Method for measuring ionic liquid alkylation acid-hydrocarbon ratio in real time

Abstract

The invention discloses a method for measuring the alkylation acid-hydrocarbon ratio of ionic liquid in real time, the solution density is calculated by measuring differential pressure, the hydrocarbon dissolving amount in the ionic liquid is further obtained, and the acid-hydrocarbon ratio of an inlet of a reactor is finally calculated, the method comprises the following steps: 1, connecting the processes of an ionic liquid reactor, a settler, an ionic liquid pump and a heat exchanger which are communicated in sequence; the ionic liquid and hydrocarbons are mixed in the reactor; 2, vertically forming a high pressure measuring opening and a low pressure measuring opening in a container or an external pipeline of the reactor, and mounting a pressure difference transmitter; and 3, calculating the acid-hydrocarbon ratio at the inlet of the reactor. The method has the beneficial effects that the condition that the alkylation reaction is incomplete due to lack of monitoring parameters of the acid-hydrocarbon ratio, and a large amount of ionic liquid runs and is damaged is avoided; the operation condition of the cyclone separator can be verified, operation data is provided for further increasing the acid-hydrocarbon ratio, and the industrial process of the ionic liquid alkylation process is promoted to a great extent.

Description

Technical Field

[0001] The invention relates to the field of petrochemical industry, and in particular to a method for real-time measurement of the acid-to-hydrocarbon ratio of ionic liquid alkylation. Background Art

[0002] Ionic liquid alkylation technology uses isobutane and butene as raw materials and chloroaluminate ionic liquid as catalyst to synthesize alkylate oil. The technology is novel and the process principle is complex. There are only 6 sets of industrialized devices in China. The process parameters that affect the quality of alkylation reaction include acid-hydrocarbon ratio, ionic liquid activity, alkane-olefin ratio, reaction temperature, reaction pressure, etc.

[0003] The acid-hydrocarbon ratio is the most critical control parameter in the ionic liquid alkylation process. Butene has good contact with ionic liquids, while isobutane has high contact difficulty with acid, which is the control step of the reaction. In order to improve the reaction conversion rate, the acid-hydrocarbon emulsification is artificially strengthened in the reactor. Although the reaction conversion rate is improved, it makes it more difficult to separate the hydrocarbon phase containing isobutane and alkylate oil from the ionic liquid at the reactor outlet.

[0004] If the acid-to-hydrocarbon ratio is too low, it is very easy to cause incomplete conversion of butene during the reaction process. The reactor outlet logistics contains olefins, and the olefins dissolve in the ionic liquid, which creates a vicious cycle and causes the ionic liquid to run away, resulting in a series of serious problems such as aggravated corrosion of subsequent unit acids and salts and unqualified product quality.

[0005] The measurement of the acid-to-hydrocarbon ratio by artificially collecting the reactor outlet logistics has a high error rate and is not real-time. The measurement and monitoring of the acid-to-hydrocarbon ratio has always been a problem that has plagued the development of ionic liquid alkylation technology and the safe and stable operation of the device. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method for real-time measurement of the acid-to-hydrocarbon ratio of ionic liquid alkylation. A differential pressure transmitter with a small range is arranged in a low line speed area such as a container or a pipeline. By measuring the differential pressure, the density can be calculated, and then the amount of dissolved hydrocarbons in the ionic liquid can be obtained. Finally, the acid-to-hydrocarbon ratio at the reactor inlet is calculated, so that the acid-to-hydrocarbon ratio can be monitored in real time during the operation of the ionic liquid alkylation, the operating conditions of the alkylation reaction can be stabilized, and the guidance of the device operation can be improved.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for real-time measurement of the acid-to-hydrocarbon ratio of ionic liquid alkylation, by measuring the differential pressure to calculate the solution density, and then obtain the amount of dissolved hydrocarbons in the ionic liquid, and finally calculate the acid-to-hydrocarbon ratio at the reactor inlet, the specific steps are:

[0008] Step 1, connecting the processes of the ionic liquid reactor, the settler, the ionic liquid pump, and the heat exchanger in sequence, and mixing the ionic liquid and the hydrocarbons in the reactor;

[0009] Step 2: vertically open high and low pressure measuring ports on the reactor container or external pipeline, and install a differential pressure transmitter;

[0010] Step 3: Calculation: The measured pressure difference is calculated by the formula Convert density and then use the formula Calculate the amount of dissolved hydrocarbons in the ionic liquid, and finally use the formula The reactor inlet acid-to-hydrocarbon ratio is calculated, where:

[0011] ρ1: miscible phase density kg / m 3 , ρ2: hydrocarbon phase density kg / m 3 , ρ3: ionic liquid density kg / m 3 , ΔP: measured pressure difference kPa, ω: hydrocarbon content in the mixed phase %, v: acid-hydrocarbon ratio, F1: mixed phase flow rate t / hF2: reactor feed flow rate t / h.

[0012] The differential pressure transmitter is connected to the lower part of the settler or to the lower connecting pipe.

[0013] The spacing between the high and low pressure measuring ports is 500 to 2000 mm.

[0014] The density of the ionic liquid is 1350 kg / m3, and the density of hydrocarbons is 550-700 kg / m3.

[0015] The hydrocarbons are alkylate and C4.

[0016] The beneficial effects of the present invention are as follows: real-time monitoring is achieved during the operation of the acid-to-hydrocarbon ratio of the ionic liquid alkylation unit, which, on the one hand, avoids incomplete alkylation reaction due to lack of monitoring parameters for the acid-to-hydrocarbon ratio, resulting in a large amount of ionic liquid loss; on the other hand, the operating status of the cyclone separator can be verified, providing operating data for further improving the acid-to-hydrocarbon ratio, thereby greatly promoting the industrialization process of the ionic liquid alkylation process. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the device for measuring the acid-to-hydrocarbon ratio of ionic liquid alkylation.

[0018] In the figure:

[0019] 1. Ionic liquid reactor 2. Settler 3. Differential pressure transmitter

[0020] 4. Ion liquid pump 5. Heat exchanger DETAILED DESCRIPTION

[0021] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments:

[0022] The device for measuring the acid-to-hydrocarbon ratio of an ionic liquid alkylation system comprises an ionic liquid reactor 1, a settler 2, a differential pressure transmitter 3, an ionic liquid pump 4, and a heat exchanger 5.

[0023] The mixed C4 raw material and ionic liquid react from bottom to top in the ionic liquid reactor 1, and the reaction products are separated in the settler 2. The upper reaction effluent enters the subsequent unit, and the lower ionic liquid is sent back to the ionic liquid reactor 1 by the ionic liquid pump 4 for recycling after sedimentation and separation.

[0024] A differential pressure transmitter with an accuracy of 0.01KPa is installed in low-line-speed areas such as containers and pipelines. By measuring the differential pressure, the density can be calculated, and then the amount of dissolved hydrocarbons in the ionic liquid can be obtained, and finally the acid-hydrocarbon ratio at the reactor inlet can be calculated.

[0025] In the acid-hydrocarbon ratio measurement method proposed by the present invention, vertical pressure measuring ports are opened in low linear speed areas such as containers and pipelines, and the spacing between the pressure measuring ports is 500-2000 mm.

[0026] In the acid-hydrocarbon ratio measurement method proposed in the present invention, the ionic liquid and hydrocarbons such as alkylate and C4 are in a liquid-liquid mixed emulsified phase without an obvious interface.

[0027] In the acid-hydrocarbon ratio measurement method proposed in the present invention, the respective densities of the ionic liquid and the hydrocarbons are known: the density of the ionic liquid is 1350 kg / m3, and the density of the hydrocarbons is 550-700 kg / m3.

[0028] like Figure 1 As shown, two setting methods of differential pressure transmitter 3 are shown.

[0029] Method 1: Add a differential pressure measuring instrument at the bottom of the settler 2, with the distance between the positive and negative pressure measuring points being 1000mm;

[0030] Method 2: Add a differential pressure measuring instrument at the inlet of the ion liquid pump, with the distance between the positive and negative pressure measuring points being 1000mm.

[0031] The mixed phase density ρ1 is calculated by differential pressure, △P=ρ1*g*h, where △P is the differential pressure measured by the instrument and the height h is fixed and known.

[0032] The hydrocarbon phase density ρ2 is calculated based on the material ratio of alkylate oil and C4 in the settler.

[0033] It is known that the density of the ionic liquid ρ3 is 1350 kg / m3, so the amount of dissolved hydrocarbons in the ionic liquid at the bottom of the settler ω = (ρ1-ρ3) / (ρ2-ρ3).

[0034] The acid-hydrocarbon ratio at the inlet of the ionic liquid reactor can be calculated in real time based on the amount of hydrocarbon dissolved in the ionic liquid, the ionic liquid mixed phase flow rate and the mixed C4 feedstock flow rate, providing data support for the smooth operation of the ionic liquid alkylation unit.

[0035] The present invention is applicable to the measured media including but not limited to ionic liquid and hydrocarbon mixture systems, any binary or multi-component medium with known density, which exists in the form of liquid-liquid, liquid-solid, gas-solid, gas-liquid, etc., to form a real-time measurement of the content of a certain medium in a homogeneous or heterogeneous mixture system.

Claims

1. A method for real-time measurement of the acid-to-hydrocarbon ratio of an ionic liquid alkylation, characterized by: The density of the solution is calculated by measuring the differential pressure, and then the amount of dissolved hydrocarbons in the ionic liquid is obtained, and finally the acid-hydrocarbon ratio at the reactor inlet is calculated. The specific steps are: Step 1, connecting the processes of the ionic liquid reactor, the settler, the ionic liquid pump, and the heat exchanger in sequence, and mixing the ionic liquid and the hydrocarbons in the reactor; Step 2: vertically open high and low pressure measuring ports on the reactor container or external pipeline, and install a differential pressure transmitter; Step 3: Calculation: The measured pressure difference is calculated by the formula Convert density and then use the formula Calculate the amount of dissolved hydrocarbons in the ionic liquid, and finally use the formula The reactor inlet acid-to-hydrocarbon ratio is calculated, where: ρ1: miscible phase density kg / m 3 , ρ2: hydrocarbon phase density kg / m 3 , ρ3: ionic liquid density kg / m 3 , ΔP: measured pressure difference kPa, ω: hydrocarbon content in the mixed phase %, v: acid-hydrocarbon ratio, F1: mixed phase flow rate t / hF2: reactor feed flow rate t / h.

2. The method for real-time measurement of the acid-to-hydrocarbon ratio of ionic liquid alkylation according to claim 1, characterized in that: The differential pressure transmitter is connected to the lower part of the settler or to the lower connecting pipe.

3. The method for real-time measurement of the acid-to-hydrocarbon ratio of ionic liquid alkylation according to claim 1, characterized in that: The spacing between the high and low pressure measuring ports is 500 to 2000 mm.

4. The method for real-time measurement of the acid-to-hydrocarbon ratio of ionic liquid alkylation according to claim 1, characterized in that: The density of the ionic liquid is 1350 kg / m3, and the density of hydrocarbons is 550-700 kg / m3.

5. The method for real-time measurement of the acid-to-hydrocarbon ratio of ionic liquid alkylation according to claim 4, characterized in that: The hydrocarbons are alkylate and C4.

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