Direct Catalytic Conversion of Ethanol to C5+ Ketones: Role of Pd–Zn Alloy on Catalytic Activity and Stability

Ethanol can be used as a platform molecule for synthesizing valuable chemicals and fuel precursors. Direct synthesis of C₅₊ ketones, building blocks for lubricants and hydrocarbon fuels, from ethanol was achieved over a stable Pd‐promoted ZnO‐ZrO₂ catalyst. The sequence of reaction steps involved in the C₅₊ ketone formation from ethanol was determined. The key reaction steps were found to be the in situ generation of the acetone intermediate and the cross‐aldol condensation between the reaction intermediates acetaldehyde and acetone. The formation of a Pd–Zn alloy in situ was identified to be the critical factor in maintaining high yield to the C₅₊ ketones and the stability of the catalyst. A yield of >70 % to C₅₊ ketones was achieved over a 0.1 % Pd‐ZnO‐ZrO₂ mixed oxide catalyst, and the catalyst was demonstrated to be stable beyond 2000 hours on stream without any catalyst deactivation.     

Non-Thermal Plasma Assisted Regeneration of Acetone Adsorbed TiO2 Surface

Improvement of indoor air quality regarding volatile organic compounds (VOCs) requires the development of innovative oxidation processes. This paper investigates the coupling of a metal oxide sorbent with non-thermal plasma (NTP) in an especially designed reactor. TiO₂ was selected as model sorbent and acetone was used as model VOC. The analyses of gas phase species at the reactor downstream have been performed using FTIR spectroscopy. In a first step, acetone adsorption on TiO₂ surface under dry air was characterized in terms of total amount adsorbed, as well as reversibly and irreversibly adsorbed fractions. Obtained results were compared and discussed with literature in terms of acetone reactive adsorption on TiO₂ surface. Mesityloxide was proposed as the major compound in the irreversibly adsorbed fraction. In a second time, acetone saturated TiO₂ surface was exposed to NTP surface discharge. Irrespectively of the injected power, <30 % of the initially adsorbed acetone has been recovered as CO, CO₂ and desorbed acetone. Finally, thermal desorptions have been performed. They evidenced that (1) NTP treatment modifies the nature of the adsorbed organic species, (2) mineralization rate is considerably improved. Based on desorbed species temporal profile analysis, carboxylates and more especially formates are suggested as major adsorbed species after NTP treatment (P_inj > 0.2 W). This hypothesis has been evaluated and confirmed. This paper finally evidenced that NTP can be used as an efficient pretreatment technique to promote the mineralization of adsorbed acetone for further thermal treatment.     

Preparation and separation characteristics of polyelectrolyte complex membranes containing sulfated carboxymethyl cellulose for water–ethanol mixtures at low pH

Novel polyelectrolyte complexes based on sulfated carboxymethyl cellulose and chitosan were prepared, containing strongly charged (sulfate (OSO₃)) and weakly charged (carboxylate (COO^?)) groups (SPECs). SPEC homogeneous membranes (SPECMs) for the pervaporation dehydration of ethanol–water mixtures were investigated. The chemical structures and compositions of SPECMs were characterized by Fourier transform infrared spectroscopy and X-ray photoelectron spectra. The swelling behavior and separation performance of SPECMs in low pH feed were evaluated. It was found that the SPECMs containing OSO₃ groups were resistant to acidic feeds and showed very good separation performance even in low pH feed. For instance, the water content in permeate for SPECM-0.35 reached as high as 95.8 wt%, which was much higher than the 60 wt% for SPECM-0 in the dehydration of water–ethanol mixtures with pH 2. The result was attributed to the interplay between the stable complexation formed by OSO₃ groups and the improved ionization degree of COO^? groups in SPECMs. Moreover, the SPECMs maintained their operation stability against acidic feeds. The SPECMs could find considerable potential application in the pervaporation dehydration of acidic feeds, especially for enhancing the conversion of ester condensation.     

A Triptycene-Based Porous Organic Polymer that Exhibited High Hydrogen and Carbon Dioxide Storage Capacities and Excellent CO2/N2 Selectivity

A novel porous organic polymer (POP) has been constructed through the condensation of triptycene tricatechol and 1,3,5‐benzenetris(4‐phenylboronic acid). This triptycene‐based POP exhibited high H₂ uptake (up to 1.84 wt% at 77 K, 1 bar), large CO₂ adsorption capacity (up to 18.1 wt% at 273K, 1 bar), and excellent CO₂/N₂ adsorption selectivity (up to 120/1). The influence of solvent on the gas adsorption performance of the POP has also been investigated.     

Direct Catalytic Conversion of Ethanol to C5+ Ketones: Role of Pd–Zn Alloy on Catalytic Activity and Stability

Ethanol can be used as a platform molecule for synthesizing valuable chemicals and fuel precursors. Direct synthesis of C₅₊ ketones, building blocks for lubricants and hydrocarbon fuels, from ethanol was achieved over a stable Pd-promoted ZnO-ZrO₂ catalyst. The sequence of reaction steps involved in the C₅₊ ketone formation from ethanol was determined. The key reaction steps were found to be the in situ generation of the acetone intermediate and the cross-aldol condensation between the reaction intermediates acetaldehyde and acetone. The formation of a Pd–Zn alloy in situ was identified to be the critical factor in maintaining high yield to the C₅₊ ketones and the stability of the catalyst. A yield of >70 % to C₅₊ ketones was achieved over a 0.1 % Pd-ZnO-ZrO₂ mixed oxide catalyst, and the catalyst was demonstrated to be stable beyond 2000 hours on stream without any catalyst deactivation.     

Effect of Sulfation of Zirconia on Catalytic Performance in the Dehydration of Aliphatic Alcohols

Catalytic dehydration of 2‐propanol and that of 1‐butanol were performed at atmospheric pressure and 150–300°C over ZrO₂ and sulfated ZrO₂ (S/ZrO₂) in a fixed‐bed, tubular reactor. The catalysts were characterized with XRD, elemental analysis, FT‐IR, N₂ physisorption, TG/DTA, TPD, and TPR. The main structures of ZrO₂ and S/ZrO₂ were monoclinic and tetragonal, respectively. As ZrO₂ was modified with sulfuric acid, its surface area and acid amount were greatly increased, whereas the pore volume, the pore diameter, and the particle size were reduced. Both samples owned weak basicity. For both reactions, only dehydration products of alkene and ether were obtained. The alcohol conversion enhanced remarkably with the catalyst acid amount and the surface area as well as the reaction temperature. In addition, the ether selectivity on S/ZrO₂ decreased with raising the reaction temperature. The activation energy was 81.0 kJ/mol in the propene formation from 2‐propanol over S/ZrO₂. The corresponding value was 94.4 kJ/mol for the dehydration of 1‐butanol.     

Vapor‐Phase Aldolization of n‐Butyraldehyde to 2‐Ethyl‐2‐Hexenal over Solid‐Base Catalysts

Vapor‐phase aldol condensation of n‐butyraldehyde to 2‐ethyl‐2‐hexenal was studied at 1 atm and 150～ 300°C in a fixed‐bed, integral‐flow reactor by using NaX, KX, γ‐Al₂O₃ and Na/NaOH/γ‐Al₂CO₃ catalysts. Ion exchange of NaX zeolite with potassium acetate solution results in a decrease of crystallinity and apparent lowering of surface area, whereas the basic strength is enhanced. Treatment of γ‐Al₂O₃ with NaOH and Na causes a large decrease of the surface area but strong enhancement of the catalyst basicity. The catalytic activity on the basis of unit surface area is in the order Na/NaOH/γ‐Al₂O₃ < KXU < KXW < NaX >γ‐Al₂O₃, in accordance with the relative catalyst basic strength. The molar ratio of trimeric to dimeric products increases with increasing the reaction temperature and the catalyst basic strength except for Na/NaOH/γ‐Al₂O₃. Very high selectivity of 2‐ethyl‐2‐hexenal (>98.5%) was observed for reactions over NaX zeolite at 150°C. Based on the FT‐IR and the catalytic results, the reaction paths are proposed as follows: self‐aldol condensation of n‐butyraldehyde, followed by dehydration produces 2‐ethyl‐2‐hexenal, which then reacts with n‐butyraldehyde and successively dehydrates to 2,4‐diethyl‐2,4‐octadienal and 1,3,5‐triethylbenzene. For the reaction over NaX, the calculated Arrhenius frequency factor and activation energy are 314 mol/g·h and 32.6 kJ/mol, respectively.     

用于苯选择加氢的Ru/Al2O3-ZrO2-NiO/堇青石蜂窝整体催化剂

使用浸涂法和氨气吸收沉积法制备了新型用于苯选择加氢的具有蛋壳型分布的Ru/Al₂O₃-ZrO₂-NiO/堇青石蜂窝整体催化剂,且在固定床整体反应器中对其性能进行了测试.该催化剂显示了较优的选择性和稳定性,并且在低的ZnSO₄浓度(0.5%问题)下环己烯产物收率可达24.7%.采用N₂吸附-脱附法,电感耦合等离子体发射光谱,光学显微镜,扫描电子显微镜及能量色散X射线光谱仪等技术研究了影响催化剂性能的因素.结果表明,NiO的引入减少了涂层中的微孔含量,有利于在低的添加剂浓度下提高环己烯选择性.ZrO₂的存在抑制了涂层的烧结,保证涂层在1373K高温焙烧后仍有较大的比表面积.Ru的蛋壳分布、薄的涂层厚度、较少的微孔含量、较大的比表面积和狭窄的孔分布可能是影响整体蜂窝催化剂中该特殊催化行为的重要因素.     

Acid–base features of ex-hydrotalcites Mg-containing and Mg-free mixed oxides

CuNiAl and MgCuNiAl mixed oxides (Cu²⁺/Ni²⁺ = 0.29 and 0.32 mol/mol) were obtained from layered double hydroxide precursors (M²⁺/Al³⁺ = 2 mol/mol) synthesized by pH-controlled co-precipitation. After structural and textural characterization (by X-ray diffraction and N₂ physisorption, respectively), the acid and basic features of the mixed oxides were investigated by adsorption microcalorimetry. NH₃ and CO₂ were used for probing the acid and basic features, respectively. By the use of temperature-programmed technique, the redox features of the oxides were investigated as well. The behaviour of the oxides as catalysts for the conversion of 4-methylpentan-2-ol at 448, 473, and 523 K under atmospheric pressure was studied in a fixed-bed reactor. The dehydration products distribution and the relative extents of the dehydration and dehydrogenation reactions are discussed in terms of the possible occurrence, depending on the lack or presence of Mg in the oxide and the reaction temperature, of either acid–base-governed E1 and E2 mechanisms or Cu-promoted reaction pathways.     

SYNERGETIC EFFECT OF SUCROSE AND ETHANOL ON FORMATION OF TRIGLYCERIDE MICROEMULSIONS

The phase behavior of soybean oil, a nonionic surfactant (ethoxylated monodiglycerides) and an aqueous phase of water containing ethanol, and sucrose was investigated at 35 and 40°C. A minimum concentration of 20 wt% ethanol was required for the formation of isotropic solutions. Addition of sucrose to the aqueous phase decreased the amount of ethanol required to form these solutions. The solubilization mechanism of the oil was investigated by small angle x-ray diffraction and polarized light microscopy. A stable lamellar liquid crystalline phase was formed for a mixture of 75/25 surfactant/sucrose solution (2.5 wt% sucrose). This phase was destabilized with increased concentrations of sucrose and liquid crystalline phases having hexagonal structures were favored at 8.75 wt% sucrose. At a ratio of 55/45 wt% of surfactant/sucrose solution (9 wt% sucrose) hexagonal structures were formed and could be destabilized or destroyed by addition of ethanol. The concept of stabilization and destabilization of liquid crystalline mesophases was applied to the solubilization of triglycerides in aqueous solutions. Two microemulsion regions were identified; oil-in-water (L₁) and water-in-oil (L₂) in systems containing soybean oil, ethoxylated monodiglycerides, and 20 wt% ethanol solution. At 55/45 wt% surfactant/20 wt% ethanol solution,7.5 wt% of soybean oil was solubilized. Addition of 10, 20, and 30 wt% sucrose, at the same ratio of surfactant to ethanol solution, increased the solubility of the oil to 9, 13.5, and 18 wt% respectively. In addition, the size of the L₁ phase increased and moved to the aqueous corner of the phase diagram and the size of the L₂ phase decreased.     

SOLVOLYSIS OF CHLORODIALKYLAND DIARYLPHOSPHINES,DIALKYL PHOSPHOROCHLORIDITES AND DIALKYL PHOSPHINYL CHLORIDES

Abstract

The kinetics of solvolysis of chlorodiethylphosphine, chloro(di-n-propyl)phosphine and chlorodiphenylphosphine was studied by conductometry in pure ethanol and in various mixed solvents, and was compared with that of dialkyl phosphorochloridites and of dialkyl and diaryl phosphinyl chlorides. The rate of ethanolysis of chloro(di-n-propyl)phosphine was found to be larger at higher initial concentrations. Addition of sulfuric or perchloric acid enhanced the rate of solvolysis, while sodium perchlorate and lithium chloride had no influence. In ethanof containing water, the rate of solvolysis of chloro(di-n-propylphosphine is approximately proportional to the concentration of water. In formic acid, the solvolysis of chloro(di-n-propyl)phosphine is slower than in ethanol. Addition of acetone to ethanol increases the rate of solvolysis of chloro(di-n-propyl)phosphine—possibly due to a condensation reaction producing a 1-chloroalkyl dialkylphosphine oxide. The rate of ethanolysis of chloro(di-n-propyl)phosphine is considerably enhanced in the presence of isobutylamine, di-n-butylamine and triethylamine. The solvolysis of di-t-butylphosphinyl chloride in absolute ethanol is very much slower than that of dimethyl and diethyl phosphinyl chloride.     

Calorimetric Study of the Acidity and Interface Effects of Tin Dioxide Layers Deposited on Another Metal Oxide

Samples with various amounts of tin oxide were prepared by impregnating γ-Al₂O₃, TiO₂(anatase), SiO₂, ZrO₂ and MgO with tin tetrachloride or tributyltin acetate solutions. After drying and calcination, the samples were characterized by chemical analysis, XRD and BET measurements. Ammonia adsorption microcalorimetry was used in order to determine the number, strength and strength distribution of surface acid sites. The influence of the adsorption temperature, evacuation temperature, amount of SnO₂ deposited and of the nature of the support on the adsorption properties were studied. This revised version was published online in July 2006 with corrections to the Cover Date.     

氧化硅负载的固体碱上乙醛的气相缩合反应

在氧化硅负载的含碱金属固体碱催化剂上乙醛能有效地缩合生成丁烯醛及丁烯醇,反应具有中等转化率、较好的选择性(约90％)和稳定性.考察了不同反应条件对催化性能的影响,并对可能的反应活性相进行了探讨.     

Decomposition of Toluene and Acetone in Packed Dielectric Barrier Discharge Reactors

The influences of TiO₂ catalytic material and glass pellet packing on the decomposition efficiency of toluene and acetone in air by dielectric barrier discharge (DBD) reactors were experimentally investigated in this study. The effects of both packing materials on the formation of byproducts such as CO and CO₂ were also evaluated. Experimental results indicate that the introduction of glass materials into the plasma zone of a wire-tube reactor would improve the decomposition efficiency of toluene and acetone compared to a nonpacked reactor. The apparent decomposition rate constant of a glass packed-bed reactor was 4.5–4.8 times greater than that of a nonpacked reactor. The results also indicate that the decomposition rate constant of toluene was approximately 2.6 times higher than that of acetone no matter which type reactor was utilized. The application of TiO₂ coated pellets in DBD reactors will enforce the hydrocarbon byproducts to further be oxidized to CO₂, notwithstanding, it will not significantly improve the performance of the reactors in the decomposition of toluene and acetone, and in the formation of CO. The results show that the best selectivity of CO₂ for acetone decomposition in a TiO₂ coated pellets packed-bed reactor was approximately 40% higher than that in a glass packed-bed reactor.     

Adsorption of reactive dye on chitosan in air-lift reactor

This study was undertaken to identify factors exerting the strongest influence on the adsorption of dye. The maximum adsorption capacity (at the adopted operating conditions) was the main parameter used to evaluate the process. In addition, the feasible adsorption capacity of chitosan was evaluated. Breakthrough experiments were carried out in a circulating air-lift reactor at a constant concentration of reactive dye Black 8 (100 mg/dm³). The tests studied different chitosan concentrations in the reactor and a range of flow intensities. The results of the breakthrough tests were compared by means of apparent mass transfer coefficients, determined by slopes at C/C ₀=1/2. The adsorption capacity of chitosan was affected to the greatest extent by the flow rate of the medium to the reactor. In turn, the utilization of the maximum adsorption capacity of chitosan, at the assumed efficiency of dye removal, was determined by chitosan concentration in the reactor.     

共沉淀法制备的镁铝氧化物催化剂上丙酮气相缩合反应

采用共沉淀法, 以氨水为沉淀剂制备了一系列具有不同Mg/Al摩尔比的镁铝氧化物催化剂, 考察了它们在丙酮气相缩合反应中的催化性能, 并通过XRD, XPS, ICP, TG-DTA和TPD等手段对催化剂的结构和性质进行了表征. 实验结果表明, 以反滴沉淀方式制备的Mg1.0AlO催化剂具有较高的反应活性和稳定性, 在反应温度为573 K条件下, 反应85 h后丙酮的转化率仍可以达到65%. 镁铝氧化物表面存在一定量强度和密度相互匹配的弱碱和强碱中心对提高催化剂的活性和稳定性有利.     

Fluorinated Porous Poly(spirobifluorene) Via Direct C‒H Arylation: Characterization,Porosity, and Gas Uptake

Considering intrinsic properties of conjugated polyfluorenes and special functions of porous polymers, synthesis of fluorinated porous poly(spirobifluorene) via direct C?H arylation polycondensation is explored. Owing to the contorted structure and cross-linking nature, the obtained polymer FPSBF shows permanent porosities with Brunauer–Emmett–Teller specific surface area up to 700 m² g^?1 and exhibits a narrow pore size distribution with the dominant pore size at about 0.63 nm, which is more suitable for adsorption of small gas molecules. Based on the measured gas physisorption isotherms with pressure up to 1.13 bar, the obtained polymer shows good uptaking capacities for hydrogen (1.30 wt% at 1.0 bar and 77 K) and methane (4.80 wt% 1.0 bar and 273 K). Moreover, FPSBF has significant adsorption selectivity for CH₄ against N₂ and the estimated ideal adsorption selectivity ratio is up to 30/1 at 1.0 bar and 273 K, which makes the material possess potential application in gas separation.     

Acetone condensation over CaO—SnO<Subscript>2</Subscript> catalyst

Aldol condensation of acetone was studied over solid base CaO—SnO₂ catalyst in the 300—450 °C temperature range and at 15—75 atm pressure in a fixed-bed reactor. The main products are mesityl oxide and isophorone. The high stability of CaO—SnO₂ catalyst performance was observed at pressure of 75 atm giving the acetone conversion of 36—41%. Increase in the temperature and pressure led to a simultaneous raise in acetone conversion. The maximum conversion of 41% was achieved at 400 °C, 75 atm and a flow rate of acetone of 8.1 g h^–1 (g catalyst)^–1.     

An Evaluation of UiO‐66 for Gas‐Based Applications

In addition to its high thermal stability, repetitive hydration/dehydration tests have revealed that the porous zirconium terephthalate UiO‐66 switches reversibly between its dehydroxylated and hydroxylated versions. The structure of its dehydroxylated form has thus been elucidated by coupling molecular simulations and X‐ray powder diffraction data. Infrared measurements have shown that relatively weak acid sites are available while microcalorimetry combined with Monte Carlo simulations emphasize moderate interactions between the UiO‐66 surface and a wide range of guest molecules including CH₄, CO, and CO₂. These properties, in conjunction with its significant adsorption capacity, make UiO‐66 of interest for its further evaluation for CO₂ recovery in industrial applications. This global approach suggests a strategy for the evaluation of metal–organic frameworks for gas‐based applications.     

Acidity and surface behaviour of alumina-boria catalysts studied by adsorption microcalorimetry of probe molecules

Acidity and basicity of alumina-boria catalysts supported on porous or non-porous alumina have been studied by adsorption microcalorimetry of probe molecules (ammonia, pyridine and sulphur dioxide). Despite decreasing in initial heats, the total acidity as determined by ammonia adsorption increased in number and strength as a function of percentage of boron oxide. Ammonia, as a strong base, was shown to cover all types sites from strong to weak acid sites. Pyridine, as a weaker probe, was shown to dose only the stronger sites of the samples which stay nearly constant after B₂O₃ coverage approaching the monolayer. The basic sites of the amphoteric alumina support are neutralized by 10 wt% of boron oxide on non-porous alumina and 20 wt% of B₂O₃ on porous alumina. The catalytic activity for partial oxidation of ethane increased with acidity and reached a maximum constant value above 20 wt% of boron oxide.