Surface acidity and cumene conversion: I. A study of γ-alumina containing fluoride, cobalt, and molybdenum additives

doi:10.1016/0021-9517(85)90365-3

Journal of Catalysis

Volume 96, Issue 1, November 1985, Pages 115-121

https://doi.org/10.1016/0021-9517(85)90365-3 Get rights and content

Abstract

A series of catalysts containing fluoride, cobalt, and molybdenum as additives to γ-alumina both individually and in combination has been prepared and studied. The surface acidity has been studied by infrared spectroscopy of adsorbed pyridine and correlated with reactivity for cumene conversion. After preheating to 400 °C in vacuo, only Lewis acidic sites are present on the surface of γ-Al₂O₃, but the addition of fluoride ion initiates some Brønsted acidity and enhances the strength of the Lewis acidic sites. The presence of MoO₃ introduces another group of Brønsted acidic sites, but CoO, as a single additive, has little effect on either the Brønsted or Lewis acidity. As expected, the presence of fluoride ion enhances the activity of all the catalysts for the cracking of cumene to benzene. Although MoO₃ enhances the Brønsted acidity of γ-Al₂O₃, rather surprisingly this increased acidity did not enhance significantly the activity of the catalyst for cumene cracking to benzene.

References (16)

Z. Sarbak et al.
Stud. Surf. Sci. Catal.
(1984)
K. Segawa et al.
J. Catal.
(1982)
H. Weigold
J. Catal.
(1983)
K. Segawa et al.
J. Catal.
(1982)
T.R. Hughes et al.
J. Catal.
(1969)
P.O. Scokart et al.
J. Colloid Interface Sci.
(1982)
V.R. Choudhary
Ind. Eng. Chem. Prod. Res. Dev.
(1977)
P.M. Boorman et al.

There are more references available in the full text version of this article.

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The heterogeneous catalysts based on single active component such as V₂O_5, MnOx and CuOx and bi-components V₂O₅-MoO₃ V₂O₅-WO₃ and V₂O₅-SbO_x supported onto TiO₂, TiO₂-SiO₂ and Al₂O₃-SiO₂ was prepared and characterized. The aerobic liquid-phase oxidation of cumene (RH) in the presence of binary catalytic system containing N-hydroxyphthalimide (NHPI) and supported V, Mn and Cu oxides has been studied. It was observed that catalytic activities of the mono metallic systems decreases in order V₂O₅ ≈ MnO_x > CuO_x, bi-metallic catalysts showed no catalytic activities. The effect of catalytic system composition comprising MnO_x or VO_x and NHPI, AIBN on the oxidation rate was studied. The major oxidations product was cumene hydroperoxide, whereas dimethyl phenyl carbinol and acetophenone were found as minor ones. The reactions scheme that summarizes the oxidation chemistry identifying the related role of heterogeneous initiation and homogeneous propagation and termination steps for oxidation of cumene via free-radical mechanism are presented.
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Nonetheless, the promoter content does not fit the same order being the same for NiMo/NitAl and NiMo/SulfAl and around 17% higher for NiMo/ChlorAl. The catalytic activity in the hydrocracking of cumene is used to test catalyst acidity and it has been related to the amount of Brønsted acid sites [37–41]. Fig. 8 shows the conversion of cumene obtained with the different catalyst.
Three different aluminum salts were used in the hydrothermal synthesis of boehmite. The salts employed were sulfate, chloride and nitrate. The prepared boehmites were calcined to obtain γ-Al₂O₃, then these supports were used to prepare NiMo/γ-Al₂O₃ catalysts and their activity was measured in the hydrotreating of Maya crude oil. The results showed that various key properties related to hydrotreating capability can be modified by using different precursor salts in the hydrothermal synthesis route of Al₂O₃ support. In this sense, in addition to pore diameter, the acidity of the alumina support plays an important role. To assess the acidity of each catalyst, additional reaction tests of the hydrocracking of cumene in a microreactor were performed. The catalysts were characterized by N₂ physisorption, XRD, FT-IR, SEM, HRTEM, and TPR.
Characterization of spent and regenerated catalysts recovered from a residue hydrotreating bench-scale reactor
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By measuring the acidity of regenerated samples by FT-IR of pyridine adsorbed it was found that the deposited compounds transformed by regeneration produce Brønsted acid sites. It is well-known the relation between hydrocracking activity and Brønsted acidity [23–31]. Our results show that the tendency in the amount of Brønsted acid sites of regenerated catalysts measured at 380 °C matches the trend in hydrocracking of cumene along the bed length.
The deactivation of a catalyst located at the first bed of a bench-scale hydrotreating reactor operated at co-current downflow mode was studied. The deactivation, caused by metal and coke depositions, is analyzed by the characterization of catalyst recovered along the reactor bed. Metals trapped in catalysts remain as metal sulfides in the spent catalysts and their amount decreases from top to bottom of the bed length whereas coke increases toward bed outlet. Deposited foulants are classified according to removability by regeneration at 550 °C. Below this temperature the removable coke by oxidation is labeled as soft coke and hard coke corresponds to carbonaceous compounds that can only be oxidized above this temperature. By ¹³C CP-MAS NMR it was found that the aromaticity of the deposited coke is constant throughout the catalytic bed. By regeneration of spent catalysts near half of the hydrodesulfurization activity is recovered. However, the hydrocracking activity is the same or higher compared with the fresh catalyst. The extra hydrocracking activity is the result of the creation of Brønsted acid sites after regeneration.
Catalyst deactivation pattern along a residue hydrotreating bench-scale reactor
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Nonethelesss, as Ni and V sulphides may contribute to the overall HDS activity, the Z1-spent sample shows the highest HDS activity of all the spent catalysts. Hydrocracking of cumene is a well-known reaction used to test acidity of hydrotreating catalysts, and it has been observed a relation between hydrocracking activity and Brönsted acidity [39–47]; so the results of HDC activity are related directly to the surface acidity. The regeneration of spent catalysts yields higher HDC activity than that measured for the fresh sample.
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These studies are demonstrated that SMD is an interesting technique to disperse guest species on mesoporous silica, but little literature explored the surface acidities of the mesoporous materials varying guest species fillings and the interactive style between host species and guest species by in situ FT-IR. It is well known that the surface acidities of catalysts play an important factor in catalytic reaction [23,24]. To the best of our knowledge the surface acidities of the adsorbents on the effect of adsorptive desulfurization have been hardly reported in details in the literatures especially in the mesoporous material respect, and here the MCM-41 material containing different MoO3 filling and employing various modification method was studied systematically, and the obtained samples by the SMD technique are well-characterized by all kinds of approaches and compared with the prepared material by the IM method.
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^†: On leave from Adam Mickiewicz University, Poznan, Poland.

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Surface acidity and cumene conversion: I. A study of γ-alumina containing fluoride, cobalt, and molybdenum additives

Abstract

Stud. Surf. Sci. Catal.

J. Catal.

J. Catal.

J. Catal.

J. Catal.

J. Colloid Interface Sci.

Ind. Eng. Chem. Prod. Res. Dev.