a bench-scale setup. The residence time across the catalytic bed was kept constant, by increasing the (normalized (0 °C, 1 atm)) volumetric flow rate proportionally to the pressure. The results show that for the granulated catalyst, the NOx conversion was independent of the pressure, indicating that the SCR kinetics are not affected by the increased pressure up to 5 bar. NH3 temperature-programmed desorption experiments showed that the catalyst NH3 adsorption increased with more than 30% when the pressure was increased from 1 bar to 4.5 bar. On the other hand, when the adsorption temperature was increased from 150 to 300 °C, the adsorption capacity decreased by approximately 60% independent on the pressure. The SCR reaction was unaffected by the increased NH3 uptake caused by the increased pressure, because only a certain fraction of the sites ( $$ {\theta}_{N{H}_3}^{\ast } $$ = 0.14) was found to be active in the SCR reaction, and these are filled up at lower NH3 partial pressure than the total number of sites. Experiments using a monolithic catalyst showed that at temperatures above 250 °C, the NOx conversion was lower at an increased pressure (3.1 bar) when the residence time was held constant. This decrease was ascribed to increased internal and external diffusion limitations at the elevated pressure.

Ring Enlargement of Methylcyclopentane over Pt/(HZSM-48+pseudoboehmite) Catalysts

Platinum catalysts loaded on a hybrid support, composed of HZSM-48 and pseudoboehmite, were applied to the synthesis of benzene through methylcyclopentane (MCP) reforming in order to investigate the effect of the addition of pseudoboehmite to Pt/HZSM-48 for ring-enlargement reaction. A total of 0.5 wt% of platinum was impregnated on the hybrid support by using the incipient wetness method. Catalyst characterization was performed with nitrogen sorption, X-ray diffraction, temperature-programmed desorption of NH3, and infrared spectroscopy of adsorbed pyridine. It was found that mesoporous structures were well-developed in Pt/(HZSM-48 + pseudoboehmite) catalyst as a result of the pseudoboehmite addition, of which the average pore size was in the range of 7–8 nm. The presence of pseudoboehmite in the catalyst increases the total amount of acid sites and weakens the acid strength, compared with those of the Pt/HZSM-48 catalyst. Lewis acid sites were more abundant than Brönsted acid sites over the Pt/(HZSM-48+pseudoboehmite) catalysts. It was found that selectivity to the ring-enlargement reaction is dominant over selectivity to the ring-opening reaction over the Pt/(HZSM-48 + pseudoboehmite) catalysts. The benzene yield over Pt/(HZSM-48 + pseudoboehmite, 1:1) catalyst reached 65.1% at 450 °C and 0.3 h−1. As well as being influenced by the mesoporous structure, the higher activity and selectivity in MCP reforming was also determined by appropriate acidity of the Pt/(HZSM-48 + pseudoboehmite) catalysts.