CN107793316A - A kind of method of microreactor synthesis methyl nitrite - Google Patents

Abstract

The invention discloses a method for synthesizing methyl nitrite with a microreactor, the main features of which are: (a) NO and _O2 are first pre-reacted in a tubular reactor to generate a mixed gas containing nitrogen oxides (b ) mixed gas and methanol in a micro-channel reactor (single channel or multi-channel) for nitration reaction to generate methyl nitrite. The hydraulic diameter of the micro-reaction channel is in the range of 100-3000 microns, the gas phase space velocity in the micro-reactor is 2000-50000h ^-1 , the N2 content in the gas phase is 40-70%, the volume ratio of NO and _O2 is 4-7, methanol and feed The molar ratio of NO is 1-2, and the yield of methyl nitrite based on _O2 after the reaction is greater than 70%. The reaction process has a short material residence time, effectively suppresses side reactions, reduces the generation of _HNO3 , etc., and the equipment is not easy to corrode. At the same time, using the characteristics of high-efficiency mass and heat transfer in microchannel reactors, the process has better operability and safety.

Description

A kind of method that microreactor synthesizes methyl nitrite

technical field

The invention relates to a method for synthesizing methyl nitrite, in particular to using a micro-reactor to continuously synthesize methyl nitrite.

Background technique

As an important organic chemical raw material, ethylene glycol is mainly used in the production of polyester fibers, plastics and rubber, and is also widely used in solvents, lubricants, plasticizers and antifreeze. There is a large gap in the supply of ethylene glycol in my country, and the dependence on imports is as high as 70%, mainly from the Middle East and North America. In view of the strong demand of the polyester industry, it is expected that the demand for ethylene glycol in my country will further increase in the future.

Ethylene glycol process routes are mainly divided into petroleum routes and coal-based routes. In recent years, the coal-based route has developed rapidly, and its economy has gradually improved. For example, the production cost of coal-to-ethylene glycol produced in Xinjiang is 2,500-3,000 yuan/ton, which is quite competitive in terms of absolute profit margin and relative cost compared with other supplying countries.

The coal-based ethylene glycol route mainly produces methyl oxalate through CO gas-phase catalytic coupling method and then hydrogenates it to ethylene glycol. After the NO generated by the coupling reaction is separated from the product, it reacts with oxygen and methanol to generate methyl nitrite again and returns to the coupling process for recycling, that is, the methyl nitrite regeneration reaction:

4NO+O ₂ +4CH ₃ OH→4CH ₃ ONO+2H ₂ O (1)

This reaction is a gas-liquid two-phase nitration reaction with fast reaction speed and large heat release. At present, packing bubbling bed is mostly used in industry for reaction, the gas-liquid contact area is low (200-2000m ^-1 ), and the mass transfer capacity is low. Therefore, the volume of the reactor equipment is often large to increase the reaction time, and the operating efficiency of the reactor is low. In addition, the material residence time in the tower reactor is long (Li et al. Ind.Eng.Chem.Res, 2013, 52:2814-2823), and it is easy to generate a large amount of nitric acid (2%～4% or even higher, CN201310416056), Severe corrosion of equipment.

Contents of the invention

The object of the invention is to provide a method for synthesizing methyl nitrite in a microreactor.

To achieve the above object, the technical scheme adopted in the present invention is as follows:

A method for synthesizing methyl nitrite with a microreactor comprises two steps of pre-reaction and micro-reaction, the pre-reaction step generates a mixed gas containing nitrogen oxide compounds, and the micro-reaction step synthesizes methyl nitrite.

The pre-reaction step uses a tubular reactor to react the mixed gas containing NO, O ₂ and N ₂ in the tubular reactor to generate a mixed gas containing N ₂ , N ₂ O ₃ and NO ₂ , and the reaction is carried out at room temperature The gas residence time is 1 to 15 minutes; or, the reaction is carried out at 80 to 120 ° C, and the residence time is 1 to 2 seconds; the molar ratio of NO to _O2 in the inlet gas of the tubular reactor is 4 to 7, preferably 4 to 5 , N ₂ volume content is 40-70%, preferably 50-55%.

The micro-reaction is carried out in a single-channel micro-reactor or a multi-channel micro-reactor, so that methanol and a mixed gas containing nitrogen oxides react to generate methyl nitrite; the molar ratio of methanol to raw material NO in the micro-reactor is 1-2 , preferably 1.2 to 1.5; the pressure range is 0.1 to 0.5 MPa, preferably 0.1 to 0.3 MPa.

In the micro-reactor, the hydraulic diameter of the single channel and/or multiple channels in the micro-reaction channel is 100-3000 microns, the length is 10-100 cm, the space velocity of the micro-reactor is 2000-50000h ^-1 , and the reaction temperature is 0-3000 50°C.

The material at the outlet of the microreactor is separated from the gas phase and the liquid phase by a gas-liquid separator. Part of the liquid phase material at the outlet is mixed with fresh methanol and returned to the microreactor for reaction. The type of gas-liquid separator can be a micro-separator with a fine grid (20-30 microns in size), a gravity separator and a cyclone separator, preferably a cyclone separator.

Compared with the prior art, the present invention has the advantages of:

1) The gas-liquid mixing efficiency is high, the reaction is efficient, and the amount of methanol used is more than 30% lower than that of the prior art. The short residence time greatly reduces the formation of by-product nitric acid.

2) The heat transfer ability is strong, the reaction process is carried out at normal temperature, and the energy consumption is low.

3) The reaction is safe, the _N2 content is low (40%-70%), and the reactor volume and power loss are reduced.

4) Parallel enlargement and scale enlargement are used together, and the capacity enlargement is simple.

Description of drawings

Figure 1 is a schematic diagram of the methyl nitrite regeneration reaction process principle. Among them, 1-mixed gas containing NO and N ₂ , 2-O ₂ , 3-N ₂ , 4-mixed gas containing N ₂ O ₃ , 5-fresh methanol, 6-recovered methanol, 7-methanol material, 8- Gas-liquid mixture after reaction, 9-product gas, ①-tubular pre-reactor, ②-micro-reactor, ③-gas-liquid separator.

Detailed ways

After the coupling reaction and separation, the mixed gas 1 mainly containing NO and N ₂ and O ₂ 2 are pre-reacted in the tubular reactor ① to form a mixed gas 4 of N ₂ O ₃ , and N ₂ 3 is used to adjust the composition of the mixed gas And purging device, the outlet gas of the tubular reactor ① enters the micro-reactor ② for esterification reaction with methanol to generate methyl nitrite, and the NO/ _O2 molar ratio range in the inlet gas contains an end value of 4 to 7, preferably 4 to 5; the _N2 volume content contains an end value of 40 to 70%, preferably 50 to 55%. After the reaction, the gas-liquid mixture 8 passes through ③-gas-liquid separator, and the methanol obtained after separation and recovery is mixed with fresh methanol 5 Return to microreactor ② for reaction.

Example 1

In the tubular reactor ① the inlet NO/O ₂ molar ratio is 4, the gas phase N ₂ volume content is 40%, the pre-reaction temperature is normal temperature, and the reaction residence time is 10 min. Single-channel microreactor ②The hydraulic diameter is 1000 microns, the gas phase space velocity is 13000h ^-1 , the methanol/NO molar ratio is 2, the reaction temperature of the microreactor is 50°C, and the system pressure is normal pressure, the volume content of methyl nitrite at the gas phase outlet was 43%, and the product yield based on _O2 was 84.6%.

Example 2

In the tubular reactor ①, the inlet NO/O ₂ molar ratio is 5, the gas phase N ₂ volume content is 60%, the pre-reaction temperature is normal temperature, and the reaction residence time is 8 min. The volume of methyl nitrite at the outlet of the gas phase is under the conditions of a single-channel microreactor ② with a hydraulic diameter of 300 microns, a gas phase space velocity of 50000 h ^-1 , a methanol/NO molar ratio of 2, a microreactor reaction temperature of 30 °C, and a system pressure of 0.2 MPa. The content was 27.3%, and the product yield based on _O2 was 85.3%.

Example 3

In the tubular reactor ①, the inlet NO/O ₂ molar ratio is 4, the gas phase N ₂ volume content is 60%, the pre-reaction temperature is 100°C, and the reaction residence time is 1.2s. Parallel multi-channel (parallel number 30) microreactor ② hydraulic diameter 1000 microns, gas phase space velocity 50000h ^-1 , gas phase N ₂ volume content 60%, NO/O ₂ = 4, methanol/NO molar ratio 2, micro reaction Under the conditions of the reactor reaction temperature of 30° C. and the system pressure of normal pressure, the volume content of methyl nitrite at the outlet of the gas phase is 31.6%, and the product yield based on oxygen is 80.2%.

Example 4

In the tubular reactor ①, the inlet NO/O ₂ molar ratio is 4, the gas phase N ₂ volume content is 60%, the pre-reaction temperature is 100°C, and the reaction residence time is 1.2s. Parallel multi-channel (parallel number 30) microreactor ② hydraulic diameter 1000 microns, gas phase space velocity 50000h ^-1 , gas phase N ₂ volume content 60%, NO/O ₂ =4, methanol/NO molar ratio 1.5, micro reaction Under the conditions of the reactor reaction temperature of 30° C. and the system pressure of normal pressure, the volume content of methyl nitrite at the outlet of the gas phase is 33%, and the product yield based on oxygen is 84.6%.

Claims (4)

1. a method for the synthesis of methyl nitrite by a microreactor, characterized in that: the method comprises two steps of pre-reaction and micro-reaction, the pre-reaction step generates the mixed gas containing nitrogen oxide compound, and the micro-reaction step synthesizes nitrous acid methyl ester. 2. the method for continuously synthesizing methyl nitrite by microreactor as claimed in claim 1, is characterized in that: described pre-reaction step adopts tubular reactor, makes the mixed gas that comprises NO, O ₂ , N ₂ in this tube A mixed gas containing N ₂ , N ₂ O ₃ and NO ₂ is generated in a type reactor. The reaction is carried out at room temperature, and the gas residence time is 1-15 minutes; or, the reaction is performed at 80-120°C, and the residence time is 1-2 minutes. seconds; the molar ratio of NO to _O2 in the inlet gas of the tubular reactor is 4-7, and the volume content of _N2 is 40-70%; The micro-reaction is carried out in a single-channel micro-reactor or a multi-channel micro-reactor, so that methanol and a mixed gas containing nitrogen oxides react to generate methyl nitrite; the molar ratio of methanol to raw material NO in the micro-reactor is 1-2 , preferably 1.2 to 1.5; the pressure range is 0.1 to 0.5 MPa, preferably 0.1 to 0.3 MPa. 3. the method for continuously synthesizing methyl nitrite by microreactor as claimed in claim ₂ , is characterized in that: NO and O in the inlet gas of described tubular reactor mol ratio is 4～ ₅ , and N volume content is 50 -55%. 4. the method for continuously synthesizing methyl nitrite as claimed in claim 2, is characterized in that: described microreactor, the hydraulic diameter of single channel and/or multichannel in the micro reaction channel is 100～3000 microns, length 10 ~100 cm, the space velocity of the microreactor is 2000~50000h ^-1 , and the reaction temperature is 0~50°C.