C4烃催化裂解增产丙烯催化剂研究进展

1 增产丙烯技术 1.1 增产丙烯的重要性 丙烯是仅次于乙烯的最重要的基本有机化工原料之一,主要用于生产聚丙烯、丙烯腈和环氧丙环等产品. 受下游衍生物需求快速增长的驱动,丙烯消费量大提高,2003年我国丙烯的表观消费量达到6158kt,比2002年增长约7.3%.     

高硅MCM-22分子筛的合成及其C4烯烃裂解性能

由于丙烯衍生物需求量迅速增长,致使全球丙烯需求增长速率超过乙烯,近年来,人们一直在寻求新的丙烯增产的方法,采用分子筛作为催化剂,通过裂解C4及C4以上富烯烃原料来获取高收率的丙烯已引起国内外学者的高度关注,Rubinm等于1990年首先合成出MCM-22分子筛,由于其特有的酸性和独特的孔结构而被广泛用于各类化学反应中,迄今尚未见文献报道MCM-22分子筛在C4烯烃裂解反应中的催化性能研究,由于高硅铝比分子筛具有相对较高的热稳定性和水热稳定性,     

ZSM-5沸石分子筛增产丙烯表面改性的研究进展

丙烯是极其重要的有机化工原料,其中用于聚丙烯占58%,用于丙烯腈、羰基合成醇、环氧丙烷和异丙苯分别占10%、8%、7%和6%左右.全球丙烯需求年均增长率为5.6%,而2007年之前乙烯需求年均增长率仅为4.6%[1～2].     

合成偏氟乙烯和含氟丙烯的催化剂及应用研究进展

由于含氟烯烃在自然界易降解、对臭氧层破坏力小、对环境友好的特性,近年来在科研和工业领域得到广泛关注.偏氟乙烯（VDF）和含氟丙烯是重要的含氟烯烃,主要用于合成氟弹性体高分子功能材料的单体和含氟树脂等.我们参照偏氟乙烯的合成发展史,主要介绍了通过催化,热裂解和共裂解方法合成偏氟乙烯过程中使用的催化剂类型、工艺条件和结果对比,综述了近年来偏氟乙烯的主要合成方法,并介绍了通过直接催化氟化法合成含氟丙烯的工艺技术及其可能机理研究进展.     

低硅铝比ZSM-5分子筛上C4烃的催化裂解反应

以低硅铝比(n(SiO2)/n(Al2O2)=20-45)的ZSM-5分子筛为催化剂,研究了混合C4烃的催化裂解反应,并对不同硅铝比的ZSM-5分子筛进行了酸性表征.混合C4烃的催化裂解反应结果表明,低硅铝比的ZSM-5分子筛具有较高的低温催化活性,高硅铝比ZSM-5分子筛催化剂上乙烯和丙烯的收率高于低硅铝比ZSM-5分子筛催化剂,低硅铝比ZSM-5分子筛上苯和甲苯的收率高于高硅铝比ZSM-5分子筛催化剂.在反应温度为625℃时,硅铝比为20的ZSM-5分子筛催化剂上乙烯、丙烯、苯和甲苯的总收率可达79.42%.酸性表征结果表明,硅铝比低的ZSM-5分子筛具有更多的Bronsted(B)酸酸量、Lewis(L)酸酸量及总酸酸量,这是低硅铝比ZSM-5分子筛具有低温高活性及高的苯和甲苯收率的原因.     

低硅铝比ZSM-5分子筛上C4烃的催化裂解反应

以低硅铝比(n(SiO2)/n(Al2O3)=20-45)的ZSM-5分子筛为催化剂, 研究了混合C4烃的催化裂解反应, 并对不同硅铝比的ZSM-5分子筛进行了酸性表征. 混合C4烃的催化裂解反应结果表明, 低硅铝比的ZSM-5分子筛具有较高的低温催化活性, 高硅铝比ZSM-5分子筛催化剂上乙烯和丙烯的收率高于低硅铝比ZSM-5分子筛催化剂, 低硅铝比ZSM-5分子筛上苯和甲苯的收率高于高硅铝比ZSM-5分子筛催化剂. 在反应温度为625 ℃时, 硅铝比为20的ZSM-5分子筛催化剂上乙烯、丙烯、苯和甲苯的总收率可达79.42%. 酸性表征结果表明, 硅铝比低的ZSM-5分子筛具有更多的Bronsted(B)酸酸量、Lewis(L)酸酸量及总酸酸量, 这是低硅铝比ZSM-5分子筛具有低温高活性及高的苯和甲苯收率的原因.     

丁烯催化裂解制丙烯/乙烯反应的热力学研究

 通过对丁烯催化裂解反应网络中各反应步骤进行热力学分析计算,结合实际反应的产物分布,探讨了各产物的形成机理及影响因素. 热力学计算结果表明,升高温度有利于丁烯裂解为丙烯和乙烯,选择合适的反应温度和压力可有效提高产物中的丙烯/乙烯比. 低碳烯烃在热力学上有很强的芳构化倾向,升高温度可抑制氢转移反应,可以通过优化反应条件和开发高选择性催化剂的方法来提高丙烯和乙烯的选择性,抑制芳烃和烷烃的生成. 在催化裂解反应条件下,C5+烃的生成量较少. 热力学计算结果在进行催化剂筛选和反应条件优化过程中得到了验证和补充.     

纳米HZSM-5沸石酸度的调节及对液化气裂解反应的影响

通过对纳米HZSM-5沸石进行钠离子浸渍改性和在小型常压固定床反应器中开展碳四液化气催化裂解制丙烯反应研究,探讨了催化剂酸度对反应选择性的影响.结果表明,钠离子改性能够选择性地去除纳米HZSM-5沸石表面的强酸中心,而对弱酸中心则基本无影响.在用钠离子改性基本上消除催化剂强酸中心的情况下,混合碳四液化气的催化裂解反应主要发生在丁烯分子上,丙烯的最高选择性可达60%,丙烯和乙烯的总选择性可达80%.     

银丝上环氧乙烷分解反应的研究

环氧乙烷是重要的有机化工原料,其合成方法主要是用银为催化剂,使乙烯直接氧化为环氧乙烷。本文拟从环氧乙烷的分解反应入手,考察一下环氧乙烷在银表面上的动力学行为。环氧乙烷的均相热分解反应早在1929年就有人于400～500℃温度范围内做过研究。之后又有人在同样温度范围内作了丙烯和二甲基汞对环氧乙烷分解产物影响的实验。结果表明丙烯的加入增加了乙醛的产率而减小了乙烯酮的产率,而二甲基汞的加入则产生相反     

SAPO-34分子筛的氮化及在甲醇制烯烃(MTO)中的应用

甲醇制烯烃(Methanol To Olefin,简称MTO)过程提供了一条不依赖石油的合成乙烯和丙烯的途径,这种合成方法可以在较大范围调节产品中乙烯和丙烯的比例,以满足市场的需求.而且甲醇可以由一些含碳的原料,如:煤、石油残渣、天然气等等这些不能直接转化为乙烯和丙烯的物质先制成合成     

Murahashi Cross-Coupling at −78 °C: A One-Pot Procedure for Sequential C−C/C−C,C−C/C−N,and C−C/C−S Cross-Coupling of Bromo-Chloro-Arenes

The coupling of organolithium reagents, including strongly hindered examples, at cryogenic temperatures (as low as −78 °C) has been achieved with high-reactivity Pd-NHC catalysts. A temperature-dependent chemoselectivity trigger has been developed for the selective coupling of aryl bromides in the presence of chlorides. Building on this, a one-pot, sequential coupling strategy is presented for the rapid construction of advanced building blocks. Importantly, one-shot addition of alkyllithium compounds to Pd cross-coupling reactions has been achieved, eliminating the need for slow addition by syringe pump.     

C3−C3′ and C6−C6′ Oxidative Couplings of Carbazoles

9-Substituted carbazoles are widely used units in materials science, and their oxidative reactions have been utilized for the synthesis and characterization of polymers. Though the oxidative mechanism of carbazoles has been known for a few decades, structural definition has remained difficult, because their polymers are generally insoluble with incomplete characterization and unknown dependence of the electrochemical potentials. The oxidative reactions of 9-substituted carbazoles should be carefully considered under specific oxidative conditions; otherwise, structure definitions could be wrong, because the IR and NMR spectra used previously cannot quantitatively analyze 3,3′-coupling and 6,6′-coupling of carbazoles. In this review, the best understanding of the C3−C3′ and C6−C6′ oxidative couplings of 9-substituted carbazoles is presented, and the benefit of these oxidative reactions from the viewpoints of electrochemical synthesis, film engineering, and the synthesis and processing of polymers is highlighted.     

C6, C7, and C8 perfluoroalkyl-substituted phosphinic acids

Reaction of red phosphorus with RfI in a 1:2 molar ratio at 230 degrees C led to the formation of a mixture of (Rf)2PI and (Rf)PI2 (Rf = C6F13, C7F15, C8F17) in about a 70:30 ratio, respectively. These mixtures were separated by vacuum distillation. (Rf)2PI (Rf = C6F13, C7F15) are yellow liquids whereas (C8F17)2PI is a yellow solid. Oxidation of (Rf)2PI with excess NO2 led to (Rf)2P(O)OH (Rf = C6F13, C7F15, C8F17) in > 90% isolated yields after aqueous hydrolysis of the anhydride intermediates. These highly fluorinated phosphinic acids are white solids with sharp melting points and are highly soluble in methyl sulfoxide (DMSO) and 1,1,2-trichlorotrifluoroethane. However, solubility in chloroform and methylene dichloride is low. These perfluoroalkylphosphinic acids were characterized by IR, NMR (1H, 19F, and 31P), and mass spectra and elemental analysis.     

Numerical simulation of C/C/C planar X-ray waveguides.

A numerical simulation was done to check the possibility of using planar C/C/C multilayers with density contrast 0.2 and 0.7 g/cm3 as an X-ray waveguide. After an optimization procedure, suitable waveguide layer thicknesses were found which provide a high degree of resonant standing wave field intensity enhancement in the core layer at incident beam energy of 13 keV. The obtained results were compared with those of the Mo/Be/Mo waveguide, whose high waveguiding capability at the same energy value was reported in the 1990s. The comparison shows that standing wave field intensity resonant enhancement provided by C/C/C planar multilayers is very high and, consequently, a guided beam can be well detected.     

Theoretical studies of C60/C70 fullerene derivatives: C60O and C70O

A semiempirical (AM1) calculation on the structures and stabilities of isomers of the fullerene derivatives C₆₀O and C₇₀O is carried out. The ozonolysis reaction mechanism and the thermodynamics of the compounds are studied. The two isomers of C₆₀O (56 bond and 66 bond) formed by an oxygen atom bridging across a C-C bond have an epoxide-like or an annulene-like structure. According to the ozonolysis reaction mechanism and kinetic factor analysis, the possible products of this ozonolysis reaction are C₆₀O with oxygen bridging over the 66 bond (C_2v) as an epoxide-like isomer and that with oxygen bridging over the 56 bond (C_s) as an annulene-like isomer. Further, the sixteen isomers of C₇₀O (both epoxide-like and annulene-like structures) have been studied with respect to the same reaction mechanism. The most possible product in this ozonolysis reaction contains oxygen bridging across in the upper part (66 bond in C₇₀O-2 or C₇₀O-4) as an epoxide-like structure. The other possible product is C₇₀O-8 (annulene-like structure), in which oxygen bridges across an broken equatorial CC bond in C₇₀ (D_5h). The vibrational frequency analysis and the electronic structure of the selected C₆₀O and C₇₀O isomers are generated for experimental characterisation. The experimental results indicate that C₆₀O and C₇₀O may decompose into the odd number fullerenes C₅₉ and C₆₉. We therefore studied the structures of C₅₉ and C₆₉ also.     

Reducing ability of supramolecular C60 dianion toward C=O, C=C and N-N bonds

Different from C60 dianion which readily reacts with electrophiles, supramolecular C60 dianion (2) generated from gamma-cyclodextrin-bicapped C60 (1) and NaBH4 (or diborate) in DMSO-H2O (9:1, v/v) is able to reduce N-N+, C=C-EWG and C=O bonds to provide the respective dihydro derivatives; 1-mediated reduction of acetophenone with NaBH4 in the presence of (Me2N)2CH2 and EtONa gives turn over frequency (TOF)/h of 400.     

Incorporating C2 into C60 films

The material formed by depositing C(2)(-) anions onto/into thin C(60) films (on graphite) at room temperature has been studied by means of thermal desorption mass spectroscopy, ultraviolet photoionization spectroscopy, atomic force microscopy (AFM), and surface enhanced Raman spectroscopy. As-prepared, C(2)/C(60) films manifest thermal desorption behaviour which differs significantly from pure C(60) films. Whereas the latter can be fully sublimed, we observe decomposition of C(2)/C(60) films to a high-temperature-stable material while predominantly C(60), C(62), and C(64) are desorbed in parallel. Deposition of C(2)(-) also leads to significantly modified electronic and vibrational properties. Based on DFT model calculations of the Raman spectra, we suggest that as-prepared C(2)/C(60) films contain appreciable amounts of polymeric networks comprising -C(2)-C(60)-C(2)-C(60)- chains. Detection of sublimed C(62) and C(64) upon heating implies that thermal decomposition of C(2)/C(60) films involves addition/uptake of C(2) units into individual fullerene cages. Correspondingly, annealing films up to various intermediate temperatures results in significant modifications to valence-band UP spectra as well as to surface topographies as imaged by AFM. The novel carbonaceous material obtained by heating to T > 950 K has a finite density of states at the Fermi level in contrast to as-prepared C(2)/C(60). It comprises fused fullerene cages.     

Iminopropadienethiones, Ar=N=C=C=C=S

Aryliminopropadienethiones 9 have been generated by flash vacuum thermolysis of isoxazolones of the type 5 and characterized by mass spectrometry and matrix isolation IR spectroscopy in conjunction with DFT calculations and chemical trapping.