Plant metal complex base catalyst and its application in preparation of alkyl hydrogen-rich fuel

Abstract

The application discloses a plant metal composite catalyst and application thereof in preparation of alkyl hydrogen-rich fuel, and belongs to the technical field of methanol fuel and catalysts thereof.The catalyst is prepared by fermenting and hybridizing plant fibers, nano zeolites and organic nutrient substances through specific composite microbial agents to form a uniform symbiotic precursor; then, the uniform symbiotic precursor is subjected to purification and activation treatment to obtain a biochar-zeolite composite carrier with multistage pores; finally, the biochar-zeolite composite carrier is kneaded with an organic ligand metal complex solution to form a catalyst, and the catalyst is calcined at low temperature in the presence of hydrogen.The catalyst realizes high dispersion and anchoring of metal nanoparticles on the biochar-zeolite composite carrier, and creates closely cooperative acid sites and metal sites.When the catalyst is used to catalyze the reaction of methanol and various hydrocarbon oils, the catalyst can efficiently promote alkylation, isomerization and hydrogenation reactions, and generate clean alkyl hydrogen-rich fuel mainly composed of high-octane isomeric alkanes and containing very low content of olefins.

Description

Technical Field

[0001] This invention relates to the field of methanol-to-fuel and catalyst technology, and particularly to plant-metal composite catalysts and their application in the preparation of alkyl hydrogen-rich fuels. Background Technology

[0002] With the continued growth of global energy demand and increasing environmental awareness, developing clean, efficient, and renewable alternative fuels has become an urgent task for scientific research and industry. Traditional petroleum-based fuels suffer from incomplete combustion, high sulfur content, and high levels of aromatics and olefins, resulting in large emissions of pollutants that do not meet the requirements of sustainable development.

[0003] Methanol, a widely available and inexpensive chemical raw material, can be derived from coal, natural gas, and biomass. Its high hydrogen-to-carbon ratio and oxygen-rich characteristics make it an ideal fuel precursor. The catalytic reaction of methanol with various petroleum fractions (such as naphtha and light crude oil) to produce high-octane clean fuels is a highly promising technological direction.

[0004] However, this technological approach faces the following key challenges:

[0005] 1) Feedstock compatibility and mass transfer barriers: Methanol and hydrocarbon oils have vastly different polarities, and after physical mixing, they easily separate into layers, forming a heterogeneous system. This severely hinders the co-adsorption and effective contact of reactant molecules at the active sites of the catalyst, resulting in low reaction efficiency and an increase in side reactions.

[0006] 2) Catalyst performance bottlenecks: Traditional hydrogenation or reforming catalysts typically use inorganic oxides such as γ-Al₂O₃ as supports, and then load noble metals or transition metals through impregnation. These catalysts have the following inherent drawbacks:

[0007] 3) Poor synergy between acidic and metallic sites: Physical impregnation makes metal particles prone to agglomeration and sintering, and the acidic centers and hydrogenation / dehydrogenation centers are spatially unevenly distributed, making it difficult to form an efficient "tandem" catalytic effect.

[0008] 4) Simple pore structure: mainly micropores, which is not conducive to the diffusion and mass transfer of macromolecular reactants and is prone to coking and deactivation.

[0009] 5) Cost and sustainability issues: They rely on non-renewable mineral supports, and high-performance catalysts often contain precious metals, resulting in high costs.

[0010] In recent years, biomass-derived carbon materials have been regarded as promising catalyst supports due to their advantages such as renewable sources, high specific surface area, and tunable pore structure. However, simply physically mixing biochar and zeolite results in weak interfacial bonding between the two, making it impossible to construct a stable and synergistic composite structure, and metals are also difficult to disperse highly on it.

[0011] Therefore, developing a novel catalyst preparation method that can fundamentally solve the problem of raw material compatibility and construct catalysts with excellent pore structure, highly dispersed active sites, and superior acid-base / metal synergistic catalytic performance is crucial for promoting the development of alkyl hydrogen-rich fuel technology. Summary of the Invention

[0012] To address the shortcomings of existing technologies, this invention attempts to construct a novel plant-metal composite catalyst by organically combining bio-fermentation hybridization with coordination chemistry regulation. Coupled with an optimized raw material pretreatment process, it achieves efficient and targeted synthesis of high-performance alkyl hydrogen-rich fuels. In other words, it proposes a plant-metal composite catalyst and its application in the preparation of alkyl hydrogen-rich fuels.

[0013] To achieve the above objectives, the present invention adopts the following technical solution:

[0014] This invention first proposes a method for preparing a plant-metal composite catalyst, comprising the following steps:

[0015] Step A1. Preparation of fermentation hybrid precursors:

[0016] Plant fiber powder, zeolite molecular sieve, and organic nutrients are mixed in a mass ratio of 5:(2-4):(3-5). A compound microbial agent accounting for 1-3% of the total mass is added to the mixed raw materials, and water is added to adjust the solid content to 10-20%. Fermentation is carried out at 35-38℃ under limited oxygen conditions for 72-96 hours until the pH of the system stabilizes at 4.0-4.5, resulting in a viscous fermentation hybrid precursor.

[0017] Plant fiber, zeolite molecular sieve and organic nutrients are converted into a homogeneous organic-inorganic hybrid slurry through microbial fermentation.

[0018] Step A2. Purification and activation of the precursor:

[0019] The fermentation hybrid precursor obtained in step A1 is spread in a ceramic or bamboo container and placed in a ventilated and light-transmitting place for "sun exposure and night leakage" treatment for 3 to 7 days. The resulting residue is separated into solid and liquid by pressure filtration or centrifugation to further remove moisture and soluble impurities, and a purified solid material is obtained. The solid material is then preliminarily dried at 80-105℃ until the moisture content is less than 15% to obtain purified and dried fermentation hybrid powder.

[0020] During the day, sunlight and ventilation are used to evaporate moisture and transform substances; at night, the ambient temperature drops, and moisture in the air condenses and permeates on the surface of the material ("night leakage"). This process can dissolve and remove some soluble ash (such as potassium salts and chloride ions) and excess organic acids produced by fermentation.

[0021] Step A3. Metal Complexation and Forming:

[0022] The fermented hybrid powder is thoroughly mixed with the pre-prepared Cu-Zn-Al metal complex solution in a kneader until a uniform paste is formed. The paste is then granulated into spherical catalyst blanks with a diameter of 1-3 mm using a granulator.

[0023] The mixing here is a "solid-liquid" mixture, where the metal complex solution serves as both an active metal source and a binder;

[0024] Step A4. Calcination and activation:

[0025] The shaped spherical catalyst preform was reduced in a hydrogen atmosphere at 250-350℃ for 2-4 hours to obtain a plant-metal composite catalyst.

[0026] During calcination, plant fibers and fermented organic matter carbonize to form biochar interwoven with zeolite; metal complexes decompose and transform into metal oxide nanoparticles with reduced metal states on their surfaces; the calcined catalyst can be used directly, and the biochar component in the catalyst provides excellent mesoporous mass transfer channels, reducing the residence time of reactants and products; at the same time, the in-situ hydrogenation capability provided by the Cu-Zn-Al component can saturate unstable intermediates (such as enaldehydes and enols) in a timely manner, inhibiting carbon deposition from the source, and extending the catalyst's single-pass life by more than 50%.

[0027] Preferably, the plant fiber is straw, rice husk, etc.; the zeolite is nano HZSM-5; and the organic nutrients are a mixture of molasses and soybean meal in a mass ratio of 1:(3-5).

[0028] Preferably, the compound microbial agent comprises Trichoderma reesei, lactic acid bacteria and Bacillus subtilis mixed in a colony ratio of 1:(0.5-0.8):(1.2-1.6).

[0029] Preferably, the metal complex solution is generated by reacting soluble salts of copper, zinc, and aluminum with organic ligands in solution, wherein the organic ligands include any of citric acid, oxalic acid, glycine, or ethylenediaminetetraacetic acid.

[0030] Preferably, the molar ratio of Cu, Zn and Al in the metal complex solution is 1:(0.5-0.8):(2.2-2.5); and the total metal concentration in the metal complex solution is 0.1-1.0 mol / L.

[0031] This invention also proposes the plant-metal composite catalyst obtained by the aforementioned preparation method and its application in the preparation of alkyl hydrogen-rich fuels, the application including the following steps:

[0032] Step S1. Preparation of feedstock oil:

[0033] Methanol and high-calorific-value light materials were mixed at high speed with a mass ratio of (6-8):(2-4) to obtain a turbid liquid (which quickly separated into layers upon standing). Immediately, a surfactant accounting for 1% of the total weight of the system was added dropwise. After stirring and mixing, a stable, non-layered, semi-transparent solution system of raw material oil was formed.

[0034] Step S2. Preparation of feedstock oil:

[0035] A plant-metal composite catalyst was loaded into a fixed-bed reactor, and the feedstock oil was fed at a feedstock weight hourly space velocity (WHSV) of 0.5-2.0 h⁻¹. -1 The fuel is pumped into a reactor at a temperature of 150-250℃ and a pressure of 0.5-2.0 MPa to obtain alkyl hydrogen-rich fuel.

[0036] The plant-metal composite catalyst of this invention is a multifunctional nanocomposite material constructed through a bio-chemical synergistic method. The catalyst support is not physically mixed, but rather hybridized at the molecular level with nanoscale HZSM-5 zeolite and degrading plant fibers and their metabolites through a microbial fermentation process. Subsequent processing forms a three-dimensional network of interwoven biochar and zeolite. This structure may have the following characteristics:

[0037] 1) Strong acidity of zeolite: provides abundant and controllable Brønsted and Lewis acid sites.

[0038] 2) Multilevel pores of biochar: It inherits the natural pores of plant fibers and forms a large number of mesopores and macropores due to fermentation and carbonization, which form a continuous system with the micropores of zeolite.

[0039] 3) Excellent stability: The biochar "matrix" firmly encapsulates the zeolite "particles", preventing phase separation or loss of components under reaction conditions.

[0040] 4) Active sites: Highly dispersed and strongly anchored metal nanocenters. Transition metals (Cu, Zn, Al) do not exist in the form of simple salts, but first form complexes with organic ligands, and then are uniformly loaded onto the hybrid precursor through a kneading process. After low-temperature hydrogen reduction, small and uniformly distributed metal or metal oxide nanoparticles are formed. These nanoparticles are firmly anchored at the biochar-zeolite interface and within the pores, exhibiting strong resistance to sintering and migration.

[0041] 5) "Acidic site-metal site" coordination: The acidic centers of the catalyst (mainly located on the zeolite) and the hydrogenation / dehydrogenation centers (metal nanoparticles) are not spatially isolated, but are designed in a nanoscale proximity range through precise preparation processes, forming microscopic "synergistic catalytic units".

[0042] Based on the aforementioned unique structure, the specially designed catalyst of this invention exhibits excellent catalytic performance in the synthesis of alkyl hydrogen-rich fuels. Given its directed design, which primarily produces isoalkanes, its mechanism of action is speculated to be a multi-step, multi-active-site synergistic catalytic process.

[0043] 1) Efficient diffusion and adsorption of reactants:

[0044] The homogenized methanol-hydrocarbon feedstock enters the catalyst's three-dimensional hierarchical pore system under pressure. The macropores and mesopores provided by biochar act as "highways," ensuring that reactant molecules rapidly approach the active region; while the micropores of zeolite act as "precision reaction chambers," performing shape-selective adsorption and pre-activation of molecules.

[0045] 2) Acidic sites initiate C-C bond construction and reconstruction:

[0046] Methanol molecules adsorbed on the strongly acidic sites of zeolite first dehydrate to form dimethyl ether, which is then converted into low-carbon olefins (such as ethylene and propylene). Simultaneously or sequentially adsorbed hydrocarbon molecules (such as straight-chain alkanes and alkenes in naphtha) undergo cracking and skeletal isomerization reactions at the acidic sites. The newly generated low-carbon olefins undergo alkylation reactions with hydrocarbon fragments in the feedstock at the acidic centers. This is a key step in constructing high-octane branched-chain alkanes (isoalkanes).

[0047] 3) Rapid hydrogenation saturation is achieved at metal sites:

[0048] Olefin intermediates generated during alkylation, cracking, and other reactions are highly reactive. If not stabilized promptly, they are prone to excessive cracking, polymerization, and coking, leading to catalyst deactivation and the production of undesirable components. In such cases, due to the high dispersion of metal nanoparticles and their close proximity to acidic centers at the nanoscale, these reactive olefin intermediates can migrate to nearby metal active sites without long-range diffusion. Under the hydrogenation action of the metal sites (Cu-Zn, etc.), the olefin intermediates are rapidly and efficiently hydrogenated to saturation, generating stable, high-octane isoalkanes.

[0049] 4) Synergistic effect and inhibition of side effects:

[0050] The nanoscale tandem cycle of olefin formation at acidic sites → hydrogen saturation at metal sites is the core of the high selectivity of this catalyst. It enables precise control of the reaction pathway, cuts off the pathways of olefin accumulation and coking, thereby significantly improving the selectivity of the target product—isoalkanes, reducing the formation of byproducts (olefins and aromatics), and greatly extending the catalyst lifetime.

[0051] In summary, the catalyst of this invention achieves a highly efficient generation-stabilization tandem catalytic mechanism through its unique integrated composite support, highly dispersed anchored metal, and nanoscale synergy, thereby enabling the directional, efficient, and stable production of high-quality alkyl hydrogen-rich fuels (subsequently, depending on the reaction conditions, hydrogen may be added during the catalytic process, which may further increase the hydrogen content of the fuel, but the conditions need further verification).

[0052] Preferably, the surfactant is any of triethanolamine, diethyl adipate, or polyethylene glycol (PEG-400). Its polar groups (-OH / -NH2) and weakly hydrophobic carbon chain structure can act as an "oil-water bridge" to reduce the interfacial tension between methanol (strongly polar) and naphtha (non-polar), promote the formation of a semi-homogeneous system between the two phases, reduce mass transfer resistance, and perfectly match experimental phenomena (such as delayed layering and prolonged homogeneous maintenance time after stirring).

[0053] Preferably, the high-calorific-value light feedstock includes naphtha, light crude oil, condensate, Fischer-Tropsch light fraction, or reformate residue.

[0054] Naphtha, commonly known as "crude gasoline," is a light oil product obtained during petroleum refining. Its boiling point range is between that of gasoline and kerosene, and it usually refers to a mixture of hydrocarbons with a distillation range of about 30°C to 200°C.

[0055] Light crude oil: Light crude oil produced by some oil fields does not require complex atmospheric and vacuum distillation and can be used directly.

[0056] Condensate oil: a byproduct of natural gas extraction, with extremely light components, making it an excellent raw material.

[0057] Fischer-Tropsch synthesis light fractions: byproducts of coal-to-oil or natural gas-to-oil processes, with high content of n-chain alkanes but low octane numbers, which can be perfectly upgraded through this process.

[0058] Reforming residue oil: rich in alkanes and cycloalkanes, it is an ideal feedstock for increasing octane number.

[0059] Compared with the prior art, the beneficial effects of the present invention are:

[0060] 1. This invention creatively utilizes a microbial fermentation process to hybridize plant fibers (straw) with nano-zeolite (HZSM-5) at the molecular / nanoscale, constructing a three-dimensional, interconnected, multi-level porous composite carrier. Cellulase and hemicellulase secreted by strains such as *Trichoderma reesei* degrade the straw into oligosaccharides and organic acids. These products, together with biopolymers (such as proteins and polysaccharides) formed by the microbial cells themselves, constitute a "bio-glue," firmly embedding and encapsulating the nano-zeolite particles within the forming biochar precursor network. This process results in a homogeneous, symbiotic hybrid, rather than a simple physical mixture.

[0061] 2. The catalyst of this invention utilizes natural ligands such as organic acids and polysaccharides produced during fermentation, which synergistically interact with subsequently introduced organic ligands such as citric acid, oxalic acid, or EDTA to react with metal ions (Cu). 2+ Zn 2+ Al 3+ Stable metal complexes are formed, achieving high dispersion and stable anchoring of the metal active centers. These complexes are uniformly fixed on the organic-inorganic framework of the hybrid precursor through ligand exchange, hydrogen bonding, and other forces. In the subsequent low-temperature hydrogen atmosphere calcination, the organic part is partially carbonized or removed, while the metal is reduced in situ in the form of nanoparticles and firmly anchored on the biochar-zeolite composite support, effectively preventing migration and aggregation at high temperatures.

[0062] 3. The catalyst of this invention achieves a synergistic catalytic effect between acidic and metal sites. Nano-HZSM-5 zeolite provides strong Brønsted and Lewis acidic centers, responsible for methanol dehydration, hydrocarbon cracking, isomerization, and alkylation reactions. Highly dispersed metal sites (such as Cu-Zn) are responsible for the rapid hydrogenation saturation of olefin intermediates. The core advantage of this catalyst lies in the fact that, through fermentation hybridization, the acidic centers (zeolite) and metal nanoparticles are "integrated" in a nanoscale adjacent space. This forms a highly efficient "microreactor," allowing olefin intermediates generated by the acidic centers to be hydrogenated and saturated into stable isoalkanes by adjacent metal sites without long-range diffusion.

[0063] 4. This invention also adds a small amount of surfactants such as triethanolamine and PEG-400, which utilize their amphiphilic structure to form a stable molecular film at the interface between methanol and oil phase, reducing interfacial tension and forming a thermodynamically stable microemulsion or colloidal solution system, thus solving the compatibility problem of methanol-hydrocarbon systems.

[0064] 5. In summary, this invention, through three core technologies—biological hybridization to construct a multi-level porous carrier, coordination chemistry to achieve high metal dispersion, and surfactant stabilization of the raw material system—synergistically solves the core problems of poor raw material compatibility, low catalyst activity and selectivity, and short lifespan in existing technologies. It successfully prepares high-octane, low-olefin, and long-life high-quality alkyl hydrogen-rich fuel, which has significant application value in the energy and chemical industry. The reaction is guided towards the formation of isoalkanes with a high H / C ratio, while maximally suppressing the formation of low H / C ratio components (olefins, aromatics) and low-calorific-value components (oxygen-containing compounds), truly achieving a balance between hydrogen richness and combustion stability. Detailed Implementation

[0065] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with existing known technologies. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0066] I. Preparation of plant-metal composite catalysts:

[0067] Preparation Example 1 (Standard Catalyst):

[0068] Step A1. Preparation of fermentation hybrid precursors:

[0069] Raw material ratio: Straw powder: Nano HZSM-5: Organic nutrients = 5:3:4;

[0070] Organic nutrients: Molasses: Soybean meal = 1:4 (by weight);

[0071] The dosage of compound microbial agent is 2% of the total mass of the mixed raw materials.

[0072] Microbial ratio: Trichoderma reesei: Lactic acid bacteria: Bacillus subtilis = 1:0.6:1.4 (colony count ratio); add water to adjust the solid content to 15%;

[0073] Fermentation conditions: 36℃, under limited oxygen conditions, for 84 hours;

[0074] Endpoint pH: 4.2;

[0075] Product state: A viscous, uniform, brownish-brown paste with a fermented sour aroma was obtained.

[0076] Step A2. Purification and activation of the precursor:

[0077] The precursor was spread flat in a bamboo container and subjected to "sun-drying and night-leaking" treatment in a well-ventilated and light-transmitted place for 5 days; then it was filtered to obtain wet residue; and then dried at 100℃ to a moisture content of 12% to obtain purified and dried fermented hybrid powder.

[0078] Product state: loose dark brown powder, without obvious lumps.

[0079] Step A3. Metal Complexation and Forming:

[0080] Preparation of metal complex solution:

[0081] Metal salts: copper nitrate, zinc nitrate, aluminum nitrate;

[0082] Organic ligand: prepared by mixing citric acid and oxalic acid in a molar ratio of 1:1;

[0083] Metal molar ratio: Cu:Zn:Al = 1:0.6:2.3;

[0084] Total metal concentration: 0.5 mol / L;

[0085] The fermented hybrid powder and the metal complex solution were mixed in a kneader at a liquid-to-solid ratio of 0.8:1 (mL / g) and kneaded until a uniform and plastic paste was formed. The paste was then extruded through a granulator and cut into spherical blanks with a diameter of 2 mm.

[0086] Green body condition: a dark green sphere with a smooth surface and moderate strength.

[0087] Step A4. Calcination and activation:

[0088] The billet was placed in a tube furnace and reduced under a pure hydrogen atmosphere (flow rate 50 mL / min).

[0089] Procedure: Increase the temperature from room temperature to 300℃ at a rate of 2℃ / min, and maintain the temperature at 300℃ for 3 hours.

[0090] After naturally cooling to 50°C, it is removed under nitrogen protection.

[0091] Final catalyst: It consists of dark gray spherical particles with slight magnetic properties.

[0092] Preparation Example 2 (High Biochar Content Catalyst):

[0093] The proportion of plant fiber was increased based on Preparation Example 1 in order to enhance the mesoporous structure and mass transfer capacity of the catalyst.

[0094] Step A1:

[0095] Raw material ratio: Straw powder: Nano HZSM-5: Organic nutrients = 6:2:4;

[0096] Compound microbial agent addition amount: 2.5%;

[0097] Solid content: 18%;

[0098] The remaining steps are the same as in Preparation Example 1.

[0099] Step A2: Same as in Preparation Example 1.

[0100] Step A3:

[0101] The preparation of the metal complex solution is the same as in Example 1.

[0102] The liquid-to-solid ratio was adjusted to 1.0:1 (mL / g) to accommodate higher organic content.

[0103] Step A4: Same as in Preparation Example 1.

[0104] Catalyst characteristics: This catalyst is expected to have a more developed mesoporous structure (from more biochar), which is conducive to the diffusion of macromolecular reactants, but the number of acidic sites per unit mass (from zeolite) may be slightly reduced.

[0105] Preparation Example 3 (High Acidity / High Metal Dispersion Catalyst):

[0106] Based on Preparation Example 1, the proportion of zeolite was increased and the metal loading was optimized to enhance acid catalytic activity and metal dispersion.

[0107] Step A1:

[0108] Raw material ratio: Straw powder: Nano HZSM-5: Organic nutrients = 5:4:4;

[0109] Fermentation time was extended to 96 hours to ensure full hybridization.

[0110] The rest is the same as in Preparation Example 1.

[0111] Step A2: Same as in Preparation Example 1.

[0112] Step A3:

[0113] Metal molar ratio: Cu:Zn:Al = 1:0.7:2.4;

[0114] Ethylenediaminetetraacetic acid (EDTA) is used as the main ligand, and its strong complexing ability ensures high dispersion of the metal.

[0115] Total metal concentration: 0.8 mol / L;

[0116] Liquid-to-solid ratio: 0.7:1 (mL / g);

[0117] Step A4: Same as in Preparation Example 1.

[0118] Catalyst characteristics: This catalyst is expected to have more acidic centers and more dispersed metal nanoparticles, making it particularly effective for reactions requiring strong acid centers and efficient hydrogenation (such as olefin saturation).

[0119] Preparation Example 4 (Economical Catalyst):

[0120] Based on Preparation Example 1, while ensuring basic performance, costs were optimized, for example, by shortening processing time and using cheaper ligands.

[0121] Step A1:

[0122] The proportion of soybean meal in organic nutrients was increased (molasses: soybean meal = 1:5) to reduce costs.

[0123] The dosage of compound microbial agent was reduced to 1.5%;

[0124] Fermentation time has been shortened to 72 hours;

[0125] Step A2:

[0126] The "sun exposure and night leakage" period has been shortened to 3 days;

[0127] The drying temperature was increased to 105°C to speed up the process.

[0128] Step A3:

[0129] The total metal concentration decreased to 0.3 mol / L;

[0130] The organic ligand used is glycine, which is less expensive.

[0131] Liquid-to-solid ratio: 0.6:1 (mL / g);

[0132] Step A4:

[0133] The reduction temperature was lowered to 250℃, and the reduction time was shortened to 2 hours.

[0134] Catalyst characteristics: The activity and lifetime of this catalyst may be slightly lower than those of standard catalysts, but the manufacturing cost is significantly reduced. It is suitable for scenarios where product requirements are not extreme and has a high cost-performance ratio.

[0135] Comparative preparation example 1 (physical mixing method):

[0136] Based on Preparation Example 1, the components were directly physically mixed without undergoing the core step of fermentation hybridization, in order to comparatively demonstrate the importance of the biological hybridization process.

[0137] Step B1 (physical mixing):

[0138] Straw powder, nano HZSM-5, dried soybean meal powder, and molasses were directly dry-mixed according to the proportions of Preparation Example 1.

[0139] No compound microbial agents are added, and no fermentation is carried out.

[0140] Step B2:

[0141] The physically mixed powder is directly moistened with water to the same solid content, and then subjected to "sun exposure and night leakage" and drying.

[0142] Product state: The powder components are obviously uneven and have clumps.

[0143] Step A3: Same as in Preparation Example 1.

[0144] Step A4: Same as in Preparation Example 1.

[0145] Catalyst characteristics: Due to the lack of a uniform hybrid structure resulting from microbial fermentation, the biochar and zeolite are loosely bonded, and the metal dispersion is poor. It is expected that the pore structure will be poor, the accessibility of active sites will be low, and the lifespan will be significantly shortened.

[0146] Comparative preparation example 2 (without fermentation step):

[0147] In step A1, no compound microbial agent is added; the mixture is simply physically mixed and then dried directly. The rest of the preparation process is the same as in Example 1.

[0148] Comparative preparation example 3 (without zeolite):

[0149] In step A1, zeolite is not added; only plant fiber and nutrients are fermented. The rest of the preparation is the same as in Example 1.

[0150] Comparative preparation example 4 (conventional impregnation method instead of metal complexation):

[0151] Step A3 was changed to impregnation with an equimolar amount of Cu, Zn, and Al nitrate solution followed by calcination (without organic ligands), and the rest of the preparation was the same as in Example 1.

[0152] Comparative preparation example 5 (high temperature calcination):

[0153] The calcination temperature in step A4 is 500℃ (not 250-350℃), and the rest of the preparation is the same as in Example 1.

[0154] Table 1. Summary of Preparation Examples and Performance Comparison

[0155] ;

[0156] These preparation examples demonstrate that by precisely controlling the process parameters of steps such as fermentation hybridization, purification and activation, and metal complexation, catalysts with different structural characteristics and performance focuses can be prepared in a "directed" manner to meet the needs of processing different raw materials or achieving different product objectives. This fully demonstrates the high degree of flexibility and controllability of this invention in catalyst design and preparation.

[0157] II. Preparation of Alkyl Hydrogen-Rich Fuels:

[0158] Example 1 (Naphtha-based):

[0159] Step S1. Preparation of feedstock oil:

[0160] Methanol and naphtha were mixed at a mass ratio of 7:3 by high-speed stirring to obtain a turbid liquid (which quickly separated into layers upon standing). Triethanolamine, accounting for 1% of the total weight of the system, was immediately added dropwise. After stirring and mixing, a stable, non-layered, semi-transparent solution system of raw oil was formed.

[0161] Step S2. Preparation of feedstock oil:

[0162] The plant-metal composite catalyst prepared in Example 3 was loaded into a fixed-bed reactor, and the feed oil was fed at a feed weight space velocity of 1 h⁻¹. -1 The mixture is pumped into a reactor at a reaction temperature of 200°C and a reaction pressure of 1 MPa to obtain alkyl hydrogen-rich fuel.

[0163] Example 2 (Light Crude Oil Base):

[0164] Step S1. Preparation of feedstock oil:

[0165] Methanol and light crude oil were mixed at a mass ratio of 6:4 by high-speed stirring to obtain a turbid liquid (which quickly separated into layers upon standing). Diethyl adipate, accounting for 1% of the total weight of the system, was immediately added dropwise. After stirring and mixing, a stable, non-layered, semi-transparent solution system of feed oil was formed.

[0166] Step S2. Preparation of feedstock oil:

[0167] The plant-metal composite catalyst prepared in Example 2 was loaded into a fixed-bed reactor, and the feedstock oil was fed at a feedstock weight hourly space velocity (WHSV) of 0.5 h⁻¹. -1 The mixture is pumped into a reactor at a reaction temperature of 150°C and a reaction pressure of 2.0 MPa to obtain alkyl hydrogen-rich fuel.

[0168] Example 3 (Condensate Oil Basis):

[0169] Step S1. Preparation of feedstock oil:

[0170] Methanol and light crude oil were mixed at a mass ratio of 8:2 by high-speed stirring to obtain a turbid liquid (which quickly separated into layers upon standing). Immediately after that, 1% of PEG-400 by weight of the total system was added dropwise. After stirring and mixing, a stable, non-layered, semi-transparent solution system of feedstock oil was formed.

[0171] Step S2. Preparation of feedstock oil:

[0172] The plant-metal composite catalyst prepared in Example 1 was loaded into a fixed-bed reactor, and the feed oil was fed at a feed weight space velocity of 2 h⁻¹. -1 The fuel is pumped into the reactor at a reaction temperature of 250°C and a reaction pressure of 0.5 MPa to obtain alkyl hydrogen-rich fuel.

[0173] Example 4 (Fischer-Tropsch synthesis of light fractions):

[0174] Step S1. Preparation of feedstock oil:

[0175] Methanol and naphtha were mixed at a mass ratio of 7:3 by high-speed stirring to obtain a turbid liquid (which quickly separated into layers upon standing). Diethyl adipate, accounting for 1% of the total weight of the system, was immediately added dropwise. After stirring and mixing, a stable, non-layered, semi-transparent solution system of raw oil was formed.

[0176] Step S2. Preparation of feedstock oil:

[0177] The plant-metal composite catalyst prepared in Example 4 was loaded into a fixed-bed reactor, and the feed oil was fed at a feed weight space velocity of 1 h⁻¹. -1 The mixture is pumped into a reactor at a reaction temperature of 200°C and a reaction pressure of 1 MPa to obtain alkyl hydrogen-rich fuel.

[0178] Example 5 (Based on reformed raffinate):

[0179] Step S1. Preparation of feedstock oil:

[0180] Methanol and reforming raffinate were mixed at a mass ratio of 7:3 by high-speed stirring to obtain a turbid liquid (which quickly separated into layers upon standing). Immediately after that, 1% of PEG-400 by weight of the total system was added dropwise. After stirring and mixing, a stable, non-layered, semi-transparent solution system of feedstock oil was formed.

[0181] Step S2. Preparation of feedstock oil:

[0182] The plant-metal composite catalyst prepared in Example 1 was loaded into a fixed-bed reactor, and the feed oil was fed at a feed weight space velocity of 1 h⁻¹. -1 The mixture is pumped into a reactor at a reaction temperature of 200°C and a reaction pressure of 1 MPa to obtain alkyl hydrogen-rich fuel.

[0183] Comparative Example 1:

[0184] The catalyst was replaced with the plant-metal composite catalyst of Comparative Preparation Example 1, and the rest was the same as in Example 1.

[0185] Comparative Example 2:

[0186] The catalyst was replaced with the plant-metal composite catalyst of Comparative Preparation Example 2, and the rest was the same as in Example 1.

[0187] Comparative Example 3:

[0188] The catalyst was replaced with the plant-metal composite catalyst of Comparative Preparation Example 3, and the rest was the same as in Example 1.

[0189] Comparative Example 4:

[0190] The catalyst was replaced with the plant-metal composite catalyst of Comparative Preparation Example 4, and the rest was the same as in Example 1.

[0191] Comparative Example 5:

[0192] The catalyst was replaced with the plant-metal composite catalyst of Comparative Preparation Example 5, and the rest was the same as in Example 1.

[0193] Comparative Example 6 (without surfactant):

[0194] In step S1, triethanolamine is not added, and the methanol-naphtha mixture is separated before use. The rest is the same as in Example 1.

[0195] Comparative Example 7 (higher temperature):

[0196] The reaction temperature in step S2 is 300°C, and the rest is the same as in Example 1.

[0197] Comparative Example 8 (without surfactant):

[0198] The reaction pressure in step S2 is 0.1 MPa, and the rest is the same as in Example 1.

[0199] III. Performance Analysis of Fuel Products:

[0200] The composition and performance of the fuel products from Examples 1-5 and Comparative Examples 1-8 are summarized in Table 2 below:

[0201] Table 2. Fuel Performance Test

[0202] ;

[0203] Data Analysis:

[0204] 1. The decisive role of catalyst performance:

[0205] Optimal performance (Examples 1 and 3): When using the high-performance catalyst in Example 3 or the standard catalyst in Example 3, and with standard or high-quality feedstocks (naphtha, condensate), the product exhibits the highest isoalkane content (>68%) and the lowest olefin content (<1%). This is attributed to the superior hydrogenation capability provided by the highly dispersed metal sites of the catalyst, which promptly saturates unstable intermediates, and the highly efficient alkylation and isomerization reactions catalyzed by abundant acid centers.

[0206] Performance collapse: Comparative Example 1 using a physically mixed catalyst or Comparative Example 3 without a zeolite catalyst resulted in a surge (>25%) in unreacted methanol and byproducts (other items) in the product, along with a high olefin content. This directly demonstrates that the composite support formed by fermentation hybridization and the acidic centers provided by zeolite are the two cornerstones for the efficient reaction, and neither can be dispensed with.

[0207] 2. The inherent impact of crude oil:

[0208] Examples 3 and 5 use condensate oil and reformate raffinate oil, respectively, which are clean in composition and rich in cycloalkanes or isoalkanes precursors. Therefore, the highest octane number (>100) can be obtained under suitable catalysts.

[0209] The Fischer-Tropsch synthesis oil of Example 4 is rich in straight-chain olefins and alkanes, and its strong hydro-isomerization capability requires a higher degree of severity even when using standard catalysts. When using a less efficient and economical catalyst (Preparation Example 4), the results are characterized by low yield, high byproducts, and short lifespan.

[0210] 3. Influence of process conditions:

[0211] Compared with Example 1, Comparative Example 6, which did not use a surfactant, resulted in impaired mass transfer between the two phases, a decrease in yield, octane number, and lifetime, and an increase in unreacted substances (other items).

[0212] Compared with Example 1, Comparative Example 7, which used an excessively high reaction temperature (300°C), significantly promoted the aromatization reaction, resulting in a surge in aromatic content (15.5%), while also exacerbating cracking and carbon deposition, thus shortening catalyst life.

[0213] Compared with Example 1, the excessively low pressure (0.1 MPa) used in Comparative Example 8 was not conducive to the hydrogenation reaction, resulting in a significant increase in olefin content (7.5%), and may also affect the conversion of methanol, leading to a decrease in yield and lifespan.

[0214] 4. Conclusion:

[0215] As shown in Table 2, and in conjunction with Table 1, a systematic evaluation demonstrates that to obtain high-yield, high-octane, and long-life high-quality alkyl hydrogen-rich fuels, it is essential to achieve efficient synergy among high-performance catalysts, suitable feedstocks, and optimized process conditions. Among these, catalysts prepared based on fermentation hybridization and metal complexation technologies are the core to achieving this goal.

[0216] In addition, this invention guides the reaction toward the formation of isoalkanes with a high H / C ratio through precise catalyst design, while suppressing the formation of low H / C ratio components (olefins, aromatics) and low calorific value components (oxygen-containing compounds) to the greatest extent, thus truly achieving a balance between hydrogen enrichment and combustion stability.

[0217] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a plant-metal composite catalyst, characterized in that, Includes the following steps: Step A1. Preparation of fermentation hybrid precursors: Plant fiber powder, zeolite molecular sieve, and organic nutrients are mixed in a mass ratio of 5:(2-4):(3-5). A compound microbial agent accounting for 1-3% of the total mass of the mixed raw materials is added, and water is added to adjust the solid content to 10-20%. Fermentation is carried out at 35-38℃ under limited oxygen conditions for 72-96 hours until the pH of the system stabilizes at 4.0-4.5, resulting in a viscous fermentation hybrid precursor. The zeolite is nano HZSM-5, and the compound microbial agent is composed of Trichoderma reesei, lactic acid bacteria, and Bacillus subtilis mixed in a colony ratio of 1:(0.5-0.8):(1.2-1.6). Step A2. Purification and activation of the precursor: The fermentation hybrid precursor obtained in step A1 is spread in a ceramic or bamboo container and placed in a ventilated and light-transmitting place for "sun exposure and night leakage" treatment for 3 to 7 days. The resulting residue is separated into solid and liquid by pressure filtration or centrifugation to obtain purified solid material. The solid material is then preliminarily dried at 80-105℃ until the moisture content is less than 15% to obtain purified and dried fermentation hybrid powder. Step A3. Metal Complexation and Forming: The fermented hybrid powder is thoroughly mixed with the pre-prepared Cu-Zn-Al metal complex solution in a kneader until a uniform paste is formed. The paste is then granulated into spherical catalyst blanks with a diameter of 1-3 mm using a granulator. Step A4. Calcination and activation: The shaped spherical catalyst preform was reduced in a hydrogen atmosphere at 250-350℃ for 2-4 hours to obtain a plant-metal composite catalyst.

2. The method for preparing the plant-metal composite catalyst as described in claim 1, characterized in that, The plant fiber is straw or rice husk; the organic nutrients are a mixture of molasses and soybean meal in a mass ratio of 1:(3-5).

3. The method for preparing the plant-metal composite catalyst as described in claim 1, characterized in that, The metal complex solution is generated by reacting soluble salts of copper, zinc, and aluminum with organic ligands in solution, wherein the organic ligands include any of citric acid, oxalic acid, glycine, or ethylenediaminetetraacetic acid.

4. The method for preparing the plant-metal composite catalyst as described in claim 1, characterized in that, The molar ratio of Cu, Zn and Al in the metal complex solution is 1:(0.5-0.8):(2.2-2.5); the total metal concentration in the metal complex solution is 0.1-1.0 mol / L.

5. The plant-metal composite catalyst obtained by any of the preparation methods described in claims 1-4.

6. The application of the plant-metal composite catalyst as described in claim 5 in the preparation of alkyl hydrogen-rich fuels, characterized in that, Includes the following steps: Step S1. Preparation of feedstock oil: Methanol and high-calorific-value light materials were mixed at high speed with a mass ratio of (6-8):(2-4) to obtain a turbid liquid. Immediately, a surfactant accounting for 1% of the total weight of the system was added dropwise. After stirring and mixing, a stable, non-layered, semi-transparent solution system of raw material oil was formed. Step S2. Preparation of feedstock oil: A plant-metal composite catalyst was loaded into a fixed-bed reactor, and the feedstock oil was fed at a feedstock weight hourly space velocity (WHSV) of 0.5-2.0 h⁻¹. -1 The fuel is pumped into a reactor at a temperature of 150-250℃ and a pressure of 0.5-2.0 MPa to obtain alkyl hydrogen-rich fuel.

7. The application of the plant-metal composite catalyst according to claim 6 in the preparation of alkyl hydrogen-rich fuels, characterized in that, The surfactant is any of triethanolamine, diethyl adipate, or polyethylene glycol.

8. The application of the plant-metal composite catalyst according to claim 6 in the preparation of alkyl hydrogen-rich fuels, characterized in that, The high-calorific-value light feedstock includes naphtha, light crude oil, condensate, Fischer-Tropsch light fractions, or reformate residue.