115-10-6Relevant articles and documents
A Mechanistic Study of the Methanol Dehydration Reaction on γ-Alumina Catalyst
Schiffino, Rinaldo S.,Merrill, Robert P.
, p. 6425 - 6435 (1993)
The dehydration of methanol over a porous γ-Al2O3 catalyst was studied using periodic square-wave modulation of the feed to a microcatalytic reactor.Online mass spectrometry was used to obtain wave forms at the exit of the reactor for methanol, dimethyl ether, water, and a carrier gas.The reaction was studied over the temperature range of 230-350 deg C.At lower temperatures, the dimethyl ether wave form went first through a maximum, decreased to a constant level during the on cycle, and then went through a second maximum at the beginning of the off cycle.At higher temperatures where the conversions increased, the relative intensity of the maximum to the level part of the wave form continuously decreased until no maximum could be observed at temperatures above 280 deg C.Water was found to have a phase lag of about 4 s with respect to dimethyl ether over the studied temperature range.The shape of the wave forms was explained in terms of a reaction mechanism which involved reactions of surface species formed from the adsorption of methanol on the γ-Al2O3 surface.The species considered were molecularly adsorbed methanol, methoxy, and hydroxyl groups.The mechanism contained two parallel reaction pathways for the production of dimethyl ether.One pathway was the reaction between molecularly adsorbed methanol and methoxy species, and the other was the reaction between two methoxy species.For the production of water, only a single step of recombination of surface hydroxyls was considered in the mechanism.Equations for the material balances of the species considered in the mechanism were numerically integrated to generate wave forms with the same shape as observed in the experimental data.
A novel sol-gel approach to highly condensed silicas at low temperature
Jorapur, Yogesh R.,Mizoshita, Norihiro,Maegawa, Yoshifumi,Nakagawa, Hiroki,Hasegawa, Takeru,Tani, Takao,Inagaki, Shinji,Shimada, Toyoshi
, p. 280 - 281 (2012)
We have discovered new Meerwein's reagent-catalyzed solgel polycondensations, which provide highly condensed silica Q4 and biphenylylene silica T3 as amorphous gels with marginal silanols starting from TEOS and 4,4′-bis(triethoxysilyl)biphenyl (BTEBph), respectively. We propose a plausible pathway for this protocol with possible silyloxonium intermediates.
Fine Control of the Pore-opening Size of the Zeolite Mordenite by Chemical Vapour Deposition of Silicon Alkoxide
Niwa, Miki,Kato, Satoshi,Hattori, Tadashi,Murakami, Yuichi
, p. 3135 - 3146 (1984)
Chemical vapour deposition (c.v.d.) of Si(OCH3)4 on the H form of mordenite has been carried out in order to control the pore-opening size without affecting its acidic properties.It has been shown that Si(OCH3)4 is deposited irreversibly on the zeolite.Because the molecular size of the alkoxide is larger than the pore size, the alkoxide does not enter the pore and the silicon compound is deposited on the external surface.The alkoxide may be deposited by reaction with hydroxide, thus covering the external surface of zeolite crystal after subsequent reactions.Calcination with oxygen removes the hydrocarbon residue and produces silica-coated H-mordenite (SiHM).The SiHM thus obtained has been characterized by temperature-programmed desorption (t.p.d.) of NH3, adsorption experiments and X-ray photoelectron spectroscopy.The deposition of the alkoxide does not change the acidity but reduces the size of pore opening.Enrichment of Si on the external surface of the zeolite is confirmed.One can therefore conclude that SiO2 covers the external surface of the zeolite, thus reducing the effective size of the pore opening.The pore size is effectively reduced by ca. 0.1 and 0.2 nm upon formation of 1-2 and 3 molecular layers of silicon oxide, respectively.
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Boulin,Simon
, p. 393 (1920)
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SYNERGISTIC EFFECT OF HOMOGENEOUS RUTHENIUM-RHODIUM CATALYSTS FOR METHANOL HOMOLOGATION
Pursiainen, Jouni,Karjalainen, Kauko,Pakkanen, Tapani A.
, p. 227 - 230 (1986)
Homogeneous solutions containing both ruthenium and rhodium complexes and methyl iodine are shown to exhibit a synergistic effect for the homologation of methanol to ethanol.Reactions were studied at pressures from 100 to 175 atm and at temperatures from 160 to 240 deg C.The highest selectivities were obtained with excess of ruthenium complexes present.Under these reaction conditions no evidence for cluster catalysis was found.
Synthesis of lower olefins from dimethyl ether in the presence of zeolite catalysts modified with rhodium compounds
Kolesnichenko,Goryainova,Biryukova,Yashina,Khadzhiev
, p. 55 - 60 (2011)
The catalytic properties of zeolite catalysts modified with rhodium compounds in the synthesis of olefins from dimethyl ether (DME) and methanol (MeOH) have been studied. The optimum concentration of rhodium in the composition of a zeolite catalyst has been determined. It has been shown that one of the possible precursors of ethylene in the conversion of DME is ethanol, which, under reaction conditions, can be formed through both the DME isomerization and methanol homologation stages.
Thermal Decomposition of Dimethyl Methylphosphonate over Manganese Oxide Catalysts
Segal, Scott R.,Cao, Lixin,Suib, Steven L.,Tang, Xia,Satyapal, Sunita
, p. 66 - 76 (2001)
The thermal oxidative decomposition of dimethyl methylphosphonate (DMMP) has been studied over amorphous manganese oxide (AMO) and Al2O3-supported manganese oxide catalysts. The reaction was carried out using air as the oxidant at te
Synthesis of isoalkanes over a core (Fe-Zn-Zr)-shell (zeolite) catalyst by CO2 hydrogenation
Wang, Xiaoxing,Yang, Guohui,Zhang, Junfeng,Chen, Shuyao,Wu, Yingquan,Zhang, Qingde,Wang, Junwei,Han, Yizhuo,Tan, Yisheng
, p. 7352 - 7355 (2016)
A kind of core-shell catalyst with Fe-Zn-Zr as the core and a zeolite (HZSM-5, Hbeta, and HY) as the shell was synthesized by a simple cladding method. The catalyst has an obvious confinement effect on the synthesis of isoalkanes by CO2 hydrogenation. Especially, the Fe-Zn-Zr@HZSM-5-Hbeta catalyst with a double-zeolite shell exhibits an extraordinary high i-HC/t-HC ratio.
Antimony Pentafluoride/Graphite Catalyzed Oxidative Carbonylation of Methyl Halides with Carbon Monoxide and Copper Oxides (or Copper/Oxygen) to Methyl Acetate
Olah, George A.,Bukala, Jozef
, p. 4293 - 4297 (1990)
Superacidic antimony pentafluoride/graphite catalyzed oxidative carbonylation of methyl halides with carbon monoxide and copper oxides (or copper metal and oxygen) gives methyl acetate (AcOMe).The reaction was investigated in a pressure reactor in the temperature range of 100 to 300 deg C and pressures of 20 to 150 atm.The oxidative carbonylation of methyl bromide (MeBr) with CO and Cu2O at 270 deg C under a pressure of 130 atm gave 48 mol percent Me2O and 33 mol percent AcOMe.Replacing Cu2O with CuO gave about 40-50percent AcOMe, with 10-20percent Me2O.Using Cu and O2 gave ca. 50percent AcOMe, with 5percent Me2O.In the reaction 5-10percent MeF is also formed due to halogen exchange.The reactivity of the methyl halides shows the decreasing order of MeBr > MeCl > MeF.
Gas-Phase Chemistry of Trimethyl Phosphite
Anderson, David R.,DePuy, Charles H.,Filley, Jonathan,Bierbaum, Veronica M.
, p. 6513 - 6517 (1984)
The reactions of trimethyl phosphite, (CH3O)3P, with the nucleophiles H2N-, CH3NH-, (CH3)2N-, HO-, H(18)O-, CH3O-, CD3O-, H-, F-, H2P-, CH2=CH-CH2- and (CH3)2C=C(CH3)CH2- were investigated.Products, branching ratios, and reaction rate constants are reported.Reactions generally proceed through an ion-dipole complex -.(CH3O)3P>, to a phosphoranide anion intermediate, -> to displacement of methoxide to form a new ion-dipole complex -.(CH3O)2PZ>.If an additional acidic hydrogen is available on the nucleophile, the major products results from proton abstraction by methoxide: -(CH3O)2PYH> -> (CH3O)2PY- + CH3OH.When the displacement of methoxide from phosphorus is sufficiently endothermic, a competing attack at carbon by the original nucleophile occurs: -(CH3O)3P> -> CH3YH + (CH3O)2PO-.Nucleophiles without an additional acidic hydrogen reacts similarly, but the final reaction products result from (1) SN2 reaction of methoxide, -> -> Z(CH3O)PO- + CH3OCH3, (2) SN2 reaction of the original nucleophile, -(CH3O)3P> -> CH3Z + (CH3O)2PO-, (3) stabilization of the phosphoranide intermediate to give the adduct Z(CH3O)3P-, and (4) expulsion of methoxide from the ion-dipole complex.Reaction mechanisms are discussed in terms of the nature of the nucleophiles, the observed products, and the thermodynamics of the displacement reaction.
Dehydrogenation of Methanol to Formaldehyde over Silicalite
Matsumura, Yasuyuki,Hashimoto, Keiji,Yoshida, Satohiro
, p. 1447 - 1448 (1984)
Formaldehyde is formed by catalytic dehydrogenation of methanol over silicalite containing sodium ions at 670-820 K.
SAPO-34 synthesized with n-butylamine as a template and its catalytic application in the methanol amination reaction
Qiao, Yuyan,Wu, Pengfei,Xiang, Xiao,Yang, Miao,Wang, Quanyi,Tian, Peng,Liu, Zhongmin
, p. 574 - 582 (2017)
SAPO-34 was synthesized with n-butylamine (BA) as a template for the first time. Crystallization temperature and initial Si amount were important factors leading to successful syntheses. Lamellar AlPO-kanemite tends to form as the major phase or as an impurity of SAPO-34 at lower crystallization temperatures, though a higher initial Si amount may offer a positive effect on the crystallization of SAPO-34 that mitigates the low temperature. Higher temperature (240 °C) can effectively suppress the generation of lamellar materials and allow the synthesis of pure SAPO-34 with a wider range of Si incorporation. The crystallization processes at 200 and 240 °C were investigated and compared. We used the aminothermal method to synthesize SAPO-34-BA at 240 °C and also found n-propylamine is a suitable template for the synthesis of SAPO-34. The SAPO-34-BA products were characterized by many techniques. SAPO-34-BA has good thermal stability, crystallinity and porosity. BA remained intact in the crystals with ～1.8 BA molecule per chabazite cage. The catalytic performance of SAPO-34 was tested in the methanol amination reaction, which showed high methanol conversion and selectivity for methylamine plus dimethylamine under the conditions investigated, suggesting that this material is a good candidate for the synthesis of methylamines.
The room temperature decomposition mechanism of dimethyl methylphosphonate (DMMP) on alumina-supported cerium oxide - Participation of nano-sized cerium oxide domains
Mitchell, Mark B.,Sheinker, Viktor N.,Cox Jr., Woodrow W.,Gatimu, Enid N.,Tesfamichael, Aron B.
, p. 1634 - 1645 (2004)
The adsorption and decomposition reactions of dimethyl methylphosphonate (DMMP) on cerium oxide supported on aluminum oxide have been examined at 25?°C. Experiments were carried out that involved dosing the reactive adsorbent with small doses of DMMP, followed by quantitative determination of the decomposition products. The results suggest that the formation reactions of methanol and dimethyl ether are competitive processes involving the same surface intermediate, which is most likely a surface methoxy species. Based on the observed results, it is proposed that the formation of dimethyl ether is due to the combination of two surface methoxy groups, while an important, if not the dominant, reaction producing methanol involves a surface methoxy group interacting with a vapor phase or physisorbed DMMP molecule. The presence of significant amounts of methoxy fragments formed upon DMMP adsorption is supported by results from diffuse reflectance spectroscopy, which also show that those groups are primarily associated with the cerium oxide domains. FT-Raman spectroscopy shows that the most active cerium oxide domains are highly dispersed two-dimensional domains or very small (a relatively narrow particle size distribution of cerium oxide crystallites on the alumina support surface from the sample preparation method. The alumina-supported cerium oxide reactive adsorbents developed as part of this study are the most active that have been reported in the literature for ambient temperature applications, decomposing approximately 775 ??mol of DMMP per gram of adsorbent at 25?°C, and strongly or irreversibly adsorbing an additional 400 ??mol, for a total capacity at room temperature of 1.1-1.2 mmol of DMMP per gram.
Discovery of Superior Cu-GaOx-HoOy Catalysts for the Reduction of Carbon Dioxide to Methanol at Atmospheric Pressure
Zohour, Bahman,Yilgor, Iskender,Gulgun, Mehmet A.,Birer, Ozgur,Unal, Ugur,Leidholm, Craig,Senkan, Selim
, p. 1464 - 1469 (2016)
Catalytic conversion of carbon dioxide to liquid fuels and basic chemicals by using solar-derived hydrogen at, or near, ambient pressure is a highly desirable goal in heterogeneous catalysis. If realized, this technology could lead to a more sustainable society together with decentralized power generation. A novel class of holmium-containing multi-metal oxide Cu catalysts, discovered through the application of high-throughput methods, is reported. In particular, ternary systems of Cu-GaOx-HoOy>Cu-CeOx-HoOy>Cu-LaOx-HoOy supported on γ-Al2O3 exhibited superior methanol production (10×) with less CO formation than previously reported catalysts at 1 atm pressure. Holmium was shown to be highly dispersed as few-atom clusters, suggesting that the formation of trimetallic sites could be the key for the promotion of methanol synthesis by Ho.
Preparation and characterization of nonmetal promoter modified CuZnAl catalysts for higher alcohol from synthesis gas through complete liquid phase method
Yu, Shi-Rui,Wang, Xiao-Dong,Huang, Wei
, p. 381 - 387 (2014)
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 eects 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/g cat h. TUeBITAK.
Superacid-Catalyzed Carbonylation of Methane, Methyl Halides, Methyl Alcohol, and Dimethyl Ether to Methyl Acetate and Acetic Acid
Bagno, Alessandro,Bukala, Jozef,Olah, George A.
, p. 4284 - 4289 (1990)
Superacid-catalyzed (BF3, BF3-H2O, HF-BF3, and CF3SO3H) carbonylation of methane and its substituted derivatives (particularly, methyl alcohol and dimethyl ether) gave acetic acid and methyl acetate.HF-BF3 was found to be the most effective catalyst, giving nearly complete conversion of methyl alcohol or dimethyl ether.CF3SO3H led to lower yields and also to the formation of methyl trifluoromethanesulfonate.Possible reaction pathways and mechanisms are discussed on the basis of experimental results.Contrasted with Rh-catalyzed carbonylation of methyl alcohol, the superacid-catalyzed reaction does not necessitate expensive catalyst and conditions necessary with sensitive organometallic catalyst system.
13C and 15N solid-state MAS NMR study of the conversion of methanol and ammonia over H-RHO and H-SAPO-34 microporous catalysts
Thursfield, Alan,Anderson, Michael W.,Dwyer, John,Hutchings, Graham J.,Lee, Darren
, p. 1119 - 1122 (1998)
13C and 15N MAS NMR have been used to study the conversion of methanol and ammonia over H-SAPO-34 and H-RHO using sealed glass ampoules as microreactors under static batch conditions. The product peaks were well resolved in the 13C NMR spectra whereas the 15N NMR spectra gave only a single broad peak making it impossible to follow the reaction by observing this nucleus. Both catalysts give the tetramethyammonium cation whereas only zeolite H-RHO produces the monomethylammonium cation.
Onium Ylide Chemistry. 3. Evidence for Competing Oxonium Ylide Formation with C-H Insertion in Meerwein's Reaction of Methylene and Methylene-d2 with Dialkyl Ethers
Olah, George A.,Doggweiler, Hans,Felberg, Jeff D.
, p. 2116 - 2120 (1984)
Meerwein's reaction of singlet methylene, produced by photolysis of diazomethane, with dialkyl ethers has been reinvestigated on the basis of reactions using CD2N2.In competition with methylene insertion into the various C-H bonds, about 10percent of methyl alkyl ether and small amounts of dimethyl ether formation are also observed.This indicates evidence for competing attack of methylene on oxygen leading to the corresponding intermediate methylenedialkyloxonium ylides which are immediately protonated by methyl alkohol (or water)impurity present in the reaction medium togive the corresponding methyldialkyloxonium ions.Dealkylative cleavage of the latter gives the observed methyl alkyl ethers.By the use of deuterium-labeled diazomethane CD2N2 it has been shown that ethylene and propylene formed under the reaction conditions are coming predominantly from diazomethane itself and not via intramolecular β-elimination of the oxonium ylides.
Electrochemically assisted synthesis of fuels by CO2 hydrogenation over Fe in a bench scale solid electrolyte membrane reactor
Ruiz, Esperanza,Martínez, Pedro J.,Morales, ángel,San Vicente, Gema,De Diego, Gonzalo,Sánchez, José María
, p. 46 - 59 (2016)
The electrochemically assisted synthesis of fuels by CO2 hydrogenation was studied over a cheap, widespread and non-precious Fe catalyst in a bench scale oxygen ion conducting membrane (YSZ) reactor. The studies were performed under conditions representative of potential practical application i.e., under atmospheric pressure, at relatively low temperatures and high gas flow rates, with varying H2/CO2 ratios and using gas compositions typical for postcombustion CO2 capture exit streams and easily scalable catalyst-electrode configurations. The Fe-TiO2 catalyst film was deposited by "dip-coating" and characterised both after pre-reduction and after testing. CO2 conversion and selectivities to CH3OH and C2H6O can be enhanced up to 4, 50 and 1.7 times, respectively, by electrochemically controlled migration of O2- promoting ions to or from the catalyst surface. The optimum temperature for the process was 325°C. Lower gas flow rates favoured the synthesis of CH3OH and C2H6O. CO2 conversion and selectivities to CH3OH and C2H6O showed a maximum for a stoichiometric H2/CO2 ratio of 3. Formation of C3H6 and CO is strongly favoured for a H2/CO2 ratio of 4 and 2, respectively, as a result of the increased and decreased hydrogen availability in the reaction system.
Support Effect of Zinc Oxide Catalyst on Synthesis of Methanol from CO2 and H2
Inoue, Takashi,Iizuka, Tokio,Tanabe, Kozo
, p. 2663 - 2664 (1987)
The synthesis of methanol from CO2 + H2 was carried out at 340-400 deg C under total pressure of 10 atm over ZnO supported MgO, Al2O3, SiO2, TiO2, ZrO2, and Nb2O5.The ZnO/ZrO2 catalyst show high activity and selectivity for methanol formation.The hydrogenation of CO2 was more selective for methanol synthesis than that of CO.
A crystalline catalyst based on a porous metal-organic framework and 12-tungstosilicic acid: Particle size control by hydrothermal synthesis for the formation of dimethyl ether
Liang, Da-Dong,Liu, Shu-Xia,Ma, Feng-Ji,Wei, Feng,Chen, Ya-Guang
, p. 733 - 742 (2011)
The strategy for obtaining a crystalline catalyst based on a porous copper-based metal-organic framework and 12-tungstosilicic acid with different particle sizes is reported. Through the control of hydrothermal synthesis and some simple treatments, catalyst samples with average particle diameters of 23, 105, and 450-μm, respectively, were prepared. This crystal catalyst has both the Bronsted acidity of 12-tungstosilicic acid and the Lewis acidity of the copper-based metal-organic framework, and has high density of accessible acid sites. Its catalytic activity was fully assessed in the dehydration of methanol to dimethyl ether. The effect of particle size on the catalytic activity of catalyst was studied, in order to select the particle size appropriate for avoiding the diffusion limitation in heterogeneous gas-phase catalysis. In the selective dehydration of methanol to dimethyl ether, this catalyst exhibited higher catalytic activity than the copper-based metal-organic framework, γ-alumina, and γ-alumina-supported 12-tungstosilicic acid catalysts. It showed high catalytic performances, even at higher space velocity or in the presence of excess water. In addition, the catalyst was also preliminarily assessed in the formation of ethyl acetate from acetic acid and ethylene. It also exhibited a high activity which was comparable with that of silica-supported 12-tungstosilicic acid catalyst. Copyright
Intrinsic Kinetics of Dimethyl Ether Synthesis from Plasma Activation of CO2 Hydrogenation over Cu–Fe–Ce/HZSM-5
Su, Tongming,Zhou, Xinhui,Qin, Zuzeng,Ji, Hongbing
, p. 299 - 309 (2017)
CO2 is activated in a plasma reactor followed by hydrogenation over a Cu–Fe–Ce/HZSM-5 catalyst, and the intrinsic kinetics of the plasma catalytic process are studied. Compared with CO2 hydrogenation using Cu–Fe–Ce/HZSM-5 alone, the CO2 conversion and the dimethyl ether selectivity for the plasma catalytic process are increased by 16.3 %, and 10.1 %, respectively, indicating that the CO2 was activated by the plasma to promote hydrogenation. A study of the intrinsic kinetics shows that the activation energies of methanol formation, the reverse water–gas shift reaction, and methanol dehydration to dimethyl ether are 149.34, 75.47, and 73.18 kJ mol?1, respectively, which are lower than if Cu–Fe–Ce/HZSM-5 is used without plasma, indicating that the activation of CO2 in the plasma reduces the activation energy of the hydrogenation reaction and improves the yield of dimethyl ether.
Mechanisms of the deactivation of SAPO-34 materials with different crystal sizes applied as MTO catalysts
Dai, Weili,Wu, Guangjun,Li, Landong,Guan, Naijia,Hunger, Michael
, p. 588 - 596 (2013)
SAPO-34 materials with comparable Bronsted acid site density but different crystal sizes were applied as methanol-to-olefin (MTO) catalysts to elucidate the effect of the crystal size on their deactivation behaviors. 13C HPDEC MAS NMR, FTIR, and UV/vis spectroscopy were employed to monitor the formation and nature of organic deposits, and the densities of accessible Bronsted acid sites and active hydrocarbon-pool species were studied as a function of time-on-stream (TOS) by 1H MAS NMR spectroscopy. The above-mentioned spectroscopic methods gave a very complex picture of the deactivation mechanism consisting of a number of different steps. The most important of these steps is the formation of alkyl aromatics with large alkyl chains improving at first the olefin selectivity, but hindering the reactant diffusion after longer TOS. The hindered reactant diffusion leads to a surplus of retarded olefinic reaction products in the SAPO-34 pores accompanied by their oligomerization and the formation of polycyclic aromatics. Finally, these polycyclic aromatics are responsible for a total blocking of the SAPO-34 pores, making all catalytically active sites inside the pores nonaccessible for further reactants.
Structure and Catalytic Activity of Alumina-Supported Pt-Co Bimetallic Catalysts. 2. Chemisorption and Catalytic Reactions
Guczi, Lazlo,Hoffer, Tamas,Zsoldos, Zoltan,Zyade, Souad,Maire, Gilbert,Garin, Francois
, p. 802 - 808 (1991)
A series od Pt1-xCox/Al2O3 bimetallic catalysts have been characterized by temperature-programmed reduction (TPR), chemisorption of hydrogen and CO, deuterium exchange using both methanol and methane, and activity for the CO/H2 reaction.A Pt-assisted reduction mechanism over the entire range of composition was established by the TPR studies as well as by the chemisorption results.An enhanced metallic dispersion for the Pt-rich catalyst and formation of bimetallic particles on the Co-rich side was also indicated.In the CO hydrogenation over the Pt-rich catalysts the predominant products are methanol and dimethyl ether whereas on the Co-rich samples hydrocarbons and higher alcohols are produced.The mechanisms of deuterium exchange with methane and methanol are significantly different, the former being catalyzed solely by metallic sites while the latter utilizes both oxide and metallic sites for stepwise and multiple exchange, respectively.On the basis of the XPS data (preceding article) as well as the chemisorption results reported here, a surface model is introduced for interpretation of the catalytic results.
ALKYL TRANSFER REACTIONS BETWEEN PROTONATED ALCOHOLS AND ETHERS. GAS-PHASE ALKYLATION OF FORMALDEHYDE
Karoas, Zeev,Meot-Ner (Mautner), Michael
, p. 1859 - 1863 (1989)
Alkyl-transfer reactions involving protonated alcohols and ethers, of the general type R2OR'+ + R''2O -> R""OR'+ + R2O, may be classified according to the degree of alkylation, i.e., the total number n of alkyl groups in the system.For systems containing two alkyl groups, the reaction is alkyl transfer between protonated and neutral alcohols, ROH2+ + ROH -> R2OH+ + H2O, and we measured rate constants for R=Me, Et, i-Pr, and t-Bu.The rate constants are (0.6-1.5) x 1E-10 cm3s-1 when R is a normal alkane and (6 +/- 1) x 1E-10 when R=i-Pr and t-Bu.The larger rate constants in the latter may be due to a lowered barrier for the initial partial R+-OH2 bond dissociation.For reaction systems containing three alkyl groups, i.e., the reactions of protonated ethers R2OH+ with alcohols R'OH, the possible channels are alkyl transfer from the alcohol, yielding R2OR'+, or alkyl transfer from the ether, yielding ROR'H+.Both processes are observed in (CH3)2OH+ + C2D5OH which yields both (CH3)2OC2D5H+ and CH3OC2D5H+.For systems containing four alkyl groups an example is the reaction(CH3)2OH+ + (CH3)2O -> (CH3)3O+ + CH3OH, which is a slow reaction with k3s-1.Finally, for the highest possible degree of alkylation, n=5, an example is methyl transfer in (CH3)OCD3+ + (CH3)2O -> (CH3)2OCH3+ + CH3OCD3 which is a very slow reaction, observed only above 500K.The rate constants for alcohols show negligible temperature dependence between 300 and 670 K, but in the most highly alkylated system the rate increases strongly with temperature, and an activation energy of 15 kcal-1 is observed.The results show that alkyl transfer occurs in systems with all possible degrees of alkylation, but the rates tend to decrease with increasing alkylation.In addition to saturated systems, alkyl transfer is also observed with unsaturated ions or neutrals.Examples are alkyl transfer between unsaturated oxocarbonium ions C2H5O+ and methanol and ethanol and between protonated alcohols and CH2O.These reactions have rate constants of (1-4) x 1E-11 cm3s-1.Depending on the temperature coefficients, the alkylation of formaldehyde may be important in astrochemical synthesis.
CATALYSTS FOR SELECTIVE OXIDATION OF METHANOL TO DIMETHOXYMETHANE AND RELATED METHODS
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Paragraph 0074-0078, (2021/10/02)
Embodiments include catalyst compositions and methods of synthesizing catalyst compositions for the selective oxidation of methanol to dimethoxymethane, as well as methods of selective oxidation of methanol to dimethoxymethane using catalyst compositions. The catalyst composition can comprise vanadium oxide and a mixed metal oxide, wherein the vanadium oxide is supported on the mixed metal oxide and wherein the mixed metal oxide includes a redox component and an acid component. The method of selective oxidation of methanol to dimethoxymethane can comprise at least the following step: contacting methanol with a catalyst composition in the presence of an oxidizing agent to produce dimethoxymethane.
Dimethyl ether synthesis process exploiting CO-rich gas
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Paragraph 0061-0096, (2021/06/09)
The present invention relates to a converter gas (Lintz-Donawiaz convert Gas) that is an excess of carbon monoxide-containing gas such as iron-iron enriched gas. Dimethyl ether using LDG). dimethyl ether. DME) A synthesis process. Is a process for producing dimethyl ether, which is a high-value product with high selectivity, utilizing whole gas as a source gas.
PROCESS FOR SYNTHESIS OF DIMETHYL ETHER
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Page/Page column 0009; 0019, (2021/09/04)
The present invention depicts a method for one pot synthesis of dimethyl ether from syngas in a simple and economical manner. The process (500A, 500B, 600) has advantages of reducing the requirement of refrigeration and at the same time producing a ready to use product. The process (500A, 500B, 600) includes the steps of separating carbon dioxide from a first stream (512, 612) comprising syngas to produce a second stream (522, 622), reacting the second stream (522, 622) in the presence of a catalyst to produce a third stream (532, 632), cooling the third stream (532, 632) to a temperature in a range from 10o C to 40o C to produce a fourth stream (542, 642), and washing and conducting a phase separation of the fourth stream (542, 642) to produce a product comprising at least 10% by volume of dimethyl ether.
