Ethane aromatization

Mo(VI)/HZSM-5 catalysts are active and selective catalysts for the conversion of CH4 to aromatics and the best activity can be obtained when Mo loading is about 2-3%. The activity and the stability of the catalyst can be improved by W addition. W(VI)/HZSM-5 catalyst exhibits excellent selectivity for ethane aromatization and thus it may be potential to be used in ethane aromatization process. The higher activity of Mo(VI)/HZSM-5 for the aromatization of CH4 and for the C-C bond cleavage in C2H6 can be attributed to the formation of CH2 that is stabilized by the formation of Mo=CH2 species. Carbon deposit on the catalyst may take part in the conversion of CH4 to aromaties. 

Hydrogen is also important in fuel production. Hydrocracking uses the partial pressure of hydrogen gas to break down complex organic molecules, and forms by-products such as ethane, aromatics, and jet fuels. Liquid hydrogen is also used as a rocket fuel. In fission-based nuclear reactors, heavy water (where deuterium replaces regular hydrogen) is used as a neutron moderator. 

Figure 1. Each sloped line represents the loci of all possible combinations of average residence times and hydrocarbon partial pressures which are consistent with a fixed pyrolysis yield pattern, i.e., constant pyrolysis selectivity lines. For liquid feedstocks, the methane-to-ethylene ratio found in the pyrolysis reactor effluent has been used as a good overall indicator of pyrolysis reactor selectivity. Low methane-to-ethylene ratios correspond to a high total yield of ethylene, propylene, butadiene and butylenes. Consequently, the yields of methane, ethane, aromatics and fuel oil are reduced. TL refore, each constant pyrolysis selectivity line shown in Figure 1 is identified with a fixed methane-to-ethylene ratio. This specific selectivity chart applies to a Kuwait heavy naphtha which is pyrolyzed to achieve a constant degree of feedstock dehydrogenation, i.e., a constant hydrogen content in the effluent liquid products, which in this case corresponds to the limiting cracking severity.

Arzumanov SS, Gabrienko AA, Freude D, Stepanov AG. In situ high temperature MAS NMR study of the mechanisms of catalysis. Ethane aromatization on Zn-modified zeolite BEA. Solid State Nucl Magn Reson 2009 35 113-9. 

Doebner-von Miller reaction Condensation of an aromatic amine with an aldehyde or ketone in the presence of hydrochloric acid to form a quinoline derivative. A general method, thus aniline and ethanal give 2-methyl-quinoline (quinaldine) and p-phenetidine. 

Mobil s High Temperature Isomerization (MHTI) process, which was introduced in 1981, uses Pt on an acidic ZSM-5 zeoHte catalyst to isomerize the xylenes and hydrodealkylate EB to benzene and ethane (126). This process is particularly suited for unextracted feeds containing Cg aHphatics, because this catalyst is capable of cracking them to light paraffins. Reaction occurs in the vapor phase to produce a PX concentration slightly higher than equiHbrium, ie, 102—104% of equiHbrium. EB conversion is about 40—65%, with xylene losses of about 2%. Reaction conditions ate temperature of 427—460°C, pressure of 1480—1825 kPa, WHSV of 10—12, and a H2/hydtocatbon molar ratio of 1.5—2 1. Compared to the MVPI process, the MHTI process has lower xylene losses and lower formation of heavy aromatics. 

In a polluted or urban atmosphere, O formation by the CH oxidation mechanism is overshadowed by the oxidation of other VOCs. Seed OH can be produced from reactions 4 and 5, but the photodisassociation of carbonyls and nitrous acid [7782-77-6] HNO2, (formed from the reaction of OH + NO and other reactions) are also important sources of OH ia polluted environments. An imperfect, but useful, measure of the rate of O formation by VOC oxidation is the rate of the initial OH-VOC reaction, shown ia Table 4 relative to the OH-CH rate for some commonly occurring VOCs. Also given are the median VOC concentrations. Shown for comparison are the relative reaction rates for two VOC species that are emitted by vegetation isoprene and a-piuene. In general, internally bonded olefins are the most reactive, followed ia decreasiag order by terminally bonded olefins, multi alkyl aromatics, monoalkyl aromatics, C and higher paraffins, C2—C paraffins, benzene, acetylene, and ethane. 

ElexibiHty allows the operator to pick and choose the most attractive feedstock available at a given point in time. The steam-cracking process produces not only ethylene, but other products as weU, such as propylene, butadiene, butylenes (a mixture of monounsaturated C-4 hydrocarbons), aromatics, etc. With ethane feedstock, only minimal quantities of other products ate produced. As the feedstocks become heavier (ie, as measured by higher molecular weights and boiling points), increasing quantities of other products are produced. The values of these other coproduced products affect the economic attractiveness and hence the choice of feedstock. 

Thermal Cracking. / -Butane is used in steam crackers as a part of the mainly ethane—propane feedstream. Roughly 0.333—0.4 kg ethylene is produced per kilogram / -butane. Primary bv-pioducts include propylene (50 57 kg/100 kg ethylene), butadiene (7-8.5 kg/100 kg), butylenes (5-20 kg/WO kg) and aromatics (6 kg/ToO kg). 

Fig. 8. Mobil s process for aromatics from ethane (38). Ref. = refrigeration CW = cooling water Stm. = steam.

Carbon monoxide, methane, ethylene, ethane, ethylene dichloride, aromatic solvent... 

Fig. 1. Some molecules with different C-C bonds. Al, ethane, CjH, (sp ) A2, ethene, C2H4 (sp ) A3, ethyne, (sp ) Bl, benzene, (aromatic) B2, coronene,...

Wojtkonski [185] has also reported on three series of melt spinnable thermotropic aromatic-aliphatic polyimines. The polyimines were prepared by reaction of 1,2-bis(4-formylphenoxy) ethane, terephthalaldehyde, or 4,4 -biphenyldicarboxaldehyde, respectively, with l,n-bis(4-amino-3-methylphenoxy) alkanes where n = 1-10, 12, 14, and 16 in dry DMAC containing 5% dry lithium chloride. The polymers decomposed at 400°C, and as the length of the flexible aliphatic segments increased, melting points decreased. Polymers with an odd... 

Natural gas and crude oils are the main sources for hydrocarbon intermediates or secondary raw materials for the production of petrochemicals. From natural gas, ethane and LPG are recovered for use as intermediates in the production of olefins and diolefms. Important chemicals such as methanol and ammonia are also based on methane via synthesis gas. On the other hand, refinery gases from different crude oil processing schemes are important sources for olefins and LPG. Crude oil distillates and residues are precursors for olefins and aromatics via cracking and reforming processes. This chapter reviews the properties of the different hydrocarbon intermediates—paraffins, olefins, diolefms, and aromatics. Petroleum fractions and residues as mixtures of different hydrocarbon classes and hydrocarbon derivatives are discussed separately at the end of the chapter. 

A higher steam/hydrocarhon ratio favors olefin formation. Steam reduces the partial pressure of the hydrocarbon mixture and increases the yield of olefins. Heavier hydrocarbon feeds require more steam than gaseous feeds to additionally reduce coke deposition in the furnace tubes. Liquid feeds such as gas oils and petroleum residues have complex polynuclear aromatic compounds, which are coke precursors. Steam to hydrocarbon weight ratios range between 0.2-1 for ethane and approximately 1-1.2 for liquid feeds. 

As feedstocks progress from ethane to heavier fractions with lower H/C ratios, the yield of ethylene decreases, and the feed per pound ethylene product ratio increases markedly. Table 3-15 shows yields from steam cracking of different feedstocks, and how the liquid by-products and BTX aromatics increase dramatically with heavier feeds. 

Propane cracking is similar to ethane except for the furnace temperature, which is relatively lower (longer chain hydrocarbons crack easier). However, more by-products are formed than with ethane, and the separation section is more complex. Propane gives lower ethylene yield, higher propylene and butadiene yields, and significantly more aromatic pyrolysis gasoline. Residual gas (mainly H2 and methane) is about two and half times that produced when ethane is used. Increasing the severity... 

However, it was found that the effect on the equilibrium formation of aromatics is not substantial due to thermodynamic considerations. A more favorable effect was found for the reaction between ethylene (formed via cracking during aromatization of propane) and hydrogen. The reverse shift reaction consumes hydrogen and decreases the chances for the reduction of ethylene to ethane byproduct. 

The condensation of aromatic rings with aldehydes or ketones is called hydroxy-alkylation. The reaction can be used to prepare alcohols, though more often the alcohol initially produced reacts with another molecule of aromatic compound (11-12) to give diarylation. For this the reaction is quite useful, an example being the preparation of l,l,l-trichloro-2, 2-bis (p-Chlorophenyl) ethane (DDT) ... 

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