The catalyst is prepared by a modified physical encapsulation method. In this study, the core–shell catalyst comprises metallic oxide Zn–Cr covered by a SAPO34 layer and is used for STO (syngas to light olefins) synthesis. The formed methanol on the Cu–ZnO–Al 2O 3 catalyst from syngas can easily be converted to DME in situ by the H-ZSM-5 layer. 39 The capsule catalyst (Cu–ZnO–Al 2O 3 was encapsulated by an H-ZSM-5 layer) for a syngas to DME (CH 3OCH 3) direct synthesis has also been successfully prepared. These linear hydrocarbons exit by diffusion through the zeolite membrane and those with a straight-chain structure have a chance of being cracked and isomerized at the acidic sites of the zeolite. Syngas passes through the zeolite membrane channels to reach the core catalyst, where it forms normal paraffins. 37–43 For instance, a Co–Al 2O 3 (shell) capsule catalyst was designed for the direct synthesis of isoparaffins from syngas via the Fischer–Tropsch synthesis. In our previous studies, several successful applications of capsule catalysts have been reported. Specifically, it can connect two or more consecutive catalytic processes into a direct synthesis. Even though it is a discovery of great importance, the challenges of suppressing highly undesirable CO 2 selectivity of approximately 50% and uneven mixing of physical mixture catalysts still need to be optimized for its further use in industrialization.Ī capsule catalyst with a tailor-made core–shell structure has been designed for several given reactions. 30–36 The light olefin selectivity breaks through the Anderson–Schulz–Flory distribution, which is beyond 58%. 21–29 For the above-mentioned findings, a new direct route for syngas to light olefin (STO) synthesis using physical mixture catalysts has been reported. 20 Using a hybrid catalyst is also a feasible way to realize the tandem catalysis reaction from complex to simple approaches. In another way, light olefins can also be obtained from methanol over a SAPO34 zeolite, namely by the methanol to olefin (MTO) process 14–19 methanol synthesis from syngas has been a mature industrial product since 1923, which was built by BASF. However, the Anderson–Schulz–Flory distribution affects the selectivity for light olefins, which is a maximum of 58% theoretically. 7–13 CO can be connected to H 2 on the surface of the catalyst and the formation of CH x ( x = 1, 2, 3) takes place to convert to C nH m by C–C coupling finally, the alkane or olefin products are formed by the hydrogenation or dehydrogenation of C nH m. To solve this problem, considerable studies on the conversion of syngas (synthesis gas, CO + H 2) to light olefins by the Fischer–Tropsch synthesis have been reported due to the cost-effective feeding stock as compared to crude oil, which is called Fischer–Tropsch to olefins (FTTO). 4 Currently, petroleum resources continue to decrease, which raises barriers for the traditional synthesis of light olefins from naphtha cracking. 1–3 Light olefins are widely used in the organic chemicals with the largest production volumes all over the world. Conversion to light olefins (C 2 to C 4) has attracted immense interest since light olefins are playing more important roles in the chemical industry for a long period. With the development of biomass reforming technology and methane mining technology in shale gas and combustible ice, syngas (a CO + H 2 mixture) can be used as a much cheaper stock with larger reserves to synthesize chemicals and energy fuels via a non-petroleum route. Introduction C1 chemistry has become a hot research area because one of the most challenging scientific issues is to find alternative energy sources for petroleum in the 21 st century. The designed capsule catalyst has superior potential for scale-up in industrial applications while simultaneously extending the capabilities of hybrid catalysts for other tandem catalysis reactions through this strategy. The light olefin space time yield (STY) of the capsule catalyst is more than twice that of the typical physical mixture catalyst. Due to the difference between the adsorption energies of the Zn–Cr metallic oxide/SAPO zeolite physical mixture and capsule catalysts, the produced water and light olefins are easily removed from the capsule catalyst after formation, suppressing the side reactions. The confinement effect, hierarchical structure and extremely short distance between the two active components result in the capsule catalyst having better mass transfer and diffusion with a boosted synergistic effect. It can not only break through the limitation of the Anderson–Schulz–Flory distribution but can also overcome the disadvantages of physical mixture catalysts, such as excessive CO 2 formation. An elegant catalyst is designed via the encapsulation of metallic oxide Zn–Cr inside of zeolite SAPO34 as a core–shell structure to realize the coupling of methanol-synthesis and methanol-to-olefin reactions.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |