n-Nonane hydroisomerization over hierarchical SAPO-11-based catalysts with sodium dodecylbenzene sulfonate as a dispersant

Abstract

To enhance the gasoline octane number, low-octane linear n-alkanes should be converted into their high-octane di-branched isomers via n-alkane hydroisomerization. Therefore, hierarchical SAPO-11-based catalysts are prepared by adding different contents of sodium dodecylbenzene sulfonate (SDBS), and they are applied in n-nonane hydroisomerization. When n(SDBS)/n(SiO2) is less than or equal to 0.125, the synthesized hierarchical molecular sieves are all pure SAPO-11, and as the SDBS content increases, the submicron particle size decreases, and the external surface area (ESA) increases. Additionally, these hierarchical SAPO-11 have smaller submicron particles and higher ESA values than conventional SAPO-11. When n(SDBS)/n(SiO2) is greater than 0.125, with increasing SDBS content (n(SDBS)/n(SiO2) = 0.25), the synthesized SAPO-11 contains amorphous materials, which leads to a decline in the ESA; with the further increase in SDBS content (n(SDBS)/n(SiO2) = 0.5), the products are all amorphous materials. These results indicate that in the case of n(SDBS)/n(SiO2) = 0.125, the synthesized SAPO-11 molecular sieve (S–S3) has the most external Brønsted acid centers and the highest ESA of these SAPO-11, and these advantages favor generation of the di-branched isomers in hydrocarbon hydroisomerization. Among these Pt/SAPO-11 catalysts, Pt/S–S3 displays the highest selectivity to entire isomers (83.4%), the highest selectivity to di-branched isomers (28.1%) and the minimum hydrocracking selectivity (15.7%) in n-nonane hydroisomerization.

Optimizing the Acid Properties of the HZSM-5 Catalyst for Increasing the p-Xylene Yield in 1-Hexene Aromatization

“…Because the pore openings of HZSM-5 (0.56 nm) were much smaller than the diameter of 2,6-lutidine (0.67 nm), 70 the total amount of EBA was calculated on the basis of 2,6-lutidine IR spectra at 200 °C. 51 As the loading of SiO 2 increased, the proportion of EBA to the total numbers of acid sites decreased continuously (Figure 3). When the TEOS concentration was increased from 0.25 to 0.75 mol/L, the proportion of EBS decreased slowly from 10.5 to 8.6%, and the proportion of EBS fell rapidly to 4.0% at a TEOS concentration of up to 1.0 mol/L.…”

“…On the basis of the areas of the characteristic band and the associated molar extinction coefficient (ε EBS = 6.8 cm μmol –1 ), the 2,6-lutidine IR spectra of Zn3Si y /Z5 are displayed in Figure S6. A noticeable adsorption peak could be observed at 1600–1675 cm –1 , which was contributed by the adsorption of 2,6-lutidine on BAS. , 2,6-Lutidine could be connected only with the external surface acid sites of Zn3Si y /Z5. Because the pore openings of HZSM-5 (0.56 nm) were much smaller than the diameter of 2,6-lutidine (0.67 nm), the total amount of EBA was calculated on the basis of 2,6-lutidine IR spectra at 200 °C .…”

“…A noticeable adsorption peak could be observed at 1600–1675 cm –1 , which was contributed by the adsorption of 2,6-lutidine on BAS. , 2,6-Lutidine could be connected only with the external surface acid sites of Zn3Si y /Z5. Because the pore openings of HZSM-5 (0.56 nm) were much smaller than the diameter of 2,6-lutidine (0.67 nm), the total amount of EBA was calculated on the basis of 2,6-lutidine IR spectra at 200 °C . As the loading of SiO 2 increased, the proportion of EBA to the total numbers of acid sites decreased continuously (Figure ).…”

“…The number of weak acid sites was obtained by subtracting the number of strong acid sites from the total number of acid sites. , The amount of EBA was measured via a 2,6-lutidine adsorption infrared experiment. The experimental procedures are same as for Py-IR except that 2,6-lutidine is used as an adsorbate …”

“…The experimental procedures are same as for Py-IR except that 2,6-lutidine is used as an adsorbate. 51 Industrial & Engineering Chemistry Research Catalyst Tests and Analytic Procedures. The aromatization of 1-hexene on these prepared catalysts was tested in a stainless-steel fixed bed reactor with an internal diameter of 13 mm.…”