Mordenite catalyst pore size

H(hydrogen)-mordenite catalyst The crystallites were approximate parallelepipeds, the long dimension of which was assumed to be the pore length. Their analysis was based on straight, parallel pores in an isothermal crystallite (2 faces permeable). They measured (initial) rates of dehydration of methanol (A) to dimethyl ether in a differential reactor at 101 kPa using catalyst fractions of different sizes. Results (for two sizes) are given in the table below, together with... 

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... 

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... 

As mentioned above the structure of zeolite and its pore size fundamentally determine the cracking property of the catalyst. The difference in activity of mordenite and zeolite catalysts (e.g. HZSM-5, Y-zeolite) is unambiguously due to variation in structure [1]. Mordenite contains pores of relatively large size (about 7 x 8 A), while the pores of... 

The results of catalyst testing runs are shown in Figures 1 and 2. With a critical molecular size of 0.5-0.55 nm for all three molecules involved in the reaction [5], the influence of pore dimensions is clearly seen as nickel deposited on a ZSM-5 support (average channel size of 0.55 nm [6]) does not deactivate rapidly, while nickel supported on USY zeolite (average channel size of 0.77 nm [6]) and nickel on mordenite (average chaimel size of 0.68 nm [6])... 

The vapor phase studies also showed that the size of the pores has an important effect on the regioselectivity of the reaction. Fig. 2 illustrates the effect of pore size on product selectivity. The highest selectivity for para-nitrotoluene was observed over H-ZSM5 followed by Mordenite, L, and MCM. The kinetic diameters of the o-, m-, and p- isomers are 6.7, 6.7, and 5.25 A respectively. Experimental results shown in Fig. 2 verify that catalysts with channel diameters of less than 7 A preferentially form the para isomer. Based on these geometric arguments alone, the small amount of ortho isomer observed with the H-ZSM5 catalyst could be generated on acid sites located on the outer surface (2). 

Microporous titanium silicate (e.g., TS-1, Ti-(3, Ti-ZSM-12, Ti-mordenite) is an effective molecular-sieve catalyst for the selective oxidation of alkanes, the hydroxyla-tion of phenol, and the epoxidation of alkenes with aqueous H202. The range of organic compounds that can be oxidized is greatly limited, however, by the relatively small pore size (about 0.6 nm) of the host framework. 

A gas phase process for thymol manufacture using medium pore-sized zeolites (erionite, mordenite, or ZSM-23) as heterogeneous catalyst was developed in 1988. It was reported that reaction temperatures were lower (230-270°C) than in the older liquid phase process. Reaction pressure was reported to be normal or slightly elevated. 

The efficacy of different catalysts at 50°C is given in the Fig.l. Among the catalysts used, HP A (unsupported and supported on KIO) and ion exchange resins (Amberlyst-15 and lndion-130) showed very high activities followed by sulphated zirconia, Filtrol-24 and KIO. The aluminium pillaring with SWy2 showed a little activity. Catalysts based on the zeolites such as H-ZSM-5, Y and mordenite did not show any activity. It appears that the pore sizes of these catalysts pose considerable intraparticle resistance for the reactant 2-MON to access the catalytic sites. 

Mordenite etc. Dodecatungstophosphoric acid (DTPA) and the ion exchange resin catalysts showed maximum activities. Clay based catalysts and sulphated zirconia showed a moderate activity. Zeolites did not demonstrate any activity to the reaction due to pore size restriction. A 100% selectivity towards the ortho product (l-acetyl-2-methoxy naphthalene) was observed for almost all the reactions for all the catalysts. The para product (2-methoxy-6-acetyl naphthalene) was formed when the aluminium chloride was used as a homogeneous catalyst with nitrobenzene as the solvent. The reaction product was isolated and conformed by the melting point, FT-IR, H-NMR, etc. The reaction is intraparticle diffusion limited. A different catalyst would be required to get p-product selectively. 

Diisopropylnaphthalene (DIPN) is an important raw material for monomers for high-performance polymers. The new Catalytica process uses a mordenite with a pore size in the range of 0.6 to 0.7 nm as the catalyst for this... 

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... 

Studied [269,272,273], Both ZSM-5 catalysts emerge as the best catalysts with the highest yields of hydrocarbon products and lowest coke formation [269], The aromatics yield tends to decrease in the order ZSM-5 >H-beta>H-mordenite>H-ferrierite/HY [273], Stefanidis et al. demonstrated that, in comparison to a range of amorphous catalysts such as alumina, zirconia/ titania, and magnesium oxide, ZSM-5 is more suitable for the reduction of undesirable compounds and production of aromatics in the upgrading of pyrolysis vapors from beech wood [274], The excellent performance of ZSM-5 is attributed to the important role of its medium pore size [269], Besides, Park et al. pointed out that ZSM-5 is more efficient than Y zeolites due to the proper distribution of strong acid sites [275],... 

Our work on the alkylation of meta-diisopropylbenzene with propene over the acid form of various 12-member ring zeolites and molecular sieves shows that these catalysts can reveal shape selective behavior (39). As the effective size of the voids increases, the ratio of the formed 1,3,5- to 1,2,4-triisopropylbenzene increases e.g., mordenite and zeolite Y give 1.1 and 2.5, respectively. Additionally, an amorphous Si02/Al203 catalyst yields a ratio of 3.5. Thus, the smaller 12-ring materials show shape selective behavior. Based on these results, extra-large pore materials such as VPI-5 may show some shape selectivity for this reaction, if acid sites can be incorporated into the material. 

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. 

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