Phase hydrogenation

Manufacture. Furfuryl alcohol has been manufactured on an industrial scale by employing both Hquid-phase and vapor-phase hydrogenation of furfural (56,57). Copper-based catalysts are preferred because they are selective and do not promote hydrogenation of the ring. 

Catalytic hydrogenation of furan to tetrahydrofuran is accompHshed in either Hquid or vapor phase. Hydrogenation of the double bonds is essentially quantitative over nickel catalysts but is generally accompanied by hydrogenolysis over the noble metals. 

Reduction. Acetaldehyde is readily reduced to ethanol (qv). Suitable catalysts for vapor-phase hydrogenation of acetaldehyde are supported nickel (42) and copper oxide (43). The kinetics of the hydrogenation of acetaldehyde over a commercial nickel catalyst have been studied (44). 

The thermal conductivity of gas-phase deuterium is about 0.73 times that of gas-phase hydrogen. This thermal conductivity difference offers a convenient method for analysis of H2—D2 mixtures. Other physical properties of D2, T2, HD, DT, and HT are Hsted in the Hterature (60). 

Tetrahydronaphthalene is produced by the catalytic treatment of naphthalene with hydrogen. Various processes have been used, eg, vapor-phase reactions at 101.3 kPa (1 atm) as well as higher pressure Hquid-phase hydrogenation where the conditions are dependent upon the particular catalyst used. Nickel or modified nickel catalysts generally are used commercially however, they are sensitive to sulfur, and only naphthalene that has very low sulfur levels can be used. Thus many naphthalene producers purify their product to remove the thionaphthene, which is the principal sulfur compound present. Sodium treatment and catalytic hydrodesulfuri2ation processes have been used for the removal of sulfur from naphthalene the latter treatment is preferred because of the ha2ardous nature of sodium treatment. 

Du Pont uses a Hquid-phase hydrogenation process that employs a palladium —platinum-on-carbon catalyst. The process uses a plug-flow reactor that achieves essentially quantitative yields, and the product exiting the reactor is virtually free of nitroben2ene. 

Hydrogenation. Gas-phase catalytic hydrogenation of succinic anhydride yields y-butyrolactone [96-48-0] (GBL), tetrahydrofiiran [109-99-9] (THF), 1,4-butanediol (BDO), or a mixture of these products, depending on the experimental conditions. Catalysts mentioned in the Hterature include copper chromites with various additives (72), copper—zinc oxides with promoters (73—75), and mthenium (76). The same products are obtained by hquid-phase hydrogenation catalysts used include Pd with various modifiers on various carriers (77—80), Ru on C (81) or Ru complexes (82,83), Rh on C (79), Cu—Co—Mn oxides (84), Co—Ni—Re oxides (85), Cu—Ti oxides (86), Ca—Mo—Ni on diatomaceous earth (87), and Mo—Ba—Re oxides (88). Chemical reduction of succinic anhydride to GBL or THF can be performed with 2-propanol in the presence of Zr02 catalyst (89,90). 

V-Alkyl or A/-aryl succinimides can be prepared from the corresponding amines (107) or from succinic anhydride, ammonia, and the corresponding alcohol (108). Succinimides are also obtained by vapor-phase hydrogenation of the corresponding maleimides ia the presence of a catalyst (109). 

Silva (1971) used the Berty reactor to execute exploratory measurements on vapor-phase hydrogenation of organic substrates that had little vapor pressure at room temperature. The substrate was measured by weight in a small ceramic boat and put on the catalyst screen beside a few particles of catalyst, also measured by weight. Then the stirring started, and the autoclave was heated to the reaction temperature. Finally the desired hydrogen pressure was applied suddenly and the reaction started. 

Valedyne differential pressure cell. 91 vapor phase hydrogenation... 

Compounds such as hydrogen sulfide and cyanides are the most common metal surface poisoners occurring in process units subject to aqueous-phase hydrogen attack. In many process units, these compounds can be effectively eliminated and hydrogen diffusion stopped by adding ammonium polysulfides and oxygen to the process streams which converts the compounds to polysulfides and thiocyanates, provided the pH is kept on the alkaline side. 

Heterogeneous reaction (Section 6.1) A reaction involving two or more substances present in different phases. Hydrogenation of alkenes is a heterogeneous reaction that takes place on the surface of an insoluble metal catalyst. 

The removal of C4-acetylenes may be effected by catalytic gas-phase hydrogenation in a gas-particle operation by a process similar to that widely used for removing acetylene from ethylene streams. However, in view of the strong polymerization tendency of the C4-fractions, it is desirable in this case to work at the lowest possible temperature. 

Methods used in the reeyeling of plasties are deseribed, and details are given of a ehemieal reeyeling teehnique used by Veba Oel in its plant in Bottrop, Germany. This liquid phase hydrogenation proeess produees high quality synthetic oils, suitable for use as refinery feedstoeks, from mixtures of vaeuum distillation residues, serap plasties and other industrial wastes. 

In-situ ultrasonic catalyst rejuvenation in three-phase hydrogenation of xylose. Chem. Eng. Sci., 54, 1583-1588. 

The degree of dissociation is very small but the diphenylcyanomethyl radical is sufficiently reactive to induce polymerization in styrene. Methyl radicals or hydrogen atoms bring about polymerization of vinyl monomers in the gas phase.Hydrogen peroxide in the presence of ferrous ions initiates polymerization in the aqueous phase or in aqueous emulsions through generation of hydroxyl radicals according to the Haber-Weiss mechanism... 

The WGS reaction is a reversible reaction, that is, it attains equilibrium with reverse WGS reaction. Thus the fact that the WGS reaction is promoted by H20(a reactant), in turn, implies that the reverse WGS reaction may also be promoted by a reactant, H2 or CO2. In fact the decomposition of the surface formates produced from H2+CO2 is promoted 8-10 times by gas-phase hydrogen. The WGS and reverse WGS reactions can conceivably proceed on different formate sites of the ZnO surface unlike usual catalytic reaction kinetics, while the occurrence of the reactant-promoted reactions does not violate the principle of microscopic reversibility[63]. 

For presulfided Co.Mo/Si02-Al203, the formation and elimination of the add sites were almost the same as those observed for non-sulfided Ck>.Mo/Si02-Al203. Presufidation with hydrogen sulfide did not affect much the conversion of the acid sites caused by gas phase hydrogen. 

The recovery of the Lewis add sites and the decrease in the protonic acid sites to the original values by outgassing gas phase hydrogen are rather slow and require a high temperature. The addition of Pt/Si02 did not affect much the restoration of Ae Lewis add sites of H-ZSM-5 by outgassing gas phase hydrogen. 

WiESSMEiER, G., Honigke, D., Heterogeneously catalyzed gas-phase hydrogenation of cis,trans,trans-1,5,9-cyclododecatriene on palladium catalysts having regular pore systems,... 

Figure3.58 Experimental results for partial gas-phase hydrogenation of, 5,9-cyclododecatrienein a Ptmicro-channel reactor[l 30],...

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