Fe Zn Double-metal Cyanide Research Articles

Synthesis of fatty monoester lubricant base oil catalyzed by Fe-Zn double-metal cyanide complex

Fatty monoester lubricant base oils as high as 96.7 mol% were prepared by reacting methyl oleate with long-chain alcohols viz., 2-ethyl-1-hexanol (C8−OH), 1-decanol (C10OH) and 1-dodecanol (C12OH) in the presence of a solid Fe-Zn double-metal cyanide (DMC) complex catalyst. Unlike many other acid catalysts, DMC doesn’t produce undesired ether side products. The catalyst was reusable in four recycling experiments with little loss in catalytic activity and ester yield. The long-chain esters prepared in the study have the desired physical properties for their application as lubricant base oils. Biolubricant base oils were synthesized by transesterification of methyl oleate (a component of biodiesel) with long-chain monohydric alcohols in presence of a reusable Fe-Zn double-metal cyanide catalyst. Fatty monoester yield as high as 96.7 mol% was obtained.

Influence of method of preparation of solid, double-metal cyanide complexes on their catalytic activity for synthesis of hyperbranched polymers

Catalytic activity of a series of Fe–Zn double-metal cyanide (DMC) complexes with varying structural and acidic properties has been investigated for the synthesis of hyperbranched polyesters (HPs) from glycerol and succinic acid/adipic acid. The DMC complexes were prepared using different complexing and co-complexing agents. Hydrophobicity of the surface, Lewis acidity and micro–mesoporous architecture are the critical features of DMC enabled control on gelation process in preparing HPs of high degree of branching. The micro–mesoporous architecture of DMC acts as a nano-reactor for reactant molecules to form primary condensation products which further polymerize yielding dendrimers. Hyperbranched polyesters of degree of branching as high as 90% could be achieved without gelation using DMC catalysts.

Factors Influencing the Kinetics of Esterification of Fatty Acids over Solid Acid Catalysts

The kinetics of esterification of fatty acids with alcohols over three different solid acid catalysts, viz., large pore zeolite-β (Hβ), micro-mesoporous Fe–Zn double-metal cyanide (DMC), and mesoporous Al-MCM-41, have been reported. Hydrophobicity of these catalysts increases in the order: Al-MCM-41 < Hβ < DMC. The chain lengths of the fatty acid (C8.0–C18.1) and alcohol (C1–C8) molecules have been varied, and their influence on kinetic parameters has been studied. The present study reveals that porosity and surface hydrophobicity of the catalyst are the two important factors other than acid properties (concentration and strength of acid centers) that influence the esterification reaction.

Esterification of fatty acids with glycerol over Fe–Zn double-metal cyanide catalyst

Abstract Solid Fe–Zn double-metal cyanide (DMC) complex exhibits high catalytic activity for esterification of fatty acids (FA) with glycerol. DMC catalysts with varying acidities were prepared by synthesizing the material at four different temperatures (10, 25, 50 and 80 °C). The catalyst prepared at 50 °C exhibited highest catalytic activity. Catalytic activity of DMC was influenced by both acidity and surface area. Complete conversion of FA was achieved at 140–200 °C under atmospheric pressure. Chain length of FA was found to influence the rate of reaction and product selectivity.

Fe–Zn double-metal cyanide complexes catalyzed biodiesel production from high-acid-value oil

A kind of solid catalyst of Fe(Ⅱ)–Zn double-metal cyanide (DMC) complexes was prepared through co-reaction of potassium ferrocyanide, zinc chloride and complexing agent of tert-butanol. This catalyst was characterized by using several techniques such as XRD, TG/FT-IR, EA, BET and SEM. And it proved to be highly active for the simultaneous transesterification of triglycerides and esterification of free fatty acids (FFAs). Results show that the catalyst has a hybrid-structure comprised of both crystal and amorphous species. Its good water-resistance depends on the amorphous state, which has surface hydrophobicity. Zn 2+ may be the active site of catalysis. The effect of various factors on the reaction was also studied, including different co-complexing agents, DMC concentration, reaction temperature, methanol/oil molar ratio, reaction time, water and fatty acid content and so on. The yield rate reached 98% under the optimum conditions, and the recovery rate maintained more than 90% after 10 batches.

Novel application of a Fe–Zn double-metal cyanide catalyst in the synthesis of biodegradable, hyperbranched polymers

The use of Fe-Zn double-metal cyanide as a solid catalyst for synthesizing biodegradable, hyperbranched polymers from diacids and glycerol has been reported, for the first time, wherein acidity, micro-mesoporosity and hydrophobicity of the catalyst played an important role in controlling gelation.

Biodiesel Production from Vegetable Oils and Animal Fat over Solid Acid Double-Metal Cyanide Catalysts

Biodiesel comprises of fatty acid alkyl esters prepared from vegetable oils or animal fat by esterification/transesterification with short-chain alcohols (methanol or ethanol, for example). It is a biodegradable renewable fuel. Its production is growing exponentially due to greater concerns about environmental protection and depletion of fossil fuel resources. Further, its production from non-edible oils and animal fat is more desirable than from edible oils due to lower cost of non-edible feedstocks and elimination of food verses fuel issues. Solid acid catalysts are ideal for conversion of such low-grade oils to biodiesel. Biodiesel from non-edible oils can be produced by two methods: (1) simultaneous esterification of fatty acids and transesterification of fatty acid glycerides and (2) hydrolysis of glycerides followed by esterification. This account reports the catalytic performance of solid, Fe–Zn double-metal cyanide (DMC) complexes and other acid catalysts in these transformations for biodiesel production. The factors influencing the catalytic performance of the solid acid catalysts in biodiesel production are discussed.

Hydrolysis of vegetable oils and fats to fatty acids over solid acid catalysts

Solid Fe-Zn double-metal cyanide (DMC) complexes exhibit high catalytic activity for hydrolysis of edible and non-edible vegetable oils and animal fat. In a batch reaction, complete conversion of vegetable oil triglycerides to fatty acids with selectivity greater than 73 wt% was obtained at temperatures as low as 463 K, autogenous pressure and with 5 wt% of catalyst. Catalytic activity of DMC was superior to Amberlyst™70, SAPO-11, H-β, HY, MoO x /Al 2O 3 and sulfated zirconia. Rates of hydrolysis were greatly enhanced when solvents (tetrahydrofuran or N, N-dimethylformamide), phase transfer agents (tetrapropyl ammonium bromide) and products (a mixture of mono-/diglycerides and fatty acids) or fatty acid was added to the feed. Surface hydrophobicity which enables high wettability and activation of glycerides on active, acidic sites of reusable DMC is attributed to be the major cause for its superior catalytic activity.

Influence of Surface Hydrophobicity on the Esterification of Fatty Acids over Solid Catalysts

The relative roles of surface acidity and hydrophobicity in the methylation of fatty acids (C 8 - C 18 ) to the corresponding methyl esters were investigated over three solid acid catalysts: Fe-Zn double-metal cyanide (DMC), sulfated zirconia (SZ), and Al-MCM-41. The esterification reaction was faster and the apparent activation energy was lower over SZ and Al-MCM-41 than on DMC because of their higher acid strength, specific surface area, and pore diameter. Over SZ and Al-MCM-41, the apparent activation energy for esterification increased with the chain length of the fatty acid. A reverse trend, however, was observed over DMC. The relative adsorption of methanol and fatty acids (compared to water) was higher on DMC than on SZ and Al-MCM-41. Hence, in addition to the acidic and textural properties, surface hydrophobicity and relative surface coverage by reactants/products also play an important role in reactions of long-chain fatty acids with alcohols on solid catalysts.

Hydrophobic, solid acid catalysts for production of biofuels and lubricants

A novel application of Fe–Zn double-metal cyanide (DMC) complexes as solid catalysts in the preparation of fatty acid alkyl esters (biodiesel/biolubricants) from vegetable oils is reported. The catalysts are hydrophobic (no H2O adsorption at reaction temperatures) and contain only Lewis acidic sites (NH3 and pyridine adsorption). Brönsted acid sites are absent (absence of 1546 and 1639 cm−1 bands on adsorption of pyridine). Basic sites are also absent (no CO2 adsorption). Unlike the homogeneous or other solid catalysts (like ZnO–Al2O3, for example), the Fe–Zn, DMC catalysts are highly active even for the simultaneous transesterification of triglycerides and esterification of the free fatty acids (FFA) present in unrefined and waste cooking oils as well as non-edible oils. They are also tolerant of water, probably, due to their surface hydrophobicity. A relationship between the transesterification activity and the concentration of strong Lewis acid sites has been observed. Coordinatively unsaturated Zn2+ ions in the structure of the Fe–Zn complex are the probable active sites.

Fe–Zn double-metal cyanide complexes as novel, solid transesterification catalysts

Fe–Zn double-metal cyanide complexes are currently used as catalysts for the ring-opening polymerization of epoxides, as well as the coupling of epoxides and CO 2 for the production of polycarbonates. We report their novel application as highly efficient solid catalysts for the transesterification reactions of carbonates. The catalysts were prepared from aqueous solutions of ZnCl 2 and K 4Fe(CN) 6 in the presence of tert-butanol (complexing agent) and tri-block copolymer EO 20PO 70EO 20 (average molecular weight, 5800; co-complexing agent). They were characterized by chemical analysis, XRD, thermal analysis, N 2 adsorption, magnetic susceptibility, SEM, and FTIR, diffuse reflectance UV–visible, EPR, and X-ray photoelectron spectroscopies. Their acidity was determined from the IR spectra of adsorbed pyridine and the temperature-programmed desorption of NH 3. Catalyst samples prepared with both complexing and co-complexing agents were found to be more acidic and catalytically active than those prepared without these agents. These catalysts are more active/selective than other solid catalysts hitherto reported. Dimethyl carbonate, for example, could be synthesized with 100% selectivity and an isolated yield of >86% by the reaction of propene carbonate with methanol. The catalysts can be recycled without significant loss in activity. Lewis acidic Zn ions are the possible active sites for the transesterification reaction.

Sequence structure of polyether catalyzed by Fe–Zn double-metal cyanide complex catalysts

A new kind of novel double-metal cyanide (DMC) complex catalyst was made and developed by reaction of an aqueous solution of zinc chloride and potassium hexacyanoferrate with complexing agents to form a precipitate of the DMC. For obtaining favorable catalyst activity, organic complexing agents such as t-butanol and polyols were employed. The complexing agent was incorporated into the catalyst structure, and was required for an active catalyst. Two kinds of polyether polyols were synthesized by the DMC catalysts. High-resolution 13C NMR and 1H NMR spectra were employed to identify the sequence and stereoirregular structure of the polyether polyols. The results showed that head–tail addition and a random stereoirregular structure were dominant in the microstructure of the polyether polyols which were made by DMC catalysts.