Mixed cresols

For uses see cresylic acids. U.S. production of cresylic acid and mixed cresols 1978 65 000 tonnes. 

Toluenesulfonic Acid. Toluene reacts readily with fuming sulfuric acid to yield toluene—sulfonic acid. By proper control of conditions, /)i7n7-toluenesulfonic acid is obtained. The primary use is for conversion, by fusion with NaOH, to i ra-cresol. The resulting high purity i7n -cresol is then alkylated with isobutylene to produce 2 (i-dii-tert-huty -para-cmso (BHT), which is used as an antioxidant in foods, gasoline, and mbber. Mixed cresols can be obtained by alkylation of phenol and by isolation from certain petroleum and coal-tar process streams. 

More problems are encountered with plasticisers because most extracts from polymer compositions are mixtures and, when separated by TLC, the amount of the individual fractions is often too small for convenient examination by 1H 1-NMR spectroscopy. Moreover, the original plasticisers themselves are often mixtures. For example, tricresyl (tritolyl)phosphate is based on mixed cresols, while most of the higher phthalate esters are based on complex mixtures of alcohols. 

Cresex [Cresol extraction] One of the Sorbex processes. This one extracts p- or m-cresol from mixed cresols, and ciesols as a class from higher alkyl phenols. By 1990, one plant had been licensed. 

Hepatic Effects. Moderate fatty degeneration was found in the liver of a woman who died after drinking 250 ml of a disinfectant, which contained 50% mixed cresols (Chan et al. 1971). The liver appeared normal in another woman who died after ingesting a disinfectant suspected of containing cresols (Dellal 1931). 

In rabbits, dermal LD50 values for cresols were 890, 300, 2,830, and 2,000 mg/kg for o-, p-, m-, and mixed cresols, respectively (Vernot et al. 1977). These values are recorded in Table 2-2. Based on these LD50 values, p-cresol appears to be more toxic dermally than o-cresol, with m-cresol being the least toxic of the three isomers. 

Hematological Effects. Hematological effects in a man, apparently exposed to cresol dermally while working with an antiseptic solution containing concentrated mixed cresols, included methemoglobinemia with massive hemolysis and the presence of numerous large Heinz bodies in the blood (Larcan et al. 1974). Similar effects have been reported following oral exposure to cresols (see Section 2.22.2). 

Neurological effects were seen in two people who were accidentally exposed to mixed cresols on the skin and later died. A l-year-old baby who had 20 ml of a cresol derivative spilled on his head was unconscious within 5 minutes autopsy revealed swelling and congestion of the brain (Green 1975). A man who fell into a vat containing a cresylic acid derivative and received burns on 15% of his body fell into a coma 9 days later (Cason 1959). A man who survived 5-6 hour immersion of his hands in a concentrated cresylic acid solution experienced persistent eye watering, followed by pain on the side of his face and, ultimately, marked facial paralysis (Klinger and Norton 1945). 

The National Toxicology Program (NTP) is performing subchronic tests of cresol toxicity in which either o-cresol or mixed cresol isomers are given to rats and mice in the feed. In addition, studies of the effects of cresols on reproduction and fertility in mice are being performed by the NTP. The results of these studies are not yet available. 

The minimum, maximum, mean, and median concentrations of mixed cresols for three unremarked groundwater data points are all 5.0 pg/L (STORET 1989). 

Mercapsol process a regenerative process for extracting mercaptans, utilizing aqueous sodium (or potassium) hydroxide containing mixed cresols as solubility promoters. 

It should be noted that mixtures of isomers are involved in many cases of organic solvents e.g., mixed xylene isomers, mixed cis- and trans-decalin, mixed 1,1- and 1,2-dichloroethane, or mixed cresols, without obvious detrimental effects on the particular application attempted. However, in the following it is assumed that definite single substances are to be dealt with. 

Emulsion flotation is analogous to carrier flotation. Here, small-sized particles become attached to the surfaces of oil droplets (the carrier droplets). The carrier droplets attach to the air bubbles and the combined aggregates of small desired particles, carrier droplets, and air bubbles float to form the froth. An example is the emulsion flotation of submicrometre-sized diamond particles with isooctane. Emulsion flotation has also been applied to the flotation of minerals that are not readily wetted by water, such as graphite, sulfur, molybdenite, and coal [623]. Some oils used in emulsion flotation include mixed cresols (cresylic acid), pine oil, aliphatic alcohols, kerosene, fuel oil, and gas oil [623], A related use of a second, immiscible liquid to aid in particle separation is in agglomeration flocculation (see Section 5.6.4). 

As in case of mixed cresols, mixed xylenols have been used for manufacture of carbolic soaps, disinfectants, wire enamels, and fire-retardant plasticizers. However, 2,4-xylenol, 2,6-xylenol, and 3,5-xylenols have been used for organic chemical synthesis. 2,6-Xylenol is a precursor for an engineering plastic polyphenylene oxide also known as polyphenylene ether. 

Cresylic acids or tar acids are other names under which mixed cresols containing all the isomers of cresols, some quantities of phenol and mixed xylenols and even some higher alkylated phenols are available in the market. 

Traditionally, cresylic acids or mixed cresols have been obtained from coal tar isolated during production of metallurgical coke (semi or smokeless) via high or low temperature carbonization of coal, primarily bituminous. 

The most prominent player in the field of cresols from coal tar had been SASOL of South Africa that has been operating coal chemical plants using pressure gasification of bituminous coals based on Lurgi process. In these plants, initially phenol and ortho-cresol are separated from the cresylic acid mixture using fractionation, and a mixture rich in cresols (upto 94%) containing some xylenols is produced and the product is marketed as mixed cresols (primarily para cresol, meta cresol, and small percentage of mixed xylenols and a very little quantity of unrecovered phenol). It has been reported that for select customers, SASOL can supply upto 99% pure cresols (metal + para cresols). 

Bituminous coal or even lignite tars have been used in Germany, Czech Republic, Russia, Ukraine, and India for recovery of mixed cresols and xylenols. However, many of these plants, particularly in Germany, are being closed down since coal carbonization processes are considered as non-eco-friendly. 

Mixed cresols are available in India both from coal and lignite carbonization plants and are also produced synthetically, particularly p-cresol, using toluene as the critical feedstock. 

M/s Neyvelli Lignite Corporation Limited, Tamilnadu produce approximately 400-425 tpa mixed cresols via carbonization of lignite. Cresols produced are coproducts along with a number of key carbonization products such as gas, phenol. 

Steel Authority India Ltd. (SAIL) has been producing approximately 100-125 tpa mixed cresols in their coke oven plant at Rourkela, Orissa State. Similarly, Dankuni Coal Complex (near Calcutta) of Coal India Ltd. (CIL) have been producing mixed cresols and xylenols to the tune of 200 tpa. Quality of cresols produced by SAIL and CIL is more or less similar to that produced by Neyvelli Lignite. 

In the following chapters monomethyl phenols or cresols and their downstream derivatives will be discussed. Uses of the mother compound in the group of hydroxybenzenes i.e., phenol and also Cs phenols i.e., xylenols and mixed cresols have been shown in Figures 1.1-1.3. Some relevant higher alkyl phenols will be examined at appropriate places. 

While mixed cresols (m-p-cresols) are mostly recovered from natural feedstocks as discussed above, para-cresol and coproduct ortho-cresol are produced via sulfonation of toluene. Meta-cresol is commercially produced as a co-product during manufacture of BHT from meto-para-cresols mixture. This is discussed in some details in the next chapter. 

In India Atul Limited, Valsad, Gujarat State is the sole manufacturer of para-cresol. Atul s technology was developed by the company s R D department at its Ankleshwar plant, Gujarat State. Strictly speaking, the technology was an adaptation of the process licensed by Honshu Chemicals Japan for production of mixed cresols (38-40% meta, 45—50% para and 5—10% or /io-cresol, phenol, and xylenols). In the first phase, Atul introduced 95-96% pure para- cresol and then gradually 98-99% pure para-cresol. 

Mitsui Petrochemical Industries Limited and Sumitomo Chemical Co. Ltd., Japan have been operating two 20,000 tpa plants wherein they produce mixed cresols (60% m-cresol and 40% p-cresol mixture) for the last many years. However, they do not separate the mixture of meta- and para-cymenes but convert the cymenes mixture to meto-para-cresols. M/s. Yanshen Petrochemicals, China near Beijing have been operating a similar 20,000 tpa meto-para-cresols plant based on alkylation of toluene. Both the Japanese and Chinese plants have been producing pure meto-cresol and BHT. Through a recent agreement, Sumitomo Chemicals sell 10,000 tpa cresols mixture to Merisol and the remaining 10,000 tpa m-p-cresols are converted pure meto-cresol and BHT. From environmental point of view, cresol plants based on alkylation of toluene are much cleaner and more eco-friendly than those based on sulfonation of toluene. 

Considering the importance of separation of pure para-cresol from a mixture of meta-para-cresols, a number of alternative processes were tried out in various academic and research institutions. These processes were mostly studied in laboratories but for various reasons could not be commercialized. Both neutral and synthetic cresols were examined. After removal of o-cresol and phenol from mixed cresols or cresylic acid, a binary mixture of var3dng composition (meta content 40-60%, para content 60 0%) is obtained. Processes for separation of pure components are briefly outlined here. 

A separation method involving use of -butyl alcohol (CAS no. [75-65-0](CH3)3COH, colorless liquid, b.p. 82.9°C, freezing point 25.5°C using 60% meta- and 40%p-cresol) has been also reported. Mixed cresols are added to 55.7% -butyl alcohol which forms an adduct having 70% p-cresol and 30% m-cresol. On progressive crystallization at 0°C and 10°C, the composition of 90% p-cresol, 10% m-cresol and also 95.5% p-cresol and 4.5% m-cresol is obtained. The Cbutyl alcohol is separated from p-cresol by distillation [15]. Here also more experimental work will be necessary to establish the commercial feasibility and economics of the process. 

Separation of relatively pure para-cresol from mixed cresols using an organic solvent and thereafter formation of a solid crystalline complex with the solvent has been reported. Piperazine and DABCO (diazabicyclo-octane) have been found to be very effective as extracting agents in this process of separation. There is very little effect of m-cresol in this process. The values of separation factor approach infinity as 100% p-cresol-base complex is crystallized. The yield of p-cresol was impressive with some aliphatic polar solvents, but... 

While phenol downstream chemistry has been well known and gradually developed during the last hundred years, cresols have been relatively unknown even some 50 years ago. Mixed cresols, also known popularly as cresylic acids, derived from coal carbonization plants and also from the spent washes... 

The disinfectant, bactericidal and fungicidal properties of individual cresols and mixed cresol or cresylic acids had been well known for the last 60 years or so. So much so that within the recommended doses as prescribed by WHO cresols were used in the manufacture of carbolic soaps. Cresols were also used in place of phenol as disinfectant in domestic applications. They were also used as wood preservatives. As mentioned earlier para-chloro-meta-cresol is now one of the preferred preservatives for leather goods. 

Bhaway, M.M. Separation of Individual Cresols from Mixed Cresols. M.Tech. Thesis IIT Bombay, 1979. 

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