Methanol synthesis yield improvement

Ozonization of A -steroids usually gives complex mixtures (however, see ref. 48). Ozonolysis became a practical step in the general synthesis of B-norsteroids with the discovery that added methanol" (or formaldehyde ) improves yields significantly. Thus, Tanabe and Morisawa prepared 5/ -hydroxy-6/ -formyl-B-norsteroids (74) from cholesterol acetate, dehydroepiandrosterone acetate and pregnenolone acetate in overall yields of 64-74% by the reaction sequence represented below. 

These final steps are not included in excerpt 4G, but if you are interested, the full article is included at the end of chapter 2.) The text describes these efforts, following the order of the entries in Table f. First, different solvents were tried beginning with methanol (entry f). Next, various alcohol mixtures were tried, but yields dropped (entries 2—4). The yield improved slightly when water was mixed with methanol (entry 5) hence, water alone was tried at different temperatures (entries 6—9). This truly is a story of scientific discovery The readers learn both what did not work and what did. This approach is quite common in papers describing organic synthesis. 

Dimethylether (DME) can be synthesized effectively fi om H2/CO2 feed by one-pot synthesis using hybrid catalyst. Hybrid catalyst is composed of mixture of methanol synthesis catalyst and soHd acid catalyst. DME is an important and valuable chemical used as solvent, propellant and raw material to hquid fuels. As shown in Fig.l, methcuiol fixjm H2/CO2 has a severe limitation of thermod3mamic equihbrium compared with that fi om H2/CO. To overcome such a limitation, in situ transformation of methanol to DME is reasonable way to improve total methanol yield (CH3OH + DME). Table 2 shows reaction behavior to DME synthesis over hybrid... 

In order to synthesize gasoline effectively from carbon dioxide through one-pass reaction system, methanol synthesis catalyst was improved. Pd and Ga were added to Cu-Zn based catalyst to optimize the state of Cu during the reaction. As the result, the space-time yield (STY) of methanol from CO2 was 1,410 gd h at 270, 80 atm and SV=18,800 /h. In second stage reactor in which H-Ga or Al-silicate was packed, methanol was converted to gasoline. Maximum selectivity to gasoline fraction was 54.4 % and STY was 312 gl h at 320 C and 15 atm. 

Struis and Stuck [6.12] have evaluated the application of membrane reactors for methanol synthesis using methanol permselective Nafion membranes. In their design calculations they utilize kinetic and membrane permeation data measured in their laboratory. They estimate that with 10 im thin membrane under methanol synthesis plant technically relevant conditions (T = 200 C, P = 40 bar, GHSV = 5000 h ), the single pass reactor yield improves by 40 %, and that the additional costs for the membrane materials correspond only to two production months. The ability of the Nafion membranes to withstand such conditions for prolonged periods still remains, however, questionable. 

It yields an ideal feedstock with H2/CO ratio of 2 1 for methanol synthesis and the Fisher-Tropsch reaction to produce linear hydrocarbons. The use of dense ceramic MRs makes it possible to combine oxygen separation from air, partial oxidation, and reforming of methane in a single step, thus enabling significant reductions of capital investment in the gas-to-liquid industry [40]. Although perovskite membranes may exhibit catalytic activity in the POM reaction, a POM catalyst is usually applied to improve the methane conversion and CO selectivity. Figure 5.7... 

The use of renewable resources for manufacturing specific performance and speciality chemicals, and for fibres to replace synthetic ones, is growing. The driver for this is improved cost/performance. In order to have a major impact on the amount of oil and gas used there is a need to convert biomass into new, large-scale basic feedstocks such as synthesis gas or methanol. Many technical developments in separation science as well as improvements in the overall yield of chemicals are required before renewable feedstocks can compete effectively with oil and gas, but the gap will continue to narrow. 

The Ter Meer reaction has not been widely exploited for the synthesis of m-dinitroaliphatic compounds. This is partly because the Kaplan-Shechter oxidative nitration (Section 1.7) is more convenient, but also because of some more serious limitations. The first is the inability to synthesize internal em-dinitroaliphatic compounds functionality which shows high chemical stability and is found in many cyclic and caged energetic materials. Secondly, the em-nitronitronate salts formed in the Ter Meer reactions often need to be isolated to improve the yield and purity of the product. Dry em-nitronitronate salts are hazardous to handle and those from nitroalkanes like 1,1,4,4-tetranitrobutane are primary explosives which can explode even when wet. Even so, it is common to use conditions that lead to the precipitation of gem-nitronitronate salts from solution, a process that both drives the reaction to completion and also provides isolation and purification of the product salt by simple filtration. Purification of em-nitronitronate salts by filtration from the reaction liquors, followed by washing with methanol or ethanol to remove occluded impurities, has been used, although these salts should never be allowed to completely dry. 

The homologation of methanol has been proved to be a most promising process for the production of oxygenated Cj chemicals. A survey of the recent literature demonstrates the considerable efforts to improve yields and selectivilies of this synthesis gas reaction. The complex influence of catalyst composition and reaction conditions has been empltasizcd, and although the course of the reaction is not fully understood, recent results suggest a mechanistic pattern similar to that of methanol carbonylation. 

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