Catalysts For Alcohol Synthesis Research Articles

Double Metal Cyanides as Efficient Solid Acid Catalysts for Synthesis of β-Amino Alcohols Under Solvent-Free Conditions

A novel application of Fe–Zn double metal cyanide complexes as solid, acid catalysts for regioselective synthesis of β-amino alcohols under solvent-free conditions via ring-opening of epoxides with amines is reported for the first time. The conversion of epoxides to β-amino alcohols is nearly 100%. In the reaction with styrene oxide, regioselective β-amino alcohol formation is higher with aromatic than with aliphatic amines. Strong Lewis acidic Zn2+ ions in the catalyst are probably the active sites in this reaction.

Effect of Zn and Mn Promoters on Copper-Iron Based Catalysts for Higher Alcohol Synthesis

The influences of zinc and manganese promoters on the structure and reaction behavior of CuFe catalyst for higher alcohol synthesis were investigated by N2 adsorption, X-ray diffraction (XRD), H2 temperature-programmed reduction (H2-TPR), in situ diffuse reflectance infrared spectroscopy (DRIFT) and CO+H2 reaction. It was found that the zinc additive suppressed the dispersion of active phases but improved their activation ability towards CO molecule due to the formation of a new spinel phase, ZnFe2O4. The presence of manganese showed a more favorable effect on the dispersion of active phases and then promoted the synergistic effect between copper and iron although the adsorption tendency towards CO declined due to the dilution effect of manganese. Compared with binary CuFe catalyst, CuZnFe catalyst had a higher activity with the decreasing of C2+OH selectivity, and CuFeMn catalyst showed improved total alcohol selectivity although both CO conversion and C2+OH selectivity decreased. The results of the doubly promoted CuFe catalyst evidently indicated the existence of synergistic effect between zinc and manganese, which modified the texture parameters, decreased the reduction temperature of Cu and altered the reduction behavior of Fe. More importantly, the abundance of CO adsorption on the CuFe catalyst was greatly increased due to the co-addition of zinc and manganese. Therefore, the overall catalytic performance of doubly promoted CuFe catalyst was superior to that of the single promoted CuFe catalyst.

K/Ni/β-Mo 2C: A highly active and selective catalyst for higher alcohols synthesis from CO hydrogenation

Nickel and potassium promoted β-Mo 2C catalysts were prepared for CO hydrogenation to higher alcohols synthesis. The results revealed that β-Mo 2C produced mainly hydrocarbons, but the addition of potassium resulted in a remarkable selectivity shift from hydrocarbons to alcohols over β-Mo 2C. Moreover, it was found that potassium enhanced the ability of chain propagation of β-Mo 2C catalyst and led to a higher selectivity to C 2 +OH. The addition of nickel further enhanced higher alcohols synthesis, which showed the optimum at 1/8–1/6 of Ni/Mo molar ratios. The characterization suggested that there might be a synergistic effect of potassium and nickel on β-Mo 2C, which favored the alcohols synthesis. The production of alcohols appeared to be relevant to the presence of Mo 4+ species, whereas the formation of hydrocarbons was closely associated with Mo 2+ and/or Mo 0 species on the surface of β-Mo 2C-based catalysts.

Co-Cu Metal Alloys from LaCo1-xCuxO3 Perovskites as Catalysts for Higher Alcohol Synthesis from Syngas

The specific surface area of ground perovskites is strongly dependent on the synthesis and pretreatment conditions. Calcining the ground LaCo1-xCuxO3-? perovskites at 5000C causes a decrease of their specific surface, but the further reductive pretreatment of the calcined sample in hydrogen leads to only a minor change in the specific surface area.The introduction of extra- and intra-perovskite lattice copper has different effects on the structure stability, reducibility and catalytic properties of LaCoO3 perovskites. Under the same pretreatment conditions the basic structure of both LaCoO3 and Cu2O/LaCoO3 samples is retained at the reduction temperature of 5000C (90 min) while that of Co-Cu based perovskites is completely collapsed producing a high dispersion of bimetallic metals and Co-Cu alloys supported on amorphous La2O3. For a series of LaCo1-xCuxO3 samples, increasing the copper content in the perovskite structure leads to an increase in the metal surface area of the reduced phase. The pretreated catalysts were tested for CO dissociation and for alcohol synthesis from syngas. The results indicated that the copper sites neighboring with cobalt atoms in the reduced perovskites decrease the activity in CO dissociation and increase the rate of higher alcohol synthesis while extra-perovkite lattice copper tends to produce methanol, methane and CO2. The overall activity in syngas conversion and higher alcohol productivity are proportional to the Co-Cu metal surface. The role of dual sites of Co and Cu for the synthesis of higher alcohols is discussed. The catalytic activity and alcohol productivity as well as product distribution depend strongly on reaction temperature and pretreatment conditions. The highest productivity of alcohols in the present study is about 73 mg/gcat/h for sample LaCo0.7Cu0.3O3.

The performances of higher alcohol synthesis over nickel modified K 2CO 3/MoS 2 catalyst

Ni modified K 2CO 3/MoS 2 catalyst was prepared and the performance of higher alcohol synthesis catalyst was investigated under the conditions: T = 280–340 °C, H 2/CO (molar radio) = 2.0, GHSV = 3000 h − 1, and P = 10.0 MPa. Compared with conventional K 2CO 3/MoS 2 catalyst, Ni/K 2CO 3/MoS 2 catalyst showed higher activity and higher selectivity to C 2 +OH. The optimum temperature range was 320–340 °C and the maximum space-time yield (STY) of alcohol 0.30 g/ml h was obtained at 320 °C. The selectivity to hydrocarbons over Ni/K 2CO 3/MoS 2 was higher, however, it was close to that of K 2CO 3/MoS 2 catalyst as the temperature increased. The results indicated that nickel was an efficient promoter to improve the activity and selectivity of K 2CO 3/MoS 2 catalyst.

Co-decorated carbon nanotube-supported Co–Mo–K sulfide catalyst for higher alcohol synthesis

Using chemical reduction-deposition method, a type of metallic cobalt-decorated multi-walled carbon nanotubes, noted as y%(mass percentage)Co/MWCNTs, was prepared. TEM, SEM and XRD measurements demonstrated that the metallic cobalt was evenly coated on the MWCNT substrate, with granule-diameter of the Co x 0 -crystallites of 5–8 nm. Using the y%Co/MWCNTs as support, a type of supported Co–Mo–K sulfide catalysts, noted as x%(Co i Mo j K k )/(y%Co/MWCNTs), for higher alcohol synthesis (HAS) was developed. It was experimentally shown that using the Co-modified MWCNTs in place of simple MWCNTs or activated carbon (AC) as the catalyst support led to a significant increase in activity of CO hydrogenation conversion and improvement in the selective formation of C2+-alcohols. Under the reaction condition of 5.0 MPa, 613 K, CO/H2/N2 = 45/45/10 (v/v) and GHSV = 3600 mlSTPh−1 g −cat. −1 , the observed STY of C1–4-alcohols reached 154.1 mgh−1g −cat. −1 at 12.6% conversion of CO over the 11.6%(Co1Mo1K0.6)/(6.4%Co/MWCNTs) catalyst, which was 1.76 and 2.33 times as high as that (87.7 and 66.1 mgh−1g −cat. −1 ) of the reference systems supported by simple MWCNTs and AC respectively. Ethanol became the predominant product of the CO hydrogenation, with carbon-based selectivity ratio of C2–4-alcohols to CH3OH reaching 3.6 in the products. It was experimentally found that using the Co-modified MWCNTs in place of simple MWCNTs or AC as the catalyst support caused little change in the apparent activation energy for the conversion of CO, but led to a slight increase in the molar percentage of catalytically active Mo-species (Mo4+) in the total Mo-amount at the surface of the functioning catalyst. Based upon the results of TPD investigation, it could be inferred that, under the reaction condition of HAS, there existed a considerably larger amount of adsorbed H-species and CO-species on the functioning catalyst, thus in favour of increasing the rate of a series of surface hydrogenation reactions in HAS.

LaCo 1− xCu xO 3− δ perovskite catalysts for higher alcohol synthesis

Perovskite-type materials LaCoO 3, LaCo 1− x Cu x O 3− δ , and Cu 2O/LaCoO 3 were synthesized by the mechano-synthesis process known as reactive grinding. Their characterization was performed by BET, X-ray diffraction, SEM, O 2-TPD, and H 2-TPR. The partial cobalt substitution by copper in perovskite lattice gives rise to a distorted structure of LaCoO 3 and influences the thermal stability and redox properties of perovskites. Temperature-programmed reduction (TPR) analysis showed a complete reduction of Co 3+, Cu 2+ to metallic state in the temperature range of 310–580 °C. A lower cobalt reduction temperature observed for LaCo 1− x Cu x O 3− δ in comparison to LaCoO 3 produces a finely dispersed bimetal on a La 2O 3 support. Quantitative TPR data showed that cobalt ions in the grain boundaries of the ground perovskites are directly reduced to metals at a relatively low temperature (310–450 °C). The existence of strong cobalt–copper interaction in perovskites could enhance the metallic dispersion of cobalt and prevent copper sintering. The reduced forms of LaCo 1− x Cu x O 3− δ catalysts were tested as alcohol synthesis catalysts in a fixed bed flow reactor system at 275 °C and space velocity of 4000 h −1 (H 2/CO = 2/1). A mixture of C 1–C 7 alcohols with the chain growth propagation factors of 0.34–0.42 was produced. The alcohol productivity is from 36.5 to 49.6 mg/g cat/h and selectivity towards higher alcohols took values in the range of 40–49.5%. The preliminary catalytic data indicated that copper located outside of the perovskite lattice is solely leading to the production of methanol and methane whereas its location in the octahedral position of the perovskite precursor framework is necessary for higher alcohol synthesis. Therefore, a uniform distribution of the metallic cobalt–copper atoms in the prereduced catalysts is crucial for the conversion of carbon monoxide and hydrogen into higher alcohols.

K/Fe/β-Mo 2C: A novel catalyst for mixed alcohols synthesis from carbon monoxide hydrogenation

A novel K/Fe/β-Mo 2C catalyst was prepared by a temperature programmed reaction method, it exhibited high yield of alcohol, especially high C 2+OH selectivity for mixed alcohol synthesis from CO hydrogenation.

Ketoreductases: stereoselective catalysts for the facile synthesis of chiral alcohols

The results of a reduction of a wide range of ketones using 31 commercially available isolated ketoreductases (KREDs) are presented. All enzymes accepted a wide substrate range. The stereoselectivity of each enzyme was measured for the reduction of benzoyl-hydroxyacetone and ethyl-3-oxobutanoate, and in each case, enzymes which produce enantiomerically pure ( R)- and ( S)-alcohols were found. The preparative scale reactions were investigated using two ketones with different hydrophobicities (benzoyl-hydroxyacetone and α-tetralone) and using enzymes with varying specific activities for their reduction. Regardless of the hydrophobicity of the substrate, high titers of ketone (0.75–1.4 M) were reduced in high yield using catalytic amounts of enzyme (1–7% g/g relative to substrate) and cofactor (0.1–0.2% equiv. relative to ketone) within 4–24 h. The cofactor was efficiently regenerated in situ via the oxidation of glucose by glucose dehydrogenase, an enzyme that has also been cloned and over-expressed. These results show that isolated ketoreductases can be quickly and easily screened against target ketones, and the reactions can be scaled to produce preparative amounts of chiral alcohols. Ketoreductase enzymes should become a standard addition to the organic chemists toolbox of asymmetric catalysts for stereoselective ketone reduction.

Ultrasonic preparation of Ni modified K 2CO 3/MoS 2 catalyst for higher alcohols synthesis

As an effective promoter for K/MoS 2 catalyst, the addition of nickel would result in a higher selectivity of hydrocarbons due to the presence of separated NiSx phase. In the present paper, a highly homogeneous and dispersed US-Ni/K/MoS 2 catalyst was prepared by ultrasonic technology under non-water environment. Compared with conversional Ni/K/MoS 2 catalyst prepared by co-precipitation method, US-Ni/K/MoS 2 catalyst showed higher productivity of alcohols with the lower selectivity of hydrocarbons. The inhibition of methanation of Ni promoter should be ascribed to the high homogeneity of US-Ni/K/MoS 2 catalyst, in which the formation of separated nickel sulfides was impressed remarkably.

Nickel and manganese co-modified K/MoS 2 catalyst: high performance for higher alcohols synthesis from CO hydrogenation

Mn and Ni co-modified K/MoS 2 catalyst for higher alcohols synthesis from syngas was prepared by co-precipitation, and its performance in CO hydrogenation was tested. The results indicated a synergistic effect between Mn and Ni on co-modified K/MoS 2 catalyst, which led to high performance for higher alcohols synthesis.

A highly active K-Co-Mo/C catalyst for mixed alcohol synthesis from CO + H2.

A highly homogeneous and dispersed K-Co-Mo/C catalyst which prepared by a sol-gel method exhibits high alcohol yield, especially high C2+ OH selectivity for mixed alcohol synthesis from CO + H2.

Effect of Manganese Promoter on the CuFeZrO<sub>2</sub> Catalyst for Higher Alcohols Synthesis

Effect of Manganese Promoter on the CuFeZrO<sub>2</sub> Catalyst for Higher Alcohols Synthesis

Cu/Mn/ZrO2 catalyst for alcohol synthesis by Fischer-Tropsch modified elements

A Cu/Mn/ZrO2 methanol synthesis catalyst modified by Fischer-Tropsch (F-T) element (Ni,Co,Fe) was prepared by an coprecipatation method. The addition of F-T elements had a great effect on the catalyst performance. The higher alcohol selectivity increased greatly compared with that of the Cu/Mn/ZrO2 catalyst when nickel and cobalt were added, while the addition of iron improved the selectivity tohydrocarbon due to the interaction of the F-T element and the Cu/Mn/ZrO2 catalyst.

Reaction and surface characterization study of Zn/Cr-based higher-alcohol synthesis catalysts X: Effects of excess promoter loading on surface chemistry

Promoter loading level significantly affects the catalytic behavior of Zn/Cr spinel higher alcohol synthesis (HAS) catalysts. In this study a 5.9 wt.% Pd-promoted Zn/Cr spinel with a 5 and 7 wt.% K promoter have been tested and compared. At 1500 psig and 400°C, the catalyst containing 5 wt.% K results in the production of slightly more butanol, less methanol and more hydrocarbons. Using ion scattering spectroscopy and X-ray photoelectron spectroscopy, differences are found between the two catalyst surfaces which must be responsible for the differences in catalytic behavior.

Reaction and surface characterization study of higher-alcohol synthesis catalysts XII: K- and Pd-promoted Zn/Cr/Mn spinel

The synthesis of higher alcohols from syngas is a potentially attractive route for the downstream production of methyl tertiary-butyl ether (MTBE), an oxygenated gasoline additive. One of the most effective types of higher alcohol synthesis (HAS) catalysts is a Zn/Cr spinel promoted with either Cs or K. Many studies have suggested that the Cr, required to form the high surface area spinel structure, is detrimental in HAS because it may enhance hydrocarbon formation. For this reason catalysts were examined in the present study in which Mn was substituted into the spinel thereby replacing some of the Cr. Two different K and Pd-promoted Zn/Cr/Mn spinel catalysts were tested for HAS using a 1:1 CO/H 2 syngas feedstream. These catalysts were promoted with 2.25 wt% K, 5.9 wt% Pd and 1.0 wt% K, 9.0 wt% Pd. The former performs better under all four reactor conditions examined (pressures of 1000 and 1500 psig and temperatures of 400°C and 440°C). At 440°C and 1500 psig the isobutanol production rate is 179 g/kg h, the total alcohol production rate is 304 g/kg h and no significant changes in the product stream composition occur over a five-day test period. The methanol-to-isobutanol mole ratio is 1.3, which is very close to the desired value of 1.0 for MTBE production. This is the most active HAS catalyst described in the literature. Surface characterization data, obtained using X-ray photoelectron spectroscopy and ion scattering spectroscopy, indicate that the Mn content in the near-surface region of the catalyst is small. The characterization data also demonstrate that the reductive pretreatments given to HAS catalysts prior to testing result in the elimination of C-containing contamination, adsorbed water and hydroxyl groups and either expose underlying K and Pd promotors or possibly induce the migration of the K and Pd to the outermost surface layers. The pretreated catalyst surface has a layered structure with an enriched K- and Pd-containing layer at the surface above the ZnO layer over the spinel support.

An efficient catalyst for the production of isobutanol and methanol from syngas. XI. K‐ and Pd‐promoted Zn/Cr/Mn spinel (excess ZnO)

A 2.25 wt% K‐ and 6.0 wt% Pd‐promoted Zn/Cr/Mn spinel (excess ZnO) higher alcohol synthesis (HAS) catalyst has been tested for the production of isobutanol and methanol at 440°C and 1500 psig. An isobutanol production rate of 179 g kg−1 h−1, a methanol‐to‐isobutanol mole ratio of 1.3 and a total alcohol rate of 304 g kg−1 h− are attained. This ratio is slightly higher than the desired value of 1.0 for MTBE production. These results are superior to others presented in the literature thus far. Surface characterization data indicate that the near‐surface region of the catalyst consists primarily of ZnO and K. Pretreating the catalyst in a reductive environment similar to that given to the catalyst before reaction tests, causes an enrichment of the K promoter at the surface. The product stream composition does not significantly change during five days of testing.

Reaction and Surface Characterization Study of Higher Alcohol Synthesis Catalysts: IX. Pd- and Alkali-Promoted Zn/Cr-Based Spinels Containing Excess ZnO

A Zn/Cr spinel support material was prepared which contains excess ZnO and then was promoted with 5.9 wt% Pd and varying amounts ranging from 0 to 7 wt% of either K or Cs. Each of these catalysts was tested at four different reactor operating conditions (T of 400 or 440°C and P of 1000 or 1500 psig) for higher alcohol synthesis (HAS) using a syngas feedstream (1 : 1 CO : H2) after reductive pretreatment. High isobutanol production rates in conjunction with low methanol-to-isobutanol mole ratios (≤1.0) and low hydrocarbon byproduct rates are desired. For the K-promoted catalysts the highest isobutanol production rates are obtained at the higher pressure and temperature settings of 1500 psig and 440°C, and methanol-to-isobutanol mole ratios below the ideal value of 1.0, which is required for downstream methyl tertiary-butyl ether (MTBE) synthesis, are obtained. The Cs-promoted catalysts generally yield higher isobutanol production rates than the K-promoted catalysts. The highest isobutanol production rate of 170 g/kg-h is obtained using the 3 wt% Cs-promoted catalyst at 1000 psig and 440°C. The lower pressure is economically advantageous with regard to process costs. Most importantly, this isobutanol production rate is quite high compared to others presented in the literature and demonstrates that Pd does enhance the synthesis of isobutanol. The catalytic activity remained stable over a 5-day test period for each catalyst. X-ray photoelectron spectroscopy (XPS) and ion scattering spectroscopy (ISS) were used to characterize these catalysts. The results obtained from these techniques indicate that pretreating the catalysts in 1×10−7Torr of H2at 300°C for 4 h causes an enrichment of the near-surface alkali-promotor concentration. A layered structure forms which consists of this enriched alkali layer and an enriched Pd and ZnO layer which reside above the Zn/Cr spinel support material. The reaction process decreases the thickness of the alkali and ZnO layers and seems to trap the Pd in a thin layer above the support material but below the alkali promotors which reside at the surface. The surface areas of these catalysts are about 80 m2/g, and they are stable with aging. The primary role of the Zn/Cr spinel is to provide a high surface-area support for the promoted ZnO.

Surface characterization study of a 1wt% K-promoted ZnO, higher alcohol synthesis catalyst

Abstract The surface of a 1 wt% K-promoted ZnO catalyst has been characterized using X-ray photoelectron spectroscopy (XPS) and ion scattering spectroscopy (ISS). This catalyst has proven to be active for higher alcohol synthesis (HAS) using a syngas feedstream of equimolar H 2 and CO to produce mixtures of methanol, isobutanol and hydrocarbons. The near-surface region of the fresh catalyst contains primarily ZnO and some adsorbed hydrocarbons, alcohol and water contamination as well. The predominant form of oxygen in the near-surface region of the as-prepared catalyst is hydroxyl groups. According to ISS, the outermost atomic layer of the fresh catalyst consists of Zn, K, C and O with Zn being the predominant element. Exposing the catalyst to 10 − 7 Torr of H 2 for 4 h at 300°C, similar to the pretreatment performed before reaction, results in elimination of the carbon contamination and removal of most of the hydroxyl groups. This exposes the underlying, K-enriched ZnO phase which is active for HAS. The 1 wt% K/ZnO catalyst also was examined after aging in the reactor for 1 week under reaction conditions. Some alcohol products are adsorbed on the aged surface as expected. Significant amounts of Na and Cl contaminate the surface of the aged catalyst, but the amount of K present is significantly reduced possibly through sublimation of K 2 O during reaction. Although K is not observed in the XPS spectra, a small amount is present in the outermost atomic layer according to ISS. An ISS depth profile indicates that the Na, Cl and K are located throughout the near-surface region. Reaction studies indicate that the catalyst activity remains stable even though the K promotor concentration is decreased during reaction. Apparently, the Na initially present in the subsurface region of the catalyst migrates to the surface and acts as a promotor along with the remaining K.

Reaction and Surface Characterization Study of Higher Alcohol Synthesis Catalysts: VII. Cs- and Pd-Promoted 1:1 Zn/Cr Spinel

A 1:1 Zn/Cr spinel catalyst promoted with 5.9 wt% Pd and 1, 3, or 5 wt% Cs has been tested for methanol and isobutanol synthesis using a 1:1 H2:CO syngas feedstream. The reactor was operated at two different temperatures (400 and 440°C) and two different pressures (1000 and 1500 psig). The higher temperature and pressure settings result in the highest isobutanol production rates over most of the catalysts examined. As the amount of Cs promotor is increased at 440°C and 1500 psig, the total alcohol production rate increases and the methanol-to-isobutanol ratio decreases. A maximum isobutanol production rate of 142 g/kg-h and a methanol-to-isobutanol mole ratio of 1.0 are attained using the 5.0 wt% Cs/ 5.9 wt% Pd-promoted Zn/Cr catalyst. Furthermore, the addition of 3 and 5 wt% Cs results in an increase in the selectivity to total alcohols. The addition of Pd to these catalysts enhances both the total alcohol production rate and isobutanol production rate compared to Cs-promoted Zn/Cr catalysts which do not contain Pd. Surface characterization studies using X-ray photoelectron spectroscopy (XPS) and ion scattering spectroscopy (ISS) were performed on the 5 wt% Cs/5.9 wt% Pd-promoted catalyst. The XPS and ISS data reveal that the fresh catalyst surface consists primarily of ZnO, ZnCr2O4, Cs2O and a small amount of PdO2. Since the catalysts are typically reduced before testing in the reactor, the catalyst sample was again characterized after a reductive pretreatment in 1×10−7Torr of H2at 300°C for 4 h. This pretreatment results in removal of the carbon contamination, thereby exposing underlying ZnO, Cs, and Pd. Characterization studies were also performed on a 5 wt% Cs/5.9 wt% Pd-promoted catalyst which had been removed from the reactor after 5 days of testing. The XPS data indicate that the near-surface region remains enriched in Cs and Pd and that the PdO2present on the pretreated catalyst is converted to PdO during reaction. Apparently, the reaction process results in agglomeration of the ZnO film present on the reduced catalyst, which is the active catalytic phase in higher alcohol synthesis (HAS).