SU1225841A1 - Continuous method of producing furfural - Google Patents

Description

This invention relates to an improved method for producing furfural, which is a valuable product in the plastics industry.

The purpose of the invention is to increase the concentration of furfural condensates by conducting the process in the liquid phase.

Example 1, Pentose hydrolyzate, containing 5% of reducing 10 substances and 0.7% sulfuric acid, is fed to a plant with a production capacity of 1000 kg / h (by hydrolyzate) or 50 kg / h for pentose sugar. The hydrolyzate preheated in the heat-15 exchanger up to 160-170 C (due to the heat of the juice furfural vapor), is then warmed up (acute superheated steam P 35-40 KGS / CM2, 1,260-280 ° C) in the ejector to 240 C. A vapor-liquid mixture 20 is sent to a separator - a water vapor separator, where an excess of the ejected vapor is separated, and a liquid mixture (dehydratable liquid + steam condensate) enters 25 into a tubular reactor. The duration of the reaction mixture in the apparatus, with kgf / cm and C, is 60 s. After completion of the dehydration reaction, the furfuso role is separated from the dehydrated dehydration in a three-stage evaporation system with a gradual depressurization: 34 kgf / cm in the tubular reactor to 20 (first), 8 (second), 1 kgf / cm (third step).

Furfural condensate in the amount of 290 kg with a concentration of furfural of 8.3% contains 24 to g of furfural, which is 75% of the theoretically possible. The spent hydrolyzate in the amount of 870 kg contains 0.013% of furfural, 0.4% of pentose sugars, the Condensate is sent to the tank furfural condensate, then rectification to obtain marketable furfural. The spent hydrolyzate through the resin bump enters the waste tank, and after the corresponding

35

five

Processing can be used in the production of fodder yeast.

Example 2. kgf / cm,, reaction 55 her. The furfural condensate in the amount of 294 kg with furfural yodentration of 8.2% contains 24.1 kg of furfural, which is 75.3% of the theoretically possible. Spent hydrolyzate in the amount of

866 kg contains 0.01% furfural, .0.4% pentose sugars. The sequence of operations is similar to example 1.

Indicators of choice of temperature range are given in the table.

235

75

68

240

60

75

245

47

75

As can be seen from the table, a decrease in the reaction temperature to 235 s results in a decrease in the yield of furfural to 68% with an increase in the reaction time to 75 s. The increase in temperature to 245 C makes the process more energy-intensive at the same yield of furfural 75%, as at 240 ° C.

Example 2 for the dehydration process at 242 ° C and reaction time of 55 s practically shows that

shows the yield () as at 240 ° C.

 The technical advantage of the proposed continuous method in comparison with the known method is that the concentration of furfural in furfural condensate increases by 3.2 and 3.5 times and amounts to 8.3 and 9.5% (instead of 2.63%), by private (52.6 and 62.5 times) the reactor volume is reduced and, with a plant capacity, 0 t / h of pentose hydrolyzate and a reaction time of 60 s, the reactor volume is 019 m3 and 016 m3 instead of

V (1jO m (as is known). The latter is especially important when creating an apparatus of high unit power: the metal intensity is small, the productivity is greater.

Remaining high-temperature (maintaining the dehydration reaction rate and yield), the process from the vapor condensate becomes liquid phase.

The liquid phase process determines the design of the reaction site, instead of

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a cascade of series-connected devices. Moreover, the advantage of pre-apparatuses is the reactor (a typical uninterrupted method of a half pipe in a pipe), which operates on the basis of furfural in comparison with the ideal displacement. It is also known that the possibility of a roll is taken only after complete j (when carrying out a liquid phase dehydration reaction in three hundred days) to create a high-intensity foam evaporation system (i.e., there, technology and reaction apparatus where the coefficient of volatility of the ufurfurolarhrate is large and powerful - .in 4-5 times higher, than when dehydrator) .ti. .

Claims (1)

CONTINUOUS METHOD FOR PRODUCING FURFUROL by treating a preheated pentose hydrolyzate with steam, which is fed to the ejector at 240-242 ° C and a pressure of 3435 kgf / cm ² in the presence of sulfuric acid, followed by isolation of the target product, characterized in that, in order to increase the concentration furfural condensates, the process is carried out in two stages by feeding the reaction mass after the ejector to the separator to separate the excess steam from the liquid phase, which is additionally kept in the reactor at 240-242 ° C for 60-55 s.