The nature of the active sites in the reactions of cumene on HY and LaY catalysts

The secondary reactions which accompany cumene cracking have been studied at 360°, 430°, 500°C, over an HY zeolite catalyst using a tubular packed bed reactor. The concept of “Optimum Performance Envelope” was used in order to identify which of the observed reaction products are primary and which are secondary. In this way, benzene, ethylbenzene, n-propylbenzene, cymene, m- and p-diisopropylbenzene, as well as propylene, i-butene, and butene have been found to be primary products, while methane, ethylene, ethane, toluene, ethyl toluene, and i- and n-butane are identified as secondary products. The initial selectivities for the primary products have been calculated, and from these, the initial kinetic rate constants. These values, as well as the activation energies of primary product formation, are compared with those obtained using a LaY zeolite catalyst. The observed differences are discussed in terms of the nature and number of the active sites on the catalyst and lead us to conclude tthat LaY and HY have identical active sites but differ in site concentration.     

The nature of active sites in the isomerization of 1-hexene on cracking catalysts

The molar ratio of cis/trans 2-hexene isomers formed from 1-hexene on NaY zeolites exchanged to various levels with protons or lanthanum ions can be explained by assuming that two types of sites are active for the 1–2 isomerization reaction. The first gives both isomers, while the second gives only the cis isomer. In HY zeolite, active sites for the isomerization reaction can be produced by substitution of the most easily replaced sodium ions, either by simple washing with water, or by calcination of a partially exchanged ammonium form. The catalyst activity and the observed ratio of cis/trans isomers formed on a partially exchanged LaY zeolite, has been found to depend on the degree of hydration of the catalyst. Ratios of cis/trans 2-hexene are closer to their equilibrium value when the reaction is carried out on ZSM-5, mordenite and amorphous silica-aluminas rather than on Y zeolite. This is explained in terms of the proportion of each type of site present, although diffusional limitations within the narrower pore structures of ZSM-5 and mordenite may also play a role.     

Catalytic conversion of palm oil to fuels and chemicals

The conversion of palm oil to hydrocarbons using a shape selective zeolite catalyst is reported in this work. Palm oil was passed over HZSM-5 catalyst in a fixed bed micro-reactor and the reactor was operated at atmospheric pressure, a temperature range of 360 to 420°C and weight hourly space velocity (WHSV) of 2 to 4 h^?1. The main objective was to study the effect of reaction temperature and oil space velocity on the conversion and selectivity of gasoline range hydrocarbons. The results show that 40 to 70wt% of the palm oil can be converted to aromatics and hydrocarbons in the gasoline, diesel and kerosene range, light gases, coke and water. The maximum gasoline range hydrocarbons yield of 40wt% of total product formed was obtained at 400°C and 2 h^?1 space velocity.     

Improving catalysts for the refining of straight-run gasoline fractions of petroleum

We propose a method for modifying catalysts based on a high-silica zeolite of the ZSM-5 type using Ni nanopowder to improve catalysts for the refining of straight-run gasoline fractions. The proposed method, which involves solid-phase mechanical mixing with Ni nanopowder, is more environmentally friendly than conventional methods of impregnation and ion exchange; the developed Ni-containing zeolite catalysts allow us to lower the temperature for the refining of low-octane gasoline fractions by 20–40°C and to increase the yield of target products containing high amounts of high-octane components, i.e., isoalkanes. The acidic and catalytic properties of high-silica zeolites containing different amounts of Ni nanopowder were studied. The activity of the catalyst systems in the conversion of straight-run gasoline fractions of petroleum was analyzed. The optimum catalyst composition and the process conditions for obtaining a maximum yield of the target product, i.e., high-octane gasoline, are determined.     

Study on Olefin Alkylation of Thiophenic Sulfur in FCC Gasoline Using La2O3-Modified HY Zeolite

HY zeolite modified by La₂O₃ on olefin alkylation of thiophenic sulfur in fluid catalytic cracking (FCC) gasoline was studied in the micro fixed-bed reactor. Reaction pressure 1.5 MPa, reaction temperature 180 °C, WHSV 3.5 h^?1, using HY zeolite modified by 2% La₂O₃, the conversion of thiophene sulfur promoted nearly 10% with good selectivity, comparing with no-modified by La₂O₃. Acidity of modification of HY zeolite with La₂O₃ was tested in Pyridine–IR, it showed that increasing the amount of weak Bronsted (B) acid and the ratio of total B acid with total Lewis (L) acid could strengthen the hydrogen transfer activity of the catalyst, which leaded to improving the capacity of thiophene alkylation. The X-ray diffraction (XRD) results showed that the structure of catalysts could be optimized by loaded proper amount of La₂O₃ for promoting the acidic properties of HY zeolite.     

Studies on the catalytic dechlorination and abatement of chlorided VOC: the cases of 2-chloropropane, 1,2-dichloropropane and trichloroethylene

The conversion of monochloropropanes and dichloropropanes over acid catalysts has been investigated in the presence of oxygen. In the temperature range of 450–550 K, dehydrochlorination of monochloropropanes to propene and HCl occurs selectively over silica–alumina, while significant formation of chlorinated by-products is observed over ZSM5 zeolite catalyst even at higher temperatures. Dichloropropanes conversion over silica–alumina catalyst gives rise mainly to chloropropenes in the temperature range 500–700 K. CO_x are predominant products only at the highest reaction temperatures (just above 700 K). Water vapor in the feed only slightly affects conversions and selectivities. Deactivation processes occur upon dichloropropane conversion, mainly due to coke deposition.

The conversion of highly chlorinated compounds, such as trichloroethylene (TCE) has been tested over silica–alumina and over HY zeolite in the presence of water vapor in the so-called “steam reforming” conditions (HVOC:water=1:2). With diluted feed (1200 ppm) on HY, reaction occurs above 800 K and formation of chlorinated by-products is minimized, CO_x being the main reaction products. At higher HVOC concentrations conversion is obtained at even lower temperature (600 K), but no more negligible by-products formation has been detected. In our conditions zeolite catalyst is more effective in TCE total conversion than silica–alumina.     

Xylene isomerization by ZSM-5 zeolite catalyst

The larger pore LaY zeolite catalyst resembles homogeneous metal chloride and heterogeneous silica-alumina acid catalysts since the results are consistent with isomerization being a series of intramolecular 1,2 shifts. On the other hand, isomerization with the smaller pore zeolite, ZSM-5, is very different and the relative rate constants appear to be influenced by diffusion and/or shape selectivity. Disproportionation is a significant reaction with LaY but not with ZSM-5 in the temperature range used for the present study. The small amount of trimethylbenzene formed at low conversions using ZSM-5 is 1,2,4-trimethylbenzene, also providing evidence of shape selectivity influencing the reaction products.     

Pools and Constraints in Methanol Conversion to Olefins and Fuels on Zeolite HZSM5

Large reserves of natural gas are causing high actual interest for olefins and automotive fuels via methanol conversion on zeolite HZSM5. The chemistry of this process involves spatial constraints in the zeolite pores and a set of reacting compounds hosted dynamically in the pores. The kinetic scheme of reactions in this pool regime is a matter of current debate––a problem being the complexity of product composition and its temporal changes. However, the multi-compound product composition, if measured accurately and even time-resolved––including the compounds retained in/on the catalyst––is a profound source of information. Methanol conversion has been studied with zeolite HZSM5 and zeolite HY accordingly. The pool mechanism has been developed further, specifically as depending on frustration for distinct reactions. Particular pools as for olefins or for gasoline are specified. Mechanism changes with reaction time and with reaction temperature are described, including the surprising phenomenon of reanimation and the mechanisms of catalyst deactivation.     

HY分子筛催化合成对乙酰氨基酚的工艺研究

研究了以HY分子筛为催化剂合成对乙酰氨基酚的工艺,对反应物的物质的量比、反应温度、反应时间、催化剂用量等反应条件进行了优化,实验确定最佳反应条件：对氨基苯酚与冰乙酸物质的量比为1∶10,反应温度为120℃,催化剂用量为1.5%,反应时间为5h。最佳条件下对乙酰氨基酚的收率可达92.05%,且实验证明HY分子筛催化活性具有良好的稳定性。     

轻汽油醚化沸石催化剂反应性能

以催化裂化轻汽油为原料对开发的RZE-3沸石型醚化催化剂的反应性能进行了研究,并与树脂型催化剂进行对比。结果表明,沸石型醚化催化剂RZE-3的烯烃转化率、产物选择性与树脂型催化剂相当。沸石型催化剂由于具有优良的热稳定性,可反复再生,克服了树脂型催化剂不能再生、废弃催化剂会对环境造成污染等缺点。醚化原料中微量碱性氮化物在沸石型催化剂强L酸中心发生强吸附,是催化剂上胶质形成的主要途径和起点。沸石型醚化催化剂RZE-3的研发成功为清洁燃料洁净生产提供了可能。     

Catalyst decay in the kinetics of methylcyclohexane dehydrogenation over Pt-NaY zeolite

The kinetics of the dehydrogenation of methylcyclohexane to toluene over platinum on NaY zeolite have been studied at 390°C and atmospheric pressure. Cumulative conversion data obtained at constant space velocity and various reaction times on stream was treated using the “Time on Stream” theory. In this way the rate constants for both dehydrogenation and catalyst decay have been determined. The reaction has been shown to occur via a series of consecutive partial dehydrogenations, with the first dehydrogenation as the rate controlling step. The influence of the partially dehydrogenated products as well as the influence of the toluene, on the deactivation of the catalyst is discussed.     

Catalytic conversion of canola oil to fuels and chemical feedstocks Part I. Effect of process conditions on the performance of HZSM-5 catalyst

The conversion of canola oil to hydrocarbons using a shape selective zeolite catalyst is reported in this work. Canola oil was passed over HZSM-5 catalyst in a fixed bed micro-reactor and the effects of reaction temperature and oil space velocity on the conversion and selectivity were studied using a statistical experimental design. The results show that 60–95 wt% of the canola oil can be converted to hydrocarbons in the gasoline boiling range, light gases and water. The gasoline fraction contained 60–70 wt% of aromatic hydrocarbons and the gases were mostly C₃ and C₄ paraffins. Furthermore, the spent catalyst could be regenerated completely at 600°C in 1 h with dry air.     

EFFECT OF NONUNIFORM DEACTIVATION ON THE OPTIMUM DESIGN OF COMPOSITE CRACKING CATALYSTS

The optimum location of the zeolite component in a silica-alumina matrix is calculated for various levels of catalyst deactivation such that gasoline selectivity from gas-oil is maximized at each deactivation level. Results when the composite cracking catalyst is uniformly deactivated are compared with those when deactivation is nonuniform. In both cases, the maximum selectivity first increases with increasing deactivation level, and then decreases. The maximum selectivity is not qualitatively altered in moving from uniform to nonuniform deactivation. However, the optimum location of the zeolite required to achieve this maximum selectivity is different in the two cases.     

镧和铈在Y型分子筛方钠石笼中的定位差异以及对FCC催化剂反应性能的影响

用新型制备工艺分别制备镧和铈改性的Y型分子筛，并通过X衍射法、分光光度法和ACE反应评价等手段考察两种稀土元素在Y型分子筛中的定位状况、制备过程中的利用率、水热稳定性以及反应性能的差异。研究发现，镧在较低能耗条件下容易实现在Y型分子筛方钠石笼中的定位。同时，镧改性的Y型分子筛还具有稀土利用率高、热和水热稳定性好等特点。ACE评价结果表明，镧改性Y型分子筛制备的催化剂在反应性能上有明显优势。     

改性复合分子筛的FCC汽油降烯烃性能研究

以催化裂化FCC汽油为原料,在固定床连续加压微反装置上,以MCM-41/ZSM-5复合分子筛为催化剂,考察金属氧化物的不同负载量条件下降烯烃反应性能、液体收率及积炭量的变化,探讨分子筛酸性中心及酸量的变化对催化剂活性的影响。结果表明,ZnO负载质量分数2%时,催化剂降烯烃和芳构化活性达到最高,液相产物中烯烃体积分数由48.91%降至19.95%,芳烃体积分数由19.02%上升至36.58%,研究法辛烷值提高4.6个单位。     

HY分子筛催化合成油酸乙酯

采用NaY分子筛催化剂,经离子交换和高温焙烧制得HY分子筛,以油酸和乙醇为原料,在间歇反应釜进行酯化反应研究。考察反应温度、原料配比、催化剂用量和反应时间等条件对酯化反应的影响。结果表明,在反应温度180 ℃、n(油酸)∶n(乙醇)＝1∶2.5、催化剂用量为原料总质量的1.0%和反应时间4 h条件下,油酸转化率可达81.18%。实验中的HY分子筛表现出较高的活性和良好的稳定性。     

十氢萘在HY和Beta分子筛上加氢开环的研究

采用高温高压反应釜研究了十氢萘在低硅铝比HY分子筛[n(Si)/n(Al)=3.2]、Beta分子筛n(Si)/n(Al)=9.7]和双功能催化剂Pt-HY、Pt-Beta上的加氢开环反应,考察了分子筛孔道结构及酸性质、贵金属Pt及反应温度等因素对十氢萘转化率和产物选择性的影响。结果表明,十氢萘在Beta分子筛上的转化率较高,且有大量脱氢缩合产物（DHC）生成。Pt引入HY和Beta分子筛后,初始反应速率升高,十氢萘转化率增加,C₁₀产物中开环异构比增大,Beta分子筛上的脱氢缩合反应得到抑制。反应温度升高可以提高十氢萘在HY分子筛上的转化率,使得C₁₀产物选择性下降,而开环异构比（ROP/Iso）增大。     

催化裂化轻汽油在ZSM-5分子筛催化剂上裂化反应的研究

以ZSM-5分子筛为催化剂，在小型固定床反应器上，进行了催化裂化轻汽油的裂化反应。考察了反应温度和空速对催化裂化轻汽油裂化反应气液相收率和产品分布的影响。实验结果表明，ZSM-5分子筛催化剂具有较强的裂化活性和氢转移活性。在保证裂化转化率的条件下，提高反应温度和空速可以抑制催化剂上氢转移反应的发生。以ZSM-5分子筛为催化剂上的催化裂化反应中，温度、空速是影响转化率和选择性的重要因素，因此可以通过改变温度、空速来提高目的产物的选择性。但是，单纯依靠改善反应条件，不能使目的产物的收率和选择性达到理想的程度，还必须对催化剂进行改性。ZSM-5分子筛催化剂上催化裂化反应的研究为ZSM-5分子筛催化剂的进一步改性，及ZSM-5分子筛催化剂在轻汽油催化裂解和汽油改质方面的进一步应用提供了试验依据。     

Hydrogenation of carbon dioxide over copper-pyrochlore/zeolite composite catalysts

The hydrogenation of CO₂ was studied over composite catalysts obtained by mixing Cu-based methanol synthesis catalyst and HY zeolite. A mechanism associating methanol synthesis and MTG (methanol to gasoline) reaction allowed the formation of C₁-C₄ hydrocarbons. It was found that the catalytic behaviors of the composite catalysts were favorably influenced by the characteristics of the methanol synthesis catalysts. The Cu-La₂Zr₂O₇ catalyst we recently developed associated with HY zeolite exhibited interesting performances in hydrocarbon synthesis. The addition of ZrO₂ to Cu---La₂Zr₂O₇/HY enhanced the ability to produce hydrocarbons. Comparing composite catalyst systems prepared with different Cu-based methanol synthesis catalysts, the effect of Na contamination on methanol and hydrocarbon formation over composite catalysts were also discussed.     

苯胺、尿素、甲醇一步法合成苯氨基甲酸甲酯

用苯胺、尿素和甲醇一步法合成了苯氨基甲酸甲酯(MPC)。考察了不同类型催化剂对MPC生成的影响。对性能最好的HY分子筛催化剂着重考察了催化剂用量,反应温度,反应时间和原料摩尔比对反应的影响。结果表明,n(C6H5NH2)∶n(NH2CONH2)∶n(CH3OH)=1∶5∶15,反应温度453 K,反应时间5 h为适宜工艺条件。在该工艺条件下,苯胺转化率和苯氨基甲酸甲酯选择性分别达到90.5%和73.5%。