Search

[Display omitted] • The adsorption energies of CO 2 on the surface oxygen vacancies of different crystalline In 2 O 3 were calculated using DFT. • The effect of the spatial distributions of two active components on the CO 2 hydrogenation to aromatics was studied. • The acidity of catalyst under different spatial distributions was studied through NH 3 -TPD. In tandem catalysts, not only good synergy between the two active components is required, but also the precise control of the spatial distribution between the two active components of metal oxides and zeolite is crucial for the migration and conversion of reaction intermediates in the direct conversion of CO 2 to hydrocarbons. The correlation between the metal and the acidic site of zeolite has traditionally been simplified as "the closer, the better". However, it should be noted that this principle only holds true for a portion of tandem catalysts. Therefore, this paper studied the effect of different crystalline In 2 O 3 (cubic phase, hexagonal phase, and mixed cubic/hexagonal phase) and sheet HZSM-5 zeolite tandem catalysts on the activity of CO 2 hydrogenation reaction under different spatial distribution. The generalized gradient approximation (GGA) of density functional theory (DFT) were used to simulate the adsorption energy of CO 2 by oxygen vacancy on c-In 2 O 3 (1 1 1) and h-In 2 O 3 (1 0 4) planes, it was found that O v1 on c-In 2 O 3 (1 1 1) and O v4 on h-In 2 O 3 (1 0 4) had the strongest adsorption energy for CO 2. In addition, it has been observed that the proximity of the two active components (e.g., during mortar mixing) results in decreased catalytic performance. This is due to the migration of metal In, which neutralizes the acid sites of zeolites and leads to inefficient conversion of methanol reaction intermediates to aromatics. As a result, CO 2 conversion and aromatic selectivity are decreased. [ABSTRACT FROM AUTHOR]

Promoting the activity of catalyst, achieving high CO2 conversion and increasing light olefins yield are important in CO2 hydrogenation to olefin. Herein, SiO2 was doped in CuO‐ZnO‐ZrO2 to form multi‐oxides of CuO‐ZnO‐ZrO2‐SiO2 by co‐precipitation method, and the multi‐oxides was mixed with SAPO‐34 molecular sieves mechanically to form a composite catalyst of CuO‐ZnO‐ZrO2‐SiO2/SAPO‐34. Compared with CuO‐ZnO‐ZrO2, doping of SiO2 increases the dispersion and thermal stability of metal oxides, provides more sites for CO2 activated, and delays the aggregation of metal particles at higher temperature. Doped SiO2 can also adsorb the water from hydrogenation process to improve the olefins yield and hinder the formation of CO from reverse water gas shift. Thus, under the condition of reaction temperature at 420 °C, pressure of 3.0 MPa, space velocity of 1800 mL gcat−1 h−1, CO2/H2 (molar ratio) of 1 : 3 and the mass ratio of CuO‐ZnO‐ZrO2‐SiO2 (containing 8 % SiO2) to SAPO‐34 of 1 : 1, the direct CO2 hydrogenation to light olefins on CuO‐ZnO‐ZrO2‐SiO2/SAPO‐34 shows that the conversion of CO2 is 53.9 % and the selectivity of light olefins is 52.9 %, while the CO selectivity is only 13.6 %. [ABSTRACT FROM AUTHOR]

Hydrogenation of CO 2 to aromatics follows the formic acid-methoxy pathway over xIn-yZr(T) solid solution and sheet HZSM-5 tandem catalysts. [Display omitted] • The addition of Zr are conducive to the formation of oxygen vacancy of In 2 O 3 surface. • Zr carrier promotes the adsorption of CO 2 by In 2 O 3 (1 1 1). • Hydrogenation of CO 2 to aromatics follows the formic acid-methoxy pathway over xIn-yZr(T) solid solution and sheet HZSM-5 tandem catalysts. The presence of acids and bases, coupled with its exceptional CO 2 adsorption capacity and thermal stability, has established zirconia as a highly esteemed promoter and carrier. Researchers have found that the In 2 O 3 supported ZrO 2 exhibits high activity and remarkable stability. Therefore, xIn-yZr(T) solid solutions were prepared with different calcination temperatures and In/Zr molar ratios. The solid solutions were then combined with sheet HZSM-5 zeolite from tandem catalysts, which were investigated for their catalytic performance in converting CO 2 to aromatics. The X-ray diffraction, scanning electron microscopy, N 2 adsorption-desorption, NH 3 temperature-programmed desorption, pyridine infrared radiation, X-ray photoelectron spectroscopy, electron paramagnetic resonance, CO 2 temperature-programmed desorption and H 2 temperature-programmed reduction characterization methods were used to investigate the physicochemical properties of catalysts. Density Functional Theory calculations were used to investigate the energy of thermal desorption and H 2 reduction to generate oxygen vacancies on the surface of In 2 O 3 (1 1 1) and Zr/In 2 O 3 (1 1 1). Additionally, the influence of oxygen vacancies on CO 2 adsorption energies was simulated. It was found that the incorporation of a moderate amount of zirconium carriers promoted the generation of oxygen vacancies and provided better metal-carrier interactions. The 4In-1Zr(500 °C)/HZSM-5 tandem catalyst exhibits excellent catalytic stability, achieving a CO 2 conversion of 24.3 % and aromatics selectivity of 37.3 %. [ABSTRACT FROM AUTHOR]

Propane dehydrogenation to propene is an endothermic reaction and CO2 hydrogenation to light olefins is an exothermic reaction. Using the CO2 hydrogenation reaction to consume the hydrogen from the propane dehydrogenation reaction, which is more favorable to propylene formation. A new method for coupling propane and CO2 to propylene is presented. The V–Fe modified KIT-6 was prepared by the ultrasonic-assisted impregnation method and used for coupling reaction of propane with CO2 to propylene. Exploring the relationship between catalytic properties and physicochemical characteristics through several characterization methods. As the appropriate amounts of V and Fe species were introduced into the framework of KIT-6, V–Fe modified KIT-6 performed large specific surface area, a highly ordered mesoporous structure and highly dispersed V and Fe active sites. The catalysis performance of V–Fe modified KIT-6 zeolites for production of propylene by propane dehydrogenation, CO2 hydrogenation and coupling reaction of C3H8 with CO2 was compared. Under the conditions of C3H8/CO2/N2 = 1:4:5, total flow rate = 20 mL/min, the temperature at 580 °C, the reaction pressure at 0.1 MPa, V/Fe molar ratio = 2 and the catalyst mass of 0.2 g, the propane conversion, propylene selectivity and yield are 37.8%, 87.0% and 32.9%, respectively. [ABSTRACT FROM AUTHOR]

Palygorskite was used as a silicon and partial aluminum source to prepare SAPO-34 molecular sieves using diethylamine, triethylamine, morpholine and tetraethylammonium hydroxide as templates. The synthesized SAPO-34 molecular sieves were characterized by using the methods of XRD, SEM, EDS, BET, FT-IR, NH 3 -TPD, H 2 -TPR and TG. Composite catalysts of CuO-ZnO-Al 2 O 3 /SAPO-34 were prepared by mechanically mixing SAPO-34 molecular sieves with CuO-ZnO-Al 2 O 3 and were used in the direct synthesis of light olefins via CO 2 hydrogenation. The results showed that SAPO-34 molecular sieves prepared by acid-treated palygorskite using tetraethylammonium hydroxide as a template had a higher specific surface area, a greater CO 2 conversion rate and higher light olefin selectivity. The CO 2 conversion rate reached 53.5%, the light olefin selectivity reached 62.1%, and the yield reached 33.2% when the reaction conditions were as follows: reaction temperature 673 K, reaction pressure 3.0 MPa, volume ratio of CO 2 /H 2 1:3 and 0.5 g composite catalyst. • SAPO-34 molecular sieves were synthesized using palygorskite as raw material. • CuO-ZnO-Al2O3/SAPO-34 catalyst was used in CO2 to light olefins reaction. • The prepared SAPO-34 molecular sieves exhibited excellent selectivity of light olefins. [ABSTRACT FROM AUTHOR]