Manipulating the architecture of titanium silicalite-1 supported Au catalysts for direct propene epoxidation with H2 and O2 Xiang Feng 1 , Chaohe Yang 1 , Xinggui Zhou 2 *, De Chen 3* and Weikang Yuan 2 1 China University of Petroleum, Qingdao, China;2 East China University of Science and Technology, Shanghai, China 3 Norwegian University of Science and Technology, Trondheim, Norway *Corresponding author: xgzhou@ecust.edu.cn; de.chen@ntnu.no Highlights  Micropore blocking is the main deactivation mechanism for propene epoxidation.  Precise manipulation of Au spatial location on support can effectively enhance stability.  Size-dependent activity and active sites are identified using unique Au/uncalcined TS-1.  The Au/TS-1 has been tested for 1000 h, which is promising for industrial application. 1. Introduction Propylene oxide (PO) as the third largest propylene derivative, is recognized as a high value-added chemical intermediate for manufacturing of polyurethane and polyether resins [1]. The green and simple production of PO by direct propylene epoxidation with H2 and O2 has attracted worldwide attention. Among the commonly used bi-functional Au/Ti-containing catalysts, Au/TS-1 catalyst exhibits superior catalytic performance. However, it always suffers from severe deactivation and poor conversion (i.e., lower than 5%)[2]. Therefore, it is of prime scientific and industrial importance to elucidate the structure-performance relationship in order to design a highly efficient catalyst for propene epoxidation with H2 and O2. In this work, the deactivation mechanism (e.g., pore blocking, site coverage or Au aggregation) was first discriminated. Based on the deactivation mechanism (micropore blocking), novel strategies to manipulate the spatial distribution of Au on TS-1 support and to improve the mass transfer ability were further developed, which are both effective in enhancing stability of Au/TS-1 catalysts. Moreover, accurate size-dependent activity and active sites of Au/TS-1 catalyst were studied by model calculation. The designed Au/TS-1 catalyst can be used and regenerated over 1000 h, which is promising for industrial application. 2. Methods The TS-1 support was synthesized by hydrothermal method[3]. In a typical process, titanium (IV) tetrabutoxide (TBOT) dissolved in isopropanol was added drop-wise to the mixture of tetraethylorthosilicate and tetrapropylammonium hydroxide (TPAOH). The gel was crystallized at 443 K for at least 18 h. The products with and without further calcination were named as TS-1 and Un-TS-1, respectively. Novel nanosized mesoporous TS-1 is prepared by the dry-gel conversion method[1]. 3. Results and discussion 3.1 Elucidation of deactivation mechanism. Aggregation of Au is normally regarded as the deactivation mechanism for Au catalysts. However, average sizes of Au NPs on Au/TS-1 catalysts at 4 and 30 h are almost the same. Therefore, carbonaceous deposits formation on different catalysts sites may be deactivation mechanisms (e.g., active site coverage and/or the pore blocking), which can be discriminated by an analysis of relative changes in the pore volumes and volumes of carbonaceous deposits (Figure 1). The Figure 1. The method to discriminate deactivation mechanism.