WO1992004302A1

WO1992004302A1 - Guanidine as a nitrogen fertilizer

Info

Publication number: WO1992004302A1
Application number: PCT/CA1991/000308
Authority: WO
Inventors: Marvin Nyborg; Michael Worsley; Kenneth Worsley
Original assignee: The Governors Of The University Of Alberta
Priority date: 1990-08-30
Filing date: 1991-08-30
Publication date: 1992-03-19
Also published as: AU8405591A; GB9018893D0

Abstract

A nitrogen fertilizer having slow nitrogen release properties comprises guanidine ammonium sulphate. A novel process for preparing guanidine ammonium sulphate comprises hydrolysing a melt of guanidine sulfamate to produce guanidine ammonium sulphate. In the production of guanidine sulfamate, sulphur dioxide as stripped from sulphur dioxide containing emissions may be used.

Description

GUANIDINE AS A NITROGEN FERTILIZER

FIELD OF THE INVENTION

This invention relates to slow nitrogen release fertilizer and a process for making the slow release nitrogen component by use of sulphur dioxide emissions. BACKGROUND OF THE INVENTION

Nitrogen fertilizer is widely used to maintain and increase the growth in a variety of plants and in particular to increase yield and protein content of non- leguminous crops. One of the significant difficulties with nitrogen fertilizers is to maintain release of the nitrogen over extended periods of time and preferably during initial application of the nitrogen fertilizer to provide for a quick release of a certain portion thereof. There are a variety of nitrogen fertilizers which tend to suit different regions of application, the most common of which are urea, anhydrous ammonia, various ammonium salts such as ammonium nitrate, ammonium sulphate and calcium nitrate. It has been found, however, that the uptake by the crop of the fertilizer is normally in the range of

50%, but could theoretically approach 100% if the rate at which the nitrogen is released is in a more controlled protracted manner. To accomplish such an end, a variety of fertilizers, which have both slow release and fast release sources of nitrogen, woudl be preferred. The fast release nitrogens are the various salts of the above type which include ammonia, ammonia salts and nitrates. The slow release nitrogens may be compounds such as sulphur coated urea. It also generally understood that the slow release forms for nitrogen must be relatively inexpensive to manufacture.

A variety of approaches have been attempted to prepare slow release fertilizers which involve the use of guanidine compounds and their salts. In the early 1900s considerable experimentation with guanidine as a

fertilizer has been reported with little success. It is now generally understood that, in the usually known processes for preparing guanidine and its salts, various forms of sulfamates are produced which inhibit plant growth. Hence use of guanidine and/or its salts in fertilizer compositions has been avoided. Guanidine and its uses have been discussed in Boivin, Jean, L., 1956 "Preparation of Guanidine from Urea Sulphur Dioxide and Ammonia under Pressure" Canadian Journal of Chemistry, Vol 34:827-838, and in Lewis, A.H., 1936 "Fertilizer Value of Some Concentrated Materials Particularly Urea and Guanidine and their Nitrates and Phosphates", Journal of Agricultural Science , Vol. 26:509-526.

It is also generally understood that manufacture of guanidine and its salts is fairly expensive for a fertilizer component which normally is in the range of $0.05 to $0.15 per pound. The manufacture, however, of guanidine can involve the use of sulphur dioxide. As is appreciated, sulphur dioxide is one of the major

contributors to "acid rain". This is a significant problem where poorly buffered lakes or forest soils become acidified with consequent loss of lake vitality and trees. Normally sulphur dioxide is let to the atmosphere through tall chimneys or sulphur dioxide is scrubbed from waste gases before release to the

atmosphere. The recovered sulphur dioxide is normally converted to elemental sulphur, sulphuric acid or calcium sulphate. As taught in United States patent 2,653,967, sulphur dioxide may be used in the manufacture of guanidine sulphate. However, it has been found that, when the conditions of this process are followed, in actual fact guanidine sulfamate is prepared. As already noted, it is generally understood in the agricultural field that sulfmates act as growth inhibitors or to some extent are poisonous to agricultural crops. Hence one would not contemplate use of sulphur dioxide emissions, such as obtained from various types of industrial processes to manufacture guanidine sulphate for use as a fertilizer. Applicants have, however, discovered quite

surprisingly an efficient, economical process for the manufacture of guanidine ammonium sulphate involving the use of sulphur dioxide from waste gases and, furthermore, have established very significant slow nitrogen release fertilizer properties for guanidine ammonium sulphate. By virtue of this discovery, a significant pollutant "sulphur dioxide" can now be converted into a useful slow release fertilizer which can be returned to the soil to enhance plant growth at a very economical cost.

Accordingly, the invention provides a process for converting sulphur dioxide from waste gas streams to a non-toxic beneficial component to be returned to the soil.

Furthermore, the invention provides a nitrogen based fertilizer having a slow nitrogen release component of guanidine ammonium sulphate.

In addition, the invention provides an economical process for the conversion of sulfamates prepared by reacting waste sulphur dioxide with urea in the presence of ammonia to give guanidine ammonium sulphate in a form which is readily used as a fertilizer component and with the additional advantages that the final composition also includes fast release ammonium sulphate fertilizer as well as elemental sulphur which is an important nutrient for plant growth.

SUMMARY OF THE INVENTION

According to an aspect of the invention, a nitrogen fertilizer is provided which has slow nitrogen release properties. The fertilizer comprises guanidine ammonium sulphate.

According to another aspect of the invention, a plant fertilizer has slow and fast nitrogen releasing properties, the fertilizer comprising an ammonium salt admixed with a guanidine based nitrogen source. The improvement comprises the guanidine based nitrogen source consisting of guanidine ammonium sulphate. According to another aspect of the invention, a process for preparing a slow nitrogen release guanidine ammonium sulphate for use in nitrogen fertilizer

comprises:

hydrolysing a melt of guanidine sulfamate with a hydrolysing agent to produce the guanidine ammonium sulphate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

There is a significant demand worldwide for nitrogen fertilizers having delayed release of nitrogen as well as quick release of nitrogen. According to this invention, this is accomplished by the provision of two components in the fertilizer mixture. The delayed release component is guanidine ammonium sulphate. The quick release component is ammonium sulphate or one of its other ammonium salts as well as various nitrates. The

composition may also optionally include elemental

sulphur. When the fertilizer components are made in accordance with this invention using sulphur dioxide from waste gases, the resultant product has a combination of all three; that is, a slow release component in the form of guanidine ammonium sulphate, a quick release component in the form of ammonium sulphate and the plant nutrient element of sulphur. This invention provides for the very important recycle of hazardous sulphur dioxide emissions to the soil through an environmentally beneficial component; i.e., guanidine ammonium sulphate, ammonium sulphate and elemental sulphur. According to this invention, the process for making these components is cost competitive with existing costs for the commercial production of the widely used ammonium sulphate

fertilizer.

There are a variety of reasons for requiring a delayed release fertilizer. In crop growth, the most significant reason is that the nitrogen fertilizer may be applied in the fall with minimal loss of nitrogen during the late winter and early spring, whether the cop is sown in the fall or else in the spring. We have found that the slow release of nitrogen as effected by bacteria in the soil is achieved by the use of the guanidine ammonium sulphate. Guanidine ammonium sulphate has the formula:

N

As is established in the following Examples, guanidine ammonium sulphate functions very effectively as a slow nitrogen release component in a fertilizer.

Various quick release components may be added, such as anhydrous ammonia, aqua-ammonia, NH₄NO₃, Ca(NO₃)₂, or (NH₄)₂SO₄. The preferred quick release component is ammonium sulphate since as will be discussed is a result of the process of this invention. As demonstrated in the following Examples, the combination of the guanidine ammonium sulphate with ammonium sulphate provides both slow and fast release properties and is as significant if not more significant than existing slow and fast release fertilizers.

As is well understood by those skilled in the art, a variety of suitable diluents, excipients, carriers, insecticides, herbicides, mixtures thereof and the like may be incorporated with the fertilizer composition to enhance the properties thereof. In a nitrogen fertilizer having just the slow release properties, the amount of guanidine ammonium sulphate in the fertilizer is

sufficient to provide a coverage of approximately 100 kg of nitrogen per hectare . In the event that a fast release component is also used, then the guanidine ammonium sulphate would make up approximately 50 kg of nitrogen per hectare and the fast release component would make up the remaining 50 kg of the nitrogen per hectare, resulting in a molar ratio of 1 mole of guanidine ammonium sulphate to 1 mole of, for example, ammonium sulphate in the fertilizer composition. In the event that sulphur is also included as a plant nutrient, it may be present as 1 mole of elemental sulphur. This mixture in the fertilizer contains approximately 29.5% nitrogen and 25.2% sulphur by weight.

The preferred process for preparing the slow and the fast nitrogen release components involves the use of sulphur dioxide emissions. The schematic for the process is as follows:

PROCESS SCHEMATIC

As is apparent from the above schematic, the process of this invention provides in combination and in the correct molar ratio, the slow release component of guanidine ammonium sulphate, the fast release component of ammonium sulphate and the plant nutrient elemental sulphur. The less desirable guanidine sulfamate as a source of nitrogen can be converted to guanidine ammonium sulphate by the hydrolysing step. It has been found that hydrolysis of guanidine sulfamate to guanidine ammonium sulphate proceeds rapidly at temperatures in the range of 150° to 200°C by simply injecting into the reaction mixture a hydrolysing agent, such as water or a weak acid. Such hydrolysing step does not affect the ammonium sulphate or elemental sulphur, so the resultant product after hydrolysis is in a form usable as a fertilizer.

Weak acids which may be used in the conversion of

guanidine sulfamate to guanidine ammonium sulphate include dilute sulphuric acid. The cost of preparing the slow and fast nitrogen release components as well as the elemental sulphur is in the range of $0.05 to $0.10 per pound which is cost competitive with other forms of fertilizer components and considerably less than the normal cost of manufacturing guanidine ammonium sulphate.

The process of this invention has a particular benefit in the global environment because it is made from sulphur dioxide emissions as well as ammonia and urea which are also byproducts of industrial processes. The sulphur dioxide emissions are normally removed from waste gases of coal burning power plants, sour natural gas processing installations and smelters. By applicants discovery that guanidine ammonium sulphate is a useful fertilizer component, the driving force now exits to manufacture large quantities of fertilizer involving the use of sulphur dioxide. Such use diverts sulphur dioxide from being emitted to the atmosphere to instead being returned to the soil in a beneficial component. It also provides for a cost effective elimination of sulphur dioxide from emissions without any waste materials, such as the previously produced calcium sulphates. It has been found that the rates of nitrogen release from the guanidine ammonium sulphate and the ammonium sulphate, as established by the following Examples, is well within the specifications for both components and to some extent provides enhanced plant growth.

The above schematic is not intended to be exclusive with respect to the process of making guanidine ammonium sulphate. It is appreciated that there are several variations in preparing a sulfamate. Sulphur dioxide and ammonium may be reacted in a gaseous phase at 150° to 200°C to prepare the solid ammonium sulfamate. The solid ammonium sulfamate may be reacted with urea as a melt at a temperature in the range of 280°C to produce the guanidine sulfamate in the presence of ammonia at a pressure of approximately 200 psi. Such process not only yields the sulfamate, but as well the ammonium sulphate and elemental sulphur. Preferably this reaction is carried out in a high pressure reactor which is capable of withstanding pressures in the range of 200 to 300 psi. Normally the reaction takes about one hour to complete conversion of urea to guanidine sulfamate with the byproducts of ammonium sulphate and elemental sulphur.

The melt mixture is then cooled to a temperature in the range of 150° to 200°C and a hydrolysing agent is injected to the reactor to hydrolyse guanidine sulfamate to prepare guanidine ammonium sulphate salt. As already noted, such hydrolysis of the sulfamate provides a reaction product which includes the desired fast release fertilizer component of ammonium sulphate and the plant nutrient of elemental sulphur. After hydrolysis is complete, which is normally a relatively fast reaction for example in the range of one half hour, the melt is then further cooled to room temperature. During such cooling process, the melt begins to solidify. At this time, the melt may be either granulated by use of

rotating trays to form granules, or sprayed to form prills. Depending upon the end use of the fertilizer, one skilled in the art can select the desired process for conversion into prills or granules. The resultant

material may then be admixed with desired diluents, excipients, carriers, insecticides, herbicides, mixtures thereof and the like. As already mentioned, the amount of nitrogen fertilizer components, whether it be totally slow or a combination of slow and fast release agents, can be used at rates up to 100 kg of nitrogen per hectare. We have found quite surprisingly that the presence of sulfamates in the composition is not totally

deleterious to the fertilizer effect. It has been found that up to 25 kg of sulfamate per hectare or slightly higher may be accommodated in the fertilizer composition without significantly inhibiting plant growth. Although the step of hydrolysing the sulfamates to the guanidine ammonium sulphate salts is very efficient, it is apparent that depending upon the time and temperature of the hydrolysis step, up to 20% or slightly higher of

unhydrolysed sulfamate may be accommodated in the

composition as used in the final fertilizer composition. Hence it is not necessary that there be 100% conversion by the process of this invention of the sulfamates to the ammonium sulphate salts of the guanidine.

The fertilizer compositions of this invention may be applied to the soils in a normal format. Usually they are applied in the granular or prill form; however, the compositions could be dissolved and applied in solution by a variety of spraying techniques.

The following Examples are intended to demonstrate various preferred embodiments of the invention as they fall within the scope of the claims and without being specifically limiting thereto.

EXAMPLE I

This example provides enabling disclosure with respect to the process and provides analysis data regarding identification of the reaction products.

192 gms of SO₂ were reacted with 47 gms of NH₃ at room temperature to give solid ammonium sulfamate. This solid was mixed with 60 gms urea and placed in a high pressure reaction vessel. The vessel was pressurized with ammonia at 200 psi and the temperature was raised to 280°C. After one hour at this temperature the contents of the vessel were cooled to 150° C and 24 gms of water was injected under pressure of approximately 200 psi. T0e reactor was held at 150° C for 1/2 an hour, then cooled to room temperature. The solid was analyzed for guanidine and it was found that guanidine was produced at 82% yield based on urea charged. The resultant solid contained guanidine ammonium sulphate, ammonium sulphate and sulphur. It is appreciated that in the production of the guanidine sulfamate, all three reactants of ammonia, sulphur dioxide and urea may be combined in the reaction vessel to give that product.

EXAMPLE II

This example shows the release of nitrogen from guanidine ammonium sulphate (G.A>S.) over time on

incubation of soil without plants. It should be noted that, in the remaining Examples, the short form G.A.S. for the above and A.S. for ammonium sulphate will be used.

There were 2 cultivated soils, 4 fertilizer

treatments, 2 methods of fertilizer application, 4 times of soil sampling, and 3 replications, Conditions, 25°C with soils maintained at 90% of field capacity water content. The soil samples were placed in 500g

containers. The one soil (Luvisolic) was low in soil organic matter (2.4%) and moderate in texture (loam).

The other soil (Chernozem) was high in soil organic matter (10.2%) and was finely textured (Clay loam).

The abbreviated results (Table 1) indicated at 12 days little of the G.A.S. had been released but by 24 or 36 days most of the G.A.S. was released. The release was slower by band placement as compared to incorporation (both of these methods of application are used in

agronomic practice). The proportions of added G.A.S. and A.S. nitrogen which appeared after 36 or 48 days were much alike (not shown).

EXAMPLE III

This example sets forth experimental results showing yield and nitrogen uptake of barley grown in soil containing no fertilizer, A.S. alone, G.A.S. alone and a mixture of A.S. and G.A.S. obtained from the process of this invention.

There were 2 soils, 4 fertilizer treatments, 2 methods of fertilizer application, 2 times of harvest, and 3 replications. Conditions, average of 18°C

temperature, barley (Hordeum vulgare, cv. Empress) was grown in plastic containers (1.2 litre volume) and soil moisture was maintained at 70 to 90% of field capacity.

The G.A.S. produced little yield increase after 28 days on the Luvisolic soil (Table 2) but after 42 days yields were similar to those produced by the A.S. The uptake of N by the barley followed the same pattern. The patterns were not as clear on the Chernozemic soil (Table 3), except that at 42 days the yield and N-uptake was approximately alike for A.S. and G.A.S.

EXAMPLE IV

This example sets forth experimental results showing yield and nitrogen uptake of barley grown in soil

containing no fertilizer. A.S. alone, G.A.S. alone, A.S. and G.A.S. from the process of this invention, and urea.

There were 13 fertilizer-rates, 2 times of harvest, 2 soils and 3 replicates. Only 8 of those treatments are given here. The yield at 28 days was less with G.A.S. than with A.S. or the mixture on the Luvisolic soil

(Table 4) or the Chernozemic soil (Table 5), and there was a similar tendency in several instances at 49 days. The yields at 49 days were similar for A.S. and the

G.A.S. -A.S. mixture for both soils. Urea, one of the most common commercial fertilizers, tended to yield less than A.S. or the G.A.S. -A.S.

The rate of application in the experiment was 45 or 60 micrograms of N per gram of soil. If these rates were expressed as kilograms of N per hectare on an area basis, the values would be somewhat higher (up to 67.5 to 90 kg N/ha). Consequently, the rates used in the experiment were slightly greater than the rates used in the field in the Prairie Provinces.

EXAMPLE V

This example compares sources of guanidine salts by yield and N-uptake of barley in the greenhouse.

There were 14 treatments, 2 times of harvest and 3 replicates. Only the Luvisolic soil was used. One of the purposes was to compare the effect on barley of the batch of G.A.S. /A.S. of the subject process and G.A.S. obtained from Aldrich Chemical Company, Inc. Milwaukee, Wisconsin. It was best to find if the behaviour of the batch of G.A.S. /A.S. was common to other batches of G.A.S. The other purpose was to find if other guanidine compounds (chloride, carbonate) influence barley as does the G.A.S. /A.S. fertilizer.

At 28 days, the two batches of G.A.S. /A.S., the guanidine chloride and the guanidine carbonate all showed delayed release of nitrogen. By 56 days, yield and N- uptake with the four guanidines were much the same at 60 ug N/g of A.S. plus 30 ug N/g guanidine as shown in Table 6. The same was true with addition of only 90 ug N/g of the guanidines. However, with only guanidines at 90 ug N/g there was initial slwoing of plant growth (apart from nitrogen deficiency during the 2 to 4 week period.

a Batch of guanidine ammonium sulphate/ammonium sulphate made by Example 1 b Guanidine ammonium sulphate from Aldrich Chemical

c Guanidine carbonate from Aldrich Chemical

d Guanidine chloride from Aldrich Chemical

EXAMPLE VI

This example explored the effect of G.A.S. on germination and seedling growth for four crop species.

The experiment was conducted in a chamber (22 to 23°C) with 30 seeds place between moistened filter paper in a series of Petri dishes. There were 3

replications of the moistening solutions of A.S. and G.A.S. at the following nitrogen concentrations: 0, 5, 15, 45, 135 and 405 parts per million. The seeds were of barley, wheat, oats and canola. rapeseed, Brassica campestris) . There were no statictically significant difference between seed germination in A.S. solution s and G.A.S. solutions. Likewise, the shoot lengths at 4, 6 and 8 days did not differ comparing the seedling in A.S. solutions to seedlings in G.A.S. solution.

EXAMPLE VII

This example explored the effect of rate of G.A.S. on yield of four crop species in the greenhouse.

The purpose was to find if G.A.S. decreases yield when sufficient A.S. nitrogen is added for optimum crop yield. The A.S. addition was 180 ug N/g, and the

additions of G.A.S. were 30, 60 and 90 ug N/g (see Table 7). There was a tendency for slightly less yield with 90 compared to 60 or 30 ug N/g of G.A.S. at 21 days (not shown). The yields at 56 days showed small but

significant yield increases from G.A.S. in some instance even though the G.A.S. nitrogen was not needed. However, there were small decreases in yield with increasing the G.A.S. rate from 60 to 90 for barley and wheat, and therefore, maximum rate of G.A.S. nitrogen could be set at around 60 ug N/g for the time being.

EXAMPLE VIII

Three controlled "in-house" field experiments, each with 20 treatments in four replicates were begun in the second October, 1989. Only 8 of those treatments are pertinent to this report. One purpose was to determine the rate at which the G.A.S. -A.S. mixture of the subject invention compared to commercial urea fertilizer in conversion to ammonium and nitrate by soil during the fall to spring period. Another purpose was to compare the yield of spring-sown barley grain in the fall of 1990, when the mixtures and urea were applied in the previous fall. Approximately 20 to 40% of the nitrogen fertilizers used in the Prairie provinces are applied in the fall (the proportion varies from year to year), but fall-applied nitrogen is only 55% (average) as effective as spring-applied nitrogen fertilizer is. The poor effectiveness of fall-applied nitrogen fertilizer is mostly through loss in soil of the ammonium and nitrate added by the fertilizer. If nitrogen fertilizer remained mostly in a form other than ammonium and nitrate it would be more resistant to loss in the wet soil found early in spring.

Soil sampled in February, 1990 had on the average only 21% as much ammonium- and nitrate-nitrogen derived from the G.A.S. /A.S. mixture treatments as compared to the amount of ammonium- and nitrate-nitrogen in the urea treatments. This result indicated that the G.A.S. /A.S. mixture was more resistant to fall to spring loss than was the urea.

The barley on the average had taken up 78 kg N ha^-1 from the G.A.S. /A.S. mixture but only 63 kg N ha^-1 from the urea.

The increase in yield of barley grain was, on the average, 1.73 t ha^-1 from the application of the

G.A.S. /A.S. mixture, but 1.46 to ha^-1 from the urea. The exemplified preferred embodiments of the invention clearly demonstrate the advantageous use of sulphur dioxide emissions to make slow and fast release fertilizer components as well as elemental sulphur plant nutrient which is not only beneficial to the environment, but also to plant growth.

Although preferred embodiments of the invention are described herein in detail, it will be understood by those skilled in the art that variations may be made thereto without departing from the spirit of the

invention or the scope of the appended claims.

Claims

1. A nitrogen fertilizer composition having slow nitrogen release properties, said fertilizer comprising guanidine ammonium sulphate.

2. A fertilizer of claim 1 further comprising ammonium sulphate to provide a fertilizer having fast and slow nitrogen release properties.

3. A fertilizer of claim 1 or 2 further comprising elemental sulphur.

4. A fertilizer of claim 1, 2 or 3 further comprising suitable diluents, excipients, carrier insecticides, herbicides and mixtures thereof.

5. In a plant fertilizer having slow and fast nitrogen releasing properties, said fertilizer comprising an ammonium salt in admixture with a guanidine based nitrogen source, the improvement comprising:

said guanidine based nitrogen source consisting of guanidine ammonium sulphate.

6. In said fertilizer of claim 5, said ammonium salt being ammonium sulphate.

7. In said fertilizer of claim 6, further comprising elemental sulphur.

8. A process for preparing a slow nitrogen release guanidine ammonium sulphate for use in nitrogen

fertilizer, said process comprising :

hydrolysing a melt of guanidine sulfamate with a hydrolysing agent to produce said guanidine ammonium sulphate.

9. A process of claim 8 wherein said melt is hydrolysed with water or a weak acid.

10. A process of claim 9 wherein said weak acid is dilute sulphuric acid.

11. A process of claim 8 wherein said guanidine

sulfamate melt is prepared by reacting a melt of ammonium sulfamate with urea to yield a melt of guanidine

sulfamate, ammonium sulphate and sulphur.

12. A process of claim 11 wherein said ammonium

sulfamate is prepared by reacting in gaseous phase a mixture of a source of ammonia and sulphur dioxide.

13. A process of claim 12 wherein said source of sulphur dioxide is waste gases containing sulphur dioxide emissions.

14. A process of any one of claims 8 through 13 wherein suitable diluents, excipients, carriers, insecticides, herbicides or mixtures thereof are admixed with said guanidine ammonium sulphate.