The present invention relates to a process for preparing a pulverulent, porous crystalline metal silicate, comprising the following steps: a) hydrothermal synthesis in an aqueous mixture comprising (A) at least one silicon source, (B) at least one metal source and (C) at least one mineralizer to obtain an aqueous suspension comprising a porous crystalline metal silicate as reaction product; and b) calcination of the reaction product, characterized in that the calcination is conducted by means of flame spray pyrolysis at an adiabatic combustion temperature within a range of 450-2200° C., wherein the suspension having a solids content of 70% by weight which is obtained in step a) is sprayed into a flame generated by combustion of a fuel in the presence of oxygen to form a pulverulent, porous crystalline metal silicate.

The present invention relates to a method for preparing ZSM-5 zeolite. The present invention can provide a method for preparing ZSM-5 zeolite comprising the steps of: preparing a first solution in a solution state by heating a mixture comprising a silica source, an alumina source, a neutralizing agent and a crystalline ZSM-5 nucleus; preparing a reaction mother liquid by mixing a second solution comprising salts into the first solution; and continuously crystallizing by continuously supplying the reaction mother liquid to a hydrothermal synthesis reactor, wherein formula [1] below is satisfied.

0.20≤W.sub.a/W.sub.b≤0.40  Formula [1]

The present invention relates to a method for preparing ZSM-5 zeolite. The present invention can provide a method for preparing ZSM-5 zeolite comprising the steps of: preparing a first solution in a solution state by heating a mixture comprising a silica source, an alumina source, a neutralizing agent and a crystalline ZSM-5 nucleus; preparing a reaction mother liquid by mixing a second solution comprising salts into the first solution; and continuously crystallizing by continuously supplying the reaction mother liquid to a hydrothermal synthesis reactor, wherein formula [1] below is satisfied.

0.20≤W.sub.a/W.sub.b≤0.40  Formula [1]

The present disclosure relates to a molecular sieve, preparation thereof and acoustic absorption material and speaker containing the same. The molecular sieve having an MFI-structure, comprising a framework and an off-framework cation, wherein the framework comprises SiO.sub.2 and a metal oxide M.sub.xO.sub.y with M comprising boron, gallium or aluminium; the off-framework cation is at least one of hydrogen ion, alkali metal ion and alkaline earth metal ion. The molecular herein can effectively prevent the failure of the molecular sieve and improve the performance stability of the speaker.

The present disclosure relates to a molecular sieve, preparation thereof and acoustic absorption material and speaker containing the same. The molecular sieve having an MFI-structure, comprising a framework and an off-framework cation, wherein the framework comprises SiO.sub.2 and a metal oxide M.sub.xO.sub.y with M comprising boron, gallium or aluminium; the off-framework cation is at least one of hydrogen ion, alkali metal ion and alkaline earth metal ion. The molecular herein can effectively prevent the failure of the molecular sieve and improve the performance stability of the speaker.

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.

The present invention pertains to the use of mesoporous ZSM-22 zeolite in a process for the cracking or conversion of a feed comprised of hydrocarbons, such as, for example, that obtained from the processing of crude petroleum, to a mixture high in propylene. Further, the present invention concerns the field of fluid catalytic cracking (FCC) processes and relates to the preparation and employment of additives based on zeolites having increased mesoporosity, such as altered ZSM-22. More particularly the present invention discloses a process for improving the production of propylene in FCC units.

The present invention pertains to the use of mesoporous ZSM-22 zeolite in a process for the cracking or conversion of a feed comprised of hydrocarbons, such as, for example, that obtained from the processing of crude petroleum, to a mixture high in propylene. Further, the present invention concerns the field of fluid catalytic cracking (FCC) processes and relates to the preparation and employment of additives based on zeolites having increased mesoporosity, such as altered ZSM-22. More particularly the present invention discloses a process for improving the production of propylene in FCC units.

Systems and methods for production of externally-pore-blocked, internally-pore-opened modified zeolite crystals, the method including mixing zeolite crystals with an organic pore blocking agent; heating the zeolite crystals mixed with the organic pore blocking agent to block internal pores of the zeolite crystals and produce internally-pore-blocked zeolite crystals; mixing the internally-pore-blocked zeolite crystals with an external pore blocking agent; and calcining the internally-pore-blocked zeolite crystals mixed with the external pore blocking agent, to re-open internal pores via decomposition of the organic pore blocking agent and to block external pores via formation of a silica layer over external pores of the zeolite crystals, forming the externally-pore-blocked, internally-pore-opened modified zeolite crystals.