Influence of Zirconium Addition in Platinum–Hexagonal Mesoporous Silica (Pt-HMS) Catalysts for Reforming of n-Heptane

Abstract

A series of platinum/zirconium–hexagonal mesoporous silica (Pt/Zr-HMS) catalysts with different molar ratios of Si/Zr have been prepared and used for reforming reaction. The prepared catalysts were characterized by XRD, XRF, NH3-TPD, FTIR, Py-IR, nitrogen sorption, SEM, and TGA (for studying the coke deposition) techniques. The effects of various amounts of zirconium on the activity, selectivity, and coke deposition in the temperature range of 200–500 °C were compared. By increasing the incorporation of Zr into the Pt-HMS structure, the acidity of catalysts increased. The results show that the catalytic activity and selectivity for desired products (especially isomerization products) increased with decreasing Si/Zr amount (or increasing zirconium content). The best i-C7 selectivity (64.1%) was observed for Zr(5)-HMS at T = 200 °C.

Reliable prediction of n-heptane isomerization over Pt/(CrOx/ZrO2)-HMS via comparative assessment of regularization networks and surface response methodologies

“…2. The XRD spectra of the components of these composite catalysts (Zr(x)-HMS) have been reported in previous work, 14 which is a reference pattern to the catalysts prepared in the present work. A comparison of obtained XRD patterns with reference patterns reveals that no peak is clearly observed for zirconia, platinum and chromium oxide structures, probably because of their good dispersion or small amounts.…”

“…Pt-supported composite catalysts were prepared by an impregnation method. According to our reported works, 13,14 aer preparing Zr-HMS using a sol-gel method, 12 wt% chromium using ammonium dichromate ((NH 4 ) 2 Cr 2 O 7 ) as a chromium source was introduced into the structure of Zr-HMS. The obtained solid was dried in an oven at 110 C overnight and calcined at 600 C for 6 h. The powder (CrO x /ZrO 2 )-HMS materials were prepared with different Cr/Zr ratios, namely 5, 10, 20, and 35.…”

“…The selection of these parameters with their specic experimental ranges was meticulously based on the preliminary screening test and frequently used in the literature. [13][14][15][16][17]25,26 The CCD routine is employed to determine the least experiments supposed to be accomplished for optimizing the input variables and output responses. By using the Design Expert soware, it is anticipated to (a) develop the experimental design, (b) obtain the best-tted mathematical model, (c) assess the succeeding regression analysis and (d) optimize the process and analysis of variance (ANOVA).…”

“…Selective conversion of n-heptane into desirable products occurs when molecular transmission between the metal and acid sites happens quickly. 14 In other words, the effective balance between the metal and acid sites is a crucial factor for the catalyst used in this process. Some of these metals such as tungsten and molybdenum have been evaluated and reported in previous works.…”

“…Some of these metals such as tungsten and molybdenum have been evaluated and reported in previous works. 13,14 In recent years, new micro/mesoporous composite materials that are suitable candidates for use as isomerization process catalysts have gained researcher's interest. 5 Both micro-and mesoporous properties of these materials endow them with excellent activity and selectivity performances for use in selective n-heptane isomerization reactions.…”