Methanol-ethylene, conversion

The first mode of the high resolution C-NMR of adsorbed molecules was recently reviewed Q-3) and the NMR parameters were thoroughly discussed. In this work we emphasize the study of the state of adsorbed molecules, their mobility on the surface, the identification of the surface active sites in presence of adsorbed molecules and finally the study of catalytic transformations. As an illustration we report the study of 1- and 2-butene molecules adsorbed on zeolites and on mixed tin-antimony oxides (4>3). Another application of this technique consists in the in-situ identification of products when a complex reaction such as the conversion of methanol, of ethanol (6 7) or of ethylene (8) is run on a highly acidic and shape-selective zeolite. When the conversion of methanol-ethylene mixtures (9) is considered, isotopic labeling proves to be a powerful technique to discriminate between the possible reaction pathways of ethylene. 

Conversion of methanol-ethylene mixtures The C isotopic labeling is a powerful technique to discriminate between the possible reaction pathways of ethylene (9,50). 

The first example of this type of a catalytic conversion is indicated in Scheme 42 [123]. This refers to, y-unsaturated esters and amides 261, which, on treatment with an excess of ammonium persulfate and a catalytic amount of diphenyl diselenide, in methanol, ethylene glycol or in water, gave the addition products 262. These, by reaction with persulfate, afforded the y-alkoxy or the y-hydroxy-a, -unsaturated derivatives 263, respectively. 

Under relatively mild conditions of methanol conversion one can be reasonably sure that ethylene is not participating fully in the quasiequilibrium. Such conditions are those of low methanol conversion, or when aqueous methanol undergoes conversion at about 300°C. Then it is possible to... 

Methanol to Ethylene Conversion, 100% Product Yield, wt-% Methanol to Propylene Conversion, 100% Product Yield, wt-% ... 

The conversion of simple organic molecules (e.g. methanol, ethanol or ethylene) can also be monitored by the use of combined TG-DTA. For instance such an analysis, applied to ethylene conversion on the acid form of ZSM-5, enabled the transformation to be interpreted in terms of five different reaction steps [25]. Another example of thermal analysis application to the study of the development of a catalyzed reaction is the use of isothermal TG for investigating the kinetics of coke deposition in inner or external zeolitic sites and its subsequent removal by oxidation in air [25]. 

It is worth noticing that, irrespective of the metal oxide, all Pd-based catalysts promote the selective conversion of ethanol to acetate ion. " No analytical data for the oxidation products of methanol, ethylene glycol and glycerol have been provided by K. P. Shen, yet one can surmise that the latter two substrates are mainly oxidized to carboxylic acid as found for other Pd-based electrocatalysts vide... 

Keywords Methanol, Ethylene, Propylene, SAPO-34, Conversion... 

In another study on the cofeeding of ethylene and methanol with isotopic labeling over a ZSM-5 catalyst, Ronning et al. [138] drew the conclusion that ethylene is unreactive and its methylation could not be an important part in the reaction network. They determined that the ethylene conversion is increased in the presence of methanol but only at rather low levels of conversion. 

Yamaguchi et al. [143] studied the methylation of ethylene with methanol to propylene over MFI zeolites with different heteroatoms. They found that an efficient catalyst based on MFI with weak acidity prevents the formation of ethylene oligomers. It was demonstrated that the MeOH could be completely converted to hydrocarbons at 500°C with a selectivity of about 50-60% to propylene over a weak acid catalyst in presence of ethylene. The ethylene conversion under such conditions was nearly zero. The authors suggested that the enhancement of propylene selectivity was caused by the methylation of ethylene with methanol. 

The reaction of methyl propionate and formaldehyde in the gas phase proceeds with reasonable selectivity to MMA and MAA (ca 90%), but with conversions of only 30%. A variety of catalysts such as V—Sb on siUca-alumina (109), P—Zr, Al, boron oxide (110), and supported Fe—P (111) have been used. Methjial (dimethoxymethane) or methanol itself may be used in place of formaldehyde and often result in improved yields. Methyl propionate may be prepared in excellent yield by the reaction of ethylene and carbon monoxide in methanol over a mthenium acetylacetonate catalyst or by utilizing a palladium—phosphine ligand catalyst (112,113). 

In addition to these principal commercial uses of molybdenum catalysts, there is great research interest in molybdenum oxides, often supported on siHca, ie, MoO —Si02, as partial oxidation catalysts for such processes as methane-to-methanol or methane-to-formaldehyde (80). Both O2 and N2O have been used as oxidants, and photochemical activation of the MoO catalyst has been reported (81). The research is driven by the increased use of natural gas as a feedstock for Hquid fuels and chemicals (82). Various heteropolymolybdates (83), MoO.-containing ultrastable Y-zeoHtes (84), and certain mixed metal molybdates, eg, MnMoO Ee2(MoO)2, photoactivated CuMoO, and ZnMoO, have also been studied as partial oxidation catalysts for methane conversion to methanol or formaldehyde (80) and for the oxidation of C-4-hydrocarbons to maleic anhydride (85). Heteropolymolybdates have also been shown to effect ethylene (qv) conversion to acetaldehyde (qv) in a possible replacement for the Wacker process. 

The performance of many metal-ion catalysts can be enhanced by doping with cesium compounds. This is a result both of the low ionization potential of cesium and its abiUty to stabilize high oxidation states of transition-metal oxo anions (50). Catalyst doping is one of the principal commercial uses of cesium. Cesium is a more powerflil oxidant than potassium, which it can replace. The amount of replacement is often a matter of economic benefit. Cesium-doped catalysts are used for the production of styrene monomer from ethyl benzene at metal oxide contacts or from toluene and methanol as Cs-exchanged zeofltes ethylene oxide ammonoxidation, acrolein (methacrolein) acryflc acid (methacrylic acid) methyl methacrylate monomer methanol phthahc anhydride anthraquinone various olefins chlorinations in low pressure ammonia synthesis and in the conversion of SO2 to SO in sulfuric acid production. 

Dehydrogenation processes in particular have been studied, with conversions in most cases well beyond thermodynamic equihbrium Ethane to ethylene, propane to propylene, water-gas shirt reaction CO -I- H9O CO9 + H9, ethylbenzene to styrene, cyclohexane to benzene, and others. Some hydrogenations and oxidations also show improvement in yields in the presence of catalytic membranes, although it is not obvious why the yields should be better since no separation is involved hydrogenation of nitrobenzene to aniline, of cyclopentadiene to cyclopentene, of furfural to furfuryl alcohol, and so on oxidation of ethylene to acetaldehyde, of methanol to formaldehyde, and so on. 

Solution Polymerization These processes may retain the polymer in solution or precipitate it. Polyethylene is made in a tubular flow reactor at supercritical conditions so the polymer stays in solution. In the Phillips process, however, after about 22 percent conversion when the desirable properties have been attained, the polymer is recovered and the monomer is flashed off and recyled (Fig. 23-23 ). In another process, a solution of ethylene in a saturated hydrocarbon is passed over a chromia-alumina catalyst, then the solvent is separated and recyled. Another example of precipitation polymerization is the copolymerization of styrene and acrylonitrile in methanol. Also, an aqueous solution of acrylonitrile makes a precipitate of polyacrylonitrile on heating to 80°C (176°F). 

As an alternate to LNG, natural gas can be chemically converted to methanol, chemical feedstocks (such as ethylene), gasoline, or diesel fuel. Most processes start with the conversion of methane to synthesis gas, a mixture of carbon monoxide and hydrogen. This can be done partial oxidation, an exothermic reaction ... 

A porphinatoaluminum alkoxide is reported to be a superior initiator of c-caprolactone polymerization (44,45). A living polymer with a narrow molecular weight distribution (M /Mjj = 1.08) is ob-tmned under conditions of high conversion, in part because steric hindrance at the catalyst site reduces intra- and intermolecular transesterification. Treatment with alcohols does not quench the catalytic activity although methanol serves as a coinitiator in the presence of the aluminum species. The immortal nature of the system has been demonstrated by preparation of an AB block copolymer with ethylene oxide. The order of reactivity is e-lactone > p-lactone. 

In the synthesis of DMC fiom the transesterification of EC and methanol, quaternary ammonium salt catalysts showed good catalytic activity. The main byproduct was ethylene glycol. The quaternary salt with the cation of bulkier alkyl chain laigth and witii more nucleophilic anion showed better reactivity. Hi temperature and large amount of catalyst increased the conversion of EC. The EC conversion and DMC selectivity increased as the pressure of CO2 increased from 250 to 350 psig. 

Removal of formaldehyde from aqueous 2-butyne-l,4-diol, or a similar solution, which is relevant in the subsequent manufacture of c -2-butene-l,4-diol, by batch reactive distillation with methanol or ethylene glycol in the presence of Indion 130 as catalyst has also been reported 98% conversion of formaldehyde was obtained by reactive distillation with 7 times the stoichiometric quantity of methanol, compared to 15% conversion obtained in a closed system (Kolah and Sharma, 1995). 

---