Silver supported catalyst for preparing anhydrous formaldehyde by direct dehydrogenation of methanol and manufacturing method thereof

Abstract

The invention is a novel supported silver catalyst for preparing anhydrous formaldehyde by direct methanol dyhydrogenation. It is prepared by a sol-gel method (SOL-GEL method), i.e. mixing a certain amount of TEOS (tetraethoxysilane) with the water or alcohol solution containging soluble Zn and Al salts, then dripping to an inorganic silver salt water solution and preparing it through gelling, ageing, drying, baking, etc. During the gelling course, the Zn and Al salt solution added make acid-alkali neutralization to some extent, which largely enhances its activity and selectivity. It not only has high catalytic activity and longer service life but also simple and convenient to prepare, having lower price and suitable for industrial application.

Description

technical field [0001] The invention belongs to the technical field of chemical industry, and in particular relates to a silver-loaded catalyst used for direct dehydrogenation of methanol to prepare anhydrous formaldehyde and a preparation method thereof. Background technique [0002] Direct dehydrogenation of methanol to anhydrous formaldehyde is an emerging route for the preparation of formaldehyde. With the development of the modern chemical industry, the demand for anhydrous formaldehyde is increasing day by day. At present, anhydrous formaldehyde is prepared from commercial formaldehyde (prepared by oxidative dehydrogenation of methanol) through rectification, extraction and other means to remove water. This process consumes In this situation, the method of direct dehydrogenation of methanol to anhydrous formaldehyde came into being, and the choice of catalyst is the key to the implementation of this scheme. Existing patent reports have catalysts composed of copper, si...

AI Technical Summary

Problems solved by technology

With the development of the modern chemical industry, the demand for anhydrous formaldehyde is increasing day by day. At present, anhydrous formaldehyde is prepared from commercial formaldehyde (prepared by oxidative dehydrogenation of methanol) through rectification, extraction and other means to remove water. This process consumes More energy, not economical, in this situation, the method of direct dehydrogenation of methanol to produce anhydrous formaldehyde came into being, and the choice of catalyst is the key to the implementation of this scheme

Existing patent reports have catalysts composed of copper, silver, and silicon (Special Publication No. 41-11853), molten zinc, potassium, indium or aluminum or alloys of these metals (Special Publication No. 47-19251), carbon-containing molten Zinc or zinc-containing alloys (Japanese Patent Opening No. 48-97808) and catalysts composed of copper, zinc, and selenium (Japanese Patent No. 52-215), etc., but most of the catalysts obtained by these methods have short life, low reactivity, and no industrial Value

And the catalyzer (patent open clear 51-1407) that is made up of copper, zinc, sulfur and the catalyzer that is made up of copper, zinc supply gaseous sulfide and carry out methanol dehydrogenation (patent open clear 51-76209), in reaction product or discharge Sulfur is mixed in the gas, which limits its industrial application due to environmental pollution and other issues

The use of a sodium-containing catalyst increases the formaldehyde yield to 70% (Appl.Catal.A: Gen., 2001 (213) 203), but its industrial application is limited due to problems such as its catalyst life and regeneration

Ag-SiO reported in Japanese patent (Japanese Patent Application No. 60-89441) 2 -ZnO catalyst obtained a methanol conversion of 69.4% and a formaldehyde yield of 51.8%. The main defect of the catalyst is that the existence of the surface basic center leads to the generation of by-product CO, which makes the selectivity of the catalyst to formaldehyde low.

We prepared Ag-SiO 2 -Al 2 o 3 Catalyst and apply it to the reaction of direct dehydrogenation of methanol to produce anhydrous formaldehyde, a methanol conversion rate of 95.0% and a formaldehyde yield of 81.2% are obtained, but the by-product DMF is formed due to the action of its acidic carrier