Catalyst supports mordenite

In China, zeolites A and X were first synthesized in 1959, followed by the industrial production of zeolite Y and mordenite. With the development of the zeolite industry, zeolites were applied in many fields as well in China. In the 1950s, zeolites were mainly used in drying, separation, and purification of gases. Since the 1960s, zeolites have been widely used as catalysts and catalyst supports in petroleum refining. At present, zeolites have become the most important adsorbents and catalysts in the petroleum industry. 

Table 2 shows the conversion of n-butane and the selectivity of each products over several kinds of zeolites and Cr catalysts supported on zeolites at 500°C. In most cases, the zeolite supports alone were found to be active for this reaction. The -butane conversion was in the order H-Mordenite (Si/Al2=18.3) > H-ZSM-5 (Si/Al2=29) > H-SSZ-35 (Si/Al2=40) >... 

A series of Pd catalysts supported on mordenite and ZSM-5 zeolites has exhibited a clear relationship between the activity and the Al203/(Al203 + Si02) ratio. When this ratio and, consequently, the anchoring capacity of the zeolite increases, the activity of the catalyst decreases, i.e., it appears as a general trend that as the interaction with the support increases, Pd becomes less active for combustion. 

As a nother means to decrease coke formation, zeolites with larger pore sizes have been studied. It is proposed that increased pore sizes allow larger molecules to reach the catalytic, acidic sites and possibly reduce coke formation. A recent patent uses an Ni-Mo catalyst supported on large pore zeolites (H-Beta, H-Y, H-mordenite) to... 

Calcined and sulfided Ni-Mo catalysts supported on ultrastable Y zeolite, NaY, mordenite and ZSM-5 were studied by high-resolution TEM [271]. In USY zeolite, Ni-Mo-S clusters were found in the supercages of the zeolite, whereas, on other zeolites, the sulfide phase was predominantly on the external surface. Bendezu et al. [272] also studied the dispersion and location of Ni-S, W-S and a Ni-W-S phase in US zeolite. 

The three-function model introduced in the preceding section has been established on an H-mordenite (HMOR) supported cobalt—palladium catalyst [12], For the sake of demonstration, model catalysts with a unique function, i.e. FI, F2 or F3, (Figure 5.1), were prepared to separately give evidence of the major role of each active site (Figure 5.1). Let us note that three functions does not necessarily mean three different active sites, but in the case of CoPd/HMOR material, three different sites were identified. 

Pt supported on an acidic support is a typical catalyst for the skeletal isomerization of light n-paraffins. The acidic supports can be acidic oxides, e.g., halogenated (Cl, F) alumina or sulfated zir-conia (Zr02/S04), or an appropriate zeolite, e.g., Mordenite. Pt-(C1, F)-alumina catalysts have a high performance at low temperatures and efficiently operate at temperatures between 115 and 150°C. Such low temperatures thermodynamically favor isomerization and thus, highly branched products are obtained. Zeolite supports are less active at lower temperatures and have to be operated at about... 

Historically, the earliest C8 aromatic isomerization catalysts tended to use amorphous supports with a halogen such as chloride or fluoride. Due to water sensitivity and corrosion issues, these were replaced by large-pore zeolites such as mordenite. The larger pore size was more favorable toward bimolecular transalkylation, whereas the chlorided alumina support tended to promote cracking. In both... 

Jao, R.-M., Leu, L.-J., and Chang, J.-R. (1996) Effects of catalyst preparation and pretreatment on light naphtha isomerization over mordenite-supported Pt catalysts. Appl Catal A., 135, 301-315. 

Zeolite-supported Re catalysts have been synthesized by chemical vapor deposition (CVD) ofMTO (CH3Re03) (3) on various zeolites such as HZSM-5, H-Beta, H-USY and H-Mordenite. HZSM-5 samples with different A1 contents were prepared by a hydrothermal synthesis method. For comparison, conventional impregnated catalysts were also prepared by an impregnation method using an aqueous solution of NH4Re04. All catalysts were pretreated at 673 K in a flow of He before use as catalyst. 

The acid function of the catalyst is supplied by the support. Among the supports mentioned in the literature are silica-alumina, silica-zirconia, silica-magnesia, alumina-boria, silica-titania, acid-treated clays, acidic metal phosphates, alumina, and other such solid acids. The acidic properties of these amorphous catalysts can be further activated by the addition of small proportions of acidic halides such as HF, BF3, SiFit, and the like (3.). Zeolites such as the faujasites and mordenites are also important supports for hydrocracking catalysts (2). 

Recently, Angelescu et a/.[92] have studied the activity and selectivity for dimerization of ethylene of various catalysts based on Ni(4,4-bipyridine)Cl2 complex coactivated with A1C1(C2H5)2 and supported on different molecular sieves such as zeolites (Y, L, Mordenite), mesoporous MCM-41 and on amorphous silica alumina. They found that this type of catalyst is active and selective for ethylene dimerization to n-butenes under mild reaction conditions (298 K and 12 atm). The complex supported on zeolites and MCM-41 favours the formation of higher amounts of n-butenes than the complex supported on silica alumina, which is more favourable for the formation of oligomers. It was also found that the concentration in 1-butene and cw-2-butene in the n-butene fraction obtained with the complex supported on zeolites and MCM-41, is higher compared with the corresponding values at thermodynamic equilibrium. 

Series of zeolite-supported iron-containing catalysts with weight percent iron (% Fe) varying from 1 to 17% Fe have been prepared from Fe3(CO) 2 and the synthetic zeolites ZSM-5, mordenite and 13X by an extraction technique. The zeolites ZSM-5 and mordenite were used in the acid form, 13X in the sodium form. 

The efficiency and selectivity of a supported metal catalyst is closely related to the dispersion and particle size of the metal component and to the nature of the interaction between the metal and the support. For a particular metal, catalytic activity may be varied by changing the metal dispersion and the support thus, the method of synthesis and any pre-treatment of the catalyst is important in the overall process of catalyst evaluation. Supported metal catalysts have traditionally been prepared by impregnation techniques that involve treatment of a support with an aqueous solution of a metal salt followed by calcination (4). In the Fe/ZSM-5 system, the decomposition of the iron nitrate during calcination produces a-Fe2(>3 of relatively large crystallite size (>100 X). This study was initiated in an attempt to produce highly-dispersed, thermally stable supported metal catalysts that are effective for synthesis gas conversion. The carbonyl Fe3(CO) was used as the source of iron the supports used were the acidic zeolites ZSM-5 and mordenite and the non-acidic, larger pore zeolite, 13X. 

Catalytic Evaluation In order to investigate support effects in these iron/zeolite catalysts prepared from Fe3(C0)12 by the extraction technique, three catalysts of similar weight percent iron loading were evaluated for their ability to catalyze synthesis gas conversion these catalysts were 15.0% Fe/ZSM-5, 16.4% Fe/Mordenite andl5.0% Fe/13X. All catalysts were evaluated under similar conditions as described in the experimental section. Catalytic data is presented in the accompanying figures in each figure the first three points for each catalyst are data obtained at 280°C, the second three points are data at 300°C. 

The catalysts evaluated are active for synthesis gas conversion the percent conversion of H2 and CO is shown for each catalyst in Figure 1 as a function of time under evaluation conditions and temperature. At 280°C the percent conversion of synthesis gas increases with time for the acidic zeolite-supported catalysts, Fe/ZSM-5 and Fe/Mordenite, but decreases for the larger pore, non-acidic zeolite-supported catalyst Fe/13X. The percent conversion increases for all catalysts at 300°C for Fe/ZSM-5 and Fe/Mordenite the conversions remain constant at this temperature for several days, although for Fe/13X the conversion increases with time. The trends in % synthesis gas conversion, particularly % CO, are reflected in the weight % hydrocarbons, carbon dioxide and water obtained in the reactor effluent over the period of evaluation, see Figure 2. It is apparent that the catalysts are effective for the production of hydrocarbons from synthesis gas, but also catalyze the water gas shift reaction the % hydrocarbons and%C02 obtained are greater at the higher temperature (300°C) whereas the % H2O is less at this temperature than at 280°C. 

Pt supported on zeolites, and particularly on modenite, have also been successfully commercialized for LSR isomerization. Pt/mordenite catalysts are less active than Pt/Cl-A Os, and are used at higher reaction temperatures (250°C), but they have the advantage of being more resistant to water and sulfur poisons present in the feed. 

The noble metal component may be either palladium or platinum the effect of the concentration of both metals on methylpentane as well as on dimethylbutane selectivity in C6 hydroisomerization on lanthanum and ammonium Y-zeolite with Si/Al of 2.5 has been studied by M.A. Lanewala et al. (5). They found an optimum of metal content for that reaction between 0.1 and 0.4 wt.-%. The noble metal has several functions (i) to increase the isomerization activity of the zeolite (ii) to support the saturation of the coke precursors and hence prevent deactivation, as was shown by H.W. Kouvenhoven et al. (6) for platinum on hydrogen mordenite (iii) to support the hydrodesulfurization activity of the catalysts in sulfur containing feedstocks. 

Zeolite-based processes have gradually displaced conventional ones, involving supported H3P04 or A1C13 as catalysts, in the manufacture of cumene, the raw material for phenol production [1, 6, 39]. A three-dimensional dealuminated mordenite (3-DDM) catalyst was developed by Dow Chemical for this purpose [39]. Dealumination, using a combination of acid and thermal treatments, increases the Si/Al ratio from 10-30 up to 100-1000 and, at the same time, changes the total pore volume and pore-size distribution of the mordenite. The... 

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