Zenon Sarbak

The effect of boron addition on hydrodesulfurization and hydrodenitrogenation activity of NiMo/Al2O3 catalysts

Abstract Studies of catalytic activity of a series of nickel–molybdenum catalysts supported on Al 2 O 3 modified with borate ions were performed for the hydrotreating of coal liquid. Decomposition of isopropyl alcohol, diacetone alcohol and ethylbenzene was performed for the characterization of acidity of the catalysts. Quinoline and carbazole hydrodenitrogenation (HDN) were used as test reactions. It was found that modification of the support with borate ions increases the acidity of nickel–molybdenum catalyst, in particular, the amount of acidity centers of intermediate strength. However, although the modification practically does not affect the hydrosulfurization activity of coal liquid, it considerably affects its HDN activity. In the latter case, it leads to an increase in the resistance to coking of the modified catalysts. This particularly applies to the HDN process in which the above catalysts are still very active after a long period of run, and hence their dehydrogenation activity rises. The high HDN activity is connected to the increasing number of acid centers of intermediate strength.

Acid−base properties and the hydrofining activity of NiMo catalysts incorporated on alumina modified with F− and Cl−

A series of studies on NiMo catalysts incorporated on to Al2O3 modified with chloride and fluoride ions was carried out. As the test reactions, the reactions of decomposition of 2-propanol and diacetone alcohol as well as of ethylbenzene were employed. The obtained catalysts were also tested in hydrofining of coal liquid. It was observed that modification of the support with fluoride and chloride ions in the studied range of concentrations increases the acidity of the catalyst. A distinctly higher increase in acidity was obtained for the modification with F− ions than with Cl− ions. The applied modifiers, on the one hand, lead to the increase in the activity of the catalysts in the reactions of decomposition of 2-propanol to propene, ethylbenzene to styrene, but on the other hand, reduce their activity in the decomposition of diacetone alcohol to acetone. Modification with Cl− and F− ions only insignificantly affects the activity of catalysts in hydrodesulfurization (HDS) of coal liquid. Introduction of fluoride ions on the support of NiMo catalyst leads to a quite large increase of the activity in hydrodenitrogenation (HDN) of coal liquid, whereas, when modified with chloride ions, these catalysts bring about a decrease in the activity of the discussed reaction. The properties of catalysts generated by ions of the modifiers, in particular the type and strength of acid centers, play a significant role in the HDN of coal liquid.

Hydrodenitrogenation activity of sulfided catalysts

Activities of hydrodenitrogenation catalysts were compared using a batch mode autoclave reactor. The hydrodenitrogenation of carbazole, a model coal nitrogen compound, was the reaction studied. The highest activity and the highest rate constant for carbazole and total nitrogen removal were found in the case of NiMo/Al2O3 catalyst.AbstractСравнивали активности катализаторов гидродеазотирования в загрузочных автоклавных реакторах. Исследовали реакцию гидродеазотирования карбазола, модельного углеазотного соединения. Наибольшая активность, наивысшая константа скорости для карбазола и полное выделение азота наблюдали в случае катализатора NiMo/Al2O3.

Desulfurization of ethanethiol over cadmium and mercury modified zeolite NaX

Abstract Modification of NaX zeolite with Cd 2+ and Hg 2+ cations by Na + ion-exchange is found to increase the reactivity for the desulfurization of ethanethiol through H 2 S splitting. The conversion of mercaptan increases with the increasing degree of ion-exchange with these cations. Cd 2+ modification is little more active compared to the Hg 2+ samples. Moreover, NaHgX samples undergo further deactivation than those containing Cd 2+ ions.

Acidity, cumene conversion and thiophene hydrodesulfurization over alumina and surface modified aluminas

Abstract The acidic and catalytic properties of alumina as well as fluoride- and sodium-modified alumina were characterized by FT-IR spectroscopy of adsorbed pyridine and t -butylcyanide (TBC), and by cumene and thiophene decomposition. Experimental evidence demonstrated that Al 2 O 3 contains a high number of Lewis acid sites. A higher number of these sites of higher strength as well as Bronsted acid sites were detected for Al 2 O 3 F − . In the case of Al 2 O 3 Na + , the concentration of Lewis acid sites was lower compared to Al 2 O 3 and also the acid strength was weaker. The Al 2 O 3 F − sample showed high activity in cumene dealkylation whereas Al 2 O 3 Na + was most active in cumene dehydrogenation. The most active catalyst for thiophene hydrodesulfurization was Al 2 O 3 Na + while Al 2 O 3 F − was a little less active and lost its original activity rapidly. It was suggested that in the first step a thiophene molecule is chemisorbed vertically through a sulfur atom on Lewis acid sites localized on the alumina surface.

Acidity and catalytic activity of cobalt-molybdena catalyst supported on alumina. The effect of incorporation sequence of sodium and fluoride ions

Two series of CoMo/Al2O3 catalysts containing F and Na ions were prepared. Acid properties of these catalysts were characterized using FT-IR spectroscopy of adsorbed pyridine and t-butyl cyanide. Their catalytic activities in cumene conversion as well as hydrodesulfurization of thiophene were also determined. In this study the catalysts were prepared in a one-step procedure (sample denotation CoMoX, where X=F− or Na+) and in a two-step procedure, with X were deposited either before (X/CoMo) or after (CoMo/X) Mo, Co and Al2O3 components. It was found that the ratio of Bronsted to Lewis acid sites decreases in the following sequence: F/CoMo>CoMo/F>CoMoF. In the same order total conversion of cumene decreases. However, cumene dealkylation decreases as follows: CoMo/F>F/CoMo>CoMoF. This order overlaps the decreasing sequence of Bronsted acid sites concentration. HDS activity of fluoride containing catalysts was the highest for the F/CoMo sample. A similar activity was shown by CoMoF catalysts, whereas the activity was the lowest for CoMo/F. The sodium-modified CoMoAl2O3 catalysts do not contain Bronsted acid sites while Lewis acid sites completely disappear after heating at 200°C, 10−5 Torr. These samples were inactive in cumene dehydrogenation. The samples containing fluoride show significantly higher HDS activity than their sodium analogues. For each series of catalysts the highest HDS activity is shown by samples prepared in the two-step procedure where F− and Na+ ions were introduced first.

Structural properties and HDS activity of NiMo catalysts supported on lanthana modified zeolite type X and Y

In the search for the active catalysts of hydrodesulfurization reaction, an attempt was made to use zeolites as supports. A series of NaLaX, Mo/NaLaX and NiMo/NaLaX as well as NaLaY, Mo/NaLaY and NiMo/NaLaY catalysts was prepared and their performance in this reaction was studied. It was shown that crystalline structure of the lanthana forms of the above zeolites only little collapsed after ion-exchange and impregnation with active Mo and NiMo components. The NiMo catalysts supported on the zeolites studied were found active in thiophene hydrodesulfurization. The catalysts with lanthana after the first step of ion exchange were the most active.

Catalytic hydrodenitrogenation of carbazole and some of its partially hydrogenated intermediate products

The catalytic hydrodenitrogenation of model heterocyclic nitrogen compounds such as carbazole, tetrahydro-and hexahydrocarbazoles has been studied. The results indicate that the hydrodenitrogenation was complete in the case of tetrahydro- and hexahydrocarbazoles and almost complete in the case of carbazole. Rate constants for the first two compounds were 3 times higher than for carbazole. The mechanistic consequences of these results are discussed.AbstractИсследовали каталитическое гидродеазотирование таких модельных гетероциклических азотных соединений, как карбазол, тетрагидро- и гексагидрокарбазолы. Гидродеазотирование было полностью завершено в случае тетрагидро- и гексагидрокарбазолов и почти завершено в случае карбазола. Константы скорости для двух первых соединений в 3 раза превышают константу скорости для карбазола. Обсуждаются механистические последствия этих результатов.

NiMo catalysts supported on anion modified zeolites type Y — structural properties and HDS activity

NiMo catalysts supported on zeolite type Y modified with various anions were investigated. The structural properties and catalytic HDS activity of obtained samples were measured. It has been shown that change in zeolite crystal structure as a result of impregnation with anions was small. However, due to these anions considerably higher HDS activity of NiMo/NaY catalysts compared to samples without anions was observed. NiMo catalysts containing fluoride anions exhibited the highest activity. An explanation of the influence of anions on the HDS activity is also presented.

Elimination of odours from the gaseous phase on CrIII- and FeIII-modified Y-type zeolites

Modified NaY-type zeolites, in which a portion of the sodium ions had been exchanged for chromium(III) or iron(III) ions, were studied as adsorbents. The modified zeolites were tested with respect to the adsorption of n-butylamine or n-butylthiol via the pulse method employing a column micro-adsorber directly attached to a gas chromatograph. Thus, 200 mg portions of the adsorbent were activated by heating at 400°C for 2 h after which the temperature was decreased to 200°C. The column was held at this temperature for 1 h and then 10 μl portions of n-butylamine and n-butylthiol were injected on to it at 15-min intervals. It was found that the zeolites containing iron(III) ions were much more effective as adsorbents (by 30%) than those containing chromium ions, with this difference reaching 60% in the case of n-butylthiol. Furthermore, zeolites containing iron(III) ions underwent much less deactivation than those with chromium(III) ions. Increasing the iron → sodium or chromium → sodium ion exchange led to increased adsorption of the organic compounds studied. It was shown that Y-type zeolites modified with iron(III) are effective adsorbents for deodorising atmospheric air.