磷钨酸插层MgAl水滑石层间距的调变及催化酯化脱酸性能

通过改变离子交换温度和时间合成了具有不同层间距的磷钨酸(H_3PW_(12)O_(40),HPW)插层MgAl水滑石(LDHs),采用XRD、FT-IR、Raman、~(31)P MAS NMR、ICP-AES和Hammett指示剂-正丁胺滴定法等表征其性质,并研究其对模型原油的催化酯化脱酸性能。高的离子交换温度有利于形成较大的层间距(d_(003)约1.46 nm),较长的交换时间有利于形成较小的层间距(d_(003)约1.05 nm)。不同的层间距源自HPW在层间不同的存在形式,P_2W_(18)O_(62)~(6-)以C_2轴倾斜于层板和PW_(11)O_(39)~(7-)以C_2轴垂直于层板的方式排列于层间时,形成d_(003)约1.46 nm的层间距;PW_(12)O_(40)~(3-)与层板发生嫁接,并以C_2轴垂直于层板的方向排列于层间时,形成d_(003)约1.05 nm的层间距。层间P_2W_(18)O_(62)~(6-)和PW_(11)O_(39)~(7-)能产生更高比例的中强酸中心,同时大的层间距有利于反应物扩散进入层间与酸中心接触,能够提高LDHs的催化酯化脱酸性能。     

12-磷钨酸插层MgAl水滑石的合成、表征及催化酯化原油脱酸性能

采用离子交换法合成了不同Mg/Al物质的量比的12-磷钨酸(H_3PW_(12)O_(40),HPW)插层水滑石(LDHs),采用XRD、FT-IR、Raman、ICP-AES、TG-DSC等分析手段表征其物化性质,Hammett指示剂-正丁胺滴定法测定其酸强度和酸量分布。进一步将其用于原油催化酯化脱酸反应,并与NO_3型LDHs对比,探讨酯化活性与催化剂性质之间的关系。结果表明,催化剂的活性主要受酸性和比表面积的影响。HPW插层LDHs的酯化活性明显优于NO3型LDHs,归因于增强的酸性和增大的比表面积。对于弱酸性的NO_3型LDHs,酯化活性与比表面积呈正向关系,Mg/Al物质的量比为4时,具有最大的比表面积和脱酸活性。而对于较强酸性的HPW插层LDHs,酯化活性主要受到酸量的影响,Mg/Al物质的量比为2的催化剂具有最高的酸量和脱酸活性。     

碳酸钾修饰水滑石吸附二氧化碳工艺条件研究

采用共沉淀法合成水滑石,等体积浸渍法将碳酸钾负载于水滑石孔道及层状结构中;在一定空速条件下,考察了吸附温度、碳酸钾添加量、活化温度对碳酸钾修饰水滑石吸附二氧化碳性能的影响;利用SEM、BET等手段对修饰后的水滑石进行了表征。在一定实验条件下,水滑石吸附容量可以达到9.10mol/kg。     

水滑石负载钾盐催化酯交换反应合成生物柴油

以水滑石为载体,负载钾盐作为酯交换合成生物柴油的催化剂,采用XRD、Hammett指示剂-苯甲酸滴定、N2吸附-脱附、TG-DSC研究了活性组分和载体类型、焙烧温度和时间以及负载量对催化剂碱性和酯交换活性的影响.H-介于9.3 ～15的中强碱量是决定催化剂活性的主要因素.钾与水滑石高温焙烧形成的相互作用物种是催化剂中强...     

CuMgAl类水滑石负载VO3-,MoO42-和WO42-催化剂的为波微波合成及其催化苯酚羟化活性

采用微波晶化法合成了三元CuMgAl类水滑石化合物前体,进一步在微波作用下制备了负载VO3-,MO42-和WO42-的类水滑石催化剂.X射线衍射、红外光谱和扫描电镜结果表明,酸根离子很好地负载在类水滑石表面.苯酚羟化反应结果显示,前体中Cu2+/Mg2+摩尔比为3:1时其催化性能最佳,苯酚转化率达到42.8%,邻/对比接近2:1.负载VO3-后催化剂活性升高,苯酚转化率最高达59.2%,而邻对比降为1.2:1.负载MoO42-的类水滑石与前体相比,苯酚转化率下降了约4%,但对苯二酚的选择性有较大提高,邻/对比达到1:6.而负载WO42-后催化剂活性和选择性明显下降.     

CuMgAl类水滑石负载VO3^-,MoO4^2-和WO4^2-催化剂的微波合成及其催化苯酚羟化活性

采用微波晶化法合成了三元CuMgAl类水滑石化合物前体,进一步在微波作用下制备了负载VO3^-,MoO4^2-和WO4^2-的类水滑石催化剂.X射线衍射、红外光谱和扫描电镜结果表明,酸根离子很好地负载在类水滑石表面.苯酚羟化反应结果显示,前体中Cu^2＋/Mg^2＋摩尔比为3：1时其催化性能最佳,苯酚转化率达到42.8%,邻/对比接近2：1.负载VO3-后催化剂活性升高,苯酚转化率最高达59.2%,而邻对比降为1.2：1.负载MoO42-的类水滑石与前体相比,苯酚转化率下降了约4%,但对苯二酚的选择性有较大提高,邻/对比达到1：6.而负载WO42-后催化剂活性和选择性明显下降.     

水滑石负载AuCu合金催化水煤气变换反应:催化性能与结构组成

以ZnAl水滑石(ZnAl-LDHs)为载体,合成了负载Au和AuCu合金的水滑石(Au/LDHs和AuCu/LDHs)用于催化水煤气变换反应(WGSR)。利用X射线粉末衍射(XRD)、高分辨率透射电镜(HRTEM)及扫描透射电子显微镜(STEM)表征了负载型催化剂的结构与组成。探讨了不同的Au和Cu物质的量之比(nAu∶nCu)对AuCu/LDHs催化WGSR性能的影响并与Au/LDHs的活性进行了对比。结果表明,负载Au纳米颗粒可明显的提升LDHs催化WGSR的活性,而负载AuCu合金后其活性又进一步的提升。当nAu∶nCu=2∶1时具有最佳的催化效率:活性为207.1μmol·gcat-1·s-1,TOF值为1.79 s-1,活化能为31.1 kJ·mol-1。通过分析对比不同样品的物理化学性质参数,探讨了不同的nAu∶nCu对Au的粒径、分散度、覆盖度及反应活性的影响。此外,X射线光电子能谱(XPS)分析表明,加入第二金属Cu形成合金后增大了Auδ+组分在体系中的含量(nAu∶nCu=2∶1时含量最高),这可能是负载体系催化WGSR具有高活性的原因。     

水滑石负载 Au 纳米粒子的制备及其催化醇氧化反应

 采用离子交换法和 NaBH4 还原法制备了 Mg-Al-水滑石 (LDH) 负载的 Au 纳米粒子 (Au/LDH) 催化剂. X 射线衍射和透射电镜结果表明, Au 粒子较均匀地分散在水滑石表面, 载体仍保持层状结构. 在温和的反应条件下, Au/LDH 对一系列醇的氧化反应表现出优异的催化性能, 如在室温常压下进行分子 O2 氧化 1-苯基乙醇的反应, 底物转化率和苯乙酮选择性都接近 100%, 而且催化剂经过多次循环使用后, 其活性未见下降. 可见, Au/LDH 催化剂在醇氧化反应中具有良好的应用前景.     

Cu-Mg-Al类水滑石的制备及其对二苯醚合成的催化性能研究

采用水热-尿素水解法制备了系列含Cu的类水滑石化合物CuxMg3-xAl1-LDHs,并考察了这些催化剂对苯酚和碘苯合成二苯醚反应的催化性能。利用X射线粉末衍射(XRD)、差热热重(TG-DTA）、H2程序升温还原(H2-TPR)和扫描电镜(SEM)等方法对催化剂进行了表征。结果表明,Cu2 含量较低时,类水滑石催化剂具有较好的结晶度和热稳定性,随Cu2 含量的增加,层板间距加大,热稳定性也随之降低。催化活性测试结果表明,适量Cu2 的掺入可使催化剂的催化活性提高,其中催化剂Cu2Mg1Al1-LDHs具有较好的催化活性,在80℃条件下二苯醚收率达到55%。     

铜铬类水滑石的表征及其催化性能

The CuCr-Hydrotalcite-like Compounds were synthesized by co-precipitation method. The samples were characterized by XRD, FTIR and N₂-adsorption/desorption measurements. The catalytic performance of the material synthesized was evaluated for the synthesis of benzion methyl ether with benzaldehyde and methanol. The result show that well crystallized hydrotalcites are obtained when n_Cu/n_Cr molar ratio is 2.0 and final value of pH is 4.3±0.2. The crystal shape is remained the same while crystallinity, surface area, pore structure and activity vary with the molar ratio of Cu to Cr. The catalytic activity is the best when the molar ratio of Cu to Cr is 2.0 at 50 ℃ andreaction time is 90 min. The highest conversion of benzaldehyde could reach 89.56％,while the selectivity of benzoin methyl ether is nearly 100％.     

Mg-Al-O-t-Bu hydrotalcite as an efficient catalyst for the transesterification of dimethyl carbonate with ethanol

Mg-Al-O-t-Bu hydrotalcite was synthesized and characterized by XRD, FT-IR and TGA-DTA. It was proved to be an active heterogeneous catalyst for the transesterification of dimethyl carbonate (DMC) with ethanol. When the reaction was carried out over Mg-Al-O-t-Bu hydrotalcite at 80°C, 7 h, molar ratio of ethanol to DMC 5:1, 1.0 wt.% of catalyst, the conversion of DMC was 86.4%, the selectivity to diethyl carbonate (DEC) was 61.2%. This heterogeneous catalyst could be used 5 times without loss of its activity.     

Metal‐free aerobic oxidative esterification of aromatic aldehydes promoted by potassium fluoride (KF)

We investigated the oxidative esterification of aldehydes with alcohols/phenols to produce a range of esters. In this approach, we conducted the reaction under metal‐free conditions at room temperature. The reactions were promoted by potassium fluoride (KF) as the additive, resulting in the desired product in good to high yields. This procedure was found to be effective for the production of aryl esters, which are challenging in most of the available reports. It is vital for this procedure not to exclude air as the source of oxygen.     

Thermal reactions of kaolinite with potassium carbonate

It was previously established that kaolinite reacts with K₂CO₃ on heating to form products of KSiAlO4 composition. In the present study we investigated the solid state reactions with K₂CO₃ of four kaolinites of different thermal stability. The mixtures were calcined at temperatures ranging from 400-700°C and washed before or after boiling with the remaining K₂CO₃. FTIR spectra indicated that the X-ray amorphous material formed after calcining the mixtures at 500-590°C had a SiAlO₄ tetrahedral framework. Attempts to convert the products to zeolites gave promising results. After calcining at 700°C under atmospheric pressure synthetic kaliophilite (KSiAlO₄) was obtained. These conditions are appreciably milder than previously reported for kaliophilite syntheses. Conversion to kalsilite increased with decreasing thermal stability of the original kaolinite. In similar reactions with KCl much less K was incorporated into the amorphous phase and kaliophilite was not obtained. The reactions of the four kaolinites with K₂CO₃ or with KCl were similar in trend, but differed in detail. This revised version was published online in July 2006 with corrections to the Cover Date.     

高酸值生物柴油原料甘油酯化脱酸研究

利用共沉淀-浸渍法制备了Al改性固体酸催化剂SO₄^2-/ZrO₂,考察了催化剂在甘油酯化脱酸制备生物柴油原料反应中的催化活性、重复利用性和再生性能,并对使用前后的催化剂进行了红外光谱分析。研究表明,添加适量Al(1%,以Al₂O₃的质量分数计)不但提高了催化剂的活性,还改善了催化剂的重复利用性和再生性能。添加Al使ZrO₂上SO₄^2-的量增加,SO₄^2-结合强度增强,减少了在酯化脱酸反应过程中SO₄^2-的流失。在SO₄^2-/ZrO₂-Al₂O₃催化剂用量为7％、甘油与酸物质的量比为6:1、反应温度为140 ℃、反应时间为4 h的条件下,酯化率可达91%以上,可将高酸值油脂的酸值从31 mg_KOH/g降低到2.8 mg_KOH/g以下,可满足生物柴油原料的要求。     

Synthesis of flavanones by use of anhydrous potassium carbonate as an inexpensive, safe, and efficient basic catalyst

Anhydrous potassium carbonate has been utilized as an inexpensive, safe, and efficient basic catalyst for the synthesis of flavanones starting either from 2′-hydroxychalcones or from 2′-hydroxyacetophenones. In both the cases the favored reaction condition was either refluxing in a solvent with added catalyst or microwave irradiation on the catalyst.     

Highly efficient esterification of carboxylic acids with alcohols by montmorillonite-enwrapped titanium as a heterogeneous acid catalyst

Montmorillonite-enwrapped titanium catalyst was found to efficiently promote the esterification of carboxylic acids with alcohols. In comparison to other catalysts reported to date, this heterogeneous catalyst offers a remarkably simple workup procedure, and is reusable without any appreciable loss in its activity and selectivity.     

Mg/Al水滑石催化碳酸二甲酯与苯酚酯交换反应

Mg/Al水滑石催化碳酸二甲酯与苯酚酯交换反应