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CO2 高效温和转化与利用是温室气体减排与绿色化学化工的研究前沿。1,6-六亚甲基二异氰酸酯 (HDI) 是一种重要的脂肪族异氰酸酯,其饱和直链烷烃结构使其广泛应用于高端聚氨酯领域。非光气 HDI 技术是绿色化学化工的典型代表,其清洁工艺开发不仅可以取代原有光气工艺路线的剧毒原料光气，避免产生对环境污染严重的副产物,而且可以通过碳酸二甲酯 (DMC) 实现经济上可行的 CO2 高值化利用。本论文针对己二胺 (HDA) 与 DMC 甲氧羰基化反应制备1,6-六亚甲基二氨基甲酸甲酯 (HDC), HDC 再进一步热解制备 HDI 的非光气两步法清洁制备 HDI 工艺存在的关键问题,设计了新型多相催化剂，深入开展了催化剂表征、构效关系、稳定性、催化机理和工艺条件优化等研究工作,为非光气清洁制备 HDI 的工程化提供了理论基础，主要结论如下：(1) 开展了 HDA 与 DMC 反应制备 HDC 过程杂多酸催化剂设计、筛选以及工艺优化研究。通过对副产物分析,确定了副产物成分,进而建立了反应网络。催化剂评价结果表明相比于其他催化剂, H4[SiW12O40] 催化剂的催化效果最优。使用 XRD、 FTIR 和 SEM 以及 NH3-TPD 等手段对催化剂进行表征,结果表明催化剂活性与其酸性有关。工艺优化结果表明,使用 H4[SiW12O40] 催化剂，优化条件下, HDA 转化率为93.2%, HDC 选择性为 64.8%，副产物选择性为 3.8%。在此基础上推测了催化反应机理，并最终通过重结晶方法分离出纯度高达 99.9% 的 HDC 产品。(2) 以负载型金属氧化物为催化剂,开展了 HDC 在低沸点溶剂中热解制备 HDI 的工艺研究。分别通过等体积浸渍法(IWI), PEG添加法(PEG) 和蒸氨沉积沉淀法(DP)制备了多种金属氧化物催化剂。结果表明,使用不同方式制备的 Co3O4/ZSM-525 催化剂的催化活性顺序为 Co3O4/ZSM-525(PEG) > Co3O4/ZSM-525(IWI) > Co3O4/ZSM-525(DP)；进一步使用 XRD, FTIR, N2吸脱附以及 NH3-TPD 和 XPS 等手段对催化剂进行了表征,结果表明，由于具有较高的表面 Co3+ 含量，晶格氧含量以及总酸性, PEG滴定方法制备的 Co3O4/ZSM-525(PEG) 催化剂活性最高。使用 Co3O4/ZSM-525(PEG) 催化剂,在优化条件下, HDC 转化率达到 100%, HDI 收率达到 92.8%。催化剂循环 5 次并未发现其活性降低。根据催化剂的物化性质,推测了催化热解反应机理。最后以 HDA 和 DMC 反应得到的 HDC 为原料，热解制备了 HDI,并使用分子蒸馏对 HDI 产品进行分离,产品纯度大于 99%，完成了两步法非光气 HDI 的全流程试验。(3) 进一步研究了 Co3O4/ZSM-525(PEG) 催化体系下的 HDC 热解制备 HDI 动力学。在不同的反应温度下计算了该热解反应的动力学参数：HDC 转化到 HMI, HMI 转化到 HDI 的活化能和指前因子分别为 39.67 kJ.mol-1, 3.23 × 102 min-1 和 114.54 kJ.mol-1, 1.35 × 1011 mol-0.49. L0.49.min-1,计算所得到的动力学模型和实验数据吻合良好。动力学研究结果表明,相比于 HMI 热解至 HDI, HDC 热解至 HMI 需要更少的活化能,更容易发生反应。因此提高温度有助于中间体 HMI 向最终产物 HDI 的转化。(4) 将一系列负载型 Zn-Co 双金属催化剂应用于 HDC 热解制备 HDI 的反应,采用 FTIR, XPS, XRD, N2 吸脱附, SEM, EDS 和 NH3-TPD 等手段对催化剂进行表征。结果表明, Zn-2Co/ZSM-5 催化剂在 ZSM-5 载体表面形成了 Zn-Co 协同作用的 ZnCo2O4 尖晶石结构,而该协同作用导致的酸性位分布使得该催化剂表现出最高的催化活性。工艺优化结果表明：使用 Zn-2Co/ZSM-5 催化剂,优化条件下, HDC 转化率为 100%, HDI 选择性 91.2%,副产物为 1.3%。催化剂循环试验结果表明，在循环过程中,由于 Zn 的流失导致了所形成的 ZnCo2O4 尖晶石结构被破坏,因此催化活性降低。;CO2 utilization to produce useful chemicals is an important research topic of huge industrial interest in green synthesis. Hexamethylene-1,6-diisocyanate (HDI) is one of the most widely used aliphatic diisocyanate because of its unique properties and high demand in industries for various high-end applications. Non-phosgene synthesis of HDI has attained considerable interest in the field of green chemistry because it can not only substitute the highly toxic phosgene method, but also provide an approach for CO2 utilization by using dimethyl carbonate (DMC) as carbonylation reagent. In this dissertation, aiming at resolving the key problems that exist in the two-step non-phosgene synthesis of HDI: (1) synthesis of hexamethylene?1,6?dicarbamate (HDC) by methoxycarbonylation of HDA with DMC; (2) thermal decomposition of HDC to HDI, various heterogeneous catalysts are designed and studied. Furthermore, characterization of catalysts, the relationships between physicochemical properties and catalytic performances, reusability of catalysts, effects of reaction parameters, catalytic mechanisms, reaction kinetics as well as product separation and purification are discussed in detail. Thus, both process and theoretical bases are supplied for the non-phosgene synthesis of HDI in this dissertation. The achievements and progress in this dissertation are as follows:(1) Synthesis of HDC by methoxycarbonylation of HDA with DMC was conducted over the bulk and hybrid heteropoly acid catalyst for the first time. The reaction network was established. The performances of bulk and hybrid heteropoly acid catalysts were evaluated. Results showed that the H4[SiW12O40] catalyst revealed the best performance compared with other catalysts. The catalysts were systematically characterized by XRD, FTIR, SEM and NH3-TPD techniques. It was found that the acidic properties were responsible for the high performance of the H4[SiW12O40] catalyst. Under the optimized reaction conditions, HDA conversion and HDC selectivity could be reached 93.2% and 64.8%, respectively, with only 3.8% by-products selectivity. A possible reaction mechanism was also proposed. Moreover, HDC was obtained with a purity of 99.9% by using the recrystallization separation method.(2) Synthesis of HDI by thermal decomposition of HDC was carried out over metal oxide supported catalyst. Different metal oxide supported catalysts were prepared by incipient wetness impregnation (IWI), PEG-additive (PEG) and deposition precipitation with ammonia evaporation (DP) methods and screened. The catalyst screening results showed that Co3O4/ZSM-525 catalysts prepared by different methods showed different performances in the order of Co3O4/ZSM-525(PEG) > Co3O4/ZSM-525(IWI) > Co3O4/ZSM-525(DP). The physicochemical properties of Co3O4/ZSM-525 catalyst were characterized by XRD, FTIR, N2 adsorption-desorption measurements, NH3-TPD and XPS. Results showed that the superior catalytic performance of Co3O4/ZSM-525(PEG) catalyst was attributed to its relative surface content of Co3+, surface lattice oxygen content and total acidity. Under the optimized reaction conditions, the HDC conversion and HDI yield could reach 100% and 92.8%, respectively, without polymerization by-products. The Co3O4/ZSM-525(PEG) catalyst could be facilely separated from the reaction mixture, and reused for 5 successive runs without degradation in catalytic performance. A possible reaction mechanism was purposed based on the physicochemical properties of the Co3O4/ZSM-525 catalysts. Moreover, HDI was obtained with a purity of >99% by the thermal decomposition of HDC obtained from the methoxycarbonylation of HDA with DMC, using molecular distillation method.(3) The kinetics of the thermal decomposition of HDC to HDI in the presence of Co3O4/ZSM-525(PEG) catalyst was then studied. Kinetic parameters were calculated by using concentration profiles at different reaction temperatures. The activation energy and pre-exponential factor for the thermal decomposition of HDC to HMI and HMI to HDI were 39.67 kJ.mol-1, 3.23 × 102 min-1 and 114.54 kJ.mol-1, 1.35 × 1011 mol-0.49. L0.49.min-1 respectively. The kinetic model was found in good agreement with the experimental data. The results showed that the thermal decomposition of HDC to HMI required less activation energy and easy to carry out compared with the thermal decomposition of HMI to HDI. Thus, the higher reaction temperature will be beneficial for the decomposition of HMI to HDI.(4) A set of bimetallic (Zn-Co) oxide supported ZSM-5 catalysts was prepared by PEG-additive method, which was further studied in the thermal decomposition of HDC to HDI in this dissertation. The physicochemical properties of the catalysts were investigated by FTIR, XPS, XRD, N2 adsorption-desorption measurements, SEM, EDS and NH3-TPD techniques. Results showed that the ZnCo2O4 spinel oxide was formed on the ZSM-5 support and provided synergetic effect between Zn and Co species for the bimetallic oxide supported catalyst. Their catalytic performances were then studied. Results showed that the Zn-2Co/ZSM-5 catalyst showed excellent catalytic performance due to the good synergetic effect between Co and Zn species, which provided a suitable contribution of acidic sites. HDC conversion of 100% with HDI selectivity of 91.2% and by-products selectivity of 1.3% could be achieved within short reaction time of 2.5 h over Zn-2Co/ZSM-5 catalyst. The reusability of the Zn-2Co/ZSM-5 catalyst showed that loss in the catalytic performance was due to the ZnO leaching into reaction mixture which led structural defects in the ZnCo2O4 cubic spinel structure.
|MUHAMMAD AMMAR. 非光气多相催化制备1,6-六亚甲基二异氰酸酯研究[D]. 中国科学院大学,2017.|
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