Abstract:
A process of preparing a silica sol is described. The process involves reacting a fresh sol with guanidine carbonate. The reaction may be conducted in the presence of a base (e.g., sodium water glass), and at a pH of from 8 to 12. The process of the present invention may also include concentrating steps. The silica sol prepared by the method of the present invention has a BET surface area of greater than or equal to 100 m2/g, and contains from 0.05 to 15% by weight of gaunidinium ions, based on the total weight of the silica gel.
Abstract:
A process of preparing a silica sol is described. The process involves reacting a fresh sol with guanidine carbonate. The reaction may be conducted in the presence of a base (e. g. , sodium water glass), and at a pH of from 8 to 12. The process of the present invention may also include concentrating steps. The silica sol prepared by the method of the present invention has a BET surface area of greater than or equal to 100 m2/g, and contains from 0.05 to 15% by weight of gaunidinium ions, based on the total weight of the silica gel.
Abstract:
The invention relates to a process for preparing 4-chlorobiphenyl by (a) reacting biphenyl and chlorine in the presence of one or more ring-chlorination catalysts, and (b) subjecting the reaction mixture obtained in step (a) to fractional distillation to obtain 4-chlorobiphenyl.
Abstract:
In the pressure swing adsorption of nitrogen from gas mixtures with less polar gas components at temperatures of between 20.degree. and 50.degree. C., wherein the gas mixture is passed through an adsorber which is filled with packings of zeolite pellets and has an inlet zone and an outlet zone, the improvement which comprises providing at least two packings in the adsorber, a packing of Li-zeolite X in the inlet zone of the adsorber and a packing of at least one of Ca-zeolite A and Ca-zeolite X in the outlet zone of the adsorber.
Abstract:
Mixtures of m- and p-dichlorobenzene can be separated by treating such mixtures in the liquid phase with a pentasil zeolite at from 20.degree. to 250.degree. C., a filtrate enriched in m-dichlorobenzene being removed and the p-dichlorobenzene being obtained by desorption of the pentasil zeolite. The pentasil zeolites may contain, as exchangeable cations, protons, cations of the first or second main group of the Mendeleev Periodic System, cations of the rare earth metals or a mixture of a plurality thereof. In order to prepare the liquid phase a solvent is used that belongs to the group of cyclic saturated hydrocarbons having 5 to 15 carbon atoms, alkyl-substituted aromatic hydrocarbons having 8 to 12 carbon atoms, and halogen-substituted aromatic hydrocarbons having 6 to 10 carbon atoms and 1 to 3 halogen atoms. The solvents ethylbenzene, chlorobenzene, p-xylene, p-chlorotoluene and dichlorobenzene are excepted. A mixture of a plurality of these solvents may also be used.
Abstract:
Dialkyl carbonates can be prepared by the reaction of carbon monoxide with alkyl nitrites in a continuous gas phase reaction, using a platinum group metal catalyst on an alumosilicate zeolite having acidic centers, preferably in the H.sup.+ form, as a support, which catalyst may optionally comprise additional material of a compound of antimony, bismuth, aluminum, copper, vanadium, niobium, tantalum, tin, iron, cobalt, nickel or a mixture of a plurality of these, and hydrogen halide being added in the course of the reaction intermittently or continuously. In this reaction, the dialkyl carbonates are formed with almost quantitative selectivity; the corresponding dialkyl oxalates cannot be detected in most cases.
Abstract:
A process for the production of silica-bound zeolite granulates is disclosed, wherein zeolite to be formed into a granulate is mixed with silica sol. The process is carried out by adding aqueous alkali metal silicate to the silica sol immediately before the silica sol is mixed with the solid zeolite to be granulated. By the described process, granulates of various grain sizes can be obtained, and the resultant granulates can have a narrow grain size distribution.
Abstract:
Para-substituted o-benzylphenols are prepared by reacting p-substituted phenols with benzylating agents in the presence of zeolites of the faujasite type at elevated temperature.
Abstract:
4-Methyl-2-cyclohexylphenol can be prepared by alkylation of p-cresol with cyclohexanol or cyclohexene by performing the reaction in the liquid phase in the presence of 1-10% by weight, based on the amount of p-cresol, of a large pore, acidic zeolite.
Abstract:
Iodine and organic iodine compounds which may be radioactive and which may be found in waste gases or vapors from nuclear reactors can be removed from such gases or vapors by passing the iodine or organic iodine compound-containing gases or vapors through a layer of binder-free silver-exchanged molecular sieve granulates of the faujasite type.