Site controls

The isomerization reaction, which is acid-site controlled, includes the conversion of alkylcyclopentanes into alkylcyclohexanes, which, in turn, are quickly converted to aromatics by dehydrogenation. In addition, isomerization also includes the conversion of feed n-paraffms into higher octane I-paraffins. 

To maintain adeqnate site control, the site safety and health snpervi-sor mnst have the anthority to enforce the SSAHP s rnles on any individ-nal present at the site, whether that individnal is an employee or an ontside contractor. If there is more than one SSAHP (i.e., if each contractor develops its own), OSHA considers it essential that the plans he integrated and enforced consistently to ensnre that on-site personnel have a clear nnder-standing of safety and health expectations, lines of anthority, and emergency response actions. 

F. All site control elements of the safety and health program must be fully implemented as described in the program. The purpose of site control requirements is to ensure that only properly trained and authorized individuals enter those areas of the site with potential hazards, and that, in the event of an emergency, rapid assistance can be rendered to employees working in the exclusion zone. This section discusses the findings of two components of site control the establishment and maintenance of site work zones and the establishment and implementation of appropriate confined space procedures. 

Site H was the only site at which the contractor had implemented comprehensive and effective site control elements. The Site H contractor had established site work zones, a buddy system, and site communication procedures consistent with 1910.120(d). This contractor had also established exclusion zones and contamination reduction zones to control migration of site contaminants to clean areas of the site when work within these areas introduced the potential for exposure to hazardous contaminants. The audit team supported this contractor s use of flexible and temporary work zone boundaries based on monitoring results and hazard determinations. 

The contractor s site control elements at Site B were not comprehensive however, the contractor s SSAHP did address site entry and training requirements and mandated that all personnel, including subcontractors and visitors entering the exclusion zone or decontamination zone, meet HAZWOPER training requirements. 

Forty-hour training was required for personnel entering the exclusion zone, and additional supervisory training was required for site supervisors. Site control procedures described in the Site C contractor s SSAHP included maintenance of site control logs at each access point, use of red tape or chainlink fencing to demarcate hot zones, and use of the buddy system in all exclusion and contamination reduction zone areas. Site communications relied almost exclusively on visual sighting of employees the plan did not describe the use of two-way radios. This suggested that all employees in hot zones can be observed continuously from the support zones. 

Signiflcant deficiencies in site control procedures existed at Site K. For example, the Site K subcontractor had not established a contamination reduction zone (CRZ), to physically separate the support zone from the exclusion zone, as required in the site plan. 

Site D lacked a sufficient CRZ and also lacked access/egress control for the exclusion zone. The site control plan did not accurately identify the function of the CRZ as a buffer zone between the exclusion zone and the support zone, and there was no buffer area between the decontamination pad and the road that runs adjacent to the pad, marked as a support zone. Also, an exclusion zone log-in procedure for tracking personnel who enter and exit this zone was not used on site as called for in the SSAHP. 

The primary contractor at Site A had identified clean zones, buffer zones, and related site control procedures in its written plan however, onsite implementation differed from those specified in the plan. For example, the exclusion zones identified in the plan at the upper pad of the wastewater treatment plant, the dredge area, and the solid waste storage area were marked with signs requiring PPE, but were not labeled with red banners as called for in the plan. In addition, the exclusion zones did not have controlled access through one point of entry as described in the plan, nor were the buffer zones established and demarcated with yellow banners. 

SAFETY AND HEALTH AUDIT QUESTIONS Safety and Health Program Site Control Training... 

An excellent way to treat such data is to use reaction probability models.(1,2) In the NMR analysis of tacticity, it is frequently possible to distinguish whether the configuration is chain-end controlled or catalytic-site controlled during polymerization. Various statistical models have been proposed. The chain-end controlled models include Bemoullian (B), and first- and second-order Markovian (Ml and M2) statistics.(1) The simplest catalytic-site controlled model is the enantiomorphic site (E) model.(3) The relationship between the chain-end and catalytic-site controlled models and possible hybrid models have been delineated in a recent article.(4)... 

For the studied catechol methylation reaction the catalyst structure and surface properties can explain the catalytic behaviour As mentioned above, the reaction at 260-350°C has to be performed over the acid catalysts. Porchet et al. [2] have shown, by FTIR experiments, the strong adsorption of catechol on Lewis acid/basic sites of the Y-AI2O3 surface. These sites control the reaction mechanism. 

The study participants (volunteers) should arrive at the field laboratory well before the daily work activities are to commence. The study participants should be directed to sit near the dressing area on a seat covered with a fresh plastic bag or tarp. The volunteers are usually instructed not to move from their seats or wander off around the test site. Control of the movements of the study participant is crucial at this point since the worker could encounter contamination and acquire some extraneous exposure not planned for the study. 

Surface Site Control of Waste Movement The purpose of site control is to achieve the following ... 

Site control at roads and residential areas will include at least the following activities ... 

Subsurface Site Control of Waste Movement 16.7.2.1 Controls of Groundwater... 

Several site control procedures can be implemented to reduce worker and public exposure to chemical, physical, biological, and safety hazards69 70 102-105 ... 

Ring-opening polymerization of racemic a-methyl-/J-propiolactone using lipase PC catalyst proceeded enantioselectively to produce an optically active (S)-enriched polymer [68]. The highest ee value of the polymer was 0.50. NMR analysis of the product showed that the stereoselectivity during the propagation resulted from the catalyst enantiomorphic-site control. 

Several isospecific Ci-symmetry catalysts have also been described including (12-15). When activated with [Ph3C]+ [B(C6F5)4]-, (12) affords highly regioregular i-PP (mmmm = 95%) with the stereochemical defects predominantly being isolated rr triads, consistent with a self-correcting enantiomorphic site-control pathway. 2,73 The isospecificity was therefore explained by a mechanism... 

The polymerization of MMA has been shown to be subject to enantiomorphic site control when the Ci-symmetric a .va-lanthanocene complexes (196) and (197) are employed as initiators.463 When the (T)-neomenthyl catalyst (196) is used, highly isotactic PMMA is produced (94% mm at — 35 °C), whereas the (-)menthyl derived (197) affords syndiorich PMMA (73% rr at 25 °C). NMR statistical analysis suggests that conjugate addition of monomer competes with enolate isomerization processes, and the relative rate of the two pathways determines the tacticity. 

An FI catalyst normally assumes a C2-symmetric trans-O, ds-N, and d.s-Cl configuration as the predominant isomer. In addition, DFT calculations suggest that a catalytically active species derived from an FI catalyst favors a C2-symmetric configuration with a trans-O, cis-N, and d.v-polymer chain/coordinated olefin arrangement. Thus, FI catalysts have been targeted as catalysts capable of producing iPP via a site-control mechanism. 

The Tj, and the isospecificity obtained with these FI catalysts represent some of the highest values for iPPs ever synthesized. The isospecific propylene polymerization proceeds via a 1,2-insertion with a site-control mechanism. 

The production of highly isotactic PPs with Zr- and Hf-FI catalysts//-Bu3Al/ Ph3CB(C6F5)4 (phenoxy-amine complexes site-controlled polymerization with 1,2-insertion) is in sharp contrast to that of highly syndiotactic PPs with Ti-FI cata-lysts/MAO (phenoxy-imine complexes chain-end controlled polymerization with 2,1-insertion), which will be described later [64]. 

A site-inversion mechanism (the key feature of which is that isomerization between diastereomeric and A configurations is rapid on the propylene-insertion time scale) based on theoretical calculations was proposed by Cavallo and coworkers in order to explain the ligand-directed chain-end controlled polymerizations (Fig. 35) [42]. The site-inversion mechanism allows chain-end control to work in concert with the site control effects. Our experimental results and the expected catalytic behavior resulting from the site-inversion mechanism concur with each other very well. 

Section 3 will deal with catalytic systems whose stereospecificity is mainly controlled by the chirality of the environment of the transition metal, independently of the possible chirality of the growing chain (chiral site stereocontrol). In particular, in Section 3.1 the chirality and stereospecificity of homogeneous catalytic systems based on metallocenes of different symmetries and in different experimental conditions will be reviewed. In Section 3.2 the chirality of model catalytic sites, which have been supposed for isospecific first-generation TiCl3-based and high-yield MgC -supported catalysts, is described. In Section 3.3 we will present a comparison between model catalytic sites proposed for heterogeneous and homogeneous stereospecific site-controlled catalysts. 

---