Preparation of acid–base bi-functional hydrotalcite based catalyst for converting Vietnamese coconut oil to green hydrocarbons

Acid–base bi-functional hydrotalcite like compounds based on partial incorporation of Al³⁺ into brucite structure of Mg(OH)₂ with various molar ratios were prepared through co-precipitation method. The co-precipitation of the precursors produced precipitations followed by drying at 120 °C for 12 h and calcination in air flow at 500 °C for 6 h to obtain the catalysts (Mg–Al HLCs). Many techniques including XRD, TG–DTA, EDX, NH₃-TPD, CO₂-TPD, GC–MS and XANES were used to characterize and optimize Mg/Al molar ratio based on the thermal stability of the Mg–Al HLCs and their activities in decarboxylation process of coconut oil. The results showed that the best molar ratio of Mg/Al was 3/1 providing a stable hydrotalcite like structure, and the catalyst possessed both acid and base sites on its surface enhancing its activity and selectivity in the decarboxylation process. The catalysts revealed high performance in the decarboxylation process of coconut oil established at 400 °C for 4 h for green hydrocarbons belonging to kerosene fractions.     

Hydrotalcite-derived Co-containing mixed metal oxide catalysts for methanol incineration

The Co–Mg–Al mixed metal oxides were prepared by calcination of co-precipitated hydrotalcite-like precursors at various temperatures (600–800 °C), characterised with respect to chemical (AAS) and phase (XRD) composition, textural parameters (BET), form and aggregation of cobalt species (UV–vis-DRS) and their redox properties (H₂-TPR, cyclic voltammetry). Moreover, the process of thermal decomposition of hydrotalcite-like materials to mixed metal oxide systems was studied by thermogravimetric method combined with the analysis of gaseous decomposition products by mass spectrometry. Calcined hydrotalcite-like materials were tested as catalysts for methanol incineration. Catalytic performance of the oxides depended on cobalt content, Mg/Al ratio and calcination temperature. The catalysts with lower cobalt content, higher Mg/Al ratio and calcined at lower temperatures (600 or 700 °C) were less effective in the process of methanol incineration. In a series of the studied catalysts, the best results, with respect to high catalytic activity and selectivity to CO₂, were obtained for the mixed oxide with Co:Mg:Al molar ratio of 10:57:33 calcined at 800 °C. High activity of this catalyst was likely connected with the presence of a Co–Mg–Al spinel-type phases, containing easy reducible Co³⁺ cations, formed during high-temperature treatment of the hydrotalcite-like precursor.     

Catalytic steam reforming of model compounds of biomass pyrolysis liquids in fluidized bed reactor with modified Ni/Al catalysts

Catalytic steam reforming of acetic acid and hydroxyacetone (acetol) as model compounds of the aqueous fraction of bio-oil (biomass derived pyrolysis liquids) was studied in fluidized bed reactor over Ni/Al catalysts modified with calcium or magnesium. Attrition tests showed that the use of small quantities of these promoters improved the mechanical strength of the reforming catalyst. An optimum Ca/Al molar ratio of 0.12 and a Mg/Al molar ratio of 0.26 leaded to attrition rates of 0.22 and 0.27 wt%/h, respectively. Steam reforming experiments were performed at 650 °C and a steam to carbon molar ratio (S/C) of 5.58. The promoted catalysts showed different acetic acid steam reforming activities depending on the Ca/Al or Mg/Al molar ratios. Magnesium modified catalysts with a Mg/Al molar ratios of 0.26 and 0.50 showed good performances with almost no activity loss with time in contrast to the calcium modified catalysts that showed higher CO and CH₄ yields. The addition of calcium generated a NiO phase with less interaction with the support. The highest H₂ yield and carbon conversion in acetic steam reforming were obtained by a magnesium promoted catalyst with a Mg/Al ratio of 0.26, while the nonpromoted Ni/Al catalyst showed the best performance in acetol steam reforming. Then, the nature of the organic compound influenced the performance of the different catalysts.     

Biodiesel Preparation from Jatropha curcas Oil Catalyzed by Hydrotalcite Loaded With K2CO3

This paper discusses the synthesis of biodiesel catalyzed by solid base of K₂CO₃/HT using Jatropha curcas oil as feedstock. Mg–Al hydrotalcite was prepared using co-precipitation methods, in which the molar ratio of Mg to Al was 3:1. After calcined at 600 °C for 3 h, the Mg–Al hydrotalcite and K₂CO₃ were grinded and mixed according to certain mass ratios, in which some water was added. The mixture was dried at 65 °C, and after that it was calcined at 600 °C for 3 h. Then, this Mg–Al hydrotalcite loaded with potassium carbonate was obtained and used as catalyst in the experiments. Analyses of XRD and SEM characterizations for catalyst showed the metal oxides formed in the process of calcination brought about excellent catalysis effect. In order to achieve the optimal technical reaction condition, five impact factors were also investigated in the experiments, which were mass ratio, molar ratio, reaction temperature, catalyst amount and reaction time. Under the best condition, the biodiesel yield could reach up to 96%.     

Formation of platinum sites on layered double hydroxides type basic supports: I. Effect of the nature of the interlayer anion on the structure characteristics of the layered aluminum-magnesium hydroxide and the formation of an oxide phase

A layered aluminum-magnesium hydroxide of the hydrotalcite type containing interlayer carbonate counterions (HT-CO₃) and activated hydrotalcite containing interlayer OH⁻ ions (HT-OH) were studied for the subsequent use as the precursors of supports for platinum catalysts. It was found that the nature of an interlayer anion in the composition of an aluminum-magnesium layered hydroxide is an important factor affecting both the formation of the oxide support and its texture characteristics. The replacement of the interlayer CO₃²⁻ anion by OH⁻ resulted in changes in the structural parameters of the initial double hydroxide: a decrease in the interlayer distance with the retention of the Mg/Al ratio and an increase in the imperfection of the layered material. X-ray diffraction studies in the temperature range of 30–900°C showed that HT-OH is characterized by the ability to form low-temperature spinel at 375°C. As a result, two types of aluminum-magnesium oxide supports, which were characterized by different pore space organizations at the same Mg: Al ratio, were obtained from the given layered hydroxides.     

Copolymerization of ethylene with acrylonitrile promoted by novel nonmetallocene catalysts with phenoxy‐imine ligands

A series of novel nonmetallocene catalysts with phenoxy‐imine ligands was synthesized by the treatment of phthaldialdehyde, substituted phenol with TiCl₄, ZrCl₄, and YCl₃ in THF. The structures and properties of the catalysts were characterized by ¹H NMR and elemental analysis. These catalysts were used for copolymerization of ethylene with acrylonitrile after activated by methylaluminoxane (MAO). The effects of copolymerization temperature, Al/M (M = Ti, Zr, and Y) ratio in mole, concentrations of catalyst and comonomer on the polymerization behaviors were investigated in detail. These results revealed that these catalysts were favorable for copolymerization of ethylene with acrylonitrile. Cat. 3 was the most favorable one for the copolymerization of ethylene with acrylonitrile, and the catalytic activity was up to 2.19 × 10⁴ g PE/mol.Ti.h under the conditions: polymerization temperature of 50 °C, Al/Ti molar ratio of 300, catalyst concentration of 1.0 × 10^–4 mol/L, and toluene as solvent. The resultant polymer was characterized by FTIR, cross‐polarization magic angle spinning, ¹³C NMR, WAXD, GPC, and DSC. The results confirmed that the obtained copolymer featured high‐weight–average molecular weight, narrow molecular weight distribution about 1.61–1.95, and high‐acrylonitrile incorporation up to 2.29 mol %. Melting temperature of the copolymer depended on the content of acrylonitrile incorporation within the copolymer chain. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis of Poly(isosorbide carbonate) <Emphasis Type="Italic">via</Emphasis> Melt Polycondensation Catalyzed by Ca/SBA-15 Solid Base

Ca/SBA-15 solid bases with different Ca/Si atomic ratios were prepared by a one-pot route and employed as catalysts for the production of poly(isosorbide carbonate) (PIC) from diphenyl carbonate and isosorbide via a transesterification polymerization process. The relationship between physicochemical properties and catalytic performance for Ca/SBA-15 in this melt process was investigated by means of various characterization techniques. It was found that basic site amount and strength were responsible for this transesterification process; the weak and medium basic sites inclined to promote polycondensation reaction. It was worth noting that strong basic sites could favor the decomposition of the resultant PIC, resulting in the decrease of weight-average molecular weight (M_w) and yield, and the sample with Ca/Si atomic ratio of 0.4 exhibited the best catalytic performance, giving PIC with M_w of 4.88 × 10⁴ g/mol and T_g of 169 °C at the optimal conditions. This excellent activity can be ascribed to the presence of rich basic sites and specific basic strength on the surface of 0.4Ca/SBA-15.     

CO<Subscript>2</Subscript> capture by Mg–Al and Zn–Al hydrotalcite-like compounds

Hydrotalcite-like compounds (HTC) are distinguished by their properties for CO₂ capture, like high surface area, basic sites, thermal stability and good adsorption/desorption efficiency. Mg–Al e Zn–Al HTCs with Al³⁺ molar ratios x = 0.20, 0.28 and 0.33 were synthesized by coprecipitation, and subsequently calcined at 400 °C. For both HTCs, X-ray diffraction patterns have attested the formation of mixed oxides through calcination. The amount of basic sites, measured by temperature-programmed desorption of CO₂, decreases as x increases. The CO₂ adsorption was performed in a thermogravimetric balance using an adsorption temperature of 50 °C. Mg–Al and Zn–Al samples with x = 0.33 molar composition presented the highest CO₂ adsorption, 0.91 and 0.21 mmol g^?1, respectively. The Langmuir isotherm fitted well to the experimental data. It was also found that increasing the number of adsorption/desorption cycles the CO₂ adsorption decreases, which is associated with the irreversible chemisorption.     

Hydrogen production from simulated hot coke oven gas by catalytic reforming over Ni/Mg（Al）O catalysts

Hydrogen production by catalytic reforming of simulated hot coke oven gas (HCOG) with toluene as a model tar compound was investigated in a fixed bed reactor over Ni/Mg(Al)O catalysts. The catalysts were prepared by a homogeneous precipitation method using urea hydrolysis and characterized by ICP, BET, XRD, TPR, TEM and TG. XRD showed that the hydrotalcite type precursor after calcination formed (Ni, Mg)Al₂O₄ spinel and Ni-Mg-O solid solution structure. TPR results suggested that the increase in Ni/Mg molar ratio gave rise to the decrease in the reduction temperature of Ni²⁺ to Ni⁰ on Ni/Mg(Al)O catalysts. The reaction results indicated that toluene and CH₄ could completely be converted to H₂ and CO in the catalytic reforming of the simulated HCOG under atmospheric pressure and the amount of H₂ in the reaction effluent gas was about 4 times more than that in original HCOG. The catalysts with lower Ni/Mg molar ratio showed better catalytic activity and resistance to coking, which may become promising catalysts in the catalytic reforming of HCOG.     

Zn-La复合氧化物催化剂用于甲醇与碳酸乙烯酯酯交换反应的研究

ZnO、La₂O₃和Zn-La复合氧化物催化剂用于甲醇与碳酸乙烯酯反应制备碳酸二甲酯和乙二醇。催化剂采用共沉淀法进行制备,并用BET、XRD、TG-DSC、CO₂-TPD和Hammett滴定等对催化剂进行表征。考察了Zn-La物质的量比、焙烧温度,反应条件（反应温度、反应时间、催化剂用量等）对催化剂活性的影响。结果表明,ZnLa复合氧化物物质的量比为2：1,焙烧温度为500℃时,催化剂表现了较好的催化效果。催化剂的活性与催化剂表面的碱性强度和碱量有关,碱量越多催化剂的活性越好。     

Polylactones. 13. Transesterification of Poly(L-Lactide) with Poly(Glycoude), Poly(β-Propio-Lactone), and Poly[ε -Caprolactone)

Homogeneous blends of poly(L-lactide) (M _n = 30 000 to 40 000) and poly(β-propiolactone) or poly(ε-caprolactone) were prepared in solution. The solvent-free blends were subjected to transesterification catalyzed by means of methyl triflate, triflic acid, boron trifluoride, or tributyltin methoxide at 100 or 150°C. At 100°C, transesterification was barely detectable even after 96 h. When poly(β-propiolactone) was used as the reactant at 150°C, degradation was faster than transesterification regardless of the catalyst. The same negative result was obtained for heterogeneous blends of poly(L-lactide) and poly(glycolide). In the case of poly(ε-caprolactone), copolyesters with slightly blocky sequences were obtained with tributyltin methoxide as catalyst, whereas the acidic catalysts caused rapid degradation. The copolyesters were characterized by means of ¹H-NMR spectroscopy with regard to their molar composition, by means of ¹³C-NMR spectroscopy with regard to their sequences, and by means of differential scanning calorimetry with regard to crystallinity.     

Transesterification of ethyl butyrate with methanol using MgO/CaO catalysts

A series of mixtures of MgO/CaO with different Mg/Ca molar ratios (between 3 and 15), as well as the corresponding pure oxides, was prepared by the coprecipitation method in a basic medium and subsequent calcination. Their textural and structural characterization was carried out by using XRD, FT-IR, SEM and N₂ sorption at 77 K. The alkalinity was studied by CO₂-TPD and catalytic decomposition of 2-propanol. The MgCa oxides obtained after calcination at 1073 K exhibit X-ray diffraction patterns with clearly visible signals corresponding to crystalline CaO and MgO. Textural properties are improved by the presence of Mg, with the porosity increased and the particle sizes decreased with respect to pure CaO. FT-IR spectroscopy reveals the presence of surface carbonate. These catalysts are active in the transesterification of ethyl butyrate with methanol at 333 K and atmospheric pressure, a model reaction to evaluate the potential of these basic catalysts in triglycerides transesterification for biodiesel production. The highest activity was found for a Mg:Ca molar ratio of 3, with conversion close to 60%, whereas MgO was inactive. Moreover, lixiviation of the active phase was not observed thus excluding the contribution of the homogeneous catalysis to the studied transesterification process.     

A novel catalytic system—NdCl3 · HMPA/AI(i‐6u)3 for copolymerization of isoprene and styrene

Co polymerization of styrene (St) and isoprene (IP) was carried out with a catalyst system composed of anhydrous lanthanide chloride hexamethyl phosphor amide complex (LnC1₃‐HMPA) and aluminum organic compound (AOC). Among the catalysts examined, catalyst NdC1₃*HMPA/Al(i‐Bu)₃ showed a high activity in the copolymerization under certain conditions giving copolymers (5%‐158 St content) with high cis‐1, 4 microstructure in IP Units (>95%). The effects of HMPA/Nd molar ratio, Al/Nd molar ratio, monomer/Nd molar ratio, St feed ratio, and the reaction time on copolymerization were examined with this catalytic system. The obtained copolymers were characterized by ¹H and ¹³C NMR spectroscopies and gel‐permeation chromatography (GPC).     

Transition metal complexes bearing 2,6-bis(imino)pyridyl: Synthesis,structure, ethylene polymerization/ oligomerization studies

A series of new complexes {2,6-bis[1-((2-methyl-4-methoxyphenyl)imino)ethyl]pyridine}Cl₂ [M=Fe(II) (2), Co(II) (3), Ni(II) (4), Cu(II) (5), Zn(II) (6)] have been synthesized. At 25°C, using 500 equiv of methylaluminoxane (MAO), the activities of Fe(II), Co(II) catalysts can reach 4.02 ×10⁶ g/mol-Fehatm for ethylene polymerization and 3.98×10⁵ g/mol-Cohatm for ethylene oligomerization. The effects of polymerization conditions such as reaction temperature, Al/M molar ratio and time on the activity of catalyst have been explored.

     

Ca6GaN5 und Ca6FeN5. Verbindungen mit [CO3]2−-isosteren Anionen [GaN3]c− und [FeN3]6−

Ca₆GaN₅ and Ca₆FeN₅: Compounds Containing [CO₃]^2?-isosteric Anions [GaN₃]^6? and [FeN₃]^6? The isotypic phases Ca₆GaN₅ and Ca₆FeN₅ (hexagonal, P6₃/mem; a = 627.7(3)/ 623,7(1) pm, c = 1219.8(3)/1233.2(6) pm; Z = 2) are prepared by reaction of Ca/Ga mixtures (molar ratio 6:1) and Fe/Ca₃N₂/Ca mixtures (molar ratios from 3:1:13 to 5:2:15) with nitrogen at temperatures of 850°C and 950°C to 1100°C, respectively. The structures contain trigonal-planar anions [MN₃]^6? which are isosteric to carbonate ions (Ga? N: 195,1(28) pm; Fe? N: 177,0(15) pm). The structures are closely related to those compounds of the hydrotalcite group.     

Transition metal complexes bearing 2,6-bis(imino)pyridyl: Synthesis,structure, ethylene polymerization/ oligomerization studies

A series of new complexes {2,6-bis[1-((2-methyl-4-methoxyphenyl)imino)ethyl]pyridine}Cl₂ [M=Fe(II) (2), Co(II) (3), Ni(II) (4), Cu(II) (5), Zn(II) (6)] have been synthesized. At 25°C, using 500 equiv of methylaluminoxane (MAO), the activities of Fe(II), Co(II) catalysts can reach 4.02 ×10⁶ g/mol-Fehatm for ethylene polymerization and 3.98×10⁵ g/mol-Cohatm for ethylene oligomerization. The effects of polymerization conditions such as reaction temperature, Al/M molar ratio and time on the activity of catalyst have been explored.     

Transesterification of dimethyl carbonate with phenol over a bimetallic molybdenum and copper catalyst

Mo-Cu bimetallic oxides were found to be efficient heterogeneous catalysts for the transesterification of dimethyl carbonate (DMC) with phenol. When the reaction was carried out between 150 and 180°C, with a molar of Mo/Cu of 1:1, molar ratio of phenol/DMC of 1:1, 4.8 wt.% of the catalyst, 9 h, the conversion of phenol was 49.9%, and the total yield of MPC and DPC was 45.4%. Catalyst reuse showed a gradual decline in the catalytic activity. The decrease in catalytic activity might be due to leaching out of Mo and Cu, and/or carbon deposition.     

Effective and recoverable homogeneous catalysts for the transesterification of dimethyl carbonate with ethanol: Lanthanide triflates

The catalytic activities of metal triflates were tested for the transesterification of dimethyl carbonate (DMC) with ethanol. It was found that yttrium triflate was the most efficient homogeneous catalyst. When the transesterification reaction was catalyzed by yttrium triflate at 76–80°C, 7 h, ethanol to DMC in 6: 1 molar ratio, 0.35 mol % of catalyst based on DMC, the conversion of DMC was 89.2%, the selectivities of diethyl carbonate (DEC) and ethyl methyl carbonate (EMC) were 85.1 and 13.6%, respectively. Yttrium triflate was reused 5 times for the transesterification without loss of its catalytic activity.     

Effect of Mg/Al atom ratio of support on catalytic performance of Co-Mo/MgO-Al2O3 catalyst for water gas shift reaction

Co-Mo-based catalysts supported on mixed oxide supports MgO-Al₂O₃ with different Mg/Al atom ratios for water gas shift reaction were studied by means of TPR, Raman, XPS and ESR. It was found that the octahedral Mo species in oxidized Co-Mo/MgO(x)-Al₂O₃ catalyst and the contents of Mo⁵⁺, Mo⁴⁺, S²⁻ and S²⁻₂ species in the functioning catalysts increased with increasing the Mg/Al atom ratio of the support under the studied experimental conditions. This is favorable for the formation of the active Co-Mo-S phase of the catalysts. Catalytic performance testing results showed that the catalysts Co-Mo/MgO-Al₂O₃ with the Mg/Al atom ratio of the support in the range of 0.475–0.525 exhibited optimal catalytic activity for the reaction.     

Significant Heterogeneous Carbonate Salt Catalyzed Acetylation of Alcohols via a Transesterification Process with Carbonate Salt‐activated Alcohol 1H NMR Evidence

Heterogeneous carbonate salt catalyzed acetylation of alcohols via a transesterification process has been developed. Various esters are furnished up to 97% yield. Established procedure is simple and air‐tolerant with readily available reagents. Ethyl acetate and isobutyl acetate are used as not only acetylating agents, but also reaction solvents in transesterification. Aliphatic linear alcohols, allylic alcohols and benzyl alcohols show high reactivities in the presence of 1 or 5 mol% Cs₂CO₃ at 125°C. Cesium carbonate can be recycled by pumping liquid phase out of reactor after reaction. During four cycle runs for reaction of 2‐phenylethanol and ethyl acetate, high yields of phenethyl acetate are provided (>60% yield). Based on experiments and ¹H NMR investigation, bifunctional catalysis is proposed, alcohol activated by carbonate ion is confirmed, and higher activity of catalytic amount than stoichiometric cesium carbonate is interpreted.