Methanol, production kinetics

Methanol Production. Kinetics, Surface Science, and Mechanisms... 

Methanol Production. Kinetics Surface Science, and Mechanisms Methanol production from CO, CO2, and H2 is an industrial process that yields about 3 X 10 kg per day. The relevant thermodynamic parameters for the two reactions are [127]... 

However, if there is no other exothermic pathway available, all the intermediate can do is revert to reactants. In such a situation, the more favorable the addition process is, the more internal energy is in the intermediate and the faster the reverse dissociation will occur. The better the addition is thermochemically, the worse it is kinetically. For the proton transfer pathway (6b), the neutral methanol product can carry off the excess energy as translational energy (and capture some of it in the newly formed OH bond) and the reaction proceeds. 

Methanol production rates over the Cu/Zn/Al, 0.04 Pd/Cu/Zn/Al, 0.09 Pd/Cu/Zn/Al, and 0.21 Pd/Al+Cu/Zn/Al catalysts in the differential kinetic regime are given in Table 2. Each point was the average of several experiments which were quite reproducible. All four catalysts gave the same rate of methanol... 

The results at differential conversions with water addition can be compared with methanol production at the finite conversion in the internal recycle reactor where the water concentration as a result of water production was similar (Table 3). The two types of experiment are analogous in that at differential conditions in the microflow reactor the catalyst was uniformly exposed to the feed concentration, whereas at finite conversions in the internal recycle reactor the catalyst was uniformly exposed to the product concentration. The methanol production rate at finite conversion was similar to the methanol production rate from COj/Hj/HjO at differential conditions for both the Cu/Zn/Al-1 and Pd impregnated catalyst. Therefore, the kinetics at the particular finite conversions, well away from equilibrium, can also be described by methanol production by CO2 hydrogenation, and the inhibition of this reaction associated with the presence of the product water. Furthermore, the Pd promotion was similar under the two reaction regimes (Table 3), reinforcing the conclusion that Pd promotion of CO2 hydrogenation is active only in the presence of water. 

R = H), which lacks the 5,6 double bond, is virtually unaffected by methanolic base. Kinetic studies of the interconversion of coralynium ion [8-methyl derivative of (128 R = OMe)] and 6 -acetylpapaverine have been made. Hydrazinolysis of the protoberberine salt (136 R = OCH2CH2N-phthaloyl) with hydrazine hydrate and hydrobromic acid gave, almost quantitatively, the unexpected product (136 R = NHCH2CH20H). This is thought to arise by Smiles rearrangement [cf. (137)]. Following this observation it was found that a variety of 6- of 8-... 

The kinetic theory model was extended to include the effect of the mass transfer coefficient between the liquid and the gas and the water gas shift reaction in the slurry bubble column reactor. The computed granular temperature was around 30 cm /sec and the computed catalyst viscosity was closed to 1.0 cp. The volumetric mass transfer coefficient estimated by the simulation has a good agreement with experimental values shown in the literature. The optimum particle size was determined for maximum methanol production in a SBCR. The size was about 60 - 70 microns, found for maximum granular temperature. This particle size is similar to FCC particle used in petroleum refining. 

The model aimed at the optimization of methanol production by methane partial oxidation at high pressures has been developed by Vedeneev and co-workers since 1988. Up to now it is one of the most successful examples of specialized models for moderate-temperature oxidative conversion of light alkanes. It is based on a deep understanding of the main ruling factors responsible for particular kinetic features of the process. Correspondingly, the blocks of elementary reactions for such features, and for the formation of methanol at high pressures in particular, were included into the kinetic scheme. 

The synthesis of methanol from C0(+C02) and H2 was also attempted by Campbell and co-workers (102) over a Cu(l 11) surface and over well-defined Cu overlayers on a ZnO(OOOl) single-crystal surface. They could set an upper limit of < 2 x 1012 molecules/cm2/s on the methanol production rate at temperatures up to 600 K and pressures up to 1500 torr. These limits are consistent with expectations based on (extrapolated) kinetics for high-surface-area Cu/ZnO catalysts. Their results also showed that C02 has extremely low reactivity for oxidation of the clean Cu(l 11) surface (102), and they argue that it is very unlikely that significant oxygen concentrations exist on the Cu(lll)-like surfaces of practical catalysts under methanol synthesis conditions (102, 103). 

The kinetic equation for methanol production is based on work by Natta et al. [137] and Cappelli and Dente [138] and accounts for the nonideal behavior of the reacting gases. 

It has also been suggested that the loss of catalytic activity of copper electrodes depends on the crystallographic properties of the electrode, the surface characteristics and the morphology . The rate of methanol synthesis from a 1 1 mixture of CO2 and H2 at a Cu(lOO) single crystal has been measured and a kinetic model has been proposed This model correctly predicts the rates of methanol production in catalysts under industrial conditions. 

In this paper, there are a number of questions about this resist that we address. First, how is the differential dissolution rate created from the chemical-amplification reaction such that the exposed and reacted material withstands the development step with aqueous tetramethylammonium hydroxide(TMAH) In order to answer this first major question it was necessary to address quantitatively several issues. How much acid is created during exposure How much methanol product remains in the film after PER (This is of concern because of its possible effect on the kinetics of the reaction.) How many cycles of catalytic reaction does the acid undergo before the desired differential dissolution rate is reached The second question to be addressed quantitatively is what are the top surface and the sidewall roughness after the resist is developed ... 

A-Tosyl-5-alkyl-5-aryl-sulphimides or the cycloalkyl-sulphimides (39 n = 2, 3, or 4) have been shown to react with hydroxide ion in methanol solution, affording either the corresponding sulphoxide, or the hemithioacetal (40), or a mixture of both products. Kinetic studies, including studies using the a-deuteriated compounds, have revealed that the formation of (40) proceeds via an lcB path that involves rate-determining cleavage of the S—N bond. ... 

The typical concentrations of methanol in an HTSC application are approximately 100 to 300 ppmw. In a Low Temperature Shift Converter (LTSC) application, the methanol production is greater than that of an HTSC application. The formation of methanol is not just related to equilibrium for an LTSC but also by the catalyst characteristics and kinetics. Therefore, the catalyst vendor should be contacted in reference to calculating the expected amount of methanol from an LTSC application. 

The products of reaction of glycerol with 2,2-dimethoxypropane in the presence of 1,2-dimethoxy-ethane have been characterized in H n.m.r. Besides the 1,2- and 1,3-acetals, dimers of the 1,2-acetal were obtained, linked through isopropylidene groups, together with a mixed acetal of glycerol and methanol. The kinetic product of isopropylidenation of the 1-C-substituted L-threo-glycerol (1) under Ohlah conditions was found to be the terminal acetal (2 which is transformed under thermodynamic control to the acetal (3). 

Pressure affects both equilibrium position and rate of reaction in methanol synthesis. From a total loop perspective, an increase (or decrease) in operating pressure affects more than merely the reaction conditions. It also affects the condensation of product (dew point) and recycle of methanol back to the converter system. Considering any gven converter, however, calculations indicate that a 10% increase in operating pressure yields about a 10% increase in methanol production if equilibrium conditions exist. When the reaction is far from equilibrium and controlled by kinetics, the increase (or decrease) in methanol production is more than proportional to the increase (or decrease) in operating... 

A 1 % increase in hydrogen concentration results in a 4% decrease in carbon oxide content and causes expected production to drop by about 1%. With a 2% increase in hydrogen concentration accompanied by a 7+% decrease in carbon oxide content, methanol production under kinetically controlled conditions drops by more than 2%. At the relative low concentrations of carbon oxides... 

At the end of this chapter, you will be able to solve a series of problems related to the kinetics of methanol production [ Page 616],... 

Anhydrous, monomeric formaldehyde is not available commercially. The pure, dry gas is relatively stable at 80—100°C but slowly polymerizes at lower temperatures. Traces of polar impurities such as acids, alkahes, and water greatly accelerate the polymerization. When Hquid formaldehyde is warmed to room temperature in a sealed ampul, it polymerizes rapidly with evolution of heat (63 kj /mol or 15.05 kcal/mol). Uncatalyzed decomposition is very slow below 300°C extrapolation of kinetic data (32) to 400°C indicates that the rate of decomposition is ca 0.44%/min at 101 kPa (1 atm). The main products ate CO and H2. Metals such as platinum (33), copper (34), and chromia and alumina (35) also catalyze the formation of methanol, methyl formate, formic acid, carbon dioxide, and methane. Trace levels of formaldehyde found in urban atmospheres are readily photo-oxidized to carbon dioxide the half-life ranges from 35—50 minutes (36). 

Dente and Ranzi (in Albright et al., eds.. Pyrolysis Theory and Industrial Practice, Academic Press, 1983, pp. 133-175) Mathematical modehng of hydrocarbon pyrolysis reactions Shah and Sharma (in Carberry and Varma, eds.. Chemical Reaction and Reaction Engineering Handbook, Dekker, 1987, pp. 713-721) Hydroxylamine phosphate manufacture in a slurry reactor Some aspects of a kinetic model of methanol synthesis are described in the first example, which is followed by a second example that describes coping with the multiphcity of reactants and reactions of some petroleum conversion processes. Then two somewhat simph-fied industrial examples are worked out in detail mild thermal cracking and production of styrene. Even these calculations are impractical without a computer. The basic data and mathematics and some of the results are presented. 

Methanol synthesis served as the model for the true mechanism. Stoichiometry, thermodynamics, physical properties, and industrial production rates were all taken from the methanol literature. Only the reaction mechanism and the kinetics of methanol synthesis were discarded. For the mechanism a four step scheme was assumed and from this the... 

The importance of the solvent, in many cases an excess of the quatemizing reagent, in the formation of heterocyclic salts was recognized early. The function of dielectric constants and other more detailed influences on quatemization are dealt with in Section VI, but a consideration of the subject from a preparative standpoint is presented here. Methanol and ethanol are used frequently as solvents, and acetone,chloroform, acetonitrile, nitrobenzene, and dimethyl-formamide have been used successfully. The last two solvents were among those considered by Coleman and Fuoss in their search for a suitable solvent for kinetic experiments both solvents gave rise to side reactions when used for the reaction of pyridine with i-butyl bromide. Their observation with nitrobenzene is unexpected, and no other workers have reported difficulties. However, tetramethylene sulfone, 2,4-dimethylsulfolane, ethylene and propylene carbonates, and salicylaldehyde were satisfactory, giving relatively rapid reactions and clean products. Ethylene dichloride, used quite frequently for Friedel-Crafts reactions, would be expected to be a useful solvent but has only recently been used for quatemization reactions. ... 

Methanol oxidation on Pt has been investigated at temperatures 350° to 650°C, CH3OH partial pressures, pM, between 5-10"2 and 1 kPa and oxygen partial pressures, po2, between 1 and 20 kPa.50 Formaldehyde and C02 were the only products detected in measurable concentrations. The open-circuit selectivity to H2CO is of the order of 0.5 and is practically unaffected by gas residence time over the above conditions for methanol conversions below 30%. Consequently the reactions of H2CO and C02 formation can be considered kinetically as two parallel reactions. 

Methanol oxidation on Ag polycrystalline films interfaced with YSZ at 500°C has been in investigated by Hong et al.52 The kinetic data in open and closed circuit conditions showed significant enhancement in the rate of C02 production under cathodic polarization of the silver catalyst-electrode. Similarly to CH3OH oxidation on Pt,50 the reaction exhibits electrophilic behavior for negative potentials. However, no enhancement of HCHO production rate was observed (Figure 8.48). The rate enhancement ratio of C02 production was up to 2.1, while the faradaic efficiencies for the reaction products defined from... 

This reversal has been demonstrated by both product and kinetic studies. In the absence of solvent nucleophilic assistance and of substituents favouring P-bromo-carbonium ion intermediates, the ionization of CTCs to bromonium (poly)bromide has been shown to occur not only for congested olefins, but more generally for "normal olefins both in aprotic chlorinated hydrocarbons and in protic solvents like acetic acid and methanol. 

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