Benzene from pyrolysis

Pyrotol A process for making benzene from pyrolysis gasoline by hydrocracking. Developed by Houdry Process and Chemical Company. In 1987, 13 units were operating worldwide. 

Aromatic Hydrocarbons. These are the most toxic of the hydrocarbons and inhalation of the vapor can cause acute intoxication. Benzene is particularly toxic and long-term exposure can cause anemia and leukopenia, even with concentrations too low for detection by odor or simple instmments. The currendy acceptable average vapor concentration for benzene is no more than 1 ppm. PolycycHc aromatics are not sufftcientiy volatile to present a threat by inhalation (except from pyrolysis of tobacco), but it is known that certain industrial products, such as coal tar, are rich in polycycHc aromatics and continued exposure of human skin to these products results in cancer. 

Petroleum-derived benzene is commercially produced by reforming and separation, thermal or catalytic dealkylation of toluene, and disproportionation. Benzene is also obtained from pyrolysis gasoline formed ia the steam cracking of olefins (35). 

Viable operating eonditions were identified experimentally for maximising the produetion of ethylene, propylene, styrene and benzene from the pyrolysis of waste produets. Data are given for pyrolysis temperature, produet reaetion time, and quench time using a batch microreactor and a pilot-plant-sized reactor. 26 refs. CANADA... 

HDA [Hydrodealkylation] A proprietary dealkylation process for making benzene from toluene, xylenes, pyrolysis naphtha, and other petroleum refinery intermediates. The catalyst,... 

Other methods, such as the direct reaction of benzene and ethylene (Fig. 2) or from pyrolysis gasoline (Fig. 3) are also used to manufacture styrene. 

To confirm reaction scheme (4) for the formation of naphthalene and biphenyl, phthalic anhydride was allowed to react with benzene-dx (Fields and Meyerson, 1966c). Barring an appreciable isotope effect, two-thirds of the naphthalene should contain a deuterium atom and one-third only protium. Biphenyl arises in two ways insertion of benzyne into a C—H bond of benzene and pyrolysis of benzene. Biphenyl from benzyne insertion should form with retention of the deuterium atom biphenyl from benzene pyrolysis should—again ignoring any isotope effect—be d0, dlt and dz on the statistical basis of losing two, one, or zero deuterium atoms from a total of twelve protiums and deuteriums in the over-all reaction of two benzene molecules. The amount of biphenyl-... 

Produots from Pyrolysis of Phthalic Anhydride in Benzene-dj... 

The similarity of the products obtained from benzene by pyrolysis and by exposure to ionizing radiation is noteworthy and suggests that... 

Benzene recovery from pyrolysis gasoline is usually above 99.5% at feed concentration above 80%. 

HDA [HydroDeAlkylation] A proprietary dealkylation process for making benzene from toluene, xylenes, pyrolysis naphtha, and other petroleum refinery intermediates. The catalyst, typically chromium oxide or molybdenum oxide, together with hydrogen gas, removes the methyl groups from the aromatic hydrocarbons, converting them to methane. The process also converts cresols to phenol. Developed by Hydrocarbon Research with Atlantic Richfield Corporation and widely licensed worldwide. 

The results presented in Fig. 17 for diffusion flames and those from shock tubes clearly indicate that fuel structure does indeed play a role in a fuel s tendency to form particulates—in significant contrast to the results observed in premixed flames. One may conclude, then, that a fundamental knowledge of a fuel s pyrolysis chemistry [51, 76] will allow one to predict its relative tendency to soot with respect to the results presented in Fig. 17. For example, cyclohexadienes are known to dehydrogenate to benzene during pyrolysis and, indeed, the data in... 

Rokstad, O. A., Olsvik, O., Jenssen, B. and Holmer, A., Ethylene, acetylene, and benzene from methane pyrolysis, in Novel Production Methods for Ethylene, Light Hydrocarbons and Aromatics (L. F. Albright, B. L. Cryness, and S. Nowak, Eds.), Marcel Dekker, New York, 1992, pp. 256-272. 

The results of pyrolysis experiments indicate that compound 1 decomposes with the formation of the pyrazyne 3. Pyrolysis in the presence of benzene results in a small but definite yield of 2-phenylpyrazine (8) from an insertion reaction with pyrazyne. This result is similar to results from pyrolysis experiments with various aromatic and heterocyclic anhydrides. Pyrazyne is also invoked to explain the formation of maleonitrile... 

The BTX fraction shows a similar variability arising from pyrolysis severity and feedstock (Table III). In general, the aromatic content ranges upwards of 50% and may reach nearly 100% in high severity operation. BTX ratios vary widely, depending on feedstock. LPG-type feeds yield benzene predominantly among the aromatics, while the heavier feeds show increased yields of toluene and C8 aromatics. In all cases benzene appears to be synthesized predominantly from paraffin or naphthene chain fragments by condensation reactions. Toluene and the C8 aromatics appear to derive principally from aromatics in the feed with some pyrolytic side-chain dealkylation. In all cases styrene predominates in the C8 fraction (7). 

The C4-naphthalene and C4-benzene data presented in this paper were collected as part of a larger study addressing the influence of pressure, temperature and time on hydrocarbon generation (Hill et al, 1994, 1996, 2(X)3). The goal of the study was to evaluate whether maturity parameters defined during oil pyrolysis could be extended to natural systems. Thus, the Devonian sourced oil from the WSCB was used to define C4-naphthalene and C4-benzene maturity parameters in the oil pyrolysis experiments and Mississippian oils from the Fort Worth Basin were used to evaluate C4-naphthalene and C4-benzene maturity parameters in natural systems. It was not the goal of this study to determine whether results from pyrolysis of a Devonian oil will compare exactly with oils from a Mississippian source. Due to facies differences between Devonian and Mississippian marine shales, the initial distribution of C4-naphthalene and C4-benzene isomers is different as discussed earlier. For this reason, we would also not expect maturity ratios from pyrolysis of a Devonian oil to exactly match maturity ratios from Mississippian Barnett Shale oils. However, if the maturity trends observed from oil pyrolysis results are valid, the C4-naphthalene and C4-benzene ratios should correlate with a well established thermal maturity parameter such as TAS in Mississippian Barnett Shale oils. 

C4-benzene and C4-naphthalene thermal maturity indicators from pyrolysis experiments... 

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