十氢萘在分子筛催化剂上的开环反应研究

在小型固定流化床(FFB)装置中研究了Y分子筛与ZSM-5分子筛催化剂上的十氢萘裂化开环反应性能,考察了温度和剂油比对Y分子筛开环反应催化性能的影响。结果表明,十氢萘在分子筛催化剂上通过环烷环开环反应生成丙烷、丙烯、丁烷、丁烯、甲基戊烷和环戊烷、环己烷等非芳烃以及苯、C_1~4烷基取代苯等单环芳烃,并通过脱氢缩合反应生成四氢萘、萘、甲基萘和菲、芘等多环芳烃甚至焦炭等。由于扩散和吸附性能的影响,ZSM-5分子筛催化剂的裂化开环反应选择性比Y分子筛催化剂的高,因此,十氢萘环烷环开环与脱氢缩合反应的相对比例(NRO/DHC)在ZSM-5分子筛催化剂上较高。在Y分子筛催化剂上,温度为450~550 ℃、剂油比为3~9,反应温度升高或者剂油比增加,双分子氢转移以及脱氢缩合反应增强,从而导致环烷环开环产物选择性降低。     

十氢萘选择性开环反应的研究进展

本文介绍了顺式和反式十氢萘的分子结构和反应特性,系统分析了十氢萘在不同催化体系下选择性开环的反应机理,包括在单功能酸性催化剂上的碳正离子机理,在单功能金属催化剂上的氢解反应机理以及基于酸性-金属双功能催化剂的双功能开环反应机理。总结了反应温度、载体酸性和分子筛孔径等工艺条件对十氢萘选择性开环反应性能的影响。最后提出了当前研究存在的不足之处,展望了亟需开展的研究课题。     

十氢萘在酸性催化剂上的反应路径及生焦研究

采用小型固定流化床装置（ACE Model C）,研究了在反应温度460-540℃下,模型化合物十氢萘在Y分子筛催化剂上的裂化反应路径及生焦机理。结果表明,十氢萘裂化的初始阶段,H+进攻十氢萘上与叔碳原子相连的C-H键和C-C键形成非经典五配位叔正碳离子是其最主要的引发反应;十氢萘裂化产物主要是丙烯、丙烷、异丁烷、异戊烷、甲基环戊烷、甲苯、二甲基苯等;产物的收率在催化剂上由大到小为,非芳烃、单环芳烃、双环芳烃;十氢萘催化生焦的机理是碳正离子机理,随反应温度和分子筛酸量的升高,双分子氢转移以及脱氢缩合能力增强,焦炭产率和转化率也随之升高。     

分子筛催化剂上正十六烷的临氢异构化反应

 对分子筛催化剂上正十六烷的临氢异构化反应进行了研究，考察了不同分子筛催化剂的活性和选择性，并对临氢异构化反应的产物分布进行了分析．在此基础上，对正十六烷的临氢异构化反应机理进行了初步探讨．结果表明，正十六烷在中孔分子筛催化剂上的临氢异构化反应主要在分子筛外表面和孔口进行，分子筛的择形作用对异构选择性的影响有限．这与一般情况下低分子量正构烷烃在择形分子筛上的临氢异构化反应有所不同．临氢异构化反应的异构选择性主要取决于催化剂酸性组分的酸性质，弱酸和中等强度的酸对异构化反应有利，而催化剂的活性则由酸性组分中B酸中心的数量和加氢组分的活性共同决定．     

分子筛催化剂表征的研究

本文采用原子吸收光谱、X射线衍射、扫描电镜、元素分析等方法分别对分子筛催化剂在催化裂化反应前后进行了表征。探讨了催化剂失活的原因，以及活化后与新鲜、失活催化剂的差别。     

不同环大小分子筛相对基分子筛催化剂上甲烷无氧芳构化反应的影响

钼基分子筛催化剂，由于不同分子筛的孔道大小及孔道形状不同，对甲烷芳构化反应表现出不同的催化性能，具有8元环孔道结构的小孔ERS－7分子筛没有催化活性，说明甲烷的芳构化反应离不开分子筛孔道作用，较小的孔道中不能生成苯等芳烃，具有10元环孔道结构的ZSM－5，ZSM－11和ZRP－1三种分子筛具有较好的催化性能，但由于其孔道大小及孔道形状的差别在催化行为上表现出一定的差异，具有10元环和12元环孔道结构的MCM－22分子筛，尤其对对苯等轻芳烃而言，催化性能最佳，具有12元环孔道结构的JQX－1以及中孔分子筛SBA－15，虽然上有一定的催化性能，但活性较低，研究结果表明，孔道大小，与苯分子动态直径相近或孔道稍大的分子筛是催化甲烷芳构化反应的良好载体，孔道过大或过小都不利于苯和萘等烃的生成。     

不同环大小分子筛对钼基分子筛催化剂上甲烷无氧芳构化反应的影响

 钼基分子筛催化剂，由于不同分子筛的孔道大小及孔道形状不同\r\n，对甲烷芳构化反应表现出不同的催化性能．具有8元环孔道结构的小\r\n孔ERS－7分子筛没有催化活性，说明甲烷的芳构化反应离不开分子筛孔\r\n道的择形作用，较小的孔道中不能生成苯等芳烃．具有10元环孔道结构\r\n的ZSM－5，ZSM－11和ZRP－1三种分子筛具有较好的催化性能，但由于\r\n其孔道大小及孔道形状的差别在催化行为上表现出一定的差异．具有1\r\n0元环和12元环孔道结构的MCM－22分子筛，尤其对苯等轻芳烃而言，催\r\n化性能最佳．具有12元环孔道结构的JQX－1以及中孔分子筛SBA－15，\r\n虽然具有一定的催化性能，但活性较低．研究结果表明，孔道大小与苯\r\n分子动态直径相近或孔道稍大的分子筛是催化甲烷芳构化反应的良好载\r\n体，孔道过大或过小都不利于苯和萘等芳烃的生成．     

关于全氢菲各异构体构象式的讨论

关于全氢菲各异构体构象式的讨论冯骏材（南京大学化学系２１００９３）全氢菲的六个构型异构体可以分别用下述各构型式表示：················（１）（２）（３）（４）（５）（６）作者曾讨论了从乙烷的锯马式交叉构象出发，推出环己烷及顺、反十氢萘构...     

甲基环戊烷在铂催化剂上氢解的动力学研究

研究了甲基环戊烷在负载型铂催化剂上的氢解动力学，建立了新的动力学模型，在Ｐｔ／ＳｉＯ２上，两个平行反应（一个生成正己烷，另一个生成甲基戊烷）在甲基环戊烷吸附脱氢过程中存在显著的焓变差异，而Ｃ－Ｃ键断裂活化能则相近，在Ａｌ２Ｏ３负载铂催化剂上，反应的表现活经能仅是在Ｐｔ／ＳｉＯ２上的一半，这是由于Ｃｌ离子的存在，改变了铂的催化性能，导致缺电子铂颗粒的形成，使反应速率的控制步骤从在Ｐｔ／ＳｉＯ２上的Ｃ     

Cyclohexane transformations over metal oxide catalysts. 2. Selective cyclohexane ring opening to form n-hexane over mono- and bimetallic rhodium catalysts

The activity of monometallic Rh and Pt catalysts and bimetallic Pt—Rh catalysts on oxide supports in cyclohexane ring opening to form n-hexane was studied. The Rh-containing catalysts are highly active and selective in this reaction. Cyclohexane dehydrogenation predominates in the case of the Pt catalysts. The use of the bimetallic alumina-supported Pt—Rh catalysts allows one to minimize the contribution of cyclohexane cracking and to enhance the selectivity for n-hexane with the yield of the latter slightly depending on the metal ratio in the bimetallic system under the experimental conditions.     

Hydrogen production by conversion of methane over nickel-supported USY-type zeolite catalysts

Hydrogen production by conversion of methane over Ni-supported zeolite catalysts was investigated, and Ni-supported USY-type zeolite (Si/Al₂ = 14.0, 360) was found to have longer catalytic lifetime than Ni-supported silica (Cab-O-Sil) catalyst, which had been reported to have the longest catalytic lifetime for this reaction.     

Ethylcyclopentane ring opening reaction over PtGe/Al2O3 catalysts prepared by controlled surface reaction

Platinum-germanium catalysts supported on a non-acidic Al₂O₃ have been prepared by adding Ge in amounts corresponding nominally to 1/8 (PtGe1/8/Al₂O₃); 1/2 (PtGe1/2/Al₂O₃); 1 (PtGe1/Al₂O₃) and 2 (PtGe2/Al₂O₃) monolayers by controlled surface reaction of Ge(n-C₄H₉)₄ to Pt/Al₂O₃. These catalysts were characterized by electron microscopy (TEM), FTIR of CO adsorption and H₂ chemisorption. The ring opening of ethylcyclopentane (ECP) was studied as a test reaction between 543 and 633 K. PtGe1/8/Al₂O₃ catalyst produced the most ring opening products (ROP) in the whole temperature range. A good agreement with statistical values of ROP was observed at low temperature, but at higher temperature, the opening became selective, producing mostly heptane. Bimetallic catalysts PtGe1/Al₂O₃ and PtGe2/Al₂O₃ led to a nonselective hydrogenolysis, similar to the monometallic platinum catalyst Pt/Al₂O₃. The catalysts PtGe1/Al₂O₃ and PtGe2/Al₂O₃ produced ROP with the lowest selectivity; instead, much aromatics and fragments were formed, in increasing amounts above 600 K.     

Phosphido‐diphosphine pincer aluminum complexes as catalysts for ring opening polymerization of cyclic esters

New aluminum alkyl complexes, supported by o‐phenylene‐derived phosphido diphosphine pro‐ligands [Ph‐PPP]‐H and [ⁱPr‐PPP]‐H ([Ph‐PPP]‐H = bis(2‐diphenylphosphinophenyl)phosphine; [ⁱPr‐PPP]‐H = bis(2‐diisopropylphosphinophenyl)phosphine) are reported. Compounds [Ph‐PPP]AlMe₂ ( 1 ), [ⁱPr‐PPP]AlMe₂ ( 2 ), and [Ph‐PPP]AlⁱBu₂ ( 3 ) have been synthesized by reaction of the pro‐ligand with the appropriate trialkyl aluminum precursor and have been characterized by ¹H, ¹³C and ³¹P NMR spectroscopy. The solution NMR data and theoretical calculations suggest for all complexes trigonal bipyramidal structures with C_2v symmetry in which the phosphido diphosphine ligand acts as a κ³ coordinated ligand. All complexes promote the ring‐opening polymerization of ε‐caprolactone, L‐ and rac‐lactide. Polyesters with controlled molecular parameters (M_n, end groups) and low polydispersities are obtained. Upon addition of isopropanol, efficient binary catalytic systems for the immortal ring‐opening polymerization of the cyclic esters are produced. Preliminary investigations show the ability of these complexes to promote copolymerization of l ‐lactide and ?‐caprolactone to achieve copolymers whose microstructures are depending on the structure of the catalyst. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 49–60     

Synthetic and natural silica‐aluminates as inorganic acidic catalysts in ring opening polymerization of cyclosiloxanes

Ring opening polymerization (ROP) of hexamethylcyclotrisiloxane (D₃) and octamethylcyclotetrasiloxane (D₄) was promoted by acid‐treated synthetic and natural silica‐aluminates. Silica‐alumina (1:3 Si/Al molar ratio) was obtained using a simple and economic route from precipitation of aluminum sulfate solutions. The material was treated in an acidic medium to improve the content of acid sites and successfully tested as inorganic acidic catalyst for ROP of D₃ or D₄ cyclosiloxanes. Natural bentonite was treated and used in a similar manner. Once the ROP reaction completed, the catalyst was easily removed and it was found that the recovered synthetic silica‐alumina was active in a second ROP reaction. The effect of the concentration and type of catalyst in respect to the molecular weight and polydispersity of polydimethylsiloxanes was analyzed: increasing the amount of silica‐alumina in ROP of D₄ from 0.05 to 0.1 g decreased the average molecular weight (M_n = 13–1.8 kDa) associated with an increase in the polydispersity (2.95 vs. 1.81). Analogous results were found with bentonite. These values suggest that an increase in the catalyst concentration led to a lower M_n, with a more homogeneous molecular chain dimension. Copyright © 2012 John Wiley & Sons, Ltd.     

Rhodium-catalyzed asymmetric ring opening of azabenzonorbornadiene with substituted piperazine nucleophiles

We have developed an asymmetric ring opening reaction of azabenzonorbornadiene with substituted piperazine. By increasing the amount of catalyst (from 2.5 to 5%) and ligands (5 to 10%) as well as addition of ammonium iodide, the products can be obtained in high yield and the reaction time shortened dramatically, but the ee values were rather low.     

Hydrogenolysis of glycerol over HY zeolite supported Ru catalysts

An enhanced active and selective catalyst consisting of ruthenium supported on dealuminated HY zeolite has been prepared by a wet impregnation method. It was found that BET surface area of Ru/HY catalysts significantly increases after HCl treatment. This treatment also increases the concentration of strong acid sites in the catalyst. The hydrogenolysis of glycerol over 5 wt% Ru/HY catalyst was investigated at 190-220 ℃, an initial H2pressure of 3-6 MPa, and in 20 wt% glycerol aqueous solution. The results indicate that HCl treated Ru/HY catalyst shows higher activity compared with the untreated Ru/HY catalyst, and that the glycerol hydrogenolysis efficiency is influenced by the porosity and acidity of the support. A selectivity to 1,2-PDO of 81.3% at a glycerol conversion of 60.1% under 3 MPa H2pressure and 220 ℃ for 10 h was achieved over the modified Ru/HY catalyst with a 1.0 mol/L HCl treatment. It has also been shown that a longer reaction time, a higher temperature and a higher H2pressure have the positive effects on the glycerol hydrogenolysis efficiency of the enhanced Ru/HY.     

New acid/base salts as co‐catalysts for the organocatalyzed ring opening polymerization of lactide

(R)‐(+)‐binaphathyl‐diyl hydrogen phosphate (BNPH)/ diazabicyclo[5.4.0]undec‐7‐ene (DBU) and (1R)‐(?)?10‐camphorsulfonic acid (CSA)/4‐dimethylaminopyridine (DMAP) acid–base salts were synthesized and assessed for the ring‐opening polymerization of rac‐lactide. They were found to be inactive toward the polymerization in the presence of a protic initiator. When used in combination with a base such as DBU or DMAP and a protic initiator, these acid/base conjugates led to well‐controlled polymerization in mild conditions (D_M < 1.1 in all cases). With DBU, the presence of the salt was found to lead to narrower molecular weight distributions than those obtained using the base alone, and to prevent undesirable transesterification reactions occurring at the end of the reaction. An increase in activity was observed using the salts in combination with DMAP as compared with DMAP alone, together with an improvement of the control over the molecular weight. The results were discussed on the basis of ¹H nuclear magnetic resonance analyzes including acid/base equilibria involving the use of two different bases. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 659–664     

Catalytic cracking of C5+ gasoline over hy zeolite

The catalytic conversion of a C5+ natural gasoline over the HY zeolite has been studied. The results show the formation of C2, C3 and C4 hydrocarbons with an apparent activation energy of ca. 39 kJ mol^-1. This revised version was published online in June 2006 with corrections to the Cover Date.