The effect of Mo(CO)₆ as a catalyst in the carbonylation of methanol to methyl formate catalyzed by potassium methoxide under CO, syngas and H₂ atmospheres.

Ph. D. University of KwaZulu-Natal, Westville 2010In patents describing the low temperature production of methanol from syngas catalysed by the Ni(CO)₄/KOCH₃ system, Mo(CO)₆ was claimed to enhance the catalytic activity of the system. However, there has been no clarity on the effect of Mo(CO)₆ and KOCH₃ in the activation of the catalyst. Work reported in this thesis showed that most of the methyl formate is produced via a normal KOCH₃ catalyzed process under a CO atm. When the KOCH₃ system is compared with the Mo(CO)₆/KOCH₃ catalyzed system, it is noted that the amount of methyl formate increases very slightly due to the addition of molybdenum hexacarbonyl. The experiments were also performed under H₂ and synags (1:1) atm in different solvents. In all cases dimethyl ether was produced with methyl formate. Preliminary carbonylation studies performed at a syngas ratio of 1:2 showed an increase in the amount of methanol produced. Increasing the amount of Mo(CO)₆ in the Mo(CO)₆/KOCH₃ reaction under syngas (1:1) increases the production of methyl formate. High Pressure infrared (HPIR) studies for Mo(CO)₆/KOCH₃ were carried out under H₂, CO, syngas (1:1) and N₂ atmospheres. The alkoxycarbonyl complex (Mo(CO)₅(COOCH₃)⁻) was observed as an intermediate in all reactions involving Mo(CO)₆ and KOCH₃. Under a hydrogen atmosphere, the metalloester (Mo(CO)₅(COOCH₃)⁻) intermediate diminished to form a bridged molybdenum hydride (µ-HMo₂(CO)₁₀⁻) species as a stable intermediate. In contrast, under syngas atmosphere, the metallloester diminished in concentration to form the bridged hydride (µ-HMo₂(CO)₁₀⁻), which also disappeared to form the molybdenum alkoxide complex (Mo(CO)₅OCH₃⁻). The role of methanol in the formation of methyl formate is also discussed. Based on the HPIR studies, different types of metalloesters (alkoxycarbonyl complexes) were synthesized by nucleophilic reactions of alkoxides with Mo(CO)₆. Reactions of potassium alkoxides (KOR, R = -CH₃, -C(CH₃)₃, -C(CH₃)₂CH₂CH₃) with Mo(CO)₆ in THF produced water soluble alkoxycarbonyl complexes (K[Mo(CO)₅(COOR)]). The reaction of KOCPh₃ with Mo(CO)₆ yielded what is believed to be the metalloester as an insoluble compound. Attempts to improve the solubility of the formed alkoxycarbonyl complexes, K[Mo(CO)₅(COOR)], by metathesis with bulkier counter ions (PPNCl, Et₄NCl and n-Bu₄NI) was not successful. The reaction of K[Mo(CO)₅(COOCH₃)] with 18-crown-6 ether produced [K(18-crown-6)][Mo(CO)₅(COOCH₃)] which was more soluble in organic solvents. The reactions of [PPN][OCH₃] and [n-Bu₄N][OCH₃] with Mo(CO)₆ produced [PPN][Mo(CO)₅(COOCH₃)] and [n-Bu₄N][Mo(CO)₅(COOCH₃)], respectively. The reactions of [K(18-crown-6)][OCH₃] and [K(15-crown-5)₂][OCH₃] with Mo(CO)₆ under reflux gave the [K(18-crown-6)][Mo(CO)₅(COOCH₃)] and [K(15-crown- 5)₂][Mo(CO)₅(COOCH₃)] complexes. Reactions of Ph₃PMo(CO)₅ with KOCH₃ and [PPN][OCH₃] yielded K[Ph₃PMo(CO)₄(COOCH₃)] and [PPN][Ph₃PMo(CO)₄(COOCH₃)]. Other alkoxycarbonyl complexes were synthesized by an alternative approach using alcohols as solvent. For example, [PPN][Mo(CO)₅(COOCH₂CH₃)] was synthesized by refluxing [PPN][OEt] with Mo(CO)₆ in ethanol. The isopropyl derivative [PPN][Mo(CO)₅(COOCH(CH₃)₂)] was synthesized by refluxing [PPN][OCH(CH₃)₂] with Mo(CO)₆ in isopropanol. Two methyl derivatives were also synthesized in methanol as Et₄N and PPN derivatives. A crystal structure of the [PPN]₂[Mo₆O₁₉] oxo cluster, obtained from the decomposition of [PPN][Mo(CO)₅(COOCH(CH₃)₂)] in acetonitrile was solved. The crystal crystallized in the monoclinic form with a space group of P-1. Another oxo cluster, [Et₄N]₂[Mo₄O₁₃], formed from the decomposition of the [Et₄N][Mo(CO)₅(COOCH₃)] derivative. The structure was solved in the monoclinic form with a space group of P 2₁/n. The alkoxycarbonyl complex, [PPN][Mo(CO)₅(COOCH₃)], was tested for catalytic behaviour under hydrogen and syngas to determine its role in the production of methyl formate. No methyl formate was produced under hydrogen, but methyl formate was produced under syngas (1:1). HPIR studies of [PPN][Mo(CO)₅(COOCH₃)] under syngas (1:1) showed that methyl formate is formed via the decomposition of [PPN][Mo(CO)₅(COOCH₃)] to Mo(CO)₆. Interesting results for the reaction of Mo(CO)₆ with KOCH₃ under syngas (1:1) were obtained in triglyme. Here longer carbon chain alcohols were produced and identified by GC and GC-MS. These alcohols include ethanol, 2-propanol, 2-butanol, 3-methyl-2-butanol, 3-pentanol, 2-methyl- 3-pentanol and 2,4-dimethyl-3-pentanol

Low temperature methanol synthesis catalysed by a copper nanoparticle-alkoxide system

Methanol (MeOH) synthesis at low temperature in a liquid medium presents the possibility of achieving full syngas conversion per pass. The Low temperature MeOH synthesis (LTMS) process is advantageous over the current technology for MeOH production since the former is thermodynamically favourable and gives a high yield per pass. The LTMS involves two main steps, (i) MeOH carbonylation to form methyl formate and (ii) hydrogenolysis of methyl formate to form MeOH. The initial aim of the present work was to develop, characterize and evaluate the catalyst system involved in the LTMS process. A once-through catalyst system involving copper (II) acetate and methoxide was used to obtain up to 92 % conversion (> 94 % selectivity to MeOH) per batch at 20 bar syngas pressure and 100 oC temperature within 2 h. XRD and TEM characterization of the slurry catalyst system revealed that about 10 ± 5 nm Cu2O/Cu0 nanoparticles were involved in the catalytic process. Decreasing Cu nanoparticles sizes led to increased MeOH production due to an increase in active Cu surface area, which enhanced methyl formate hydrogenolysis. Agglomeration of the Cu nanoparticles in the course of MeOH production was identified as a major cause for the deactivation of the Cu nanoparticle component of the LTMS catalyst system. Furthermore, with the aim of investigating the role of solvents polarity on the LTMS, MeOH production maximized for solvents with dielectric constant (ɛ) around 7.2, similar to the polarity of diglyme. A probe of possible side reactions of the main intermediate revealed that, in the presence of methoxide, low polar solvents enhanced decarbonylation of methyl formate while high polar solvents enhanced a nucleophilic substitution to form dimethyl ether and sodium formate. Relatively moderate polar solvents such as diglyme appeared to give a good balance in minimizing possible side reactions of methyl formate and therefore enhanced MeOH production. In addition, the spinning disk reactor (SDR) was used to synthesize on-purpose Cu nanoparticles with predefined particle sizes for catalysing the LTMS reaction. By maintaining the same chemical recipe, Cu nanoparticle sizes were tuned down to 3 nm when physical conditions were varied to shorten for example micromixing time, mean residence time and relative residence time distribution. This subsequently led to uniform nucleation and ultimately formation of smaller Cu nanoparticle sizes with narrow particle size distribution. At the end, a model was proposed for a complete LTMS process with the help of Aspen HYSYS simulation tool, using an air-blown autothermal reformer, for a full conversion per pass at 60 bar syngas (0.31 CO: 0.62 H2: 0.07 N2) and 100 oC MeOH synthesis temperature.publishedVersio

Study on Reactivity and Utilization of Halogenated Organic Compounds

取得学位: 博士(工学), 授与番号: 乙第1395号, 授与年月日: 平成6年9月30日, 授与大学: 金沢大

Glycerol Carbonate as a Versatile Alkylating Agent for the Synthesis of β-Aryloxy Alcohols

The possibility to use glycerol carbonate (GlyC) as an innovative alkylating agent for phenolic compounds in solventless conditions and in the presence of a catalytic amount of both homogeneous and heterogeneous bases is herein described. In particular, the peculiar, polyfunctional structure of GlyC allows one to obtain the formation not only of the mono-phenoxy-1,2-propanediol (MPP) analogue but also of 1,3-diphenoxy-2-propanol (DPP), the latter being elusive using the more traditional, toxic, and carcinogenic reagents such as glycidol and/or 3-chloro-1,2-propandiol. The production of DPP is indeed possible due to the in situ formation of a reactive intermediate, 4-(phenoxy)methyl-1,3-dioxolane-2-one (PhOGlyC), which may undergo a consecutive nucleophilic attack of a phenolate, leading to the selective formation of the disubstituted product. This reaction is nonetheless in competition with PhOGlyC decarboxylation that finally limits DPP yield up to 20%, with an MPP yield up to roughly 60% in the optimized conditions (atmospheric pressure, 140 degrees C, 5 h using Cs2CO3 as the basic catalyst) starting directly from a GlyC/phenolic mixture. For this reason, a multistep synthetic strategy has also been developed, first by obtaining the quantitative formation and isolation of the PhOGlyC intermediate and then by promoting the consecutive reaction with phenol, in this way obtaining a DPP yield of 66% after only 1 h of reaction at 170 degrees C. The obtained phenyl glyceryl ethers are interesting drugs scaffolds (i.e., guaifenesin, mephenesin), intermediates in the preparation of active pharmaceutical ingredients (e.g., chlorphenesin carbamate, methocarbamol), and hydrotropic solvents; preliminary evaluations of MPP and DPP biodegradability and use as alternative surfactants have also been described in this paper

CO2 electro-valorization to dimethyl carbonate from methanol using potassium methoxide and the ionic liquid [bmim][Br] in a filter-press electrochemical cell

BACKGROUND: The electrochemical valorization of CO2 into added-value products appears a promising strategy for reducing CO2 emissions and mitigating climate change. Dimethyl carbonate (DMC) is an environmentally friendly valuable chemical, with multiple applications, and has been suggested as a potential gasoline additive. However, DMC has traditionally been produced from hazardous phosgene and CO routes, which encourages the interest in developing new processes. The aim of this work is to study the valorization process for the direct electrosynthesis of DMC from CO2 and methanol using CH3OK and the ionic liquid 1-butyl-3-methylimidazolium bromide, avoiding the addition of carcinogenic compounds. RESULTS: The evolution of the concentration of DMC was studied in a filter-press electrochemical cell with anodic and cathodic compartments separated by a Nafion 117 membrane, operating for 48 h. A final DMC concentration of 15.07 mmol L-1 was observed. Analysis of the by-products obtained in the process revealed the formation of tetramethyl orthocarbonate and dimethoxymethane, which were detected and quantified in the liquid phase. A simplified reaction scheme was also proposed based on the results obtained. CONCLUSION: Unlike all previous work that used an undivided cell, the new experimental results of this study using a divided cell can serve as a reference for further research to overcome current limitations.Financial support to project ENE2010-14828 is gratefully acknowledged. Isabel Garcia-Herrero also acknowledges the FPI postgraduate research grant (BES-2011-047906)

Catalytic transformation of propylene carbonate into dimethyl carbonate and propylene glycol.

Dialkyl carbonates are important industrial compounds that have a low toxicity and are readily biodegrade, also replacing some highly toxic and corrosive reagents in organic chemistry. There are a number of synthetic routes towards the synthesis of dialkyl carbonates, including two commercial processes (ENIChem S.p.A. and UBE Industries, LTD). The ENIChem process involves the carbonylation of methanol in the presence of CuCl2 as a catalyst. The major drawback of this process is in the use of an explosive gas mixture (CO/O2) under certain conditions. The UBE process is a two step reaction, whereby the methanol reacts with O2 and NO in the presence of a PdCl2 catalyst to form methyl nitrite and water, followed by carbonylation of methyl nitrite to form DMC and reform NO. The major drawback associated with this process is in the combination of methanol, nitric oxide and oxygen which is also explosive under some conditions. The transesterification reaction between a cyclic carbonate and an alcohol in the presence of a catalyst provide an alternative route towards synthesis of dialkyl carbonates, producing a glycol as by-product. This synthetic route is environmentally friendly, decreases explosion possibilities, and the reagents employed in this process are less hazardous than those of other processes. The main aim of this study was to identify and optimise the catalyst systems that could promote the transesterification reaction effectively. A number of homogeneous and heterogeneous, acidic or basic catalysts were evaluated during this study. The study revealed that basic homogeneous catalysts such as TBD, DBU, DBN, MTBD, DABCO, and Verkade bases are effective for the transesterification reaction. The basic heterogeneous catalysts such as Amberlites® IRA 96, IRA 67 and IRA 400 showed good catalytic behaviour, but they eventually became deactivated. On the other hand, homogeneous Lewis acids such as La(OTf)3, Gd(OTf)3, and Sm(OTf)3 demonstrated good activity, even though they need high temperatures, i.e. 150 °C. The heterogeneous acidic systems such as Amberlyst® 15, Amberlyst® 36, silica, alumina, etc., showed much lower activity, if any was observed. ix Due to the fact that these reactions were carried out above room temperature and analysed at room temperature in the GC, it was important to understand the equilibrium shift under such temperature variations, and NMR studies were used here. There was no significant difference in equilibrium conversion between the NMR reactions and the autoclave reactions (analysed in a GC), indicating slight influence of temperature variation. The results obtained from the NMR study were used to calculate the reaction kinetics. The calculations indicated a direct proportional increase of the rate with respect to the catalysts pKa values.Prof. D.B.G. William

Electrosynthesis of dimethyl carbonate from methanol and CO2 using potassium methoxide and the ionic liquid [bmim][Br] in a filter-press cell: A study of the influence of cell configuration

BACKGROUND: The valorization of CO2 into added-value products appears to be a promising strategy for reducing CO2 emissions. Dimethyl carbonate (DMC) is an environmentally friendly valuable product, with multiple applications, suggested as a potential gasoline additive. However, DMC has traditionally been produced from hazardous phosgene and CO routes, which encourages the interest in developing new processes. The purpose of this work is to study the influence of the membrane in a filter-press electrochemical cell for the valorization of CO2 by the electrosynthesis of DMC from methanol in the presence of the ionic liquid [bmim][Br] and CH3OK and avoiding the addition of carcinogens. RESULTS: The performance of the process has been studied using six different anion exchange membranes in comparison with an undivided configuration and our previous study using a cationic exchange membrane. A significant increase in the initial reaction rate is achieved when no membrane is employed. Regardless of which membrane is used, an additional resistance seems to be introduced. A final concentration of 85mmolL-1 was obtained up to 48h without membrane, which is a 6-fold increase over our previous work. CONCLUSIONS: Although better results were obtained when no membrane was used, study of the divided cell has provided experimental evidence that can serve as a reference for the evaluation of future improvements in this electrosynthesis.This work was conducted under the framework of the Spanish Ministry of Science and Innovation Project ENE2010-14828. Isabel Garcia-Herrero also acknowledges receipt of the FPI postgraduate research grant (BES-2011-047906). FuMA-Tech GmbH is also thanked for its great support and the supply of membranes

The possibilities of utilization of carbon dioxide for the preparation of dimethyl carbonate from methanol

Rešerše přípravy a výroby dimethylkarbonátu z methanolu a oxidu uhličitého, s využitím oxidu uhličitého jako významného odpadu z chemického průmyslu.Research preparation and manufacture of dimethyl carbonate from carbon dioxide and methanol, with advantage of carbon dioxide as significant waste from chemical industry.