低硅铝比ZSM-5分子筛的合成及其正庚烷裂化反应性能

以氨水为矿化剂,通过添加NH₄⁺离子水热合成了具有较低骨架硅铝比的ZSM-5分子筛。通过X射线衍射(XRD)、扫描电镜(SEM)、固体核磁共振(MAS-NMR)等表征手段,研究了硅源、铝源、矿化剂、阳离子等对ZSM-5分子筛的结晶度、形貌尺寸和骨架硅铝比等的影响,研究了ZSM-5分子筛的骨架硅铝比对正庚烷催化裂化反应的影响。研究表明,投料硅铝比越低,铝原子越难进入到分子筛骨架中;当氨水为矿化剂、正硅酸四乙酯为硅源时可以合成骨架硅铝比较低的氢型ZSM-5分子筛,添加NH₄⁺离子可以增强骨架铝的嵌入,进一步降低分子筛的骨架硅铝比(24.2)。正庚烷裂化反应结果表明,降低分子筛的骨架硅铝比可以提高正庚烷裂化反应的活性,但会降低低碳烯烃的选择性。     

晶种导向下干胶法合成ZSM-5分子筛

以廉价水玻璃为硅源,在晶种替代有机模板剂的条件下采用干胶法合成了ZSM-5分子筛。利用XRD、SEM、TEM、FTIR、N₂吸附-脱附和NH₃-TPD等分析方法对合成样品进行了表征和测试,考察了合成条件对ZSM-5分子筛晶化过程的影响。结果表明,在硅铝比（n/n）为30~70,钠硅比（n/n）为0.12~0.20时都可以得到结晶度良好的ZSM-5分子筛。研究发现,干胶法合成ZSM-5,在不引入外加水的情况下也可以得到ZSM-5样品,外加水的引入能够有效地提高晶化速率;与水热法合成ZSM-5分子筛相比,干胶法可以显著地缩短晶化时间,同时,合成样品的晶体尺寸也有所减小。     

晶种导向干凝胶法制备成型ZSM-5分子筛

在干凝胶法制备ZSM-5 分子筛的体系中添加晶种导向剂, 控制分子筛的生长, 制备了纳米沸石组装的无粘结剂成型多级孔ZSM-5 分子筛, 一步完成纳米分子筛的制备及组装成型, 即克服了传统纳米粒子难以过滤分离的问题, 同时组装所形成的多级孔有助于改善分子在催化剂内的扩散, 从而提高催化反应效率. 以硅胶、薄水铝石为原料, 四丙基氢氧化铵(TPAOH)和ZSM-5 晶种导向胶作为粘结剂, 通过混捏、挤条得到直径2 mm的条状前驱物, 随后通过干凝胶转换法制备成型分子筛. 所用晶种导向剂组成为0.35TPAOH:1SiO₂:20H₂O:4C₂H₅OH. 通过X射线衍射(XRD), 热重(TG)分析和傅里叶变换红外(FTIR)光谱等方法对分子筛晶化过程进行了表征, 结果表明晶种导向剂加入量对分子筛生长速度及多级孔结构均有影响. 当所加晶种导向剂中TPAOH与SiO₂的摩尔比为0.025时, 经过3 h晶化, 分子筛相对结晶度达到100%. 扫描电镜(SEM)结果表明, 合成的分子筛尺寸约为200 nm, 组装形成的多级孔分子筛的介孔体积为0.28 cm³·g^-1. 通过NH₃ 程序升温脱附(NH₃-TPD)考察了所得成型分子筛的酸性, 发现该分子筛酸性与市售的粉末H-ZSM-5分子筛类似.     

四丙基氢氧化铵改性纳米HZSM-5分子筛及其在甲醇制汽油中的催化性能

采用四丙基氢氧化铵(TPAOH)溶液对纳米ZSM-5分子筛进行改性, 运用X射线衍射、扫描电镜、²⁷Al和²⁹Si固体核磁、X射线光电子能谱、N₂物理吸附脱附法和NH₃程序升温脱附等手段对所制样品进行了表征, 并评价了其催化甲醇制汽油反应性能. 结果表明, 改性后的HZSM-5相对结晶度增加, 晶体形貌更加规整, 表面硅铝比增加, 比表面积和微孔表面积增大, 强酸位酸量增多. 同时, TPAOH改性不仅可以使分子筛脱硅脱铝, 而且伴有二次晶化补硅补铝, 改变了分子筛的硅铝分布. 改性的HZSM-5在甲醇制汽油反应中的稳定性大幅度提高, 其寿命由70h增至170h以上, 随着TPAOH处理时间的增加, 催化剂寿命增加, 氢转移反应加快, 导致油相产品中异构烷烃增多, 烯烃减少.     

氟硅酸铵改性纳米HZSM-5分子筛催化甲醇制丙烯

在静态条件下, 采用不同浓度的氟硅酸铵溶液对纳米ZSM-5分子筛进行了改性处理. 利用粉末X射线衍射(XRD)、²⁷Al 魔角旋转固体核磁共振(²⁷Al MAS NMR)、X射线荧光光谱(XRF)、X射线光电子能谱(XPS)、N₂ 吸附、透射电镜(TEM)、NH₃程序升温脱附(NH₃-TPD)、吡啶吸附红外光谱(Py-IR)等技术对改性前后纳米ZSM-5分子筛的骨架结构、织构性质、酸性质进行了表征. 并在常压、反应温度为450℃、甲醇质量空速(WHSV)为1 h^-1的条件下, 研究了改性前后纳米HZSM- 的甲醇制丙烯(MTP)催化性能. 结果表明, 合适浓度的氟硅酸铵处 理能够选择性地脱除纳米ZSM-5 分子筛的外表面铝, 从而使得HZSM-5 的酸密度降低, 比表面积和孔容增大, MTP催化性能显著提高. 氟硅酸铵改性后纳米HZSM-5 的丙烯选择性和丙烯/乙烯(P/E)质量比分别由原来的 28.8%和2.6提高到45.1%和8.0, 催化剂寿命增加了近2倍.     

ZSM-5、ZSM-57分子筛和丝光沸石间的转晶规律

考察了硅铝比、碱度、有机胺模板剂、晶化时间及温度等合成条件对ZSM-5、ZSM-57 分子筛和丝光沸石之间相互转晶的影响. 发现较高的碱度、较长的晶化时间有利于合成丝光沸石；较低的碱度、较高的诱导晶化温度、较长的晶化时间有利于合成低硅铝比的ZSM-57 分子筛；合成低硅铝比的ZSM-5分子筛则需要在能合成丝光沸石和ZSM-57 分子筛的碱度区间内精确调节碱度, 缩短晶化时间、降低诱导晶化温度、加入适当晶种, 有利于合成低硅铝比的ZSM-5 分子筛. 合成条件稍微改变, 会导致各种沸石之间发生转晶, 晶化产物出现两种或两种以上的晶型.     

利用Taguchi法以高岭土为原料制备高硅NaY分子筛

采用Taguchi试验方法优化出了以高岭土为原料制备高硅NaY分子筛的最佳合成参数,考察了硅溶胶的加入量、反应体系的碱度、加水量以及晶化时间对NaY分子筛硅铝比和结晶度的影响。结果表明,高硅NaY分子筛的最佳合成条件是：反应体系各组分的物质的量比为7.5SiO₂∶1.0Al₂O₃∶2.2Na₂O∶120H₂O,晶化时间为16 h。同时发现,对合成样品性能的影响最为显著的因素是硅溶胶的加入量和碱度。采用X射线衍射、N₂静态容量吸附法和扫描电镜对利用最佳条件所合成样品的硅铝比、比表面积、孔分布以及表观形貌进行了表征。结果显示,以高岭土原料制备的NaY分子筛比参考样品拥有更高的硅铝比和更大的比表面积。     

具有纳米线镶嵌结构ZSM-5/L复合分子筛的合成及表征

采用两步晶化法,以四丙基氢氧化铵预处理ZSM-5为晶种,快速合成了纳米线镶嵌结构ZSM-5/L复合分子筛.通过XRD、SEM-EDX、TEM和N₂吸附-脱附等手段对合成样品的物理化学性质进行了表征.孔道性质表明复合分子筛具有微孔和介孔的多级孔道结构,椭球的L分子筛镶嵌在纳米线的ZSM-5分子筛周围.晶种预处理影响了溶胶的电荷及分子筛的形貌,当合成样品中ZSM-5的质量分数小于2%（重量百分比）时,凝胶的负电荷较多,易形成椭球状L分子筛;当合成样品中ZSM-5的质量分数大于2%（重量百分比）时,zeta电位在-39.822~-42.352 mV之间波动,ZSM-5分子筛的形貌从长条状逐渐转变为纳米线状.阳离子比影响复合分子筛中L分子筛形成,当阳离子比R=n（K₂O）/（n（K₂O）+n（Na₂O））小于0.6时,不利于L型分子筛的形成;当阳离子比大于0.6,即K⁺较多Na⁺较少时,有利于L型分子筛中α-钙霞石笼的形成.     

高岭土微球上无胺法ZSM-5的原位合成

无胺体系中,采用水热法在焙烧高岭土微球上原位晶化合成了ZSM-5分子筛。考察了晶化温度、晶化时间、晶种加入量以及合成体系硅铝比等主要因素对分子筛合成的影响,得出了较佳的原位晶化合成条件。采用XRD、SEM、N₂吸附脱附等手段对合成样品进行了表征。结果表明：在高岭土微球上合成出了颗粒尺寸小于1 μm的小晶粒原位ZSM-5分子筛;晶化产物的比表面积、总孔容、微孔表面积和微孔孔容均明显增大,微孔分布集中于0.54 nm。     

硅源量和晶化时间对SAPO-34分子筛结构和性能的影响

以吗啡啉为模板剂合成了SAPO-34分子筛，研究了晶化液SiO₂/Al₂O₃比(硅源量)的影响。当SiO₂/Al₂O₃ ≥ 0.6时，能合成出纯净的SAPO-34分子筛;SiO₂/Al₂O₃=1.0时，分子筛骨架中出现“硅岛”结构，此时合成的分子筛样品具有最高的(乙烯+丙烯)选择性。继续增大硅铝比对(乙烯+丙烯     

High-pressure transitions in MgAl2O4 and a new high-pressure phase of Mg2Al2O5

Phase transitions in MgAl₂O₄ were examined at 21-27 GPa and 1400-2500 °C using a multianvil apparatus. A mixture of MgO and Al₂O₃ corundum that are high-pressure dissociation products of MgAl₂O₄ spinel combines into calcium-ferrite type MgAl₂O₄ at 26-27 GPa and 1400-2000 °C. At temperature above 2000 °C at pressure below 25.5 GPa, a mixture of Al₂O₃ corundum and a new phase with Mg₂Al₂O₅ composition is stable. The transition boundary between the two fields has a strongly negative pressure-temperature slope. Structure analysis and Rietveld refinement on the basis of the powder X-ray diffraction profile of the Mg₂Al₂O₅ phase indicated that the phase represented a new structure type with orthorhombic symmetry (Pbam), and the lattice parameters were determined as a=9.3710(6) Å, b=12.1952(6) Å, c=2.7916(2) Å, V=319.03(3) Å³, Z=4. The structure consists of edge-sharing and corner-sharing (Mg, Al)O₆ octahedra, and contains chains of edge-sharing octahedra running along the c-axis. A part of Mg atoms are accommodated in six-coordinated trigonal prism sites in tunnels surrounded by the chains of edge-sharing (Mg, Al)O₆ octahedra. The structure is related with that of ludwigite (Mg, Fe²⁺)₂(Fe³⁺, Al)(BO₃)O₂. The molar volume of the Mg₂Al₂O₅ phase is smaller by 0.18% than sum of molar volumes of 2MgO and Al₂O₃ corundum. High-pressure dissociation to the mixture of corundum-type phase and the phase with ludwigite-related structure has been found only in MgAl₂O₄ among various A²⁺B³⁺₂O₄ compounds.     

MAS-NMR investigations of the crystallization behaviour of lithium aluminum silicate (LAS) glasses containing P2O5 and TiO2 nucleants

Lithium aluminum silicate (LAS) glass of composition (mol%) 20.4Li₂O-4.0Al₂O₃-68.6SiO₂-3.0K₂O-2.6B₂O₃-0.5P₂O₅-0.9TiO₂ was prepared by melt quenching. The glass was then nucleated and crystallized based on differential thermal analysis (DTA) data and was characterized by ²⁹Si, ³¹P, ¹¹B and ²⁷Al MAS-NMR. XRD and ²⁹Si NMR showed that lithium metasilicate (Li₂SiO₃) is the first phase to c form followed by cristobalite (SiO₂) and lithium disilicate (Li₂Si₂O₅). ²⁹Si MAS-NMR revealed a change in the network structure already for the glasses nucleated at 550 °C. Since crystalline Li₃PO₄, as observed by ³¹P MAS-NMR, forms concurrently with the silicate phases, we conclude that crystalline Li₃PO₄ does not act as a nucleating agent for lithium silicate phases. Moreover, ³¹P NMR indicates the formation of M-PO₄ (M=B, Al or Ti) complexes. The presence of BO₃ and BO₄ structural units in all the glass/glass-ceramic samples is revealed through ¹¹B MAS-NMR. B remains in the residual glass and the crystallization of silicate phases causes a reduction in the number of alkali ions available for charge compensation. As a result, the number of trigonally coordinated B (BO₃) increases at the expense of tetrahedrally coordinated B (BO₄). The ²⁷Al MAS-NMR spectra indicate the presence of tetrahedrally coordinated Al species, which are only slightly perturbed by the crystallization.     

Al含量对Pt-SO2-4 /ZrO2-Al2O3固体超强酸催化

通过向SO^2-₄ /ZrO₂催化剂中同时引入适量的Pt和Al₂O₃, 制备出了具有较高催化性能和稳定性的Pt-SO^2-₄ /ZrO₂-Al₂O₃型固体超强酸催化剂. 以正戊烷异构化反应为探针, 考察了Al含量对催化剂性能的影响; 并采用X射线衍射(XRD)、比表面积测定(BET)、红外(IR)光谱、程序升温还原(TPR)、热重-差热分析(TG-DTA)和氨-程序升温脱附(NH₃-TPD)手段对催化剂进行了表征. 结果表明, Al能够提高ZrO₂的晶化温度, 抑制硫的分解, 增加催化剂的比表面积, 增强硫氧键的结合, 提高催化剂的还原性能, 增加催化剂的酸强度和酸总量. 当Al₂O₃含量(质量分数, w)为5.0%时, Pt-SO^2-₄ /ZrO₂-Al₂O₃固体超强酸催化剂的催化活性最好, 在100 h内异戊烷收率可稳定在52.0%以上, 选择性在98.2%以上.     

Characterization and evaluation of Fe2O3/Al2O3 oxygen carrier prepared by sol–gel combustion synthesis

The sol-gel combustion synthesis (SGCS) for oxygen carrier (OC) to be used in chemical looping combustion (CLC) was first designed and experimented in this work, which is a new method of OC synthesis by combining sol-gel technique and solution combustion synthesis. Cheap hydrated metal nitrates and urea were adopted as precursors to prepare Fe₂O₃/Al₂O₃ OC at the molar ratio to unity (Fe1Al1), which was characterized through various means, including Fourier transforms infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential thermal analysis (DTA), X-ray diffractor (XRD), and N₂ isothermal adsorption/desorption method. FTIR analysis on the chemical structure of the dried gel of Fe1Al1 indicated that urea was partly hydrolyzed and the hydrated basic carbonate was formed by the combination of groups such as (Fe(_1−yAl_y)_1−xO_1−3x, CO₃²⁻ and -OH-. By analyzing the staged products during SGCS, calcination was found as a necessary step to produce Fe₂O₃/Al₂O₃ OC with separate phases of α-Fe₂O₃ and α-Al₂O₃. Through TGA-DTA, the decomposition of the dried gel was found to undergo five stages. The analysis of the evolved gases from the gel decomposition using FTIR partially confirmed the staged decomposition and assisted a better understanding of the mechanism of SGCS. XRD identification further substantiated the necessity of calcination to synthesize Fe₂O₃/Al₂O₃ OC with separate phases of α-Fe₂O₃ and α-Al₂O₃, though it was not necessary for the synthesis of single phase α-Fe₂O₃ and α-Al₂O₃. Structural characterization performed on N₂ adsorption analyzer displayed that the pore shape of Fe1Al1 particles was heterogeneous. Finally, H₂ temperature-programmed reduction (TPR) of Fe1Al1 products in TGA indicated that the reduction reaction of Fe1Al1 OC after calcination was a single step reaction from α-Fe₂O₃ to Fe, and calcination benefited to improve the transfer rate of the lattice oxygen from the OC to fuel H₂. Furthermore, four times of reduction and oxidization (redox) reaction by alternating with H₂ and air demonstrated the synthesized OC had good reactivity and sintering-resistance, much suitable to be used in the realistic CLC. Overall, the SGCS method was found superior to other existent methods to prepare Fe₂O₃/Al₂O₃ OC for CLC application.     

Crystal-chemistry of mullite-type aluminoborates Al18B4O33 and Al5BO9: A stoichiometry puzzle

Orthorhombic Al₂O₃-rich aluminoborate is an important ceramic material for which two slightly different compositions have been assumed: Al₅BO₉ (5Al₂O₃:B₂O₃) and Al₁₈B₄O₃₃ (9Al₂O₃:2B₂O₃). The formula Al₁₈B₄O₃₃ (=Al_4.91B_1.09O₉) was derived from results of chemical analyses when crystal structure data were not yet available. Subsequent structural investigations indicated Al₅BO₉ composition. Nevertheless, Al₁₈B₄O₃₃ was still accepted as the correct stoichiometry assuming that additional B replaces 9% Al.Powder samples of both compositions and ones with excess boron were prepared by solid state reactions between α-Al₂O₃ and B₂O₃/H₃BO₃ at temperatures above 1100 °C and single-crystals were grown from flux at 1100 and 1550 °C. Products were investigated by single-crystal and powder XRD, ¹¹B and ²⁷Al solid-state MAS-NMR, Raman and FTIR spectroscopy as well as Laser-ablation ICP-MS. No indication of the predicted 9% B→Al substitution was found. LA ICP-MS indicated 12.36(27) wt% B₂O₃ corresponding to Al_4.97B_1.03O₉. Hence, the suggested Al₁₈B₄O₃₃ stoichiometry can be excluded for all synthesized samples. A very low amount of Al vacancies at a five-fold coordinated site are likely, charge balanced by an additional nearby three-fold coordinated B site. All evidences indicate that the title compound should be reported as Al_5−xB_1+xO₉ with x<0.038(6), which is close to Al₅BO₉.     

ZrO4/SiO2-Al2O3催化肉桂醛MPV转移加氢性能

以九水合硝酸铝（Al（NO₃）₃·9H₂O）与正硅酸乙酯（TEOS）为前驱盐,采用溶胶-凝胶法制备一系列不同Al₂O₃含量的SiO₂-Al₂O₃复合氧化物,并通过浸渍硝酸氧锆引入ZrO₂,制备ZrO₂/SiO₂-Al₂O₃复合氧化物催化剂,考察催化剂在肉桂醛（CAL）MPV转移加氢中的催化性能,并结合N₂物理吸附、X射线粉末衍射（XRD）、傅里叶变换红外光谱（FTIR）、NH₃-程度升温脱附（NH₃-TPD）、Py-原位红外（Py-IR）等技术,研究催化剂结构、织构以及表面性质与其催化性能间的构效关系.研究表明,所制备的催化剂均以L酸为主,并含有少量B酸中心,这使得加氢产物以肉桂醇（COL）为主,并含有少量1-苯丙烯-2-丙基醚（CPE）.Al₂O₃含量不仅影响催化剂表面的酸中心数量,而且对催化剂的织构参数有较大影响.随Al₂O₃含量的增加,催化剂表面L酸与B酸中心均有所增加,而孔径则持续变小,这使得催化反应呈现CAL转化率先增加后减少、目标产物COL选择性先稍有减小后有所增加的趋势.在Si/Al比为2时,催化剂具有最优的催化性能,优化反应条件下,CAL转化率达96%,目标产物COL选择性达90%.     

Controlled synthesis and luminescent properties of Eu(Eu), Dy-doped Sr3Al2O6 phosphors by hydrothermal treatment and postannealing approach

In this work, Sr₃Al₂O₆: Eu²⁺ (Eu³⁺), Dy³⁺ phosphors have been prepared by hydrothermal treatment and subsequently postannealing approach, using Sr(NO₃)₂, Al(NO₃)₃·9H₂O, and CO(NH₂)₂ as starting materials. The as-obtained phosphors were characterized by means of XRPD, FESEM, and PL techniques. In addition, many reaction parameters were studied in detail, including the initial mole ratios, hydrothermal reaction temperature, calcination temperature and calcination atmosphere. Remarkably, two scientific merits exist herein: Sr₃Al₂O₆: Eu²⁺ (Eu³⁺), Dy³⁺ phosphors can be selectively obtained in a reducing atmosphere (H₂/Ar, 20%+80%) and in air, respectively; adding certain amount of sodium citrate can alter the shape and size of Sr₃Al₂O₆: Eu²⁺ (Eu³⁺), Dy³⁺ phosphors in essence. Besides, the luminescent properties of Sr₃Al₂O₆: Eu²⁺ (Eu³⁺), Dy³⁺ phosphors were studied by excitation spectra, emission spectra and decay curves.     

溶剂极性对微波辐射老化制备前驱体及CuO/ZnO/Al2O3催化剂结构的影响

在制备CuO/ZnO/Al2O3催化剂的老化过程中,采用微波辐射老化技术,着重研究了溶剂极性对前躯体物相组成,烧后CuO/ZnO/Al2O3催化剂结构及其在浆态床合成甲醇工艺中催化性能的影响。通过XRD、DTG、H2-TPR,FTIR、HR-TEM和XPS对前驱体及催化剂表征表明,沉淀母液在微波辐射条件下进行老化,溶剂的极性对前躯体物相组成及催化剂结构影响显著。随着溶剂极性的增大,Zn2+/Cu2+取代Cu2(CO3)(OH)2/Zn5(CO3)2(OH)6中Cu2+/Zn2+的取代反应增强,使得前躯体中(Cu,Zn)5(CO3)2(OH)6和(Cu,Zn)2(CO3)(OH)2物相的含量增多,结晶度提高,导致烧后CuO/ZnO/Al2O3催化剂中CuO-ZnO协同作用增强,且CuO晶粒减小,表面Cu含量增加,催化剂活性和稳定性提高。水溶剂的极性最大,制备的催化剂活性和稳定性最好,甲醇的时空收率(STY)和平均失活率分别为320 mg.g-1.h-1和0.11%.d-1。     

Alkylation of phenol with dimethyl carbonate over AlPO4, Al2O3 and AlPO4-Al2O3 catalysts

The vapor-phase catalytic alkylation of phenol with dimethyl carbonate over different AlPO₄ (Al/P=1), Al₂O₃ and AlPO₄-Al₂O₃ (5–25 wt.% Al₂O₃) catalysts produces anisole (O-alkylation) as the major reaction product althougho-cresol (C-alkylation) and methylanisoles were also found. The reaction is first order in phenol while O-and C-alkylation follow parallel processes. As compared with methanol, DMC is far more effective as a methylating agent, and the methylation proceeds at a lower temperature and with higher O-alkylation selectivity.     

α-Fe2O3/SiO2纳米颗粒混合体系表面的酸碱性质及其对重金属离子的吸附行为

以Fe(NO₃)₃·9H₂O和正硅酸乙酯(TEOS)为原料, 通过溶胶-凝胶法和辅助模板法分别制备了纳米α-Fe₂O₃和SiO₂, 并对所合成样品进行了粉末X射线衍射(XRD)和BET表征. 使用自动电位滴定仪测定了α-Fe₂O₃/SiO₂纳米颗粒混合体系的表面酸碱性质. 研究了在不同pH下α-Fe₂O₃/SiO₂混合体系对Cu²⁺、Pb²⁺、Zn²⁺离子的吸附行为. 基于上述实验数据, 用WinSGW软件计算了α-Fe₂O₃/SiO₂混合体系表面酸碱配位常数, 并得出结论: α-Fe₂O₃/SiO₂混合体系表面反应为单一脱质子反应≡XOH ⇔ ≡XO^-+ H⁺(lg K = -8.19±0.15), 明显区别于同时具有加质子和脱质子反应的α-Fe₂O₃/SiO₂/γ-Al₂O₃, α-Fe₂O₃/γ-Al₂O₃和SiO₂/γ-Al₂O₃等纳米颗粒混合体系. 在此基础上拟合得到α-Fe₂O₃/SiO₂混合体系吸附重金属离子Cu²⁺、Pb²⁺、Zn²⁺的表面络合反应平衡常数分别为:
≡XOH + M²⁺ ⇔ ≡XOM⁺+ H⁺ [lg K = -3.1, -3.6, -3.8 (M = Cu, Pb, Zn)].
≡XOH＋M²⁺＋H₂O ⇔≡XOMOH＋2H⁺[lg K = -8.8, -8.0, -10.5 (M = Cu, Pb, Zn)]