HMOR分子筛在二甲醚羰基化反应中具有类似酶催化的优异性能.关于骨架铝的分布和反应活性位的识别是研究该反应机理的关键科学问题.早期的工作是基于理论计算研究二甲醚羰基化活性位点,但缺乏直接的谱学证据.通过在不同温度下焙烧NH_(4)...HMOR分子筛在二甲醚羰基化反应中具有类似酶催化的优异性能.关于骨架铝的分布和反应活性位的识别是研究该反应机理的关键科学问题.早期的工作是基于理论计算研究二甲醚羰基化活性位点,但缺乏直接的谱学证据.通过在不同温度下焙烧NH_(4)MOR制备了一系列HMOR催化剂,通过多种谱学表征手段研究分子筛骨架铝的稳定性以及铝原子落位信息,进一步通过二甲醚羰基化反应活性关联MOR分子筛的酸性和铝分布关系获得反应机理的谱学证据.首先从XRD(X-Ray diffraction)和SEM(Scanning electron microscope)发现经过不同温度焙烧,MOR分子筛结晶度和宏观形貌没有发生明显变化,但是通过一维^(29)Si,^(27)Al和^(1)H魔角旋转固体核磁谱(MAS NMR)发现分子筛局部环境发生了脱铝现象,产生了明显的缺陷羟基以及B酸量的下降.焙烧温度对HMOR分子筛骨架Al稳定性的影响较大,随着温度升高,脱铝逐渐加剧.定量^(1)H MAS NMR结合红外(IR)光谱提供了HMOR分子筛不同孔道B酸含量的分布.进一步使用2D^(27)Al MQ MAS NMR的方法以及结合切片分峰拟合技术区分出分子筛骨架中的四种不同T位点,发现当温度低于600℃,不同T位脱铝速率相当;当焙烧温度为600℃时,T3位点的Al原子脱除速率加快.最后研究了二甲醚羰基化反应性能与酸分布和铝分布的关系,获得羰基化反应活性中心的确凿谱学证据,T3-O33位置的Al位是羰基化反应的活性中心.展开更多
60% white corundum used for aggregate, 5% aluminium powder for fixed additions and 35% various additives for matrix were prepared for specimens 1#,2#,3#. They were mixed uniformly with the suitable resin as a binder a...60% white corundum used for aggregate, 5% aluminium powder for fixed additions and 35% various additives for matrix were prepared for specimens 1#,2#,3#. They were mixed uniformly with the suitable resin as a binder and pressed under pressure of 315 ton forging press, then dried at 200℃ for 24 h. Effects of various additives on 1500 ℃×2 h creep properties of Al3CON reinforced corundum composite were researched. The experimenal results show that creep coefficients of specimens 1#,2#,3# at 1500 ℃×2 h are 1.4×10^- 4, -9.4×10^-4, -22.6×10^-4, respectively. Crushing strength of the slide plate added with suitable additive A after fired at 1500 ℃ ×3 h reaches to 225 MPa, the creep rate is positive all the time from 0% to 0.014% at 1500 ℃ for 2 h. The microstructure result analysis shows that reinforced phases of Al3CON fiber composite have been formed after fired with Al powder in coke at high temperatures for specimen 1#, and the strength of the composite is increased. The hot modulus of rupture is up to 59 MPa at 1400 ℃ and the RUL is obviously higher than that at 1700 ℃. Its service life is two times as that of Al2O3-C slide plate when used in the process of pouring steel. The mechanism of creep rate resistance of the composites can be discovered by means of SEM and EDAX analysis. It is concluded that the active Al3CON and Al2O3 multiphases that were formed by N2 in gas, C, Al and Al2O3 inside the matrix of the composites during in-situ reaction,which gives the composites outstanding creep rate resistance for the dense zone resuiting from Al3CON oxidation that inhibits contraction at the high temperature. Besides, the matrix will turn into the multiphase with high refractoriness, N content and its Al3CON reinforced fiber will further increase accordingly. In addition, Al3CON formed by Al2O3 and C, Al in the matrix with N2 in gas will inhibit the creep rate and also greatly improve the creep rate resistance of the composites.展开更多
A new calcium aluminate cement CA-670 was studied in the system of tabular alumina, white fused alumina （WFA）, and bauxite based low cement castables. The flow ability, strength development, and hot strength （ HMOR...A new calcium aluminate cement CA-670 was studied in the system of tabular alumina, white fused alumina （WFA）, and bauxite based low cement castables. The flow ability, strength development, and hot strength （ HMOR ） were investigated. Different types of additives were used for the CA-670 bonded castables. The results show CA-670 provides a good workability for each type of＂ castables. CA-670 displays a good compatibility with different types of additives. Testing on different batches of CA-670 shows good reproducible properties in each castable, which manifests good consistency and reliability of CA-670.展开更多
基金This work was supported by the National Natural Science Foundation of China （No.51006110 and No.51276183） and the National Natural Research Foundation of China/Japan Science and Technology Agency （No.51161140331）.
文摘HMOR分子筛在二甲醚羰基化反应中具有类似酶催化的优异性能.关于骨架铝的分布和反应活性位的识别是研究该反应机理的关键科学问题.早期的工作是基于理论计算研究二甲醚羰基化活性位点,但缺乏直接的谱学证据.通过在不同温度下焙烧NH_(4)MOR制备了一系列HMOR催化剂,通过多种谱学表征手段研究分子筛骨架铝的稳定性以及铝原子落位信息,进一步通过二甲醚羰基化反应活性关联MOR分子筛的酸性和铝分布关系获得反应机理的谱学证据.首先从XRD(X-Ray diffraction)和SEM(Scanning electron microscope)发现经过不同温度焙烧,MOR分子筛结晶度和宏观形貌没有发生明显变化,但是通过一维^(29)Si,^(27)Al和^(1)H魔角旋转固体核磁谱(MAS NMR)发现分子筛局部环境发生了脱铝现象,产生了明显的缺陷羟基以及B酸量的下降.焙烧温度对HMOR分子筛骨架Al稳定性的影响较大,随着温度升高,脱铝逐渐加剧.定量^(1)H MAS NMR结合红外(IR)光谱提供了HMOR分子筛不同孔道B酸含量的分布.进一步使用2D^(27)Al MQ MAS NMR的方法以及结合切片分峰拟合技术区分出分子筛骨架中的四种不同T位点,发现当温度低于600℃,不同T位脱铝速率相当;当焙烧温度为600℃时,T3位点的Al原子脱除速率加快.最后研究了二甲醚羰基化反应性能与酸分布和铝分布的关系,获得羰基化反应活性中心的确凿谱学证据,T3-O33位置的Al位是羰基化反应的活性中心.
基金Funded by the National Torch Plan of China (No. 2005EB031110)the Key Scientific and Technical Innovation Project of Xi’an University of Ar-chitecture and Technology ( No. ZX 0402)
文摘60% white corundum used for aggregate, 5% aluminium powder for fixed additions and 35% various additives for matrix were prepared for specimens 1#,2#,3#. They were mixed uniformly with the suitable resin as a binder and pressed under pressure of 315 ton forging press, then dried at 200℃ for 24 h. Effects of various additives on 1500 ℃×2 h creep properties of Al3CON reinforced corundum composite were researched. The experimenal results show that creep coefficients of specimens 1#,2#,3# at 1500 ℃×2 h are 1.4×10^- 4, -9.4×10^-4, -22.6×10^-4, respectively. Crushing strength of the slide plate added with suitable additive A after fired at 1500 ℃ ×3 h reaches to 225 MPa, the creep rate is positive all the time from 0% to 0.014% at 1500 ℃ for 2 h. The microstructure result analysis shows that reinforced phases of Al3CON fiber composite have been formed after fired with Al powder in coke at high temperatures for specimen 1#, and the strength of the composite is increased. The hot modulus of rupture is up to 59 MPa at 1400 ℃ and the RUL is obviously higher than that at 1700 ℃. Its service life is two times as that of Al2O3-C slide plate when used in the process of pouring steel. The mechanism of creep rate resistance of the composites can be discovered by means of SEM and EDAX analysis. It is concluded that the active Al3CON and Al2O3 multiphases that were formed by N2 in gas, C, Al and Al2O3 inside the matrix of the composites during in-situ reaction,which gives the composites outstanding creep rate resistance for the dense zone resuiting from Al3CON oxidation that inhibits contraction at the high temperature. Besides, the matrix will turn into the multiphase with high refractoriness, N content and its Al3CON reinforced fiber will further increase accordingly. In addition, Al3CON formed by Al2O3 and C, Al in the matrix with N2 in gas will inhibit the creep rate and also greatly improve the creep rate resistance of the composites.
文摘A new calcium aluminate cement CA-670 was studied in the system of tabular alumina, white fused alumina （WFA）, and bauxite based low cement castables. The flow ability, strength development, and hot strength （ HMOR ） were investigated. Different types of additives were used for the CA-670 bonded castables. The results show CA-670 provides a good workability for each type of＂ castables. CA-670 displays a good compatibility with different types of additives. Testing on different batches of CA-670 shows good reproducible properties in each castable, which manifests good consistency and reliability of CA-670.
