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Karatun, O. N.; Proskurin, A. L.; Ovcharov, S. N.

doi:10.1023/a:1012312022464

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“…We must take into account that the cations of zinc, gallium, and rare earth elements from the group of Ce, La, Nd, and Pr which were introduced into the zeolite also had an effect on the increase in the catalytic activ ity of the tested samples and the selectivity of forma tion of aromatic hydrocarbon in the conversion of pro pane, because the introduction of these modifiers led to a change in the number and ratio of acid sites [9,[15][16][17][18]. The introduction of gallium contributed to the formation of strong Lewis sites, which catalyze the dehydrogenation reaction.…”

Section: Resultsmentioning

confidence: 99%

A study of propane aromatization on a zeolite-containing catalyst with different Si/Al ratios

et al. 2012

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79Aromatic hydrocarbons are an important feedstock for producing a significant part of the products of organic synthesis and the petrochemical industry. At present, their industrial production is based mainly on the hydroconversion of liquid pyrolysis products and the catalytic reforming of gasoline fractions. Under conditions of constant shortage of benzene, the devel opment of catalytic aromatization processes for vari ous hydrocarbon materials is of current concern.To date, a few process technologies for the aroma tization of light hydrocarbons have been developed. The Cyclar process for the conversion of low molecu lar weight paraffins (mostly propane and butanes) to aromatic hydrocarbons is based on the dehydrocy clodimerization of light paraffins using the technology of continuous regeneration of a spherical catalyst, which consists of a high silica zeolite, a base metal as a promoter, and an inert binder.A metallosilicate catalyst, which provides the selectivity of formation of aromatic hydrocarbons, is used in the Z forming process for producing a ben zene-toluene-xylene (BTX) fraction and hydrogen from liquefied petroleum gases and light naphtha. The above described conversion processes, which are based on the use of a fixed or moving catalyst bed, provide the production of aromatic hydrocarbons at a level of 50-60% of propane feedstock and 56-66% of butane feedstock involving the recycling of the unconverted residue.The Arben process is based on the conversion of a liquefied gas in a fluidized bed of a microspherical cat alyst with its continuous air regeneration; it is per formed in one isothermal reactor with an embedded regenerator. We also know the Alifar process for pro ducing aromatic hydrocarbons from individual pro pane and butanes or from their mixtures.For the competent use of low molecular weight hydrocarbons, studies in the field of production of the BTX fraction from the С 2 -С 4. fraction are carried out in OAO Nizhnekamskneftekhim.Effective catalysts for producing aromatic hydro carbons through the conversion of paraffins or С 2 -С 12 olefins are high silica zeolites of the pentasil group: ZSM 5, ZSM 11, TsVM, TsVN, etc.; most of the researchers attribute the catalytic activity of these cat alysts to the acid-base properties of their surface resulting from the presence of protic (Brönsted) and aprotic (Lewis) acid sites [1][2][3][4]. The ratio of Lewis and Brönsted sites depends on the zeolite structure, the composition of the frame, the thermal stability of the hydroxyl cover, and the chemical nature of the sub stances used to modify the internal and external sur face of the catalysts [5][6][7]. It is assumed that the con tent of Brönsted sites is roughly proportional to the number of aluminum atoms in the zeolite unit cell [8]. The content of Lewis sites is also proportional to the amount of aluminum contained in the zeolite [4].One of the important factors that affect the level and pattern of conversion of lower paraffins on zeolite containing catalysts is the content of aluminum and t...

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Section: Resultsmentioning

confidence: 99%