Syngas To Light Olefins Research Articles

Effect of zeolite topological structure in bifunctional catalyst on direct conversion of syngas to light olefins

Bifunctional catalyst composed of metal oxide and zeolite (OX-ZEO) is a promising strategy for the direct conversion of syngas to light olefins (STO), where the structure of zeolite plays a vital role in determining the selectivity of product. Herein, three kinds of silicoaluminophosphate zeolites with different topological structures, i.e., the ERI(SP17), AEI(SP18) and CHA(SP34), were hydrothermally synthesized, after the combination with Mn-Ga oxide, the prepared OX-ZEO was applied for STO reaction. The variation in the crystallization time for SP17 synthesis has a great impact on the generation of impurity phase of SAPO-5, where a crystallization time of 48–96 h is found to be beneficial in synthesizing SP17 zeolite with pure phase. SP17 zeolite with a crystallization time of 96 h, possesses the micropores and columnar morphology, where the small cage-defining 8-ring size of SP17 shows the olefins selectivity of 87.0% at a low CO conversion of 19.4%, significantly deviating towards the major fraction of ethylene (45.6%) than that of butene (8.2%). In a contrast, SP18 and SP34 zeolites with the same and large cage-defining 8-ring size, are richer in propylene and butene fractions than that of ethylene in overall similar olefins selectivity of 87.0% and 87.1% at CO conversion of 28.7% and 28.5%, respectively. Interestingly, it is further interpreted that the SP17 sample generated more carbon species during the reaction due to the small 8-ring size, while those amounts of carbon species were restricted in the hierarchical pore structure and plate-like morphology in SP18 and SP34 samples.

Unraveling the role of GaZrOx structure and oxygen vacancy in bifunctional catalyst for highly active and selective conversion of syngas into light olefins

The direct conversion of syngas to light olefins (STO) over metal oxide-zeolite (OX-ZEO) bifunctional catalyst has aroused wide interest. However, due to unmatched reaction temperature for CO conversion to oxygenated hydrocarbons over metal oxide (200–300 °C) and C−C coupling reaction over zeolite (350–450 °C), it is still a great challenge to achieve both high light olefins selectivity and high CO conversion; moreover, the reaction mechanism needs to be further studied. Herein, the Ga-Zr oxide is taken as a probe oxide to mix with SAPO-34 zeolite for STO. A high light olefins selectivity of 88.6% is achieved at an extremely high CO conversion of 51.6% with a stable activity for 200 h. The incorporation of Ga into ZrO2 generates the GaZrOx solid solution structure with abundant concentration of oxygen vacancy and hydroxy group, the strong synergetic effect between Ga and Zr in GaZrOx benefits the CO activation and CH3O* formation at high temperatures (280–430 °C), providing a compatible temperature match for C−C coupling over SAPO-34. The GaZrOx is a promising and potential catalyst for industrial application in direct conversion of syngas to olefins, aromatics, and liquid fuels.

Direct conversion process from syngas to light olefins - A process design study

The scope in this project is the design of a synthesis gas to light olefins (C2, C3) process including a technical and economical evaluation. The challenges in this project are to find a catalyst for the direct conversion to light olefins and to implement this in a process. New and promising concepts for reaction and separation are evaluated and compared to proven technologies. An iron catalyst with MnO and K2O promoters has been selected to catalyze the reaction towards olefins. The CO conversion is sufficiently large (90.4 mole%), but the selectivity towards C2-C3 olefins is only 49.7 mole%. The process is designed according to the systematic process synthesis techniques. The design of the reactor and the separators have been developed. An inlet of 500 t/h syngas yields 47 t/h ethylene and 51 t/h propylene. This is in total 98 t of desired product per hour. The rest of the inlet stream is converted to H2O (226 t/h), CO2 (67 t/h) CH4 (52 t/h) and 56 C4 and alifatics. A large amount of reactant is converted into byproducts. An economic evaluation based on market prices for products and raw materials shows a positive result. Further research can make the process more attractive. The carbon efficiency is too low (CO2 and CH4 are produced) and should be increased by improving the catalyst. The available catalyst data such as selectivity, conversion and lifetime is limited and should be subject of further research.