Method for preparing acrylic acid through lactic acid dehydration by use of phosphate-pyrophosphate composite catalyst of alkaline-earth metal
A composite catalyst, alkaline earth metal technology, applied in the preparation of carboxylates, carbon-based compounds, chemical instruments and methods, etc., can solve the problems of short catalyst life, low lactic acid conversion rate, poor acrylic acid selectivity, etc. Low cost, broad development and application prospects, and environment-friendly effects
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Embodiment 1
[0023] Here, the alkaline earth metal calcium is used as an example to describe in detail the preparation process of the catalyst and its application in the catalytic dehydration reaction of lactic acid to prepare acrylic acid; other alkaline earth metals such as strontium and barium phosphates and pyrophosphates are similar to the preparation of calcium-based catalysts. Prepared by exchange reaction of soluble alkaline earth metal salts with sodium phosphate and sodium pyrophosphate. The activity evaluation methods of the prepared strontium-based catalysts and barium-based catalysts are similar to those of the calcium-based catalysts.
[0024] Calcium-based catalysts, i.e. calcium phosphate-calcium pyrophosphate composite catalysts, were prepared and evaluated for their catalytic activity as follows:
[0025] (1) Preparation of calcium phosphate-calcium pyrophosphate composite catalyst
[0026] 1) Calcium phosphate is prepared by reacting calcium chloride and sodium phosphat...
Embodiment 2
[0031] Calcium-based catalyst catalyzes the dehydration of lactic acid to prepare acrylic acid. Calcium phosphate and calcium pyrophosphate were prepared respectively by the aforementioned method. Catalyst composition: Wt (calcium phosphate): Wt (calcium pyrophosphate) = 40:60, and the particle size of the catalyst is 40-50 mesh. Take 0.3-0.4g of the catalyst and fill it in a quartz tube with an inner diameter of 4mm. The height of the catalyst is 30-40mm. The other end of the porcelain shavings is sealed with quartz wool, the schematic diagram of which is attached figure 1 shown. Lactic acid feed concentration is Wt (lactic acid)=20%, hydroquinone inhibitor concentration is Wt (hydroquinone)=0.3%, and the liquid space velocity of feed is 2.0h -1 , high-purity nitrogen is used as the carrier gas, the purge rate is 1.2mL / min, and the reaction temperature is 400°C, the conversion rate of lactic acid is 98%, the selectivity of acrylic acid is 59%, and the selectivity of acetal...
Embodiment 3
[0033] The catalyst composition is the same as in Example 2, that is, Wt (calcium phosphate): Wt (calcium pyrophosphate)=40:60. The catalytic performance of the catalyst was investigated under different process conditions. Take 0.4 g of the catalyst, the particle size of the catalyst is 40-50 mesh, and the filling method is the same as that in Example 2.
[0034] (1) Lactic acid feed concentration is Wt (lactic acid)=20%, and the liquid space velocity of feed is 2.0h -1 , high-purity nitrogen was used as the carrier gas, and the process conditions were fixed at a purge rate of 1.2mL / min. The influence of the reaction temperature was investigated, and the results are shown in Table 1.
[0035] (2) The reaction temperature is 400°C, and other process conditions are the same as (1). The results of the influence of lactic acid concentration on the reaction are shown in Table 2.
[0036] (3) The process conditions described in (2) are the same, and the influence of the carrier ga...
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