Role of zirconium in direct CO2 hydrogenation to lower olefins on oxide/zeolite bifunctional catalysts

A Critical Look at Direct Catalytic Hydrogenation of Carbon Dioxide to Olefins

“…[96] Excellent reviewsonthe advances in CO 2 hydrogenation to hydrocarbons, alkanes, and alcohols are available, covering the methanol-mediated route, amongo ther strategies in the period until 2017. [98] Synergy between both phases decreases CO selectivity,t herebyi ncreasing olefin selectivity.T he desired synergy is achievedi ft he components are in close contact. The metal oxide component of the bifunctionalc atalystisr esponsible for CO 2 conversion to methanoland the zeolitecomponent is responsible for further methanol conversion through selective CÀCc oupling.…”

“…[37,97] Herein, we focus on recent reports on this topic (2017-2018). [87,98] Metal oxides and zeolites are usually incorporated togetheri n the reactor;thus forming aphysical mixture obtained by physical grinding( mortar-mixing method or shaking method). [98] Synergy between both phases decreases CO selectivity,t herebyi ncreasing olefin selectivity.T he desired synergy is achievedi ft he components are in close contact.…”

“…The Cu/ZnO/Al 2 O 3 system currently employed for methanol synthesis from mixed syngas exhibitslimited activity in CO 2 hydrogenation, so it is not ag ood candidate. [98] These new oxygen vacancies can stabilizet he key intermediates,d ecreasing the amount of the side product CO. [93,98] However, the presenceo f > 40 %C Oi nt he product mixture is still ap roblem in this type of reaction. These studies indicate that the oxygen vacancies of In 2 O 3 and Ga 2 O 3 may be the catalytic sites at which CO 2 is activated and hydrogenated to methanol.…”

“…[93] The authors showedt hat the incorporation of Zr into In 2 O 3 created new kinds of vacancies that enhanced the activity,r elativet oI n 2 [98] The composite catalystw ith a4 :1 atomic ratio of In/Zn showedt he highest CO 2 conversion (26.2 %);7 4.5 %l ower olefins were obtained among the hydrocarbons, resulting in aO /P ratio of 3.5. [93] The authors showedt hat the incorporation of Zr into In 2 O 3 created new kinds of vacancies that enhanced the activity,r elativet oI n 2 [98] The composite catalystw ith a4 :1 atomic ratio of In/Zn showedt he highest CO 2 conversion (26.2 %);7 4.5 %l ower olefins were obtained among the hydrocarbons, resulting in aO /P ratio of 3.5.…”

“…[119,120] Common deactivation problems, such as coking and thermalsintering, were reported for iron-based catalysts during MFTS CO 2 hydrogenation. [98] SAPO-34 suffers more from coking than ZSM-5 because of itss mallerp ore size. Further carbidization of c-Fe 5 C 2 gives q-Fe 3 C, which is not active in FTS.…”