Glyoxylic Acid CAS 298-12-4

The experimental device is received Figure 1. Nitric acid and glyoxal are pumped right into the microreactor via pump 1 and pump 2 respectively according to a molar proportion of 0.85:1. The experiment is executed utilizing segmented temperature control. At the t1 temperature, glyoxal and glyoxal are The nitric acid is combined and responded in the activator, and the combined solution continues to respond in the microchannel at t2 temperature level; after that the response is satiated in an area of coil linked to the microchannel at 10 to 15 ° C, and the reaction service enters the collection container via the back pressure shutoff, the product is gotten for evaluation.

When the molar proportion of nitric acid (35%) to glyoxal (40%) is 0.85:1, the glyoxal flow price (Q1) is 4.7 mL/min and the nitric acid circulation price (Q2) is 5.3 mL/min. The total house time is 4min54s, of which the home time in section t1 is 54s and the home time in area t2 is 4min. When the back pressure valve pressure is 0.5 MPa, the impact of temperature on conversion price and selectivity is as shown in the table. Figure 2 shows keeping the t2 temperature level at 40 ° C and analyzing the influencing factors of the t1 temperature. Figure 3 shows controlling the t1 temperature level to 80 ° C and analyzing the influencing variables of the t2 temperature level.

It can be ended from Figure 2 and Number 3 that when t1 raises from 40 ° C to 90 ° C, the conversion rate increases from 15% to 95%, the selectivity boosts from 20% to 58%, and after that lowers to 45%. The factor might be that when the temperature level is lower, the response price is slower and only a small amount of glyoxal is oxidized by nitric acid. As the temperature level increases, the response is gradually launched, so the conversion price and selectivity rise; but when the temperature is raised from 80 As the temperature continues to rise, the item will certainly remain to be oxidized right into oxalic acid, so the selectivity reduces; when t1 = 40 ° C, the temperature is reduced, and it is harder for glyoxal to be oxidized, and glyoxal is easy to polymerize and develop More autopolymers and consequently lower selectivity. When t2 increases from 20 ° C to 50 ° C, the conversion rate increases from 70% to 90%, and the selectivity boosts from 42% to 60%, and afterwards lowers to 40%. Analysis of the reason may be that the reaction has been started at the t1 temperature level. At the t2 temperature, glyoxal continues to join the reaction, so the conversion rate boosts; when t2 boosts from 20 ° C to 40 ° C, due to the polymerized glyoxal After preheating for an amount of time at the t1 temperature level, the existing component begins to depolymerize. At the t2 temperature, although the temperature level is reduced, the depolymerization reaction can not quit right away. Currently, the depolymerization rate is above the polymerization price, so the selectivity slowly raises. When t2 remains to increase from 40 ° C, the conversion of glyoxylic acid to oxalic acid is advertised, so the selectivity decreases. As a result, t1 = 80 ° C and t2 = 40 ° C were chosen in the next experiment.

NO is produced throughout the oxidation of glyoxal by nitric acid. Researches have actually shown that the visibility of NO in the system advertises the oxidation of glyoxal, that is, NO reacts with nitric acid to generate nitrous acid, and afterwards nitrous acid reacts with glyoxal to create Glyoxylic acid. Under the conditions of gas promo, pressure likewise plays a terrific duty in promoting the reaction. Number 4 reveals the effect of stress on the conversion price and selectivity of the response. This figure reveals that when the pressure increases, the conversion rate and selectivity of the reaction increase. This is due to the fact that when the pressure is low, the mixing effect in the system is poor and the system is unstable. Nonetheless, when the stress continues to boost, it is challenging to separate the NO created from glyoxylic acid. When glyoxylic acid and nitric acid are called and mixed, the nitrous acid created straight responds with glyoxylic acid, creating the nitrous acid in contact with glyoxal in the system to The content reduces and the response price reductions, so the conversion price and selectivity decline at the same time. As a result, the pressure of 1.0 MPa is the very best choice during the response procedure.

The trouble of this procedure is to stop the peroxidation of glyoxal. Therefore, in addition to the influencing elements that have to be considered in traditional reactors such as temperature and stress, staged feeding can additionally be taken into consideration. If the first feed quantity is also small, the reaction rate will certainly be reduced and the response time will be lengthened; if the initial feed quantity is way too much, glyoxylic acid will certainly be easily oxidized, which will quickly lead to a decrease in selectivity. In the process of making use of a microchannel reactor to accomplish connection, very first feed the initial response item with a molar proportion of nitric acid to glyoxal from 0.3:1, and after that include 0.12 mol of nitric acid to the 3rd reaction piece. This way, the conversion rate and selectivity of the reaction can reach more than 70%. Additionally, compared with the standard pot procedure, the quantity of nitric acid utilized in the whole response process is lowered, and the post-processing pressure is reduced.

This type of nitric acid oxidation reaction releases a lot of heat, and peroxidation products are conveniently produced during the reaction. Since the microchannel reactor has excellent heat transfer and warm transfer effects, it can accurately manage the reaction problems. For that reason, for response types where the temperature level is difficult to regulate in standard activators or where the selectivity of the response is reduced due to backmixing, better speculative outcomes can be accomplished through segmented temperature control and segmented feeding in microchannel reactors. Compared to typical pot responses, the advantages of microchannel activators are mainly reflected in:

① Experimental control of reaction problems (temperature, stress, flow) accurately.

② Double-sided warm exchange has excellent advantages for chain reactions with large heat dissipation.

③ Continual flow activator, without back-mixing, raises the selectivity of the response.

④ It inhabits a small location and can be used in chemical plant and research laboratory experiments.