Gruter Gert-Jan M, Sipos Laszlo, Adrianus Dam Matheus
Avantium Chemicals BV, Zekeringstraat 29, 1014BV Amsterdam, The Netherlands.
Comb Chem High Throughput Screen. 2012 Feb 1;15(2):180-8. doi: 10.2174/138620712798868374.
High Throughput experimentation has been well established as a tool in early stage catalyst development and catalyst and process scale-up today. One of the more challenging areas of catalytic research is polymer catalysis. The main difference with most non-polymer catalytic conversions is the fact that the product is not a well defined molecule and the catalytic performance cannot be easily expressed only in terms of catalyst activity and selectivity. In polymerization reactions, polymer chains are formed that can have various lengths (resulting in a molecular weight distribution rather than a defined molecular weight), that can have different compositions (when random or block co-polymers are produced), that can have cross-linking (often significantly affecting physical properties), that can have different endgroups (often affecting subsequent processing steps) and several other variations. In addition, for polyolefins, mass and heat transfer, oxygen and moisture sensitivity, stereoregularity and many other intrinsic features make relevant high throughput screening in this field an incredible challenge. For polycondensation reactions performed in the melt often the viscosity becomes already high at modest molecular weights, which greatly influences mass transfer of the condensation product (often water or methanol). When reactions become mass transfer limited, catalyst performance comparison is often no longer relevant. This however does not mean that relevant experiments for these application areas cannot be performed on small scale. Relevant catalyst screening experiments for polycondensation reactions can be performed in very efficient small scale parallel equipment. Both transesterification and polycondensation as well as post condensation through solid-stating in parallel equipment have been developed. Next to polymer synthesis, polymer characterization also needs to be accelerated without making concessions to quality in order to draw relevant conclusions.
如今,高通量实验已成为早期催化剂开发以及催化剂和工艺放大过程中的一项成熟工具。催化研究中较具挑战性的领域之一是聚合物催化。与大多数非聚合物催化转化的主要区别在于,产物不是一个定义明确的分子,催化性能不能仅通过催化剂活性和选择性轻易表达。在聚合反应中,形成的聚合物链可能具有各种长度(导致分子量分布而非确定的分子量)、不同的组成(当生产无规或嵌段共聚物时)、可能具有交联(通常会显著影响物理性能)、可能具有不同的端基(通常会影响后续加工步骤)以及其他几种变化。此外,对于聚烯烃,传质和传热、对氧气和水分的敏感性、立构规整性以及许多其他固有特性使得该领域相关的高通量筛选成为一项艰巨的挑战。对于在熔体中进行的缩聚反应,通常在分子量适中时粘度就已经很高,这极大地影响了缩合产物(通常是水或甲醇)的传质。当反应受传质限制时,催化剂性能比较往往不再相关。然而,这并不意味着不能在小规模上对这些应用领域进行相关实验。缩聚反应的相关催化剂筛选实验可以在非常高效的小规模平行设备中进行。已经开发出了平行设备中的酯交换、缩聚以及通过固相后缩聚反应。除了聚合物合成,聚合物表征也需要加速,同时不能在质量上妥协,以便得出相关结论。