Effect Of Catalyst Properties Research Articles

Dehydrogenation of Diethylene Glycol to Para-Dioxanone over Cu/SiO2 Catalyst: Effect of Structural and Surface Properties

Para-dioxanone, a typical monomer for high-performance biomedical polymers, is generally obtained from the catalytic dehydrogenation of diethylene glycol. In this work, Cu/SiO2 catalysts were prepared by two different methods and applied in diethylene glycol dehydrogenation. The effects of catalyst properties on the performance of para-dioxanone production were systematically explored by combined techniques. The results showed that the high specific surface area and regular pore structure of the catalyst promoted and stabilized the high dispersion of the copper species with an abundant Cu-Si interface, thereby providing numerous reactive sites. The appropriate Cu0/Cu+ ratio in the active components produced efficient synergy, which was responsible for the excellent dehydrogenation performance. In addition, the low surface acid density (0.532 μmol/m2) of the catalyst greatly reduced the occurrence of diethylene glycol dehydration, thus improving para-dioxanone selectivity over 90% with promising stability.

Neurofuzzy modelling on the influence of Pt–Sn catalyst properties in direct ethanol fuel cells performance: Fuzzy inference system generation and cell power density optimization

Pt-based materials are commonly employed as catalysts in the electrooxidation of ethanol in direct ethanol fuel cells (DEFC). However, due to the complex nature of electrooxidation, the effect of catalyst properties on fuel cell power generation is not easily described by mechanistic models. Fuzzy systems can be used instead precisely for their ability to provide a more direct and qualitative/semiquantitative cause-effect relationship. In this study, a neurofuzzy model was developed to relate the effect of 5 input variables (4 catalyst properties, namely, crystal size, surface area, presence of PtSn phase and Pt L3-edge whiteline integrated intensity, and the cell potential) on cell current density. The fuzzy inference system (FIS) structure was constructed in MATLAB with ANFIS (Adaptive network-based FIS) based on experimental data used for training and validation. A 4-variable FIS (not including integrated intensity) was initially created and used as a basis for developing the 5-variable FIS, thus addressing the issue of fewer experimental data points available for integrated intensity. Both FIS structures exhibited very good fits to experimental data. The addition of integrated intensity as an input variable did not affect the fitted fuzzy model parameters for the other input variables and, therefore, a broader and more relevant model that included an electronic property of the catalyst was created. Response surface analyses, corroborated by particle swarm optimization, indicated that decreasing crystal size has the greatest effect in maximizing power density. Medium potentials and medium integrated intensity are also favorable. In addition, presence of the PtSn phase in moderate amounts is not unfavorable. With these values it was possible to predict the optimization of the power density value to 24.3 mW/cm2, compared to the best experimental value of 19.6 mW/cm2.

Effect of catalyst properties on selectivity in CO2 methanation with coupling pathway of RWGS and CO methanation

The multiplicity of catalyst structures and modification strategies makes possible different reaction pathways and selectivity of CO2 methanation, and the reaction mechanism is also controversial.

Impact of acid site concentration and temperature on the operating regime, activity and selectivity in methanol-to-olefins conversion over H-ZSM-5

The effect of Si/Al ratio on operating regime, activity and selectivity in methanol-to-olefins conversion has been assessed over H-ZSM-5 zeolites with high (Si/Al=25), moderate (Si/Al=40) and low (Si/Al=140) acid site concentration, in a wide temperature (325 – 450 °C) and space time range (0.44 – 110.0 kgcat s molMeOH-1). For Si/Al=25 no stable regime is achieved, shifting immediately from transition to deactivation, while Si/Al=140 always ensures stable operation. At lower Si/Al ratio and increasing temperature, reaction pathways shift to produce more C3-C5 olefins. Suppression of bimolecular methylation and hydride transfer in favour of monomolecular alkene cracking is at the origin of such behaviour, either by increased acid sites distance or due to reduced physisorbed concentrations and activation energy differences. The latter phenomena cause a peculiar conversion decrease with increasing temperature between 350 and 400 °C. Consistent, well-designed data acquisition allowed insights into the complex mechanism and the effect of catalyst properties and temperature thereon.

Hierarchical nano-sized ZnZr-Silicalite-1 multifunctional catalyst for selective conversion of ethanol to butadiene

Direct conversion of ethanol to butadiene (ETB) is a promising process for the production of renewable butadiene, but it still confronts great obstacles such as low butadiene selectivity and poor stability. Here, we report a hierarchical nano-sized ZnZr-Silicalite-1 multifunctional catalyst with high catalytic performance and stability in direct ETB process, and it was prepared by a facile one-pot crystallization process. The hierarchical nano-sized ZnZr-Silicalite-1 multifunctional catalyst achieved excellent butadiene selectivity of 61.4% and ethanol conversion of 89.8% at 350 °C and 0.38 h−1. More importantly, it possessed superior stability compared to the previously reported catalyst systems. The effect of catalyst properties on catalytic performance were investigated using multiple characterized techniques. The results displayed that the ZnZr-Silicalite-1 catalyst possessed a hierarchical nano-sized structure, synergistic effects of various active centers, and suitably balanced acid-base properties. These properties realized excellent catalytic performance and stability for direct ETB conversion.

Experimental Study of the Effect of Catalyst Properties on Hydrodynamics and Mass Transfer in a Slurry Reactor

Experimental Study of the Effect of Catalyst Properties on Hydrodynamics and Mass Transfer in a Slurry Reactor

Photocatalytic degradation of metoprolol by TiO2 nanotube arrays and UV-LED: Effects of catalyst properties, operational parameters, commonly present water constituents, and photo-induced reactive species

The aim of this study was to evaluate the use of self-organized TiO2 nanotube arrays (TNAs) as immobilized catalyst and UV-LED as light source (UV-LED/TNAs) for photocatalytic degradation of the β-blocker metoprolol (MTP) from aqueous solution. Firstly we employed electrochemical anodization to synthesize self-organized TNAs, and the effect of anodization potential and annealing temperature was examined. Characterization by SEM demonstrated a linear relation between the diameter of TiO2 nanotubes produced and the anodization potential, while Raman measurement revealed the vital role of annealing on crystallographic composition of the anodic produced TiO2 nanotubes. Regarding their performance in photocatalytic MTP degradation, surface morphology and crystallographic composition of the TNAs were found to impose crucial influence: only TNAs with diameter not smaller than 53nm enabled rapid MTP degradation, and highest MTP degradation was obtained when a mixture of anatase and rutile were present in the TNAs. Secondly, the effect of operational parameters, i.e initial MTP concentration, pH, was investigated. Initial MTP concentration at low level had no detrimental effect on the process performance. Rapid MTP degradation and high total removal were achieved in a wide pH range (3–11). To evaluate the applicability of TNAs for water treatment, experiments were first carried out in the presence of three different commonly present water constituents, i.e bicarbonate ions, phosphate ions, and natural organic matters (NOMs). The results show that bicarbonate and phosphate ions have no inhibitory effect at concentration levels up to 200mg/L, and NOMs exhibit detrimental effect when their concentration exceeds 5mg/L. The total removal MTP degradation reduced from 87.09±0.09% to 62.05±0.08% when tap water samples were applied, demonstrating reasonable efficacy for practical applications. Regarding the degradation mechanism, formic acid and tert-butanol were added as scavenger for photo-generated holes (h+) and hydroxyl radicals (·OH), respectively. The obtained results demonstrate that primary degradation process occurred in liquid phase with participation of hydroxyl radicals in the liquid phase (·OH liquid), while smaller portion of MTP were degraded on the catalysis surface via reaction with h+ and hydroxyl radicals adsorbed on the catalyst surface (·OH surface). Other reactive species, e.g photo generated electrons and superoxide radical anions, did also play a minor role in MTP degradation. The mechanistic aspect was further confirmed by identification of degradation products by LC–MS/MS. The TNAs exhibited good stability after repeated use under varied operation conditions.

Carbon dioxide hydrogenation over nickel-, ruthenium-, and copper-based catalysts: Review of kinetics and mechanism

ABSTRACTThis study critically reviews the mechanism of CO2 hydrogenation over Ni, Ru, and Cu, and the effect of catalyst properties and operating conditions on reaction kinetics. Most studies have reported the presence of CO and formate species on Ni-, Ru-, and Cu-based catalysts, where subsequent conversion of these species depends on the type of catalyst and the physicochemical properties of the catalyst support. Methane is the major product that forms during CO2 hydrogenation over Ni and Ru catalysts, while methanol and CO are mainly produced on Cu catalysts. A different approach for catalyst formulations and/or process development is required where long chain hydrocarbons are desired.

The Effects of Catalyst Properties on the Conversion of Biomass via Catalytic Fast Hydropyrolysis

Catalytic fast hydropyrolysis (CFHP) is an attractive and alternative method for thermochemical conversion of biomass to fuels. The objective of the present work is to determine the effects of support porosity, acidity, and impregnated metal species on the CFHP product distribution. CFHP of Miscanthus x giganteus in the presence of SiO2 and Al2O3 results in high solid and low volatile product yields, due to the lack of Bronsted acidity, whereas CFHP with the acidic and shape-selective ZSM-5 returns high volatile products yield and aromatic selectivity. Increasing ZSM-5 acidity reduces monoaromatic hydrocarbon (MAH) and solid yield, but increases yields to naphthalenes, polyaromatic hydrocarbons, and carbon oxides. Ni supported on mesoporous ZSM-5 slightly increases aromatic yields and decreases solid yield. Impregnation of Ni on all supports significantly shifts CFHP selectivity from solids to CH4. Ni, Ru, and Pd impregnated on ZSM-5 all have different effects on the CFHP product distribution. Improved MA...

Removal of toxic HCN and recovery of H2-rich syngas via catalytic reforming of product gas from gasification of polyimide over Ni/Mg/Al catalysts

The recycling of N-containing plastics by pyrolysis or steam-reforming is typically complicated by the generation of toxic HCN. In this study, polyimide, as an example of an N-containing plastic, was gasified and the product gas was reformed over various Ni/Mg/Al catalysts. Effects of catalyst properties, steam, and temperature on the HCN removal and H2-rich syngas production were investigated. More than 99% HCN removal (compared with pyrolytic conditions) and ∼3000mLg−1 of H2-rich syngas with a H2/CO ratio of 10.4 were simultaneously achieved at 800°C in the presence of a reduced-Ni1.0Mg3.6Al4.8 catalyst, then HCN was mainly converted into N2. On the other hand, non-reduced same catalyst enhanced hydrolysis of HCN into NH3 with more than 98% HCN removal at 800°C, which is also a beneficial finding to recover useful NH3 from HCN, directly. Therefore, the present work achieved that the improvement of the H2-rich syngas yield and quality, and conversion of toxic HCN into non-toxic N2 or useful NH3 using the same catalyst, simultaneously.

Effect of Catalyst Properties on Hydrocracking of Pyrolytic Lignin to Liquid Fuel in Supercritical Ethanol

The metal-acid bifunctional catalysts have been used for bio-oil upgrading and pyrolytic lignin hydrocracking. In this work, the effects of the metal-acid bifunctional catalyst properties, including acidity, pore size and supported metal on hydrocracking of pyrolytic lignin in supercritical ethanol and hydrogen were investigated at 260 °C. A series of catalysts were prepared and characterized by BET, XRD, and NH3-TPD techniques. The results showed that enhancing the acidity of the catalyst without metal can promote pyrolytic lignin polymerization to form more solid and condensation to produce more water. The pore size of microporous catalyst was smaller than mesoporous catalyst. Together with strong acidity, it caused pyrolytic lignin further hydrocrack to numerous gas. Introducing Ru into acidic catalysts promoted pyrolytic lignin hydrocracking and inhibited the polymerization and condensation, which caused the yield of pyrolytic lignin liquefaction product to increase significantly. Therefore, bifunctional catalyst with high hydrocracking activity metal Ru supported on materials with acidic sites and mesopores was imperative to get satisfactory results for the conversion of pyrolytic lignin to liquid products under supercritical conditions and hydrogen atmosphere.

Heterogeneous photocatalysis on construction materials: effect of catalyst properties on the efficiency for degrading NOx and self cleaning

This paper analyzes the effect of some properties of different catalysts on the photocatalytic activity. The efficiency has been determined for two different processes: NOx abatement and self-cleaning for Rhodamine B and tobacco extract being, the TiO2 based photocatalyst, supported as coatings on white mortar. Eight different catalysts were tested, seven commercial ones and one home-made catalyst with improved visible light absorption properties. Additionally, some of them were submitted to exposition to water and/or calcinations to alter their physical properties. A kinetic approach was used to evaluate the photocatalytic activity, being the first reaction constant (for NO) and just empirical constants (for self-cleaning) the parameters used for the comparison of the different materials. As a result, the efficiency, even for ranking, is dependent on the type of contaminant used in the experiment. In general, NO oxidation and tobacco followed similar trends while no clear relations were found for Rhodamine B.

Production of Bio-oil from Algal Biomass and Its Up-gradation: Recent Developments

AbstractAlgae, particularly microalgae are getting strong ground as a potential and environment friendly feedstock for biodiesel production in recent years due to its high growth rate (biomass yield) and high lipid content in some species. In the present paper the potential of algae as a feedstock for bio-oil production has been described. Mechanistic approach and optimum conditions for the algal growth as well as bio-oil production has been explained. Performance of various types of photo bioreactors has been critically analyzed to select suitable route for algal growth. Conventional methods such as mechanical and chemical extraction processes for the production of bio-oil form algal biomass have been described along with recent developments including supercritical extraction and microwave assisted processes. Various processes and catalysts for the up-gradation of bio-oil to biodiesel along with recent developments have also been described and compared. Effects of catalyst properties on the up-gradation of bio-oil have been critically analyzed for designing more efficient catalyst and consequently to improve the efficiency of the up-gradation process. Production of drop-in bio-fuel through hydrotreating of bio-oil is described. World scenario on the production of bio-fuel from algal biomass has also been provided.

Catalytic performance of nano crystalline H-ZSM-5 in ethanol to gasoline (ETG) reaction

HZSM-5 zeolites of varying acidity and porosity were prepared under various synthesis conditions, and the effect of catalyst properties on the conversion of ethanol to gasoline reaction was investigated. Special emphasis is given to understand the role of strong acidity in effective oligomerization of olefin intermediates and their effective conversion to gasoline range hydrocarbons (most of it contains aromatics and isoparaffins) through hydrogen transfer (HT) reactions. The nano crystalline ZSM-5 (NZ) catalyst having high acidity and stacking order of mesoporosity showed high gasoline yields. The micro crystalline ZSM-5 (Catalyst Z) also exhibited comparable acidity with NZ, but could not give higher gasoline yields due to the absence of mesopores in the catalyst. Where as, catalyst ZA (micro crystalline) with low acidity and absence of mesopores produced considerable amount of propylene along with less gasoline. The studies envisioned the need of strong acidity and mesoporosity for effective conversion of olefin intermediates into C5+ oligomers and their conversion to gasoline through HT reactions.

Effect of catalyst properties on the cracking of polypropylene pyrolysis waxes under FCC conditions

The catalytic cracking of polyolefin pyrolysis waxes has been studied under conditions that mimic the operation of a catalytic cracking unit (FCC). Two commercial catalysts of different properties were used. Yields and compositions of the lumps (dry gases, LPG, gasoline and coke) were compared with those corresponding to the actual feed in the refinery (vacuum gas-oil). The effect of process operating conditions (temperature and contact time) is significant. Catalyst acidity has a significant effect on conversion (at a temperature around 525 °C) and on yields and compositions of lumps (in the 500–550 °C range). The main effect of increasing catalyst acidity is an increase in coke content on the catalyst by decreasing the yield to dry gases. Due to the higher hydrogen transfer capacity, the gasoline obtained using the catalyst with higher acidity has a higher aromatic (especially C 6–C 8) and paraffinic content, and lower olefin content, being these two latter fractions less branched. An increase in catalyst acidity leads to a lower yield of light olefins and to an increase in the yield of paraffins.

Effect of Catalyst Properties on Membrane Degradation Rate and the Underlying Degradation Mechanism in PEMFCs

Nafion membrane degradation was studied in a polymer electrolyte membrane fuel cell (PEMFC) under accelerated decay conditions. Fluoride emission rate (FER) determined by fuel cell effluent water analysis was used to quantify the membrane degradation. Membrane degradation is most likely caused either directly or indirectly by the species formed as a result of the and reaction on the catalyst. To further understand the mechanism, the effects of the catalyst location, type, its interaction with and , and cell current density on the FER were investigated and their implications on the underlying membrane degradation mechanism are discussed.

The effect of catalyst properties on the in situ reduction of sulfur in FCC gasoline

In this paper, the results of a study on the effects of catalyst properties and contaminant metals on FCC gasoline sulfur are reported. Data for four steamed deactivated FCC catalysts showed that the higher the unit cell size (UCS) of an FCC catalyst, the lower the sulfur concentration in FCC gasoline. These results suggest a mechanism that explains gasoline sulfur reduction through a hydrogen transfer step resulting in saturation of thiophenes. The effects of contaminant metals, that usually exist on FCC catalysts (Ni and V), on FCC gasoline sulfur, were examined for both equilibrium and deactivated catalysts. The presence of these metals lowers gasoline sulfur dramatically. Vanadium (V) in its highest oxidation step is most effective. It appears that these metals catalyze the cyclization of long alkyl-thiophenes to form alkyl-benzothiophenes boiling outside the gasoline range. Finally, it was observed that the presence of ZSM-5 additive resulted in an increase in gasoline sulfur.

Effects of Catalyst Properties on Asphaltenes Composition During Hydrotreating of Heavy Oils

Three NiMo commercial catalysts were used for carrying out hydrotreating (HDT) experiments in a high-pressure pilot plant. Maya crude oil was employed as HDT feed. All hydrotreated products and their corresponding precipitated asphaltenes fractions were characterized by elemental analysis and metals contents. Extraction of asphaltenes was carried out according to the method described in ASTM D-3279. It was observed from our characterization results that while nitrogen and metals content in asphaltenes increase sulfur decrease as the reaction temperature is increased. This different behavior was attributed to the localization of each heteroatom in the asphaltene molecule. Pore size of catalysts showed the major influence on hydrotreated product asphaltenes composition.

Effect of catalyst properties and operating conditions on hydroprocessing of high-metals feeds.

Catalytic hydroprocessing of high metals heavy oils, containing over 480 ppm Ni + V, was carried out in trickle bed pilot units. The analyses of the used catalysts (coke, metals content, and vanadium distribution) were correlated with the deactivation runs. The deactivation by coke is very much dependent on the catalyst physical properties (mean pore diameter), rather than on the chemical properties, and on the nature of the feed. As metals removal is a diffusion-controlled reaction, catalysts and operating conditions that increase the Thiele modulus, e.g., high activity and small pore catalysts, high hydrogen pressures and temperatures, show a stronger deactivation by feed metals. In this case, most of the vanadium was deposited in the outer edge of the catalyst particle. Unconventional vanadium profiles along the reactor length were obtained under certain conditions. Based on these data, a kinetic model was proposed which considers that demetallization is a complex reaction that occurs through a series of consecutive and parallel reactions.

Hydroprocessing of solvent-refined coal: effect of catalyst properties

Etude de l'hydrotraitement sur des catalyseurs Ni−Mo/Al 2 O 3 d'un melange a 50% d'un extrait de charbon par le procede SRC-I et d'huile de creosote en vue de determiner l'influence des proprietes du catalyseur sur le degre d'hydrogenation, de desulfuration, de denitrification et de conversion de la fraction a point d'ebullition superieur a 728°K