阅读说明：本技术 一种阳极电解质及其甲酸和氢联产系统与应用 (Anode electrolyte, formic acid and hydrogen co-production system and application thereof ) 是由 唐文思 谭华桥 李阳光 于 2021-08-10 设计创作，主要内容包括：本发明涉及一种阳极电解质及其甲酸和氢联产系统与应用,属于化学品制备技术领域。解决了现有技术中生物质制甲酸的方法产率低、选择性差、反应条件苛刻,对设备要求高的技术问题。本发明的阳极电解质,包括多金属氧酸盐、生物质和水。本发明利用具有氧化还原功能的多金属氧酸盐作为催化剂和电子传递剂；在阳极侧先利用多金属氧酸盐将生物质氧化,得到含有氢质子的还原态多酸和氧化产物甲酸；还原态的多酸在阳极表面被氧化,同时释放氢质子；在外加电场的作用下,氢质子通过质子交换膜,在阴极侧得到电子析出氢气。本发明的甲酸和氢联产系统和方法产率高、选择性高、成本低、条件温和、设备要求低。(The invention relates to an anolyte, a formic acid and hydrogen co-production system and application thereof, belonging to the technical field of chemical preparation. Solves the technical problems of low yield, poor selectivity, harsh reaction conditions and high equipment requirements of the method for preparing the formic acid from the biomass in the prior art. The anode electrolyte comprises polyoxometallate, biomass and water. The invention uses polyoxometallate with redox function as catalyst and electron transfer agent; oxidizing the biomass by using polyoxometallate on the anode side to obtain reduction-state polyacid containing hydrogen protons and oxidation product formic acid; the reduction-state polyacid is oxidized on the surface of the anode, and hydrogen protons are released at the same time; under the action of an external electric field, hydrogen protons pass through the proton exchange membrane, and electrons are obtained at the cathode side to precipitate hydrogen. The formic acid and hydrogen co-production system and method have the advantages of high yield, high selectivity, low cost, mild conditions and low equipment requirement.)

1. An anolyte, characterized by comprising a polyoxometalate, biomass, and water.

2. The anolyte of claim 1, wherein said polyoxometallate is H₄[PVMo₁₁O₄₀]、H₅[PV₂Mo₁₀O₄₀]、H₆[PV₃Mo₉O₄₀]、H₇[PV₄Mo₈O₄₀]、H₈[PV₅Mo₇O₄₀]、H₉[PV₆Mo₆O₄₀]One or more of; the concentration of the oxometallate in the anolyte is 0.01-0.1 mol/L.

3. The anolyte of claim 1, wherein the biomass is one or more of glucose, fructose, white granulated sugar, starch, cellulose and straw, and the concentration of the biomass in the anolyte is 0.1-4 mol/L.

4. The use of the anolyte as claimed in claim 1 for the electrolysis of biomass to produce formic acid and for the electrolysis of water to produce hydrogen.

5. A formic acid and hydrogen co-production system containing the anolyte of claim 1, comprising an electrolytic cell, anolyte, catholyte, anode, cathode, proton exchange membrane, power supply, thermostat, and leads;

the proton exchange membrane is arranged in the electrolytic cell, the electrolytic cell is divided into an anode electrolytic cell and a cathode electrolytic cell, and a catalyst is loaded on the cathode side of the proton exchange membrane;

the anolyte and the anode are arranged in the anolyte, and the anode is partially or completely inserted into the anolyte and is connected with the positive electrode of the power supply through a lead;

the cathode electrolyte and the cathode are arranged in the cathode electrolytic cell, and the cathode is partially or completely inserted into the cathode electrolyte and is connected with the negative electrode of the power supply through a lead;

the constant temperature device keeps the constant temperature of the anolyte and the catholyte when the formic acid and hydrogen co-production system works, and the constant temperature is 60-100 ℃.

6. Formic acid and hydrogen co-production system according to claim 5,

the proton exchange membrane is a naphthol membrane;

the anode is graphite felt;

the cathode is a Pt sheet;

the catholyte is a sulfuric acid aqueous solution or a phosphoric acid solution, and the concentration is 0.1-3 mol/L.

7. A formic acid and hydrogen co-production system as defined in claim 5, wherein the molar ratio of anolyte to catholyte is from 1:1 to 1: 2.

8. The formic acid and hydrogen co-production system of claim 5, wherein the catalyst is a mixture of one or more of platinum, rhodium, palladium, nickel, chromium, titanium, nitrogen-doped carbon, and molybdenum carbide, and the loading is 0.1-10 mg/cm²。

9. A formic acid and hydrogen co-production system as defined in claim 8, wherein the voltage of said power supply is 1.0-1.4 v.

10. A formic acid and hydrogen coproduction system as defined in claim 5, wherein the thermostatic device is a thermostatic waterbath device, and the electrolytic bath is disposed in the thermostatic waterbath device.

Technical Field

The invention relates to an anolyte, a formic acid and hydrogen co-production system and application thereof, belonging to the technical field of chemical preparation.

Background

Formic acid is a colorless liquid with pungent odor, has weak electrolyte, strong acidity and corrosiveness, and is widely used in the fields of textiles, leather, medicines, agriculture, rubber and the like. In recent years, H has been used for its low toxicity and flammability under ambient conditions₂The capacity is as high as 53g/L, which makes formic acid a promising hydrogen storage material and hydrogen carrier.

Industrial production of formic acid is mainly based on fossil fuels, so large-scale production of formic acid from renewable resources is more favorable for slowing down carbon emissions and coping with global warming. The biomass is used as the largest carbon resource in the world, and has the advantages of low price, easy obtainment, renewability and the like. Therefore, the preparation of formic acid from biomass has attracted people's attention. In the prior art, three methods are mainly used for preparing formic acid from biomass: acid hydrolysis, wet oxidation and catalytic oxidation. However, acid hydrolysis has the disadvantages of low yield and poor product selectivity. Wet oxidation has high selectivity under alkaline conditions, but requires a large amount of acid to neutralize the alkali at the later stage. The catalytic oxidation needs to be carried out at high temperature and high pressure, the requirement on equipment is high, most oxidation only occurs on the surface of an electrode, the chemical reaction rate is greatly limited, and only the single activity of biomass oxidation reaction or hydrogen evolution reaction exists. Therefore, the development of a biomass formic acid preparation method which has high yield, high product selectivity, mild conditions and environmental friendliness is an urgent problem to be solved.

Disclosure of Invention

In view of the above, the invention provides a system and a method for coproducing formic acid and hydrogen, which aim to solve the technical problems of low yield, poor selectivity, harsh reaction conditions and high equipment requirements of the method for preparing formic acid from biomass in the prior art.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows.

The invention provides an anode electrolyte, which comprises polyoxometallate, biomass and water.

Preferably, the polyoxometallate is H₄[PVMo₁₁O₄₀]、H₅[PV₂Mo₁₀O₄₀]、H₆[PV₃Mo₉O₄₀]、H₇[PV₄Mo₈O₄₀]、H₈[PV₅Mo₇O₄₀]、H₉[PV₆Mo₆O₄₀]One or more of; more preferably H₆[PV₃Mo₉O₄₀]。

Preferably, the concentration of the polyoxometallate in the anode electrolyte is 0.01-0.1 mol/L.

Preferably, the biomass is one or more of glucose, fructose, white granulated sugar, starch, cellulose and straw.

Preferably, the concentration of biomass in the anolyte is 0.1-4 mol/L.

The invention also provides application of the anode electrolyte in preparation of formic acid by electrolyzing biomass and production of hydrogen by electrolyzing water.

The invention also provides a formic acid and hydrogen co-production system containing the anolyte, which comprises an electrolytic bath, the anolyte, the catholyte, an anode, a cathode, a proton exchange membrane, a power supply, a constant temperature device and a plurality of leads;

the proton exchange membrane is arranged in the electrolytic cell, the electrolytic cell is divided into an anode electrolytic cell and a cathode electrolytic cell, and a catalyst is loaded on the cathode side of the proton exchange membrane;

the anolyte and the anode are arranged in the anolyte, and the anode is partially or completely inserted into the anolyte and is connected with the positive electrode of the power supply through a lead;

the cathode electrolyte and the cathode are arranged in the cathode electrolytic cell, and the cathode is partially or completely inserted into the cathode electrolyte and is connected with the negative electrode of the power supply through a lead;

the constant temperature device keeps the constant temperature of the anolyte and the catholyte when the formic acid and hydrogen co-production system works, and the constant temperature is 60-100 ℃.

Preferably, the proton exchange membrane is a naphthol membrane.

Preferably, the anode is a graphite felt.

Preferably, the cathode is a Pt sheet.

Preferably, the catholyte is a sulfuric acid aqueous solution or a phosphoric acid solution, and the concentration is 0.1-3 mol/L.

Preferably, the molar ratio of anolyte to catholyte is 1:1 to 1:2, more preferably 1: 1.

Preferably, the catalyst is one or a mixture of more of platinum, rhodium, palladium, nickel, chromium, titanium, nitrogen-doped carbon and molybdenum carbide, and the loading amount is 0.1-10 mg/cm²(ii) a More preferably, the catalyst is platinum, rhodium or palladium, and the loading is 0.2-1 mg/cm²(ii) a More preferably, the catalyst is nickel, chromium or titanium, and the loading is 1-10 mg/cm²(ii) a More preferably, the catalyst is nitrogen-doped carbon or nitrogen-doped molybdenum carbide, and the loading is 1-10 mg/cm²(ii) a Particularly preferably, the catalyst is platinum with a loading of 0.2 to 1mg/cm²。

Preferably, the voltage of the power supply is 1.0-1.4 v.

Preferably, the constant temperature device is a constant temperature water bath device, and the electrolytic bath is arranged in the constant temperature water bath device.

The principle of the invention is as follows: the invention utilizes polyoxometallate with redox function as a catalyst and an electron transfer agent. On the anode side, the biomass is oxidized by polyoxometallate to obtain reduced polyacid containing hydrogen protons and oxidation product formic acid. The reduced polyacid is oxidized at the anode surface, releasing hydrogen protons. Under the action of an external electric field, hydrogen protons pass through the proton exchange membrane, and electrons are obtained at the cathode side to precipitate hydrogen.

Compared with the prior art, the invention has the beneficial effects that:

1. according to the anolyte, the proton exchange membrane, the electrolytic cell and the liquid catalyst are utilized to directly electrolyze the biomass with high polymerization degree to produce hydrogen, the biomass can be directly oxidized by the oxidation-type substance in the mixed liquid of the anolyte, and therefore any other noble metal catalyst is not needed on the anode side.

2. The co-production system and the method of the formic acid and the hydrogen have the advantages of specific anode product, high liquid selectivity and high cathode hydrogen evolution efficiency, can generate the formic acid serving as a hydrogen storage material, and can obtain pure formic acid in a distillation mode.

3. According to the formic acid and hydrogen co-production system and method, biomass, particularly agricultural wastes such as corn straws and wheat straws are used as raw materials for hydrogen production through electrolysis, so that the agricultural wastes are reasonably utilized, the environmental problem caused by traditional straw combustion is solved, the overpotential of hydrogen evolution can be reduced by using the biomass, and the production cost is greatly reduced.

4. The formic acid and hydrogen co-production system and the method have the advantages of mild conditions and low energy consumption.

Drawings

In order to more clearly illustrate the technical solution of the present invention, the drawings used in the detailed description will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without inventive labor.

FIG. 1 is a schematic diagram of the formic acid and hydrogen co-production process of the present invention;

FIG. 2 is a schematic diagram of the configuration of the formic acid and hydrogen co-production system of the present invention;

in the figure, 1, a power supply, 2, an anode, 3, a cathode, 4, an anode electrolytic cell, 5, a cathode electrolytic cell, 6, a proton exchange membrane, 7 and a constant temperature device.

Detailed Description

For a further understanding of the invention, preferred embodiments of the invention are described below in conjunction with the detailed description, but it is to be understood that the description is intended to further illustrate the features and advantages of the invention and not to limit the claims to the invention.

The anode electrolyte comprises polyoxometallate, biomass and water.

In the above technical scheme, the polyoxometallate is preferably H₄[PVMo₁₁O₄₀]、H₅[PV₂Mo₁₀O₄₀]、H₆[PV₃Mo₉O₄₀]、H₇[PV₄Mo₈O₄₀]、H₈[PV₅Mo₇O₄₀]、H₉[PV₆Mo₆O₄₀]One or more of; more preferably H₆[PV₃Mo₉O₄₀]. The concentration of the oxometallate in the anolyte is preferably 0.01 to 0.1 mol/L.

In the technical scheme, the biomass is one or more of glucose, fructose, white granulated sugar, starch, cellulose and straw. The concentration of the biomass in the anolyte is 0.1-4 mol/L. The cellulose and straw may preferably be pretreated by acid washing.

The invention also provides application of the anode electrolyte in preparation of formic acid by electrolyzing biomass and hydrogen production by electrolyzing water, and particularly relates to application of polyoxometallate as a catalyst in a process of producing formic acid by electrolyzing biomass and an electron carrier in a process of producing hydrogen by electrolyzing water.

As shown in fig. 2, the formic acid and hydrogen co-production system of the present invention comprises an electrolytic cell, an anolyte, a catholyte, an anode 2, a cathode 3, a proton exchange membrane 6, a power supply 1, a thermostat 7 and a plurality of wires; the proton exchange membrane 6 is arranged in the electrolytic cell, the electrolytic cell is divided into an anode electrolytic cell 4 and a cathode electrolytic cell 5, and the cathode side of the proton exchange membrane 6 is loaded with a catalyst; the anolyte and the anode 2 are arranged in the anolyte, and the anode 2 is partially or completely inserted into the anolyte and is connected with the positive electrode of the power supply 1 through a lead; the cathode electrolyte and the cathode 3 are arranged in the cathode electrolytic cell 5, and the cathode 3 is partially or completely inserted into the cathode electrolyte and is connected with the negative electrode of the power supply through a lead; the constant temperature device 7 keeps the constant temperature of the anolyte and the catholyte when the formic acid and hydrogen co-production system works, and the constant temperature is 60-100 ℃.

In the technical scheme, the constant temperature device is preferably a constant temperature water bath device, and the electrolytic bath is arranged in the constant temperature water bath device. The temperature has a great influence on the degradation of biomass, and it is very critical to select a suitable temperature, and it can be understood that the skilled person can take values within the above range according to the actual needs, for example, the temperature can be 60 ℃, 70 ℃, 80 ℃, 90 ℃, 100 ℃ and so on.

In the above technical solution, the proton exchange membrane 6 is preferably a naphthol membrane; the anode 2 is preferably a graphite felt; the cathode 3 is preferably a Pt sheet.

In the above technical scheme, the catholyte is not excessively limited, and conventional catholyte, such as sulfuric acid aqueous solution and phosphoric acid solution, can be adopted. Preferably H₃PO₄The water solution is used as the cathode electrolyte, and the concentration of the water solution can be selected to be 0.1-3 mol/L.

In the above technical solution, the molar ratio of the anolyte to the catholyte is preferably 1:1 to 1:2, and more preferably 1: 1.

In the technical scheme, the catalyst is preferably one or a mixture of more of platinum, rhodium, palladium, nickel, chromium, titanium, nitrogen-doped carbon and molybdenum carbide, and the loading amount is 0.1-10 mg/cm²(ii) a More preferably, the catalyst is platinum, rhodium or palladium, and the loading is 0.2-1 mg/cm²(ii) a More preferably, the catalyst is nickel, chromium or titanium, and the loading is 1-10 mg/cm²(ii) a More preferably, the catalyst is nitrogen-doped carbon or nitrogen-doped molybdenum carbide, and the loading is 1-10 mg/cm²(ii) a Particularly preferably, the catalyst is platinum with a loading of 0.2 to 1mg/cm²。

As shown in fig. 1, the chemical reaction equation in the process of producing formic acid by electrolyzing biomass and producing hydrogen by electrolyzing water is as follows:

in the anode electrolytic cell:

biomass + H₂O + oxidation state polyacid → formic acid + CO₂+ reducing polyacid + H⁺(1)

On the anode side:

reduced polyacid-e^-→ oxidized polyacid (2)

On the cathode side:

H⁺+e^-→1/2H₂(3)

the clean chemical reaction is as follows:

biomass + H for coproducing formic acid and electrolyzed water to produce hydrogen₂O → formic acid + CO₂+H₂(4)

From the above reaction equation: the main functions of the polyoxometallate in the whole electrolytic process are as follows:

(1) the oxidation state polyacid is used as an oxidant to degrade the biomass macromolecules; the reduced polyacid serves as a charge carrier to transfer electrons to the cell anode. (2) The polyacid gains and loses electrons in the whole process, and the structure of the polyacid is not changed, so the polyacid is used as an electrocatalytic catalyst.

As shown in formula (2), under the action of an external electric field, the reduced polyacid is oxidized again on the anode to the oxidized polyacid; h generated in the anode reaction cell⁺Enters the cathode side through the proton exchange membrane and is reduced into H at the cathode side₂As shown in equation (3).

The biomass is oxidized by heating the oxidized form polyacid in an aqueous solution, and the oxidized form polyacid is itself reduced to the lower form of heteropolyblue. The heteropoly blue with low valence state is transferred to the electrolytic anode and is oxidized into polyacid with oxidation state under the action of the electrolytic anode. And hydrogen is generated under the action of the electrolytic cathode.

The terms used in the present invention generally have meanings commonly understood by those of ordinary skill in the art, unless otherwise specified. In order to make those skilled in the art better understand the technical solution of the present invention, the present invention will be further described in detail with reference to the following embodiments.

In the following examples, various procedures and methods not described in detail are conventional methods well known in the art. Materials, reagents, devices, instruments, apparatuses and the like used in the following examples are commercially available unless otherwise specified.

Example 1

Method for producing formic acid and hydrogen by direct electrolysis of glucose-polyacid

Step one, preparing an anolyte

5g of polyacid H are taken₆[PV₃Mo₉O₄₀]Dissolved in 30mL of water and then added with 0.5g of glucose.

Step two, building a system

As shown in fig. 2, comprises an electrolytic bath, an anode electrolyte, a cathode electrolyte, an anode 2, a cathode 3, a proton exchange membrane 6, a power supply 1, a constant temperature device 7 and a plurality of leads. Proton exchange membrane 6(Nafion model 117, membrane at 1mol L)^-1H₂SO₄And 3% of H₂O₂Is pretreated for 30 minutes in boiling solution, and then is washed and soaked in deionized water) is placed in an electrolytic cell, the electrolytic cell is divided into an anode electrolytic cell 4 and a cathode electrolytic cell 5, and the cathode side of a proton exchange membrane 6 is loaded with a catalyst; the anolyte and the anode 2 are arranged in an anolyte tank 4, and the anode 2 is partially or completely inserted into the anolyte and is connected with the positive electrode of a power supply through a lead; catholyte (1mol/L H₃PO₄Solution) and a cathode 3 are placed in a cathode electrolytic cell 5, and the cathode 3 is partially or completely inserted into the catholyte and connected with the negative electrode of the power supply through a lead; the constant temperature device 7 keeps the constant temperature of the anolyte and the catholyte when the formic acid and hydrogen co-production system works, the constant temperature is 90 ℃, the anode 2 is a graphite felt, and the cathode 3 is a platinum sheet.

Step three, the process of producing formic acid by electrolyzing biomass and producing hydrogen by electrolyzing water

The voltage of 1.0v is applied to the two sides of the cathode 3 and the anode 2, the magnitude of the applied voltage can be controlled by an electrochemical workstation, the current magnitude in the circuit is measured, and the generated hydrogen is collected in the cathode electrolytic cell 5.

When glucose is used as the raw material, since glucose is highly susceptible to H₆[PV₃Mo₉O₄₀]Oxidation, which can be totally oxidized to formic acid and CO under relatively mild conditions₂. The clean chemical equation is:

C₆H₁₂O₆+H₂O→CO₂+HCOOH+H₂(5)

example 2

The procedure was the same as in example 1, except that only glucose in step one was changed to fructose.

Example 3

The process was the same as in example 1, only the glucose in step one was changed to white sugar.

Example 4

The process is the same as in example 1, only the glucose in step one is exchanged for starch.

Example 5

System for producing formic acid and hydrogen by direct electrolysis of cellulose-polyacid

Step one, cellulose pretreatment

0.5g of cellulose is taken, 10mL of 73% concentrated sulfuric acid is added, stirring is carried out for 12h, the concentrated sulfuric acid is diluted to 1% by adding water, boiling is carried out for 12h, and then concentration is carried out to 30mL, so as to obtain a cellulose solution.

Step two, preparing an anolyte

5g of polyacid H are taken₆[PV₃Mo₉O₄₀]Add to 30mL of cellulose solution.

Step three, building a system

As shown in fig. 2, comprises an electrolytic bath, an anode electrolyte, a cathode electrolyte, an anode 2, a cathode 3, a proton exchange membrane 6, a power supply 1, a constant temperature device 7 and a plurality of leads. Proton exchange membrane 6(Nafion117 type, membrane at 1mol/L H)₂SO₄And 3% of H₂O₂Is pretreated for 30 minutes in boiling solution, and then is washed and soaked in deionized water) is placed in an electrolytic cell, the electrolytic cell is divided into an anode electrolytic cell 4 and a cathode electrolytic cell 5, and the cathode side of a proton exchange membrane 6 is loaded with a catalyst; the anolyte and the anode 2 are arranged in the anolyte, and the anode is partially or completely inserted into the anolyte and is connected with the positive electrode of the power supply through a lead; catholyte (1mol/L H₃PO₄Solution) and a cathode 3 are placed in a cathode electrolytic cell, and the cathode 3 is partially or completely inserted into the cathode electrolytic solution and is connected with the negative electrode of the power supply through a lead; the constant temperature device 7 keeps the electrolyte of the anode and the electrolyte of the cathode 3 at constant temperature when the formic acid and hydrogen co-production system works, the constant temperature is 90 ℃, the anode is a graphite felt, and the cathode is a platinum sheet.

Step four, the process of producing formic acid by electrolyzing biomass and producing hydrogen by electrolyzing water

The voltage of 1.0v is applied to the two sides of the cathode 3 and the anode 2, the magnitude of the applied voltage can be controlled by an electrochemical workstation, the current magnitude in the circuit is measured, and the generated hydrogen is collected in the cathode electrolytic cell 5.

Example 6

As in example 5, only the cellulose was replaced with straw.

Measurement of formic acid production from electrolytic Material of examples 1 to 4: the organic substances present in the anode electrolytic cell and oxidized are subjected to detailed chemical analysis by analysis means such as liquid phase and nuclear magnetism. Through detection, the proportion of the final product is different in the polyacid environment with different concentrations. Only formic acid was detected for the liquid phase product. For gas phase products, the gas products from the anode were collected and analyzed by gas chromatography, CO₂Is the only gaseous product. The effect of different biomass on the yield of the product formic acid was compared and the results are shown in table 1.

TABLE 1 Effect of polyacid usage on the product formic acid

Determination of production of formic acid from electrolyzed biomass in examples 1 to 4 determination of hydrogen production from electrolyzed water: and collecting hydrogen by a drainage gas collection method. The anodic solution was at 5gH₆[PV₃Mo₉O₄₀]Dissolved in 30mL of water, 0.5g of glucose was added, and the voltage was applied at 1.0 v. After the electrolysis was complete, 486mL of H was prepared₂The required electric quantity is 3720C, and the Faraday efficiency can be calculated to be 113% according to Faraday's law. There may be the following sources for faradaic efficiency exceeding 100%: (1) the polyacid is directly oxidized by oxygen in the anode. (2) The polyacid is reduced by the biomass and then diffuses to the other side of the cell. (3) The reduced heteropoly blue directly leads electrons to hydrogen ions of the cathode through a lead to produce hydrogen gas.

The electrical energy consumption for hydrogen production under these conditions was 2.12kWh/Nm^-3 H₂The optimum PEM water electrolysis Energy consumption (4.2 kWh/Nm) reported in the literature (Carmo, M.et. al., A comprehensive review on PEM water electrolysis. International journal Hydrogen Energy,2013.38(12): p.4901-4934.) is similar to that reported in the literature^-3) Compared with the same amount of hydrogen produced, the energy can be saved by 49.5 percent.

Determination of formic acid production from the electrolyzed biomass of examples 5 and 6: the liquid product was determined by liquid chromatography analysis. The formic acid yield of the cellulose was 40.8%. The yield of formic acid in the straw is 0.183 g.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.