Background for this classification summary
- Visit the Classification Index to see other groups.
- The summary on this page follows the classification scheme of Elsner and Hoelzer, 2016. Quantitative Survey and Structural Classification of Hydraulic Fracturing Chemicals Reported in Unconventional Gas Production. Environmental Science and Technology. 3290-3314. DOI: 10.1021/acs.est.5b02818.
- Elsner and Hoelzer’s thorough and influential article provides a wealth of chemical context about fracking materials including health and environmental implications and suggestions for deeper analysis. However, the work was based partially on a early set of FracFocus (through 2013). Subsequent years have added new materials and millions more records. To extend their analysis to the rest of the FracFocus materials, we used Google’s Gemini to assist us in assigning classifications in line with EH’s methodology.
- Analysis from a FracFocus download, Jan 2025.
- Masses are not available for all records, so reported masses below are sums of only the available masses. See documentation.
- To provide useful technical information about these chemical groups, we use generative AI tools to assist with summaries (Google’s Gemini). These tools are prompted with details of the classification scheme (by Elsner and Hoelzer, 2016) and information about reported chemicals in the group. To limit inaccuracies, we feed the resulting output to competing models (OpenAI’s ChatGPT) to check for accuracy and ambiguity. In addition, we consulted Fink, Johannes, “Petroleum Engineer’s Guide to Oil Field Chemicals and Fluids” Third Edition. (2021) Gulf Professional Publishing. 1028pp.
- Functions reported here are summarized from the FracFocus field “Purpose.” There are limitations to this data: not all chemical records have a reported purpose (the “systems approach” explicitly excludes “Purpose” values from chemical records). Furthermore, “Purpose” typically describes the product, not individual chemicals within the product. The individual ingredient may serve a chemical role in the product that is different from the reported “purpose” (for example, synthetic polymers might be labeled “proppant”, but they are not primary proppants, but rather coatings for sand grains to enhance their performance.) In general, consider these “functions” as the larger purpose played by the product that contains the ingredient.
Amines, as reported to FracFocus, are a class of organic compounds derived from ammonia (NH₃), where one or more hydrogen atoms are replaced with organic groups. These compounds are characterized by a nitrogen atom with a lone pair of electrons, making them basic and nucleophilic.1
The Amines group is subdivided based on structural characteristics:
- Amine – aminoalcohols (19 reported chemicals)
- Mono- and polyamines (41)
- Amine – alkoxylated (16)
- Amine oxides (6)
- Amine – unspecified (7)
Between 2014 and 2024, FracFocus recorded 61,600 entries for amines, with a total reported mass of 244,000,000 pounds.
Products containing these amines serve various functions in hydraulic fracturing, including use as surfactants, proppants, emulsifier controls, corrosion inhibitors, crosslinkers, breakers, biocides, and iron control agents. The versatility of amines arises from their ability to act as bases, nucleophiles, and ligands. Their properties can be fine-tuned by modifying the organic groups attached to the nitrogen atom, allowing for diverse chemical applications.
Subclass: amine – aminoalcohol
Number of reported materials: 19
The “amine – aminoalcohol” subgroup within the Amines category consists of compounds that contain both an amine functional group (-NRâ‚‚)—where R can be hydrogen or an organic group—and a hydroxyl group (-OH) on an alkyl chain. These compounds are commonly referred to as alkanolamines.
Commonly Reported Compounds:
- Simple alkanolamines, including:
- Ethanolamine (141-43-5) – Also known as monoethanolamine (MEA)
- Diethanolamine (DEA, 111-42-2)
- Triethanolamine (TEA, 102-71-6)
- Salts of alkanolamines, such as:
- Triethanolamine hydrochloride (637-39-8)
- Triethanolammonium glycolate (68299-02-5)
The presence of both amine and hydroxyl groups allows these molecules to engage in diverse chemical interactions, making them useful in hydraulic fracturing as pH adjusters, corrosion inhibitors, and potentially as components of emulsifiers or surfactants.
Most common amine – aminoalcohol:
| Material | Name | Records and mass |
|---|---|---|
111-42-2 | Diethanolamine | 19,000 records — 84,200,000 pounds |
102-71-6 | Triethanolamine | 2,500 records — 14,500,000 pounds |
141-43-5 | Ethanolamine | 1,920 records — 3,390,000 pounds |
637-39-8 | Triethanolamine hydrochloride | 503 records — 43,400 pounds |
Subclass: mono- and polyamines
Number of reported materials: 41
The “mono- and polyamines” subgroup within the Amines category includes compounds that contain one or more amine functional groups (-NRâ‚‚), where R can be hydrogen or an organic group. This category excludes aminoalcohols and encompasses both simple amines and polyamines with multiple nitrogen atoms.
Commonly Reported Compounds:
- Simple amines and polyamines, such as:
- Diethylenetriamine (DETA, 111-40-0) – A polyamine with three nitrogen atoms, used in various industrial applications.
- Methenamine (Hexamethylenetetramine, 100-97-0) – A heterocyclic compound with four nitrogen atoms, known for its stability and reactivity.
- Fatty amine derivatives, including:
- Amines, dicoco alkylmethyl (61788-62-3) – Likely included for its ability to reduce surface tension.
- More complex reaction products, such as:
- Fatty acids, tall-oil, reaction products with diethylenetriamine (61790-69-0).
- 1,2-Ethanediamine, N¹-(2-aminoethyl)-N²-[2-[(2-aminoethyl)amino]ethyl]-, polymer with 2-methyloxirane and oxirane (68815-65-6).
The structural diversity of these amines allows them to serve various functions in hydraulic fracturing, including corrosion inhibition, pH control, crosslinking, and clay stabilization.
Most common mono- and polyamines:
| Material | Name | Records and mass |
|---|---|---|
100-97-0 | Methenamine | 8,710 records — 104,000,000 pounds |
| 61788-62-3 | Amines, dicoco alkylmethyl | 1,650 records — 1,450,000 pounds |
| 61790-69-0 | Fatty acids, tall-oil, reaction products with diethylenetriamine | 1,440 records — 128,000 pounds |
111-40-0 | Diethylenetriamine | 1,380 records — 2,090,000 pounds |
| 68815-65-6 | 1,2-Ethanediamine, N1-(2-aminoethyl)-N2-[2-[(2-aminoethyl)amino]ethyl]-, polymer with 2-methyloxirane and oxirane | 775 records — 1,650,000 pounds |
Subclass: amine- alkoxylated
Number of reported materials: 16
The “amine – alkoxylated” subgroup within FracFocus’s Amines category consists of amine compounds modified by the addition of alkylene oxide units, typically ethylene oxide (ethoxylation) or propylene oxide (propoxylation). This modification increases water solubility and adjusts the hydrophilic-lipophilic balance (HLB), influencing the compound’s surfactant properties.
Commonly Reported Compounds:
- PEG-10 Hydrogenated Tallow Amine (61791-26-2) – A hydrogenated tallow amine (derived from animal fat) ethoxylated with approximately 10 ethylene oxide units.
- Amines, polyethylenepoly-, ethoxylated, phosphonomethylated, sodium salts (70900-16-2) – A polyethylene polyamine derivative modified with ethoxylation and phosphonomethylation.
- Poly(oxy-1,2-ethanediyl), alpha,alpha’-[(dodecylimino)di-2,1-ethanediyl]bis[omega-hydroxy-] (31017-83-1) – A complex ethoxylated amine-based surfactant.
- Amines, C14-18; C16-18-unsaturated, alkyl, ethoxylated (68155-39-5) – An ethoxylated fatty amine, often used for surface-active properties.
- Bis[omega-hydrogenpoly(oxyethylene)]oleylamine (26635-93-8) – An ethoxylated oleylamine, contributing to emulsification and dispersion.
The alkoxylation process significantly enhances the surfactant properties of these amines, making them valuable for emulsification, dispersion, and wetting in hydraulic fracturing fluids.
Most common amine- alkoxylated:
| Material | Name | Records and mass |
|---|---|---|
| 61791-26-2 | PEG-10 Hydrogenated tallow amine | 11,600 records — 13,100,000 pounds |
| 70900-16-2 | Amines, polyethylenepoly-, ethoxylated, phosphonomethylated, sodium salts | 954 records — 4,080,000 pounds |
| 31017-83-1 | Poly(oxy-1,2-ethanediyl), alpha,alpha’-[(dodecylimino)di-2,1-ethanediyl]bis[omega-hydroxy-] | 572 records — 93,200 pounds |
| 68155-39-5 | Amines, C14-18; C16-18-unsaturated, alkyl, ethoxylated | 274 records — 17,500 pounds |
26635-93-8 | Bis[omega-hydrogenpoly(oxyethylene)]oleylamine | 268 records — 1,130,000 pounds |
Subclass: amine oxides
Number of reported materials: 6
The “amine oxides” subgroup within the Amines category consists of compounds where a tertiary amine (R₃N) has been oxidized to form an amine N-oxide (R₃N→O). In these compounds, the nitrogen is bonded to three organic groups and one oxygen atom, resulting in a polar, nonionic structure.
Commonly Reported Compounds:
- N,N-Dimethyl-methanamine-N-oxide (1184-78-7) – Also known as Trimethylamine N-oxide, a small, highly polar molecule.
- Longer-chain alkyl dimethylamine oxides, including:
- N,N-Dimethyldecylamine oxide (2605-79-0).
- 1-Decanamine, N-decyl-N-methyl-, N-oxide (100545-50-4).
- C10-16-alkyldimethyl amine N-oxides (70592-80-2) – A mixture of alkyl dimethylamine oxides with varying chain lengths.
- More complex structures, such as:
- Amides, coco, N-[3-(dimethylamino)propyl], N-oxides (68155-09-9) – A coconut-derived amide-based amine oxide.
Properties & Applications:
The N-oxide functionality increases water solubility and reduces basicity compared to the parent amine, improving compatibility with other surfactants.
Amine oxides are polar, nonionic surfactants, commonly used in hydraulic fracturing fluids.
Their foam-boosting and viscosity-enhancing properties make them valuable in friction reducers and emulsifiers.
Most common amine oxides:
| Material | Name | Records and mass |
|---|---|---|
1184-78-7 | N,N-Dimethyl-methanamine-N-oxide | 284 records — 117,000 pounds |
100545-50-4 | 1-Decanamine, N-decyl-N-methyl-, N-oxide | 138 records — 135,000 pounds |
2605-79-0 | N,N-Dimethyldecylamine oxide | 134 records — 247,000 pounds |
| 68155-09-9 | Amides, coco, N-[3-(dimethylamino)propyl], N-oxides | 99 records — 244,000 pounds |
| 70592-80-2 | C10-16-alkyldimethyl amine N-oxides | 34 records — 20,600 pounds |
Subclass: amine – unspecified
Number of reported materials: 7
The “amine – unspecified” subgroup within FracFocus’s Amines category includes amine-containing compounds that do not fit into the other, more specific subgroups (such as aminoalcohols, alkoxylated amines, amine oxides, or mono- and polyamines). This category often encompasses mixtures or compounds with less precisely defined structures.
Commonly Reported Compounds:
- Amines, C12-16-alkyldimethyl (68439-70-3) – A tertiary alkyl amine with a C12-16 alkyl chain.
- 2-Aminoethanol hydrochloride (2002-24-6) – The hydrochloride salt of ethanolamine, which is an aminoalcohol but may be classified here due to its salt form.
- β-Alanine, N-(2-carboxyethyl)-N-(2-ethylhexyl)-, sodium salt (1:1) (94441-92-6) – An amino acid derivative with ethylhexyl and sodium salt groups.
- β-Alanine, N-(2-carboxyethyl)-N-dodecyl-, monosodium salt (14960-06-6) – Another amino acid derivative, this one containing dodecyl and sodium salt groups.
- Fatty acids, C18-unsatd., dimers, polymers with diethylenetriamine and tall-oil fatty acids (68139-75-3) – A complex reaction product made from polymerized fatty acids and diethylenetriamine, with applications in surfactants and other formulations.
The functions of these compounds can vary, potentially serving as: Corrosion inhibitors and Surfactants
Most common amine – unspecified:
| Material | Name | Records and mass |
|---|---|---|
| 68439-70-3 | Amines, C12-16-alkyldimethyl | 980 records — 346,000 pounds |
2002-24-6 | 2-Aminoethanol hydrochloride | 924 records — 943,000 pounds |
14960-06-6 | beta-Alanine, N-(2-carboxyethyl)-N-dodecyl-, monosodium salt | 254 records — 6,630 pounds |
94441-92-6 | .beta.-Alanine, N-(2-carboxyethyl)-N-(2-ethylhexyl)-, sodium salt (1:1) | 248 records — 19,000 pounds |
| 68139-75-3 | Fatty acids, C18-unsatd., dimers, polymers with diethylenetriamine and tall-oil fatty acids | 111 records — 2,040,000 pounds |
- All molecular structure images courtesy of the US EPA, except where noted. ↩︎