Dimethyl reforming

Because of their cyclic structures, cycloalkanes have two faces as viewed edge-on, a "top" face and a "bottom" face. As a result, isomerism is possible in substituted cycloalkanes. For example, there are two different 1,2-dimethyl-cyclopropane isomers, one with the two methyl groups on the same face of the ring and one with the methyls on opposite faces (Figure 4.2). Both isomers are stable compounds, and neither can be converted into the other without breaking and reforming chemical bonds. Make molecular models to prove this to yourself. 

Work on mercury alkyls has been done by Heitz and Adloff (31-33), who studied Hg(CH3)2, Hg(C2Hj)2 and HgPh2. They found no isotope effect between " Hg, Hg, and ° Hg, and no correlation with the respective conversion coefficients. They also noted that the retentions could not be satisfactorily explained by exchange of the respective ligands, and thus concluded that the molecules are reformed by an epithermal not by a thermal process. Parent yields were typically 74, 15, and 8% for the diphenyl-, dimethyl- and diethylmercury, respectively. 

Dimethyl ether is produced from natural gas via combined reforming and downstream DME synthesis. Technical data for a typical DME plant are based on information provided by Haldor Topsoe (personal communication, October, 2002) (see Table 7.15). 

Depending on the reason for converting the produced gas from biomass gasification into synthesis gas, for applications requiring different H2/CO ratios, the reformed gas may be ducted to the water-gas shift (WGS, Reaction 4) and preferential oxidation (PROX, Reaction 5) unit to obtain the H2 purity required for fuel cells, or directly to applications requiring a H2/CO ratio close to 2, i.e., the production of dimethyl ether (DME), methanol, Fischer-Tropsch (F-T) Diesel (Reaction 6) (Fig. 7.6). 

Br-atom initiated oxidation of dimethyl sulfide (DMS) in a large-volume reaction chamber gave SO2, CHsSBr, and DMSOJ A rapid addition of Br atoms to DMS takes place, forming an adduct that mainly reforms reactants but also decomposes unimolecularly to form CHsSBr and CH3 radicals. DMSO is formed from the reaction of BrO radicals with DMS. The reaction CH3O2 + Br CH3O + BrO is postulated as the source of BrO radicals. 

Paraquat (1,1 dimethyl, 4,4 bipyridyl) is a nonselective contact herbicide. It is used almost exclusively as a dichloride salt and usually is formulated to contain surfactants. Both its herbicidal and toxicological properties are dependent on the ability of the parent cation to undergo a single electron addition, to form a free radical that reacts with molecular oxygen to reform the cation and concomitantly produce a superoxide anion. This oxygen radical may directly or indirectly cause cell death. Diquat, l,T-ethylene-2,2 -dipyridylium, is a charged quaternary ammonium compound often found as the dibromide salt. The structure of diquat dibromide and that of the closely related herbicide paraquat can be seen in Fig. 4.5. 

As we learned in Chapters 3 and 4, many inorganic compounds, not just ammonia, are derived from synthesis gas, made from methane by steam-reforming. In the top 50 this would include carbon dioxide, ammonia, nitric acid, ammonium nitrate, and urea. No further mention need be made of these important processes. We discussed MTBE in Chapter 7, Section 4, and Chapter 10, Section 9, since it is an important gasoline additive and C4 derivative. In Chapter 10, Section 6, we presented -butyraldehyde, made by the 0x0 process with propylene and synthesis gas, which is made from methane. In Chapter 11, Section 8, we discussed dimethyl terephthalate. Review these pertinent sections. That leaves only two chemicals, methanol and formaldehyde, as derivatives of methane that have not been discussed. We will take up the carbonylation of methanol to acetic acid, now the most important process for making this acid. Vinyl acetate is made from acetic... 

Invited 15. Kimichika Fukushima (AITEL Corporation) First-Principle Analysis of Metal Oxides and Investigation of Catalytic Properties for Dimethyl Ether Steam Reforming... 

First-Principles Investigation of Dimethyl Ether Steam Reforming... 

Process Economics Program Report SRI International. Menlo Park, CA, Isocyanates IE, Propylene Oxide 2E, Vinyl Chloride 5D, Terephthalic Acid and Dimethyl Terephthalate 9E, Phenol 22C, Xylene Separation 25C, BTX, Aromatics 30A, o-Xylene 34 A, m-Xylene 25 A, p-Xylene 93-3-4, Ethylbenzene/Styrene 33C, Phthalic Anhydride 34B, Glycerine and Intermediates 58, Aniline and Derivatives 76C, Bisphenol A and Phosgene 81, C1 Chlorinated Hydrocarbons 126, Chlorinated Solvent 48, Chlorofluorocarbon Alternatives 201, Reforming for BTX 129, Aromatics Processes 182 A, Propylene Oxide Derivatives 198, Acetaldehyde 24 A2, 91-1-3, Acetic Acid 37 B, Acetylene 16A, Adipic Acid 3 B, Ammonia 44 A, Caprolactam 7 C, Carbon Disulfide 171 A, Cumene 92-3-4, 22 B, 219, MDA 1 D, Ethanol 53 A, 85-2-4, Ethylene Dichloride/Vinyl Chloride 5 C, Formaldehyde 23 A, Hexamethylenediamine (HMDA) 31 B, Hydrogen Cyanide 76-3-4, Maleic Anhydride 46 C, Methane (Natural Gas) 191, Synthesis Gas 146, 148, 191 A, Methanol 148, 43 B, 93-2-2, Methyl Methacrylate 11 D, Nylon 6-41 B, Nylon 6,6-54 B, Ethylene/Propylene 29 A, Urea 56 A, Vinyl Acetate 15 A. 

As described in earlier chapters, the volatility of solvents is of crucial important in their applications. In 2007, the groups of Liotta, Eckert and Jessop first reported on the formation and use of piperylene sulfone (PS) as a recyclable alternative to dimethyl sulfoxide (DMSO) (Figure 9.11). DMSO, in addition to dimethylformamide (DMF) and hexamethylphosphoramide (HMPA), is a widely used dipolar, aprotic solvent. However, it is difficult to remove from products by distillation and is rarely recycled. In contrast, PS decomposes cleanly at temperatures above 100°C to give ra -l,3-pentadiene and sulfur dioxide, which reform PS at room temperature (Figure 9.11). 

Preheated natural gas is fed at about 600°C to the reformer and exits at about 880°C and 2.1 MPa. Methanol synthesis is then performed over copper-based catalysts at about 240-270°C and 10.3 MPa. The product gas contains about 5% methanol. By-products are 1-2% dimethyl ether and 0.3-0.5% higher alcohols. Because of equilibrium limitations, conversion of synthesis gas is only a few percent per pass in the catalytic reactor, and the product gas stream after... 

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