Transalkylation of Alklaromatic Hydrocarbons in Contact with a Zeo Lte Catalyst Compostion

Content Provider	Semantic Scholar
Author	Mitsche, Roy T. Michalko, Edward
Copyright Year	2017
Abstract	OF THE DISCLOSURE iA catalyst composition which is particularly effective as a catalyst with respect to the transalkylation or dis proportionation of toluene to form benzene and poly methylbenzene products. The catalyst comprises a zeolite with a mordenite crystal structure containing alumina fixed in combination therewith. The catalyst is charac terized by a method of preparation. Crystalline aluminosilicates, or zeolites, are well known in the art and have found extensive application as hdyrocarbon conversion catalysts or as a component thereof. Such materials are of an ordered crystalline structure comprising cages or cavities interconnected by Smaller pores and channels of a definite size range char acteristic of each crystalline aluminosilicate variety. Since the dimensions of the pores and channels are such as to accept molecules of certain dimension while rejecting those of larger dimension, these materials have come to be known as molecular sieves and utilized in many ways taking advantage of these properties. The crystalline aluminosilicates, hereinafter referred to as Zeolites, are generally described as a three dimensional network of fundamental structural units con sisting of silicon-centered SiO, and aluminum-centered AlO4 tetrahedra interconnected by a mutual sharing of apical oxygen atoms. To effect a chemical balance, each AlO4 tetrahedra has a cation associated therewith, usually Sodium. In most cases, the cation is subsequently ex changed with a hydrogen ion to yield the hydrogen or active form of the zeolite. The SiO4 and AlO4 tetrahedra are arranged in a definite geometric pattern often visualized either in terms of chains, layers or polyhedra, all formed by the linking of the tetrahedra. In any case, the zeolites comprise well defined intracrystalline dimensions including intracrystal line channels and pore openings whose narrowest cross Section has essentially a uniform diameter. The various Zeolites may be clasisfied according to the geometric pat tern of their framework with its attendant pore size, and by the SiO2/Al2O3 mole ratio of their compostion. Mordenite is a particular zeolite, highly siliceous in nature, and generally characterized by a SiO/AlO mole ratio of from about 6 to about 12 as manufactured or found in its natural state. The mordenite crystal struc ture comprises four and five membered rings of SiO, and AlO4 tetrahedra so arranged that the resulting crys tal lattice comprises pores and channels running parallel along the crystal axis to give a tubular configuration. This structure is unique among the zeolites since the channels or tubes do not intersect and access to the cages or cavities is in only one direction. For this reason, the nordenite structure is frequently referred to a two dimensional. This is in contrast to other well-known zeo lites, for example faujasite and Zeolite A, in which the cages can be entered from three directions. Conventional mordenite exhibits an unusual acid sta bility attributed to its siliceous nature, and the SiO/Al2O3 5
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