Unconventional, highly selective CO2 adsorption in zeolite SSZ-13

Low-pressure adsorption of carbon dioxide and nitrogen was studied in both acidic and copper-exchanged forms of SSZ-13, a zeolite containing an 8-ring window. Under ideal conditions for industrial separations of CO(2) from N(2), the ideal adsorbed solution theory selectivity is >70 in each compound. For low gas coverage, the isosteric heat of adsorption for CO(2) was found to be 33.1 and 34.0 kJ/mol for Cu- and H-SSZ-13, respectively. From in situ neutron powder diffraction measurements, we ascribe the CO(2) over N(2) selectivity to differences in binding sites for the two gases, where the primary CO(2) binding site is located in the center of the 8-membered-ring pore window. This CO(2) binding mode, which has important implications for use of zeolites in separations, has not been observed before and is rationalized and discussed relative to the high selectivity for CO(2) over N(2) in SSZ-13 and other zeolites containing 8-ring windows.     

Structure and synthesis of SSZ-63: toward an ordered form of zeolite beta

The synthesis, characterization, and structure elucidation of the borosilicate zeolite SSZ-63 are described. SSZ-63 is synthesized using the 1-cyclodecyl-1-methylpyrrolidinium cation as a structure-directing agent. The structural model for SSZ-63 was determined by comparison of its powder X-ray diffraction pattern with those of zeolite beta and its polytype structures. Whereas conventional zeolite beta may be described as a random intergrowth of polytypes A and B, SSZ-63 is more accurately described as a random intergrowth of polytypes B and C(H) (the hypothetical polytype C proposed by Higgins). Polytype C(H) is essentially an ordered intergrowth (of polytypes A and B) in which one of the crystallographic projections is equivalent to those in polytype A and another projection is equivalent to those in polytype B. Unlike zeolite beta, which possesses significant disorder related to layer shifts along both the a- and b-crystallographic axes, the structure of SSZ-63 has little disorder associated with the translations of layers in the a-direction. DIFFaX simulations of the powder diffraction patterns, electron diffraction, and high-resolution transmission electron microsocopy data all support the proposed model.     

Studies of the synthesis of SSZ-25 zeolite in a "mixed-template" system

The synthesis of aluminosilicate zeolite, SSZ-25, is described using a two-component organic guest molecule strategy. This method has been recently described by us and is quite effective in crystallizing a variety of aluminosilicate zeolites with reduction in template cost. In this instance the original organic guest component used in the discovery of SSZ-25, N',N',N'-trimethyl-2-adamantammonium cation, is used in conjunction with a variety of smaller amines. The amine is the major organic component in the synthesis and the quaternary ammonium compound, while a minor component, is essential for structure direction to the desired zeolite product. Studies here show that the adamantyl component is preferentially taken up during crystal growth. Our studies showed that the use of the multi-organic component approach to synthesis resulted in a faster and cheaper route to crystallizing SSZ-25. The SSZ-25 has been described in the literature as having the MWW topology and as such has two different channel systems accessed by 10-ring openings; the channel systems do not intersect. One set of 10-rings open into large cavities. In this study we used NMR spectroscopy to examine the as-made materials and to see if the two organic components are used in different capacities in the synthesis, probing if the admantyl component is only found in these larger cavities. The crystalline products could be affected by solvent extraction with polar solvents like dimethylformamide: the X-ray powder patterns and elemental analyses changed with solvent treatment. The solvent-treated crystals were studied by NMR spectroscopy, elemental analysis, and argon adsorption. The two-component organic guest approach was also found to be quite flexible not only with regard to the amine, but also towards the quaternary ammonium compounds. Non-adamantyl polycyclic templates could be used, and polar but non-quaternized adamantyl derivatives also succeeded in directing towards SSZ-25 formation. On the other hand. in one instance it was shown that the two-component approach favors SSZ-25 as the kinetic product but at longer run times Ostwald ripening was observed, leading to the disappearance of SSZ-25 and formation of ferrierite zeolite and quartz.     

Structure-directing agent location and non-centrosymmetric structure of fluoride-containing zeolite SSZ-55

Single crystals of pure silica zeolite SSZ-55 were prepared using the fluoride route. Single-crystal X-ray diffraction at a synchrotron source revealed the framework structure of the material, but the unit cell (orthorhombic a = 12.905(2) A, b = 21.344(4) A, c = 5.1279(10)) is too small to accommodate ordered arrays of the organic structure-directing agent. Molecular modeling was used to simulate the docking of the structure-directing agent in the channels of the material, and this revealed a strong space-filling interaction with a number of possible orientations of the organic cation. The overall non-centrosymmetric structure of the solid (spacegroup C222(1)) was confirmed using second harmonic generation experiments.     

Conversion of CO_2 and H_2 into propane over InZrO_x and SSZ-13 composite catalyst

Direct converting carbon dioxide into hydrocarbon fuels and value-added chemicals would offer a very attractive approach for efficient utilization of CO₂ as a carbon resource.Although,olefins,aromatics and gasoline have been successfully synthesized by CO₂ hydrogenation,highly selective conversion of CO₂ and H₂ into C₂₊hydrocarbon is still challenging due to a high C-C coupling barrier and inhibiting the production of other long-chain hydrocarbons.Here,we report a composite catalyst made of InZrO_x and SSZ-13 molecular sieve(InZrO_x+SSZ-13),which exhibits 74.5% propane selectivity at 623 K.The 8-MR micropores and the higher strength of the acid for SSZ-13 benefit the formation of propane.Compared with pure InO_x and m-ZrO₂ the composite oxide InZrO_x containing more oxygen vacancies,exhibits to be more readily reduced by H₂ and easier to adsorb and desorb CO₂ within the reaction temperature.All those could be beneficial to the activation and conversion of H₂ and CO₂.The catalytic performance of InZrO_x+SSZ-13 in CO₂ hydrogenation provides a potential for production of propane.     

Improved thermogravimetric system for processing of oil sludge using HY zeolite catalyst

The oil sludge residue presents an aggregate of hydrocarbons, organic and inorganic impurities, and water. The microporous and mesoporous zeolites are considered promising catalysts for processing of petroleum residues generated in refining processes. The aim of this work was to study the degradation of petroleum sludge obtained from primary processing, with applications of an improved thermogravimetry system and HY zeolite, at specific temperature ranges and degradation times, in order to obtain light gases and distillate fuels. The NaY zeolite was synthesized under hydrothermal treatment of a gel containing sodium silicate, sodium aluminate, and water. The obtained solid material was filtered, dried and calcined, and then ion-exchanged with ammonium chloride and calcined in order to obtain its protonic acid form (HY). The samples’ characterization by TG/DTG, XRD, and SEM proved that the crystalline structure of the faujasite zeolite was obtained. The thermal and catalytic degradation of the petroleum sludge was performed with 1.0 g of sample containing 10% of HY zeolite in the temperatures of 100, 200, 300, 400, and 500 °C, varying the time from 0 to 60 min to each temperature, using an oven with temperature program system, adapted with a Shimadzu precision balance. The curves obtained with this system evidenced that the presence of HY zeolite improves the degradation of the residue, with decreasing of the activation energy for the processes, as determined using the Arrhenius model.

     

Organocations in zeolite synthesis: fused bicyclo [l.m.0] cations and the discovery of zeolite SSZ-48

A set of zeolite synthesis experiments is described where lattice substitution is varied in the context of the structure of particular structure-directing organocations (at times referred to as templates). In this particular series, the organocations are constructed as members of a fused bicyclo organonitrogen class of compounds, described as having ring construction [l.m.n], where n = 0. We show that these compounds can best be achieved from starting cyclic ketones that are converted to imines via a Beckman rearrangement reaction. A particular approach to the Beckmann reaction works best in our hands. In some instances isomeric organocations are made and separated. Often their use in zeolite synthesis led to different products. There is a high correlation for the space-filling details of the guest organocations and the type of crystalline host lattice developed in the synthesis. In one instance involving isomers of a decahydroquinoline derivative, a new zeolite, SSZ-48, is discovered and contains only one of the isomers. Characterization of the isomers and their use in the zeolites is followed by (13)C MAS NMR analyses. Some details of the new zeolite are given and it is shown that a reasonable symmetry operation predicting a 14-ring zeolite could be generated under similar conditions to SSZ-48 (a 12-ring zeolite).     

Dual template synthesis of a highly mesoporous SSZ-13 zeolite with improved stability in the methanol-to-olefins reaction

The dual template synthesis of zeolite SSZ-13 by use of trimethyl-adamantanammonium hydroxide and a diquaternary-ammonium mesoporogen induces considerable mesoporosity without impeding zeolite microporosity. The strongly improved accessibility of Br?nsted sites in mesoporous SSZ-13 increases its stability during application as an acid catalyst in the methanol-to-olefins reaction.     

CO2 poisoning effect on HY zeolite dehydration catalyst

The poisoning effect of CO₂ on a HY catalyst for the dehydration of 2-(2-hydroxyethyl)-pyridine (HEP) to 2-vinylpyridine (VP) has been investigated by FT-IR analysis in the presence and absence of pyridine. CO₂ was found to adsorb on sites not occupied by pyridine,i.e. on weak basic sites accompanying the strongly acidic sites, characteristic of Y zeolites in the protonated form. When the basic sites are occupied by preadsorbed CO₂, HEP dehydration cannot take place any more through the minor mechanism, involving a couple of acid-base sites, and the reaction proceeds only through the major mechanism, involving a carbocation intermediate, on Br?nsted acid sites only.     

含NiY分子筛的加氢裂化催化剂载体研究

采用水热晶化法,合成出了含骨架杂原子Ni的NiY分子筛。分别以Y分子筛和NiY分子筛作为载体,通过等体积浸渍法担载金属活性组分Ni、Mo,制备加氢裂化催化剂。通过NH₃-TPD表征催化剂的表面酸性、固定床反应器评价催化剂的加氢裂化性能。结果表明,将Ni引入分子筛骨架中,可以调变催化剂的表面酸性,提高其裂化和脱硫活性,并减少催化剂上的积炭。     

含有多级孔复合分子筛的复合催化剂上合成气一步制二甲醚

以Beta分子筛为核、Y型分子筛为壳层的多级孔复合分子筛(BFZ)作为甲醇脱水催化剂用于固定床中合成气一步法制备二甲醚,并与纯Y型分子筛进行了比较,研究了二甲醚合成催化反应活性与甲醇脱水催化剂孔道结构和酸性之间的关系.结果表明,复合分子筛HBFZ具有中等强度的酸性和中孔孔道结构,有利于提高合成气制备二甲醚的催化反应活性.二甲醚直接合成催化剂由工业CuO/ZnO/Al₂O₃催化剂(CZA)与分子筛(HBFZ、HY)采用机械混合方法制备;催化评价结果显示,CZA/HBFZ比CZA/HY具有更优的催化活性和稳定性.在250 ℃, 5.0 MPa 和 1 500 h^-1的反应条件下,CZA/HBFZ催化剂上CO的转化率和DME的选择性分别达到94.2%和67.9%.     

APUSM technology for the production of BTX and LPG from pyrolysis gasoline using metal promoted zeolite catalyst

SK Corporation developed an advanced pyrolysis gasoline (pygas) upgrading (APU^SM) technology based on a catalytic process for producing valuable benzene, toluene and xylenes (BTX) and liquefied petroleum gas (LPG) from pygas containing aromatics and non-aromatic hydrocarbons. Hydrodealkylation of heavy aromatics and hydrocracking of non-aromatic hydrocarbons occurred with facility in the conversion of pygas over a proprietary catalyst, metal promoted zeolite. This catalytic process produced benzene and toluene with high purity corresponding to chemical grade while giving mixed xylenes with reduced ethylbenzene. In the present study, we described novel features of the APU^SM technology in terms of the process and catalyst. The influence of the process conditions was also examined. This technology has been commercially proven, and hence is available for licensing through Axens, which is a major engineering and licensing company.     

Molecular chemistry in a zeolite: genesis of a zeolite Y-supported ruthenium complex catalyst

Dealuminated zeolite Y was used as a crystalline support for a mononuclear ruthenium complex synthesized from cis-Ru(acac)2(C2H4)2. Infrared (IR) and extended X-ray absorption fine structure spectra indicated that the surface species were mononuclear ruthenium complexes, Ru(acac)(C2H4)2(2+), tightly bonded to the surface by two Ru-O bonds at Al(3+) sites of the zeolite. The maximum loading of the anchored ruthenium complexes was one complex per two Al(3+) sites; at higher loadings, some of the cis-Ru(acac)2(C2H4)2 was physisorbed. In the presence of ethylene and H2, the surface-bound species entered into a catalytic cycle for ethylene dimerization and operated stably. IR data showed that at the start of the catalytic reaction, the acac ligand of the Ru(acac)(C2H4)2(2+) species was dissociated and captured by an Al(3+) site. Ethylene dimerization proceeded approximately 600 times faster with a cofeed of ethylene and H2 than without H2. These results provide evidence of the importance of the cooperation of the Al(3+) sites in the zeolite and the H2 in the feed for the genesis of the catalytically active species. The results presented here demonstrate the usefulness of dealuminated zeolite Y as a nearly uniform support that allows precise synthesis of supported catalysts and detailed elucidation of their structures.     

AgY zeolite as catalyst for the effective three-component synthesis of propargylamines

The preparation of substituted propargylamines via three-component reaction between aldehydes, terminal alkynes, and secondary amines following an environmentally acceptable methodology has been developed. The process has been carried out under solvent-free conditions in the presence of AgY zeolite. The catalyst can be easily recovered and reused for at least four cycles without significant decreases in yield and selectivity.     

Preparation and some properties of ion-exchange rhenium zeolite catalyst

Conclusions The rhenium zeolite catalyst, obtained from NaY by ion exchange with diethylenediaminedioxorhenium chloride, has a lower activity in the hydrogenation of benzene than the catalyst obtained by impregnating NaY with ammonium perrhenate solution.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1181–1183, May, 1976.The authors express their gratitude to B. N. Ivanov-Emin for assistance in the work.     

含稀土超强酸催化剂S2O8^2-/ZrO2-SiO2-Sm2O3的结构表征

目前有很多关于硫酸促进性固体超强酸催化剂的研究报道[1],其中硫酸浸渍氧化锆这类催化剂易制备,对于骨架异构、酯化和其他反应具有很高的活性.近年来,关于这类催化剂的制备、表征和应用的报道很多[2,3].