Catalytic behaviors of copper phosphide supported on various oxides (SiO2, γ-Al2O3, and USY zeolite) have been evaluated for deoxygenation of oleic acid and compared with nickel and cobalt ...phosphides. All catalysts were prepared by the hydrogen reduction of metal phosphate precursors. CoP and Ni2P were obtained on USY zeolite, while Cu3P was formed on USY and SiO2 supports. On the contrary, the metallic Cu phase was stabilized on γ-Al2O3 support. Metal phosphide particles were highly dispersed on the USY support. Cu3P/USY exhibited much larger surface area and higher acidity compared to Cu3P/SiO2, owing to the textural and acidic properties of the USY zeolite support. All supported catalysts gave an oleic acid conversion close to 100% at 340 °C. Ni2P/USY, CoP/USY, and Cu/γ-Al2O3 favored the deoxygenation of oleic acid to alkane products such as heptadecane and octadecane. Highly selective production of octadecane (98%) through hydrodeoxygenation pathway occurred on Cu/γ-Al2O3. In contrast, the supported Cu3P catalysts favored cyclization and aromatization to form cyclic and aromatic compounds such as dodecylcyclohexane, heptylcyclopentane, and dodecylbenzene. Cu3P/SiO2 provided dodecylbenzene in higher yield (46%) than Cu3P/USY (33%).
Oxidative coupling of methane (OCM) is a reaction to directly convert methane into high value-added hydrocarbons (C2+) such as ethylene and ethane using molecular oxygen and a catalyst. This work ...investigated lanthanum oxide catalysts for OCM, which were promoted with alkaline-earth metal oxides (Mg, Ca, Sr, and Ba) and prepared by the solution-mixing method. The synthesized catalysts were characterized using X-ray powder diffraction, CO2-programmed desorption, and X-ray photoelectron spectroscopy. The comparative performance of each promoter showed that promising lanthanum-loaded alkaline-earth metal oxide catalysts were La-Sr and La-Ba. In contrast, the combination of La with Ca or Mg did not lead to a clear improvement of C2+ yield. The most promising LaSr50 catalyst exhibited the highest C2+ yield of 17.2%, with a 56.0% C2+ selectivity and a 30.9% CH4 conversion. Catalyst characterization indicated that their activity was strongly associated with moderate basic sites and surface-adsorbed oxygen species of O2 –. Moreover, the catalyst was stable over 25 h at a reactor temperature of 700 °C.
In the present study, a thermodynamic analysis of the autothermal reforming of dimethyl ether (DME) for the production of hydrogen was carried out. The results clearly indicated that the carbon ...formation behavior, the boundary conditions between coke-free and coking regions, and the equilibrium composition of the reformate were dependent on the steam/DME ratio, O
2/DME ratio, temperature, and pressure of the system. For instance, carbon formation was effectively suppressed as the steam/DME ratio increased from 0 to 5, the O
2/DME ratio increased from 0 to 3, or the temperature rose from 100 to 1000
°C. In contrast, carbon formation was enhanced as the pressure was increased from 0.5 to 10
atm. The boundary temperature of coke-free operation decreased with an increase in the steam/DME and O
2/DME ratios. More specifically, at a steam/DME ratio of 3–5 and an O
2/DME ratio of 0–3, the boundary temperature ranged from 50 to 280
°C (when CH
4 formation was promoted) and 380 to 670
°C (when CH
4 formation was suppressed), respectively. Furthermore, at elevated temperatures, H
2 and CO formations were enhanced, and CH
4 formation was inhibited. The addition of steam enhanced H
2 production while reducing CO formation. On the contrary, an increase in the O
2/DME ratio reduced H
2 production while enhancing CO formation. Interestingly, the desired temperature for thermo-neutral condition, in which energy consumption was zero, can be achieved by correctly controlling the O
2/DME and steam/DME ratios.
► The temperature of coke-free operation decreased with an increase in the steam/DME and O
2/DME ratio. Namely, at a steam/DME ratio of 3–5 and an O
2/DME ratio of 0–3, the temperature ranged from 50 to 280
°C (favoring CH
4 formation) and 380 to 470
°C (unfavorable for CH
4formation), respectively. ► The elevated temperatures and steam/DME ratios, but O
2/DME ratios increased H
2 formation. The thermo-neutral conditions can be achieved at appropriate steam/DME and O
2/DME ratios.
A simple thermal treatment remarkably enhances the activity and durability of CuFe2O4–Al2O3 composite catalysts in reforming dimethyl ether for hydrogen production. The most effective treatment ...temperature range is 700 to 800 °C. The active phase, CuFe1.5Al0.5O4 formed through a solid‐state reaction between CuFe2O4 and Al2O3, and the original phase, CuFe2O4, contribute synergistically to the enhancement.
Effects of Ni doping on the catalytic behavior of Cu x Ni1−x Fe2O4 (x = 1, 0.95, 0.90, 0.50) mixed with Al2O3 were investigated in steam reforming of dimethyl ether for hydrogen production. The ...stability of the catalyst was significantly enhanced by doping Ni species to CuFe2O4. Formation of CuNi alloy was confirmed as the amount of Ni addition increased. The suppression of the sintering rate was clearly evidenced over Ni-doped catalysts as compared with the undoped one, while the effect on carbon deposition rate was unclear. Nevertheless, an increasing amount of Ni dopant to Cu−Fe spinel retarded the conversion of dimethyl ether and led to high selectivity to CH4 and CO.
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•The crystallinity was significantly improved after NaOH treatment.•The NaOH treatment yielded a positive result on the textural properties.•The glycerol conversion boosted over the ...NaOH treated sample.
One of the most potential byproducts of transesterification that has been produced in a large amount is glycerol. Converting glycerol into Solketal via catalytic acetalization using natural zeolites is an interesting route to improve its economic value. Natural zeolites are abundant and inexpensive catalysts with low crystallinity and surface area. Thus, modification of its properties is required to improve material characteristics and alter the transesterification reaction. Investigation of the effect of NaOH concentration treatment on the Bayah natural zeolite was performed from 0.1 to 0.4 M NaOH at 65 °C and 30 min of mixing. Physical characteristic analysis, such as X-ray diffraction, proves that natural zeolite from Bayah was identified predominantly as clinoptilolite. The crystallinity significantly improved after NaOH treatment and could reach a high crystallinity material at 0.4 M NaOH. The textural properties using nitrogen physisorption are also shown by a high surface area of 164 m2/g (from parent Z-0.4; 19 m2/g). In addition, the mesopore volume also improved after alkali treatment, increasing the mass transfer of molecules. The application of modified natural zeolite for glycerol acetalization was tested in a glass tube reactor at a temperature of 50 °C for 90 min showing a significant alteration in conversion from 3.5 % (parent zeolite) to 90.4 % (modified zeolite).
Influences of solid–acid catalyst on dimethyl ether steam reforming (DME SR) and DME hydrolysis for hydrogen production were investigated. Series of zeolite (JRC-ZHM20(5), JRC-ZHM90(1) as H-mordenite ...type and JRC-Z5-90H(1) as ZSM-5 type) and of alumina (ALO8, TA1301, TA3301, DK503, NKHD24, NKHO24 and NK324) were used as acidic catalysts for DME hydrolysis. The composite catalysts of the acidic catalyst and CuFe
2O
4 spinel catalyst were employed for DME SR. DME SR activity strongly depended on the acidic catalyst that is active for DME hydrolysis. The hydrolysis of DME, the rate-determining step in DME SR, is equilibrium-controlled. Zeolite exhibited high activity for DME SR at a low temperature range of 200–275
°C, since the hydrolysis could effectively proceed over strong BrØnsted acid-sites approaching its equilibrium. Alumina possessing Lewis acid-sites was active for DME hydrolysis in the higher temperature range from 275 to 450
°C. CO
2 and CO with relatively small amounts of CH
4 were found as primary carbon-containing compounds when alumina was used as the acidic catalyst. In the case of zeolite, besides those carbon compounds, C
3H
8,
i-C
4H
10, and
n-C
4H
10 were detected during SR and hydrolysis of DME. It was found that not only the acid amount of the acidic catalysts, but also the acid strength and the type of acid-site definitely affected the steam reforming and hydrolysis activity. γ-Alumina (ALO8) mixed with CuFe
2O
4 exhibited the highest DME conversion and hydrogen production with optimum reforming temperature at 350–375
°C. Stable activity for DME hydrolysis was attained over ALO8 with high durability for 25
h.
In the present work, the solvent-free hydrodeoxygenation of palm oil as a representative triglyceride model compound to diesel-like hydrocarbons was evaluated in a batch reactor using Pt-decorated ...MoO2 catalysts. The catalysts with various Pt loadings (0.5–3%) were synthesized by an incipient wetness impregnation method. The metallic Pt and MoO2 phases were detected in the XRD patterns of as-prepared catalysts after the reaction and acted as active components for the deoxygenation reactions. The XPS experiments confirmed the existence of metallic Pt and PtO x species. The XANES investigation of Mo L3-edge spectra elucidated a change in the valence state by the transformation of MoO3 into MoO2 species after the deoxygenation reaction. The TEM observation revealed the formation of Pt nanoparticles in the range of 1–3 nm decorated on MoO2 species. The number of acid sites increased with stronger metal–support interactions on increasing the Pt loading. The catalytic performance of the MoO2 catalyst significantly improved with a small amount of Pt decoration. However, the further increase in Pt loading did not relatively increase the deoxygenation activity due to the formation of the agglomerated Pt particles. The high performance of the decorated catalysts could be attributed to the moderate acidity from the Pt dispersed on MoO2 toward decarbonylation and decarboxylation reactions.
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