| Monochloroacetic acid is an important organic chemical intermediates, which is widely used in pesticides, medicine, dyes, CMC, spices, food preservatives and various fine chemical products. Currently, the main technology of monochloroacetic acid production at home is catalytic chlorination of acetic acid in gap method, using acetic anhydride or sulful as catalyst. But no matter what kind of catalyst is used, they will inevitably produce 10% to 20% chloroacetic acid mother liquor after purified crystalline. The mother solution not only improves production costs but also causes pollution of the environment. Therefore, to develop a high activity and high selectivity of hydrogenation catalyst which is used in continuous hydrogenation after continuous acetic acid chlorination, in order to achieve zero emissions of monochloroacetic acid mother liquor and monochloroacetic acid production process of continuous, have very important significance.The amorphous alloy is a kind of new material with short-range ordering and long-range disordering. The unique structure provides many excellent catalytic properties, such as highly catalytic activity and selectivity, highly resistance to poisoning, etc. Moreover, the less environmental pollution during the catalyst preparation is in good accordance with the current trend of green chemical engineering.Therefore, the amorphous alloys have attracted increasing concerns for their special structure and catalytic properties. In this paper, supported Pd-B/C amorphous alloy catalyst was prepared by chemical reduction method.The catalytic performance of Pd-B/C was investigated for the hydrodechlorination of acetic acid chloride solution to high purity monochloroacetic. The follows were in details:(1)The Pd-B/C amorphous alloy catalysts were prepared with KBH4 reduction, high surface area of activated carbon as the catalyst support. The amorphous structure of the catalysts were verified by XRD. Influence of catalyst precursor prepared by heat treatment temperature, alkalinity reducing agent, metallic Pd loading on Pd-B/C amorphous alloy catalyst performance were investigated. Experiment results indicate the optimum conditions for preparing the catalyst: heat treatment temperature of the catalyst precursors 200℃(calcined 2h), reducing agent alkalinity 0.25mol/L (NaOH), metallic Pd loading of 0.8%.(2)The influence of different hydrogenation reaction temperatures on Pd-B/C amorphous alloy catalyst chloroacetic acid chloride solution selective hydrogenation to high purity monochloroacetic acid were studied. The results showed that, at 130℃and 3h, the conversion of dichloroacetic acid was 56.43%.But with the continuous increment of the reaction temperature, the catalytic activity and selectivity was less affected.(3) By doping transition metal (Ru, Co, Ag, Y) and rare earth metals (Ce, La, Nd, Th) in the Pd-B/C amorphous alloy catalysts, the influence of metal additives on amorphous alloy catalyst performance were studied. The results show that Ru, La, Ce, Th modified Pd-B/C amorphous alloy catalyst can significantly improve the catalytic hydrogenation activity and selectivity. After reaction of 3h, the conversion rate of dichloroacetic acid reached 100%, and the selectivity of monochloroacetic acid was also more than 80%. But the addition of Ag and Nd would adversely affect the catalytic properties. Add Co and Y as additives, the catalytic activity and selectivity have little influence.(4) The Pd/C catalysts were prepared by H2 reduction at different temperatures, and catalytic performance were studied in the hydrodechlorination reaction of acetic acid chloride solution to high purity monochloroacetic. The results show that under the conditions of 250℃prepared Pd/C catalysts has the highest activity. After reaction of 3h, DCA's conversion rate reached 100%, and MCA yield was 85.70%.Compared with Pd-B/C amorphous alloy catalyst made by KBH4 the reduction method, Pd-B/C catalysts showed better catalytic activity and selectivity.(5)The catalytic hydrogenation stability of Pd-B/C amorphous alloy catalyst was investigated in the end. And we have a comparsion with Pd/C catalyst made by the H2 reduction method. The results show that, Pd-B/C catalyst is much higher than the stability of Pd/C catalyst. Pd-B/C catalysts used 19 times, the 5h conversion of dichloroacetic acid was still able to maintain above 60%. However Pd/C catalyst in the use of 14 times, the conversion of dichloroacetic acid dropped to 30%.Through the above study, we think that supported the Pd-B/C amorphous alloy catalysts used in acid chloride solution in the selective hydrodechlorination reaction to the preparation of high purity monochloroacetic acid, showing high conversion, high selectivity superior and good stability, is a potential catalyst for future industrial application.
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