Active Acid Catalyst Research Articles

Bioinspired Synthesis of Novel Different Nanoparticles and its Utility in Biodiesel and Animals Applications

Because of its ability to speed up the reaction, the catalyst is critical to its success. Most catalysts are either homogeneous or heterogeneous. It has been shown that utilizing a heterogeneous catalyst, which is easier to remove from the product after the reaction has been finished. Because of the large surface area of the Nano-catalyst results in high catalytic efficiency. To enhance the performance of catalysts a range of various types of support materials have been used. SO42--ZnO and So42-/TiO active acid catalyst was prepared and characterized. ZnO nanoparticles catalyst synthesized by precipitation of zinc nitrate for comparison with supported catalyst. Sulphated zinc oxide (SO42--ZnO) and sulphated titania (SO42-/TiO) catalysts were synthesized using impregnation methods, to test their efficacy in biodiesel production. Various waste oils from different wastes such as mutton or beef tallow, chicken fat, and methanol are preferred to use during the esterification of waste animal fat oils using solid acid catalysts to produce biodiesel. Biodiesel synthesis generates a substantial amount of glycerol as a byproduct. Effect of optimum parameters such as temperature 60 degree centigrade (°C) shown 90% yield, time 1 hour resulted in 85% yield, catalyst dose 2wt% resulted in 80% yield, stirring speed 250rpm resulted in 80% yield, methanol to oil ratio12:1 resulted as 85.5% yield for transesterification of waste fat oil. It is valuable that the supported acid catalysts showed more yield than simply synthesized ZnO nanocatalyst similarly sulphated zinc oxide showed more FAME yield than sulphated titania.

Synthesis of SO<sub>4</sub><sup>2–</sup>/ZrO<sub>2</sub> Solid Acid and Na<sub>2</sub>O/ZrO<sub>2</sub> Solid Base Catalysts Using Hydrothermal Method for Biodiesel Production from Low-Grade Crude Palm Oil

Biodiesel is a renewable energy source that can be produced through esterification as well as transesterification reactions. This work presents a series of zirconia catalysts synthesized by hydrothermal method on various concentrations in acidic (H2SO4 0.3, 0.5, and 0.7 M) and basic (NaOH 1, 2, 3, and 4 M) solution to get a catalyst with the highest acidity or basicity. Characterizations of the catalysts were performed by FTIR, XRD, SEM-EDX, surface area analysis, acidity, and basicity test. The most active acid catalyst activity was evaluated for the esterification of low-grade crude palm oil (LGCPO), while the solid base catalyst was utilized for the transesterification reaction. The solid acid catalyst of 0.7 M SO42–/ZrO2 60 °C; 24 h was denoted as the most active acid catalyst with a total acidity of 1.86 mmol g–1, while 4 M Na2O/ZrO2 60 °C; 24 h catalyst was considered as the solid base catalyst with the highest total basicity of 3.75 ± 0.12 mmol g–1. The optimized acid catalyst exhibited a 31 times higher acidity than commercial ZrO2. The concentration of free fatty acids (FFA) decreased to 68.87% in the esterification reaction. The solid base catalyst of 4 M Na2O/ZrO2 60 °C; 24 h successfully converted LGCPO into biodiesel by 68.55% through a transesterification reaction.

Stable monovalent aluminum(i) in a reduced phosphomolybdate cluster as an active acid catalyst.

Low-valent aluminum Al(i) chemistry has attracted extensive research interest due to its unique chemical and catalytic properties but is limited by its low stability. Herein, a hourglass phosphomolybdate cluster with a metal-center sandwiched by two benzene-like planar subunits and large steric-hindrance is used as a scaffold to stabilize low-valent Al(i) species. Two hybrid structures, (H3O)2(H2bpe)11[AlIII(H2O)2]3{[AlI(P4MoV6O31H6)2]3·7H2O (abbr. Al6{P4Mo6}6) and (H3O)3(H2bpe)3[AlI(P4MoV6O31H7)2]·3.5H2O (abbr. Al{P4Mo6}2) (bpe = trans-1,2-di-(4-pyridyl)-ethylene) were successfully synthesized with Al(i)-sandwiched polyoxoanionic clusters as the first inorganic-ferrocene analogues of a monovalent group 13 element with dual Lewis and Brønsted acid sites. As dual-acid catalysts, these hourglass structures efficiently catalyze a solvent-free four-component domino reaction to synthesize 1,5-benzodiazepines. This work provides a new strategy to stabilize low-valent Al(i) species using a polyoxometalate scaffold.

Biofuels production by esterification of oleic acid with ethanol using a membrane assisted reactor in vapour permeation configuration

Biodiesel production by performing the oleic acid esterification reaction in a new reactor system, realized by coupling the batch reactor with a tubular permeoselective membrane, has been investigated. Such reactor configuration was adopted to remove the water produced as by-product during the reaction thus increasing the oleic acid conversion and the alkyl ester production. The activity of acid catalysts and zeolites was evaluated in presence of methanol and ethanol. The membrane resulted much more selective towards water separation when ethanol was used, allowing to force thermodynamic equilibrium at higher conversion values. Very interesting results in terms of oleic acid conversion were achieved with both methanol and ethanol (96% and 98% respectively) in presence of a commercial Amberlyst-15 catalyst, at 80 °C, at a low membrane surface to gas volume ratio (0.20 cm−1) and low acid/alcohol molar ratio (2/1 and 1/1 respectively). Over zeolite samples, conversion values higher than 60% were obtained at 100 °C after 5 h in the esterification reaction performed in vapor permeation configuration.

Effects of Weight Hourly Space Velocity and Catalyst Diameter on Performance of Hybrid Catalytic-Plasma Reactor for Biodiesel Synthesis over Sulphated Zinc Oxide Acid Catalyst

Biodiesel synthesis through transesterification of soybean oil with methanol on hybrid catalytic-plasma reactor over sulphated zinc oxide (SO42-/ZnO) active acid catalyst was investigated. This research was aimed to study effects of Weight Hourly Space Velocity (WHSV) and the catalyst diameter on performance of the hybrid catalytic-plasma reactor for biodiesel synthesis. The amount (20.2 g) of active sulphated zinc oxide solid acid catalysts was loaded into discharge zone of the reactor. The WHSV and the catalyst diameter were varied between 0.89 to 1.55 min-1 and 3, 5, and 7 mm, respectively. The molar ratio of methanol to oil as reactants of 15:1 is fed to the reactor, while operating condition of the reactor was kept at reaction temperature of 65 oC and ambient pressure. The fatty acid methyl ester (FAME) component in biodiesel product was identified by Gas Chromatography - Mass Spectrometry (GC-MS). The results showed that the FAME yield decreases with increasing WHSV. It was found that the optimum FAME yield was achieved of 56.91 % at WHSV of 0.89 min-1 and catalyst diameter of 5 mm and reaction time of 1.25 min. It can be concluded that the biodiesel synthesis using the hybrid catalytic-plasma reactor system exhibited promising the FAME yield.

Experimental study of catalytic degradation of polypropylene by acid-activated clay and performance of Ni as a promoter

ABSTRACTCatalytic and thermal cracking of polypropylene was performed in a batch reactor. Effect of hydrochloric acid activation on kaolin clay, effects of catalysts (acid-activated clays), promoter (5 wt% Ni), and cracking temperatures on the liquid oil yield were investigated. Results show optimized liquid yield (71.9%) obtained at 470°C with kaolin clay activated with 3 M HCl. Acid-activated catalysts were analyzed using XRD and the results reveal the reduction in peaks’ intensities. Weight loss of polypropylene was investigated by thermogravimetric analysis. FTIR and GCMS techniques were employed to analyze the liquid products.

Heteropoly tungstate supported on tantalum oxide: a highly active acid catalyst for the selective conversion of fructose to 5-hydroxy methyl furfural

A series of tungstophosphoric acid (TPA) catalysts supported on tantalum oxide (Ta2O5) were prepared and characterized by FT-infrared, X-ray diffraction, Laser Raman and temperature programmed desorption of ammonia. Characterization results suggest the presence of intact TPA on Ta2O5. The catalyst acidity varied with changes in TPA content and treatment temperature. The catalyst with 20 wt% TPA on Ta2O5 calcined at 300 °C exhibited maximum acidity. These catalysts were evaluated for the selective dehydration of fructose to 5-hydroxy methyl furfural (HMF). The catalysts showed near complete conversion of fructose and the yield of HMF depended on the acidity of the catalysts. The conversion and selectivity in the de hydration of fructose also depends on the reaction temperature and catalyst weight. The catalysts are stable and reusable with consistent activity.

Active Acid Catalyst of Sulphated Zinc Oxide for Transesterification of Soybean Oil with Methanol to Biodiesel

Active solid acid catalysts of sulphated zinc oxide (SO42--ZnO and SO42-/ZnO) were prepared and characterized. The solid acid catalysts were investigated for their performance on transesterification of soybean oil with methanol to produce biodiesel. The SO42--ZnO and SO42-/ZnO catalysts were prepared by coprecipitation and impregnation respectively to compare their performance for biodiesel production. The catalysts were characterized by X-ray Diffraction (XRD) and Fourier Transform Infra Red (FT-IR), while the fatty acid methyl ester (FAME) component in biodiesel product was identified by Gas Chromatography - Mass Spectrometer (GC-MS) and FT-IR. The SO42--ZnO catalyst, prepared by coprecipitation, showed better performance for the transesterification process than the SO42-/ZnO catalyst, prepared by wet impregnation. The trend of performance of both catalyst was due to effect of sulfonate incorporation into the zinc oxide structure to form active acid sites. From the catalyst testing on transesterification of soybean oil with methanol at mild conditions (temperature of 65 °C, methanol to oil mole ratio of 6, and 4 wt% of catalyst loading), the SO42--ZnO catalyst exhibited promising FAME yield of 80.19% at 4h reaction time. Therefore, the SO42--ZnO catalyst showed potential as a catalyst for transesterification of soybean oil to produce biodiesel.

New insights into the strength and accessibility of acid sites of sulfonated hydrothermal carbon

Sulfonation of hydrothermal carbon leads to a very active acid catalyst, in spite of the very low surface area determined by N2 physisorption and the even distribution of sulfonic groups, as demonstrated by scanning transmission electron microscopy analysis. However, CO2 adsorption at 273K indicates the presence of ultramicropores, not detected with N2 at 77K. Acidity was characterized by different procedures, but the most relevant was 31P solid state NMR of adsorbed triethylphosphine oxide. The solvent used for the adsorption is crucial, as the solid seems not to be acidic in hexane, but it shows acidic groups comparable to arylsulfonic ones when the adsorption takes place in methanol. This is probably due to the breakage of the network of hydrogen bonds that forms the ultramicropores, leading to an improved accessibility to the sites. This result is in agreement with the hydrophilicity of the solid, demonstrated by water adsorption.

Sulfonic acid functionalised ordered mesoporous materials as catalysts for fine chemical synthesis

The synthesis of highly active acid catalysts supported on ordered mesoporous materials has eluded chemists until 1998, when Wim M. Van Rhijn et al. explored three different routes to tether sulfonic acid on mesoporous silica. This viewpoint sheds light on this landmark and explores its significant impact on material science and green catalysis.

Self-assembly synthesis of a high-content sulfonic acid group functionalized ordered mesoporous polymer-based solid as a stable and highly active acid catalyst

A stable and highly active ordered mesoporous polymer-based acid catalyst has been prepared via a simple surfactant templating approach and oxidation treatment. The composition and nanostructure are characterized by XRD, NMR, XPS, TEM, nitrogen sorption, elemental and chemical analysis. The sulfonic acid groups have been anchored within the well-arranged channels of the polymer-based matrix. Even with a high –SO3H group loading (up to about 27.4 wt%) on the mesoporous polymer-based material, the ordered mesostructure and high surface area (∼400 m2 g−1) can be retained and the functional moieties are highly chemically accessible. With the large number of acid sites (0.93–2.38 H+ mmol g−1 determined by acid–base titration) and the hydrophobic character, the mesoporous polymer-based solid exhibits unique catalytic performance in acid-catalyzed reactions such as condensation and acetalization, not only high activity (per site yield of bisphenol-A is over 45 in the condensation of phenol and acetone) but also excellent stability. Loss in acidic loading and activity is negligible even after the catalyst is reused 20 times in the acetalization of butanediol and aldehyde. The stability is most likely attributed to the hydrophobic nature of the mesoporous polymer-based solids, which favors the diffusion of water and thereby inhibits the poisoning of acidic sites caused by water generating in the reaction. Moreover, with large mesopores, the diffusion of reactants and products can be promoted and hence the catalytic activity can be further increased.

Magnetic nanoparticle supported polyoxometalates (POMs) via non-covalent interaction: reusable acid catalysts and catalyst supports for chiral amines

Magnetic polyoxometalates (POMs) are obtained by a simple sonication between functionalized magnetic nanoparticles and polyoxometalates. This material can be used not only as a highly active acid catalyst, but also as a catalyst support for chiral amines.

Fractality and activity of acid catalysts in the liquid-phase synthesis of ethyl tert-butyl ether

A study was carried out on the synthesis of ethyl tert-butyl ether from ethanol and 2-methylpropene on silica gel samples modified by the addition of ZrO2 and Al2O3. A decrease in the turnover frequency (TOF) of the reaction is observed with increasing acidity of surface of the modified silica gels. A relationship was found between the TOF of the reaction and the fractal dimension of the catalyst. The TOF of the reaction decreases with increasing fractal dimension of the catalyst.

Reactions of hexane isomers on H-mordenite at moderate temperatures in liquid and gas phases: the effect of cyclic hydrocarbons

H-mordenite, a more active acid catalyst than HZSM-5, showed features of a carbocationic/cationoidic isomerization in the reaction of liquid 3-methylpentane, but not of liquid hexane. The carbocationic isomerization features were not seen in the gas phase, for either reactant. Thus, there are mechanistic differences between the reactions of alkanes in the liquid phase and in the vapor phase on the zeolite. The liquid-phase reaction of hexane in the presence of methylcyclopentane, cyclopentane, and deuteromethylcyclopentane showed the absence of hydride transfer catalysis. The label redistribution between deuterated and nondeuterated reactants showed that the products were formed from olefinic reaction intermediates, although none were found in the products desorbed. Each olefin exchanged repeatedly hydrogen with the catalyst before being hydrogenated and desorbed. The possibility that alkenyl cations retained on the catalyst play a role, as in trifluoromethanesulfonic acid, is discussed. As the space requirement of hydride transfer is smaller than that of β-cracking, the results speak against protonated alkanes (“carbonium” ions) in the catalysis on zeolites. The type of activation observed in superacid catalysts, where the standard carbocationic mechanism operates, does not occur in zeolites. The chemisorbed alkenes may be formed by one-electron oxidation or by dehydrogenation on tetracoordinated aluminum atoms, either in the lattice or in cages (extralattice aluminum).

Absence of correlation of hydrogen bond donor ability with acid strength and catalytic activity of acid catalysts

Two liquids, acetic acid and hexafluoroisopropanol (HFIP), and two solids, silica gel and polymethacrylic acid (PMA), were compared for hydrogen bond donor ability, acid strength, and catalytic activity in typical acid‐catalyzed reactions, inversion of sugar and cleavage of acetone dimethyl ketal. In each pair, the weaker acid (HFIP and silica gel, respectively) was much the stronger hydrogen bond donor, but was totally devoid of catalytic activity, which the poor hydrogen bond donor but stronger acids (acetic and methacrylic acid, respectively) exhibited. A strong hydrogen bond donor (e.g., HFIP) enhances, however, the catalytic activity of the acid catalyst (AcOH). Thus, hydrogen bond donor ability is not a measure of acid strength. A correlation of the two properties is possible only when each group (acids and bases) involved in the comparison consists of very close structural relatives. Such a correlation cannot be extrapolated to any other case.

Methods for preparing thermally stable and active acid catalysts by incorporation of lanthanum into Y, desilicated Y and X zeolites

The incorporation of La3+ ions by ion exchange into the Na forms of X, Y and desilicated Y zeolites does not alter the thermal stability of these materials, while it dramatically increases their activity in the acid-catalysed hydrocracking/ hydroisomerization of n-octane. On the other hand, lanthanum ions, when ion-exchanged into the ammonium forms of these zeolites, stabilize the acid forms currently obtained by calcination of the corresponding ammonium zeolites at high temperatures. Interestingly, high catalytic performances are obtained when the amount of La3+ ions incorporated into the Na forms of these zeolites is equal to or higher than 70% of the cationic capacity of these materials, which now become as active and selective as the LaH or ultrastabilized HY zeolites.

Development of Acidity on Sol-Gel Prepared TiO2-SiO2 Catalysts

ABSTRACTThree different TiO2-SiO2 gels (Xerogel, Carbogel and Aerogel) are more active acid catalysts than other reference samples used here. As deduced from FTIR, XRD and XANES studies, the structural properties of these gels are quite different to each other, thus revealing the strong influence of the drying treatment. It is found that the degree of Si-O-Ti linking and the surface acidity follows the same trend (X 〉 C 〉 A). We conclude that supercritical drying at 600 K and 190 bars can induce Ti leaching followed by redeposition in the narrower pores of the gel. These effects modify both the textural and surface chemical properties of the resulting material.

Infrared study on the adsorbed state of ammonia on heteropoly compounds

A heteropoly compound is one of the strongly active acid catalysts which can be used for several acid catalyzed reaction. One property of heteropoly compounds as a solid acid catalyst is that there are acid sites on the surface as well as in the bulk. The other property of these catalysts is that nitrogen compounds such as pyridine and ammonia are easily adsorbed as a pseudo-liquid phase in the bulk. Kim et al. reported that there was no correlation between the adsorbed amounts of pyridine and those of ammonia on heteropoly compounds. They suggested that ammonia could be adsorbed on an acid site of a heteropoly compound as well as on a metal cation. The adsorption of ammonia as an amine structure on copper containing heteropoly compound was discussed by Saito et al. However, a systematic study on the adsorbed state of ammonia on the heteropoly compound was not reported. This paper reports an investigation of the infrared spectra of ammonia adsorbed on a heteropoly compound to illustrate the possible states of the adsorbed ammonia.