Hydrocarbon Conversions

Formation of the hydroperoxide is a chain reaction requiring free radicals as chain carriers. These are formed by an initiation mechanism, but additional ones may arise from decomposition of the hydroperoxide, and, if so, accelerate conversion. Hydrocarbon autoxidation will be examined in more detail in the next Chapter (see Example 9.3 in Section 9.6.2). 

Catalyst Reaction temperature (X) CO conversion (%) Hydrocarbons specific rate of formation C2-C4 selectivity (%) C3H,/C3H, ratio Oxygenates specific rate of formation ... 

Dehydrogenation reactions are difficult. High temperatures and low pressures are required to achieve reasonable per-pass conversions. Hydrocarbon dehydrogenation reactions are endothermic to the tune of about 30-35 kcal/mol and thus have large heat input requirements. The equilibrium constant, Kp, of a typical dehydrogenation reaction, A B + aH2, starting with 1 mol of A, mmol of B, and nmol of an... 

In conclusion future efforts in structural bulk and surface modifications are needed urgently unless ceria will stay an academic subject for research. This is illustrated by the following figure (Fig. 13.6) showing percentage of conversion (hydrocarbon combustion) versus temperature using a catalyst containing ceria as support or ceria-other oxide solid solution. Two dashed temperature zones are clearly evidenced ... 

Experiment Reagent Catalyst Temp °C WHSV3 h-1 Conversion % Hydrocarbon CH4 C2 4 Selectivity C2H6 C3H6 (% C3H8, , b by mass) 0 c 4 5+ mole % ycv mole ratio... 

Catalyst CO conversion (%) Hydrocarbon formation rate Selectivity (%) ... 

If inert material is to be added, then ease of separation is an important consideration. For example, steam is added as an inert to hydrocarbon cracking reactions and is an attractive material in this respect because it is easily separated from the hydrocarbon components by condensation. If the reaction does not involve any change in the number of moles, inert material has no effect on equilibrium conversion. 

Even if all of the elements described so far have been present within a sedimentary basin an accumulation will not necessarily be encountered. One of the crucial questions in prospect evaluation is about the timing of events. The deformation of strata into a suitable trap has to precede the maturation and migration of petroleum. The reservoir seal must have been intact throughout geologic time. If a leak occurred sometime in the past, the exploration well will only encounter small amounts of residual hydrocarbons. Conversely, a seal such as a fault may have developed early on in the field s history and prevented the migration of hydrocarbons into the structure. 

The objective of any exploration venture is to find new volumes of hydrocarbons at a low cost and in a short period of time. Exploration budgets are in direct competition with acquisition opportunities. If a company spends more money finding oil than it would have had to spend buying the equivalent amount in the market place there is little Incentive to continue exploration. Conversely, a company which manages to find new reserves at low cost has a significant competitive edge since it can afford more exploration, find and develop reservoirs more profitably, and can target and develop smaller prospects. 

Poorly sorted sediments comprise very different particle sizes, resulting in a dense rock fabric wifh low porosify. As a resulf the connate water saturation is high, leaving little space for the storage of hydrocarbons. Conversely, a very well sorted sediment will have a large volume of space between the evenly sized components, a lower connate water saturation and hence a larger capacity to store hydrocarbons. Connate water is the water which remains in the pore space after the entry of hydrocarbons. 

An exploration or appraisal well, if successful, can be converted to a subsea producer if hydrocarbons are discovered. In this case the initial well design would have to allow for any proposed conversion. 

A few illustrative examples are the following. Photohydrogenation of acetylene and ethylene occurs on irradiation of Ti02 exposed to the gases, but only if TiOH surface groups are present as a source of hydrogen [319]. The pho-toinduced conversion of CO2 to CH4 in the presence of Ru and Os colloids has been reported [320]. Platinized Ti02 powder shows, in the presence of water, photochemical oxidation of hydrocarbons [321,322]. Some of the postulated reactions are ... 

The conversion of the compounds under investigation into coloured derivatives (e.g., the separation of carbonyl compounds by conversion into their 2 4-dinitrophenylhydrazones, etc. of hydrocarbons through their picrates of alcohols through their 3 5-dinitrobenzoates of glucose, fructose and other simple sugars through their p-phenylazobenzoyl esters). 

The simpler nitrop>arafIins (nitromethane, nitroethane, 1- and 2-nitroproj)ane) are now cheap commercial products. They are obtained by the vapour phase nitration of the hydrocarbons a gaseous mixture of two mols of hydrocarbon and 1 mol of nitric acid vapour is passed through a narrow reaction tube at 420-476°. Thus with methane at 476° a 13 per cent, conversion into nitro methane is obtained ethane at 420° gives a 9 1 mixture of nitroethane (b.p. 114°) and nitromethane (b.p. 102°) propane at 420° afifords a 21 per cent, yield of a complex mixture of 1- (b.p. 130-6°) and 2-nitropropane (b.p. 120°), nitroethane and nitromethane, which are separated by fractional distillation. 

Dehydrogenation (the conversion of alicycllc or hydroaroraatic compounds into their aromatic counterparts by removal of hydrogen and also, in some cases, of other atoms or groups) finds wide appUcation in the determination of structure of natural products of complex hydroaroraatic structure. Dehydrogenation is employed also for the synthesis of polycyclic hydrocarbons and their derivatives from the readily accessible synthetic hydroaroraatic compounds. A very simple example is the formation of p-raethylnaphthalene from a-tetra-lone (which is itself prepared from benzene—see Section IV,143) ... 

This isomerization, which must proceed through a 1,2,3-trienylanine, is not "contra-thermodynamic", since with a catalytic amount of potassium tert.-butoxide the same result is obtained. Enyne ethers, H2C=CH-CsC-0R, undergo a similar conversion into HCeC-CH=CH-OR upon interaction with alkali metal amides in liquid NH3, followed by hydrolysis . Enyne sulphides, H2C=CH-CsC-SR, and the hydrocarbons H2C=CH-CsC-R (R = or phenyl) give only tars or polymeric products under... 

In 1997, UOP announced the PX-Plus process which also uses a selectivated catalyst to convert toluene to para-rich xylenes. Pina commercialized a TDP process known as the (T2PX) process in 1984 (70). It uses a proprietary catalyst to react toluene at 42—48% conversion with selectivities to benzene of 42 wt % and to xylenes of 46 wt %. The xylenes produced are at equiUbrium. Typical commercial operating conditions of 390—495°C, H2 partial pressure of 4.1 Mpa, H2/hydrocarbon molar ratio of 4 1, and LHSV of 1—2/h. Pina s first commercial implementation occurred in 1985 at their Port Arthur refinery. 

Commercial production of acetic acid has been revolutionized in the decade 1978—1988. Butane—naphtha Hquid-phase catalytic oxidation has declined precipitously as methanol [67-56-1] or methyl acetate [79-20-9] carbonylation has become the technology of choice in the world market. By-product acetic acid recovery in other hydrocarbon oxidations, eg, in xylene oxidation to terephthaUc acid and propylene conversion to acryflc acid, has also grown. Production from synthesis gas is increasing and the development of alternative raw materials is under serious consideration following widespread dislocations in the cost of raw material (see Chemurgy). 

Hydrogenolysis Process. Patty alcohols are produced by hydrogenolysis of methyl esters or fatty acids ia the presence of a heterogeneous catalyst at 20,700—31,000 kPa (3000—4500 psi) and 250—300°C ia conversions of 90—98%. A higher conversion can be achieved using more rigorous reaction conditions, but it is accompanied by a significant amount of hydrocarbon production. 

The cobalt catalyst can be introduced into the reactor in any convenient form, such as the hydrocarbon-soluble cobalt naphthenate [61789-51 -3] as it is converted in the reaction to dicobalt octacarbonyl [15226-74-17, Co2(CO)g, the precursor to cobalt hydrocarbonyl [16842-03-8] HCo(CO)4, the active catalyst species. Some of the methods used to recover cobalt values for reuse are (11) conversion to an inorganic salt soluble ia water conversion to an organic salt soluble ia water or an organic solvent treatment with aqueous acid or alkah to recover part or all of the HCo(CO)4 ia the aqueous phase and conversion to metallic cobalt by thermal or chemical means. 

Secondary alcohols (C q—for surfactant iatermediates are produced by hydrolysis of secondary alkyl borate or boroxiae esters formed when paraffin hydrocarbons are air-oxidized ia the presence of boric acid [10043-35-3] (19,20). Union Carbide Corporation operated a plant ia the United States from 1964 until 1977. A plant built by Nippon Shokubai (Japan Catalytic Chemical) ia 1972 ia Kawasaki, Japan was expanded to 30,000 t/yr capacity ia 1980 (20). The process has been operated iadustriaHy ia the USSR siace 1959 (21). Also, predominantiy primary alcohols are produced ia large volumes ia the USSR by reduction of fatty acids, or their methyl esters, from permanganate-catalyzed air oxidation of paraffin hydrocarbons (22). The paraffin oxidation is carried out ia the temperature range 150—180°C at a paraffin conversion generally below 20% to a mixture of trialkyl borate, (RO)2B, and trialkyl boroxiae, (ROBO). Unconverted paraffin is separated from the product mixture by flash distillation. After hydrolysis of residual borate esters, the boric acid is recovered for recycle and the alcohols are purified by washing and distillation (19,20). 

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