Aluminosilicate Catalysts Research Articles

In situ modification of pyrolysis products of macromolecules in an analytical pyrolyser

An application of pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) is presented for the fast on-line testing of solid catalysts activity in upgrading pyrolysis oils and/or gases of natural and synthetic polymers. Evaluation of the chemical conversion by a catalyst is simply and quickly performed in a Py-GC/MS instrument without any modification either of the micropyrolyser or the GC inlet. The pyrolysis products evolved from the sample pass through catalyst microbeds of some mm length and the GC/MS analysis of the converted products is performed on-line. Modification of polyolefin, styrene copolymer, polyester, polyamide, brominated epoxy resin and wood pyrolysate was carried out applying sodium type zeolite and medium acidic mesoporous aluminosilicate in the microbeds. The primary pyrolysis products are converted over the microbeds due to the catalytic activity of the bed material. Intramolecular hydrogen transfer reactions promoted by Na zeolite results in the isomerisation of alkenes and alkadienes evolved by pyrolysis from polyethylene and polypropylene. These basic catalysts were found to be effective for the elimination of brominated phenols from the pyrolysate of brominated epoxy resin. Cracking of alkane and alkene oligomer products of polyolefins to light isoalkenes occur over acidic mesoporous aluminosilicate. Certain compounds with polar groups evolved from polyester, polyamide, cellulose or lignin are removed by this catalyst. Alkenylaromatic compounds are simultaneously hydrogenated and polyaromatised in pyrolysis oils of styrene copolymers over both acidic and basic aluminosilicate catalysts tested.

Reactions of Epoxides Prepared from Some Monoterpenes with Acetic Anhydride on Aluminosilicate Catalysts.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Catalytic dehydration of methanol to dimethyl ether (DME) over solid-acid catalysts

A series of solid-acid catalysts with different components contents were prepared by coprecipitation (sol–gel) method. These samples comprised γ-alumina and modified γ-Al 2O 3 with silica. The effects of silica various contents have been investigated on purpose to determine an optimum one. Dehydration of methanol to dimethyl ether (DME) on solid-acid catalysts was studied in a fixed-bed flow reactor at a temperature of 300 °C under atmospheric pressure and a GHSV of 15,600 h −1. The catalysts have been characterized using BET, TGA, XRD, NH 3–TPD and elemental analysis techniques and also the results are reported. According to the experimental results, the pure γ-Al 2O 3 catalyst shown a good catalytic activity, but this sample undergoes a fairly rapid and irreversible deactivation. Silica-modified catalysts have shown better performance compared to the untreated γ-Al 2O 3. It was found that surface areas increase with increasing in the silica loading at aluminosilicate catalysts. Also, by modifying alumina with silica, it was observed that the surface acidity of aluminosilicate catalysts increased with increasing in silica loading. The sample with 6 wt% silica loading has exhibited the best conversion without any by-product.

Mesostructured aluminosilicate alkylation catalysts for the production of aromatic amine antioxidants

The conversion of diphenylamine (DPA) and α-methylstyrene (AMS) to the antioxidants mono- and dicumenyldiphenylamine was carried out over mesostructured aluminosilicate catalysts with hexagonal (2% Al-MCM-41), wormhole (2% Al-HMS), and lamellar/vesicular (2% Al-MSU-G) framework structures. A commercial acid-treated clay catalyst, Engelhard F-20, was included for comparison perposes. The yields of the desired antioxidant, namely dicumenyldiphenylamine (DCDPA), increased in the order F-20 (∼57%)<2% Al-MCM-41 (∼85%)<2% Al-HMS, 2% Al-MSU-G (∼90%) when the reaction was carried out under stoichiometric reaction conditions at 90 °C. The DCDPA yields obtained with the mesostructured catalysts are the highest reported to date for this technologically important antioxidant. A heteropolyacid catalyst, H 3PW 12O 40· xH 2O (PW 12) supported on mesostructured wormhole HMS and lamellar/vesicular MSU-G silica, also was examined as a catalyst for DCDPA production. The supported catalyst systems, however, afforded lower maximum yields of DCDPA (∼73–80%) in comparison to the mesostructured aluminosilicate catalysts. The exceptionally high yields of alkylated products obtained with the mesoporous aluminosilicate catalysts in comparison to the F-20 clay and the supported PW 12 catalysts are attributable in part to intermediate acid strengths that minimize completing dimerization reactions of the AMS alkylating agent. Also, the pore structures of the mesostructured catalysts facilitate access to active sites on the framework walls and provide more efficient transport of reagents to framework reaction centers. Also, the regular mesoporosity of the aluminosilicate catalysts makes these structures less prone to pore plugging and to the masking of acidity through the adsorption of the high molecular weight reaction products.

Mesostructured aluminosilicate alkylation catalysts for the production of aromatic amine antioxidants

The conversion of diphenylamine (DPA) and α -methylstyrene (AMS) to the antioxidants mono- and dicumenyldiphenylamine was carried out over mesostructured aluminosilicate catalysts with hexagonal (2% Al-MCM-41), wormhole (2% Al-HMS), and lamellar/vesicular (2% Al-MSU-G) framework structures. A commercial acid-treated clay catalyst, Engelhard F-20, was included for comparison perposes. The yields of the desired antioxidant, namely dicumenyldiphenylamine (DCDPA), increased in the order F-20 (∼57%)<2% Al-MCM-41 (∼85%)<2% Al-HMS, 2% Al-MSU-G (∼90%) when the reaction was carried out under stoichiometric reaction conditions at 90 °C. The DCDPA yields obtained with the mesostructured catalysts are the highest reported to date for this technologically important antioxidant. A heteropolyacid catalyst, H 3 PW 12 O 40 · x H 2 O (PW 12 ) supported on mesostructured wormhole HMS and lamellar/vesicular MSU-G silica, also was examined as a catalyst for DCDPA production. The supported catalyst systems, however, afforded lower maximum yields of DCDPA (∼73–80%) in comparison to the mesostructured aluminosilicate catalysts. The exceptionally high yields of alkylated products obtained with the mesoporous aluminosilicate catalysts in comparison to the F-20 clay and the supported PW 12 catalysts are attributable in part to intermediate acid strengths that minimize completing dimerization reactions of the AMS alkylating agent. Also, the pore structures of the mesostructured catalysts facilitate access to active sites on the framework walls and provide more efficient transport of reagents to framework reaction centers. Also, the regular mesoporosity of the aluminosilicate catalysts makes these structures less prone to pore plugging and to the masking of acidity through the adsorption of the high molecular weight reaction products.

Manufacture of White Vaseline by Hydrogenation Treatment of Mixed Feedstock

A new method of manufacturing Vaseline from Azerbaidzhan crudes by hydrogenation treatment is proposed. It is shown that hydrogenation on nickel aluminosilicate catalyst at relatively low temperatures (300–320°C) ensures a high yield (80–88% in feedstock) of medical Vaseline that satisfies current requirements.

An attempt to improve the pozzolanic activity of waste aluminosilicate catalyst

The so-called pozzolanic activity of waste catalysts from fluidised cracking was investigated. For this purpose a series of cement mixtures with this waste material were prepared and subsequently the pastes and mortars were produced. Waste aluminosilicate catalyst was used both in raw form and after grinding in a ball mill for 60 min. The hydrating mixtures were subjected to the calorimetric measurements in a non-isothermal/non-adiabatic calorimeter. After an appointed time of curing the hydrating materials were studied by thermal analysis methods (TG, DTG, DTA). The pozzolanic activity factors were determined, basing on the compressive strength data. The increased activity of cement — ground pozzolana systems has been thus proved. An accelerated Ca(OH)2 consumption as well as higher strength were found for materials containing ground waste catalyst, as compared to those, mixed with the raw one. Thus grinding was also proved to result in mechanical activation in the case of the waste catalyst from fluidised cracking.

Cracking on Modified Zeolite–Aluminosilicate Catalysts

Cracking on Modified Zeolite–Aluminosilicate Catalysts

Liquid hydrocarbon fuels from palm oil by catalytic cracking over aluminosilicate mesoporous catalysts with various Si/Al ratios

The production of liquid fuels from palm oil was studied at atmospheric pressure, reaction temperature of 723 K and weight hourly space velocity of 2.5 h −1 in a fixed bed micro-reactor containing aluminosilicate mesoporous material as cracking catalysts. The aluminosilicate materials with different Si/Al ratios were synthesized by direct (sol–gel and hydrothermal) and post-synthesis (ion-exchange and grafting) methods. The synthesized materials were characterized for their crystallinity, surface area, average pore size, elemental composition and acidity. The role of aluminum present in the mesoporous catalyst was studied in terms of its cracking activity. Palm oil conversions of 80–90 wt% with high selectivity to liquid hydrocarbon products were obtained. The catalysts prepared by sol–gel and grafting methods showed lower activity due to the presence of octahedrally coordinated Al in the framework. The activity of the catalyst increased with the aluminum content up to an optimum level. The higher Al content decreased the crystallinity and therefore catalytic activity for the cracking of palm oil.

Reactions of Epoxides Prepared from Some Monoterpenes with Acetic Anhydride on Aluminosilicate Catalysts

Reactions of epoxides prepared from α-, β-pinenes and camphene with acetic anhydride on aluminosilicate catalysts (clay K-10, zeolite β) were investigated affording various products of skeleton rearrangements: mono- and diacetates with five- and six-membered rings, and also with norbornane and pinane cores.

Synthesis of α-tocopherol (vitamin E), vitamin K1-chromanol, and their analogs in the presence of aluminosilicate catalysts Tseokar-10 and Pentasil

The highly effective heterogeneous catalysts, the aluminosilicates Tseokar-10 and Pentasil, were found to condense hydroquinones with tertiary isoprenoid allylic alcohols. Using these catalysts d,l-α-tocopherol, (2RS,4 R,8 R)-α-tocopherol, and vitamin К1-chromanol with chiral homogeneous side chains were synthesized in high yields. The analogs of α-tocopherol – chromanols and chromenols with the terminal isopropylidene group in the side chain – were synthesized, whose selective ozonolysis resulted in the corresponding chromanes with ω-formylor ω-hydroxyl groups in the side chain.

Zeolite Pore Entrance Effect on Shape Selectivity in Naphthalene Isopropylation

Naphthalene alkylation with propylene was studied over various large-pore zeolites and also over amorphous aluminosilicate catalysts. Isomeric distribution of isopropylnaphthalenes and diisopropylnaphthalenes were compared at different temperatures. Surprisingly, higher α-selectivity in monoalkylation and higher concentration of bulky isomers in diisopropylation was observed in the products obtained over zeolites than over amorphous aluminosilicate catalysts. The explanation of such results was proposed to be a specific shape-selectivity effect of alkylation reaction occurring in the entrances to the pores of zeolite. This type of shape selectivity can be very significant and conceal other shape-selectivity effects such as β-selectivity of reactions occurring inside the pores. Results available from the literature, indicating this type of shape selectivity, were also discussed.

ChemInform Abstract: Reactions of Some Terpenes and Their Derivatives with Acylating Agents in the Presence of Aluminosilicate Catalysts.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The reaction of naphthalene with benzyl chloride over an MCM-41 solid acid catalyst: a kinetic study

The reaction of naphthalene with benzyl chloride in cyclohexane at 80 °C was carried out in a slurry batch reactor, over an MCM-41 aluminosilicate catalyst. The concentration of benzyl chloride and of the products, two benzylnaphthalene isomers (M) and a mixture of several dibenzyl derivatives (D), was determined as a function of time, in runs where the initial concentrations of both reactants were varied ( C BzCl 0 from 0.03 to 0.05 mol/l; C NA 0 from 0.20 to 0.30 mol/l). Kinetic models were applied in order to interpret the measurements.

Vapour phase hydrogenation of naphthalene on a novel Ni-containing mesoporous aluminosilicate catalyst

The vapour phase hydrogenation of naphthalene was investigated on a novel Ni-containing Si/Al mesoporous catalyst, comparing its chemical–physical characteristics and catalytic behaviour with those of a commercial Ni-SiO 2/Al 2O 3 catalyst. The catalytic tests were carried out in a fixed bed reactor, operating at 6.0 MPa and the effect of various reaction parameters was investigated (temperature, contact time, H 2/naphthalene ratio, presence of dibenzothiophene (DBT) in the feed). The activity expressed as hourly productivity per litre of catalyst (as well as the yield %) was very similar to that of the commercial catalyst, while considerably better hourly productivity per kilogram of catalyst was observed both in hydrogenation and hydrogenolysis reactions, although the stability to DBT remained low. The higher activity for the mesoporous catalyst was even more interesting considering its lower Ni-content. However this catalyst was not stable at high temperature, due to deposition of heavy products and sintering of nickel particles, suggesting that its application should be limited to temperatures lower than 300 °C.

ChemInform Abstract: Alkylation of o‐Cresol with Caryophyllene on Acidic Aluminosilicate Catalysts.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Isolation and identification of diisopropylnaphthalene isomers in the alkylation products of naphthalene

GC analysis of diisopropylnaphthalene (DIPN) isomers is presented. Naphthalene was repeatedly alkylated with propylene over an amorphous aluminosilicate catalyst under different preparation conditions, and then pure isomers or at least DIPN fractions enriched in individual isomers were isolated from the alkylates and analysed using GC–MS, IR and NMR techniques. Eight of the ten possible isomers appeared in the chromatograms; seven of them (1,3-, 1,4-, 1,5-, 1,6-, 1,7-, 2,6- and 2,7-) were separated and identified, while the eighth one was indirectly proved to be 2,3-DIPN. The remaining two isomers (1,2- and 1,8-DIPN) were not found in the products.

Alkylation of Phenols by Caryophyllene on Acid Aluminosilicate Catalysts

The reactions of the natural sesquiterpene caryophyllene with phenols on various solid acid catalysts gave the corresponding terpenylphenols and phenyl terpenyl ethers with essentially caryolane structures. The selectivity of the process and yield of product can be raised by varying the catalyst and solvent.

Structural elucidation of microporous and mesoporous catalysts and molecular sieves by high-resolution electron microscopy.

Twenty years ago, one of us embarked (Bursill, L. A.; Lodge, E. A.; Thomas, J. M. Zeolitic structures as revealed by high-resolution electron microscopy. Nature 1980, 286, 111-113) on the study of zeolites (renowned for their electron-beam sensitivity) by high-resolution transmission electron microscopy (HRTEM). In the ensuing years, high-resolution imaging aided by optical diffractometry has yielded details of the open framework structures of a number of new aluminosilicate and aluminophosphate molecular sieves and catalysts. The nature of intergrowth and recurrently twinned structures, as well as new types of structural imperfection in hitherto uncharacterized materials, has also been elucidated. With continued improvements in instrumental development, encompassing higher accelerating voltages, better objective lenses and vacua, computational advances, and the arrival of slow-scan CCD detectors, electron crystallographic methods and HRTEM imaging now enable the ab initio three-dimensional structures of micro- and mesoporous solids, with their occluded structure-directing organic species, to be determined. High-resolution scanning transmission electron microscopy using subnanometric probes provides supplementary structural and ultramicro analytical information and electron spectroscopic imaging (at the attogram level). In its high-angle annular dark-field mode, it is capable of locating and determining the composition of individual nanoparticle catalysts (consisting of just a few atoms) supported on porous hosts.

Super-microporous aluminosilicate catalysts via primary amine templating

Super-microporous aluminosilicate catalysts possessing pores in the range 14–20 A may be prepared via primary amine templating alone or in combination with post-synthesis Al-grafting.