Heavy Wax Research Articles

Fischer-Tropsch Synthesis for the Production of Sustainable Aviation Fuel: Formation of Tertiary Amines from Ammonia Contaminants.

Fischer-Tropsch synthesis combined with product workup is a promising route toward synthetic aviation fuel from renewable hydrogen and carbon sources like biomass, CO2, and waste. Cost savings can be achieved by reducing the number of gas treatment steps in new plants, but the consequence of contaminants in the feed needs investigation. While feeding 2.6 ppmV ammonia to a Fischer-Tropsch reactor, it was shown that ammonia was predominantly chemically converted into organic amines, with most nitrogen found in the water phase (89%), followed by heavy wax (7%) and light wax (1%). The concentration difference between water and light wax was shown to be due to the post-condensation separation of amines on polarity. Amines up to a chain length of 120 were detected in the heavy wax with MALDI-FT-ICR-MS, which, in combination with the high nitrogen content, suggests that amines have a similar chain growth probability compared to the main hydrocarbon products. Detailed product analysis with three independent analytical techniques showed that tertiary N,N-dimethylalkylamines were by far the most abundant amine class. This suggests that ammonia is decomposed on the cobalt surface and, potentially as a dimethylamine fragment, incorporated in the growing chain. Further evidence was obtained from the abundance of trimethylamine and from the reconciled nitrogen product analysis up to C100, which showed that the amine product distribution followed from naphtha onward the same ASF kinetics as alkanes and oxygenates while being distinctively different from the alkene distribution. The presented findings provide further avenues for studies of the Fischer-Tropsch reaction mechanism and indicate the opportunity of cost saving on gas treatment, while further validation is required to assess the impact on hydrocracking and product quality.

Possible use of spent FCC catalyst for upgrading of wax from the pyrolysis of plastics to liquid fuel

The cracking of heavy wax derived from mixed plastics (high-density polyethylene, low-density polyethylene, and polypropylene) to chemical and fuel purposes was explored using spent fluid catalytic cracking catalyst (spent FCC). The wax cracking was performed by a fixed-bed pyrolysis reactor with a slow heating rate. All catalysts, when compared to other catalysts (HY zeolite and MCM-41), could enhance liquid oil and gas production. While the spent FCC catalyst produced the highest liquid oil with least amount of coke production. The influence of spent FCC catalyst ratio on product distribution revealed that a catalyst-wax ratio of up to 1:1 resulted in a higher liquid oil yield than a low ratio. Additionally, the increase of cracking temperature promoted more oil production; however, at high temperature (above 400 °C) the evaporation of wax became more significant, and consequently a high portion of produced wax was obtained. Therefore, under suitable conditions, the spent FCC catalyst demonstrated the possibility of upgrading the heavy wax into liquid fuels and chemicals. In addition, this study also compared the products obtained from two processing routes using the spent FCC catalyst. The first route involved the pyrolysis of plastics into wax and then cracking the wax into liquid fuel, while the second route involved a one-step process that directly converted plastics into liquid fuel. The spent FCC catalyst promoted the production of diesel-range hydrocarbons and suppressed the aromatic production for the wax cracking. By contrast, the spent FCC catalyst significantly enhanced aromatic production during the cracking of mixed plastics.

Statistical prediction and sensitivity analysis of kinetic rate constants for efficient thermal valorization of plastic waste into combustible oil and gases

Sensitivity analyses of rate constants for chemical kinetics of the pyrolysis reaction are essential for the efficient valorization of plastic waste into combustible liquids and gases. Finding the role of individual rate constants can provide important information on the process conditions, quality, and quantity of the pyrolysis products. The reaction temperature and time can also be reduced through these analyses. For sensitivity analysis, one possible approach is to estimate the kinetic parameters using MLRM (multiple linear regression model) in SPSS. To date, no research reports on this research gap are documented in the published literature. In this study, MLRM is applied to kinetic rate constants, which slightly differ from experimental data. The experimental and statistically predicted rate constants varied up to 200% from their original values to perform sensitivity analysis using MATLAB software. The product yield was examined after 60 min of thermal pyrolysis at a fixed temperature of 420 °C. The predicted rate constant “k(8)” with a slight difference of 0.02 and 0.04 from the experiment revealed 85% oil yield and 40% light wax after 60 min of operation. The heavy wax was missing from the products under these conditions. This rate constant can be utilized to maximize the commercial-scale extraction of liquids and light waxes from thermal pyrolysis of plastics.

Biodegradation of paraffin wax using Bacillus sp. SASH for quality improvement of crude oil properties

Biodegradation has become the most preferred and sustainable mean of reducing paraffin wax, removing paraffin deposition in pipelines and improving the flow of petroleum products. The current study focuses on the isolation of bacteria that has the capability to utilize paraffin as a sole carbon source and has been screened using 2,6-dichlorophenol indophenol (DCPIP) dye as redox indicator. The bacterium was identified as Bacillus sp. SASH according to its 16S rRNA gene sequence analysis. It is a moderate halophile that can grow in seawater at pH 7 and 37 °C. Bacillus sp. SASH was able to degrade various paraffinic products such as paraffin wax, heavy wax distillates, and liquid paraffin and it showed up to 84% paraffin wax degradation. Gas chromatography–mass spectrometry analysis revealed that higher carbon chains after retention time of 18 min were removed after treatment of the wax with the bacterium. Bacillus sp. SASH enhanced the flow of different petroleum products by reducing their viscosity and pour point values. It was also able to reduce the viscosity and improve the flow of crude oil by 60%.

Analysis of Statistically Predicted Rate Constants for Pyrolysis of High-Density Plastic Using R Software.

The surge in plastic waste production has forced researchers to work on practically feasible recovery processes. Pyrolysis is a promising and intriguing option for the recycling of plastic waste. Developing a model that simulates the pyrolysis of high-density polyethylene (HDPE) as the most common polymer is important in determining the impact of operational parameters on system behavior. The type and amount of primary products of pyrolysis, such as oil, gas, and waxes, can be predicted statistically using a multiple linear regression model (MLRM) in R software. To the best of our knowledge, the statistical estimation of kinetic rate constants for pyrolysis of high-density plastic through MLRM analysis using R software has never been reported in the literature. In this study, the temperature-dependent rate constants were fixed experimentally at 420 °C. The rate constants with differences of 0.02, 0.03, and 0.04 from empirically set values were analyzed for pyrolysis of HDPE using MLRM in R software. The added variable plots, scatter plots, and 3D plots demonstrated a good correlation between the dependent and predictor variables. The possible changes in the final products were also analyzed by applying a second-order differential equation solver (SODES) in MATLAB version R2020a. The outcomes of experimentally fixed-rate constants revealed an oil yield of 73% to 74%. The oil yield increased to 78% with a difference of 0.03 from the experimentally fixed rate constants, but light wax, heavy wax, and carbon black decreased. The increased oil and gas yield with reduced byproducts verifies the high significance of the conducted statistical analysis. The statistically predicted kinetic rate constants can be used to enhance the oil yield at an industrial scale.

Catalytic hydrocracking of heavy wax from pyrolysis of plastic wastes using Pd/Hβ for naphtha-ranged hydrocarbon production

The catalytic hydrocracking of heavy wax derived from the pyrolysis of waste plastics was conducted for valuable naphtha production on the bifunctional catalyst. As the result of the support screening to prepare the bifunctional catalyst, the acidic Hβ was chosen, which exhibited the reasonable wax conversion (64%) and the highest saturated and unsaturated hydrocarbon content (98%) in naphtha fraction at 380 ̊C. Then, Pd was impregnated on the Hβ as an active metal, and ≥ 0.6% Pd could dramatically improve the cracking and hydrogenation activities of the Hβ even at 360 ̊C from 47.9% to >97.5% conversion. Also, the liquid product mainly composed of saturated hydrocarbons (<2% olefin and >88% paraffins), which is quite suitable for naphtha. Especially, Pd[0.6]/Hβ, having 0.012 of the metal/acids ratio, exhibited the highest hydrocracking activity (99.2% conversion and 97.8% naphtha fraction in liquid), and that of >0.012 led catalyst’s isomerization activity increased.

Utilization of liquid product through pyrolysis of LDPE and C/LDPE as commercial wax.

In this study, pyrolysis of low-density polyethylene (LDPE) and LDPE with aluminum (C/LDPE) wastes was carried out with different heating rates (5, 10,20 °C/min) at different temperatures (400, 600, 800 °C). Product yields of LDPE and C/LDPE wastes were compared, and optimum liquid products wereanalyzed to utilize as commercial waxes for future use. The properties of pyrolyzed wastes was investigated with proximate, elemental analysis, and TGA.The as-produced liquid from pyrolysis of wastes was characterized by different characteristic tools, such as elemental analyses, GC-MS analyses, 1H-NMRtests, FT-IR spectra, the density, melting point, and carbon residue to compare commercial waxes. As a result of pyrolysis, the highest liquid product yieldwas achieved at 800 °C with 5 °C/min heating rate (85.87%) and at 600 °C with 5 °C/min heating rate (71.3%) for LDPE and C/LDPE, respectively. Theresults indicated that the derived liquid products are similar to commercial heavy wax.

Catalytic cracking of chlorinated heavy wax from pyrolysis of plastic wastes to low carbon-range fuels: Catalyst effect on properties of liquid products and dechlorination

Catalytic conversion of useless chlorinated heavy wax (chlorine, 0.14 wt%) obtained from pyrolysis of refuse plastic fuel was studied using iron oxide impregnated HY zeolite to produce a useful liquid product. It was found that the largest liquid fraction (gasoline and kerosene/ diesel, 66.9 wt.%) with very low chlorine content was achieved when using Fe[3]/HY among impregnated HY catalysts. This demonstrated that the Fe impregnated HY catalyst had a dual function of catalytic cracking of HY zeolite and dechlorination of iron oxide. Excessive impregnation of Fe, i.e., Fe[20]/HY, showed the least cracking activity of heavy wax owing to the catalyst having lowest total acid sites, but yielded liquid product with the lowest chlorine content (60 ppm) among the tested catalysts. The spent catalysts were deposited by a significant amount of soft coke and chlorine, and they were totally restored by thermal treatment in air (700 ℃).

Pyro-Oil and Wax Recovery from Reclaimed Plastic Waste in a Continuous Auger Pyrolysis Reactor

The increasing global waste plastic pollution is urging people to take immediate actions on effective plastic recycling and processing. In this work, we report the results of processing reclaimed plastic wastes from unsanitary landfill site in Kuwait by using a bench scale continuous auger pyrolysis system. The plastic feedstock was characterised. After a simple thermal densification process, the material was fed to the pyrolysis system at 500 °C. The pyro-oil and wax products were collected and characterised. The process mass balance was developed on dry basis, and the yields of pyro-oil, light wax, heavy wax and gases were 5.5, 23.8, 69.4 and 1.3 wt%, respectively. The findings have indicated that the reclamation of plastic waste from landfill was feasible in terms of the product distribution and characteristics. Further liquid analysis confirmed that the liquid products contained fractions that are comparable to petrol and diesel fuels. The wax products are viable and have potential application as coating, covering and lubrication.

Retrieving Leaf Chlorophyll Content by Incorporating Variable Leaf Surface Reflectance in the PROSPECT Model

Leaf chlorophyll content plays a vital role in plant photosynthesis. The PROSPECT model has been widely used for retrieving leaf chlorophyll content from remote sensing data over various plant species. However, despite wide variations in leaf surface reflectance across different plant species and environmental conditions, leaf surface reflectance is assumed to be the same for different leaves in the PROSPECT model. This work extends the PROSPECT model by taking into account the variation of leaf surface reflection. In the modified model named PROSPECT-Rsurf, an additional surface layer with a variable refractive index is bounded on the N elementary layers. Leaf surface reflectance (Rs) is characterized by the difference between the refractive indices of leaf surface and interior layers. The specific absorption coefficients of the leaf total chlorophyll and carotenoids were recalibrated using a cross-calibration method and the refractive indices of leaf surface and interior layers were obtained during model inversion. Chlorophyll content (Cab) retrieval and spectral reconstruction in the visible spectral region (VIS, 400–750 nm) were greatly improved using PROSPECT-Rsurf, especially for leaves covered by heavy wax or hard cuticles that lead to high surface reflectance. The root mean square error (RMSE) of chlorophyll estimates decreased from 11.1 µg/cm2 to 8.9 µg/cm2 and the Pearson’s correlation coefficient (r) increased from 0.81 to 0.88 (p &lt; 0.01) for broadleaf samples in validation, compared to PROSPECT-5. For needle leaves, r increased from 0.71 to 0.89 (p &lt; 0.01), but systematic overestimation of Cab was found due to the edge effects of needles. After incorporating the edge effects in PROSPECT-Rsurf, the overestimation of Cab was alleviated and its estimation was improved for needle leaves. This study explores the influence of leaf surface reflectance on Cab estimation at the leaf level. By coupling PROSPECT-Rsurf with canopy models, the influence of leaf surface reflectance on canopy reflectance and therefore canopy chlorophyll content retrieval can be investigated across different spatial and temporal scales.

Synthesis of ZnO Nanoparticles for Wax Deposition Control and Oil Upgrading: Effect of Ratio of Zinc Acetate Dihydrate to Oxalic Acid Dihydrate

In the current paper, fundamental aspects of heavy oil and wax deposition problems are defined. Wax or in another term is cloud point occur when the oil starts to precipitate. When it’s started to precipitate, it can cause major problem to industry of oil and gas. In this study, ZnO nanoparticles were chosen to study the effect of varying molar ratio from 1:1, 1:2, 1:3 to the morphology and size of the nanoparticle. The structures and properties were recognized with energy dispersive X-ray (EDX), field emission scanning electron microscopy (FE-SEM), and X-ray diffraction (XRD) methods. EDX and FE-SEM is to study the morphology of ZnO structure while XRD is to determine the purity and size of the nanoparticle. From the study, 1:1 ratio has the smallest size of nanoparticle with 10.37 nm while 1:2 and 1:3 give the size of 12.3 nm and 16.37 nm respectively. As the molar ratio is increases, the size of nanoparticle become bigger. The influenced of ZnO nanoparticles on rheological behaviour of model oils and the wax content is reported. From the study, the addition of ZnO nanoparticle reduced the rheology behaviour of crude oil by varying nanoparticle sizes, temperature and shear rate. ZnO nanoparticle can reduce the deposition of wax up to 50% with influenced of smaller nanoparticle size. Effect of size of nanoparticle highly impact the viscosity and wax content. This prove that, by introducing nanoparticle into crude oil, wax content can be reduced thus decrease the chance for crude to precipitate.

Ordered Mesoporous Co3O4−Al2O3Binary Metal Oxides for CO Hydrogenation to Hydrocarbons: Synergy Effects of Phosphorus Modifier for an Enhanced Catalytic Activity and Stability

AbstractThe synergy effects of phosphorus modifier on highly ordered mesoporous binary metal oxides of Co3O4−Al2O3(m‐CoAl), prepared by nanocasting method using a hard template of KIT‐6, were observed by an enhanced catalytic and structural stability of the m‐CoAl during CO hydrogenation to hydrocarbons. The enhanced structural stability of the ordered mesoporous structures on the phosphorous‐modified m‐CoAl at an optimal amount of phosphorous modifier below 0.3 wt%P (P(3)/m‐CoAl) was attributed to the partial formation of thermally stable metal phosphates under a reductive Fischer‐Tropsch synthesis (FTS) reaction condition. The positive effects of the phosphorous modifier were originated from the partially formed SiO2‐like AlPO4phases on the outer surfaces of the m‐CoAl, as well as from partially formed irreducible and thermally stable spinel‐type cobalt aluminates (CoAl2O4). The hydrophobic SiO2‐like tridymite AlPO4surfaces on the ordered matrices of the P/m‐CoAl also effectively prevented the heavy wax (or coke precursors) depositions. The structural instability of the P/m‐CoAl was observed at a higher phosphorous content above 0.5wt%P by preferentially forming the largely segregated mixed metal oxides such as Co3O4−CoAl2O4−Co3(PO4)2through the phase transformations of the surface excess AlPO4.

Spatially confined cobalt nanoparticles on zirconium phosphate-modified KIT-6 for an enhanced stability of CO hydrogenation to hydrocarbons

The positive effects of zirconium phosphate (ZrP)-modified highly ordered mesoporous KIT-6 support for an insignificant aggregation of the supported cobalt nanoparticles (CoZrP/KIT-6) were investigated by CO hydrogenation to hydrocarbons such as Fischer-Tropsch synthesis (FTS) reaction. The roles of the newly formed ZrP phases on the KIT-6 were mainly explained in terms of metal dispersion with its modulated metal-support interaction as well as suppressed coke formations. The mesoporous KIT-6 surfaces modified with partial ZrP nanoparticles at an optimum molar ratio of P/Zr = 0.2 significantly enhanced the catalytic stability with a higher C5+ selectivity through the preferential formations of the spatial confined cobalt nanoparticles in the matrices of the well-dispersed ZrP nanoparticles on the mesoporous KIT-6 surfaces. The superior catalytic activity and stability were mainly attributed to the inhibited aggregations of the intimately interacted cobalt nanoparticles in the ZrP matrices due to a preferential presence of the highly dispersed and thermally stable hydrophobic ZrP phases. This was also responsible for the less formation of coke precursors such as cobalt carbides or heavy wax hydrocarbons. However, the different types of coke precursors on the used CoZrP/KIT-6 largely altered the catalytic stability and activity with the simultaneous aggregations of cobalt nanoparticles by forming the abundant heavy hydrocarbons on the unstable CoZrP(2)/KIT-6 prepared at a higher P/Zr ratio of 2 as well as by forming the inactive coke-derived cobalt carbides on the unmodified CoZrP(0)/KIT-6 and Co/KIT-6 under the reductive FTS reaction condition.

Fischer–Tropsch synthesis: Effect of catalyst particle (sieve) size range on activity, selectivity, and aging of a Pt promoted Co/Al2O3 catalyst

Abstract The effect of cobalt–alumina catalyst particle (sieve) size range on the performance of a traditional cobalt catalyst (platinum promoted cobalt/alumina) was investigated during Fischer–Tropsch synthesis (FTS) using a continuously stirred tank reactor (CSTR). In this study, the catalyst was sieved into four different size ranges: 20–63, 63–106, 106–180 and 180–355 μm. CO conversion varied with varying sieve size range under similar reaction conditions. With increasing catalyst sieve size, the CO conversion decreased, except for the smallest sieve size range (20–63 μm). These results are consistent with the view that, for the larger sieve size range, losses in CO conversion beyond catalyst aging may be explained by filling of the interior of the catalyst particle with heavy wax, thereby blocking available catalytically active sites. The adverse selectivities are directly the result of significant deactivation, since in FT synthesis, selectivity is a function of CO conversion. The loss in CO conversion for the 20–63 μm range catalyst was higher compared to the other three catalysts; due to the presence of heavy wax (Polywax 3000), the results suggest that the small particles tended to flocculate to larger clusters or were small enough to move at the speed of the liquid.

Solvent refining of heavy wax distillate for the removal of carcinogenic compounds

Neat ethylacetoacetate (EAA) and its mixtures with a co-solvent and an anti-solvent have been studied for refining of heavy wax distillate fraction to produce substantially non-carcinogenic base oil. The co-solvent and anti-solvent used are dipropylene glycol (DPG) and ethylene glycol (EG) respectively. The solubility characteristics of the main solvent and its mixed solvent systems were studied. Selection of the optimum solvent mixture and extraction variables has been studied. The effect of co-solvent and anti-solvent addition on the carcinogenic potential and raffinate quality has been determined under clearly comparable conditions.

Volatile compounds, quality attributes, mineral composition and pericarp structure of South African litchi export cultivars Mauritius and McLean's Red

AbstractBACKGROUND: The aim of this research was to identify the differences in volatile compounds, mineral composition, quality parameters and pericarp structure (at different fruit developmental stages) between two South African litchi export cultivars, Mauritius and McLean's Red, in order to provide a better understanding of the plant intraspecific variation.RESULTS: Citronellol and geraniol were predominant in the aroma profile of cv. Mauritius and conferred characteristic floral, rose, citrus and fruity aromas. In cv. McLean's Red, germacrene D was predominant in the sesquiterpene fraction. Germacrene D and muurolene are associated with a woody smell. Cv. Mauritius had lower soluble solid content/titratable acidity ratio and higher ascorbic acid content than cv. McLean's Red. Cv. McLean's Red had lower pericarp hue angle and higher anthocyanin concentration, which correlated negatively. Significant differences in fruit mineral content and pattern of cuticle accumulation were noted between the two cultivars. The parallel cuticular lines formed a network with intercellular ridges and heavy wax deposits in cv. McLean's Red. Cv. Mauritius showed higher weight loss at 25 °C, suggesting that the dense wax deposits and cuticle structure in cv. McLean's Red could limit moisture loss.CONCLUSION: This investigation shows evidence for the lack of sweet and rose‐like fragrance in litchi cv. McLean's Red. It is the first study to compare volatile compounds responsible for the differing aromas of two South African litchi cultivars. Litchi cultivar improvement and breeding programmes are focused on expansion of the season and yield. The reported information is useful for selection of cultivars and for cultivar breeding programmes focusing on fruit quality and storage potential. Copyright © 2008 Society of Chemical Industry

Elucidation of reaction network and effective control of carbon number distribution in the three phase Fischer–Tropsch synthesis

This article is to deal with the secondary reactions of 1-olefins during Fischer–Tropsch and to selectively synthesize the “FT” products in the desired range (middle distillates and wax) by controlling the pathway reaction shown in the Figure below. In this study, around 90% selectivity in middle distillates and heavy wax has been achieved in olefin-added FT synthesis. We have also experimentally evidenced the disproportionate reaction of 1-olefins in the presence of hydrogen only. Reactions over olefins introduced during FT synthesis have been studied in a trickle bed reactor. Incorporation of 1-olefins into a growing alkyl chain could remarkably enhance the selectivity up to around 90% in heavy wax or middle distillate from syngas and could decrease the yields of lighter hydrocarbons with a higher CO conversion compared to the conventional FT synthesis. Results showed two significant processes the degradation of 1-olefins with successive demethylation, and its chain growth with incorporation by methylene species formed from demethylation, which is defined as the disproportionate reaction. The disproportionate reaction is competitive with introduced 1-olefins incorporating CH 2 species formed from syngas into heavier hydrocarbons and is effectively controllable; Such control strongly depends on the process conditions. In general, the elimination of diffusion limitations for introduced 1-olefins and operating conditions that give a high intrinsic chain growth probability ( α value) are favorable for suppressing the disproportionate reaction and for promoting the chain growth by the incorporation of syngas-formed CH 2 species to increase the yields of heavier FT products.

Catalytic Oxidative Cracking of Heavy Wax Distillates, Slack Wax, and Polyethylene Wastes to Yield Liquid and Gas Fuels

A petroleum waxy distillate, slack waxes, and plastic wastes were charged in an autoclave with 0.6 wt% of hydroquinone as a catalyst. Oxidative cracking process is conducted at 410°C, in oxygen atmosphere of 0.15 MPa for a time of reaction 30 min. Different analytical parameters are used to investigate the physicochemical properties of the products obtained and their corresponding virgin feed stocks. The obtained oily products were distilled to petroleum boiling range like fractions such as gasoline, kerosene, gas oil, and residue. These products have petroleum fuels like properties according to the ASTM test methods. Moreover, the composition of the obtained liquids and liberated gases during the cracked products were identified quantitatively using gas chromatographic technique. Results show that such oxidative cracking process can be used for upgrading petroleum heavy fractions.

Effective control of carbon number distribution during Fischer–Tropsch synthesis over supported cobalt catalyst

Effective control of carbon number distribution in FTS has been demonstrated with co-fed 1-olefins in a trickle bed reactor. Addition of 1-octene or 1-dodecene in the n-paraffin solvent could greatly enhance the selectivity of heavy wax and increase the middle distillate to a certain extent directly from syngas, with a marked increase in CO conversion while suppressing the formation of lighter hydrocarbon products compared to the conventional FTS. In the case of co-fed 1-dodecene, the disproportionate reaction was obviously observable, which resulted in a symmetrical product distribution and gave a much higher selectivity in the middle distillate.

Effects of leaf epicuticular wax on the movement, foraging behavior, and attack efficacy of Diaeretiella rapae

AbstractPlant morphological characters can affect the foraging abilities of natural enemies. Heavy wax blooms have been shown to impede predators searching for herbivores on various species in the genus Brassica (Brassicaceae). This study determined whether epicuticular wax affected the foraging behavior of the braconid wasp Diaeratiella rapae (M’Intosh) (Hymenoptera: Braconidae) as it searched for its aphid host Brevicoryne brassicae L. (Homoptera: Aphididae) on the leaves of cauliflower varieties with heavy or light wax blooms. Wasps on the variety with a heavier wax bloom foraged more slowly, groomed more often and for longer periods of time, fell from the leaves more often, took longer to find colonies of aphids, and attacked them at a lower rate than wasps foraging on the variety with a lighter wax bloom. When epicuticular wax was removed from the leaves, the wasp's foraging efficiency and efficacy improved significantly on the cauliflower variety with a heavy wax bloom. The amount of epicuticular wax present on a leaf was shown to impede the ability of a parasitoid to forage, locate, and attack its host.