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Section 17. Chemistry
Aghayev Akbar Ali, Ph.D., in Chemistry, professor Head of Petrochemistry and chemical engineering department, Sumgait State University, Republic of Azerbaijan Gadjieva Xejale Amiraslan, postdoctoral student of Petrochemistry and chemical engineering department, Sumgait State University
Abushova Zijafet Baxram, assistant professor of Petrochemistry and chemical engineering department, Sumgait State University
Shirinov Panax Maqomed, candidate for a degree of Petrochemistry and chemical engineering department, Sumgait State University
E-mail: irapon.sdu@mail.ru
ALKILATION OF 4-METHYLPHENOL WITH 1- AND 2- PROPANOLS OVER PALLADIUM-CONTANING ZEOLITE
Abstract: The article describes comparative alkylation of 4-methylphenol with 1- and 2-propanol over palladium-containing high silica zeolite. It reveals the possibility of highly selective (90.5-96.5%) synthesis of a mixture of 2-propyl-4-methylphenol and 2.6-dipropyl-4-methylphenol with 1-propanol and the preparation of a mixture of 2-isopropyl-4-methylphenol and 2.6-diisopropyl-4-methylphenol, with a total selectivity of89.0-94.0%, for 4-methylphenol and 2-propanol reaction.
Keywords: 4-methylphenol, 1-propanol, 2-propanol, palladium-containing zeolite, alkylation, 2-propyl-4-meth-ylphenol, 2-isopropyl-4-methylphenol, selectivity, yield.
Phenol alkylation with propanols and propene over various catalysts (1-3) have a number of significant drawbacks: low selectivity and low yield of individual propyl - (isopropyl) phenol isomers, a complex mixture of the produced alkylphe-nols, which requires additional separation cycles, as well as low stability of the catalysts, and complexity of technology and increase in investment costs as a result. Methylphenols catalytic alkylation with propanols over ferrite catalysts leads to more favourable results (4).
This report presents the results of a study of 4-methylphe-nol with 1- and 2-propanol over zeolite catalysts.
10 cm3 of studied zeolite catalyst was loaded into the continuous flow reactor. The temperature of the reactor rose in a stream of hydrogen at a rate of 200 °C/hour to 450 °C. At this temperature, the catalyst was regenerated and activated for 3 hours. After that, the temperature was lowered to the reaction temperature and a mixture of cresol and propanol
was loaded. All reagents were preheated in the steam chamber to the desired temperature before being put into the reactor. Experiments were conducted for 1 hour.
The study of liquid products was performed by gas-liquid chromatography (GLC), on a Chrom-5 chromatograph with a flame ionization detector. Apiezon-M deposited on chro-matone-N was chosen as the liquid phase. The analysis was conducted with the temperature rate of 8 °C/min. within the range of 80-220 °C, helium was used as a carrier gas; its consumption rate was 60 ml/min.
Proton MR spectra of propyl and isopropyl cresol derivatives were recorded using Bruker AV-300 (300 MHz, H2NMR), country of origin: Germany.
High-silica zeolites are obtained by the crystallization of organic and inorganic silica gels under hydrothermal synthesis conditions at elevated temperatures (150-180 °C). Hydrogen catalysts were obtained by ion exchange with a three and
Section 17. Chemistry
fourfold excess of ammonium nitrate, followed by calcination at 500 °C. In order to increase the degree of decatising and decrease the number of stages, ion exchange was performed under hydrothermal conditions at 220 °C. The nitrile content in the obtained samples ranged from 1.5-4.25% of the volume capacity. Before the experiments, the catalysts were activated in a stream of air and then hydrogen for 5 hours at 450 °C. Palladium was introduced by ion exchange between the zeolite and the aqueous solution of [Pd(NH3)4]Cl2. The palladium content was 0.1-2.0% wt. of the dry weight of the zeolite.
The table shows the comparative results of 4-methylphe-nol alkylation with 1- and 2-propanol over Pd/H-ZSM-5. It can be seen that the main resultants of 4-methylphenol alkylation with 1-propanol are 4-methylphenol propyl ether, 2-propyl-4-methylphenol and 2.6-dipropyl-4-methylphenol. The total selectivity of these resultants in the feedstock decreases by increasing the partial pressure of the alcohol.
With a twofold molar excess of 4-methylphenol in the feedstock, the total selectivity of these resultants equals 96.5%, and at a molar ratio of 4-methylphenol/1-propanol = 0.5/1, it equals 90.5%. The molar ratio of the starting components in the feedstock has a significant effect on the composition of the alkylated resultants. A change in the 4-methylphenol/1-propanol molar ratio from 1/0.5 to 0.5/1 reduces the selectivity of the formation of 2-propyl-4-methylphenol from 88.5% to 71.0% and leads to an increase in the yield of 2.6-dipro-pyl-4-methylphenol per reacted 4-methylphenol from 6.0 to 15.0%, and the selectivity of the formation of 4-methylphenol propyl ether varies only slightly. Similar dependence is observed in the case of 4-methylphenol alkylation with 2-propanol. Unlike the previous reaction, 4-methylphenol isopropyl
It should be noted that in addition to the above basic resultants of these reactions, the formation of small amounts of other resultants such as dipropyl or diisopropyl ether, 3-pro-pyl-4-methylphenol or 3-isopropylphenol, can be observed. Apparently, under the conditions of the alkylation process,
ether does not form and the main resultants are 2-isopro-pyl-4-methylphenol and 2.6-diisopropyl-4-methylphenol.
With an increase in the molar fraction of alcohol in the feedstock, the total selectivity of 2-isopropyl-4-methylphenol and 2.6-diisopropyl-4-methylphenol decreases first by 2.5%, and then by another 1.5% and equals 89.0% (at a molar ratio of 4-methylphenol/2- propanol = 0.5/1). In this case, a substantial change is observed in the composition of mono- and diisopropyl-4-methylphenols. In a two-fold molar excess of cresol in the feedstock, the selectivity for the formation of 2-isopropyl-4-methylphenol and 2.6-diisopropyl-4-methyl-phenol are 89.0 and 5.0%, respectively. The increase in the partial pressure of the alcohol in the feedstock doubles the yields of mono- and diisopropyl-4-methylphenols per reacted p-Cresol as follows: the yield of 2-isopropyl-4-methylphenol decreases to 70.0%, and the yield of 2.6-diisopropyl-4-meth-ylphenol increases to 19.0%.
When comparing parameters of the alcohol alkylation in the feedstock, it doubles the yields of mono- and diisopro-pyl-4-methylphenols per reacted p-Cresol as follows: the yield of 2-isopropyl-4-methylphenol decreases to 70.0%, and the yield of 2.6-diisopropyl-4-methylphenol increases to 19.0%.
It can be seen that 4-methylphenol 1- and 2-propanol, in
1-propanol alkylation, the original cresol has deeper changes than 2-propanol alkylation, namely, the conversion of 4-meth-ylphenol is higher by 8.0-13.0%. However, when comparing the selectivity of the basic mono-C3-derivatives formation of 4-methylphenol, there is a slight advantage in reaction of p-Cre-sol with 1-propanol. The yields of2-propyl-4-methylphenol and
2-isopropyl-4-methylphenol, calculated by the missed 4-methylphenol, are respectively 37.1-48.7% and 29.4-39.5%.
partial intermolecular dehydration of the alcohol and isom-erization of the obtained C3-derivatives of p-Cresol take place.
In summary, it has been shown that palladium-containing high-silica zeolite in the alkylation of 4-methylphenol with 1- and 2-propanol have sufficient activity and selectivity.
Table 1.- Results of 4-methylphenol alkylation with 1- and 2-propanol over Pd/H-ZSM-5 Reaction occurs at: t:350 °C, u - 0.8 h-1
Name 4-methylphenol - 1-propanol 4-methylphenol - 2-propanol
Cresol/propanol molar ratio 1/0.5 1/1 0.5/1 1/0.5 1/1 0.5/1
Conversion of 4-methylphenol 41.0 58.0 65.5 33.0 45.0 56.5
The yield of resultants per reacted 4-meth-ylphenol,% 4-methylphenol propyl (isopropyl) ether 2-propyl-4-methylphenol 2.6-dipropyl-4-methylphenol 2-isopropyl-4-methylphenol 2.6-diisopropyl-4-methylphenol 2.0 90.5 4.0 4.0 84.0 6.0 4.0 72.5 14.0 89.0 5.0 82.5 9.0 70.0 19.0
Over this catalyst, higher conversion of 4-methylphenol is observed when interacting with 1-propanol by 8.0-13.0% relative to 2-propanol. The yields of 2-propyl-4-methyl-
phenol and 2-isopropyl-4-methylphenol per p-Cresol are 37.1-48.7% and 29.4-39.5% respectively.
Список литературы:
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2. Yadav Ganapati D., Salgaonkar Sanket S. Selectivity engineering of 2.6-diizopropil phenol in izopropylation of phenol Cs25H05PW12O40 / K-10 Clay // Ind. And Eng.Chem. Res. 2005.- 44.- No. 6.- P. 1706-1715.
3. Zvi Rappopart. The chemistry of functional qrups. The chemistry of phenols. Part 2 An. Inter. Science 2003.- 1629 p.
4. Тагиев Д. Б., Агаева Н. А., Назарова М. К. Каталитическое алкилирование крезолов пропанолом-1 // ЖПХ, 2013.86.- No. 8.- С. 1278-1281.
