High-silica Zeolite Catalyst Research Articles

High-silica KFI zeolite: highly efficient synthesis and catalysis in methanol amination reaction

The hydrogen form of low-silica KFI zeolite, with a Si/Al ratio of 3.2 (referred to as H-KFI-3.2), has been shown to possess significant selectivity for monomethylamine (MMA) and dimethylamine (DMA) in methanol amination reactions. However, its industrial viability for MMA and DMA synthesis has been hindered by its relatively low methanol (MeOH) conversion and yield of MMA plus DMA. In this study, we synthesize high-silica KFI zeolite with an elevated framework Si/Al ratio of 5.4 (designated as KFI-5.4) using a novel K+ and 18-crown-6 complex [referred to as (K+)CCH, with a ratio of 18-crown-6 to K+ of 2.85] as an organic structure-directing agent. Control experiments have demonstrated that the presence of both K+ and OH- ions is essential for the formation of KFI-5.4 zeolite. The hydrogen form of KFI-5.4 (H-KFI-5.4) exhibits significantly enhanced MeOH conversion (95.2%) and yield (75.1%) of MMA plus DMA compared to the low-silica H-KFI-3.2 under similar reaction conditions. This represents the highest level of catalytic performance among reported small-pore zeolites to date. Furthermore, the yield and selectivity of MMA plus DMA can be further improved by modifying KFI-5.4 with an appropriate loading of Na+, which suppresses the formation of the by-product dimethyl ether. This study introduces a new high-silica KFI zeolite catalyst with exceptional MeOH conversion and yield for the production of MMA plus DMA.

SEAL PRODUCTS AND THEIR ROLE IN THE PROCESS OF CONVERSION OF ISOBUTENE ON A HIGH SILICA ZEOLITE CATALYST

Conversion of isobutene on a high silica zeolite catalyst in the temperature interval (473-773 K) has been studied. The formation of liquid reaction products is observed at the temperature 473 K, whereas gaseous products form after 523K. Maximum yield of liquid products is observed at the temperature 573 K and makes up 67 %. With increase of contact time the yield of liquid reaction products shifts towards high temperatures. Formation of aromatic hydrocarbons is observed at the reaction temperature higher than 573 K. At the temperature 673 K the main mass of liquid products consists of aromatic hydrocarbons. The activity of H-form of HSZ (HHSZ) in the process of conversion of isobutene in the formation of liquid reaction products occurs only when 6-8% of seal products accumulate on its surface. By the method of ammonia adsorption on the initial and coked catalyst their acidic properties have been studied. It was shown that at the beginning of the process decrease in acidic properties of the catalyst occurs due to accumulation of seal products on it. Key words: catalyst, activity, isobutene, zeolite, seal products, temperature, heterogen, chromatography, spectroscopy.

WHEN CHOOSING CATALYSTS FOR THE CONVERSION OF ISOBUTYLENE PRINCIPLES OF QUALITY AND QUANTITY

Catalysts play an extremely important role in wildlife and industry. Today it is difficult to describe chemistry and petrochemistry without catalytic processes. Catalytic processes account for 80-85% of oil refining. Therefore, the problem of choosing a catalyst is of interest both from the point of view of quality and quantity. In this paper, the activity of a high silicon zeolite catalyst used in the conversion of isobutene was studied at various temperatures, and it was determined that a sample of the zeolite catalyst during the process initially had no catalytic activity during the conversion of isobutene. The release of liquid products is observed only after the formation of 5-8% of compaction products (PM) on the surface within 25-30 minutes from the beginning. Consequently, modifiers have a positive effect on catalytic activity. In this case, the number and strength of the acid sites of the catalyst changes. The study of isobutene conversion process showed that the formation of liquid products is observed at 150°C. It was shown that in this case in the temperature range 150°C-300°C liquid products of isobutene reaction consist of primarily from aliphatic and at 350°C- 450°C from aromatic hydrocarbons. The process of conversion of hexane-1 on the high-silica zeolite catalyst is studied and it was shown that the decomposition of hexene-1 into ethene and propene is occure at the beginning, at 250°C and then the process takes place in a mixture of the two olefins. It was shown by the using of XRD, TG/DTA methods, that the formed products of seals in the conversion of isobutene and 1-hexene over the high silica zeolite catalyst,is composed of two phases that differ from each other in thermal stability. The obtained liquid products during the conversion of isobutene at 150°C-300°C can be used as high-octane gasoline fractions as motor fuel component. The adsorbed NH3 probe molecules method showed that during the conversion of propene, isobutene and hexene-1, the amount of acid sites of spent catalysts is reduced by 43-50%. In this state, the catalyst exhibits high catalytic activity. Keywords: catalyst, activity, isobutene, zeolite.

Hydrothermal and supercritical ethanol processing of woody biomass with a high-silica zeolite catalyst

The effects of high-silica ZSM-5 on the yields, as well as compositions, of bio-oil and solid residue obtained from oak wood sawdust were investigated. The catalyst, in concentrations from 5 to 40 wt% of the raw lignocellulose material, was tested in hydrothermal (HT) and supercritical ethanol (SCE) media. The highest bio-oil yields were 11.0 and 32.4 wt% for HT and SCE processing, respectively, and were obtained by using 20 wt% ZSM-5. After the noncatalytic and catalytic HT processing and noncatalytic SCE processing of lignocellulose, the major products were phenols, whereas esters were the major products in the bio-oils obtained from the catalytic SCE processing of oak wood sawdust. The use of ZSM-5 increased the relative contents of the ester compounds in the bio-oils from the SCE processing, while the catalyst did not significantly change the composition of the bio-oils produced from the HT processing of oak wood sawdust. The highest heating values of the bio-oils were 27.11 and 25.65 MJ kg−1 for HT and SCE processing, respectively, and were obtained from the noncatalytic runs. The amount of recovered carbon in the bio-oils from the catalytic runs was higher than that from the noncatalytic runs for both HT and SCE processing. The carbon content of the solid residues for both HT and SCE processing decreased with the use of a catalyst. An increase in the catalyst concentration led to a decrease in the carbon content of the solid residues in SCE and HT processing.

Breaking Structural Energy Constraints: Hydrothermal Crystallization of High-Silica Germanosilicates by a Building-Unit Self-Growth Approach.

Zeolites, a class of crystalline microporous materials, have a wide range of practical applications, in particular serving as key catalysts in petrochemical and fine-chemical processes. Millions of zeolite topologies are theoretically possible. However, to date, only 235 frameworks with various tetrahedral element compositions have been discovered in nature or artificially synthesized, among which approximately 50 topologies are available in pure-silica forms. Germanosilicates are becoming an important zeolite family, with a rapidly increasing number of topological structures having unusual double four-membered ring (D4R) building units and large-pore or extra-large-pore systems. The synthesis of their high-silica analogues with higher (hydro)thermal stability remains a great challenge, because the formation of siliceous D4R units is kinetically and thermodynamically unfavorable in hydrothermal systems. Herein, it is demonstrated that such D4R-containing high-silica zeolites with unexpected crystalline topologies (ECNU-24-RC and IM-20-RC) are readily constructed by a versatile route. This strategy provides new opportunities for the synthesis of high-silica zeolite catalysts that are hardly obtainable by conventional hydrothermal synthesis and may also facilitate a breakthrough in increasing the number and types of zeolite materials with practical applications.

Thermal conversion of mechanically activated mixtures of aspen wood-zeolite catalysts in a supercritical ethanol

The mechanical activation of the mixture of aspen wood – high silica zeolite catalysts increases the wood thermal conversion in supercritical ethanol and rises the yield of liquid products. TH-HSZ-30 with Si/Al = .Zeolite catalysts allow to fractionate the mechanically activated wood in supercritical ethanol at 270 °C on solid lignocellulose and on soluble products from hemicelluloses, presented by furfural, 5-hydroxymethylfurfural, levulinic acid and ethyl esters. The elevated temperature (350 °C) decreases the yield of liquid products due to the intensification of secondary reactions of their transformation to gases and chars.The possible mechanism of wood catalytic conversion to bio-liquids in supercritical ethanol is discussed.

Manufacturing of low-pour-point fuels using high-silica zeolite catalysts

The results of research and development study on a dewaxing catalyst: improvement in the technology of synthesis of the zeolite component, selection of promotion conditions, and the development of technology for production and use of the catalyst, are presented. It has been found that the hydrothermal treatment of silica gel for 12–24 h at a temperature of 100–120°C leads to the formation of pores of a 100–200 A radius. Use of the treated silica gel and temperature elevation from 130 to 170°C leads to reduction of the crystallization time from 120 to 48 h and the formation of high-silica zeolite with a particle size of 1–6 µm3. The zeolite promoted with zinc by ion exchange exhibits a higher dewaxing activity than its zinc-promoted samples prepared by impregnating or batch mixing. Furthermore, the introduction of a second promoter (phosphorus compound) into the catalyst reduces the dewaxing temperature by 45°C relative to the initial sample. On the basis of these data, the catalyst production technology as applied to the equipment of the Angarsk plant has been worked out. The designed catalyst DEP-1 in combined use with the hydrotreating catalyst AGKD-400 provides the manufacture of diesel fuel base stock with a cloud point of −38°C, a cold filter plugging point of −41°C (for class 3 diesel), type III according to GOST R 52368-2005 (EN 590: 2009).

Изучение термического превращения механохимически активированной древесины осины в присутствии высококремнеземного цеолитного катализатора

Изучение термического превращения механохимически активированной древесины осины в присутствии высококремнеземного цеолитного катализатора

Nature of condensation products in but-1-ene aromatization on high-silica zeolite catalyst

The aromatization of but-1-ene on the H-form of pentasil-type zeolite catalyst (SiO2/Al2O3 = 54) is studied in the temperature range from 573 to 723 K. It is shown that in the range of 623 to 723 K, the liquid phase consists mainly of aromatic hydrocarbons. The results from differential thermal and X-ray diffraction analyses show that graphite-like depositions can form in zeolite channels during the conversion of but-1-ene on the H-form of zeolite catalyst at 673 K and more than 20 h. The activity of the catalyst remains virtually the same.

Highly selective formation of propylene from methanol over high-silica EU-1 zeolite catalyst

Abstract High-silica EU-1 zeolite (SiO2/Al2O3 = ~ 400) was tested in methanol to propylene (MTP) reaction and was found to be a very efficient catalyst. In comparison with the other three high-silica zeolites, i.e. ZSM-48, ZSM-5, and beta zeolites, a higher propylene selectivity (52%) and remarkably high propylene/ethylene (P/E) ratio (15) were obtained under the operating conditions of T = 450 °C, P = 0.1 MPa, and WHSV = 1.5 h− 1. Besides, a substantially low amount of C5 + hydrocarbons, especially aromatics is another prominent feature of the product distribution over high-silica EU-1 catalyst.

Conversion of C4 Fraction of Hydrocarbon Pyrolysis Products Over ZVM+2 % Zn High-Silica Zeolite Catalyst

Conversion of C 4 fraction of hydrocarbon pyrolysis products over high-silica zeolite catalyst ZVM modified by 2 mas % of Zn within the temperature range of 623-823 K and volumetric flow rates of 1000-10000 h -1 has been investigated. The yield and chemical composition of gaseous and liquid products have been determined under various conditions. It has been shown that the initial fraction is converted almost completely (98-100 %); the yield of C 6-C8 lower arenes is 44.2-65.4 % within all investigated ranges of temperature and volumetric flow rates.

Effect of coke formation on the transformations of butylenes on a high-silica zeolite catalyst

The transformations of butylenes on a high-silica zeolite catalyst (HHSZC) at 423–773 K were studied. Liquid reaction products formed above 443 K. The liquid phase of the reaction products mainly consisted of aliphatic hydrocarbons at 448–523 K and aromatic hydrocarbons at 623–723 K. The catalyst activity in the formation of liquid products did not show itself until 4–6% consolidation products (CPs) accumulated on its surface. DTA and gravimetric studies showed that CPs were nonuniform in composition. Some of the CPs were removed by decomposition under nitrogen, while others by oxidation with oxygen. It was inferred from ammonia adsorption data that the accumulation of CPs on the surface of HHSZC led to a decrease in the number of acid centers.

10.1007/s11494-008-1003-y

Conversion of dimethyl ether over high-silica zeolite catalysts of the ZSM-5 type was studied. It was shown that the introduction of metals into the catalyst composition affects the activity and selectivity of the catalysts. It was found that the catalysts modified with Zr and P are most selective for light olefins. The influence of the addition of water to feedstock on the yields of the desired products was demonstrated; the results are similar to the data obtained by the Lurgi company.

C2–C4 Alkenes Conversion over ZVM+2 % Zn High-Silica Zeolite Catalyst at High Volumetric Flow Rates

C2–C4 alkenes conversion over high-silica zeolite catalyst modified with 2 mas % of Zn has been investigated at the laboratory plant of flow type within temperatures ranges of 723–773 K and volumetric flow rates 1000–30000 h-1. It has been shown that a propylene high conversion and high yield of liquid catalizate containing lower arenes are achieved at space velocities of 20000 h-1.

Densification products in conversion of ethylene on a high-silica zeolite catalyst

Fundamental aspects of the conversion of ethylene on a high-silica zeolite catalyst in the temperature range 200–400°C were studied. The methods of differential-thermal and X-ray phase analysis were employed to examine the formation of coking products on the surface of the zeolite catalyst in the conversion of ethylene at 350–450°C

Ordered silicon vacancies in the framework structure of the zeolite catalyst SSZ-74

Physico-chemical characterization of the high-silica zeolite catalyst SSZ-74 (ref. 1) suggested that it, like the related materials TNU-9 (ref. 2) and IM-5 (ref. 3), has a multidimensional 10-ring channel system. Such pore systems are ideal for many petrochemical applications, and indeed SSZ-74 has been shown to be a good catalyst for a wide variety of reactions. The elucidation of its framework structure, however, proved to be difficult. Comparable problems were encountered with TNU-9 and IM-5, which were synthesized with related structure-directing agents. Their framework structures, which are the two most complex ones known, both have 24 Si atoms in the asymmetric unit, and were finally solved by combining high-resolution powder diffraction data with information derived from high-resolution electron microscopy images. Therefore, a similar approach, using the powder charge-flipping algorithm to combine the two types of data and molecular modelling to help to locate the structure-directing agent, was applied to SSZ-74. This procedure eventually revealed a most unusual 23-Si-atom framework structure (|(C(16)H(34)N(2))(4)&Si(92)(4)O(184)(OH)(8)]) with ordered Si vacancies.

Production of lower unsaturated hydrocarbons via catalytic conversion of dimethyl ether

Conversion of dimethyl ether over high-silica zeolite catalysts of the ZSM-5 type was studied. It was shown that the introduction of metals into the catalyst composition affects the activity and selectivity of the catalysts. It was found that the catalysts modified with Zr and P are most selective for light olefins. The influence of the addition of water to feedstock on the yields of the desired products was demonstrated; the results are similar to the data obtained by the Lurgi company.

Beckmann rearrangement reaction: About the role of defect groups in high silica zeolite catalysts

The aim of this paper is to investigate the role played by the zeolitic defect groups on the catalytic behavior of Silicalite-1 in Beckmann rearrangement reaction. Samples of Silicalite-1 catalysts were prepared and activated by different post-synthesis procedures. Catalytic activity and deactivation rate of the different catalysts were correlated with the different types of hydroxyl population. FT-IR and NMR techniques were used in order to determine the amount of defect groups and the different silanol types. The results show that Silicalite-1 is a good catalyst for Beckmann rearrangement reaction and when the geminal silanols are present the catalyst deactivate faster.

Vapor phase Beckmann rearrangement using high silica zeolite catalyst

Vapor phase Beckmann rearrangement of cyclohexanone oxime to e-caprolactam has been studied using high silica zeolite catalysts. Catalysts with different crystal sizes and gel-ageing times have been activated by ionic exchange in different conditions by means of a highly basic solution and a nearly neutral solution both containing ammonium salts. Samples have been calcined at different temperatures in order modify the number of defective sites. We observed that samples exchanged by means of a highly basic solution (pH > 10) and calcined at a relatively lower temperature (450 °C) show the most interesting catalytic results. X-ray powder diffraction patterns of these samples show retention of the unit cell symmetry (orthorhombic cell) if compared to the dried sample. NH3-TPD confirms the low acidity of high silica zeolites, however a higher amount of desorbed ammonia is observed for the samples exchanged at higher pH and calcined at 450 °C. Due to silanol nests the IR spectra of the same samples show the formation of Si–NH2 bonds which are absent in the same material exchanged by other methods. Such sites seem to promote the high stability of the high silica zeolite catalysts also to the regeneration which is needed to remove the heavy carbonaceous compounds from the catalyst surface.

Effects of air pollutants on the cerium exchanged high silica zeolite catalyst: a Fourier transform infrared study

The interaction of air pollutants such as nitric oxide (NO) and carbon monoxide (CO) gases on the cerium exchanged ZSM-5 material was studied by FT-IR spectroscopy. Highly crystalline and pure H-ZSM-5 was used for preparing the cerium exchanged material. The cerium exchanged ZSM-5 material was characterised by conventional techniques such as ICP-OES, nitrogen sorption capacity (BET), XRD and XPS. X-ray photoelectron spectroscopy identified the presence of both Ce III and Ce IV species on the surface of the prepared catalysts. The in situ interaction of NO and CO on the cerium exchanged ZSM-5 was studied using an FT-IR Pyrex/quartz cell. The adsorption of NO gas led to the formation of nitrous oxide, mono- and dinitrosyl complexes of cerium, nitrogen dioxide and nitrate species. The adsorption of CO gas led to the formation of mono-, di- and tricarbonyl complexes of cerium and carbon dioxide and carbonate species. The types of NO and CO sites on the Ce-ZSM-5 catalyst are similar to those observed on copper exchanged catalysts, in particular Cu-SAPO-34 and Cu-ZSM-5.