Titanate Catalyst Research Articles

Transient studies on methane oxidative coupling over alkali-metal promoted titanate catalysts

A transient method to study the role of the different oxygen species involved in oxidative coupling of methane is discussed. The method is applied to two new active catalysts for this process, which are based on alkali metal loaded titanates of lanthanum and nickel and also to a lithium/titania catalyst used in previous works. The results show that the participation of lattice oxygen in the formation of C2 products depends on the Li loading and the type of titanate used.

Methane oxidative coupling over titanate catalysts

The oxidative coupling of methane was studied by cofeeding methane and oxygen over a series of titanate catalysts. Many of the titanate catalysts were good combustion catalysts and had poor hydrocarbon selectivities. Calcination and reduction pretreatments were shown to affect the activity of some catalysts: while they had little influence on other titanate catalysts. The lanthanum titanate catalyst had the best hydrocarbon selectivities of the titanates studied, exhibiting methane conversions of 20% and hydrocarbon selectivities of better than 50% for a variety of operating conditions. The effect of operating conditions were studied, and there appears to be an optimum to achieve high yields of ethane and ethylene. The catalyst was studied over a seventy-two hour period and showed very little change with time-on-stream. The lanthanum titanate catalyst activated methane at much lower temperatures than other catalysts; however, its hydrocarbon selectivity was poorer at lower temperatures.

Syntheses of polyacetylene by alkyl aluminium and titanate having long alkyl chains

We present novel methods of synthesizing polyacetylene in order to obtain highly-conducting polymers. To enhance the conductivity of polyacetylene, we tried to improve the novel methods proposed by Naarmann and Shirakawa and to synthesize highly-conducting polyacetylene by controlling the reactivity of the Ziegler catalyst. As a result, we have found that one of the most effective methods is to introduce long alkyl chains into alkyl aluminiums and alkyl titanates as Ziegler catalysts and depress the polymerization rate. We employ triethyl, trihexyl, trioctyl and tridecyl derivatives as alkyl aluminiums and tetrabutyl, tetrahexyl and tetraoctyl derivatives as alkyl titanates. Thus we obtain polyacetylene with good stretchability and high electrical conductivity. The maximum stretching ratio is up to ten. The electrical conductivity of polyacetylene increases with increasing stretching ratio. In particular, polyacetylene prepared using trioctyl aluminium and tetrabutyl titanate catalysts shows a conductivity as high as 24 000 S/cm at a stretching ratio of eight after being doped with iodine.

Catalytic hydrotreating of coal liquids

Liquids obtained by direct hydrogenation of a Spanish subbituminous coal have been ‘up-graded’ by catalytic hydrotreatment. The catalysts used were a commercially available Ni-Mo catalyst and a nickel hydrous titanate catalyst prepared in this laboratory. Liquid products were analysed for: oil, asphaltene and preasphaltene formation, elemental analysis, boiling range distribution, aromaticity ( 1H n.m.r. and FT-i.r.) and heteroatom removal. The results indicated that the upgraded liquids exhibited lower aromaticity and lower heteroatoms content than raw liquids. HT-400E catalyst displays the best behaviour, as regards hydrogenation and oil formation. On the removal of nitrogen and sulphur, both catalysts show a high efficiency, HT-400E catalyst being more efficient. The utilization of nickel hydrous titanate catalyst produces liquids of lower aromaticity.

Raman and NMR Studies of Hydrous Sodium Titanates

ABSTRACTRaman and solid state 17O NMR spectroscopies have been used to determine the molecular structure of amorphous hydrous sodium titanate catalyst support materials prepared by hydrolysis of titanium isopropoxide. Three types of oxygens have been identified: oxygens bridging three titanium atoms, oxygens bridging two titaniums, and non-bridging oxygens. Changes in the relative populations of the different oxygen types have been used to help understand the ion-exchange and polymerization properties of hydrous titanates.

Hydrous metal oxide ion exchangers for preparation of catalysts for direct coal liquefaction

A group of hydrous oxide ion-exchange compounds which can be used to prepare hydrogenation catalysts by a novel synthesis route has been identified. These materials offer several advantages including high surface area, dispersion of any metal or mixture of metals and promoters over a wide concentration range, and adjustment of substrate acidity as well as active metal oxidation state. Catalysts prepared by exchanging the Na ion of sodium hydrous titanate for Ni, Mo and Pd were tested for use in direct coal liquefaction. Results of hydrogenation experiments performed with the addition of the catalysts to a slurry of a bituminous coal in a coal derived solvent demonstrated that hydrous titanate catalysts with active metal loadings as low as 1% were equally effective for liquefying coal as a commercial Ni-Mo/Al/sub 2/O/sub 3/ catalyst containing 15% wt active metals.

Asymmetric induction bny enantiotopically differentiating retro‐claisen reaction of P{rochiral bicyclic β‐diketones

AbstractThe possibility of preparing cycloalkanones with an asymmetric β‐C‐atom by enantiotopically differentiating retro‐Claisen reactions of bicyclic diketones a (Scheme l) is tested with the decalin‐1,8‐diones 1 and 7, as well as with the bicyclo[3.3.0]octane‐2,8‐diones 10 and 11. Treatment of the reactive dione 1 with chiral tetra‐alkyl titanate catalysts results in a low optical induction (13%, Scheme 2). Cleavage with the Nasalts of a‐amino‐alcohols and hydrolysis of the resulting amides or esters gives much better optical yields, reaching 86% ee with dione 1 and (−)‐ephedrine (Scheme 3). Almost as efficient is N‐methylephedrine with 75% optical induction (Scheme 5). Lower enantiotopical differentiation is, however, observed with (−)‐ephedrine and diones 7 (44% ee), 10 (8% ee), and 11 (48% ee) (Schemes 3 and 4, Table l), or with dione 1 and L‐prolinol (37% ee) or (−)‐2‐amino‐1‐butanol (11% ee) (Scheme 5, Table 2). The moderate chemical yields of these transformations (500–70%) can be ascribed to side‐reactions of the ketones under the strongly basic conditions.

Study of the photocatalytic decomposition of water vapor over a nickel(II) oxide-strontium titanate (SrTiO3) catalyst

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStudy of the photocatalytic decomposition of water vapor over a nickel(II) oxide-strontium titanate (SrTiO3) catalystKazunari Domen, Shuichi Naito, Takaharu Onishi, Kenzi Tamaru, and Mitsuyuki SomaCite this: J. Phys. Chem. 1982, 86, 18, 3657–3661Publication Date (Print):September 1, 1982Publication History Published online1 May 2002Published inissue 1 September 1982https://doi.org/10.1021/j100215a032RIGHTS & PERMISSIONSArticle Views1429Altmetric-Citations147LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (629 KB) Get e-Alerts

Water Photolysis by UV Irradiation of Rhodium Loaded Strontium Titanate Catalysts. Relation between Catalytic Activity and Nature of the Deposit from Combined Photolysis and ESCA Studies

AbstractPhotochemical water splitting (H2O → H2 + 1/2O2) has been shown to occur on UV irradiation of aqueous suspensions of strontium titanate, modified by surface photodeposition of rhodium species.7 Further improvement of the catalytic materials has now been achieved, using thermal deposition techniques. The most active material, prepared by heating rhodium chloride impregnated SrTiO3 powder at 500°C in air, allowed one to produce appreciable quantities of (H2 + 1/2O2) gas and to reach high turnover numbers on the catalytic material. The photolysis efficiency presents a strong pH dependence with an optimum around pH ∼ 14 and increases markedly when the wavelength of the light decreases from 400 to 300 nm. The amount of rhodium deposited also has a marked effect with an optimum at about 0.2–0.3% Rh by weight. ESCA studies have provided information about the nature of the catalytic deposit and about its relation to the activity of the materials. Catalytic efficiency and mechanistic aspects are discussed. The oxidation state of the rhodium species has a drastic influence: whereas SrTiO3 loaded with reduced rhodium shows no catalytic activity, the efficiency increases on progressive oxidation of the deposited metal to surface rhodium(III) species, as detected by ESCA. The photoactive step may involve both band‐gap excitation of the semi‐conductor support and direct UV excitation of the deposited Rh(III) species.

Chromic titanate catalysts for high‐melt‐index polyethylene by the particle‐form process

AbstractA novel thermal activation procedure for ethylene polymerization catalysts made from silica, a chromium compound, and a titanium ester greatly increases the melt index of the polyethylene product under commericla polymerization conditions in comparison with conventional air activation. The novel activation has two steps. The first is heating under a reducing gas atmosphere (N2 + CO). The second step is partial oxidation at a lower temperature for a shorter time. The size of the melt index increase is related to the average oxidation number of the chromium, but oxidized chromium can be reduced and the effect persists with less intensity. Additionally, the magnitude of the effect is dependent upon gas flow rates during activation and prior chemical and thermal history of the chromium–silica combination. Since titanium is required for the two‐step activation to be effective in increasing melt index, titanium atoms have a critical influence on the catalyst active sites. An experiment with tetraethoxysilane added to the catalyst shows that titanium and chromium atoms must be next nearest neighbors (separated by oxygen atoms).

Polyesters containing ring units in main chains. I. Preparation and stereochemistry of monomers and polyesters

AbstractCycloalkanone (C5–C8, C12, and C15) or cycloalkane (C5 and C6) ring‐containing monomeric diesters and the polyesters derived from them were prepared, and their configurations were studied by 13C‐NMR spectroscopy. Absolute configurations were determined for ring sizes 5, 6, and 7. Configurational change during reduction of a ketonic group of monomeric diesters with ring sizes 5 and 6 was discussed in terms of the steric effect of ring substituents on the ketonic group. In the polycondensation reaction epimerization of the ring units was observed in 5‐, 6‐, and 7‐membered cycloalkanones and not in others, which is explained by steric hindrance by the ring substituents against attack of tetrabutyl titanate catalyst on the ketonic group.

Polymerization of acetaldehyde. I. A new polymerization process with tetraisopropyl titanate catalyst

Polymerization of acetaldehyde. I. A new polymerization process with tetraisopropyl titanate catalyst

1,4 polymerization of isoprene by titanate catalyst systems

AbstractTitanates are versatile in the 1,4 polymerization of isoprene. The (R′O)4Ti/RAlCl2 catalyst gives either cis‐ or trans‐1,4‐polyisoprene, depending on the nature of both the titanate and the solvent. Primary titanates give cis‐1,4‐polyisoprene in both aliphatic and aromatic solvents. Secondary titanates give cis‐polyisoprene in aliphatic solvents, and trans‐1,4‐polyisoprene in aromatic solvents. Tertiary titanates give trans‐polyisoprene in both aliphatic and aromatic solvents. A mechanism is postulated which takes into consideration the role of the solvent. ESR studies of the various titanate–RAlCl2 catalysts were made; the paramagnetic structures are related to polymerization mechanisms.