【作者】 申延明；

【导师】 刘长厚； 张振祥；

【作者基本信息】 大连理工大学 ， 工业催化， 2009， 博士

【摘要】 甲基异丁基酮（MIBK）是一种优良的有机溶剂,先进的生产方法是丙酮气相缩合加氢一步法,该工艺关键的技术是开发高效的双功能催化剂,即催化剂同时具有缩合、加氢以及适宜的酸、碱性质。目前开发的贵金属和过渡金属催化剂均是采用浸渍法或沉淀法制得,催化剂热稳定差、活性组分分布不均、丙酮转化率低或MIBK选择性差。类水滑石化合物是一种层状的化合物,层板的化学组成具有可调控性,层间阴离子具有可交换性,基于类水滑石的这些特性,本文将Pd、Cu、Ni三种活性组分引入水滑石层板中,制得含有活性金属的三元类水滑石,焙烧这些类水滑石前体得到活性组分均匀分散的催化剂,通过调节类水滑石前体中金属组分的含量以及M²⁺/M³⁺比,得到催化性能较好的丙酮气相缩合加氢合成MIBK催化剂。由于ZrO₂既是酸催化剂,又是碱催化剂,能够调节催化剂的酸碱性,因此,本文又将Zr引入到上述三元类水滑石中,制得含Zr的四元类水滑石,焙烧后得到ZrO₂修饰的催化剂,以进一步调节催化剂的酸碱性、活组分的分散性,提高催化性能。由于水滑石层间阴离子具有可交换性,本文又将PdCl₄^2-引入水滑石层间,并以其为前体制得Pd基催化剂。采用共沉淀方法,以NaOH和Na₂CO₃为沉淀剂,在pH=9-10,晶化温度60℃,晶化时间12小时下合成出不同M²⁺/M³⁺、不同金属含量的层状结构完整的PdMgAl、CuMgAl、NiMgAl类水滑石,并以这些类水滑石为前体制备了M/Mg（Al）O（M=Pd、Cu、Ni）催化剂,通过化学分析、XRD、IR、SEM、SEM-EDS面扫描、DTA、比表面积测定、CO₂-TPD、TPR等测试手段探讨了金属离子含量、M²⁺/M³⁺比对类水滑石结构、热分解过程结构的变化以及催化剂的酸碱性、活性金属分散性和还原性的影响,并进行了丙酮气相缩合加氢制取MIBK催化性能的研究。同样采用共沉淀的方法制备了不同Zr含量的PdMgAlZr、CuMgAlZr及NiMgAlZr四元类水滑石,探讨了Zr含量对类水滑石结构,衍生催化剂的碱性、活性金属分散性和还原性以及催化性能的影响。研究结果表明,M²⁺/M³⁺=2-4,Pd含量0.1-1mol%,或Cu、Ni含量1-10mol%可以合成晶相单一、层状结构完整的PdMgAl、CuMgAl、NiMgAl类水滑石,500℃焙烧这些类水滑石能够得到以MgO晶相为主、活性金属组分均匀分散的弱碱性催化剂,催化丙酮气相缩合加氢制取MIBK的性能优于浸渍法和沉淀法制备的催化剂;Zr含量不超过20mol%能够合成晶相单一、层状结构完好的PdMgAlZr、CuMgAlZr及NiMgAlZr类水滑石,Zr的加入提高了活性组分在催化剂中的分散程度,适当地添加Zr可以增加催化剂的碱性,提高催化性能。本文还探讨了利用PdCl₄^2-插入MgAl-NO₃型水滑石层间的方式,制得MgAl-PdCl₄水滑石,并测试了其衍生催化剂的催化性能,结果表明MIBK的选择性为23-43%,而DIBK的选择性可达30%,该催化剂适于联产MIBK和DIBK。更多还原

【Abstract】 Methyl isobutyl ketone （MIBK） is a good origanic slovent and the advanced process for producing MIBK is one-step synthesis by gas-phase condensation and hydrogenation of acetone. In this process, the key technology is to develop the multi-fuctional catalyst, which has both the ability of hydrogenateon and condensation, as well as suitable acid-base sites. The catalysts made from noble or transition metals by impregenation or coprecipatation have bad thermal stability and low acetone conversion or MIBK selectivity. Hydrotalcite-like compounds （HTLcs） are layered compounds. The composition of the metals in the sheets can be adjusted and the anions between the layers can be exchanged. In this paper, based on these special properties of HTLcs, HTLcs containing palladium, copper or nickel are synthesized in order to introduce them into the sheets of MgAl hydrotalcite, then the prepared HTLcs are calcined to give their corresponing composite oxides. It is expected that the resulted catalysts have better catalytic activity in the synthesis of MIBK from acetone gas phase condensation and hydrogenateon by adjusting metal molar contents and M²⁺/M³⁺ molar ratios in the sheets of HTLcs precursors. ZrO₂ is both acid and base catalyst and has the ability to adjust acid-base strength of catalyst, thus it is introduced into the above catalysts by calcining HTLcs containing zirconium in order to further adjust the dispersion and the acid-base strength of the above catalysts. Because of the exchangable property of anions between the sheets of HTLcs, PdCl₄^2- is intercalated into the space of sheets so as to prepare Pd-based catalyst via this PdCl₄-intercalated HTLcs.In this paper, PdMgAl, CuMgAl and NiMgAl HTLcs with different metal molar contents and M²⁺/M³⁺ molar ratios are synthesized at pH=9-10, aging temperature of 60℃and aging time of 12 hours by coprecipatation using NaOH and Na₂CO₃ as the precipitator, then M/Mg（Al）O（M=Pd, Cu, Ni） catalysts are prepared by calcining the resulted HTLcs. The resulted samples are characterized by the titrition with EDTA, XRD, IR, SEM, SEM-EDS, DTA, CO₂-TPD, TPR and BET special surface area mesurement. Some effects such as the metal molar contents, M²⁺/M³⁺ molar ratios on the structure of HTLcs and the phase change during the thermal treatment, metal dispersion and the reducibility, and base strength of the derived mixedcomposite oxides are discussed. Then the catalytic acitivities of acetone gas-phase condensation and hydrogenation over these catalysts are tested. PdMgAlZr, CuMgAlZr and NiMgAlZr HTLcs are prepared by the same method. The effects of Zr molar contents on the structure of PdMgAlZr, CuMgAlZr and NiMgAlZr HTLcs and base strength, metal dispersion and reducibility, and catalytic activities of the derived composite oxides are investigated. It is showed that PdMgAl, CuMgAl and NiMgAl HTLcs with single hydrotalcite phase and perfect layered structure can be prepared at M²⁺/M³⁺ molar ratios in the range of 2 and 4 along with Pd molar contents of 0.1-1mol%, Cu or Ni molar contents of 1-10mol%. Highly-dispersed metal-based catalysts with MgO phase and weak base strength are then obtained by calcining the resulted HTLcs and they have better catalytic acitivities than those prepared by impregenation and coprecipatation in the synthesis of MIBK from acetone gas-phase condensation and hydrogenation. PdMgAlZr, CuMgAlZr and NiMgAlZr HTLcs with single hydrotalcite phase and better layered structure can be prepared at Zr molar contents not more than 20mol%. The introduction of Zr into the catalyst precursors improves the dispersions of metals on the resulted catalysts and the base strength and then the catalytic activities of the catalysts can be improved with suitable Zr molar contents.MgAl-PdCl₄ HTLcs are prepared by exchanging NO₃^- in the spaces of MgAl-NO₃ HTLcs using PdCl₄^2-. Then the catalytic activities of the catalysts derived from MgAl-PdCl₄ HTLcs are studied. It is showed that MIBK selectivity is in the range of 23% and 43%, DIBK selectivity is about 30%. The resulted catalysts are suitable for combining production of MIBK and DIBK.更多还原