Complete Liquid-phase Technology Research Articles

Ethanol synthesis from syngas over Cu/Zn/Al-B catalysts: The promoting effect of boron

ABSTRACT Ethanol synthesis from syngas was studied over Cu/Zn/Al catalysts promoted with different B contents using the complete liquid-phase technology. It is found that ethanol selectivity is strongly influenced by B content. When the B content is 6.0 wt%, the ethanol selectivity is the highest (37.6%). The characterization results indicated that a suitable B promoter prevents the growth of copper particles, strengthens the interaction between Cu and Al or Zn species, increases the relative amount of Cu2O on the catalysts surface, and keeps the balance of Cu+–Cu°.

Higher alcohols synthesis via CO hydrogenation on Cu/Zn/Al/Zr catalysts without alkalis and F–T elements

A series of Cu/Zn/Al/Zr catalysts without alkalis and F–T elements, were prepared with various atomic ratios of Al/Zr by complete liquid-phase technology and tested for higher alcohols synthesis from CO hydrogenation. The results showed that the Cu/Zn/Al catalyst exhibited excellent higher alcohols selectivity, reaching approximately 58.8%. With the increase of Zr/Al atomic ratio, the catalytic activity and stability increased, but methanol became the dominant product in the liquid products over Cu/Zn/Zr catalyst. It was concluded that Al favored the formation of higher alcohols and Zr was beneficial to improve the stability of catalysts. Characterization results showed that the addition of Zr improved the dispersion of Cu and made the catalyst easier to be reduced. It also favored the stability of pore structure and decreased the amount of weak acidic sites. It was also found that the amount of the weak acidic sites played a key role in the higher alcohols formation and the amount of weak acidic sites decrease might lead to the deactivation of catalysts.

Influence of acidic and alkaline silica sols on the performance of Cu/Zn/Al slurry catalysts

A series of Cu/Zn/Al/Si slurry catalysts were prepared using acidic and alkaline silica sols by the complete liquid-phase technology. The samples were characterized with XRD, H2-TPR, FT-IR, BET, NH3-TPD, XPS and TEM techniques. Addition of acidic silica sol to the catalyst gave the highest CO conversion and dimethyl ether (DME) selectivity, being 65.38% and 76.26% respectively. The acidic silica sol weakens the interaction between Cu and other components, resulting in a rapid reduction of Cu species and exposure of more active lattice planes of Cu0. In addition, the acidic/alkaline properties of silica sol also influence the number and the strength of acid sites in the sample. It was found that both the strong and the weak acid sites decreased in the strength. The acidic silica sol significantly increased the weak acid sites, mesopores and specific surface area, consequently promoting the methanol dehydration and increasing the DME selectivity.

The facile preparation of Cu–Zn–Al oxide composite catalysts with high stability and performance for the production of dimethyl ether using modified aluminum alkoxide

Modified aluminum alkoxide prepared by alcoholysis was used as an aluminum source in the complete liquid-phase technology for the preparation of slurry catalysts. The use of the modified aluminum alkoxide afforded control over the rate of the hydrolysis/condensation reactions during the preparation of the catalyst precursors, thereby generating catalysts with a fine nano-structured active metal and metallic oxide particles. Four types of Cu–Zn–Al (molar ratio is 2:1:4) catalysts were prepared using different procedures. These catalysts were tested for CO hydrogenation at 553K, 4.0MPa and H2/CO=1.0 in a kettle with a mechanical agitator. The results indicated that the activity of the catalysts was greatly dependent on the rate of the hydrolysis/condensation reactions, and the catalyst with the best catalytic performance was obtained by controlling the hydrolysis/alcoholysis rate during catalyst synthesis by pre-alcoholysis of AIP as the aluminum source, over which the CO conversion and dimethyl ether selectivity could reach 62.6% and 62.5%, respectively.

Experimental and Theoretical Studies of Ethanol Synthesis from Syngas over CuZnAl Catalysts without Other Promoters

Ethanol synthesis from syngas over CuZnAl catalyst without other promoters is studied using theoretical and experimental methods. The possible reaction paths of the ethanol synthesis in thermodynamic and dynamic over Cu cluster and Cu–O species adsorbed on ZnO surface are systematically identified at the molecular level. Three possible paths involving the formation of CH3 as the key intermediate are proposed, which are COH, CHOH, CH2OH, and CH3; CHO, CH, CH2, and CH3; and CH3OH and CH3. CO insertion into the CH3 intermediate produces CH3CO, which is further hydrogenated to yield CH3CHO and CH3CHOH and finally obtain ethanol. The CuZnAl catalyst, which is prepared by complete liquid-phase technology, has high ethanol selectivity and stability because of the strong interaction between Cu species and ZnO. In summary, the coexistence of both Cu0 and Cu+ is necessary for ethanol synthesis from syngas over CuZnAl catalyst without other promoters.

Preparation and characterization of nonmetal promoter modified CuZnAl catalysts for higher alcohol from synthesis gas through complete liquid phase method

A complete liquid phase technology and a function regulator were applied to prepare CuZnAl catalysts for higher alcohol synthesis. Characterizations showed that the introduction of the function regulator can change the reduction ability of copper oxides and the surface basicity of catalysts. Activity tests indicated that the selectivity of higher alcohol is high when considerable medium-strong basicity and the synergistic effects of copper ion and metal copper exist on the catalytic surface. The optimized modified CuZnAl catalyst without any metal additives provides a CO conversion of 28.9%, C2+OH selectivity of up to 42.8%, and hydrocarbon selectivity of 2.5%, with a total alcohol selectivity of 67.4% under the reaction conditions of 5.0 MPa, 250 °C, H2/CO = 1, and a gas hourly space velocity of 360 mL/gcat h.

Ethanol Synthesis from Synthesis Gas Over Complexing Agent Modified Cu-ZnO/Al2O3 Prepared by Complete Liquid-Phase Technology

Complexing agents were introduced to Cu-ZnO/Al2O3 catalysts prepared by complete liquid-phase technology. Characterization shows that the introduction of appropriate proportion of complexing agents can stabilize copper ions and increase the catalystic surface basicity. As a result, the selectivity of ethanol was enhanced in the CO hydrogenation reaction. Activity tests indicate that the Cu-ZnO/Al2O3 catalyst effectively catalyzed syngas conversion to ethanol in a slurry reactor, while CO conversion of 17.0%, ethanol selectivity of 24.5% reached under the reaction conditions of 250°C, 5.0 MPa, H2/CO = 1, gas hourly space velocity of 360 ml/(g cat · h) and without alkali metals promoter.

The effect of CuO–ZnO–Al2O3 catalyst structure on the ethanol synthesis from syngas

CuO–ZnO–Al2O3 catalysts were prepared by complete liquid phase technology with different addition sequences. The results indicated that the catalyst prepared by the addition of (C3H7O)3Al to Cu(NO3)2 and Zn(NO3)2 solutions shows excellent ethanol selectivity at the initial stages of reaction, reaching approximately 40%. X-ray photoelectron spectroscopy results showed that ethanol synthesis requires a higher Cu+ content and higher Cu/Zn ratio on the catalyst surface. The temperature-programmed reduction test revealed strong interactions between Cu species and zinc or aluminum oxide. The increase in the difficulty of catalyst reduction indicated higher ethanol selectivity.

Synthesis of AlOOH slurry catalyst and catalytic activity for methanol dehydration to dimethyl ether

AlOOH slurry catalysts were prepared by complete liquid-phase technology from aluminum iso-propoxide (AIP). Dehydration of methanol to dimethyl ether (DME) over these catalysts was investigated in slurry reactor. The catalysts were characterized by X-ray diffraction (XRD), nitrogen adsorption, temperature-programmed desorption of ammonia (NH 3–TPD). The results showed that the slurry catalysts had high specific surface area and pore volume, and the specific surface area and the strength of weak acidic sites were influenced considerably by the molar ratio of H 2O/AIP and HNO 3/AIP. Activity tests indicated that AlOOH slurry catalysts had excellent catalytic activity and stability in slurry reactor for the dehydration of methanol to dimethyl ether, and the activity correlated well with the strength of weak acidic sites of catalysts, which can be controlled by changing the H 2O/AIP and HNO 3/AIP molar ratios. The average methanol conversion at even stage reaches nearly 80% and DME selectivity almost 100% over CAT-P1 catalyst. No deactivation was found during the reaction of 500 h. It is also expected that CAT-P1 becomes a promising methanol dehydration catalyst for the STD process based on CuZuAl methanol synthesis catalyst.

Effect of La and Mn Promoters on Structure and Performance of CuZr Catalyst Prepared by Complete Liquid-Phase Technology

Effect of La and Mn Promoters on Structure and Performance of CuZr Catalyst Prepared by Complete Liquid-Phase Technology

Effect of Carbon Promoters on the Performance of Cu-Zn-Al Catalyst Prepared by Complete Liquid-Phase Technology

Cu-Zn-Al slurry catalysts were prepared by a complete liquid-phase technology and characterized by X-ray diffraction,N2 adsorption,H2 temperature-programmed reduction,and NH3 temperature-programmed desorption.The effects of carbon nanotubes and carbon microspheres as promoters on catalyst performance for alcohol synthesis were investigated.The results indicated that the Cu-Zn-Al methanol synthesis catalysts showed activity for the synthesis of higher alcohols and hydrocarbons.Cu0 particles with larger grain size were conducive to the growth of carbon chains.Adding carbon microspheres can significantly decrease the size of Cu0 particles and improve the selectivity for methanol.

Synthesis of methanol and ethanol over CuZnAl slurry catalyst prepared by complete liquid-phase technology

A new method, named the complete liquid-phase technology, has been applied to prepare catalysts for methanol synthesis. Its main innovative thought lies in preparing slurry catalysts directly from raw solution. Activity tests indicate that the CuZnAl slurry catalyst prepared by the new method can efficiently catalyze conversion of syngas to ethanol in a slurry reactor, while CO conversion reaches 35.9% and ethanol selectivity is more than 20%, with a total alcohol selectivity of more than 87%. No deactivation was found during the 192 h reaction.

The Dehydration of Methanol to Dimethyl Ether over a Novel Slurry Catalyst

A novel slurry catalyst for dehydration of methanol was prepared by complete liquid-phase technology. Its main innovative thought lies in preparing the slurry catalysts directly from solution. The catalysts were characterized using X-ray diffraction, Brunauer–Emmett–Teller, and NH3-TPD. It was found that the main crystal phase of slurry catalyst was boehmite AlO(OH). Also, it was observed that slurry catalyst had a high surface area and pore volume. Activity tests indicated that the slurry catalyst has shown better performance compared to the commercial γ-Al2O3: the highest methanol conversion was 84.4% at the temperature of 280°C, dimethyl ether selectivity nearly reached 100%. The catalyst showed a good stability during the long-term test of 500 h.