A method for modifying a composite polypropylene catalyst

Abstract

This invention relates to the field of surface engineering and synergistic regulation of external donors in polyolefin catalytic systems, and particularly to a method for modifying a composite polypropylene catalyst, comprising: step S1 drying a support composed of titanium tetrachloride and magnesium chloride at 100°C for 3 hours under inert gas protection, with the inert gas dew point being -70 to -60°C; step S2 preferentially coordinating titanium active centers located on the surface of the support; step S3 forming a continuous hydrophobic layer on the surface of the support; and step S4 obtaining the modified catalyst. This invention utilizes a complete process involving low-temperature solvent-free coordination with diphenylphosphine, pulsed gas-solid grafting of linear methylphenylsiloxane at absolute pressure of 0.062 to 0.068 MPa and 70°C, online infrared-triggered pulse endpoint, alternating purging and nano-zinc stearate chlorine-capturing stabilization, and fluidized bed aging to obtain a modified catalyst with high isotactic index, good hydrogen sensitivity, high activity retention, and uniform powder morphology.

Description

Technical Field

[0001] This invention relates to the field of surface engineering and synergistic regulation of external donors in polyolefin catalytic systems, and particularly to a method for modifying a composite polypropylene catalyst. Background Technology

[0002] Existing Ziegler-Natta systems often use silanes or siloxanes as external donors to control the isotactic index and hydrogen sensitivity. However, under high-water-content micro-trace environments and long-cycle gas-phase polymerization, they frequently encounter problems such as activity decay and powder morphology fluctuations. Traditional "mixed addition" or "single contact" routes cannot simultaneously guarantee moisture resistance, stereoselectivity, hydrogen sensitivity consistency, and powder workability. Therefore, it is necessary to develop a combined approach of sequential surface engineering and closed-loop process control to obtain a continuous, well-bonded, and uniformly distributed hydrophobic layer, while also considering polymerization performance and powder properties. Summary of the Invention

[0003] To overcome the aforementioned technical deficiencies, the present invention aims to provide a method for modifying a composite polypropylene catalyst. This method involves a complete process: low-temperature solvent-free coordination with diphenylphosphine; pulsed gas-solid grafting of linear methylphenylsiloxane at an absolute pressure of 0.062 to 0.068 MPa and 70°C; online infrared-triggered pulse endpoint; alternating purging and nano-zinc stearate chlorine-capturing stabilization; and fluidized bed aging. This process yields a modified catalyst with a high isotactic index, good hydrogen sensitivity, high activity retention, and uniform powder morphology.

[0004] This invention discloses a method for modifying a composite polypropylene catalyst, comprising the following steps:

[0005] Step S1: Dry the support composed of titanium tetrachloride and magnesium chloride at 100°C for 3 hours under inert gas protection, with the inert gas dew point being -70 to -60°C;

[0006] Step S2: Diphenylphosphine ethane is contacted with the support obtained in step S1 at 40°C in a solvent-free manner for 2 hours. The mass ratio of diphenylphosphine ethane to support is 1:20, and the water content of the system is 20 to 30%. This allows it to preferentially align with the titanium active centers located on the carrier surface;

[0007] Step S3: Under absolute pressure of 0.062 to 0.068 MPa, linear methylphenylsiloxane is introduced at 70°C using pulsed gas-solid contact. A total of 10 pulses are performed, with each feed lasting 15 to 20 seconds and an interval of 90 seconds between two adjacent feeds. The total silicon dosage is 1.00 mg / g based on silicon element, so that a continuous hydrophobic layer is formed on the surface of the carrier.

[0008] Step S4: Aging at 50°C for 6 hours in a fluidized bed under nitrogen protection to obtain the modified catalyst;

[0009] The steps are performed in sequence: first step S2, then step S3. After step S3, the water contact angle of the catalyst is 98 to 102°, the surface silicon content is 3.5 to 4.5 wt%, and the acid site density decreases by 25 to 35%.

[0010] Preferably, after step S2, the surface P:Ti atomic ratio measured by X-ray photoelectron spectroscopy is 0.05 to 0.10, and the area of ​​the coordination characteristic peak of diphenylphosphine ethane and titanium fluctuates within 20 to 30 minutes under in-situ infrared monitoring, which is 2% to 5%.

[0011] Preferably, each pulse feed in step S3 is triggered by the rate of change of absorbance of the characteristic peak of linear methylphenylsiloxane in the outlet gas phase by online infrared spectroscopy. When the absorbance drops to 20% to 30% of the value at the start of the pulse, the next feed is started until the predetermined number of pulses is completed.

[0012] Preferably, the linear methylphenylsiloxane has a linear structure, the molar fraction of phenyl is 30 to 40 mol%, and the number average molecular weight Mn is 700 to 850 g / mol.

[0013] Preferably, step S4 employs fluid aging with an apparent gas velocity of 1.0 to 1.2 times the minimum fluidization velocity, a bed temperature fluctuation of 0.5 to 1.0 °C, and a standard deviation of surface silicon content calculated by energy dispersive spectroscopy of 0.15 to 0.25 wt%.

[0014] Preferably, after step S3, alternating purging is performed, first purging with nitrogen for 8 to 12 minutes, then purging with argon for 8 to 12 minutes, and purging ends when the total organosilicon content in the exhaust gas drops to 5 to 10 ppmv.

[0015] Preferably, after step S3 is completed, nano-zinc stearate with a particle size of 80 to 120 nm is sprayed once at 55°C by dry powder atomization. The treatment time is 6 min, the amount of treatment agent is 0.25 wt% of the mass of the modified catalyst, and the titratable chlorine content is 0.03 to 0.05 wt% as determined by titration.

[0016] Preferably, steps S2 and S3 are solvent-free, and the nitrogen gas used is... The content is 1 to 3 ppmv. The content is 1 to 3 ppmv, and the dew point is -75 to -70℃.

[0017] Preferably, under the conditions of propylene gas-phase polymerization at 70°C, a total pressure of 2.0 MPa, and a hydrogen partial pressure of 0.10 MPa, the obtained polymer has an isotactic index of 97.5% to 98.5%, a 24-hour activity retention rate of 85% to 90%, and a melt flow rate slope with respect to hydrogen partial pressure of 10 to 14 g / 10. .

[0018] Preferably, the surface formed in step S3 The layer thickness is 2 to 5 nm, and X-ray photoelectron spectroscopy is used to analyze it. and The S–O–Ti bonded components obtained by peak fitting account for the surface area The proportion of the total peak area is 45% to 55%.

[0019] After adopting the above technical solution, compared with the prior art, the beneficial effect of the present invention is that, under constant propylene gas phase conditions (70℃, 2.0MPa, total hydrogen partial pressure 0.10MPa, propylene water content 50%), Under these conditions, the catalyst prepared by this method achieves an isotactic index of 97.5% to 98.5%, a 24-hour activity retention rate of 85% to 90%, and a hydrogen sensitivity slope of 10 to 14 g / 10 min· This significantly reduced the RSD of fine powder segments and particle size, and controlled the standard deviation of surface silicon distribution within 0.16 to 0.25 wt%, demonstrating that the combination of "phosphine coordination followed by siloxane pulse grafting and narrow vacuum window" and subsequent stabilization has a systematic improving effect; more specifically:

[0020] In existing technologies, industrial polypropylene commonly uses the Ziegler–Natta system ( / carrier, The co-catalyst, in conjunction with silane / siloxane external donors, operates in gas phase, slurry, or bulk processes; common modification methods include single continuous feeding or solvent impregnation to improve the isotactic index and adjust hydrogen sensitivity; quality control mainly relies on offline post-testing methods such as XPS, DRIFTS, TPD, and TEM; there are also schemes that simultaneously mix phosphorus / nitrogen-containing ligands with silicon-containing donors in an attempt to improve selectivity and moisture resistance through synergistic effects.

[0021] The following problems exist in the above-mentioned prior art:

[0022] Layer heterogeneity and fluctuation: uneven distribution of modified layer thickness and bonding, Si–O–Ti ratio and Batch-to-batch variations in thickness lead to activity decay and hydrogen sensitivity drift;

[0023] Endpoint cannot be determined: Single-stage, single-endpoint processing lacks online signals and closed-loop triggering, making it difficult to stably control absolute pressure, dew point and instantaneous partial pressure of modifier within a narrow window, and easily resulting in residue or excess.

[0024] Competitive adsorption: Simultaneous mixed contact is prone to mutual passivation and competition for active sites, making it difficult to balance isotactic index, hydrogen sensitivity and activity maintenance;

[0025] Powder engineering deficiencies: High particle size RSD and fine powder range, bed thickness... Increased fluctuations are affecting continuous operation;

[0026] Residues and environmental burden: The solvent system brings the risk of drying and residues; side reactions result in higher titratable chlorine levels.

[0027] In this invention, a sequential surface engineering process is employed: S1 carrier drying (100°C, 3h); S2 low-temperature solvent-free phosphine coordination (diphenylphosphine ethane, 40°C, 2h); S3 pulsed gas-solid grafting of siloxane (70°C, 2h). =0.062–0.068 MPa, 10 pulses, each 15–20 s, 90 s interval); after S3, alternately purge until the total organosilicon in the exhaust gas is 5–10 ppmv; nano stabilization (nano zinc stearate 0.25 wt%, 55°C, 6 min); S4 fluidized bed aging (50°C, 6 h); triggered by online closed loop: the end point of each pulse is defined as the online infrared absorbance dropping to 20–30% of the initial value. Stabilize at 0.0031–0.0036 MPa to ensure complete reaction and avoid excess; maintain a solvent-free and low dew point environment throughout the process. , Each 1-3 ppmv reduces residues and side reactions, and facilitates intrinsically safe management of the equipment; thereby achieving the following beneficial effects:

[0028] Evaluation window uniformity: 70℃ =2.0MPa =0.10MPa, propylene moisture 50 The control systems were: A (siloxane grafting only, continuous feeding) and B (phosphine and siloxane mixed and contacted simultaneously).

[0029] Polymerization performance is improved and stabilized simultaneously: isotactic index 97.5%-98.5% (A: 96.8%, B: 97.4%); 24h activity retention: 85%–90% (A: 80.2%, B: 83.5%); hydrogen sensitivity slope: 10–14 g / 10min. (A: 9.0, B: 10.8); The formulation positioning is more linear and controllable.

[0030] Surface chemistry "quantitative-structural-thickness determination": Si–O–Ti ratio: 45%–55%; Thickness: 2–5 nm; Water contact angle: 98°–102°; Acid site density reduction: 25%–35%; Surface Si content: 3.5–4.5 wt%, in-plane standard deviation 0.16–0.25 wt% (A: 0.35, B: 0.28), coverage uniformity improved by 29%–54%.

[0031] Enhanced process consistency and reproducibility: Online infrared spectral threshold triggering at 20%–30%. Stable; alternating purge endpoint 5–10 ppmv (measured by online gas chromatography); batch-to-batch RSD of key indicators such as surface Si and Si–O–Ti was significantly reduced (n=3, p<0.05 for most indicators).

[0032] Powder Engineering and Operational Improvement: Particle Size :20–22 RSD: 10.5%–15.0% (A: 17.2%, B: 14.5%); Fine powder <10 : 1.00%–1.50% (A: 2.00%, B: 1.60%); The 24-hour online pressure drop curve is more stable and the peak value is lower, reducing the risk of wall adhesion and unplanned downtime.

[0033] Residual and green safety are superior to the control: titratable chlorine: 0.03%–0.05% (A: 0.070%, B: 0.055%); total organosilicon in exhaust gas: ≤10ppmv; solvent-free and low dew point throughout the process, making it more environmentally friendly and intrinsically safe.

[0034] Device compatibility and scale-up friendly: Without changing the basic structure and aggregation window of the Ziegler-Natta system, only pulses and online thresholds are introduced in the modification section; facilitating smooth scale-up and standardized quality control. Attached Figure Description

[0035] Figure 1 A schematic block diagram of the process flow and online infrared closed-loop triggering logic for S3 pulsed gas-solid grafting.

[0036] Figure 2 S3 segment of Example 1, marked with 10 pulses and the 30% threshold line. and Schematic diagram of superimposed curves;

[0037] Figure 3 S3 segment of the 25% threshold closed loop in Example 2 and Schematic diagram of superimposed curves;

[0038] Figure 4 For Example 3, the 20% threshold closed loop and S3 segment of the waveform and Schematic diagram of superimposed curves;

[0039] Figure 5 Let A = 0.0123·C + 0.0011. =0.998 Schematic diagram of online infrared calibration curve;

[0040] Figure 6 A schematic diagram comparing the peak area stability in the 20–30 min interval for DRIFTS coordination monitoring in Examples 1–3;

[0041] Figure 7 XPS values ​​for the Si–O–Ti area ratio of Examples 1-3 and Controls A / B Fitting diagram;

[0042] Figure 8 For XPS Fitting diagram of chemical shift versus FWHM variation;

[0043] Figure 9 For TEM cross-sectional thickness measurement, Examples 1-3 Thickness box line diagram;

[0044] Figure 10 This is a schematic diagram of the Si surface scanning thermal analysis of the SEM-EDS surface.

[0045] Figure 11 Examples 1-3 and Controls A / B -TPD curve diagram;

[0046] Figure 12 This is a schematic diagram of the water contact angle;

[0047] Figure 13 This is a schematic diagram showing the online yield and pressure drop curves of Examples 1-3 and Control A / B;

[0048] Figure 14 This is a schematic diagram showing the linear fitting and slope comparison of melt flow rate with hydrogen partial pressure.

[0049] Figure 15 for A schematic diagram of the particle size distribution curves compared with RS and the fine powder segment. Detailed Implementation

[0050] The advantages of the present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments.

[0051] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0052] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The singular forms “a,” “the,” and “the” as used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0053] It should be understood that although the terms first, second, third, etc., may be used in this disclosure to describe various information, such information should not be limited to these terms. These terms are used only to distinguish information of the same type from one another. For example, without departing from the scope of this disclosure, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0054] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0055] In the description of this invention, unless otherwise specified and limited, it should be noted that the terms "installation", "connection" and "linking" should be interpreted broadly. For example, they can refer to mechanical or electrical connections, or internal connections between two components. They can be direct connections or indirect connections through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0056] In the following description, suffixes such as "module," "part," or "unit" used to denote elements are used only for the convenience of the description of the invention and have no specific meaning in themselves. Therefore, "module" and "part" can be used interchangeably.

[0057] This embodiment will describe in detail the modification method of the composite polypropylene catalyst through Examples 1-3. The core is: S1: The support is dried at 100°C for 3 hours under inert gas protection; S2: Diphenylphosphine ethane is contacted with the support at 40°C without solvent for 2 hours, with a mass ratio of 1:20 and a water content of 20 to 30%. Coordination preferentially occurs at the titanium active center; S3: Linear methylphenylsiloxane is introduced using pulsed gas-solid contact at an absolute pressure of 0.062 to 0.068 MPa and a temperature of 70°C. Ten pulses are administered, each lasting 15 to 20 seconds with a 90-second interval. The total silicon dosage is 1.00 mg / g. The next pulse is triggered when the online infrared absorbance decreases to 20% to 30% of the initial value. The pulse grafting and closed-loop triggering logic is as follows: Figure 1 As shown; different thresholds and pulse durations affect and See the impact Figure 2 , Figure 3 , Figure 4 S3: After alternating purging until the total organosilicon content in the exhaust gas is 5 to 10 ppmv, atomize and spray 0.25 wt% nano-zinc stearate (80 to 120 nm particle size) at 55°C for 6 min; S4: age in a fluidized bed at 50°C for 6 h. Functional thresholds: water contact angle 98 to 102°; surface silica 3.5 to 4.5 wt%; acid site density decrease of 25% to 35%. Thickness 2 to 5 nm; Si–O–Ti content 45% to 55%.

[0058] Examples 1-3 share common conditions and requirements regarding materials, equipment, environment, and safety, as detailed below:

[0059] Materials, reagents and gases: Carrier: / Solid, loss on ignition ≤0.5wt%, surface water ≤0.05wt%.

[0060] Diphenylphosphine: ≥99.5wt%.

[0061] Linear methylphenylsiloxane: phenyl molar fraction 30 to 40 mol%, Mn 700 to 850 g / mol.

[0062] Nano zinc stearate: primary particle size 80 to 120 nm, agglomerate size 200 to 300 nm, moisture content ≤0.05 wt%.

[0063] Nitrogen and argon: ultra-high purity grade. and As defined in each embodiment, the dew point is -75 to -70°C.

[0064] Propylene: ≥99.9%, Moisture 50% Hydrogen ≥ 99.999%.

[0065] Equipment and Dosage:

[0066] 2L jacketed fixed-bed reactor with inert lining; K-type thermocouples distributed at three points with a deviation ≤0.3℃.

[0067] Absolute pressure sensor: 0–0.2 MPa, error ≤0.2%. Mass flow controller: 0–2.0 L / min, error ≤1%.

[0068] Online infrared: optical path 10cm, sampling 2Hz. Dry glove box: ≤1ppmv, ≤1ppmv.

[0069] Analyze the balance to obtain 0.1 mg. Perform other measurements according to the test method.

[0070] Safety and environmental control:

[0071] The entire process is equipped with anti-static grounding, and anti-static clothing and wristbands are monitored online; exhaust gas is adsorbed by cold traps and activated carbon, and total hydrocarbons are monitored online; the ambient temperature is 22 to 25℃, and the relative humidity is 40% to 45%.

[0072] Test methods, spectral criteria and statistical definitions:

[0073] 1) Online infrared spectral calibration: A = 0.0123·C + 0.0011, =0.998, drift <0.5% / h, calibration curve and linear fit are as follows Figure 5 As shown.

[0074] 2) Absolute pressure sensing: linearity error ≤0.2%, short-term repeatability ±0.0005MPa.

[0075] 3) XPS: , Reference 103.5eV, Reference 458.6 eV, GL(30), FWHM 1.1–1.6 eV; The peak fitting and Si–O–Ti area ratio are shown in the figure. Figure 7 , The differences in chemical shift and linearity are shown in the figure. Figure 8 The thickness of the overburden layer was determined using an overburden layer model and verified by TEM. Representative thickness statistical distributions are shown in [reference needed]. Figure 9 .

[0076] 4) DRIFTS: Background , Resolution, accumulated 64 times; uniform integration interval for coordination bands, see comparison of 20–30 min coordination peak area stability in Examples 1–3. Figure 6 .

[0077] 5) SEM-EDS surface scanning: field of view ≥ 300×300 , grid ≥ 20×20; output surface mean and standard deviation (wt%).

[0078] 6) Water contact angle: Powder tableting, titration 5 At 25℃ and RH 40–50%, report the static angle; for typical contact angles, see appearance. Figure 12 .

[0079] 7) Pretreatment at 120℃ for 60 min, adsorption for 30 min, and then increasing to 600℃ at a rate of 10℃ / min; total acid sites were calculated based on peak area. Desorption curves for each sample are shown below. Figure 11 .

[0080] 8) Particle size: Dry laser scattering, RSD and fine powder <10 Loose packing density is determined according to GB / T20080; particle size distribution curves are shown below. Figure 15 .

[0081] 9) Polymerization evaluation: 1L fluidized bed, 70℃, =2.0MPa, =0.10MPa, propylene moisture 50 Continuous operation for 24 hours; II. Using the heptane-insoluble method, the melt flow rate is calculated according to ISO 1133; the hydrogen sensitivity slope is regressed at three points: 0.06, 0.10, and 0.14 MPa. The linear fit and slope comparison of the melt flow rate to the hydrogen partial pressure are shown in [reference needed]. Figure 14 .

[0082] Statistical scope: Unless otherwise specified, n=3, report mean ± standard deviation; significance test is two-tailed t-test. =0.05.

[0083] Example 1 (Endpoint 1)

[0084] Purpose and principle: To set a lower absolute pressure At a pressure of 0.062 MPa and an online threshold of 30%, controlled grafting with a short pulse duration (15 s) was achieved, demonstrating the effect of low threshold density on Si–O–Ti formation and in-plane uniformity. S2 employed solvent-free phosphine coordination at 40℃ to ensure preferential occupation of titanium sites and reduce the non-selective adsorption of subsequent siloxanes.

[0085] Equipment and Calibration:

[0086] Reactor: 2L jacketed fixed bed (inert liner);

[0087] Pressure gauge: measuring range 0–0.2MPa, linearity error ≤0.2%, zero point and full scale are calibrated at 70℃;

[0088] Mass flow controller (MFC): 0–2.0 L / min, error ≤1%, calibrated with dry nitrogen;

[0089] Online infrared: optical path 10cm, sampling 2Hz; according to the calibration curve A=0.0123C+0.001 ( Input methodology; background data was collected in three samples of dry nitrogen and averaged.

[0090] Glove box: ≤1ppmv ≤1ppmv;

[0091] Safety: The grounding resistance of the entire equipment is ≤10Ω; exhaust gas cold trap (-30°C) + activated carbon.

[0092] Raw material and proportion calculations:

[0093] Carrier: / 20.00g of solids;

[0094] Diphenylphosphine ethane (DPPE): 1.00 g (mass ratio to carrier 1:20);

[0095] Linear methylphenylsiloxane (linear, g / mol;

[0096] Target silicon addition: =1.00 mg / g (based on carrier), corresponding to a total silicon content of 20.00 mg. Divide into 10 equal pulses and calculate the single pulse. ≈0.100 mg / g;

[0097] Stabilizer: Nano zinc stearate atomized, 0.25wt% (based on carrier), 6min;

[0098] Carrier gas: Ar and Ar, each with a purity ≥99.999% and a dew point ≤-70℃.

[0099] It should be noted that dividing the total silicon amount into 10 equal parts can limit the instantaneous surface concentration in each step to a range that does not form local agglomeration; the 15s pulse duration and 90s interval have been confirmed by preliminary experiments to make the surface reaction approximately first-order decay and sufficient diffusion supply at 70℃.

[0100] Process steps:

[0101] Step S1: Drying and Replacement (Inert gas includes, but is not limited to, nitrogen / argon):

[0102] 20.00g of carrier was placed in the glove box and connected to the reactor; 1.0 L / min; heat to 100 °C at 2 °C / min, hold at that temperature for 3 h; temperature probe three-point deviation ≤ 0.3 °C; after natural cooling to 40 °C, maintain... 1.5 L / min. In this step, 100°C for 3 hours can reduce the surface adsorbed water to 20–30%. The window satisfies the trace polar environment required for S2 coordination while avoiding carrier embrittlement caused by excessive dehydration.

[0103] Step S2: Low-temperature solvent-free phosphine coordination:

[0104] At 40℃, 1.00g of DPPE was added using an inert, rapid-feeding hopper. Stir at 1.0 L / min and 300 rpm; after 2 h of contact, let stand for 30 min, then take 0.10 g of sample for DRIFTS analysis: the coordination peak area fluctuated by 2.1–2.5% in the 20–30 min range; then take 0.20 g for rapid XPS analysis: P:Ti = 0.050 ± 0.004. Judgment criteria: DRIFTS fluctuation ≤ 3%, P:Ti within 0.05 ± 0.01 is considered "in place". In step S2, prior coordination at titanium sites forms a "site template", reducing the disordered adsorption of siloxanes in S3 and avoiding competition and passivation caused by simultaneous mixing.

[0105] Step S3: Pulse-based gas-solid grafting:

[0106] set up =0.062MPa, T=70℃; Online infrared spectral threshold=0.30× Linear methylphenylsiloxane vapor was added using a pulse valve: each injection lasted 15 seconds, with a 90-second interval, for a total of 10 injections. The results were recorded. , , Online trigger logic: When When the voltage drops to the 30% threshold, the system automatically ends the current pulse and enters the interval period; if the threshold is not reached within 15 seconds, the duration is extended by 2–3 seconds, but the total duration does not exceed 20 seconds; after the pulse ends, the pressure is maintained for 5 minutes; check. Is the surface stable at 0.003-0.004 MPa? In step S3, the 30% threshold corresponds to the surface reaction being close to the diffusion control inflection point, which can balance sufficient reaction and minimal residue. The narrow band represents bed fluidization stability and repeatable instantaneous partial pressure.

[0107] Alternating purging and stabilization afterwards:

[0108] Alternating blowdown: 1.0 L / min for 8 min → Ar 1.0 L / min for 8 min, circulated to exhaust gas total organosilicon ≤8ppmv; nano-zinc stearate, 0.25wt% of the carrier, was atomized and sprayed at 55℃ using a dual-fluid nozzle for 6 min; subsequently Purge for 5 minutes. Alternating purging and stabilization are then performed. Alternating purging utilizes the difference in diffusion coefficients to accelerate desorption. Nano-zinc stearate neutralizes trace amounts of chloride in the solid phase and passivates Lewis acid sites, reducing titratable chlorine and subsequent side reactions.

[0109] Step S4: Fluidized bed aging

[0110] At 50℃ and apparent gas velocity 1.0× Fluidization for 6 hours, bed temperature fluctuation ≤0.5℃; cooling, The solid was collected under positive pressure, yielding 19.70g of powder.

[0111] Online recording and batch release standards:

[0112] 10-pulse raw table: Pulse#, , T Threshold , , , ;

[0113] Release criteria: Surface Si 3.5–3.8 wt%; Si–O–Ti 45–48%; 2.3–2.7 nm; water contact angle ≥98°; titratable chlorine ≤0.055 wt%; particle size RSD ≤15.5%.

[0114] Deviation handling: If any pulse fails to reach the threshold within 15 seconds, the time limit is extended to a maximum of 20 seconds; if it still fails to reach the threshold, an "abnormal shutdown" is triggered, and the process enters a 12-minute period. Purge, reset, and then start the next pulse.

[0115] Original Record Table 1 (10 pulses)

[0116]

[0117] Characterization and statistics: Lower limit of 100° system, measured as 98.5±0.4°; Surface Si: 3.60±0.08wt%, distribution =0.25wt%; Acid site decrease: 26.2±1.1%; Si–O–Ti; 46±2%; Thickness: 2.5±0.2nm; Titratable chlorine: 0.050±0.004wt%; RSD = 15.0 ± 0.6%, fine powder <10μm is 1.50 ± 0.10 wt%, loose packing density is 0.31 ± 0.01 g / mL; n = 3.

[0118] Evaluation of propylene gas-phase polymerization:

[0119] 1L reactor, 70℃ =2.0MPa, =0.10MPa; catalyst 0.200g, =15:1. 24-hour continuous operation: =97.6±0.2%, melt flow rate 9.8±0.3 g / 10 min, hydrogen sensitivity slope 10.5±0.4 g / 10 The activity retention rate was 85.5 ± 1.2%.

[0120] Example 2 (Midpoint)

[0121] Purpose and Principle:

[0122] by A combination of 0.065 MPa, a threshold of 25%, and a single pulse duration of 18 s yielded higher bonding density and lower in-plane ripple. This window was designed to balance reaction rate and diffusion supply, aiming to be as close as possible to the Si–O–Ti ratio and... The statistical "median working condition" of thickness.

[0123] Equipment and Calibration:

[0124] Same as in Example 1 above; however, the online infrared spectral integration time constant is adjusted from 0.25s to 0.35s to improve the noise resistance of threshold determination.

[0125] Raw materials and proportions:

[0126] Carrier 20.00g; DPPE 1.00g;

[0127] Linear methylphenylsiloxane, total silicon content 20.00 mg, administered in 10 pulse aliquots;

[0128] The carrier gas and stabilizer are the same as those in Example 1 above.

[0129] Process steps:

[0130] Step S1: Drying and Replacement (Inert gas includes, but is not limited to, nitrogen / argon):

[0131] 20.00g of carrier was placed in the glove box and connected to the reactor; 1.0 L / min; heat to 100 °C at 2 °C / min, hold at that temperature for 3 h; temperature probe three-point deviation ≤ 0.3 °C; after natural cooling to 40 °C, maintain... 1.5 L / min. In this step, 100°C for 3 hours can reduce the surface adsorbed water to 20–30%. The window provides a trace polar environment necessary for S2 coordination while avoiding carrier embrittlement caused by excessive dehydration. It should be noted that, consistent with Example 1 above, the aim is to control the surface water content at 25°C. To enhance the repeatability of coordination in step S2.

[0132] Step S2: Low-temperature solvent-free phosphine coordination:

[0133] At 40℃ 1.0 L / min, solvent-free contact for 2 h, standing for 37 min; DRIFTS fluctuation 3.4 ± 0.4%; XPSP:Ti = 0.075 ± 0.005. Step S2 moderately increases P:Ti to indicate more sufficient coordination coverage, providing a more uniform "pre-mixed base" for subsequent siloxane grafting.

[0134] Step S3 Pulse-based gas-solid grafting (main difference):

[0135] set up =0.065MPa, T=70℃; online infrared spectral threshold=25%; single pulse 18s, interval 90s, total 10 pulses; =0.003-0.004MPa. Online trigger criterion: Stop when any pulse reaches 25%; if the threshold is reached 12-14 seconds earlier, it is automatically shortened to 15 seconds to avoid oversupply; hold pressure for 15 minutes. In this step S3, the 25% threshold corresponds to a deeper surface reaction and diffusion contribution, combined with a slightly higher... It can increase the Si–O–Ti ratio and layer thickness, while suppressing residue through automatic time reduction.

[0136] Alternating purging and stabilization afterwards:

[0137] Alternating blowdown: 10 min → Ar 10 min, until exhaust gas 8 ppmv; 55℃, nano zinc stearate 0.25 wt%, 6 min; Purge for 5 minutes. In this Example 2, the post-alternating purging and stabilization process is slightly longer than in Example 1 to match the desorption requirements after deeper grafting.

[0138] Step S4: Fluidized bed aging

[0139] At 50℃ and apparent gas velocity 1.0× After 6 hours of fluidization, the bed temperature fluctuation was ≤0.75℃. In this embodiment, a gas velocity slightly higher than the minimum fluidization rate helps to eliminate agglomeration nuclei and homogenize surface stress.

[0140] Online recording and release: Record 10 pulses of the same caliber; focus on the first 3 pulses. Whether it shortens sequentially (a manifestation of gradual saturation of surface sites).

[0141] Release criteria: Surface Si 3.9-4.1 wt%; Si–O–Ti 49-51%; 3.3–3.7 nm; water contact angle ≥99.5°; titratable chlorine ≤0.045 wt%; particle size RSD ≤13.0%.

[0142] Deviation handling:

[0143] If any two consecutive pulses All <12s; adjust the interval from 90s to 120s to avoid excessive enrichment on the outer layer; if the exhaust gas is still >10ppmv in the Ar section: switch to 12 minutes, then Ar for 12 minutes until the target is met.

[0144] Original record table 2 (10 pulses)

[0145]

[0146] Characterization and Statistics:

[0147] Water contact angle: 100.0±0.3°; Surface Si: 4.02±0.06wt%; =0.20wt%; Acid site decrease: 30.1±1.0%; Si–O–Ti: 50±2%; Thickness: 3.5±0.2nm; Titratable chlorine: 0.040±0.003wt%; RSD = 12.5 ± 0.5%, fine powder < 10 The content was 1.20±0.08wt%, and the loose bulk density was 0.33±0.01g / mL; n=3.

[0148] Evaluation of propylene gas-phase polymerization:

[0149] 1L reactor, 70℃ =2.0MPa, =0.10MPa; catalyst 0.200g, =15:1. 24-hour continuous operation: =98.1±0.2%, melt flow rate 10.6±0.3 g / 10 min, hydrogen sensitivity slope 12.0±0.4 g / 10 min The activity retention rate was 87.8 ± 1.0%.

[0150] Example 3 (Endpoint 2)

[0151] Purpose and Principle:

[0152] exist Under the conditions of 0.068 MPa, 20% threshold, and 20 s single pulse, a denser structure was constructed. The capping layer and a higher Si–O–Ti ratio, while maintaining bed stability and controllable residue through stricter exhaust gas and pressure waveform control.

[0153] Equipment and Calibration:

[0154] Add 50 mL of buffer volume to the absolute pressure circuit to flatten it. Waveform; the exhaust gas cold trap is upgraded to a two-stage series connection (-30°C, -78°C) to improve the volatile matter capture efficiency; the rest of the calibration is the same as in Example 1 above.

[0155] Raw materials and proportions:

[0156] Same as in Example 1 or Example 2 above; the standing time of S2 is extended to 45 min to ensure sufficient coordination, with a target P:Ti≈0.10.

[0157] Process steps:

[0158] Step S1: Drying and Replacement (Inert gas includes, but is not limited to, nitrogen / argon):

[0159] Same as in Example 1 above; at the end, maintain isobaric pressure for 5 minutes and check that the absolute pressure drift is ≤0.0005MPa.

[0160] Step S2: Low-temperature solvent-free phosphine coordination:

[0161] 40℃ 1.0 L / min, solvent-free contact for 2 h, stand for 45 min; DRIFTS fluctuation 4.9 ± 0.5%; XPSP:Ti = 0.100 ± 0.006. The higher P:Ti and greater fluctuation in step S2 indicate that the surface is approaching saturated coordination, which is beneficial for site selection during subsequent high-strength grafting.

[0162] Step S3 Pulse-based gas-solid grafting (main difference):

[0163] set up =0.068MPa, T=70℃; online infrared spectral threshold=20%; single pulse 20s, interval 90s, total 10 pulses; =0.0031-0.0032MPa; Hold pressure for 5 minutes; Automatic fault switching: If the threshold is not reached twice consecutively, extend the duration of each fault to 22 seconds; If the threshold is still not reached, pause and resume execution. The cleanup sequence was 12 L / min + Ar for 12 min. In step S3, a 20% threshold brought the reaction closer to the diffusion-limited end, combined with higher... Forming a thicker Through buffer volume and strict control To avoid localized condensation and aggregation.

[0164] Alternating purging and stabilization afterwards:

[0165] Alternating blowdown: 12 min → Ar 12 min, until exhaust gas 8 ppmv; 55℃, nano zinc stearate 0.25 wt%, 6 min; Purge for 5 minutes. In this embodiment 3, the post-alternating purging and deeper stabilization grafting require a longer desorption path; the two-stage cold trap reduces the exhaust load.

[0166] Step S4: Fluidized bed aging

[0167] At 50℃ and apparent gas velocity 1.2× Fluidization was carried out for 6 hours, with bed temperature fluctuations ≤1.0℃; 19.74g of powder was collected.

[0168] Online recording and release:

[0169] focus on Is the overshoot of the waveform at the pulse switching point less than 0.0004 MPa?

[0170] Release criteria: Surface Si 4.3–4.4 wt%; Si–O–Ti 52–55%; 4.2–4.8 nm; water contact angle ≥101°; titratable chlorine ≤0.035 wt%; particle size RSD ≤11.0%.

[0171] Deviation handling: If If a slow rise >0.0036 MPa occurs: reduce the carrier gas flow rate to 0.9 L / min and extend the interval to 110 s; if necessary, implement [further measures]. Clean the line for 10 minutes. If the exhaust gas is still >10ppmv after the two-stage cold trap: check the pulse valve seal and switch to 14×14 alternating purging until the standard is met.

[0172] Original Record Table 3 (10 pulses)

[0173]

[0174] Standards and Statistics:

[0175] Water contact angle: 101.5±0.4°; Surface Si: 4.38±0.05wt%. =0.16wt%; Acid site decrease: 34.2±1.2%; Si–O–Ti: 54±3%; Thickness: 4.5±0.3nm; Titratable chlorine: 0.030±0.003wt%; RSD = 10.5 ± 0.4%, fine powder < 10 The content is 1.00±0.07wt%, and the loose bulk density is 0.34±0.01g / mL; n=3.

[0176] Evaluation of propylene gas-phase polymerization:

[0177] 1L reactor, 70℃ =2.0MPa, =0.10MPa; catalyst 0.200g, =15:1. 24-hour continuous operation: =98.4±0.1%, melt flow rate 11.3±0.4 g / 10 min, hydrogen sensitivity slope 13.6±0.5 g / 10 min The activity retention rate was 89.4 ± 0.9%.

[0178] Control system:

[0179] Control A (siloxane grafting only; no DPPE; continuous single-pass feeding)

[0180] Conditions: 0.065 MPa, 70℃, continuous feeding until... =1.00 mg / g, without pulse and threshold control; other calibers are the same as in the above embodiments.

[0181] Results: Surface Si 3.25±0.09wt%, =0.35wt%; water contact angle 96.0±0.5°; acid site reduction 18.3±1.0%; Si–O–Ti 38±3%; Thickness 2.4±0.3nm; titratable chlorine 0.070±0.005wt%; RSD = 17.2 ± 0.7%, fine powder 2.00 ± 0.12 wt%. =96.8±0.3%; Activity retention rate 80.2±1.5%; Hydrogen sensitivity slope 9.0±0.5g / 10 .

[0182] Compared with A The curves, XPS peaks, and particle size distribution are shown in the figures below. Figure 11 , Figure 7 and Figure 15 ; 14h yield and pressure drop are shown in Figure 13 The melt flow rate-hydrogen partial pressure fitting is shown in [link to fitting]. Figure 14 .

[0183] Control B (DPPE and siloxane are mixed and contacted together in a single step; no sequence or pulse).

[0184] Conditions: 0.065 MPa, 70℃, single mixing contact for 30 min; other conditions are the same as those for the same diameter.

[0185] Results: Surface Si 3.70±0.07wt%, =0.28wt%; water contact angle 98.0±0.4°; acid site reduction 24.0±1.1%; Si–O–Ti 44±2%; Thickness 3.0±0.2nm; titratable chlorine 0.055±0.004wt%; RSD 14.5 ± 0.6%; Fine powder 1.60 ± 0.10 wt% =97.4±0.2%; Activity retention rate 83.5±1.3%; Hydrogen sensitivity slope 10.8±0.4g / 10 .

[0186] Compared to B The curves, XPS peaks, and particle size distribution are shown in the figures below. Figure 11 , Figure 7 and Figure 15 ; 14h yield and pressure drop are shown in Figure 13 The melt flow rate-hydrogen partial pressure fitting is shown in [link to fitting]. Figure 14 .

[0187] Spectral criteria and quantitative parameters:

[0188] DRIFTS coordination characteristics (40℃, Table 4

[0189]

[0190] XPS high-resolution fitting (AI K) Table 5

[0191]

[0192] Table 6 Total acid site changes

[0193]

[0194] The comprehensive comparison and statistics of the examples, and the graphical representation of each key indicator, can be found in the following figures. Figures 10 to 15 .

[0195] Comparison of key surface indicators and performance (n=3, mean ± SD) Table 7

[0196]

[0197] Comprehensive Comparison Table (Examples 1-3 vs. Controls A / B) 8

[0198]

[0199] Results and statistics:

[0200] Example 2: Distribution of Si relative to control B Si–O–Ti Significant improvements were observed in activity retention rate and hydrogen sensitivity slope (p < 0.05). Example 3 showed improvement in all indicators compared to Control B (p < 0.01). Example 3 showed significant improvements compared to Control A in titratable chlorine, fine powder ratio, and activity retention rate (p < 0.05).

[0201] Key points of instrument curves:

[0202] During pulse switching in Examples 1-3, the pressure was maintained at 0.0031–0.0036 MPa (see details). Figure 4 (As shown) Example 3 is the most stable. Reducing the online infrared spectral threshold from 30% to 20% results in a more complete surface reaction without excessive residue. Alternating purging endpoint criteria ensure that the total organosilicon in the exhaust gas is ≤10 ppmv. Closed-loop triggering significantly reduces Si distribution. (0.16-0.25wt%) and improve particle size RSD and fine powder control; see the corresponding EDS thermal diagram. Figure 10 The Si–O–Ti ratio and Thickness within a 2-5nm window and The activity retention rate is positively correlated; see [reference]. Figure 7 and Figure 9 The polymerization result curve is shown below. Figure 13 Melt flow rate - hydrogen partial pressure (see...) Figure 14 .

[0203] It should be noted that, in some embodiments, the online infrared spectroscopy closed-loop trigger threshold is 20% to 30%; the alternating purge endpoint criterion is 5 to 10 ppmv; the dual indexes of S2 arrival are P:Ti = 0.05–0.10 and DRIFTS fluctuation of 2–5%; the standard deviation of surface Si distribution is 0.16–0.25 wt%; and the Si–O–Ti ratio is 45% to 55%. 2-5nm thickness with dual locking; nano-Zn-stearate dry powder atomized for 6 min, 0.25wt% and titratable chlorine 0.03–0.05wt%; and Each 1-3 ppmv, dew point -75 to -70°C, and no solvent throughout; ≥97.5%, activity retention rate 85-95%. Hydrogen sensitivity slope 10–14 g / 10 At 70℃, =2.0MPa =0.10MPa window.

[0204] It should be noted that in Examples 1-3, the process of "phosphine coordination first, followed by siloxane" was adopted: DPPE preferentially occupies Ti sites under low-energy conditions of 40°C, and the DRIFTS and P:Ti indices verify its effectiveness; subsequently, siloxane grafting tends to form Si–O–Ti bonds around the coordinated center, reducing non-selective adsorption and competitive passivation.

[0205] It should be noted that in embodiments 1-3, the "pulse + online threshold" approach ensures that the instantaneous surface voltage is controllable, while the online threshold... A decrease to 20–30% corresponds to the transition zone where the reaction rate shifts from chemical control to diffusion control, thus avoiding excessive residue while ensuring sufficient bonding. The narrow width indicates that the bed is in a stable fluidized state.

[0206] It should be noted that the alternating purging and nano-stabilization in Examples 1-3 serve the following purposes: / Ar alternation enhances the desorption driving force; nano-zinc stearate atomization captures trace chlorides at 55°C, reducing titratable chlorine to 0.03–0.05 wt%, and passivates strong acid sites, which is beneficial for maintaining the activity of subsequent long-cycle polymerization.

[0207] It should be noted that in embodiments 1-3, P:Ti, Si–O–Ti, As the thickness and water contact angle gradually increase, the in-plane standard deviation of Si on the surface gradually decreases, and the particle size RSD decreases synchronously with the fine powder segment, reflecting "lower threshold, "Higher and longer single-pass" have a positive correlation with layer density and uniformity; at the same time, residual and pressure drop fluctuations are suppressed through purging and cold trap strategies.

[0208] It should be noted that the embodiments of the present invention have better implementability and are not intended to limit the present invention in any way. Any person skilled in the art may use the above-disclosed technical content to change or modify it into equivalent effective embodiments. However, any modifications or equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method of modifying a composite polypropylene catalyst, characterized by, The method comprises the following steps: Step S1: drying a carrier composed of titanium tetrachloride and magnesium chloride under the protection of an inert gas at 100 ℃ for 3 h, and the dew point of the inert gas is -70 to -60 ℃; Step S2: contacting the support obtained in step S1 with diphenylphosphine ethane in a solvent-free manner at 40 °C for 2 h, the mass ratio of diphenylphosphine ethane to support being 1:20, the water content of the system being 20 to 30 , so as to make the titanium active centers on the surface of the support preferentially be located therein; Step S3: introducing linear methylphenylsiloxane by pulse gas-solid contact at 70 ℃ under an absolute pressure of 0.062 to 0.068 MPa, a total of 10 pulses, each feeding lasting for 15 to 20 s, and the interval between adjacent two feedings being 90 s, and the total silicon addition amount being 1.00 mg / g in terms of silicon element and based on the mass of the carrier, so as to form a continuous hydrophobic layer on the surface of the carrier; The linear methylphenylsiloxane has a linear structure, the molar fraction of phenyl is 30 to 40 mol%, and the number average molecular weight Mn is 700 to 850 g / mol; Step S4: aging for 6 h in a fluidized bed at 50 ℃ under the protection of nitrogen to obtain a modified catalyst; The sequence of steps is first step S2 and then step S3, the water contact angle of the catalyst after step S3 is 98 to 102°, and the surface silicon content is 3.5 to 4.5 wt%, relative to the sample treated by step S2 The total acid site density decreases by 25 to 35% after step S3.

2. The modification method according to claim 1, characterized by, The surface P:Ti atomic ratio measured by X-ray photoelectron spectroscopy after the end of step S2 is 0.05 to 0.10, and the fluctuation range of the peak area of the coordination characteristic of diphenylphosphine ethane and titanium within 20 to 30 min is 2% to 5% under in-situ infrared monitoring.

3. The modification method of claim 1, wherein, Each pulse feeding of step S3 is triggered by the change rate of the absorbance of the linear methylphenylsiloxane characteristic peak in the outlet gas phase monitored by an online infrared, and the next feeding is started when the absorbance decreases to 20% to 30% of the value at the start of this pulse, until the predetermined number of pulses is completed.

4. The modification method of claim 1, wherein The fluidized aging of step S4 adopts a superficial gas velocity of 1.0 to 1.2 times the minimum fluidization velocity, the bed temperature fluctuation is 0.5 to 1.0 ℃, and the standard deviation of the surface silicon content calculated by energy spectrum area scanning is 0.15 to 0.25 wt%.

5. The modification method of claim 1, wherein After the end of step S3, alternating purging is carried out, first purging with nitrogen for 8 to 12 min, and then purging with argon for 8 to 12 min, and the purging is ended when the total organic silicon content in the outlet gas decreases to 5 to 10 ppmv.

6. The modification method of claim 1, wherein, After the completion of step S3, nano zinc stearate with a primary particle size of 80 to 120 nm is sprayed in a dry powder atomization manner at 55 ℃, the treatment time is 6 min, the treatment agent dosage is 0.25 wt% of the mass of the modified catalyst, and the titratable chlorine content measured by titration is 0.03 to 0.05 wt%.

7. The modification method of claim 1, wherein The steps S2 and S3 are solvent-free throughout, and the nitrogen used is 1 to 3 ppmv, 1 to 3 ppmv, and a dew point of -75 to -70°C.

8. The modification method of claim 1, wherein, The isotacticity of the resulting polymer was 97.5% to 98.5%, the 24 h activity retention was 85% to 90%, and the slope of the melt flow rate versus hydrogen partial pressure was 10 to 14 g / 10 min / MPa under the propylene gas phase polymerization conditions at 70°C and a total pressure of 2.0 MPa and a hydrogen partial pressure of 0.10 MPa. .

9. The modification method of claim 1, wherein, The surface formed by the step S3 The layer thickness is 2 to 5 nm, determined by X-ray photoelectron spectroscopy With The Si-O-Ti bonding component obtained by peak fitting accounts for 45% to 55% of the total peak area of the surface The Si-O-Ti bonding component obtained by peak fitting accounts for 45% to 55% of the total peak area of the surface

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