CN106370713A - Light gas olefin arsenic content detection method - Google Patents

Abstract

The invention discloses a light gas olefin arsenic content detection method. The method utilizes a mixed acid absorption liquid obtained by mixing of bromine water, hydrogen peroxide, hydrochloric acid and nitric acid solutions to realize olefin enrichment and utilizes a Microcoulometry method to determine arsenic content of gas olefin. The method realizes fast and accurate detection of arsenic content of olefin and solves the problem that devices used by the existing detection method have high prices, long analysis time and low accuracy.

Description

The detection method of arsenic content in a kind of light gas alkene

Technical field

The invention belongs to petrochemicals measure field, more particularly, it relates to a kind of measure in light gas alkene The method of arsenic element.

Background technology

With the increasingly dilution of petroleum resources, oil composition becomes more complicated, the crude oil arsenic content that some oil fields produce Also constantly raise, the arsenic in gaseous state is generally based on arsenic hydride and first arsenic.Arsenide in petroleum hydrocarbon will have a strong impact on its processing, Because arsenic and catalyst activity component binding ability are strong, can make hydrofinishing cobalt-molybdenum catalyst, hydrocarbon conversion nickel catalyst, Methanation nickel catalyst, ammonia synthesis Fe-series catalyst, the palladium in ethylene industry, platinum, nickel catalyst, in olefin polymerization process Metallocene-type polymerisation catalyst etc. produce permanent be poisoned, arsenide brings great negative effect to oil hydrocarbon processing, After therefore determining olefin feedstock before manufacture and producing, the arsenic content of product is very important.

The analysis of arsenic measure commonly used be diethylamine dithiocarbonic acid silver spectrophotography, use sampling Graphite Furnace Atomic Absorption Method, Atomic fluorophotometry, small-hole drilling etc..The data precision of Part Methods can not meet the needs of production technology, and investment is relatively Greatly, repeatability is also bad.

Small-hole drilling is to produce titrant according to electrolysis to react with measured matter, and automatically adjusts with measured matter content size Section input current, the method that content of material is determined by the electricity consuming.Small-hole drilling is low with its instrument cost, simple to operate, The advantages of analysis is quick, sensitivity is high is used widely in the part such as petrochemical industry, environmental conservation, and small-hole drilling is except being used for Outside the mensure of arsenic, it is also used for Determination of Trace Sulfur, nitrogen, halogen etc. and measures.For small-hole drilling, document " micro-coulometric determination lightweight stone Trace arsenic in oil product " describe using micro-coulometric determination light liquids oil product arsenic content, document " micro-coulometric determination weight Arsenic in whole raw oil " work mainly done is the arsenic content measuring in reformate, the two is all to utilize concentrated sulphuric acid to extract oil sample Take.Due to arsenic content be applied to detection liquid for the microcoulomb method, and the arsenic in gas can not directly be entered using small-hole drilling Row detection.

Content of the invention

The technical problem to be solved is to provide arsenic content in a kind of light gas alkene simple to operation Detection method, by absorbing liquid enrichment arsenic element, using the arsenogen cellulose content in micro-coulometric determination gaseous olefin.

For solving above-mentioned technical problem, the present invention adopts the following technical scheme that

In a kind of light gas alkene, the detection method of arsenic content is it is characterised in that comprise the following steps:

(1) prepare standard solution: inorganic arsenic solution is configured to the arsenic standard solution that concentration is 100 μ g/ml；

(2) olefin samples pre-treatment: olefin gas to be measured are quantitatively injected the series connection absorption plant equipped with nitration mixture absorbing liquid In, the arsenic element in alkene then enters in mixed acid solution, absorbs after finishing, and forms prepare liquid after the solution heating of enrichment is steamed Body sample immigration generating bottle is to be measured, and described nitration mixture absorbing liquid is mixed by bromine water, hydrogen peroxide, hydrochloric acid, salpeter solution；

(3) demarcation of instrument: carrier gas accesses instrument gas circuit, under suitable flow velocity, the arsenic standard solution preparing is used Microscale sampler injects titration cell, calculates the response rate according to the data recording, and stablizes the response rate by adjustment bias；

(4) sample to be tested detection: reducing agent is mixed with described liquid sample, arsenic ion is reduced to arsenic hydride, With carrier gas, described arsine gas is brought into titration cell in the lump to absorb and the current potential after small-hole drilling detection absorption arsenic hydride Change, is calculated the content of arsenic element in alkene.

The volume ratio of described bromine water, hydrogen peroxide, hydrochloric acid and nitric acid is 8:8:1:1.

Described inorganic arsenic solution is arsenious weak acid solution.

Described reducing agent is potassium borohydride or sodium borohydride.

Described liquid sample after steaming is 10ml.

Bromine water in described nitration mixture absorbing liquid is mixed with volume ratio 20:1 with bromine simple substance by saturation bromine water.

The aqueous solution mass concentration of described potassium borohydride is 3%.

The aqueous solution of every 100 milliliters of described potassium borohydrides adds sodium hydroxide or the potassium hydroxide of 0.5g.

Described small-hole drilling monitoring electrolyte used is by 0.07g potassium bromide, 800ml pure water, 150ml acetic acid, 50ml Concentrated sulphuric acid and 0.8-1.2g solid iodine proportioning form.

The present invention using for reference on the basis of forefathers utilize small-hole drilling to measure the arsenic content of oil product, by absorbing liquid and The selection of reducing agent, investigates and optimizes, and has obtained measuring the monitoring method of arsenic content in light gas alkene.

The signal of telecommunication that the present invention is detected is linear related to the arsenic content in alkene, therefore can quickly and accurately examine Survey the arsenic content in alkene, overcome that instrument and equipment existing for existing detection method is expensive, length analysis time, accuracy Not high shortcoming.The detection means that the inventive method is adopted has that structure is simple, easily operated, with low cost, selectivity strong, The advantages of operation and maintenance cost is few, life-span length sensitivity is high and reproducible.The detection method of the present invention be equally applicable to gasoline, The various oil products such as diesel oil, weight Petroleum, crude oil, residual oil.

Brief description

The present invention is described in detail with reference to the accompanying drawings and detailed description:

Fig. 1 is detection device thereof structural representation of the present invention；

Fig. 2 is enriched with the principle schematic of arsenic hydride for the present invention.

Specific embodiment

Used by the embodiment of the present invention, coulomb arsenic analyser operating parameter setting value is as follows:

Arsenic analyser operating parameter set point is as follows:

Measurement range: 1ppb～ppm～%,

Mensuration mode: micro-coulometric titration,

Input impedance: ≮ 106 ω, output voltage: ± 24v,

Bias: 0～400mv, baseline drift: ≯ 5 μ v/20min,

Range: point high-load and two grades of low content, > 1ppm high-load shelves,

Data processing: microcomputer control process,

Analysis time: 5～10min,

Power supply: 220v～, 50hz, power: 40w,

Carrier gas is high pure nitrogen.

With reference to Fig. 1 and Fig. 2, absorption enriching step and the arsenic content step of in propylene arsenic are discussed in detail.

In Fig. 1, effusion meter 2 has high pure nitrogen entrance 1, and the gas outlet of effusion meter 2 is connected to the air inlet of generating bottle 4, The gas outlet of generating bottle 4 is communicated to titration cell 8 through lead acetate cotton 5, and the bottle stopper of generating bottle 4 can plug 5ml syringe 3.Micro- The reference electrode 6 of coulomb instrument 11, measuring electrode 7, anode electrode 9 and cathode electrode 10 insert the relevant position of titration cell respectively. Microcoulomb instrument 11 is also connected with printer 12.

The absorption enriching step of arsenic in propylene:

(1) prepare nitration mixture absorbing liquid: the volume ratio of bromine water, hydrogen peroxide, hydrochloric acid and nitric acid is 8:8:1:1.

(2) six 20ml absorption bottle sebific ducts are connected in series, and add 15ml nitration mixture absorbing liquid in each absorption bottle.

(3) 100ml syringes draw quantitative propylene gas to be measured according to default, and another 100ml syringe is drawn Nitrogen, two syringes pass through the air inlet of t type pipe access in parallel series connection absorption bottle unit, connect the whole absorption of detection after finishing The air-tightness of device unit.

(4) syringe that first will be equipped with propylene gas at the uniform velocity pushes, and under test gas are injected series connection absorption plant, gas velocity Degree controls in about 20ml min^-1, after treating propylene gas injection, with another syringe by the nitrogen of 2 to 3 times of propylene volumes The speed injection series connection absorption plant that gas maintains like is it is therefore an objective to purge whole series unit it is ensured that under test gas are fully contacted Nitration mixture absorbing liquid in all absorption bottles.

(5) question response terminates, and three absorption bottles are that a unit proceeds in the 200ml beaker that concentrated sulphuric acid boiled, go from Sub- water washing absorption bottle, washing liquid is poured in beaker in the lump, and the liquid heating evaporation that has been enriched with about 30 minutes is (depending on solution clear And volume is about 10ml), move into the ash that concentrated sulphuric acid boiled after cooling₃Generating bottle is to be measured.

(6) the blank experiment nitrogen post-heating that 45ml absorbing liquid absorbs same volume is evaporated to 10ml and moves into blank generation Bottle is to be measured.

The determination step of arsenic content:

(1) prepare electrolyte, proportioning is 0.07g potassium bromide, 800ml pure water, 150ml acetic acid, 50ml concentrated sulphuric acid and few Amount (0.8-1.2g) solid iodine.

(2) fully rinse titration cell with fresh electrolyte, waste liquid is discharged by reference arm and cathode leg, is subsequently adding fresh electricity Solution liquid, makes electrolyte be higher than that electrode 8～10mm is advisable, then directly adds several small solid bodies i in titration cell₂, in electrolyzer Must not there is bubble；Open power switch device, adjustment titration cell mixing speed is to electrolyte eddy；Open carrier gas gas circuit, make Gas flow rate adjusts in 20～30ml/min；

(3) prepare kbh₄Solution, takes 3g kbh₄In 100ml water, it is subsequently adding 0.5gnaoh (or koh), fully dissolve Standby.

(4) empty generating bottle is accessed carrier gas gas circuit, make instrument be in standard specimen shelves with Instrument working state key, i.e. " standard specimen " lamp Bright.After instrument balance, extract 10ul arsenic standard solution with microscale sampler, after start key, with microscale sampler by arsenic mark Quasi- solution instills in titration cell, measures the response rate, is biased according to response rate correction, till the response rate is 90%～110%.

(5) blank generating bottle is accessed carrier gas gas circuit, make instrument be in blank shelves with Instrument working state key, i.e. " blank " Lamp is bright.After instrument balance, use 5ml syringe, extract 3ml kbh4 solution, after start key, penetrated with syringe needle and send out Raw bottle rubber stopper, kbh4 is instilled in generating bottle, makes the arsenic ion in generating bottle test solution be reduced to ash3, analysis result simultaneously prints Achieve.

(6) sample generating bottle is accessed carrier gas gas circuit, make instrument be in sample shelves with Instrument working state key, i.e. " sample " Lamp is bright.After instrument balance, use 5ml syringe, extract 3ml kbh₄Solution, after start key, is penetrated with syringe needle and sends out Raw bottle rubber stopper, by kbh₄Instill in generating bottle, make the arsenic ion in generating bottle test solution be reduced to ash₃, analysis result simultaneously prints Achieve.

Arsenic cubage process is as follows:

In sample, arsenic content is calculated as follows:

$x_1=\frac{a}{v\·k}$

$x_2=\frac{a\×(273+t)\×101325\×22410}{v\×273\×p\·m\·k}$

In formula:

x₁Sample arsenic content, ng/ml；

x₂Sample arsenic content, ng/g；

The arsenic content that a microcoulomb analyser shows, ng；

The gas sample volume of v injection, ml；

The absorbance of k absorbing liquid, %；

P atmospheric pressure, pa；

T specimen temperature, DEG C；

The molal weight of m propylene, g/mol.

K value takes 75%.

First, accuracy, the response rate of instrument of the present invention are investigated.

Table 1: the arsenic response rate of instrument is investigated.

From the data of table 1 can be seen that the instrument response rate good it is ensured that the reliability of data.

The propylene gas containing 4000ppb and 3000ppb arsenic hydride are taken to test respectively with the method for the present invention, c₁For string The detected value of first three absorption bottle pregnant solution of receipts or other documents in duplicate unit, c₂For the detected value of rear three absorption bottle pregnant solutions, investigate nitration mixture whereby Absorbance, experimental data is shown in Table 2.

Table 2 is investigated for nitration mixture absorbance.

As shown by data in table 2, the accuracy of this method and repeatability are all preferable.

2nd, the present invention is directed to light gas alkene, and the selection to absorbing liquid and reducing agent is investigated.

Experiment early stage compares through a large amount of different proportions, from the volume ratio difference of bromine water, hydrogen peroxide, hydrochloric acid and nitric acid For 3:3:1:1,5:5:1:1,8:8:1:1, finally found that the absorbance of 8:8:1:1 is higher, then continue to explore according to this ratio, choosing It is respectively 8:8:2:1,8:8:1:2,8:8:1:1, no nitric acid state with the volume ratio of bromine water, hydrogen peroxide, hydrochloric acid and nitric acid, no Salt acid condition has done several groups of experiments respectively, experimental result such as table 3 below:

Table 3 is that the selection to absorbing liquid is investigated.

Bromine water: hydrogen peroxide: hydrochloric acid: nitric acid	Absorbance/%
		8:8:2:1	72.9
8:8:1:2	75.7
		8:8:1:1	74.6
8:8:1:0	64.2
		8:8:0:1	58.1

The volume ratio of known bromine water, hydrogen peroxide, hydrochloric acid and nitric acid is 8:8:1:1, and next we only change bromine water certainly The proportioning of body, and remaining acid content constant rate, take bromine water and the volume ratio of bromine simple substance to be respectively as follows: 0:1,10:1,20:1,1:0 Do several groups of experiments respectively, data such as table 4 below:

Table 4 is the investigation of bromine water and bromine simple substance proportioning.

The absorbance of absorbing liquid is as the following formula:

$k=\frac{c_1-c_2}{c_1},$

In formula: k absorbance；

c₁Detected value after the enrichment of first three absorption tube；

c₂Detected value after three absorption tube enrichments afterwards.

From table 4 it is known that nitration mixture absorbing liquid to the absorbance of arsenic with liquid the content of excessive bromine reduce and decline, During experiment, the absorbance more than 90% in perbromo- simple substance, but if all replacing the saturation bromine water can be with bromine Very big hidden danger is caused, from preparing the set-up procedure to series connection absorption plant for the absorbing liquid, bromine simple substance is not stopping to wave in experiment Send out, this has no small impact to instrument and operator, secondly as strong corrosivity, often does one group of absorption experiment, string The silica gel tube of connection is just scrapped substantially, and this is very uneconomical, and the degree volatilized is difficult to control to, and comes to needing stable absorbance Say to be also insecure.For pure saturation bromine water, operational risk is minimum, but absorbance is minimum, then finally selectes Bromine water is the proportioning as " bromine water " in nitration mixture for the 20:1 with the volume ratio of bromine simple substance, and during calculating, k value takes 75%.

3rd, due to the unstability of potassium borohydride, in order to ensure accuracy and the repeatability of mensure, we have done following again Several groups of experiments.Respectively with the batch of potassium borohydride, the concentration of potassium borohydride and add sodium hydroxide amount as investigate project, Data such as table 5 below:

Table 5:khb₄The impact of quality is investigated.

khb4Quality	10 μ l100mg/l arsenic standard solution detected values/ppm
		1	97.9
2	102.9
		3	105.6

For the quality of potassium borohydride, this is objectively uncontrollable, and due to the difference of batch, the quality of medicine is agreed Surely it is slightly different, this just causes some impacts to reduction reaction.From the point of view of the data of table 4, impact is not very big, but often more Newly it is necessary to can be measured testing through checking when a collection of potassium borohydride medicine.

Table 6:khb₄The impact of concentration is investigated.

With regard to kbh₄The selection of solution concentration, works as kbh₄When concentration is excessive, reduction reaction can be more violent, and reaction generates Arsenic hydride tolerance can be excessive, and carrier gas picks enter titration cell excessive velocities, instrument may be formed with impact and sensitivity is made Become impact；Work as kbh₄When concentration is too low, the ability of reduction arsenic again may be weaker, and the insufficient of reduction reaction may not be by instrument Device is captured, and causes measured value low.

The impact of table 7naoh addition is investigated.

Naoh addition/g	10 μ l100mg/l arsenic standard solution detected values/ppm
		0.1	91.2
0.5	102.9
		1	95.7

kbh₄In h⁺It is very easy under environment decompose, so its aqueous solution must be allowed to keep the alkalescence of appropriateness steady to improve it Qualitative.On the other hand, the alkali of addition again can not be excessive, otherwise can affect reduction reaction, leads to acidity when reacting too low.? 70.4 detected value, in table 3.7, once occurred in the experiment adding 0.1g, post analysis reason finds that solution of potassium borohydride is prepared Time and minute every excessive, are placed it cannot be guaranteed that the stablizing of potassium borohydride for a long time, so must be now with the current.Experiment Show, the addition of potassium hydroxide is advisable with 0.5g.

Should be noted when operating the correlation step of the present invention:

(1) all should carry out under aeration status during standard specimen demarcation and sample analysis, carrier gas is high pure nitrogen.

(2) in order to ensure the susceptiveness of instrument, the electrolyte liquid of titration cell also needs often to change.

(3) during sample heating evaporation, the pregnant solution in beaker is necessarily careful not to dryout, otherwise Lower result.

(4) in order to prevent cross-contamination, for the sampling bottle of high-load and low content sample analysis, extractor and generating bottle Etc. use all should be strictly separated.

The above-mentioned description to embodiment includes some exploratory parts, and this part is to obtain on the basis of many experiments To conclusion it is therefore an objective to being understood that for ease of those skilled in the art and using invention.Skilled Personnel obviously easily various modifications can be made to these examples, and it is real that General Principle described herein is applied to other Apply in example without through performing creative labour.Therefore, the invention is not restricted to above-described embodiment, those skilled in the art are according to this The announcement of invention, the improvement made without departing from scope and modification all should be within protection scope of the present invention.

Claims (9)

1. in a kind of light gas alkene the detection method of arsenic content it is characterised in that comprising the following steps:

(1) prepare standard solution: inorganic arsenic solution is configured to the arsenic standard solution that concentration is 100 μ g/ml；

(2) olefin samples pre-treatment: by olefin gas to be measured quantitatively injection equipped with the series connection absorption plant of nitration mixture absorbing liquid, alkene Arsenic element in hydrocarbon then enters in mixed acid solution, absorbs after finishing, and forms testing liquid sample after the solution heating of enrichment is steamed Product immigration generating bottle is to be measured, and described nitration mixture absorbing liquid is mixed by bromine water, hydrogen peroxide, hydrochloric acid, salpeter solution；

(3) demarcation of instrument: carrier gas accesses instrument gas circuit, under suitable flow velocity, by the arsenic standard solution preparing with micro Sampler injects titration cell, calculates the response rate according to the data recording, and stablizes the response rate by adjustment bias；

(4) sample to be tested detection: reducing agent is mixed with described liquid sample, arsenic ion is reduced to arsenic hydride, with carrying Gas is brought described arsine gas into titration cell in the lump and is absorbed and the potential change after small-hole drilling detection absorption arsenic hydride, It is calculated the content of arsenic element in alkene.

2. in light gas alkene according to claim 1 arsenic content detection method it is characterised in that: described bromine water, The volume ratio of hydrogen peroxide, hydrochloric acid and nitric acid is 8:8:1:1.

3. in light gas alkene according to claim 1 arsenic content detection method it is characterised in that: described inorganic arsenic Solution is arsenious weak acid solution.

4. in light gas alkene according to claim 1 arsenic content detection method it is characterised in that: described reducing agent For potassium borohydride or sodium borohydride.

5. in light gas alkene according to claim 1 arsenic content detection method it is characterised in that: described after steaming Liquid sample is 10ml.

6. in light gas alkene according to claim 1 arsenic content detection method it is characterised in that: described nitration mixture is inhaled The bromine water received in liquid is mixed with volume ratio 20:1 with bromine simple substance by saturation bromine water.

7. in light gas alkene according to claim 4 arsenic content detection method it is characterised in that: described hydroboration The aqueous solution mass concentration of potassium is 3%.

8. in light gas alkene according to claim 7 arsenic content detection method it is characterised in that: every 100 milliliters The aqueous solution of described potassium borohydride adds sodium hydroxide or the potassium hydroxide of 0.5g.

9. in light gas alkene according to claim 1 arsenic content detection method it is characterised in that: described microcoulomb Method monitoring electrolyte used is solid by 0.07g potassium bromide, 800ml pure water, 150ml acetic acid, 50ml concentrated sulphuric acid and 0.8-1.2g Body iodine proportioning forms.