MXPA97000506A

MXPA97000506A - Production of oxidized humic acids by an oxygen-alco process

Info

Publication number: MXPA97000506A
Application number: MXPA/A/1997/000506A
Authority: MX
Inventors: E Lebo Stuart Jr; R Wirtz Kevin; L Dickman Stephen
Original assignee: Lignotech Usa Inc
Priority date: 1996-01-26
Filing date: 1997-01-20
Publication date: 1998-01-01

Abstract

The present invention relates to a method for producing oxidized humic acid concentrates, characterized in that it comprises the steps of: a) dissolving a mine containing enálcali humic acid to form a reaction mixture, b) reacting the mixture with an oxidant under temperature conditions and pressure and for a sufficient time, to cause the oxidation of the humic acid-containing ore to produce an oxidized humic acid concentrate, and c) to separate the oxidized humic acid concentrate from the reaction mixture.

Description

PRODUCTION OF OXIDIZED HUMIC ACIDS BY AN OXYGEN-ALKALINE PROCESS BACKGROUND OF THE INVENTION This invention relates to the production of oxidized humic acids, by alkaline / air oxidation of ores containing humic acid. The production by the alkaline / air oxidation process described herein, provides humic acids which have better solubility in acid systems and which are different from humic acids produced by previous processes. A prior process for producing humic acids is described in U.S. Pat. No. 4,912,256. It involves mixing coal with an aqueous medium to produce a sludge that has a pH in the range of 4-9. The sludge thus produced is reacted with a gaseous oxidant such as air or oxygen under conditions of temperature and pressure for a sufficient time to cause the oxidation of the carbon. Separation of the reaction product from the aqueous medium produces an oxidized carbon containing humic acids. Under the conditions employed in this process, however, the humic acids contained in these carbons are only slightly oxidized and are not isolated as a discrete product. Another oxidative process described in the patent South African No. 87/9232, involves the oxidation of carbon in the dry state in a fluid bed reactor. Carbon with particle size in the range of 100 microns to 3 mm, is heated from 150 to 300 ° C under a partial pressure of oxygen for a time of 30 to 600 minutes to produce oxidized carbons containing humic acids. Alkali is not used in this procedure, however. Still another method for producing humic acids from oxidized carbons is described in U.S. Pat. No. 5,004,831. The procedure involves mixing oxidized coal with aqueous alkali, heating the mixture from 100 to 180 ° C under sufficient pressure to avoid evaporation of water, and maintaining the elevated temperature for a sufficient time to extract a substantial amount of the available humic acids. Like the other methods described above, however, this method does not employ conditions that promote extensive oxidation of the humic acids contained in the carbon. Traditional methods to produce humic acids from ores that contain humic acid, involve extraction with alkali. An example of this extraction process is described in the U.S. patent. No. 4,319,041. It involves mixing ores that contain humic acid with water and caustic soda and extraction of the humic acids by agitation at pH 6.5-8.0. The times required in this procedure are quite long, however, and the humic acids produced are not oxidized. COMPENDIUM OF THE INVENTION The present invention is a simple process for producing oxidized humic acids. The method comprises the steps of (a) dissolving an ore containing humic acid in alkali to form a reaction mixture; (b) subjecting the mixture to reaction with an oxidant under conditions of temperature and pressure and for a sufficient time to cause oxidation of the humic acid-containing ore to produce an oxidized humic acid concentrate; (c) separating the oxidized humic acid concentrate from the reaction mixture. Optionally, the reaction mixture can be saturated with oxygen before the start of the oxidation reaction. The method of the invention particularly comprises reacting ores containing humic acid with oxygen under alkaline conditions at a temperature between 100 ° C and 200 ° C for at least 0.5 hour, but usually for 1 to 6 hours, to produce oxidized humic acids which are soluble at pH as low as 2.9 and formed in yields of at least 70%. Suitable oxygen pressures in the process are .3515 to 14.06 kg / cm2 (5 to 200 psi) and convenient alkali sources for the process include sodium hydroxide, potassium hydroxide, ammonium hydroxide, lithium hydroxide and / or combinations of these materials. The procedure. , particularly requires reacting with oxygen an ore containing humic acid such as leonardite, in the presence of sodium hydroxide of 15 to 30% and 170 ° C for 1 hour. The separation of insolubles by filtration, centrifugation or sedimentation provides oxidized humic acids soluble at pH 3.0 or higher at yields of at least 70%. If convenient, the oxidized humic acids can be formed into a powder, preferably by spray drying. The process described here produces oxidized humic acids with good yield from ores containing humic acid. An important feature of the invention is that the oxidized humic acids produced in the process have improved solubility in acid solutions. Another advantage is that the oxidized humic acids produced in the process are isolated either as a liquid concentrate or as a dry powder. A third advantage of the procedure is that it is quick and easy. A final advantage is that the oxidized humic acids produced by the process are superior viscosity reducing agents when compared to humic acids prepared by previous methods. DETAILED DESCRIPTION OF THE PREFERRED MODALITY According to the invention, a process for producing oxidized humic acid concentrates, includes the steps of (a) dissolving a mine containing humic acid in alkali to form a reaction mixture; (b) subjecting the mixture to reaction with an oxidant under conditions of temperature and pressure for a sufficient time to cause oxidation of the humic acid-containing ore to produce an oxidized humic acid concentrate; (c) separating the oxidized humic acid concentrate from the reaction mixture. The liquid concentrate obtained by the process can also be formed into a powder, preferably by spray drying, if desired. As used in the specification, the term "ore containing humic acid" is defined to include lignites (especially leonardite), bituminous coals and peat, as well as artificial humic acids such as the products of the oxidative polymerization of quinones. The preferred ore is leonardite due to its easy availability and relatively inexpensive cost. The average particle size of the ore is usually less than about 3 mm. Preferably, the average particle size of the ore varies in the range of 10-1000 microns and more preferably, the average particle size is in the range of 10-100 microns. In this way, finer ore particles result in the reaction that occurs with relative ease, allowing the reaction to be completed in a relatively shorter period of time. The first step of the process of the invention involves dissolving the ore containing humic acid in alkali. Any alkali that provides sufficient alkalinity can be used to adjust the pH enough to dissolve the ore containing humic acid. Preferably, the pH of the reaction mixture is 9-13, with 10-12 preferred and pH 11 more preferred. Examples of alkali that can be used to dissolve the humic acid-containing ore include sodium hydroxide, potassium hydroxide, ammonium hydroxide, lithium hydroxide, sodium carbonate, potassium carbonate, lithium carbonate and mixtures thereof. More preferably, sodium hydroxide is used because of its ready availability. It should be noted that calcium hydroxide probably will not be used since it will form an insoluble component. If the alkali used is sodium hydroxide, it preferably comprises 10-30% by weight of the reaction mixture. If the alkali used is potassium hydroxide, it preferably comprises 14-42% by weight of the reaction mixture. If the alkali used is ammonium hydroxide, it preferably comprises 9-26% by weight of the reaction mixture. If the alkali used is lithium hydroxide, it preferably comprises 6-18% by weight of the reaction mixture. The second stage of the process involves reacting the mixture under conditions of temperature and pressure and for a sufficient time to produce concentrated oxidized humic acid. The reaction of preference is carried out in a closed pressure vessel, equipped with a suitable distributor or stirring mechanism, to ensure effective mass and thermal transfer between the liquid, solid and gaseous phases contained therein. The closed container should be calibrated at .1406 to 70.3 kg / cm2 (2-1000 psi), preferably .1406 to 28.12 kg / cm2 (2-400 psi) to avoid evaporation of water. The reaction is carried out at a temperature between about 100 ° C to 200 ° C. Preferably, the reaction temperature is in the range between 140 ° C to 180 ° C and more preferably between 160 ° C and 170 ° C. The mixture is reacted at about 0.5-6 hours with a preferred reaction time which is 1-4 hours depending on the reaction temperature. In any case, the reaction step is continued for a period of time sufficient to produce an oxidized humic acid concentrate with yields of at least about 70%. These oxidized humic acid concentrates are soluble at pH as low as about 2.9. The oxidant employed in the oxidation step of the present process is preferably a gaseous oxidant which is bubbled through the reaction mixture at a charge of .3515-14.06 kg / cm2 (5-200 psi). The oxidant is chosen from oxygen, air and its mixtures, with the preferred oxidant that is oxygen. The oxidation step is carried out for a sufficient time and under sufficient pressure and temperature to ensure substantially complete oxidation of the humic acid-containing ore. After the reaction is completed, the undissolved solids present in the reaction mixture of the concentrated humic acid concentrate are separated by filtration, sedimentation and / or centrifugation. Upon completion of the process, a liquid product is formed which is a minimum of 5%, preferably a minimum of 16% of oxidized humic acid in the aqueous solution. The product pH is typically between 7-9, but pH 8.5 is preferred.

E EMPLO X The above characteristics and advantages of the invention are achieved according to a preferred embodiment by mixing ores containing humic acid such as leonardite with 15% sodium hydroxide until the ore substantially dissolves. During the dissolution process, air is bubbled into the mixture such that the mixture becomes saturated. The solids content of the mixture during this process is 5-40% by weight, but preferably 20-30% by weight and more preferably 22-25% by weight. In this example, the solids content is determined as 22% by weight. After dissolution of the ore in the sodium hydroxide, the saturated mixture is transferred to a pressure reactor and heated to 170 ° C. The mixture is then reacted at 170 * C for one hour during which time air is bubbled through the mixture. After the reaction, the undissolved solids present in the mixture are removed by filtration, sedimentation and / or centrifugation. At the end of the process, a liquid product is formed which is a minimum of 16% oxidized humic acid in aqueous solution. The pH of the product is 8.5 and the precipitation pH (ie the pH at which the material becomes insoluble and forms a precipitate) is 4.2. It is apparent from the above example that the process of this invention is a simple and relatively inexpensive process for producing oxidized humic acid concentrates.

An additional procedural advantage is that conditions can be varied to control the oxidation rate. Table 1 shows how sodium hydroxide, oxygen concentration and / or temperature can be varied to produce humic acid concentrates with varying degrees of oxidation and therefore pH of precipitation. EXAMPLE 2 One of the intended uses of the oxidized humic acids produced by the process described herein are viscosity reducers. Table 2 shows that compared to humic acids of simple alkaline extraction, the oxidized humic acids produced by the process described herein are superior dispersants for systems such as kaolin clay. While the clay dispersion of kaolin is given as an example, a person skilled in the art will also envision the use of these products in other organic and inorganic systems such as ceramics and agricultural chemicals. It also hopes that like other humic acid extracts, the humic acid concentrates formed by the process described herein are beneficial for the growth of plants. When added to soil even in small amounts, these products are known to stimulate plant growth, improve color and germination of seeds. Due to its lower pH of precipitation, it is also expected that the humic acid concentrates formed by the process described here will have improved compatibility in liquid fertilizer solutions. They can also be used in combination with dry fertilizers, to soak and / or sprinkle on seeds before planting and to make micro-nutrients for foliar application and / or for the soil. While this description details the preferred embodiment of the present invention, other embodiments of the invention may be designed without departing from the basic intention of this disclosure, the full scope of which is determined by the following claims. TABLE 1 EFFECT OF PRESSURE OF OXYGEN AND CONCENTRATION OF LCALI IN PERFORMANCE AND DH OF PRECIPITATION OF OXIDIZED HUMIC ACIDS Load of TempeRendiPrecipi Oxygen Loading Allocation kg / cm2 (psi) (%) (° C)% pH .703 (10 ) 15 170 73 4.2 .703 (10) 30 170 71 3.7 14.06 (200) 15 170 75 4.9 14.06 (200) 30 170 70 3.2 .703 (10) 22.5 140 77 3.9 7.03 (100) 22.5 140 75 3.3 7.03 (100 ) 30 140 72 2.9 TABLE 2 DISPERSION DATA - CAOLÍN CLAY FAN TO 40% Load Charge of TempeViscosity Oxygen Alkali rate cps kg / cm2 (psi) (%) (° C) 0 (0) 30 30 59.703 (10) 30 170 24 14.06 (200) 30 170 13

Claims

CLAIMS 1. A method for producing oxidized humic acid concentrates, characterized in that it comprises the steps of: (a) dissolving a mine containing humic acid in alkali to form a reaction mixture; (b) reacting the mixture with an oxidant under conditions of temperature and pressure and for a sufficient time, to cause the oxidation of the humic acid-containing ore to produce an oxidized humic acid concentrate; and (c) separating the oxidized humic acid concentrate from the reaction mixture.
2. The method according to claim 1, characterized in that the ore containing humic acid is chosen from lignites, bituminous coals, peat and mixtures thereof.
3. The method according to claim 1, characterized in that the ore containing humic acid is leonardite.
4. The method according to claim 1, characterized in that the alkali is selected from sodium hydroxide, potassium hydroxide, ammonium hydroxide, lithium hydroxide, sodium carbonate, potassium carbonate, lithium carbonate and mixtures thereof.
The method according to claim 1, characterized in that the alkali is sodium hydroxide and comprises 10-30% by weight of the reaction mixture.
6. The method according to claim 1, characterized in that the alkali is potassium hydroxide and comprises 14-42% by weight of the reaction mixture.
7. The method according to claim 1, characterized in that the alkali is ammonium hydroxide and comprises 9-26% by weight of the reaction mixture.
8. The method according to claim 1, characterized in that the oxidant is chosen from oxygen, air and mixtures thereof.
9. The method according to claim 8, characterized in that the oxidant during reaction is bubbled through the reaction mixture at a charge of .3515 to 14.06 kg / cm2 (5-200 psi).
10. The method according to claim 1, characterized in that the reaction mixture is reacted for 0.5-6 hours.
The method according to claim 1, characterized in that the step of reacting the mixture is carried out at a temperature of 100 ° C-200 ° C.
The method according to claim 1, characterized in that it includes the additional step of forming the oxidized humic acid concentrate in a powder form.
The method according to claim 1, characterized in that it includes the step of saturating the reaction mixture with oxygen before reacting the mixture.
14. A method for producing oxidized humic acid concentrates, characterized in that it comprises the steps of: (a) dissolving an ore containing humic acid in alkali at a concentration of 5-40% solids to form a reaction mixture; (b) react the mixture at 100 ° C-200 ° C with oxygen for at least 0.5 hour; and (c) separating the oxidized humic acid concentrates resulting from the reaction mixture.
15. The method according to claim 14, characterized in that the alkali is sodium hydroxide and comprises 10-30% by weight of the reaction mixture.
The method according to claim 14, characterized in that the alkali is potassium hydroxide and comprises 14-42% by weight of the reaction mixture.
17. The method according to claim 14, characterized in that the alkali is ammonium hydroxide and comprises 9-26% by weight of the reaction mixture.
18. The method according to claim 14, characterized in that the oxygen used in the reaction step is bubbled through the reaction mixture at a loading of .703 to 14.06 kg / cm2 (10-200 psi).
19. The method according to claim 14, characterized in that the mixture is reacted for 1-4 hours.
20. The method according to claim 14, characterized in that it includes the step of saturating the reaction mixture with oxygen before reacting the mixture.