Chromium-free catalyst for gas-phase fluorination and application thereof

#The present invention relates to a chromium-free catalyst for gas-phase fluorination and use thereof. Particularly, the present invention relates to a chromium-free fluorinated catalyst used for preparation of hydrofluoroolefins (HFOs) or hydrochlorofluor oolefins (HCFOs) through gas-phase fluorination of halohydrocarbons.

#In fluorine chemical industry, gas phase fluorination of halohydrocarbons is often used for preparation of hydrofluoroolefins and hydrochlorofluoroolefins, which has the following advantages: simple devices, easiness for continuous large-scale production, safety and the like. Fluorinated catalysts play a critical role in gas-phase fluorination reaction of halohydrocarbons. Presently, the catalysts for gas-phase fluorination used industrially are chromium-containing fluorinated catalysts.

#Chinese Patent No. CN94106793.9 disclosed that a fluoride precursor was prepared by the precipitation of a mixture of Cr(NO3)3 and In(NO3)3 with ammonia water, and then the precursor was subjected to calcination and fluorination with HF to obtain a fluorinated catalyst composed of indium, chromium, oxygen and fluorine.

#A catalyst precursor with a Fe content of 20.0%, a Mg content of 77.0% and a La content of 3.0% was prepared by dissolving a certainamount of FeCl3.6H2O, MgCl2.6H2O and La(NO3)3.6H2O in water, adding precipitant ammonia water at 60° C. to the obtained a solution, maintaining the PH of the solution between 7.5 and 8.5 to precipitate it completely under stirring, filtering the resulted slurry, washing the precipitate to a neutral PH with deionized water and drying the precipitate at 120° C. The precursor was then compressed and shaped. After roasting at 450° C. in a muffle furnace for 8 hours, the shaped precursor was loaded into a tubular reactor and heated to 300° C., and fluorinated for 1 hour by introducing hydrogen fluoride gas. The temperature was increased to 400° C. at a heating rate of 1° C./min, and the fluorination reaction was continued for 8 hours to obtain a chromium-free gas phase fluorination catalyst.

#60 ml chromium-free gas phase fluorination catalyst obtained in Example 1 was loaded into a nickel tubular fixed-bed reactor with an inner diameter of 38 mm. HF and 1,1,2,3-tetrachloropropene (HCC-1230xa) were introduced into the reactor to conduct the reaction. The molar ratio of HF to HCC-1230xa was controlled to be 15:1; the contact time was 10.9 seconds; and the reaction temperature was 260° C. After a reaction time of 20 hours, the reaction products were subjected to water washing and alkaline washing to remove HCl and HF, and then analyzed by gas chromatography. The conversion rate of HCC-1230xa was 100% and the selectivity to HCFO-1233xf was 99.4%. After a reaction time of 1,000 hours, the reaction products were subjected to water washing and alkaline washing to remove HCl and HF, and then analyzed by gas chromatography. The conversion rate of HCC-1230xa was 100% and the selectivity to HCFO-1233xf was 92.5%.

#The catalyst preparation process in Example 2 was substantially the same as that in Example 1 except that MgCl2.6H2O was replaced with CaCl2 and La(NO3)3.6H2O was replaced with Y(NO3)3.6H2O. The obtained catalyst precursor had a Fe content of 20.0%, a Ca content of 77.0% and a Y content of 3.0%. The precursor was then compressed and shaped. After roasting at 450° C. in a muffle furnace for 8 hours, the shaped precursor was loaded into a tubular reactor and heated to 300° C., and fluorinated for 1 hour by introducing hydrogen fluoride gas. The temperature was increased to 400° Cat a heating rate of 1° C./min, and the fluorination reaction was continued for 8 hours to obtain a chromium-free gas phase fluorination catalyst.