改性丝光沸石催化剂上合成2,6-二异丙基萘

采用盐酸处理以及水热处理结合酸处理两种方法对氢型丝光沸石(HM)进行脱铝改性,制备了一系列脱铝HM催化剂,并以脱铝HM沸石为载体负载磷钨杂多酸(PW),制备负载杂多酸催化剂,用XRD、FT-IR和NH3-TPD等手段对这些催化剂的结构及酸性质进行了表征,在100mL间歇式不锈钢高压反应釜中对其在萘的异丙基化反应中的催化性能进行了考察。结果发现,随着脱铝深度的增加,HM沸石的酸量下降,酸强度降低,将PW负载于脱铝HM沸石载体上,其酸性质得到改善。上述催化剂的异丙基化反应结果表明,脱铝HM沸石的活性和2,6-DIPN选择性均大大高于未经改性的HM沸石;将PW负载于脱铝HM沸石上,其活性均有不同程度的上升,但对2,6-DIPN的选择性有所下降。催化剂的表征和反应结果显示,催化剂的活性和选择性与其孔结构和酸性质密切相关。     

氧化物改性丝光沸石催化剂上合成2,6-二异丙基萘

采用浸渍法负载B、P、Mg、La、Zr和Ce修饰水汽脱铝氢型丝光沸石,并采用固定床反应器对改性后丝光沸石催化萘烷基化反应的性能进行评价,结果表明,负载Ce是提高2,6-二异丙基萘选择性的有效方法。随着Ce浸渍量的增加,萘转化率降低,2,6-二异丙基萘的选择性提高,改性HM分子筛催化剂具有良好的再生性能。     

Hβ沸石催化合成2,6-二异丙基萘

采用高压釜对Hβ沸石催化剂的萘异丙基化催化反应性能进行评价。系统考察了溶剂用量、异丙醇与萘的物质的量比、Hβ沸石用量、反应温度及反应时间等因素对异丙基化反应的影响,优化了反应条件。实验结果表明,合成2,6-二异丙基萘(2,6-DIPN)适宜的反应条件是：溶剂十氢萘用量25 mL·（0.05 mol-萘）^-1,n(异丙醇)∶n(萘)=2.5∶1,催化剂用量15%,反应温度270 ℃,反应时间6 h,此时萘的转化率达66.41%,DIPN及2,6-DIPN的收率分别达到18.72%和3.41%,同时2,6-DIPN和2,7-DIPN的比值达到1.56。覆硅改性Hβ沸石,在基本不改变孔道性能的前提下,有效钝化其外表面酸性位,从而改善其催化萘异丙基化反应的综合性能。硅油沉积量为0.4 mL·g^-1时,萘转化率81.21%,2,6-DIPN收率7.60%,2,6-DIPN与2,7-DIPN的比值保持在1.52的较高水平。     

萘的择形烷基化催化剂的改性研究

以丝光沸石为催化剂，用萘和异丙醇烷基化反应选择性合成2，6-二异丙基萘并对沸石脱钠、强酸脱铝、水蒸气处理、浸渍活性组分等处理，探讨了反应时间、反应温度、活性组分对沸石催化剂的影响。在250℃反应3h，铯(Ce)浸渍沸石催化剂的转化率和选择性都比较好，转化率达31．59％，β-/α-的选择性达6．8，2，6-/2，7-的选择性高达2．95。     

丝光沸石上精萘的择形异丙基化反应

2,6-二异丙基萘(2,6-D IPN)是制备高级聚酯材料PEN和液晶聚合物的原料。该文以精萘和丙烯为原料,以水汽脱铝氢型丝光沸石(SDHM)代替传统的傅-克催化剂,在0.5 L高压釜中进行择形异丙基化反应,得到了高选择性和高收率的2,6-D IPN。不同来源的精萘中的含氮量对催化剂的活性产生很大影响。含氮量越低,异丙基化效果越好。为了减缓催化剂的失活,反应在氢氛下进行,以降低稠环芳烃的脱氢和结焦。和氮氛下的结果相比,氢氛下精萘的转化率和2,6-D IPN的产率均显著提高,其连续反应7釜的平均值分别达到90%和35%。     

Fe酸性沸石催化剂对2-异丙基萘择形歧化反应的影响

采用等体积浸渍法制备不同含量Fe₂O₃改性的MP-01催化剂，研究其催化2-异丙基萘歧化反应的性能。结果表明，2-异丙基萘择形歧化的最佳条件为反应温度210 ℃，采用质量分数2%Fe₂O₃改性后的MP-01催化剂，反应2 h，2-异丙基萘转化率为41.2%，目的产物2,6-二异丙基萘选择性为41.2%，二异丙基萘选择性为33.5%，选择性高于未负载Fe₂O₃的MP-01催化剂。Fe₂O₃的改性使催化剂表面酸性减少，抑制了非择形催化反应的发生，提高了2,6-二异丙基萘和二异丙基萘选择性。推荐2,6-二异丙基萘制备工艺路线，包括反应和分离两部分，反应主要包含烷基化、烷基转移和2-异丙基萘歧化3个反应。     

不同沸石分子筛催化剂上萘与异丙醇的烷基化反应

考察了USY、Hβ、HMCM-22、HM、HZSM-5等5种沸石分子筛在萘与异丙醇烷基化反应中的催化性能,并用XRD和NH3-TPD等手段对催化剂的物化性质进行了表征。实验结果发现,沸石分子筛的酸性质和孔结构是影响其活性和选择性的主要因素,以弱酸和中强酸为主的酸性中心以及十二元环开放的孔道有利于提高催化剂活性,而与目标产物2,6-二异丙基萘的分子直径接近的一维孔道有利于其选择性的提高。     

2,6-二异丙基萘与2,7-二异丙基萘的吸附分离

萘异丙基化反应的目标产物2,6-二异丙基萘(2,6-DIPN)与主要副产物2,7-二异丙基萘(2,7-DIPN)的性质相近,经过精馏和结晶后不能完全分离。选用阳离子改性后的Y沸石分子筛作吸附剂,甲苯作脱附剂,将2,6-DIPN与2,7-DIPN进行吸附分离。实验表明:NaY和PdY分子筛对2,6-DIPN的吸附性能较强,LiY和KY对2,7-DIPN吸附性能较强;NaY吸附剂的再生性能良好。     

2,6-二异丙基萘的合成与分离技术的进展

2,6-二异丙基萘(2,6-DIPN)是一种重要的化合物,可用于制取高级聚酯材料和液晶聚合物。本文论述了由萘经选择性烷基化生成2,6-DIPN的研究进展,着重阐述了合成2,6-DIPN所用催化剂的研究;还总结了从异构体中分离2,6-DIPN的方法,并对吸附分离法做了详细阐述;指出由萘作原料,沸石分子筛作催化剂制备2,6-DIPN是石油萘生产的理想的技术方向。     

萘与异丙醇在脱Al超稳Y沸石催化剂上的烷基化

采用水蒸气和NH4NO3水溶液对超稳Y沸石（USY）进行脱Al,并采用过量浸渍法制备了脱Al USY负载磷钨酸（PW）催化剂,用X射线衍射（XRD）、液N2吸附-脱附和吸附吡啶一红外（Py-IR）技术对催化剂进行了表征．结果表明：水蒸气脱铝后的USY保持了较高的比表面积、较高的相对结晶度、规则的孔径分布和较大的L酸量．萘与异丙醇烷基化反应结果表明：水蒸气脱铝USY催化剂具有最大的萘转化率92．3％和45．9％的DIPN选择性,其中届IPN选择性达到94．4％,β,β＇位选择性为85．3％,适宜反应条件为活化温度550℃,反应温度160℃,平衡时间150min;反应4次后萘的转化率保持在73％以上,β,β＇-DIPN选择性无明显下降．     

Ceria-modification of H-mordenites: The deactivation of external acid sites in the isopropylation of biphenyl and the isomerization of 4,4′-diisopropylbiphenyl

Ceria-modification is an effective method for the deactivation of external acid sites of H-mordenite (HM). The selectivity for 4,4′-diisopropylbiphenyl (4,4′-DIPB) in the isopropylation of BP over dealuminated HM such as HM(128) decreased with raising reaction temperatures or with decreasing propylene pressures. The decrease of the selectivity during the isopropylation is due to the isomerization of 4,4′-DIPB. Ceria-modification of HM(128) was highly effective for the prevention of the isomerization. The selectivity for 4,4′-DIPB was also improved in the case of HM with low SiO₂/Al₂O₃ ratio such as HM(10). The enhancement of the selectivities of 4,4′-DIPB by ceria-modification is ascribed to the decrease of external acid sites which are active in non-regioselective alkylation and isomerization of products.     

On the isopropylation of naphthalene over zeolite catalysts in the high-pressure fixed-bed flow reactor

Catalytic performances of various dealuminated mordenite catalysts for the isopropylation of naphthalene by isopropyl alcohol with decalin or cyclohexane as a solvent were investigated in a high-pressure fixed-bed flow reactor. It was found that dealumination of H-mordenite could substantially improve the catalytic conversion, selectivity and stability. The catalyst with steam treatment at 700 °C followed by acid leaching was revealed to exhibit high and comparatively stable conversion of ca. 37% with the high 2,6-/2,7-DIPN ratio of ca. 3. Reaction conditions, such as reaction temperature, pressure, space velocity and solvent, could significantly influence the catalytic performance, except for the 2,6-/2,7-DIPN ratio. The catalytic behavior is discussed in relation with catalyst porosity and acidity.     

De-t-butylation of t-butylphenols over dealuminated zeolites in liquid-solid system

Liquid-solid phase de-t-butylation of p-t-butylphenols was carried out over original and dealuminated zeolites to determine the effect of catalyst pore size and acidity on the reaction rate and catalyst fouling rate. The de-t-butylation rate over the original zeolites was mainly dependent upon their micro pore sizes. Although the dealumination by acid leaching decreased strong acid sites, the de-t-butylation rate over dealuminated HY zeolite was higher than that on the original zeolite. The present dealumination is a useful method to prepare an acid catalyst for de-t-butylation in a liquid-solid system.     

负载杂多酸(盐)的表征及其在苹果酯合成反应中的催化性能

用浸渍法制备了一系列负载型磷钨酸及其铯盐催化剂,载体包括超稳Y沸石（USY）、脱铝超稳Y沸石（DUSY）、SiO₂和SBA-15,测定了催化剂的比表面积和酸强度,并在乙酰乙酸乙酯与乙二醇液相缩合制取苹果酯反应中考察了催化剂的性能.结果表明,这些负载型杂多化合物催化剂都表现出较高的催化活性.然而,催化剂在水中的溶脱性能实验表明,负载型磷钨酸催化剂存在严重的活性组分流失现象,不能重复使用,而DUSY负载的磷钨酸铯盐催化剂不仅表现出较高的催化活性,而且显示出较好的重复使用性能.在优化的反应条件下30% (质量分数) Cs_2.5H_0.5PW/DUSY催化剂上乙酰乙酸乙酯的转化率可达98.7%,苹果酯的选择性大于97%.     

Activity and selectivity of high-silica mordenites in the disproportionation of ethylbenzene

The disproportionation of ethylbenzene was investigated over high-silica zeolites prepared by both direct crystallization and dealumination. It was found that dealumination increases the rate of the reaction and improves the life time of the mordenite catalysts. It was shown, however, that the catalytic performance of dealuminated mordenites is not unambiguously related to the number of the Al atoms per unit cell, N^F_Al, remaining in the framework. Rather, it depends on the method of dealumination. Catalysts prepared via heat treatment of NH₄-mordenites and subsequent acid leaching proved to be superior to those having the same N^F_Al but were obtained by acid leaching of Na–mordenite. A mordenite sample prepared through the former method and possessing a Si/Al ratio of, e.g., 11.5 exhibited a rather high activity and catalytic stability compared to materials obtained via the second procedure. The differences in the catalytic performance of mordenites produced through different methods are discussed in terms of microporosity and both density and strength of acidic sites. In particular, it is inferred that the so-called isolated (0-NNN) Al atoms play an important role. The conditions for preparation of mordenites are outlined that are favorable for the enhanced formation of p-diethylbenzene.     

Shape-selective alkylation of biphenyl over mordenites: effects of dealumination on shape-selectivity and coke deposition

To understand the relationships between shape-selectivity and coke deposition in the alkylation of biphenyl over H-mordenite (HM), thermogravimetric analyses were examined for the catalyst after the reaction. The coke deposition during the catalysis was very severe over HM with low SiO/Al₂O₃ ratio, however, dealumination enhanced the decrease of coke deposition. Over highly dealuminated HM, volatile organic compounds, mainly biphenyl derivatives, were observed in addition to carbonaceous deposits. The deposits are produced from biphenyl derivatives on acid sites in the HM pore, and the ease of their formation is governed by acid site density and acid strength. The decrease of carbonaceous deposits and the increase of encapsulated biphenyl derivatives are related with the increase of both selectivity and yield of 4,4-diisopropylbiphenyl (4,4-DIPB). The increase of reaction temperature up to 250°C enhanced the catalysis over highly dealuminated HM, however, further increase of the temperature resulted in extensive decrease of the selectivity of 4,4-DIPB. Coke deposition also increased with the temperature although its level was low. The composition of 4,4-DIPB in encapsulated DIPB isomers remained as high as 80% in spite of a change of the distribution of bulk products.     

A novel method for enhancing on-stream stability of fluid catalytic cracking (FCC) gasoline hydro-upgrading catalyst: Post-treatment of HZSM-5 zeolite by combined steaming and citric acid leaching

This article describes a novel modification method consisting of steaming and subsequent citric acid leaching to finely tune acidity and pore structure of HZSM-5 zeolite and thereby to enhance the on-stream stability of the zeolite derived fluid catalytic cracking (FCC) gasoline hydro-upgrading catalyst. A series of dealuminated HZSM-5 zeolites and their derived catalysts were prepared and characterized by X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), ²⁷Al MAS NMR, nitrogen adsorption, temperature programmed desorption of ammonium (NH₃-TPD) and infrared (IR) spectroscopy of chemisorbed pyridine. The results showed that the citric acid leaching could preferentially remove the extra-framework Al (EFAl) species formed by steaming treatment and thus reopen the EFAl-blocked pore channels of the steamed zeolite. The steaming treatment at a suitable temperature and subsequent citric acid leaching not only decreased the strength of acid sites to a desirable degree but also increased the ratio of medium and strong Lewis acidity to medium and strong Brönsted acidity, both of which conferred the resulting catalyst with superior selectivity to aromatics, good hydroisomerization activity and gasoline research octane number (RON) preservability, as well as enhanced on-stream stability. The results fully demonstrated that the treatments by steaming and followed citric acid leaching can serve as an important method for adjusting the physicochemical properties of HZSM-5 zeolite.     

Transalkylation of toluene and 1,2,4-trimethylbenzene over large pore zeolites

Large pore zeolites, H-beta, H-mordenite (H-MOR) and H-omega, were dealuminated by steam treatment followed by acid leaching and were applied for transalkylation of toluene and 1,2,4-trimethylbenzene. The acidic properties of catalysts were examined by using TPD of ammonia and in situ FT-IR spectroscopy in the OH stretching region as well as pyridine adsorbed catalysts. XRD, mid-infrared spectroscopy and and MAS-NMR techniques were employed to investigate the structural changes of zeolites during dealumination process. Among the parent zeolites, H-beta and H-MOR showed high activity for transalkylation. H-omega showed very low activity although its acidity turned out to be high compared to that of H-MOR or H-beta. Over dealuminated samples, the activity was in the order H-MOR>H-omega≈H-beta unlike over the parent zeolites. It was observed that a large number of Brønsted acid sites were present in small pores and cages in H-MOR and H-omega. After dealumination, the activity and stability were substantially improved for H-MOR and H-omega but decreased for H-beta. H-MOR and H-omega tended to have more open structure and some of occluded acid sites became exposed to the main channels of 12-MR by dealumination. Such structural changes are believed to compensate for the loss of total acid sites to bring about the enhanced activity and stability over H-MOR and H-omega. Dealuminated H-omega, however, was deactivated rather rapidly. Consequently, H-MOR could be considered as a good acid catalyst for transalkylation of toluene and 1,2,4-trimethylbenzene after treatment by steam followed by acid leaching.     

Dealumination of Zeolite Beta Catalyst Under Controlled Conditions for Enhancing its Activity in Acylation and Esterification

This work deals with the dealumination of zeolite beta under different conditions to optimize its catalytic performance. The dealumination was carried out either using oxalic or tartaric acid solution of different pH values or steaming up to 500 °C. The dealuminated zeolite samples were characterized using X-ray diffraction, N₂-physisorption, ICP, ²⁷Al NMR and NH₃-TPD. Their catalytic activities were studied for acylation reaction of 2-methoxy naphthalene or naphthalene with acetic anhydride and esterification of benzyl alcohol with hexanoic acid. Among the dealuminated samples examined, those treated with oxalic acid or tartaric acid at pH 2 showed high activity. The high activity can be correlated with the relative increase in the amount of strong acid sites and with the enhanced accessibility of the reactants to the active sites, which are caused by removal of extra-framework Al species on the acid treatments.