EP0569110A1

How To Remove Sulfur From Wax

Info

Publication number: EP0569110A1
Application number: EP93250125A
Authority: EP
Inventors: Gabriella Julianna Toeneboehn; William Alan Welsh
Original assignee: WR Grace and Co Conn; WR Grace and Co
Current assignee: WR Grace and Co Conn; WR Grace and Co
Priority date: 1992-05-05
Filing date: 1993-05-04
Publication date: 1993-11-10
Also published as: CA2094988A1; ECSP930925A; CO4180404A1; US5298638A; TR27056A; HU9301292D0; PL298814A1; SK41693A3; NZ247051A; HUT67458A; CZ73493A3; KR930023447A; JPH0633086A; AU3511593A

Abstract

A process for removal of sulfur-containing compounds from fatty materials is disclosed, in which the fatty material is contacted with a silica hydrogel. Use of this adsorptive process prior to hydrogenation improves oil quality and decreases hydrogenation times.

Description

Background OF THE INVENTION

Fatty acrid-based materials (fatty materials) such equally glyceride oils, wax esters, milk fat, and other fatty acrid compounds accept a long history of use since many of these materials are naturally derived from plants (e.g., vegetable oils) or animals (due east.g., tallow, milk fat, fish oil, etc.).
While these fatty materials oftentimes have been direct used in their crude country, for utilize in modern commercial products, these materials are typically subjected to a refining process. Refining processes may be used to remove various contaminants and impurities which are undesirable for reasons of health, performance, aesthetics, etc.
The fatty material may contain impurities such equally colour bodies, chlorophyll, phospholipids (phosphatides), trace metals, free fat acids, gums, soaps, and/or other impurities. This variety of diverse impurities has led to the development of numerous refining processes involving particular combinations of chemical and/or concrete treatment steps. A detailed review of refining processes for removal of these impurities may be found in the "Handbook for Soy Oil Processing and Utilization," David R. Erikson et al. (ed.), ASA/AOCS Monograph (1980).
Fatty materials may also comprise sulfur, either in the form of naturally occurring sulfur compounds or in the form of contaminants from various processing or refining steps. For instance, certain glyceride oils, most notably canola and rapeseed oils are known to contain small amounts of sulfur in the form of episulfides, isothiocyanates, thiocyanates, oxazolidinethiones, sulfates and sulfur-containing fatty acids. These oil soluble sulfur compounds are the product of enzymatic decomposition of sulfur-containing glucosinolates in the plant seed, which occurs during processing of the seed. Fish oils are also known to comprise naturally occurring sulfur-containing compounds. Substantial proportions of sulfur are removed in degumming and alkali refining operations, but refined canola oils, for instance, may still contain upwardly to 9 or more ppm sulfur.
Sulfur compounds present both artful and refining problems, They are implicated in the production of unpleasant odors during heating of the oils or other fatty materials. In improver, these sulfur compounds poison the catalysts used during hydrogenation, resulting in either increased catalyst usage (with a corresponding increase in the disposal burden) or longer hydrogenation times resulting in lower product rates. This is an economically important consideration, since enormous quantities of fatty materials are hydrogenated, a reaction in which some of the double bonds are removed in order to modify the fabric's viscosity (e.g., converting canola oil into margarine). Sulfur has not been found to exist removed during conventional refining or oil treatment methods to sufficient extents to avoid problems in hydrogenation. In fact, total sulfur content may increase during treatment with activated bleaching earth (ABE).
1 result of the poisoning of nickel hydrogenation catalysts by sulfur is a shift in selectivity toward increased isomerization of triglyceride double bonds from the naturally occurring cis olefin isomer to non-naturally occurring trans olefin isomer. This reaction is idea to occur when a triglyceride fatty cloth adsorbs on the catalyst but is not hydrogenated earlier desorption. The increased trans isomer content typically raises the melting betoken only also has been cited as a health event relative to the more naturally occurring cis isomer.
The presence of cis and trans isomers can be studied by infrared spectroscopy while the level of unsaturation can be quantified by NMR techniques. Thus, the ratio of cis-to-trans can exist calculated and compared at a constant level of double bond hydrogenation. Higher cis/trans ratios would exist observed when a catalyst was less sulfur poisoned. Thus, 1 possible consequence of adsorptive sulfur removal prior to hydrogenation would be less trans isomer and therefore a higher cis/trans ratio, resulting in a more natural product.
F. Cho-Ah-Ying et al., "Adsorptive Removal of Sulfur from Canola Oil," Fatty. Sci. Technol., No. 4, pp. 132-v (1991), describes an investigation of physical adsorption of sulfur using alumina, alumina-silicate, diatomaceous silica and TriSyl® silica gel (Davison Division, West. R. Grace & Co.-Conn.) in conjunction with bleaching earths. The article reports that compared to the unactivated TriSyl® silica gel, the activated adsorbent (dried at 240°C for 3 hours) had a higher chapters for adsorbing Raney® nickel sulfur at all concentrations used. For that reason, Cho-Ah-Ying opted to utilize the activated silica gel adsorbent throughout the experiments. The article reports that the addition of ii or 4% alumina, alumina-silicate, diatomaceous silica and silica gel (presumably the unactivated form) did non farther amend the removal of sulfur.

SUMMARY OF THE INVENTION

The invention provides a concrete adsorption process for the removal of sulfur compounds from fat materials. Amorphous silica hydrogels have been found to exhibit excellent capacity for adsorption of the enzymatic decomposition products of sulfur-containing glucosinolates. This process for removal of sulfur compounds from fatty materials comprises:

(a) selecting a fat material comprising sulfur-containing compounds;
(b) selecting a silica hydrogel;
(c) contacting the fatty material of stride (a) and the silica hydrogel of pace (b); and
(d) assuasive sulfur to be adsorbed onto said silica hydrogel.

The invention too provides a process for decreasing hydrogenation times for the hydrogenation of fat materials using hydrogenation catalysts, in which the fatty material is treated by contact with a silica hydrogel prior to hydrogenation to reduce the level of sulfur-containing compounds in the fatty fabric.
In improver, the invention provides an improved hydrogenated fatty fabric, having an increased cis-to-trans olefin isomer ratio. The sulfur adsorption process decreases isomerization of cis isomers to trans isomers, which typically are formed as a result of poisoning of the hydrogenation catalyst.
Preferably, the silica hydrogel used in this process has a full volatiles content of, at least about 25 wt.%. In alternative embodiments, the silica hydrogel is treated with an acid selected from an organic acid, and inorganic acid or an acrid common salt.

DETAILED DESCRIPTION OF THE INVENTION

Broadly, the invention relates to the treatment of whatever fatty material comprising sulfur-containing compounds where the fat cloth is contacted with a silica hydrogel for purposes of removing sulfur compounds from the fatty material. More than specifically, silica hydrogels have been found to exist effective for adsorption of enzymatic decomposition or hydrolysis products of sulfur-containing glucosinolates. Removal of these compounds from fatty materials improves the quality of those materials, since the sulfur compounds cause unpleasant odors upon heating. Important economic benefits can also be realized past the removal of these sulfur compounds, which poison hydrogenation catalysts, especially nickel hydrogenation catalysts. The upshot is an improved hydrogenation operation, either by reduction in hydrogenation times or catalyst usage.

The Fatty Materials

As discussed above, the fatty materials may be glyceride oils, wax esters, milk fat or other fatty acid compounds. This invention is expected to exist of particular importance in the processing of canola or rapeseed oils, and the processing of wet-milled corn oil and fish oils, which comprise the offending sulfur-containing compounds. All the same, the process of the invention can be used for any fatty material comprising sulfur-containing compounds, such as episulfides, isothiocyanates, thiocyanates, oxazolidinethiones, and sulfur-containing amino acids. Decomposition products of isothiocyanates (hydrogen sulfide and other sulfides) are specially active catalyst poisons and are as well considered "sulfur-containing compounds" as that term is used herein.
Corn oil likewise contains sulfur compounds, although from dissimilar sources. Natural sulfur compounds may exist absorbed and metabolized from the soil every bit nutrients, In addition, during wet milling, SO₂ is added as a preservative, and the resulting sulfur content of corn oil may be about 20-30 ppm. The SO₂ will react with cysteine and cystine to form trace amounts of sulfur-containing proteins in the oil. Fish oils, for example, mackeral oil, contain naturally occurring sulfur compounds. Other fat materials may incorporate or become contaminated with sulfur compounds which may be removed past the process of this invention.
The fatty textile may be treated according to the invention at any convenient fourth dimension or stage in refining or handling. Most preferably, the fatty material will be treated prior to hydrogenation, in order to maximize the benefits to the hydrogenation process.

The Silica Hydrogel Adsorbent

The adsorbent used for the sulfur removal of this invention will exist a silica hydrogel. It has been found that amorphous silica hydrogels accept an analogousness for the types of sulfur-containing compounds described above and tin can be used quite effectively in a process for the adsorptive removal of those compounds from fatty materials. This is a surprising discovery, since the Cho-Ah-Ying article discussed in a higher place teaches that activated (stale) silicas are preferred for this purpose.
According to the nowadays invention, silica hydrogel adsorbents are used, with the silica hydrogel component of the adsorbent having a total volatiles content ("Television") of at least about 25 wt.%, preferably at least nigh 40 wt.%, most preferably at least about 65 wt.%. The adsorbent may be used with other compositions which are either inert to the fatty material and its contaminants, or which are present for the purpose of removing i or more other contaminants from the fatty material (that is, contaminants other than sulfur-containing compounds). For example, the silica hydrogel may be used in conjunction with bleaching earth for the removal of trace metals and/or colour bodies.
The particle size of the silica hydrogel is not believed to be critical to the invention, but will be selected on the basis of operating requirements. It will be preferred to use particle sizes upward to well-nigh 250 microns, but that is not required.
Mostly, fines < three microns are to be avoided due to filtration problems. Ultra large (> 250 micron) particles may present adsorption problems due to diffusion resistance. Preferably the adsorbent would be used at a loading (weight %, as is based on oil to be treated) of 0.05-five.0%, more preferably at 0.i-4.0% and most preferably at 0.1-two.0%.
The purity of the amorphous silica used in this invention is non believed to be critical in terms of the adsorption of phospholipids. However, where the finished products are intended to exist nutrient grade oils care should exist taken to ensure that the silica used does not contain leachable impurities which could compromise the desired purity of the product(southward). Information technology is preferred, therefore, to employ a substantially pure amorphous silica, although minor amounts, i.e., less than about xx%, preferably less than 10%, of other inorganic constituents may be present. For example, suitable silicas may comprise atomic number 26 as Fe₂O₃, aluminum equally Al₂O₃, titanium as TiO₂, calcium as CaO, sodium as Na₂O, zirconium every bit ZrO₂, and/or trace elements.
In improver to standard amorphous silica hydrogels, acid-treated hydrogels may be used as the adsorbents of this invention. If desired, a mixture of standard and acrid-treated hydrogels may be used. Acrid-treated hydrogels may be prepared by treating a silica hydrogel with an organic or inorganic acid or an acid salt such that acid is retained in the pores of the hydrogel, for example, as taught in U.S. four,877,765 and U.Southward. iv,939,115. That is, organic acids such as citric acid, tartaric acid, etc., or inorganic acids such as sulfuric acid, phosphoric acid, hydrochloric acid, etc., may be used. The acid-treated hydrogel may be prepared by slurrying the silica hydrogel in an acidic solution, or past whatsoever other manner which is user-friendly, such as by the methods described in the above-mentioned U.S. patents.

The Handling Process

The adsorption procedure of this invention may be conducted in any fashion which provides adequate contact betwixt the hydrogel and the fatty material to promote adsorption of sulfur on the adsorbent. The treatment protocol will depend on the refinery set-up, and its selection would be inside the cognition and power of i of ordinary skill in the art. Contact may be past batch or continuous processing, so long as sufficient contact is maintained between the fatty cloth and the silica hydrogel to upshot the adsorption.
The fatty textile may be treated at any convenient temperature at which it is a liquid. It is preferred, however, to heat the fatty material to near 40-160°C, almost preferably between 70 to 120°C. The adsorption of this invention may be conducted under vacuum, or at atmospheric pressure. Temperature and pressure should be selected to protect the fatty cloth from harm. For example, at atmospheric pressure and with exposure to air, it will be preferred to operate beneath about seventy°C, whereas with the utilise of vacuum, the fatty textile may tolerate temperatures up to about 260°C.
Post-obit this treatment, the silica hydrogel is removed from the fatty material. Removal of the sulfur-containing adsorbent preferably occurs prior to the hydrogenation of the fatty material. Nevertheless, the adsorbent need not be removed immediately following contact with the fatty cloth, and information technology may exist convenient to subject the fat material to other processing steps prior to adsorbent removal. For example, the fatty material may be contacted with an additional adsorbent for removal of chlorophyll or other contaminants, afterward which both the sulfur-adsorbent and the chlorophyll-adsorbent may be removed simultaneously in a single step.
Any convenient separation may be employed. Information technology may be virtually user-friendly to remove the adsorbent from the fatty material past filtration. Culling methods, such equally centrifugation or settling, will exist acceptable from the standpoint of sulfur removal, although they may be less economical in the overall context of a refinery.
The sulfur-depleted fatty material may then be used or candy every bit desired. For glyceride oils, it is expected that hydrogenation would exist the nigh frequent subsequent processing pace. It is at present known that removal of sulfur-containing compounds by adsorption onto baggy silica hydrogels volition reduce hydrogenation times and therefore hydrogenation goad usage. This removal of sulfur compounds as well yields a hydrogenated product having an unusually loftier ratio of cis-to-trans olefin isomers, preferably a ratio greater than five.0.
The examples which follow are given for illustrative purposes and are not meant to limit the invention described herein. The following abbreviations have been used throughout in describing the invention:

°C -: degrees Centigrade
°F -: degrees Fahrenheit
FTIR -: Fourier Transformed Infrared
gm -: gram(south)
ICP -: inductively coupled plasma emission spectroscopy
kg -: kilogram(s)
ppm -: parts per 1000000
RI -: refractive index
rpm -: revolutions per minute
wt.% -: weight per centum

Example I (Sulfur Removal)

A super degummed canola oil containing five.8 ppm total sulfur was used in this instance. Sulfur analysis was measured by inductively coupled plasma (ICP) atomic emission spectroscopy. The silica hydrogel adsorbent used was TriSyl® silica hydrogel (Davison Partitioning, W. R. Grace & Co.-Conn.). Control Adsorbent #1 was a stale silica hydrogel (TriSyl® silica oven dried at 200°C for 2 hours). Command Adsorbent #2 was a commercial premium activated bleaching globe (ABE).
Adsorptive treatments were conducted by heating multiple 300.0 gm batches of canola oil in a glass flask for 20 minutes in a h2o bath to lxx°C. Adsorbent was then added to the level indicated in Tabular array I and stirred into the oil with a mixer set at 1400 rpm. The flask was transferred to a 100°C water bath and placed nether vacuum at 60 torr force per unit area for 40 minutes with continued stirring. The oil was then removed from the bath and cooled to below 70° while vacuum was maintained. The vacuum was then asunder and the adsorbent filtered from the oil.
Table I shows the results in terms of total sulfur remaining in each treated oil sample. The observed performance of the dried silica gel (Control Adsorbent #1) was consistent with the literature reports that dried silica reduces sulfur content. The ABE (Control Adsorbent #two) was ineffective in reducing full sulfur. The performance of the silica hydrogel adsorbent was surprisingly better than expected based on the literature, peculiarly when considered on a silica basis, as shown in Table I (last cavalcade). On that basis, the silica hydrogel outperformed the dried silica control.

Example 2 (Hydrogenation)

Afterwards the adsorbent treatments of Example I, quantities of the treated oil samples were then bleached past treatment with ABE as required to obtain oil with depression phosphorus and chlorophyll A levels consistent with specifications for pre-hydrogenation glyceride oil (typically < one.0 ppm phosphorus and < .05 ppm ChlA). Oils treated in Example I with Control Adsorbent #2 were not separately treated here with ABE.
The treated oil samples were then hydrogenated in a stirred tank reactor, under nonselective conditions, using refractive index (RI) at twoscore°C as an in-process measure of the degree of hydrogenation. Detailed hydrogenation conditions were as follows:

· 180°C
· xxx psi
· 600 rpm agitation
· 500 gm oil samples from combined Case I batches
· 0.01 wt.% Ni-AOCS Reference Goad #2*
· Endpoint: RI = 1.4616 at 40°C

Figure imgb0002

EXAMPLE Iii

Oils from Example 2 were compared subsequently hydrogenation for their cis and trans isomer contents. Fourier Transformed Infrared (FTIR) information were collected for each sample in indistinguishable or triplicate using a Nicolet 205 FTIR (32 scans, 4 cm⁻¹ resolution, capillary film betwixt salt plates). Peak intensities were obtained by integrating over a divers, baseline-corrected spectral region. The results are listed in Tabular array Iii showing the ratio of integrated bands for trans (915-870 cm⁻¹) and cis (750-700 cm⁻¹) double bonds. The precision of the FTIR peak intensity calculation is estimated to exist ten% relative.

Table III

	Usage (wt.% (As Is)		Cis/Trans Ratio
	Silica	ABE
Control Adsorbent #ii just	--	three.5	4.6
Hydrogel + ABE	3.0	1.nine	12.0

Claims

A process for removal of sulfur-containing compounds from fatty materials comprising

(a) selecting a fat material comprising sulfur-containing compounds;

(b) selecting a silica hydrogel;

(c) contacting the fatty material of step (a) and the silica hydrogel of step (b);

(d) allowing sulfur to exist adsorbed onto said silica hydrogel; and

(due east) optionally followed past a drying step.
The process of claim one in which said fatty material is selected from the group consisting of glyceride oils, specially canola oil, rapeseed oil, fish oil or corn oil, wax esters, milk fat, other fat acid compounds and mixtures thereof.
The procedure of claim 2 in which said oil is caustic refined canola or rapeseed oil.
The process of claims one to 3 in which the silica hydrogel is subsequently separated from the sulfur-depleted fatty material.
The process of claims 1 to 4 in which said silica hydrogel has a full volatiles content of at least nigh 25 wt.%.
The process of claims ane to 5 in which the silia hydrogel has been treated with an acid selected from an organic acid, inorganic acrid or acrid table salt.
An improved procedure for the refining of fatty materials using bleach globe equally an adsorbent, which procedure comprises the steps of phospholipid removal, bleaching and deodorizing, the comeback comprising removing sulfur by contacting said fat textile with a silica hydrogel, said fat fabric having been treated by contact with a bleaching globe adsorbent to reduce phospholipids and chlorophyll, if whatsoever, to commercially acceptable levels prior to contacting the fatty material with said silica hydrogel.
The improved process of claim 7 in which said silica hydrogel has a full volatiles content of at least 25 wt.%.
The improved process of claims 7 or eight in which the silica hydrogel has been treated with an organic acid, an inorganic acid, or an acid salt.
A fatty material having a ratio of cis-to-trans olefin isomers greater than five.0, said fatty cloth having been treated with a silica hydrogel prior to hydrogenation to remove sulfur-containing compounds.