Methanol, reaction dehydration

Iron(II) bromide [7789-46-0] FeBr2, can be prepared by reaction of iron and bromine ia a flow system at 200°C and purified by sublimation ia oitrogea or uader vacuum. Other preparative routes iaclude the reactioa of Fe202 with HBr ia a flow system at 200—350°C, reactioa of iroa with HBr ia methanol, and dehydration of hydrated forms. FeBr2 crystallizes ia a layered lattice of the Cdfy type and has a magnetic moment of... 

As shown in Eq. 6.59, Rapoport has prepared sinefungin, nucleoside antibiotics, via nitro-aldol reaction, dehydration, and reduction with Zn in acetic add.115a [i-Nitrostyrenes are selectivity reduced to the corresponding oximes by indium metal in aqueous methanol under neutral conditions.11515... 

ZnO exhibits varied catalytic properties, being active for hydrogenation and dehydrogenation reactions, dehydration of alcohols, methanol synthesis, and other reactions. ZnO is a wide-band n-type semiconductor with surface states present in the band gap. It can be doped with cations, and defects can be generated by treatment under oxidizing or reducing conditions (which change the availability of electrons at the surface). 

Description Formaldehyde solutions are produced by oxidation with methanol in the air. In the UIF process, the reaction occurs on the surface of a silver-crystal catalyst at temperatures of 620°C-680°C, where the methanol is dehydrated and partly oxidized ... 

The product profiles for 2-propanol dehydration on VOAIPO4 show only one product (propene) but for methanol reaction (Fig.6) on the same catalyst shows two types of products (DME and C2+ hydrocarbons). But within 40-45 mol% conversion the decomposition product is negligible. As it is marked both DME and C2+ are present from the onset of the reaction which indicate that both reaction products are formed by direct dehydration. The downward deviation marked, in case of DME plot indicates the instability of the product. It means DME further dehydrates to C2+ hydrocarbons in a secondary reaction. All other catalysts also show nearly similar behaviour. Thus the path way for the formation of C2+ hydrocarbons on M0.05AI095PO4 catalysts is a combination of parallel and consecutive (primary and secondary) reactions. 

Methanol dehydrogenates to methyl formate over fresh WC and P-W2C powders with selectivities higher than 90% (109,110). The dominant side reaction is the decomposition to synthesis gas. Over WC and P-W2C modified with oxygen, methanol selectively dehydrates to dimethylether at 473 K and at higher reaction temperatures, C2-C4 olefins are produced (47). Thus, the dehydrodimerization of methanol apparently requires WC sites. These sites are titrated by chemisorbed oxygen. Thus, oxygen on the surface inhibits the formation of methyl formate and introduces a surface acid function WO that catalyzes dehydration by carbenium-ion type catalysis. 

Consider the dimethyl ether (DME) process shown in Figure B.1.1 (Unit 200) and Tables B.1.1 and B.1.2. The process is quite straightforward and consists of a gas-phase catalytic reaction in which methanol is dehydrated to give DME with no appreciable side reactions. 

Two possible carbocation reaction schemes have been published. There is presently much debate over the nature of the intermediate from which the primary olefins—ethylene, propylene, and the butenes—are formed. According to Hutchings and Hunter [22] this would be an oxonium methylylide, produced from the methoxy carbenium ion, CHj generated out of methanol by dehydration (Fig. 24). According to Arstad et al. [102], Wei et al. [28], and Dahl and Kolboe [90] the intermediate(s) they call carbon pool with which methanol reacts would be the hexamethylbenzenium ion or a similar compound. They maiidy deduce this from the analysis of the catalyst after conversion of the methanol in a batch mode. 

The reaction of N-methyl-(p-dimethylamino)thiobenzamide (99) with a number of a-haloketones and a-bromoheptaldehyde gave stable 4-hydroxythiazolinium salts (100), which could be subsequently dehydrated by methanolic hydrogen chloride to the thiazolium salts (101), (Scheme 44) (622). 

Dimethyl Ether. Synthesis gas conversion to methanol is limited by equiUbrium. One way to increase conversion of synthesis gas is to remove product methanol from the equiUbrium as it is formed. Air Products and others have developed a process that accomplishes this objective by dehydration of methanol to dimethyl ether [115-10-6]. Testing by Air Products at the pilot faciUty in LaPorte has demonstrated a 40% improvement in conversion. The reaction is similar to the Hquid-phase methanol process except that a soHd acid dehydration catalyst is added to the copper-based methanol catalyst slurried in an inert hydrocarbon Hquid (26). 

Mobil MTG and MTO Process. Methanol from any source can be converted to gasoline range hydrocarbons using the Mobil MTG process. This process takes advantage of the shape selective activity of ZSM-5 zeoHte catalyst to limit the size of hydrocarbons in the product. The pore size and cavity dimensions favor the production of C-5—C-10 hydrocarbons. The first step in the conversion is the acid-catalyzed dehydration of methanol to form dimethyl ether. The ether subsequendy is converted to light olefins, then heavier olefins, paraffins, and aromatics. In practice the ether formation and hydrocarbon formation reactions may be performed in separate stages to faciHtate heat removal. 

Methyl /-Butyl Ether. MTBE is produced by reaction of isobutene and methanol on acid ion-exchange resins. The supply of isobutene, obtained from hydrocarbon cracking units or by dehydration of tert-huty alcohol, is limited relative to that of methanol. The cost to produce MTBE from by-product isobutene has been estimated to be between 0.13 to 0.16/L ( 0.50—0.60/gal) (90). Direct production of isobutene by dehydrogenation of isobutane or isomerization of mixed butenes are expensive processes that have seen less commercial use in the United States. 

The reaction is mn for several hours at temperatures typically below 100°C under a pressure of carbon monoxide to minimise formamide decomposition (73). Conversions of a-hydroxyisobutyramide are near 65% with selectivities to methyl a-hydroxyisobutyrate and formamide in excess of 99%. It is this step that is responsible for the elimination of the acid sludge stream characteristic of the conventional H2SO4—ACH processes. Because methyl formate, and not methanol, is used as the methylating agent, formamide is the co-product instead of ammonium sulfate. Formamide can be dehydrated to recover HCN for recycle to ACH generation. 

Methylphenol. This phenol, commonly known as o-cresol, is produced synthetically by the gas phase alkylation of phenol with methanol using modified alumina catalysis or it may be recovered from naturally occurring petroleum streams and coal tars. Most is produced synthetically. Reaction of phenol with methanol using modified zeoHte catalysts is a concerted dehydration of the methanol and alkylation of the aromatic ring. 2-Methylphenol [95-48-7] is available in 55-gal dmms (208-L) and in bulk quantities in tank wagons and railcars. 

The / f/-butanol (TBA) coproduct is purified for further use as a gasoline additive. Upon reaction with methanol, methyl tert-huty ether (MTBE) is produced. Alternatively the TBA is dehydrated to isobutylene which is further hydrogenated to isobutane for recycle ia the propylene oxide process. 

Cupric chloride or copper(II) chloride [7447-39 ], CUCI2, is usually prepared by dehydration of the dihydrate at 120°C. The anhydrous product is a dehquescent, monoclinic yellow crystal that forms the blue-green orthohombic, bipyramidal dihydrate in moist air. Both products are available commercially. The dihydrate can be prepared by reaction of copper carbonate, hydroxide, or oxide and hydrochloric acid followed by crystallization. The commercial preparation uses a tower packed with copper. An aqueous solution of copper(II) chloride is circulated through the tower and chlorine gas is sparged into the bottom of the tower to effect oxidation of the copper metal. Hydrochloric acid or hydrogen chloride is used to prevent hydrolysis of the copper(II) (11,12). Copper(II) chloride is very soluble in water and soluble in methanol, ethanol, and acetone. 

There is a scattered body of data in the literature on ordinary photochemical reactions in the pyrimidine and quinazoline series in most cases the mechanisms are unclear. For example, UV irradiation of 4-aminopyrimidine-5-carbonitrile (109 R=H) in methanolic hydrogen chloride gives the 2,6-dimethyl derivative (109 R = Me) in good yield the 5-aminomethyl analogue is made similarly (68T5861). Another random example is the irradiation of 4,6-diphenylpyrimidine 1-oxide in methanol to give 2-methoxy-4,6-diphenyl-pyrimidine, probably by addition of methanol to an intermediate oxaziridine (110) followed by dehydration (76JCS(P1)1202). 

Allylic A" -3-hydroxyls are particularly reactive, although some difficulty arises because this system is prone to acid-catalysed dehydration to the 3,5-diene. A" -3-Methyl ethers are readily prepared by direct, p-toluenesulfonic acid-catalysed reaction with methanol. 

The pharmacological versatility of this general substitution strategy is further illustrated by diazonium coupling of 14 with 2-nitrobenzenediazonium chloride to produce biarylal-dehyde 18. Formation of the oxime with hydroxylamine is followed by dehydration to the nitrile. Reaction with anhydrous methanolic hydrogen chloride leads to imino ether and addition-elimination of ammonia leads to the antidepressant amid-ine, nitrafudam (20). ... 

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