CeO2 is an excellent potential material for CO2 hydrogenation attributed to the highly tunable properties including metal–support interaction and abundant oxygen vacancy. In this work, four CeO2 supports with structurally well-defined different shapes and crystal facets are hydrothermally prepared, and their effects on the composition of Pd species and oxygen vacancy over Pd/CeO2 catalysts have been intensively investigated in the reduction of CO2 to methanol. The 2Pd/CeO2-R (rods) shows the highest concentration and number of oxygen vacancies, where the (110) facet with high surface oxygen mobility and low oxygen vacancy formation energy is exposed over the CeO2-R surface. The oxygen mobility at the interface of (111) and (100) facets mainly observed on 2Pd/CeO2-P (polyhedrons) is higher than the single (111) and (100) facets mainly observed on 2Pd/CeO2-O (octahedrons) and 2Pd/CeO2-C (cubs), respectively. The presence of Pd highly promotes the formation of oxygen vacancies by providing dissociated H atoms to facilitate the removal of surface O in ceria support under a H2 atmosphere. Both the Pd x Ce1–x Oδ solid solution dominated on CeO2-R and the PdO species dominated on CeO2-O are reduced to metallic Pd after reduction with 6–10 nm average particle size. As revealed by density functional theory (DFT) calculations, in contrast to the single Pd0 atom on CeO2 and the thermodynamically most unstable Pd x Ce1−x Oδ solid solution, the Pd0 nanoparticles are the most stable species under the realistic reaction conditions. The 2Pd/CeO2-R shows the highest catalytic activity as the abundantly available oxygen vacancies function as CO2 adsorption and activation sites. Moreover, oxygen vacancy reactivity is correlated with its formation energy. The lower formation energy facilitates the formation of oxygen vacancy; however, the reactivity of each oxygen vacancy is lower as the TOFoxygen vacancy of 2Pd/CeO2-O is 15 times as that of 2Pd/CeO2-R. Thus, a suitable oxygen vacancy formation energy is likely favorable for enhancing CO2 reactivity. DFT calculations indicate that the CH3OH formation is most probably from the formate (HCOO*) pathway via the C–O bond cleavage in H2COOH*, with the reduction of HCOO* to HCOOH* as the rate-limiting step. These results would provide experimental and theoretical insights into the rational design of an effective catalyst for CO2 hydrogenation.

A composite Na/Fe and SiO2-coated HZSM-5 catalyst system has been developed for the highly selective production of aromatics (93–95%), especially para-xylene, in the liquid phase and light olefins in the gas phase from CO2.

The conversion efficiency of CO2 in CO2-FTS over Fe-based catalysts is significantly enhanced by driving the conversion of the CO intermediate via the FTS reaction over a second kind of FT component, Co or Ru, without WGS activity.

No abstract

Palladium particles of different sizes obtained directly and indirectly by various methods were studied to clarify the particle size effect in the selective hydrogenation of cinnamaldehyde (CAL).

A desired selectivity to lower olefins has been achieved by combination of K and S promoters.

No abstract

Iron-based Fischer-Tropsch (FT) synthesis in combination with hydroisomerization in the presence of zeolitesfor the synthesis of isoparaffins from CO 2 /H 2 wasc onducted in af ixed-bed reactor.R elative to supported iron catalysts,t he precipitated one efficiently converted intermediate CO into hydrocarbonsb y supplying ah igh density of FT active sites on the catalyst surface. Removing water by interstage cooling and promoting the CO conversion step in the FT synthesis were effective approaches in achieving ah igh CO 2 conversion,b ecause of an increase in the driving force to the reaction equilibrium. Particle mixing of 92.6 Fe7.4 Kw ith either 0.5 Pd/b or HZSM-5z eolite effectively hydroisomerized the resulting FT hydrocarbons into gasoline-range isoparaffins. Particularly,H ZSM-5d isplayed ah igher isoparaffin selectivity at approximately 70 %, which resulted from easier hydrocracking and hydroisomerization of the olefinic FT primary products.The high energy density and ease of transport of gasoline and other liquid hydrocarbons have made them the mainstay of the world's transportation infrastructure. Although researchers continuet op ursuet he use of low-carbon gases such as methane and hydrogen as transportation fuels ande ven though electric cars are proliferating, there is no good alternative to liquid fuels for long-distancet rucks and other heavy vehicles, as well as aviation.[1] Given the limited availability of crude oil and the conversion of coal into synthetic liquid fuelb ys yngas (a mixtureo fCOand H 2 )followed by Fischer-Tropsch synthesis (FTS), [2][3][4][5][6][7][8][9] this dependence poses major security and environmental problems.[10] Arguably, the conversion and utilization of such carbon-rich fossil fuels are the main contributors to the emission of the greenhouseg as CO 2 ,w hichl eads to climate change.[11] Reducing CO 2 emissions must indeed be an urgent and long-term task for sustainable development in the energy and environmentals ectors. [12,13] It has been confirmedf or many years that the hydrogenationr eactioni sa mongst the most important chemical conversionso fh ighly concentrated CO 2 . [11,14] However,w epoint out that, authentically, to realize the recycling of CO 2 ,h ydrogen sources cannotb eg enerated by remaining fossil fuels but from splitting water by electrolysis or othercleavage reactions. [15][16][17][18][19] The aim to reach CO 2 production of fuels has prompted some researchers to focus on FTS by using CO 2 in place of CO. [20][21][22][23][24][25][26] Iron catalysts are no doubt the bestc hoice for CO 2 -based FTS, because they also catalyze the reversew ater-gas shift (RWGS)r eactiont oc leave one of the oxygen atoms in CO 2 to make CO [Eq. (1)].T he CO thus generated can then be combined with H 2 to make acombination known as renewable syngas, whichc an be converted into hydrocarbonsb yF TS [Eq. (2)].A st he chain propagation mechanism of FTS is to synthesize aw ide distribution of normalh ydrocarbons unsuitable as gasoline fuel, it is desired that ah ighly selec...