The present invention relates to a process for preparing zeolite crystals having a multimodal particle size distribution, and the sizes of which are between 0.02 μm and 20 μm, said process comprising a first introduction of one or more seeding agents into the tubular reactor or upstream of the tubular reactor, and at least one second introduction of one or more, identical or different, seeding agents into the tubular reactor.

The present invention relates to a process for preparing zeolite crystals having a multimodal particle size distribution, and the sizes of which are between 0.02 μm and 20 μm, said process comprising a first introduction of one or more seeding agents into the tubular reactor or upstream of the tubular reactor, and at least one second introduction of one or more, identical or different, seeding agents into the tubular reactor.

Disclosed is a process for producing mixed xylenes and C.sub.9+ hydrocarbons in which an aromatic hydrocarbon feedstock comprising benzene and/or toluene is contacted with an alkylating agent comprising methanol and/or dimethyl ether under alkylation conditions in the presence of an alkylation catalyst to produce an alkylated aromatic product stream comprising the mixed xylenes and C.sub.9+ hydrocarbons. The mixed xylenes are subsequently converted to para-xylene, and the C.sub.9+ hydrocarbons and its components may be supplied as motor fuels blending components. The alkylation catalyst comprises a molecular sieve having a Constraint Index in the range from greater than zero up to about 3. The molar ratio of aromatic hydrocarbon to alkylating agent is in the range of greater than 1:1 to less than 4:1.

Disclosed is a process for producing mixed xylenes and C.sub.9+ hydrocarbons in which an aromatic hydrocarbon feedstock comprising benzene and/or toluene is contacted with an alkylating agent comprising methanol and/or dimethyl ether under alkylation conditions in the presence of an alkylation catalyst to produce an alkylated aromatic product stream comprising the mixed xylenes and C.sub.9+ hydrocarbons. The mixed xylenes are subsequently converted to para-xylene, and the C.sub.9+ hydrocarbons and its components may be supplied as motor fuels blending components. The alkylation catalyst comprises a molecular sieve having a Constraint Index in the range from greater than zero up to about 3. The molar ratio of aromatic hydrocarbon to alkylating agent is in the range of greater than 1:1 to less than 4:1.

A porous ceramic honeycomb body including a substrate of intersecting porous walls forming axial channels extending from a first end face to a second end face. An active portion of the walls include a zeolite catalyst disposed inside pores thereof and/or is comprised of an extruded zeolite and a three way catalyst (TWC) is disposed on wall surfaces of at least a portion of the active portion.

A porous ceramic honeycomb body including a substrate of intersecting porous walls forming axial channels extending from a first end face to a second end face. An active portion of the walls include a zeolite catalyst disposed inside pores thereof and/or is comprised of an extruded zeolite and a three way catalyst (TWC) is disposed on wall surfaces of at least a portion of the active portion.

A porous ceramic honeycomb body including a substrate of intersecting porous walls forming axial channels extending from a first end face to a second end face. An active portion of the walls include a zeolite catalyst disposed inside pores thereof and/or is comprised of an extruded zeolite and a three way catalyst (TWC) is disposed on wall surfaces of at least a portion of the active portion.

The present disclosure relates to a preparing method of a zeolite core/silica zeolite shell composite, which includes adding a zeolite seed crystal into a gel solution containing a silicon-source compound, a structure directing agent and a fluorine anion-source compound, and then, crystallizing the gel solution for growing a silica zeolite shell containing a crystal structure which is coherent with that of the zeolite seed crystal; a zeolite core/silica zeolite shell composite prepared by the preparing method above; and catalytic use of the zeolite core/silica zeolite shell composite.

A method for preparing an MAZ framework type zeolite is disclosed using a trimethylphenylammonium cation as a structure directing agent. The MAZ framework type zeolite, in its as-synthesized form, contains in its intracrystalline pores the trimethylphenylammonium cation. The resultant MAZ framework type zeolite crystals have an average crystallite size of greater than 5 m.

Provided is a method for producing a MAZ-type zeolite, the method having an environmental impact which has been reduced as much as possible while not using a structure-directing agent as far as possible. In the method for producing a MAZ-type zeolite according to the present invention: (1) a silica source, an alumina source, an alkali source and water are mixed so as to form a reaction mixture that has a composition represented by a specific molar ratio; (2) a MAZ-type zeolite, which has a SiO.sub.2/Al.sub.2O.sub.3 ratio of 5-10, has an average particle diameter of at least 0.1 m and does not contain an organic compound, is added, as a seed crystal, into the reaction mixture in an amount of 0.1-30 weight % relative to the silica components in the reaction mixture; and (3) the reaction mixture, into which the seed crystal has been added, is heated at 80-200 C. in a closed system.