Study On The Technology And Kinetics Of Gas-phase Photo-chlorination Of Pyridine

2-Chloro yridine is a kind of important and fine chemical material. Lately a serial of new-style pesticide and medicine using 2-chloropyridine as raw material were developed. In home and abroad, there is a fast-rising trend of demand for 2-chloropyroidine and its derive productive.The methods to produce 2-chloropyridine include liquid phase photo-chlorination method, gas phase thermal-chlorination method, gas-phase photochl-orination method, gas phase catalysis chlorination method, etc. Gas phase photo-chlorination method is the most valuable in industry. The report of this method is mainly about the depiction of process and reaction machanism. So far, the systemic optimization of process condintions and experiment study on reaction dynamics havn't been carried out.Because the reaction of chlorination of pyridine is consecutive and exothermal, the reactor which has effective admixture effect, excellent isothermal quality, ideal flow pattern was required in the experiment of optimization process condintions and kinetics of gas-phase photo-chloination of pyridine. A new kind of chlorination loop glass reactor with the volume of 200ml was designed and adopted in this paper. It was heated by oil-bath.The reactor has large heat-exchanging area, gas flow approximating plug flow. Some influencing factors such as different wavelength light, reactant ratio, reaction time and temperature on the yield of 2-chloropyrindine were studied in the experiment. The optimum reaction condition was obtained, The higher yield of 2-chloropyridine could be obtained by the blue light-catalysis chlorination of pyridine than by the others , catalysis chlorination.reaction, temperature was 170¹80℃,n (Cl₂): n (C₆H₅N) =1.5—2:1, space time was 100s, the conversion of pyridine reached 70%, the selectivity of 2-chloropyridine was about 95%.Mechanism of reaction was submitted, the kinetic model of pyridine photochlori-nation in gaseous phase was built. Under the condition of using blue light, the temperature ranged from 160°C to 190°C, and the mole ratio of pyridine to chlorine being 1:1 —2.5. Through estimating of the parameters of the models, the reaction rate constants and the reaction activation energy were obtained.In order to study the scaling effect of the reactor design, a modified chlorination tube galss reactor with the volume of 1396ml was designed in this paper, an analog experiment was done in this reactor. There are many burrs in the reactor. These burrs have excellent radial mixing intensive effect. Some of effects such as the light strength, reactant ratio, reaction time and temperature on the yield of 2-chloro-pyrindine were studied in the reactor. The result showed that the light strength was 88 W, the concentration of water between forty percents and sixty percents was suited. As the reaction condition was identical to the reaction condition of process optimization. The pyridine conversion reached seventy percents too. On the other hand, 2-chloropyridine selectivity declined ten percents. It was induced by the non-isothermal quality and non-deal flow.The preliminary separation experiment of chlorination production was carried out, the raw production was handled with simple distillation and then rectification under vacuum, the purity of 2-chloropyridine reached 99.3%.