Applications Of Nanozeolites In Dynamic Kinetic Resolution

Zeolites are a kind of excellent candidates on the catalysis, adsorption and ionic exchange because of their microporous framework structure and acid/base activity. With the development of the nanoscience and nanotechnology, researches of nanoscaled zeolite particles (nanozeolites) are widely attracted considerable attentions because of their shorter microporous channels, much larger external surface areas, abundant active sites, good biological compatibility as well as reliable, simple and convenient assembly comparing with micro-sized zeolites. These peculiar characteristics of nanozeolites endow their potential applications as building blocks and perfect biocompatible materials in many non-traditional areas such as adsorption, assembly, biosensors, electronics and biotechnology. However, the difficult manipulation of nanozeolite particles severely limit their applications, whereas the conventional calcination will lead to the lessening of accessible active surface because their irreversible aggregation at the high temperature condition. Various methods of nanozeolite assembly are used to solve these problems. Recently, an improved polymerization-induced colloid aggregation (im-PICA) method was developed to prepare the nanozeolite microsphere (ZMS) with a hierarchical porous structure and a micrometer size from nanozeolite colloidal solutions. The as-prepared ZMSs not only well retain the characteristics of nanozeolites, such as the much larger external areas, abundant active sites, but also possess excellent sphere morphologies. Therefore, it’s expected that the ZMSs have much more advatages comparing with the conventional zeolites in the pertroleum catalysis and other fields. With the development of industry of fine chemicals, the needs of excellent catalysts are increasing. However, excellent acidic catalysts of ZMSs seldom are used as catalysts of fine chemicals at low temperature in the organic phase. Additionally, the research of diffusion on the nanozeolites is also paid less attention at the low temperature in the organic phase, and lack of the diffusion method in the liquid phase to futher limit the research of nanozeolites microspheres.Meanwhile, easy modification and excellent biocompatibility of ZMSs with hierarchical structures make them promising candidates of the carriers of the biological active moleculars to achieve the high activity and stability. However, researchers pay more attentions on their applications of either acidic properties of inherent micropores or promising enzyme immobilized carriers because of their large external surface.The thesis is focusing on the "Applications of nanozeolites on the dynamic kinetic resolution ", which include three parts."The formation of nanozeolite H-β microspheres (P-ZMSs) prepared by im-PICA method and their characterization" is discussed in detail, firstly. And both "Catalytic performance of β-ZMS in one-pot dynamic kinetic resolution of aromatic sec-alcohols" and "the possibilities and influences of integrated chem-enzymatic bi-functional catalysts of CALB@β-ZMS-PDDA " are systemically investigated.Chpater2described the preparation of β-ZMSs using im-PICA at different pH values. On the basis of research of preparation of P-ZMS using im-PICA by our group, the im-PICAprocess was adjusted optimized of adjusting the pH value, the ratio of urea to formadehyde (U/F) and the concentrations of nanozeolites. Additionally, the characterizations of nanozeolites β and P-ZMS, which is the prerequisite of the later researches, were provided in details. Finally, the kinetic processes of various organic amine impulses towards to nanozeolites, incuding n-butylamine, tert-butylamine and2,6-di-tert-butylpyridine, were dissucced to study the diffusion of substrates in the liquid fulfilled micropore of nanozeolites. On the basis of it, the acidic porperties of β-ZMS were tested on the auto-titrimeter with differents rates of organic amines.Charpter3studied the catalytic performances of β-ZMS in one-pot dynamic kinetic resolution of aromatic sec-alcohols. Hβ-ZMSs prepared by im-PICA, combined with an immobilized lipase B from Candida antarctica (commercially available Novozym(?)435), is applied as a racemization catalyst to the one-pot dynamic kinetic resolution (DKR) of aromatic sec-alcohols. The DKRs of various aromatic sec-alcohols can be carried out with high selectivity and conversion under optimum conditions. Importantly, it is found that, compared to commercial zeolites β (C-β),β-ZMSs display high selectivity for small sec-alcohol molecules because their shorter microporous channels reduce the diffusion time of substrate/product in the three-dimensional framework, and thereby decrease the possibility of secondary reactions. However, the β-ZMSs show a high racemization rate in the DKR of large sec-alcohol molecules, such as racemic1-(1-naphthyl)-ethanol, thanks to their abundant accessible active sites. This observation will not only benefit the performance of acidic zeolite catalysts in one-pot DKR systems but also provide a new perspective on the application of nanozeolites in catalysis. Charpter4investigated the possibilities and influences of integrated chem-enzymatic bi-functional catalysts of CALB@β-ZMS-PDDA. The uniform H-β nanozeolite microspheres modified by polyelectrolytes (β-ZMSs-PEs) with a large and adjustable secondary pore architecture immobilized the lipase B from Candida Antarctica as the synergistic chem-enzymatic bi-functional catalysts were applied to one-pot DKRs of aromatic sec-alcohols. It’s found that the β-ZMS-PEs played the important roles in both racemization process and lipase immobilization, and the lipase immobilized on the different polyelectrolytes modified surface of β-ZMS display the different transesterification activity. The CALB immobilized on polydiallyldimethylammonium chloride (PDDA) modified P-ZMSs, showing the highest esterification activity with the highest selectivity of amied products. Thus, the intergrated CALB@β-ZMS-PDDA displayed high conversion with high selectivity in the DKRs, such as>91.8%yield and93%selectivity in the DKR of1-phenylethanol at50℃in cyclohexane. In addtion, the other substrates of aromatic sec-alcohols are also applicated in the DKRs catalyzed by the CALB@β-ZMS-PDDA and accomplished successfully. The results achieved the utilization of the large surface and inherent micropores of nanozeolites, which will provide a new possibility for the nanozeolites application in the fine chemical industry.In summary, this thesis expanded our knowledge and understanding for nanozeolite and their applications, providing a new and instructive sight for the nanozeolites materials and other nanomaterials.