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Roel Prins - One of the best experts on this subject based on the ideXlab platform.
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Hydrodenitrogenation of 2-Methylpyridine and its intermediates 2-methylpiperidine and tetrahydro-Methylpyridine over sulfided NiMo/γ-Al2O3
Journal of Catalysis, 2007Co-Authors: Huamin Wang, Changhai Liang, Roel PrinsAbstract:Abstract The reaction network and mechanism of the hydrodenitrogenation (HDN) of 2-Methylpyridine and 2-methylpiperidine were studied at 280–340 °C and 1–3 MPa in the absence and presence of H2S over sulfided NiMo/γ-Al2O3. By the addition of 2-ethylpiperidine to the HDN of 2-Methylpyridine and of 2-ethylpyridine to the HDN of 2-methylpiperidine, the mutual inhibiting effects of 2-Methylpyridine and 2-methylpiperidine could be determined. 2-Ethylpyridine hardly affected the HDN of 2-methylpiperidine, but 2-ethylpiperidine strongly retarded the hydrogenation of 2-Methylpyridine and promoted its denitrogenation at low partial pressure and inhibited it at high partial pressure. Substantial amounts of 2,3,4,5-tetrahydro-6-Methylpyridine were detected in the HDN reactions; thus, its HDN was studied. This imine intermediate reacted very rapidly to 2-methylpiperidine by hydrogenation. 2-Methylpiperidine reacted to 1-hexylamine and even more strongly to 2-hexylamine. The final hydrocarbon products were 1-hexene, 2-hexene, and hexane. Based on these results and on previous HDN studies of dialkylamines, we propose that 2-Methylpyridine first reacts by hydrogenation to 2-methylpiperidine and that both react to the imines 2,3,4,5-tetrahydro-2-Methylpyridine and 2,3,4,5-tetrahydro-6-Methylpyridine. Breaking of the first C N bond and ring opening of the imines occurs as a result of the addition of H2S, elimination, and hydrogenation, forming amino-hexanethiols. The amino-hexanethiols react by hydrogenolysis to hexylamines, and the second C N bond is broken by hexylimine formation, H2S addition, and NH3 elimination.
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competitive hydrodesulfurization of 4 6 dimethyldibenzothiophene hydrodenitrogenation of 2 Methylpyridine and hydrogenation of naphthalene over sulfided nimo γ al2o3
Journal of Catalysis, 2004Co-Authors: Marina Egorova, Roel PrinsAbstract:Abstract The hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT) was studied at 340 °C and 5 MPa in the presence of 2-Methylpyridine and 2-methylpiperidine. Both N-containing molecules inhibited the HDS. The inhibitory effect of 2-methylpiperidine on the direct desulfurization and hydrogenation pathways of the HDS was slightly stronger than that of 2-Methylpyridine. The desulfurization of 4,6-dimethyltetrahydrodibenzothiophene, an intermediate in the hydrogenation pathway, was extremely difficult in the presence of N-containing molecules. 4,6-DMDBT, in turn, inhibited the hydrogenation of 2-Methylpyridine to 2-methylpiperidine but did not affect the CN bond cleavage in the hydrodenitrogenation of 2-methylpiperidine. The use of toluene as an aromatic solvent had no effect on the HDS of dibenzothiophene and 4,6-DMDBT at 340 °C. Naphthalene inhibited the HDS of dibenzothiophene and 4,6-DMDBT without changing the product distributions. Both S-containing molecules suppressed the hydrogenation of naphthalene to the same extent.
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mutual influence of the hds of dibenzothiophene and hdn of 2 Methylpyridine
Journal of Catalysis, 2004Co-Authors: Marina Egorova, Roel PrinsAbstract:Abstract The influence of 2-Methylpyridine and 2-methylpiperidine on the hydrodesulfurization of dibenzothiophene (DBT) and the effect of DBT on the hydrodenitrogenation of 2-Methylpyridine and 2-methylpiperidine were studied over a sulfided NiMo/Al 2 O 3 catalyst at 5 MPa, 35 kPa H 2 S, and 300 and 340 °C. Both N-containing molecules strongly suppressed the hydrogenation pathway of the hydrodesulfurization of DBT and inhibited the direct desulfurization route at both reaction temperatures. The inhibitory effect on the direct desulfurization was stronger for 2-Methylpyridine than for 2-methylpiperidine. H 2 S promoted the hydrogenation of 2-Methylpyridine up to 10 kPa and inhibited it at higher partial pressures. H 2 S had a positive influence on the hydrodenitrogenation conversions of 2-methylpiperidine and 2-Methylpyridine. DBT had a negative effect on the hydrogenation of 2-Methylpyridine, but did not influence the CN bond cleavage of 2-methylpiperidine. Therefore, CN and CS bond breaking takes place at different active sites, whereas the hydrogenation sites for N- and S-containing molecules may be the same.
Marina Egorova - One of the best experts on this subject based on the ideXlab platform.
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competitive hydrodesulfurization of 4 6 dimethyldibenzothiophene hydrodenitrogenation of 2 Methylpyridine and hydrogenation of naphthalene over sulfided nimo γ al2o3
Journal of Catalysis, 2004Co-Authors: Marina Egorova, Roel PrinsAbstract:Abstract The hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT) was studied at 340 °C and 5 MPa in the presence of 2-Methylpyridine and 2-methylpiperidine. Both N-containing molecules inhibited the HDS. The inhibitory effect of 2-methylpiperidine on the direct desulfurization and hydrogenation pathways of the HDS was slightly stronger than that of 2-Methylpyridine. The desulfurization of 4,6-dimethyltetrahydrodibenzothiophene, an intermediate in the hydrogenation pathway, was extremely difficult in the presence of N-containing molecules. 4,6-DMDBT, in turn, inhibited the hydrogenation of 2-Methylpyridine to 2-methylpiperidine but did not affect the CN bond cleavage in the hydrodenitrogenation of 2-methylpiperidine. The use of toluene as an aromatic solvent had no effect on the HDS of dibenzothiophene and 4,6-DMDBT at 340 °C. Naphthalene inhibited the HDS of dibenzothiophene and 4,6-DMDBT without changing the product distributions. Both S-containing molecules suppressed the hydrogenation of naphthalene to the same extent.
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mutual influence of the hds of dibenzothiophene and hdn of 2 Methylpyridine
Journal of Catalysis, 2004Co-Authors: Marina Egorova, Roel PrinsAbstract:Abstract The influence of 2-Methylpyridine and 2-methylpiperidine on the hydrodesulfurization of dibenzothiophene (DBT) and the effect of DBT on the hydrodenitrogenation of 2-Methylpyridine and 2-methylpiperidine were studied over a sulfided NiMo/Al 2 O 3 catalyst at 5 MPa, 35 kPa H 2 S, and 300 and 340 °C. Both N-containing molecules strongly suppressed the hydrogenation pathway of the hydrodesulfurization of DBT and inhibited the direct desulfurization route at both reaction temperatures. The inhibitory effect on the direct desulfurization was stronger for 2-Methylpyridine than for 2-methylpiperidine. H 2 S promoted the hydrogenation of 2-Methylpyridine up to 10 kPa and inhibited it at higher partial pressures. H 2 S had a positive influence on the hydrodenitrogenation conversions of 2-methylpiperidine and 2-Methylpyridine. DBT had a negative effect on the hydrogenation of 2-Methylpyridine, but did not influence the CN bond cleavage of 2-methylpiperidine. Therefore, CN and CS bond breaking takes place at different active sites, whereas the hydrogenation sites for N- and S-containing molecules may be the same.
Sevgi Haman Bayari - One of the best experts on this subject based on the ideXlab platform.
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normal coordinate analysis of 4 aminopyridine effect of substituent on pyridine ring in metal complexes of 4 substituted pyridines
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2001Co-Authors: A Topacli, Sevgi Haman BayariAbstract:Abstract The normal coordinate analysis has been performed for 4-aminopyridine (4-apy) assuming C 2v molecular symmetry. A Urey–Bradley force field has been used. The force constants are adjusted to fit the observed frequencies for 4-apy and its deuterated species. The vibrational assignment has been made on the basis of the calculated frequencies and potential energy distributions. The calculated frequencies were in good agreement with the observed frequencies. The substituent effect upon the Mnitrogen (ligand) (L=4-methlypyridine, 4-ethylpyridine, 4-vinylpyridine, 4-aminopyridine and 4-cyanopyridine) and pyridine ring frequencies has also been investigated. The frequency shifts are found to be sensitive to the substituent in the 4-position of the pyridine ring.
Dilip Kumar Adhikari - One of the best experts on this subject based on the ideXlab platform.
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Degradation of pyridine and 4-Methylpyridine by Gordonia terrea IIPN1
Biodegradation, 2008Co-Authors: Tsering Stobdan, Amita Sinha, Ravindra Pal Singh, Dilip Kumar AdhikariAbstract:Gordonia terrea IIPN1 was isolated and characterized from soils collected at petroleum drilling sites. The strain was able to catabolize pyridine and 4-Methylpyridine as sole carbon and nitrogen source. The strain failed to catabolize other pyridine derivatives. Growing cells completely degraded 30 mM of pyridine in 120 h with growth yield of 0.29 g g^−1. Resting Cells grown on 5 mM pyridine degraded 4-Methylpyridine without a lag time and vice versa. Supplementary carbon and nitrogen source did not significantly change the specific growth rate and degradation rate by the resting cells.
Ibrahim A. Z. Al-ansari - One of the best experts on this subject based on the ideXlab platform.
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Ground- and excited-state spectroscopic studies on [1-(4-methoxyphenyl)-3-(amino)-2,4-(dicyano)-9,10-tetrahydrophenanthrene]
Journal of Fluorescence, 1996Co-Authors: Ibrahim A. Z. Al-ansariAbstract:The effects of polar and nonpolar solvents on both the ground and the excited-state properties of [1-(4-methoxyphenyl)-3-(amino)-2,4-(dicyano)-9,10-tetrahydrophenanthrene] is examined. Light absorption results in a population of a locally excited (LE) first singlet state (S_1, n π^*) which shows sensitivity to the polarity of the surrounding solvent and hydrogen-bonding ability to the quencher 4-Methylpyridine. Relaxation of this state leads to an intramolecular charge-transfer state (ICT) which leads to a large Stokes shift in polar solvents and an excited-state dipole moment of μ_e= 10D. The quenching of the fluorescence state by 4-Methylpyridine studied in n -hexane and acetonitrile at room temperature is found to be efficient and a positive deviation from linearity was observed in the Stern-Volmer plots even at concentrations of 4-Methylpyridine below 0.4 M. This is explained as a result of the occurrence of both a dynamic and a static quenching mechanism. The static quenching constants ( K _sv) along with those obtained by visible spectroscopy ( K _GS) indicate that the ground-state complex is weak and relatively solvent dependent.
