Interaction of hydrogen and n‐pentane with sulfated zirconia

Interaction of hydrogen with sulfated zirconia catalysts was studied in situ at 473 K. Interaction of hydrogen with the sample evacuated at 673 K leads to the formation of new hydroxyl groups (wide bands near 3330 cm⁻¹) and water (1620 cm⁻¹). In the case of the sample evacuated at 873 K, SOH groups (3660 cm⁻¹) and zirconium hydrides (1555 cm⁻¹) form. Adsorption of n‐pentane on sulfated zirconia catalysts in the range of 253–383 K was studied. It was shown that hydrides and protonated cyclopentadienes form at low temperatures. At higher temperatures, aromatic compounds are formed mainly. The reaction mechanism is discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Highly effective P-modified HZSM-5 catalyst for the cracking of C4 alkanes to produce light olefins

A series of HZSM-5 zeolites modified by different amounts of phosphorus (P/HZSM-5) were prepared. The physicochemical features of P/HZSM-5 catalysts were characterized by means of XRD, BET, NH₃-TPD, FT-IR spectra of adsorbed pyridine, etc., and their performances for the catalytic cracking of the mixed C₄ alkanes to produce light olefins were investigated. The results indicated that phosphorus (P) modification not only modulated the amount of acidic sites and the percentage of weak acidic sites in total acidic sites, but also regulated the acid type, i.e., the ratio of L/B (Lewis acid/Brönsted acid). The introduction of P also altered the basic characteristics of HZSM-5 which was evidenced by CO₂-TPD analysis. Consequently, P modification with suitable amount was favorable for enhancing the selectivity to light olefins, especially to propene. At the temperature of 650 °C, the maximum yields of propene and ethene were achieved 25.6 and 33.9%, which were higher than those over parent HZSM-5 by 7 and 4.5%, respectively. Aromatics yield was found to be decreased with the increasing P loading due to the reduction of strong acid and the formation of new basic site which inhibited the hydrogen transfer reaction. All this indicates that P-modified HZSM-5 zeolites are effective catalysts for the cracking of mixed C₄ alkanes to produce more light olefins.     

PREDICTION OF MOLAR VOLUMES, VAPOR PRESSURES AND SUPERCRITICAL SOLUBILITIES OF ALKANES BY EQUATIONS OF STATE

A generalized cubic equation of state which can represent all the cubic equations is introduced and thermodynamic property relations for it are presented. Five cubic equations of states with respective mixing rules are used to predict molar volumes and vapor pressures of pure alkanes (from methane till n-tritriacontane) and solubilities of solid wax components (high molecular weight alkanes) in supercritical solvents. They are the RK (Redlich-Kwong), MMM (Mohsennia-Modarress-Mansoori), RM (Riazi-Mansoori), PR (Peng-Robinson), and SRK (Soave-Redlich-Kwon) equations of state. The experimental data necessary to compare the equations of state are taken from the literature. It is demonstrated that the SRK equation of state is more accurate for predicting vapor pressures of alkanes. The RM equation of state is shown to be more accurate for predicting molar volumes of saturated and sub-cooled liquid alkanes as well as molar volumes of alkanes in their supercritical condition. For the solubility of wax components in supercritical solvents it is shown that the MMM equation of state gives the least AAD% for the 270 data points of 10 binary systems studied consisting of a high molecular weight alkane and supercritical ethane and carbon dioxide.     

Synthesis of ω‐amino‐α‐phenylcarbonate alkanes and their polymerization to [n]‐polyurethanes

Aliphatic [n]‐polyurethanes have recently been synthesized from ω‐isocyanato‐α‐alkanols or, more traditionally, by cationic ring‐opening polymerization of cyclourethanes or by the Bu₂Sn(OMe)₂‐promoted polycondensation of ω‐hydroxy‐α‐O‐phenylurethane alkanes. For the latter procedures, the conditions employed do not seem to be suitable for highly functionalized monomers. In contrast, the polymerization of ω‐amino‐α‐phenylcarbonate alkanes is expected to occur under milder conditions. ω‐Amino‐α‐phenylcarbonate alkanes have been synthesized from 6‐aminohexanol (1) and 3‐aminopropanol (6). The procedure involves the N‐Boc protection of the amino group, followed by activation of the alcohol. Removal of the N‐Boc affords the corresponding ω‐amino‐1‐O‐phenyloxycarbonyloxyalkane hydrochlorides. Other oligomeric comonomers between 1 and 6 have been prepared. The polymerization of these precursors takes place in the absence of metal catalysts to afford the corresponding linear and regioregular [n]‐polyurethanes. The procedure described is useful for the preparation of stable ω‐amino‐α‐phenylcarbonate alkane derivatives, which possess varied chain lengths between the terminal functions. These monomers yield [n]‐polyurethanes having various structures starting from just two aminoalkanols. The polyurethanes were obtained in high yields, with reasonable molecular weight and polydispersity values, and they were characterized spectroscopically and thermally. These studies reveal constitutionally uniform structures that are free of carbonate or urea linkages. Copyright © 2010 Society of Chemical Industry     

Hydroisomerization of Renewable and Fossil n-Alkanes over Bifunctional Dealuminated ZSM-5 Catalysts

The hydroisomerization of two long-chain n-alkane mixtures was investigated over bifunctional Pt/H-ZSM-5 catalysts before and after dealumination of preshaped zeolite/binder pellets. The hydroisomerization over the dealuminated catalysts leads to more isomers and less cracking products. Consequently, higher ratios of multi- to mono-branched isomerization products are formed as expected for large- rather than medium-pore zeolites. This indicates a higher availability of space in the vicinity of the active sites and provides an attractive route to make medium-pore zeolites suitable for upgrading higher boiling hydrocarbon feeds.     

铂系低碳烷烃脱氢催化剂研究进展

综述了近年来国内外铂系低碳烷烃脱氢催化剂的技术现状与研究进展。首先从热力学角度论述了低碳烷烃脱氢反应与相关副反应的反应机理,随后分别从活性位点性能与催化脱氢的关系,氧化铝、分子筛等载体的作用,以及锡、碱金属、碱土金属、过渡金属等助剂改性对催化剂的影响等3个方面分析了铂系低碳烷烃脱氢催化剂的优势与存在的问题,进而探究了铂系脱氢催化剂的失活原因。最后对铂系脱氢催化剂的研究前景做了展望,提出该系列催化剂的主要发展方向包括降低贵金属铂的负载量、提高催化剂的稳定性、减少积炭副反应等。     

高甜度蔗糖衍生物的研究(Ⅰ)——三氯蔗糖及其制备原理

三氯蔗糖是一种全新概念的食品甜味剂,具有甜度高、甜味特性好、安全性高等突出优点,代表着当前强力甜味剂的最高成就.目前全世界仅英国Tate&Lyle公司有生产,但其生产技术尤其是核心步骤与工艺参数秘而不宣.本文首先讨论蔗糖卤代衍生物的增甜原理,及通过全基团保护法制备三氯蔗糖的原则.     

The Influence of Basic Volcanic Fluids on Gaseous Products of Source Rocks

The aspects, such as composition, temperature, viscosity, and fluidity, of basic volcanic fluids are greatly different from acidic volcanic fluids. In order to further complement the conceptual model of the influence of volcanic fluids on source rocks in petroliferous basins, this research uses the thermal simulation experiment to analyze the characteristics and reasons of the ratio of alkanes to acid, dry coefficient, and carbon isotope in the dry and fluid systems. The results show that, the ratio of alkanes to acid of all samples in the two systems will increase with the rise of temperature and presents features of the dry system higher than the fluid system, which indicates that the basic volcanic fluids restrain the generation of gaseous hydrocarbons. The dry coefficient of the fluid system at the range of 300–400°C is greater than that of the dry system, while smaller at the range of 400–450°C, which indicates that the basic volcanic fluids promote the generation of CH₄ in low temperature. In the two systems, δ¹³CO₂ of all samples have no obvious change as the rising of temperature, but in the fluid system the proportion of carbon isotopic will increase with the rising of temperature, which shows that carbonate exists in the volcanic fluids. The carbon isotopes of gaseous hydrocarbon in three samples are presented as δ¹³C₁ < δ¹³C₂ < δ¹³C₃, and it accords to general pyrolysis regularity without reversal phenomenon, which indicates alkane gases produced by pyrolysis of three samples are of organic origin.     

LIQUID PHASE CO-OXIDATION OF THIOPHENOL AND STYRENE BY OXYGEN AND t-BUTYL HYDROPEROXIDE

ABSTRACT

Instability problems in both shale and petroleum derived middle distillate jet fuels have been correlated with the presence of peroxidic species. Although a good body of knowledge exists concerning the formation of peroxides in the liquid phase, relatively little is known about the reaction/ decomposition pathways available when other functional groups are present, since sulfur is the most abundant heteroatam present in jet fuels, the reaction of t-butyl hydroperoxide (tBKP) and/or oxygen with thiophenol in the presence of the active olefin, styrene, was examined in deaerated benzene at 120°C. The complex product mixture was analyzed by combined capillary column GC/MS. Major products included acetone, t-butanol and isdbutylene from the tBHP. Thiophenol and styrene combined to form addition products. Phenyl disulfide was observed from the thiophenol. The results indicated that although the product slate was complex, it was possible to explain the product mix in terms of a few competing reactions.     

正辛烷脱氢生成直链烯烃的热力学分析

计算了不同反应条件下正辛烷脱氢生成直链烯烃的主反应热力学平衡参数。计算结果显示,ΔH随温度上升变化不大,正辛烷脱氢反应的平衡常数较小。反应平衡时的产物中,1 辛烯含量最少,顺 4 辛烯次之;产品中绝大部分是双键位于第2到第4碳的烯烃,并且反式辛烯的物质的量大于相应的顺式。温度是一个很敏感的热力学参数,随着温度的升高,正辛烷的平衡转化率呈较大幅度的增加;增加体系压力和氢/烃摩尔比可以明显降低正辛烷的平衡转化率,同时这些参数处于较低值时的影响较大。