n-Heptane isomerization activities of Pt catalyst supported on micro/mesoporous composites

Pt loaded on a series of MCM-48 silica and composites with HZSM-5 zeolite, HY zeolite, or TiO2 has been prepared and studied for n-heptane isomerization reaction at 200–350 °C. The structural characterization, acid distribution, and morphology of these catalysts were characterized by X-ray diffraction, Fourier transform infrared, UV–Vis diffuse reflectance, scanning electron microscope, temperature-programmed desorption of NH3, and nitrogen adsorption–desorption methods. The results show that these catalysts have a good selectivity to multi branched isomers, while producing low aromatic compounds. Also, these new composite catalysts prove the catalytic stability during the time of reaction. The most desirable results, and significantly higher n-heptane conversion and isomerization selectivity were achieved with Pt/MCM48-HZSM5 catalyst.

The effect of indium introduction method on the properties of Pt/In/Al2O3-Cl reforming catalyst

The effect of 0.3 wt.% indium, which was introduced at the steps of alumina peptization or impregnation, on the properties of platinumalumina reforming catalysts was studied. Doping with indium at the impregnation step produced a smaller decrease in the total acidity of the support and hence in the heptane conversion for the corresponding Pt/In/Al2O3-Cl catalyst. The most pronounced decrease in selectivity of hydrogenolysis and hydrocracking and the maximum i-C5-7 : toluene selectivity ratio were observed for this sample as compared to the undoped catalysts with indium introduction at the peptization step.

Zinc supported on acid-activated montmorillonite for aromatization reactions

A Na-montmorillonite (Na-MMT) was activated with HNO3 (20 wt.%) solution at various temperatures and times to obtain acid-activated MMT (Acid-MMT). Zinc (4 wt.%) was supported on Acid-MMT via the impregnation method using Zn(NO3)2⋅6H2O as a precursor. The catalytic performance of the Zn/Acid-MMT for the aromatization of heptane was investigated. The amount and distribution of acidity of Acid-MMT, which could be adjusted by changing the acid activation time and temperature, significantly affected the heptane conversion and aromatics content. As a result, an efficient Zn/Acid-MMT catalyst for the aromatization reaction was obtained by optimizing the acid-treatment conditions of Na-MMT.

Performance of MFI Zeolite Catalysts in n-heptane Conversion Reaction Test

The aromatization of n-heptane, one of the main components of light naphtha, has been investigated over HZSM-5 (Si/Al = 33.9) and Zn-HZSM-5: Zn1-HZSM-5 (0.86% Zn); Zn2-HZSM-5 (1.35% Zn) and Zn3-HZSM-5 (2.89% Zn) catalysts prepared by the ion exchange with 10M aqueous solution of Zn(NO3)2. The catalytic activity measurement was performed by the chromatographic pulse method in the temperature range of 673 - 823K. The presence of zinc in Zn-HZSM-5 catalysts provided a significant increase in total aromatics selectivity due to the improvement of dehydrogenation activity by Zn incorporation. The Zn species facilitated the aromatization by converting paraffin�s into corresponding olefins which, in turn, were the aromatics precursors. Therefore, both acidity and zinc incorporation played important roles in the aromatization of n-heptane. Over 773 K the activity and selectivity of the Zn-HZSM-5 catalysts decrease very probably due to the loss of zinc ions.

Study on n-heptane Conversion Over Ni-HZSM-5 Zeolite Catalysts

The conversion of n-heptanes by the chromatographic pulse method in the temperature range of 673 - 823K on the MFI zeolites modified by ion exchange with Ni(NO3)2 aqueous solutions was studied. The catalysts, HZSM-5 (SiO2/Al2O3 = 33.9), and Ni-HZSM-5 (wt. % Ni, 0.57, 1.09, 1.34,) having different acid strength distribution exhibit a conversion and a yield of aromatics depending on temperature and metal content. The highest selectivity for n-heptanes aromatization was obtained on the catalyst Ni3-HZSM-5 (wt. % Ni 1.34) at 823K. The metal actions and the acidic properties of zeolites have an important effect on the aromatization of n-heptanes.

Performance of Ag-HZSM-5 Zeolite Catalysts in n-heptane Conversion

The conversion of n-heptanes into aromatic hydrocarbons benzene, toluene and xylenes (BTX), by the chromatographic pulse method in the temperature range of 673 - 823K was performed over the HZSM-5 and Ag-HZSM-5 zeolites modified by ion exchange with AgNO3 aqueous solutions. The catalysts, HZSM-5 (SiO2/Al2O3 = 33.9), and Ag-HZSM-5 (Ag1-HZSM-5 wt. % Ag1.02, Ag2-HZSM-5 wt. % Ag 1.62; and Ag3-HZSM-5 wt. % Ag 2.05 having different acid strength distribution exhibit a conversion and a yield of aromatics depending on temperature and metal content. The yield of aromatic hydrocarbons BTX appreciably increased by incorporating silver cations Ag+ into HZSM-5.

EFFECT OF SUPPORT ON MOLYBDENUM OXIDE ACIDITY FOR N-HEPTANE ISOMERIZATION

Skeletal isomerization of alkanes into the corresponding branched isomers has attracted many attentions as a reaction to produce clean fuel with high octane quality. In this study, molybdenum oxide (MoO3) catalyst supported on mesostructured silica nanoparticles (MSN), HZSM-5 and MCM-41 activity were being tested towards n-heptane isomerization at 623 K. The catalyst acidity was characterized by using FTIR pre-adsorb pyridine. The results showed that MoO3-MSN possesses highest Lewis acid and lowest Brönsted acid concentrations. The catalytic testing towards n-heptane isomerization showed that MoO3-MSN exhibited the highest n-heptane conversion of 18.7 % at 623 K. It was suggested that the high Lewis acid in the MoO3-MSN may facilitate the formation of active protonic acid sites from molecular hydrogen through hydrogen spillover mechanism and hence improves the n-heptane conversion.