积碳对MCM-22分子筛催化剂上1-丁烯骨架异构化反应的影响

采用氨程序升温脱附、热重-差热分析、气相色谱-质谱、元素分析、氮吸附及扫描电镜对1-丁烯骨架异构化反应中 MCM-22分子筛催化剂(简称催化剂)表面的积碳进行了表征和分析。结合催化剂活性的变化,对积碳的种类、位置、影响因素以及积碳对反应机理的影响进行了探讨。分析结果表明,适量的积碳有益于改进催化剂的催化性能,催化剂的酸中心强度、浓度和孔结构对积碳的形成均有很大的影响。反应初期积碳主要在催化剂的外表面形成,并导致外表面的大量酸中心被覆盖,而后在其内表面缓慢积碳。在反应过程中,催化剂表面形成的脂肪烃类积碳逐渐向不饱和的芳香烃类积碳转变。1-丁烯骨架异构化反应主要通过单分子机理进行。     

Simultaneous extraction and purification of myricetin from Chamaecyparis obtusa by multi‐phase extraction with ionic liquid‐modified mesoporous MCM‐41

BACKGROUND: Multi‐phase extraction is a novel method for the simultaneous extraction and separation of myricetin from Chamaecyparis obtusa . In this research, an amino ionic liquid‐modified MCM‐41 was used as the sorbent and the sample was packed with it into a cartridge. A fixed volume of solvent was then use to extract the target compound with several repetitions and to remove the myricetin to the sorbent. The washing and elution of solvent were investigated. RESULTS: FT‐IR and element contents tests confirmed that the ionic liquid groups were successfully immobilized on MCM‐41. 0.184 mg myricetin was extracted with five repetitions of 1.0 mL methanol. Then 2.0 mL n‐hexane and water were removed all the interference and 1.0 mL methanol was purified 0.1 mg myricetin from 0.2 g ionic liquid‐modified MCM‐41. CONCLUSION: Base on a comparison with traditional extraction methods, the low deviation error (3.16%), small amount of solvent required, highly selective separation and stability of the proposed method justify continuing its development. Copyright © 2011 Society of Chemical Industry     

Study of hydrogen adsorption properties on MCM-41 mesoporous materials modified with nickel

MCM-41 samples were modified with different Ni loadings by wet impregnation method and characterized by XRD, ICP, EPMA-EDS, N₂ adsorption–desorption and hydrogen adsorption at 77 K at high and low pressure conditions. The hydrogen adsorption studies for the MCM-41 host and the impregnated samples showed that small amounts of Ni ions in MCM-41 improved the hydrogen storage capacity by spillover effect.     

An Adaptive Numerical Integration Algorithm with Automatic Result Verification for Definite Integrals

We present a verified numerical integration algorithm with an adaptive strategy for smooth integrands. Verified representations of the remainder term are derived and a new adaptive strategy is given which delivers a desired integral enclosure with an error usually bounded by a specified error bound. Here, we discuss the distribution of the specified error bound onto the subintervals used in the algorithm more closely and present numerical results depending on the distribution of the error. Received March 15, 1999; revised December 1, 1999     

碱源对MCM-22分子筛合成的影响

研究了氧化铝在碱性环境中的溶解热力学,在n(SiO2)/n(Al2O3)=60、n(H2O)/n(SiO2)=24.5、n(HMI)/n(SiO2)=0.1的条件下,分别以NaOH、KOH和Ba(OH)2为碱源合成分子筛。以NaOH为碱源、当n(Na+)/n(Al2O3)的比值小于0.049时,合成产物为无定型物;当该比值大于等于0.049、小于等于0.123时,合成产物为MCM-22分子筛;而当该比值等于0.245时,合成产物转化为ZSM-35分子筛。以KOH为碱源时,在研究的范围内,即n(K+)/n(SiO2)的比值在0.0031～0.0873范围内时,合成产物均为无定型物。以Ba(OH)2为碱源,当n(Ba2+)/n(SiO2)的比值小于等于0.0031时,合成产物为无定型物;当该比值大于等于0.0062、小于等于0.0488时,合成产物均为Ba-ZSM-35分子筛,且结晶度随该比值的升高而逐渐降低。在一定条件下,Na+的存在对MCM-22分子筛的合成是必不可少的。     

Microeconomic impacts of investments in high speed trains in Spain

In this paper, we analyze the effects of new high-speed trains (HST) on passengers’ mobility in Spain. The construction of several new HST lines is planned in the Transport Infrastructure Masterplan of the Spanish Ministry of Transport and Public Works (MOTPW) for the period 2000–2010, and they are expected to cause a major change in the transport sector. Our objectives are twofold: firstly, we estimate the modal split (market shares of air, rail, bus and private car) in the equilibria induced by the new high speed lines; and secondly we calculate the number of passengers for these new HST services, in order to evaluate the revitalization of railways in the horizon 2010. Data stem from a mobility survey carried out by the MOTPW. A gravity model is estimated to forecast passenger flows between Spanish provinces in 2010, and we also estimate a multinomial logit model to calibrate passengers’ choice of transport mode. Results indicate that the impacts of new HST services will vary across routes, and they depend on the spatial location of the new routes.     

Hydroxylation of phenol by iron(II)-phenanthroline(Phen)/MCM-41 zeolite

MCM-41 mesoporous molecular sieve and iron(II)-Phen/MCM-41 have been prepared and characterized by XRD, IR, NH₃-TPD, BET and UV-Vis. The iron(II)-Phen/MCM-41 molecular sieve + 30% H₂O₂ system is capable of performing hydroxylation of phenol.     

Selective hydroxylation of phenol employing Cu–MCM-41 catalysts

We studied the oxidation reaction of phenol in aqueous and acetonitrile media under mild conditions, employing Cu-modified MCM-41 mesoporous catalysts. The stability of the catalysts under reaction conditions was confirmed by XRD, UV–VIS and FTIR techniques. Results obtained indicate that the selective oxidation of phenol with H₂O₂ by a radical substitution mechanism produces three main reaction products: catechol, hydroqinone and benzoquinone.     

Duration time‐series models with proportional hazard

Abstract. The analysis of liquidity in financial markets is generally performed by means of the dynamics of the observed intertrade durations (possibly weighted by price or volume). Various dynamic models for duration data have been considered in the literature, such as the Autoregressive Conditional Duration (ACD) model. These models are often excessively constrained, introducing, for example, a deterministic link between conditional expectation and variance in the case of the ACD model. Moreover, the stationarity properties and the patterns of the stationary distributions are often unknown. The aim of this article is to solve these difficulties by considering a duration time series satisfying the proportional hazard property. We describe in detail this class of dynamic models, discuss its various representations and provide the ergodicity conditions. The proportional hazard copula can be specified either parametrically, or nonparametrically. We discuss estimation methods in both contexts, and explain why they are efficient, that is, why they reach the parametric (respectively, nonparametric) efficiency bound.     

The economic effects of local authority mergers: empirical evidence for German city regions

Cooperation of neighbouring local authorities in the provision of regional public goods can be efficiency enhancing due to economies of scale, a better realisation of fiscal equivalence or dynamic efficiency gains. While the need for such cooperation between local authorities is undisputed, there are different positions concerning the form the cooperation should take. Some argue that local authority mergers are the most efficient and democratic strategy. Others argue that functional cooperation is more appropriate and that mergers reduce the welfare enhancing effects of competition between local authorities. Based on the conditions in Germany that can be interpreted as a natural experiment it is shown in a cross-section analysis that local authority mergers in monocentric city regions have indeed significant economic effects. All else equal the financial situation of city regions where the core and the hinterland are separate administrative districts is worse than in single district regions. Radical mergers of core cities and suburban towns in the 60s and 70s led to higher economic growth in the period 1980–1998.