Intrinsic Kinetics of Ethanol Dehydration Over Lewis Acidic Ordered Mesoporous Silicate,Zr-KIT-6

Lewis acidic Zr-KIT-6 catalyst was tested for ethanol dehydration. Under the reaction conditions studied (T = 300–380 °C, P = 1 atm, P _ethanol = 5 % in N₂), Zr-KIT-6 materials showed high ethylene selectivity (~80 %) with stable activity (60 h). The activation energy for ethanol dehydration to ethylene, estimated from intrinsic rate constants normalized with respect to the Lewis acid sites, was approximately 79 ± 1 kJ/mol.     

Intrinsic Kinetics of Ethanol Dehydration Over Lewis Acidic Ordered Mesoporous Silicate,Zr-KIT-6

Lewis acidic Zr-KIT-6 catalyst was tested for ethanol dehydration. Under the reaction conditions studied (T = 300–380 °C, P = 1 atm, P _ethanol = 5 % in N₂), Zr-KIT-6 materials showed high ethylene selectivity (~80 %) with stable activity (60 h). The activation energy for ethanol dehydration to ethylene, estimated from intrinsic rate constants normalized with respect to the Lewis acid sites, was approximately 79 ± 1 kJ/mol.

     

Enhanced Activity via Surface Modification of Fe-Based Fischer–Tropsch Catalyst Precursor with Titanium Butoxide

The surface of a model iron catalyst precursor was modified with titanium butoxide to introduce Fe–O–Ti interactions in a controlled manner and to investigate the role of these interactions in the catalyst. The reduction of the model catalyst precursors in hydrogen at 350 °C for 16 h leads to the formation of α-Fe and an iron–titanium mixed oxide, due to the incorporation of Ti into the iron oxide structure. The α-Fe phase is transformed into χ-Fe₅C₂ during the Fischer–Tropsch synthesis at 250 °C, whilst the Fe–Ti mixed oxide phase is preserved. A higher reaction temperature of 300 °C is required to transform some the oxide phase into a carbide phase under Fischer–Tropsch conditions. The intrinsic activity of the iron carbide phase in samples also containing the Fe–Ti mixed oxide phase is at a reaction temperature of 250 °C ca. 20 % more active than in the sample, which does not contain the mixed oxide.     

Significant Improvement in Activity and Stability of Pt/TiO2 Catalyst for Water Gas Shift Reaction Via Controlling the Amount of Na Addition

Na promoted Pt/TiO₂ catalysts have been studied under high severity, near equilibrium, conditions for use as a single stage WGS catalyst. Addition of 3 wt% Na to a 1 wt% Pt/TiO₂ catalyst has been found to improve water gas shift activity significantly compared to Pt/TiO₂, Pt/CeO₂, and Pt–Re/TiO₂ catalysts. This catalyst is stable when the reaction temperature is higher than 250 °C. Deactivation occurred when the reaction temperature was lower than 250 °C, however, returning the temperature to higher than 250 °C fully recovered activity. TEM observations revealed that addition of Na inhibited Pt particle sintering. These results suggest that Na promoted Pt/TiO₂ is a promising single stage water gas shift catalyst for small scale hydrogen production.     

Novel Silver Loaded Hydroxyapatite Catalyst for the Selective Catalytic Reduction of NOx by Propene

A novel and high performance silver loaded hydroxyapatite (HAp) catalyst for the selective catalytic reduction (SCR) of NO_x by propene is reported for the first time. The catalysts with variable silver contents have been prepared and characterized extensively by different techniques such as XRD, XPS, BET-surface area, TPR, TPD and ICP analyses. The DeNO_x activities of these catalysts are measured at reaction temperature ranged from 250 to 500 °C. The 1.5 wt.% Ag/HAp is found to be best among all the catalysts studied showing about 70% conversion and 60% selectivity towards N₂ formation at 375 °C in oxygen rich atmosphere.     

Effect of Silver Loading on the Lean NOx Reduction with Methanol Over Ag–Al2O3

The influence of silver loading on the lean NO_x reduction activity using methanol as reductant has been studied for alumina supported silver catalysts. In general, increasing the silver loading (0–3 wt%), in Ag–Al₂O₃, shifts or extends the activity window, for lean NO_x reduction towards lower temperatures. In particular Ag–Al₂O₃ with 3 wt% silver is active for NO_x reduction under methanol-SCR conditions in a broad temperature interval (200–500 °C), with high activity in the low temperature range (maximum around 300 °C) typical for exhaust gases from diesel and other lean burn engines. Furthermore, increasing the C/N molar ratio enhances the reduction of NO_x. However, too high C/N ratios results in poor selectivity to N₂.     

NiCoFe/C cathode electrocatalysts for direct ethanol fuel cells

A direct ethanol fuel cell (DEFC), which is less prone to ethanol crossover, is reported. The cell consists of PtRu/C catalyst as the anode, Nafion^® 117 membrane, and Ni–Co–Fe (NCF) composite catalyst as the cathode. The NCF catalyst was synthesized by mixing Ni, Co, and Fe complexes into a polymer matrix (melamine-formaldehyde resins), followed by heating the mixture at 800 °C under inert atmosphere. TEM and EDX experiments suggest that the NCF catalyst has alloy structures of Ni, Co and Fe. The catalytic activity of the NCF catalyst for the oxygen reduction reaction (ORR) was compared with that of commercially available Pt/C (CAP) catalyst at different ethanol concentrations. The decrease in open circuit voltage (V_oc) of the DEFC equipped with the NCF catalysts was less than that of CAP catalyst at higher ethanol concentrations. The NCF catalyst was less prone to ethanol oxidation at cathode even when ethanol crossover occurred through the Nafion^®117 film, which prevents voltage drop at the cathode. However, the CAP catalyst did oxidize ethanol at the cathode and caused a decrease in voltage at higher ethanol concentrations.     

Sintering of Colloidal Ru/γ-Al2O3 Catalyst in Hydrogen

Colloidal 5.1 wt% Ru/γ-Al₂O₃ catalyst was prepared by a microwave assisted, solvothermal reduction of RuCl₃ in ethylene glycol in the presence of γ-Al₂O₃. The catalyst subjected to heat-treatment in hydrogen up to 700 °C, was characterized by BET, XRD, TEM and H₂ chemisorption. As-prepared catalyst contained Ru nanoparticles with mean size of 1.5 nm and narrow size distribution uniformly distributed over the support. The nanoparticles were stable on the alumina to 500 °C, but treatment at 600–700 °C caused some sintering of Ru due to migration and coalescence of a part of smallest ruthenium nanoparticles. However, even after H₂ treatment at 700 °C, large amount of Ru nanoparticles with sizes of 1–3 nm remained in the catalyst. H₂ chemisorption data revealed decrease of Ru dispersion from 0.28 to 0.19 by hydrogen treatment at 700 °C and were in good correspondence with TEM results. On the contrary, mean crystallite sizes obtained from XRD were strongly overestimated.     

Two Reaction Pathways in the Selective Catalytic Reduction of NO x by C6H14 Over Ag–Al2O3 with H2 Co-Feeding

The NO _x reduction with n-C₆H₁₄ was studied over a 3% Ag/Al₂O₃ catalyst in the presence of hydrogen. The catalyst performance was evaluated by varying the H₂ concentration from 0 to 1600 ppm and by comparing the results with blank runs in which an empty reactor with no catalyst was used. Two distinct reaction pathways were revealed: one at low-temperature (T_react < 370 °C) and another one at high-temperature (T_react > 370–390 °C). Co-feeding of H₂ promotes the reaction within the 150–360 °C interval. The high-temperature pathway (T_react > 370–390 °C) seems to be almost independent of hydrogen co-feeding. The homogeneous gas-phase NO _x oxidation initiated by NO presumably plays an important role in this high-temperature pathway.     

Selective Production of H2 from Ethanol at Low Temperatures over Rh/ZrO2–CeO2 Catalysts

A series of Rh catalysts on various supports (Al₂O₃, MgAl₂O₄, ZrO₂, and ZrO₂–CeO₂) have been applied to H₂ production from the ethanol steam reforming reaction. In terms of ethanol conversion at low temperatures (below 450 °C) with 1wt% Rh catalysts, the activity decreases in the order: Rh/ZrO₂–CeO₂ > Rh/Al₂O₃ > Rh/MgAl₂O₄ > Rh/ZrO₂. Support plays a very important role on product selectivity at low temperatures (below 450 °C). Acidic or basic supports favor ethanol dehydration, while ethanol dehydrogenation is favored over neutral supports at low temperatures. The Rh/ZrO₂–CeO₂ catalyst exhibits the highest CO₂ selectivity up to 550 °C, which is due to the highest water gas shift (WGS) activity at low temperatures. Among the catalysts evaluated in this study, the 2wt% Rh/ZrO₂–CeO₂ catalyst exhibited the highest H₂ yield at 450 °C, which is possibly due to the high oxygen storage capacity of ZrO₂–CeO₂ resulting in efficient transfer of mobile oxygen species from the H₂O molecule to the reaction intermediate.     

Clean Baeyer–Villiger Oxidation Using Hydrogen Peroxide as Oxidant Catalyzed by Aluminium Trichloride in Ethanol

Baeyer–Villiger oxidation of ketones was carried out using AlCl₃ as catalyst, H₂O₂ (30%) as oxidant in innocuity and environmentally friendly ethanol conditions. Cyclic ketones and acyclic ketones were transformed into the corresponding lactones or esters in 5–24 h at 40–70 °C with very high conversion and selectivity. A possible reaction mechanism was also given.     

A Study of the NOx Selective Catalytic Reduction with Ethanol and Its By-products

The NOx selective catalytic reduction (SCR) with ethanol has been investigated over alumina supported silver catalyst with a special attention to the main involved reactions depending on the temperature test. With this aim, the possible reducers from ethanol transformations were also evaluated (C₂H₅OH, CH₃CHO, C₂H₄, CO). In addition, the contributions of the gas phase reactions and the alumina support were also pointed out. Based on the C-products and N-compounds distributions, it is assumed that at low temperature (T < 300 °C), ethanol reacts firstly with NO + O₂ to produce acetaldehyde and N₂. For higher temperatures, two reaction pathways have been proposed, supported by the CH₃CHO-SCR results: a direct reaction between NO₂ and CH₃CHO, or via –NCO species.     

Bio-oil production from Glycyrrhiza glabra through supercritical fluid extraction

Glycyrrhiza glabra was liquefied by ethanol and acetone in an autoclave under high pressure using potassium hydroxide or sodium carbonate as the catalyst, as well as without catalyst at various temperatures (250, 270 and 290 °C) for producing bio-oil. The experimental results show that the yield of the main liquefaction product (bio-oil) was influenced significantly by liquefaction parameters such as solvent type, and catalyst type and temperature. The results showed that the maximum bio-oil yield was obtained in acetone (79%) at 290 °C without catalyst. The products of liquefaction (bio-oil) were analysed and characterized using various methods including elemental analysis, Fourier transform infrared spectroscopy and gas chromatography–mass spectrometry. GC–MS identified 131 and 147 different compounds in the bio-oils obtained at 270 and 290 °C, respectively.     

Non-hydrolytic Sol–Gel Preparation of Silver Alumina Based Catalysts for the HC-SCR of NOx

The preparation of Ag/Al₂O₃ catalysts by nonhydrolytic sol–gel process leads to highly efficient HC-deNOx materials thanks to the silver ability to diffuse toward the surface. The presence of niobium as co-catalyst, with a Nb content comprised between 1 and 3 wt%, enhances the NO reduction efficiency at low temperatures (<250 °C).     

Preparation of meso-structured silica–calcium mixed oxide (MSCMO) catalyst for converting Vietnamese rubber seed oil to biodiesel

This report covered some new contributions in catalyst preparation and characterization. Meso-structured silica–calcium mixed oxide catalyst possessed both acidic and basic sites was synthesized through co-condensation method in alkaline environment using tetraethylorthosilicate, CaO, and cetyltrimethylammoniumbromide. The co-condensation process was established at 90 °C for 24 h obtaining white-gel precipitate which was dried at 120 °C followed by calcination at 550 °C for 5 h. The as-synthesized catalyst was used in conversion of rich free fatty acid rubber seed oil (22 %wt) in Vietnam to fatty acid methyl esters (FAMEs) in mild conditions such as temperature of 120 °C, time of 4 h, catalyst dosage of 3 %wt, methanol/oil mass ratio of 2.5/1 and agitating speed of 550 rpm achieving the reaction yield of 95.4 %. The catalyst were characterized by various techniques such as X-ray diffraction, transmission electron spectroscopy, Nitrogen Adsorption–Desorption Analysis (BET), temperature programmed desorption (NH₃ and CO₂-TPD). Especially, X-ray absorption spectroscopies was applied to explain the occurrence of acid and base sites on catalysts surface. The analysis showed the sixfold coordinated calcium sites characterizing for the mixed oxide structure of CaO–SiO₂. The results helped to simulate the bonding structure around the Ca sites indicating the electrostatic charge differences along the Ca–O–Si connections and the ability for occurring the defect sites containing the O^2? moieties corresponding to the acidity and basicity of the catalysts respectively. Gas chromatography–mass spectroscopy was also used to determine the composition of the FAMEs showing high purity of these products.     

Redox Isotherms for Vanadia Supported on Zirconia

Calcination of a Pt/Ba/CeO₂ catalyst at 700 °C and subsequent reduction in hydrogen, carbon monoxide or propene at 350–550 °C resulted in a considerable improvement of its NO _x storage-reduction (NSR) properties compared to those of a freshly prepared Pt/Ba/CeO₂ catalyst. This behavior is traced back to the temporary formation of BaPtO₃ perovskite which leads after reduction to well-distributed Pt particles in intimate contact with the barium-containing phases. The oxidation and reduction of platinum is reversible which can be exploited for the design of “self-regenerating” NSR-catalysts under lean (>600 °C) and rich (>400 °C) reaction conditions. The formation of the BaPtO₃-perovskite may not only be interesting for NSR-catalysis, but generally for Pt-based catalysts where a high dispersion of Pt is important.     

Preparation of bimodal mesoporous silica containing cerious salt and its application as catalyst for the synthesis of biodiesel by esterification

A kind of bimodal mesoporous silica catalyst modified with ammonium cerous sulfate (ACS/BMMS) was synthesized and applied in the esterification of free fatty acid and alcohol. The characterization results including XRD, N₂ adsorption and desorption, FTIR, ²⁹Si-NMR and TEM showed that ACS/BMMS has orderly arranged bimodal mesopores, the small mesopore diameter is about 4.0–6.0 nm and the large mesopore diameter is in the range of 7.0–9.0 nm. The chemical interaction existed between silica group Si (OH)₂(OSi)₂ and the NH₄ ⁺, SO₄ ^2? and Ce-O groups of cerious salt. When the loading is not more than 10%, cerious salt dispersed finely on the supports. Oleic acid and methanol were used as the raw material of probe reaction; ACS/BMMS had significantly better activity than the ACS/SBA-15, ACS/SBA-16, ACS/MCM-41, BMMS and bulk ACS. The optimum loading of ACS is 10%, the optimum reaction conditions are reaction temperature 140 °C, reaction time 2 h, mole ratio of methanol to oleic acid 2.0 and the dosage of catalyst 4.0%, in above situation the conversion of oleic acid is about 94.0%, the reusability of ACS/BMMS is much better than bulk ACS. The kinetic study showed that the esterification of oleic acid and methanol on ACS/BMMS match Eley–Rideal model very well.     

ACCELERATION OF THE WET OXIDATION REACTION OF PIPERAZINE BY HETEROGENEOUS Ru/TiO2 CATALYST

Wet air oxidation is a candidate technique for the effective treatment of wastewater contaminated by nitrogenous organic pollutants. Piperazine (PZ) is a cyclic diamine representing this class of compounds. In the present work, the wet oxidation reaction of PZ was studied for the first time. It was found that, in the studied range of temperatures of 180°–230°C and O₂ partial pressures of 0.69–2.07 MPa, the oxidation process was slow. Total organic carbon (TOC) conversion at 230°C and 0.69 MPa O₂ partial pressure was just 52% after 2 h. The investigated reaction was accelerated by a heterogeneous Ru/TiO₂ catalyst. Maximum TOC conversion (91%) was achieved during catalytic wet oxidation at 210°C and 1.38 MPa O₂ pressure. Kinetic data were collected over the range of temperatures 180°–210°C, O₂ partial pressures 0.34–1.38 MPa, and catalyst loading 0.11–0.66 kg/m³. The lumped TOC concentration decay was a two-step first-order process.     

Photocatalytic Activity of AgBr as an Environmental Catalyst

The photocatalytic activity of AgBr has been investigated. AgBr(N₂) was prepared by solid(AgNO₃)–solid(KBr) reaction at different temperatures in a stream of N₂. AgBr(N₂) prepared at 250 °C showed the highest H₂ generation activity although the larger crystallites of Ag were observed. When the preparation was carried out under air [AgBr(air)] at 250 °C, the photoactivity and the crystallization of Ag were lowered by the formation of silver oxides species in AgBr(air) probably during the natural cooling under air. It is pointed out however that the amount of hydrogen of both AgBr(N₂) and AgBr(air) increased linearly increasing with reaction time regardless of the formation of large Ag crystallites even after UV irradiation for 50 h. This suggests that the behavior of Ag formed might be different from that of the latent image in the photographic process.     

Effects of temperature,reaction time,atmosphere, and catalyst on hydrothermal liquefaction of Chlorella

Hydrothermal liquefaction (HTL) is the direct conversion of wet biomass into bio-oil at high temperature (200–400°C) and high pressure (10–25 MPa). In this work, we investigated HTL with 4.5 g of Chlorella and 45 ml of water/ethanol (1:1 vol. ratio) in a 100 ml reactor. Bio-oils produced are characterized via elemental analysis, thermogravimetric analysis, and gas chromatography–mass spectrometry (GC–MS). HTL of Chlorella was investigated at 240 and 250°C for 0 and 15 min under an air or H₂ atmosphere and with and without 5% zeolite Y. Temperature increased the bio-oil yield from 38.75% at 240°C to 43.04% at 250°C for 15 min reaction time. Longer reaction time increased the bio-oil yield at 250°C from 39.14% for 0 min to 43.04% for 15 min. The H₂ atmosphere had a significant effect for HTL at 240°C. Zeolite Y increased the bio-oil yield significantly from 32.03% to 43.06% at 250°C for 0 min. The carbon content of bio-oil increased with the temperature while the oxygen content decreased. The boiling point distribution of bio-oils in the range of 110–300°C varies with temperature, and atmosphere. At 240°C for 15 min, the 110–300°C range increased from 31.19% in air (240-15-air) to 39.25% in H₂ (240-15-H₂). The H₂ atmosphere increased the content of hydrocarbons, alcohols, and esters from 69.61% in air (240-0-air) to 82.83% in H₂ (240-0-H₂). Overall, temperature, reaction time, atmosphere, and catalyst all significantly influenced the yield and/or quality of bio-oils from HTL of Chlorella.