Acetylation of 2-methoxynaphthalene with acetic anhydride over a series of dealuminated HBEA zeolites

The liquid phase acylation of 2-methoxynaphthalene with acetic anhydride was carried out in a batch reactor at 120°C over a series of HBEA zeolites resulting from dealumination of a commercial sample by treatment with chlorhydric acid or with ammonium hexafluorosilicate. Lewis acid sites which correspond to extraframework aluminium species and to transient-state species (aluminium atoms which are leaving the framework) were preferentially removed. With all the HBEA samples, acetylation of 2-methoxynaphthalene leads preferentially to 1-acetyl-2-methoxynaphtalene, this compound undergoing isomerization into 2-acetyl-6-methoxynaphthalene and 1-acetyl-7-methoxynaphthalene as well as deacylation. A maximum in acetylation and isomerization activities is found for a Si/Al ratio between 20 and 35. The low activity of the commercial sample can be related to limitations in the desorption of acetylated products from the zeolite micropores caused by the large amount of extraframework aluminium species present on this sample. Lewis acid sites were shown to be completely inactive for acetylation and isomerization reactions. This revised version was published online in July 2006 with corrections to the Cover Date.     

Y分子筛/介孔Al-SBA-15复合材料与脱铝Y分子筛的表征和重油加氢裂化性能

采用两步法和水热-化学方法制备了具有高水热稳定性的Y分子筛/介孔Al-SBA-15复合材料和含有介孔的脱铝Y分子筛,用浸渍法制备了加氢裂化催化剂,并利用XRD、N2 吸附、SEM、XRF和TEM等分析手段对Y分子筛/介孔Al-SBA-15复合材料、含有介孔的脱铝Y分子筛及其催化剂的物化性质进行了对比分析。相同条件下催化剂的重油加氢裂化性能对比评价结果表明,以Y分子筛/介孔Al-SBA-15复合材料为载体的加氢裂化催化剂的中间馏分油收率和中油选择性高达66.21%和84.5%,比以脱铝Y分子筛为载体的催化剂分别提高了5.68%和5.7%。     

Enhanced hydrocarbon cracking activity of Y zeolites

It has been known for a long time that faujasite zeolites that have been steamdealuminated to form USY zeolite are much more active than the unsteamed parent material for hydrocarbon cracking. A popular model to explain this phenomenon is the generation of active sites of unusually high activity. In this paper, a brief review of recent advances towards understanding this phenomenon is presented. Evidence suggests that steaming does not generate sites of new chemical or catalytic properties for cracking. An alternate model is summarized that incorporates a change in the dominant cracking reaction mechanism as a function of conversion, and raises the possibility that the rates of bimolecular and oligomeric cracking are influenced by pore diffusion.     

129Xe-NMR study of coke distribution in dealuminated HY zeolites

Zeolites coking has been studied by¹²⁹Xe-NMR technique. The distribution of the coke is heterogeneous on the supercage surface at low cokage level. When coking increases up to 10% the supercages are lined with coke and the residual internal volume consists of narrow channels. Beyond 10% the coke also affects the external surface of the zeolites, with the formation of coke microcavities between the crystallites. This technique has also enabled us to show the role of extra-framework Al in the cracking activity of zeolites.     

催化裂化汽油在多元沸石基催化剂上加氢改质研究

采用浸渍法分别制备了以丝光沸石（HM）、Hβ和HZSM-5及其组合为载体的沸石基Ni-Mo-P催化剂,考察了载体组成对催化裂化汽油加氢改质反应性能的影响。结果表明,由适宜比例的三者组合得到的沸石基Ni-Mo-P催化剂具有良好的加氢异构化、脱硫、芳构化活性及稳定性,可在催化裂化汽油脱硫降烯烃的同时保证产品的辛烷值不降低。考察了工艺条件对三元沸石基Ni-Mo-P催化剂反应性能的影响。在温度300 ℃、氢油体积比350、液相体积空速2.5 h-1和反应压力1.5 MPa反应条件下,催化裂化汽油异构烷烃收率、芳烃收率、脱硫率及液相收率分别达41.9%、31.7%、51.0%和98.3% 。     

Infrared spectroscopic study of the acid properties of dealuminated BEA zeolites

A series of HBEA samples were prepared by dealumination through three different methods (steaming, treatments with hydrochloric acid and ammonium hexafluorosilicate (HFS) solutions) of a parent sample with total and framework Si:Al ratios of 12.5 and 33, respectively, constituted of 20 nm crystallites. The samples were characterized by XRD, nitrogen adsorption and pyridine adsorption–desorption followed by IR spectroscopy. Whereas the three dealumination treatments have practically no effect on crystallinity and nitrogen adsorption properties, they cause large changes in the ranges of the O–H bond stretching modes (3300–3800 cm⁻¹) and of the most intense IR absorption of pyridine (1400–1700 cm⁻¹). Treatments with HCl or HFS cause the most significant changes: disappearance of the 3662 and 3782 cm⁻¹ bands corresponding to extraframework Al species and to tricoordinated Al species partially connected to the framework, respectively, appearance of additional bands at 1603 and 1446 cm⁻¹ ascribed to a new type of pyridine species coordinated to Lewis sites (PyL₂) and for desorption temperatures above 350 °C, of a band at 1462 cm⁻¹ generally ascribed to iminium ions, apparently at the expense of the PyL₂ band. In agreement with this formation of iminium ions, desorption at high temperatures causes the complete disappearance of pyridinium ions without complete restoration of the acidic bridging hydroxyl band. PyL₂ species are proposed to be pyridine molecules coordinated to Lewis sites and interacting through hydrogen bond with protonic sites.     

Characterization of Y zeolites dealuminated by solid-state reaction with ammonium hexafluorosilicate

In the present work the solid-state dealumination of Y zeolite with ammonium hexafluorosilicate for various reaction times was studied. A detailed characterization of the porosity of the samples, and their hydrophobic-hydrophilic properties, was made. The characterization techniques used, besides the low temperature nitrogen adsorption and the room temperature water adsorption, include also the FTIR, the powder XRD and the ²⁷Al and ²⁹Si MAS NMR. These techniques showed evidence for the complex mechanism of dealumination that for sufficiently long times of reaction allows the partial reconstitution of the structure. Due to this mechanism the evolution of the Si/Al ratio, as well as the porosity and the hydrophobic-hydrophilic properties, do not run monotonically with the time.     

Hydrodesulfurization over noble metals supported on ZSM-5 zeolites

Pt/HZSM-5 showed high and stable catalytic activity for the hydrodesulfurization of thiophene at 400°C and its catalytic activity was higher than that of commercial CoMo/Al₂O₃ catalyst. Pt/HZSM-5 zeolite was not poisoned by hydrogen sulfide in the hydrodesulfurization of thiophene and hydrocracking of hydrocarbons. The catalytic activity of Pt/HZSM-5 decreased with increase of SiO₂/Al₂O₃ ratio in HZSM-5. The Brønsted acid site of HZSM-5 and spillover hydrogen formed on Pt particle in Pt/HZSM-5 catalyst play an important role for the hydrodesulfurization of thiophene.     

Solid-state ion exchange of rhodium chloride with highly dealuminated Y-type zeolite DAY by thermal treatment and in the presence of carbon monoxide

The solid-state ion exchange of Rh chloride with highly dealuminated Y zeolite has been studied by in situ FTIR spectroscopy. Thermal treatment in vacuum and calcination in oxygen up to 600°C results in an exchange limited to ca. 25% at temperatures higher than 400°C. The ion exchange can be performed much more effectively (over 50%) and at lower temperatures (100–150°C) in the presence of CO in the gas phase. A linear correlation has been found between the formation of well-defined Rh(CO) ₂ ⁺ species and the simultaneous loss of acid hydroxyl groups for samples treated at different conditions. From these results a model is proposed with the formation of Rh subcarbonyls, the migration of these species to the cation positions of the zeolite and, finally, the formation of the stable well-defined Rh(CO) ₂ ⁺ species at these positions as essential steps of the ion exchange in the presence of CO.     

Effect of acid strength distribution on de-t-butylation rate and catalyst fouling rate

De-t-butylation of t-butylbenzenes was carried out over a pyridine poisoned solid acidic catalyst to determine the effect of acid strength distribution on the reaction rate and catalyst fouling rate. The acid sites on the solid acidic catalyst were divided into three groups by their acid strength. Moderate acid sites, which were effective for the de-t-butylation but ineffective for the coke formation, were exclusively left on the catalyst surface by the partial poisoning. It is found that the present modification of the catalyst is useful in preparing an acid catalyst without catalyst fouling by coke deposition.     

多级孔分子筛对四氢萘加氢生产轻质芳烃的影响

以多级孔Y分子筛为酸性组分,四硫代钼酸铵为金属前驱物,采用孔饱和浸渍法制备预硫化型催化剂,采用XRD、BET、TEM、NH3-TPD和Py-IR等分析方法表征分子筛结构性质。以四氢萘为模型化合物,在高压加氢微反装置上考察多级孔Y分子筛对四氢萘选择性加氢裂化性能的影响。结果表明,与参比分子筛相比,介孔比例高、介孔孔径尺寸适宜、介孔集中度高和酸性适中的多级孔Y型分子筛能够强化四氢萘转化及提高C_6~C_(10)和C_6~C_8单环芳烃收率;介孔孔径尺寸过大或介孔集中度低会提高重产物收率。实验条件下,C_6~C_(10)和C_6~C_8单环芳烃收率分别可达41.5%和24.0%。     

Hydrocracking of diphenylmethane and tetralin over bifunctional NiW sulfide catalysts supported on three kinds of zeolites

Hydrocracking reactions of diphenylmethane and tetralin were carried out over three kinds of zeolites with or without NiW sulfide to discuss the roles of catalytic bifunctionality in two types of hydrocracking reactions. It was found that strong acid sites were not needed for the hydrocracking of diphenylmethane, while the conversion of tetralin required relatively strong acid sites. Ultra-stable Y zeolite with strong acidity exhibited high hydrocracking activity for both reactions. In contrast, mordenite catalysts did not show high activity for either hydrocracking, though isomerization of tetralin and excess hydrocracking to gaseous products proceeded. The superior performances of ultra-stable Y zeolite in the tetralin hydrocracking were suggested to be related to the hydrogen transfer ability. In most cases, the loading of NiW sulfide enhanced catalytic activity. In the diphenylmethane hydrocracking, the role of NiW sulfide was found to supply active hydrogen to the hydrocracking active sites on zeolite and to prevent polymerization of benzyl cations. In the tetralin hydrocracking, the dehydrogenated products from tetralin were re-hydrogenated over NiW sulfide.     

沸石催化剂在炼油和石油化工中的应用

介绍了沸石作为一种具有独特结构的催化剂在炼油与石化生产过程的应用现状与发展趋势。其中包括在催化裂化、加氢裂化与加氢精制、异构化、烷基化加工过程以及乙苯、异丙苯、直链烷基苯、己内酰胺等石化产品生产中的应用新进展。认为沸石催化剂无毒无害的特性及其相关绿色工艺适应环保发展趋势，将获得越来越广泛的应用。     

影响CeY分子筛吸附脱硫性能因素的研究

通过液相离子交换法对NaY分子筛进行改性制得CeY分子筛,采用静态法考察了改性CeY分子筛中铈离子的负载量、焙烧温度、铈的价态、吸附水和分子筛骨架的结构对CeY分子筛吸附脱硫性能的影响。采用XRD和ICP分别对不同CeY分子筛的骨架结构及阳离子负载量进行了分析。结果表明,二次交换后,离子交换度达到88.9%,分子筛已达到交换平衡;最佳焙烧温度为500 ℃,温度过高会破坏分子筛的骨架结构;Ce(Ⅳ)Y的脱硫性能明显好于Ce(Ⅲ)Y;分子筛上的吸附水对硫化物的吸附能力也有较大的影响。     

汽油在钾修饰MCM-22分子筛上的烷基化脱硫

在固定床上考察了钾修饰的MCM-22分子筛上模拟催化裂化汽油中的噻吩烷基化脱硫。结果表明,催化剂的强酸有利于噻吩烷基化脱硫反应活性。钾处理显著降低了MCM-22分子筛的强酸数量,对弱酸的影响则相对较小。随着负载钾质量分数的增加,催化剂反应活性显著降低,而噻吩烷基化反应选择性却存在一最佳值,另外,催化剂的稳定性可以得到一定程度改善。     

Selective synthesis of 2-methylquinoline over zeolites

The selective vapour-phase synthesis of 2-methylquinoline by alkylation of quinoline with methanol was carried out over HY, HZSM-5(30), CrHY, CeHY, LaHY, LaKHY and CeHZSM-5(30) zeolites in a fixed-bed reactor at atmospheric pressure. The yields of 2-methylquinoline over modified zeolites, especially those of doubly promoted LaKHY, were found to be higher than those of unmodified zeolites. The maximum yield of 2-methylquinoline obtained was 60.6 wt% at 91.5 wt% selectivity over LaKHY zeolite. The active sites responsible for this methylation were found to be more on Lewis acidic sites available over zeolite systems. This revised version was published online in July 2006 with corrections to the Cover Date.     

Isomerization of hexane on PtAu nanoparticles supported on zeolites

When lead-based anti-knock additives were withdrawn, petrol was enriched with benzene and benzene derivatives in order to maintain an excellent octane number. However, because of their toxicity, it is planned to eliminate these also and to replace them by methylated alkanes, whence the importance of n-alkane isomerization.

Some PtAu-zeolite catalysts tested for n-hexane isomerization reveal that the addition of gold to platinum generally changes the activity and/or the selectivity for methylpentane to the detriment of cracking. The influence of the zeolite structure is also important. At 275 °C, the activity and selectivity of PtAu-HZSM5 are about 75%, showing that this catalyst can be useful for such a reaction.     

多羟基羧酸与氟化铵复合改性超稳Y分子筛

针对高产中间油馏分型加氢裂化对催化剂的性能需求,采用多羟基羧酸和氟化铵对超稳Y分子筛USY进行复合脱铝改性。通过对两种试剂不同加入顺序以及单独脱铝效果的考察,初步探明了两种试剂复合脱铝的改性机理,并且通过BET、XRD、FT-IR和NH_3-TPD等手段对改性分子筛样品的结构及性能进行了表征。结果表明,同时加入多羟基羧酸和氟化铵可以有效减缓结晶度的降低,同时适量的增加B酸的含量,是最可行的改性体系。     

O-alkylation of phenol derivatives over basic zeolites

Alkali metal loaded zeolite X was used to catalyze O-alkylation of phenol derivatives in the presence of excess methanol. The reactivity of zeolite in the O-alkylation increased as the basicity of ion-exchanged metals increased. The super base originated from cesium oxide particles in zeolite cavities was as equally active as the ion-exchanged cesium cation. Hence the reactivity of the Cs loaded zeolite was found to be proportional to the total amount of cesium in zeolites. In addition to mono and dialkylphenols, the phenol derivatives with hydroxy, amino, nitro and chloride group were also used as reactants to investigate the effect of acidity of reactants on the reaction. The conversion increased as the acidity of hydroxy group of reactant increased. But the strong acidity resulted in rapid deactivation of the catalyst. Except for aminophenol the reaction products were the corresponding O-alkylated products regardless of functional groups attached and for aminophenol, N-alkylated product was produced due to the strong acidity of the amino group. The high selectivity to O-alkylation reaction over base catalyst was not a function of the conversion and thought to have resulted from the suppression of the side reactions such as C-alkylation of phenol and anisole which occurred predominantly on the acidic sites.     

高硅铝比小晶粒分子筛的合成及应用进展

小晶粒分子筛具有较大比表面积和短孔道,在炼油和石油化工反应中表现出优异的催化性能。分子筛晶粒越小,热稳定性和水热稳定性越差。结晶度相近的沸石分子筛结构稳定性主要受粒径和骨架硅铝比的影响。综述了小晶粒分子筛的合成方法,认为提高硅铝比可以提高小晶粒分子筛的热稳定性和水热稳定性。介绍了高硅铝比小晶粒沸石分子筛的制备及研究进展,认为高硅铝比小晶粒分子筛的合成仍是未来研究趋势。