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A mechanism has been proposed for this process, and rate constants and efficiencies of initiation measured. Unable to display preview. Download preview PDF. Skip to main content. Advertisement Hide. The mechanism of benzaldehyde oxidation by ozonated oxygen.

US20030229247A1 - Process for producig carboxylic acids - Google Patents

Authors Authors and affiliations I. Komissarova V. Komissarov E. Physical Chemistry. This process is experimental and the keywords may be updated as the learning algorithm improves. This is a preview of subscription content, log in to check access. Briner, Adv. Google Scholar.

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Denisov, and Z. Denisov, N. Mitskevich, and V. Synthesis of Organic Preparations [Russian translation], Vol. The investigation of the influence of POC catalyst concentration on the process of MP oxidation showed absence of the induction period and increasing of the initial reaction speed with increasing catalyst concentration Fig.

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Kinetic curves of accumulation in DPQ during the MP oxidation reaction in toluene according to the composition of the catalyst system. Kinetic curves of DPQ accumulation during the oxidation reaction of MP in toluene according to the composition of the catalyst system. Thus, the meaning of incepted speed of reactions in the model systems in presence of oxygen shows that individual components accelerates the oxidation of MP being the part of the catalyst — aqueous solution of potassium hydroxide Fig.

While concentration of dimethylsulfoxide and dimethylsulfone increases and reaction of catalyst concentration aqueous solution of potassium hydroxide remains unchangeable the speed of reaction increases. In addition, the reaction of oxidation of MP in presence of both components dimethylsulfoxide or dimethylsulfone was carried out.


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In this reaction, the composition of the model alkaline solution to the composition of POC catalyst was approached. As one can see from the Fig. These compounds were identified in the composition of alkaline phenol oxidation and allow increasing the initial reaction speed and decreasing induction period. Kirov, got qualification of engineer, specialty — chemical technology of synthetic rubber. The same year entered postgraduate …. Mercaptan removal and waste treatment technologies. E-mail: timurhadidchemist gmail.

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Figure 1. A two-step process of the BP synthesis. Experimental part A bubble type cylindrical reactor is loaded with Elemental POC catalyst composition Table. Shanina, G. Zaikov, N. Journal of Applied Polymer Science. Borisova, L. Fazlieva, Zh. Fokkho, M. Promyshlennikova, E. Cherezova, A.

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Khusainov, N. Russian Journal of Applied Chemistry. Wattenberg, J. Coccia, L. The corresponding vapor is condensed and most of the condensate is refluxed to the reactor, with some condensate being withdrawn to control reactor water concentration two moles of water are formed per mole of paraxylene reacted. The residence time is typically 30 minutes to 2 hours, depending on the process. Depending on oxidation reactor operating conditions, e.

The effluent, i. They are thereafter fed to a separate purification step or directly to a polymerization process. The main impurity in the crude TA is 4 carboxybenzaldehyde 4-CBA , which is incompletely oxidized paraxylene, although p-tolualdehyde and p-toluic acid can also be present along with undesirable color formers. By conducting the oxidation reaction according to the invention as described in greater detail below, it is possible to substantially reduce the formation of impurities in the final TA product and effectively control solvent and precursor degradation.

The present invention is an improved process for producing aromatic carboxylic acids by catalytic liquid phase oxidation of a corresponding precursor in a suitable solvent. In particular, the present invention is an improved process for the catalytic liquid phase oxidation of paraxylene to produce terephthalic acid. The process of the present invention comprises sequential steps of feeding the reactants, including a suitable solvent, to a first reaction zone at elevated pressure wherein the temperature and the uptake of oxygen are controlled and any terephthalic acid which forms remains in solution, and then feeding the resulting reaction medium to a second oxidation reaction zone.

In a preferred embodiment of the invention, the process comprises: []. The resulting terephthalic acid can be recovered from the reaction medium exiting the second reaction zone by any convenient means. While the preferred embodiment of the invention is described herein in terms of an improved oxidation system for converting paraxylene to terephthalic acid, it will be recognized that the invention is applicable to producing a range of aromatic carboxylic acids, and particularly phthalic acids, by catalytic liquid phase oxidation of a corresponding precursor in a suitable solvent.

The invention resides in the discovery that the conversion of the precursor to its corresponding carboxylic acid can be substantially improved by carrying out the oxidation reaction in at least two stages, or zones, which comprise: []. In addition to maintaining the solvent:precursor mass ratio as described, the uptake of oxygen in the first reaction zone is limited to a value which is less than that required for full conversion of the precursor to its corresponding carboxylic acid.

The corresponding carboxylic acid can have one or more acid groups, depending on the precursor. Oxygen uptake in the first reaction zone is controlled by one or more of the following methods: i maintaining oxygen supply within a predetermined range; ii maintaining catalyst concentration within a predetermined range; iii limiting the residence time defined as the reactor liquid volume divided by the reactor feed rate within the first reaction zone to less than about 6 minutes, but preferably less than 4 minutes; and iv optionally removing heat from the reaction zone.

One aspect of the invention is limiting the uptake of oxygen within the reaction medium in the first reaction zone to a value less than that required for full conversion of the precursor to the corresponding aromatic carboxylic acid. Preferably, the oxygen uptake within the reaction medium in the first reaction zone is less than 70 percent of the oxygen required for full conversion of the precursor to the corresponding carboxylic acid. Simultaneously while feeding the reaction medium to the second reactor the pressure of the reaction medium is reduced to a value in the range of from kPa to less than 2, kPa.

The carboxylic acid which results can be recovered from the final reaction medium, which is typically a slurry of acid crystals, by conventional methods. In one embodiment of the invention, a feed stream comprising a solvent and an oxidation catalyst is prepared and oxygen is dissolved directly into the feed stream. The oxygenated feed stream is then fed continuously and simultaneously with the precursor into the first oxidation reaction zone, which is a plug flow reaction zone. Immediately upon entering the first reaction zone the precursor, e.

The mechanism of benzaldehyde oxidation by ozonated oxygen

The reaction medium is then fed to a second, more conventional, reactor as described above. The process of the invention is particularly applicable to producing terephthalic acid by catalytic liquid phase oxidation of paraxylene in a solvent comprising acetic acid and water. The present invention resides in the discovery that it is possible to produce aromatic carboxylic acids with improved efficiency and quality compared to the processes of the prior art.

The present invention is characterized by a two-stage process. The first stage is carried out in a first reaction zone at a relatively high pressure, e. The second stage is carried out in a second reaction zone at a lower pressure than the first stage, e.


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The first reaction zone of the process is characterized by a relatively high solvent:precursor mass ratio in the range of from , and a relatively high pressure, e. Best results for the overall process have been observed when the solvent:precursor mass ratio in the first reaction zone is in the range of from For the purposes of this disclosure, the solvent:precursor mass ratio is defined as follows: [].

The first reaction zone is optionally cooled to control the temperature of the reaction medium as it exits the first reaction zone. Temperature control can be established, for example, by placing an internal cooling coil or other cooling device within the first reaction zone, by employing a cooling jacket to surround the reactor or by circulating the reaction medium through a heat exchanger located externally from the reactor. Catalyst control can be established by, for example, routing some of the catalyst-containing mother liquor directly to the second reaction zone, bypassing the first reaction zone.

The invention is characterized in that the terephthalic acid TA formed in the first reaction zone remains substantially in solution.


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It is more preferred to have only a trace, e. It is most preferred to avoid precipitation of solid terephthalic acid in the first reaction zone. Formation of terephthalic acid in the first reaction zone is limited by limiting oxygen uptake in the first reaction zone. Precipitation of terephthalic acid is prevented by maintaining a high solvent:precursor mass ratio, by maintaining a sufficiently high reaction medium temperature, and by selecting an appropriate coolant e.

On exiting the first reaction zone, the pressure of the reaction medium is reduced simultaneously as it is fed to a more conventional oxidation reactor. This reactor could typically be a stirred tank reactor or a bubble column reactor, for example. Pressure reduction can be conveniently accomplished by passing the reaction medium through one or a plurality of pressure letdown valves positioned about the periphery of the reactor. Best results have been obtained when the reaction medium is dispersed rapidly upon entering the second reactor.

http://bbmpay.veritrans.co.id/mujeres-solteras-en-padrenda.php Rapid dispersion can be achieved by using established methods for dispersing paraxylene-containing feeds in conventional reactors. In a stirred tank reactor, for example, this would include injecting the reaction medium into the reactor below the liquid line in close proximity to the discharge from an agitator impeller. Rapid dispersion of the reaction medium can be achieved in a bubble column reactor by injecting the reaction medium in close proximity to the air feeds.

Referring now to the drawings, FIG. As mentioned above, the process will be described as it relates to the production of terephthalic acid, although the invention is applicable to the production of a range of aromatic carboxylic acids and mixtures thereof. In the illustrated embodiment shown in FIG. In practice the feed stream will comprise a mixture comprising i recycled solvent, recycled mother liquor and catalyst, line 11 , ii reactor condensate from the second reactor, line 12 , and iii fresh acetic acid make-up, line The mixed feed stream will contain typical catalyst components e.

Optionally, but not shown, control of catalyst concentration in the first reaction zone can be achieved by bypassing some of the catalyst-containing mother liquor, line 11 , directly to second reactor However, the temperature of the feed stream is not critical. The pressure of feed stream [] 10 is raised via a suitable pump 14 to a value of at least about, but generally in excess of about, 2, kPa, and the feed stream is introduced continuously and simultaneously into a first stirred tank reactor 15 with paraxylene, via line 16 , and a source of oxygen, via line The supply of oxygen via line [] 17 can be air, oxygen-enriched air, oxygen mixed with a gas such as, for example, carbon dioxide, or essentially pure oxygen.

When the source of oxygen includes nitrogen or another sparingly soluble carrier gas, the extent of cooling in the first reaction zone and its operating pressure are preferably chosen such that the vapor present in the first reaction zone is fuel-lean, i. When the source of oxygen includes a soluble carrier gas or when essentially pure oxygen is used, the extent of cooling in the first reaction zone and its operating pressure are preferably chosen such that there is no vapor phase present in the first reaction zone.