The present invention relates to process for synthesizing zeolite X crystals comprising at least one step of adding seeding agent(s) into a synthesis gel and at least one step of forming zeolite X crystals at a temperature strictly greater than 120 C., preferably equal to or greater than 130 C.

The present invention relates to process for synthesizing zeolite X crystals comprising at least one step of adding seeding agent(s) into a synthesis gel and at least one step of forming zeolite X crystals at a temperature strictly greater than 120 C., preferably equal to or greater than 130 C.

Provided are: a silver-carrying zeolite molded article in which aggregation of silver is inhibited and which has excellent capability of dispersing silver, when compared to conventional silver-carrying zeolite molded articles; and a method for producing the silver-carrying zeolite molded article. In the silver-carrying zeolite molded article, the molar ratio of Si/Al.sub.2 is 2.0-3.0, the molar ratio of (alkali metal+Ag)/Al is 0.9-1.1, the total amount of SiO.sub.2, Al.sub.2O.sub.3, Ag.sub.2O, and alkali metal oxides is 90 wt % or more, the contained amount of silver ions is 5 wt % or more, and only a single type of zeolite is contained. The molded article can be produced by subjecting a zeolite molded article having zeolite purity of 90% or more to an ion exchange treatment using a silver-containing aqueous solution.

Provided are: a silver-carrying zeolite molded article in which aggregation of silver is inhibited and which has excellent capability of dispersing silver, when compared to conventional silver-carrying zeolite molded articles; and a method for producing the silver-carrying zeolite molded article. In the silver-carrying zeolite molded article, the molar ratio of Si/Al.sub.2 is 2.0-3.0, the molar ratio of (alkali metal+Ag)/Al is 0.9-1.1, the total amount of SiO.sub.2, Al.sub.2O.sub.3, Ag.sub.2O, and alkali metal oxides is 90 wt % or more, the contained amount of silver ions is 5 wt % or more, and only a single type of zeolite is contained. The molded article can be produced by subjecting a zeolite molded article having zeolite purity of 90% or more to an ion exchange treatment using a silver-containing aqueous solution.

The present invention relates to a method for preparing LiCa-LSX molecular sieves with mixed cations and applications thereof. The method comprises the following steps; preparing CaLSX molecular sieves; replacing all Na.sup.+ in NaLSX molecular sieves with Ca.sup.2+ by multiple times of exchange with a solution containing Ca.sup.2+; changing CaLSX molecular sieves to LiCa-LSX molecular sieves by exchange with Li.sup.+, wherein a solution containing Li.sup.+ is used, and the exchanged sample is directly filtered in vacuum without washing and dried at normal temperature; and activating and pre-treating the sample to obtain LiCa-LSX molecular sieves with mixed cations. The LiCa-LSX molecular sieves can be used as selective adsorbents for N.sub.2 and O.sub.2 in oxygen production processes by PSA/VPSA. In the present invention, the loss of Li.sup.+ caused by the replacement of Li.sup.+ with H.sup.+ because of hydrolysis is avoided, the cost is reduced and the treatment time is short.

The present invention relates to a method for preparing LiCa-LSX molecular sieves with mixed cations and applications thereof. The method comprises the following steps; preparing CaLSX molecular sieves; replacing all Na.sup.+ in NaLSX molecular sieves with Ca.sup.2+ by multiple times of exchange with a solution containing Ca.sup.2+; changing CaLSX molecular sieves to LiCa-LSX molecular sieves by exchange with Li.sup.+, wherein a solution containing Li.sup.+ is used, and the exchanged sample is directly filtered in vacuum without washing and dried at normal temperature; and activating and pre-treating the sample to obtain LiCa-LSX molecular sieves with mixed cations. The LiCa-LSX molecular sieves can be used as selective adsorbents for N.sub.2 and O.sub.2 in oxygen production processes by PSA/VPSA. In the present invention, the loss of Li.sup.+ caused by the replacement of Li.sup.+ with H.sup.+ because of hydrolysis is avoided, the cost is reduced and the treatment time is short.

The present invention relates to a process for preparing zeolite crystals continuously, comprising the continuous introduction of a composition capable of generating zeolite crystals into at least one crystallization reaction zone subjected to stirring means, giving said composition a flow characterized by a relative Reynolds number Re.sub.r of between 40 and 50 000, and the continuous recovery of the crystals formed according to a flow characterized by a net Reynolds number Re.sub.n of between 1 and 1500.

Provided is a heavy metal adsorbent consisting of a zeolite with a median diameter on a volume basis of 10.0 ?m or more and a pore volume measured in a pore volume calculation range of 10 nm to 1000 nm by a mercury intrusion method of 0.1000 cm.sup.3/g or less.

Provided is a heavy metal adsorbent consisting of a zeolite with a median diameter on a volume basis of 10.0 ?m or more and a pore volume measured in a pore volume calculation range of 10 nm to 1000 nm by a mercury intrusion method of 0.1000 cm.sup.3/g or less.

Provided is a heavy metal adsorbent consisting of a zeolite with a median diameter on a volume basis of 10.0 ?m or more and a pore volume measured in a pore volume calculation range of 10 nm to 1000 nm by a mercury intrusion method of 0.1000 cm.sup.3/g or less.